Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
a safe and efficient hemostasis is one of the most important factors in minimally invasive surgery .
hemostasis can be achieved by sutures , clips , application of hemostyptica or thermic coagulation .   for thermic coagulation , high - frequency ( hf ) coagulation in monopolar or bipolar mode , cold plasma , and ultrasonic coagulation
klingele compared the ultrasonic technique with the bipolar technique in dissected vessels and examined the tissue damage .
underwood et al . measured the differences in operative time , blood loss and complications when using bipolar or ultrasonic technique in colectomies and fundoplications [ 7 , 8 ] .
sutton   et al . examined the lateral thermal spread using monopolar and bipolar diathermy , the harmonic scalpel and ligasure by measuring the maximum temperature . in our present study
the tests were performed on perfused , isolated pig liver in a minimally invasive model with a pulsatile organ perfusion ( p.o.p . ) trainer . for analysis
a complete laparoscopic equipment setup for minimally invasive surgery was used together with a p.o.p .
the experimental procedure began with heating the isolated , frozen liver in a water - cooled vacuum in order to warm it up to about 30c35c before the actual start of the experiment .
the pump of the trainer was activated to check the correct function ( figure 2 ) .
small open vessels on the liver surface were closed with sutures . after a final check of the correct connection of blood vessels ,
after 30 minutes , the tissue temperature was detected by the laboratory thermometer at 5-minute intervals until it reached 37c .   to start the experiment ,
a 2 - 3  cm thick slice of the liver was resected to create a deep tissue bleeding .
after closure of the cover , the pump was activated again ; the bleeding area was photodocumented ( figure 3 ) .
the cut surface was divided horizontally in two halves . only the upper half was coagulated to see the difference to untreated tissue and calculate the tissue loss ( figure 4 ) .
the coagulation was started using one of the four techniques until the bleeding could be stopped .   using ultrasonic coagulation
, it was not possible to create hemostasis in preliminary experiments for hemostasis   of large bleeding areas in perfused pig liver .
after 5 minutes , the cell walls were highlighted and a first approach of coagulated tissue became visible .
the bleeding did not stop ; the extraction of tissue by the mechanical vibrations of the ultrasonic applicator could be observed .
after 10  minutes , there was an increase of foam ; after 15  minutes , we saw extracted tissue without sufficient hemostasis ( figures 5 and 6 ) .
based on these preliminary tests , the ultrasonic technique was not considered for   further experiments and pathological examination .   using the other devices , after stopping the pump and opening the cover ,
the tissue was fixed on a cork plate and placed in formalin solution after photodocumentation .   from the resected tissue ,
10  cuts in 510  mm distance were made , each cut was examined at 10 points microscopically ( figure 7 ) .
furthermore , the maximum tissue damage was determined to compare the tissue loss caused by the different techniques .
the high - frequency coagulation devices were used with the settings shown in table 1 .
the gas flow had little effect ( cooling ) on the coagulation performance . with 1.5  l / min gas flow ,
forced coag  was chosen because the required output voltage of the monopolar technique for a similar coagulation is significantly higher than in bipolar technology .
the tissue structure changes on the necrotic side the color is darker in the thermally damaged area .
microscopically the necrotic cells are not clearly defined and shrank because of the evaporated water . in addition , the color is very dark compared with the nondamaged tissue .
the 10 measuring points are lined up linearly , so that the measurements cover a distance of 1  mm of the tissue sample .
the tissue loss is measured in relation to the lower half of the untreated sample at the point of greatest loss .
the measurement can be easily carried out macroscopically ( figure 4 ) .   for statistical evaluation of tissue damage and tissue loss ,
we measured the coagulation time of 3  different techniques ( monopolar , bipolar , and cold plasma ) on 4 experimental days .
ultrasonic coagulation was excluded , because hemostasis of large bleeding areas could not be reached .   as shown in figure 9 , the shortest time
there was almost no difference between monopolar ( 11  min ) and cold plasma ( 11.25  min ) . to determine the tissue loss ,
the height difference between the coagulated area and the untreated area was macroscopically analyzed and measured in mm ( figure 10 ) .
the minimal tissue loss was 4  mm ( bipolar coagulation ) ; the maximal tissue loss of 8  mm occurred using cold plasma coagulation . on average ,
the tissue loss was the least in bipolar technique ( 4.5  mm ) , more in monopolar technique ( 6.0  mm ) , and most in cold plasma coagulation ( 7.5  mm ) .
the depth of tissue necrosis was analyzed microscopically and measured in mm ( figure 11 ) .
the lowest value was found in cold plasma coagulation ( 0.157  mm ) , the highest in monopolar coagulation ( 0.598  mm ) .
the slightest average damage to the tissue was observed in cold plasma coagulation with a mean of 0.264  mm .
bipolar coagulation led to an average depth of 0.346  mm , monopolar coagulation of 0.459  mm .
bipolar coagulation of large bleeding areas of the perfused pig liver led to a rapid   hemostasis causing moderate tissue damage and depth loss .
the worst results occurred with monopolar coagulation compared to bipolar technique ( coagulation time + 33.3% , tissue loss + 33.3% , tissue damage + 32.7% ) .
ultrasonic coagulation was excluded because large bleeding areas could not be treated sufficiently and hemostasis was not reached .
the aim of this study was to examine whether there are differences between the common coagulation techniques in a minimally invasive model concerning the efficiency of hemostasis and local tissue damage [ 1 , 3 ] . the experiments were done with isolated , perfused pig livers .
the use of ultrasonic coagulation did not lead to a complete hemostasis even after 15-minute coagulation time .
the termination resulted from the application form of energy causing foam formation and extraction of tissue components .
the benefits of ultrasonic technology in minimally invasive surgery are clear in the preparation and dissection of tissue , the use close to other organs , and the closure of isolated vessels of up to 57  mm . in our model , it was not useful for coagulation of large bleeding areas .
the first parameter in this study was the coagulation time until a sufficient hemostasis was reached .
a good instrument should be safe and quick to reduce damage to lateral tissue and to minimize the energy flow to the patient .
we know from clinical use that with longer monopolar coagulation time more and more necrotic tissue sticks to the instrument and is pulled out .
the average tissue loss was 4.5  mm in bipolar technique and 6.0  mm in monopolar technique ( cold plasma coagulation 7.5  mm ) .
the depth of tissue damage by coagulation was the third parameter in this study . because of the high efficiency of bipolar coagulation , less energy was needed to stop the bleeding .
this resulted in an average depth of tissue necrosis of 0.346  mm in bipolar coagulation and 0.459  mm in monopolar coagulation .
it showed the longest coagulation time and the highest tissue loss , while the depth of tissue damage was the lowest in this study .
one possible explanation could be the gas , which is pressed into the tissue during the contactless coagulation .
it leads to a deep dissection of necrotic tissue and a rapid shrinkage of the particles ( figure 13 ) .
this indicates a low degree of necrosis and corresponds with the previously mentioned results ( figure 14 ) .
after monopolar coagulation , we regularly see black carbonized tissue ( figure 15 ) , after cold plasma coagulation grey - brown to black tissue ( figure 16 ) . in summary ,
the collateral tissue damage consisted of the tissue loss and the tissue necrosis in the depth . when both factors are added , the total damage can be calculated ( table 2 ) .
the results of this work came from experiments on isolated pig livers in an in vitro test environment and can not be easily transferred to human application .
perfusion of the isolated liver was achieved with colored saline solution and not with blood , what restricts hemostasis and prolongs the coagulation time .
this is one reason for the relatively long coagulation time that we measured in the perfused liver .
further studies have to show the presumed superiority of bipolar technique . in our surgical department
the experimental study showed differences between several coagulation techniques in a minimally invasive model for hemostasis in deep liver bleeding .
ultrasonic coagulation , which is very useful in dissection of tissue and coagulation of isolated vessels , did not lead to a sufficient hemostasis in large bleeding areas .
the bipolar technique was the form of coagulation with the highest efficiency and the least tissue damage .

Answer:
hemostasis in minimally invasive surgery causes tissue damage . regardless of the method of production of thermal energy ,
 a quick and safe coagulation is essential for its clinical use . in this study
 we examined the tissue damage in the isolated perfused pig liver using monopolar , bipolar , cold plasma , and ultrasonic coagulation . in a
 minimally invasive in vitro setup , a 2 - 3  cm slice of the edge of the perfused pig liver was resected .
 after hemostasis was achieved , liver tissue of the coagulated area was given to histopathological examination .
 the depth of tissue necrosis , the height of tissue loss , and the time until sufficient hemostasis was reached were analyzed .
 the lowest risk for extensive tissue damage could be shown for the bipolar technique , combined with the highest efficiency in hemostasis .
 using cold plasma , coagulation time was longer with a deeper tissue damage .
 monopolar technique showed the worst results with the highest tissue damage and a long coagulation time .
 ultrasonic coagulation was not useful for coagulation of large bleeding areas .
 in summary , bipolar technique led to less tissue damage and best coagulation results in our minimally invasive model .
 these results could be important to recommend bipolar coagulation for clinical use in minimally invasive surgery .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
hyperpigmentation of the gingiva has always been a concern to certain patients , especially young females .
although melanin pigmentation of the gingiva is completely benign and does not present a medical problem , its unaesthetic appearance as  black gums  is more pronounced in patients having a high smile line ( gummy smile ) .
 gummy smile  can be due to incomplete passive eruption , maxillary protrusion , hyperactive muscle of lips , short lip , gingival enlargement , etc .
gingival depigmentation can also be performed by surgical blade , coarse diamond bur , electrosurgery , cryosurgery or lasers . considering the advantages of lasers over other modalities of treatment , this article will focus on the management of such a case using gaalas diode lasers of 810 nm .
a 22-year - old female patient was referred with a complaint of gummy smile and hyperpigmented gingiva [ figure 1 ] . on examination , pseudopockets ( approximately 23 mm ) were detected in the maxillary and mandibular anteriors along with generalized excessive amount of melanin pigmentation on the gingiva [ figure 2 ] .
the patient was explained about the treatment options and informed that , after depigmentation , melanin pigmentation tends to recur and , as gingivectomy is also performed simultaneously , the overall appearance would be worth doing it .
profile view of gummy smile with hyper melanin pigmentation of the gingiva intraoral view of gummy smile with hyper melanin pigmentation of the gingiva gingivectomy and depigmentation were planned in the 1525 region and the 3444 region using a 810 nm diode laser .
although procedures like this can be performed under topical anesthesia , infiltration was planned as the patient was anxious and sensitive . under infiltration anesthesia with 2% lignocaine ( with 1:100,000 adrenaline ) , an 810 nm gaalas diode laser ( picasso)*(picasso , by amd lasers ) was used in contact mode with the gingival tissues .
e gel was prescribed for local application -three to four times a day for 2 days . because a large area of the raw wound was kept exposed , antibiotic cap .
immediate postoperative view of gingivectomy and depigmentation using an 810 nm diode laser the patient reported no adverse effects or discomfort during the postoperative healing phase .
she was happy and satisfied with 6-month postoperative results [ figures 4 and 5 ] .
gingivectomy and depigmentation were planned in the 1525 region and the 3444 region using a 810 nm diode laser .
although procedures like this can be performed under topical anesthesia , infiltration was planned as the patient was anxious and sensitive .
under infiltration anesthesia with 2% lignocaine ( with 1:100,000 adrenaline ) , an 810 nm gaalas diode laser ( picasso)*(picasso , by amd lasers ) was used in contact mode with the gingival tissues .
e gel was prescribed for local application -three to four times a day for 2 days . because a large area of the raw wound was kept exposed , antibiotic cap .
immediate postoperative view of gingivectomy and depigmentation using an 810 nm diode laser the patient reported no adverse effects or discomfort during the postoperative healing phase .
she was happy and satisfied with 6-month postoperative results [ figures 4 and 5 ] .
diode laser is a versatile laser and has been successfully used at three wavelengths : 980 nm , 810 nm and , more recently , 940 nm .
it has numerous soft tissue applications , viz frenectomy , crown lengthening , gingival depigmentation , troughing , etc . in a diode laser ,
the substance stimulated to produce a coherent light beam is a semiconductor . this technology has produced a laser that is compact and economic .
a diode laser has become an important tool in the dental armamentarium due to its exceptional ease of use and affordability .
the diode laser is well absorbed by melanin , hemoglobin and other chromophores that are present in periodontal disease .
this provides the diode laser with broad clinical utility : it cuts precisely , coagulates , ablates and vaporizes the target tissue with much less trauma , improved postoperative healing and faster recovery time .
melanin pigmentation in gingiva is present only when melanin granules synthesized by melanocytes are transferred to the keratinocytes .
therefore , recurrence of the pigmentation is inevitable and has been reported from 24 h to 8 years following surgery .
conventional procedures for corrections of pigmented gingiva consist of surgical stripping with scalpel , use of electrosurgery , cryosurgery or a coarse diamond bur . however , the laser is the least - invasive and predictable method of performing this procedure .
it has a high level of precision , requires minimal anesthesia and causes very low collateral tissue damage .
cases where only gingivectomy is required can be performed without anesthesia or under topical anesthesia , but because both gingivectomy and depigmentation were planned together in this patient and a significantly larger area needs to be operated upon , infiltration anesthesia was given .
given the incredible ease of use and its versatility in treating soft tissue , the diode laser becomes the
patients with complaints of hyperpigmented gingiva should also be assessed for the presence of gummy smile .
once the amount of gingiva displayed is reduced by gingivectomy , the patient 's concern for hyperpigmented gingiva will also reduce . as a result , in most of the cases , a repeat surgery for depigmentation

Answer:
hyperpigmentation of gingiva becomes more pronounced if it is associated with
  gummy smile .
  correction of gummy smile and depigmentation together are key to complete patient satisfaction .
 an 810 nm ( 1.5 w , pulsed ) gaalas diode laser was used to achieve the desired results in a 22-year - old female patient .
 the 6-month follow - up results showed excellent color and contour of the gingiva .
 mere depigmentation without correcting gummy smile may look cosmetically good but esthetically unacceptable .
 diode laser was used as it is known to be an excellent tool as compared with other conventional surgical procedures in terms of patient and operator comfort .


Question:
You will be shown the title of a chemistry paper, together with sections excerpted from the body of the paper. The paper sections may include HTML tags like `<p>` and `</p>`; please ignore these. Your task is to write an abstract for the paper. Your response should include the abstract and no other text.

Title:
Geometric and energetic data from quantum chemical calculations of halobenzenes and xylenes Authors

Paper sections:
Value of the Data

• All 1505 possible halobenzenes and three xylenes are explicitly shown in this paper with numbering, IUPAC name, PubChem CID and SMILES. These can be used as a reference for both theoretical and experimental work involving this class of compounds. • Geometric and energetic data can be used for further analysis to understand relative stability of isomers.

In particular, the unexpected trend in relative stability of isomers are of particular interest to scientists in a similar manner to cis and gauche effect. The data set includes many examples where steric hindrance alone fails to account for the behaviour observed in halobenzenes and xylenes. • Raw data as well as associated scripts and codes are provided so that interested researchers can reproduce our data and perform calculation at other levels of theory or for other relevant class of compounds.

Vibrational spectrum and other detailed information can be extracted from output files as needed. There are many potential uses of the spectral information, for example, detection of xylene for food safety application [1] and understanding formation of polychlorinated biphenyls (PCBs). [2] The data can also be a test set for molecular modelling software packages.

Data Description

A total of 1505 unique compounds of benzene, including all degrees of substitution with F, Cl, Br, and I atoms, and three isomers of xylene were investigated. Classification and counting of the 1505 compounds are exhaustively shown in Tables 1 and 2 with specific examples in Figures 1, 2 and 3. The main difference between Table 1 and Table 2 is the treatment of hydrogen atom. In Table 1, hydrogen is treated in the same way as halogen and this leads to the binomial coefficients ( 5 𝑘 ) for five kinds of elements. In Table 2, hydrogen is treated in a special way and this leads to binomial coefficients ( 4 𝑘 ) for four kinds of halogen atoms. Table 3 summarizes the total number of Q-Chem 5.2.1 [3] output files for different classes of compounds, types of calculation (geometry optimization/frequency calculation) and levels of theory (HF, B3LYP, MP2, and CCSD)

In supplementary information, summary table files (.csv) are provided per level of theory.

• Geometric data of 12 bond lengths, 12 bond angles and 12 torsional angles in a single csv file • Energetic data, in separate files, include electronic energy (Eelec) in Hartree, thermal correction to enthalpy (Hcorr) in kcal mol -1 , zero-point vibrational energy (EZPE) in kcal mol -1 and entropy (S) in cal mol -1 K -1 . The following associated files are also provided.

• Raw Q-Chem output files (.out) for all compounds.

• Geometry in Z-matrix and Cartesian coordinate format (.xyz) for all compounds.

• Wolfram Mathematica notebook (benzene.nb) and associated script (script.txt).

Experimental Design, Materials, and Methods

Due to prohibitive computational cost, frequency calculations at MP2 and CCSD levels of theory were excluded and only benzene to dihalobenzenes and xylenes were selected for CCSD optimization jobs. The output files were processed by custom-made scripts and Wolfram Mathematica 12.0[4] codes to extract geometric and energetic data of all halobenzene compounds in a similar manner to our previous work. [5] Data from the three xylene compounds are provided for reference purpose and were read from IQmol 2.13 manually. [6] Table 1 List of all compounds by the number of elements bonded to carbon atoms (In total, there are 1,505 benzene and halobenzene compounds with 210 possible empirical formulas.) a See Figure 1. b See Figure 2.

Number of structures

) =60  Table 2 List of all compounds by different degrees of substitution to benzene (In total, the number of compounds and empirical formulas is the same as in Table 1.)

Benzene 0 C6H6

Answer: This article presents theoretical data on geometric and energetic features of halobenzenes and xylenes. Data were obtained from ab initio geometry optimization and frequency calculations at HF, B3LYP, MP2 and CCSD levels of theory on 6-311++G(d,p) basis set. In total, 1504 structures of halobenzenes, three structures of xylenes and one structure of benzene were generated and processed by custom-made codes in Mathematica. The quantum chemical calculation was completed in Q-Chem software package. Geometric and energetic data of the compounds are presented in this paper as supplementary tables. Raw output files as well as codes and scripts associated with production and extraction of data are also provided.


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
we measured the differences in stiffness between extrafloral nectaries of v. faba and the tissue that surrounds them .
we mounted 20 stipules from 20 , 18-day - old plants on adhesive tape that was attached ( sticky side up ) to the surface of a piece of flat styrofoam .
we did a penetrometer test to measure the initial modulus of rigidity of the spot being tested , using a texture analyzer ( ta.xt2i , stable micro systems , surrey , uk ) fitted with a 10 stainless steel cone moving at 0.5  mm / s . in each stipule
, one measurement was done in the center of the extrafloral nectary and 3 measurements were done in random locations on the stipule . for each stipule , an average
stipule stiffness  was calculated from these 3 measurements and this value was compared with the measured stiffness of the extrafloral nectary on that stipule .

Answer:
abstractextrafloral nectaries play an important role in plant defense against herbivores by providing nectar rewards that attract ants and other carnivorous insects
 . however , extrafloral nectaries can themselves be targets of herbivory , in addition to being exploited by nectar - robbing insects that do not provide defensive services .
 we recently found that the extrafloral nectaries of vicia faba plants , as well as immediately adjacent tissues , exhibit high concentrations of chemical toxins , apparently as a defense against herbivory . here
 we report that the nectary tissues of this plant also exhibit high levels of structural stiffness compared to surrounding tissues , likely due to cell wall lignification and the concentration of calcium oxalate crystals in nectary tissues , which may provide an additional deterrent to herbivore feeding on nectary tissues .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
dual energy photon absorptiometry ( dxa ) has long been the standard for monitoring areal bmd ( abmd ) .
we have compared vbmd measured by high resolution peripheral computerized tomography ( hr - pqct ) with the results obtained by dxa ( abmd ) in a group of 49 of healthy premenopausal , normally menstruating women , aged 21 - 45 , spanning a range of bmi ( 18.5 - 46.5 ) .
they were exercising less than 4 hours per week , and did not have conditions or medications known to affect bone ; we wanted to see if the results of scanning with hr - pqct paralleled those of dxa in subjects with a wide range of bmi .
the subjects gave informed consent and the study was approved by our institutional review board .
using data from 187 females between 18 and 45 yrs , the mean and standard deviation for the total body bone density by dxa are 1.2044 and 0.1107 . using these results and assuming a correlation between the two measurements of bmd equal to 0.7 , gives a standard deviation for the difference between two measurements equal to 0.0857 .
a sample of size 45 has a power of 80% for detecting a difference between mean bmd of the two instruments equal to 0.0386 .
this corresponds to detecting a difference equal to 3.2% of the mean areal bmd of all bones in all areas was measured by dxa ( ge lunar idxa , hawaii , usa ) in whole body mode .
participants were measured on the same densitometer with the same software , scan speed and technologist .
the long term precision was 0.35% , and the least significant change for bmd measurements was 1.00% .
the software provides values for the masses of muscle , fat , and bone for the whole body and specific regions .
structural bone parameters of the non - dominant distal radius and left distal tibia were assessed by hr - pqct ( xtremect scanco medical ag , brutisellen , switzerland . ) a stack of 110 slices with a nominal voxel size of 82 m was obtained with the most distal computerized tomographic ( ct ) slice placed 9.5 mm from the endplate of the radius or 22.5 mm from the endplate of the tibia .
the coefficient of variation ( cv ) of a phantom containing hydroxyl - apatite ( ha ) rods embedded in resin ( qem .
the voi was automatically separated into a cortical area ( ct ar ) and trabecular area ( tb ar ) .
d100 is the average vbmd in a scanned region one scan of the distal radius was excluded because the subject was unable to control the shaking of her hand .
areal bmd of all bones in all areas was measured by dxa ( ge lunar idxa , hawaii , usa ) in whole body mode .
participants were measured on the same densitometer with the same software , scan speed and technologist .
the long term precision was 0.35% , and the least significant change for bmd measurements was 1.00% .
the software provides values for the masses of muscle , fat , and bone for the whole body and specific regions .
structural bone parameters of the non - dominant distal radius and left distal tibia were assessed by hr - pqct ( xtremect scanco medical ag , brutisellen , switzerland . ) a stack of 110 slices with a nominal voxel size of 82 m was obtained with the most distal computerized tomographic ( ct ) slice placed 9.5 mm from the endplate of the radius or 22.5 mm from the endplate of the tibia .
the coefficient of variation ( cv ) of a phantom containing hydroxyl - apatite ( ha ) rods embedded in resin ( qem .
the voi was automatically separated into a cortical area ( ct ar ) and trabecular area ( tb ar ) .
d100 is the average vbmd in a scanned region one scan of the distal radius was excluded because the subject was unable to control the shaking of her hand .
table 1 shows that the average and compact bone density ( hr - pqct ) are both higher in the radius than in the tibia whereas dxa shows a higher bone density for the legs ( weight bearing bone ) compared to the arms .
slice area ( which reflects cross sectional area ) and cortical thickness are greater in the tibia than in the radius , and this difference in geometry makes it difficult to interpret the difference in volumetric bone density ( hr - pqct ) ; bone strength is dependent inter alia on cross sectional area and cortical thickness .
figure 1 shows that bmd arms is significantly correlated with % fat whereas d100 ( average vbmd by hr - pqct ) , is non - significantly correlated with % fat .
table 2 shows that there is significant r between bmd ( dxa ) of legs and arms with bmi as well as w and % fat , whereas there is no significant r between d100 ( hr - pqct ) and these variables .
there is no significant r between age and bmd or between age and d100 radius but there is a significant r between age and d100 tibia table 3 shows that sl area ( cross sectional area ) tibia is correlated with w , bmi , % fat , age .
adult bones expand in diameter throughout adult life , apparently in adaptation to changing mechanical demands    seen by hr - pqct , but not by dxa .
the increased bone cross sectional area should decrease bmd ( dxa ) with increased bmi , instead of the increase which we found .
figure 2 shows the r between d100 radius v % fat and bmd arms v % fat .
the residuals of d100 ( hr - pqct ) / bmd ( dxa ) plotted against % fat have no significant r with the radius / arms ( r = 0.186 ns ) but for the tibia / legs , r=0.378 p<0.01 are shown in figure 3 .
bolotin et al showed that all soft tissue ( fat and muscle ) inhomogeneities could cause inaccuracies as large as 20 - 50% in bmd measured by dxa .
they reported that the ratio of fat to lean , and the ratio of yellow to red bone marrow in the region of interest ( roi ) has a major effect on the measured bmd .
we have shown in vitro that surrounding fat markedly alters the result of bmd measured by dxa .
bosy - westphal has shown that the configuration of fat and muscle around the bone and fat within the bone can markedly alter the measured bmd result .
this is probably because dxa can distinguish only two components in one pixel using the attenuation ratio of two different x - ray energies , whereas the output actually consists of three components , bone , fat , and muscle . in pixels containing bone , the composition of the soft tissue
can not be measured , and so in those pixels , soft tissue has to be extrapolated from adjacent areas .
this assumption is invalid if the composition of the soft tissue in front of or behind the bone or the bone marrow fat differs in composition from soft tissue next to the bone .
an undetected loss of fat either in front of , behind , or within the bone leads to an increase in pixel density that may lead to an overestimation of bmd .. the difference in r between bmi and the bone parameters measured by hr - pqct and those measured by dxa may possibly be explained by a difference in the effect of fat on the absorption of x - rays causing an artifactual increase in bmd measured by dxa .
the measurement of bmd by hr - pqct did not parallel those of dxa in subjects with increasing bmi .
our results by hr - pqct were obtained with scanco i which has a voxel size of 82 m .
the results of scanco i partially depend on identification of bone obtained by the absorption of x - rays in the voi .
this study should be repeated with scanco ii.which is a second generation hr - pqct scanner with a voxel size of 61 m .
this will provide a geometric measurement of the amount of bone , the result of which does not depend on the absorption of x - rays .
we have shown by radiogrammetry that geometric measurements of bone thickness are not altered by surrounding fat .
the decreased dependence ( with scanco ii ) on absorption of x - rays , may permit a more accurate assessment of the ability of hr - pqct to measure bmd independently of the amount of surrounding fat .
hr - pqct shows that increasing bmi is associated with increased bone cross - section .
this would tend to decrease measured bmd ( dxa ) as opposed to the increase which we observed with increasing bmi .
our study suggests that the increased bmd ( dxa ) found with increased bmi may partly be an artifact caused by absorption of x - rays by fat and muscle .
it is important to validate the measurement of bmd by dxa in the context of obesity because of the large number of studies which depend on it .

Answer:
objectivewas to compare the measurement of areal bone mineral density ( abmd ) by dual energy x - ray absorptiometry ( dxa ) with the measurement of volumetric bone mineral density ( vbmd ) by high resolution peripheral computerised tomography(hr - pqct ) in subjects with a wide range of body mass indices ( bmi).subjectswe scanned the arms and legs of 49 premenopausal women , aged 21 - 45 , with bmi from 18.5 - 46.5 , by high resolution peripheral computerized tomography ( hr - pqct ) and found that there was a non - significant change in volumetric bmd ( vbmd ) associated with increased bmi whereas abmd ( dxa ) was associated with a positive significant increase.hr-pqct scans a slice at the extremity of the tibia and radius , whereas dxa scans the entire leg and arm.resultsthe correlation coefficients ( r ) of bmd ( dxa ) of the legs with bmi were 0.552 p<0.001 , % fat 0.378 , p<0.01 , and w 0.633 , p<0.001 .
 the r of bmd ( dxa ) of the arms with bmi 0.804 p<0.001 , with % fat 0.599 p<0.001 , and with w 0.831 p<0.001 whereas the r of the average bone density ( d 100 ) of legs and arms measured by hr - pqct with bmi , w , and % fat , were not significant.conclusionsalthough hr - pqct and dxa scan different parts of the bone , the high r of bmd with bmi and low r of bone density measured by hr - pqct with bmi suggests that bmd measured by dxa is artifactually increased in the presence of obesity .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
cervical spondylosis is a common cause of chronic neck pain , radiculopathy and/or myelopathy resulting in significant disability .
when patients do not respond to conservative therapy , anterior cervical discectomy and fusion ( acdf ) usually is used to achieve neural decompression , maintain cervical lordosis , and provide segmental stabilization . in our practice , it was often found that patients with cervical spondylosis tended to have concomitant cervical vertigo symptoms such as tinnitus , headache , blur vision , and palpitation .
recent studies have indicated that cervical spondylosis patients with cervical vertigo symptoms could be managed successfully with acdf . in this study , we report 2 cases of cervical spondylosis with concomitant cervical vertigo and hypertension that were treated successfully with acdf .
this study obtained the approval of the medical ethics committee of our hospital ( general hospital of armed police force , beijing , china ) .
case 1 , a 49-year - old female , was admitted with 2 years of history of chronic neck pain , headache , and episodic vertigo and tinnitus .
episode occurred 1 to 2 times every day , and lasted 1 to 2  h each time .
she felt numbness of both upper extremities and weakness of all 4 extremities for 1 year .
physical examination showed that limited neck motion , slightly diminished sensation in both arms , and brisk deep tendon reflexes .
radiographic examination of the cervical spine showed mild diminution in the height of the c5/6 disc space ( figure 1 ) .
magnetic resonance imaging ( mri ) scan showed cord compression by a large central herniation of c5/6 disc with signs of myelomalacia ( figure 2 ) .
lateral radiograph of cervical spine before operation showed slight narrowing of the c5/6 disc space . t2-weighted sagittal magnetic resonance imaging ( mri ) revealed a large herniation of c5/6 disc before operation , with marked compression of cervical cord , resulting in myelomalacia .
the patient had a 2-year history of hypertension , blood pressure was 160/100  mmhg at onset , and then controlled in the normal range ( 110130/7080  mmhg ) by oral medications ( betaloc , 100  mg , once daily ; enalapril , 10  mg , once daily ) .
case 2 , a 60-year - old male , was admitted with 10 years of history of chronic neck pain and stiffness .
he also experienced vertigo , palpitation , nausea and vomiting with noted numbness of upper limbs , and heaviness of 4 limbs for over 6 months before admission .
radiographic examination of the cervical spine revealed large anterior and posterior spur formation at the c5/6 and c6/7 disc levels , severe diminution in the height of the c5/6 disc space , and moderate diminution in the height of the c6/7 disc space .
mri scan showed cervical canal stenosis with marked cord compression secondary to spondylotic changes in c5/6 and c6/7 discs .
the patient had a 1-year history of hypertension ( maximum at 180/120  mmhg ) , which was controlled within the normal range by oral medications ( irbesartan , 150  mg , once daily ; nifedipine sustained release tablets , 20  mg , once daily ; amlodiping besylate , 5  mg , once daily ) .
cervical spondylotic myelopathy was diagnosed and subsequently cervical anterior surgery was recommended for the 2 patients preoperatively based on clinical findings consistent with imaging study .
case 1 underwent acdf at the c5/6 disc level ( figures 3 and 4 ) .
after surgery , strength in all 4 limbs was significantly recovered , and symptoms of neck pain , headache , vertigo , and tinnitus disappeared .
interestingly , her blood pressure also dropped to within the normal range after surgery even without oral medications .
lateral radiograph of cervical spine 3 months after operation showed anterior cervical plate fixation with cage fusion at c5/6 disc level .
t2-weighted sagittal magnetic resonance imaging ( mri ) 7 days after operation showed disappearance of cord compression at c5/6 disc level .
his symptoms of cervical vertigo completely disappeared , numbness of both upper limbs significantly released , and muscle strength of 4 limbs obviously increased . similarly to case 1 ,
her cervical vertigo never recurred , and her blood pressure remained normal without the use of antihypertensive medications .
case 2 has undergone a follow - up of 14 months , the patient never had cervical vertigo anymore , and his blood pressure remained normal throughout ( 120130/7585  mmhg ) .
clinical results indicated that acdf can eliminate the concomitant vertigo symptoms in the 2 patients .
however , the exact mechanisms of resolution of symptoms can not be elucidated precisely . because cervical spondylosis is a common disease , vertigo occurred in patients with cervical spondylosis is of particular importance .
one previous study showed that vertigo was present in 50% of patients with cervical spondylosis , whereas another study identified cervical spondylosis as the cause of dizziness in 65% of elderly patients .
it has been shown that the patients with cervical spondylosis complaining of vertigo have significant lower blood flow parameters than non - vertigo patients with cervical spondylosis .
insufficient blood supply to posterior circulation is called vertebrobasilar insufficiency . the most common complaint in patients with vertebrobasilar insufficiency
insufficient blood supply does not necessarily cause symptoms if there is sufficient collateral circulation , whereas a full range of symptoms commonly occur as a result of an insufficient terminal vessel .
the vascular supply to the vestibulocochlear organ , being an end artery , makes this organ more susceptible to vertebrobasilar insufficiency .
neurons , axons , and hair cells in the vestibulocochlear system are known to respond to ischemia by depolarizing , causing transient hyperexcitability with ectopic discharges , manifesting as tinnitus , vertigo , and dizziness .
it was hypothesized that vertebral artery insufficiency secondary to cervical spondylosis could result in vertigo .
however , the mechanisms of vertigo caused by cervical spondylosis are not clear so far .
the mechanical compression on vertebral artery from spurs of the luschka joint was considered as a main mechanism .
the reduction of vertebral artery flow can be more obvious with the rotation and hyperextension of the head . in our current study
in addition , mechanical compression can not explain some other symptoms such as palpitation , nausea , vomiting , etc .
recent clinical studies by hong et al and li et al demonstrated that the stimulation of the sympathetic nerve fibers other than the compression of the vertebral artery induces these symptoms such as vertigo , tinnitus , nausea , and vomiting .
current study clearly indicates that hypertension can be associated with cervical spondylosis , as a secondary condition .
we speculate that the mechanisms of hypertension induced by cervical spondylosis could be the same as that of cervical vertigo .
it is well known that cervical disc , dura mater , and posterior longitudinal ligament are rich in sympathetic fibers .
sympathetic nerve fibers distributed around the vertebral artery have been implicated in the autoregulation of vertebrobasilar artery blood flow and cerebral blood flow .
it has been evidenced that sympathetic nerve activity withdraws the blood flow , whereas sympathectomy can increase it .
a previous study investigated sympathetic and parasympathetic changes incited by the stimulation of nerves around the proximal vertebral artery in cat model and found subsequent papillary changes , pulse and blood pressure changes .
elevation in levels of inflammatory cytokines has been detected in painful discs of humans , and thought to be related to degeneration and pain . the pathogenic change in the painful disc
is featured with the formation of zones of vascularized granulation tissue and extensive innervation extending from the outer layer of the annulus fibrosus into the nucleus pulposus .
degenerative changes in the disc , such as loss of the normal structure and a mechanical load , can lead to abnormal motion , which can provoke mechanical stimulation .
mechanical stimuli , which are normally innocuous to disc nociceptors can , in certain circumstances such as inflammation , generate an amplified response termed peripheral sensitization .
the vertebral arteries are mainly innervated by nerve fibers from the cervical sympathetic ganglia ( 13 ) .
innervation in cervical disc is analogous to that in the lumbar spine , receiving innervation posteriorly from the sinuvetebral nerves , laterally from the vertebral nerve , and anteriorly from the sympathetic trunks .
recently , an animal study   revealed a reciprocal neural connection between cervical spinal and sympathetic ganglia .
it seems likely that stimulation of sympathetic nerve fibers in the pathologically degenerative disc and surrounding tissues produce sympathetic excitation , and induce a sympathetic reflex to cause vertebrobasilar insufficiency and hypertension .
improvement of neurological function , resolution of vertigo , and recovery of blood pressure following surgery could be attributed to the excision of degenerative and herniated cervical disc , the decompression of the dura mater and posterior longitudinal ligament , and the stabilization of degenerated segment .
chronic neck pain is one of the major symptoms in patients with cervical spondylosis , whereas some studies have indicated that resting blood pressure levels may be elevated in patients with persistent pain . in healthy individuals ,
these interactions are believed to reflect a homeostatic feedback loop that helps restore arousal levels in the presence of acutely painful stimuli .
a role for baroreceptors in this feedback loop appears likely , with pain triggering sympathetically driven blood pressure increases , resulting in increased stimulation of baroreceptors , which in turn activates descending pain inhibitory pathways .
previous studies suggested that blood pressure / pain regulatory relationship may be substantially altered in chronic pain conditions .
a retrospective study by bruehl et al suggested that chronic pain could be associated with increased risk of hypertension .
their study found that over 39% of patients with chronic pain were diagnosed with clinical hypertension , compared with only 21% of pain - free internal medicine patients .
they thought that chronic pain - related impairments in overlapping systems modulating both pain and blood pressure would result in a higher prevalence of clinically diagnosed hypertension in patients with chronic pain than in comparable pain - free patients .
our study indicates a possible relation between chronic neck pain and hypertension . if chronic neck pain could lead to hypertension through sympathetic arousal and failure of normal homeostatic pain regulatory mechanisms , early treatment for resolution of chronic neck pain may have a beneficial impact on cardiovascular disease risk in patients with cervical spondylosis
we report here 2 patients of cervical spondylosis with concomitant cervical vertigo and hypertension that were treated successfully with anterior cervical discectomy and fusion .
stimulation of sympathetic nerve fibers in pathologically degenerative disc could produce sympathetic excitation , and induce a sympathetic reflex to cause cervical vertigo and hypertension .
in addition , chronic neck pain could contribute to hypertension development through sympathetic arousal and failure of normal homeostatic pain regulatory mechanisms .
early treatment for resolution of symptoms of cervical spondylosis may have a beneficial impact on cardiovascular disease risk in patients with cervical spondylosis .

Answer:
abstractcervical spondylosis and hypertension are all common diseases , but the relationship between them has never been studied .
 patients with cervical spondylosis are often accompanied with vertigo .
 anterior cervical discectomy and fusion is an effective method of treatment for cervical spondylosis with cervical vertigo that is unresponsive to conservative therapy .
 we report 2 patients of cervical spondylosis with concomitant cervical vertigo and hypertension who were treated successfully with anterior cervical discectomy and fusion .
 stimulation of sympathetic nerve fibers in pathologically degenerative disc could produce sympathetic excitation , and induce a sympathetic reflex to cause cervical vertigo and hypertension .
 in addition , chronic neck pain could contribute to hypertension development through sympathetic arousal and failure of normal homeostatic pain regulatory mechanisms.cervical spondylosis may be one of the causes of secondary hypertension .
 early treatment for resolution of symptoms of cervical spondylosis may have a beneficial impact on cardiovascular disease risk in patients with cervical spondylosis .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
since dental ceramic restorations have been introduced in 20 century,1 reproduction of natural appearance of teeth has been a major concern in dentistry . for metal - ceramic restorations ,
light reflection from an opaque porcelain layer to mask the metal substrate resulted in opaque appearance and therefore , their use in high esthetic area was limited.2 glass ceramic restorations without metal substrate induced more light transmission and accordingly , they improved the ability to reproduce the appearance of tooth structure.3 despite the esthetic advantage of glass ceramics , the demands for stronger ceramic restorations have increased . as a result
, high strength zirconia - based ceramics combined with cad / cam technology have broadened the range of their applications in dentistry.4 however , cohesive failure of the veneering porcelain has been reported as a major drawback56 and thereby , fabricating monolithic zirconia restoration which consists of a single zirconia material without any veneering could be an alternative approach to obviate the veneering failure.7 the esthetic value of dental ceramic restorations is influenced by several factors , such as color , translucency , fluorescence , surface texture and shape.8 furthermore , the overall color of ceramic restorations can be influenced by the thickness of the ceramic , the thickness and the color of luting agent , and the color of the underlying tooth structure .
9 several studies investigated the effect of the thickness on overall color and translucency of ceramic restorations.291011121314 changes of color and translucency may be expected when the thickness of porcelain layer changes , although the direction of color change may depend on the specific components of the ceramic systems.15 due to its inherent white and opaque appearance , monolithic zirconia can be colored in a pre - sintered state to match adjacent teeth . in a clinical situation , there could be a thickness reduction during the process of occlusal adjustment by dentists .
however , there have been no reported studies regarding the changes of color and translucency as a function of changes in thickness using monolithic zirconia .
the purpose of this study was to evaluate the effect of the amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics .
the null hypothesis to be tested was that there was no significant difference in color and translucency between monolithic zirconia ceramics with different amount of thickness reduction .
one - hundred sixty - five square - shaped specimens from presintered yttria - stabilized tetragonal zirconia blocks ( lot no . : b 105566 , b 105583 , b 105565 , b 88712 ; bruxzir , glidewell laboratories , newport beach , ca , usa ) were colored with coloring liquid ( lot no . : 40127 , 40129 ; tanaka zircolor , a2 , tanaka dental , skokie , il , usa ) and assigned to 5 groups according to the number of coloring liquid application ( group i ( one time ) to v ( five times ) , n = 33 per each group ) following the same protocol used in our previous study.7 the specimens were heated in a furnace ( austromat basic , dekema dental - keramikfen gmbh , freilassing , germany ) with a step sintering procedure ; sintering at 950 for 10 minutes and at 1,500 for 2 hours .
after sintering , the thickness adjustment was performed in the same manner as was used in our previous studies.716 accordingly , the final dimensions of the specimens were 16.3 mm  16.3 mm  2.0 mm .
each group was then divided into eleven subgroups ( n = 3 per each subgroup ) by reducing the thickness of 0.1 to 1.0 mm in increments of 0.1-mm on the colored surface using a horizontal grinding machine ( hrg-150 , am technology , asan , korea ) ; subgroup 0 ( no reduction ) , subgroup 1 ( 0.1 mm reduction ) to subgroup 10 ( 1.0 mm reduction ) .
color parameters were obtained from cie - lab ( commission internationale de l'eclairage l , a , b ) color space relative to d65 on a reflection spectrophotometer ( cm-3500d , konica minolta , tokyo , japan ) . for the instrument ,
diffuse illumination was used and the reflected light was measured ( cie diffuse/8-degree ) at the center and each quarter of the specimen . a 3-mm diameter aperture for diffuse illumination and 3-mm measurement area
each of l , a and b values was measured against a black background ( cm - a 101b , konica minolta , tokyo , japan , l = 0.1099 , a = 0.2107 , and b = -0.4292 ) and a white background ( cm - a120 , konica minolta , tokyo , japan , l = 96.6880 , a = -0.1755 , and b = -0.1236 ) in the reflectance mode with specular component excluded ( sce ) at 10 nm intervals in the wavelength range of visible light , 400 - 700 nm .
optical contact was obtained by placing a drop of distilled water ( refractive index : 1.33 , approximately ) between each specimen and a background.11 spectral reflectance against a white background was recorded at 10 nm intervals in the range of 400 to 700 nm . color difference between each subgroup was calculated using cie lab color - difference formula17 denoted by eab = [ ( l ) + ( a ) + ( b ) ] .
l , a , and b refer to the difference on lightness , red / green axis , and yellow / blue axis , respectively . to determine the color difference , the average cie values against a black background were used . for translucency measurements , translucency parameter
tp value was calculated by the color difference between values against a black and a white background18 which is denoted by tp = [ ( lb - lw ) + ( ab - aw ) + ( bb - bw ) ] .
diffuse transmittance measurement was performed using an integrating sphere with the aperture size of 9.5 mm in diameter .
all measurements , therefore , were made at the center and each quarter of the specimen and values were averaged .
, chicago , il , usa ) and the  level was set at 0.05 .
normal distribution of each color value and tp value was verified with shapiro - wilk test . to identify
if there is any significant difference in color and tp values among subgroups , one - way anova was carried out followed by multiple comparison scheff test .
pearson correlation and linear regression was fitted to test for a relationship between the amount of thickness reduction and color and tp values .
3 showed means of cie l , a and b values of each group against a black background in the reflectance mode as a function of the amount of thickness reduction , respectively .
cie a value generally increased , while cie b value decreased with the increase of thickness reduction in all groups .
correlation analyses between l , a or b values against a black background in the reflectance mode and the amount of thickness reduction were conducted .
there were negative , but weak correlations between l value and the amount of thickness reduction in most groups ( -0.58 < r < 0.34 , 0.09 < r < 0.34 ) .
there were positive correlations between a value and the amount of thickness reduction in all groups ( 0.72 < r < 0.85 , 0.52 < r < 0.73 ) .
there were negative correlations between b value and the amount of thickness reduction in all groups ( -0.86 < r < -0.07 , 0.00 < r < 0.74 ) .
average spectral reflectance curves against a white background of each subgroup within groups were obtained ( fig .
4 ) . there was a significant difference between subgroup 0 and other subgroups through the entire spectrum and the values of spectral reflectance in other subgroups were lower than subgroup 0 .
the interpretation of the color difference for this study is based on the visual matching study of johnston and kao19 who found that color difference of 3.7 eab unit was acceptable for resin composites .
color differences between subgroup 0 and other subgroups were clinically perceptible ( eab > 3.7 ) ( fig . 5 )
color differences between subgroup 1 and 2 were within the range of perceptibility threshold ( eab < 3.7 ) except group ii .
color differences between subgroup 2 and 3 were within the range of perceptibility threshold except group v. color differences between subgroup 3 and 4 , 4 and 5 , 5 and 6 , 6 and 7 , 7 and 8 , 8 and 9 , 9 and 10 were within the range of perceptibility threshold in all groups .
means of tp for each subgroup within groups are calculated and ranged from 2.27 to 5.34 ( table 1 ) .
highly significant correlations were found out between tp values and the amount of thickness reduction in all groups ( r > 0.94 , r > 0.89 , p < .001 ) .
spectral transmittance of each subgroup exhibited similar spectral behavior through the entire spectrum and transmittance generally increased with increasing the amount of thickness reduction in all groups ( fig .
according to the results of this in vitro study , the null hypothesis could be rejected because there were significant differences in l , a or b values and tp values between monolithic zirconia specimens with different amount of thickness reduction .
the effect of various changes in thickness of each layer on the final appearance of layered metal - ceramic structures has been studied.212152021 l value substantially increased with the decrease of porcelain thickness212 and the direction of color changes were dependent on porcelain shade and the type of metal - ceramic alloy .
increasing the thickness of dentin porcelain produced more scattering and absorption of the incident light and less light reflected back from the opaque layer .
with regard to all - ceramic systems , l value generally decreased due to increased absorption of incident light with thicker specimens , while a and b values increased as the ceramic thickness increased.101113 there might be a difference in the amount of light reflection at the opaque core between all - ceramic systems with different core translucency .
douglas and przybylska2 demonstrated that the semi - translucent all - ceramic systems were less affected by reduced porcelain thicknesses compared to metal - ceramics . in this study ,
the changes in l value showed a different feature compared to metal - ceramic or all - ceramic systems .
there was a significant decrease in l value at initial reduction , but there were no further significant changes on l value in most groups ( fig .
1 ) . the different aspect of change might come from different optical and structural properties since monolithic zirconia ceramic is polycrystalline monolayer without any veneering .
it can be inferred that there might be reduced scattering due to the reduced thickness which induces lower l value at first 0.1 mm reduction . however , as the thickness reduction proceeds , monolithic zirconia itself could act as an opaque core and induce internal reflection.22 thus , reduced reflection might compensate increased internal reflection and l value could be relatively stable .
chromatically , a value increased , while b value generally decreased with increasing thickness reduction . regarding the shift in chroma ,
b value was more sensitive to the change of thickness than a value showing minimal shifts in a value .
21113 according to the study of douglas and brewer,23 dental observers were more sensitive and critical to the color difference in redness than yellowness for metal - ceramic crowns .
however , their study was conducted with metalceramic crowns and therefore , further study should be performed to determine whether there is any difference in subjective color assessment between a and b value for monolithic zirconia restorations .
3 ) , group ii exhibited noticeable changes in a and b values down to 0.2 mm reduction and group iii ; to 0.3 mm reduction , group iv ; to 0.6 mm reduction , and group v ; to 0.5 mm reduction .
there was no distinct difference in a and b values between groups after around 0.6 mm reduction .
it can be inferred that the more coloring liquid is applied , the deeper the coloring liquid infiltrates .
in addition , one time of coloring liquid application might infiltrate 0.1 mm deep through monolithic zirconia specimen , two times of application ; 0.2 mm deep , three times of application ; 0.3 mm deep , and four or five times of application ; around 0.6 mm deep through monolithic zirconia specimen .
this study exhibited a perceptible color difference from no reduction ( eab > 3.7 ) even after first 0.1 mm reduction regardless of the number of coloring liquid applications .
antonson and anusavice14 investigated the translucency of dental core and veneering ceramics as a function of ceramic thickness .
there was a positive linear correlation between contrast ratio and thickness ( r > 0.81 ) .
hefffernan et al . investigated the effect of the thickness of core materials,24 and the thickness of veneered core materials25 on the translucency of the specimens .
o'keefe et al.26 suggested that the thickness of the porcelain veneer was the primary factor affecting light transmission and not the opacity .
tp values generally increased as the amount of thickness reduction increased in all groups ( r > 0.89 , p < .001 ) . based on lambert 's law,27 decreasing the thickness of material
the fraction of incident light that is reflected , absorbed , and transmitted depends upon the thickness of the specimen as well as the scattering and absorption characteristics.28 this in vitro study has several potential limitations .
the first limitation is that even application of coloring liquid on the specimens and exact amount of the increase of coloring liquid were difficult to control .
secondly , possible pressure fluctuation inside the furnace during the sintering process might have induced uneven color of the specimens .
thirdly , the aperture diameter of spectrophotometer for reflectance measurement was 3 mm and possible edge loss would have affected the color measurement .
finally , this study was conducted with limited color of shade a2 and with a specific kind of monolithic zirconia system and coloring liquid .
therefore , the influence of varied color combinations with different monolithic zirconia systems should be further studied .
increasing thickness reduction reduces lightness and increases a reddish , bluish appearance , and translucency of monolithic zirconia ceramics .

Answer:
purposethis study investigated the effect of amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics.materials and methodsone - hundred sixty - five monolithic zirconia specimens ( 16.3 mm  16.3 mm  2.0 mm ) were divided into 5 groups ( group i to v ) according to the number of a2-coloring liquid applications .
 each group was then divided into 11 subgroups by reducing the thickness up to 1.0 mm in 0.1-mm increments ( subgroup 0 to 10 , n=3 ) .
 colors and spectral distributions were measured according to cielab on a reflection spectrophotometer .
 all measurements were performed on five different areas of each specimen .
 color difference ( e*ab ) and translucency parameter ( tp ) were calculated .
 data were analyzed using one - way anova and multiple comparison scheff test ( =.05).resultsthere were significant differences in cie l * between subgroup 0 and other subgroups in all groups .
 cie a * increased ( 0.52<r2<0.73 ) , while cie b * decreased ( 0.00<r2<0.74 ) in all groups with increasing thickness reduction .
 perceptible color differences ( e *
 ab>3.7 ) were obtained between subgroup 0 and other subgroups .
 tp values generally increased as the thickness reduction increased in all groups ( r2>0.89 , p<.001).conclusionincreasing thickness reduction reduces lightness and increases a reddish , bluish appearance , and translucency of monolithic zirconia ceramics .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
six a17 bac and one fosmid library were used to create mt3.5 ( table s1 ) .
most were processed by sanger paired - end sequencing of 3 - 6 kb shotgun libraries .
sequences were downloaded in february / march 2009 with scaffolding performed by aligning all bac and fosmid ends against contigs and then anchored and ordered primarily by optical mapping .
separately , 25 gb of illumina sequence was generated using short ( 375 nt ) inserts plus 2.1 gb from a 5 kb mate - pair library , then assembled using clcbio ( www.clcbio.com ) and soap ( http://soap.genomics.org.cn/ ) .
five tissues were used for rna - seq analysis with ~10 million illumina 36 bp reads per library ( table s12 ) .
three tissues were used for small rna analysis with ~3 million reads per illumina library ( figures s17-s18 , table s16 , datafile s9 ) .
six a17 bac and one fosmid library were used to create mt3.5 ( table s1 ) .
most were processed by sanger paired - end sequencing of 3 - 6 kb shotgun libraries .
sequences were downloaded in february / march 2009 with scaffolding performed by aligning all bac and fosmid ends against contigs and then anchored and ordered primarily by optical mapping .
separately , 25 gb of illumina sequence was generated using short ( 375 nt ) inserts plus 2.1 gb from a 5 kb mate - pair library , then assembled using clcbio ( www.clcbio.com ) and soap ( http://soap.genomics.org.cn/ ) .
five tissues were used for rna - seq analysis with ~10 million illumina 36 bp reads per library ( table s12 ) .
three tissues were used for small rna analysis with ~3 million reads per illumina library ( figures s17-s18 , table s16 , datafile s9 ) .

Answer:
legumes ( fabaceae or leguminosae ) are unique among cultivated plants for their ability to carry out endosymbiotic nitrogen fixation with rhizobial bacteria , a process that takes place in a specialized structure known as the nodule .
 legumes belong to one of the two main groups of eurosids , the fabidae , which includes most species capable of endosymbiotic nitrogen fixation 1 .
 legumes comprise several evolutionary lineages derived from a common ancestor 60 million years ago ( mya ) .
 papilionoids are the largest clade , dating nearly to the origin of legumes and containing most cultivated species 2 .
 medicago truncatula ( mt ) is a long - established model for the study of legume biology .
 here we describe the draft sequence of the mt euchromatin based on a recently completed bac - assembly supplemented with illumina - shotgun sequence , together capturing ~94% of all mt genes . a whole - genome duplication ( wgd )
 approximately 58 mya played a major role in shaping the mt genome and thereby contributed to the evolution of endosymbiotic nitrogen fixation .
 subsequent to the wgd , the mt genome experienced higher levels of rearrangement than two other sequenced legumes , glycine max ( gm ) and lotus japonicus ( lj ) .
 mt is a close relative of alfalfa ( m. sativa ) , a widely cultivated crop with limited genomics tools and complex autotetraploid genetics . as such
 , the mt genome sequence provides significant opportunities to expand alfalfa s genomic toolbox .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
a maximum mouth opening that is smaller than the size of a complete denture can make prosthetic treatment challenging .
this article describes a simple technique used to fabricate maxillary and mandibular custom sectional impression trays for making definitive impressions in patients with microstomia .
microstomia is defined as an abnormally small oral orifice.1 this disorder is described as a reduction in the oral aperture size associated with facial burns , diffuse scleroderma , traumatic injuries , and surgical reconstruction involving the orbicularis oris muscle .
microstomia can result in multiple debilitating sequelae such as inability to masticate , droolin g , speech problems due to poor articulation , impaired delivery of oral hygiene and dental care , and psychological problems secondary to facial disfigurement.28 several methods of prosthodontic treatment for microstomia patients have been presented , and numerous devices to expand the oral commissure have been described.3,912 the prosthetic rehabilitation of microstomia patients presents difficulties at all stages , from preliminary impressions to prosthesis fabrication.13 because such patients have small oral openings , using conventional methods for making definitive dental impressions and fabricating dentures may be extremely difficult .
making the accurate impressions represents the initial difficulty in the prosthetic rehabilitation of such patients .
the recommended techniques for obtaining preliminary impressions for microstomia patients include the use of modeling plastic impression compound , the use of stock impression trays with heavy and light body silicone impression materials , and flexible impression trays with silicone putty .
the casts obtained from these preliminary impressions are then used for making custom sectional impression trays .
these trays typically consist of 2 locking devices or assemblies , 1 situated anteriorly and the other posteriorly , which join and provide stability to both the sections of the trays .
after the definitive impressions are made , these trays are reassembled extraorally and are poured in dental stone to obtain definitive , working casts .
several studies have described various techniques that are used for making custom sectional impression trays.1418 different devices used for connecting the custom sectional trays include hinges,14 plastic building blocks ( lego ; lego systems inc , enfield , conn .
, usa),15,16 orthodontic expansion screws,17 or locking levers.18 this article describes a simple , cost - effective , and time - saving method for fabricating custom sectional impression trays using easily available dual die - pins and sleeves as potential devices for interlocking the sectional trays .
the locking mechanism design includes an anterior locking assembly for the maxillary and mandibular custom trays and a posterior locking assembly for only the maxillary custom tray .
by using the conventional method , fabricate the maxillary and mandibular custom sectional impression trays by using autopolymerizing acrylic resin ( dpi - rr , dental products of india , mumbai , india ) on the preliminary casts .
make the handles of the trays ( minimum dimensions with 13 mm height , 10 mm length , and 10 mm width ) such that they incorporate the metal sleeves of the dual die - pins ( m.r .
section both the custom impression trays at the midline by using a diamond disk ( dfs , germany ) .
steps in the fabrication of the anterior lock assembly in the maxillary and mandibular custom sectional impression trays : - the assembly basically consists of 2 dual die - pins and 2 sleeves .
closely juxtapose the 2 sleeves such that the smaller keyway of 1 sleeve faces the larger keyway of the other sleeve .
join these sleeves by inserting the 2 dual die - pins and making the assembly a rigid joint ( figure 1a  d ) .
- make a slot on the inside portion of the handles on each half of the sectioned custom trays to incorporate the sleeve ( figure 2a & b ) .
- attach the sleeves in the slots by using the autopolymerizing acrylic resin as mentioned previously ( figure 3 ) .
- verify the position of the attached sleeves by inserting die - pins such that the halves juxtapose precisely in both the sectioned trays . -
fabricate an anterior assembly for the mandibular sectional tray in a similar manner ( figure 7 ) .
steps in the fabrication of the posterior lock assembly in the maxillary custom sectional tray : - cut the 2 dual die - pins that are attached to sleeves halfway through their heights ( figure 4 ) by using a carborundum disk ( dentorium , new york , usa ) .
only the broader upper halves are used for fabricating the posterior assembly and the lower halves are discarded .
- attach the half - cut sleeves on the posterior parts of the sectioned custom tray halves using acrylic resin such that the greatest dimension of each sleeve is oriented in the anteroposterior direction .
check for parallelism between the sleeves using a dental surveyor and verify the fit of the die - pins in the respective sleeves ( figure 5 ) . -
fabricate an acrylic resin block ( 6 mm height , 10 mm width , and 4 mm longer than the distance between the 2 attached sleeves ) using the autopolymerizing acrylic resin ( figure 4 ) . - transfer the respective points of the half - cut die - pin heads on the acrylic bar by using a pressure spot indicator ( coltene psi , switzerland ) and drill slightly oversized holes in the acrylic bar on the marked points by using a bur ( 261-ef023 , brasseler , usa )
- with the closely juxtaposed sectioned trays and the die - pins of the anterior assembly placed in position , secure the heads of the half - cut die - pins into the holes by using the autopolymerizing acrylic resin ( figure 5 & figure 6 ) .
the 2-piece custom - made tray described above allows for a functional impression to be made despite the difficulties associated with microstomia .
the anterior locking assembly described in this article does not require any special alteration in the conventional custom tray design .
the die - pins with metal sleeves used in this technique provide a greater degree of stability and a precise union of the 2 sections of the tray .
the joint can be made more rigid by activating the 2 prongs of each dual die - pin away from each other .
this technique used for fabricating custom sectional impression trays does not require any special devices or complex locking joints .
the only additional materials used are the dual die - pins which are commercially available at a minimum cost .
it is often difficult to use conventional methods for fabricating dentures for patients with limited mouth opening .
this article described a simple , time - saving , and cost - effective method used to fabricate custom sectional impression trays for making definitive impressions in patients with microstomia .

Answer:
objective : a maximum mouth opening that is smaller than the size of a complete denture can make prosthetic treatment challenging .
 this article describes a simple technique used to fabricate maxillary and mandibular custom sectional impression trays for making definitive impressions in patients with microstomia .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
we report a 32-year - old iranian male diagnosed with a case of miliary tuberculosis affecting the prostate .
computerized tomography increased the clinical suspicion of miliary tuberculosis extending to the prostate where a trans - rectal urethral biopsy was obtained .
a strong clinical suspicion and availability of sophisticated tests with confirmation by biopsy , polymerase chain reaction , and culture are needed in order to avoid misdiagnosis of complicated miliary tuberculosis cases .
miliary tuberculosis is a rare form of a tuberculosis infection that results from massive lymphohematogenous dissemination of the mycobacterium tuberculosis bacilli.1 this form of infection , which accounts for 2.8% of all tuberculosis infections , usually involves the extrapulmonary organs.2 from extrapulmonary tuberculosis only 22% affects the genitourinary system , while tuberculosis of the prostate gland is seen in only 2.7% of genitourinary tuberculosis.3,4 due to the rare involvement of the prostate , very scarce literature of the subject , and non - specific symptoms , the clinical suspicion of prostate tuberculosis is difficult .
here we report a case of a young , previously healthy , immunocompetent patient with miliary tuberculosis involving the prostate .
we present a case of a 32-year - old immunocompetent iranian male who presented to the emergency room with a generalized tonic - clonic seizure lasting for 3 minutes .
furthermore , he did not have any genitourinary symptoms , including dysuria , hematuria , or penile discharge .
a computerized tomography ( ct ) scan of the head failed to show any acute central nervous system insult .
prior to this admission , he gave history of an admission 12 months ago to a hospital outside the country , where he complained of fatigue , weight loss , and fever .
reports from the hospital showed that he also had chronic moderate ascites and a left pleural effusion .
however , several laboratory and imaging tests were done and it was concluded that there was no evidence of infectious disease , chronic liver disease , or malignancy . it was recommended that he may need more investigations or a laparoscopy with peritoneal tissue biopsy , which was not done . upon the latest admission ,
the respiratory rate was 12 breaths per minute , the body temperature was 36.9c , and the blood pressure was 112/70 mmhg .
digital rectal examination was not performed since the patient did not have any genitourinary or gastrointestinal symptoms . during this hospitalization ,
the laboratory investigations , urine routine and microscopy , cultures , virology screen , including human immunodeficiency virus , as well as the autoimmune markers did not show any significant issues .
also , three sets of sputum acid - fast bacilli smears were done , which were all negative .
a lumber puncture was also performed with a normal initial pressure , 0 mmcell count , glucose of 4.1 mm per liters , and protein of 764 mg per liter . at the same time
a magnetic resonance image of the brain was done concluding multifocal enhancing foci suggestive of an infective process ( figure 1 ) . due to his previous history , ct - chest ,
the abdominal ct showed mild peritoneal ascites with evidence of mild splenomegaly . the ascetic fluid taken was translucent and yellow in color and the serum - ascites albumin gradient 5 gram per liter ( 0.5 gram per deciliter )
furthermore , the analysis was negative for ziehl  neelsen , gram stain , and culture .
the pelvis ct also showed an enlargement of the prostate and a right prostate lesion extending to the seminal vesicles ( faint ring enhancing lesion measuring 32.73 cm ) ( figure 2 ) .
the case was discussed with the patient and he agreed to start anti - tuberculosis treatment and to have a trans - rectal biopsy of the prostate .
the biopsy showed multiple slides of necrotizing granulomata suggestive of tuberculosis ( figure 3 ) .
neelsen stain was also performed , and the diagnosis of miliary tuberculosis was confirmed ( figure 4 ) . he was started on anti - tuberculosis therapy with isoniazid , rifampicin , ethambutol , pyrazinamide , and pyridoxine for 12 months . at follow - up
the patient was asymptomatic with a normal physical examination and laboratory tests with no drug side effects .
this complication is seen in 1%3% of all tuberculosis cases.5 although most cases of miliary tuberculosis are treatable , the mortality rate among young adults with miliary tuberculosis remains 15% 20% and for adults 25%30%.2 one of the main causes for these high mortality rates includes late detection of disease caused by non - specific symptoms .
tuberculosis of the prostate is rare and the literature is scarce . most often , the cases are under - reported , and easily missed .
patients with prostatic tuberculosis usually present with non - specific symptoms except in rare cases .
these rare cases present with irritative voiding symptoms , terminal dysuria or hemospermia.6 however this was not the case in our patient .
the patient was asymptomatic and like most cases in the literature , tuberculosis of the prostate was diagnosed incidentally . as in our case , tuberculosis of the prostate
is mainly diagnosed by pathologists where a trans - rectal ultrasound guided biopsy of the prostate is the mainstay of the diagnosis.7 as wang and chang have demonstrated , it was the clinical usefulness of the contrast enhanced ct for the diagnosis of tuberculosis of the prostate in which low density multiple and bilateral lesions with irregular borders are seen that prompted us to further investigate the prostate.8 once the disease is diagnosed , the patient should receive a full course of anti - tubercular therapy .
often , the presentation can be non - specific and misleading , as in our case .
a strong clinical suspicion and availability of sophisticated tests with confirmation by biopsy , polymerase chain reaction , and culture are needed in order to avoid misdiagnosis of complicated miliary tuberculosis cases .

Answer:
introductiontuberculosis of the prostate is a rare complication of miliary tuberculosis.case presentationwe report a 32-year - old iranian male diagnosed with a case of miliary tuberculosis affecting the prostate .
 the patient was admitted to the hospital with convulsions .
 computerized tomography increased the clinical suspicion of miliary tuberculosis extending to the prostate where a trans - rectal urethral biopsy was obtained .
 the biopsy revealed multiple necrotizing granulomata suggestive of tuberculosis.conclusiona strong clinical suspicion and availability of sophisticated tests with confirmation by biopsy , polymerase chain reaction , and culture are needed in order to avoid misdiagnosis of complicated miliary tuberculosis cases .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
we have demonstrated that , melatonin is a bioprecursor of hypnotic acetyl metabolites produced by enzymatic acetylation of melatonin and 2-oxomelatonin under the control of acetyltransferases , most probably the nat enzymes . in 1994 , in our laboratory , we developed a specific and highly sensitive gas chromatography - mass spectrometry ( gc - ms ) method to assay , simultaneously and distinct ! ) , plasma concentrations of endogenous melatonin ( d0melatonin ) and exogenous melatonin ( d7-melatonin ) , in which 7 atoms of h have been substituted by 7 atoms of deuterium .
using the same human volunteers ( 12 young subjects in june 1994 and 12 elderly subjects in october 1994 ) , we determined the pharmacokinetics of exogenous d7-melatonin , when given orally and intravenously , and the kinetics of the pineal secretion of endogenous d0-melatonin . ,   the results shown in figure 2 led to the following conclusions : secretion of melatonin by the pineal gland occurs only during the night .
pharmacokinetic analysis shows that the rate of melatonin secretion by the pineal gland is constant throughout the whole nocturnal pineal melatonin production , for the same subject .
the beginning and end of melatonin secretion from the pineal gland are the same for each subject , whatever the season and night , length .
duration of melatonin pineal secretion is between 7.5 and 8 h. therefore , melatonin secretion and sleep are contemporaneous .
there is a large interindividual variability in the amount , of melatonin released in plasma by the pineal gland during the night in young and old subjects alike .
results of previous related studies show that melatonin secretion , and therefore the presence of melatonin in the central nervous system ( cns ) , is necessary for the induction and maintenance of nocturnal sleep . however , the presence of melatonin in the cns is insufficient for the induction and maintenance of sleep . indeed , figure 3 and table
i show results of observations in chicks in an alternate light ( l)-dark ( d ) program ( l / d , 12 h:12 h ) , in which the light phase lasted from 8.00 am until 8.00 pm .
when melatonin was administered intramuscularly ( pectoralis major muscle ) during the light phase from 2.00 pm to 8.00 pm , the chicks did not .
the absence of a hypnotic effect during the light phase correlated with the very low level of nat activity in the pineal glands of chicks measured at the same times .
in contrast , when chicks were observed in a 7-day permanent light , program ( l / l , 12 h:12 h ) , during which nat activity level was constantly higher , the administration of melatonin induced a significant , hypnotic effect .
the duration of sleep ( between 4 and 5 h ) was much greater than that , observed with diazepam ( between 1 and 2 h ) when it .
was administered intramuscularly at the same dose ( 1 m per 100 g body weight , at 2.00 pm ) .
these results lead to the following conclusions : the simultaneous presence of melatonin and nat in the cns ( pineal gland ) is a necessary and sufficient condition for the induction and maintenance of sleep .
in contrast to the classic so - called  hypnotic drugs  ( eg , benzodiazepines , barbiturates , zopiclone , and zolpidem ) , melatonin does not have direct , hypnotic properties related to its chemical structure .
during the development of the gc - ms method for the assay of melatonin in plasma , our attention was focussed on the chemical reactivity of melatonin at position 3 , which allows cyciization of the side chain after acylation .
this proceeds by nucleophilic attack and leads to a fluoroacyl--carboline ( figure 4 ) . considering our previous observations
, we assumed that melatonin undergoes enzymatic acetylation during the night , under the control of nat , and that this leads to an n - acetyl--carboline , which we call carbo2 .
we conclude that melatonin is a bioprecursor of hypnotic acetyl metabolites , such as carbo2 .
chick pineal glands were observed during an alternate light - dark program at 37c for 7 days . in the middle of dark phase ,
they were treated with phjacetyl coenzyme a and melatonin ( or 2-oxomelatonin ) for 30 min .
figure 5 and figure 6 show that melatonin ( or 2-oxomelatonin ) undergoes an aeetylation that is significantly higher ( p<0.002 , in the middle of dark phase ; p<0.0005 , 1 h before end of dark phase [ or p<0.00005 for 2oxomelatonin over the whole dark phase ] ) than that observed in controls ( nonsignificant when melatonin was replaced by phosphate buffer ) .
gc - ms indicated the biosynthesis of [ h]carbo2 for five chick pineal glands collected in the middle of dark phase ( table ii ) .
we have synthesized several acetyl derivatives , such as carbo2 ( figure 7 ) , which is an n-acetyl-p-carboline.we have found 20 to 40 pg carbo2 per gram of lamb pineal gland collected on the middle of the dark phase of an alternate light - dark program . the hypnotic activity of carbo2 has been observed and measured in chicks and beagles : in chicks , the tests were performed at 2.00 pm , in the middle of light phase , a time at which nat activity in the pineal gland is very low .
the results are presented in table iii , together with some reference compounds . the essential role of acetyl group is demonstrated by the fact that 10-mcthoxyharmalan ( as well as harmaline ) , which is the product of jv - deacetylation of compound carbo2 , does not exhibit any hypnotic effect .
in contrast , it induces excitatory effects in chicks by increasing locomotor activity in beagles , polysomnographic studies showed that when carbo2 was administered intravenously , it induced   sleep of longer duration and shorter time latencies than the sleep induced by zolpidem and diazepam ( table iv ) . the most interesting feature , which provides more support for our assumption , is the eeg architecture of the sleep produced , which is similar to that of physiological sleep ( see results with placebo in table iv ) , characterized by the significant proportion of slow - wave deep sleep and rapid eye movement ( rem ) sleep , in sharp contrast to the eeg sleep architecture observed with gabaergic ( gaba , -aminobutyric acid ) compounds , such as zolpidem or diazepam , which induce mainly drowsiness ( light sleep ) and little rem sleep .
chick pineal glands were observed during an alternate light - dark program at 37c for 7 days . in the middle of dark phase ,
they were treated with phjacetyl coenzyme a and melatonin ( or 2-oxomelatonin ) for 30 min .
figure 5 and figure 6 show that melatonin ( or 2-oxomelatonin ) undergoes an aeetylation that is significantly higher ( p<0.002 , in the middle of dark phase ; p<0.0005 , 1 h before end of dark phase [ or p<0.00005 for 2oxomelatonin over the whole dark phase ] ) than that observed in controls ( nonsignificant when melatonin was replaced by phosphate buffer ) .
gc - ms indicated the biosynthesis of [ h]carbo2 for five chick pineal glands collected in the middle of dark phase ( table ii ) .
we have synthesized several acetyl derivatives , such as carbo2 ( figure 7 ) , which is an n-acetyl-p-carboline.we have found 20 to 40 pg carbo2 per gram of lamb pineal gland collected on the middle of the dark phase of an alternate light - dark program .
the hypnotic activity of carbo2 has been observed and measured in chicks and beagles : in chicks , the tests were performed at 2.00 pm , in the middle of light phase , a time at which nat activity in the pineal gland is very low .
the essential role of acetyl group is demonstrated by the fact that 10-mcthoxyharmalan ( as well as harmaline ) , which is the product of jv - deacetylation of compound carbo2 , does not exhibit any hypnotic effect .
in contrast , it induces excitatory effects in chicks by increasing locomotor activity in beagles , polysomnographic studies showed that when carbo2 was administered intravenously , it induced   sleep of longer duration and shorter time latencies than the sleep induced by zolpidem and diazepam ( table iv ) . the most interesting feature , which provides more support for our assumption , is the eeg architecture of the sleep produced , which is similar to that of physiological sleep ( see results with placebo in table iv ) , characterized by the significant proportion of slow - wave deep sleep and rapid eye movement ( rem ) sleep , in sharp contrast to the eeg sleep architecture observed with gabaergic ( gaba , -aminobutyric acid ) compounds , such as zolpidem or diazepam , which induce mainly drowsiness ( light sleep ) and little rem sleep .
we have evidenced the role played by melatonin in both inducing and maintaining nocturnal sleep .
melatonin is the bioprecursor of hypnotic acetyl metabolites , such as carbo2 , which result from the enzymatic acetylation of melatonin ( and 2-oxomelatonin ) by nat .
since insomnia and sleep disorders may be due to a lack of nat enzymes in the pineal gland , a therapeutic approach to sleep disorders could be suggested .
patients with insomnia may be treated by administering hypnotic acetyl metabolites of melatonin or their synthetic analogs .

Answer:
pharmacokinetic studies of melatonin in young and elderly human volunteers , and the measurement of hypnotic effects in chicks under alternate light - dark or permanent light conditions , show that melatonin is a bioprecursor of hypnotic acetyl metabolites produced by the enzymatic acetylation of both melatonin and 2-oxomelatonin under the control of serotonin n - acetyltransferases ( nats ) , which are present in the pineal gland .
 the acetyl metabolite of melatonin , which we call carbo2 , is an n - acetyl--carboline .
 the electroencephalographs ( eeg ) architecture of the sleep produced by this compound is similar to thai of physiological sleep , and is characterized by the significant proportion of slow - wave deep sleep and rapid eye movement sleep .
 this is in sharp contrast to the eeg sleep architecture observed with gabaergic ( gaba , -aminobutyric acid ) compounds .
 since insomnia and sleep disorders are believed to be due to a lack of nat enzymes in the pineal gland , a new therapeutic approach of sleep disorders by administration of such hypnotic acetyl metabolites of melatonin , or synthetic analogs thereof , can be en visaged .