Estimation of body fat by DXA and the four compartment model in Mexican youth

The objective of this study was to validate the estimation of body fat (%BF) by DXA (Dual-Energy X-Ray AbsorciomDPX-MD) against the four compartment model (4C) of body composition in 32 Mexican pubertal girls and boys (aged 9-14 y; F=16). The mean of the difference between DXA and 4C model was -3.5 %BF (p=0.171). The limits of agreement (95% = 2 SD) were +5% to -12%BF. The precision of estimated limits of y the confidence intervals were -1.9% to -5.1%BF (P = 0.050). The concordance correlation coefficient was p = 0.85. The test of accuracy for coincidence of slop intercepts between DXA and the 4C model showed no coincidence (p < 0.05). The precision by R2 explained 83% of the variance (SEE, 4.1%). The individual accuracy assess by the total error was 5.6%. The group mean accuracy by two way analysis of variance of body fat did not show interaction between method (DXA-4C model) and separate analysis of gender and overweight. However, there was an effect of method (p = 0.043) in the presence of overweight (p < 0.001). In conclusion, the estimation of percent of body fat by DXA was not precise and accurate in a group of Mexican children. However, results do not limit the utility of DXA for the measurements of body composition and its relation with health outcomes, especially in follow up studies.     

Selection of the more adequate prediction index to estimate the frame size a group of institutionalized and free living elderly in Venezuela. (Preliminary study)

The objective of the study was to identify an easy to measure indicator of body frame size to allow refinement of anthropometric nutritional evaluation. Body dimensions and frame indices related to height, which might be potential frame size predictors in the elderly, were studied. In 307 subjects (163 women, 144 men) aged 60-99 years of whom 187 were institutionalized and 120 free-living outpatients, weight, height, mid-arm circumference; triceps, subscapular, midthigh and calf skinfolds; elbow, wrist, femur and biacromial widths, were measured. Body mass index, upper arm muscle area, upper arm fat area, fat percentage, sum of skinfolds and frame indices were calculated. Results were calculated in function of age, sex and life-style. Biacromial breadth, biacromial/height index, wrist breadth and wrist/height index gave variable correlations with indices of body mass and body fat. Femur breadth and femur/height index were significantly correlated with body fat indices. Elbow breadth, humerus/height index were not correlated to body fat indices, but were significantly correlated with weight, height and fat free mass. Elbow breadth and humerus/height index fulfilled most of the criteria of good predictors of body frame size in the group pf elderly studied.     

A fat mass and obesity-associated gene polymorphism influences fat mass in exercise-trained individuals

Background

A single nucleotide polymorphism (SNP) in the fat mass and obesity-associated (FTO) gene is a strong predictor of obesity in humans. The FTO SNP (rs1421085) results in a T to C nucleotide substitution that may result in an increased risk for obesity in individuals who carry at least one C allele. The purpose of this investigation was to characterize the FTO genotype in a cohort of exercise-trained men and women.

Methods

We tested 108 exercise-trained individuals that included professional mixed martial arts fighters, competitive distance runners, collegiate swimmers, stand-up paddlers as well as a cohort of recreational bodybuilders. Body composition was assessed via dual-energy x-ray absorptiometry (DXA). Saliva samples were collected in order to genotype participants and quantify cortisol levels.

Results

The physical characteristics of the subjects were as follows (mean±SD): body weight 74.5±15.6 kg; height 171.5±9.5 cm; bone mineral content 2.8±0.7 kg; fat mass 15.7±5.5 kg; lean body mass 55.9±14.4 kg; % body fat 21.6±7.0. Independent samples t tests showed that C allele carriers (n =?54) had significantly higher fat mass t(106)?=?3.13, p <?0.01 and body fat percentage t(106)?=?2.68, p?<?0.01, relative to the TT group (n?=?54) (i.e., fat mass: C/??17.3 ±5.6 kg, TT 14.2±4.6 kg; body fat percentage: C/? group 23.4±7.4%, TT group 19.9±6.2). No other measures of body composition were associated with the FTO genotype (i.e., body mineral density, bone mineral content, or lean body mass). Moreover, cortisol levels were significantly higher in the TT group relative to the C allele carriers t(106)?=?2.37, p =?0.02 (i.e., TT 0.35 ±0.35 μg/dL, C/??0.22±0.16 μg/dL).

Conclusions

Our findings demonstrate a relationship between C allele carriers on the FTO gene and a predisposition to a higher fat mass and body fat percentage. In addition, we found no relationship between cortisol and fat mass. However, due to the cross-sectional nature of this investigation, we cannot infer causality regarding the FTO gene and body composition.

     

Performance enhancement with supplements: incongruence between rationale and practice

Background

Methods used to estimate percent body fat can be classified as a laboratory or field technique. However, the validity of these methods compared to multiple-compartment models has not been fully established. This investigation sought to determine the validity of field and laboratory methods for estimating percent fat (%fat) in healthy college-age women compared to the Siri three-compartment model (3C).

Methods

Thirty Caucasian women (21.1 ± 1.5 yrs; 164.8 ± 4.7 cm; 61.2 ± 6.8 kg) had their %fat estimated by BIA using the BodyGram? computer program (BIA-AK) and population-specific equation (BIA-Lohman), NIR (Futrex^® 6100/XL), a quadratic (SF3JPW) and linear (SF3WB) skinfold equation, air-displacement plethysmography (BP), and hydrostatic weighing (HW).

Results

All methods produced acceptable total error (TE) values compared to the 3C model. Both laboratory methods produced similar TE values (HW, TE = 2.4%fat; BP, TE = 2.3%fat) when compared to the 3C model, though a significant constant error (CE) was detected for HW (1.5%fat, p ≤ 0.006). The field methods produced acceptable TE values ranging from 1.8 – 3.8 %fat. BIA-AK (TE = 1.8%fat) yielded the lowest TE among the field methods, while BIA-Lohman (TE = 2.1%fat) and NIR (TE = 2.7%fat) produced lower TE values than both skinfold equations (TE > 2.7%fat) compared to the 3C model. Additionally, the SF3JPW %fat estimation equation resulted in a significant CE (2.6%fat, p ≤ 0.007).

Conclusion

Data suggest that the BP and HW are valid laboratory methods when compared to the 3C model to estimate %fat in college-age Caucasian women. When the use of a laboratory method is not feasible, NIR, BIA-AK, BIA-Lohman, SF3JPW, and SF3WB are acceptable field methods to estimate %fat in this population.     

On the Determination of Continuous Submicrometer Liquid Aerosol-Size Distributions with Low Pressure Impactors

The aspects associated with the determination of continuous submicrometer aerosol-size distributions using multijet low pressure impactors have been studied. Multiple sets of error-free and noisy, simulated data sets have been inverted, and impactors have been compared with the differential mobility particle-size analysis (DMA) method by using well-defined, laboratory-generated liquid oleic acid aerosols tagged with ammonium fluorescein. Impactors included in this study were a Berner-type impactor HAUKE 25/0.015 (BLPI), a modified University of Washington Mark 5 impactor (KLPI), and the impactor designed at the University of Florida (LLPI). The inversion of simulated error-free impactor data (i.e., the data with perfect kernel functions) for unimodal submicrometer aerosols with a small (2.5%) stage mass error estimate yields results very close to input distributions, when the method based on constrained regularization is used in the inversion. When the error estimate is increased, inverted spectra are flattened. However, they remain clearly unimodal. When normally distributed random error is added to the data and the error estimate for each data point equals the standard deviation of the random error, the fraction of bimodal and trimodal inverted spectra increases with a rise in the random error level and with the asymmetricity of the kernel functions. When the random error level and data error estimates are equal to or smaller than 10%, inverted spectra are mainly unimodal close to input distribution for both error-free and noisy data. The inversion of impactor data from the detailed laboratory experiments (i.e., the data with real kernel functions) indicates that only BLPI kernel functions are accurate enough to yield unimodal distributions close to those measured with the DMA. When the stage mass error estimate is increased beyond the stage mass determination error, unimodal spectra also for the KLPI and LLPI are found. The decrease of the BLPI stage mass error estimate below the experimental error increases the agreement with DMA results. In most cases the error estimate for BLPI stage masses can be decreased to 2.5%, indicating the validity of both BLPI submicrometer kernel functions and the fluorometric method used to determine stage mass concentrations.The aspects associated with the determination of continuous submicrometer aerosol-size distributions using multijet low pressure impactors have been studied. Multiple sets of error-free and noisy, simulated data sets have been inverted, and impactors have been compared with the differential mobility particle-size analysis (DMA) method by using well-defined, laboratory-generated liquid oleic acid aerosols tagged with ammonium fluorescein. Impactors included in this study were a Berner-type impactor HAUKE 25/0.015 (BLPI), a modified University of Washington Mark 5 impactor (KLPI), and the impactor designed at the University of Florida (LLPI). The inversion of simulated error-free impactor data (i.e., the data with perfect kernel functions) for unimodal submicrometer aerosols with a small (2.5%) stage mass error estimate yields results very close to input distributions, when the method based on constrained regularization is used in the inversion. When the error estimate is increased, inverted spectra are flattened. However, they remain clearly unimodal. When normally distributed random error is added to the data and the error estimate for each data point equals the standard deviation of the random error, the fraction of bimodal and trimodal inverted spectra increases with a rise in the random error level and with the asymmetricity of the kernel functions. When the random error level and data error estimates are equal to or smaller than 10%, inverted spectra are mainly unimodal close to input distribution for both error-free and noisy data. The inversion of impactor data from the detailed laboratory experiments (i.e., the data with real kernel functions) indicates that only BLPI kernel functions are accurate enough to yield unimodal distributions close to those measured with the DMA. When the stage mass error estimate is increased beyond the stage mass determination error, unimodal spectra also for the KLPI and LLPI are found. The decrease of the BLPI stage mass error estimate below the experimental error increases the agreement with DMA results. In most cases the error estimate for BLPI stage masses can be decreased to 2.5%, indicating the validity of both BLPI submicrometer kernel functions and the fluorometric method used to determine stage mass concentrations.The aspects associated with the determination of continuous submicrometer aerosol-size distributions using multijet low pressure impactors have been studied. Multiple sets of error-free and noisy, simulated data sets have been inverted, and impactors have been compared with the differential mobility particle-size analysis (DMA) method by using well-defined, laboratory-generated liquid oleic acid aerosols tagged with ammonium fluorescein. Impactors included in this study were a Berner-type impactor HAUKE 25/0.015 (BLPI), a modified University of Washington Mark 5 impactor (KLPI), and the impactor designed at the University of Florida (LLPI). The inversion of simulated error-free impactor data (i.e., the data with perfect kernel functions) for unimodal submicrometer aerosols with a small (2.5%) stage mass error estimate yields results very close to input distributions, when the method based on constrained regularization is used in the inversion. When the error estimate is increased, inverted spectra are flattened. However, they remain clearly unimodal. When normally distributed random error is added to the data and the error estimate for each data point equals the standard deviation of the random error, the fraction of bimodal and trimodal inverted spectra increases with a rise in the random error level and with the asymmetricity of the kernel functions. When the random error level and data error estimates are equal to or smaller than 10%, inverted spectra are mainly unimodal close to input distribution for both error-free and noisy data. The inversion of impactor data from the detailed laboratory experiments (i.e., the data with real kernel functions) indicates that only BLPI kernel functions are accurate enough to yield unimodal distributions close to those measured with the DMA. When the stage mass error estimate is increased beyond the stage mass determination error, unimodal spectra also for the KLPI and LLPI are found. The decrease of the BLPI stage mass error estimate below the experimental error increases the agreement with DMA results. In most cases the error estimate for BLPI stage masses can be decreased to 2.5%, indicating the validity of both BLPI submicrometer kernel functions and the fluorometric method used to determine stage mass concentrations.The aspects associated with the determination of continuous submicrometer aerosol-size distributions using multijet low pressure impactors have been studied. Multiple sets of error-free and noisy, simulated data sets have been inverted, and impactors have been compared with the differential mobility particle-size analysis (DMA) method by using well-defined, laboratory-generated liquid oleic acid aerosols tagged with ammonium fluorescein. Impactors included in this study were a Berner-type impactor HAUKE 25/0.015 (BLPI), a modified University of Washington Mark 5 impactor (KLPI), and the impactor designed at the University of Florida (LLPI). The inversion of simulated error-free impactor data (i.e., the data with perfect kernel functions) for unimodal submicrometer aerosols with a small (2.5%) stage mass error estimate yields results very close to input distributions, when the method based on constrained regularization is used in the inversion. When the error estimate is increased, inverted spectra are flattened. However, they remain clearly unimodal. When normally distributed random error is added to the data and the error estimate for each data point equals the standard deviation of the random error, the fraction of bimodal and trimodal inverted spectra increases with a rise in the random error level and with the asymmetricity of the kernel functions. When the random error level and data error estimates are equal to or smaller than 10%, inverted spectra are mainly unimodal close to input distribution for both error-free and noisy data. The inversion of impactor data from the detailed laboratory experiments (i.e., the data with real kernel functions) indicates that only BLPI kernel functions are accurate enough to yield unimodal distributions close to those measured with the DMA. When the stage mass error estimate is increased beyond the stage mass determination error, unimodal spectra also for the KLPI and LLPI are found. The decrease of the BLPI stage mass error estimate below the experimental error increases the agreement with DMA results. In most cases the error estimate for BLPI stage masses can be decreased to 2.5%, indicating the validity of both BLPI submicrometer kernel functions and the fluorometric method used to determine stage mass concentrations.     

Predictive accuracy of body mass index in estimating body fatness measured by bioelectrical impedance

The aim of this study was to determinate the performance of body mass index (BMI) for the diagnosis of obesity and as a predictor of body fatness in adult Chilean subjects. We conducted a study in 433 women (18-73 years old; BMI: 19.7 to 69.7 kg/m2) and 264 men (18-83 y.; BMI: 19.1 to 54.8 kg/m2). Bioelectrical resistance was measured by impedance method and fat mass percent (FM%) was calculated by fatness-specific equations developed by Segal et al. Obesity was defined as a BMI of at least 30 kg/m2. Increased fatness was defined by the FM% cut-off points of at least 25% for men and at least 30% for women. Sixty-four percent of women and 23.6% of men with BMI below 30 kg/m2 had FM% higher than 30% and 25%, respectively. A value of BMI of 26 kg/m2 in women and 30 kg/m2 in men had the best agreement to the cut-off points of fatness according to sensitivity vs. specificity analysis The following equations were developed to predict individual fatness: women FM% = 0.96 x BMI + 0.154 x age + 1.44 (r2 = 0.75; standard error 3.8%); men FM% = 0.99 x BMI + 0.141 x age - 9.914 (r2 = 0.66; standard error 4.4%). Differences between measured and predicted FM% presented a wide variation, with a range of +/- 2 sd of 7.5% in women and 8.8% in men. The commonly used value of BMI 330 kg/m2 as a cut-off point for obesity does not have adequate sensitivity and specificity for the screening of increased fatness subjects, specially in women. In this study BMI shows a low reliability as a predictor of individual body fatness, particularly in men and in subjects with a BMI below 30 kg/m2.     

Body Mass Index,percent body fat,and regional body fat distribution in relation to leptin concentrations in healthy,non-smoking postmenopausal women in a feeding study

Background  

The relationship between BMI and leptin has been studied extensively in the past, but previous reports in postmenopausal women have not been conducted under carefully controlled dietary conditions of weight maintenance using precise measures of body fat distribution. The aim of the present study was to examine the association between serum leptin concentration and adiposity as estimated by BMI and dual energy x-ray absorptiometry (DEXA) measures (percent body fat, central and peripheral fat, and lean mass) in postmenopausal women.     

Fourier Transform Near Infrared Spectroscopy: A Newly Developed,Non-Invasive Method To Measure Body Fat

An FT-NIR technique is reported to provide a fast, accurate and low cost method of determining in-vivo human body fat content. The body fat content of 353 healthy subjects (154 males and 199 females) of various height, weight, and age were measured by FT-NIR and compared to 420 subjects investigated by magnetic resonance imaging (MRI). The procedure involved scanning each subject's upper ear that provided a necessary reflectance surface and proved representative of the subject's subcutaneous fat content. The average FT-NIR spectrum was compared to a reference mixture with known and similar fat content and composition to that of humans. The FT-NIR response was incorporated into an empirical equation using the ratio of subcutaneous to total body fat from MRI data, taking into account the subject's gender, height, weight and age. The results on the two data sets were similar and demonstrated that the FT-NIR technique can be used to obtain a measure of the body fat content of individuals, similar to that using MRI. In addition, the FT-NIR was used to more accurately monitor the fat content of sleep apnea patients.     

Investigations in mass transfer enhancement in textiles with ultrasound

A novel application of ultrasound is for the intensification of wet textile treatments, in which mass transfer in the inter- and intra-yarn pores of the textile is the basic physical mechanism. This paper describes a simple methodology for the estimation of mass transfer enhancement in ultrasonic textile treatments. For this study, washing of EMPA 101 fabric, soiled with carbon soot and olive oil, is selected as a model process. In the absence of precise knowledge of the convection velocity resulting due to transient cavitation, a semi-empirical method is used to estimate mass transfer enhancement. The experimental soil removal rate during model process is determined by precise time-controlled ultrasonic treatment of the textile, with the source of cavitation nuclei located close to the textile surface. The mass transfer in the textile during the model process is found to occur in two distinct steps, characterized by two different convective diffusion coefficients. This effect is explained in terms of uneven soil distribution in the inter- and intra-yarn region. The mass transfer enhancement factor, defined as ratio of convective diffusion coefficient to molecular diffusion coefficient of soil particles, is found to be in the range 1000-2000. In addition, it is found that the mass transfer enhancement increases with acoustic pressure amplitude during textile treatment. A qualitative estimate of the convection velocities generated in the vicinity of the bubble is provided using numerical simulations of bubble dynamics equation.     

Adsorption of Radionuclides from Aqueous Solutions by Inorganic Adsorbents

Abstract

Radionuclides such as ¹³⁷Cs and ⁸⁵Sr were removed from dilute aqueous solutions by means of inorganic adsorbents, MS-13X and chabazite. Adsorption data of radionuclides on the inorganic adsorbents were satisfactorily correlated by the Dubinin-Astakov (DA) equation. Gaussian-type distributions of adsorption energies were obtained from the parameters of the DA equation by applying the condensation approach. A surface diffusion model was applied to estimate the intraparticle mass transfer of radionuclides. The range of surface diffusion coefficients estimated was 3.2 × 10^?12 to 3.5 × 10^?11 m²/s. The adsorption model, which describes the surface diffusion mechanism with the DA equation, satisfactorily simulated the adsorption behavior of radionuclides on zeolites in batch adsorbers.     

Perceived body image in men and women with type 2 diabetes mellitus: correlation of body mass index with the figure rating scale

Background  

Body mass index (BMI) is often used as an objective surrogate estimate of body fat. Increased BMI is directly associated with an increase in metabolic disease, such as type 2 diabetes mellitus (T2DM). The Stunkard Figure Rating Scale (FRS) is a subjective measure of body fat, and self-perceptions of body image conceivably impact the development and treatment of T2DM. This study examined the self-perception of body image to various levels of BMI among those with T2DM.     

非牛顿特性对偏心圆筒内流体混沌混合的影响

Effect of fluid elasticity and shear-thinning viscosity on the chaotic mixing between two alternately rotating cylinders has been studied. The h-p finite element method is used to obtain high accurate solutions of the steady flow. The unsteady, periodic flow is simulated using the piecewise-steady approximation. Characteristics of the chaotic mixing axe analyzed by examining the asymptotic coverage of a passive tracer and the lineal stretching ofthe fluid elements in the annulus. For the viscoelastic fluids modeled by the upper-convected Maxwell constitutive equation (UCM), our computation predicts little effect of the fluid elasticity on the mixing patterns. On the other hand, the shear-thinning viscosity, modeled by the Carreau equation, has a large impact on the advection of a passive tracer and the distribution of lineal stretching. We find that the zones of the lowest stretching match remarkably well with the regular zones in the tracer-coverage plotting. Our study reveals the vital importance of reducing the discretization errors of the velocity field in the numerical simulation of chaotic flows.     

Prevalence and magnitude of body weight and image dissatisfaction among women in dietetics majors

Some authors have suggested that body weight dissatisfaction may be high in students majoring in dietetics. Therefore, this study was conducted to examine the extent of body weight and image dissatisfaction in a sample of women in dietetics major. Additionally, predictors of magnitude of body weight dissatisfaction were analyzed. Participants were 62 volunteers with normalweight whose mean age was 21.87 +/- 1.89 years old (non-random sample). The assessment instruments included anthropometric measurements, a somatomorphic matrix test and an eating disorders inventory (EDI-2). Data were analyzed using SPSS vs. 15.0. A larger proportion of students chose an ideal body weight lower than actual weight (67.7%) and body image with less body fat and more muscle mass than actual values (56.4%). The magnitude of body weight dissatisfaction was associated with muscle mass and body fat dissatisfaction, and with the subscale of EDI-2 "body dissatisfaction". So, from a public health standpoint, we consider important to continue working in this line of research with the aim of better understanding the extent of body weight dissatisfaction in women dietitians, and how this dissatisfaction could interfere with their professional practice.     

A simple,accurate model for viscosities of polymer blends

The accurate but complex McAllister model for the melt viscosities (η) of binary polymer blends has been greatly simplified by dropping the terms involving only mole fraction and molecular weight, by switching from mole fraction to mass fraction, and by making the model explicit in dynamic, rather than kinematic, viscosity. The simpler Lecyar model was tested side-by-side with the McAllister in five binary systems and at seven levels of shear rate from 5 to 500 s^?1 in each system. For the 35 pairs of curves fitted, the rms standard error of estimate was 0.0945 (In η), for the Lecyar model versus 0.0911 for the McAllister; the difference corresponds to only 0.4 percent additional error in the blend viscosity. Comparison of results in two systems, reported by Carley and Crossan (12) with those of other workers, indicate that the differences among what appear to be comparable, self-consistent data sets are much greater than the within-set errors of rheometric measurement and model fitting.     

Comparison of the NHANES dietary screener questionnaire to the Automated Self-Administered 24-Hour Recall for Children in the Healthy Communities Study

Background

A dietary screener questionnaire (DSQ) was used to assess dietary outcomes among children in the Healthy Communities Study (HCS), a study of the relationships between programs and policies to prevent child obesity and child diet, physical activity and weight outcomes.

Methods

To compare dietary intake estimates derived from the DSQ against those from the Automated Self-Administered 24-Hour Recalls for Children (ASA24-Kids) among children, a measurement error model, using structural equation modelling, was utilized to estimate slopes, deattenuated correlation coefficients, and attenuation factors by age and sex, ethnicity, and BMI status.

Participants/setting

A randomly selected sub-sample of HCS participants aged 4–15 years in 130 communities throughout the U.S. who completed the DSQ and up to two ASA24-Kids recalls (n?=?656;13% of HCS participants).

Results

For most nutrient/foods examined, the DSQ yielded larger mean intake estimates than the ASA24-Kids, and agreement between the two measures varied by food/nutrient, age and sex, ethnicity, and BMI category. Deattenuated correlation coefficients of 0.4 or greater were observed for added sugars from SSBs (0.54), fruits and vegetables (0.40), and dairy foods (0.50). Lower deattenuated correlation coefficients were seen for total added sugars (0.37), whole grains (0.34), and fiber (0.34). Attenuation factors were most severe for total added sugars intake among overweight children, and for several other dietary outcomes among children aged 9–11 years.

Conclusions

The DSQ was found to be a tool with acceptable agreement with the ASA24-Kids for measuring multiple dietary outcomes of interest in the HCS, although there may be potential due to measurement error to underestimate results (bias towards the null). In future studies, measurement error modelling and regression calibration may be possible solutions to correct for bias due to measurement error in most food/nutrient intake estimates from the DSQ when used among children.

     

Use of knee height to correct the body height of elderly Hispanics

Loss of stature in certain elderly subjects can be attributed to diseases such as osteoporosis, as well as to age and generational effects. In addition, many elders cannot stand straight for accurate measurement. For these cases, total height can be estimated with regression equations based on knee height. The aims of this study were, firstly, to evaluate the applicability of regression equations based on knee height for estimation of stature and, secondly, to document the differences between measured and estimated height in a group of elderly Hispanics with postural problems (n = 166) in comparison with a group of elderly Hispanic without postural problems (n = 270). Using both, estimated and measured height, we also calculated the body mass index (BMI) of both groups of elders. Statistical analyses were done with paired t-tests, within sex and study group. Within the group with postural problems, estimated height was higher than the measured height for both men (p < or = 0.001) and women (p < or = 0.001). There were no significant differences between measured and estimated height in the group without postural problems. Furthermore, in the group with postural problems, BMI values calculated with estimated height were lower than those estimated with the measured height, and these differences were also significant for both men (p < or = 0.001) and women (p < or = 0.001). With the aging of the Latin American population, there is a need for more nutrition and health research among elders. In order to do this we need to develop and use methods and criteria appropriate for each population.     

Comparison of two methods for the direct determination of fat in butter,blended spreads,and margarine

A German (GE) method and a New Zealand (NZ) method for the direct determination of total fat in spreadable fats were compared in a pilot collaborative study to obtain preliminary information regarding the precision and the level of fat content determined. The study comprised six products, including butter, blended fat products, and margarine with a fat content in the range of 39—82%, and four laboratories. The GE method, based on a Soxhlet extraction using petroleum ether, yielded a repeatability estimate of 0.41 g/100 g and a reproducibility estimate of 0.79 g/100 g. The NZ method, based on an extraction of the fat by thorough shaking of the sample with petroleum ether followed by phase separation, yielded a repeatability estimate of 0.32 g/100 g and a reproducibility estimate of 0.62 g/100 g. The difference in precision estimates between the two methods was significant for repeatability, but not for reproducibility. The better repeatability of the NZ method was probably partly due to the use of a superior sample preparation procedure which ensured that any inhomogeneity developed inside the sample container during transport or storage was removed. The average fat content as determined by the NZ method was 0.20 g/100 g higher than that determined by the GE method, but for individual samples no constant bias was observed. However, an inverse correlation between the bias and the fat content of the product suggested that the anhydrous sodium sulphate used in the GE method interfered with the fat recovery when analysing samples containing a high percentage of water. Thus, according to this study, the NZ method seems to have certain advantages over the GE method with respect to the results obtained.     

Comparative analysis of body composition assessment methods in healthy men and in chronic obstructive pulmonary disease patients: anthropometry, bioelectrical impedance and dual-energy X-ray absorptiometry

The aim of this study was to examine the agreement between the results of body fat (BF and BF%), fat-free mass (FFM) and FFM index (FFMI= FFM/height2) as estimated by skinfold anthropometry (ANT), bioelectrical impedance (BIA) and dual-energy X-ray absorptiometry (DXA) in two groups of men (> or = 50 y), one comprising healthy individuals (n=23) and the other, patients with chronic obstructive pulmonary disease (COPD) (n=24). Comparisons between body composition techniques were done by repeated measures ANOVA; the Bland & Altman procedure was used to analyse agreement. RESULTS AND CONCLUSIONS: 1) comparison between healthy and COPD groups showed significant differences between all studied variables; 2) in the healthy group, values for BF, BF%, FFM and FFMI were not significantly different when BIA or ANT was compared to DXA; however, in COPD, values for BF and BF% were significantly higher and for FFM and FFMI significantly lower when BIA was compared to DXA; in contrast, no differences were shown between values for these variables when ANT was compared with DXA; 3) Bland & Altman test, in both groups, showed no agreement between BIA and DXA and between ANT and DXA; it was also shown that body fat was overestimated and fat free mass underestimated by BIA in relation to DXA.     

油页岩颗粒的热解模型

以实验为依据,分析了油页岩的热解机理及特性,并充分考虑了油页岩中挥发分在整个热解过程的作用,在此基础上建立了与油页岩固有热解特性相适应的热解模型。在能量方程中考虑了油页岩挥发分的热解反应吸热量及其挥发分的释放对油页岩固体颗粒质量的影响,并根据油页岩的热解特性,采用分阶段模型来描述油页岩的热解过程,以减小一步本征动力学方程带来的较大误差,还对模型进行了实验验证。     

Crystallization Kinetics of Cocoa Fat Systems: Experiments and Modeling

Isothermal crystallization kinetics of unseeded and seeded cocoa butter and milk chocolate is experimentally investigated under quiescent conditions at different temperatures in terms of the temporal increase in the solid fat content. The theoretical equations of Avrami based on one-, two- and three-dimensional crystal growth are tested with the experimental data. The equation for one-dimensional crystal growth represents well the kinetics of unseeded cocoa butter crystallization of form α and β′. This is also true for cocoa butter crystal seeded milk chocolate. The sterical hindrance due to high solids content in chocolate restricts crystallization to lineal growth. In contrast, the equation for two-dimensional crystal growth fits best the seeded cocoa butter crystallization kinetics. However, a transition from three- to one-dimensional growth kinetics seems to occur. Published data on crystallization of a single component involving spherulite crystals are represented well by Avrami’s three-dimensional theoretical equation. The theoretical equations enable the determination of the fundamental crystallization parameters such as the probability of nucleation and the number density of nuclei based on the measured crystal growth rate. This is not possible with Avrami’s approximate equation although it fits the experimental data well. The crystallization can be reasonably well defined for single component systems. However, there is no model which fits the multicomponent crystallization processes as observed in fat systems.