Correlated probit analysis of repeatedly measured ordinal and continuous outcomes with application to the Health and Retirement Study.

The Health and Retirement Study was designed to evaluate changes in health and labor force participation during and after the transition from working to retirement. Every 2 years, participants provided information about their self-rated health (SRH), body mass index (BMI), smoking status, and other characteristics. Our goal was to assess the effects of smoking and gender on trajectories of change in BMI and SRH over time. Joint longitudinal analysis of outcome measures is preferable to separate analyses because it allows to account for the correlation between the measures, to test the effects of predictors while controlling type I error, and potentially to improve efficiency. However, because SRH is an ordinal measure while BMI is continuous, formulating a joint model and parameter estimation is challenging. A joint correlated probit model allowed us to seamlessly account for the correlations between the measures over time. Established estimating procedures for such models are based on quasi-likelihood or numerical approximations that may be biased or fail to converge. Therefore, we proposed a novel expectation-maximization algorithm for parameter estimation and a Monte Carlo bootstrap approach for standard errors approximation. Expectation-maximization algorithms have been previously considered for combinations of binary and/or continuous repeated measures; however, modifications were needed to handle combinations of ordinal and continuous responses. A simulation study demonstrated that the algorithm converged and provided approximately unbiased estimates with sufficiently large sample sizes. In the Health and Retirement Study, male gender and smoking were independently associated with steeper deterioration in self-rated health and with lower average BMI. Copyright © 2016 John Wiley & Sons, Ltd.

Yeast strains from Livingston Island, Antarctica.

Five yeast strains were isolated from soil and moss samples from the Livingston Island (Antarctica) and identified according to morphological cultural and physiological characteristics. All strains had an optimum growth temperature of 15 degrees C: none grew above 25 degrees C. They assimilated D-glucose, D-galactose, sucrose, cellobiose, trehalose, 2-keto-D-gluconate, D-xylose, D-ribose and melezitose. Four of them were nonfermentative, only one, which formed pseudomycelium fermented glucose, galactose, trehalose. Two strains were identified as pink-red yeasts belonging to genus Rhodotorula--R. minuta and R. mucilaginosa; two were related to the genus Cryptococcus--C. albidus and C. laurentii; one was Candida oleophila.

Lipid composition of some yeast strains from Livingston Island, Antarctica.

Yeast strains Cryptococcus albidus, Cryptococcus laurentii, Rhodotorula minuta were isolated from a moss sample. Candida oleophila and Rhodotorula mucilaginosa were isolated from a soil sample taken from Livingston Island. Antarctica. Fatty acid, phospholipid, sterol and tocopherol composition was determined in separated lipid fraction after fermentation in a medium containing glucose, peptone and yeast extract. Unsaturated fatty acids, mainly oleic (51-65%) and linoleic (9.5-16.8%), predominated in triacylglycerols. Sterols represent ca. 120-930 mg per kg dry biomass. The content of major phospholipids (phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine) was ca. 100-800 mg/kg. The amount of tocopherols (mainly gamma- and delta-tocopherol) was 2.1-6.3 mg/kg.

Preparation and preliminary characterization of exopolysaccharides by yeast Rhodotorula acheniorum MC.

The effects of various carbon and nitrogen sources on the synthesis of exopolysaccharides by Rhodotorula acheniorum MC were studied. The dynamic viscosity of cell-free culture broths during exopolysaccharide synthesis were measured. The highest values for the viscosity (10.14 MPa.s) and crude polysaccharide productivity (6.6 g/L) were obtained in a medium supplied with 5% sucrose. Ammonium sulfate was the most favorable nitrogen source for exopolysaccharide synthesis. The value of pH played a determinant role, and the obligatory condition for exopolysaccharide production was low (pH 1.7-2.0) during the fermentation. The chemical composition and sugar constituents of the crude exopolysaccharides were determined. Mannose was the main monosaccharide component, and its concentration was the highest (69.13%) in the crude exopolysaccharide synthesized in the medium that included 5% sucrose as a carbon source.

Formation of carotenoids by rhodotorula glutinis in whey ultrafiltrate.

The growth and carotenoid biosynthesis of the yeast Rhodotorula glutinis was studied by cocultivation with Lactobacillus helveticus in cheese ultrafiltrate containing 3.9% and 7.1% lactose. By growing this mixed culture in a 15-L fermentor MBR AG (Switzerland) at an air flow rate of 0.5 L/L min and agitation at 220 rpm for 6 days, a total yield of carotenoids of 268 mug/g dry cells wasobtained. Carotenoids were formed almost parallel with the cell growth, anda maximum production was reached at an early stationary phase. A high-performance liquid chromatographic system (HPLC) permitting simultaneous determination of major carotenoid pigments was used. The three main pigments (torularhodin, beta-carotene, and torulene) were formed in Rhodotorula glutinis, and reached a maximum concentration as follows: 182.0, 43.9, 23.0 mug,g dry cells. (c) 1994 John Wiley & Sons, Inc.

[Pesticide residues in honey]. / Ostatuchni kolichestva pestitsidi v pchelen med.

Investigated were a total of 40 samples of flower honey from seven regions of the country (the districts of Mihailovgrad, Gorna Oryahovitsa, Turgovishte, Plovdiv, Pazarjik, Sliven, and Byala Slatina). In 20 per cent of the samples there were traces of the phosphororganic pesticides trichlorfon and DDVF, and in 32 per cent - traces of chlororganic insecticides - HChCH and DDE. The studies made use of the agar diffusion, thin layer chromatography, and gas chromatography methods. It was established that honey was a product that was negligibly contaminated with pesticides. The residual amounts found were minimal (0.0002 to 0.00060 ppm) and were within the range of the admissible Bulgarian and international standards concerning the respective pesticides in food products. These amounts were found to correspond to the values established by other authors.

[Comparative testing of methods for determining arsenic in food products]. / Sravnitelno izpitvane na metodi za opredeliane na arsen v khranitelni produkti.

Two methods for arsenic determination on food products were tested, namely: with silver diethylthiourea and after molybdenum blue as presented in AOAC--1975. Better repeatability of results was observed when the method with silver diethylthiourea was used (94--96%). It is recommended that this method be included in BSS. In order to improve the repeatability of results in case the molybdenum blue method is used it is recommended that the contruction of the standard curve follows the entire analytical course post mineralization.

[Determination of sorbic acid, its salts and salicylic acid in food products of animal origin]. / Opredeliane na sorbinovata kiselina, neinite soli i salitsilovata kiselina v khranitelni produkti ot zhivotinski proizkhod.

A foreign method for quantitative assay of sorbic acid and natrium sorbate in food stuff of plant origin was applied by the authors for food stuffs of animal origin. The conservant of the food stuff was isolated by water vapour distillation. Sorbic acid and natrium sorbate assay was performed on part of the distillate colorimetrically at wave length lambda--532 nm. The method proved highly sensitive (2 gammas and 94% reproduction). It can be used in conservant assay of various fish assortments, canned food, roe and some types of cheese. A qualitative method for proving the presence of salicylic acid is proposed, using water vapour distillation of the biological material. Part of the distillate produced is treated directly by 1% ferriammonium sulfate water solution. A violet tint of the solution proves the presence of salicylic acid in the product studied.

[Determination of benzoic acid and its salts in food products of animal origin]. / Opredeliane na benzoenata kiselina i solite i v khranitelni produkti ot zhivotinski proizkhod.

A modification of the method for determining benzoic acid and its salts by water-vapour distillation and extraction of the biological material conservant and its titrimetrical determination is proposed. The thin layer chromatography method (TLC) is used parallelly for the identification of the conservant. The advantage of the proposed method consists in that the same distiller is used for quantitative titrimetrical determination and for TLC assessment. The method possesses high sensitivity 1 gamma in TLC scoring and 0.1 mg in titrimetric determination. It is applied for the determination of conservants in various fish assortments, canned fish and roe.

[Thin-layer chromatographic demonstration of the herbicide zenkor]. / Tunkosloinokhromatografsko dokazvane na kherbitsida zenkor

Established were the thin-layer chromatography conditions for the demonstration of the herbicide Zenkor as a pure substance and a preparation. Comparative experiments were carried out applying Thomson and Stanley's thin-layer chromatography conditions and the authors' personal ones. Most adequate proved to be the following conditions: sorbent-Kieselgel 60F 254 (Merck); solvent -- chloroform: 1,4-dioxan (9:1); developer -- ultraviolet light (authors' technique). Essential with this method is the preliminary (prior to apply the pure substances on the thin-layer chromatographic plaque) moving of the plaque in the indicated mobile phase (authors' technique). Under these thin-layer chromatography conditions work is made feasible and the method is fast and simple, achieving high sensitivity -- 0.5 mug Zenkor.