Reported health status among farmers and nonfarmers in nine rural districts

Farmers appear to have a lower morbidity and mortality rate than other occupational groups. Whether this better health is due to exposure to farming or to the well-known fact that rural populations have better health than urban ones, irrespective of occupation, is not clear. To explore this problem, all male farmers in nine administrative areas and age-matched nonfarmers from the same rural areas were sampled and invited to participate in a survey. 1782 (76%) men responded. We found that farmers had somewhat lower rates of outpatient health care utilization for causes other than trauma and fewer hospital admissions. These differences were independent of the urban-rural factor and could not be explained by traditional determinants of health and health care utilization. Other factors, linked to farming or to farmers' lifestyles, are probably involved.     

HIV and hepatitis B infection and risk behavior in young gay and bisexual men

A random conical tilt reconstruction of negatively stained Saccharomyces cerevisiae fatty acid synthase was used as a model to compute a three-dimensional reconstruction from untilted stain specimens of the molecules in multiple orientations using a three-dimensional projection alignment method. The resulting structure (24 A resolution) has a more uniform resolution than the initial structure and the handedness revealed in the random conical tilt method is preserved. In a similar approach, this model was used to compute a 21-A-resolution frozen-hydrated structure from untilted specimens of the molecules in multiple orientations. Even though the reconstructions are in close agreement, the stain structure appears to enhance the protein density associated with less robust features. These procedures significantly reduce the time and effort required to obtain a three-dimensional reconstruction from frozen-hydrated data with a resolution that is comparable to the best obtained by more laborious methods. The agreement between the stain and frozen-hydrated reconstructions affords convincing evidence concerning the validity of the structure and the information afforded by the two reconstructions significantly enhances the structural analysis of the molecule.     

Low temperature acid catalyzed curing of melamine resin systems

Summary Melamine resins having a high concentration of secondary amino groups (-NH-CH₂OR groups) are able to cure at low temperature under strongly acidic conditions. It is shown by spectroscopic methods that the characteristic curing reaction of this type of resin proceeds via an imino group intermediate.Analogous reactions are proposed for the self-curing of the melamine resin and the co-condensation with hydroxyl containing polymers.     

Lipase Catalyzed Transesterification of Unsaturated Lipids in a Microemulsion

A series of triglycerides having varying degrees of unsaturation of the acyl groups has been transesterified with stearic acid. It is shown that the position of the double bonds, not the degree of unsaturation, is the decisive factor in the rate of reaction. A A-6 double bond, which is present in petroselinic acid and ylinolenic acid, prevents reaction. Unsymmetrical triglycerides containing only one acyl group with δ-6 unsaturation reacts regiospecifically with the A-6 acyl group facing away from the enzyme. γ-Linolenic acid can be incorporated into an unhindered triglyceride through lipase catalyzed transesterification, indicating that the active site can in fact accommodate a δ-6 fatty acid, although not the corresponding triglyceride.     

Generalized linear models with clustered data: Fixed and random effects models

The statistical analysis of mixed effects models for binary and count data is investigated. In the statistical computing environment R, there are a few packages that estimate models of this kind. The package lme4 is a de facto standard for mixed effects models. The package glmmML allows non-normal distributions in the specification of random intercepts. It also allows for the estimation of a fixed effects model, assuming that all cluster intercepts are distinct fixed parameters; moreover, a bootstrapping technique is implemented to replace asymptotic analysis. The random intercepts model is fitted using a maximum likelihood estimator with adaptive Gauss-Hermite and Laplace quadrature approximations of the likelihood function. The fixed effects model is fitted through a profiling approach, which is necessary when the number of clusters is large. In a simulation study, the two approaches are compared. The fixed effects model has severe bias when the mixed effects variance is positive and the number of clusters is large.     

Evaluation of energy efficiency in biofuel drying by means of energy and exergy analyses

The calculation of heat consumption is based on the First Law and it gives quantitative information about the energy used in drying. However, it does not pay any attention to the quality of the energy used in drying. To take into account the quality of the energy, attention must be paid to the Second Law, too. Especially in those cases where the energy used in drying may be converted to mechanical work, it is important to consider the Second Law is. In this paper, the energy efficiency of biofuel drying in a pulp and paper mill is evaluated on the basis of energy and exergy analysis. The evaluation is based on the determination of the heat consumption and the irreversibility rate for energy and exergy analysis, respectively. The evaluation methods are applied to two different drying systems, single-stage-drying with partial recycle of spent air, and multi-stage-drying. Both drying systems are also provided with a heat recovery unit in which the inlet air is pre-heated using the outlet air of the dryer. There are two alternative heat sources available for the drying energy, steam at a pressure of 3 bar and water at a temperature of 80 °C. The results show that the heat consumption is only dependent to a small extent on the heat source type or the drying system. On the other hand, the irreversibility rate depends to a considerable on the heat source and the drying system.     

Defluidisation of fluidised beds during gasification of biomass

Defluidisation and agglomeration during fluidised bed gasification of biomass is analysed and discussed. It is argued that the agglomeration and defluidisation processes, in principle, closely resemble those that determine the behaviour of glass during glass processing. Crucial properties for working with glass melts are the viscosity, stickiness, surface tension, etc. It is, however, (very) difficult to theoretically quantify these properties through thermodynamics or other theoretical means. Hence it will be problematic to theoretically predict agglomeration and defluidisation. Models for predicting defluidisation must therefore probably be of an empirical nature. As a consequence of this, a number of fluidised bed gasification tests were empirically analysed with respect to defluidisation. In total 145 tests were evaluated; of these 51 defluidised or exhibited some kind of bed disturbance. A number of fuels and bed materials were included in the analysis using a multivariate statistical approach.Based on the analysis an empirical regression equation for predicting the defluidisation temperature during fluidised bed gasification is suggested.     

Water vapor sorption and diffusivity in bark

Physical properties of importance in drying processes have been compiled for bark, including spruce, pine, and birch in Sweden. Water vapor sorption isotherms were determined for the bark of these trees. At 95% relative humidity and 25°C, outer birch bark reached a moisture ratio (kg water/kg dry mass) of 5%, whereas inner birch bark, spruce bark, and pine bark reached moisture ratios of 21, 28, and 25%, respectively. The transverse water vapor diffusivity in samples of spruce bark, pine bark, inner birch bark, and outer birch bark were determined to be 1.1–1.7 · 10^?6, 2.2–9.2 · 10^?7, 1.5–2.6 · 10^?6, and 4.3–13 · 10^?8 m²/s, respectively. The in-plane diffusivity was of the same magnitude as the transverse diffusivity in inner birch bark, whereas in outer birch bark the in-plane diffusivity was several times higher than the transverse diffusivity. These data can be used to model the drying behavior and can thus aid in the design of efficient bark drying processes.