Alternating current chronopotentiometry—III. Electroreduction of silver(I), cadmium(II), and thallium(I) in calcium nitrate tetrahydrate melt

The electroreduction of silver(I) on a platinum electrode and of cadmium(II) and thallium(I) on a mercury electrode has been studied by alternating current chronopotentiometry. Expected relations for the diffusion controlled, one-electron deposition of an insoluble substance are obeyed for silver(I); but reduction of cadmium(II) on mercury is more complex. Nucleation of metallic thallium is the rate controlling process during the early stages of the reduction of thallium(I).     

Heat transfer coefficient for constant flow solar collector/storage systems

An earlier expression for the heat transfer coefficient between the heated surface and the flowing fluid used in the investigation of the performance of a few collector/storage systems leads to results which are physically impractical. In this communication we derive the correct expression for the heat transfer coefficient in terms of the parameters of the tube, i.e. its length and circumference. The effect of the modified form of the heat transfer coefficient on the performance of a typical system, namely a ground collector system, has been studied in detail.     

Performance of a thermal trap flat-plate solar energy collector

The performance of a thermal trap flat-plate solar energy collector has been investigated theoretically and validated experimentally, from the point of view of stagnation temperature. The theoretical model is based on the periodic solution of the heat conduction equation and takes into account the internal emission of the thermal trap material. The model explains the experimental measurements fairly well. It is found that the trap material should have an optimal thickness in order to obtain the maximum plate temperature.The thickness of the air gap between the trap material and the cover has only a very marginal effect on the stagnation temperature.     

Transient behaviour of salt gradient stabilised shallow solar ponds

This paper presents the results of experimental and analytical investigations of the transient thermal processes in a salt gradient stabilised pond of shallow (10 cm) depth, useful for short-term storage applications. A small convective sublayer (about 3 cm thick) of uniform temperature tends to form at the bottom of the pond. The convective-non-convective zone boundary below the gradient zone exhibits movements with time of day as well as from day to day. This suggests that only local properties and local gradients are relevant to the stability condition. A thin oil layer cover at the pond surface considerably enhances the temperature in the pond and aids its stability. A simple transient thermal model of the pond is developed. The observed temperatures and depths of the zones are in close agreement with theory.     

Seamless warping of diffusion tensor fields

To warp diffusion tensor fields accurately, tensors must be reoriented in the space to which the tensors are warped based on both the local deformation field and the orientation of the underlying fibers in the original image. Existing algorithms for warping tensors typically use forward mapping deformations in an attempt to ensure that the local deformations in the warped image remains true to the orientation of the underlying fibers; forward mapping, however, can also create ldquoseamsrdquo or gaps and consequently artifacts in the warped image by failing to define accurately the voxels in the template space where the magnitude of the deformation is large (e.g., |Jacobian| > 1). Backward mapping, in contrast, defines voxels in the template space by mapping them back to locations in the original imaging space. Backward mapping allows every voxel in the template space to be defined without the creation of seams, including voxels in which the deformation is extensive. Backward mapping, however, cannot reorient tensors in the template space because information about the directional orientation of fiber tracts is contained in the original, unwarped imaging space only, and backward mapping alone cannot transfer that information to the template space. To combine the advantages of forward and backward mapping, we propose a novel method for the spatial normalization of diffusion tensor (DT) fields that uses a bijection (a bidirectional mapping with one-to-one correspondences between image spaces) to warp DT datasets seamlessly from one imaging space to another. Once the bijection has been achieved and tensors have been correctly relocated to the template space, we can appropriately reorient tensors in the template space using a warping method based on Procrustean estimation.     

A simple procedure for selection and sizing of indirect passive solar heating systems

Equivalent sol-air temperatures have been defined for four indirect gain passive solar heating concepts, namely, mass wall, water wall, Trombe wall and solarium. Steady state thermal efficiencies have also been defined as a measure of the ability of each system to deliver heat into the living space.

Design curves have been developed which relate the average instantaneous solar radiation incident on the passive element to thermal efficiency for different values of ambient temperature. These curves are useful in selection of an appropriate passive heating concept for a particular location.

It is inferred that a solarium is most effective at very low levels of incident radiation and low ambient temperature. Water walls and Trombe walls are most efficient at higher levels of incident radiation.

A simple procedure has been developed for a first approximation of sizing the selected system using these design curves and a minimum of meteorological information, namely, monthly average of daily global solar radiation, monthly average maximum and minimum ambient temperatures.     

Analysis of trans fatty acids in deep frying oils by three different approaches

Simulated frying experiments were performed on three different types of oils with French fries as the fried food. Comparison of frying oil samples was then made with their control counterparts (i.e. oil samples heated without food). Three different methods, gas chromatography (GC), attenuated total reflection (ATR) AOCS method Cd 14d-99 and attenuated total reflection negative second derivative absorbance (−2D ATR), were applied to quantify total trans fats. The total trans fats were found to be higher in the frying oil samples as compared to the control samples, which might be due to the presence of a high amount of trans fats in the pre-fried and frozen French fries. In general, the ATR AOCS method Cd 14d-99 produced lower amounts of trans fatty acids and the −2D ATR absorbance method produced higher amounts when compared with those obtained by gas chromatography.     

Thermal modeling and performance analysis of industrial-scale metal hydride based hydrogen storage container

In this paper, a performance analysis of a metal hydride based hydrogen storage container with embedded cooling tubes during absorption of hydrogen is presented. A 2-D mathematical model in cylindrical coordinates is developed using the commercial software COMSOL Multiphysics 4.2. Numerical results obtained are found in good agreement with experimental data available in the literature. Different container geometries, depending upon the number and arrangement of cooling tubes inside the hydride bed, are considered to obtain an optimum geometry. For this optimum geometry, the effects of various operating parameters viz. supply pressure, cooling fluid temperature and overall heat transfer coefficient on the hydriding characteristics of MmNi_4.6Al_0.4 are presented. Industrial-scale hydrogen storage container with the capacity of about 150 kg of alloy mass is also modeled. In summary, this paper demonstrates the modeling and the selection of optimum geometry of a metal hydride based hydrogen storage container (MHHSC) based on minimum absorption time and easy manufacturing aspects.     

Evaluation of tilapia skin gelatin as a mammalian gelatin replacer in acid milk gels and low-fat stirred yogurt

Tilapia skin gelatin (TSG) was studied in a 3-stage process (cooling, annealing, and heating) for pure gelatin gels and in a 4-stage process (acidification, cooling, annealing, and heating) for acid milk gels and cultured yogurt. The aim was to evaluate the use of TSG as a replacement for mammalian gelatin in yogurt. In pure TSG gels, stronger gels with higher melting temperatures were formed with increasing TSG concentrations. Compared with bovine gelatin (BG), which gelled at a concentration of 2.5%, TSG gels had lower gelling (14.1°C) and melting (24°C) temperatures but comparable storage moduli during annealing. In acid milk gels, addition of TSG increased the firmness of the gels with increasing concentration. Gelling and melting points of TSG in milk gels were observed at sufficient concentrations during cooling and heating. Strands and sheets were observed in the electron micrographs of milk gels with 1% TSG and a very dense structure was observed with 2.5% TSG. Yogurt with 0.4% TSG had similar viscosity, consistency, pseudoplasticity, and thixotropy as yogurt containing 0.4% BG; no difference was perceived by sensory panelists according to a triangle test. Addition of 0.4% TSG completely prevented whey separation from the acid milk gel and yogurt. The results suggest that TSG could be a suitable replacement for mammalian gelatin in low-fat stirred yogurt.     

Increased thermal tolerance in Cronobacter sakazakii strains in reconstituted milk powder due to cross protection by physiological stresses

Cronobacter sakazakii (C. sakazakii) is an opportunistic, neonatal, and food borne pathogen primarily associated with the contamination of powdered infant formula (PIF). The pathogen is reported to overcome the food safety barriers such as increased acidity, heat treatment, and so on. This study evaluates the thermal tolerance of C. sakazakii strains independently at 52, 55, and 58°C in reconstituted PIF after exposure to physiological stresses: refrigeration (4°C for 24 hr), starvation (37°C for 48 hr), and desiccation (25°C for 4 days). The Log₁₀ CFU/ml and D-values indicated that survival rate of all the strains decreased significantly (p < .05) after desiccation as compared to those of the control condition (without stress exposure). However, cold stress increased the thermal tolerance of all strains at all temperatures (52, 55, and 58°C) as indicated by increased D-values. Among the tested strains, C. sakazakii strain N15 was found to be the most resistant to thermal treatment after each stress exposure as depicted by principal component analysis (PCA). No apparent correlation between thermal tolerance and starvation stress was observed. The findings indicate that prior exposure to stress conditions may induce cross protection to thermal treatment in C. sakazakii.