Thermoforming of foam sheet

Thermoforming is a widely used process for the manufacture of foam sheet products. Polystyrene foam food trays for instance can be produced by first heating the thermoplastic foam sheet, causing the gas contained to build up pressure and expand, after which a vacuum pressure can be applied to draw the sheet in the required form on the mould. This production method appears to be a very sensitive process with respect to e.g. the sheet temperature, the pressures applied and the cooling time. More problems can be foreseen when for environmental reasons the blowing agent will be adapted (for instance replaced by a gas with a lower molecular weight). To gain more insight in the occuring phenomena the large deformations of a foam structure have been analysed using finite element modelling. To this end a constitutive model has to be defined. Starting from the basic theory given by Gibson & Ashby [1], the behaviour of a closed cubic cell has been elaborated for large strains. The total stiffness is then the sum of the contributions of the edges and faces of the cell and the gas contained in it. The large deformations cause anisotropy of the cells [2], which influences their tangential stiffness. The constitutive model developed here includes the effects of internal gas pressure and the evolving anisotropy

A Mid-Cretaceous Origin of Sociality in Xylocopine Bees with Only Two Origins of True Worker Castes Indicates Severe Barriers to Eusociality

The origin of sterile worker castes, resulting in eusociality, represents one of the major evolutionary transitions in the history of life. Understanding how eusociality has evolved is therefore an important issue for understanding life on earth. Here we show that in the large bee subfamily Xylocopinae, a simple form of sociality was present in the ancestral lineage and there have been at least four reversions to purely solitary nesting. The ancestral form of sociality did not involve morphological worker castes and maximum colony sizes were very small. True worker castes, entailing a life-time commitment to non-reproductive roles, have evolved only twice, and only one of these resulted in discrete queen-worker morphologies. Our results indicate extremely high barriers to the evolution of eusociality. Its origins are likely to have required very unusual life-history and ecological circumstances, rather than the amount of time that selection can operate on more simple forms of sociality

Whole-blood transcriptomic signatures induced during immunization by chloroquine prophylaxis and Plasmodium falciparum sporozoites

A highly effective vaccine that confers sterile protection to malaria is urgently needed. Immunization under chemoprophylaxis with sporozoites (CPS) consistently confers high levels of protection in the Controlled Human Malaria infection (CHMI) model. To provide a broad, unbiased assessment of the composition and kinetics of direct ex vivo human immune responses to CPS, we profiled whole-blood transcriptomes by RNA-seq before and during CPS immunization and following CHMI challenge. Differential expression of genes enriched in modules related to T cells, NK cells, protein synthesis, and mitochondrial processes were detected in fully protected individuals four weeks after the first immunization. Non-protected individuals demonstrated transcriptomic changes after the third immunization and the day of treatment, with upregulation of interferon and innate inflammatory genes and downregulation of B-cell signatures. Protected individuals demonstrated more significant interactions between blood transcription modules compared to non-protected individuals several weeks after the second and third immunizations. These data provide insight into the molecular and cellular basis of CPS-induced immune protection from P. falciparum infection

The Neurophysiology of Auditory Hallucinations – A Historical and Contemporary Review

Electroencephalography and magnetoencephalography are two techniques that distinguish themselves from other neuroimaging methodologies through their ability to directly measure brain-related activity and their high temporal resolution. A large body of research has applied these techniques to study auditory hallucinations. Across a variety of approaches, the left superior temporal cortex is consistently reported to be involved in this symptom. Moreover, there is increasing evidence that a failure in corollary discharge, i.e., a neural signal originating in frontal speech areas that indicates to sensory areas that forthcoming thought is self-generated, may underlie the experience of auditory hallucinations

Edge effect causes apparent fractal correlation dimension of uniform spatial raindrop distribution

Lovejoy and Schertzer (1990a) presented a statistical analysis of blotting paper observations of the (twodimensional) spatial distribution of raindrop stains. They found empirical evidence for the fractal scaling behavior of raindrops in space, with potentially far-reaching implications for rainfall microphysics and radar meteorology. In particular, the fractal correlation dimensions determined from their blotting paper observations led them to conclude that “drops are (hierarchically) clustered” and that “inhomogeneity in rain is likely to extend down to millimeter scales”. Confirming previously reported Monte Carlo simulations, we demonstrate analytically that the claims based on this analysis need to be reconsidered, as fractal correlation dimensions similar to the ones reported (i.e. smaller than the value of two expected for uniformly distributed raindrops) can result from instrumental artifacts (edge effects) in otherwise homogeneous Poissonian rainfall. Hence, the results of the blotting paper experiment are not statistically significant enough to reject the Poisson homogeneity hypothesis in favor of a fractal description of the discrete nature of rainfall. Our analysis is based on an analytical expression for the expected overlap area between a circle and a square, when the circle center is randomly (uniformly) distributed inside the square. The derived expression ( r2−8r3/3+r4/2, where r denotes the ratio between the circle radius and the side of the square) can be used as a reference curve against which to test the statistical significance of fractal correlation dimensions determined from spatial point patterns, such as those of raindrops and rainfall cells.Postprint (published version

A systematic analysis on tomato powder quality prepared by four conductive drying technologies

Four pilot-scale conductive dryers, namely a vacuum drum dryer (VDD), a drum dryer (DD), an agitated thin film dryer (ATFD) and a refractance window dryer (RWD), were used to dry tomato puree. Drying induced colour differences between the reconstituted puree and the original puree and strongly affected the volatile and non- volatile profiles of the powders. Principal component analysis (PCA) identified four separated groups corresponding to the different drying methods, indicating that the drying methods caused significant variance in compound profiles. Subsequently, pairwise comparison of different dried powders was performed by partial least square discriminant analysis (PLS-DA). This resulted in a selection of discriminative volatile and non-volatile markers. RWD and VDD produced powders with high volatile markers that may be related to aroma retention. Conversely, DD dried products contained more non-volatile markers that can be related to taste perception. ATFD processed powders had a lower level of discriminant compounds. Industrial relevance: Tomato products are frequently thermally processed and dehydrated. However, processing negatively affects the sensory quality of tomato products. In this study, four conductive drying processes, i.e. vacuum drum drying (VDD), drum drying (DD), agitated thin film drying (ATFD) and refractance window drying (RWD) were studied for being energy-efficient drying methods, while suitable for mild (e.g. due to the reduced pressure) drying of pastes and slurries, such as tomato puree. The pilot-scale drying experiments and subsequent statistical analyses of results on quality markers contributed to unravel the impact of the different conductive drying technologies on tomato powder quality. This study may be considered a starting point for selection of conductive drying technologies for the efficient production of high quality tomato powders and other vegetable powders