On the optimal numerical time integration for Lagrangian DEM within implicit flow solvers

We investigate a selection of nominally first, second and fourth order time integration schemes with application to particle collision simulation using the discrete element method (DEM). The motivation being the typical requirement to efficiently two-way couple a continuum flow obtained with a finite volume solver employing an iterative implicit solution method to Lagrangian DEM. Using the linear force model to simulate particle repulsion, the actual order of accuracy with respect to initial separation (‘free motion’), timestep, stiffness, damping and impact velocity is investigated. Due to the discontinuities of the inter-particle repulsive force upon contact, we find that without damping, the numerical schemes tested are generally limited to second order accuracy. The addition of damping can reduce actual order of accuracy further depending on the inter-particle free motion. This finding is compared against a continual interaction case (without free motion) where it is found that the expected higher order accuracy is recovered.     

Diet, nutrition, and cancer

Evidence pertaining to the role of dietary factors in carcinogenesis comes from both epidemiological studies and laboratory experiments. In 1982, the Committee on Diet, Nutrition, and Cancer of the National Research Council conducted a comprehensive evaluation of this evidence. That assessment as well as recent epidemiological and laboratory investigations suggest that a high fat diet is associated with increased susceptibility to cancer of different sites, particularly the breast and colon, and to a lesser extent, the prostate. Current data permit no definitive conclusions about other dietary macroconstituents including cholesterol, total caloric intake, protein, carbohydrates and total dietary fiber. Specific components of fiber, however, may have a protective effect against colon cancer. In epidemiological studies, frequent consumption of certain fruits and vegetables, especially citrus fruits and carotene-rich and cruciferous vegetables, is associated with a lower incidence of cancers at various sites. The specific components responsible for these effects are not clearly identified, although the epidemiological evidence appears to be most consistent for a protective effect of carotene on lung cancer and less so for vitamins A and C and various cancer sites. The laboratory evidence is most consistent for vitamin A deficiency and enhanced tumorigenesis, and for the ability of various nonnutritive components in cruciferous vegetables to block in-vivo carcinogenesis. The data for minerals and carcinogenesis are extremely limited, although preliminary evidence from both epidemiological and laboratory studies suggests that selenium may protect against overall cancer risk. Frequent consumption of cured, pickled, or smoked foods, possibly because they may contain nitrosamines or polycyclic aromatic hydrocarbons, appears to increase the risk of esophageal or stomach cancer, however, the specific causative agents in these foods are not clearly identified. Excessive alcohol consumption among smokers appears to be associated with an elevated risk of cancers of the oral cavity, esophagus, larynx, and respiratory tract. The mechanisms of action of dietary factors on carcinogenesis are poorly understood. The NRC committee, and more recently, the National Cancer Institute and the American Cancer Society have proposed interim dietary guidelines to lower the risk of cancer. These guidelines are consistent with general dietary recommendations proposed by U.S. government agencies for maintenance of good health.(ABSTRACT TRUNCATED AT 400 WORDS)     

UVB Radiation Variably Affects n-3 Fatty Acids but Elevated Temperature Reduces n-3 Fatty Acids in Juvenile Atlantic Salmon (Salmo salar)

Temperature and ultraviolet B radiation (UVB 290–320?nm) are inextricably linked to global climate change. These two variables may act separately, additively, or synergistically on specific aspects of fish biochemistry. We raised Atlantic Salmon (Salmo salar) parr for 54?days in outdoor tanks held at 12 and 19?°C and, at each temperature, we exposed them to three spectral treatments differing in UV radiation intensity. We quantified individual fatty acid (FA) mass fractions in four tissues (dorsal muscle, dorsal and ventral skin, and ocular tissue) at each temperature?×?UV combination. FA composition of dorsal muscle and dorsal and ventral skin was not affected by UV exposure. Mass fractions of 16:0, 18:0, and saturated fatty acids (SFA) were greater in dorsal muscle of warm-reared fish whereas 18:3n-3, 20:2, 20:4n-6, 22:5n-3, 22:6n-3, n-3, n-6, polyunsaturated fatty acids (PUFA), and total FA were significantly higher in cold-reared fish. Mass fractions of most of the FA were greater in the dorsal and ventral skin of warm-reared fish. Cold-reared salmon exposed to enhanced UVB had higher ocular tissue mass fractions of 20:2, 20:4n-6, 22:6n-3, n-3, n-6, and PUFA compared to fish in which UV had been removed. These observations forecast a host of ensuing physiological and ecological responses of juvenile Atlantic Salmon to increasing temperatures and UVB levels in native streams and rivers where they mature before smolting and returning to the sea.     

Object color preferences

In this article, we investigate how context influences color preferences by comparing preferences for “contextless” colored squares with preferences for colors of a variety of objects (e.g., walls, couches, and T‐shirts). In experiment 1, we find that hue preferences for contextless squares generalize relatively well to hue preferences for imagined objects, with the substantial differences being in the saturation and lightness dimensions. In experiments 2 and 3, we find that object color preferences are relatively invariant when the objects are (a) imagined to be the color that is presented as a small square, (b) depicted as colored images of objects, and (c) viewed as actual physical objects. In experiment 4, we investigate the possibility that object color preferences are related to the degree to which colors help objects fulfill particular functions or outcomes. We also discuss relations between our results and previous theories of color preference. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 393–411, 2013     

Kant and the brain: A new empirical hypothesis.

Immanuel Kant's three great Critiques stand among the bulkier monuments of Enlightenment thought. The first is best known; the last had until recently been rather less studied. But his final Critique contains, I contend, a remarkable development of his theory of how human beings create and use systems of knowledge. While Kant was not himself concerned with the neuronal substrates of cognition, I argue this development yields a novel empirical hypothesis susceptible of experimental investigation. Here I present the Kantian motivation and describe experimental work aimed at testing predictions arising from the new hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of electroluminescent structures based on gallium arsenide ion-implanted with ytterbium and oxygen

Light-emitting diodes based on GaAs crystals ion-implanted with ytterbium and oxygen were fabricated. The current-voltage and capacitance-voltage characteristics of these diodes were analyzed. The deep-level centers were studied by the deep-level transient spectroscopy. The electroluminescence spectra of the structures include the emission lines related to optical transitions within the 4f shell of Yb³⁺ ions.     

Respiratory disease in workers exposed to colophony solder flux fumes: continuing health concerns

The objectives of this study were to establish the prevalence of respiratory, eye, nose and throat symptoms of likely work-relation in workers exposed to colophony solder flux fumes and to assess their lung function. A cross-sectional study was conducted in four medium-sized electronics firms in which control measures to capture solder flux fume were absent or visibly ineffective. All female solders and women working adjacent to soldering stations completed an administered questionnaire concerning symptoms, work history and current soldering frequency. Measurements were made of their forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) during the course of a working shift, using a Vitallograph-Compact portable spirometer. Using weekly hours of soldering as a crude index of current exposure, workers were classified into high (> or = 37 h/wk) and low (< or = 20 h/wk) exposure groups, and their health responses were compared in the analysis. Individuals with symptoms suggestive of work-related asthma were also asked to provide serial peak flow measurements over a further 2-week period, and adequate returns were charted and read by two physicians experienced in the diagnosis of occupational asthma. Data were collected on 152 female workers (overall participation rate = 97%). Symptoms of recurrent, persistent wheeze and/or chest tightness were reported by 75 (49%) of interviewees; 36 (24%) gave a history typical of occupational asthma and six more (4%) a history of pre-existing asthma worsened at work. Twenty-one (14%) of the workforce complained of recurrent breathlessness on moderate exertion; 41 workers (27%) had work-related symptoms of the nose or throat and 25 (16%) had work-related eye symptoms. The odds ratios for 'all wheeze', shortness of breath, and work-related eye, nose and chest symptoms were all significantly greater (raised about 4-5 fold) in women who soldered > or = 37 h/wk when compared with those soldering < or = 20 h/wk. After adjustment by logistic regression for atopy, age and smoking status even higher risk estimates were generally obtained. The odds ratios (OR) and 95% confidence intervals (CI) for high vs. low were: for 'all wheeze', OR = 7.2, CI = 2.5-20.7; for work-related eye symptoms, OR = 5.2, CI = 1.4-19.8; for work-related nasal symptoms, OR = 4.0, CI = 1.4-11.1 and for occupational asthma symptoms, OR = 5.2, CI = 1.4-14.2. Mean FEV1 and FVC percentage difference from expected were slightly lower in full-time solderers than in part-time solderers, but the differences were not significant. Thirty-seven of the 51 workers (73%) who were asked to carry out serial peak flow measurements completed an adequate return: 27 of these records confirmed the presence of asthma, and in all of the cases the history suggested onset post-dating employment in soldering. Eleven peak flow records were indicative of occupational asthma. The health problems associated with colophony solder flux were documented over 18 years ago, but are still clearly apparent in situations where adequate control has not been achieved.     

Reactive oxygen species and antioxidants in signal transduction and gene expression

Reactive oxygen species (ROS) are produced by cellular metabolic reactions, and have been implicated in the pathogenesis of several diseases, including atherosclerosis, cancer, and Alzheimer's disease. Interestingly, clinical and epidemiologic studies have, in some cases, indicated that antioxidant nutrients may be effective in disease prevention. However, the efficacy of specific antioxidants in disease prevention is often both controversial and inconclusive. In an effort to elucidate the role of ROS and antioxidants in disease development and prevention, the chemistries of ROS and antioxidants have been examined extensively. Recently, molecular and cellular approaches have demonstrated that ROS and antioxidants can directly affect the cellular signaling apparatus and, consequently, the control of gene expression. This new research provides the link between ROS and antioxidant chemistries and the mechanisms of disease processes and prevention. This review illustrates how ROS function as potential intracellular and extracellular signaling molecules and how antioxidants can affect this process.