Experimental investigation of adverse effect of frost formation on microchannel evaporators,part 1: Effect of fin geometry and environmental effects

This study experimentally investigated the frost growth on louvered folded fins in microchannel heat exchangers when used in outdoor air-source heat pump systems. The effects of surface temperature, fin geometries, and air environmental conditions were studied. The overall aim was to isolate and quantify the effect of geometry from surface temperature effects. Experimental data of frost weight, local frost thickness, air pressure drop across the coils, time of frost–defrost cycles and heat transfer rates were recorded. Data showed that the frosting time and the frost growth rates depended mainly on the local fin surface temperature. Lower fin density was beneficial because it delayed the blockage of the air flow. The fin length and fin depth had minor effects on frosting performance. The air humidity had a fairly significant effect on rate of frost formation while air velocity seemed to have a small effect on the frost growth rate.     

The Role of Aluminum in the Detonation and Post‐Detonation Expansion of Selected Cast HMX‐Based Explosives

In order to improve understanding of how aluminum contributes in non‐ideal explosive mixtures, cast‐cured formulations have been analyzed in a series of cylinder tests and plate‐pushing experiments. This study describes the contribution of 15 % aluminum (median size of 3.2 μm) vs. lithium fluoride (an inert substitute for aluminum; <5 μm) in cast‐cured HMX formulations in different temporal regimes. Small cylinder tests were performed to analyze the detonation and wall velocities (1–20 μs) for these formulations. Near‐field blast effects of 58 mm diameter spherical charges were measured at 152 mm and 254 mm using steel plate acceleration. Pressure measurements at 1.52 m gave information about free‐field pressure at several milliseconds. While the observed detonation velocities for all formulations were within uncertainty, significantly higher cylinder wall velocities, plate velocities, and pressures were observed for the aluminum formulations at ≥2 μs. Additionally, hydrocode calculations were performed to determine how non‐ideal behavior affected the plate test results. Collectively, this work gives a clearer picture of how aluminum contributes to detonation on timescales from 1 μs to about 2 ms, and how the post‐detonation energy release contributes to wall velocities and blast effects. The experiments indicate that significant aluminum reactions occur after the CJ plane, and continue to contribute to expansion at late times.     

Characterization of O157:H7 and other Escherichia coli isolates recovered from cattle hides, feces, and carcasses

In a previous study, the seasonal prevalence was reported for stx+ Escherichia coli O157:H7 in feces and on hides and carcasses of cattle at processing. Overall, 1,697 O157:H7 isolates have now been characterized for the incidence of (i) eae(O157), hlyA, stx1, and stx2 in the recovered isolates and (ii) presumptive rough and presumptive nonmotile isolates. Seven O157:H7 isolates (0.4%) lacked stx genes, although they carried eae and hlyA. All but one of the isolates carried both eae and hlyA. Approximately two-thirds of the isolates (64% when one isolate per sample was considered) carried both stx1 and stx2. E. coli O157:H7 cells that harbored both stx1 and stx2 were more often recovered from hides in the fall (79% of the fall hide isolates) and winter (84% of the winter hide isolates) than in the spring (53%) and summer (59%). Isolates recovered from preevisceration carcasses showed a similar but not statistically significant trend. Twenty-three of the 25 O157:H7 isolates carrying stx1 but not stx2 were recovered during summer. Fifteen presumptive rough and 117 presumptive nonmotile stx+ O157:H7 isolates were recovered. Ten (67%) of the presumptive rough isolates were recovered during summer. Ninety-five of the presumptive nonmotile isolates (81%) were recovered during fall. Forty-eight percent of the false-positive isolates (175 of 363) tentatively identified as O157:H7 were O157+ H7- and lacked eae(O157), hlyA, and stx. These data suggest that in beef processing samples (i) there are minor seasonal variations in the prevalence of stx genes among E. coli O157:H7 isolates, (ii) presumptive rough and presumptive nonmotile stx+ O157:H7 isolates are present, (iii) E. coli O157:H7 isolates lacking stx genes may be rare, and (iv) O157+ H7- isolates lacking stx genes can result in many false-positive results.     

Understanding massively multiplayer online role‐playing game addiction: A hedonic management perspective

Massively multiplayer online role‐playing game (MMORPG) addiction presents a serious issue worldwide and has attracted increasing attention from academic and other public communities. This article addresses this critical issue and fills research gaps by proposing and testing a research model of MMORPG addiction. Building on the conceptual foundation of the hedonic management model of addiction and the technology affordance perspective, we develop a research model explaining how MMORPG affordances (ie, achievement, social and immersion affordances) are associated with the duality of hedonic effects (ie, perceived positive mood enhancement and perceived negative mood reduction) and the extent of MMORPG addiction. Using structural equation modelling, we empirically test our research model with 406 MMORPG players. The results show that both perceived positive mood enhancement and perceived negative mood reduction positively correlate with the extent of MMORPG addiction. Furthermore, achievement and immersion affordances are positively associated with the duality of hedonic effects, whereas social affordance is not. Our study contributes to the growing body of technology addiction literature by revealing the relationships between the two hedonic effects and the extent of MMORPG addiction, and by offering a contextualised explanation of the role of MMORPG affordances in these relationships. We offer an alternative perspective on the far‐reaching, unintended relationships between technological affordances and addictive technology use. Our study provides game developers and policymakers with insights into preventing MMORPG addiction to create an entertaining, healthy virtual playground.     

Assessment of pitting corrosion in bare and passivated (wet scCO2-induced patination and chemical passivation) hot-dip galvanized steel samples with SVET,FTIR, and SEM (EDS)

In this study, the local electrochemical activity of untreated and passivated (natural or chemical passivation) zinc specimens was observed during immersion in a 0.1-M NaCl solution. The localized anodic activity during the exposure, measured with the scanning vibrating electrode technique, was linked to zinc dissolution by the pitting corrosion mechanism. It was correlated to specific corrosion products characterized by Fourier transmission infrared (FTIR) microscopy. FTIR molecule maps were produced from individual pitting corrosion sites (100–200 µm in width). With argon ion beam milling and latest energy-dispersive X-ray spectroscopy (EDS) technology, element maps with a high spatial resolution (≪100 nm) were recorded from abrasion- and beam-sensitive corrosion products, showing a residual layer structure. This study demonstrates the capability of FTIR mapping, cross-section polishing, and state-of-the-art scanning electron microscopy imaging, and EDS element mapping to produce high-resolution elemental, molecular, and visual information about pitting corrosion mechanisms on a hot-dip galvanized steel sample.     

A 3D-QSAR Study of Analogs of (Z)-5-Decenyl Acetate, A Pheromone Component of the Turnip Moth, Agrotis segetum

The methodology of three-dimensional quantitative structure-activity relationships (3D-QSAR) has been employed to develop a quantitative model for the relationship between single-cell activities for a large set of analogs of (Z)-5-decenyl acetate, a pheromone component of the turnip moth, Agrotis segetum, and the structural characteristics of the analogs. The method of partial least squares (PLS) projections to latent structures has been used to delineate the relationships between measured activities and chemical structures. The training set includes 42 compounds, and a test set of seven molecules has been employed to assess the predictivity of the model. The model derived is able to calculate the activities of the seven test compounds with an average unsigned error of 0.3, close to the experimental error. Contour maps of regression-like coefficients from transformed PLS components display electronic and nonbonded features of high importance for the observed variation in the activities of compounds in the training set. The contours for the nonbonded (van der Waals) field support previous conclusions that the interaction between the pheromone component and its receptor is characterized by a high steric complementarity.     

Particles from fires—a screening of common materials found in buildings

Small combustion generated particles are known to have a negative impact on human health and on the environment. In spite of the huge amount of particles generated locally in a fire accident, few investigations have been made on the particles from such fires. In this article, 24 different materials or products, typically found in buildings have been exposed to burning conditions in order to examine their particle generating capacity. In addition, a carbon fibre based composite material was tested in order to investigate if asbestos‐resembling particles could be generated in a fire situation. The majority of the experiments were performed in the small‐scale cone calorimeter, and some further data were collected in intermediate scale (SBI) and full scale (room‐corner) tests. Additional testing of the composite material was made in a small‐scale tubular reactor. The amount of particles and particle size distributions were measured by the use of a low‐pressure impactor and particle aerodynamic diameter sizes from 30 nm to 10 μm were measured. The results from the project show that the yield of particles generated varied significantly between materials but that the shape of mass and number size distributions were very similar for all the materials tested. The maximum amount of particles was obtained from materials that did not burn well (e.g. flame retarded materials). Well‐burning materials, e.g. wood materials, tend to oxidize all available substances and thereby minimize the amount of particles in the smoke gas. It was found that asbestos‐resembling particles could be produced from under‐ventilated combustion of the composite material tested. Copyright © 2003 John Wiley & Sons, Ltd.     

Parental mosaicism and autosomal dominant mutations causing structural abnormalities of collagen I are frequent in families with osteogenesis imperfecta type III/IV

Protein-chemical and molecular studies were conducted on all osteogenesis imperfecta (OI) type III/IV patients referred to our hospital during the last 15 y. Of a total of 16 OI type III/IV patients studied, 15 patients were heterozygous for a mutation in one of the two genes coding for collagen I, COL1A1 or COL1A2. Cultured fibroblasts from these 15 patients produced both normal and abnormal collagen I molecules, pointing to a dominant-negative effect of the mutation. Nine mutations had not been described previously. Parental mosaicism was demonstrated in three families. In the 16th child the causative mutation was not found. In conclusion, OI type III/IV in most patients of Western European ancestry is caused by dominant mutations in the genes for collagen I, and recurrence of OI is caused in most cases by parental gonadal mosaicism.     

Cyberbullying on social networking sites: A literature review and future research directions

Cyberbullying on social networking sites is an emerging societal issue that has drawn significant scholarly attention. The purpose of this study is to consolidate the existing knowledge through a literature review and analysis. We first discuss the nature, research patterns, and theoretical foundations. We then develop an integrative framework based on social cognitive theory to synthesize what is known and identify what remains to be learned, with a focus on the triadic reciprocal relationships between perpetrators, victims, and bystanders. We discuss the key findings and highlight opportunities for future research. We conclude this paper by noting research contributions and limitations.