Estimating the residual fatigue lifetimes of impact‐damaged composites using thermoelastic stress analysis

A new experimental method is presented for quantifying impact damage and estimating the remaining fatigue lifetime of impact damaged polymer matrix composite materials. The procedure is demonstrated using composites of glass fiber reinforced polyurethane produced by injection molding and structural reaction injection molding. Thermoelastic stress analysis (TSA) was used to quantify the stress concentration associated with impact‐damage in test samples of each composite. Following impact and TSA imaging, the samples were fatigued to failure over a range of stress amplitudes. The TSA‐derived stress concentration factors were used to determine a modified stress amplitude that collapsed the impact‐fatigue data onto a master stress‐life curve. This approach provides a quantitative measure of impact damage and a practical methodology for estimating the residual fatigue lifetime of impact; damaged composites.     

TBT causes regime shift in shallow lakes

Tributyltin (TBT) is an organotin compound used since the early 1960s as a biocide in boat antifouling paints. Its use has been linked to a host of negative effects in marine ecosystems including malformations and imposex in Mollusca and acute toxicity in many other aquatic animals. Yet, the consequences of TBT use in freshwaters are largely unknown. Here, for the first time we reveal that TBT may have caused hitherto unsuspected damage to freshwater ecosystems. Through an analysis of dated sediment cores collected from a system of recreationally boated, shallow lakes, we show that first evidence of TBT is associated with a dramatic loss of submerged vegetation and associated diverse animal communities. Cause and effect are difficult to unravel in our study. However, we hypothesize that TBT, through reducing populations of grazing organisms in lakes already affected by eutrophication, promoted the replacement of macrophytes by phytoplankton, ultimately leading to a regime shift in the ecosystem. Our findings may have parallels in freshwater ecosystems all over the world.     

Physico-chemical and mechanical properties of nanocomposites prepared using cellulose nanowhiskers and poly(lactic acid)

A range of nanocomposites were prepared using cellulose nanowhiskers (CNWs) and poly(lactic acid) (PLA) via a solvent casting process. Acid hydrolysis process was used to produce CNWs from bleached cotton. Structural morphology and surface topography of the CNWs and nanocomposites were examined using transmission (TEM) and scanning electron microscopy. TEM images revealed rod-like whiskers in the nano-scale region which were dispersed within the PLA matrix. The presence of the functional groups of CNWs and PLA were confirmed via FTIR analysis. Tensile tests were conducted on thin films and the nanocomposites containing 1 wt% CNWs showed a 34 and 31% increase in tensile strength and modulus, respectively, compared to pure PLA. The dynamic mechanical analysis showed that the tensile storage modulus also increased in the visco-elastic temperature region with increasing CNWs content in the nanocomposites. Thermogravimetric analysis showed that all the materials investigated were thermally stable from room temperature to 210 °C. A positive effect of CNWs on the crystal nucleation of PLA polymer in the nanocomposites was observed using differential scanning calorimetry and X-ray diffraction analysis. The degradation profiles of the nanocomposites in deionised water over 1 week revealed a mass loss of 1.5–5.6% at alternate temperatures (25, 37 and 50 °C) and at the same conditions the swelling ratio and water uptake were seen to increase with CNWs content in the nanocomposites, which was strongly influenced by the presence of crystalline CNWs.     

Occupant Tenability in Single Family Homes: Part II: Impact of Door Control,Vertical Ventilation and Water Application

This paper describes experimental investigations of fire service ventilation and suppression practices in full-scale residential structures, including a one-story, 112 m², 3 bedroom, 1 bathroom house with 8 total rooms and a two-story 297 m², 4 bedroom, 2.5 bathroom house with 12 total rooms. The two-story house featured a modern open floor plan, two-story great room and open foyer. Seventeen experiments were conducted varying fire location, ventilation locations, the size of ventilation openings and suppression techniques. The experimental series was designed to examine the impact of several different tactics on tenability: door control, vertical ventilation size, and exterior suppression. The results of these experiments examine potential occupant and firefighter tenability and provide knowledge the fire service can use to examine their vertical ventilation and exterior suppression standard operating procedures and training content. It was observed that door control performed better at controlling the thermal exposure to occupants than did fully opening the door. Additionally, the impact of increased vertical ventilation area was minimal, and only slightly reduced the thermal exposure to occupants in a few non-fire rooms. In the two-story structure, the non-fire rooms on the second floor consistently had larger thermal fractional effective rate (FER) values (approximately 2.5× the thermal risk to oocupants) than did the non-fire rooms on the first floor. Water application was also shown to reduce the thermal risk to occupants 60 s after water application 1/3rd the original values on second floor rooms of the two-storry structure and by at least 1/5th of the original values on the first floor rooms of both structures. Data also showed that the impact of front door ventilation on the toxic gases exposure was minimal, as the toxic gases FER actually increased after front door ventilation for several experiments. However, after vertical ventilation there was a 30% reduction in the toxic gases exposure rate in two of the one-story structure experiments.     

Effect of a varying effective thermal conductivity term on heat conduction through a physical model of a hydride bed

This paper investigates the effect of implementing a varying effective thermal conductivity term on heat transfer simulations within a metal hydride (MH) reactor. The work presented utilises a 1D transient heat transfer analysis comparing simulations either with a fixed effective thermal conductivity or a varying effective thermal conductivity. This builds on previously published work in the literature that has investigated varying effective thermal conductivity for metal hydrides at a single point. The results of these simulations are compared to experimental work for validation.     

Weak mismatch epitaxy and structural Feedback in graphene growth on copper foil

Graphene growth by low-pressure chemical vapor deposition on low cost copper foils shows great promise for large scale applications. It is known that the local crystallography of the foil influences the graphene growth rate. Here we find an epitaxial relationship between graphene and copper foil. Interfacial restructuring between graphene and copper drives the formation of (n10) facets on what is otherwise a mostly Cu(100) surface, and the facets in turn influence the graphene orientations from the onset of growth. Angle resolved photoemission shows that the electronic structure of the graphene is decoupled from the copper indicating a weak interaction between them. Despite this, two preferred orientations of graphene are found, ±8° from the Cu[010] direction, creating a non-uniform distribution of graphene grain boundary misorientation angles. Comparison with the model system of graphene growth on single crystal Cu(110) indicates that this orientational alignment is due to mismatch epitaxy. Despite the differences in symmetry the orientation of the graphene is defined by that of the copper. We expect these observations to not only have importance for controlling and understanding the growth process for graphene on copper, but also to have wider implications for the growth of two-dimensional materials on low cost metal substrates.      

Analysis of the Transient Single-Phase Thermal Performance of Micro-Channel Heat Sinks

The objective of this study is to examine the transient single-phase thermal behavior of micro-channel heat sinks during startup and over a short-duration power surge, and to investigate the effects of property and geometry parameters on this behavior. The transient analysis required the solution of three-dimensional conjugate heat transfer in the heat sink. These solutions were obtained numerically using the finite control-volume method and the numerical accuracy of the results was carefully assessed. Accuracy of the numerical model was validated by comparisons with available experimental data. The behavior of heat sinks with different values for the fin width, channel width, material thickness between the top of the channels and top of the heat sink, and different sink materials was examined during startup from a uniform initial temperature with a uniform input heat flux, followed by a short-duration power surge from the steady-state condition. It is concluded that increasing the fin width or channel width increases the steady-state and maximum transient temperatures in the solid, and that increasing the material thickness between the heat-sink channels and the chip or using a material with larger density and specific heat increases the transient period and lowers the maximum transient temperature in the solid during the power surge.     

Assessment of the validity of maturity metrics for predicting the volatile composition of Concord grape juice

Total soluble solids (TSS) are typically used as the sole metric for maturity of Concord grapes. However, the reliability of TSS in predicting the aroma composition of finished juice for grapes sourced from multiple sites has not been investigated. This study sought to determine the validity of TSS in predicting the aroma composition of the juice while also investigating other potentially useful indicators, including pH, titratable acidity (TA), and TSS:TA ratio. Grapes were harvested from 9 sites in the Lake Erie Concord Grape Belt and stratified from north to south and east to west. The key aroma compounds methyl anthranilate ("grapey") and trans-2-hexenal ("herbaceous") were quantified along with several other odorants. It was observed that while TSS was a robust predictor of monomeric anthocyanin content across sites, it was a poor predictor of aroma compounds in the finished juice. Conversely, pH, TA, and TSS:TA ratio were all significantly correlated with methyl anthranilate and trans-2-hexenal concentrations (P < 0.05) in samples equal to or exceeding 15 Brix, the industry minimum for grape maturity. These results indicate that parameters related to acidity are better predictors of aroma composition than TSS, which may aid in efforts to minimize herbaceous off-aromas and optimize the aroma composition of the finished juice.     

Wireless capsule endoscopy video segmentation using an unsupervised learning approach based on probabilistic latent semantic analysis with scale invariant features

Since wireless capsule endoscopy (WCE) is a novel technology for recording the videos of the digestive tract of a patient, the problem of segmenting the WCE video of the digestive tract into subvideos corresponding to the entrance, stomach, small intestine, and large intestine regions is not well addressed in the literature. A selected few papers addressing this problem follow supervised leaning approaches that presume availability of a large database of correctly labeled training samples. Considering the difficulties in procuring sizable WCE training data sets needed for achieving high classification accuracy, we introduce in this paper an unsupervised learning approach that employs Scale Invariant Feature Transform (SIFT) for extraction of local image features and the probabilistic latent semantic analysis (pLSA) model used in the linguistic content analysis for data clustering. Results of experimentation indicate that this method compares well in classification accuracy with the state-of-the-art supervised classification approaches to WCE video segmentation.     

Contraception in mice immunized with recombinant zona pellucida subunit 3 proteins correlates with Th2 responses and the levels of interleukin 4 expressed by CD4+ cells

The immune responses and contraceptive effect in mice were tested following immunization with purified recombinant zona pellucida (ZP) proteins produced using a vaccinia (v) virus T7 mammalian expression system. Female BALB/c and CBA mice were immunized with recombinant mouse (m) ZP3 (vmZP3) or pig (p) ZPC (vpZPC) using Freund's adjuvants and boosted three times. Fertility and mean litter size were significantly reduced in groups of BALB/c mice immunized with recombinant vmZP3 and vpZPC compared with controls treated with Freund's adjuvants alone. In CBA mice, fertility and mean litter size were significantly reduced in groups of animals immunized with vmZP3 but not with vpZPC compared with the controls. Most infertile animals treated with vmZP3 and a single infertile BALB/c mouse treated with vpZPC lacked mature follicles in the ovaries, whilst no abnormalities were detected in the remaining vpZPC treated, fertile vmZP3 treated and control mice. All mice (both fertile and infertile) immunized with vmZP3 and vpZPC produced IgG antibodies, but the levels of total IgG, IgG1 and IgG2a did not correlate with infertility. All BALB/c and CBA mice immunized with vmZP3 and vpZPC showed greater delayed type hypersensitivity responses in the footpads after challenge with their respective antigens than controls, but these did not differ between the fertile and infertile mice. There was, however, a significant correlation between infertility and the levels of the Type 2 T helper cell (Th2) cytokine interleukin 4 produced by CD4+ cells from vmZP3 immunized mice in response to stimulation with vmZP3 and this did not apply to the levels of the Type 1 T helper cell (Th1) cytokine interferon gamma or the general proliferation response. The results support the conclusion that induction of Th2 responses in individual mice determines whether infertility develops in response to immunization with zona pellucida proteins.