In this paper we demonstrate through-the-thickness imaging of barely visible impact damage in a two-dimensional woven, carbon fiber epoxy laminate using pulsed phase thermography (PPT). Specifically ...we calibrate the defect depth with blind frequency for the particular material system using a specimen with simulated defects in the form of polymer foam inclusions. The calibrated depth versus blind frequency relation is then applied to specimens with barely visible impact damage due to low-velocity impacts. The polymer foam reproduces the irregular boundaries and thin nature of the delaminations, but does not reproduce through-the-thickness variations. The extent of delamination at different depths was reconstructed as a function of depth for varying levels of impact energy. The extent of damage imaged using PPT corresponded well with visual observations and microscopy images.
The effects of compression, positive-grid growth, electrolyte stratification and uniformity across a series string of cells during deep-cycling service of valve-regulated lead/acid batteries are ...considered. Without adequate control, each of these will cause premature failure. Although substantial improvements in cycleability have been made in recent years, more understanding and optimization of these factors is necessary for further improvements. In particular, little is known about the changes in the properties of separators during service that effect compressive forces on the positive plate, and more knowledge is required on the influence of grid growth and on the influence of cell design on electrolyte stratification in valve-regulated batteries. In addition, the paper considers the progressive variation between cells in long series strings, which is a major cause of early failure of these designs.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The oxidation of the 1-thiochromanones 1-3 by dimethyldioxirane (DMD) produced the corresponding sulfoxides 4-6 or sulfones 7-9; their relative amounts depended on the amount of oxidant used. A low ...diastereoselectivity was observed in the sulfoxidation of the 2-substituted 1-thiochromanones 2 and 3, due to the small steric differentiation during the DMD attack. An unusual reactivity pattern was found in the DMD oxidation of the 1-thiochromones 10-12, in that the sulfoxides 13-15 were more reactive toward the electrophilic oxidizing agent than the corresponding sulfides. The observed anomaly may be explained in terms of transannular stabilization of the transition structure (TS) for the sulfone formation, promoted through favorable conformational effects in the sulfoxide. Higher sulfoxide/sulfone ratios were found in solvents of greater hydrogen bond donor capacity, which is in accordance with the postulated stabilizing effect.
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IJS, KILJ, NUK, PNG, UL, UM
Combining spatially explicit land cover data from remote-sensing and faunal data from field observations is increasingly applied for landscape-scale habitat and biodiversity assessments, but without ...modelling changes quantitatively over time. In a novel approach, we used a long-term time series including historical map data to predict the influence of one century of tropical forest change on keystone species or indicator groups in the Kakamega–Nandi forests, western Kenya. Four time steps of land cover data between 1912/13 and 2003, derived from Landsat satellite imagery, aerial photography and old topographic maps, formed the basis for extrapolating species abundance data on the army ant Dorylus wilverthi, the guild of ant-following birds and three habitat guilds of birds differing in forest dependency. To predict the species' spatio-temporal distribution, we combined spatially explicit geographical information system (GIS)-based modelling with statistical modelling, that is, ordinary least square (OLS) regression models for D. wilverthi and simultaneous autoregressive (SAR) models for ant-following birds. We directly related bird habitat guilds to five forest classes as distinguished in the land cover time series. Extrapolation results over time predict dramatic losses in abundance for D. wilverthi (56%), ant-following birds (58%) and forest bird individuals in general (47%) due to a forest loss of 31% and small-scale fragmentation within the past century. Extrapolations based on a scenario of further deforestation revealed the negative consequences of clearing and splitting up continuous forest into isolated patches, whereas a reforestation scenario suggests the positive impact of natural forest regrowth and indigenous-tree planting. This study demonstrates the high potential of integrating remotesensing and field-based faunal data for landscape-scale quantitative assessments over time. In addition, it shows the suitability of extrapolation studies for evaluating measures of forest conservation.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
498.
CARD15 and Crohn's disease Peters, KE; Cavanaugh, JA
Journal of gastroenterology and hepatology,
July 2004, Volume:
19, Issue:
7
Journal Article
Peer reviewed
Open access
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Inspired by the observation of a distributed time delay in the nonlinear response of an optical resonator, we investigate the effects of a similar delay on a noise-driven mechanical oscillator. For a ...delay time that is commensurate with the inverse dissipation rate, we find stable limit cycles. For longer delays, we discover a regime of chaotic dynamics associated with a double scroll attractor. We also analyze the effects of time delay on the spectrum and oscillation amplitude of the oscillator. Our results point to new opportunities for nonlinear energy harvesting, provided that a nonlinearity with distributed time delay can be implemented in mechanical systems.
Blood parasites are widespread in birds, several are pathogenic and may affect the fitness of their hosts, and their evolution. By reanalyzing recently published data I show that parts of the ...variation in prevalences of parasites in the blood of African rainforest birds and the occurrence of similar or same parasite haplotypes in rather unrelated birds are well understood when considering the ecological aspects of foraging of some of these birds. Specialized ant-following birds, which regularly follow the massive swarm raids of army ants and feed on insects flushed by the ants, have higher prevalences of nematode microfilariae (~10x), Trypanosoma (~10x), and Plasmodium parasites (~2x) and a much higher probability of infection with multiple parasites than other birds. Moreover, birds regularly attending army ant swarms share identical Trypanosoma haplotypes and show genetically similar microfilariae haplotypes. I conclude that ant-following increases the probability of birds to get infected with blood parasites and may facilitate the switch of a parasite species from one host species to another. The costs of higher parasite intensities involved when specializing on following ant swarms may have influenced the evolution of foraging behaviour in birds of African rainforests and may help to explain the relatively low number of specialized ant-following bird species on the African continent.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NMLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
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