Thermoluminescence of ZnO

The thermoluminescent behavior of polycrystalline ZnO was studied as a function of the temperature and partial pressure of oxygen of the heat treatment. Two peaks were observed, a broad peak at about 150°K and a well defined peak at 182°K. Analysis of the data obtained from the high temperature peak is consistent with the existence of a defect complex involving a copper impurity at 0.4 eV and a zinc vacancy 2.4 eV below the conduction band.     

Benzimidazole and Benzoxazole Zinc Chelators as Inhibitors of Metallo-β-Lactamase NDM-1

Bacterial expression of β-lactamases, which hydrolyze β-lactam antibiotics, contributes to the growing threat of antibacterial drug resistance. Metallo-β-lactamases, such as NDM-1, use catalytic zinc ions in their active sites and hydrolyze nearly all clinically available β-lactam antibiotics. Inhibitors of metallo-β-lactamases are urgently needed to overcome this resistance mechanism. Zinc-binding compounds are promising leads for inhibitor development, as many NDM-1 inhibitors contain zinc-binding pharmacophores. Here, we evaluated 13 chelating agents containing benzimidazole and benzoxazole scaffolds as NDM-1 inhibitors. Six of the compounds showed potent inhibitory activity with IC₅₀ values as low as 0.38 μM, and several compounds restored the meropenem susceptibility of NDM-1-expressing E. coli. Spectroscopic and docking studies suggest ternary complex formation as the mechanism of inhibition, making these compounds promising for development as NDM-1 inhibitors.     

Uniaxial nonlinear viscoelastic viscoplastic modeling of polypropylene

This paper presents the application of the Schapery viscoelastic and the Perzyna viscoplastic models to strain recovery data of polypropylene. In a previous study, the recovery of strain after monotonic uniaxial tensile loading was measured to gather information on the viscoelasticity and viscoplasticity. The viscoplastic strains from several load histories were determined and are used to calibrate the viscoplastic model. The parameters of the one-dimensional Schapery model are then found by nonlinear optimization using the strain recovery history. The prediction of stress relaxation and creep behavior is investigated.     

Platelet-endothelial cell adhesion molecule-1 (PECAM-1/CD31) tyrosine phosphorylation state changes during vasculogenesis in the murine conceptus

Vasculogenesis, the differentiation of mesodermal cells to angioblasts and the subsequent formation of blood islands and blood vessels by angioblasts in the conceptus, is a dynamic process modulated, in part, by cell-extracellular matrix and cell-cell interactions in the presence of a variety of growth factors and morphogens. In this report we demonstrate differential tyrosine phosphorylation of platelet-endothelial cell adhesion molecule-1 (PECAM-1) during the formation of blood islands and vessels from clusters of extraembryonic and embryonic angioblasts in the murine conceptus. In addition, we identify the phosphorylation of a particular tyrosine residue in the PECAM-1 cytoplasmic domain, Tyr686, which has the potential of mediating binding to Src homology 2 domain-containing proteins, affecting PECAM-1 cellular localization and endothelial cell migration.     

Evapotranspiration calculated from remote multispectral and ground station meteorological data

Evapotranspiration was evaluated by combining remotely sensed reflected solar radiation and surface temperatures with ground station meteorological data (incoming solar radiation, air temperature, windspeed, and vapor pressure) to calculate net radiation and sensible heat flux. Soil heat flux was estimated as a fraction of the net radiation. Instantaneous values of ET were calculated for 18 wheat plots for 44 cloudless days over a growing season. Three of the 18 plots contained lysimeters which provided data to compare against the instantaneous values. For the remaining plots, daily ET was estimated from the instantaneous data and compared with values calculated from soil water contents measured with a neutron moisture meter. For generally clear sky conditions, the comparisons indicated that ET could be adequately evaluated using a combination of remotely sensed and ground based meteorological data. The results suggest that ET maps of relatively large areas could be made using this method with data from airborne sensors. The extent of the area covered appears to be limited by the distance that air temperature and windspeed data can be extrapolated.     

Elevated pitting wear of injection molded polyetheretherketone (PEEK) rolls

The increased pitting wear of PEEK rolls applied as bearing elements in drawer guide rails was investigated. Similar to findings for PEEK gear wheels the increased pitting occurred only in the presence of lubricants. Simple assumptions found in literature to explain this effect for PEEK gear wheels could be disproved within this research. Moreover, high irreversible deformations during the rolling process of PEEK rolls which were observed in a previous study were shown to not influence the mechanical properties of the surface material significantly. Additionally, the chemical analysis of the tribological system with Raman spectroscopy excluded a chemical reason for the intensified pitting. A detailed microscopic analysis of unstressed PEEK rolls combined with microtome cuts of the surfaces showed distinct pre-cracks in the outermost surface region which were not visible to the naked eye. Assuming a crack growth mechanism that was strongly supported by the fluid pressure of grease enclosed in the surface pre-cracks the injection molding process was adapted in order to improve the surface quality of the PEEK rolls. By this way the fatigue lifetime of the latter was increased by a factor of 2–3 which was crucial for the practical application.     

Mode I delamination fatigue crack growth in unidirectional fiber reinforced composites: Development of a standardized test procedure

Selected mode I fatigue data from five different types of fiber-reinforced, polymer–matrix composites tested in two round robins organized by the American Society for Testing and Materials subcommittee D30.06 and European Structural Integrity Society Technical Committee 4, respectively, are analyzed and discussed. The focus is on experimental scatter (in-laboratory and inter-laboratory) and on schemes for quantitative data analysis. It is shown that in spite of considerable scatter different composites can be distinguished and, under certain assumptions, a relative ranking be established. Further, effects from limited experimental measurement resolution are noted and implications for the test procedure and use of the test data in design of composite structures discussed. For comparative purposes, a rough ranking of different composites is feasible with test data generated within 24 h per specimen in an industrial test environment.