Home About us Contact
|
Home About us Contact | ||
|
|
||
Slight Shift (slight + shift)
Selected AbstractsStructural, electrical and optical properties of Ge implanted GaSe single crystals grown by Bridgman techniqueCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2006H. Karaa Abstract Structural, optical and electrical properties of Ge implanted GaSe single crystal have been studied by means of X-Ray Diffraction (XRD), temperature dependent conductivity and photoconductivity (PC) measurements for different annealing temperatures. It was observed that upon implanting GaSe with Ge and applying annealing process, the resistivity is reduced from 2.1 × 109 to 6.5 × 105 ,-cm. From the temperature dependent conductivities, the activation energies have been found to be 4, 34, and 314 meV for as-grown, 36 and 472 meV for as-implanted and 39 and 647 meV for implanted and annealed GaSe single crystals at 500°C. Calculated activation energies from the conductivity measurements indicated that the transport mechanisms are dominated by thermal excitation at different temperature intervals in the implanted and unimplanted samples. By measuring photoconductivity (PC) measurement as a function of temperature and illumination intensity, the relation between photocurrent (IPC) and illumination intensity (,) was studied and it was observed that the relation obeys the power law, IPC ,,n with n between 1 and 2, which is indication of behaving as a supralinear character and existing continuous distribution of localized states in the band gap. As a result of transmission measurements, it was observed that there is almost no considerable change in optical band gap of samples with increasing annealing temperatures for as-grown GaSe; however, a slight shift of optical band gap toward higher energies for Ge-implanted sample was observed with increasing annealing temperatures. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Unraveling Deterministic Mesoscopic Polarization Switching Mechanisms: Spatially Resolved Studies of a Tilt Grain Boundary in Bismuth FerriteADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Brian J. Rodriguez Abstract The deterministic mesoscopic mechanism of ferroelectric domain nucleation is probed at a single atomically-defined model defect: an artificially fabricated bicrystal grain boundary (GB) in an epitaxial bismuth ferrite film. Switching spectroscopy piezoresponse force microscopy (SS-PFM) is used to map the variation of local hysteresis loops at the GB and in its immediate vicinity. It is found that the the influence of the GB on nucleation results in a slight shift of the negative nucleation bias to larger voltages. The mesoscopic mechanisms of domain nucleation in the bulk and at the GB are studied in detail using phase-field modeling, elucidating the complex mechanisms governed by the interplay between ferroelectric and ferroelastic wall energies, depolarization fields, and interface charge. The combination of phase-field modeling and SS-PFM allows quantitative analysis of the mesoscopic mechanisms for polarization switching, and hence suggests a route for unraveling the mechanisms of polarization switching at a single defect level and ultimately optimizing materials properties through microstructure engineering. [source] Thermal and mechanical properties of uncrosslinked and chemically crosslinked polyethylene/ethylene vinyl acetate copolymer blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007H. A. Khonakdar Abstract Uncrosslinked and chemically crosslinked binary blends of low- and high-density polyethylene (PE), with ethylene vinyl acetate copolymer (EVA), were prepared by a melt-mixing process using 0,3 wt % tert -butyl cumyl peroxide (BCUP). The uncrosslinked blends revealed two distinct unchanged melting peaks corresponding to the individual components of the blends, but with a reduced overall degree of crystallinity. The crosslinking further reduced crystallinity, but enhanced compatibility between EVA and polyethylene, with LDPE being more compatible than HDPE. Blended with 20 wt % EVA, the EVA melting peak was almost disappeared after the addition of BCUP, and only the corresponding PE melting point was observed at a lowered temperature. But blended with 40% EVA, two peaks still existed with a slight shift toward lower temperatures. Changes of mechanical properties with blending ratio, crosslinking, and temperature had been dominated by the extent of crystallinity, crosslinking degree, and morphology of the blend. A good correlation was observed between elongation-at-break and morphological properties. The blends with higher level of compatibility showed less deviation from the additive rule of mixtures. The deviation became more pronounced for HDPE/EVA blends in the phase inversion region, while an opposite trend was observed for LDPE/EVA blends with co-continuous morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3261,3270, 2007 [source] Commercial taxane formulations induce stomatocytosis and increase blood viscosityBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2001Michael Mark Taxanes are antineoplastic drugs which have cardiovascular side effects of unknown mechanism. We investigated their influence on blood viscosity and erythrocyte morphology. Whole blood was incubated in vitro with increasing concentrations of Taxol®, Taxotere®, paclitaxel (0 , 100 ,M) and the vehicles Cremophor-EL and Tween 80 (0 , 5% vol) for 1 h at 37°C. Plasma and whole blood viscosity (Haematocrit 45%) were measured and erythrocyte morphology was assessed on glutaraldehyde-fixed cells. The same investigations were performed in seven patients before and after a Taxol®-infusion. Taxol® and Taxotere® induced a dose- and time-dependent stomatocytic shape transformation of erythrocytes. Paclitaxel alone had no effect, but the vehicles cremophor-EL and Tween 80, used in Taxol® and Taxotere®, respectively, induced a comparable degree of stomatocytosis. This suggests a preferential intercalation of these substances into the inner hemileaflet of the membrane lipid bilayer. Associated with this shape change a dose-dependent increase in plasma and whole blood viscosity was observed. Neither shape nor viscosity changes were reversible upon removal of the agents. After the infusion of 130 , 300 mg Taxol® in patients a slight shift towards stomatocytosis and an increase in whole blood viscosity at high shear rate from 5.09±0.30 to 5.44±0.38 mPa.s (P<0.05) were confirmed. Commercial taxane drug formulations induce stomatocytosis and increase blood viscosity, which is due to their formulation vehicles. These findings may contribute to the understanding of the cardiovascular side effects of these drugs. British Journal of Pharmacology (2001) 134, 1207,1214; doi:10.1038/sj.bjp.0704387 [source] Enduring, ephemeral and emerging issues in public administration in Canada: Trends in Canadian Public Administration over fifty years (1958,2007)CANADIAN PUBLIC ADMINISTRATION/ADMINISTRATION PUBLIQUE DU CANADA, Issue 4 2007Barbara Wake Carroll It is the 50th anniversary issue of the Journal, and it is the last issue to be published by the Institute of Public Administration of Canada. For this issue, we have not produced a "special issue" in the sense of commissioning particular articles. Instead, we have brought together a number of articles that were already in the "pipeline" but that the editors thought made a particular contribution to public administration in Canada. This introductory article, or editor's review, is a retrospective analysis of the content of the Journal. It would appear that while there has been a slight shift towards public policy and a greater concern with provincial and local administration, cpa has maintained an enduring interest in its core areas of administrative theory and political and legal institutions. The content is also compared with findings of the content of other journals and also other analyses of cpa. This review is followed by commentaries by former editors and associate editors on their experiences with the Journal. [source] The Naturalness versus Wildness Debate: Ambiguity, Inconsistency, and Unattainable ObjectivityRESTORATION ECOLOGY, Issue 1 2007Ben Ridder Abstract The naturalness versus wildness debate has gained some prominence in recent years and has seen considerable discussion of issues akin to those that have generated such tension between restorationists and preservationists. This debate is hampered by the terms in which it is framed. The primary meaning of both naturalness and wildness relates to the description of processes or behavior that lack human intervention. This enables human activities and artifacts (such as childbirth, food, and medicine) to be rated according to naturalness. However, when the terms are applied to the description of species and ecosystems, process-oriented definitions are forgotten in favor of historical benchmarks. This can result in serious inconsistencies between those who adhere to the different interpretations, exemplified by the tendency of conservationists to view "naturalness" as being consistent with human intervention in natural processes. The choice of one or the other interpretation is motivated by whether one prioritizes the conservation of biodiversity or minimizing human intervention. There have been claims that naturalness provides an objective measure for assessing biodiversity and calls for value-laden terms to be avoided. Yet, the values are central, and the best that can be hoped for is that the debate be framed using terms that are more indicative of these underlying values. It is suggested here that naturalness versus wildness be recast as "protecting biodiversity" versus "respect for nature's autonomy." Not only do these terms avoid the ambiguities of their forebears but they also expose the debate as the result of slight shifts in value priorities rather than fundamentally opposed worldviews. [source] | ||||||||||