bluuebunny/crossref_metadata_2025 huggingface dataset:
Class, gender and chance: the social division of welfare and occupational pensions in the United Kingdom
Authors: MEYER TRAUTE , BRIDGEN PAUL
Published: March 2008

The social division of welfare literature emphasises the extent to which occupational-pension provision is distributed on the basis of class and gender. As most previous commentators have at least implicitly recognised, however, a significant proportion of less advantaged people are covered. This paper argues that the patterns of access and their distributional consequences must be considered more systematically, and that in this context, the diversity of employers' pension schemes are investigated. When this is done, it emerges that in the United Kingdom, the spread of occupational provision beyond the most privileged workers means that some vulnerable individuals avoid poverty in retirement. At the same time, however, the main determinant of which less advantaged people are covered and which not is chance. While class and gender are important predictors of who receives occupational pensions, access for the disadvantaged arises mainly as an accident of an employment decision made for reasons unrelated to savings or pensions criteria. This paper argues that the implication is that unsustainable justice-based arguments are currently used by policy makers to sanction the current distribution of UK pension incomes. The paper concludes by discussing the implications of the findings for the appropriateness of recent UK policy proposals and for international debates about pension reform.
Receptive-field structure of optic flow responsive Purkinje cells in the vestibulocerebellum of pigeons
Authors: WINSHIP IAN R. , WYLIE DOUGLAS R.W.
Published: March 2008

Neurons sensitive to optic flow patterns have been recorded in the the olivo-vestibulocerebellar pathway and extrastriate visual cortical areas in vertebrates, and in the visual neuropile of invertebrates. The complex spike activity (CSA) of Purkinje cells in the vestibulocerebellum (VbC) responds best to patterns of optic flow that result from either self-rotation or self-translation. Previous studies have suggested that these neurons have a receptive-field (RF) structure that “approximates” the preferred optic flowfield with a “bipartite” organization. Contrasting this, studies in invertebrate species indicate that optic flow sensitive neurons are precisely tuned to their preferred flowfield, such that the local motion sensitivities and local preferred directions within their RFs precisely match the local motion in that region of the preferred flowfield. In this study, CSA in the VbC of pigeons was recorded in response to a set of complex computer-generated optic flow stimuli, similar to those used in previous studies of optic flow neurons in primate extrastriate visual cortex, to test whether the receptive field was of a precise or bipartite organization. We found that these RFs were not precisely tuned to optic flow patterns. Rather, we conclude that these neurons have a bipartite RF structure that approximates the preferred optic flowfield by pooling motion subunits of only a few different direction preferences.
Expansion of visual receptive fields in experimental glaucoma
Authors: KING WAYNE MICHAEL , SARUP VIMAL , SAUVÉ YVES , MORELAND COLLEEN M. , CARPENTER DAVID O. , SHARMA S.C.
Published: March 2008

Glaucoma is a major cause of blindness and is characterized by death
of retinal ganglion cells. In a rat model of glaucoma in which intraocular
pressure is raised by cautery of episcleral veins, the somata and
dendritic arbors of surviving retinal ganglion cells expand. To assess
physiological consequences of this change, we have measured visual
receptive-field size in a primary retinal target, the superior colliculus.
Using multiunit recording, receptive-field sizes were measured for
glaucomatous eyes and compared to both those measured for contralateral
control eyes and to homolateral eyes of unoperated animals. Episcleral
vein occlusion increased intraocular pressure. This was accompanied by a
significant increase in receptive-field size across the superior
colliculus. The expansion of receptive fields was proportional to both
degree and duration of the increase of intraocular pressure. We suggest
that this increase in the size of receptive fields of glaucomatous eyes
may be related to the increase in the size of dendritic arbors of the
surviving ganglion cells in retina.
Distribution and origin of patterned ground on Mullins Valley debris-covered glacier, Antarctica: the roles of ice flow and sublimation
Authors: Levy Joseph S. , Marchant David R. , Head James W.
Published: March 2008

We map polygonally patterned ground formed in sublimation tills that overlie debris-covered glaciers in Mullins Valley and central Beacon Valley, in southern Victoria Land, Antarctica, and distinguish five morphological zones. Where the Mullins Valley debris-covered glacier debouches into Beacon Valley, polygonal patterning transitions from radial (orthogonal) intersections to non-oriented (hexagonal) intersections, providing a time-series of polygon evolution within a single microclimate. We offer the following model for polygon formation and evolution in the Mullins Valley system. Near-vertical cracks that ultimately outline polygons are produced by thermal contraction in the glacier ice. Some of these cracks may initially be oriented radial to maximum surface velocities by pre-existing structural stresses and material weaknesses in the glacier ice. In areas of relatively rapid flow, polygons are oriented down-valley forming an overall fan pattern radial to maximum ice velocity. As glacier flow moves the cracks down-valley, minor variations in flow rate deform polygons, giving rise to deformed radial polygons. Non-oriented (largely hexagonal) polygons commonly form in regions of stagnant and/or near-stagnant ice. We propose that orientation and morphology of contraction-crack polygons in sublimation tills can thus be used as an indicator of rates of subsurface ice flow.
Calving giant icebergs: old principles, new applications
Authors: Kenneally J.P. , Hughes T.
Published: March 2008

Earth-orbiting satellites can now monitor calving of large icebergs from ice shelves bordering the marine West Antarctic Ice Sheet, and recent calving events have stimulated interest in calving mechanisms. To advance this interest pioneering work in brittle and ductile fracture mechanics is reviewed, leading to a new application to calving of giant icebergs from Antarctic ice shelves. The aim is to view iceberg calving as more than terminal events for Antarctic ice when glaciologists lose interest. Instead calving launches Antarctic ice into the larger dynamic system of Earth's climate machine. This encourages a holistic approach to glaciology.
On the atmosphere for astronomers above Dome C, Antarctica
Authors: Sadibekova T. , Fossat E. , Genthon C. , Krinner G. , Aristidi E. , Agabi K. , Azouit M.
Published: March 2008

This paper describes a comparison between balloon radio-soundings made in summer at the Concordia station, Dome C, Antarctica and coincident model-based meteorological analyses. The comparison allows the assessment of the reliability of the analyses in summer. This allows the use of the winter analyses within an estimated range of uncertainty, while the first in situ measurements are just becoming available. The astronomical interest is to produce an estimate of atmospheric turbulence during the Antarctic winter at this very promising site. For this work the 6-hourly ECMWF operational analyses were used, concurrently with the data obtained in situ by the radio-sounding made at Concordia with standard meteorological balloons and sondes during four summer seasons (November–January), from December 2000 to the end of January 2004.
NEW ORLEANS IS NOT THE EXCEPTION: Re-politicizing the Study of Racial Inequality
Authors: Frymer Paul , Strolovitch Dara Z. , Warren Dorian T.
Published: March 2008

Although political science provides many useful tools for analyzing the effects of natural and social catastrophes such as Hurricane Katrina and its aftermath, the scenes of devastation and inequality in New Orleans suggest an urgent need to adjust our lenses and reorient our research in ways that will help us to uncover and unpack the roots of this national travesty. Treated merely as exceptions to the “normal” functioning of society, dramatic events such as Katrina ought instead to serve as crucial reminders to scholars and the public that the quest for racial equality is only a work in progress. New Orleans, we argue, was not exceptional; it was the product of broader and very typical elements of American democracy—its ideology, attitudes, and institutions. At the dawn of the centuryafter“the century of the color-line,” the hurricane and its aftermath highlight salient features of inequality in the United States that demand broader inquiry and that should be incorporated into the analytic frameworks through which American politics is commonly studied and understood. To this end, we suggest several ways in which the study of racial and other forms of inequality might inform the study of U.S. politics writ large, as well as offer a few ideas about ways in which the study of race might be re-politicized. To bring race back into the study of politics, we argue for greater attention to the ways that race intersects with other forms of inequality, greater attention to political institutions as they embody and reproduce these inequalities, and a return to the study of power, particularly its role in the maintenance of ascriptive hierarchies.
Rainwater chemistry at a high‐altitude station, Mt. Lulin, Taiwan: Comparison with a background station, Mt. Fuji
Authors: Wai Ka Ming , Lin Neng‐Huei , Wang Sheng‐Hsiang , Dokiya Yukiko
Published: March 2008

Samples of rainwater were collected at a high‐altitude site in east Asia between April 2003 and May 2005. The volume weighted mean pH value for the whole sampling period was 5.12, approaching that of typical natural water. Non‐sea‐salt (nss) SO42− and NH4+ were the most abundant anion and cation, respectively, both existing mostly in the form of (NH4)2SO4. Chloride was excessive in most of the samples. The signature of biomass burning in south and Southeast Asia was evident in the Mt. Lulin samples. Concentrations of chemical species were found to be elevated in the spring months, owing to the emissions from south/Southeast Asia and peak biomass burning activities and frequent dust storms (in the Indian Thar Desert). In the summer and fall seasons our samples are mainly influenced by marine air masses. The episodic species concentrations measured at the summit of Mt. Fuji during the spring were due to the influence of volcanic emissions from Miyake‐Jima. Tropical cyclones (TC) over the western Pacific region and deep convections play important roles in the transport of boundary layer pollutants to the free troposphere, although their influence is not frequently detected at Mt. Lulin and Mt. Fuji. The rainwater chemistry at Mt. Lulin and Mt. Fuji were examined together with the aerosol chemistry obtained from the TRACE‐P and ACE‐Asia campaigns. The analysis of the Mt. Lulin data set demonstrates its background characteristics of the rainwater chemistry in east Asia.
Sediment load and floodplain deposition rates: Comparison of the Fly and Strickland rivers, Papua New Guinea
Authors: Swanson Kathleen M. , Watson Elizabeth , Aalto Rolf , Lauer J. Wesley , Bera Marie T. , Marshall Andrew , Taylor Mark P. , Apte Simon C. , Dietrich William E.
Published: March 2008

Rates of aggradation and infilling of accommodation space along lowland channels in response to postglacial sea level rise should depend on sediment supply. The Strickland and Fly rivers join at just 6 m above sea level and have experienced the same Holocene sea level rise. Historically, the Strickland has carried about 7 times the sediment load and 1.4 times the water discharge as the Fly. Therefore we hypothesize that the lowland Strickland floodplain should be more developed and consequently should presently be capturing proportionately less sediment than the floodplain of the lowland Fly River. We use mine‐derived elevated Pb and Ag concentrations in 111 shallow (<1 m) floodplain cores collected in 2003 to determine deposition rates across the lower Strickland floodplain. Sediment deposition rates decrease across the floodplain with distance from the channel bank, and the average rate of deposition is 1.4 cm/a over the first 1 km. Overbank deposition along the lowland sandbedded Strickland results in ∼13% loss of the total load, ∼0.05%/km of channel length of the main stem. Deposition rates over the first 1 km from the channel bank on the Strickland are about 10 times those on the Fly (for estimated natural sediment loads); however, the proportional loss per channel length on the Strickland is less than that on the Fly (0.09%/km of main stem channel length) because of an extensive network of tributary and tie channels that convey sediment to the floodplain on the Fly. Furthermore, the lateral migration of the Strickland channel is ∼5 times that on the Fly, such that most overbank deposits on the Strickland are returned to the channel, causing the net loss of sediment to the floodplain to be small. We conclude that the Strickland River, which has a much higher overbank deposition rate than the Fly River as a function of distance from channel bank, nonetheless has significantly less net accumulation than the Fly because (1) a large proportion of the sediment load is conveyed up tributaries and tie channels on the Fly, and (2) lateral migration (which presumably results from the higher load) on the Strickland sweeps sediment back into the channel. Hence our field observations support our initial hypothesis, though the primary reason for this is because of active lateral migration rather than low overbank deposition rates.
238U‐230Th‐226Ra‐210Pb‐210Po, 232Th‐228Ra, and 235U‐231Pa constraints on the ages and petrogenesis of Vailulu'u and Malumalu Lavas, Samoa
Authors: Sims Kenneth W. W. , Hart S. R. , Reagan M. K. , Blusztajn J. , Staudigel H. , Sohn R. A. , Layne G. D. , Ball L. A. , Andrews J.
Published: March 2008

We report 238U‐230Th‐226Ra‐210Pb‐210Po, 232Th‐228Ra and 235U‐231Pa measurements for a suite of 14 geologically and geochemically well‐characterized basaltic samples from the Samoan volcanoes Vailulu'u, Malumalu, and Savai'i. Maximum eruption ages based on the presence of parent‐daughter disequilibria indicate that Vailulu'u is magmatically productive with young lavas (<8 Ka) resurfacing both its summit crater and lower flanks. 210Pb and 210Po measurements indicate that several flows have erupted within its summit crater in the past 100 years, with the newest observed flow being erupted in November of 2004. For lavas which have eruption ages that are demonstrably young, relative to the half‐lives of 230Th, 231Pa, and 226Ra, we interpret their 238U ‐230Th, 235U‐231Pa and 230Th ‐ 226Ra disequilibria in terms of the magmatic processes occurring beneath the Samoan Islands. (230Th/238U) > 1 indicates that garnet is required as a residual phase in the magma sources for all these lavas. The large range of (238U/232Th) and (230Th/232Th) is attributed to long‐term source variation. The Samoan basalts are all alkaline basalts and show significant 230Th and 231Pa excesses but limited variability, indicating that they have been derived by small but similar extents of melting. Their (230Th/238U), (231Pa/235U) and Sm/Nd fractionation are consistent with correlations among other ocean island basalt suites (particularly Hawaii) which show that (230Th/238U) and (231Pa/235U) of many OIBS can be explained by simple time‐independent models. Interpretation of the 226Ra data requires time‐dependent melting models. Both chromatographic porous flow and dynamic melting of a garnet peridotite source can adequately explain the combined U‐Th‐Ra and U‐Pa data for these Samoan basalts. Several young samples from the Vailulu'u summit crater also exhibit significant 210Pb deficits that reflect either shallow magmatic processes or continuous magma degassing. In both cases, decadal residence times are inferred from these 210Pb deficits. The young coeval volcanism on Malumalu and Vailulu'u suggests the Samoa hot spot is currently migrating to the northeast due to dynamic interaction with the Tonga slab.
Aerosol and trace‐gas measurements in the Darwin area during the wet season
Authors: Allen G. , Vaughan G. , Bower K. N. , Williams P. I. , Crosier J. , Flynn M. , Connolly P. , Hamilton J. F. , Lee J. D. , Saxton J. E. , Watson N. M. , Gallagher M. , Coe H. , Allan J. , Choularton T. W. , Lewis A. C.
Published: March 2008

The composition of the planetary boundary layer in regions of deep tropical convection has a profound impact on the Tropical Tropopause Layer (TTL). The Aerosol and Chemical Transport in tropIcal conVEction (ACTIVE) aircraft campaign was conducted from November 2005 to February 2006 from Darwin, Australia, to characterize the influence of both monsoonal and localized land‐based deep convection on the composition of the TTL. This paper summarizes the composition of the potential inflow to such convection in terms of aerosol particle size and composition, carbon monoxide, and ozone, as measured in the lowest 4 km of the atmosphere by the NERC Dornier‐228 aircraft during 28 flights in different meteorological regimes over the course of ACTIVE. Six contrasting periods are identified in the boundary layer background as a result of the prevailing meteorology and sources of pollution. The campaign began with a relatively polluted and variable biomass burning season in November, followed by a transition to the monsoon season through December with much less burning. A clean maritime flow dominated the wet‐active, and dry‐inactive, monsoon period in January; it was followed by a monsoon break period in February, with a return to continental flow and a more premonsoon background state. Deep convective systems, capable of transporting boundary layer air to the TTL, were observed daily outside of the monsoon periods. The chemical composition of submicron aerosols in the premonsoon periods was dominated by a mix of fresh and aged organic material with significant black carbon, well‐correlated with carbon monoxide indicating a common burning source, while marine aerosol during the monsoon changed markedly between the wet and dry phases. High concentrations of coarse‐mode aerosols were also observed in the monsoon: the clean, marine air masses and high surface winds imply that sea salt may be the dominant aerosol type under these conditions. The climatology presented here will provide a valuable data set for model simulation of chemical and aerosol transport by deep convection in the Darwin region.
Changes in daily climate extremes in the eastern and central Tibetan Plateau during 1961–2005
Authors: You Qinglong , Kang Shichang , Aguilar Enric , Yan Yuping
Published: March 2008

Changes in indices of climate extremes are analyzed on the basis of daily maximum and minimum surface air temperature and precipitation at 71 meteorological stations with elevation above 2000 m above sea level in the eastern and central Tibetan Plateau (TP) during 1961–2005. Twelve indices of extreme temperature and nine indices of extreme precipitation are examined. Temperature extremes show patterns consistent with warming during the studied period, with a large proportion of stations showing statistically significant trends for all temperature indices. Stations in the northwestern, southwestern, and southeastern TP have larger trend magnitudes. The regional occurrence of extreme cold days and nights has decreased by −0.85 and −2.38 d/decade, respectively. Over the same period, the occurrence of extreme warm days and nights has increased by 1.26 and 2.54 d/decade, respectively. The number of frost days and ice days shows statistically significant decreasing at the rate of −4.32 and −2.46 d/decade, respectively. The length of growing season has statistically increased by 4.25 d/decade. The diurnal temperature range exhibits a statistically decreasing trend at a rate of −0.20°C per decade. The extreme temperature indices also show statistically significant increasing trends, with larger values for the index describing variations in the lowest minimum temperature. In general, warming trends in minimum temperature indices are of greater magnitude than those for maximum temperature. Most precipitation indices exhibit increasing trends in the southern and northern TP and show decreasing trends in the central TP. On average, regional annual total precipitation, heavy precipitation days, maximum 1‐day precipitation, average wet days precipitation, and total precipitation on extreme wet days show nonsignificant increases. Decreasing trends are found for maximum 5‐day precipitation, consecutive wet days, and consecutive dry days, but only the last is statistically significant.
Predictions of the electrical conductivity and charging of the cloud particles in Jupiter's atmosphere
Authors: Whitten R. C. , Borucki W. J. , O'Brien K. , Tripathi S. N.
Published: March 2008

The electrical conductivity and electrical charge on cloud particles (composed of ammonia, ammonium hydrosulfide, and water) in the atmosphere of Jupiter are computed for pressures between 5.5 and 0.1 bars. The source of ionization is galactic cosmic rays (GCR). The distribution of charge among the various reservoirs is a function of altitude and the total area of the aerosol particles. For pressures below 4 bars, the electrons are scavenged efficiently by the cloud particles, decreasing the electron‐ion recombination rate and resulting in increased positive ion abundance over that in the absence of the particles. For the upper regions of each cloud layer, the area of the aerosols and the large diffusion rate of the electrons cause most aerosol particles to be negatively charged. Near the bases of the cloud layers, the larger total area of the aerosols causes most of the charge, positive and negative, to reside on particles. Where clouds are present, the reduction of the electron conductivity ranges from a factor of 30 at 0.1 bar to 104 at 4 bars. At pressures near 1 bar and 4 bars, the positive ion conductivity increases by a factor of 10 over that expected for the clear atmosphere. A parametric study of negative ions shows that they are likely to be insignificant. For altitudes below the 0.3‐bar level the predicted positive and negative conductivities are well below the detection limit of the relaxation and mutual impedance instruments such as those employed on the Huygens entry probe.
Fibrillin–integrin interactions in health and disease
Authors: Jovanović Jelena , Iqbal Sarah , Jensen Sacha , Mardon Helen , Handford Penny
Published: March 2008

Human fibrillin-1 is the major structural protein of extracellular matrix 10–12 nm microfibrils. It has a disulfide-rich modular organization which consists primarily of cbEGF (Ca2+-binding epidermal growth factor-like) domains and TB (transforming growth factor β-binding protein-like) domains. TB4 contains an RGD (Arg-Gly-Asp) integrin-binding motif. The atomic structure of this region has been solved by X-ray crystallography and shows the TB4 and flanking cbEGF domains to be arranged as a tetragonal pyramid with N- and C-termini exposed at opposite ends of the fragment. The RGD integrin-binding motif is located within a flexible loop. We have used a variety of biophysical, biochemical and cell biology methods to investigate the molecular properties of integrin–fibrillin-1 interactions and have demonstrated that recombinant fibrillin-1 domain fragments mediate binding to integrins αVβ3, α5β1 and αVβ6. Integrin αVβ3 is a high-affinity fibrillin-1 receptor (Kd ∼40 nM), whereas integrins αVβ6 and α5β1 show moderate-affinity (Kd ∼450 nM) and low-affinity (Kd >1 μM) binding respectively. Different patterns of α5β1 distribution are seen when human keratinocytes and fibroblasts are plated on to fibrillin domain fragments compared with those seen for fibronectin, suggesting that fibrillin may cause a lesser degree or different type of intracellular signalling. A number of disease-causing mutations which affect the TB4 domain have been identified. These are being investigated for their effects on integrin binding and/or changes in intramolecular structure.
NMR implementation of adiabatic SAT algorithm using strongly modulated pulses
Authors: Mitra Avik , Mahesh T. S. , Kumar Anil
Published: March 2008

NMR implementation of adiabatic algorithms face severe problems in homonuclear spin systems since the qubit selective pulses are long and during this period, evolution under the Hamiltonian and decoherence cause errors. The decoherence destroys the answer as it causes the final state to evolve to mixed state and in homonuclear systems, evolution under the internal Hamiltonian causes phase errors preventing the initial state to converge to the solution state. The resolution of these issues is necessary before one can proceed to implement an adiabatic algorithm in a large system where homonuclear coupled spins will become a necessity. In the present work, we demonstrate that by using “strongly modulated pulses” (SMPs) for the creation of interpolating Hamiltonian, one can circumvent both the problems and successfully implement the adiabatic SAT algorithm in a homonuclear three qubit system. This work also demonstrates that the SMPs tremendously reduce the time taken for the implementation of the algorithm, can overcome problems associated with decoherence, and will be the modality in future implementation of quantum information processing by NMR.
Temperature dependences of mechanisms responsible for the water-vapor continuum absorption. I. Far wings of allowed lines
Authors: Ma Q. , Tipping R. H. , Leforestier C.
Published: March 2008

It is well known that the water-vapor continuum plays an important role in the radiative balance in the Earth’s atmosphere. This was first discovered by Elsasser almost 70years ago, and since that time there has been a large body of work, both experimental and theoretical, on this topic. It has been experimentally shown that for ambient atmospheric conditions, the continuum absorption scales quadratically with the H2O number density and has a strong, negative temperature dependence (T dependence). Over the years, there have been three different theoretical mechanisms postulated: Far wings of allowed transitions, water dimers, and collision-induced absorption. Despite the improvements in experimental data, at present there is no consensus on which mechanism is primarily responsible for the absorption. The first mechanism proposed was the accumulation of the far-wing absorption of the strong allowed transitions. Later, absorption by water dimers was proposed and this mechanism provides a qualitative explanation for the strong, negative T dependence. Recently, some atmospheric modelers have proposed that collision-induced absorption is one of the major contributors. However, based on improvements in the theoretical calculation of accurate far-wing line shapes, ab initio dimer calculations, and theoretical collision-induced absorptions, it is now generally accepted that the dominant mechanism for the absorption in the infrared (IR) windows is that due to the far wings. Whether this is true for other spectral regions is not presently established. Although all these three mechanisms have a negative T dependence, their T dependences will be characterized by individual features. To analyze the characteristics of the latter will enable one to assess their roles with more certainty. In this paper, we present a detailed study of the T dependence of the far-wing absorption mechanism. We will then compare our theoretical calculations with the most recent and accurate experimental data in the IR windows. The results of our calculations are found to agree very well with measurements in the 800–1200cm−1 region. We conclude from this work that the T dependence in the IR window region predicted by the far-wing theory is negative and moderately strong. Its pattern is not simple and it could vary significantly as the frequency of interest varies.
Local structure of Pt and Pd ions in Ce1−xTixO2: X-ray diffraction, x-ray photoelectron spectroscopy, and extended x-ray absorption fine structure
Authors: Baidya Tinku , Priolkar K. R. , Sarode P. R. , Hegde M. S. , Asakura K. , Tateno G. , Koike Y.
Published: March 2008

Ce 1 − x − y Ti x Pt y O 2 − δ (x=0.15; y=0.01) and Ce1−x−yTixPdyO2−δ (x=0.25; y=0.02 and 0.05) are found to be good CO oxidation catalysts [T. Baidya et al., J. Phys. Chem. B 110, 5262 (2006); T. Baidya et al., J. Phys. Chem. C 111, 830 (2007)]. A detailed structural study of these compounds has been carried out by extended x-ray absorption fine structure along with x-ray diffraction and x-ray photoelectron spectroscopy. The gross cubic fluorite structure of CeO2 is retained in the mixed oxides. Oxide ion sublattice around Ti as well as Pt and Pd ions is destabilized in the solid solution. Instead of ideal eight coordinations, Ti, Pd, and Pt ions have 4+3, 4+3, and 3+4 coordinations creating long and short bonds. The long Ti–O, Pd–O, and Pt–O bonds are ∼2.47Å (2.63Å for Pt–O) which are much higher than average Ce–O bonds of 2.34Å.
Temperature dependent reflectivity and anisotropic magnetization reversal in magnetically doped quasi-two-dimensional charge density wave alloys A0.01NbSe2 (A=Cr,Mn,Fe)
Authors: Isakovic A. F. , Smith R. , Evans-Lutterodt K. , Thorne R. E. , Carr G. L.
Published: March 2008

We report on a pronounced magnetic anisotropy of magnetically doped quasi-two-dimensional charge density wave (CDW) NbSe2 at doping concentrations near 1%, and on temperature dependent reflectance, both phenomena above NbSe2 superconducting transition (7.2K). Unusual spikes in magnetization reversal are noticeable near 20K, below the CDW transition (33K), and disappear as temperature nears the superconducting transition. In the far infrared region of the spectrum, we find two sudden jumps in reflectivity, one near the CDW transition, the other near 18K. This second increase in reflectivity combined with unusual magnetization reversal is potentially indicative of an additional order parameter in the system, possibly a mixed state of the CDW and a spin density wave, or, alternatively, it represents a far infrared signature of dramatically altered quasiparticles scattering near 20K.
Photoisomerization of cyanine derivatives in 1-butyl-3-methylimidazolium hexafluorophosphate and aqueous glycerol: Influence of specific interactions
Authors: Mali K. S. , Dutt G. B. , Mukherjee T.
Published: March 2008

Photoisomerization of two cyanine derivatives, 3,3′-diethyloxadicarbocyanine iodide (DODCI) and merocyanine 540 (MC 540), has been investigated in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate and aqueous glycerol (93wt% glycerol +7wt% water) by measuring fluorescence lifetimes and quantum yields. The aim of this work is to understand how the rates of photoisomerization of DODCI and MC 540 are influenced by specific solute-solvent interactions besides the viscosity of the medium. For DODCI, it has been observed that the nonradiative rate constants, which represent the rates of photoisomerization, are almost identical in the ionic liquid and aqueous glycerol at given temperature, indicating that viscosity is the sole parameter that governs the rate of photoisomerization. In contrast, the photoisomerization rate constants of MC 540 have been found to be a factor of 2 higher in aqueous glycerol compared to the ionic liquid. The observed behavior is due to the zwitterionic character of MC 540, a consequence of which, the twisted state gets stabilized by the solute-solvent hydrogen bonding interactions in aqueous glycerol, thus lowering the barrier for isomerization.
Near-resonant energy transfer from highly vibrationally excited OH to N2
Authors: Burtt Kelly D. , Sharma Ramesh D.
Published: March 2008

The probability per collision P(T) of near-resonant vibration-to-vibration energy transfer (ET) of one quantum of vibrational energy from vibrational levels ν=8 and ν=9 of OH to N2(ν=0), OH(ν)+N2(0)→OH(ν−1)+N2(1), is calculated in the 100–350K temperature range. These processes represent important steps in a model that explains the enhanced 4.3μm emission from CO2 in the nocturnal mesosphere. The calculated energy transfer is mediated by weak long-range dipole-quadrupole interaction. The results of this calculation are very sensitive to the strength of the two transition moments. Because of the long range of the intermolecular potential, the resonance function, a measure of energy that can be efficiently exchanged between translation and vibration-rotation degrees of freedom, is rather narrow. A narrow resonance function coupled with the large rotational constant of OH is shown to render the results of the calculation very sensitive to the rotational distribution, or the rotational temperature if one exists, of this molecule. The calculations are carried out in the first and second orders of perturbation theory with the latter shown to give ET probabilities that are an order of magnitude larger than the former. The reasons for the difference in magnitude and temperature dependence of the first- and second-order calculations are discussed. The results of the calculations are compared with room temperature measurements as well as with an earlier calculation. Our calculated results are in good agreement with the room temperature measurements for the transfer of vibrational energy for the exothermic OH(ν=9) ET process but are about an order lower than the room temperature measurements for the exothermic OH(ν=8) ET process. The cause of this discrepancy is explored. This calculation does not give the large values of the rate coefficients needed by the model that explains the enhanced 4.3μm emission from CO2 in the nocturnal mesosphere.
Achieving three-peak white organic light-emitting devices using wavelength-selective mirror electrodes
Authors: Lu Yin-Jui , Chang Chih-Hao , Lin Chun-Liang , Wu Chung-Chih , Hsu Hsiang-Lun , Chen Liang-Jyi , Lin Yu-Ting , Nishikawa Ryuji
Published: March 2008

We report an effective approach based on wavelength-selective mirrors for implementing three-peak white-emitting organic light-emitting devices (OLEDs). Such three-peak white OLEDs have electroluminescence spectra matching better with the transmission spectra of typical color filters and thus give much enhanced color gamut for full-color OLED display applications. The wavelength-selective mirror uses the metal/dielectric stack that is compatible with the OLED fabrication.
Thermally stimulated current in high resistivity Cd0.85Mn0.15Te doped with indium
Authors: Wrobel J. M. , Gubański A. , Płaczek-Popko E. , Rezmer J. , Becla P.
Published: March 2008

Charge carrier traps in Cd0.85Mn0.15Te doped with indium were studied using thermally stimulated current measurements. The investigations were performed in temperatures ranging from 100to300K. Four peaks in the current spectrum were identified. From the initial rise method and the best fit of the spectrum to the theoretical model, the activation energies and the relaxation parameters for the corresponding traps were determined.
Quantum efficiency of ambipolar light-emitting polymer field-effect transistors
Authors: Zaumseil Jana , McNeill Christopher R. , Bird Matt , Smith Darryl L. , Paul Ruden P. , Roberts Matthew , McKiernan Mary J. , Friend Richard H. , Sirringhaus Henning
Published: March 2008

The emission characteristics and external quantum efficiencies of ambipolar polymer light-emitting field-effect transistors are investigated as a function of applied voltage, current density, and ratio of hole to electron mobility. Green-emitting poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) with balanced electron and hole mobilities and red-emitting poly((9,9-dioctylfluorene)-2,7- diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2′,2″-diyl) (F8TBT) with strongly unbalanced hole and electron mobilities as semiconducting and emissive polymers are compared. The current-voltage and light output characteristics of the two types of light-emitting transistors were found to be fundamentally alike independent of mobility ratio. Device modeling allowing for a single (Langevin-type) charge recombination mechanism was able to reproduce the device characteristics for both cases but could not replicate the experimentally observed dependence of external quantum efficiency on current density. The increase of quantum efficiency with current density up to a saturation value could be indicative of a trap-assisted nonradiative decay mechanism at the semiconductor-dielectric interface. Optical output modeling confirmed that the maximum external quantum efficiency of F8BT light-emitting transistors of 0.8% is consistent with complete recombination of all charges and a singlet exciton fraction of 25%.
Unusually low thermal conductivity of gallium nitride nanowires
Authors: Guthy Csaba , Nam Chang-Yong , Fischer John E.
Published: March 2008

We report measurements of thermal conductivity κ on individual gallium nitride nanowires (GaN NWs) with diameters ranging from 97to181nm grown by thermal chemical vapor deposition. We observed unexpectedly small κ values, in the range of 13–19W∕mK at 300K, with very weak diameter dependence. We also observe unusual power law κ∼Tn behavior with n=1.8 at low temperature. Electron-energy-loss-spectroscopy measurements indicate Si and O concentrations in the ranges of 0.1–1 and 0.01–0.1at.%, respectively. Based on extensive numerical calculations, we conclude that both the unexpectedly low κ and the T1.8 dependence are caused by unusually large mass-difference scattering, primarily from Si impurities. Our analysis also suggests that mass-difference scattering rates are significantly enhanced by the reduced phonon group velocity in nanoscale systems. Planar defects running the length of the NW, previously characterized in detail, may also play a role in limiting the phonon mean free path.
Theory of laser enhancement and suppression of cold reactions: The fermion-boson Li6+Li27↔ℏωLi6Li7+Li7 radiative collision
Authors: Li Xuan , Parker Gregory A. , Brumer Paul , Thanopulos Ioannis , Shapiro Moshe
Published: March 2008

We present a nonperturbative time-dependent quantum mechanical theory of the laser catalysis and control of a bifurcating A+BC↔ℏω0ABC*(v)↔ℏω0AB+C reaction, with ABC*(v) denoting an intermediate, electronically excited, complex of ABC in the vth vibrational state. We apply this theory to the low collision energy fermion-boson light-induced exchange reaction, Li6(S2)+Li27(Σu+3)↔ℏω0(Li6Li7Li7)*↔ℏω0Li6Li7(Σ+3)+Li7(S2). We show that at very low collision energies and energetically narrow (∼0.01cm−1) initial reactant wave packets, it is possible to tune the yield of the exchange reaction from 0 to near-unity (yield ⩾99%) values. Controllability is somewhat reduced at collisions involving energetically wider (∼1cm−1) initial reactant wave packets. At these energetic bandwidths, the radiative reactive control, although still impressive, is limited to the 0%–76% reactive-probabilities range.
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nanolayer induced enhancement of the 1.53μm photoluminescence in Er3+ doped a-Al2O3 thin films
Authors: Toudert J. , Núñez-Sánchez S. , Jiménez de Castro M. , Serna R.
Published: March 2008

A structured film formed by an active Er3+-doped amorphous Al2O3 layer located between two amorphous silicon nanolayers (NLs) in as-grown conditions shows an enhancement of the photoluminescence (PL) intensity and lifetime at 1.53μm of one order of magnitude when compared to a similar Er3+-doped film without silicon NLs. The film can be pumped even under nonresonant excitation conditions as a result of a long range energy transfer from the a-Si NLs to the Er3+ ions. In addition, the PL shows a single exponential decay with a lifetime value as high as 2.4ms. The lifetime enhancement is associated with an improvement of the emission efficiency of the Er3+ ions.
Strong magnetoelectric coupling at microwave frequencies in metallic magnetic film/lead zirconate titanate multiferroic composites
Authors: Pettiford C. , Lou J. , Russell L. , Sun N. X.
Published: March 2008

Strong magnetoelectric coupling was observed at microwave frequencies in metallic magnetic film/lead zirconate titanate [Pb(Zr,Ti)O3] multiferroic composites, in which the magnetic films were either FeCoB or FeGaB with relatively high saturation magnetostriction constants between 40 and 70ppm and narrow ferromagnetic resonance linewidths of ∼20Oe at 10GHz. Large electrostatically induced ferromagnetic resonance frequency shifts of 50–110MHz at ∼2.3GHz were observed. These metallic magnetic film/Pb(Zr,Ti)O3 multiferroic composites with large electrostatic tunability of the ferromagnetic resonance frequency provide great opportunities for integrated microwave multiferroic devices.
Misfit dislocation dipoles and critical parameters of buried strained nanoscale inhomogeneity
Authors: Fang Q. H. , Liu Y. W. , Chen J. H.
Published: March 2008

A theoretical model is suggested which describes the generation of the misfit dislocation dipole in the system of the soft infinite matrix containing a circular stiff nanoscale inhomogeneity. The critical conditions of misfit dislocation dipole formation and the equilibrium position (preferred location) of the misfit dislocation dipole are given. The influence of the ratio of the shear modulus, the misfit stain, and the equilibrium position of the dislocation on the critical radius of the inhomogeneity is investigated.
Light-induced magnetization precession in GaMnAs
Authors: Rozkotová E. , Němec P. , Horodyská P. , Sprinzl D. , Trojánek F. , Malý P. , Novák V. , Olejník K. , Cukr M. , Jungwirth T.
Published: March 2008

We report the dynamics of the transient polar Kerr rotation (KR) and of the transient reflectivity induced by femtosecond laser pulses in ferromagnetic (Ga,Mn)As with no external magnetic field applied. It is shown that the measured KR signal consists of several different contributions, among which only the oscillatory signal is directly connected with the ferromagnetic order in (Ga,Mn)As. The origin of the light-induced magnetization precession is discussed and the magnetization precession damping (Gilbert damping) is found to be strongly influenced by annealing of the sample.
Femtosecond laser induced coordination transformation and migration of ions in sodium borate glasses
Authors: Liu Yin , Zhu Bin , Wang Li , Qiu Jianrong , Dai Ye , Ma Hongliang
Published: March 2008

We report on the coordination transformation of B3+ ions and migration of Na+ and O2− ions in sodium borate glasses, induced by 250kHz, 800nm femtosecond laser irradiation. Micro-Raman spectra show that the ratio of the integrated intensity of the two peaks at 806 and 774cm−1 decreases at first and then increases with increasing distance from the center of the laser modified zone. Electron dispersive x-ray spectra show that a portion of Na+ and O2− ions migrate from the vicinity of focal point after the femtosecond laser irradiation. A possible mechanism is proposed to explain the observed phenomena.
Phase-velocity measurement of a tightly focused Gaussian beam by use of sum frequency generation
Authors: Wang Ke , Qian Liejia , Qiu Ping , Zhu Heyuan
Published: March 2008

In this letter, the nonuniform phase-velocity distribution of a tightly focused Gaussian beam is experimentally measured, both in the axial and the radial dimensions, through a nonlinear optical approach in a form of off-axis sum frequency generation. The experimental results demonstrate the superluminal phase-velocity distribution near the Gaussian beam axis around the focal plane, in agreement with the theoretical expectation.
An alternative of spectroscopic ellipsometry: The double-reference method
Authors: Kézsmárki I. , Bordács S.
Published: March 2008

We have developed a method conceptually different from ellipsometric techniques which allows the determination of the complex refractive index by simultaneously measuring the unpolarized normal-incidence reflectivity relative to the vacuum and another reference media such as diamond, GaAs, CdTe, etc. From these two quantities, the complex optical response can be directly obtained without Kramers–Kronig transformation. Due to its transparency and large refractive index from the far-infrared to the soft ultraviolet regions, diamond can be ideally used as a second reference over the whole optical spectrum. The experimental arrangement is rather simple compared to ellipsometry.
Nanocrystallization and interfacial tension of sol-gel derived memory
Authors: Wu Chi-Chang , Tsai Yi-Jen , Chu Min-Ching , Yang Shao-Ming , Ko Fu-Hsiang , Liu Pin-Lin , Yang Wen-Luh , You Hsin-Chiang
Published: March 2008

The formation of the nanocrystals (NCs) by using the sol-gel spin-coating method at various annealing temperatures had been studied. The film started to form the islands at 600°C annealing, and finally transferred into NCs at 900°C. A model was proposed to explain the transformation of thin film. The morphology of sol-gel thin film at 600°C annealing was varied and had higher interfacial energy. The crystallized process at 900°C annealing could minimize the energy. The retention for 900°C annealed sample exhibited less than 30% charge loss after 106s at 125°C measurement.
Defects and symmetry influence on visible emission of Eu doped nanoceria
Authors: Babu Suresh , Schulte Alfons , Seal Sudipta
Published: March 2008

Europium doped cerium oxide particles of 10nm were synthesized by room temperature chemical precipitation technique and annealed at 500 and 900°C to study its effect on luminescence. X-ray photoelectron spectroscopic result shows an increase in Ce3+ concentration from 20% to 23% on Eu doping but decreases to 8% on annealing. Raman studies show a progressive blueshift from 461to464cm−1 due to local symmetry ordering with temperature. Emission intensity varies with the wavelength of excitation and observed transitions indicate the presence of Eu3+ in different symmetry environments.
Generation of squeezed states of nanomechanical resonator using three-wave mixing
Authors: Huo Wen Yi , Long Gui Lu
Published: March 2008

We propose a scheme for generating squeezed states of nanomechanical resonator in a solid state circuit system which consists of a nanomechanical resonator, a superconducting Cooper-pair box, and a superconducting transmission line resonator. The nonlinear interaction between the nanomechanical resonator and superconducting transmission line resonator can be implemented by setting the external biased flux of the Cooper-pair box at some special values. The squeezed states of the nanomechanical resonator can be generated by degenerate three-wave mixing and the Cooper-pair box plays the role of “nonlinear medium” in the squeezing process.
Mechanism and kinetics of pore formation in membranes by water-soluble amphipathic peptides
Authors: Lee Ming-Tao , Hung Wei-Chin , Chen Fang-Yu , Huang Huey W.
Published: March 2008

How antimicrobial peptides form pores in membranes is of interest as a fundamental membrane process. However, the underlying molecular mechanism, which has potential applications in therapeutics, nonviral gene transfer, and drug delivery, has been in dispute. We have resolved this mechanism by observing the time-dependent process of pore formation in individual giant unilamellar vesicles (GUVs) exposed to a melittin solution. An individual GUV first expanded its surface area at constant volume and then suddenly reversed to expanding its volume at constant area. The area expansion, the volume expansion, and the point of reversal all match the results of equilibrium measurements performed on peptide–lipid mixtures. The mechanism includes a negative feedback that makes peptide-induced pores stable with a well defined size, contrary to the suggestion that peptides disintegrate the membrane in a detergent-like manner.