bluuebunny/crossref_metadata_2025 huggingface dataset:
Embodying and Transgressing Race in the Novels of John Gregory Brown
Authors: MICHAILIDOU ARTEMIS
Published: November 2006

This essay will discuss corporeal and racial representation in the work of John Gregory Brown, a little-known, yet immensely rewarding, New Orleans novelist. Placing the discussion within the rich literary tradition of the American South, I will focus on the male protagonists of his first two novels – Decorations in a Ruined Cemetery (1994) and The Wrecked, Blessed Body of Shelton Lafleur (1996) – and examine why Brown's characters constantly shift between different racial positions, and how notions such as racial purity or fixed subjectivity are exposed and interrogated. My analysis will also address physical defect, and explore how Brown destabilizes the ideal of the body as a privileged locus of authoritative wholeness. I will be arguing that, as a cultural and racial signifier, the body in Brown's work is linked with fluidity and fragmentation, and that the boundaries between whiteness and blackness are continuously reshaped by the characters' ambiguous perceptions of themselves as subversive, multi-racial subjects. The conclusion will maintain that both novels offer new insights into the interaction between corporeal representation and racial identity, which make an important contribution to the tradition of American and, particularly, southern literature.
Visions of Diversity: Cultural Pluralism and the Nation in the Folk Music Revival Movement of the United States and Canada, 1958–65
Authors: MITCHELL GILLIAN A. M.
Published: November 2006

This article focusses on the concept of cultural pluralism in the North American folk music revival of the 1960s. Building on the excellent work of earlier folk revival scholars, the article looks in greater depth at the “vision of diversity” promoted by the folk revival in North America – at the ways in which this vision was constructed, at the reasons for its maintenance and at its ultimate decline and on the consequences of this for anglophone Canadian and American musicians and enthusiasts alike.
Mammakarzinome mit nichtinflammatorischer Hautbeteiligung: Neue Daten revidieren das traditionelle Bild einer «klassischen» kliniko-pathologischen Entität
Authors: Güth  , Wight  , Singer
Published: November 2006

Historisch begründet führt die Hautbeteiligung bei Mammakarzinomen zur Klassifikation des Tumors in die höchste Tumorkategorie, bzw. in das höchste nichtmetastasierte Tumorstadium (aktuelle TNM-Klassifikation: T4/Stadium III). Das wohl wichtigste Prinzip des TNM-Klassifikationssystems ist jedoch die Beachtung der Grundregel, dass homogene Gruppen von Tumoren ähnlicher Ausdehnung und ähnlicher Prognose in einer Stadienkategorie zusammengefasst werden sollten. Neuere Studien belegen, dass die TNM-Stadieneinteilung zu revidieren ist, da zurzeit nur aufgrund des Parameters «Hautbeteiligung» unterschiedliche Subgruppen von Tumoren mit stark differierenden prognostischen und therapeutischen Konsequenzen in einer Stadiengruppe zusammengefasst sind. Entsprechend ist unsere Empfehlung, dass die mit den TNM-Kategorien T4a–c klassifizierten Karzinome lediglich durch ihre Tumorgrösse eingeteilt werden sollten. Die T4-Kategorie sollte nur noch die prognostisch sehr ungünstigen inflammatorischen Karzinome (T4d) beinhalten.
What controls the oceanic dimethylsulfide (DMS) cycle? A modeling approach
Authors: Six K. D. , Maier‐Reimer E.
Published: November 2006

We implemented a process‐based DMS module into the global carbon cycle ocean model (HAMOCC5) which includes a simple module for plankton dynamics and investigated the regional and seasonal variations of the marine sulfur cycle. The turnover rates within the DMS cycle are only poorly known. Therefore we developed, on the basis of a global DMS data set, an optimization routine for the free parameters controlling DMS production and removal. The resulting seasonal and regional distributions of DMS concentration are fully consistent with the underlying hydrodynamical and biogeochemical processes. We investigated a series of DMS model approaches with various complexities. The distinction between different DMS producing phytoplankton species and the consideration of the regionally and seasonally varying bacterial activity on converting dDMSP to DMS and on DMS consumption appears to have a crucial effect on the quality of the results in the given model conception.
Large accumulation of anthropogenic CO2 in the East (Japan) Sea and its significant impact on carbonate chemistry
Authors: Park Geun‐Ha , Lee Kitack , Tishchenko Pavel , Min Dong‐Ha , Warner Mark J. , Talley Lynne D. , Kang Dong‐Jin , Kim Kyung‐Ryul
Published: November 2006

This paper reports on a basin‐wide inventory of anthropogenic CO2 in the East (Japan) Sea determined from high‐quality alkalinity, chlorofluorocarbon, and nutrient data collected during a summertime survey in 1999 and total dissolved inorganic carbon data calculated from pH and alkalinity measurements. The data set comprises measurements from 203 hydrographic stations and covers most of the East Sea with the exception of the northwestern boundary region. Anthropogenic CO2 concentrations are estimated by separating this value from total dissolved inorganic carbon using a tracer‐based (chlorofluorocarbon) separation technique. Wintertime surface CFC‐12 data collected in regions of deep water formation off Vladivostok, Russia, improve the accuracy of estimates of anthropogenic CO2 concentrations by providing improved air‐sea CO2 disequilibrium values for intermediate and deep waters. Our calculation yields a total anthropogenic CO2 inventory in the East Sea of 0.40 ± 0.06 petagrams of carbon as of 1999. Anthropogenic CO2 has already reached the bottom of the East Sea, largely owing to the effective transport of anthropogenic CO2 from the surface to the ocean interior via deep water formation in the waters off Vladivostok. The highest specific column inventory (vertically integrated inventory per square meter) of anthropogenic CO2 of 80 mol C m−2 is found in the Japan Basin (40°N−44°N). Comparison of this inventory with those for other major basins of the same latitude band reveal that the East Sea values are much higher than the inventory for the Pacific Ocean (20−30 mol C m−2) and are similar to the inventory for the North Atlantic (66−72 mol C m−2). The substantial accumulation of anthropogenic CO2 in the East Sea during the industrial era has caused the aragonite and calcite saturation horizons to move upward by 80−220 m and 500−700 m, respectively. These upward movements are approximately 5 times greater than those found in the North Pacific. Both the large accumulation of anthropogenic CO2 and its significant impact on carbonate chemistry in the East Sea suggest that this sea is an important site for monitoring the future impact of the oceanic invasion of anthropogenic CO2.
Modeling the size and shape of Saturn's magnetopause with variable dynamic pressure
Authors: Arridge C. S. , Achilleos N. , Dougherty M. K. , Khurana K. K. , Russell C. T.
Published: November 2006

The location and shape of a planetary magnetopause is principally determined by the dynamic pressure, Dp, of the solar wind, the orientation of the planet's magnetic dipole with respect to the solar wind flow, and by the distribution of stresses inside the magnetosphere. The magnetospheres of Saturn and Jupiter have strong internal plasma sources compared to the solar wind source and also rotate rapidly, causing an equatorial inflation of the magnetosphere and consequently the magnetopause. Empirical studies using Voyager and Pioneer data concluded that the kronian magnetopause was Earth‐like in terms of its dynamics (Slavin et al., 1985) as revealed by how the position of the magnetopause varies with dynamic pressure. In this paper we present a new pressure‐dependent model of Saturn's magnetopause, using the functional form proposed by Shue et al. (1997). To establish the pressure‐dependence, we also use a new technique for fitting a pressure‐dependent model in the absence of simultaneous upstream pressure measurements. Using a Newtonian form of the pressure balance across the magnetopause boundary and using model rather than minimum variance normals, we estimate the solar wind dynamic pressure at each crossing. By iteratively fitting our model to magnetopause crossings observed by the Cassini and Voyager spacecraft, in parallel with the pressure balance, we obtain a model which is self‐consistent with the dynamic pressure estimates obtained. We find a model whose size varies as ∼Dp−1/4.3 and whose flaring decreases with increasing dynamic pressure. This is interpreted in terms of a different distribution of fields and particles stresses which has more in common with the jovian magnetosphere compared with the terrestrial situation. We compare our model with the existing models of the magnetopause and highlight the very different geometries. We find our results are consistent with recent MHD modeling of Saturn's magnetosphere (Hansen et al., 2005).
A geomagnetic estimate of mean paleointensity
Authors: Voorhies C. V.
Published: November 2006

A statistical hypothesis about Earth's magnetic field is tested against paleomagnetism by combining it with the present field to estimate mean paleointensity. The estimate uses the satellite era geomagnetic multipole power spectrum Rn, which gives the mean square magnetic induction represented by spherical harmonics of degree n averaged over the sphere of radius a = 6371.2 km. The hypothesis asserts that low‐degree multipole powers of the core source field, Rnc, are distributed as chi‐square with 2n + 1 degrees of freedom and theoretical expectation values {Rnc} = K(n + 1/2)[n(n + 1)]−1(c/a)2n + 4, where c is the 3480 km radius of Earth's core. The implied field is usually mainly dipolar and can be primarily axial. Amplitude K is estimated by fitting theoretical to observational spectra of degrees 1–12. The resulting calibrated expectation spectrum is summed through degree 12 to estimate expected square intensity {F2}. This sum also estimates mean square paleointensity, averaged over geologic time as well as the sphere, in so far as the present field spectrum is a fair sample of that generated in the past by core geodynamic processes. Previously, we excluded dominant degrees 1 and 2 from the fit, but not the sum, to “predict” mean paleointensity from the 1980 Magsat nondipole field. The new estimate fits all Rn of degrees 1–12 self‐consistently and yields {F2} = (37.3 ± 4.3 μT)2. Expected paleointensity {F} is about 34.4 ± 4.9 μT; expected virtual axial dipole moment is about (6.51 ± 0.94) × 1022 Am2. These estimates are within the range of published paleomagnetic determinations of mean paleointensity; therefore the statistical hypothesis passes this test.
Sub‐mesoscale lateral density structure in the oceanic surface mixed layer
Authors: Hosegood Phil , Gregg Michael C. , Alford Matthew H.
Published: November 2006

We investigate the horizontal scales of density variability in the surface mixed layer (SML) in the North Pacific Subtropical Front (STF) during a period of highly variable atmospheric forcing. Wavelet analysis shows that horizontal density variability is not restricted to scales, L, ≥10 km as previously suggested but extends to L = 2 km. The limiting L varies strongly with location and corresponds to a local internal Rossby radius that accounts for transient stratification above the seasonal thermocline. Density compensation in the SML, achieved when temperature and salinity effects cancel in their effect on density, occurs at 30°N at the climatological front associated with the northern boundary of the STF where large thermohaline gradients are observed. At 28°N, however, temperature gradients within the SML are not compensated by salinity, and horizontal density gradients result in 2 ≤ L ≤ 10 km. Our observations suggest dynamic processes restratify the SML at scales rarely resolved by numerical models of the SML.
Vicarious calibration of the Ocean PHILLS hyperspectral sensor using a coastal tree‐shadow method
Authors: Filippi Anthony M. , Carder Kendall L. , Davis Curtiss O.
Published: November 2006

Ocean color remote‐sensing systems require highly accurate calibration (<0.5%) for accurate retrieval of water properties. This accuracy is typically achieved by vicarious calibration which is done by comparing the atmospherically corrected remote‐sensing data to accurate estimates of the water‐leaving radiance. Here we present a new method for vicarious calibration of a hyperspectral sensor that exploits shadows cast by trees and cliffs along coastlines. Hyperspectral Ocean PHILLS imagery was acquired over East Sound and adjacent waters around Orcas Island, Washington, USA, in August, 1998, in concert with field data collection. To vicariously calibrate the PHILLS data, a method was developed employing pixel pairs in tree‐shaded and adjacent unshadowed waters, which utilizes the sky radiance dominating the shaded pixel as a known calibration target. Transects extracted from East Sound imagery were calibrated and validated with field data (RMSE = 0.00033 sr−1), providing validation of this approach for acquiring calibration‐adjustment data from the image itself.
On the cause of abrupt vegetation collapse in North Africa during the Holocene: Climate variability vs. vegetation feedback
Authors: Liu Zhengyu , Wang Yi , Gallimore Robert , Notaro Michael , Prentice I. Colin
Published: November 2006

The abrupt desertification over the northern Africa in the mid‐Holocene is studied in both a complex and a simple coupled climate‐vegetation model. In contrast to the previous mechanism that relies on strong positive vegetation‐climate feedback and the resulted multiple equilibria, we propose a new mechanism in which the abrupt desertification is caused by low frequency climate variability, rather than a positive vegetation‐climate feedback. The implication of this new mechanism to modelling and observation is also discussed.
“Early/slow” events: A new category of VLF perturbations observed in relation with sprites
Authors: Haldoupis C. , Steiner R. J. , Mika Á. , Shalimov S. , Marshall R. A. , Inan U. S. , Bösinger T. , Neubert T.
Published: November 2006

Analysis of subionospheric VLF transmissions, observed in relation with sprites, has led to the identification of a new category of VLF perturbations caused by the direct effects of tropospheric lightning on the overlying lower ionosphere. They constitute a large subset of the so‐called “early/fast” events where now the term “fast,” which implies rapid onset durations less than ∼20 ms, does not apply. In contrast with early/fast, the perturbations have a gradual growth and thus “slow” onset durations ranging from about 0.5 to 2.5 s; thus these events are labeled herein as “early/slow.” They are indicative of a new physical process at work which, following a sprite‐causative cloud‐to‐ground discharge, leads to a gradual buildup of conductivity changes in the lower ionosphere which must be responsible for the long onset durations of the observed perturbations. Analysis of broadband VLF sferic recordings, made with a two‐channel receiver near the sprite producing storms, shows that the growth phase of an early/slow event coincides with the occurrence of complex and dynamic lightning action. This is composed of a few sequential cloud‐to‐ground lightning strokes and clusters (bursts) of sferics which are attributable to intracloud lightning. We postulate that the long onset durations are due to secondary ionization buildup in the upper D region below the nighttime VLF reflection heights, caused mainly by the impact on sprite‐produced electrons of sequential electromagnetic pulses radiated upward from horizontal in‐cloud discharges.
Deformation of olivine‐spinel aggregates in the system (Mg,Ni)2GeO4 deformed to high strain in torsion: Implications for upper mantle anisotropy
Authors: Mecklenburgh Julian , Zhao Yong‐Hong , Heidelbach Florian , Mackwell Steve
Published: November 2006

Deformation of mantle phases to high strain is fundamental for understanding mantle dynamics. However, it is technically challenging to perform deformation experiments yielding accurate mechanical results at the high pressures required for certain mantle phases, such as wadsleyite and ringwoodite. Deformation experiments on analog materials of such high‐pressure phases can provide insight into the deformation properties of the mantle. The (Mg,Ni)2GeO4 system undergoes the olivine‐spinel transformation at much lower pressures than the silicate counterpart. Hence the high strain deformation properties of an olivine‐spinel rock can be studied at experimentally tractable pressures and temperatures. Experiments were conducted in a gas medium deformation apparatus at constant angular velocity, a temperature of 1473 K, and 300 MPa confining pressure. At these conditions with a Mg/(Mg + Ni) ratio of 0.9, the resulting aggregate comprised 70% olivine, 30% spinel, and <1% orthopyroxene. The applied strain rate ranged from 10−4 to 10−5 s−1, yielding shear stresses supported by the samples of between 100 and 250 MPa. Samples were deformed to a range of shear strains between γ = 1 and γ = 7 in order to study the microstructural development during high strain deformation. In these experiments, the spinel phase did not deform to produce a crystallographic preferred orientation (CPO). The olivine phase produced a CPO which is consistent with slip on the [001](hk0) slip system. If this slip system is dominant in olivine below 250–300 km in the upper mantle, the observed seismic anisotropy can be explained without resorting to changes in flow regime or deformation mechanism at this depth.
Revisiting a hydrological analysis framework with International Satellite Land Surface Climatology Project Initiative 2 rainfall, net radiation, and runoff fields
Authors: Koster Randal D. , Fekete Balázs M. , Huffman George J. , Stackhouse Paul W.
Published: November 2006

The International Satellite Land Surface Climatology Project Initiative 2 (ISLSCP‐2) data set provides the data needed to characterize the surface water budget across much of the globe in terms of energy availability (net radiation) and water availability (precipitation) controls. The data, on average, are shown to be consistent with Budyko's decades‐old framework, thereby demonstrating the continuing relevance of Budyko's semiempirical relationships. This consistency, however, appears only when a small subset of the data with hydrologically suspicious behavior is removed from the analysis. In general, the precipitation, net radiation, and runoff data also appear consistent in their interannual variability and in the phasing of their seasonal cycles.
Prediction of viscosity for molecular fluids at experimentally accessible shear rates using the transient time correlation function formalism
Authors: Pan Guoai , McCabe Clare
Published: November 2006

Nonequilibrium molecular dynamics (NEMD) simulations were performed and the transient time correlation function (TTCF) method applied to calculate the shear viscosity of n-decane. Using the TTCF method we were able to calculate the viscosity at shear rate orders of magnitude lower than is possible by direct NEMD simulation alone. For the first time for a molecular fluid, we were able to simulate shear rates accessible by experimental measurements, which are typically performed at shear rates well below those accessible by NEMD simulation. The TTCF method allows us to close the gap between the lowest shear rates accessible by MD simulation and the highest shear rates possible in experimental studies. Additionally a multiple time step method for Gaussian thermostatted SLLOD equations of motion was developed following earlier work [G. A. Pan et al., J. Chem. Phys. 122, 4114 (2005)] for atomic fluids.
Mode selective tunneling dynamics observed by high resolution spectroscopy of the bending fundamentals of N14H2D and N14D2H
Authors: Snels Marcel , Hollenstein Hans , Quack Martin
Published: November 2006

High resolution (0.004 and 0.01cm−1 instrumental bandwidth) interferometric Fourier transform infrared spectra of N14H2D and N14D2H were measured on a Bomem DA002 spectrometer in a supersonic jet expansion and at room temperature. We report the analysis of the bending fundamentals of N14H2D with term values Tv(s)=1389.9063(2)cm−1 and Tv(a)=1390.4953(2)cm−1 for the ν4b fundamental and Tv(s)=1605.6404(7)cm−1 and Tv(a)=1591.0019(7)cm−1 for the ν4a fundamental, and of N14D2H with term values of Tv(s)=1233.3740(2)cm−1 and Tv(a)=1235.8904(2)cm−1 for the ν4a fundamental and Tv(s)=1461.7941(9)cm−1 and Tv(a)=1461.9918(19)cm−1 for the ν4b fundamental. In all cases Tv(s) gives the position of the symmetric inversion sublevel (with positive parity) and Tv(a) the position of the antisymmetric inversion sublevel (with negative parity). The notation for the fundamentals ν4a and ν4b is chosen by correlation with the degenerate ν4 mode in the C3v symmetric molecules NH3 and ND3. The degeneracy is lifted in Cs symmetry and a indicates the symmetric, b the antisymmetric normal mode with respect to the Cs symmetry plane in NH2D and ND2H. Assignments were established with certainty by means of ground state combination differences. About 20 molecular parameters of the effective S-reduced Hamiltonian could be determined accurately for each fundamental. In particular, the effect of Fermi resonances of the 2ν2 overtone with the ν4a bending mode was observed, leading to an increased inversion splitting in the case of ND2H and to a strongly increased inversion splitting and an inverted order of the two inversion levels in NH2D. Rotational perturbations observed with the ν4b bending fundamentals are probably due to Coriolis interactions with the inversion overtone 2ν2. The results are important for understanding isotope effects on the inversion in ammonia as well as its selective catalysis and inhibition by excitation of different vibrational modes, as treated by quantum dynamics on high dimensional potential hypersurfaces of this molecule.
Evidence of mobile charged impurities in organic heterojunction photovoltaic devices
Authors: Heggie D. A. , MacDonald B. L. , Hill I. G.
Published: November 2006

Organic photovoltaic heterojunction devices consisting of copper phthalocyanine and 3,4,9,10-perylene-tetracarboxylic dianhydride (CuPc-PTCDA) show time dependent short circuit current under both AM1.5D and 465nm illuminations, but not under longer-wavelength illumination. Higher energy photons result in a short circuit current that decays, and sometimes changes sign, with a time scale on the order of minutes. This is attributed to short-wavelength absorption in PTCDA leading to spontaneous exciton dissociation and free holes within the PTCDA. Charged impurities in PTCDA, formed by the trapping of these free holes, drift inside the device forming a Helmholtz double layer at the indium tin oxide contact resulting in a redistribution of the internal electric fields and a corresponding shift in short circuit current.
Noncommutative geometry, topology, and the standard model vacuum
Authors: Dawe Martins R. A.
Published: November 2006

As a ramification of a motivational discussion for previous joint work, in which equations of motion for the finite spectral action of the standard model were derived, we provide a new analysis of the results of the calculations therein, switching from the perspective of spectral triple to that of Fredholm module and thus from the analogy with Riemannian geometry to the premetrical structure of the noncommutative geometry. Using a suggested noncommutative version of Morse theory together with algebraic K theory to analyze the vacuum solutions, the first two summands of the algebra for the finite triple of the standard model arise up to Morita equivalence. We also demonstrate a new vacuum solution whose features are compatible with the physical mass matrix.
Tuning gastropod locomotion: Modeling the influence of mucus rheology on the cost of crawling
Authors: Lauga Eric , Hosoi A. E.
Published: November 2006

Common gastropods such as snails crawl on a solid substrate by propagating muscular waves of shear stress on a viscoelastic mucus. Producing the mucus accounts for the largest component in the gastropod’s energy budget, more than 20 times the amount of mechanical work used in crawling. Using a simple mechanical model, we show that the shear-thinning properties of the mucus favor a decrease in the amount of mucus necessary for crawling, thereby decreasing the overall energetic cost of locomotion.
Computer simulation of angle-resolved x-ray photoelectron spectroscopy measurements for the study of surface and interface roughnesses
Authors: Oswald S. , Oswald F.
Published: November 2006

The development of nanoscale materials is always closely connected with their characterization. One powerful method of nondestructive analysis in the nanometer-depth region is angle-resolved x-ray photoelectron spectroscopy (ARXPS). The interpretation of such ARXPS measurements, however, needs model calculations based on a priori assumptions of the (typically unknown) surface structure under investigation. For rough surfaces, there often can be uncertainties, misinterpretations, and/or artifacts. In this paper a calculation method is presented which allows ARXPS intensities to be simulated conveniently and rapidly for almost any sample structure. The presented algorithms can be easily extended to include other physical effects (e.g., elastic scattering) and can also be used for other problems where spatial resolution for the description of absorption processes is needed. Illustrative calculations for selected surface structures (overlayers on rough substrates, island formation, and clusters) demonstrate how these simulations can help to estimate the limits of ARXPS analyses. Some previous findings (e.g., the “magic angle” for overlayers on rough surfaces) are critically examined. For more complicated small structures (islands and clusters), a complex interplay of various parameters must be considered. For small islands, edge and shadowing effects result in a general overestimation of the surface coverage, and near-surface clusters are often interpreted as artificially mixed layers of the materials.
Time-resolved x-ray excited optical luminescence from SnO2 nanoribbons: Direct evidence for the origin of the blue luminescence and the role of surface states
Authors: Zhou X. T. , Heigl F. , Murphy M. W. , Sham T. K. , Regier T. , Coulthard I. , Blyth R. I. R.
Published: November 2006

Time-resolved x-ray excited optical luminescence (XEOL) and x-ray absorption near edge structures have been employed to study the origin of the multicolor luminescence from SnO2 nanoribbons. The authors find that the yellow-green luminescence has a long lifetime while the blue luminescence a short one. The luminescence is attributed to the radiative decay of trapped electrons in oxygen vacancies just below the conduction band and electrons in the conduction band to intrinsic surface states in the band gap.
Compositional dependence of longitudinal sound velocities of piezoelectric (111) InxGa(1−x)As measured by picosecond ultrasonics
Authors: Wen Yu-Chieh , Chou Li-Chang , Lin Hao-Hsiung , Lin Kung-Hsuan , Kao Tzeng-Fu , Sun Chi-Kuang
Published: November 2006

Picosecond ultrasonic experiments were performed to generate and detect acoustic pulses in piezoelectric (111) epilayers of InxGa(1−x)As, and the longitudinal sound velocities in the [111] direction of InxGa(1−x)As were thus directly determined by controlling the indium content x. We found that the sound velocity exhibits an obvious bowing with different alloy compositions and can be described as a quadratic function of VL(x)=458x2−1451x+5414. This result supports a nonlinear compositional dependence of the elastic constants of InxGa(1−x)As and indicates that the linear-interpolation approximation is inapplicable for estimating sound velocity in this specific case.
The lowest A′2 excited state of the water-hydroxyl complex
Authors: Crawford T. Daniel , Abrams Micah L. , King Rollin A. , Lane Joseph R. , Schofield Daniel P. , Kjaergaard Henrik G.
Published: November 2006

Vertical and adiabatic excitation energies of the lowest A′2 excited state in the water-hydroxyl complex have been determined using coupled cluster, multireference configuration interaction, multireference perturbation theory, and density-functional methods. A significant redshift of about 0.4eV in the vertical excitation energy of the complex compared to that of the hydroxyl radical monomer is found with the coupled cluster calculations validating previous results. Electronic excitation leads to a structure with near-equal sharing of the hydroxyl hydrogen by both oxygen atoms and a concomitantly large redshift of the adiabatic excitation energy of approximately 1eV relative to the vertical excitation energy. The combination of redshifts ensures that the electronic transition in the complex lies well outside the equivalent excitation in the hydroxyl radical monomer. The complex is approximately five times more strongly bound in the excited state than in the ground state.
Density functional theory investigation of the polarizability and second hyperpolarizability of polydiacetylene and polybutatriene chains: Treatment of exact exchange and role of correlation
Authors: Champagne Benoît , Bulat Felipe A. , Yang Weitao , Bonness Sean , Kirtman Bernard
Published: November 2006

The static polarizability and second hyperpolarizability of increasingly large polydiacetylene and polybutatriene (PBT) chains have been evaluated using the optimized effective potential for exact exchange (OEP-EXX) method developed by Yang and Wu [Phys. Rev. Lett. 89, 143002 (2002)], where the unknown part of the effective potential is expressed as a linear combination of Gaussian functions. Various conventional atomic orbital basis sets were employed for the exchange potential (X basis) as well as for the Kohn-Sham orbitals [molecular orbital (MO) basis]. Our results were compared to coupled-perturbed Hartree-Fock (CPHF) calculations and to ab initio correlated values obtained at various levels of approximation. It turns out that (a) small conventional basis sets are, in general, unsatisfactory for the X basis; (b) the performance of a given X basis depends on the MO basis and is generally improved when using a larger MO basis; (c) these effects are exaggerated for the second hyperpolarizability compared to the polarizability; (d) except for the second hyperpolarizability of PBT chains, using 6-311++G** for the X basis gives reasonable agreement with the CPHF results for all MO basis sets; (e) our results suggest that in the limit of a complete X basis the OEP-EXX values may approach the CPHF data; and (f) in general, the quality of a given conventional X basis degrades with the length of the oligomer, which correlates with the fact that the number of X basis functions becomes a smaller fraction of the number required to reproduce exactly the finite-basis-set Hartree-Fock energies. Linear and especially nonlinear electric field responses constitute a very stringent test for assessing the quality of functionals and potentials; appropriately tailored basis sets are needed to describe the latter. Finally, this study further highlights the importance of electron correlation effects on linear and nonlinear responses, for which correlated functionals with OEP are required.
The transition from an ionizing electron collecting plasma sheath into an anodic double layer as a bifurcation
Authors: Conde L. , Ferro Fontán C. , Lambás J.
Published: November 2006

The electron attracting plasma sheath adjacent to the surfaces of a positively polarized electrode transforms into an anodic double layer over a threshold bias potential. The proposed one-dimensional model for this transition considers the contribution of the low production of charges by electron impact in the sheath, which develops a positive space charge in front of the electrode. The stationary electric field of this ionizing plasma sheath as well as the plasma potential spatial profile are obtained from the numerical solutions of a nonlinear integral equation derived from the Poisson equation. The stationary transition process is governed by a bifurcation driven by the bias potential of the electrode, which is the parameter controlled in the experiments. Below a bias potential threshold a single and stable ionizing plasma sheath is obtained. Past this critical voltage two possible values are found for the electric field close to the surface of the electrode. The double layer space plasma profile corresponds to low electric fields while a ionizing plasma sheath is found for higher values. It is conjectured that the abrupt transition occurs when the plasma sheath becomes unstable for bias voltage over a threshold and the double layer develops. The discontinuities in the current voltage characteristic curves observed in the experiments as the double layer upsurges or disappears would be explained as jumps between the two possible branches of this bifurcation.
An approximate method in transport theory. II
Authors: Loyalka S. K. , Naz S.
Published: November 2006

Maxwell had constructed first approximate solutions of the basic slip problems in the rarefied gas flows by distinguishing between incident and outgoing distributions at a surface. He used a single parameter approximation to the incident distribution and a conservation relation. The method has been improved in the recent past through the use of two conservation relations and two-parameter approximations to the incident distribution. We have explored in this work a method to improve upon these latter approximations by using an arbitrary order parameter representation of the incident distribution. For a test problem, we have considered the Milne problem of one speed transport [S. K. Loyalka, Phys. Fluids 24, 1912 (1982)]. We have found that a three-parameter representation yields a result for extrapolation distance that is accurate to four figures. We have explored approximations up to order 512, and we have found that the accuracy of results is improved systematically with the order of the approximation, and results of any desired accuracy can be obtained.
Strong optical activity in chiral metamaterials of metal screw hole arrays
Authors: Miyamaru Fumiaki , Hangyo Masanori
Published: November 2006

The authors demonstrate the change of the polarization of the electromagnetic wave induced by chiral metamaterials in the terahertz region. The polarization of the incident terahertz wave changes dramatically after transmitting through the chiral metamaterials made of the array of screw holes in metal slabs. A strong resonant polarization change (ellipticity and polarization azimuth) is observed at frequencies corresponding to the standing cavity modes of the metal waveguide with a finite length. Such experimental results indicate that the metal screw hole arrays work as a strong optically active material.
Magnetic-field-induced birefringence and particle agglomeration in magnetic fluids
Authors: Di Ziyun , Chen Xianfeng , Pu Shengli , Hu Xiao , Xia Yuxing
Published: November 2006

Birefringent effect dependent on magnetic intensity and wavelength in a water-based Fe3O4 magnetic fluid over the wavelength range of 400–700nm is studied in this letter. The results are compared with the theory proposed by Llewellyn [J. Phys. D 16, 95 (1983)], in which the optical anistropic properties of the magnetic fluid due to the aggregation of the particles at a relatively low density is suggested. It is shown that the degree of aggregation corresponds to the value of the axial ratio of the aggregated particles. So does the magnitude of the birefringence.
Generalized Keller-Simmons formula for nonisothermal plasma-assisted sputtering depositions
Authors: Palmero A. , Rudolph H. , Habraken F. H. P. M.
Published: November 2006

A general description of the relation between the sputtering rate and the deposition rate in plasma-assisted sputtering deposition has been developed. The equation derived yields the so-called Keller-Simmons [IBM J. Res. Dev. 23, 24 (1979)] formula in the limit of zero thermal gradients in the deposition system. It is shown that the Keller-Simmons formula can still be applied to fit the experimental results if the characteristic pressure-distance product, p0L0, is related to the temperature of the sputter cathode and the growing film. Using this relation, it is found that the variations in the values for p0L0 for different experimental conditions agree with the thus far not well understood experimental trends reported in the literature.
Switching electron current in a semiconductor nanowire via controlling the carrier injection from the electrode
Authors: Jin C. H. , Zhang Z. Y. , Wang J. Y. , Chen Q. , Peng L.-M.
Published: November 2006

Well characterized in situ electron field-emission measurements have been made on individual ZnO nanowires (NWs) inside a transmission electron microscope. It is found that the electron field-emission current from a semiconductor NW is determined not only by the NW/vacuum interface, but also by the Schottky barrier formed at the electrode/NW interface. It is demonstrated that the electron injection efficiency through the Schottky barrier and therefore the final electron emission current can be modulated by electronic excitations in the metal electrode, and it is proposed that this phenomenon could be used to design Schottky barrier switches for nanoelectronics.
Low-loss single-mode terahertz waveguiding using Cytop
Authors: de los Reyes Glenda , Quema Alex , Ponseca Carlito , Pobre Romeric , Quiroga Reuben , Ono Shingo , Murakami Hidetoshi , Estacio Elmer , Sarukura Nobuhiko , Aosaki Ko , Sakane Yoshihiko , Sato Hideki
Published: November 2006

A polymer-based, Cytop planar photonic crystal waveguide (PPCW) was designed for guiding terahertz radiation. Results indicate that the propagation and coupling losses in the 0.2–1.1THz range are relatively small for a sheetlike thickness design. Spectral analysis of the transmission data reveals frequency selectivity of the PPCW. Calculations of the spatial distribution of the terahertz electric field through the waveguide show evidence of single-mode propagation at a 0.45THz central frequency. The highly transparent nature of Cytop from deep ultraviolet to the far infrared region indicates its potential use as an integral component in hybrid optics.
Tunable, low loss Bi1.5Zn1.0Nb1.5O7∕Ba0.6Sr0.4TiO3∕Bi1.5Zn1.0Nb1.5O7 sandwich films
Authors: Wang Sheng-Xiang , Guo Ming-Sen , Sun Xiao-Hua , Liu Tao , Li Mei-Ya , Zhao Xing-Zhong
Published: November 2006

Bi 1.5 Zn 1.0 Nb 1.5 O 7 ∕ Ba 0.6 Sr 0.4 Ti O 3 ∕ Bi 1.5 Zn 1.0 Nb 1.5 O 7 (BZN/BST/BZN) sandwich films were deposited by radio frequency magnetron sputtering. The relative permittivity and dielectric loss of the sandwich films were measured using planar Pt∕BZN∕BST∕BZN∕Pt∕Ti∕SiO2∕Si capacitor structures. The sandwich films with thickness of about 280nm exhibited relative permittivity around 206–247 and dielectric loss tangent (tanδ) less than 0.008 at 1MHz. Films annealed at 750°C had an ∼11% relative tunability of the permittivity at a maximum applied bias field of 0.77MV∕cm. The sandwich films are not ferroelectric at room temperature.
Ferroelectric domain periodicities in nanocolumns of single crystal barium titanate
Authors: Schilling A. , Bowman R. M. , Gregg J. M. , Catalan G. , Scott J. F.
Published: November 2006

A focused ion beam microscope has been used to mill rectangular “picture-frame” shapes from single crystal barium titanate. The lengths of the sides of the picture frames were of the order of 3–5μm, while the side width and thickness dimensions were of the order of 100–500nm. Such aspect ratios meant that each of the frame sides approximates to a column with rectangular cross section. Scanning transmission electron microsopy was used to characterize the ferroelectric domain configurations associated with these nanocolumns. It was found that conventional stripe domain patterns occurred in all cases, down to columnar cross-section sizes of the order of ∼100×100nm2. Despite the geometry of the columns rendering the ferroelectric as shape constrained in two dimensions, the domain periodicity was only noticeably sensitive to variations in the magnitude of one of those dimensions. Such observations were rationalized using arguments based on those used by Kittel [Phys. Rev. 70, 965 (1946)] and Mitsui and Furuichi [Phys. Rev. 90, 193 (1953)] for predicting the equilibrium domain periodicities in macroscopic slabs of ferroic material.
Long flexible polymers interacting with ellipsoids, cylinders, and needles
Authors: Eisenriegler E.
Published: November 2006

The depletion interactions of ellipsoidal colloidal particles in a solution of long polymer chains are analyzed. Of primary concern are the limiting cases in which the ellipsoid reduces to a cylinder of infinite length and finite radius and a “needle” of finite length and vanishing radius. Relations are obtained between the polymer effects induced by a needle that is much shorter than the polymer size and by a cylinder with radius much smaller than the polymer size. These imply exact quantitative results for the orientation-dependent depletion interaction between a short needle and a wall. Qualitative differences between the needle and thin disk are discussed.
Characteristic behavior of short-term dynamics in reorientation for Gay-Berne particles near the nematic-isotropic phase transition temperature
Authors: Satoh Katsuhiko
Published: November 2006

A specific transition behavior was found in the tumbling motion near the nematic-isotropic phase boundary using molecular dynamics simulations of the Gay-Berne mesogenic model under isobaric conditions at a reduced pressure P* of 2.0. The relaxation time for the motion obtained from the second-rank orientational time correlation function and the rotational diffusion coefficient showed a clear jump at the nematic-isotropic phase transition temperature. Regardless of the temperature dependence of the relaxation time, the change in the rotational diffusion coefficient evaluated from the orientational order parameters and the relaxation time agreed qualitatively with that of real mesogens. The rotational viscosity coefficients γ1 and γ2 were obtained from the simulation data for the relaxation time for the short-term dynamics and for the rotational diffusion coefficients. γ1 was proportional to ⟨P2⟩2, where ⟨P2⟩ is the second-rank orientational parameter. Furthermore, the rotational behavior of the model was compared with that of the Debye approximation in the isotropic phase.
Dynamics in atomistic simulations of phospholipid membranes: Nuclear magnetic resonance relaxation rates and lateral diffusion
Authors: Wohlert Jakob , Edholm Olle
Published: November 2006

It is shown that a long, near microsecond, atomistic simulation can shed some light upon the dynamical processes occurring in a lipid bilayer. The analysis focuses on reorientational dynamics of the chains and lateral diffusion of lipids. It is shown that the reorientational correlation functions exhibits an algebraic decay (rather than exponential) for several orders of magnitude in time. The calculated nuclear magnetic resonance relaxation rates agree with experiments for carbons at the C7 position while there are some differences for C3. Lateral diffusion can be divided into two stages. In a first stage occurring at short times, t<5 ns, the center of mass of the lipid moves due to conformational changes of the chains while the headgroup position remains relatively fixed. In this stage, the center of mass can move up to ∼0.8 nm. The fitted short-time diffusion coefficient is D1=13×10−7 cm2 s−1 On a longer time scale, the diffusion coefficient becomes D2=0.79×10−7 cm2 s−1.
Direct monitoring of the excited state population in biased SiGe valence band quantum wells by femtosecond resolved photocurrent experiments
Authors: Rauter P. , Fromherz T. , Bauer G. , Vinh N. Q. , Murdin B. N. , Phillips J. P. , Pidgeon C. R. , Diehl L. , Dehlinger G. , Grützmacher D.
Published: November 2006

The authors report a direct measurement of the optical phonon intersubband hole relaxation time in a SiGe heterostructure and a quantitative determination of hole relaxation under electrically active conditions. The results were obtained by femtosecond resolved pump-pump photocurrent experiments using a free electron laser (wavelength 7.9μm). Additionally, the intensity dependence of the nonlinear photocurrent response was measured. Both types of experiments were simulated using a density matrix description. With one parameter set, a consistent modeling was achieved confirming the significance of the extracted heavy hole relaxation times. For an intersublevel spacing of 160meV, a value of 550fs was obtained.
Site selective studies of Er3+ emission centers in Er-implanted 6H-SiC
Authors: Glukhanyuk V. , Kozanecki A.
Published: November 2006

In this work the high resolution site selective photoluminescence (PL) using Fourier transform spectrometer and PL excitation spectra near 1.54μm in Er-implanted 6H-SiC were investigated. Direct evidence for the existence of three different Er3+ emitting centers which dominate luminescence at 1.54μm has been presented. The Stark splitting of the I9∕24 excited states and I15∕24 ground states for all three centers were determined. All centers reveal low local symmetry, probably due to complexes with impurities and defects.
Extinction analysis of dielectric multilayer microspheres
Authors: Petukhova Alla , Paton Andrew S. , Gourevich Ilya , Kumacheva Eugenia , Saarinen Jarkko J. , Sipe John E.
Published: November 2006

This letter reports optical properties of spherical dielectric particles with alternating layers of high and low refractive indices. The authors “predesigned” and synthesized polymer microspheres with alternating polystyrene and poly(trifluoroethyl methacrylate) layers of various thicknesses. Extinction of the microspheres was examined in a broad spectral range. A multipole expansion of electromagnetic field was applied for calculating the extinction efficiency of the particles. Excellent agreement was obtained between experimental and theoretical extinction curves.
Tracer diffusion in hard sphere fluids from molecular to hydrodynamic regimes
Authors: Sokolovskii R. O. , Thachuk M. , Patey G. N.
Published: November 2006

Molecular dynamics is employed to investigate tracer diffusion in hard sphere fluids. Reduced densities (ρ*=ρσ3, σ is the diameter of bath fluid particles) ranging from 0.02 to 0.52 and tracers ranging in diameter from 0.125σ to 16σ are considered. Finite-size effects are found to pose a significant problem and can lead to seriously underestimated tracer diffusion constants even in systems that are very large by simulation standards. It is shown that this can be overcome by applying a simple extrapolation formula that is linear in the reciprocal cell length L−1, allowing us to obtain infinite-volume estimates of the diffusion constant for all tracer sizes. For higher densities, the range of tracer diameters considered spans diffusion behavior from molecular to hydrodynamic regimes. In the hydrodynamic limit our extrapolated results are clearly consistent with the theoretically expected slip boundary conditions, whereas the underestimated values obtained without extrapolation could easily be interpreted as approaching the stick limit. It is shown that simply adding the Enskog and hydrodynamic contributions gives a reasonable qualitative description of the diffusion behavior but tends to overestimate the diffusion constant. We propose another expression that fits the simulation results for all densities and tracer diameters.