bluuebunny/crossref_metadata_2025 huggingface dataset:
Rediscovering the future
Authors: Evans Daniel J.
Published: May 2007

The state of Washington initiated a comprehensive citizen involvement program called Alternatives for Washington—a look at how residents envisioned the future of the state. And the governor says officials had better be ready to listen to the people, the “voice of the future echoing back to our colonial past,” an articulate citizenry working in continuous partnership with government.
Voter education and participation: Pennsylvania local referenda
Authors: Gamm Larry
Published: May 2007

In a study of seven municipalities with local government study commissions, which voted on recommendations at a referendum, there is some evidence that in those with relatively better educated and well‐to‐do citizens, increasing numbers of voters over time were likely to pick up at least some very general information on the referenda issues and that they were more likely to vote on such items.
Community incorporation analysis: A computer‐based approach
Authors: Langley Charlotte , Spaulding William E.
Published: May 2007

Municipal incorporation is often sought as a means of obtaining better response to the needs of citizens in terms of service and local governmental control. A computer model can provide valuable augmentation to an incorporation study, using actual city data which permits a “look ahead” at service requirements and longer‐term financial consequences.
In vivo measurements of changes in pH triggered by oxalic acid in leaf tissue of transgenic oilseed rape
Authors: Zou Qiu‐Ju , Liu Sheng‐Yi , Dong Xu‐Yan , Bi Yan‐Hua , Cao Yuan‐Cheng , Xu Qiao , Zhao Yuan‐Di , Chen Hong
Published: May 2007

Oxalic acid (OA), a non‐host‐specific toxin secreted by Sclerotinia sclerotiorum during pathogenesis, has been demonstrated to be a major phytotoxic and pathogenic factor. Oxalate oxidase (OXO) is an enzyme associated with the detoxification of OA, and hence the introduction of an OXO gene into oilseed rape (Brassica napus L.) to break down OA may be an alternative way of increasing the resistance of the plant to Sclerotinia sclerotiorum. In order to investigate the activation of OXO in transgenic oilseed rape, a convenient and accessible method was used to monitor changes in pH in response to stress induced by OA. The pH sensor, a platinum microcylinder electrode modified using polyaniline film, exhibited a linear response within the pH range from 3 to 7, with a Nernst response slope of 70 mV/pH at room temperature. The linear correlation coefficient was 0.9979. Changes induced by OA in the pH values of leaf tissue of different oilseed rape species from Brassica napus L. were monitored in real time in vivo using this electrode. The results clearly showed that the transgenic oilseed rape was more resistant to OA than non‐transgenic oilseed rape. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of astragalosides in the roots of Astragalus spp. using liquid chromatography tandem atmospheric pressure chemical lonization mass spectrometry
Authors: Xu Qing , Ma Xiaoqiong , Liang Xinmiao
Published: May 2007

A high‐performance liquid chromatography tandem atmospheric pressure chemical ionization mass spectrometry method (HPLC‐APCI‐MS) has been developed for the characterization of astragalosides in the extracts of the roots of Astragalus spp. The [M − H]− ions of astragalosides could be clearly observed in selected ion monitoring mode and APCI‐MS‐MS was used to further identify the structures of the astragalosides. Twelve astragalosides in the extracts of Radix Astragali obtained from Shandong in China were separated and identified. Using this method, astragalosides could be clearly identified and the profiles of these astragalosides could also be used to distinguish Astragalus spp. from different habitat regions. Copyright © 2007 John Wiley & Sons, Ltd.
Atrp synthesis of abc lipophilic–hydrophilic–fluorophilic triblock copolymers
Authors: Shunmugam Raja , Smith Cartney E. , Tew Gregory N.
Published: May 2007

New ABC triblock copolymers that contain lipophilic, hydrophilic, and fluorophilic blocks are reported. These new block copolymers were synthesized via sequential controlled/living atom transfer radical polymerization. The formation of block copolymers was confirmed by size exclusion chromatography, 1H, and 19F NMR. In direct comparison to the ABC copolymer, the corresponding ABA′ polymer did not produce a gel up to 45 wt % polymer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2601–2608, 2007
ACE inhibitors: their properties and role in hypertension
Authors: Ooi Sze‐Yuan , Ball Stephen
Published: May 2007

ACE inhibitors are now the first‐line choice of treatment of hypertension in younger patients, and a second‐line choice in all patient groups. Our Drug Review considers their properties and the evidence for their use in hypertension, followed by further sources of information, an analysis of pre scription data and the Datafile. Copyright © 2007 Wiley Interface Ltd
Über die Stabilität der Lösungen Hillscher Differentialgleichungen mit drei unabhängigen Parametern. Erste Mitteilung: Über die Gleichung yn+(λ+γ1cosx+γ2cos2x)y=0
Authors: Klotter Karl , Kotowski Gertrud
Published: May 2007

Das Stabilitätsverhalten der Lösungen der genannten Differentialgleichung wird dadurch untersucht, daß der Stabilitätskörper im λ‐γ1‐γ2‐Raum bestimmt wird. Zur Darstellung dienen Schnitte γ2=const durch diesen Körper. Der Schnitt γ2=0 stellt die „Struttsche Karte”︁ für die Mathieusche Differentialgleichung dar.
Das Impulsverfahren zur näherungsweisen Berechnung der laminaren Reibungsschicht
Authors: Mangler Werner
Published: May 2007

Um die Tragweite und die Grenzen des von Kármán [2] und Pohlhausen [3] zuerst verwendeten Impulssatzverfahrens abzuschätzen, wird ein verhältnismäßig allgemeiner (einparametriger) Ansatz für das Geschwindigkeitsprofil in der laminaren Reibungsschicht untersucht.
Die Verdunstungsgeschwindigkeit von Wolken. (Die numerische Integration eines Wärmeleitungsvorganges)
Authors: Oswatitsch Kl.
Published: May 2007

Sieht man von allen Bewegungsvorgängen ab, so stellt das Verdunsten von Wolken ein Wärmeleitungs‐ und Diffusionsproblem dar, bei welchem die Tropfen als Wärmesenken und Wasserdampfquellen anzusehen sind. Nach Aufstellen des Grundgleichungssystems wird ein numerisches Lösungsverfahren angegeben und an einem Beispiel angewendet.
Zur Herleitung der Ähnlichkeitsbedingungen aus der Identität der Differentialgleichungen
Authors: Schiller Ludwig
Published: May 2007

Die übliche Herleitung der Ähnlichkeitsbedingungen aus den Differentialgleichungen gründet sich darauf, daß in ähnlichen Fällen die dimensionslosen Gleichungen identisch sein müssen. Im folgenden wird gezeigt, daß durch bestimmte Wahl der Dimensionslosen die Gleichungen stets identisch gemacht werden können, so daß sich dann die Ähnlichkeitsbedingungen auf die Identität der Grenzbedingungen beschränken.
Zur Behandlung nichtstationärer Verdichtungsstöße und Detonationswellen
Authors: Schultz‐Grunow F.
Published: May 2007

Es wird gezeigt, daß man die Veränderlichkeit eines Verdichtungsstoßes und auch einer Detonationswelle in einem Zustandsdiagramm, dessen Koordinaten die Gas‐ und die Schallgeschwindigkeit sind, besonders leicht verfolgen kann.
Prenatal diagnosis by amniocentesis and chorionic villus biopsy of mtDNA mutation 8993T>G
Authors: Pettman R. , Hurley T. , Addis J. , Robinson B. , Scott H. , Kronick J. B.
Published: May 2007

The mtDNA mutation 8993T>G is associated with neurogenic muscle weakness, ataxia and retinitis pigmentosa (NARP) and Leigh syndrome. There are few reported cases of prenatal testing for mtDNA disorders. Specifically for 8993T>G, there are six cases in which prenatal diagnosis has been reported. We describe prenatal diagnosis in a 36‐year‐old G3P1 woman with 33% heteroplasmy in white blood cells. She had a previous child who died from Leigh disease (92% heteroplasmy). She underwent prenatal testing by both CVS and amniocentesis of the 8993T>G heteroplasmy levels. This is the first reported case in which both procedures were used. Heteroplasmy was similar in both tissues (58.6% CVS and 55% amniocentesis), in support of the theory that this testing is reliable and may be considered in prenatal cases where this mutation is known in the mother. To date, her child is 20 months old and developing normally. Heteroplasmy determination in the child was refused. Although the infant is developmentally normal, consistent with the observation that levels of heteroplasmy below 60% are compatible with a mild phenotype, this conclusion must be tempered by the limited period of observation and the fact that patients with the NARP phenotype often present later than 20 months of age.
A new genus and new species of free-living marine nematodes from the Yellow Sea, China
Authors: Huang Yong , Zhang Zhinan
Published: May 2007

A new genus and one new species of free-living marine nematodes Paramarylynnia gen. nov., Paramarylynnia
subventrosetata sp. nov. from the Yellow Sea, China are described and illustrated. Paramarylynnia gen. nov. is characterized
by a cuticle with transverse rows of even dots; absence of lateral differentiation; gubernaculum large and
dilated at the distal end, no distal dentation; precloacal supplements absent; tail conico-cylindrical.The type
species of Paramarylynnia gen. nov. is Paramarylynnia subventrosetata sp. nov.
Sperm ultrastructure of Microhedyle remanei, an interstitial acochlidian gastropod with dermal fertilization
Authors: Neusser Timea P. , Heß Martin , Haszprunar Gerhard , Schrödl Michael
Published: May 2007

The ultrastructure of sperm of an acochlidian opisthobranch is described for the first time in detail, in
the tiny, gonochoristic Microhedyle remanei (Microhedylidae) from Bermuda. Transmission electron microscopy
(TEM) shows the spermatozoa of M. remanei sharing many plesiomorphic features with
opisthobranch gastropods, such as having an apical spiral nucleus with a basal invagination filled with a
bell-shaped centriolar derivative; there is a single glycogen helix embedded into matrix and paracrystalline
material. Sperm of M. remanei are characterized by possessing a strongly helically coiled nucleus with
up to five keels terminating into one very prominent and intertwined keel. The sperm midpiece shows the
glycogen helix which is very densely arranged. This clearly differs from Hedylopsis ballantinei, a member of
the related acochlidian family Hedylopsidae, where three glycogen helices with different lengths and a
probably much shorter nucleus are present. This variation among acochlidian sperm may be phylogenetically
relevant and may be related to special acochlidian reproductive features such as sperm transfer via
hypodermic injection or dermal fertilization via spermatophores.
Organ weights of Pontoporia blainvillei and Sotalia guianensis (Cetacea: Pontoporiidae and Delphinidae)
Authors: Weber Rosas Fernando C. , de Oliveira Márcia R. , de Mattos Gália Ely
Published: May 2007

Weights of kidneys, heart, lungs, liver, adrenals, eyes and tongue of the northern form of franciscana
(Pontoporia blainvillei) and the estuarine dolphin (Sotalia guianensis) incidentally caught in fishing nets are
presented and related to total body weight. Because of the smaller body size of the northern form of
P. blainvillei, its actual organ weights were all smaller than those of the southern form reported in the
literature. However, the lungs and adrenals of the northern form were proportionally greater than those
of the southern form. The relative weight of the males' left kidney (N=18) and females' liver (N=17) were
significantly heavier in this study than the proportions presented elsewhere in the literature for the
southern form of the species. However, the females' kidneys, males' right kidney and males' liver did not
differ between the northern and southern forms, and a larger number of individuals of both geographical
forms should be analysed. The actual weights of the S. guianensis internal organs were all greater than those
reported in the literature for S. fluviatilis. Additionally, the body-to-organ mass proportions of kidneys,
heart and lungs of S. guianensis were also greater than those of S. fluviatilis. This study provides comparative
data that can be used when examining the systematics of both species and provides a baseline for future
examinations of the post-mortem conditions of these cetacean species.
Packing my Library
Authors: Deaville James
Published: May 2007

In reviewing and packing my musicological library in preparation for a move, I came across documentation for a variety of studies and projects from the late 1970s and early 1980s that were based upon an electronic future for musical scholarship. Twenty years ago, such pioneering musicologists as Ian Bent, Barry S. Brook, Jan LaRue, and William Malm were assembling large searchable databases of writings, music, and instruments, even as theorists like Mario Baroni, Allen Forte, and Arthur Wenk were exploring computer technology to analyze and devise “grammars” of melodic construction and to identify and compare pitch-class sets. In those pre-Oakland (barely pre-Contemplating Music) days of the American Musicological Society, the gathering of such sources was considered an honorable practice—indeed, we owe the eminently useful RILM to the perspicacious Brook. While these collections of data ostensibly were to enable comprehensiveness in study and serve the purposes of comparative analysis, they ultimately did not lead to interpretation, not at least of the critical type that Joseph Kerman and later Lawrence Kramer and Susan McClary were advocating.
Prediction of the 1‐AU arrival times of CME‐associated interplanetary shocks: Evaluation of an empirical interplanetary shock propagation model
Authors: Kim K.‐H. , Moon Y.‐J. , Cho K.‐S.
Published: May 2007

The traveltimes of interplanetary (IP) shocks at 1 AU associated with coronal mass ejections (CMEs) can be predicted by the empirical shock arrival (ESA) model of Gopalswamy et al. [2004] based on a constant IP acceleration. We evaluate the ESA model using 91 IP shocks identified from sudden commencement (SC)/sudden impulse (SI) on the Earth and by examining the solar wind data from the ACE and WIND satellites during the period of 1997 to 2002. Out of 91 CME‐IP shock pairs, 55 events (∼60%) were predicted within ±12 hours from the ESA model. The ESA model predicted ∼59% (43 out of 73) of the events during solar maximum (1999–2002) and ∼67% (12 out of 18) of the events during solar minimum (1997–1998) within ±12 hours from the predicted curve. Comparing the predicted (Tmod) and observed (Tobs) shock arrival times during solar maximum, we find that the deviations (ΔT = Tobs − Tmod) of shock arrival times from the ESA model strongly correlate with the CME initial speeds (VCME) (linear correlation, r = 0.77). Such a strong correlation indicates that the constant IP acceleration in the ESA model is not reasonably well applied for all VCME. From the linear regression analysis, we obtain a linear fit to the relationship (r = −0.62) between IP shock traveltime T (in hours) and VCME (in kilometer per second) during the solar maximum, which can be expressed as T = 76.86 − 0.02VCME. In addition, we find that the IP shocks associated with the fast CMEs corresponding to strong SC/SI events have short traveltimes compared with other fast CMEs and that there is a negative correlation between the SC/SI strength and the IP shock traveltime. We suggest that this negative correlation is due to not only the VCME but also the CME mass/density and discuss the influence of the mass/density of CME on the arrival time of IP shock at 1 AU.
Sensitivity of the retrieval of the inherent optical properties of marine particles in coastal waters to the directional variations and the polarization of the reflectance
Authors: Chami Malik , Platel Michael Defoin
Published: May 2007

The influences of the directional variations and the polarization of the marine reflectance on the retrieval of the inherent optical properties (IOP) (i.e., absorption, scattering, and backscattering coefficients) of water constituents in coastal waters are examined. First, an inversion algorithm based on artificial neural network (NN) methodology is developed using a synthetic data set. The simulations were carried out using a radiative transfer model that accounts for the polarization state of light in the ocean. The simulated data included various directional effects of the particles. The data set is also constrained by observations collected in optically representative coastal waters. In particular, the relationships that exist between the IOP were taken into account, thus making the data set realistic. The results showed that the total IOP were correctly retrieved while the performance of the algorithm to derive the IOP of each water component significantly degrades. However, the inclusion of the directional variations and the polarization of the reflectance in the algorithm improved the accuracy of retrieval of the scattering properties by 15%–60% and 65%–75%, respectively. The phytoplankton and noncovarying particles (i.e., nonalgal particles) scattering and backscattering coefficients were derived with an accuracy of 25% and 15% respectively. These results demonstrate the potential of using the polarized signal to separate the total IOP into contribution of biogenic and highly refractive particles in coastal waters. Therefore the development of in situ instrumentation able to measure the polarization properties of the particles is recommended.
Correcting photolysis rates on the basis of satellite observed clouds
Authors: Pour‐Biazar Arastoo , McNider Richard T. , Roselle Shawn J. , Suggs Ron , Jedlovec Gary , Byun Daewon W. , Kim Soontae , Lin C. J. , Ho Thomas C. , Haines Stephanie , Dornblaser Bright , Cameron Robert
Published: May 2007

Clouds can significantly affect photochemical activities in the boundary layer by altering radiation intensity, and therefore their correct specification in the air quality models is of outmost importance. In this study we introduce a technique for using the satellite observed clouds to correct photolysis rates in photochemical models. This technique was implemented in EPA's Community Multiscale Air Quality modeling system (CMAQ) and was tested over a 10 day period in August 2000 that coincided with the Texas Air Quality Study (TexAQS). The simulations were performed at 4 and 12 km grid size domains over Texas, extending east to Mississippi, for the period of 24 to 31 August 2000. The results clearly indicate that inaccurate cloud prediction in the model can significantly alter the predicted atmospheric chemical composition within the boundary layer and exaggerate or underpredict ozone concentration. Cloud impact is acute and more pronounced over the emission source regions and can lead to large errors in the model predictions of ozone and its by‐products. At some locations the errors in ozone concentration reached as high as 60 ppb which was mostly corrected by the use of our technique. Clouds also increased the lifetime of ozone precursors leading to their transport out of the source regions and causing further ozone production down‐wind. Longer lifetime for nitrogen oxides (NOx = NO + NO2) and its transport over regions high in biogenic hydrocarbon emissions (in the eastern part of the domain) led to increased ozone production that was missing in the control simulation. Over Houston‐Galveston Bay area, the presence of clouds altered the chemical composition of the atmosphere and reduced the net surface removal of reactive nitrogen compounds. Use of satellite observed clouds significantly improved model predictions in areas impacted by clouds. Errors arising from an inconsistency in the cloud fields can impact the performance of photochemical models used for case studies as well as for air quality forecasting. Air quality forecast models often use the model results from the previous forecast (or some adjusted form of it) for the initialization of the new forecast. Therefore such errors can propagate into the future forecasts, and the use of observed clouds in the preparation of initial concentrations for air quality forecasting could be beneficial.
Long‐term changes in the South China Sea summer monsoon revealed by station observations of the Xisha Islands
Authors: Liang Jianyin , Yang Song , Li Cunhui , Li Xia
Published: May 2007

The authors depict the long‐term changes in the South China Sea (SCS) summer monsoon using observational data of the Xisha Islands. The SCS monsoon is an important component of the Asian monsoon system, and its long‐term changes have seldom been explored because of the unavailability of reliable data. The daily Xisha station observations provide an important source of information for understanding the changes in the monsoon. The intensity of the SCS summer monsoon measured by kinetic energy decreased significantly from 1958–1977 to 1978–2004. This change in monsoon was mainly caused by the weakening of the meridional component of lower tropospheric winds, and the weakening in the mean flow was signaled by decreased frequency of strong southerlies (6 m s−1 and above) of the daily winds. The weakening of the monsoon was also associated with increases in sea surface temperature and surface and lower tropospheric air temperatures over SCS, which occurred more frequently when daily surface temperature reaches 29°C and higher. The long‐term warming of the lower troposphere was accompanied by cooling at the upper troposphere, destabilizing the local atmosphere. However, from 1958–1977 to 1978–2004, the long‐term change in Xisha precipitation tended to decrease; furthermore, in fact, the station precipitation became less variable. Thus besides local air‐sea interaction, large‐scale atmospheric forcing also plays an important role in causing the long‐term change of the Xisha precipitation. Indeed, the warming of Xisha was linked to large‐scale warming in the tropics including SCS and was associated with smaller thermal contrast between the Asian continent and the surrounding oceans, which weakened monsoon circulation.
Observed and simulated vertically resolved optical properties of continental aerosols over southeastern Italy: A closure study
Authors: Barnaba F. , Tafuro A. M. , De Tomasi F. , Perrone M. R.
Published: May 2007

A 2.5‐year data set of Raman lidar measurements performed in Lecce within the European Aerosol Research Lidar Network and a numerical model are used to characterize continental aerosols over southeast Italy. Continental conditions are selected by means of back trajectories, limiting the data set to cases of advection from the European continent. The model is used to constrain the relevant aerosol microphysical parameters needed to reproduce the altitude‐resolved optical properties measured by lidar, namely, aerosol extinction (α), backscatter (β), and lidar ratio (LR = α/β) at 351 nm. The observed variability of α, β, and LR is simulated by randomly varying, within appropriate ranges, all the microphysical parameters describing the aerosol composition and size distribution (assumed as bimodal). An optimal model configuration capable of reproducing within ±10% the mean optical properties retrieved by lidar, including their vertical pattern, is presented and discussed with sensitivity studies. Results indicate rather clean continental aerosols to characterize the site, with water‐soluble fine‐mode aerosols (dry modal radius of 0.05–0.10 μm) accounting for 98–99% of the total number of particles. The (dry) imaginary refractive index of fine‐mode particles is extended up to 0.02 to better fit the lidar data. This suggests some mixing of water‐soluble substances with more absorbing material. Coarse‐mode particles (modal radius 0.4–0.5 μm) are shown to play a crucial role in determining the observed vertical profile of β and LR. Finally, an altitude‐resolved relationship linking α to β is derived. This could be usefully employed in continental conditions to invert the lidar measurements when only the elastic signal is available (for example, in daylight).
Near‐infrared optical constants of pyroxene as a function of iron and calcium content
Authors: Denevi B. W. , Lucey P. G. , Hochberg E. J. , Steutel D.
Published: May 2007

We derive the imaginary coefficient of the complex index of refraction (k) from reflectance spectra of 30 pyroxenes using the method of Lucey (1998). We apply the modified Gaussian model of Sunshine et al. (1990) to these k spectra to obtain two continuum parameters and nine Gaussian parameters that describe the 1, 2, and 1.2 μm crystal field absorptions. This method takes advantage of the redundancy in the data and minimizes the number of free parameters, resulting in a compact expression of optical constants that is less susceptible to noise in the data and contamination from terrestrial weathering. Multiple regression results indicate that the continuum and Gaussian parameters are well predicted by pyroxene FeO and CaO contents; thus a complete k spectrum for pyroxene can be derived from arbitrary FeO and CaO concentrations. The uncertainty is highest for the 1.2 μm M1 crystal field absorption in both orthopyroxene and clinopyroxene. These k spectra can be used with radiative transfer theory to produce model reflectance spectra of particulate silicate surfaces at different viewing geometries, particle sizes, levels of space weathering, and mixtures with other minerals.
A comparative quadrant analysis of turbulence in a plant canopy
Authors: Yue Wusi , Meneveau Charles , Parlange Marc B. , Zhu Weihong , van Hout René , Katz Joseph
Published: May 2007

Large‐eddy simulation (LES) of turbulence in plant canopies has traditionally been validated using bulk statistical quantities such as mean velocity and variance profiles. However, turbulent exchanges between a plant canopy and the atmosphere are dominated by large‐scale coherent structures, and therefore LES must also be validated using statistical tools that are sensitive to details of coherent structures. In this study, LES and measurements using particle image velocimetry (PIV) are compared near the top of the canopy by means of a quadrant‐hole analysis of turbulent kinetic energy, vorticity, and dissipation rate. The LES resolves coarse features of individual corn plants and uses the Lagrangian scale‐dependent dynamic subgrid model. At the measurement location, there is good agreement between the LES predictions and the field data in terms of most conditionally sampled quantities, confirming the applicability of LES for fundamental studies of vegetation‐air interactions and coherent structures. The simulation results confirm that sweeps (the fourth‐quadrant events) contribute the largest fraction of turbulent kinetic energy, vorticity, and dissipation rate inside the plant canopy. The magnitudes of the vorticity and dissipation rate at the top of the canopy are highest in the first quadrant (rare events of outward interactions).
Reactive magnetron sputtering of tungsten disulfide (WS2−x) films: Influence of deposition parameters on texture, microstructure, and stoichiometry
Authors: Weiß V. , Seeger S. , Ellmer K. , Mientus R.
Published: May 2007

Tungsten disulfide (WS2−x) films (0.07⩽x⩽0.7) were prepared by reactive magnetron sputtering from a tungsten target in rare gas/H2S atmospheres and at substrate temperatures up to 620°C. The nucleation and growth of the films were investigated by in situ energy dispersive x-ray diffraction (EDXRD) and by ex situ techniques such as electron microscopy, elastic recoil detection analysis, and x-ray reflectivity. From the EDXRD analysis it was found that the films always nucleate with the (001) planes, i.e., the van der Waals planes, parallel to the substrate surface. For high deposition rates and/or low substrate temperatures a texture crossover from the (001) to the (100) crystallite orientation occurs during the growth. High deposition rates, low substrate temperatures, or low sputtering pressures lead to a significant lattice expansion of the crystallites in the c direction (up to 3%). This is most probably caused by a disturbed or turbostratic film growth induced by the energetic bombardment during film deposition. Reflected and neutralized energetic ions (Ar0,S0) from the tungsten target and negative ions (S−) accelerated in the cathode dark space constitute the main sources of the energetic bombardment leading to crystallographic defects. The energy of these particles can be tailored by (i) thermalization between target and substrate in the sputtering gas or (ii) by a reduction of the discharge or target voltage, respectively, by high frequency excitation of the plasma. Films deposited under favorable conditions with respect to low particle energies and at substrate temperatures higher than 200°C exhibit a significant sulfur deficiency of up to about 5at.% compared to the stoichiometric composition of WS2. This is ascribed to an energetic particle bombardment-induced sulfur desorption from the growing films.
Transition from Bohm to classical diffusion due to edge rotation of a cylindrical plasma
Authors: Maggs J. E. , Carter T. A. , Taylor R. J.
Published: May 2007

The outer region of the plasma column of a large, linear plasma device is rotated in a controlled fashion by biasing a section of the vacuum chamber wall positive with respect to the cathode (Er<0). The magnitude and temporal dependence of the observed cross-field current, produced when the bias voltage is applied, is consistent with ion current arising from ion-neutral collisions. Flow speeds in the outer regions of the plasma column exceed the local sound speed. In the nonrotating plasma column, cross-field, radial particle transport proceeds at the Bohm diffusion rate. Rotation, above a threshold bias voltage, reduces cross-field transport from Bohm to classical rates, leading to steeper radial density profiles. Reduction of particle transport is global and not isolated to the region of flow shear. The transition from the nonrotating to the rotating plasma edge in the linear plasma column is similar to the low confinement to high confinement mode transition observed in tokamaks when Er<0.
Simulation studies of non-neutral plasma equilibria in an electrostatic trap with a magnetic mirror
Authors: Gomberoff K. , Fajans J. , Wurtele J. , Friedman A. , Grote D. P. , Cohen R. H. , Vay J.-L.
Published: May 2007

The equilibrium of an infinitely long, strongly magnetized, non-neutral plasma confined in a Penning-Malmberg trap with an additional mirror coil has been solved analytically [J. Fajans, Phys. Plasmas 10, 1209 (2003)] and shown to exhibit unusual features. Particles not only reflect near the mirror in the low field region, but also may be weakly trapped in part of the high field region. The plasma satisfies a Boltzmann distribution along field lines; however, the density and the potential vary along field lines. Some other simplifying assumptions were employed in order to analytically characterize the equilibrium; for example the interface region between the low and high field regions was not considered. The earlier results are confirmed in the present study, where two-dimensional particle-in-cell (PIC) simulations are performed with the Warp code in a more realistic configuration with an arbitrary (but physical) density profile, realistic trap geometry and magnetic field. A range of temperatures and radial plasma sizes are considered. Particle tracking is used to identify populations of trapped and untrapped particles. The present study also shows that it is possible to obtain local equilibria of non-neutral plasmas using a collisionless PIC code, by a scheme that uses the inherent numerical collisionality as a proxy for physical collisions.
Ab initio melting curve of molybdenum by the phase coexistence method
Authors: Cazorla C. , Gillan M. J. , Taioli S. , Alfè D.
Published: May 2007

Ab initio calculations of the melting curve of molybdenum for the pressure range 0–400 GPa are reported. The calculations employ density functional theory (DFT) with the Perdew-Burke-Ernzerhof exchange-correlation functional in the projector augmented wave (PAW) implementation. Tests are presented showing that these techniques accurately reproduce experimental data on low-temperature body-centered cubic (bcc) Mo, and that PAW agrees closely with results from the full-potential linearized augmented plane-wave implementation. The work attempts to overcome the uncertainties inherent in earlier DFT calculations of the melting curve of Mo, by using the “reference coexistence” technique to determine the melting curve. In this technique, an empirical reference model (here, the embedded-atom model) is accurately fitted to DFT molecular dynamics data on the liquid and the high-temperature solid, the melting curve of the reference model is determined by simulations of coexisting solid and liquid, and the ab initio melting curve is obtained by applying free-energy corrections. The calculated melting curve agrees well with experiment at ambient pressure and is consistent with shock data at high pressure, but does not agree with the high-pressure melting curve deduced from static compression experiments. Calculated results for the radial distribution function show that the short-range atomic order of the liquid is very similar to that of the high-T solid, with a slight decrease of coordination number on passing from solid to liquid. The electronic densities of states in the two phases show only small differences. The results do not support a recent theory according to which very low dTm∕dP values are expected for bcc transition metals because of electron redistribution between s-p and d states.
Faceting during GaAs quantum dot self-assembly by droplet epitaxy
Authors: Heyn Ch. , Stemmann A. , Schramm A. , Welsch H. , Hansen W. , Nemcsics Á.
Published: May 2007

Strain-free GaAs quantum dots (QDs) are grown in a self-assembled fashion by applying Ga droplet epitaxy. The QDs are studied using electron diffraction and atomic force microscopy. Two distinct regimes are observed for the QD shape. QDs whose volume exceeds approximately 3×105 Ga atoms are shaped like truncated pyramids with side facets having an angle of about 55°. Smaller QDs are pyramidlike with 25° facets.
Direct imaging of a laser mode via midinfrared near-field microscopy
Authors: Moreau Virginie , Bahriz Michael , Colombelli Raffaele , Lemoine Paul-Arthur , De Wilde Yannick , Wilson Luke R. , Krysa Andrey B.
Published: May 2007

Fabry-Pérot standing waves inside a midinfrared quantum cascade laser have been imaged using an apertureless scanning near-field optical microscope. The devices emit at λ≈7.7μm and they feature air-confinement waveguides, with the optical mode guided at the semiconductor-air interface. A consistent portion of the mode leaks evanescently from the device top surface and can be detected in the near field of the device. Imaging of the evanescent wave across a plane parallel to the device surface allows one to directly assess the effective light wavelength inside the laser material, yielding the effective index of refraction. Imaging across a plane perpendicular to the device surface allows one to directly measure the electric field decay length, which is found in excellent agreement with the numerical simulations.
Multipath-switching device utilizing a GaAs-based multiterminal nanowire junction with size-controlled dual Schottky wrap gates
Authors: Kasai Seiya , Nakamura Tatsuya , Shiratori Yuta
Published: May 2007

A multipath-switching device using a multiterminal nanowire junction with size-controlled dual gates is proposed and demonstrated experimentally. The device switches a number of output terminals according to multiple-valued input voltages for electrons entering from a root terminal. The switching function is implemented by dual gating on multiple nanowires with different threshold voltages Vth. Systematic Vth shift is made by changing gate lengths in nanometer scale. A triple-path-switching device is fabricated using AlGaAs∕GaAs etched nanowires and nanometer-scale Schottky wrap gates. Its correct operation is confirmed at room temperature. Obtained results are explained by a simple analytical model.
Fabrication of Zr–N codoped p-type ZnO thin films by pulsed laser deposition
Authors: Kim H. , Cepler A. , Osofsky M. S. , Auyeung R. C. Y. , Piqué A.
Published: May 2007

N-doped and Zr–N codoped p-type ZnO films were grown on sapphire substrates by pulsed laser deposition. The carrier type and conduction are very sensitive to N2O deposition pressure. p-type conduction is observed only for films grown at an intermediate pressure range (5×10−5–5×10−4Torr). The Zr–N codoped ZnO films grown at 500°C in 5×10−5Torr of N2O show p-type conduction behavior with a low resistivity of 0.026Ωcm, a carrier concentration of 5.5×1019cm−3, and a mobility of 4.4cm2V−1s−1. The p-type conduction behavior of Zr–N codoped ZnO films is also confirmed by the rectifying I-V characteristics of p-n heterojunctions (p-ZnO∕n-Si).
Characterization of power induced heating and damage in fiber optic probes for near-field scanning optical microscopy
Authors: Dickenson Nicholas E. , Erickson Elizabeth S. , Mooren Olivia L. , Dunn Robert C.
Published: May 2007

Tip-induced sample heating in near-field scanning optical microscopy (NSOM) is studied for fiber optic probes fabricated using the chemical etching technique. To characterize sample heating from etched NSOM probes, the spectra of a thermochromic polymer sample are measured as a function of probe output power, as was previously reported for pulled NSOM probes. The results reveal that sample heating increases rapidly to ∼55–60°C as output powers reach ∼50nW. At higher output powers, the sample heating remains approximately constant up to the maximum power studied of ∼450nW. The sample heating profiles measured for etched NSOM probes are consistent with those previously measured for NSOM probes fabricated using the pulling method. At high powers, both pulled and etched NSOM probes fail as the aluminum coating is damaged. For probes fabricated in our laboratory we find failure occurring at input powers of 3.4±1.7 and 20.7±6.9mW for pulled and etched probes, respectively. The larger half-cone angle for etched probes (∼15° for etched and ∼6° for pulled probes) enables more light delivery and also apparently leads to a different failure mechanism. For pulled NSOM probes, high resolution images of NSOM probes as power is increased reveal the development of stress fractures in the coating at a taper diameter of ∼6μm. These stress fractures, arising from the differential heating expansion of the dielectric and the metal coating, eventually lead to coating removal and probe failure. For etched tips, the absence of clear stress fractures and the pooled morphology of the damaged aluminum coating following failure suggest that thermal damage may cause coating failure, although other mechanisms cannot be ruled out.
Intact endothelial cell sheet harvesting from thermoresponsive surfaces coated with cell adhesion promoters
Authors: Moran Martin T , Carroll William M , Gorelov Alexander , Rochev Yuri
Published: May 2007

Recently, with the development of smart polymers, research has looked to using thermoresponsive polymers as cell culture substrates. These novel surfaces allow the cultivation of cells without enzymes using the thermoresponsive phase transition property of poly(
N
-isopropylacrylamide) (PNIPAAm). However, this requires expensive techniques to generate a sufficiently thin film that allows cell adhesion. In this study, we looked at simple solvent cast films which normally show poor cell adhesion, but here the films are coated with cell adhesion promoters (CAPs) to improve cell growth without altering the copolymer thermoresponsive behaviour.

A copolymer of PNIPAAm and
N
-
tert
-butylacrylamide (NtBAm) with a ratio of 85 : 15, respectively, was synthesized and solvent cast. The copolymer films were coated with CAPs, such as collagen, fibronectin and laminin, to increase their cell adhesion and growth properties. Cell activity measured by the alamarBlue assay showed similar results for coated copolymer films and standard tissue culture plastic controls. Deposition of CAPs on to the copolymer films was characterized by scanning electron microscopy and atomic force microscopy. Cell detachment from the copolymer films is not affected by the surface coatings of CAPs, and endothelial cells are recovered as an intact sheet, which has great potential for uses in tissue engineering applications. The results demonstrate a versatile method for the cultivation of cells while eliminating the need for the use of digestive enzymes such as trypsin. This study shows that cultivation on physically bonded PNIPAAm copolymers is viable and achievable by relatively simple methods.
Genetic and environmental contributions to population group differences on the Raven's Progressive Matrices estimated from twins reared together and apart
Authors: Rushton J. Philippe , Bons Trudy Ann , Vernon Philip A , Čvorović Jelena
Published: May 2007

We carried out two studies to test the hypothesis that genetic and environmental influences explain population group differences in general mental ability just as they do individual differences within a group. We estimated the heritability and environmentality of scores on the diagrammatic puzzles of the Raven's Coloured and/or Standard Progressive Matrices (CPM/SPM) from two independent twin samples and correlated these estimates with group differences on the same items. In Study 1, 199 pairs of 5- to 7-year-old monozygotic (MZ) and dizygotic (DZ) twins reared together provided estimates of heritability and environmentality for 36 puzzles from the CPM. These estimates correlated with the differences between the twins and 94 Serbian Roma (both
r
s=0.32;
N
s=36;
p
s<0.05). In Study 2, 152 pairs of adult MZ and DZ twins reared apart provided estimates of heritability and environmentality for 58 puzzles from the SPM. These estimates correlated with the differences among 11 diverse samples including (i) the reared-apart twins, (ii) another sample of Serbian Roma, and (iii) East Asian, White, South Asian, Coloured and Black high school and university students in South Africa. In 55 comparisons, group differences were more pronounced on the more heritable and on the more environmental items (mean
r
s=0.40 and 0.47, respectively;
N
s=58;
p
s<0.05). After controlling for measurement reliability and variance in item pass rates, the heritabilities still correlated with the group differences, although the environmentalities did not. Puzzles found relatively difficult (or easy) by the twins were those found relatively difficult (or easy) by the others (mean
r
=0.87). These results suggest that population group differences are part of the normal variation expected within a universal human cognition.
Time-of-flight neutron powder diffraction with a thick-walled sample cell
Authors: Gray E. MacA. , Smith R. I. , Pitt M. P.
Published: May 2007

The time-of-flight diffraction techniques that are normally practiced at pulsed neutron sources afford opportunities that are not readily available at continuous fixed-wavelength sources. The present work concerns the increasing trend in materials science to study samples in complex non-ambient environments, such as high gas pressure. Taking the example of a sample cell in which a material is studied under fluid pressure, the optimization of the cell design for best data collection rate is considered. The design of primary- and scattered-beam masks for eliminating background scattering from the sample cell and the correction of the data for cell and sample attenuation are addressed. The outputs of this work include a simple expression for the optimum wall thickness of a thick-walled sample cell, a procedure for accurately determining the required mask aperture width for any scattering angle, more compact expressions for some of the results of the work of Paalman & Pings [J. Appl. Phys.(1962),33, 2635–2639] on absorption corrections, and guidance as to the correction of diffraction profiles for cell and background effects. Examples are given, drawn from studies of materials under hydrogen gas pressures up to 1800 bar in cells constructed from Ti2.1Zr and Inconel.
Extending the charge-flipping method towards structure solution from incomplete data sets
Authors: Palatinus Lukáš , Steurer Walter , Chapuis Gervais
Published: May 2007

The charge-flipping method tends to fail if applied to an incomplete diffraction data set. The reason is artifacts induced in the density maps by Fourier transforming the data. It is shown that the missing data can be sufficiently well approximated on the basis of the Patterson map of the unknown structure optimized by the maximum entropy method (MEM). Structures that could not be solved by the original charge-flipping algorithm can be solved by the proposed method. The method has been tested on experimental data of one inorganic and two organic structures and on several types of missing data. In many cases, up to 50% of missing reflections, or even more, can be tolerated and the structure can still be reconstructed by charge flipping.
Quantitative analysis of lamellar structures in brush polymer thin films by synchrotron grazing-incidence X-ray scattering
Authors: Yoon Jinhwan , Jin Kyeong Sik , Kim Hyun Chul , Kim Gahee , Heo Kyuyoung , Jin Sangwoo , Kim Jehan , Kim Kwang-Woo , Ree Moonhor
Published: May 2007

In this study, a grazing-incidence X-ray scattering (GIXS) formula was derived for lamellar structures formed in thin films supported on substrates, and a comprehensive numerical analysis was performed using the scattering formula. A quantitative analysis was conducted of lamellar structures formed in nanometre-scaled thin films of a brush polymer, poly[oxy(n-decylthiomethylenyl)ethylene], supported on silicon substrates, by GIXS measurements during cooling and subsequent heating, and data analysis was performed using the scattering formula. This analysis provided details (long period, sub-layers and their thicknesses, volume fraction, bristle paracrystal distortion factor, and orientation) of the lamellar structure with varying temperature that are not easily obtained using conventional techniques. Moreover, a molecular structure model and electron density profiles were established.
Contrast variation by anomalous X-ray scattering applied to investigation of the interface morphology in a giant magnetoresistance Fe/Cr/Fe trilayer
Authors: Feygenson Mikhail , Kentzinger Emmanuel , Ziegenhagen Nicole , Rücker Ulrich , Goerigk Günter , Wang Yingang , Brückel Thomas
Published: May 2007

The structural properties of an epitaxically grown Fe/Cr/Fe trilayer were studied with anomalous X-ray scattering. Two different X-ray energies have been used: (i)E1= 5985 eV to match the maximum contrast of the Fe/Cr interface close to the Cr absorptionKedge; (ii)E2= 6940 eV where the Fe/Cr interface displays the lowest contrast. The specular reflectivity and longitudinal diffuse scans together with ω scans for both energies were measured. The simulations within the frame of the distorted-wave Born approximation allowed a quantitative description of the morphology of each interface. The roughness, Hurst parameter and the thickness of every layer, as well as an oxidation effect at the surface of the sample, are derived. The strength and limitations of the method are discussed.