bluuebunny/crossref_metadata_2025 huggingface dataset:
Data reduction for prediction: A case study on robust coding of age and family history for the risk of having a genetic mutation
Authors: Steyerberg Ewout W. , Balmaña Judith , Stockwell David H. , Syngal Sapna
Published: October 2007

Data reduction is often desired in the development of a prediction model, for example for effects of age and family history in the identification of subjects having a genetic mutation. We aimed to evaluate a strategy for model simplification by robust coding of related predictors. We considered 898 patients suspected of having Lynch syndrome, which is caused primarily by mutations in the mismatch repair genes, MLH1 or MSH2. The presence of colorectal cancer (CRC) and endometrial cancer in patients and their relatives was related to mutation prevalence with logistic regression analysis. The performances of simplified and more complex models were quantified with a concordance statistic (c), which was corrected for optimism by cross‐validation and bootstrapping. External validation was performed in 1016 patients.

The first challenge was the coding of age at diagnosis of CRC, where we forced effects to be identical in patients, in 1st degree and in 2nd degree relatives, by taking the sum of the ages at diagnosis. As a further simplification, CRC diagnosis in 2nd degree relatives was weighted half that of 1st degree relatives. These data reduction approaches were also followed for endometrial cancer. The simplified model used 7 instead of 17 degrees of freedom (df) for a more complex model incorporating individual predictor effects. The optimism‐corrected c was higher (0.79 instead of 0.77), but the external c was similar (0.78 for the simplified and more complex models). A stepwise selected model performed slightly worse (external c=0.77). In conclusion, a prediction model could be developed with relatively few df that captured effects of age at diagnosis across patients and relatives per type of cancer in the family. Such robust coding may especially be relevant for modeling in relatively small data sets. Copyright © 2007 John Wiley & Sons, Ltd.
Early sonographic prenatal diagnosis of seizures
Authors: Sheizaf B. , Mazor M. , Landau D. , Burstein E. , Bashiri A. , Hershkovitz R.
Published: October 2007

Fetal seizures are an unusual phenomenon. When diagnosed by ultrasonography, they are frequently associated with malformations and carry a poor prognosis. We describe first trimester seizures in two siblings with arthrogryposis multiplex congenita. In both cases, convulsions appeared before other sonographic signs of the disease. Review of the literature revealed 11 other cases of fetal seizures diagnosed by ultrasound, all later in gestation. Fetal seizures may be the first manifestation of defective neural and motor development. Therefore, in pregnancies at high risk for neuromuscular disease, early sonographic evaluation of fetal motility, in addition to the anatomical survey, is advised. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
Engaging Nurses in Genetics: The Strategic Approach of the NHS National Genetics Education and Development Centre
Authors: Kirk Maggie , Tonkin Emma , Burke Sarah
Published: October 2007

The UK government announced the establishment of an NHS National Genetics Education and Development Centre in its Genetics White Paper. The Centre aims to lead and coordinate developments to enhance genetics literacy of health professionals. The nursing program takes a strategic approach based on Ajzen's Theory of Planned Behavior, using the UK nursing genetics competences as the platform for development. The program team uses innovative approaches to raise awareness of the relevance of genetics, working collaboratively with policy stakeholders, as key agents of change in promoting competence. Providing practical help in preparing learning and teaching resources lends further encouragement. Evaluation of the program is dependent on gathering baseline data, and the program has been informed by an education needs analysis. The challenges faced are substantial and necessitate international collaboration where expertise and resources can be shared to produce a global system of influence to facilitate the engagement of non‐genetic nurses.
Family‐based Detection for Hereditary Hemochromatosis
Authors: Reyes Michele , Dunet Diane O. , Isenberg Karen Bandel , Trisolini Michael , Wagener Diane K.
Published: October 2007

The purpose of this study was to examine motivators for and barriers to family‐based detection for hereditary hemochromatosis (HH). HH patients (n = 60) and HH siblings (n = 25) participated in one‐on‐one or group interviews. Patients and siblings understood that HH “runs in families,” but not that siblings are at higher HH risk than other family members. Patient motivators included concern for siblings’ health, seriousness of untreated HH, and doctor's encouragement to tell siblings that they need to seek diagnostic testing. Siblings were motivated by the seriousness of HH. Barriers included lack of symptoms, belief that HH was rare, and assumption that their doctor would have mentioned the risk of HH. Family‐based detection continues to be a feasible part of an overall public health strategy to promote early detection of HH. Greater awareness of HH and its potential consequences, especially among high‐risk groups, provides an additional potential avenue for public health action.
Effects of anthropogenic disturbances on the butterfly assemblage in an urban green area: the changes from 1990 to 2005 in Kanazawa Castle Park, Japan
Authors: Ohwaki Atsushi , Tanabe Shin‐Ichi , Nakamura Koji
Published: October 2007

Kanazawa Castle Park (KCP) is an isolated urban green area in Kanazawa, Japan. A mature forest had developed there since 1949, but it was partially deforested from 1996 to 1999. Moreover, most of the grasslands in KCP were removed from 2000 to 2002. In this study, we report the damage to the butterfly assemblage by these anthropogenic disturbances and subsequent recovery after the disturbances, using previous literature on the butterfly assemblage in KCP from 1990 to 1994 and our monitoring data from 1999 to 2005. In addition, to understand urbanization effects, we also compared the butterfly assemblage of KCP with that of Tawara, a satoyama area 6 km away from KCP. Before the urbanization around KCP, KCP might have had a butterfly assemblage similar to Tawara. The previous articles indicate that 33 species lived in KCP before the partial deforestation. The number of generalist species (multivoltine and polyphagous species) was similar in KCP and Tawara (22 vs. 19), but that of specialist species (uni‐bivoltine and oligophagous species) was lower in KCP than in Tawara (5 vs. 15). Six species, composed of a bamboo grass feeder, mantle feeders, herb/grass feeders, and a multi‐feeder, disappeared from KCP after the deforestation and have not yet recolonized. The grassland removal also affected herb/grass feeders negatively, but they have been recovering quickly following the partial grassland recovery. Some species that disappeared after the deforestation were sporadically found from 2000 to 2005 probably due to immigration from the surrounding rural areas (the nearest one is 2 km away). For recolonization of the lost species, recovery of the interior and edge of the forest, which are the habitats for these species, is necessary.
Taurodontismus und Klinefelter-Syndrom
Authors: Steffen R.
Published: October 2007

Dieser Fallbericht soll die Zusammenhänge zwischen dem Krankheitsbild des Klinefelter-Syndroms mit dem des dentalen Erscheinungsbildes des Taurodontismus zeigen. Der Fall eines Jungen wird geschildert, welcher vom Klinefelter-Syndrom betroffen ist und damit verbunden taurodontisch ausgebildete Zahnanlagen besitzt. Dabei wird exemplarisch gezeigt, wie wichtig ein geregelter zahnärztlicher Recall bei Patienten mit erkanntem Taurodontismus ist. Die Zusammenarbeit mit weiteren Spezialisten, um wie in diesem Fall eine genetische Erkrankung diagnostizieren zu können, ist von hoher klinischer Relevanz.
Elvis and Darmstadt, or: Twentieth-Century Music and the Politics of Cultural Pluralism
Authors: CLARKE DAVID
Published: October 2007

[PART 1] Contemporary musical production and consumption have become increasingly pluralist, seemingly bearing out postmodernist accounts of the eroding distinction between ‘high’ and ‘low’ cultures. Accordingly, accounts of twentieth-century music ought to be able to narrate these different musical spheres – emblematized by the phenomena of Elvis and Darmstadt – together. While such gestures are not altogether absent from some recent histories of twentieth-century music, the results suggest that a more developed theorization of cultural pluralism is needed, one that also has a political dimension. Liberalism is one polity that espouses cultural pluralism and value pluralism, ideas that are not entirely separable from postmodernist relativism. Both epistemes are limited, however, by a disinclination towards dialectical thought and by the absence of ideology critique. [PART 2] Theoretical concepts from Slavoj Žižek (influenced by Lacanian psychoanalysis, and Laclau and Mouffe’s ideas of radical democracy) hold the potential for a post-Marxian model of ideology critique that might galvanize approaches to musical pluralism. Such an application could be relevant to various kinds of music, without giving a priori preference to one musical style over another – as was the case with Adorno. That said, these ideas have significant resonances with Adorno’s negative dialectics, and are valuable in developing a form ofstrong relativismthat could dialecticize a dialogical approach to musical pluralism. This suggests the possilbity of construing pluralism not as the achievement of stasis (or ‘the end of history’), but as a means of effecting social and historical movement beyond the present cultural paradigm.
Ionospheric responses to the October 2003 superstorm: Longitude/local time effects over equatorial low and middle latitudes
Authors: Abdu Mangalathayil A. , Maruyama Takashi , Batista Inez S. , Saito Susumo , Nakamura Maho
Published: October 2007

Ionospheric responses to the major magnetic storm disturbances of October 2003 are investigated using database selected in the Brazilian and Japanese‐Asian longitude sectors. Data obtained from latitudinally spaced digisondes in the equatorial and low‐latitude sites in Brazil and from the Asian and Japanese ionosonde network, the total electron content data from the extensive Japanese GPS receiver chain, and magnetometer data from the Pacific equatorial electrojet stations are analyzed during the period 28–31 October. Prompt penetrating (PP) dawn‐dusk polar cap electric fields produce large F region plasma uplift on the dayside and eveningside, while the associated westward electric field on the nightside produces large downdraft of the F region plasma, and causes development of westward electrojet current, observed for the first time. Episodes of PP electric field effects appear to be of larger intensity over Brazil than over Asian longitudes. Equatorial anomaly, development due to undershielding as well as overshielding electric fields, was observed in the Brazilian and in the Asian sectors. Disturbance dynamo electric field causes large nighttime F layer uplifts that are modulated by strong meridional winds in both sectors. The disturbance electric field local time variation patterns are compared with the results of recent global model (MTIEGCM) simulation by Richmond et al. (2003) and validated in some cases. Transients of transequatorial winds, flipping direction from southward to northward, in the widely separated longitude sectors, were diagnosed to be present toward the final recovery phase of the storm. These results are presented and discussed in this paper.
Numerical modeling of ocean‐ice interactions under Pine Island Bay's ice shelf
Authors: Payne Antony J. , Holland Paul R. , Shepherd Andrew P. , Rutt Ian C. , Jenkins Adrian , Joughin Ian
Published: October 2007

A two‐dimensional numerical model is used to simulate the dynamics of buoyant, meltwater‐rich plumes flowing beneath the ice shelf occupying much of Pine Island Bay, West Antarctica. Recent studies have shown that this ice shelf, along with all others fringing the Amundsen Sea, is thinning rapidly. In the model, both the Coriolis effect and subshelf topography are important in controlling plume dynamics and the spatial distribution of ice melt. Melt is concentrated in a narrow zone within ∼20 km of the grounding line where steep subshelf slopes and access to warm ambient water allow melt rates to exceed 100 m yr−1. The plume generated by entrainment of ambient water into the meltwater in these areas is guided by the topography of the ice shelf underside and exits the ice shelf at three distinct outflow locations. Melt rates generated along the course of the plume are higher (approximately 2.5×) than rates elsewhere. The model suggests that the observed ice shelf thinning rates could have resulted from a hypothetical instantaneous 0.25°C warming of the ambient water entrained by the plume. A context for this value is provided by the 40‐year warming trend documented by Jacobs et al. (2002) for Circumpolar Deep Water in the nearby Ross Sea.
Evolution of lightning in an isolated hailstorm of moderate size in the tropics
Authors: Kamra A. K. , Pawar S. D.
Published: October 2007

Evolution of lightning activity in a tropical hailstorm of moderate size that developed in the premonsoon season at Pune (18°32′N, 73°51′E, 559 m above sea level) is studied from the measurements of surface electric field, the Maxwell current and thunder. Total flash rate is counted from the electric field record, and the cloud‐to‐ground (CG) flash rate is estimated from the visual observations. Precise timings of their occurrence were confirmed from the observations of overshoot in the Maxwell current records. The storm exhibited an almost constant rate of one CG flash every 1 to 2 min over the whole life time of the storm. The ratio of intracloud (IC) to CG flashes (IC/CG) increased with the increase in total flash rate. In the convective stage of the storm, field changes from consecutive flashes were generally found to alternate in polarity. Moreover, in this stage, field changes occur in pairs, the first field change of each pair being of negative polarity and the second one of positive polarity. The two field changes in a pair occur with an average time difference of 14.3 ± 8.4 s while two consecutive pairs appear after 29.3 ± 9.1 s. In between the convective and mature stages, our observations suggest the occurrence of the phenomenon of rain gush and the field excursion associated with falling precipitation. Development of the mature stage was marked with rapid transitions in the surface electric field and the Maxwell current polarities from negative to positive. Further, total flash rate and IC/CG ratio sharply increase, and the lightning‐induced electric field changes become almost exclusively of negative polarity. Observations suggest possibly a lifting up of the charging region in mature stage of the storm. The dissipating stage of the storm witnessed hail and rain showers, sharp transition of electric field and the Maxwell current from positive to negative polarity and occurrence of a few positive CG discharges. Our observations are consistent with the general belief that that some lightning flashes, by neutralizing and depositing charge in the region of opposite polarity, change the charge distribution so as to trigger another discharge in the storm.
Narrowing of the discrete auroral arc by the ionosphere
Authors: Streltsov Anatoly V.
Published: October 2007

We investigate the role of the ionosphere in the development of intense, narrow discrete auroral arcs. Our study shows that interactions between a pair of downward and upward magnetic field‐aligned currents (FACs) and the ionosphere can lead to the narrowing of the upward current channel and broadening of the downward current channel such that the total width of the initial current pair remains the same. In this case the intensity of the upward current increases, and the intensity of the large‐scale downward current decreases. Conditions promoting this asymmetry between the upward and downward FACs include low ionospheric conductivity (≤1 mho) and a moderate magnitude of the current density (≤5 μA/m2). Simulations show that the ionosphere causes significant asymmetry not only in the structure and amplitude of the currents but also in the structure and amplitude of the corresponding parallel electric fields. The dynamics of the parallel electric field in the upward current channel is similar to the dynamics of the current itself, but the dynamics of the field in the downward current channel differs from the dynamics of the current. The major difference is that the width of the downward current channel becomes broader with time but the scale size of the parallel electric field becomes smaller inside the channel. This effect is quite important for understanding the parallel electron acceleration in the auroral zone. In particular, it may explain why the so‐called “black” auroral arcs, which are produced by the electrons flowing along the magnetic field lines from the ionosphere, always appear in the form of very narrow, discrete dark lines.
Longitudinal and topographic variations in North Atlantic tidal and inertial energy around latitudes 30 ± 10°N
Authors: van Haren Hans
Published: October 2007

Open ocean kinetic energy is investigated at dominant inertial and semidiurnal tidal frequencies using historic current observations from the North Atlantic Ocean, around midlatitudes. Focus is on possible energy variations due to major topography changes between the eastern (Canary) and western (Hatteras, Sohm) basins, thereby crossing the Mid‐Atlantic Ridge (MAR). While, in open basins on both sides of MAR, semidiurnal kinetic energy drops in magnitude by some 50% between latitudes 20°N < ϕ < 28°N, in agreement with TPXO‐elevation data, an even larger longitudinal dependence is observed. West of MAR, semidiurnal energy is up to 30 times less than east of it. Inertial kinetic energy is either decreasing (by a factor of 2−4) westward or more or less independent of longitude. This contrasts strongly with westward intensified near‐surface inertial energy fluxes previously found. The latter fluxes also did not show an increase (by a factor of 5−10) for 25°N < ϕ < 30°N as observed here for inertial energy in both basins. West of MAR, the internal wave background level for frequencies up to sixth diurnal is much less, by a factor of 3−10, at tidal‐inertial interaction frequencies than east of MAR. No significant atmospheric or large‐scale vorticity influence, or seasonal variations therein, is found on inertial energy content across the basin. As no individual peaks are observed at frequencies K1, O1 and M1, S1, direct diurnal tidal forcing and subharmonic resonance must be accompanied by nonlinear interactions in possibly enhancing inertial energy at the critical diurnal latitude.
Miocene forebulge development previous to broken foreland partitioning in the southern Central Andes, west‐central Argentina
Authors: Dávila Federico M. , Astini Ricardo A. , Jordan Teresa E. , Gehrels George , Ezpeleta Miguel
Published: October 2007

In the distal region of the modern flat‐slab segment in the southern Central Andes, an unusual stack of middle Miocene paleosols together with regional upwarping and normal faulting indicate episodic aggradation and condensed sedimentation contemporaneous with the principal stage of foreland basin development associated with foreland flexure farther to the west. These features are consistent with development of a forebulge zone during the early stages of a proposed asymmetric foreland basin system. Sedimentary thickness farther east and far from the Cordilleran tectonic loads suggests accommodation and preservation driven by “nonisostatic” dynamic subsidence. Regional overlapping relationships and basin modeling suggest that the Modern broken foreland (present Sierras Pampeanas) can be interpreted as a reactivation of a formerly partitioned broad forebulge.
Fungal communities from methane hydrate-bearing deep-sea marine sediments in South China Sea
Authors: Lai Xintian , Cao Lixiang , Tan Hongming , Fang Shu , Huang Yali , Zhou Shining
Published: October 2007

To elucidate fungal diversity in methane hydrate-bearing deep-sea marine sediments in the South China Sea, internal transcribed spacer (ITS) regions of rRNA genes from five different sediment DNA samples were amplified and phylogenetically analyzed. Total five ITS libraries were constructed and 413 clones selected randomly were grouped into 24 restriction patterns by Amplified Ribosomal DNA Restriction Analysis (ARDRA). ITS sequences of 44 representative clones were determined and compared with the GenBank database using gapped-BLAST. The phylogenetic analysis showed that the ITS sequences (71–97% similarity) were similar to those of Phoma, Lodderomyces, Malassezia, Cryptococcus, Cylindrocarpon, Hortaea, Pichia, Aspergillus and Candida. The remaining sequences were not associated to any known fungi or fungal sequences in the public database. The results suggested that methane hydrate-bearing deep-sea marine sediments harbor diverse fungi. This is the first report on fungal communities from methane hydrate-bearing deep-sea marine sediments in South China Sea.
Streptococcus pyogenes serotype-dependent and independent changes in infected HEp-2 epithelial cells
Authors: Klenk Michael , Nakata Masanobu , Podbielski Andreas , Skupin Bianka , Schroten Horst , Kreikemeyer Bernd
Published: October 2007

The adherence, internalization and persistence of the human pathogen Streptococcus pyogenes (group A streptococci, GAS) to and within host cells were studied, and the induced responses of the infected epithelial cells were investigated. Next to common cellular responses on GAS infection, many responses of the infected HEp-2 epithelial cells are GAS serotype-specific. Moreover, several cellular responses do not correlate with the actual bacterial numbers adherent, internalized and persistent within the cells or the production of major cytolysins, as demonstrated for cytoskeletal pathways, cytokine release and apoptosis induction in infected cells. Measurement of activated caspases and caspase inhibition experiments uncovered activation of multiple caspase pathways by all GAS serotypes tested (M1, M3, M6 and M18). However, caspase 9 played a central role for M6 infections. During the persistence phase of the interaction, a differential and dynamic behavior of the infecting GAS serotype strains was found. After 14 h of host cell contact, all serotype strains caused host cell damage by virtually equal portions of apoptosis induction and necrosis mechanisms, as revealed by measurements of CK18Asp396/CK18 ratios. Between 14 and 24 h, persisting serotype M1 bacteria pertained this effect, whereas the serotype M6 GAS strain induced a major shift to necrotic mechanisms, and the serotype M3 and M18 GAS strains stimulated less necrosis, but shifted their host cells to apoptosis induction. Together, our study revealed that many cellular responses do not belong to general and uniform pathways, which are exploited by all GAS serotypes, explaining many of the already published discordant results.
Persistent BioPerl
Authors: Lapp Hilmar
Published: October 2007

I present BioSQL, a generic and highly extensible relational model for storing biological sequences, sequence clusters, genes, sequence features, sequence and feature annotation, and ontology terms. BioSQL also represents the interoperable persistence API among the Bio* life science programming toolkits (BioPerl, Biojava, Biopython, BioRuby), each of which has a language-binding to the BioSQL schema. I specifically present the Bioperl-db software, which in a transparent manner makes BioPerl objects persistent using BioSQL.
Collagen-bound low density lipoprotein modifies endothelial cell adhesion to type V collagen: Implications for atherosclerosis
Authors: Lorkowski Stefan , Rauterberg Jürgen , Harrach-Ruprecht Bärbel , Troyer David
Published: October 2007

Low density lipoprotein (LDL) is retained in the extracellular matrix of the arterial wall where it is considered to be atherogenic, but little is known about how cell adhesion to the matrix is affected by collagen-bound LDL. We tested the effect of native, oxidized and acetylated LDL reacted with adsorbed monomeric type I, III and V collagen on endothelial cell adhesion to collagen using a colorimetric adhesion assay. We found that none of the LDL species affected adhesion to type I and III collagen, but that collagen-bound native and acetylated LDL enhanced attachment to type V collagen, whereas bound oxidized LDL inhibited adhesion to this collagen. We suggest that oxidized LDL associated with type V collagen in the arterial wall would favor de-endothelialization and contribute to atherogenesis and thrombosis.
Proteasome function is required to maintain muscle cellular architecture
Authors: Haas Kevin F. , Woodruff Elvin , Broadie Kendal
Published: October 2007

Background information. Protein degradation via the UPS (ubiquitin—proteasome system) plays critical roles in muscle metabolism and signalling pathways. The present study investigates temporal requirements of the UPS in muscle using conditional expression of mutant proteasome β subunits to cause targeted inhibition of proteasome function.

Results and conclusions. The Drosophila GeneSwitch system was used, with analyses of the well‐characterized larval somatic body wall muscles. This method acutely disrupts proteasome function and causes rapid accumulation of polyubiquitinated proteins, specifically within the muscle. Within 12 h of transgenic proteasome inhibition, there was a gross disorganization of muscle architecture and prominent muscle atrophy, progressing to the arrest of all co‐ordinated movement by 24 h. Progressive muscle architecture changes include rapid loss of sarcomere organization, loss of nuclei spacing/patterning, vacuole formation and the accumulation of nuclear and cytoplasmic aggregates at the ultrastructural level. At the neuromuscular junction, the highly specialized muscle membrane folds of the subsynaptic reticulum were rapidly lost. Within 24 h after transgenic proteasome inhibition, muscles contained numerous autophagosomes and displayed highly elevated expression of the endoplasmic reticulum chaperone GRP78 (glucose‐regulated protein of 78 kDa), indicating that the loss of muscle maintenance correlates with induction of the unfolded protein response. Taken together, these results demonstrate that the UPS is acutely required for maintenance of muscle and neuromuscular junction architecture, and provides a Drosophila genetic model to mechanistically evaluate this requirement.
Double-hybrid density functional theory for excited electronic states of molecules
Authors: Grimme Stefan , Neese Frank
Published: October 2007

Double-hybrid density functionals are based on a mixing of standard generalized gradient approximations (GGAs) for exchange and correlation with Hartree-Fock (HF) exchange and a perturbative second-order correlation part (PT2) that is obtained from the Kohn-Sham (GGA) orbitals and eigenvalues. This virtual orbital-dependent functional (dubbed B2PLYP) contains only two empirical parameters that describe the mixture of HF and GGA exchange (ax) and of the PT2 and GGA correlation (ac), respectively. Extensive testing has recently demonstrated the outstanding accuracy of this approach for various ground state problems in general chemistry applications. The method is extended here without any further empirical adjustments to electronically excited states in the framework of time-dependent density functional theory (TD-DFT) or the closely related Tamm-Dancoff approximation (TDA-DFT). In complete analogy to the ground state treatment, a scaled second-order perturbation correction to configuration interaction with singles (CIS(D)) wave functions developed some years ago by Head-Gordon et al. [Chem. Phys. Lett. 219, 21 (1994)] is computed on the basis of density functional data and added to the TD(A)-DFT∕GGA excitation energy. The method is implemented by applying the resolution of the identity approximation and the efficiency of the code is discussed. Extensive tests for a wide variety of molecules and excited states (of singlet, triplet, and doublet multiplicities) including electronic spectra are presented. In general, rather accurate excitation energies (deviations from reference data typically <0.2eV) are obtained that are mostly better than those from standard functionals. Still, systematic errors are obtained for Rydberg (too low on average by about 0.3eV) and charge-transfer transitions but due to the relatively large ax parameter (0.53), B2PLYP outperforms most other functionals in this respect. Compared to conventional HF-based CIS(D), the method is more robust in electronically complex situations due to the implicit account of static correlation effects by the GGA parts. The (D) correction often works in the right direction and compensates for the overestimation of the transition energy at the TD level due to the elevated fraction of HF exchange in the hybrid GGA part. Finally, the limitations of the method are discussed for challenging systems such as transition metal complexes, cyanine dyes, and multireference cases.
Turbulent acceleration of superthermal electrons
Authors: Ryu C.-M. , Rhee T. , Umeda T. , Yoon P. H. , Omura Y.
Published: October 2007

In a recent paper it was suggested on the basis of weak turbulence theory that the collisionality of a plasma, coupled with nonlinear wave-particle interaction, is crucial for the acceleration of electrons by Langmuir turbulence to a superthermal energy level. In this Letter, fully nonlinear Vlasov and particle-in-cell (PIC) simulation techniques are employed to further verify this potentially important finding. The previous conclusion is fully confirmed by observing the expected difference between the Vlasov and PIC simulation results in the weak beam regime. However, in the strong beam regime, both the Vlasov and PIC simulations are found to produce a high-energy tail population, which indicates that there may be other mechanisms in the high beam speed situation, that are responsible for the generation the superthermal electrons.
A method for analysis of multicomponent systems of interacting aromatic molecules in solution
Authors: Evstigneev Maxim P. , Evstigneev Vladislav P. , Davies David B.
Published: October 2007

A method has been developed for analyzing multicomponent mixtures containing N different types of noncovalently interacting aromatic molecules using spectroscopic data [nuclear magnetic resonance (NMR), UV-vis, fluorescence, circular dichroism]. The method is based on an algorithmical approach to modeling of the N-component dynamic equilibrium (N-STOCH algorithm), dealing with numbers in N-based numerical systems as analogs of molecular complexes being formed in solution. A basic property of the algorithm is the ability to incorporate any known specificity of molecular interactions without constructing complex mathematical formulas. The utility of the N-STOCH algorithm was demonstrated by using as an example the NMR investigation of the dissociation of a heteroassociation complex of two anticancer drugs on addition of caffeine.
Molecular beam induced changes in adsorption behavior of NO on NiO(111)∕Ni(111)
Authors: Zion B. D. , Sibener S. J.
Published: October 2007

We have examined the adsorption behavior at ∼110K of NO on NiO(111) overlayers prepared on a Ni(111) substrate. High-resolution electron-energy-loss spectroscopy shows fundamental changes in the vibrational spectrum for the beam dosed surface in comparison with the background dosed surface. Three vibrational peaks are observed after beam dosing, two of which are not observed after conventional background dosing. The peaks can be assigned to NO stretches for a previously observed NO state, a new NO bonding geometry, and a new NO2 surface species, previously unobserved under NO dosing. The difference is accounted for by increased NO uptake due both to kinetically activated adsorption and to increased exposure.
Roles of pH and acid type in the anodic growth of porous alumina
Authors: Friedman Adam L. , Brittain Derrick , Menon Latika
Published: October 2007

Several theoretical models have been formulated to explain the growth of porous structures in anodized alumina. Using some basic assumptions, these models predict the size and shape of the pores in the anodic porous alumina as functions of pH and voltage. Additionally, they address issues of stability in the pore growth. In this work, we have carried out a systematic experimental investigation to study the stability phase diagram as a function of pH and applied voltage. We also obtain the dependence of pore dimensions on the pH, voltage, and acid type. Based on our results, and insight gained from recent chemical analysis of the porous alumina anodization process, we conclude that the models must include an appropriate weighting factor to account for the oxidation and dissolution mechanism during the pore formation.
Fast-electron transport and induced heating in aluminum foils
Authors: Santos J. J. , Debayle A. , Nicolaï Ph. , Tikhonchuk V. , Manclossi M. , Batani D. , Guemnie-Tafo A. , Faure J. , Malka V. , Honrubia J. J.
Published: October 2007

Beams of fast electrons have been generated from the ultra-intense laser interaction (6×1019W cm−2, 40fs) with aluminum foil targets. The dynamics of fast-electron propagation as well as the level of induced in-depth heating have been investigated using the optical emission from the foil’s rear side. The dependence of the emitted signals spectrum and size on the target thickness allowed the identification of the coherent (coherent transition radiation) and incoherent (thermal radiation) mechanisms of the optical emission. We demonstrate a two-temperature energy distribution for the laser-generated fast-electron population: a divergent bulk component (θbulk=35°±5°) with ≈35% of the laser focal spot energy and a 400–600keV temperature, plus a relativistic tail highly collimated (θtail=7°±3°), with a 10MeV temperature and a periodic modulation in microbunches, representing less than 1% of the laser energy. Important yields of thermal emission, observed for targets thinner than 50μm, are consequence of a hot plasma near the front surface. The important heating at shallow depth (<15μm) results from collective mechanisms associated to the fast-electron transport, in particular from a resistive heating upon the neutralizing return current of background electrons. For deeper layers, because of the bulk component divergence, the fast-electron energy losses are dominated by collisions.
Hole mobility in silicon inversion layers: Stress and surface orientation
Authors: Sun Guangyu , Sun Yongke , Nishida Toshikazu , Thompson Scott E.
Published: October 2007

Hole transport in the p-type metal-oxide-semiconductor field-effect-transistor (p-MOSFET) inversion layer under arbitrary stress, surface, and channel orientation is investigated by employing a six-band k∙p model and finite difference formalism. The piezoresistance coefficients are calculated and measured at stresses up to 300MPa via wafer-bending experiments for stresses of technological importance: uniaxial and biaxial stresses on (001) and (110) surface oriented p-MOSFETs with ⟨110⟩ and ⟨111⟩ channels. With good agreement in the measured and calculated small stress piezoresistance coefficients, k∙p calculations are used to give physical insights into hole mobility enhancement at large stress (∼3GPa). The results show that the maximum hole mobility is similar for (001)∕⟨110⟩, (110)∕⟨110⟩, and (110)∕⟨111⟩ p-MOSFETs under uniaxial stress, although the enhancement factor is different. Strong quantum confinement and a low density of states cause less stress-induced mobility enhancement for (110) p-MOSFETs. For (001) p-MOSFETs, the dominant factor for the improved hole mobility is reduced conductivity effective mass at small stress and lower phonon scattering rate at large stress.
Atomic layer deposition of TiO2 from tetrakis-dimethyl-amido titanium or Ti isopropoxide precursors and H2O
Authors: Xie Qi , Jiang Yu-Long , Detavernier Christophe , Deduytsche Davy , Van Meirhaeghe Roland L. , Ru Guo-Ping , Li Bing-Zong , Qu Xin-Ping
Published: October 2007

Atomic layer deposition (ALD) of TiO2 thin films using Ti isopropoxide and tetrakis-dimethyl-amido titanium (TDMAT) as two kinds of Ti precursors and water as another reactant was investigated. TiO2 films with high purity can be grown in a self-limited ALD growth mode by using either Ti isopropoxide or TDMAT as Ti precursors. Different growth behaviors as a function of deposition temperature were observed. A typical growth rate curve-increased growth rate per cycle (GPC) with increasing temperatures was observed for the TiO2 film deposited by Ti isopropoxide and H2O, while surprisingly high GPC was observed at low temperatures for the TiO2 film deposited by TDMAT and H2O. An energetic model was proposed to explain the different growth behaviors with different precursors. Density functional theory (DFT) calculation was made. The GPC in the low temperature region is determined by the reaction energy barrier. From the experimental results and DFT calculation, we found that the intermediate product stability after the ligand exchange is determined by the desorption behavior, which has a huge effect on the width of the ALD process window.
Beryllium deposition on International Thermonuclear Experimental Reactor first mirrors: Layer morphology and influence on mirror reflectivity
Authors: De Temmerman G. , Baldwin M. J. , Doerner R. P. , Nishijima D. , Seraydarian R. , Schmid K. , Kost F. , Linsmeier Ch. , Marot L.
Published: October 2007

Metallic mirrors will be essential components of the optical diagnostic systems in the International Thermonuclear Experimental Reactor (ITER). Reliability of these systems may be affected by mirror reflectivity changes induced by erosion and/or deposition of impurities (carbon, beryllium). The present study aims to assess the effect of beryllium (Be) deposition on the reflectivity of metallic mirrors and to collect data on the optical quality of these layers in terms of morphology, roughness, etc. Mirrors from molybdenum and copper were exposed in the PISCES-B linear plasma device to collect eroded material from graphite and beryllium targets exposed to beryllium-seeded deuterium plasma. After exposure, relative reflectivity of the mirrors was measured and different surface analysis techniques were used to investigate the properties of the deposited layers. Be layers formed in PISCES-B exhibit high levels of porosity which makes the reflectivity of the Be layers much lower than the reflectivity of pure Be. It is found that if Be deposition occurs on ITER first mirrors, the reflectivity of the coated mirrors will strongly depend on the layer morphology, which in turn depends on the deposition conditions.
Enhancing UV photoconductivity of ZnO nanobelt by polyacrylonitrile functionalization
Authors: He J. H. , Lin Yen H. , McConney Michael E. , Tsukruk Vladimir V. , Wang Zhong L. , Bao Gang
Published: October 2007

UV photodetector fabricated using a single ZnO nanobelt (NB) has shown a photoresponse enhancement up to 750 times higher than that of a bare ZnO NB after coating with ∼20nm plasma polymerized acrylonitrile (PP-AN) nanoscale film. The mechanism for this colossal photoconductivity is suggested as a consequence of the efficient exciton dissociation under UV illumination due to enhanced electron transfer from valence band of ZnO NB to the PP-AN and then back to the conduction band of ZnO. This process has demonstrated an easy and effective method for improving the performance of the nanowire∕NB-based devices, possibly leading to supersensitive UV detector for applications in imaging, photosensing, and intrachip optical interconnects.
Linewidth characteristics of a filterless tunable erbium doped fiber ring laser
Authors: Deepa V. , Vijaya R.
Published: October 2007

The linewidth characteristics of a continuous wave erbium doped fiber ring laser whose tunability is controlled by intracavity loss are studied in this work. The spectral linewidth of such a filterless laser is measured experimentally, and its characteristics are analyzed using the existing analytical model of fiber laser. The long length of the cavity results in lasing into multiple longitudinal modes, thus leading to a broad linewidth. The extent of this broadening is found to depend on the intracavity attenuation and pump powers. Under the given experimental conditions, for a fiber of length 12m, the linewidth increases up to 4.5nm corresponding to an additional cavity loss of 5dB, while it increases up to 8nm for a loss of 1.2dB for a fiber of length 4.6m. The linewidth decreases with further increase in intracavity loss for both cases. In this work, the linewidth dependence on the intracavity loss is directly linked to the spectral dependence of the threshold power for each length. The linewidth increases with pump power irrespective of the intracavity attenuation, and this is explained through the nature of the amplified spontaneous emission from the fiber at different pump powers. The experimental results and the subsequent analysis are useful for the design of a filterless tunable laser with a narrow linewidth using erbium doped fiber in the ring configuration.
AlAs quantum wells: Transport properties of the two-dimensional electron gas
Authors: Gold A. , Marty R.
Published: October 2007

We present a theory of the transport properties at zero temperature of the electron gas in AlAs. The two-dimensional electron gas in AlAs has a valley degeneracy gv=1 for a quantum well width LLc. We calculate the mobility for interface-roughness scattering and for impurity scattering. In addition we discuss the single-particle relaxation time (Dingle temperature) and the magnetoresistance in a parallel magnetic field. We discuss how transport measurements can be used to get information about microscopic parameters of disorder and many-body effects. Experimental results obtained for the mobility, the magnetoresistance, and the metal-insulator transition are discussed and compared with our theory.
Electroluminescent and carrier transport mechanisms of MgxZn1−xO∕Si heterojunctions
Authors: Chen Peiliang , Ma Xiangyang , Li Dongsheng , Zhang Yuanyuan , Yang Deren
Published: October 2007

Mg x Zn 1 − x O  (x≈0.19) films were, respectively, deposited by reactive sputtering on the heavily arsenic-doped (n+), lightly phosphorus-doped (n−), heavily boron-doped (p+), and lightly boron-doped (p−) silicon substrates. The sputtered MgxZn1−xO films were n-type with an electron concentration of 4.1×1017cm−3. Moreover, the energy-band gap of the MgxZn1−xO films was determined to be ∼3.67eV. The MgxZn1−xO∕n−-Si and MgxZn1−xO∕p−-Si heterojunctions showed rectifying behavior to different degrees while the MgxZn1−xO∕n+-Si and MgxZn1−xO∕p+-Si heterojunctions did not possess rectifying function. The MgxZn1−xO∕n+-Si heterojunction exhibited UV near-band-edge and visible defect-related electroluminescence (EL) under the forward bias but only visible EL under reverse bias; while the MgxZn1−xO∕n−-Si heterojunction only emitted relatively weak UV and visible EL under the forward bias. On the other hand, the MgxZn1−xO∕p+-Si heterojunction was electroluminescent in the visible region under the forward bias while in both the UV and visible regions under the reverse bias; and the MgxZn1−xO∕p−-Si heterojunction did not exhibit detectable EL under either forward or reverse bias. The mechanisms of the EL and carrier transport for the above-mentioned heterojunctions have been tentatively explained in terms of their energy-band structures.
Stresses in textured and polycrystalline cubic films by Raman spectroscopy: Application to diamond
Authors: Gries T. , Vandenbulcke L. , Simon P. , Canizares A.
Published: October 2007

The determination of the stress/strain level in cubic films is carried out here by polarized Raman spectroscopy. The Voigt-Reuss-Hill averaging technique has been used for calculating the phonon deformation potentials in textured cubic films, especially here in diamond. With the corresponding elastic constants known, the resolution of the secular equation has allowed us to calculate the strain/stress configuration from the shifts and splitting of textured diamond polycrystalline films. For isotropic polycrystalline films, the results obtained by averaging over the different textures compare very well to the results obtained with the complete averaging procedure of Anastassakis [J. Appl. Phys. 86, 249 (1999)]. With both averaging methods, the stress/strain level in polycrystalline films are evaluated with a fairly good accuracy, either for biaxial isotropic in-plane stresses due to thermal expansion mismatch between the film and the titanium alloy substrates or for anisotropic stresses induced by permanent deformations of titanium tensile specimens. The difference between these averaging procedures and a method using the addition of the contributions of different textures is shown for evaluating the strains/stresses in diamond films. A slightly more accurate method is obtained because of the different influences of the various textures on the Raman shifts. However, the textured polycrystalline state being averaged with a method that results in an effective hexagonal symmetry, this approach is still insufficient to take into account the influence of the in-plane orientation of each crystallite relative to strong anisotropic biaxial stresses, an influence which is shown experimentally and theoretically for one texture, along the [110] direction of growth.
Enhancement and reduction of line broadening due to Auger scattering in modulation-doped InGaAs∕GaAs quantum dot devices
Authors: Nilsson H. H. , Zhang J.-Z. , Galbraith I.
Published: October 2007

We calculate the line broadening of various Auger processes in modulation-doped InGaAs∕GaAs quantum dot (QD) semiconductor optical amplifiers (SOAs), involving scattering of carriers between wetting-layer states and confined QD states. We find that, as a result of p doping, the optical gain and the linewidth are significantly enhanced, while in shallow dots, n doping surprisingly leads to a reduction in the homogeneous linewidth. Our findings support the development of high-speed QD lasers and SOAs incorporating p doping and using optical amplifiers with n-doped shallow QDs for wavelength-division-multiplexing applications.
Mask haze formation in deep ultraviolet lithography
Authors: Wu Banqiu , Kumar Ajay
Published: October 2007

Studies on mask haze formation mechanism in deep ultraviolet lithography were carried out. A nucleation-growth model was proposed, showing a nuclei critical dimension exists. When larger than critical dimension, nucleus grows with system Gibbs energy decrease. The model also shows the spontaneousness for small haze to merge with large haze and existence of a critical distance, beyond which nuclei grow independently. The haze formation region on a plot of composition versus temperature was indicated by the model. Photochemical dissociation of molecular oxygen plays an important role in haze growth. The proposed mechanism agreed well with previously published experimental results.