bluuebunny/crossref_metadata_2025 huggingface dataset:
Necessary conditions for the N‐representability of pair distribution functions
Authors: Ayers Paul W. , Davidson Ernest R.
Published: January 2006

A necessary condition for the N‐representability of the electron pair density proposed by one of the authors (E. R. D.) is generalized. This shows a link between this necessary condition and other, more widely known, N‐representability conditions for the second‐order density matrix. The extension to spin‐resolved electron pair densities is considered, as is the extension to higher‐order distribution functions. Although quantum mechanical systems are our primary focus, the results are also applicable to classical systems, where they reduce to an inequality originally derived by Garrod and Percus. As a simple application, bounds to the average angle between an electron pair are derived. It is shown that computational methods based on variational minimization of the energy with respect to the electron pair density can give extremely poor results unless robust N‐representability constraints are considered. For reference, constraints for the N‐representability of the pair density are summarized. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Conformational and electronic study ofN‐acetyl‐L‐isoleucine‐N‐methylamide using DFT and IPCM calculations
Authors: Rodríguez Ana M. , Koo Joseph C. P. , Rojas Dante E. , Peruchena Nélida M. , Enriz Ricardo D.
Published: January 2006

A conformational and electronic study onN‐acetyl‐L‐isoleucine‐N‐methylamide was carried out. All side‐chain as well as backbone conformations were explored for this compound. Multidimensional conformational analysis predicts 81 structures in the case ofN‐acetyl‐L‐isoleucine‐N‐methylamide, 53 relaxed structures were determined at the DFT (B3LYP/6‐31G(d)) level of theory. An exhaustive electronic study employing the atoms‐in‐molecules (AIM) method was carried out. In addition, the effects of three solvents (water, acetonitrile, and chloroform) were included in the calculations using the isodensity polarizable continuum model (IPCM) method. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Density functional crystal orbital study of cyano‐substituted poly(para‐phenylene‐vinylene) and poly(quinoxaline‐vinylene)
Authors: Bartha F. , Howard I. A. , Geerlings P. , Van Alsenoy C. , Vanderzande D. , Cleij T. J. , Bogár F.
Published: January 2006

We have calculated the optical and electronic properties of several conjugated organic polymers: poly(p‐phenylene‐vinylene) (PPV) and its derivatives. Cyano substitutions on the phenylene ring: poly(2,5‐dicyano‐p‐phenylene‐vinylene) (2,5‐DCN‐PPV) and on the vinylene linkage: poly(p‐phenylene‐7(,8)‐(di)cyano‐vinylene) are considered. In addition, poly(quinoxaline‐vinylene) (PQV) is studied. The infinite isolated quasi‐1D chains are treated with periodic boundary conditions, using atomic basis sets. In a comparative study of PPV, some issues regarding the selection of the functionals and basis sets are discussed and excitation energies derived from time‐dependent and from ordinary methods are compared. It is concluded that for these polymers the calculations are informative at the B3LYP/6‐31G** density functional theory (DFT) level. The absolute values might change with improved methods, but the similarity of the polymers suggests that the relative characterization is adequate. Band structures are communicated along with characteristics of the highest occupied and the lowest unoccupied crystal orbitals (HOCO and LUCO). Electron affinities, ionization potentials, valence and conduction bandwidths, and effective masses at the bandgap are given. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Investigation of several unique tandem mass spectrometric fragmentation patterns of NFDEIDR, an orcokinin analog, and its N‐terminal dimethylated form
Authors: Fu Qiang , Li Lingjun
Published: January 2006

Orcokinins are a family of myotropic neuropeptides widely present in various decapod crustaceans and insect species. The majority of the orcokinins identified to date share a conserved sequence of NFDEIDR at their N‐termini. Electrospray ionization quadrupole time‐of‐flight tandem mass spectrometric (ESI‐QTOF‐MS/MS) analysis of doubly charged orcokinin precursor ions reveals the presence of a y(n − 1) + 10 peak, which is more intense than that for the y(n − 1) ion. To elucidate the identity of this novel fragment ion and understand the mechanism underlying this fragmentation, we employed a combined approach involving the use of isotopic N‐terminal dimethylation, methyl esterification, and isotope‐encoded NFDEIDR. Comparison of the fragmentation patterns of these chemically modified orcokinin analogs allowed the determination of the structure of the y(n − 1) + 10 ion as y(n − 1) + COH2O. The yx + COH2O ions, along with the yx + CO and yx + CONH3 ions, are also present in the MS/MS spectra of NFDEIDR and several other peptides. Additionally, we report two other unusual fragmentation ions in the MS/MS spectra of N‐terminal dimethyl NFDEIDR (2+), which yields the novel fragment ions of the y(n − 1) + 38 ion and the [M+2H–59]2+ ion. These two ion series involve the neutral loss of the asparagine side chain. The same sets of ions are also present in other peptides with dimethyl‐modified asparagines at the N‐terminus. The competition between the side‐chain loss and loss of dimethylamine is described. The loss of the side chain of N‐terminal dimethyl Asp1 is reported as well. We also report for the first time the neutral loss of ammonia from the N‐terminal amino group of Asn1 and the loss of CO2 from the side chain of aspartic acid. Copyright © 2006 John Wiley & Sons, Ltd.
Combined use of gas chromatography and selected ion flow tube mass spectrometry for absolute trace gas quantification
Authors: Kubišta Jiří , Španěl Patrik , Dryahina Kseniya , Workman Clive , Smith David
Published: January 2006

The value of the gas chromatography (GC) and selected ion flow tube mass spectrometry (SIFT‐MS) combination for the analysis of trace gases is demonstrated by the quantification of acetone in air samples using the three precursor ions available to SIFT‐MS, viz. H3O+, NO+ and O, and by the separation of the isomers 1‐propanol and 2‐propanol, and their analysis using H3O+ precursor ions. It is shown that the GC/SIFT‐MS combination allows for accurate trace gas quantification obviating the regular, time‐consuming calibrations that are usually required for the more commonly used detectors of GC systems, and the positive identification of isomers in mixtures that is often challenging using SIFT‐MS alone. Thus, the GC/SIFT‐MS combination paves the way to more confident analyses of complex mixtures such as exhaled breath. Copyright © 2006 John Wiley & Sons, Ltd.
Nuclear signalling through phospholipase C and phosphatidyl 4,5‐bisphosphate
Authors: Ho Ka Kei , Mann David J.
Published: January 2006

Phosphoinositides are key signalling intermediates with well established roles in transducing ligand mediated signals from the cell surface to the cytosol. Over recent years, strong evidence has accumulated for a role for phosphoinositides within the nucleus. Here we discuss recent advances in our understanding of a key phosphoinositide species phosphatidylinositol 4,5‐bisphosphate (PtdIns(4,5)P2) in the nucleus. The activation/nuclear translocation mechanisms of phospholipase C family members are reviewed and the roles of nuclear PtdIns(4,5)P2, from the generation of the second messenger molecules inositol 1,4,5‐trisphosphate and diacylglycerol to putative functions in the co‐ordination of multiprotein complexes involved in transcription will be discussed.
Questionnaire for assessing parents' concerns about their child with hydrocephalus
Authors: Kulkarni Abhaya V
Published: January 2006

The many concerns of parents of children with hydrocephalus have not previously been assessed using a reliable, quantitative measurement. The development and preliminary use of a questionnaire to measure the concerns of these parents is reported. A general health status measure for hydrocephalus was developed concurrently. Items were generated primarily from parent focus groups resulting in a comprehensive list of 22 unique parental concern items. The most important of these items, as selected by another sample of parents of 60 children (27 females, 33 males; mean age 8y 4mo, [SD 4y 6mo]) were retained for the final questionnaire. This 9‐item parental concerns questionnaire was tested for reliability and construct validity (by assessing correlations with various independent measures of health status, including Health Utilities Index‐2 and Impact‐on‐Family Scale) using a cohort consisting of the parents of 80 children (39 females, 41 males; mean age 10y, [SD 3y 6mo]). An exploratory analysis was performed to determine which patient variables were associated with greater parental concern. The parental concerns questionnaire demonstrated excellent test‐retest reliability (0.86, 95% CI 0.77–0.92) and internal consistency (Cronbach's alpha=0.89). As expected, interrater reliability was somewhat lower (0.67, 95% CI 0.49–0.79). Construct validity was demonstrated by consistently moderate Pearson's correlations with several independent measures of the child's health. The presence of epilepsy and younger patient age appeared to be significantly associated with greater parental concern. This new questionnaire has demonstrated very good psychometric properties. It can be used to broaden the scope of future clinical research in pediatric hydrocephalus to include the impact on parents.
Functional independence among young adults with spina bifida, in relation to hydrocephalus and level of lesion
Authors: Verhoef Marjolein , Barf Hans A , Post Marcel WM , van Asbeck Floris W A , Gooskens Rob HJM , Prevo Arie J H
Published: January 2006

Knowledge about the level of functional independence that can be expected in adulthood might support decisions on the treatment of newborn infants with spina bifida. This study determined functional independence among young adults with spina bifida and its relationships with pathological characteristics known from birth (hydrocephalus and level of lesion). Data were collected from medical records and by physical examination. Functional independence was assessed on six domains (self‐care, sphincter control, transfers, locomotion, communication, and social cognition) using the Functional Independence Measure (FIM). Participants were 165 patients with spina bifida (69 males, 96 females; age range 16 to 25y, mean 20y 9mo [SD 2.9]; 117 with hydrocephalus). Patients without hydrocephalus were independent for all FIM domains except sphincter control, as were patients with hydrocephalus with a lesion level below L2. Most patients with hydrocephalus and a lesion at L2 or above were dependent as regards sphincter control (98%), locomotion (79%), and self‐care (54%), and quite a few needed support in transfers (38%), social cognition (29%), and communication (15%).
Decreased activities of mitochondrial respiratory chain complexes in non‐mitochondrial respiratory chain diseases
Authors: MBBS Joannie Hui , Kirby Denise M , Thorburn David R , Boneh A vihu
Published: January 2006

The aim of this study was to illustrate the difficulties in establishing a diagnosis of mitochondrial respiratory chain (MRC) disorders based on clinical grounds in combination with intermediate activities of the MRC enzyme complexes. We reviewed retrospectively all medical and laboratory records of patients initially considered likely to have MRC disorders on clinical grounds, and subsequently diagnosed with other disorders (n=20; 11 males, 9 females). Data were retrieved from hospital records, referral letters, and results of enzymatic analysis at a reference laboratory. Clinical symptoms included developmental delay, epilepsy, hypotonia, movement disorder, spastic quadriplegia, tetany, microcephaly, visual problems, carpopedal spasms, dysmorphism, hearing loss, muscle weakness and rhabdomyolysis, and fulminant hepatitis. Blood and cerebrospinal fluid lactate levels were elevated in 13/20 and 9/20 respectively. One or more MRC complex activities (expressed as ratios relative to citrate synthase and/or complex II activity) were less than 50% of control mean activity in 11/20 patients (including patients with deficiencies of pyruvate dehydrogenase complex, pantothenate kinase, holocarboxylase synthetase, long‐chain hydroxy acyl‐CoA dehydrogenase, molybdenum co‐factor, and neonatal haemochromatosis). One patient had a pattern suggestive of mitochondrial proliferation. We conclude that intermediate results of MRC enzymes should be interpreted with caution and clinicians should be actively looking for other underlying diagnoses.
Visual side‐effects from transdermal scopolamine (hyoscine)
Authors: Firth Alison Y , Walker Karen
Published: January 2006

Transdermal scopolamine may be used to reduce drooling in children with disabilities. Side‐effects include dilated pupils and a reduction in the near point of accommodation (the closest point at which clear vision is possible). Two male children with epilepsy, one with spinal dysraphism (aged 7y 6mo) and one with cerebral palsy (aged 5y 8mo), who have undergone treatment for drooling with transdermal scopolamine are described. Near visual acuity was reduced, and both children showed dilated pupils with reduced or no response to light. These responses became normal on cessation of the scopolamine patch. As the effect of this drug may be cumulative, and many patients are unable to communicate difficulties, clinicians need to be aware of these possible side‐effects.
Visual Culture and Catholicism in the Irish Free State, 1922–1949
Authors: TURPIN JOHN
Published: January 2006

In the newly independent Irish Free State, a triumphalist Catholicism was embodied visually in mass-produced imagery and revivalist architecture. The Academy of Christian Art was set up in 1929 to regenerate Catholic art and architecture, but it failed to address the challenge of Modernism. A debate between eclectic and modern form was most acute in architecture, where the Hiberno-Romanesque and the neo-Classical were favoured by lay and cleric alike. Stained glass was the one form where Modernism was influential. The culmination of populist Catholicism and its visual representation was the Eucharistic Congress of 1932 with its temporary public altars and massive spectacle: a manifestation of Irish national identity.
Magnetic enhancement is linked to and precedes hematite formation in aerobic soil
Authors: Torrent José , Barrón Vidal , Liu Qingsong
Published: January 2006

Soil formation usually increases magnetic susceptibility, most often by increasing the concentrations of magnetite and maghemite, which are two ferrimagnetic iron oxides. Here we provide evidence that magnetic enhancement in aerobic soils not affected by detrital magnetic inputs or thermal transformation of other iron oxides is mostly due to the formation of maghemite, which is later transformed into hematite—the iron oxide that gives red color to soil. We show that the maghemite/hematite ratio is influenced by the particular environment and the degree of soil development, so it constitutes an effective tool for paleoenvironmental and planetary studies.
Transient electric field at high altitudes due to lightning: Possible role of induction field in the formation of elves
Authors: Lu Gaopeng
Published: January 2006

Space and time behaviors of electric field perturbation vector at high altitudes driven by lightning return stroke are examined in terms of its three individual components (i.e., electrostatic, induction, and radiation) with transmission line model, by specifying the current form in a return stroke channel, which is presumed to be vertically oriented. The result shows that at 90 km altitude, the induction E‐field dominates in a small region with a radius of ∼11 km (depending on the speed of return stroke) directly above the lightning region, with a magnitude comparable to radiation field and a relatively longer timescale. We conclude that in addition to the radiation field considered in previous theoretical modeling, the induction component in lightning E‐field is likely one new energy source for the creation of elves. This might be able to explain the observed pancake shape of some elves with a luminous central part, while the more complete modeling including the formation mechanism of elves is required.
Isotopic composition of stratospheric ozone
Authors: Liang Mao‐Chang , Irion Fredrick W. , Weibel Jason D. , Miller Charles E. , Blake Geoffrey A. , Yung Yuk L.
Published: January 2006

We present a kinetic calculation for the isotopic composition of stratospheric ozone. The calculated enrichments of 49O3 and 50O3 are in agreement with atmospheric measurements made at midlatitudes. Integrating the kinetic fractionation processes in the formation and photolysis of ozone, we obtain enrichments of ∼7.5–10.5 and ∼7.5–12.5% (referenced to atmospheric O2) for δ49O3 and δ50O3, respectively, at altitudes between 20 and 35 km; the photolysis in the Hartley band of ozone is responsible for the observed altitude variation. The overall magnitude of the ozone enrichments (∼10%) is large compared with that commonly known in atmospheric chemistry and geochemistry. The heavy oxygen atom in ozone is therefore useful as a tracer of chemical species and pathways that involve ozone or its derived products. For example, the mass anomalies of oxygen in two greenhouse gases, CO2 and N2O, are likely the consequences of the transfer of heavy oxygen atoms from ozone.
Absorption spectra of liquid water and aqueous buffers between 0.3 and 3.72THz
Authors: Xu Jing , Plaxco Kevin W. , Allen S. James
Published: January 2006

We have developed a terahertz absorption spectrometer suitable for strongly absorbing liquids such as water, and have precisely measured the absorption spectrum of water between 0.3 and 3.72THz (10–124cm−1). We have also examined the absorption spectra of aqueous 50mM potassium phosphate buffers at pH 3 and 8, and find that they do not differ significantly from pure distilled de-ionized water.
System for simulating fluctuation diagnostics for application to turbulence computations
Authors: Bravenec R. V. , Nevins W. M.
Published: January 2006

Present-day nonlinear microstability codes are able to compute the saturated fluctuations of a turbulent fluid versus space and time, whether the fluid be liquid, gas, or plasma. They are therefore able to determine turbulence-induced fluid (or particle) and energy fluxes. These codes, however, must be tested against experimental data not only with respect to transport but also characteristics of the fluctuations. The latter is challenging because of limitations in the diagnostics (e.g., finite spatial resolution) and the fact that the diagnostics typically do not measure exactly the quantities that the codes compute. In this work, we present a system based on IDL® analysis and visualization software in which user-supplied “diagnostic filters” are applied to the code outputs to generate simulated diagnostic signals. The same analysis techniques as applied to the measurements, e.g., digital time-series analysis, may then be applied to the synthesized signals. Their statistical properties, such as rms fluctuation level, mean wave numbers, phase and group velocities, correlation lengths and times, and in some cases full S(k,ω) spectra, can then be compared directly to those of the measurements.
Density determination of focused-electron-beam-induced deposits with simple cantilever-based method
Authors: Utke I. , Friedli V. , Michler J. , Bret T. , Multone X. , Hoffmann P.
Published: January 2006

Freestanding deposits are grown on a silicon cantilever from a precursor gas by an electron induced process. Deposit mass determination is performed with an atomic force microscopy setup, where the cantilever resonance frequency shift, resulting from mechanical removal of the deposit, is measured. Deposits from hexafluoroacetylacetonato–Cu(I)–vinyltrimethylsilane show densities ranging from 2.05±0.45 to 3.75±0.55g∕cm3. Deposits from tetramethoxysilane have a constant density of (1.9±0.3)g∕cm3. Densities of deposits from Co2(CO)8 and [RhCl(PF3)2]2 are linearly related to their composition. The ratio of impinging electrons per deposited atom, beam heating, and thermal stability of the precursor molecule determine the density and composition in focused-electron-beam-induced deposits.
Path-integral Monte Carlo simulation of the recombination of two Al atoms embedded in parahydrogen
Authors: Wang Qian , Alexander Millard H.
Published: January 2006

We report the use of path-integral Monte Carlo (PIMC) simulations in the study of the stability against recombination of two Al atoms trapped in solid parahydrogen (pH2) at 4 K. The many-body interactions involving open-shell Al atoms are described with a pairwise additive Hamiltonian model. To estimate the lifetime against recombination, we use PIMC simulations to define an effective potential averaged over the position of the pH2 molecules, followed by a transition-state treatment. Different initial embedding sites are explored. If the initial substitution sites are within a distance of ∼13bohrs, the Al atoms will significantly distort the lattice structure to allow recombination, with an accompanying release of energy during the process. For substitution distances longer than ∼14bohrs, the dispersion of Al atoms is shown to be metastable, with lifetimes varying from ∼30min to several days. The electronic anisotropy is a factor that helps to stabilize the dispersion.
Ultrathin Rh films on Ru(0001): Oxidation in confinement
Authors: He Yunbin , Seitsonen Ari P. , Over Herbert
Published: January 2006

Ultrathin rhodium films with a thickness ranging from 1 to a few monolayers were deposited on a single-crystal Ru(0001) surface in order to investigate the oxidation behavior of ultrathin epitaxial films on a dissimilar substrate. It is found that rhodium grows on Ru(0001) initially layer by layer, adapting the in-plane lattice parameters of Ru(0001). When exposing Rh films to oxygen environment (∼4.8×106L O2 exposure) at 660K, 2–4 ML Rh films form a surface oxide composed of (9×9) O–Rh–O trilayers. Quite in contrast, oxidation of the 1 ML Rh∕Ru(0001) film leads to a poorly ordered oxide with a rutile structure reminiscent of RuO2(110) on Ru(0001). The oxidized 1 ML Rh∕Ru(0001) film contains much more oxygen than the oxidized thicker Rh films. Lower temperatures (535K) and high doses of oxygen lead to a (1×1)-O overlayer on the 1 ML Rh∕Ru(0001) surface, whose atomic geometry resembles closely that of the (1×1)-O phase on clean Ru(0001).
A generalized quantum chemical approach for elastic and inelastic electron transports in molecular electronics devices
Authors: Jiang Jun , Kula Mathias , Luo Yi
Published: January 2006

A generalized quantum chemical approach for electron transport in molecular devices is developed. It allows one to treat devices where the metal electrodes and the molecule are either chemically or physically bonded on equal footing. An extension to include the vibration motions of the molecule has also been implemented which has produced the inelastic electron-tunneling spectroscopy of molecular electronics devices with unprecedented accuracy. Important information about the structure of the molecule and of metal-molecule contacts that are not accessible in the experiment are revealed. The calculated current-voltage (I-V) characteristics of different molecular devices, including benzene-1,4-dithiolate, octanemonothiolate [H(CH2)8S], and octanedithiolate [S(CH2)8S] bonded to gold electrodes, are in very good agreement with experimental measurements.
Quantum dynamics of Ne–Br2 vibrational predissociation: The role of continuum resonances as doorway states
Authors: García-Vela A. , Janda K. C.
Published: January 2006

Wave-packet simulations of the Ne–Br2(B,υ′) vibrational predissociation dynamics in the range υ′=16–29 are reported. The aim is to interpret recent time-dependent pump-probe experiments [Cabrera et al., J. Chem. Phys. 123, 054311 (2005)]. Good agreement is found between the calculated and the experimental lifetimes corresponding to decay of the Ne–Br2(B,υ′) initial state and to appearance of Br2(B,υ<υ′) products. The simulations show that up to υ′∼22 the dynamics is dominated by direct predissociation, while for higher υ′ levels an indirect intramolecular vibrational relaxation mechanism of dissociation becomes increasingly important. Such a mechanism occurs via coupling of the initial state in the υ′ vibrational manifold to nearly degenerate resonances embedded in the continuum of the lower υ<υ′ manifolds, which act as intermediate doorway states to dissociation. The role of the intermediate resonances manifests itself in multiexponential behavior and oscillations in the time-dependent population curves associated with the initial complex state, the final product states, and the Ne–Br2(B,υ<υ′) intermediate complexes. Analysis of the Ne–Br2(B,υ<υ′) intermediate population shows that the continuum resonances are supported by centrifugal barriers involving excitation of the internal rotation of the complex. We find that the coupling between the intermediate state resonances and the continuum product state wave functions extend to Ne–Br2 distances greater than 15Å. In the light of the results, a structure of the spectrum of continuum resonances is suggested and discussed.
The coaxial multipactor experiment (CMX): A facility for investigating multipactor discharges
Authors: Graves T. P. , LaBombard B. , Wukitch S. , Hutchinson I.
Published: January 2006

A multipactor discharge is a resonant condition for electrons in an alternating electric field. This discharge can be disruptive to rf circuits, cavities, and resonators. The coaxial multipactor experiment (CMX) investigates these discharges in parallel plate and coaxial transmission line geometries at frequencies from 40to150MHz with goals of measuring the electron energy distributions. CMX has a unique experimental setup that allows the transmission line to pass continuously through a short vacuum region. Retarding potential analyzers with secondary electron suppression measure the electron current as a function of bias voltage. Both parallel plate and coaxial multipactor experiments provide detailed measurements of the electron energy distributions under a variety of rf frequencies and electrode materials.
The development of a rapid quenching device for the study of the dependence of glass structure on fictive temperature
Authors: Kiczenski T. J. , Stebbins Jonathan F.
Published: January 2006

We have constructed a rapid quenching device with an estimated quench rate of 1×105°C∕s in order to explore the structural changes of glasses formed with varying quench rates. This apparatus quenches the sample in an inert atmosphere and recovers 100% of the sample, allowing the study of small (∼20–50mg), isotopically enriched samples that can greatly facilitate nuclear magnetic resonance (NMR) studies of nuclei with low natural abundance (such as O17 and Si29). An O17-enriched Ca-boroaluminosilicate glass was formed with a high quench rate using this apparatus, and a clear increase in the amount of nonbridging oxygens with increasing quench rate was observed. Additionally, B11 NMR spectra of E-glass samples formed with a wide variety of fictive temperatures showed a decrease in the proportion of B[4] in E-glass with increasing fictive temperature, in accordance with previous studies. The changing proportion of B[4] present in the E-glass sample with changing quench rate was used as a rough method of confirmation of the calculated quench rate.
The self-calibration of a retarding-type Mott spin polarimeter with a large collection angle
Authors: Iori K. , Miyamoto K. , Narita H. , Sakamoto K. , Kimura A. , Qiao S. , Shimada K. , Namatame H. , Taniguchi M.
Published: January 2006

We have developed a compact retarding-type Mott spin polarimeter with a large collection angle at the Hiroshima Synchrotron Radiation Center and obtained a reliable value of the effective Sherman function by a self-calibration method. The spin polarization of secondary electrons was evaluated by extrapolation of the left-right scattering asymmetry at the zero energy-loss limit, which enabled us to obtain the effective Sherman function (Seff) and the figure of merit of our polarimeter at different operating conditions.
Plastic deformation of a continuous organic light emitting surface
Authors: Bhattacharya R. , Wagner S. , Tung Y.-J. , Esler J. , Hack M.
Published: January 2006

A continuous organic light emitting diode (OLED) surface was shaped by plastic deformation from flat to dome. The OLED dome, now under an average tensile strain of 2.2%, remained operational. This shapeability is achieved by combining a substrate and a device structure that keep functioning in the plastic deformation regime. The technique of conformally shaping a continuous macroelectronic surface could become useful for the manufacture of arbitrarily shaped solid state light sources and mechanical transducers.
Band alignment between (100) Si and amorphous LaAlO3, LaScO3, and Sc2O3: Atomically abrupt versus interlayer-containing interfaces
Authors: Afanas’ev V. V. , Stesmans A. , Edge L. F. , Schlom D. G. , Heeg T. , Schubert J.
Published: January 2006

Incorporation of a ∼1-nm-thick SiOx interlayer is found to have little effect on the band alignment between a (100) Si substrate and amorphous LaAlO3, LaScO2, and Sc2O3 insulators. All of these materials are found to give the same band offsets irrespective of differences in their composition, even when contacting Si directly. This suggests that the bulk electron states and properties of the semiconductor and insulator layer play a much more important role in determining the band lineup at the interface than any dipoles related to particular bonding configurations encountered in the transition region between Si and these oxides.
Carrier injection and transport characteristics of copper phthalocyanine thin films under low to extremely high current densities
Authors: Matsushima Toshinori , Sasabe Hiroyuki , Adachi Chihaya
Published: January 2006

We investigated current density-voltage (J-V) characteristics of copper phthalocyanine (CuPc) thin films depending on active device areas. We prepared CuPc thin-film devices with active areas smaller than S=625μm2 using a photolithography technique. The maximum breakdown current density (JMAX) and voltage (VMAX) of the devices markedly increased as the active area was decreased from S=625 to 7.9μm2. In the smallest device, with S=7.9μm2, we obtained not only an extremely high current density of JMAX=128kA∕cm2 at VMAX=9.2V, but also unique J-V characteristics, indicating that the carrier conduction process shifted from the Fowler-Nordheim tunneling injection mechanism to shallow-trap and trap-free space-charge-limited current mechanisms.
Coherent phase control of the product branching ratio in the photodissociation of dimethylsulfide
Authors: Nagai Hidekazu , Ohmura Hideki , Ito Fumiyuki , Nakanaga Taisuke , Tachiya Masanori
Published: January 2006

Coherent phase control of the photodissociation reaction of the dimethylsulfide has been achieved by means of quantum-mechanical interference between one- and three-photon transitions. Dimethylsulfide was irradiated by fundamental and frequency-tripled outputs of a visible laser (600.5–602.5 nm), simultaneously to yield CH3S+ and CH3SCH2+ fragment ions. The branching ratio of the two product channels could be modulated with variation of the phase difference between the light fields. This accounted for the difference between the molecular phases of the two product channels. The phase lag was observed to have a maximum value of 8° at 601.5 nm. This is the first result of a selective bond breaking in a polyatomic molecule by the coherent phase control.
Fabrication and microwave absorption of carbon nanotubes∕CoFe2O4 spinel nanocomposite
Authors: Che R. C. , Zhi C. Y. , Liang C. Y. , Zhou X. G.
Published: January 2006

A large-scale carbon nanotube∕CoFe2O4 (CNTs∕CoFe2O4) spinel nanocomposite has been fabricated by a chemical vapor deposition method using CoFe2O4 nanoparticles as catalysts. A uniform mixture of CNTs and CoFe2O4 nanoparticles was obtained simultaneously. The structure and chemical composition of the product were investigated using various techniques, such as x-ray diffraction, high-resolution transmission electron microscopy, and electron energy loss spectroscopy. It was found that the particles functionalized on CNTs were cubic phase CoFe2O4. Microwave absorption of the CNT∕CoFe2O4 nanocomposites at 2–18 GHz is evidently enhanced, as compared with that of both pure CNTs and CoFe2O4 nanoparticles. The enhancement mechanism is discussed based on magnetization hysteresis loop measurement and electromagnetic theory.
Metallic conductivity and metal-semiconductor transition in Ga-doped ZnO
Authors: Bhosle V. , Tiwari A. , Narayan J.
Published: January 2006

This letter reports the metallic conductivity in Ga:ZnO system at room temperature and a metal-semiconductor transition (MST) behavior at low temperatures. Zn0.95Ga0.05O films, deposited by pulsed laser deposition in the pressure range of ∼10−2Torr of oxygen, were found to be crystalline and exhibited degeneracy at room temperature with the electrical resistivity close to 1.4×10−4Ωcm and transmittance >80% in the visible region. Temperature dependent resistivity measurements of these highly conducting and transparent films also showed, for the first time, a MST at ∼170K. Mechanisms responsible for these observations are discussed in the terms of dopant addition and its effect on ionization efficiency of oxygen vacancies.
Growth of aligned carbon nanotubes on carbon microfibers by dc plasma-enhanced chemical vapor deposition
Authors: Chen L.-H. , AuBuchon J. F. , Chen I.-C. , Daraio C. , Ye X.-R. , Gapin A. , Jin S. , Wang C. M.
Published: January 2006

It is shown that unidirectionally aligned carbon nanotubes can be grown on electrically conductive network of carbon microfibers via control of buffer layer material and applied electric field during dc plasma chemical vapor deposition growth. Ni catalyst deposition on carbon microfiber produces relatively poorly aligned nanotubes with significantly varying diameters and lengths obtained. The insertion of Ti 5nm thick underlayer between Ni catalyst layer and C microfiber substrate significantly alters the morphology of nanotubes, resulting in much better aligned, finer diameter, and longer array of nanotubes. This beneficial effect is attributed to the reduced reaction between Ni and carbon paper, as well as prevention of plasma etching of carbon paper by inserting a Ti buffer layer. Such a unidirectionally aligned nanotube structure on an open-pore conductive substrate structure may conveniently be utilized as a high-surface-area base electrodes for fuel cells, batteries, and other electrochemical and catalytic reactions.
Schottky barrier heights of metal contacts to n-type gallium nitride with low-temperature-grown cap layer
Authors: Lee M. L. , Sheu J. K. , Lin S. W.
Published: January 2006

The Schottky barrier heights of metal contacts, including WSi0.8, Cr, Ti, Pt, and Ni, on n-type gallium nitride (GaN) with a GaN cap layer grown at low-temperature (LTG) were studied. Higher barriers can be formed by introducing LTG GaN on top of the conventional structures. The higher Schottky barrier observed in samples with the LTG GaN cap layer may be due to the facts that the high-resistivity LTG GaN layer may passivate the surface defects (pits) formed from threading dislocations or it may cause the Fermi-level pinning effect at the metal/semiconductor interface, revealing a weak dependence of Schottky barrier height on the metal work function. The measured barrier heights of the LTG GaN-capped samples were 1.02–1.13eV.
NiO films consisting of vertically aligned cone-shaped NiO rods
Authors: Zhang Zhengjun , Zhao Ye , Zhu Minmin
Published: January 2006

By thermally heating a nickel foil in a vacuum of ∼5×10−2Torr, films consisting of vertically aligned cone-shaped NiO microrods were deposited on Si (001) substrates at a temperature of <300°C. The NiO rods were grown along ⟨001⟩ directions by stacking the NiO (001) nanoslices, and are ∼10μm long with a sharp nanosized tip. Due to this morphology, the NiO film exhibited a threshold field of ∼6.5V∕μm in field emission and a field enhancement factor of 2130 that is sufficiently high for field emission applications. The optical band gap of the NiO film was estimated to be ∼3.68eV from the optical absorption measurement and was almost a constant upon heating. In addition, the NiO film exhibited a strong photoluminescence at ∼674nm when excited by a 514 nm Ar+ laser, which might be attributed to the oxygen vacancies.
In situ x-ray imaging of nanoparticle agglomeration in fluidized beds
Authors: Jenneson Paul Michael , Gundogdu Ozcan
Published: January 2006

A high spatial (down to 400 nm) and temporal resolution (down to 1 ms) x-ray imaging apparatus has been designed to study the agglomeration of arc plasma synthesized zinc oxide nanoparticles (average diameter of 50 nm) in fluidized beds under different gas flow velocities. The mean volume distribution of the nanoparticle agglomerates was determined with x-ray microtomography and found to correspond to a lognormal distribution with a mean value of 0.70×109μm3 and a variance of 3.6×1021 (μm3)2. The average density of the agglomerates was found to be 2.9gcm−3 compared to 5.6gcm−3 for the individual nanoparticles. The powder assembly was then dynamically imaged using an x-ray image intensifier coupled to a digital camera using a field of view of 24.20 mm by 32.25 mm and a temporal resolution of 40 ms. Sequential frames were captured into computer memory for a range of gas flow velocities from 0.026ms−1 to 0.313ms−1. The breakup energy of the agglomerates was calculated to be approximately 2×10−8J using a combination of dynamic observations and physical properties of the agglomerate system extracted from the x-ray microtomographic data.
Ferrite-ferroelectric layered structures for electrically and magnetically tunable microwave resonators
Authors: Semenov A. A. , Karmanenko S. F. , Demidov V. E. , Kalinikos B. A. , Srinivasan G. , Slavin A. N. , Mantese J. V.
Published: January 2006

It is demonstrated experimentally that a layered structure consisting of ferrite and ferroelectric thin films can be used as an electrically and magnetically tunable microwave resonator. The dual tunability is realized through the application of a bias electric field to the ferroelectric layer (thus changing its dielectric constant), and a bias magnetic field to the ferrite layer. The resonator having central frequency f0≅5GHz and bandwidth Δf=3.5MHz demonstrated a broadband (∼300Δf) tunability through the variation of the bias magnetic field, and a narrow-band (∼2Δf) tunability through the variation of the bias electric field.
Demonstration of a 4H SiC betavoltaic cell
Authors: Chandrashekhar M. V. S. , Thomas Christopher I. , Li Hui , Spencer M. G. , Lal Amit
Published: January 2006

A betavoltaic cell in 4H SiC is demonstrated. A p-n diode structure was used to collect the charge from a 1mCi Ni-63 source. An open circuit voltage of 0.72V and a short circuit current density of 16.8nA∕cm2 were measured in a single p-n junction. A 6% lower bound on the power conversion efficiency was obtained. A simple photovoltaic-type model was used to explain the results. Fill factor and backscattering effects were included in the efficiency calculation. The performance of the device was limited by edge recombination.
Biological indicators of stream health using macroinvertebrate assemblage composition: a comparison of sensitivity to an urban gradient
Authors: Walsh Christopher J.
Published: January 2006

Biological indicators are increasingly being used as integrative measures of ecosystem health in streams, particularly indicators using macroinvertebrate assemblage composition. Several indicators of this type have been advocated, including biotic indices based on taxa sensitivities, richness indices and ratios of observed to expected taxa from models predicting assemblage composition in streams with little human impact (O/E scores). The present study aimed to compare the sensitivity of indicators of each of these types (all used for legislated objectives for stream protection in Victoria, Australia) to a gradient of urban disturbance in 16 streams in a small area in eastern Melbourne. The biotic index SIGNAL and number of Ephemeroptera, Plecoptera or Trichoptera families were the most sensitive indicators, whereas total number of families and O/E scores from Australian river assessment system (AUSRIVAS) models were least sensitive. Differences in sensitivity were not the result of sampling or taxonomic inadequacies. AUSRIVAS and similar models might be improved by using only predictor variables that are not affected by human impacts and by sounder approaches to model selection. Insensitivities of indicators and misclassification of sites by the Victorian objectives show that assessment of indicators against disturbance gradients is critical for setting management objectives based on biological indicators.
Is all salinity the same? I. The effect of ionic compositions on the salinity tolerance of five species of freshwater invertebrates
Authors: Zalizniak Liliana , Kefford Ben J. , Nugegoda Dayanthi
Published: January 2006

Salts of marine origin, predominantly consisting of Na+ and Cl− ions, are dominant in most Australian inland saline waters. The proportions of other ions, Ca2+, Mg2+, SO42–, HCO3− and CO32–, in the water may influence salinity tolerance of freshwater organisms and thus the effect of increasing salinity may vary with difference in ionic proportions. We exposed freshwater invertebrates to different concentrations of four ionic compositions and compared them with commercial sea salt (Ocean Nature). They were: synthetic Ocean Nature (ONS) and three saline water types (ONS but without: SO42–, HCO3− and CO32– (S1); Ca2+, HCO3− and CO32– (S2); and Ca2+ and Mg2+ (S3)), which are considered to be the predominant saline water types in south-eastern Australia and the Western Australian wheatbelt. The 96-h LC50 values for the five media were determined for six invertebrate species and sub-lethal responses were observed for two species. There were no differences between responses of invertebrates to various ionic compositions in acute toxicity tests. However, in prolonged sub-lethal tests, animals reacted differently to the various ionic compositions. The greatest effect was observed in water types lacking Ca, for which plausible physiological mechanisms exist. Variation in ionic proportions should be taken into account when considering sub-lethal effects of salinity on freshwater invertebrates.
Energy and nutrient fluxes from rivers and streams into terrestrial food webs
Authors: Ballinger Andrea , Lake P. S.
Published: January 2006

Ecologists long have been aware that there is flux of energy and nutrients from riverine systems to the surrounding terrestrial landscape and vice versa. Riparian ecotones are diverse and ecologically important. Consequently, there is substantial literature examining faunal-mediated transfers of energy and nutrients from rivers into terrestrial food webs. A wide variety of taxa has been shown to utilise riparian resources, from species specialised for existence at the aquatic–terrestrial interface to opportunistic predators and scavengers. Outputs from rivers may be influenced by productivity gradients, channel geometry and the condition of the exchange surface. Until recently, consideration of faunal-transferred, allochthonous inputs has been peripheral to other research questions. The development of general models of inter-habitat transfers, together with advances in technology, has placed questions about the ecological importance of riverine outputs squarely on the research agenda. Researchers now are investigating how aquatic subsidies influence food-web dynamics at landscape scales. However, ecologists continue to largely ignore subsidisation of terrestrial food webs by energy and nutrients from floodwaters in lowland river–floodplain systems. The dearth of information about the benefits of flooding to terrestrial consumers appears to have resulted in underestimation of the gross ecological impacts of river regulation.
Telomere tethering at the nuclear periphery is essential for efficient DNA double strand break repair in subtelomeric region
Authors: Therizols Pierre , Fairhead Cécile , Cabal Ghislain G. , Genovesio Auguste , Olivo-Marin Jean-Christophe , Dujon Bernard , Fabre Emmanuelle
Published: January 2006

In the yeast Saccharomyces cerevisiae that lacks lamins, the nuclear pore complex (NPC) has been proposed to serve a role in chromatin organization. Here, using fluorescence microscopy in living cells, we show that nuclear pore proteins of the Nup84 core complex, Nup84p, Nup145Cp, Nup120p, and Nup133p, serve to anchor telomere XI-L at the nuclear periphery. The integrity of this complex is shown to be required for repression of a URA3 gene inserted in the subtelomeric region of this chromosome end. Furthermore, altering the integrity of this complex decreases the efficiency of repair of a DNA double-strand break (DSB) only when it is generated in the subtelomeric region, even though the repair machinery is functional. These effects are specific to the Nup84 complex. Our observations thus confirm and extend the role played by the NPC, through the Nup84 complex, in the functional organization of chromatin. They also indicate that anchoring of telomeres is essential for efficient repair of DSBs occurring therein and is important for preserving genome integrity.
Activation-dependent substrate recruitment by the eukaryotic translation initiation factor 2 kinase PERK
Authors: Marciniak Stefan J. , Garcia-Bonilla Lidia , Hu Junjie , Harding Heather P. , Ron David
Published: January 2006

Regulated phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α) by the endoplasmic reticulum (ER) stress-activated protein kinase PERK modulates protein synthesis and couples the production of ER client proteins with the organelle's capacity to fold and process them. PERK activation by ER stress is known to involve transautophosphorylation, which decorates its unusually long kinase insert loop with multiple phosphoserine and phosphothreonine residues. We report that PERK activation and phosphorylation selectively enhance its affinity for the nonphosphorylated eIF2 complex. This switch correlates with a marked change to the protease sensitivity pattern, which is indicative of a major conformational change in the PERK kinase domain upon activation. Although it is dispensable for catalytic activity, PERK's kinase insert loop is required for substrate binding and for eIF2α phosphorylation in vivo. Our findings suggest a novel mechanism for eIF2 recruitment by activated PERK and for unidirectional substrate flow in the phosphorylation reaction.
The Use of Gene Expression Analysis and Proteomic Databases in The Development of a Screening System To Determine The Value of Natural Medicinal Products
Authors: Katz Sidney , Harris Robert , Lau Jeffrey Tien-Yau , Chau Adeline
Published: January 2006

A rapid throughput screening system involving gene expression analysis was developed in order to investigate the potential of bioactive chemicals contained in natural health products as effective drug therapy, in particular the ability of these chemicals to alleviate the inflammatory response in human airway epithelial cells. A number of databases were searched to retrieve the information needed to properly analyze the gene expression profiles obtained. The gene expression of human bronchial epithelial cells infected with rhinovirus and/or exposed to platelet activating factor was analyzed. Following analysis of the gene expression data the total number of expressed proteins that may potentially act as a marker for monitoring the modulation of airway inflammation was narrowed to 19. Further studies will involve selecting antibodies for these proteins, culturing airway epithelial cells in the presence of extracts of natural health products, extracting the proteins and identifying them by western blot analysis.