bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct and glia-mediated effects of GABA on development of central olfactory neurons
Authors: Mallory Heather S. , Gibson Nicholas J. , Hayashi Jon H. , Nighorn Alan J. , Oland Lynne A.
Published: July 2012

Previously studied for its role in processing olfactory information in the antennal lobe, GABA also may shape development of the olfactory pathway, acting either through or on glial cells. Early in development, the dendrites of GABAergic neurons extend to the glial border that surrounds the nascent olfactory lobe neuropil. These neuropil glia express both GABAAand GABABreceptors, about half of the glia in acute cultures responded to GABA with small outward currents, and about a third responded with small transient increases in intracellular calcium. The neuronal classes that express GABAin vivo, the local interneurons and a subset of projection neurons, also do so in culture. Exposure to GABA in culture increased the size and complexity of local interneurons, but had no effect on glial morphology. The presence of glia alone did not affect neuronal morphology, but in the presence of both glia and GABA, the growth-enhancing effects of GABA on cultured antennal lobe neurons were eliminated. Contact between the glial cells and the neurons was not necessary. Operatingin vivo, these antagonistic effects, one direct and one glia mediated, could help to sculpt the densely branched, tufted arbors that are characteristic of neurons innervating olfactory glomeruli.
Analysis of glutathione S-transferase genes polymorphisms and the risk of schizophrenia in a sample of Iranian population
Authors: Kashani Farah Lotfi , Kordi-Tamandani Dor Mohammad , Sahranavard Roya , Hashemi Mohammad , Kordi-Tamandani Farzaneh , Torkamanzehi Adam
Published: July 2012

Glutathione S-transferases (GSTs) are major intracellular antioxidants, which, impaired in their function, are involved in the progress of schizophrenia (SCZ). The aim of this case-control study was to investigate the association between the polymorphism of glutathione S-transferases M1 (GSTM1), T1 (GSTT1), the glutathione S-transferase P1 gene (GSTP1) and SCZ. We isolated genomic DNA from peripheral blood of 93 individuals with SCZ and 99 healthy control subjects' genotypes analyzing them for GSTM1, GSTT1 and GSTP1 using polymerase chain reaction. The analysis of the gene–gene interaction between GSTs indicated that the magnitude of the association was greater for the combined AG/GSTT1 & GSTM1 genotypes (OR = 2.51; 95% CI: 1.13–5.63, P = 0.02). The AG and combined AG + GG genotypes of GSTP1 increased the risk of SCZ (OR = 1.83; 95% CI: 0.94–3.75 and OR = 1.71; 95% CI: 0.92–3.19, respectively). The genotypes of GSTT/NULL, NULL/GSTM and NULL/NULL increased the risk of SCZ (OR = 2.05; 95% CI: 0.9–4.74; OR = 2.0; 95% CI: 1.68–2.31; and OR = 1.8; 95% CI: 0.57–2.46, respectively). The present study supports previous data that suggest that impairment in the function of GSTs genes may increase the risk of SCZ.
What Americans think of international humanitarian law
Authors: Gutierrez Brad A. , DeCristofaro Sarah , Woods Michael
Published: July 2012

The United States' foreign policy in the first decade of the twenty-first century and its involvement in armed conflicts in Iraq and Afghanistan have given rise to a reinvigorated interest in international humanitarian law (IHL), commonly referred to in the United States as the law of armed conflict. Conversations about whether to classify detainees as prisoners of war, debates about what constitutes torture, and numerous surveys attempting to measure the public's knowledge about and views on the rules of war are offering an opportunity to examine Americans' views on IHL. This article will reflect on those views, providing numerous examples to illustrate the complexities encountered when near universally accepted legal standards of conduct are layered upon the fluid and unpredictable realities of modern warfare. The article will also highlight the impact that battlefield activities can have on domestic debates over policy choices and national conscience.
Kognitive und körperliche Erregung in der Phase vor dem Einschlafen
Authors: Gieselmann Annika , de Jong-Meyer Renate , Pietrowsky Reinhard
Published: July 2012

Zusammenfassung. Theoretischer Hintergrund: Die Pre-Sleep Arousal Scale (PSAS) gilt als Goldstandard zur Erfassung kognitiver und körperlicher Erregung in der Phase vor dem Einschlafen. Fragestellung: Bestimmung der Gütekriterien der deutschen Übersetzung. Methode: Die 16 übersetzten Items wurden 268 überwiegend studentischen Versuchspersonen vorgelegt, um dimensionale Struktur, Reliabilität und Validität des Fragebogens zu überprüfen. Ergebnisse: Die zweidimensionale Struktur der Originalversion konnte repliziert werden, allerdings empfiehlt es sich, Item 16 aus dem Itempool auszuschließen. Die interne Konsistenz ist gut bis sehr gut. Bezüglich der Validität eigneten sich beide Skalen zur Diskriminierung zwischen guten und schlechten Schläfern und waren beide erwartungsgemäß stärker mit Einschlaf- als mit Durchschlafproblemen assoziiert. Schlussfolgerung: Mit der deutschen Übersetzung der PSAS kann kognitive und körperliche Erregung ökonomisch, reliabel und valide erfasst werden.
Integration einer existenziellen Perspektive in ein kognitiv-behaviorales Schmerzbewältigungsprogramm
Authors: Gebler Florian , Maercker Andreas
Published: July 2012

Zusammenfassung. Hintergrund: In der vorliegenden Studie wird das Einbeziehen einer existenziellen Perspektive in ein kognitiv-behaviorales Schmerzbewältigungsprogramm empirisch überprüft. Die existenzielle Perspektive hat einen akkommodativen Schwerpunkt im Gegensatz zum assimilativen Fokus herkömmlicher Programme. Hypothesen: Beide Behandlungsgruppen sollten im Prä-Post-Vergleich eine signifikant geringere schmerzbedingte Behinderung als auch eine signifikant höhere Lebensqualität aufweisen. Die Experimentalgruppe sollte darüber hinaus einen signifikant höheren Therapieerfolg als die Kontrollgruppe aufweisen. Methode: 149 Patienten mit chronischen Schmerzen nahmen im Rahmen eines interdisziplinären Klinikaufenthaltes entweder an einer rein kognitiv-behavioralen Schmerzbewältigungsgruppe (n = 70) oder an einem existenziell ergänzten Gruppenprogramm (n = 79) teil. Die Auswertung der Prä-Post-Vergleiche erfolgte mit einer MANOVA mit Messwiederholung sowie nachfolgenden zweifaktoriellen Varianzanalysen mit Messwiederholung. Ergebnisse: Beide Behandlungsgruppen zeigen signifikante Verbesserungen bei großen Effektstärken. Die Experimentalgruppe zeigt darüber hinaus einen signifikant höheren Therapieerfolg hinsichtlich schmerzbedingter Behinderung bei kleiner Effektgröße. Weiterhin ergaben sich ein differenzieller Effekt für die Personen mit niedrigerem Ausbildungsgrad sowie höhere Zufriedenheitswerte für die existenzielle Intervention. Schlussfolgerung: Die Ergebnisse zeigen, dass auch im Rahmen eines umfassenden stationären Klinikaufenthaltes die Implementierung einer existenziellen Intervention einen bedeutsamen zusätzlichen Effekt haben kann. Dies scheint insbesondere für die große Gruppe der Patienten mit formal niedrigerem Ausbildungsgrad zu gelten.
Effekte therapeutenbegleiteter versus patientengeleiteter Exposition bei Panikstörung mit Agoraphobie
Authors: Lang Thomas , Helbig-Lang Sylvia , Gloster Andrew T. , Richter Jan , Hamm Alfons O. , Fehm Lydia , Fydrich Thomas , Gerlach Alexander L. , Ströhle Andreas , Alpers Georg W. , Gauggel Siegried , Kircher Tilo , Deckert Jürgen , Höfler Michael , Arolt Volker , Wittchen Hans-Ulrich
Published: July 2012

Zusammenfassung. Theoretischer Hintergrund: Die Rolle der Therapeutenbegleitung während Expositionsübungen bei Panikstörung mit Agoraphobie (P/A) ist bislang ungeklärt. Eine kürzlich durchgeführte klinische Studie (MAC-Studie) lieferte Hinweise auf ein günstigeres Behandlungsergebnis bei Therapeutenbegleitung. Fragestellung: Wie lassen sich Effekte therapeutenbegleiteter Exposition (T+) im Vergleich zu Exposition ohne Therapeutenbegleitung (T–) erklären? Methode: Daten von 301 Patienten, die eine expositionsbasierte KVT mit bzw. ohne Therapeutenbegleitung erhalten hatten, wurden analysiert. Untersucht wurden der Einfluss der initialen Störungsschwere, des Sicherheitsverhaltens sowie differenzielle Effekte der Bedingungen auf die Angst vor der Angst. Zusätzlich wurde überprüft, inwieweit die Übungshäufigkeit in den Behandlungsbedingungen variiert und einen Mediator des Behandlungserfolgs darstellt. Ergebnisse: Störungsschwere und Sicherheitsverhalten zeigten keine differenziellen Effekte zwischen den Bedingungen; die T+ Bedingung führte jedoch zu stärkeren Reduktionen der Angst vor der Angst im Angstsensitivitätsindex. Patienten der T+ Bedingung führten häufiger selbständig Expositionsübungen durch, während Patienten in T– im Durchschnitt länger übten. Die Übungshäufigkeit stellte dabei einen Mediator des Behandlungserfolgs dar. Schlussfolgerungen: Günstigere Effekte einer therapeutenbegleiteten Exposition gehen auf stärkere Reduktionen der Angst vor der Angst sowie auf eine höhere Übungshäufigkeit im Selbstmanagement zurück.
Comparison of the predictions of universal scaling of the saturation dependence of the air permeability with experiment
Authors: Ghanbarian‐Alavijeh Behzad , Hunt Allen G.
Published: July 2012

We compare predictions of the saturation dependence of air permeability from percolation theory with experimental results taken from the last 60 years. We selected experiments with sufficient density of data points to verify a functional dependence. The typical number of such data points was about 10, but actual values ranged from 4 to 31. The predicted saturation dependence is a universal power law in the air‐filled porosity (less a threshold value) with an exponent of 2.00. Our investigation showed that the experimental power was 2.028 ± 0.028 with an R2 value, averaged across all the experiments, of greater than 0.96 for database 1 (including 16 samples from the literature) and 1.814 ± 0.386 with an R2value of larger than 0.90 for database 2 (including 23 samples from Tang et al. (2011)). The threshold value of the air‐filled porosity could be predicted reasonably from the wet end of the soil water retention curves. The threshold varied systematically with soil texture. We also compare the proposed model with three other methods, e.g., Millington and Quirk, Burdine‐Brooks‐Corey, and Kawamoto et al., in estimation of air permeability. The results indicate that the universal scaling approach estimates air permeability more accurately than other methods. Thus, we believe that we have confirmed the universal scaling predicted as well as demonstrated its usefulness in predicting the air permeability.
Increasing atmospheric burden of ethanol in the United States
Authors: de Gouw J. A. , Gilman J. B. , Borbon A. , Warneke C. , Kuster W. C. , Goldan P. D. , Holloway J. S. , Peischl J. , Ryerson T. B. , Parrish D. D. , Gentner D. R. , Goldstein A. H. , Harley R. A.
Published: July 2012

The use of ethanol as a transportation fuel in the U.S. increased significantly from 2000–2009, and in 2010 nearly all gasoline contained 10% ethanol. In accordance with this increased use, atmospheric measurements of volatile organic compounds in Los Angeles in 2010 were significantly enriched in ethanol compared to measurements in urban outflow in the Northeast U.S. in 2002 and 2004. Mixing ratios of acetaldehyde, an atmospheric oxidation product of ethanol, decreased between 2002 and 2010 in Los Angeles. Previous work has suggested that large‐scale use of ethanol may have detrimental effects on air quality. While we see no evidence for this in the U.S., our study indicates that ethanol has become a ubiquitous compound in urban air and that better measurements are required to monitor its increase and effects.
Scales of variability of black carbon plumes over the Pacific Ocean
Authors: Weigum N. M. , Stier P. , Schwarz J. P. , Fahey D. W. , Spackman J. R.
Published: July 2012

Scales of spatial variability of black carbon (BC) aerosol plumes are quantified during the HIPPO aircraft campaign, which flew multiple missions from pole‐to‐pole over the Pacific ocean. During the first three missions of HIPPO, over 400 vertical profiles of BC concentrations were obtained using a Single Particle Soot Photometer (SP2). In this work, a total of 100 plumes are identified and analyzed. Due to the nature of the HIPPO flight track, the plume length scale is defined along the slanted flight track, having both vertical and horizontal components. These plumes comprise 57% of the total BC mass measured and have a median scale of 113 km. An analysis of BC variability based on autocorrelation functions confirms that most of BC's variability exists on scales similar to the majority of measured plume scales, with a range of 85–155 km. The plume scales are compared to an effective along‐track global circulation model (GCM) resolution, which ranges from 20 km for low altitudes and steep ascents to 230 km for high altitudes and shallower ascents. The results suggest that plumes characterized predominantly by their horizontal variation at these scales are too small to be captured by GCMs running at resolutions currently suitable for climate simulations.
Could satellite altimetry have improved early detection and warning of the 2011 Tohoku tsunami?
Authors: Hamlington B. D. , Leben R. R. , Godin O. A. , Gica E. , Titov V. V. , Haines B. J. , Desai S. D.
Published: July 2012

The 2011 Tohoku tsunami devastated Japan and affected coastal populations all around the Pacific Ocean. Accurate early warning of an impending tsunami requires the detection of the tsunami in the open ocean. While the lead‐time was not sufficient for use in warning coastal populations in Japan, satellite altimetry observations of the tsunami could have been used to improve predictions and warnings for other affected areas. By comparing to both model results and historical satellite altimeter data, we use near‐real‐time satellite altimeter measurements to demonstrate the potential for detecting the 2011 Tohoku tsunami within a few hours of the tsunami being generated. We show how satellite altimeter data could be used to both directly detect tsunamis in the open ocean and also improve predictions made by models.
A global picture of the first abrupt climatic event occurring during the last glacial inception
Authors: Capron E. , Landais A. , Chappellaz J. , Buiron D. , Fischer H. , Johnsen S. J. , Jouzel J. , Leuenberger M. , Masson‐Delmotte V. , Stocker T. F.
Published: July 2012

The orbital‐scale transition from the last interglacial to glacial climate corresponds to the progressive organization of global millennial‐scale climate variability. Here, we investigate the structure and the global fingerprint of the first warming event occurring during the last glacial inception, the Greenland InterStadial 25 (GIS 25). Using centennial to decadal‐resolution measurements ofδ18O and δD in the ice together with δ15N, δ18O2 and CH4in the trapped air, we show that GIS 25 does not coincide with large environmental changes at lower latitudes. Such an equivocal fingerprint questions whether GIS 25 is simply a smaller amplitude version of later rapid events or whether it reflects a more regional northern hemisphere origin for the initiation of the millennial‐scale climatic variability. After this ambiguous first rapid event, the onset of the global millennial‐scale variability ‐characteristic of the last glacial period‐ occurs as a short (300 years) event ending GIS 25.
An east‐west SST anomaly pattern in the midlatitude North Atlantic Ocean associated with winter precipitation variability over eastern China
Authors: Liu Ge , Ji Liren , Wu Renguang
Published: July 2012

Winter precipitation tends to vary consistently over most regions of eastern China. The present study reveals that the variation in winter precipitation over eastern China is positively correlated to an east‐west sea surface temperature (SST) anomaly pattern in the midlatitudes and high latitudes of the North Atlantic Ocean. When the SST is higher (lower) in the eastern North Atlantic Ocean and lower (higher) in the western North Atlantic Ocean, winter precipitation over eastern China tends to be above (below) normal. The east‐west SST anomaly pattern in the North Atlantic modifies the atmospheric circulation over the Atlantic Ocean and Europe, and the anomalous circulation extends to downstream East Asia through the propagation of Rossby waves and exerts influence on winter precipitation over eastern China. The formation of the east‐west SST anomaly pattern in the North Atlantic may be associated with anomalies in the North Atlantic thermohaline circulation and in surface winds over the North Atlantic Ocean.
Multiwave out-of-normal band-edge lasing in cholesteric liquid crystals
Authors: Palto S. P. , Shtykov N. M. , Umanskii B. A. , Barnik M. I.
Published: July 2012

We have investigated the lasing effect in dye-doped cholesteric liquid crystals, where the photonic stop-band for light propagating along the helical axis coinciding with the layer normal is strongly shifted to longer wavelengths with respect to the luminescence band of the dye. In the absence of overlapping of the photonic and luminescence bands, the well-known lasing effect along the normal at the stop-band edges is forbidden. However, the lasing is still allowed for out-of-normal directions, for which the photonic band is shifted to shorter wavelengths corresponding to the luminescence band. Despite of the out-of-normal light propagation, the positive feedback necessary for the lasing is still available in a case of the monodomain cholesteric layer, when its thickness is much less than the optical pumping aperture. We have observed a significantly increased energy threshold for the out-of-normal lasing modes despite they are characterized by lower threshold gain compared to the modes propagating along the helix axis. The increased energy threshold is explained in terms of continuous distribution of the lasing emission over a large angular sector and energy leakage caused by the leaky lasing into the substrates.
Direct current-biased InAs spin-filter cascades
Authors: Jacob Jan , Lehmann Hauke , Merkt Ulrich , Mehl Sebastian , Hankiewicz Ewelina M.
Published: July 2012

We study dc-biased spin-transport in InAs two-stage spin-filter cascades. The cascades allow all-electrical generation and detection of spin-polarized currents in an all-semiconductor device. The application of a dc bias simplifies the interpretation of the experimental results, enhances the signal-to-noise ratio, and paves the way for more definite measurements in magnetic fields.
Predicting global solar radiation for South America
Authors: Korachagaon Iranna , Bapat V. N.
Published: July 2012

Solar energy is one of the most promising renewable energy sources. The availability of the solar energy potential data is very scarce and often not readily accessible. The main objective of this study was to estimate the monthly average global solar radiation at various locations for South America, by the generalized Iranna-Bapat’s model. Iranna-Bapat’s model is developed to estimate the value of global solar radiation at any location on earth surface. This model uses the most commonly measurable meteorological parameters such as ambient temperature, humidity, wind-speed, moisture for a given location. A total of 35 locations spread across the continent are used to validate this model. The computed values from Iranna-Bapat’s model are compared with the measured values. Iranna-Bapat’s model demonstrated acceptable results, and statistically displayed lower values of RMSEs. Therefore this model could be a good estimator for predicting the global solar radiation at other locations for South America, where such data is not available.
Excitation and emission spectra of rubidium in rare-gas thin-films
Authors: Gerhardt Ilja , Sin Kyungseob , Momose Takamasa
Published: July 2012

To understand the optical properties of atoms in solid state matrices, the absorption, excitation, and emission spectra of rubidium doped thin-films of argon, krypton, and xenon were investigated in detail. A two-dimensional spectral analysis extends earlier reports on the excitation and emission properties of rubidium in rare-gas hosts. We found that the doped crystals of krypton and xenon exhibit a simple absorption-emission relation, whereas rubidium in argon showed more complicated spectral structures. Our sample preparation employed in the present work yielded different results for the Ar crystal, but our peak positions were consistent with the prediction based on the linear extrapolation of Xe and Kr data. We also observed a bleaching behavior in rubidium excitation spectra, which suggests a population transfer from one to another spectral feature due to hole-burning. The observed optical response implies that rubidium in rare-gas thin-films is detectable with extremely high sensitivity, possibly down to a single atom level, in low concentration samples.
Insights into symmetric and asymmetric vortex mergers using the core growth model
Authors: Jing Fangxu , Kanso Eva , Newton Paul K.
Published: July 2012

We revisit the two vortex merger problem (symmetric and asymmetric) for the Navier-Stokes equations using the core growth model for vorticity evolution coupled with the passive particle field and an appropriately chosen time-dependent rotating reference frame. Using the combined tools of analyzing the topology of the streamline patterns along with the careful tracking of passive fields, we highlight the key features of the stages of evolution of vortex merger, pinpointing deficiencies in the low-dimensional model with respect to similar experimental/numerical studies. The model, however, reveals a far richer and delicate sequence of topological bifurcations than has previously been discussed in the literature for this problem, and, at the same time, points the way towards a method of improving the model.
Synergistic etch rates during low-energetic plasma etching of hydrogenated amorphous carbon
Authors: Hansen T. A. R. , Weber J. W. , Colsters P. G. J. , Mestrom D. M. H. G. , van de Sanden M. C. M. , Engeln R.
Published: July 2012

The etch mechanisms of hydrogenated amorphous carbon thin films in low-energetic (<2 eV) high flux plasmas are investigated with spectroscopic ellipsometry. The results indicate a synergistic effect for the etch rate between argon ions and atomic hydrogen, even at these extremely low kinetic energies. Ion-assisted chemical sputtering is the primary etch mechanism in both Ar/H2 and pure H2 plasmas, although a contribution of swift chemical sputtering to the total etch rate is not excluded. Furthermore, ions determine to a large extent the surface morphology during plasma etching. A high influx of ions enhances the etch rate and limits the surface roughness, whereas a low ion flux promotes graphitization and leads to a large surface roughness (up to 60 nm).
Axisymmetric solutions of the pressure-gradient system
Authors: Hu Yanbo
Published: July 2012

A family of self-similar and global bounded weak solutions are constructed rigorously for all positive time to the two-dimensional pressure-gradient system in this paper. By using the axisymmetric and self-similar assumptions, the equations are reduced to a system of ordinary differential equations, from which we obtain detailed structures of solutions as well as their existence. On this basis, we explore the behavior of characteristics near the sonic boundary.
The effect of Peltier heat during current activated densification
Authors: Becker A. , Angst S. , Schmitz A. , Engenhorst M. , Stoetzel J. , Gautam D. , Wiggers H. , Wolf D. E. , Schierning G. , Schmechel R.
Published: July 2012

It is shown that current-activated pressure-assisted densification (CAPAD) is sensitive to the Peltier effect. Under CAPAD, the Peltier effect leads to a significant redistribution of heat within the sample during the densification. The densification of highly p-doped silicon nanoparticles during CAPAD and the properties of the obtained samples are investigated experimentally and by computer simulation. Both, simulation and experiments, indicate clearly a higher temperature on the cathode side and a decreasing temperature from the center to the outer shell. Furthermore, computer simulations provide additional insights into the temperature profile which explain the anisotropic properties of the measured sample.
Breakdown of the pseudopotential approximation for magnetizabilities and electric multipole moments. II. The importance of gauge invariance for large-core semi-local pseudopotentials
Authors: Schwerdtfeger Peter , van Wüllen Christoph , Cheeseman James R.
Published: July 2012

In a previous paper we pointed out that core contributions to the static magnetizability are non-negligible, and can therefore lead to erroneous results within the pseudopotential approximation [P. Schwerdtfeger, B. Assadollahzadeh, U. Rohrmann, R. Schäfer, and J. R. Cheeseman, J. Chem. Phys. 134, 204102 (2011)10.1063/1.3591338]. In a recent paper van Wüllen showed that additional terms arising from the gauge-invariant condition for the semi-local part of a pseudopotential operator can lead to non-negligible contributions to the magnetizability tensor, which are sensitive to the gauge origin and basis set chosen [C. van Wüllen, J. Chem. Phys. 136, 114110 (2012)10.1063/1.3694535]. These terms were neglected in previous calculations as they were assumed to be small. In this paper we analyze the importance of the gauge-dependent semi-local pseudopotential correction term in detail for AuF and clusters of Sn showing that it leads indeed to very large corrections to the paramagnetic term for large-core pseudopotentials. Without this correction the results become very sensitive to the basis set applied. This now resolves some of the unusual large paramagnetic contributions reported before for both AuF and Sn2.
Entropy production in non-equilibrium fluctuating hydrodynamics
Authors: Gradenigo Giacomo , Puglisi Andrea , Sarracino Alessandro
Published: July 2012

Fluctuating entropy production is studied for a set of linearly coupled complex fields. The general result is applied to non-equilibrium fluctuating hydrodynamic equations for coarse-grained fields (density, temperature, and velocity), in the framework of model granular fluids. We find that the average entropy production, obtained from the microscopic stochastic description, can be expressed in terms of macroscopic quantities, in analogy with linear non-equilibrium thermodynamics. We consider the specific cases of driven granular fluids with two different kinds of thermostat and the homogeneous cooling regime. In all cases, the average entropy production turns out to be the product of a thermodynamic force and a current: the former depends on the specific energy injection mechanism, the latter takes always the form of a static correlation between fluctuations of density and temperature time-derivative. Both vanish in the elastic limit. The behavior of the entropy production is studied at different length scales and the qualitative differences arising for the different granular models are discussed.
Elastic constants of langasite and alpha quartz at high temperatures measured by antenna transmission acoustic resonance
Authors: Nakamura N. , Sakamoto M. , Ogi H. , Hirao M.
Published: July 2012

A method for measuring elastic constants of piezoelectric materials at high temperature up to 1224 K is proposed. It determines all independent elastic constants by measuring resonance frequencies of a rectangular parallelepiped piezoelectric specimen contactlessly using its own piezoelectricity with an antenna. Without using conventional contacting piezoelectric transducers, vibrational sources are excited directly in the specimen by the oscillating electric field. Capability of the method is demonstrated by measuring the elastic constants of langasite at high temperature up to 1224 K, and temperature coefficients of the elastic constants are determined. In addition, elastic constants of alpha quartz are measured at high temperature up to just below the alpha-beta phase transition temperature. Considering the local deformation with temperature increment, an interpretation based on the strain energy reduction is proposed for the unusual temperature dependence of C66. Furthermore, the internal-friction tensor is measured, and the relationship between the observed anisotropy in internal friction and the structural evolution with temperature increment is discussed.
Energy transfer kinetics in oxy-fluoride glass and glass-ceramics doped with rare-earth ions
Authors: Sontakke Atul D. , Annapurna K.
Published: July 2012

An investigation of donor-acceptor energy transfer kinetics in dual rare earths doped precursor oxy-fluoride glass and its glass-ceramics containing NaYF4 nano-crystals is reported here, using three different donor-acceptor ion combinations such as Nd-Yb, Yb-Dy, and Nd-Dy. The precipitation of NaYF4 nano-crystals in host glass matrix under controlled post heat treatment of precursor oxy-fluoride glasses has been confirmed from XRD, FESEM, and transmission electron microscope (TEM) analysis. Further, the incorporation of dopant ions inside fluoride nano-crystals has been established through optical absorption and TEM-EDX analysis. The noticed decreasing trend in donor to acceptor energy transfer efficiency from precursor glass to glass-ceramics in all three combinations have been explained based on the structural rearrangements that occurred during the heat treatment process. The reduced coupling phonon energy for the dopant ions due to fluoride environment and its influence on the overall phonon assisted contribution in energy transfer process has been illustrated. Additionally, realization of a correlated distribution of dopant ions causing clustering inside nano-crystals has also been reported.
Magnetoelectric properties of flexible BiFeO3/Ni tapes
Authors: Yan L. , Zhuo M. , Wang Z. , Yao J. , Haberkorn N. , Zhang S. , Civale L. , Li J. , Viehland D. , Jia Q. X.
Published: July 2012

We report ferroelectric (FE), ferromagnetic, and magnetoelectric (ME) properties of BiFeO3 films directly deposited on flexible magnetic Ni tapes. Without use of metal-oxide and/or noble metal buffer layer between the BiFeO3 and the Ni, both ferroelectric and magnetic properties of the film and the substrate are preserved. X-ray diffraction and transmission electron microscopy analyses confirm the formation of preferentially oriented (110) BiFeO3 film on Ni tapes. The BiFeO3 film has a saturation polarization and a piezoelectric d33 coefficient of 69 μC/cm2 and 52 pm/V, respectively. The BiFeO3/Ni tape shows a magnetoelectric coefficient of 3.5 mV/cm·Oe.
Optical properties of ultrathin InAs quantum-well-heterostructures
Authors: Samti R. , Raouafi F. , Chaouach M. , Maaref M. , Sakri A. , Even J. , Gerard J.-M. , Jancu J.-M
Published: July 2012

Band structure calculations of complete InAs monolayer in AlGaAs/GaAs quantum wells are performed within the framework of the extended-basis sp3d5s* tight-binding model. We show that the optical properties can be tuned from the quantum well energy below the GaAs band-gap depending on the well thickness and the position of the probe. The results are supported by differential reflectivity measurements and represent a concept for optoelectronic devices with an operation wavelength widely tuneable around 850 nm employing GaAs process technology.
Ab initio chemical kinetics for the ClOO + NO reaction: Effects of temperature and pressure on product branching formation
Authors: Raghunath P. , Lin M. C.
Published: July 2012

The kinetics and mechanism for the reaction of ClOO with NO have been investigated by ab initio molecular orbital theory calculations based on the CCSD(T)/6-311+G(3df)//PW91PW91/6-311+G(3df) method, employed to evaluate the energetics for the construction of potential energy surfaces and prediction of reaction rate constants. The results show that the reaction can produce two key low energy products ClNO + 3O2 via the direct triplet abstraction path and ClO + NO2 via the association and decomposition mechanism through long-lived singlet pc-ClOONO and ClONO2 intermediates. The yield of ClNO + O2 (1△) from any of the singlet intermediates was found to be negligible because of their high barriers and tight transition states. As both key reactions initially occur barrierlessly, their rate constants were evaluated with a canonical variational approach in our transition state theory and Rice–Ramspergen–Kassel–Marcus/master equation calculations. The rate constants for ClNO + 3O2 and ClO + NO2 production from ClOO + NO can be given by 2.66 × 10−16 T1.91 exp(341/T) (200–700 K) and 1.48 × 10−24 T3.99 exp(1711/T) (200–600 K), respectively, independent of pressure below atmospheric pressure. The predicted total rate constant and the yields of ClNO and NO2 in the temperature range of 200–700 K at 10–760 Torr pressure are in close agreement with available experimental results.
A field programmable gate array unit for the diagnosis and control of neoclassical tearing modes on MAST
Authors: O’Gorman T. , Naylor G. , Gibson K. J. , Huang B. , McArdle G. J. , Scannell R. , Shibaev S. , Snape J. A. , Thomas-Davies N.
Published: July 2012

A real-time system has been developed to trigger both the MAST Thomson scattering (TS) system and the plasma control system on the phase and amplitude of neoclassical tearing modes (NTMs), extending the capabilities of the original system. This triggering system determines the phase and amplitude of a given NTM using magnetic coils at different toroidal locations. Real-time processing of the raw magnetic data occurs on a low cost field programmable gate array (FPGA) based unit which permits triggering of the TS lasers on specific amplitudes and phases of NTM evolution. The MAST plasma control system can receive a separate trigger from the FPGA unit that initiates a vertical shift of the MAST magnetic axis. Such shifts have fully removed m/n = 2/1 NTMs instabilities on a number of MAST discharges.
Radial profile measurement of electron temperature in edge stochastic magnetic field layer of LHD using intensity ratio of extreme ultraviolet line emissions
Authors: Wang Erhui , Morita Shigeru , Kobayashi Masahiko , Murakami Izumi , Goto Motoshi , Dong Chunfeng
Published: July 2012

Vertical profile of neon line emissions in 30–650 Å wavelength range has been observed in horizontally elongated plasma cross section of Large Helical Device (LHD). Intensity ratio between the neon line emissions is studied to measure the radial profile of electron temperature in the edge stochastic magnetic field layer of LHD. The edge temperature profile successfully obtained from the line ratio of NeVIII 2s-3p to 2p-3s transitions is compared with the simulation based on three-dimensional edge transport code. The result shows a reasonably good agreement with the edge temperature profile analyzed from atomic data and analysis structure code. The electron temperature at last closed flux surface measured from the intensity ratio is also in good agreement with that measured from Thomson scattering.
A 16-channel heterodyne electron cyclotron emission radiometer on J-TEXT
Authors: Yang Z. J. , Phillips P. E. , Zhuang G. , Xiao J. S. , Huang H. , Rowan W. L. , Wang Z. J.
Published: July 2012

To study equilibrium temporal dynamics and the mechanisms of magnetohydrodynamic instabilities, a 16-channel heterodyne electron cyclotron emission (ECE) radiometer has been developed to view the J-TEXT tokamak from the low field side. The ECE radiometer detects second-harmonic extraordinary mode in the frequency band of 94–125 GHz which corresponds to resonances from 1.8 T to 2.2 T. This ECE system consists of an ECE transmission line, a radio frequency unit, and two 8-channel intermediate frequency units. An in situ blackbody calibration source is applied for system calibration by comparison of hot and cold sources in order to provide an absolute temperature measurement.
Compact solid-state neutral particle analyzer in current mode
Authors: Zhu Y. B. , Bortolon A. , Heidbrink W. W. , Celle S. L. , Roquemore A. L.
Published: July 2012

Solid state neutral particle analyzer (ssNPA) arrays are operated in current mode on the DIII-D tokamak and the National Spherical Torus Experiment (NSTX). Compared with conventional pulse-counting NPAs, current-mode operation sacrifices energy resolution to obtain economical, high-bandwidth, pitch-angle resolved measurements. With the success from a new three-channel near-vertical-view current mode ssNPA on DIII-D, the apertures on an existing array on NSTX were expanded to increase the particle influx. The sightlines of both arrays intersect heating beams, enabling both active and passive charge exchange measurements. The spatial resolution at beam intersection is typically 5 cm on both devices. Directly deposited ultra-thin foils on the detector surface block stray photons below the energy of 1 keV and also set low energy threshold about 25 keV for deuterium particle detection. Oscillations in neutral flux produced by high frequency magnetohydrodynamics (MHD) instabilities are readily detected.
Vibration mitigation in J-TEXT far-infrared diagnostic systems
Authors: Li Q. , Chen J. , Zhuang G. , Wang Z. J. , Gao L. , Chen W.
Published: July 2012

Optical structure stability is an important issue for far-infrared (FIR) phase measurements. To ensure good signal quality, influence of vibration should be minimized. Mechanical amelioration and optical optimization can be taken in turn to decrease vibration's influence and ensure acceptable measurement. J-TEXT (Joint Texal Experiment Tokamak, formerly TEXT-U) has two FIR diagnostic systems: a HCN interferometer system for electron density measurement and a three-wave polarimeter-interferometer system (POLARIS) for electron density and Faraday effect measurements. All use phase detection techniques. HCN interferometer system has almost eliminated the influence of vibration after mechanical amelioration and optical optimization. POLARIS also obtained first experimental results after mechanical stability improvements and is expected to further reduce vibration's influence on Faraday angle to 0.1° after optical optimization.
Application of hydrogenation to low-temperature cleaning of the Si(001) surface in the processes of molecular-beam epitaxy: Investigation by scanning tunneling microscopy, reflected high-energy electron diffraction, and high resolution transmission electron microscopy
Authors: Arapkina L. V. , Krylova L. A. , Chizh K. V. , Chapnin V. A. , Uvarov O. V. , Yuryev V. A.
Published: July 2012

Structural properties of the clean Si(001) surface obtained as a result of low-temperature (470–650 °C) pre-growth annealings of silicon wafers in a molecular-beam epitaxy chamber have been investigated. To decrease the cleaning temperature, a silicon surface was hydrogenated in the process of a preliminary chemical treatment in HF and NH4F aqueous solutions. It has been shown that smooth surfaces composed of wide terraces separated by monoatomic steps can be obtained by dehydrogenation at the temperatures ≳600 °C, whereas clean surfaces obtained at the temperatures <600 °C are rough. It has been found that there exists a dependence of structural properties of clean surfaces on the temperature of hydrogen thermal desorption and the process of the preliminary chemical treatment. The frequency of detachment/attachment of Si dimers from/to the steps and effect of the Ehrlich-Schwoebel barrier on ad-dimer migration across steps have been found to be the most probable factors determining a degree of the resultant surface roughness.
Crystal phase dependent photoluminescence of 6,13-pentacenequinone
Authors: De Marco P. , Bisti F. , Fioriti F. , Passacantando M. , Bittencourt C. , Lettieri S. , Ambrosio A. , Maddalena P. , Prezioso S. , Santucci S. , Ottaviano L.
Published: July 2012

Films of 6,13-pentacenequinone (PQ, C22H12O2) of nominal thicknesses 5 and 30 nm grown in high vacuum onto SiO2 have been UV (325 nm) excited and their photoluminescence (PL) response has been investigated with the support of parallel scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD) experiments. The photoluminescence spectra typically show a multiplet structure that can be ultimately assigned to the sum of the emission spectra from two different crystal phases, namely the “bulk” and the “thin film” phase, emitting respectively in the 500–600 nm and 600–750 nm spectral ranges. The assignment is done via the systematic parallel SEM and XRD investigation of the samples. Data are also discussed in comparison with PL spectra of PQ reported in the literature. The blue shift of the “bulk” phase PL spectrum is assigned to its smaller (about 9% less than in the “thin film” phase) molecular packing density in the ab-plane, and accordingly, to a decreased π–π orbital overlap.
Visible to vacuum ultraviolet dielectric functions of epitaxial graphene on 3C and 4H SiC polytypes determined by spectroscopic ellipsometry
Authors: Boosalis A. , Hofmann T. , Darakchieva V. , Yakimova R. , Schubert M.
Published: July 2012

Spectroscopic ellipsometry measurements in the visible to vacuum-ultraviolet spectra (3.5–9.5 eV) are performed to determine the dielectric function of epitaxial graphene on SiC polytypes, including 4H (C-face and Si-face) and 3C SiC (Si-face). The model dielectric function of graphene is composed of two harmonic oscillators and allows the determination of graphene quality, morphology, and strain. A characteristic van Hove singularity at 4.5 eV is present in the dielectric function of all samples, in agreement with observations on exfoliated as well as chemical vapor deposited graphene in the visible range. Model dielectric function analysis suggests that none of our graphene layers experience a significant degree of strain. Graphene grown on the Si-face of 4H SiC exhibits a dielectric function most similar to theoretical predictions for graphene. The carbon buffer layer common for graphene on Si-faces is found to increase polarizability of graphene in the investigated spectrum.
A multi-detector, digitizer based neutron depth profiling device for characterizing thin film materials
Authors: Mulligan P. L. , Cao L. R. , Turkoglu D.
Published: July 2012

Neutron depth profiling (NDP) is a mature, nondestructive technique used to characterize the concentration of certain light isotopes in a material as a function of depth by measuring the residual energy of charged particles in neutron induced reactions. Historically, NDP has been performed using a single detector, resulting in low intrinsic detection efficiency, and limiting the technique largely to high flux research reactors. In this work, we describe a new NDP instrument design with higher detection efficiency by way of spectrum summing across multiple detectors. Such a design is capable of acquiring a statistically significant charged particle spectrum at facilities limited in neutron flux and operation time.
Oxygen incorporation in homoepitaxial N-polar GaN grown by radio frequency-plasma assisted molecular beam epitaxy: Mitigation and modeling
Authors: Storm D. F. , Katzer D. S. , Meyer D. J. , Binari S. C.
Published: July 2012

We have investigated the effect of gallium deposition and desorption cycles and ultrathin (15 Å) AlN layers on the oxygen impurity concentrations in homoepitaxial N-polar GaN layers. Secondary ion mass spectroscopy (SIMS) indicates that three Ga deposition and desorption cycles reduce the total oxygen by 70%–80%, while ten cycles reduces the total oxygen by more than 90%. We present a model of surface segregation and incorporation which accurately captures the distribution of oxygen in these layers. By fitting the model to the SIMS data, we are able to determine the fraction of an oxygen layer adsorbed on a GaN surface which segregates upon initiation of epitaxial GaN growth. Under the conditions investigated, we find this fraction to be 80%.
Effect of metals and annealing on specific contact resistivity of GeTe/metal contacts
Authors: Chua E. K. , Zhao R. , Shi L. P. , Chong T. C. , Schlesinger T. E. , Bain J. A.
Published: July 2012

The circular transfer length method was employed to extract the specific contact resistivity, ρc of GeTe (amorphous and crystalline state) with metals (Ni, W, TiW) to quantify the series contact resistance. The ρc of amorphous-GeTe with metals was also determined for different annealing conditions. Higher metal work functions produce lower ρc for both GeTe states and the ρc was reduced further for annealing temperatures greater than the GeTe crystallization temperature. This is suggested to be a consequence of the higher temperature required to diffuse sufficient interstitial metallic atoms to transform the GeTe covalent bonding at the interface to metallic bonding.
Investigation of Gd and Tb plasmas for beyond extreme ultraviolet lithography based on multilayer mirror performance
Authors: Li Bowen , Otsuka Takamitsu , Higashiguchi Takeshi , Yugami Noboru , Jiang Weihua , Endo Akira , Dunne Padraig , O’Sullivan Gerry
Published: July 2012

Recent work on multilayer mirror development for beyond extreme ultraviolet lithography indicates that their optimum reflectivity occurs at either 6.63 nm or 6.66 nm which may be too short a wavelength for Gd-based plasma sources. Calculations performed for Tb12+ to Tb28+ ions show that if the mirror reflectivity is fixed at one of these values, Tb may be a better source, though Gd is capable of providing greater intensity if the full reflection curve of the mirrors is exploited. Theoretical simulation shows that the Tb emission peaks close to 6.51 nm at an optimum electron temperature close to 120 eV.
Intrinsic ultrathin topological insulators grown via molecular beam epitaxy characterized by in-situ angle resolved photoemission spectroscopy
Authors: Lee J. J. , Schmitt F. T. , Moore R. G. , Vishik I. M. , Ma Y. , Shen Z. X.
Published: July 2012

We demonstrate the capability of growing high quality ultrathin (10 or fewer quintuple layers) films of the topological insulators Bi2Se3 and Bi2Te3 using molecular beam epitaxy. Unlike previous growth techniques, which often pin the Fermi energy in the conduction band for ultrathin samples, our samples remain intrinsic bulk insulators. We characterize these films using in-situ angle resolved photoemission spectroscopy, which is a direct probe of bandstructure, and ex-situ atomic force microscopy. We find that the conduction band lies above the Fermi energy, indicating bulk insulating behavior with only the surface states crossing the Fermi energy. The use of a thermal cracker allows for more stoichiometric flux rates during growth, while still creating intrinsically doped films, paving the way for future improvements in growth of topological insulators.
Cascaded field enhancement in plasmon resonant dimer nanoantennas compatible with two-dimensional nanofabrication methods
Authors: Toroghi Seyfollah , Kik Pieter G.
Published: July 2012

Cascaded field enhancement is demonstrated in asymmetric plasmon resonant dimer nanoantennas consisting of shape-tuned ellipsoidal nanoparticles. The nanoparticles that make up the dimer have identical thickness, suggesting that the presented approach can be used to design cascaded dimer antennas compatible with standard two-dimensional top-down nanofabrication tools such as electron beam lithography and nano-imprint lithography. Cascaded excitation is achieved by modification of the in-plane particle aspect ratios in a way that keeps the resonance frequency of the individual particles fixed while significantly changing their polarizability. The achievable field enhancement is evaluated as a function of the particle volume ratio and spacing.
Comparison of Nb- and Ta-doping of anatase TiO2 for transparent conductor applications
Authors: Anh Huy Huynh , Aradi Bálint , Frauenheim Thomas , Deák Peter
Published: July 2012

Nb- or Ta-doped anatase TiO2 was shown to be a viable candidate for replacing indium-tin-oxide as a transparent conductive oxide. Calculating the electronic structures we find that Ta has the considerably higher solubility and lower optical effective mass of the two dopants. Our calculations also show that a reducing atmosphere is necessary for efficient dopant incorporation, and oxygen vacancies do not necessarily play a role in their activation.