bluuebunny/crossref_metadata_2025 huggingface dataset:
Light regulation of Ca2+in the cone photoreceptor synaptic terminal
Authors: CHOI SUE-YEON , JACKMAN SKYLER , THORESON WALLACE B. , KRAMER RICHARD H.
Published: November 2008

Retinal cones are depolarized in darkness, keeping voltage-gated Ca2+channels open and sustaining exocytosis of synaptic vesicles. Light hyperpolarizes the membrane potential, closing Ca2+channels and suppressing exocytosis. Here, we quantify the Ca2+concentration in cone terminals, with Ca2+indicator dyes. Two-photon ratiometric imaging of fura-2 shows that global Ca2+averages ~360 nM in darkness and falls to ~190 nM in bright light. Depolarizing cones from their light to their dark membrane potential reveals hot spots of Ca2+that co-label with a fluorescent probe for the synaptic ribbon protein ribeye, consistent with tight localization of Ca2+channels near ribbons. Measurements with a low-affinity Ca2+indicator show that the local Ca2+concentration near the ribbon exceeds 4μM in darkness. The high level of Ca2+near the ribbon combined with previous estimates of the Ca2+sensitivity of release leads to a predicted dark release rate that is much faster than observed, suggesting that the cone synapse operates in a maintained state of synaptic depression in darkness.
Who Is Afraid of Numbers?
Authors: LIAO S. MATTHEW
Published: November 2008

In recent years, many non-consequentialists such as Frances Kamm and Thomas Scanlon have been puzzling over what has come to be known as the Number Problem, which is how to show that the greater number in a rescue situation should be saved without aggregating the claims of the many, a typical kind of consequentialist move that seems to violate the separateness of persons. In this article, I argue that these non-consequentialists may be making the task more difficult than necessary, because allowing aggregation does not prevent one from being a non-consequentialist. I shall explain how a non-consequentialist can still respect the separateness of persons while allowing for aggregation.
ENSO and variability of the Antarctic Peninsula pelagic marine ecosystem
Authors: Loeb Valerie J. , Hofmann Eileen E. , Klinck John M. , Holm-Hansen Osmund , White Warren B.
Published: November 2008

The West Antarctic Peninsula region is an important source of Antarctic krill (Euphausia superba) in the Southern Ocean. From 1980–2004 abundance and concentration of phytoplankton and zooplankton, krill reproductive and recruitment success and seasonal sea ice extent here were significantly correlated with the atmospheric Southern Oscillation Index and exhibited three- to five-year frequencies characteristic of El Niño–Southern Oscillation (ENSO) variability. This linkage was associated with movements of the Southern Antarctic Circumpolar Current Front and Boundary, a changing influence of Antarctic Circumpolar Current and Weddell Sea waters, and eastward versus westward flow and mixing processes that are consistent with forcing by the Antarctic Dipole high-latitude climate mode. Identification of hydrographic processes underlying ecosystem variability presented here were derived primarily from multi-disciplinary data collected during 1990–2004, a period with relatively stable year-to-year sea ice conditions. These results differ from the overwhelming importance of seasonal sea ice development previously established using 1980–1996 data, a period marked by a major decrease in sea ice from the Antarctic Peninsula region in the late 1980s. These newer results reveal the more subtle consequences of ENSO variability on biological responses. They highlight the necessity of internally consistent long-term multidisciplinary datasets for understanding ecosystem variability and ultimately for establishing well-founded ecosystem management. Furthermore, natural environmental variability associated with interannual- and decadal-scale changes in ENSO forcing must be considered when assessing impacts of climate warming in the Antarctic Peninsula–Weddell Sea region.
Biofilm formation in the life cycle of the cellulolytic actinomycete Thermobifida fusca
Authors: Alonso A. N. , Pomposiello P. J. , Leschine S. B.
Published: November 2008

Actinomycetes have been used with enormous success in industrial processes; however, little is known about biofilm formation by these filamentous microbes, or community development on insoluble substrates such as cellulose. We hypothesized that biofilm formation is a general strategy used by actinomycetes in the degradation of cellulose, and that it may serve as a means for these microbes to secure nutrients and persist in their environments. The objective of this study was to examine biofilm production byThermobifida fusca, an actinomycete that rapidly degrades cellulose by means of a well-characterized extracellular cellulase system.Thermobifida fuscacells grew as biofilms attached to both nutritive (e.g. dialysis tubing membrane) and non-nutritive surfaces. Dialysis tubing was colonized byT. fuscaaleuriospores but not by mycelial pellets, except when mycelial pellets were disrupted by sonication. Microscopic examination of surface-attached growth revealed structures characteristic of biofilms, with cells embedded in fibrous material suggestive of an extracellular polymeric matrix. Concanavalin A bound to the extracellular polymeric substance of biofilms and mycelial pellets, indicating alpha-linkedd-mannosyl and/or alpha-linkedd-glucosyl residues. The carbohydrate content of both biofilms and mycelial pellets increased during growth. Also, DNase I inhibited biofilm production, suggesting a role for extracellular DNA inT. fuscabiofilm development. Cellulose degradation and expression ofcelE(encoding endoglucanase E5) was similar forT. fuscabiofilms and mycelial pellets. Results of this study indicate that, in the life cycle of this actinomycete, cellulose is specifically colonized by aleuriospores, which germinate, grow and degrade cellulose, ultimately developing into biofilms encased in a carbohydrate-containing exopolymeric matrix, a hallmark of biofilm production.
Therapiewünsche und Behandlungszufriedenheit bei ambulanten Krebspatienten und deren Ehepartnern
Authors: Lüddeckens Th. , Mörgeli H. , Zwahlen D. , Jenewein J. , Büchi St.
Published: November 2008

Zielsetzung: Ziel dieser Untersuchung war es bei ambulanten Krebspatienten und deren Ehepartnern die Zufriedenheit mit der medizinischen und psychosozialen Betreuung sowie das Ausmass von bisher nicht berücksichtigten Unterstützungsbedürfnissen im bestehenden Versorgungssystem zu erfassen. Methode: Ambulant behandelte Patienten im Kanton Zürich mit unterschiedlichen Krebsarten und in verschiedenen Stadien der Erkrankung sowie ihre Ehepartner wurden schriftlich befragt. Insgesamt konnten 224 Ehepaare in die Untersuchung einbezogen werden. Resultate: Die Bedürfnisse der Patienten wurden in allen untersuchten Bereichen signifikant besser abgedeckt als die der Ehepartner. Eine hohe Zufriedenheit gab es in den Bereichen Verständnis und Vertrauen durch Ärzte und Pflegende und Informationen über die Erkrankung. Eine tiefere Zufriedenheit zeigte sich in den Bereichen Informationen über Behandlungsangebote und über die Frage, was der Betroffene selbst für sein seelisches Wohl tun könnte. Ehepartner und Ärzte stellten für die Patienten die bei weitem wichtigsten Hilfspersonen dar, während dies bei den Ehepartnern Freunde und Familienangehörige waren. Andere Personen oder Hilfsangebote spielten eine nur untergeordnete Rolle. Eine erhebliche Anzahl von Patienten und Ehepartnern berichteten in wichtigen Bereichen über einen nicht gedeckten Bedarf an Unterstützung oder Beratung. Schlussfolgerung: Die Wünsche und Bedürfnisse der Ehepartner werden in den bestehenden ambulanten onkologischen Versorgungsstrukturen signifikant weniger abgedeckt als die der Patienten. Da Ehepartner eine sehr grosse psychosoziale Belastung infolge der Erkrankung des Partners und durch ihre neuen Aufgaben zu tragen haben, sollten die Bedürfnisse der Angehörigen in der klinischen Arbeit stärker berücksichtigt werden. Zudem sollten diejenigen Betroffenen mit dem höchsten Unterstützungsbedarf gezielt erfasst werden und die bestehenden Hilfsangebote besser kommuniziert werden.
Circumpolar thinning of Arctic sea ice following the 2007 record ice extent minimum
Authors: Giles Katharine A. , Laxon Seymour W. , Ridout Andy L.
Published: November 2008

September 2007 marked a record minimum in sea ice extent. While there have been many studies published recently describing the minimum and its causes, little is known about how the ice thickness has changed in the run up to, and following, the summer of 2007. Using satellite radar altimetry data, covering the Arctic Ocean up to 81.5° North, we show that the average winter sea ice thickness anomaly, after the melt season of 2007, was 0.26 m below the 2002/2003 to 2007/2008 average. More strikingly, the Western Arctic anomaly was 0.49 m below the six‐year mean in the winter of 2007/2008. These results show no evidence of short‐term preconditioning through ice thinning between 2002 and 2007 but show that, after the record minimum ice extent in 2007, the average ice thickness was reduced, particularly in the Western Arctic.
Multi‐satellite measurements of large diurnal warming events
Authors: Gentemann Chelle L. , Minnett Peter J. , Le Borgne Pierre , Merchant Christopher J.
Published: November 2008

Diurnal warming events between 5 and 7 K, spatially coherent over large areas (∼1000 km), are observed in independent satellite measurements of ocean surface temperature. The majority of the large events occurred in the extra‐tropics. Given sufficient heating (from solar radiation), the location and magnitude of these events appears to be primarily determined by large‐scale wind patterns. The amplitude of the measured diurnal heating scales inversely with the spatial resolution of the different sensors used in this study. These results indicate that predictions of peak diurnal warming using wind speeds with a 25 km spatial resolution available from satellite sensors and those with 50–100 km resolution from Numerical Weather Prediction models may have underestimated warming. Thus, the use of these winds in modeling diurnal effects will be limited in accuracy by both the temporal and spatial resolution of the wind fields.
Multidecadal and multicentennial variability of the meridional overturning circulation
Authors: Park W. , Latif M.
Published: November 2008

The variability of the meridional overturning circulation (MOC) simulated in a multimillenial control integration of the Kiel Climate Model (KCM) displays enhanced variability relative to the red background at decadal and centennial timescales. The multidecadal variability is the model's version of the Atlantic Multidecadal Variability (AMV), often referred to as Atlantic Multidecadal Oscillation (AMO). While multidecadal variability originates in the North Atlantic, multicentennial variability is driven in the Southern Ocean. Both multidecadal and multicentennial variability are associated with considerable changes in sea ice extent. This may be important to understand the different evolution of sea ice cover in the Northern and Southern Hemisphere during the most recent decades, with a strong decline observed in the North and almost no trend in the South.
Identifying global dust source areas using high‐resolution land surface form
Authors: Koven Charles D. , Fung Inez
Published: November 2008

Dust originates from specific, landscape‐scale (≈1–10 km) features; however, dust erodibility is commonly parameterized in global climate models using grid‐cell‐scale (≈1–5°) relationships. We examine surface characteristics from the high‐ resolution (90 m at equator) global Shuttle Radar Topography Mission digital elevation model and aerosol optical thickness (AOT) measurements from the Multiangle Imaging Spectroradiometer (MISR) instrument to find landscape‐scale characteristics common to dust producing regions. Regions with climatologically high aerosol optical thickness are associated with extremely low‐slope landscapes at ≈5 km scale that also have high‐elevation variance, likely due to aeolian features. We refer to these landscape characteristics as “levelness” and “residual landscape roughness,” and we extrapolate these relationships globally to identify geomorphologically based dust erodibility functions on the basis of levelness and residual landscape roughness criteria. We test these with the Dust Entrainment and Deposition model embedded in the Model for Atmospheric Transport and Chemistry global atmospheric tracer transport model, driven by reanalysis meteorology. The modeled global dust spatial distributions calculated with these erodibility parameters agree well with observations of MISR AOT and deposition and in the modeling framework used here represent an improvement over existing parameterizations in predicting the spatial patterns of dust sources in the Sahara and the relative amount of emission of sources in the Dust Belt to those in the Southern Hemisphere; however, agreement with observations is less good in high‐relief areas such as the Asian dust source regions, possibly because of the coarse resolution of the meteorological fields used to drive the model.
Polymorphic (NH): As Polyimidogen and Ammonium Azide Structure-types
Authors: Bucknum Michael
Published: November 2008

This paper reports a productive discussion of bonding principles in the non-metallic 2nd row hydrides. It suggests the inversion of a bonding character, potentially from hydrides of B & C, which may display unsaturation and electronic deficiency accompanied by electronic delocalization in 1D or 2D or 3D. Contrasted with the opposite possibility, within the finite number of hydrides of N, O and F, that display apparently extensive H-bonding and subsequently proton delocalization in 1D and 2D (in HF & ice polymorphs, respectively), and now potentially in 3D in a corresponding hydride of N called Rice's blue material, or perhaps polyimidogen. Where polyimidogen is a crystalline NH lattice that is a polymorph of the ammonium azide structure-type thus.
The CHMP4b- and Src-docking sites in the Bro1 domain are autoinhibited in the native state of Alix
Authors: Zhou Xi , Pan Shujuan , Sun Le , Corvera Joe , Lee Yu-Chen , Lin Sue-Hwa , Kuang Jian
Published: November 2008

The Bro1 domain of Alix [ALG-2 (apoptosis-linked gene 2)-interacting protein X], which plays important roles in endosomal sorting and multiple ESCRT (endosomal sorting complex required for transport)-linked processes, contains the docking sites for the ESCRT-III component CHMP4b (charged multivesicular body protein 4b) and the regulatory tyrosine kinase, Src. Although the structural bases for these docking sites have been defined by crystallography studies, it has not been determined whether these sites are available in the native state of Alix. In the present study, we demonstrate that these two docking sites are unavailable in recombinant Alix under native conditions and that their availabilities can be induced by detergents. In HEK (human embryonic kidney)-293 cell lysates, these two docking sites are not available in cytosolic Alix, but are available in membrane-bound Alix. These findings show that the native state of Alix does not have a functional Bro1 domain and predict that Alix's involvement in endosomal sorting and other ESCRT-linked processes requires an activation step that relieves the autoinhibition of the Bro1 domain.
Desferroxamine infusion increases cerebral blood flow: a potential association with hypoxia-inducible factor-1
Authors: Sorond Farzaneh A. , Shaffer Michele L. , Kung Andrew L. , Lipsitz Lewis A.
Published: November 2008

Finding an effective means to improve cerebral perfusion during hypoxic/ischaemic stress is essential for neuroprotection. Studies in animal models of stroke have shown that desferroxamine activates HIF-1 (hypoxia-inducible factor-1), reduces brain damage and promotes functional recovery. The present study was designed to investigate the effects of desferroxamine infusion on the cerebral circulation in humans. Fifteen volunteers were enrolled in a randomized double-blind placebo-controlled crossover study. We measured cerebral blood flow velocity by transcranial Doppler ultrasonography in the middle cerebral artery, arterial blood pressure, end-tidal CO2, as well as HIF-1 protein and serum lactate dehydrogenase concentrations in response to 8 h of desferroxamine compared with placebo infusion. Cerebrovascular resistance was calculated from the ratio of steady-state beat-to-beat values for blood pressure to blood flow velocity. We found that desferroxamine infusion was associated with a significant cerebral vasodilation. Moreover, decreased cerebrovascular resistance was temporally correlated with an increased HIF-1 protein concentration as well as HIF-1 transcriptional activation, as measured by serum lactate dehydrogenase concentration. The findings of the present study provide preliminary data suggesting that activators of HIF-1, such as desferroxamine, may protect neurons against ischaemic injury by dilating cerebral vessels and enhancing cerebral perfusion.
Herzerkrankungen und Zahnstörfelder
Authors: Lechner Johann
Published: November 2008

Die klassische „Chronische Kieferostitis” oder NICO
(Neuralgia Inducing Cavitational Osteonecrosis) ist ein Phänomen, das in
der Medizin bis heute kaum wahrgenommen wird. NICO ist eine Mangelversorgung in
Form einer chronisch-trophischen Störung im Kieferknochen. Sie zeichnet
sich histologisch aus durch Vermehrung der Fettzellen und mukoide Degeneration
der Spongiosa. Damit ist die NICO eine „Silent inflammation”. Die
Diagnostik dieser Erkrankung ist schwierig. Mit computergestützter
Ultraschalltechnik kann eine wissenschaftlich abgesicherte Diagnose eines
ostitischen/osteolytischen Kieferareals gestellt werden. Aus der Vielfalt der
systemischen Wirkungen eines NICO-Zahnstörfeldes werden Herzbeschwerden
speziell beleuchtet, die mit einer Kasuistik aus der Praxis des Autors belegt
wird.
Sonar mapping suggests that the English Channel was created by two megafloods
Authors: Schwarzschild Bertram
Published: November 2008

Until about 450 thousand years ago, Britain and France were connected by a land bridge, even at times of high sea level.
A physicist proselytizes about countering global warming
Authors: Feder Toni
Published: November 2008

Moving to Mars is not the solution to global warming, says John Houghton. Rather, through lectures on such impacts as sea-level rise, droughts, and floods, he hopes to mobilize Christians to reduce human-induced climate change on Earth.
Echolocation in dolphins and bats
Authors: Au Whitlow W. L. , Simmons James A.
Published: November 2008

Stately dolphins and flittering bats both use biosonar for navigating and for catching prey. The details of their echolocation systems, though, have evolved to reflect their different physiologies and environments.
Eyes on the LHC
Authors: Gianotti Fabiola , Quigg Chris
Published: November 2008

Particle physicists don’t know for sure what explorations at the Large Hadron Collider will bring. But they do know that many mysteries in their field point toward solutions at the LHC’s impressive TeV energy scale.
Quantum-state resolved reactive scattering at the gas-liquid interface: F+squalane (C30H62) dynamics via high-resolution infrared absorption of nascent HF(v,J)
Authors: Zolot Alexander M. , Dagdigian Paul J. , Nesbitt David J.
Published: November 2008

Exothermic chemical reaction dynamics at the gas-liquid interface have been investigated by colliding a supersonic beam of F atoms [Ecom=0.7(3)kcal∕mol] with a continuously refreshed liquid hydrocarbon (squalane) surface under high vacuum conditions. Absolute HF(v,J) product densities are determined by infrared laser absorption spectroscopy, with velocity distributions along the probe axis derived from high resolution Dopplerimetry. Nascent HF(v⩽3) products are formed in a highly nonequilibrium (inverted) vibrational distribution [⟨Evib⟩=13.2(2)kcal∕mol], reflecting insufficient time for complete thermal accommodation with the surface prior to desorption. Colder, but still non-Boltzmann, rotational state populations [⟨Erot⟩=1.0(1)kcal∕mol] indicate that some fraction of molecules directly scatter into the gas phase without rotationally equilibrating with the surface. Nascent HF also recoils from the liquid surface with excess translational energy, resulting in Doppler broadened linewidths that increase systematically with internal HF excitation. The data are consistent with microscopic branching in HF-surface dynamics following the reactive event, with (i) a direct reactive scattering fraction of newly formed product molecules leaving the surface promptly and (ii) a trapping desorption fraction that accommodates rotationally (though still not vibrationally) with the bulk liquid. Comparison with analogous gas phase F+hydrocarbon processes reveals that the liquid acts as a partial “heat sink” for vibrational energy flow on the time scale of the chemical reaction event.
Korea superconducting tokamak advanced research vacuum and gas puffing system
Authors: Seo Seong-Heon , Kim H. T. , Kim K. P. , Kim Y. O. , Kim W. C. , Yang H. L. , Oh Y. K. , Jeong Seung Ho
Published: November 2008

A piezoelectric valve, which has a flow rate of about 463 mbarl/s, has been installed to fuel the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. The valve flow rate is in situ calibrated by analyzing the pressure rise curve while fueling the vessel at a constant rate. The calibration method and results are presented. In addition to the flow rate, other vacuum system parameters, such as the pumping speed and the vessel volume, were experimentally obtained. Based on these measurements, a KSTAR vacuum system simulator was developed to calculate the valve drive signal to obtain a programmed pressure trace. An arbitrarily shaped pressure trace was successfully controlled in KSTAR with this hardware and software system.
Kinetic and theoretical study of the reaction of Cl atoms with a series of linear thiols
Authors: Garzón Andrés , Albaladejo José , Notario Alberto , Peña-Ruiz Tomás , Fernández-Gómez Manuel
Published: November 2008

The reactions of Cl with a series of linear thiols: 1-propanethiol (k1), 1-butanethiol (k2), and 1-pentanethiol (k3) were investigated as a function of temperature (in the range of 268–379K) and pressure (in the range of 50–200Torr) by laser photolysis-resonance fluorescence. Only 1-propanethiol has previously been studied, but at 1Torr of total pressure. The derived Arrhenius expressions obtained using our kinetic data were as follows: k1=(3.97±0.44)×10−11exp[(410±36)∕T], k2=(1.01±0.16)×10−10exp[(146±23)∕T], and k3=(1.28±0.10)×10−10exp[(129±25)∕T] (in units of cm3molecule−1s−1). Moreover, a theoretical insight into mechanisms of these reactions has also been pursued through ab initio Möller–Plesset second-order perturbation treatment calculations with 6-311G** basis set. Optimized geometries have been obtained for transition states and molecular complexes appearing along the different reaction pathways. Furthermore, molecular energies have been calculated at QCISD(T) level in order to get an estimation of the activation energies. Finally, the nature of the molecular complexes and transitions states is analyzed by using kinetic-potential and natural bond orbital total energy decomposition schemes.
Magnetic exchange couplings from noncollinear spin density functional perturbation theory
Authors: Peralta Juan E. , Barone Veronica
Published: November 2008

We propose a method for the evaluation of magnetic exchange couplings based on noncollinear spin density functional calculations. The method employs the second derivative of the total Kohn–Sham energy of a single reference state, in contrast to approximations based on Kohn–Sham total energy differences. The advantage of our approach is twofold: It provides a physically motivated picture of the transition from a low-spin to a high-spin state, and it utilizes a perturbation scheme for the evaluation of magnetic exchange couplings. The latter simplifies the way these parameters are predicted using first principles: It avoids the nontrivial search for different spin states that needs to be carried out in energy difference methods, and it opens the possibility of “black-boxifying” the extraction of exchange couplings from density functional theory calculations. We present proof of concept calculations of magnetic exchange couplings in the H–He–H model system and in an oxovanadium bimetallic complex where the results can be intuitively rationalized.
Flow-structure interaction effects on a jet emanating from a flexible nozzle
Authors: Murugappan S. , Gutmark E. J. , Lakhamraju R. R. , Khosla S.
Published: November 2008

In recent years, a wide variety of applications have been found for the use of pulsed jets in the area of flow control. The goal of the current study was to identify the flow field and mixing characteristics associated with an incompressible elongated jet emitted from a flexible nozzle. The shape of the nozzle was that of a high aspect ratio jet deforming from a fully opened to a completely closed configuration. The jet was characterized by a pulsatile flow that was self-excited by the motion of the flexible tube. The frequency of excitation was found to be between 150 and 175 Hz and the Strouhal number (nondimensional frequency) varied from 0.17 to 0.45. The jet flow was dominated by vortices that were shed from the nozzle with an axis parallel to the major axis. The vortices in the near field were quasi-two-dimensional so that measurements performed at the center plane represented the dynamics of the entire vortex. The nozzle excited two different modes depending on the tension applied to the flexible nozzle and the volumetric flow through it. The first was a flapping mode, which was associated with alternate shedding of vortices. This caused strong steering of the jet to one side or the other. The second mode was a symmetric mode that was associated with the formation of counter-rotating vortex pairs. Turbulence and jet spread in the measured planes were much larger in the first mode than the second one.
High-pressure melting curve of hydrogen
Authors: Davis Sergio M. , Belonoshko Anatoly B. , Johansson Börje , Skorodumova Natalia V. , van Duin Adri C. T.
Published: November 2008

The melting curve of hydrogen was computed for pressures up to 200GPa, using molecular dynamics. The inter- and intramolecular interactions were described by the reactive force field (ReaxFF) model. The model describes the pressure-volume equation of state solid hydrogen in good agreement with experiment up to pressures over 150GPa, however the corresponding equation of state for liquid deviates considerably from density functional theory calculations. Due to this, the computed melting curve, although shares most of the known features, yields considerably lower melting temperatures compared to extrapolations of the available diamond anvil cell data. This failure of the ReaxFF model, which can reproduce many physical and chemical properties (including chemical reactions in hydrocarbons) of solid hydrogen, hints at an important change in the mechanism of interaction of hydrogen molecules in the liquid state.
Noise-induced effective oscillation in oil-water membrane oscillator
Authors: Li Yaping , Xing Yi , Cao Weiliang , Li Qianshu
Published: November 2008

Noise-induced oscillation (NIO) was investigated in a model of an oil-water membrane oscillator. First, we analyzed an unexcitable region and an excitable region of the system by proposing a critical threshold of NIO appearance and found a linearlike relation between the critical threshold and noise intensity. Then the phenomenon of noise-induced coherence resonance was investigated by calculating the signal-to-noise ratio. Furthermore, it was found that an optimal noise intensity range could most improve the appearance of effective oscillation (EO). The presence of EO regions made the stochastic model show EO at a more extended region than the deterministic description.
Direct evidence of detwinning in polycrystalline Ni–Mn–Ga ferromagnetic shape memory alloys during deformation
Authors: Nie Z. H. , Peng R. Lin , Johansson S. , Oliver E. C. , Ren Y. , Wang Y. D. , Liu Y. D. , Deng J. N. , Zuo L. , Brown D. E.
Published: November 2008

In situ time-of-flight neutron diffraction and high-energy x-ray diffraction techniques were used to reveal the preferred reselection of martensite variants through a detwinning process in polycrystalline Ni–Mn–Ga ferromagnetic shape memory alloys under uniaxial compressive stress. The variant reorientation via detwinning during loading can be explained by considering the influence of external stress on the grain/variant orientation-dependent distortion energy. These direct observations of detwinning provide a good understanding of the deformation mechanisms in shape memory alloys.
Similarity reduction, generalized symmetries, recursion operator, and integrability of coupled Volterra system
Authors: Sahadevan R. , Balakrishnan S.
Published: November 2008

It is shown that the coupled Volterra system governed by two-coupled nonlinear partial differential–difference equations (PDΔEs) has many integrability properties such as Lax representation, infinitely many generalized (nonpoint) symmetries and polynomial conserved densities, and a recursion operator. A systematic investigation on the continuous point symmetries of the coupled Volterra system shows that it admits a three dimensional nilpotent Lie algebra. By exploiting the obtained continuous point symmetries a similarity reduction is obtained.
Subwavelength imaging based on frequency scanning
Authors: Maslovski Stanislav , Alitalo Pekka , Tretyakov Sergei
Published: November 2008

A new principle of subwavelength imaging based on frequency scanning is considered. It is shown that it is possible to reconstruct the spatial profile of an external field exciting an array (or coupled arrays) of subwavelength-sized resonant particles with a frequency scan over the whole band of resonating array modes. During the scan it is enough to measure and store the values of the near field at one or at most two points. After the scan the distribution of the near field can be reconstructed with simple postprocessing. The proposed near-field microscope has no moving parts.
An atomistic-based correction of the effective-mass approach for investigating quantum dots
Authors: Rodríguez-Bolívar S. , Gómez-Campos F. M. , Carceller J. E.
Published: November 2008

In this work, we propose a correction to the effective mass approach (EMA) to be used in Si quantum dot simulations. This correction tries to connect the different ways of modeling quantum dots within tight binding (considering the actual positions of the atoms and using additional atoms to passivate the surfaces) with those within the EMA, adapting the size of the simulated quantum dots to take the difference into account. With this aim, we implemented a 6×6 k⋅p calculation for the valence band and used a nonparabolic and anisotropic model for the conduction band to study hole and electron confinement, respectively. We then tested and used a very fast computational algorithm to obtain the electron and hole spectra in both cubic- and spherical-shaped quantum dots.
Multiple pulse thermal damage thresholds of materials for x-ray free electron laser optics investigated with an ultraviolet laser
Authors: Hau-Riege Stefan P. , London Richard A. , Bionta Richard M. , Soufli Regina , Ryutov Dmitri , Shirk Michael , Baker Sherry L. , Smith Patrick M. , Nataraj Pradeep
Published: November 2008

Optical elements to be used for x-ray free electron lasers (XFELs) must withstand multiple high-fluence pulses. We have used an ultraviolet laser to study the damage of two candidate materials, crystalline Si and B4C-coated Si, emulating the temperature profile expected to occur in optics exposed to XFEL pulses. We found that the damage threshold for 105 pulses is ∼20% to 70% lower than the melting threshold.
Thermal noise of microcantilevers in viscous fluids
Authors: Bellon L.
Published: November 2008

We present a simple theoretical framework to describe the thermal noise of a microscopic mechanical beam in a viscous fluid: we use the Sader approach to describe the effect of the surrounding fluid (added mass and viscous drag) and the fluctuation dissipation theorem for each flexural modes of the system to derive a general expression for the power spectrum density of fluctuations. This prediction is compared with an experimental measurement on a commercial atomic force microscopy cantilever in a frequency range covering the two first resonances. A very good agreement is found on the whole spectrum, with no adjustable parameters but the thickness of the cantilever.
Fourier transform infrared spectroscopy of annealed silicon-rich silicon nitride thin films
Authors: Scardera G. , Puzzer T. , Conibeer G. , Green M. A.
Published: November 2008

A correlation between bonding changes in silicon-rich silicon nitride films, subjected to high temperature annealing under N2 ambient, and the formation of silicon nanocrystals is presented. The postannealing appearance of a shoulder between 1000 and 1100 cm−1 in the Fourier transform infrared (FTIR) spectra of silicon-rich silicon nitride films is attributed to a reordering in the films toward an increased SiN4 bonding configuration resulting from the precipitation of silicon nanocrystals. The FTIR monitoring of bonding changes in these films allows for the indirect verification of silicon nanocrystal formation.
Multiferroic properties of Ni0.5Zn0.5Fe2O4–Pb(Zr0.53Ti0.47)O3 ceramic composites
Authors: Zhang Hongfang , Or Siu Wing , Chan Helen Lai Wa
Published: November 2008

We present a powder-in-sol precursor hybrid processing route to synthesize dense, homogenous, and fine-grained Ni0.5Zn0.5Fe2O4–Pb(Zr0.53Ti0.47)O3 (NZFO–PZT) multiferroic ceramic composites and report their ferromagnetic-ferroelectric characteristics. Nanosized NZFO ferromagnetic powders are dispersed into PZT ferroelectric sol-gel precursor and uniformly distributed slurry is prepared by ball-milling mixing of the powder-precursor suspension prior to be sintered at low temperatures to form the composites. The composites show simultaneous effects of ferromagnetism and ferroelectricity at room temperature with excellent magnetic and dielectric properties for frequencies over 10 MHz. The coexistence of inductive and capacitive natures in the composites favors size reduction and design simplification in many passive electronic devices such as integrated filters and microwave absorbers.
Influence of annealing on the Er luminescence in Si-rich SiO2 layers coimplanted with Er ions
Authors: Kanjilal A. , Rebohle L. , Voelskow M. , Skorupa W. , Helm M.
Published: November 2008

The impact of rapid thermal annealing (RTA) in producing samples by sequential implantation of Si and Er ions into a 200 nm SiO2 layer combined with different annealing cycles as well as the corresponding room-temperature visible and infrared photoluminescence (PL) have been studied. The Er-related PL intensity at 1533 nm for the samples prepared by implanting Si with subsequent annealing, followed by Er implantation, and final annealing (type I) was found to be stronger than the one produced similarly but without the first annealing step (type II). In fact, the 1533 nm peak intensity in the optimized RTA processed sample is comparable to the PL yield of the furnace-annealed sample. Moreover, the excitation wavelength (405 nm) was found to be suitable for exciting the Si=O related point defects in the SiO2 layer and can provide a PL band with a maximum at ∼580 nm. While this band was further intensified in the presence of Si nanocrystals (Si NCs), it became weaker by introducing additional Er3+ ions with a concomitant rise of the 1533 nm Er PL, confirming the visible range pumping of Er3+. The detailed spectral analyses suggest that the 580 nm band is the result of the excitation/deexcitation mechanism in molecule such as states in the Si=O or the Si=O state mediated recombination of carriers in Si NCs according to the model proposed by [Wolkin et al., Phys. Rev. Lett. 82, 197 (1999)]. The samples were further characterized by transmission electron microscopy and Fourier-transform infrared spectroscopy. The time-resolved PL measurements and a modeling by rate equations were also performed to determine and justify the energy migration mechanism from Si NC to the neighboring Er3+.
Detailed analysis of the microwave-detected photoconductance decay in crystalline silicon
Authors: Lauer K. , Laades A. , Übensee H. , Metzner H. , Lawerenz A.
Published: November 2008

An approach to evaluate the microwave-detected photoconductance decay (MWPCD) is developed, which allows to extract the minority carrier lifetime as a function of the excess carrier density from a single MWPCD measurement. The method is shown to be applicable to thin (w≲200 μm) silicon wafers with low minority carrier recombination at the surfaces and bulk lifetimes in the range of about 1–100 μs. Comparison of the MWPCD results with minority carrier lifetime measurements using the quasi-steady-state photoconductance method reveals very good agreement between both types of measurement. Only when the photoconductance exceeds 30% of the dark conductivity, is a deviation observed, because then the MWPCD signal is no longer directly proportional to the excess carrier density. Minority carrier trapping is found to affect the MWPCD signal only in the tail of the measured photoconductance decay. The evaluation method is used to map the interstitial iron content with high spatial resolution, as well as to determine the minority carrier trap density. An excellent agreement between numerical simulation and measured MWPCD signal is found revealing the assumptions made for the evaluation approach to be valid. This evaluation of the MWPCD measurement is well suited to characterize silicon of low purity and low crystalline quality, which is often employed to solar cells with high spatial resolution.
Observation of band bending of metal/high-k Si capacitor with high energy x-ray photoemission spectroscopy and its application to interface dipole measurement
Authors: Kakushima K. , Okamoto K. , Tachi K. , Song J. , Sato S. , Kawanago T. , Tsutsui K. , Sugii N. , Ahmet P. , Hattori T. , Iwai H.
Published: November 2008

Band bendings of Si substrates have been observed using hard x-ray photoemission spectroscopy. With a capability of collecting photoelectrons generated as deep as 40 nm, the binding energy shift in a core level caused by the potential profile at the surface of the substrate results in a spectrum broadening. The broadening is found to be significant when heavily doped substrates are used owing to its steep potential profile. The surface potential of the substrate can be obtained by deconvolution of the spectrum. This method has been applied to observe the band bending profile of metal-oxide-semiconductor capacitors with high-k gate dielectrics. By comparing the band bending profiles of heavily-doped n+- and p+-Si substrates, the interface dipoles presented at interfaces can be estimated. In the case of W gated La2O3/La-silicate capacitor, an interface dipole to shift the potential of −0.45 V has been estimated at La-silicate/Si interface, which effectively reduces the apparent work function of W. On the other hand, an interface dipole of 0.03–0.07 V has been found to exist at Hf-silicate/SiO2 interface for W gated HfO2/Hf-silicate/SiO2 capacitor.
An equivalent condition for a sequence to be the sequence of partial entropies
Authors: Falniowski Fryderyk
Published: November 2008

We show that a sequence is the sequence of partial entropies of some dynamical system with respect to a partition of the phase space if and only if it is non-negative, increasing, and has decreasing increments.
Analytical modeling of magnetic Rayleigh–Taylor instabilities in compressible fluids
Authors: Liberatore Stéphane , Bouquet Serge
Published: November 2008

The magnetic Rayleigh–Taylor instability (MRTI) is investigated in the case of compressible plasmas. The goal of this work is highlighting the influence of both the magnetic field and the compressibility of the material on the growth rate of the Rayleigh–Taylor instability, compared to the classical growth rate derived for incompressible fluids. Our analytical linear models are derived in the framework of the ideal magnetohydrodynamics theory. Three general dispersion relations are obtained: (1) Two for stratified fluids, including compressible (denoted CS∥ when the wave vector k is parallel to the equilibrium magnetic field B0 and CS⊥ when k⊥B0) and incompressible (denoted IS∥ and IS⊥) and (2) one for incompressible uniform density fluids, including finite mass (denoted Ifm) and infinite (denoted IU). For k⊥B0, Ifm, IU, and IS⊥ are unmagnetized cases. Comparisons of those various configurations are performed and several differences are pointed out. The main results are as follows: Stratification weakens the MRTI while compressibility has a destabilizing effect. The magnetic field enhances these phenomena. The CS∥ and IU configurations have an identical cutoff wave number. The upper fluid (also called heavy fluid) is more sensitive to compressibility than the light one when k∥B0. Finally, the CS∥ case is more sensitive than the CS⊥ one to physical variations.
Ferroelectric properties of chemically synthesized perovskite BiFeO3–PbTiO3 thin films
Authors: Sakamoto Wataru , Iwata Asaki , Yogo Toshinobu
Published: November 2008

Ferroelectric BiFeO3–PbTiO3 thin films with near morphotropic phase boundary composition were synthesized on Pt/TiOx/SiO2/Si substrates by chemical solution deposition. Perovskite BiFeO3–PbTiO3 single-phase thin films were successfully fabricated at 600 °C by optimizing several processing conditions, such as the PbTiO3 content. Typical ferroelectric polarization-electric field (P-E) hysteresis loops were observed for (1−x)BiFeO3–xPbTiO3 (x=0.2, 0.3, 0.4, 0.5) thin films, which contained some leakage current components at room temperature. In the low temperature region, the BiFeO3–PbTiO3 thin films demonstrated improved insulating resistance and exhibited relatively saturated P-E hysteresis loops. Among these films, 0.7BiFeO3-0.3PbTiO3 thin films exhibited the largest remanent polarization, and the remanent polarization (Pr) and coercive field (Ec) at −190 °C were approximately 60 μC/cm2 and 230 kV/cm, respectively. Furthermore, Mn doping of the BiFeO3–PbTiO3 thin films was effective in changing the dominant leakage current factors and improving the ferroelectric properties of the resultant thin films at room temperature. The Pr and Ec values of 5 mol % Mn-doped 0.7BiFeO3-0.3PbTiO3 films at room temperature were approximately 40 μC/cm2 and 100 kV/cm, respectively. Potentially large remanent polarization (∼90 μC/cm2) was also demonstrated by the BF-PT thin films.
Influence of a preplasma on electron heating and proton acceleration in ultraintense laser-foil interaction
Authors: Nuter R. , Gremillet L. , Combis P. , Drouin M. , Lefebvre E. , Flacco A. , Malka V.
Published: November 2008

Two-dimensional particle-in-cell simulations are performed to study laser-induced proton acceleration from solid-density targets in the presence of laser-generated preformed plasma. The preplasma generation and hydrodynamics are described using a one-dimensional Lagrangian code. The electron acceleration mechanism is shown to depend on the plasma scale length, exhibiting a transition from j⃗×B⃗ heating to standing wave heating as smoother and smoother profiles are considered. Accordingly, the relativistic electron temperature and the cutoff proton energy are found to increase with the preplasma characteristic length.
Tuning of magnetism in SrRuO3 thin films on SrTiO3 (001) substrate by control of the twin and strain amount in the buffer layer
Authors: Lee B. W. , Jung C. U. , Kawasaki M. , Tokura Y.
Published: November 2008

Control of the magnetic easy axis in SrRuO3 thin films is important for tunnel junction studies incorporating this layer and for wider device applications. Previously, we demonstrated control of the magnetic easy axis in SrRuO3 thin films on SrTiO3 (110) substrates by introducing tunable anisotropic strain through a CaHfO3 buffer layer. However, our method was not directly applicable due to the existence of twins in the CaHfO3 layer that grew on the SrTiO3 (001) substrate. Twins appeared partly because of the crystal structure of CaHfO3, which has large orthorhombic distortion (a−b)/a=2.5%. Here, we used a miscut SrTiO3 (001) substrate to create a twin-free CaHfO3 layer on the substrate, even though the large mismatch between the CaHfO3 and SrTiO3 (001) substrates led to relaxed growth behavior. The crystal quality of the CaHfO3 layer, as determined by the shape of the rocking curve and existence of twins, was markedly improved by use of the miscut substrate. In addition, the SrRuO3 film grown on top of this buffer layer was of high quality and tensile strain and had an in-plane magnetic easy axis.
Green light emission from InGaN multiple quantum wells grown on GaN pyramidal stripes using selective area epitaxy
Authors: Feng W. , Kuryatkov V. V. , Chandolu A. , Song D. Y. , Pandikunta M. , Nikishin S. A. , Holtz M.
Published: November 2008

Selective area epitaxy has been used to grow pyramidal GaN stripes, followed by InGaN multiple quantum well (MQW) structures, in order to produce long-wavelength green light emission. Stripes oriented along ⟨112¯0⟩ produce smooth {11¯01} sidewall facets. The room-temperature optical properties are investigated by cathodoluminescence spectroscopy using a scanning electron microscope. MQWs grown in unmasked reference regions exhibit emission at 450 nm. The stripe sidewalls emit light with peak wavelength of 500 nm with consistent linewidth and intensity. The stripe ridge emits light with peak intensity at wavelength of ∼550 nm. Based on the spatial extent of the 550 nm emission, the ridge is estimated to be ∼250 nm wide. The large redshift is produced by the enhanced presence of indium species due to lateral vapor diffusion and surface migration in selective area epitaxy.
Magnetic steering of a helicon double layer thruster
Authors: Charles C. , Boswell R. W. , Cox W. , Laine R. , MacLellan P.
Published: November 2008

The ion beam generated by a helicon double layer has been electrically steered up to 20° off axis by using a solenoid placed normal to the two axial solenoids of the helicon plasma source without significantly changing the beam exhaust velocity.
Codoping of boron and phosphorus in silicon nanowires synthesized by laser ablation
Authors: Fukata N. , Mitome M. , Bando Y. , Seoka M. , Matsushita S. , Murakami K. , Chen J. , Sekiguchi T.
Published: November 2008

Codoping of boron (B) and phosphorus (P) atoms was performed during the synthesis of silicon nanowires (SiNWs) by laser ablation. The observation of a local vibrational mode of B clearly showed B doping in codoped SiNWs, while Fano broadening due to heavy B doping disappeared, indicating compensation by P donors. The electrospin resonance signal of conduction electrons also disappeared due to compensation by B acceptors. These results indicate that codoping of B and P atoms was achieved in SiNWs during laser ablation.
Ab initio investigation on oxygen defect clusters in UO2+x
Authors: Geng Hua Y. , Chen Ying , Kaneta Yasunori , Kinoshita Motoyasu
Published: November 2008

Oxygen defect clustering in uranium dioxide had been indicated in powder neutron diffraction measurements, and an empirical clustering mechanism had been proposed to explain the data. However, using first-principles LSDA+U calculations, we find that this empirical model, in fact, cannot work. A more physically reasonable model is proposed based on a thermodynamical competition between point defects and cuboctahedral clusters. This mechanism interprets the puzzled origin of the observed asymmetric interstitial O′ and O″ naturally. It also gives a good and consistent agreement with all available experimental data, except the high occupation of the O″ site.