bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution, pattern, and partitioning of deformation during oblique continental rifting: Inferences from lithospheric‐scale centrifuge models
Authors: Agostini Andrea , Corti Giacomo , Zeoli Antonio , Mulugeta Genene
Published: November 2009

Oblique rifting is investigated through centrifuge experiments that reproduce extension of a continental lithosphere containing a preexisting weakness zone. During extension, this weakness localizes deformation, and different rift obliquity is obtained by varying its trend with respect to the stretching direction. Model results show that deformation is mostly controlled by the obliquity angle α (defined as the angle between the orthogonal to the rift trend and the extension direction). For low obliquity (α < 45°), rifting is initially characterized by activation of large, en echelon boundary faults bordering a subsiding rift depression, with no deformation affecting the rift floor. Increasing extension results in the abandonment of the boundary faults and the development of new faults within the rift depression. These faults are orthogonal to the direction of extension and arranged in two en echelon segments linked by a complex transfer zones, characterized by strike‐slip component of motion. In these models, a strong strain partitioning is observed between the rift margins, where the boundary fault systems have an oblique‐slip motion, and the valley floor that away from the transfer zones is affected by a pure extension. Moderate obliquity (α = 45°) still results in a two‐phase rift evolution, although boundary fault activity is strongly reduced, and deformation is soon transferred to the rift depression. The fault pattern is similar to that of low‐obliquity models, although internal faults become slightly oblique to the orthogonal to the direction of extension. Deformation partitioning between the rift margins and the valley floor is still observed but is less developed than for low‐obliquity rifting. For high obliquity (α > 45°), no boundary faults form, and the extensional deformation affects the rift depression since early stages of extension. Dominance of the strike‐slip motion over extension leads to the development of oblique‐slip and nearly pure strike‐slip faults, oblique to both the rift trend and the orthogonal to the extension direction, with no strain partitioning between the margins and the rift floor. These results suggest that oblique reactivation of preexisting weaknesses plays a major role in controlling rift evolution, architecture, and strain partitioning, findings that have a significant relevance for natural oblique rifts.
Modeling the physical and biogeochemical response of a marine shelf system to a tropical cyclone
Authors: Condie S. A. , Herzfeld M. , Margvelashvili N. , Andrewartha J. R.
Published: November 2009

We describe the first use of a fully integrated biogeochemical model to explore the response of a marine shelf system to a tropical cyclone. Ocean currents, nutrients, sediments and plankton dynamics were simulated under conditions representative of Tropical Cyclone Bobby, which traversed the Australian North West Shelf in February 1995. Results show strong upwelling of nutrients and a phytoplankton bloom. While chlorophyll changes were similar to those estimated from satellite data in other coastal systems exposed to cyclonic conditions, the overall phytoplankton response was limited by cyclone induced sediment resuspension and the net contribution to annual primary production on the shelf was relatively small. In contrast, sediment loads exported off the shelf during Bobby were found to be more than 50 times modeled annual loads in years with little cyclone exposure and equivalent to at least 20 years of annual river‐loads to the North West Shelf.
Does the North Atlantic Oscillation show unusual persistence on intraseasonal timescales?
Authors: Keeley S. P. E. , Sutton R. T. , Shaffrey L. C.
Published: November 2009

Previous studies have argued that the autocorrelation of the winter North Atlantic Oscillation (NAO) index provides evidence of unusually persistent intraseasonal dynamics. We demonstrate that the autocorrelation on intraseasonal time‐scales of 10–30 days is sensitive to the presence of interannual variability, part of which arises from the sampling of intraseasonal variability and the remainder of which we consider to be “externally forced”. Modelling the intraseasonal variability of the NAO as a red noise process we estimate, for winter, ∼70% of the interannual variability is externally forced, whereas for summer sampling accounts for almost all of the interannual variability. Correcting for the externally forced interannual variability has a major impact on the autocorrelation function for winter. When externally forced interannual variability is taken into account the intrinsic persistence of the NAO is very similar in summer and winter (∼5 days). This finding has implications for understanding the dynamics of the NAO.
Ion velocity filter effect observed in dayside hydrogen aurora
Authors: Holmes J. M. , Kozelov B. V. , Peters N. J. , Deehr C. S. , Lorentzen D. A. , Sigernes F.
Published: November 2009

Observations of dayside auroral hydrogen emissions of Hα (λ656.3 nm) were carried out using spectrometers on Svalbard at Ny‐Ålesund (NYA: 76.3°N, 111.0°E CGM) and Longyearbyen (LYR: 75.3°N, 111.9°E CGM). Using a Monte Carlo model, simulated Doppler profiles were fitted to the spectra to estimate precipitating proton energy. A difference in energy was found between the sites for approximately 45 minutes. When combined with measurements of antisunward convection, the energies are consistent with the inverse variation of ion energy with latitude observed by satellites in the cusp region, known as the ion velocity filter. This is the first measurement of the ion velocity filter effect in the dayside aurora using ground‐based optical instrumentation. The increasing difference in energy observed is interpreted as a measure of the decreasing merging rate at the magnetopause.
Nature and causes of protracted droughts in southeast Australia: Comparison between the Federation, WWII, and Big Dry droughts
Authors: Verdon‐Kidd Danielle C. , Kiem Anthony S.
Published: November 2009

Three protracted droughts have occurred during the instrumental history of Southeast Australia (SEA) – the “Federation” (∼1895–1902), “World War II” (∼1937–1945) and the “Big Dry” (∼1997–present). This paper compares the nature and causes of these droughts in order to better inform drought management strategies in SEA. It is shown that the three droughts differ in terms of severity, spatial footprint, seasonality and seasonal rainfall make‐up. This diversity arises due to the fact that the droughts are driven by different climatic teleconnections with the Pacific, Indian and Southern Oceans. Importantly, this study highlights potential flaws with drought forecasting and management in SEA and emphasises the need for further research into understanding and representing hydroclimatic drivers of drought.
Modulation of NTC frequencies by Pc5 ULF pulsations: Experimental test of the generation mechanism and magnetoseismology of the emitting surface
Authors: Grimald S. , Foullon C. , Décréau P. M. E. , Le Rouzic G. , Suraud X. , Vallières X.
Published: November 2009

Nonthermal continuum (NTC) radiation is believed to be emitted by the conversion of an electrostatic wave into an electromagnetic one, which takes place at the Earth's magnetic equator. It is generally accepted that the frequency of the electrostatic wave at the source meets a local characteristic frequency placed in between two multiples of the electron cyclotron frequency, fce, which results in emission of a narrow band frequency element. In an event on 14 August 2003, we compare oscillations of the central frequency of distinct NTC frequency elements observed from Cluster orbiting near perigee, with simultaneous Pc5 Ultra Low Frequency (ULF) pulsations in the magnetic field observed from the same platform. The latter magnetic perturbations are interpreted as magnetohydrodynamic poloidal waves, where fundamental and second harmonic modes coexist. The NTC oscillation and the fundamental wave have similar periods, but are phase shifted by a quarter of period. From the correlation between both signals, and the proximity of the NTC source (localized via triangulation) with Cluster, we infer that the poloidal perturbations are spatially uniform between the source and the satellites. From the phase shift between signals, we conclude that the electrostatic wave which converts into NTC is mainly governed by the plasma density, affected by movements of the magnetic field lines. Furthermore, we demonstrate that the observations can be used to perform a magnetoseismology of the emitting surface. The results show a steepening of the plasmapause density profile near the satellites, which can be responsible for the generation of NTC emission.
Frictionally heated electrons in the high‐latitude D region
Authors: Brower Laura , Thayer Jeffrey P. , St.‐Maurice Jean‐Pierre
Published: December 2009

A semiempirical, physical model of electron momentum and energy in the D region is developed to investigate natural mechanisms for enhancing D region electron temperatures. The modeled D region electron temperatures are enhanced in the presence of strong magnetospherically mapped electric fields and are independent of the D region electron density. Results indicate that electric field strengths exceeding 50 mV/m cause significant frictional heating of the D region electron gas. Balanced by elastic and inelastic collisions with neutrals, frictional heating can heat the D region electron gas up to 3 times the neutral temperature. Sondrestrom incoherent scatter radar (ISR) measurements during the Halloween storm of October 2003 observed an anticorrelation between the locally observed electric field strength and the measured D region backscattered power. It is found through modeling that D region electron temperatures are enhanced during the time of the observed decrease in backscattered power. The electron temperature dependency in the ISR total cross section accounts for the decrease in backscattered power. The natural increase in D region electron temperatures due to strong magnetospheric electric fields can have implications on polar D region chemistry, conductivity, and plasma diffusion.
Influence of gas hydrate morphology on the seismic velocities of sands
Authors: Priest Jeffrey A. , Rees Emily V. L. , Clayton Christopher R. I.
Published: November 2009

This paper reports the results of a series of resonant column tests on specimens where gas hydrate has been formed in sands using an “excess water” technique. In these specimens the amount of hydrate formed is restricted by the amount of gas in the specimen and with an excess of water being present in the pore space. Results of resonant column tests carried out to determine compressional and shear wave velocities suggest that gas hydrate formed in this way are frame supporting. In contrast, the behavior observed in sands where the hydrate is formed from finite water where the remaining pore space is saturated with methane gas, termed in this paper the “excess gas” method, exhibits a cementing behavior, while tetrahydrofuran‐hydrate sands or where the hydrate is formed from dissolved methane within the pore water, exhibit a pore‐filling behavior for hydrate saturations less than 40%. For sands where the hydrate is formed using the excess water method, much larger volumes of hydrate are required before a significant increase in shear wave velocity occurs, although increases in compressional wave velocity are seen at lower hydrate contents. These results suggest that hydrate interaction with the sediment is strongly dependent on morphology, and that natural hydrate may exhibit contrasting seismic signatures depending upon the geological environment in which it forms.
Surface energy budget over the South Pole and turbulent heat fluxes as a function of an empirical bulk Richardson number
Authors: Town Michael S. , Walden Von P.
Published: November 2009

Routine radiation and meteorological data at South Pole Station are used to investigate historical discrepancies of up to 50 W m−2 in the monthly mean surface energy budget and to investigate the behavior of turbulent heat fluxes under stable atmospheric temperature conditions. The seasonal cycles of monthly mean net radiation and turbulent heat fluxes are approximately equal, with a difference of 40 W m−2 between summer and winter, while the seasonal cycle of subsurface heat fluxes is only a few W m−2. For an 8‐month period (the winter of 2001), we calculate two estimates of turbulent heat fluxes, one from Monin‐Obukhov (MO) similarity theory and one as the residual of the surface energy budget (i.e., subsurface heat fluxes minus net radiation, where all fluxes toward the snow surface are positive). The turbulent fluxes from MO theory agree well with the residual of the energy budget under lapse conditions. However, under stable conditions MO theory underestimates turbulent fluxes by approximately 40–60%. The relationship between turbulent heat fluxes as a residual of the energy budget, temperature inversion strength, and wind shear as a function of the bulk Richardson number (Rib) is examined under stable conditions (i.e., positive Rib). The Rib used here is calculated from 10‐m wind speeds and 0‐ to 2‐m temperature inversion strength. No critical value of Rib is found where the turbulent heat fluxes drop to zero. However, a threshold (Rib = 0.05) exists below which 70% of the turbulent energy fluxes can be explained by only the temperature inversion strength. For Rib > 0.05, the relationship between turbulent heat fluxes and temperature inversion strength decreases, while the importance of wind shear to turbulent heat transfer increases. Above Rib = 0.05, a growing linear correlation also exists between atmospheric temperature inversion strength and wind shear. Thus, inversion strength and wind shear are not independent predictors of turbulent heat flux for extremely stable conditions. The exact values of the correlation coefficients and Rib threshold are likely specific to the experimental conditions; however, their implications are probably valid for all stable flows. Knowledge of the time‐varying surface characteristics would help to generalize these parameters.
Clouds and water vapor in the Northern Hemisphere summertime stratosphere
Authors: Dessler A. E.
Published: November 2009

Cloud top observations from the Cloud‐Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) instrument and water vapor measured by the Microwave Limb Sounder (MLS) are used to study the occurrence of clouds in the Northern Hemisphere (NH) summertime lower stratosphere (20°−70°N) and their relation to water vapor. At low latitudes, clouds in the stratosphere tend to occur in regions of intense convection, while at high latitudes, there is little longitudinal preference for the clouds. In general, the 0.1% cloud top occurrence contour tends to be found ∼3 km or 40–50 K of potential temperature above the tropopause. At midlatitudes, the occurrence of clouds above the tropopause is associated with enhanced water vapor, suggesting that clouds are associated with moistening events in the lower stratosphere. In the subtropics, the occurrence of clouds is associated with reduced water vapor, suggesting that clouds are associated with dehydration events. Our results are consistent with hydration or dehydration being determined by the local relative humidity. Low relative humidity allows significant evaporation of lofted cloud ice, which is thought to be the key to moistening events. High relative humidity inhibits evaporation of lofted cloud ice and encourages in situ formation of clouds that are thought to play a role in dehydration.
A 1600 year multiproxy record of paleoclimatic change from varved sediments in Lake Xiaolongwan, northeastern China
Authors: Chu Guoqiang , Sun Qing , Wang Xiaohua , Li Dong , Rioual Patrick , Qiang Liu , Han Jingtai , Liu Jiaqi
Published: November 2009

A multiproxy record from Lake Xiaolongwan, northeastern China, reveals distinct stratigraphical patterns in organic carbon, total nitrogen, organic carbon isotope, nitrogen isotope, clastic content and dinocyst concentration, over the past 1600 years. High atomic C/N ratios in the sediment suggest that a large amount of organic matter in the sediments is derived from vascular plants and soil in the catchment. Based on the good agreement between cyclical variations of δ13Corg in the sediments and the spring drought index from historical documents, we interpret that the variation of δ13Corg in the sediments is an indicator of humidity or precipitation in the study area. Several notable drought periods with heavier δ13Corg occurred during AD 490–570, AD 780–990, AD 1360–1450, AD 1590–1670 and the last 150 years. These century‐scale drought episodes correspond to solar activity. It suggests that solar forcing plays an important role for the δ13Corg variation in the sediments through driving the changes in humidity/vapor pressure deficit. Dinocyst concentration is high during most of the Medieval Warm Period, and low during the European Dark Age and the Little Ice Age. The increase in dinocyst concentration is generally synchronous with decrease of δ15N value. The δ15N values in the studied lake are most likely influenced by the duration and intensification of lake overturn, which regulates the amount of depleted δ15N nutrients (dissolved organic nitrogen and ammonium) and dinoflagellate blooms.
Validation of aerosol extinction and water vapor profiles from routine Atmospheric Radiation Measurement Program Climate Research Facility measurements
Authors: Schmid Beat , Flynn Connor J. , Newsom Rob K. , Turner David D. , Ferrare Richard A. , Clayton Marian F. , Andrews Elisabeth , Ogren John A. , Johnson Roy R. , Russell Philip B. , Gore Warren J. , Dominguez Roseanne
Published: November 2009

The accuracy with which vertical profiles of aerosol extinction σep(λ) can be measured using routine Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) measurements and was assessed using data from two airborne field campaigns, the ARM Aerosol Intensive Operation Period (AIOP, May 2003), and the Aerosol Lidar Validation Experiment (ALIVE, September 2005). This assessment pertains to the aerosol at its ambient concentration and thermodynamic state (i.e., σep(λ) either free of or corrected for sampling artifacts) and includes the following ACRF routine methods: Raman lidar, micropulse lidar (MPL), and in situ aerosol profiles (IAP) with a small aircraft. Profiles of aerosol optical depth τp(λ), from which the profiles of σep(λ) are derived through vertical differentiation, were measured by the NASA Ames Airborne Tracking 14‐channel Sun photometer (AATS‐14); these data were used as benchmark in this evaluation. The ACRF IAP σep(550 nm) were lower by 11% (during AIOP) and higher by 1% (during ALIVE) when compared to AATS‐14. The ACRF MPL σep(523 nm) measurements were higher by 24% (AIOP) and 19–21% (ALIVE) compared to AATS‐14, but the correlation improved significantly during ALIVE. In the AIOP, a second MPL operated by NASA showed a smaller positive bias (13%) with respect to AATS‐14. The ACRF Raman lidar σep(355 nm) measurements were larger by 54% (AIOP) and by 6% (ALIVE) compared to AATS‐14. The large bias in the Raman lidar measurements during AIOP stemmed from a gradual loss of Raman lidar sensitivity starting about the end of 2001 going unnoticed until after AIOP. A major refurbishment and upgrade of the instrument and improvements to a data processing algorithm led to the significant improvement and very small bias in ALIVE. Finally, we find that during ALIVE the Raman lidar water vapor densities ρw are 8% larger when compared to AATS‐14, whereas in situ measured ρw aboard two different aircraft are smaller than the AATS‐14 values by 0.3–3%.
Coeval compressional deformation and volcanism in the central Andes, case studies from northern Chile (23°S–24°S)
Authors: González Gabriel , Cembrano José , Aron Felipe , Veloso Eugenio E. , Shyu J. Bruce H.
Published: November 2009

In this contribution we examine the relationship between active compression and construction of Pleistocene volcanoes in the present‐day magmatic arc of the central Andes (23°S–24°S). Deformation produced several N–S striking, ∼40 km long subparallel ridges. These ridges formed by folding of Pliocene ignimbrites and upper Pliocene and Pleistocene lavas; they are asymmetrical in profile and have a gentle back limb and steeper frontal limb. Andesitic monogenetic volcanoes show a close spatial relationship with the ridges; some volcanoes are on the hinge zone, whereas others lay on the sides of the ridges. We interpret this spatial pattern as a result of magma storage and migration along a system of subhorizontal reservoirs and reverse faults. Magma reservoirs probably formed along flat portions of reverse faults between ramp structures that serve as episodic magma transport pathways.
Contextual Thematic Group Treatment for Individuals With Dementia
Authors: Pimentel Jane
Published: December 2009

Purpose: Group treatment for individuals with dementia is an option to target activity and participation for residents in long-term care facilities to engage them in meaningful conversation and potentially improve their quality of life. The purpose of this article is to describe a theme-based group treatment approach that capitalizes on the use of the environment through context.

Method: Rationale for this group treatment approach is presented, including a brief description and evidence supporting clinical techniques utilized. These include reminiscence therapy, multisensory stimulation, and use of environmental aids. In addition, background is provided regarding capitalizing on memory and linguistic strengths and compensating for weaknesses. Modifications of clinician behaviors are presented to best facilitate successful group interactions.

Results and Conclusions: The article culminates in a detailed description of contextual thematic group treatment. This description includes an example lesson plan with corresponding rationale for activities. Data supporting the individual clinical techniques utilized in this group treatment approach are adequate; however, the evidence supporting the combination of these techniques in this format is meager and requires further investigation.
Improved performance of poly(3-hexylthiophene)/zinc oxide hybrid photovoltaics modified with interfacial nanocrystalline cadmium sulfide
Authors: Spoerke Erik D. , Lloyd Matthew T. , McCready Erica M. , Olson Dana C. , Lee Yun-Ju , Hsu Julia W. P.
Published: November 2009

To improve zinc oxide/poly(3-hexylthiophene) (ZnO/P3HT) hybrid solar cell performance, we introduce a nanocrystalline cadmium sulfide (CdS) film at the ZnO/P3HT heterojunction, creating a cascading energy band structure. Current-voltage characteristics under AM1.5 illumination show that, compared to unmodified ZnO/P3HT devices, CdS modification leads to an approximate doubling of the open-circuit voltage and a mild increase in fill factor, without sacrificing any short-circuit current. These characteristics double the power conversion efficiency for devices with an interfacial CdS layer. External quantum efficiency spectra reveal definite photocurrent contributions from the CdS layer, confirming the cascading band structure. The mechanisms behind open-circuit voltage increase are discussed.
Asymptotic analysis of the Engle–Pereira–Rovelli–Livine four-simplex amplitude
Authors: Barrett John W. , Dowdall Richard J. , Fairbairn Winston J. , Gomes Henrique , Hellmann Frank
Published: November 2009

The semiclassical limit of a four-simplex amplitude for a spin foam quantum gravity model with an Immirzi parameter is studied. If the boundary state represents a nondegenerate four-simplex geometry, the asymptotic formula contains the Regge action for general relativity. A canonical choice of phase for the boundary state is introduced and is shown to be necessary to obtain the results.
Scalable multiplexed detector system for high-rate telecom-band single-photon detection
Authors: Brida G. , Degiovanni I. P. , Piacentini F. , Schettini V. , Polyakov S. V. , Migdall A.
Published: November 2009

We present an actively multiplexed photon-counting detection system at telecom wavelengths that overcomes the difficulties of photon-counting at high rates. We find that for gated detectors, the heretofore unconsidered deadtime associated with the detector gate is a critical parameter, that limits the overall scalability of the scheme to just a few detectors. We propose and implement a new scheme that overcomes this problem and restores full scalability that allows an order of magnitude improvement with systems with as few as 4 detectors. When using just two multiplexed detectors, our experimental results show a 5× improvement over a single detector and a greater than 2× improvement over multiplexed schemes that do not consider gate deadtime.
On a logarithmic deformation of the supersymmetric bc-system on curved manifolds
Authors: Vogeler Kirsten , Flohr Michael
Published: November 2009

Frenkel et al. (“Instantons beyond topological theory. I,” e-print hep-th/0610149; “Instantons beyond topological theory. II,” e-print hep-th/0803.3302) claimed that a certain class of theories on compact Kähler manifolds and, in particular, the “gauged” supersymmetric bc-system on CP1 are modeled by logarithmic conformal field theories. We discuss that proposition for the bc-system on CP1 and thereby confirm their conjecture. Consequently, the property of being a logarithmic conformal field theory can be interpreted as an effect of gravity.
A model of reaction field in gas-injected arc-in-water method to synthesize single-walled carbon nanohorns: Influence of water temperature
Authors: Poonjarernsilp Chantamanee , Sano Noriaki , Tamon Hajime , Charinpanitkul Tawatchai
Published: December 2009

The method to synthesize single-walled carbon nanohorns (SWCNHs) using gas-injected arc in water (GI-AIW) has been experimentally studied. GI-AIW is known as one of the cost-effective methods to obtain SWCNHs. It was revealed that the yield of SWCNHs significantly decreases with the increase in water temperature although the purity of SWCNHs is not dependent on the temperature change. Then the model of relevant reactions in the GI-AIW system was proposed by accounting the emission of carbon vapor, formation of SWCNHs, and diffusion of water vapor in three zones inside the cathode hole (arc plasma zone, quenching zone, and downstream zone). The side reaction between H2O and C produces H2 gas and consumes a certain amount of carbon vapor, resulting in the hindered SWCNH formation. Moreover the observation of the optical spectra emitting from the arc plasma zone strongly supported that the H2 generating reaction does not occur at arc plasma zone since N2 flow can purge H2O out. The model proposed in this study can precisely explain the correlation between H2 gas production and water temperature.
Thermal transport in CO2 laser irradiated fused silica: In situ measurements and analysis
Authors: Yang Steven T. , Matthews Manyalibo J. , Elhadj Selim , Draggoo Vaughn G. , Bisson Scott E.
Published: November 2009

In situ spatial and temporal temperature measurements of pristine fused silica surfaces heated with a 10.6 μm CO2 laser were obtained using an infrared radiation thermometer based on a mercury cadmium telluride camera. Laser spot sizes ranged from 250 to 1000 μm diameter with peak axial irradiance levels of 0.13–16 kW/cm2. For temperatures below 2800 K, the measured steady-state surface temperature is observed to rise linearly with both increasing beam size and incident laser irradiance. The effective thermal conductivity estimated over this range was approximately 2 W/m-K, in good agreement with classical calculations based on phonon heat capacities. Similarly, time-dependent temperature measurements up to 2000 K yielded thermal diffusivity values which were close to reported values of 7×10−7 m2/s. Above ∼2800 K, the fused silica surface temperature asymptotically approaches 3100 K as laser power is further increased, consistent with the onset of evaporative heat losses near the silica boiling point. These results show that in the laser heating regime studied here, the T3 temperature dependent thermal conductivity due to radiation transport can be neglected, but at temperatures above 2800 K heat transport due to evaporation must also be considered. The thermal transport in fused silica up to 2800 K, over a range of conditions, can then be adequately described by a linear diffusive heat equation assuming constant thermal properties.
Temperature dependence of exciton complexes photoluminescence spectra in self-assembled InAs/GaAs quantum rings
Authors: Zhang Weiwei , Gong Ming , Li Chuan-Feng , Guo Guang-Can , He Lixin
Published: November 2009

We investigate the temperature dependent photoluminescence (PL) spectra of exciton complexes in the self-assembled InAs/GaAs quantum rings (QRs) by using an atomistic pseudopotential method and a configuration-interaction treatment of many-particle effects. We find, unlike in quantum dots, the biexciton XX and positive trion X+ in QRs show multitransition peaks even at very low temperatures, and the PL spectra are very sensitive to the temperature. The peculiar temperature dependent spectra of XX and X+ is due to the unique electronic structures and the strong many-body correlation effects in the QRs.
Quasiparticle trapping in three terminal ferromagnetic tunneling devices
Authors: Latempa R. , Aprili M. , Petković I.
Published: November 2009

Hybrid superconductor/ferromagnet structures have been investigated recently to address the interplay between ferromagnetism and superconductivity. They also are very promising for the investigation of out of equilibrium superconductivity. Here, we show how it is possible for out of equilibrium excitations produced in a superconducting thin film (S) to be localized in a ferromagnetic trap (F). Specifically, a ferromagnetic nanovolume in good contact with S represents a potential well for the quasiparticles (QPs) at the gap edge. As the superconducting proximity effect is highly suppressed in F, QPs get efficiently trapped and they share their energy with the free electrons in the trap. The electronic temperature Te in the trap can be increased by up to 60% from the bath temperature at 320 mK as measured by tunneling spectroscopy using a second junction.
Anisotropy effects in homogenized magnetodielectric photonic crystals
Authors: Cerdán-Ramírez V. , Zenteno-Mateo B. , Sampedro M. P. , Palomino-Ovando M. A. , Flores-Desirena B. , Pérez-Rodríguez F.
Published: November 2009

Exact analytic formulas for calculating the effective permittivity, permeability, and crossed magnetoelectric tensors for photonic crystals in the long-wavelength limit are presented. The formulas are valid for arbitrary Bravais lattice and form of inclusions, which can be dielectric, magnetic, or chiral. We have applied them to study the optical anisotropy of homogenized magnetodielectric three-dimensional photonic crystals, which can be induced by the type of Bravais lattice or the form of the inclusion even in the case when the photonic crystal is composed of isotropic materials. It is established that the electromagnetic modes, propagating in such anisotropic magnetodielectric metamaterials, are extraordinary, unlike the modes in homogenized nonmagnetic dielectric composites, where at least one mode is ordinary.
Electrical analysis of organic interlayer based metal/interlayer/semiconductor diode structures
Authors: Güllü Ö. , Türüt A.
Published: November 2009

In this work, metal/interlayer/semiconductor (MIS) diodes formed by coating of an organic film to p-Si semiconductor substrate were prepared. Metal(Al)/interlayer (phenolsulfonphthalein=PSP)/semiconductor(p-Si) MIS device had a good rectifying behavior. By using the forward bias I-V characteristics, the values of ideality factor (n) and barrier height (Φb) for the Al/PSP/p-Si MIS diode were obtained as 1.45 and 0.81 eV, respectively. It was seen that the Φb value of 0.81 eV calculated for the Al/PSP/p-Si MIS diode was significantly larger than value of 0.50 eV of conventional Al/p-Si Schottky diodes. Modification of the interfacial potential barrier of Al/p-Si diode was achieved by using a thin interlayer of the PSP organic material. This has been attributed to the fact that the PSP organic interlayer increases the effective barrier height by influencing the space-charge region of Si. The interface-state density of the MIS diode was determined, and the interface-state density was found to vary from 3.00×1013 to 2.99×1012 eV−1 cm−2.
Windowless microfluidic platform based on capillary burst valves for high intensity x-ray measurements
Authors: Vig Asger Laurberg , Haldrup Kristoffer , Enevoldsen Nikolaj , Thilsted Anil Haraksingh , Eriksen Johan , Kristensen Anders , Feidenhans’l Robert , Nielsen Martin Meedom
Published: November 2009

We propose and describe a microfluidic system for high intensity x-ray measurements. The required open access to a microfluidic channel is provided by an out-of-plane capillary burst valve (CBV). The functionality of the out-of-plane CBV is characterized with respect to the diameter of the windowless access hole, ranging from 10 to 130 μm. Maximum driving pressures from 22 to 280 mbar corresponding to refresh rates of the exposed sample from 300 Hz to 54 kHz is demonstrated. The microfluidic system is tested at beamline ID09b at the ESRF synchrotron radiation facility in Grenoble, and x-ray scattering measurements are shown to be feasible and to require only very limited amounts of sample, <1 ml/h of measurements without recapturing of sample. With small adjustments of the present chip design, scattering angles up to 30° can be achieved without shadowing effects and integration on-chip mixing and spectroscopy appears straightforward.
Breakdown of silicon particle detectors under proton irradiation
Authors: Väyrynen S. , Räisänen J. , Kassamakov I. , Tuominen E.
Published: November 2009

Silicon particle detectors made on Czochralski and float zone silicon materials were irradiated with 7 and 9 MeV protons at a temperature of 220 K. During the irradiations, the detectors were biased up to their operating voltage. Specific values for the fluence and flux of the irradiation were found to cause a sudden breakdown in the detectors. We studied the limits of the fluence and the flux in the breakdown as well as the behavior of the detector response function under high flux irradiations. The breakdown was shown to be an edge effect. Additionally, the buildup of an oxide charge is suggested to lead to an increased localized electric field, which in turn triggers a charge carrier multiplication. Furthermore, we studied the influences of the type of silicon material and the configuration of the detector guard rings.
Molecular structure of extended defects in monolayer-scale pentacene thin films
Authors: Seo S. , Evans P. G.
Published: November 2009

The growth of pentacene thin films for applications in thin-film transistors and other organic electronic devices results in a variety of extended structural defects including dislocations, grain boundaries, and stacking faults. We have used scanning tunneling microscopy (STM) to probe the molecular-scale structure of grain boundaries and stacking faults in a pentacene thin film on a Si (001) surface modified with styrene. Styrene/Si (001) substrates produce pentacene films that are structurally similar to those grown on insulating substrates, but which are sufficiently smooth and conductive for STM studies. STM images show two types of grain boundaries: in-plane high-angle tilt grain boundaries at the junctions between pentacene islands, and twist boundaries between molecular layers. Segments of the tilt grain boundaries are faceted along low-energy crystallographic directions. Stacking faults are found in the plane of individual pentacene grains. Two rows of molecules near the stacking fault are shifted along the surface normal by 60 pm. Electronically relevant trap states may thus be associated with stacking faults in pentacene thin films.
Modified proton radiography arrangement for the detection of ultrafast field fronts
Authors: Quinn K. , Wilson P. A. , Ramakrishna B. , Romagnani L. , Sarri G. , Cecchetti C. A. , Lancia L. , Fuchs J. , Pipahl A. , Toncian T. , Willi O. , Clarke R. J. , Neely D. , Notley M. , Gallegos P. , Carroll D. C. , Quinn M. N. , Yuan X. H. , McKenna P. , Borghesi M.
Published: November 2009

The experimental arrangement for the investigation of high-field laser-induced processes using a broadband proton probe beam has been modified to enable the detection of the ultrafast motion of field fronts. It is typical in such experiments for the target to be oriented perpendicularly with respect to the principal axis of the probe beam. It is demonstrated here, however, that the temporal imaging properties of the diagnostic arrangement are altered drastically by placing the axis (or plane) of the target at an oblique angle to the transverse plane of the probe beam. In particular, the detection of the motion of a laser-driven field front along a wire at a velocity of (0.95±0.05)c is described.
Quantum mechanical corrections to simulated shock Hugoniot temperatures
Authors: Goldman Nir , Reed Evan J. , Fried Laurence E.
Published: November 2009

We present a straightforward method for the inclusion of quantum nuclear vibrational effects in molecular dynamics calculations of shock Hugoniot temperatures. Using a Grüneisen equation of state and a quasiharmonic approximation to the vibrational energies, we derive a simple, postprocessing method for calculation of the quantum corrected Hugoniot temperatures. We have used our novel technique on ab initio simulations of shock compressed water and methane. Our results indicate significantly closer agreement with all available experimental temperature data for these two systems. Our formalism can be easily applied to a number of different shock compressed molecular liquids or solids, and has the potential to decrease the large uncertainties inherent in many experimental Hugoniot temperature measurements of these systems.
Crossflow instability of finite Bödewadt flows: Transients and spiral waves
Authors: Lopez Juan M. , Marques Francisco , Rubio Antonio M. , Avila Marc
Published: November 2009

The flow in an enclosed rotating cylinder with a stationary lower end wall is investigated numerically. For fast rotation rates, the flow in the interior is primarily in the azimuthal direction, with an angular momentum distribution very close to that corresponding to solid-body rotation for about the inner-half radius. The differential rotation sets up a large-scale circulation that is primarily present in the boundary layers on the rotating top and sidewalls and the stationary bottom wall, with a very weak effusive component throughout the bulk interior providing a matching between the boundary layer flows on the top and bottom. The top end wall boundary layer has a profile that very closely matches the von Kármán solution for a rotating disk boundary layer; it is stable and very robust to finite disturbances for all rotation rates considered. The boundary layer on the stationary bottom end wall has a profile that agrees with the Bödewadt solution for a stationary disk with an ambient flow in solid-body rotation. This boundary layer is not robust, suffering crossflow instability to multiarmed spiral waves via a supercritical Hopf bifurcation, as well as being susceptible to axisymmetric circular waves that travel radially inward where the boundary layer profile is most inflectional. In the absence of any external forcing, the circular waves are transitory, but low amplitude forcing can sustain them indefinitely, whereas the spiral waves are essentially unaffected by the external forcing.
Weak-link behavior of grain boundaries in superconducting Ba(Fe1−xCox)2As2 bicrystals
Authors: Lee S. , Jiang J. , Weiss J. D. , Folkman C. M. , Bark C. W. , Tarantini C. , Xu A. , Abraimov D. , Polyanskii A. , Nelson C. T. , Zhang Y. , Baek S. H. , Jang H. W. , Yamamoto A. , Kametani F. , Pan X. Q. , Hellstrom E. E. , Gurevich A. , Eom C. B. , Larbalestier D. C.
Published: November 2009

We show that despite the low anisotropy, strong vortex pinning, and high irreversibility field Hirr close to the upper critical field Hc2 of Ba(Fe1−xCox)2As2, the critical current density Jgb across [001] tilt grain boundaries (GBs) of thin film Ba(Fe1−xCox)2As2 bicrystals is strongly depressed, similar to high-Tc cuprates. Our results suggest that weak-linked GBs are characteristic of both cuprates and pnictides because of competing orders, low carrier density, and unconventional pairing symmetry.
A density functional theory for vapor-liquid interfaces using the PCP-SAFT equation of state
Authors: Gross Joachim
Published: November 2009

A Helmholtz energy functional for inhomogeneous fluid phases based on the perturbed-chain polar statistical associating fluid theory (PCP-SAFT) equation of state is proposed. The model is supplemented with a capillary wave contribution to the surface tension to account for long-wavelength fluctuations of a vapor-liquid interface. The functional for the dispersive attraction is based on a nonlocal perturbation theory for chain fluids and the difference of the perturbation theory to the dispersion term of the PCP-SAFT equation of state is treated with a local density approximation. This approach suggested by Gloor et al. [Fluid Phase Equilib. 194, 521 (2002)] leads to full compatibility with the PCP-SAFT equation of state. Several levels of approximation are compared for the nonlocal functional of the dispersive attractions. A first-order non-mean-field description is found to be superior to a mean-field treatment, whereas the inclusion of a second-order perturbation term does not contribute significantly to the results. The proposed functional gives excellent results for the surface tension of nonpolar or only moderately polar fluids, such as alkanes, aromatic substances, ethers, and ethanoates. A local density approximation for the polar interactions is sufficient for carbon dioxide as a strongly quadrupolar compound. The surface tension of acetone, as an archetype dipolar fluid, is overestimated, suggesting that a nonisotropic orientational distribution function across an interface should for strong dipolar substances be accounted for.
Increasing organic vertical carrier mobility for the application of high speed bilayered organic photodetector
Authors: Tsai Wu-Wei , Chao Yu-Chiang , Chen En-Chen , Zan Hsiao-Wen , Meng Hsin-Fei , Hsu Chain-Shu
Published: November 2009

The direct influence of the vertical carrier mobility on the frequency response of bilayered organic photodiodes (PDs) is investigated for the first time. With fullerene as the acceptor material, changing vertical hole mobility from 2.3×10−5 to 2.8×10−4 cm2/V s increases PD bandwidth from 10 to 80 MHz under a 4 V operation. The influence of deposition rate on vertical hole mobility of pentacene film is also discussed. Our results facilitate the application of bilayered organic PDs on the detection of very-high-frequency optical signals.
Hyers–Ulam stability on a generalized quadratic functional equation in distributions and hyperfunctions
Authors: Chung Jae-Young , Kim Dohan , Rassias John Michael
Published: November 2009

We consider the Hyers–Ulam stability of a generalized quadratic functional equation in the spaces of distributions of Schwartz and hyperfunctions of Gelfand modulo bounded distributions and hyperfunctions.
Robust localized modes in bilayer graphene induced by an antisymmetric kink potential
Authors: Martinez J. C. , Jalil M. B. A. , Tan S. G.
Published: November 2009

When bilayer graphene is gated with a kink potential, pair particle localization occurs at the kink where a particle (electron) and its chiral partner (hole) are held in balance by electrostatic coupling. Zero-energy states (zero modes) are always present in pairs and occur at the same point in the dispersion graph, regardless of kink strength. The robust and binary nature of the kink-induced modes, which are topologically protected against disorder, and the ease with which a kink is created suggest applications in switching devices or information storage.
Painlevé singularity structure analysis of three component Gross–Pitaevskii type equations
Authors: Kanna T. , Sakkaravarthi K. , Kumar C. Senthil , Lakshmanan M. , Wadati M.
Published: November 2009

In this paper, we have studied the integrability nature of a system of three-coupled Gross–Pitaevskii type nonlinear evolution equations arising in the context of spinor Bose–Einstein condensates by applying the Painlevé singularity structure analysis. We show that only for two sets of parametric choices, corresponding to the known integrable cases, the system passes the Painlevé test.
A debubbler for microfluidics utilizing air-liquid interfaces
Authors: Cheng Daming , Jiang Hongrui
Published: November 2009

We present a debubbler for the removal of air bubbles in aqueous liquids in microfluidics. The debubbler is realized through an array of cylinder-shaped air-liquid interfaces, or air-pillars, formed directly into the microfluidic channels by surface tension. The debubbler demonstrated effective trapping and removal of both chemically generated bubbles (several nanoliters to several microliters in volume) and air slugs with several microliters in volume, which were formed by high infusion rates of bubble series introduced into the microchannel.
Direct absorption spectroscopy of water clusters formed in a continuous slit nozzle expansion
Authors: Moudens A. , Georges R. , Goubet M. , Makarewicz J. , Lokshtanov S. E. , Vigasin A. A.
Published: November 2009

In this article, we report on a Fourier transform infrared study of absorption bands belonging to small-sized water clusters formed in a continuous slit nozzle expansion of water vapor seeded in argon carrier gas. Clear signatures of free and H-bonded OH vibrations in water aggregates from dimer to pentamer are seen in our spectra. Following an increase in argon backing pressure, the position of the cluster absorption bands varies from those characteristics of isolated water aggregates in the gas phase to those known for clusters trapped in a static argon matrix. These variations can be interpreted in terms of sequential solvation of the water clusters by an increasing number of argon atoms attached to water clusters. Our measured spectra are in good agreement with those obtained previously either for free or Ar coated small-sized water clusters using pulsed slit-jet expansions. Our results are equally in accord with those originating from a variety of tunable laser based techniques using molecular beams or free jets or from the study of water aggregates embedded in rare gas matrices. Distinctions are reported, however, and discussed. Ab initio calculations have made it possible to speculate on the average size of an argon solvation shell around individual clusters as well as on the development of the OH stretch vibrational shifts in mixed (H2O)mArn clusters having different compositions and architectures.
High surface-enhanced Raman scattering activity from Au-decorated individual and branched tin oxide nanowires
Authors: Jiang Xuejiao , Zhang Liangliang , Wang Taihong , Wan Qing
Published: December 2009

Individual tin oxide (SnO2) nanowire and three-dimensional (3D) branched SnO2 nanowires decorated with Au nanoparticles are investigated as the substrates for surface-enhanced Raman scattering (SERS) application. Rhodamine B, isothiocyanate with a concentration of 1.0 μM/l can be easily detected due to the localized surface plasmon resonance of the Au nanoparticles on the SnO2 nanowire. The SERS enhancement factors of the individual Au-coated nanowire and 3D branched SnO2 nanowires are estimated to be 1.1×107 and 1.0×107, respectively. The high SERS activity of the 3D branched SnO2 nanowires is due to the plentiful Au droplets and the formation of lots of “hot spots” in regions between adjacent Au droplets on tips of the branches.