bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid barotropic sea level rise from ice sheet melting
Authors: Lorbacher K. , Marsland S. J. , Church J. A. , Griffies S. M. , Stammer D.
Published: May 2012

Sea level rise associated with idealized Greenland and Antarctic ice sheet melting events is examined using a global coupled ocean sea‐ice model that has a free surface formulation and thus can simulate fast barotropic motions. The perturbation experiments follow the Coordinated Ocean‐ice Reference Experiment (CORE) version III. All regions of the global ocean experience a sea level rise within 7–8 days of the initialization of a polar meltwater input of 0.1 Sv (1 Sv ≡ 106 m3 s−1). The fast adjustment contrasts sharply with the slower adjustment associated with the smaller steric sea level evolution that is also connected with melt events. The global mean sea level rises by 9 mm yr−1 when this forcing is applied either from Greenland or Antarctica. Nevertheless, horizontal inter‐basin gradients in sea level remain. For climate adaption in low‐lying coastal and island regions, it is critical that the barotropic sea level signal associated with melt events is taken into consideration, as it leads to a fast sea level rise from melting ice sheets for the bulk of the global ocean. A linear relation between sea level rise and global meltwater input is further supported by experiments in which idealized melting occurs only in a region east or west of the Antarctic Peninsula, and when melting rates are varied between 0.01 Sv and 1.0 Sv. The results indicate that in ocean models that do not explicitly represent the barotropic signal, the barotropic component of sea level rise can be added off‐line to the simulated steric signal.
Local and large‐scale atmospheric responses to reduced Arctic sea ice and ocean warming in the WRF model
Authors: Porter David F. , Cassano John J. , Serreze Mark C.
Published: May 2012

The Weather Research and Forecasting (WRF) model is used to explore the sensitivity of the large‐scale atmospheric energy and moisture budgets to prescribed changes in Arctic sea ice and sea surface temperatures (SSTs). Observed sea ice fractions and SSTs from 1996 and 2007, representing years of high and low sea ice extent, are used as lower boundary conditions. A pan‐Arctic domain extending into the North Pacific and Atlantic Oceans is used. ERA‐Interim reanalysis data from 1994 to 2008 are employed as initial and lateral forcing data for each high and low sea ice simulation. The addition of a third ensemble, with a mixed SST field between years 1996 and 2007 (using 2007 SSTs above 66°N and 1996 values below), results in a total of three 15‐member ensembles. Results of the simulations show both local and remote responses to reduced sea ice. The local polar cap averaged response is largest in October and November, dominated by increased turbulent heat fluxes resulting in vertically deep heating and moistening of the Arctic atmosphere. This warmer and moister atmosphere is associated with an increase in cloud cover, affecting the surface and atmospheric energy budgets. There is an enhancement of the hydrologic cycle, with increased evaporation in areas of sea ice loss paired with increased precipitation. Most of the Arctic climate response results from within‐Arctic changes, although some changes in the hydrologic cycle reflect circulation responses to midlatitude SST forcing, highlighting the general sensitivity of the Arctic climate.
Developing a new mode for observation of ionospheric disturbances by digital ionosonde in ionospheric vertical sounding
Authors: Chen Kun , Zhu Zhengping , Ning Baiqi , Lan Jiaping , Sun Fenglou
Published: May 2012

Detecting Doppler frequency shifts from ionospheric high‐frequency echoes is an important way to study ionospheric disturbances. This paper presents and realizes a new mode for observation of ionospheric disturbances using a combination of coded pulses and echo phase measurement analysis in ionospheric vertical sounding based on the Canadian Advanced Digital Ionosonde (CADI) platform. Experimental results show that the newly developed mode for observation of ionospheric disturbances on CADI can acquire accurate Doppler ionogram (Dopplionogram) and obtain temporal and spatial variations of the velocity of ionospheric disturbances in real time so that it has essential value in observation and research of ionospheric disturbances. The application of the new mode for observation of ionospheric disturbances in ionospheric vertical sounding opens up a new, effective way by which much more ionospheric information can be acquired with existing common ionospheric sounding instruments.
Interfacing a one‐dimensional lake model with a single‐column atmospheric model: 2. Thermal response of the deep Lake Geneva, Switzerland under a 2 × CO2 global climate change
Authors: Perroud Marjorie , Goyette Stéphane
Published: May 2012

In the companion to the present paper, the one‐dimensional k‐ε lake model SIMSTRAT is coupled to a single‐column atmospheric model, nicknamed FIZC, and an application of the coupled model to the deep Lake Geneva, Switzerland, is described. In this paper, the response of Lake Geneva to global warming caused by an increase in atmospheric carbon dioxide concentration (i.e., 2 × CO2) is investigated. Coupling the models allowed for feedbacks between the lake surface and the atmosphere and produced changes in atmospheric moisture and cloud cover that further modified the downward radiation fluxes. The time evolution of atmospheric variables as well as those of the lake's thermal profile could be reproduced realistically by devising a set of adjustable parameters. In a “control” 1 × CO2 climate experiment, the coupled FIZC‐SIMSTRAT model demonstrated genuine skills in reproducing epilimnetic and hypolimnetic temperatures, with annual mean errors and standard deviations of 0.25°C ± 0.25°C and 0.3°C ± 0.15°C, respectively. Doubling the CO2 concentration induced an atmospheric warming that impacted the lake's thermal structure, increasing the stability of the water column and extending the stratified period by 3 weeks. Epilimnetic temperatures were seen to increase by 2.6°C to 4.2°C, while hypolimnion temperatures increased by 2.2°C. Climate change modified components of the surface energy budget through changes mainly in air temperature, moisture, and cloud cover. During summer, reduced cloud cover resulted in an increase in the annual net solar radiation budget. A larger water vapor deficit at the air‐water interface induced a cooling effect in the lake.
Sulfur isotopic compositions of fumarolic and plume gases at Mount Etna (Italy) and inferences on their magmatic source
Authors: Liotta M. , Rizzo A. , Paonita A. , Caracausi A. , Martelli M.
Published: May 2012

Here we report new data on the sulfur isotopic compositions (δ34S) of fumarolic and plume gases collected at Mount Etna volcano during 2008–2009. While low‐temperature fumaroles are affected by postmagmatic processes that modify the pristine isotopic signature, high‐temperature and plume gases allow establishment of aδ34S range of ∼0 ± 1‰ for magmatic SO2. We compared our data with those from S dissolved in primitive melt inclusions from 2002 lava and in whole rocks that erupted during the past two thousand years. Such a comparison revealed that δ34S is systematically lower for magmatic gases than for sulfur dissolved in the melt. We modeled how isotopic fractionation due to magma degassing process may vary δ34S value in both the melt and gaseous phases. This modeling required assessment of the fractionation factor (αgas‐melt). The most recent measurements on the oxidation state of sulfur in basaltic melt inclusions indicate that nearly all S is dissolved as sulfate (S6+), which would be possible in oxidized magmatic systems (ΔNNO ≥ 1). Under these conditions the exsolved gaseous phase is depleted with respect to the melt and the proposed model fits both gas and melt data, and constrains the Etnean magmatic δ34S to 1.0 ± 1.5‰. It is remarkable that the assessed redox conditions—which are significantly more oxidizing than previously thought—are able to explain why the dominant sulfur species measured in the Etnean plume is SO2.
Persistent longitudinal features in the low‐latitude ionosphere
Authors: Kil H. , Lee W. K. , Kwak Y.‐S. , Oh S.‐J. , Paxton L. J. , Zhang Y.
Published: May 2012

Various longitudinal wave patterns exist in the low‐latitude ionosphere, but the investigation has been limited to the wave number (WN) 3 and 4 patterns. This study extends the investigation to the wave patterns that have not yet been explored. The persistent ionospheric wave patterns are investigated by using the measurements of the ion density during March 1999–June 2004 by the first Republic of China satellite. The investigation is performed with data sets in the magnetic south (20°S–0°) and magnetic north (0°–20°N). The dominant wave features in plasma density are the WN1, WN2, WN3, and WN4 patterns. Among them, the WN1 pattern in the magnetic south during the June solstice is the most pronounced feature. Except for this component, the WN3 pattern is the most persistent and pronounced feature. Fundamental difference exists between the WN1 and WN2 patterns and the WN3 and WN4 patterns. First, the wave phases in the south and north are the same in the WN3 and WN4 patterns, but they are opposite in the WN1 and WN2 patterns. Second, the amplitudes of the WN3 and WN4 patterns show similar annual variation in the south and north, but those of the WN1 and WN2 patterns show opposite annual trends in the opposite hemispheres. These observations indicate that the WN1 and WN2 patterns and the WN3 and WN4 patterns are created by different mechanisms. We discuss the creation of the WN1 and WN2 patterns in association with the geomagnetic field configuration.
Very large array observations of disturbed ion flow from the plasmasphere to the nighttime ionosphere
Authors: Helmboldt J. F. , Intema H. T.
Published: May 2012

We present the results of a multiscale analysis of TEC fluctuations using a roughly five‐hour observation of the bright radio source Virgo A with the Very Large Array (VLA) at 74 MHz in its B configuration. Our analysis combines data sensitive to fine‐scale structure (∼10 km and <0.001 TECU in amplitude) along the line of sight to Virgo A as well as larger structures (hundreds of km) observed using several (∼30) moderately bright sources in the field of view. The observations span a time period from midnight to dawn local time during 1 March 2001. Several groups of magnetic eastward directed (MED), wavelike disturbances were identified and determined to be located within the plasmasphere (2.1 < L < 2.9). We have also detected evidence of non‐wavelike structures associated with these disturbances which are propagating roughly toward magnetic north. These likely represent a non‐uniform density flow from the plasmasphere toward the nighttime ionosphere. AE andKp indices and GPS TEC data indicate that during the observations, there were low levels of geomagnetic activity accompanied by somewhat localized depletions in ionospheric density. Thus, the observed plasmaspheric disturbance may be part of a flow triggered by these ionospheric depletions, likely associated with forcing from the lower atmosphere which is typically more prominent during quiet geomagnetic conditions. In addition, we have also observed several roughly westward directed and southeast directed waves located within the ionosphere. They are coincident in time with the plasmaspheric disturbances and may be related to the deposition of material onto the nighttime ionosphere.
Improved Arteriole‐to‐Venule Ratio of Retinal Vessels Resulting From Bariatric Surgery
Authors: Lammert Alexander , Hasenberg Till , Kräupner Caroline , Schnülle Peter , Hammes Hans‐Peter
Published: May 2012

Obesity causes increased morbidity and mortality from metabolic and cardiovascular disease (CVD). We investigated the effect of bariatric surgery on endothelial dysfunction (ED) in retinal vessels as a marker of metabolic and cardiovascular risk in patients with obesity WHO III. Thirty consecutive patients (19/11, w/m) were evaluated by anthropometry, lipid profile, and oral glucose tolerance test before and after bariatric surgery (Mannheim Obesity Study (MOS); NCT 00770276). Risk stratification was performed by the presence of metabolic syndrome (MetS) according to ATP‐III (adult treatment panel‐III). Subclinical atherosclerosis was assessed by measurement of intima‐media thickness (IMT). Flicker light response of retinal vessels was used as measures of ED. We measured their arteriole‐to‐venule ratio (AVR) for evaluation of vascular pathology. After a median of 9 months following bariatric surgery, mean weight loss was 39.4 kg (37.3%). Remission of impaired glucose metabolism was achieved in 53.3% of affected patients. Dyslipidemia improved significantly (triglycerides −61.3 mg/dl, P < 0.0001, total cholesterol −28.2 mg/dl, P = 0.002, and low‐density lipoprotein cholesterol were reduced −24.5 mg/dl, P = 0.008). This resulted in a significant reduction of patients classified for MetS (27 vs. 9, P < 0.0001). Adiponectin increased by 2.08 µg/l (P = 0.032) and high sensitivity C‐reactive protein (hs‐CRP) and soluble intercellular cell adhesion molecule (sICAM) decreased (−7.3 mg/l, P < 0.0001 and −146.4 ng/ml, P = 0.0006). AVR improved significantly (+0.04, P < 0.0001), but neither Flicker light response nor IMT changed significantly. Retinal AVR is ameliorated after bariatric intervention. As an increased AVR results from either or both widening retinal arteriolar caliber and narrowing retinal venular caliber, an improvement in small vessel profile is evident 9 months after bariatric surgery.
The activation mechanism of ACK1 (activated Cdc42-associated tyrosine kinase 1)
Authors: Lin Qiong , Wang Jian , Childress Chandra , Yang Wannian
Published: May 2012

ACK [activated Cdc42 (cell division cycle 42)-associated tyrosine kinase; also called TNK2 (tyrosine kinase, non-receptor, 2)] is activated in response to multiple cellular signals, including cell adhesion, growth factor receptors and heterotrimeric G-protein-coupled receptor signalling. However, the molecular mechanism underlying activation of ACK remains largely unclear. In the present study, we demonstrated that interaction of the SH3 (Src homology 3) domain with the EBD [EGFR (epidermal growth factor receptor)-binding domain] in ACK1 forms an auto-inhibition of the kinase activity. Release of this auto-inhibition is a key step for activation of ACK1. Mutation of the SH3 domain caused activation of ACK1, independent of cell adhesion, suggesting that cell adhesion-mediated activation of ACK1 is through releasing the auto-inhibition. A region at the N-terminus of ACK1 (Leu10–Leu14) is essential for cell adhesion-mediated activation. In the activation of ACK1 by EGFR signalling, Grb2 (growth-factor-receptor-bound protein 2) mediates the interaction of ACK1 with EGFR through binding to the EBD and activates ACK1 by releasing the auto-inhibition. Furthermore, we found that mutation of Ser445 to proline caused constitutive activation of ACK1. Taken together, our studies have revealed a novel molecular mechanism underlying activation of ACK1.
A urea channel from Bacillus cereus reveals a novel hexameric structure
Authors: Huysmans Gerard H. M. , Chan Nathan , Baldwin Jocelyn M. , Postis Vincent L. G. , Tzokov Svetomir B. , Deacon Sarah E. , Yao Sylvia Y. M. , Young James D. , McPherson Michael J. , Bullough Per A. , Baldwin Stephen A.
Published: May 2012

Urea is exploited as a nitrogen source by bacteria, and its breakdown products, ammonia and bicarbonate, are employed to counteract stomach acidity in pathogens such as Helicobacter pylori. Uptake in the latter is mediated by UreI, a UAC (urea amide channel) family member. In the present paper, we describe the structure and function of UACBc, a homologue from Bacillus cereus. The purified channel was found to be permeable not only to urea, but also to other small amides. CD and IR spectroscopy revealed a structure comprising mainly α-helices, oriented approximately perpendicular to the membrane. Consistent with this finding, site-directed fluorescent labelling indicated the presence of seven TM (transmembrane) helices, with a cytoplasmic C-terminus. In detergent, UACBc exists largely as a hexamer, as demonstrated by both cross-linking and size-exclusion chromatography. A 9 Å (1 Å=0.1 nm) resolution projection map obtained by cryo-electron microscopy of two-dimensional crystals shows that the six protomers are arranged in a planar hexameric ring. Each exhibits six density features attributable to TM helices, surrounding a putative central channel, while an additional helix is peripherally located. Bioinformatic analyses allowed individual TM regions to be tentatively assigned to the density features, with the resultant model enabling identification of residues likely to contribute to channel function.
A column‐based rapid method for the simultaneous isolation of DNA, RNA, miRNA and proteins
Authors: Rajput Sandeep K. , Dave Vivek P. , Rajput Ankita , Pandey Hausila P. , Datta Tirtha K. , Singh Rakesh K.
Published: May 2012

In the 21st century, systems biology is a holistic approach to understand life by the cross‐talk study between the genome, Rnome and proteome of a cell. We describe a column‐based rapid method for the simultaneous extraction of DNA, RNA, miRNA (microRNA) and proteins from the same experimental sample without prior fractionation, which allows a direct correlation between genomic, epigenomic, transcriptomic and proteomic data. This method provides a simple and effective way to analyse each of these biomolecules without affecting yield and quality. We also show that isolated biomolecules are of the highest purity and compatible for all the respective downstream applications, such as PCR amplification, RT—PCR (reverse transcription—PCR), real‐time PCR, reverse Northern blotting, SDS/PAGE and Western blot analysis. The buffers and reagents used in this method are optimized extensively to achieve the cost effective and reliable procedure to separate the functional biomolecules of the cell.
Overexpression of phosphatase regenerating liver 3 in oesophageal squamous cell carcinoma associated with metastasis and its comparison with phosphatase regenerating liver 1
Authors: Lou Xi , Liu Yuqiong , Ke Guo , Lei Jun‐Yi , Li Huixiang
Published: May 2012

Expression of PRL3 (phosphatase of regenerating liver 3) protein was examined with immunohistochemistry in 60 cases of ESCC (oesophageal squamous cell carcinoma) with matched lymph node metastasis (n=40) and 6 cases of oesophageal adenocarcinoma. Its associations with PRL1 and clinicopathological parameters were analysed. The results showed the frequency of PRL3 protein expression was significantly higher in ESCC (39/60, 65%) than in normal oesophageal mucosa (0/20, P<0.001); higher in ESCC with lymph node metastasis (30/40, 75%) than in ESCC without lymph node metastasis (9/20, P=0.022), as well as higher in metastatic ESCC in lymph node (38/40, 95%) than in the primary ESCC (39/60, 65%, P<0.001). PRL3 was expressed in 1 out of 6 oesophageal adenocarcinomas, but showed no nuclear staining of PRL1. Expression of PRL3 protein was positively associated with the grade and partially with the stage of ESCC. These results suggest that expression of PRL3 protein may be involved in the metastasis of ESCC and serve as a biomarker for prediction of ESCC metastasis.
Note: Wearable near-infrared spectroscopy imager for haired region
Authors: Kiguchi M. , Atsumori H. , Fukasaku I. , Kumagai Y. , Funane T. , Maki A. , Kasai Y. , Ninomiya A.
Published: May 2012

A wearable optical topography system was developed that is based on near-infrared spectroscopy (NIRS) for observing brain activity noninvasively including in regions covered by hair. An avalanche photo diode, high voltage dc-dc converter, and preamplifier were placed in an electrically shielded case to be safely mounted on the head. Rubber teeth and a glass rod were prepared to clear away hair and reach the scalp. These devices realized for the first time a wearable NIRS imager for any region of the cortex. The activity in the motor cortex during finger tapping was successfully observed.
Surface properties of stoichiometric and defect-rich indium oxide films grown by MOCVD
Authors: Himmerlich M. , Wang Ch. Y. , Cimalla V. , Ambacher O. , Krischok S.
Published: May 2012

The influence of metalorganic chemical vapor deposition growth conditions on the indium oxide surface properties is investigated using photoelectron spectroscopy. Particular attention is paid to nanocrystalline samples grown at fairly low temperatures which are known for their high sensitivity to ozone. The results are compared to measurements on In2O3 films in cubic and rhombohedral crystal structure. It is shown that the growth conditions have a strong impact on the physical properties and that samples grown at 200 °C or below are highly oxygen-deficient and rich in defects, influencing the surface chemical and electronic properties and resulting in high ozone sensitivity.
Efficient analysis of highly complex nuclear magnetic resonance spectra of flexible solutes in ordered liquids by using molecular dynamics
Authors: Weber Adrian C. J. , Pizzirusso Antonio , Muccioli Luca , Zannoni Claudio , Meerts W. Leo , de Lange Cornelis A. , Burnell E. Elliott
Published: May 2012

The NMR spectra of n-pentane as solute in the liquid crystal 5CB are measured at several temperatures in the nematic phase. Atomistic molecular dynamics simulations of this system are carried out to predict the dipolar couplings of the orientationally ordered pentane, and the spectra predicted from these simulations are compared with the NMR experimental ones. The simulation predictions provide an excellent starting point for analysis of the experimental NMR spectra using the covariance matrix adaptation evolutionary strategy. This shows both the power of atomistic simulations for aiding spectral analysis and the success of atomistic molecular dynamics in modeling these anisotropic systems.
Intermittent contact interaction between an atomic force microscope cantilever and a nanowire
Authors: Knittel I. , Ungewitter L. , Hartmann U.
Published: May 2012

We investigate in theory and experiment the intermittent contact interaction between an atomic force microscope (AFM) cantilever and a nanowire under ambient conditions. The nanowire is modeled as a spring reacting instantaneously to any change of the force between the wire and the cantilever. This implies that the cantilever is subject to an “effective” force-distance relation, containing not only the surface forces but also the deflection of the nanowire. Experimentally, CVD-grown tin oxide nanowires and lithographically structured silicon nanowire arrays were investigated by intermittent contact AFM. By comparison of experimental and simulated distance-dependent resonance curves it is found that the nanowires behave like “fast nanosprings” and that the adhesion force is one of the key factors determining distance-dependent resonance curves. The results are fully applicable to a scenario in which a cantilever equipped by a nanowire interacts with a surface.
Self consistent tight binding model for dissociable water
Authors: Lin You , Wynveen Aaron , Halley J. W. , Curtiss L. A. , Redfern P. C.
Published: May 2012

We report results of development of a self consistent tight binding model for water. The model explicitly describes the electrons of the liquid self consistently, allows dissociation of the water and permits fast direct dynamics molecular dynamics calculations of the fluid properties. It is parameterized by fitting to first principles calculations on water monomers, dimers, and trimers. We report calculated radial distribution functions of the bulk liquid, a phase diagram and structure of solvated protons within the model as well as ac conductivity of a system of 96 water molecules of which one is dissociated. Structural properties and the phase diagram are in good agreement with experiment and first principles calculations. The estimated DC conductivity of a computational sample containing a dissociated water molecule was an order of magnitude larger than that reported from experiment though the calculated ratio of proton to hydroxyl contributions to the conductivity is very close to the experimental value. The conductivity results suggest a Grotthuss-like mechanism for the proton component of the conductivity.
Exceptional high Seebeck coefficient and gas-flow-induced voltage in multilayer graphene
Authors: Li Xuemei , Yin Jun , Zhou Jianxin , Wang Qin , Guo Wanlin
Published: May 2012

Seebeck coefficient of graphene is an important parameter for defining its thermoelectric performance and thus practical applications, such as gas-flow-induced voltage. Here, we find a unique layer-dependence of the graphene Seebeck coefficient that exceptionally increases with increasing thickness to reach a peak value at six layers that is ∼77% higher than monolayer and ∼296% higher than graphite, unlike the monotonic decrease in electric resistance. However, the gas flow-induced voltage is significantly higher in 2, 4, 5, 6, and 7 layered graphene samples than in 1, 3, and 8 layered ones, against the prevailing wisdom that it should be proportional to Seebeck coefficient.
Preparation of PVA/Co/Ag film and evaluation of its magnetic and microstructural properties
Authors: Banerjee M. , Sachdev Preeti , Mukherjee G. S.
Published: May 2012

PVA/Co/Ag film has been prepared by sputtering Co followed by Ag in polyvinyl alcohol (PVA) matrix film by IBS technique, so as to get a 9 nm (thick) layer of Co metal nanoparticles followed by a protective 4 nm (thick) layer of Ag nanoparticles. Grazing incidence x-ray diffraction (GIXRD) pattern of the film reveals the formation of nanocrystalline Co with hcp phase. GIXRD pattern also indicates that there is no change in the crystalline structure of PVA even after sputtering of the metallic nanoparticles. The average particle size of Co nanoparticles as evaluated using Scherrer formula is found to be about 2.64 nm. UV visible absorption pattern of the film sample showed SPR peaks of Co and Ag metals in their nano size level embedded in the PVA matrix system. XPS study confirms the metallic nature of Co and Ag nanoparticles; and the depth profiling study reveals that both the metal nanoparticles have been embedded in the PVA matrix system. Surface morphology of such film has been studied using AFM; and the magnetic behaviour of the film studied by using MOKE shows soft ferromagnetic behaviour in this PVA/Co/Ag system.
Synergetic effects of double laser pulses for the formation of mild plasma in water: Toward non-gated underwater laser-induced breakdown spectroscopy
Authors: Sakka Tetsuo , Tamura Ayaka , Nakajima Takashi , Fukami Kazuhiro , Ogata Yukio H.
Published: May 2012

We experimentally study the dynamics of the plasma induced by the double-laser-pulse irradiation of solid target in water, and find that an appropriate choice of the pulse energies and pulse interval results in the production of an unprecedentedly mild (low-density) plasma, the emission spectra of which are very narrow even without the time-gated detection. The optimum pulse interval and pulse energies are 15–30 μs and about ∼1 mJ, respectively, where the latter values are much smaller than those typically employed for this kind of study. In order to clarify the mechanism for the formation of mild plasma we examine the role of the first and second laser pulses, and find that the first pulse produces the cavitation bubble without emission (and hence plasma), and the second pulse induces the mild plasma in the cavitation bubble. These findings may present a new phase of underwater laser-induced breakdown spectroscopy.
Electronic and optical properties of free-standing and supported vanadium nanowires
Authors: Singh Poorva , Nautiyal Tashi , Auluck Sushil
Published: May 2012

We have investigated theoretically the electronic and optical properties of free-standing and substrate-supported ultrathin nanowires (NWs) of the transition metal vanadium. Ground state of the structures studied, except free-standing zigzag geometry, is found to be magnetic in nature. We show that for some structures, study of the antiferromagnetic state necessitates considering various possible configurations. All the structures, except dimerized, show metallic behavior. Structure with helical geometry possesses decent value of magnetic moment and is exceptionally stable as well as most stiff of all the structures studied. The plasma frequency and dielectric function nicely exhibit the anisotropy due to one-dimensional nature of the nanowires. The latter is structure-dependent and markedly different from that of bulk. More realistic case of linear chains supported on a substrate shows fair impact of the substrate in comparison with free-standing case. There is substantial charge redistribution on relaxing the geometry. The d-states are in general shifted to lower energies and the peaks in the density of states are broadened, resulting in softening of the structures in the optical spectra.
Minimum quench power dissipation and current non-uniformity in international thermonuclear experimental reactor type NbTi cable-in-conduit conductor samples under direct current conditions
Authors: Rolando G. , van Lanen E. P. A. , Nijhuis A.
Published: May 2012

The level of current non-uniformity in NbTi cable-in-conduit conductors (CICCs) sections near the joints in combination with the magnetic field profile needs attention in view of proper joint design. The strand joule power and current distribution at quench under DC conditions of two samples of ITER poloidal field coil conductors, as tested in the SULTAN facility, and of the so called PFCI model coil insert, have been analyzed with the numerical cable model JackPot. The precise trajectories of all individual strands, joint design, cabling configuration, spatial distribution of the magnetic field, sample geometry, and experimentally determined interstrand resistance distributions have been taken into account. Although unable to predict the quench point due to the lack of a thermal-hydraulic routine, the model allows to assess the instantaneous strand power at quench and its local distribution in the cable once the quench conditions in terms of current and temperature are experimentally known. The analysis points out the relation of the above mentioned factors with the DC quench stability of both short samples and coils. The possible small scale and local electrical-thermal interactions were ignored in order to examine the relevance of such effects in the overall prediction of the CICC performance. The electromagnetic code shows an excellent quantitative predictive potential for CICC transport properties, excluding any freedom for matching the results. The influence of the local thermal effects in the modeling is identified as being marginal and far less than the generally accepted temperature margin for safe operation.
Lévy stable distributions via associated integral transform
Authors: Górska K. , Penson K. A.
Published: May 2012

We present a method of generation of exact and explicit forms of one-sided, heavy-tailed Lévy stable probability distributions gα(x), 0 ⩽ x < ∞, 0 < α < 1. We demonstrate that the knowledge of one such a distribution gα(x) suffices to obtain exactly \documentclass[12pt]{minimal}\begin{document}$g_{\alpha ^{p}}(x)$\end{document}gαp(x), p = 2, 3, …  . Similarly, from known gα(x) and gβ(x), 0 < α, β < 1, we obtain gαβ(x). The method is based on the construction of the integral operator, called Lévy transform, which implements the above operations. For α rational, α = l/k with l < k, we reproduce in this manner many of the recently obtained exact results for gl/k(x). This approach can be also recast as an application of the Efros theorem for generalized Laplace convolutions. It relies solely on efficient definite integration.
Chemisorption on semiconductors: The role of quantum corrections on the space charge regions in multiple dimensions
Authors: Ciucci Francesco , de Falco Carlo , Guzman Marcelo I. , Lee Sara , Honda Tomonori
Published: May 2012

The chemisorption of O2 on nanoscale n-doped CdS semiconductors is computed in terms of a Wolkenstein isotherm coupled to the Schrödinger Poisson equation. Present numerical results show the dependence of the chemisorbed charge and the differential capacitance on oxygen partial pressure. A comparison against the classical Poisson-Boltzmann approach shows a higher chemisorbed charge in the quantum model, but a greater differential capacitance in the classical case.
Experimental and simulation study of undesirable short-period deformation in piezoelectric deformable x-ray mirrors
Authors: Nakamori Hiroki , Matsuyama Satoshi , Imai Shota , Kimura Takashi , Sano Yasuhisa , Kohmura Yoshiki , Tamasaku Kenji , Yabashi Makina , Ishikawa Tetsuya , Yamauchi Kazuto
Published: May 2012

To construct adaptive x-ray focusing optics whose optical parameters can be varied while performing wavefront correction, ultraprecise piezoelectric deformable mirrors have been developed. We computationally and experimentally investigated undesirable short-period deformation caused by piezoelectric actuators adhered to the substrate during mirror deformation. Based on the results of finite element method analysis, shape measurements, and the observation of x-ray reflection images, a guideline is developed for designing deformable mirrors that do not have short-period deformation errors.
Osmotic virial coefficients for model protein and colloidal solutions: Importance of ensemble constraints in the analysis of light scattering data
Authors: Siderius Daniel W. , Krekelberg William P. , Roberts Christopher J. , Shen Vincent K.
Published: May 2012

Protein-protein interactions in solution may be quantified by the osmotic second virial coefficient (OSVC), which can be measured by various experimental techniques including light scattering. Analysis of Rayleigh light scattering measurements from such experiments requires identification of a scattering volume and the thermodynamic constraints imposed on that volume, i.e., the statistical mechanical ensemble in which light scattering occurs. Depending on the set of constraints imposed on the scattering volume, one can obtain either an apparent OSVC, A2,app, or the true thermodynamic OSVC, \documentclass[12pt]{minimal}\begin{document}${B_{22}^{osm}}$\end{document}B22osm, that is rigorously defined in solution theory [M. A. Blanco, E. Sahin, Y. Li, and C. J. Roberts, J. Chem. Phys. 134, 225103 (2011)10.1063/1.3596726]. However, it is unclear to what extent A2,app and \documentclass[12pt]{minimal}\begin{document}${B_{22}^{osm}}$\end{document}B22osm differ, which may have implications on the physical interpretation of OSVC measurements from light scattering experiments. In this paper, we use the multicomponent hard-sphere model and a well-known equation of state to directly compare A2,app and \documentclass[12pt]{minimal}\begin{document}${B_{22}^{osm}}$\end{document}B22osm. Our results from the hard-sphere equation of state indicate that A2,app underestimates \documentclass[12pt]{minimal}\begin{document}${B_{22}^{osm}}$\end{document}B22osm, but in a systematic manner that may be explained using fundamental thermodynamic expressions for the two OSVCs. The difference between A2,app and \documentclass[12pt]{minimal}\begin{document}${B_{22}^{osm}}$\end{document}B22osm may be quantitatively significant, but may also be obscured in experimental application by statistical uncertainty or non-steric interactions. Consequently, the two OSVCs that arise in the analysis of light scattering measurements do formally differ, but in a manner that may not be detectable in actual application.
Separation of blood cells using hydrodynamic lift
Authors: Geislinger T. M. , Eggart B. , Braunmüller S. , Schmid L. , Franke T.
Published: May 2012

Using size and deformability as intrinsic biomarkers, we separate red blood cells (RBCs) from other blood components based on a repulsive hydrodynamic cell-wall-interaction. We exploit this purely viscous lift effect at low Reynolds numbers to induce a lateral migration of soft objects perpendicular to the streamlines of the fluid, which closely follows theoretical prediction by Olla [J. Phys. II 7, 1533, (1997)]. We study the effects of flow rate and fluid viscosity on the separation efficiency and demonstrate the separation of RBCs, blood platelets, and solid microspheres from each other. The method can be used for continuous and label-free cell classification and sorting in on-chip blood analysis.
Ultrahigh electromechanical response in (1−x)(Na0.5Bi0.5)TiO3-xBaTiO3 single-crystals via polarization extension
Authors: Ge Wenwei , Luo Chengtao , Zhang Qinhui , Devreugd Chris P. , Ren Yang , Li Jiefang , Luo Haosu , Viehland D.
Published: May 2012

The dielectric, ferroelectric, and electric field-induced strain response of [001]-and [101]-oriented 0.944Na0.5Bi0.5TiO3-0.056BaTiO3 (0.944NBT-0.056BT) single crystals were investigated as a function of temperature and dc bias (E). An ultrahigh electromechanical response with large amplitude longitudinal piezoelectric coefficients as high as d33 = 2500 pm/V was found in [001]PC oriented 0.944NBT-0.056BT single crystals near a depolarization temperature of Td = 130 °C. In-situ XRD revealed that the enhanced piezoelectric properties resulted from a polarization extension between a polar pseudocubic phase with a slight tetragonal (P4bm) distortion and a polar tetragonal one with a large tetragonal distortion of c/a = 1.02. Our findings indicate a potential approach to high performance lead-free piezoelectrics, via polarization extension.
Nonreciprocal light transmission in silicon by Raman-induced asymmetry of the permittivity tensor
Authors: Krause Michael
Published: May 2012

We consider the effect of Raman-induced nonreciprocal light transmission in silicon and show that it can be understood as the consequence of the asymmetry of an effective permittivity tensor at the Stokes wavelength. This viewpoint enables the derivation of a necessary condition for this effect: the pumping electric field must have components along two different crystallographic axes which are oscillating out of phase with respect to each other.
Spin accumulation in a multi-arm Aharonov-Bohm-Fano interferometer
Authors: Gong Wei-Jiang , Han Yu , Kariuki Francis N. , Du An
Published: May 2012

The spin accumulation properties of a multi-arm Aharonov-Bohm-Fano interferometer are investigated by considering spin bias in the leads. We find that the spin accumulations in the quantum dots (QDs) can be adjusted independently by changing the magnetic fluxes through the sub-rings formed by the QD-lead and lead-lead couplings. When analyzing the quantum interference effect, we find that the Aharonov-Bohm-Fano interference mechanism is a necessary condition to realize the spin accumulation. Based on the numerical results, we propose that such a structure has a significant potential as a candidate for a spin-manipulating device.
High-aspect-ratio grooves fabricated in silicon by a single pass of femtosecond laser pulses
Authors: Ma Yuncan , Shi Haitao , Si Jinhai , Ren Hai , Chen Tao , Chen Feng , Hou Xun
Published: May 2012

High-aspect-ratio grooves have been fabricated in silicon by a single pass of femtosecond laser pulses in water and ambient air. Scanning electron microscopy and energy dispersive x-ray spectroscopy were employed to image for the morphology of the photoinduced grooves and analyze the chemical composition in the surrounding of the grooves. It was observed that the sidewall of the grooves fabricated in water was much smoother than that in ambient air, and there were homogeneous nano-scale protrusions on the sidewall of the grooves fabricated in water. Meanwhile, oxygen species, which was incorporated into the grooves fabricated in air, was not observed in those in water.
Acoustic transmission through asymmetric grating structures made of cylinders
Authors: Xu Shengjun , Qiu Chunyin , Liu Zhengyou
Published: May 2012

Based on the multiple scattering theory, we have developed a highly efficient numerical method to calculate the acoustic transmission and reflection coefficients for complex grating structures made of cylinders. This method can provide the detailed information for each independent diffraction order, which is particularly useful in studying the exotic transmission behavior through spatially asymmetric gratings. Our numerical results manifest that, in general, such gratings produce asymmetric transmission if only the frequency is high enough to create the nonzero order diffraction. An intuitive and valid scheme is further proposed to suppress the transmission along one of the incident directions, producing an almost unidirectional acoustic transmission. Such kind of unidirectional transmission could be very useful in designing acoustic rectifying devices.
Retention behavior of composites consisting of ferroelectric particles embedded in dielectric polymers
Authors: Lehnert T. , Adam J. , Veith M.
Published: May 2012

As ferroelectric ceramic/polymer composites may offer the possibility to lower the operating voltage of state of the art polymer ferroelectric memories, the retention behavior of these composites needs to be studied. This work presents for the first time the polarization decay of a ceramic/polymer composite memory and discusses some influencing parameters. The existence of a depolarization field in such particulate structures, which is responsible for the polarization loss is demonstrated by finite element simulations, and first theoretical predictions are generated how to reduce this depolarizing field. Interestingly, first results from the experimental approach of varying the ionic concentration in the surrounding medium of the particles contradict these theoretical assumptions.
Studying femtosecond-laser hyperdoping by controlling surface morphology
Authors: Winkler Mark T. , Sher Meng-Ju , Lin Yu-Ting , Smith Matthew J. , Zhang Haifei , Gradečak Silvija , Mazur Eric
Published: May 2012

We study the fundamental properties of femtosecond-laser (fs-laser) hyperdoping by developing techniques to control the surface morphology following laser irradiation. By decoupling the formation of surface roughness from the doping process, we study the structural and electronic properties of fs-laser doped silicon. These experiments are a necessary step toward developing predictive models of the doping process. We use a single fs-laser pulse to dope silicon with sulfur, enabling quantitative secondary ion mass spectrometry, transmission electron microscopy, and Hall effect measurements. These measurements indicate that at laser fluences at or above 4 kJ m−2, a single laser pulse yields a sulfur dose >(3 ± 1) × 1013 cm−2 and results in a 45-nm thick amorphous surface layer. Based on these results, we demonstrate a method for hyperdoping large areas of silicon without producing the surface roughness.
Electron kappa distribution and steady-state Langmuir turbulence
Authors: Yoon Peter H.
Published: May 2012

In a recent pair of papers, the present author discussed a self-consistent theory of asymptotically steady-state electron distribution function and Langmuir turbulence intensity in one [P. H. Yoon, Phys. Plasmas 18, 122303 (2011)] and three [P. H. Yoon, Phys. Plasmas 19, 012304 (2012)] dimensions. The resulting electron distribution function is a type of kappa distribution that features a non-Maxwellian energetic tail component. However, while the one-dimensional solution is rigorously correct, the three-dimensional solution, which was obtained using the cylindrical coordinate representation, contains two features that may be inconsistent for field-free plasmas. One is the assumption that the resonance condition can be approximated by ω-k·v≈ω-k∥v∥. Needless to say, this is not the most general condition. The second inconsistency is that while the electron distribution is isotropic in velocity, the Langmuir turbulence intensity depends on the wave propagation direction. While these features may not be too unrealistic in the presence of an implicit ambient magnetic field, they certainly cannot be correct if the plasma is genuinely unmagnetized. In the present paper, we rectify such shortcomings by properly reformulating the problem using a spherical coordinate system in a truly free-field plasma.
Quantum point contact with large subband energy spacings
Authors: Um Y. J. , Oh Y. H. , Seo M. , Lee S. , Chung Y. , Kim N. , Umansky V. , Mahalu D.
Published: May 2012

Quantum point contact (QPC) with an extra metallic gate in between the split gates of a conventional QPC was fabricated and studied. Clear conductance quantization was observed at 4.2 K when a proper positive voltage was set to the middle gate of the QPC. The maximum energy spacing between the ground and the first exited state of the QPC was around 7 meV which is at least a few times larger than that of conventional QPCs. Using same approach, a possibility of making a relatively clean and long 1D wire has been tested.
Transmission of electron through monolayer graphene laser barrier
Authors: Sinha C. , Biswas R.
Published: May 2012

The present theoretical model deals with the transmission property of the Dirac fermions in the Floquet sidebands for the laser radiated graphene nanostructure. The laser assisted structure behaves as a tunneling barrier that leads to asymmetric transmission around the normal to the interface and is capable to confine the massless Dirac particles in a monolayer graphene strip. The absence of the Klein tunneling and the presence of a large number of controlling parameters would make the time dependent vector potential barrier superior over the electrostatic and magnetic barriers towards the opto-electronic device fabrication.
Inter-wafer bonding strength characterization by laser-induced shock waves
Authors: Youssef George , Moulet Caroline , Goorsky Mark S. , Gupta Vijay
Published: May 2012

A previously developed laser spallation experiment to measure the tensile strength of thin film interfaces is extended to quantify the intrinsic tensile strength of bonded wafers. In this experiment, a laser generated compressive stress wave on the back surface of one wafer reflects into a tensile wave after reflecting from the free surface of the second wafer to separate the inter-wafer bond. Optical interferometery is used in conjunction with a wave mechanics simulation to quantify the bond strength. The technique was used to study the dependence of the inter-wafer bond strength on the annealing temperature which varied between 200 °C and 1100 °C. A peak bond strength value of 3.91 GPa is reported at 1100 °C. We show that the measured bond strength values compares well with the bonding energies measured by alternate methods.
Surface chemistry and morphology effects on optoelectronic transport at metal/nanostructured silicon/silicon structures
Authors: Ambrico Marianna , Di Mundo Rosa , Francesco Ambrico Paolo , d’Agostino Riccardo , Ligonzo Teresa , Palumbo Fabio
Published: May 2012

This work enlighten on the modification of the electrical and optoelectronic properties at metal/silicon interface, where the silicon surface is nanostructured by single step mask-less CF4 plasma in reactive ion etching mode. The electrical transport across metal/nanotextured silicon/silicon structure has been correlated with morphological variations of surface topological features and chemistry. The results evidence that such nanostructures enhance the photovoltaic behavior and affect electrical and optoelectronic transport to a different extent, depending not only on surface texturing but also on surface chemistry.