bluuebunny/crossref_metadata_2025 huggingface dataset:
Micromanipulation medium osmolarity compromises zebrafish (Danio rerio) embryo and cell survival in chimaerism experiments
Authors: Cardona-Costa J. , Francisco-Simão M. , Pérez-Camps M. , García-Ximénez F.
Published: November 2009

In zebrafish chimaerism experiments, the cell injection can involve intra-embryonic cell lyses by osmolar effects. Moreover, the donor cells can be injured during manipulation due to osmolar changes into the transplant pipette. Therefore, the present study aimed to assess the effects of manipulation medium osmolarity on embryonic survival and donor cell viability.

In Experiment I, 0.1 μl to 0.15 μl approximately of an isosmolar solution (300 mOsm) was injected into recipient embryos, which were kept at 300 (E1) or 30 mOsm (E2). Survival at day 1 was significantly higher in the E2 group than in E1 (E1: 68% vs E2: 81%, p < 0.05), but after 5 days embryo survival in the E1 group was slightly higher. In Experiment II, donor cells from zebrafish embryos were exposed (or not) to a possible osmolarity change (inner pipette medium: 300 mOsm vs external medium: 30 or 300 mOsm) using two different micropipette outer diameters, 40–50 and 60–70 μm. Cell mechanical damage was detected in the 40–50 μm pipette (p < 0.05), but not by the handling medium osmolarity. Results recommend the use of a 300 mOsm manipulation medium and bore-sized pipettes adjusted as closely as possible to the donor cell size.
Effects of a multifaceted treatment program for executive dysfunction after acquired brain injury on indications of executive functioning in daily life
Authors: SPIKMAN JACOBA M. , BOELEN DANIELLE H.E. , LAMBERTS KIRSTEN F. , BROUWER WIEBO H. , FASOTTI LUCIANO
Published: November 2009

A multicenter randomized control trial (RCT) was conducted to evaluate the effects of a treatment for dysexecutive problems after acquired brain injury (ABI) on daily life functioning. Seventy-five ABI patients were randomly allocated to either the experimental treatment, multifaceted strategy training for executive dysfunction, or a control treatment, computerized cognitive function training. Assessment took place before, directly after, and 6 months post-treatment. The primary outcome measure, the Role Resumption List (RRL), and two other follow-up measures, the Treatment Goal Attainment (TGA) and the Executive Secretarial Task (EST), were indications of daily life executive functioning. The experimental group improved significantly more over time than the controls on the RRL and attained significantly higher scores on the TGA and EST. We conclude that our treatment has resulted in significant improvements of executive functioning in daily life, lasting at least 6 months post-treatment. Although control patients’ satisfaction and subjective well-being were at the same level, the experimental group had better abilities to set and accomplish realistic goals, to plan, initiate, and regulate a series of real-life tasks, and to resume previous roles with respect to work, social relations, leisure activities, and mobility. (JINS, 2010, 16, 118–129.)
Extreme prematurity and neuropsychological outcome in the preschool years
Authors: RAZ SARAH , DEBASTOS ANGELA K. , NEWMAN JULIE BAPP , BATTON DANIEL
Published: November 2009

With the increasing survival of extremely preterm (EP) birth infants in the surfactant era, the longer-term outcome of infants born at the threshold of viability has become a vital topic of study. The goal of this investigation was twofold. First, while taking into account the influence of sociodemographic confounds, we wished to investigate neuropsychological outcome differences between two groups of EP preschoolers: 23–24 weeks (n= 20), and 25–26 weeks’ (n= 21) gestation at delivery. Second, we wished to explore whether, within the population of EP preschoolers, gestational maturity accounts for a unique portion of the variance in neuropsychological outcome, over and above the variance explained by ante-, peri-, and neonatal complications, or treatment factors. The findings revealed group differences, ranging from .70 to .80 of a standard deviation in general intellectual abilities, nonverbal intelligence, and global motor performance, in favor of the more mature EP group. Additionally, gestational maturity was found to explain a unique portion of the variance in global intellectual and motor abilities. These findings are interpreted from the perspective that gestational age is an index of the vulnerability of the central nervous system to disruption of developmentally regulated processes. (JINS, 2010,16, 169–179.)
Using probabilistic climate change information from a multimodel ensemble for water resources assessment
Authors: Manning L. J. , Hall J. W. , Fowler H. J. , Kilsby C. G. , Tebaldi C.
Published: November 2009

Increasing availability of ensemble outputs from general circulation models (GCMs) and regional climate models (RCMs) permits fuller examination of the implications of climate uncertainties in hydrological systems. A Bayesian statistical framework is used to combine projections by weighting and to generate probability distributions of local climate change from an ensemble of RCM outputs. A stochastic weather generator produces corresponding daily series of rainfall and potential evapotranspiration, which are input into a catchment rainfall‐runoff model to estimate future water abstraction availability. The method is applied to the Thames catchment in the United Kingdom, where comparison with previous studies shows that different downscaling methods produce significantly different flow predictions and that this is partly attributable to potential evapotranspiration predictions. An extended sensitivity test exploring the effect of the weights and assumptions associated with combining climate model projections illustrates that under all plausible assumptions the ensemble implies a significant reduction in catchment water resource availability.
Evaluation of Multiangle Imaging Spectroradiometer cloud motion vectors using NOAA radar wind profiler data
Authors: Hinkelman Laura M. , Marchand Roger T. , Ackerman Thomas P.
Published: November 2009

Cloud motion vectors obtained stereoscopically by the Multiangle Imaging Spectroradiometer (MISR) are evaluated. The reference data for this assessment is taken from 23 sites in NOAA's radar wind profiler network located across the central United States. Agreement between the two data sets is appraised as a function of cloud top height, MISR wind retrieval quality estimates, and version of the stereoscopic retrieval algorithm. For “Best Winds” retrievals, the comparison between matched MISR and NOAA profiler wind components yields biases of about 1.3 m s−1 with standard deviations of 4–6 m s−1. Comparisons are better for winds retrieved close to the surface than at high altitudes. Updates to the MISR stereoscopic retrieval algorithm have improved the level of agreement over time. Tightening of MISR data quality standards has also improved agreement, but at the expense of decreasing the number of available MISR wind vector estimates.
Rainfall redistribution in a tropical forest: Spatial and temporal patterns
Authors: Zimmermann Alexander , Zimmermann Beate , Elsenbeer Helmut
Published: November 2009

The investigation of throughfall patterns has received considerable interest over the last decades. And yet, the geographical bias of pertinent previous studies and their methodologies and approaches to data analysis cast a doubt on the general validity of claims regarding spatial and temporal patterns of throughfall. We employed 220 collectors in a 1‐ha plot of semideciduous tropical rain forest in Panama and sampled throughfall during a period of 14 months. Our analysis of spatial patterns is based on 60 data sets, whereas the temporal analysis comprises 91 events. Both data sets show skewed frequency distributions. When skewness arises from large outliers, the classical, nonrobust variogram estimator overestimates the sill variance and, in some cases, even induces spurious autocorrelation structures. In these situations, robust variogram estimation techniques offer a solution. Throughfall in our plot typically displayed no or only weak spatial autocorrelations. In contrast, temporal correlations were strong, that is, wet and dry locations persisted over consecutive wet seasons. Interestingly, seasonality and hence deciduousness had no influence on spatial and temporal patterns. We argue that if throughfall patterns are to have any explanatory power with respect to patterns of near‐surface processes, data analytical artifacts must be ruled out lest spurious correlation be confounded with causality; furthermore, temporal stability over the domain of interest is essential.
Ratio of 36Cl/Cl in ground ice of east Siberia and its application for chronometry
Authors: Blinov A. , Alfimov V. , Beer J. , Gilichinsky D. , Schirrmeister L. , Kholodov A. , Nikolskiy P. , Opel T. , Tikhomirov D. , Wetterich S.
Published: November 2009

Abundance of the cosmogenic nuclide chlorine‐36 (36Cl) was measured together with the chloride (Cl−) concentration in different horizons of Quaternary permafrost samples collected from various types of ground ice in the northeastern part of Siberia. The 36Cl/Cl in 32 samples ranged in value from 2.4 × 10−14 to 1.4 × 10−12. Nonetheless, after a few extreme values were excluded, these 36Cl/Cl ratios provided a local permafrost chronometry. The general concordance of the modeled ages with geological expectations and other chronological methods supports the potential power of the proposed dating method. However, the large observed change in ratios from higher to lower values during the transition from Last Glacial Maximum to Holocene climatic conditions remains unexplained. An attempt to make use of the corresponding beryllium‐10 (10Be) absolute concentrations in the same samples failed because input of 10Be attached to particulate matter into permafrost is unknown. Further 36Cl/Cl serial measurements of modern precipitation and fossil ground ice are needed to refine this dating method into a practical tool with a clear protocol.
Anomalously deep mantle transition zone below Central Europe: Evidence of lithospheric instability
Authors: Hetényi György , Stuart Graham W. , Houseman Gregory A. , Horváth Frank , Hegedűs Endre , Brückl Ewald
Published: November 2009

The depths of the 410 and 660 km phase transitions provide critical information on the thermal state of the mantle transition zone (MTZ) and, by implication, on the circulation of the upper mantle. We analyze converted seismic waves to produce a high resolution image of these discontinuities beneath the Pannonian Basin of Central Europe. Models to explain the extension of the basin in the Middle Miocene involve subduction roll‐back and gravitational instability of an over‐thickened lithosphere. We find that cold dense material appears to have accumulated in the MTZ, consistent with the idea of supply from several subduction episodes, or upper mantle overturn. Variation in depth of the 660 km discontinuity by as much as 40 km suggests that cold lithospheric mantle is ponding on top of this phase transition. Where the phase transition is deepest, eventual transfer of this material into the lower mantle may be expected to develop.
From earthquake centroid to spatial‐temporal rupture evolution: Mw 6.3 Movri Mountain earthquake, June 8, 2008, Greece
Authors: Gallovič F. , Zahradník J. , Křížová D. , Plicka V. , Sokos E. , Serpetsidaki A. , Tselentis G‐A.
Published: November 2009

We propose a new strategy to reveal the spatial‐temporal evolution of the earthquake rupture process from near‐regional data, without assuming a constant rupture velocity. The approach is based on a conjugate gradient method, for which we express analytically the required waveform‐misfit derivative with respect to slip on the fault. The derivative is given by back‐propagation of residual seismograms towards the source. A good initial source approximation is necessary, being obtained from hypocenter location and centroid‐moment tensor solution. The iterative approach then gradually reveals major characteristics of the source process. As an application, we investigate a line source model of a damaging Mw6.3 earthquake in Greece, revealing predominantly unilateral rupture propagation and two or three main slip patches, one of which being significantly delayed, indicating a temporary rupture arrest. The region of largest slip coincides with the region of least abundant aftershocks between hypocenter and centroid. The method has application potential for shakemaps, emergency response, and/or aftershock hazard assessment.
Spectroscopic capture of 1 Hz volcanic SO2 fluxes and integration with volcano geophysical data
Authors: McGonigle A. J. S. , Aiuppa A. , Ripepe M. , Kantzas E. P. , Tamburello G.
Published: November 2009

Here we present a novel spectroscopic approach to capturing, with unprecedented time resolution and accuracy, volcanic SO2 fluxes. This is based on two USB2000 spectrometers, coupled to cylindrical lens telescopes, each collecting light which has transited horizontal sections of the rising plume. We report on field data from Stromboli volcano, in which the entire emission rate from the volcano was measured, as well as flux signatures associated with individual crater explosions. The latter were integrated with seismic and thermal data, demonstrating correlations in both cases, and representing the first such geophysical‐geochemical data corroboration on this timescale. Such a holistic empirical capability could significantly expedite our understanding of explosive volcanic processes.
A generalized model for the air‐sea transfer of dimethyl sulfide at high wind speeds
Authors: Vlahos Penny , Monahan Edward C.
Published: November 2009

The air‐sea exchange of dimethyl sulfide (DMS) is an important component of ocean biogeochemistry and global climate models. Both laboratory experiments and field measurements of DMS transfer rates have shown that the air‐sea flux of DMS is analogous to that of other significant greenhouse gases such as CO2 at low wind speeds (<10 m/s) but that these DMS transfer rates may diverge from other gases as wind speeds increase. Herein we provide a mechanism that predicts the attenuation of DMS transfer rates at high wind speeds. The model is based on the amphiphilic nature of DMS that leads to transfer delay at the water‐bubble interface and becomes significant at wind speeds above >10 m/s. The result is an attenuation of the dimensionless Henry's Law constant (H) where (Heff = H/(1 + (Cmix/Cw) ΦB) by a solubility enhancement Cmix/Cw, and the fraction of bubble surface area per m2 surface ocean.
Improved water allocation utilizing probabilistic climate forecasts: Short‐term water contracts in a risk management framework
Authors: Sankarasubramanian A. , Lall Upmanu , Souza Filho Francisco Assis , Sharma Ashish
Published: November 2009

Probabilistic, seasonal to interannual streamflow forecasts are becoming increasingly available as the ability to model climate teleconnections is improving. However, water managers and practitioners have been slow to adopt such products, citing concerns with forecast skill. Essentially, a management risk is perceived in “gambling” with operations using a probabilistic forecast, while a system failure upon following existing operating policies is “protected” by the official rules or guidebook. In the presence of a prescribed system of prior allocation of releases under different storage or water availability conditions, the manager has little incentive to change. Innovation in allocation and operation is hence key to improved risk management using such forecasts. A participatory water allocation process that can effectively use probabilistic forecasts as part of an adaptive management strategy is introduced here. Users can express their demand for water through statements that cover the quantity needed at a particular reliability, the temporal distribution of the “allocation,” the associated willingness to pay, and compensation in the event of contract nonperformance. The water manager then assesses feasible allocations using the probabilistic forecast that try to meet these criteria across all users. An iterative process between users and water manager could be used to formalize a set of short‐term contracts that represent the resulting prioritized water allocation strategy over the operating period for which the forecast was issued. These contracts can be used to allocate water each year/season beyond long‐term contracts that may have precedence. Thus, integrated supply and demand management can be achieved. In this paper, a single period multiuser optimization model that can support such an allocation process is presented. The application of this conceptual model is explored using data for the Jaguaribe Metropolitan Hydro System in Ceara, Brazil. The performance relative to the current allocation process is assessed in the context of whether such a model could support the proposed short‐term contract based participatory process. A synthetic forecasting example is also used to explore the relative roles of forecast skill and reservoir storage in this framework.
A dimensionless number describing the effects of recharge and geometry on discharge from simple karstic aquifers
Authors: Covington M. D. , Wicks C. M. , Saar M. O.
Published: November 2009

The responses of karstic aquifers to storms are often used to obtain information about aquifer geometry. In general, spring hydrographs are a function of both system geometry and recharge. However, the majority of prior work on storm pulses through karst has not studied the effect of recharge on spring hydrographs. To examine the relative importance of geometry and recharge, we break karstic aquifers into elements according to the manner of their response to transient flow and demonstrate that each element has a characteristic response timescale. These fundamental elements are full pipes, open channels, reservoir/constrictions, and the porous matrix. Taking the ratio of the element timescale with the recharge timescale produces a dimensionless number, γ, that is used to characterize aquifer response to a storm event. Using sets of simulations run with randomly selected element parameters, we demonstrate that each element type has a critical value of γ below which the shape of the spring hydrograph is dominated by the shape of the recharge hydrograph and above which the spring hydrograph is significantly modified by the system geometry. This allows separation of particular element/storm pairs into recharge‐dominated and geometry‐dominated regimes. While most real karstic aquifers are complex combinations of these elements, we draw examples from several karst systems that can be represented by single elements. These examples demonstrate that for real karstic aquifers full pipe and open channel elements are generally in the recharge‐dominated regime, whereas reservoir/constriction elements can fall in either the recharge‐ or geometry‐dominated regimes.
Mexico at the Vanguard: A New Era in Medicines of Biotechnological Origin
Authors: Boardman Ernesto Saro
Published: November 2009

This paper seeks to highlight Mexico's interest in being at the forefront in Latin America and at the same time at the international level with the major players in the field of biotech medicines. Mexico has just adopted an amendment to the General Health Law that would allow the regulatory approval of biocomparable drugs (some countries refer to these as biosimilar or biogeneric drugs). Such reform consists in the incorporation of Article 222 Bis, which describes what is regarded as a biotechnology medicine, distinguishes between innovative and biocomparable medicines, sets the requirements to obtain sanitary registration and for marketing, describes the regulations regarding the pharmacovigilance of these products, as well as the studies that are necessary to demonstrate the quality, safety and efficacy of a biocomparable medicine which is supported with reference to an innovative medicine, and taking into consideration the Opinion of the Committee of New Molecules through the Subcommittee for the Evaluation of Biotechnology Products. This amendment also includes the assignment of the same International Non-propriety Name (INN) as for the reference product. The goal of the reform is to encourage competitiveness in Mexico by regulating the manufacture and approval of these medicines making them more affordable and hence fostering their access to the population.
Non-contact detection of myocardium’s mechanical activity by ultrawideband RF-radar and interpretation applying electrocardiography
Authors: Thiel F. , Kreiseler D. , Seifert F.
Published: November 2009

Electromagnetic waves can propagate through the body and are reflected at interfaces between materials with different dielectric properties. Therefore the reason for using ultrawideband (UWB) radar for probing the human body in the frequency range from 100 MHz up to 10 GHz is obvious and suggests an ability to monitor the motion of organs within the human body as well as obtaining images of internal structures. The specific advantages of UWB sensors are high temporal and spatial resolutions, penetration into object, low integral power, and compatibility with established narrowband systems. The sensitivity to ultralow power signals makes them suitable for human medical applications including mobile and continuous noncontact supervision of vital functions. Since no ionizing radiation is used, and due to the ultralow specific absorption rate applied, UWB techniques permit noninvasive sensing with no potential risks. This research aims at the synergetic use of UWB sounding combined with magnetic resonance imaging (MRI) to gain complementary information for improved functional diagnosis and imaging, especially to accelerate and enhance cardiac MRI by applying UWB radar as a noncontact navigator of myocardial contraction. To this end a sound understanding of how myocardial’s mechanic is rendered by reflected and postprocessed UWB radar signals must be achieved. Therefore, we have executed the simultaneous acquisition and evaluation of radar signals with signals from a high-resolution electrocardiogram. The noncontact UWB illumination was done from several radiographic standard positions to monitor selected superficial myocardial areas during the cyclic physiological myocardial deformation in three different respiratory states. From our findings we could conclude that UWB radar can serve as a navigator technique for high and ultrahigh field magnetic resonance imaging and can be beneficial preserving the high resolution capability of this imaging modality. Furthermore it can potentially be used to support standard electrocardiography (ECG) analysis by complementary information where sole ECG analysis fails, e.g., electromechanical dissociation.
Free flexural vibration studies of double-walled carbon nanotubes with different boundary conditions and modeled as nonlocal Euler beams via the Galerkin method
Authors: Shakouri A. , Lin R. M. , Ng T. Y.
Published: November 2009

In this work, a numerical Galerkin approach which can handle different boundary conditions in a general manner is presented to study the free vibration of double-walled carbon nanotubes (DWCNTs) modeled as nonlocal Euler beams. The effects of small scale, different boundary conditions, and geometrical parameters on the vibration of DWCNTs are examined in detail. It is also observed from the numerical results that the higher modes of DWCNT vibration (where the inner and outer nanotubes vibrate out of phase) are dominated by van der Waals interaction between the inner and outer nanotubes, and small scale effect and boundary conditions are noted to have minimal consequence on the first higher natural frequency mode of a DWCNT.
Direct high-resolution ion beam-profile imaging using a position-sensitive Faraday cup array
Authors: Panitzsch Lauri , Stalder Michael , Wimmer-Schweingruber Robert F.
Published: November 2009

Ion sources have wide-spread use in a multitude of applications. For many, an accurate knowledge, or better, an accurate imaging, of the beam profile and intensity is an important criterion. We are developing an ion source to calibrate instruments for space-based measurements of solar wind and suprathermal particles in the energy range from below 1 keV/nuc to above 200 keV/nuc. In order to establish accurate beam profiles for calibration purposes, we have developed a new method based on an array of very small (∅=0.3mm) Faraday cups. Here, we describe the experimental setup and discuss how to achieve several requirements such as a large thermal load due to the ∼40W of beam power.
Magnetoresistance and electroresistance of highly resistive states in thin nonhomogeneous La0.67Ca0.33MnO3 films
Authors: Ašmontas S. , Anisimovas F. , Gradauskas J. , Maneikis A. , Kiprijanovič O. , Vengalis B.
Published: November 2009

The magnetoresistive and electroresistive properties of thin nonhomogeneous La0.67Ca0.33MnO3 films have been investigated after thermocycling from 200 to 80 K. Highly resistive states with an additional low temperature resistance peak near 95 K were revealed in the films using probe currents as low as 1 μA. The film resistance at the peak is sensitive to the probe current strength and the applied magnetic field. The highly resistive state is metastable and is associated with the formation of martensitic inclusions during the thermocycling. The exhibition of memory effects during the cooling also suggests the idea of the presence of martensitic-type transformations.
Drift-diffusion modeling of photocurrent transients in bulk heterojunction solar cells
Authors: Hwang Inchan , McNeill Christopher R. , Greenham Neil C.
Published: November 2009

We utilize a time-dependent drift-diffusion model incorporating electron trapping and field-dependent charge separation to explore the device physics of organic bulk-heterojunction solar cells based on blends of poly(3-hexylthiophene) (P3HT) with a red polyfluorene copolymer. The model is used to reproduce experimental photocurrent transients measured in response to a step-function excitation of light of varied intensity. The experimental photocurrent transients are characterized by (i) a fast rise of order 1 μs followed by (ii) a slow rise of order 10–100 μs that evolves into a transient peak at high intensity, (iii) a fast decay component after turn-off and (iv) a long-lived tail with magnitude that does not scale linearly with light intensity or steady-state photocurrent. The fast rise and decay components are explained by the transport of mobile carriers while the slow rise and decay components are explained by slower electron trapping and detrapping processes. The transient photocurrent peak at high intensities with subsequent decay to the steady-state value is explained by trap-mediated space-charge effects. The build-up of trapped electrons in the device produces reduction in the strength of the electric field near the transparent anode that increases the likelihood of bimolecular recombination, and lowers the overall efficiency of charge dissociation in the device. Notably the model demonstrates that a reduction in free charge generation rate by space-charge effects is as significant as bimolecular recombination in this device assuming Langevin-type bimolecular recombination. The model is also used to explore the dynamics of charge separation with an upper bound of 50 ns set for the lifetime of electron-hole pairs, and to provide an estimate of the trap density of 1.3×1022 m−3.
Magnetic moment investigation by frequency mixing techniques
Authors: Teliban I. , Thede C. , Chemnitz S. , Bechtold C. , Quadakkers W. J. , Schütze M. , Quandt E.
Published: November 2009

Gas turbines and other large industrial equipments are subjected to high-temperature oxidation and corrosion. Research and development of efficient protective coatings is the main task in the field. Also, knowledge about the depletion state of the coating during the operation time is important. To date, practical nondestructive methods for the measurement of the depletion state do not exist. By integrating magnetic phases into the coating, the condition of the coating can be determined by measuring its magnetic properties. In this paper, a new technique using frequency mixing is proposed to investigate the thickness of the coatings based on their magnetic properties. A sensor system is designed and tested on specific magnetic coatings. New approaches are proposed to overcome the dependency of the measurement on the distance between coil and sample that all noncontact techniques face. The novelty is a low cost sensor with high sensibility and selectivity which can provide very high signal-to-noise ratios. Prospects and limitations are discussed for future use of the sensor in industrial applications.
Size quantization effect in highly stable UV emitting HgTe nanoparticles: Structure and optical properties
Authors: Hussain A. M. P. , Sarangi S. N. , Sahu S. N.
Published: November 2009

We report a simple one pot aqueous chemical synthesis route to fabricate very small and highly stable HgTe nanoparticles (NPs) capped with L-cysteine ethyl ester hydrochloride (LEEH). The LEEH concentration has found to be critical for desired size NP synthesis. Structural analyses by grazing angle x-ray diffraction and high resolution electron microscopy studies indicate HgTe NPs to exhibit a fcc phase with ⟨111⟩ prominent reflection having monodispersed NP size of around 2.0 nm. A strong size quantization effect marked by a prominent excitonic absorption at 4.436 eV blueshifted by 4.586 eV from the bulk band gap value has been observed in their optical absorption studies. A strong and narrow Gaussian fluorescence emission at 3.3 eV has been observed for 2.0 nm NP size whose width is being narrowed down with increasing LEEH concentration. The strong UV range absorption and emission have been observed for the first time in HgTe NPs.
Magnetic frustration effect in Mn-rich Sr2Mn1−xFexMoO6 system
Authors: Poddar Asok , Mazumdar Chandan
Published: November 2009

Variation in lattice parameters and magnetic properties of Sr2Mn1−xFexMoO6 (0≤x≤0.4) has been studied in the present work. Our findings suggest that the crystal structures at room temperature for all the compositions studied here are pseudocubic in nature. Substitution of as small as 10% Fe in place of Mn destroys the long range antiferromagnetic ordering observed in Sr2MnMoO6 and introduces local magnetic frustration, i.e., short range ferromagnetic interactions centered around the substituted Fe atoms, although the shape of the magnetic susceptibility creates an illusion of antiferromagnetic ordering. Different local structural environments around Mn and Fe atoms are thought to be responsible for the presence of such magnetic frustration. The results have been compared with those observed previously in SrLaMnMoO6. Our detailed measurements and interpretations are clearly at variance with the magnetic phase diagrams of Mn-rich phases of Sr2Mn1−xFexMoO6 compounds reported earlier, although the experimental results appear to be similar in both cases.
Temperature-dependent electrical behavior of La0.7Sr0.3MnO3-buffered Bi0.9La0.1FeO3 thin films
Authors: Wang Y. , Wang J.
Published: November 2009

Temperature-dependent ferroelectric and dielectric behaviors of La0.7Sr0.3MnO3-buffered Bi0.9La0.1FeO3 thin films were investigated. It was observed that the coercive voltage remarkably increases with decreasing temperature, and for a fixed driving voltage the area of hysteresis loop demonstrates a maximum at a certain temperature, revealing the competition between the coercivity and driving voltage. The dielectric constant versus ac electric field evolves from the nonlinear behavior at room temperature, which is ascribed to the reversible bending movement of domain walls, to the linear Rayleigh law at 90 K, indicating the increased density of pinning centers and suppressed domain wall motion. The fatigue resistance is deteriorated at the low temperature as a result of the enhanced domain pinning.
Quantum scattering of relativistic particles in Safko–Witten spacetime
Authors: Mota Herondy F. S. , Bezerra V. B.
Published: November 2009

Relativistic quantum particles are considered in the background gravitational field due to a tubular matter source with an axial interior magnetic field and a vanishing exterior magnetic field, which is a solution of the combined Einstein–Maxwell fields with cylindrical symmetry. In this background, whose gravitational field outside the tubular matter source is locally flat, we analyze the problem concerning the scattering of scalar and spinor particles and show up that this process depends on the geometrical features of the gravitational field in the interior region as well as on the topological features of the gravitational field in the exterior region.
Angular normal modes of a circular Coulomb cluster
Authors: Lupinski L. W. , Madsen M. J.
Published: November 2009

We investigate the angular normal modes for small oscillations about an equilibrium of a single-component Coulomb cluster confined by a radially symmetric external potential to a circle. The dynamical matrix for this system is a Laplacian symmetrically circulant matrix and this result leads to an analytic solution for the eigenfrequencies of the angular normal modes. We also show the limiting dependence of the largest eigenfrequency for large numbers of particles.
A diffraction-limited scanning system providing broad spectral range for laser scanning microscopy
Authors: Yu Jiun-Yann , Liao Chien-Sheng , Zhuo Zong-Yan , Huang Chen-Han , Chui Hsiang-Chen , Chu Shi-Wei
Published: November 2009

Diversified research interests in scanning laser microscopy nowadays require broadband capability of the optical system. Although an all-mirror-based optical design with a suitable metallic coating is appropriate for broad-spectrum applications from ultraviolet to terahertz, most researchers prefer lens-based scanning systems despite the drawbacks of a limited spectral range, ghost reflection, and chromatic aberration. One of the main concerns is that the geometrical aberration induced by off-axis incidence on spherical mirrors significantly deteriorates image resolution. Here, we demonstrate a novel geometrical design of a spherical-mirror-based scanning system in which off-axis aberrations, both astigmatism and coma, are compensated to reach diffraction-limited performance. We have numerically simulated and experimentally verified that this scanning system meets the Marechàl condition and provides high Strehl ratio within a 3°×3° scanning area. Moreover, we demonstrate second-harmonic-generation imaging from starch with our new design. A greatly improved resolution compared to the conventional mirror-based system is confirmed. This scanning system will be ideal for high-resolution linear/nonlinear laser scanning microscopy, ophthalmoscopic applications, and precision fabrications.
Ultrasonic harmonic generation from fatigue-induced dislocation substructures in planar slip metals and assessment of remaining fatigue life
Authors: Cantrell John H.
Published: November 2009

An analytical model is presented of the microelastic-plastic nonlinearities resulting from the interactions of a stress perturbation with dislocation substructures and cracks that evolve during cyclic fatigue of planar slip metals. The interactions are quantified by a material nonlinearity parameter β extracted from acoustic (ultrasonic) harmonic generation measurements. The β parameter for a given fatigue state is highly sensitive to the volume fractions of active persistent Luders bands (PLBs) and PLB internal stresses, as well as to the densities, loop lengths, and dipole heights of the dislocation monopoles and dipoles that form the PLBs. The β parameter is predicted to increase monotonically with the increase in the hardness of the metal during cyclic loading, thus allowing an unambiguous assessment of the remaining life of the material. The model is applied to the calculation of β as a function of percent full fatigue life of IN100 nickel-base superalloy. The theoretical predictions are in good agreement with experimental measurements reported in the literature of IN100 samples fatigued in strain-controlled, low cycle, fully reversed loading.
Nonlinear refraction properties of nickel oxide thin films at 800 nm
Authors: de Melo Ronaldo P. , da Silva Blenio J. P. , dos Santos Francisco Eroni P. , Azevedo A. , de Araújo Cid B.
Published: November 2009

Measurements of the nonlinear refractive index, n2, of nickel oxide films prepared by controlled oxidation of nickel films deposited on substrates of soda-lime glass are reported. The structure and morphology of the samples were characterized by scanning electron microscopy, atomic force microscopy, and x-ray diffractometry. Samples of excellent optical quality were prepared. The nonlinear measurements were performed using the thermally managed eclipse Z-scan technique at 800 nm. A large value of n2≈10−12 cm2/W and negligible nonlinear absorption were obtained.
A criterion for evaluating glass-forming ability of alloys
Authors: Zhang Guo-Hua , Chou Kuo-Chih
Published: November 2009

A criterion defined as θ=(Tx+Tg)/Tl[(Tx−Tg)/Tl]α (where Tx is the onset crystallization temperature, Tg is the glass transition temperature, Tl is liquidus temperature, and α is an exponent) is proposed to evaluate the glass-forming ability of alloy systems. Regression analysis between the logarithm of the critical cooling rate ln Rc and θ yields value of α=0.0728. There exists a fine linear relationship between criterion θ and ln Rc with a coefficient of determination R2=0.942. The obtained relationship can be expressed as: ln Rc=(30.10±0.91)−(27.93±0.97) θ. The comparisons of θ with all other relevant parameters: φ{=Trg[(Tx−Tg)/Tg]0.143}, γ[=Tx/(Tl+Tg)], Trg(=Tg/Tl), β[=TxTg/(Tl−Tx)2], δ[=Tx/(Tl−Tg)] show that this criterion has the best ability for evaluating the GFA of alloys.
Analysis of inhomogeneous Ge/SiC heterojunction diodes
Authors: Gammon P. M. , Pérez-Tomás A. , Shah V. A. , Roberts G. J. , Jennings M. R. , Covington J. A. , Mawby P. A.
Published: November 2009

In this article Schottky barrier diodes comprising of a n-n germanium-silicon carbide (Ge–SiC) heterojunction are electrically characterized. Circular transmission line measurements prove that the nickel front and back contacts are Ohmic, isolating the Ge/SiC heterojunction as the only contributor to the Schottky behavior. Current-voltage plots taken at varying temperature (IVT) reveal that the ideality factor (n) and Schottky barrier height (SBH) (Φ) are temperature dependent and that incorrect values of the Richardson constant (A∗∗) are being produced, suggesting an inhomogeneous barrier. Techniques originally designed for metal-semiconductor SBH extraction are applied to the heterojunction results to extract values of Φ and A∗∗ that are independent of temperature. The experimental IVT data are replicated using the Tung model. It is proposed that small areas, or patches, making up only 3% of the total contact area will dominate the I-V results due to their low SBH of 1.033 eV. The experimental IVT data are also analyzed statistically using the extracted values of Φ to build up a Gaussian distribution of barrier heights, including the standard deviation and a mean SBH of 1.126 eV, which should be analogous to the SBH extracted from capacitance-voltage (C-V) measurements. Both techniques yield accurate values of A∗∗ for SiC. However, the C-V analysis did not correlate with the mean SBH as expected.
Theoretical investigation of half metallicity in Fe/Co/Ni doped ZnSe material systems
Authors: Amin B. , Ahmad Iftikhar
Published: November 2009

In the present investigation, we evaluated the half-metallic-ferromagnetic/antiferromagnetic nature of Fe/Co/Ni doped ZnSe material systems. Our calculations show that for the majority spin channel, Zn0.75Fe0.25Se, Zn0.75Co0.25Se, and Zn0.75Ni0.25Se, are semiconductors, and for the minority spin channel, they are conductors and hence are predicted to be half-metallic ferromagnetic/antiferromagnetic in nature. Furthermore Zn0.75Fe0.25Se and Zn0.75Ni0.25Se are ferromagnetic and Zn0.75Co0.25Se is antiferromagnetic. The structural, electronic, and magnetic properties of these materials are also calculated and discussed in detail.
A photoelectron and double photoionization study of the valence electronic structure of 1,4-bromofluorobenzene
Authors: Elshakre M. , Storchi L. , Kloda T. , Linusson P. , Heijkenskjöld F. , Gengelbach A. , Karlsson L. , Hansson T. , Tarantelli F. , Feifel R.
Published: November 2009

Conventional photoelectron and time-of-flight photoelectron-photoelectron coincidence (TOF-PEPECO) spectra have been measured for the outer valence region of the 1,4-bromofluorobenzene molecule. The photoelectron spectra were recorded using HeIα radiation from a resonance source, and the TOF-PEPECO spectra were recorded using HeIIα radiation from a pulsed resonance source. The former provide energies of the cationic states and the latter of the dicationic states. The spectra are adequately interpreted with the aid of accurate Green’s function calculations, showing very significant correlation effects. The lowest double ionization energy is found at 23.45 eV associated with the (4b1)−2X A11 dicationic state.
Arrhenius behavior of hydrocarbon fuel photochemical reaction rates by thermal lens spectroscopy
Authors: Astrath N. G. C. , Astrath F. B. G. , Shen J. , Zhou J. , Michaelian K. H. , Fairbridge C. , Malacarne L. C. , Pedreira P. R. B. , Santoro P. A. , Baesso M. L.
Published: November 2009

The temperature dependence of thermo-optical and photochemical reaction properties of hydrocarbon fuels is investigated using thermal lens spectroscopy. We consider the time dependence of the absorption coefficient due to the photoinduced chemical reaction (PCR) and species diffusion to evaluate nonequilibrium characteristics of the samples. The measured temperature dependences of the reaction rates are found to follow the Arrhenius correlation. Experimental results for thermophysical properties of the samples and an analysis of the connection between PCR properties and the chemistry of the samples are also presented.
Quantum mechanical/molecular mechanical/continuum style solvation model: Linear response theory, variational treatment, and nuclear gradients
Authors: Li Hui
Published: November 2009

Linear response and variational treatment are formulated for Hartree–Fock (HF) and Kohn–Sham density functional theory (DFT) methods and combined discrete-continuum solvation models that incorporate self-consistently induced dipoles and charges. Due to the variational treatment, analytic nuclear gradients can be evaluated efficiently for these discrete and continuum solvation models. The forces and torques on the induced point dipoles and point charges can be evaluated using simple electrostatic formulas as for permanent point dipoles and point charges, in accordance with the electrostatic nature of these methods. Implementation and tests using the effective fragment potential (EFP, a polarizable force field) method and the conductorlike polarizable continuum model (CPCM) show that the nuclear gradients are as accurate as those in the gas phase HF and DFT methods. Using B3LYP/EFP/CPCM and time-dependent-B3LYP/EFP/CPCM methods, acetone S0→S1 excitation in aqueous solution is studied. The results are close to those from full B3LYP/CPCM calculations.
Geometry dependent current-voltage characteristics of ZnO nanostructures: A combined nonequilibrium Green’s function and density functional theory study
Authors: Yang Zhiwen , Wen Bin , Melnik Roderick , Yao Shan , Li Tingju
Published: November 2009

Current-voltage (I-V) characteristics of different ZnO nanostructures were studied using a combined nonequilibrium Green’s function and density functional theory techniques with the two-probe model. It was found that I-V characteristics of ZnO nanostructures depend strongly on their geometry. For wurtzite ZnO nanowires, currents decrease with increasing lengths under the same applied voltage conditions. The I-V characteristics are similar for single-walled ZnO nanotubes and triangular cross section ZnO nanowires but they are different from I-V characteristics of hexagonal cross section ZnO nanowires. Finally, our results are discussed in the context of calculated transmission spectra and densities of states.
High reflectivity airgap distributed Bragg reflectors realized by wet etching of AlInN sacrificial layers
Authors: Altoukhov Alexei , Levrat Jacques , Feltin Eric , Carlin Jean-François , Castiglia Antonino , Butté Raphaël , Grandjean Nicolas
Published: November 2009

The authors report on the achievement of a vertically oriented three pair airgap/GaN distributed Bragg reflector realized by controlled oxidation and wet-chemical etching of AlInN sacrificial layers. Microreflectivity measurements exhibit high peak reflectivity values of 87% around 500 nm after the oxidation process and 90% around 600 nm after the etching process in overall good agreement with simulations. The broad stopband of airgap/GaN mirrors, about 250 nm wide, results from the strong refractive index contrast between air and GaN layers.
Non-Markovian quantum jumps in excitonic energy transfer
Authors: Rebentrost Patrick , Chakraborty Rupak , Aspuru-Guzik Alán
Published: November 2009

We utilize the novel non-Markovian quantum jump (NMQJ) approach to stochastically simulate exciton dynamics derived from a time-convolutionless master equation. For relevant parameters and time scales, the time-dependent, oscillatory decoherence rates can have negative regions, a signature of non-Markovian behavior and of the revival of coherences. This can lead to non-Markovian population beatings for a dimer system at room temperature. We show that strong exciton-phonon coupling to low frequency modes can considerably modify transport properties. We observe increased exciton transport, which can be seen as an extension of recent environment-assisted quantum transport concepts to the non-Markovian regime. Within the NMQJ method, the Fenna–Matthew–Olson protein is investigated as a prototype for larger photosynthetic complexes.
Molecular dynamics simulation of cooling: Heat transfer from a photoexcited peptide to the solvent
Authors: Park Sang-Min , Nguyen Phuong H. , Stock Gerhard
Published: November 2009

A systematic molecular dynamics (MD) simulation study of the photoinduced heat transfer from the model peptide N-methylacetamide (NMA) to various solvents is presented, which considers four types of solvent (water, dimethyl sulfoxide, chloroform, and carbon tetrachloride), and in total 24 different force field models for these solvents. To initiate nonstationary energy flow, an initial temperature jump of NMA is assumed and nonequilibrium MD simulations are performed. As expected from simple theoretical models of heat transfer, the cooling process is proportional to the heat capacity CV and—to some extent—to the viscosity η of the solvent. The complex interplay of Coulomb and Lennard-Jones interactions is studied by scaling these interaction energies. The study reveals that realistic changes (≲10%) of the Lennard-Jones and Coulomb parameters do not change the cooling time considerably. Including polarizibility, on the other hand, appears to enhance the energy dissipation. Moreover, the solvent’s internal degrees of freedom may significantly participate in the heat transfer. This is less so for water, which possesses only three high-frequency vibrational modes, but certainly so for the larger solvent molecules dimethyl sulfoxide and chloroform, which possess several low-frequency vibrational modes. For water, the simulated cooling rate is in excellent agreement with experiment, while only qualitative agreement (up to a factor of 2) is found for the other considered solvents. The importance of the force field model and quantum-mechanical effects to correctly describe the cooling process is discussed in some detail.