bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction of maternal mortality: The need for voluntary blood donors
Authors: Cruz J.R.
Published: March 2007

Objective: To explore the relationship between maternal mortality and availability of blood for transfusion at the country level in Latin American and Caribbean countries. Method: The association of blood availability with maternal mortality, expressed either as national maternal mortality ratio or proportion of maternal deaths due to hemorrhage, in selected Latin American and Caribbean countries was analyzed by non‐parametric methods. Result: An inverse correlation was found between blood availability and both maternal mortality ratio (p < 0.002) and proportion of deaths due to hemorrhage (p < 0.05). Conclusion: Limited availability of blood for transfusion in countries with high maternal mortality ratios may hinder comprehensive care of mothers. The results presented here underscore the need for the formation of voluntary blood donors in the pursuit of improved maternal health.
A novel model to study the biological effects of red wine at the molecular level
Authors: Canali Raffaella , Ambra Roberto , Stelitano Cecilia , Mattivi Fulvio , Scaccini Cristina , Virgili Fabio
Published: March 2007

Several food items of plant origin, and in particular red wine, have been reported to protect from cardiovascular disease (CVD) development, thanks to their polyphenol components. Polyphenols undergo complex metabolic transformation during digestion and intestinal absorption. Here we report a novel model to study the effects of complex food matrices, applied to red wine, on gene expression in cultured primary human endothelial cells that takes into account the polyphenol metabolic transformation. Red wine was administered to human volunteers acting as ‘bio-reactors’. Serum (RWS) obtained after 40 min was utilized to enrich endothelial cell culture media. The expression of specific genes involved in cell adhesion (vascular cell adhesion molecule (VCAM), intercellular adhesion molecule (ICAM) and monocytes chemoattractant protein (MCP-1)) and fibrinolysis (tissue-plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1) and plasminogen activator inhibitor-2 (PAI-2)) was considered as a molecular marker of cell function and related to the effects of RWS. The gene expression profile determined by RWS incubation was significantly different from that observed after the addition of red wine. Data obtained by this approach indicate the importance of taking into account the complex metabolic transformation of polyphenols that occurs during absorption when studying their effect on human health.
Ultrasound-guided, intraglandular injection of botulinum toxin A in children suffering from excessive salivation
Authors: Gerlinger I , Szalai G , Hollódy K , Németh A
Published: March 2007

Background: The aim of this study was to describe the authors' minimally invasive procedure developed to significantly decrease excessive salivation in children suffering from chronic neurological diseases, using botulinum toxin A.

Objective: Ultrasound-guided, intraglandular injection of botulinum toxin blocks the parasympathetic innervation of salivary glands, resulting in a temporary decrease in saliva production and improved quality of life, lasting about three to four months.

Materials and methods: Prior to introducing the method into clinical practice, animal experiments were conducted in order to verify the lack of histological changes three months following botulinum toxin administration. Twenty-one children were included in the clinical study, with ages ranging from two and a half to 14 years.

Results: The animal studies did not reveal any histological changes three months after botulinum toxin administration. Although botulinum toxin A proved to be ineffective in a single case, the majority of the other 20 patients responded well, with a highly significant reduction of their symptoms. The parents of 18 responder children requested repeated treatment with botulinum toxin A. However, two families refused to be further involved in the study, despite good results. The protein content of saliva, regulated by sympathetic innervation, was not affected by the treatment.

Conclusion: This minimally invasive method, applied repeatedly three to four times a year, may be a viable alternative to surgical procedures such as submandibular duct relocation, duct ligature or nervus tympanicus neurectomy.
Optimising outcome assessment of voice interventions, I: reliability and validity of three self-reported scales
Authors: Webb A L , Carding P N , Deary I J , MacKenzie K , Steen I N , Wilson J A
Published: March 2007

Background:

There is an increasing choice of voice outcome research tools, but good comparative data are lacking.

Objective:

To evaluate the reliability and validity of three voice-specific, self-reported scales.

Design:

Longitudinal, cohort comparison study.

Setting:

Two UK voice clinics: the Freeman Hospital, Newcastle upon Tyne, and the Glasgow Royal Infirmary.

Participants:

One hundred and eighty-one patients presenting with dysphonia.

Main outcome measures:

All patients completed the vocal performance questionnaire, the voice handicap index and the voice symptom scale. For comparison, each patient's voice was recorded and assessed perceptually using the grade–roughness–breathiness–aesthenia–strain scale. The reliability and validity of the three self-reported vocal performance measures were assessed in all subjects, while 50 completed the questionnaires again to assess repeatability.

Results:

The results of the 170 participants with completed data sets showed that all three questionnaires had high levels of internal consistency (Cronbach's alpha = 0.81–0.95) and repeatability (voice handicap index = 0.83; vocal performance questionnaire = 0.75; voice symptom scale = 0.63). Concurrent and criterion validity were also good, although, of the grade–roughness–breathiness–aesthenia–strain subscales, roughness was the least well correlated with the self-reported measures.

Conclusion:

The vocal performance questionnaire, the voice handicap index and the voice symptom scale are all reliable and valid instruments for measuring the patient-perceived impact of a voice disorder.
Auto-laydown robot for space solar module
Authors: Wu Yuexin , Zhao Hui , Fu Zhuang , Zhao Yanzheng , Li Peibo
Published: March 2007

This paper discusses about auto-laydown robot (ALR), which is applied to performing the laydown process of a solar module on earth. The robot consists of an adhesive dispensing mechanism, an auto-laydown mechanism, a pneumatic system and a control system. The method of gripping solar cells is described based on pneumatic technology. Meanwhile, a new method of controlling adhesive thickness and area during dispensing is proposed in this paper. The robot realizes the automatic laydown process of solar modules and can control the laydown pressure effectively. Compared with the manual method, the robot could control the dispensing volume and the adhesive area between solar modules and panel substrates, by means of experiments. The novel ALR greatly improves the laydown quality of solar modules and meets the lightweight trend of solar cells development.
A Survey in Mathematics for Industry An efficient method for the numerical simulation of magneto-mechanical sensors and actuators
Authors: SCHINNERL M. , KALTENBACHER M. , LANGER U. , LERCH R. , SCHÖBERL J.
Published: March 2007

The dynamic behaviour of magneto-mechanical sensors and actuators can be completely described by Maxwell's and Navier-Lamé's partial differential equations (PDEs) with appropriate coupling terms reflecting the interactions of these fields and with the corresponding initial, boundary and interface conditions. Neglecting the displacement currents, which can be done for the classes of problems considered in this paper, and introducing the vector potential for the magnetic field, we arrive at a system of degenerate parabolic PDEs for the vector potential coupled with the hyperbolic PDEs for the displacements.Usually the computational domain, the finite element discretization, the time integration, and the solver are different for the magnetic and mechanical parts. For instance, the vector potential is approximated by edge elements whereas the finite element discretization of the displacements is based on nodal elements on different meshes. The most time consuming modules in the solution procedure are the solvers for both, the magnetical and the mechanical finite element equations arising at each step of the time integration procedure. We use geometrical multigrid solvers which are different for both parts. These multigrid solvers enable us to solve quite efficiently not only academic test problems, but also transient 3D technical magneto-mechanical systems of high complexity such as solenoid valves and electro-magnetic-acoustic transducers. The results of the computer simulation are in very good agreement with the experimental data.
Reconsidering the change in global biosphere productivity between the Last Glacial Maximum and present day from the triple oxygen isotopic composition of air trapped in ice cores
Authors: Landais A. , Lathiere J. , Barkan E. , Luz B.
Published: March 2007

We present a global model to infer past biosphere productivity using the record of triple isotopic composition of atmospheric oxygen. Our model incorporates recent determinations of the mass‐dependent relationships between δ17O and δ18O associated with leaf transpiration and various O2 uptake processes. It also considers the spatial and seasonal variations of vegetation distribution, climatic conditions, and isotopic composition of meteoric water. On the basis of this model, we provide global estimates for the Last Glacial Maximum (LGM) and the present of (1) the triple isotopic composition of leaf water, (2) isotopic fractionation factors for terrestrial dark respiration in soils and in leaves as well as total terrestrial respiration, (3) relationships between δ17O and δ18O associated with terrestrial biological steady state, and (4) 17O anomalies issued from both the terrestrial and oceanic biospheres. Using these data and the vegetation distribution simulated by the ORCHIDEE model, we estimated that the rate of global biological productivity during the LGM was 60–75% of the present rate. Our value for the LGM is at the lower end of previous estimates and suggests that the rise in biosphere productivity since the last glacial is larger than previously thought.
MODIS‐derived ocean color products along the China east coastal region
Authors: Wang Menghua , Tang Junwu , Shi Wei
Published: March 2007

Ocean water‐leaving radiance spectra extending from the visible (blue) to the near‐infrared (NIR) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) measurements are reported here for the China east coastal region. The China east coastal region contains some of the most consistently highly turbid coastal waters to be found anywhere. For turbid waters, standard MODIS data processing often produces significant errors in the derived ocean color products due to significant ocean water‐leaving radiance contributions at the two NIR bands. In this paper, we demonstrate an atmospheric correction approach using MODIS short wave infrared (SWIR) bands for deriving more accurate ocean color products in coastal regions. The ocean is generally still black at the SWIR bands even for very turbid waters due to much stronger water absorption at the SWIR wavelengths. The approach has been tested for and applied to various coastal regions (e.g., the U.S. and China east coastal regions) using MODIS data. In situ data collected along the China east coastal region have been used to validate performance of the algorithm. Using MODIS Aqua measurements from July of 2002 to December of 2005, seasonal variations in the visible and the NIR ocean water‐leaving radiances for the Hangzhou Bay in the China east coastal region are derived and analyzed. Very significant ocean NIR contributions along various locations in the China east coastal region (e.g., Hangzhou Bay) are observed.
Longitudinal variations in the equatorial vertical drift in the topside ionosphere
Authors: Hartman W. A. , Heelis R. A.
Published: March 2007

The vertical ion drift is important for understanding and modeling the electrodynamics at low latitudes. Measurements from the ion drift meter on the Defense Meteorological Satellite Program (DMSP) F15 are used to examine longitudinal variations in the vertical ion drift at the dip equator in the topside ionosphere. Local time was restricted to 0930 and the data were organized by month for 2001 and 2002. Two features were found contributing to the longitudinal variations in the electrodynamics. Meridional winds contribute to the equatorial vertical ion drift at the 830 km magnetic apex due to their dynamo action at the foot points of the magnetic field lines in the F region at magnetic latitudes near 15°. Electric fields producing a downward perturbation drift at 0930 are produced by hemispheric differences in the dynamo current due primarily to the different orientation of the magnetic meridian relative to the terminator. This produces the seasonally dependent variation as a function of longitude that is observed. A wavenumber‐4 longitudinal variation also appears to be present throughout the year but is more influential during equinox conditions. This variation also shows a seasonal cycle, shifting east during northern summer and west during northern winter. Further analysis would be required to isolate the characteristics of a wavenumber‐4 driver from the wavenumber‐4 component of the Fourier series used here to fit the data.
Aerosol radiative forcing efficiency in the UV region over southeastern Mediterranean: VELETA2002 campaign
Authors: Díaz A. M. , García O. E. , Díaz J. P. , Expósito F. J. , Utrillas M. P. , Martínez‐Lozano J. A. , Alados‐Arboledas L. , Olmo F. J. , Lorente J. , Cachorro V. , Horvath H. , Labajo A. , Sorribas M. , Vilaplana J. M. , Silva A. M. , Elias T. , Pujadas M. , Rodrigues J. A. , González J. A.
Published: March 2007

Atmospheric aerosol effects on spectral global UV irradiance were evaluated during the VELETA2002 field campaign between 8 and 19 July 2002 in southeast Spain. In the first stage, seven UV spectroradiometer and six CIMEL Sun photometer measurements were carried out simultaneously, allowing them to be calibrated and intercompared. The mean ratio obtained for the global irradiance between the spectroradiometers, with regards to a reference instrument, ranges from 0.98 up to 1.04 with standard deviations that oscillate between ±0.01 and ±0.17. In particular, the two spectroradiometers used to obtain the aerosol forcing efficiencies have a ratio of 1.000 ± 0.001. The aerosol optical depth (AOD) obtained with the CIMEL Sun photometers has a standard deviation of lower than ±0.01 for all the channels. Under clear sky conditions, the diurnal aerosol forcing efficiency (ΔDFe) and fractional diurnal forcing efficiency (ΔFDFe) was calculated for two Mediterranean stations: Armilla (691 m.a.s.l.) within the boundary layer and Sabinas (2200 m.a.s.l) on the lower limit of the free troposphere and 25 km away from the first station. The ΔDFe values obtained at Armilla range between −2.72 ± 0.45 W m−2/τ380 and −2.88 ± 0.45 W m−2/τ440 and between −3.22 ± 0.61 W m−2/τ380 and −3.40 ± 0.62 W m−2/τ440 at Sabinas station; the ΔFDFe values range from −8.0 ± 1.4%/τ380 to −8.6 ± 1.3%/τ440 and −12.0 ± 2.3%/τ380 to −12.6 ± 2.3%/τ440 at the two stations, respectively. Also, an experimental aerosol transmittance factor, CT, used to obtain UV satellite derived products was found as a result of the dependence of the global irradiance with the AOD, under cloudless conditions. The average aerosol attenuation factor, η, obtained from the CT, is 6 ± 2% under weakly absorbing aerosols, with a negligible spectral dependence.
Volcanism and volatile recycling on a one‐plate planet: Applications to Venus
Authors: Elkins‐Tanton L. T. , Smrekar S. E. , Hess P. C. , Parmentier E. M.
Published: March 2007

The surface of Venus displays volcanic features indicating eruption of lavas with a wide range of viscosities. We present numerical experiments showing that lithospheric gravitational instabilities can produce lavas with compositions consistent with the range of volcanic forms seen on Venus. The presence of incompatible elements and their oxides (specifically, water, carbon dioxide, and alkali elements) in trace‐ to percent‐level concentrations in the Venusian mantle allows the formation of a variety of magmatic source regions. The pressure and temperature paths that the dense lithospheric materials travel as they sink into the Venusian mantle indicate that the lithospheric material may devolatilize as it sinks, enriching the surrounding upper mantle, or it may itself melt. These processes can produce magmas with a variety of compositions and viscosities, potentially consistent with the range of Venusian volcanic forms. These processes also suggest that Venus may recycle incompatible elements internally. Indeed, if Venus began with an internal volatile content, then no amount of partial melting can make it entirely volatile‐free even in the absence of recycling into the interior. These models therefore suggest geodynamic processes that can produce a range of magmatic activity and retain some interior volatiles on a one‐plate planet.
Velocity change of the Amery Ice Shelf, East Antarctica, during the period 1968–1999
Authors: King Matt A. , Coleman Richard , Morgan Peter J. , Hurd Rachael S.
Published: March 2007

Historic velocity measurements of Antarctica's ice sheet represent vital baseline values that allow ice flow velocity variations to be observed over multidecadal timescales, such as those due to climate change. Using velocity values derived from geodetic quality measurements made in the 1960s and from more recent GPS and remote sensing studies during the 1990s, we examine the variability of ice flow velocities of the northern Amery Ice Shelf, East Antarctica, over the 30‐year period, 1968–1999. The historic ice shelf velocities are reexamined using original field notes and the previous data analyses are shown to be erroneous, yielding positional and velocity errors of up to 4 km and 150 m/yr respectively. Once corrected, these historic measurements are shown to be in close (1–5 m/yr) general agreement with GPS‐derived velocities from the 1990s at similar geographical locations, providing one of the first precise constraints on multidecadal ice shelf velocity variations on a large Antarctic ice shelf. Comparison of the terrestrial and GPS velocities with spatially dense velocity measurements from remote sensing imagery reveals a systematic bias in the latter of up to ±30 m/yr, mostly due to propagation of unmodeled vertical ice shelf motion due to tides and atmospheric pressure variations. We therefore excluded the remote sensing velocities from further comparison and suggest caution in the interpretation of similarly derived ice shelf velocities. Velocity differences between the GPS and terrestrial surveys were compared at nine geographical locations suggesting a small (∼2.2 m/yr or ∼0.6%), but statistically significant, slowdown of the ice shelf.
Killer electrons from the angry Sun did not stop the pagers
Authors: Bodeau Michael
Published: March 2007

On 19 May 1998 at 2210 UT, pager service in North America was interrupted. The cause was traced to a failure of a computer on board the Galaxy 4 (G4) spacecraft. Because the satellite failure followed an extended period of elevated high‐energy electron flux that began earlier in April and May, electrostatic charging and discharging within the satellite initially appeared to be the cause of the failure. The failure of another (non‐Boeing) satellite, Equator‐S, earlier in the high flux storm strengthened the case for electrostatic discharge. The media picked up the story, reporting it in terms of “killer electrons from an angry Sun.” However, killer electrons did not cause the failure. A review of the space weather experienced by G4 and other similar Boeing satellites since their launches forced the investigation team to conclude that space weather was not a plausible cause. The experience of Galaxy 4 is not unique. A review of satellite anomaly databases shows that the rate of nondamaging anomalies increases during periods of elevated fluxes of high‐energy electrons, but, at an industry or fleet‐wide level, there is no correlation of failures with electron flux. This article reviews the evidence that led the investigation team to reject space weather as the root cause of this particular anomaly.
Slip rate gradients along the eastern Kunlun fault
Authors: Kirby Eric , Harkins Nathan , Wang Erqi , Shi Xuhua , Fan Chun , Burbank Douglas
Published: March 2007

Whether strike‐slip fault systems in Eurasia accomplish eastward extrusion of Tibetan crust and lithosphere depends largely on the kinematics of deformation at the fault tip. Here we present new slip rate determinations using millennial‐scale geomorphic markers from sites along the easternmost segment of the Kunlun fault in north central Tibet. This fault system represents one of the major strike‐slip faults within the Indo‐Asian collision zone, has been argued to exhibit uniform slip rates along much of its length, and plays a central role in models for eastward extrusion of Tibetan lithosphere. Displaced fluvial terrace risers along tributaries of the Yellow River, coupled with14C ages of terrace material, provide constraints on slip rates over late Pleistocene to Holocene time. Results indicate that slip rates decrease systematically along the eastern ∼150 km of the fault from >10 to <2 mm/yr. These data challenge the view that slip along the Kunlun fault remains uniform along the entire length of the fault and instead reveal gradients in displacement similar to those expected at fault tips. Moreover, slip along the fault appears to terminate within the thickened crust of the plateau, and therefore any extrusion of Tibetan lithosphere accomplished by slip along the Kunlun fault must be absorbed by internal deformation of the plateau surrounding the fault tip.
Negative filament tension in the Luo-Rudy model of cardiac tissue
Authors: Alonso S. , Panfilov A. V.
Published: March 2007

Scroll waves are vortices that occur in three-dimensional excitable media. Scroll waves have been observed in a variety of systems including cardiac tissue, where they are associated with cardiac arrhythmias. The disorganization of scroll waves into chaotic behavior is thought to be the mechanism of ventricular fibrillation, which lethality is widely known. One of the possible mechanisms of scroll wave instability is negative filament tension, which was studied theoretically using low-dimensional models of excitable medium. In this article we perform a numerical study of negative filament tension using the Luo-Rudy phase 1 model, which is widely used in cardiac electrophysiology. We show that this instability exists in this model, study its manifestation and discuss its relation to cardiac arrhythmogenesis.
Cluster synchronization and spatio-temporal dynamics in networks of oscillatory and excitable Luo-Rudy cells
Authors: Kanakov O. I. , Osipov G. V. , Chan C.-K. , Kurths J.
Published: March 2007

We study collective phenomena in nonhomogeneous cardiac cell culture models, including one- and two-dimensional lattices of oscillatory cells and mixtures of oscillatory and excitable cells. Individual cell dynamics is described by a modified Luo-Rudy model with depolarizing current. We focus on the transition from incoherent behavior to global synchronization via cluster synchronization regimes as coupling strength is increased. These regimes are characterized qualitatively by space-time plots and quantitatively by profiles of local frequencies and distributions of cluster sizes in dependence upon coupling strength. We describe spatio-temporal patterns arising during this transition, including pacemakers, spiral waves, and complicated irregular activity.
Micromagnetic modeling of magnetization switching driven by spin-polarized current in magnetic tunnel junctions
Authors: Finocchio G. , Azzerboni B. , Fuchs G. D. , Buhrman R. A. , Torres L.
Published: March 2007

This paper presents results of micromagnetic simulations of magnetization switching driven by spin-polarized current in magnetic tunnel junctions. For the studied structures, and for all the simulated currents, the switching occurs via nucleation process. A complete study of how a misalignment of the applied field and nonidealities in the shape of the sample affect the switching behavior has also been performed. The main results are as follows: (a) The switching mechanism does not change qualitatively by introducing a misalignment and (b) In contrast, the switching mechanism changes qualitatively when a nonideal shape is introduced. Lastly, simulations that include the effects of a 77K thermal bath are presented; these indicate that the switching times are shorter than for zero temperature simulations (sometimes also less than 50%).
High-temperature residual stresses in thin films characterized by x-ray diffraction substrate curvature method
Authors: Keckes J. , Eiper E. , Martinschitz K. J. , Köstenbauer H. , Daniel R. , Mitterer C.
Published: March 2007

A new x-ray technique to determine temperature dependencies of macroscopic stresses in thin films by characterizing the substrate curvature is introduced. The technique is demonstrated on polycrystalline TiN and Al thin films deposited on Si(100) wafers. The structures are thermally cycled in the temperature range of 25–400°C using a newly developed heating chamber attached to a commercial x-ray diffractometer. The curvature of the freestanding samples was determined by the rocking curve measurement of substrate Si 400 reflections at different lateral positions of the samples, and the stresses are calculated using Stoney’s formula. The results show that the magnitude of the stress is in good agreement with the results obtained by other techniques. For the practical application of the technique, the sample mounting and the temperature control are of great importance.
Decorated pottery study: Analysis of pigments by x-ray absorbance spectroscopy measurements
Authors: Barilaro D. , Crupi V. , Majolino D. , Venuti V. , Barone G. , D’Acapito F. , Bardelli F. , Giannici F.
Published: March 2007

Characterization of pigments on decorated pottery fragments has been fully carried out by nondestructive x-ray absorbance spectroscopy (XAS). The samples were a series of pottery shards excavated from the archeological site of Caltagirone (Sicily, Italy), a well-known ceramic production center. Aesthetical criteria and morphological observations allowed us to attribute the samples to quite different historical periods, starting from the 18th century B.C. up to the 16th century A.D. An extensive time interval led us to suppose that different materials and techniques were used for the production of the ceramic paste and also for the preparation of pigments. XAS measurements were performed at the Cu and Fe K-edges. The analysis was carried out both in the near-edge (x-ray absorption near-edge spectroscopy, XANES) and in the extended (extended x-ray absorption fine structure, EXAFS) region. From the results, we observed Fe oxides as the main pigmenting agents in the most ancient fragment, while in the other ceramic shards, besides Fe oxides, copper oxides were also found. Oxidation states and local environments of the atoms present were characterized.
A simple density functional fractional occupation number procedure to determine the low energy transition region of spin-flip reactions
Authors: Wang Shu-Guang , Chen Xian-Yang , Eugen Schwarz W. H.
Published: March 2007

A computationally simple three-step procedure to survey the energy landscape and to determine the molecular transition structure and activation energy at the intersection of two weakly coupled electronic potential energy surfaces of different symmetry is suggested. Only commercial software is needed to obtain the transition states of, for instance, spin-flip reactions. The computational expense is only two to three times larger than that of the standard determination of an adiabatic reaction path. First, the structures of the two electronic initial and final states along a chosen reaction coordinate are individually optimized. At the “projected crossing,” the two states have the same energy at the same value of the reaction coordinate, but different state-optimized partial structures. Second, the unique optimized structure of a low energy crossing point between the two states is determined with the help of the density functional fractional occupation number approach. Finally, the respective energy of the two states at the crossing is estimated by a single point calculation. The prescription is successfully applied to some simple topical examples from organic and from inorganic chemistry, respectively, concerning the spin-flip reactions H33CS+→H21CSH+ and Mo7CO2→Mo5CO2→O3MoCO.
Exact path integral treatment of a diatomic molecule potential
Authors: Benamira F. , Guechi L. , Mameri S. , Sadoun M. A.
Published: March 2007

A rigorous evaluation of the path integral for Green’s function associated with a four-parameter potential for a diatomic molecule is presented. A closed form of Green’s function is obtained for different shapes of this potential. When the deformation parameter λ is λ<0 or 0<λ<1, it is found that the quantization conditions are transcendental equations that require a numerical solution. For λ⩾1 and r∊](1∕η)lnλ,∞[, the energy spectrum and the normalized wave functions of the bound states are derived. Particular cases of this potential which appear in the literature are also briefly discussed.
Energetics of the dipole flip-flop motion in a ferroelectric polymer chain
Authors: Cai Lei , Wang Xuewen , Darici Yesim , Zhang Jiandi , Dowben P. A.
Published: March 2007

The authors report on a study of dipole flip-flop “local” transition in ferroelectric polyvinylidene fluoride [P(VDF)] chains, using total energy calculation based on the density functional theory. The calculated results indicate that a simple flipping of a single electric dipole moment is energetically allowed. Furthermore, such a flipping involves no change either in bond length, bond angle, or the orientation of the chain. The calculations also show that on a thin film of ordered chains, strong dipole interactions existing in P(VDF) could cause modulation of the dipole orientation thus forming superlattices on P(VDF) films. These results are in good agreement with recent scanning tunnel microscope experimental measurements. Furthermore, our calculations show that partial flipping may also exist and extend over a length of several monomers during the flip-flop transition.
Magnetic friction due to vortex fluctuation
Authors: Dias R. A. , Rapini M. , Coura P. Z. , Costa B. V.
Published: March 2007

We use Monte Carlo and molecular dynamics simulation to study a magnetic tip-sample interaction. Our interest is to understand the mechanism of heat dissipation when the forces involved in the system are magnetic in essence. We consider a magnetic crystalline substrate composed of several layers interacting magnetically with a tip. The set is put thermally in equilibrium at temperature T by using a numerical Monte Carlo technique. By using that configuration we study its dynamical evolution by integrating numerically the equations of motion. Our results suggest that the heat dissipation in this system is closed related to the appearing of vortices in the sample.
Tailoring the magnetic properties of mechanically hardest Co–Fe–Ta–B glassy thin films
Authors: Sharma Parmanand , Kimura Hisamichi , Inoue Akihisa
Published: March 2007

In the present paper, we focus on the unique magnetic properties, such as spin reorientation transition (SRT) and Curie temperature (TC), of mechanically hardest Co–Fe–Ta–B glassy alloy in thin film form. The effect of dilution with Zr on the magnetic properties of this alloy is also reported. The SRT temperature is found to be reversible and can be tailored to any desirable value from 100K to above room temperature by controlling the film thickness or by different methods of film deposition. In addition, while maintaining the ability to tailor SRT, we can also vary the TC of these films from 450K down to helium temperatures by appropriate dilution of the alloy with Zr. All the Zr added Co–Fe–Ta–B alloy thin films are structurally amorphous, but magnetically versatile and tunable. Our results indicate that the amorphous∕glassy magnetic thin film materials are quite promising for versatile magnetic manipulations and device development.
Photoinduced charge transfer phase transition in cesium manganese hexacyanoferrate
Authors: Matsuda Tomoyuki , Tokoro Hiroko , Hashimoto Kazuhito , Ohkoshi Shin-ichi
Published: March 2007

Cesium manganese hexacyanoferrate, Cs1.51Mn[Fe(CN)6], shows a thermal phase transition between MnII–NC–FeIII [high-temperature (HT) phase] and MnIII–NC–FeII [low-temperature (LT) phase] with phase transition temperatures of 170K (HT→LT) and 230K (LT→HT). The LT phase shows ferromagnetism with Curie temperature of 7K and coercive field of 60Oe. Irradiating with 532nm laser light converts the LT phase into the photoinduced (PI) phase, which does not have spontaneous magnetization. The electronic state of the PI phase corresponds to that of the HT phase and the relaxation temperature from the PI to the LT phase is observed at 90K.
Chetaev versus vakonomic prescriptions in constrained field theories with parametrized variational calculus
Authors: Bibbona Enrico , Fatibene Lorenzo , Francaviglia Mauro
Published: March 2007

Starting from a characterization of admissible Chetaev and vakonomic variations in a field theory with constraints we show how the so called parametrized variational calculus can help to derive the vakonomic and the nonholonomic field equations. We present an example in field theory where the nonholonomic method proved to be unphysical.
Are many-body electronic polarization effects important in liquid water?
Authors: Iuchi Satoru , Izvekov Sergei , Voth Gregory A.
Published: March 2007

Many-body electronic polarization effects may be important for an accurate description of aqueous environments. As a result, numerous polarizable water models have been developed to include explicit polarization effects in intermolecular potential functions. In this paper, it is shown for liquid water at ambient conditions that such many-body polarization interactions can be decomposed into effective pairwise contributions using the force-matching (FM) method [Izvekov et al., J. Chem. Phys. 120, 10896 (2004)]. It is found that an effective pairwise water model obtained by the FM method can accurately reproduce various bulk structural and thermodynamic properties obtained from an accurate fully polarizable water model. In addition, the effective pairwise water model also provides a reasonable description of the water liquid-vapor interface, thus exhibiting a degree of transferability to heterogeneous environments. These results suggest that the role and importance of many-body electronic polarization effects in aqueous systems might be fruitfully explored relative to the best possible pairwise decomposable bulk phase model as the reference state.
Microstructural, magnetic, and optical properties of Zn1−x(Mnx∕2Cox∕2)O (x=0.1 and 0.2) semiconducting nanoparticles
Authors: Mandal S. K. , Nath T. K. , Das A. K. , Karmakar Debjani
Published: March 2007

We have investigated structural, magnetic, and optical properties of Zn1−x(Mnx∕2Cox∕2)O (x=0.1 and 0.2) diluted magnetic semiconducting nanoparticles synthesized by chemical “pyrophoric reaction process.” X-ray diffraction analysis clearly shows that the samples are single phase in ZnO wurtzite structure, where the average crystallite size of samples is found to be in the nanometric regime (∼10nm). From the Curie-Weiss fit, as well as from the calculated value of effective exchange constant (Jex), which is found to be negative, we can assert that the nature of magnetic ground state of both of these samples are antiferromagnetic (AFM). This is further established by the concave nature of isothermal Arrott-Belov-Kouvel plots at the ground state (5K) without having any spontaneous magnetization in both of the samples. When both Mn and Co dopant concentrations (x) are increased in the ZnO matrix, the magnitude of AFM interaction (∣Jex∣) is found to enhance. This observed magnetic behavior has been best explained through the bound magnetic polaron-polaron interaction model. The semiconducting band gap of those nanoparticles has been estimated using recorded optical absorbance spectra.
Magnetocapacitance in a ferromagnetic metal tunnel junction system
Authors: Kim Kyoo , Min B. I.
Published: March 2007

We have studied the magnetocapacitance (MC) of a ferromagnetic (FM) metal-oxide-FM metal tunnel junction. The capacitance changes linearly as the magnetic field increases, and its amount depends on the shape of the density of state at the Fermi level of a FM metal. We have also investigated the effect of the bandwidth change induced by the electron-electron interaction on the MC. We have found that the effect of the bandwidth change on the MC can be substantial near the magnetic phase boundary.
The effect of temperature on strain rate sensitivity in a nanocrystalline Ni–Fe alloy
Authors: Li Hongqi , Choo Hahn , Liaw Peter K.
Published: March 2007

The effect of strain rate on mechanical properties at room temperature (RT) and a cryogenic temperature (77K) was studied in a nanocrystalline Ni–20%Fe alloy (grain size: 22nm). The activation volume, strain rate sensitivity, strain hardening rate, and microstructural changes were also characterized. The results show that this nanocrystalline alloy has a combination of high strength and large plastic strain at both temperatures. At 77K, the strength increased dramatically without a loss in the plasticity. Calculations demonstrate that the effect of temperature on yield strength, activation volume, and strain rate sensitivity is strongly dependent on the grain size. The high strain rate sensitivity and strong yield strength dependence on temperature are due to small activation volumes at fine grain sizes. In addition, at 77K, both the activation volume and strain rate sensitivity exponent decreased significantly. The effect of temperature on the strain hardening capability in this nanograined alloy is opposite to what was observed for the large-grained metals. Comprehensive analysis suggests that the deformation at 20nm is still dominated by dislocations. However, the dislocation generation models may be different at RT and 77K.
A supersonic beam of cold lithium hydride molecules
Authors: Tokunaga S. K. , Stack J. O. , Hudson J. J. , Sauer B. E. , Hinds E. A. , Tarbutt M. R.
Published: March 2007

We have developed a source of cold LiH molecules for Stark deceleration and trapping experiments. Lithium metal is ablated from a solid target into a supersonically expanding carrier gas. The translational, rotational, and vibrational temperatures are 0.9±0.1, 5.9±0.5, and 468±17K, respectively. Although they have not reached thermal equilibrium with the carrier gas, we estimate that 90% of the LiH molecules are in the ground state, XΣ+1(v=0,J=0). With a single 7ns ablation pulse, the number of molecules in the ground state is 4.5±1.8×107 molecules / sr. A second, delayed, ablation pulse produces another LiH beam in a different part of the same gas pulse, thereby almost doubling the signal. A long pulse, lasting 150μs, can make the beam up to 15 times more intense.
A first-principles investigation on the mechanism of nitrogen dissolution in the Na flux method
Authors: Kawahara M. , Kawamura F. , Yoshimura M. , Mori Y. , Sasaki T. , Yanagisawa S. , Morikawa Y.
Published: March 2007

The origin of the drastic enhancement of the N solubility in Na-rich GaxNa1−x liquid alloys compared to pure Ga and Ga-rich alloys is clarified using density functional theory. Liquid simulations show that Ga atoms tend to aggregate in Ga-rich alloys, while Ga atoms are isolated or form small clusters in Na-rich alloys. The calculated N solubility for model crystals shows good agreement with the experimental results. In Ga-rich alloys, the interaction between Ga and N is weak because Ga interacts strongly with surrounding Ga atoms. In Na-rich alloys, Ga–N bond becomes strong because Ga is chemically active, leading to the enhancement of the N solubility.
Magnetohydrodynamic drag reduction and its efficiency
Authors: Shatrov V. , Gerbeth G.
Published: March 2007

We present results of direct numerical simulations of a turbulent channel flow influenced by electromagnetic forces. The magnetohydrodynamic Lorentz force is created by the interaction of a steady magnetic field and electric currents fed to the fluid via electrodes placed at the wall surface. Two different cases are considered. At first, a time-oscillating electric current and a steady magnetic field create a spanwise time-oscillating Lorentz force. In the second case, a stationary electric current and a steady magnetic field create a steady, mainly streamwise Lorentz force. Besides the viscous drag, the importance of the electromagnetic force acting on the wall is figured out. Regarding the energetic efficiency, it is demonstrated that in all cases a balance between applied and flow-induced electric currents improves the efficiency significantly. But even then, the case of a spanwise oscillating Lorentz force remains with a very low efficiency, whereas for the self-propelled regime in the case of a steady streamwise force, much higher efficiencies are found. Still, no set of parameters has yet been found for which an energetic breakthrough, i.e., a saved power exceeding the used power, is reached.
Stimulated forward Raman scattering of a laser in a magnetized plasma
Authors: Sajal Vivek , Dahiya Deepak , Tripathi V. K.
Published: March 2007

A Gaussian laser beam propagating through a low-density plasma in the presence of an azimuthal magnetic field undergoes stimulated forward Raman scattering producing a lower hybrid wave and two radially localized electromagnetic sideband waves. The radial widths of the sidebands are of the order of the spot size of the pump, whereas the radial width of the lower hybrid wave depends on the growth rate of the Raman process. The nonlocal effect arising, due to the azimuthal magnetic field, reduces the region of nonlocal interaction and hence the growth rate. The growth rate of stimulated Raman forward scattering first increases on increasing magnetic field, maximizes at some optimum value of magnetic field, and then decreases.
Radiative emission from multiphoton-excited semiconductor quantum dots
Authors: Han T.-T. , Fu Y. , Ågren H.
Published: March 2007

Optical transitions in CdS semiconductor quantum dots (QDs) have been studied by the Monte Carlo method based on probability calculations of the time-dependent Schrödinger equation. It has been demonstrated that excited by a continuous-wave laser, an assembly of CdS QDs, whose radii range from 2to5nm centered at 3.7nm, shows an emission peak around 2.65eV in the optical emission spectrum, which corresponds to optical transitions among degenerate sublevels close to the ground sublevels in the conduction and valence bands of a CdS QD having a radius of 3.7nm. For resonant one-photon excitation, the emission peak is very sharp, while for resonant two-photon excitation, the emission peak becomes blueshifted and broadened. The inclusion of the nonradiative electron-phonon processes makes the two-photon excitation peak significantly sharper and shows a better agreement with experimental work, thus demonstrating the upconversion luminescence of the QDs required for many applications including bioimaging.
Magnetoresistance and anomalous Hall effect in magnetic ZnO films
Authors: Xu Qingyu , Hartmann Lars , Schmidt Heidemarie , Hochmuth Holger , Lorenz Michael , Schmidt-Grund Rüdiger , Sturm Chris , Spemann Daniel , Grundmann Marius , Liu Yuzi
Published: March 2007

Magnetotransport measurements were performed on n-type conducting Co-doped ZnO and Mn-doped ZnO films prepared by pulsed laser deposition on a-plane sapphire substrates, and positive magnetoresistance (MR) was observed at low temperature. The positive MR decreases drastically with the free electron concentration n exceeding 1019cm−3 and reveals almost the same dependency on n for Co-doped ZnO and Mn-doped ZnO. This hints towards a similar s-d exchange constant in both types of magnetic ZnO films. For Co-doped ZnO, the saturated anomalous Hall resistivity increases with decreasing electron concentration. No anomalous Hall effect was observed in Mn-doped ZnO. Within a free electron approximation the positive MR may be related with the spin polarization of conducting electrons due to s-d exchange interactions. The modeled spin splitting of the conduction band is smaller than 10meV.
X-ray imaging with grazing-incidence microscopes developed for the LIL program
Authors: Rosch R. , Boutin J. Y. , le Breton J. P. , Gontier D. , Jadaud J. P. , Reverdin C. , Soullié G. , Lidove G. , Maroni R.
Published: March 2007

This article describes x-ray imaging with grazing-incidence microscopes, developed for the experimental program carried out on the Ligne d’Intégration Laser (LIL) facility [J. P. Le Breton et al., Inertial Fusion Sciences and Applications 2001 (Elsevier, Paris, 2002), pp. 856–862] (24kJ, UV—0.35nm). The design includes a large target-to-microscope (400–700mm) distance required by the x-ray ablation issues anticipated on the Laser MégaJoule facility [P. A. Holstein et al., Laser Part. Beams 17, 403 (1999)] (1.8MJ) which is under construction. Two eight-image Kirkpatrick-Baez microscopes [P. Kirkpatrick and A. V. Baez J. Opt. Soc. Am. 38, 766 (1948)] with different spectral wavelength ranges and with a 400mm source-to-mirror distance image the target on a custom-built framing camera (time resolution of ∼80ps). The soft x-ray version microscope is sensitive below 1keV and its spatial resolution is better than 30μm over a 2-mm-diam region. The hard x-ray version microscope has a 10μm resolution over an 800-μm-diam region and is sensitive in the 1–5keV energy range. Two other x-ray microscopes based on an association of toroidal/spherical surfaces (T/S microscopes) produce an image on a streak camera with a spatial resolution better than 30μm over a 3mm field of view in the direction of the camera slit. Both microscopes have been designed to have, respectively, a maximum sensitivity in the 0.1–1 and 1–5keV energy range. We present the original design of these four microscopes and their test on a dc x-ray tube in the laboratory. The diagnostics were successfully used on LIL first experiments early in 2005. Results of soft x-ray imaging of a radiative jet during conical shaped laser interaction are shown.
Symmetry breaking of the fluid density profiles in closed nanoslits
Authors: Berim Gersh O. , Ruckenstein Eli
Published: March 2007

The density profiles in a fluid interacting with the two identical solid walls of a closed long slit were calculated for wide ranges of the number of fluid molecules in the slit and temperature by employing a nonlocal density functional theory. Using argon as the sample fluid and considering the walls composed of solid carbon dioxide, it is shown that the density profile corresponding to the stable state of the fluid considerably changes its shape with increasing average density ρav of the fluid inside the slit. Temperature dependent critical values ρsb1 and ρsb2 of ρav were identified, such that for ρsb1⩽ρav⩽ρsb2 the stable state of the system is described by an asymmetric density profile whereas outside this range it is described by a symmetric one. Hence a spontaneous symmetry breaking of the fluid density distribution in a closed slit with identical walls can take place. On the basis of the results obtained for closed slits, the symmetry breaking in open slits was also examined.