bluuebunny/crossref_metadata_2025 huggingface dataset:
D
−
∕
H
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negative ion production versus plasma parameters in a volume negative ion source
Authors: Mori Shigefumi , Fukumasa Osamu
Published: January 2008

Pure volume production of D− negative ions is studied in rectangular negative ion source equipped with an external magnetic filter (MF). Plasma parameters (ne and Te) in D2 plasmas are varied mainly in the downstream region by changing the magnetic field intensity of the MF (i.e., BMF). Production and control of D2 plasma is nearly the same as that of H2 plasmas, although the values of ne and Te in D2 plasma are slightly higher than that of H2 plasmas in both the source and the extraction regions. On D−∕H− production, however, it appears some different points. By varying the BMF, H− production in the extraction region is remarkably changed corresponding to the variation of ne and Te in the extraction region. On the other hand, D− production is not so varied under the same discharge conditions in H2 plasmas. This difference in D− production is not well explained only variation of ne and Te in D2 plasmas. Optimum BMF and gas pressure for D− production is slightly higher than that for H− production.
Design, construction, and first commissioning results of superconducting source for ions at NSCL/MSU
Authors: Závodszky P. A. , Arend B. , Cole D. , DeKamp J. , Doleans M. , Machicoane G. , Marti F. , Miller P. , Moskalik J. , Nurnberger W. , Ottarson J. , Vincent J. , Wu X. , Zeller A.
Published: January 2008

A new electron cyclotron resonance ion source (ECRIS) was constructed at the NSCL/MSU to replace the existing SC-ECRIS. This ECRIS operates at 18+14.5GHz microwave frequencies with a planned upgrade to 24–28GHz in the second phase of commissioning. A superconducting hexapole coil system produce the radial magnetic field; the axial trapping is produced with six superconducting solenoid coils enclosed in an iron yoke to allow the optimization of the distance between the plasma electrode and the resonant zone in the plasma. We report the details of the design, construction, and initial commissioning results of this new ECRIS.
Schrödinger equation Monte Carlo in two dimensions for simulation of nanoscale metal-oxide-semiconductor field effect transistors
Authors: Chen Wanqiang , Register Leonard F. , Banerjee Sanjay K.
Published: January 2008

A quantum transport simulator, Schrödinger equation Monte Carlo in two dimensions (SEMC-2D), is presented that provides a rigorous yet reasonably computationally efficient quantum mechanical treatment of real scattering processes within quantum transport simulations of nanoscale metal-oxide-semiconductor field effect transistors (MOSFETs). This work represents an extension of an early version of SEMC for simulating quantum transport and scattering in quasi-one-dimensional device geometries such as encountered in conventional and quantum-cascade lasers. In many respects SEMC is simply a variation on nonequilibrium Green’s function techniques, with scattering as well as carrier injection into the simulation region treated via Monte Carlo techniques. In this regard, SEMC also represents a quantum analog of semiclassical Monte Carlo. Scattering mechanisms considered include crystal momentum randomizing acoustic and optical intra- and intervalley scattering (and intra- and intersubband scattering), and nonrandomizing surface roughness scattering. Simulation results for nanoscale dual-gate MOSFET geometries are provided that illustrate the method and the continuing need for accurate modeling of scattering even in nanoscale MOSFETs.
First-principles investigation of the asymmetric contact effect on current-voltage characteristics of a molecular device
Authors: Zhang Z. , Yang Z. , Yuan J. , Qiu M.
Published: January 2008

The properties of electronic transport in an electronic device composed of a spatially symmetric phenyldithiolate molecule sandwiched between two gold electrodes with asymmetric contact are investigated by the first-principles study. It is found that the I-V and G-V characteristics of a device show significant asymmetry and the magnitudes of current and conductance depend remarkably on the variation of molecule-metal distance at one of the two contacts. Namely, an asymmetric contact would lead to the weak rectifying effects on the current-voltage characteristics of a molecular device. We also calculate self-consistently other microscopic quantities such as the local density of states, the total density of states, and the distribution of charges in the asymmetric molecular models under the applied bias. The results show that the highest-occupied molecular orbital (HOMO) is responsible for the resonant tunneling and the shifting of the HOMO due to the charging of the device under the bias voltage is the intrinsic origin of asymmetric I(G)-V characteristics.
Depletion potentials in colloidal mixtures of hard spheres and rods
Authors: Li Weihua , Yang Tao , Ma Hong-ru
Published: January 2008

The depletion potential between a hard sphere and a planar hard wall, or two hard spheres, imposed by suspended rigid spherocylindrical rods is computed by the acceptance ratio method through the application of Monte Carlo simulation. The accurate results and ideal-gas approximation results of the depletion potential are determined with the acceptance ratio method in our simulations. For comparison, the depletion potentials are also studied by using both the density functional theory and Derjaguin approximations. The density profile as a function of positions and orientations of rods, used in the density functional theory, is calculated by Monte Carlo simulation. The potential obtained by the acceptance ratio method is in good agreement with that of density functional theory under the ideal-gas approximation. The comparison between our results and those of other theories suggests that the acceptance ratio method is the only efficient method used to compute the depletion potential induced by nonspherical colloids with the volume fraction beyond the ideal-gas approximation.
A quantum equation of motion for chemical reaction systems on an adiabatic double-well potential surface in solution based on the framework of mixed quantum-classical molecular dynamics
Authors: Yamada Atsushi , Okazaki Susumu
Published: January 2008

We present a quantum equation of motion for chemical reaction systems on an adiabatic double-well potential surface in solution in the framework of mixed quantum-classical molecular dynamics, where the reactant and product states are explicitly defined by dividing the double-well potential into the reactant and product wells. The equation can describe quantum reaction processes such as tunneling and thermal excitation and relaxation assisted by the solvent. Fluctuations of the zero-point energy level, the height of the barrier, and the curvature of the well are all included in the equation. Here, the equation was combined with the surface hopping technique in order to describe the motion of the classical solvent. Applying the present method to model systems, we show two numerical examples in order to demonstrate the potential power of the present method. The first example is a proton transfer by tunneling where the high-energy product state was stabilized very rapidly by solvation. The second example shows a thermal activation mechanism, i.e., the initial vibrational excitation in the reactant well followed by the reacting transition above the barrier and the final vibrational relaxation in the product well.
Computing accurate potentials of mean force in electrolyte solutions with the generalized gradient-augmented harmonic Fourier beads method
Authors: Khavrutskii Ilja V. , Dzubiella Joachim , McCammon J. Andrew
Published: January 2008

We establish the accuracy of the novel generalized gradient-augmented harmonic Fourier beads (ggaHFB) method in computing free-energy profiles or potentials of mean force (PMFs) through comparison with two independent conventional techniques. In particular, we employ umbrella sampling with one dimensional weighted histogram analysis method (WHAM) and free molecular dynamics simulation of radial distribution functions to compute the PMF for the Na+–Cl− ion-pair separation to 16Å in 1.0M NaCl solution in water. The corresponding ggaHFB free-energy profile in six dimensional Cartesian space is in excellent agreement with the conventional benchmarks. We then explore changes in the PMF in response to lowering the NaCl concentration to physiological 0.3 and 0.1M, and dilute 0.0M concentrations. Finally, to expand the scope of the ggaHFB method, we formally develop the free-energy gradient approximation in arbitrary nonlinear coordinates. This formal development underscores the importance of the logarithmic Jacobian correction to reconstruct true PMFs from umbrella sampling simulations with either WHAM or ggaHFB techniques when nonlinear coordinate restraints are used with Cartesian propagators. The ability to employ nonlinear coordinates and high accuracy of the computed free-energy profiles further advocate the use of the ggaHFB method in studies of rare events in complex systems.
Three-dimensional crystalline Si film growth by the Ni silicide mediation
Authors: Kim Joondong , Han Chang-Soo , Park Yun Chang , Anderson Wayne A.
Published: January 2008

Three-dimensional crystalline Si films were grown by the Ni silicide mediation. The metal-induced growth method, which is a spontaneous reaction of metal and silicon, forms a silicide layer first then induces the crystalline Si growth. By controlling the reaction between Ni and Si, the silicide formation was modulated. The NiSi2 migration crystallizes a Si film behind and mediates crystalline Si above it. The mechanism of silicide-mediated three-dimensional Si crystallization and the thin Si film Schottky photodiode are presented.
Compositional inhomogeneity of a high-efficiency InxGa1−xN based multiple quantum well ultraviolet emitter studied by three dimensional atom probe
Authors: Galtrey M. J. , Oliver R. A. , Kappers M. J. , McAleese C. , Zhu D. , Humphreys C. J. , Clifton P. H. , Larson D. , Cerezo A.
Published: January 2008

An InxGa1−xN based multiple quantum well structure emitting in the ultraviolet, which has the highest reported efficiency (67%) at its wavelength (380nm), was analyzed with the three-dimensional atom probe. The results reveal gross discontinuities and compositional variations within the quantum well layers on a 20–100nm length scale. In addition, the analysis shows the presence of indium in the AlyGa1−yN barrier layers, albeit at a very low level. By comparing with analogous epilayer samples, we suggest that the quantum well discontinuities we observe may play an important role in improving the efficiency of these structures.
Controlling the angular response of magnetoresistance in Co∕Cu multilayered nanowires using Co crystallographic orientation
Authors: Tan Liwen , McGary Patrick D. , Stadler Bethanie J. H.
Published: January 2008

Ordered nanoporous templates with monodispersed pore diameters were used for the fabrication of multilayered Co∕Cu nanowires. The c-axis alignment of Co layers was controlled in order to study the angular variation of the magnetoresistance (ΔMR). When the Co easy axis was in plane (perpendicular to the wire axes), the arrays were magnetically anisotropic and they had a low angular ΔMR (0.08%). This was most likely due to anisotropic magnetoresistance. However, when the Co c axis was out of plane (parallel to wire axes), the arrays were magnetically isotropic but they had larger angular ΔMR (1.33%). The maximum MR was 7% for the whole array. This control of the angular response will be useful in designing sensors for a variety of applications.
Fe-nanoparticle coated anisotropic magnet powders for composite permanent magnets with enhanced properties
Authors: Marinescu M. , Liu J. F. , Bonder M. J. , Hadjipanayis G. C.
Published: January 2008

Utilizing the chemical reduction of FeCl2 with NaBH4 in the presence of 2:17 Sm–Co powders, we synthesized composite Sm(Co0.699Fe0.213Cu0.064Zr0.024)7.4/nano-Fe anisotropic hard magnetic powders. The average particle size of the hard magnetic core powder was 21μm while the soft magnetic Fe nanoparticles deposited uniformly on the core powder had a particle size smaller than 100nm. Different reaction protocols, such as immersion of the hard magnetic core powder in each reagent, the use of microemulsion (micelle) technique, or doubling the weight ratio of FeCl2 to core powder, led to different degrees of magnetic coupling of the hard and soft magnetic components of the composite powder. A reaction time of 180s led to deposition of 3.5wt% Fe nanoparticles and improved magnetic properties of the composite powder compared to the uncoated Sm(Co0.699Fe0.213Cu0.064Zr0.024)7.4 powder. The respective magnetic hysteresis parameters were 4πM18kOe=11.3kG, 4πMr=11kG, and Hci>20kOe with a smooth demagnetization curve.
Estimation of pump-out and positive radial electric field created by electron cyclotron resonance heating in magnetic confinement devices
Authors: Castejón F. , Eguilior S. , Calvo I. , López-Bruna D. , García-Regaña J. M.
Published: January 2008

A fast approximate technique for calculating the outward electron flux induced by electron cyclotron resonance heating in magnetic confinement devices with ripple is presented. A model based on Langevin equations that allows one to compute the microscopic flux into the loss cone in momentum space is used. The outward macroscopic electron flux is also obtained for given plasma profiles. This extra flux causes the onset of a positive ambipolar electric field whose time evolution is demonstrated to depend strongly on the poloidal damping for electrons.
Effect of polarity of self-assembled monolayers on morphology and magnetic properties of a deposited magnetic material
Authors: Ahmad S. N. , Shaheen S. A. , Rao S. G. , Magana D. , Strouse G. F.
Published: January 2008

With the decreasing size of devices, the ability to organize materials and control their physical properties through spatial and morphology manipulation becomes critical. Here, we show that the nature of the organic functional group at the top surface of the self-assembled monolayers can strongly influence the growth of a metallic thin film on the monolayer, as a chemical reaction may occur at the interface. We have sputtered Permalloy (Ni79Fe21) on patterned templates of polar and nonpolar self-assembled monolayers. Uniform film formation is observed on polar regions, and cluster/dropletlike structures are formed on the nonpolar regions. A similar behavior in morphology is observed for the deposition of Permalloy on a substrate having single component self-assembled monolayers. Magnetic measurements reveal that Permalloy exhibits a superparamagnetic behavior when deposited on a nonpolar self-assembled monolayer substrate, whereas a ferromagnetic behavior is observed for Permalloy deposited on a polar self-assembled monolayer substrate. Thus, a systematic deposition of Permalloy on polar and nonpolar self-assembled monolayers allows a control on morphology and the magnetic properties due to the difference in wettability of the terminal organic functional groups of the self-assembled monolayers.
Photoinduced absorption in B-doped hydrogenated amorphous silicon alloys applied to all-optical modulators
Authors: Summonte C. , Della Corte F. G. , Nigro M. A. , Desalvo A.
Published: January 2008

All-optical modulators have been fabricated, based on the infrared photoinduced absorption produced within an optical waveguide upon visible light illumination. The modulation data are analyzed by means of simulation software based on a numerical mode solver. It is found that the modulation depth increases for pump illumination energy closer to the energy gap of the guiding material, while illumination at varying intensity shows a sublinear dependence of the photoinduced absorption. The results are discussed in terms of occupation statistics of gap states. It is shown that the major contribution to the photoinduced signal derives from the modulation of the occupation of tail states under illumination. Modeling of the phenomenon allows one to predict the behavior of a given device and opens the way to practical applications.
Analytical impurity transport model: Coupling between particle and charge state transports in tokamak plasmas
Authors: Shurygin V. A.
Published: January 2008

Interpretation and understanding of a set of coupled continuity equations commonly used in impurity tokamak transport studies are found to be syncretic and inadequate, since they do not distinguish between the cross-field fluxes of impurity particles and of their charge states (cs). An analytical approach to impurity transport studies previously developed is generalized to the case of diffusive-convective cs dynamics and provides a set of dimensionless parameters to describe the impurity behavior more correctly than using empirical coefficients D and V, which, in turn, have to be interpreted in terms of their cs, rather than of particles. An analytical transport model (ATM) with underlying interpretation is proposed. It is based on the solutions of two separate transport problems for impurity cs and particles instead of a single one. It is shown that ATM consistently explains two groups of available empirical dependences regarding the scaling D∝ne−1 and the profiles of V∕D, which are shown to be the density profile gradients, ∇nZ∕nZ and suggests the neoclassical scale of the particle diffusion coefficient.
Investigation of magnetic interactions in large arrays of magnetic nanowires
Authors: Fodor P. S. , Tsoi G. M. , Wenger L. E.
Published: January 2008

The magnetic interactions in large arrays of ordered magnetic nanowires with 12–48nm diameter and 55–95nm spacing were investigated using modified Henkel plots. The measurements for nanowire arrays ac demagnetized with the field applied parallel to the nanowire axis (the easy magnetization axis) indicate that the dominant interaction during the switching process is the magnetostatic coupling between the nanowires. Nevertheless, while the strength of the magnetostatic interactions increases with the magnetic moment associated with the nanowires, the increase is not linear with respect to the volume of the nanowires. Moreover, the dependence of the remanence curves on the field history suggests that even for magnetic nanowire systems with high geometric anisotropy, the magnetic pole structure of the nanowires can be complex. This conclusion is also supported by the field dependence of the initial magnetization curves.
Equilibrium rotation in field-reversed configurations
Authors: Steinhauer Loren
Published: January 2008

The turbulence that drives anomalous transport in field-reversed configurations (FRCs) is believed to break the otherwise closed magnetic surfaces inside the separatrix. This places electrons in the core of the plasma in electrical contact with those in the periphery. This effect was proposed and investigated in the context of spheromaks [D. D. Ryutov, Phys. Plasmas 14, 022506 (2007)]. The opening up of internal magnetic field lines serves to regulate the electrostatic potential in the interior of the plasma, and in turn drives ion rotation. In effect, “end-shorting,” a well-known phenomenon in the FRC scrape-off layer, also extends into the plasma interior. For conditions relevant to experiments, the ion rotation can be expressed in terms of equilibrium properties (density and temperature gradients) and as such is the “equilibrium” rotation. This theory is incomplete in that it neglects evolving, transport-related effects that modify the equilibrium and, indirectly, the rotation rate. Consequently, the equilibrium rotation theory is only partially successful in predicting experimental results: although it predicts the average rotation well, the estimated degree of rotational shear seems unlikely, especially at late times in the plasma lifetime.
The instabilities induced by electrostatic fields and gradients in a plasma shock front
Authors: He Yong , Hu Xiwei , Jiang Zhonghe , Lü Jianhong
Published: January 2008

The linear instabilities induced by the electrostatic fields and gradients of equilibrium parameters in a plasma shock front are analyzed for the plasma shock structure. Small perturbations as well as the steady-state shock structure are described by a set of coupled two-fluid and Poisson equations. The dispersion relations are obtained at high frequency in two cases, in which the wave vectors are, respectively, parallel and perpendicular to the shock propagation direction. The imaginary parts of the frequency (growth rates) of the instabilities are dependent on the fields and the gradients.
Nonlinear adjustment of a front over escarpment
Authors: Bouchut F. , Scherer E. , Zeitlin V.
Published: January 2008

We present the results of fully nonlinear numerical simulations of the geostrophic adjustment of a pressure front over topography, represented by an escarpment with a linear slope. The results of earlier simulations in the linear regime are confirmed and new essentially nonlinear effects are found. Topography influences both fast and slow components of motion. The fast unbalanced motion corresponds to inertia-gravity waves (IGW). The IGW emitted during initial stages of adjustment break and form the localized dissipation zones. Due to topography, the IGW activity is enhanced in certain directions. The slow balanced motion corresponds to topographic Rossby waves propagating along the escarpment. As shown, at large enough nonlinearities they may trap fluid/tracer and carry it on. There are indications that nonlinear topographic waves form a soliton train during the adjustment process. If the coastal line is added to the escarpment at the shallow side (continental shelf), secondary fronts related to the propagation of the coastal Kelvin waves appear.
Origin of the spin-triplet Andreev reflection at ferromagnet/s-wave superconductor interface
Authors: Feng Cui Di , Zheng Zhi Ming , Ji Yi Qun , Niu Zhi Ping , Xing D. Y.
Published: January 2008

To understand the origin of the spin-triplet Andreev reflection which may appear at a ferromagnet (F)/s-wave superconductor (S) interface, we study tunneling conductance spectra of F/2DEG/s-wave S tunnel junctions, with 2DEG the two-dimensional electron gas with Rashba spin-orbit coupling and subject to a magnetic field. It is found that both spin-flip and broken time-reversal symmetry in the 2DEG are conditions necessary to giving rise to the novel Andreev reflection and spin-triplet pairing correlations.
Field evaporation behavior during irradiation with picosecond laser pulses
Authors: Sha G. , Cerezo A. , Smith G. D. W.
Published: January 2008

A field-ion specimen made of a low thermal diffusivity material, field evaporated using picosecond laser pulses incident from one side, is shown to develop different curvatures between the incident side and the “shadow” side of the specimen apex. Differences of approximately 2.6 and 1.5V∕nm in evaporation field were observed between the two regions of a type 304 stainless steel tip evaporated at 50K with pulsed laser intensities of 0.04 and 0.02nJ∕μm2ps, respectively. This indicates that diffraction of the laser beam cannot ensure uniform illumination and heating over the tip apex.
The formation of pentagon-heptagon pair defect by the reconstruction of vacancy defects in carbon nanotube
Authors: Lee Gun-Do , Wang C. Z. , Yoon Euijoon , Hwang Nong-Moon , Ho K. M.
Published: January 2008

The reconstruction process of vacancy hole in carbon nanotube is investigated by tight-binding molecular dynamics simulations and by ab initio total energy calculations. In the molecular dynamics simulation, a vacancy hole is found to reconstruct into two separated pentagon-heptagon pair defects. As the result of reconstruction, the radius of the carbon nanotube is reduced and the chirality of the tube is partly changed. During the vacancy hole healing process, the formation of pentagonal and heptagonal rings is proceeded by the subsequent Stone-Wales [Chem. Phys. Lett. 128, 501 (1986)] transformation.
Resonating modes of vibrating microcantilevers in liquid
Authors: Ghatkesar Murali Krishna , Braun Thomas , Barwich Viola , Ramseyer Jean-Pierre , Gerber Christoph , Hegner Martin , Lang Hans Peter
Published: January 2008

A study of nanomechanical cantilevers vibrating at various resonating modes in liquid is presented. Resonant frequency spectrum with 16 well resolved flexural modes is obtained. The quality factor increased from 1 at mode 1 to 30 at mode 16. The theoretical estimate of eigenfrequency using the Elmer–Dreier model [F.-J. Elmer and M. Dreier, J. Appl. Phys. 81, 12 (1997)] and Sader’s extended viscous model [C. A. Van Eysden and J. E. Sader, J. Appl. Phys. 101, 044908 (2007)] matched well with the experimental data. The apparent mass of the liquid comoved by the oscillating cantilevers decreased asymptotically with mode number.
Au–ZnO: A tunable localized surface plasmonic nanocomposite
Authors: Mishra Y. K. , Mohapatra S. , Singhal R. , Avasthi D. K. , Agarwal D. C. , Ogale S. B.
Published: January 2008

In this letter, we report the thermal processing controlled tunability of localized surface plasmon resonance (LSPR) of Au nanoparticles embedded in ZnO matrix. Au–ZnO nanocomposite films were prepared by atom beam cosputtering and were annealed from 200to600°C in Ar. A regular redshift ∼110nm (from 505to615nm) in LSPR peak with increase in annealing temperature up to 600°C is observed. Transmission electron microscopy results confirm the formation of Au nanoparticles supported by ZnO nanorods at annealing temperature of 600°C. The Au–ZnO nanocomposite exhibits significant enhancement in the Raman signal for C70 molecules.
Nanofluid with tunable thermal properties
Authors: Philip John , Shima P. D. , Raj Baldev
Published: January 2008

We experimentally demonstrate the tunable thermal property of a magnetically polarizable nanofluid that consists of a colloidal suspension of magnetite nanoparticles with average diameter of 6.7nm. Controlling the linear aggregation length from nano- to micron scales, the thermal conductivity (TC) of the nanofluid has been enhanced up to 216%, using 4.5vol% of nanoparticles. Repeated magnetic cycling shows that the TC enhancement is reversible. It has been confirmed that the large enhancement in TC is due to the efficient transport of heat through percolating nanoparticle paths. Our findings offer promising applications in “smart” cooling devices.
A type of poly(vinylidene fluoride-trifluoroethylene) copolymer exhibiting ferroelectric relaxor behavior at high temperature (∼100°C)
Authors: Bao Hui-Min , Jia Cheng-Liang , Wang Chang-Chun , Shen Qun-Dong , Yang Chang-Zheng , Zhang Q. M.
Published: January 2008

We report a class of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymers synthesized via reductive dechlorination from P(VDF-CTFE) [termed as the reduced P(VDF-TrFE) copolymer], which exhibit ferroelectric relaxor behavior at high temperature (∼100°C). It was found that the reduced P(VDF-TrFE) 66∕34mol% copolymer has very high content of head-to-head and tail-to-tail defects, which may act as random defects, leading to the observed ferroelectric relaxor at high temperature. Furthermore, the reduced copolymer also exhibits a high melting point (∼200°C), which also makes it attractive for high-temperature dielectric applications.
Effect of oxygen on the electronic configuration of Gd2O3∕Ge heterojunctions
Authors: Perego M. , Molle A. , Fanciulli M.
Published: January 2008

The band structure of the Gd2O3∕Ge heterojunction was investigated by x-ray photoelectron spectroscopy and was found to be very sensitive to variations of oxygen content in the oxide film. A 0.6eV decrease of the valence band offset (VBO) has been observed after in situ O2 postdeposition annealing (PDA). The VBO value obtained after PDA is 2.8eV in excellent agreement with data reported in the literature. The extra oxygen, supplied during PDA, is stably incorporated in the Gd2O3 matrix. Moreover, this extra oxygen limits moisture adsorption during air exposure and helps to stabilize the electronic configuration of the Gd2O3∕Ge heterojunction.
Thermal and magnetic field-induced martensite-austenite transition in Ni50.3Mn35.3Sn14.4 ribbons
Authors: Hernando B. , Llamazares J. L. Sánchez , Santos J. D. , Escoda Ll. , Suñol J. J. , Varga R. , Baldomir D. , Serantes D.
Published: January 2008

Thermal and field-induced martensite-austenite transition was studied in melt spun Ni50.3Mn35.3Sn14.4 ribbons. Its distinct highly ordered columnarlike microstructure normal to ribbon plane allows the direct observation of critical fields at which field-induced and highly hysteretic reverse transformation starts (H=17kOe at 240K), and easy magnetization direction for austenite and martensite phases with respect to the rolling direction. Single phase L21 bcc austenite with TC of 313K transforms into a 7M orthorhombic martensite with thermal hysteresis of 21K and transformation temperatures of MS=226K, Mf=218K, AS=237K, and Af=244K.
Selectivity of Black Death mortality with respect to preexisting health
Authors: DeWitte Sharon N. , Wood James W.
Published: January 2008

Was the mortality associated with the deadliest known epidemic in human history, the Black Death of 1347–1351, selective with respect to preexisting health conditions (“frailty”)? Many researchers have assumed that the Black Death was so virulent, and the European population so immunologically naïve, that the epidemic killed indiscriminately, irrespective of age, sex, or frailty. If this were true, Black Death cemeteries would provide unbiased cross-sections of demographic and epidemiological conditions in 14th-century Europe. Using skeletal remains from medieval England and Denmark, new methods of paleodemographic age estimation, and a recent multistate model of selective mortality, we test the assumption that the mid-14th-century Black Death killed indiscriminately. Skeletons from the East Smithfield Black Death cemetery in London are compared with normal, nonepidemic cemetery samples from two medieval Danish towns (Viborg and Odense). The results suggest that the Black Death did not kill indiscriminately—that it was, in fact, selective with respect to frailty, although probably not as strongly selective as normal mortality.
Suppressor role of activating transcription factor 2 (ATF2) in skin cancer
Authors: Bhoumik Anindita , Fichtman Boris , DeRossi Charles , Breitwieser Wolfgang , Kluger Harriet M. , Davis Sean , Subtil Antonio , Meltzer Paul , Krajewski Stan , Jones Nic , Ronai Ze'ev
Published: January 2008

Activating transcription factor 2 (ATF2) regulates transcription in response to stress and growth factor stimuli. Here, we use a mouse model in which ATF2 was selectively deleted in keratinocytes. Crossing the conditionally expressed ATF2 mutant with K14-Cre mice (K14.ATF2
f/f
) resulted in selective expression of mutant ATF2 within the basal layer of the epidermis. When subjected to a two-stage skin carcinogenesis protocol [7,12-dimethylbenz[
a
]anthracene/phorbol 12-tetradecanoate 13-acetate (DMBA/TPA)], K14.ATF2
f/f
mice showed significant increases in both the incidence and prevalence of papilloma development compared with the WT ATF2 mice. Consistent with these findings, keratinocytes of K14.ATF2
f/f
mice exhibit greater anchorage-independent growth compared with ATF2 WT keratinocytes. Papillomas of K14.ATF2
f/f
mice exhibit reduced expression of presenilin1, which is associated with enhanced β-catenin and cyclin D1, and reduced Notch1 expression. Significantly, a reduction of nuclear ATF2 and increased β-catenin expression were seen in samples of squamous and basal cell carcinoma, as opposed to normal skin. Our data reveal that loss of ATF2 transcriptional activity serves to promote skin tumor formation, thereby indicating a suppressor activity of ATF2 in skin tumor formation.
MicroRNA-373 induces expression of genes with complementary promoter sequences
Authors: Place Robert F. , Li Long-Cheng , Pookot Deepa , Noonan Emily J. , Dahiya Rajvir
Published: January 2008

Recent studies have shown that microRNA (miRNA) regulates gene expression by repressing translation or directing sequence-specific degradation of complementary mRNA. Here, we report new evidence in which miRNA may also function to induce gene expression. By scanning gene promoters
in silico
for sequences complementary to known miRNAs, we identified a putative miR-373 target site in the promoter of E-cadherin. Transfection of miR-373 and its precursor hairpin RNA (pre-miR-373) into PC-3 cells readily induced E-cadherin expression. Knockdown experiments confirmed that induction of E-cadherin by pre-miR-373 required the miRNA maturation protein Dicer. Further analysis revealed that cold-shock domain-containing protein C2 (CSDC2), which possesses a putative miR-373 target site within its promoter, was also readily induced in response to miR-373 and pre-miR-373. Furthermore, enrichment of RNA polymerase II was detected at both E-cadherin and CSDC2 promoters after miR-373 transfection. Mismatch mutations to miR-373 indicated that gene induction was specific to the miR-373 sequence. Transfection of promoter-specific dsRNAs revealed that the concurrent induction of E-cadherin and CSDC2 by miR-373 required the miRNA target sites in both promoters. In conclusion, we have identified a miRNA that targets promoter sequences and induces gene expression. These findings reveal a new mode by which miRNAs may regulate gene expression.
Radio frequency analog electronics based on carbon nanotube transistors
Authors: Kocabas Coskun , Kim Hoon-sik , Banks Tony , Rogers John A. , Pesetski Aaron A. , Baumgardner James E. , Krishnaswamy S. V. , Zhang Hong
Published: January 2008

The potential to exploit single-walled carbon nanotubes (SWNTs) in advanced electronics represents a continuing, major source of interest in these materials. However, scalable integration of SWNTs into circuits is challenging because of difficulties in controlling the geometries, spatial positions, and electronic properties of individual tubes. We have implemented solutions to some of these challenges to yield radio frequency (RF) SWNT analog electronic devices, such as narrow band amplifiers operating in the VHF frequency band with power gains as high as 14 dB. As a demonstration, we fabricated nanotube transistor radios, in which SWNT devices provide all of the key functions, including resonant antennas, fixed RF amplifiers, RF mixers, and audio amplifiers. These results represent important first steps to practical implementation of SWNTs in high-speed analog circuits. Comparison studies indicate certain performance advantages over silicon and capabilities that complement those in existing compound semiconductor technologies.
Transitive homology-guided structural studies lead to discovery of Cro proteins with 40% sequence identity but different folds
Authors: Roessler Christian G. , Hall Branwen M. , Anderson William J. , Ingram Wendy M. , Roberts Sue A. , Montfort William R. , Cordes Matthew H. J.
Published: January 2008

Proteins that share common ancestry may differ in structure and function because of divergent evolution of their amino acid sequences. For a typical diverse protein superfamily, the properties of a few scattered members are known from experiment. A satisfying picture of functional and structural evolution in relation to sequence changes, however, may require characterization of a larger, well chosen subset. Here, we employ a “stepping-stone” method, based on transitive homology, to target sequences intermediate between two related proteins with known divergent properties. We apply the approach to the question of how new protein folds can evolve from preexisting folds and, in particular, to an evolutionary change in secondary structure and oligomeric state in the Cro family of bacteriophage transcription factors, initially identified by sequence-structure comparison of distant homologs from phages P22 and λ. We report crystal structures of two Cro proteins, Xfaso 1 and Pfl 6, with sequences intermediate between those of P22 and λ. The domains show 40% sequence identity but differ by switching of α-helix to β-sheet in a C-terminal region spanning ≈25 residues. Sedimentation analysis also suggests a correlation between helix-to-sheet conversion and strengthened dimerization.
Neuroimaging analysis of an anesthetic gas that blocks human emotional memory
Authors: Alkire Michael T. , Gruver Robin , Miller Jason , McReynolds Jayme R. , Hahn Emily L. , Cahill Larry
Published: January 2008

It is hypothesized that emotional arousal modulates long-term memory consolidation through the amygdala. Gaseous anesthetic agents are among the most potent drugs that cause temporary amnesia, yet the effects of inhalational anesthesia on human emotional memory processing remain unknown. To study this, two experiments were performed with the commonly used inhalational anesthetic sevoflurane. In experiment 1, volunteers responded to a series of emotional and neutral slides while under various subanesthetic doses of sevoflurane or placebo (no anesthesia). One week later, a mnemonic boost for emotionally arousing stimuli was evident in the placebo, 0.1%, and 0.2% sevoflurane groups, as measured with a recognition test. However, the mnemonic boost was absent in subjects who received 0.25% sevoflurane. Subsequently, in experiment 2, glucose PET assessed brain-state-related activity of subjects exposed to 0.25% sevoflurane. Structural equation modeling of the PET data revealed that 0.25% sevoflurane suppressed amygdala to hippocampal effective connectivity. The behavioral results show that 0.25% sevoflurane blocks emotional memory, and connectivity results demonstrate that this dose of sevoflurane suppresses the effective influence of the amygdala. Collectively, the findings support the hypothesis that the amygdala mediates memory modulation by demonstrating that suppressed amygdala effectiveness equates with a loss of emotional memory.
Vascular mechanical properties and endothelial function in pre‐eclampsia with special reference to bilateral uterine artery notch
Authors: BRODSZKI J. , LÄNNE T. , LAURINI R. , STREVENS H. , WIDE‐SWENSSON D. , MARŠÁL K.
Published: January 2008

Objectives. To assess whether women with pre‐eclampsia (PE) have different properties of the blood vessel wall compared to healthy pregnant controls. Further, to evaluate endothelial function and vascular mechanical properties in women with PE with special regard to its association with bilateral uterine artery notch and placental histopathology. Participants. Some 57 Caucasian pregnant women: 23 with uncomplicated pregnancies and normal uterine artery Doppler, and 34 with PE, the PE group comprising 2 subgroups according to the presence (n = 20) or absence (n = 14) of bilateral uterine artery notches. Methods. Ultrasonic echo‐tracking assessed the elastic properties of the common carotid artery, abdominal aorta and popliteal artery. Flow‐mediated dilatation (FMD) of the brachial artery was measured by ultrasonography. Histopathological examination of the placenta was carried out in 46 pregnancies: 18 uncomplicated pregnancies, 15 with PE with bilateral notch, and 13 with PE without bilateral notch. Results. There were no significant differences in carotid, aortic or popliteal vessel wall stiffness either between women with PE and controls or within the PE group. FMD was significantly lower in women with PE than in controls (p = 0.03). The lowest FMD was observed in pre‐eclamptic women with bilateral uterine artery notches 9.5% (SD: 5.3) compared to 11.6% (SD: 5.4) in pre‐eclamptic women without bilateral uterine artery notch, and 13.4% (SD: 4.0) in controls (p = 0.01). Bilateral uterine artery notching was significantly associated with a lower FMD (OR: 0.87; 95% CI: 0.77–0.98). There were significantly more placentas with high ischaemic score in the bilateral notch group than in the group with PE and normal circulation. Conclusions. There were no differences in vessel wall stiffness between women with PE and healthy controls. Women with PE showed signs of endothelial dysfunction, significantly more pronounced in women with bilateral uterine artery notch. Bilateral uterine artery notch was associated with ischaemic pathology of the placenta. Notwithstanding, a significant number of placentas in the PE group failed to show noteworthy ischaemic or other morphological changes that could explain the role of the placenta in the development of PE.
Effects of antepartum electronic fetal monitoring on maternal emotional state
Authors: MANCUSO ALFREDO , DE VIVO ANTONIO , FANARA GIUSI , DENARO ANTONIO , LAGANÀ DAVIDE , MARIA ACCARDO FRANCO
Published: January 2008

Background. To evaluate the emotional state of pregnant women undergoing computerised cardiotocography (cCTG). Methods. A questionnaire including questions about socio‐demographic background, personal obstetric history and physician‐patient relationship was given to 204 pregnant women about to undergo cCTG. The Edinburgh Post‐natal Depression Scale (EPDS) was used to assess patients’ mood state before CTG, while the Spielberger State‐Trait Anxiety Inventory (STAI) was used to evaluate anxiety levels before and after this examination. Results. Mean STAI T‐anxiety score did not differ before and after CTG (p = 0.38), but higher levels of basal anxiety were found in women who had undergone only occasional prenatal controls (p = 0.04), as well as smokers (p = 0.01), and women preferring a vaginal delivery (p = 0.01). The mean STAI S‐anxiety score of 43.6±4.03 before the cardiotographic examination, increased to 45.2±5.4 after this test with a statistically significant difference (p = 0.0001). This increase was found to be correlated with the presence of obstetric complications during the current pregnancy (p = 0.036) and a lower number of fetal active movements (p = 0.029). Based on the EPDS, 22 patients (14.1%) were found to be depressed, but this condition was not correlated with significant increases in anxiety levels. Conclusions. Anxiety levels in pregnant women who undergo routine CTG are increased, and this emotional reaction seems to be influenced by the perception of fetal movement during the examination, and is more evident in pregnancies affected by obstetric complications.
Regression of pelvic girdle pain after delivery: follow‐up of a randomised single blind controlled trial with different treatment modalities
Authors: ELDEN H. , HAGBERG H. , FAGEVIK OLSEN M. , LADFORS L. , OSTGAARD H.C.
Published: January 2008

Objective. An earlier publication showed that acupuncture and stabilising exercises as an adjunct to standard treatment was effective for pelvic girdle pain during pregnancy, but the post‐pregnancy effects of these treatment modalities are unknown. The aim of this follow‐up study was to describe regression of pelvic girdle pain after delivery in these women. Design. A randomised, single blind, controlled trial. Setting. East Hospital and 27 maternity care centres in Göteborg, Sweden. Population. Some 386 pregnant women with pelvic girdle pain. Methods. Participants were randomly assigned to standard treatment plus acupuncture (n = 125), standard treatment plus specific stabilising exercises (n = 131) or to standard treatment alone (n = 130). Main outcome measures. Primary outcome measures: pain intensity (Visual Analogue Scale). Secondary outcome measure: assessment of the severity of pelvic girdle pain by an independent examiner 12 weeks after delivery. Results. Approximately three‐quarters of all the women were free of pain 3 weeks after delivery. There were no differences in recovery between the 3 treatment groups. According to the detailed physical examination, pelvic girdle pain had resolved in 99% of the women 12 weeks after delivery. Conclusions. This study shows that irrespective of treatment modality, regression of pelvic girdle pain occurs in the great majority of women within 12 weeks after delivery.
Alteration of peripheral CD4+CD25+ regulatory T lymphocytes in pregnancy and pre‐eclampsia
Authors: HU DONGXIAO , CHEN YAN , ZHANG WUWEN , WANG HANZHI , WANG ZHENGPING , DONG MINYUE
Published: January 2008

Objectives. To clarify the change of peripheral CD4+CD25+ regulatory T lymphocytes in normal pregnancy and pre‐eclampsia and to explore its role in the pathogenesis of pre‐eclampsia. Methods. Twenty‐seven women with pre‐eclampsia, 27 with normal third trimester pregnancy and 27 healthy non‐pregnant women were recruited. Blood samples were taken and surface antigen CD4 and CD25 were labelled with fluorescence‐conjugated antibodies. CD4+CD25+ regulatory T cells were analysed by flow cytometry, and the proportion in T cells and the amount of regulatory T lymphocytes were calculated. Results. The amount and the proportion of regulatory T cells were not significantly different among non‐pregnant, normal pregnancy and pre‐eclampsia groups (p>0.05 for both). There were no significant differences in the proportion and the amount of CD4+CD25+ regulatory T cells between mild and severe pre‐eclampsia subgroups (p>0.05 for both). Conclusions. No significant change of peripheral regulatory T cells was observed in the current investigation, suggesting other mechanisms rather than CD4+CD25+ regulatory T cells were involved in the pathogenesis of pre‐eclampsia.
Dystocia in labour – risk factors, management and outcome: a retrospective observational study in a Swedish setting
Authors: SELIN LOTTA , WALLIN GUNNAR , BERG MARIE
Published: January 2008

Background. Labour dystocia (LD) is associated with adverse maternal and child outcomes. This study investigated obstetric risk factors, frequency of interventions and delivery outcomes for LD. Methods. A retrospective, observational, study of 1,480 deliveries was undertaken in a Swedish district hospital during 2000 and 2001. Results. LD was identified in 21% of deliveries, 16.7% of which ended in caesarean section (CS) compared to 1.7% of deliveries without LD. Multiparity with no previous vaginal delivery (OR = 6.0), epidural analgesia (EDA) at cervical dilation ≤5 cm (OR = 4.6), primiparity (OR = 4.5), gestational age ≥42 weeks (OR = 3.1), birth weight >4,000 g (OR = 2.7) and EDA at cervical dilation >5 cm (OR = 2.0) were major independent risk factors for LD. Conclusions. In delivery management, special attention should be directed to primiparous women and multiparous women with no previous vaginal delivery. Women given EDA, especially at cervical dilation ≤5 cm are also of particular interest. Furthermore, rigorous routines for LD diagnosis and oxytocin augmentation are important.
Sublingual nitroglycerin seems to be effective in the management of retained placenta
Authors: EKERHOVD ERLING , BULLARBO MARIA
Published: January 2008

Background. A common approach in the management of retained placenta is administration of oxytocin followed by controlled cord traction. Previously it has also been demonstrated that intravenously administered nitroglycerin facilitates manual extraction of retained placenta. The purpose of the present trial was to examine the success rate and safety of sequential administration of intravenous oxytocin in combination with sublingual nitroglycerin for the delivery of retained placenta. Methods. The report is a chart review of 24 women with retained placenta despite intravenously administered oxytocin. The women were given sublingual nitroglycerin (1 mg) to promote detachment of the placenta. Some 5 min after resorption of the tablets, controlled cord traction was carried out for a maximum of 5 min. In addition, changes in blood pressure following treatment with nitroglycerin and total blood loss during delivery were registered. Results. Twenty‐one of the women delivered the placenta successfully following sublingual administration of nitroglycerin. The procedure failed in 3 women and operative manual removal under regional or general anesthesia was undertaken. No complications due to nitroglycerin were registered. Conclusions. Sequential administration of oxytocin and nitroglycerin seems to be an effective and safe procedure in the management of retained placenta. However, larger studies are needed to confirm the encouraging results of the present trial.