bluuebunny/crossref_metadata_2025 huggingface dataset:
Localized surface plasmon resonance enhanced magneto-optical activity in core-shell Fe–Ag nanoparticles
Authors: Wang L. , Yang K. , Clavero C. , Nelson A. J. , Carroll K. J. , Carpenter E. E. , Lukaszew R. A.
Published: April 2010

Metallic nanoparticles (NPs) are suitable platforms for miniaturized biosensing based on their optical and magneto-optical properties. It is possible to enhance the sensitivity of specific kinds of NPs by exploiting their optical and magneto-optical properties under suitable external magnetic field modulation. Here, the magneto-optical properties of Fe–Ag core-shell ferromagnet-noble metal NPs have been investigated as a function of the incident light frequency. For Fe–Ag NPs with a concentration ratio around 25:75, an optical absorption band centered at 3 eV due to localized surface plasmon resonance (LSPR) excitation is observed. A strong enhancement of the Faraday rotation is also observed, greatly exceeding the value estimated for pure Fe NPs, also associated with the LSPR excitation. Our findings open up the possibility of highly sensitive miniaturized magneto-optically modulated biosensing.
Prediction of realistic entropy behavior from mixed state magnetization data for first order phase transition materials
Authors: Das S. , Amaral J. S. , Amaral V. S.
Published: April 2010

We present here the influence of the phase transformation on the magnetic and magnetocaloric properties of a typical first order system (MnAs) having mixed-phase state near the transition temperature. We use chemical doping to introduce various field and temperature dependent thermodynamic functions into the system. From the nature of the phase transformation with different thermodynamics and the magnetic entropy behavior treating Maxwell’s relation on magnetization data, we modeled the mixed-phase state of the system with magnetization. This lead to distinguish the contribution of entropy influenced by phase transformation obtained from incorrect application of Maxwell’s relation on the nonequilibrium system and mixed state and a realistic entropy value can be obtained subjected to simple correction to the experimental nonequilibrium magnetization data and using Maxwell’s relation.
Effect of reactive gas (oxygen/chlorine/fluorine) etching on the magnetic flux of a high moment write pole material
Authors: Zhang Jinqiu , Liu Feng , Chen Lifan , Miloslavsky Lena
Published: April 2010

Effect of reactive gas (oxygen/chlorine/fluorine) etching on NiFe magnetic properties was investigated. Experimental data showed 40% magnetic property degradation for F-containing gas etching, 10% degradation for O-containing gas etching, and 5% degradation for Cl-containing gas etching processes. X-ray diffraction analysis indicated that the crystallographic orientation remained the same upon the reactive gas etching, which is due to the low ion energy in plasma etching process as opposed to ion milling process with high input energy. It is proposed that the reported magnetic property degradation was mainly caused by the nonmagnetic dead layer formation, rather than the changes in the crystallographic orientation. The dead layer was determined by the NiFe thickness dependence of remnant magnetic flux variations between pre-etched and postetched samples. The dead layer remained nearly constant for O-containing gas etching process with increasing plasma processing time. The nonmagnetic dead layer of ∼40–50 Å formed in O-containing etching gas was observed in transmission electron microscopy cross-sectional image and was in very good agreement with the calculated value based on magnetic flux measurements. Combined magnetic and physical characterizations suggest that the dead layer thickness saturates at the initial stage of the plasma etching and magnetic property remained unchanged with increasing etching duration upon formation of the dead layer.
Effects of B and Si contents on glass-forming ability and soft-magnetic properties in (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x glassy alloys
Authors: Sun Huaijun , Man Qikui , Dong Yaqian , Shen Baolong , Kimura Hisamichi , Makino Akihiro , Inoue Akihisa
Published: April 2010

The effects of B and Si contents on the glass-forming ability (GFA) and soft-magnetic properties of (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x (x=22–30) alloys were investigated. The thermal stability of the supercooled liquid increased with increasing the B and Si contents from x=24 to 28, and accompanying the decreases of liquidus temperature of alloys. As a result, The (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x bulk glassy alloys with diameters up to 3.5 mm were synthesized in the composition range of x=24–28. In addition to high GFA, the Co-based glassy alloys exhibit excellent soft-magnetic properties as well, i.e., moderate saturation magnetization of 0.51–0.72 T, low coercive force of 0.4–1.5 A/m, and high initial permeability of 22 340–29 570 at 1 kHz under a field of 1 A/m.
Efficiency test of filtering methods for the removal of transcranial magnetic stimulation artifacts on human electroencephalography with artificially transcranial magnetic stimulation-corrupted signals
Authors: Zilber Nicolas A. , Katayama Yoshinori , Iramina Keiji , Erich Wintermantel
Published: April 2010

A new approach is proposed to test the efficiency of methods, such as the Kalman filter and the independent component analysis (ICA), when applied to remove the artifacts induced by transcranial magnetic stimulation (TMS) from electroencephalography (EEG). By using EEG recordings corrupted by TMS induction, the shape of the artifacts is approximately described with a model based on an equivalent circuit simulation. These modeled artifacts are subsequently added to other EEG signals—this time not influenced by TMS. The resulting signals prove of interest since we also know their form without the pseudo-TMS artifacts. Therefore, they enable us to use a fit test to compare the signals we obtain after removing the artifacts with the original signals. This efficiency test turned out very useful in comparing the methods between them, as well as in determining the parameters of the filtering that give satisfactory results with the automatic ICA.
In vitro stimulation with a strongly pulsed electromagnetic field on rat basophilic leukemia cells
Authors: Choi J. W. , Shin S. C. , Kim S. , Chung E. R. , Bang J. H. , Cho G. I. , Choi S. D. , Park Y. S. , Jang T. S. , Yoo Y. M. , Lee S. S. , Hwang D. G.
Published: April 2010

In this study, the effects of pulsed electromagnetic field stimulation with a strong magnetic field on rat basophilic leukemia (RBL-2H3) cells were investigated to confirm the efficacy of the magnetic stimulator for biomedical applications. The maximum intensity of the magnetic field generated from the stimulation coil was 0.203 T, and the transition time was 126 μs. The oscillation time and frequency of the pulsed field were almost 0.1 ms and 8 kHz, respectively. The cell count as well as the mRNA expression and DNA sequence of the cytokine genes, such as the tumor necrosis factor-α (TNF-α) and interleukin-4 (IL-4), of the stimulated RBL-2H3 cells were analyzed with a hemocytometer and via reverse transcriptase polymerase chain reaction to determine the physiological response under a strong pulse field. After 12 h stimulation, cell death was observed at an increasing scale with the increase in the stimulation time. On the other hand, the cells that were stimulated for 10 min almost doubled as the interval time between the stimulations was extended.
Temperature dependence of the magnetostriction of stress annealed Galfenol measured under tension
Authors: Restorff J. B. , Wun-Fogle M.
Published: April 2010

Galfenol (Fe100−xGax) is a relatively new, highly magnetostrictive active material with strains of about 330 ppm as a slow cooled single crystal and about 280 ppm as a highly textured polycrystal at x=∼18.4. Four main advantages over other materials are (1) Galfenol’s structural strength; (2) the ability of a single composition to operate over the temperature range of −269–+150 °C (for stress annealed rods, higher for unannealed rods); (3) the ability of stress annealed Galfenol to provide full performance under stresses ranging from at least −160 to +30 MPa (compressive stresses are negative); and (4) the ability to use standard metal working techniques. The magnetostriction and magnetization of two stress annealed, highly textured Fe81.6Ga18.4 rods were measured at temperatures between −50 and +100 °C and tensile stresses of approximately +1, +10, +20, +30, and +40 MPa. Measurements were taken inside an environmental chamber using a spring to supply the stress. A stress change of about 2 MPa between −50 and +100 °C was typical. The saturation magnetostriction is nearly independent of stress up to 20 MPa, drops only slightly at 30 MPa, and falls off rapidly at 40 MPa. At a given stress, the saturation magnetostriction decreases roughly linearly at ∼0.3×10−6/°C.
Magnetic anisotropy of nonmodulated Ni–Mn–Ga martensite revisited
Authors: Heczko Oleg , Straka Ladislav , Novak Vaclav , Fähler Sebastian
Published: April 2010

Magnetic anisotropy of single crystal Ni50.5Mn30.4Ga19.1 having nonmodulated (NM) martensite structure (c=0.660 nm and b=a=0.547 nm at room temperature) was determined in the range of 10–300 K. The single variant microstructure needed for proper anisotropy determination was prepared by 40 MPa tensile stress in comparison with previous measurements where detwinned microstructure was obtained by compression. The tensile stress process yield the single variant microstructure with easy plane magnetic anisotropy and negligible second anisotropy constant in contrast of two anisotropy constants of the same order for compressed sample. The absolute value of anisotropy constant increases from 2.6×105 J/m3 at 300 K to 5×105 J/m3 at 10 K.
Magnetostriction and magnetization of tension annealed rods of Fe82Ga18
Authors: Jones N. J. , Restorff J. B. , Wun-Fogle M. , Clark A. E.
Published: April 2010

Slow and fast growth textured polycrystalline rods of Fe82Ga18 have been annealed at 300 and 600 °C under 50 MPa of tensile stress for 20 min. The rods showed a built-in positive internal stress of ∼20 MPa (300 °C annealing) to ∼30 MPa (600 °C annealing), corresponding to an induced uniaxial anisotropy energy from −4 to −5.5 kJ/m3. Slow growth samples showed better alignment of moments along the rod axis due to better grain alignment. After a 600 °C annealing without applied stress, the sample properties showed no remnants of any prior stress annealing treatments and were better than the as-received unannealed samples.
Synthesis and characterization of polymer nanocomposites containing magnetic nanoparticles
Authors: De La Cruz-Montoya Edwin , Rinaldi Carlos
Published: April 2010

Magnetic poly(methyl methacrylate) nanocomposites were prepared using oleic acid coated cobalt ferrite and magnetite nanoparticles. Both nanofillers had a similar effect in shifting the glass transition temperature from that of the neat polymer. The cobalt ferrite nanocomposite had magnetic hysteresis at 2 and 300 K and the magnetite nanocomposite had magnetic hysteresis at 2 K and superparamagnetic behavior at 300 K. Surprisingly, zero field cooled magnetization measurements for the cobalt ferrite nanocomposite showed a peak at ∼250 K, in contrast with measured hysteresis at 300 K. On the other hand, ac susceptibility measurements up to 400 K did not show any peaks for the cobalt ferrite nanocomposite. These measurements suggest the importance of ac susceptibility measurements in characterizing the magnetic properties of polymer nanocomposites.
Magnetic properties of FeCo alloys measured by energy-loss magnetic chiral dichroism
Authors: Warot-Fonrose B. , Gatel C. , Calmels L. , Serin V. , Snoeck E. , Cherifi S.
Published: April 2010

The energy loss magnetic chiral dichroism (EMCD) in a transmission electron microscope to study magnetic devices of reduced dimensions is a young and very promising technique. It relies on the study of electron energy loss spectra acquired in specific locations of the diffraction pattern. The sensitivity of the method to the magnetic properties is investigated on a series of FexCo1−x alloys. The spectra can reflect modifications of magnetic or structural properties and the iron-cobalt alloys present the advantage of having a crystal structure which remains body centered cubic on a wide composition range. A significant variation of the EMCD signal as a function of the composition of the alloy has been detected and attributed to changes in the magnetic moment.
Magnetic vortex dynamics on a picoseconds timescale in a hexagonal Permalloy pattern
Authors: Shim Je-Ho , Kim Dong-Hyun , Mesler Brooke , Moon Jung-Hwan , Lee Kyung-Jin , Anderson Erik , Fischer Peter
Published: April 2010

We observed a motion of magnetic vortex core in a hexagonal Permalloy pattern by means of soft x-ray microscopy. Pump-probe stroboscopic observation on a picosecond timescale has been carried out after exciting a ground state vortex structure by an external field pulse of 1 ns duration. Vortex core is excited off from the center position of the hexagonal pattern but the analysis of the core trajectory reveals that the motion is nongyrotropic.
Atom-by-atom simulations of chemical vapor deposition of nanoporous hydrogenated silicon nitride
Authors: Houska J. , Klemberg-Sapieha J. E. , Martinu L.
Published: April 2010

Amorphous hydrogenated silicon nitride (SiNH) materials prepared by plasma-enhanced chemical vapor deposition (PECVD) are of high interest because of their suitability for diverse applications including optical coatings, gas/vapor permeation barriers, corrosion resistant, and protective coatings and numerous others. In addition, they are very suitable for structurally graded systems such as those with a graded refractive index. In parallel, modeling the PECVD process of SiN(H) of an a priori given SiN(H) ratio by atomistic calculations represents a challenge due to: (1) different (and far from constant) sticking coefficients of individual elements, and (2) expected formation of N2 (and H2) gas molecules. In the present work, we report molecular-dynamics simulations of particle-by-particle deposition process of SiNH films from SiHx and N radicals. We observe formation of a mixed zone (damaged layer) in the initial stages of film growth, and (under certain conditions) formation of nanopores in the film bulk. We investigate the effect of various PECVD process parameters (ion energy, composition of the SiHx+N particle flux, ion fraction in the particle flux, composition of the SiHx radicals, angle of incidence of the particle flux) on both (1) deposition characteristics, such as sticking coefficients, and (2) material characteristics, such as dimension of the nanopores formed. The results provide detailed insight into the complex relationships between these process parameters and the characteristics of the deposited SiNH materials and exhibit an excellent agreement with the experimentally observed results.
Discrete-time classical and quantum Markovian evolutions: Maximum entropy problems on path space
Authors: Pavon Michele , Ticozzi Francesco
Published: April 2010

The theory of Schrödinger bridges for diffusion processes is extended to classical and quantum discrete-time Markovian evolutions. The solution of the path-space maximum entropy problems is obtained from the a priori model in both cases via a suitable multiplicative functional transformation. In the quantum case, nonequilibrium time reversal of quantum channels is discussed and space-time harmonic processes are introduced.
Three kinds of coupling integrable couplings of the Korteweg–de Vries hierarchy of evolution equations
Authors: Zhang Yufeng , Tam Honwah
Published: April 2010

We introduce three kinds of column-vector Lie algebras Ls(s=1,2,3). By making invertible linear transformations we get the corresponding three induced Lie algebras. According to the defined loop algebras L̃s of the Lie algebras Ls(s=1,2,3), we establish three various isospectral problems. Then by applying Tu scheme, we obtain three different coupling integrable couplings of the Korteweg–de Vries (KdV) hierarchy and further reduce them to three kinds of explicit coupling integrable couplings of the KdV equation. One of the coupling integrable couplings of the KdV hierarchy of evolution equations possesses Hamiltonian structure obtained by using the quadratic-form identity and it is Liouville integrable.
A new proof of the higher-order superintegrability of a noncentral oscillator with inversely quadratic nonlinearities
Authors: Rañada Manuel F. , Rodríguez Miguel A. , Santander Mariano
Published: April 2010

The superintegrability of a rational harmonic oscillator (noncentral harmonic oscillator with rational ratio of frequencies) with nonlinear “centrifugal” terms is studied. In the first part, the system is directly studied in the Euclidean plane; the existence of higher-order superintegrability (integrals of motion of higher order than 2 in the momenta) is proved by introducing a deformation in the quadratic complex equation of the linear system. The constants of motion of the nonlinear system are explicitly obtained. In the second part, the inverse problem is analyzed in the general case of n degrees of freedom; starting with a general Hamiltonian H and introducing appropriate conditions for obtaining superintegrability, the particular “centrifugal” nonlinearities are obtained.
Theoretical investigation of the interaction of CH4 with Al2 and Al3 neutral and charged clusters
Authors: Alexandrou E. I. , Groß A. , Bacalis N. C.
Published: April 2010

We have studied the interaction of CH4 with Al2 and Al3 neutral and charged clusters in the two lowest lying spin states using density functional theory. These calculations, via extended search, are used to determine the stable positions of H and CH3 near the cluster, and the transition state to break the H–CH3 bond. In all cases, stable methyl-aluminum-hydrides are possible. The H desorption is studied by means of vibration analysis and application of transition state theory. A common observed trend is that, in breaking the H–CH3 bond, the interacting H atom is attached to the “surface” of the clusters attracting some negative charge of ≈0.2e. The charge transfer is illustrated using the corresponding orbitals near the transition state in conjunction with the computed Mulliken population analysis. Thermal vibrations, generally, do not enhance the reaction. In all exothermic cases, the binding energy toward CH3+HAlncharge increases with increasing charge of the original Aln(q=−1,0,1) cluster. Although Al lacks occupied d-orbitals, the small Al clusters reduce the (free methane) CH3–H dissociation barrier except for Al3(q=−1,0). The relevant reactions in desorption require ∼400–700 °C.
Study of electromagnetic fluctuations in high beta plasma of a large linear device
Authors: Awasthi L. M. , Mattoo S. K. , Jha R. , Singh R. , Kaw P. K.
Published: April 2010

Observation of electromagnetic fluctuations in lower hybrid range of frequencies is reported in a large volume linear plasma device. The instability is observed in the plasma core when a narrow multifilamentary source is used and it is absent when a broad source is used. This instability is observed in high beta plasma and it is characterized by broadband turbulent spectra with central frequency ω=5×104 s−1 and wave number k⊥=0.2 cm−1 and satisfies the condition k⊥ρe≤1, where ρe is the electron Larmor radius. When increasing the axial magnetic field reduces plasma beta, the instability weakens in magnitude and magnetic component is totally suppressed at plasma beta less than 0.5. Several possible explanations are considered and it is indicated that either the pressure gradient modified by energetic electrons or the electron temperature gradient may be responsible for the instability.
Large-scale simulations of fluctuating biological membranes
Authors: Pasqua Andrea , Maibaum Lutz , Oster George , Fletcher Daniel A. , Geissler Phillip L.
Published: April 2010

We present a simple, and physically motivated, coarse-grained model of a lipid bilayer, suited for micron scale computer simulations. Each ≈25 nm2 patch of bilayer is represented by a spherical particle. Mimicking forces of hydrophobic association, multiparticle interactions suppress the exposure of each sphere’s equator to its implicit solvent surroundings. The requirement of high equatorial density stabilizes two-dimensional structures without necessitating crystalline order, allowing us to match both the elasticity and fluidity of natural lipid membranes. We illustrate the model’s versatility and realism by characterizing a membrane’s response to a prodding nanorod.
Impulse and particle dislodgement under turbulent flow conditions
Authors: Celik Ahmet O. , Diplas Panayiotis , Dancey Clinton L. , Valyrakis Manousos
Published: April 2010

In this study, we investigated the role of turbulence fluctuations on the entrainment of a fully exposed grain near threshold flow conditions. Experiments were carried out to measure synchronously the near bed flow velocity and the particle movement for a range of flow conditions and resulting particle entrainment frequencies. We used a simplified bed geometry consisted of spherical particles to reduce the complexities associated with the variations in the bed and flow details in an effort to identify the underlying dominant physical mechanism. An analysis was performed based on common force approximations using near bed flow velocity. Turbulence fluctuations were treated as impulses, which are products of magnitude and duration of applied force. It is demonstrated that besides the magnitude of the instantaneous forces applied on a sediment grain, their duration is important as well in determining whether a particle will be entrained by a turbulent flow event. Frequency of particle entrainment varied remarkably with minute changes in gross flow parameters. Impulse imparted on the sediment grain by turbulent flow was found to be well represented by a log-normal distribution. We obtained a (log-normal) probability density function (pdf) dependent on only the coefficient of variation of the impulse (impulse intensity). Relation of the impulse intensity to the particle Reynolds number, Re∗, was established. The sensitivity of the computed impulse to the critical force level, as well as the influence of the critical impulse level on the dislodgement events, was explored. Particle entrainment probabilities were found using the derived pdf as well as experimental observations and a good agreement between the two is reported. Implications of the presented impulse concept and our experimental findings for sediment mobility at low bed shear stress conditions are also discussed.
Note: Determination of effective gas diffusion coefficients of stainless steel films with differently shaped holes using a Loschmidt diffusion cell
Authors: Astrath N. G. C. , Shen J. , Astrath F. B. G. , Zhou J. , Huang C. , Yuan X. Z. , Wang H. , Navessin T. , Liu Z. S. , Vlajnic G. , Bessarabov D. , Zhao X.
Published: April 2010

In this work, an in-house made Loschmidt diffusion cell is used to measure the effective O2–N2 diffusion coefficients through four porous samples of different simple pore structures. One-dimensional through-plane mass diffusion theory is applied to process the experimental data. It is found that both bulk diffusion coefficient and the effective gas diffusion coefficients of the samples can then be precisely determined, and the measured bulk one is in good agreement with the literature value. Numerical computation of three-dimensional mass diffusion through the samples is performed to calculate the effective gas diffusion coefficients. The comparison between the measured and calculated coefficient values shows that if the gas diffusion through a sample is dominated by one-dimensional diffusion, which is determined by the pore structure of the sample, these two values are consistent, and the sample can be used as a standard sample to test a gas diffusion measurement system.
Nonlocal hyper-Rayleigh scattering from liquid nitrobenzene
Authors: Shelton David P.
Published: April 2010

Hyper-Rayleigh scattering (HRS) from liquid nitrobenzene was measured for several combinations of linear polarized incident and scattered light, for a range of scattering angles near 90°. The observations show that the HRS intensity is dominated by the polar transverse collective mode contribution, and support a model where the long range dipole-dipole orientation correlations in a polar liquid result in coherent HRS from β(1), the vector part of the molecular first hyperpolarizability β, whereas HRS from the octupolar part β(3) remains local and incoherent.
Chain of excitation spot generation by aperture engineering
Authors: Mondal Partha Pratim
Published: April 2010

An optical technique is proposed for obtaining multiple excitation spots. Phase-matched counter propagating extended depth-of-focus fields were superimposed along the optical axis for generating multiple localized excitation spots. Moreover, the filtering effect due to the optical mask increases the lateral resolution. Proposed technique introduces the concept of simultaneous multiplane excitation and improves three-dimensional resolution.
A pulse system for spectrum analysis of magnetoelastic biosensors
Authors: Shen Wen , Mathison Leslie C. , Petrenko Valery A. , Chin Bryan A.
Published: April 2010

In this paper, a pulse system is reported whereby it is possible to detect concentrations of bacteria using small magnetoelastic biosensors. The system also allows detection using multiple sensors, where a control sensor can be used to compensate for environmental variables. This system removes the bias magnetic field and thus eliminates an error source. An equation is derived to describe the mechanical vibration of a sensor in a pulse system. Both frequency domain and time domain signals were studied to determine the optimum pulse power. The system was verified with a control sensor and a detection sensor to detect bacteria.
Modeling of porous silicon junction field effect transistor gas sensors: Insight into NO2 interaction
Authors: Barillaro G. , Lazzerini G. M. , Strambini L. M.
Published: April 2010

In this paper a lumped parameter electrical model for porous silicon junction field effect transistor (PSJFET) gas sensors is presented and experimentally validated. The PSJFET is an integrated p-channel JFET device modified with a porous silicon layer, the latter acting as sensing element. The model is described by using an analytical closed-form expression, which quantitatively links the sensor current to the analyte concentration in the environment, and validated by using experimental data of PSJFETs exposed to both synthetic air and NO2 with concentration of 300 ppb. Best fitting of experimental data with the proposed model allows one to get quantitative information on the effect of NO2 adsorption/desorption at the PS surface on electrical PS parameters, such as its conductance and surface charge density.
Numerical study of period multiplication and chaotic phenomena in an atmospheric radio-frequency discharge
Authors: Zhang Jiao , Wang Yanhui , Wang Dezhen
Published: April 2010

In this paper, a computational study of period multiplication and chaotic behavior of radio-frequency (rf) dielectric-barrier discharge (DBD) in atmospheric argon using an one-dimension fluid model was reported. These complex nonlinear behaviors are closely associated with the current-voltage characteristics of rf DBD, and mainly occur in γ-mode of rf DBD with relatively larger negative differential conductivity. With varying the discharge parameter rf DBD in γ-mode undergoes a transition from single-period discharge to chaos through period doubling bifurcation. When period multiplication and chaos take place, the sheath electric field bifurcates to cause the regular or irregular fluctuation in sheath thickness, consequently resulting in the period multiplication or chaotic behavior of the discharge current density. The spatial characteristics of rf period multiplication or chaotic discharges are also investigated.
Conical intersections in triplet excited states of methylene from the anti-Hermitian contracted Schrödinger equation
Authors: Snyder James W. , Rothman Adam E. , Foley Jonathan J. , Mazziotti David A.
Published: April 2010

A conical intersection in triplet excited states of methylene is computed through the direct calculation of two-electron reduced density matrices (2-RDMs) from solutions of the anti-Hermitian contracted Schrödinger equation (ACSE). The study synthesizes recent extensions of the ACSE method for the treatment of excited states [G. Gidofalvi and D. A. Mazziotti, Phys. Rev. A 80, 022507 (2009)] and arbitrary-spin states [A. E. Rothman, J. J. Foley, and D. A. Mazziotti, Phys. Rev. A 80, 052508 (2009)]. We compute absolute energies of the 1 B31, 1 A32, and 2 B31 states of methylene (CH2) and the location of the conical intersection along the 1 A32−2 B31 potential-energy surfaces. To treat multireference correlation, we seed the ACSE with an initial 2-RDM from a multiconfiguration self-consistent field (MCSCF) calculation. The ACSE produces energies that significantly improve upon those from MCSCF and second-order multireference many-body perturbation theory, and the 2-RDMs from the ACSE nearly satisfy necessary N-representability conditions. Comparison of the results from augmented double-zeta and triple-zeta basis sets demonstrates the importance of augmented (or diffuse) functions for determining the location of the conical intersection.
High efficiency X-band magnetically insulated line oscillator with a separate cathode
Authors: Xiao Renzhen , Song Wei , Song Zhimin , Sun Jun , Shao Hao , Chen Changhua
Published: April 2010

An X-band magnetically insulated line oscillator (MILO) with a separate cathode has been proposed in order to improve microwave output characteristics. The separate cathode consists of three parts with gradually decreased radii, which are divided by two deep grooves, and only partial cathode surfaces are allowed to emit electrons. In particle-in-cell simulation, high-power microwave with a power of 6.9 GW, frequency of 9.26 GHz, and efficiency of 20.6% is generated, compared with that of 12.2% obtained in a conventional cathode X-band MILO, and the power ratio of the output transverse-electromagnetic mode to transverse-magnetic (TM01) mode is increased from 4 to 27.
Identification of pseudodiatomic behavior in polyatomic bond dissociation: Reaction force analysis
Authors: Murray Jane S. , Toro-Labbé Alejandro , Gutiérrez-Oliva Soledad , Politzer Peter
Published: April 2010

An interesting uniformity that has been observed for diatomic molecular dissociation has been demonstrated to apply to many single bonds in polyatomic molecules as well. The energy to reach a key point in the bond-breaking process, at which it changes from simply stretching to transition to products, is for most cases a nearly constant fraction of the dissociation energy. The point at which this change occurs corresponds to the minimum of the reaction force F(R) for the dissociation, F(R) being the negative gradient of the potential energy along the reaction coordinate. Thirty nine single bonds were analyzed at the B3PW91/6-31++G(3d,2p) level. Both adiabatic and vertical stretching were considered; those bonds for which these give essentially the same results are labeled “pseudodiatomic.”
Mechanical control of magnetic states of finite carbon chains encapsulated in single wall carbon nanotubes
Authors: Xu B. , Lin J. Y. , Feng Y. P.
Published: April 2010

Effects of a lateral strain on finite carbon chains encapsulated in armchair carbon nanotubes are investigated using spin-polarized density functional theory. A strain induced transition between magnetic and nonmagnetic states of the encapsulated carbon chain is predicted at certain value of the applied strain which can be easily achieved experimentally, due to variation in interaction strength between the single wall carbon nanotube and the encapsulated carbon chain. Furthermore, this transition is reversible within a certain range of the applied strain. The proposed mechanical control of magnetic state of the hybrid system opens possibility for nanodevices such as mechanomagnetic switch or piezomagnetic sensors.
Modeling of colloid agglomeration inhibition inside a slitlike pore
Authors: Barcenas Mariana , Douda Janna , Duda Yurko , Orea Pedro
Published: April 2010

An extended particle agglomeration control model and Monte Carlo simulation methodology were used to describe the behavior of the colloidal aggregation process in presence of inhibitor as a confined fluid. In this work results about the mean cluster size, Z, with respect to different variables, temperature, inhibitor concentration and pore size, are presented and showed that Z strongly depends on the slitlike pore size. In addition, a temperature interval where the heating of the system leads to the particle clustering was found.
Ab initio study of shock compressed oxygen
Authors: Wang Cong , Zhang Ping
Published: April 2010

Quantum molecular dynamic simulations are introduced to study the shock compressed oxygen. The principal Hugoniot points derived from the equation of state agree well with the available experimental data. With the increase in pressure, molecular dissociation is observed. Electron spin polarization determines the electronic structure of the system under low pressure, while it is suppressed at the pressure higher than 30 GPa. Particularly, nonmetal-metal transition and optical properties of shock compressed oxygen are also discussed.
Effect of postdeposition annealing on the structural and electrical characteristics of Yb2TiO5 charge trapping layers
Authors: Pan Tung-Ming , Jung Ji-Shing , Wu Xin-Chang
Published: April 2010

In this letter, we proposed a metal-oxide-high-k-oxide-silicon-type (MOHOS) memory structure incorporating a high-k Yb2TiO5 charge trapping layer and the subsequent postdeposition annealing treatment. The effect of postdeposition annealing on the structural properties of Yb2TiO5 charge trapping layers was explored by x-ray diffraction, transmission electron microscopy, and x-ray photoelectron spectroscopy. The Yb2TiO5 MOHOS-type device annealed at 800 °C exhibited a larger memory window of 2.8 V and a smaller charge loss of 10% than did those prepared at other annealing temperatures. This outcome is attributed to the higher probability for trapping the charge carrier due to the formation of a well-crystallized Yb2TiO5 structure and a thin low-k interfacial layer.
Circuit model for a periodic array of slits sandwiched between two dielectric slabs
Authors: Rodríguez-Berral Raúl , Mesa Francisco , Medina Francisco
Published: April 2010

This paper proposes an equivalent circuit model that uses lumped elements and transmission lines to explain the transmission of electromagnetic waves through a conducting screen periodically perforated with slits and sandwiched between two different dielectric slabs. The present model relies on the impedance-matching point of view, previously introduced by some of the authors, rather than on the surface plasmon polariton concept. Thus, the model constitutes a simple and insightful framework that easily leads to accurate qualitative and quantitative predictions about the nature of the transmission spectrum of such structures.
High-speed all-optical terahertz polarization switching by a transient plasma phase modulator
Authors: Wen Haidan , Daranciang Dan , Lindenberg Aaron M.
Published: April 2010

We demonstrate high-speed all-optical polarization switching of broadband terahertz frequency electromagnetic fields with subpicosecond switch-on time. This is achieved through the use of a two-plasma configuration in an orthogonal geometry in which one plasma modulates the relative phase of a two-color optical pump field, enabling rapid terahertz polarization modulation at rates limited by the repetition-rate of the control pulse.
Stretching of turbulent eddies generates cavitation near a stagnation point
Authors: Lu Yuan , Gopalan Balaji , Celik Emine , Katz Joseph , Van Wie David M.
Published: April 2010

Cavitation inherently occurs in regions with low pressure. However, in recent experiments involving a high-speed bubbly jet impinging on a blunt body, we have observed rapid growth and stretching of bubbles near the stagnation point. The analysis of holographic particle image velocimetry data shows that turbulent eddies which originated from the jet are being stretched by the strain field in the vicinity of the stagnation point to form powerful vortices. Their strength and size along with the local strain rate are sufficient for decreasing the pressure in the vortex core below the vapor pressure, explaining the occurrence of cavitation in this region.
The viscosity and thermal conductivity of pure monatomic gases from their normal boiling point up to 5000 K in the limit of zero density and at 0.101325 MPa
Authors: Bich E. , Millat J. , Vogel E.
Published: April 2010

The kinetic theory of gases in the limit of zero density and that of moderately dense gases is used to generate accurate tables of the viscosity and thermal conductivity of the pure monatomic gases for zero density and for a pressure of 0.101325 MPa. The theoretically-based tables cover the temperature range from the normal boiling point of the relevant gas up to 5000 K. The associated uncertainties of the proposed data are detailed in the paper. A comparison of the correlated data with experimental results and some other recent correlations is given.
Experimental Stark widths and shifts for spectral lines of neutral and ionized atoms
Authors: Konjević N. , Wiese W. L.
Published: April 2010

A critical review of the available experimental data on Stark widths and shifts for spectral lines of non-hydrogenic neutral atoms and positive ions has been carried out. The review covers the period from 1983 through the end of 1988 and represents a continuation of earlier critical reviews up to 1982. Data tables containing the selected experimental Stark broadening parameters are presented with estimated accuracies. Guidelines for the accuracy estimates have been done developed during the previous reviews and are summarized. The data are arranged according to elements and spectra, and these are presented in alphabetical and numerical order, respectively. Comparisons with comprehensive calculations based either on the semiclassical theory, or—for multiply ionized atoms—on the modified semiempirical approximation, are made whenever possible, since the comparison with theory has often been a principal motivation for the experiments.
Preclinical model of organotypic culture for pharmacodynamic profiling of human tumors
Authors: Vaira Valentina , Fedele Giuseppe , Pyne Saumyadipta , Fasoli Ester , Zadra Giorgia , Bailey Dyane , Snyder Eric , Faversani Alice , Coggi Guido , Flavin Richard , Bosari Silvano , Loda Massimo
Published: April 2010

Predicting drug response in cancer patients remains a major challenge in the clinic. We have perfected an ex vivo, reproducible, rapid and personalized culture method to investigate antitumoral pharmacological properties that preserves the original cancer microenvironment. Response to signal transduction inhibitors in cancer is determined not only by properties of the drug target but also by mutations in other signaling molecules and the tumor microenvironment. As a proof of concept, we, therefore, focused on the PI3K/Akt signaling pathway, because it plays a prominent role in cancer and its activity is affected by epithelial–stromal interactions. Our results show that this culture model preserves tissue 3D architecture, cell viability, pathway activity, and global gene-expression profiles up to 5 days ex vivo. In addition, we show pathway modulation in tumor cells resulting from pharmacologic intervention in ex vivo culture. This technology may have a significant impact on patient selection for clinical trials and in predicting response to small-molecule inhibitor therapy.
MLCK-dependent exchange and actin binding region-dependent anchoring of ZO-1 regulate tight junction barrier function
Authors: Yu Dan , Marchiando Amanda M. , Weber Christopher R. , Raleigh David R. , Wang Yingmin , Shen Le , Turner Jerrold R.
Published: April 2010

The perijunctional actomyosin ring contributes to myosin light chain kinase (MLCK)-dependent tight junction regulation. However, the specific protein interactions involved in this process are unknown. To test the hypothesis that molecular remodeling contributes to barrier regulation, tight junction protein dynamic behavior was assessed by fluorescence recovery after photobleaching (FRAP). MLCK inhibition increased barrier function and stabilized ZO-1 at the tight junction but did not affect claudin-1, occludin, or actin exchange in vitro. Pharmacologic MLCK inhibition also blocked in vivo ZO-1 exchange in wild-type, but not long MLCK
−/−
, mice. Conversely, ZO-1 exchange was accelerated in transgenic mice expressing constitutively active MLCK. In vitro, ZO-1 lacking the actin binding region (ABR) was not stabilized by MLCK inhibition, either in the presence or absence of endogenous ZO-1. Moreover, the free ABR interfered with full-length ZO-1 exchange and reduced basal barrier function. The free ABR also prevented increases in barrier function following MLCK inhibition in a manner that required endogenous ZO-1 expression. In silico modeling of the FRAP data suggests that tight junction-associated ZO-1 exists in three pools, two of which exchange with cytosolic ZO-1. Transport of the ABR-anchored exchangeable pool is regulated by MLCK. These data demonstrate a critical role for the ZO-1 ABR in barrier function and suggest that MLCK-dependent ZO-1 exchange is essential to this mechanism of barrier regulation.
Divergent susceptibilities of human herpesvirus 6 variants to type I interferons
Authors: Jaworska Joanna , Gravel Annie , Flamand Louis
Published: April 2010

Two distinct human herpesvirus 6 (HHV-6) variants infect humans. HHV-6B is the etiologic agent of roseola and is associated with life-threatening neurological diseases, such as encephalitis, as well as organ transplant failure. The epidemiology and disease association for HHV-6A remain ill-defined. Specific anti-HHV-6 drugs do not exist and classic antiherpes drugs have secondary effects that are often problematic for transplant patients. Clinical trials using IFN were also performed with inconclusive results. We investigated the efficacy of type I IFN (α/β) in controlling HHV-6 infection. We report that cells infected with laboratory strains and primary isolates of HHV-6B are resistant to IFN-α/β antiviral actions as a result of improper IFN-stimulated gene (ISGs) expression. In contrast, HHV-6A-infected cells were responsive to IFN-α/β with pronounced antiviral effects observed. Type II IFN (γ)-signaling was unaltered in cells infected by either variant. The HHV-6B immediate-early 1 (IE1) physically interacts with STAT2 and sequestrates it to the nucleus. As a consequence, IE1B prevents the binding of ISGF3 to IFN-responsive gene promoters, resulting in ISG silencing. In comparison, HHV-6A and its associated IE1 protein displayed marginal ISG inhibitory activity relative to HHV-6B. The ISG inhibitory domain of IE1B mapped to a 41 amino acid region absent from IE1A. Transfer of this IE1B region resulted in a gain of function that conferred ISG inhibitory activity to IE1A. Our work is unique in demonstrating type I IFN signaling defects in HHV-6B-infected cells and highlights a major biological difference between HHV-6 variants.
Estradiol inhibits ongoing autoimmune neuroinflammation and NFκB-dependent CCL2 expression in reactive astrocytes
Authors: Giraud Sébastien N. , Caron Cécile M. , Pham-Dinh Danielle , Kitabgi Patrick , Nicot Arnaud B.
Published: April 2010

Astroglial reactivity associated with increased production of NFκB-dependent proinflammatory molecules is an important component of the pathophysiology of chronic neurological disorders such as multiple sclerosis (MS). The use of estrogens as potential anti-inflammatory and neuroprotective drugs is a matter of debate. Using mouse experimental allergic encephalomyelitis (EAE) as a model of chronic neuroinflammation, we report that implants reproducing pregnancy levels of 17β-estradiol (E2) alleviate ongoing disease and decrease astrocytic production of CCL2, a proinflammatory chemokine that drives the local recruitment of inflammatory myeloid cells. Immunohistochemistry and confocal imaging reveal that, in spinal cord white matter EAE lesions, reactive astrocytes express estrogen receptor (ER)α (and to a lesser extent ERβ) with a preferential nuclear localization, whereas other cells including infiltrated leukocytes express ERs only in their membranes or cytosol. In cultured rodent astrocytes, E2 or an ERα agonist, but not an ERβ agonist, inhibits TNFα-induced CCL2 expression at nanomolar concentrations, and the ER antagonist ICI 182,170 blocks this effect. We show that this anti-inflammatory action is not associated with inhibition of NFκB nuclear translocation but rather involves direct repression of NFκB-dependent transcription. Chromatin immunoprecipitation assays further indicate that estrogen suppresses TNFα-induced NFκB recruitment to the
CCL2
enhancer. These data uncover reactive astrocytes as an important target for nuclear ERα inhibitory action on chemokine expression and suggest that targeting astrocytic nuclear NFκB activation with estrogen receptor α modulators may improve therapies of chronic neurodegenerative disorders involving astroglial neuroinflammation.
Net charge per residue modulates conformational ensembles of intrinsically disordered proteins
Authors: Mao Albert H. , Crick Scott L. , Vitalis Andreas , Chicoine Caitlin L. , Pappu Rohit V.
Published: April 2010

Intrinsically disordered proteins (IDPs) adopt heterogeneous ensembles of conformations under physiological conditions. Understanding the relationship between amino acid sequence and conformational ensembles of IDPs can help clarify the role of disorder in physiological function. Recent studies revealed that polar IDPs favor collapsed ensembles in water despite the absence of hydrophobic groups—a result that holds for polypeptide backbones as well. By studying highly charged polypeptides, a different archetype of IDPs, we assess how charge content modulates the intrinsic preference of polypeptide backbones for collapsed structures. We characterized conformational ensembles for a set of protamines in aqueous milieus using molecular simulations and fluorescence measurements. Protamines are arginine-rich IDPs involved in the condensation of chromatin during spermatogenesis. Simulations based on the ABSINTH implicit solvation model predict the existence of a globule-to-coil transition, with net charge per residue serving as the discriminating order parameter. The transition is supported by quantitative agreement between simulation and experiment. Local conformational preferences partially explain the observed trends of polymeric properties. Our results lead to the proposal of a schematic protein phase diagram that should enable prediction of polymeric attributes for IDP conformational ensembles using easily calculated physicochemical properties of amino acid sequences. Although sequence composition allows the prediction of polymeric properties, interresidue contact preferences of protamines with similar polymeric attributes suggest that certain details of conformational ensembles depend on the sequence. This provides a plausible mechanism for specificity in the functions of IDPs.