bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of P addition on nanocrystallization and high temperature magnetic properties of low B and Nb containing FeCo nanocomposites
Authors: Roy Rajat K. , Shen S. , Kernion S. J. , McHenry M. E.
Published: February 2012

The P content dependencies of the nanocrystallization behaviors and high temperature magnetic properties of the Fe54.6Co29.4Si2.8(B0.8−YPY)14Nb1Cu1 (Y = 0, 0.2, and 0.3) alloys have been investigated. Alloys were prepared by melt spinning and subsequently annealed in an argon atmosphere to induce nanocrystallization. P addition increases primary crystallization temperature (Tx1), thermal stability (ΔTx), and activation energy (QJMA) for secondary crystallization in as-cast alloys. The saturation induction (Bs) of 1.68 T for as-cast P free alloy decreases continuously with the addition of P. However, the soft magnetic properties are enhanced for P added alloys. The XRD pattern reveals that grain refinement increases with increasing P contents. Alloys annealed at 430 °C confirm primary nanocrystallization of α-FeCo in the amorphous matrix, while annealing at 550 °C causes secondary crystallization of other non-magnetic phases as well. The magnetic moment of as-cast and annealed alloys, measured by vibrating sample magnetometry (VSM), has minimum values at two temperatures, labeled Tc1, Tc2, prior to secondary crystallization, corresponding to the ferromagnetic transitions of as-quenched amorphous and residual amorphous phase, respectively. The stabilization of amorphous phase delays primary crystallization, resulting in increase of Tc1 for P-rich as-cast alloys.
Skin effect suppression for Cu/CoZrNb multilayered inductor
Authors: Sato Noriyuki , Endo Yasushi , Yamaguchi Masahiro
Published: February 2012

The Cu/Co85Zr3Nb12 multilayer is studied as a conductor of a spiral inductor to suppress the skin effect at the 5 GHz range (matches IEEE 802.11 a standard) using negative-permeability in CoZrNb films beyond the ferromagnetic resonance frequency. The skin effect suppression becomes remarkable when the thickness of Cu in each period of the multilayer, tCu, is less than the skin depth of Cu at the targeting frequency. For the 5 GHz operation, tCu ≤ 750 nm. The resistance of the Cu/CoZrNb multilayered spiral inductor decreases as much as 8.7%, while keeping the same inductance of 1.1 nH as that of a similar air core. Accordingly, Q = 16. Therefore, the proposed method can contribute to realize a high-Q spiral inductor. We also study the potentially applicable frequency of this method. Given a soft magnetic material with Ms = 105 emu/cc and Hk = 5 Oe, the method can be applied at 700 MHz, the lowermost carrier frequency band for the 4th generation cellular phone system.
Oscillatory magnetic anisotropy due to quantum well states in thin ferromagnetic films (invited)
Authors: Przybylski M. , Dąbrowski M. , Bauer U. , Cinal M. , Kirschner J.
Published: February 2012

Magnetic anisotropy depends strongly on the density of states at the Fermi level. If significant contributions to magnetocrystalline anisotropy energy (MAE) are due to spin-polarized quantum well states (QWS), a significant increase of MAE can occur periodically as a function of film thickness. The oscillation period L is determined by the wavelength of the corresponding electron waves. The uniaxial magnetic anisotropy of fcc-Co is found to oscillate with a period of 2.3 ML. In contrast, in bcc-Fe, the uniaxial magnetic anisotropy oscillates with a period of 5.9 ML. We attribute such oscillations to QWS in a minority-spin d-band at the Fermi level.
Physical, electrical and magnetic properties of nano-sized Co-Cr substituted magnesium ferrites
Authors: Javed Iqbal Muhammad , Ahmad Zahoor , Meydan Turgut , Melikhov Yevgen
Published: February 2012

Co-Cr substituted magnesium ferrite nanomaterials (Mg1−xCoxCrxFe2−xO4 with x = 0.0−0.5) have been prepared by the polyethylene glycol assisted micro emulsion method. X-ray diffraction analysis confirms the single-phase cubic close-packed lattice formation of synthesized materials. Hysteresis loops are measured up to field of 4 MA/m and high field region of these loops are modeled using the Law of Approach to saturation to calculate the magnetocrystalline anisotropy constant. The saturation magnetization of the samples increases initially from 148 kA/m for x = 0.0 to 299 kA/m (x = 0.3) and then decreases to 187 kA/m (x = 0.5). Curie temperature for this series is found to be in the range of 618-766 K. Room temperature resistivity increases gradually from 7.5 × 108 Ω cm (x = 0.0) to 3.47 × 109 Ω cm (x = 0.5). Additionally, dielectric measurements are carried out at room temperature in a frequency range of 100 Hz to 3 MHz. With improvement in the values of the above-mentioned properties, the synthesized materials could be suitable for potential application in some magnetic and microwave devices.
Mechanical properties of highly oriented FeSe0.5Te0.5 superconductor
Authors: Luiz Pimentel Júnior Jorge , Pureur Paulo , Santos Lopes Cristiano , Carlos Serbena Francisco , Eugênio Foerster Carlos , Aparecida da Silva Simone , Roberto Jurelo Alcione , Luiz Chinelatto Adilson
Published: February 2012

We have synthesized highly oriented samples of the superconducting compound FeSe0.5Te0.5 and investigated its mechanical properties. These samples were characterized by scanning electron microscopy (SEM) with energy-dispersive analysis, x-ray diffraction, and electrical resistivity. The measured critical temperature is TC~ 14.5 K. Hardness and elastic modulus on the ab- and a(b)c-plane were obtained by instrumented indentation. The samples’ morphology consists of plate-like crystals with a lamellar structure. Two phases were observed with a typically eutectic microstructure composed by white and gray lamellas when observed with SEM using backscattered electrons. The white phase is richer in Te and poorer in Se than the gray phase. No significant differences in hardness and elastic modulus were observed between ab- and a(b)c-planes. Hardness profiles indicated values in the range 0.6–0.8 GPa at deep tip penetration depths, while the elastic modulus showed values in between 20–25 GPa. Cracking was occasionally observed in the ab-plane and at low loads.
Electrical properties of individual NiFe/Pt multilayer nanowires measured in situ in a scanning electron microscope
Authors: Elawayeb Mohamed , Peng Yong , Briston Kevin J. , Inkson Beverley J.
Published: February 2012

The electrical properties of individual NiFe/Pt multilayer nanowires have been measured in situ by nanomanipulators in a scanning electron microscope. The electrical measurement of ∼50 nm diameter individual NiFe/Pt multilayer nanowires with polycrystalline microstructure shows that the nanowires have a resistivity of ∼2.2 × 10−7 Ω m (corresponding to a conductivity of ∼4.5× 106 Ω−1 m−1) and average resistance of individual NiFe-Pt interfaces of ∼0.2 Ω. The maximum failure current density of an individual NiFe/Pt nanowire was measured to be ∼9.63 × 1011 A m−2.
Superconductivity in the vicinity of ferromagnetism in oxygen free perovskite MgCNi3: An experimental and density functional theory study
Authors: Kumar Anuj , Jha Rajveer , Kumar Singh Shiva , Kumar Jagdish , Ahluwalia P. K. , Tandon R. P. , Awana V. P. S.
Published: February 2012

We report synthesis, structural, magnetic, specific heat, and density functional theory (DFT) studies on the MgCNi3 superconductor. Polycrystalline MgCNi3 samples are synthesized through the standard solid state reaction route and found to crystallize in the cubic perovskite structure with space group Pm3m, without any detectable trace of Ni impurity. Both AC and DC magnetization exhibited superconducting transition (Tc) at around 7.25 K. The lower critical field (Hc1) and irreversibility field (Hirr) are around 140 Oe and 11 kOe, respectively, at 2 K. The upper critical field (Hc2) being determined from in-field AC susceptibility measurements is 11.6 kOe and 91.70 kOe with 50% and 90% diamagnetism criteria, respectively. Heat capacity (Cp) measurements are carried out under an applied field of up to 140 kOe and down to 2 K. The Sommerfeld constant (γ) and Debye temperature (ΘD) as determined from low temperature fitting of Cp(T) data to the Sommerfeld-Debye model are 36.13 mJ/mol K2 and 263.13 K, respectively. The Bardeen-Cooper-Schrieffer (BCS) parameter (2Δ/KBTc) is around 3.62, suggesting MgCNi3 to be an intermediate coupled BCS superconductor with value λ = 0.69. Although the DFT calculations exhibited the compound to be non-magnetic but with spin fluctuations, the experimental isothermal magnetization MH loops at 20, 50, 100, 200, and 300 K showed some ferromagnetic nature in this compound with coercive field (Hc) of around 50 Oe at 20 K. The Ni3d states play dominant roles near the Fermi levels and there is strong hybridization between Ni3d and C2p states. It seems that MgCNi3 is superconducting in close proximity of ferromagnetism.
Na incorporation into Cu(In,Ga)Se2 thin-film solar cell absorbers deposited on polyimide: Impact on the chemical and electronic surface structure
Authors: Song X. , Caballero R. , Félix R. , Gerlach D. , Kaufmann C. A. , Schock H.-W. , Wilks R. G. , Bär M.
Published: February 2012

Na has deliberately been incorporated into Cu(In,Ga)Se2 (“CIGSe”) chalcopyrite thin-film solar cell absorbers deposited on Mo-coated polyimide flexible substrates by adding differently thick layers of NaF in-between CIGSe absorber and Mo back contact. The impact of Na on the chemical and electronic surface structure of CIGSe absorbers with various Cu-contents deposited at comparatively low temperature (420 °C) has been studied using x-ray photoelectron and x-ray excited Auger electron spectroscopy. We observe a higher Na surface content for the Cu-richer CIGSe samples and can distinguish between two different chemical Na environments, best described as selenide-like and oxidized Na species, respectively. Furthermore, we find a Cu-poor surface composition of the CIGSe samples independent of Na content and — for very high Na contents — indications for the formation of a (Cu,Na)–(In,Ga)–Se like compound. With increasing Na surface content, also a shift of the photoemission lines to lower binding energies could be identified, which we interpret as a reduction of the downward band bending toward the CIGSe surface explained by the Na-induced elimination of InCu defects.
Fluid flows in a librating cylinder
Authors: Sauret Alban , Cébron David , Le Bars Michael , Le Dizès Stéphane
Published: February 2012

The flow in a cylinder driven by time-harmonic oscillations of the rotation rate, called longitudinal librations, is investigated. Using a theoretical approach and axisymmetric numerical simulations, we study two distinct phenomena appearing in this librating flow. First, we investigate the occurrence of a centrifugal instability near the oscillating boundary, leading to the so-called Taylor-Görtler vortices. A viscous stability criterion is derived and compared to numerical results obtained for various libration frequencies and Ekman numbers. The strongly nonlinear regime well above the instability threshold is also documented. We show that a new mechanism of spontaneous generation of inertial waves in the bulk could exist when the sidewall boundary layer becomes turbulent. Then, we analyse the librating flow below the instability threshold and characterize the mean zonal flow correction induced by the nonlinear interaction of the boundary layer flow with itself. In the frequency regime where inertial modes are not excited, we show that the mean flow correction in the bulk is a uniform rotation, independent of the Ekman number and cylinder aspect ratio, in perfect agreement with the analytical results of Wang [“Cylindrical tank of fluid oscillating about a state of steady rotation,” J. Fluid. Mech. 41, 581 (1970)]. When inertial modes are resonantly excited, the mean flow correction is found to have a more complex structure. Its amplitude still scales as the square of the libration amplitude but now depends on the Ekman number.
Trajectory-guided configuration interaction simulations of multidimensional quantum dynamics
Authors: Habershon Scott
Published: February 2012

We propose an approach to modelling multidimensional quantum systems which uses direct-dynamics trajectories to guide wavefunction propagation. First, trajectory simulations are used to generate a sample of dynamically relevant configurations on the potential energy surface (PES). Second, the sampled configurations are used to construct an n-mode representation of the PES using a greedy algorithm. Finally, the time-dependent Schrödinger equation is solved using a configuration interaction expansion of the wavefunction, with individual basis functions derived directly from the 1-mode contributions to the n-mode PES. This approach is successfully demonstrated by application to a 20-dimensional benchmark problem describing tunnelling in the presence of coupled degrees of freedom.
The thermodynamic limits of magnetic recording
Authors: Richter H. J. , Lyberatos A. , Nowak U. , Evans R. F. L. , Chantrell R. W.
Published: February 2012

Thermal stability of the recorded information is generally thought to set the limit of the maximum possible density in magnetic recording. It is shown that basic thermodynamics always cause the probability of success of the write process to be less than 100%. This leads to a thermally induced error rate, which eventually limits the maximum possible density beyond that given by the traditional thermal stability limit. While the thermally induced error rate is negligible for recording of simple single domain particles, it rapidly increases in the presence of a write assist, in particular if the write assist is accomplished by an increased recording temperature. For the ultimate recording system that combines thermally assisted writing with a recording scheme that uses one grain per bit, the upper bound for the maximum achievable density is 20 Tbit/inch2 for a bit error rate target of 10−2.
Parabolic polarization splitting of Tamm states in a metal-organic microcavity
Authors: Brückner R. , Sudzius M. , Hintschich S. I. , Fröb H. , Lyssenko V. G. , Kaliteevski M. A. , Iorsh I. , Abram R. A. , Kavokin A. V. , Leo K.
Published: February 2012

We observe hybrid states of cavity photons and Tamm plasmons in an organic microcavity with an incorporated thin silver layer of increasing thickness up to 40 nm. Via μ-photoluminescence spectroscopy, we investigate their angular dependence. At oblique angles, we observe a TE-TM polarization splitting of more than 40 meV for each mode. An analytical model is developed to describe the coupling of Tamm plasmons and cavity photons and to account for the splitting of the orthogonally polarized resonances.
Effects of the transparent cathode on the performance of a relativistic magnetron with axial radiation
Authors: Li Wei , Liu Yong-gui , Zhang Jun , Shu Ting , Yang Han-wu , Fan Yu-wei , Yuan Cheng-wei
Published: February 2012

Experimental investigation of the transparent cathode used in a relativistic magnetron with axial radiation is reported in this paper. The transparent cathode is composed of six separate stalks with the diameter of 6 mm. Under the working condition of 549 kV and ∼0.38 T, the relativistic magnetron with the transparent cathode experimentally produces a 550 MW microwave. The radiation mode is TE11 at the frequency of 2.35 GHz. The total efficiency is 16.7%. The variations of the relative positions between the separate stalks and the anode blocks can perform the maximum difference of 4 ns in microwave duration. Compared with the conventional solid cathode, the transparent cathode provides faster startup time of 12 ns, relatively wider pulse duration of 35% and relatively higher efficiency of 10.6%.
The dependence of extracted current on discharge gas pressure in neutral beam ion sources on HL-2A tokamak
Authors: Wei H. L. , Cao J. Y. , Rao J. , Lei G. J. , Jiang S. F. , Liu H. , Yu L. M. , Xie W. M. , Li M. , Yang X. F. , Zou G. Q. , Lu D. L. , Duan X. R.
Published: February 2012

The discharge gas pressure is a key factor to influence the extracted current of ion source. In this paper, the dependence of extracted current on discharge gas pressure was investigated in detail at different arc discharge currents. The discharge gas pressure with a very broad range (0.1 Pa–2.7 Pa) was scanned for the first time. It is turned out that, with the increasing of discharge gas pressure, the extracted current increases and the arc voltage decreases at different arc currents; however, when the discharge gas pressure exceeds a certain value, the extracted current decreases. For the same discharge gas pressure, the higher the arc current, the higher the arc voltage and the extracted current are. The arc efficiency was also calculated, and its dependence on gas pressure was almost the same with the dependence of extracted current on gas pressure, but at the same discharge gas pressure, the lower the arc current, the higher the arc efficiency is and the lower the extracted current is.
Rectifying behaviors induced by BN-doping in trigonal graphene with zigzag edges
Authors: Deng X. Q. , Zhang Z. H. , Tang G. P. , Fan Z. Q. , Qiu M. , Guo C.
Published: February 2012

Based on nonequilibrium Green’s functions in combination with density-function theory, the transport properties of trigonal graphenes, with the vertex carbon atom substituted by one phosphorus or boron atom and bounded through a B-N pair, coupled to gold electrodes are investigated. The rectification behavior can be observed because a potential barrier similar to the p-n junction is formed in the B-N region of central molecule. When the size of a central molecule is enlarged, rectification ratio is improved greatly since the barrier height in it is enhanced as well.
Twin-Foucault imaging method
Authors: Harada Ken
Published: February 2012

A method of Lorentz electron microscopy, which enables observation two Foucault images simultaneously by using an electron biprism instead of an objective aperture, was developed. The electron biprism is installed between two electron beams deflected by 180° magnetic domains. Potential applied to the biprism deflects the two electron beams further, and two Foucault images with reversed contrast are then obtained in one visual field. The twin Foucault images are able to extract the magnetic domain structures and to reconstruct an ordinary electron micrograph. The developed Foucault method was demonstrated with a 180° domain structure of manganite La0.825Sr0.175MnO3.
X-ray spatial frequency heterodyne imaging
Authors: Wu Binbin , Liu Yanan , Rose-Petruck Christoph , Diebold Gerald J.
Published: February 2012

We derive an expression for the electric field at the image plane from the Kirchhoff-Fresnel integral for a grating in contact with an object in an x-ray, in-line imaging configuration that shows the grating to give a heterodyning effect. We also show how image contrast in a harmonic of the grating is enhanced depending on the first space derivative of the phase function. Experiments are reported where a Fourier component of the image intensity gives contrast at the edges of objects significantly larger than that found with conventional in-line phase contrast imaging.
Strain-vorticity induced secondary motion in shallow flows
Authors: Kamp Leon P. J.
Published: February 2012

Deviations from two-dimensionality of a shallow flow that is dominated by bottom friction are quantified in terms of the spatial distribution of strain and vorticity as described by the Okubo-Weiss function. This result is based on a Poisson equation for the pressure in a quasi-horizontal (primary) flow. It is shown that the Okubo-Weiss function specifies vertical pressure gradients, which for their part drive vertical (secondary) motion. An asymptotic expansion of these gradients based on the smallness of the vertical to horizontal scale ratio demonstrates that the sign and magnitude of secondary circulation inside the fluid layer is dictated by the signs and magnitude of the Okubo-Weiss function. As a consequence of this, secondary motion as well as nonzero horizontal divergence do also depend on the strength, i.e., the Reynolds number of the primary flow. The theory is exemplified by two generic vortical structures (monopolar and dipolar structures). Most importantly, the theory can be applied to more complicated turbulent shallow flows in order to assess the degree of two-dimensionality using measurements of the free-surface flow only.
Asymptotic stability of vacuum twisting type II metrics
Authors: Natorf Włodzimierz
Published: February 2012

We generalize the result of Lukács et al. on asymptotic stability of the Schwarzschild metric with respect to perturbations in the Robinson-Trautman class of metrics to the case of Petrov type II twisting metrics, under the condition of asymptotic flatness at future null infinity. The Bondi energy is used as the Lyapunov functional and we prove that the “final state” of such metrics is the Kerr metric.
Manganese dioxide modified silicon nanowires and their excellent catalysis in the decomposition of methylene blue
Authors: Gao Weiwei , Shao Mingwang , Yang Li , Zhuo Shujuan , Ye Shiyong , Lee Shuit-tong
Published: February 2012

A redox between hydrofluoric acid and ammonium fluoride-treated silicon nanowires and potassium permanganate solution was investigated. The results showed that MnO2 nanoparticles might grow on the surface of silicon nanowires, which was confirmed with the transmission electron microscope. These MnO2 modified silicon nanowires were employed as catalysts in the decomposition of methylene blue using sodium borohydride as the reducing agent, which exhibited excellent catalysis with its reaction rate 6 times larger than the unsupported MnO2.
Full band atomistic modeling of homo-junction InGaAs band-to-band tunneling diodes including band gap narrowing
Authors: Cho Woo-Suhl , Luisier Mathieu , Mohata Dheeraj , Datta Suman , Pawlik David , Rommel Sean L. , Klimeck Gerhard
Published: February 2012

A homo-junction In0.53Ga0.47As tunneling diode is investigated using full-band, atomistic quantum transport approach based on a tight-binding model (TB) and the non-equilibrium Green’s function formalism. Band gap narrowing (BGN) is included in TB by altering its parameters using the Jain-Roulston model [S. C. Jain and D. J. Roulston, Solid-State Electron. 34, 453 (1991)]. BGN is found to be critical in the determination of the current peak and the second turn-on in the forward bias region. Empirical excess current that mimics additional recombination paths must be added to the calculation to model the diode behavior in the valley current region. Overall, the presented model reproduces experimental data well.
Thermal and structural dependence of the band gap of quantum dots measured by a transparent film heater
Authors: Yeon Woo Ju , Kumar Tripathy Suraj , Kim Kyungnam , Han Chang-Soo
Published: February 2012

We report the temperature dependence of the optical absorption and emission spectra of quantum dots (QDs) for three different nanocrystal (NC) structures (CdSe core, CdSe/CdS core/shell, and CdSe/CdS/ZnS core/multishell) in the solid film state. For this, a transparent single-walled carbon nanotube (SWCNT) film attached to a QD thin layer was tested as a heater. The temperature dependence of spectral shifts in both absorption and emission of QDs was measured in the range 300–450 K, and the Stokes shift was calculated by measuring the energy difference between the absorption and emission peaks. We found that the Stokes shift decreased as QD shells were added and the temperature was increased, indicating a weaker electron–phonon coupling in the QDs with additional shells at higher temperature. Finally, the band gap of the QDs was measured as a function of temperature. The Debye temperature was obtained by empirically fitting the energy band gap.
Protein phosphatase 1 subunit Ppp1r15a/GADD34 regulates cytokine production in polyinosinic:polycytidylic acid-stimulated dendritic cells
Authors: Clavarino Giovanna , Cláudio Nuno , Dalet Alexandre , Terawaki Seigo , Couderc Thérèse , Chasson Lionel , Ceppi Maurizio , Schmidt Enrico K. , Wenger Till , Lecuit Marc , Gatti Evelina , Pierre Philippe
Published: February 2012

In response to inflammatory stimulation, dendritic cells (DCs) have a remarkable pattern of differentiation that exhibits specific mechanisms to control the immune response. Here we show that in response to polyriboinosinic:polyribocytidylic acid (pI:C), DCs mount a specific integrated stress response during which the transcription factor ATF4 and the growth arrest and DNA damage-inducible protein 34 (GADD34/Ppp1r15a), a phosphatase 1 (PP1) cofactor, are expressed. In agreement with increased GADD34 levels, an extensive dephosphorylation of the translation initiation factor eIF2α was observed during DC activation. Unexpectedly, although DCs display an unusual resistance to protein synthesis inhibition induced in response to cytosolic dsRNA, GADD34 expression did not have a major impact on protein synthesis. GADD34, however, was shown to be required for normal cytokine production both in vitro and in vivo. These observations have important implications in linking further pathogen detection with the integrated stress response pathways.
Chimpanzees’ flexible targeted helping based on an understanding of conspecifics’ goals
Authors: Yamamoto Shinya , Humle Tatyana , Tanaka Masayuki
Published: February 2012

Humans extensively help others altruistically, which plays an important role in maintaining cooperative societies. Although some nonhuman animals are also capable of helping others altruistically, humans are considered unique in our voluntary helping and our variety of helping behaviors. Many still believe that this is because only humans can understand others’ goals due to our unique “theory of mind” abilities, especially shared intentionality. However, we know little of the cognitive mechanisms underlying helping in nonhuman animals, especially if and how they understand others’ goals. The present study provides the empirical evidence for flexible targeted helping depending on conspecifics’ needs in chimpanzees. The subjects of this study selected an appropriate tool from a random set of seven objects to transfer to a conspecific partner confronted with differing tool-use situations, indicating that they understood what their partner needed. This targeted helping, (i.e., selecting the appropriate tool to transfer), was observed only when the helpers could visually assess their partner's situation. If visual access was obstructed, the chimpanzees still tried to help their partner upon request, but failed to select and donate the appropriate tool needed by their partner. These results suggest that the limitation in chimpanzees’ voluntary helping is not necessarily due to failure in understanding others’ goals. Chimpanzees can understand conspecifics’ goals and demonstrate cognitively advanced targeted helping as long as they are able to visually evaluate their conspecifics’ predicament. However, they will seldom help others without direct request for help.
Optimal inference of sameness
Authors: van den Berg Ronald , Vogel Michael , Josić Krešimir , Ma Wei Ji
Published: February 2012

Deciding whether a set of objects are the same or different is a cornerstone of perception and cognition. Surprisingly, no principled quantitative model of sameness judgment exists. We tested whether human sameness judgment under sensory noise can be modeled as a form of probabilistically optimal inference. An optimal observer would compare the reliability-weighted variance of the sensory measurements with a set size-dependent criterion. We conducted two experiments, in which we varied set size and individual stimulus reliabilities. We found that the optimal-observer model accurately describes human behavior, outperforms plausible alternatives in a rigorous model comparison, and accounts for three key findings in the animal cognition literature. Our results provide a normative footing for the study of sameness judgment and indicate that the notion of perception as near-optimal inference extends to abstract relations.
Cortical topography of intracortical inhibition influences the speed of decision making
Authors: Wilimzig Claudia , Ragert Patrick , Dinse Hubert R.
Published: February 2012

The neocortex contains orderly topographic maps; however, their functional role remains controversial. Theoretical studies have suggested a role in minimizing computational costs, whereas empirical studies have focused on spatial localization. Using a tactile multiple-choice reaction time (RT) task before and after the induction of perceptual learning through repetitive sensory stimulation, we extend the framework of cortical topographies by demonstrating that the topographic arrangement of intracortical inhibition contributes to the speed of human perceptual decision-making processes. RTs differ among fingers, displaying an inverted U-shaped function. Simulations using neural fields show the inverted U-shaped RT distribution as an emergent consequence of lateral inhibition. Weakening inhibition through learning shortens RTs, which is modeled through topographically reorganized inhibition. Whereas changes in decision making are often regarded as an outcome of higher cortical areas, our data show that the spatial layout of interaction processes within representational maps contributes to selection and decision-making processes.
The protein kinase Akt1 regulates the interferon response through phosphorylation of the transcriptional repressor EMSY
Authors: Ezell Scott A. , Polytarchou Christos , Hatziapostolou Maria , Guo Ailan , Sanidas Ioannis , Bihani Teeru , Comb Michael J. , Sourvinos George , Tsichlis Philip N.
Published: February 2012

The protein kinases Akt1, Akt2, and Akt3 possess nonredundant signaling properties, few of which have been investigated. Here, we present evidence for an Akt1-dependent pathway that controls interferon (IFN)-regulated gene expression and antiviral immunity. The target of this pathway is EMSY, an oncogenic interacting partner of BRCA2 that functions as a transcriptional repressor. Overexpression of EMSY in hTERT-immortalized mammary epithelial cells, and in breast and ovarian carcinoma cell lines, represses IFN-stimulated genes (ISGs) in a BRCA2-dependent manner, whereas its knockdown has the opposite effect. EMSY binds to the promoters of ISGs, suggesting that EMSY functions as a direct transcriptional repressor. Akt1, but not Akt2, phosphorylates EMSY at Ser209, relieving EMSY-mediated ISG repression. The Akt1/EMSY/ISG pathway is activated by both viral infection and IFN, and it inhibits the replication of HSV-1 and vesicular stomatitis virus (VSV). Collectively, these data define an Akt1-dependent pathway that contributes to the full activation of ISGs by relieving their repression by EMSY and BRCA2.
Human genetic variation altering anthrax toxin sensitivity
Authors: Martchenko Mikhail , Candille Sophie I. , Tang Hua , Cohen Stanley N.
Published: February 2012

The outcome of exposure to infectious microbes or their toxins is influenced by both microbial and host genes. Some host genes encode defense mechanisms, whereas others assist pathogen functions. Genomic analyses have associated host gene mutations with altered infectious disease susceptibility, but evidence for causality is limited. Here we demonstrate that human genetic variation affecting capillary morphogenesis gene 2 (
CMG2
), which encodes a host membrane protein exploited by anthrax toxin as a principal receptor, dramatically alters toxin sensitivity. Lymphoblastoid cells derived from a HapMap Project cohort of 234 persons of African, European, or Asian ancestry differed in sensitivity mediated by the protective antigen (PA) moiety of anthrax toxin by more than four orders of magnitude, with 99% of the cohort showing a 250-fold range of sensitivity. We find that relative sensitivity is an inherited trait that correlates strongly with
CMG2
mRNA abundance in cells of each ethnic/geographical group and in the combined population pool (
P
= 4 × 10
−11
). The extent of
CMG2
expression in transfected murine macrophages and human lymphoblastoid cells affected anthrax toxin binding, internalization, and sensitivity. A
CMG2
single-nucleotide polymorphism (SNP) occurring frequently in African and European populations independently altered toxin uptake, but was not statistically associated with altered sensitivity in HapMap cell populations. Our results reveal extensive human diversity in cell lethality dependent on PA-mediated toxin binding and uptake, and identify individual differences in
CMG2
expression level as a determinant of this diversity. Testing of genomically characterized human cell populations may offer a broadly useful strategy for elucidating effects of genetic variation on infectious disease susceptibility.
Impaired neurotransmission caused by overexpression of α-synuclein in nigral dopamine neurons
Authors: Lundblad Martin , Decressac Mickael , Mattsson Bengt , Björklund Anders
Published: February 2012

We used in vivo amperometry to monitor changes in synaptic dopamine (DA) release in the striatum induced by overexpression of human wild-type α-synuclein in nigral DA neurons, induced by injection of an adeno-associated virus type 6 (AAV6)–α-synuclein vector unilaterally into the substantia nigra in adult rats. Impairments in DA release evolved in parallel with the development of degenerative changes in the nigrostriatal axons and terminals. The earliest change, seen 10 d after vector injection, was a marked, ≈50%, reduction in DA reuptake, consistent with an early dysfunction of the DA transporter that developed before any overt signs of axonal damage. At 3 wk, when the first signs of axonal damage were observed, the amount of DA released after a KCl pulse was reduced by 70–80%, and peak DA concentration was delayed, indicating an impaired release mechanism. At later time points, 8–16 wk, overall striatal innervation density was reduced by 60–80% and accompanied by abundant signs of axonal damage in the form of α-synuclein aggregates, axonal swellings, and dystrophic axonal profiles. At this stage DA release and reuptake were profoundly reduced, by 80–90%. The early changes in synaptic DA release induced by overexpression of human α-synuclein support the idea that early predegenerative changes in the handling of DA may initiate, and drive, a progressive degenerative process that hits the axons and terminals first. Synaptic dysfunction and axonopathy would thus be the hallmark of presymptomatic and early-stage Parkinson disease, followed by neuronal degeneration and cell loss, characteristic of more advanced stages of the disease.
Polycation-siRNA nanoparticles can disassemble at the kidney glomerular basement membrane
Authors: Zuckerman Jonathan E. , Choi Chung Hang J. , Han Han , Davis Mark E.
Published: February 2012

Despite being engineered to avoid renal clearance, many cationic polymer (polycation)-based siRNA nanoparticles that are used for systemic delivery are rapidly eliminated from the circulation. Here, we show that a component of the renal filtration barrier—the glomerular basement membrane (GBM)—can disassemble cationic cyclodextrin-containing polymer (CDP)-based siRNA nanoparticles and, thereby, facilitate their rapid elimination from circulation. Using confocal and electron microscopies, positron emission tomography, and compartment modeling, we demonstrate that siRNA nanoparticles, but not free siRNA, accumulate and disassemble in the GBM. We also confirm that the siRNA nanoparticles do not disassemble in blood plasma in vitro and in vivo. This clearance mechanism may affect any nanoparticles that assemble primarily by electrostatic interactions between cationic delivery components and anionic nucleic acids (or other therapeutic entities).
Seasonal Influenza Vaccine Compliance among Hospital-Based and Nonhospital-Based Healthcare Workers
Authors: Rebmann Terri , Wright Kathleen S. , Anthony John , Knaup Richard C. , Peters Eleanor B.
Published: February 2012

Background.

Influenza vaccination among nonhospital healthcare workers (HCWs) is imperative, but only limited data are available for factors affecting their compliance.

Objective.

To examine the factors influencing influenza vaccine compliance among hospital and nonhospital HCWs.

Design and Setting.

A vaccine compliance questionnaire was administered to HCWs working in myriad healthcare settings in March-June 2011.

Methods.

Online and paper surveys were used to assess compliance with the 2010/2011, 2009/2010, and H1N1 influenza vaccines and to examine factors that predicted the uptake of the 2010/2011 seasonal influenza vaccine.

Results.

In all, 3,188 HCWs completed the survey; half of these (n = 1,719) reported no hospital work time. Compliance rates for all 3 vaccines were significantly higher (P< .001) among hospital versus nonhospital HCWs. In logistic regression stratified by hospital versus nonhospital setting, and when controlling for demographics and past behavior, the determinants of vaccination against the 2010/2011 seasonal influenza among nonhospital-based HCWs included having a mandatory vaccination policy, perceived importance, no fear of vaccine adverse effects, free and on-site access, and perceived susceptibility to influenza. Determinants of hospital-based HCW vaccine compliance included having a mandatory vaccination policy, belief that HCWs should be vaccinated every year, occupational health encouragement, perceived importance of vaccination, on-site access, and no fear of vaccine adverse effects. The strongest predictor of compliance for both worker groups was existence of a mandatory vaccination policy.

Conclusions.

The reasons for vaccine uptake among nonhospital-based versus hospital-based HCWs differed. Targeted interventions should be aimed at workers in these settings to increase their vaccine compliance, including implementing a mandatory vaccination policy.

Infect Control Hosp Epidemiol 2012;33(3):243-249
The Efficacy of Daily Bathing with Chlorhexidine for Reducing Healthcare-Associated Bloodstream Infections: A Meta-analysis
Authors: O'Horo John C. , Silva Germana L. M. , Munoz-Price L. Silvia , Safdar Nasia
Published: February 2012

Design.

Systematic review and meta-analysis of randomized controlled trials and quasi-experimental studies to assess the efficacy of daily bathing with chlorhexidine (CHG) for prevention of healthcare-associated bloodstream infections (BSIs).

Setting.

Medical, surgical, trauma, and combined medical-surgical intensive care units (ICUs) and long-term acute care hospitals.

Participants.

Inpatients.

Methods.

Data on patient population, diagnostic criteria for BSIs, form and concentration of topical CHG, incidence of BSIs, and study design were extracted.

Results.

One randomized controlled trial and 11 nonrandomized controlled trials reporting a total of 137,392 patient-days met the inclusion criteria; 291 patients in the CHG arm developed a BSI over 67,775 patient-days, compared with 557 patients in the control arm over 69,617 catheter-days. CHG bathing resulted in a reduced incidence of BSIs: the pooled odds ratio using a random-effects model was 0.44 (95% confidence interval, 0.33–0.59; P< .00001). Statistical heterogeneity was moderate, with an I2 of 58%. For the subgroup of studies that examined central line–associated BSIs, the odds ratio was 0.40 (95% confidence interval, 0.27–0.59).

Conclusions.

Daily bathing with CHG reduced the incidence of BSIs, including central line-associated BSIs, among patients in the medical ICU. Further studies are recommended to determine the optimal frequency, method of application, and concentration of CHG as well as the comparative effectiveness of this strategy relative to other preventive measures available for reducing BSIs. Future studies should also examine the efficacy of daily CHG bathing in non-ICU populations at risk for BSI.

Infect Control Hosp Epidemiol 2012;33(3):257-267
Spectrum of Gastroparesis in Children
Authors: Waseem Shamaila , Islam Saleem , Kahn Genie , Moshiree Baharak , Talley Nicholas J.
Published: February 2012

Background:

Gastroparesis (GP) is characterized by delayed gastric emptying in the absence of mechanical outlet obstruction. Symptoms may include nausea, vomiting, bloating, early satiety, abdominal pain, and weight loss. Delayed gastric emptying of a solid‐phase meal assessed by radionuclear scintigraphy is the criterion standard for diagnosis. The prevalence of GP is difficult to estimate due to the lack of a validated, widely available diagnostic test that can be applied in primary care. The extent of this problem in children is unknown.

Methods:

We studied a cohort of children with GP diagnosed by radionuclear scintigraphy to identify demographics, symptoms, comorbidities, treatment, and outcomes. A retrospective analysis of 239 patients between ages 0 and 21 years was performed.

Results:

The mean age of presentation was 7.9 years, and boys and girls were almost equally affected, that is, 48.5% and 51.5%, respectively. Vomiting was the most frequent presenting symptom (68%), followed by abdominal pain (51%), nausea (28%), weight loss (27%), early satiety (25%), and bloating (7%). Almost 75% of patients responded to intravenous erythromycin administered provocatively during gastric scintigraphy. In a majority of the patients, no cause was identified, that is, idiopathic GP (70%), followed by drugs (18%) and postsurgical (12.5%) causes. Only 4% patients had diabetic GP, and our population was essentially narcotic naïve (2%). After an average of 24 months' follow‐up, the most common complication was esophageal reflux (67%). Despite different therapeutic modalities, by the end of the follow‐up period, a significant improvement in symptoms was reported by an average of 60%, regardless of sex, age, or degree of emptying delay.

Conclusions:

GP has a good prognosis in childhood despite different etiologies, symptom presentation, and therapy.
Reactivity of human convalescent sera with influenza virus hemagglutinin protein mutants at antigenic site A
Authors: Nobusawa Eri , Omagari Katsumi , Nakajima Setsuko , Nakajima Katsuhisa
Published: February 2012

How the antibodies of individual convalescent human sera bind to each amino acid residue at the antigenic sites of hemagglutinin (HA) of influenza viruses, and how the antigenic drift strains of influenza viruses are selected by human sera, is not well understood. In our previous study, it was found by a binding assay with a chimeric HA between A/Kamata/14/91 (Ka/91) and A/Aichi/2/68 that convalescent human sera, following Ka/91 like (H3N2) virus infection, bind to antigenic site A of Ka/91 HA. Here using chimeric HAs possessing single amino acid substitutions at site A, it was determined how those human sera recognize each amino acid residue at antigenic site A. It was found that the capacity of human sera to recognize amino acid substitutions at site A differs from one person to another and that some amino acid substitutions result in all convalescent human sera losing their binding capacity. Among these amino acid substitutions, certain ones might be selected by chance, thus creating successive antigenic drift. Phylogenetic analysis of the drift strains of Ka/91 showed amino acid substitutions at positions 133, 135 and 145 were on the main stream of the phylogenetic tree. Indeed, all of the investigated convalescent sera failed to recognize one of them.
Re‐prescribing of causative drugs in persons discharged after serious drug‐induced upper gastrointestinal bleeding
Authors: Dall M. , dePont Christensen R. , Schaffalitzky de Muckadell O. B. , Lassen A. T. , Hallas J.
Published: February 2012

Background

Several drug classes are known to be associated with serious upper gastrointestinal bleeding (UGIB), among others NSAID, low‐dose acetylsalicylic acid (ASA), vitamin K antagonists (VKA), clopidogrel and selective serotonin reuptake inhibitors (SSRIs). There are few data on how and to what extent these drugs are reintroduced in patients who have been discharged after a bleeding episode related to any of them.

Aim

To assess if physicians re‐prescribed potential causative drugs after an episode of UGIB and to explore whether drugs with antihaemostatic action (DAHA) are re‐prescribed without a gastro‐protective agent.

Methods

By use of the Kaplan–Meyer method, we estimated the time from UGIB to re‐prescribing for 3652 cases who were all admitted to hospital with a diagnosis of serious upper gastrointestinal bleeding from 1995 to 2006. Data on drug exposure were retrieved from a Danish prescription database, a recent study on drug‐related UGIB, and The National Board of Health in Denmark.

Results

One‐year rates of re‐prescribing after UGIB were; 82%, 25%, 43%, 68%, 55%, 71% for SSRIs, NSAID, low‐dose ASA, VKA, clopidogrel and dipyridamol, respectively. However, re‐prescribing rates without proton pump inhibitors (PPIs) were markedly lower 25%, 3%, 5%, 1%, 17% and 6%, respectively. Non‐users of DAHA had a prevalence of PPI use of about 30% a few months after an UGIB.

Conclusions

Drugs with antihaemostatic action are re‐prescribed to a large extent after an episode of upper gastrointestinal bleeding, but usually covered by PPIs. This use of PPI is specific for users of drugs with antihaemostatic action.
Are there new threshold and goals in the treatment of arterial hypertension?
Authors: Segura Julian , Ruilope Luis M.
Published: February 2012

Eur J Clin Invest 2012

Background  About half of the global burden of cardiovascular disease has been attributed to high blood pressure (BP). Worldwide, 7·6 million premature deaths (about 13·5% of the global total), 54% of strokes, and 47% of cases of ischemic heart disease were caused by high BP in 2001.

Methods and results  All guidelines agree that pharmacological treatment of patients with hypertension should be initiated as soon as BP rises >140/90 mmHg. Available data support the reduction of BP to values to <140/90 mmHg, but do not favor a reduction to <130/80 mmHg in patients with diabetes or a history of cardiovascular disease because of the absence of evidence obtained in prospective studies.

Conclusions  This review updates the controversies and challenges involved in the treatment of patients with established arterial hypertension, such as the progression of high‐normal BP to overt hypertension, the choice of appropriate threshold and goal BP levels, the adequate number of drugs to be used since the early stages of hypertension, and which type of combination therapy offers most advantages to the patient.