551 research outputs found
Bipolar-Driven Large Magnetoresistance in Silicon
Large linear magnetoresistance (MR) in electron-injected p-type silicon at
very low magnetic field is observed experimentally at room temperature. The
large linear MR is induced in electron-dominated space-charge transport regime,
where the magnetic field modulation of electron-to-hole density ratio controls
the MR, as indicated by the magnetic field dependence of Hall coefficient in
the silicon device. Contrary to the space-charge-induced MR effect in unipolar
silicon device, where the large linear MR is inhomogeneity-induced, our results
provide a different insight into the mechanism of large linear MR in
non-magnetic semiconductors that is not based on the inhomogeneity model. This
approach enables homogeneous semiconductors to exhibit large linear MR at low
magnetic fields that until now has only been appearing in semiconductors with
strong inhomogeneities.Comment: 23 pages, 4 figures (main text), 6 figures (supplemental material
Superconductivity suppression of Ba0.5K0.5Fe2-2xM2xAs2 single crystals by substitution of transition-metal (M = Mn, Ru, Co, Ni, Cu, and Zn)
We investigated the doping effects of magnetic and nonmagnetic impurities on
the single-crystalline p-type Ba0.5K0.5Fe2-2xM2xAs2 (M = Mn, Ru, Co, Ni, Cu and
Zn) superconductors. The superconductivity indicates robustly against impurity
of Ru, while weakly against the impurities of Mn, Co, Ni, Cu, and Zn. However,
the present Tc suppression rate of both magnetic and nonmagnetic impurities
remains much lower than what was expected for the s\pm-wave model. The
temperature dependence of resistivity data is observed an obvious low-T upturn
for the crystals doped with high-level impurity, which is due to the occurrence
of localization. Thus, the relatively weak Tc suppression effect from Mn, Co,
Ni, Cu, and Zn are considered as a result of localization rather than
pair-breaking effect in s\pm-wave model.Comment: 8 pages, 9 figures, to be published in Phys. Rev.
Thermal equation of state and thermodynamic properties of iron carbide Fe 3 C to 31 GPa and 1473 K
Resent experimental and theoretical studies suggested preferential stability of Fe 3 C over Fe 7 C 3 at the condition of the Earth's inner core. Previous studies showed that Fe 3 C remains in an orthorhombic structure with the space group Pnma to 250 GPa, but it undergoes ferromagnetic (FM) to paramagnetic (PM) and PM to nonmagnetic (NM) phase transitions at 6–8 and 55–60 GPa, respectively. These transitions cause uncertainties in the calculation of the thermoelastic and thermodynamic parameters of Fe 3 C at core conditions. In this work we determined P‐V‐T equation of state of Fe 3 C using the multianvil technique and synchrotron radiation at pressures up to 31 GPa and temperatures up to 1473 K. A fit of our P‐V‐T data to a Mie‐Gruneisen‐Debye equation of state produce the following thermoelastic parameters for the PM‐phase of Fe 3 C: V 0 = 154.6 (1) Å 3 , K T 0 = 192 (3) GPa, K T ′ = 4.5 (1), γ 0 = 2.09 (4), θ 0 = 490 (120) К, and q = −0.1 (3). Optimization of the P‐V‐T data for the PM phase along with existing reference data for thermal expansion and heat capacity using a Kunc‐Einstein equation of state yielded the following parameters: V 0 = 2.327 cm 3 /mol (154.56 Å 3 ), K T 0 = 190.8 GPa, K T ′ = 4.68, Θ E10 = 305 K (which corresponds to θ 0 = 407 K), γ 0 = 2.10, e 0 = 9.2 × 10 −5 K −1 , m = 4.3, and g = 0.66 with fixed parameters m E 1 = 3 n = 12, γ ∞ = 0, β = 0.3, and a 0 = 0. This formulation allows for calculations of any thermodynamic functions of Fe 3 C versus T and V or versus T and P . Assuming carbon as the sole light element in the inner core, extrapolation of our equation of state of the NM phase of Fe 3 C suggests that 3.3 ± 0.9 wt % С at 5000 К and 2.3 ± 0.8 wt % С at 7000 К matches the density at the inner core boundary. Key Points We present a P‐V‐T EOS for PM‐Fe 3 C with support from thermodynamic analyses We discuss uncertainties in magnetic transitions We applied EOS data for modeling carbon content in the corePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/101805/1/jgrb50396.pd
Transport coefficients of O(N) scalar field theories close to the critical point
We investigate the critical dynamics of O(N)-symmetric scalar field theories
to determine the critical exponents of transport coefficients as a second-order
phase transition is approached from the symmetric phase. A set of stochastic
equations of motion for the slow modes is formulated, and the long wavelength
dynamics is examined for an arbitrary number of field components, , in the
framework of the dynamical renormalization group within the
expansion. We find that for a single component scalar field theory, N=1, the
system reduces to the model C of critical dynamics, whereas for the model
G is effectively restored owing to dominance of O(N)-symmetric charge
fluctuations. In both cases, the shear viscosity remains finite in the critical
region. On the other hand, we find that the bulk viscosity diverges as the
correlation length squared, for N=1, while it remains finite for .Comment: revised for publication in PR
Delta degrees of freedom in antisymmetrized molecular dynamics and (p,p') reactions in the delta region
Delta degrees of freedom are introduced into antisymmetrized molecular
dynamics (AMD). This is done by increasing the number of basic states in the
AMD wave function, introducing a Skyrme-type delta-nucleon potential, and
including reactions in the collision description.
As a test of the delta dynamics, the extended AMD is applied to (p,p)
recations at MeV for a C target. It is found that the
ratio and the absolute values for delta peak and quasielastic peak (QEP) in the
C(p,p) reaction are reproduced for angles \Theta_{\rm lab} \agt
40^\circ, pointing to a correct treatment of the delta dynamics in the
extended AMD. For forward angles the QEP is overestimated. The results of the
AMD calculations are compared to one-step Monte Carlo (OSMC) calculations and a
detailed analysis of multi-step and delta potential effects is given. As
important side results we present a way to apply a Gallilei invariant theory
for (N,N) reactions up to MeV which ensures
approximate Lorentz invariance and we discuss how to fix the width parameter
of the single particle momentum distribution for outgoing nucleons in the
AMD calculation.Comment: 28 pages, revtex, 12 figures included, figures are also available
upon request as postscript files from the authors (e-mail:
[email protected]), submitted to Phys. Rev.
Probing the Inhibitor versus Chaperone Properties of sp2-Iminosugars towards Human β-Glucocerebrosidase: A Picomolar Chaperone for Gaucher Disease
A series of sp2-iminosugar glycomimetics differing in the reducing or nonreducing character, the configurational pattern (d-gluco or l-ido), the architecture of the glycone skeleton, and the nature of the nonglycone substituent has been synthesized and assayed for their inhibition properties towards commercial glycosidases. On the basis of their affinity and selectivity towards GH1 β-glucosidases, reducing and nonreducing bicyclic derivatives having a hydroxylation profile of structural complementarity with d-glucose and incorporating an N′-octyl-isourea or -isothiourea segment were selected for further evaluation of their inhibitory/chaperoning potential against human glucocerebrosidase (GCase). The 1-deoxynojirimycin (DNJ)-related nonreducing conjugates behaved as stronger GCase inhibitors than the reducing counterparts and exhibited potent chaperoning capabilities in Gaucher fibroblasts hosting the neuronopathic G188S/G183W mutation, the isothiourea derivative being indeed one of the most efficient chaperone candidates reported up to date (70% activity enhancement at 20 pM). At their optimal concentration, the four selected compounds promoted mutant GCase activity enhancements over 3-fold; yet, the inhibitor/chaperoning balance became unfavorable at much lower concentration for nonreducing as compared to reducing derivatives.España Ministerio de Economía y Competitividad (contract numbers CTQ2015-64425-C2-1-R and SAF2016-76083-R)Junta de Andalucía contract number FQM2012-146
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