Search Results - (Author, Cooperation:F. C. Chou)

2018-05-19

Institute of Physics (IOP)

1367-2630

Physics

2018-08-09

American Physical Society (APS)

0031-9007

1079-7114

Physics

Condensed Matter: Electronic Properties, etc.

2018-10-04

American Physical Society (APS)

1098-0121

1095-3795

Physics

Magnetism

2018-03-07

American Physical Society (APS)

1098-0121

1095-3795

Physics

Structure, structural phase transitions, mechanical properties, defects

2018-05-05

Institute of Physics (IOP)

1367-2630

Physics

2018-05-01

American Physical Society (APS)

1098-0121

1095-3795

Physics

Surface physics, nanoscale physics, low-dimensional systems

2015-01-17

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

1089-7550

AIP Digital Archive

Physics

Magnetic characterization has been performed on the cubic phases λ-Li0.07Mn2O4, Li0.98Mn2O4, and the tetragonal phase Li1.82Mn2O4, prepared by electrochemical cycling of a single starting LiMn2O4 spinel. The magnitude of the negative Weiss constant increases with x in LixMn2O4, indicating that antiferromagnetic interactions increase in strength as the Mn4+ concentration decreases. Spin-glass behavior is observed in all three materials, as previously seen in nearly stoichiometric LiMn2O4 [Jang et al., Appl. Phys. Lett. 74, 2504 (1999)]. A short-range antiferromagnetic correlation is observed in Li2Mn2O4 at temperatures below the paramagnetic temperature regime, which is ascribed to collective Jahn–Teller distortion causing a two-dimensional nearest-Mn-neighbors interaction. © 2000 American Institute of Physics.

Electronic Resource

1471-4159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Abstract— Chromatography of myelin basic protein (BP) on carboxymethylcellulose gives a pattern of multiple components, of which three are major. Component 1 is considered the unmodified species of BP while component 2 has been found to be modified primarily by deamidation and component 3 by phosphorylation (Chouet al., 1976)./〉 In contrast to BP prepared from tissue delipidated in the standard fashion in chloroform–methanol (CM powder), BP prepared from tissue delipidated first in acetone and then in chloroform–methanol (ACM powder) gave an elution pattern on carboxymethylcellulose characterized by a decrease in component 1 and an increase in the earlier eluting, less basic components. Studies with radiolabelled component 1 showed that this difference in elution patterns was due to the partial conversion of component 1 to less basic components during the extraction of ACM powder at neutral pH. The components derived from component 1 (D2, D3 and D4) were then isolated and subjected to tryptic peptide map analyses and determination of their carboxy-terminal arginine content and content of phosphorus. None of the derived components contained phosphorus but tryptic peptide map analyses did show the presence of two minor peptides, T14M2 and T20M, previously found in component 2 from CM powder and considered to be the deamidation products of their parent peptides T14 and T20 (Chouet al., 1976). In addition components D3 and D4 were shown to have lost appreciable arginine from their carboxy-termini. Since none of the efforts to reduce enzyme activity in vitro had any appreciable effect on components 2 and 3 it was concluded that phosphorylation probably occurs exclusively in vivo, that deamidation occurs both in vivo and in vitro and that loss of carboxy-terminal arginine occurs exclusively in vitro.

Electronic Resource

1471-4159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

In the Lewis rat, fragment 43–88 of the highly encephalitogenic guinea-pig basic protein has been previously shown to retain the full activity of the parent protein. In the present studies this fragment was subjected to controlled chymotryptic digestion so that cleavage occurred only at tyrosine 67, generating two peptides, residues 43-67 and residues 68-88. When compared on an equimolar basis peptide 68-88 had the same encephalitogenic activity as the intact fragment and induced the same degree of immunologically specific cell response as measured by the in vitro lymphocyte stimulation test. Peptide 68-88 was further fragmented by selective tryptic cleavage at arginine 78 after blocking lysine 73 with citraconic anhydride. The two peptides, residues 68-78 and residues 79-88, were not encephalitogenic, indicating that residues adjacent to the point of cleavage contribute to the active site.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

LiMn2O4 spinel exhibits spin-glass behavior below 25 K. A cusp in the ac susceptibility appears at 25 K, below which the susceptibility increases with decreasing frequency. The dc magnetization shows irreversibility, and relaxation of remanent magnetization is seen on the macroscopic time scale. The randomness and frustration necessary for spin-glass behavior are explained in a manner compatible with the cation and charge ordering present in this material. © 1999 American Institute of Physics.

Electronic Resource

1432-1181

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

Zusammenfassung Diese Arbeit zeigt eine numerische Studie über den Einfluß der Wärmeleitung an der Wandoberfläche auf die laminare Mischkonvektion in der thermischen Eintrittszone von horizontalen, rechteckigen Kanälen. Neben der RayleighzahlRa und dem Kanalverhältnis γ von Breite zu Höhe, spielt der WärmeleitungsparameterK=k w t/(k f D e ) eine wichtige Rolle im Wärmetransport. Ein numerisches Verfahren der Lösungsauswertung der Wirbel-Geschwindigkeits-Gleichung ist entwickelt worden, um bestehende Differenzial-Gleichungssysteme zu lösen, die als Randbedingung gekoppelt sind die Wärmeleitung der Wandoberfläche berücksichtigen. Das lokale Reibungsfaktorverhältnis und Nusseltzahlvariationen sind fürPr=0,7,Ra=104, 3×104 und 105 und γ=0,2, 0,5, 1, 2 und 5 undK=0,01, 0,1 und 1 aufgezeigt. Der Einfluß der Wärmeleitung an der Wandoberfläche auf die Nusseltzahl ist als sehr bedeutend angesehen worden, wenn der Wert von γ kleiner als 1 ist. Die asymptotischen Lösungen fürz → ∞ sind mit den vorhandenen numerischen Ergebnissen verglichen worden und dabei wurde eine gute Übereinstimmung festgestellt.

Abstract This paper presents a numerical study of the effect of peripheral wall heat conduction on laminar mixed convection in the thermal entrance region of horizontal rectangular channels. In addition to the Rayleigh numberRa and the channel aspect ratio (width-to-height) γ, the wall heat conduction parameterK=k w t/(k f D e ) plays an important role in heat transfer. A numerical method of solution utilizing the vorticity-velocity formulation is developed to solve the system of governing partial differential equations coupled with the boundary condition equation considering peripheral wall heat conduction. Local friction factor ratio and Nusselt number variations are shown forPr=0.7,Ra=104, 3×104, and 105, γ=0.2, 0.5, 1, 2 and 5,K=0.01, 0.1 and 1. The effect of peripheral wall heat conduction on Nusselt number is found to be significant when the value of γ is less than 1. The asymptotic solutions forz→∞ are compared with the existing numerical results and good agreement is indicated.

Electronic Resource

1573-7357

76.60.Es ; 74.90.+n ; 75.90.Pp

Springer Online Journal Archives 1860-2000

Physics

Abstract The effects induced by charge defects on the spin dynamics and on the static properties of antiferromagnetic cuprates, as detected through NMR-NQR and μ+SR, are addressed. Information on hole localization and evidence supporting hole segregation are presented.

Electronic Resource

1572-9605

Phase separation ; hole doping ; La2−x Sr x CuO4

Springer Online Journal Archives 1860-2000

Electrical Engineering, Measurement and Control Technology

Physics

Abstract The diffusion of the excess oxygen during phase separation in La2CuO4+δ was studied using thermal history-dependent normal state magnetic susceptibilityϰ(T, t) measurements versus temperatureT and timet as a probe. A large thermal hysteresis ofϰ(T) was observed for La2CuO4.044 between data obtained after quenching to 5 K and then warming, and data obtained while or after slowly cooling from 300 K. A model for the excess oxygen diffusion is presented, from which theϰ(T, t) data yield aT-independent activation energy of 0.24(3) eV for the diffusion coefficient of the excess oxygen from 150 to 220 K. In related work, we have used139La NQR andμSR measurements to probe the antiferromagnetic (AF) region (x〈0.02) of the La2−x Sr x CuO4 system below the Néel temperatureT N(x), from which we extract the Cu+2 staggered magnetizationM †(x, T). M†(x, T=0), extrapolated from above 30 K, was successfully modeled with spin-wave theory, assuming that the doped holes are mobile and are situated in walls in the CuO2 plane which uncouple undoped AF domains; these domains are coupled to those in adjacent CuO2 planes. This agreement supports the previous hypothesis that microsegregation of the (mobile) doped holes into domain walls occurs above ∼30 K, consistent with the phenomenology of Emery and Kivelson. Below ∼30 K, an anomalous increase inM †(x, T) is observed, such thatM †(x, T=0) is nearly independent ofx. We interpret this effect as arising from localization of the doped holes below ∼30 K.

Electronic Resource