The influence of transverse magnetic field on Gunn effect threshold

The effect of magnetic field has been studied on the Gunn effect threshold electric field for short planar Gunn devices. For low magnetic fields, experimental results are in good agreement with the theoretical results but a large increase in threshold electric field has been observed for higher magnetic fields.     

A new satellite in the L-X-ray emission spectrum of tungsten-74

Using a 40 cm curved mica crystal spectrograph of the transmission type, the existence of a high frequency satellite at λ = 1268.84 X.U. in the L-emission spectrum of tungsten has been established for the first time. Based on the multiple ionisation theory, the satellite has been assigned to the transition L₂M₄ → M₄². According to the satellite nomenclature scheme proposed by Nigam and Mathur, this satellite would be designated Lβ₁₄.Kaufman's observation of a line at 1270.2 X.U. and its assignment to the octupole transition has been critically examined.     

Weak charge-lattice coupling requires reinterpretation of stripes of charge order in La1-xCaxMnO3

Modulations in manganites attributed to stripes of charge/orbital/spin order are thought to result from strong electron-lattice interactions that lock the superlattice and parent lattice periodicities. Surprisingly in La1-xCaxMnO3 (x>0.5,90 K), convergent beam (3.6 nm spot) electron diffraction patterns rule out charge stacking faults and indicate a superlattice with uniform periodicity. Moreover, large area electron diffraction peaks are sharper than simulations with stacking faults. Since the electron-lattice coupling does not lock the two periodicities (to yield stripes) it may be too weak to strongly localize charge.     

Quantum critical behaviour in the CePd2Si2/CeNi2Ge2 system

We have explored the vicinity of the antiferromagnetic quantum critical point in the related heavy fermion metals CePd₂Si₂ and CeNi₂Ge₂ as a function of hydrostatic pressure. The normal state resistivity of the antiferromagnet CePd2Si2 near the critical pressure, at which magnetic order disappears, varies as ρ ～ T^χ(1:1 < χ < 1:4) over nearly two orders of magnitude in temperature up to about 30 K. This anomalous form for the resistivity appears to defy not only Fermi-liquid theory, but also simple phenomenological models for the effect of spin fluctuations close to a quantum critical point. An analogous unconventional behaviour is observed in the ambient pressure resistivity of the electronically and structurally equivalent, non-magnetic metal CeNi₂Ge₂. At pressures above 15 kbar, a new and unexpected superconducting transition appears in CeNi₂Ge₂ below 220 mK, which rises to higher temperatures with increasing pressure, reaching 400 mK at 26 kbar.     

Defect modes due to H− - D− pair impurities in KCl and KBr

Localised modes due to H^? - D^? pair impurities aligned in the [110] direction in KCl and KBr have been computed using a Green's function approach. The defect space used consists of 12 particles; the two defect ions (H^? and D^?) and their ten nearest neighbours (K⁺ ions). The system has C_2ν site symmetry around the defect ions, and this property has been used to block diagonalise the relevant 36 × 36 matrix by group theoretical techniques. Various irreducible representations thus obtained have been used to compute the defect modes. Numerical values of the various Green's functions computed on the basis of neutron-fitted shell model parameters were used. Mass changes as well as changes in the short range interactions were considered while forming the perturbation matrix. The localised modes computed are seen to be in good agreement with the experimentally observed values.     

Piezoelectricity in uniaxially stretched and plasticized nylon 11 films

The combined effect of uniaxial stretching and plasticization of nylon 11 films on the resulting piezoelectric response was studied. Three different kinds of samples were studied for nylon 11 α′-form films: (1) uniaxially stretched at 150°C, (2) samples uniaxially stretched at 150°C and then plasticized by immersion in 2-ethyl 1,3-hexanediol, and (3) samples plasticized and then uniaxially stretched. The largest piezoelectric response was obtained from the samples which were plasticized prior to uniaxial stretching under identical poling conditions. For the case of nylon 11 δ′-form films, two different kinds of experiments were performed: (1) samples uniaxially stretched at room temperature were subsequently plasticized by immersion in the plasticizer and a comparison of their piezoelectric response made with that of the unplasticized samples as a function of poling field; (2) the plasticizer content dependence of the piezoelectric response from these samples was studied. In both cases, d₃₁ was observed to be higher for the plasticized films compared with the unplasticized films. The piezoelectric stress constant e₃₁ showed a small decrease with plasticization. X-ray diffraction studies indicated a small conversion of δ′-phase to α′-phase with plasticization. No significant changes were observed in the x-ray diffraction scans taken before and after poling.     

Width-fluctuation effects in angular correlation in inelastic nucleon scattering

The effects of level-width fluctuations on the nucleon-gamma angular correlations and double-differential cross sections have been studied on the basis of Moldauer's formulation. Computational procedures for pursuing the width-fluctuation studies on a routine basis for reactions following the compound nucleus mechanism have been developed. The width-fluctuation effects in (n, n'γ) reactions with ²⁴Mg and ⁵⁶Fe have been calculated. These calculations indicate that the inclusion of width-fluctuation considerations significantly reduces the double differential cross sections compared to those made on the basis of Hauser-Feshbach theory. However, as expected, the shape of the angular correlation function is not siginificantly altered by the width-fluctuation corrections.     

On the origin of convention: Evidence from symmetric bargaining games

We use a dynamical systems approach to model the origin of bargaining conventions and report the results of a symmetric bargaining game experiment. Our experiment also provides evidence on the psychological salience of symmetry and efficiency. The observed behavior in the experiment was systematic, replicable, and roughly consistent with the dynamical systems approach. For instance, we do observe unequal-division conventions emerging in communities of symmetrically endowed subjects.