New constraints on parameters in the minimal supersymmetric model

New constraints on parameters are found to avoid charge- and/or color-breaking minima and instability of the scalar potential in the minimal low energy supergravity model. They eliminate a wide region of parameters. As a result, m_t is tightly bounded in the no-scale model. They are also applicable to the superstring inspired model with no extra U(1).     

Spin-lattice relaxation and magnetization transfer in intracranial tumors in vivo: Effects of Gd-DTPA on relaxation parameters

Spin-lattice relaxation time T₁ and relaxation parameters in magnetization transfer (MT) imaging were measured in 11 intracranial tumors before and after injection of Gd-DTPA at 0.1 T by using the inversion recovery method and the saturation transfer technique, respectively. Preinjection T₁ relaxation times of the tumors were longer than those of white matter, but after Gd-enhancement the relaxation times of most tumors were in the same range as those of white matter. Gd-DTPA shortened the apparent relaxation time in the presence of off-resonance saturation pulse (T_1α) due to marked shortening of the relaxation time of mobile water (T_1w). Gd-DTPA decreased the magnetization transfer contrast (MTC) but did not influence on the magnetization transfer rate (R_wm). The parameters MTC and R_wm differed clearly between Gd-enhanced tumors and normal brain, whereas the relaxation time T_1α was in many Gd-enhanced tumors in the same range as in normal brain.     

Empirical pseudopotential band structure parameters of 4H-SiC using a genetic algorithm fitting routine

In this paper, the viability of using a genetic algorithm to find band structure parameters for empirical pseudopotential method (EPM) calculations is demonstrated by applying a genetic algorithm to find the EPM parameters for 4H-SiC. The form of the pseudopotential for 4H-SiC and the 19 form factors found by the genetic algorithm to fit the band structure to experimentally measured indirect energy gap and direct optical gaps are given. In addition, the effective masses for the conduction band minimum are extracted from the calculated band structure. It is shown that the genetic algorithm provides an effective, automated way to find parameters that give reasonably good fits to both the band gaps and the effective masses simultaneously.     

Solid-state NMR spectroscopy using the lost I spin magnetization in polarization transfer experiments

A variation of the cross polarization (CP) experiment is discussed. The method requires two scans where the difference signal is equivalent to the I spin magnetization that is transferred to the S spins. The acquired signal is equivalent to F1 sum projection of a two-dimensional (2D) heteronuclear correlation experiment and is obtained by just two scans without the need to increment the indirect time domain t(1). Any polarization transfer method and any kind of spin manipulations during the t(1) incrementation period of a 2D NMR experiment can be applied. The method allows fast measurements of the CP transfer, particularly if various S spins signal overlap and is good for spectral editing of I spin signals with contact to S spins. Various examples for biomaterials are presented. Most importantly, this novel approach is ideal for detailed investigations of organic-mineral interfaces in bone, here demonstrated for O-phospho-l-serine as simple model compound.     

Spontaneous magnetization of the Ising model on a union Jack lattice

A formula for the spontaneous magnetization of the Ising model on a Union Jack lattice is proposed. Our result agrees with the exact low-temperature series expansion up to the 24th order.     

Spontaneous magnetization of the Ising model on a layered square lattice

We have studied the Ising model on a layered square lattice with four different coupling constants and two different magnetic moments. The partition function at zero magnetic field is derived exactly. We propose a formula for the spontaneous magnetization which agrees with the exact low-temperature series expansion up to the 16th order and reduces to the exact result of Au-Yang and McCoy in a special case.     

Longitudinal assessment of mouse renal injury using high-resolution anatomic and magnetization transfer MR imaging

The purpose of this study is to evaluate the utility of high-resolution non-invasive endogenous high-field MRI methods for the longitudinal structural and quantitative assessments of mouse kidney disease using the model of unilateral ureter obstruction (UUO). T₁-weighted, T₂-weighted and magnetization transfer (MT) imaging protocols were optimized to improve the regional contrast in mouse kidney. Conventional T₁ and T₂ weighted images were collected in UUO mice on day 0 (~ 3 h), day 1, day 3 and day 6 after injury, on a 7 T small animal MRI system. Cortical and medullary thickness, corticomedullary contrast and Magnetization Transfer Ratio (MTR) were assessed longitudinally. Masson trichrome staining was used to histologically assess changes in tissue microstructure. Over the course of UUO progression there were significant (p < 0.05) changes in thickness of cortex and outer medulla, and regional changes in T₂ signal intensity and MTR values. Histological changes included tubular cell death, tubular dilation, urine retention, and interstitial fibrosis, assessed by histology. The MRI measures of renal cortical and medullary atrophy, cortical–medullary differentiation and MTR changes provide an endogenous, non-invasive and quantitative evaluation of renal morphology and tissue composition during UUO progression.     

Sensitivity of a continuum vocal fold model to geometric parameters, constraints, and boundary conditions

The influence of key dimensional parameters, motion constraints, and boundary conditions on the modal properties of an idealized, continuum model of the vocal folds was investigated. The Ritz method and the finite element method were used for the analysis. The model's vibratory modes were determined to be most sensitive to changes in the anterior-posterior length of the vocal fold model, due to the influence of three-dimensional stress components acting in the transverse plane. Anterior/ posterior boundary conditions were found to have a significant influence on the vibratory response. Overestimation of modal frequencies resulted when vibration of the structure was restricted to the transverse plane. The overestimation of each modal frequency was proportional to the ratio of longitudinal to transverse Young's modulus, and was significant for ratio values less than 20.     

Spontaneous magnetization of the Ising model on a 4–8 lattice

The spontaneous magnetization of the Ising model on a 4–8 lattice with six different coupling constants and two different magnetic moments is studied. A formula for the spontaneous magnetization is proposed. The result agrees with the exact low-temperature series expansions up to the 12th order.     

Joint constraints on cosmological parameters using future multi-band gravitational wave standard siren observations

Gravitational waves(GWs) from compact binary coalescences can be used as standard sirens to explore the cosmic expansion history. In the next decades, it is anticipated that we could obtain the multi-band GW standard siren data(from nanohertz to a few hundred hertz), which are expected to play an important role in cosmological parameter estimation. In this work, we provide, for the first time to the best of our knowledge, joint constraints on cosmological parameters using the future multi-band G...     

Numerical investigation of the effect of material parameters on magnetization reversal of a magnetic nanoparticle

The dependence of the magnetization reversal field of an elliptic submicrometer magnetic particle on the parameters of the material and sample configuration has been numerically studied. A method for calculating the magnetostatic field using the Fourier transform has been described in detail. The simulation results have demonstrated, in particular, that the normalized magnetization reversal field of a particle is independent of the exchange length at its rather large values.     

Analytical results on the magnetization of the Hamiltonian Mean-Field model

The violent relaxation and the metastable states of the Hamiltonian Mean-Field model, a paradigmatic system of long-range interactions, is studied using a Hamiltonian formalism. Rigorous results are derived algebraically for the time evolution of selected macroscopic observables, e.g., the global magnetization. The high- and low-energy limits are investigated and the analytical predictions are compared with direct N-body simulations. The method we use enables us to re-interpret the out-of-equilibrium phase transition separating magnetized and (almost) unmagnetized regimes.     

Anatomy of field effects on magnetization dynamics and spin transfer noise

Spin transfer-related phenomena in nanomagnets have attracted extensive studies. In this paper we shall focus on analysis of individual and combined effects of the external, anisotropy, and demagnetization fields on magnetization dynamics and spin transfer noise. It is found that individual roles of the external, anisotropy, and demagnetization fields, as well as the combined roles of external plus anisotropy fields and anisotropy plus demagnetization fields, do not change the behavior of current induced magnetization switching. Such magnetization reversal procedures are of low noise. Our dynamics and power spectral density calculations show that it is the demagnetization field that plays a major role in inducing spin transfer noise: the demagnetization field itself or in combination with the anisotropy field will result in wave-like switching; moreover, the demagnetization field, together with the external field (not too small), will lead to precession and hence the system would be in noisy states. Our modeling work for an elliptical Py alloy is qualitatively consistent with Cornell's experiment and simulation [Science 307 (2005) 228].     

Semiclassical analysis and the magnetization of the Hofstadter model

The magnetization and the de Haas-van Alphen oscillations of Bloch electrons are calculated near commensurate magnetic fluxes. Two phases that appear in the quantization of mixed systems--the Berry phase and a phase first discovered by Wilkinson--play a key role in the theory.     

磁性纳米线反磁化过程的截椭球链模型

依据实际的纳米线形貌，提出了描述磁性纳米线反磁化过程的截椭球链模型.基于此模型，推导了纳米线反磁化过程中不可逆磁化的临界场和矫顽力在一致转动和对称扇形模式下的表达式.同时，还研究了椭球间接触角、单轴磁晶各向异性、外场与链轴方向夹角、截椭球个数和椭球形状因子对临界场和矫顽力的影响.利用该模型解释了镍纳米线的反磁化过程可能是对称扇形的模式. 关键词： 截椭球链模型 反磁化 一致转动 对称扇形     

Spontaneous magnetization of the Ising model on a square lattice with non-crossing diagonal interactions

We have studied the spontaneous magnetization of the Ising model on a square lattice with non-crossing diagonal interactions. It is discovered that the formula derived by Vaks, Larkin and Ovchinnikov in 1965 does not agree with the series expansions. However their formula agrees with the series expansions for the spontaneous magnetization of a semi-ferromagnetic model.     

Static and dynamic correlation functions of a Landau-Ginzburg model near the magnetization curve

A recently developed method for treating static Goldstone modes is extended to the dynamics of purely dissipative Landau-Ginzburg models. The extension hinges on the existence of fluctuation-dissipation relations which closely link the dynamic and the static problem. This connection, and previous work on the static problem, suggest that a perturbative approach to the dynamic Goldstone singularities should be possible. We present such a perturbation theory. For a nonconserved order parameter we show to two loop order that our approach is internally consistent. We give approximate expressions for both static and dynamic correlation functions in the whole critical region, including the magnetization curve.