Two dimensional scaling of resistance in flux flow region in Tl2Ba2CaCu2O8Tl_2Ba_2CaCu_2O_8 thin films

The resistance of $Tl_2Ba_2CaCu_2O_8$ thin films has been measured when the angle between the applied fields and $ab$-plane of the film is changed continuously at various temperatures. Under various magnetic fields, the resistance can be well scaled in terms of the c-axis component of the applied fields at the same temperature in the whole angle range. Meanwhile, we show that the measurement of resistance in this way is a complementary method to determine the growth orientation of the anisotropic high-$T_c$ superconductors.Comment: 11 pages, 8 figures. Have been published in Physica

Complication prevalence following use of tutoplast-derived human acellular dermal matrix in prosthetic breast reconstruction: A retrospective review of 203 patients

SummaryUse of human acellular dermal matrix (ADM) during prosthetic breast reconstruction has increased. Several ADM products are available produced by differing manufacturing techniques. It is not known if outcomes vary with different products. This study reports the complication prevalence following use of a tutoplast-derived ADM (T-ADM) in prosthetic breast reconstruction. We performed a retrospective chart review of 203 patients (mean follow-up times 12.2 months) who underwent mastectomy and immediate prosthetic breast reconstruction utilizing T-ADM, recording demographic data, surgical indications and complication (infection, seroma, hematoma, wound healing exceeding three weeks and reconstruction failure). During a four-year period, 348 breast reconstructions were performed Complications occurred in 16.4% of reconstructed breasts. Infection occurred in 6.6% of breast reconstructions (3.7% – major infection, requiring intravenous antibiotics and 2.9% minor infection, requiring oral antibiotics only). Seromas occurred in 3.4% and reconstruction failure occurred in 0.6% of breast reconstructions. Analysis suggested that complication prevalence was significantly higher in patients with a BMI >30 (p = 0.03). The complication profile following T-ADM use is this series is comparable to that reported for with other ADM products. T-ADM appears to be a safe and acceptable option for use in ADM-assisted breast reconstruction

Kondo spin liquid and magnetically long-range ordered states in the Kondo necklace model

A simplified version of the symmetric Kondo lattice model, the Kondo necklace model, is studied by using a representation of impurity and conduction electron spins in terms of local Kondo singlet and triplet operators. Within a mean field theory, a spin gap always appears in the spin triplet excitation spectrum in 1D, leading to a Kondo spin liquid state for any finite values of coupling strength $t/J$ (with $t$ as hopping and $J$ as exchange); in 2D and 3D cubic lattices the spin gaps are found to vanish continuously around $(t/J)_c\approx 0.70$ and $(t/J)_c\approx 0.38$, respectively, where quantum phase transitions occur and the Kondo spin liquid state changes into an antiferromagnetically long-range ordered state. These results are in agreement with variational Monte Carlo, higher-order series expansion, and recent quantum Monte Carlo calculations for the symmetric Kondo lattice modelComment: Revtex, four pages, three figures; to be published in Physical Review B1, 1 July (2000

Near-optimal two-mode spin squeezing via feedback

We propose a feedback scheme for the production of two-mode spin squeezing. We determine a general expression for the optimal feedback, which is also applicable to the case of single-mode spin squeezing. The two-mode spin squeezed states obtained via this feedback are optimal for j=1/2 and are very close to optimal for j>1/2. In addition, the master equation suggests a Hamiltonian that would produce two-mode spin squeezing without feedback, and is analogous to the two-axis countertwisting Hamiltonian in the single mode case.Comment: 10 pages, 6 figures, journal versio

Doping dependent Irreversible Magnetic Properties of Ba(Fe1-xCox)2As2 Single Crystals

We discuss the irreversible magnetic properties of self-flux grown Ba(Fe1-xCox)2As2 single crystals for a wide range of concentrations covering the whole phase diagram from the underdoped to the overdoped regime, x=0.038, 0.047, 0.058, 0.071, 0.074, 0.10, 0.106 and 0.118. Samples were characterized by a magneto-optical method and show excellent spatial uniformity of the superconducting state. The overall behavior closely follows classical Bean model of the critical state. The field-dependent magnetization exhibits second peak at a temperature and doping - dependent magnetic field, Hp. The evolution of this fishtail feature with doping is discussed. Magnetic relaxation is time-logarithmic and unusually fast. Similar to cuprates, there is an apparent crossover from collective elastic to plastic flux creep above Hp. At high fields, the field dependence of the relaxation rate becomes doping independent. We discuss our results in the framework of the weak collective pinning and show that vortex physics in iron-based pnictide crystals is much closer to high-Tc cuprates than to conventional s-wave (including MgB2) superconductors.Comment: for the special issue of Physica C on iron-based pnictide superconductor

Critical Exponents for Three-Dimensional Superfluid--Bose-Glass Phase Transition

The critical phenomenon of the zero temperature superfluid--Bose-glass phase transition for hard-core bosons on a three-dimensional disordered lattice is studied using a quantum real-space renormalization-group method. The correlation-length exponent $\nu$ and the dynamic exponent z are computed. The critical exponent z is found to be 2.5 for compressible states and 1.3 for incompressible states. The exponent $\nu$ is shown to be insensitive to z as that in the two-dimensional case, and has value roughly equal to 1.Comment: 11 pages, REVTE

Exclusive Studies of Charged-Particle Emission in 1-H and 3-He-Induced Reactions on Heavy Nuclei

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Study of heterogeneous nucleation of eutectic Si in high-purity Al-Si alloys with Sr addition

The official published version can be accessed from the link below - Copyright @ 2010 The Minerals, Metals & Materials Society and ASM InternationalAl-5 wt pct Si master-alloys with controlled Sr and/or P addition/s were produced using super purity Al 99.99 wt pct and Si 99.999 wt pct materials in an arc melter. The master-alloy was melt-spun resulting in the production of thin ribbons. The Al matrix of the ribbons contained entrained Al-Si eutectic droplets that were subsequently investigated. Differential scanning calorimetry, thermodynamic calculations, and transmission electron microscopy techniques were employed to examine the effect of the Sr and P additions on eutectic undercoolings and nucleation phenomenon. Results indicate that, unlike P, Sr does not promote nucleation. Increasing Sr additions depressed the eutectic nucleation temperature. This may be a result of the formation of a Sr phase that could consume or detrimentally affect potent AlP nucleation sites.This work is financially supported by the Higher Education Commission of Pakistan and managerially supported from the OAD

Instability of vortex array and transitions to turbulent states in rotating helium II

We consider superfluid helium inside a container which rotates at constant angular velocity and investigate numerically the stability of the array of quantized vortices in the presence of an imposed axial counterflow. This problem was studied experimentally by Swanson {\it et al.}, who reported evidence of instabilities at increasing axial flow but were not able to explain their nature. We find that Kelvin waves on individual vortices become unstable and grow in amplitude, until the amplitude of the waves becomes large enough that vortex reconnections take place and the vortex array is destabilized. The eventual nonlinear saturation of the instability consists of a turbulent tangle of quantized vortices which is strongly polarized. The computed results compare well with the experiments. Finally we suggest a theoretical explanation for the second instability which was observed at higher values of the axial flow