Enhanced noise at high bias in atomic-scale Au break junctions

Heating in nanoscale systems driven out of equilibrium is of fundamental importance, has ramifications for technological applications, and is a challenge to characterize experimentally. Prior experiments using nanoscale junctions have largely focused on heating of ionic degrees of freedom, while heating of the electrons has been mostly neglected. We report measurements in atomic-scale Au break junctions, in which the bias-driven component of the current noise is used as a probe of the electronic distribution. At low biases ($<$ 150~mV) the noise is consistent with expectations of shot noise at a fixed electronic temperature. At higher biases, a nonlinear dependence of the noise power is observed. We consider candidate mechanisms for this increase, including flicker noise (due to ionic motion), heating of the bulk electrodes, nonequilibrium electron-phonon effects, and local heating of the electronic distribution impinging on the ballistic junction. We find that flicker noise and bulk heating are quantitatively unlikely to explain the observations. We discuss the implications of these observations for other nanoscale systems, and experimental tests to distinguish vibrational and electron interaction mechanisms for the enhanced noise.Comment: 30 pages, 7 figure

PRDM14 is expressed in germ cell tumors with constitutive overexpression altering human germline differentiation and proliferation.

Germ cell tumors (GCTs) are a heterogeneous group of tumors occurring in gonadal and extragonadal locations. GCTs are hypothesized to arise from primordial germ cells (PGCs), which fail to differentiate. One recently identified susceptibility loci for human GCT is PR (PRDI-BF1 and RIZ) domain proteins 14 (PRDM14). PRDM14 is expressed in early primate PGCs and is repressed as PGCs differentiate. To examine PRDM14 in human GCTs we profiled human GCT cell lines and patient samples and discovered that PRDM14 is expressed in embryonal carcinoma cell lines, embryonal carcinomas, seminomas, intracranial germinomas and yolk sac tumors, but is not expressed in teratomas. To model constitutive overexpression in human PGCs, we generated PGC-like cells (PGCLCs) from human pluripotent stem cells (PSCs) and discovered that elevated expression of PRDM14 does not block early PGC formation. Instead, we show that elevated PRDM14 in PGCLCs causes proliferation and differentiation defects in the germline

The open string pair-production rate enhancement by a magnetic flux

We extend the amplitude calculations of \cite{Lu:2009yx} to exhaust the remaining cases for which one set of D$_p$ branes carrying a flux (electric or magnetic) is placed parallel at separation to the other set carrying also a flux but with the two fluxes sharing at most one common field-strength index. We then find that the basic structure of amplitudes remains the same when the two fluxes share at least one common index but it is more general when the two fluxes share no common index. We discuss various properties of the amplitudes such as the large separation limit, the onset of various instabilities and the open string pair production. In particular, when one flux is electric and weak and the other is magnetic and fixed, we find that the open string pair production rate is greatly enhanced by the presence of this magnetic flux when the two fluxes share no common field-strength index and this rate becomes significant when the separation is on the order of string scale.Comment: 33 pages, no figures, a few points refined to the published version JHEP09(2009)09

Current-Induced Effects in Nanoscale Conductors

We present an overview of current-induced effects in nanoscale conductors with emphasis on their description at the atomic level. In particular, we discuss steady-state current fluctuations, current-induced forces, inelastic scattering and local heating. All of these properties are calculated in terms of single-particle wavefunctions computed using a scattering approach within the static density-functional theory of many-electron systems. Examples of current-induced effects in atomic and molecular wires will be given and comparison with experimental results will be provided when available.Comment: revtex, 10 pages, 8 figure

Search for the standard model Higgs boson in the H → ZZ → ℓ^+ℓ^−τ^+τ^− decay channel in pp collisions at √s = 7 TeV

A search is reported for the standard model Higgs boson in the H → ZZ → ℓ^+ℓ^−τ^+τ^− decay mode, where ℓ = μ or e, in proton-proton collisions at √s = 7TeV , corresponding to an integrated luminosity of 4.7 fb^(−1) collected with the CMS detector at the LHC. No evidence is found for a significant deviation from the background expectation. An upper limit four to twelve times larger than the predicted value is set at 95% confidence level for the product of the standard model Higgs boson production cross section and decay branching fraction in the mass range 190 < m_H < 600 GeV