Novel BRAF Alteration in a Sporadic Pilocytic Astrocytoma

Pilocytic astrocytoma (PA) is the most frequently encountered glial tumor (glioma or astrocytoma) in children. Recent studies have identified alterations in the BRAF serine/threonine kinase gene as the likely causative mutation in these childhood brain tumors. The majority of these genetic changes involve chromosome 7q34 tandem duplication, resulting in aberrant BRAF fusion transcripts. In this paper, we describe a novel KIAA1549:BRAF fusion transcript in a sporadic PA tumor associated with increased ERK activation and review the spectrum of BRAF genetic alterations in this common pediatric low-grade central nervous system neoplasm

Interface Reactions and Electrical Characteristics of Au/GaSb Contacts

The reaction of Au with GaSb occurs at a relatively low temperature (100 C). Upon annealing, a AuSb{sub 2} compound and several Au-Ga phases are produced. Phase transitions occur toward higher Ga concentration with increasing annealing temperatures. Furthermore, the depth of the contact also increases with increased annealing temperature. They found that the AuSb{sub 2} compound forms on the GaSb surface, with the compound crystal partially ordered with respect to the substrate. The transition of Schottky- to ohmic-contact behavior in Au/n-type GaSb occurs simultaneously with the formation of the AuGa compound at about a 250 C annealing temperature. This ohmic contact forms without the segregation of dopants at the metallic compound/GaSb interface. Therefore it is postulated that transition from Schottky- to ohmic-contact behavior is obtained through a series of tunneling transitions of electrons through defects in the depletion region in the Au/n-type GaSb contacts. Contact resistivities of 6-7 x 10{sup -6} {Omega}-cm{sup 2} were obtained with the annealing temperature between 300 and 350 C for 30 seconds. In Au/p-type GaSb contacts, the resistivity was independent of the annealing temperature. This suggested that the carrier transport in p-type contact dominated by thermionic emission

Fermion Production in the Background of Minkowski Space Classical Solutions in Spontaneously Broken Gauge Theory

We investigate fermion production in the background of Minkowski space solutions to the equations of motion of $SU(2)$ gauge theory spontaneously broken via the Higgs mechanism. First, we attempt to evaluate the topological charge $Q$ of the solutions. We find that for solutions $Q$ is not well-defined as an integral over all space-time. Solutions can profitably be characterized by the (integer-valued) change in Higgs winding number $\Delta N_H$. We show that solutions which dissipate at early and late times and which have nonzero $\Delta N_H$ must have at least the sphaleron energy. We show that if we couple a quantized massive chiral fermion to a classical background given by a solution, the number of fermions produced is $\Delta N_H$, and is not related to $Q$.Comment: Version to be published. Argument showing that the topological charge of solutions is undefined has been strengthened and clarified. Conclusions unchange

Generation and Suppression of Decoherence in Artificial Environment for Qubit System

It is known that a quantum system with finite degrees of freedom can simulate a composite of a system and an environment if the state of the hypothetical environment is randomized by external manipulation. We show theoretically that any phase decoherence phenomena of a single qubit can be simulated with a two-qubit system and demonstrate experimentally two examples: one is phase decoherence of a single qubit in a transmission line, and the other is that in a quantum memory. We perform NMR experiments employing a two-spin molecule and clearly measure decoherence for both cases. We also prove experimentally that the bang-bang control efficiently suppresses decoherence.Comment: 25 pages, 7 figures; added reference

Convergence theorems for quantum annealing

We prove several theorems to give sufficient conditions for convergence of quantum annealing, which is a protocol to solve generic optimization problems by quantum dynamics. In particular the property of strong ergodicity is proved for the path-integral Monte Carlo implementation of quantum annealing for the transverse Ising model under a power decay of the transverse field. This result is to be compared with the much slower inverse-log decay of temperature in the conventional simulated annealing. Similar results are proved for the Green's function Monte Carlo approach. Optimization problems in continuous space of particle configurations are also discussed.Comment: 19 page

Cooling atoms into entangled states

We discuss the possibility of preparing highly entangled states by simply cooling atoms into the ground state of an applied interaction Hamiltonian. As in laser sideband cooling, we take advantage of a relatively large detuning of the desired state, while all other qubit states experience resonant laser driving. Once spontaneous emission from excited atomic states prepares the system in its ground state, it remains there with a very high fidelity for a wide range of experimental parameters and all possible initial states. After presenting the general theory, we discuss concrete applications with one and two qubits.Comment: 16 pages, 6 figures, typos correcte