Slip energy barriers in aluminum and implications for ductile versus brittle behavior

We conisder the brittle versus ductile behavior of aluminum in the framework of the Peierls-model analysis of dislocation emission from a crack tip. To this end, we perform first-principles quantum mechanical calculations for the unstable stacking energy $\gamma_{us}$ of aluminum along the Shockley partial slip route. Our calculations are based on density functional theory and the local density approximation and include full atomic and volume relaxation. We find that in aluminum $\gamma_{us} = 0.224$ J/m$^2$. Within the Peierls-model analysis, this value would predict a brittle solid which poses an interesting problem since aluminum is typically considered ductile. The resolution may be given by one of three possibilites: (a) Aluminum is indeed brittle at zero temperature, and becomes ductile at a finite temperature due to motion of pre-existing dislocations which relax the stress concentration at the crack tip. (b) Dislocation emission at the crack tip is itself a thermally activated process. (c) Aluminum is actually ductile at all temperatures and the theoretical model employed needs to be significantly improved in order to resolve the apparent contradiction.Comment: 4 figures (not included; send requests to [email protected]

Nonperturbative Determination of Heavy Meson Bound States

In this paper we obtain a heavy meson bound state equation from the heavy quark equation of motion in heavy quark effective theory (HQET) and the heavy meson effective field theory we developed very recently. The bound state equation is a covariant extention of the light-front bound state equation for heavy mesons derived from light-front QCD and HQET. We determine the covariant heavy meson wave function variationally by minimizing the binding energy $\bar{\Lambda}$. Subsequently the other basic HQET parameters $\lambda_1$ and $\lambda_2$, and the heavy quark masses $m_b$ and $m_c$ can also be consistently determined.Comment: 15 pages, 1 figur

Persistent Current of Free Electrons in the Plane

Predictions of Akkermans et al. are essentially changed when the Krein spectral displacement operator is regularized by means of zeta function. Instead of piecewise constant persistent current of free electrons on the plane one has a current which varies linearly with the flux and is antisymmetric with regard to all time preserving values of $\alpha$ including $1/2$. Different self-adjoint extensions of the problem and role of the resonance are discussed.Comment: (Comment on "Relation between Persistent Currents and the Scattering Matrix", Phys. Rev. Lett. {\bf 66}, 76 (1991)) plain latex, 4pp., IPNO/TH 94-2

Controlled Quantum Secret Sharing

We present a new protocol in which a secret multiqubit quantum state $\ket{\Psi}$ is shared by $n$ players and $m$ controllers, where $\ket{\Psi}$ is the encoding state of a quantum secret sharing scheme. The players may be considered as field agents responsible for carrying out a task, using the secret information encrypted in $\ket{\Psi}$, while the controllers are superiors who decide if and when the task should be carried out and who to do it. Our protocol only requires ancillary Bell states and Bell-basis measurements.Comment: 6 pages, 0 figure, RevTeX4; published version with minor change

Gamma-ray Spectral Evolution of NGC1275 Observed with Fermi-LAT

We report on a detailed investigation of the high-energy gamma-ray emission from NGC\,1275, a well-known radio galaxy hosted by a giant elliptical located at the center of the nearby Perseus cluster. With the increased photon statistics, the center of the gamma-ray emitting region is now measured to be separated by only 0.46' from the nucleus of NGC1275, well within the 95% confidence error circle with radius ~1.5'. Early Fermi-LAT observations revealed a significant decade-timescale brightening of NGC1275 at GeV photon energies, with a flux about seven times higher than the one implied by the upper limit from previous EGRET observations. With the accumulation of one-year of Fermi-LAT all-sky-survey exposure, we now detect flux and spectral variations of this source on month timescales, as reported in this paper. The average >100 MeV gamma-ray spectrum of NGC1275 shows a possible deviation from a simple power-law shape, indicating a spectral cut-off around an observed photon energy of E = 42.2+-19.6 GeV, with an average flux of F = (2.31+-0.13) X 10^{-7} ph/cm^2/s and a power-law photon index, Gamma = 2.13+-0.02. The largest gamma-ray flaring event was observed in April--May 2009 and was accompanied by significant spectral variability above E > 1-2 GeV. The gamma-ray activity of NGC1275 during this flare can be described by a hysteresis behavior in the flux versus photon index plane. The highest energy photon associated with the gamma-ray source was detected at the very end of the observation, with the observed energy of E = 67.4GeV and an angular separation of about 2.4' from the nucleus. In this paper we present the details of the Fermi-LAT data analysis, and briefly discuss the implications of the observed gamma-ray spectral evolution of NGC1275 in the context of gamma-ray blazar sources in general.Comment: 20 pages, 6 figures, accepted for publication in the Ap

Chaotic to ordered state transition of cathode-sheath instabilities in DC glow discharge plasmas

Transition from chaotic to ordered state has been observed during the initial stage of a discharge in a cylindrical dc glow discharge plasma. Initially it shows a chaotic behavior but increasing the discharge voltage changes the characteristics of the discharge glow and shows a period substraction of order 7 period $\to$ 5 period $\to$3 period $\to$1 period i.e. the system goes to single mode through odd cycle subtraction. On further increasing the discharge voltage, the system goes through period doubling, like 1 period $\to$ 2 period $\to$ 4 period. On further increasing the voltage, the system goes to stable state without having any oscillations.Comment: chathode-sheath, instabilities, chaos, period-subtraction, bifurcation, dc-discharg

A staged approach with vincristine, adriamycin, and dexamethasone followed by bortezomib, thalidomide, and dexamethasone before autologous hematopoietic stem cell transplantation in the treatment of newly diagnosed multiple myeloma

Bortezomib-based regimens have significant activities in multiple myeloma (MM). In this study, we tested the efficacy of a total therapy with a staged approach where newly diagnosed MM patients received vincristine/adriamycin/dexamethsone (VAD). VAD-sensitive patients (≥75% paraprotein reduction) received autologous hematopoietic stem cell transplantation (auto-HSCT), whereas less VAD-sensitive patients (<75% paraprotein reduction) received bortezomib/thalidomide/dexamethasone (VTD) for further cytoreduction prior to auto-HSCT. On an intention-to-treat analysis, a progressive increase of complete remission (CR) rates was observed, with cumulative CR rates of 48% after HSCT. Seven patients progressed leading to three fatalities, of which two had central nervous system disease. The 3-year overall survival and event-free survival were 75.1% and 48.3%, respectively. Six patients developed oligoclonal reconstitution with new paraproteins. In the absence of anticoagulant prophylaxis, no patients developed deep vein thrombosis. The staged application of VAD+/–VTD/auto-HSCT resulted in an appreciable response rate and promising survivals. Our approach reduced the use of bortezomib without compromising the ultimate CR rate and is of financial significance for less affluent communities

Review of Nanomedicine

The field of nanomedicine holds vast potential for the improvement of health care around the world and the coming nanomedical revolution will surely bring innovative solutions to many of the difficulties we currently encounter in the realm of patient treatment. Nanomedicine is a relatively new field for scientific inquiry. It is defined as the use of nanoscale devices or materials to diagnose and cure diseases by actively interacting at the molecular level within a cellular system. In the context of nanotechnology, the “molecular level” refers to structures less than 100 nanometers in diameter. Given the breadth of this definition of nanomedicine, it can be narrowed and made more applicable when only those devices or medicines designed to function on the nanoscale are considere

Patterns of antihypertensive prescribing, discontinuation and switching among a Hong Kong Chinese population from over one million prescriptions

Hypertension is an alarming public health problem among Chinese. The present study evaluated the prescribing patterns, discontinuation and switching profiles of antihypertensive agents and their associated factors in one Hong Kong Chinese population. Data were retrieved from computerized records for patients prescribed anti-hypertensive agents in government primary care clinics of Hong Kong from January, 2004 to June, 2007. A total of 1,069,836 antihypertensive drug visits, representing 67,028 patients, were analyzed. The most commonly prescribed drugs were Calcium Channel Blockers (CCBs) (49%), b-Blockers (BBs) (46%) and Angiotensin-Converting Enzyme Inhibitors (ACEIs) (19%). Thiazide diuretic prescribing was low (13%) and on the decline (14% in 2004 to 12% in 2007). Prescribing of ACEIs was rising (16% in 2004 to 23% in 2007). Patients’ age, gender, and socio-economic status were independent predictors of class of anti-hypertensive prescribed but explained less than 3.5% of the variation observed. Drug discontinuation was highest for BBs (21%) and lowest for CCBs (12%). The high rates of discontinuation in BBs remained apparent after controlling for confounding variables. Switching was less common than discontinuation and was most likely with thiazide diuretics. To summarize, prescribing of CCBs and BBs were high and that of thiazide diuretics particularly low in this Chinese population when compared with international trends. CCBs may be a particularly favorable antihypertensive treatment in Chinese, given the high discontinuation rates of BBs and international guidelines advising against the use of BBs as first-line therapy. The low use of thiazide diuretics warrants further clinical and cost effectiveness studies among Chinese

Magnetic flux in mesoscopic rings: Quantum Smoluchowski regime

Magnetic flux in mesoscopic rings under the quantum Smoluchowski regime is investigated. Quantum corrections to the dissipative current are shown to form multistable steady states and can result in statistical enhancement of the magnetic flux. The relevance of quantum correction effects is supported v ia the entropic criterion. A possible application for a qutrit architecture of quantum information is proposed.Comment: 7 pages, 2 figure