Spin injection from perpendicular magnetized ferromagnetic δ\delta-MnGa into (Al,Ga)As heterostructures

Electrical spin injection from ferromagnetic $\delta$-MnGa into an (Al,Ga)As p-i-n light emitting diode (LED) is demonstrated. The $\delta$-MnGa layers show strong perpendicular magnetocrystalline anisotropy, enabling detection of spin injection at remanence without an applied magnetic field. The bias and temperature dependence of the spin injection are found to be qualitatively similar to Fe-based spin LED devices. A Hanle effect is observed and demonstrates complete depolarization of spins in the semiconductor in a transverse magnetic field.Comment: 4 pages, 3 figure

The Kinematics and Physical Conditions pf the Ionized Gas in Markarian 509. II. STIS Echelle Observations

We present observations of the UV absorption lines in the luminous Seyfert 1 galaxy Mrk 509, obtained with the medium resolution (lambda/Delta-lambda ~ 40,000) echelle gratings of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. The spectra reveal the presence of eight kinematic components of absorption in Ly-alpha, C IV, and N V, at radial velocities of -422, -328, -259, -62, -22, +34, +124, and +210 km s^-1 with respect to an emission-line redshift of z = 0.03440, seven of which were detected in an earlier Far Ultraviolet Spectrographic Explorer (FUSE) spectrum. The component at -22 km s^-1 also shows absorption by Si IV. The covering factor and velocity width of the Si IV lines were lower than those of the higher ionization lines for this component, which is evidence for two separate absorbers at this velocity. We have calculated photoionization models to match the UV column densities in each of these components. Using the predicted O VI column densities, we were able to match the O VI profiles observed in the FUSE spectrum. Based on our results, none of the UV absorbers can produce the X-ray absorption seen in simultaneous Chandra observations; therefore, there must be more highly ionized gas in the radial velocity ranges covered by the UV absorbers.Comment: 30 pages, three figures (Figure 1 is in color). Accepted for publication in the Astrophysical Journa

Evaluation of an inflammation-based prognostic score in patients with inoperable gastro-oesophageal cancer

There is increasing evidence that the presence of an ongoing systemic inflammatory response is associated with poor outcome in patients with advanced cancer. The aim of the present study was to examine whether an inflammation-based prognostic score (Glasgow Prognostic score, GPS) was associated with survival, in patients with inoperable gastro-oesophageal cancer. Patients diagnosed with inoperable gastro-oesophageal carcinoma and who had measurement of albumin and C-reactive protein concentrations, at the time of diagnosis, were studied (n=258). Clinical information was obtained from a gastro-oesophageal cancer database and analysis of the case notes. Patients with both an elevated C-reactive protein (>10 mg l−1) and hypoalbuminaemia (<35 g l−1) were allocated a GPS score of 2. Patients in whom only one of these biochemical abnormalities was present were allocated a GPS score of 1, and patients with a normal C-reactive protein and albumin were allocated a score of 0. On multivariate survival analysis, age (hazard ratio (HR) 1.22, 95% CI 1.02–1.46, P<0.05), stage (HR 1.55, 95% CI 1.30–1.83, P<0.001), the GPS (HR 1.51, 95% CI 1.22–1.86, P<0.001) and treatment (HR 2.53, 95% CI 1.80–3.56, P<0.001) were significant independent predictors of cancer survival. A 12-month cancer-specific survival in patients with stage I/II disease receiving active treatment was 67 and 60% for a GPS of 0 and 1, respectively. For stage III/IV disease, 12 months cancer-specific survival was 57, 25 and 12% for a GPS of 0, 1 and 2, respectively. In the present study, the GPS predicted cancer-specific survival, independent of stage and treatment received, in patients with inoperable gastro-oesophageal cancer. Moreover, the GPS may be used in combination with conventional staging techniques to improve the prediction of survival in patients with inoperable gastro-oesophageal cancer

Nonequilibrium perturbation theory for complex scalar fields

Real-time perturbation theory is formulated for complex scalar fields away from thermal equilibrium in such a way that dissipative effects arising from the absorptive parts of loop diagrams are approximately resummed into the unperturbed propagators. Low order calculations of physical quantities then involve quasiparticle occupation numbers which evolve with the changing state of the field system, in contrast to standard perturbation theory, where these occupation numbers are frozen at their initial values. The evolution equation of the occupation numbers can be cast approximately in the form of a Boltzmann equation. Particular attention is given to the effects of a non-zero chemical potential, and it is found that the thermal masses and decay widths of quasiparticle modes are different for particles and antiparticles.Comment: 15 pages using RevTeX; 2 figures in 1 Postscript file; Submitted to Phys. Rev.

Chiral Surface States in the Bulk Quantum Hall Effect

In layered samples which exhibit a bulk quantum Hall effect (QHE), a two-dimensional (2d) surface ``sheath" of gapless excitations is expected. These excitations comprise a novel 2d chiral quantum liquid which should dominate the low temperature transport along the field (z-axis). For the integer QHE, we show that localization effects are completely absent in the ``sheath", giving a metallic z-axis conductivity. For fractional filling $\nu =1/3$, the ``sheath" is a 2d non-Fermi liquid, with incoherent z-axis transport and $\sigma_{zz} \sim T^3$. Experimental implications for the Bechgaard salts are discussed.Comment: 4 pages, RevTeX 3.0, with two encapsulated postscript figures, which can be automatically included in-text if desired. The complete postscript file is available on the WWW at http://www.itp.ucsb.edu/~balents/sheath.p

Nonequilibrium perturbation theory for spin-1/2 fields

A partial resummation of perturbation theory is described for field theories containing spin-1/2 particles in states that may be far from thermal equilibrium. This allows the nonequilibrium state to be characterized in terms of quasiparticles that approximate its true elementary excitations. In particular, the quasiparticles have dispersion relations that differ from those of free particles, finite thermal widths and occupation numbers which, in contrast to those of standard perturbation theory evolve with the changing nonequilibrium environment. A description of this kind is essential for estimating the evolution of the system over extended periods of time. In contrast to the corresponding description of scalar particles, the structure of nonequilibrium fermion propagators exhibits features which have no counterpart in the equilibrium theory.Comment: 16 pages; no figures; submitted to Phys. Rev.

Calibration and Characterization of Single Photon Counting Cameras for Short-Pulse Laser Experiments

The photon counting efficiency of various CCD based cameras was studied as a function of x-ray energy and exposure. A pair of Spectral Instruments Model 800 CCD cameras fitted with 16 {micro}m thick back-illuminated CCDs were calibrated at low x-ray energy using two well established histogram methods, a standard pixel for pixel histogram and the single pixel event histogram method. In addition, two new thick substrate CCDs were evaluated for use at high energy. One was a commercially available Princeton Instruments LCX1300 deep depletion CCD camera while the other was a custom designed 650 {micro}m thick partially depleted CCD fitted to a SI 800 camera body. It is shown that at high x-ray energy, only a pixel-summing algorithm was able to derive spectral data due to the spreading of x-ray events over many pixels in the thicker substrate CCDs. This paper will describe the different algorithms used to extract spectra and the absolute detection efficiencies using these algorithms. These detectors will be very useful to detect high-energy x-ray photons from high-intensity short pulse laser interactions