Prospect for room temperature tunneling anisotropic magnetoresistance effect: density of states anisotropies in CoPt systems

Tunneling anisotropic magnetoresistance (TAMR) effect, discovered recently in (Ga,Mn)As ferromagnetic semiconductors, arises from spin-orbit coupling and reflects the dependence of the tunneling density of states in a ferromagnetic layer on orientation of the magnetic moment. Based on ab initio relativistic calculations of the anisotropy in the density of states we predict sizable TAMR effects in room-temperature metallic ferromagnets. This opens prospect for new spintronic devices with a simpler geometry as these do not require antiferromagnetically coupled contacts on either side of the tunnel junction. We focus on several model systems ranging from simple hcp-Co to more complex ferromagnetic structures with enhanced spin-orbit coupling, namely bulk and thin film L1$_0$-CoPt ordered alloys and a monatomic-Co chain at a Pt surface step edge. Reliability of the predicted density of states anisotropies is confirmed by comparing quantitatively our ab initio results for the magnetocrystalline anisotropies in these systems with experimental data.Comment: 4 pages, 2 figure

Materials for engine applications above 3000 deg F: An overview

Materials for future generations of aeropropulsion systems will be required to perform at ever-increasing temperatures and have properties superior to the current state of the art. Improved engine efficiency can reduce specific fuel consumption and thus increase range and reduce operating costs. The ultimate payoff gain is expected to come when materials are developed which can perform without cooling at gas temperatures to 2200 C (4000 F). An overview is presented of materials for applications above 1650 C (3000 F), some pertinent physical property data, and the rationale used: (1) to arrive at recommendations of material systems that qualify for further investigation, and (2) to develop a proposed plan of research. From an analysis of available thermochemical data it was included that such materials systems must be composed of oxide ceramics. The required structural integrity will be achieved by developing these materials into fiber-reinforced ceramic composites

Exchange bias and interface electronic structure in Ni/Co3O4(011)

A detailed study of the exchange bias effect and the interfacial electronic structure in Ni/Co3O4(011) is reported. Large exchange anisotropies are observed at low temperatures, and the exchange bias effect persists to temperatures well above the Neel temperature of bulk Co3O4, of about 40 K: to ~80 K for Ni films deposited on well ordered oxide surfaces, and ~150 K for Ni films deposited on rougher Co3O4 surfaces. Photoelectron spectroscopy measurements as a function of Ni thickness show that Co reduction and Ni oxidation occur over an extended interfacial region. We conclude that the exchange bias observed in Ni/Co3O4, and in similar ferromagnetic metallic/Co3O4 systems, is not intrinsic to Co3O4 but rather due to the formation of CoO at the interface.Comment: 8 pages, 6 figures. Accepted for publication in Physical Review B

Flow dynamics of Byrd Glacier, East Antarctica

Force-balance calculations on Byrd Glacier, East Antarctica, reveal large spatial variations in the along-flow component of driving stress with corresponding sticky spots that are stationary over time. On the large scale, flow resistance is partitioned between basal (�80%) and lateral (�20%) drag. Ice flow is due mostly to basal sliding and concentrated vertical shear in the basal ice layers, indicating the bed is at or close to the pressure-melting temperature. There is a significant component of driving stress in the across-flow direction resulting in nonzero basal drag in that direction. This is an unrealistic result and we propose that there are spatial variations of bed features resulting in small-scale flow disturbances. The grounding line of Byrd Glacier is located in a region where the bed slopes upward. Nevertheless, despite a 10% increase in ice discharge between December 2005 and February 2007, following drainage of two subglacial lakes in the catchment area, the position of the grounding line has not retreated significantly and the glacier has decelerated since then. During the speed-up event, partitioning of flow resistance did not change, suggesting the increase in velocity was caused by a temporary decrease in basal effective pressure

Experimental application of sum rules for electron energy loss magnetic chiral dichroism

We present a derivation of the orbital and spin sum rules for magnetic circular dichroic spectra measured by electron energy loss spectroscopy in a transmission electron microscope. These sum rules are obtained from the differential cross section calculated for symmetric positions in the diffraction pattern. Orbital and spin magnetic moments are expressed explicitly in terms of experimental spectra and dynamical diffraction coefficients. We estimate the ratio of spin to orbital magnetic moments and discuss first experimental results for the Fe L_{2,3} edge.Comment: 11 pages, 2 figure

Tamoxifen therapy reduced platelet counts without change in platelet function

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109840/1/cptclpt2005247.pd

Giant Magnetoelectric Effect via Strain-Induced Spin-Reorientation Transitions in Ferromagnetic Films

It is shown theoretically that a giant magnetoelectric susceptibility exceeding 10^-6 s/m may be achieved in the ferromagnetic/ferroelectric epitaxial systems via the magnetization rotation induced by an electric field applied to the substrate. The predicted magnetoelectric anomaly results from the strain-driven spin-reorientation transitions in ferromagnetic films, which take place at experimentally accessible misfit strains in CoFe2O4 and Ni films.Comment: 7 pages, 3 figure

Fast Quasi-Newton Algorithms for Penalized Reconstruction in Emission Tomography and Further Improvements via Preconditioning

OAPA This paper reports on the feasibility of using a quasi-Newton optimization algorithm, limited-memory Broyden- Fletcher-Goldfarb-Shanno with boundary constraints (L-BFGSB), for penalized image reconstruction problems in emission tomography (ET). For further acceleration, an additional preconditioning technique based on a diagonal approximation of the Hessian was introduced. The convergence rate of L-BFGSB and the proposed preconditioned algorithm (L-BFGS-B-PC) was evaluated with simulated data with various factors, such as the noise level, penalty type, penalty strength and background level. Data of three 18F-FDG patient acquisitions were also reconstructed. Results showed that the proposed L-BFGS-B-PC outperforms L-BFGS-B in convergence rate for all simulated conditions and the patient data. Based on these results, L-BFGSB- PC shows promise for clinical application

Weak decays of 4He-Lambda

We measured the lifetime and the mesonic and non-mesonic decay rates of the 4He-Lambda hypernucleus. The hypernuclei were created using a 750 MeV/c momentum K- beam on a liquid 4He target by the reaction 4He(K-,pi-)4He-Lambda. The 4He-Lambda lifetime was directly measured using protons from Lambda p -> n p non-mesonic decay (also referred to as proton-stimulated decay) and was found to have a value of tau = 245 +/- 24 ps. The mesonic decay rates were determined from the observed numbers of pi-'s and pi0's as Gamma_pi-/Gamma_tot = 0.270 +/- 0.024 and Gamma_pi0/Gamma_tot = 0.564 +/- 0.036, respectively, and the values of the proton- and neutron-stimulated decay rates were extracted as Gamma_p/Gamma_tot = 0.169 +/- 0.019 and Gamma_n/Gamma_tot <= 0.032 (95% CL), respectively. The effects of final-state interactions and possible 3-body Lambda N N decay contributions were studied in the context of a simple model of nucleon-stimulated decay. Nucleon-nucleon coincidence events were observed and were used in the determination of the non-mesonic branching fractions. The implications of the results of this analysis were considered for the empirical Delta I = 1/2 rule and the decay rates of the 4H-Lambda hypernucleus.Comment: 15 pages, 11 figures, published in PRC, revised content to match published versio

Individual variation in age‐dependent reproduction: Fast explorers live fast but senesce young?

Adaptive integration of life history and behaviour is expected to result in variation in the pace‐of‐life. Previous work focused on whether ‘risky’ phenotypes live fast but die young, but reported conflicting support. We posit that individuals exhibiting risky phenotypes may alternatively invest heavily in early‐life reproduction but consequently suffer greater reproductive senescence. We used a 7‐year longitudinal dataset with >1,200 breeding records of >800 female great tits assayed annually for exploratory behaviour to test whether within‐individual age dependency of reproduction varied with exploratory behaviour. We controlled for biasing effects of selective (dis)appearance and within‐individual behavioural plasticity. Slower and faster explorers produced moderate‐sized clutches when young; faster explorers subsequently showed an increase in clutch size that diminished with age (with moderate support for declines when old), whereas slower explorers produced moderate‐sized clutches throughout their lives. There was some evidence that the same pattern characterized annual fledgling success, if so, unpredictable environmental effects diluted personality‐related differences in this downstream reproductive trait. Support for age‐related selective appearance was apparent, but only when failing to appreciate within‐individual plasticity in reproduction and behaviour. Our study identifies within‐individual age‐dependent reproduction, and reproductive senescence, as key components of life‐history strategies that vary between individuals differing in risky behaviour. Future research should thus incorporate age‐dependent reproduction in pace‐of‐life studies