Theory of Current-Induced Magnetization Precession

We solve appropriate drift-diffusion and Landau-Lifshitz-Gilbert equations to demonstrate that unpolarized current flow from a non-magnet into a ferromagnet can produce a precession-type instability of the magnetization. The fundamental origin of the instability is the difference in conductivity between majority spins and minority spins in the ferromagnet. This leads to spin accumulation and spin currents that carry angular momentum across the interface. The component of this angular momentum perpendicular to the magnetization drives precessional motion that is opposed by Gilbert damping. Neglecting magnetic anisotropy and magnetostatics, our approximate analytic and exact numerical solutions using realistic values for the material parameters show (for both semi-infinite and thin film geometries) that a linear instability occurs when both the current density and the excitation wave vector parallel to the interface are neither too small nor too large. For many aspects of the problem, the variation of the magnetization in the direction of the current flows makes an important contribution.Comment: Submitted to Physical Review

Polarized Parton Distributions in the Nucleon

The distribution of the spin of the nucleon among its constituents can be parametrized in the form of polarized parton distribution functions for quarks and gluons. Using all available data on the polarized structure function $g_1(x,Q^2)$, we determine these distributions both at leading and next-to-leading order in perturbation theory. We suggest three different, equally possible scenarios for the polarized gluon distribution, which is found to be only loosely constrained by current experimental data. We examine various possibilities of measuring polarized parton distributions at future experiments.Comment: 18 pages, LATEX, 6 figures available as .uu fil

Kaon and Pion Production in Central Au+Au Collisions at \sqrt{s_{NN}}=62.4 GeV

Invariant pT spectra and rapidity densities covering a large rapidity range(-0.1 < y < 3.5) are presented for $\pi^{\pm}$ and $K^{\pm}$ mesons from central Au+Au collisions at $\sqrt{s_{NN}}$ = 62.4 GeV. The mid-rapidity yields of meson particles relative to their anti-particles are found to be close to unity ($\pi^-/\pi^+ \sim 1$, $K^-/K^+ \sim 0.85$) while the anti-proton to proton ratio is $\bar{p}/p \sim 0.49$. The rapidity dependence of the $\pi^-/\pi^+$ ratio is consistent with a small increase towards forward rapidities while the $K^-/K^+$ and $\bar{p}/p$ ratios show a steep decrease to $\sim$ 0.3 for kaons and 0.022 for protons at $y\sim 3$. It is observed that the kaon production relative to its own anti-particle as well as to pion production in wide rapidity and energy ranges shows an apparent universal behavior consistent with the baryo-chemical potential, as deduced from the $\bar{p}/p$ ratio, being the driving parameter.Comment: Submitted to PLB, 6 journal pages, 7 figure

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele

Treatment of venous thromboembolism with low-molecular-weight heparin: a synthesis of the evidence published in systematic literature reviews

Objective: To evaluate the methodology and cumulative evidence presented in systematic reviews of clinical trials comparing low-molecular-weight heparin (LMWH) with unfractionated heparin (UFH) for the treatment of venous thromboembolism. Methods: We reviewed all systematic reviews of clinical trials published until March 2002. Fourteen systematic literature reviews were published between 1994 and 2000. Deficiencies in methodological quality were common, particularly in the description of search strategies, assessment of clinical trial quality, and methods used to combine results. Results: Results of reviews indicate that LMWH is superior to UFH for the treatment of venous thromboembolism, particularly in reducing mortality. Patients with isolated deep venous thrombosis or deep venous thrombosis with concomitant pulmonary embolism seemed to have similar benefit. However, the benefits of LMWH over UFH were smaller in magnitude in reviews that included more recent clinical trials