Recent Extreme Ultraviolet Solar Spectra and Spectroheliograms

Extreme ultraviolet solar spectra and spectroheliogram analyse

Taking Off the SOCS: Cytokine Signaling Spurs Regeneration

Strategies to improve function after CNS injuries must contend with the failure of axons to regrow after transection in adult mammals. In this issue of Neuron, Smith et al. provide an important advance by demonstrating that SOCS3 acts as a key negative regulator of adult optic nerve regeneration

Effective Kinetic Theory for High Temperature Gauge Theories

Quasiparticle dynamics in relativistic plasmas associated with hot, weakly-coupled gauge theories (such as QCD at asymptotically high temperature $T$) can be described by an effective kinetic theory, valid on sufficiently large time and distance scales. The appropriate Boltzmann equations depend on effective scattering rates for various types of collisions that can occur in the plasma. The resulting effective kinetic theory may be used to evaluate observables which are dominantly sensitive to the dynamics of typical ultrarelativistic excitations. This includes transport coefficients (viscosities and diffusion constants) and energy loss rates. We show how to formulate effective Boltzmann equations which will be adequate to compute such observables to leading order in the running coupling $g(T)$ of high-temperature gauge theories [and all orders in $1/\log g(T)^{-1}$]. As previously proposed in the literature, a leading-order treatment requires including both $22$ particle scattering processes as well as effective ``$12$'' collinear splitting processes in the Boltzmann equations. The latter account for nearly collinear bremsstrahlung and pair production/annihilation processes which take place in the presence of fluctuations in the background gauge field. Our effective kinetic theory is applicable not only to near-equilibrium systems (relevant for the calculation of transport coefficients), but also to highly non-equilibrium situations, provided some simple conditions on distribution functions are satisfied.Comment: 40 pages, new subsection on soft gauge field instabilities adde

The SUMO deconjugating peptidase Smt4 contributes to the mechanism required for transition from sister chromatid arm cohesion to sister chromatid pericentromere separation

The pericentromere chromatin protrudes orthogonally from the sister-sister chromosome arm axis. Pericentric protrusions are organized in a series of loops with the centromere at the apex, maximizing its ability to interact with stochastically growing and shortening kinetochore microtubules. Each pericentromere loop is ∼50 kb in size and is organized further into secondary loops that are displaced from the primary spindle axis. Cohesin and condensin are integral to mechanisms of loop formation and generating resistance to outward forces from kinesin motors and anti-parallel spindle microtubules. A major unanswered question is how the boundary between chromosome arms and the pericentromere is established and maintained. We used sister chromatid separation and dynamics of LacO arrays distal to the pericentromere to address this issue. Perturbation of chromatin spring components results in 2 distinct phenotypes. In cohesin and condensin mutants sister pericentric LacO arrays separate a defined distance independent of spindle length. In the absence of Smt4, a peptidase that removes SUMO modifications from proteins, pericentric LacO arrays separate in proportion to spindle length increase. Deletion of Smt4, unlike depletion of cohesin and condensin, causes stretching of both proximal and distal pericentromere LacO arrays. The data suggest that the sumoylation state of chromatin topology adjusters, including cohesin, condensin, and topoisomerase II in the pericentromere, contribute to chromatin spring properties as well as the sister cohesion boundary

Analysis of small-diameter wood supply in northern Arizona - Final report

Forest management to restore fire-adapted ponderosa pine ecosystems is a central priority of the Southwestern Region of the USDA Forest Service. Appropriately-scaled businesses are apt to play a key role in achieving this goal by harvesting, processing and selling wood products, thereby reducing treatment costs and providing economic opportunities. The manner in which treatments occur across northern Arizona, with its multiple jurisdictions and land management areas, is of vital concern to a diversity of stakeholder groups. To identify a level of forest thinning treatments and potential wood supply from restoration byproducts, a 20-member working group representing environmental non-governmental organizations (NGOs), private forest industries, local government, the Ecological Restoration Institute at Northern Arizona University (NAU), and state and federal land and resource management agencies was assembled. A series of seven workshops supported by Forest Ecosystem Restoration Analysis (ForestERA; NAU) staff were designed to consolidate geographic data and other spatial information and to synthesize potential treatment scenarios for a 2.4 million acre analysis area south of the Grand Canyon and across the Mogollon Plateau. A total of 94% of the analysis area is on National Forest lands. ForestERA developed up-to-date remote sensing-based forest structure data layers to inform the development of treatment scenarios, and to estimate wood volume in three tree diameter classes of 16" diameter at breast height (dbh, 4.5' above base). For the purposes of this report, the group selected a 16" dbh threshold due to its common use within the analysis landscape as a break point differentiating "small" and "large" diameter trees in the ponderosa pine forest type. The focus of this study was on small-diameter trees, although wood supply estimates include some trees >16" dbh where their removal was required to meet desired post-treatment conditions.4 There was no concurrence within the group that trees over 16" dbh should be cut and removed from areas outside community protection management areas (CPMAs)..

Classical Limit of Demagnetization in a Field Gradient

We calculate the rate of decrease of the expectation value of the transverse component of spin for spin-1/2 particles in a magnetic field with a spatial gradient, to determine the conditions under which a previous classical description is valid. A density matrix treatment is required for two reasons. The first arises because the particles initially are not in a pure state due to thermal motion. The second reason is that each particle interacts with the magnetic field and the other particles, with the latter taken to be via a 2-body central force. The equations for the 1-body Wigner distribution functions are written in a general manner, and the places where quantum mechanical effects can play a role are identified. One that may not have been considered previously concerns the momentum associated with the magnetic field gradient, which is proportional to the time integral of the gradient. Its relative magnitude compared with the important momenta in the problem is a significant parameter, and if their ratio is not small some non-classical effects contribute to the solution. Assuming the field gradient is sufficiently small, and a number of other inequalities are satisfied involving the mean wavelength, range of the force, and the mean separation between particles, we solve the integro- partial differential equations for the Wigner functions to second order in the strength of the gradient. When the same reasoning is applied to a different problem with no field gradient, but having instead a gradient to the z-component of polarization, the connection with the diffusion coefficient is established, and we find agreement with the classical result for the rate of decrease of the transverse component of magnetization.Comment: 22 pages, no figure

Quasiparticle transport equation with collision delay. II. Microscopic Theory

For a system of non-interacting electrons scattered by neutral impurities, we derive a modified Boltzmann equation that includes quasiparticle and virial corrections. We start from quasiclassical transport equation for non-equilibrium Green's functions and apply limit of small scattering rates. Resulting transport equation for quasiparticles has gradient corrections to scattering integrals. These gradient corrections are rearranged into a form characteristic for virial corrections