15,259 research outputs found
Illumination in binaries
We give a simple, but accurate method that can be used to account for
illumination in compact binary systems which have a low-mass companion, even if
spherically symmetric illumination of the secondary star (not necessarily on
the main sequence) is not assumed. This is done by introducing a multiplicative
factor Phi in the Stefan-Boltzmann surface boundary condition, which accounts
for the blocking of the intrinsic secondary flux by X-ray heating of the
photospheric layers. Numerical fits and tables for Phi are given for
unperturbed effective temperatures in the range 2500 - 5600 K and log g in the
range 1.0 - 5.0Comment: 5 pages, 3 figures. Accepted for publication in Astronomy and
Astrophysics Supplement Serie
Crystal structures and growth mechanism for ultrathin films of ionic compound materials: FeO(111) on Pt(111)
The growth and atomic structures of epitaxial iron-oxide films on Pt(111) were studied with scanning tunneling microscopy and high-resolution low-energy electron diffraction. During the initial layer-by-layer growth of FeO(111) four different structures are formed as the coverage increases to 2.5 monolayers, then a three-dimensional growth of Fe3O4(111) islands begins. The structural transformations demonstrate that the relaxations within the FeO(111) films and the Stranski-Krastanov growth mode are induced by electrostatic surface energies, which dominate the energetics of thin film systems made up of ionic compound materials
A-Type KV Channels in Dorsal Root Ganglion Neurons: Diversity, Function, and Dysfunction
A-type voltage-gated potassium (Kv) channels are major regulators of neuronal excitability that have been mainly characterized in the central nervous system. By contrast, there is a paucity of knowledge about the molecular physiology of these Kv channels in the peripheral nervous system, including highly specialized and heterogenous dorsal root ganglion (DRG) neurons. Although all A-type Kv channels display pore-forming subunits with similar structural properties and fast inactivation, their voltage-, and time-dependent properties and modulation are significantly different. These differences ultimately determine distinct physiological roles of diverse A-type Kv channels, and how their dysfunction might contribute to neurological disorders. The importance of A-type Kv channels in DRG neurons is highlighted by recent studies that have linked their dysfunction to persistent pain sensitization. Here, we review the molecular neurophysiology of A-type Kv channels with an emphasis on those that have been identified and investigated in DRG nociceptors (Kv1.4, Kv3.4, and Kv4s). Also, we discuss evidence implicating these Kv channels in neuropathic pain resulting from injury, and present a perspective of outstanding challenges that must be tackled in order to discover novel treatments for intractable pain disorders
Vector constants of motion for time-dependent Kepler and isotropic harmonic oscillator potentials
A method of obtaining vector constants of motion for time-independent as well
as time-dependent central fields is discussed. Some well-established results
are rederived in this alternative way and new ones obtained.Comment: 18 pages, no figures, regular Latex article forma
Comprehensive Analysis of Arkansas Teacher Salaries: State, Region, and District
School funding has been an area of contention in the courts of nearly every state. Many of these court cases have challenged the constitutionality of state funding formulas, arguing the funding system was inadequate or inequitable because poor urban or rural districts often faced a disadvantage in garnering tax dollars for education. Specific to Arkansas, in the 1983 decision Dupree v. Alma School District, the Arkansas Supreme Court declared the state’s funding system was not meeting its constitutional requirements
Measuring Energy Supply Risks: A G7 Ranking
The security of energy supply has again become a similarly hot topic as it was during the oil crises in the 1970s, not least due to the recent historical oil price peaks. In this paper, we analyze the energy security situation of the G7 countries using a statistical risk indicator and empirical energy data for the years 1978 through 2007.We find that Germany’s energy supply risk has risen substantially since the oil price crises of the 1970s, whereas France has managed to reduce its risk dramatically, most notably through the deployment of nuclear power plants. As a result of the legally stipulated nuclear phase-out, Germany’s supply risk can be expected to rise further and to approach the level of Italy.Due to its resource poverty, Italy has by far the highest energy supply risk among G7 countries.Herfindahl Index, Energy Supply Risk Indicator
Germany's Solar Cell Promotion: Dark Clouds on the Horizon
This article demonstrates that the large feed-in tariffs currently guaranteed for solar electricity in Germany constitute a subsidization regime that, if extended to 2020, threatens to reach a level comparable to that of German hard coal production, a notoriously outstanding example of misguided political intervention. Yet, as a consequence of the coexistence of the German Renewable Energy Sources Act (EEG) and theEUEmissions Trading Scheme (ETS), the increased use of renewable energy technologies does not imply any additional emission reductions beyond those already achieved by ETS alone. Similarly disappointing is the net employment balance, which is likely to be negative if one takes into account the opportunity cost of this form of solar photovoltaic support. Along the lines of the International Energy Agency (IEA 2007:77), we therefore recommend the immediate and drastic reduction of the magnitude of the feed-in tariffs granted for solar-based electricity. Ultimately, producing electricity on this basis is among the most expensive greenhouse gas abatement options.Energy policy, energy security, learning effects
Outstanding Educational Performance Awards: Highlighting High-Achieving Arkansas Schools, 2012
- …