Thresholds For Dielectric-Breakdown In Laser-Irradiated Diamond

We report on picosecond laser-induced damage experiments that were carried out on a natural type-IIa diamond and a thick specimen of high-quality chemically vapor-deposited (CVD) diamond. In conjunction with earlier measurements performed elsewhere on an \u27\u27optically thick\u27\u27 single crystal, it is shown that for spot sizes (2omega) ranging from 3 to 60 mum, the breakdown field strength (E(BD)) at the damage threshold of diamond obeys a pattern best described as follows: E(BD) congruent-to A/square-root 2omega, where A = 30.7 and 38.7 MV mu1/2/cm at 532 and 1064 nm, respectively. The case of CVD diamond demonstrates that if problems arising from localized high absorption at the deposition surface can be avoided, this material should be of much promise for contemplated high-power free-electron laser window applications

How Protostellar Outflows Help Massive Stars Form

We consider the effects of an outflow on radiation escaping from the infalling envelope around a massive protostar. Using numerical radiative transfer calculations, we show that outflows with properties comparable to those observed around massive stars lead to significant anisotropy in the stellar radiation field, which greatly reduces the radiation pressure experienced by gas in the infalling envelope. This means that radiation pressure is a much less significant barrier to massive star formation than has previously been thought.Comment: 4 pages, 2 figures, emulateapj, accepted for publication in ApJ Letter

Molecular Line Emission from Massive Protostellar Disks: Predictions for ALMA and the EVLA

We compute the molecular line emission of massive protostellar disks by solving the equation of radiative transfer through the cores and disks produced by the recent radiation-hydrodynamic simulations of Krumholz, Klein, & McKee. We find that in several representative lines the disks show brightness temperatures of hundreds of Kelvin over velocity channels ~10 km s^-1 wide, extending over regions hundreds of AU in size. We process the computed intensities to model the performance of next-generation radio and submillimeter telescopes. Our calculations show that observations using facilities such as the EVLA and ALMA should be able to detect massive protostellar disks and measure their rotation curves, at least in the nearest massive star-forming regions. They should also detect significant sub-structure and non-axisymmetry in the disks, and in some cases may be able to detect star-disk velocity offsets of a few km s^-1, both of which are the result of strong gravitational instability in massive disks. We use our simulations to explore the strengths and weaknesses of different observational techniques, and we also discuss how observations of massive protostellar disks may be used to distinguish between alternative models of massive star formation.Comment: 15 pages, 9 figures, emulateapj format, accepted for publication in ApJ. Resolution of figures severely degraded to fit within size limits. Download the full paper from http://www.astro.princeton.edu/~krumholz/recent.htm

Modernizing Water Law: The Example of Florida

This Article takes a national view of the modernization of water law. Using Florida as an example, it identifies some of the most important and controversial challenges faced by states. Part II provides an overview of the process of water law reform. As states attempt to improve water management, they have modified their common law water allocation systems with an overlay of statutory law. Often, the process occurs in a piecemeal fashion, resulting in a patchwork of rules -- common law and statutory, old and new. In rare cases -- including that of Florida -- the process may be more comprehensive, one through which states supplement or supplant their common law with modem statutory codes. Part III examines the evolutionary path of Florida, a state that has adopted a generally wholesale reform in modem times. Because this reform took place in 1972 -- at the dawn of the environmental era -- the reform reflects modem environmental and public interest sensibilities. Part IV turns from process to substance, identifying five challenges that plague virtually all states: (1) advancing the public interest while allocating water among competing users; (2) retaining sufficient water in natural streams, lakes, and aquifers to maintain vibrant aquatic ecosystems; (3) ensuring that adequate water supplies will be available for future needs; (4) determining the extent to which managers should transfer water from places of relative abundance to places of relative scarcity; and (5) determining the role, if any, of the free market 4 in allocating water resources within states

Modernizing Water Law: The Example of Florida

This Article takes a national view of the modernization of water law. Using Florida as an example, it identifies some of the most important and controversial challenges faced by states. Part II provides an overview of the process of water law reform. As states attempt to improve water management, they have modified their common law water allocation systems with an overlay of statutory law. Often, the process occurs in a piecemeal fashion, resulting in a patchwork of rules -- common law and statutory, old and new. In rare cases -- including that of Florida -- the process may be more comprehensive, one through which states supplement or supplant their common law with modem statutory codes. Part III examines the evolutionary path of Florida, a state that has adopted a generally wholesale reform in modem times. Because this reform took place in 1972 -- at the dawn of the environmental era -- the reform reflects modem environmental and public interest sensibilities. Part IV turns from process to substance, identifying five challenges that plague virtually all states: (1) advancing the public interest while allocating water among competing users; (2) retaining sufficient water in natural streams, lakes, and aquifers to maintain vibrant aquatic ecosystems; (3) ensuring that adequate water supplies will be available for future needs; (4) determining the extent to which managers should transfer water from places of relative abundance to places of relative scarcity; and (5) determining the role, if any, of the free market 4 in allocating water resources within states

Social Anxiety and the Recall of Interpersonal Information

Sixty subjects classified as high or low in social anxiety participated in a structured heterosocial interaction under conditions of either high or low social-evaluative threat. Following the interaction, subjects were asked to recall detailed information about the interaction partner’s appearance and the content of the conversation. Socially anxious subjects recalled less information and made more errors in recall than nonanxious subjects. Contrary to prediction, social-evaluative threat did not affect recall. Anxious subjects also reported greater self-focused attention during the interaction. High self-focused attention was associated with superior recall for nonanxious subjects but associated with more frequent omission errors for anxious subjects. Results support cognitive-behavioral formulations of social anxiety which propose that socially anxious individuals engage in self-focused thinking which may impair their ability to process social information

Evidence for low-density lipoprotein–induced expression of connective tissue growth factor in mesangial cells

Evidence for low-density lipoprotein–induced expression of connective tissue growth factor in mesangial cells.BackgroundAlthough hyperlipidemia is a risk factor for the progression of renal damage, the relationship between increased plasma lipoproteins and glomerular injury is poorly defined. Connective tissue growth factor (CTGF) is emerging as a key determinant of progressive fibrotic diseases and its expression is up-regulated by diabetes. To define the mechanisms through which low-density lipoproteins (LDLs) promote glomerular injury, we evaluated whether LDL can modulate the expression of CTGF and collagen I.MethodsThe effects of LDL on CTGF and collagen I expression were carried out in rat mesangial cells.ResultsTreatment of mesangial cells with LDL for 24 hours produced a significant increase in the protein levels of CTGF and collagen I compared to unstimulated controls. To explore if CTGF and collagen I are downstream targets for regulation by transforming growth factor-β (TGF-β), mesangial cells were treated with various concentration of TGF-β for 24 hours. TGF-β produced a concentration-dependent increase in the protein levels of CTGF and collagen I. The increase in CTGF and collagen I induced by LDL was significantly inhibited by neutralizing anti-TGF-β antibodies. Inhibition of p38mapk or p42/44mapk activities did not affect LDL-induced TGF-β1, CTGF, and collagen I expression, whereas inhibition of c-Jun NH2-terminal kinase (JNK) suppressed LDL-induced TGF-β, CTGF, and collagen I expression.ConclusionThese findings implicate JNK pathway and TGF-β1 as key players in LDL signaling leading to CTGF and collagen I expression in mesangial cells. The data also point to a potential mechanistic pathway through which lipoproteins may promote glomerular injury

Sub-Alfvenic Non-Ideal MHD Turbulence Simulations with Ambipolar Diffusion: I. Turbulence Statistics

Most numerical investigations on the role of magnetic fields in turbulent molecular clouds (MCs) are based on ideal magneto-hydrodynamics (MHD). However, MCs are weakly ionized, so that the time scale required for the magnetic field to diffuse through the neutral component of the plasma by ambipolar diffusion (AD) can be comparable to the dynamical time scale. We have performed a series of 256^3 and 512^3 simulations on supersonic but sub-Alfvenic turbulent systems with AD using the Heavy-Ion Approximation developed in Li, McKee, & Klein (2006). Our calculations are based on the assumption that the number of ions is conserved, but we show that these results approximately apply to the case of time-dependent ionization in molecular clouds as well. Convergence studies allow us to determine the optimal value of the ionization mass fraction when using the heavy-ion approximation for low Mach number, sub-Alfvenic turbulent systems. We find that ambipolar diffusion steepens the velocity and magnetic power spectra compared to the ideal MHD case. Changes in the density PDF, total magnetic energy, and ionization fraction are determined as a function of the AD Reynolds number. The power spectra for the neutral gas properties of a strongly magnetized medium with a low AD Reynolds number are similar to those for a weakly magnetized medium; in particular, the power spectrum of the neutral velocity is close to that for Burgers turbulence.Comment: 37 pages, 11 figures, 4 table