Inward transport of a toroidally confined plasma subject to strong radial electric fields

Digitally implemented spectral analysis techniques were used to investigate the frequency-dependent fluctuation-induced particle transport across a toroidal magnetic field. When the electric field pointed radially inward, the transport was inward and a significant enhancement of the plasma density and confinement time resulted

Ion confinement and transport in a toroidal plasma with externally imposed radial electric fields

Strong electric fields were imposed along the minor radius of the toroidal plasma by biasing it with electrodes maintained at kilovolt potentials. Coherent, low-frequency disturbances characteristic of various magnetohydrodynamic instabilities were absent in the high-density, well-confined regime. High, direct-current radial electric fields with magnitudes up to 135 volts per centimeter penetrated inward to at least one-half the plasma radius. When the electric field pointed radially toward, the ion transport was inward against a strong local density gradient; and the plasma density and confinement time were significantly enhanced. The radial transport along the electric field appeared to be consistent with fluctuation-induced transport. With negative electrode polarity the particle confinement was consistent with a balance of two processes: a radial infusion of ions, in those sectors of the plasma not containing electrodes, that resulted from the radially inward fields; and ion losses to the electrodes, each of the which acted as a sink and drew ions out of the plasma. A simple model of particle confinement was proposed in which the particle confinement time is proportional to the plasma volume. The scaling predicted by this model was consistent with experimental measurements

Determination of Strong-Interaction Widths and Shifts of Pionic X-Rays with a Crystal Spectrometer

Pionic 3d-2p atomic transitions in F, Na, and Mg have been studied using a bent crystal spectrometer. The pionic atoms were formed in the production target placed in the external proton beam of the Space Radiation Effects Laboratory synchrocyclotron. The observed energies and widths of the transitions are E=41679(3) eV and Γ=21(8) eV, E=62434(18) eV and Γ=22(80) eV, E=74389(9) eV and Γ=67(35) eV, in F, Na, and Mg, respectively. The results are compared with calculations based on a pion-nucleus optical potential

Concerted reductive coupling of an alkyl chloride at Pt(IV)

Oxidation of a doubly cyclometallated platinum(II) complex results in two isomeric platinum(IV) complexes. Whereas the trans isomer is robust, being manipulable in air at room temperature, the cis isomer decomposes at −20 °C and above. Reductive coupling of an alkyl chloride at the cis isomer gives a new species which can be reoxidised. The independence of this coupling on additional halide rules out the reverse of an SN2 reaction, leaving a concerted process as the only sensible reaction pathway

The 2s atomic level in muonic 208-Pb

Relative intensities and energy measurements of 2s level in muonic Pb-20

L1551NE - Discovery of a Binary Companion

L1551NE is a very young (class 0 or I) low-mass protostar located close to the well-studied L1551 IRS5. We present here evidence, from 1.3mm continuum interferometric observations at ~1'' resolution, for a binary companion to L1551NE. The companion, whose 1.3mm flux density is ~1/3 that of the primary component, is located 1.43'' (~230 A.U. at 160pc) to the southeast. The millimeterwave emission from the primary component may have been just barely resolved, with deconvolved size ~0.82"x0.70" (~131x112 A.U.). The companion emission was unresolved (<100 A.U.). The pair is embedded within a flattened circum-binary envelope of size ~5.4'' x 2.3'' (~860 x 370 A.U.). The masses of the three components (i.e. from the cicumstellar material of the primary star and its companion, and the envelope) are approximately 0.044, 0.014 and 0.023 Mo respectively.Comment: 8 pages, 1 figur

Low-Reynolds number swimming in gels

Many microorganisms swim through gels, materials with nonzero zero-frequency elastic shear modulus, such as mucus. Biological gels are typically heterogeneous, containing both a structural scaffold (network) and a fluid solvent. We analyze the swimming of an infinite sheet undergoing transverse traveling wave deformations in the "two-fluid" model of a gel, which treats the network and solvent as two coupled elastic and viscous continuum phases. We show that geometric nonlinearities must be incorporated to obtain physically meaningful results. We identify a transition between regimes where the network deforms to follow solvent flows and where the network is stationary. Swimming speeds can be enhanced relative to Newtonian fluids when the network is stationary. Compressibility effects can also enhance swimming velocities. Finally, microscopic details of sheet-network interactions influence the boundary conditions between the sheet and network. The nature of these boundary conditions significantly impacts swimming speeds.Comment: 6 pages, 5 figures, submitted to EP

Reconstruction and thermal stability of the cubic SiC(001) surfaces

The (001) surfaces of cubic SiC were investigated with ab-initio molecular dynamics simulations. We show that C-terminated surfaces can have different c(2x2) and p(2x1) reconstructions, depending on preparation conditions and thermal treatment, and we suggest experimental probes to identify the various reconstructed geometries. Furthermore we show that Si-terminated surfaces exhibit a p(2x1) reconstruction at T=0, whereas above room temperature they oscillate between a dimer row and an ideal geometry below 500 K, and sample several patterns including a c(4x2) above 500 K.Comment: 12 pages, RevTeX, figures 1 and 2 available in gif form at http://irrmawww.epfl.ch/fg/sic/fig1.gif and http://irrmawww.epfl.ch/fg/sic/fig2.gi

Determinants of Medical Costs Following a Diagnosis of Depression

Objective: Assess the determinants of medical costs for depressed individuals. Method: Using medical insurance claims for a population of depressed individuals with employer provided insurance, we estimated multivariate models of the costs for general medical care, exclusive of costs for mental health services, following diagnosis. Explanatory variables included provider choice (psychiatrist or non-physician mental health specialist), treatment choice (medication, psychotherapy, or combination treatment); treatment adequacy as defined by APA guidelines; characteristics of depression symptoms and severity; and other demographic characteristics. Results: On average, there were increases in the costs for general medical services in the year following diagnosis of a depressive disorder. The increases in general medical costs were slightly higher when depressed persons received a treatment for depression when compared to those who did not receive a treatment for depression. Among those treated, there was no significant difference between those who received an adequate course of treatment when compared with those who did not. Significant predictors of high medical costs following diagnosis included choice of a non-psychiatrist as the initial provider, high pre-period medical costs, and several measures of severity. Conclusions: Our findings suggest that a diagnosis of depression is associated with increases in costs for general medical care. These increases are more modest when care is initially provided by a psychiatrist

Psychotherapy in Antidepressant Patients

Depression is a condition with various modes of treatment, including pharmacotherapy, psychotherapy, and some combination of each. The role of psychotherapy in the treatment of depression relative to the role of pharmacotherapy is not well understood, and guidelines for psychotherapy in the primary care setting differ from guidelines for specialty care. There is little evidence about the circumstances in actual practice that affect the use of psychotherapy in conjunction with pharmacotherapy. We retrospectively identify the most important factors associated with the use of psychotherapy in combination with pharmacotherapy in the treatment of depression. Specifically, we study provider choice, health plan characteristics, and patient characteristics. We use a comprehensive medical and pharmacy claims data sample of 1,023 individuals during 1992–1994. We select persons prescribed with an antidepressant medication and diagnosed with a depressive disorder by a primary care physician, psychiatrist, or non-physician mental health specialist. Controlling for depression diagnosis and severity, comorbidity, and demographics, we examine the role of provider type and plan benefit characteristics. We study the intensity of psychotherapy using zero-inflated count regression, the intensity of pharmacotherapy using truncated count regression, and the likelihood of relapse of depression using logistic regression. Patients initially seeing a psychiatrist receive more than double the amount of psychotherapy and slightly more pharmacotherapy than patients of other providers. An additional prescription for antidepressant medication reduces by five percent the likelihood of relapse into depression, but the amount of psychotherapy does not affect relapse. Patients seeing a psychiatrist are half as likely to relapse, independent of any effect of psychotherapy. Case management and coinsurance rates do not affect the amount of psychotherapy, but the presence of case management has a positive effect on the amount of pharmacotherapy and on the likelihood of relapse. We find no discernible pattern of complementarity or substitution between pharmacotherapy and psychotherapy across providers. Although the amount of psychotherapy provided in conjunction with medication does not affect the rate of relapse to depression, psychotherapy may nonetheless provide beneficial outcomes not studied here. Choice of a psychiatrist reduces the likelihood of relapse, independent of the number of psychotherapy sessions and antidepressant prescriptions. The effect of provider choice on relapse could be an artifact of differences in provider follow-up practices or could represent a difference in provider skills. Managed care strategies do not appear to reduce the intensity of depression treatment, but case management does increase the likelihood of relapse. Pharmacotherapy and psychotherapy appear to be neither substitutes nor complements in the treatment of depression, suggesting that treatment is individualized. Choice of psychiatrist as the initial provider appears to reduce the likelihood of relapse, suggesting models of coordinated care may be beneficial. The link between psychiatrists and more psychotherapy is consistent with the hypothesis that patients resistant to treatment may nonetheless receive high quality care. Managed care tools such as case management and coinsurance rates do not appear to restrict the use of either psychotherapy or pharmacotherapy. The association of case management with an increased likelihood of relapse suggests that plan characteristics can affect outcomes. Our study focuses on psychotherapy combined with medication and does not psychotherapy alone in the treatment of depression, which may be a preferred mode of treatment for some. Outcomes other than relapse, as well as costs, should also be considered. Our findings that psychiatrists are associated with a decreased likelihood of relapse and that case management is associated with an increased likelihood of relapse despite a correlation with greater pharmacotherapy intensity present avenues for additional study