Stroma-free hemoglobin increases blood pressure and GFR in the hypotensive rat: role of nitric oxide.

The short-term systemic and renal hemodynamic effects of two stroma-free hemoglobin (SFH) solutions, one unmodified and the other modified by cross-linking, were examined in anesthetized rats after hemorrhagic hypotension. Both forms of SFH increased mean arterial pressure (MAP) and glomerular filtration rate (GFR) to baseline (prehemorrhage) values. The increase in MAP induced by unmodified SFH was greater than the increase in MAP caused by an albumin solution isoncotic to the unmodified SFH solution. Similarly, the increase in MAP caused by the modified SFH was also substantially greater than that induced by an albumin solution of comparable oncotic pressure to the modified SFH solution. Both unmodified and modified SFH increased GFR. As with MAP, the increase in GFR induced by both SFH solutions was greater than that associated with the oncotically matched albumin solutions. In separate experiments, the effects of nitric oxide (NO) inhibition with N omega-nitro-L-arginine methyl ester (L-NAME) on MAP after hemorrhagic hypotension and subsequent infusion of unmodified SFH or albumin were also examined. In the albumin-infused rats, L-NAME increased MAP. In marked contrast, NO inhibition with L-NAME had no further effect on MAP when infused after SFH. We conclude that both unmodified and modified SFH solutions acutely improve MAP and GFR by the combined effects of intravascular volume expansion resulting from the colloid effect of the protein and by inactivation of NO.

Endothelin receptor A blockade alters hemodynamic response to nitric oxide inhibition in rats.

We examined the extent to which the systemic and renal vasoconstriction induced by nitric oxide (NO) inhibition in vivo is mediated by endothelin (ET). We examined the effects of BQ-610, a specific ETA-receptor antagonist, after NO inhibition with N omega-nitro-L-arginine methyl ester (L-NAME) in the anesthetized rat. Mean arterial pressure (MAP) increased after L-NAME infusion from 107 +/- 2 to 133 +/- 3 mmHg (P

Ultra-fast spin dynamics in the 2s2p^2 configuration of C^+ studied by time-dependent R-matrix theory

We employ time-dependent R-matrix theory to study ultra-fast dynamics in the doublet 2s2p(2) configuration of C+ for a total magnetic quantum number M = 1. In contrast to the dynamics observed for M = 0, ultra-fast dynamics for M = 1 is governed by spin dynamics in which the 2s electron acts as a flag rather than a spectator electron. Under the assumption that m(S) = 1/2, m(2s) = 1/2 allows spin dynamics involving the two 2p electrons, whereas m(2s) = -1/2 prevents spin dynamics of the two 2p electrons. For a pump-probe pulse scheme with (h) over bar omega(pump) = 10.9 eV and (h) over bar omega(probe) = 16.3 eV and both pulses six cycles long, little sign of spin dynamics is observed in the total ionization probability. Signs of spin dynamics can be observed, however, in the ejected-electron momentum distributions. We demonstrate that the ejected-electron momentum distributions can be used for unaligned targets to separate the contributions of initial M = 0 and M = 1 levels. This would, in principle, allow unaligned target ions to be used to obtain information on the different dynamics in the 2s2p(2) configuration for the M = 0 and M = 1 levels from a single experime

THE EXPANSION HISTORY OF ALUMINUM TARGETS RELEVANT TO X-RAY LASER SCHEMES

For the first time, the technique of point projection absorption spectroscopy - which uses an intense, point source of X-rays to project and spectrally disperse an image of a plasma onto a detector- has been shown to be applicable to the study of expanding aluminium plasmas generated by approximately 80ps (2-omega) laser pulses. Massive, stripe targets of approximately 125-mu-m width and wire targets of 25-mu-m diameter have been studied. Using a PET Bragg crystal as the dispersive element, a resolving power of approximately 3500 was achieved with spatial resolution at the 5-mu-m level in frame times of the order of 80ps. Reduction of the data for times up to 150ps after the peak of the incident laser pulse produced estimates of the temperature and densities present, as a function of space and time.

Haloalkane degradation and assimilation by Rhodococcus rhodochrous NCIMB -13064

The bacterium Rhodococcus rhodochrous NCIMB 13064, isolated from an industrial site, could use a wide range of 1-haloalkanes as sole carbon source but apparently utilized several different mechanisms simultaneously for assimilation of substrate. Catabolism of 1-chlorobutane occurred mainly by attack at the C-1 atom by a hydrolytic dehalogenase with the formation of butanol which was metabolized via butyric acid. The detection of small amounts of gamma-butyrolactone in the medium suggested that some oxygenase attack at C-4 also occurred, leading to the formation of 4-chlorobutyric acid which subsequently lactonized chemically to gamma-butyrolactone. Although 1-chlorobutane-grown cells exhibited little dehalogenase activity on 1-chloroalkanes with chain lengths above C-10, the organism utilized such compounds as growth substrates with the release of chloride. Concomitantly, gamma-butyrolactone accumulated to 1 mM in the culture medium with 1-chlorohexadecane as substrate. Traces of 4-hydroxybutyric acid were also detected. It is suggested that attack on the long-chain chloroalkane is initiated by an oxygenase at the non-halogenated end of the molecule leading to the formation of an omega-chlorofatty acid. This is degraded by beta-oxidation to 4-chlorobutyric acid which is chemically lactonized to gamma-butyrolactone which is only slowly further catabolized via 4-hydroxybutyric acid and succinic acid. However, release of chloride into the medium during growth on long-chain chloroalkanes was insufficient to account for all the halogen present in the substrate. Analysis of the fatty acid composition of 1-chlorohexadecane-grown cells indicated that chlorofatty acids comprised 75% of the total fatty acid content with C-14:0, C-16:0, C-16:1, and C-18:1 acids predominating. Thus the incorporation of 16-chlorohexadecanoic acid, the product of oxygenase attack directly into cellular lipid represents a third route of chloroalkane assimilation. This pathway accounts at least in part for the incomplete mineralization of long-chain chloroalkane substrates. This is the first report of the coexistence of a dehalogenase and the ability to incorporate long-chain haloalkanes into the lipid fraction within a single organism and raises important questions regarding the biological treatment of haloalkane containing effluents.

Long-chain haloalkanes are incorporated into fatty-acids by Rhodococcus rhodochrous NCIMB-13064

The fatty acid composition of the cellular lipids of Rhodococcus rhodochrous NCIMB 13064 grown on various long-chain haloalkanes has been investigated and the influence of halogen substituents, carbon chain length and the position of halogen substitution in the growth substrate explored. Of the total fatty acids present in cells grown on 1-chloro-, 1-bromo- and 1-iodohexadecane, 75, 90 and 81%, respectively, were substituted in the omega-position by the corresponding halogen but only 1% of the fatty acids present after growth on 1-fluorotetradecane were fluorinated in this position. The extent of the halofatty acid incorporation with different halogen substituents in the growth substrate appears to reflect the degree to which oxygenase attack is restricted to the non-halogenated end of the haloalkane. Studies of the fatty acid composition of cells after growth on a series of 1-chloroalkanes containing an even number of carbon atoms between C-10 and C-18 indicated chlorofatty acid incorporation from C-12 to C-18 substrates at levels ranging from 21% with C-12 to 75% with C-16. The chlorofatty acids formed by initial oxidation of the chloroalkane were chain-lengthened or chain-shortened by from two to eight carbon atoms, with accompanying desaturation in some instances. Substantial quantities of a methyl-branched C-19:0 chlorofatty acid were also present with several chloroalkane substrates, When the fatty acid composition of cells after growth on 1-bromoalkanes containing an odd number of carbon atoms between C-11 and C-17 was examined, the incorporation of bromofatty acids was observed with C-13, C-15 and C-17 substrates; a maximum of 76% was recorded for the C-15 bromoalkane. As with even chain-length chloroalkanes, both chain-lengthening and -shortening occurred predominantly via two-carbon units so that most bromoacids present possessed an odd number of carbon atoms, When 1-bromododecane or 2-bromododecane were substrates, overall incorporations of bromofatty acids into the lipid fraction were very similar, demonstrating that the position of halogen substitution in the haloalkane was not critical in determining the extent of incorporation of the haloacids into cellular lipids. The results of the study indicate a mechanism by which degradation products of chlorinated paraffins could enter the biological food chain.

Asymptotic layer-type model of high pressure direct current glow discharge in electronegative gases

Here a self-consistent one-dimensional continuum model is presented for a narrow gap plane-parallel dc glow discharge. The governing equations consist of continuity and momentum equations for positive and negative ions and electrons coupled with Poisson's equation. A singular perturbation method is developed for the analysis of high pressure dc glow discharge. The kinetic processes of the ionization, electron attachment, and ion-ion recombination are included in the model. Explicit results are obtained for the asymptotic limits: delta=(r(D)/L)(2)--> 0, omega=(r(S)/L)(2)--> 0, where r(D) is the Debye radius, r(S) is recombination length, and L is the gap length. The discharge gap divides naturally into four layers with multiple space scales: anode fall region, positive column, transitional region, cathode fall region and diffusion layer adjacent to the cathode surface, its formation is discussed. The effects of the gas pressure, gap spacing and dc voltage on the electrical properties of the layers and its dimension are investigated. (C) 2000 American Institute of Physics. [S0021-8979(00)00813-6].

Mixing operators on spaces with weak topology

We prove that a continuous linear operator T on a topological vector space X with weak topology is mixing if and only if the dual operator T' has no finite dimensional invariant subspaces. This result implies the characterization of hypercyclic operators on the space $\omega$ due to Herzog and Lemmert and implies the result of Bayart and Matheron, who proved that for any hypercyclic operator T on $\omega$, $T\oplus T$ is also hypercyclic.

On the required shape corrections to the local density and generalized gradient approximations to the Kohn-Sham potentials for molecular response calculations of (hyper)polarizabilities and excitation energies

It is well known that shape corrections have to be applied to the local-density (LDA) and generalized gradient (GGA) approximations to the Kohn-Sham exchange-correlation potential in order to obtain reliable response properties in time dependent density functional theory calculations. Here we demonstrate that it is an oversimplified view that these shape corrections concern primarily the asymptotic part of the potential, and that they affect only Rydberg type transitions. The performance is assessed of two shape-corrected Kohn-Sham potentials, the gradient-regulated asymptotic connection procedure applied to the Becke-Perdew potential (BP-GRAC) and the statistical averaging of (model) orbital potentials (SAOP), versus LDA and GGA potentials, in molecular response calculations of the static average polarizability alpha, the Cauchy coefficient S-4, and the static average hyperpolarizability beta. The nature of the distortions of the LDA/GGA potentials is highlighted and it is shown that they introduce many spurious excited states at too low energy which may mix with valence excited states, resulting in wrong excited state compositions. They also lead to wrong oscillator strengths and thus to a wrong spectral structure of properties like the polarizability. LDA, Becke-Lee-Yang-Parr (BLYP), and Becke-Perdew (BP) characteristically underestimate contributions to alpha and S-4 from bound Rydberg-type states and overestimate those from the continuum. Cancellation of the errors in these contributions occasionally produces fortuitously good results. The distortions of the LDA, BLYP, and BP spectra are related to the deficiencies of the LDA/GGA potentials in both the bulk and outer molecular regions. In contrast, both SAOP and BP-GRAC potentials produce high quality polarizabilities for 21 molecules and also reliable Cauchy moments and hyperpolarizabilities for the selected molecules. The analysis for the N-2 molecule shows, that both SAOP and BP-GRAC yield reliable energies omega(i) and oscillator strengths f(i) of individual excitations, so that they reproduce well the spectral structure of alpha and S-4.(C) 2002 American Institute of Physics.

RADIATIVE SIGNATURES OF RELATIVISTIC SHOCKS

Particle-in-cell simulations of relativistic, weakly magnetized collisionless shocks show that particles can gain energy by repeatedly crossing the shock front. This requires scattering off self-generated small length-scale magnetic fluctuations. The radiative signature of this first-order Fermi acceleration mechanism is important for models of both the prompt and afterglow emission in gamma-ray bursts and depends on the strength parameter a = lambda e/delta B/mc(2) of the fluctuations (lambda is the length scale and vertical bar delta B vertical bar is the magnitude of the fluctuations). For electrons (and positrons), acceleration saturates when the radiative losses produced by the scattering cannot be compensated by the energy gained on crossing the shock. We show that this sets an upper limit on both the electron Lorentz factor gamma <10(6) (n/1 cm(-3))(-1/6)(-1/6) and on the energy of the photons radiated during the scattering process h omega(max) <40Max(a, 1)(n/1 cm(-3))(1/6)(-1/6) eV, where n is the number density of the plasma and (gamma) over bar is the thermal Lorentz factor of the downstream plasma, provided a <a(crit) similar to 10(6). This rules out "jitter" radiation on self-excited fluctuations with a <I as a source of gamma rays, although high-energy photons might still be produced when the jitter photons are upscattered in an analog of the synchrotron self-Compton process. In fluctuations with a > 1, radiation is generated by the standard synchrotron mechanism, and the maximum photon energy rises linearly with a, until saturating at 70 MeV, when a = a(crit).

LINEAR ACCELERATION EMISSION IN PULSAR MAGNETOSPHERES

Linear acceleration emission occurs when a charged particle is accelerated parallel to its velocity. We evaluate the spectral and angular distribution of this radiation for several special cases, including constant acceleration (hyperbolic motion) of finite duration. Based on these results, we find the following general properties of the emission from an electron in a linear accelerator that can be characterized by an electric field E acting over a distance L: (1) the spectrum extends to a cutoff frequency (h) over bar omega(c)/mc(2) approximate to L(E/E(Schw))(2)/(lambda) over bar (C), where E(Schw) = 1.3 x 10(18) V m(-1) is the Schwinger critical field and (lambda) over bar (C) = (h) over bar /mc = 3.86 x 10(-13) m is the Compton wavelength of the electron, (2) the total energy emitted by a particle traversing the accelerator is 4/3 alpha(f)(h) over bar omega(c) in accordance with the standard Larmor formula where alpha(f) is the fine-structure constant, and (3) the low frequency spectrum is flat for hyperbolic trajectories, but in general depends on the details of the accelerator. We also show that linear acceleration emission complements curvature radiation in the strongly magnetized pair formation regions in pulsar magnetospheres. It dominates when the length L of the accelerator is less than the formation length rho/gamma of curvature photons, where rho is the radius of curvature of the magnetic field lines and gamma the Lorentz factor of the emitting particle. In standard static models of pair creating regions linear acceleration emission is negligible, but it is important in more realistic dynamical models in which the accelerating field fluctuates on a short length scale.

Piezoresponse force microscopy of ferroelectric thin films: Frequency dependence of phase imaging

The objective of this work is an evaluation of quantitative measurements of piezoresponse force microscopy for nanoscale characterization of ferroelectric films. To this end, we investigate how the piezoresponse phase difference Delta Phi between c domains depends on the frequency omega of the applied ac field much lower than the cantilever first resonance frequency. The main specimen under study was a 102 nm thick film of Pb(Zr(0.2)Ti(0.8))O(3). For the sake of comparison, a 100 nm thick PbTiO(3) film was also used. From our measurements, we conclude a frequency dependent behavior Delta Phi similar to omega(-1), which can only be partially explained by the presence of adsorbates on the surface. (C) 2008 American Institute of Physics.

Temperature dependence of the mid-infrared dielectric function of YBCO in the ab plane

We have excited mid-infrared surface plasmons in two YBCO thin films of contrasting properties using attenuated total reflection of light and found that the imaginary part of the dielectric function decreases linearly with reduction in temperature. This result is in contrast with the commonly reported conclusion of infrared normal reflectance studies. If sustained it may clarify the problem of understanding the normal state properties of YBCO and the other cuprates. The dielectric function of the films, epsilon = epsilon(1) + i epsilon(2), was determined between room temperature and 80K: epsilon(1) was found to be only slightly temperature dependent but somewhat sample dependent, probably as a result of surface and grain boundary contamination. The imaginary part, epsilon(2), (and the real part of the conductivity, sigma(1),) decreased linearly with reduction in temperature in both films. Results obtained were: for film 1: epsilon(1) = - 14.05 - 0.0024T and epsilon(2) - 4.11 + 0.086T and for film 2: epsilon(1) = - 24.09 + 0.0013T and epsilon(2) = 7.66 + 0.067T where T is the temperature in Kelvin. An understanding of the results is offered in terms of temperature-dependent intrinsic intragrain inelastic scattering and temperature-independent contributions: elastic and inelastic grain boundary scattering and optical interband (or localised charge) absorption. The relative contribution of each is estimated. A key conclusion is that the interband (or localised charge) absorption is only similar to 10%. Most importantly, the intrinsic scattering rate, 1/tau, decreases linearly with fall in temperature, T, in a regime where current theory predicts dependence on frequency, omega, to dominate. The coupling constant, lambda, between the charge carriers and the thermal excitations has a value of 1.7, some fivefold greater than the far infrared value. These results imply a need to restate the phenomenology of the normal state of high temperature superconductors and seek a corresponding theoretical understanding.

Dimensionality, Reliability and Validity of the InterRAI Depression Rating Scale in a Canadian Palliative Care Population

A reliable and valid instrument is needed to screen for depression in palliative patients. The interRAI Depression Rating Scale (DRS) is based on seven items in the interRAI Palliative Care instrument. This study is the first to explore the dimensionality, reliability and validity of the DRS in a palliative population. Palliative home care patients (n = 5,175) residing in Ontario (Canada) were assessed with the interRAI Palliative Care instrument. Exploratory factor analysis and Mokken scale analysis were used to identify candidate conceptual models and evaluate scale homogeneity/performance. Confirmatory factor analysis compared models using standard goodness-of-fit indices. Convergent and divergent validity were investigated by examining polychoric correlations between the DRS and other items. The “known groups” test determined if the DRS meaningfully distinguished among client subgroups. The non-hierarchical two factor model showed acceptable fit with the data, and ordinal alpha coefficients of 0.83 and 0.82 were observed for the two DRS subscales. Omega hierarchical (ωh) was 0.78 for the bifactor model, with the general factor explaining three quarters of the common variance. Despite the multidimensionality evident in the factor analyses, bifactor modelling and the Mokken homogeneity coefficient (0.34) suggest that the DRS is a coherent scale that captures important information on sub-constructs of depression (e.g., somatic symptoms). Higher correlations were seen between the DRS and mood and psychosocial well-being items, and lower correlations with functional status and demographic variables. The DRS distinguished in the expected manner for known risk factors (e.g., social support, pain). The results suggest that the DRS is primarily unidimensional and reliable for use in screening for depression in palliative care patients.

Low Noise Amplifier With Integrated Balanced Antenna for 60 GHz Wireless Communications

The implementation of a dipole antenna co-designed and monolithically integrated with a low noise amplifier (LNA) on low resistivity Si substrate (20 Omega . cm) manufactured in 0.35 mu m commercial SiGe HBT process with f(T)/f(max) of 170 GHz and 250 GHz is investigated theoretically and experimentally. An air gap is introduced between the chip and a reflective ground plane, leading to substantial improvements in efficiency and gain. Moreover, conjugate matching conditions between the antenna and the LNA are exploited, enhancing power transfer between without any additional matching circuit. A prototype is fabricated and tested to validate the performance. The measured 10-dB gain of the standalone LNA is centered at 58 GHz with a die size of 0.7 mm x 0.6 mm including all pads. The simulated results showed antenna directivity of 5.1 dBi with efficiency higher than 70%. After optimization, the co-designed LNA-Antenna chip with a die size of 3 mm x 2.8 mm was characterized in anechoic chamber environment. A maximum gain of higher than 12 dB was obtained.