Mechanisms for the effect of electric and magnetic fields on biological systems Semiannual status report, Jan. 1969 - Jun. 1969

Electric field effects on dielectric properties and molecular arrangements of cholesteric liquid crystal

Mechanisms for the effect of electric and magnetic fields on biological systems Semiannual status report, Jun. - Dec. 1969

Electric and magnetic field effects on structure and properties of cholesteric liquid crystal

Vasopressin lowers renal epoxyeicosatrienoic acid levels by activating soluble epoxide hydrolase

Activation of the thick ascending limb (TAL) Na+-K+-2Cl--cotransporter (NKCC2) by the antidiuretic hormone arginine-vasopressin (AVP) is an essential mechanism of renal urine concentration and contributes to extracellular fluid and electrolyte homeostasis. AVP effects in the kidney are modulated by locally and/or by systemically produced epoxyeicosatrienoic acid derivates (EET). The relation between AVP and EET metabolism has not been determined. Here we show that chronic treatment of AVP-deficient Brattleboro rats with the AVP V2 receptor analog desmopressin (dDAVP; 5ng/h, 3d) significantly lowered renal EET levels (-56 +/- 3% for 5,6-EET, -50 +/- 3.4% for 11,12-EET, and -60 +/- 3.7% for 14,15-EET). The abundance of the principal EET-degrading enzyme soluble epoxide hydrolase (sEH) was increased at the mRNA (+160 +/- 37%) and protein levels (+120 +/- 26%). Immunohistochemistry revealed dDAVP-mediated induction of sEH in connecting tubules and cortical and medullary collecting ducts, suggesting a role of these segments in the regulation of local interstitial EET signals. Incubation of murine kidney cell suspensions with 1 {mu}M 14,15-EET for 30 min reduced phosphorylation of NKCC2 at the AVP-sensitive threonine residues T96 and T101 (-66 +/-5%; p<0.05) while 14,15-DHET had no effect. Concomitantly, isolated perfused cTAL pretreated with 14,15-EET showed a 30% lower transport current under high and a 70% lower transport current under low symetric chloride concentrations. In sum, we have shown that activation of AVP signaling stimulates renal sEH biosynthesis and enzyme activity. The resulting reduction of EET tissue levels may be instrumental for increased NKCC2 transport activity during AVP-induced antidiuresis

Assessing goodness-of-fit for evaluation of dose-proportionality

For the clinical development of a new drug, the determination of dose-proportionality is an essential part of the pharmacokinetic evaluations, which may provide early indications of non-linear pharmacokinetics and may help to identify sub-populations with divergent clearances. Prior to making any conclusions regarding dose-proportionality, the goodness-of-fit of the model must be assessed to evaluate the model performance. We propose the use of simulation-based visual predictive checks to improve the validity of dose-proportionality conclusions for complex designs. We provide an illustrative example and include a table to facilitate review by regulatory authorities

13C NMR and static magnetic susceptibility in C60 superconductors : Possible influence of Kondo impurity

The static spin susceptibility, χsSQ and χsNMR, in C60 superconductors K3C60 and Rb3C60 was studied using a dc superconducting quantum interference device magnetometer and 13C NMR. We found that χsSQ has a peculiar temperature (T) dependence behaving as (1-CT2) with a positive constant C∼(1×10-6) deg-2, contrary to the almost T independent χsNMR. These observations indicate a possibility that there exist Kondo-like impurities, whose Kondo temperature is ∼500 K and whose content is ∼0.001 spins per carbon. On the basis of these studies, the lattice constant dependence of the intrinsic spin susceptibility was established to be dχs/da0=(5.7±0.4)×10-4 emu/mol C60/Å in A3C60 superconductors where A is an alkali metal

Measurement of event shapes in deep inelastic scattering at HERA

Inclusive event-shape variables have been measured in the current region of the Breit frame for neutral current deep inelastic ep scattering using an integrated luminosity of 45.0 pb^-1 collected with the ZEUS detector at HERA. The variables studied included thrust, jet broadening and invariant jet mass. The kinematic range covered was 10 < Q^2 < 20,480 GeV^2 and 6.10^-4 < x < 0.6, where Q^2 is the virtuality of the exchanged boson and x is the Bjorken variable. The Q dependence of the shape variables has been used in conjunction with NLO perturbative calculations and the Dokshitzer-Webber non-perturbative corrections (`power corrections') to investigate the validity of this approach.Comment: 7+25 pages, 6 figure

Search for lepton-flavor violation at HERA

A search for lepton-flavor-violating interactions $e p \to \mu X$ and $e p\to \tau X$ has been performed with the ZEUS detector using the entire HERA I data sample, corresponding to an integrated luminosity of 130 pb^{-1}. The data were taken at center-of-mass energies, $\sqrt{s}$, of 300 and 318 GeV. No evidence of lepton-flavor violation was found, and constraints were derived on leptoquarks (LQs) that could mediate such interactions. For LQ masses below $\sqrt{s}$, limits were set on $\lambda_{eq_1} \sqrt{\beta_{\ell q}}$, where $\lambda_{eq_1}$ is the coupling of the LQ to an electron and a first-generation quark $q_1$, and $\beta_{\ell q}$ is the branching ratio of the LQ to the final-state lepton $\ell$ ($\mu$ or $\tau$) and a quark $q$. For LQ masses much larger than $\sqrt{s}$, limits were set on the four-fermion interaction term $\lambda_{e q_\alpha} \lambda_{\ell q_\beta} / M_{\mathrm{LQ}}^2$ for LQs that couple to an electron and a quark $q_\alpha$ and to a lepton $\ell$ and a quark $q_\beta$, where $\alpha$ and $\beta$ are quark generation indices. Some of the limits are also applicable to lepton-flavor-violating processes mediated by squarks in $R$-Parity-violating supersymmetric models. In some cases, especially when a higher-generation quark is involved and for the process $e p\to \tau X$, the ZEUS limits are the most stringent to date.Comment: 37 pages, 10 figures, Accepted by EPJC. References and 1 figure (Fig. 6) adde

Dissociation of virtual photons in events with a leading proton at HERA

The ZEUS detector has been used to study dissociation of virtual photons in events with a leading proton, gamma^* p -> X p, in e^+p collisions at HERA. The data cover photon virtualities in two ranges, 0.03<Q^2<0.60 GeV^2 and 2<Q^2<100 GeV^2, with M_X>1.5 GeV, where M_X is the mass of the hadronic final state, X. Events were required to have a leading proton, detected in the ZEUS leading proton spectrometer, carrying at least 90% of the incoming proton energy. The cross section is presented as a function of t, the squared four-momentum transfer at the proton vertex, Phi, the azimuthal angle between the positron scattering plane and the proton scattering plane, and Q^2. The data are presented in terms of the diffractive structure function, F_2^D(3). A next-to-leading-order QCD fit to the higher-Q^2 data set and to previously published diffractive charm production data is presented

Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha_s

Multijet production rates in neutral current deep inelastic scattering have been measured in the range of exchanged boson virtualities 10 < Q2 < 5000 GeV2. The data were taken at the ep collider HERA with centre-of-mass energy sqrt(s) = 318 GeV using the ZEUS detector and correspond to an integrated luminosity of 82.2 pb-1. Jets were identified in the Breit frame using the k_T cluster algorithm in the longitudinally invariant inclusive mode. Measurements of differential dijet and trijet cross sections are presented as functions of jet transverse energy E_{T,B}{jet}, pseudorapidity eta_{LAB}{jet} and Q2 with E_{T,B}{jet} > 5 GeV and -1 < eta_{LAB}{jet} < 2.5. Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant alpha_s(M_Z), determined from the ratio of the trijet to dijet cross sections, is alpha_s(M_Z) = 0.1179 pm 0.0013(stat.) {+0.0028}_{-0.0046}(exp.) {+0.0064}_{-0.0046}(th.)Comment: 22 pages, 5 figure

The dependence of dijet production on photon virtuality in ep collisions at HERA

The dependence of dijet production on the virtuality of the exchanged photon, Q^2, has been studied by measuring dijet cross sections in the range 0 < Q^2 < 2000 GeV^2 with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb^-1. Dijet cross sections were measured for jets with transverse energy E_T^jet > 7.5 and 6.5 GeV and pseudorapidities in the photon-proton centre-of-mass frame in the range -3 < eta^jet <0. The variable xg^obs, a measure of the photon momentum entering the hard process, was used to enhance the sensitivity of the measurement to the photon structure. The Q^2 dependence of the ratio of low- to high-xg^obs events was measured. Next-to-leading-order QCD predictions were found to generally underestimate the low-xg^obs contribution relative to that at high xg^obs. Monte Carlo models based on leading-logarithmic parton-showers, using a partonic structure for the photon which falls smoothly with increasing Q^2, provide a qualitative description of the data.Comment: 35 pages, 6 eps figures, submitted to Eur.Phys.J.