Unconstrained Astrometric Orbits for Hipparcos Stars with Stochastic Solutions

A considerable number of astrometric binaries whose positions on the sky do not obey the standard model of mean position, parallax and linear proper motion, were observed by the Hipparcos satellite. Some of them remain non-discovered, and their observational data have not been properly processed with the more adequate astrometric model that includes nonlinear orbital motion. We develop an automated algorithm based on "genetic optimization", to solve the orbital fitting problem with no prior information about the orbital elements is available (from, e.g., spectroscopic data or radial velocity monitoring). We test this method on Hipparcos stars with known orbital solutions in the catalog, and further apply it to stars with stochastic solutions, which may be unresolved binaries. At a confidence level of 99%, orbital fits are obtained for 65 stars, most of which have not been known as binary. A few of the new probable binaries with A-type primaries with periods 444-2015 d are chemically peculiar stars, including Ap and \lambda Boo type. The anomalous spectra of these stars are explained as admixture of the light from the unresolved, sufficiently bright and massive companions. We estimate the apparent orbits of four stars which have been identified as members of the 300 Myr-old UMa kinematic group. Another four new nearby binaries may include low-mass M-type or brown dwarf companions. Similar astrometric models and algorithms can be used for binary stars and planet hosts observed by SIM PlanetQuest and Gaia

Acute Downregulation of ENaC by EGF Involves the PY Motif and Putative ERK Phosphorylation Site

The epithelial sodium channel (ENaC) is expressed in a variety of tissues, including the renal collecting duct, where it constitutes the rate-limiting step for sodium reabsorption. Liddle's syndrome is caused by gain-of-function mutations in the β and γ subunits of ENaC, resulting in enhanced Na reabsorption and hypertension. Epidermal growth factor (EGF) causes acute inhibition of Na absorption in collecting duct principal cells via an extracellular signal–regulated kinase (ERK)–dependent mechanism. In experiments with primary cultures of collecting duct cells derived from a mouse model of Liddle's disease (β-ENaC truncation), it was found that EGF inhibited short-circuit current (Isc) by 24 ± 5% in wild-type cells but only by 6 ± 3% in homozygous mutant cells. In order to elucidate the role of specific regions of the β-ENaC C terminus, Madin-Darby canine kidney (MDCK) cell lines that express β-ENaC with mutation of the PY motif (P616L), the ERK phosphorylation site (T613A), and C terminus truncation (R564stop) were created using the Phoenix retroviral system. All three mutants exhibited significant attenuation of the EGF-induced inhibition of sodium current. In MDCK cells with wild-type β-ENaC, EGF-induced inhibition of Isc (<30 min) was fully reversed by exposure to an ERK kinase inhibitor and occurred with no change in ENaC surface expression, indicative of an effect on channel open probability (Po). At later times (>30 min), EGF-induced inhibition of Isc was not reversed by an ERK kinase inhibitor and was accompanied by a decrease in ENaC surface expression. Our results are consistent with an ERK-mediated decrease in ENaC open probability and enhanced retrieval of sodium channels from the apical membrane

Identification of Regulatory Phosphorylation Sites in a Cell Volume– and Ste20 Kinase–dependent ClC Anion Channel

Changes in phosphorylation regulate the activity of various ClC anion transport proteins. However, the physiological context under which such regulation occurs and the signaling cascades that mediate phosphorylation are poorly understood. We have exploited the genetic model organism Caenorhabditis elegans to characterize ClC regulatory mechanisms and signaling networks. CLH-3b is a ClC anion channel that is expressed in the worm oocyte and excretory cell. Channel activation occurs in response to oocyte meiotic maturation and swelling via serine/threonine dephosphorylation mediated by the type I phosphatases GLC-7α and GLC-7β. A Ste20 kinase, germinal center kinase (GCK)-3, binds to the cytoplasmic C terminus of CLH-3b and inhibits channel activity in a phosphorylation-dependent manner. Analysis of hyperpolarization-induced activation kinetics suggests that phosphorylation may inhibit the ClC fast gating mechanism. GCK-3 is an ortholog of mammalian SPAK and OSR1, kinases that bind to, phosphorylate, and regulate the cell volume–dependent activity of mammalian cation-Cl− cotransporters. Using mass spectrometry and patch clamp electrophysiology, we demonstrate here that CLH-3b is a target of regulatory phosphorylation. Concomitant phosphorylation of S742 and S747, which are located 70 and 75 amino acids downstream from the GCK-3 binding site, are required for kinase-mediated channel inhibition. In contrast, swelling-induced channel activation occurs with dephosphorylation of S747 alone. Replacement of both S742 and S747 with glutamate gives rise to kinase- and swelling-insensitive channels that exhibit activity and biophysical properties similar to those of wild-type CLH-3b inhibited by GCK-3. Our studies provide novel insights into ClC regulation and mechanisms of cell volume signaling, and provide the foundation for studies aimed at defining how conformational changes in the cytoplasmic C terminus alter ClC gating and function in response to intracellular signaling events

EPR and optical spectroscopy of the Yb3+ cubic center in ß-PbF2

Optical spectroscopy and EPR are employed to study a ß-PbF2 crystal doped with Yb3+ ions. The presence of only one paramagnetic center, the Yb3+ ion with cubic symmetry, is established. Its optical lines are identified, the empirical system of energy levels is constructed, and the phenomenological crystal field potential is determined. The information on the phonon spectrum of the ß-PbF2 crystal is obtained from the electron-vibrational structure of the optical absorption and luminescence spectra. © 2001 MAIK "Nauka/Interperiodica"

EPR and optical spectroscopy of Yb3+ ions in CaF2: An analysis of the structure of tetragonal centers

CaF2 crystals doped with Yb3+ ions have been studied by electron paramagnetic resonance (EPR) and optical spectroscopy. EPR spectra of paramagnetic centers (PCs) for cubic (Tc) and tetragonal (T tet) symmetries were identified. Empirical energy level diagrams were established and crystal field parameters were determined. Information on the CaF2:Yb3+ phonon spectra was obtained from the electron-vibrational structure of the optical spectra. The crystal field parameters were used to analyze the crystal lattice distortions in the vicinity of the Yb3+ ion. Within the framework of a superposition model, it is established that four F- ions located symmetrically with respect to the fourfold axis from the side of the ion-compensator approach the impurity ion and deviate from the PC axis. The second set of four fluorine ions also approaches the Yb3+ ion and the PC axis. The ion-compensator F - also approaches considerably the impurity ion

Optical spectroscopy of Yb3+ in the Cs2NaYF6 single crystal

Results of the optical spectroscopy investigation of the cubic paramagnetic center Yb3+ ion in the Cs2NaYF6 single crystal are presented. The Stark level energies of the Yb3+ multiplets are established from absorption, luminescence and excitation luminescence spectra and the crystal field parameters are calculated. Information about the phonon spectra of Cs2NaYF6 crystals is obtained from the electron-vibrational structure of the optical absorption and luminescence spectra. © 2007

眼科この1年

A trigonal Yb3+ paramagnetic center in the CsCaF3 single crystal was studied by magnetic resonance and optical spectroscopy methods. The structural model of the complex and the empirical energy level scheme were established. The transferred hyperfine interaction parameters and the crystal field ones were determined. The crystal field parameters were used to analyze the lattice distortions in the vicinity of Yb3+ using the superposition model. © 2010 Springer-Verlag

Electron paramagnetic resonance and optical spectroscopy of Yb3+ ions in SrF2 and BaF2; an analysis of distortions of the crystal lattice near Yb3+

SrF2 and BaF2 crystals, doped with the Yb3+ ions, have been investigated by electron paramagnetic resonance and optical spectroscopy. As-grown crystals of SrF2 and BaF2 show the two paramagnetic centres for the cubic (Tc) and trigonal (T4) symmetries of the Yb3+ ions. Empirical diagrams of the energy levels were established and the potentials of the crystal field were determined. Information was obtained on the SrF2 and BaF2 phonon spectra from the electron-vibrational structure of the optical spectra. The crystal field parameters were used to analyse the crystal lattice distortions in the vicinity of the impurity ion and the F- ion compensating for the excess positive charge in T4. Within the frames of a superposition model, it is shown that three F- ions from the nearest surrounding cube, located symmetrically with respect to the C3 axis from the side of the ion-compensator, approach the impurity ion and cling to the axis of the centre when forming T4. The F- ion located on the axis of the centre between the Yb3+ ion and ion-compensator, also approaches close to the impurity ion

Magnetic Resonance and Optical Spectroscopy of Yb3+ in CsCaF3 Single Crystal: An Analysis of Distortions of the Crystal Lattice near Yb3+

A trigonal Yb3+ paramagnetic center in the CsCaF3 single crystal was studied by magnetic resonance and optical spectroscopy methods. The structural model of the complex and the empirical energy level scheme were established. The transferred hyperfine interaction parameters and the crystal field ones were determined. The crystal field parameters were used to analyze the lattice distortions in the vicinity of Yb3+ using the superposition model. © 2010 Springer-Verlag