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2007-11-19 | The MINERvA Neutrino Interaction Experiment | The MINERvA neutrino interaction experiment in the NuMI beam at Fermilab will
measure several aspects of neutrino interactions in the few GeV energy region.
We will make cross section and form factor measurements using a fine-grained
fully active scintillator (CH) target, and also investigate nuclear effects on
neutrin... | 0711.3029v1 |
2007-11-20 | Beyond 1D: spectral line formation with 3D hydrodynamical model atmospheres of red giants | We present the results of realistic, 3D, hydrodynamical, simulations of
surface convection in red giant stars with varying effective temperatures and
metallicities. We use the convection simulations as time-dependent,
hydrodynamical, model atmospheres to compute spectral line profiles for a
number of ions and molecules... | 0711.3186v1 |
2007-11-22 | Stroemgren metallicity calibration: the m1, b-y relation | We performed a new calibration of the Stroemgren metallicity index m1 based
on the b-y color of cluster red giant stars. The current
Metallicity-Index-Color relation is not linear in the color range 0.40 < b-y <
1.0, but provides iron abundances of cluster and field red giants with an
accuracy of ~ 0.25 dex. | 0711.3534v1 |
2007-11-29 | Magnetoelectric Effects on Composite Nano Granular $Fe/TiO_{2-δ}$ Films | Employing a new experimental technique to measure magnetoelectric response
functions, we have measured the magnetoelectric effect in composite films of
nano granular metallic iron in anatase titanium dioxide at temperatures below
50 K. A magnetoelectric resistance is defined as the ratio of a transverse
voltage to bias... | 0711.4776v1 |
2007-12-03 | Temporal evolution of magnetic elements | We study the structure and evolution of the magnetic field of the quiet Sun
by investigating weak spectro-polarimetric signals. To this end, we observed a
quiet region close to the disk center with the German VTT in Tenerife, July 07,
2006. We recorded 38 scans of the same area. Each scan was eight arcsec wide
and obse... | 0712.0234v1 |
2007-12-05 | $θ_{13}$, $δ$ and the neutrino mass hierarchy at a $γ=350$ double baseline Li/B $β$-Beam | We consider a $\beta$-Beam facility where $^8$Li and $^8$B ions are
accelerated at $\gamma = 350$, accumulated in a 10 Km storage ring and let
decay, so as to produce intense $\bar \nu_e$ and $\nu_e$ beams. These beams
illuminate two iron detectors located at $L \simeq 2000$ Km and $L \simeq 7000$
Km, respectively. The... | 0712.0796v3 |
2007-12-06 | Editorial: Statistics and forensic science | Forensic science is usually taken to mean the application of a broad spectrum
of scientific tools to answer questions of interest to the legal system.
Despite such popular television series as CSI: Crime Scene Investigation and
its spinoffs--CSI: Miami and CSI: New York--on which the forensic scientists
use the latest ... | 0712.0974v1 |
2007-12-16 | Evidence of magnetic field wrapping around penumbral filaments | We employ high-spatial resolution spectropolarimetric observations from the
Solar Optical Telescope on-board the Hinode spacecraft to investigate the fine
structure of the penumbral magnetic fields. The Stokes vector of two neutral
iron lines at 630 nm is inverted at every spatial pixel to retrieve the
depth-dependence... | 0712.2548v1 |
2007-12-18 | Defect-induced ferromagnetism in fullerenes | Based on the ab initio electronic structure calculations the picture of
ferromagnetism in polimerized C60 is proposed which seems to explain the whole
set of controversial experimental data. We have demonstrated that, in contrast
with cubic fullerene, in rhombohedral C60 the segregation of iron atoms is
energetically u... | 0712.2928v2 |
2007-12-18 | Metallicity estimates of Galactic Cepheids based on Walraven photometry | We present new empirical and theoretical calibrations of two photometric
metallicity indices based on Walraven photometry. The empirical calibration
relies on a sample of 48 Cepheids for which iron abundances based on high
resolution spectra are available in the literature. They cover a broad range in
metal abundance (... | 0712.3006v1 |
2007-12-20 | Determining element abundances of [WC]-type Central Stars for probing stellar evolution and nucleosynthesis | [WC]-type CSPNs are hydrogen-deficient Central Stars of Planetary Nebulae
showing strong stellar winds and a carbon-rich chemistry. We have analyzed new
high-resolution spectra of [WC]-type CSPNs with the Potsdam Wolf-Rayet (PoWR)
non-LTE expanding atmosphere models, using upgraded model atoms and atomic
data. Previous... | 0712.3453v1 |
2007-12-21 | Criteria for mixing rules application for inhomogeneous astrophysical grains | The analysis presented in this paper verifies which of the mixing rules are
best for real components of interstellar dust in possible wide range of
wavelengths.The DDA method with elements of different components with various
volume fractions has been used. We have considered 6 materials: ice, amorphous
carbon, graphit... | 0712.3796v3 |
2008-01-01 | A Self-Consistent NLTE-Spectra Synthesis Model of FeLoBAL QSOs | We present detailed radiative transfer spectral synthesis models for the Iron
Low Ionization Broad Absorption Line (FeLoBAL) active galactic nuclei (AGN)
FIRST J121442.3+280329 and ISO J005645.1-273816. Detailed NLTE spectral
synthesis with a spherically symmetric outflow reproduces the observed spectra
very well acros... | 0801.0321v2 |
2008-01-03 | Spin orbit precession damping in transition metal ferromagnets | We provide a simple explanation, based on an effective field, for the
precession damping rate due to the spin-orbit interaction. Previous effective
field treatments of spin-orbit damping include only variations of the state
energies with respect to the magnetization direction, an effect referred to as
the breathing Fer... | 0801.0549v1 |
2008-01-04 | Could the Ultra Metal-poor Stars be Chemically Peculiar and Not Related to the First Stars? | Chemically peculiar stars define a class of stars that show unusual elemental
abundances due to stellar photospheric effects and not due to natal variations.
In this paper, we compare the elemental abundance patterns of the ultra
metal-poor stars with metallicities [Fe/H] $\sim -5 $ to those of a subclass of
chemically... | 0801.0752v1 |
2008-01-14 | The Effects of Mass Loss on the Evolution of Chemical Abundances in Fm Stars | Self-consistent stellar models including all effects of atomic diffusion and
radiative accelerations as well as mass loss are evolved from the pre main
sequence for stars of 1.35-1.5, M$_{\odot}$ at solar metallicity (Z=0.02). A
mass loss rate similar to the solar mass loss rate is sufficient to reproduce
observations ... | 0801.2122v1 |
2008-01-16 | Observing the strong gravity regime of accreting black holes with Simbol-X | The X-ray reflection features of irradiated accretion disks around black
holes enable us to probe the effects of strong gravity. We investigate to which
precision the reflection signs, i.e. the iron K-line and the Comptonized hump,
can be observed with Simbol-X for nearby Seyfert galaxies. The simulations
presented inc... | 0801.2450v2 |
2008-01-17 | Abundances of Planetary Nebula NGC2392 | The spectra of the planetary nebula NGC2392 is reanalysed using spectral
measurements made in the mid-infrared with the Spitzer Space Telescope. The aim
is to determine the chemical composition of this object. We also make use of
IUE and ground based spectra. Abundances determined from the mid-infrared
lines, which are... | 0801.2767v1 |
2008-01-18 | Spectra of W$^{39+}$-W$^{47+}$ in the 12 nm to 20 nm region observed with an EBIT light source | We observed spectra of highly ionized tungsten in the extreme ultraviolet
with an electron beam ion trap (EBIT) and a grazing incidence spectrometer at
the National Institute of Standards and Technology. Stages of ionization were
distinguished by varying the energy of the electron beam between 2.1 keV and
4.3 keV and c... | 0801.2817v1 |
2008-01-24 | Accretion discs, coronae and jets in black hole binaries: prospects for Simbol-X | The phenomenology of accretion disc, coronnae and jets in X-ray binaries is
rather well established. However the structure of the accretion flow in the
various spectral states is still debated and the connection between the hot
flow and compact jet is far from being understood. Simbol-X should address
these two importa... | 0801.3767v1 |
2008-01-30 | X-ray Emissions from Three-dimensional Magnetohydrodynamic Coronal Accretion Flows | We calculate the radiation spectrum and its time variability of the black
hole accretion disk-corona system based on the three-dimensional
magnetohydrodynamic simulation. In explaining the spectral properties of active
galactic nuclei (AGNs), it is often assumed that they consist of a
geometrically thin, optically thic... | 0801.4613v1 |
2008-01-30 | Cosmic Ray Velocity and Electric Charge Measurements in the AMS experiment | The Alpha Magnetic Spectrometer (AMS) is a particle physics detector designed
to measure charged cosmic ray spectra with energies up to the TeV region and
with high energy photon detection capability up to few hundred GeV. It will be
installed on the International Space Station (ISS) in 2008 and will operate for
more t... | 0801.4656v1 |
2008-02-06 | Chandra unveils a binary Active Galactic Nucleus in Mrk463 | We analyse Chandra, XMM-Newton and HST data of the double-nucleus
Ultraluminous Infrared Galaxy (ULIRG), Mrk463. The Chandra detection of two
luminous ($\mathrm{L}_\mathrm{2-10 keV}=1.5\times10^{43}$ and
$3.8\times10^{42}$ erg cm$^{-2}$ s$^{-1}$), unresolved nuclei in Mrk~463
indicates that this galaxy hosts a binary A... | 0802.0825v1 |
2008-02-12 | Detection of supernovae neutrinos with neutrino-iron scattering | The $\nu_e-^{56}$Fe cross section is evaluated in the projected quasiparticle
random phase approximation (PQRPA). This model solves the puzzle observed in
RPA for nuclei with mass around $^{12}$C, because it is the only RPA model that
treats the Pauli principle correctly. The cross sections as a function of the
inciden... | 0802.1553v2 |
2008-02-12 | Giant orbital moments are responsible for the anisotropic magnetoresistance of atomic contacts | We study here, both experimentally and theoretically, the anisotropy of
magnetoresistance in atomic contacts. Our measurements on iron break junctions
reveal an abrupt and hysteretic switch between two conductance levels when a
large applied field is continuously rotated. We show that this behaviour stems
from the coex... | 0802.1595v1 |
2008-02-12 | Electronic transport in iron atomic contacts: from the infinite wire to realistic geometries | We present a theoretical study of spin polarized transport in Fe atomic
contacts using a self-consistent tight-binding Hamiltonian in a non-orthogonal
$s$, $p$ and $d$ basis set, the spin-polarization being obtained from a
non-collinear Stoner-like model and the transmission probability from the
Fisher-Lee formula. The... | 0802.1598v1 |
2008-02-28 | On the Cepheid Metallicity Dichotomy | With the aid of stellar atmosphere models, we derive iron abundances [Fe/H]
from the OGLE B, V, I photometry on the Magellanic Cloud Cepheids. We show that
in both clouds the average metallicities of the first overtone variables are
lower than those of the fundamental ones (by ~0.2 and ~0.3 dex in the LMC and
SMC, resp... | 0802.4166v1 |
2008-03-04 | Magneto-Dielectric phenomena in charge and spin frustrated system of layered iron oxide | Dielectric and magnetic phenomena in spin and charge frustrated system RFe2O4
(R is a rare-earth metal ion) are studied. An electronic model for charge, spin
and orbital degrees in a pair of triangular-lattice planes is derived. We
analyze this model by utilizing the mean-field approximation and the
Monte-Carlo simulat... | 0803.0394v1 |
2008-03-04 | Light Vector Mesons in the Nuclear Medium | The light vector mesons ($\rho$, $\omega$, and $\phi$) were produced in
deuterium, carbon, titanium, and iron targets in a search for possible
in-medium modifications to the properties of the $\rho$ meson at normal nuclear
densities and zero temperature. The vector mesons were detected with the CEBAF
Large Acceptance S... | 0803.0492v1 |
2008-03-05 | Hall effect and magnetoresistance in the normal state of the superconductor LaO$_{0.9}$F$_{0.1-x}$FeAs | By using a two-step method, we successfully synthesized the iron based new
superconductor LaO$_{0.9}$F$_{0.1-x}$FeAs. The Hall effect and
magnetoresistance were measured in wide temperature region. A negative Hall
coefficient R_H has been found implying a dominant conduction by electron-like
charge carriers in this mat... | 0803.0623v3 |
2008-03-06 | Properties of the ultraviolet flux of type Ia supernovae: an analysis with synthetic spectra of SN 2001ep and SN 2001eh | The spectral properties of type Ia supernovae in the ultraviolet (UV) are
investigated using the early-time spectra of SN 2001ep and SN 2001eh obtained
using the Hubble Space Telescope (HST). A series of spectral models is computed
with a Monte Carlo spectral synthesis code, and the dependence of the UV flux
on the ele... | 0803.0871v2 |
2008-03-06 | Tight-Binding Theory of Manganese and Iron Oxides | The electronic structure is found to be understandable in terms of free-atom
term values and universal interorbital coupling parameters, since
self-consistent tight-binding calculations indicate that Coulomb shifts of the
d-state energies are small. Special-point averages over the bands are seen to
be equivalent to tre... | 0803.0994v1 |
2008-03-17 | Point-Contact Spectroscopy of Iron-Based Layered Superconductor LaO$_{0.9}$F$_{0.1-δ}$FeAs | We present point-contact spectroscopy data for junctions between a normal
metal and the newly discovered F-doped superconductor
LaO$_{0.9}$F$_{0.1-\delta}$FeAs (F-LaOFeAs). A zero-bias conductance peak was
observed and its shape and magnitude suggests the presence of Andreev bound
states at the surface of F-LaOFeAs, wh... | 0803.2405v3 |
2008-03-20 | Bimodality in low luminosity E and S0 galaxies | Stellar population characteristics are presented for a sample of low
luminosity early-type galaxies (LLEs) in order to compare them with their more
luminous counterparts. Long-slit spectra of a sample of 10 LLEs were taken with
the ESO New Technology Telescope, selected for their low luminosities. Line
strengths were m... | 0803.3025v1 |
2008-03-22 | Iron-based layered superconductor LaO$_{1-x}$F$_x$FeAs: an antiferromagnetic semimetal | We have studied the newly found superconductor compound LaO$_{1-x}$F$_x$FeAs
through the first-principles density functional theory calculations. We find
that the parent compound LaOFeAs is a quasi-2-dimensional antiferromgnetic
semimetal with most carriers being electrons and with a magnetic moment of
$2.3\mu_B$ locat... | 0803.3286v1 |
2008-03-23 | Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO$_{1-x}$F$_x$} | For a newly discovered iron-based high $T_c$ superconductor
LaFeAsO$_{1-x}$F$_x$, we have constructed a minimal model, where inclusion of
all the five Fe $d$ bands is found to be necessary. Random-phase approximation
is applied to the model to investigate the origin of superconductivity. We
conclude that the multiple s... | 0803.3325v2 |
2008-03-24 | Fast Variability of Nonthermal X-Ray Emission in Cassiopeia A: Probing Electron Acceleration in Reverse-Shocked Ejecta | Recent discovery of the year-scale variability in the synchrotron X-ray
emission of the supernova remnant (SNR) RX J1713.7-3946 has initiated our study
of multi-epoch X-ray images and spectra of the young SNR Cassiopeia A based on
the Chandra archive data taken in 2000, 2002, and 2004. We have found
year-scale time var... | 0803.3410v1 |
2008-03-24 | Atomic Processes in Planetary Nebulae and H II Regions | Spectroscopic studies of Planetary Nebulae (PNe) and H {\sc ii} regions have
driven much development in atomic physics. In the last few years the
combination of a generation of powerful observatories, the development of ever
more sophisticated spectral modeling codes, and large efforts on mass
production of high qualit... | 0803.3457v1 |
2008-03-25 | The effect of rotation on the abundances of the chemical elements of the A-type stars in the Praesepe cluster | We study how chemical abundances of late B-, A- and early F-type stars evolve
with time, and we search for correlations between the abundance of chemical
elements and other stellar parameters, such as effective temperature and Vsini.
We have observed a large number of B-, A- and F-type stars belonging to open
clusters ... | 0803.3540v1 |
2008-03-26 | Realistic calculations of nuclear disappearance lifetimes induced by neutron-antineutron oscillations | Realistic calculations of nuclear disappearance lifetimes induced by
neutron-antineutron oscillations are reported for oxygen and iron, using
antineutron nuclear potentials derived from a recent comprehensive analysis of
antiproton atomic X-ray and radiochemical data. A lower limit of 3.3 x 10E8 s
on the neutron-antine... | 0803.3696v3 |
2008-03-29 | Superconductivity at 52 K in iron-based F-doped layered quaternary compound Pr[O1-xFx]FeAs | Since the discovery of copper oxide superconductor in 1986 [1], extensive
efforts have been devoted to the search of new high-Tc superconducting
materials, especially high-Tc systems other than cuprates. The recently
discovered quaternary superconductor La[O1-xFx]FeAs with the superconducting
critical transition Tc of ... | 0803.4283v1 |
2008-04-01 | Structural identification of cubic iron-oxide nanocrystal mixtures: X-ray powder diffraction versus quasi-kinematic transmission electron microscopy | Two novel (and proprietary) strategies for the structural identification of a
nanocrystal from either a single high-resolution (HR) transmission electron
microscopy (TEM) image or a single precession electron diffraction pattern are
proposed and their advantages discussed in comparison to structural
fingerprinting from... | 0804.0063v1 |
2008-04-06 | Mott State and Quantum Critical Points in Rare-Earth Oxypnictides $RO_{1-x}F_xFeAs$ ($R=La, Sm, Nd, Pr, Ce$) | We investigate the magnetic phase diagram of the newly discovered iron-based
high temperature oxypnictide superconductors of the type RO$_{1-x}$F$_x $FeAs,
with rare earths R=La, Sm, Nd, Pr and Ce by means of {\it ab initio} SGGA and
SGGA+U density functional computations. We find undoped LaOFeAs to be a Mott
insulator... | 0804.0866v3 |
2008-04-07 | The Wall and The Ball: A Study of Domain Referent Spreadsheet Errors | The Cell Error Rate in simple spreadsheets averages about 2% to 5%. This CER
has been measured in domain free environments. This paper compares the CERs
occurring in domain free and applied domain tasks. The applied domain task
requires the application of simple linear algebra to a costing problem. The
results show tha... | 0804.0943v1 |
2008-04-10 | Theory of magnetic excitations in iron-based layered superconductors | Based on the effective four-band model we analyze the spin response in the
normal and superconducting states of the Fe-pnictide superconductors. While the
normal state spin excitations are dominated by the continuum of the
interorbital antiferromagnetic fluctuations and the intraband spin density wave
fluctuations, the... | 0804.1793v2 |
2008-04-16 | Superconductivity and Phase Diagram in the Iron-based Arsenic-oxides ReFeAsO1-delta (Re = rare earth metal) without F-Doping | Here we report a new class of superconductors prepared by high pressure
synthesis in the quaternary family ReFeAsO1-delta (Re = Sm, Nd, Pr, Ce, La)
without fluorine doping. The onset superconducting critical temperature (Tc) in
these compounds increases with the reduction of Re atom size, and the highest
Tc obtained so... | 0804.2582v3 |
2008-04-21 | Probing protoneutron star density profile from neutrino signals | Supernovae of Type II is a phenomenon that occurs at the end of evolution of
massive stars when the iron core of the star exceeds a mass limit. After
collapse of the core under gravity the shock wave alone does not succeed in
expelling the mass of the star and in this sense the role of neutrinos is the
most important m... | 0804.3247v1 |
2008-04-23 | Superconductivity at 53.5 K in GdFeAsO1-delta | Here we report the fabrication and superconductivity of the iron-based
arsenic-oxide GdFeAsO1-delta compound with oxygen-deficiency, which has an
onset resistivity transition temperature at 53.5 K. This material has a same
crystal structure as the newly discovered high-Tc ReFeAsO1-delta family (Re =
rare earth metal) a... | 0804.3727v3 |
2008-04-28 | Thorium-doping induced superconductivity up to 56 K in Gd1-xThxFeAsO | Following the discovery of superconductivity in an iron-based arsenide
LaO1-xFxFeAs with a superconducting transition temperature (Tc) of 26 K[1], Tc
was pushed up surprisingly to above 40 K by either applying pressure[2] or
replacing La with Sm[3], Ce[4], Nd[5] and Pr[6]. The maximum Tc has climbed to
55 K, observed i... | 0804.4290v2 |
2008-05-02 | Commensurate Spin Density Wave in LaOFeAs: A Local Probe Study | We present a detailed study on the magnetic order in the undoped mother
compound LaOFeAs of the recently discovered Fe-based superconductor
LaO$_{1-x}$F$_x$FeAs. In particular, we present local probe measurements of the
magnetic properties of LaOFeAs by means of $^{57}$Fe M\"ossbauer spectroscopy
and muon spin relaxati... | 0805.0264v2 |
2008-05-06 | Flux-lattice melting in LaO$_{1-x}$F$_{x}$FeAs: first-principles prediction | We report the theoretical study of the flux-lattice melting in the novel
iron-based superconductor $LaO_{0.9}F_{0.1}FeAs$ and
$LaO_{0.925}F_{0.075}FeAs$. Using the Hypernetted-Chain closure and an
efficient algorithm, we calculate the two-dimensional one-component plasma pair
distribution functions, static structure fa... | 0805.0632v2 |
2008-05-06 | Pulsation-Initiated Mass Loss in Luminous Blue Variables: A Parameter Study | Luminous blue variables (LBVs) are characterized by semi-periodic episodes of
enhanced mass-loss, or outburst. The cause of these outbursts has thus far been
a mystery. One explanation is that they are initiated by kappa-effect
pulsations in the atmosphere caused by an increase in luminosity at
temperatures near the so... | 0805.0764v1 |
2008-05-07 | Processing and Characterization of Precision Microparts from Nickel-based Materials | The objective of this research was to study the influence of electroplating
parameters on electrodeposit characteristics for the production of nickel (Ni)
and nickel-iron (Ni-Fe) microparts by photoelectroforming. The research focused
on the most relevant parameter for industry, which is the current density,
because it... | 0805.0866v1 |
2008-05-09 | Evidence for electromagnetic granularity in the polycrystalline iron-based superconductor LaO0.89F0.11FeAs | The new rare-earth arsenate superconductors are layered, low carrier density
compounds with many similarities to the high-Tc cuprates. An important question
is whether they also exhibit weak-coupling across randomly oriented
grain-boundaries. In this work we show considerable evidence for such
weak-coupling by study of... | 0805.1282v1 |
2008-05-12 | MOST detects SPBe pulsations in HD 127756 & HD 217543: Asteroseismic rotation rates independent of vsini | The MOST (Microvariability and Oscillations of Stars) satellite has
discovered SPBe (Slowly Pulsating Be) oscillations in the stars HD 127756
(B1/B2 Vne) and HD 217543 (B3 Vpe). For HD 127756, 30 significant frequencies
are identified from 31 days of nearly continuous photometry; for HD 217543, up
to 40 significant fre... | 0805.1720v1 |
2008-05-14 | Intrinsic Properties of Stoichiometric LaOFeP | DC and ac magnetization, resistivity, specific heat, and neutron diffraction
data reveal that stoichiometric LaOFeP is metallic and non-superconducting
above T = 0.35 K, with gamma = 12.5 mJ/mol*K. Neutron diffraction data at room
temperature and T = 10 K are well described by the stoichiometric, tetragonal
ZrCuSiAs st... | 0805.2149v1 |
2008-05-14 | Theory of the Magnetic Moment in Iron Pnictides | We show that the combined effects of spin-orbit, monoclinic distortion, and
p-d hybridization in tetrahedrally coordinated Fe in LaOFeAs invalidates the
naive Hund's rule filling of the Fe d-levels. The two highest occupied levels
have one electron each but as a result of the p-d hybridization have very
different on-si... | 0805.2167v2 |
2008-05-14 | MuSR studies of RE(O,F)FeAs (RE = La, Nd, Ce) and LaOFeP systems: possible incommensurate/stripe magnetism and superfluid density | Muon spin relaxation (MuSR) measurements in iron oxy-pnictide systems have
revealed: (1) commensurate long-range order in undoped LaOFeAs; (2) Bessel
function line shape in La(O0.97F0.03)FeAs which indicates possible
incommensurate or stripe magnetism; (3) anomalous weak magnetism existing in
superconducting LaOFeP, Ce... | 0805.2186v1 |
2008-05-19 | Suzaku Observation of Group of Galaxies NGC 507: Temperature and Metal Distributions in the Intra-cluster Medium | Temperature and abundance distributions of the intra-cluster medium (ICM) in
the NGC 507 group of galaxies were studied with Suzaku. Observed concentric
annular spectra were well-represented by a two temperature model for ICM, and
we found steeper abundance gradients for Mg, Si, S, and Fe compared with O in
the central... | 0805.2771v1 |
2008-05-19 | Impact of impellers on the axisymmetric magnetic mode in the VKS2 dynamo experiment | In the VKS2 (von K\'arm\'an Sodium 2) successful dynamo experiment of
September 2006, the magnetic field that was observed showed a strong
axisymmetric component, implying that non axisymmetric components of the flow
field were acting. By modeling the induction effect of the spiraling flow
between the blades of the imp... | 0805.2805v2 |
2008-05-19 | Electromagnetic properties and electronic structure of iron-based layered superconductor LaOFeP | Structural, electronic, and magnetic properties of undoped and aliovalent-ion
(Ca, F)-doped LaOFeP, which undergo superconducting transitions at transition
temperatures (Tc) 4-7 K [Kamihara et al, J. Am. Chem. Soc. 128, 10012, (2006)],
were investigated. Tc of the samples varied from 2.4 to 5.5 K in the undoped
samples... | 0805.2983v1 |
2008-05-21 | A Numerical Renormalization Group Study of the Superconducting and Spin Density Wave Instabilities in MFeAsO$_{1-x}$F$_x$ Compounds | We apply the fermion renormalization group method, implemented numerically by
Honerkamp et.al., to a two-band model of FeAs-based materials. At half filling
we find the $(\pi,0)$ or $(0,\pi)$ spin density wave order and a sub-dominant
superconducting pairing tendency. Due to a topological reason, the spin density
wave ... | 0805.3343v3 |
2008-05-22 | Pseudogap Value in the Energy Spectrum of LaOFeAs: Fixed Spin Moment Treatment | The experimental data available up to date in literature corresponding to the
paramagnetic - spin density wave transition in nonsuperconducting LaOFeAs are
discussed. In particular, we pay attention that upon spin density wave
transition there is a relative decrease of the density of states on the Fermi
level and a pse... | 0805.3453v1 |
2008-05-22 | The Araucaria Project: the Local Group Galaxy WLM--Distance and metallicity from quantitative spectroscopy of blue Supergiants | The quantitative analysis of low resolution spectra of A and B supergiants is
used to determine a distance modulus of 24.99 +/- 0.10 mag (995 +/- 46 Kpc) to
the Local Group galaxy WLM. The analysis yields stellar effective temperatures
and gravities, which provide a distance through the Flux weighted
Gravity--Luminosit... | 0805.3555v1 |
2008-05-30 | Chemical Abundances in 35 Metal-Poor Stars. I. Basic Data | We carried out a homogeneous abundance study for various elements, including
$\alpha$-elements, iron peak elements and $n$-capture elements for 35
metal-poor stars with a wide metallicity range
($-3.0\lesssim$[Fe/H]$\lesssim-0.5$). High-resolution ($R\simeq30$k), high
signal-to-noise($S/N\geq110$) spectra with a wavele... | 0805.4663v1 |
2008-06-03 | Critical Fields and Anisotropy of NdO0.82F0.18FeAs Single Crystals | The newly discovered iron-based superconductors have stimulated enormous
interests in the field of superconductivity. Since the new superconductor is a
layered system, the anisotropy is a parameter with the first priority to know.
Meanwhile any relevant message about the critical fields (upper critical field
and irreve... | 0806.0532v1 |
2008-06-04 | Symmetry of superconducting states with two orbitals on a tetragonal lattice: application to $LaO_{1-x}F_{x}FeAs$ | We use group theory to classify the superconducting states of systems with
two orbitals on a tetragonal lattice. The orbital part of the superconducting
gap function can be either symmetric or anti-symmetric. For the orbital
symmetric state, the parity is even for spin singlet and odd for spin triplet;
for the orbital ... | 0806.0712v3 |
2008-06-04 | Electronic structure of oxygen-free 38K superconductor Ba1-xKxFe2As2 in comparison with BaFe2As2 from first principles | Based on first-principles FLAPW-GGA calculation, we have investigated
electronic structure of newly discovered oxygen-free 38K superconductor
Ba1-xKxFe2As2 in comparison with parent phase - tetragonal ternary iron
arsenide BaFe2As2. The density of states, magnetic properties, near-Fermi bands
compositions, together wit... | 0806.0750v1 |
2008-06-04 | Valence band and core level photoemission spectros-copy of LaFeAsO$_{1-x}$F$_{x}$ | We have investigated the electronic structure of LaFeAsO$_{1-x}$F$_{x}$ (x =
0; 0.1; 0.2) by angle-integrated photoemission spectroscopy and local density
approximation (LDA) based band structure calculations. The valence band
consists of a low energy peak at E = -0.25 eV and a broad structure around E =
-5 eV in quali... | 0806.0833v2 |
2008-06-06 | Superconductivity in hole-doped (Sr$_{1-x}$K$_x$)Fe$_2$As$_2$ | A series of layered (Sr$_{1-x}$K$_x$)Fe$_2$As$_2$ compounds with nominal x=0
to 0.40 are synthesized by solid state reaction method. Similar to other parent
compounds of iron-based pnictide superconductors, the pure SrFe$_2$As$_2$ shows
a strong resistivity anomaly near 210 K, which was ascribed to the
spin-density-wav... | 0806.1209v1 |
2008-06-09 | Non-LTE Spectral Analysis of Extremely Hot Post-AGB Stars: Constraints for Evolutionary Theory | Spectral analysis by means of Non-LTE model-atmosphere techniques has arrived
at a high level of sophistication: fully line-blanketed model atmospheres which
consider opacities of all elements from H to Ni allow the reliable
determination of photospheric parameters of hot, compact stars. Such models
provide a crucial t... | 0806.1432v1 |
2008-06-16 | Structural and magnetic phase diagram of CeFeAsO1-xFx and its relationship to high-temperature superconductivity | We use neutron scattering to study the structural and magnetic phase
transitions in the iron pnictides CeFeAsO1-xFx as the system is tuned from a
semimetal to a high-transition-temperature (high-Tc) superconductor through
Fluorine (F) doping x. In the undoped state, CeFeAsO develops a structural
lattice distortion foll... | 0806.2528v1 |
2008-06-16 | Antiferromagnetic transition in EuFe$_2$As$_2$: A possible parent compound for superconductors | Ternary iron arsenide EuFe$_2$As$_2$ with ThCr$_2$Si$_2$-type structure has
been studied by magnetic susceptibility, resistivity, thermopower, Hall and
specific heat measurements. The compound undergoes two magnetic phase
transitions at about 200 K and 20 K, respectively. The former was found to be
accompanied with a s... | 0806.2591v2 |
2008-06-16 | Electronic structure and exotic exchange splitting in spin-density-wave states of BaFe$_2$As$_2$ | The magnetic properties in the parent compounds are often intimately related
to the microscopic mechanism of superconductivity. Here we report the first
direct measurements on the electronic structure of a parent compound of the
newly discovered iron-based superconductor, BaFe$_2$As$_2$, which provides a
foundation for... | 0806.2627v2 |
2008-06-22 | Thermodynamic properties of Ba1-xMxFe2As2 (M = La and K) | The specific heat $C(T)$ of BaFe$_2$As$_2$ single crystal, electron-doped
Ba$_{0.7}$La$_{0.3}$Fe$_2$As$_2$ and hole-doped Ba$_{0.5}$K$_{0.5}$Fe$_2$As$_2$
polycrystals were measured. For undoped BaFe$_2$As$_2$ single crystal, a very
sharp specific heat peak was observed at 136 K. This is attributed to the
structural and... | 0806.3573v2 |
2008-06-24 | Electronic Structure and Electron Correlation in LaFeAsO_{1-x}F_x and LaFePO_{1-x}F_x | Photoemission spectroscopy is used to investigate the electronic structure of
the newly discovered iron-based superconductors LaFeAsO_{1-x}F_x and
LaFePO_{1-x}F_x. Line shapes of the Fe 2p core-level spectra suggest an
itinerant character of Fe 3d electrons. The valence-band spectra are generally
consistent with band-s... | 0806.3860v1 |
2008-06-26 | High Energy Observations of AGN Jets and their Future Prospects | In next five years, dramatic progress is anticipated for the AGN studies, as
we have two important missions to observe celestial sources in the high energy
regime: GLAST and Suzaku. In this talk, I will summarize recent highlights in
studies of AGN jets, focusing on the high-sensitivity X-ray observations that
may shed... | 0806.4240v1 |
2008-07-03 | Coulomb Parameter U and Correlation Strength in LaFeAsO | First principles constrained density functional theory scheme in Wannier
functions formalism has been used to calculate Coulomb repulsion U and Hund's
exchange J parameters for iron 3d electrons in LaFeAsO. Results strongly depend
on the basis set used in calculations: when O-2p, As-4p, and Fe-3d orbitals and
correspon... | 0807.0547v1 |
2008-07-04 | Pressure Effect on Superconductivity of Iron-based Arsenic-oxide ReFeAsO0.85 (Re=Sm and Nd) | Here we report pressure effect on superconducting transition temperature (Tc)
of ReFeAsO0.85 (Re= Sm and Nd) system without fluorine doping. In-situ
measurements under high pressure showed that Tc of the two compounds decrease
monotonously over the pressure range investigated. The pressure coefficients
dTc/dP in SmFeAs... | 0807.0675v2 |
2008-07-06 | Momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals measured by angle resolved photoemission spectroscopy | We use angle resolved photoemission spectroscopy (ARPES) to study the
momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals.
We find that the Gamma hole pocket is fully gapped below the superconducting
transition temperature. The value of the superconducting gap is 15 +- 1.5 meV
and its anisotr... | 0807.0815v1 |
2008-07-07 | Optical spectroscopy of superconducting Ba{0.55}K{0.45}Fe2As2: evidence for strong coupling to low energy bosons | Optical spectroscopy on single crystals of the new iron arsenide
superconductor Ba{0.55}K{0.45}Fe2As2 shows that the infrared spectrum consists
of two major components: a strong metallic Drude band and a well separated mid
infrared absorption centered at 0.7 eV. It is difficult to separate the two
components unambiguou... | 0807.1040v1 |
2008-07-08 | Possibility of Unconventional Pairing Due to Coulomb Interaction in Fe-Based Pnictide Superconductors: Perturbative Analysis of Multi-Band Hubbard Models | Possibility of unconventional pairing due to Coulomb interaction in
iron-pnictide superconductors is studied by applying a perturbative approach to
realistic 2- and 5-band Hubbard models. The linearized Eliashberg equation is
solved by expanding the effective pairing interaction perturbatively up to
third order in the ... | 0807.1168v2 |
2008-07-09 | The chemical evolution of Manganese in different stellar systems | Aims. To model the chemical evolution of manganese relative to iron in three
different stellar systems: the solar neighbourhood, the Galactic bulge and the
Sagittarius dwarf spheroidal galaxy, and compare our results with the recent
and homogeneous observational data. Methods. We adopt three chemical evolution
models w... | 0807.1463v1 |
2008-07-09 | Lattice and magnetic instabilities in CaFe2As2: A single crystal neutron diffraction study | Neutron diffraction measurements of a high quality single crystal of CaFe2As2
are reported. A sharp transition was observed between the high temperature
tetragonal and low temperature orthorhombic structures at TS = 172.5K (on
cooling) and 173.5K (on warming). Coincident with the structural transition we
observe a rapi... | 0807.1525v3 |
2008-07-10 | Structural Chemistry, Spin Order, and the Distinction Between the Cuprate and Pnictide High-Temperature Superconductors | In the cuprate and iron-pnictide systems, valence changes induce
high-temperature superconductivity while the local structural chemistry and
local spin order both independently generate the attractive interactions
responsible for the high transition temperature. We argue that together they
favor d-wave singlet supercon... | 0807.1673v5 |
2008-07-15 | Physical and kinematical properties of the X-ray absorber in the broad absorption line quasar APM 08279+5255 | We have re-analyzed the X-ray spectra of the gravitational lensed
high-redshift BAL QSO APM 08279+5255, observed with the XMM-Newton and Chandra
observatories. Previous studies (Hasinger et al. 2002; Chartas et al. 2002)
detected unusual, highly-ionized iron absorption features, but differed in
their interpretation of ... | 0807.2372v1 |
2008-07-16 | Columnar magnetic structure coupled with orthorhombic distortion in the antiferromagnetic iron arsenide SrFe$_2$As$_2$ | Neutron powder diffraction experiments were carried out on polycrystalline
SrFe$_2$As$_2$ in order to determine the magnetic structure and its
relationship with the crystallographic one. Below $T_0$=205 K, magnetic
reflections appear simultaneously with the onset of the orthorhombic
distortion. From a detailed Rietveld... | 0807.2608v1 |
2008-07-18 | Pressure-induced volume-collapsed tetragonal phase of CaFe2As2 as seen via neutron scattering | Recent investigations of the superconducting iron-arsenide families have
highlighted the role of pressure, be it chemical or mechanical, in fostering
superconductivity. Here we report that CaFe2As2 undergoes a pressure-induced
transition to a non-magnetic, volume "collapsed" tetragonal phase, which
becomes superconduct... | 0807.3032v3 |
2008-07-20 | Electronic structure of LaFe1-xCoxAsO from first principle calculations | Based on the first-principles calculations, we have investigated the
geometry, binding properties, density of states and band structures of the
novel superconductor LaFe1-xCoxAsO and its parent compounds with the ZrCuSiAs
structure. We demonstrate that La-O bond and TM-As (TM=Fe or Co) bond are both
strongly covalent, ... | 0807.3153v2 |
2008-07-24 | Evidence for Strong Itinerant Spin Fluctuations in the Normal State of CeFeAsO(0.89)F(0.11) Iron-Oxypnictides | The electronic structure in the normal state of CeFeAsO0.89F0.11 oxypnictide
superconductors has been investigated with x-ray absorption and photoemission
spectroscopy. All the data exhibit signatures of Fe d-electron itinerancy.
Exchange multiplets appearing in the Fe 3s core level indicate the presence of
itinerant s... | 0807.3781v2 |
2008-07-24 | Modeling UX Ursae Majoris: An abundance of challenges | We present a system model for optical and far UV spectra of the nova-like
variable UX UMa involving a white dwarf, secondary star, gas stream, hot spot
and accretion disk using our code BINSYN and based on an initially adopted
system distance. Calculated SED intensity data successfully fit successive
tomographically-ex... | 0807.3920v1 |
2008-07-25 | Superconductivity and Crystal Structures of (Ba1-xKx)Fe2As2 (x = 0 - 1) | We report on doping dependencies of structural parameters and superconducting
transition temperatures in the solid solution (Ba1-xKx)Fe2As2. As the main
effect of doping on the crystal structure, we find linear decreasing As-Fe-As
bond angles and Fe-Fe distances, equivalent to an elongation of the FeAs4
tetrahedra alon... | 0807.4096v2 |
2008-07-28 | Superconductivity at 27 K in tetragonal FeSe under high pressure | A huge enhancement of the superconducting transition temperature Tc was
observed in tetragonal FeSe superconductor under high pressure. The onset
temperature became as high as 27 K at 1.48 GPa and the pressure coefficient
showed a huge value of 9.1 K/GPa. The upper critical field Hc2 was estimated to
be ~ 72 T at 1.48 ... | 0807.4315v2 |
2008-07-29 | Anisotropic pairing in the iron pnictides | We determine the anisotropy of the spin fluctuation induced pairing gap on
the Fermi surface of the FeAs based superconductors as function of the exchange
and Hund's coupling $J_{H}$. We find that for sufficiently large $J_{H}$,
nearly commensurate magnetic fluctuations yield a fully gapped
$s^{\pm}$-pairing state with... | 0807.4566v2 |
2008-07-31 | Evidence for Unconventional Superconductivity in Arsenic-Free Iron-Based Superconductor FeSe : A ^77Se-NMR Study | We report the results of $^{77}$Se--nuclear magnetic resonance (NMR) in
$\alpha$-FeSe, which exhibits a similar crystal structure to the
LaFeAsO$_{1-x}$F$_x$ superconductor and shows superconductivity at 8 K. The
nuclear-spin lattice relaxation rate $1/T_1$ shows $T^3$ behavior below the
superconducting transition temp... | 0808.0040v3 |
2008-08-03 | Magnetic and Transport Studies on Electron-doped CeFeAsO1-xFx Superconductor | The magnetic and transport behaviors of cerium substituted iron oxy-arsenide
superconductor with x = 0.1 to 0.4 fluoride (F) doping have been investigated
in this report. Temperature dependent susceptibility and resistivity
measurements showed the 0.1 F-doped sample (CeFeAsO0.9F0.1) has a
superconducting transition tem... | 0808.0296v1 |
2008-08-04 | Tellurium substitution effect on superconductivity of the alpha-phase Iron Selenide | We have carried out a systematic study of the PbO-type compound
FeSe_{1-x}Te_x (x = 0~1), where Te substitution effect on superconductivity is
investigated. It is found that superconducting transition temperature reaches a
maximum of Tc=15.2K at about 50% Te substitution. The pressure-enhanced Tc of
FeSe0.5Te0.5 is mor... | 0808.0474v2 |
2008-08-06 | The correlation of black hole mass with metallicity index of host spheroid | We investigate the correlation between the mass of the supermassive black
holes (SMBHs) and metal abundance, using existing data sets. The SMBH mass
$M_{bh}$ is well correlated with integrated stellar feature of Mgb. For 28
galaxies, the best-fit $M_{bh}$-Mgb relation has a small scatter, which is an
equivalent level w... | 0808.0769v1 |
2008-08-06 | Granularity and vortex dynamics in LaO_0.92F_0.08FeAs as probed by harmonics of the AC magnetic susceptibility | Fundamental and higher harmonics of the AC magnetic susceptibility have been
measured on a LaO_0.92F_0.08FeAs sample as a function of the temperature, at
various amplitudes and frequencies of the AC magnetic field, with a small
superimposed DC field parallel to the AC field. The granularity of the sample
has been inves... | 0808.0804v1 |
2008-08-10 | 59-Co and 75-As NMR Investigation of Electron-Doped High Tc Superconductor BaFe(1.8)Co(0.2)As(2) (Tc = 22K) | We report an NMR investigation of the superconductivity in BaFe(2)As(2)
induced by Co doping (Tc=22K). We demonstrate that Co atoms form an alloy with
Fe atoms and donate carriers without creating localized moments. Our finding
strongly suggests that the underlying physics of iron-pnictide superconductors
is quite diff... | 0808.1420v2 |
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