905 research outputs found
Infinite Layer LaNiO(2): Ni(1+)is not Cu(2+)
The Ni ion in LaNiO has the same formal ionic configuration as
does Cu in isostructural CaCuO, but it is reported to be nonmagnetic and
probably metallic whereas CaCuO is a magnetic insulator. From ab initio
calculations we trace its individualistic behavior to (1) reduced
mixing due to an increase of the separation of site energies () of at least 2 eV, and (2) important Ni mixing with
La states that leads to Fermi surface pockets of La
character that hole-dope the Ni 3d band.Correlation effects do not appear to be
large in LaNiO. However, ad hoc increase of the intraatomic repulsion on
the Ni site (using the LDA+U method) is found to lead to a novel correlated
state: (i) the transition metal and states undergo
consecutive Mott transitions, (ii) their moments are antialigned leading
(ideally) to a "singlet" ion in which there are two polarized orbitals, and
(iii) mixing of the upper Hubbard band with the La
states leaves considerable transition metal 3d character in a band pinned to
the Fermi level. The magnetic configuration is more indicative of a Ni
ion in this limit, although the actual charge changes little with U.Comment: 7 pages, 8 figure
The Suzaku Observation of NGC 3516: Complex Absorption and the Broad and Narrow Fe K Lines
We present results from a 150 ksec Suzaku observation of the Seyfert 1.5 NGC
3516 in October 2005. The source was in a relatively highly absorbed state. Our
best-fit model is consistent with the presence of a low-ionization absorber
which has a column density near 5 * 10^{22} cm^{-2} and covers most of the
X-ray continuum source (covering fraction 96-100%). A high-ionization absorbing
component, which yields a narrow absorption feature consistent with Fe K XXVI,
is confirmed. A relativistically broadened Fe K alpha line is required in all
fits, even after the complex absorption is taken into account; an additional
partial-covering component is an inadequate substitute for the continuum
curvature associated with the broad Fe line. A narrow Fe K alpha emission line
has a velocity width consistent with the Broad Line Region. The low-ionization
absorber may be responsible for producing the narrow Fe K alpha line, though a
contribution from additional material out of the line of sight is possible. We
include in our model soft band emission lines from He- and H-like ions of N, O,
Ne and Mg, consistent with photo-ionization, though a small contribution from
collisionally-ionized emission is possible.Comment: Accepted for publication in PASJ (Suzaku second special issue). 36
pages, 10 figure
Suzaku wide-band X-ray Spectroscopy of the Seyfert 2 AGN in NGC 4945
Suzaku observed a nearby Seyfert 2 galaxy NGC4945, which hosts one of the
brightest active galactic nuclei above 20 keV. Combining data from the X-ray
CCD camera (XIS) and the Hard X-ray Detector (HXD), the AGN intrinsic nuclear
emission and its reprocessed signals were observed simultaneously. The
intrinsic emission is highly obscured with an absorbing column of cm, and was detectable only above keV. The
spectrum below 10 keV is dominated by reflection continuum and emission lines
from neutral/ionized material. Along with a neutral iron K line, a
neutral iron K and a neutral nickel K line were detected for the
first time from this source. The neutral lines and the cold reflection
continuum are consistent with both originating in the same location. The
Compton down-scattered shoulder in the neutral Fe-K line is
in flux of the narrow core, which confirms that the line originates from
reflection rather than transmission. The weakness of the Compton shoulder also
indicates that the reflector is probably seen nearly edge-on. Flux of the
intrinsic emission varied by a factor of within ks, which
requires the obscuring material to be geometrically thin. Broadband spectral
modeling showed that the solid angle of the neutral reflector is less than a
few . All this evidence regarding the reprocessed
signals suggests that a disk-like absorber/reflector is viewed from a near
edge-on angle.Comment: 11 pages, 11 figure
Precision Fe Kalpha and Fe Kbeta Line Spectroscopy of the Seyfert 1.9 Galaxy NGC 2992 with Suzaku
We present detailed time-averaged X-ray spectroscopy in the 0.5--10 keV band
of the Seyfert~1.9 galaxy NGC 2992 with the Suzaku X-ray Imaging Spectrometers
(XIS). We model the complex continuum in detail. There is an Fe K line emission
complex that we model with broad and narrow lines and we show that the
intensities of the two components are decoupled at a confidence level >3sigma.
The broad Fe K line has an EW of 118 (+32,-61) eV and could originate in an
accretion disk (with inclination angle greater than ~30 degrees). The narrow Fe
Kalpha line has an EW of 163 (+47,-26) eV and is unresolved FWHM <4090 km/s)
and likely originates in distant matter. The absolute flux in the narrow line
implies that the column density out of the line-of-sight could be much higher
than measured in the line-of-sight, and that the mean (historically-averaged)
continuum luminosity responsible for forming the line could be a factor of
several higher than that measured from the data. We also detect the narrow Fe
Kbeta line with a high signal-to-noise ratio and describe a new robust method
to constrain the ionization state of Fe responsible for the Fe Kalpha and Fe
Kbeta lines that does not require any knowledge of possible gravitational and
Doppler energy shifts affecting the line energies. For the distant
line-emitting matter (e.g. the putative obscuring torus) we deduce that the
predominant ionization state is lower than Fe VIII (at 99% confidence),
conservatively taking into account residual calibration uncertainties in the
XIS energy scale and theoretical and experimental uncertainties in the Fe K
fluorescent line energies. From the limits on a possible Compton-reflection
continuum it is likely that the narrow Fe Kalpha and Fe Kbeta lines originate
in a Compton-thin structure.Comment: Abstract is abridged. Accepted for publication in the Suzaku special
issue of PASJ (November 2006). 18 pages, 6 figure
Alterations in Diastolic Function in Masked Hypertension: Findings from the Masked Hypertension Study
BACKGROUND In a prior study of patients with diabetes, diastolic function was similarly impaired in masked hypertension (MHT) and sustained hypertension (SHT). We evaluated whether MHT is associated with impaired diastolic function compared with SHT and sustained normotension (NT) in the general population.
METHODS From February 2005 to December 2010, 798 participants without a history of cardiovascular disease or treated hypertension, were enrolled in the Masked Hypertension Study. Participants underwent clinic blood pressure (CBP) and 24-hour ambulatory blood pressure (ABP) measurements. A 2-dimensional Doppler echocardiogram was performed to evaluate diastolic function,s cardiac structure, volume, and systolic function. The 9 CBPs obtained across 3 clinic visits and awake ABP measurements were averaged. Clinic hypertension was defined as systolic/diastolic blood pressure (SBP/DBP) ≥ 140/90 mmHg. Ambulatory hypertension was defined as awake SBP/DBP ≥ 135/85mm Hg. MHT was defined as having ambulatory but not clinic hypertension. White-coat hypertensives (n = 8) were excluded from the analysis.
RESULTS Of the 790 participants, 116 (14.7%) participants had MHT, 37 (4.7%) participants had SHT, and 637 (80.6%) participants had NT. After age, sex, race/ethnicity, and body mass index adjustment, compared with NT, E’-velocities were significantly lower in MHT (P < 0.01) and SHT (P < 0.05), and E/E’ ratios were significantly higher MHT (P < 0.05) and SHT (P < 0.05). These associations were independent of left ventricular mass. Diastolic function parameters did not significantly differ between MHT and SHT.
CONCLUSIONS Diastolic function was impaired in MHT compared with NT independent of changes in left ventricular mass
Stress relaxation and creep experiments with the atomic force microscope: a unified method to calculate elastic moduli and viscosities of biomaterials (and cells)
We show that the atomic force microscope can perform stress relaxation and
creep compliance measurements on living cells. We propose a method to obtain
the mechanical properties of the studied biomaterial: the relaxation time, the
elastic moduli and the viscosity.Comment: 17 pages, three figure
The Swift BAT Perspective on Non-thermal Emission in HIFLUGCS Galaxy Clusters
The search for diffuse non-thermal, inverse Compton (IC) emission from galaxy
clusters at hard X-ray energies has been underway for many years, with most
detections being either of low significance or controversial. In this work, we
investigate 14-195 keV spectra from the Swift Burst Alert Telescope (BAT)
all-sky survey for evidence of non-thermal excess emission above the
exponentially decreasing tail of thermal emission in the flux-limited HIFLUGCS
sample. To account for the thermal contribution at BAT energies, XMM-Newton
EPIC spectra are extracted from coincident spatial regions so that both thermal
and non-thermal spectral components can be determined simultaneously. We find
marginally significant IC components in six clusters, though after closer
inspection and consideration of systematic errors we are unable to claim a
clear detection in any of them. The spectra of all clusters are also summed to
enhance a cumulative non-thermal signal not quite detectable in individual
clusters. After constructing a model based on single-temperature fits to the
XMM-Newton data alone, we see no significant excess emission above that
predicted by the thermal model determined at soft energies. This result also
holds for the summed spectra of various subgroups, except for the subsample of
clusters with diffuse radio emission. For clusters hosting a diffuse radio
halo, a relic, or a mini-halo, non-thermal emission is initially detected at
the \sim5-sigma confidence level - driven by clusters with mini-halos - but
modeling and systematic uncertainties ultimately degrade this significance. In
individual clusters, the non-thermal pressure of relativistic electrons is
limited to \sim10% of the thermal electron pressure, with stricter limits for
the more massive clusters, indicating that these electrons are likely not
dynamically important in the central regions of clusters.Comment: 25 pages, 15 figures; some figure and table numbering differs from
published ApJ version: please see that for superior formattin
Probing the atmosphere of a solar-like star by galactic microlensing at high magnification
We report a measurement of limb darkening of a solar-like star in the very
high magnification microlensing event MOA 2002-BLG-33. A 15 hour deviation from
the light curve profile expected for a single lens was monitored intensively in
V and I passbands by five telescopes spanning the globe. Our modelling of the
light curve showed the lens to be a close binary system whose centre-of-mass
passed almost directly in front of the source star. The source star was
identified as an F8-G2 main sequence turn-off star. The measured stellar
profiles agree with current stellar atmosphere theory to within ~4% in two
passbands. The effective angular resolution of the measurements is <1
micro-arcsec. These are the first limb darkening measurements obtained by
microlensing for a Solar-like star.Comment: Accepted for publication in A&A Letters. 5 pages, 2 embedded colour
ps figures plus 1 jpg figure. Version with all figures embedded available
from: http://www.roe.ac.uk/~iab/moa33paper
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