5,880 research outputs found
Kidney Diseases Caused by Complement Dysregulation: Acquired, Inherited, and Still More to Come
Inherited and acquired dysregulation of the complement alternative pathway plays an important role in multiple renal diseases. In recent years, the identification of disease-causing mutations and genetic variants in complement regulatory proteins has contributed significantly to our knowledge of the pathogenesis of complement associated glomerulopathies. In these diseases defective complement control leading to the deposition of activated complement products plays a key role. Consequently, complement-related glomerulopathies characterized by glomerular complement component 3 (C3) deposition in the absence of local immunoglobulin deposits are now collectively described by the term “C3 glomerulopathies.” Therapeutic strategies for reestablishing complement regulation by either complement blockade with the anti-C5 monoclonal antibody eculizumab or plasma substitution have been successful in several cases of C3 glomerulopathies. However, further elucidation of the underlying defects in the alternative complement pathway is awaited to develop pathogenesis-specific therapies
Testing Galactic Magnetic Field Models using Near-Infrared Polarimetry
This work combines new observations of NIR starlight linear polarimetry with
previously simulated observations in order to constrain dynamo models of the
Galactic magnetic field. Polarimetric observations were obtained with the Mimir
instrument on the Perkins Telescope in Flagstaff, AZ, along a line of constant
Galactic longitude (\ell = 150\circ) with 17 pointings of the 10' \times 10'
field of view between -75\circ < b < 10\circ, with more frequent pointings
towards the Galactic midplane. A total of 10,962 stars were photometrically
measured and 1,116 had usable polarizations. The observed distribution of
polarization position angles with Galactic latitude and the cumulative
distribution function of the measured polarizations are compared to predicted
values. While the predictions lack the effects of turbulence and are therefore
idealized, this comparison allows significant rejection of A0-type magnetic
field models. S0 and disk-even halo-odd magnetic field geometries are also
rejected by the observations, but at lower significance. New predictions of
spiral-type, axisymmetric magnetic fields, when combined with these new NIR
observations, constrain the Galactic magnetic field spiral pitch angle to
-6\circ \pm 2\circ.Comment: 11 pages, 10 figures, Accepted for publication in Ap
Sensorized Skin With Biomimetic Tactility Features Based on Artificial Cross-Talk of Bimodal Resistive Sensory Inputs
Tactility in biological organisms is a faculty that relies on a variety of specialized receptors. The bimodal sensorized skin, featured in this study, combines soft resistive composites that attribute the skin with mechano- and thermoreceptive capabilities. Mimicking the position of the different natural receptors in different depths of the skin layers, a multi-layer arrangement of the soft resistive composites is achieved. However, the magnitude of the signal response and the localization ability of the stimulus change with lighter presses of the bimodal skin. Hence, a learning-based approach is employed that can help achieve predictions about the stimulus using 4500 probes. Similar to the cognitive functions in the human brain, the cross-talk of sensory information between the two types of sensory information allows the learning architecture to make more accurate predictions of localization, depth, and temperature of the stimulus contiguously. Localization accuracies of 1.8 mm, depth errors of 0.22 mm, and temperature errors of 8.2 °C using 8 mechanoreceptive and 8 thermoreceptive sensing elements are achieved for the smaller inter-element distances. Combining the bimodal sensing multilayer skins with the neural network learning approach brings the artificial tactile interface one step closer to imitating the sensory capabilities of biological skin
Brown Beauty: Body Image, Latinas, and the Media
This paper examines the understudied Latina population and the effects of media on their body image. To date, research has ignored this population or aggregated all Latin-American sub-cultures into one general category, missing the nuances of each culture. A review of current literature utilizing cultivation theory and social comparison theory is offered. Important findings suggest that social support and ethnic identity may offer a buffering effect between media exposure and body dissatisfaction, but more research needs to clarify this process. The effects of media and the internalization of the ‘thin ideal’ become stronger the longer Latina women live in the United States and acculturate to mainstream culture. Implications for body image research include psychological issues, such as lower self-esteem, depression, and anxiety, and can often lead to disordered eating. Future directions for studies are discussed
A multiwavlength study of PSR B0628-28: The first overluminous rotation-powered pulsar?
The ROSAT source RX J0630.8-2834 was suggested by positional coincidence to
be the X-ray counterpart of the old field pulsar PSR B0628-28. This
association, however, was regarded to be unlikely based on the computed
energetics of the putative X-ray counterpart. In this paper we report on
multiwavelength observations of PSR B0628-28 made with the ESO/NTT observatory
in La Silla, the Jodrell Bank radio observatory and XMM-Newton. Although the
optical observations do not detect any counterpart of RX J0630.8-2834 down to a
limiting magnitude of V=26.1 mag and B=26.3 mag, XMM-Newton observations
finally confirmed it to be the pulsar's X-ray counterpart by detecting X-ray
pulses with the radio pulsar's spin-period. The X-ray pulse profile is
characterized by a single broad peak with a second smaller peak leading the
main pulse component by ~144 degree. The fraction of pulsed photons is (38 +-
7)% with no strong energy dependence in the XMM-Newton bandpass. The pulsar's
X-ray spectrum is well described by a single component power law with photon
index 2.63^{+0.23}_{-0.15}, indicating that the pulsar's X radiation is
dominated by non-thermal emission processes. A low level contribution of
thermal emission from residual cooling or from heated polar caps, cannot be
excluded. The pulsar's spin-down to X-ray energy conversion efficiency is
obtained to be ~16% for the radio dispersion measure inferred pulsar distance.
If confirmed, PSR B0628-28 would be the first X-ray overluminous
rotation-powered pulsar identified among all ~1400 radio pulsars known today.Comment: Accepted for publication in ApJ. Find a paper copy with higher
resolution images at
ftp://ftp.xray.mpe.mpg.de/people/web/astro-ph-0505488_rev2.pd
Evolutionary calculations of phase separation in crystallizing white dwarf stars
We present an exploration of the significance of Carbon/Oxygen phase
separation in white dwarf stars in the context of self-consistent evolutionary
calculations. Because phase separation can potentially increase the calculated
ages of the oldest white dwarfs, it can affect the age of the Galactic disk as
derived from the downturn in the white dwarf luminosity function. We find that
the largest possible increase in ages due to phase separation is 1.5 Gyr, with
a most likely value of approximately 0.6 Gyr, depending on the parameters of
our white dwarf models.
The most important factors influencing the size of this delay are the total
stellar mass, the initial composition profile, and the phase diagram assumed
for crystallization. We find a maximum age delay in models with masses of 0.6
solar masses, which is near the peak in the observed white dwarf mass
distribution. We find that varying the opacities (via the metallicity) has
little effect on the calculated age delays.
In the context of Galactic evolution, age estimates for the oldest Galactic
globular clusters range from 11.5 to 16 Gyr, and depend on a variety of
parameters. In addition, a 4 to 6 Gyr delay is expected between the formation
of the globular clusters and that of the Galactic thin disk, while the observed
white dwarf luminosity function gives an age estimate for the thin disk of 9.5
+/-1.0 Gyr, without including the effect of phase separation. Using the above
numbers, we see that phase separation could add between 0 to 3 Gyr to the white
dwarf ages and still be consistent with the overall picture of Galaxy
formation. Our calculated maximum value of 1.5 Gyr fits within these bounds, as
does our best guess value of 0.6 Gyr.Comment: 13 total pages, 8 figures, 3 tables, accepted for publication in the
Astrophysical Journal on May 25, 199
Magnetoelastic coupling in triangular lattice antiferromagnet CuCrS2
CuCrS2 is a triangular lattice Heisenberg antiferromagnet with a rhombohedral
crystal structure. We report on neutron and synchrotron powder diffraction
results which reveal a monoclinic lattice distortion at the magnetic transition
and verify a magnetoelastic coupling. CuCrS2 is therefore an interesting
material to study the influence of magnetism on the relief of geometrical
frustration.Comment: 6 pages, 6 figures, 1 tabl
Mode identification of Pulsating White Dwarfs using the HST
We have obtained time-resolved ultraviolet spectroscopy for the pulsating DAV
stars G226-29 and G185-32, and for the pulsating DBV star PG1351+489 with the
Hubble Space Telescope Faint Object Spectrograph, to compare the ultraviolet to
the optical pulsation amplitude and determine the pulsation indices. We find
that for essentially all observed pulsation modes, the amplitude rises to the
ultraviolet as the theoretical models predict for l=1 non-radial g-modes. We do
not find any pulsation mode visible only in the ultraviolet, nor any modes
whose phase flips by 180 degrees; in the ultraviolet, as would be expected if
high l pulsations were excited. We find one periodicity in the light curve of
G185-32, at 141 s, which does not fit theoretical models for the change of
amplitude with wavelength of g-mode pulsations.Comment: Accepted for publication in the Astrophysical Journal, Aug 200
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