1,357 research outputs found
Cascades from early adolescent impulsivity to late adolescent antisocial personality disorder and alcohol use disorder
Cascades from early adolescent impulsivity to late adolescent antisocial personality disorder and alcohol use disorder
UV Imaging Polarimetry of the peculiar Seyfert 2 galaxy Mrk 477
We present the results of UV imaging polarimetry of the Seyfert 2 galaxy Mrk
477 taken by the Faint Object Camera onboard the Hubble Space Telescope (HST).
From a previous HST UV image (lambda ~ 2180A), Mrk 477 has been known to have
a pointlike bright UV hotspot in the central region, peculiar among nearby
Seyfert 2 galaxies. There are also claims of UV/optical variability, unusual
for a Seyfert 2 galaxy. Our data show that there is an off-nuclear scattering
region ~ 0."6 (~ 500 pc) NE from the hotspot. The data, after the subtraction
of the instrumental effect due to this bright hotspot region, might indicate
that the scattered light is also detected in the central 0."2 radius region and
is extended to a very wide angle. The hotspot location is consistent with the
symmetry center of the PA pattern, which represents the location of the hidden
nucleus, but our data do not provide a strong upper limit to the distance
between the symmetry center and the hotspot. We have obtained high spatial
resolution color map of the continuum which shows that the nuclear spiral arm
of 0."4 scale (~ 300pc) is significantly bluer than the off-nuclear mirror and
the hotspot region. The nature of the hotspot is briefly discussed.Comment: To appear in Ap
Wilson ratio in Yb-substituted CeCoIn5
We have investigated the effect of Yb substitution on the Pauli limited,
heavy fermion superconductor, CeCoIn. Yb acts as a non-magnetic divalent
substituent for Ce throughout the entire doping range, equivalent to hole
doping on the rare earth site. We found that the upper critical field in
(Ce,Yb)CoIn is Pauli limited, yet the reduced (H,T) phase diagram is
insensitive to disorder, as expected in the purely orbitally limited case. We
use the Pauli limiting field, the superconducting condensation energy and the
electronic specific heat coefficient to determine the Wilson ratio (),
the ratio of the specific heat coefficient to the Pauli susceptibility in
CeCoIn. The method is applicable to any Pauli limited superconductor in the
clean limit.Comment: 5 pages, 1 table, 4 figure
A Hardy inequality in twisted waveguides
We show that twisting of an infinite straight three-dimensional tube with
non-circular cross-section gives rise to a Hardy-type inequality for the
associated Dirichlet Laplacian. As an application we prove certain stability of
the spectrum of the Dirichlet Laplacian in locally and mildly bent tubes.
Namely, it is known that any local bending, no matter how small, generates
eigenvalues below the essential spectrum of the Laplacian in the tubes with
arbitrary cross-sections rotated along a reference curve in an appropriate way.
In the present paper we show that for any other rotation some critical strength
of the bending is needed in order to induce a non-empty discrete spectrum.Comment: LaTeX, 20 page
Motion-base simulator study of control of an externally blown flap STOL transport aircraft after failure of an outboard engine during landing approach
A moving-base simulator investigation of the problems of recovery and landing of a STOL aircraft after failure of an outboard engine during final approach was made. The approaches were made at 75 knots along a 6 deg glide slope. The engine was failed at low altitude and the option to go around was not allowed. The aircraft was simulated with each of three control systems, and it had four high-bypass-ratio fan-jet engines exhausting against large triple-slotted wing flaps to produce additional lift. A virtual-image out-the-window television display of a simulated STOL airport was operating during part of the investigation. Also, a simple heads-up flight director display superimposed on the airport landing scene was used by the pilots to make some of the recoveries following an engine failure. The results of the study indicated that the variation in visual cues and/or motion cues had little effect on the outcome of a recovery, but they did have some effect on the pilot's response and control patterns
UV Imaging Polarimetry of the Seyfert 2 Galaxy Mrk 3
We present UV imaging polarimetry data of the Seyfert 2 galaxy Mrk 3 taken by
the Hubble Space Telescope. The polarized flux is found to be extended to ~1
kpc from the nucleus, and the position angles of polarization are
centrosymmetric, confirming that the polarization is caused by scattering. We
determine the location of the hidden nucleus as the center of this
centrosymmetric pattern. From the polarization images taken in two broad bands,
we have obtained the color distribution of the polarized flux. Some regions
have blue polarized flux, consistent with optically-thin dust scattering, but
some bright knots have a color similar to that of Seyfert 1 nucleus. Also, the
recent Chandra X-ray observation suggests that the ratio of scattered UV flux
to scattered X-ray flux is rather similar to the intrinsic UV/X-ray ratio in a
Seyfert 1 nucleus, if the observed extended X-ray continuum is scattered light.
While the scattered X-ray would be essentially from electron scattering, the UV
slope and UV/X-ray ratio both being similar to Seyfert 1's would lead to two
possibilities as to the nature of the UV scatterers. One is that the UV may
also be scattered by electrons, in which case the scattering gas is somehow
dust-free. The other is that the UV is scattered by dust grains, but the
wavelength-independent UV scattering with low efficiency indicated by the UV
slope and UV/X-ray ratio would suggest that the grains reside in UV-opaque
clouds, or the dust might be mainly composed of large grains and lacks
small-grain population.Comment: 15 pages, 8 figures (plus 2 color versions of grayscale figures), To
appear in ApJ; minor corrections for the proofs of the manuscrip
Nuclear Bar Catalyzed Star Formation: 13^CO, C18^O and Molecular Gas Properties in the Nucleus of Maffei 2
(Abridged) We present resolution maps of CO, its isotopologues, and HCN from
in the center of Maffei 2. The J=1-0 rotational lines of 12^CO, 13^CO, C18^O
and HCN, and the J=2-1 lines of 13^CO and C18^O were observed with the OVRO and
BIMA arrays. The 2-1/1-0 line ratios of the isotopologues constrain the bulk of
the molecular gas to originate in low excitation, subthermal gas. From LVG
modeling, we infer that the central GMCs have n(H_2) ~10^2.75 cm^-3 and T_k ~
30 K. Continuum emission at 3.4 mm, 2.7 mm and 1.4 mm was mapped to determine
the distribution and amount of HII regions and dust. Column densities derived
from C18^O and 1.4 mm dust continuum fluxes indicate the CO conversion factor
in the center of Maffei 2 is lower than Galactic by factors of ~2-4. Gas
morphology and the clear ``parallelogram'' in the Position-Velocity diagram
shows that molecular gas orbits within the potential of a nuclear (~220 pc)
bar. The nuclear bar is distinct from the bar that governs the large scale
morphology of Maffei 2. Giant molecular clouds in the nucleus are nonspherical
and have large linewidths. Dense gas and star formation are concentrated at the
sites of the x_1-x_2 orbit intersections of the nuclear bar, suggesting that
the starburst is dynamically triggered.Comment: 50 pages, 14 figures, accepted for publication in Ap
9. Effect of insecticide-treated bed nets on haemoglobin values, prevalence and multiplicity of infection with Plasmodium falciparum in a randomized controlled trial in Tanzania
A randomized controlled trial of insecticide-treated bed nets (ITNs) was conducted in an area of high malaria transmission in Tanzania in order to assess the effects of ITNs on infection and anaemia. One hundred and twenty-two children, aged 5 to 24 months, were randomly allocated to 2 groups, one of which received ITNs. Outcome measures were assessed in 6 consecutive months with monthly cross-sectional surveys. These measures were haemoglobin values, Plasmodium falciparum prevalence and density, and multiplicity of infection determined by polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP) of the msp2 locus. There was a significant increase in mean heamoglobin values and a significant decrease of 16·4% in microscopically determined P. falciparum prevalence in children in the ITN group six months after the start of the trial. Both effects were more pronounced in younger children. However, no significant difference was observed in parasite density or multiplicity of infection among infected children. Comparison with PCR results indicated that microscopically subpatent parasitaemia was more frequently found in children in the ITN group. This, together with the observed similar multiplicity in the 2 groups, suggests that infections are maintained despite ITN use, owing to the chronicity of infections. This study shows that ITNs reduce the risk of anaemia in highly exposed young children. The virtually unchanged multiplicity of infection indicates that the potentially protective concomitant immunity is not compromise
Biogenesis of mitochondrial porin
We review here the present knowledge about the pathway of import and assembly of porin into mitochondria and compare it to those of other mitochondrial proteins. Porin, like all outer mitochondrial membrane proteins studied so far is made as a precursor without a cleavble lsquosignalrsquo sequence; thus targeting information must reside in the mature sequence. At least part of this information appears to be located at the amino-terminal end of the molecule. Transport into mitochondria can occur post-translationally. In a first step, the porin precursor is specifically recognized on the mitochondrial surface by a protease sensitive receptor. In a second step, porin precursor inserts partially into the outer membrane. This step is mediated by a component of the import machinery common to the import pathways of precursor proteins destined for other mitochondrial subcompartments. Finally, porin is assembled to produce the functional oligomeric form of an integral membrane protein wich is characterized by its extreme protease resistance
- …