6,934 research outputs found
Reply to "Comment on 'Scalar-tensor gravity coupled to a global monopole and flat rotation curves' "
In Brans-Dicke theory of gravity we explain how the extra constant value in
the formula for rotation velocities of stars in a galactic halo can be obtained
due to the global monopole field. We argue on a few points of the preceding
Comment and discuss improvement of our model.Comment: 4 pages, RevTeX4 fil
Field-induced confinement in (TMTSF)2ClO4 under accurately aligned magnetic fields
We present transport measurements along the least conducting c direction of
the organic superconductor (TMTSF)2ClO4, performed under an accurately aligned
magnetic field in the low temperature regime. The experimental results reveal a
two-dimensional confinement of the carriers in the (a,b) planes which is
governed by the magnetic field component along the b' direction. This 2-D
confinement is accompanied by a metal-insulator transition for the c axis
resistivity. These data are supported by a quantum mechanical calculation of
the transverse transport taking into account in self consistent treatment the
effect of the field on the interplane Green function and on the intraplane
scattering time
A photonic-crystal optical antenna for extremely large local-field enhancement
We propose a novel design of an all-dielectric optical antenna based on photonic-band-gap confinement. Specifically, we have engineered the photonic-crystal dipole mode to have broad spectral response (Q ~70) and well-directed vertical-radiation by introducing a plane mirror below the cavity. Considerably large local electric-field intensity enhancement ~4,500 is expected from the proposed design for a normally incident planewave. Furthermore, an analytic model developed based on coupled-mode theory predicts that the electric-field intensity enhancement can easily be over 100,000 by employing reasonably high-Q (~10,000) resonators
Selective remodeling of cardiolipin fatty acids in the aged rat heart
BACKGROUND: The heart is rich in cardiolipin, a phospholipid acylated in four sites, predominately with linoleic acid. Whether or not aging alters the composition of cardiolipin acyl chains is controversial. We therefore measured the fatty acid concentration of cardiolipin in hearts of 4, 12 and 24 month old rats that consumed one diet, adequate in fatty acids for the duration of their life. RESULTS: The concentration (nmol/g) of linoleic acid was decreased in 24 month old rats (3965 ± 617, mean ± SD) vs 4 month old rats (5525 ± 656), while the concentrations of arachidonic and docosahexaenoic acid were increased in 24 month old rats (79 ± 9 vs 178 ± 27 and 104 ± 16 vs 307 ± 68 for arachidonic and docosahexaenoic acids, 4 months vs 24 months, respectively). Similar changes were not observed in ethanolamine glycerophospholipids or plasma unesterified fatty acids, suggesting specificity of these effects to cardiolipin. CONCLUSION: These results demonstrate that cardiolipin remodeling occurs with aging, specifically an increase in highly unsaturated fatty acids
Multiple Stellar Populations in the Globular Cluster omega Centauri as Tracers of a Merger Event
The discovery of the Sagittarius dwarf galaxy, which is being tidally
disrupted by and merging with the Milky Way, supports the view that the halo of
the Galaxy has been built up at least partially by the accretion of similar
dwarf systems. The Sagittarius dwarf contains several distinct populations of
stars, and includes M54 as its nucleus, which is the second most massive
globular cluster associated with the Milky Way. The most massive globular
cluster is omega Centauri, and here we report that omega Centauri also has
several distinct stellar populations, as traced by red-giant-branch stars. The
most metal-rich red-giant-branch stars are about 2 Gyr younger than the
dominant metal-poor component, indicating that omega Centauri was enriched over
this timescale. The presence of more than one epoch of star formation in a
globular cluster is quite surprising, and suggests that omega Centauri was once
part of a more massive system that merged with the Milky Way, as the
Sagittarius dwarf galaxy is in the process of doing now. Mergers probably were
much more frequent in the early history of the Galaxy and omega Centauri
appears to be a relict of this era.Comment: 7 pages, 3 figures, Latex+nature.sty (included), To appear in
November 4th issue of Natur
Simple scheme for expanding a polarization-entangled W state by adding one photon
We propose a simple scheme for expanding a polarization-entangled W state. By
mixing a single photon and one of the photons in an n-photon W state at a
polarization-dependent beam splitter (PDBS), we can obtain an (n+1)-photon W
state after post-selection. Our scheme also opens the door for generating
n-photon W states using single photons and linear optics.Comment: 3 pages, 2 figure
Quantum teleportation via a W state
We investigate two schemes of the quantum teleportation with a state,
which belongs to a different class from a Greenberger-Horne-Zeilinger class. In
the first scheme, the state is shared by three parties one of whom, called
a sender, performs a Bell measurement. It is shown that quantum information of
an unknown state is split between two parties and recovered with a certain
probability. In the second scheme, a sender takes two particles of the
state and performs positive operator valued measurements in two ways. For two
schemes, we calculate the success probability and the average fidelity. We show
that the average fidelity of the second scheme cannot exceed that of the first
one.Comment: 7 pages, 1 figur
Body-Focused Repetitive Behaviors and Non-Suicidal Self-Injury: A Comparison of Clinical Characteristics and Symptom Features
Body-focused repetitive behaviors (BFRBs) and non-suicidal self-injury (NSSI) are recognized as distinct categories in the DSM-5. However, definitions and assessment of NSSI sometimes encompasses behaviors similar to BFRBs, and little data exist about their clinical differences. The current study examined clinical characteristics and symptom features associated with NSSI vs. BFRBs. The current sample included 1523 individuals who endorsed moderate to severe NSSI (n = 165) or BFRBs: hair pulling group (n = 102), skin picking group (n = 216), nail picking group (n = 253), nail biting group (n = 487), and cheek biting group (n = 300). Responders were asked to complete questionnaires on clinical features relevant for BFRBs and NSSI. NSSI and BFRBs had significant differences on several clinical features. Individuals in the NSSI group were more likely than individuals with BFRBs to report engaging in the behavior for social-affective reasons (i.e., to get out of doing something, or receive attention from others). Individuals in the NSSI group were also more likely to engage in the behavior to regulate tension and feelings of emptiness, and to experience relief during the act. In contrast, individuals in the BFRB groups were more likely to engage in the behavior automatically without reflective awareness, to reduce boredom, or to fix appearance. The NSSI group obtained significantly higher scores on questionnaires assessing stress, anxiety, depression, and harm avoidance. Overall, the results showed several notable differences between NSSI and BFRBs that are consistent with clinical literature and definitions of these problems in the DSM-5
Optical study on doped polyaniline composite films
Localization driven by disorder has a strong influence on the conducting
property of conducting polymer. A class of authors hold the opinion that
disorder in the material is homogeneous and conducting polymer is disordered
metal close to Anderson-Mott Metal-Insulator transition, while others treat the
disorder as inhomogeneous and have the conclusion that conducting polymer is a
composite of ordered metallic regions and disordered insulating regions. The
morphology of conducting polymers is an important factor that have influence on
the type and extent of disorder. Different protonic acids used as dopants and
moisture have affection on polymer chain arrangement and interchain
interactions. A PANI-CSA film, two PANI-CSA/PANI-DBSA composite films with
different dopants ratio, and one of the composite films with different moisture
content are studied. Absolute reflectivity measurements are performed on the
films. Optical conductivity and the real part of dielectric function are
calculated by Kramers-Kronig(KK) relations. and
derivate from simple Drude model in low frequency range
and tendencies of the three sample are different and non-monotonic. The
Localization Modified Drude model(LMD) in the framework of Anderson-Mott theory
can not give a good fit to the experimental data. By introducing a distribution
of relaxation time into LMD, reasonable fits for all three samples are
obtained. This result supports the inhomogeneous picture.Comment: 6 figures, 7 page
Evaluation of the Impact of Iterative Reconstruction Algorithms on Computed Tomography Texture Features of the Liver Parenchyma Using the Filtration-Histogram Method
OBJECTIVE: To evaluate whether computed tomography (CT) reconstruction algorithms affect the CT texture features of the liver parenchyma. MATERIALS AND METHODS: This retrospective study comprised 58 patients (normal liver, n = 34; chronic liver disease [CLD], n = 24) who underwent liver CT scans using a single CT scanner. All CT images were reconstructed using filtered back projection (FBP), hybrid iterative reconstruction (IR) (iDOSE⁴), and model-based IR (IMR). On arterial phase (AP) and portal venous phase (PVP) CT imaging, quantitative texture analysis of the liver parenchyma using a single-slice region of interest was performed at the level of the hepatic hilum using a filtration-histogram statistic-based method with different filter values. Texture features were compared among the three reconstruction methods and between normal livers and those from CLD patients. Additionally, we evaluated the inter- and intra-observer reliability of the CT texture analysis by calculating intraclass correlation coefficients (ICCs). RESULTS: IR techniques affect various CT texture features of the liver parenchyma. In particular, model-based IR frequently showed significant differences compared to FBP or hybrid IR on both AP and PVP CT imaging. Significant variation in entropy was observed between the three reconstruction algorithms on PVP imaging (p 0.75) for CT imaging without filtration. CONCLUSION: CT texture features of the liver parenchyma evaluated using the filtration-histogram method were significantly affected by the CT reconstruction algorithm used
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