3,785 research outputs found
Multi-wavelength Stellar Polarimetry of the Filamentary Cloud IC5146: I. Dust Properties
We present optical and near-infrared stellar polarization observations toward
the dark filamentary clouds associated with IC5146. The data allow us to
investigate the dust properties (this paper) and the magnetic field structure
(Paper II). A total of 2022 background stars were detected in -, -,
-, and/or -bands to mag. The ratio of the polarization
percentage at different wavelengths provides an estimate of ,
the wavelength of peak polarization, which is an indicator of the small-size
cutoff of the grain size distribution. The grain size distribution seems to
significantly change at 3 mag, where both the average and dispersion
of decrease. In addition, we found
0.6-0.9 m for mag, which is larger than the 0.55 m
in the general ISM, suggesting that grain growth has already started in low
regions. Our data also reveal that polarization efficiency (PE ) decreases with as a power-law in -, -, and
-bands with indices of -0.710.10, -1.230.10 and -0.530.09.
However, -band data show a power index change; the PE varies with
steeply (index of -0.950.30) when mag but softly
(index of -0.250.06) for greater values. The soft decay of PE in
high regions is consistent with the Radiative Aligned Torque model,
suggesting that our data trace the magnetic field to mag.
Furthermore, the breakpoint found in -band is similar to the where we
found the dispersion significantly decreased. Therefore, the
flat PE- in high regions implies that the power index changes result
from additional grain growth.Comment: 31 pages, 17 figures, and 3 tables; accepted for publication in Ap
A Critical Examination of Hypernova Remnant Candidates in M101. II. NGC 5471B
NGC 5471B has been suggested to contain a hypernova remnant because of its
extraordinarily bright X-ray emission. To assess its true nature, we have
obtained high-resolution images in continuum bands and nebular lines with the
Hubble Space Telescope, and high-dispersion long-slit spectra with the Kitt
Peak National Observatory 4-m echelle spectrograph. The images reveal three
supernova remnant (SNR) candidates in the giant HII region NGC 5471, with the
brightest one being the 77x60 pc shell in NGC 5471B. The Ha velocity profile of
NGC 5471B can be decomposed into a narrow component (FWHM = 41 km/s) from the
background HII region and a broad component (FWHM = 148 km/s) from the SNR
shell. Using the brightness ratio of the broad to narrow components and the Ha
flux measured from the WFPC2 Ha image, we derive an Ha luminosity of
(1.4+-0.1)x10^39 ergs/s for the SNR shell. The [SII]6716,6731 doublet ratio of
the broad velocity component is used to derive an electron density of ~700
cm^-3 in the SNR shell. The mass of the SNR shell is thus 4600+-500 Mo. With a
\~330 km/s expansion velocity implied by the extreme velocity extent of the
broad component, the kinetic energy of the SNR shell is determined to be
5x10^51 ergs. This requires an explosion energy greater than 10^52 ergs, which
can be provided by one hypernova or multiple supernovae. Comparing to SNRs in
nearby active star formation regions, the SNR shell in NGC 5471B appears truly
unique and energetic. We conclude that the optical observations support the
existence of a hypernova remnant in NGC 5471B.Comment: 27 pages, 9 figures, to appear in May 2002 issue of The Astronomical
Journa
Recovery from Anorexia Nervosa in contemporary Taiwan: A multiple-case qualitative investigation from a cultural-contextual perspective
Grounded in a cultural and contextual perspective, the current study examined the lived experiences and the recovery pathways of three Taiwanese women diagnosed with various subtypes of anorexia nervosa, at varying stages of their recovery. Specifically, using a multiple-case qualitative method, this study explored the complex, dynamic interactions of sociocultural factors and forces (i.e., cultural, familial, and societal influences) that impinge upon the three Taiwanese female participants in relation to living with anorexia nervosa in contemporary Taiwan. Data were collected based on in-depth, semi-structured interviews with the participants and relevant written materials and journal entries provided by these participants. The data were first analyzed within each case and then again across all cases. Accordingly, we present the results of the study by illustrating each participant’s story and narrative of struggling with and recovering from anorexia. We then describe three main culturally-related themes that emerged from the cross-case analysis, which pertain specifically to the recovery process of the participants under the East-West ‘biculturalism’ in Taiwan: 1) anorexia as a function of the conflictual bicultural self; 2) recovery as a pathway towards an integrated bicultural self; and 3) the paradoxical roles of Chinese cultural heritage in anorexia and recovery. Findings of the study highlight the role of local cultural factors/forces, including Chinese familism, Confucianism, filial piety, face-saving, gender role prescriptions, biculturalism, Westernization, and self-relation-coordination, in affecting and shaping Taiwanese women’s struggling with anorexia. Implications and recommendations for future research and clinical interventions are discussed
ONLINE AUCTION EFFECTIVENESS: OPTIMAL SELLING STRATEGIES FOR ONLINE AUCTION MARKET
The introduction of internet auction has significantly widened the pool of consumers who participate in auctions and increased the number of companies attempting to sell their products in an auction format. Previous empirical research on auctions has focused almost exclusively on the behavior of professional bidders. In this study, we collect data on a large number of internet auctions to explore the outcome of the auction in a real marketplace. In particular, we focus on the characteristic of seller, auction parameter and the effect of supply and demand, and examine these impacts on auction effectiveness
Realizing bending waveguides with anisotropic epsilon-near-zero metamaterials
We study metamaterials with an anisotropic effective permittivity tensor in
which one component is near zero. We find that such an anisotropic metamaterial
can be used to control wave propagation and construct almost perfect bending
waveguides with a high transmission rate (>95%). This interesting effect
originates in the power flow redistribution by the surface waves on the input
and output interfaces, which smoothly matches with the propagating modes inside
the metamaterial waveguide. We also find that waves in such anisotropic
epsilon-near-zero materials can be reflected by small-sized perfect magnetic
conductor defects. Numerical calculations have been performed to confirm the
above effects
catena-Poly[[[bisÂ(4-aminoÂbenzoato-κO)copper(II)]-μ-1,1′-(pentane-1,5-diÂyl)diimidazole] trihydrate]
In the title compound, {[Cu(C7H6NO2)2(C11H16N4)]·3H2O}n, each CuII atom is coordinated by two O atoms from two 4-aminoÂbenzoate anions, and two N atoms from two different 1,1′-(pentane-1,5-diÂyl)diimidazole (biim-5) ligands, to furnish a distorted square-planar geometry. The biim-5 ligand coordinates to two copper(II) cations, acting as a bridging ligand; as a result the copper(II) cations are connected to form an infinite chain structure. The polymeric chains are linked through a variety of hydrogen bonds to form a three-dimensional structure
Using DMA to Simultaneously Acquire Young's Relaxation Modulus and Time-dependent Poisson's Ratio of a Viscoelastic Material
AbstractA method to obtain the Young's relaxation modulus and time-dependent Poisson's ratio simultaneously by using DMA is developed with the assumption of constant bulk modulus instead of constant Poisson's ratio. The constant bulk modulus is then calculated by either instantaneous response or the equilibrium response of the time-dependent Poisson's ratio. The modulating Young's moduli and characteristic times that measured by DMA are corrected analytically by using the developed formulas. The time-dependent Poisson's ratio is then obtained from the corrected modulating Young's moduli and the constant bulk modulus. As an application example, the method is applied to the DMA measurement of an epoxy molding compound (EMC). Although the correction to Young's relaxation modulus is very small, the viscoelastic Poisson's ratio varies significantly over time from 0.4 to 0.496, and can’t be assumed as a constant
- …