37,072 research outputs found
The 1982 ASEE-NASA Faculty Fellowship program (Aeronautics and Research)
The NASA/ASEE Summer Faculty Fellowship Program (Aeronautics and Research) conducted at the NASA Goddard Space Flight Center during the summer of 1982 is described. Abstracts of the Final Reports submitted by the Fellows detailing the results of their research are also presented
Radio observations of the cool gas, dust, and star formation in the first galaxies
We summarize cm through submm observations of the host galaxies of z ~ 6
quasars. These observations reveal the cool molecular gas (the fuel for star
formation), the warm dust (heated by star formation), the fine structure line
emission (tracing the CNM and PDRs), and the synchrotron emission. Our results
imply active star formation in ~ 30% of the host galaxies, with star formation
rates ~ 10^3 M_sun/year, and molecular gas masses ~ 10^10 M_sun. Imaging of the
[CII] emission from the most distant quasar reveals a 'maximal starburst disk'
on a scale ~ 1.5 kpc. Gas dynamical studies suggest a departure of these
galaxies from the low-z M_{BH} -- M_{bulge} relation, with the black holes
being, on average, 15 times more massive than expected. Overall, we are
witnessing the co-eval formation of massive galaxies and supermassive black
holes within 1 Gyr of the Big Bang.Comment: First Stars and Galaxies: Challenges in the Next Decade, AIP, 2010;
Austin TX (eds Whelan, Bromm, Yoshida); 7 page
Dust emission and star formation toward a redshift 5.5 QSO
We report observations of the low-luminosity z = 5.50 quasar RD
J030117+002025 (RD0301 hereafter) at 250 GHz (1.20mm) using the Max-Planck
Millimeter Bolometer (MAMBO) array at the IRAM 30-meter telescope. The quasar
was detected with a 1.2mm flux density of 0.87 +-0.20 mJy. The lack of
detectable 1.4 GHz radio emission indicates that the millimeter emission is of
thermal nature, making RD0301 the most distant dust-emission source known. When
matching a 50K grey body thermal far-infrared (FIR) spectrum to the observed
millimeter flux we imply a FIR luminosity ~4x10^12 L_sun, which is comparable
to the quasar's optical luminosity. If the FIR luminosity arises from massive
star formation, the implied star formation rate would be ~600 M_sun/yr,
comparable to that of the starburst galaxies which dominate the average star
formation and FIR emission in the early Universe. The FIR luminosity of RD0301
is close to the average of that found in optically far more luminous
high-redshift quasars. The comparably high millimeter to optical brightness
ratio of RD0301 is further evidence for that there is no strong correlation
between the optical and millimeter brightness of high-redshift quasars,
supporting the idea that in high-redshift quasars the dust is not heated by the
AGN, but by starbursts.Comment: 4 pages, 2 figures, accepted by Astronomy & Astrophysics Letter
Resolution and sensitivity of a Fabry-Perot interferometer with a photon-number-resolving detector
With photon-number resolving detectors, we show compression of interference
fringes with increasing photon numbers for a Fabry-Perot interferometer. This
feature provides a higher precision in determining the position of the
interference maxima compared to a classical detection strategy. We also
theoretically show supersensitivity if N-photon states are sent into the
interferometer and a photon-number resolving measurement is performed.Comment: 8 pages, 12 figures, 1 table, minor extensions, title changed, new
figures added, reference correcte
Effects of lattice mismatch on interfacial structures of liquid and solidified Al in contact with hetero-phase substrates: MD simulations
Published under licence in IOP Conference Series: Material Science and Engineering by IOP Publishing Ltd. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.In this study, the effects of the misfit on in-plane structures of liquid Al and interfacial structure of solidified Al in contact with the heterophase substrates have been investigated, using molecular dynamics (MD) simulations. The MD simulations were conducted for Al/fcc (111) substrates with varied misfits. The order parameter and atomic arrangement indicated that the in-plane ordering of the liquid at the interface decreases significantly with an increase of the misfit, i.e., solid-like for small misfit and liquid-like for large misfit. Further, our MD simulation results revealed that a perfect orientation relationship forms at the interface between the substrate and the solidified Al for a misfit of less than -3% and the boundary is coherent. With an increase in the misfit, Shockley partial and extended dislocations form at the interface, and the boundary becomes a semi-coherent or low-angle twist boundary.EPSR
Soft power: Power of attraction or confusion?
Despite its popularity soft power remains power of confusion. The paper examines the concept, with a special focus on the nature and sources of soft power. Nyeâs notion of soft power is largely ethnocentric and based on the assumption that there is a link between attractiveness and the ability to influence others in international relations. This poses two problems: Firstly, a country has many different actors. Some of them like the attraction and others donât. Whether the attraction will lead to the ability to influence the policy of the target country depends on which groups in that country find it attractive and how much control they have on policymaking. Secondly, policymaking at the state level is far more complicated than at the personal level; and has different dynamics that emphasise the rational considerations. This leaves little room for emotional elements thus significantly reducing the effect of soft power. Given the nature of soft power being uncontrollable and unpredictable, it would be impossible to wield soft power in any organised and coordinated fashion as Nye suggested. Furthermore, the relationship between two countries is shaped by many complex factors. It is ultimately decided by the geopolitics and strategic interests of nations, in which soft power may play only a limited role. The paper also discusses the link between soft power and nation branding as both concepts are concerned with a nationâs influence on the world stage. Public diplomacy is a subset of nation branding that focuses on the political brand of a nation; whereas nation branding is about how a nation as whole to reshape the international opinions. A successful nation branding campaign will help create a more favourable and lasting image among the international audience thus further enhancing a countryâs soft power
High Energy Neutrino Flashes from Far-Ultraviolet and X-ray Flares in Gamma-Ray Bursts
The recent observations of bright optical and x-ray flares by the Swift
satellite suggest these are produced by the late activities of the central
engine. We study the neutrino emission from far-ultraviolet and x-ray flares
under the late internal shock model. We show that the efficiency of pion
production in the highest energy is comparable to or higher than the unity, and
the contribution from such neutrino flashes to a diffuse very high energy
neutrino background can be larger than that of prompt bursts if the total
baryonic energy input into flares is comparable to the radiated energy of
prompt bursts. These signals may be detected by IceCube and are very important
because they have possibilities to probe the nature of flares (the baryon
loading, the photon field, the magnetic field and so on).Comment: 4 pages, 3 figures, version published in PR
The critical Ising lines of the d=2 Ashkin-Teller model
The universal critical point ratio is exploited to determine positions of
the critical Ising transition lines on the phase diagram of the Ashkin-Teller
(AT) model on the square lattice. A leading-order expansion of the ratio in
the presence of a non-vanishing thermal field is found from finite-size scaling
and the corresponding expression is fitted to the accurate perturbative
transfer-matrix data calculations for the square clusters with
.Comment: RevTex, 4 pages, two figure
Ionization near-zones associated with quasars at z ~ 6
We analyze the size evolution of HII regions around 27 quasars between z=5.7
to 6.4 ('quasar near-zones' or NZ). We include more sources than previous
studies, and we use more accurate redshifts for the host galaxies, with 8 CO
molecular line redshifts and 9 MgII redshifts. We confirm the trend for an
increase in NZ size with decreasing redshift, with the luminosity normalized
proper size evolving as: R_{NZ,corrected} = (7.4 \pm 0.3) - (8.0 \pm 1.1)
\times (z-6) Mpc. While derivation of the absolute neutral fraction remains
difficult with this technique, the evolution of the NZ sizes suggests a
decrease in the neutral fraction of intergalactic hydrogen by a factor ~ 9.4
from z=6.4 to 5.7, in its simplest interpretation. Alternatively, recent
numerical simulations suggest that this rapid increase in near-zone size from
z=6.4 to 5.7 is due to the rapid increase in the background photo-ionization
rate at the end of the percolation or overlap phase, when the average mean free
path of ionizing photons increases dramatically. In either case, the results
are consistent with the idea that z ~ 6 to 7 corresponds to the tail end of
cosmic reionization. The scatter in the normalized NZ sizes is larger than
expected simply from measurement errors, and likely reflects intrinsic
differences in the quasars or their environments. We find that the near-zone
sizes increase with quasar UV luminosity, as expected for photo-ionization
dominated by quasar radiation.Comment: 16 pages, aas format, 4 figures, to appear in the ApJ letter
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