2,037 research outputs found
100 Years Later, It Is Still So Powerful : Navigating the Effects of the Armenian Genocide and its Trauma on Armenian American Youth
This thesis examines the effects of the Armenian Genocide on five Armenian American university students ages 18 to 29 in the San Francisco Bay Area. The impact of this event from 100 years ago is passed down generationally and still affects the current descendants of its survivors. Since this genocide is still denied by Turkey, its perpetrators, and by the United States, the impact on Armenians has increased as each generation fights for official recognition.
By conducting semi-structured qualitative interviews, the participants revealed its impact on their identity. This thesis was grounded in intergenerational trauma transmission theory and collective memory theory. The participant narratives revealed that this traumatic event from 100 years ago still affects Armenian American identity and is heightened by the denial. The genocide serves as a collective memory marker for Armenians. The participant narratives also serve as counter-stories to the denial discourse. Their narratives reveal what factors have mobilized the younger generation of Armenian Americans into collective action for global recognition of this genocide. These results can be used as a tool for human rights educators, those active in the genocide recognition, and can be included in genocide curriculum
Radioactive Probes of the Supernova-Contaminated Solar Nebula: Evidence that the Sun was Born in a Cluster
We construct a simple model for radioisotopic enrichment of the protosolar
nebula by injection from a nearby supernova, based on the inverse square law
for ejecta dispersion. We find that the presolar radioisotopes abundances
(i.e., in solar masses) demand a nearby supernova: its distance can be no
larger than 66 times the size of the protosolar nebula, at a 90% confidence
level, assuming 1 solar mass of protosolar material. The relevant size of the
nebula depends on its state of evolution at the time of radioactivity
injection. In one scenario, a collection of low-mass stars, including our sun,
formed in a group or cluster with an intermediate- to high-mass star that ended
its life as a supernova while our sun was still a protostar, a starless core,
or perhaps a diffuse cloud. Using recent observations of protostars to estimate
the size of the protosolar nebula constrains the distance of the supernova at
0.02 to 1.6 pc. The supernova distance limit is consistent with the scales of
low-mass stars formation around one or more massive stars, but it is closer
than expected were the sun formed in an isolated, solitary state. Consequently,
if any presolar radioactivities originated via supernova injection, we must
conclude that our sun was a member of such a group or cluster that has since
dispersed, and thus that solar system formation should be understood in this
context. In addition, we show that the timescale from explosion to the creation
of small bodies was on the order of 1.8 Myr (formal 90% confidence range of 0
to 2.2 Myr), and thus the temporal choreography from supernova ejecta to
meteorites is important. Finally, we can not distinguish between progenitor
masses from 15 to 25 solar masses in the nucleosynthesis models; however, the
20 solar mass model is somewhat preferred.Comment: ApJ accepted, 19 pages, 3 figure
Near Resonantly Enhanced Schlieren for Wake Flow Visualisation in Shock Tunnels
A new variant of the resonantly enhanced schlieren or shadowgraph technique has been developed for visualising flows with small density gradients using seeded lithium metal as the resonant species. The novelty of the technique lies in the use of a diode laser as the light source for the visualisation rather than systems based upon solid-state-pumped dye lasers or spectral lamps. We present time-resolved visualisations of near-wake flows around a cylinder in a hypersonic freestream in a shock tunnel, showing flow structures that cannot be resolved using a conventional standard schlieren system. Furthermore, a method of removing, at least partially, the limitation related to line-ofsight visualisation is demonstrated
Hypersomnia associated with bilateral posterior hypothalamic lesion - A polysomnographic case study
We examined an obese 58-year-old patient with a bilateral posterior hypothalamic lesion of unknown etiology. A 24-hour polysomnography revealed a markedly increased total sleep time (17.6 h). During daytime, only 3 continuous wake phases occurred. REM periods occurred only between 5 p.m. and 6 a.m. We conclude from our results that, similar to the results from animal experiments, the posterior hypothalamus in humans plays a critical role in the maintenance of wakefulness. Copyright (C) 2003 S. Karger AG, Basel
Spin Waves in Quantum Antiferromagnets
Using a self-consistent mean-field theory for the Heisenberg
antiferromagnet Kr\"uger and Schuck recently derived an analytic expression for
the dispersion. It is exact in one dimension () and agrees well with
numerical results in . With an expansion in powers of the inverse
coordination number () we investigate if this expression can be
{\em exact} for all . The projection method of Mori-Zwanzig is used for the
{\em dynamical} spin susceptibility. We find that the expression of Kr\"uger
and Schuck deviates in order from our rigorous result. Our method is
generalised to arbitrary spin and to models with easy-axis anisotropy \D.
It can be systematically improved to higher orders in . We clarify its
relation to the expansion.Comment: 8 pages, uuencoded compressed PS-file, accepted as Euro. Phys. Lette
Spectra of comet P/Halley at R = 4 - 8 AU
Spectra of Comet Halley (lambda lambda = 3400-6500 A) were acquired at pre- and post-perihelion distances of 4.8 AU on 1985 Feb. 17 (Coma V equals 18.9 mag) and 1987 Feb. 1 (coma V = 15.9 mag) using the 4.5-m Multiple-Mirror Telescope (MMT) and the CTIO 4.0-m telescope, respectively. The CN(0,0) violet system band flux at 4.8 AU was approx. 15 times greater at the post-perhelion phase compared to pre-perihelion. Additional post-perihelion spectra, obtained on 1986 Nov. 28 to 30 with the MTT, showed CN(0,0) and very weak C3 4040 A emission. The MMT data are one-dimensional spectra (aperture: 5 arc sec diameter) obtained with an intensified Reticon while the CTIO data are two-dimensional spectra (slit length = 280 arc sec) obtained with a 2D-Frutti photon counting system. Extended CN(0,0) emission was detected in the 1987 Feb. 1 (at 4.8 AU) spectra to a distance of at least 70 arc sec in the solar and anti-solar directions. Additional CCD spectra obtained with the KPNO 2.2-meter telescope on 1988 Feb. 20 (at 7.9 AU) show scattered solar continuum approx. 32 arc sec diameter. However, no emission features were detected at 7.9 AU
Thermal history modeling of the H chondrite parent body
The cooling histories of individual meteorites can be empirically
reconstructed by using ages from different radioisotopic chronometers with
distinct closure temperatures. For a group of meteorites derived from a single
parent body such data permit the reconstruction of the cooling history and
properties of that body. Particularly suited are H chondrites because precise
radiometric ages over a wide range of closure temperatures are available. A
thermal evolution model for the H chondrite parent body is constructed by using
all H chondrites for which at least three different radiometric ages are
available. Several key parameters determining the thermal evolution of the H
chondrite parent body and the unknown burial depths of the H chondrites are
varied until an optimal fit is obtained. The fit is performed by an 'evolution
algorithm'. Empirical data for eight samples are used for which radiometric
ages are available for at least three different closure temperatures. A set of
parameters for the H chondrite parent body is found that yields excellent
agreement (within error bounds) between the thermal evolution model and
empirical data of six of the examined eight chondrites. The new thermal model
constrains the radius and formation time of the H chondrite parent body
(possibly (6) Hebe), the initial burial depths of the individual H chondrites,
the average surface temperature of the body, the average initial porosity of
the material the body accreted from, and the initial 60Fe content of the H
chondrite parent body.Comment: 16 pages, 7 figure
Non-iterative vortex-based smearing correction for the actuator line method
The actuator line method (ALM) is extensively used in wind turbine and rotor
simulations. However, its original uncorrected formulation overestimates the
forces near the tip of the blades and does not reproduce well forces on
translating wings. The recently proposed vortex-based smearing correction for
the ALM is a correction based on physical and mathematical properties of the
simulation that allows for a more accurate and general ALM. So far, to correct
the forces on the blades, the smearing correction depended on an iterative
process at every time step, which is usually slower, less stable and less
deterministic than direct methods. In this work, a non-iterative process is
proposed and validated. First, we propose a formulation of the non-linear
lifting line that is equivalent to the ALM with smearing correction, showing
that their results are practically identical for a translating wing. Then, by
linearizing the lifting line method, the iterative process of the correction is
substituted by the direct solution of a small linear system. No significant
difference is observed in the results of the iterative and non-iterative
corrections, both in wing and rotor simulations. Additional contributions of
the present work include the use of a more accurate approximation for the
velocity induced by a smeared vortex segment and the implementation of a
free-vortex wake model to define the vortex sheet, that contribute to the
accuracy and generality of the method. The results present here may motivate
the adoption of the ALM by other communities, for example, in fixed-wing
applications.Comment: 30 pages, 9 figure
Graphene on Si(111)7x7
We demonstrate that it is possible to mechanically exfoliate graphene under
ultra high vacuum conditions on the atomically well defined surface of single
crystalline silicon. The flakes are several hundred nanometers in lateral size
and their optical contrast is very faint in agreement with calculated data.
Single layer graphene is investigated by Raman mapping. The G and 2D peaks are
shifted and narrowed compared to undoped graphene. With spatially resolved
Kelvin probe measurements we show that this is due to p-type doping with hole
densities of n_h \simeq 6x10^{12} cm^{-2}. The in vacuo preparation technique
presented here should open up new possibilities to influence the properties of
graphene by introducing adsorbates in a controlled way.Comment: 8 pages, 7 figure
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