339 research outputs found
Removing Orbital Debris with Lasers
Orbital debris in low Earth orbit (LEO) are now sufficiently dense that the
use of LEO space is threatened by runaway collisional cascading. A problem
predicted more than thirty years ago, the threat from debris larger than about
1 cm demands serious attention. A promising proposed solution uses a high power
pulsed laser system on the Earth to make plasma jets on the objects, slowing
them slightly, and causing them to re-enter and burn up in the atmosphere. In
this paper, we reassess this approach in light of recent advances in low-cost,
light-weight modular design for large mirrors, calculations of laser-induced
orbit changes and in design of repetitive, multi-kilojoule lasers, that build
on inertial fusion research. These advances now suggest that laser orbital
debris removal (LODR) is the most cost-effective way to mitigate the debris
problem. No other solutions have been proposed that address the whole problem
of large and small debris. A LODR system will have multiple uses beyond debris
removal. International cooperation will be essential for building and operating
such a system.Comment: 37 pages, 15 figures, in preparation for submission to Advances in
Space Researc
An Equation of State of a Carbon-Fibre Epoxy Composite under Shock Loading
An anisotropic equation of state (EOS) is proposed for the accurate
extrapolation of high-pressure shock Hugoniot (anisotropic and isotropic)
states to other thermodynamic (anisotropic and isotropic) states for a shocked
carbon-fibre epoxy composite (CFC) of any symmetry. The proposed EOS, using a
generalised decomposition of a stress tensor [Int. J. Plasticity \textbf{24},
140 (2008)], represents a mathematical and physical generalisation of the
Mie-Gr\"{u}neisen EOS for isotropic material and reduces to this equation in
the limit of isotropy. Although a linear relation between the generalised
anisotropic bulk shock velocity and particle velocity was
adequate in the through-thickness orientation, damage softening process
produces discontinuities both in value and slope in the -
relation. Therefore, the two-wave structure (non-linear anisotropic and
isotropic elastic waves) that accompanies damage softening process was proposed
for describing CFC behaviour under shock loading. The linear relationship
- over the range of measurements corresponding to non-linear
anisotropic elastic wave shows a value of (the intercept of the
- curve) that is in the range between first and second
generalised anisotropic bulk speed of sound [Eur. Phys. J. B \textbf{64}, 159
(2008)]. An analytical calculation showed that Hugoniot Stress Levels (HELs) in
different directions for a CFC composite subject to the two-wave structure
(non-linear anisotropic elastic and isotropic elastic waves) agree with
experimental measurements at low and at high shock intensities. The results are
presented, discussed and future studies are outlined.Comment: 12 pages, 9 figure
Biopedagogies and Indigenous knowledge: examining sport for development and peace for urban Indigenous young women in Canada and Australia
This paper uses transnational postcolonial feminist participatory action research (TPFPAR) to examine two sport for development and peace (SDP) initiatives that focus on Indigenous young women residing in urban areas, one in Vancouver, Canada, and one in Perth, Australia. We examine how SDP programs that target urban Indigenous young women and girls reproduce the hegemony of neoliberalism by deploying biopedagogies of neoliberalism to \u27teach\u27 Indigenous young women certain education and employment skills that are deemed necessary to participate in competitive capitalism. We found that activities in both programs were designed to equip the Indigenous girls and young women with individual attributes that would enhance their chances of future success in arenas valued by neoliberal capitalism: Eurocentric employment, post-secondary education and healthy active living. These forms of \u27success\u27 fall within neoliberal logic, where the focus is on the individual being able to provide for oneself. However, the girls and young women we interviewed argued that their participation in the SDP programs would help them change racist and sexist stereotypes about their communities and thereby challenged negative stereotypes. Thus, it is possible that these programs, despite their predominant use of neoliberal logic and biopedagogies, may help to prepare the participants to more successfully negotiate Eurocentric institutions, and through this assist them participants in contributing to social change. Nevertheless, based on our findings, we argue that SDP programs led by Indigenous peoples that are fundamentally shaped by Indigenous voices, epistemologies, concerns and standpoints would provide better opportunities to shake SDP\u27s current biopedagogical foundation. We conclude by suggesting that a more radical approach to SDP, one that fosters Indigenous self-determination and attempts to disrupt dominant relations of power, could have difficulty in attracting the sort of corporate donors who currently play such important roles in the current SDP landscape
Hyperfine Spectroscopy of Isotopically Engineered Group-IV Color Centers in Diamond
A quantum register coupled to a spin-photon interface is a key component in
quantum communication and information processing. Group-IV color centers in
diamond (SiV, GeV, and SnV) are promising candidates for this application,
comprising an electronic spin with optical transitions coupled to a nuclear
spin as the quantum register. However, the creation of a quantum register for
these color centers with deterministic and strong coupling to the spin-photon
interface remains challenging. Here, we make first-principles predictions of
the hyperfine parameters of the group-IV color centers, which we verify
experimentally with a comprehensive comparison between the spectra of spin
active and spin neutral intrinsic dopant nuclei in single GeV and SnV emitters.
In line with the theoretical predictions, detailed spectroscopy on large sample
sizes reveals that hyperfine coupling causes a splitting of the optical
transition of SnV an order of magnitude larger than the optical linewidth and
provides a magnetic-field insensitive transition. This strong coupling provides
access to a new regime for quantum registers in diamond color centers, opening
avenues for novel spin-photon entanglement and quantum sensing schemes for
these well-studied emitters
1962: Abilene Christian College Bible Lectures - Full Text
THE RESTORATION PRINCIPLEâ
Being the Abilene Christian College Annual Bible Lectures 1962
Price: $3.95
Published by
ABILENE CHRISTIAN COLLEGE
STUDENTS EXCHANGE
ACC Station Abilene, Texa
Heritability and mechanisms of n-3 long chain polyunsaturated fatty acid deposition in the flesh of Atlantic salmon
N-3 long chain polyunsaturated fatty acids (n-3LC-PUFA) are essential components of vertebrate membrane lipids and are crucially deficient in modern Western diets. The main human dietary source for n-3LC-PUFA is fish and seafood, particularly oily fish and over 50% of global fish production is currently supplied by aquaculture. However, increasing pressure to include vegetable oils, which are devoid of n-3LC-PUFA, in aquaculture feeds reduces the content of these crucial nutrients in farmed fish flesh. The aim of this study was to measure the heritability and infer mechanisms determining flesh n-3LC-PUFA content in Atlantic salmon. This was achieved by analysing flesh lipid parameters in 48 families of Atlantic salmon, and by measuring differences in hepatic mRNA expression in families with high and low flesh n-3LC-PUFA. The results show that flesh n-3LC-PUFA level is a highly heritable trait (h2 = 0.77±0.14) and indicate the involvement of increased lipid transport, most likely in the form of very low density lipoprotein (VLDL) from liver. This increase in lipid transport may be associated with increased activity of a transcription factor, hepatic nuclear factor 4α (HNF4α), possibly as a result of family differences in transforming growth factor ÎČ1 (TgfÎČ1) signalling. This study paves the way for identification of quantitative trait loci and gene interaction networks that are associated with levels of n-3LC-PUFA in fish flesh. Such markers can be used to assist the sustainable production of Atlantic salmon and provide optimal levels of critical nutrients for human consumers
Positive and negative effects of antipsychotic medication: an international online survey of 832 recipients
Background: Antipsychotic medication is currently the treatment of choice for psychosis, but few studies directly survey the first hand experience of recipients.
Objectives: To ascertain the experiences and opinions of users of an international sample of antipsychotic drugs regarding positive and negative effects.
Method: An online direct-to-consumer questionnaire was completed by 832 users of antipsychotics, from 30 countries â predominantly USA, UK and Australia. This is the largest such sample to date.
Results: Over half (56%) thought the drugs reduced the problems they were prescribed for, but 27% thought they made them worse. Slightly less people found the drugs generally âHelpfulâ (41%) than found them âUnhelpfulâ (43%). While 35% reported that their âquality of lifeâ was âimprovedâ, 54% reported that it was made âworseâ. The average number of adverse effects reported was 11, with an average of five at the âsevereâ level. Fourteen effects were reported by 57% or more participants, most commonly: âDrowsiness, feeling tired, sedationâ (92%), âLoss of motivationâ (86%), âSlowed thoughtsâ (86%), and âEmotional numbingâ (85%). Suicidality was reported to be a side effect by 58%. Older people reported particularly poor outcomes and high levels of adverse effects. Duration of treatment was unrelated to positive outcomes but significantly related to negative outcomes. Most respondents (70%) had tried to stop taking the drugs. The most common reasons people wanted to stop were the side effects (64%) and worries about long-term physical health (52%). Most (70%) did not recall being told anything at all about side effects.
Conclusions Clinical implications are discussed, with a particular focus on the principles of informed consent, and involving patients in decision making about their own lives
Developmental Regulation of Hepatitis B Virus Biosynthesis by Hepatocyte Nuclear Factor 4α
The host cellular factors that promote persistent viral infections in vivo are, in general, poorly understood. Utilizing the hepatitis B virus (HBV) transgenic mouse model of chronic infection, we demonstrate that the nuclear receptor, hepatocyte nuclear factor 4α (HNF4α, NR2A1), is essential for viral biosynthesis in the liver. The dependency of HBV transcription on HNF4α links viral biosynthesis and persistence to a developmentally regulated transcription factor essential for host viability
Molecular imaging of glycan chains couples cell-wall polysaccharide architecture to bacterial cell
Biopolymer composite cell walls maintain cell shape and resist forces in plants, fungi and
bacteria. Peptidoglycan, a crucial antibiotic target and immunomodulator, performs this role
in bacteria. The textbook structural model of peptidoglycan is a highly ordered, crystalline
material. Here we use atomic force microscopy (AFM) to image individual glycan chains in
peptidoglycan from Escherichia coli in unprecedented detail. We quantify and map the extent
to which chains are oriented in a similar direction (orientational order), showing it is much
less ordered than previously depicted. Combining AFM with size exclusion chromatography,
we reveal glycan chains up to 200 nm long. We show that altered cell shape is associated
with substantial changes in peptidoglycan biophysical properties. Glycans from E. coli in its
normal rod shape are long and circumferentially oriented, but when a spheroid shape is
induced (chemically or genetically) glycans become short and disordered
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