755 research outputs found
Traumatic brain injury: future assessment tools and treatment prospects
Traumatic brain injury (TBI) is widespread and leads to death and disability in millions of individuals around the world each year. Overall incidence and prevalence of TBI are likely to increase in absolute terms in the future. Tackling the problem of treating TBI successfully will require improvements in the understanding of normal cerebral anatomy, physiology, and function throughout the lifespan, as well as the pathological and recuperative responses that result from trauma. New treatment approaches and combinations will need to be targeted to the heterogeneous needs of TBI populations. This article explores and evaluates the research evidence in areas that will likely lead to a reduction in TBI-related morbidity and improved outcomes. These include emerging assessment instruments and techniques in areas of structural/chemical and functional neuroimaging and neuropsychology, advances in the realms of cell-based therapies and genetics, promising cognitive rehabilitation techniques including cognitive remediation and the use of electronic technologies including assistive devices and virtual reality, and the emerging field of complementary and alternative medicine
AdS/CFT and gravity
The radiation-dominated k=0 FRW cosmology emerges as the induced metric on a
codimension one hypersurface of constant extrinsic curvature in the
five-dimensional AdS-Schwarzschild solution. That we should get FRW cosmology
in this way is an expected result from AdS/CFT in light of recent comments
regarding the coupling of gravity to "boundary" conformal field theories. I
remark on how this calculation bears on the understanding of Randall and
Sundrum's "alternative to compactification." A generalization of the AdS/CFT
prescription for computing Green's functions is suggested, and it is shown how
gravity emerges from it with a strength G_4 = 2 G_5/L. Some numerical bounds
are set on the radius of curvature L of AdS_5. One of them comes from
estimating the rate of leakage of visible sector energy into the CFT. That rate
is connected via a unitarity relation to deviations from Newton's force law at
short distances. The best bound on L obtained in this paper comes from a match
to the parameters of string theory. It is L < 1 nm if the string scale is 1
GeV. Higher string scales imply a tighter bound on L.Comment: 27 pages, two figures, latex. v2: No log in first correction to
Newton's law! Refs added, other minor improvements. v3: Refinements and
further ref
Upper limits on the strength of periodic gravitational waves from PSR J1939+2134
The first science run of the LIGO and GEO gravitational wave detectors
presented the opportunity to test methods of searching for gravitational waves
from known pulsars. Here we present new direct upper limits on the strength of
waves from the pulsar PSR J1939+2134 using two independent analysis methods,
one in the frequency domain using frequentist statistics and one in the time
domain using Bayesian inference. Both methods show that the strain amplitude at
Earth from this pulsar is less than a few times .Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo
Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July
200
Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
The predictive mirror: interactions of mirror and affordance processes during action observation
An important question for the study of social interactions is how the motor actions of others are represented. Research has demonstrated that simply watching someone perform an action activates a similar motor representation in oneself. Key issues include (1) the automaticity of such processes, and (2) the role object affordances play in establishing motor representations of others’ actions. Participants were asked to move a lever to the left or right to respond to the grip width of a hand moving across a workspace. Stimulus-response compatibility effects were modulated by two task-irrelevant aspects of the visual stimulus: the observed reach direction and the match between hand-grasp and the affordance evoked by an incidentally presented visual object. These findings demonstrate that the observation of another person’s actions automatically evokes sophisticated motor representations that reflect the relationship between actions and objects even when an action is not directed towards an object
DER OKONOMISCHE EFFEKT EINER ERHOHUNG DER ARBEITSLOSENLEISTUNGEN : NEUBETRACHT UNTER VERWENDUNG DES ATKINSON MODELLS
In der zweiten Halfte der 1970er begannen sich wirtschaftliche Kennziffern industrialisierter Staaten rapide zu verschlechtern. Gleichzeitig ruckte der Wohlfahrtsstaat als Ursache in das Zentrum der Kritik. Einige Wirtschaftswissenschaftler, insbesondere die deutschen Neo- Liberalisten, hatten bereits seit den 1950ern eine kritische Haltung zum wohlfahrtsstaatlichen Konzept eingenommen. Seit den 1970ern gesellten sich zu diesen Liberalisten auch viele Wirtschaftswissenschaftler, die zuvor den Wohlfahrtsstaat unterstutzt hatten. A.B. Atkinson wies jedoch daraufhin, daB viele der verwandten okonomischen Analysen auf un- fundierten theoretischen Modellen basierten, die die eigentlichen Merkmale des sozialen Wohlfahrtsprogramms auBer Acht lieBen. In der vorliegenden Arbeit gehen wir daher, den wirtschaftlichen Auswirkungen der Arbeitslosenversicherung in Einklang mit Atkinsons Kritik nach. Es gelang ihm gegenteilige Ergebnisse zu dem popularen Shapiro und Stiglitz Shirking Modell, durch Einfuhrung zweier Annahmen, d.h. Arbeitslosenleistungen werden identifizierten Shirkern vorenthalten und Arbeitslosenleistungen werden generell nur fur einen bestimmten Zeitraum angeboten, nachzuweisen. In der vorliegenden Arbeit zeigen wir, daB Gehalt basierende Arbeitslosenleistungen sich positiv auf Produktivitat und Beschaftigung auswirken. Zeitliche Begrenzung und eine ansteigende Sockelleistung alleine haben nicht die gleichen Ergebnisse im Shapiro und Stiglitz Modell
Private Sector Union Density and the Wage Premium: Past, Present, and Future
The rise and decline of private sector unionization were among the more important features of the U.S. labor market during the twentieth century. Following a dramatic spurt in unionization after passage of the depression-era National Labor Relations Act (NLRA) of 1935, union density peaked in the mid-1950s, and then began a continuous decline. At the end of the century, the percentage of private wage and salary workers who were union members was less than 10 percent, not greatly different from union density prior to the NLRA
The Rac GTP Exchange Factor TIAM-1 Acts with CDC-42 and the Guidance Receptor UNC-40/DCC in Neuronal Protrusion and Axon Guidance
The mechanisms linking guidance receptors to cytoskeletal dynamics in the growth cone during axon extension remain mysterious. The Rho-family GTPases Rac and CDC-42 are key regulators of growth cone lamellipodia and filopodia formation, yet little is understood about how these molecules interact in growth cone outgrowth or how the activities of these molecules are regulated in distinct contexts. UNC-73/Trio is a well-characterized Rac GTP exchange factor in Caenorhabditis elegans axon pathfinding, yet UNC-73 does not control CED-10/Rac downstream of UNC-6/Netrin in attractive axon guidance. Here we show that C. elegans TIAM-1 is a Rac-specific GEF that links CDC-42 and Rac signaling in lamellipodia and filopodia formation downstream of UNC-40/DCC. We also show that TIAM-1 acts with UNC-40/DCC in axon guidance. Our results indicate that a CDC-42/TIAM-1/Rac GTPase signaling pathway drives lamellipodia and filopodia formation downstream of the UNC-40/DCC guidance receptor, a novel set of interactions between these molecules. Furthermore, we show that TIAM-1 acts with UNC-40/DCC in axon guidance, suggesting that TIAM-1 might regulate growth cone protrusion via Rac GTPases in response to UNC-40/DCC. Our results also suggest that Rac GTPase activity is controlled by different GEFs in distinct axon guidance contexts, explaining how Rac GTPases can specifically control multiple cellular functions
Megascopic Quantum Phenomena. A Critical Study of Physical Interpretations
A megascopic revalidation is offered providing responses and resolutions of
current inconsistencies and existing contradictions in present-day quantum
theory. As the core of this study we present an independent proof of the
Goldstone theorem for a quantum field formulation of molecules and solids.
Along with phonons two types of new quasiparticles appear: rotons and
translons. In full analogy with Lorentz covariance, combining space and time
coordinates, a new covariance is necessary, binding together the internal and
external degrees of freedom, without explicitly separating the centre-of-mass,
which normally applies in both classical and quantum formulations. The
generally accepted view regarding the lack of a simple correspondence between
the Goldstone modes and broken symmetries, has significant consequences: an
ambiguous BCS theory as well as a subsequent Higgs mechanism. The application
of the archetype of the classical spontaneous symmetry breaking, i.e. the
Mexican hat, as compared to standard quantum relations, i.e. the Jahn-Teller
effect, superconductivity or the Higgs mechanism, becomes a disparity. In
short, symmetry broken states have a microscopic causal origin, but transitions
between them have a teleological component. The different treatments of the
problem of the centre of gravity in quantum mechanics and in field theories
imply a second type of Bohr complementarity on the many-body level opening the
door for megascopic representations of all basic microscopic quantum axioms
with further readings for teleonomic megascopic quantum phenomena, which have
no microscopic rationale: isomeric transitions, Jahn-Teller effect, chemical
reactions, Einstein-de Haas effect, superconductivity-superfluidity, and
brittle fracture.Comment: 117 pages, 17 sections, final revised version from 20 May 2019 but
uploaded after the DOI was know
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