370 research outputs found
Altered cochlear innervation in developing and mature naked and Damaraland mole rats
Compared to many other rodent species, naked mole rats (Heterocephalus glaber) have elevated auditory thresholds, poor frequency selectivity, and limited ability to localize sound. Because the cochlea is responsible for encoding and relaying auditory signals to the brain, we used immunofluorescence and quantitative image analysis to examine cochlear innervation in mature and developing naked mole rats compared to mice (Mus musculus), gerbils (Meriones unguiculatus), and Damaraland mole rats (Fukomys damarensis), another subterranean rodent. In comparison to mice and gerbils, we observed alterations in afferent and efferent innervation as well as their patterns of developmental refinement in naked and Damaraland mole rats. These alterations were, however, not always shared similarly between naked and Damaraland mole rats. Most conspicuously, in both naked and Damaraland mole rats, inner hair cell (IHC) afferent ribbon density was reduced, whereas outer hair cell afferent ribbon density was increased. Naked and Damaraland mole rats also showed reduced lateral and medial efferent terminal density. Developmentally, naked mole rats showed reduced and prolonged postnatal reorganization of afferent and efferent innervation. Damaraland mole rats showed no evidence of postnatal reorganization. Differences in cochlear innervation specifically between the two subterranean rodents and more broadly among rodents provides insight into the cochlear mechanisms that enhance frequency sensitivity and sound localization, maturation of the auditory system, and the evolutionary adaptations occurring in response to subterranean environments
Z boson pair production at LHC in a stabilized Randall-Sundrum scenario
We study the Z boson pair production at LHC in the Randall-Sundrum scenario
with the Goldberger-Wise stabilization mechanism. It is shown that
comprehensive account of the Kaluza-Klein graviton and radion effects is
crucial to probe the model: The KK graviton effects enhance the cross section
of on the whole so that the resonance peak of the radion becomes
easy to detect, whereas the RS effects on the process are
rather insignificant. The and invariant-mass distributions are presented
to study the dependence of the RS model parameters. The production of
longitudinally polarized Z bosons, to which the SM contributions are
suppressed, is mainly due to KK gravitons and the radion, providing one of the
most robust methods to signal the RS effects. The sensitivity bounds
on with are also obtained such that
the effective weak scale of order 5 TeV can be experimentally
probed.Comment: 28 pages, LaTex file, 18 eps figure
Deformation independent open brane metrics and generalized theta parameters
We investigate the consequences of generalizing certain well established
properties of the open string metric to the conjectured open membrane and open
Dp-brane metrics. By imposing deformation independence on these metrics their
functional dependence on the background fields can be determined including the
notorious conformal factor. In analogy with the non-commutativity parameter
in the string case, we also obtain `generalized' theta
parameters which are rank q+1 antisymmetric tensors (polyvectors) for open
Dq-branes and rank 3 for the open membrane case. The expressions we obtain for
the open membrane quantities are expected to be valid for general background
field configurations, while the open D-brane quantities are only valid for one
parameter deformations. By reducing the open membrane data to five dimensions,
we show that they, modulo a subtlety with implications for the relation between
OM-theory and NCYM, correctly generate the open string and open D2-data.Comment: 24 pages, LaTe
Light-like noncommutativity and duality from open strings/branes
In this paper we perform some non-trivial tests for the recently obtained
open membrane/D-brane metrics and `generalized' noncommutativity parameters
using Dp/NS5/M5-branes which have been deformed by light-like fields. The
results obtained give further evidence that these open membrane/D-brane metrics
and `generalized' noncommutativity parameters are correct. Further, we use the
open brane data and supergravity duals to obtain more information about
non-gravitational theories with light-like noncommutativity, or `generalized'
light-like noncommutativity. In particular, we investigate various duality
relations (strong coupling limits). In the light-like case we also comment on
the relation between open membrane data (open membrane metric etc.) in six
dimensions and open string data in five dimensions. Finally, we investigate the
strong coupling limit (high energy limit) of five dimensional NCYM with
\Theta^{12}=\Theta^{34}. In particular, we find that this NCYM theory can be UV
completed by a DLCQ compactification of M-theory.Comment: 24 pages, Latex. v2:Comments and references added. v3:Version
published in JHE
Quasinormal modes from potentials surrounding the charged dilaton black hole
We clarify the purely imaginary quasinormal frequencies of a massless scalar
perturbation on the 3D charged-dilaton black holes. This case is quite
interesting because the potential-step appears outside the event horizon
similar to the case of the electromagnetic perturbations on the large
Schwarzschild-AdS black holes. It turns out that the potential-step type
provides the purely imaginary quasinormal frequencies, while the
potential-barrier type gives the complex quasinormal modes.Comment: 19 pages, 8 figure
Search for supersymmetry with a dominant R-parity violating LQDbar couplings in e+e- collisions at centre-of-mass energies of 130GeV to 172 GeV
A search for pair-production of supersymmetric particles under the assumption
that R-parity is violated via a dominant LQDbar coupling has been performed
using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV.
The observed candidate events in the data are in agreement with the Standard
Model expectation. This result is translated into lower limits on the masses of
charginos, neutralinos, sleptons, sneutrinos and squarks. For instance, for
m_0=500 GeV/c^2 and tan(beta)=sqrt(2) charginos with masses smaller than 81
GeV/c^2 and neutralinos with masses smaller than 29 GeV/c^2 are excluded at the
95% confidence level for any generation structure of the LQDbar coupling.Comment: 32 pages, 30 figure
Diverse Beliefs and Time Variability of Risk Premia
Why do risk premia vary over time? We examine this problem theoretically and empirically by studying the effect of market belief on risk premia. Individual belief is taken as a fundamental primitive state variable. Market belief is observable; it is central to the empirical evaluation and we show how to measure it. Our asset pricing model is familiar from the noisy REE literature but we adapt it to an economy with diverse beliefs. We derive equilibrium asset prices and implied risk premium. Our approach permits a closed form solution of prices; hence we trace the exact effect of market belief on the time variability of asset prices and risk premia. We test empirically the theoretical conclusions. Our main result is that, above the effect of business cycles on risk premia, fluctuations in market belief have significant independent effect on the time variability of risk premia. We study the premia on long positions in Federal Funds Futures, 3- and 6-month Treasury Bills (T-Bills). The annual mean risk premium on holding such assets for 1-12 months is about 40-60 basis points and we find that, on average, the component of market belief in the risk premium exceeds 50% of the mean. Since time variability of market belief is large, this component frequently exceeds 50% of the mean premium. This component is larger the shorter is the holding period of an asset and it dominates the premium for very short holding returns of less than 2 months. As to the structure of the premium we show that when the market holds abnormally favorable belief about the future payoff of an asset the market views the long position as less risky hence the risk premium on that asset declines. More generally, periods of market optimism (i.e. "bull" markets) are shown to be periods when the market risk premium is low while in periods of pessimism (i.e. "bear" markets) the market's risk premium is high. Fluctuations in risk premia are thus inversely related to the degree of market optimism about future prospects of asset payoffs. This effect is strong and economically very significant
Active fixturing: literature review and future research directions
Fixtures are used to fixate, position and support workpieces and represent a crucial tool in manufacturing. Their performance determines the result of the whole manufacturing process of a product. There is a vast amount of research done on automatic fixture layout synthesis and optimisation and fixture design verification. Most of this work considers fixture mechanics to be static and the fixture elements to be passive. However, a new generation of fixtures has emerged that has actuated fixture elements for active control of the part–fixture system during manufacturing operations to increase the end product quality. This paper analyses the latest studies in the field of active fixture design and its relationship with flexible and reconfigurable fixturing systems. First, a brief introduction is given on the importance of research of fixturing systems. Secondly, the basics of workholding and fixture design are visited, after which the state-of-the-art in active fixturing and related concepts is presented. Fourthly, part–fixture dynamics and design strategies which take these into account are discussed. Fifthly, the control strategies used in active fixturing systems are examined. Finally, some final conclusions and prospective future research directions are presented
Density functional theory based screening of ternary alkali-transition metal borohydrides: A computational material design project
The dissociation of molecules, even the most simple hydrogen molecule, cannot be described accurately within density functional theory because none of the currently available functionals accounts for strong on-site correlation. This problem led to a discussion of properties that the local Kohn-Sham potential has to satisfy in order to correctly describe strongly correlated systems. We derive an analytic expression for the nontrivial form of the Kohn-Sham potential in between the two fragments for the dissociation of a single bond. We show that the numerical calculations for a one-dimensional two-electron model system indeed approach and reach this limit. It is shown that the functional form of the potential is universal, i.e., independent of the details of the two fragments.We acknowledge funding by the Spanish MEC (Grant No. FIS2007-65702-C02-01), “Grupos Consolidados UPV/EHU del Gobierno Vasco” (Grant No. IT-319-07), and the European Community through e-I3 ETSF project (Grant Agreement No. 211956).Peer reviewe
Density functional theory based screening of ternary alkali-transition metal borohydrides: A computational material design project
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