717 research outputs found
Radiative Generation of the LMA Solution from Small Solar Neutrino Mixing at the GUT Scale
We show that in see-saw models with small or even vanishing lepton mixing
angle , maximal , zero and zero CP
phases at the GUT scale, the currently favored LMA solution of the solar
neutrino problem can be obtained in a rather natural way by Renormalization
Group effects. We find that most of the running takes place in the energy
ranges above and between the see-saw scales, unless the charged lepton Yukawa
couplings are large, which would correspond to a large in the
Minimal Supersymmetric Standard Model (MSSM). The Renormalization Group
evolution of the solar mixing angle is generically larger than
the evolution of and . A large enhancement occurs
for an inverted mass hierarchy and for a regular mass hierarchy with . We present numerical examples of the evolution of the
lepton mixing angles in the Standard Model and the MSSM, in which the current
best-fit values of the LMA mixing angles are produced with vanishing solar
mixing angle at the GUT scale.Comment: 10 pages, 6 figures; reference added, minor changes in the text;
results unchanged; final version to appear in JHE
Weak Field Black Hole Formation in Asymptotically AdS Spacetimes
We use the AdS/CFT correspondence to study the thermalization of a strongly
coupled conformal field theory that is forced out of its vacuum by a source
that couples to a marginal operator. The source is taken to be of small
amplitude and finite duration, but is otherwise an arbitrary function of time.
When the field theory lives on , the source sets up a
translationally invariant wave in the dual gravitational description. This wave
propagates radially inwards in space and collapses to form a black
brane. Outside its horizon the bulk spacetime for this collapse process may
systematically be constructed in an expansion in the amplitude of the source
function, and takes the Vaidya form at leading order in the source amplitude.
This solution is dual to a remarkably rapid and intriguingly scale dependent
thermalization process in the field theory. When the field theory lives on a
sphere the resultant wave either slowly scatters into a thermal gas (dual to a
glueball type phase in the boundary theory) or rapidly collapses into a black
hole (dual to a plasma type phase in the field theory) depending on the time
scale and amplitude of the source function. The transition between these two
behaviors is sharp and can be tuned to the Choptuik scaling solution in
.Comment: 50 pages + appendices, 6 figures, v2: Minor revisions, references
adde
Detecting Microscopic Black Holes with Neutrino Telescopes
If spacetime has more than four dimensions, ultra-high energy cosmic rays may
create microscopic black holes. Black holes created by cosmic neutrinos in the
Earth will evaporate, and the resulting hadronic showers, muons, and taus may
be detected in neutrino telescopes below the Earth's surface. We simulate such
events in detail and consider black hole cross sections with and without an
exponential suppression factor. We find observable rates in both cases: for
conservative cosmogenic neutrino fluxes, several black hole events per year are
observable at the IceCube detector; for fluxes at the Waxman-Bahcall bound,
tens of events per year are possible. We also present zenith angle and energy
distributions for all three channels. The ability of neutrino telescopes to
differentiate hadrons, muons, and possibly taus, and to measure these
distributions provides a unique opportunity to identify black holes, to
experimentally constrain the form of black hole production cross sections, and
to study Hawking evaporation.Comment: 20 pages, 9 figure
Morphology and magnetism of multifunctional nanostructured -FeO films: Simulation and experiments
This paper introduces a new approach for simulating magnetic properties of
nanocomposites comprising magnetic particles embedded in a non-magnetic matrix,
taking into account the 3D structure of the system in which particles'
positions correctly mimic real samples. The proposed approach develops a
multistage simulation procedure in which the size and distribution of particles
within the hosting matrix is firstly attained by means of the Cell Dynamic
System (CDS) model. The 3D structure provided by the CDS step is further
employed in a Monte Carlo (MC) simulation of zero-field-cooled/field-cooled
(ZFC/FC) and magnetic hysteresis loops ( curves) for the system.
Simulations are aimed to draw a realistic picture of the as-produced ultra-thin
films comprising maghemite nanoparticles dispersed in polyaniline. Comparison
(ZFC/FC and curves) between experiments and simulations regarding
the maximum of the ZFC curve (), remanence () and
coercivity () revealed the great accuracy of the multistage approach
proposed here while providing information about the system's morphology and
magnetic properties. For a typical sample the value we found experimentally for
(54 K) was very close to the value provided by the
simulation (53 K). For the parameters depending on the nanoparticle clustering
the experimental values were consistently lower ( = 0.32 and =
210 Oe) than the values we found in the simulation ( = 0.53 and
= 274 Oe). Indeed, the approach introduced here is very promising for the
design of real magnetic nanocomposite samples with optimized features.Comment: 19 pages (one column), 5 figure
Mechanisms of IRF2BPL-related disorders and identification of a potential therapeutic strategy
The recently discovered neurological disorder NEDAMSS is caused by heterozygous truncations in the transcriptional regulator IRF2BPL. Here, we reprogram patient skin fibroblasts to astrocytes and neurons to study mechanisms of this newly described disease. While full-length IRF2BPL primarily localizes to the nucleus, truncated patient variants sequester the wild-type protein to the cytoplasm and cause aggregation. Moreover, patient astrocytes fail to support neuronal survival in coculture and exhibit aberrant mitochondria and respiratory dysfunction. Treatment with the small molecule copper ATSM (CuATSM) rescues neuronal survival and restores mitochondrial function. Importantly, the in vitro findings are recapitulated in vivo, where co-expression of full-length and truncated IRF2BPL in Drosophila results in cytoplasmic accumulation of full-length IRF2BPL. Moreover, flies harboring heterozygous truncations of the IRF2BPL ortholog (Pits) display progressive motor defects that are ameliorated by CuATSM treatment. Our findings provide insights into mechanisms involved in NEDAMSS and reveal a promising treatment for this severe disorder
Nondestructive monitoring of ageing of Alkali resistant Glass fiber reinforced cement (GRC)
Glass fiber reinforced cement (GRC) is a composite material made of portland cement mortar and alkali resistant (AR) fibers. AR fibers are added to portland cement to give the material additional flexural strength and toughness. However, ageing deteriorates the fibers and as a result the improvement in the mechanical properties resulted from the fiber addition disappears as the structure becomes
old. The aim of this paper is monitoring GRC ageing by nondestructive evaluation (NDE) techniques. Two different NDE techniques (1) nonlinear impact resonant acoustic spectroscopy analysis and (2) propagating ultrasonic guided waves are used for this purpose. Both techniques revealed a reduction of the nonlinear behavior in the GRC material with ageing. Specimens are then loaded to failure to obtain their strength and stiffness. Compared to the un-aged specimens,
the aged specimens are found to exhibit more linear behavior, have more stiffness but less toughness. Finally, undisturbed fragments on the fracture surface from mechanical tests are inspected under the electron microscope, to understand the fundamental mechanisms that cause the change in the GRC behavior with ageing.The authors want to acknowledge the financial support of the Ministerio de Ciencia e Innovacion MICINN, Spain, and FEDER funding (Ondacem Project: BIA 2010-19933) and BES-2011-044624. Also thanks to PAID-02-11 Program from Universitat Politecnica de Valencia.Eiras FernĂĄndez, JN.; Kundu, T.; Bonilla Salvador, MM.; Paya Bernabeu, JJ. (2013). Nondestructive monitoring of ageing of Alkali resistant Glass fiber reinforced cement (GRC). Journal of Nondestructive Evaluation - NDT and E International. 32:300-314. https://doi.org/10.1007/s10921-013-0183-yS30031432Bentur, A., Fibre, M.S.: Reinforced Cementitious Composites, 2nd edn. 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Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Evidence of stochastic resonance in the mating behavior of Nezara viridula (L.)
We investigate the role of the noise in the mating behavior between
individuals of Nezara viridula (L.), by analyzing the temporal and spectral
features of the non-pulsed type female calling song emitted by single
individuals. We have measured the threshold level for the signal detection, by
performing experiments with the calling signal at different intensities and
analyzing the insect response by directionality tests performed on a group of
male individuals. By using a sub-threshold signal and an acoustic Gaussian
noise source, we have investigated the insect response for different levels of
noise, finding behavioral activation for suitable noise intensities. In
particular, the percentage of insects which react to the sub-threshold signal,
shows a non-monotonic behavior, characterized by the presence of a maximum, for
increasing levels of the noise intensity. This constructive interplay between
external noise and calling signal is the signature of the non-dynamical
stochastic resonance phenomenon. Finally, we describe the behavioral activation
statistics by a soft threshold model which shows stochastic resonance. We find
that the maximum of the ensemble average of the input-output cross-correlation
occurs at a value of the noise intensity very close to that for which the
behavioral response has a maximum.Comment: 6 pages, 4 figures, to appear in EPJ B (2008
Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV
A search for a Higgs boson decaying into two photons is described. The
analysis is performed using a dataset recorded by the CMS experiment at the LHC
from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an
integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross
section of the standard model Higgs boson decaying to two photons. The expected
exclusion limit at 95% confidence level is between 1.4 and 2.4 times the
standard model cross section in the mass range between 110 and 150 GeV. The
analysis of the data excludes, at 95% confidence level, the standard model
Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The
largest excess of events above the expected standard model background is
observed for a Higgs boson mass hypothesis of 124 GeV with a local significance
of 3.1 sigma. The global significance of observing an excess with a local
significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is
estimated to be 1.8 sigma. More data are required to ascertain the origin of
this excess.Comment: Submitted to Physics Letters
Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV
The Lambda(b) differential production cross section and the cross section
ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum
pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7
TeV using data collected by the CMS experiment at the LHC. The measurements are
based on Lambda(b) decays reconstructed in the exclusive final state J/Psi
Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and
Lambda to proton pion, using a data sample corresponding to an integrated
luminosity of 1.9 inverse femtobarns. The product of the cross section times
the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls
faster than that of b mesons. The measured value of the cross section times the
branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06
+/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for
anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are
statistical and systematic, respectively.Comment: Submitted to Physics Letters
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