94 research outputs found
Average shape of fluctuations for subdiffusive walks
We study the average shape of fluctuations for subdiffusive processes, i.e.,
processes with uncorrelated increments but where the waiting time distribution
has a broad power-law tail. This shape is obtained analytically by means of a
fractional diffusion approach. We find that, in contrast with processes where
the waiting time between increments has finite variance, the fluctuation shape
is no longer a semicircle: it tends to adopt a table-like form as the
subdiffusive character of the process increases. The theoretical predictions
are compared with numerical simulation results.Comment: 4 pages, 6 figures. Accepted for publication Phys. Rev. E (Replaced
for the latest version, in press.) Section II rewritte
Spin and energy transfer in nanocrystals without transport of charge
We describe a mechanism of spin transfer between individual quantum dots that
does not require tunneling. Incident circularly-polarized photons create
inter-band excitons with non-zero electron spin in the first quantum dot. When
the quantum-dot pair is properly designed, this excitation can be transferred
to the neighboring dot via the Coulomb interaction with either {\it
conservation} or {\it flipping} of the electron spin. The second dot can
radiate circularly-polarized photons at lower energy. Selection rules for spin
transfer are determined by the resonant conditions and by the strong spin-orbit
interaction in the valence band of nanocrystals. Coulomb-induced energy and
spin transfer in pairs and chains of dots can become very efficient under
resonant conditions. The electron can preserve its spin orientation even in
randomly-oriented nanocrystals.Comment: 13 pages, 3 figure
Knowledge-based energy functions for computational studies of proteins
This chapter discusses theoretical framework and methods for developing
knowledge-based potential functions essential for protein structure prediction,
protein-protein interaction, and protein sequence design. We discuss in some
details about the Miyazawa-Jernigan contact statistical potential,
distance-dependent statistical potentials, as well as geometric statistical
potentials. We also describe a geometric model for developing both linear and
non-linear potential functions by optimization. Applications of knowledge-based
potential functions in protein-decoy discrimination, in protein-protein
interactions, and in protein design are then described. Several issues of
knowledge-based potential functions are finally discussed.Comment: 57 pages, 6 figures. To be published in a book by Springe
Exploring flavor structure of supersymmetry breaking from rare B decays and unitarity triangle
We study effects of supersymmetric particles in various rare B decay
processes as well as in the unitarity triangle analysis. We consider three
different supersymmetric models, the minimal supergravity, SU(5) SUSY GUT with
right-handed neutrinos, and the minimal supersymmetric standard model with U(2)
flavor symmetry. In the SU(5) SUSY GUT with right-handed neutrinos, we consider
two cases of the mass matrix of the right-handed neutrinos. We calculate direct
and mixing-induced CP asymmetries in the b to s gamma decay and CP asymmetry in
B_d to phi K_S as well as the B_s--anti-B_s mixing amplitude for the unitarity
triangle analysis in these models. We show that large deviations are possible
for the SU(5) SUSY GUT and the U(2) model. The pattern and correlations of
deviations from the standard model will be useful to discriminate the different
SUSY models in future B experiments.Comment: revtex4, 36 pages, 10 figure
Enterovirus 71 encephalomyelitis and Japanese encephalitis can be distinguished by topographic distribution of inflammation and specific intraneuronal detection of viral antigen and RNA
Aims: To investigate if two important epidemic viral
encephalitis in children, Enterovirus 71 (EV71)e ncephalomyelitis and Japanese encephalitis (JE) whose clinical and pathological features may be nonspecific and overlapping, could be distinguished.
Methods: Tissue sections from the central nervous system of infected cases were examined by light microscopy, immunohistochemistry and in situ hybridization. Results: All 13 cases of EV71 encephalomyelitis collected from Asia and France invariably showed stereotyped distribution of inflammation in the spinal cord, brainstem, hypothalamus, cerebellar dentate nucleus and, to a lesser extent, cerebral cortex and meninges. Anterior pons, corpus striatum, thalamus, temporal lobe, hippocampus and cerebellar cortex were always uninflamed. In contrast, the eight JE cases studied showed inflammation involving most neuronal areas of the central nervous system, including the areas that were uninflamed in EV71 encephalomyelitis. Lesions in both infections were nonspecific, consisting of perivascular and parenchymal infiltration by inflammatory cells,
oedematous/necrolytic areas, microglial nodules and neuronophagia. Viral inclusions were absent.
Conclusions:
Immunohistochemistry and in situ hybridization assays
were useful to identify the causative virus, localizing viral antigens and RNA, respectively, almost exclusively to neurones. The stereotyped distribution of inflammatory
lesions in EV71 encephalomyelitis appears to be very
useful to help distinguish it from JE
Quantum dots coordinated with conjugated organic ligands: new nanomaterials with novel photophysics
CdSe quantum dots functionalized with oligo-(phenylene vinylene) (OPV) ligands (CdSe-OPV nanostructures) represent a new class of composite nanomaterials with significantly modified photophysics relative to bulk blends or isolated components. Single-molecule spectroscopy on these species have revealed novel photophysics such as enhanced energy transfer, spectral stability, and strongly modified excited state lifetimes and blinking statistics. Here, we review the role of ligands in quantum dot applications and summarize some of our recent efforts probing energy and charge transfer in hybrid CdSe-OPV composite nanostructures
Microflares and the Statistics of X-ray Flares
This review surveys the statistics of solar X-ray flares, emphasising the new
views that RHESSI has given us of the weaker events (the microflares). The new
data reveal that these microflares strongly resemble more energetic events in
most respects; they occur solely within active regions and exhibit
high-temperature/nonthermal emissions in approximately the same proportion as
major events. We discuss the distributions of flare parameters (e.g., peak
flux) and how these parameters correlate, for instance via the Neupert effect.
We also highlight the systematic biases involved in intercomparing data
representing many decades of event magnitude. The intermittency of the
flare/microflare occurrence, both in space and in time, argues that these
discrete events do not explain general coronal heating, either in active
regions or in the quiet Sun.Comment: To be published in Space Science Reviews (2011
An Observational Overview of Solar Flares
We present an overview of solar flares and associated phenomena, drawing upon
a wide range of observational data primarily from the RHESSI era. Following an
introductory discussion and overview of the status of observational
capabilities, the article is split into topical sections which deal with
different areas of flare phenomena (footpoints and ribbons, coronal sources,
relationship to coronal mass ejections) and their interconnections. We also
discuss flare soft X-ray spectroscopy and the energetics of the process. The
emphasis is to describe the observations from multiple points of view, while
bearing in mind the models that link them to each other and to theory. The
present theoretical and observational understanding of solar flares is far from
complete, so we conclude with a brief discussion of models, and a list of
missing but important observations.Comment: This is an article for a monograph on the physics of solar flares,
inspired by RHESSI observations. The individual articles are to appear in
Space Science Reviews (2011
A search for resonances decaying into a Higgs boson and a new particle X in the XH → qqbb final state with the ATLAS detector
A search for heavy resonances decaying into a Higgs boson (H) and a new particle (X) is reported, utilizing 36.1 fb−1 of proton–proton collision data at collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. The particle X is assumed to decay to a pair of light quarks, and the fully hadronic final state is analysed. The search considers the regime of high XH resonance masses, where the X and H bosons are both highly Lorentz-boosted and are each reconstructed using a single jet with large radius parameter. A two-dimensional phase space of XH mass versus X mass is scanned for evidence of a signal, over a range of XH resonance mass values between 1 TeV and 4 TeV, and for X particles with masses from 50 GeV to 1000 GeV. All search results are consistent with the expectations for the background due to Standard Model processes, and 95% CL upper limits are set, as a function of XH and X masses, on the production cross-section of the resonance
Combination of searches for Higgs boson pairs in pp collisions at \sqrts = 13 TeV with the ATLAS detector
This letter presents a combination of searches for Higgs boson pair production using up to 36.1 fb(-1) of proton-proton collision data at a centre-of-mass energy root s = 13 TeV recorded with the ATLAS detector at the LHC. The combination is performed using six analyses searching for Higgs boson pairs decaying into the b (b) over barb (b) over bar, b (b) over barW(+)W(-), b (b) over bar tau(+)tau(-), W+W-W+W-, b (b) over bar gamma gamma and W+W-gamma gamma final states. Results are presented for non-resonant and resonant Higgs boson pair production modes. No statistically significant excess in data above the Standard Model predictions is found. The combined observed (expected) limit at 95% confidence level on the non-resonant Higgs boson pair production cross-section is 6.9 (10) times the predicted Standard Model cross-section. Limits are also set on the ratio (kappa(lambda)) of the Higgs boson self-coupling to its Standard Model value. This ratio is constrained at 95% confidence level in observation (expectation) to -5.0 < kappa(lambda) < 12.0 (-5.8 < kappa(lambda) < 12.0). In addition, limits are set on the production of narrow scalar resonances and spin-2 Kaluza-Klein Randall-Sundrum gravitons. Exclusion regions are also provided in the parameter space of the habemus Minimal Supersymmetric Standard Model and the Electroweak Singlet Model. For complete list of authors see http://dx.doi.org/10.1016/j.physletb.2019.135103</p
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