20,512 research outputs found
Characterization of K+ currents and the cAMP-dependent modulation in cultured Drosophila mushroom body neurons identified by lacZ expression
Electrophysiological analysis of cultured neurons provides a potential approach toward understanding the physiological defects that may contribute to abnormal behavior exhibited by mutants of the fruit fly Drosophila. However, its application has been restricted by an inability to identify a particular functional or anatomical subpopulation of neurons from the CNS. To study neurons composing the CNS mushroom body proposed as a center for insect olfactory learning, we utilized a Drosophila enhancer detector line that expresses a lacZ reporter gene in these neurons and identified them in acutely dissociated larval CNS cultures by vital fluorescent staining. The patch-clamp analysis suggests that whole-cell voltage-activated K+ currents can be classified into two types in identified mushroom body neurons. Type 1 current comprises a TEA-sensitive slowly inactivating current and noninactivating component while type 2 current contains a 4-AP-sensitive transient A-current and a noninactivating component. Application of cAMP analogs induced distinct modulation of type 1 and type 2 currents. Our results demonstrate that the expression of the lacZ gene and the subsequent staining do not significantly alter the different types of K+ currents. This initial characterization provides a basis for further analysis of mutations that impair learning and memory resulting from an abnormal cAMP cascade preferentially expressed in the mushroom body
Treatment with convalescent plasma for influenza A (H5N1) infection [9]
published_or_final_versio
QCD evolution of naive-time-reversal-odd fragmentation functions
We study QCD evolution equations of the first transverse-momentum-moment of
the naive-time-reversal-odd fragmentation functions - the Collins function and
the polarizing fragmentation function. We find for the Collins function case
that the evolution kernel has a diagonal piece same as that for the
transversity fragmentation function, while for the polarizing fragmentation
function case this piece is the same as that for the unpolarized fragmentation
function. Our results might have important implications in the current global
analysis of spin asymmetries.Comment: 8 pages,4 figure
Time-reversal-symmetry-broken quantum spin Hall effect
Quantum spin Hall (QSH) state of matter is usually considered to be protected
by time-reversal (TR) symmetry. We investigate the fate of the QSH effect in
the presence of the Rashba spin-orbit coupling and an exchange field, which
break both inversion and TR symmetries. It is found that the QSH state
characterized by nonzero spin Chern numbers persists when the
TR symmetry is broken. A topological phase transition from the TR
symmetry-broken QSH phase to a quantum anomalous Hall phase occurs at a
critical exchange field, where the bulk band gap just closes. It is also shown
that the transition from the TR symmetry-broken QSH phase to an ordinary
insulator state can not happen without closing the band gap.Comment: 5 pages, 5 figure
Optimal queue-size scaling in switched networks
We consider a switched (queuing) network in which there are constraints on
which queues may be served simultaneously; such networks have been used to
effectively model input-queued switches and wireless networks. The scheduling
policy for such a network specifies which queues to serve at any point in time,
based on the current state or past history of the system. In the main result of
this paper, we provide a new class of online scheduling policies that achieve
optimal queue-size scaling for a class of switched networks including
input-queued switches. In particular, it establishes the validity of a
conjecture (documented in Shah, Tsitsiklis and Zhong [Queueing Syst. 68 (2011)
375-384]) about optimal queue-size scaling for input-queued switches.Comment: Published in at http://dx.doi.org/10.1214/13-AAP970 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Qualitative properties of -fair policies in bandwidth-sharing networks
We consider a flow-level model of a network operating under an -fair
bandwidth sharing policy (with ) proposed by Roberts and
Massouli\'{e} [Telecomunication Systems 15 (2000) 185-201]. This is a
probabilistic model that captures the long-term aspects of bandwidth sharing
between users or flows in a communication network. We study the transient
properties as well as the steady-state distribution of the model. In
particular, for , we obtain bounds on the maximum number of flows
in the network over a given time horizon, by means of a maximal inequality
derived from the standard Lyapunov drift condition. As a corollary, we
establish the full state space collapse property for all . For the
steady-state distribution, we obtain explicit exponential tail bounds on the
number of flows, for any , by relying on a norm-like Lyapunov
function. As a corollary, we establish the validity of the diffusion
approximation developed by Kang et al. [Ann. Appl. Probab. 19 (2009)
1719-1780], in steady state, for the case where and under a local
traffic condition.Comment: Published in at http://dx.doi.org/10.1214/12-AAP915 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Transition Form Factors and Decay Rates with Extraction of the CKM parameters , ,
A systematic calculation for the transition form factors of heavy to light
mesons () is carried out
by using light-cone sum rules in the framework of heavy quark effective field
theory. The heavy quark symmetry at the leading order of expansion
enables us to reduce the independent wave functions and establish interesting
relations among form factors. Some relations hold for the whole region of
momentum transfer. The meson distribution amplitudes up to twist-4 including
the contributions from higher conformal spin partial waves and light meson mass
corrections are considered. The CKM matrix elements , and
are extracted from some relatively well-measured decay channels. A
detailed prediction for the branching ratios of heavy to light meson decays is
then presented. The resulting predictions for the semileptonic and radiative
decay rates of heavy to light mesons () are found to be compatible with the current experimental data
and can be tested by more precise experiments at B-factory, LHCb, BEPCII and
CLEOc.Comment: 23 pages, 32 figures, 25 tables,published version, minor corrections
and references adde
Generarized Cubic Model for BaTiO-like Ferroelectric Substance
We propose an order-disorder type microscopic model for BaTiO-like
Ferroelectric Substance. Our model has three phase transitions and four phases.
The symmetry and directions of the polarizations of the ordered phases agree
with the experimental results of BaTiO. The intermediate phases in our
model are known as an incompletely ordered phase, which appears in a
generalized clock model.Comment: 6 pages, 4figure
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