582 research outputs found
Modeling of Spiking-Bursting Neural Behavior Using Two-Dimensional Map
A simple model that replicates the dynamics of spiking and spiking-bursting
activity of real biological neurons is proposed. The model is a two-dimensional
map which contains one fast and one slow variable. The mechanisms behind
generation of spikes, bursts of spikes, and restructuring of the map behavior
are explained using phase portrait analysis. The dynamics of two coupled maps
which model the behavior of two electrically coupled neurons is discussed.
Synchronization regimes for spiking and bursting activity of these maps are
studied as a function of coupling strength. It is demonstrated that the results
of this model are in agreement with the synchronization of chaotic
spiking-bursting behavior experimentally found in real biological neurons.Comment: 9 pages, 12 figure
Azimuthal Correlation in Lepton-Hadron Scattering via Charged Weak-Current Processes
We consider the azimuthal correlation of the final-state particles in charged
weak-current processes. This correlation provides a test of perturbative
quantum chromodynamics. The azimuthal asymmetry is large in the semi-inclusive
processes in which we identify a final-state hadron, say, a charged pion
compared to that in the inclusive processes in which we do not identify
final-state particles and use only the calorimetric information. In
semi-inclusive processes the azimuthal asymmetry is more conspicuous when the
incident lepton is an antineutrino or a positron than when the incident lepton
is a neutrino or an electron. We analyze all the possible charged weak-current
processes and study the quantitative aspects of each process. We also compare
this result to the ep scattering with a photon exchange.Comment: 25 pages, 2 Postscript figures, uses RevTeX, fixes.st
On measuring alpha in B(t)-> rho^\pm pi^\mp
Defining a most economical parametrization of time-dependent B-> rho^\pm
pi^\mp decays, including a measurable phase alpha_{eff} which equals the weak
phase alpha in the limit of vanishing penguin amplitudes, we propose two ways
for determining alpha in this processes. We explain the limitation of one
method, assuming only that two relevant tree amplitudes factorize and that
their relative strong phase, delta_t, is negligible. The other method, based on
broken flavor SU(3), permits a determination of alpha in B^0-> rho^\pm pi^\mp
in an overconstrained system using also rate measurements of B^{0,+}-> K^* pi
and B^{0,+}->rho K. Current data are shown to restrict two ratios of penguin
and tree amplitudes, r_\pm, to a narrow range around 0.2, and to imply an upper
bound |alpha_{eff} - alpha| < 15 degrees. Assuming that delta_t is much smaller
than 90 degrees, we find alpha =(93\pm 16) degrees and (102 \pm 20) degrees
using BABAR and BELLE results for B(t)-> rho^\pm pi^mp. Avoiding this
assumption for completeness, we demonstrate the reduction of discrete
ambiguities in alpha with increased statistics, and show that SU(3) breaking
effects are effectively second order in r_\pm.Comment: 23 pages, 2 figures, data and references updated, to be published in
Phys. Rev.
Mekanisme Imbal Jasa Lingkungan Di Sub-das Cikapundung (Studi Kasus Pada Desa Cikole Dan Desa Suntenjaya Kabupaten Bandung Barat)
Mekanisme Imbal Jasa Lingkungan (IJL) merupakan salah satu upaya dalampengelolaan sub-DAS. Mekanisme ini telah diimplementasikan di sub-DAS Cikapundung.Kesepakatan program IJL di sub-DAS Cikapundung terjadi antara kelompok tani Giri PutriDesa Cikole dengan Pustanling dan kelompok tani Syurga Air dengan PT Aetra. BPLHDberperan sebagai mediator dalam kesepakatan ini. Pada pelaksanaannya, mekanisme IJL disub-DAS Cikapundung dikategorikan sebagai mekanisme IJL yang belum sepenuhnyamencerminkan mekanisme IJL yang berkelanjutan. Kriteria mekanisme IJL yangberkelanjutan seharusnya memenuhi aspek-aspek: realistic, voluntarily, conditional, danpro-poor (Munawir, 2009). Pada mekanisme IJL di sub-DAS Cikapundung hal ini belumsepenuhnya terjadi.Berdasarkan hal tersebut, penelitian ini bertujuan untuk merumuskan strategi yangdapat dilakukan agar mekanisme IJL di sub-DAS Cikapundung menjadi berkelanjutan.Metode yang digunakan pada penelitian ini adalah metode kualitatif. Pengumpulan datadilakukan melalui wawancara dan kuisioner dengan kelompok tani Syurga Air dan GiriPutri, PT Aetra, Pustanling, BPLHD, serta LP3ES. Analisis yang dilakukan adalah analisiskesenjangan, analisis peran faktor dan analisis SWOT. Mekanisme IJL di sub-DASCikapundung belum berjalan secara berkelanjutan dikarenakan masalah dalamkelembagaan dalam pengelolaan dan monitoring perkembangannya di lapangan. Selain itudana yang diberikan kepada kelompok tani juga masih tergolong belum mencukupi untukaktivitas konservasi lahan. Untuk mewujudkan mekanisme IJL yang berkelanjutan makadiperlukan upaya-upaya strategis terutama dalam kaitannya dengan kelembagaan mediasikesepakatan dengan pembentukan lembaga mediator mekanisme IJL yang bukan dariinstitusi pemerintah agar fasilitasi, advokasi dan koordinasi mekanisme IJL berjalan lebihoptimal, juga perlu dilakukan upaya untuk meningkatkan kepatuhan pada regulasi terkaitIJL, meningkatkan optimalisasi setiap forum pertemuan, meningkatkan kinerjastakeholders, serta melakukan negosiasi dengan potential buyer
Model Independent Extraction of Without Heavy Quark Symmetry
A new method to extract is proposed based on a sum--rule for
semileptonic decays of the meson. The method relies on much weaker
assumptions than previous approaches which are based on heavy--quark symmetry.
This sum--rule only relies on the assumption that the virtual
pair content of the meson can be neglected. The extraction of the CKM
matrix element also requires that the sum--rule saturates in the kinematically
accessible region.Comment: 10 pages revtex3 manuscript. No figures, U. of MD PP #94--086. With
our apologies, some innocuous errors corrected and some references added that
had been brought to our attentio
Quark-binding effects in inclusive decays of heavy mesons
We present a new approach to the analysis of quark-binding effects in
inclusive decays of heavy mesons within the relativistic dispersion quark
model. Various differential distributions, such as electron energy spectrum,
- and -distributions, are calculated in terms of the meson soft
wave function which also determines long-distance effects in exclusive
transition form factors. Using the quark-model parameters and the meson
wave function previously determined from the description of the exclusive transitions within the same dispersion approach, we provide numerical
results on various distributions in the inclusive decays.Comment: revtex, 18 pages, preprint HD-THEP-99-50 (Heidelberg) and
RM3-TH/99-13 (Roma
Hysteresis and bi-stability by an interplay of calcium oscillations and action potential firing
Many cell types exhibit oscillatory activity, such as repetitive action
potential firing due to the Hodgkin-Huxley dynamics of ion channels in the cell
membrane or reveal intracellular inositol triphosphate (IP) mediated
calcium oscillations (CaOs) by calcium-induced calcium release channels
(IP-receptor) in the membrane of the endoplasmic reticulum (ER). The
dynamics of the excitable membrane and that of the IP-mediated CaOs have
been the subject of many studies. However, the interaction between the
excitable cell membrane and IP-mediated CaOs, which are coupled by
cytosolic calcium which affects the dynamics of both, has not been studied.
This study for the first time applied stability analysis to investigate the
dynamic behavior of a model, which includes both an excitable membrane and an
intracellular IP-mediated calcium oscillator. Taking the IP
concentration as a control parameter, the model exhibits a novel rich spectrum
of stable and unstable states with hysteresis. The four stable states of the
model correspond in detail to previously reported growth-state dependent states
of the membrane potential of normal rat kidney fibroblasts in cell culture. The
hysteresis is most pronounced for experimentally observed parameter values of
the model, suggesting a functional importance of hysteresis. This study shows
that the four growth-dependent cell states may not reflect the behavior of
cells that have differentiated into different cell types with different
properties, but simply reflect four different states of a single cell type,
that is characterized by a single model.Comment: 29 pages, 6 figure
Perturbative contribution to the sin(phi) asymmetry in inclusive pi^{+} electroproduction
We consider the sin(phi) single target-spin asymmetry in deep-inelastic
pi^{+} inclusive electroproduction off a longitudinally polarized target. We
show that at larger transverse momentum of the outgoing hadron the evaluated
asymmetry decreases if one takes into account the first order alpha_S
perturbative contribution to the cross section, integrated over the azimuthal
angle. This leads to good agreement with recent HERMES data.Comment: 4 pages with one figure, LaTeX, typos corrected. Contribution to the
Proceedings of the QCD'00 Euroconference, Montpellier, 6-13th July 2000, to
appear in the Nucl. Phys. B (Proc. Suppl.
Bloch-Nordsieck cancellations beyond logarithms in heavy particle decays
We investigate the one-loop radiative corrections to the semileptonic decay
of a charged particle at finite gauge boson mass. Extending the Bloch-Nordsieck
cancellation of infrared logarithms, the subsequent non-analytic terms are also
found to vanish after eliminating the pole mass in favor of a mass defined at
short distances. This observation justifies the operator product expansion for
inclusive decays of heavy mesons and implies that infrared effects associated
with the summation of the radiative corrections are suppressed by at least
three powers of the mass of the heavy decaying particle.Comment: LATEX, 7 pages, one figure appended as uu-encoded ps-file,
MPI-PhT/94-1
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