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

Global duality in heavy flavor hadronic decays

We show that heavy meson hadronic decay widths satisfy quark-hadron duality when smeared over the heavy quark mass, M, to an accuracy of order 1/M^2.Comment: 11 pages, 3 figs, revte

Wind Loads on Transmission Line Structures in Simulated Downbursts

Downbursts pose a recognized threat to transmission line networks in South-east Queensland, and many other regions around the world. However, when assessing the structural adequacy of transmission line structures, design codes assume that an atmospheric boundary layer profile provide the basis of wind loading in the design process. Such assumptions may be leaving transmission networks exposed to an unquantified level of threat to a meteorological event that will likely cause the most severe loading on the structure during its lifetime. An analytical/stochastic method of simulating downburst winds has been used to explore the quasi-static loading conditions that occur during downbursts. These are presented in comparison to several existing transmission tower design codes, and the implications with regard to the structural adequacy of transmission line structures is discussed

An Exploratory Lattice Study of Spectator Effects in Inclusive Decays of the Lambda_b Baryon

A possible explanation of the apparent disrepency between the theoretical prediction and experimental measurement of the ratio of lifetimes $\tau(\Lambda_b)/\tau(B_d)$ is that ``spectator effects'', which appear at $O(1/m_b^3)$ in the heavy quark expansion, contribute significantly. We investigate this possibility by computing the corresponding operator matrix elements in a lattice simulation. We find that spectator effects are indeed significant, but do not appear to be sufficiently large to account for the full discrepency. We stress, however, that this is an exploratory study, and it is important to check our conclusions on a larger lattice and using a larger sample of gluon configurations.Comment: 12 pages, Latex. One correction: in the original version of the paper, in eqs.10, 11, 12 and 39, the values of the pion masses appeared interchange

Localized transverse bursts in inclined layer convection

We investigate a novel bursting state in inclined layer thermal convection in which convection rolls exhibit intermittent, localized, transverse bursts. With increasing temperature difference, the bursts increase in duration and number while exhibiting a characteristic wavenumber, magnitude, and size. We propose a mechanism which describes the duration of the observed bursting intervals and compare our results to bursting processes in other systems.Comment: 4 pages, 8 figure

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

Promoting Harmonious Work Passion among Unmotivated Employees: A Two-Nation Investigation of the Compensatory Function of Cooperative Psychological Climate

This research draws on self-determination theory to investigate (a) the role of cooperative psychological climate in promoting harmonious work passion among employees with low intrinsic motivation; and (b) the mediating role of harmonious passion in linking cooperative psychological climate to behavioral outcomes. We propose that cooperative psychological climate facilitates harmonious passion and, in particular, plays a compensatory role among employees with low intrinsic motivation. In turn, harmonious passion is expected to facilitate both task performance and interpersonal helping, thereby linking cooperative psychological climate to these employee behaviors. We test the model using data from employees and their supervisors across two countries (Singapore and Brazil) and find cross-national evidence that cooperative psychological climate compensates for low intrinsic motivation to predict harmonious passion. Harmonious passion also positively predicts task performance and interpersonal helping, but only in the Brazilian sample. This research enriches the nomological network of harmonious passion, provides an alternative pathway to driving employee passion when intrinsic motivation is lacking, and underscores the value of considering the joint roles of passion predictors so as to reap the performance benefits of harmonious work passion

Identification of E2/E3 Ubiquitinating Enzymes and Caspase Activity Regulating Drosophila Sensory Neuron Dendrite Pruning

SummaryUbiquitin-proteasome system (UPS) is a multistep protein degradation machinery implicated in many diseases. In the nervous system, UPS regulates remodeling and degradation of neuronal processes and is linked to Wallerian axonal degeneration, though the ubiquitin ligases that confer substrate specificity remain unknown. Having shown previously that class IV dendritic arborization (C4da) sensory neurons in Drosophila undergo UPS-mediated dendritic pruning during metamorphosis, we conducted an E2/E3 ubiquitinating enzyme mutant screen, revealing that mutation in ubcD1, an E2 ubiquitin-conjugating enzyme, resulted in retention of C4da neuron dendrites during metamorphosis. Further, we found that UPS activation likely leads to UbcD1-mediated degradation of DIAP1, a caspase-antagonizing E3 ligase. This allows for local activation of the Dronc caspase, thereby preserving C4da neurons while severing their dendrites. Thus, in addition to uncovering E2/E3 ubiquitinating enzymes for dendrite pruning, this study provides a mechanistic link between UPS and the apoptotic machinery in regulating neuronal process remodeling

Model Independent Extraction of ∣Vbc∣|V_{\rm bc}| Without Heavy Quark Symmetry

A new method to extract $|V_{\rm bc}|$ is proposed based on a sum--rule for semileptonic decays of the $B$ 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 $c \overline{c}$ pair content of the $B$ 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

Shape and soft functions of HQET and SCET in the 't Hooft Model

The main application of Heavy Quark Effective Theory (HQET) and of Soft Collinear Effective Theory (SCET) is in establishing factorization theorems for exclusive and semi-inclusive decays of heavy mesons. However, the calculation of the soft factors from the HQET or SCET factorization relations is, as usual, impeded by the non-perturbative aspect of the strong interactions. In the hope of gaining some insights into some of these quantities we compute them in the 't Hooft model. We find that the B-meson shape function is exactly given by the square of the B-meson light-cone wave-function. The structure of the B-pi structure function is more complicated: it is given by the product of wave-functions or by a resonant sum depending on the kinematics. The result simplifies dramatically in the chiral limit, where it can be compared with general arguments based on Heavy Meson-Chiral Perturbation theory. No attempt is made to use these results for applications to phenomenology.Comment: 17 pages, 5 figure