An Optimized Structure-Function Design Principle Underlies Efficient Signaling Dynamics in Neurons.

Dynamic signaling on branching axons is critical for rapid and efficient communication between neurons in the brain. Efficient signaling in axon arbors depends on a trade-off between the time it takes action potentials to reach synaptic terminals (temporal cost) and the amount of cellular material associated with the wiring path length of the neuron's morphology (material cost). However, where the balance between structural and dynamical considerations for achieving signaling efficiency is, and the design principle that neurons optimize to preserve this balance, is still elusive. In this work, we introduce a novel analysis that compares morphology and signaling dynamics in axonal networks to address this open problem. We show that in Basket cell neurons the design principle being optimized is the ratio between the refractory period of the membrane, and action potential latencies between the initial segment and the synaptic terminals. Our results suggest that the convoluted paths taken by axons reflect a design compensation by the neuron to slow down signaling latencies in order to optimize this ratio. Deviations in this ratio may result in a breakdown of signaling efficiency in the cell. These results pave the way to new approaches for investigating more complex neurophysiological phenomena that involve considerations of neuronal structure-function relationships

FPCP Theory Overview

We first review some aspects of the determination of the sides and angles of the unitarity triangle. We pay particular attention to theory shortcomings, and present many alternative proposals for the determination of |Vub| (which at present is problematic). We then turn our attention to the more general question: What have we learned so far about flavor physics and where do we go from here? We argue that the aim of Flavor Physics should be to establish or rule out Minimal Flavor Violating interactions up to a scale of 10 TeV.Comment: Talk presented at Flavor Physics & CP Violation Conference, Bled, 2007; latex, 7 p

Accuracy of prediction of infarct-related arrhythmic circuits from image-based models reconstructed from low and high resolution MRI.

Identification of optimal ablation sites in hearts with infarct-related ventricular tachycardia (VT) remains difficult to achieve with the current catheter-based mapping techniques. Limitations arise from the ambiguities in determining the reentrant pathways location(s). The goal of this study was to develop experimentally validated, individualized computer models of infarcted swine hearts, reconstructed from high-resolution ex-vivo MRI and to examine the accuracy of the reentrant circuit location prediction when models of the same hearts are instead reconstructed from low clinical-resolution MRI scans. To achieve this goal, we utilized retrospective data obtained from four pigs ~10 weeks post infarction that underwent VT induction via programmed stimulation and epicardial activation mapping via a multielectrode epicardial sock. After the experiment, high-resolution ex-vivo MRI with late gadolinium enhancement was acquired. The Hi-res images were downsampled into two lower resolutions (Med-res and Low-res) in order to replicate image quality obtainable in the clinic. The images were segmented and models were reconstructed from the three image stacks for each pig heart. VT induction similar to what was performed in the experiment was simulated. Results of the reconstructions showed that the geometry of the ventricles including the infarct could be accurately obtained from Med-res and Low-res images. Simulation results demonstrated that induced VTs in the Med-res and Low-res models were located close to those in Hi-res models. Importantly, all models, regardless of image resolution, accurately predicted the VT morphology and circuit location induced in the experiment. These results demonstrate that MRI-based computer models of hearts with ischemic cardiomyopathy could provide a unique opportunity to predict and analyze VT resulting for from specific infarct architecture, and thus may assist in clinical decisions to identify and ablate the reentrant circuit(s)

Transborder Identity Development: A Photovoice Constructivist Grounded Theory Study of Transfronterizx Students in Postsecondary and Higher Education at the San Diego-Tijuana Border Region

The purpose of this photovoice constructivist grounded theory study is to illustrate the intersections and developmental processes of a transborder identity among Transfronterizx students in postsecondary and higher education institutions at the San Diego-Tijuana border region by examining the psychosocial and cognitive-structural factors that influenced their social identities. To generate the findings of this study, I conducted 11 photovoice focus groups and 20 one-on-one photovoice interviews in three grounded theory data collection and analysis phases, consisting of 691 photos with 32 current and former Transfronterizx students in postsecondary and higher education institutions at the San Diego-Tijuana border region. The intersections and developmental processes of a transborder identity are illustrated in a model grounded by the thoughts, feelings, and experiences participants shared about their academic trajectories, transborder performances and salient social identities at the San Diego-Tijuana borderlands. Transborder identity is defined by five in-vivo themes representing the meanings Transfronterizx students ascribed to themselves in relationship to others and their environment at the San Diego-Tijuana borderlands: (1) We Speak English, We Speak Spanish, We Speak Spanglish, (2) Soy De Aquí y Soy de Allá (3) Building Bridges, Not Walls, (4) We Have to Adapt to Live in these Situations and (5) Las Ganas de Salir Adelante. The findings also illustrate the current realities lived by Transfronterizx students during the COVID-19 pandemic. Implications for future research, practice and policy centered on fostering the development and success of Transfronterizx students in postsecondary and higher education institutions at the San Diego-Tijuana border region are addressed

Mixings, Lifetimes, Spectroscopy and Production of Heavy Flavor at the Tevatron

The Fermilab Tevatron offers unique opportunities to perform measurements of the heavier B hadrons that are not accessible at the Upsilon(4S) resonance. In this summary, we describe some recent heavy flavor results from the DO and CDF collaborations and discuss prospects for future measurements.Comment: To appear in Proceedings of the XXI International Symposium on lepton and Photon Interactions at High Energies, Fermilab, August 200

Opportunistic Localization Scheme Based on Linear Matrix Inequality

Enabling self-localization of mobile nodes is an important problem that has been widely studied in the literature. The general conclusions is that an accurate localization requires either sophisticated hardware (GPS, UWB, ultrasounds transceiver) or a dedicated infrastructure (GSM, WLAN). In this paper we tackle the problem from a different and rather new perspective: we investigate how localization performance can be improved by means of a cooperative and opportunistic data exchange among the nodes. We consider a target node, completely unaware of its own position, and a number of mobile nodes with some self-localization capabilities. When the opportunity occurs, the target node can exchange data with in-range mobile nodes. This opportunistic data exchange is then used by the target node to refine its position estimate by using a technique based on Linear Matrix Inequalities and barycentric algorithm. To investigate the performance of such an opportunistic localization algorithm, we define a simple mathematical model that describes the opportunistic interactions and, then, we run several computer simulations for analyzing the effect of the nodes duty-cycle and of the native self-localization error modeling considered. The results show that the opportunistic interactions can actually improve the self-localization accuracy of a strayed node in many different scenarios