Tyrosine phosphorylation of cortactin by the FAK-Src complex at focal adhesions regulates cell motility.

BackgroundCell migration plays an important role in many physiological and pathological processes, including immune cell chemotaxis and cancer metastasis. It is a coordinated process that involves dynamic changes in the actin cytoskeleton and its interplay with focal adhesions. At the leading edge of a migrating cell, it is the re-arrangement of actin and its attachment to focal adhesions that generates the driving force necessary for movement. However, the mechanisms involved in the attachment of actin filaments to focal adhesions are still not fully understood.ResultsSignaling by the FAK-Src complex plays a crucial role in regulating the formation of protein complexes at focal adhesions to which the actin filaments are attached. Cortactin, an F-actin associated protein and a substrate of Src kinase, was found to interact with FAK through its SH3 domain and the C-terminal proline-rich regions of FAK. We found that the autophosphorylation of Tyr(397) in FAK, which is necessary for FAK activation, was not required for the interaction with cortactin, but was essential for the tyrosine phosphorylation of the associated cortactin. At focal adhesions, cortactin was phosphorylated at tyrosine residues known to be phosphorylated by Src. The tyrosine phosphorylation of cortactin and its ability to associate with the actin cytoskeleton were required in tandem for the regulation of cell motility. Cell motility could be inhibited by truncating the N-terminal F-actin binding domains of cortactin or by blocking tyrosine phosphorylation (Y421/466/475/482F mutation). In addition, the mutant cortactin phosphorylation mimic (Y421/466/475/482E) had a reduced ability to interact with FAK and promoted cell motility. The promotion of cell motility by the cortactin phosphorylation mimic could also be inhibited by truncating its N-terminal F-actin binding domains.ConclusionsOur results suggest that cortactin acts as a bridging molecule between actin filaments and focal adhesions. The cortactin N-terminus associates with F-actin, while its C-terminus interacts with focal adhesions. The tyrosine phosphorylation of cortactin by the FAK-Src complex modulates its interaction with FAK and increases its turnover at focal adhesions to promote cell motility

Maximizing Energy-Efficiency in Multi-Relay OFDMA Cellular Networks

This contribution presents a method of obtaining the optimal power and subcarrier allocations that maximize the energy-efficiency (EE) of a multi-user, multi-relay, orthogonal frequency division multiple access (OFDMA) cellular network. Initially, the objective function (OF) is formulated as the ratio of the spectral-efficiency (SE) over the power consumption of the network. This OF is shown to be quasi-concave, thus Dinkelbach's method can be employed for solving it as a series of parameterized concave problems. We characterize the performance of the aforementioned method by comparing the optimal solutions obtained to those found using an exhaustive search. Additionally, we explore the relationship between the achievable SE and EE in the cellular network upon increasing the number of active users. In general, increasing the number of users supported by the system benefits both the SE and EE, and higher SE values may be obtained at the cost of EE, when an increased power may be allocated.Comment: 6 pages, 5 figures, 1 table, to appear in Proc. IEEE 2013 56th Global Communications Conference (GLOBECOM 2013), Atlanta, USA, December, 201

A Two-Stage Allocation Scheme for Delay-Sensitive Services in Dense Vehicular Networks

Driven by the rapid development of wireless communication system, more and more vehicular services can be efficiently supported via vehicle-to-everything (V2X) communications. In order to allocate radio resource with the reasonable implementation complexity in dense urban intersection, a two-stage allocation algorithm is proposed in this paper, whose main objective is to minimize delay and ensure reliability. In particular, as for the first stage, the allocation policy is based on traffic density information (TDI), which is different from utilizing channel state information (CSI) and queue state information (QSI) in the second stage. Moreover, in order to reflect the influence of TDI on delay, a macroscopic vehicular mobility model is employed in this paper. Simulation results show that the proposed algorithm can acquire an asymptotically optimal performance with the acceptable complexity

DISCOVERY AND DEVELOPMENT OF RARE EARTH ACTIVATED BINARY METAL HALIDE SCINTILLATORS FOR NEXT GENERATION RADIATION DETECTORS

This work focuses on discovery and development of novel binary halide scintillation materials for radiation detection applications. A complete laboratory for raw materials handling, ampoule preparation, material rapid synthesis screening, single crystal growth, sample cutting, polishing and packaging of hygroscopic halide scintillation materials has been established. Ce3+ and Eu2+ activated scintillators in three binary systems: Alkali Halide – Rare Earth Halide (AX–REX3), Alkali Halide – Alkaline Earth Halide (AX–AEX2) and Alkalin Earth Halide – Rare Earth Halide (AEX2–REX3) were systematically studied. Candidates for new scintillation materials in the three systems were selected based on a set of selection rules. A total of 42 Ce3+ or Eu2+ activated binary halide scintillation material candidates were synthesized and characterized. Among all synthesized candidates, 10 - 15 candidate materials were found to be highly promising in terms of high scintillation light output, fast scintillation decay or desirable emission wavelength. Three most promising candidates, Cs3EuI5, CsGd2Cl7:Ce3+ and CsSrI3:Eu2+ were selected for single crystal growth and further evaluation. Technologies for single crystal growth of hygroscopic halide scintillation materials were developed. Detailed design of experimental apparatuses was discussed. Single crystals were successfully grown via Bridgman or Vertical Gradient Freeze techniques. Study on optical and scintillation properties was performed. Possibility of using CsGd2Cl7:Ce3+ as a neutron detector was confirmed. CsSrI3:Eu2+ shows extraordinary scintillation light output (73,000 ph/MeV), excellent energy resolution (3.9%) and ease for crystal growth. A scaled-up crystal growth was carried out. A bulk crystal of 1” diameter CsSrI3:Eu2+ was successfully grown. Energy level structure and charge carrier traps in CsSrI3:Eu2+ were investigated. Potential of CsSrI3:Eu2+ in various radiation detection applications were evaluated

Aerodynamic Analysis of an MAV-Scale Cycloidal Rotor System Using a Stuctured Overset RANS Solver

A compressible Reynolds-Averaged Navier-Stokes solver was used to investigate the performance and flow physics of the cycloidal rotor (cyclocopter). This work employed a computational methodology to understand the complex aerodynamics of the cyclocopter and its relatively unexplored application for MAVs. The numerical code was compared against performance measurements obtained from experiment and was seen to exhibit reasonable accuracy. With validation of the flow solver, CFD predictions were used to gain qualitative insight into the flowfield. Time histories revealed large periodic variations in thrust and power. In particular, the virtual camber effect was found to significantly influence the vertical force time history. Spanwise thrust and flow visualizations showed a highly three-dimensional flowfield with large amounts of blade shedding and blade-vortex interaction. Overall, the current work seeks to provide unprecedented insight into the cyclocopter flowfield with the goal of developing an accurate predictive tool to refine the design of future cyclocopter configurations

Firm-Specific Variation and Openness in Emerging Markets

This paper compares the comovement of individual stock returns across emerging markets. Campbell et al. (2001) and Morck et al. (2000) show that the US in the post war period saw rising firm specific stock return variations and thus declining comovement. We detect a similar, albeit weaker, pattern in most, but not all, emerging markets. We further find that higher firm-specific variation is associated with greater capital market openness, but not goods market openness. Moreover, this relationship is magnified by institutional integrity (good government). Goods market openness is associated with higher market-wide variation.http://deepblue.lib.umich.edu/bitstream/2027.42/40009/3/wp623.pd

Firm-Specific Variation and Openness in Emerging Markets

This paper compares the comovement of individual stock returns across emerging markets. Campbell et al. (2001) and Morck et al. (2000) show that the US in the post war period saw rising firm specific stock return variations and thus declining comovement. We detect a similar, albeit weaker, pattern in most, but not all, emerging markets. We further find that higher firm-specific variation is associated with greater capital market openness, but not goods market openness. Moreover, this relationship is magnified by institutional integrity (good government). Goods market openness is associated with higher market-wide variation.