Activated dynamics and effective temperature in a steady state sheared glass

We conduct nonequilibrium molecular dynamics simulations to measure the shear stress, the average inherent structure energy, and the effective temperature $T_{eff}$ of a sheared model glass as a function of bath temperature $T$ and shear strain rate. For $T$ above the glass transition temperature $T_0$, the rheology approaches a Newtonian limit and $T_{eff}$ approaches $T$ as the strain rate approaches zero, while for $T<T_0$, the shear stress approaches a yield stress and $T_{eff}$ approaches a limiting value near $T_0$. In the shear-dominated regime at high $T$, high strain rate or at low $T$, we find that the shear stress and the average inherent structure energy each collapse onto a single curve as a function of $T_{eff}$. This indicates that $T_{eff}$ is controlling behavior in this regime.Comment: 4 pages, 2 figures. Revised to include additional data. Inherent structure energy results were included, and much of the shear transformation zone discussion was remove

Geometric principles of second messenger dynamics in dendritic spines.

Dendritic spines are small, bulbous protrusions along dendrites in neurons and play a critical role in synaptic transmission. Dendritic spines come in a variety of shapes that depend on their developmental state. Additionally, roughly 14-19% of mature spines have a specialized endoplasmic reticulum called the spine apparatus. How does the shape of a postsynaptic spine and its internal organization affect the spatio-temporal dynamics of short timescale signaling? Answers to this question are central to our understanding the initiation of synaptic transmission, learning, and memory formation. In this work, we investigated the effect of spine and spine apparatus size and shape on the spatio-temporal dynamics of second messengers using mathematical modeling using reaction-diffusion equations in idealized geometries (ellipsoids, spheres, and mushroom-shaped). Our analyses and simulations showed that in the short timescale, spine size and shape coupled with the spine apparatus geometries govern the spatiotemporal dynamics of second messengers. We show that the curvature of the geometries gives rise to pseudo-harmonic functions, which predict the locations of maximum and minimum concentrations along the spine head. Furthermore, we showed that the lifetime of the concentration gradient can be fine-tuned by localization of fluxes on the spine head and varying the relative curvatures and distances between the spine apparatus and the spine head. Thus, we have identified several key geometric determinants of how the spine head and spine apparatus may regulate the short timescale chemical dynamics of small molecules that control synaptic plasticity

A non-apoptotic role for caspase-9 in muscle differentiation

Caspases, a family of cysteine proteases most often investigated for their roles in apoptosis, have also been demonstrated to have functions that are vital for the efficient execution of cell differentiation. One such role that has been described is the requirement of caspase-3 for the differentiation of skeletal myoblasts into myotubes but, as yet, the mechanism leading to caspase-3 activation in this case remains elusive. Here, we demonstrate that caspase-9, an initiator caspase in the mitochondrial death pathway, is responsible for the activation of caspase-3 in differentiating C2C12 cells. Reduction of caspase-9 levels, using an shRNA construct, prevented caspase-3 activation and inhibited myoblast fusion. Myosin-heavy-chain expression, which accompanies myoblastic differentiation, was not caspase-dependent. Overexpression of Bcl-xL, a protein that inhibits caspase-9 activation, had the same effect on muscle differentiation as knockdown of caspase-9. These data suggest that the mitochondrial pathway is required for differentiation; however, the release of cytochrome c or Smac (Diablo) could not be detected, raising the possibility of a novel mechanism of caspase-9 activation during muscle differentiation.</jats:p

Early diagnosis and intervention in cystic fibrosis: Imagining the unimaginable

Cystic fibrosis is the most common life-shortening genetic disease affecting Caucasians, clinically manifested by fat malabsorption, poor growth and nutrition, and recurrent sinopulmonary infections. Newborn screening programs for cystic fibrosis are now implemented throughout the United States and in many nations worldwide. Early diagnosis and interventions have led to improved clinical outcomes for people with cystic fibrosis. Newer cystic fibrosis transmembrane conductance regulator potentiators and correctors with mutation-specific effects have increasingly been used in children, and these agents are revolutionizing care. Indeed, it is possible that highly effective modulator therapy used early in life could profoundly affect the trajectory of cystic fibrosis lung disease, and primary prevention may be achievable

Step size of the rotary proton motor in single FoF1-ATP synthase from a thermoalkaliphilic bacterium by DCO-ALEX FRET

Thermophilic enzymes can operate at higher temperatures but show reduced activities at room temperature. They are in general more stable during preparation and, accordingly, are considered to be more rigid in structure. Crystallization is often easier compared to proteins from bacteria growing at ambient temperatures, especially for membrane proteins. The ATP-producing enzyme FoF1-ATP synthase from thermoalkaliphilic Caldalkalibacillus thermarum strain TA2.A1 is driven by a Fo motor consisting of a ring of 13 c-subunits. We applied a single-molecule F\"orster resonance energy transfer (FRET) approach using duty cycle-optimized alternating laser excitation (DCO-ALEX) to monitor the expected 13-stepped rotary Fo motor at work. New FRET transition histograms were developed to identify the smaller step sizes compared to the 10-stepped Fo motor of the Escherichia coli enzyme. Dwell time analysis revealed the temperature and the LDAO dependence of the Fo motor activity on the single molecule level. Back-and-forth stepping of the Fo motor occurs fast indicating a high flexibility in the membrane part of this thermophilic enzyme.Comment: 14 pages, 7 figure

Superconductivity in NdFe1-xCoxAsO (0.05 < x < 0.20) and rare-earth magnetic ordering in NdCoAsO

The phase diagram of NdFe1-xCoxAsO for low cobalt substitution consists of a superconducting dome (0.05 < x < 0.20) with a maximum critical temperature of 16.5(2) K for x = 0.12. The x = 1 end member, NdCoAsO, is an itinerant ferromagnet (TC = 85 K) with an ordered moment of 0.30(1) BM at 15 K. Below TN = 9 K, Nd spin-ordering results in the antiferromagnetic coupling of the existing ferromagnetic planes. Rietveld analysis reveals that the electronically important two-fold tetrahedral angle increases from 111.4 to 115.9 deg. in this series. Underdoped samples with x = 0.046(2) and x = 0.065(2) show distortions to the orthorhombic Cmma structure at 72(2) and 64(2) K, respectively. The temperature dependences of the critical fields Hc2(T) near Tc are linear with almost identical slopes of 2.3(1) T K-1 for x = 0.065(2), x = 0.118(2) and x = 0.172(2). The estimated critical field Hc2(0) and correlation length for optimally doped samples are 26(1) T and 36(1) Angstrom. A comparison of the maximum reported critical temperatures of well-characterized cobalt doped 122- and 1111-type superconductors is presented.Comment: accepted to PR

The Crystal Structure of the Extracellular 11-heme Cytochrome UndA Reveals a Conserved 10-heme Motif and Defined Binding Site for Soluble Iron Chelates

Members of the genus Shewanella translocate deca- or undeca-heme cytochromes to the external cell surface thus enabling respiration using extracellular minerals and polynuclear Fe(III) chelates. The high resolution structure of the first undeca-heme outer membrane cytochrome, UndA, reveals a crossed heme chain with four potential electron ingress/egress sites arranged within four domains. Sequence and structural alignment of UndA and the deca-heme MtrF reveals the extra heme of UndA is inserted between MtrF hemes 6 and 7. The remaining UndA hemes can be superposed over the heme chain of the decaheme MtrF, suggesting that a ten heme core is conserved between outer membrane cytochromes. The UndA structure has also been crystallographically resolved in complex with substrates, an Fe(III)-nitrilotriacetate dimer or an Fe(III)-citrate trimer. The structural resolution of these UndA-Fe(III)-chelate complexes provides a rationale for previous kinetic measurements on UndA and other outer membrane cytochromes

A Third-Year Review of Design and Packaging of Sensor Systems

Faculty from the Electrical Engineering and Design Engineering Technology Departments at Trine University have developed a joint design module for upper-level courses in their respective disciplines. In this module, student teams collaborate in designing and prototyping the electronics and packaging for a hand-held sensor system. The principal objective of the collaboration is for students to incorporate design factors external to their discipline in a program-focused design project. This effort advances the students\u27 abilities to work effectively in multidisciplinary teams during their senior capstone courses. The design module was introduced in the fall 2011 semester, and was repeated in fall 2012 and fall 2013. An assessment, conducted with current and former participants in fall 2013, demonstrates the efficacy of the project

An assessment of financial sector rescue programmes

We analyse the wide array of rescue programmes adopted in several countries, following Lehman Brothers’ default in September 2008, in order to support banks and other financial institutions. We first provide an overview of the programmes, comparing their characteristics, magnitudes and participation rates across countries. We then consider the effects of the programmes on banks’ risk and valuation, looking at the behaviour of CDS premia and stock prices. We then proceed to analyse the issuance of government guaranteed bonds by banks, examining their impact on banks’ funding and highlighting undesired effects and distortions. Finally, we briefly review the recent evolution of bank lending to the private sector. We draw policy implications, in particular as regards the way of mitigating the distortions implied by such programmes and the need for an exit strategy.bank asset guarantees, capital injection, banks, financial sector, financial crisis, bank consolidation, bank mergers and acquisitions, event studies, government guaranteed bonds, credit crunch, exit strategy

The LBV HR Car has a partner: Discovery of a companion with the VLTI

Luminous Blue Variables (LBVs) are massive stars caught in a post-main sequence phase, during which they are losing a significant amount of mass. As, on one hand, it is thought that the majority of massive stars are close binaries that will interact during their lifetime, and on the other, the most dramatic example of an LBV, Eta Car, is a binary, it would be useful to find other binary LBVs. We present here interferometric observations of the LBV HR Car done with the AMBER and PIONIER instruments attached to ESO's Very Large Telescope Interferometer (VLTI). Our observations, spanning two years, clearly reveal that HR Car is a binary star. It is not yet possible to constrain fully the orbit, and the orbital period may lie between a few years and several hundred years. We derive a radius for the primary in the system and possibly resolve as well the companion. The luminosity ratio in the H-band between the two components is changing with time, going from about 6 to 9. We also tentatively detect the presence of some background flux which remained at the 2% level until January 2016, but then increased to 6% in April 2016. Our AMBER results show that the emission line forming region of Br gamma is more extended than the continuum emitting region as seen by PIONIER and may indicate some wind-wind interaction. Most importantly, we constrain the total masses of both components, with the most likely range being 33.6 and 45 solar masses. Our results show that the LBV HR Car is possibly an Eta Car analog binary system with smaller masses, with variable components, and further monitoring of this object is definitively called for.Comment: A&A, in pres