Probing equilibrium glass flow up to exapoise viscosities

Glasses are out-of-equilibrium systems aging under the crystallization threat. During ordinary glass formation, the atomic diffusion slows down rendering its experimental investigation impractically long, to the extent that a timescale divergence is taken for granted by many. We circumvent here these limitations, taking advantage of a wide family of glasses rapidly obtained by physical vapor deposition directly into the solid state, endowed with different "ages" rivaling those reached by standard cooling and waiting for millennia. Isothermally probing the mechanical response of each of these glasses, we infer a correspondence with viscosity along the equilibrium line, up to exapoise values. We find a dependence of the elastic modulus on the glass age, which, traced back to temperature steepness index of the viscosity, tears down one of the cornerstones of several glass transition theories: the dynamical divergence. Critically, our results suggest that the conventional wisdom picture of a glass ceasing to flow at finite temperature could be wrong.Comment: 4 figures and 1 supplementary figur

LES of an Inclined Jet into a Supersonic Turbulent Crossflow

This short article describes flow parameters, numerical method, and animations of the fluid dynamics video "LES of an Inclined Jet into a Supersonic Turbulent Crossflow" (http://ecommons.library.cornell.edu/bitstream/1813/14073/3/GFM-2009.mpg [high-resolution] and http://ecommons.library.cornell.edu/bitstream/1813/14073/2/GFM-2009-web.m1v [low-resolution] video). We performed large-eddy simulation with the sub-grid scale (LES-SGS) stretched-vortex model of momentum and scalar transport to study the gas-dynamics interactions of a helium inclined round jet into a supersonic ($M=3.6$) turbulent (\Reth$=13\times10^3$) air flow over a flat surface. The video shows the temporal development of Mach-number and magnitude of density-gradient in the mid-span plane, and isosurface of helium mass-fraction and \lam_2 (vortical structures). The identified vortical structures are sheets, tilted tubes, and discontinuous rings. The vortical structures are shown to be well correlated in space and time with helium mass-fraction isosurface ($Y_{\rm He}=0.25$).Comment: 7 pages, 1 figure, 1 table, article describing fluid dynamics video submitted to Gallery of Fluid Motion, APS-DFD 200

Modifications of high harmonic spectra by ion resonant transitions

High-order harmonic generation is considered in a system consisting of an ion with an internal degree of freedom plus an outer electron. The theoretical treatment is both quantum-mechanical and classical. The emphasis is on the core resonance effects, which can significantly modify the harmonic spectra, with appearance of anomalous peaks. Under some assumptions, the spectral amplitude of the resonant harmonic of the system dipole moment can be obtained by evaluation of such amplitude within a single-electron approximation and multiplication of the result by a correcting factor. The latter depends on the polarizability of the ion and of a free electron at the harmonic frequency. Copyright \ua9 1996 by MAHK Hayka/Interperiodica Publishing

Engineering a static verification tool for GPU kernels

We report on practical experiences over the last 2.5 years related to the engineering of GPUVerify, a static verification tool for OpenCL and CUDA GPU kernels, plotting the progress of GPUVerify from a prototype to a fully functional and relatively efficient analysis tool. Our hope is that this experience report will serve the verification community by helping to inform future tooling efforts. © 2014 Springer International Publishing

Towards a Formal Verification Methodology for Collective Robotic Systems

We introduce a UML-based notation for graphically modeling systems’ security aspects in a simple and intuitive way and a model-driven process that transforms graphical specifications of access control policies in XACML. These XACML policies are then translated in FACPL, a policy language with a formal semantics, and the resulting policies are evaluated by means of a Java-based software tool

CD40 ligand and MCP-1 as predictors of cardiovascular events in diabetic patients with stroke

Aim: Up-regulation of soluble CD40 ligand (sCD40L) and of monocyte chemoattractant protein-1 (MCP-1) has been found in diabetes and in patients with acute cerebral ischemia. We asked whether (i) the two molecules are similarly upregulated among non-lacunar and lacunar diabetic strokes and (ii) sCD40L and/or MCP-1 predict the risk of cardiovascular events in this setting.Methods: Ninety patients with type 2 diabetes mellitus presenting with an acute ischemic stroke (compared with 45 control subjects) were evaluated on admission and up to 36 months (median 24 months) after the event.Results: Diabetic patients with acute stroke had higher plasma CD40L and MCP-1 than controls (p<0.0001), with no significant differences among lacunar and non-lacunar strokes. On multiple regres-sion analysis, only higher sCD40L quartiles and older age were associated with higher MCP-1 quar-tiles. Forty-eight percent of patients experienced vascular events. Cox regression analysis showed that only the presence of higher sCD40L values independently predicted the recurrence of vascular events.Conclusion: Up-regulation of inflammatory molecules, such as CD40L and MCP-1, is involved in the advanced stage of atherosclerotic cerebro-vascular disease and is associated with increased risk of recurrence of cardiovascular events.AIM: Up-regulation of soluble CD40 ligand (sCD40L) and of monocyte chemoattractant protein-1 (MCP-1) has been found in diabetes and in patients with acute cerebral ischemia. We asked whether (i) the two molecules are similarly upregulated among non-lacunar and lacunar diabetic strokes and (ii) sCD40L and/or MCP-1 predict the risk of cardiovascular events in this setting. METHODS: Ninety patients with type 2 diabetes mellitus presenting with an acute ischemic stroke (compared with 45 control subjects) were evaluated on admission and up to 36 months (median 24 months) after the event. RESULTS: Diabetic patients with acute stroke had higher plasma CD40L and MCP-1 than controls (p<0.0001), with no significant differences among lacunar and non-lacunar strokes. On multiple regression analysis, only higher sCD40L quartiles and older age were associated with higher MCP-1 quartiles. Forty-eight percent of patients experienced vascular events. Cox regression analysis showed that only the presence of higher sCD40L values independently predicted the recurrence of vascular events. CONCLUSION: Up-regulation of inflammatory molecules, such as CD40L and MCP-1, is involved in the advanced stage of atherosclerotic cerebro-vascular disease and is associated with increased risk of recurrence of cardiovascular events

Theory of x-ray absorption by laser-dressed atoms

An ab initio theory is devised for the x-ray photoabsorption cross section of atoms in the field of a moderately intense optical laser (800nm, 10^13 W/cm^2). The laser dresses the core-excited atomic states, which introduces a dependence of the cross section on the angle between the polarization vectors of the two linearly polarized radiation sources. We use the Hartree-Fock-Slater approximation to describe the atomic many-particle problem in conjunction with a nonrelativistic quantum-electrodynamic approach to treat the photon-electron interaction. The continuum wave functions of ejected electrons are treated with a complex absorbing potential that is derived from smooth exterior complex scaling. The solution to the two-color (x-ray plus laser) problem is discussed in terms of a direct diagonalization of the complex symmetric matrix representation of the Hamiltonian. Alternative treatments with time-independent and time-dependent non-Hermitian perturbation theories are presented that exploit the weak interaction strength between x rays and atoms. We apply the theory to study the photoabsorption cross section of krypton atoms near the K edge. A pronounced modification of the cross section is found in the presence of the optical laser.Comment: 13 pages, 3 figures, 1 table, RevTeX4, corrected typoe