Evanescent field optical readout of graphene mechanical motion at room temperature

Graphene mechanical resonators have recently attracted considerable attention for use in precision force and mass sensing applications. To date, readout of their oscillatory motion has typically required cryogenic conditions to achieve high sensitivity, restricting their range of applications. Here we report the first demonstration of evanescent optical readout of graphene motion, using a scheme which does not require cryogenic conditions and exhibits enhanced sensitivity and bandwidth at room temperature. We utilise a high $Q$ microsphere to enable evanescent readout of a 70 $\mu$m diameter graphene drum resonator with a signal-to-noise ratio of greater than 25 dB, corresponding to a transduction sensitivity of $S_{N}^{1/2} =$ 2.6 $\times 10^{-13}$ m $\mathrm{Hz}^{-1/2}$. The sensitivity of force measurements using this resonator is limited by the thermal noise driving the resonator, corresponding to a force sensitivity of $F_{min} = 1.5 \times 10^{-16}$ N ${\mathrm{Hz}}^{-1/2}$ with a bandwidth of 35 kHz at room temperature (T = 300 K). Measurements on a 30 $\mu$m graphene drum had sufficient sensitivity to resolve the lowest three thermally driven mechanical resonances.Comment: Fixed formatting errors in bibliograph

Acoustic Identification of Liquefaction Potential

The interparticle arrangement, or fabric, of sands is a key determinant of sample rigidity. This rigidity, in large part, determines the velocity and attenuation of acoustic transmissions in a test specimen, as well as its resistance to liquefaction. Utilizing high frequency small-amplitude compressional wave transmissions, different fabric arrangements of standard triaxial samples of the same sand have been reliably identified from their acoustic response. Both the compressional wave velocity and attenuation were used to determine the acoustic signature of a sample. Cyclic triaxial testing of the same laboratory-prepared samples revealed that there is direct relationship between the acoustic response of a sample prepared by a particular method and its resistance to liquefaction. The effect of stress history, induced by pre-shaking, on the resistance to liquefaction of a test sample was also detected by changes in the acoustic signature

An Efficient Implementation of the Gauss-Newton Method Via Generalized Krylov Subspaces

The solution of nonlinear inverse problems is a challenging task in numerical analysis. In most cases, this kind of problems is solved by iterative procedures that, at each iteration, linearize the problem in a neighborhood of the currently available approximation of the solution. The linearized problem is then solved by a direct or iterative method. Among this class of solution methods, the Gauss-Newton method is one of the most popular ones. We propose an efficient implementation of this method for large-scale problems. Our implementation is based on projecting the nonlinear problem into a sequence of nested subspaces, referred to as Generalized Krylov Subspaces, whose dimension increases with the number of iterations, except for when restarts are carried out. When the computation of the Jacobian matrix is expensive, we combine our iterative method with secant (Broyden) updates to further reduce the computational cost. We show convergence of the proposed solution methods and provide a few numerical examples that illustrate their performance

Residual Strength of Liquefied Sand: Laboratory vs. Field Measurements

Determining the residual strength of liquefied sand is essential for estimating post-earthquake stability of vulnerable earth structures, or calculating runout of liquefaction flow slides. Current practice is to select values from a database of back-calculated residual strengths from failure case histories, which have been related to representative penetration test resistance numbers in the failed materials. Given the uncertainties involved, it is desirable to compare the field data with laboratory tests under controlled conditions. This paper describes residual strength measurements for a uniform fine sand using two recently-developed tests designed to impose large strains and strain rates: a modified triaxial test in which a metal coupon is dragged through the liquefied sample by an external dead weight, and a ring shear device which can impose constant rates of strain on the liquefied sand. In all cases, a stress-thinning behavior is observed; however, coupon movement through the liquefied sand is basically laminar, representing conditions in the interior of a flowing mass, while the rotating ring creates a well-defined contact shear band and higher resistance, which might be considered more representative of flow at the base of a sliding mass. Comparison with back-calculated field values shows that coupon residual strengths plot at the lower bound, and ring shear results at the upper bound, of backcalculated field values

Structure of smectic defect cores: an X-ray study of 8CB liquid crystal ultra-thin films

We study the structure of very thin liquid crystal films frustrated by antagonistic anchorings in the smectic phase. In a cylindrical geometry, the structure is dominated by the defects for film thicknesses smaller than 150 nm and the detailed topology of the defects cores can be revealed by x-ray diffraction. They appear to be split in half tube-shaped Rotating Grain Boundaries (RGB). We determine the RGB spatial extension and evaluate its energy per unit line. Both are significantly larger than the ones usually proposed in the literatureComment: 4 page

Production of α\alpha-particle condensate states in heavy-ion collisions

The fragmentation of quasi-projectiles from the nuclear reaction $^{40}Ca$ + $^{12}C$ at 25 MeV/nucleon was used to produce excited states candidates to $\alpha$-particle condensation. The experiment was performed at LNS-Catania using the CHIMERA multidetector. Accepting the emission simultaneity and equality among the $\alpha$-particle kinetic energies as experimental criteria for deciding in favor of the condensate nature of an excited state, we analyze the $0_2^+$ and $2_2^+$ states of $^{12}$C and the $0_6^+$ state of $^{16}$O. A sub-class of events corresponding to the direct 3-$\alpha$ decay of the Hoyle state is isolated.Comment: contribution to the 2nd Workshop on "State of the Art in Nuclear Cluster Physics" (SOTANCP2), Universite Libre de Bruxelles (Belgium), May 25-28, 2010, to be published in the International Journal of Modern Physics

Entanglement entropy of two disjoint intervals in c=1 theories

We study the scaling of the Renyi entanglement entropy of two disjoint blocks of critical lattice models described by conformal field theories with central charge c=1. We provide the analytic conformal field theory result for the second order Renyi entropy for a free boson compactified on an orbifold describing the scaling limit of the Ashkin-Teller (AT) model on the self-dual line. We have checked this prediction in cluster Monte Carlo simulations of the classical two dimensional AT model. We have also performed extensive numerical simulations of the anisotropic Heisenberg quantum spin-chain with tree-tensor network techniques that allowed to obtain the reduced density matrices of disjoint blocks of the spin-chain and to check the correctness of the predictions for Renyi and entanglement entropies from conformal field theory. In order to match these predictions, we have extrapolated the numerical results by properly taking into account the corrections induced by the finite length of the blocks to the leading scaling behavior.Comment: 37 pages, 23 figure

Spinal Muscular Atrophy autophagy profile is tissue-dependent: differential regulation between muscle and motoneurons

Motoneurona; Neurodegeneració; Malaltia neuromuscularMotoneurona; Neurodegeneración; Enfermedad neuromuscularMotoneuron; Neurodegeneration; Neuromuscular diseaseSpinal muscular atrophy (SMA) is a neuromuscular genetic disease caused by reduced survival motor neuron (SMN) protein. SMN is ubiquitous and deficient levels cause spinal cord motoneurons (MNs) degeneration and muscle atrophy. Nevertheless, the mechanism by which SMN reduction in muscle contributes to SMA disease is not fully understood. Therefore, studies evaluating atrophy mechanisms in SMA muscles will contribute to strengthening current knowledge of the pathology. Here we propose to evaluate autophagy in SMA muscle, a pathway altered in myotube atrophy. We analized autophagy proteins and mTOR in muscle biopsies, fibroblasts, and lymphoblast cell lines from SMA patients and in gastrocnemius muscles from a severe SMA mouse model. Human MNs differentiated from SMA and unaffected control iPSCs were also included in the analysis of the autophagy. Muscle biopsies, fibroblasts, and lymphoblast cell lines from SMA patients showed reduction of the autophagy marker LC3-II. In SMA mouse gastrocnemius, we observed lower levels of LC3-II, Beclin 1, and p62/SQSTM1 proteins at pre-symptomatic stage. mTOR phosphorylation at Ser2448 was decreased in SMA muscle cells. However, in mouse and human cultured SMA MNs mTOR phosphorylation and LC3-II levels were increased. These results suggest a differential regulation in SMA of the autophagy process in muscle cells and MNs. Opposite changes in autophagy proteins and mTOR phosphorylation between muscle cells and neurons were observed. These differences may reflect a specific response to SMN reduction, which could imply diverse tissue-dependent reactions to therapies that should be taken into account when treating SMA patients.The authors wish to thank the consenting parents and patients. This work was supported by grants from Instituto de Salud Carlos III, Fondo de Inversiones Sanitarias, Unión Europea, Fondo Europeo de Desarrollo Regional (FEDER) “Una manera de hacer Europa” (PI17/00231, PI20/00098), AGAUR (2014 SGR 1087), and Fundació La Marató TV3 (73/C/2020). AG is a Serra Hunter Fellow from Generalitat de Catalunya, AS holds a fellowship from Universitat de Lleida and M.J.P-G was awarded the Marie-Curie fellowship (BP-B 00083). We thank Elaine Lilly, PhD, for English language revision of the manuscript

Análisis aerobiológico del polen de Cupressaceae en Granada (sureste P. Ibérica): su repercusión en la población atópica

XV lnternational A.P.L.E. Symposium of Palynolog

Aspirin and its Metabolites Enhance the Expression of Vascular Endothelial Growth Factor in Retinal Pigment Epithelial Cell Cultures – Implications in the Pathophysiology of Age-Related Macular Degeneration

Purpose: An estimated 19.3% of adults, especially the elderly in the United States regularly use Aspirin for cardioprotection. Recently, multiple cohort studies have concluded that regular aspirin use for 10-15 years was associated with a statistically significant increase in the risk of incident age-related and neovascular acute macular degeneration. It has been hypothesized that aspirin or its metabolites induce the expression of vascular endothelial growth factor (VEGF). Materials & Methods: Retinal pigment epithelial cells, ARPE-19 (ATCC®CRL-2302™) were cultured. The cells were grown to achieve 95% confluence and then the media was changed. Cells cultured under blue light, red light, or darkness were subjected to a challenge with high dose aspirin (0.925 mg/dL), low dose aspirin (0.325 mg/dL), or hippuric acid (0.325 mg/dL). Light was generated using 2 red or blue LEDs powered by 3v CR2032 batteries. The 24-well plate was incubated with or without drugs in blue light, red light or darkness at 37C for 16 hours. The supernatants were harvested, and VEGF was quantified. One-way ANOVA using Dunnett’s multiple comparison test was performed to analyze statistical significance. Results: Cells exposed to blue light or darkness and hippuric acid showed a statistically significant increase in VEGF secretion (P=0.0012). However, cells exposed to red light with hippuric acid challenge showed no significant difference from the mean of cells exposed to darkness and sham control. Conclusions: Retinal pigment epithelial cells challenged with oxidative stress provided by blue light or darkness in the presence of hippuric acid increased VEGF secretion, suggesting a possible cause for neovascularization in age-related macular degeneration. RPE cells exposed to red light, known to abrogate oxidative stress, had decreased levels of VEGF induction by hippuric acid