Characterization of a defective PbWO4 crystal cut along the a-c crystallographic plane: structural assessment and a novel photoelastic stress analysis

Among scintillators, the PWO is one of the most widely used, for instance in CMS calorimeter at CERN and PANDA project. Crystallographic structure and chemical composition as well as residual stress condition, are indicators of homogeneity and good quality of the crystal. In this paper, structural characterization of a defective PbWO4 (PWO) crystal has been performed by X-ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and Photoelasticity in the unusual a-c crystallographic plane. XRD and EDS analysis have been used to investigate crystallographic orientation and chemical composition, while stress distribution, which indicates macroscopic inhomogeneities and defects, has been obtained by photoelastic approaches, in Conoscopic and Sphenoscopic configuration. Since the sample is cut along the a-c crystallographic plane, a new method is proposed for the interpretation of the fringe pattern. The structural analysis has detected odds from the nominal lattice dimension, which can be attributed to the strong presence of Pb and W. A strong inhomogeneity over the crystal sample has been revealed by the photoelastic inspection. The results give reliability to the proposed procedure which is exploitable in crystals with other structures.Comment: 18 pages, 10 figures, revised versio

Annual and semiannual variations of vertical total electron content during high solar activity based on GPS observations

Annual, semiannual and seasonal variations of the Vertical Total Electron Content (VTEC) have been investigated during high solar activity in 2000. In this work we use Global IGS VTEC maps and Principal Component Analysis to study spatial and temporal ionospheric variability. The behavior of VTEC variations at two-hour periods, at noon and at night is analyzed. Particular characteristics associated with each period and the geomagnetic regions are highlighted. <br><br> The variations at night are smaller than those obtained at noon. At noon it is possible to see patterns of the seasonal variation at high latitude, and patterns of the semiannual anomaly at low latitudes with a slow decrease towards mid latitudes. At night there is no evidence of seasonal or annual anomaly for any region, but it was possible to see the semiannual anomaly at low latitudes with a sudden decrease towards mid latitudes. In general, the semiannual behavior shows March–April equinox at least 40 % higher than September one. Similarities and differences are analyzed also with regard to the same analysis done for a period of low solar activity

Molecular dynamics simulations of reflection and adhesion behavior in Lennard-Jones cluster deposition

We conduct molecular dynamics simulations of the collision of atomic clusters with a weakly-attractive surface. We focus on an intermediate regime, between soft-landing and fragmentation, where the cluster undergoes deformation on impact but remains largely intact, and will either adhere to the surface (and possibly slide), or be reflected. We find that the outcome of the collision is determined by the Weber number, We i.e. the ratio of the kinetic energy to the adhesion energy, with a transition between adhesion and reflection occurring as We passes through unity. We also identify two distinct collision regimes: in one regime the collision is largely elastic and deformation of the cluster is relatively small but in the second regime the deformation is large and the adhesion energy starts to depend on the kinetic energy. If the transition between these two regimes occurs at a similar kinetic energy to that of the transition between reflection and adhesion, then we find that the probability of adhesion for a cluster can be bimodal. In addition we investigate the effects of the angle of incidence on adhesion and reflection. Finally we compare our findings both with recent experimental results and with macroscopic theories of particle collisions.Comment: 18 pages, 13 figure

Towards semantic software engineering environments

Software tools processing partially common set of data should share an understanding of what these data mean. Since ontologies have been used to express formally a shared understanding of information, we argue that they are a way towards Semantic SEEs. In this paper we discuss an ontology-based approach to tool integration and present ODE, an ontology-based SEE

Quantum dynamics of a vibrational mode of a membrane within an optical cavity

Optomechanical systems are a promising candidate for the implementation of quantum interfaces for storing and redistributing quantum information. Here we focus on the case of a high-finesse optical cavity with a thin vibrating semitransparent membrane in the middle. We show that robust and stationary optomechanical entanglement could be achieved in the system, even in the presence of nonnegligible optical absorption in the membrane. We also present some preliminary experimental data showing radiation-pressure induced optical bistability.Comment: 6 pages, 2 figures. Work presented at the conference QCMC 2010 held on 19-23 July 2010 at the University of Queensland, Brisbane, Australi

The inelastic Takahashi hard-rod gas

We study a one-dimensional fluid of hard-rods interacting each other via binary inelastic collisions and a short ranged square-well potential. Upon tuning the depth and the sign of the well, we investigate the interplay between dissipation and cohesive or repulsive forces. Molecular dynamics simulations of the cooling regime indicate that the presence of this simple interparticle interaction is sufficient to significantly modify the energy dissipation rates expected by the Haff's law for the free cooling. The simplicity of the model makes it amenable to an analytical approach based on the Boltzmann-Enskog transport equation which allows deriving the behaviour of the granular temperature. Furthermore, in the elastic limit, the model can be solved exactly to provide a full thermodynamic description. A meaningful theoretical approximation explaining the properties of the inelastic system in interaction with a thermal bath can be directly extrapolated from the properties of the corresponding elastic system, upon a proper re-definition of the relevant observables. Simulation results both in the cooling and driven regime can be fairly interpreted according to our theoretical approach and compare rather well to our predictions.Comment: 14 pages RevTex, 9 eps figure

SMAC — A Modular Open Source Architecture for Medical Capsule Robots

The field of Medical Capsule Robots (MCRs) is gaining momentum in the robotics community, with applications spanning from abdominal surgery to gastrointestinal (GI) endoscopy. MCRs are miniature multifunctional devices usually constrained in both size and on-board power supply. The design process for MCRs is time consuming and resource intensive, as it involves the development of custom hardware and software components. In this work, we present the STORM Lab Modular Architecture for Capsules (SMAC), a modular open source architecture for MCRs aiming to provide the MCRs research community with a tool for shortening the design and development time for capsule robots. The SMAC platform consists of both hardware modules and firmware libraries that can be used for developing MCRs. In particular, the SMAC modules are miniature boards of uniform diameter (i.e., 9.8 mm) that are able to fulfill five different functions: signal coordination combined with wireless data transmission, sensing, actuation, powering and vision/illumination. They are small in size, low power, and have reconfigurable software libraries for the Hardware Abstraction Layer (HAL), which has been proven to work reliably for different types of MCRs. A design template for a generic SMAC application implementing a robust communication protocol is presented in this work, together with its finite state machine abstraction, capturing all the architectural components involved. The reliability of the wireless link is assessed for different levels of data transmission power and separation distances. The current consumption for each SMAC module is quantified and the timing of a SMAC radio message transmission is characterized. Finally, the applicability of SMAC in the field of MCRs is discussed by analysing examples from the literature

A wireless platform for in vivo measurement of resistance properties of the gastrointestinal tract

Active locomotion of wireless capsule endoscopes has the potential to improve the diagnostic yield of this painless technique for the diagnosis of gastrointestinal tract disease. In order to design effective locomotion mechanisms, a quantitative measure of the propelling force required to effectively move a capsule inside the gastrointestinal tract is necessary. In this study, we introduce a novel wireless platform that is able to measure the force opposing capsule motion, without perturbing the physiologic conditions with physical connections to the outside of the gastrointestinal tract. The platform takes advantage of a wireless capsule that is magnetically coupled with an external permanent magnet. A secondary contribution of this manuscript is to present a real-time method to estimate the axial magnetic force acting on a wireless capsule manipulated by an external magnetic field. In addition to the intermagnetic force, the platform provides real-time measurements of the capsule position, velocity, and acceleration. The platform was assessed with benchtop trials within a workspace that extends 15 cm from each side of the external permanent magnet, showing average error in estimating the force and the position of less than 0.1 N and 10 mm, respectively. The platform was also able to estimate the dynamic behavior of a known resistant force with an error of 5.45%. Finally, an in vivo experiment on a porcine colon model validated the feasibility of measuring the resistant force in opposition to magnetic propulsion of a wireless capsule

Type 2 diabetes and reduced exercise tolerance: A review of the literature through an integrated physiology approach

The association between type 2 diabetes mellitus (T2DM) and heart failure (HF) is well established. Early in the course of the diabetic disease, some degree of impaired exercise capacity (a powerful marker of health status with prognostic value) can be frequently highlighted in otherwise asymptomatic T2DM subjects. However, the literature is quite heterogeneous, and the underlying pathophysiologic mechanisms are far from clear. Imaging-cardiopulmonary exercise testing (CPET) is a non-invasive, provocative test providing a multi-variable assessment of pulmonary, cardiovascular, muscular, and cellular oxidative systems during exercise, capable of offering unique integrated pathophysiological information. With this review we aimed at defying the cardiorespiratory alterations revealed through imaging-CPET that appear specific of T2DM subjects without overt cardiovascular or pulmonary disease. In synthesis, there is compelling evidence indicating a reduction of peak workload, peak oxygen assumption, oxygen pulse, as well as ventilatory efficiency. On the contrary, evidence remains inconclusive about reduced peripheral oxygen extraction, impaired heart rate adjustment, and lower anaerobic threshold, compared to non-diabetic subjects. Based on the multiparametric evaluation provided by imaging-CPET, a dissection and a hierarchy of the underlying mechanisms can be obtained. Here we propose four possible integrated pathophysiological mechanisms, namely myocardiogenic, myogenic, vasculogenic and neurogenic. While each hypothesis alone can potentially explain the majority of the CPET alterations observed, seemingly different combinations exist in any given subject. Finally, a discussion on the effects -and on the physiological mechanisms-of physical activity and exercise training on oxygen uptake in T2DM subjects is also offered. The understanding of the early alterations in the cardiopulmonary response that are specific of T2DM would allow the early identification of those at a higher risk of developing HF and possibly help to understand the pathophysiological link between T2DM and HF

Response adaptation in barrel cortical neurons facilitates stimulus detection during rhythmic whisker stimulation in anesthetized mice

Rodents use rhythmic whisker movements at frequencies between 4 and 12 Hz to sense the environment that will be disturbed when the animal touches an object. The aim of this work is to study the response adaptation to rhythmic whisker stimulation trains at 4 Hz in the barrel cortex and the sensitivity of cortical neurons to changes in the timing of the stimulation pattern. Longitudinal arrays of four iridium oxide electrodes were used to obtain single-unit recordings in supragranular, granular, and infragranular neurons in urethane anesthetized mice. The stimulation protocol consisted in a stimulation train of three air puffs (20 ms duration each) in which the time interval between the first and the third stimuli was fixed (500 ms) and the time interval between the first and the second stimuli changed (regular: 250 ms; “accelerando”: 375 ms; or “decelerando” stimulation train: 125 ms interval). Cortical neurons adapted strongly their response to regular stimulation trains. Response adaptation was reduced when accelerando or decelerando stimulation trains were applied. This facilitation of the shifted stimulus was mediated by activation of NMDA receptors because the effect was blocked by AP5. The facilitation was not observed in thalamic nuclei. Facilitation increased during periods of EEG activation induced by systemic application of IGF-I, probably by activation of NMDA receptors, as well. We suggest that response adaptation is the outcome of an intrinsic cortical information processing aimed at contributing to improve the detection of “unexpected” stimuli that disturbed the rhythmic behavior of exploratio