2,920 research outputs found

    Adiabatic quantum dynamics of a random Ising chain across its quantum critical point

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    We present here our study of the adiabatic quantum dynamics of a random Ising chain across its quantum critical point. The model investigated is an Ising chain in a transverse field with disorder present both in the exchange coupling and in the transverse field. The transverse field term is proportional to a function Γ(t)\Gamma(t) which, as in the Kibble-Zurek mechanism, is linearly reduced to zero in time with a rate τ1\tau^{-1}, Γ(t)=t/τ\Gamma(t)=-t/\tau, starting at t=t=-\infty from the quantum disordered phase (Γ=\Gamma=\infty) and ending at t=0t=0 in the classical ferromagnetic phase (Γ=0\Gamma=0). We first analyze the distribution of the gaps -- occurring at the critical point Γc=1\Gamma_c=1 -- which are relevant for breaking the adiabaticity of the dynamics. We then present extensive numerical simulations for the residual energy EresE_{\rm res} and density of defects ρk\rho_k at the end of the annealing, as a function of the annealing inverse rate τ\tau. %for different lenghts of the chain. Both the average Eres(τ)E_{\rm res}(\tau) and ρk(τ)\rho_k(\tau) are found to behave logarithmically for large τ\tau, but with different exponents, [Eres(τ)/L]av1/lnζ(τ)[E_{\rm res}(\tau)/L]_{\rm av}\sim 1/\ln^{\zeta}(\tau) with ζ3.4\zeta\approx 3.4, and [ρk(τ)]av1/ln2(τ)[\rho_k(\tau)]_{\rm av}\sim 1/\ln^{2}(\tau). We propose a mechanism for 1/ln2τ1/\ln^2{\tau}-behavior of [ρk]av[\rho_k]_{\rm av} based on the Landau-Zener tunneling theory and on a Fisher's type real-space renormalization group analysis of the relevant gaps. The model proposed shows therefore a paradigmatic example of how an adiabatic quantum computation can become very slow when disorder is at play, even in absence of any source of frustration.Comment: 10 pages, 11 figures; v2: added references, published versio

    Exclusive b→sνν¯ induced transitions in the RS c model

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    We study a set of exclusive B and Bs decay modes induced by the rare b→sνν¯ transition in the RS c model, an extra-dimensional extension of the standard model with warped 5D metric and extended gauge group. We discuss the role of correlations among the observables, and their importance for detecting the predicted small deviations from the standard model expectations

    Exclusive b → s ν ν induced transitions in the RSc model

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    We study a set of exclusive B and Bs decay modes induced by the rare (Formula presented.) transition in the RSc model, an extra-dimensional extension of the standard model with warped 5D metric and extended gauge group. We discuss the role of correlations among the observables, and their importance for detecting the predicted small deviations from the standard model expectations

    Easy Scheme Outlining the Various Morphological and Vascular Abnormalities of the Lymph Node Structure Associated with Recent COVID-19 Vaccination, Each with a Different Clinical/Diagnostic Management

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    Throughout this recent ongoing SARS-CoV-2 pandemic, the European Society of Breast Imaging have surely contributed in improving the management of unilateral axillary adenopathy appearance homolaterally to the side of vaccine inoculation. After considering the patient's COVID-19 history of vaccination, our group produced a day-to-day scheme that evaluates meticulously the probability of mammary malignancy, according to the lymph node characteristics including vascular abnormalities. It comprises of a UN (ultrasound node) score ranging from 2 to 5, that increases with the suspicion of malignancy. In this setting and in view of the additional incoming COVID-19 boost-dose vaccinations, we believe our model could be of great utility to radiologist when assessing patients whom do not have a straight forward diagnosis, in order to reduce breast cancer missed diagnosis, avoid delaying vaccinations, reduce rescheduling of breast imaging examinations and lastly avoid unnecessary lymph node biopsies

    Second harmonic generation on self-assembled GaAs/Au nanowires with thickness gradient

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    Here we investigated the SH generation at the wavelength of 400 nm (pump laser at 800 nm, 120 fs pulses) of a "metasurface" composed by an alternation of GaAs nano-grooves and Au nanowires capping portions of flat GaAs. The nano-grooves depth and the Au nanowires thickness gradually vary across the sample. The samples are obtained by ion bombardment at glancing angle on a 150 nm Au mask evaporated on a GaAs plane wafer. The irradiation process erodes anisotropically the surface, creating Au nanowires and, at high ion dose, grooves in the underlying GaAs substrate (pattern transfer). The SHG measurements are performed for different pump linear polarization angle at different positions on the "metasurface" in order to explore the regions with optimal conditions for SHG efficiency. The pump polarization angle is scanned by rotating a half-wave retarder plate. While the output SH signal in reflection is analyzed by setting the polarizer in s or p configuration in front of the detector. The best polarization condition for SHG is obtained in the configuration where the pump and second harmonic fields are both p polarized, and the experiments show a SH polarization dependence of the same symmetry of bulk GaAs. Thus, the presence of gold contributes only as field localization effect, but do not contributes directly as SH generator

    Obese patients with a binge eating disorder have an unfavorable metabolic and inflammatory profile

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    To evaluate whether obese patients with a binge eating disorder (BED) have an altered metabolic and inflammatory profile related to their eating behaviors compared with non-BED obese.A total of 115 White obese patients consecutively recruited underwent biochemical, anthropometrical evaluation, and a 75-g oral glucose tolerance test. Patients answered the Binge Eating Scale and were interviewed by a psychiatrist. The patients were subsequently divided into 2 groups according to diagnosis: non-BED obese (n = 85) and BED obese (n = 30). Structural equation modeling analysis was performed to elucidate the relation between eating behaviors and metabolic and inflammatory profile.BED obese exhibited significantly higher percentages of altered eating behaviors, body mass index (P < 0.001), waist circumference (P < 0.01), fat mass (P < 0.001), and a lower lean mass (P < 0.001) when compared with non-BED obese. Binge eating disorder obese also had a worse metabolic and inflammatory profile, exhibiting significantly lower high-density lipoprotein cholesterol levels (P < 0.05), and higher levels of glycated hemoglobin (P < 0.01), uric acid (P < 0.05), erythrocyte sedimentation rate (P < 0.001), high-sensitive C-reactive protein (P < 0.01), and white blood cell counts (P < 0.01). Higher fasting insulin (P < 0.01) and higher insulin resistance (P < 0.01), assessed by homeostasis model assessment index and visceral adiposity index (P < 0.001), were observed among BED obese. All differences remained significant after adjusting for body mass index. No significant differences in fasting plasma glucose or 2-hour postchallenge plasma glucose were found. Structural equation modeling analysis confirmed the relation between the altered eating behaviors of BED and the metabolic and inflammatory profile.Binge eating disorder obese exhibited an unfavorable metabolic and inflammatory profile, which is related to their characteristic eating habits

    Signals of Warped Extra Dimensions at the LHC

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    We discuss the signatures of the spin-2 graviton excitations predicted by the Randall-Sundrum model with one warped extra dimension, in dilepton and diphoton production at LHC. By using a specific angular analysis, we assess the ranges in mass and coupling constant where such gravitons can be discriminated against competitor spin-1 and spin-0 objects, that potentially could manifest themselves in these processes with the same mass and rate of events. Depending on the value of the coupling constant to quarks and leptons, the numerical results indicate graviton identification mass ranges up to 1.1-2.4 TeV and 1.6-3.2 TeV for LHC nominal energy of 14 TeV and time-integrated luminosity of 10 and 100~fb1{\rm fb}^{-1}, respectively.Comment: 8 pages, Talk given at QCD@Work - International Workshop on QCD - Theory and Experiment, 20 - 23 June, 2010, Martina Franca Ital

    Development of a self-powered piezo-resistive smart insole equipped with low-power BLE connectivity for remote gait monitoring

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    The evolution of low power electronics and the availability of new smart materials are opening new frontiers to develop wearable systems for medical applications, lifestyle monitoring, and performance detection. This paper presents the development and realization of a novel smart insole for monitoring the plantar pressure distribution and gait parameters; indeed, it includes a piezoresistive sensing matrix based on a Velostat layer for transducing applied pressure into an electric signal. At first, an accurate and complete characterization of Velostat-based pressure sensors is reported as a function of sizes, support material, and pressure trend. The realization and testing of a low-cost and reliable piezoresistive sensing matrix based on a sandwich structure are discussed. This last is interfaced with a low power conditioning and processing section based on an Arduino Lilypad board and an analog multiplexer for acquiring the pressure data. The insole includes a 3- axis capacitive accelerometer for detecting the gait parameters (swing time and stance phase time) featuring the walking. A Bluetooth Low Energy (BLE) 5.0 module is included for transmitting in real-time the acquired data toward a PC, tablet or smartphone, for displaying and processing them using a custom Processing® application. Moreover, the smart insole is equipped with a piezoelectric harvesting section for scavenging energy from walking. The onfield tests indicate that for a walking speed higher than 1 ms−1, the device’s power requirements (i.e., P = 5.84 mW ) was fulfilled. However, more than 9 days of autonomy are guaranteed by the integrated 380-mAh Lipo battery in the total absence of energy contributions from the harvesting section
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