2,797 research outputs found

    Spectra of ultrabroadband squeezed pulses and the finite-time Unruh-Davies effect

    Full text link
    We study spectral properties of quantum radiation of ultimately short duration. In particular, we introduce a continuous multimode squeezing operator for the description of subcycle pulses of entangled photons generated by a coherent-field driving in a thin nonlinear crystal with second order susceptibility. We find the ultrabroadband spectra of the emitted quantum radiation perturbatively in the strength of the driving field. These spectra can be related to the spectra expected in an Unruh-Davies experiment with a finite time of acceleration. In the time domain, we describe the corresponding behavior of the normally ordered electric field variance.Comment: 11 pages, 5 figure

    The psychometric properties of the Portuguese version of the Personality Inventory for DSM-5

    Get PDF
    The DSM-5 Section III proposes a hybrid dimensional-categorical model of conceptualizing personality and its disorders that includes assessment of impairments in personality functioning (criterion A) and maladaptive personality traits (criterion B). The Personality Inventory for the DSM-5 is a new dimensional tool, composed of 220 items organized into 25 facets that delineate ?ve higher order domains of clinically relevant personality differences, and was developed to operationalize the DSM-5 model of pathological personality traits. The current studies address the internal consistency (study 1), the test-retest reliability (study 2) and the criterion validity (studies 3 and 4) of the Portuguese version of the PID-5 in samples of native speaking psychology students. Results indicated good internal consistency reliabilities and good temporal stability reliabilities for the majority of the PID-5 traits. The correlational pattern of the PID-5 traits with two measures of personality was in accordance with theoretical expectations and showed its concurrent validity.info:eu-repo/semantics/acceptedVersio

    Characterization of polypropylene (PP) and poly(ethylene terephthalate) (PET) multifilament braided textile structures for Achilles tendon partial substitution

    Get PDF
    When tendon injuries present a too large damage extension, the conventional treatment options do not result, so a new prosthetic device needs to be developed to partially replace a tendon. Therefore, in this study, different braided textile structures based on polypropylene (PP) and poly (ethylene terephthalate) (PET) multifilament yarns were developed, using a textile technology-based technique, in order to mimic the fibrous structure of tendons. Structures with different architectures were developed using different PP or PET yarns number and different braiding take-up rates, which consequently leads to different braid angles. The braids architecture influenced the porosity level, swelling profile, wicking ability and mostly their mechanical behavior. It was observed that the load at failure of the braids was mainly controlled by the number of yarns, but the strain level was mostly influenced by the take-up rate and consequently by the braid angle. Regarding the stiffness level, it results from a combination of the yarns number and braid angle. The structure based on 16 PET yarns, produced with the highest take-up rate, revealed a very promising creep and force-relaxation behavior for the final application, as well as a very interesting fatigue resistance.Authors acknowledge the financial support from FCT (Fundação para a Ciência e a Tecnologia), through the Grant SFRH/BD/88829/2012, Project PEst-C/EME/UI0285/2011 and Project UIDB/50006/2020

    Collateral and Debt Maturity Choice. A Signaling Model

    Get PDF
    This paper derives optimal loan policies under asymmetric information where banks offer loan contracts of long and short duration, backed or unbacked with collateral. The main novelty of the paper is that it analyzes a setting in which high quality firms use collateral as a complementary device along with debt maturity to signal their superiority. The least-cost signaling equilibrium depends on the relative costs of the signaling devices, the difference in firm quality and the proportion of good firms in the market. Model simulations suggest a non-monotonic relationship between firm quality and debt maturity, in which high quality firms have both long-term secured debt and short-term secured or non-secured debt.

    Effect of Hemodynamic Changes in Plasma Propofol Concentrations Associated with Knee-Chest Position in Spinal Surgery: A Prospective Study

    Get PDF
    Background: Anesthesia induction and maintenance with propofol can be guided by target-controlled infusion (TCI) systems using pharmacokinetic (Pk) models. Physiological variables, such as changes in cardiac output (CO), can influence propofol pharmacokinetics. Knee-chest (KC) surgical positioning can result in CO changes. Objectives: This study aimed to evaluate the relationship between propofol plasma concentration prediction and CO changes after induction and KC positioning. Methods: This two-phase prospective cohort study included 20 patients scheduled for spinal surgery. Two different TCI anesthesia protocols were administered after induction. In phase I (n = 9), the loss of consciousness (LOC) concentration was set as the propofol target concentration and CO changes following induction and KC positioning were quantified. In phase II (n = 11), based on data from phase I, two reductions in the propofol target concentration on the pump were applied after LOC and before KC positioning. Propofol plasma concentrations were measured at different moments in both phases: after induction and after KC positioning. Results: Schnider Pk model showed a good performance in predicting propofol concentration after induction; however, after KC positioning, when a significant drop in CO occurred, the measured propofol concentrations were markedly underestimated. Intended reductions in the propofol target concentration did not attenuate HD changes. In the KC position, there was no correlation between the propofol concentration estimated by the Pk model and the measured concentration in plasma, as the latter was much higher (P = 0.013) while CO and BIS decreased significantly (P < 0.001 and P = 0.004, respectively). Conclusions: Our study showed that the measured propofol plasma concentrations during the KC position were significantly underestimated by the Schnider Pk model and were associated with significant CO decrease. When placing patients in the KC position, anesthesiologists must be aware of pharmacokinetic changes and, in addition to standard monitoring, the use of depth of anesthesia and cardiac output monitors may be considered in high-risk patients.This work was partially funded by the Foundation for Science and Technology, FCT, through national (MEC) and European structural (FEDER) funds, in the scope of the research projects UID/MAT/04106/2019 (CIDMA/UA), UID/CEC/00127/2019 (IEETA/UA) and UID/MAT/00144/2019 (CMUP/UP). This work was also partially suported by Portugal 2020 under the Competitiveness and Internationalization Operational Program, and by the European Regional Development Fund through project SOCA-Smart Open Campus (CENTRO-01-0145-FEDER-000010), acknowledgements from Sonia Gouveia. Aura Silva also acknowledges the postdoctoral grant by FCT (ref. SFRH/BPD/75697/2011).info:eu-repo/semantics/publishedVersio
    • …
    corecore