Efficiency of inefficient endoreversible thermal machines

We present a study of the performance of endoreversible thermal machines optimized with respect to the thermodynamic force associated with the cold bath in the regime of small thermodynamic forces. These thermal machines can work either as an engine or as a refrigerator. We analyze how the optimal performances are determined by the dependence of the thermodynamic flux on the forces. The results are motivated and illustrated with a quantum model, the three level maser, and explicit analytical expressions of the engine efficiency as a function of the system parameters are given

Toxoplasma gondii down modulates cadherin expression in skeletal muscle cells inhibiting myogenesis

<p>Abstract</p> <p>Background</p> <p><it>Toxoplasma gondii </it>belongs to a large and diverse group of obligate intracellular parasitic protozoa. Primary culture of mice skeletal muscle cells (SkMC) was employed as a model for experimental toxoplasmosis studies. The myogenesis of SkMC was reproduced <it>in vitro </it>and the ability of <it>T. gondii </it>tachyzoite forms to infect myoblasts and myotubes and its influence on SkMC myogenesis were analyzed.</p> <p>Results</p> <p>In this study we show that, after 24 h of interaction, myoblasts (61%) were more infected with <it>T. gondii </it>than myotubes (38%) and inhibition of myogenesis was about 75%. The role of adhesion molecules such as cadherin in this event was investigated. First, we demonstrate that cadherin localization was restricted to the contact areas between myocytes/myocytes and myocytes/myotubes during the myogenesis process. Immunofluorescence and immunoblotting analysis of parasite-host cell interaction showed a 54% reduction in cadherin expression at 24 h of infection. Concomitantly, a reduction in M-cadherin mRNA levels was observed after 3 and 24 h of <it>T. gondii-</it>host cell interaction.</p> <p>Conclusions</p> <p>These data suggest that <it>T. gondii </it>is able to down regulate M-cadherin expression, leading to molecular modifications in the host cell surface that interfere with membrane fusion and consequently affect the myogenesis process.</p

Optimal selection of customers for a last-minute offer

We analyze a short-term revenue optimization problem that involves the optimal targeting of customers for a promotion in which a finite number of perishable items are sold on a last-minute offer. The goal is to select the subset of customers to whom the offer will be made available in order to maximize the expected return. Each client replies with a certain probability and reports a specific value that may depend on the customer type, so that the selected subset has to balance the risk of not selling all the items with the risk of assigning an item to a low value customer. We show that {\em threshold strategies}, which select all those clients with values above a certain optimal threshold, may fail to achieve the maximal revenue. However, using a linear programming relaxation, we prove that they attain a constant factor of the optimal value. Specifically, the achieved factor is ${1\over 2}$ when a single item is to be sold, and approaches 1 as the number of available items grows to infinity. Furthermore, for the single item case, we propose an upper bound based on an exponential size linear program that allows us to obtain a threshold strategy achieving at least ${2\over 3}$ of the optimal revenue. Additionally, although the complexity status of the problem is open, we provide a polynomial time approximation scheme for the single item case, which leads to policies that might have very little structure. Finally we perform a brief computational study of the proposed policies and observe that their performance on randomly generated instances is significantly better than the theoretical predictions

Directional field-dependence of magnetoimpedance effect on integrated YIG/Pt-stripline system

We investigated the magnetization dynamics through the magnetoimpedance effect in an integrated YIG/Pt-stripline system in the frequency range of 0.5 up to 2.0 GHz. Specifically, we explore the dependence of the dynamic magnetic behavior on the field orientation by analyzing beyond the traditional longitudinal magnetoimpedance effect of the transverse and perpendicular setups. We disclose here the strong dependence of the effective damping parameter on the field orientation, as well as verification of the very-low damping parameter values for the longitudinal and transverse configurations. We find considerable sensitivity results, bringing to light the facilities to integrate ferrimagnetic insulators in current and future technological applications.This research was funded by CNPq grand numbers 304943/2020-7 and 407385/2018-5, Capes grand number 88887.573100/2020-00 and FCT grant number CTTI-31/18-CF(2)

High performance of metallic thin films for resistance temperature devices with antimicrobial properties

Titanium-copper alloy films with stoichiometry given by Ti1−xCux were produced by magnetron co-sputtering technique and analyzed in order to explore the suitability of the films to be applied as resistive temperature sensors with antimicrobial properties. For that, the copper (Cu) amount in the films was varied by applying different DC currents to the source during the deposition in order to change the Cu concentration. As a result, the samples showed excellent thermoresistivity linearity and stability for temperatures in the range between room temperature to 110 °C. The sample concentration of Ti0.70Cu0.30 has better characteristics to act as RTD, especially the αTCR of 1990 ×10−6°C−1. The antimicrobial properties of the Ti1−xCux films were analyzed by exposing the films to the bacterias S. aureus and E. coli, and comparing them with bare Ti and Cu films that underwent the same protocol. The Ti1−xCux thin films showed bactericidal effects, by log10 reduction for both bacteria, irrespective of the Cu concentrations. As a test of concept, the selected sample was subjected to 160 h reacting to variations in ambient temperature, presenting results similar to a commercial temperature sensor. Therefore, these Ti1−xCux thin films become excellent antimicrobial candidates to act as temperature sensors in advanced coating systems.This work was supported by FCT-UIDB/04650/2020. A.L.R.S. thanks CAPES (88887.572905 /2020-00) and CNPq. M.A.C. thanks CAPES (8887.573100/2020-00) and CNPq. A.F. thanks the FCT (CTTI-31/18-C.F. (2) junior researcher contract)