Electronic, electrical and thermoelectric properties of Ba0.95Ca0.05Ti0.95Y0.05O2.975 compound: Experimental study and DFT-mBJ calculation.

This article explores the impact of co-doping BaTiO3 ceramics with Ca2+ and Y3+ using solid-state reactions to improve its dielectric constant and decrease losses. The oxide BCTYO (Ba0.95Ca0.05Ti0.95Y0.05O2.975) exhibits a tetragonal crystal structure, characterized by a space group of P4mm. By examining the behavior of the doped BaTiO3 sample and performing simulations, researchers can better understand the underlying mechanisms and optimize material properties for specific applications. DFT study shows a semiconductor behavior with an indirect gap (Eg = 2.5 eV). The partial DOS proves that the hybridization between the orbitals Ti 3d, Y 3d, and O 2p is responsible for the band gap and the hopping processes. The analysis of conductivity curves provides evidence for the semiconductor characteristics of the material under investigation. By determining the activation energy (Ea) through analyzing Ln(fmax) and conductivity as a function of 1000/T, the interconnection between conduction and relaxation phenomena is demonstrated. The study of the real part of the dielectric permittivity (ε') shows a transition at Tc = 380 K. The obtained results are promising and indicate that the studied material has the potential for various electronic applications (energy storage and diode fabrication …). Moreover, the thermal, electrical, and thermoelectric characteristics were examined utilizing the semi-classical Boltzmann theory. The findings revealed an intriguing result, suggesting that Ba0.95Ca0.05Ti0.95Y0.05O2.975 holds promise as a potential candidate for application in thermoelectric devices.

Effect of frequency on the classical and relaxor ferroelectric behavior of substituted titanate Ba0.7Er0.16Ca0.05Ti0.91Sn0.09O3.

In the present work, we synthesized the perovskite Ba0.70Er0.16Ca0.05Ti0.91Sn0.09O3 compound (BECTSO) by a solid-state reaction and sintering at 1200 °C. The effects of doping on the structural, electrical, dielectric, and ferroelectric characteristics of the material are examined in this work. X-ray powder diffraction analysis shows that BECTSO crystallizes in a tetragonal structure with space group P4mm. A detailed study of the dielectric relaxation of the BECTSO compound has been reported for the first time. Classical low-frequency ferroelectric and high-frequency relaxor ferroelectric behaviors have been studied. The study of the real part of the permittivity (ε') as a function of temperature demonstrated a high dielectric constant and identified a phase transition from the ferroelectric phase to the paraelectric phase at Tc = 360 K. The analysis of conductivity curves shows two behaviors: semiconductor behavior for f < 106 Hz and metallic behavior for f >106 Hz. The relaxation phenomenon is dominated by the short-range motion of the charge carriers. The BECTSO sample could be considered as a potential lead-free material for next-generation non-volatile memory devices and wide-temperature range capacitor applications.

Study of physical properties of the Li0.5MgFe1.5O3.5 ferrite nanoparticles.

In the present research study, the structural, optical, magnetic, electrical and dielectrical properties of the spinel ferrite Li0.5MgFe1.5O3.5, synthesized using a sol-gel auto-combustion method were studied. X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy revealed that this sample crystallizes in a cubic spinel structure with space group Fd3̄m. Moreover, the optical investigation by UV-visible spectroscopy has revealed that the band gap for our sample is (E g = 2.87 eV), which shows that our compound is a potential candidate for optoelectronic applications. The values of the remanent magnetization M r = 0.13 emu g-1, of the coercive field H C = 4.65 Oe deduced from the hysteresis loop, are very low, suggesting the superparamagnetic behavior of our sample. Additionally, the temperature coefficient of resistance (TCR) is -19% affirmed that Li0.5MgFe1.5O3.5 ferrite is a good candidate for detecting infrared radiation and infrared bolometric applications. Indeed, the activation energies were calculated from the imaginary part of the impedance, the electrical conductivity, and the imaginary part of the modulus, thus demonstrating that the charge carriers involved in the processes of conduction and relaxation are the same.

[Invasive mechanical ventilation in patients with solid tumor or hematological malignancy]. / Ventilation mécanique invasive chez le patient d'onco-hématologie.

Invasive mechanical ventilation in onco-hematology patients has become relatively routine, and is now part and parcel of their care pathway. Nevertheless, specific complications and subsequent therapeutic possibilities require discussion. To a greater extent than with regard to other patient populations, cooperation between specialist and ICU physician is mandatory, the objective being to more comprehensively assess a therapeutic project before or during the period of invasive mechanical ventilation. After an overview of recent results concerning ventilated patients in intensive care, this review aims to describe the specific complications and factors associated with mortality in this population.

Feasibility and Safety of Active Physiotherapy in the Intensive Care Unit for Intubated Patients with Malignancy.

OBJECTIVES: Physiotherapy leads to improvements in critically ill patients who receive mechanical ventilation. However, cancer patients have not been included in previous studies on this subject. This study explored the feasibility and safety of physiotherapy in the intensive care unit for patients with malignancy. DESIGN: Observational prospective single-centre study, comparing cancer and control patients. PATIENTS: All consecutive patients admitted to the intensive care unit who needed invasive mechanical ventilation for more than 2 days with no contraindication to physiotherapy were included in the study. METHODS: The main outcome was the proportion of physiotherapy sessions at the prescribed level in each group. RESULTS: A total of 60 patients were included within 1 year. A total of 576 days were screened for physiotherapy sessions and 367 physiotherapy-days were analysed (137 days for control patients and 230 days for cancer patients). The ratio of physiotherapy sessions performed/prescribed did not differ between groups: 0.78 (0.47-1) in the control group vs 0.69 (0.6-1) in the cancer group (odds ratio 1.18 (IC95% 0.74-1.89); p = 0.23). A sensitivity analysis including patient effect as random variable confirmed those results (odds ratio 1.16 (0.56-2.38), p = 0.69). Adverse events occurred with the same frequency in cancer patients and non-cancer patients. CONCLUSION: Physiotherapy in cancer patients who require intubation is feasible and safe. However, only two-thirds of prescribed physiotherapy sessions were performed. Studies are warranted to explore the barriers to physiotherapy in the intensive care unit setting.

Study of the structural, electronic, magnetic and magnetocaloric properties of La0.5Ca0.5Mn0.9V0.1O3 sample: first-principles calculation (DFT-MFT).

This paper presents a correlation between experimental and theoretical approaches to study the structural, electronic, magnetic, and magnetocaloric properties of La0.5Ca0.5Mn0.9V0.1O3. The studied compound crystallizes in the Pbnm orthorhombic space group. The calculated DOS using the DFT + U method proves that La0.5Ca0.5Mn0.9V0.1O3 sample exhibits semi-metallic behavior, which is preferred in spintronic applications. The calculated PDOS proves that the high hydration among Mn 3d, V 3d and O 2p at the Fermi energy level is responsible for the FM behavior of La0.5Ca0.5Mn0.9V0.1O3. The magnetic moment has been calculated using DFT results by estimating the valence electron population. The optical properties show high light absorption in the UV region. By using the Bean-Rodbell method, the magnetic phase shows a second-order transition where η = 0.85, and the exchange parameter λ is found to be 1.19 T g-1 emu-1. Based on the mean-field theory, the saturation magnetization (M 0), the Landé factor (g), and the total angular momentum (J) were determined. These parameters were used to simulate magnetization as a function of the magnetic field at different temperatures as well as the variation of the magnetic entropy change ΔS M (T).

Polarization characterization of a Mach-Zehnder interferometer.

Polarization characterization of a Mach-Zehnder interferometer, based on the state of polarization (SOP) and power measurement at the interferometer output, is presented. We study the SOP and degree of polarization (DOP) of the output light, first as a function of the light power in each arm of the interferometer for a fixed input SOP and DOP, and second as a function of the SOP's in each arm of the interferometer for a fixed input power. Stokes formalism and the Poincaré sphere are used for simultaneous representation of the SOP and DOP, as well as their evolution. It is shown that the SOP and DOP stability and also the output light power are highly dependent on the light source coherence. Knowledge of these different parameters leads to configurations that allow simultaneous control of the SOP and DOP. We can hence realize a quasi-monochromatic nonpolarized light source, which is useful for the polarization-independent characterization of optical components.