Impact of High-Power Short-Duration Radiofrequency Ablation on Esophageal Temperature Dynamic

Background: High-power short-duration (HP-SD) radiofrequency ablation (RFA) has been proposed as a method for producing rapid and effective lesions for pulmonary vein isolation. The underlying hypothesis assumes an increased resistive heating phase and decreased conductive heating phase, potentially reducing the risk for esophageal thermal injury. The objective of this study was to compare the esophageal temperature dynamic profile between HP-SD and moderate-power moderate-duration (MP-MD) RFA ablation strategies. Methods: In patients undergoing pulmonary vein isolation, RFA juxtaposed to the esophagus was delivered in an alternate sequence of HP-SD (50 W, 8–10 s) and MP-MD (25 W, 15–20 s) between adjacent applications (distance, ≤4 mm). Esophageal temperature was recorded using a multisensor probe (CIRCA S-CATH). Temperature data included magnitude of temperature rise, maximal temperature, time to maximal temperature, and time return to baseline. In swine, a similar experimental design compared the effect of HP-SD and MP-MD on patterns of esophageal injury. Results: In 20 patients (68.9±5.8 years old; 60% persistent atrial fibrillation), 55 paired HP-SD and MP-MD applications were analyzed. The esophageal temperature dynamic profile was similar between HP-SD and MP-MD ablation strategies. Specifically, the magnitude of temperature rise (2.1 °C [1.4–3] versus 2.0 °C [1.5–3]; P =0.22), maximal temperature (38.4 °C [37.8–39.3] versus 38.5 °C [37.9–39.4]; P =0.17), time to maximal temperature (24.9±7.5 versus 26.3±6.8 s; P =0.1), and time of temperature to return to baseline (110±23.2 versus 111±25.1 s; P =0.86) were similar between HP-SD and MP-MD ablation strategies. In 6 swine, esophageal injury was qualitatively similar between HP-SD and MP-MD strategies. Conclusions: Esophageal temperature dynamics are similar between HP-SD and MP-MD RFA strategies and result in comparable esophageal tissue injury. Therefore, when using a HP-SD RFA strategy, the shorter application duration should not prompt shorter intervals between applications.

METHODOLOGY FOR DETERMINING THE MAIN INDICATORS OF THE TEMPERATURE AND DYNAMIC CHARACTERISTICS OF THE COOLING SYSTEM OF AN ENERGY VEHICLE DURING OPERATION

The efficiency of internal combustion engines of energy facilities operating in the conditions of enterprises of the agro-industrial complex depends on the stability of the thermal regime of the engine. Its provision is entrusted to the cooling system, in this article which is a radiator with a polyurethane core. The temperature regime of the engine operation affecting a number of factors is given and described - these are design parameters (design features of the radiator and the features of the working process of the radiator, taking into account the operating conditions of the tractor) and operational, which take into account the operating mode of the tractor and natural and climatic conditions. According to the research results during the operation of the tractor in steady conditions, the temperature of the coolant in the system is stable, respectively, the temperature field of the air flow at the inlet and outlet of the radiator with a polyurethane core also stabilizes. To take them into account, the coefficient of thermal properties of the radiator is introduced, which depends on the external and internal temperature-dynamic effects of the environment, and a diagram is constructed that shows the dependence of the temperature of the coolant flowing in the radiator on the generated load of the tractor during operation in the field. At the same time, the temperature-dynamic characteristic of the tractor does not depend on the design features of the engine, but on the power developed by the engine. Therefore, the heat removed from the engine into the coolant is calculated by us through the engine power. Based on this, the characteristic of the thermal balance of the engine and the heat transfer of the radiator during the operation of the tractor at full load are considered, taking into account the change in gears within the speed limits, a graph of the thermal balance of the engine and radiator versus speed is built. Based on the calculations, it was concluded that the use of the characteristics of the traction-dynamic balance of the tractor can serve as the basis for the general analysis and calculated and experimental operating modes of the automotive polymer radiator and the cooling system as a whole, taking into account the loads, climatic conditions and operating parameters of the cooling system

Enhanced Electroplasticity through Room-Temperature Dynamic Recrystallization in a Mg-3Al-1Sn-1Zn Alloy

It has been well known that electric pulse can be utilized to enhance the plasticity of metals, which is attributed to the change of dislocation dynamics, e.g., localized planar slip to homogeneous wavy slip. Here, we show another effect of pulse current, which facilitates texture weakening through room-temperature dynamic recrystallization and additionally improve the plasticity of a polycrystalline Mg-3Al-1Sn-1Zn alloy. By conducting a tensile test under electrical pulse, we found that the peak flow stress and fracture strain depend strongly on current density. As peak current densities increases, the flow stress drops and the fracture strain increases. Our Electron Backscatter Diffraction results suggest that dynamic recrystallization occurs at room temperature, which develops a weakened texture. Our work provides a new insight into electroplasticity mechanism in Mg alloys.

Low Temperature Dynamic Chromatography for the Separation of the Interconverting Conformational Enantiomers of the Benzodiazepines Clonazolam, Flubromazolam, Diclazepam and Flurazepam

Benzodiazepines (BZDs) are an important class of psychoactive drugs with hypnotic-sedative, myorelaxant, anxiolytic and anticonvulsant properties due to interaction with the GABAa receptor in the central nervous system of mammals. BZDs are interesting both in clinical and forensic toxicology for their pharmacological characteristics and potential of abuse. The presence of a non-planar diazepine ring generates chiral conformational stereoisomers, even in the absence of stereogenic centers. A conformational enrichment of BZD at the binding sites has been reported in the literature, thus making interesting a stereodynamic screening of a wide range of BZDs. Herein, we report the investigation of three stereolabile 1,4-benzodiazepine included in the class of “designer benzodiazepines” (e.g., diclazepam, a chloro-derivative of diazepam, and two triazolo-benzodiazepines, flubromazolam and clonazolam) and a commercially available BZD known as flurazepam, in order to study the kinetic of the “ring-flip” process that allows two conformational enantiomers to interconvert at high rate at room temperature. A combination of low temperature enantioselective dynamic chromatography on chiral stationary phase and computer simulations of the experimental chromatograms allowed us to measure activation energies of enantiomerization (ΔG‡) lower than 18.5 kcal/mol. The differences between compounds have been correlated to the pattern of substitutions on the 1,4-benzodiazepinic core.

Experimental studies on the dynamic viscoelastic properties of basalt fiber-reinforced asphalt mixtures

To study the influence of basalt fibers on the viscoelastic mechanical properties of asphalt concrete (AC) mixtures, unconfined compressive dynamic modulus tests were performed on styrene–butadiene–styrene (SBS)-modified AC mixtures reinforced with various contents of basalt fibers ranging from 0.2 to 0.5% by weight at five temperatures and six load frequencies, and the dynamic moduli and phase angles of the mixtures were measured. Compared with the test results of the control mixture (with no basalt fibers), the data show that the high-temperature dynamic modulus of the mixtures initially increases and subsequently decreases with increasing fiber content and reaches its maximum value when the basalt fiber content is 0.3%, while the low-temperature dynamic modulus decreases monotonically with increasing fiber content. Furthermore, the phase angle of the mixtures initially decreases and later increases with increasing fiber content and reaches its minimum value when the basalt fiber content is 0.3%. These behaviors indicate that the addition of basalt fiber improves the high-temperature rutting resistance and low-temperature cracking resistance of the SBS-modified AC mixtures. In addition, the results of the wheel rut test exhibit a good correlation with the results of the dynamic modulus test, revealing the reliability of the dynamic modulus test for evaluating the high-temperature rutting resistance of basalt-fiber-reinforced AC mixtures.

Research on Short-term Aging of Lignin Modified Asphalt

In order to study the micro-aging mechanism of lignin-modified asphalt, different asphalt samples were prepared with lignin content of 0% and 12% by mass. The conventional asphalt index test and high-temperature dynamic shear rheological test were used to analyze the different asphalt samples. The change law of the performance of modified lignin modified asphalt with thermal oxygen aging time. The results show that adding appropriate amount of lignin to each asphalt will increase the penetration and ductility of the base asphalt, reduce the softening point, and significantly improve the high-temperature stability; comparative analysis before and after DSR aging, the complex shear modulus G* increases and The decrease of phase angle δ indicates that lignin can improve the high-temperature rheological properties of asphalt.