Boiling Heat Transfer and Pressure Drop of R1234ze(E) inside a Small-Diameter 2.5 mm Microfin Tube

Currently, the development of high-performance and compact heat exchangers with small- diameter tubes having a hydraulic diameter of less than 5 mm is needed in order to improve the performance of the heat exchanger and to reduce the refrigerant charge for air-conditioning systems. The effects of surface tension and shear stress on boiling heat transfer and flow characteristics become dominant as the tube diameter decreases. In addition, these effects are different from those in conventional-diameter tubes. It is necessary to clarify boiling heat transfer and pressure drop to facilitate the design of evaporators. Furthermore, low global warming potential refrigerants such as HFOs have been attracting attention. However, only limited research is available on the boiling heat transfer and pressure drop of HFO refrigerants in small-diameter microfin tubes. This study experimentally investigated the boiling heat transfer and pressure drop of R1234ze(E) in a horizontal small-diameter microfin tube having 2.5 mm outer diameter and 2.1 mm equivalent diameter. The boiling heat transfer and pressure drop were measured in a mass velocity range of 100–400 kg/(m2s) and heat flux range of 5–20 kW/m2 at a saturation temperature of 15°C. The boiling heat transfer coefficient at the mass velocity of 200 kg/(m2s) exhibited the highest value at the dominant region of tin liquid film evaporation heat transfer. The measured boiling heat transfer coefficient agreed well with previous correlations in only the dominant region of forced convection evaporation. The frictional pressure drop increased with increasing mass velocity and vapor quality. The measured pressure drop agreed well with previous correlations for conventional-diameter microfin tubes

Hitomi X-Ray Studies of Giant Radio Pulses from the Crab Pulsar

To search for giant X-ray pulses correlated with the giant radio pulses (GRPs) from the Crab pulsar, we performed a simultaneous observation of the Crab pulsar with the X-ray satellite Hitomi in the 2300 keV band and the Kashima NICT radio telescope in the 1.41.7 GHz band with a net exposure of about 2 ks on 2016 March 25, just before the loss of the Hitomi mission. The timing performance of the Hitomi instruments was confirmed to meet the timing requirement and about 1000 and 100 GRPs were simultaneously observed at the main pulse and inter-pulse phases, respectively, and we found no apparent correlation between the giant radio pulses and the X-ray emission in either the main pulse or inter-pulse phase. All variations are within the 2 fluctuations of the X-ray fluxes at the pulse peaks, and the 3 upper limits of variations of main pulse or inter-pulse GRPs are 22% or 80% of the peak flux in a 0.20 phase width, respectively, in the 2300 keV band. The values for main pulse or inter-pulse GRPs become 25% or 110%, respectively, when the phase width is restricted to the 0.03 phase. Among the upper limits from the Hitomi satellite, those in the 4.510 keV and 70300 keV bands are obtained for the first time, and those in other bands are consistent with previous reports. Numerically, the upper limits of the main pulse and inter-pulse GRPs in the 0.20 phase width are about (2.4 and 9.3) 10(exp 11) erg cm(exp 2), respectively. No significant variability in pulse profiles implies that the GRPs originated from a local place within the magnetosphere. Although the number of photon-emitting particles should temporarily increase to account for the brightening of the radio emission, the results do not statistically rule out variations correlated with the GRPs, because the possible X-ray enhancement may appear due to a >0.02% brightening of the pulse-peak flux under such conditions

Pressure stress delays cyclooxygenase-2 expression induced by interleukin-1β in cultured human pulmonary artery smooth muscle cells

Introduction: Pulmonary artery smooth muscle cells (PASMCs) play an important role in the sequence of events leading to the formation of pulmonary hypertension (PH). However, little is known about the direct effects of high pressure on the function and intercellular signaling pathways of PASMCs. The aim of this study was to evaluate the effect of pressure stress that simulates PH on interleukin (IL)-1β- or angiotensin II-induced cyclooxygenase-2 (COX-2) expression in cultured human PASMCs. Methods: Either 20 or 60 mmHg atmospheric pressure was applied to PASMCs by a pressure-loading apparatus. Protein expression and phosphorylation were analyzed by western blotting. mRNA expression was analyzed by quantitative real-time reverse transcription-polymerase chain reaction. Results: IL-1β-induced COX-2 protein expression peaked at 6 h in non-pressurized cells, whereas COX-2 expression was delayed, peaking at 12 h, in 20 and 60 mmHg pressurized cells. Both pressures also delayed the time to peak COX-2 mRNA expression induced by IL-1β. In addition, pressure stress delayed the time to peak mitogen-activated protein kinase (MAPK) phosphorylation induced by IL-1β. In contrast, angiotensin II-induced transient COX-2 mRNA expression and MAPK phosphorylation were not affected by pressure stress. Conclusion: These results suggest that pressure stress delays IL-1β-induced COX-2 expression via the delayed activation of MAPKs in PASMCs, and the effects of pressure stress differ according to the bioactive substance being stimulated. Our results demonstrate that the application of pressure stress to PASMCs directly alters cell function, which may provide a basic insight into our understanding of the pathogenesis of PH

Clarifying the Dialogue-Level Performance of GPT-3.5 and GPT-4 in Task-Oriented and Non-Task-Oriented Dialogue Systems

Although large language models such as ChatGPT and GPT-4 have achieved superb performances in various natural language processing tasks, their dialogue performance is sometimes not very clear because the evaluation is often done on the utterance level where the quality of an utterance given context is the evaluation target. Our objective in this work is to conduct human evaluations of GPT-3.5 and GPT-4 to perform MultiWOZ and persona-based chat tasks in order to verify their dialogue-level performance in task-oriented and non-task-oriented dialogue systems. Our findings show that GPT-4 performs comparably with a carefully created rule-based system and has a significantly superior performance to other systems, including those based on GPT-3.5, in persona-based chat

Surface Hydrogenation of Boron-Doped Diamond Electrodes by Cathodic Reduction

Boron-doped diamond (BDD) has attracted much attention as a promising electrode material especially for electrochemical sensing systems, because it has excellent properties such as a wide potential window and low background current. It is known that the electrochemical properties of BDD electrodes are very sensitive to the surface termination such as to whether it is hydrogen- or oxygen-terminated. Pretreating BDD electrodes by cathodic reduction (CR) to hydrogenate the surface has been widely used to achieve high sensitivity. However, little is known about the effects of the CR treatment conditions on surface hydrogenation. In this Article, we report on a systematic study of CR treatments that can achieve effective surface hydrogenation. As a result, we found that the surface hydrogenation could be improved by applying a more negative potential in a lower pH solution. This is because hydrogen atoms generated from protons in the CR treatment contribute to the surface hydrogenation. After CR treatments, BDD surface could be hydrogenated not completely but sufficiently to achieve high sensitivity for electrochemical sensing. In addition, we confirmed that hydrogenation with high repeatability could be achieved