Direct Cell-Cell Communication via Membrane Pores,Gap Junction Channels,and Tunneling Nanotubes: Medical Relevance of Mitochondrial Exchange

The history of direct cell-cell communication has evolved in several small steps. First discovered in the 1930s in invertebrate nervous systems, it was thought at first to be an exception to the “cell theory”, restricted to invertebrates. Surprisingly, however, in the 1950s, electrical cell-cell communication was also reported in vertebrates. Once more, it was thought to be an exception restricted to excitable cells. In contrast, in the mid-1960s, two startling publications proved that virtually all cells freely exchange small neutral and charged molecules. Soon after, cell-cell communication by gap junction channels was reported. While gap junctions are the major means of cell-cell communication, in the early 1980s, evidence surfaced that some cells might also communicate via membrane pores. Questions were raised about the possible artifactual nature of the pores. However, early in this century, we learned that communication via membrane pores exists and plays a major role in medicine, as the structures involved, “tunneling nanotubes”, can rescue diseased cells by directly transferring healthy mitochondria into compromised cells and tissues. On the other hand, pathogens/cancer could also use these communication systems to amplify pathogenesis. Here, we describe the evolution of the discovery of these new communication systems and the potential therapeutic impact on several uncurable diseases.     

外啮合齿轮泵的间隙优化

液压传动属于低效率的传动,液压泵作为主要能量转换装置,对系统总效率影响很大.本文从节能的角度出发,建立齿轮泵间隙优化模型.以CBZb2系列泵为例,得到各型号泵的优化间隙,并求得优化间隙下的效率,与试验结果进行了对比分析.     

百万千瓦超超临界汽轮机中压缸整体总装工艺技术

介绍了上海汽轮机有限公司1000MW超超临界汽轮机中压缸整体总装的工艺技术。本文从工艺方法、工装设备、检测手段等方面,对1000MW超超临界汽轮机中压缸在厂内整体总装的工艺技术进行了阐述。     

叶轮式分级机的环隙对分级性能的影响

有关环隙对叶轮式超细分级机性能的影响研究尚未有公开发表的资料,本文在这方面做了一些初步的实验研究。实验研究发现：环隙对分级性能的影响很大,把环隙作为调控参数很有前途。     

A review of nanofluid heat transfer and critical heat flux enhancement—Research gap to engineering application

As a novel strategy to improve heat transfer characteristics of fluids by the addition of solid particles with diameters below 100 nm, nanofluids exhibit unprecedented heat transfer properties and are being considered as potential working fluids to be used in high heat flux systems such as electronic cooling systems, solar collectors, heat pipes, and nuclear reactors. The present paper reviews the state-of-the-art nanofluid studies on such topics as thermo-physical properties, convective heat transfer performance, boiling heat transfer performance, and critical heat flux (CHF) enhancement. It is indicated that the current experimental data of nanofluids thermal properties are neither sufficient nor reliable for engineering applications. Some inconsistent or contradictory results related to thermo-physical properties, convective heat transfer performance, boiling heat transfer performance, and CHF enhancement of nanofluids are found in data published in the literature. No comprehensive theory explains the energy transfer processes in nanofluids. To bridge the research gaps for nanofluids' engineering application, the urgent work are suggested as follows. (1) Nanofluid stability under both quiescent and flow conditions should be evaluated carefully; (2) A nanofluid database of thermo-physical properties, including detailed characterization of nanoparticle sizes, distribution, and additives or stabilizers (if used), should be established, in a worldwide cooperation of researchers; (3) More experimental and numerical studies on the interaction of suspended nanoparticles and boundary layers should be performed to uncover the mechanism behind convective heat transfer enhancement by nanofluids; (4) Bubble dynamics of boiling nanofluids should be investigated experimentally and numerically, together with surface tension effects, by considering the influences of nanoparticles and additives if used, to identify the exact contributions of solid surface modifications and suspended nanoparticles to CHF enhancement in boiling heat transfer. Once we acquire such details about the above key issues, we will gain more confidence in conducting application studies of nanofluids in different areas with more efficiency.     

Switching characteristics of vacuum gap switch employing UV‐laser triggering

The switching time and arc‐ignition probability of a sustained main discharge in a laser trigger vacuum gap were measured. The third harmonic beam of an Nd:YAG pulse laser (wavelength 355 nm, energy 5 mJ/pulse, power density 4 × 10⁷ W/cm²) was used to trigger the gap. The main electrodes 85 mm in diameter were made of oxygen‐free copper. The gap length was 1.6 mm and the experimental chamber was evacuated to about 1.3 × 10⁴ Pa by a turbomolecular pump. The UV beam from the laser was focused at normal incidence onto the grounded cathode. The switching time decreased and the arc‐ignition probability increased with increasing applied voltage. The switching time was 326 ns at 15 kV with a circuit inductance of 107 μH. Its jitter was 24.8 ns. The advantageous results obtained with the UV beam are compared to the previously reported data on triggered vacuum gaps. © 2000 Scripta Technica, Electr Eng Jpn, 132(3): 8–13, 2000     

Size dependence of energy gaps in small carbon clusters: the origin of broadband luminescence

The visible broadband luminescence from carbon-related films has recently been attributed to the band-tail states caused by the variations in the energy gap of individual sp² carbon clusters due to their difference in size and/or shape. In this paper, these band-tail states are classified into two parts: localized and confined. The localized states result from the structural deviation from graphite-like configuration, and the associated luminescence may be described by using the conventional theory for amorphous materials. The confined states are generated due to the existence of stable graphite-like local structures with various sizes and are the main factor for giving efficient, room-temperature luminescence. Our calculations of a series of small hexagonal carbon clusters with first-principle and semi-empirical methods demonstrate that the energy-gap distribution, due to the difference in size, is considerably broad, which may explain the broadband feature of luminescence. Calculations for some tetrahedral clusters were also made for comparison.     

贴壁式定子间隙的设计和计算

贴壁式定子是贯流式机组中的一种重要结构形式,它利用灯泡体外壳作为发电机定子机架,直接将热量传给河道中的河水。定子铁心与定子机座壁的接触程度将直接影响传热效果。间隙的大小受水压,设备自重,磁拉力和热膨胀等影响,其中以热膨胀的影响因素最大。定子的实际变形并非均匀,在灯泡体内喷涂一层较软的传热材料,如铜,锡等,可改善其接触程度,有利于传热。     

Complex susceptibility analysis of magneto-fluids: Optical band gap and surface studies on the nanomagnetite-based particles

An aqueous stable magnetic fluid containing Fe₃O₄ nano-particles with a mean diameter of 4–7 nm, which is in the range of super-paramagnetism, is prepared. The particles are synthesized via co-precipitation method from ferrous and ferric solutions. X-ray diffraction, transmission electron microscopy, transformer method are used to study the physical properties of the magnetic fluids and powders. A method is given to analyze and resolve the real and imaginary parts of the measured complex susceptibility of magnetic fluids. The band gap parameters of the magneto-nanopowders such as the direct-, indirect-band gap energies, Fermi energy and Urbach energy are determined. A comparative study between the different techniques used to calculate the powder particle size is presented. Adsorption of nitrogen gas is used to identify and determine the particles mean diameter and to study their microstructure, the magnetic properties and surface porosity. The study showed that the total pore system of the magnetic nano-powders consists mainly of mesopores.     

Investigation on the effect of EDM process variables and environments on acoustic emission signals

Abstract

The performance of electrical discharge machining (EDM) primarily depends on the spark quality generated in the inter-electrode gap (IEG) between the tool and workpiece. A method for obtaining accurate information about the spark gap is required to effectively monitor the EDM process. The rise and fall of thermal energy in the discharge zone at a rapid rate during the dielectric breakdown produces high-pressure shock waves. This work explores the suitability of using acoustic emission (AE) generated from these shock waves and the elastic AE waves released on the workpiece due to the induced stress to monitor the performance and spark gap in EDM. The information content of the AE signals acquired at various machining conditions was extracted using AE RMS, spectral energy and peak amplitude. These features were able to well discriminate the machining condition, tool material, workpiece material, flushing pressure, current density, the initial surface roughness of the tool. Additionally, the AE signal features had a good and consistent correlation with the performance parameters, including material removal rate, surface roughness (Ra and Rq) and tool wear. The findings lay the groundwork to develop an effective, non-intrusive in-situ AE-monitoring system for performance and IEG condition in EDM.