Surfaces of cryosections: is cryosectioning ‘cutting’ or ‘fracturing’?

In order to determine if cryosectioning involves ‘fracturing’ or ‘cutting’ we examined the surfaces obtained in cryosectioning by a metal-replicating procedure commonly used in freeze-fracture microscopy. Platinum-carbon replicas were made of the surfaces of both the sections and the complementary surfaces of the sample stubs from which the sections were cut. When samples of frozen red cells were sectioned at ?120°C with large knife advancements (1 μm), the chips produced did not resemble sections. Membrane fracture faces, produced by splitting of the lipid bilayer, were found in electron micrographs of replicas of the sample stubs. This demonstrates that a cryomicrotome can be used to produce large intact replicas. When dull knives were used with small knife advancements, both smooth and fractured regions were found. The sections produced with dull knives had a snowflake appearance in the light microscope. When sharp knives were used with small advancements (0·1 μm), replicas of the surfaces were free of fracture faces and the sections had a cellophane-like appearance in the light microscope. Therefore, in cryosectioning a different process other than ‘fracturing’ is responsible. This ‘cutting’ process may be micromelting of a superficial layer by the mechanism of melting-point depression from the pressure exerted by the sharp edge of the knife.     

Improving the performance of an RF resonant cavity water-cut meter using an impedance matching network

In multiphase flow measurement, one of the most challenging issues is to define an adequate technology for a specific scenario, taking into account the measurement accuracy, implementation feasibility and costs. The electromagnetic technology based on resonant cavities is often employed in water-cut meters to measure two-phase flows such as water/oil and water/gas mixtures. The main disadvantage of this technology is the electromagnetic signal attenuation that occurs as the water content decreases. This undesirable behavior is amplified due to the impedance mismatch between the sensor ports and the transmitter/receiver modules. This paper presents a study to implement an impedance matching network in order to improve the instrument performance. Impedance matching networks were built, taking into account the matching for a 100%, 50% and, also, for the worst case of 0% of water fraction where there is a significant signal attenuation. The implemented networks improved the signal amplitude ratio between the first resonant mode and the other modes, increasing the identification accuracy of the first resonance peak.     

Determination of defocus values using ‘Fourier images’ for high resolution electron microscopy

The phenomenon of Fourier images is used to calibrate defocus steps of a high resolution transmission electron microscope. Results compare well with measurements from an optical diffractogram.     

The efficient and unbiased estimation of nuclear size variability using the ‘selector’

The selector was used to make an unbiased estimation of nuclear size variability in one benign naevocellular skin tumour and one cutaneous malignant melanoma. The results showed that the estimates obtained using the selector were comparable to those obtained using the more time consuming Cavalieri-disector approach. Employing ‘optical sections’, the selector was found to be between five and ten times more efficient than the Cavalieri-disector method when using physical sections.     

Identification of airway characteristics using the input impedance

To understand how the input impedance determined at the throat correlates with changes in the dynamic characteristics of the airways, a simplified 5-lobe model is developed and simulated. The model takes into account some realistic conditions such as varying cross-sectional areas, flexible wall properties and branching. The lobe terminal impedances are implemented in the model to predict the input impedance at the throat. The effects of airway constrictions and wall elastance variations on this impedance are determined for a range of frequencies. It is concluded that the developed model is capable of predicting various physiological changes in the airway passages.     

A variable cell culture chamber for ‘open’ and ‘closed’ cultivation,perfusion and high microscopic resolution of living cells

A multipurpose chamber is described for growing and testing cultured cells. The chamber can be converted from a perfusion chamber to an ‘Open’ or ‘closed’ culture system. The chamber provides optimum conditions for microscopy using all common objectives and condensers for different microscopic methods.     

半导体激光干涉仪在信号倍频处理中的应用

半导体异质结激光器在注入的电流发生变化时 ,输出激光的光频也随之改变。适当地设计干涉仪的参数 ,可检测这种变化。提出了可将干涉仪设计为信号倍频器及调制器 ,通过实验给出了分析方法与结论     

A ‘pocket guide’ to total internal reflection fluorescence

The phenomenon of total internal reflection fluorescence (TIRF) was placed in the context of optical microscopy by Daniel Axelrod over three decades ago. TIRF microscopy exploits the properties of an evanescent electromagnetic field to optically section sample regions in the close vicinity of the substrate where the field is induced. The first applications in cell biology targeted investigation of phenomena at the basolateral plasma membrane. The most notable application of TIRF is single‐molecule experiments, which can provide information on fluctuation distributions and rare events, yielding novel insights on the mechanisms governing the molecular interactions that underpin many fundamental processes within the cell. This short review intends to provide a ‘one stop shop’ explanation of the electromagnetic theory behind the remarkable properties of the evanescent field, guide the reader through the principles behind building or choosing your own TIRF system and consider how the most popular applications of the method exploit the evanescent field properties.     

A method of measuring ‘zero-wear’ of the cylinder liner

In this paper, new methods of linear wear estimation of the cylinder liner are proposed. They can be used if the deepest honed valleys remain unaltered during the wear process. In the first part of the paper, the possibility of using various amplitude parameters as measures of wear is studied. The second part presents a new procedure for cylinder liner wear analysis based on the ‘fax-film’ method that allows us to estimate the wear of the cylinder liner without disassembly of the cylinder-piston-piston ring group.     

A fully automated, ‘thimble-size’ scanning tunnelling microscope

A novel, fully automated high-stability, high-eigenfrequency scanning tunnelling microscope (STM) has been developed. Its key design feature is the application of two piezoelectric ceramic tubes, one for the x-y-z motion of the tip and one for a linear motor (‘nano-worm’) used for the coarse positioning of the tip relative to the specimen. By means of the nano-worm, the tip can be advanced in steps between 16 and 0·2 nm. The walking distance is >2 mm, with a maximum speed of 2000 steps/s. The nano-worm positioning implies that this STM is fully controlled by electronic means, and that no mechanical coupling is needed, which makes operation of the STM extremely convenient. The axial-symmetry construction is rigid, small and temperature-compensated, yielding reduced sensitivity to mechanical and acoustic vibrations and temperature variations. The sample is simply placed on a piece of invar which surrounds the scanner tube and the nano-worm and is held by gravity alone. This allows for easy sample mounting. The performance of the microscope has been tested in air by imaging a variety of surfaces, including graphite and biological samples.     

Matrices pattern using FIB; ‘Out‐of‐the‐box’ way of thinking

Focused ion beam (FIB) is an extremely valuable tool in nanopatterning and nanofabrication for potentially high‐resolution patterning, especially when refers to He ion beam microscopy. The work presented here demonstrates an ‘out‐of‐the‐box’ method of writing using FIB, which enables creating very large matrices, up to the beam‐shift limitation, in short times and with high accuracy unachievable by any other writing technique. The new method allows combining different shapes in nanometric dimensions and high resolutions for wide ranges.     

便携式在线局放信号源系统的设计

针对智能电网局部放电检测技术实际运用中的问题,对ADF4350频率合成器的基本原理与工作特性进行了研究,应用了锁相环、滤波器组、同步信号提取、程控开关等技术,提出了一套基于AVR Atmega128单片机控制ADF4350的硬件电路结构和软件程序设计方法,得到了一种能实际应用在智能电网局部放电监测的多频段信号源。现场工作人员通过用户端操作板上的简单操作,进行模式选择与设定,就可以方便地实现现场在线监测。研究结果表明,该信号源覆盖了局放信号的全部频点,现场测试时锁相效果良好、携带方便、性能可靠。     

The effect of humidity on the ‘swing’ of cricket balls

The suggestion is made that the observed increase in the swing under conditions of high humidity is caused by condensation shock. The moisture in the rapidly expanding air close to the ball does not condense when the saturation limit is reached but continues in an unstable, supersaturated state until violent condensation occurs, probably at the lowest pressure attained. This condensation shock assists the seam in upsetting the laminar boundary-layer. Calculations show that this effect can occur only when the relative humidity in the ambient air is nearly 100%.     

The importance of current density ‘focusing’ in STM image resolution

In a previous paper we incorporated Tersoff and Hamann's model of an STM tip into Lang's transfer Hamiltonian result for the tunnelling current density and applied the resulting simple expression to Tersoff's six-plane-wave model of a monolayer of graphite. In this paper the results for a more realistic model of a graphite surface and a more complete selection of tip positions are presented. They support the previous conclusions that the normal component of the current density takes on both positive and negative values in a complex flow pattern and that its lateral falloff away from the (projected) tip position is much slower than expected from the extraordinary lateral resolution (～1 Å) evident in the best STM images of graphite. This shows that sharp ‘focusing’ of the current density directly under the tip is not a necessary condition for high lateral resolution.     

Stability characteristics of gas-lubricated bearings supported on rubber ‘O’ rings

A simplified design method is given against instability of an externally pressurized gas journal bearing supported on rubber ‘O’ rings. The stability characteristics (onset whirl speed and whirl ratio) are derived and expressed in closed form in terms of ‘O’ ring material properties and fluid film behaviour.     

An anti-roll plate for flattening of ‘dry’ ultrathin frozen sections

A simple anti-roll plate has been designed for use in preparing ‘dry’ ultrathin frozen sections. The plate, which is made of a strip of a glass cover slip and attached close to the edge of a glass knife, prevents curling of the sections.     

轮机模拟器中传感器信号模拟器的设计

轮机模拟器系统是现代航海教育的必备设施,它通过硬件和仿真软件相结合的方式模拟船舶机舱自动化的运行过程,该系统中大多数传感器信号都是通过信号模拟器模拟的.以5600国际标准箱(TEU)集装箱轮自动化机舱为模型,结合当前嵌入式技术特点开发了一款新型信号模拟器,可精确地模拟出多种常用传感器标准信号源,操作方便、工作可靠.