SEM observation of the insect prepared by microwave irradiation

The ptilinum of the fly and the compound eye are among the most fragile organs encountered during conventional procedures of morphological sample fixation. In order to identify a fixative suitable for preparing such samples for scanning electron microscopy, we examined various fixation conditions using microwave irradiation (MWI). The conditions examined were: (i) fixatives; (ii) temperature; (iii) concentration; (iv) duration; (v) dehydration; and (vi) substitution. The identified optimal conditions were 5% glutaraldehyde with MWI (350 W, 5 min). The MWI was continued until the maximal temperature of 75 degrees C was attained, followed by intermittent irradiation to maintain a temperature of 75 degrees C. After irradiation, the sample was left at room temperature for 24 h in the fixative and then dehydrated in increasing concentrations of ethanol. Each step in the ethanol series lasted for 24 h. The final absolute ethanol step included three solution changes, with each incubation lasting 1 h. A subsequent stepwise substitution of t-butyl alcohol for ethanol was conducted by reducing the ratio of 100% ethanol to t-butyl alcohol from 2:1 to 1:1 and then 1:2 (24 h each). The substitution was completed by three solution changes using 100% t-butyl alcohol, 30 min each. The best results were obtained by freeze-drying samples using t-butyl alcohol. The use of MWI improved fixative permeation, which occurred at a uniform rate throughout the sample. Comparison with temperature in a water bath at 75 degrees C indicated that the fixation effect of MWI was due to its heat generation in addition to some unknown mechanism.     

Acanthamoeba castellanii: ultrastructure of trophozoites using fast freeze-fixation followed by freeze-substitution.

In recent years, the use of fast-freeze fixation followed by freeze-substitution has been shown to be the procedure that best satisfies the ultrastructural preservation of cellular components due to the rapidity of the fixation procedure and the reduction of artifacts compared to chemical fixation. When these techniques were used to study the fine structure of axenically cultured trophozoites of Acantamoeba castellanii, an improved preservation of the whole cell was observed. The ground substance of the cytoplasm is densely packed with fibrogranular material which is frequently removed with the use of conventional techniques. Also, the ultrarapid physical stabilization allows the visualization of fusion and fission processes of cytoplasmic vacuoles and vesicles. The nuclear structure and cytoplasmic microfilaments as well as membranous structures were clearly identified. Low temperature techniques combine the advantage of fast-freeze fixation for the physical stabilization of organic molecules and their stabilization by the substitution medium at low temperature giving rise not only to a better preservation of the cell ultrastructure but providing a favorable basis for immunocytochemistry at the electron microscopy level.     

高压冷冻及冷冻替代技术在不同生物样品超微结构中的应用

高压冷冻仪在固定样品时,高压和冷冻基本是同步发生的,使得生物样品在数毫秒的时间内被瞬时固定,保证其内部结构接近于生理状态,有效减少了化学固定法中的化学试剂对细胞结构的破坏,极大程度保存了细胞在近似自然状态下的超微结构.本文分别采用化学固定法(CF)和高压冷冻固定法(HPF)对小鼠的睾丸组织、Hela细胞和酵母进行了样品...     

Influence of surrounding media on preservation of cell wall ultrastructure of Candida albicans revealed by low temperature scanning electron microscopy.

Influence of surrounding media on the surface structures of the cell wall of Candida albicans was discussed with respect to the preservation of ultrastructure during the specimen preparation for scanning electron microscopy. The fibrillar structure of the cell surface was distinctly identified by the rapid-freezing technique. It was difficult, however, to observe this structure by the conventional specimen preparation technique. The reason for the difference between these two preparation techniques was studied using a low temperature SEM. Through investigating the influence of each step of the conventional technique on the fibrillar structure, it was found that the fibrils were drastically deformed and disappeared during the dehydration step in ethanol above 80% in concentration. In order to study which physicochemical properties participated in this disappearance phenomenon, yeast cells were treated with various media: solutions in different pH ranges and at different salt concentrations, ionic solutions, surfactants, formamide, dimethyl sulfoxide, acetone and Fehling's solution. As a result, the fibrillar structure was found well preserved when the medium had an affinity for the constituent molecules of the fibrils. When without affinity, the fibrils suffered a remarkable deformation. The mechanism of this deformation is discussed in terms of molecular interaction of solute and solvent.     

适合光镜和电镜诊断肾小球疾病的固定剂选择

目的：为了使已经石蜡包埋的肾穿组织脱蜡后进行电镜观察,关键是选择适当的固定剂。方法：在石蜡包埋前,肾穿组织分别用甲醛、戊二醛及戊二醛、锇酸双固定。根据光镜和电镜观察结果,选择能兼顾光镜和电镜的固定剂。结果：甲醛固定不能有效保存肾穿组织的超微结构,锇酸的固定能有效地保存超微结构,但严重影响了光镜切片的染色;而戊二醛与甲醛相比,较好地保存了肾穿组织的超微结构,同时又不影响光镜切片的染色。结论：在石蜡包     

Percutaneous transluminal microwave balloon angioplasty

Microwave balloon angioplasty (MBA), which combines conventional balloon angioplasty techniques with microwave heating to help enlarge the lumen of narrowed arteries and reduce the occurrence of restenosis, is discussed. An apparatus for the delivery of MBA using 2450 MHz heating power is described. Using this apparatus, local arterial wall temperatures as higher 90°C were obtained during MBA on anesthetized rabbits. Tissue modification of the arterial walls due to simultaneous ballooning and heating was observed     

A new microwave device for rapid thermal fixation of the murine brain.

A microwave applicator was developed to provide rapid thermal fixation of enzymes in the murine brain. Although the power output of the device is only 1.3 kW, whole-brain levels of acetyicholine after microwave fixation are comparable to those observed at a power output of 5 kW, and are markedly higher than those obtained by a conventional method (freezing) of fixation.     

高压冷冻-冷冻替代技术在神经组织超微结构中的应用

采用高压冷冻-冷冻替代技术对小鼠和线虫这两种模式生物的神经组织进行了样品制备、超薄切片和电镜观察,并在取材方式上进行了摸索,旨在比较化学固定法(CF)、高压冷冻固定法(HPF)和化学-高压冷冻联合固定法(CF+ HPF)三种不同方式对神经组织超微结构的影响,促进高压冷冻-冷冻替代技术在神经生物学中的应用.透射电镜观察结果显示:与传统的化学固定相比,高压冷冻固定对神经组织样品具有较好的优势,能够减少化学处理所产生的人工假象;另一方面,对于不同动物的神经组织而言,所适用的固定方式也不相同,鼠脑适用于活检枪(biopsy gun)取样后直接进行HPF固定,所得结构比较完整,神经组织微观结构清晰.而在高压冷冻之前选用CF进行预固定,能加大样品结构保存的完整性,但在膜的细腻程度上不如直接进行高压冷冻制样的结果.线虫样品由于存在较厚的体壁保护,它更适于直接进行HPF处理,从而缩短了固定前的滞留时间,可有效保留腹部神经元超微结构.     

Design of Microwave Filters With Arbitrary Frequency Response Based on Digital Methods

This letter presents a novel general technique for the design of microwave filters with arbitrary frequency response. It is based on the translation of the microwave specifications to the digital domain, where the well known and readily available digital filter design techniques are applied. By means of these digital techniques, the method provides a straightforward procedure to calculate the poles and zeros corresponding to the analog frequency response that satisfies the target specifications. From the poles and zeros, the microwave filter can be readily obtained using conventional techniques. As an example to demonstrate the proposed technique, a filter with user-defined specifications over two independent passbands has been implemented and successfully tested in microstrip technology.     

微波在免疫组织化学中的应用

本文综述微波技术在免疫组织化学中的应用两头及其进展，着重介绍了微波在组织固定、抗原恢复和免疫染色方面的应用，并对微波免疫组织化学的应用前景进行了展望 。     

An Investigation of the Thermal and Athermal Effects of Microwave Irradiation on Erythrocytes

Erythrocytes heated by either microwave irradiation or conventional techniques were examined for loss of hemoglobin (Hb) and potassium (K+). In all experiments, microwave heated red blood cells (RBC's) were directly compared with RBC's warmed to the same temperature by use of an adjustable incubator and with RBC's maintained at room temperature. Microwave irradiation was carried out at either 2.45 GHz or in selected 0.5 GHz swept frequency regions in the 12.5-18 GHz range. Sample temperature was continuously monitored in both microwave heated and conventionally heated samples by use of a relatively nonperturbing liquid crystal optic fiber temperature probe. When rabbit RBC's were warmed by 3.7°C for 45 min by either irradiation (2.45 GHz, 10 mW/cm2) or conventional heating, no additional Hb or K+ was released into the supernatant. In contrast, when rabbit RBC's were rapidly warmed from room temperature to 37°C by either technique, the heated erythrocytes lost significantly more of both Hb and K+ than equivalent RBC's maintained at room temperature. In addition, RBC's warmed to 41.5°C by either technique lost far more Hb and K+ than those warmed to 37°C. In all experiments, Hb and K+ were lost in equal amounts by microwave heated and conventionally heated erythrocytes warmed at the same rate to the same final temperature. Thus, at all frequencies and power levels tested, any increased loss of either Hb or K+ from microwave irradiated rabbit RBC's should be ascribed to thermal effects on the stability and/or permeability of the erythrocyte membrane.     

微波辅助化学浴沉积法制备ZnO薄膜

采用微波辅助化学浴沉积法在玻璃衬底上制备了氧化锌(ZnO)薄膜。初步探讨了化学浴沉积法制备ZnO薄膜的反应机理。X射线衍射分析结果表明所得的ZnO薄膜为六方纤锌矿结构的多晶薄膜,不具有任何晶面的择优生长取向;随着反应时间从15min延长至30min,薄膜结晶性能提高,晶粒尺寸从27nm长大到73nm。扫描电子显微镜分析显示反应沉积12min时,薄膜比较均匀、致密,无裂纹出现;反应沉积25min后,薄膜厚度增加,同时出现开裂现象。     

A waveguide irradiation chamber for destruction of red palm weevils (Rhynchophorus ferrugineus) inside a block sample of a palm tree trunk.

A simple waveguide irradiation chamber at 2.45 GHz. was locally constructed for controlled laboratory experiments to assess the potentiality of using microwave heating for irradiation of weevils (RPW) inside healthy and infected palm tree trunks. The chamber consists of an aluminum rectangular waveguide with one of its broad sides removed for easy insertion of the block samples of the palm tree trunk. A rectangular aluminum plate, with the same dimensions as the removed wall section was made to slide-in and cover the tree block sample after its insertion in the waveguide to insure continuity of metallic walls. Temperature rise in the samples were monitored by thermocouples inserted through holes drilled at different positions along one of the waveguide side walls. Results showed that 100% mortality rate could be obtained with the RPW samples at distances not more than 2-3 cm from the leading edge of healthy tree block samples and 4-5 cm from leading edge of infected samples. Hot spots were observed at the leading edge of the tree samples due to high absorption of microwave at these regions.     

Millimeter-wave monolithic integrated circuit characterization by apicosecond optoelectronic technique

The characterization of microwave and millimeter-wave monolithic integrated circuits (MIMICs) using picosecond pulse-sampling techniques is developed with emphasis on improving broadband coverage and measurement accuracy. GaAs photoconductive switches are used for signal generation and sampling operations. The measured time-domain response allows the spectral transfer function of the MIMIC to be obtained. This measurement technique is verified by characterization of the frequency response (magnitude and phase) of a reference 50-Ω microstrip line and a two-stage K_a-band MIMIC amplifier. The measured broadband results agree with those obtained from conventional frequency-domain measurements using a network analyzer. The application of this optical technique to on-wafer MIMIC characterization is described     

Zr0.8Sn0.2TiO4微波介质陶瓷材料的掺杂改性

以Zr0 .8Sn0 .2 TiO4 作为主配方 ,以ZnO ,La2 O3,Fe2 O3和NiO作为改性剂 ,采用传统陶瓷制备工艺 ,对其进行了掺杂改性的初步探索。在优选的配方和工艺条件下 ,得到Zr0 .8Sn0 .2 TiO4 添加0 .5wt%ZnO(即质量分数为 0 .5 %的ZnO)的相对介电常数εr≈ 33.2 31,品质因数Q≈ 5 5 2 8(7GHz) ;添加 0 .5wt %ZnO ,0 .5wt?2 O3和 0 .2wt%NiO ,其εr≈ 33.73,Q≈ 5 2 5 4(7GHz) ;添加 1wt%ZnO和 0 .5wt %La2 O3,材料的εr≈ 37.996 ,Q≈ 4 72 3(7GHz)。     

激光诱导碳纳米管制备石墨烯纳米带及其电学性能分析

通过将纳米管解压缩可以很容易地生产石墨烯纳米带,因为碳纳米管结构可以被认为是卷起的石墨烯筒。这是一种特殊的2D石墨结构,具有出色的性能。应用领域广泛,包括晶体管、光学和微波通信设备、生物传感器、化学传感器、电子存储和处理设备以及纳米机电系统和复合材料。通过扫描电子显微镜（SEM）观察薄膜的形貌,通过拉曼光谱法表征石墨烯的性质,并通过半导体参数测量系统测量薄膜的电导率。拉曼光谱表明,通过优化工艺可以增强石墨烯的拉曼特性。碳纳米管制备石墨烯带的两个重要参数是激光能量密度和辐照时间。在这项研究中,通过准分子激光辐照碳纳米管薄膜来生产石墨烯纳米带。实验结果表明,在150 mJ的激光能量下,观察到连接时碳纳米管没有打开。在450 mJ的能量下,可以有效地破坏碳纳米管,并且使其部分地形成石墨烯带。此时,膜的电导率达到最大值。由于蓄热作用,在碳纳米管壁上出现大量的多孔结构。     

Adaptive Polarization Contrast Techniques for Through-Wall Microwave Imaging Applications

In this paper, we describe and utilize polarization contrast techniques of the adaptive polarization difference imaging algorithm and its transient modification for through-wall microwave imaging (TWMI) applications. Originally developed for optical imaging and sensing of polarization information in nature, this algorithm is modified to serve for target detection purposes in a through-wall environment. The proposed techniques exploit the polarization statistics of the observed scene for the detection and identification of changes within the scene and are not only capable of mitigating and substantially removing the wall effects but also useful in detecting motion, when conventional Doppler techniques are not applicable. Applications of the techniques to several TWMI scenarios including both homogeneous and periodic wall cases are presented.     

Rapid microwave fixation of rat brain.

A new microwave device which inactivates brain enzymes rapidly and uniformly is described. From the results obtained with microwave irradiation at two power levels (0.8 kW and 4.5 kW), it has been demonstrated that the high power microwave irradiation has several advantages over the low power irradiation. In its application to neurochemical studies, significant increase in the DOPAC level was found in the irradiated brain, while there were no statistical differences in the levels of NE, DA, 5-HT and 5-HIAA between microwave irradiation and decapitation. Significant increase in the Ach level and marked reduction of the choline level were observed after microwave irradiation. There were no significant differences in the level of cyclic GMP in the brain between the two methods of sacrifice, while significant reduction of the cyclic AMP level was observed in the irradiated brain.     

Three-dimensional analysis of protein aggregate body in Saccharomyces cerevisiae cells.

Modified genes of peroxisomal isocitrate lyase of Candida tropicalis (CT-ICL) were constructed and expressed in Saccharomyces cerevisiae cells. We observed subcellular localization of expressed products of the mutant CT-ICL genes by immunoelectron microscopy. An unknown structure termed a protein aggregate body (PAB) storing the expressed product was observed in cytoplasm in various mutants (Kamasawa et al. (1996) J. Electron Microsc. 45: 491-497). We chose two typical cells harbouring the mutant ICL genes delta 550 and delta 237-339 to analyse the ultrastructure and three-dimensional (3D) structure of PABs. The PABs had a homogeneous matrix with a wavy periphery in the cell image using a high-pressure freezing fixation method. Although PABs could not be separated from the cytoplasm or mitochondria under a confocal fluorescence microscope, 3D reconstruction of serial electron micrographs clearly showed the PAB was an independent structure of varying size and had the shape of an incomplete sphere. A cell was sometimes observed to have multiple PABs.