Dynamic response of ferrofluidic deformable mirrors using elastomer membrane and overdrive techniques

The experimental results obtained with a ferrofluidic deformable mirror controlled by electro-magnet actuators are presented here. Using a step input through a single actuator, we obtained a steady-state settling time of 100?ms; however, different combinations of overdrive inputs can be used to decrease it to 25?ms. A new technique which consists of laying down an elastomer membrane, coated with an aluminum film, on the ferrofluid is also discussed. By adding the membrane on the ferrofluid, it further decreases the time response by a factor of 2. Furthermore, the thin aluminum layer improves the reflectivity of the mirror. Finally, using the membrane and the overdrive techniques combined, the time response is improved by a factor of 20. Numerical simulations show that ferrofluidic mirrors using membranes and improved electronics should reach settling times of the order of a millisecond. Presumably, even lower settling times could be possible.     

Measurement of thermal conductivity of fluid using single and dual wire transient techniques

A modified measurement device to measure thermal conductivity of fluids using transient hot-wire technique has been designed, developed, tested and presented in this paper. The equipment is designed such that the thermal conductivity could be measured using both single wire sensor of different length and dual wire sensor. The sensor, which is also a heater, is a platinum micro-wire of 50 μm diameter. The influence of wire length on the measurement of thermal conductivity of fluids is tested using two single wires of length 50 mm and 100 mm. The thermal conductivity is also measured using a dual hot wire arrangement; which is achieved by placing the 100 mm and 50 mm wires in a Wheatstone bridge with the 100 mm wire as the sensor and 50 mm wire as a compensation wire. The apparatus requires a 100 ml of test fluid to perform the experiment. The testing temperature of the test fluid during the experimentation can be suitably varied by the choice of heat exchange fluid used in the apparatus. Water is chosen as testing fluids for primary standards. When compared to single wires, the thermal conductivity of the fluids measured is consistent with dual-wire method with an uncertainty of ±0.25%.     

The mapping of vortex fields around single and dual bluff bodies

The development and use of a system to measure important parameters of the vortex field in a coordinate grid around several single bluff bodies and dual bluff body combinations are described. Two hot wire sensors were used: a reference sensor at a fixed position and a moving sensor with position coordinates adjusted by using computer control. The strength, frequency and regularity of the vortex shedding are found from the auto-power spectral density of the moving sensor signal. The phase difference between moving and reference sensor signals is found from the cross-power spectral density function between the signals. The results are presented as maps of vortex parameters plotted as a function of sensor position coordinates. The main features of these maps, including the enhancement of vortex shedding from certain dual bluff body combinations, is then discussed.     

Current SEM techniques for de- and re-construction of centromeres to determine 3D CENH3 distribution in barley mitotic chromosomes

Combined light microscopic (LM) and field emission scanning electron microscopic (FESEM) techniques with FluoroNanogold labelling allowed quantification and high resolution analysis of 3D distribution of the centromere-specific histone H3 variant CENH3 in barley mitotic chromosomes. Chromosomes were investigated with fluorescence LM, conventional FESEM, low-voltage FESEM and combined FIB/FESEM techniques for unprecedented comprehensive analysis to determine chromatin distribution patterns in the centromere. Using data from FIB/FESEM sectioning of centromeric regions of chromosomes, it was possible to render 3D reconstruction of the CENH3 distribution with highest resolution achieved to date. Complementary data derived from each approach show that CENH3 localizes not only to the primary constriction, but also in the pericentric regions and is distributed exclusively in the interior, rather than on the surface, of the centromere. This is relevant for understanding kinetochore assembly and digresses from current models of centromere structure. We emphasize here this broad microscopic approach, focusing on technical aspects of combined FESEM techniques, for which advantages and limitations are discussed, providing a relevant example--in the field of centromeric research--for application to investigations of other subcellular biological structures.     

A comparison of techniques and images obtained using SEAM and SPAM

Images of a circuit have been obtained with similar techniques. Using two scanning acoustic microscopes—a SEAM (scanning electron acoustic microscope) and a SPAM (scanning photoacoustic microscope)—an examination of the surface and subsurface images has shown varied details while highlighting the differences between the above techniques. This paper presents in the first instance the experimental arrangements with the recorded results, followed by a comparison between them.     

Detection and quantitative assessment of image aberrations from single HRTEM lattice images

For utilizing the full capabilities of quantitative high-resolution transmission electron microscopy in materials characterization, a precise knowledge of the various aberrations blurring the object information is essential. Here, we describe an extended approach to the detection and quantitative assessment of image aberrations from lattice images of crystal samples. The approach is based on a theoretical analysis of five-beam lattice images in the presence of all relevant optical aberrations and for partial beam coherence. Compact analytical expressions for linear and nonlinear image Fourier coefficients as explicit functions of the aberration parameters are derived. In particular, a fundamental relationship between the occurrence of erroneous image symmetries and the simultaneous presence of optical misalignments and partial beam coherence is established. An image analysis procedure is proposed which allows for the detection of even- and odd-order residual aberrations and for the quantitative determination of defocus, two-fold astigmatism and axial coma if the three-fold astigmatism is known. For coma-free images, the three-fold astigmatism can also be determined quantitatively. Moreover, the procedure allows for a reliable detection of crystal misalignment for images of wedge-shaped crystal samples.     

Bundles of hexagonally arranged tubules in timothy grass pollen: Detection of a novel pollen component using anhydrous fixation and image analysis techniques in transmission electron microscopy

Pollen from timothy grass (Phleum pratense L.) was subjected to various aqueous and non‐aqueous fixation and preparation protocols for transmission electron microscopy. Only in the cytoplasm of anhydrously prepared pollen grains were conspicuous inclusions observed that range in size from less than 1 μm up to 8 or 10 μm. These bodies have so far not been described in the literature. Higher magnifications show that these inclusions consist of bundles of hexagonally arranged small tubules. In order to obtain details of the ultrastructure of this novel pollen component, TEM micrographs of ultrathin sections of hexagonally arranged tubules were analyzed using Fourier transform techniques of image analysis. It was found that the tubules form groups with quasi‐periodic hexagonal arrangement, with an average centre‐to‐centre spacing between the neighbouring tubules of approximately 42 nm. Individual tubules are formed by 12 or 13 particles. The outer diameter of the tubules ranges between 22 and 24 nm. From our experiments, we conclude that the quasi‐periodic hexagonally arranged tubules forming conspicuous cytoplasmic inclusions in dry timothy grass pollen grains are structurally similar to microtubules.     

Preservation of EDTA-expanded grid-mounted chromosomes and nuclei for electron microscopy using a specially designed freeze-dryer

We describe methods for freezing and drying EDTA-expanded, fixed metaphase chromosomes and nuclei, attached to grids as whole-mounts, for transmission electron microscopy. These methods use a special apparatus that is simple to construct. While separate freezers and dryers are commercially available, one for freezing blocks of tissue by slamming them against a cold metal surface, and the other for vacuum drying the frozen tissue, our apparatus is designed for gentler, cryogenic liquid plunge freezing and drying, sequentially, in the same apparatus, thus avoiding any compression or damage to the sepcimen. Use of a cryoprotectant is not essential; however, good results are obtained more often when 20% ethanol is used. Freezing is accomplished by rapid propulsion of the grid, with specimens attached, into slushy N₂ (-210°C) within the drying chamber; drying is automatic, by either sublimation under vacuum or by solvent substitution using absolute ethanol followed by acetone, which, in turn, is removed with a critical-point dryer. The apparatus offers a means of drying chromosomes and nuclei in an expanded state, and avoids the shrinkage of these structures that occurs during stepwise passage through increasing concentrations of ethanol or acetone.     

Vibration analysis of rotating machinery using time-frequency analysis and wavelet techniques

Time-frequency analysis, including the wavelet transform, is one of the new and powerful tools in the important field of structural health monitoring, using vibration analysis. Commonly-used signal analysis techniques, based on spectral approaches such as the fast Fourier transform, are powerful in diagnosing a variety of vibration-related problems in rotating machinery. Although these techniques provide powerful diagnostic tools in stationary conditions, they fail to do so in several practical cases involving non-stationary data, which could result either from fast operational conditions, such as the fast start-up of an electrical motor, or from the presence of a fault causing a discontinuity in the vibration signal being monitored. Although the short-time Fourier transform compensates well for the loss of time information incurred by the fast Fourier transform, it fails to successfully resolve fast-changing signals (such as transient signals) resulting from non-stationary environments. To mitigate this situation, wavelet transform tools are considered in this paper as they are superior to both the fast and short-time Fourier transforms in effectively analyzing non-stationary signals. These wavelet tools are applied here, with a suitable choice of a mother wavelet function, to a vibration monitoring system to accurately detect and localize faults occurring in this system. Two cases producing non-stationary signals are considered: stator-to-blade rubbing, and fast start-up and coast-down of a rotor. Two powerful wavelet techniques, namely the continuous wavelet and wavelet packet transforms, are used for the analysis of the monitored vibration signals. In addition, a novel algorithm is proposed and implemented here, which combines these two techniques and the idea of windowing a signal into a number of shaft revolutions to localize faults.     

Remote measurement of liquid flow using turbine and fiber optic techniques

This paper deals with the development of a low cost, intelligent liquid flow measuring system, based on fiber optic technology. Fiber optic sensing as well as communication is used to measure flow, at a distance, using basic turbine flow meter. The blades of the turbine meter are used to modulate the light falling on it. The frequency of the pulses generated depends on the number of blades and is measured by the microcontroller and displayed on the hyper terminal. With proper calibration, relationship between output frequency and flow rate is appreciably linear and accuracy is ±0.4%.     

Failure classification using poles and corresponding residuals of transfer function

Using the relationship between coefficients and poles and corresponding residuals of a transfer function as well as their dependence on various physical influences, a method for failure classification is proposed in this paper. Experiments show that poles and residuals used as features permit a better classification than the use of coefficients. The method is applicable when parts of the system can be modelled by linear quasi-time-invariant transfer characteristics, the parameters of which depend on external physical influences (see Fig 1). This situation is frequently encountered in electromechanical systems.

Changes of parameters are required to be either step-like or slow compared with the system dynamics. Hence influences as varied as temperature changes, fatigue and production tolerances can be treated. Parameter variations that result in structural changes are allowed. The approach is also applicable using poles and zeroes as features instead of poles and residuals. The advantage of the latter approach is the fixed relationship between poles and residuals.     

Automated tracking of migrating cells in phase-contrast video microscopy sequences using image registration

Analysis of in vitro cell motility is a useful tool for assessing cellular response to a range of factors. However, the majority of cell-tracking systems available are designed primarily for use with fluorescently labelled images. In this paper, five commonly used tracking systems are examined for their performance compared with the use of a novel in-house cell-tracking system based on the principles of image registration and optical flow. Image registration is a tool commonly used in medical imaging to correct for the effects of patient motion during imaging procedures and works well on low-contrast images, such as those found in bright-field and phase-contrast microscopy. The five cell-tracking systems examined were Retrac, a manual tracking system used as the gold standard; CellTrack, a recently released freely downloadable software system that uses a combination of tracking methods; ImageJ, which is a freely available piece of software with a plug-in for automated tracking (MTrack2) and Imaris and Volocity, both commercially available automated tracking systems. All systems were used to track migration of human epithelial cells over ten frames of a phase-contrast time-lapse microscopy sequence. This showed that the in-house image-registration system was the most effective of those tested when tracking non-dividing epithelial cells in low-contrast images, with a successful tracking rate of 95%. The performance of the tracking systems was also evaluated by tracking fluorescently labelled epithelial cells imaged with both phase-contrast and confocal microscopy techniques. The results showed that using fluorescence microscopy instead of phase contrast does improve the tracking efficiency for each of the tested systems. For the in-house software, this improvement was relatively small (<5% difference in tracking success rate), whereas much greater improvements in performance were seen when using fluorescence microscopy with Volocity and ImageJ.     

Four-dimensional factor analysis of confocal image sequences (4D-FAMIS) to detect and characterize low copy numbers of human papillomavirus DNA by FISH in HeLa and SiHa cells

Visualization and localization of specific DNA sequences were performed by fluorescence in situ hybridization, confocal laser scanning microscopy (CLSM), and four-dimensional factor analysis of biomedical image sequences (4D-FAMIS). HeLa and SiHa cells containing, respectively 20–50 and 1–2 copies per cell of human papillomavirus (HPV) DNA type 18 and 16 integrated in cellular DNA were used as models. HPV-DNA was identified using DNA probes containing the whole genome of HPV-DNA type 18 or 16, and DNA–DNA hybrids were revealed by alkaline phosphatase and Fast Red. Cell nuclei were counterstained with thiazole orange (TO) or TOTO-iodide. 4D image sequences were obtained using successive dynamic or spectral sequences of images on different optical sections from CLSM. The location of fluorescent signals within the preparations was determined by FAMIS. This original method summarizes image sequences into a reduced number of images called factor images, and curves called factors. Factors estimate different individual physical behaviours in the sequence such as extinction velocity, spectral patterns and depth emission profiles. Factor images correspond to spatial distributions of the different factors. We distinguished between Fast Red and nucleus stainings in HPV-DNA hybridization signals by taking into account differences in their extinction velocities (fluorescence decay rate) or spectral patterns, and in their focus (depth emission profiles). In HeLa cells, factor images showed that Fast-Red-stained targets could be distinguished from nucleus stainings, and were located on different focal planes of the nuclei. In SiHa cells, 4D-FAMIS determined as few as 1–2 copies per cell of HPV-DNA type 16 located in continuous focal planes. Therefore, 4D-FAMIS, together with CLSM, made the detection and characterization of low copy numbers of genes in whole cells possible.     

On the detection of MX-precipitates in microalloyed steels using energy-filtering TEM

The properties of microalloyed steels and HSLA steels depend predominantly on the size and composition of nanometre-sized MX precipitates consisting of Nb, Ti, V, C and N. In this work we present a rapid and powerful method for visualizing these small precipitates directly in the steel matrix. This can be achieved by energy-filtering TEM in a 200-kV microscope. We have recorded elemental maps (three-window method) and jump-ratio images (two-window method) using the inner-shell ionization edges; e.g. Fe-M₂₃, Fe-L₂₃, V-M₂₃, V-L₂₃, Nb-N₂₃, Nb-M₄₅, C-K and N-K edges. We have found that precipitates in a steel matrix can be best visualized by recording the jump-ratio image of the matrix element. If the specimens are thinner than 30 nm and high resolution in the images and low detection limits are essential, low energy-loss edges should be used preferentially; in the case of steels the Fe-M₂₃ edge should be used instead of the Fe-L₂₃ edge. If the jump-ratio images are recorded with the Fe-M₂₃ edge, precipitates about 2 nm in diameter may be detected. With thicker samples and if high resolution is not as essential, higher energy-loss edges are preferable, because diffraction effects are less possible. The chemical composition of the larger precipitates (10 nm) could be determined by recording EDX spectra using an STEM probe. We found Nb and V with an atomic ratio of about 3, but we could not detect carbon or nitrogen in the spectra. The Nb and V distribution could be best visualized with a jump-ratio image including both the Nb-N₂₃ and the V-M₂₃ edges. However, it was not possible to image the carbon or nitrogen content of the precipitates unequivocally due to overlapping of the C-K and N-K edges with the Nb-M₄₅ edge.     

Evaluating the lucrative role of probiotics in the aquaculture using microscopic and biochemical techniques

The present study focused to elucidate the promising role of probiotics in the fish culture, by employing microscopic and biochemical parameters to rationalize the possible outcomes. After preliminary feeding trial histopathological analysis revealed clear and visible changes in the intestinal and liver cells of CTRL (control group) compared to probiotics supplemented group, the bacterial inoculations resulted in shorten and swelled villi, while liver kupffer cells increased many folds in the CTRL. Moreover, there was clear hypertrophy and lamellar fusion in the gills tissues examined under microscope. Furthermore, intriguing results were obtained, such as a substantial increase in the weight gain, specific growth rate (%BW/day), FCE%, survival%, and improved secretions of amylase, cellulase, and protease activities. Likewise, high crude protein, fats content, while low moisture and total Ash was noticed in EXP I (Probiotics supplemented) compared to CTRL. The microscopic and biochemical analysis disclosed the positive role of probiotics on the fish health, thus we suggest its supplementations in the fish diet.     

A simplified preparation procedure of plant material for elemental analysis by ESI and EELS techniques

Living plant cells were embedded in the water-soluble resin Nanoplast FB 101 and cut into ultrathin sections. Non-vacuolated cells of algae and fungi showed a satisfactory preservation of fine structure. First results of elemental mapping by the ESI technique indicate that phosphorus and sulphur are neither extracted nor dislocated within the cells. The authors are members of the ‘Study Group for Electron Microscopy’ at the Hannover School of Veterinary Medicine.     

激光自动对焦中离焦量的探测与计算方法

根据激光光线聚焦状态不同对应被测面上激光光斑形状不同的特点,通过引入辅助激光束,分析了调焦CCD采集的激光光斑图像信息,进而根据光斑形状及半径等信息确定被测面对焦状态。针对实验中每隔相同离焦距离采集的一系列光斑图像,提出了相应的图像处理方案,以提取所需光斑半径信息,进而进行光斑半径与离焦量转换。实验结果表明,光斑半径与离焦量呈线性关系,最大线性范围灵敏度为2.342像素/μm,最高可实现0.43μm分辨率。     

机械CAD与计算机仿真技术在生产设备设计中的应用

这里叙述了机械CAD与计算机仿真技术在生产设备设计中的应用,提出机械机构虚拟原型系统“制造”技术观点。