ALBERT

Description: Polysaccharides account for more than 90% of the content of fungal cell walls, but the mechanism underlying the formation of the architecture of the cell walls, which consist of microfibrils embedded in an amorphous wall matrix, remains unknown. We used electron microscopy to investigate ten different fungal cell-wall polysaccharides to determine whether they could self-assemble into the fibrillar or amorphous component of fungal cell walls in a test tube without enzymes. The ultrastructures formed by precipitating β-1,3-glucan and β-1,6-glucan are different depending on the existence of branching in the molecule. Linear β-1,3-glucan and linear β-1,6-glucan precipitate into a fibrillar ultrastructure. Branched β-1,6-glucan, mannan and glycogen precipitates are amorphous. Branched β-1,3-glucan forms a fibrillar plus amorphous ultrastructure. Self-assembly among combinations of different linear and branched cell-wall polysaccharides results in an ultrastructure that resembles that of a yeast cell wall, which suggests that self-assembly of polysaccharides may participate in the development of the three-dimensional architecture of the yeast cell wall.

Description: When considering drug delivery, the amount of drug that can be carried at a particular time and how the drug is incorporated efficiently into cells are important parameters. Transferrin (Tf)-conjugated nanocarriers have been used for the targeted delivery of drugs to cancer cells due to the availability of receptor-mediated clathrin-dependent endocytosis. In general, however, endocytosis seems to differ according to the size and shape of carriers. Large substances are generally internalized into cells by phagocytosis. We studied the internalization mechanism of Tf-conjugated nanoparticles (diameter, 522 nm). Tf-conjugated polystyrene particles were incorporated into cells by receptor-mediated endocytosis with large clathrin-coated vesicles even though their diameter was 〉500 nm and despite that fact that clathrin-coated vesicles have a diameter of 100 nm. This finding suggests that signals for internalization generated by stimulated Tf receptors (TfRs) activate clathrin-mediated endocytosis preferentially. Whether these larger particles could deliver drugs more efficiently than smaller particles was then examined. The toxicity of larger Tf-conjugated biodegradable nanoparticles (poly(lactic-co-glycolic acid)) encapsulating doxorubicin (diameter, 216 ± 38 nm) was appreciably dependent on the number of Tf molecules conjugated on a particle and the number of TfRs expressed on the cell membrane. Larger Tf-conjugated particles delivered drugs to cancer cells expressing many TfRs more selectively than their smaller counterparts (diameter, 56 ± 9 nm) if they were decorated with an appropriate number of Tf molecules.

Description: Structural biology relies on good-quality protein crystals in order for structure determination. Many factors affect the growth process of a protein crystal including the way it nucleates and the types of damage and contamination during its growth. Although the nucleation process and quality of a crystal is vital to structure determination, they are both under-studied areas of research. Our research begins to explore ways of measuring the quality of protein crystals, using TEM, thus overcoming the problems associated with viewing wet specimens in a vacuum. Our current understanding of nucleation is that it is a two-step mechanism involving the formation of nuclei from dense liquid clusters; however; it is still unclear whether nuclei first start as amorphous aggregates or as crystalline lattices. Potentially, electron diffraction may be capable of uncovering this process. Using TEM imaging and diffraction of lysozyme as a model protein crystal, we report the internal two-dimensional strain and the density of crystallites in a protein crystal, at a resolution never seen before. The TEM diffraction shows unique features of crystal mosaicity that can be directly correlated to TEM images.

Description: The cotyledon of legume seeds is a storage organ that provides nutrients for seed germination and seedling growth. The spatial and temporal control of the degradation processes within cotyledons has not been elucidated. Calcium oxalate (CaOx) crystals, a common calcium deposit in plants, have often been reported to be present in legume seeds. In this study, micro-computed tomography (micro-CT) was employed at the SPring-8 facility to examine the three-dimensional distribution of crystals inside cotyledons during seed maturation and germination of Lotus miyakojimae (previously Lotus japonicus accession Miyakojima MG-20). Using this technique, we could detect the outline of the embryo, void spaces in seeds and the cotyledon venation pattern. We found several sites that strongly inhibited X-ray transmission within the cotyledons. Light and polarizing microscopy confirmed that these areas corresponded to CaOx crystals. Three-dimensional observations of dry seeds indicated that the CaOx crystals in the L. miyakojimae cotyledons were distributed along lateral veins; however, their distribution was limited to the abaxial side of the procambium. The CaOx crystals appeared at stage II (seed-filling stage) of seed development, and their number increased in dry seeds. The number of crystals in cotyledons was high during germination, suggesting that CaOx crystals are not degraded for their calcium supply. Evidence for the conservation of CaOx crystals in cotyledons during the L. miyakojimae germination process was also supported by the biochemical measurement of oxalic acid levels.

Description: The electron irradiation damage of MFI-type zeolite was estimated under various accelerating voltages of 100, 200 and 300 kV from successively captured high-resolution transmission electron microscopy (HRTEM) images. To determine the optimal accelerating voltage for HRTEM imaging of electron-sensitive MFI zeolite, the critical dose was estimated from the disappearance of a specific fast Fourier transform spot calculated from experimental images. Based only on the electron dose, a higher voltage was more advantageous. However, taking into account the minimum dose for imaging with a CCD camera, the optimal accelerating voltage for imaging MFI zeolite was 200 kV. The minimum dose for image detection with a CCD camera was surmised from the output/input signal ratio dependence on the accelerating voltage and the contrast range in simulated HRTEM images.

Description: The magnetic field generated by a magnetic recording head is evaluated using electron holography. A magnetic recording head, which is connected to an electric current source, is set on the specimen holder of a transmission electron microscope. Reconstructed phase images of the region around the magnetic pole show the change in the magnetic field distribution corresponding to the electric current applied to the coil of the head. A simulation of the magnetic field, which is conducted using the finite element method, reveals good agreement with the experimental observations.

Description: A new multilayer-coated varied line-spaced grating, JS4000, was fabricated and tested for extending the upper limit of a grating X-ray spectrometer for electron microscopy. This grating was designed for 2–3.8 keV at a grazing incidence angle of 1.35°. It was revealed that this new multilayer structure enables us to take soft-X-ray emission spectra continuously from 1.5 to 4.3 keV at the same optical setting. The full-width at half maximum of Te-L α1,2 (3.8 keV) emission peak was 27 eV. This spectrometer was applied to indium tin oxide particles and clearly resolved Sn-L α (3444 eV) and In-L β1 (3487 eV) peaks, which could not be resolved by a widely used energy-dispersive X-ray spectrometer.

Description: For development of advanced materials, characterization using a scanning transmission electron microscope (STEM) including analysis via X-ray energy-dispersive spectrometry and electron energy-loss spectrometry is essential. Recent advances in aberration-corrected instruments have offered large-scale data acquisition at a high resolution for limited acquisition times both in imaging and in analysis. Further advanced procedures are required to analyze such large-scale datasets more efficiently including quantification. In addition, more simplified tuning procedures are crucial to the best possible resolution in the latest aberration-corrected instruments. In this review article, several approaches to perform advanced electron microscopy, which the author has been developing with his colleague, are described as ‘Microscopy Hacks’. These are (i) quantification and elemental/chemical-imaging procedures, (ii) advanced statistical approaches to handle large-scale datasets and (iii) instrument characterization and tuning procedures including the latest development of an ad hoc autotuning procedure for aberration-corrected STEM imaging.

Description: The crystal structure of a new type of molybdenum oxide crystal encapsulated in a single-walled carbon nanotube (CNT) was examined via diffraction and spectroscopic techniques using both X-rays and electron beams. This new type of molybdenum oxide crystal has a chemical bonding state of MoO 3 , as confirmed by X-ray absorption spectroscopy, and the MoO 3 units exhibit axial symmetry, as clarified by electron diffraction from bundled and individual CNTs encapsulating the crystal. To obtain three-dimensional information on the structure, a cross-sectional sample was prepared using a conventional dimple and ion-mill method. High-resolution transmission electron microscopy images exhibit ring-like shapes that originated from the arrangement of the MoO 3 units inside the CNTs, as observed along the tube axis. The units are spaced 0.36 nm from each other in a ring arrangement and the distance between each ring is 0.391 nm.

Description: This review summarizes the recent advances in three-dimensional (3D) imaging techniques and their application to polymer nanostructures, for example, microphase-separated structures of block copolymers. We place particular emphasis on the method of transmission electron microtomography (electron tomography for short; hereafter abbreviated as ET). As a result of recent developments in ET, truly quantitative 3D images of polymer nanostructures can now be obtained with subnanometer resolution. The introduction of scanning optics in ET has made it possible to obtain large amounts of 3D data from micrometer-thick polymer specimens by using conventional electron microscopes at a relatively low accelerating voltage, 200 kV. Thus, ET covers structures over a wide range of thicknesses, from a few nanometers to several hundred nanometers, which corresponds to quite an important spatial range for hierarchical polymer nanostructures. ET provides clear 3D images and a wide range of new structural information that cannot be obtained using other methods. Information traditionally derived from conventional microscopy or scattering methods can be directly acquired from 3D volume data. ET is a versatile technique that is not restricted to only polymer applications; it can also be used as a powerful characterization tool in energy applications such as fuel cells.

Description: The performances of a newly developed 80–200 kV cold field emission gun (CFEG) transmission electron microscope (TEM) integrating a spherical aberration corrector for a TEM image-forming lens have been evaluated. To begin, we show that the stability of both emission and probe currents makes use of this new CFEG much friendlier. The energy spread of electrons emitted from the CFEG has been measured as a function of emission current and shows a very last 0.26 eV energy resolution at 200 kV and even 0.23 eV at 80 kV. The combination of the CFEG and the CEOS™ aberration corrector, associated with enhanced mechanical and electrical stabilities of this new microscope, allows reaching an information transfer below 75 pm at 200 and 80 pm at 80 kV. This unseen resolution at 200 kV has allowed us to study the structure of CoPt nanoparticles by observing direct images of their atomic arrangement along the high indexes zone axis. We have evidenced the presence of defects in these nanostructures that are not parallel to the electron beam. The precise stoichiometry of two iron oxides, FeO and Fe 2 O 3 , has been determined from an analysis of iron valence state that was obtained from a direct analysis of EELS fine structures spectrum of the two oxides.

Description: Data mining from noisy data/images is one of the most important themes in modern science and technology. Statistical image processing is a promising technique for analysing such data. Automation of particle pickup from noisy electron micrographs is essential, especially when improvement of the resolution of single particle analysis requires a huge number of particle images. For such a purpose, reference-based matching using primary three-dimensional (3D) model projections is mainly adopted. In the matching, however, the highest peaks of the correlation may not accurately indicate particles when the image is very noisy. In contrast, the density and the heights of the peaks should reflect the probability distribution of the particles. To statistically determine the particle positions from the peak distributions, we have developed a density-based peak search followed by a peak selection based on average peak height, using multi-reference alignment (MRA). Its extension, using multi-reference multiple alignment (MRMA), was found to enable particle pickup at higher accuracy even from extremely noisy images with a signal-to-noise ratio of 0.001. We refer to these new methods as stochastic pickup with MRA (MRA-StoPICK) or with MRMA (MRMA-StoPICK). MRMA-StoPICK has a higher pickup accuracy and furthermore, is almost independent of parameter settings. They were successfully applied to cryo-electron micrographs of Rice dwarf virus. Because current computational resources and parallel data processing environments allow somewhat CPU-intensive MRA-StoPICK and MRMA-StoPICK to be performed in a short period, these methods are expected to allow high-resolution analysis of the 3D structure of particles.

Description: The sensory nerve endings of the rat tongue, cheek and palate were studied using immunohistochemical staining and transmission electron microscopy analysis. The specimens were fixed in modified Karnovsky solution and embedded in Spurr resin. Substance P, calcitonin gene-related peptide (CGRP)- and protein gene product 9.5 (PGP b9.5)-containing nerve fibers in the rat tongue, cheek and palate were examined by electronic microscopical analysis and immunohistochemical localization. These fibers run very close to the basal lamina of the epithelium and extend into the filliform and fungiform papillae. Numerous plexiform fibers immunoreactive for substance P, CGRP and PGP 9.5 were found in the connective tissue of mucosa. Electron microscopic observations showed clearly immunostained nerve fibers, which are located very close to the basal lamina of epithelial cells. Some electron-dense granules may be observed in the axoplasms of both substance P and CGRP immunoreactive fibers. Several lamellar corpuscles into the subepithelial connective tissue papillae, Merkel corpuscles and numerous thin unmyelinated and myelinated axons were observed. The terminal axons revealed numerous mitochondria, neurofilaments, microtubules and clear vesicles in the base of axoplasmic protrusions. The lamellar cells showed caveolae and interlamelar spaces filled by amorphous substance. Between the lamellar cells and axoplasmic membrane, and in the adjacent lamellae region, desmosome-type junctions were observed. The quantitative and morphometric analysis showed nerve endings with an average area of 4.83 ± 3.4 μm 2 and 19.4 internal mitochondria in this site and the organized corpuscles with an average area of 79.24 ± 27.24 μm 2 and 24.23 internal mitochondria in this place. All the structures observed are involved in the transmission of pain and mechanoreceptors stimulus of these oral mucosae.

Description: The F-actin cytoskeleton of Cryptococcus neoformans is known to comprise actin cables, cortical patches and cytokinetic ring. Here, we describe a new F-actin structure in fungi, a perinuclear F-actin collar ring around the cell nucleus, by fluorescent microscopic imaging of rhodamine phalloidin-stained F-actin. Perinuclear F-actin rings form in Cryptococcus neoformans treated with the microtubule inhibitor Nocodazole or with the drug solvent dimethyl sulfoxide (DMSO) or grown in yeast extract peptone dextrose (YEPD) medium, but they are absent in cells treated with Latrunculin A. Perinuclear F-actin rings may function as ‘funicular cabin’ for the cell nucleus, and actin cables as intracellular ‘funicular’ suspending nucleus in the central position in the cell and moving nucleus along the polarity axis along actin cables.

Description: To evaluate the advantages of combination of two advanced electron microscopic technologies such as serial block-face scanning electron microscopy and double-axis electron beam tomography, we analyzed the three-dimensional morphology of cellular relationships between dendritic and plasma cells in the synovial membrane from patients with rheumatoid arthritis, using the combined approach.

Description: The low-energy Ar-ion milling method was used to prepare ultrathin specimens for transmission electron microscope observation. The samples were thinned initially by a usual focused ion beam technique or typical Ar-ion milling with a high energy of 2–10 keV and were thinned additionally by an Ar-ion beam with an energy less than 1 keV, typically 500–900 eV. This low-energy ion beam was scanned over the specimen, and secondary electrons induced by the ion beam could be detected to form secondary electron images with a resolution of a few micrometre. Because a desired area can be selected and thinned by the low-energy ion beam, redeposition or cross contamination from irradiation of a metal grid that supports the sample can be prevented. It was shown that the low-energy Ar-ion beam thins a surface amorphous damage layer preferentially and effectively rather than a crystal specimen. Images from ultrathin specimens of two different materials revealed a detailed structure.

Description: Off-axis electron holography can be used to measure the inner potential of a specimen from its reconstructed phase image and is thus a powerful technique for materials scientists. However, abrupt reversals of contrast from white to black may sometimes occur in a digitally reconstructed phase image, which results in inaccurate information. Such phase distortion is mainly due to the digital reconstruction process and weak electron wave amplitude in some areas of the specimen. Therefore, digital image processing can be applied to the reconstruction and restoration of phase images. In this paper, fringe reconnection processing is applied to phase image restoration of a crystal structure image. The disconnection and wrong connection of interference fringes in the hologram that directly cause a 2 phase jump imperfection are correctly reconnected. Experimental results show that the phase distortion is significantly reduced after the processing. The quality of the reconstructed phase image was improved by the removal of imperfections in the final phase.

Description: Diabetes causes oxidative stress, which in turn generates excessive free radicals resulting in cellular damage. Vitamin C is an antioxidant that protects tissues and organs from oxidative stress. The thymus is one of the most important lymphoid organs, which regulates T-lymphocyte proliferation and maturation. The aim of this study is to investigate the protective effects of vitamin C on the thymus of streptozotocin (STZ)-induced diabetic rats. The mitotic activity and cell integrity of thymic lymphocytes were explored. Wistar Albino rats were divided into three groups: control (Group 1), STZ-diabetes (Group 2) and vitamin C-treated STZ-diabetics (Group 3). Rats received a single intraperitoneal injection of 45 mg/kg STZ to induce diabetes. Vitamin C (20 mg/kg) was administered intragastrically. Semithin and ultrathin sections were examined under a light or an electron microscope, respectively. Considerable numbers of mitotic lymphocytes were observed in the thymus of control rats. In the diabetic rats, however, numbers of mitotic lymphocytes decreased to ~57% of controls, and cell division abnormalities were observed. Additionally, diabetic rats showed degeneration in the structure of the thymus including trabecular thickening, accumulation of lipid vacuoles, heterochromatic nuclei and loss of mitochondrial cristae. Degradation of medullar and cortical integrity was also detected. In the vitamin C-treated STZ-diabetic group, the structure of the thymus and mitotic activity of the lymphocytes were similar to the control group. These results suggest that vitamin C protects the thymus against injury caused by diabetes and restores thymocyte mitotic activity.

Description: We investigated the stability of Pd/ZnO polar interfaces formed by internal oxidation of Pd–Zn alloys by using high-resolution transmission electron microscopy, electron energy-loss spectroscopy and convergent-beam electron diffraction. At 1273 K, a $$(111{)}_{\mathrm{Pd}}/(000\overline{2}{)}_{\mathrm{ZnO}}$$ polar interface defaceted and transformed into a curved interface, while another (111) Pd /(0002) ZnO polar interface retained its flatness. The $$(111{)}_{\mathrm{Pd}}/(000\overline{2}{)}_{\mathrm{ZnO}}$$ polar interface lost some stability over non-polar interfaces at 1273 K, while the (111) Pd /(0002) ZnO polar interface remained stable.

Description: Transmission electron microscope (TEM) observation of light metal hydrides is complicated by the instability of these materials under electron irradiation. In this study, the electron kinetic energy dependences of the interactions of incident electrons with lithium, sodium and magnesium hydrides, as well as the constituting element effect on the interactions, were theoretically discussed, and electron irradiation damage to these hydrides was examined using in situ TEM. The results indicate that high incident electron kinetic energy helps alleviate the irradiation damage resulting from inelastic or elastic scattering of the incident electrons in the TEM. Therefore, observations and characterizations of these materials would benefit from increased, instead decreased, TEM operating voltage.

Description: Synaptic plasticity is the process by which long-lasting changes take place at synaptic connections. The phenomenon itself is complex and can involve many levels of organization. Some authors separate forms into adaptations that have positive or negative consequences for the individual. It has been hypothesized that an increase in the number of synapses may represent a structural basis for the enduring expression of synaptic plasticity during some events that involve memory and learning; also, it has been suggested that perforated synapses increase in number after some diseases and experimental situations. The aim of this study was to analyze whether dopamine depletion induces changes in the synaptology of the corpus striatum of rats after the unilateral injection of 6-OHDA. The findings suggest that after the lesion, both contralateral and ipsilateral striata exhibit an increased length of the synaptic ending in ipsilateral (since third day) and contralateral striatum (since Day 20), loss of axospinous synapses in ipsilateral striatum and a significant increment in the number of perforated synapses, suggesting brain plasticity that might be deleterious for the spines, because this type of synaptic contacts are presumably excitatory, and in the absence of the modulatory effects of dopamine, the neuron could die through excitotoxic mechanisms. Thus, we can conclude that the presence of perforated synapses after striatal dopamine depletion might be a form of maladaptive synaptic plasticity.

Description: Unlike in vitro protein dynamics, intracellular protein dynamics are intricately regulated by protein–protein interactions or interactions between proteins and other cellular components, including nucleic acids, the plasma membrane and the cytoskeleton. Alteration of these dynamics plays a crucial role in physiological phenomena such as gene expression and cell division. Live-cell imaging via microscopy with the inherent properties of fluorescent proteins, i.e. photobleaching and photoconversion, or fluorescence correlation spectroscopy, provides insight into the movement of proteins and their interactions with cellular components. This article reviews techniques based on photo-induced changes in the physicochemical properties of fluorescent proteins to measure protein dynamics inside living cells, and it also discusses the strengths and weaknesses of these techniques.

Description: We have developed a method of atomic force microscopy (AFM)-assisted scanning tunneling spectroscopy (STS) under ambient conditions. An AFM function is used for rapid access to a selected position prior to performing STS. The AFM feedback is further used to suppress vertical thermal drift of the tip–sample distance during spectroscopy, enabling flexible and stable spectroscopy measurements at room temperature.

Description: To elucidate high-temperature plastic deformation (creep) mechanism in materials, it is essential to observe dislocation motion under tensile loading. There are many reports on in situ transmission electron microscopy (TEM) observations in the literature; however, the relationship between the dislocation motion and shear stress in 9Cr steel is still not clear. In this study, in order to evaluate this relationship quantitatively, in situ TEM observations were carried out in conjunction with finite element method (FEM) analysis. A tensile test sample was strained at an elevated temperature (903 K) inside a transmission electron microscope, and the stress distribution in the strained sample was analyzed by FEM. The dislocation behavior was clearly found to depend on the shear stress. At a shear stress of 66 MPa, both the dislocation velocity and mobile dislocation density were low. However, a high shear stress level of 95 MPa caused a noticeable increase in the dislocation velocity and mobile dislocation density. Furthermore, in this article, we discuss the dependence of the dislocation behavior on stress. The results presented here also indicate that the relationship between the microstructure and the strength of materials can be revealed by the methods used in this work.

Description: A dual-axis 360° rotation specimen holder was developed for use in reconstructing the three-dimensional (3D) distribution of a magnetic field using a combination of electron holography and tomography. Pillar-shaped specimens are used to obtain accurate reconstruction without a missing angle. The holder's rotation rod can be turned 〉360°; the pillar is set ±45° to the azimuth for both x - and y -axis rotation. Two rotation series of holograms in individual axes are recorded for vector field tomography. The two vector components of the magnetic field are reconstructed directly from the two series of holograms, and the remaining component is calculated using Maxwell's equation, div B = 0. As a result, all 3D magnetic fields are reconstructed.

Description: A new type of electrochemical cell was developed for in situ transmission electron microscopy observation that enables the electrode materials to be conveniently changed. The electrochemical cell was used to observe the electrochemical growth or dissolution of copper islands on a gold film with simultaneous cyclic voltammetry measurements. The copper islands could be explained by three-dimensional growing model.

Description: Aerosol-assisted CVD synthesis, characterisation and gas-sensing application of gold-functionalised tungsten oxide Journal of Sensors and Sensor Systems, 3, 325-330, 2014 Author(s): F. Di Maggio, M. Ling, A. Tsang, J. Covington, J. Saffell, and C. Blackman Tungsten oxide nanoneedles (NNs) functionalised with gold nanoparticles (NPs) have been integrated with alumina gas-sensor platforms using a simple and effective co-deposition method via aerosol-assisted chemical vapour deposition (AACVD) utilising a novel gold precursor, (NH 4 )AuCl 4 . The gas-sensing results show that gold NP functionalisation of tungsten oxide NNs improves the sensitivity of response to ethanol, with sensitivity increasing and response time decreasing with increasing amount of gold.

Description: Objectifying user attention and emotion evoked by relevant perceived product components Journal of Sensors and Sensor Systems, 3, 315-324, 2014 Author(s): R. Schmitt, M. Köhler, J. V. Durá, and J. Diaz-Pineda A company's aim is to develop products that engage user attention and evoke positive emotions. Customers base their emotional evaluation on product components that are relevant for their perception. This paper presents findings of both identifying relevant product components and measuring emotions evoked by relevant perceived product components. To validate results, the comparison with self-reporting methods identifies similarities and differences between explicit expressed and implicit recorded customer requirements. On the one hand, eye tracking is applied to deduce the attention provoked by perceived product components. In order to link the product strategy with product components, the paper presents results considering the fact that the gaze track is affected by current thoughts. (Köhler et al., 2013, 2014a, b; Köhler and Schmitt, 2012) On the other hand, since self-reporting tools are only useful for obtaining information about the conscious part of customers' emotions, there is a need for measurement methods that measure the changes in physiological signals (bio-signals). Arousal is similar to emotional intensity and is related to the galvanic skin response. Positive or negative emotions are defined by the valence that is measured by facial electromyography. Findings are presented that relate changes in bio-signals on the aesthetical design to the global product impression as well as to emotions and, subsequently, linking changes in physiological signals to the evaluation of semantic concepts and design parameters. The presented approach provides conclusions and valid information about products as well as product components that provoke certain emotions and about product components linked to a certain product concept, which could be part of a product strategy. Consequently, hard facts and special design rules for emotional product design can be deduced.

Description: Challenges for Wireless Mesh Networks to provide reliable carrier-grade services Advances in Radio Science, 9, 377-382, 2011 Author(s): D. von Hugo and N. Bayer Provision of mobile and wireless services today within a competitive environment and driven by a huge amount of steadily emerging new services and applications is both challenge and chance for radio network operators. Deployment and operation of an infrastructure for mobile and wireless broadband connectivity generally requires planning effort and large investments. A promising approach to reduce expenses for radio access networking is offered by Wireless Mesh Networks (WMNs). Here traditional dedicated backhaul connections to each access point are replaced by wireless multi-hop links between neighbouring access nodes and few gateways to the backbone employing standard radio technology. Such a solution provides at the same time high flexibility in both deployment and the amount of offered capacity and shall reduce overall expenses. On the other hand currently available mesh solutions do not provide carrier grade service quality and reliability and often fail to cope with high traffic load. EU project CARMEN (CARrier grade MEsh Networks) was initiated to incorporate different heterogeneous technologies and new protocols to allow for reliable transmission over "best effort" radio channels, to support a reliable mobility and network management, self-configuration and dynamic resource usage, and thus to offer a permanent or temporary broadband access at high cost efficiency. The contribution provides an overview on preliminary project results with focus on main technical challenges from a research and implementation point of view. Especially impact of mesh topology on the overall system performance in terms of throughput and connection reliability and aspects of a dedicated hybrid mobility management solution will be discussed.

Description: Meteor radar measurements of mean winds and tides over Collm (51.3° N, 13° E) and comparison with LF drift measurements 2005–2007 Advances in Radio Science, 9, 335-341, 2011 Author(s): C. Jacobi An all-sky VHF meteor radar (MR) has been continuously operated at Collm (51.3° N, 13° E) since summer 2004. The radar measures meteor parameters, diffusion coefficients, and horizontal winds in the mesopause region. There exists a temporal overlap of the MR wind measurements with co-located low-frequency (LF) ionospheric drift measurements until 2007. Comparison of MR and LF semidiurnal tidal phases allows to empirically determine the virtual height overestimation of LF reflection heights due to the group retardation of LF waves. LF reference heights have to be reduced by up to 20 km to match real heights. Correction of LF heights for group retardation allows to determine the wind underestimation by the LF method compared with meteor radar measurements and opens the possibility to continue long-term trend analysis using mesosphere/lower thermosphere winds.

Description: The applications of the hard disk drive (HDD) in mobile and compact devices pose higher requirement on the vibration-rejection capability of HDD servo control. A novel vibration-compensation method is proposed in this paper. It is an add-on feedforward scheme, and the add-on feature will be turned on only in the specific vibration environment. The scheme comprises two parts: the vibration detection through the analysis of the vibration sensor output, and the vibration compensation through the add-on feature. One major advantage of this method over conventional methods applied in HDD is that the vibration rejection in some frequencies can be improved without the compromise of the performance in other frequencies. The scheme is not based on an accurate modeling, therefore, it is less sensitive to the variation of the plant parameters. The transient response in switching on or off the add-on feature is shortened by the reset control. The scheme is implemented in real HDD, and the experimental results prove the effectiveness of the scheme.

Description: This paper focuses on scaled teleoperation systems interacting with soft tissues and presents an optimal control scheme to maximize the operator's kinesthetic perception of remote soft environments while maintaining the stability in macro-micro interactions. Two performance metrics are defined to quantify the kinesthetic perception of the surgeons and the position tracking ability of the master-slave system. Kinesthetic perception is defined based on psychophysics by using two metrics, which relate to the detection and discrimination of stimulus. This paper then employs a multiconstrained optimization approach to get an optimal solution in the presence of the stability-performance tradeoff wherein the objective is to enhance the kinesthetic perception while maintaining the tracking and robust stability for interactions between macro and microworlds. Simplified stability constraints for scaled teleoperation systems are designed based on Llewellyn's absolute stability criterion for the optimization procedure, which provides easy and effective design guidelines for selecting control gains. Experiments with phantom soft tissues have been conducted using scaled force-position control architecture, scaled position-position control architecture, and scaled four-channel control architecture to verify the proposed control scheme. Results prove the effectiveness of this algorithm in enhancing the kinesthetic perception of surgeons for scaled teleoperation systems. Psychophysical experiments were then performed to compare our approach with similar contemporary research methods that further validated its efficacy.

Description: For automating the remote voice detection using a laser Doppler vibrometer (LDV), we integrate a pan-tilt-zoom (PTZ) camera, a mirror, and a pan-tilt unit (PTU) with the LDV to form a multimodal sensing system. With the assistance of vision and active control components, the LDV can automatically select the best reflective surfaces, point the laser beam to the selected surfaces, and quickly focus the laser beam. For accomplishing these functions, distance measurement and sensor calibration methods are proposed using the triangulation between the PTZ camera and the mirrored LDV laser beam. Based on both the measured distances and the return signal levels of the LDV, a fast and automatic LDV focusing algorithm is designed. Furthermore, strategies and related image-processing techniques in surface selection and laser pointing are designed. Experimental results are shown to validate the performance improvement of the LDV in remote automatic voice detection by using the multimodal system.

Description: This paper considers the trajectory tracking problem of hybrid machines. A hybrid machine here refers to a machine that is driven by the constant velocity (CV) motors and servomotors in a proper configuration. The hybrid machine is a meaningful tradeoff between task flexibility and power capacity. However, this system has brought a new challenge to control due to the velocity fluctuation in the CV motor. The velocity fluctuation problem is caused mainly by the uncontrollable input current and the time-varying workload. In addition, the dynamic parameters are uncertain, which further increases the control difficulty. In this paper, we propose an adaptive control law for the trajectory tracking and demonstrate the effectiveness of this control law on a 2-DOF closed-chain five-bar hybrid mechanism driven by one servomotor and one CV motor. The principle of the proposed controller is to properly design the servomotor control input that can compensate not only the uncertainty in the servomotor but also the uncertainty in the CV motor. By the proposed adaptive control law, it can be theoretically proved that the position/velocity tracking errors of the joint associated with the servomotor and the velocity tracking error of the joint associated with the CV motor are convergent to zero as time goes to infinity. Finally, the simulation examples are given to illustrate the effectiveness of the proposed method.

Description: In this paper, a vision-based algorithm for estimating tip interaction forces on a deflected atomic orce microscope (AFM) cantilever is described. Specifically, we propose that the algorithm can estimate forces acting on an AFM cantilever being used as a nanomanipulator inside a scanning electron microscope (SEM). The vision-based force sensor can provide force feedback in real time, a feature absent in many SEMs. A methodology based on cantilever slope detection is used to estimate the forces acting on the cantilever tip. The technique was tested on a scaled model of the nanoscale AFM cantilever and verified using theoretical estimates as well as direct strain measurements. Artificial SEM noise was introduced in the macroscale images to characterize our sensor under varying levels of noise and other SEM effects. Prior knowledge about the cantilever is not required, and the algorithm runs independent of human input. The method is shown to be effective under varying noise levels, and demonstrates improving performance as magnification levels are decreased. Therefore, we conclude that the vision-based force sensing algorithm is best suited for continuous operation of the SEM, fast scanning rates, and large fields-of-view associated with low magnification levels.

Description: Robot-assisted microinjection has attracted considerable attention from both engineering and biological communities, due to its advantages of high precision and throughput. This paper addresses two issues in the development of enable technologies for robot-assisted microinjection. One is the microforce measurement during the embryo-injection process. A new injection force-sensing scheme based on a simply supported beam structure is reported. The model combining mechanoelectrical transduction of the beam and the polyvinylidene fluoride sensing material is theoretically investigated. The other issue to be addressed is the manipulation strategy to mimic human-injection operation, which is based on force sensing and control techniques. A set of microinjection experiments on zebrafish embryos is performed to demonstrate the effectiveness of the proposed robot-assisted manipulation methodology. Experimental results show that satisfied survival rate of the injected cells can be obtained, which is comparable to manual operation by human expert.

Description: Temporal difference (TD) constitutes a class of methods for learning predictions in multistep prediction problems. The most important application of these methods is to temporal credit assignment in reinforcement learning. Although these TD procedures work in theory and in principle, its success is contingent on proper selection of parametric values. As well, its learning is majorly based on repeated exposures, which may not always be practical or feasible. This paper examines the issues of the efficient and general implementation of TD for hardware implementation of reinforcement learning algorithms by synthesizing the series of discounted sum of rewards along time. The proposed algorithm eliminates all step size parameters and improves data efficiency based on a synthetic approach of Grey theory. This paper also presents the stability of the proposed algorithm from the viewpoint of Grey theory. The algorithm along with a critic-actor reinforcement learning model is implemented in a System-on-a-Programmable-Chip (SOPC) board. In addition to comparing with the renowned model, adaptive heuristic critic (AHC), the results of experiments demonstrate that the proposed control mechanism can learn to control a system with very little a priori knowledge. Meanwhile, the effect of uncertainty in interactions between the system and the environment can be relaxed to some extent in the learning process of the proposed reinforcement learning agent.

Description: This paper studies the design of a robust discrete-time sliding-mode control (DT–SMC) for a high precision electrohydraulic actuator (EHA) system. Nonlinear friction in the hydraulic actuator can greatly influence the performance and accuracy of the hydraulic actuators, and it is difficult to accurately model the nonlinear friction characteristics. In this paper, it is proposed to characterize the frictions as an uncertainty in the system matrices. Indeed, the effects of variations of the nonlinear friction coefficients are considered as norm-bounded uncertainties that span a bounded region to cover a wide range of the real actuator friction. For such a discrete-time dynamic model, for the EHA system with system uncertainty matrices and a nonlinear term, a sufficient condition for existence of stable sliding surfaces is proposed by using the linear matrix inequality approach. Based on this existence condition, a DT–SMC is developed such that the reaching motion satisfies the discrete-time sliding mode reaching condition for uncertain systems. Simulation and experimental studies on the EHA system illustrate the effectiveness and applicability of the proposed method.

Description: This paper focuses on the integration of inertial measurement unit (IMU) with two real-time kinematic global positioning system (GPS) units in an adaptive Kalman filter (KF) for driftless estimation of a vehicle’s attitude and position in 3-D. The observability analysis reveals that 1) integration of a single GPS with IMU does not constitute an observable system; and 2) integration of two GPS units with IMU results in a locally observable system provided that the line connecting two GPS antennas is not parallel with the vector of the measured acceleration, i.e., the sum of inertial and gravitational accelerations. The latter case makes it possible to compensate the error in the estimated orientation due to gyro drift and its bias without needing additional instrument for absolute orientation measurements, e.g., magnetic compass. Moreover, in order to cope with the fact that GPS systems sometimes lose their signal and receive inaccurate position data, the self-tuning filter estimates the covariance matrix associated with the GPS measurement noise. This allows the KF to incorporate GPS measurements in the data fusion process heavily only when the information received by GPS becomes reliably available. Finally, test results obtained from a mobile robot moving across uneven terrain demonstrate driftless 3-D pose estimation.

Description: This paper presents a novel active body weight support (BWS) method, which is capable of virtually offloading full or partial body mass for a potential application of enhancing treadmill-based locomotion rehabilitation. The mass-offloading capability is realized by actively compensating a desired amount of body weight and inertia force using an acceleration-feedback scheme. The method has been studied by dynamics simulations and a specially designed nonhuman experiment. In the simulation study, the human and the BWS device were modeled as a multibody dynamical system interacting dynamically with the treadmill. The ground reaction forces were recorded as the dynamic load on the person. A cam-slider-based experiment was designed and conducted to test the engineering feasibility of the mass-offloading capability. Both the simulation and experiment results demonstrated that the BWS system can compensate any desired amount of gravity force and inertia force and, therefore, has the effect of virtually reducing the mass of a person attached to the system.

Description: This paper describes a magnetic levitation system that uses a planar array of 16 cylindrical coils to levitate a platform containing two permanent disk magnets. Position and orientation feedback for closed-loop levitation control is provided by an optical rigid-body motion tracker and wireless LED markers. The actuation model for the levitation system across the full translation and rotation ranges was calculated using electromagnetic finite element analysis and validated with force and torque measurements between a single magnet and coil using motion stages and a six-axis force sensor. The transformation from the set of coil currents to the force and torque generated on the levitated body is recalculated in real time at each update of the levitated platform position and orientation obtained from the motion tracker using a precomputed single magnet and coil actuation model, and redundant kinematic control methods are used to find the least squares set of coil currents to generate the forces and torques needed to stabilize the levitated platform by proportional-derivative feedback control. The approximately $80 times 80 times 25$ mm translation range of the implemented levitation system is comparable to the dimensions of the levitated magnet platform. The rotation ranges are $pm 40^circ$ in roll and $pm 15^circ$ in pitch, with unlimited yaw. The horizontal translation ranges can be extended by adding coils to the array, and the vertical translation and tilt rotation ranges are limited by heat dissipation in the coils. Analysis and control methods of the system are described, and large range translation and rotation trajectory following experimental results are given.

Description: This paper discusses the use of voice coil actuators to enhance the performance of shift-by-wire systems. This innovative purely electric actuation approach was implemented and applied to a Formula SAE race car. The result was more compact and faster than conventional solutions, which usually employ pneumatic actuators. The designed shift-by-wire system incorporates a control unit based on a digital signal processor, which runs the control algorithms developed for both gear shifting and launching the car. The system was successfully validated through laboratory and on-track tests. In addition, a comparative test with an equivalent pneumatic counterpart was carried out. This showed that an effective use of voice coil actuators enabled the upshift time to be almost halved, thus proving that these actuators are a viable solution to improving shift-by-wire system performance.

Description: This paper explores a robust $mu$ -synthesis control scheme for structural resonance vibration suppression of high-speed rotor systems supported by active magnetic bearings (AMBs) in the magnetically suspended double-gimbal control moment gyro (MSDGCMG). The derivation of a nominal linearized model about an operating point was presented. Sine sweep test was conducted on each component of AMB control system to obtain parameter variations and high-frequency unmodeled dynamics, including the structural resonance modes. A fictitious uncertainty block was introduced to represent the performance requirements for the augmented system. Finally, D-K iteration procedure was employed to solve the robust $mu$ -controller. Rotor run-up experiments on the originally developed MSDGCMG prototype show that the designed $mu$ -controller has a good performance for vibration rejection of structural resonance mode with the excitation of coupling torques. Further investigations indicate that the proposed method can also ensure the robust stability and performance of high-speed rotor system subject to the reaction of a large gyro torque.

Description: Many minimally invasive surgical procedures are now performed using teleoperated robotic systems. However, such commercially available systems do not provide significant force feedback to the surgeon. This reduces surgeon's dexterity and increases tissue trauma when performing the operation. In this paper, a compact and lightweight forceps’ manipulator using pneumatic artificial muscles (PAMs) for minimally invasive surgery is presented, which allows for the perception of manipulation force without the usage of the force sensor. The main advantage of this concept is that no force sensor has to be integrated into surgical instruments and inserted into the patient's body. Rather, a disturbance observer is integrated into the slave-side controller for the estimation of the external force acting at the forcep's tip. This approach reduces costs and stabilizability demands for forceps’ manipulator while enables haptic feedback to the surgeons. Results of force perception experiments and comparison with forceps’ manipulator driven by pneumatic cylinders are presented to validate the concepts.

Description: Active disturbance rejection control method that can actively compensate nonlinear model uncertainties and unpredictable external disturbances is proposed for an accurate position tracking of an ionic polymer–metal composite actuator. An empirical model of the electroactive polymer actuator is constructed by fitting the step response of the actuator. Experimental results show that the present active disturbance rejection control scheme can substantially improve the control performance in the tracking of various reference motions including step, sinusoidal, trapezoidal, and sawtooth wave profiles. The proposed scheme offers an innovative solution for the position tracking of an ionic polymer–metal composite actuator with highly nonlinear dynamics.

Description: This paper explores the design methodology and effectiveness of small-scale magnetorheological dampers (MRDs) in applications that require variable damping. Previously, applications of MRD have been chiefly limited to vehicle shock absorbers and seismic vibration attenuators. There has been recent biomedical interest in active-damping technology, however, particularly in the field of rehabilitation robotics. The topic at hand is the feasibility of developing MRDs that would be functionally and cosmetically adequate for actuation of an upper limb tremor suppression orthosis. A Bingham plastic model is used to determine MRD's functional characteristics, and experimental data are presented to validate the mathematical model. The feasibility of applying the developed small-scale MRDs to attenuation of tremorous motion is explored.

Description: In order to fulfill the requirements of low energy consumption and two sensing directions, a novel bidirectional acceleration switch is proposed by utilizing the magnetic-fields-based tristable mechanism that can maintain the three stable states without input power and with high position accuracy and repeatability. The bidirectional acceleration switch mainly consists of an inertial mass supported by two parallel elastic beams, two metal contact points, and four permanent magnets with one imbedded in the inertial mass and the other three fixed in the case along the vertical direction. Based on the magnetic charge model, the nonlinear magnetic force is analyzed, and then, a static design model of the bidirectional switch is established by considering the elastic force, the magnetic force, the contact force, and the inertial force. To validate the feasibility of the design method, a miniature sample of the switch is fabricated. The results of the centrifugal experiment show that the threshold accelerations in two directions are 53.0 and -52.0 g, respectively, which are close to the design values of 55.0 and -50.0 g, correspondingly. In addition, the threshold values can be adjusted by changing the relative distances among the four magnets.

Description: In this paper, we report on the design, modeling, and experimental testing of a piezoelectric-driven microgripper making use of both an integrated gripping force sensor and an integrated tip displacement sensor. In the developed microgripper, a stack piezoelectric ceramic actuator is used to simultaneously obtain the tip displacement and the gripping force. A novel monolithic compliant mechanism is proposed to act as the microdisplacement transmission mechanism to obtain the large tip displacement and to provide the possibility of integrating both the gripping force sensor and the tip displacement sensor into the microgripper. The relationship between the gripping force, tip displacement, input force, and input displacement of the piezoelectric-driven microgripper and the dynamic model are established using the pseudorigid-body-model method. The characteristics of the developed microgripper are tested and the case of gripping an optical fiber is presented. The experimental results indicate that: 1) the theoretical model for the developed microgripper matched well with the measured results; 2) the integrated gripping force sensor and tip displacement sensor could accurately measure the gripping force and tip displacement; 3) the developed microgripper could achieve a displacement magnification of $16.0 times$ with respect to the stack piezoelectric ceramic actuator to realize the large tip displacement with high resolution but is also able to possess the parallel movement of its gripping jaws and the constant displacement magnification.

Description: This paper experimentally verifies that a multiple-client–server architecture based on switched Ethernet can be used as a real-time communication standard for possible applications in factory automation, by observing the effects of packet delays, network congestion, and packet loss on the performance of a networked control system (NCS). The NCS experimental setup used in this research involves real-time feedback control of multiple plants connected to one or more controllers over the network. A multiclient–multiserver (MC–MS) architecture on a local area network (LAN) was developed using user datagram protocol as the communication protocol. In the single-client–single-server (SC–SS) system, as the Ethernet link utilization increased over 82%, the average packet delays and steady-state error of a dc motor speed-control system increased by 2231% and 304%, respectively. As the link utilization increased beyond the threshold, employing an additional server in the NCS reduced average packet delays and also overcame the negative effects of Ethernet's flow control mechanism. The MC–MS architecture is tested with artificially generated random packet loss. The standard deviation of steady-state error (SSE) at 80% utilization with packet loss is found to be 70.2% less than SC–SS and 200% less than multiclient–single-server architecture. The MC–MS architecture remained stable till 70% of control or measurement packet loss.

Description: In this paper, a novel 5-degrees-of-freedom robot for performing needle-based interventions on small animal subjects is presented. The robot can realize dexterous alignment of the needle using two parallel mechanisms, and has a syringe mechanism to insert needles to subjects. Operations on small animals require high accuracy positioning during needle insertion. The kinematic calibration procedure of the robot using an optical tracker as an external sensor is presented to enhance accuracy of the system. After the kinematic calibration, the positioning accuracy of the needle tip is measured as 0.4 mm RMS. The robot design is light weight, and has a motion bandwidth of 4 Hz. The robot can track reference trajectories with a closed-loop controller.

Description: This paper describes an efficient control strategy for a piezoelectric microactuator using charge recovery. For piezoelectric actuators, as well as other actuators that behave primarily as capacitive loads, energy consumption can be reduced by minimizing the number of times an actuator is charged and by recovering stored energy when it is turned off. An integer programming-based algorithm is used to drive microrobotic legs powered by piezoelectric actuators to a specified angle in a specified time using minimum energy. Partial charge recovery is incorporated; this allows the use of a more flexible controller than a pure on–off controller, with two or more intermediate voltage levels between the minimum and maximum voltages available to improve positioning accuracy. Simulated and experimental tests show that a prototype piezoelectric robotic leg joint achieved controlled movements with one third of the energy consumed by a pure on–off controller.

Description: This paper reports the design, development, and magnetic resonance imaging (MRI) compatibility evaluation of an actuated transrectal prostate robot for MRI-guided needle intervention in the prostate. The robot performs actuated needle MRI guidance with the goals of providing $1)$ MRI compatibility; $2)$ MRI-guided needle placement with accuracy sufficient for targeting clinically significant prostate cancer foci; $3)$ reducing interventional procedure times (thus increasing patient comfort and reducing opportunity for needle targeting error due to patient motion); $4)$ enabling real-time MRI monitoring of interventional procedures; and $5)$ reducing the opportunities for error that arise in manually actuated needle placement. The design of the robot, employing piezoceramic-motor actuated needle guide positioning and manual needle insertion, is reported. Results of an MRI compatibility study show no reduction of MRI signal-to-noise ratio (SNR) with the disabled motors. Enabling the motors reduces the SNR by 80% without radio frequency (RF) shielding, but the SNR is only reduced by 40–60% with RF shielding. The addition of RF shielding is shown to significantly reduce image SNR degradation caused by the presence of the robotic device. An accuracy study of MRI-guided biopsy needle placements in a prostate phantom is reported. The study shows an average in-plane targeting error of 2.4 mm with a maximum error of 3.7 mm. These data indicate that the system’s needle targeting accuracy is similar to that obtained with a previously reported manually actuated system, and is sufficient to reliably sample clinically significant prostat- cancer foci under MRI guidance.

Description: A novel rotary nanomotor is described using two axially aligned, opposing chirality nanotube shuttles. Based on intershell screw-like motion of nanotubes, rotary motion is generated by electrostatically pulling the two cores together. Simulations using molecular dynamics show the generation of rotation from armchair nanotube pairs and their actuation properties. The simulation results point toward the use of these motors as building blocks in nanoelectromechanical systems and nanorobotic systems for sensing, actuation, and computation applications.

Description: A typical mechatronic problem (modeling, identification, and design) entails finding the best system topology as well as the associated parameter values. The solution requires concurrent and integrated methodologies and tools based on the latest theories. The experience on natural evolution of an engineering system indicates that the system topology evolves at a much slower rate than the parametric values. This paper proposes a two-loop evolutionary tool, using a hybrid of genetic algorithm (GA) and genetic programming (GP) for design optimization of a mechatronic system. Specifically, GP is used for topology optimization, while GA is responsible for finding the elite solution within each topology proposed by GP. A memory feature is incorporated with the GP process to avoid the generation of repeated topologies, a common drawback of GP topology exploration. The synergic integration of GA with GP, along with the memory feature, provides a powerful search ability, which has been integrated with bond graphs (BG) for mechatronic model exploration. The software developed using this approach provides a unified tool for concurrent, integrated, and autonomous topological realization of a mechatronic problem. It finds the best solution (topology and parameters) starting from an abstract statement of the problem. It is able to carry out the process of system configuration realization, which is normally performed by human experts. The performance of the software tool is validated by applying it to mechatronic design problems.

Description: This paper presents a nanomanipulation system for operation inside scanning electron microscopes (SEM). The system is compact, making it capable of being mounted onto and demounted from an SEM through the specimen-exchange chamber (load-lock) without breaking the high vacuum of the SEM. This advance avoids frequent opening of the high-vacuum chamber, thus, incurs less contamination to the SEM, avoids lengthy pumping, and significantly eases the exchange of end effectors (e.g., nanoprobes and nanogrippers). The system consists of two independent 3-DOF Cartesian nanomanipulators driven by piezomotors and piezoactuators. High-resolution optical encoders are integrated into the nanomanipulators to provide position feedback for closed-loop control. The system is characterized, yielding the encoders’ resolution of 2 nm and the piezoactuators’ resolution of 0.7 nm. A look-then-move control system and a contact-detection algorithm are implemented for horizontal and vertical nanopositioning.

Description: This paper presents a new method for the design of distributed controllers that achieves component swapping modularity (CSM) in control systems. Our approach, referred to as the direct method, is based on solving a bilevel optimization problem to obtain the distributed controller gains directly. In the previously proposed three-step method, the distributed controllers were obtained by matching with a precomputed centralized controller. To illustrate our approach, we consider an engine idle speed control problem, where CSM is achieved with respect to the throttle actuator. The results indicate that the direct method can significantly improve the CSM metric compared to the three-step method. In addition, for a certain distributed control structure, the direct method enables the designer to tradeoff between desired system performance and CSM.

Description: This study designs an optimal single-pulse stimulus in pacemakers to treat sudden cardiac arrest, while minimizing the pulse amplitude and reducing the delivered energy. Based on theYanagihara, Noma, and Irisawa (YNI) model that describes the potential behavior of a sinoatrial node in a heart, it develops the frequency entrainment between irregular YNI-response and optimal single-pulse. This study derives the minimum amplitude of the optimal single-pulse for successful entrainment. Simulation results confirm that the proposed optimal single pulse is effective to induce rapid response of sudden cardiac arrest for heartbeat recovery, while a reduction in delivered energy of 91%, comparing with conventional pulse. This study will be helpful not only for the treatment of sudden cardiac arrest but also for prolonging battery longevity and reducing the stimuli pain on patients with implantable medical devices.

Description: In this paper, a new actuator with adjustable stiffness (AwAS) is presented. AwAS is capable of controlling the position and stiffness of a joint, independently. The proposed actuator can regulate the joint stiffness through a wide range with minimum energy consumption by means of a small motor. This is possible due to its novel mechanical configuration that achieves the stiffness regulation not through the control of spring pretension (as in most of the existing variable stiffness joints) but by using the variable lever arm principle. The regulation of the lever arm length is achieved through the displacement of the spring elements. An important consequence of this mechanism is that the displacement needed to change the stiffness is perpendicular to the forces generated by the spring. This helps to reduce the energy/power required to regulate the stiffness. It is experimentally shown that AwAS is capable of minimizing energy consumption through exploiting the natural dynamics in real time for both fixed and variable frequency motions.

Description: IP-based mobility management for heterogeneous wireless access Advances in Radio Science, 10, 319-325, 2012 Author(s): H. J. Einsiedler and D. von Hugo Future high quality communication services will be offered in an integrated or converged network infrastructure maintaining both fixed wireless and mobile access via multi-mode user terminals. A support of various scenarios of user and/or terminal mobility within a common IP-based infrastructure requires intelligently designed control protocols. A major challenge is to provide seamless (i.e. lossless and low delay) handover between different radio cells and operator domains to enable continuation of unicast and multicast sessions while using network resources most efficiently. IETF (Internet Engineering Task Force) is specifying related IP mobility management protocols to be applicable also to a flat architecture as envisaged by Next Generation (Mobile) Networks (NGNs/NGMNs). The contribution will describe operator requirements towards such an approach. Both single-domain and multi-domain scenarios will be discussed based on federation ideas. Already existing solutions are taken into consideration and application of solution proposals towards a Distributed Mobility Management (DMM) currently under evaluation within IETF will be outlined.

Description: This paper introduces a methodology for designing real-time controllers capable of enforcing desired trajectories on microrobotic insects in vertical flight and hovering. The main idea considered in this work is that altitude control can be translated into a problem of lift force control. Through analyses and experiments, we describe the proposed control strategy, which is fundamentally adaptive with some elements of model-based control. In order to test and explain the method for controller synthesis and tuning, a static single-wing flapping mechanism is employed in the collection of experimental data. The fundamental issues relating to the stability, performance, and stability robustness of the resulting controlled system are studied using the notion of an input-output linear time-invariant (LTI) equivalent system, which is a method for finding an internal model principle (IMP) based representation of the considered adaptive laws, using basic properties of the $z$ -transform. Empirical results validate the suitability of the approach chosen for designing controllers and for analyzing their fundamental properties.

Description: This paper presents an integrated direct/indirect adaptive robust control scheme for a class of nonlinear dynamic systems preceded by unknown nonsymmetric, nonequal slope dead-zone nonlinearity. Departing from existing approximate adaptive dead-zone compensations, this paper uses indirect parameter estimation algorithms along with on-line condition monitoring to obtain an accurate estimation of the unknown dead zone when certain relaxed persistent-excitation conditions are satisfied—a theoretical result that cannot be achieved with the existing methods. Such a result is obtained by making full use of the fact that though not being linearly parameterized globally, the unknown dead zone can still be linearly parameterized perfectly within certain known working ranges. With these accurate estimates of dead-zone parameters, perfect dead-zone compensation is then constructed and utilized in the development of a performance-oriented adaptive robust control algorithm for the overall system. Consequently, asymptotic output tracking is achieved even in the presence of unknown dead zone. In addition, the proposed algorithm achieves certain guaranteed robust transient performance and final tracking accuracy even when the entire system may be subjected to other uncertain nonlinearities and time-varying disturbances. The proposed algorithm is also experimentally tested on a linear motor drive system preceded by a simulated unknown nonsymmetric dead zone. Comparative experimental results obtained validate the effectiveness of dead-zone compensation and the high-performance nature of the proposed approach in practical implementation.

Description: We propose an application-specified integrated circuit (ASIC)-based vibration damping system implementing a semiactive controlling method called synchronized switch damping on inductor (SSDI). The ASIC integrates high-voltage switches and diodes for an “energy-extracting” passive LC shunt circuit and a controlling part for synchronous voltage inversion on the piezoelectric transducer. The controlling part has two channels, each including a range-adaptive voltage divider with protection and a peak detector with switch-control output. The system has been tested with both cantilever beam and three-side-clamped-plate structures. Cantilever beam testing shows a 15 dB damping in forced harmonic regime and a fivefold damping rate in pulsed-excitation transient response. For the three-side-clamped-plate case, wideband SSDI damping effects are observed. The damping efficiency for each mode depends on the electromechanical coupling factor and the mapping of the piezoelectric-insert damping zones. It also depends on the excitation level, and begins to increase rapidly with vibration magnitude when the piezoelectric transducer's voltage peaks exceed a certain threshold voltage $(sim 0.5$ V for the system).

Description: Dielectric elastomer actuators (DEAs) have raised interest in the field of mobile robotics. In such a field, actuator design requires a fundamental understanding of DEA energy conversion performance. To provide insight into DEA mechanical work, energy consumption, and efficiency, this paper proposes a simple thermodynamic description completed by experimental loss factors obtained over a broad range of operating conditions and modes. Extensive data gathered on cone actuators show practical efficiency limits of $sim 26%$ for acrylic actuators (VHB 4905) operating under constant charge mode and $sim 18%$ for silicone actuators operating under constant voltage mode. While charge recovery could raise these limits to $sim 60%$ , the study of a DEA rotary motor shows significant efficiency degradation caused by unconstrained electrode boundaries.

Description: The problem of perimeter detection and monitoring has a variety of applications. In this paper, a hybrid system of finite states is proposed for multiple autonomous robotic agents with the purpose of hazardous spill perimeter detection and tracking. In the system, each robotic agent is assumed to be in one of three states: searching, pursuing, and tracking. The agents are prioritized based on their states, and a potential field is constructed for agents in each state. For an agent in the tracking state, the agent’s location and velocity as well as those of its closest leading and trailing agents are utilized to control its movement. The convergence of the tracking algorithm is analyzed for multiple spills under certain conditions. Simulation and experiment results show that with the proposed method, the agents can successfully detect and track the spills of various shapes, sizes, and movements.

Description: The accuracy and resolution of metrological devices (coordinate measuring machines -CMM-, interferometers, etc.) are greatly affected by their robustness to external vibrations. This is especially important in the case of micrometric and nanometric microscopes, such as atomic force microscopes (AFM). In such cases, active vibration control strategies are frequently used, requiring actuators capable of fast and accurate responses. Piezoelectric actuators meet these requirements but they suffer from two major drawbacks, hysteresis, and rate dependence, which must be taken into consideration in the design of the control strategy. The present work proposes a novel active vibration control strategy using piezoelectric actuators for metrological devices affected by low external loads. The control strategy combines a classical sky-hook feedback with a feedforward control. The effect of hysteresis is minimized by compensating the senstivity variations of the actuator in oscillatory movements. For the design of the feedforward law, the present work demonstrates that a stack piezoelectric actuator working as a damper admits a mathematical description fulfilling differential flatness. It also proposes a formulation of the active vibration damping problem in terms of a trajectory tracking command perfectly fitted to the flatness-based control law. This strategy obtains damping improvements in the entire frequency range of operation without the instability problems derived from high feedback gains.

Description: Periodicity frequently occurs in hard disk drives (HDDs) whose servo systems with periodic phenomena can be usually modeled as linear periodically time-varying (LPTV) systems. This paper discusses optimal $H_{infty}$ control synthesis for discrete-time LPTV systems via discrete Riccati equations. First, an explicit minimum entropy $H_{infty}$ controller for general time-varying systems is obtained. Subsequently, the developed control synthesis algorithm is applied to LPTV systems and it is shown that the resulting controllers are periodic. The proposed control synthesis technique is evaluated through both single and multirate optimal $H_{infty}$ track-following control designs. The single-rate servo design shows that our proposed control synthesis technique is more numerically robust in calculating optimal $H_{infty}$ controllers for discrete-time linear time-invariant systems than the MATLAB function of “hinfsyn,” while the multirate servo design validates its ability of synthesizing multirate controllers to achieve the robust performance of a desired error-rejection function. Moreover, an experimental study—in which the developed control synthesis algorithm on a real HDD with missing position error signal sampling data is implemented—further demonstrates its effectiveness in handling LPTV systems with a large period and attaining desirable disturbance attenuation.

Description: This paper proposes a surgical manipulator with workspace-conversion ability for both minimally invasive surgery (MIS) and open surgery. The focus of the proposed surgical manipulator is on its potential use in places such as battlefields, army camps, and rural areas rather than in civilian hospitals. The proposed surgical manipulator has a workspace for MIS with a virtual remote center of motion and has a workspace for open surgery like that of an articulated manipulator. The mechanism of the surgical manipulator is proposed and implemented in this paper. A new distal rolling joint with two spiral wire ropes is also implemented. Several experiments to validate the feasibility of the surgical manipulator were carried out. Two fundamentals of laparoscopic surgery tasks were performed to compare the performance of the surgical manipulator with other MIS systems. The workspace conversion from MIS to open surgery was implemented. The workspace-conversion ability enables the surgical manipulator to attach or detach the surgical tool unit without human assistance or an assistant robot.

Description: An intelligent cane robot is designed for aiding the elderly and handicapped people's walking. The robot consists of a stick, a group of sensors, and an omnidirectional basis driven by three Swedish wheels. Recognizing the user's walking intention plays an important role in the motion control of our cane robot. To quantitatively describe the user's walking intention, a concept called “intentional direction (ITD)” is proposed. Both the state model and the observation model of ITD are obtained by enumerating the possible walking modes and analyzing the relationship between the human–robot interaction force and the walking intention. From these two models, the user's walking intention can be online inferred using the Kalman filtering technique. Based on the estimated intention, a new admittance motion control scheme is proposed for the cane robot. Walking experiments aided by the cane robot on a flat ground and slope are carried out to validate the proposed control approach. The experimental results show that the user feels more natural and comfortable when our intention-based admittance control is applied.

Description: Dynamically substructured systems (DSS) play an important role in modern testing methods. DSS enables full-size critical components of a complete system to be tested physically in real-time, while the remaining parts of the system run in parallel as a real-time simulation. The performance of DSS testing is influenced by the synchronization of the physical and numerical substructures, which necessitates the design of a DSS controller. Since the testing signal is known and can be assumed to be a perfectly measured disturbance, the DSS control can be viewed as a regulation control problem with measured disturbance attenuation. A potential problem with DSS control arises from actuator saturation, which can be encountered in DSS transfer systems and can significantly influence the testing accuracy. This paper demonstrates the application of a novel robust disturbance rejection antiwindup (AW) technique, to cope with the actuator saturation problem in DSS. Implementation results from a hydraulically-actuated DSS test rig confirm the advantage of using this novel approach over some other existing AW approaches. Furthermore, some specific practical issues are discussed for the AW compensator design, such as the tuning of parameters.

Description: We have built an anatomically correct testbed (ACT) hand with the purpose of understanding the intrinsic biomechanical and control features in human hands that are critical for achieving robust, versatile, and dexterous movements, as well as rich object and world exploration. By mimicking the underlying mechanics and controls of the human hand in a hardware platform, our goal is to achieve previously unmatched grasping and manipulation skills. In this paper, the novel constituting mechanisms, unique muscle to joint relationships, and movement demonstrations of the thumb, index finger, middle finger, and wrist of the ACT Hand are presented. The grasping and manipulation abilities of the ACT Hand are also illustrated. The fully functional ACT Hand platform allows for the possibility to design and experiment with novel control algorithms leading to a deeper understanding of human dexterity.

Description: Ankle-foot orthoses (AFOs) can be used to ameliorate the impact of impairments to the lower limb neuromuscular motor system that affect gait. Existing AFO technologies include passive devices with fixed and articulated joints, semiactive devices that modulate damping at the joint, and active devices that make use of a variety of technologies to produce power to move the foot. Emerging technologies provide a vision for fully powered, untethered AFOs. However, the stringent design requirements of light weight, small size, high efficiency, and low noise present significant engineering challenges before such devices will be realized. Once such devices appear, they will present new opportunities for clinical treatment of gait abnormalities.

Description: For the demands of surgical navigation, this paper proposes some simple 3-D point reconstruction methods. These methods regard the perpendicular feet on back-projection lines as the measurements of a 3-D point, since these feet are close to the 3-D point. And then the methods utilize the distance between 3-D point and camera and error propagation rules to adjust the weights of the feet. Finally, the weighted average of these feet is taken as the final estimation for the 3-D point. They are easy to implement, and can be used in both biocular systems and multiocular systems. Especially, as these methods have closed-form solutions, their errors can be predicted by using error propagation rules. Experiments show that they are faster and more accurate than iterative methods and their error covariance matrix can be exactly predicted.

Description: This paper presents the development and evaluation of a miniature, three-axis, fiber-optic force sensor. The sensor is manufactured using low-cost, high-resolution rapid prototyping techniques and is integrated with a catheter to enable the detection of force during MRI-guided cardiac ablation procedures. The working principle is based on reflective light-intensity modulation. A force sensitive structure (flexure) is employed to vary the distance and orientation of an integrated reflector when a force is applied at the catheter tip. In this way, the light is modulated accordingly and the force can be calculated. The sensor has a high sensitivity and an adequate linear response along all three orthogonal axes $(F_{x}, F_{y}$ , and $F_{z})$ and a working range of around 0.5 N. Low-noise, high-gain electronics provide a force resolution of less than 1 gm force. Experiments demonstrate the ability of the sensor to acquire accurate force readings in a dynamic environment. MRI-compatibility experiments are performed in a clinical 1.5-T MR scanner.

Description: This paper proposes an underactuated modular climbing robot with flat dry elastomer adhesives. This robot is designed to achieve high speed, high payload, and dexterous motions that are typical drawbacks of previous climbing robots. Each module is designed as a tread-wheeled mechanism to simultaneously realize high speed and high adhesive force. Two modules are connected by compliant joints, which induce a positive preload on the front wheels resulting in stable climbing and high payload capacity. Compliant joints also help the robot to perform various transitions. An active tail is adopted to regulate the preload of the second module. Force transfer equations are derived and stable operating conditions are verified. The stiffness coefficients of the compliant joints and the active tail force are determined optimally to satisfy the constraints of stable operation. The prototype two-module robot achieves 6- $hbox{cm}/hbox{s}$ speed and 500- $hbox{g}$ payload capacity on vertical surfaces. The abilities of flat surface locomotion, internal, external, and thin-wall transitions, and overcoming various sized obstacles are validated through experiment. The principle of joint compliance can be adopted in other climbing robots to enhance their stability and transition capability.

Description: Adaptive sliding mode and integral sliding mode grasped object slip prevention controllers are implemented for a prosthetic hand and compared to a proportional derivative shear force feedback slip prevention controller as well as a sliding mode controller without slip prevention capabilities. Slip of grasped objects is detected by band-pass filtering the shear force derivative to amplify high frequency vibrations that occur as the grasped object slides relative to the fingers. The integral sliding mode slip prevention controller provides a robust design framework for slip prevention while addressing the issue of reducing the amount of deformation that the grasped object experiences to prevent slip. Averaged results from bench top experiments show that the integral sliding mode slip prevention controller produces the least amount of deformation to the grasped object while simultaneously preventing the object from being dropped.

Description: Haptic interaction in slow virtual environments (VEs) can become unstable due to the phase lag introduced in the control loop by the slow update rate of the VE. Increasing the physical damping and/or limiting the contact stiffness rendered to users can mitigate the destabilizing effect of the low VE update rate. However, large physical damping and compliant virtual contacts decrease the sense of presence in VEs, especially during interaction with rigid virtual objects. To increase the maximum virtual contact stiffness that can be rendered to users without increasing the interface damping, this paper proposes a control strategy based on multirate wave communications between a haptic interface and a VE updated at a slow and fixed rate. The multirate wave communications are shown to be guaranteed passive only if the decrease of the wave sampling rate at the connection between the haptic interface and the VE does not cause aliasing. Therefore, an antialiasing low-pass filter is placed before the wave rate drop in the communications. The passivity condition is verified analytically and numerically for multirate haptic interaction in VEs with various contact stiffnesses and update rates. The transparency of haptic interaction in slow VEs to which users connect via passive multirate wave communications is investigated analytically in the frequency domain. Experiments validate that passive multirate wave communications can render stiffer contact in slow VEs than conventional direct coupling, and illustrate the destabilizing effect of the aliasing caused by the sampling rate drop in the communications.

Description: In this paper, we describe a method of adaptive feedforward control that can achieve zero residual vibration in rest-to-rest motion of a vibratory system. When a finite impulse response filter is used to preshape a command input, zero residual vibration is achieved for any input signal if the impulse response of the filter satisfies a condition of orthogonality with respect to the impulse response of the system under control. An equivalent condition involving sets of measured I/O data is derived that forms the basis of a direct method of adaptively tuning filter coefficients during motion. The approach requires no prior model of the system and can be applied to multimode and multiinput systems under arbitrary and nonrepetitive motions. Versions of the algorithm employing recursive least-squares techniques are developed and analyzed. As a special case of the general adaptation problem, tuning of impulse-based shapers with fixed impulse timings can also be achieved. An experimental implementation on a two-link rigid-flexible manipulator is presented. The method is thereby shown to be realizable and effective for real-world motion control problems.

Description: This paper describes a linear motor design for ultrahigh acceleration and high velocity, as well as the driving performance of the motor. First, because of its ease of control, a moving-permanent-magnet linear synchronous motor (MPM LSM) was selected. The overall structure of the motor, which consists of a table to which the permanent magnets (PMs) are attached and two fixed electromagnet (EM) lines between which the PMs move, was selected based on the simplicity of the structure and the ease of gap adjustment. The dimensions of the EMs and PMs are optimized numerically to achieve a high thrust density that can provide an acceleration of 100G or greater to the mover, which comprises PMs, spacers, and a frame. The prototype MPM LSM has a working range of 1.5 m. The mover, including the guide parts, has a length of 444 mm and a mass of 4.79 kg. The measured peak thrust was greater than $5 times 10^3$ N, and the measured average thrust was $4.03 times 10^3$ N. The prototype driven by a rectangular current command produced a maximum acceleration of greater than 100G and a velocity higher than 12 m/s for a moving distance of 0.6 m.

Description: STF Optimierung von single-bit CT ΣΔ Modulatoren basierend auf skalierten Filterkoeffizienten Advances in Radio Science, 10, 313-317, 2012 Author(s): C. Widemann, C. Zorn, T. Brückner, M. Ortmanns, and W. Mathis Die vorliegende Arbeit beschäftigt sich mit dem Signalübertragungsverhalten von single-bit continuous-time (CT) ΣΔ Modulatoren. Dabei liegt der Fokus der Untersuchung auf dem Peaking der Signaltransferfunktion (STF). Dieser Effekt kann die Performance und die Stabilität des Gesamtsystems negativ beeinflussen, da bei auftretendem STF-Peaking Signale außerhalb des Signalbands verstärkt werden. In dieser Arbeit wird ein neuer Ansatz zur Reduktion des Peakings vorgestellt, der auf der Optimierung der Systemdynamik basiert. Dabei werden die Filterkoeffizienten des Modulators systematisch angepasst. Anhand eines Beispielsystems wird gezeigt, dass der Ansatz genutzt werden kann, um das Übertragungsverhalten des Modulators abhängig vom Ausgangssystem zu verändern. So kann entweder die Systemsperformance verbessert werden, ohne Peaking in der STF zu erzeugen, oder das STF-Peaking reduziert werden, ohne die Systemperformance stark zu beeinflussen.

Description: Differential Algebraic Equations of MOS Circuits and Jump Behavior Advances in Radio Science, 10, 327-332, 2012 Author(s): P. Sarangapani, T. Thiessen, and W. Mathis Many nonlinear electronic circuits showing fast switching behavior exhibit jump effects which occurs when the state space of the electronic system contains a fold. This leads to difficulties during the simulation of these systems with standard circuit simulators. A method to overcome these problems is by regularization, where parasitic inductors and capacitors are added at the suitable locations. However, the transient solution will not be reliable if this regularization is not done in accordance with Tikhonov's Theorem. A geometric approach is taken to overcome these problems by explicitly computing the state space and jump points of the circuit. Until now, work has been done in analyzing example circuits exhibiting this behavior for BJT transistors. In this work we apply these methods to MOS circuits (Schmitt trigger, flip flop and multivibrator) and present the numerical results. To analyze the circuits we use the EKV drain current model as equivalent circuit model for the MOS transistors.

Description: The dry weight of tendon tissue is accounted for mainly by collagen fibers. Accordingly, the tendon-healing process primarily involves repair of collagen fibers. During the remodeling phase of tendon healing, newly proliferating collagen fibers are transformed into a mature repaired tendon. Despite the importance of this phenomenon, the details of fibrous rebuilding have not been reported previously. The aim of this study was to visualize the ultrastructural changes and to obtain a clear understanding of the reorganization of the collagen fibers in the tendon repair site, using rat Achilles tendons. We used scanning electron microscopy (SEM) with cell maceration as the main method of analysis. Pretreatment with cell maceration removed the cellular components successfully. This allowed precise visualization of each collagen fiber and the three-dimensional network of the fibers. This study was the first to apply the cell-maceration/SEM method to observe tendon tissue. Seven days after surgery, new collagen fibers grew extensively in the repair site in a random arrangement. Fourteen days after surgery, the collagen fibers began to form an axial arrangement. Near the tendon stump, this change progressed from the outer layer to the core region. On the other hand, in the middle of the repair site, it progressed from the core to the outer layer. Change in the axial arrangement of collagen fibers contributes to the connection between the repair site and the tendon stump and to the separation of the repair site from the paratenon.

Description: We have used transient electron-beam-induced current (EBIC) to map minority carrier lifetime distributions in multicrystalline Silicon (mc-Si). In this technique, the electron beam from a scanning transmission electron microscope was on–off modulated while the sample was scanned. The resulting transient EBIC was analyzed to form a lifetime map. An analytical function was introduced as part of the analysis in determining this map. We have verified this approach using numerical simulations and have reproduced a lifetime map for an mc-Si wafer.

Description: We study in situ behavior of platinum single atoms on amorphous carbon (a-carbon) using a spherical aberration-corrected transmission electron microscope (AC-TEM). Diffusion of single atoms, bi-atoms, clusters (〈1 nm) and nanoparticles (〈3 nm) was recorded in the same image with a time resolution of 1 s, and such diffusion matches the expected mechanism of Ostwald ripening, which was seen on these samples. In situ AC-TEM shows promise for dynamical observation of single atom diffusion, which is important for understanding nanosized catalysts and ceramic sintering processes. We apply in situ AC-TEM to image platinum (Pt) nanoparticles on a-carbon, which is a model catalyst system for the real Pt electrode catalysts using alloys and core–shell structures supported on carbon/oxide composite materials in the proton exchange membrane fuel cell.

Description: The oviduct is an important organ for successful mammalian reproduction. In this work, human oviducts were inseminated and their explants analyzed using scanning electron microscopy in order to study, at a finer ultrastructual level, the interaction between spermatozoon and oviduct in vitro . Results show unequivocally a spermatozoon tightly attached through the acrosomal region of its head to several cilia of the human tubal epithelial cells. This finding proves that spermatozoa do indeed adhere to the endosalpinx, a fact of utmost relevance for the physiology of the reproductive process, since it supports the idea of a spermatozoa reservoir being formed in the oviduct, which is also briefly discussed.

Description: Mitochondria in all eukaryotes are essential organelles responsible for adenosine triphosphate synthesis, calcium homeostasis and steroidogenesis. Because the structure and distribution of mitochondria are highly diverse depending on their function and cellular conditions, it is important to develop a rapid and accurate method to assess their morphology. In this study, we visualize whole mitochondria in cultured cells using high-voltage electron microscopy (HVEM). Compared with conventional transmission electron microscopic approaches, the present method does not require thin sectioning and thus requires less time for image acquisition and processing. Furthermore, compared with fluorescence-based light microscopic approaches, our method provides more accurate size information. Thus, we propose that HVEM is a useful tool for rapid and accurate analysis of mitochondrial morphology and distribution in a cell.

Description: This paper presents a three-fingered, eight-DOF hand, 100 N Hand II, which can exert a grasping force of 100 N. A force-magnification drive, which can maintain a large grasping force without energy consumption, allows the hand to exert such large grasping force, and a high-speed driving mechanism enables all joints to perform high-speed motions of over 400°/s. In our previous prototype (100 N Hand I), a screw and nut mechanism was used to implement force magnification. The linear motion of this mechanism was translated to rotational joint motion via a linkage mechanism, producing a relatively small motion range for each joint and with large palm dimensions. 100 N Hand II employs a worm gear instead of a screw and nut mechanism, so it can magnify the torque at an arbitrary joint angle. This improved force-magnification drive increases the motion range of each joint and reduces the palm size. The force and speed are confirmed experimentally.

Description: Training simulators that provide realistic visual and haptic feedback during cell indentation tasks are currently investigated. Complex cell geometry inherent to biological cells and intricate mechanical properties drive the need for precise mechanical and numerical modeling to assure accurate cell deformation and force calculations. Advances in alternative finite-element formulation, such as the mass-tensor approach, have reached a state, where they are applicable to model soft-cell deformation in real time. The geometrical characteristics and the mechanical properties of different cells are determined with atomic force microscopy (AFM) indentation. A real-time, haptics-enabled simulator for cell centered indentation has been developed, which utilizes the AFM data (mechanical and geometrical properties of embryonic stem cells) to accurately replicate the indentation task and predict the cell deformation during indentation in real time. This tool can be used as a mechanical marker to characterize the biological state of the cell. The operator is able to feel the change in the stiffness during cell deformation between fixed and live cells in real time. A comparative study with finite-element simulations using a commercial software and the experimental data demonstrate the effectiveness of the proposed physically based model.

Description: This paper considers the analysis and application of magnetic gearbox and magnetic coupling technologies and issues surrounding their use in high performance servo control systems. An analysis of a prototype magnetic coupling is used as a basis for demonstrating the underlying nonlinear torque transfer characteristics, nonlinear damping, and “pole-slipping” features when subjected to overtorque (overload) conditions. It is also shown how pole-slipping results in a consequential loss of control. A theoretical investigation into the suppression of mechanical torsional resonances in transmission systems encompassing these highly compliant magnetically coupled components is included along with experimental results from a demonstrator drive train. Automatic detection of pole slipping and a reconfigurable controller are also investigated. By addressing these issues, the proposed techniques extend the application scope of magnetic gear/coupling technologies to more demanding applications than those hitherto considered possible-specifically, for use in servo control systems and high-bandwidth mechanical drive trains.