Dexterous manipulation of an object by means of multi‐DOF robotic fingers with soft tips

This article analyzes the dynamics of motion of various setups of two multiple degree‐of‐freedom (DOF) fingers that have soft tips, in fine manipulation of an object, and shows performances of their motions via computer simulation. A mathematical model of these dynamics is described as a system of nonlinear differential equations expressing motion of the overall fingers‐object system together with algebraic constraints due to tight area contacts between the finger‐tips and surfaces of the object. First, problems of (1) dynamic, stable grasping and (2) regulation of the object rotational angle by means of a setup of dual two‐DOF fingers, are treated. Second, the problem of regulating the position of the object mass center by means of a pair of two‐DOF and three‐DOF fingers is considered. Third, a set of dual three‐DOF fingers is treated, in order to let it perform a sophisticated task, which is specified by a periodic pattern of the object posture and a constant internal force. In any case, there exist sensory‐motor coordinations, which are described by analytic feedback connections from sensing to actions at finger joints. In the cases of setpoint control problems, convergences of motion to secure grasping together with the specified object rotational angle and/or the specified object mass center position, are proved theoretically. A constraint stabilization method (CSM) is used for solving numerically the differential algebraic equations to show performances of the proposed sensory‐feedback schemes. © 2002 Wiley Periodicals, Inc.     

MR cholangiopancreatography with single-shot fast-spin-echo sequences]

Imaging quality of MR cholangiopancreatography (MRCP) has recently made a great advance, and MRCP plays an important part in the diagnosis of pancreticobiliary diseases. To obtaining excellent-quality MRCP images, three conditions are required: fluid-to-background contrast, high spatial resolution, and suppression of respiratory motion artifacts. Respiratory motion artifacts, whose suppression is especially important for MRCP, can be controlled by the use of breath-holding, signal averaging, or respiratory triggering. These images are implemented in either single-slice technique or multi-slice technique. We have performed MRCP prior to endoscopic retrograde cholangiopancreatography (ERCP) in more than 100 patients. MRCP images were obtained as maximum-intensity-projection (MIP) reconstruction images and thick-slice projection images by using single-shot fast-spin-echo sequence, and MIP reconstruction images by using respiratory-triggered fast-spin-echo sequence. We reviewed MRCP imaging with single-shot fast-spin-echo sequences.     

High-power TE CO2laser with graphite electrodes

A high-power CW TE CO2laser using a new graphite anode structure and a novel Mo wire cathode is described. A uniform discharge for laser excitation is obtained. The device produces a CW output of 6 kW.     

A differential-geometric approach for 2D and 3D object grasping and manipulation

This article presents an expository work on a differential-geometric treatment of fundamental problems of 2D and 3D object grasping and manipulation by a pair of robot fingers with multi-joints under holonomic or nonholonomic constraints. First, Lagrange’s equation of motion of a fingers-object system whose motion is confined to a vertical plane is derived under holonomic constraints when rolling contacts between finger-ends and object surfaces are permitted. Then, a class of control signals called “blind grasping” and constructed without knowing the object kinematics or using any external sensing like vision or tactile sensation is shown to realize stable object grasping in a dynamic sense. Stability of motion and its convergence to an equibrium manifold are treated on the basis of differential geometry of solution trajectories of the closed-loop dynamics on the constraint manifolds. Second, a mathematical model of 3D object grasping and manipulation by a pair of multi-joint robot fingers is derived under the assumption that spinning motion of rotation around the opposing axis between contact points does no more arise. It is shown that, differently from the 2D case, the instantaneous axis of rotation of the object is time-varying, which induces a nonholonomic constraint expressed as a linear differential equation of rotational motion of the pinched object. It is shown that there is a class of control signals constructed without knowing the object kinematics or using external sensings that can realize “blind grasping” in a dynamic sense. Finally, it is shown that the proposed differential geometric treatment of stability can naturally cope with redundancy resolution problems of surplus degrees-of-freedom (d.f.) of the overall fingers-object system, which is closely related to Bernstein’s d.f. problem.     

Sub-millimeter-long carbon nanotubes repeatedly grown on and separated from ceramic beads in a single fluidized bed reactor

A semi-continuous fluidized-bed process is reported which rapidly converts acetylene into carbon nanotubes (CNTs). Catalysts are first immobilized on ceramic beads and CNTs are then grown on the beads and then separated from them in a repetitive process accomplished within a single reactor simply by switching gases at a fixed temperature. CNTs of 6–10 nm diameter, three walls on average, 0.4 mm length and 99 wt.% purity were synthesized at an yield of over 70% in a reactor residence time shorter than 0.3 s. The easy and efficient production of such CNTs with in situ separation from the catalysts may accelerate the development of CNT-based nanotechnology industries.     

Functionalized Bilayer Membranes as Artificial Transaminase: Modification of the Active Site and Its Consequence in Catalytic Efficiency

The transamination reaction of l-phenylalanine with pyruvate as catalyzed by the artificial transaminase formed with synthetic bilayer aggregates was examined in aqueous media under mild kinetic conditions. Each catalyst system was constructed with a combination of a synthetic peptide lipid, a hydrophobic vitamin B₆ derivative, and metal ions. Modification of the active site in the present artificial transaminase was performed by changing a combination of molecular components constituting the catalytic system. While the catalytic activity was scarcely influenced by differences in aggregate structure, single- or multi-walled bilayer, and in copper-(II) concentration, molecular structures of the hydrophobic vitamin B₆ and an amino acid residue of the peptide lipid had significant effects on the reactivity.     

Noncentrosymmetric phase of submicron NaNbO<Subscript>3</Subscript> crystallites

The temperature and pressure characteristics of a noncentrosymmetric crystal modification of NaNbO₃ were studied by Raman spectroscopy. A transition towards the bulk-like structure of NaNbO₃ occurs in the temperature range from 280 to 360 °C. High-pressure Raman spectroscopy revealed successive pressure-induced phase transitions at around 2, 6.5 and 10 GPa. Raman scattering profiles recorded above 7 GPa correspond to those reported for the bulk. The temperature-induced spectral changes were completely reversible between −150 and 450 °C. Those induced by pressure were almost reversible from ambient pressure up to 15.9 GPa. Piezoresponse force microscopy demonstrated the occurrence of piezoelectric activity for submicron NaNbO₃ crystals with particle size ranging from 200 to 400 nm. The noncentrosymmetric crystallographic structure plays a critical role for the enhancement of piezoelectricity.     

Evaluation of standing‐sitting support system with passive rotational seat mechanism in standing motion

Since a decrease in muscle mass of elderly people, the physical burden of them in standing‐sitting motion of a seat are increasing than young people. For this problem, several standing‐sitting support systems have been developed, and evaluations of these systems focusing on a reduction of physical load have been discussed. However, these evaluations are of support systems with an active actuators or of support systems when they use a handrail and a standing aid. Thus, an evaluation of a support system with only passive actuators has not been reported. In this paper, in standing motion with using a standing‐sitting support system with passive rotational seat mechanism which our group proposes, we objectively evaluate an effectiveness of the passive rotational seat mechanism by statistical analysis.     

Roles of CCL2-CCR2 Axis in the Tumor Microenvironment

Chemokines are a small family of cytokines that were first discovered as chemotactic factors in leukocytes during inflammation, and reports on the relationship between chemokines and cancer progression have recently been increasing. The CCL2-CCR2 axis is one of the major chemokine signaling pathways, and has various functions in tumor progression, such as increasing tumor cell proliferation and invasiveness, and creating a tumor microenvironment through increased angiogenesis and recruitment of immunosuppressive cells. This review discusses the roles of the CCL2-CCR2 axis and the tumor microenvironment in cancer progression and their future roles in cancer therapy.     

Activated carbon nanofiber produced from electrospun polyacrylonitrile nanofiber as a highly efficient formaldehyde adsorbent

Electrospun polyacrylonitrile (PAN)-based nanofiber with a uniform diameter of ca. 800 nm was carbonized and steam-activated to produce activated carbon nanofiber with tailored microporosity and abundant nitrogen-containing functional groups as highly efficient adsorption sites. A remarkable amount of formaldehyde, a typical indoor pollutant, was adsorbed onto the pore surface of the PAN-based activated carbon nanofibers even at a low concentration (ca. 11 ppm), demonstrating more than twice as long as breakthrough time of formaldehyde adsorption as compared to conventional activated carbon fibers of larger fiber diameter. The tailored shallow microporosity was considered to afford the preferential adsorption of formaldehyde also in a humid environment.