Realistic imitation of mosquito's proboscis: Electrochemically etched sharp and jagged needles and their cooperative inserting motion

Aiming at the use in low-invasive medical treatments, this paper proposes a realistic imitation of mosquito's proboscis. A silicon needle is electrochemically etched, making the three-dimensionally sharp tip with finely smooth surface. The jagged shank shape is machined by a deep reactive ion etching (DRIE). The combined needles comprising a central straight needle and two outer jagged needles are fabricated, imitating a labrum and two maxillas of the mosquito, respectively. The cooperative motion of the three needles imitating the mosquito's motion is realized by applying PZT actuators independently to all the needles. The effectiveness of inserting these needles cooperatively was experimentally confirmed. Considering practical medical application, a biodegradable polymer needle with three-dimensionally sharp tip is also developed. The fabrication process based on micromolding is as follows: a nickel negative cavity is made by electroplating on a silicon sharp needle, to which melted polymer is injected, and it is finally released using a lost molding technique. The effectiveness of sharp tip for easy insertion was experimentally proven.     

Understanding user commands by evaluating fuzzy linguistic information based on visual attention

This article proposes a method for understanding user commands based on visual attention. Normally, fuzzy linguistic terms such as “very little” are commonly included in voice commands. Therefore, a robot’s capacity to understand such information is vital for effective human-robot interaction. However, the quantitative meaning of such information strongly depends on the spatial arrangement of the surrounding environment. Therefore, a visual attention system (VAS) is introduced to evaluate fuzzy linguistic information based on the environmental conditions. It is assumed that the corresponding distance value for a particular fuzzy linguistic command depends on the spatial arrangement of the surrounding objects. Therefore, a fuzzy-logic-based voice command evaluation system (VCES) is proposed to assess the uncertain information in user commands based on the average distance to the surrounding objects. A situation of object manipulation to rearrange the user’s working space is simulated to illustrate the system. This is demonstrated with a PA-10 robot manipulator.     

Central pattern generators based on Matsuoka oscillators for the locomotion of biped robots

Biologically inspired control approaches based on central pattern generators (CPGs) with neural oscillators have been drawing much attention for the purpose of generating rhythmic motion for biped robots with human-like locomotion. This article describes the design of a neural-oscillator-based gait-rhythm generator using a network of Matsuoka oscillators to generate a walking pattern for biped robots. This includes the proper consideration of the oscillator’s parameters, such as a time constant for the adaptation rate, coupling factors for mutual inhibitory connections, etc., to obtain a stable and desirable response from the network. The article examines the characteristics of a CPG network with six oscillators, and the effect of assigning symmetrical and asymmetrical coupling coefficients among oscillators within the network structure under different possible inhibitions and excitations. The kinematics and dynamics of a five-link biped robot have been modeled, and its joints are actuated through simulation by the torques output from the neural rhythm generator to generate the trajectories for hip, knee, and ankle joints. The parameters of the neural oscillators are tuned to achieve flexible trajectories. The CPG-based control strategy is implemented and tested through a simulation. This work was presented in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007     

A fuzzy logic based approach to the SLAM problem using pseudolinear models with multiframe data association

This paper presents an alternative solution to simultaneous localization and mapping (SLAM) problem by applying a fuzzy Kalman filter using pseudolinear process and measurement models. Nonlinear process model and observation model are formulated as pseudo-linear models and rewritten with a composite model whose local models are linear according to Takagi-Sugeno (T-S) fuzzy model. Using the Kalman filter theory, each local T-S model is filtered to find the local estimates. The linear combination of these local estimates gives the global estimate for the complete system. Data association to correspond features to the observed measurement is proposed with two sensor frames obtained from two sensors. The above system is implemented and simulated with Matlab to claim that the proposed method yet finds a better solution to the SLAM problem, though nonlinearity is directly involved in the Kalman filter equations, compared to the conventional approach. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Glycine 85 of the trp-repressor of E.coli is important in forming the hydrophobic tryptophan binding pocket: experimental and computational approaches

Experimental and computational analyses were performed on thecorepressor (L-tryptophan) binding site of the trp-repressorof Escherichia coli to investigate the ligandprotein interactions.Gly 85, one of the residues forming the hydrophobic pocket ofthe binding site, was systematically replaced with Ala, Val,Leu and Trp by cassette mutagenesis. Biochemical characterizationshowed that all these mutations caused significant decreasesin tryptophan binding activity. Free energy perturbation calculationswere performed for the mutants and were consistent with theexperimental results. The lack of a side chain at position 85was concluded to be essential for binding the corepressor; thestructure of the binding pocket was suggested to be tight inthe vicinity of Gly85.     

A 13.5‐in. Quad‐FHD flexible CAAC‐OS AMOLED display with long‐life OLED device structure

In this study, the device structure of a white tandem organic light‐emitting diode (OLED) was changed to control the emission area and thereby achieve less luminance decay. A long‐life 13.5‐inch 4 K flexible c‐axis‐aligned crystal oxide semiconductor (CAAC‐OS) active‐matrix OLED with less color shift and high resolution was fabricated using this long‐life white OLED, transfer technology, and a CAAC‐OS field‐effect transistor.     

Participation of free fatty acids in the oxidation of purified soybean oil during microwave heating

Effects of 0 to 1.0% levels of caprylic, capric, lauric, myristic, palmitic or stearic acid on the oxidative stability of purified soybean oil were investigated under microwave heating conditions. A prooxidative effect of the fatty acids introduced into the systems was established. The extent of this effect depended on the acyl chin and levels of added fatty acids. During microwave heating, the oxidative rate of purified soybean oil by the fatty acids was rapid compared to the addition of their corresponding hydrocarbons; the shorter the chainlength and the higher the levels of fatty acids, the more accelerated was the thermal oxidation in the oil. The results are explained on the basis of the catalytic effect of the carboxylic group on the formation of free radicals by the decomposition of hydroperoxides. Therefore, particular attention should be paid to the free fatty acid content, which affects the oxidative stability of purified soybean oil.     

Flow and fracture behaviour of Ni3(Al·Ti) single crystals tested in tension

The deformation and the fracture behaviour of the [0 0 1] orientated Ni₃(Al.Ti) single crystals were investigated to determine the relation between the positive temperature dependence of the flow stress in the -phase and the malleability of nickel-base superalloys. The positive temperature dependence of the flow stress is observed in the [0 0 1] orientation below about 1000 K (T _p) and the failure occurs in a catastrophic and brittle manner after considerable plastic deformation. The room temperature fracture stress increases with increase in the angle between the [0 0 1] orientation and the tensile axis at 290 K, and it is well expressed by a crack propagation criterion only by considering the effect of the normal stress on the {1 0 0} cleavage plane. The cleavage fracture stress for the [0 0 1] orientation is nearly independent of temperature below T _p, while the elongation decreases with temperature in contrast to the yield stress. The cleavage fracture of Ni₃(Al.Ti) single crystals is explained by the rapid decrease of the mobile dislocation density due to a dislocation pinning mechanism based on the cube cross-slipping of the screw superdislocations which causes the positive temperature dependence of the flow stress. The insufficiency of the malleability of nickel-base superalloys seems to be attributed to that of the -Ni₃ (Al.Ti) phase, and the hot working of nickel-base superalloys near T _p in the -phase should be avoided.     

Effect on inhibitory activity of mutation at reaction site P4 of the Streptomyces subtilisin inhibitor, SSI

The protein Streptomyces subtilisin inhibitor, SSI, efficientlyinhibits a bacterial serine protease, subtilisin BPN'. We recentlydemonstrated that functional change in SSI was possible simplyby replacing the amino acid residue at the reactive P1 site(methionine 73) of SSI. The present paper reports the additionaleffect of replacing methionine 70 at the P4 site of SSI(Lys73)on inhibitory activity toward two types of serine proteases,trypsin (or lysyl endopeptidase) and subtilisin BPN'. Conversionof methionine 70 at the P4 site of SSI(Lys73) to glycine oralanine resulted in increased inhibitory activity toward trypsinand lysyl endopeptidase, while replacement with phenylalanineweakened the inhibitory activity toward trypsin. This suggeststhat steric hindrance at the P4 site of SSI(Lys73) is an obstaclefor its binding with trypsin. In contrast, the same P4 replacementshad hardly any effect on inhibitory activity toward subtilisinBPN'. Thus the subsite structure of subtilisin BPN' is tolerantto these replacements. This contrast in the effect of P4 substitutionmight be due to the differences in the S4 subsite structuresbetween the trypsin-like and the subtilisin-like proteases.These findings demonstrate the importance of considering structuralcomplementarity, not only at the main reactive site but alsoat subsites of a protease, when designing stronger inhibitors.     

Preparation and properties of urethane acrylate-epoxy interpenetrating polymer networks containing silica nanoparticles

Summary In this study, interpenetrating polymer networks (IPNs) and IPN composite materials were prepared by in situ polymerization of urethane dimethacrylate (UDMA) and bisphenol-A diglycidyl ether epoxy resin (DGEBA) with or without silica nanoparticles. Dynamic mechanical analysis (DMA), three-point bending test, thermogravimetric analysis (TGA) and visible spectrometry were performed to evaluate the physical properties of the resulting IPNs and IPN composite materials. The IPNs showed high transparency and higher elastic modulus and strength than that of each homopolymer at ratio of UDMA/ DGEBA is 70/30. The IPN composites maintained high transparency in spite of the addition of silica nanoparticles. Moreover, elastic modulus and surface hardness of the IPN composites increased with increasing silica content.