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.     

Multiple melting behavior of syndiotactic 1,2‐polybutadiene

A differential scanning calorimetry study on a typical thermoplastic elastomer, syndiotactic 1,2‐polybutadiene, crystallized from the melt is presented. Endotherms observed upon heating for samples isothermally crystallized from the melt exhibited a double melting profile. The peak temperature of the endotherm that appeared at a lower temperature (low endotherm) showed stronger dependence on the heating rate than that appearing at a higher temperature (high endotherm). The results of partial melting experiments demonstrated that the high endotherm is not affected at all by melting of only the crystals responsible for the low endotherm, indicating that the double melting behavior is due to the existence of two crystalline species with different stabilities. Structures and melting mechanisms of these two different crystalline species are discussed on the basis of the observed difference in superheating behaviors upon melting. The results on overall rate of isothermal crystallization are also presented.     

Development of gas electron multiplier foils with a laser etching technique

Fine-pitch gas electron multiplier (GEM) foils have been produced for cosmic X-ray polarimeters using a carbon dioxide laser etching technique. The finest hole pitch of the foil which can be produced repeatedly is and the smallest hole diameter is . The electron amplification factor was measured as a function of applied voltage. The behavior of the factor is almost the same as the -pitch standard foil fabricated by CERN. Our GEMs had no rate-dependent gain instability, which is expected of the GEMs having holes of good cylindrical geometry. The amplification factor of the foil in a mixture of 70% argon and 30% carbon dioxide reaches about 5000 without any micro-discharge at a voltage of 570 V between foil electrodes.     

Synthesis of metastable cubic tungsten carbides by electrical explosion of tungsten wire in liquid paraffin

This paper describes experiments addressing the synthesis of WC_1?x (metastable cubic tungsten carbide). The experiments involved exploding tungsten wires of different diameters by passing high-current electric pulses through them. This was done while the wire was immersed in a liquid-paraffin media. The explosion was studied using a high-speed video camera and by analysis of the voltage and current signals. The different stages of the wire explosion were explained based on an analysis of the recorded signals and simple thermodynamic considerations. In most of the experiments, the wire was sublimated, and the formation of carbide particles occurred due to a chemical reaction between the explosion products and the paraffin, as well as the rapid condensation of the vapors. The synthesized powders were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA). It was found that, regardless of the experimental conditions, the WC_1?x phase contained approximately 42.5?at.% carbon. If the energy injected into the wire was not sufficient to completely evaporate the tungsten, large particles consisting of WC, W₂C, and W phases were formed via the liquid-state diffusion mechanism.     

Enhanced cellular uptake of lactosomes using cell-penetrating peptides

Polymeric micelles that are composed of synthetic polymers are generally size controllable and can be easily modified for various applications. Lactosomes (A₃B-type) are biodegradable polymeric micelles composed of an amphipathic polymer, including three poly(sarcosine) blocks and a poly(l-lactic acid) block. Lactosomes accumulate in tumors in vivo through the enhanced permeability and retention (EPR) effect, even on frequently administering them. However, lactosomes cannot be efficiently internalized by cells. To improve cellular uptake of lactosomes, cell-penetrating peptide (CPP)-modified lactosomes were prepared. Seven CPPs (including EB1 and Pep1) were used, and most of them improved the cellular uptake efficiency of lactosomes. In particular, EB1- and Pep1-modified lactosomes were efficiently internalized by cells. In addition, by using CPP-modified and photosensitizer-loaded lactosomes, we demonstrated the photoinduced killing of mammalian cells, including human cancer cells. Accumulation of the EB1-modified lactosomes in NCI-N87 tumors was shown by in vivo imaging. Thus, this study demonstrated that the CPP-modified lactosome is a promising drug carrier.     

Sequential molecularly targeted drug therapy including axitinib for a patient with end‐stage renal failure and metastatic renal cell carcinoma

A 62‐year‐old male patient with end‐stage renal disease and metastatic renal cell carcinoma (RCC) was referred to our hospital. Sequential targeted therapy consisting of sorafenib, sunitinib, and everolimus was administered, but the patient's disease gradually progressed. Axitinib was subsequently administered at a decreased dose of 6 mg/day for 2 weeks, after which the dose was escalated to 10 mg/day. Axitinib therapy was maintained for a total of 6 months without severe adverse effects. Sequential molecularly targeted drug therapy including axitinib, with careful monitoring, is one possible treatment option for patients with metastatic RCC with renal impairment.     

Design of controller switching strategy for reusable launch vehicle with elevon jamming failure

When a reusable launch vehicle (RLV) returns to earth, it flies just by gliding without thrust. In this phase, one of the most likely and important faults to occur in the airframe is a jamming of the elevon. To tolerate this failure, the flight control system must keep stability and performance during such a failure. One of the effective ways to overcome this problem is to switch the controllers based on the information of the detected failure in the plant. Generally speaking, the controller must have integrators so as to yield the zero steady‐state error for the controlled output even if there exist some perturbations in the plant dynamics. In this paper, the design of controller switching scenario is addressed especially focusing on the decision of the controller state at the instant of switching the controllers with integrator. Then, the proposed switching scenario is applied to the control of ALFLEX (Automatic Landing FLight EXperiment), which is the automatic landing experimental vehicle being developed for RLV, considering the occurrence of the jamming fault. Some simulations are shown to verify the usefulness of the proposed idea. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 80–90, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20356     

Study on quantitative classification of seasonal snow using specific surface area and intrinsic permeability

The release mechanism of snow avalanches depends on the mechanical properties of snow, which are closely related to snow microstructure. Previous observations show that snow microstructure can be described qualitatively on the basis of snow types. However, the qualitative determination of snow types may become subjective. Therefore, it is essential to quantitatively classify snow. The specific surface area (SSA) and intrinsic permeability (k₀) are closely related to the snow microstructure. In particular, we believe that the former parameter reflects the features of the grains, and the latter parameter indicates the characteristics of the pores. Measurements of the specific surface area per unit snow volume (SSAV) and the intrinsic permeability were performed on the naturally deposited dry snow in Hokkaido prefecture, Japan, during the winter of 2007–2008. SSAV was measured using a stereological method, where the section planes of snow samples were prepared, imaged, and analyzed, and the SSA per unit mass (SSAM) was obtained by dividing SSAV by the snow density. The value of SSAV indicates only the area size, while the value of SSAM indicates the snow microstructure. k₀ was measured in situ using an air permeameter with a double cylinder, and it was calculated assuming a laminar flow in order to satisfy Darcy's law. The results showed that the correlation between SSAM and k₀ could be used to clearly distinguish the snow types. In addition, we could confirm certain changes in SSAM and k₀ accompanied by the occurrence of the two processes of temperature gradient and melt-freezing metamorphism, which occur in the snow cover.     

Synthesis of hollow silica microparticles from bacterial templates

Hollow inorganic particles have attracted great interest because of their unique physicochemical properties. In this study, hollow silica microparticles were prepared using a rod-shaped gram-negative bacterium, Escherichia coli (KP7600), as a biological template. Silica nanoparticles were generated in addition to coated biological templates when the reaction rate was increased, so control of reaction rate is important for coating silica smoothly onto the bacterial surface. Silica coating was also carried out using the fixed cells (with and without internal water) using glutaraldehyde as templates. When the fixed cells without internal water were used as templates, no rod-shaped particles were observed after calcination of the synthesized particles. By contrast, silica hollow particles were formed using the fixed cells with internal water as templates. This means that the internal water inside biological cells acts as an initiator for hydrolysis of tetraethyl orthosilicate (TEOS) and results in the formation of smooth silica shell surface and indicates that the use of dry cultured bacteria templates is not required. Thus, there is a significant benefit in using gram-negative bacteria as templates for producing hollow silica microparticles, compared with the method using dried gram-positive bacteria templates.     

Large enhancement of fluorescence efficiency from CdSe/ZnS quantum dots induced by resonant coupling to spatially controlled surface plasmons

Nanoengineered fluorescent response is reported from semiconductor core-shell (CdSe/ZnS) quantum dots in proximity to the surface plasmon polariton field of periodic Ag nanoparticle arrays. Tuning the surface plasmon polariton resonance to the quantum dot exciton emission band results in an enhancement of up to approximately 50-fold in the overall fluorescence efficiency, in a design where each Ag nanoparticle is interconnected by a continuous Ag thin film. Propagating modes of surface plasmon resonances have a direct impact on the fluorescence enhancement.