Publications by authors named "Yoshiki Shimizu"

Spherical Ag particles have received considerable attention because of their unique properties as well as their applications in various fields. In the present study, the synthesis of micrometer-scale spherical Ag particles with an extremely narrow size distribution is demonstrated using a simple capacitively coupled atmospheric-pressure plasma reactor with an inkjet head. Droplets of a Ag nitrate aqueous solution are ejected from the inkjet head to synthesize Ag particles.

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This study demonstrates cross-linking-filler composites in which covalent bonds between the fillers and polymer chains act as the main cross-linking points for the development of flexible and thermally conductive materials. Cross-linking-filler composites are fabricated using functionalized hexagonal boron nitride (hBN) fillers and polyrotaxane, called slide-ring polymers. The hBN particles modified with a carbon layer were produced by plasma processing in hydroquinone aqueous solution and functionalized with isocyanate groups.

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Although hexagonal boron nitride (hBN) is a thermally conductive and electrically insulating filler in composite materials, surface modification remains difficult, which limits its dispersibility and functionalization. In this study, carbon layer formation on hBN particles by plasma processing in hydroquinone aqueous solution was investigated as a surface modification technique. Carbon components with features of polymeric hydrogenated amorphous carbon were found to be uniformly distributed on the hydroquinone-aided plasma-modified hBN (HQpBN) particles.

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CEL-III is a hemolytic lectin purified from the marine invertebrate Cucumaria echinata. New expression system of CEL-III was constructed, and the recombinant thioredoxin-fused CEL-III (Trx-CEL-III) showed strong hemolytic and carbohydrate-binding activity as same as authentic CEL-III. Mutation analysis of Trx-CEL-III suggested that carbohydrate binding to subdomain 1α and 2β of CEL-III might be important for the hemolytic activity.

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We present a study quantitatively demonstrating that the method of synthesis (gas phase, fixed bed, non-fixed bed) represents a determining factor in the level of crystallinity in growing single wall carbon nanotubes (SWCNTs). Using far infrared spectroscopy, the "effective length" (associated with the level of crystallinity) was estimated for CNTs grown using various synthetic methods (lab-produced and supplemented by commercially purchased SWCNTs) as a metric for crystallinity (i.e.

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The importance of hydrogen in carbon nanotube (CNT) synthesis has been known as it supports the critical processes necessary for CNT growth, such as catalyst reduction. However, within the scope of our mini microplasma CNT synthesis reactor, we found that hydrogen was critical for unexpected reasons. Without hydrogen, CNT growth was inhibited and characterized by amorphous carbon particles.

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Atherosclerosis is a macrophage-related inflammatory disease that remains a leading cause of death worldwide. Magnetic iron oxide (IO) nanocrystals are clinically used as magnetic resonance imaging contrast agents and their application as a detection agent for macrophages in arterial lesions has been studied extensively. We recently fabricated heparin-modified calcium phosphate (CaP) nanoparticles loaded with a large number of IO nanocrystals via coprecipitation from a supersaturated CaP solution supplemented with heparin and ferucarbotran (IO nanocrystals coated with carboxydextran).

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Background: A 2017 meta-analysis of data from 25 randomised controlled trials (RCTs) of vitamin D supplementation for the prevention of acute respiratory infections (ARIs) revealed a protective effect of this intervention. We aimed to examine the link between vitamin D supplementation and prevention of ARIs in an updated meta-analysis.

Methods: For this systematic review and meta-analysis, we searched MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, Web of Science, and the ClinicalTrials.

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To evaluate the effects of 25-hydroxyvitamin D (25OHD) on symptoms at the onset of the upper respiratory tract infection (URTI) in subjects with insufficient or deficient serum 25-hydroxyvitamin D levels, we conducted a post hoc analysis of data from a randomized, placebo-controlled study; the subjects received 10 μg of 25OHD per day or a placebo for 16 weeks. The Wisconsin Upper Respiratory Symptom Survey-21 was used to determine URTI. The study endpoints included WURSS-21 scores, number of URTI events, and proportion of medication (antibiotics, antipyretic analgesics) usage.

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Article Synopsis
  • A 2017 meta-analysis indicated that vitamin D supplementation might protect against acute respiratory infections (ARIs), leading to further research with 20 additional randomized controlled trials (RCTs) since then.
  • A systematic review and meta-analysis was conducted, analyzing data from 45 eligible RCTs involving over 73,000 participants to evaluate the efficacy of vitamin D in preventing ARIs.
  • The findings showed that vitamin D supplementation reduced the risk of ARIs overall, particularly when given daily, in moderate doses (400-1000 IU), and for periods shorter than 12 months, although no significant differences were found based on initial vitamin D levels.
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The development of stretchable elastomer composites with considerable mechanical strength and electrical conductivity is desired for future applications in communication tools, healthcare, and robotics. Herein, we have developed a novel stretchable elastomer composite by employing a slide-ring (SR) material as a matrix for restoration and graphene oxide (GO) as a precursor for a conductive filler. Highly dispersed GO in an organic solvent, prepared via a new method developed by the authors, allowed the uniform dispersion of GO into the matrix by simply mixing the solvent and SR.

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A 69-year-old man was admitted because of subacute development of lower limb weakness from one month ago. He showed central obesity, gynecomastia, dorsal fat pad ("buffalo hump"), and proximal muscle weakness in the lower extremities (manual muscle test 4). Needle EMG, muscle MRI and labolatry screening including CPK were negative for neuromuscular diseases, except for the hypogenitalism accidentally detected in MRI.

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A 48-year-old woman with a 3-month history of spontaneously resolving stiff leg symptom at the age of 43 years presented with progressive onset of leg rigidity, walking difficulty, and myoclonic jerks. On admission she had marked stiffness in her foot joints with symmetric sustained dorsiflexion of the ankles and toes, with spontaneous and reflex myoclonic jerks easily provoked by knee tendon tap. She appeared to have a spastic gait due to stiffness in her legs.

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Calcium phosphate (CaP) coating is an effective method for surface-functionalization of bioinert materials and for production of osteoconductive implants. Recently, we developed a laser-assisted biomimetic process (LAB process) for facile and area-specific CaP coating. In this study, the LAB process was applied to chemically stable and mechanically durable poly(etheretherketone) (PEEK), which has become widely used as an orthopedic and dental implant material.

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We present NiO/Ni composite particles with face-centered cubic (fcc) structure prepared by a pulsed laser irradiation of NiO nanoparticles dispersed in liquid. The sizes of particles and the Ni content in NiO/Ni composites were controlled by tuning the laser parameters, such as laser fluence and irradiation time. We found that the weight fraction of Ni has a significant impact on magnetic properties of composite particles.

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We developed a facile one-pot fabrication process for magnetic iron oxide-calcium phosphate (IO-CaP) composite nanoparticles via coprecipitation in labile supersaturated CaP solutions containing IO nanocrystals. All the source solutions used were clinically approved for injection, including water and magnetic IO nanocrystals (ferucarbotran, used as a negative magnetic resonance imaging (MRI) contrast agent). This ensured that the resulting nanoparticles were pathogen- and endotoxin-free.

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We successfully produced water-dispersible reduced graphene oxide (rGO) by pH tuning liquid-phase photoreduction. In this method, the stabilizers and chemical modification usually used for dispersing rGO are not required. The stable carboxyl groups continue to ionize throughout the photoreduction process under alkaline conditions and continue to provide water-dispersible rGO.

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The electrical transport and thermoelectric property of boron carbide nanowires synthesized by a carbothermal method are reported. It is demonstrated that the nanowires achieve a higher Seebeck coefficient and power factor than those of the bulk samples. The conduction mechanism of the nanowires at low temperatures below 300 K is different from that of the sintered-polycrystalline and single-crystal bulk samples.

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Unlabelled: We achieved rapid, surfactant-free, and one-pot fabrication of antibacterial calcium phosphate (CaP) submicrospheres containing silver nanoparticles by combining physical laser and chemical coprecipitation processes. In this physicochemical process, weak pulsed laser irradiation (20min) was performed on a labile CaP reaction mixture supplemented with silver ions as a light-absorbing agent. The silver content in the submicrospheres was controlled for a wide range (Ag/P elemental ratio varied from 0.

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Surface-mediated gene delivery systems have many potential applications in tissue engineering. We recently fabricated an assembly consisting of DNA-amorphous calcium phosphate (DNA-ACP) nanocomposite spheres on a polymer substrate via coprecipitation in a labile supersaturated calcium phosphate (CaP) solution and demonstrated the assembly's high gene delivery efficacy. In this study, we conducted a detailed investigation of the coprecipitation process in solution and revealed that the negatively charged DNA molecules were immobilized in the ACP spheres during the initial stage of coprecipitation and functioned as both sphere-dispersing and size-regulating agents.

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A salt-free procedure for the generation of a wide variety of metal(0) particles, including Fe, Co, Ni, and Cu, was achieved using 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene (1), which reduced the corresponding metal precursors under mild conditions. Notably, Ni particles formed in situ from the treatment of Ni(acac)2 (acac = acetylacetonate) with 1 in toluene exhibited significant catalytic activity for reductive C-C bond-forming reactions of aryl halides in the presence of excess amounts of 1. By examination of high-magnification transmission electron microscopy images and electron diffraction patterns, we concluded that amorphous Ni nanoparticles (Ni aNPs) were essential for the high catalytic activity.

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In this paper, we have further developed our simple (one-pot) and rapid (short irradiation time) laser fabrication process of submicrometer spheres composed of amorphous calcium iron phosphate. In our previous process, laser irradiation was applied to a calcium phosphate (CaP) reaction mixture supplemented with ferric ions (Fe(3+)) as a light-absorbing agent. Because the intention of the present study was to fabricate magnetite-encapsulated CaP-based submicrometer spheres, ferrous ions (Fe(2+)) were used as a light-absorbing agent rather than ferric ions.

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Simple, mild, and area-specific calcium phosphate (CaP) coating techniques are useful for the production and surface modification of biomaterials. In this study, an area-specific CaP coating technique for polymer substrates was successfully developed using a liquid-phase laser process. In the proposed method, Nd-YAG laser light (355 nm, 30 Hz, and 1-3 W) irradiated an ethylene-vinyl alcohol copolymer (EVOH) substrate immersed in a supersaturated CaP solution for various periods of time (up to 30 min).

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Submicrometer-sized tetragonal zirconia spheres are synthesized by carbon-assisted selective pulsed laser heating in a liquid medium at room temperature. Sphere formation and phase transformation from the monoclinic to the tetragonal phase are only observed by laser irradiation of a colloidal solution containing raw zirconia mechanically milled with nanocarbon. This result indicates that nanocarbon, having close contact with zirconia particles, plays a very important role in forming submicrometer-sized tetragonal zirconia spheres.

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We report the synthesis of Au-based submicrometer-sized spherical particles with uniform morphology/size and integrated porosity-magnetic property in a single particles. The particles are synthesized by a two-step process: (a) selective pulsed laser heating of colloidal nanoparticles to form particles with Au-rich core and Fe-rich shell and (b) acid treatment which leads to formation of porous architecture on particle surface. The simple, fast, inexpensive technique that is proposed demonstrates very promising perspectives for synthesis of composite particles.

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