Application of a genetically engineered macrophage cell line for evaluating cellular effects of UV/US-treated poly(ethylene terephthalate) microplastics.

Microplastic (MP) pollution is a global environmental problem. To understand the biological effects of MPs on humans, it is essential to evaluate the response of human cells to model plastic particles that mimic environmental MPs in a sensitive and non-invasive manner. In this study, we investigated the preparation of poly(ethylene terephthalate) (PET) fragments with properties similar to those of environmental MPs by combining photo-oxidative degradation via ultraviolet (UV) irradiation with mechanical pulverization and hydrolysis via ultrasound (US) exposure. Combination of UV and US treatments decreased the particle size of PET fragments to 10.2 µm and increased their crystallinity and Young's modulus to 35.7 % and 0.73 GPa, respectively, while untreated PET fragments showed the particle size of 18.9 µm, the crystallinity of 33.7 %, and Young's modulus of 0.48 GPa. In addition, an increase in negative surface potential and O/C ratio were observed for UV/US-treated PET fragments, suggesting surface oxidation via UV/US treatment. Cytokine secretion from human macrophages was evaluated by a highly sensitive inflammation evaluation system using the HiBiT-based chemiluminescence detection method developed by genome editing technology. UV/US-treated PET fragments induced a 1.4 times higher level of inflammatory cytokine secretion on inflammatory macrophages than untreated ones, suggesting that the biological responses of PET fragments could be influenced by changes in material properties via oxidation. In conclusion, UV/US treatment enables efficient preparation of model plastic particles and is expected to provide new insights into the evaluation of biological effects using human cells. (240 words).

Fabrication of Polypropylene Nanoplastics Via Thermal Oxidation Reaction for Human Cells Responsiveness Studies.

With the current worldwide increasing use of plastics year by year, nanoplastics (NPs) have become a global threat to environmental and public health concerns. Among plastics, polypropylene (PP) is widely used in industrial and medical applications. Owing to the lack of validated detection methods and standard materials for PP NPs, understanding the impact of PP NPs on the environmental and biological systems is still limited. Here, isotactic polypropylene (iPP) was fabricated into oxidized polypropylene micro/nanoplastics (OPPs) via a thermal oxidation using hydrogen peroxide (H2O2) under various heating temperatures. The resulting OPPs were investigated in terms of the size distribution, surface chemistry, morphology, and thermal property as well as their concentration-dependent cytotoxicity to a human intestinal epithelial cell line (Caco-2), which could be a route to uptake NPs into the body through the food chain. The average diameters of the OPPs decrease with increasing reaction temperature. The OPPs obtained at 175 °C (OPP175) were spherical in shape and had a rough surface, with size distributions of approximately 0.14 ± 0.02 µm. A significant increase in the carbonyl content of the oxidized product was confirmed by Fourier transform infrared and X-ray photoelectron spectroscopy analyses. Caco-2 cells were exposed to OPP175 in a dose-dependent manner, and a significant loss of cell viability occurred at the concentration of 100 µg/mL. Thus, this study provides a fundamental approach for the fabrication of a model of NPs for the urgently demanded in vitro and in vivo studies to assess the potential impact of NPs on biological systems.

Phase-matching condition for THz wave generation via difference frequency generation using InxGa1-xSe mixed crystals.

Terahertz (THz) waves at 9.7, 10.1 and 10.6 THz were generated via difference frequency generation in high-quality InxG1-xaSe mixed crystals with a relatively high indium compositions (x = 0.040, 0.048, 0.074) grown from an indium flux. The phase-matching angle for THz wave generation was measured for each indium content. As a result, it is confirmed that the incident angle of the excitation light satisfying the phase-matching condition is shifted to a higher angle with an increase in the indium content.

Terahertz wave generation via difference frequency generation using 2D InxGa1-xSe crystal grown from indium flux.

We demonstrate the generation of THz waves (frequency 9.7 THz) using difference frequency generation in an InxGa1-xSe mixed crystal grown from In flux. The amount of indium and the lattice constant of the crystal were evaluated using electron micro probe analysis and X-ray diffraction, respectively. We believe that the Ga sites were substituted by In atoms in the InxGa1-xSe crystal because the In content, estimated according to the Vegard's law, was similar to that measured by EPMA. The maximum power of the generated THz wave was 39 pJ and the conversion efficiency was 1.7×10-5 J-1. This conversion efficiency was 28 times larger than that reported for undoped GaSe crystal.

Viscosity measurement of Xanthan-Poly(vinyl alcohol) mixture and its effect on the mechanical properties of the hydrogel for 3D modeling.

Biomodels made of poly(vinyl alcohol) (PVA) are demanded because they can represent the geometries and mechanical properties of human tissues realistically. Injecting and molding, commonly used in three-dimensional (3D) modeling, help to represent the blood vessels accurately. However, these techniques sometimes require higher pressures than the upper pressure limit of the dispensers for pouring in high viscosity materials; the material viscosity should therefore be lower. Moreover, the mechanical properties of the biomodels should be reproduced. This study proposes a PVA solution through the addition of xanthan gum (XG) for 3D modeling, which lowers liquid viscosity while maintaining the mechanical properties of biomodels. XG is known to facilitate the achievement of non-Newtonian fluidity; however, the effects of XG on a PVA solution and PVA hydrogel (PVA-H) are not confirmed. The viscosity measurement using 15 wt% PVA with XG solution (PVA/XG) shows that it will provide easier pouring than 17 wt% PVA solution. The tensile test using the PVA-H of PVA(15 wt%)/XG(0.2 wt%) reveals that the gel is comparable in Young's modulus to 17 wt% PVA-H. X-ray diffraction shows the crystalline structures of the PVA/XG gel and PVA-H are identical. Thus, this PVA/XG would be useful for fabricating biomodels using injection molding techniques.

Ultrahigh Vacuum Synthesis of Strain-Controlled Model Pt(111)-Shell Layers: Surface Strain and Oxygen Reduction Reaction Activity.

In this study, we perform ultrahigh vacuum (UHV) and arc-plasma synthesis of strain-controlled Pt(111) model shells on Pt-Co(111) layers with various atomic ratios of Pt/Co and an oxygen reduction reaction (ORR) activity enhancement trend against the surface strain induced by lattice mismatch between the Pt shell and Pt-Co alloy-core interface structures was observed. The results showed that the Pt(111)-shell with 2.0% compressive surface strain vs intrinsic Pt(111) lattice gave rise to a maximum activity enhancement, ca. 13-fold higher activity than that of clean Pt(111). This study clearly demonstrates that the UHV-synthesized, strain-controlled Pt shells furnish useful surface templates for electrocatalysis.

Measurements of glucose concentration in aqueous solutions using reflected THz radiation for applications to a novel sub-THz radiation non-invasive blood sugar measurement method.

The terahertz (THz) frequency range corresponds to molecular vibrations or relaxation modes such as those for the hydrogen bond. Most biomolecules are activated only in aqueous solutions, thus, to understand the function and structure of biomolecules, it is necessary to investigate the characteristics of electromagnetic waves in hydrated samples. THz radiation causes little damage to the human body, thus it is expected that it can be applied for noninvasive examinations. However, spectrometry of the transmitted light is difficult, since the absorption of THz radiation in water is extremely high. In this study, we used sub-THz radiation (frequencies near to 0.1 THz), where the absorption is lower than for THz radiation, to measure the reflectance of a glucose water solution. We found that the reflectance decreases in proportion with the glucose concentration. These results suggest that sub-THz radiation can be used in the noninvasive measurement of blood glucose levels.

Low-Friction Adsorbed Layers of a Triblock Copolymer Additive in Oil-Based Lubrication.

The tribological properties of the dilute solution of an ABA triblock copolymer, poly(11-acrylamidoundecanoic acid)-block-poly(stearyl methacrylate)-block-poly(11-acrylamidoundecanoic acid (A5S992A5), in poly(α-olefin) (PAO) confined between mica surfaces were investigated using the surface forces apparatus (SFA). Friction force was measured as a function of applied load and sliding velocity, and the film thickness and contact geometry during sliding were analyzed using the fringes of equal chromatic order (FECO) in the SFA. The results were contrasted with those of confined PAO films; the effects of the addition of A5S992A5 on the tribological properties were discussed. The thickness of the A5S992A5/PAO system varied with time after surface preparation and with repetitive sliding motions. The thickness was within the range from 40 to 70 nm 1 day after preparation (the Day1 film), and was about 20 nm on the following day (the Day2 film). The thickness of the confined PAO film was thinner than 1.4 nm, indicating that the A5S992A5/PAO system formed thick adsorbed layers on mica surfaces. The friction coefficient was about 0.03 to 0.04 for the Day1 film and well below 0.01 for the Day2 film, which were 1 or 2 orders of magnitude lower than the values for the confined PAO films. The time dependent changes of the adsorbed layer thickness and friction properties should be caused by the relatively low solubility of A5S992A5 in PAO. The detailed analysis of the contact geometry and friction behaviors implies that the particularly low friction of the Day2 film originates from the following factors: (i) shrinkage of the A5S992A5 molecules (mainly the poly(stearyl methacrylate) blocks) that leads to a viscoelastic properties of the adsorbed layers; and (ii) the intervening PAO layer between the adsorbed polymer layers that constitutes a high-fluidity sliding interface. Our results suggest that the block copolymer having relatively low solubility in a lubricant base oil is effective at forming low-friction adsorbed layers in oil-based lubrication.

Efficient terahertz detection in a sheet cavity using a nonlinear optical parametric process.

We designed and simulated a GaP-based sheet cavity structure for room-temperature THz wave detection via a nonlinear optical (NLO) parametric process, using photonic conversion from THz frequencies to the optical domain. The sheet cavity structure consisted of a GaP rectangular waveguide for THz waves. Pump enhancement in the cavity and strong confinement of the THz wave in the waveguide resulted in a high power conversion efficiency of 1% (detection at 5 THz). The noise equivalent power for THz wave detection using an optical single-photon detector was estimated to be in the order of a few fW Hz(-1/2), which was higher than that obtained using room-temperature bolometers, field-effect transistors, and other NLO processes.

Friction of polymer hydrogels studied by resonance shear measurements.

The friction between an elastomer and a hard surface typically has two contributors, i.e., the interfacial and deformation components. The friction of viscoelastic hydrogel materials has been extensively studied between planar gel and planar substrate surfaces from the viewpoint of an interfacial interaction. However, the geometry of the contact in practical applications is much more complex. The contribution of geometric and elastic deformation terms of a gel to friction could not be neglected. In this study, we used resonance shear measurements (RSMs) for characterizing the shear response of a glass sphere on a flat polymer hydrogel, a double network (DN) gel of 2-acrylamide-2-methylpropanesulfonic acid and N,N-dimethylacrylamide. The contact mechanics conformed to the Johnson-Kendall-Roberts theory. The observed resonance curves exhibited rather sharp peaks when the DN gel and the silica sphere were brought into contact, and their intensity and frequency increased with the increase in the normal load. We proposed a simple physical model of the shearing system, and the elastic (k2) and viscous (b2) parameters of the interface between a silica sphere and a flat DN gel were obtained. The friction force from elastic deformation and viscous dissipation terms was then estimated using the obtained parameters. It was revealed that the elastic parameter (k2) increased up to 1780 N m(-1) at a normal load of 524 mN, while the viscous parameter (b2) was zero or quite low (<0.1 N s m(-1)) for a silica sphere (radius of 18.4 mm). Thus, the friction force between a flat DN gel and a silica sphere in air was dominated by the elastic term due to the local deformation by contact with the silica sphere. By adding water, the elastic parameter (k2) remained the same, while the viscous parameter (b2) slightly increased. However, the viscous term fviscous was still much smaller than felastic. To the best of our knowledge, this study was the first quantitative estimation of the contribution of the elastic deformation term to the friction in the case when deformation of non-flat contact regions occurs. The obtained results can be basic knowledge for designing gels for applications such as artificial cartilages and sliding bearings.

Concept of annular vector beam generation at terahertz wavelengths via a nonlinear parametric process.

In this paper, we describe our theoretical investigation and calculations for a terahertz (THz)-wave profile generated by difference frequency mixing (DFM) of focused, cylindrically symmetric, and polarized optical vector beams. Using vector diffraction theory, the second-order nonlinear polarization was estimated from the electric field components of the optical pump beams penetrating uniaxial, birefringent nonlinear optics (NLO) crystals, GaSe and CdSe. The approximate beam patterns of the THz waves were simulated using DFM formulation. The intensity patterns of the THz waves for GaSe and CdSe showed sixfold symmetry and cylindrical symmetry, respectively, based on the nonlinear susceptibility tensor of the crystals. As the phase-matching angle θ(PM) was constant with respect to the c axis of the NLO crystals, an annular vector beam with a narrow width was expected.

Pump enhanced monochromatic terahertz-wave parametric oscillator toward megawatt peak power.

Pump enhanced optical parametric oscillation under a cavity phase matching configuration is an effective way to obtain monochromatic THz waves with high pulse energy. Numerical simulations are conducted for THz wave generations using a GaP sheet cavity. By optimizing the optical pulse duration and cavity configuration, the estimated peak power of THz waves is 4 MW at 3 THz, which corresponds to the photon conversion efficiency of η≈0.81. Our proposed scheme can generate a THz wave with high pulse energy, which is suitable for the nonlinear optical effects in the THz frequency region.

THz-wave generation via difference frequency mixing in strained silicon based waveguide utilizing its second order susceptibility χ((2)).

Terahertz (THz) wave generation via difference frequency mixing (DFM) process in strain silicon membrane waveguides by introducing the straining layer is theoretically investigated. The Si(3)N(4) straining layer induces anisotropic compressive strain in the silicon core and results in the appearance of the bulk second order nonlinear susceptibility χ((2)) by breaking the crystal symmetry. We have proposed waveguide structures for THz wave generation under the DFM process by .using the modal birefringence in the waveguide core. Our simulations show that an output power of up to 0.95 mW can be achieved at 9.09 THz. The strained silicon optical device may open a widow in the field of the silicon-based active THz photonic device applications.

Design of a GaP/Si composite waveguide for CW terahertz wave generation via difference frequency mixing.

We design a GaP/Si composite waveguide to achieve efficient terahertz (THz) wave generation under collinear phase-matched difference frequency mixing (DFM) between near-infrared light sources. This waveguide structure provides a strong mode confinement of both near-infrared sources and THz wave, resulting in an efficient mode overlapping. The numerical results show that the waveguide can produce guided THz wave (5.93 THz) with a power conversion efficiency of 6.6×10(-4) W(-1). This value is larger than previously obtained with the bulk GaP crystal: 0.5×10(-9) W(-1) [J. Lightwave Technol.27, 3057 (2009)]. Our proposed composite waveguide can be achieved by bridging the telecom wavelength and THz frequency region.

Elliptically polarized THz-wave generation from GaP-THz planar waveguide via collinear phase-matched difference frequency mixing.

We carried out terahertz (THz)-wave generation from the GaP planar waveguides under collinear phase-matched difference-frequency mixing of two near-infrared sources. TE- and TM-mode of THz-waves were generated simultaneously by adjusting the polarization direction of two incident infrared sources. The phase shift between TE- and TM-mode of THz-wave in the waveguide was dependent on the waveguide length and contributed to the generation of the elliptical polarized THz-wave. The ellipticity of generated THz-wave increased as waveguide length increased. We indicated the possibility of control of rotational direction of elliptical polarization of emitted THz wave.

Continuous wave terahertz wave spectrometer based on diode laser pumping: potential applications in high resolution spectroscopy.

We constructed a high resolution terahertz (THz) spectroscopic system with an automatic scanning control using a continuous wave (cw) THz wave generator based on difference frequency generation method by excitation of phonon-polariton mode in GaP. The pump and signals lasers were compact, tunable external cavity laser, and distributed feedback (DFB) lasers, respectively. The generated THz waves were tuned automatically by changing the temperature of the DFB laser using a system control. We present the water vapor transmission characteristics of the THz wave and also absorption spectrum of a white polyethylene in the frequency range of 1.97-2.45 THz. The spectroscopic measurements performed at an output power level of 2 nW, which was obtained with a 15-mm-long GaP crystal at 2 THz. The advantage of this cw THz spectrometer is wide frequency tuning range (0.7-4.42 THz) with an estimated linewidth of full width at quarter maximum <8 MHz and this system has a potential application in high resolution spectroscopy.

Single-frequency coherent terahertz-wave generation using two Cr:forsterite lasers pumped using one Nd:YAG laser.

We have developed a compact terahertz-wave generator using two small Cr:forsterite lasers with single Nd:YAG laser pumping based on difference frequency generation in a GaP crystal. A Cr:forsterite laser was constructed with diffraction gratings, by which the pulse duration and delay time of the Cr:forsterite laser depend on the Cr:forsterite laser energy and the cavity length. The Cr:forsterite laser energy was tuned using the optical alignment and pumping energy. Temporal overlap of two Cr:forsterite laser pulses was realized at the GaP crystal. A single-frequency terahertz wave was generated at energy of 4.7 pJ around 2.95 THz using a 30-cm-long Cr:forsterite laser system.

Small and rough colony pseudomonas aeruginosa with elevated biofilm formation ability isolated in hospitalized patients.

Pseudomonas aeruginosa is a key pathogen of nosocomial infection, and causes persistent infection in patients with specific diseases like cystic fibrosis (CF). It has been reported that patients affected with CF discharge, at a high frequency, small colony variants with high adherence ability. In routine laboratory testing, we found atypical small and rough type (SR) colony variants of P. aeruginosa. The SRs and the counterpart wild type (WT) colonies showed similar biochemical features, antimicrobial susceptibilities, pulsed-field gel electrophoresis (PFGE) profiles, serotypes, and twitching motilities. The biofilm formation abilities of all the SR colonies, however, were extremely elevated as compared to those of the counterpart WT colonies. The frequency of SR-positive patients was 3.1% of the P. aeruginosa-positive inpatients (5/160), and that of the SR isolates was 0.6% of the P. aeruginosa strains (6/970) isolated in our laboratory over a period of 6 months. The SR-positive patients did not have any common disease or particular antibiotics treatment. The PFGE profiles showed that the SRs and the counterpart WTs were identical to each other, and also that three of the five SR/WT pairs were clonally similar. The three pairs were recovered from the feces, urine, and endotracheal secretion, respectively, of three patients hospitalized in two distinct wards. The results suggest that P. aeruginosa spontaneously produced highly adherent SR colonies in hospitalized patients, and these colonies may tend to spread in a hospital.

GaP Raman Terahertz high accuracy spectrometer and its application to detect organic and inorganic crystalline defects.

One of the most important uses of THz spectrometry is to detect defects in molecular structure or in crystals efficiently. We applied GaP Raman THz (GRT) spectrometer to detect and evaluate defects in inorganic and organic materials. High THz-wave absorption due to high defect density of GaSe crystal lowered the efficiency of THz wave generation, when the crystal is used as nonlinear material for DFG (Difference Frequency Generation). Defects in organic molecules could be observed as changes in frequency, intensities of the absorption, and broadenings of the spectra.

[A bacteriological study of multiple-drug-resistant Pseudomonas aeruginosa isolates derived from 2 patients].

We investigated the isolation circumstances of multiple-drug-resistant Pseudomonas aeruginosa (MDRP) in the UOEH hospital and the bacterial analysis of isolated MDRP. From January to October 2003, MDRP was isolated from 2 patients. During this period, the isolation frequency of MDRP was 0.57% (2/350). Case 1 had 2 MDRP isolates from catheter urine, and case 2 had 5 MDRP isolates from pus. Regarding serotype, 2 isolates from case 1 were B type and the other 16 isolates from case 2 were E type. Pyomelanin was produced by 9 isolates of 16 E type isolates. The same PFGE patterns were observed in 2 isolates from case 1; that is, 9 pyomelanin producers from case 2 and the other 7 isolates from case 2, respectively. Metallo-beta-lactamase was produced by 2 isolates from case 1. bla(IMP) was detected from the 2 isolates by PCR, and the clones from case 1 were quite different from the clones from case 2. Regarding the pyomelanin producing isolates from case 2, although the clones were the same genetically, the MICs of imipenem and meropenem increased from 8 to > 32 microg/ml with the progress of time. In the UOEH hospital, 6 patients with MDRP isolates have been isolated so far, but these 6 patients are not correlated with each other. It is important that we detect and report MDRP as early as possible to prevent nosocomial infection.