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Highlights: [•] Aromatic chlorinated dopants for GI POFs for transmission at 850nm were prepared. [•] Optical properties of doped poly(pentafluorostyrene) were examined. [•] Doped poly(pentafluorostyrene) showed no absorption losses at 850nm. [•] Doped poly(pentafluorostyrene) also satisfied numerical aperture requirement. [•] Thermal stability of poly(pentafluorostyrene) was not affected by the dopants. [ABSTRACT FROM AUTHOR]

Copolymerizations of hexafluoroisobutylene (HFIB) with vinyl pentafluorobenzoate (VPFB) and vinyl trifluoroacetate (VTFA) were carried out in bulk using perfluorodibenzoyl peroxide as the radical initiator. The copolymers obtained were characterized by proton and fluorine NMR spectroscopy. The monomer reactivity ratios in the polymerization of HFIB with VPFB were r1 (HFIB) = 0, r2 (VPFB) = 0.373, and r1 r2 = 0. The results indicated that these copolymers have alternating structures. Similarly, the copolymers of HFIB and VTFA also showed alternating structures. The films of HFIB- co-VPFB were prepared by casting THF solution of polymers. Films obtained were flexible and transparent. The refractive indices of copolymers were 1.4549, 1.4490, and 1.4438 at 532, 633, and 839 nm, respectively. The average Tgs of HFIB- co-VTFA and HFIB- co-VPFB were 52 and 71 °C, respectively. From these results, the Tg of the hypothetical HFIB homopolymer is postulated to be in between 70 and 90 °C, which may be useful in the assessment of Tgs of HFIB copolymers with other vinyl monomers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Bis(hexafluoroisopropyl) fumarate (BHFIPF) did not homopolymerize with free radical initiators. However, BHFIPF yielded alternating copolymers with styrene in bulk with Azobisisobutyronitrile (AIBN) as a radical initiator. The monomer reactivity ratios of BHFIPF ( M1) and styrene ( M2) were calculated as r1 = 0.00 and r2 = 0.02. BHFIPF also copolymerized with vinyl pentafluorobenzoate (VPFB) in bulk and in pentafluoroisopropanol solution to produce an alternating copolymer. The reactivity ratios of BHFIPF ( M1) with VPFB ( M2) were r1 = 0.00 and r2 = 0.05 in bulk and r1 = 0.01 and r2 = 0.11 in pentafluoroisopropanol, respectively. The glass transition temperatures ( Tg) of the BHFIPF-styrene and BHFIPF-VPFB copolymers were 107 and 86 °C, respectively. The BHFIPF-styrene copolymer was thermally stable, and the thermal degradation temperature ( Td) was 400 °C, whereas the Td of BHFIPF-VPFB copolymer was 240 °C. The films obtained by casting from tetrahydrofuran (THF) solutions of these copolymers were flexible and transparent. Their refractive indices were 1.4048 for the BHFIPF-styrene copolymer, and 1.3980 for the BHFIPF-VPFB copolymer at 633 nm, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 [ABSTRACT FROM AUTHOR]

• The creep deformation of an epoxy adhesive is comprehensively analyzed. • Time-dependence of nano-creep in physical-contact optical connectors is observed. • Adhesive creep model for the connectors using a rheological approach is described. • Obtained results and reported exposure-test results agree with our model. • Long-term deformation behavior and reliability of the connectors is predicted. We describe a comprehensive analysis of the nano-creep deformation of an epoxy adhesive used in physical-contact optical fiber connectors. To design a highly reliable multicore fiber connector and predict the long-term reliability of commercially installed optical connectors, we focus on the change in fiber withdrawal, which is a key parameter for achieving physical-contact connection. We also propose an adhesive creep model that includes long-term time dependence by detailing through a finite element analysis the parameters that influence the fiber withdrawal, such as shear stress with connection, thermal stress, residual stress, swelling, and cure shrinkage. The measurement results for fiber withdrawal under several environmental conditions provided in this paper support the behaviors considered in our proposed model. From our obtained short-term results and rheological approach, we predict the nano-creep deformation observed in the connector over the long term by applying the time-temperature superposition principle, and discuss the correspondence with exposure test results. Our verified mechanism and estimated values of creep deformation prove the high reliability of the optical connectors and also provide guidelines for determining the need to update installed connectors and for designing future connection devices such as physical-contact multicore fiber connectors. [ABSTRACT FROM AUTHOR]

We have proposed a light-emitting diode (LED) downlight lens that is made of a highly scattered optical transmission (HSOT) polymer. The HSOT polymer contains optimized heterogeneous structures that produce homogeneously scattered light with forward directivity. The full width at half maximum of the illuminance distribution angle can be increased from 16.7° to 37.9° as the concentration of the scattering particles in the HSOT polymer LED downlight lenses of identical shape is increased from 0.015 to 0.100 wt%. The colors in an illuminated area are highly uniform, which is not discernible by the human eye, with a high output efficiency greater than 85 %. [ABSTRACT FROM AUTHOR]

To study the effects of fluorine substituent of polystyrene (PSt) on gradient-index fiber-optic properties, a poly(para-fluorostyrene) (P(p-FSt))-based graded-index plastic optical fiber (GI POF) is fabricated, and its properties are compared with those of a PSt-based GI POF. The para-fluorine substitution positively affects the glass transition temperature ( T g ) of the core, wavelength dispersion of the optimum refractive index profile, bandwidth, and attenuation. The core T g of the P(p-FSt)-based GI POF is 88 °C, which is higher than that of the PSt-based GI POF by 9 °C when both fibers have an identical numerical aperture (NA = 0.2). The optimum refractive index profile coefficient for the P(p-FSt)-based GI POF varies from 2.2 to 2.1 in the 600–800 nm range, whereas that for the PSt-based GI POF varies from 2.6 to 2.3 in the same wavelength region. The bandwidth of the P(p-FSt)-based GI POF is intrinsically higher than that of PSt-based GI POF. Moreover, the fiber attenuation of the P(p-FSt)-based GI POF was significantly smaller than that of the PSt-based GI POF over the source wavelength range. Our study demonstrates that P(p-FSt) has favorable properties as a GI POF base material. [ABSTRACT FROM AUTHOR]

Perfluoropolymer membranes have found commercial use because of their unique gas separation properties and chemical resistance. To date, studies of gas transport in perfluoropolymers have been limited largely to variants of the commercially available polymers, Teflon ® AF, Cytop, and Hyflon ® AD. Here, we describe gas transport in composite membranes fabricated from copolymers of perfluoro(2-methylene-4,5-dimethyl-1,3-dioxolane) and perfluoro(2-methylene-1,3-dioxolane). These new perfluoro copolymer membranes have superior gas separation performance compared to the commercial perfluoropolymers for a number of gas pairs, including H 2 /CH 4 , He/CH 4 , N 2 /CH 4 , and CO 2 /CH 4 . For example, membranes based on 57 mol% perfluoro(2-methylene-1,3-dioxolane) show H 2 /CH 4 selectivity of 130 combined with a H 2 permeance of 700 gpu. These values far exceed an upper bound for commercial perfluoropolymers. The transport properties of the new perfluoro membranes depend strongly on the copolymer composition with increasing amounts of the efficient packing monomer perfluoro(2-methylene-1,3-dioxolane), yielding membranes with higher size selectivity and lower permeance. [ABSTRACT FROM AUTHOR]

Abstract: Copolymerization is a useful way of modifying the physical properties of a material to meet specific needs, but it can result in a significant light scattering loss due to dielectric fluctuations in the material. Ideal random copolymers are known to be more transparent; however, the light-scattering properties of such copolymers in bulk have not been fully studied. In this paper, two representative ideal random copolymers were synthesized: methyl methacrylate (MMA)/benzyl methacrylate (BzMA) and MMA/2,2,2-trifluoroethyl methacrylate (TFEMA). The effects of copolymer composition and polymerization temperature on the light-scattering properties were investigated. Polarized light scattering (V V) in copolymers was more sensitive to the polymerization temperature. Higher temperatures were necessary to homogenize the dielectric fluctuations and minimize excess light scattering. However, once the heterogeneous structures vanished, the copolymer bulk exhibited low scattering losses, which are comparable with homopolymers, over the entire range of copolymer compositions. [Copyright &y& Elsevier]

Highlights: [•] Perfluorinated ideal random copolymers are synthesized and characterized. [•] The copolymers can be amorphous or crystalline depending on the composition. [•] The amorphous copolymers are transparent and soluble in fluorinated solvents. [•] The T gs of the copolymers do not change linearly with the composition. [•] They are thermally stable (>378°C) and have low refractive index (1.32–1.34). [ABSTRACT FROM AUTHOR]

Poly-(methyl methacrylate-co-benzyl methacrylate) polarization-maintaining optical fibers are known for their high response to normal stress. In this report, responses to higher stress levels up to 0.45 MPa were investigated. The stress amplitude and direction in the fiber cross section were calculated and analyzed with a coincident mode-field obtained from the near-field pattern. The stress amplitude varies significantly in the horizontal direction and is considered to create multiple phases, explaining the measurement results. To investigate possible permanent deformation, the core yield point profile was analyzed. Although it largely exceeds the average applied stress, the calculated stress distribution indicates that the core could partially experience stress that exceeds the yield point. [ABSTRACT FROM AUTHOR]

Abstract: Perfluorinated monomer (perfluoro-2-methylene-4,5-dimethyl-1,3-dioxolane), its precursor (perfluoro-2,4,5-trimethyl-1,3-dioxolane-2-carboxylic acid), as well as their hydrocarbon precursor (methyl 2,4,5-trimethyl-1,3-dioxolane-2-carboxylate), were prepared and studied by 1D- and advanced 2D NMR techniques. For both perfluorinated compounds, the structures of their possible isomers were proven by 2D NMR spectroscopy. Due to the large 19F spectral window, this study used selective versions of the correlation spectroscopy (COSY) and nuclear Overhauser effect spectroscopy (NOESY) experiments to provide better resolution and sensitivity. In addition, a new variation of the gradient heteronuclear single quantum coherence spectroscopy (gHSQC) sequence was successful for observing two-bond 19F 13C correlations. Compared with the gradient heteronuclear multiple bond correlation spectroscopy (gHMBC) spectrum, the 2 J FC gHSQC spectrum is greatly simplified due to the absence of splittings caused by multi-quantum coherence. Quantitative 1H or 19F 1D NMR was used to confirm the resonance assignments and to calculate the ratio of isomers. The configurational compositions of perfluorinated compounds and their hydrocarbon precursor support the idea that fluorination by elemental fluorine is a free radical process. [Copyright &y& Elsevier]

Copolymers of methyl methacrylate (MMA) with 2,3,4- and 2,4,6-trifluorophenyl maleimides (TFPMIs) were synthesized by a free radical initiator, azobisisobutyronitrile, in 1,4-dioxane and also in bulk. The refractive indexes of the copolymers were in the range of 1.49-1.52 at 532 nm. The Tgs were 133-195 °C depending on copolymer compositions. In addition, the copolymers were thermally stable, Td > 350 °C. The orientational and photoelastic birefringence of the copolymers were also investigated. As both of the orientational and photoelastic birefringences of PMMA are negative, whereas those of poly(TFPMI)s are positive, we could obtain nearly zero orientational and photoelastic birefringence polymers when the ratios of 2,3,4-TFPMI/MMA were 15/85 and 5/95 mol %, respectively. For 2,4,6-TFPMI, zero orientational and photoelastic birefringences could be obtained when the ratios of 2,4,6-TFPMI/MMA were 12/88 and 3/97 mol %, respectively. The Tgs of those copolymers with zero birefringences were in the range of 135-140 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Abstract: We designed and synthesized quaternary copolymers of methyl methacrylate (MMA), 2,2,2-trifluoroethyl methacrylate (TFEMA), benzyl methacrylate (BzMA), and 3,3,5-trimethylcyclohexyl methacrylate (TMCHMA) and we investigated their birefringence, thermal properties, and other optical properties. When the copolymer composition was MMA/TFEMA/BzMA/TMCHMA = 50:38:8:4, 40:30:7:23, or 30:21:7:42 (wt%), a zero–zero-birefringence polymer that exhibited neither orientational nor photoelastic birefringence was obtained. We demonstrated that such zero–zero-birefringence polymers with a variety of compositions could be successfully prepared in the quaternary system by using the same compensation method as applied in ternary random copolymerization. We also demonstrated that the glass-transition temperature (T g) and refractive index (n D) of these copolymers could be controlled with high accuracy while retaining their zero–zero-birefringence property. We can therefore predict the type of birefringence, the T g, and the n D of a particular copolymer before polymerization. Zero–zero-birefringence polymers with the most appropriate characteristics can then be synthesized selectively by quaternary copolymerization. [Copyright &y& Elsevier]

Radial refractive index profiles within the graded index plastic optical fiber (GI-POF) is formed by adding a dopant to a polymer. This addition of the dopant significantly decreased the Tg of the polymer due to the plasticization. This disadvantage made the installation of the GI-POF difficult, especially in vehicle networks in which high thermal stability is required. We have suggested 9-bromophenanthrene (BPT) as a novel dopant induced less plasticization for poly(methyl methacrylate) (PMMA) than the conventional dopants. However, although the fabricated GI-POF using BPT had high enough thermal stability for vehicle networks, the attenuation was 800 dB/km and it could not be used. This high attenuation was caused by contaminant in the fabrication process of fibers. In this study, we succeeded to fabricate a GI-POF with low-attenuation and high-thermal stability using highly pure BPT. Its attenuation was improved to 240 dB/km at 650 nm, which was enough transparency for vehicle networks. The Tg of the GIPOF was improved to 107 °C from 90 °C. The thermal stability of the GI-POF below 85 °C/dry and 75 °C/85%RH was demonstrated to be as high as that of the commercially available step index POF. The bandwidth of the GI-POF could be estimated over 4.0 GHz for the 50-m fiber. These results demonstrated that our GI-POF should qualify to be used in vehicle network. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1464-1469, 2011 [ABSTRACT FROM AUTHOR]

Abstract: 2-Trifluoromethyl styrene (2TFMS), 2,5-bis(trifluoromethyl) styrene (25BTFMS), and 3,5-bis(trifluoromethyl) styrene (35BTFMS) were synthesized. These styrenes were readily polymerized in bulk and also in solution using AIBN as a free radical initiator. The polymerization rate of these trifluoromethyl substituted styrenes and other monomers such as styrene (St), pentafluorostyrene (PFS) and 4-trifluoromethyl-tetrafluorostyrene (TFMTFS) were measured in benzene and dioxane by monitoring the 1H NMR spectra of the double bond hydrogen. The order of polymerization rates was TFMTFS > 35BTFMS > 25BTFMS > PFS > 2TFMS > St. Tg s of styrene polymers with CF3 substituted on the ortho position of the phenyl ring were much higher than those of the meta and para substituted styrenes due to the steric hindrance of the bulky CF3 group close to the polymer main chain, which resulted in a decrease in the segment mobility of the polymer chains and an increasing Tg of the polymers. The copolymers of 2TFMS with methyl methacrylate (MMA) and also 25BTFMS with trifluoroethyl methacrylate (TFEMA) were prepared. Tg s of the copolymers were in the range of 120–145 °C and the copolymers were transparent and thermally stable. The copolymer films were flexible and exhibited high transmittance as the homopolymers of MMA and TFEMA. Thus, these copolymers may be utilized as novel optical materials. [Copyright &y& Elsevier]

Abstract: As a novel base material for low-loss graded index plastic optical fibers (GI POFs) in gigabit home networks, a copolymer of methyl methacrylate (MMA) and pentafluorophenyl methacrylate (PFPMA) was prepared and its thermal and optical properties were investigated. When the PFPMA content in the monomer feed was 0–50mol%, both the glass transition temperature (T g) and the decomposition temperature of the copolymer were higher than that for PMMA, which is the base material for many commercially available POFs. The transmittance of the copolymer was also found to be higher than that of PMMA since it has fewer C–H bonds per unit volume. As the core material of GI POFs, MMA-co-PFPMA (65/35mol%), which had the highest T g of 118°C was utilized. A low-loss GI POF with an attenuation of 172–185dB/km at the emission wavelengths of a high-speed light source (670–680nm) was successfully obtained for the first time. [Copyright &y& Elsevier]

The synthesis of perfluoro‐3‐methylene‐2,4‐dioxabicyclo[3,3,0] octane (D), its radical homopolymerization, and copolymerization with fluoroolefins are presented. Fluorodioxolane (D) was synthesized through direct fluorination of the corresponding hydrocarbon precursor in a fluorinated solvent by F2/N2 gas. It was polymerized in bulk using perfluorodibenzoyl peroxide as the initiator. The resulting homopolymer had a limited solubility in fluorinated solvents, and its glass transition temperature (Tg) was in the range of 180–190 °C. The polymeric films prepared by casting from hot hexafluorobenzene (HFB) solution were transparent with low refractive index (1.329 at 633 nm). These films were thermally stable (Td > 350 °C), and were hard and brittle. The copolymers of monomer (D) were prepared with fluorovinyl monomers such as chlorotrifluoroethylene (CTFE), perfluoropropyl vinyl ether, perfluoromethyl vinyl ether, and vinylidene fluoride. The kinetics of radical copolymerization of monomer (D) with CTFE led to the assessment of the reactivity ratios of both comonomers: rD = 3.635 and rCTFE = 0.737 at 74 °C, respectively. The copolymers obtained were soluble in HFB and perfluoro‐2‐butyltetrahydrofuran, with Tg in the range of 84–145 °C depending on the copolymer composition. The films of the copolymers were flexible and clear with a low refractive index (1.3350–1.3770 at 532 nm). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6571–6578, 2009 [ABSTRACT FROM AUTHOR]

Surface-modified ZnTe nanoparticles were mixed in a zero-birefringence polymer matrix. Transmission electron microscopy images revealed that aggregates of ZnTe nanoparticles with a diameter of ∼20 nm were uniformly dispersed in the polymer. The transmittance of ZnTe nanocomposites rapidly decreased at wavelengths shorter than the critical wavelength corresponding to the band gap of ZnTe nanoparticles, an effect which became significant as the volume fraction of particles increased. In this way, the optical characteristic of ZnTe nanoparticles was added to the polymer. The intrinsic zero-birefringence was confirmed in the heat-drawn ZnTe nanocomposites. As the ZnTe nanocomposites were left in air, a lowering of transmittance was observed. This was due to the oxidation of Zn and the resultant deposition of Te in the ZnTe nanocomposite, as the light absorption of Te is significant. The formation of oxygen non-permeable SiO2 films onto the ZnTe nanocomposite by the sol-gel method was useful in preventing oxidation so that the decrement of transmittance decreased from 47.2% to 14.9% at 530 nm near the ZnTe band gap. [ABSTRACT FROM AUTHOR]

Abstract: Five perfluoro-4,5-substituted-2-methylene-1,3-dioxolane monomers were synthesized. These monomers were found to readily polymerized by a free radical initiator in bulk and/or in solutions. Homopolymerization rates were determined using in situ 19F NMR measurements and found to be 0.25 to 1.66×10−4 molL−1 s−1 in 1,1,2-trichlorotrifluoroethane at 41°C using the perfluorodibenzoyl peroxide as an initiator. The rates depend on the substituents on the 4 and 5 positions of the dioxolane. The purified polymers were thermally stable (up to 350°C). They show low refractive indexes (1.33–1.36 at 532nm). They are transparent from UV to near IR region and have high glass transition temperatures (100–170°C). [Copyright &y& Elsevier]

A novel coloration phenomenon in a colloidal dispersion with an amphiphilic polymer was found. The dispersion consists of tetrahydrofuran (THF), an aqueous solution of sodium thiosulfate (Na2S2O3·5H2O), and hydroxypropylcellulose (HPC). The dispersion was emulsified by HPC as an amphiphilic polymer, so that the aqueous phase was confined in droplets in the THF matrix. It typically appeared bluish violet at room temperature and turned into blue with increasing temperature. In this system, the refractive indices of the inside and outside of the droplet coincided at a certain wavelength at which the light passes through without scattering, which is called the Christiansen effect. The color observed was successfully simulated by Mie''s scattering theory in combination with the Christiansen effect. [Copyright &y& Elsevier]

A high efficiency optical coupler has been developed for high speed plastic optical fiber communication. The coupler was designed for a small photo acceptance area photodiode based on the shape of compound parabolic concentrator. The theoretical efficiency of the coupler for graded index plastic optical fiber (GI-POF) was simulated with ray trace simulation, and the coupling loss was calculated less than 0.4 dB. The coupler was batch fabricated in a glass substrate using sand blast technique. The reflection layer of reflectance 90% was formed by Gold/Nickel mirror plating method. The coupler was bonded with a custom designed high speed PIN photodiode. The photocurrent was 20% higher than the current of a ball lens type PIN photodiode. The cut-off frequency was over 1 Gbps at reverse bias of 1.5 V. [Copyright &y& Elsevier]

We report a method for compensating the birefringence of optical polymers by doping them with inorganic birefringent crystals. In this method, an inorganic birefringent material is chosen that has the opposite birefringence to that of the polymer and has rod-shaped crystals that are oriented when the polymer chains are oriented. The birefringence of the polymer is thus compensated by the opposing birefringence of the crystal. Birefringence is minimized in various polymer optical devices by adjusting process conditions, because it degrades the performance of devices. This method minimizes it, independent of process conditions, which potentially improves the productivity of devices. [ABSTRACT FROM AUTHOR]

Most existing displays utilize polarization technologies to produce images and improve image quality. However, polarized light from displays causes color mura because of the birefringence of the polymer films used. Thus, eliminating color degradation remains a challenge despite the incorporation of complex polarization technologies such as retardation films. Our proposed random depolarization film (RDF) addresses this issue by randomizing the polarization of light from displays. Chromaticity measurements demonstrate that the RDF effectively compensates for color mura due to low-cost polymer films. Notably, the RDF compensation mechanism is independent of the RDF position and light source spectrum. Therefore, the RDF could be an innovative solution for color degradation in existing displays.

Kamiue M, Tsubahara A, Ito T, Koike Y. Effects of repetitive peripheral magnetic stimulation on knee joint extensor strength in older persons receiving day services. Jpn J Compr Rehabil Sci 2024; 15: 49-57., Objective: To verify the effects of repetitive peripheral magnetic stimulation (rPMS) on knee joint extensor strength and motor ability in older adults receiving day services., Methods: Thirty Hz rPMS using Talent Pro ® was applied to the bilateral vastus lateralis, vastus medialis, and rectus femoris of 12 older persons (mean age 83.8 ± 4.5 years) attending a day service center and receiving functional training by a physical therapist. The intervention was performed for 20 minutes per day, three times per week, for a total of 4 weeks. Evaluations before and after the intervention included maximum voluntary contraction (MVC), knee extensor torque induced by rPMS (rPMS-induced torque), pain (visual analog scale: VAS), thigh circumference, comfortable 5-m walking time, 30-second chair-stand test (CS-30), Timed-Up-and-Go Test (TUG), and Functional Reach Test (FRT). MVC and rPMS-induced torque were measured using the μ-Tas F-1 ® ., Results: MVC significantly increased in both lower limbs after the intervention (right/left: 72.4 ± 23.5 Nm/72.9 ± 23.0 Nm) compared with immediately before the intervention (right/left: 59.9 ± 17.2 Nm/64.5 ± 21.0 Nm). No significant changes were observed in MVC between one month before the intervention and immediately before the start of the intervention, and between the end of the intervention and one month after the end of the intervention. rPMS-induced torque, TUG, and CS-30 improved significantly after the intervention compared with immediately before the intervention., Conclusion: Intervention using rPMS increases MVC- and rPMS-induced torque and improves motor ability in older adults. Because rPMS is a simple means of increasing muscle strength, it is expected to be widely used in the future., (©2024 Kaifukuki Rehabilitation Ward Association.)

Polarized light emitted from most displays causes blackout and color change problems when viewed through polarized sunglasses. These problems are addressed by random depolarization films (RDFs) doped with birefringent particles. These dopant particles, however, scatter light and degrade the sharpness of the displayed images. To maintain the image sharpness, we designed an RDF based on modulation transfer function measurements of displays with different pixel pitches. RDFs doped with larger particles achieved higher modulations; however, particles larger than a specific size caused undesirable sparkles on the displayed image. A display with a larger pixel pitch achieved higher modulations, suggesting that the RDF is particularly suitable for large-screen displays.

Liquid crystal displays and organic light-emitting diode displays emit polarized light through polarizers and quarter-wave plates, which cause blackout and color change problems when the displays are viewed through polarizers, such as polarized sunglasses. Random depolarization films (RDFs) are polymer films doped with calcite particles, which randomize the polarization of light emitted from displays to resolve polarization problems. To realize displays without any color change, we investigate the retardation values and fabrication conditions required for RDFs. Analysis of the transmittance spectra and interference colors of different RDFs suggested that retardation values of approximately 600-1200 nm are sufficient to realize real-color displays. In addition, the color change measurements of displays with the RDFs revealed that an optimal dopant particle size exists and that the RDFs doped with 3.6 and 7.3 µm calcite particles achieved chromaticity changes of less than 0.02 for all 24 colors in the Macbeth chart.

This Letter reports, to the best of our knowledge, the first study in which error-free four-level pulse-amplitude modulation (PAM-4) transmission has been achieved using a graded-index plastic optical fiber (GI POF) without the use of forward error correction (FEC) techniques, at a high data rate (>50 G b / s ), for short-reach applications (10 m). The GI POF that is developed has the characteristic microscopic heterogeneities in the fiber core material, which provide distinct mode coupling and significantly stabilize PAM-4 data transmission. The results of the study in this Letter indicate that the GI POF achieves highly stable PAM-4 transmission without the need for the current FEC techniques, which seriously increase the communication delay and power consumption of the transmission systems. Our GI POF material is paving the way for "material changes the system" approaches for achieving unprecedented optical interconnects in real time at a high speed and with low power consumption.

This study achieves real-color displays using a randomizing effect based on the concept of "natural light." At present, most displays emit linearly polarized light, which causes essential blackout and color degradation problems when the displays are viewed through polarizers such as sunglasses. To address this, complex polarization-control technologies are added to existing displays, but the problems remain unresolved. In contrast, this study randomizes the polarization using a polymer film called a random depolarization film (RDF) that is doped with specific birefringent crystal particles. The RDF placed on a display reproduces colors that are very close to the natural colors seen in reality without the need for complex polarization technologies. We believe that it has the potential to change the approach to color-reproducing technology for displays.

We developed a graded-index plastic optical fiber (GI POF) that enables lower-noise radio frequency (RF) transmission than conventional multimode fibers for short-distance household applications (<100 m ). It is shown that reflection noise degrades RF transmission, regardless of the carrier frequency, through the spurious generation that accompanies the RF modulation of a vertical-cavity surface-emitting laser. The GI POF with distinctive mode coupling, which is closely related to its microscopic polymer structure, suppresses noise and spurious generation to improve transmission quality. Our low-noise radio-over-GI-POF technology will offer significant advantages for optical wiring systems for broadcast and communication in small- and medium-scale buildings.

Introduction: This open-label, parallel-group, exploratory study examined the effects of two dipeptidyl peptidase 4 (DPP4) inhibitors on glycemic variability (GV) in patients with type 2 diabetes., Methods: Randomized patients with glycated hemoglobin A1c of at least 6.5% to less than 8.5% received trelagliptin 100 mg (n = 13) once weekly or alogliptin 25 mg (n = 14) once daily for 29 days. Continuous glucose monitoring was performed before the start of the treatment period (baseline) and from day 21 to 29, inclusive. The primary endpoint was change from baseline in the standard deviation (SD) of 24-h blood glucose values, measured daily for 7 days (day 22-28) of the treatment period. Secondary and additional efficacy endpoints included changes in glycemic parameters and the rate of DPP4 inhibition, respectively. Adverse events (AEs) were monitored to assess safety., Results: Mean change from baseline in the SD of 24-h blood glucose (95% confidence interval) at day 28 was - 7.35 (- 15.13, 0.44) for trelagliptin and - 11.63 (- 18.67, - 4.59) for alogliptin. In both treatment groups, glycemic parameters improved and the rate of DPP4 inhibition was maintained. Three patients reported AEs; no severe treatment-emergent AEs were reported in either group., Conclusion: Once-weekly trelagliptin and once-daily alogliptin improved glycemic control and reduced GV without inducing hypoglycemia., Trial Registration: ClinicalTrials.gov (NCT02771093) and JAPIC (JapicCTI-163250)., Funding: Takeda Pharmaceutical Company, Ltd.

We introduce a graded-index plastic optical fiber (GI POF) design for very short-distance household applications, in which the transmission quality is predominantly determined by system noise rather than the loss and bandwidth. The developed GI POF has strong mode coupling with low accompanying scattering loss, which is closely related to the specific microscopic heterogeneities in the core material. Such characteristic mode coupling significantly decreases reflection noise, improving the transmission quality compared with silica GI multimode fiber (MMF) for lengths below 30 m. Moreover, in the GI POF link, the transmission quality tends to improve with increasing fiber length, despite the increased loss and decreased bandwidth. This feature suggests that the system noise can be controlled by the microscopic heterogeneous properties of the GI POF for a very short MMF link, where the fiber loss and bandwidth are sufficiently low and high, respectively. This unconventional concept for optical-fiber design can advance fiber-optic communication in emerging applications in households located near optical network terminals.

Background: Based on non-clinical data, it is expected that azilsartan, an angiotensin II receptor blocker, will help improve insulin resistance in addition to its hypotensive action. The present study is aimed to explore the effect of azilsartan compared to telmisartan on insulin sensitivity in hypertensive patients in the clinical setting., Methods: This multicenter, randomized, open-label, parallel-group exploratory study was conducted in Japan. We randomized adult patients (≥20 years old) with grade I or II essential hypertension and coexisting type 2 diabetes (1:1) to receive either oral azilsartan (20 mg/day;17 patients) or telmisartan (40 mg/day;16 patients) for 12 weeks. The primary endpoint was the change in the homeostasis model assessment ratio of insulin resistance (HOMA-R) from the baseline at the end of the treatment period. We also evaluated its safety and efficacy on other diabetes-related variables and blood pressure., Findings: The mean changes in HOMA-R at the end of treatment were 0.22 (95% CI, -1.09-1.52) in the azilsartan group and -0.23 (95% CI, -0.72-0.27) in the telmisartan group. We found no clinically remarkable changes between the groups in diabetes-related variables such as fasting blood glucose, fasting insulin, HbA1c (NGSP), HOMA-β, or 1,5-anhydroglucitol. Reductions in clinic systolic and diastolic blood pressure were observed at week 4 and the reduced levels were maintained throughout the treatment period in both groups. No serious treatment-emergent adverse events (TEAEs) were observed. Only one drug-related TEAE (mild decrease in blood pressure) was reported in one patient in the azilsartan group., Conclusion: Neither azilsartan nor telmisartan had any clinically remarkable effects on insulin resistance parameters when administered for 12 weeks to patients with grade I or II essential hypertension and coexisting type 2 diabetes mellitus. Azilsartan (20 mg/day) and telmisartan (40 mg/day) exerted comparable antihypertensive effects., Trial Registration: ClinicalTrials.gov NCT02079805., Competing Interests: The authors have read the journal policy and the authors of this manuscript have the following competing interests: MN, RS, and YY declare no competing interests. YK is an employee of the funder, Takeda Pharmaceutical Company Limited. NK reports fees for lecturing from Takeda Pharmaceutical, Astellas, MSD, Ono Pharmaceutical, Kissei Pharmaceutical, Kyowa Hakko Kirin, Kowa, Sanofi, Daiichi-Sankyo, Taisho Toyama Pharmaceutical, Sumitomo Dainippon Pharma, Mitsubishi Tanabe Pharma, Terumo, Eli Lilly Japan, Boehringer Ingelheim Japan, Novartis and Novo Nordisk Pharma. NK also reports a grant from Astellas as a principle investigator of a collaborative clinical study. MA is an employee of A2 Healthcare Corporation. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

[Purpose] This study compared lower garment-lifting postural control characteristics during toilet-related activities between healthy participants and a post-stroke patient, and studied changes in the stroke patient's characteristics during rehabilitation. [Participants and Methods] Six healthy individuals and one stroke participant with right hemiparesis were asked to lift a pair of pants with the left arm while on the toilet. During the process, we measured the mean percentage of body weight (%BW) on each leg and the foot center of pressure (COP) using portable force plates. Measurements were conducted twice for the stroke participant during rehabilitation. [Results] In healthy participants, the %BW and respective COP indices for both legs were not different during lifting, but the COP sway velocity and excursion were greater in the anterior-posterior (AP) than the lateral axis in both legs. In the stroke participant, no marked change was seen in the high %BW of the non-paretic leg while lifting during rehabilitation, but both legs' COP positional asymmetry improved on the AP axis and the COP sway velocity and excursion of the non-paretic leg increased. [Conclusion] Facilitating selective COP mobility on the AP axis of the non-paretic leg during lower garment lifting could become an effective intervention for stroke patients.

The emission properties of a graded-index thermoplastic polymer optical fiber and a step-index thermosetting one, both doped with rhodamine 6G, have been studied. The work includes a detailed analysis of the amplified spontaneous emission together with a study of the optical gains and losses of the fibers. The photostability of the emission of both types of fibers has also been investigated. Comparisons between the results of both doped polymer optical fibers are presented and discussed.

N-(alkyl-substituted) maleimides (RMIs) were proposed as materials useful for the development of a zero-zero-birefringence polymer that exhibits no birefringence. We analyzed the optical and thermal properties of poly(RMI)s, such as the refractive index, birefringence, and glass transition temperature. The characteristics of the obtained polymers varied significantly because the shift of the density and polarizability derived from the change of the substituent structure influenced the optical properties, and the bulkiness of the substituents influenced the thermal properties. We also designed a zero-zero-birefringence polymer using N-ethyl maleimide (EMI) as a comonomer, and the obtained copolymer had no birefringence, relatively high heat resistance, and high transparency.

We experimentally demonstrate that a graded-index plastic optical fiber (GI POF) can significantly reduce reflection noise in a multimode fiber link with a vertical-cavity surface-emitting laser (VCSEL). By directly observing beams backreflected to the VCSEL, we show that the noise reduction effect is closely related to random mode coupling because of light scattering by microscopic heterogeneities in the GI POF core material. This suggests that intrinsic mode coupling can lower the self-coupling efficiency of the light backreflected to the VCSEL cavity through beam quality degradation. Using GI POFs, low-cost radio-over-fiber systems for indoor networks can be realized without optical isolators or fiber end-face polishing.

We have evaluated and compared modal noise induced in a graded-index silica multimode fiber (GI-MMF) link and a graded-index plastic optical fiber (GI-POF) link with the misaligned fiber connections. In radio over fiber (RoF) systems using these optical fibers, modal noise appears as unwanted amplitude modulation in the received signal, and results in degradation of the RoF transmission performance. In this work, we have evaluated the modal noise induced in GI-MMFs and GI-POFs with its same core diameter of 50 μm. Our results show that GI-POFs have an inherently higher tolerance to misaligned connection and less modal noise than GI-MMFs in terms of both the error-vector magnitude and the speckle pattern of the transmitted signals.

In this work we analyze experimentally and theoretically the properties of amplified spontaneous emission (ASE) in a rhodamine-6G-doped graded-index polymer optical fiber. A theoretical model based on the laser rate equations describes the ASE features successfully. The dependence of the ASE threshold and efficiency on fiber length is analyzed in detail.

Intrinsic mode coupling in a graded-index plastic optical fiber (GI POF) is investigated using the developed coupled power theory for a GI POF with a microscopic heterogeneous core. The results showed that the intrinsic material properties can induce random power transitions between all the guided modes, whereas the structural deformation of microbending results in nearest-neighbor coupling. It was numerically demonstrated that efficient group-delay averaging due to intrinsic mode coupling brings the pronounced bandwidth enhancement in fibers with much shorter length than the case of glass multimode fibers.

A low loss graded index polymer optical fiber (GI POF) with a wide wavelength range around 650 nm is fabricated using a copolymer of methyl methacrylate and pentafluorophenyl methacrylate as a polymer matrix. Dopant hydrophobicity similar to that of the polymer matrix is an important factor in maintaining the low loss of the GI POF. No loss increment is observed under damp heat conditions of 75°C and 85% relative humidity when using 9-bromo phenanthrene as the high refractive index dopant required to form the GI profile. The copolymer based GI POF can provide an inexpensive premise network with long-term stability.

We propose a novel method of graded index plastic optical fiber (GI POF) to enhance bandwidth. Recently, it has been reported that perfluorinated GI POF with a double cladding structure had much higher bandwidth than theoretical value. The result of analysis of this fiber indicates that the high-bandwidth property is obtained because higher order modes are attenuated at a core and cladding polymer boundary. In addition, it does not induce large increment of attenuation of lower order modes and bending loss. Then, by adopting the rod-in-tube method, we control differential mode attenuation of PMMA based GI POF, and it is proved that bandwidth of GI POF can be enhanced by utilizing scattering of the core and cladding polymer boundary.