Control of solute permeability based on pH-induced reversible conformational change in block copolypeptide membrane

An ABBA-type block copolypeptide membrane composed of L -glutamic acid (A) and L -leucine (B) was prepared, and a solute permeability of the membrane was studied. According to the observation of electron microscope, the membrane had the phase-separated morphology that the domains consisting of poly(L -glutamic acid) blocks are emebedded in a continuous matrix of the poly(L -leucine) phase. The reversible conformational change of the poly(L -glutamic acid) from α-helix to random coil induced by changing the pH of the external medium was presumed to occur in the domains on the basis of the results of infrared absorption spectra. In the pH dependence of the diffusion coefficients of KCl, NaCl, and LiCl in the membrane, a considerable decrease was found at about pH 4, and thought to result from the conformational transition. In an acidic medium, the permeability of KCl, NaCl, and NiCl was higher then that of glucose, but this order was reversed in higher pHs. These results indicate that the poly(L -glutamic acid) domains in the membrane function as channels for solute transport.     

R/G and Y/B opponent-color mechanisms revealed in temporal integration for bichromatically mixed lights

In the present study, the critical durations for temporal integration at theshold were obtained for bichromatically mixed (red/green and yellow/blue) test lights presented against darkness and achromatic backgrounds of different intensities. Critical durations crucially depended on the mixing ratio of the red and green components: it was shortest when red and green components were balanced in intensity canceling chromaticness of both components, and longer for red and green monochromatic lights. This trend was pronounced with backgrounds of higher intensities but was not obvious with dim backgrounds. The results of yellow/blue condition showed that critical durations were shorter when yellow component was dominant, as well as when yellow and blue components were balanced in intensity canceling chromaticness of both components, but when blue monochromatic light was dominant, it was longer than in other mixture conditions and changed less with the elevation of the background intensity. The results were interpreted as demonstraing the red/green and yellow/blue opponet-color mechanism's participation.     

Enhancing water flux through semipermeable polybenzimidazole membranes by adding surfactant‐treated CNTs

In this study, surfactant‐treated carbon nanotubes (CNTs) were incorporated into polybenzimidazole (PBI) matrix to prepare the PBI/CNT composite membranes with CNT content in the range of 0 to 15 wt %. The composite membranes were fabricated by spin‐coating. The membrane morphology, mechanical property, and water and salt transport properties were investigated to characterize the additive effect of CNTs. The tensile strength of all the PBI/CNT composite membranes was lower than that of pristine PBI membrane, indicating the weak interaction between CNT and PBI. In addition, water flux increased without reducing the salt rejection when CNTs were homogeneously dispersed in the PBI matrix at a less than 7.5 wt % content. On the other hand, at 10 wt % and higher CNT content, submicro‐scaled cellular structure was formed, and both the water flux and salt rejection decreased. The well‐dispersed CNTs in the PBI matrix via weak interaction preferentially improve the water permeability by 1.7 times without depressing the salt rejection. The incorporation of well‐dispersed CNTs in polymer matrix provides a promising and facile option for improvement in the water transport properties through the polymeric semipermeable membranes with intrinsically low water permeability such as PBI. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45875.     

Biodegradability study of copolyesteramides based on diacid chlorides,diamines, and diols

Copolyesteramides were synthesized by polycondensation of diacid chlorides, diamines, and diols of varying methylene group chain length. The composition of the synthesized polymer was determined with nuclear magnetic resonance (NMR) analysis. The biodegradation of the polymers was evaluated both with enzymatic hydrolysis and activated sludge test. The polymers were hydrolyzed with lipases from Rhizopus arrhizus, Rhizopus delemar, Candida cylindracea, and an esterase from hog liver, whereas trypsin and α‐chymotrypsin did not have any apparent effect upon them. Enzymatic hydrolysis was found to be greatly affected by the polymer composition and structure. The degradation results obtained from the activated sludge test were in satisfactory agreement with those from enzymatic hydrolysis. The water‐soluble parts of hydrolyzed products were more susceptible to degradation of their ester bonds rather than their amide bonds. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 774–784, 2002     

Biodegradability of Plastics

Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed.     

Extension of the Newcomb equation into the vacuum for the stability analysis of tokamak edge plasmas

The formulation for solving numerically the two-dimensional Newcomb equation has been extended to calculate the vacuum energy integral by using a vector potential method. According to this extension, a stability code MARG2D has been adapted, and coded for parallel computing in order to reduce substantially the CPU time. The MARG2D code enables a fast stability analysis of ideal external MHD modes from low to high toroidal mode numbers on the basis of the single physical model, and then the code works as a powerful tool in an integrated simulation where it is combined with transport codes, and also in the analysis of tokamak edge plasma experiments.     

Conservative global gyrokinetic toroidal full-f five-dimensional Vlasov simulation

A new conservative global gyrokinetic toroidal full-f five-dimensional Vlasov simulation (GT5D) is developed using a novel non-dissipative conservative finite difference scheme. The scheme guarantees numerical stability by satisfying relevant first principles in the modern gyrokinetic theory, and enables robust and accurate simulations of tokamak micro-turbulence. GT5D is verified through comparisons of zonal flow damping tests, linear analyses of ion temperature gradient driven (ITG) modes, and nonlinear ITG turbulence simulations against a global gyrokinetic toroidal δf particle code. In the comparison, global solutions of the ITG turbulence are identified quantitatively by using two gyrokinetic codes based on particle and mesh approaches.     

Heat transfer around a circular cylinder in separated air flow

An experimental study has been conducted to determine the heat transfer characteristics around a circular cylinder attached to the separated flow of air shed from a fence. The fence was located vertically to the flow with a height of H = 40 mm. d/H was constant at 0.638, where d is the cylinder diameter of 25.5 mm. X/H were 0.50 and 0.775 and Y/H ranged from 0.525 to 1.50, where X and Y are, respectively, the distances between the axis of the cylinder and the front face of the fence, and the bottom wall of the test section. The Reynolds number based on the cylinder diameter and the velocity of the undisturbed flow ranged from 1.9 × 10⁴ to 6.0 × 10⁴. It was found that the maximum local Nusselt number changes drastically in the vicinity of Y/H = 1.0–1.11 and that the maximum mean Nusselt number occurs in the neighborhood of Y/H = 1.24–1.43 for X/H = 0.50 and 1.3–1.4 for X/H = 0.775. © 1999 Scripta Technica, Heat Trans Asian Res, 28(3): 211–226, 1999     

Modification of Acid Anhydride-cured Epoxy Resins By N-Phenyl- maleimide–Styrene Copolymers and N-Phenylmaleimide–Styrene– p-Hydroxystyrene Terpolymers

N-Phenylmaleimide–styrene copolymers (PMS) and reactive N-phenylmaleimide–styrene–p-hydroxystyrene (HSt) terpolymers (PMSH) containing p-hydroxyphenyl groups were used to improve the toughness of bisphenol A diglycidyl ether epoxy resin cured with methyl hexahydrophthalic anhydride. PMS and PMSH were effective modifiers for epoxies. The morphologies of the modified resins depended on modifier structure and content. The most effective modification for the cured resins was attained because of the co-continuous structure of the modified resins in both PMS and PMSH modification systems. When using 15wt% of PMS (M¯_w 125000), the fracture toughness, K_IC, for the modified resin increased by 230%, with retention of flexural modulus and glass transition temperature, but with a loss of flexural strength, compared with the values for the unmodified epoxy resin. When using PMSH as the reactive modifier, the efficiency decreased with increase in HSt content, because of the increasing extent of dispersion of the PMSH-rich continuous phases. In the modification with 10wt% PMSH (1·0mol% HSt unit, M¯_w 294000), the modified resin had balanced physical properties. © of SCI.     

An increased ratio of interleukin-1 receptor antagonist to interleukin-1alpha in inflammatory skin diseases

IL-1 receptor antagonist (IL-1ra) is a cytokine that competitively binds the IL-1 receptor to antagonize IL-1 activity without any agonist function. Previous experiments indicated that the ratio of IL-1ra to IL-1alpha in the normal stratum corneum (SC) was much higher in the sun-exposed face than in the sun-protected area, upper arms. It was also reported by another laboratory that IL-1ra is increased in the lesional skin of psoriatic patients. This study was designed to measure the contents of IL-1alpha and IL-1ra in non-lesional and pathological SC obtained from inflammatory skin diseases including psoriasis and non-psoriatic dermatoses such as atopic dermatitis. The SC materials were obtained with a non-invasive tape-stripping method. Their soluble fractions were prepared and assayed for IL-1alpha and IL-1ra by enzyme-linked immunosorbent assays. As a result we confirmed the previous findings that the ratio of IL-1ra to IL-1alpha in the normal SC was much higher in the face than in the sun-protected sites, the trunk as well as extremities. Next, we found that IL-1alpha contents were significantly reduced in the SC samples obtained from inflammatory skin regardless of whether their IL-1ra contents increased or unchanged. Moreover, we noted that an increased ratio of IL-1ra to IL-1alpha in the SC was not specific to psoriasis, but was also found in other inflammatory skin diseases including atopic dermatitis. This ratio was found to become lower after successful treatment of these skin lesions with topical glucocorticoids. We conclude from these observations that the increased ratio of IL-1ra to IL-1alpha in the SC is a non-specific phenomenon that can occur in any inflammatory skin diseases regardless of the inflammatory pattern, probably reflecting a skin regulation process against various kinds of inflammation.