Dynamic buckling experiments of fluid-structure-coupled co-axial thin cylinder

The purpose of this paper is to clarify dynamic buckling behaviours such as buckling mode and buckling pressure for thin cylindrical shells immersed in fluid subjected to seismic excitations. For this purpose, dynamic buckling experiments of thin cylindrical shells placed inside a rigid liquid container are carried out using a shaking table. These shells and the container are intended to represent thermal baffles and a main vessel of a fast breeder reactor, respectively. The fluid pressure caused by horizontal excitation induces buckling deformation which involves flower-shaped deformation, which is a type of external pressure buckling. The buckling pressure is measured with various types of the test cylinders under seismic excitations and this pressure is confirmed to agree with static buckling pressure predicted by static buckling analysis. It is also found that sub-harmonic vibration occurs under a certain sinusoidal excitation inducing a sudden increase in response displacement at a lower pressure level than the buckling pressure under seismic excitations. Based on these experiments, it is pointed out that, in seismic design, to prevent the buckling of thermal baffles, static buckling analyses can be used as long as sub-harmonic vibration does not occur.     

Adsorption of Biomineralization Protein Mms6 on Magnetite (Fe3O4) Nanoparticles

Biomineralization is an elaborate process that controls the deposition of inorganic materials in living organisms with the aid of associated proteins. Magnetotactic bacteria mineralize magnetite (Fe₃O₄) nanoparticles with finely tuned morphologies in their cells. Mms6, a magnetosome membrane specific (Mms) protein isolated from the surfaces of bacterial magnetite nanoparticles, plays an important role in regulating the magnetite crystal morphology. Although the binding ability of Mms6 to magnetite nanoparticles has been speculated, the interactions between Mms6 and magnetite crystals have not been elucidated thus far. Here, we show a direct adsorption ability of Mms6 on magnetite nanoparticles in vitro. An adsorption isotherm indicates that Mms6 has a high adsorption affinity (Kd = 9.52 µM) to magnetite nanoparticles. In addition, Mms6 also demonstrated adsorption on other inorganic nanoparticles such as titanium oxide, zinc oxide, and hydroxyapatite. Therefore, Mms6 can potentially be utilized for the bioconjugation of functional proteins to inorganic material surfaces to modulate inorganic nanoparticles for biomedical and medicinal applications.     

Chemistry,Properties, and in Vitro and in Vivo Applications of 2′‐O‐Methoxyethyl‐4′‐thioRNA,a Novel Hybrid Type of Chemically Modified RNA

We report the synthesis, properties, and in vitro and in vivo applications of 2′‐O‐methoxyethyl‐4′‐thioRNA (MOE‐SRNA), a novel type of hybrid chemically modified RNA. In its hybridization with complementary RNA, MOE‐SRNA showed a moderate improvement of T_m value (+3.4 °C relative to an RNA:RNA duplex). However, the results of a comprehensive comparison of the nuclease stability of MOE‐SRNA relative to 2′‐O‐methoxyethylRNA (MOERNA), 2′‐O‐methyl‐4′‐thioRNA (Me‐SRNA), 2′‐O‐methylRNA (MeRNA), 4′‐thioRNA (SRNA), and natural RNA revealed that MOE‐SRNA had the highest stability (t_1/2>48 h in human plasma). Because of the favorable properties of MOE‐SRNA, we evaluated its in vitro and in vivo potencies as an anti‐microRNA oligonucleotide against miR‐21. Although the in vitro potency of MOE‐SRNA was moderate, its in vivo potency was significant for the suppression of tumor growth (similar to that of MOERNA).     

Isolation and characterization of barosensitive mutants of Saccharomyces cerevisiae obtained by UV mutagenesis

Using UV mutagenesis, 2 high-pressure (HP) sensitive (barosensitive) mutants of Saccharomyces cerevisiae were obtained. The HP inactivation of the mutants, as well as their parent strains, followed 1st-order kinetics in the range of 175 to 250 MPa within 600 s. Both mutants showed larger 1st-order inactivation rate constant values or significant loss of viabilities, compared with their parent strains in the pressure range tested. The inactivation rate constant value of one of the mutants was comparable with that of a previously reported highly barosensitive strain, which was generated by deletion of hsp104 in a trehalose deficient strain. The activation volume values of HP inactivation reactions in the 2 mutants were apparently equivalent with those of their parent strains. This suggested that the mutation did not bring drastic volume changes of the key molecules for HP inactivation. Their auxotrophic properties, growth, and ethanol fermentation were identical in mutant and parent strains. The mutants could therefore be useful for fermentations where control by HP processing is desired.     

Stability of oil–water primary emulsions stabilised with varying levels of casein and whey proteins affected by high-intensity ultrasound

This study evaluates physical and chemical stability of ultrasound-assisted grape seed oil primary emulsions stabilised by varying compositions of caseins to whey proteins (80:20, 60:40, 50:50 and 40:60) at different sono-operating conditions (81.9 and 117.0 J mL⁻¹). Physical and chemical stabilities were influenced by both sonication energy densities and milk protein compositions. Emulsions prepared at 81.9 J mL⁻¹ energy density with ≥40% whey protein fraction (60:40, 50:50, 40:60 and WPI) showed greater physical stability than the emulsions sonicated at 117.0 J mL⁻¹ which exhibited physical instability due to the depletion flocculation mechanism at the critical casein concentration (≥40%). The emulsion oxidative stability was found to be affected by sonication conditions as 117.0 J mL⁻¹ induced the oxidation reactions once the whey concentration exceeds 40%. Therefore, ultrasound prepared emulsions with casein to whey ratios of 60:40, 50:50, 40:60 and WPI at 81.9 J mL⁻¹ energy density was found to be stable for 10 days at 4 °C.     

Inflammatory Molecules Associated with Ultraviolet Radiation-Mediated Skin Aging

Skin is the largest and most complex organ in the human body comprised of multiple layers with different types of cells. Different kinds of environmental stressors, for example, ultraviolet radiation (UVR), temperature, air pollutants, smoking, and diet, accelerate skin aging by stimulating inflammatory molecules. Skin aging caused by UVR is characterized by loss of elasticity, fine lines, wrinkles, reduced epidermal and dermal components, increased epidermal permeability, delayed wound healing, and approximately 90% of skin aging. These external factors can cause aging through reactive oxygen species (ROS)-mediated inflammation, as well as aged skin is a source of circulatory inflammatory molecules which accelerate skin aging and cause aging-related diseases. This review article focuses on the inflammatory pathways associated with UVR-mediated skin aging.     

Generalization of effect of oxygen exposure on formation and performance of carbon molecular sieve membranes

Previously, a pyrolysis method was developed to control separation performance of carbon molecular sieve (CMS) membranes by doping with trace oxygen. This method involved oxygen exposure during pyrolysis to tune the selective pore windows. During the development, it was observed that oxygen concentration in inert gas, rather than the total amount of oxygen exposed controls performance. In this study, we hypothesized that mass transfer of oxygen in CMS membranes during pyrolysis is governed by chemical reaction at critical pore opening. Effect of thermal soak time, inert flow rate, and precursor thickness were conducted to test this hypothesis with 6FDA/BPDA-DAM and Matrimid® polymer precursors. Results of oxygen consumption from pyrolysis process and CO₂/CH₄ separation performance showed that the process is likely governed by reaction kinetics. This observation implies simplicity and easy scale-up for the oxygen “doping” method on CMS formation by tuning the oxygen concentration in the pyrolysis atmosphere.     

Theory of volume phase transition of slide-ring gels

Volume phase transition is a phenomenon in which gels drastically swell or shrink with an infinitesimal change in the external environment. This behavior is well explained by the Flory–Rehner–Tanaka theory. However, some assumption in the theory breaks down in a slide-ring gel composed of grand canonical chains in which the segment number between cross-linking junctions can change. The stress–strain behavior of the slide-ring gel is in a qualitative agreement with the free junction model, in which the segment number changes to maximize the entropy under the condition that the total sum of the segment number is constant. However, the model cannot work well to isotropic swelling of the slide-ring gel. To describe the volume phase transition of the slide-ring gel, we propose a new theory based on the free junction model with the effects of dangling strands, uncross-linked cyclic molecules (free rings), and high elongation. As a result, it turns out that the exchange of segments between effective and dangling strands leads to the suppression of the volume phase transition in the highly cross-linked gel and the promotion in the loosely cross-linked one. The suppression and promotion of the volume phase transition became more obvious as free rings decreased.