Ultimate strength of compressed stiffened plates and minimum stiffness ratio of their stiffeners

A theoretical investigation into the effectiveness of a stiffener against the ultimate strength of a stiffened plate is carried out. Series of the buckling analyses, the elastic large deflection analyses and the elastic-plastic large deflection analyses are performed by the analytical method and the finite element method on the stiffened plate under thrust. Experiments are also carried out on the stiffened plate under thrust to confirm the theoretical results.On buckling of a stiffened plate, it is well known that ther exxists a minimum stiffness ratio of a stiffener to the plate, $\text{λ}{}^{\mathrm{B}}{}_{\min }$, which gives the maximum limiting value of the buckling strength. Concerning the ultimate strength it was confirmed that there exists a significant stiffness ratio of a st stiffener to the plate, $\text{λ}{}^{\mathrm{U}}{}_{\min }$ similar to $\text{λ}{}^{\mathrm{B}}{}_{\min }$ for the buckling strength.It was also found that there are three typical collapse modes for the stiffened plate under thrust, that is: (1) MODE OO, overall collapse after overall buckling; (2) MODE LO, overall collapse after local buckling; (3) MODE LL, local collapse after local buckling.Approximatelmethods are proposed to evaluate the ultimate strength and $\text{λ}{}^{\mathrm{U}}{}_{\min }$ of a multi-stiffened plate under thrust.The effects of initial imperfections such as welding residual stresses and initial deflection on ultimate strength and $\text{λ}{}^{\mathrm{U}}{}_{\min }$ of a stiffened plate under thrust are also discussed.     

Formation of hydroxyapatite layer on bioactive Ti and Ti–6Al–4V by simple chemical technique

Bioactive coatings on cp-Ti and Ti–6Al–4V were prepared by a simple chemical technique. Specimens of cp-Ti and Ti–6Al–4V were initially immersed in a 5 M NaOH solution at 60 °C for 24 h which resulted in the formation of a porous network structure composed of Na₂Ti₅O₁₁ and TiO₂. The specimens were then immersed in a Ca-rich solution either at 60 °C or at 36.5 °C for 24 h. During this treatment Na⁺ was released and Ti–OH groups were formed. Subsequently, TiO₂ dissociated from the Ti–OH group and combined with calcium ions to form calcium titanate (CaTiO₃), which was embedded in a titania gel layer during the immersion period. The specimens were then immersed in r-SBF at 36.5 °C for 1–30 days. After immersion in r-SBF for 3 days, HAp (hydroxyapatite) spheroids began to deposit on the substrates, and within a week the surfaces were covered. The HAp spheroids were 5 μm in size with a Ca/P ratio of 1.68 which was close to bone-like apatite (1.67). The average thicknesses of HAp layer after immersion in r-SBF for 3 days, 1 week, and 2 weeks were 3.8, 5.6, and 6.4 μm, respectively. A scratch test, used to evaluate the adhesive strength of the HAp layer, showed that the HAp layer was not scraped off until the applied load reached 26 N.     

Roles of rare earth oxide additives in millimeter-wave sintering of AlN

Roles of rare earth oxide (RE2O3) additives in millimeter-wave(MM) sintering of AlN were investigated from the standpoints of phase diagram, heating characteristics of rare earth oxides, and morphology of intergranular oxide phase. In the millimeter-wave sintering of AlN, densification temperature decreased with the decrease of the ionic radius of rare earth ion and was closely related with the eutectic temperature in the RE2O3-Al2O3 binary system. The lowest densification temperature in the millimeter-wave sintering of AlN with Yb2O3 additive was attributed to the largest heating rate of Yb2O3·Al2O3 binary oxide under millimeter-wave radiation. Furthermore, the lowest densification temperature could be attained while selecting the Yb2O3 content so as to form the intergranular phase with the eutectic composition in the Yb2O3-Al2O3 binary system. The result showed good agreement with the above mentioned during the sintering of Si3N4 with Yb2O3-Al2O3 additive. From TEM observation, it was verified that film-like intergranular oxide phase formed under millimeter-wave radiation was favorable for attaining high thermal conductivity in the Yb2O3 added AlNs.     

Enhanced growth inhibition of hepatic multicellular tumor spheroids by lactosylated poly(ethylene glycol)-siRNA conjugate formulated in PEGylated polyplexes

PEGylated polyplexes (lac-PEGylated polyplexes) composed of poly(L-lysine) and lactosylated poly(ethylene glycol)-small interfering RNA conjugate, which inhibits the RecQL1 gene product, were revealed to show an appreciable growth inhibition of multicellular HuH-7 spheroids (human hepatocarcinoma cell lines) for up to 21 days (IC(50)=6 nM); this system used as an in vitro three-dimensional (3D) model mimicking the in vivo biology of tumors. The PEGylated polyplexes thus prepared had a size of approximately 110 nm with clustered lactose moieties on their periphery as targeting ligands for the asialoglycoprotein-receptor-expressing HuH-7 cells. In contrast, OligofectAMINE/siRNA (cationic lipoplex) was observed to have almost no growth-inhibitory effect against HuH-7 spheroids, even though the lipoplex showed a stronger growth-inhibitory effect than the lac-PEGylated polyplexes on conventional monolayer-cultured HuH-7 cells. The FITC-tagged conjugate in the lac-PEGylated polyplexes showed smooth penetration into the HuH-7 spheroids compared with that in the lipoplexes, as observed by confocal fluorescence-scanning microscopy. This indicates that the small size of approximately 100 nm and the reduced nonspecific interaction due to the nonionic and hydrophilic lactosylated PEG layer contributes to the smooth penetration of the PEGylated polyplexes into the spheroid interior, eventually facilitating their uptake into the cells composing the spheroids. Cellular apoptosis indicating programmed cell death was also observed in the HuH-7 spheroids treated with the PEGylated polyplexes, revealing that the observed growth inhibition was indeed induced by the RNAi of the RecQL1 siRNA. These data suggest that the smart PEGylated polyplexes can indeed penetrate into the multiple cell layers of 3D tumor masses in vivo, exerting therapeutic effects through the RNAi.     

Detection of irradiated meat, fish and their products by measuring 2-alkylcyclobutanones levels after frozen storage

2-Alkylcyclobutanones, such as 2-dodecylcyclobutanone and 2-tetradecylcyclobutanone, were analyzed to assess the irradiation history of irradiated meats or fish, and cooked foods with irradiated ingredients, which had been stored frozen for up to one year. The purpose of the study was to show that irradiated meats could be detected even after having been stored in the distribution system. 2-Alkylcyclobutanones showed a small decrease in irradiated raw meats that had been stored frozen for one year. Cooked foods, such as pancake and fried chicken made with irradiated eggs and chicken, respectively, contained detectable levels of 2-alkylcyclobutanones after storage frozen for one year. The 2-alkylcyclobutanones became undetectable in highly dried samples, such as feed for lab animals, during the same period.     

Investigation of pathways of advanced glycation end-products accumulation in macrophages

Advanced glycation end-products (AGE) play a role in the pathogenesis of several diseases, including diabetic complications and atherosclerosis. In atherosclerotic lesions of human aortas, AGE are localized in the extracellular matrix and intracellularly in foam cells. Two interpretations are possible for AGE accumulation inside macrophages, one is endocytic uptake of extracellular AGE-proteins by scavenger receptors; the other is intracellular AGE formation inside the macrophages. In the present study, we determined the pathways involved in AGE accumulation inside macrophages. RAW 264.7 cells, a murine macrophage cell line, incubated with BSA and 1600 mM glucose for 40 weeks, recognized heavily modified AGE- BSA. In contrast, the cells showed no ligand activity for mildly modified AGE-BSA, prepared by incubating BSA with 50 mM glucose for 24 weeks. Nepsilon-(carboxymethyl)lysine (CML)-modified proteins of about 65 kDa were detected in human monocyte-derived macrophages incubated for 7 days with 30 mM glucose and phorbol myristate acetate. Furthermore, CML was generated when glycated protein was incubated with hypochloric acid. Taken together, our results indicate that AGE detected inside foam cells in atherosclerotic lesions are generated intracellularly rather than representing endocytic uptake of extracellular AGE-proteins by scavenger receptors.     

Deciphering the Biological Significance of ADAR1–Z-RNA Interactions

Adenosine deaminase acting on RNA 1 (ADAR1) is an enzyme responsible for double-stranded RNA (dsRNA)-specific adenosine-to-inosine RNA editing, which is estimated to occur at over 100 million sites in humans. ADAR1 is composed of two isoforms transcribed from different promoters: p150 and N-terminal truncated p110. Deletion of ADAR1 p150 in mice activates melanoma differentiation-associated protein 5 (MDA5)-sensing pathway, which recognizes endogenous unedited RNA as non-self. In contrast, we have recently demonstrated that ADAR1 p110-mediated RNA editing does not contribute to this function, implying that a unique Z-DNA/RNA-binding domain α (Zα) in the N terminus of ADAR1 p150 provides specific RNA editing, which is critical for preventing MDA5 activation. In addition, a mutation in the Zα domain is identified in patients with Aicardi–Goutières syndrome (AGS), an inherited encephalopathy characterized by overproduction of type I interferon. Accordingly, we and other groups have recently demonstrated that Adar1 Zα-mutated mice show MDA5-dependent type I interferon responses. Furthermore, one such mutant mouse carrying a W197A point mutation in the Zα domain, which inhibits Z-RNA binding, manifests AGS-like encephalopathy. These findings collectively suggest that Z-RNA binding by ADAR1 p150 is essential for proper RNA editing at certain sites, preventing aberrant MDA5 activation.     

Polypropylene composites with fine particles of poly(styrene‐divinylbenzene)

Polypropylene composites were prepared by copolymerizing styrene and divinylbenzene in molten polypropylene by using an extruder. The resultant copolymers are of very fine particles uniformly dispersed in polypropylene phase with no aggregation. The properties of the resultant polypropylene composites were studied: crystalline structure, and mechanical, dynamic viscoelastic, and thermal properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1614–1620, 2000     

Short‐circuit phenomenon through hot gas ejected from molded case circuit breakers during high current interruption process and prevention of its occurrence

An experimental investigation on short‐circuit phenomenon through ejected hot gas between source‐side terminals in molded case circuit breakers (MCCBs) was performed. The rate of occurrence of the short‐circuit phenomenon was found to increase with the peak value of the breaking current and with the order of the breaking test. The conductance of the ejected hot gas was also found to rise with the peak value of the breaking current and with the order of the breaking test. These results indicate that the hot gas of high conductance is the cause of the short‐circuit phenomenon. Some effective means were taken in the MCCB to reduce the conductance of the hot gas. Decreasing the conductance of the hot gas successfully prevented the occurrence of short‐circuit phenomenon. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 22–29, 2000