Divide-and-Conquer Algorithms for Partitioning Hypergraphs and Submodular Systems

The submodular system k-partition problem is a problem of partitioning a given finite set V into k non-empty subsets V ₁,V ₂,…,V _k so that $\sum_{i=1}^{k}f(V_{i})$ is minimized where f is a non-negative submodular function on V. In this paper, we design an approximation algorithm for the problem with fixed k. We also analyze the approximation factor of our algorithm for the hypergraph k-cut problem, which is a problem contained by the submodular system k-partition problem.     

Genetic and chemical diversity of Eleutherococcus senticosus and molecular identification of Siberian ginseng by PCR-RFLP analysis based on chloroplast trnK intron sequence

Siberian ginseng (SG), the rhizome and root of Eleutherococcus senticosus, has been used as a tonic and anti-fatigue agent in northeastern Asia from ancient time. In recent years, SG has been becoming fairly popular as dietary supplements and health foods worldwide. In order to establish a convenient and sensitive method for authentication, chloroplast trnK intron sequences of 6 Eleutherococcus species were determined and compared. Genetic polymorphism, representing by 14 types of trnK intron sequence, in E. senticosus was observed. However, characteristic nucleotide markers stable within this species enabled clear discrimination of it from other congeners. A PCR-RFLP method was further developed, which was demonstrated to be efficient for authentication of crude drugs as well as health foods. Quantitative evaluation of three main bioactive constituents indicated chemical diversity in E. senticosus collected from northeast China and the results suggested good producing areas of SG. The chemical data clearly revealed that E. sessliflorus was unsuitable to be used as SG.     

Mechanical properties of friction stir butt welds of high nitrogen-containing austenitic stainless steel

In this study, the friction stir butt welding of 2-mm-thick high nitrogen-containing stainless steel (HNS; Ni-free austenitic stainless steel containing 1 mass% nitrogen) plates was performed using a load-controlled friction stir welding (FSW) machine with a Si₃N₄-based tool at various welding speeds, i.e., 50 mm/min, 100 mm/min, 200 mm/min and 300 mm/min, and a constant tool rotating speed of 400 rpm. To determine the optimum welding conditions to create reliable HNS FSW joints, the effect of the heat input on the mechanical properties of the HNS FSW joints was studied. The mechanical properties were evaluated by the Vickers hardness test and the tensile strength test. Full-penetrated and defect-free butt welded joints were successfully produced, under all the applied welding conditions. The stir zones consisted of very fine grained structures and showed an increase in the Vickers hardness. These joints also showed a higher tensile strength and yield strength than the base metal. In particular, the FSW welds obtained at a welding speed of 100 mm/min, which showed the best mechanical properties, had a relatively higher Vickers hardness, which indicates a good relationship between the welding parameter (heat input) and the hardness profile due to the microstructure refinements. It was estimated that these welding conditions were optimal, and under these conditions both grain growth and α-phase formation were prevented.     

Low energy Xe+ ion beam machining of ULE® substrates for EUVL projection optics – Evaluation of high-spatial frequency roughness

Ion beam figuring (IBF) is a suitable technology for the final shape correction of substrates used in the projection optics of EUVL tools. In order to achieve HSFR below 0.10 nm rms, we have conducted our research on ion beam machining of the ULE® substrate by Xe⁺ ion beam with energy less than 2 keV. The HSFR of the unprocessed ULE® surface was 0.06 nm rms, whereas the HSFR of the ULE® substrate machined by under 0.7 keV Xe⁺ ion beam was less than 0.08 nm rms. This HSFR (0.08 nm rms) is lower than that (0.10 nm rms) of the ULE® substrate machined with Ar⁺ ion beam. Therefore, Xe⁺ ion beam with energy under 0.7 keV can be used for figure error correction of the ULE® substrates for projection optics used in commercially available EUVL exposure tools.     

Current concept of the treatment of biliary atresia

Hepatic portoenterostomy (Kasai operation) for the patient with biliary atresia (BA) can restore the bile flow in approximately 80% of children operated on before 60 days of life [1]. However, in terms of long-term survival, according to a recent nationwide survey among the major pediatric centers in Japan, only 325 of 2013 patients had more than 10 years' survival, and only 157 patients (7.8%) remained jaundice-free with normal liver function [2]. About 20% of BA cases without jaundice are generally able to survive for long periods; and most of those patients have portal hypertension or abnormal liver function [3-5]. As the results of liver transplantation have improved, controversy has arisen over the optimal care of these children [4, 6, 7]. Some investigators have claimed that transplantation is the favored primary therapy for most patients with BA [8]. We are thus at a turning point concerning the primary therapy of BA, which makes it necessary to determine the exact indications for the Kasai portoenterostomy and the timing of liver transplantation. This paper describes our strategy for the optimal treatment of BA patients based on our 117 patients who have had various form of portoenterostomy.     

Emergence and takeover of YMDD motif mutant hepatitis B virus during long-term lamivudine therapy and re-takeover by wild type after cessation of therapy

Treatment of hepatitis B virus (HBV) with lamivudine is effective in suppressing virus replication and results in reduced inflammatory activity. However, the emergence of lamivudine-resistant mutant virus, with amino acid substitution in the YMDD motif of DNA polymerase, has been reported. We report the emergence and takeover of YMDD mutant and re-takeover by wild type during and after long-term lamivudine therapy. YMDD mutants were detected in five patients who showed DNA breakthrough (HBV DNA becoming detectable after a period of DNA negativity), which occurred after 9 to 14 months of lamivudine therapy. Four of five mutants had amino acid sequence YIDD, and the remaining mutant had YVDD. Patients with high HBV-DNA titer and/or hepatitis B e antigen tended to develop breakthrough (P = .038). Using a sensitive and specific polymerase chain reaction (PCR)-based method developed in this study, the emergence of YMDD mutants was detected 1 to 4 months before DNA breakthrough, but not detected in any of the pretreatment sera. The mutants were predominant at breakthrough, but were replaced by wild-type virus 3 to 4 months after cessation of therapy in the two patients who discontinued therapy. One of these patients had a relapse of hepatitis. Mutant continued to replicate in the remaining three patients who continued to receive treatment, and relapse occurred in only one of these patients. Our results suggest that the replication of YMDD mutant viruses is less than wild type and is re-overtaken by wild type after cessation of therapy. Re-administration of lamivudine, possibly combined with other antiviral therapy, might be useful in some patients experiencing hepatitis with lamivudine-resistant variants.     

Effect of Physical Aging on the Creep Deformation of an Epoxy Resin

This paper is concerned with an experimental study of the theinfluence of physical aging and temperature on the creep deformation ofepoxy resin. Master curves for various aging conditions were found tocollapse into a single smooth curve corresponding to a reference agingcondition after suitable horizontal translation. It is proposed that theresulting curve be designated the master-master curve and thecorresponding time scale the reduced-reduced time. In addition, theamount of horizontal translation, the aging parameter, can be used toestimate the aging process. We have also shown that there is one-to-onecorrespondence between the aging parameter and polymer density.     

Stress Intensity Controlled Kinetic Crack Growth and Stress History Dependent Life Prediction with Statistical Variability

Consistent with viscoelastic behavior, a power law form in terms of the stress intensity factor is used to specify crack kinetics (growth rate) in the central crack problem under Mode I conditions. The crack growth rate is integrated to obtain the crack size and thereby the stress intensity factor as a function of time. The crack is allowed to grow in a controlled, load dependent manner until it reaches the size at which it becomes unstable. The corresponding time at which this occurs is taken as the lifetime of the material under the specified load history. The special cases of constant load (creep rupture) and constant strain rate to failure are found to have a very simple relationship with each other. This lifetime relationship is verified through the comparison with corresponding data upon a polymeric composite. Finally the creep rupture case is generalized to a probabilistic formalism. The theoretically predicted lifetime distribution functions are verified with data, also upon a polymeric composite. Possible extension of the entire formalism to cyclic fatigue in metals is discussed. Dedicated to Professor Z.P. Bažant for his many contributions.     

Verification method for durability of reinforced concrete structures subjected to salt attack under high temperature conditions

Immersion tests of concrete specimens, corrosion tests of reinforced concrete specimens and combination tests of carbonation and chloride ion penetration of concrete specimens were conducted under high temperature. Verification method of durability against salt attack to reinforced concrete structures under high temperature was discussed. The obtained results were summarized as follows. (a) Diffusion coefficient of chloride ion in concrete increased as temperature rose. The relationship between the logarithm of diffusion coefficient and the reciprocal of temperature showed linearity. (b) The chloride ion concentration of reinforcing steel corrosion initiation did not decrease at high temperature. (c) Diffusion coefficient of chloride ion might be larger in carbonated concrete. (d) Based on the test results, a verification method of durability against salt attack on reinforced concrete structures under high temperature up to 65 °C, for avoiding steel corrosion, was proposed.