Curvature-induced phase transitions in the inflationary universe - Supersymmetric Nambu-Jona-Lasinio Model in de Sitter spacetime -

The phase structure associated with the chiral symmetry is thoroughly investigated in de Sitter spacetime in the supersymmetric Nambu-Jona-Lasinio model with supersymmetry breaking terms. The argument is given in the three and four space-time dimensions in the leading order of the 1/N expansion and it is shown that the phase characteristics of the chiral symmetry is determined by the curvature of de Sitter spacetime. It is found that the symmetry breaking takes place as the first order as well as second order phase transition depending on the choice of the coupling constant and the parameter associated with the supersymmetry breaking term. The critical curves expressing the phase boundary are obtained. We also discuss the model in the context of the chaotic inflation scenario where topological defects (cosmic strings) develop during the inflation.Comment: 29 pages, 6 figures, REVTe

New Development of the J -Based Fracture Testing Technique for Ceramic-Matrix Composites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65733/1/j.1151-2916.1994.tb09756.x.pd

Engineering ductile fracture in brittle-matrix composites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43023/1/10855_2004_Article_BF00455611.pd

Space-time evolution induced by spinor fields with canonical and non-canonical kinetic terms

We study spinor field theories as an origin to induce space-time evolution. Self-interacting spinor fields with canonical and non-canonical kinetic terms are considered in a Friedman-Robertson-Walker universe. The deceleration parameter is calculated by solving the equation of motion and the Friedman equation, simultaneously. It is shown that the spinor fields can accelerate and decelerate the universe expansion. To construct realistic models we discuss the contributions from the dynamical symmetry breaking.Comment: 16 pages, 19 figure

Experimental determination of the stress-crack opening relation in fibre cementitious composites with a crack-tip singularity

A J -based-fracture-testing method is presented for determining the bridging-stress-crackopening-displacement (σ-δ) relationship in fibre-reinforced composites where the crack-tip toughness is not negligible. The J -based technique originally proposed for concrete has been well-established for cementitious composites where the fracture process is primarily dominated by the formation of a fracture-process zone and the contribution of the crack-tip toughness is negligibly small. In this study, the J -based technique is further extended to cover materials for which the crack-tip stress singularity coexists with the fracture-process zone. This extended version of the J -based technique explicitly accounts for the crack-tip singularity while considering the fracture-process zone. This newly derived testing technique has been applied to a high-strength-mortar (HSM) reinforced with carbon and steel fibres where the fibrebridging toughness can be of the same order of magnitude as the crack-tip toughness. The validity of the σ-δ relationships deduced has been examined by comparing with results obtained from direct uniaxial tension tests. It is suggested that the J -based-fracture-testing technique can provide reasonable σ-δ relationships and fracture parameters in a fibrereinforced HSM.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44728/1/10853_2004_Article_BF00356823.pd

MSH3 polymorphisms and protein levels affect CAG repeat instability in huntington's disease mice

Expansions of trinucleotide CAG/CTG repeats in somatic tissues are thought to contribute to ongoing disease progression through an affected individual's life with Huntington's disease or myotonic dystrophy. Broad ranges of repeat instability arise between individuals with expanded repeats, suggesting the existence of modifiers of repeat instability. Mice with expanded CAG/CTG repeats show variable levels of instability depending upon mouse strain. However, to date the genetic modifiers underlying these differences have not been identified. We show that in liver and striatum the R6/1 Huntington's disease (HD) (CAG)~100 transgene, when present in a congenic C57BL/6J (B6) background, incurred expansion-biased repeat mutations, whereas the repeat was stable in a congenic BALB/cByJ (CBy) background. Reciprocal congenic mice revealed the Msh3 gene as the determinant for the differences in repeat instability. Expansion bias was observed in congenic mice homozygous for the B6 Msh3 gene on a CBy background, while the CAG tract was stabilized in congenics homozygous for the CBy Msh3 gene on a B6 background. The CAG stabilization was as dramatic as genetic deficiency of Msh2. The B6 and CBy Msh3 genes had identical promoters but differed in coding regions and showed strikingly different protein levels. B6 MSH3 variant protein is highly expressed and associated with CAG expansions, while the CBy MSH3 variant protein is expressed at barely detectable levels, associating with CAG stability. The DHFR protein, which is divergently transcribed from a promoter shared by the Msh3 gene, did not show varied levels between mouse strains. Thus, naturally occurring MSH3 protein polymorphisms are modifiers of CAG repeat instability, likely through variable MSH3 protein stability. Since evidence supports that somatic CAG instability is a modifier and predictor of disease, our data are consistent with the hypothesis that variable levels of CAG instability associated with polymorphisms of DNA repair genes may have prognostic implications for various repeat-associated diseases

Direct CP violation in semi-inclusive flavor-changing neutral current decays in the MSSM without R−R-parity

Semi-inclusive decays, \hlx, are studied in the framework of the minimal supersymmetric standard model without $R-$parity, where \qh (\ql) are the second or third (first or second) generation quarks with the same charge and $\xi$ is a vector meson formed by q_j \qb_j. The study is focused on the contributions of sfermions with $m_{\sf} < m_{\rm top}$. In this mass region, CP asymmetries in top decays can be induced by taking into account the decay-widths of the exchanged-bosons, while in light-quark decays it can be generated due to the long-distance effects. The contributions of sfermions also alter the branching-ratios destructively or constructively depend on the phases of complex couplings of the $R-$parity violation interactions.Comment: 12 pages, LaTeX, 6 figures are include

Pull-out simulations of a capped carbon nanotube in carbon nanotube-reinforced nanocomposites

Author name used in this publication: Zhou, L.2012-2013 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe