A thermostable leucine aminopeptidase from Bacillus kaustophilus CCRC 11223

Two degenerate primers established from the consensus sequences of bacterial leucine aminopeptidases (LAP) were used to amplify a 360-bp gene fragment from the chromosomal DNA of thermophilic Bacillus kaustophilus CCRC 11223 and the amplified fragment was successfully used as a probe to clone a leucine aminopeptidase (lap) gene from a genomic library of the strain. The gene consists of an open reading frame (ORF) of 1,494 bp and encodes a protein of 497 amino acid residues with a calculated molecular mass of 53.7 kDa. The complete amino acid sequence of the cloned enzyme showed greater than 30% identity with prokaryotic and eukaryotic LAPs. Phylogenetic analysis showed that B. kaustophilus LAP is closely related to the enzyme from Bacillus subtilis and is grouped with the M17 family. His(6)-tagged LAP was generated in Escherichia coli by cloning the coding region into pQE-30 and the recombinant enzyme was purified by nickel-chelate chromatography. The pH and temperature optima for the purified enzyme were 8 and 65degreesC, respectively, and 50% of its activity remained after incubation at 60degreesC for 32 min. The enzyme preferentially hydrolyzed L-leucine-p-nitroanilide (L-Leu-p-NA) followed by Cys derivative

A new constitutive model for prediction of impact rates response of polypropylene

This paper proposes a new constitutive model for predicting the impact rates response of polypropylene. Impact rates, as used here, refer to strain rates greater than 1000 1/s. The model is a physically based, three-dimensional constitutive model which incorporates the contributions of the amorphous, crystalline, pseudo-amorphous and entanglement networks to the constitutive response of polypropylene. The model mathematics is based on the well-known Glass-Rubber model originally developed for glassy polymers but the arguments have herein been extended to semi-crystalline polymers. In order to predict the impact rates behaviour of polypropylene, the model exploits the well-known framework of multiple processes yielding of polymers. This work argues that two dominant viscoelastic relaxation processes – the alpha- and beta-processes – can be associated with the yield responses of polypropylene observed at low-rate-dominant and impact-rates dominant loading regimes. Compression test data on polypropylene have been used to validate the model. The study has found that the model predicts quite well the experimentally observed nonlinear rate-dependent impact response of polypropylene

Antiferromagnetism and superconductivity of the two-dimensional extended t–J model

The mechanism of high-temperature superconductivity (HTS) and the correlation between the antiferromagnetic long-range order (AFLRO) and superconductivity (SC) phases are the central issues of the study of HTS theory. SC and AFLRO of the hole-doped two-dimensional extended t- J model are studied by the variational Monte Carlo method. The results show that SC is greatly enhanced by the long-range hopping terms t' and t" for the optimal and overdoped cases. The phase of coexisting SC and AFM in the t-J model disappears when t and t" are included. It is concluded that the extended t-J model provides a more accurate description for HTS than the traditional t-J model does. The momentum distribution function n(k) and the shape of Fermi surface play critical roles for establishing the phase diagram of HTS materials

B -> J/psi K^* Decays in QCD Factorization

The hadronic decay B -> J K^* is analyzed within the framework of QCD factorization. The spin amplitudes A_0, A_\parallel and A_\perp in the transversity basis and their relative phases are studied using various different form-factor models for B-K^* transition. The effective parameters a_2^h for helicity h=0,+,- states receive different nonfactorizable contributions and hence they are helicity dependent, contrary to naive factorization where a_2^h are universal and polarization independent. QCD factorization breaks down even at the twist-2 level for transverse hard spectator interactions. Although a nontrivial strong phase for the A_\parallel amplitude can be achieved by adjusting the phase of an infrared divergent contribution, the present QCD factorization calculation cannot say anything definite about the phase phi_\parallel. Unlike B -> J/psi K decays, the longitudinal parameter a_2^0 for B -> J/psi K^* does not receive twist-3 corrections and is not large enough to account for the observed branching ratio and the fraction of longitudinal polarization. Possible enhancement mechanisms for a_2^0 are discussed.Comment: 21 pages, 1 figure, a table and a reference added, some typos correcte

Systematic Cu-63 NQR studies of the stripe phase in La(1.6-x)Nd(0.4)Sr(x)CuO(4) for 0.07 <= x <= 0.25

We demonstrate that the integrated intensity of Cu-63 nuclear quadrupole resonance (NQR) in La(1.6-x)Nd(0.4)Sr(x)CuO(4) decreases dramatically below the charge-stripe ordering temperature T(charge). Comparison with neutron and X-ray scattering indicates that the wipeout fraction F(T) (i.e. the missing fraction of the integrated intensity of the NQR signal) represents the charge-stripe order parameter. The systematic study reveals bulk charge-stripe order throughout the superconducting region 0.07 <= x <= 0.25. As a function of the reduced temperature t = T/T(charge), the temperature dependence of F(t) is sharpest for the hole concentration x=1/8, indicating that x=1/8 is the optimum concentration for stripe formation.Comment: 10 pages of text and captions, 11 figures in postscript. Final version, with new data in Fig.

Updated Analysis of a_1 and a_2 in Hadronic Two-body Decays of B Mesons

Using the recent experimental data of $B\to D^{(*)}(\pi,\rho)$, $B\to D^{(*)} D_s^{(*)}$, $B\to J/\psi K^{(*)}$ and various model calculations on form factors, we re-analyze the effective coefficients a_1 and a_2 and their ratio. QCD and electroweak penguin corrections to a_1 from $B\to D^{(*)}D_s^{(*)}$ and a_2 from $B\to J/\psi K^{(*)}$ are estimated. In addition to the model-dependent determination, the effective coefficient a_1 is also extracted in a model-independent way as the decay modes $B\to D^{(*)}h$ are related by factorization to the measured semileptonic distribution of $B\to D^{(*)}\ell \bar\nu$ at $q^2=m_h^2$. Moreover, this enables us to extract model-independent heavy-to-heavy form factors, for example, $F_0^{BD}(m_\pi^2)=0.66\pm0.06\pm0.05$ and $A_0^{BD^*}(m_\pi^2)=0.56\pm0.03\pm0.04$. The determination of the magnitude of a_2 from $B\to J/\psi K^{(*)}$ depends on the form factors $F_1^{BK}$, $A_{1,2}^{BK^*}$ and $V^{BK^*}$ at $q^2=m^2_{J/\psi}$. By requiring that a_2 be process insensitive (i.e., the value of a_2 extracted from $J/\psi K$ and $J/\psi K^*$ states should be similar), as implied by the factorization hypothesis, we find that $B\to K^{(*)}$ form factors are severely constrained; they respect the relation $F_1^{BK}(m^2_{J/\psi})\approx 1.9 A_1^{BK^*}(m^2_{J/\psi})$. Form factors $A_2^{BK^*}$ and $V^{BK^*}$ at $q^2=m^2_{J/\psi}$ inferred from the measurements of the longitudinal polarization fraction and the P-wave component in $B\to J/\psi K^*$ are obtained. A stringent upper limit on a_2 is derived from the current bound on \ov B^0\to D^0\pi^0 and it is sensitive to final-state interactions.Comment: 33 pages, 2 figures. Typos in Tables I and IX are corrected. To appear in Phys. Rev.

Do solar neutrinos decay?

Despite the fact that the solar neutrino flux is now well-understood in the context of matter-affected neutrino mixing, we find that it is not yet possible to set a strong and model-independent bound on solar neutrino decays. If neutrinos decay into truly invisible particles, the Earth-Sun baseline defines a lifetime limit of \tau/m \agt 10^{-4} s/eV. However, there are many possibilities which must be excluded before such a bound can be established. There is an obvious degeneracy between the neutrino lifetime and the mixing parameters. More generally, one must also allow the possibility of active daughter neutrinos and/or antineutrinos, which may partially conceal the characteristic features of decay. Many of the most exotic possibilities that presently complicate the extraction of a decay bound will be removed if the KamLAND reactor antineutrino experiment confirms the large-mixing angle solution to the solar neutrino problem and measures the mixing parameters precisely. Better experimental and theoretical constraints on the $^8$B neutrino flux will also play a key role, as will tighter bounds on absolute neutrino masses. Though the lifetime limit set by the solar flux is weak, it is still the strongest direct limit on non-radiative neutrino decay. Even so, there is no guarantee (by about eight orders of magnitude) that neutrinos from astrophysical sources such as a Galactic supernova or distant Active Galactic Nuclei will not decay.Comment: Very minor corrections, corresponds to published versio

Observation of Orbitally Excited B_s Mesons

We report the first observation of two narrow resonances consistent with states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+, \bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1}) = 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.Comment: Version accepted and published by Phys. Rev. Let

Global Search for New Physics with 2.0/fb at CDF

Data collected in Run II of the Fermilab Tevatron are searched for indications of new electroweak-scale physics. Rather than focusing on particular new physics scenarios, CDF data are analyzed for discrepancies with the standard model prediction. A model-independent approach (Vista) considers gross features of the data, and is sensitive to new large cross-section physics. Further sensitivity to new physics is provided by two additional algorithms: a Bump Hunter searches invariant mass distributions for "bumps" that could indicate resonant production of new particles; and the Sleuth procedure scans for data excesses at large summed transverse momentum. This combined global search for new physics in 2.0/fb of ppbar collisions at sqrt(s)=1.96 TeV reveals no indication of physics beyond the standard model.Comment: 8 pages, 7 figures. Final version which appeared in Physical Review D Rapid Communication