AMPLE clusters and truncates ab initio protein structure predictions, producing search models for molecular replacement. Here, an interesting degree of complementarity is shown between targets solved using the different ab initio modelling programs QUARK and ROSETTA. Search models derived from either program collectively solve almost all of the all-helical targets in the test set. Initial solut...

We calculate the decay width for Λb → Λceν̄ in the frame work of a nonrelativistic quark (NRQ) model of heavy baryons where the light quarks play the role of spectators. Our calculation does not make an explicit use of the heavy quark symmetry. The branching ratio for the above process as calculated here agrees reasonably well with the experimental value. Electronic address: [email protected]....

Spin-dependent parton distributions in the polarized virtual photon are investigated in QCD up to the next-to-leading order (NLO). In the case Λ 2 P 2 Q , where Q 2 ( P ) is the mass squared of the probe (target) photon, parton distributions can be predicted completely up to the NLO, but they are factorization-scheme-dependent. Parton distributions are analyzed in four different factorization s...

The reaction γ + p → η + p is investigated in the quark model approach. The quark model predicts that the off-shell contributions from the resonance S11(1535) dominate the η ′ production in the threshold region. We find that the coulping constant αη′NN from the fit to a few total cross section data is small. The results of the total and differential cross sections are presented at different ene...

Abstract. In this talk I review studies of hadron properties in bosonized chiral quark models for the quark flavor dynamics. Mesons are constructed from Bethe–Salpeter equations and baryons emerge as chiral solitons. Such models require regularization and I show that the two–fold Pauli–Villars regularization scheme not only fully regularizes the effective action but also leads the scaling laws ...

Quark spin and orbital angular momentum in the nucleon are calculated in symmetry-breaking chiral quark model. The results are compared with data and other models. Synopsis: Recent measurements show (1) strong flavor asymmetry of the antiquark sea 1 : ¯ d > ¯ u, (2) nonzero strange quark content 2 : < ¯ ss > = 0, (3) sum of quark spins is small 3 : < s z > q+¯ q = 0.1 − 0.2, and (4) antiquark s...

Quark spin and orbital angular momentum in the nucleon are calculated in symmetry-breaking chiral quark model. The results are compared with data and other models. Synopsis: Recent measurements show (1) strong flavor asymmetry of the antiquark sea 1 : ¯ d > ¯ u, (2) nonzero strange quark content 2 : < ¯ ss > = 0, (3) sum of quark spins is small 3 : < s z > q+¯ q = 0.1 − 0.2, and (4) antiquark s...

We discuss the net quark and isovector fluctuations as well as off-diagonal quark flavor susceptibilities along the chiral phase transition line in the Nambu–Jona-Lasinio (NJL) model. The model is formulated at non-zero quark and isospin chemical potentials with non-vanishing vector couplings in the iso-scalar and iso-vector channels. We study the influence of the quark chemical potential on th...