Defect production due to quenching through a multicritical point

We study the generation of defects when a quantum spin system is quenched through a multicritical point by changing a parameter of the Hamiltonian as t/tau, where tau is the characteristic timescale of quenching. We argue that when a quantum system is quenched across a multicritical point, the density of defects (n) in the final state is not necessarily given by the Kibble-Zurek scaling form n similar to 1/tau(d nu)/((z nu+1)), where d is the spatial dimension, and. and z are respectively the correlation length and dynamical exponent associated with the quantum critical point. We propose a generalized scaling form of the defect density given by n similar to 1/(tau d/(2z2)), where the exponent z(2) determines the behavior of the off-diagonal term of the 2 x 2 Landau-Zener matrix at the multicritical point. This scaling is valid not only at a multicritical point but also at an ordinary critical point.

Aducts of Lanthanide Perchlorates with N,N,N',N'-Tetramethyl Oxydiacetamide

Lanthanide coordination complexes with unidentate and bidentate amide ligands have been widely reported in the literature[l].In contrast, however, coordination compounds with tridentate ligands and with ligands containing ether oxygen as donor atoms to lanthanides have received little attention. In this paper we report the preparation and characterization of complexes formed by the interaction of the lanthanide perchlorates with N, N, N', N'- tetramethyloxydiacetamide (TMODA). The new complexes have been characterized by analysis, conductance, IR and electronic spectra. In addition, ~H and '3C NMR spectra of the ligand and its diamagnetic La ~+ and y3+ complexes are also discussed.

Renormalization of the axial-vector current in QCD

Following the method of Ioffe and Smilga, the propagation of the baryon current in an external constant axial-vector field is considered. The close similarity of the operator-product expansion with and without an external field is shown to arise from the chiral invariance of gauge interactions in perturbation theory. Several sum rules corresponding to various invariants both for the nucleon and the hyperons are derived. The analysis of the sum rules is carried out by two independent methods, one called the ratio method and the other called the continuum method, paying special attention to the nondiagonal transitions induced by the external field between the ground state and excited states. Up to operators of dimension six, two new external-field-induced vacuum expectation values enter the calculations. Previous work determining these expectation values from PCAC (partial conservation of axial-vector current) are utilized. Our determination from the sum rules of the nucleon axial-vector renormalization constant GA, as well as the Cabibbo coupling constants in the SU3-symmetric limit (ms=0), is in reasonable accord with the experimental values. Uncertainties in the analysis are pointed out. The case of broken flavor SU3 symmetry is also considered. While in the ratio method, the results are stable for variation of the fiducial interval of the Borel mass parameter over which the left-hand side and the right-hand side of the sum rules are matched, in the continuum method the results are less stable. Another set of sum rules determines the value of the linear combination 7F-5D to be ≊0, or D/(F+D)≊(7/12). .AE

An elementary approach to gap theorems

Using elementary comparison geometry, we prove: Let (M, g) be a simply-connected complete Riemannian manifold of dimension >= 3. Suppose that the sectional curvature K satisfies -1-s(r) <= K <= -1, where r denotes distance to a fixed point in M. If lim(r ->infinity) e(2r) s(r) = 0, then (M, g) has to be isometric to H-n.The same proof also yields that if K satisfies -s(r) <= K <= 0 where lim(r ->infinity) r(2) s(r) = 0, then (M, g) is isometric to R-n, a result due to Greene and Wu.Our second result is a local one: Let (M, g) be any Riemannian manifold. For a E R, if K < a on a geodesic ball Bp (R) in M and K = a on partial derivative B-p (R), then K = a on B-p (R).

CD4+ alpha beta T cell and gamma delta T cell responses to Mycobacterium tuberculosis. Similarities and differences in Ag recognition, cytotoxic effector function, and cytokine production.

CD4+ and gamma delta T cells are activated readily by Mycobacterium tuberculosis. To examine their role in the human immune response to M. tuberculosis, CD4+ and gamma delta T cells from healthy tuberculin-positive donor were studied for patterns of Ag recognition, cytotoxicity, and cytokine production in response to M. tuberculosis-infected mononuclear phagocytes. Both T cell subsets responded to intact M. tuberculosis and its cytosolic Ags. However, CD4+ and gamma delta T cells differed in the range of cytosolic Ags recognized: reactivity to a wide m.w. range of Ags for CD4+ T cells, and a restricted pattern for gamma delta T cells, with dominance of Ags of 10 to 15 kDa. Both T cell subsets were equally cytotoxic for M. tuberculosis-infected monocytes. Furthermore, both CD4+ and gamma delta T cells produced large amounts of IFN-gamma: mean pg/ml of IFN-gamma in supernatants was 2458 +/- 213 for CD4+ and 2349 +/- 245 for gamma delta T cells. By filter-spot ELISA (ELISPOT), the frequency of IFN-gamma-secreting gamma delta T cells was one-half of that of CD4+ T cells in response to M. tuberculosis, suggesting that gamma delta T cells on a per cell basis were more efficient producers of IFN-gamma than CD4+ T cells. In contrast, CD4+ T cells produced more IL-2 than gamma delta T cells, which correlated with diminished T cell proliferation of gamma delta T cells compared with CD4+ T cells. These results indicate that CD4+ and gamma delta T cell subsets have similar effector functions (cytotoxicity, IFN-gamma production) in response to M. tuberculosis-infected macrophages, despite differences in the Ags recognized, IL-2 production, and efficiency of IFN-gamma production.

Buckled nano rod - a two state system: quantum effects on its dynamics

We consider a suspended elastic rod under longitudinal compression. The compression can be used to adjust potential energy for transverse displacements from the harmonic to the double well regime. The two minima in potential energy curve describe two possible buckled states. Using transition state theory (TST) we have calculated the rate of conversion from one state to other. If the strain epsilon = 4 epsilon c the simple TST rate diverges. We suggest a method to correct this divergence for quantum calculations. We also find that zero point energy contributions can be quite large so that single mode calculations can lead to large errors in the rate.

A dynamic renormalization group study of active nematics

We carry out a systematic construction of the coarse-grained dynamical equation of motion for the orientational order parameter for a two-dimensional active nematic, that is a nonequilibrium steady state with uniaxial, apolar orientational order. Using the dynamical renormalization group, we show that the leading nonlinearities in this equation are marginally irrelevant. We discover a special limit of parameters in which the equation of motion for the angle field bears a close relation to the 2d stochastic Burgers equation. We find nevertheless that, unlike for the Burgers problem, the nonlinearity is marginally irrelevant even in this special limit, as a result of a hidden fluctuation-dissipation relation. 2d active nematics therefore have quasi-long-range order, just like their equilibrium counterparts.

Polymer drift in a solvent by force acting on one polymer end

We investigate the effect of hydrodynamic interactions on the non-equilibrium drift dynamics of an ideal flexible polymer pulled by a constant force applied at one polymer end using the perturbation theory and the renormalization group method. For moderate force, if the polymer elongation is small, the hydrodynamic interactions are not screened and the velocity and the longitudinal elongation of the polymer are computed using the renormalization group method. Both the velocity and elongation are nonlinear functions of the driving force in this regime. For large elongation we found two regimes. For large force but finite chain length L the hydrodynamic interactions are screened. For large chain lengths and a finite force the hydrodynamic interactions are only partially screened, which in three dimensions results in unusual logarithmic corrections to the velocity and the longitudinal elongation.

A spectroscopic study of the interaction of isoflavones with human serum albumin

Genistein and daidzein, the major isoflavones present in soybeans, possess a wide spectrum of physiological and pharmacological functions. The binding of genistein to human serum albumin (HSA) has been investigated by equilibrium dialysis, fluorescence measurements, CD and molecular visualization. One mole of genistein is bound per mole of HSA with a binding constant of 1.5 +/- 0.2 X 10(5) m(-1). Binding of genistein to HSA precludes the attachment of daidzein. The ability of HSA to bind genistein is found to be lost when the tryptophan residue of albumin is modified with N-bromosuccinimide. At 27 degrees C (pH 7.4), van't Hoff's enthalpy, entropy and free energy changes that accompany the binding are found to be -13.16 kcal.mol(-1), -21 cal.mol(-1)K(-1) and -6.86 kcal.mol(-1), respectively. Temperature and ionic strength dependence and competitive binding measurements of genistein with HSA in the presence of fatty acids and 8-anilino-1-naphthalene sulfonic acid have suggested the involvement of both hydrophobic and ionic interactions in the genistein-HSA binding. Binding measurements of genistein with BSA and HSA, and those in the presence of warfarin and 2,3,5-tri-iodobenzoic acid and Forster energy transfer measurements have been used for deducing the binding pocket on HSA. Fluorescence anisotropy measurements of daidzein bound and then displaced with warfarin, 2,3,5-tri-iodobenzoic acid or diazepam confirm the binding of daidzein and genistein to subdomain IIA of HSA. The ability of HSA to form ternery complexes with other neutral molecules such as warfarin, which also binds within the subdomain IIA pocket, increases our understanding of the binding dynamics of exogenous drugs to HSA.

Reproductive behavior and health in consanguineous marriages

In many regions of Asia and Africa, consanguineous marriages currently account for approximately 20 to 50% of all unions, and preliminary observations indicate that migrants from these areas continue to contract marriages with close relatives when resident in North America and Western Europe. Consanguinity is associated with increased gross fertility, due at least in part to younger maternal age at first livebirth. Morbidity and mortality also may be elevated, resulting in comparable numbers of surviving offspring in consanguineous and nonconsanguineous families. With advances in medicine and public health, genetic disorders will account for an increased proportion of disease worldwide. Predictably, this burden will fall more heavily on countries and communities in which consanguinity is strongly favored, as the result of the expression of deleterious recessive genes. However, studies conducted in such populations indicate that the adverse effects associated with inbreeding are experienced by a minority of families.

Roofed polyquinanes: synthesis and electronic structure

Starting from readily available norbornenobenzoquinone 7 and employing a photothermal metathesis reaction as the main strategy, novel "roofed" polyquinane bisenones 3 and 13 have been synthesized. Among these, the former is potentially serviceable for further elaboration to dodecahedrane 1. Catalytic hydrogenation of 3 provided the dione 12, which fully inscribes the circumference of dodecahedrane sphere. The "roofed" C-16-bisenone 3 has been successfully annulated to C19-bisenone 24 and C19-trisenone 26 by employing the Greene methodology and Pauson-Khand reaction, respectively. The molecular structures of 3 and 13 were computed using molecular mechanics and semiempirical MO methods. The nonbonded distances between the double bonds vary strongly with the method employed. The interactions between the pi-MO's were, therefore, probed by means of photoelectron (PE) spectroscopy. Comparison with the PE spectra of a series of model systems with increasing complexity enabled an unambiguous assignment of the observed peaks. The symmetric and antisymmetric combinations of the pi-MO's of the enone moieties of 3 and 13 show large splittings, characteristic of propano-bridged systems in which through-space and through-bond effects act in concert.

Excitation and relaxation energies of trans-stilbene: Confined singlet, triplet, and charged bipolarons

The π-electronic excitations and excited-state geometries of trans-stilbene (tS) are found by combining exact solutions of the Pariser-Parr-Pople (PPP) model and semiempirical Parametric Method 3 (PM3) calculations. Comprehensive comparisons with tS spectra are obtained and related to the fluorescence and topological alternation of poly(paraphenylenevinylene) (PPV). The one-photon absorption and triplet of tS correspond, respectively, to singlet and triplet bipolarons confined to two phenyls, while the tS2- ground state is a confined charged bipolaron. Independent estimates of the relaxation energy between vertical and adiabatic excitation show the bipolaron binding energy to depend on both charge and spin, as expected for interacting π electrons in correlated or molecular states. Complete configuration interaction within the PPP model of tS accounts for the singlet-triplet gap, for the fine-structure constants and triplet-triplet spectra, for two-photon transitions and intensities, and for one-photon spectra and the radiative lifetime, although the relative position of nearly degenerate covalent and ionic singlets is not resolved. The planar PM3 geometry and low rotational barrier of tS agree with resolved rotational and vibrational spectra in molecular beams. PM3 excitation and relaxation energies for tS bipolarons are consistent with experiment and with PPP results. Instead of the exciton model, we interpret tS excitations in terms of states that are localized on each ring or extended over an alternating chain, as found exactly in Hückel theory, and find nearly degenerate transitions between extended and localized states in the singlet, triplet, and dianion manifolds. The large topological alternation of the extended system increases the ionicity and interchanges the order of the lowest one- and two-photon absorption of PPV relative to polyenes.

Interaction of Sesbania mosaic virus movement protein with the coat protein - implications for viral spread

Sesbania mosaic virus (SeMV) is a single-stranded positive-sense RNA plant virus belonging to the genus Sobemovirus. The movement protein (MP) encoded by SeMV ORF1 showed no significant sequence similarity with MPs of other genera, but showed 32% identity with the MP of Southern bean mosaic virus within the Sobemovirus genus. With a view to understanding the mechanism of cell-to-cell movement in sobemoviruses, the SeMV MP gene was cloned, over-expressed in Escherichia coli and purified. Interaction of the recombinant MP with the native virus (NV) was investigated by ELISA and pull-down assays. It was observed that SeMV MP interacted with NV in a concentration- and pH-dependent manner. Analysis of N- and C-terminal deletion mutants of the MP showed that SeMV MP interacts with the NV through the N- terminal 49 amino acid segment. Yeast two-hybrid assays confirmed the in vitro observations, and suggested that SeMV might belong to the class of viruses that require MP and NV/coat protein for cell-to-cell movement.

Barrier crossing in one and three dimensions by a long chain

We consider the Kramers problem for a long chain polymer trapped in a biased double-well potential. Initially the polymer is in the less stable well and it can escape from this well to the other well by the motion of its N beads across the barrier to attain the configuration having lower free energy. In one dimension we simulate the crossing and show that the results are in agreement with the kink mechanism suggested earlier. In three dimensions, it has not been possible to get an analytical `kink solution' for an arbitrary potential; however, one can assume the form of the solution of the nonlinear equation as a kink solution and then find a double-well potential in three dimensions. To verify the kink mechanism, simulations of the dynamics of a discrete Rouse polymer model in a double well in three dimensions are carried out. We find that the time of crossing is proportional to the chain length, which is in agreement with the results for the kink mechanism. The shape of the kink solution is also in agreement with the analytical solution in both one and three dimensions.