Cold three-body collisions in hydrogen-hydrogen-alkali atomic system

We have studied hydrogen-hydrogen-alkali three-body systems in the adiabatic hyperspherical representation. For the spin-stretched case, there exists a single $X$H molecular state when $X$ is one of the bosonic alkali atoms: $^7$Li, $^{23}$Na, $^{39}$K, $^{87}$Rb and $^{133}$Cs. As a result, the {\em only} recombination process is the one that leads to formation of $X$H molecules, H+H+$X$$\rightarrow$$X$H+H, and such molecules will be stable against vibrational relaxation. We have calculated the collision rates for recombination and collision induced dissociation as well as the elastic cross-sections for H+$X$H collisions up to a temperature of 0.5 K, including the partial wave contributions from $J^\Pi$=$0^+$ to $5^-$. We have also found that there is just one three-body bound state for such systems for $J^\Pi$=$0^+$ and no bound states for higher angular momenta.Comment: 10 pages, 5 figures, 4 table

Investigation of factors influencing the immunogenicity of hCG as a potential cancer vaccine

Human hCG and its β‐subunit (hCGβ) are tumour autocrine growth factors whose presence in the serum of cancer patients has been linked to poorer prognosis. Previous studies have shown that vaccines, which target these molecules and/or the 37 amino acid C‐terminal hCGβ peptide (hCGβCTP), induce antibody responses in a majority of human recipients. Here we explored whether the immunogenicity of vaccines containing an hCGβ mutant (hCGβR68E, designed to eliminate cross‐reactivity with luteinizing hormone) or hCGβCTP could be enhanced by coupling the immunogen to different carriers (KLH or Hsp70) using different cross‐linkers (EDC or GAD) and formulated with different adjuvants (RIBI or Montanide ISA720). While there was little to choose between KLH and Hsp70 as carriers, their influence on the effectiveness of a vaccine containing the BAChCGβR68E mutant was less marked, presumably because being a foreign species, this mutant protein itself might provide T‐helper epitopes. The mutant provided a significantly better vaccine than the hCGβCTP peptide irrespective of the carrier used, how it was cross‐linked to the carrier or which adjuvant was used when hCG was the target. Nonetheless, for use in humans where hCG is a tolerated self‐protein, the need for a carrier is of fundamental importance. Highest antibody titres were obtained by linking the BAChCGβR68E to Hsp70 as a carrier by GAD and using RIBI as the adjuvant, which also resulted in antibodies with significantly higher affinity than those elicited by hCGβCTP peptide vaccine. This makes this mutant vaccine a promising candidate for therapeutic studies in hCGβ‐positive cancer patients

Optimal interlayer hopping and high temperature Bose–Einstein condensation of local pairs in quasi 2D superconductors

Both FeSe and cuprate superconductors are quasi 2D materials with high transition temperatures and local fermion pairs. Motivated by such systems, we investigate real space pairing of fermions in an anisotropic lattice model with intersite attraction, V, and strong local Coulomb repulsion, U, leading to a determination of the optimal conditions for superconductivity from Bose–Einstein condensation. Our aim is to gain insight as to why high temperature superconductors tend to be quasi 2D. We make both analytically and numerically exact solutions for two body local pairing applicable to intermediate and strong V. We find that the Bose–Einstein condensation temperature of such local pairs pairs is maximal when hopping between layers is intermediate relative to in-plane hopping, indicating that the quasi 2D nature of unconventional superconductors has an important contribution to their high transition temperatures

Numerical Approximations Using Chebyshev Polynomial Expansions

We present numerical solutions for differential equations by expanding the unknown function in terms of Chebyshev polynomials and solving a system of linear equations directly for the values of the function at the extrema (or zeros) of the Chebyshev polynomial of order N (El-gendi's method). The solutions are exact at these points, apart from round-off computer errors and the convergence of other numerical methods used in connection to solving the linear system of equations. Applications to initial value problems in time-dependent quantum field theory, and second order boundary value problems in fluid dynamics are presented.Comment: minor wording changes, some typos have been eliminate

Noise-induced perturbations of dispersion-managed solitons

We study noise-induced perturbations of dispersion-managed solitons by developing soliton perturbation theory for the dispersion-managed nonlinear Schroedinger (DMNLS) equation, which governs the long-term behavior of optical fiber transmission systems and certain kinds of femtosecond lasers. We show that the eigenmodes and generalized eigenmodes of the linearized DMNLS equation around traveling-wave solutions can be generated from the invariances of the DMNLS equations, we quantify the perturbation-induced parameter changes of the solution in terms of the eigenmodes and the adjoint eigenmodes, and we obtain evolution equations for the solution parameters. We then apply these results to guide importance-sampled Monte-Carlo simulations and reconstruct the probability density functions of the solution parameters under the effect of noise.Comment: 12 pages, 6 figure

A statistical mechanics approach to autopoietic immune networks

The aim of this work is to try to bridge over theoretical immunology and disordered statistical mechanics. Our long term hope is to contribute to the development of a quantitative theoretical immunology from which practical applications may stem. In order to make theoretical immunology appealing to the statistical physicist audience we are going to work out a research article which, from one side, may hopefully act as a benchmark for future improvements and developments, from the other side, it is written in a very pedagogical way both from a theoretical physics viewpoint as well as from the theoretical immunology one. Furthermore, we have chosen to test our model describing a wide range of features of the adaptive immune response in only a paper: this has been necessary in order to emphasize the benefit available when using disordered statistical mechanics as a tool for the investigation. However, as a consequence, each section is not at all exhaustive and would deserve deep investigation: for the sake of completeness, we restricted details in the analysis of each feature with the aim of introducing a self-consistent model.Comment: 22 pages, 14 figur

Influence of Amino Acid Substitutions in the Nisin Leader Peptide on Biosynthesis and Secretion of Nisin by Lactococcus lactis

Structural genes for small lanthionine-containing antimicrobial peptides, known as lantibiotics, encode N-terminal leader sequences which are not present in the mature peptide, but are cleaved off at some stage in the maturation process. Leader sequences of the different lantibiotics share a number of identical amino acid residues, but they are clearly different from sec-dependent protein export signal sequences. We studied the role of the leader sequence of the lantibiotic nisin, which is produced and secreted by Lactococcus lactis, by creating site-directed mutations at various positions in the leader peptide sequence. Mutations at Arg-1 and Ala-4, but not at the conserved Pro-2, strongly affected the processing of the leader sequence and resulted in the extracellular accumulation of a biologically inactive precursor peptide. Amino acid analysis and 1H NMR studies indicated that the precursor peptide with an Ala-4 → Asp mutation contained a modified nisin structural part with the (mutated) unmodified leader sequence still attached to it. The Ala-4 → Asp precursor peptide could be activated in vitro by enzymatic cleavage with trypsin, liberating nisin. These results confirmed that cleavage of the leader peptide is the last step in nisin maturation and is necessary to generate a biologically active peptide. Several mutations, i.e. Pro-2 → Gly, Pro-2 → Val, Asp-7 → Ala, Lys-9 → Leu, Ser-10 → Ala/Ser-12 → Ala and Val-11 → Asp/Val-13 → Glu in the leader peptide did not have any detectable effect on nisin production and secretion, although some of them affected highly conserved residues. When mutations were created in the -18 to -15 region of the nisin leader peptide (i.e. Phe-18 → Leu, Leu-16 → Lys, Asp-15 → Ala), no secretion or intracellular accumulation could be detected of nisin or its precursors. This suggested that these conserved residues are involved in the maturation process and may interact with lantibiotic-specific modifying enzymes.

Chemoenzymatic Probes for Detecting and Imaging Fucose-α(1-2)-galactose Glycan Biomarkers

The disaccharide motif fucose-α(1-2)-galactose (Fucα(1-2)Gal) is involved in many important physiological processes, such as learning and memory, inflammation, asthma, and tumorigenesis. However, the size and structural complexity of Fucα(1-2)Gal-containing glycans have posed a significant challenge to their detection. We report a new chemoenzymatic strategy for the rapid, sensitive detection of Fucα(1-2)Gal glycans. We demonstrate that the approach is highly selective for the Fucα(1-2)Gal motif, detects a variety of complex glycans and glycoproteins, and can be used to profile the relative abundance of the motif on live cells, discriminating malignant from normal cells. This approach represents a new potential strategy for biomarker detection and expands the technologies available for understanding the roles of this important class of carbohydrates in physiology and disease

Geometry and symmetries of multi-particle systems

The quantum dynamical evolution of atomic and molecular aggregates, from their compact to their fragmented states, is parametrized by a single collective radial parameter. Treating all the remaining particle coordinates in d dimensions democratically, as a set of angles orthogonal to this collective radius or by equivalent variables, bypasses all independent-particle approximations. The invariance of the total kinetic energy under arbitrary d-dimensional transformations which preserve the radial parameter gives rise to novel quantum numbers and ladder operators interconnecting its eigenstates at each value of the radial parameter. We develop the systematics and technology of this approach, introducing the relevant mathematics tutorially, by analogy to the familiar theory of angular momentum in three dimensions. The angular basis functions so obtained are treated in a manifestly coordinate-free manner, thus serving as a flexible generalized basis for carrying out detailed studies of wavefunction evolution in multi-particle systems.Comment: 37 pages, 2 eps figure

Immunoglobulin G; structure and functional implications of different subclass modifications in initiation and resolution of allergy.

IgE and not IgG is usually associated with allergy. IgE lodged on mast cells in skin or gut and basophils in the blood allows for the prolonged duration of allergy through the persistent expression of high affinity IgE receptors. However, many allergic reactions are not dependent on IgE and are generated in the absence of allergen specific and even total IgE. Instead, IgG plasma cells are involved in induction of, and for much of the pathogenesis of, allergic diseases. The pattern of IgG producing plasma cells in atopic children and the tendency for direct or further class switching to IgE are the principle factors responsible for long-lasting sensitization of mast cells in allergic children. Indirect class switching from IgG producing plasma cells has been shown to be the predominant pathway for production of IgE while a Th2 microenvironment, genetic predisposition, and the concentration and nature of allergens together act on IgG plasma cells in the atopic tendency to undergo further immunoglobulin gene recombination. The seminal involvement of IgG in allergy is further indicated by the principal role of IgG4 in the natural resolution of allergy and as the favourable immunological response to immunotherapy. This paper will look at allergy through the role of different antibodies than IgE and give current knowledge of the nature and role of IgG antibodies in the start, maintenance and resolution of allergy