On the Birkhoff factorization problem for the Heisenberg magnet and nonlinear Schroedinger equations

A geometrical description of the Heisenberg magnet (HM) equation with classical spins is given in terms of flows on the quotient space $G/H_+$ where $G$ is an infinite dimensional Lie group and $H_+$ is a subgroup of $G$. It is shown that the HM flows are induced by an action of $\mathbb{R}^2$ on $G/H_+$, and that the HM equation can be integrated by solving a Birkhoff factorization problem for $G$. For the HM flows which are Laurent polynomials in the spectral variable we derive an algebraic transformation between solutions of the nonlinear Schroedinger (NLS) and Heisenberg magnet equations. The Birkhoff factorization for $G$ is treated in terms of the geometry of the Segal-Wilson Grassmannian $Gr(H)$. The solution of the problem is given in terms of a pair of Baker functions for special subspaces of $Gr(H)$. The Baker functions are constructed explicitly for subspaces which yield multisoliton solutions of NLS and HM equations.Comment: To appear in Journal of Mathematical Physic

Elisa and HPLC analyses of deoxynivalenol in maize and wheat

Deoxynivalenol (DON) is a part of the family of mycotoxins called trichothecenes which are produced by a number of different Fusarium mold species. The presence of DON in 25 wheat and 25 maize samples was examined by Enzyme Linked Immunosorbent Assay (ELISA) and High Performance Liquid Chromatography (HPLC) methods. The presence of DON was detected and determined in 5 (20%) maize and 6 (25%) wheat samples by both of the methods. Correlation between ELISA and HPLC results was established, with the correlation coefficients (r) of 0.9691 and 0.9735 for wheat and maize samples, respectively. The results obtained by ELISA method were significantly higher than those obtained by HPLC method. This fact can be explained by the presence of conjugated or masked mycotoxins in the samples, especially DON-3-glucoside (DON-3-Glc), which could not be determined by HPLC method due to the lack of external standards. Contrary to this, being insufficiently selective towards masked DON, ELISA method measures total DON content of a sample. According to the obtained results, ELISA can be used as a reliable screening method, but the confirmation of positive results must be done by HPLC method

Structures of monomeric and oligomeric forms of the Toxoplasma gondiiperforin-like protein 1

Toxoplasma and Plasmodium are the parasitic agents of toxoplasmosis and malaria, respectively, and use perforin-like proteins (PLPs) to invade host organisms and complete their life cycles. The Toxoplasma gondii PLP1 (TgPLP1) is required for efficient exit from parasitophorous vacuoles in which proliferation occurs. We report structures of the membrane attack complex/perforin (MACPF) and Apicomplexan PLP C-terminal β-pleated sheet (APCβ) domains of TgPLP1. The MACPF domain forms hexameric assemblies, with ring and helix geometries, and the APCβ domain has a novel β-prism fold joined to the MACPF domain by a short linker. Molecular dynamics simulations suggest that the helical MACPF oligomer preserves a biologically important interface, whereas the APCβ domain binds preferentially through a hydrophobic loop to membrane phosphatidylethanolamine, enhanced by the additional presence of inositol phosphate lipids. This mode of membrane binding is supported by site-directed mutagenesis data from a liposome-based assay. Together, these structural and biophysical findings provide insights into the molecular mechanism of membrane targeting by TgPLP1

Novel Modifications of Parallel Jacobi Algorithms

We describe two main classes of one-sided trigonometric and hyperbolic Jacobi-type algorithms for computing eigenvalues and eigenvectors of Hermitian matrices. These types of algorithms exhibit significant advantages over many other eigenvalue algorithms. If the matrices permit, both types of algorithms compute the eigenvalues and eigenvectors with high relative accuracy. We present novel parallelization techniques for both trigonometric and hyperbolic classes of algorithms, as well as some new ideas on how pivoting in each cycle of the algorithm can improve the speed of the parallel one-sided algorithms. These parallelization approaches are applicable to both distributed-memory and shared-memory machines. The numerical testing performed indicates that the hyperbolic algorithms may be superior to the trigonometric ones, although, in theory, the latter seem more natural.Comment: Accepted for publication in Numerical Algorithm

Automatic control of haul truck travel speed on open pits

Expanding raw materials production demands necessitates higher exploitation rates and capacities. Therefore, open pit mines resort to increasing their overall depth and hence introduce further machine related technical problems. Haul trucks experience intensified dynamic effects during traveling, resulting in a significant maintenance cost increase. The most influencing effects occur during the truck braking and stopping process, especially when heavily loaded. Current technical solutions in most haul truck configurations disregard plethora of these effects to lower their production cost. The dynamic effects should be defined according to specific conditions on an open pit and applied for modifying currently employed systems for automatic truck speed control (ASC). It is the purpose of this paper to present the ASC system employed on the haul truck and key points for further modification and development. Firstly, the paper presents basic aspects of the truck braking/stopping process. Secondly, a description of the BelAZ 75306 traction drive and braking systems is provided, followed by key features of the BelAZ 75306 ASC system. Finally, presented information is summarized, indicating flaws and recommendations for further improvement of the BelAZ 75306 ASC system employed on the open pit - 'Veliki Krivelj', Bor, Serbia

The Use of Pork from Entire Male and Immunocastrated Pigs for Meat Products—An Overview with Recommendations

Due to the strong public initiative in Europe and increased regulator focus to mitigate pain, surgical castration of pigs is being gradually abandoned, while the importance of other sex categories like entire males (EM) and immunocastrates (IC) increases. Although beneficial for animal welfare and economics, their use also brings forward several quality problems. Besides the occurrence of boar taint in EM, these include excessive carcass leanness, softer fat, meat color and pH deviations, inferior water holding capacity and increased meat toughness. In this paper, the raw material differences between the male sex categories and their influence on product quality are reviewed, and possible solutions are presented. Using EM for dried or thermally processed products may result in lower processing yields and inferior sensory quality, which may partially be prevented by applying specific processing adaptations. Immunocastration is a viable solution, especially when prolonging the vaccination to slaughter interval. Low to medium levels of boar taint can be effectively managed in most of the meat products, applying procedures like cooking, microbial inoculation or masking (by spices and especially smoking), while highly tainted material can be valorized only by combining various methods and/or with dilution of the tainted meat.info:eu-repo/semantics/publishedVersio

Gravastar energy conditions revisited

We consider the gravastar model where the vacuum phase transition between the de Sitter interior and the Schwarzschild or Schwarzschild-de Sitter exterior geometries takes place at a single spherical delta-shell. We derive sharp analytic bounds on the surface compactness (2m/r) that follow from the requirement that the dominant energy condition (DEC) holds at the shell. In the case of Schwarzschild exterior, the highest surface compactness is achieved with the stiff shell in the limit of vanishing (dark) energy density in the interior. In the case of Schwarzschild-de Sitter exterior, in addition to the gravastar configurations with the shell under surface pressure, gravastar configurations with vanishing shell pressure (dust shells), as well as configurations with the shell under surface tension, are allowed by the DEC. Respective bounds on the surface compactness are derived for all cases. We also consider the speed of sound on the shell as derived from the requirement that the shell is stable against the radial perturbations. The causality requirement (sound speed not exceeding that of light) further restricts the space of allowed gravastar configurations.Comment: LaTeX/IOP-style, 16 pages, 2 figures, changes wrt v1: motivation for eq. (6) clarified, several referecnes added (to appear in Class. Quantum Grav.

B --> pi and B --> K transitions in partially quenched chiral perturbation theory

We study the properties of the B-->pi and B-->K transition form factors in partially quenched QCD by using the approach of partially quenched chiral perturbation theory combined with the static heavy quark limit. We show that the form factors change almost linearly when varying the value of the sea quark mass, whereas the dependence on the valence quark mass contains both the standard and chirally divergent (quenched) logarithms. A simple strategy for the chiral extrapolations in the lattice studies with Nsea=2 is suggested. It consists of the linear extrapolations from the realistically accessible quark masses, first in the sea and then in the valence quark mass. From the present approach, we estimate the uncertainty induced by such extrapolations to be within 5%.Comment: Published versio

B-->pi and B-->K transitions in standard and quenched chiral perturbation theory

We study the effects of chiral logs on the heavy-->light pseudoscalar meson transition form factors by using standard and quenched chiral perturbation theory combined with the static heavy quark limit. The resulting expressions are used to indicate the size of uncertainties due to the use of the quenched approximation in the current lattice studies. They may also be used to assess the size of systematic uncertainties induced by missing chiral log terms in extrapolating toward the physical pion mass. We also provide the coefficient multiplying the quenched chiral log, which may be useful if the quenched lattice studies are performed with very light mesons.Comment: 33 pages, 8 PostScript figures, version to appear in PR

Radial stability analysis of the continuous pressure gravastar

Radial stability of the continuous pressure gravastar is studied using the conventional Chandrasekhar method. The equation of state for the static gravastar solutions is derived and Einstein equations for small perturbations around the equilibrium are solved as an eigenvalue problem for radial pulsations. Within the model there exist a set of parameters leading to a stable fundamental mode, thus proving radial stability of the continuous pressure gravastar. It is also shown that the central energy density possesses an extremum in rho_c(R) curve which represents a splitting point between stable and unstable gravastar configurations. As such the rho_c(R) curve for the gravastar mimics the famous M(R) curve for a polytrope. Together with the former axial stability calculations this work completes the stability problem of the continuous pressure gravastar.Comment: 17 pages, 5 figures, References corrected, minor changes wrt v1, matches published versio