On the Cartan Model of the Canonical Vector Bundles over Grassmannians

We give a representation of canonical vector bundles over Grassmannian manifolds as non-compact affine symmetric spaces as well as their Cartan model in the group of the Euclidean motions.Comment: 6 page

Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. III: Role of particle-number projection

Starting from HFB-6, we have constructed a new mass table, referred to as HFB-8, including all the 9200 nuclei lying between the two drip lines over the range of Z and N > 6 and Z < 122. It differs from HFB-6 in that the wave function is projected on the exact particle number. Like HFB-6, the isoscalar effective mass is constrained to the value 0.80 M and the pairing is density independent. The rms errors of the mass-data fit is 0.635 MeV, i.e. better than almost all our previous HFB mass formulas. The extrapolations of this new mass formula out to the drip lines do not differ significantly from the previous HFB-6 mass formula.Comment: 9 pages, 7 figures, accepted for publication in Phys. Rev.

Giant magnetoresistance in semiconductor / granular film heterostructures with cobalt nanoparticles

We have studied the electron transport in SiO${}_2$(Co)/GaAs and SiO${}_2$(Co)/Si heterostructures, where the SiO${}_2$(Co) structure is the granular SiO${}_2$ film with Co nanoparticles. In SiO${}_2$(Co)/GaAs heterostructures giant magnetoresistance effect is observed. The effect has positive values, is expressed, when electrons are injected from the granular film into the GaAs semiconductor, and has the temperature-peak type character. The temperature location of the effect depends on the Co concentration and can be shifted by the applied electrical field. For the SiO${}_2$(Co)/GaAs heterostructure with 71 at.% Co the magnetoresistance reaches 1000 ($10^5$ %) at room temperature. On the contrary, for SiO${}_2$(Co)/Si heterostructures magnetoresistance values are very small (4%) and for SiO${}_2$(Co) films the magnetoresistance has an opposite value. High values of the magnetoresistance effect in SiO${}_2$(Co)/GaAs heterostructures have been explained by magnetic-field-controlled process of impact ionization in the vicinity of the spin-dependent potential barrier formed in the semiconductor near the interface. Kinetic energy of electrons, which pass through the barrier and trigger the avalanche process, is reduced by the applied magnetic field. This electron energy suppression postpones the onset of the impact ionization to higher electric fields and results in the giant magnetoresistance. The spin-dependent potential barrier is due to the exchange interaction between electrons in the accumulation electron layer in the semiconductor and $d$-electrons of Co.Comment: 25 pages, 16 figure

Identification of Trace Element-Containing Proteins in Genomic Databases

Development of bioinformatics tools provided researchers with the ability to identify full sets of trace element–containing proteins in organisms for which complete genomic sequences are available. Recently, independent bioinformatics methods were used to identify all, or almost all, genes encoding selenocysteine-containing proteins in human, mouse, and Drosophila genomes, characterizing entire selenoproteomes in these organisms. It also should be possible to search for entire sets of other trace element–associated proteins, such as metal-containing proteins, although methods for their identification are still in development

Semi-analytical hybrid approach for modelling wave motion excited by a piezoelectric transducer in a laminate with multiple cracks

A semi-analytical hybrid approach is presented here to simulate the dynamic behaviour of a multi-layered elastic waveguide with a system of delaminations and a piezoelectric transducer mounted on the surface of the waveguide. The proposed hybrid approach combines the advantages of the frequency domain spectral element method, which is applied to discretize a complex-shaped piezoelectric structure, and the boundary integral equation method employed to simulate wave propagation in multi-layered waveguide with multiple delaminations. The proposed method is applicable to the multi-parameter analysis of the phenomena related to elastic wave scattering and excitation. The advantages of the presented extended semi-analytical hybrid approach method along with the results of the parametric analysis of wave propagation in the considered structures are discussed

Synthesis and Characterization of Electro-Explosive Magnetic Nanoparticles for Biomedical Applications

Nowadays there are new magnetic nanostructures based on bioactive metals with low toxicity and high efficiency for a wide range of biomedical applications including drugs delivery, antimicrobial drugs design, cells' separation and contrasting. For such applications it is necessary to develop highly magnetic particles with less than100 nm in size. In the present study magnetic nanoparticles Fe, Fe[3]O[4] and bimetallic Cu/Fe with the average size of 60- 90 nm have been synthesized by electrical explosion of wire in an oxygen or argon atmosphere. The produced nanoparticles have been characterized with transmission electron microscopy, X-ray phase analysis, and nitrogen thermal desorption. The synthesized particles have shown antibacterial activity to gram-positive (S. aureus, MRSA) and gramnegative (E. coli, P. aeruginosa) bacteria. According to the cytological data Fe, Fe[3]O[4]and Cu/Fe nanoparticles have effectively inhibited viability of cancer cell lines Neuro-2a and J774. The obtained nanoparticles are promising for new antimicrobial drugs and antitumor agents' developmen

Synthesis and Characterization of Electro-Explosive Magnetic Nanoparticles for Biomedical Applications

Nowadays there are new magnetic nanostructures based on bioactive metals with low toxicity and high efficiency for a wide range of biomedical applications including drugs delivery, antimicrobial drugs design, cells' separation and contrasting. For such applications it is necessary to develop highly magnetic particles with less than100 nm in size. In the present study magnetic nanoparticles Fe, Fe[3]O[4] and bimetallic Cu/Fe with the average size of 60- 90 nm have been synthesized by electrical explosion of wire in an oxygen or argon atmosphere. The produced nanoparticles have been characterized with transmission electron microscopy, X-ray phase analysis, and nitrogen thermal desorption. The synthesized particles have shown antibacterial activity to gram-positive (S. aureus, MRSA) and gramnegative (E. coli, P. aeruginosa) bacteria. According to the cytological data Fe, Fe[3]O[4]and Cu/Fe nanoparticles have effectively inhibited viability of cancer cell lines Neuro-2a and J774. The obtained nanoparticles are promising for new antimicrobial drugs and antitumor agents' developmen

Thiol peroxidase deficiency leads to increased mutational load and decreased fitness in saccharomyces cerevisiae

Thiol peroxidases are critical enzymes in the redox control of cellular processes that function by reducing low levels of hydroperoxides and regulating redox signaling. These proteins were also shown to regulate genome stability, but how their dysfunction affects the actual mutations in the genome is not known. Saccharomyces cerevisiae has eight thiol peroxidases of glutathione peroxidase and peroxiredoxin families, and the mutant lacking all these genes (Δ8) is viable. In this study, we employed two independent Δ8 isolates to analyze the genome-wide mutation spectrum that results from deficiency in these enzymes. Deletion of these genes was accompanied by a dramatic increase in point mutations, many of which clustered in close proximity and scattered throughout the genome, suggesting strong mutational bias. We further subjected multiple lines of wild-type and Δ8 cells to long-term mutation accumulation, followed by genome sequencing and phenotypic characterization. Δ8 lines showed a significant increase in nonrecurrent point mutations and indels. The original Δ8 cells exhibited reduced growth rate and decreased life span, which were further reduced in all Δ8 mutation accumulation lines. Although the mutation spectrum of the two independent isolates was different, similar patterns of gene expression were observed, suggesting the direct contribution of thiol peroxidases to the observed phenotypes. Expression of a single thiol peroxidase could partially restore the growth phenotype of Δ8 cells. This study shows how deficiency in nonessential, yet critical and conserved oxidoreductase function, leads to increased mutational load and decreased fitness.National Institutes of Health (GM065204

Three natural mechanical systems on Stiefel varieties

We consider integrable generalizations of the spherical pendulum system to the Stiefel variety $V(n,r)=SO(n)/SO(n-r)$ for a certain metric. For the case of V(n,2) an alternative integrable model of the pendulum is presented. We also describe a system on the Stiefel variety with a four-degree potential. The latter has invariant relations on $T^*V(n,r)$ which provide the complete integrability of the flow reduced on the oriented Grassmannian variety $G^+(n,r)=SO(n)/SO(r)\times SO(n-r)$.Comment: 14 page

The Maslov index and nondegenerate singularities of integrable systems

We consider integrable Hamiltonian systems in R^{2n} with integrals of motion F = (F_1,...,F_n) in involution. Nondegenerate singularities are critical points of F where rank dF = n-1 and which have definite linear stability. The set of nondegenerate singularities is a codimension-two symplectic submanifold invariant under the flow. We show that the Maslov index of a closed curve is a sum of contributions +/- 2 from the nondegenerate singularities it is encloses, the sign depending on the local orientation and stability at the singularities. For one-freedom systems this corresponds to the well-known formula for the Poincar\'e index of a closed curve as the oriented difference between the number of elliptic and hyperbolic fixed points enclosed. We also obtain a formula for the Liapunov exponent of invariant (n-1)-dimensional tori in the nondegenerate singular set. Examples include rotationally symmetric n-freedom Hamiltonians, while an application to the periodic Toda chain is described in a companion paper.Comment: 27 pages, 1 figure; published versio