476 research outputs found
Calculation of hyperfine splitting in mesons using configuration interaction approach
The spin - spin mass splitting of light, heavy and mixed mesons are described
within a good accuracy in the potential model with screened potential. We
conclude that the long - distance part of the potential cannot be pure scalar
and that a vector - scalar mixture is favoured. With the same parameters which
gives correct average mass spectrum excellent spin - spin splittings of heavy
quarkonia is obtained. The results are obtained by going beyond usually used
perturbation method, namely using configuration interaction approach.Comment: 8 pages, LaTe
A Parallel Distributed Strategy for Arraying a Scattered Robot Swarm
We consider the problem of organizing a scattered group of robots in
two-dimensional space, with geometric maximum distance between robots. The
communication graph of the swarm is connected, but there is no central
authority for organizing it. We want to arrange them into a sorted and
equally-spaced array between the robots with lowest and highest label, while
maintaining a connected communication network.
In this paper, we describe a distributed method to accomplish these goals,
without using central control, while also keeping time, travel distance and
communication cost at a minimum. We proceed in a number of stages (leader
election, initial path construction, subtree contraction, geometric
straightening, and distributed sorting), none of which requires a central
authority, but still accomplishes best possible parallelization. The overall
arraying is performed in time, individual messages, and
travel distance. Implementation of the sorting and navigation use communication
messages of fixed size, and are a practical solution for large populations of
low-cost robots
Glueball Masses in Relativistic Potential Model
The problem of glueball mass spectra using the relativistic Dirac equation is
studied. Also the Breit-Fermi approach used to obtaining hyperfine splitting in
glueballs. Our approach is based on the assumption, that the nature and the
forces between two gluons are the short-range. We were to calculate the
glueball masses with used screened potential.Comment: 7 pages, LaTe
The role of relativistic kinematics in describing two-quark systems
An attempt to incorporate relativistic kinematics in the description of light
quark systems is made. It seems that the way of such an incorporation suggested by R.Gaida and his collaborators is very promising. Comparison of
these results with the experimental data concerning a boson mass spectrum shows that this approach is among the best theoretical interpretations
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Spin Effects in Two Quark System and Mixed States
Based on the numeric solution of a system of coupled channels for vector
mesons (- and -waves mixing) and for tensor mesons (- and -waves
mixing) mass spectrum and wave functions of a family of vector mesons
in triplet states are obtained. The calculations are performed using
a well known Cornell potential with a mixed Lorentz-structure of the
confinement term. The spin-dependent part of the potential is taken from the
Breit-Fermi approach. The effect of singular terms of potential is considered
in the framework of the perturbation theory and by a configuration interaction
approach (CIA), modified for a system of coupled equations. It is shown that
even a small contribution of the -wave to be very important at the
calculation of certain characteristics of the meson states.Comment: 12 pages, LaTe
Position of eukaryotic translation initiation factor eIF1A on the 40S ribosomal subunit mapped by directed hydroxyl radical probing
The universally conserved eukaryotic initiation factor (eIF), eIF1A, plays multiple roles throughout initiation: it stimulates eIF2/GTP/Met-tRNAiMet attachment to 40S ribosomal subunits, scanning, start codon selection and subunit joining. Its bacterial ortholog IF1 consists of an oligonucleotide/oligosaccharide-binding (OB) domain, whereas eIF1A additionally contains a helical subdomain, N-terminal tail (NTT) and C-terminal tail (CTT). The NTT and CTT both enhance ribosomal recruitment of eIF2/GTP/Met-tRNAiMet, but have opposite effects on the stringency of start codon selection: the CTT increases, whereas the NTT decreases it. Here, we determined the position of eIF1A on the 40S subunit by directed hydroxyl radical cleavage. eIF1A's OB domain binds in the A site, similar to IF1, whereas the helical subdomain contacts the head, forming a bridge over the mRNA channel. The NTT and CTT both thread under Met-tRNAiMet reaching into the P-site. The NTT threads closer to the mRNA channel. In the proposed model, the NTT does not clash with either mRNA or Met-tRNAiMet, consistent with its suggested role in promoting the āclosedā conformation of ribosomal complexes upon start codon recognition. In contrast, eIF1A-CTT appears to interfere with the P-site tRNA-head interaction in the āclosedā complex and is likely ejected from the P-site upon start codon recognition
Position of eukaryotic translation initiation factor eIF1A on the 40S ribosomal subunit mapped by directed hydroxyl radical probing
The universally conserved eukaryotic initiation factor (eIF), eIF1A, plays multiple roles throughout initiation: it stimulates eIF2/GTP/Met-tRNAiMet attachment to 40S ribosomal subunits, scanning, start codon selection and subunit joining. Its bacterial ortholog IF1 consists of an oligonucleotide/oligosaccharide-binding (OB) domain, whereas eIF1A additionally contains a helical subdomain, N-terminal tail (NTT) and C-terminal tail (CTT). The NTT and CTT both enhance ribosomal recruitment of eIF2/GTP/Met-tRNAiMet, but have opposite effects on the stringency of start codon selection: the CTT increases, whereas the NTT decreases it. Here, we determined the position of eIF1A on the 40S subunit by directed hydroxyl radical cleavage. eIF1A's OB domain binds in the A site, similar to IF1, whereas the helical subdomain contacts the head, forming a bridge over the mRNA channel. The NTT and CTT both thread under Met-tRNAiMet reaching into the P-site. The NTT threads closer to the mRNA channel. In the proposed model, the NTT does not clash with either mRNA or Met-tRNAiMet, consistent with its suggested role in promoting the āclosedā conformation of ribosomal complexes upon start codon recognition. In contrast, eIF1A-CTT appears to interfere with the P-site tRNA-head interaction in the āclosedā complex and is likely ejected from the P-site upon start codon recognition
Fatigue Failure Analysis for Bolt-Nut Connections having Slight Pitch Differences using Experimental and Finite Element Methods
In this paper, fatigue failure is considered, for bolt-nut connections, when a slight pitch difference is introduced between the bolt and the nut. To improve the fatigue life, three types of pitch difference are produced on the specimens and the experimental results are compared and discussed in terms of FEM analysis. Considering the standard bolt-nutconnection of Ī±=0 Ī¼m, the bolt fracture does not happen at the No. 1 thread by introducing a slight pitch difference of Ī±=5 Ī¼m and Ī±=15 Ī¼m, as observed from the experiments. Furthermore, it is found that the fatigue life can be extended by introducing suitable pitch differences. The effect of bolt-nut fitted clearance, on the fatigue failure is also investigated
GalR, GalX and AraR co-regulate d-galactose and l-arabinose utilization in Aspergillus nidulans
Filamentous fungi produce a wide variety of enzymes in order to efficiently degrade plant cell wall polysaccharides. The production of these enzymes is controlled by transcriptional regulators, which also control the catabolic pathways that convert the released monosaccharides. Two transcriptional regulators, GalX and GalR, control d-galactose utilization in the model filamentous fungus Aspergillus nidulans, while the arabinanolytic regulator AraR regulates l-arabinose catabolism. d-Galactose and l-arabinose are commonly found together in polysaccharides, such as arabinogalactan, xylan and rhamnogalacturonan I. Therefore, the catabolic pathways that convert d-galactose and l-arabinose are often also likely to be active simultaneously. In this study, we investigated the interaction between GalX, GalR and AraR in d-galactose and l-arabinose catabolism. For this, we generated single, double and triple mutants of the three regulators, and analysed their growth and enzyme and gene expression profiles. Our results clearly demonstrated that GalX, GalR and AraR co-regulate d-galactose catabolism in A. nidulans. GalX has a prominent role on the regulation of genes of d-galactose oxido-reductive pathway, while AraR can compensate for the absence of GalR and/or GalX.Peer reviewe
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