See-Saw Masses for Quarks and Leptons in SU(5)

We build on a recent paper by Grinstein, Redi and Villadoro, where a see-saw like mechanism for quark masses was derived in the context of spontaneously broken gauged flavour symmetries. The see-saw mechanism is induced by heavy Dirac fermions which are added to the Standard Model spectrum in order to render the flavour symmetries anomaly-free. In this letter we report on the embedding of these fermions into multiplets of an SU(5) grand unified theory and discuss a number of interesting consequences.Comment: 15 pages, 4 figures (v3: outline restructured, modified mechanism to cancel anomalies

Combinatorial aspect of fashion

Simulations are performed according to the Axelrod model of culture dissemination, with modified mechanism of repulsion. Previously, repulsion was considered by Radillo-Diaz et al (Phys. Rev. E 80 (2009) 066107) as dependent on a predefined threshold. Here the probabilities of attraction and repulsion are calculated from the number of cells in the same states. We also investigate the influence of some homogeneity, introduced to the initial state. As the result of the probabilistic definition of repulsion, the ordered state vanishes. A small cluster of a few percent of population is retained only if in the initial state a set of agents is prepared in the same state. We conclude that the modelled imitation is successful only with respect to agents, and not only their features

Evaluation and improvement of model algorithms for predicting belowground carbon allocation in forests

Rapidly rising concentrations of atmospheric carbon dioxide (CO 2) influence forest productivity by stimulating plant growth. It can also modify carbon partitioning patterns, altering the global carbon cycle. Nitrogen and carbon cycles are tightly linked; with changes in nitrogen availability affecting ecosystem carbon allocation by shifting carbon to roots for nitrogen uptake. This paper discusses a modification to the PnET-CN model (Aber et al. 1997) developed to shift plant carbon allocation belowground in response to nitrogen limitation. According to functional equilibrium models of plant carbon allocation, a nitrogen control mechanism alters belowground carbon estimates by increasing carbon allocation to fine roots when nitrogen resources are low. Testing of the modified mechanism with data from three free-air CO 2 enrichment (FACE) forests supported the mechanism by allocating more carbon to fine roots. Application of the model with data from five northeastern forests, under a variety of global climate change scenarios, also supported the modified mechanism with an increase in soil carbon storage

Asymmetry in Charmed Particles Production in Σ−\Sigma^{-} beam

We present the calculation of the inclusive $x_F$-distributions of charmed hadrons, produced in high-energy $\Sigma^-$-beam. The calculation is based on the modified mechanism of charmed quarks fragmentation as well as on the mechanism of $c$-quark recombination with the valence quarks from initial hadrons. We predict the additional asymmetry in the production of charmed hadrons due to the different distributions of the valence s and d quarks in $\Sigma^-$-beam.Comment: 19 pages, Latex, 6 figure

Laser-modified one- and two-photon absorption:Expanding the scope of optical nonlinearity

It is shown that conventional one-photon and two-photon absorption processes can be made subject to nonlinear optical control, in each case significantly modifying the efficiency of absorption, through the effect of a secondary, off-resonant stimulus laser beam. The mechanistic origin of these laser-modified absorption processes, in which the stimulus beam emerges unchanged, is traced to higher-order terms in standard perturbation treatments. These normally insignificant terms become unusually prominent when the secondary optical stimulus is moderately intense. Employing a quantum formulation, the effects of the stimulus beam on one-photon and two-photon absorption are analyzed, and calculations are performed to determine the degree of absorption enhancement, and the form of spectral manifestation, under various laser intensities. The implications of differences in selection rules are also considered and exemplified, leading to the identification of dark states that can be populated as a result of laser-modified absorption. Attention is also drawn to the possibility of quantum nondemolition measurements, based on such a form of optical nonlinearity

A new mechanistic proposal for the aromatic cycle of the MTO process based on a computational investigation for H-SSZ-13

The paring mechanism of the aromatic cycle of the hydrocarbon pool is reinvestigated based on the heptamethylbenzenium cation adsorbed within H-SSZ-13 using quantum chemical calculations. Based on the outcome of our calculations we propose a modified mechanism to that presently existing in the literature, where ring contraction starts from hexamethylmethylenecyclohexadiene. After protonation and ring contraction, the unsaturated methylene side chain remains throughout this mechanism. This new mechanistic proposal avoids the formation of antiaromatic intermediates present in current proposals for the paring mechanism. The barriers for the modified paring mechanism are found to be significantly lower than those for the original proposal, being in the range from 130–150 kJ mol−1 at 400 °C and are thus accessible at typical MTO conditions

Load balancing of communication channels with the use of routing protocols

In the article the authors propose a method for load-balancing of network resources forthe case which uses a routing protocols. In the first part of the article the authors present currentlyused algorithms for load balancing and possibilities of their modification. Through the introductionof additional hardware components for each node: the agent and the probe; it is possible to monitorand control the current system performance. The whole analyzed network is treated as a complexsystem. This allows to eliminate overloading of route nodes (through ongoing analysis of the optimaloperating point for a given node). Load balancing can be achieved using a modified mechanism ofECMP. The proposed approach allows for dynamic adjustment of load to network resources and thuseffectively to balance network traffic