23,834 research outputs found
Hilbert Space of Isomorphic Representations of Bosonized Chiral
We analyse the Hilbert space structure of the isomorphic gauge non-invariant
and gauge invariant bosonized formulations of chiral for the particular
case of the Jackiw-Rajaraman parameter . The BRST subsidiary conditions
are found not to provide a sufficient criterium for defining physical states in
the Hilbert space and additional superselection rules must to be taken into
account. We examine the effect of the use of a redundant field algebra in
deriving basic properties of the model. We also discuss the constraint
structure of the gauge invariant formulation and show that the only primary
constraints are of first class.Comment: LaTeX, 19 page
Definição da malha de amostragem da condutividade elétrica do solo para obtenção de zonas de manejo em pomar de videira.
O desenvolvimento de metodologias capazes de reduzir o número de amostragens no campo e garantir a confiabilidade dos mapas da variabilidade espacial dos atributos do solo é fundamental para a aplicabilidade da agricultura de precisão. Este trabalho foi desenvolvido em Petrolina ? PE com o objetivo de analisar as diferentes zonas homogêneas da condutividade elétrica aparente do solo (CEa), obtidas em função de várias intensidades amostrais, em um pomar de 1,6 ha de videira de mesa irrigada por microaspersão. Foi utilizado um medidor portátil de CEa, que possibilitou a avaliação nas camadas de solo de 0-0,4 m e 0-0,8 m. Os dados de duas coletas realizadas em 2012 e 2013 foram submetidos à análise geoestatÃstica, interpolação por krigagem e geração de mapas de contorno, os quais auxiliaram na delimitação e avaliação das diferentes zonas homogêneas. Foi possÃvel definir o número de amostras necessárias para delimitar com confiabilidade as zonas homogêneas, e auxiliar o produtor na tomada de decisão quanto ao manejo de solo
SnoN Facilitates Axonal Regeneration after Spinal Cord Injury
Adult CNS neurons exhibit a reduced capacity for growth compared to developing neurons, due in part to downregulation of growth-associated genes as development is completed. We tested the hypothesis that SnoN, an embryonically regulated transcription factor that specifies growth of the axonal compartment, can enhance growth in injured adult neurons. In vitro, SnoN overexpression in dissociated adult DRG neuronal cultures significantly enhanced neurite outgrowth. Moreover, TGF-β1, a negative regulator of SnoN, inhibited neurite outgrowth, and SnoN over-expression overcame this inhibition. We then examined whether SnoN influenced axonal regeneration in vivo: indeed, expression of a mutant form of SnoN resistant to degradation significantly enhanced axonal regeneration following cervical spinal cord injury, despite peri-lesional upregulation of TGF-β1. Thus, a developmental mechanism that specifies extension of the axonal compartment also promotes axonal regeneration after adult CNS injury
Europium nitride: A novel diluted magnetic semiconductor
Europium nitride is semiconducting and contains non-magnetic \3+, but
sub-stoichiometric EuN has Eu in a mix of 2+ and 3+ charge states. We show that
at \2+ ~concentrations near 15-20% EuN is ferromagnetic with a Curie
temperature as high as 120 K. The \3+ ~polarization follows that of the \2+,
confirming that the ferromagnetism is intrinsic to the EuN which is thus a
novel diluted magnetic semiconductor. Transport measurements shed light on the
likely exchange mechanisms.Comment: 5 page
Subthreshold characteristics of pentacene field-effect transistors influenced by grain boundaries.
Grain boundaries in polycrystalline pentacene films significantly affect the electrical characteristics of pentacene field-effect transistors (FETs). Upon reversal of the gate voltage sweep direction, pentacene FETs exhibited hysteretic behaviours in the subthreshold region, which was more pronounced for the FET having smaller pentacene grains. No shift in the flat-band voltage of the metal-insulator-semiconductor capacitor elucidates that the observed hysteresis was mainly caused by the influence of localized trap states existing at pentacene grain boundaries. From the results of continuous on/off switching operation of the pentacene FETs, hole depletion during the off period is found to be limited by pentacene grain boundaries. It is suggested that the polycrystalline nature of a pentacene film plays an important role on the dynamic characteristics of pentacene FETs
Emergent bipartiteness in a society of knights and knaves
We propose a simple model of a social network based on so-called
knights-and-knaves puzzles. The model describes the formation of networks
between two classes of agents where links are formed by agents introducing
their neighbours to others of their own class. We show that if the proportion
of knights and knaves is within a certain range, the network self-organizes to
a perfectly bipartite state. However, if the excess of one of the two classes
is greater than a threshold value, bipartiteness is not observed. We offer a
detailed theoretical analysis for the behaviour of the model, investigate its
behaviou r in the thermodynamic limit, and argue that it provides a simple
example of a topology-driven model whose behaviour is strongly reminiscent of a
first-order phase transitions far from equilibrium.Comment: 12 pages, 5 figure
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