1,754 research outputs found
Fluctuations in Hadronic and Nuclear Collisions
We investigate several fluctuation effects in high-energy hadronic and
nuclear collisions through the analysis of different observables. To introduce
fluctuations in the initial stage of collisions, we use the Interacting Gluon
Model (IGM) modified by the inclusion of the impact parameter. The inelasticity
and leading-particle distributions follow directly from this model. The
fluctuation effects on rapidity distributions are then studied by using
Landau's Hydrodynamic Model in one dimension. To investigate further the
effects of the multiplicity fluctuation, we use the Longitudinal Phase-Space
Model, with the multiplicity distribution calculated within the hydrodynamic
model, and the initial conditions given by the IGM. Forward-backward
correlation is obtained in this way.Comment: 22 pages, RevTex, 8 figures (included); Invited paper to the special
issue of Foundation of Physics dedicated to Mikio Namiki's 70th. birthda
Monitoramento do impacto de genótipos de sorgo tolerantes e sensíveis à toxidez de alumínio sobre as comunidades microbianas da rizosfera.
Geoestatística no estudo de modelagem temporal da precipitação.
A análise geoestatística é uma poderosa ferramenta utilizada em estudos de dependência espacial. No que tange à dependência temporal, poucas são as análises realizadas com essa metodologia. Neste trabalho foi utilizada a técnica de geoestatística para ajustar um modelo de série temporal de precipitação, cujo poder é avaliado em predizer valores futuros. O estudo foi realizado na Bacia do Rio Itapemirim em uma série de precipitação mensal de 1940 a 2006. O modelo geoestatístico foi comparado com um modelo de séries temporais de Box e Jenkins. O modelo geoestatístico ajustado foi aquele com 96 vizinhos utilizados na previsão e erro relativo absoluto médio de 80,46. A metodologia de geoestatistica apresentou melhores resultados na estimação da precipitação mensal, em relação ao modelo SARIMA (2,1,1)(0,1,1)12
Doping-dependent study of the periodic Anderson model in three dimensions
We study a simple model for -electron systems, the three-dimensional
periodic Anderson model, in which localized states hybridize with
neighboring states. The states have a strong on-site repulsion which
suppresses the double occupancy and can lead to the formation of a Mott-Hubbard
insulator. When the hybridization between the and states increases, the
effects of these strong electron correlations gradually diminish, giving rise
to interesting phenomena on the way. We use the exact quantum Monte-Carlo,
approximate diagrammatic fluctuation-exchange approximation, and mean-field
Hartree-Fock methods to calculate the local moment, entropy, antiferromagnetic
structure factor, singlet-correlator, and internal energy as a function of the
hybridization for various dopings. Finally, we discuss the relevance of
this work to the volume-collapse phenomenon experimentally observed in
f-electron systems.Comment: 12 pages, 8 figure
Metal-sensitive and thermostable trypsin from the crevalle jack (Caranx hippos) pyloric caeca: purification and characterization
Background: Over the past decades, the economic development and world population growth has led to increased for food demand. Increasing the fish production is considered one of the alternatives to meet the increased food demand, but the processing of fish leads to by-products such as skin, bones and viscera, a source of environmental contamination. Fish viscera have been reported as an important source of digestive proteases with interesting characteristics for biotechnological processes. Thus, the aim of this study was to purify and to characterize a trypsin from the processing by-products of crevalle jack (Caranx hippos) fish.Results: A 27.5 kDa trypsin with N-terminal amino acid sequence IVGGFECTPHVFAYQ was easily purified from the pyloric caeca of the crevalle jack. Its physicochemical and kinetic properties were evaluated using N-alpha-benzoyl-(DL)-arginine-p-nitroanilide (BApNA) as substrate. in addition, the effects of various metal ions and specific protease inhibitors on trypsin activity were determined. Optimum pH and temperature were 8.0 and 50 degrees C, respectively. After incubation at 50 degrees C for 30 min the enzyme lost only 20% of its activity. K-m, k(cat), and k(cat)/K-m values using BApNA as substrate were 0.689 mM, 6.9 s(-1), and 10 s(-1) mM(-1), respectively. High inhibition of trypsin activity was observed after incubation with Cd2+, Al3+, Zn2+, Cu2+, Pb2+, and Hg2+ at 1 mM, revealing high sensitivity of the enzyme to metal ions.Conclusions: Extraction of a thermostable trypsin from by-products of the fishery industry confirms the potential of these materials as an alternative source of these biomolecules. Furthermore, the results suggest that this trypsin-like enzyme presents interesting biotechnological properties for industrial applications.Financiadora de Estudos e Projetos (FINEP/RECARCINE)Petroleo do Brasil S/A (PETROBRAS)Secretaria Especial de Aquicultura e Pesca (SEAP/PR)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundacao de Apoio a Ciencia e Tecnologia do Estado de Pernambuco (FACEPE)Univ Fed Pernambuco, Lab Enzimol LABENZ, Dept Bioquim CCB, BR-50670910 Recife, PE, BrazilUniv Fed Pernambuco, LIKA, BR-50670910 Recife, PE, BrazilUniversidade Federal de São Paulo, Dept Biofis, Escola Paulista Med, BR-04044020 São Paulo, BrazilUniv Fed Pernambuco, Lab Glicoprot, Dept Bioquim CCB, BR-50670910 Recife, PE, BrazilUniversidade Federal de São Paulo, Dept Biofis, Escola Paulista Med, BR-04044020 São Paulo, BrazilWeb of Scienc
Critical temperature for the two-dimensional attractive Hubbard Model
The critical temperature for the attractive Hubbard model on a square lattice
is determined from the analysis of two independent quantities, the helicity
modulus, , and the pairing correlation function, . These
quantities have been calculated through Quantum Monte Carlo simulations for
lattices up to , and for several densities, in the
intermediate-coupling regime. Imposing the universal-jump condition for an
accurately calculated , together with thorough finite-size scaling
analyses (in the spirit of the phenomenological renormalization group) of
, suggests that is considerably higher than hitherto assumed.Comment: 5 pages, 6 figures. Accepted for publication in Phys. Rev.
Low temperature properties of the fermionic mixtures with mass imbalance in optical lattice
We study the attractive Hubbard model with mass imbalance to clarify low
temperature properties of the fermionic mixtures in the optical lattice. By
combining dynamical mean-field theory with the continuous-time quantum Monte
Carlo simulation, we discuss the competition between the superfluid and density
wave states at half filling. By calculating the energy and the order parameter
for each state, we clarify that the coexisting (supersolid) state, where the
density wave and superfluid states are degenerate, is realized in the system.
We then determine the phase diagram at finite temperatures.Comment: 5 pages, 4 figures, accepted for publication in J. Phys. Soc. Jp
Estimating the inelasticity with the information theory approach
Using the information theory approach, in both its extensive and nonextensive
versions, we estimate the inelasticity parameter of hadronic reactions
together with its distribution and energy dependence from and
data. We find that the inelasticity remains essentially constant in energy
except for a variation around , as was originally expected.Comment: 14 pages, 8 figures. Misprints correcte
Local Dynamics and Strong Correlation Physics I: 1D and 2D Half-filled Hubbard Models
We report on a non-perturbative approach to the 1D and 2D Hubbard models that
is capable of recovering both strong and weak-coupling limits. We first show
that even when the on-site Coulomb repulsion, U, is much smaller than the
bandwith, the Mott-Hubbard gap never closes at half-filling in both 1D and 2D.
Consequently, the Hubbard model at half-filling is always in the
strong-coupling non-perturbative regime. For both large and small U, we find
that the population of nearest-neighbour singlet states approaches a value of
order unity as as would be expected for antiferromagnetic order. We
also find that the double occupancy is a smooth monotonic function of U and
approaches the anticipated non-interacting limit and large U limits. Finally,
in our results for the heat capacity in 1D differ by no more than 1% from the
Bethe ansatz predictions. In addition, we find that in 2D, the heat capacity vs
T for different values of U exhibits a universal crossing point at two
characteristic temperatures as is seen experimentally in a wide range of
strongly-correlated systems such as , , and . The
success of this method in recovering well-established results that stem
fundamentally from the Coulomb interaction suggests that local dynamics are at
the heart of the physics of strongly correlated systems.Comment: 10 pages, 16 figures included in text, Final version for publication
with a reference added and minor corrections. Phys. Rev. B, in pres
Enhancement of the Physicochemical Properties of Pt(dien)(nucleobase) (2+) for HIVNCp7 Targeting
Physicochemical properties of coordination compounds can be exploited for molecular recognition of biomolecules. The inherent π-π stacking properties of [Pt(chelate)(N-donor)]2+([PtN4]) complexes were modulated by systematic variation of the chelate (diethylenetriamine and substituted derivatives) and N-donor (nucleobase or nucleoside) in the formally substitution-inert PtN4 coordination sphere. Approaches to target the HIV nucleocapsid protein HIVNCp7 are summarized building on (i) assessment of stacking interactions with simple tryptophan or tryptophan derivatives to (ii) the tryptophan-containing C-terminal zinc finger and (iii) to the full two-zinc finger peptide and its interactions with RNA and DNA. The xanthosine nucleoside was identified as having significantly enhanced stacking capability over guanosine. Correlation of the LUMO energies of the modified nucleobases with the DFT π-stacking energies shows that frontier orbital energies of the individual monomers can be used as a first estimate of the π-stacking strength to Trp. Cellular accumulation studies showed no significant correlation with lipophilicity of the compounds, but all compounds had very low cytotoxicity suggesting the potential for antiviral selectivity. The conceptual similarities between nucleobase alkylation and platination validates the design of formally substitution-inert coordination complexes as weak Lewis acid electrophiles for selective peptide targeting
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