371 research outputs found
Chemical composition of oysters from São Paulo and Paraná, Brazil
During the years 1966/67 a comparative study of the chemical composition of oysters was performed on protein, water, ash, trimethylamine oxide, trimethylamine, crude glycogen, iron (Fe+ + +) , calcium, magnesium, total and inorganic phosphorus, with oysters coming from the lagoon regions of the State of São Paulo, namely Cananéia and Bertioga Channel (Santos), and from the State of Paraná. The oyster discussed here is the species found on mangrove tree stilt roots. It was determined as Ostrea arborea Chemnitz, by Dr. Hugo de Souza Lopes, Museu Nacional do Rio de Janeiro. Other zoologists have placed the present species in the genus Crassostrea. Appraisal of the analytical results of the oysters was made taking into consideration the reproductive cycle and the meteorological conditions of the three regions under study. A seasonal variation was observed regarding fat, crude glycogen, dry matter and energy content when related to fresh and dry matter, and of protein when expressed in relation to dry matter. The seasonal variation are related to the reproductive cycle of oysters and is probably influenced by water temperature variations which depend on the solar radiation incidence, and also by phytoplankton abundance. We endeavoured to determine the season when distinct phases of the oyster reproductive cycle occurs, fattening, ripening, gonadal and sexual products discharge, for each one of the three regions studied, as well as the most favorable time of the year for comsumption (winter and spring). This paper shows that oysters are a complementary source of food and income, that their production must be managed for an optimum return to the population inhabiting the lagoon regions of Brazil southern coast.Durante 1966-1967, foi efetuado um estudo comparativo da variação da composição química da ostra (proteína, matéria graxa, água, cinza, óxido de trimetilamina, glicogênio cru, cálcio, magnésio, ferro (Fe+ + + ), fósforo total e inorgânico), proveniente de regiões lagunares do Estado de São Paulo: Cananéia e Canal da Bertioga (Santos), e do Estado do Paraná: Paranaguá. A análise dos resultados foi efetuada, levando-se em consideração o ciclo reprodutivo da ostra e as condições meteorológicas das três regiões em estudo. Com base no observado pode-se considerar o seguinte: 1 - Os teores de umidade das ostras analisadas estão mais próximos dos obtidos por outros autores no gênero Crassostrea do que no gênero Ostrea; 2 - Os teores de magnésio mais elevados que os de cálcio, divergem da maioria dos dados de outros autores, concordando somente com os de NELSON & COULSON (1939), para Crassostrea gigas da costa do Pacífico, Estados Unidos. 3 - Os teores de proteína e cinzas, são em geral mais baixos que os constatados por outros autores; 4 - Foi constatada em 19 análises, dentre 32, a presença de óxido de trimetilamina (TMO), divergindo das observações de ausência total de TMO feita por NORRIS & BERNOIT (1945), para O. japonica, no Pacífico, e DYER (1952), para O. virginica, no Atlântico, únicos que citam trabalhos de TMO em ostra; 5 - Os valores energéticos observados se revelaram mais baixos que os constatados por RUSSEL (1923), TULLEY (1935) e KRVARIC (1953); 6 - Foi observada uma variação sazonal nos teores energéticos das ostras: inverno e primavera, elevados; verão e outono, baixos, concordando com RUSSEL, TULLEY e KRVARIC (op. cit.); 7 - Foi constatada variação sazonal correspondente entre si para os teores de glicogênio, matéria graxa e matéria seca, para a expressão em função da matéria fresca e seca; 8 - A proteína somente apresentou variação sazonal quando expressa em função da matéria seca, sendo oposta à de glicogênio e matéria graxa; 9 - As variações de glicogênio, matéria graxa e matéria seca, estão relacionadas com o ciclo reprodutivo das ostras, sugerindo os seguintes períodos propostos por MATSUMOTO et al. (1934) e analisados para as nossas condições: a) "Fattening": Paranaguá - julho à agosto/66; fevereiro à abril/67; Cananéia - maio à julho/66; março à abril/67; Santos - março à maio/66; julho à agosto/66; março à abril/67. b) "Gonadal ripening": Paranaguá - agosto à outubro/66; Santos - agosto à setembro/66; novembro à dezembro/66. c) "Discharge of sexual products": Paranaguá - maio à julho/66; outubro a dezembro/66; janeiro à fevereiro/67; Cananéia - julho/66 à março/67; abril à julho/67; Santos - maio à junho/66; setembro à outubro/66; dezembro/66 à março/67. 10 - As variações do ciclo reprodutivo são evidenciadas pela variações dos teores de glicogênio, matéria graxa e matéria seca, estando possivelmente relacionadas com a temperatura da água e esta com a radiação solar recebida (Q); 11 - Observou-se uma relação inversa da energia solar recebida (Q) e os teores de glicogênio e de matéria seca das ostras analisadas; 12 - As semelhanças observadas entre a composição química das ostras procedentes de Paranaguá, Cananéia e Canal da Bertioga (Santos), poderão ser consequentes da semelhança dos fatores meteorológicos atuantes, temperatura da água e do ar, precipitação e radiação solar; 13 - É possível que as variações da composição química e portanto o ciclo reprodutivo, observados para 1966/67, influenciados pelas condições meteorológicas desse período, sejam representativos para cada região em virtude da concordância deste período com o representativo da região; 14 - As ostras apresentam melhores características para o consumo, sob o ponto de vista energético e aceitabilidade durante o inverno e primavera; 15 - A determinação da matéria seca poderá ser usada, nas nossas condições, como indicadores das variações dos teores de glicogênio e matéria graxa e, conseqüentemente, do ciclo de reprodução
Multiple G-It\^{o} integral in the G-expectation space
In this paper, motivated by mathematic finance we introduce the multiple
G-It\^{o} integral in the G-expectation space, then investigate how to
calculate. We get the the relationship between Hermite polynomials and multiple
G-It\^{o} integrals which is a natural extension of the classical result
obtained by It\^{o} in 1951.Comment: 9 page
The Dirac-Dowker Oscillator
The oscillator-like interaction is introduced in the equation for the
particle of arbitrary spin, given by Dirac and re-written to a matrix form by
Dowker.Comment: LaTeX file, 4pp. Preprint EFUAZ 94-0
Relating pseudospin and spin symmetries through charge conjugation and chiral transformations: the case of the relativistic harmonic oscillator
We solve the generalized relativistic harmonic oscillator in 1+1 dimensions,
i.e., including a linear pseudoscalar potential and quadratic scalar and vector
potentials which have equal or opposite signs. We consider positive and
negative quadratic potentials and discuss in detail their bound-state solutions
for fermions and antifermions. The main features of these bound states are the
same as the ones of the generalized three-dimensional relativistic harmonic
oscillator bound states. The solutions found for zero pseudoscalar potential
are related to the spin and pseudospin symmetry of the Dirac equation in 3+1
dimensions. We show how the charge conjugation and chiral
transformations relate the several spectra obtained and find that for massless
particles the spin and pseudospin symmetry related problems have the same
spectrum, but different spinor solutions. Finally, we establish a relation of
the solutions found with single-particle states of nuclei described by
relativistic mean-field theories with scalar, vector and isoscalar tensor
interactions and discuss the conditions in which one may have both nucleon and
antinucleon bound states.Comment: 33 pages, 10 figures, uses revtex macro
Vibrations and fractional vibrations of rods, plates and Fresnel pseudo-processes
Different initial and boundary value problems for the equation of vibrations
of rods (also called Fresnel equation) are solved by exploiting the connection
with Brownian motion and the heat equation. The analysis of the fractional
version (of order ) of the Fresnel equation is also performed and, in
detail, some specific cases, like , 1/3, 2/3, are analyzed. By means
of the fundamental solution of the Fresnel equation, a pseudo-process ,
with real sign-varying density is constructed and some of its properties
examined. The equation of vibrations of plates is considered and the case of
circular vibrating disks is investigated by applying the methods of
planar orthogonally reflecting Brownian motion within . The composition of
F with reflecting Brownian motion yields the law of biquadratic heat
equation while the composition of with the first passage time of
produces a genuine probability law strictly connected with the Cauchy process.Comment: 33 pages,8 figure
Comment on ``the Klein-Gordon Oscillator''
The different ways of description of the particle with oscillator-like
interaction are considered. The results are in conformity with the previous
paper of S. Bruce and P. Minning.Comment: LaTeX file, 5p
Statistical Properties of Functionals of the Paths of a Particle Diffusing in a One-Dimensional Random Potential
We present a formalism for obtaining the statistical properties of
functionals and inverse functionals of the paths of a particle diffusing in a
one-dimensional quenched random potential. We demonstrate the implementation of
the formalism in two specific examples: (1) where the functional corresponds to
the local time spent by the particle around the origin and (2) where the
functional corresponds to the occupation time spent by the particle on the
positive side of the origin, within an observation time window of size . We
compute the disorder average distributions of the local time, the inverse local
time, the occupation time and the inverse occupation time, and show that in
many cases disorder modifies the behavior drastically.Comment: Revtex two column 27 pages, 10 figures, 3 table
Brownian Simulations and Uni-Directional Flux in Diffusion
Brownian dynamics simulations require the connection of a small discrete
simulation volume to large baths that are maintained at fixed concentrations
and voltages. The continuum baths are connected to the simulation through
interfaces, located in the baths sufficiently far from the channel. Average
boundary concentrations have to be maintained at their values in the baths by
injecting and removing particles at the interfaces. The particles injected into
the simulation volume represent a unidirectional diffusion flux, while the
outgoing particles represent the unidirectional flux in the opposite direction.
The classical diffusion equation defines net diffusion flux, but not
unidirectional fluxes. The stochastic formulation of classical diffusion in
terms of the Wiener process leads to a Wiener path integral, which can split
the net flux into unidirectional fluxes. These unidirectional fluxes are
infinite, though the net flux is finite and agrees with classical theory. We
find that the infinite unidirectional flux is an artifact caused by replacing
the Langevin dynamics with its Smoluchowski approximation, which is classical
diffusion. The Smoluchowski approximation fails on time scales shorter than the
relaxation time of the Langevin equation. We find the unidirectional
flux (source strength) needed to maintain average boundary concentrations in a
manner consistent with the physics of Brownian particles. This unidirectional
flux is proportional to the concentration and inversely proportional to
to leading order. We develop a BD simulation that maintains
fixed average boundary concentrations in a manner consistent with the actual
physics of the interface and without creating spurious boundary layers
Maximum likelihood drift estimation for a threshold diffusion
We study the maximum likelihood estimator of the drift parameters of a
stochastic differential equation, with both drift and diffusion coefficients
constant on the positive and negative axis, yet discontinuous at zero. This
threshold diffusion is called drifted Oscillating Brownian motion.For this
continuously observed diffusion, the maximum likelihood estimator coincide with
a quasi-likelihood estimator with constant diffusion term. We show that this
estimator is the limit, as observations become dense in time, of the
(quasi)-maximum likelihood estimator based on discrete observations. In long
time, the asymptotic behaviors of the positive and negative occupation times
rule the ones of the estimators. Differently from most known results in the
literature, we do not restrict ourselves to the ergodic framework: indeed,
depending on the signs of the drift, the process may be ergodic, transient or
null recurrent. For each regime, we establish whether or not the estimators are
consistent; if they are, we prove the convergence in long time of the properly
rescaled difference of the estimators towards a normal or mixed normal
distribution. These theoretical results are backed by numerical simulations
Relativistic quantum mechanics of a Dirac oscillator
The Dirac oscillator is an exactly soluble model recently introduced in the
context of many particle models in relativistic quantum mechanics. The model
has been also considered as an interaction term for modelling quark confinement
in quantum chromodynamics. These considerations should be enough for
demonstrating that the Dirac oscillator can be an excellent example in
relativistic quantum mechanics. In this paper we offer a solution to the
problem and discuss some of its properties. We also discuss a physical picture
for the Dirac oscillator's non-standard interaction, showing how it arises on
describing the behaviour of a neutral particle carrying an anomalous magnetic
moment and moving inside an uniformly charged sphere.Comment: 19 pages, 1 figur
- …