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1.
Onody RN de Medeiros NG 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》1999,60(3):3234-3238
We introduce an age-structured asexual population model containing all the relevant features of evolutionary aging theories. Beneficial as well as deleterious mutations, heredity, and arbitrary fecundity are present and managed by natural selection. An exact solution without aging is found. We show that fertility is associated with generalized forms of the Fibonacci sequence, while mutations and natural selection are merged into an integral equation which is solved by Fourier series. Average survival probabilities and Malthusian growth exponents are calculated and indicate that the system may exhibit mutational meltdown. The relevance of the model in the context of fissile reproduction groups like many protozoa and coelenterates is discussed. 相似文献
2.
Isoperimetric inequalities are applied to a moving-boundaryproblem for doubly-connected domains. This problem occurs forexample in electrochemistry, in which case the domains in questionare the electrolyte of an electrolytic cell. The two electrodessurrounding the electrolyte are assumed to grow or dissolve,at different rates in general, by electrochemical reaction.We obtain optimal estimates showing, for example, that the leastchange in volume of each electrode always occurs in sphericalsymmetry. 相似文献
3.
TORBJØRN LORENTZEN 《Natural Resource Modeling》2008,21(3):416-435
Abstract Global warming is expected to affect the ecosystem in the Northeast Atlantic, and substantial changes will also affect the aquaculture industry. Farming of salmon and trout is the biggest aquaculture industry in Norway, with an export value of about 3 billion US dollars in 2007. The objective of the paper is to analyze the potential economic effect a general increase in sea temperature can have on the Norwegian salmon aquaculture industry. The assessment of the economic impact of global warming is made possible by estimating a growth function, which explicitly includes sea water temperature. The analysis compares the economic effect of a climate change on fish farming plants in the south and the north of Norway. The scenarios are based on a model with monthly seasonal variation in temperature. 相似文献
4.
M. P.?LoboEmail author R. N.?Onody 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,45(4):533-537
The Y chromosomes are genetically degenerated and do not recombine
with their matching partners X. Recombination of XX pairs is
pointed out as the key factor for the Y chromosome degeneration.
However, there is an additional evolutionary force driving
sex-chromosomes evolution. Here we show this mechanism by means of
two different evolutionary models, in which sex chromosomes with
non-recombining XX and XY pairs of chromosomes is considered. Our
results show three curious effects. First, we observed that even
when both XX and XY pairs of chromosomes do not recombine, the Y
chromosomes still degenerate. Second, the accumulation of
mutations on Y chromosomes followed a completely different pattern
then those accumulated on X chromosomes. And third, the models may
differ with respect to sexual proportion. These findings suggest
that a more primeval mechanism rules the evolution of Y
chromosomes due exclusively to the sex-chromosomes asymmetry
itself, i.e., the fact that Y chromosomes never experience female
bodies. Over aeons, natural selection favored X chromosomes
spontaneously, even if at the very beginning of evolution, both XX
and XY pairs of chromosomes did not recombine. 相似文献
5.
REMEDIOS GONZÁLEZ-LUQUE MANUELA MERCHÁN MERCEDES RUBIO LUIS SERRANO-ANDRÉS BJÖRN O. ROOS MIGUEL-ÁNGEL MIRANDA 《Molecular physics》2013,111(13):1977-1982
The lower excited states of 2-benzoylthiophene have been studied using ab initio quantum chemical methods based on multiconfigurational wave functions. Six singlet and six triplet excited states have been characterized. The geometry has been optimized for the two lowest triplet states, which are responsible for the photoreactivity of the chromophore in the photosensitizing drug tiaprofenic acid. The T1(π → π?) and T2(n → π?) states have been found to be close in energy with the π → π? state slightly lower. The excited states have been characterized using density difference and spin density plots. The different photochemical behaviour of the two triplet states can be rationalized from the theoretical data. 相似文献
6.
BJÖRN O. ROOS 《Molecular physics》2013,111(1-2):87-91
Results are presented from a theoretical study of the × 6Σ+, A 6Σ+ and 6Δ electronic states of CrH using multiconfiguration second-order perturbation theory in the multi-state formalism (MS-CASPT2). It is shown that the results for the spectroscopic constants and radiative lifetimes for the A state are in agreement with experiment and an earlier multireference configuration interaction study only if the two close lying × and A states are allowed to interact at a level of approximation that includes dynamic correlation. 相似文献
7.
R. N. Onody G. M. Favaro E. R. Cazaroto 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(4):487-493
The GARCH (p, q) model is a very interesting stochastic process with
widespread applications and a central role in empirical finance. The
Markovian GARCH (1, 1) model has only 3 control parameters and a
much discussed question is how to estimate them when a series of
some financial asset is given. Besides the maximum likelihood
estimator technique, there is another method which uses the
variance, the kurtosis and the autocorrelation time to determine
them. We propose here to use the standardized 6th moment. The set
of parameters obtained in this way produces a very good probability
density function and a much better time autocorrelation function.
This is true for both studied indexes: NYSE Composite and FTSE 100.
The probability of return to the origin is investigated at different
time horizons for both Gaussian and Laplacian GARCH models. In spite
of the fact that these models show almost identical performances
with respect to the final probability density function and to the
time autocorrelation function, their scaling properties are,
however, very different. The Laplacian GARCH model gives a better
scaling exponent for the NYSE time series, whereas the Gaussian
dynamics fits better the FTSE scaling exponent. 相似文献
8.
L. O. BJÖRN 《Photochemistry and photobiology》1969,10(2):125-129
Abstract— Photoinactivation in vitro at pH 7.0 of catalases from different sources (bovine liver, spinach leaves, and Micrococcus lysodeikticus) was studied. The wavelength of the inactivating light was close to the Soret peak of catalase. No great difference in light sensitivity between soluble catalases were found; the inactivation cross sections found ranged from 3.8.10-4 to 5.0. 10-4 Å2 /molecule. The inactivation quantum yield is 2.2. 10-5 for bovine liver catalase and 3.110-5 for Micrococcus catalase. The quantum yield for soluble spinach catalase is of a similar order of magnitude. There are some indications of a greater resistance to photodestruction of the spinach leaf catalase activity associated with small particles. 相似文献
9.
Considering the nucleon as consisting entirely of its valence quarks confined independently in a scalar-vector harmonic potential;
unpolarized structure functions F
1(x, μ
2) and F
2(x, μ
2) are derived in the Bjorken limit under certain simplifying assumptions; from which valence quark distribution functions
u
v(x, μ
2) and d
v(x, μ
2) are appropriately extracted satisfying the normalization constraints. QCD-evolution of these input distributions from a
model scale of μ
2=0.07 GeV2 to a higher Q
2 scale of Q
0
2
=15 GeV2 yields xu
v(x, Q
0
2
) and xd
v(x, Q
0
2
) in good agreement with experimental data. The gluon and sea-quark distributions such as G(x, Q
0
2
) and q
s(x, Q
0
2
) are dynamically generated with a reasonable qualitative agreement with the available data; using the leading order renormalization
group equations with appropriate valence-quark distributions as the input. 相似文献
10.
L. O. BJÖRN 《Photochemistry and photobiology》1971,13(1):5-20
Abstract— –Small amounts of N -methyl phenazonium methosulphate (PMS) added to a suspension of Chlorella pyrenoidosa accelerate the emission of the long-lived far-red induced afterglow without greatly changing the amount of light emitted. The effect is noticeable in dilute suspensions at a PMS concentration of 10-9 M. The concept of afterglow unit is introduced and defined as that part of the sample in which the rate of energy reemission can be controlled by a single molecule of PMS. The number of chlorophyll molecules per afterglow unit is about 105 . It is possible that the afterglow unit is identical to the thylakoid.
The rate constant for the final first order decay phase of afterglow at room temperature is about 0.7 min-1 without PMS and about 3 times larger for a unit with one PMS molecule.
Diuron (DCMU) lowers the rate of afterglow decay. Desaspidin on the other hand decreases the amount of light emitted without affecting the decay rate. Carbonylcyanide- m -chlorophenyl hydrazone (CCCP) decreases the afterglow over the whole time-range and increases the decay rate. A kinetic model is developed to account for the results. 相似文献
The rate constant for the final first order decay phase of afterglow at room temperature is about 0.7 min
Diuron (DCMU) lowers the rate of afterglow decay. Desaspidin on the other hand decreases the amount of light emitted without affecting the decay rate. Carbonylcyanide- m -chlorophenyl hydrazone (CCCP) decreases the afterglow over the whole time-range and increases the decay rate. A kinetic model is developed to account for the results. 相似文献