17,208 research outputs found
Time evolution of the Partridge-Barton Model
The time evolution of the Partridge-Barton model in the presence of the
pleiotropic constraint and deleterious somatic mutations is exactly solved for
arbitrary fecundity in the context of a matricial formalism. Analytical
expressions for the time dependence of the mean survival probabilities are
derived. Using the fact that the asymptotic behavior for large time is
controlled by the largest matrix eigenvalue, we obtain the steady state values
for the mean survival probabilities and the Malthusian growth exponent. The
mean age of the population exhibits a power law decayment. Some Monte
Carlo simulations were also performed and they corroborated our theoretical
results.Comment: 10 pages, Latex, 1 postscript figure, published in Phys. Rev. E 61,
5664 (2000
A Bit-String Model for Biological Aging
We present a simple model for biological aging. We studied it through
computer simulations and we have found this model to reflect some features of
real populations.Comment: LaTeX file, 4 PS figures include
The Heumann-Hotzel model for aging revisited
Since its proposition in 1995, the Heumann-Hotzel model has remained as an
obscure model of biological aging. The main arguments used against it were its
apparent inability to describe populations with many age intervals and its
failure to prevent a population extinction when only deleterious mutations are
present. We find that with a simple and minor change in the model these
difficulties can be surmounted. Our numerical simulations show a plethora of
interesting features: the catastrophic senescence, the Gompertz law and that
postponing the reproduction increases the survival probability, as has already
been experimentally confirmed for the Drosophila fly.Comment: 11 pages, 5 figures, to be published in Phys. Rev.
Monte Carlo Simulations of Sexual Reproduction
Modifying the Redfield model of sexual reproduction and the Penna model of
biological aging, we compare reproduction with and without recombination in
age-structured populations. In contrast to Redfield and in agreement with
Bernardes we find sexual reproduction to be preferred to asexual one. In
particular, the presence of old but still reproducing males helps the survival
of younger females beyond their reproductive age.Comment: 8 pages, plain tex, 7 EPS figures, to appear in PHYSICA
The quadrupole collective model from a Cartan-Weyl perspective
The matrix elements of the quadrupole variables and canonic conjugate
momenta, emerging from collective nuclear models are calculated within a
basis. Using a harmonic oscillator implementation of the
SU(1,1) degree of freedom, it can be shown that the matrix elements of the
quadrupole phonon creation and annihilation operators can be calculated in a
pure algebraic way, making use of an intermediate state method.Comment: Special issue of journal of physics for the QTS5 conferenc
Roman Sculpture in Context: Selected Papers in Ancient Art and Architecture, Volume 6
Marice Rose is a contributing author, Body/Culture: Display and Reception of the Farnese Hercules, Chapter 10, pp 177-197.
This volume tackles a pressing issue in Roman art history: that many sculptures conventionally used in our scholarship and teaching lack adequate information about their find locations. Questions of context are complex, and any theoretical and methodological reframing of Roman sculpture demands academic transparency. This volume is dedicated to privileging content and context over traditions of style and aesthetics. Through case studies, the chapters illustrate multivariate ways to contextualize ancient objects. The authors encourage Roman art historians to look beyond conventional interpretations; to reclaim from the study of Greek sculpture the Roman originals that are too often relegated to discussions of copies and models ; to consider the multiple, dynamic, and shifting contexts that one sculpture could experience over the centuries of its display; and to recognize that postantique receptions can also offer insight into interpretations of ancient viewers. The collected topics were originally presented in three conference sessions: Grounding Roman Sculpture (Archaeological Institute of America, 2019); Ancient Sculpture in Context (College Art Association, 2017); and Ancient Sculpture in Context II: Reception (College Art Association, 2019).https://digitalcommons.fairfield.edu/visualandperformingarts-books/1022/thumbnail.jp
Synthesis, Characterization, and Photochemical Properties of a New Square Mn(I)-Ru(II) Complex Using Pyrazine as Bridge Ligand
The photochemical properties of the complexes cis,fac-[Ru(phen)(2)(pz)(2)-Mn(CO)(3)Br](2)(4+) (I), cis-[Ru(phen)(2)(pz)(2)](2+) (II), and fac-Mn(CO)(3)(pz)(2)Br (III) where phen is phenanthroline and pz is pyrazine in acetonitrile solution are reported. the three complexes were characterized using H-1 NMR, UV-vis and FTIR spectroscopy and electrochemical (cyclic voltammetry and spectroelectrochemical) techniques. the complexes show intense absorption in the visible region assigned to the population of MLCT excited states. the absorption spectrum of I is the sum of the spectra of the mononuclear species II and III, and the two oxidation potentials at +1.10 and +1.56V versus Ag/AGCl observed in I are ascribed to the different coordination environments of metal centers. the photolysis in the acetonitrile solution resulted in the pz dissociation to give the monoacetonitrile complexes for I, II, and III, respectively.Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, BrazilFundacao Univ Fed Grande Dourados, Fac Ciencias Exatas & Tecnol, BR-79804970 Dourados, MS, BrazilUniversidade Federal de São Paulo, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Ciencias Farmaceut, BR-14040901 Ribeirao Preto, SP, BrazilUniversidade Federal de São Paulo, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Ciencias Farmaceut, BR-14040901 Ribeirao Preto, SP, BrazilWeb of Scienc
Nuclear moments for the neutrinoless double beta decay II
The recently developed formalism for the evaluation of nuclear form factors
in neutrinoless double beta decay is applied to , ,
, , and nuclei. Explicit analytical
expressions that follows from this theoretical development, in the single mode
model for the decay of , have been worked out. They are useful both
for testing the full numerical calculations, and for analytically checking the
consistency with other formalisms. Large configuration space calculations are
compared with previous studies, where alternative formulations were used. Yet,
besides using the G-matrix as residual interaction, we here use a simple
-force. Attention is paid to the connected effects of the short range
nuclear correlations and the finite nucleon size. Constraints on lepton number
violating terms in the weak Hamiltonian (effective neutrino Majorana mass and
effective right-handed current coupling strengths) are deduced.Comment: 18 pages, latex, minor changes, to appear in Nucl. Phys.
Mach's principle: Exact frame-dragging via gravitomagnetism in perturbed Friedmann-Robertson-Walker universes with
We show that the dragging of the axis directions of local inertial frames by
a weighted average of the energy currents in the universe is exact for all
linear perturbations of any Friedmann-Robertson-Walker (FRW) universe with K =
(+1, -1, 0) and of Einstein's static closed universe. This includes FRW
universes which are arbitrarily close to the Milne Universe, which is empty,
and to the de Sitter universe. Hence the postulate formulated by E. Mach about
the physical cause for the time-evolution of the axis directions of inertial
frames is shown to hold in cosmological General Relativity for linear
perturbations. The time-evolution of axis directions of local inertial frames
(relative to given local fiducial axes) is given experimentally by the
precession angular velocity of gyroscopes, which in turn is given by the
operational definition of the gravitomagnetic field. The gravitomagnetic field
is caused by cosmological energy currents via the momentum constraint. This
equation for cosmological gravitomagnetism is analogous to Ampere's law, but it
holds also for time-dependent situtations. In the solution for an open universe
the 1/r^2-force of Ampere is replaced by a Yukawa force which is of identical
form for FRW backgrounds with The scale of the exponential
cutoff is the H-dot radius, where H is the Hubble rate, and dot is the
derivative with respect to cosmic time. Analogous results hold for energy
currents in a closed FRW universe, K = +1, and in Einstein's closed static
universe.Comment: 23 pages, no figures. Final published version. Additional material in
Secs. I.A, I.J, III, V.H. Additional reference
Comments on Anomaly Cancellations by Pole Subtractions and Ghost Instabilities with Gravity
We investigate some aspects of anomaly cancellation realized by the
subtraction of an anomaly pole, stressing on some of its properties in
superspace. In a local formulation these subtractions can be described in terms
of a physical scalar, an axion and related ghosts. They appear to be necessary
for the unitarization of the theory in the ultraviolet, but they may generate
an infrared instability of the corresponding effective action, signalled by
ghost condensation. In particular the subtraction of the superanomaly multiplet
by a pole in superspace is of dubious significance, due to the different nature
of the chiral and conformal anomalies. In turn, this may set more stringent
constraints on the coupling of supersymmetric theories to gravity.Comment: 18 pages. Revised version. To appear in "Classical and Quantum
Gravity
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