1,437 research outputs found
Ferrimagnetism of dilute Ising antiferromagnets
It is shown that nearest-neighbor antiferromagnetic interactions of identical
Ising spins on imbalanced bipartite lattice and imbalanced bipartite
hierarchical fractal result in ferrimagnetic order instead of antiferromagnetic
one. On some crystal lattices dilute Ising antiferromagnets may also become
ferrimagnets due to the imbalanced nature of the magnetic percolation cluster
when it coexists with the percolation cluster of vacancies. As evidenced by the
existing experiments on , such ferrimagnetism is inherent
property of bcc lattice so thermodynamics of these compounds at low can be
similar to that of antiferromagnet on imbalanced hierarchical fractal.Comment: 6 pages, 4 figure
Introducao, avaliacao e caracterizacao de selecoes de goiabeiras (Psidium guajava L.) na chapada do Araripe-Pernambuco: II - caracteristicas produtivas.
Uma avaliacao do comportamento de 21 selecoes de goiabeiras, cultivadas sob regime de sequeiro na Chapada do Araripe- Pernambuco, e apresentada ressaltando-se as suas caracteristicas produtivas. A producao das goiabeiras com 3 1/2 anos de idade, relativa a safra de setembro/90 a setembro/91 variou de 10,1 a 52,9 kg/planta, para selecoes White Selection of Florida 2 e Patillo 2.3, respectivamente. Ja com relacao ao numero de frutos colhidos, verifica-se uma variacao de 77 na selecao White Selection of Florida-2 ate 743 na selecao IPA B-22.1. Observou-se uma tendencia entre as selecoes estudadas, de maior peso medio dos frutos para as selecoes com o menor numero de frutos por planta
The Academics Athletics Trade-off: Universities and Intercollegiate Athletics
This analysis focuses on several key issues in the Football Bowl Subdivision (FBS). The intrinsic benefits of athletic programs are discussed in the first section. Trends in graduation rates and academic performance among athletes and how they correlate with the general student body are discussed in the second section. Finally, an overview of the revenues and expenses of athletic department budgets are discussed in an effort to gain a better understanding of the allocation of funds to athletics. In spite of recent growth in revenues and expenses, the athletic department budget comprises on average only 5 percent of the entire university budget at an FBS school, though spending and revenues have increased dramatically in recent years. In the grand scheme of things, American higher education faces several other, arguably more pressing, areas of reform. However, athletics is a significant and growing dimension of higher education that warrants in-depth examination
Evidence for the Decay Sigma+ -> p mu+ mu-
We report the first evidence for the decay Sigma+ -> p mu+ mu- from data
taken by the HyperCP experiment(E871) at Fermilab. Based on three observed
events, the branching ratio is B(Sigma+ -> p,mu+,mu-) = [8.6 +6.6,-5.4(stat)
+/-5.5(syst)] x 10**-8. The narrow range of dimuon masses may indicate that the
decay proceeds via a neutral intermediate state, Sigma+ -> p P0, P0 -> mu+ mu-,
with a P0 mass of 214.3 +/- 0.5 MeV/c**2 and branching ratio B(Sigma+ -> p P0;
P0 -> mu+ mu-) = [3.1 +2.4,-1.(stat) +/-1.5(syst)] x 10**-8.Comment: As published in PR
Analytical and computational study of magnetization switching in kinetic Ising systems with demagnetizing fields
An important aspect of real ferromagnetic particles is the demagnetizing
field resulting from magnetostatic dipole-dipole interaction, which causes
large particles to break up into domains. Sufficiently small particles,
however, remain single-domain in equilibrium. This makes such small particles
of particular interest as materials for high-density magnetic recording media.
In this paper we use analytic arguments and Monte Carlo simulations to study
the effect of the demagnetizing field on the dynamics of magnetization
switching in two-dimensional, single-domain, kinetic Ising systems. For systems
in the ``Stochastic Region,'' where magnetization switching is on average
effected by the nucleation and growth of fewer than two well-defined critical
droplets, the simulation results can be explained by the dynamics of a simple
model in which the free energy is a function only of magnetization. In the
``Multi-Droplet Region,'' a generalization of Avrami's Law involving a
magnetization-dependent effective magnetic field gives good agreement with our
simulations.Comment: 29 pages, REVTeX 3.0, 10 figures, 2 more figures by request.
Submitted Phys. Rev.
Search for the Lepton-Number-Violating Decay
A sensitive search for the lepton-number-violating decay has been performed using a sample of hyperons
produced in 800 GeV/ -Cu collisions. We obtain at 90% confidence, improving on the best
previous limit by four orders of magnitude.Comment: 9 pages, 5 figures, to be published in Phys. Rev. Let
Measurement of the Alpha Asymmetry Parameter for the Omega- to Lambda K- Decay
We have measured the alpha parameter of the Omega- to Lambda K- decay using
data collected with the HyperCP spectrometer during the 1997 fixed-target run
at Fermilab. Analyzing a sample of 0.96 million Omega- to Lambda K^-, Lambda to
p pi- decays, we obtain alpha_Omega*alpha_Lambda =
[1.33+/-0.33(stat)+/-0.52(syst)] x 10^{-2}. With the accepted value of
alpha_Lambda, alpha_Omega is found to be [2.07+/-0.51(stat)+/-0.81(syst)] x
10^{-2}.Comment: 5 pages, 4 figures, to be appeared as a Rapid Communication in Phys.
Rev.
Existence of radial stationary solutions for a system in combustion theory
In this paper, we construct radially symmetric solutions of a nonlinear
noncooperative elliptic system derived from a model for flame balls with
radiation losses. This model is based on a one step kinetic reaction and our
system is obtained by approximating the standard Arrehnius law by an ignition
nonlinearity, and by simplifying the term that models radiation. We prove the
existence of 2 solutions using degree theory
Tunneling Via Individual Electronic States in Ferromagnetic Nanoparticles
We measure electron tunneling via discrete energy levels in ferromagnetic
cobalt particles less than 4 nm in diameter, using non-magnetic electrodes. Due
to magnetic anisotropy, the energy of each tunneling resonance shifts as an
applied magnetic field rotates the particle's magnetic moment. We see both
spin-increasing and decreasing tunneling transitions, but we do not observe the
spin degeneracy at small magnetic fields seen previously in non-magnetic
materials. The tunneling spectrum is denser than predicted for independent
electrons, possibly due to spin-wave excitations.Comment: 4 pages, 4 figures. Improved by comments from referees, to appear in
Phys. Rev. Let
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