34,661 research outputs found
Hispanic Immigration and Spanish Maintenance as Indirect Measures of Ethnicity: Reality and Perceptions
Many supporters of official English have accused U.S. Hispanics of refusing to learn English and rejecting the traditional assimilationist model by clinging to their ethnolinguistic identity. An analysis of U.S. Census data from the last thirty years refutes these claims. The picture of U.S. Hispanic maintenance of ethnolinguistic identity has evolved. Here we show that while adult Spanish loyalty has decreased, youth Spanish loyalty has increased; however, Spanish maintenance does not occur at the expense of English proficiency. Once recent immigrants are subtracted from the Hispanic population, U.S. Census figures show clearly that long-term limited English proficiency has decreased substantially. This analysis clearly supports the conclusions of experts who have noted that Hispanic youth are embracing a bilingual model, one which allows them to maintain their ethnolinguistic identity while acquiring the English skills necessary for success in the United States
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Finite element approximation of non-Fickian polymer diffusion
The problem of nonlinear non-Fickian polymer diffusion as modelled by a diffusion
equation with an adjoined spatially local evolution equation for a viscoelastic
stress is considered (see, for example, Cohen, White & Witelski, SIAM J. Appl. Math.
55, pp. 348–368, 1995). We present numerical schemes based, spatially, on the
Galerkin finite element method and, temporally, on the Crank-Nicolson method. Special
attention is paid to linearising the discrete equations by extrapolating the value
of the nonlinear term from previous time steps. Optimal a priori error estimates are
given, based on the assumption that the exact solution possesses certain regularity
properties, and numerical experiments are given to support these error estimates
Engaging fathers in preventive services: fathers and family centres
Although many fathers are spending more time caring for their children in the home, men continue to be conspicuous by their absence from mainstream family support services. Family centres - community-based services for families in need and at risk - are no exception to this, despite widespread enthusiasm for developing work with fathers in these settings.
This qualitative study by the independent Policy Research Bureau focuses on the attitudes and experiences of over 90 fathers, mothers and staff in thirteen family centres across England and Wales. The study revealed that while family centres often cater well to fathers in particular circumstances, such as lone parents, fathers in more ordinary circumstances tended to be deterred by the feminised atmosphere of centres and by the limited range of activities more likely to appeal to men.
The research strongly suggested that there is a need for greater clarity about who family centres are really intended for, in order to develop good practice in working with fathers in family support settings
Rapid analytical determination of glutaraldehyde concentrations
Technique utilizes the iodimetric procedure which adds unknown excess of bisulfite to glutaraldehyde /GA/ then titrates unreacted bisulfite with standard iodine isotope to determine GA concentrations. Technique may interest microscopists, food researchers, biochemical or medical laboratories, and drug manufacturers
Neutron therapy of cancer
Reports relate applications of neutrons to the problem of cancer therapy. The biochemical and biophysical aspects of fast-neutron therapy, neutron-capture and neutron-conversion therapy with intermediate-range neutrons are presented. Also included is a computer program for neutron-gamma radiobiology
Considerations on command and response language features for a network of heterogeneous autonomous computers
The design of a uniform command language to be used in a local area network of heterogeneous, autonomous nodes is considered. After examining the major characteristics of such a network, and after considering the profile of a scientist using the computers on the net as an investigative aid, a set of reasonable requirements for the command language are derived. Taking into account the possible inefficiencies in implementing a guest-layered network operating system and command language on a heterogeneous net, the authors examine command language naming, process/procedure invocation, parameter acquisition, help and response facilities, and other features found in single-node command languages, and conclude that some features may extend simply to the network case, others extend after some restrictions are imposed, and still others require modifications. In addition, it is noted that some requirements considered reasonable (user accounting reports, for example) demand further study before they can be efficiently implemented on a network of the sort described
Decoherence induced CPT violation and entangled neutral mesons
We discuss two classes of semi-microscopic theoretical models of stochastic
space-time foam in quantum gravity and the associated effects on entangled
states of neutral mesons, signalling an intrinsic breakdown of CPT invariance.
One class of models deals with a specific model of foam, initially constructed
in the context of non-critical (Liouville) string theory, but viewed here in
the more general context of effective quantum-gravity models. The relevant
Hamiltonian perturbation, describing the interaction of the meson with the foam
medium, consists of off-diagonal stochastic metric fluctuations, connecting
distinct mass eigenstates (or the appropriate generalisation thereof in the
case of K-mesons), and it is proportional to the relevant momentum transfer
(along the direction of motion of the meson pair). There are two kinds of
CPT-violating effects in this case, which can be experimentally disentangled:
one (termed ``omega-effect'') is associated with the failure of the
indistinguishability between the neutral meson and its antiparticle, and
affects certain symmetry properties of the initial state of the two-meson
system; the second effect is generated by the time evolution of the system in
the medium of the space-time foam, and can result in time-dependent
contributions of the $omega-effect type in the time profile of the two meson
state. Estimates of both effects are given, which show that, at least in
certain models, such effects are not far from the sensitivity of experimental
facilities available currently or in the near future. The other class of
quantum gravity models involves a medium of gravitational fluctuations which
behaves like a ``thermal bath''. In this model both of the above-mentioned
intrinsic CPT violation effects are not valid.Comment: 16 pages revtex, no figure
Formation of porous surface layers in reaction bonded silicon nitride during processing
An effort was undertaken to determine if the formation of the generally observed layer of large porosity adjacent to the as-nitride surfaces of reaction bonded silicon nitrides could be prevented during processing. Isostatically pressed test bars were prepared from wet vibratory milled Si powder. Sintering and nitriding were each done under three different conditions:(1) bars directly exposed to the furnance atmosphere; (2) bars packed in Si powder; (3) bars packed in Si3N4 powder. Packing the bars in either Si of Si3N4 powder during sintering retarded formation of the layer of large porosity. Only packing the bars in Si prevented formation of the layer during nitridation. The strongest bars (316 MPa) were those sintered in Si and nitrided in Si3N4 despite their having a layer of large surface porosity; failure initiated at very large pores and inclusions. The alpha/beta ratio was found to be directly proportional to the oxygen content; a possible explanation for this relationship is discussed
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