147,046 research outputs found
Reaching DEEP in Math (Developing Educational Excellence and Proficiency in Mathematics)
This paper describes the DEEP in Math Program developed in the academic year 1998-1999 from a collaborative effort of the Louisiana Systemic lnitiative Program (LaSlP) and the Louisiana Department of Education (LDE). It includes evidence of impressive results in low achieving schools and in high-poverty districts targeted by the effort. The plan was for LaSlP to give intensive content and leadership training in Summer 1999 and academic year 1999-2000 to carefully selected. well-qualified math leaders. These leaders were then employed full-time in the 1999-2000 academic year and beyond by their local education authorities to work with all math teachers in a few designated schools at some cohesive subset of grades 3-8
Size Gap for Zero Temperature Black Holes in Semiclassical Gravity
We show that a gap exists in the allowed sizes of all zero temperature static
spherically symmetric black holes in semiclassical gravity when only
conformally invariant fields are present. The result holds for both charged and
uncharged black holes. By size we mean the proper area of the event horizon.
The range of sizes that do not occur depends on the numbers and types of
quantized fields that are present. We also derive some general properties that
both zero and nonzero temperature black holes have in all classical and
semiclassical metric theories of gravity.Comment: 4 pages, ReVTeX, no figure
Effects of Quantized Scalar Fields in Cosmological Spacetimes with Big Rip Singularities
Effects of quantized free scalar fields in cosmological spacetimes with Big
Rip singularities are investigated. The energy densities for these fields are
computed at late times when the expansion is very rapid. For the massless
minimally coupled field it is shown that an attractor state exists in the sense
that, for a large class of states, the energy density of the field
asymptotically approaches the energy density it would have if it was in the
attractor state. Results of numerical computations of the energy density for
the massless minimally coupled field and for massive fields with minimal and
conformal coupling to the scalar curvature are presented. For the massive
fields the energy density is seen to always asymptotically approach that of the
corresponding massless field. The question of whether the energy densities of
quantized fields can be large enough for backreaction effects to remove the Big
Rip singularity is addressed.Comment: PRD version. References added. Several minor corrections and changes.
22 pages, 3 figure
Qualification Phase for the Applications Technology Satellite Apogee Rocket Motor Technical Memorandum, Jul. - Aug. 1966
Qualifications tests on applications technology satellite apogee rocket motor assemblie
Plasma wave observations near the plasmapause with the S3-A satellite
The electric field noise phenomena is described which was observed by the S3-A spacecraft near the plasmapause during the magnetic storm of 16 to 17 December, 1971. The occurrence is noted of a region of intense, low frequency (20 Hz to 500 Hz) electrostatic noise bursts just outside the plasmapause boundary. These noise bursts occurred concurrent with the rapid decrease in 24.3 or = E or = 35.1 keV ring current protons mirroring near the equator during this storm and may be responsible for the pitch angle diffusion and loss of these particles. The characteristics of other phenomena, such as whistlers, ELF hiss, and banded chorus, observed near the plasmapause during this period are also discussed
Coherent instabilities of intense high-energy "white" charged-particle beams in the presence of nonlocal effects within the context of the Madelung fluid description
A hydrodynamical description of coherent instabilities that take place in the
longitudinal dynamics of a charged-particle coasting beam in a high-energy
accelerating machine is presented. This is done in the framework of the
Madelung fluid picture provided by the Thermal Wave Model. The well known
coherent instability charts in the complex plane of the longitudinal coupling
impedance for monochromatic beams are recovered. The results are also
interpreted in terms of the deterministic approach to modulational instability
analysis usually given for monochromatic large amplitude wave train propagation
governed by the nonlinear Schr\"odinger equation. The instability analysis is
then extended to a non-monochromatic coasting beam with a given thermal
equilibrium distribution, thought as a statistical ensemble of monochromatic
incoherent coasting beams ("white" beam). In this hydrodynamical framework, the
phenomenon of Landau damping is predicted without using any kinetic equation
governing the phase space evolution of the system.Comment: 14 pages, 1 figur
A method of billing third generation computer users
A method is presented for charging users for the processing of their applications on third generation digital computer systems is presented. For background purposes, problems and goals in billing on third generation systems are discussed. Detailed formulas are derived based on expected utilization and computer component cost. These formulas are then applied to a specific computer system (UNIVAC 1108). The method, although possessing some weaknesses, is presented as a definite improvement over use of second generation billing methods
On gigahertz spectral turnovers in pulsars
Pulsars are known to emit non-thermal radio emission that is generally a
power-law function of frequency. In some cases, a turnover is seen at
frequencies around 100~MHz. Kijak et al. have reported the presence of a new
class of ''Gigahertz Peaked Spectrum'' (GPS) pulsars that show spectral
turnovers at frequencies around 1 GHz. We apply a model based on free-free
thermal absorption to explain these turnovers in terms of surrounding material
such as the dense environments found in HII regions, Pulsar Wind Nebulae
(PWNe), or in cold, partially ionized molecular clouds. We show that the
turnover frequency depends on the electron temperature of the environment close
to the pulsar, as well as the emission measure along the line of sight. We
fitted this model to the radio fluxes of known GPS pulsars and show that it can
replicate the GHz turnover. From the thermal absorption model, we demonstrate
that normal pulsars would exhibit a GPS-like behaviour if they were in a dense
environment. We discuss the application of this model in the context of
determining the population of neutron stars within the central parsec of the
Galaxy. We show that a non-negligible fraction of this population might exhibit
high-frequency spectral turnovers, which has implications on the detectability
of these sources in the Galactic centre.Comment: 7 pages, 3 figures, Accepted for publication in MNRA
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