5,948 research outputs found
Revisiting the theoretical DBV (V777 Her) instability strip: the MLT theory of convection
We reexamine the theoretical instability domain of pulsating DB white dwarfs
(DBV or V777 Her variables). We performed an extensive -mode nonadiabatic
pulsation analysis of DB evolutionary models considering a wide range of
stellar masses, for which the complete evolutionary stages of their progenitors
from the ZAMS, through the thermally pulsing AGB and born-again phases, the
domain of the PG1159 stars, the hot phase of DO white dwarfs, and then the DB
white dwarf stage have been considered. We explicitly account for the evolution
of the chemical abundance distribution due to time-dependent chemical diffusion
processes. We examine the impact of the different prescriptions of the MLT
theory of convection and the effects of small amounts of H in the almost
He-pure atmospheres of DB stars on the precise location of the theoretical blue
edge of the DBV instability strip.Comment: Proceedings, 16th European White Dwarf Workshop, Barcelona, 200
Radiation measurements in the new tandem accelerator FEL
The measurements of both spontaneous and stimulated emissions of radiation in
the newly configured Israeli EA-FEL are made for the first time. The radiation
at the W-band was measured and characterized. The results match the predictions
of our earlier theoretical modeling and calculations.Comment: 4 pages, 3 figures, FEL 2003 Conference repor
Eliciting Intelligence With the Scharff Technique:Interviewing More and Less Cooperative and Capable Sources
The objective was to compare the efficacy of the Scharff technique (conceptualized as 5 tactics) with the direct approach (open and direct questions) as a means of eliciting intelligence from human sources. The interview techniques were used with 4 different types of sources varying in their levels of both cooperation and capability to provide information as follows: (a) less willing/less able, (b) less willing/ more able, (c) more willing/less able, and (d) more willing/more able. The sources (N ï° 200) were given information about a notional planned terrorist attack and instructed to strike a balance between not revealing too much or too little information in a subsequent interview. Overall, the Scharff technique resulted in significantly more new information than the direct approach, particularly for the less cooperative sources. Furthermore, sources interviewed with the Scharff technique had a more difficult time reading the interviewerâs information objectives and consistently underestimated how much new information they revealed. The study substantiates the Scharff technique as an effective human- intelligence gathering tool
Broken-symmetry-adapted Green function theory of condensed matter systems:towards a vector spin-density-functional theory
The group theory framework developed by Fukutome for a systematic analysis of
the various broken symmetry types of Hartree-Fock solutions exhibiting spin
structures is here extended to the general many body context using spinor-Green
function formalism for describing magnetic systems. Consequences of this theory
are discussed for examining the magnetism of itinerant electrons in nanometric
systems of current interest as well as bulk systems where a vector spin-density
form is required, by specializing our work to spin-density-functional
formalism. We also formulate the linear response theory for such a system and
compare and contrast them with the recent results obtained for localized
electron systems. The various phenomenological treatments of itinerant magnetic
systems are here unified in this group-theoretical description.Comment: 17 page
Analytical comparison of transient and steady state visual evoked cortical potentials
To better describe the linear-dynamic properties of the human visual-cortical response system, transient and steady state Visual Evoked Response Potentials (VERP) were observed. The stimulus presentation device provided both the evoking stimulus (flickering or pulsing lights) and a video task display. The steady state stimulus was modulated by a complex, ten frequency, sum-of-sines, wave. The transient VERP was the time-locked average of the EEG to a series of narrow light pulses (pulse width of 10 msec). The Fourier transform of the averaged pulses had properties that approximate band limited white noise, i.e., a flat spectrum over the frequency region spanned by the 10 summed sines. The Fourier transform of both the steady state and the transient evoked potentials resulted in transfer that are equivalent and therefore comparable. To investigate the effects of task loading on evoked potentials, a grammatical reasoning task was provided. Results support the relevancy of continued application of a systems engineering approach for describing neurosensory functioning
Child care center policies and practices for management of ill children
OBJECTIVES:
The objectives of this study were to 1) describe child care staff knowledge and beliefs regarding upper respiratory tract infections and antibiotic indications and 2) evaluate child care staff reported reasons for a) exclusion from child care, b) referral to a health care provider, and c) recommending antibiotics for an ill child. METHODS:
A longitudinal study based in randomly selected child care centers in Massachusetts. Staff completed a survey to assess knowledge regarding common infections. For six weeks, staff completed a record of absences each day, describing the reason for an absence, and advice given to the parents regarding exclusion, referral to a health care provider, and obtaining antibiotics. Exclusions for the specific illness/symptom were defined as appropriate or inappropriate based on national guidelines. RESULTS:
A large proportion of child care staff incorrectly believed that antibiotics are indicated for bronchitis (80.5%) and green rhinorrhea (80.5%) in children. For 82.2% of absences, the circumstances or reasons for the absence were discussed with a child care staff member. Of 538 absences due to illness that child care staff discussed with parents, there were 45 inappropriate exclusions (8.4% of illnesses discussed), 91 appropriate exclusions (16.9% of illnesses discussed), and 402 cases (74.7%) in which no recommendation for exclusion was made. CONCLUSIONS:
Misconceptions regarding the need for antibiotics for URIs are common among child care staff. However, day care staff do not pressure parents to seek medical attention or antibiotics
A mixed ultrasoft/normconserved pseudopotential scheme
A variant of the Vanderbilt ultrasoft pseudopotential scheme, where the
normconservation is released for only one or a few angular channels, is
presented. Within this scheme some difficulties of the truly ultrasoft
pseudopotentials are overcome without sacrificing the pseudopotential softness.
i) Ghost states are easily avoided without including semicore shells. ii) The
ultrasoft pseudo-charge-augmentation functions can be made more soft. iii) The
number of nonlocal operators is reduced. The scheme will be most useful for
transition metals, and the feasibility and accuracy of the scheme is
demonstrated for the 4d transition metal rhodium.Comment: 4 pages, 2 figure
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