2,221 research outputs found
Dynamic effects of electromagnetic wave on a damped two-level atom
We studied the dynamic effects of an electromagnetic(EM) wave with circular
polarization on a two-level damped atom. The results demonstrate interesting ac
Stark split of energy levels of damped atom. The split levels have different
energies and lifetimes, both of which depend on the interaction and the damping
rate of atom. When the frequency of the EM wave is tuned to satisfy the
resonance condition in the strong coupling limit, the transition probability
exhibits Rabi oscillation. Momentum transfer between atom and EM wave shows
similar properties as the transition probability under resonance condition. For
a damped atom interacting with EM field, there exists no longer stable state.
More importantly, if the angular frequency of the EM wave is tuned the same as
the atomic transition frequency and its amplitude is adjusted appropriately
according to the damping coefficients, we can prepare a particular 'Dressed
State' of the coupled system between atom and EM field and can keep the system
coherently in this 'Dressed state' for a very long time. This opens another way
to prepare coherent atomic states.Comment: latex, 2 figure
Dehydrated Alfalfa Meal in Growing-Finishing Swine Rations
It has been suggested by many investigations that certain ingredients contain unidentified growth factors of bene fit to the growing pig. One of the ingredients that has been suggested as a source of unidentified growth factors is alfalfa meal. This trial was part of a larger experiment participated in by several states in the North Central region. The objectives were to determine the effects of low levels of dehydrated alfalfa meal in a com-soybean meal type ration fed to growing-finishing swine
Fish Solubles in Rations for Early Weaned Pigs
This experiment was a continuation of a project covering several aspects of the nutrition of young pigs. The results of previous work reported at the 1966 Swine Field Day ( A.S. Series 66-21) showed that a simple corn-soybean meal fortified ration was equal to a more complex diet that also contained rolled oats, dried skim milk and sugar. Therefore, the current experiment was designed to compare a basal corn-soybean meal type ration with a similar ration containing 3% fish solubles. Fish solubles are a good source of high quality protein and also may contain an identified growth factor(s). The experiment was designed to study the effect of fish solubles on palatability of the ration as well as its effect on growth and feed conversion
Adaptation of Ultrasonics in the Selection Program
A useful selection tool available to swine producers in recent years has been the ultrasonic animal tester, more commonly called the Sonoray. In creasing numbers of swine producers across the nation have adapted the sonoray to their selection programs in an attempt to more accurately evaluate breeding herd replacements. This report is intended to demonstrate ways that a South Dakota swine producer could use the sonoray in a selection program for total herd improvement. The use of the sonoray could aid the purebred producer in three ways. Number one, the sonoray could be used to select the best gilts after a preliminary selection has been made. Secondly , the information is an aid to prospective breeding stock customers. Third, the producer could utilize ultrasonic information when selecting herd sire replacements
The case for the development and use of "ecologically valid" measures of executive function in experimental and clinical neuropsychology
This article considers the scientific process whereby new and better clinical tests of executive function might be developed, and what form they might take. We argue that many of the traditional tests of executive function most commonly in use (e.g., the Wisconsin Card Sorting Test; Stroop) are adaptations of procedures that emerged almost coincidentally from conceptual and experimental frameworks far removed from those currently in favour, and that the prolongation of their use has been encouraged by a sustained period of concentration on “construct-driven” experimentation in neuropsychology. This resulted from the special theoretical demands made by the field of executive function, but was not a necessary consequence, and may not even have been a useful one. Whilst useful, these tests may not therefore be optimal for their purpose. We consider as an alternative approach a function-led development programme which in principle could yield tasks better suited to the concerns of the clinician because of the transparency afforded by increased “representativeness” and “generalisability.” We further argue that the requirement of such a programme to represent the interaction between the individual and situational context might also provide useful constraints for purely experimental investigations. We provide an example of such a programme with reference to the Multiple Errands and Six Element tests
Dissipative Dynamics of an Open Bose Einstein Condensate
As an atomic Bose Einstein condensate (BEC) is coupled to a source of
uncondensed atoms at the same temperature and to a sink (extraction towards an
atom laser) the idealized description in terms of a Gross-Pitaevsky equation
(GP) no longer holds. Under suitable physical assumptions we show that the
dissipative BEC obeys a Complex Ginzburg Landau equation (CGL) and for some
parameter range it undergoes a space time patterning. As a consequence, the
density of BEC atoms within the trap displays non trivial space time
correlations, which can be detected by monitoring the density profile of the
outgoing atom laser. The patterning condition requires a negative scattering
length, as e.g. in Li. In such a case we expect a many domain collapsed
regime, rather than a single one as reported for a closed BEC.Comment: 13 pages, 5 figures, submitt. to Optics Comm., 18th Aug. 99 (special
issue Scully Festschrift
Electronic structure, exchange interactions and Curie temperature in diluted III-V magnetic semiconductors: (GaCr)As, (GaMn)As, (GaFe)As
We complete our earlier (Phys. Rev. B, {\bf 66}, 134435 (2002)) study of the
electronic structure, exchange interactions and Curie temperature in (GaMn)As
and extend the study to two other diluted magnetic semiconductors (GaCr)As and
(GaFe)As. Four concentrations of the 3d impurities are studied: 25%, 12.5%,
6.25%, 3.125%. (GaCr)As and (GaMn)As are found to possess a number of similar
features. Both are semi-metallic and ferromagnetic, with similar properties of
the interatomic exchange interactions and the same scale of the Curie
temperature. In both systems the presence of the charge carriers is crucial for
establishing the ferromagnetic order. An important difference between two
systems is in the character of the dependence on the variation of the number of
carriers. The ferromagnetism in (GaMn)As is found to be very sensitive to the
presence of the donor defects, like As antisites. On the other hand,
the Curie temperature of (GaCr)As depends rather weakly on the presence of this
type of defects but decreases strongly with decreasing number of electrons. We
find the exchange interactions between 3d atoms that make a major contribution
into the ferromagnetism of (GaCr)As and (GaMn)As and propose an exchange path
responsible for these interactions. The properties of (GaFe)As are found to
differ crucially from the properties of (GaCr)As and (GaMn)As. (GaFe)As does
not show a trend to ferromagnetism and is not half-metallic that makes this
system unsuitable for the use in spintronic semiconductor devices
Combining speech and earcons to assist menu navigation
Proceedings of the 9th International Conference on Auditory Display (ICAD), Boston, MA, July 7-9, 2003.Previous research on non-speech audio interfaces has demonstrated that they can enhance performance on menu navigation tasks. Most of this work has focused on tasks in which the menu is not spoken and visual representation of the menu is accessible throughout the task. In this paper we explore the potential benefits that earcons, a type of structured sound, might bring to spoken menu systems for which a visual representation is not available. Evaluation of two spoken menu systems that differ only in whether they also employ earcons, indicates that the use of earcons improves task performance by reducing the number of keystrokes required, while also increasing the time spent for each task
Social and cultural origins of motivations to volunteer a comparison of university students in six countries
Although participation in volunteering and motivations to volunteer (MTV) have received substantial attention on the national level, particularly in the US, few studies have compared and explained these issues across cultural and political contexts. This study compares how two theoretical perspectives, social origins theory and signalling theory, explain variations in MTV across different countries. The study analyses responses from a sample of 5794 students from six countries representing distinct institutional contexts. The findings provide strong support for signalling theory but less so for social origins theory. The article concludes that volunteering is a personal decision and thus is influenced more at the individual level but is also impacted to some degree by macro-level societal forces
Disjoining Potential and Spreading of Thin Liquid Layers in the Diffuse Interface Model Coupled to Hydrodynamics
The hydrodynamic phase field model is applied to the problem of film
spreading on a solid surface. The disjoining potential, responsible for
modification of the fluid properties near a three-phase contact line, is
computed from the solvability conditions of the density field equation with
appropriate boundary conditions imposed on the solid support. The equation
describing the motion of a spreading film are derived in the lubrication
approximation. In the case of quasi-equilibrium spreading, is shown that the
correct sharp-interface limit is obtained, and sample solutions are obtained by
numerical integration. It is further shown that evaporation or condensation may
strongly affect the dynamics near the contact line, and accounting for kinetic
retardation of the interphase transport is necessary to build up a consistent
theory.Comment: 14 pages, 5 figures, to appear in PR
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