14,198 research outputs found
An investigation into pilot and system response to critical in-flight events. Volume 1: Executive summary
Critical in-flight events (CIFE) that threaten the aircraft were studied. The scope of the CIFE was described and defined with emphasis on characterizing event development, detection and assessment; pilot information requirements, sources, acquisition, and interpretation, pilot response options, decision processed, and decision implementation and event outcome. Detailed scenarios were developed for use in simulators and paper and pencil testing for developing relationships between pilot performance and background information as well as for an analysis of pilot reaction decision and feedback processes. Statistical relationships among pilot characteristics and observed responses to CIFE's were developed
An investigation into pilot and system response to critical in-flight events. Volume 2: Appendix
Materials relating to the study of pilot and system response to critical in-flight events (CIFE) are given. An annotated bibliography and a trip summary outline are presented, as are knowledge surveys with accompanying answer keys. Performance profiles of pilots and performance data from the simulations of CIFE's are given. The paper and pencil testing materials are reproduced. Conditions for the use of the additive model are discussed. A master summary of data for the destination diversion scenario is given. An interview with an aircraft mechanic demonstrates the feasibility of system problem diagnosis from a verbal description of symptoms and shows the information seeking and problem solving logic used by an expert to narrow the list of probable causes of aircraft failure
The application of amino acid racemization in the acid soluble fraction of enamel to the estimation of the age of human teeth
Estimation of age-at-death for skeletonised forensic remains is one of the most significant problems in forensic anthropology. The majority of existing morphological and histological techniques are highly inaccurate, and show a bias towards underestimating the age of older individuals. One technique which has been successful in forensic age estimation is amino acid racemization in dentine. However, this method cannot be used on remains where the post-mortem interval is greater than 20 years. An alternative approach is to measure amino acid racemization in dental enamel, which is believed to be more resistant to change post-mortem. The extent of amino acid racemization in the acid soluble fraction of the enamel proteins was determined for modem known age teeth. A strong correlation was observed between the age of the tooth and the extent of racemization. No systematic bias in the direction of age estimation errors was detected. For the majority of teeth analyzed, the presence of dental caries did not affect the results obtained. In a minority of cases, carious teeth showed a higher level of racemization than would be expected given the age of the individual. These results indicate that amino acid racemization in enamel has the potential to be used in age estimation of skeletal remains. (C) 2007 Elsevier Ireland Ltd. All rights reserved
Collective Excitations of a Two-Component Bose Condensate at Finite Temperature
We compare the collective modes for Bose-condensed systems with two
degenerate components with and without spontaneous intercomponent coherence at
finite temperature using the time-dependent Hartree-Fock approximation. We show
that the interaction between the condensate and non-condensate in these two
cases results in qualitatively different collective excitation spectra. We show
that at zero temperature the single-particle excitations of the incoherent Bose
condensate can be probed by intercomponent excitations.Comment: 4 pages, 3 figures, Submitted to PR
A study of ASRS reports involving general aviation and weather encounters
Consideration is given to the nature and characteristics of problems involving dissemination of weather information, use of this information by pilots, its adequacy for the purpose intended, the ability of the air traffic control system to cope with weather related incidents, and the various aspects of pilot behavior, aircraft equipment, and NAVAIDS affecting flights in which weather figures. It is concluded from the study that skill and training deficiencies of general aviation pilots are not major factors in weather related occurrences, nor is lack of aircraft equipment. Major problem causes are identified with timely and easily interpreted weather information, judgement and attitude factors of pilots, and the functioning of the air traffic control system
Number-of-Particle Fluctuations and Stability of Bose-Condensed Systems
In this paper we show that a normal total number-of-particle fluctuation can
be obtained consistently from the static thermodynamic relation and dynamic
compressibility sum rule. In models using the broken U(1) gauge symmetry, in
order to keep the consistency between statics and dynamics, it is important to
identify the equilibrium state of the system with which the density response
function is calculated, so that the condensate particle number , the
number of thermal depletion particles , and the number of
non-condensate particles can be unambiguously defined. We also show
that the chemical potential determined from the Hugenholtz-Pines theorem should
be consistent with that determined from the equilibrium equation of state. The
anomalous fluctuation of the number of non-condensate particles is an
intrinsic feature of the broken U(1) gauge symmetry. However, this anomalous
fluctuation does not imply the instability of the system. Using the random
phase approximation, which preserves the U(1) gauge symmetry, such an anomalous
fluctuation of the number of non-condensate particles is completely absentComment: 9 pages, submitted to PR
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Zebrafish studies identify serotonin receptors mediating antiepileptic activity in Dravet syndrome.
Dravet syndrome is a life-threatening early-onset epilepsy not well controlled by antiepileptic drugs. Drugs that modulate serotonin (5-HT) signalling, including clemizole, locaserin, trazodone and fenfluramine, have recently emerged as potential treatment options for Dravet syndrome. To investigate the serotonin receptors that could moderate this antiepileptic activity, we designed and synthesized 28 novel analogues of clemizole, obtained receptor binding affinity profiles, and performed in vivo screening in a scn1lab mutant zebrafish (Danio rerio) model which recapitulates critical clinical features of Dravet syndrome. We discovered three clemizole analogues with 5-HT receptor binding that exert powerful antiepileptic activity. Based on structure-activity relationships and medicinal chemistry-based analysis, we then screened an additional set of known 5-HT receptor specific drug candidates. Integrating our in vitro and in vivo data implicates 5-HT2B receptors as a critical mediator in the mechanism of seizure suppression observed in Dravet syndrome patients treated with 5-HT modulating drugs
Two-fluid dynamics for a Bose-Einstein condensate out of local equilibrium with the non-condensate
We extend our recent work on the two-fluid hydrodynamics of a Bose-condensed
gas by including collisions involving both condensate and non-condensate atoms.
These collisions are essential for establishing a state of local thermodynamic
equilibrium between the condensate and non-condensate. Our theory is more
general than the usual Landau two-fluid theory, to which it reduces in the
appropriate limit, in that it allows one to describe situations in which a
state of complete local equilibrium between the two components has not been
reached. The exchange of atoms between the condensate and non-condensate is
associated with a new relaxational mode of the gas.Comment: 4 pages, revtex, 1 postscript figure, Fig.1 has been correcte
Rapid turnover of effector-memory CD4(+) T cells in healthy humans
Memory T cells can be divided into central-memory (T(CM)) and effector-memory (T(EM)) cells, which differ in their functional properties. Although both subpopulations can persist long term, it is not known whether they are maintained by similar mechanisms. We used in vivo labeling with deuterated glucose to measure the turnover of CD4(+) T cells in healthy humans. The CD45R0(+)CCR7(-) T(EM) subpopulation was shown to have a rapid proliferation rate of 4.7% per day compared with 1.5% per day for CD45R0(+)CCR7(+) T(CM) cells; these values are equivalent to average intermitotic (doubling) times of 15 and 48 d, respectively. In contrast, the CD45RA(+)CCR7(+) naive CD4(+) T cell population was found to be much longer lived, being labeled at a rate of only 0.2% per day (corresponding to an intermitotic time of approximately 1 yr). These data indicate that human CD4(+) T(EM) cells constitute a short-lived cell population that requires continuous replenishment in vivo
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