10,567 research outputs found
Optomechanics with molecules in a strongly pumped ring cavity
Cavity cooling of an atom works best on a cyclic optical transition in the
strong coupling regime near resonance, where small cavity photon numbers
suffice for trapping and cooling. Due to the absence of closed transitions a
straightforward application to molecules fails: optical pumping can lead the
particle into uncoupled states. An alternative operation in the far
off-resonant regime generates only very slow cooling due to the reduced
field-molecule coupling. We predict to overcome this by using a strongly driven
ring-cavity operated in the sideband cooling regime. As in the optomechanical
setups one takes advantage of a collectively enhanced field-molecule coupling
strength using a large photon number. A linearized analytical treatment
confirmed by full numerical quantum simulations predicts fast cooling despite
the off-resonant small single molecule - single photon coupling. Even ground
state cooling can be obtained by tuning the cavity field close to the
Anti-stokes sideband for sufficiently high trapping frequency. Numerical
simulations show quantum jumps of the molecules between the lowest two trapping
levels, which can be be directly and continuously monitored via scattered light
intensity detection
The NASA-Lewis program on fusion energy for space power and propulsion, 1958-1978
An historical synopsis is provided of the NASA-Lewis research program on fusion energy for space power and propulsion systems. It was initiated to explore the potential applications of fusion energy to space power and propulsion systems. Some fusion related accomplishments and program areas covered include: basic research on the Electric Field Bumpy Torus (EFBT) magnetoelectric fusion containment concept, including identification of its radial transport mechanism and confinement time scaling; operation of the Pilot Rig mirror machine, the first superconducting magnet facility to be used in plasma physics or fusion research; operation of the Superconducting Bumpy Torus magnet facility, first used to generate a toroidal magnetic field; steady state production of neutrons from DD reactions; studies of the direct conversion of plasma enthalpy to thrust by a direct fusion rocket via propellant addition and magnetic nozzles; power and propulsion system studies, including D(3)He power balance, neutron shielding, and refrigeration requirements; and development of large volume, high field superconducting and cryogenic magnet technology
In-Suit Doppler Technology Assessment
The objective of this program was to perform a technology assessment survey of non-invasive air embolism detection utilizing Doppler ultrasound methodologies. The primary application of this technology will be a continuous monitor for astronauts while performing extravehicular activities (EVA's). The technology assessment was to include: (1) development of a full understanding of all relevant background research; and (2) a survey of the medical ultrasound marketplace for expertise, information, and technical capability relevant to this development. Upon completion of the assessment, LSR was to provide an overview of technological approaches and R&D/manufacturing organizations
Effects of the Zanzibar School-Based Deworming Program on Iron Status of Children.
We evaluated the effects of the Zanzibar school-based deworming program on the iron status of primary school children. Parasitologic and nutritional assessments were carried out at baseline, 6 mo, and 12 mo in 4 nonprogram schools (n = 1002), 4 schools in which students received twice-yearly deworming (n = 952), and 4 schools in which students received thrice-yearly deworming (n = 970) with 500 mg generic mebendazole. Schools were randomly selected for evaluation and allocated to program groups. Relative to no treatment, thrice-yearly deworming caused significant decreases in protoporphyrin concentrations and both deworming regimens caused marginally significant increases in serum ferritin concentrations. The average annual changes in protoporphyrin concentrations were -5.9 and -23.5 micromol/mol heme in the control and thrice-yearly deworming groups, respectively (P < 0.001). The average changes in ferritin concentration were 2.8 and 4.5 microg/L, respectively (P = 0.07). Deworming had no effect on annual hemoglobin change or prevalence of anemia. However, the relative risk of severe anemia (hemoglobin < 70 g/L) was 0.77 (95% confidence limits: 0.39, 1.51) in the twice-yearly deworming group and 0.45 (0.19, 1.08) in the thrice-yearly deworming group. The effects on prevalence of high protoporphyrin values and incidence of moderate-to-severe anemia (hemoglobin < 90 g/L) were significantly greater in children with > 2000 hookworm eggs/g feces at baseline. We estimate that this deworming program prevented 1260 cases of moderate-to-severe anemia and 276 cases of severe anemia in a population of 30,000 schoolchildren in 1 y. Where hookworm is heavily endemic, deworming programs can improve iron status and prevent moderate and severe anemia, but deworming may be needed at least twice yearly
Direct Measurement of the g-Factor of Composite Fermions
The activation gap of the fractional quantum Hall states at constant
fillings and 2/5 has been measured as a function of the
perpendicular magnetic field . A linear dependence of on is
observed while approaching the spin polarization transition. This feature
allows a direct measurement of the -factor of composite fermions which
appears to be heavily renormalized by interactions and strongly sensitive to
the electronic filling factor.Comment: 4 pages, 4 figures Changed content: Fokus more on g-factors (and less
on other details
Protoneutron stars in the Brueckner-Hartree-Fock approach and finite-temperature kaon condensation
We study the properties of hot neutrino-trapped beta-stable stellar matter
using an equation of state of nuclear matter within the Brueckner-Hartree-Fock
approach including three-body forces, combined with a standard chiral model for
kaon condensation at finite temperature. The properties of (proto)neutron stars
are then investigated within this framework.Comment: 10 pages, 5 figures, 2 tables, PRC in pres
Averages of Fourier coefficients of Siegel modular forms and representation of binary quadratic forms by quadratic forms in four variables
Let be a a negative discriminant and let vary over a set of
representatives of the integral equivalence classes of integral binary
quadratic forms of discriminant . We prove an asymptotic formula for for the average over of the number of representations of by an
integral positive definite quaternary quadratic form and obtain results on
averages of Fourier coefficients of linear combinations of Siegel theta series.
We also find an asymptotic bound from below on the number of binary forms of
fixed discriminant which are represented by a given quaternary form. In
particular, we can show that for growing a positive proportion of the
binary quadratic forms of discriminant is represented by the given
quaternary quadratic form.Comment: v5: Some typos correcte
Flight demonstration of laser diode initiated ordnance
A program has been initiated by NASA Headquarters to validate laser initiated ordnance in flight applications. The primary program goal is to bring together a team of government and industry members to develop a laser initiated ordnance system having the test and analysis pedigree to be flown on launch vehicles. The culmination of this effort was a flight of the Pegasus launch vehicle which had two fin rockets initiated by this laser system. In addition, a laser initiated ordnance squib was fired into a pressure bomb during thrusting flight. The complete ordnance system comprising a laser diode firing unit, fiber optic cable assembly, laser initiated detonator, and laser initiated squib was designed and built by The Ensign Bickford Company. The hardware was tested to the requirements of the Pegasus launch vehicle and integrated into the vehicle by The Ensign Bickford Company and the Orbital Sciences Corporation. Discussions include initial program concept, contract implementation, team member responsibilities, analysis results, vehicle integration, safing architecture, ordnance interfaces, mission timeline and telemetry data. A complete system description, summary of the analyses, the qualification test results, and the results of flight are included
Tunable sub-luminal propagation of narrowband x-ray pulses
Group velocity control is demonstrated for x-ray photons of 14.4 keV energy
via a direct measurement of the temporal delay imposed on spectrally narrow
x-ray pulses. Sub-luminal light propagation is achieved by inducing a steep
positive linear dispersion in the optical response of Fe M\"ossbauer
nuclei embedded in a thin film planar x-ray cavity. The direct detection of the
temporal pulse delay is enabled by generating frequency-tunable spectrally
narrow x-ray pulses from broadband pulsed synchrotron radiation. Our
theoretical model is in good agreement with the experimental data.Comment: 8 pages, 4 figure
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