1,903 research outputs found
Characterization of the space shuttle reaction control system engine
A computer program was developed and written in FORTRAN 5 which predicts the transient and steady state performance and heat transfer characteristics of a pulsing GO2/GH2 rocket engine. This program predicts the dynamic flow and ignition characteristics which, when combined in a quasi-steady state manner with the combustion and mixing analysis program, will provide the thrust and specific impulse of the engine as a function of time. The program also predicts the transient and steady state heat transfer characteristics of the engine using various cooling concepts. The computer program, test case, and documentation are presented. The program is applicable to any system capable of utilizing the FORTRAN 4 or FORTRAN 5 language
Attentional Bias And Training In Individuals With High Dental Anxiety
Dental anxiety is common and associated with negative outcomes. According to information-processing models, anxiety is maintained by maladaptive patterns of processing threatening information. Furthermore, attention training interventions can reduce anxiety in one session. Fifty-three individuals with high levels of dental anxiety completed a Posner reaction-time task. Participants were randomized to attention training or control using a dot-probe task, and then attentional bias was remeasured using another Posner task. Participants then completed a script-driven imaginal exposure task. Results indicated that individuals high in dental anxiety exhibit threat-relevant attentional bias. There was mixed evidence about the efficacy of attention training. On the one hand, training did not eliminate attentional bias and training condition did not predict distress during the imagery task. On the other hand, cue dependency scores in the control group were higher for dental than neutral cues, but did not differ in the training group. In addition, cue dependency scores for both dental and neutral cues predicted subjective anxiety in anticipation of the imagery task. The mixed results of training are considered in terms of the possibility that it enhanced attentional control, rather than reducing bias
Via Hexagons to Squares in Ferrofluids: Experiments on Hysteretic Surface Transformations under Variation of the Normal Magnetic Field
We report on different surface patterns on magnetic liquids following the
Rosensweig instability. We compare the bifurcation from the flat surface to a
hexagonal array of spikes with the transition to squares at higher fields. From
a radioscopic mapping of the surface topography we extract amplitudes and
wavelengths. For the hexagon--square transition, which is complex because of
coexisting domains, we tailor a set of order parameters like peak--to--peak
distance, circularity, angular correlation function and pattern specific
amplitudes from Fourier space. These measures enable us to quantify the smooth
hysteretic transition. Voronoi diagrams indicate a pinning of the domains. Thus
the smoothness of the transition is roughness on a small scale.Comment: 17 pages, 14 figure
Spectroscopy of Na: Bridging the two-proton radioactivity of Mg
The unbound nucleus Na, the intermediate nucleus in the two-proton
radioactivity of Mg, was studied by the measurement of the resonant
elastic scattering reaction Ne(p,Ne)p performed at 4 A.MeV.
Spectroscopic properties of the low-lying states were obtained in a R-matrix
analysis of the excitation function. Using these new results, we show that the
lifetime of the Mg radioactivity can be understood assuming a sequential
emission of two protons via low energy tails of Na resonances
Theory of Thermodynamic Magnetic Oscillations in Quasi-One-Dimensional Conductors
The second order correction to free energy due to the interaction between
electrons is calculated for a quasi-one-dimensional conductor exposed to a
magnetic field perpendicular to the chains. It is found that specific heat,
magnetization and torque oscillate when the magnetic field is rotated in the
plane perpendicular to the chains or when the magnitude of magnetic filed is
changed. This new mechanism of thermodynamic magnetic oscillations in metals,
which is not related to the presence of any closed electron orbits, is applied
to explain behavior of the organic conductor (TMTSF)ClO.Comment: 11 pages + 5 figures (included
Positive Youth Development: Developing, Implementing, and Sustaining Music-Based Services for Emerging Adults Experiencing Homelessness
Research suggests that comprehensive services that consider the complex and interconnected needs of emerging adults experiencing homelessness may be more effective than interventions with a singular focus. There is little research that demonstrates how agencies that implement programs for individuals experiencing homelessness develop and sustain meaningful services for emerging adults, especially under conditions of increasing austerity. This study targets this gap in the literature by investigating how one transitional living program for emerging adults experiencing homelessness developed a music studio. Specifically, this study examines the factors and processes that were involved in developing, implementing, and sustaining the music studio. Findings suggest an ongoing organizational commitment to Positive Youth Development plays an important role
Theoretical study of the two-proton halo candidate Ne including contributions from resonant continuum and pairing correlations
With the relativistic Coulomb wave function boundary condition, the energies,
widths and wave functions of the single proton resonant orbitals for Ne
are studied by the analytical continuation of the coupling constant (ACCC)
approach within the framework of the relativistic mean field (RMF) theory.
Pairing correlations and contributions from the single-particle resonant
orbitals in the continuum are taken into consideration by the resonant
Bardeen-Cooper-Schrieffer (BCS) approach, in which constant pairing strength is
used. It can be seen that the fully self-consistent calculations with NL3 and
NLSH effective interactions mostly agree with the latest experimental
measurements, such as binding energies, matter radii, charge radii and
densities. The energy of 2s orbital is slightly higher than that
of orbital, and the occupation probability of the
2s orbital is about 20%, which are in accordance with the
shell model calculation and three-body model estimation
Destruction of density-wave states by a pseudo-gap in high magnetic fields: application to (TMTSF)ClO
A model is presented for the destruction of density-wave states in
quasi-one-dimensional crystals by high magnetic fields. The model is consistent
with previously unexplained properties of the organic conductors
(TMTSF)ClO and (BEDT-TTF)MHg(SCN) (M=K,Rb,Tl). As the magnetic
field increases quasi-one-dimensional density-wave fluctuations increase,
producing a pseudo-gap in the electronic density of states near the transition
temperature. When the pseudo-gap becomes larger than the mean-field transition
temperature formation of a density-wave state is not possible.Comment: 4 pages, RevTeX, 2 figures in uuencoded compressed tar file. Small
changes to text and Figure 1. Final version to appear in Physical Review
Letter
Efferocytosis is an innate antibacterial mechanism
Mycobacterium tuberculosis persists within macrophages in an arrested phagosome and depends upon necrosis to elude immunity and disseminate. Although apoptosis of M. tuberculosis-infected macrophages is associated with reduced bacterial growth, the bacteria are relatively resistant to other forms of death, leaving the mechanism underlying this observation unresolved. We find that after apoptosis, M. tuberculosis-infected macrophages are rapidly taken up by uninfected macrophages through efferocytosis, a dedicated apoptotic cell engulfment process. Efferocytosis of M. tuberculosis sequestered within an apoptotic macrophage further compartmentalizes the bacterium and delivers it along with the apoptotic cell debris to the lysosomal compartment. M. tuberculosis is killed only after efferocytosis, indicating that apoptosis itself is not intrinsically bactericidal but requires subsequent phagocytic uptake and lysosomal fusion of the apoptotic body harboring the bacterium. While efferocytosis is recognized as a constitutive housekeeping function of macrophages, these data indicate that it can also function as an antimicrobial effector mechanism.Behar, Fortune, and Remold labs for reagents, helpful discussion, and insights. TIM4-blocking antibodies were a generous gift of Vijay Kuchroo. Members of the Harvard Electron Microscopy Core Facility helped in the preparation, staining, and operation of the electron microscope. The Small Animal Biocontainment (ABC) Suite is supported by CFAR 5P30AI060354. T.R.R and S.M.F were supported by CFAR 5P30AI060354, DP2-0d001378, and T32-AI07387. C.N.A. is the recipient of a fellowship from FCT. S.M.B and H.G.R. were supported by R56AI084161 and R01AI072143
Charge Order with Structural Distortion in Organic Conductors: Comparison between \theta-(ET)2RbZn(SCN)4 and \alpha-(ET)2I3
Charge ordering with structural distortion in quasi-two-dimensional organic
conductors \theta-(ET)2RbZn(SCN)4 (ET=BEDT-TTF) and \alpha-(ET)2I3 is
investigated theoretically. By using the Hartree-Fock approximation for an
extended Hubbard model which includes both on-site and intersite Coulomb
interactions together with Peierls-type electron-lattice couplings, we examine
the role of lattice degrees of freedom on charge order. It is found that the
experimentally observed, horizontal charge order is stabilized by lattice
distortion in both compounds. In particular, the lattice effect is crucial to
the realization of the charge order in \theta-(ET)2RbZn(SCN)4, while the
peculiar band structure whose symmetry is lower than that of
\theta-(ET)2RbZn(SCN)4 in the metallic phase is also an important factor in
\alpha-(ET)2I3 together with the lattice distortion. For \alpha-(ET)2I3, we
obtain a phase transition from a charge-disproportionated metallic phase to the
horizontal charge order with lattice modulations, which is consistent with the
latest X-ray experimental result.Comment: 10 pages, 13 figures, to appear in J. Phys. Soc. Jpn. Vol. 77 (2008)
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