21,912 research outputs found
Pioneer 10 Jupiter atmospheric definition results: A summary
The various entry probes for measuring outer planetary atmospheric compositions are discussed. Considered are chemical components and physical accumulation processes observable by spectroscopic studies, as well as pressure gauges, temperature gauges, accelerometers, nephelometers, and visible and infrared sensors for determining abundances
Understanding Physical Conditions in High Redshift Galaxies through C I Fine Structure Lines: Data and Methodology
We probe the physical conditions in high redshift galaxies, specifically, the
Damped Lyman-alpha Systems (DLAs) using neutral carbon (CI) fine structure
lines and molecular hydrogen (H2). We report five new detections of CI and
analyze the CI in an additional 2 DLAs with previously published data. We also
present one new detection of H2 in a DLA. We present a new method of analysis
that simultaneously constrains \emph{both} the volume density and the
temperature of the gas, as opposed to previous studies that a priori assumed a
gas temperature. We use only the column density of CI measured in the fine
structure states and the assumption of ionization equilibrium in order to
constrain the physical conditions in the gas. We present a sample of 11 CI
velocity components in 6 DLAs and compare their properties to those derived by
the global CII* technique. The resulting median values for this sample are:
= 69 cm^{-3}, = 50 K, and = 3.86 cm^{-3} K, with
standard deviations, sigma_{n(HI)} = 134 cm^{-3}, sigma_T = 52 K, and
sigma_{log(P/k)} = 3.68 cm^{-3} K. This can be compared with the integrated
median values for the same DLAs : = 2.8 cm^{-3}, = 139 K, and
= 2.57 cm^{-3} K, with standard deviations sigma_{n(HI)} = 3.0
cm^{-3}, sigma_T = 43 K, and sigma_{log(P/k)} = 0.22 cm^{-3} K. Interestingly,
the pressures measured in these high redshift CI clouds are similar to those
found in the Milky Way. We conclude that the CI gas is tracing a
higher-density, higher-pressure region, possibly indicative of post-shock gas
or a photodissociation region on the edge of a molecular cloud. We speculate
that these clouds may be direct probes of the precursor sites of star formation
in normal galaxies at high redshift.Comment: Accepted for publication in Ap
Time to guide: evidence for delayed attentional guidance in contextual cueing
Contextual cueing experiments show that, when displays are repeated, reaction times (RTs) to find a target decrease over time even when the observers are not aware of the repetition. Recent evidence suggests that this benefit in standard contextual cueing tasks is not likely to be due to an improvement in attentional guidance (Kunar, Flusberg, Horowitz, & Wolfe, 2007). Nevertheless, we ask whether guidance can help participants find the target in a repeated display, if they are given sufficient time to encode the display. In Experiment 1 we increased the display complexity so that it took participants longer to find the target. Here we found a larger effect of guidance than in a condition with shorter RTs. Experiment 2 gave participants prior exposure to the display context. The data again showed that with more time participants could implement guidance to help find the target, provided that there was something in the search stimuli locations to guide attention to. The data suggest that, although the benefit in a standard contextual cueing task is unlikely to be a result of guidance, guidance can play a role if it is given time to develop
Synthesis of aromatic secondary diamines
A series of N-methyl substituted aromatic polyamides derived from the secondary aromatic diamines, 4,4'-bis(methylamino)diphenylmethane, 3,3'-bis(methylamino) diphenylmethane, 4,4'-bis(methylamino)benzophenone or 3,3'-bis(methylamino)benzophenone and isophthaloyl dichloride, terphthaloyl dichloride or 3,3'diphenylmethane dicarboxylic acid dichloride was prepared by high temperature solution polymerization in s-tetrachloroethane. Compared to analogous unsubstituted and partially N-methylated aromatic polyamides, the full N-methylated polyamides exhibited significantly lower glass transition temperatures, reduced crystallinity, improved thermal stability and good solubility in chlorinated solvents
An Analysis of Expansion and Relocation Sites for Major League Soccer
This research develops a model of optimal locations for Major League Soccer teams and investigates the important underlying factors.soccer; MLS; regression; probit; demand; location
Collisional Transfer of Population and Orientation in NaK
We report current work to study transfer of population and orientation in collisions of NaK molecules with argon and potassium atoms using polarization labeling (PL) and laser- induced fluorescence (LIF) spectroscopy. In the PL experiment, a circularly polarized pump laser excites a specific NaK A1Ī£ +(v 0=16, J 0 ) ā X1Ī£ +(v 00=0, J 0 Ā± 1) transition, creating an orientation (non-uniform MJ0 level distribution) in both levels. The linearly polarized probe laser is scanned over various 31Ī (v, J 0Ā±1) ā A1Ī£ +(v 0=16, J 0 ) transitions. The probe laser passes through a crossed linear polarizer before detection, and signal is recorded if the probe laser polarization has been modified by the vapor (which occurs when it comes into resonance with an oriented level). Using both spectroscopic methods, analysis of weak collisional satellite lines adjacent to these directly populated lines, as a function of argon buffer gas pressure and cell temperature, allows us to discern separately the effects collisions with argon atoms and potassium atoms have on the population and orientation of the molecule. In addition, code has been written which provides a theoretical analysis of the process, through a solution of the density matrix equations of motion for the system
Polarization Spectroscopy and Collisions in NaK
We report current work to study transfer of population and orientation in collisions of NaK molecules with argon and potassium atoms using polarization labeling (PL) and laser-induced fluorescence (LIF) spectroscopy. In the PL experiment, a circularly polarized pump laser excites a specific NaK A1Ī£ +(v=16, J) ā X1Ī£ +(v=0, J Ā± 1) transition, creating an orientation (non-uniform MJ level distribution) in both levels. The linear polarized probe laser is scanned over various 3 1Ī (v=8, J 0 Ā± 1) ā A1Ī£ +(v=16, J 0 ) transitions. The probe laser passes through a crossed linear polarizer before detection, and signal is recorded if the probe laser polarization has been modified by the vapor (which occurs when it comes into resonance with an oriented level). In addition to strong direct transitions (J 0 = J), we also observe weak collisional satellite lines (J 0 = J Ā±n with n = 1, 2, 3, ...) indicating that orientation is transferred to adjacent rotational levels during a collision. An LIF experiment (with linear polarized pump and probe beams) gives information on the collisional transfer of population. From these data, cross sections for both processes can be determined. We experimentally distinguish collisions of NaK with argon atoms from collisions with alkali atoms
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