11,188 research outputs found
Gas phase reaction rates of some positive ions with water at 296 K
Measuring rate constants for reactions of various gas phases with water by flowing afterglow techniqu
Kinetics and mechanism of the formation of water cluster ions from O2(plus) and H2O in He, Ar, N2, and O2 at 296 K
The reaction sequence leading from O2(+) to H3O(+)-H2O was examined in He, Ar, N2 and O2 carrier gases in a flowing afterglow system. The rate constants for the reactions were measured and the kinetic analysis for their determination is presented. For M = N2, two new steps involving the formation and reaction of O2(+)-N2 were proposed and examined. The rate constants are discussed and compared with other experimental values
Study of combustion experiments in space
The physical bases and scientific merits were examined of combustion experimentation in a space environment. For a very broad range of fundamental combustion problems, extensive and systematic experimentation at reduced gravitational levels (0 g 1) are viewed as essential to the development of needed observations and related theoretical understanding
Potts-Percolation-Gauss Model of a Solid
We study a statistical mechanics model of a solid. Neighboring atoms are
connected by Hookian springs. If the energy is larger than a threshold the
"spring" is more likely to fail, while if the energy is lower than the
threshold the spring is more likely to be alive. The phase diagram and
thermodynamic quantities, such as free energy, numbers of bonds and clusters,
and their fluctuations, are determined using renormalization-group and
Monte-Carlo techniques.Comment: 10 pages, 12 figure
Global Management Effectiveness Study: Integrated Social and Ecological Report for Non-node and Node Sites
The purpose of this study is to provide a critical assessment of the implementation, impact, and performance of Marine Managed Area (MMA) projects to serve as a basis for improved planning and implementation of new MMA projects worldwide. The specific objectives of the study are (1) to determine the socioeconomic, governance and ecological effects of MMAs; (2) to determine the critical factors influencing MMA effects, as well as the impact of the timing of those factors on the effects of the MMA; and (3) to provide tools for predicting MMA effects based on ecological, socioeconomic and governance variable
Parallel Algorithm and Dynamic Exponent for Diffusion-limited Aggregation
A parallel algorithm for ``diffusion-limited aggregation'' (DLA) is described
and analyzed from the perspective of computational complexity. The dynamic
exponent z of the algorithm is defined with respect to the probabilistic
parallel random-access machine (PRAM) model of parallel computation according
to , where L is the cluster size, T is the running time, and the
algorithm uses a number of processors polynomial in L\@. It is argued that
z=D-D_2/2, where D is the fractal dimension and D_2 is the second generalized
dimension. Simulations of DLA are carried out to measure D_2 and to test
scaling assumptions employed in the complexity analysis of the parallel
algorithm. It is plausible that the parallel algorithm attains the minimum
possible value of the dynamic exponent in which case z characterizes the
intrinsic history dependence of DLA.Comment: 24 pages Revtex and 2 figures. A major improvement to the algorithm
and smaller dynamic exponent in this versio
Detecting a Currency's Dominance or Dependence using Foreign Exchange Network Trees
In a system containing a large number of interacting stochastic processes,
there will typically be many non-zero correlation coefficients. This makes it
difficult to either visualize the system's inter-dependencies, or identify its
dominant elements. Such a situation arises in Foreign Exchange (FX) which is
the world's biggest market. Here we develop a network analysis of these
correlations using Minimum Spanning Trees (MSTs). We show that not only do the
MSTs provide a meaningful representation of the global FX dynamics, but they
also enable one to determine momentarily dominant and dependent currencies. We
find that information about a country's geographical ties emerges from the raw
exchange-rate data. Most importantly from a trading perspective, we discuss how
to infer which currencies are `in play' during a particular period of time
Strongly Non-Equilibrium Bose-Einstein Condensation in a Trapped Gas
We present a qualitative (and quantitative, at the level of estimates)
analysis of the ordering kinetics in a strongly non-equilibrium state of a
weakly interacting Bose gas, trapped with an external potential. At certain
conditions, the ordering process is predicted to be even more rich than in the
homogeneous case. Like in the homogeneous case, the most characteristic feature
of the full-scale non-equilibrium process is the formation of superfluid
turbulence.Comment: 4 pages, revtex, no figures. Submitted to PR
Spatial Reorientation of Sensorimotor Balance Control in Altered Gravity
Sensorimotor coordination of body segments following space flight are more pronounced after landing when the head is actively tilted with respect to the trunk. This suggests that central vestibular processing shifts from a gravitational frame of reference to a head frame of reference in microgravity. A major effect of such changes is a significant postural instability documented by standard head-erect Sensory Organization Tests. Decrements in functional performance may still be underestimated when head and gravity reference frames remained aligned. The purpose of this study was to examine adaptive changes in spatial processing for balance control following space flight by incorporating static and dynamic tilts that dissociate head and gravity reference frames. A second aim of this study was to examine the feasibility of altering the re-adaptation process following space flight by providing discordant visual-vestibular-somatosensory stimuli using short-radius pitch centrifugation
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