| 51. |
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| 52. |
- Harri, A.-M., et al.
(författare)
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Mars Science Laboratory relative humidity observations: Initial results
- 2014
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Ingår i: Journal of Geophysical Research - Planets. - 2169-9097 .- 2169-9100. ; 119:9, s. 2132-2147
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Tidskriftsartikel (refereegranskat)abstract
- The Mars Science Laboratory (MSL) made a successful landing at Gale crater early August 2012. MSL has an environmental instrument package called the Rover Environmental Monitoring Station (REMS) as a part of its scientific payload. REMS comprises instrumentation for the observation of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements. We concentrate on describing the REMS-H measurement performance and initial observations during the first 100 MSL sols as well as constraining the REMS-H results by comparing them with earlier observations and modeling results. The REMS-H device is based on polymeric capacitive humidity sensors developed by Vaisala Inc., and it makes use of transducer electronics section placed in the vicinity of the three humidity sensor heads. The humidity device is mounted on the REMS boom providing ventilation with the ambient atmosphere through a filter protecting the device from airborne dust. The final relative humidity results appear to be convincing and are aligned with earlier indirect observations of the total atmospheric precipitable water content. The water mixing ratio in the atmospheric surface layer appears to vary between 30 and 75 ppm. When assuming uniform mixing, the precipitable water content of the atmosphere is ranging from a few to six precipitable micrometers.
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| 53. |
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| 54. |
- Herr, Werner, et al.
(författare)
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Hybrid fast multipole method applied to beam-beam collisions in the strong-strong regime
- 2001
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Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 4:5, s. 37-45
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Tidskriftsartikel (refereegranskat)abstract
- The strong-strong interactions of two colliding beams are simulated by tracking the motion of a set of macroparticles. The field generated by each distribution is evaluated using the fast multipole method together with some elements of particle-mesh methods. This technique allows us to check the exact frequencies of the coherent modes and the frequencies of oscillations of individual particles in the beam. The agreement between the simulations and analytical calculations is largely improved. Furthermore, it is an efficient method to study the coherent modes in the case of separated beams.
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| 55. |
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| 56. |
- Hochberg, David, et al.
(författare)
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Complex reaction noise in a molecular quasispecies model
- 2006
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Ingår i: Chemical Physics Letters. - : Elsevier. - 0009-2614 .- 1873-4448. ; 423:1-3, s. 54-58
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Tidskriftsartikel (refereegranskat)abstract
- We have derived exact Langevin equations for a model of quasispecies dynamics. The inherent multiplicative reaction noise is complex and its statistical properties are specified completely. The numerical simulation of the complex Langevin equations is carried out using the Cholesky decomposition for the noise covariance matrix. This internal noise, which is due to diffusion-limited reactions, produces unavoidable spatio-temporal density fluctuations about the mean field value. In two dimensions, this noise strictly vanishes only in the perfectly mixed limit, a situation difficult to attain in practice
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| 57. |
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| 58. |
- Hochberg, David, et al.
(författare)
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Path integral evaluation of the one-loop effective potential in field theory of diffusion-limited reactions
- 2007
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Ingår i: Physica A. - : Elsevier BV. - 0378-4371 .- 1873-2119. ; 278:2, s. 238-254
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Tidskriftsartikel (refereegranskat)abstract
- The well-established effective action and effective potential framework from the quantum field theory domain is adapted and successfully applied to classical field theories of the Doi and Peliti type for diffusion controlled reactions. Through a number of benchmark examples, we show that the direct path integral calculation of the effective potential in fixed space dimension d = 2 to one-loop order reduces to a small set of simple elementary functions, irrespective of the microscopic details of the specific model. Thus the technique, which allows one to obtain with little additional effort, the potentials for a wide variety of different models, represents an alternative to the standard model-dependent diagram-based calculations. The renormalized effective potential, effective equations of motion and the associated renormalization group equations are computed in d = 2 spatial dimensions for a number of single species field theories of increasing complexity.
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| 59. |
- Hochberg, David, et al.
(författare)
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Reaction-noise induced homochirality
- 2006
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 431:1-3, s. 185-189
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Tidskriftsartikel (refereegranskat)abstract
- Starting from the chemical master equation, we employ field theoretic techniques to derive Langevin-type equations that exactly describe the stochastic dynamics of the Frank chiral amplification model with spatial diffusion. The intrinsic multiplicative noise properties are completely and rigorously derived by this procedure. We carry out numerical simulations in two spatial dimensions. When the inherent spatio-temporal fluctuations are properly included, then complete chiral amplification results from a purely racemic initial configuration. Phase separation can also arise in which the enantiomers coexist in spatially segregated domains separated by a sharp racemic interface or boundary.
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| 60. |
- Hochberg, David, et al.
(författare)
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Spatiotemporal patterns driven by autocatalytic internal reaction noise
- 2005
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 122:21
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Tidskriftsartikel (refereegranskat)abstract
- The influence that intrinsic local-density fluctuations can have on solutions of mean-field reaction-diffusion models is investigated numerically by means of the spatial patterns arising from two species that react and diffuse in the presence of strong internal reaction noise. The dynamics of the Gray-Scott (GS) model [P. Gray and S. K. Scott, Chem. Eng. Sci. 38, 29 (1983); P. Gray and S. K. Scott, Chem. Eng. Sci.39, 1087 (1984); P. Gray and S. K. Scott,J. Phys. Chem. 89, 22 (1985)] with a constant external source is first cast in terms of a continuum field theory representing the corresponding master equation. We then derive a Langevin description of the field theory and use these stochastic differential equations in our simulations. The nature of the multiplicative noise is specified exactly without recourse to assumptions and turns out to be of the same order as the reaction itself, and thus cannot be treated as a small perturbation. Many of the complex patterns obtained in the absence of noise for the GS model are completely obliterated by these strong internal fluctuations, but we find novel spatial patterns induced by this reaction noise in the regions of parameter space that otherwise correspond to homogeneous solutions when fluctuations are not included
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