1,663 research outputs found
A hierarchy of models related to nanoflows and surface diffusion
In last years a great interest was brought to molecular transport problems at
nanoscales, such as surface diffusion or molecular flows in nano or
sub-nano-channels. In a series of papers V. D. Borman, S. Y. Krylov, A. V.
Prosyanov and J. J. M. Beenakker proposed to use kinetic theory in order to
analyze the mechanisms that determine mobility of molecules in nanoscale
channels. This approach proved to be remarkably useful to give new insight on
these issues, such as density dependence of the diffusion coefficient. In this
paper we revisit these works to derive the kinetic and diffusion models
introduced by V. D. Borman, S. Y. Krylov, A. V. Prosyanov and J. J. M.
Beenakker by using classical tools of kinetic theory such as scaling and
systematic asymptotic analysis. Some results are extended to less restrictive
hypothesis
Fluctuations of g-factors in metal nanoparticles: Effects of electron-electron interaction and spin-orbit scattering
We investigate the combined effect of spin-orbit scattering and
electron-electron interactions on the probability distribution of -factors
of metal nanoparticles. Using random matrix theory, we find that even a
relatively small interaction strength %(ratio of exchange constant and mean
level %spacing \spacing ) significantly increases -factor
fluctuations for not-too-strong spin-orbit scattering (ratio of spin-orbit rate
and single-electron level spacing 1/\tau_{\rm so} \spacing \lesssim 1), and
leads to the possibility to observe -factors larger than two.Comment: RevTex, 2 figures inserte
Knudsen Effect in a Nonequilibrium Gas
From the molecular dynamics simulation of a system of hard-core disks in
which an equilibrium cell is connected with a nonequilibrium cell, it is
confirmed that the pressure difference between two cells depends on the
direction of the heat flux. From the boundary layer analysis, the velocity
distribution function in the boundary layer is obtained. The agreement between
the theoretical result and the numerical result is fairly good.Comment: 4pages, 4figure
A note on the lattice Boltzmann method beyond the Chapman Enskog limits
A non-perturbative analysis of the Bhatnagar-Gross-Krook (BGK) model kinetic
equation for finite values of the Knudsen number is presented. This analysis
indicates why discrete kinetic versions of the BGK equation, and notably the
Lattice Boltzmann method, can provide semi-quantitative results also in the
non-hydrodynamic, finite-Knudsen regime, up to . This may
help the interpretation of recent Lattice Boltzmann simulations of microflows,
which show satisfactory agreement with continuum kinetic theory in the
moderate-Knudsen regime.Comment: 7 PAGES, 1 FIGUR
Studies of spin-orbit scattering in noble-metal nanoparticles using energy level tunneling spectroscopy
The effects of spin-orbit scattering on discrete electronic energy levels are
studied in copper, silver, and gold nanoparticles. Level-to-level fluctuations
of the effective -factor for Zeeman splitting are characterized, and the
statistics are found to be well-described by random matrix theory predictions.
The strength of spin-orbit scattering increases with atomic number and also
varies between nanoparticles made of the same metal. The spin-orbit scattering
rates in the nanoparticles are in order-of-magnitude agreement with bulk
measurements on disordered samples.Comment: 4 pages, 3 figures, 1 in colo
Dynamique de croissance et taux de mortalité de Rhizophora spp. dans les mangroves de l'estuaire du Rio del Rey: Site de Bamusso (Sud-Ouest Cameroun)
Objectifs : L’objectif des présents travaux est de clarifier le stock du peuplement de Rhizophora ssp. du site par la détermination de ses paramètres de structure spatiale et d'évaluer sa croissance annuelle.Méthodologie et résultats : La méthode d'étude est celle des transects. Deux transects de 100mx10m distantes de 5km orientés WNW-ESE et perpendiculaires au principal chenal ont été établis au hasard .Chaque transect était subdivisé en trois placettes de 20mx10m et chaque placettes scindé en deux sous placettes de 20mx5m. Les mesures (Diamètre et hauteur) ont été effectuées à l'intérieur de chaque sous placette pendant trois campagnes (2009, 2012, 2014). Les résultats montrent que les diamètres moyens pour le transect1(T1) sont de 4,76 ± 0,23cm; 5,09± 0,25cm et 5,43±0,28cm contre 26,53 ± 1,72cm; 24,66 ± 1,90cm et 25,26 ± 1,93cm pour le transect2 (T2) respectivement pour 2009; 2012 et 2014. Les hauteurs moyennes varient de 4,51 ± 0,16 m (2009); 4,74 ± 0,18m (2012) et 4,98 ± 0,2m (2014) pour T1 contre 20,20± 1,22m; 18,86 ± 1,35 m et 19,29 ±1,39m pour T2. L'analyse de la croissance du peuplement montre que les diamètres d'exploitation du bois de la mangrove affectionnée par les riverains se situent dans l'intervalle (5-30cm). Le test d'ANOVA montre une différence significative (P<0,05) pour les paramètres, de structure et une différence non significative (P>0,05) de la croissance annuelle entre T1 et T2.Conclusion et application des résultats : Cette étude a montré un taux de mortalité relativement faible (m=2,27%) qui présage d'une pression anthropique faible sur cet écosystème. L'étude de la dynamique réalisée permet de recommander ce site dans le processus REDD+ pour le calcul du carbone bleu indispensable dans la lutte contre le phénomène de changement climatique. Mots clés: Transect, Diamètre; Hauteur; Nombre d'individus, BamussoGrowth dynamic and death rate of Rhizophora spp. within mangrove's forest of Rio del Rey estuary (South-West Cameroon)Objective: This study was conducted to clarify the stock of Rhizophora ssp and to assess its growth within the study area.Methodology and results: Transect method was carried out during this study. So, two transects of 100 m in length, 10 m in width and 0.1 ha in area each distance to 5km oriented WNW-ESE and perpendicular to themain channel were established randomly . Each transect was divided in three plots of 20mx10m each and each plot separated in two subplots of 20mx5m each. Measures (Diameter and height) were collected within each subplot during three data collections campaigns (2009,2012,and 2014). The results show that mean diameters of transect1(T1) were 4.76 ± 0.23cm; 5.09± 0.25cm and 5.43±0.28cm to 26.53 ± 1.72cm; 24.66 ± 1.90cm and 25.26 ± 1.93cm for transect2 (T2) respectively in 2009; 2012 et 2014. Mean height values were 4.51 ± 0.16 m (2009); 4.74 ± 0.18m (2012) and 4.98 ± 0.2m (2014) for T1 to 20.20± 1.22m; 18.86 ± 1.35 m and 19.29 ±1.39m for T2. Study of growth show that used diameters of mangrove woods by neighborhood are inside class 5-30cm. The one-way ANOVA test showed a significant difference (P<0.05) for structure parameters and no significant difference (P>0,05) for annual growth between T1 and T2.Conclusion and application of findings: This study showed a relatively weak annual death rate of trees (m=2.27%) dues to a weak anthropogenic pressure in this ecosystem. This dynamic study will recommend the site to the REDD+ process in order to estimate its blue carbon stock important to fight against climate change.Key words: Transect, Diameter, Height, Number of individuals, Bamuss
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