68 research outputs found
Diffusion over a saddle with a Langevin equation
The diffusion problem over a saddle is studied using a multi-dimensional
Langevin equation. An analytical solution is derived for a quadratic potential
and the probability to pass over the barrier deduced. A very simple solution is
given for the one dimension problem and a general scheme is shown for higher
dimensions.Comment: 13 pages, use revTeX, to appear in Phys. Rev. E6
Tumor necrosis factor-alpha enhances mRNA expression and secretion of interleukin-6 in cultured human airway smooth muscle cells
Airway smooth muscle (ASM) is considered to be an end-target cell for the
effects of mediators released during airway wall inflammation. Several
reports suggest that activated ASM may be capable of generating various
proinflammatory cytokines. We investigated the effects of tumor necrosis
factor (TNF)-alpha, a potent proinflammatory cytokine, on cultured human
ASM cells by examining the expression and release of the cytokine
interleukin (IL)-6, cell proliferation, and the expression pattern of
c-fos and c-jun, two nuclear proto-oncogenes constituting the activator
protein-1 transcription factor. Growth-arrested cell monolayers were
stimulated with human recombinant TNF-alpha in a concentration- and
time-dependent manner. TNF-alpha stimulated the expression of IL-6
messenger RNA (mRNA), which was detected after 15 min, reaching a maximum
at 1 h. IL-6 protein was readily detected in ASM cell-conditioned medium
after 2 h of TNF-alpha stimulation. Protein levels increased in a time-
and concentration-dependent manner. Release of IL-6 elicited by TNF-alpha
was significantly inhibited by dexamethasone, cycloheximide, and
nordihydroguaiaretic acid (NDGA). TNF-alpha did not alter DNA biosynthesis
up to 48 h or cell numbers up to 120 h. Northern blot analysis of
proto-oncogene expression revealed that c-fos and c-jun mRNA levels were
elevated after 30 min of TNF-alpha incubation with maximum levels at 1 h
and 45 min, respectively. Expression of c-fos mRNA was downregulated by
NDGA. Four hours of TNF-alpha treatment resulted in translocation of c-jun
immunofluorescence from the cytoplasm to the nucleus in human ASM cells.
Our results suggest that despite the lack of a mitogenic response to
TNF-alpha, upregulation of primary response genes in human ASM cells may
account for the induction of proinflammatory cytokines, such as IL-6, in
human airways
Measurement of Leading Proton and Neutron Production in Deep Inelastic Scattering at HERA
Deep--inelastic scattering events with a leading baryon have been detected by
the H1 experiment at HERA using a forward proton spectrometer and a forward
neutron calorimeter. Semi--inclusive cross sections have been measured in the
kinematic region 2 <= Q^2 <= 50 GeV^2, 6.10^-5 <= x <= 6.10^-3 and baryon p_T
<= MeV, for events with a final state proton with energy 580 <= E' <= 740 GeV,
or a neutron with energy E' >= 160 GeV. The measurements are used to test
production models and factorization hypotheses. A Regge model of leading baryon
production which consists of pion, pomeron and secondary reggeon exchanges
gives an acceptable description of both semi-inclusive cross sections in the
region 0.7 <= E'/E_p <= 0.9, where E_p is the proton beam energy. The leading
neutron data are used to estimate for the first time the structure function of
the pion at small Bjorken--x.Comment: 30 pages, 9 figures, 2 tables, submitted to Eur. Phys.
Charmonium Production in Deep Inelastic Scattering at HERA
The electroproduction of J/psi and psi(2S) mesons is studied in elastic, quasi-elastic and inclusive reactions for four momentum transfers 2 Q^2 80 GeV^2 and photon-proton centre of mass energies 25 W 180 GeV. The data were taken with the H1 detector at the electron proton collider HERA in the years 1995 to 1997. The total virtual photon-proton cross section for elastic J/psi production is measured as a function of Q^2 and W. The dependence of the production rates on the square of the momentum transfer from the proton (t) is extracted. Decay angular distributions are analysed and the ratio of the longitudinal and transverse cross sections is derived. The ratio of the cross sections for quasi-elastic psi(2S) and J/psi meson production is measured as a function of Q^2. The results are discussed in terms of theoretical models based upon perturbative QCD. Differential cross sections for inclusive and inelastic production of J/psi mesons are determined and predictions within two theoretical frameworks are compared with the data, the non-relativistic QCD factorization approach including colour octet and colour singlet contributions, and the model of Soft Colour Interactions
Influence of the discrete production term on the computation of turbulent flow in a stirred vessel
The present work is devoted to the prediction of the mean flow and turbulence properties in a baffled vessel equipped with a Rushton turbine
Influence of the discrete production term on the computation of turbulent flow in a stirred vessel
The present work is devoted to the prediction of the mean flow and turbulence properties in a baffled vessel equipped with a Rushton turbine
Modèles du 1er ordre appliques a l'écoulement dans le plan de résolution d'une cuve agitée idéalisée
Un modèle de turbulence du 1er ordre de type (k-Є) couplé avec équations de l'hydrodynamique est appliqué à l'étude de l'écoulement en cuve agitée, moyennant des hypothèses de stationnarité et de symétrie de révolution. L'algorithme de pression implicite à opérateur séparé (PISO) est choisi pour la résolution du problème en variables Vitesse-Pression la discrétisation est faite selon la méthode des volumes finis l'influence des conditions aux limites de (k-Є) se fait sentir par : modification de l'allure du jet ; déplacement du centre de recirculation
Etude numérique de l'écoulement turbulent dans une cuve agitée munie d'une turbine de Rushton
On présente une étude numérique par la méthode des volumes finis tridimensionnels de l'écoulement moyen et de la turbulence dans une cuve agitée munie d'une turbine de Rushton. La zone de la turbine est modélisée à partir de résultats expérimentaux. Un modèle à viscosité effective du type k-epsilon est employé pour introduire les effets de la turbulence. La détermination des bilans d'énergie totale implique l'utilisation de schémas numériques cohérents et consistants notamment pour le calcul des termes de production de turbulence et des interactions aux parois. Des comparaisons globales et locales montrent un bon accord qualitatif avec les résultats expérimentaux mais pour un accord quantitatif une modélisation plus complète est encore nécessaire
Phylogenetic position of the rainbow sardine Dussumieria (Dussumieriidae) and its bearing on the early evolution of the Clupeoidei.
The fish family Dussumieriidae (suborder Clupeoidei), commonly called round herrings, is traditionally considered to be a key taxon for understanding the evolution of the Clupeoidei because some of its morphological characteristics have been interpreted as being either derived or primitive, such as the nearly complete absence of abdominal scutes. Recent molecule-based studies showed that the Dussumieriidae is likely not a monophyletic group. None of those studies, however, included the genus Dussumieria (rainbow sardines) which is the type genus of the family Dussumieriidae. Herein, we investigated the phylogenetic position of Dussumieria within the Clupeoidei, using a dataset of complete mitogenomic sequences, including five newly determined using high-throughput sequencing technology. In the inferred phylogenetic reconstructions, the Dussumieriidae was never recovered as monophyletic, and Dussumieria was not exclusively related to any other of the three dussumieriid genera. Although the position of Dussumieria is not fully resolved, this genus represents a major evolutionary lineage within the Clupeoidei, along with the Engraulidae, Pristigasteridae, Clupeinae, Etrumeus, and two unnamed clades, one containing the Chirocentridae and Spratelloidinae and the other containing the Ehiravinae, Dorosomatinae, and Alosinae. Our results allow some comments regarding the early evolution of the Clupeoidei. In particular, they strongly support the hypothesis that the W-shaped pelvic scute does not represent a good phylogenetic character within the Clupeoidei as either it is primitive or, alternatively, it has independently evolved several times
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