Linear Theory of Electron-Plasma Waves at Arbitrary Collisionality

The dynamics of electron-plasma waves are described at arbitrary collisionality by considering the full Coulomb collision operator. The description is based on a Hermite-Laguerre decomposition of the velocity dependence of the electron distribution function. The damping rate, frequency, and eigenmode spectrum of electron-plasma waves are found as functions of the collision frequency and wavelength. A comparison is made between the collisionless Landau damping limit, the Lenard-Bernstein and Dougherty collision operators, and the electron-ion collision operator, finding large deviations in the damping rates and eigenmode spectra. A purely damped entropy mode, characteristic of a plasma where pitch-angle scattering effects are dominant with respect to collisionless effects, is shown to emerge numerically, and its dispersion relation is analytically derived. It is shown that such a mode is absent when simplified collision operators are used, and that like-particle collisions strongly influence the damping rate of the entropy mode.Comment: 23 pages, 10 figures, accepted for publication on Journal of Plasma Physic

Effect of Annona Formulations on Non-target Invertebrates and on Physicochemical Water Parameters at Semi-field Condition

Plant extracts from the genus Annona exhibit insecticidal properties and thus, may offer an alternative to synthetic insecticides. In the present study larvicidal efficacy of formulations of Annona squamosa and A. montana were evaluated against Anopheline and Culicine larvae in the laboratory and semi-field conditions. In the laboratory there was no significant difference (t=0.5313, p>0.05) in the effectiveness of the A. squamosa formulation at 50 μg/ml and above between An. gambiae and Culex quinquefasciatus by day 4. Significant difference (t= 2.649, p<0.05) was observed for A. montana formulation at higher concentration than 50 μg/ml since An. gambiae was more susceptible than Cx. quinquefasciatus. In semi-field condition the efficacy of the two formulations against Anopheline was not quite significant (t= 2.504, p>0.05). The activity of A. montana leaf powder against Culicines was significantly lower compared to A. squamosal (t=3.827, P<0.05). The variation in water parameters had no significant effect on the efficacy of the formulations. The formulations did not affect the survival of the 9 invertebrate groups tested during the period of study except for the Order Ephemeroptera (Mayflies) whose mortalities was more than 85%. The\ud formulations have proven to offer an alternative to synthetic insecticides

Universal features of cell polarization processes

Cell polarization plays a central role in the development of complex organisms. It has been recently shown that cell polarization may follow from the proximity to a phase separation instability in a bistable network of chemical reactions. An example which has been thoroughly studied is the formation of signaling domains during eukaryotic chemotaxis. In this case, the process of domain growth may be described by the use of a constrained time-dependent Landau-Ginzburg equation, admitting scale-invariant solutions {\textit{\`a la}} Lifshitz and Slyozov. The constraint results here from a mechanism of fast cycling of molecules between a cytosolic, inactive state and a membrane-bound, active state, which dynamically tunes the chemical potential for membrane binding to a value corresponding to the coexistence of different phases on the cell membrane. We provide here a universal description of this process both in the presence and absence of a gradient in the external activation field. Universal power laws are derived for the time needed for the cell to polarize in a chemotactic gradient, and for the value of the smallest detectable gradient. We also describe a concrete realization of our scheme based on the analysis of available biochemical and biophysical data.Comment: Submitted to Journal of Statistical Mechanics -Theory and Experiment

The thiazide sensitive sodium chloride co-transporter NCC is modulated by site-specific ubiquitylation.

The renal sodium chloride cotransporter, NCC, in the distal convoluted tubule is important for maintaining body Na(+) and K(+) homeostasis. Endogenous NCC is highly ubiquitylated, but the role of individual ubiquitylation sites is not established. Here, we assessed the role of 10 ubiquitylation sites for NCC function. Transient transfections of HEK293 cells with human wildtype (WT) NCC or various K to R mutants identified greater membrane abundance for K706R, K828R and K909R mutants. Relative to WT-NCC, stable tetracycline inducible MDCKI cell lines expressing K706R, K828R and K909R mutants had significantly higher total and phosphorylated NCC levels at the apical plasma membrane under basal conditions. Low chloride stimulation increased membrane abundance of all mutants to similar or greater levels than WT-NCC. Under basal conditions K828R and K909R mutants had less ubiquitylated NCC in the plasma membrane, and all mutants displayed reduced NCC ubiquitylation following low chloride stimulation. Thiazide-sensitive sodium-22 uptakes were elevated in the mutants and internalization from the plasma membrane was significantly less than WT-NCC. K909R had increased half-life, whereas chloroquine or MG132 treatment indicated that K706 and K909 play roles in lysosomal and proteasomal NCC degradation, respectively. In conclusion, site-specific ubiquitylation of NCC plays alternative roles for NCC function

The Lyapunov Spectrum of a Continuous Product of Random Matrices

We expose a functional integration method for the averaging of continuous products $\hat{P}_t$ of $N\times N$ random matrices. As an application, we compute exactly the statistics of the Lyapunov spectrum of $\hat{P}_t$. This problem is relevant to the study of the statistical properties of various disordered physical systems, and specifically to the computation of the multipoint correlators of a passive scalar advected by a random velocity field. Apart from these applications, our method provides a general setting for computing statistical properties of linear evolutionary systems subjected to a white noise force field.Comment: Latex, 9 page

An integrated approach to define new plays in mature oil basins: the example from the Middle Magdalena Valley basin (Colombia)

An integrated approach to detect new areas of potential interest associated with stratigraphic traps in mature basins is presented. The study was carried out in the Middle Magdalena Valley basin, Colombia. The workflow integrates outcrop and subsurface interpretationsoffacies,activityoffaults,anddistributionofdepocenters and paleocurrents and makes use of them to construct a threedimensionalexploration-scalegeocellularfaciesmodelofthebasin. The outcrop and well log sedimentological analysis distinguished faciesassociationsofalluvialfan,overbank, floodplain,andchannel fill,thelastoneconstitutingthereservoirrock.Theseismicanalysis showedthattectonicactivitywas coevalwiththedepositionofthe productive units in the basin and that the activity ended earlier (before the middle Miocene) along the western margin than along the eastern margin. Paleogeographic reconstructions depict transverse and longitudinal fluvial systems, alluvial fans adjacent to the activebasinmargins,and floodplainfaciesdominatingthestructural highs and the southwestern depositional limit. These reconstructions provided statistical data (lateral variograms) to construct the model. The exploration-scale facies model depicts the complete structureofthebasininthreedimensionsandthegrossdistribution of the reservoir and seal rocks. The predictive capability of the model was evaluated positively, and the model was employed to detect zones of high channel fill facies probability that form bodies that are isolated or that terminate upward in pinchouts or are truncated bya fault. Our approach canprovehelpfulinimproving general exploration workflows in similar settings

Notes about Passive Scalar in Large-Scale Velocity Field

We consider advection of a passive scalar theta(t,r) by an incompressible large-scale turbulent flow. In the framework of the Kraichnan model the whole PDF's (probability distribution functions) for the single-point statistics of theta and for the passive scalar difference theta(r_1)-theta(r_2) (for separations r_1-r_2 lying in the convective interval) are found.Comment: 19 pages, RevTe