Problemas en el cultivo de la yuca

Information on some diseases and pests that attack cassava, as well as the symptoms induced by nutritional deficiencies and toxicities and damage resulting from the misuse of herbicides are given in this manual. Specific and general recommendations regarding the control of the described problems are included. Disease control on a commercial scale is discussed. Formulae suggested for stake treatment before planting and storage and a key for identifying some cassava diseases are annexed. Color photos on symtomatology are included. (AS)En este manual se presenta informacion sobre algunas de las enfermedades y plagas que atacan a la yuca, como tambien los sintomas inducidos por deficiencias y toxicidades nutricionales y danos debidos al uso incorrecto de los herbicidas. Se incluyen recomendaciones generales y especificas para el control de los problemas descritos. Se discute el control de las enfermedades en escala comercial. Se anexan formulas sugeridas para el tratamiento de la estaca antes de la siembra y del almacenamiento y una clave para identificar algunas de las enfermedades de la yuca. Se incluyen fotos a color sobre la sintomatologia. (RA

Field problems in cassava

Information on some diseases and pests that attack cassava, as well as the symptoms induced by nutritional deficiencies and toxicities and damage resulting from the misuse of herbicides are given in this manual. Specific and general recommendations regarding the control of the described problems are included. Disease control on a commercial scale is discussed. Formulae suggested for stake treatment before planting and storage and a key for identifying some cassava diseases are annexed. Color photos on symtomatology are included. (AS)En este manual se presenta informacion sobre algunas de las enfermedades y plagas que atacan a la yuca, como tambien los sintomas inducidos por deficiencias y toxicidades nutricionales y danos debidos al uso incorrecto de los herbicidas. Se incluyen recomendaciones generales y especificas para el control de los problemas descritos. Se discute el control de las enfermedades en escala comercial. Se anexan formulas sugeridas para el tratamiento de la estaca antes de la siembra y del almacenamiento y una clave para identificar algunas de las enfermedades de la yuca. Se incluyen fotos a color sobre la sintomatologia. (RA

Self-assembly mechanism in colloids: perspectives from Statistical Physics

Motivated by recent experimental findings in chemical synthesis of colloidal particles, we draw an analogy between self-assembly processes occurring in biological systems (e.g. protein folding) and a new exciting possibility in the field of material science. We consider a self-assembly process whose elementary building blocks are decorated patchy colloids of various types, that spontaneously drive the system toward a unique and predetermined targeted macroscopic structure. To this aim, we discuss a simple theoretical model -- the Kern-Frenkel model -- describing a fluid of colloidal spherical particles with a pre-defined number and distribution of solvophobic and solvophilic regions on their surface. The solvophobic and solvophilic regions are described via a short-range square-well and a hard-sphere potentials, respectively. Integral equation and perturbation theories are presented to discuss structural and thermodynamical properties, with particular emphasis on the computation of the fluid-fluid (or gas-liquid) transition in the temperature-density plane. The model allows the description of both one and two attractive caps, as a function of the fraction of covered attractive surface, thus interpolating between a square-well and a hard-sphere fluid, upon changing the coverage. By comparison with Monte Carlo simulations, we assess the pros and the cons of both integral equation and perturbation theories in the present context of patchy colloids, where the computational effort for numerical simulations is rather demanding.Comment: 14 pages, 7 figures, Special issue for the SigmaPhi2011 conferenc

Strange Stars with a Density-Dependent Bag Parameter

We have studied strange quark stars in the framework of the MIT bag model, allowing the bag parameter B to depend on the density of the medium. We have also studied the effect of Cooper pairing among quarks, on the stellar structure. Comparison of these two effects shows that the former is generally more significant. We studied the resulting equation of state of the quark matter, stellar mass-radius relation, mass-central-density relation, radius-central-density relation, and the variation of the density as a function of the distance from the centre of the star. We found that the density-dependent B allows stars with larger masses and radii, due to stiffening of the equation of state. Interestingly, certain stellar configurations are found to be possible only if B depends on the density. We have also studied the effect of variation of the superconducting gap parameter on our results.Comment: 23 pages, 8 figs; v2: 25 pages, 9 figs, version to be published in Phys. Rev. (D

The fermion dynamical symmetry model for the even--even and even--odd nuclei in the Xe--Ba region

The even--even and even--odd nuclei $^{126}$Xe-$^{132}$Xe and $^{131}$Ba-$^{137}$Ba are shown to have a well-realized $SO_8 \supset SO_6 \supset SO_3$ fermion dynamical symmetry. Their low-lying energy levels can be described by a unified analytical expression with two (three) adjustable parameters for even--odd (even--even) nuclei that is derived from the fermion dynamical symmetry model. Analytical expressions are given for wavefunctions and for $E2$ transition rates that agree well with data. The distinction between the FDSM and IBM $SO_6$ limits is discussed. The experimentally observed suppression of the the energy levels with increasing $SO_5$ quantum number $\tau$ can be explained as a perturbation of the pairing interaction on the $SO_6$ symmetry, which leads to an $SO_5$ Pairing effect for $SO_6$ nuclei.Comment: submitted to Phys. Rev. C, LaTeX, 31 pages, 8 figures with postscript files available on request at [email protected]

A realistic example of chaotic tunneling: The hydrogen atom in parallel static electric and magnetic fields

Statistics of tunneling rates in the presence of chaotic classical dynamics is discussed on a realistic example: a hydrogen atom placed in parallel uniform static electric and magnetic fields, where tunneling is followed by ionization along the fields direction. Depending on the magnetic quantum number, one may observe either a standard Porter-Thomas distribution of tunneling rates or, for strong scarring by a periodic orbit parallel to the external fields, strong deviations from it. For the latter case, a simple model based on random matrix theory gives the correct distribution.Comment: Submitted to Phys. Rev.

Quantitative predictions on auxin-induced polar distribution of PIN proteins during vein formation in leaves

The dynamic patterning of the plant hormone auxin and its efflux facilitator the PIN protein are the key regulator for the spatial and temporal organization of plant development. In particular auxin induces the polar localization of its own efflux facilitator. Due to this positive feedback auxin flow is directed and patterns of auxin and PIN arise. During the earliest stage of vein initiation in leaves auxin accumulates in a single cell in a rim of epidermal cells from which it flows into the ground meristem tissue of the leaf blade. There the localized auxin supply yields the successive polarization of PIN distribution along a strand of cells. We model the auxin and PIN dynamics within cells with a minimal canalization model. Solving the model analytically we uncover an excitable polarization front that triggers a polar distribution of PIN proteins in cells. As polarization fronts may extend to opposing directions from their initiation site we suggest a possible resolution to the puzzling occurrence of bipolar cells, such we offer an explanation for the development of closed, looped veins. Employing non-linear analysis we identify the role of the contributing microscopic processes during polarization. Furthermore, we deduce quantitative predictions on polarization fronts establishing a route to determine the up to now largely unknown kinetic rates of auxin and PIN dynamics.Comment: 9 pages, 4 figures, supplemental information included, accepted for publication in Eur. Phys. J.

Feed, food and fuel: Competition and potential impacts on small-scale crop-livestock-energy farming systems

CGIAR System-wide Livestock Programm

Effect of dietary vitamin D3 and 25-hydroxyvitamin D3 supplementation on plasma and milk 25-hydroxyvitamin D3 concentration in dairy cows

Milk enriched with vitamin D by supplementing dairy cow diets could provide a valuable dietary source of vitamin D, but information on the feasibility of this approach is limited. In the current study, the effects of supplementing dairy cows with either vitamin D3 or 25(OH) D3 over the transition/early lactation period on plasma and milk vitamin D concentrations were compared. Sixty dairy cows were randomly allocated to one of four dietary treatments from 14 days pre-calving to 56 days post-calving. Treatments were a control diet (Control) for both pre-calving and post-calving periods containing 0.625 mg/day vitamin D3; a pre-calving diet supplemented with 6 mg 25(OH) D3/day, but with a post-calving diet matching that of the control diet (25(OH) D3 pre-calving); the control diet pre-calving but with the post-calving diet supplemented with 2 mg vitamin D3/day (D3max), and the control diet pre-calving but with the post-calving diet supplemented with 1.5 mg 25(OH) D3/day (25(OH) D3 post-calving). No treatment effect on milk yield, composition or 25(OH) D3 concentration was observed. However there was an interaction of treatment and time for plasma 25(OH) D3 concentration; this increased within two weeks of supplementation for the 25(OH) D3 pre-calving treatment (peaking just after calving, 202 ng/ml), whereas that of the 25(OH) D3 post-calving group had a slower response following supplementation, continuing to increase at 56 days. There were correlations between plasma and milk 25(OH) D3 concentrations at days 4 and 14 of lactation, but not at later sampling times. The D3max treatment did not increase 25(OH) D3 concentration in plasma or milk. Overall, results from this study indicate that supplemental 25(OH) D3 is an effective means of enhancing dairy cow plasma 25(OH) D3 concentrations compared with vitamin D3 supplementation, but not necessarily milk concentrations

Mechanics: non-classical, non-quantum

A non-classical, non-quantum theory, or NCQ, is any fully consistent theory that differs fundamentally from both the corresponding classical and quantum theories, while exhibiting certain features common to both. Such theories are of interest for two primary reasons. Firstly, NCQs arise prominently in semi-classical approximation schemes. Their formal study may yield improved approximation techniques in the near-classical regime. More importantly for the purposes of this note, it may be possible for NCQs to reproduce quantum results over experimentally tested regimes while having a well defined classical limit, and hence are viable alternative theories. We illustrate an NCQ by considering an explicit class of NCQ mechanics. Here this class will be arrived at via a natural generalization of classical mechanics formulated in terms of a probability density functional