Seasonal changes in chemical composition and construction costs of grapevine tissues

Modelling of the whole-vine carbon balance requires accurate estimates of tissue construction costs, i.e. the amount of glucose involved in the synthesis of a unit of biomass. In order to quantify construction costs during the vine's growth cycle, chemical compositions of leaves, stems, fruits, fine roots and trunk of 10-year-old grapevines (cv. Merlot) were determined in two seasons. Tissue construction costs were estimated using (i) an approach based on the quantification of the amount of glucose required for the synthesis of major chemical components of vine organs by the most probable metabolic pathways (coded as CCp) and (ii) a simpler technique in which costs were derived from tissue ash, carbon and nitrogen concentrations (coded as CCw). Both methods were well-correlated in all grapevine tissues despite CCp values were higher than CCwestimates. Grapevine leaves had higher concentrations of compounds with a high proportion of C and N atoms (proteins, lipids and phenolics) and higher CCw values throughout the season than other tissues. Small variation in CCw values however were observed seasonally in vegetative tissues despite their chemical composition varied considerably with plant development. Significant changes in CCw appeared in berry tissues between fruit set and maturity, reflecting a proportional increase in concentration of inexpensive metabolites (soluble sugars and organic acids)

Local Stabilization of Time-Delay Nonlinear Discrete-Time Systems Using Takagi-Sugeno Models and Convex Optimization

A convex condition in terms of linear matrix inequalities (LMIs) is developed for the synthesis of stabilizing fuzzy state feedback controllers for nonlinear discrete-time systems with time-varying delays. A Takagi-Sugeno (T-S) fuzzy model is used to represent exactly the nonlinear system in a restricted domain of the state space, called region of validity. The proposed stabilization condition is based on a Lyapunov-Krasovskii (L-K) function and it takes into account the region of validity to determine a set of initial conditions for which the actual closed-loop system trajectories are asymptotically stable and do not evolve outside the region of validity. This set of allowable initial conditions is determined from the level set associated to a fuzzy L-K function as a Cartesian product of two subsets: one characterizing the set of states at the initial instant and another for the delayed state sequence necessary to characterize the initial conditions. Finally, we propose a convex programming problem to design a fuzzy controller that maximizes the set of initial conditions taking into account the shape of the region of validity of the T-S fuzzy model. Numerical simulations are given to illustrate this proposal

Non-volatile tuning of normally-on and off states of deep depletion ZrO2/O-terminated high voltage diamond MOSFET

Based on the stability of the deep depletion regime in diamond and the outstanding properties of this promising material for its use in power devices, p-channel deep depletion metal oxide semiconductor field effect transistors were fabricated on a (001) Ib nitrogen-doped high pressure high temperature diamond substrate. Taking advantage of the new concept of the non-volatile diamond-based photo switch, it is demonstrated that it is possible to tune the normally-on and normally-off states of the transistor by configuring the pn-junction space charge region. The devices under study was designed following an interdigital-like and a circular-like architectures presenting low threshold voltages (between 3 V and −3 V), an on/off ratio of 107 and a critical electric field numerically assessed of 9 MV.cm−1 at room temperature. This new degree of freedom opens the route for diamond based power electronics.8 página

Managing the Cascading Risks of Droughts: Institutional Adaptation in Transboundary River Basins

Transboundary river basins experience complex coordination challenges during droughts. The multiscale nature of drought creates potential for spillovers when upstream adaptation decisions have cascading impacts on downstream regions. This paper advances the institutional analysis and development (IAD) framework to examine drought adaptation decision‐making in a multijurisdictional context. We integrate concepts of risk management into the IAD framework to characterize drought across its natural and human dimensions. A global analysis identifies regions where severe droughts combine with institutional fragmentation to require coordinated adaptation. We apply the risk‐based IAD framework to examine drought adaptation in the Rio Bravo/Grande—an archetypical transboundary river shared by the United States and Mexico and by multiple states within each country. The analysis draws on primary data and a questionnaire with 50 water managers in four distinct, yet interlinked, “institutional catchments,” which vary in terms of their drought characteristics, socioeconomic attributes, and governance arrangements. The results highlight the heterogeneity of droughts and uneven distribution of their impacts due to the interplay of drought hazards and institutional fragmentation. Transboundary water sharing agreements influence the types and sequence of interactions between upstream and downstream jurisdictions, which we describe as spillovers that involve both conflict and cooperation. Interdependent jurisdictions often draw on informal decision‐making venues (e.g., data sharing, operational decisions) due to the higher transaction costs and uncertainty associated with courts and planning processes, yet existing coordination and conflict resolution venues have proven insufficient for severe, sustained droughts. Observatories will be needed to measure and manage the cascading risks of drought

The application of a mechanistic model to analyze the factors that affect the lactation curve parameters of dairy sheep in Mexico

Pollott́s mechanistic model has been designed to describe lactation curve parameters based on the known biology of milk production and can be useful for analyzing the factors that affect this process. A total of 553 lactations (9956 weekly test-day records) of crossbred dairy sheep from four commercial farms located in Mexico, were analyzed to investigate environmental factors that influenced lactation curve parameters, using Pollott’s 5-parameter additive model. This model was fitted to each lactation using an iterative nonlinear procedure. The estimated parameters were maximum milk secretion potential (MSmax), relative rate of increase in cell differentiation (GR), maximum secretion loss (MSLmax), relative rate of decline in cell numbers (DR) and the proportion of parenchyma cells dead at parturition. A general linear model procedure was used to determine the effect of type of lambing, lambing number, flock and lambing season on total lactation milk yield (TMY), lactation length and estimated parameters of the Pollott model. Ewes had an average milk yield of 74.4 L with an average lactation length of 140 days. Flock had a significant (P < 0.05) effect on most of the analyzed traits, which can be explained by the different farmś management practices. The TMY were significantly (P = 0.005) higher for twin-lambing than single-lambing lactations. Sheep in their first lambing had lower TMY than those in their fourth lambing (P = 0.01), possibly explained by the lower values of MSmax (2.85 vs. 5.3 L) and the decrease in DR throughout life (P = 0.03). However, the relative GR was greatest (P = 0.04) during first lambing and then decreased as lambing number increased. Both lambing number and type of lambing also affected milk yield. The parameters of the Pollott model can be useful to explain, with a biological approximation, the dynamics of differentiation, secretion and death of mammary cells in dairy sheep

Collective and independent-particle motion in two-electron artificial atoms

Investigations of the exactly solvable excitation spectra of two-electron quantum dots with a parabolic confinement, for different values of the parameter R_W expressing the relative magnitudes of the interelectron repulsion and the zero-point kinetic energy of the confined electrons, reveal for large R_W a remarkably well-developed ro-vibrational spectrum associated with formation of a linear trimeric rigid molecule composed of the two electrons and the infinitely heavy confining dot. This spectrum transforms to one characteristic of a "floppy" molecule for smaller values of R_W. The conditional probability distribution calculated for the exact two-electron wave functions allows for the identification of the ro-vibrational excitations as rotations and stretching/bending vibrations, and provides direct evidence pertaining to the formation of such molecules.Comment: Published version. Latex/Revtex, 5 pages with 2 postscript figures embedded in the text. For related papers, see http://www.prism.gatech.edu/~ph274c

Condición de un pastizal del este del Chaco

The aim of this study was to assess the condition of a grassland of Eastern Chaco. The work was done on a livestock ranch in Makalle (Chaco). Vegetation is characterized by herbaceous plants dominated by warm season grasses. Proportion of preferred, intermediate and undesirable species was determined, based on their forage attributes. Quantity of annuals and weed species, percent bare soil, vigour of best species and dry matter yield (Kg DM/ha) were also determined. The grassland had 40.4% preferred species with good vigour, low percentage of weeds (2%) and low bare soil (2%). Dry matter yield was 1639.1 kg DM/ha (seasonal mean). Condition was rated good to excellent. No deterioration was detected.El objetivo del presente trabajo fue establecer la condición de un pastizal del este de la provincia del Chaco. El trabajo se realizó en un establecimiento ganadero ubicado en la Localidad de Makallé. Se caracteriza por la presencia de un estrato herbáceo con predominio de gramíneas, de ciclo de crecimiento primavero-estival. Se determinó la proporción de especies clasificadas como preferidas, intermedias y/o indeseables, según sus características forrajeras; la cantidad de plantas anuales o malezas; la proporción de suelo desnudo; el vigor de las mejores especies y la producción estacional de materia seca. Teniendo en cuenta que el pastizal evaluado está integrado por un 40,4% de forrajeras preferidas que tuvieron un vigor alto; la cantidad de malezas fue baja (2%) al igual que la proporción de suelo desnudo sin cobertura vegetal (2%) y la producción forrajera fue de 1.639,1 kg/ha (promedio estacional). Se puede inferir en que la condición del pastizal es buena a excelente. No hay indicios en la vegetación y la producción del pastizal que manifiesten el comienzo de su deterioro

Effect of tannins from tropical plants on methane production from ruminants: A systematic review

Methane (CH4) is a greenhouse gas generated during the feed fermentation processes in the rumen. However, numerous studies have been conducted to determine the capacity of plant secondary metabolites to enhance ruminal fermentation and decrease CH4 production, especially those plants rich in tannins. This review conducted a descriptive analysis and meta-analysis of the use of tannin-rich plants in tropical regions to mitigate CH4 production from livestock. The aim of this study was to analyse the effect of tannins supplementation in tropical plants on CH4 production in ruminants using a meta-analytic approach and the effect on microbial population. Sources of heterogeneity were explored using a meta-regression analysis. Final database was integrated by a total of 14 trials. The ‘meta’ package in R statistical software was used to conduct the meta-analyses. The covariates defined a priori in the current meta-regression were inclusion level, species (sheep, beef cattle, dairy cattle, and cross-bred heifers) and plant. Results showed that supplementation with tropical plants with tannin contents have the greatest effects on CH4 mitigation. A negative relationship was observed between the level of inclusion and CH4 emission (−0.09), which means that the effect of CH4 mitigation is increasing as the level of tannin inclusion is higher. Therefore, less CH4 production will be obtained when supplementing tropical plants in the diet with a high dose of tannins