Calidad postcosecha: recubrimiento antimicrobiano en morrones

En los últimos años ha habido mayor demanda de vegetales saludables y desarrollo de tecnologías verdes para brindar una mayor duración y garantizar la reducción de pérdidas postcosecha. En este estudio se emplea recubrimiento anti microbiano y se hace un seguimiento de parámetros de calidad en morrones.Área: Ciencias Agrícolas, Producción y Salud Animal

Open String Thermodynamics and D-Branes

We study the thermodynamics of open superstrings in the presence of $p$-dimensional D-branes. We get some finite temperature dualities relating the one-loop canonical free energy of open strings to the self-energy of D-branes at dual temperature. For the open bosonic string the inverse dual temperature is, as expected, the dual length under T-duality, $4\pi^{2}\alpha^{'}/\beta$. On the contrary, for the $SO(N)$, type-I superstring the dual temperature is given by $\beta$-duality, $2\pi^{2}\alpha^{'}/\beta$. We also study the emergence of the Hagedorn singularity in the dual description as triggered by the coupling of the D-brane to unphysical tachyons as well as the high temperature limit.Comment: 16 pages, harvmac (b), epsf, 2 figures included. Minor changes; discussion in section 4 has been expanded and two footnotes and a reference adde

Optimum sizing of cogeneration plants by means of a genetic algorithm optimization: A case study

In the context of increasing energy consumption, multi-generation systems such as combined heat and power generation (CHP) are attractive to meet the increasingly stringent requirements regarding energy saving in buildings. Hospitals are great consumers of energy, both electrical and thermal: the use of heating and cooling equipment for maintaining satisfactory comfort and indoor air quality for the patients as well as the adoption of several electrical health equipment result in the highest energy consumption per unit floor area of the entire building sector. In the present study, co/tri-generation systems\u2019 optimal set-up, size and operation are investigated for small/medium size hospital facilities. More specifically, after the presentation of the energy consumption profiles for a medium size hospital with 600 beds, set as reference case for this study, a parametric analysis has been carried out varying the peak loads of the user. For each of the proposed scenarios, the optimal plant configuration (sizing of all the energy production systems) has been outlined by means of a numerical code (Trigen 3.0) in-house developed. Afterwards, in order to optimize the load distribution in a smart grid characterized by electrical, thermal, cooling and fuel energy fluxes, an ulterior numerical investigation has been performed. The software, named EGO (Energy Grids Optimizer) consists of a genetic algorithm procedure: it defines the optimal load distribution of a number of energy systems operating into a smart grid based on the minimization of an objective function which expresses the total cost of energy production. Finally, an economic analysis has been carried out in order to evaluate the profitability of the proposed CHP-heat pump scenario

Thermodynamic Evaluation of Repowering Options for a Small-size Combined Cycle with Concentrating Solar Power Technology☆

Abstract The increasing penetration of low-carbon technologies and enhancements in fossil-fuelled power plants efficiency are some of the most important and up to date research topics. Renewable energy, in particular solar, has the potential of meeting the world energy needs while addressing environmental concerns, but technological advances in renewable energy electricity production are necessary to become competitive with conventional technologies. New opportunities to increase the penetration of renewables energies, smoothing out renewables variability and intermittency problems, come out from the hybridization concept. Hybrid renewable-fossil fuel systems join the advantages of both renewable energies and programmable devices. Among all the renewable technologies available for hybridization, Concentrating Solar Power (CSP) with parabolic trough is the most diffused because of its relatively conventional technology and ease of scale-up. CSP hybrids are well established worldwide, predominantly with natural gas: the hybridization options for CSP ranging from feed water heating, reheat steam, live steam to steam superheating. Based on a detailed thermodynamic cycle model of a reference small-size one pressure level Combined Cycle (CC) plant, the impact of CSP addition is thoroughly evaluated. Different hybrid schemes are evaluated and compared considering CC off-design operation. The goal of this study is to evaluate, from a thermodynamic point of view, three repowering options of a small-size CC with a CSP system in a hybrid system configuration and to quantify their potential benefits in terms of system's performance increase. In particular, the optimal size of CSP plant is shown for each investigated hybrid repowering options. The changes in CC steam cycle operating parameters are presented together with CC performance increase. It is shown that solar hybridization into an existing CC plant may give rise to a substantial benefit from a thermodynamic point of view

Low-temperature district heating networks for complete energy needs fulfillment

In order to reduce fossil fuels consumption and pollutant emissions, high contribution is given by district heating. In particular, the integration with renewable energy may lead to a significant increase in energy conversion efficiency and energy saving. Further benefits can be achieved with low temperature networks, reducing the heat dissipations and promoting the exploitation of low enthalpy heat sources. The aim of the paper is the analysis of the potential related to the conversion of existing district heating networks, to increase the exploitation of renewables and eliminate pollutant emissions in the city area. Further aim, in this context, is the optimization \u2013 from both energy production and operation management viewpoints \u2013 of a low temperature district heating network for the fulfillment of the connected users\u2019 energy needs. To this respect, a traditional network with a fossil fuel driven thermal production plant has been considered and compared with a low temperature district heating scenario, including geothermal heat pumps, photovoltaic panels and absorption chillers. These scenarios have been analyzed and optimized with a developed software, demonstrating the reduction of primary energy consumption and CO2 pollutant emissions achievable with low temperature networks. In addition, a preliminary economic comparative evaluation on the variable costs has been carried out. Future studies will investigate the economic aspect also from the investment costs viewpoint

Dynamical supersymmetry breaking from unoriented D-brane instantons

We study the non-perturbative dynamics of an unoriented Z_5-quiver theory of GUT kind with gauge group U(5) and chiral matter. At strong coupling the non-perturbative dynamics is described in terms of set of baryon/meson variables satisfying a quantum deformed constraint. We compute the effective superpotential of the theory and show that it admits a line of supersymmetric vacua and a phase where supersymmetry is dynamically broken via gaugino condensation.Comment: 24 pages, 1 figur

Toward a Systematic Holographic QCD: A Braneless Approach

Recently a holographic model of hadrons motivated by AdS/CFT has been proposed to fit the low energy data of mesons. We point out that the infrared physics can be developed in a more systematic manner by exploiting backreaction of the nonperturbative condensates. We show that these condensates can naturally provide the IR cutoff corresponding to confinement, thus removing some of the ambiguities from the original formulation of the model. We also show how asymptotic freedom can be incorporated into the theory, and the substantial effect it has on the glueball spectrum and gluon condensate of the theory. A simple reinterpretation of the holographic scale results in a non-perturbative running for alpha_s which remains finite for all energies. We also find the leading effects of adding the higher condensate into the theory. The difficulties for such models to reproduce the proper Regge physics lead us to speculate about extensions of our model incorporating tachyon condensation.Comment: 27 pages, LaTe

combined heat and power generation systems design for residential houses

Abstract Nowadays cogeneration is recognized as one of the most effective techniques to meet the increasingly stringent requirements regarding energy efficiency increase and energy saving in buildings. In this context, the aim of this study is the definition of reference parameters for the optimal energy systems design in residential applications. To this purpose, a generation scenario with cogeneration units, heat pumps, auxiliary boilers and chillers (both compression and absorption machines) has been set for the fulfillment of residential users' needs (in terms of electrical, thermal and cooling loads). For a given number of involved households, commercial cogeneration units have been selected, sized on the basis of the electrical peak need, and the generation scenario has been optimized by an in-house developed software, obtaining the optimal energy systems design and operation. Then, a parametric analysis has been carried out varying the number of considered households in order to define the optimal range of the energy systems size. In particular, specific values in terms of installed power for household and installed power for unitary peak load have been determined. For completeness, an economic analysis has been finally carried out for the evaluation of the return on investment and of the differential net present value – with respect to a standard generation scenario (only natural gas boilers for thermal needs fulfillment and electricity purchase from the grid for electrical and cooling needs) – considering a time horizon of ten years

Carbon burial on river-dominated continental shelves: Impact of historical changes in sediment loading adjacent to the Mississippi River

Seabed cores collected on the continental shelf adjacent to the Mississippi River show a direct temporal correlation between decreases in mass accumulation rate (factor of 2-3) and suspended sediment loads in the river. This mid 20th century decline is not apparent shelf-wide due to sediment focusing and biological seabed mixing. Total organic carbon diagenetic loss rate across this sediment age interval is relatively uninterrupted when coffected for the non-steady state mass flux. This suggests that organic carbon burial rates in oxic bottom water settings on river-dominated continental margins are directly proportional to lithogenic flux. Variations in OM remineralization rates due to changes in the composition (marine vs. terrestrial) of the particulate OM flux at the sediment surface are a second-order effect that cannot be distinguished in the bulk carbon sediment record at these oxic sites; although they may significantly alter the OM degradation-induced CO2 flux to the overlying water column

Field-induced quantum critical point in CeCoIn_5

The resistivity of CeCoIn_5 was measured down to 20 mK in magnetic fields of up to 16 T. With increasing field, we observe a suppression of the non-Fermi liquid behavior, rho~T, and the development of a Fermi liquid state, with its characteristic rho=rho_0+AT^2 dependence. The field dependence of the T^2 coefficient shows critical behavior with an exponent of ~4/3. This is evidence for a new field-induced quantum critical point, occuring in this case at a critical field which coincides with the superconducting upper critical field H_c2.Comment: 2 pages, 2 figures, submitted to M2S-Rio 2003 Proceeding