A general interior anisotropic solution for a BTZ vacuum in the context of the Minimal Geometric Deformation decoupling approach

In this work we implement the Minimal Geometric Deformation decoupling method to obtain general static interior solutions for a BTZ vacuum from the most general isotropic solution in $2+1$ dimensions including the cosmological constant $\Lambda$. We obtain that the general solution can be generated only by the energy density of the original isotropic sector, so that this quantity plays the role of a generating function. Although as a particular example we study the static star with constant density, the method here developed can be easily applied to more complex situations described by other energy density profiles.Comment: Accepted in EPJC. References correcte

Identifying Fiscal Policy Shocks in Chile and Colombia

Structural VAR and Structural VEC models were estimated for Chile and Colombia, aiming at identifying fiscal policy shocks in both countries between 1990 and 2005. The impulse responses obtained allow the calculation of a peso-for-peso ($/$) effect on output of a shock to public spending and to the government's net tax revenues, providing a good notion of the incidence of fiscal policy shocks in both countries. When public finances are under control, as they are in Chile, fiscal policy seems to be more effective than when they lack stability and credibility, as seems to be the case of Colombia since the mid nineties.

IDENTIFYING FISCAL POLICY SHOCKS IN CHILE AND COLOMBIA

Structural VAR and Structural VEC models were estimated for Chile and Colombia, aiming at identifying fiscal policy shocks in both countries between 1990 and 2005. The impulse responses obtained allow the calculation of a pesofor- peso ($/$) effect on output of a shock to public spending and to the government's net tax revenues, providing a good notion of the incidence of fiscal policy shocks in both countries. When public finances are under control, as they are in Chile, fiscal policy seems to be more effective than when they lack stability and credibility, as seems to be the case of Colombia since the mid nineties.Identification, Fiscal Policy, SVAR, SVEC

Black hole shadow of a rotating polytropic black hole by the Newman--Janis algorithm without complexification

In this work, starting from a spherically symmetric polytropic black hole, a rotating solution is obtained by following the Newman--Janis algorithm without complexification. Besides studying the horizon, the static conditions and causality issues of the rotating solution, we obtain and discuss the shape of its shadow. Some other physical features as the Hawking temperature and emission rate of the rotating polytropic black hole solution are also discussed.Comment: 9 pages, 2 figures, some references adde

Paving the Way for a Green Transition in the Design of Sensors and Biosensors for the Detection of Volatile Organic Compounds (VOCs)

The efficient and selective detection of volatile organic compounds (VOCs) provides key information for various purposes ranging from the toxicological analysis of indoor/outdoor environments to the diagnosis of diseases or to the investigation of biological processes. In the last decade, different sensors and biosensors providing reliable, rapid, and economic responses in the detection of VOCs have been successfully conceived and applied in numerous practical cases; however, the global necessity of a sustainable development, has driven the design of devices for the detection of VOCs to greener methods. In this review, the most recent and innovative VOC sensors and biosensors with sustainable features are presented. The sensors are grouped into three of the main industrial sectors of daily life, including environmental analysis, highly important for toxicity issues, food packaging tools, especially aimed at avoiding the spoilage of meat and fish, and the diagnosis of diseases, crucial for the early detection of relevant pathological conditions such as cancer and diabetes. The research outcomes presented in the review underly the necessity of preparing sensors with higher efficiency, lower detection limits, improved selectivity, and enhanced sustainable characteristics to fully address the sustainable manufacturing of VOC sensors and biosensors

La dolarización financiera: experiencia internacional y perspectivas para Colombia

Currencies in developing countries are not freely convertible; they show higher inflation and volatility levels and show periods of sharp appreciation and depreciation. These characteristics not only are a challenge for economic authorities, but also call attention to their ability to fully comply with the functions of money. Colombia, despite its disciplined monetary background, has not escaped from occasional queries about the convenience of keeping the Colombian peso. Just a few countries have chosen to fully replace their local currency with a foreign one in order to assume the entire functions of domestic currency, but there are many economies which have permitted partial dollarization. Based on international experience and Colombia’s characteristics, this paper concludes that financial dollarization would be costly, with limited and merely potential benefits.financial dollarization, partial dollarization, foreign exchange risk, balance sheet effect

Unsteady state series CSTR modeling of removal of ammonia nitrogen from domestic wastewater treated in a vertical flow constructed wetland

This work shows simulation results for subsurface vertical flow constructed wetland (VFCW) using a series CSTR model. The VFCW considered received the outflow from a domestic wastewater treatment plant. In addition, it was planted with Cyperus sp. and filter media was unsaturated. The model was based on an unsteady state mass balance for ammonia, nitrites, and nitrates, using one to three series CSTRs. Nitrogen transformation mechanisms considered were ammonification, nitrification, plant uptake and denitrification. The following effects were evaluated: the number of reacting CSTRs from one to three; the occurrence of the reaction in second and third CSTRs for the case that three CSTRs hold; the use of either equal or different values of reaction rate parameters between CSTRs; and the discretization of the reaction rate parameters. The inflow and outflow measurements of ammonium, nitrites, and nitrates were used for model calibration. The estimated parameters included the reaction rate coefficients and reactor water volume. The coefficient of determination (R2) evidenced a satisfactory capability of simulating outlet pollutant concentrations. Two and three reacting CSTRs achieved similar R2 value (0.54-0.55), whereas one reacting CSTR achieved an R2 of 0.39, and three CSTRs with reaction only in the first tank achieved an R2 of 0.42. Discretization of the nitrification rate for the case of two reacting CSTRs led to an R2 of 0.94. The parameter sensitivity analysis revealed a significant effect of model parameters on the R2 value

Nanocellulose from Spanish Harvesting Residues to Improve the Sustainability and Functionality of Linerboard Recycling Processes

The hornification processes undergone by the fibers in the paper industry recycling processes lead to the loss of properties of the final products, which exhibit poor mechanical properties. Among the most promising solutions is the reinforcement of secondary fibers with cellulose nanofibers. The present work addresses two important issues: the efficient production of cellulose nanofibers from scarcely exploited agricultural wastes such as horticultural residues and vine shoots, and their application as a reinforcement agent in recycled linerboard recycling processes. The effect of the chemical composition and the pretreatment used on the nanofibrillation efficiency of the fibers was analyzed. Chemical pretreatment allowed a significantly higher nanofibrillated fraction (45–63%) than that produced by mechanical (18–38%), as well as higher specific surface areas (>430 m2/g). The application of the nanofibers as a reinforcing agent in the recycled linerboard considerably improved the mechanical properties (improvements of 15% for breaking length, 220–240% for Young’s modulus and 27% for tear index), counteracting the loss of mechanical properties suffered during recycling when using chemically pretreated cellulose nanofibers from horticultural residues and vine shoots. It was concluded that this technology surpasses the mechanical reinforcement produced by conventional mechanical refining used in the industry and extends the number of recycling cycles of the products due to the non-physical modification of the fibers

Beneficio social potencial de la investigación en ganado de carne y leche en Colombia.

La rentabilidad y el proceso de adopción tecnológica en la actividad agropecuaria, se analiza como una función dependiente de la estructura productiva-institucional y de políticas prevalentes para el subsector a nivel de país. La demanda por conocimiento (tecnología) y la distribución de los beneficios que ésta puede generar (comportamiento) están predeterminados por la estructura de producción, las políticas y contexto institucional del subsector. En este documento se examinan los siguientes aspectos: los objetivos generales de la investigación pecuaria, la productividad potencial pecuaria, las ventajas potenciales y costos de la investigación, la distribución de las prebendas al productor, los niveles de privilegios, el flujo de costos y ganancias para el período 1978-1985. Con base al estudio realizado se pudo establecer que las investigaciones hechas por el Instituto Colombiano Agropecuario (ICA) en producción animal, además de definir las posibilidades tecnológicas del país, indican que la disponibilidad actual puede generar beneficios sociales agregados, superiores a las inversiones ejecutadas para el período considerado. Con respecto al comportamiento de la tecnología según condiciones ecológicas y naturaleza de los sistemas de producción, se estableció que las tasas diferenciales en el proceso de adopción y rentabilidad de un paquete tecnológico dado, se explican por razones estructurales de la producción, el mercado y las políticas para el subsector. En el incremento de la oferta de leche y carne, los cálculos de la utilidad social, resultan subestimados, lo cual proviene del supuesto de disponibilidad tecnológica constante para el período estudiado y la no estimación del valor de la producción de subproductos generados por cada una de las especies: leche, carne y pieles, así como la expansión de la industria de los insumos que puede resultar de la incorporación de la tecnología disponibleGanado de carne-Ganadería carn