AN EXERGY COST ANALYSIS OF A COGENERATION PLANT

The exergy analysis, including the calculation of the unit exergetic cost of all flows of the cogeneration plant, was the main purpose of the thermoeconomic analysis of the STAG (STeam And Gas) combined cycle CHP (Combined Heat and Power) plant. The combined cycle cogeneration plant is composed of a GE10 gas turbine (11250 kW) coupled with a HRSG (Heat Recovery Steam Generator) and a condensing extraction steam turbine. The GateCycleTM Software was used for the modeling and simulation of the combined cycle CHP plant thermal scheme, and calculation of the thermodynamic properties of each flow (Mass Flow, Pressure, Temperature, Enthalpy). The entropy values for water and steam were obtained from the Steam Tab software while the entropy and exergy of the exhaust gases were calculated as instructed by. For the calculation of the unit exergetic cost was used the neguentropy and Structural Theory of Thermoeconomic. The GateCycleTM calculations results were exported to an Excel sheet to carry out the exergy analysis and the unit exergetic cost calculations with the thermoeconomic model that was created for matrix inversion solution. Several simulations were performed varying separately five important parameters: the Steam turbine exhaust pressure, the evaporator pinch point temperature, the steam turbine inlet temperature, Rankine cycle operating pressure and the stack gas temperature to determine their impact in the recovery cycle heat exchangers transfer area, power generation and unit exergetic cost

Infección por el virus de la leucemia felina (FeLV) y linfomas mediastínicos : dos casos clínicos

Se describen los hallazgos clínicos, radiológicos y analíticos en dos casos de gatos menores de dos años, que se presentaron con un cuadro clínico de caquexia, vómitos y disnea. En ambos casos las radiografías evidenciaron la presencia de masas intratorácicas; la analítica basada en test ELISA para FeLV y FIV y las necropsias efectuadas, parecen demostrar la relación existente entre gato joven, FeLV y el desarrollo de masas tumorales mediastínicas.The clinical, radiologycal and analytic discovery, are described in two cases of cats under two years of age which were presented with dyspnea, vomiting and caquexia. In both cases the radiographs showed the presence of intrathoracic masses; ELISA test for FeLV and FIV and the necropsy demostrated the relation of young cat and FeLV with the development of mediastinic tumoral masses

Sustainable Use of Recycled Asphalt Pavement in Soil Stabilization

This study addresses unused recycled asphalt pavement (RAP) incorporated into sedimentary soil from the Guabirotuba Formation in Curitiba, Southern Brazil. Different percentages of RAP, ranging from 0% to 80% by weight, were mixed with the pure soil, with and without the addition of pozzolanic Portland cement. Tests were conducted to evaluate the mixtures' compaction properties, mechanical strength, and expansion after curing for up to 28 days. The results showed that adding RAP improved the mixtures' unconfined compressive strength (qu) and splitting tensile strength (qt). Up to 60% RAP, the qu increased by 260 kPa, and the qt increased by 340 kPa compared to the pure soil. The California Bearing Ratio (CBR) tests demonstrated an 18.62% improvement when 80% RAP was added to the untreated soil. In addition, the RAP also reduced the expansion of the compacted blends, with values decreasing from 1.19% to 0.88% with 80% RAP replacement. The expansion value was further reduced to 0.86% when the cement was added. The cement-soil-RAP compacted blends showed suitability for subgrade reinforcement, meeting the criteria of expansion 2%. Additionally, 3% cement and 40% RAP mixtures were suitable as a sub-base layer, with expansion 20%. The results provide valuable insights into utilizing RAP as an alternative material in soil improvement techniques employing the novelty porosity-to-cement index. Doi: 10.28991/CEJ-2023-09-09-016 Full Text: PD

Composite Electrodes Based on Carbon Materials Decorated with Hg Nanoparticles for the Simultaneous Detection of Cd(II), Pb(II) and Cu(II)

Monitoring water quality has become a goal to prevent issues related to human health and environmental conditions. In this sense, the concentration of metal ions in water sources is screened, as these are considered persistent contaminants. In this work, we describe the implementation of customized graphite electrodes decorated with two types of Hg nanoparticles (Hg-NPs), optimized toward the electrochemical detection of Cd, Pb and Cu. Here, we combine Hg, a well-known property to form alloys with other metals, with the nanoscale features of Hg-NPs, resulting in improved electrochemical sensors towards these analytes with a substantial reduction in the used Hg amount. Hg-NPs were synthesized using poly(diallyldimethylammonium) chloride (PDDA) in a combined role as a reducing and stabilizing agent, and then appropriately characterized by means of Transmission Electron Microscopy (TEM) and Zeta Potential. The surface of composite electrodes with optimized graphite content was modified by the drop-casting of the prepared Hg-NPs. The obtained nanocomposite electrodes were morphologically characterized by Scanning Electron Microscopy (SEM), and electrochemically by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The results show that the Hg-NP-modified electrodes present better responses towards Cd(II), Pb(II) and Cu(II) detection in comparison with the bare graphite electrode. Analytical performance of sensors was evaluated by square-wave anodic stripping voltammetry (SWASV), obtaining a linear range of 0.005-0.5 mg·L−1 for Cd2+, of 0.028-0.37 mg·L−1 for Pb2+ and of 0.057-1.1 mg·L−1 for Cu2+. Real samples were analyzed using SWASV, showing good agreement with the recovery values of inductively coupled plasma-mass spectrometry (ICP-MS) measurement

Evaluation of macroseismic intensities in Mexico from recent earthquakes using ¿Sintió un sismo? (Did you feel it?)

Macroseismic investigations with data collected through online surveys has acquired relevance in recent years. Its easy access and low cost allow assessments of the severity of an earthquake from its effects as observed by the population. Furthermore, it is possible to generate attenuation curves for a particular region, visualize the condition of the buildings from a zip code-averaged distribution map, and estimate possible site effects. In regions without a good coverage of seismic networks, macroseismic intensities have proved to be a substitute for instrumental data. In this paper intensity maps for four earthquakes in different regions of Mexico are presented, based on data from the database of ¿Sintió un sismo? program, an online survey implemented in 2014. Less attenuation was found in areas considered tectonically stable than in those considered as active regions. RESUMEN Las investigaciones macrosísmicas utilizando datos recolectados a partir de encuestas en línea han adquirido un gran auge en los últimos años. Su fácil acceso y bajo costo permiten realizar evaluaciones de la severidad del sismo a partir de los efectos observados por la población. Además es posible generar curvas de atenuación para una región en particular, visualizar el estado de las construcciones y los posibles efectos de sitio. En regiones donde no se tiene una buena cobertura de redes sísmicas, las intensidades macrosísmicas han demostrado ser un gran sustituto de datos instrumentales. En este trabajo se presentan mapas de intensidades macrosísmicas para cuatro sismos en distintos puntos del país. Los datos se obtuvieron de la base de datos del programa ¿Sintió un sismo?, una encuesta en línea implementada en el 2014. Encontramos que la atenuación es menor en zonas consideradas tectónicamente estables que en regiones activas

Delay of Gratification in Costa Rican Preschoolers: Effect of Trust in the Experimenter and the Socio-Economic Status: Postergación de la gratificación en preescolares costarricenses: efecto de la confianza en el experimentador y el estatus socioeconómico

This study analyzed the effect of confidence in the experimenter on the performance of a group of Costa Rican preschoolers on self-control. In addition, the effect of socioeconomic status on performance on the marshmallow task was analyzed by a comparison of children from both different schools (public vs private) and different socioeconomic contexts within each school. The sample of participants was 67 children (26 girls, M of age = 63 months, SD = 6.03). Effects were found, both of the confidence in the experimenter and of the socio-economic status in self-control. The implications of this study for future studies with children and families are discussed.Este estudio analizó el efecto de la confianza en la persona experimentadora sobre el desempeño de un grupo de niñas(os) preescolares costarricenses en el autocontrol. Adicionalmente, se analizó el efecto del estatus socioeconómico en el desempeño en la tarea de la golosina por medio de una comparación de niños provenientes tanto de diferentes escuelas (pública vs privada) como de distintos contextos socioeconómicos al interior de cada escuela. La muestra de participantes fue de 67 niños(as) (26 niñas, M de edad = 63 meses, D.T. = 6.03). Se encontraron efectos, tanto de la confianza en la persona experimentadora, como del contexto socioeconómico en el autocontrol. Se discuten las implicaciones de este estudio para futuros trabajos con niñas y niños, y familias

High resolution HLA-A, -B, -C and -DRB1 allele and haplotype frequencies in the Costa Rica Central Valley population

The Costa Rica Central Valley population (CCVP) is the major population in this country, accounting for over 60% of the Costa Rican inhabitants concentrated since colonial times in a 2,500 km2 intermontane region. Interesting historic, demographic and genetic characteristics of this hybrid population have attracted researchers interested in testing genetic associations for various diseases. However, no study describing Human Leukocyte Antigen (HLA) frequencies by molecular methods had been performed. We have recently described low resolution HLA allele group and haplotype frequencies in a sample of this population. In this report, we extend our study to high resolution by sequence-based typing of exons 2, 3 and 4 for class I, and exon 2 for HLA-DRB1. DNA was extracted from blood or saliva samples from a cohort of 205 non-related healthy donors recruited as part of the University of Costa Rica’s Centre for Research in Hematology and Related Disorders (CIHATA) DNA bank. All participants were born in the CCVP and gave informed consent. A total of 37 HLA-A, 61 HLA-B, 24 HLA-C and 38 HLA-DRB1 alleles were seen in this sample. The five most frequent alleles for these genes are HLA-A*02:01:01, HLA-A*24:02:01, HLA-A*03:01:01, HLA-A*01:01:01, HLA-A*68:01:02, HLA-B*07:02:01, HLA-B*40:02:01, HLA-B*35:01:01, HLA-B*44:02:01, HLA-B*14:02:01, HLA-C*04:01:01, HLA-C*07:02:01, HLA-C*03:05, HLA-C*06:02:01, HLA-C*07:01:01, HLA-DRB1*13:01:01G, HLA-DRB1*04:07:01G, HLA-DRB1*15:01:01G, HLA-DRB1*03:01:01G, and HLA-DRB1*07:01:01G. Preliminary haplotype estimation results show, as a proxy for admixture proportions, that 68% of the extended haplotypes are Caucasian, while 23% are Amerindian in origin and 9% are clearly Sub-Saharan African. Principal coordinates analysis based on HLA-A and –B allele group frequencies reveals that this population clusters among other admixed groups with strong Caucasian component that lie closely to Iberian populations