Massive Blooms of Chattonella subsalsa Biecheler (Raphidophyceae) in a Hypereutrophic, Tropical Estuary—Guanabara Bay, Brazil

Cell concentrations of the potentially harmful raphidophyte Chattonella subsalsa Biecheler were quantified in surface waters of Guanabara Bay, a heavily eutrophicated estuarine system in tropical Brazil, from February 2014 to January 2018. Cells were imaged and quantified in live samples by means of an automated imaging system (FlowCam®). Bloom episodes (>0.1 × 106 cells L−1) were observed in 37 samples, mostly in a shallow (<10 m) area with extremely high nutrient and organic matter loads (average total P = 19 μM and total N = 344 μM), intermediate salinity (average 24.5), and low water transparency (average Secchi depth = 0.54 m) due to continental runoff. Blooms in this area reached up to 13.3 × 106 cells L−1. C. subsalsa cell concentration was correlated with parameters linked to eutrophication of the bay. On a monthly basis, C. subsalsa abundance was correlated with a period of positive Multivariated El Niño/Southern Oscilation Index (MEI) that lasted from the beginning of 2015 to mid-2016 (known as Godzilla El Niño), indicating a potential influence of regional climate on the occurrence of C. subsalsa. Notably, at least six fish kill episodes were reported in the Bay during this period which, added to the toxicity of C. subsalsa strains isolated from the bay to Artemia nauplia (48h-LC50 = 7.3 × 106 cells L−1), highlights the threat that this HAB species poses to the environment. This is the first report of recurrent, massive C. subsalsa blooms in Guanabara Bay. Regardless of the influence of climatic forcing in favoring C. subsalsa development, reducing nutrient loads would be the best strategy to mitigate blooms of this and other potentially harmful algae in Guanabara Bay

Conductas sexuales de riesgo y algunos factores predisponentes en los adolescentes del Noveno A\uf1o de Educaci\uf3n B\ue1sica, Primero y Segundo A\uf1o del Ciclo Diversificado de la Unidad Educativa Nacional "Zarina De Azuaje". \uc1rea de Influencia del Ambulatorio

Con cl objetivo de determinar las conductas sexuales de riesgo y algunos factores predisponentes en los adolescentes del Noveno A\uf1o de Educaci\uf3n B\ue1sica y Ciclo Diversificado de ]a Unidad Educativa Nacional "Zarina de Azuaje" de Pueblo Nuevo, se realiz\uf3 una investigaci\uf3n descriptiva de corte transversal, con un muestreo intencional a conveniencia, representada por 645 adolescentes. Se aplic\uf3 una encuesta an\uf3nima, encontr\ue1ndose que de la poblaci\uf3n estudiada la mayor\ueda pertenecen a la etapa media de la adolescencia; 76,6% del sexo femenino y 75,4% del sexo masculino. Predomin\uf3 el nivel socio?econ\uf3mico IV para el sexo femenino y el nivel III para el sexo masculino. 36,5% del sexo femenino pertenece a familias nucleares completas y 40,5% del sexo masculino a incompletas. La mayor\ueda pertenece a familias normofuncionales, 2,5% de sexo masculino pertenece a familias gravemente disfuncionales. El 42% de las adolescentes present\uf3 antecedentes de embarazo en la adolescencia y 28,4% para los del sexo masculino. El consumo de drogas. fue mayor en la etapa tard\ueda de la adolescencia (2,6%) y 1,2% en la etapa media. El consumo de alcohol y cl nivel de actividad sexual se incrementa a medida que avanza la edad. El nivel de actividad sexual IV ? V es mayor en cl sexo masculino (47,7%). El mayor porcentaje de los adolescentes de ambos sexos inician las relaciones sexuales entre los 14 y 15 a\uf1os. En cuanto al n\ufamero de parejas sexuales se evidencia predominio de una sola pareja. La mayor\ueda de los adolescentes conocen los m\ue9todos anticonceptivos 29,2% de los adolescentes en la etapa media y tard\ueda no usan m\ue9todos anticonceptivos. Las adolescentes usan menos los m\ue9todos anticonceptivos que los varones. Los resultados servir\ue1n para, reorientar hacia planes que fomenten factores protectores a los adolescentes y que reduzcan los factores de riesgo que los alejen de su bienestar

Autogenous and drying shrinkage of structural concretes incorporating recycled concrete aggregates from different sources

The main relevant difference between recycled concrete aggregates (RCAs) in comparison with the companion natural ones, is the presence of the Attached Mortar content which confers to the RCAs higher porosity and, consequently, higher water absorption capacity. In the last decades, several studies have been performed worldwide for unveiling the role of the employed RCAs on the resulting concrete mixture performances at both fresh and hardened states. On the other hand, the effects of RCA on the early-age and/or long-term concrete deformations (e.g., shrinkage) are still very limited. In this context, this article summarizes the results of a wide experimental campaign aimed at evaluating the influence of RCAs on the autogenous and drying shrinkage of normal (35 MPa) and high (60 MPa) strength recycled aggregate concrete (RAC) mixtures. A total of 10 mixtures were realized by considering the variation of both the original source and size of employed RCAs. The results showed a clear correlation between the intrinsic properties (i.e., Attached Mortar content) of the employed RCAs and the resulting concrete deformation. Moreover, although the drying shrinkage is higher for RAC mixtures, the presence of a more porous aggregates mitigates the observed autogenous shrinkage. Consequently, the overall total shrinkage result to be almost unaffected by the presence of the recycled particles

Effects of Freeze-Thaw and Wet-Dry Cycles on Tension Stiffening Behavior of Reinforced RAC Elements

In the last several decades, the growth of Construction and Demolition Waste (CDW) production and the increased consumption of natural resources have led to promoting the use of secondary raw materials for a more sustainable construction. Specifically, the use of Recycled Concrete Aggregate (RCA), derived from waste concrete, for the production of Recycled Aggregate Concrete (RAC) has attracted a significant interest both in industry and in academia. However, the use of RAC in field applications still finds some barriers. In this context, the present study investigates experimentally the effects of freeze-thaw and wet-dry cycles on the stress transfer mechanisms of reinforced RAC elements through tension stiffening tests. First of all, the paper presents a detailed analysis of the degradation due to the aging process of RAC with RCAs obtained from different sources. Particularly, the results of tension stiffening tests are analyzed in terms of crack formation and propagation, matrix tensile strength contribution and steel-to-concrete bond. The results highlight that the pre-cracking elastic modulus, the first crack strength as well as the maximum concrete strength are strongly influenced by the presence of the Attached Mortar (AM) in RCA, as the former affects the concrete's open porosity. Therefore, the amount of AM is identified as the key parameter for the evaluation of durability of reinforced RAC members: a degradation-law is also proposed which correlates the initial concrete open porosity with the damage observed in reinforced RAC elements

Fusidic acid and heparin lock solution for the prevention of catheter-related bloodstream infections in critically ill neonates: A retrospective study and a prospective, randomized trial

OBJECTIVE: Catheter-related bloodstream infections (CRBSIs) are one of the main morbidities in critically ill neonates. The objective of the present study was to assess the efficacy of a fusidic acid-heparin lock in the prevention of CRBSIs. DESIGN: A preliminary retrospective study showed that staphylococcal infections were largely prevalent. We planned a prospective, randomized trial to ascertain whether fusidic acid and heparin lock of central venous catheters would reduce the incidence of CRBSIs. SETTING: Level III neonatal intensive care unit. PATIENTS: One hundred three neonates were enrolled and randomly assigned to a treatment group (n = 50) or control group (n = 53). INTERVENTIONS: Fusidic acid (4 mg/mL) and heparin (10 IU/mL) lock in the treatment group. MEASUREMENTS AND MAIN RESULTS: The treatment group showed significantly lower incidence of CRBSIs (6.6 vs. 24.9 per 1000 catheter days; p < .01; relative risk 0.28; 95% confidence interval 0.13-0.60). No staphylococcal infections occurred in the treatment group, while in the control group Staphylococcus remained the main agent of CRBSI. Cost analysis comparing the present study and for the treatment of CRBSIs proved that antibiotic lock is financially favorable. CONCLUSIONS: Fusidic acid-heparin lock solution reduced the incidence of CRBSIs in our neonatal intensive care unit. However, we recommend basing antibiotic lock on local CRBSI epidemiology. With regard to fusidic acid, further and broader studies could be useful to confirm our results. © 2007 The Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies

Water Absorption by Capillarity, Physical and Mechanical Properties of Concrete Containing Recycled Concrete Aggregate with Partial Cement Replacement by Metakaolin

An alternative way to mitigate the impact generated by the Construction and Demolition Waste (CDW) on the environment is recycling this material in order to utilize it as Recycled Concrete Aggregates (RCA) in concrete. Studies carried out demonstrated that while using a scientific mix-design, it is possible to have a Recycled Aggregate Concrete (RAC) with mechanical properties similar the ones in conventional concrete. However, the durability of the recycled concrete is still a matter that should be explored further. The use of Supplementary Cementitious Materials (SCMs), such as metakaolin, has been shown to be efficient when partially replacing cement. It has the ability to improve the packaging of concrete by decreasing the volume of the pores of the material and, consequently, reducing the water absorption capacity of RAC, since RCA presents greater water absorption compared to natural aggregates. Therefore, the aim of this study is to evaluate the durability and mechanical behavior of RAC with 60 MPa of compressive strength by totally replacing the natural coarse aggregate by RCA. Also, part of the cement was replaced by metakaolin. The coarse aggregate considered in this research has 19 mm as nominal maximum size. Total absorption, capillarity absorption, compressive strength test and tensile strength test were carried out for all mixtures. The research results showed that the use of metakaolin offset the increase in capillary absorption in recycled concrete caused by the use of RCA, reaching a value close to concrete with only natural aggregate and without metakaolin for this durability parameter

Flexural Behavior of Reinforced Concrete Beams Made with Recycled Concrete Aggregates

The reuse of Construction and Demolition Waste (CDW) to produce new materials is an effective method for reducing the negative impacts from the inadequate waste disposition, in addition to bringing economic and environmental benefits to the industry. The use of Recycled Concrete Aggregate (RCA) in concrete is a technique widely disseminated, however, using this material for structural applications is a target of distrust among professionals in the construction sector. Therefore, the purpose of this study is to analyze the influence of using RCA to replace 100% of course natural coarse aggregates with size fraction 9.5-19 mm in the flexural behavior of reinforced normal-strength concrete beams (35 MPa). In addition to a reference mixture produced with only natural aggregates, a Recycled Aggregate Concrete (RAC) mixture was designed, according to the well-known Compressible Packing Model (CPM), using RCA from demolition waste. The mechanical behavior of the concrete mixtures was characterized by compressive and splitting tensile tests. A pair of flexural critical beams of each concrete mixture was tested under a supported four-point loading condition at the age of 28 days. All tested beams had 240 cm length and rectangular cross section of 20 x 30 cm(2). The experimental cracking, yielding and ultimate load of the beams were measured. Besides that, the load-strain behavior for concrete was obtained, as well as the load-deflection behavior. The results showed that the flexural behavior of RAC beams was not negatively affected by the presence of RCAs

Influence of wetting and drying cycles on physical and mechanical behavior of recycled aggregate concrete

Recently, concerns have been rising about the impact of increasing the depletion of natural resources and the relevant generation of construction and demolition waste, on the environment and economy. Therefore, several efforts have been made to promote sustainable efficiency in the construction industry and the use of recycled aggregates derived from concrete debris for new concrete mixtures (leading to so-called recycled aggregate concrete, RAC) is one of the most promising solutions. Unfortunately, there are still gaps in knowledge regarding the durability performances of RAC. In this study, we investigate durability of structural RAC subjected to wet-dry cycles. We analyze the results of an experimental campaign aimed at evaluating the degradation process induced by wetting and drying cycles on the key physical and mechanical properties of normal-and high-strength concrete, produced with coarse recycled concrete aggregates (RCAs) of different sizes and origins. On the basis of the results we propose a degradation law for wetting and drying cycles, which explicitly makes a possible correlation between the initial concrete porosity, directly related to the specific properties of the RCAs and the resulting level of damage obtained in RAC samples

Use of Post-Consumer Plastics in the Production of Wood-Plastic Composites for Building Components: A Systematic Review

This systematic review study adopted the PRISMA methodology to investigate recent research on wood-plastic composites (WPC) utilizing post-consumer plastics in the construction industry. Initially, 3111 articles were selected from academic databases using keywords such as “wood and plastic composites”, “WPC”, “polymer”, “recycled”, “waste”, “construction”, and “sustainability.” After stringent exclusion criteria, 15 relevant studies on plastic waste composites were identified. These studies often employ post-consumer plastics like polypropylene and high-density polyethylene, along with plant-based fillers, aiming to enhance mechanical properties and reduce reliance on virgin materials. Analysis of these studies revealed that the optimal plastic composition in the composites ranged from 40% to 45% wood and from 50% to 60% plastic, with the extrusion process being the most employed for shaping. Specific factors, such as the use of compatibilizers and the particle size of raw materials, were identified as significant influencers on composite strength. These materials exhibited high thermal stability, rendering them suitable for construction applications exposed to high temperatures. The diversity of plastic waste explored in the studies underscores the potential to tailor thermal properties to specific application demands. These composites facilitate closed-loop plastic recycling, enabling their reintegration into the production chain and offering opportunities for lightweight, durable, and high-performance products in the construction industry. However, beyond the factors examined in the studies, a meticulous assessment of the fire resistance, weather resistance, ultraviolet resistance, moisture absorption, dimensional stability, degradation, long-term durability, impact strength, recyclability, and cost-effectiveness of the material is crucial. Thoughtful consideration of these factors is essential to achieving a comprehensive understanding of the potential and limitations of recycled plastic composites in promoting energy efficiency and sustainability in the construction industry