Particle size distribution and specific surface area of SCM's compared through experimental techniques

Supplementary cementitious materials (SCMs) are mainly used to produce a green concrete. To reach that goal effectively, it is highly important to adequately characterize the SCMs. It is well known that particle size distribution (PSD) and fineness of SCMs have a great influence on concrete properties. Traditionally, cement fineness has been assessed by the specific surface area (SSA) through the Blaine method (BM). However, the BM has the simplification of considering ideal spherical shape particles. The BET theory has also been used to calculate SSA, however, also some assumptions may lead to inaccuracy in the calculations. Both PSD and SSA can be evaluated through Laser Diffractometry (LD), but this technique also considers ideal spherical particles as a simplification. Regardless of the mentioned drawbacks, these techniques provide useful information to characterize SCMs provided that the limitations are considered. In this paper, Ground Granulated Blast Furnace Slag (GGBFS), Natural Pozzolan (NP) and Limestone Powder (LP) are tested using the BM, LD, and nitrogen adsorption. Particle texture and shape are assessed through petrography and scanning electron microscope (SEM). Results from BM, BET and LD are compared, analysing the possible effects of particle shape and texture

Estudio petrográfico de rocas cuarcíticas del área de Balcarce (provincia de Buenos Aires) : Factibilidad de uso como agregado para hormigón

Las cuarcitas de la Formación Balcarce se explotan desde la década del 30 en el partido de Gral. Pueyrredón (provincia de Buenos Aires). En Balcarce existen afloramientos naturales con un espesor máximo de 90m sobre los cuales se han desarrollado canteras que se hallan inactivas desde hace más de 30 años. Para evaluar la potencial reactividad frente a la RAS de las cuarcitas al ser utilizadas como agregado en hormigón, se realizaron estudios petrográficos (IRAM 1649) según la norma IRAM 1531 y ensayos físicos: método acelerado de la barra de mortero y prisma de hormigón (IRAM 1674 y 1700). Son cuarcitas de grano medio a fino, de color blanco grisáceo que intercalan con bancos de arcilla de 10 a 50 cm de espesor determinadas por DRX como illita y caolinita. El resultado del análisis petrográfico indica que la roca posee en general, granos de cuarzo con ángulo de extinción ondulante (AEO) menor a 15º y que el contenido de cuarzo microcristalino es inferior al 1%, no superando el límite de 5% que establece la norma IRAM 1531. Además, la expansión medida en los ensayos físicos no supera los límites establecidos en las normas vigentes, por lo que se califica a la cuarcita como apta para su uso como agregado en hormigón.Facultad de Ciencias Naturales y Museo (FCNM

Estudio petrográfico de rocas cuarcíticas del área de Balcarce (provincia de Buenos Aires) : Factibilidad de uso como agregado para hormigón

Las cuarcitas de la Formación Balcarce se explotan desde la década del 30 en el partido de Gral. Pueyrredón (provincia de Buenos Aires). En Balcarce existen afloramientos naturales con un espesor máximo de 90m sobre los cuales se han desarrollado canteras que se hallan inactivas desde hace más de 30 años. Para evaluar la potencial reactividad frente a la RAS de las cuarcitas al ser utilizadas como agregado en hormigón, se realizaron estudios petrográficos (IRAM 1649) según la norma IRAM 1531 y ensayos físicos: método acelerado de la barra de mortero y prisma de hormigón (IRAM 1674 y 1700). Son cuarcitas de grano medio a fino, de color blanco grisáceo que intercalan con bancos de arcilla de 10 a 50 cm de espesor determinadas por DRX como illita y caolinita. El resultado del análisis petrográfico indica que la roca posee en general, granos de cuarzo con ángulo de extinción ondulante (AEO) menor a 15º y que el contenido de cuarzo microcristalino es inferior al 1%, no superando el límite de 5% que establece la norma IRAM 1531. Además, la expansión medida en los ensayos físicos no supera los límites establecidos en las normas vigentes, por lo que se califica a la cuarcita como apta para su uso como agregado en hormigón.Facultad de Ciencias Naturales y Museo (FCNM

Estudio petrográfico de rocas cuarcíticas del área de Balcarce (provincia de Buenos Aires) : Factibilidad de uso como agregado para hormigón

Las cuarcitas de la Formación Balcarce se explotan desde la década del 30 en el partido de Gral. Pueyrredón (provincia de Buenos Aires). En Balcarce existen afloramientos naturales con un espesor máximo de 90m sobre los cuales se han desarrollado canteras que se hallan inactivas desde hace más de 30 años. Para evaluar la potencial reactividad frente a la RAS de las cuarcitas al ser utilizadas como agregado en hormigón, se realizaron estudios petrográficos (IRAM 1649) según la norma IRAM 1531 y ensayos físicos: método acelerado de la barra de mortero y prisma de hormigón (IRAM 1674 y 1700). Son cuarcitas de grano medio a fino, de color blanco grisáceo que intercalan con bancos de arcilla de 10 a 50 cm de espesor determinadas por DRX como illita y caolinita. El resultado del análisis petrográfico indica que la roca posee en general, granos de cuarzo con ángulo de extinción ondulante (AEO) menor a 15º y que el contenido de cuarzo microcristalino es inferior al 1%, no superando el límite de 5% que establece la norma IRAM 1531. Además, la expansión medida en los ensayos físicos no supera los límites establecidos en las normas vigentes, por lo que se califica a la cuarcita como apta para su uso como agregado en hormigón.Facultad de Ciencias Naturales y Museo (FCNM

Arapaima gigas stocks have declined drastically in the lower Tocantins River in the Amazon Microregion

Abstract Arapaima gigas, an emblematic species of the Amazon region and a longstanding primary fishing resource, currently holds a “Data Deficient” status on the International Union for Conservation of Nature Red List, and is listed as an endangered species in Brazil. The Tocantins River is the most extensively modified large tributary of the Amazon Basin, and thus can affect the dynamics of ichthyofaunal populations. Over a period of 1 year, representatives of the fishing communities and fishermen from 25 fishing communities from four municipalities in the lower Tocantins River region were interviewed, and the obtained information was evaluated based on the literature to survey the population abundance status of A. gigas in the region and its impact on local communities. Among the fishermen interviewed, only one reported still encountering and fishing A. gigas on Jaracuera Island. The disappearance of A. gigas in the region are viewed as having economically disastrous consequences for the residents. Additionally, other endemic fish species are no longer observed in this locality either. If fishery management officials do not work together with local communities, A. gigas could disappear from the northern region of Brazil, where information on the dynamics of A. gigas fishing is lacking

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Catálogo Taxonômico da Fauna do Brasil: setting the baseline knowledge on the animal diversity in Brazil

The limited temporal completeness and taxonomic accuracy of species lists, made available in a traditional manner in scientific publications, has always represented a problem. These lists are invariably limited to a few taxonomic groups and do not represent up-to-date knowledge of all species and classifications. In this context, the Brazilian megadiverse fauna is no exception, and the Catálogo Taxonômico da Fauna do Brasil (CTFB) (http://fauna.jbrj.gov.br/), made public in 2015, represents a database on biodiversity anchored on a list of valid and expertly recognized scientific names of animals in Brazil. The CTFB is updated in near real time by a team of more than 800 specialists. By January 1, 2024, the CTFB compiled 133,691 nominal species, with 125,138 that were considered valid. Most of the valid species were arthropods (82.3%, with more than 102,000 species) and chordates (7.69%, with over 11,000 species). These taxa were followed by a cluster composed of Mollusca (3,567 species), Platyhelminthes (2,292 species), Annelida (1,833 species), and Nematoda (1,447 species). All remaining groups had less than 1,000 species reported in Brazil, with Cnidaria (831 species), Porifera (628 species), Rotifera (606 species), and Bryozoa (520 species) representing those with more than 500 species. Analysis of the CTFB database can facilitate and direct efforts towards the discovery of new species in Brazil, but it is also fundamental in providing the best available list of valid nominal species to users, including those in science, health, conservation efforts, and any initiative involving animals. The importance of the CTFB is evidenced by the elevated number of citations in the scientific literature in diverse areas of biology, law, anthropology, education, forensic science, and veterinary science, among others