Absolute Density
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2021 ◽  
Galina Makashova ◽  
Stepan Yukhtarov

Abstract Proppant is one of the key aspects of a successful fracturing treatment and subsequent well production, and its quality is strictly controlled by ISO 13503-2, an international standard for proppant testing. Proppant suppliers, oilfield companies and their clients all around the world rely on the standard measurement procedures and limit values to ensure the quality of a product they produce or use for fracturing operations. ISO 13503-2 prescribes testing procedures; however, the standard does not contain information about uncertainty of final measurements. This information is essential for consistent quality assurance, for resolving inconsistencies between different laboratories, and for comparing properties of different products. An interlaboratory study was organized to evaluate the precision of ISO 13503-2 proppant testing. Four proppant samples were distributed among proppant quality control laboratories all around the world; 17 laboratories participated in the study. The obtained test data were used to calculate repeatability and reproducibility standard deviations (in accordance with ISO 5725-2) and uncertainty of ISO 13503-2 test data (in accordance with ISO 21748). The study showed that most proppant parameters measured using ISO 13503-2 methods yielded high uncertainty. For example, for turbidity and acid solubility values, the uncertainty was up to ±50%. Uncertainty of roundness and sphericity values was ±0.1 since the values are estimated by operator, making the test quite subjective. For crush resistance, the highest uncertainty among tested samples, ±40%, was observed for an HSP 30/50 sample measured at 15,000 psi stress. For absolute density, a systematic difference between values obtained using gas pycnometers from different manufactures was observed; also, the equipment differs by repeatability characteristics. The results of the interlaboratory study allowed estimating the uncertainty of ISO 13503-2 test methods. It was shown that high measurement uncertainty for some critical proppant parameters should be considered for correct interpretation of the obtained test results.

2021 ◽  
Vol 51 (3) ◽  
pp. 630
Ane Cristine Fortes da Silva ◽  
Fernando José Freire ◽  
César Henrique Alves Borges ◽  
Emmanoella Costa Guaraná Araujo ◽  
Ernandes Macedo da Cunha Neto ◽  

The objective is to quantify the carbon content (C) of the reservoirs of plant biomass of different species in a fragment of the Atlantic Forest in Northeast Brazil. Ten species of high absolute density were selected. We sampled biomass from the leaf and wood compartments of each species to determine the C content. There was a difference in leaf C levels between species. The C content in leaves of species varied between 451.4 and 456.7 g kg-1. The C content of the wood of species varied between 451.7 and 456.8 g kg-1. The group formed by the families Burseraceae, Moraceae, and Sapotaceae showed higher average levels of C in leaves. The Burseraceae family had the highest average C content in the species' wood. The use of a pre-established carbon content (500 g kg-1) may generate inconsistent estimates higher than the real values for the species and families in an Atlantic Forest environment. We suggest that C stock estimates use specific levels for species and/or families, contributing to a more realistic estimate of C storage patterns in the shoot biomass of Atlantic Forest species.Keywords: Carbon concentration; Carbon sequestration; Tropical Rainforest.

2021 ◽  
Vol 51 (3) ◽  
pp. 604
Yasmim Yathiara Gomes Araújo Morais ◽  
Fernando José Freire ◽  
Rosival Barros de Andrade Lima ◽  
Edilane Alice de Alcântara Assunção ◽  
Shyrlaine Lilian Moura Leão ◽  

Rainfall is the main source of water in forest ecosystems and stemflow is an important pathway for nutrients to enter these ecosystems. Thus, this study aimed to evaluate effective precipitation in a fragment of tropical forest and stemflow nutrient input of tree species in different periods of rainfall. Total precipitation and throughfall were measured using rain gauges inside and at the edge of the fragment. After a phytosociological survey, nine species with the highest absolute density in the fragment were chosen and three individuals were selected. Water collectors were fixed around their trunk to collect stemflow water. The stemflow water was measured in milliliters, and pH, electrical conductivity and the input of K, P and Na were determined. Based on the throughfall and stemflow, the effective precipitation was calculated. The stemflow nutrient input presented the following decreasing order: Na>K>P. The high input of Na can be explained by the fact that the fragment is close to the coastal area. Stemflow of forest species proved to be an important pathway for nutrients to enter forest ecosystems, effectively participating in nutrient cycling.

eLife ◽  
2021 ◽  
Vol 10 ◽  
James Rae ◽  
Charles Ferguson ◽  
Nicholas Ariotti ◽  
Richard I Webb ◽  
Han-Hao Cheng ◽  

Genetic tags allow rapid localization of tagged proteins in cells and tissues. APEX, an ascorbate peroxidase, has proven to be one of the most versatile and robust genetic tags for ultrastructural localization by electron microscopy. Here we describe a simple method, APEX-Gold, which converts the diffuse oxidized diaminobenzidine reaction product of APEX into a silver/gold particle akin to that used for immunogold labelling. The method increases the signal to noise ratio for EM detection, providing unambiguous detection of the tagged protein, and creates a readily quantifiable particulate signal. We demonstrate the wide applicability of this method for detection of membrane proteins, cytoplasmic proteins and cytoskeletal proteins. The method can be combined with different electron microscopic techniques including fast freezing and freeze substitution, focussed ion beam scanning electron microscopy, and electron tomography. Quantitation of expressed APEX-fusion proteins is achievable using membrane vesicles generated by a cell-free expression system. These membrane vesicles possess a defined quantum of signal, which can act as an internal standard for determination of the absolute density of expressed APEX-fusion proteins. Detection of fusion proteins expressed at low levels in cells from CRISPR-edited mice demonstrates the high sensitivity of the APEX-Gold method.

2020 ◽  
Vol 67 (10) ◽  
pp. 2273-2277
Nicola Zambelli ◽  
Silvia Zanettini ◽  
Giacomo Benassi ◽  
Andrea Bettati ◽  
Andrea Zappettini

2020 ◽  
Vol 50 (3) ◽  
pp. 1660
Dráuzio Correia Gama ◽  
Robério Anastácio Ferreira ◽  
Janisson Batista de Jesus ◽  
José Monteiro do Nascimento Júnior

The study of spatial distribution of tree populations has proven to be important for revealing how individuals are horizontally organized in the environment, facilitating the structural understanding and forms of colonization and dispersion of propagules. The present work aimed at studying the pattern of spatial distribution of tree species Copaiferaarenicola [(Ducke) J. Costa e L.P.Queiroz] and its structural relation with the altimetric profile in a Caatinga fragment in Ribeira do Pombal municipality, Bahia. Census of all individuals in the area with circumference at breast height (CBH) ≥ 6 cm was performed. The spatial distribution analysis was conducted for the whole population using Ripley K univariate function, with maximum search radius (h) of 128 m. 409 individuals were found, corresponding to absolute density of 89.49 ind. ha-1 and 0.681 m². ha-1 of basal area. The group of C. arenicola individuals corresponds to a stable population in expansion phase, presenting higher number of young and medium individuals. The pattern of spatial distribution of individuals in the area under study was the uniform arrangement. None of the altimetric classes of the area had a different influence on the structure and distribution of arboreal individuals.

2019 ◽  
Vol 27 (25) ◽  
pp. 36580 ◽  
Lena Worbs ◽  
Jannik Lübke ◽  
Nils Roth ◽  
Amit K. Samanta ◽  
Daniel A. Horke ◽  

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