Autor: Vargas, A. - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Averages of uniformly continuous retractions
Autorzy:: Jiménez-Vargas, A.
Mena-Jurado, J.
Nahum, R.
Navarro-Pascual, J.
Powiązania:: https://bibliotekanauki.pl/articles/1217171.pdf
Data publikacji:: 1999
Wydawca:: Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:: uniformly retraction
Lipschitz retraction
extreme point
Opis:: Let X be an infinite-dimensional complex normed space, and let B and S be its closed unit ball and unit sphere, respectively. We prove that the identity map on B can be expressed as an average of three uniformly retractions of B onto S. Moreover, for every 0≤ r < 1, the three retractions are Lipschitz on rB. We also show that a stronger version where the retractions are required to be Lipschitz does not hold.
Źródło:: Studia Mathematica; 1999, 135, 1; 75-81
0039-3223
Pojawia się w:: Studia Mathematica
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: A review on mineral waste for chemical-activated binders: mineralogical and chemical characteristics
Autorzy:: Sedira, N.
Castro-Gomes, J.
Kastiukas, G.
Zhou, X.
Vargas, A.
Powiązania:: https://bibliotekanauki.pl/articles/89164.pdf
Data publikacji:: 2017
Wydawca:: Politechnika Wrocławska. Wydział Geoinżynierii, Górnictwa i Geologii. Instytut Górnictwa
Tematy:: mineral waste
mining waste
alkali activated materials
alkaline solutions
chemical composition
Opis:: This review discusses the potential of alkali-activated materials obtained from mineral waste. A brief historical background on alkali-activated materials is presented. Recent advances in the development of binders obtained from mineral wastes and alkali-activated solutions are described. The scope of this state of the art review is to identify current knowledge in support that mineral waste can be used for the production of alkali-activated binders. In addition, this review identifies the chemical activators that can be effectively utilized for such purposes in the age when wastes are still viewed by industry as dis-posable. Some mineral wastes which are discussed can be viewed as a new resource for recycling and recovery which will offer important economic and social benefits.
Źródło:: Mining Science; 2017, 24; 29-58
2300-9586
2353-5423
Pojawia się w:: Mining Science
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Influence of glycerol and temperature on the rheological properties of potato starch solutions
Autorzy:: Ayala, G.
Vargas, R.A.
Agudelo, A.C.
Powiązania:: https://bibliotekanauki.pl/articles/24305.pdf
Data publikacji:: 2014
Wydawca:: Polska Akademia Nauk. Instytut Agrofizyki PAN
Tematy:: glycerol
temperature
rheological property
potato starch
solution
pseudoplastic behaviour
rheological model
Opis:: Effects of temperature and glycerol concentration on rheological properties of potato starch solutions were investi- gated. The flow behaviour (shear stress against shear rate) was fitted to various models: power law, Herschel-Bulkley, Bingham, modified Bingham and Casson models. However, it was found that the Herschel-Bulkley model describes better the flow behaviour observed at various temperatures and glycerol concentrations, for flow behaviour index values between 0.44 and 0.78, typical of pseudoplastic solutions. The effect of glycerol concentration on each of the fitting parameters for Herschel-Bulkley model was well modelled by a second-degree polynomial at various temperatures. The simultaneous influence of glycerol concentration and tempe- rature on shear stress could be represented empirically by a second- degree polynomial function that includes linear coupling between concentration and temperature. Finally, the variation of the con- sistency coefficient with both temperature and glycerol concentra- tion was well described by an exponential expression, with an acti- vation energy value of 2.78 kJ mol -1 . The results indicate that both glycerol content and temperature have the effect of diluting potato starch solutions.
Źródło:: International Agrophysics; 2014, 28, 3
0236-8722
Pojawia się w:: International Agrophysics
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Incrustation of alpha-particle emitters in the source backing: influence on activity measurements
Autorzy:: Jurado-Vargas, M.
Fernández-Timón, A.
Powiązania:: https://bibliotekanauki.pl/articles/146904.pdf
Data publikacji:: 2012
Wydawca:: Instytut Chemii i Techniki Jądrowej
Tematy:: alpha-particle spectrometry
Monte Carlo (MC) simulation
SRIM
Opis:: Alpha particles emitted from radioactive sources are often measured using a 2pi counting geometry in order to determine the activity with a low deviation. The ratio C2pi/A (counting rate/activity) can, however, deviate from the theoretical value of 0.5 because of backscattering in the backing material, scattering and absorption of alpha particles in the source. The experimental counting rates are, therefore, corrected for these effects (backscattering for all sources, plus self-absorption for sources of non-negligible thickness) to determine the real source activity. However, the corrections needed for situations corresponding to alpha-particle sources in which the radionuclides are not deposited but incrusted in the backing material have not been considered. The aim of the present work was therefore to study the influence that incrustation in the backing can have on the total detection efficiency, and hence on the activity estimated for the source. To this end, we used the Monte Carlo computer code SRIM to model the behaviour of the alpha particles in the backing material.
Źródło:: Nukleonika; 2012, 57, 4; 569-573
0029-5922
1508-5791
Pojawia się w:: Nukleonika
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Application of the new Monte Carlo code AlfaMC to the calibration of alpha-particle sources
Autorzy:: Jurado Vargas, M.
Fernández Timón, A.
García Orellana, C.
Powiązania:: https://bibliotekanauki.pl/articles/148497.pdf
Data publikacji:: 2015
Wydawca:: Instytut Chemii i Techniki Jądrowej
Tematy:: alpha-particle spectrometry
code AlfaMC
Monte Carlo simulation
scattering and self-absorption
Opis:: Measurements of α-particle sources require corrections to the counting rate due to scattering and self- -absorption in the source and the backing material. In this study, we describe a simple procedure to estimate these corrections using the new Monte Carlo code AlfaMC to consider the effects of scattering and self-absorption conjointly, and so to determine the activity of α emitters. The procedure proposed was applied to 235UO2 sources deposited on highly polished platinum backings. In general, the dependence of the efficiency with source thickness was in good agreement with a simple model considering a linear and a hyperbolic behavior for thin and thick sources, respectively, although significant deviations from this model were found for very thin sources. For these very thin sources, the Monte Carlo simulation revealed to be as a required method in the primary calibration of α-particle sources. The efficiency results obtained by simulation with AlfaMC were in agreement with available efficiency data.
Źródło:: Nukleonika; 2015, 60, No. 3, part 2; 651-655
0029-5922
1508-5791
Pojawia się w:: Nukleonika
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Characterization and feasibility of biomass fuel pellets made of Colombian timber, coconut and oil palm residues regarding European standards
Autorzy:: Forero Núnez, C. A.
Jochum, J.
Sierra Vargas, F. E.
Powiązania:: https://bibliotekanauki.pl/articles/363258.pdf
Data publikacji:: 2012
Wydawca:: Uniwersytet Warmińsko-Mazurski w Olsztynie
Tematy:: biomass
coconut shells
oil palm shells
pellets
renewable energy
biomasa
energia odnawialna
orzech kokosowy
palma olejowa
skorupa
owoc
Opis:: Strong correlation between economic development, energy demand and fossil fuels utilization during last decades has caused some negative impacts worldwide, based on it, the renewable resources for energy production should be employed to mitigate these effects. Nowadays, biomass is one of the most prominent renewable sources, but factors such as low density and high moisture content are some drawbacks. In order to overcome these problems, some companies use different types of biomass to provide solid biofuels with higher energy density, mechanical resistance and standardized dimensions. Wood pellet industry has increased exponentially during last years, faster than timber industries; therefore, new raw materials should be evaluated to guarantee pellets demand in the near future. Some of them are agricultural residues. Colombia is a country with an interesting potential for biomass production because there is a rising generation of agricultural products. This work aims to assess main properties of Colombian timber industry residues, coconut shells and oil palm shells and compare the characteristics of pellets made from these raw materials with European standards. Pellets made from these feedstocks have an average density between 850 and 1025kg·m-3, low ash contents and heating values around 18000kJ·kg-1. Coconut shell pellets have low compression ratios and problems during pretreatment; whereas, sawdust, wood shavings and oil palm shell pellets proved to be an attractive opportunity for pellet industry development in Colombia.
Źródło:: Environmental Biotechnology; 2012, 8, 2; 67-76
1734-4964
Pojawia się w:: Environmental Biotechnology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Serum cytokines and activation ex vivo of CD4plus and CD8plus T cells in chagasic chronic Mexican patients
Autorzy:: Cruz-Robles, David
Vargas-Alarcón, Gilberto
Ortíz-Muñiz, Rocio
Reyes, Pedro A.
Monteon, Victor M.
Powiązania:: https://bibliotekanauki.pl/articles/972123.pdf
Data publikacji:: 2017
Wydawca:: Polskie Towarzystwo Parazytologiczne
Tematy:: Chagas discase
cytokines
chronic chagasic cardiomyopathy
Opis:: The clinical manifestations of human Chagas disease are associated with several factors, including immunological alterations, in this regard, many studies propose that tissue damage might be more severe in the absence of immune regulatory mechanisms, other factors are the genetic background of host and parasite. Trypanosoma cruzi population is genetically, biochemistry and pathogenic diverse along the Latin-America continent and phylogenetic ally are divided into six intra-species lineages TcI-VI. The TcI lineage has a wide distribution with heterogeneous virulence and pathogenesis within strains. In Mexico, the main circulating lineage is TcI in human infections. We analyzed intracytoplasmic cytokines of unstimulated peripheral T lymphocytes, and the level of cytokines (IL-2, IL-4, IL-12, IL-10, IFN-γ and sIL-2R) in the serum of Mexican chagasic subjects. The population studied consisted of 15 asymptomatic individuals, 17 patients with chronic chagasic cardiopathy (CCC), 20 patients with cardiopathy but negative serology for T. cruzi, and 10 healthy subjects. The analysis of CD4+ cells revealed that CCC and asymptomatic patients have higher CD25+ and CD69 activation markers than controls. The Th1 subset (CD4+/IFN- γ +) was higher in CCC than in asymptomatic and control subjects, whereas Th2 subset was markedly high in asymptomatic subjects. Circulating cytokines were below level detection with the exception of IL-2 and sIL-2R. Infection with Mexican Trypanosoma cruzi strains in asymptomatic chagasic subjects have a tendency for a Th2 response with higher CD8+/IFN-γ T cells. In contrast, CCC patients have low levels of intracellular IFN- γ and IL-2 cytokines. In both groups circulating serum cytokines are below the detectable level.
Źródło:: Annals of Parasitology; 2017, 63, 4; 299-308
0043-5163
Pojawia się w:: Annals of Parasitology
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Kelvin-Helmholtz instabilities in the Colorado River Delta, Gulf of California
Autorzy:: Carbajal, N.
Vargas, J.T.
Rodriguez, J.H.G.
Montano Ley, Y.
Salas de Leon, D.A.
Powiązania:: https://bibliotekanauki.pl/articles/2078904.pdf
Data publikacji:: 2021
Wydawca:: Polska Akademia Nauk. Instytut Oceanologii PAN
Tematy:: Kelvin-Helmholtz instability
Colorado River Delta
tidal current
bottom sediment
bathymetry
suspended sediment
satellite image
Opis:: In the Colorado River Delta, the interaction of tidal currents and sea-bottom sediment formed, in geological times, large-scale seabed patterns known as sandbanks. These patterns are oriented along the delta, almost parallel to the dominant tidal flow, with the bathymetry having an undulating character across the delta. Calculations and analysis showed that the interaction of tidal currents with the bathymetry causes velocity shears, faster flowing over the ridges than in the troughs. Kelvin-Helmholtz instabilities emerge from the velocity shear, and a large amount of suspended sediment makes the instabilities visible in satellite images. The physical and dynamic conditions allowed us to find an explanation for the existence of these Kelvin-Helmholtz instabilities. Since sandbanks have been observed in different seas such as the North Sea, The Gulf of Korea, the Gulf of Khambhat in India, the Jiangsu coast in China, the Persian Gulf, and Moreton Bay in Australia, the results suggest the existence of instabilities in these areas. Satellite images, intense tidal currents, undulating topography, and suspended sediment made it possible to explain the generation and identification of KelvinHelmholtz instabilities.
Źródło:: Oceanologia; 2021, 63, 3; 321-328
0078-3234
Pojawia się w:: Oceanologia
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Assessment of buccal mucosa genotoxicity in insecticide-exposed urban fumigators in Cali, Colombia
Autorzy:: Londoño-Velasco, Elizabeth
Asencio-Santofimio, Helberg
Ortega-Avila, Jose G.
Rosero-Caldón, Aldair B.
Aristizabal-Grisales, Juan C.
Rey-Henao, Laura
Vargas-Rivera, Jairo A.
Vergara-Escudero, Enrique
Powiązania:: https://bibliotekanauki.pl/articles/28762056.pdf
Data publikacji:: 2024-03-05
Wydawca:: Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
Tematy:: insecticides
occupational exposure
buccal micronucleus cytome assay
DNA damage
biomarker
personal protective equipment
Opis:: Objectives This study aimed to evaluate cytogenetic damage in the buccal mucosa of non-exposed subjects (N = 33) and insecticide-exposed fumigators (N = 31) in the urban area of Cali, Colombia. Material and Methods Through a questionnaire sociodemographic data, anthropometric measurements, state of health, and lifestyle were collected. Buccal micronucleus cytome (BMCyt) assay was using for evaluate cytogenetic damage. Results The study showed that all fumigators used adequate personal protective equipment (PPE) and had low alcohol consumption. The authors did not find significant differences in BMCyt biomarkers between the groups (p > 0.05). Multivariate analysis showed a 13% increase in micronucleus (MN) frequency for every year of increasing age (OR = 1.13, p = 0.029), and higher MN with the decrease in daily fruit consumption (OR = 4.71, p = 0.084), without statistical significance. Conclusions The results between groups could be related to healthy habits and PPE use among the subjects.
Źródło:: International Journal of Occupational Medicine and Environmental Health; 2024, 37, 1; 128-137
1232-1087
1896-494X
Pojawia się w:: International Journal of Occupational Medicine and Environmental Health
Dostawca treści:: Biblioteka Nauki

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