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Wyszukujesz frazę "de Lima, A. P." wg kryterium: Autor


Wyświetlanie 1-7 z 7
Tytuł:
Defects in Decomposing Copper Alloys Studied by Positrons
Autorzy:
Mikhalenkov, V. S.
de Lima, A. P.
Lopes Gil, C.
Powiązania:
https://bibliotekanauki.pl/articles/2008115.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
81.30.Mh
Opis:
The evolution of defect structure during isochronal annealing of water-quenched Cu-4.83 at.% In and Cu-4.94 at.% Sn alloys was studied by measuring positron lifetime and Doppler broadening of annihilation line. The behaviour of annihilation parameters in both alloys is found to be analogous. In as-quenched alloys one component of about 180 ps is detected in the lifetime spectra. It remains intact up to the annealing temperature of 450 K and is attributed to positron annihilation at quenched-in vacancies associated with alloying atoms. When going above this temperature, the short component appears in the lifetime spectra, while intensity of the long component starts to drop giving evidence to the reduction of defect concentration. This process is observed to develop up to 550 K; thereafter all annihilation parameters level off. After crossing the phase separation temperature they begin to vary again since the defect structure comes into dependence on cooling conditions. The obtained results are discussed in terms of defect structure evolution in the course of precipitate formation.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 615-622
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Trapping in Porous Solids: Means and Limitations for Structural Studies
Autorzy:
Kajcsos, Zs.
Liszkay, L.
Duplâtre, G.
Varga, L.
Lohonyai, L.
Pászti, F.
Szilágyi, E.
Lázár, K.
Kótai, E.
Pál-Borbély, G.
Beyer, H. K.
Caullet, P.
Patarin, J.
Azenha, M. E.
Gordo, P. M.
Lopes Gil, C.
de Lima, A. P.
Ferreira Marques, M.
Powiązania:
https://bibliotekanauki.pl/articles/2042216.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
61.43.Gt
Opis:
Positron annihilation techniques are used for the structural investigation of solids but the interpretation of results in grainy and porous media is still unclear. A unique picture can be obtained assuming that the dominant process is Ps trapping in competing "extended free volume" sites. In samples with a large amount of free volumes near-saturation Ps trapping will rule the lifetime pattern, and very long lifetimes of over 100 ns might arise from o-Ps trapped in mesopores. It is shown that lifetime parameters must be corrected for the 3γ/2γ counting efficiency ratio. The results demonstrate the high sensitivity of Ps to mesopores in zeolites but also that Ps-trapping poses limitations on the applicability of lifetime to structural investigation in porous systems. The evolution of the lifetime spectra upon changes in the sample and measuring conditions should be considered in a complex way, observing not only changes in some selected components but in the whole lifetime pattern simultaneously.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 729-737
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on the Structure of Defects in a-Si:H Films by Positron Annihilation and Micro-Raman Spectroscopy
Autorzy:
Gordo, P.
de Lima, A.
Ferreira Marques, M.
Kajcsos, Zs.
Powiązania:
https://bibliotekanauki.pl/articles/1812497.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.66.Jg
78.70.Bj
78.30.Ly
Opis:
Thin films of hydrogenated amorphous silicon deposited on glass and crystalline silicon substrates by rf plasma enhanced chemical vapor deposition at different rf power were studied using slow positron beam and the Raman scattering spectroscopy in order to verify the influence of that deposition parameter on the film defect structure and on the degree of disorder. By positron annihilation spectroscopy, it was found that there are mainly two types of defects in the films: large vacancy clusters or voids and small vacancy type defects. By micro-Raman spectroscopy it was observed that the degree of structural disorder is lower for the film with large vacancy clusters and this finding was related to structural relaxation process. Light soaking induced changes attributed to major atomic rearrangements were also observed.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1373-1378
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Methodological aspects of the quantification of dispersible clay and its relationship with soil properties along a catena under no-till management
Autorzy:
de Paula, A.L.
Giarola, N.F.B.
de Lima, R.P.
Wiecheteck, L.H.
da Silva, A.P.
Powiązania:
https://bibliotekanauki.pl/articles/2082881.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Agrofizyki PAN
Tematy:
soil structure
erodibility
aggregation
Opis:
Continuous no-till management of sloping cultivated areas can promote soil property transformations, causing changes in aggregation and dispersion. The objective of this work was (i) to quantify the readily and mechanically dispersible clays using different methods and (ii) to examine their relationships with soil properties along a catena under no-till management. For this study, the catena was divided into three distinct parts: crest, upper-slope and mid-slope positions. Undisturbed soil cores were sampled at each slope position to determine the following soil properties: organic carbon, Ca2+, Mg2+, K+, Al3+, P, pH, cation exchange capacity and total clay content. Additionally, the levels of readily dispersible clay were measured using turbidimeter and hydrometer methods, whereas mechanically dispersible clay was quantified using the turbidimeter method. We observed high influence of total clay content and organic carbon on soil flocculation; P, Mg2+ and cation exchange capacity were positively related to clay dispersion. Soil management and water transport downslope are probably influencing changes in soil properties and determining the distribution of dispersible clay contents along the catena. No relationships were observed between readily dispersible clay measured using turbidimeter and hydrometer in terms of quantity. Hydrometer and turbidimeter measurements can deliver significantly different results regarding dispersible clay quantification, potentially leading to misinterpretations concerning the amount of clay dispersed in water.
Źródło:
International Agrophysics; 2020, 34, 2; 273-280
0236-8722
Pojawia się w:
International Agrophysics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Free-Volume Studies in Polycaprolactone/Poly(propylene oxide) Urethane/Urea Membranes by Positron Lifetime Spectroscopy
Autorzy:
Ferreira Marques, M.
Gordo, P.
de Lima, A.
Queiroz, D.
Norberta de Pinho, M.
Major, P.
Kajcsos, Zs.
Powiązania:
https://bibliotekanauki.pl/articles/1812490.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.41.+e
78.70.Bj
82.30.Gg
Opis:
Positron annihilation lifetime spectroscopy was used to study the free volume parameters in polypropylene oxide-based tri-isocyanate terminated prepolymer/polycaprolactone diol bi-soft urethane/urea membranes (PU/PCL) with PCL content from 5 up to 25 wt%. Positron annihilation lifetime spectroscopy measurements carried out in the temperature range 298-324 K mirrored the phase separation of the various soft and hard segments present in the membranes. The size and amount of free volume holes determined by positron annihilation lifetime spectroscopy appear to be correlated with the $CO_2$ gas permeability through the membranes.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1359-1364
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Calculation of the influence of slot geometry on the magnetic flux density of the air gap
Autorzy:
Lima, R. A. de
Coimbra, A. C. P.
Almeida, T.
Gomes, V. M.
Pereira, T. M.
Alves, A. J.
Calixto, W. P.
Powiązania:
https://bibliotekanauki.pl/articles/136264.pdf
Data publikacji:
2017
Wydawca:
EEEIC International Barbara Leonowicz Szabłowska
Tematy:
Carter's factor
finite element method
rotating machines
Opis:
The objective of this work is to investigate the influence of slotted air gap constructive parameters on magnetic flux density of rotating machines. For this purpose, different approaches were used to solve the air gap field diagram using finite element method and the magnetic field distribution uniformity was evaluated by Carter's factor calculation on two-dimensional and three-dimensional models. Sensitivity analysis of slot constructive parameters was performed and results show that slot geometry modifies the magnetic flux on air gap and shifts the air gap magnetic equipotential midline of double slotted machines. Finally, minimization of Carter’s factor on two-dimensional model presents an optimized slot geometry with a near uniform magnetic flux density distribution.
Źródło:
Transactions on Environment and Electrical Engineering; 2017, 2, 1; 81-89
2450-5730
Pojawia się w:
Transactions on Environment and Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phytochemical potential of Ficus species for the control of the phytonematode Meloidogyne javanica
Autorzy:
Alves, J.R.
De Assis, J.N.
Padua, C.C.A.
Balbino, H.M.
Lima, L.L.
De Souza Gouveia, A.
Vital, C.E.
Buonicontro, D.S.
De Freitas, L.G.
Leite, J.P.V.
De Oliveira Ramos, H.J.
Powiązania:
https://bibliotekanauki.pl/articles/2082765.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
gas chromatography/mass spectrometry (GC/MS)
metabolite profiling
pest
control
phytochemistry
Opis:
Root-knot nematodes, genus Meloidogyne, are among the most plant damaging pathogens worldwide. The action of natural products against plant pathogens has been investigated to assess their effectiveness in the control of diseases. Thus, the present study aimed to evaluate the phytochemistry potential of the Ficus species for the control of Meloidogyne javanica. In vitro inhibitory activity assays were performed with crude ethanolic extracts of leaves and branches from 10 Ficus species. Among these, Ficus carica extracts exhibited strong paralysis activity against second stage juveniles (J2) (EC50 = 134.90 μg ∙ ml–1 ), after 72 hours. In addition, high efficacy was observed in egg-hatching inhibition at different embryonic stages. Microscopy analysis revealed severe morphological alterations in the nematode tissues at the J2 stage, as well as immotility of juveniles released from eggs in the presence of F. carica extracts. The efficacy of the treatments for the other species was very low. These differences were supported by the variation in the compound classes, mainly for alkaloids and metabolite profiles by Gas Chromatography/Mass Spectrometry (GC/MS) when F. carica was compared with the other species. The results indicated that F. carica is a promising source for the isolation and identification of molecules capable of acting in the control of M. javanica.
Źródło:
Journal of Plant Protection Research; 2020, 60, 2; 193-206
1427-4345
Pojawia się w:
Journal of Plant Protection Research
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-7 z 7

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