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Wyszukujesz frazę "Addition" wg kryterium: Temat


Wyświetlanie 1-2 z 2
Tytuł:
Changes of stainless steels surface morphology as a result of interaction with intense pulsed plasma beams containing ions of rare earth elements
Autorzy:
Sartowska, B.
Piekoszewski, J.
Waliś, L.
Składnik-Sadowska, E.
Barlak, M.
Powiązania:
https://bibliotekanauki.pl/articles/146323.pdf
Data publikacji:
2008
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
intense plasma pulses
stainless steel
surface modification
REE addition
Opis:
Among different methods used in surface engineering such as CVD, PVD, ion implantation etc., the techniques using high intensity ion or plasma beams are relatively new ones. The results reported thus far show that the treatment of steel surface with high intensity plasma pulses can lead to changes of its morphology and mechanical properties. Stainless steels have very good corrosion resistance, but they have low hardness and poor tribological properties. The intense pulsed plasma beams were used for modification of alloyed steels especially austenitic (1.4301 and 1.4401) and ferritic (1.4016) stainless steels with various content of alloying elements. Samples were irradiated with 2, 5 or 10 short (μs scale) intense (density of energy was about 5 J/cm2) pulses. Heating and cooling processes were of non-equilibrium type. In all samples the near surface layer of the thickness in μm range was melted and simultaneously doped with cerium and lanthanum. The aim of this work was to investigate the changes of stainless steel surface morphology after melting, rare earth elements (REE) addition and rapid solidification after interaction with intense pulsed plasma beams. The surface morphology was analyzed using a scanning electron microscopy (SEM) technique. Changes of surface roughness were determined by profilometric measurements. The efficiency of REE addition process was also determined.
Źródło:
Nukleonika; 2008, 53, suppl. 2; 43-48
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Computational study of substrate isotope effect probes of transition state structure for acetylcholinesterase catalysis
Autorzy:
Sikorski, R..
Malany, S.
Seravalli, J.
Quinn, D.
Powiązania:
https://bibliotekanauki.pl/articles/147114.pdf
Data publikacji:
2002
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
acetylcholinesterase
carbonyl addition reactions
enzyme mechanisms
quantum mechanical calculations
transition state structure
Opis:
Secondary isotope effects for carbonyl addition reactions of methyl thioacetate, acetone and acetaldehyde have been calculated by ab initio quantum mechanical methods in an effort to interpret measured beta-deuterium isotope effects on acetylcholinesterase- catalyzed hydrolysis of acetylthiocholine. The calculated beta-deuterium isotope effect for equilibrium addition of methanol to methyl thioacetate is D3Keq = 0.965, and the corresponding effect for addition of methoxide ion to methyl thioacetate wherein three waters are hydrogen bonded to the carbonyl oxyanion is D3Keq = 1.086. Neither of these calculated isotope effects is as inverse as the experimental beta-deuterium isotope effect for acetylcholinesterase-catalyzed hydrolysis of acetylthiocholine, D3kE = 0.90š0.03. Structural comparisons show that the water-solvated methoxide adduct of methyl thioacetate is more expanded than is the neutral methanol addition adduct, and suggest that the degree to which the isotope effect is inverse (i.e. less than) is inversely correlated to the degree of expansion of the adduct. A similar correlation of beta-deuterium and beta-deuterium secondary isotope effects with the degree of expansion of the adducts is found for equilibrium additions of methanol and methoxide ion to acetaldehyde. These computational results suggest that the markedly inverse beta-deuterium isotope effect for the acetylcholinesterase reaction arises from enzymic compression of the transition state.
Źródło:
Nukleonika; 2002, 47,suppl.1; 9-12
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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