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91.
Samples of two high-density polyethylenes having different crystallinity levels were gamma irradiated under vacuum at doses ranging from 20 to 300 kGy. Subsequently, the vials containing the irradiated samples were exposed to different post-irradiation treatments. Parts of the specimens were annealed while still under vacuum. The annealing time was 4 h and the annealing temperatures 110 °C or 150 °C. Others were exposed directly to air opening the vials without any thermal treatment. It was verified that in all cases the dosage to produce an incipient gel increases with the crystallinity of the initial sample. The amount of gel produced after exposing specimens of the same polymer to a given dose increases with the annealing temperature. The largest increment in the amount of gel produced at the completion of the post-irradiation treatment was found on the samples with the highest initial crystallinity level.Evidence of oxidation was found in all irradiated samples. The extent of oxidation depends on the initial crystallinity of the sample, the irradiation dose and the type of post-irradiation treatment. The heat of fusion measured in the annealed samples decreases with the gel content while the fusion temperature was slightly affected. Ductile or brittle behaviors were observed after testing specimens under tensile stress. The yield stress increases proportionally to the crystallinity level that, in turn, depends on the total dosage applied to the samples. The extensibility of ductile samples is determined by the amount of gel produced regardless of the degree of initial crystallinity and the type of annealing process applied to each sample. 相似文献
92.
Mamie Sancy Jorge Pavez Miguel A. Gulppi Ivanildo Luiz de Mattos Ramiro Arratia‐Perez Cristian Linares‐Flores Maritza Paez Tebello Nyokong José H. Zagal 《Electroanalysis》2011,23(3):711-718
We have studied the trends in catalytic activity of several Co macrocyclics confined on the surface graphite electrodes for the oxidation of thiocyanate. A plot of log i (at constant E) versus the formal potential of the catalyst gives a volcano correlation, indicating that the Co(II/I) redox potential needs to be tuned, in order to achieve maximum reactivity. Graphite electrodes modified with Co phthalocyanine at pH 4 exhibit linear amperometric response for thiocyanate concentration in the range 10?7 and 10?3 M. Theoretical calculations show that electrocatalytic activity (as log i at constant E) plotted versus the energy of the LUMO of the Co complex also gives a volcano correlation. 相似文献
93.
94.
V. Hernandez Perez B.J. Azzopardi R. Kaji M.J. da Silva M. Beyer U. Hampel 《International Journal of Multiphase Flow》2010,36(11-12):908-915
A conductance wire mesh sensor system has been employed on a vertical 67 mm diameter pipe with the up flow of air and water mixtures. The measuring system provides time and cross-sectionally resolved information about the spatial distribution of the phases. Statistical information can be extracted and used to identify flow patterns. The fully resolved data has revealed a hitherto unreported structure has been seen in churn flow which could be linked to the wisps in wispy-annular flow. 相似文献
95.
Filip Cuyckens Rob Hurkmans Jose M. Castro‐Perez Laurent Leclercq Russell J. Mortishire‐Smith 《Rapid communications in mass spectrometry : RCM》2009,23(2):327-332
Mass defect, neutral loss and isotope filtration techniques were applied to electrospray ionization mass spectrometry (ESI‐MS) data obtained for in vivo and in vitro samples of drug metabolism studies. A combination of these post‐acquisition processing techniques was shown to be more powerful than the use of one of these tools alone for the detection in complex matrices of metabolites of candidate drugs with a characteristic isotope pattern (e.g. containing bromine, chlorine, or a high proportion of radiolabeled drug (12C/14C)) or characteristic neutral losses. In combination with ‘all‐in‐one’ data acquisition this methodology is able to perform software‐driven constant neutral loss scanning for an unlimited number of mass differences at any time after analysis. Highly selective MS chromatograms were obtained with excellent correlation with their corresponding radiochromatograms. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
96.
D. Oyola Lozano L. E. Zamora G. A. Perez Alcazar Y. A. Rojas H. Bustos J. M. Greneche 《Hyperfine Interactions》2005,161(1-4):203-209
In this work we report the magnetic and structural properties obtained by Mössbauer spectrometry, Vibrating Sample Magnetometer and X-ray diffraction of milled powders with initial composition Nd2(Fe100 ? x Nb x )14B with x = 0 and x = 4. The mixtures were ball milled for different times up to 240 h. Structural and microstructural parameters were derived from high statistics X-ray patterns and discussed as a function of milling time. The Mössbauer spectra of the samples were fitted by means of a sextet and an hyperfine field distribution, associated to a pure iron phase (α-Fe) and a disordered iron-based phase, respectively. The α-Fe grain size decreases from 50 nm for 6 h up to 5 nm for 240 h milling time. The Vibrating Sample Magnetometer results allow to conclude that these samples behave as soft ferromagnets. 相似文献
97.
J. Cederkäll M. Lipoglavšek M. Palacz J. Persson J. Blomqvist A. Ataċ C. Fahlander H. Grawe A. Johnson W. Klamra J. Kownacki A. Likar L.–O. Norlin J. Nyberg R. Schubart D. Seweryniak G. de Angelis P. Bednarczyk Z. Dombrádi D. Foltescu M. Górska D. Jerrestam S. Juutinen E. Mäkelä B. M. G. Perez M. de Poli H. A. T. Shizuma Ö. Skeppstedt G. Sletten S. Törmänen 《The European Physical Journal A - Hadrons and Nuclei》1998,1(1):7-9
New excited states have been observed in the neutron deficient isotope 98Ag following the 58Ni+50Cr →108Te* heavy–ion reaction. One of these states may be interpreted as a maximum spin aligned state of the πg9/2
−3νg7/2 configuration. Other possible interpretations within the nuclear shell model are discussed as well.
Received: 24 October 1997 相似文献
98.
J.Hernández Mendez R.Carabias Martínez E.Rodriguez Gonzalo J.Perez Trancon 《Analytica chimica acta》1990
The amperometric determination of parathion in the presence of its metabolites paraoxon and p-nitrophenol in a flow-injection system is reported. The method is based on the measurement of the oxidation signal yielded by p-nitrophenol on hydrolysis of parathion in the presence of Pd(II) or Hg(II). The oxidation of the metabolite was preferred to its reduction as it avoids the removal of oxygen, which poses major problems in flow-through configurations. 相似文献
99.
Patrizia Cafarelli Adriana De Stefanis Giorgio Perez Anthony A.G. Tomlinson 《Reaction Kinetics and Catalysis Letters》2005,86(1):163-169
Summary Pillared clays have been monitored for catalytic destruction of halocarbons. In comparison with HZSM-5 zeolites, the catalysts tested give higher chlorohydrocarbons destruction with polymers formation. Fluorochlorohydro-carbons are destroyed as well. 相似文献
100.
Perez F Aku-leh C Richards D Jusserand B Smith LC Wolverson D Karczewski G 《Physical review letters》2007,99(2):026403
The g-factor enhancement of the spin-polarized two-dimensional electron gas was measured directly over a wide range of spin polarizations, using spin flip resonant Raman scattering spectroscopy on two-dimensional electron gases embedded in Cd(1-x)Mn(x)Te semimagnetic quantum wells. At zero Raman transferred momentum, the single-particle spin flip excitation, energy Z*, coexists in the Raman spectrum with the spin flip wave of energy Z, the bare giant Zeeman splitting. We compare the measured g-factor enhancement with recent spin-susceptibility enhancement theories and deduce the spin-polarization dependence of the mass renormalization. 相似文献