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931.
Leda M. F. Gottschalk Ronaldo Nobrega Elba P. S. Bon 《Applied biochemistry and biotechnology》2003,108(1-3):799-807
The effect of aeration on lignin peroxidase production by Streptomyces viridosporus T7A was studied in a bench-scale bioreactor using a previously optimized growth medium (0.65% yeast extract and 0.1% corn
oil, pH7.0) at 37°C and natural pH. Airflow rates of 0.3, 1.0, and 1.5 vvm and a fixed agitation of 200 rpm were initially
studied followed by 1.0 vvm and 200, 300, 400, and 500 rpm. The use of 1.0 vvm and 400 rpm increased enzyme concentration
1.8-fold (100–180 U/L) and process productivity 4.8-fold (1.4–6.7 U/[L·h]) in comparison with the use of 200 rpm and 0.3 vvm.
The inexpensive corn oil, used as carbon source, besides its antifoam properties, proved to be nonrepressive for enzyme production. 相似文献
932.
We study the ill-posedness question for the one-dimensional Zakharov system and a generalization of it in one and higher dimensions. Our point of reference is the criticality criteria introduced by Ginibre, Tsutsumi and Velo (1997) to establish local well-posedness.
933.
R. F. Mamin S. A. Migachev M. F. Sadykov I. V. Lunev V. V. Izotov Yu. A. Gusev 《JETP Letters》2003,78(11):718-721
The action of illumination on the conducting and dielectric properties of lead magnoniobate was investigated. The photostimulated currents were examined and the spectral dependence of photoconductivity in the region of diffuse phase transition was obtained. It was found that the illumination affects the dielectric properties and that its action is memorized at temperatures below room temperature. The role of defect states in the formation of relaxor properties is discussed on the basis of the obtained data. 相似文献
934.
A. Cannizzo R. Boscaino F.M. Gelardi M. Leone 《Journal of Physics and Chemistry of Solids》2003,64(12):2437-2443
We report an experimental study on the relationship between the optical activity of Ge-oxygen deficient centers and dynamic properties and conformational heterogeneity of vitreous matrix in silica. We focus our attention on the absorption band at ∼5.2 eV (B2β) and on the two related emissions at ∼4.2 eV (αE) and at ∼3.1 eV (β). From the temperature dependence of B2β band we estimate a mean energy value of 26 meV for local vibrational modes coupled to the electronic transition, suggesting that the chromophore and its surrounding have access to low frequency dynamics. From the thermal behavior of the two emissions we distinguish the two competitive relaxation processes from the first singlet excited state S1: the radiative one, giving rise the αE band, and the thermally activated intersystem-crossing process between S1 and the triplet state T1, originating the β band. The intersystem-crossing rate increases on increasing the temperature, determining an opposite thermal behavior of the intensity of the two emissions. However, this temperature dependence cannot be rationalized by a simple Arrhenius law and the αE decay kinetics at high temperatures do not follow a single exponential law, suggesting a complex landscape of configurational energies of the process. 相似文献
935.
Bobik V. V. Bobonich F. M. Belokopytov Yu. V. 《Theoretical and Experimental Chemistry》2003,39(6):364-368
We have used potentiometric titration with tetrabutylammonium hydroxide to determine the acid center content on the outer surface of dealuminated natural and synthetic mordenites. We have established a symbatic relationship between the 2,2-dimethylbutane content in the hydroisomerization products of n-hexane on dealuminated palladium-containing mordenites and the number of their external acid centers. We have studied the possibility of partial deactivation of such centers during ion-exchange deposition of palladium on the catalysts, using a tetraammine palladium solution. 相似文献
936.
937.
938.
Microscopic petrified grains were collected from a mafic–ultramafic pipe, NE of Dreikeesh, NW Syria. The grains were identified as anthers/gynoecia in herb/grass flowers. Three of the grains showed evidence of magnetism, two slowly dissolved in concentrated HCl, and three microprobed grains showed a montmorillonitic composition. Iron originating from pyroxene was oxidized to magnetite. Released silica formed the mineral suite agate–chalcedony–opal. Warm/cold paleoclimatic fluctuations, occurring during late Pliocene–Holocene, depended on water vapor, CO2 production, and cinders in the atmosphere. Most of these were associated with changing volcanic/tectonic events. Fluctuations were controlled by heat reflected from the Earth's surface being absorbed by water vapor and CO2, which both re-reflected the heat back to the surface, thus, raising the temperature. This cycle was repeated several times during late Pliocene–Holocene. 相似文献
939.
Delauré B. Beck M. Golovko V. V. Kozlov V. Phalet T. Schuurmans P. Severijns N. Vereecke B. Versyck S. Beck D. Quint W. Ames F. Reisinger K. Forstner O. Deutsch J. Bollen G. Schwarz S. 《Hyperfine Interactions》2003,150(1-4):91-105
We present data from three seasons of experimental field work designed to recreate ancient Andean coastal ceramic firing techniques. Based on the recent discovery of two different archaeological ceramic production sites in the La Leche river valley of northern coastal Peru, the opportunity arose to apply Mössbauer spectroscopy and other analytical methods to reconstruct ancient firing procedures. Two sets of firings took place in 1993 and 1997 in Batán Grande using a partially restored Formative kiln from about 800 BC, local hardwood and cow dung as fuel. A third experiment followed in 2000 after the discovery of a Middle Sicán ceramics workshop in use between ca. AD 950 and 1050 at Huaca Sialupe, where an exact replica of an ancient kiln was built from local clay, and fired with local wood and cow dung. Additionally, inverted urns found at Huaca Sialupe were tested for their potential use as furnaces for metal working. Mössbauer spectroscopy was used to compare the physical and chemical state of specimens produced in the field experiments with ancient ceramics and with specimens produced in controlled laboratory experiments. 相似文献
940.