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61.
Nadja Radchenkova Spasen Vassilev Ivan Panchev Gianluca Anzelmo Iva Tomova Barbara Nicolaus Margarita Kuncheva Kaloyan Petrov Margarita Kambourova 《Applied biochemistry and biotechnology》2013,171(1):31-43
Synthesis of innovative exocellular polysaccharides (EPSs) was reported for few thermophilic microorganisms as one of the mechanisms for surviving at high temperature. Thermophilic aerobic spore-forming bacteria able to produce exopolysaccharides were isolated from hydrothermal springs in Bulgaria. They were referred to four species, such as Aeribacillus pallidus, Geobacillus toebii, Brevibacillus thermoruber, and Anoxybacillus kestanbolensis. The highest production was established for the strain 418, whose phylogenetic and phenotypic properties referred it to the species A. pallidus. Maltose and NH4Cl were observed to be correspondingly the best carbon and nitrogen sources and production yield was increased more than twofold in the process of culture condition optimization. After purification of the polymer fraction, a presence of two different EPSs, electroneutral EPS 1 and negatively charged EPS 2, in a relative weight ratio 3:2.2 was established. They were heteropolysaccharides consisting of unusual high variety of sugars (six for EPS 1 and seven for EPS 2). Six of the sugars were common for both EPSs. The main sugar in EPS 1 was mannose (69.3 %); smaller quantities of glucose (11.2 %), galactosamine (6.3 %), glucosamine (5.4 %), galactose (4.7 %), and ribose (2.9 %) were also identified. The main sugar in EPS 2 was also mannose (33.9 %), followed by galactose (17.9 %), glucose (15.5 %), galactosamine (11.7 %), glucosamine (8.1 %), ribose (5.3 %), and arabinose (4.9 %). Both polymers showed high molecular weight and high thermostability. 相似文献
62.
C. Risacher V. Belitsky V. Vassilev I. Lapkin A. Pavolotsky 《International Journal of Infrared and Millimeter Waves》2005,26(6):867-879
We present the results of the development of a 275–370 GHz, fixed-tuned double sideband (DSB) receiver based on superconductor-insulator-superconductor (SIS) junction mixer. The mixer block uses a full height rectangular waveguide and employs a novel radial-like probe structure with integrated bias-T. The measured uncorrected receiver noise temperature is 30–50 K corresponding to about 2–3 quantum noise across the full frequency band with an IF from 3.8 to 7.6 GHz. The mixer is to be used on the Atacama Pathfinder EXperiment (APEX) submillimeter telescope in Chile. 相似文献
63.
64.
A tensor invariant is defined on a quaternionic contact manifold in terms of the curvature and torsion of the Biquard connection involving derivatives up to third order of the contact form. This tensor, called quaternionic contact conformal curvature, is similar to the Weyl conformal curvature in Riemannian geometry and to the Chern–Moser tensor in CR geometry. It is shown that a quaternionic contact manifold is locally quaternionic contact conformal to the standard flat quaternionic contact structure on the quaternionic Heisenberg group, or equivalently, to the standard 3-Sasakian structure on the sphere iff the quaternionic contact conformal curvature vanishes. 相似文献
65.
Chalcogenide glasses from the Ag2Te-As2Se3-CdTe system were synthesized. The basic physicochemical parameters such as density (d), microhardness (HV) and the temperatures of phase transformations (the glass transition Tg, crystallization Tcr and melting Tm) were measured. Compactness and some thermomechanical characteristics such as volume (Vh) and formation energy (Eh) of micro-voids in the glassy network, as well as the module of elasticity E were calculated. The overall mean bond energy 〈E〉, the mean coordination number Z, the mean bond energy of the average cross-linking/atom and the average bond energy per atom of the “remaining matrix”— and , as well as the average heteropolar bond energy Ehb, the degree of “cross-linking/atom” Pp and the radial bond strength were determined.The correlation between the composition and properties of the Ag2Te-As2Se3-CdTe glasses was established and comprehensively discussed. 相似文献
66.
K. Konstantinov S. Karbanov V. Vassilev 《Zeitschrift für Physik B Condensed Matter》1990,81(2):151-154
The effect of Sb superconducting materials with nominal composition Bi1.6Pb0.4–x
Sb
x
Sr2Ca2Cu3O
y
(x=0.01–0.14) and Bi1.5Pb0.5–x
Sb
x
Sr2Ca2Cu3O
y
(x=0.025–0.12) has been investigated. These materials were subjected to DTA, ICP emission spectrometry, SEM, XRD and electric resistance measurements. It was found that the introduction of Sb raises the melting temperature of the material, it also raisesT
c
(up to 110K) at several defined stoichiometric ratios. A certain lack of correspondence between the 2223 phase volume and theT
c
value was noticed and a possible explanation has been proposed. 相似文献
67.
Helmut Duddeck Blagoy Blagoev Nikolina D. Berova Vassil Vassilev 《Magnetic resonance in chemistry : MRC》1983,21(2):122-124
Three diastereomeric bornane derivatives have been assigned configurational structures by 13C NMR measurements in the presence of Yb(dpm)3. 相似文献
68.
X‐Ray, DSC and magnetic susceptibility measurements were performed with NiBi specimens in the interval from room temperature to 700 K. The hypothesis of solid‐state transitions in this phase was not confirmed. Thermal and magnetic effects are observed, but they are due to the existence of small amount of phases others than NiBi (i.e. unreacted Ni and Bi). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
69.
Phosphonylmethylaminocyclopentane‐1‐carboxylic acid was synthesized using Kabachnik–Fields reaction conditions in high yield and was characterized by NMR (1H, 31P, and 13C) and FAB spectroscopy. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:229–230, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10124 相似文献
70.
G. P. Vassilev 《Crystal Research and Technology》1991,26(3):345-347
The correlation between the short range parameters and some thermodynamic properties has been examined for 44 binary alloys. Qualitative agreements have been obtained in the majority of the systems. Some previsions have been made for the controversially cases. 相似文献