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991.
The object under study is an aortic valve, located in the aortic annulus. The aortic valve leaflet has been assumed to be a three-dimensional object. The computations were performed using the Ansys Multiphysics system. The result of our analysis takes the form of a model describing the interaction between two domains. The opening of the aortic valve model was obtained by iteration process. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
992.
Neli Koseva Piotr Kurcok Grazyna Adamus Kolio Troev Marek Kowalczuk 《Macromolecular Symposia》2007,253(1):24-32
Summary: Results on synthesis of poly(3-hydroxybutyrate)s possessing one or two hydroxyl groups at one terminus of the chain and carboxylic group at the other chain end are reported. These polymers were further functionalised via transesterification with dimethyl H-phosphonate thus incorporating a reactive/biodegradable center in the polyester backbone. Block/star-like copolymers composed of hydrophilic PEG and hydrophobic poly(3-hydroxybutyrate) segments linked by phosphoester moiety were also obtained. Chemical structure and composition of the reaction products were analysed applying different spectroscopic techniques (1H, and 31P NMR, IR and ESI-MS) and size exclusion chromatography was applied to describe molecular weight averages and distribution. 相似文献
993.
994.
Marek Kozicki Piotr Maras Krzysztof Rybka Tadeusz Biegański Sławomir Kadłubowski Loukas Petrokokkinos 《Macromolecular Symposia》2007,254(1):345-352
Summary: The new polymer gel dosimeter, based on the modification of the VIPAR gel composition, is described for the purpose of radiation dose distribution measurement in radiotherapy. It features increased concentration of the two VIPAR substrates: N-vinylpyrrolidone (8%) and gelatine (7.5%) (N,N′-methylenebisacrylamide was maintained at 4%), and the addition of copper sulphate (0.0008%) and ascorbic acid (0.007%) in order to facilitate the preparation through elimination of the need for deoxygenation of the gel. Following the exposure to ionizing radiation, polymerisation and cross-linking of the new gel monomers occurs retaining the spatial distribution of absorbed dose and causing opacity of the gel. Quantitative parameters of the new gel dose response were studied using magnetic resonance imaging to relate polymerisation induced physicochemical changes of the gel to dose. The dose threshold is found significantly lower than that of the original VIPAR gel. The linear part of measured spin-spin relaxation rate R2(D) ( = 1/T2(D)) reaches up to 35 Gy. Its slope and an intercept are slightly higher relative to the original VIPAR. The efficiency of the new polymer gel-magnetic resonance imaging dosimeter was also tested for dose verification of a 3D dose distribution planned by a commercially available treatment planning software (Eclipse External Beam v.6.5) and delivered by a 6 MV medical linear accelerator. The new polymer gel is proposed to be called, VIPARnd (after VIPAR-normoxic-double). 相似文献
995.
Piotr Koziol Cristinel Mares Ibrahim Esat 《International Journal of Solids and Structures》2008,45(7-8):2140-2159
The paper analyses theoretically the surface vibration induced by a point load moving uniformly along a infinitely long beam embedded in a two-dimensional viscoelastic layer. The beam is placed parallel to the traction-free surface and the layer under the beam is assumed to be a half space. The response due to a harmonically varying load is investigated for different load frequencies. The influence of the layer damping and moving load speed on the level of vibrations at the surface is analysed and analytical closed form solutions in the integral form for the displacement amplitude and the amplitude spectra are derived. Approximate displacement values depending on Young’s modulus and mass density of layers are obtained. The mathematical model is described by the Euler–Bernoulli beam equation, Navier’s elastodynamic equation of motion for the elastic medium and appropriate boundary and continuity conditions. A special approximation method based on the wavelet theory is used for calculation of the displacements at the surface. 相似文献
996.
An efficient method for the synthesis of nojirimycin- and pyrrolidine-based iminosugar derivatives has been developed. The strategy is based on the partial reduction in sugar-derived lactams by Schwartz’s reagent and tandem stereoselective nucleophilic addition of cyanide or a silyl enol ether dictated by Woerpel’s or diffusion control models, which affords amino-modified iminosugars, such as ADMDP or higher nojirimycin derivatives. 相似文献
997.
998.
The analysis presented focuses on the extent to which the thermal loading resulting from a difference between the curing and service temperatures and from variations in the thermal-expansion coefficients from layer to layer can affect the growth of delaminations. Square laminate plates containing circular delaminations are examined. The reinforcement combinations for the delaminated layer and the core plate considered are [0°]/[90°], [90°]/[0°], [0°]/[±45°]
s
, and [±45°]
s
/[0°]. The analysis is carried out using the FEM. The strain energy release rate components are calculated using the modified crack-closure integral method. The results obtained show that, for all the reinforcement combinations studied, with the exception of [±45°]
s
/[0°], a temperature drop considerably reduces all the strain energy release rate components, but only minor changes in their proportion occur. In the case of the [±45°]
s
/[0°] plates, all these components increase, and noticeable changes in their proportion are also observed. 相似文献
999.
M. Czanta C. Strietzel H. J. Besch H. F. Beyer F. Bosch R. Deslattes F. Förster A. Gumberidze G. Hölzer P. Indelicato C. Kozhuharov O. Klepper A. Krämer D. Liesen T. Ludziejewski X. Ma B. Manil G. Menzel N. Pavel A. Simionovici M. Steck T. Stöhlker S. Toleikis J. Tschischgale A. H. Walenta O. Wehrhan 《Hyperfine Interactions》2001,132(1-4):487-490
Crystal spectrometry and absorption edge technique have the capability to overcome the gap in accuracy between experiment
and theory in the strong field domain of QED. New results are presented which indicate the capacity of these methods to measure
the energies of X-rays emitted by highly charged heavy ions at modern storage rings with a precision sensitive to second order
corrections to the Lambshift in H-like very heavy ions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
1000.
M. Králorá H. Mouchorá J. Janoušek 《Isotopes in environmental and health studies》2013,49(11):435-436
Es war Ziel dieser Arbeit, zu ermitteln, welchen Einfluß höhere Dosen von Stickstoffdüngemitteln in Form von KNO3 auf die Menge des in der Pflanze fixierten Luftstickstoffs haben. Als Versuchspflanze wählten wir Pferdebohnen (Vicia faba, Chlumetzer Abart) wegen ihrer vielseitigen Verwendung in der Landwirtschaft und ihrer besonderen experimentellen Eignung. 相似文献