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121.
Microwave heating of ceramic composites 总被引:1,自引:0,他引:1
The microwave heating of a ceramic composite is modelled andanalysed. The composite consists of many small ceramic particlesembedded in a ceramic cement. The composite is assumed to bewell insulated, and each particle is assumed to be in imperfectthermal contact with the surrounding cement. Based on thesetwo assumptions an asymptotic theory exploiting the small Biotnumber and small non-dimensional contact conductance is developed.Our asymptotic theory yields a set of nonlinear partial differentialequations which govern the temperature in the composite. Theseare reduced to a set of coupled nonlinear ordinary differentialequations in which the surface area of each particle entersas a parameter. Recent experiments with such composites haveshown that the steady-state temperature of the composite isstrongly dependent upon the radii of the embedded particles.Our model captures this effect. In fact, our analysis showsthat the assumption of imperfect thermal contact between theparticles and the ceramic cement is essential for this trendto be established. 相似文献
122.
Two new dipeptide isosteres derived from L-leucine and meso-tartaric acid derivatives, named 6-endo-BTL and 6-endo-BtL, were inserted in a small peptide by means of SPPS, and the conformational features of the resulting peptides 3 and 4 were studied by NMR, IR, and molecular modeling techniques. The presence of a reverse turn conformation was observed in all the structures, suggesting the key role of the scaffolds as reverse turn promoters. Peptides 3 and 4 did not adopt a preferred conformation as indicated by the presence of equilibria between open turn and intramolecular hydrogen-bonded structures. 6-endo-BTL-peptide 3 showed a 3:1 mixture of conformers. The major conformer adopted mainly an open turn structure in equilibrium with hydrogen-bonded structures. The minor conformer displayed a better organized structure with a 14-membered ring hydrogen-bond typical of a beta-hairpin-like structure, in equilibrium with a gamma-turn, too. 6-endo-BtL-peptide 4 showed a unique conformer, and did not adopt as good a conformation as 3, due to the bulky equatorial substituent at C-2. Thus, marked structural differences between peptides containing 6-endo-BTL and 6-endo-BtL scaffolds as reverse turn inducers exist. 相似文献
123.
Avi Efraty J. Potenza S.S. Sandhu R. Johnson M. Mastropaolo R. Bystrek D.Z. Denney R.H. Herber 《Journal of organometallic chemistry》1974,70(2):C24-C26
Nucleophilic addition of phosphines to the cyclobutadiene ring in [(h4-C4H4)Fe(CO)2 NO]+PF6? leads to the formation of (exo-phosphonium-h3-cyclobutenyl) dicarbonylnitrosyliron hexafluorophosphate. 相似文献
124.
Drew AJ Lee SL Charalambous D Potenza A Marrows C Luetkens H Suter A Prokscha T Khasanov R Morenzoni E Ucko D Forgan EM 《Physical review letters》2005,95(19):197201
Superconducting and magnetic order are usually mutually exclusive, and are found to coexist in relatively few materials. We have obtained direct evidence for a spin-density wave (SDW) coexisting with bulk superconductivity in a ferromagnetic-superconducting trilayer. In the superconducting state the amplitude of the SDW is enhanced and modeling the data also suggests a pi/2 phase shift of one component of the SDW, implying a profound coupling of these two forms of order. 相似文献
125.
Bernardi A Arosio D Manzoni L Monti D Posteri H Potenza D Mari S Jiménez-Barbero J 《Organic & biomolecular chemistry》2003,1(5):785-792
Two new cholera toxin (CT) ligands (4 and 5) are described. The new ligands were designed starting from the known GM1 mimics 2 and 3 by replacement of their GalNAc residue with the C4 isomer GlcNAc. As predicted by molecular modelling, the conformational properties of the equivalent pairs 2-4 and 3-5 are very similar and their affinity for CT is of the same order of magnitude. NMR experiments have also proved that 5 occupies the GM1-binding site of the toxin and have revealed its bound conformation. 相似文献
126.
127.
Mode degeneration and mode conversion in multimode optical fibres are the main subjects of this work. In particular it is shown how fluctuations of the core shape can cause a rapid degeneration among the modes with the same azimuthal mode number. This allows a rigorous single variable approach to the second problem obtaining evident simplifications. The formalism proposed is applied to the study of mode distribution in the general case of microbending, of core-radius fluctuations in fibres with power law profiles and for simultaneous presence of microbending and ellipticity in parabolic fibres with differential mode attenuation. 相似文献
128.
A two-photon laser-induced fluorescence study on the transport of ground-state atomic hydrogen in a supersonic plasma jet, generated from an Ar-H (2) mixture, reveals an unexpected shock pattern. Whereas both the axial-velocity profile and the temperature profile of hydrogen atoms along the jet centerline can be interpreted in terms of a supersonic expansion of an Ar-H gas mixture, the H-atom density profiles do not satisfy the well established Rankine-Hugoniot relation leading to a nonconservation of the forward flux. The experimental results show that H atoms escape from the supersonic expansion by a diffusion process due to strong density gradients between the core of the jet and its vicinity. 相似文献
129.
Three-dimensional holographic images of extended diffusing objects are simultaneously recorded and reconstructed by optical cross correlation in a second-order nonlinear crystal. An interaction geometry in which the phase-matched object and reference fields propagate slightly noncollinearly is particularly convenient for producing these second-harmonic-generated holograms. 相似文献
130.
Silvia Panzeri Daniela Arosio Silvia Gazzola Laura Belvisi Monica Civera Donatella Potenza Francesca Vasile Isabell Kemker Thomas Ertl Norbert Sewald Oliver Reiser Umberto Piarulli 《Molecules (Basel, Switzerland)》2020,25(24)
Integrin ligands containing the tripeptide sequences Arg-Gly-Asp (RGD) and iso-Asp-Gly- Arg (isoDGR) were actively investigated as inhibitors of tumor angiogenesis and directing unit in tumor-targeting drug conjugates. Reported herein is the synthesis, of two RGD and one isoDGR cyclic peptidomimetics containing (1S,2R) and (1R,2S) cis-2-amino-1-cyclopentanecarboxylic acid (cis-β-ACPC), using a mixed solid phase/solution phase synthetic protocol. The three ligands were examined in vitro in competitive binding assays to the purified αvβ3 and α5β1 receptors using biotinylated vitronectin (αvβ3) and fibronectin (α5β1) as natural displaced ligands. The IC50 values of the ligands ranged from nanomolar (the two RGD ligands) to micromolar (the isoDGR ligand) with a pronounced selectivity for αvβ3 over α5β1. In vitro cell adhesion assays were also performed using the human skin melanoma cell line WM115 (rich in integrin αvβ3). The two RGD ligands showed IC50 values in the same micromolar range as the reference compound (cyclo[RGDfV]), while for the isoDGR derivative an IC50 value could not be measured for the cell adhesion assay. A conformational analysis of the free RGD and isoDGR ligands by NMR (VT-NMR and NOESY experiments) and computational studies (MC/EM and MD), followed by docking simulations performed in the αVβ3 integrin active site, provided a rationale for the behavior of these ligands toward the receptor. 相似文献