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151.
Negative thermal expansion materials can experience significant stresses when they are used in composites. Under ambient conditions Zr2(WO4)(PO4)2 displays anisotropic negative thermal expansion (NTE) (, , , at 0 GPa). The effect of hydrostatic pressure on its thermal expansion characteristics was investigated by neutron diffraction between 300 and 60 K at pressures up to 0.3 GPa. No phase transitions were observed in the pressure and temperature range examined. The material was found to have a bulk modulus, B0, of 61.3(8) GPa at ambient temperature, and unlike some other NTE materials, pressure had no detectable effect on thermal expansion (, , , at 0.3 GPa). 相似文献
152.
A. H. Jay W. W. Stevenson E. W. Colbeck S. W. Craven W. Murray N. T. Wilkinson W. J. Agnew R. Treje C. Benedicks G. A. Medwedewa W. P. Remin F. Willems J. J. Berzelius Ed. Houdremont P. Klinger G. Blaschczyk P. Klineer und W. Koch 《Fresenius' Journal of Analytical Chemistry》1944,127(1):43-46
Ohne Zusammenfassung 相似文献
153.
Y. H. Chen C. I. Wilkinson J. Woodhead J. P. R. David C. C. Button P. N. Robson 《Journal of Crystal Growth》1997,170(1-4):394-398
Vertical cavity surface emitting lasers (VCSELs) based on InGaP lase in the visible close to 650 nm. The polarisation characteristics of these devices are unlike other VCSELs in that they are stable and reproducible and show no switching with increased current. We describe the polarisation characteristics for such devices where the structures were grown on different orientation wafers. We show that polarisation selectivity increases directly with the degree of spontaneous ordering in the InGaP quantum wells, but not with the wafer offset angle. 相似文献
154.
X-ray crystallographic study of K[OsO2(O2CMe)3]· 2MeCO2H shows that the anion has cis dioxo, one chelate and two trans monodentate acetato groups. 相似文献
155.
Wilkinson I Garcia IA Whitaker BJ Hamard JB Blanchet V 《Physical chemistry chemical physics : PCCP》2010,12(48):15766-15779
We present velocity map images of the NO, O((3)P(J)) and O((1)S(0)) photofragments from NO(2) excited in the range 7.6 to 9.0 eV. The molecule was initially pumped with a visible photon between 2.82-2.95 eV (440-420 nm), below the first dissociation threshold. A second ultraviolet laser with photon energies between 4.77 and 6.05 eV (260-205 nm) was used to pump high-lying excited states of neutral NO(2) and/or probe neutral photoproducts. Analysis of the kinetic energy release spectra revealed that the NO photofragments were predominantly formed in their ground electronic state with little kinetic energy. The O((3)P(J)) and O((1)S(0)) kinetic energy distributions were also dominated by kinetically 'cold' fragments. We discuss the possible excitation schemes and conclude that the unstable photoexcited states probed in the experiment were Rydberg states coupled to dissociative valence states. We compare our results with recent time-resolved studies using similar excitation and probe photon energies. 相似文献
156.
Air-trapping on biocompatible nanopatterns 总被引:1,自引:0,他引:1
Martines E Seunarine K Morgan H Gadegaard N Wilkinson CD Riehle MO 《Langmuir : the ACS journal of surfaces and colloids》2006,22(26):11230-11233
The occurrence of air-trapping inside poly-eta-caprolactone nanopits was investigated by measuring the contact angles of water droplets on a set of defined nanotopographies. It is shown that the advancing angles follow the Cassie-Baxter theory, thus revealing the presence of air bubbles inside the biodegradable nanopatterns. The importance of these observations for the definition of hydrophilicity/hydrophobicity and in the context of in vitro cell behavior is discussed. 相似文献
157.
Moss SJ Carletti I Olano C Sheridan RM Ward M Math V Nur-E-Alam M Braña AF Zhang MQ Leadlay PF Méndez C Salas JA Wilkinson B 《Chemical communications (Cambridge, England)》2006,(22):2341-2343
We report the directed biosynthesis of borrelidin analogues and their selective anti-proliferative activity against human cancer cell lines. 相似文献
158.
Fox OD Cookson J Wilkinson EJ Drew MG MacLean EJ Teat SJ Beer PD 《Journal of the American Chemical Society》2006,128(21):6990-7002
Polymetallic nanodimensional assemblies have been prepared via metal directed assembly of dithiocarbamate functionalized cavitand structural frameworks with late transition metals (Ni, Pd, Cu, Au, Zn, and Cd). The coordination geometry about the metal centers is shown to dictate the architecture adopted. X-ray crystallographic studies confirm that square planar coordination geometries result in "cagelike" octanuclear complexes, whereas square-based pyramidal metal geometries favor hexanuclear "molecular loop" structures. Both classes of complex are sterically and electronically complementary to the fullerenes (C(60) and C(70)). The strong binding of these guests occurred via favorable interactions with the sulfur atoms of multiple dithiocarbamate moieties of the hosts. In the case of the tetrameric copper(II) complexes, the lability of the copper(II)-dithiocarbamate bond enabled the fullerene guests to be encapsulated in the electron-rich cavity of the host, over time. The examination of the binding of fullerenes has been undertaken using spectroscopic and electrochemical methods, electrospray mass spectrometry, and molecular modeling. 相似文献
159.
160.
Small angle neutron scattering (SANS) and fluorescence correlation spectroscopy (FCS) measurements were carried out on agarose hydrogels to link their microscopic structure to the diffusivity of solutes at different scales. SANS allowed for the determination of the distribution of void volumes within the gels. They were shown to be compatible with a random network of cylindrical fibers as described by the Ogston model. FCS measured solute diffusivity in spaces similar in size to the void volumes, and thus, the results reflected the gel heterogeneity. Solute diffusivity was predicted by modeling the gel as microscopic geometrical cells. Variations in the diffusivity of solutes of different sizes could be predicted from the structural parameters of the gel using theory, taking into account obstruction by cylindrical cells and solute hydrodynamics. Prediction of the FCS autocorrelation functions for solutes from a cell model demonstrated a lack of sensitivity of this technique for multicomponent analysis. 相似文献