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91.
Simulation of the Adhesion of Particles to Surfaces 总被引:1,自引:0,他引:1
The removal of micrometer and submicrometer particles from dielectric and metal films represents a challenge in postchemical mechanical polishing cleaning. Proper modeling of the adhesive force between contaminant particles and these films is needed to develop optimal solutions to postchemical mechanical polishing cleaning. We have previously developed and experimentally validated a model to describe the adhesion between spherical particles and thin films. This simulation expands previous models to characterize the adhesive interaction between asymmetrical particles, characteristic of a polishing slurry, and various films. Our simulation accounts for the contact area between particles and substrates, as well as the morphology of the surfaces. Previous models fail to accurately describe the contact of asymmetrical particles interacting with surfaces. By properly accounting for nonideal and geometry and morphology, the simulation predicts a more accurate adhesive force than predictions based upon an ideal van der Waals model. The simulation is compared to experimental data taken for both semi-ideal particle-substrate systems (polystyrene latex spheres in contact with silicon films) and asymmetrical systems (alumina particles in contact with various films). Copyright 2001 Academic Press. 相似文献
92.
Yanyan Zhao Ole Tietz Wei-Li Kuan Abdul K. Haji-Dheere Stephen Thompson Benjamin Vallin Elisabetta Ronchi Gergely Tth David Klenerman Franklin I. Aigbirhio 《Chemical science》2020,11(18):4773
Soluble forms of aggregated tau misfolded protein, generally termed oligomers, are considered to be the most toxic species of the different assembly states that are the pathological components of neurodegenerative disorders. Therefore, a critical biomedical need exists for imaging probes that can identify and quantify them. We have designed and synthesized a novel fluorescent probe, pTP-TFE for which binding and selectivity profiles towards aggregated tau and Aβ proteins were assessed. Our results have shown pTP-TFE to be selective for early forms of soluble tau aggregates, with high affinity of dissociation constants (Kd) = 66 nM, and tenfold selectivity over mature tau fibrils. Furthermore, we found that pTP-TFE is selective for tau over Aβ aggregates and had good cell permeability. This selectivity of pTP-TFE towards early forms of aggregated tau protein ex vivo was also supported with studies on human brain tissue containing tau and Aβ pathology. To the best of our knowledge, this is the first fluorescent molecule to be reported to have this form of selectivity profile, which suggests that pTP-TFE is a unique probe candidate for imaging-based detection of early stages of Alzheimer''s disease and other tauopathies. pTP-TFE imaging probe can distinguish soluble tau aggregated proteins from other aggregated proteins enabling earlier detection of neurodegenerative diseases. 相似文献
93.
Lee B Seifert S Riley SJ Tikhonov G Tomczyk NA Vajda S Winans RE 《The Journal of chemical physics》2005,123(7):074701
The size evolution of platinum nanoparticles formed on a SiO2/Si(111) substrate as a function of the level of surface coverage with deposited clusters has been investigated. The anisotropic shapes of sub-nanometer-size nanoparticles are changed to isotropic on the amorphous substrate as their sizes increased. Using anomalous grazing incidence small-angle x-ray scattering (AGISAXS), the scattering from nanoparticles on the surface of a substrate is well separated from that of surface roughness and fluorescence. We show that AGISAXS is a very effective method to subtract the background and can provide unbiased information about particle sizes of less than 1 nm. 相似文献
94.
Graham DL Lowe PN Grime GW Marsh M Rittinger K Smerdon SJ Gamblin SJ Eccleston JF 《Chemistry & biology》2002,9(3):375-381
The formation of complexes between small G proteins and certain of their effectors can be facilitated by aluminum fluorides. Solution studies suggest that magnesium may be able to replace aluminum in such complexes. We have determined the crystal structure of RhoA.GDP bound to RhoGAP in the presence of Mg(2+) and F(-) but without Al(3+). The metallofluoride adopts a trigonal planar arrangement instead of the square planar structure of AlF(4)(-). We have confirmed that these crystals contain magnesium and not aluminum by proton-induced X-ray emission spectroscopy. The structure adopted by GDP.MgF(-) possesses the stereochemistry and approximate charge expected for the transition state. We suggest that MgF3(-) may be the reagent of choice for studying phosphoryl transfer reactions. 相似文献
95.
Isoelectric focusing within a fused silica capillary (cIEF) has proved to be a powerful and practical method for high-resolution separation of analytes from complex biological mixtures. This technique overcomes many of the problems of isoelectric focusing within slab gel media. However current cIEF systems commonly utilize UV detection which limits the detail of analyte structural information that is obtained during analysis. The use of mass spectrometry (MS) as the detection system provides much greater structural information about the detected analytes allowing accurate relative molecular mass (M(r)) determination for proteins and polypeptides. We have constructed a cIEF-MS interface and compared the separation of standard proteins analyzed by cIEF-UV with cIEF-MS. This allowed rapid optimization of the cIEF-MS system performance. Further we have demonstrated the use of MS as a detection system provides accurate M(r) information and can provide analyte modification details. These factors increase the likelihood of absolute identification for physiological proteins within complex in vivo-derived mixtures. To demonstrate the value of cIEF-MS in such analyses we have undertaken an examination of cerebrospinal fluid (CSF), and tentatively identified a number of constituent proteins. We have also analyzed whole blood from control and diabetic patients. We show that glycated alpha- and beta- chains of hemoglobin are found in almost equal abundance in diabetic patient blood. From these results we suggest cIEF-MS is an efficient and useful tool for the separation and examination of in vivo-derived analytes within physiological fluids. 相似文献
96.
Cy(3)PCuMe (1) undergoes reversible ligand redistribution at low temperature in solution to form the tight ion pair [Cu(PCy(3))(2)][CuMe(2)] (3). The structure of 3 was assigned on the basis of (i) the stoichiometry of the 1 = 3 equilibrium, (ii) the observation of a triplet for the PCy(3) C1 (13)C NMR resonance due to virtual coupling to two (31)P nuclei, and (iii) reverse synthesis of 1 by combining separately generated Cu(PCy(3))(2)(+) and CuMe(2)(-) ions. Complex 1 and [Cu(PCy(3))(2)][PF(6)] (5) coordinate additional PCy(3) to form (Cy(3)P)(2)CuMe and [Cu(PCy(3))(3)][PF(6)], respectively, while 3 does not. Complex 1, free PCy(3), and (bipy)(2)FeEt(2) (2) each initiate the polymerization of acrylonitrile. In each case, the polyacrylonitrile contains branches that are characteristic of an anionic polymerization mechanism. The major initiator in acrylonitrile polymerization by 1 is PCy(3), which is liberated from 1. A transient iron hydride complex is proposed to initiate acrylonitrile polymerization by 2. 相似文献
97.
Moon J Garoff S Wynblatt P Suter R 《Langmuir : the ACS journal of surfaces and colloids》2004,20(2):402-408
We explore the equilibrium wetting behavior and precursor film growth in pure and alloy metallic systems. The systems exhibit equilibrium "pseudopartial" wetting, that is, a thin film in equilibrium with a nonzero contact angle in both liquid and solid states. The film spreading kinetics clearly indicates a diffusive transport mechanism. The alloying has only a small impact on the equilibrium wetting properties but strongly affects the transport during the growth of the precursor film. 相似文献
98.
McClean S Robinson RC Shaw C Smyth WF 《Rapid communications in mass spectrometry : RCM》2002,16(5):346-354
The characterisation of selected indole alkaloids in a quadrupole ion trap mass spectrometer is presented. Fragmentation profiles for tryptamine, 5-hydroxytryptamine (5-HT), N'-methyl 5-hydroxytryptamine (N'-methyl 5-HT), N',N'-dimethyl 5-hydroxytryptamine (bufotenine), N',N',N'-trimethyl 5-hydroxytryptamine (5-HTQ), and N',N'-dimethyl 5-methoxytryptamine (5-MeODMT) are presented with proposed structures given for each product ion observed. Such MS(n) experiments can be used to differentiate the isobaric molecular ions of the compounds 5-HTQ (M(+)) and 5-MeODMT (MH(+)). The quantitative determination of certain indole alkaloids in the skin secretions of the Australian Golden Bell frog, Litoria aurea, by LC/ESI-ion trap MS is also presented. The concentrations of 5-HT, N'-methyl 5-HT and 5-HTQ were found to be 2.68, 0.26 and 0.54 microg per mg of skin secretion, respectively. 相似文献
99.
Hubbard AL Davidson GJ Patel RH Wisner JA Loeb SJ 《Chemical communications (Cambridge, England)》2004,(2):138-139
Formation of a [3]catenane containing dibenzo-24-crown ether wheels and a large dipyridiniumethane ring is templated by formation of a host-guest adduct between the [3]catenane and the external crown ether. 相似文献
100.
Stephen Cradock Donald C. McKean Moray W. MacKenzie 《Journal of Molecular Structure》1981,74(2):265-276
We have obtained microwave spectra of fully and partially deuterated germyl halides GeD3X and GeHD2X (X = F, Cl, Br, I) and analysed the infrared spectra in the GeH stretching region of the asymmetric species. The resulting Ao and Bo values have been combined with existing data on GeH3X to give improved structures for the germyl halides. The values of the HGeX angles obtained show a correlation with GeH stretching frequencies, as in methyl compounds, but there appears to be no such correlation between stretching frequencies and GeH bond lengths. 相似文献