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61.
Moilanen P Talmant M Nicholson PH Cheng S Timonen J Laugier P 《The Journal of the Acoustical Society of America》2007,122(4):2439-2445
It was reported in a previous study that simulated guided wave axial transmission velocities on two-dimensional (2D) numerically reproduced geometry of long bones predicted moderately real in vitro ultrasound data on the same bone samples. It was also shown that fitting of ultrasound velocity with simple analytical model yielded a precise estimate (UTh) for true cortical bone thickness. This current study expands the 2D bone model into three dimensions (3D). To this end, wave velocities and UTh were determined from experiments and from time-domain finite-difference simulations of wave propagation, both performed on a collection of 10 human radii (29 measurement sites). A 3D numerical bone model was developed with tuneable fixed material properties and individualized geometry based on X-ray computed tomography reconstructions of real bones. Simulated UTh data were in good accordance (root-mean-square error was 0.40 mm; r(2)=0.79, p<0.001) with true cortical thickness, and hence the measured phase velocity can be well estimated by using a simple analytical inversion model also in 3D. Prediction of in vitro data was improved significantly (by 10% units) and the upgraded bone model thus explained most of the variability (up to 95% when sites were carefully matched) observed in in vitro ultrasound data. 相似文献
62.
Sanders showed in 1960, within the framework of two-dimensional elasticity, that in any body a certain integral I around a closed curve containing a crack is path-independent. I is equal to the rate of release of potential energy of the body with respect to crack length. Here we first derive, in a simple way, Sanders' integral I for a loaded elastic body undergoing finite deformations and containing an arbitrary void. The strain energy density need not be homogeneous nor isotropic and there may be body forces. In the absence of body forces, for flat continua, and for special forms of the strain energy density, it is shown that I reduces to the well-known vector and scalar path-independent integrals often denoted by J, L, and M. 相似文献
63.
Legido-Quigley C McDermott L Vilca-Melendez H Murphy GM Heaton N Lindon JC Nicholson JK Holmes E 《Electrophoresis》2011,32(15):2063-2070
Bile flow restoration is a crucial step in the recovery process post transplantation of the liver. Here, metabolic trajectories based on changes in bile secretion - a known marker of functionality - have been utilised as an approach for discovering bile fluxes during transplantation. A total of ten liver transplants were monitored and from these 68 bile samples from both donors and recipients were collected and analysed using ultra-performance LC-MS in combination with multivariate statistical analysis. Based on the principal component scores constructed from the total bile fingerprint, differentiation of the bile acid concentrations before and after transplantation was detected. A trend was also observed, by constructing metabolic trajectories, whereby the post-transplant profiles approached the position of pre-transplant profiles within 30-60?min of the restoration of bile secretion function. The ten major conjugated bile acid salts were measured and a significant increase in concentrations of taurocholic acid and taurochenodeoxycholic acid were seen after transplantation. In addition, the ratios of secondary bile acids detected in gall bladder and hepatic bile were measured before and after transplantation. This study suggests that bile acid ratios in the donor liver at the pre-transplant and post-transplant stage may be important and that profiling of secreted bile after transplantation may aid clinical assessment and progress post-transplantation. 相似文献
64.
This paper addresses the long-standing problem of the so-called Gibbs dividing surface and the use of helium as a “non-adsorbing” gas for the determination of the “helium”-void volume and thence the Gibbs excess. Using helium is subject to some uncertainty because helium does adsorb (to call it a non-adsorbing gas is misleading) and it is able to access pore spaces that other larger adsorbates cannot. On the other hand, even helium atoms can not physically probe all the space described by the helium-void volume. To avoid these difficulties, we suggest an alternative to the formulation of the Gibbs dividing surface and the definition of the excess amount. We illustrate this with the two common tools to study adsorption—the volumetric and gravimetric techniques, and justify our new analysis with a computer simulation of a number of model adsorption systems. Furthermore, we also show that by using the correct accessible volume and inaccessible volume the excess amount obtained from a volumetric experiment is exactly the same as that obtained from a gravimetric experiment. 相似文献
65.
Prof. Dr. Michael I. Bruce Maryka Gaudio Benjamin C. Hall Brian K. Nicholson Gary J. Perkins Brian W. Skelton Allan H. White 《无机化学与普通化学杂志》2011,637(9):1207-1212
The preparation, characterisation and single‐crystal XRD molecular structure determinations of four complexes containing –CC–MLn end‐groups, namely Ru{C≡CFc′(I)}(dppe)Cp ( 1 ), the vinylidene [Os(=C=CH2)(PPh3)2Cp]PF6 ( 2 ), trans‐Pt(C≡CC6H4‐4‐C≡CPh){C≡CC6H4‐4‐C2Ph[Co2(μ‐dppm)(CO)4]}(PPh3)2 ( 3 ), and C6H4{μ3‐C2[AuRu3(CO)9(PPh3)]}2‐1,4 ( 4 ) are reported. In these compounds a range of –CC– environments is found, extending from the σ‐bonded alkynyl group in 1 to examples where the C2 unit interacts with either a proton (in vinylidene 2 ), by bridging a dicobalt carbonyl moiety (in 3 ) or the AuRu3 cluster in 4 . Changes in geometry are rationalised by considering the various bonding modes. 相似文献
66.
Tsoi WC James DT Kim JS Nicholson PG Murphy CE Bradley DD Nelson J Kim JS 《Journal of the American Chemical Society》2011,133(25):9834-9843
The nature of main in-plane skeleton Raman modes (C=C and C-C stretch) of poly(3-hexylthiophene) (P3HT) in pristine and its blend thin films with [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) is studied by resonant and nonresonant Raman spectroscopy and Raman simulations. Under resonant conditions, the ordered phase of P3HT with respect to its disordered phase is identified by (a) a large shift in the C=C mode peak position to lower wavenumber (~21 cm(-1) shift), (b) a narrower fwhm of the C=C mode (~9 cm(-1) narrower), (c) a larger intensity of the C-C mode relative to the C=C mode (~56% larger), and (d) a very small Raman dispersion (~5 cm(-1)) of the C=C mode. The behavior of the C=C and C-C modes of the ordered and disordered phases of P3HT can be explained in terms of different molecular conformations. The C=C mode of P3HT in P3HT:PCBM blend films can be reproduced by simple superposition of the two peaks observed in different phases of P3HT (ordered and disordered). We quantify the molecular order of P3HT after blending with PCBM and the subsequent thermal annealing to be 42 ± 5% and 94 ± 5% in terms of the fraction of ordered P3HT phase, respectively. The increased molecular order of P3HT in blends upon annealing correlates well with enhanced device performance (J(SC), -4.79 to -8.72 mA/cm(2) and PCE, 1.07% to 3.39%). We demonstrate that Raman spectroscopy (particularly under resonant conditions) is a simple and powerful technique to study molecular order of conjugated polymers and their blend films. 相似文献
67.
Altun M Kramer HB Willems LI McDermott JL Leach CA Goldenberg SJ Kumar KG Konietzny R Fischer R Kogan E Mackeen MM McGouran J Khoronenkova SV Parsons JL Dianov GL Nicholson B Kessler BM 《Chemistry & biology》2011,18(11):1401-1412
Converting lead compounds into drug candidates is a crucial step in drug development, requiring early assessment of potency, selectivity, and off-target effects. We have utilized activity-based chemical proteomics to determine the potency and selectivity of deubiquitylating enzyme (DUB) inhibitors in cell culture models. Importantly, we characterized the small molecule PR-619 as a broad-range DUB inhibitor, and P22077 as a USP7 inhibitor with potential for further development as a chemotherapeutic agent in cancer therapy. A striking accumulation of polyubiquitylated proteins was observed after both selective and general inhibition of cellular DUB activity without direct impairment of proteasomal proteolysis. The repertoire of ubiquitylated substrates was analyzed by tandem mass spectrometry, identifying distinct subsets for general or specific inhibition of DUBs. This enabled identification of previously unknown functional links between USP7 and enzymes involved in DNA repair. 相似文献
68.
Victor A. Nicholson 《Journal of mathematical chemistry》2006,40(2):105-117
This article proves the laundry embedding theorem. It considers surface triples (S,G,J) in S
3 where S is a 2-manifold with boundary, G is a circle-with-chords, and J is an arc. The surfaces satisfy an embedding condition called laundry which is similar to being unknotted. The theorem gives elementary necessary and sufficient conditions for two triples to be equivalent by ambient isotopy. The theorem introduces a new topological invariant called turn. The surfaces of interest can arise from the augmented ribbon model of unknotted single domain protein. 相似文献
69.
W. K. Nicholson 《Periodica Mathematica Hungarica》1990,21(1):31-34
A simple proof of an extension of Faith's correspondence theorem for projective modules is given for a Morita context (R, V, W, S) in whichVWV=V andWVW=W.Research supported by N.S.E.R.C. (Canada), Grant No. A 8075. 相似文献
70.
Propagation of ultrasound in a number of thin solid elastic waveguides is described from the Pochhammer theory. The waveguides discussed have radii equal to the radii of stylets of the most frequently used biopsy needles. The group velocities of the modes and the form of the particle amplitudes of the lowest longitudinal and flexural modes in each of the styles at a frequency of 3.5 MHz are presented. 相似文献