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991.
992.
Gerard G. Henn Colin Birkinshaw Martin Buggy Eric Jones 《Macromolecular bioscience》2001,1(6):219-222
Poly(D ,L ‐lactide) has been evaluated as a material for the manufacture of intra‐medullary plugs to be used in total hip arthoplasty. Plugs were manufactured by compression moulding and subjected to in‐vitro and in‐vivo degradation. In‐vitro hydrolysis was carried out by immersion in phosphate buffered saline (Ringer's solution) at 37°C and rates of degradation were relatively rapid with molecular weight halving after 30 days. In‐vivo degradation was assessed by implantation into dogs followed by retrieval at intervals up to 24 months. Molecular weight was found to reduce to half the original value in about 190 days. It is thought that this difference in degradation rate is because of diffusional control of the overall process. Histology showed that the implanted plugs were resorbed over 24 months. 相似文献
993.
994.
Structures of Ionic Di(arenesulfonyl)amides. 3. Four Sodium Di(arenesulfonyl)amides: Lamellar Layers Exhibiting Short C–H…O(nitro), C–H…F–C, or C–I…I–C Interlayer Contacts Low‐temperature X‐ray crystal structures are reported for NaN(SO2C6H4‐4‐X)2 · n H2O, where X = NO2 and n = 3 ( 1 , monoclinic, space group P21, Z = 2), X = F and n = 3 ( 2 , monoclinic, P21/c, Z = 4), X = F and n = 1 ( 3 , orthorhombic, Pccn, Z = 8), or X = I and n = 1 ( 4 , monoclinic, P21/c, Z = 4). The four compounds are examples of layered inorgano‐organic solids where the inorganic component is comprised of metal cations, N(SO2)2 groups and H2O molecules and the outer regions are formed by the 4‐substituted phenyl rings of the folded anions. In the two‐dimensional coordination networks, the cations adopt either an octahedral [Na(O–S)2(OH2)4] ( 1 , 2 ) or a distorted monocapped octahedral [NaN(O–S)4(OH2)2] ( 3 , 4 ) environment. Taking into account the differing crystal symmetries within the two pairs of compounds, it is remarkable that the trihydrates 1 / 2 and the monohydrates 3 / 4 each display chemically identical and nearly isometric Na–O or Na–O/N networks. In the crystal packings, parallel layers are connected through weak hydrogen bonds C–H…O(nitro) ( 1 ) or C–H…F ( 2 , 3 ), or through short “type I” I…I contacts ( 4 ). There is good evidence that the strikingly distinct crystal symmetries in the halogenated homologues 3 / 4 are determined by the specific complementarity requirements of the interlayer binding centres. 相似文献
995.
996.
L. Jones Tarcius Doss A. K. Pani S. Padhy 《Numerical Methods for Partial Differential Equations》1997,13(4):393-416
Based on a Landau-type transformation, both continuous and discrete in time L2-Galerkin methods are applied to a single-phase Stefan-type problem in one space dimension. Optimal rates of convergence in Lℵ, L∞, and H1-norms are derived and computational results are presented. © 1997 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 13: 393–416, 1997 相似文献
997.
Harald Grger Davoud Tehranfar Jürgen Martens Jens R. Goerlich Holger Thnnessen Peter G. Jones Reinhard Schmutzler 《Heteroatom Chemistry》1997,8(3):207-215
The addition of dimethylphosphine oxide and its trimethylsiloxyphosphorus(III) derivative, generated in situ, to 3-thiazolines was found to yield dimethyl 4-thiazolidinylphosphine oxides via three different synthetic routes. The structures of two products were confirmed by X-ray analysis; common features include approximate envelope conformations of the five-membered rings and hydrogen bonding of the form N–H· · ·O=P. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8 : 207–215, 1997. 相似文献
998.
999.
E. D. T. Atkins M. J. Hill N. A. Jones S. J. Cooper 《Journal of Polymer Science.Polymer Physics》1998,36(13):2401-2412
Chain-folded lamellar crystals of nylon 2 4 have been prepared from dilute solution by addition of poor solvent. Two crystal structures are observed at room temperature: a monoclinic form I, precipitated at elevated temperature, and a less-defined, orthorhombic form II, precipitated at room temperature. The unit cell parameters for both forms are similar to those reported for its isomer, nylon 3. Nylon 2 4 form II is a liquid–crystal-like or disordered phase, consisting of hydrogen-bonded sheets in poor register in the hydrogen bond direction. Form I crystals have two characteristic interchain spacings of 0.41 nm and 0.39 nm at room temperature and on heating, exhibit a structural transformation and a Brill temperature (250°C) characteristic of many other even–even nylons. Nylon 2 4 is a member of the nylon 2 Y and nylon 2N 2(N+1) families, and the form I crystals show behavior commensurate with both. We propose they contain a proportion of intersheet hydrogen bonds at room temperature, similar to that for the nylon 2 Y family, and the short dimethylene alkane segments mean that the structure consists of hydrogen-bonded a-sheets, with an amide unit in each fold, similar to that of nylon 4 6. The fold geometry and sheet structure is compared with chain-folded apβ-sheet polypeptides and nylon 3. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2401–2412, 1998 相似文献
1000.
M. Carmen Blanco Eduardo J. Fernndez Peter G. Jones Antonio Laguna Jos M. Lpez-de-Luzuriaga M. Elena Olmos 《Angewandte Chemie (International ed. in English)》1998,37(21):3042-3043
The covalent radius of Au I is about 0.07 Å smaller than that of AgI. This was determined from the crystal structures of the isostructural complexes [N(PPh3)][{Au(C6F5)3(μ-PPh2)}2M] (M=Au (structure shown in the picture), Ag). These mixed AuIII–M phosphides were synthesized from [Au(C6F5)3(PPh2H)], the first gold complex to contain a secondary phosphane. 相似文献