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Digitale Medien

Models of Curves and Finite Covers (1999)

Liu, Qing ; Lorenzini, Dino

Springer

Compositio mathematica 118 (1999), S. 61-102

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ISSN: 1570-5846

Schlagwort(e): branch locus ; covers ; curves ; discrete valuation ring ; models ; semi-stable ; simultaneous resolution.

Quelle: Springer Online Journal Archives 1860-2000

Thema: Mathematik

Notizen: Abstract Let K be a discrete valuation field with ring of integers O K .Letf : X ! Y be a finite morphism of curves over K. In this article, we study some possible relationships between the models over O K of X and of Y. Three such relationships are listed below. Consider a Galois cover f : X ! Y of degree prime to the characteristic of the residue field, with branch locus B. We show that if Y has semi-stable reduction over K,thenX achieves semi-stable reduction over some explicit tame extension of K.B/.WhenK is strictly henselian, we determine the minimal extension L=K with the property that X L has semi-stable reduction. Let f : X ! Y be a finite morphism, with g.Y/ 〉 2. We show that if X has a stable model X over O K ,thenY has a stable model Y over O K , and the morphism f extends to a morphism X ! Y. ! Y. Finally, given any finite morphism f : X ! Y, is it possible to choose suitable regular models X and Y of X and Y over O K such that f extends to a finite morphism X ! Y ?As wasshown by Abhyankar, the answer is negative in general. We present counterexamples in rather general situ-ations, with f a cyclic cover of any order 〉 4. On the other hand, we prove, without any hypotheses on the residual characteristic, that this extension problem has a positive solution when f is cyclic of order 2 or 3.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1001141725199

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Digitale Medien

Cyclopolymerization, 24.Part 23: cf. ref.6 Cyclopolymerizability of an unconjugated triene with functional groups with no homopolymerization tendency: Radical polymerizations of N,N-diallyl-2-(methoxy-carbonyl)allylamine (1997)

Kodaira, Toshiyuki ; Liu, Qing-Qing ; Urushisaki, Michio

Weinheim : Wiley-Blackwell

Macromolecular Chemistry and Physics 198 (1997), S. 3089-3104

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ISSN: 1022-1352

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: N,N-Diallyl-2-(methoxycarbonyl)allylamine (1a), a trifunctional compound with functional groups of low homopolymerizability, was synthesized and its radical cyclopolymerizability was investigated. Monomer 1a was polymerized to yield high molecular weight polymers with a considerably high polymerization rate; the degree of cyclization (DC) of poly(1a) was about 55%, irrespective of the polymerization conditions, while bifunctional compounds with functional groups of low homopolymerizability have been known to yield highly cyclized polymers. Pendant unsaturations detected in poly(1a) were found to consist almost exclusively of allyl groups. The acryloyl groups and one of the allyl groups of 1a can be regarded as one functional group in a pair with high polymerizability, since N-allyl-N-propyl-2-(methoxycarbonyl)allylamine which has the structure of 1a with one of its allyl groups saturated has been known to yield linear polymers with a DC of 100%. This consideration indicates that 1a has similar cyclopolymerizability to unsymmetrical bifunctional monomers the functional groups of which have high and low homopolymerizability. This is the reason why 1a has low cyclopolymerizability, since such unsymmetrical bifunctional monomers have generally low cyclopolymerizability. The high polymerization tendency of 1a is attributed to the high conjugative nature of the acryloyl group as proven by 13C NMR.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/macp.1997.021981009

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Digitale Medien

Collagen/apatite coating on 3-dimensional carbon/carbon composite (1998)

Li, Shihong ; Zheng, Zhongguang ; Liu, Qing ; [weitere]

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 40 (1998), S. 520-529

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ISSN: 0021-9304

Schlagwort(e): 3D carbon/carbon composite ; collagen/apatite composite ; coating ; grafting ; phosphorylation ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Medizin , Technik allgemein

Notizen: A three-dimensional carbon/carbon composite (3D C/C) was studied as potential bone-repairing material; its major mechanical properties were found to be closer to those of human bone than other common bone-repairing materials available. In vitro calcification tests revealed that as-received 3D C/C is almost bioinert in simulated body fluid (SBF) over an immersion period of 4 weeks. To improve the bioactivity of 3D C/C, surface modification was accomplished through two practical routes: (1) grafting with polyethylene glycol (PEG) and (2) phosphorylation and precalcification. After grafting with α, ω di(aminopropyl) polyethylene glycol 800 (NH2-PEG-NH2), a continuous layer of calcium phosphate was formed on the surface of 3D C/C in SBF after 4 weeks. Phosphorylated 3D C/C samples have the ability to induce apatite precipitation after precalcification in a saturated Ca(OH)2 solution for 1 week. To speed up the coating process, a calcification solution with collagen was developed in which a collagen/apatite coating layer can be formed on 3D C/C in 9 h in ambient conditions. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 520-529, 1998.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

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Digitale Medien

Composite biomaterials with chemical bonding between hydroxyapatite filler particles and PEG/PBT copolymer matrix (1998)

Liu, Qing ; de Wijn, Joost R. ; van Blitterswijk, Clemens A.

Hoboken, NJ : Wiley-Blackwell

Journal of Biomedical Materials Research 40 (1998), S. 490-497

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ISSN: 0021-9304

Schlagwort(e): hydroxyapatite ; Polyactive™ ; composites ; interface ; mechanical properties ; surface grafting ; coupling agent ; diisocyanate ; Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Medizin , Technik allgemein

Notizen: In an effort to make composites from hydroxyapatite and a PEG/PBT copolymer (Polyactive™ 70/30), chemical linkages were introduced between the filler particles and polymer matrix using hexamethylene diisocyanate as a coupling agent. Infrared spectra (IR) and thermal gravimetric analysis (TGA) confirmed the presence of Polyactive™ 70/30 on the surface of HA filler particles. The amount of chemically bound polymer was 4.7 wt.%, as determined by TGA. The mechanical properties of the composites, that is, tensile strength and Young's modulus, were improved significantly by the introduction of a chemical linkage between the filler particles and polymer matrix compared to control composites. This method provides an effective way to introduce chemical linkage between HA filler particles and a polymer matrix. By optimizing the grafting process, a further improvement of the mechanical properties in the composites can be expected. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 490-497, 1998.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

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