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71.
J. R. Gillmor R. W. Connelly R. H. Colby J. S. Tan 《Journal of Polymer Science.Polymer Physics》1999,37(16):2287-2295
The effect of an added polyanion, sodium poly(styrene sulfonate) (NaPSS), on the thermoreversible gelation and remelting of gelatin gels has been investigated by polarimetry and rheology. The presence of NaPSS can either enhance or reduce collagenlike helix formation, depending on the polymer concentration relative to that of gelatin and the gelation temperature. At temperatures < 20°C, the helical content is reduced by increasing the amount of added NaPSS, demonstrating the disruption of helical structure of gelatin by the polyanion. Synchronous measurements of optical rotation and modulus at 25°C, in both gelation and remelting, indicate that the optical rotation at the gel point for the pure gelatin is lowered on addition of NaPSS. At low frequency, the storage modulus of gelatin is increased by the addition of a small amount of NaPSS relative to that of gelatin, but decreased with excess NaPSS. The mechanical properties of gelatin with and without NaPSS will be discussed in light of the competition between network junction formation by strands of triple helices among gelatin chains and temporary ionic crosslinking between gelatin and the polyanion. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2287–2295, 1999 相似文献
72.
R. Connelly P.W. Fowler S.D. Guest B. Schulze W.J. Whiteley 《International Journal of Solids and Structures》2009,46(3-4):762-773
Maxwell’s rule from 1864 gives a necessary condition for a framework to be isostatic in 2D or in 3D. Given a framework with point group symmetry, group representation theory is exploited to provide further necessary conditions. This paper shows how, for an isostatic framework, these conditions imply very simply stated restrictions on the numbers of those structural components that are unshifted by the symmetry operations of the framework. In particular, it turns out that an isostatic framework in 2D can belong to one of only six point groups. Some conjectures and initial results are presented that would give sufficient conditions (in both 2D and 3D) for a framework that is realized generically for a given symmetry group to be an isostatic framework. 相似文献
73.
74.
Robert Connelly Erik D. Demaine Martin L. Demaine Sándor P. Fekete Stefan Langerman Joseph S. B. Mitchell Ares Ribó Günter Rote 《Discrete and Computational Geometry》2010,44(2):439-462
We extend linkage unfolding results from the well-studied case of polygonal linkages to the more general case of linkages
of polygons. More precisely, we consider chains of nonoverlapping rigid planar shapes (Jordan regions) that are hinged together
sequentially at rotatable joints. Our goal is to characterize the families of planar shapes that admit locked chains, where some configurations cannot be reached by continuous reconfiguration without self-intersection, and which families
of planar shapes guarantee universal foldability, where every chain is guaranteed to have a connected configuration space. Previously, only obtuse triangles were known to
admit locked shapes, and only line segments were known to guarantee universal foldability. We show that a surprisingly general
family of planar shapes, called slender adornments, guarantees universal foldability: roughly, the distance from each edge along the path along the boundary of the slender
adornment to each hinge should be monotone. In contrast, we show that isosceles triangles with any desired apex angle <90°
admit locked chains, which is precisely the threshold beyond which the slender property no longer holds. 相似文献
75.
Tabb DL Shah MB Strader MB Connelly HM Hettich RL Hurst GB 《Journal of the American Society for Mass Spectrometry》2006,17(7):903-915
We report an automated method for determining charge states from high-resolution mass spectra. Fourier transforms of isotope packets from high-resolution mass spectra are compared to Fourier transforms of modeled isotopic peak packets for a range of charge states. The charge state for the experimental ion packet is determined by the model isotope packet that yields the best match in the comparison of the Fourier transforms. This strategy is demonstrated for determining peptide ion charge states from "zoom scan" data from a linear quadrupole ion trap mass spectrometer, enabling the subsequent automated identification of singly- through quadruply-charged peptide ions, while reducing the numbers of conflicting identifications from ambiguous charge state assignments. We also apply this technique to determine the charges of intact protein ions from LC-FTICR data, demonstrating that it is more sensitive under these experimental conditions than two existing algorithms. The strategy outlined in this paper should be generally applicable to mass spectra obtained from any instrument capable of isotopic resolution. 相似文献
76.
Proisy N Sharp SY Boxall K Connelly S Roe SM Prodromou C Slawin AM Pearl LH Workman P Moody CJ 《Chemistry & biology》2006,13(11):1203-1215
A series of benzo-macrolactones of varying ring size and conformation has been prepared by chemical synthesis and evaluated by structural and biological techniques. Thus, 12- to 16-membered lactones were obtained by concise routes, involving ring-closing metathesis as a key step. In enzyme assays, the 13-, 15-, and 16-membered analogs are good inhibitors, suggesting that they can adopt the required conformation to fit in the ATP-binding site. This was confirmed by cocrystallization of 13-, 14-, and 15-membered lactones with the N-terminal domain of yeast Hsp90, showing that they bind similarly to the "natural" 14-membered radicicol. The most active compounds in the ATPase assays also showed the greatest growth-inhibitory potency in HCT116 human colon cancer cells and the established molecular signature of Hsp90 inhibition, i.e., depletion of client proteins with upregulation of Hsp70. 相似文献
77.
Adams CJ Baber RA Connelly NG Harding P Hayward OD Kandiah M Orpen AG 《Dalton transactions (Cambridge, England : 2003)》2006,(14):1749-1757
Deprotonation of mixtures of the triazene complexes [RhCl(CO)2(p-MeC6H4NNNHC6H4Me-p)] and [PdCl(eta(3)-C3H5)(p-MeC6H4NNNHC6H4Me-p)] or [PdCl2(PPh3)(p-MeC6H4NNNHC6H4Me-p)] with NEt3 gives the structurally characterised heterobinuclear triazenide-bridged species [(OC)2Rh(mu-p-MeC6H4NNNC6H4Me-p)2PdLL'] {LL' = eta(3)-C3H5 1 or Cl(PPh3) 2} which, in the presence of Me3NO, react with [NBu(n)4]I, [NBu(n)4]Br, [PPN]Cl or [NBu(n)4]NCS to give [(OC)XRh(mu-p-MeC6H4NNNC6H4Me-p)2PdCl(PPh3)]- (X = I 3-, Br 4-, Cl 5- or NCS 6-) and [NBu(n)4][(OC)XRh(mu-p-MeC6H4NNNC6H4Me-p)2Pd(eta(3)-C3H5)], (X = I 7- or Br 8-). The allyl complexes 7- and 8- undergo one-electron oxidation to the corresponding unstable neutral complexes 7 and 8 but, in the presence of the appropriate halide, oxidative substitution results in the stable paramagnetic complexes [NBu(n)4][X2Rh(mu-p-MeC6H4NNNC6H4Me-p)2Pd(eta(3)-C3H5)], (X = I 9- or Br 10-). X-Ray structural (9-), DFT and EPR spectroscopic studies are consistent with the unpaired electron of 9- and 10- localised primarily on the Rh(II) centre of the [RhPd]4+ core, which is susceptible to oxygen coordination at low temperature to give Rh(III)-bound superoxide. 相似文献
78.
79.
López-Gómez MJ Connelly NG Haddow MF Hamilton A Lusi M Baisch U Orpen AG 《Dalton transactions (Cambridge, England : 2003)》2011,40(17):4647-4659
The potassium salts of the new S(2)N-heteroscorpionate ligand hydrobis(methimazolyl)(3,5-dimethylpyrazolyl)borate [HB(mt)(2)(pz(3,5-Me))](-) and its known analogue hydrobis(methimazolyl)(pyrazolyl)borate [HB(mt)(2)(pz)](-) (prepared from KTp' or KTp and methimazole, Hmt), and the adduct KTp·Hmt have polymeric structures in the solid state (the first a ladder and the other two chains). The iridaboratranes [IrHLL'{B(mt)(2)X}] (X = pz(3,5-Me) or pz), prepared from the heteroscorpionate anion and [{Ir(cod)(μ-Cl)}(2)] (LL' = cod), subsequent carbonylation [LL' = (CO)(2)] and then reaction with phosphine [LL' = (CO)(PR(3)), R = Ph or Cy], have a pendant pyrazolyl ring and a bicyclo-[3.3.0] cage formed by an S(2)-bound B(mt)(2) fragment. The binuclear species [(cod)HIr{μ-B(mt)(3)}IrCl(cod)], the only isolated product of the reaction of KTm with [{Ir(cod)(μ-Cl)}(2)], also has an S(2)-bound iridaboratrane unit but with the third mt ring linked to square planar iridium(I). 相似文献
80.
Generic Global Rigidity 总被引:1,自引:0,他引:1
Robert Connelly 《Discrete and Computational Geometry》2005,33(4):549-563
Suppose a finite configuration of labeled
points p = (p1,. . . ,pn) in Ed is given along with
certain pairs of those points determined by a graph G such that the
coordinates of the points of p are generic, i.e., algebraically
independent over the integers. If another corresponding configuration
q = (q1,. . . ,qn) in Ed is given such that the
corresponding edges of G for p and q have the same
length, we provide a sufficient condition to ensure that p and
q are congruent in Ed. This condition, together with recent
results of Jackson and Jordán, give necessary and sufficient conditions for
a graph being generically globally rigid in the plane. 相似文献