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41.
The lattice parameters of a series of hydrogenated polybutadiene (HPB) model copolymers is measured as a function of branch content between 0 and 73 ethyl branches per 1000 C atoms. Expansion of the a and b axes nearly ceases for branch contents greater than 20 per 1000 C atoms. The c axis is seen to contract by a small amount with increased branching. The major cause of lattice expansion is limitation of crystal thickness by exclusion of branch points from the lamellar crystals coupled with surface stress on thin lamellae. A small fraction of ethyl branches are incorporated in the crystal; these expand the lattice by an additional amount. 相似文献
42.
J. L. Ojeda J. A. Cristóbal J. T. Alcalá 《Annals of the Institute of Statistical Mathematics》2008,60(3):519-543
In this paper, we propose two bootstrap-based model checking tests for a parametric linear model when data are affected by
length-bias. These tests are based on the measure of the discrepancy between nonparametric and parametric estimators for the
regression function when the data are drawn under a length-biased mechanism. We consider two different discrepancy measures:
the supremum and the integral of the quadratic difference between the parametric and nonparametric estimators. 相似文献
43.
Depolarized small-angle light scattering from spherulites in semicrystalline polymers gives rise to a characteristic cloverleaf pattern. For scattering from a single spherulite, the position of the maximum in scattered intensity is readily related to the spherulite radius. For a distribution of spherulites, the maximum should be related to some characteristic measure of the distribution. It is shown for a wide variety of distributions that this characteristic radius is a ratio of high moments of the size distribution, specifically R* ≈ 〈R7〉/〈R6〉. The shape of the light-scattering profile should in principal be related to the nature of the spherulite distribution. Calculations of scattering profiles from a variety of distributions fail to demonstrate this, owing to the strong dependence of scattering power on spherulite size. Exceptions are noted for the case of certain bimodal distributions. 相似文献
44.
Buckley Crist Costas Metaxas 《Journal of polymer science. Part A, Polymer chemistry》2004,42(11):2081-2091
Intrinsic true stress–true strain response was evaluated at room temperature for three linear polyethylene samples deformed in conventional tensile tests. It was observed that high crystallinity is associated with a low rate of strain hardening that results in a sharp neck and a large drop in nominal stress. The maximum and minimum deformation loads are accounted for by Considère's analysis of neck initiation and stabilization, respectively. Following stabilization, neck propagation occurs at a load or nominal stress that is lower than the yield stress. The jump analysis of Ericksen and Hutchinson/Neale predicts steady state neck propagation stresses that are in very good (ca. 10%) agreement with experiment. Although the jump analysis is done in terms of uniaxial stress, the actual value of the propagation stress is established by the triaxial stress state in the neck shoulders. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2081–2091, 2004 相似文献
45.
Alvaro Bernalte-García M. Angeles Díaz-Díez Fernando J. García-Barros Francisco J. Higes-Rolando Cristóbal Valenzuela-Calahorro 《Transition Metal Chemistry》1996,21(3):197-199
Summary The reaction of NiII ions with 2-(benzylamino)-2-deoxy-d-glycero-l-gluco. heptonic acid (BnGa:C14H21NO7) or 2-(benzylamino)-2-deoxy-d-glycero-d-talo heptonic acid (BnMa:C14H21NO7) in water yields complexes of formulae [Ni(BnGa)2(H2O)2] and [Ni(BnMa)2]·2H2O, respectively, which were characterized by elemental analysis, spectral techniques (u.v.-vis.-n.i.r. and i.r.), magnetic susceptibility measurements, thermal measurements (t.g. and d.s.c.) and X-ray powder diffraction. Both complexes are octahedral with two positions of the coordination sphere occupied by nitrogen atoms. Moreover, in [Ni(BnMa)2]·2H2O four oxygen atoms of bridging carboxylate groups are coordinated to the metal ion, while in [Ni(BnGa)2(H2O)2] only an oxygen atom of each carboxylate group is bound to NiII. In this case, the coordination is completed via two water molecules. 相似文献
46.
G. Valensi R. H. Crist F. B. Brown L. Williams A. H. Wilson Busby L. S. Echols Jr M. A. Smith F. L. Hayes C. H. Townes H. K. Alber A. Knoll J. Schukal E. P. Barrett W. E. Holbrook J. S. Blair A. V. Grosse W. N. Ipatjew H. J. Hall G. B. Bachman A. Klemenc A. Stock H. Kühne A. Bellmann J. Haller W. H. Albrecht K. P. GRohr H. Hillemann H. A. Wilhelm W. MacNevin H. S. Clark K. R. More R. F. Humphreys W. W. Watson P. A. Anderson G. Atchison D. O. Holland H. Sieben T. Langer 《Analytical and bioanalytical chemistry》1944,127(1):197-202
47.
48.
David G. Ahern Judith A. Egan Richard P. Nugent Crist N. Filer 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):1029-1031
The high specific activity tritiation of oxymorphone and pentamorphone is described. 相似文献
49.
Some advantages, disadvantages, and anomalies of various donors in glycosidations are discussed. By studying several two‐component donor/acceptor‐diol reactions, it is shown that regiopreferences are not very sensitive to the type of donor used. However, in competitive glycosidations within a given type of donor and between different types of donor, it is shown that regio‐ and chemoselectivities must be indexed to donor reactivity. 相似文献
50.
Dr. María Mar Quesada-Moreno Dr. Pablo Pinacho Dr. Cristóbal Pérez Dr. Marina Šekutor Prof. Dr. Peter R. Schreiner Prof. Dr. Melanie Schnell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(20):6198-6203
Fluorinated derivatives of biological molecules have proven to be highly efficient at modifying the biological activity of a given protein through changes in the stability and the kind of docking interactions. These interactions can be hindered or facilitated based on the hydrophilic/hydrophobic character of a particular protein region. Diadamantyl ether (C20H30O) possesses both kinds of docking sites, serving as a good template to model these important contacts with aromatic fluorinated counterparts. In this work, an experimental study on the structures of several complexes between diadamantyl ether and benzene as well as a series of fluorinated benzenes is reported to analyze the effect of H→F substitution on the interaction and structure of the resulting molecular clusters using rotational spectroscopy. All experimentally observed complexes are largely dominated by London dispersion interactions with the hydrogen-terminated surface areas of diadamantyl ether. Already single substitution of one hydrogen atom with fluorine changes the preferred docking site of the complexes. However, the overall contributions of the different intermolecular interactions are similar for the different complexes, contrary to previous studies focusing on the difference in interactions using fluorinated and non-fluorinated molecules. 相似文献