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261.
Urh Černigoj Jana Vidič Ana Ferjančič Urša Sinur Klemen Božič Nina Mencin Anže Martinčič Celjar Pete Gagnon Aleš Štrancar 《Electrophoresis》2021,42(24):2619-2625
Elution of strong and weak anion exchangers with sodium chloride gradients is commonly employed for analysis of sample mixtures containing different isomers of plasmid DNA. Gradient elution of a weak anion exchanger (diethylaminoethyl) in the presence of guanidine hydrochloride (Gdn) roughly doubles resolution between open-circular (oc) and supercoiled (sc) isomers. It also improves resolution among sc, linear, and multimeric/aggregated forms. Sharper elution peaks with less tailing increase sensitivity about 30%. However, elution with an exclusively Gdn gradient to 900 mM causes more than 10% loss of plasmid. Elution with a sodium chloride gradient while maintaining Gdn at a level concentration of 300 mM achieves close to 100% recovery of sc plasmid while maintaining the separation improvements achieved by exclusively Gdn elution. Corresponding improvements in separation performance are not observed on a strong (quaternary amine) anion exchanger. Other chaotropic salts do not produce a favorable result on either exchanger, nor does the inclusion of surfactants or EDTA. Selectivity of the diethylaminoethyl-Gdn method is orthogonal to electrophoresis, but with better quantification than agarose electrophoresis, better quantitative accuracy than CE, and resolution approaching CE. 相似文献
262.
Pete L. Clark 《Proceedings of the American Mathematical Society》2007,135(3):617-624
Using Serre's proposed complement to Shih's Theorem, we obtain as a Galois group over for at least new primes . Assuming that rational elliptic curves with odd analytic rank have positive rank, we obtain Galois realizations for of the primes that were not covered by previous results; it would also suffice to assume a certain (plausible, and perhaps tractable) conjecture concerning class numbers of quadratic fields. The key issue is to understand rational points on Atkin-Lehner twists of . In an appendix, we explore the existence of local points on these curves.
263.
Agrawal SK Sanabria-Delong N Jemian PR Tew GN Bhatia SR 《Langmuir : the ACS journal of surfaces and colloids》2007,23(9):5039-5044
We observe large-scale structures in hydrogels of poly(l-lactide)-poly(ethylene oxide)-poly(l-lactide) (PLLA-PEO-PLLA) ranging in size from a few hundred nanometers to several micrometers. These structures are apparent through both ultra-small angle scattering (USAS) techniques and confocal microscopy. The hydrogels showed power law scattering in the USAS regime, which is indicative of scattering from fractal structures. The fractal dimension of the scattering from hydrogels revealed that the gels have large size aggregates with a mass fractal structure over the nanometer-to-micrometer length scales. The aggregates also seem to become more "dense" with an increase in the molecular weight of crystalline PLLA domains. Visualization through confocal microscopy confirms that the gels have a microstructure of interspersed micrometer-sized polymer inhomogeneities with water channels running between them. The presence of micrometer-sized water channels in the hydrogels has very important implications for biomedical applications. 相似文献
264.
Mild and selective vanadium-catalyzed oxidation of benzylic, allylic, and propargylic alcohols using air 总被引:1,自引:0,他引:1
Transition metal-catalyzed aerobic alcohol oxidation is an attractive method for the synthesis of carbonyl compounds, but most catalytic systems feature precious metals and require pure oxygen. The vanadium complex (HQ)(2)V(V)(O)(O(i)Pr) (2 mol %, HQ = 8-quinolinate) and NEt(3) (10 mol %) catalyze the oxidation of benzylic, allylic, and propargylic alcohols with air. The catalyst can be easily prepared under air using commercially available reagents and is effective for a wide range of primary and secondary alcohols. 相似文献
265.
Redundancy is the qualitative property which makes Hilbert space frames so useful in practice. However, developing a meaningful
quantitative notion of redundancy for infinite frames has proven elusive. Though quantitative candidates for redundancy exist,
the main open problem is whether a frame with redundancy greater than one contains a subframe with redundancy arbitrarily
close to one. We will answer this question in the affirmative for ℓ
1-localized frames. We then specialize our results to Gabor multi-frames with generators in M
1(R
d
), and Gabor molecules with envelopes in W(C, l
1). As a main tool in this work, we show there is a universal function g(x) so that, for every ε =s> 0, every Parseval frame {f
i
}
i=1
M
for an N-dimensional Hilbert space H
N
has a subset of fewer than (1+ε)N elements which is a frame for H
N
with lower frame bound g(ε/(2M/N − 1)). This work provides the first meaningful quantative notion of redundancy for a large class of infinite frames. In addition,
the results give compelling new evidence in support of a general definition of redundancy given in [5]. 相似文献
266.
This study documents the presence of stable complexes between monoclonal IgM and genomic DNA in freshly harvested mammalian cell culture supernatants. 75% of the complex population elutes from size exclusion chromatography with the same retention volume as IgM. DNA comprises 24% of the complex mass, corresponding to an average of 347 base pairs per IgM molecule, distributed among fragments smaller than about 115 base pairs. Electrostatic interactions appear to provide most of the binding energy, with secondary stabilization by hydrogen bonding and metal affinity. DNA-dominant complexes are unretained by bioaffinity chromatography, while IgM-dominant complexes are retained and coelute with IgM. DNA-dominant complexes are repelled from cation exchangers, while IgM-dominant complexes are retained and partially dissociated. Partially dissociated forms elute in order of decreasing DNA content. The same pattern is observed with hydrophobic interaction chromatography. All complex compositions bind to anion exchangers and elute in order of increasing DNA content. A porous particle anion exchanger was unable to dissociate DNA from IgM. Monolithic anion exchangers, offering up to 15-fold higher charge density, achieved nearly complete complex dissociation. The charge-dense monolith surface appears to outcompete IgM for the DNA. Monoliths also exhibit more than double the IgM dynamic binding capacity of the porous particle anion exchanger, apparently due to better surface accessibility and more efficient mass transfer. 相似文献
267.
Zhang F Long GG Jemian PR Ilavsky J Milam VT Lewis JA 《Langmuir : the ACS journal of surfaces and colloids》2008,24(13):6504-6508
A new colloidal stabilization mechanism, known as nanoparticle "haloing" (Tohver, V.; Smay, J. E.; Braem, A.; Braun, P. V.; Lewis, J. A. Proc. Natl. Acad. Sci. U.S.A. 2001, 98, (16), 8950-8954), has been predicted theoretically and inferred experimentally in microsphere-nanoparticle mixtures that possess high charge and size asymmetry. The term "halo" implies the existence of a nonzero separation distance between the highly charged nanoparticles and the negligibly charged microspheres that they surround. By means of ultrasmall-angle X-ray scattering, we have quantified the microsphere-nanoparticle separation distance as well as the number of nanoparticles and their lateral separation distance within the self-organized halos that form in these binary mixtures. 相似文献
268.
269.
Doug H. Rose Falah S. Hasoon Ramesh G. Dhere Dave S. Albin Rosine M. Ribelin Xiaonan S. Li Yoxa Mahathongdy Tim A. Gessert Pete Sheldon 《Progress in Photovoltaics: Research and Applications》1999,7(5):331-340
This paper details the laboratory processes used to fabricate CdS/CdTe solar cells at the National Renewable Energy Laboratory. The basic fabrication technique includes low‐pressure chemical vapor deposited SnO2 , chemical‐bath deposited CdS, close‐spaced sublimated CdTe, solution‐CdCl2 treatment, and an acid‐contact etch, followed by application of a doped‐graphite paste. This paper also describes the results of a reproducibility study in which cells were produced by multiple operators with an average AM1·5 efficiency of 12·6%. And finally, this paper discusses process sensitivities and alternative cell fabrication procedures and reports the fabrication of a cell with an AM1·5 efficiency of 15·4%. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献