Simultaneous iteration for the matrix eigenvalue problem

Let B be a given positive definite Hermitian matrix, and assume the matrix P satisfies the “normality” condition PB^?1P^HB=B^?1P^HBP, where P^H denotes the Hermitian of P. In this paper, we develop an accelerated version of simultaneous iteration for partial solution of the eigenproblem Px=λx. Convergence together with sharp error bounds is obtained. The results are then applied to the solution of the symmetric eigenproblem Ax=λBx, where the algorithms are shown to be improvements over existing techniques.     

Water-soluble copolymers. X. Copolymers of acrylamide with N-(1,1-dimethyl-3-oxybutyl)acrylamide and N,N-dimethylacrylamide: Solution properties

Dilute solution properties of copolymers of acrylamide (AM) with N-(1,1-dimethyl-3-oxybutyl)acrylamide (DAAM) and with N,N-dimethylacrylamide (DMAM) have been studied as a function of composition, temperature, time, and added electrolytes sodium chloride and calcium chloride. Unlike the AM-DMAM copolymers, the AM-DAAM copolymers show solution viscosity increases in the presence of added NaCl and CaCl₂ and decreases with increasing temperature which are related to copolymer composition. The unusual viscosity behavior of the DAAM-AM copolymers is suspected to be due to chain extension resulting from intramolecular hydrogen bonding and other cooperative associations along the macromolecular backbone.     

Deeply virtual compton scattering off the neutron

The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e,e'gamma)X cross section measured at Q2=1.9 GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_{q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.     

Molecular deformation and free-solution electrophoresis of DNA-uncharged polymer conjugates at high field strengths: theoretical predictions. Part 1: hydrodynamic segregation

Recent advancements in DNA sequencing by end-labeled free-solution electrophoresis (ELFSE) show the promise of this novel technique which overcomes the need for a gel by using a label (or drag-tag) to render the free solution mobility of the DNA size-dependent. It is the attachment of an uncharged drag-tag molecule of a set size to various lengths of DNA in the sample that selectively slows down smaller DNA chains which have less force to pull the drag-tag than larger DNA. So far, only globally random coil conformations have been associated with ELFSE, i.e., the DNA and the label together form a single, undeformed hydrodynamic unit. This paper investigates the conditions under which the DNA and label will segregate into two hydrodynamically distinct units, based on a theoretical approach developed for the electrophoresis of polyampholytes. Optimal experimental conditions tailored to the available label sizes and voltages are predicted along with insight into ideal label architecture.     

Water-Soluble Random and Graft Copolymers for Utilization in Enhanced Oil Recovery

Copolymer structure has a marked effect on solution properties and thus behavioral characteristics of water-soluble copolymers utilized in enhanced oil recovery. The ability of random and graft copolymers to maintain large hydrodynamic volumes in dilute solutions in the presence of mono- and divalent electrolytes is critical for mobility control. The differences in viscosity behavior are described for a series of random and graft copolymers of acryl-amide with sodium-2-acrylamido-2-methylpropane sulfonate (NaAMPS), diacetone acrylamide (DAAM), and sodium acrylate (NaA) as a function of polymer microstructure, temperature, concentration, and added electrolytes. Copolymers of AM-NaAMPS show enhanced salt tolerance and phase stability over their AM-NaA counterparts with similar compositions and molecular weights. The AM-DAAM copolymers show unusual solution behavior with increases in viscosity in the presence of added salt.     

Water-Soluble Copolymers. XX. Copolymers of Acrylamide with Sodium 3-(N-Propyl)Acrylamido-3-Methylbutanoate: Solution Properties

Dilute solution properties of copolymers of acrylamide (AM) with sodium 3-(N-propyl)acrylamido-3-methylbutanoate (NaPAMB) of known molecular weight have been studied as a function of composition, temperature, time, pH, and added electrolytes. Phase separation and potentiometric studies have also been performed. The AM-NaPAMB copolymers possess lower molecular weights and solution viscosities than the AM-NaAMB copolymers. In addition, the AM-NaPAMB polymers exhibit moderate viscosity-temperature coefficients and poor salt tolerance. These polymers undergo phase separation in the presence of divalent cations as a function of temperature. The observed properties can be related to the steric and hydrophobic effects caused by the presence of the n-propyl substituent at the amide nitrogen.     

Liquid‐Phase Enantioselective Chromatographic Resolution Using Interpenetrated,Homochiral Framework Materials

Effective separation of mixtures of enantiomers is of continuing interest in analytical and preparative chromatography, with new materials frequently designed and tested. We report two new enantiomerically pure 2D→3D interpenetrated materials used as stationary liquid chromatographic (LC) phases that are shown to resolve selected racemic mixtures with enantiomeric and chemical selectivity. Dicarboxylate ligands derived from amino acids on naphthalene and perylene cores form 2D frameworks that interpenetrate to give 3D structures. Selectivity is initially tested by uptake from solution; subsequent LC methods show that the materials exhibit resolution of racemic analytes in ‘micro‐columns’ and that the two closely related materials show markedly different selectivity for different analytes with much greater activity than the ligands alone. Comparison with a close‐packed analogue suggests that the separation activity is largely due to surface effects.