Analytic solution of the anisotropic bidomain equations for myocardial tissue: the effect of adjoining conductive regions

The anisotropic bidomain model for the propagation of electrical activation in the human myocardium H consists of coupled elliptic-parabolic partial differential equations for the transmembrane potential Vm, intracellular potential phi(i), and extracellular potential phi(e) in H, together with quasi-static equations for the potential distribution phiB in the surrounding (passive) isotropic extracardiac regions B. Four local parameters sigma((i,e) (l,t)) specify the conductivities in the longitudinal (l) and transverse (t) directions with respect to cardiac muscle fibers. Continuous current flow is required at the interface S(H) between H and B. We derive analytic formulas for Vm, phi(e), phi(i), and phiB for plane wave propagation in a uniformly anisotropic slab surmounted by a homogeneous region of conductivity sigmaB. No assumptions are required regarding the anisotropy ratios of the conductivity coefficients. The properties of these solutions are examined with a view to providing insight into the effect of the passive region B on the propagation of Vm and phi(e) in H. We show that for a suitably chosen boundary condition, the problem can be reduced to solving the bidomain equations in H alone.     

On the combinatorial derivation of the coefficients in the product density method

Zusammenfassung Die KoeffizientenC _r ⁿ in der Produktdichtenmethode (vgl. [3]) werden unmittelbar aus den Postulaten für die Verteilung kombinatorisch abgeleitet. Das Resultat wird in einen vonStevens gegebenen Ausdruck übergeführt.     

Nuclear polarization by electron paramagnetic resonance in paramagnetic crystals

The possibility of the polarization of nuclei in paramagnetic salts by saturation of electron paramagnetic resonance is theoretically analyzed. The proposed method assumes saturation of the forbidden transition of the typeM=±1, m=±1, ±2, for mutually perpendicular external magnetic and high-frequency fields. The analysis is carried out for the case of a large quadrupole moment of the nucleus. The degree of orientation attained is comparable in order of magnitude with Overhauser's method. This method is particularly suitable for the polarization of nuclei of transuranium elements.

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. M=± 1, m==±1, ±2 . . . .

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In conclusion the author would like to thank J. Burget, J. ajko, M. Kolá and M. ott for helping in the laborious solution of system (16).     

Einige neue Erkenntnisse über die Degradation von Titanaten im Zusammenhang mit der Exoemission

Ohne Zusammenfassung

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Treatment of Be+ ( 1 s? 1)2S Auger resonance with different decouplings of the dilated electron propagator

The diagonal 2ph-TDA and quasiparticle decouplings of the dilated electron propagator (based on an underlying bi-variational SCF) are utilized to calculate energy and width of the Be⁺(1_s ⁻¹)²S Auger resonance for the first time. Comparison with experimental and other theoretical results reveals that the renormalized infinite order diagonal 2ph-TDA decoupling seems to offer a less balanced approach to the treatment of resonances than the second-order decoupling. The diagonal quasiparticle approximation to the self energy is seen to offer an effective and economic alternative to the non-diagonal propagator calculations.     

Characterization (certification) of three wheat flours and a wheat gluten reference material (NIST RM 8436, 8437, 8438 and 8418) for essential and toxic major, minor and trace element constituents

Summary Three wheat flours, Durum Wheat Flour (NIST RM 8436), Hard Red Spring Wheat Flour (NIST RM 8437), Soft Winter Wheat Flour (NIST RM 8438) and Wheat Gluten (NIST RM 8418) Reference Materials were characterized for essential and toxic major, minor and trace elemental composition by analysts in an interlaboratory cooperative characterization campaign. Extensive application of widely varied analytical methods yielded 16–27 best estimate and 3–8 informational concentration values for each of these materials. These reference materials are intended for analytical quality control of element determinations in flour and flour products as well as other agricultural/food materials with related matrices.Contribution No. 92–145 from Centre for Land and Biological Resources Research     

One-parameter imbedding techniques for the solution of nonlinear boundary-value problems

A powerful numerical tool for the solution of nonlinear boundary-value problems —the one-parameter imbedding technique—is suggested. The basic principle is more than twenty years old; however, its numerical utilization has had only a few restricted applications up until recent times. The methods are divided into two categories: one- and multi-loop techniques. It is shown that the multi-loop techniques are of correct and incorrect type. Based on correct procedures new iteration techniques may be developed. Numerical solutions of differential equations arising for the one-parameter imbedding methods are presented along with the corresponding iteration techniques. Some typical imbedding procedures are discussed, and practical application of the method is demonstrated on calculated examples.     

Gas-phase and solution conformations of the alpha-L-iduronic acid structural unit of heparin

The IdoA2S structural unit of heparin (subunit G) may oscillate among the three conformations (4C1, 1C4, and 2So). Only the twisted boat conformation allowed the biologically active pentasaccharide unit of heparin (DEFGH) to bind to antithrombin. Our work reports, in detail, the results of systematic large-scale theoretical investigations of the three basic conformations (4C1, 1C4, and 2So) of the IdoA2S structural unit of heparin, its anionic forms, and its sodium salt using the B3LYP/6-311++G(d, p) and B3LYP/6-31+G(d) model chemistries. According to our calculations, the most stable structure of these molecules corresponds to the 2So skew-boat conformation. This form is also the most stable in a water solution. The 2So conformation of neutral molecules is not maintained in the anionic species. With anions, both 1C4 and 4C1 conformations are present. The relative stability of individual species of the substituted iduronic acid affects extra stabilization by means of intramolecular hydrogen bonds. The calculated macroscopic pKa of 1,4-DiOMe IdoA2S are as follows: pKa = 0.25 for the terminal C(2)-OSO3H group, pKa = 3.67 for the terminal C(5)-CO2H group, and pKa = 14.00 for the C(3)-OH hydroxyl group. The computed Gibbs interaction energies, DeltaGdegrees , for the reaction 1,4-DiOMe IdoA2S(2-) + 2Na+ <==> 1,4-DiOMe IdoA2SNa2 (4C1, 1C4, and 2So conformations) are negative and span a rather small energy interval (from -1244 to -1290 kJ mol(-1)).     

Affinity liquid chromatography and capillary electrophoresis of seminal plasma proteins

Interactions of boar, bull, and human seminal plasma proteins with heparin and phosphorylcholine were studied by affinity LC using heparin immobilized to a Toyopearl support. A step gradient elution from 0.15 to 1.50 M NaCl was employed to elute the seminal plasma proteins. Relative amounts of the heparin-binding fraction of seminal plasma proteins (H+) in seminal plasma of three species were determined. Further on, the fraction of seminal plasma proteins interacting with phosphorylcholine-binding proteins (P+) was evaluated. P+ proteins were not found in human seminal plasma and their highest amount was present in bull seminal plasma. A CE method was developed for separation of seminal plasma proteins. Various capillaries and separation conditions were tested; the best resolution was obtained in a bare-silica capillary, with a micellar system consisting of a 0.02 M borate buffer and 0.05 M SDS pH 10.0. The optimized conditions were applied to the identification of the components in boar plasma.