Ultrasonic technology for enhanced oil recovery from failing oil wells and the equipment for its implemention

A new method for the ultrasonic enhancement of oil recovery from failing wells is described. The technology involves lowering a source of power ultrasound to the bottom of the well either for a short treatment before removal or as a permanent placement for intermittent use. In wells where the permeability is above 20 mD and the porosity is greater than 15% ultrasonic treatment can increase oil production by up to 50% and in some cases even more. For wells of lower permeability and porosity ultrasonic treatment alone is less successful but high production rates can be achieved when ultrasound is applied in conjunction with chemicals. An average productivity increase of nearly 3 fold can be achieved for this type of production well using the combined ultrasound with chemical treatment technology.     

Conditions for positive definiteness of M-matrices

The present paper concentrates on conditions that are necessary and sufficient for M-matrices to be positive definite. The obtained results can be used in the analysis of productivity of the Leontief input-output model.     

Square‐Planar Ruthenium(II) Complexes: Control of Spin State by Pincer Ligand Functionalization

Functionalization of the PNP pincer ligand backbone allows for a comparison of the dialkyl amido, vinyl alkyl amido, and divinyl amido ruthenium(II) pincer complex series [RuCl{N(CH₂CH₂PtBu₂)₂}], [RuCl{N(CHCHPtBu₂)(CH₂CH₂PtBu₂)}], and [RuCl{N(CHCHPtBu₂)₂}], in which the ruthenium(II) ions are in the extremely rare square‐planar coordination geometry. Whereas the dialkylamido complex adopts an electronic singlet (S=0) ground state and energetically low‐lying triplet (S=1) state, the vinyl alkyl amido and the divinyl amido complexes exhibit unusual triplet (S=1) ground states as confirmed by experimental and computational examination. However, essentially non‐magnetic ground states arise for the two intermediate‐spin complexes owing to unusually large zero‐field splitting (D>+200 cm^?1). The change in ground state electronic configuration is attributed to tailored pincer ligand‐to‐metal π‐donation within the PNP ligand series.     

On the mechanism for the photooxidation of aromatic azides containing a secondary N–H bond: A sequence of intramolecular transformations with the formation of heterocyclic oximes

During the photooxidation of aromatic azides containing a secondary N–H bond at the para-position, a sequence of intramolecular transformations of nitroso oxides led to the formation of heterocyclic oximes along with the corresponding nitroso and nitro compounds.     

Phosphorylation reaction in cAPK protein kinase-free energy quantum mechanical/molecular mechanics simulations

We present results of a theoretical analysis of the phosphorylation reaction in cAMP-dependent protein kinase using a combined quantum mechanical and molecular mechanics (QM/MM) approach. Detailed analysis of the reaction pathway is provided using a novel QM/MM implementation of the nudged elastic band method, finite temperature fluctuations of the protein environment are taken into account using free energy calculations, and an analysis of hydrogen bond interactions is performed on the basis of calculated frequency shifts. The late transfer of the substrate proton to the conserved aspartate (D166), the activation free energy of 15 kcal/mol, and the slight exothermic (-3 kcal/mol) character of the reaction are all consistent with the experimental data. The near attack conformation of D166 in the reactant state is maintained by interactions with threonine-201, asparagine-177, and most notably by a conserved water molecule serving as a strong structural link between the primary metal ion and the D166. The secondary Mg ion acts as a Lewis acid, attacking the beta-gamma bridging oxygen of ATP. This interaction, along with a strong hydrogen bond between the D166 and the substrate, contributes to the stabilization of the transition state. Lys-168 maintains a hydrogen bond to a transferring phosphoryl group throughout a reaction process. This interaction increases in the product state and contributes to its stabilization.     

The Implications of (2S,4S)‐Hydroxyproline 4‐O‐Glycosylation for Prolyl Amide Isomerization

The conformations of peptides and proteins are often influenced by glycans O‐linked to serine (Ser) or threonine (Thr). (2S,4R)‐4‐Hydroxyproline (Hyp), together with L ‐proline (Pro), are interesting targets for O‐glycosylation because they have a unique influence on peptide and protein conformation. In previous work we found that glycosylation of Hyp does not affect the N‐terminal amide trans/cis ratios (K_trans/cis) or the rates of amide isomerization in model amides. The stereoisomer of Hyp—(2S,4S)‐4‐hydroxyproline (hyp)—is rarely found in nature, and has a different influence both on the conformation of the pyrrolidine ring and on K_trans/cis. Glycans attached to hyp would be expected to be projected from the opposite face of the prolyl side chain relative to Hyp; the impact this would have on K_trans/cis was unknown. Measurements of ³J coupling constants indicate that the glycan has little impact on the C^γ‐endo conformation produced by hyp. As a result, it was found that the D ‐galactose residue extending from a C^γ‐endo pucker affects both K_trans/cis and the rate of isomerization, which is not found to occur when it is projected from a C^γ‐exo pucker; this reflects the different environments delineated by the proline side chain. The enthalpic contributions to the stabilization of the trans amide isomer may be due to disruption of intramolecular interactions present in hyp; the change in enthalpy is balanced by a decrease in entropy incurred upon glycosylation. Because the different stereoisomers—Hyp and hyp—project the O‐linked carbohydrates in opposite spatial orientations, these glycosylated amino acids may be useful for understanding of how the projection of a glycan from the peptide or protein backbone exerts its influence.     

Mathematical modeling of methoxyanabasine C11H16N2O polymer solution ultrafiltration

This work covers the mathematical modeling of ultrafiltration with immobile membranes for physiologically-active of methoxyanabasine C₁₁H₁₆N₂O polymer solution. Methoxyanabasine is used as low toxic antineoplastic drug. On the basis of theoretical and experimental analysis of mass transfer and hydrodynamics, it is offered the mathematical model of permeability of membranes at an ultrafiltration of polymer solutions. Further the formulas for determination of factor of concentration polarization and ultrafiltration selectivity are calculated.