Cell reactions in gastric tube and colon transplants in stenoses of esophageal anastomosis.

We studied morphological and cell characteristics of stenosis of esophagogastric and esophagocolonic anastomosis. It was demonstrated that sclerogenesis in the gastric transplants is associated with hypertrophy of leiomyocytes, hyperelastosis foci, degenerative and atrophic modifications of the glands, and foveolar cell hypersecretion. In colonic transplant, collagen synthesis predominates in the esophageal anastomosis and can be associated with proliferation of blood capillaries; hyperplastic reactions of leiomyocytes and elastic fibers are minor, colonocytes exhibit high secretory activity.

Effect of esophagoplasty on structural reorganization of colon transplant.

We studied ultrastructural reorganization of the colon transplant in delayed period after esophagoplasty. It was found that during functioning of the artificial esophagus, a complex of adaptive and pathologic processes occurs in the mucosa. Focal sclerosis of the mucosa and slight epithelial degeneration with hyperplasia and hypersecretion of goblet cells were found in biopsy specimens with stenosis of the anastomosis.

Interpolating moving least-squares methods for fitting potential energy surfaces: Improving efficiency via local approximants.

The local interpolating moving least-squares (IMLS) method for constructing potential energy surfaces is investigated. The method retains the advantageous features of the IMLS approach in that the ab initio derivatives are not required and high degree polynomials can be used to provide accurate fits, while at the same time it is much more efficient than the standard IMLS approach because the least-squares solutions need to be calculated only once at the data points. Issues related to the implementation of the local IMLS method are investigated and the accuracy is assessed using HOOH as a test case.

Experimental and computational studies of the phenyl radical reaction with allene.

The kinetics for the gas-phase reaction of phenyl radicals with allene has been measured by cavity ring-down spectrometry (CRDS), and the mechanism and initial product branching have been elucidated with the help of quantum-chemical calculations. The absolute rate constant measured by the CRDS technique can be expressed by the following Arrhenius equation: kallene (T=301-421 K)=(4.07+/-0.

Experimental and theoretical studies of the phenyl radical reaction with propene.

The kinetics for the reaction of C6H5 with propene has been measured by cavity ring-down spectrometry (CRDS) at temperatures 296-496 K under an Ar pressure of 40 Torr. The total rate constant can be given by the following Arrhenius expression (in units of cm3 mol(-1) s(-1)): k(C6H5 + C3H6) = 10(11.93+/-0.

The reaction of phenyl radical with molecular oxygen: a G2M study of the potential energy surface.

Ab initio G2M calculations have been performed to investigate the potential energy surface for the reaction of C6H5 with O2. The reaction is shown to start with an exothermic barrierless addition of O2 to the radical site of C6H5 to produce phenylperoxy (1) and, possibly, 1,2-dioxaspiro[2.5]octadienyl (dioxiranyl, 8) radicals.

Urea and urea nitrate decomposition pathways: a quantum chemistry study.

Electronic structure calculations have been performed to investigate the initial steps in the gas-phase decomposition of urea and urea nitrate. The most favorable decomposition pathway for an isolated urea molecule leads to HNCO and NH3. Gaseous urea nitrate formed by the association of urea and HNO3 has two isomeric forms, both of which are acid-base complexes stabilized by the hydrogen-bonding interactions involving the acidic proton of HNO3 and either the O or N atoms of urea, with binding energies (D0(o), calculated at the G2M level with BSSE correction) of 13.

Interpolating moving least-squares methods for fitting potential-energy surfaces: further improvement of efficiency via cutoff strategies.

In standard applications of interpolating moving least squares (IMLS) for fitting a potential-energy surface (PES), all available ab initio points are used. Because remote ab initio points negligibly influence IMLS accuracy and increase IMLS time-to-solution, we present two methods to locally restrict the number of points included in a particular fit. The fixed radius cutoff (FRC) method includes ab initio points within a hypersphere of fixed radius.

Reaction of phenyl radicals with acetylene: quantum chemical investigation of the mechanism and master equation analysis of the kinetics.

The mechanism of the C(6)H(5) + C(2)H(2) reaction has been investigated by various quantum chemical methods. Electrophilic addition to the CC triple bond is found to be the only important mode of phenyl radical attack on acetylene. The initially formed chemically activated C(6)H(5)C(2)H(2) adducts may follow several isomerization pathways in competition with collisional stabilization and H-elimination.

Experimental and computational studies of the phenyl radical reaction with propyne.

The kinetics for the gas-phase reaction of phenyl radical with propyne has been measured by cavity ring-down spectrometry (CRDS), and the mechanism and initial product branching have been elucidated with the help of quantum chemical calculations. Absolute rate constants measured by the CRDS technique can be expressed by the following Arrhenius equation: (k/cm(3) mol(-1) s(-1)): k(propyne)(T=301-428 K)=(3.68+/-0.