Solitonic-exchange mechanism of surface~diffusion

We study surface diffusion in the framework of a generalized Frenkel-Kontorova model with a nonconvex transverse degree of freedom. The model describes a lattice of atoms with a given concentration interacting by Morse-type forces, the lattice being subjected to a two-dimensional substrate potential which is periodic in one direction and nonconvex (Morse) in the transverse direction. The results are used to describe the complicated exchange-mediated diffusion mechanism recently observed in MD simulations [J.E. Black and Zeng-Ju Tian, Phys. Rev. Lett. {\bf 71}, 2445-2448(1993)].Comment: 22 Revtex pages, 9 figures to appear in Phys. Rev.

Master equation approach to the conjugate pairing rule of Lyapunov spectra for many-particle thermostatted systems

The master equation approach to Lyapunov spectra for many-particle systems is applied to non-equilibrium thermostatted systems to discuss the conjugate pairing rule. We consider iso-kinetic thermostatted systems with a shear flow sustained by an external restriction, in which particle interactions are expressed as a Gaussian white randomness. Positive Lyapunov exponents are calculated by using the Fokker-Planck equation to describe the tangent vector dynamics. We introduce another Fokker-Planck equation to describe the time-reversed tangent vector dynamics, which allows us to calculate the negative Lyapunov exponents. Using the Lyapunov exponents provided by these two Fokker-Planck equations we show the conjugate pairing rule is satisfied for thermostatted systems with a shear flow in the thermodynamic limit. We also give an explicit form to connect the Lyapunov exponents with the time-correlation of the interaction matrix in a thermostatted system with a color field.Comment: 10 page

THE ROLE OF SCHWANN CELLS IN THE PATHOLOGY OF THE HUMAN APPENDIX IN CHILDREN

Objective: To compare the immunohistochemical (IHC) characteristics of appendices removed from children with acute appendicitis and chronic pain syndrome (CP) in the right lower quadrant of the abdomen (RLQA), as well as to define clinical and morphological correlations. Methods: The structure of fifty-one appendices of children aged 5-14 years who underwent appendectomy for chronic appendicitis/CP in the RLQA (24 patients, Group 1) and acute appendicitis (27 patients, Group 2) was assessed. Image analysis of histological sections stained with hematoxylin-eosin and immunohistochemically for S100 protein and proliferating cell nuclear antigen (PCNA) was performed. Results: Image analysis showed the presence of a significantly higher volume density (VD) and numerical density (ND) (p<0.05) of immunoreactive cells when stained for S100 protein, as well as the ND of intramural ganglia (p<0.05) against the background of minimal histological changes in the wall of the appendix in patients of Group 1 compared to Group 2. On the contrary, the ND of PCNA-immunoreactive cells was significantly higher in patients of Group 2 against the background of pronounced inflammatory changes in the appendix (p<0.01). In the biopsy samples of the Group 1 patients, a significantly higher ND of the lymphoid nodule germinal centers was also noted (p<0.05), while the ND of tingible body macrophages was higher in Group 2 patients (p<0.001). These results demonstrate differences in neuroimmune parameters in the appendices in the two described nosologic groups and indicate the possible role of the appendiceal neural component as a prerequisite for developing CP in the RLQA in childre

Paroxysmal supraventricular tachycardia in patient with dilated cardiomyopathy and concomitant cardiac conduction defects: a case report and discussion

Patients with dilated cardiomyopathy (DCM) often have intraventricular conduction disorders, which contribute to aggravation of heart failure, are progressive in most cases and can specify the prognosis of the disease. Paroxysmal supraventricular arrhythmias in such patients proceed with severe clinical manifestations, often accompanied by hemodynamic instability and syncope. A case report of patient (59 years old) with DCM, reduced left ventricular ejection fraction (35-37%), left bundle branch block, and paroxysmal orthodromic reciprocating tachycardia is presented. When an electrode was inserted on the right ventricular (RV) apex during the radiofrequency ablation, a third-degree atrioventricular (AV) block was recorded. This was maintained during the operation and was recurrent when trying to remove the electrode from the RV apex, and therefore there was a need for temporary and then permanent cardiac pacing therapy. Given DCM, reduced left ventricular ejection fraction, left bundle branch block, and the expected high percentage of RV pacing, a decision was made to implant a cardiac resynchronization therapy defibrillator. The literature review considers risk factors for formation of third-degree AV block during cardiac catheterization, methods of its prevention, as well as discusses the prognostic significance of catheter-induced conduction disorders, and indications for temporary and permanent cardiac pacing therapy