Spatial-Temporal Structure of Mixed-Age Forest Boundary: The Simplest Mathematical Model

The modeling of forest ecosystems is one of IIASA's continuous research activities in the Environment Program. There are two main approaches to this modeling: a) simulation and b) qualitative (analytical). This paper belongs to the latter. Analytical models allow the prediction of the behavior of key variables of ecosystems and can be used to organize and analyze data produced by simulation models or obtained by observations. This paper is devoted to the study of a simple mathematical model of spatially distributed non-even-age forests. The main tools used in the paper are new methods of qualitative theory of non-linear differential equations. This work is a continuation of the cooperation in forest modeling at IIASA started in 1986-1989 by W. Clark, H. Shugart, R. Fleming and the authors of this paper

The two-parameter soliton family for the interaction of a fundamental and its second harmonic

For a system of interacting fundamental and second harmonics the soliton family is characterized by two independent parameters, a soliton potential and a soliton velocity. It is shown that this system, in the general situation, is not Galilean invariant. As a result, the family of movable solitons cannot be obtained from the rest soliton solution by applying the corresponding Galilean transformation. The region of soliton parameters is found analytically and con rmed by numerical integration of the steady equations. On the boundary of the region the solitons bifurcate. For this system there exist two kinds of bifurcation: supercritical and subcritical. In the rst case the soliton amplitudes vanish smoothly as the boundary is approached. Near the bifurcation point the soliton form is universal, determined from the nonlinear Schrodinger equation. For the second type of bifurcations the wave amplitudes remain nite at the boundary. In this case the Manley-Rowe integral increases inde nitely as the boundary is approached, and therefore according to the VK-type stability criterion, the solitons are unstable

THE INFLUENCE OF COMORBID ENDEMIC GOITER ON THE QUALITY OF LIFE OF PATIENTS WITH GASTROINTESTINAL PATHOLOGY

The impairment of adaptive mechanisms of functional systems of the body plays an important role in the occurrence of gastrointestinal diseases. This impairment is caused by unfavorable ecological and radiation conditions, external stress factors, food containing carcinogens, macro - and microelements deficiency. Technogenic environmental pollution contributes to decrease in the level of iodine in the body and more severe course of thyroid pathology. Diseases of the digestive and endocrine systems and their combination will occupy one of the leading places among the existing pathologies according to the forecasts of WHO experts in the XXI century. Adaptation of the body to various environmental influences is the most important factor in the quality of life. The relevance of the study was determined by the high incidence of psychological disadaptation, borderline personality disorders and, as a consequence, decrease in the quality of life in patients with gastrointestinal pathology and hypothyroidism. The article presents the results of comparative analysis of the quality of life indications of patients with gastric ulcer and / or gastroesophageal reflux disease in combination with hypothyroidism. The Russian-language analogue of the international questionnaire SF36 was used to analyze the indicatoions of patients\u27 quality of life. The results of the study will allow to formulate the diagnosis exactly and organize adequate, comprehensive multidisciplinary treatment

Bifurcations of Solitary Waves

The paper provides a brief review of the recent results devoted to bifurcations of solitary waves. The main attention is paid to the universality of soliton behavior and stability of solitons while approaching supercritical bifurcations. Near the transition point from supercritical to subcritical bifurcations, the stability of two families of solitons is studied in the frame-work of the generalized nonlinear Schrodinger equation. It is shown that one-dimensional solitons corresponding to the family of supercritical bifurcations are stable in the Lyapunov sense. The solitons from the subcritical bifurcation branch are unstable. The development of this instability results in the collapse of solitons. Near the time of collapse, the pulse amplitude and its width exhibit a self-similar behavior with a small asymmetry in the pulse tails due to self-steepening

Особенности лечения заднего импиджмент-синдрома голеностопного сустава у артистов балета и спортсменов

35 posterior ankle arthroscopies for posterior ankle impingement were performed within the period of time between January 2014-April 2015. Radiological investigation and MRI were held preoperatively. The examinations and operations revealed the following findings: os trigonum 21 (60%), posterior lateral fracture 6 (17%), Stieda process 8 (23%). The patients were tested on the scale of AOFAS pre and post-operatively. In comparison with preoperational period all the patients recognized the decrease or full disappearance of pain syndrome as well as functional improvements (AOFAS 59,8 preoperatively to 93,9 2 months postoperatively). The posterior ankle arthroscopy is an efficient and relatively safe method for posterior ankle impingement treatment which works efficiently to eliminate or decrease pain syndrome and helps to recover the function of plantaris.С января 2014 г. по апрель 2015 г. было выполнено 35 артроскопий голеностопного сустава пациентам в возрасте от 13 до 35 лет по поводу заднего импиджмент-синдрома. До операции всем пациентам выполнены рентгенография и магнитно-резонансная томография. В ходе проведенных обследований и операций были обнаружены: os trigonum у 21 (60%), перелом заднелатерального отростка таранной кости - у 6 (17%) и отросток Stieda - у 8 (23%) пациентов. Спустя 2 месяца после операции у всех пациентов отмечено значительное снижение или исчезновение болевого синдрома, а также улучшение функциональных способностей по сравнению с предоперационным периодом. До операции средний балл по шкале AOFAS составил 59,8; через 2 месяца после операции - 93,9. Артроскопия заднего отдела голеностопного сустава является эффективным и относительно безопасным методом лечения заднего импиджмент-синдрома голеностопного сустава, эффективно снижает болевой синдром и улучшает функциональное состояние голеностопного сустава

Angular momenta creation in relativistic electron-positron plasma

Creation of angular momentum in a relativistic electron-positron plasma is explored. It is shown that a chain of angular momentum carrying vortices is a robust asymptotic state sustained by the generalized nonlinear Schrodinger equation characteristic to the system. The results may suggest a possible electromagnetic origin of angular momenta when it is applied to the MeV epoch of the early Universe.Comment: 20 pages, 6 figure

On the Stability Analysis of the Standing Forest Boundary

It is well known that many existing models of forest age structure dynamics describe time dynamics for a local area. However, it is known that real forest areas have age structures that vary from one gap to another. Local gaps are integrated into a joint forest ecosystem by various seed dispersion mechanisms and by the penetration of roots. The work of Antonovsky et al. (1989) was used as a base model for a qualitative description of a spatially distributed monospecies mixed age forest. This phenomenological model employs a diffusion term corresponding to various processes of "young" tree dispersion. The model allows one to predict the possibility of the existence of a stationary or traveling forest boundary. From one side of the boundary, the modeled forest demonstrates an equilibrium state with non-zero age class densities, while from the other side, there are no trees of the studied type. As was shown, the model analyzes the changes in the behavior of the forest boundary caused by an increase in the tree mortality rate due to anthropogenic impacts (from acid rain, for example). The present paper is devoted to studying the ability of the forest to resist the internal "negative" forces of forest ecosystems and external impacts on changes in the standing forest boundary (on a given model level)

Finite time singularities in a class of hydrodynamic models

Models of inviscid incompressible fluid are considered, with the kinetic energy (i.e., the Lagrangian functional) taking the form ${\cal L}\sim\int k^\alpha|{\bf v_k}|^2d^3{\bf k}$ in 3D Fourier representation, where $\alpha$ is a constant, $0<\alpha< 1$. Unlike the case $\alpha=0$ (the usual Eulerian hydrodynamics), a finite value of $\alpha$ results in a finite energy for a singular, frozen-in vortex filament. This property allows us to study the dynamics of such filaments without the necessity of a regularization procedure for short length scales. The linear analysis of small symmetrical deviations from a stationary solution is performed for a pair of anti-parallel vortex filaments and an analog of the Crow instability is found at small wave-numbers. A local approximate Hamiltonian is obtained for the nonlinear long-scale dynamics of this system. Self-similar solutions of the corresponding equations are found analytically. They describe the formation of a finite time singularity, with all length scales decreasing like $(t^*-t)^{1/(2-\alpha)}$, where $t^*$ is the singularity time.Comment: LaTeX, 17 pages, 3 eps figures. This version is close to the journal pape