Branching Processes and Multi-Particle Production

The general theory of the branching processes is used for establishing the relation between the parameters $k$ and $\bar n$ of the negative binomial distribution. This relation gives the possibility to describe the overall data on multiplicity distributions in $pp (p\bar p)$-collisions for energies up to 900 GeV and to make several interesting predictions for higher energies. This general approach is free from ambiguities associated with the extrapolation of the parameter $k$ to unity.Comment: 13 pages, (8 figures available on request), DUKE-TH-93-5

Pyrene, a Test Case for Deep-Ultraviolet Molecular Photophysics

We determined the complete relaxation dynamics of pyrene in ethanol from the second bright state, employing experimental and theoretical broadband heterodyne detected transient grating and two-dimensional photon echo (2DPE) spectroscopy, using pulses with duration of 6 fs and covering a spectral range spanning from 250 to 300 nm. Multiple lifetimes are assigned to conical intersections through a cascade of electronic states, eventually leading to a rapid population of the lowest long-living excited state and subsequent slow vibrational cooling. The lineshapes in the 2DPE spectra indicate that the efficiency of the population transfer depends on the kinetic energy deposited into modes required to reach a sloped conical intersection, which mediates the decay to the lowest electronic state. The presented experimental–theoretical protocol paves the way for studies on deep-ultraviolet-absorbing biochromophores ubiquitous in genomic and proteic systems

Quantum criticality at cryogenic melting of polar bubble lattices

Quantum fluctuations (QFs) caused by zero-point phonon vibrations (ZPPVs) are known to prevent the occurrence of polar phases in bulk incipient ferroelectrics down to 0K1-3. On the other hand, little is known about the effects of QFs on the recently discovered topological patterns in ferroelectric nanostructures4-9. Here, by using an atomistic effective Hamiltonian within classical Monte Carlo (CMC) and path integral quantum Monte Carlo (PI-QMC)1,3,10,11, we unveil how QFs affect the topology of several dipolar phases in ultrathin Pb(Zr0.4Ti0.6)O3 (PZT) films. In particular, our PI-QMC simulations show that the ZPPVs do not suppress polar patterns but rather stabilize the labyrinth4, bimeron5 and bubble phases12,13 within a wider range of bias field magnitudes. Moreover, we reveal that quantum fluctuations induce a quantum critical point (QCP) separating a hexagonal bubble lattice from a liquid-like state characterized by spontaneous motion, creation and annihilation of polar bubbles at cryogenic temperatures. Finally, we show that the discovered quantum melting is associated with anomalous physical response, as, e.g., demonstrated by a negative longitudinal piezoelectric coefficient.Comment: Nature communication, accepted, 21 pages, 4 Fig

A problem of the study and regeneration of small rivers on Tatarstan territory

© SGEM2017 All Right Reserved. The numerous cases of the upper headwaters drying are observed in the plains of the Middle Volga region. The reasons of the streamflow change pertain to the reduction of forest vegetation and the change of its species composition. More than 1000 cartographic materials for more than 200 years, as well as aerial and satellite imagery were used during the research of forest vegetation breadth. Currently, the forest and the forest-field landscapes prevail in the north of Tatarstan, where coniferous-deciduous forests are widespread. The forest-fields, as well as the field landscapes are common in the west and south of Tatarstan, where deciduous forests and forest-steppe are prevalent. In the field landscapes the water runoff in the flood time increases to 65% of the total annual runoff, while the monthly summer runoff of low water reduces by 2.5 times compared to forest landscapes. The studies have shown that over the past about140 years the quantity of the first-order watercourses has reduced by 1.5 times in the area of mixed forests, whilst in the forest-steppe zone the quantity of the first-order watercourses has decreased by nearly 2.7 times. At the same time woodland in different regions of Tatarstan has decreased by 1.6-2.8 times for the same period of time. Low of the forest cover (17.9%), as well as the species composition of forests, in which the coniferous species as the most valuable for the infiltration does not exceed 24% from the forest area, are characterized for of Tatarstan territory. Coniferous plantations by more than half are presented the unstable monocultures of pine

The role of vegetation in conservation of small rivers in the Middle Volga

© 2015, Mediterranean Center of Social and Educational Research. All rights reserved. The numerous cases of the upper headwaters drying are observed in the plains of the Middle Volga region. The reasons of the streamflow change pertain to the reduction of forest vegetation and the change of its species composition. The studies have shown that over the past 120 years the quantity of the first-order watercourses has reduced by 1.5 times in the areas of coniferous and mixed forests, whilst in the forest-steppe zone the quantity of the first-order watercourses has decreased by nearly 2.5 times

Simulation of photo-excited adenine in water with a hierarchy of equations of motion approach

We present a theoretical method to simulate the electronic dynamics and two-dimensional ultraviolet spectra of the nucleobase adenine in water. The method is an extension of the hierarchy of equation of motion approach to treat a model with one or more conical intersections. The application to adenine shows that a two-level model with a direct conical intersection between the optically bright state and the ground state, generating a hot ground state, is not consistent with experimental observations. This supports a three-level model for the decay of electronically excited adenine in water as was previously proposed in [Prokhorenko et al., J. Phys. Chem. Lett. 7, 4445 (2016)]

Giant electrocaloric response in the prototypical Pb(Mg,Nb)O3_{3} relaxor ferroelectric from atomistic simulations

An atomistic effective Hamiltonian is used to investigate electrocaloric (EC) effects of Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$ (PMN) relaxor ferroelectrics in its ergodic regime, and subject to electric fields applied along the pseudocubic [111] direction. Such Hamiltonian qualitatively reproduces (i) the electric field-versus-temperature phase diagram, including the existence of a critical point where first-order and second-order transitions meet each other; and (ii) a giant EC response near such critical point. It also reveals that such giant response around this critical point is microscopically induced by field-induced percolation of polar nanoregions. Moreover, it is also found that, for any temperature above the critical point, the EC coefficient-versus-electric field curve adopts a maximum (and thus larger electrocaloric response too), that can be well described by the general Landau-like model proposed in [Jiang et al, Phys. Rev. B 96, 014114 (2017)] and that is further correlated with specific microscopic features related to dipoles lying along different rhombohedral directions. Furthermore, for temperatures being at least 40 K higher than the critical temperature, the (electric field, temperature) line associated with this maximal EC coefficient is below both the Widom line and the line representing percolation of polar nanoregions.Comment: 6 pages, 5 figure

Phyto-geographical approach in creation urban landscapes (by the example of Kazan City)

A great emphasis in the urbanized landscapes is laid on the reconstruction of the existing natural vegetation and the formation of artificial greenery. Green construction projects must take into account data on the biological characteristics of tree species and their adaptation to the specific growing conditions, as well as understand the peculiarity of the geographical conditions and abiotic environmental factors emerging in urban environment. We have identified 99 species and forms on the territory of the residential areas of Kazan, as well as held biomorphological analysis of the morphostructural and ecological features of dendroflora. Based on data on landscape features within the urban areas we have distinguished 10 types of plants subject to their anthropogenic transformation. For each of them, we have conducted assessment of their habitat conditions by indication methods, as well as proposed groups of species of trees and shrubs able to form sustainable plant communities

ЗАДАЧА З ІМПУЛЬСНОЮ ДІЄЮ ДЛЯ ОДНОГО РІВНЯННЯ КОЛИВАНЬ СТРУНИ

The development of modern science and technology requires thestudy of problems for differential equations describing processes withshort-term changes, or which are influenced by external forces, theduration of which can be neglected when compiling relevantmathematical models. Such tasks are found in thermophysics,mechanics, chemical technologies, biology, management theory and other branches of science and technology, where they studyprocesses under the influence of short-term forces and calledsystems with impulse action. Such systems contain differentialequations, an equation describing gaps in the first kind at moments ofimpulse action and impulse conditions. The presence of impulseaction substantially changes and complicates the behavior of thetrajectories of such problems, even for relatively simple differentialequations. The study of differential equations with impulse actionbegan with the development of nonlinear mechanics and attracted theattention of many researchers to the possibility to really describe theprocesses in nonlinear systems. In spite of the large number of worksdevoted to various questions of the theory of differential equationswith impulse action, a large number of problems of the qualitativetheory of such equations remain open for many cases. There is theinfluence of impulse action in fixed and non-fixed moments of time. Inthis paper we consider the process of oscillation of a string withinstantaneous increase of energy at moments when the full energy ofa string reaches this critical level. That is, the moments of impulseaction are not predetermined, but regulated by the process itself. Forsuch a task there are conditions for the existence of solutions forwhich the impulse action is carried out an infinite number of times andconstructed such solutions.Исследуется процесс колебаний струны с импульсным воздействием в моменты времени, когда полная энергия колебаний струныдостигает заданного критического значения. Определены условиясуществования решений, для которых импульсное воздействиепроисходит бесконечное количество раз и записано вид решений.Досліджено процес коливання струни з імпульсною дією при досягненні енергії коливання струни заданого критичного рівня. Визначено умови існування розв’язків, для яких імпульсна дія відбувається нескінчену кількість разів та записано вигляд розв’язків

INFLUENCE OF CHANGE OF POSITION OF FEMUR PROXIMAL SEGMENT ELEMENTS ON DIAGNOSTICS AND TREATMENT TACTICS OF HIP JOINT PATHOLOGY

The aim. of the research was to create diagnostic method for determination of attitude position of elements of femur proximal segment for understanding of development of hip joint pathology and determination of surgical tactics of treatment. The method of precise determination of angle interrelations between the elements of hip joint with use of multispiral computed tomograms. Offered method of diagnostics of estimation of position of elements of femur proximal segment is a necessary way of research of understanding for development of degenerative changes in hip joint and. also for determination of tactics and. method of treatment