Cluster formation for multi-strain infections with cross-immunity

Many infectious diseases exist in several pathogenic variants, or strains, which interact via cross-immunity. It is observed that strains tend to self-organise into groups, or clusters. The aim of this paper is to investigate cluster formation. Computations demonstrate that clustering is independent of the model used, and is an intrinsic feature of the strain system itself. We observe that an ordered strain system, if it is sufficiently complex, admits several cluster structures of different types. Appearance of a particular cluster structure depends on levels of cross-immunity and, in some cases, on initial conditions. Clusters, once formed, are stable, and behave remarkably regularly (in contrast to the generally chaotic behaviour of the strains themselves). In general, clustering is a type of self-organisation having many features in common with pattern formation

Thermonuclear burn-up in deuterated methane CD4CD_4

The thermonuclear burn-up of highly compressed deuterated methane CD$_4$ is considered in the spherical geometry. The minimal required values of the burn-up parameter $x = \rho_0 \cdot r_f$ are determined for various temperatures $T$ and densities $\rho_0$. It is shown that thermonuclear burn-up in $CD_4$ becomes possible in practice if its initial density $\rho_0$ exceeds $\approx 5 \cdot 10^3$ $g \cdot cm^{-3}$. Burn-up in CD$_2$T$_2$ methane requires significantly ($\approx$ 100 times) lower compressions. The developed approach can be used in order to compute the critical burn-up parameters in an arbitrary deuterium containing fuel

Статеві особливості фізичного розвитку студентів

Sexual features of physical development of students studied at the technical specialties of higher educational establishments were studied. According to our data, there is not the authentic distinctions on calendar age between young men and girls. However, they differ by physical development and functional age. The rate of physical development of the girls is more than of the young men. The girls’ physical development is characterized by formation of internal system interrelations between elements of the functional system.Вивчалися статеві особливості фізичного розвитку у студентів технічних спеціальностей вищих навчальних закладів. Згідно з наведеними даними, між юнаками та дівчатами немає достовірної різниці за календарним віком. Однак, як за темпом фізичного розвитку, так і за показниками функціонального віку спостерігається достовірна різниця. У студенток фізико-технічного факультету спостерігається більший темп фізичного розвитку, ніж у студентів того ж факультету. Фізичний розвиток у дівчат характеризується формуванням внутрішньосистемних взаємозв’язків між елементами функціональної системи.Вивчалися статеві особливості фізичного розвитку у студентів технічних спеціальностей вищих навчальних закладів. Згідно з наведеними даними, між юнаками та дівчатами немає достовірної різниці за календарним віком. Однак, як за темпом фізичного розвитку, так і за показниками функціонального віку спостерігається достовірна різниця. У студенток фізико-технічного факультету спостерігається більший темп фізичного розвитку, ніж у студентів того ж факультету. Фізичний розвиток у дівчат характеризується формуванням внутрішньосистемних взаємозв’язків між елементами функціональної системи

Compressible flow structures interaction with a two-dimensional ejector: a cold-flow study

An experimental study has been conducted to examine the interaction of compressible flow structures such as shocks and vortices with a two-dimensional ejector geometry using a shock-tube facility. Three diaphragm pressure ratios ofP4 =P1 = 4, 8, and 12 have been employed, whereP4 is the driver gas pressure andP1 is the pressure within the driven compartment of the shock tube. These lead to incident shock Mach numbers of Ms = 1:34, 1.54, and 1.66, respectively. The length of the driver section of the shock tube was 700 mm. Air was used for both the driver and driven gases. High-speed shadowgraphy was employed to visualize the induced flowfield. Pressure measurements were taken at different locations along the test section to study theflow quantitatively. The induced flow is unsteady and dependent on the degree of compressibility of the initial shock wave generated by the rupture of the diaphragm

Basic principles of arch prosthetics

The development of prosthetic dentistry provides improvement of different dental prostheses to increase the level of dental care efficiency. The manual is aimed to provide comprehension of the present day views on the arch prostheses production considering theoretical and practical value of classical techniques. The manual contains the programme material on prosthetic dentistry educational discipline and concerns the issues discussed in the section «Arch prosthetics». The current methods of arch prostheses fixation are widely covered in the manual as well as planning approaches and prosthesis design choice. Particular attention is paid to the basic technological stages of prostheses manufacturing. The text is illustrated with the color drawings improving the presented material comprehension, the list of questions is directed on self-control of acquired knowledge. The authors will be sincerely grateful to colleagues for constructive remarks and useful suggestions in improving the presented material. Authentic translation from Ukrainian Language

First Principles Modeling of Nonlinear Incidence Rates in Seasonal Epidemics

In this paper we used a general stochastic processes framework to derive from first principles the incidence rate function that characterizes epidemic models. We investigate a particular case, the Liu-Hethcote-van den Driessche's (LHD) incidence rate function, which results from modeling the number of successful transmission encounters as a pure birth process. This derivation also takes into account heterogeneity in the population with regard to the per individual transmission probability. We adjusted a deterministic SIRS model with both the classical and the LHD incidence rate functions to time series of the number of children infected with syncytial respiratory virus in Banjul, Gambia and Turku, Finland. We also adjusted a deterministic SEIR model with both incidence rate functions to the famous measles data sets from the UK cities of London and Birmingham. Two lines of evidence supported our conclusion that the model with the LHD incidence rate may very well be a better description of the seasonal epidemic processes studied here. First, our model was repeatedly selected as best according to two different information criteria and two different likelihood formulations. The second line of evidence is qualitative in nature: contrary to what the SIRS model with classical incidence rate predicts, the solution of the deterministic SIRS model with LHD incidence rate will reach either the disease free equilibrium or the endemic equilibrium depending on the initial conditions. These findings along with computer intensive simulations of the models' Poincaré map with environmental stochasticity contributed to attain a clear separation of the roles of the environmental forcing and the mechanics of the disease transmission in shaping seasonal epidemics dynamics