Natural selection and asymmetry: the points of intersection

The vast majority of contemporary scientists resolve Wienner's dilemma "to know nothing about everything or to know everything about nothing" in favor of the second possibility. Avalanche-like increase of scientific knowledge urges scientists to operate with an enormous amount of information concentrated in such a narrow field that its area really tends to zero. Sadly as it may sound, the hyperbole "nothing about everything" is often relevant to all branches of their own discipline in whose investigation scientists are not directly engaged. In this respect biology does not make any exception. Several decades ago, it seemed that scientists who study the action of the natural selection and those dealing with cell biology have very little to tell to each other. Fortunately, trends appear in the last decades which permit to throw bridges between these areas. The application of DNA-sequences in examination of phylogenetic relationships is an example in this respect. We believe that asymmetry in man could be another example. Both the symmetry and its "alter ego", asymmetry, are undoubtedly results of the natural selection. On the other hand, the ontogenetic pathways towards bilateral symmetry and the extent of deviations from it are genetically determined at cell and molecular levels. Though complicated, this relationship is so regular that one kind of asymmetry became a measure for the intensity and effectiveness of one of the forms of natural selection.Biomedical Reviews 1992; 1: 63-68

A probabilistic model for gene content evolution with duplication, loss, and horizontal transfer

We introduce a Markov model for the evolution of a gene family along a phylogeny. The model includes parameters for the rates of horizontal gene transfer, gene duplication, and gene loss, in addition to branch lengths in the phylogeny. The likelihood for the changes in the size of a gene family across different organisms can be calculated in O(N+hM^2) time and O(N+M^2) space, where N is the number of organisms, $h$ is the height of the phylogeny, and M is the sum of family sizes. We apply the model to the evolution of gene content in Preoteobacteria using the gene families in the COG (Clusters of Orthologous Groups) database

Joint scaling laws in functional and evolutionary categories in prokaryotic genomes

We propose and study a class-expansion/innovation/loss model of genome evolution taking into account biological roles of genes and their constituent domains. In our model numbers of genes in different functional categories are coupled to each other. For example, an increase in the number of metabolic enzymes in a genome is usually accompanied by addition of new transcription factors regulating these enzymes. Such coupling can be thought of as a proportional "recipe" for genome composition of the type "a spoonful of sugar for each egg yolk". The model jointly reproduces two known empirical laws: the distribution of family sizes and the nonlinear scaling of the number of genes in certain functional categories (e.g. transcription factors) with genome size. In addition, it allows us to derive a novel relation between the exponents characterising these two scaling laws, establishing a direct quantitative connection between evolutionary and functional categories. It predicts that functional categories that grow faster-than-linearly with genome size to be characterised by flatter-than-average family size distributions. This relation is confirmed by our bioinformatics analysis of prokaryotic genomes. This proves that the joint quantitative trends of functional and evolutionary classes can be understood in terms of evolutionary growth with proportional recipes.Comment: 39 pages, 21 figure

The peculiarities of perspective students selection mechanism by the future employers-enterprise

© 2015, Canadian Center of Science and Education. All rights reserved. The search of qualified staff is an up-to-date problem for all enterprises. In this regard the aim of the research is the development of perspective students selection mechanism by the future employers. One of the sub-stages of the algorithm is the formation of the resource and reserve groups of students by the enterprise representatives and by tutors of the faculty of professional educational institutions. The formation of the resource and reserve groups of students with flexible system of transition from one group into another according to the results of their progress, according to participation extracurricular life of the institute, participation at the international, All-Russian scientific and practical conferences, allow to intensify the process of their self-preparation by means of creation of the natural competitive environment in educational institution of professional education. It also helps to do the selection by employers and to distribute perspective students taking into account their potential opportunities and professional interests

The didactic construct of design technologies in the educational process of modern university

© 2015, Mediterranean Center of Social and Educational Research. All rights reserved. The relevance of the problem of arranging the educational process in modern university using design technology remains one of the most demanded in educating the future experts for modern production. Therefore, the objective of this article is to submit a scientific rationale for the didactic construct of design technologies in higher educational process as a productive educational model focused on educating a student's personality - a future professional demanded by today's job market. The paper submits theoretic and methodological foundations for designing and implementing project technologies into the university educational process, the nature and structure of the didactic construct of these technologies as a system category (the learning objectives, syllabus, the means of pedagogical partnership including motivation and teaching tools, arrangement of the educational process, the subjects of the learning process, the results of the activity and the level of professional proficiency). The article submissions may be useful for the teachers of educational institutions in the system of continuing professional education, young scientists, post graduate students, the university counselors, the attendants of the advanced training and retraining courses. It is also recommended for undergraduates and students participating in the research work

Search for the QCD critical point in nuclear collisions at the CERN SPS

Pion production in nuclear collisions at the SPS is investigated with the aim to search, in a restricted domain of the phase diagram, for power-laws in the behavior of correlations which are compatible with critical QCD. We have analyzed interactions of nuclei of different size (p+p, C+C, Si+Si, Pb+Pb) at 158$A$ GeV adopting, as appropriate observables, scaled factorial moments in a search for intermittent fluctuations in transverse dimensions. The analysis is performed for $\pi^+\pi^-$ pairs with invariant mass very close to the two-pion threshold. In this sector one may capture critical fluctuations of the sigma component in a hadronic medium, even if the $\sigma$-meson has no well defined vacuum state. It turns out that for the Pb+Pb system the proposed analysis technique cannot be applied without entering the invariant mass region with strong Coulomb correlations. As a result the treatment becomes inconclusive in this case. Our results for the other systems indicate the presence of power-law fluctuations in the freeze-out state of Si+Si approaching in size the prediction of critical QCD.Comment: 31 pages, 11 figure

Inclusive production of charged pions in p+C collisions at 158 GeV/c beam momentum

The production of charged pions in minimum bias p+C interactions is studied using a sample of 377000 inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area ranging from 0 to 1.8 GeV/c in transverse momentum and from -0.1 to 0.5 in Feynman x. Inclusive invariant cross sections are given on a grid of 270 bins per charge thus offering for the first time a dense coverage of the projectile hemisphere and of the cross-over region into the target fragmentation zone.Comment: 31 pages, 30 figures, submitted to European Journal of Physic

System-size and centrality dependence of charged kaon and pion production in nucleus-nucleus collisions at 40A GeV and158A GeV beam energy

Measurements of charged pion and kaon production are presented in centrality selected Pb+Pb collisions at 40A GeV and 158A GeV beam energy as well as in semi-central C+C and Si+Si interactions at 40A GeV. Transverse mass spectra, rapidity spectra and total yields are determined as a function of centrality. The system-size and centrality dependence of relative strangeness production in nucleus-nucleus collisions at 40A GeV and 158A GeV beam energy are derived from the data presented here and published data for C+C and Si+Si collisions at 158A GeV beam energy. At both energies a steep increase with centrality is observed for small systems followed by a weak rise or even saturation for higher centralities. This behavior is compared to calculations using transport models (UrQMD and HSD), a percolation model and the core-corona approach.Comment: 32 pages, 14 figures, 4 tables, typo table II correcte

Phase-space dependence of particle-ratio fluctuations in Pb+Pb collisions from 20A to 158A GeV beam energy

A novel approach, the identity method, was used for particle identification and the study of fluctuations of particle yield ratios in Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS). This procedure allows to unfold the moments of the unknown multiplicity distributions of protons (p), kaons (K), pions ($\pi$) and electrons (e). Using these moments the excitation function of the fluctuation measure $\nu_{\text{\text{dyn}}}$[A,B] was measured, with A and B denoting different particle types. The obtained energy dependence of $\nu_{\text{dyn}}$ agrees with previously published NA49 results on the related measure $\sigma_{\text{dyn}}$. Moreover, $\nu_{\text{dyn}}$ was found to depend on the phase space coverage for [K,p] and [K,$\pi$] pairs. This feature most likely explains the reported differences between measurements of NA49 and those of STAR in central Au+Au collisions

Measurement of event-by-event transverse momentum and multiplicity fluctuations using strongly intensive measures Δ[PT,N]\Delta[P_T, N] and Σ[PT,N]\Sigma[P_T, N] in nucleus-nucleus collisions at the CERN Super Proton Synchrotron

Results from the NA49 experiment at the CERN SPS are presented on event-by-event transverse momentum and multiplicity fluctuations of charged particles, produced at forward rapidities in central Pb+Pb interactions at beam momenta 20$A$, 30$A$, 40$A$, 80$A$, and 158$A$ GeV/c, as well as in systems of different size ($p+p$, C+C, Si+Si, and Pb+Pb) at 158$A$ GeV/c. This publication extends the previous NA49 measurements of the strongly intensive measure $\Phi_{p_T}$ by a study of the recently proposed strongly intensive measures of fluctuations $\Delta[P_T, N]$ and $\Sigma[P_T, N]$. In the explored kinematic region transverse momentum and multiplicity fluctuations show no significant energy dependence in the SPS energy range. However, a remarkable system size dependence is observed for both $\Delta[P_T, N]$ and $\Sigma[P_T, N]$, with the largest values measured in peripheral Pb+Pb interactions. The results are compared with NA61/SHINE measurements in $p+p$ collisions, as well as with predictions of the UrQMD and EPOS models.Comment: 12 pages, 14 figures, to be submitted to PR