Strong neutral sweeps occurring during a population contraction

A strong reduction in diversity around a specific locus is often interpreted as a recent rapid fixation of a positively selected allele, a phenomenon called a selective sweep. Rapid fixation of neutral variants can however lead to similar reduction in local diversity, especially when the population experiences changes in population size, e.g., bottlenecks or range expansions. The fact that demographic processes can lead to signals of nucleotide diversity very similar to signals of selective sweeps is at the core of an ongoing discussion about the roles of demography and natural selection in shaping patterns of neutral variation. Here we quantitatively investigate the shape of such neutral valleys of diversity under a simple model of a single population size change, and we compare it to signals of a selective sweep. We analytically describe the expected shape of such neutral sweeps and show that selective sweep valleys of diversity are, for the same fixation time, wider than neutral valleys. On the other hand, it is always possible to parametrize our model to find a neutral valley that has the same width as a given selected valley. We apply our framework to the case of a putative selective sweep signal around the gene Quetzalcoatl in D. melanogaster and show that the valley of diversity in the vicinity of this gene is compatible with a short bottleneck scenario without selection. Our findings provide further insight in how simple demographic models can create valleys of genetic diversity that may falsely be attributed to positive selection.

COMPARATIVE ANALYSIS OF TERM-METAPHORS IN ENGLISH AND RUSSIAN CONSTRUCTION TERMINOLOGY

Purpose : To identify similarities and differences in the metaphorical way of formation of English and Russian construction terms, to identify the main lexical-semantic groups of common words that are the main sources of formation of term-metaphors in both languages . Methods . Comparative, descriptive and definitional methods were used to analyze language units and their dictionary definitions, identify similarities and national peculiarities of this method of term-formation. Results . Metaphorical transfer of commonly used concepts to special concepts is one of the sources of replenishment and updating of terminology. Groups of commonly used words and attributes that were used for naming special concepts are highlighted. Cases of using term-metaphors to form new terms using morphological means, word composition, or syntactic method are considered. The semantic relations between term- metaphors in Russian and English terminology are investigated. Conclusions. The article considers one of the ways of semantic term-formation, which is based on comparing the features of a new special concept with the features of an already known original concept, which contributes to the rapid fixation of this new concept in the mind of a specialist. Differences in the formation of term- metaphors should be taken into account when translating special texts.

Histomorphological Assessment of Formalin versus Nonformalin Fixatives in Diagnostic Surgical Pathology

Introduction Fixation is the critical step in the preservation of tissues in diagnostic pathology. The formalin is an economical and excellent fixative with the inherent property of adequate fixation. The well-established side effects of formalin include mucosal irritation, upper respiratory diseases, and corrosive injury to the gastrointestinal tract. In addition, substantial evidence exists regarding the potential role of formaldehyde as a human carcinogen. The carcinogenic and toxic effects of formalin encourage searching for alternative fixatives for tissue fixation. However, “the formalin dogma” has severely hampered the search for alternative fixatives for many years. Material and Methods Ninety tissues of liver and skeletal muscle obtained during autopsies were immersed in adequate amounts of the following fixatives: formalin (10%), methyl alcohol (70%), and acetone (100%). The comparison among the three was made based on time for fixation, preservation of tissue architecture, cell borders, cytoplasm, nuclear contours, chromatin texture, and uniformity of staining. Results The tissue preserved in formalin undergoes rapid fixation compared with alcohol and acetone. The tissue architecture, cell border characteristics of alcohol and acetone was found satisfactory compared with formalin. The cytoplasm and nuclear contour were superior with the formalin. The chromatin texture and uniformity of staining were similar with all the three fixatives. Conclusion The formalin is considered superior to most of the parameters, whereas both methyl alcohol and acetone showed nearly equivalent scores. Hence, owing to the potential human health hazards and carcinogenicity of formalin, no rational reasons hamper the complete substitution of formalin with alternative fixatives such as alcohol and acetone in diagnostic pathology and medical research.

Customized Orbit and Frontal Bone Implants

Orbitocranial reconstruction objectives include creation of a solid barrier between intracranial contents and the environment allowing restoration of physiologic homeostasis and restoration of aesthetic craniofacial contours. Historically, bone grafts have been used for reconstruction but were fraught with unpredictable resorption and imperfect contouring given the complex anatomy of the orbitofrontal bones. With advances in three-dimensional modeling technology, alloplastic custom implants in orbital and frontal bone reconstruction have allowed for rapid fixation reducing surgical times and improved cosmesis.

Factors That Determine the Adhesive Strength in a Bioinspired Bone Tissue Adhesive

Phosphoserine-modified cements (PMCs) are a family of wet-field tissue adhesives that bond strongly to bone and biomaterials. The present study evaluated variations in the adhesive strength using a scatter plot, failure mode, and a regression analysis of eleven factors. All single-factor, continuous-variable correlations were poor (R2 < 0.25). The linear regression model explained 31.6% of variation in adhesive strength (R2 = 0.316 p < 0.001), with bond thickness predicting an 8.5% reduction in strength per 100 μm increase. Interestingly, PMC adhesive strength was insensitive to surface roughness (Sa 1.27–2.17 μm) and the unevenness (skew) of the adhesive bond (p > 0.167, 0.171, ANOVA). Bone glued in conditions mimicking the operating theatre (e.g., the rapid fixation and minimal fixation force in fluids) produced comparable adhesive strength in laboratory conditions (2.44 vs. 1.96 MPa, p > 0.986). The failure mode correlated strongly with the adhesive strength; low strength PMCs (<1 MPa) failed cohesively, while high strength (>2 MPa) PMCs failed adhesively. Failure occurred at the interface between the amorphous surface layer and the PMC bulk. PMC bonding is sufficient for clinical application, allowing for a wide tolerance in performance conditions while maintaining a minimal bond strength of 1.5–2 MPa to cortical bone and metal surfaces.

Mitonuclear speciation

Current models of speciation assume that species arise when nuclear genotypes diverge following the disruption of gene flow between populations. This chapter explores the idea that speciation is specifically the result of divergence in coadapted mitonuclear gene complexes with divergence of most nuclear genes playing little or no role in speciation. To maintain mitonuclear coadaptation, nuclear genes must coevolve with rapidly changing mitochondrial genes. According to the mitonuclear compatibility concept of species, mitonuclear coevolution in isolated populations leads to speciation because population-specific mitonuclear coadaptations create between-population mitonuclear incompatibilities and hence barriers to gene flow between populations. In addition, selection for adaptive divergence of products of mitochondrial genes can lead to rapid fixation of novel mitochondrial genotypes between populations and consequently to disruption in gene flow between populations as the initiating step in animal speciation. The chapter considers the evidence for the involvement of mitonuclear compatibility in the process of speciation and the implications for this new concept of speciation and species.