Numerical streamline patterns at swimmer's surface using RANS equations

The objective of this article is to perform a numerical modeling on the flow dynamics around a competitive female swimmer during the underwater swimming phase for a velocity of 2.2 m/s corresponding to national swimming levels. Flow around the swimmer is assumed turbulent and simulated with a computational fluid dynamics method based on a volume control approach. The 3D numerical simulations have been carried out with the code ANSYS FLUENT and are presented using the standard k-ω turbulence model for a Reynolds number of 6.4 × 10(6). To validate the streamline patterns produced by the simulation, experiments were performed in the swimming pools of the National Institute of Sports and Physical Education in Paris (INSEP) by using the tufts method.     

Dinosaurs and other tetrapods in an Early Cretaceous bauxite-filled fissure, northwestern Romania

The bauxite mine at Cornet near Oradea in northwestern Romania produced thousands of bones in an excavation in 1978, mainly from ornithopod dinosaurs and rarer pterosaurs. Bird specimens reported previously from this fauna are equivocal. The fossils are disarticulated bones in good condition which occur highly concentrated in lenses within bauxite clays, which are dated as Berriasian (earliest Cretaceous). The bauxite represents detrital material washed into deep fissures and caves formed within a karst of uplifted Tithonian (latest Jurassic) marine limestones. The bones are generally uniform in size and shape, and they are abraded, evidence for considerable transport and for winnowing of the deposit. The area was one of several islands on the northern shore of Tethys, and it was inundated by the sea later in the Early Cretaceous. There is evidence for insular adaptations in the dinosaur faunas. The ornithopod dinosaurs may include several taxa, but they are smaller on average than an assemblage of typical Wealden ornithopods, perhaps because of dwarfing on the island. In addition, sauropods are absent and theropods are barely represented in the fauna. The fauna is geographically significant since it shows relationships with western Europe and with Asia.     

Silencing of cryptic prophages in Corynebacterium glutamicum

DNA of viral origin represents a ubiquitous element of bacterial genomes. Its integration into host regulatory circuits is a pivotal driver of microbial evolution but requires the stringent regulation of phage gene activity. In this study, we describe the nucleoid-associated protein CgpS, which represents an essential protein functioning as a xenogeneic silencer in the Gram-positive Corynebacterium glutamicum. CgpS is encoded by the cryptic prophage CGP3 of the C. glutamicum strain ATCC 13032 and was first identified by DNA affinity chromatography using an early phage promoter of CGP3. Genome-wide profiling of CgpS binding using chromatin affinity purification and sequencing (ChAP-Seq) revealed its association with AT-rich DNA elements, including the entire CGP3 prophage region (187 kbp), as well as several other elements acquired by horizontal gene transfer. Countersilencing of CgpS resulted in a significantly increased induction frequency of the CGP3 prophage. In contrast, a strain lacking the CGP3 prophage was not affected and displayed stable growth. In a bioinformatics approach, cgpS orthologs were identified primarily in actinobacterial genomes as well as several phage and prophage genomes. Sequence analysis of 618 orthologous proteins revealed a strong conservation of the secondary structure, supporting an ancient function of these xenogeneic silencers in phage-host interaction.     

Deep Crustal Communities of the Juan de Fuca Ridge Are Governed by Mineralogy

Volcanic ocean crust contains a global chemosynthetic microbial ecosystem that impacts ocean productivity, seawater chemistry and geochemical cycling. We examined the mineralogical effect on community structure in the aquifer ecosystem by using a four-year in situ colonization experiment with igneous minerals and glasses in Integrated Ocean Drilling Program Hole 1301A on the Juan de Fuca Ridge. Microbial community analysis and scanning electron microscopy revealed that olivine phases and iron-bearing minerals bore communities that were distinct from iron-poor phases. Communities were dominated by Archaeoglobaceae, Clostridia, Thermosipho, Desulforudis and OP1 lineages. Our results suggest that mineralogy determines microbial composition in the subseafloor aquifer ecosystem.     

Comparative dendroclimatic study of Scots pine, Norway spruce, and silver fir in the Vrancea Range, Eastern Carpathian Mountains

Using dendroclimatical methods, we compared the growth response to climate fluctuations of three of the main Romanian Carpathian Mountains coniferous species, Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies Karst.) and silver fir (Abies alba Mill.), growing intermixed in a unique stand. Climate and soil conditions were therefore the same for all the trees studied. The experimental site was chosen to be representative of the south-exposed sites in the Romanian Carpathian Mountains, where pine occurs naturally. In order to investigate the consequences of fluctuations in climate at different temporal scales, we examined both inter-annual and decadal time-steps. An index of soil water deficit was computed to investigate the consequences of drought. Our study reveals that species exhibited different responses to precipitation, temperature or drought. Overall, pine was the most sensitive to precipitation, while spruce showed a higher response to temperature at high frequency for both the current and the previous growing seasons, and to soil water deficit. Fir was the least sensitive species of the comparison. However, for all species, decadal modulations of growth show precipitation as a common and strong driver on the dry south-facing slopes. The results show that Scots pine would be affected more than fir by increased drought frequency and could in the future be replaced on the xeric sites.     

Chromosome numbers and meiotic analysis in the pre-breeding of <Emphasis Type="BoldItalic">Brachiaria decumbens</Emphasis> (Poaceae)

A total of 44 accessions of Brachiaria decumbens were analysed for chromosome count and meiotic behaviour in order to identify potential progenitors for crosses. Among them, 15 accessions presented 2n = 18; 27 accessions, 2n = 36; and 2 accessions, 2n = 45 chromosomes. Among the diploid accessions, the rate of meiotic abnormalities was low, ranging from 0.82% to 7.93%. In the 27 tetraploid accessions, the rate of meiotic abnormalities ranged from 18.41% to 65.83%. The most common meiotic abnormalities were related to irregular chromosome segregation, but chromosome stickiness and abnormal cytokinesis were observed in low frequency. All abnormalities can compromise pollen viability by generating unbalanced gametes. Based on the chromosome number and meiotic stability, the present study indicates the apomictic tetraploid accessions that can act as male genitor to produce interspecific hybrids with B. ruziziensis or intraspecific hybrids with recently artificially tetraploidized accessions.     

Direct Quantification of the Attempt Frequency Determining the Mechanical Unfolding of Ubiquitin Protein

Understanding protein dynamics requires a comprehensive knowledge of the underlying potential energy surface that governs the motion of each individual protein molecule. Single molecule mechanical studies have provided the unprecedented opportunity to study the individual unfolding pathways along a well defined coordinate, the end-to-end length of the protein. In these experiments, unfolding requires surmounting an energy barrier that separates the native from the extended state. The calculation of the absolute value of the barrier height has traditionally relied on the assumption of an attempt frequency, υ^‡. Here we used single molecule force-clamp spectroscopy to directly determine the value of υ^‡ for mechanical unfolding by measuring the unfolding rate of the small protein ubiquitin at varying temperatures. Our experiments demonstrate a significant effect of the temperature on the mechanical rate of unfolding. By extrapolating the unfolding rate in the absence of force for different temperatures, varying within the range spanning from 5 to 45 °C, we measured a value for the activation barrier of ΔG^‡ = 71 ± 5 kJ/mol and an exponential prefactor υ^‡ ∼4 × 10⁹ s⁻¹. Although the measured prefactor value is 3 orders of magnitude smaller than the value predicted by the transition state theory (∼6 × 10¹² s⁻¹), it is 400-fold higher than that encountered in analogous experiments studying the effect of temperature on the reactivity of a protein-embedded disulfide bond (∼10⁷ m⁻¹ s⁻¹). This approach will allow quantitative characterization of the complete energy landscape of a folding polypeptide from highly extended states, of capital importance for proteins with elastic function.