Explore the vast range of titles available.

Background Diverse architectures of nervous systems (NSs) such as a plexus in cnidarians or a more centralized nervous system (CNS) in insects and vertebrates are present across Metazoa, but it is unclear what selection pressures drove evolution and diversification of NSs. One underlying aspect of this diversity lies in the cellular and molecular mechanisms driving neurogenesis, i.e. generation of neurons from neural precursor cells (NPCs). In cnidarians, vertebrates, and arthropods, homologs of SoxB and bHLH proneural genes control different steps of neurogenesis, suggesting that some neurogenic mechanisms may be conserved. However, data are lacking for spiralian taxa. Results To that end, we characterized NPCs and their daughters at different stages of neurogenesis in the spiralian annelid Capitella teleta. We assessed cellular division patterns in the neuroectoderm using static and pulse-chase labeling with thymidine analogs (EdU and BrdU), which enabled identification of NPCs that underwent multiple rounds of division. Actively-dividing brain NPCs were found to be apically-localized, whereas actively-dividing NPCs for the ventral nerve cord (VNC) were found apically, basally, and closer to the ventral midline. We used lineage tracing to characterize the changing boundary of the trunk neuroectoderm. Finally, to start to generate a genetic hierarchy, we performed double-fluorescent in-situ hybridization (FISH) and single-FISH plus EdU labeling for neurogenic gene homologs. In the brain and VNC, Ct-soxB1 and Ct-neurogenin were expressed in a large proportion of apically-localized, EdU+ NPCs. In contrast, Ct-ash1 was expressed in a small subset of apically-localized, EdU+ NPCs and subsurface, EdU− cells, but not in Ct-neuroD+ or Ct-elav1+ cells, which also were subsurface. Conclusions Our data suggest a putative genetic hierarchy with Ct-soxB1 and Ct-neurogenin at the top, followed by Ct-ash1, then Ct-neuroD, and finally Ct-elav1. Comparison of our data with that from Platynereis dumerilii revealed expression of neurogenin homologs in proliferating NPCs in annelids, which appears different than the expression of vertebrate neurogenin homologs in cells that are exiting the cell cycle. Furthermore, differences between neurogenesis in the head versus trunk of C. teleta suggest that these two tissues may be independent developmental modules, possibly with differing evolutionary trajectories.

This paper provides a fundamental understanding of “false friend” formation, i.e., hidden defects associated with lack of fusion, using an experimental setup that allowed an insight into the processing zone based on high-speed synchrotron X-ray imaging. The setup enabled the welding of a lap joint of AISI 304 high-alloy steel sheets (X5CrNi18-10/1.4301), with the ability to adjust different gap heights between top and bottom sheet (up to 0.20 mm) and to acquire high-speed X-ray images at 100 kHz simultaneously with the welding process. On this basis, a time-resolved description of the “false friend” formation can be provided by visualizing the interaction between keyhole and melt pool during laser welding and solidification processes within the gap area. The bridgeability of the gap was limited due to the gap height and insufficient melt supply leading to the solidification of the bridge. The distance between the solidified bridge and the keyhole increased with time, while the keyhole and melt pool dynamics initiated the formation of new melt bridges whose stability was defined by melt flow conditions, surface tension, and gap heights. The alternating formation and solidification of melt bridges resulted in entrapped areas of lacking fusion within the weld, i.e., “false friends.” Finally, based on the results of this study, a model concept is presented that concludes the main mechanisms of “false friend” formation.

Plasma transferred arc (PTA) welded coatings are used to improve surface properties of mechanical parts. Advantages are the high reliability of the process and the low dilution of substrate and coating material. Processing of surfaces by PTA welding is restricted at the time to flat horizontal position. Furthermore, industry is interested in the development of strategies for coating with PTA in constraint position as complex three-dimensional (3D) parts could be then easily processed as well. Under commercial aspects, the process design can be optimized to increase process efficiency and to reduce heat input during the welding process. Process optimization involves the determination of guidelines for PTA welding in constraint positions as well. Modeling the process gives an alternative to reduce the experimental effort to optimize the welding process. Results of simulation studies of the PTA welding process are given in the present work. It will be shown that coating conditions can be optimized by varying plasma gas flow, heat input and heat flow, process speed, or powder injection with regard to welding in constraint positions. The defined controlling of the PTA welding allows modification of process management with less experimental effort and to develop coating strategies for processing in different positions. In experimental investigations, the developed coating strategies are confirmed by producing PTA coatings in constraint position as well as complex 3D parts.

Nowadays, wire-arc spraying of chromium steel has gained an important market share for corrosion and wear protection applications. However, detailed studies are the basis for further process optimization. In order to optimize the process parameters and to evaluate the effects of the spray parameters DoE-based experiments had been carried out with high-speed camera shoots. In this article, the effects of spray current, voltage, and atomizing gas pressure on the particle jet properties, mean particle velocity and mean particle temperature and plume width on X46Cr13 wire are presented using an online process monitoring device. Moreover, the properties of the coatings concerning the morphology, composition and phase formation were subject of the investigations using SEM, EDX, and XRD-analysis. These deep investigations allow a defined verification of the influence of process parameters on spray plume and coating properties and are the basis for further process optimization.

The original tail of lizards is a segmental structure, each segment containing a vertebra. We examine how the growth of the original tail of Anolis grahami is characterized as a single structure and as a structure composed of discrete segments. It is hypothesized that the tail grows isometrically both in its entirety and regionally. The results reveal that the entire tail grows isometrically with reference to SVL but that this isometric growth pattern results from differential growth in successive regions of the tail. Segmentally the tail grows faster proximally than distally and incorporates a middle transitional region. These findings may have implications for the various patterns of tail growth in squamates with different functional roles of the tail.

The purpose of this work was to investigate the ovarian renin-angiotensin system (RAS) during severe ovarian hyperstimulation syndrome (OHSS) with ascites and pleural effusion. Two patients who developed severe OHSS after ovarian stimulation for in vitro fertilization were investigated. Both patients presented ascites and pleural effusion. Blood, ascites, and pleural fluid were simultaneously sampled during therapeutic paracentesis and thoracocentesis. Renin activity, active renin, prorenin, and angiotensin II immunoreactivity (Ang II-ir) were measured simultaneously in plasma, ascites, and pleural fluid. Prorenin, renin activity, active renin, and Ang II-ir levels were much higher than normal plasmatic laboratory norms in the three compartments. Prorenin and Ang II-ir levels were the highest in the ascites, while they were in the same range in the pleural fluid and in the plasma. The present findings provide additional evidence for the ovarian origin of the prorenin and Ang II-ir in the ascites of severe OHSS.

A total of 62 Mallard (Anas platyrhynchos) females were captured at their nests in eastern South Dakota during 1990 and 1991. Females were captured on an island, a peninsula cut off from the mainland by excavation, and a peninsula protected by an electric fence that deters mammals. Loop harnesses were used to attach radio transmitters to females to evaluate possible effects of marking females on survival of their ducklings and to determine the influence of brood rearing on female survival. No difference was found in duckling (P = 0.999) or brood (P = 0.458) (e.g., one or more ducklings alive in brood) survival to 7 d for females marked from 1 d prior to hatch to immediately post hatch (still in nest) compared with those marked at 3-9 d before hatch (P = 0.081). There also were no differences in survival by age class between marked broods that did not suffer total mortality and unmarked broods (P > 0.05). If survival of broods was influenced by harness attachments on females, it likely occurred in females suffering total brood loss early in brood rearing. Marked females with broods had poorer survival to 21 d than marked females that had lost or abandoned their clutches or broods (73.5% vs. 100%, P < 0.001). /// Durante el 1990 y 1991 se capturaron, en sus nidos, un total de 62 individuos de Anas platyrhynchos en un estudio que se llevó a cabo en Dakota del Sur. Las hembras fueron capturadas en islas, penínsulas separadas por excavación de tierra firme y una península protegida de mamíferos depredadores por una verja electrificada. Se utilizaron arneses en forma de lazo para montar los radiotransmisores a hembras y evaluar el posible efecto de los artefactos en la supervivencia de los patitos y la influencia de la crianza en la supervivencia de la hembra. No se encontraron diferencias significativas en la supervivencia de patitos (P = 0.999) o camadas (P = 0.458) (ej. uno o más patitos vivos en cada camada) hasta los siete días de edad para hembras marcadas el día previo al eclosionamiento o un día inmediatamente después (todavía en el nido) esto en comparación a hembras a las cuales se les colocó el radiotransmisor 3-9 días previo al eclosionamiento (P = 0.081). Tampoco se encontró diferencia en la supervivencia de patitos (arreglados en grupos por edades) entre camadas que no sufrieron mortalidad total y camadas no marcadas (P > 0.05). Si acaso hubo influencia de los radiotransmisores en la supervivencia de las camadas, ésta ocurrió en hembras que perdieron toda la camada poco tiempo después del eclosionamiento. Las hembras con camadas, que fueron marcadas, tuvieron una supervivencia menor (hasta los 21 días), que aquellas (también con radiotransmisores) que perdieron o abandonaron sus nidos o sus patitos a bien temprana edad (73.5% vs. 100%, P < 0.001).

Barriers to reproduction are often how progress in speciation is measured. Nonetheless, a key unresolved question is the extent to which reproductive barriers diminish gene flow in incipient species in nature. The Sierra Nevada foothill endemic Mimulus glaucescens and the widespread M. guttatus are considered to be distinct species based on contrasting vegetative traits, but barriers to reproduction are not readily apparent, although these species are not known to hybridize in nature. To explore boundaries between taxa, we examined 15 potential reproductive barriers between species in a Northern California area of broad sympatry. Most barriers, with the exception of ecogeographic isolation, were weak, and total isolation for each species was estimated to be incomplete. Population genomic analyses of range-wide and broadly sympatric accessions revealed that gene flow between these taxa is common across the range, and rampant within areas of sympatry. Thus, despite fairly strong ecological differentiation - which may be involved in maintenance of vegetative differences ecological isolation is a weak barrier to gene flow in this system. This work underscores the value of combining classical measures of reproductive isolation with estimates of natural gene flow for studies of speciation in natural communities. Competing Interest Statement The authors have declared no competing interest. Footnotes * re-ordered authors; error in first submission

In an investigation of the postnatal growth of the vertebral column of the Norway rat (Rattus norvegicus), we recorded hind-foot length as a standard metric, along with skull, tail, femur, and tibia lengths, against which to compare the growth of axial components. We confirmed a nonlinear relationship of head-body length against hind-foot length, tail length, and tibia length across the time course from neonate to adult and also discovered a nonlinear relationship between both skull and femur length to head-body length. Differences in growth rate are directly related to preweaning and postweaning periods. The pattern of differential growth was distinctly least pronounced for femoral length. We therefore advocate the latter as the most appropriate to use as an easily measured proxy for growth across the entire neonate to adult growth period. This study reveals implications for the choice of optimal variables used as size proxies and also suggests functional implications of shifts in form-function relationships from unweaned to weaned individuals. However, variation in body form across mammals and altricial versus precocial modes of natal expression will continue to complicate the search for appropriate comparative metrics in the study of the development and evolution of body form.