First Trace for Irregular Shock Wave Process in Weak Mach Reflection

Referring to von Neumann's words, transition from a two- to a three-shock reflection configuration in the weak domain presents some very considerable theoretical difficulties. It nonetheless remains an observed fact that such a transition does indeed occur in the real world. This paper describes the novel experimental technique and the results which for the first time did yield a "footprint" that something quite out-of-the-ordinary is taking place within the base of the reflected wave where the latter butts the point of shock confluence. The results of the work presented here remained puzzling initially, for they seemed to contradict some preconceived outcome. It was only years later that the specific detail which was first considered to be misleading could be interpreted. It disclosed that the flow through the reflected shock is being forced to deviate from the classic Rankine-Hugoniot shock transformation process. This departure then enables the unyielding boundary conditions to be fulfilled and three-shock reflection to get established. This occurs with some lag past detachment of RR, this interval being required for the properties to adjust to the imposed conditions. The hypothesis of the departure from classic shock theory has been verified in the wind tunnel and was confirmed

Outlanders in an unusual habitat : Holothuria mammata (Grube, 1840) behaviour on seagrass meadows from Ria Formosa (S Portugal)

Holothuria mammata is one of the new target species from the Mediterranean and Atlantic. Usually, it inhabits rocky bottoms, staying in crevices and holes during the day and leaving them in the night for feeding on sandy bottoms. However, it can be found in unusual habitats such as seagrass with diurnal and nocturnal feeding. This study provides information for the first time on the behaviour, density and small scale distribution of H. mammata in a seagrass habitat from Ria Formosa (S Portugal). To reach these aims, a mark/recapture methodology was used. Abundance was estimated through R statistical software v.2.15.3 (package “Rcapture”). The minimum area method was applied in GRASS GIS v.6.4.2 for home range. Size distribution was estimated applying a ShapiroWilk test. Rayleigh test for randomness was applied to study the directionality of movements. A circular one-way ANOVA was used to test for differences in movement direction. Capture probability was higher on seagrass than sand and the total length of the individuals ranged from 13 to 25cm. Movement speed was between 4.7 and 14.7 m day-1. Movements were not directional. H. mammata differs in its behaviour from the related Holothuria arguinensis occurring in the same habitat

Quantifying pigment cover to assess variation in animal colouration

The study of animal colouration addresses fundamental and applied aspects relevant to a wide range of fields, including behavioural ecology, environmental adaptation and visual ecology. Although a variety of methods are available to measure animal colours, only few focus on chromatophores (specialized cells containing pigments) and pigment migration. Here, we illustrate a freely available and user friendly method to quantify pigment cover (PiC) with high precision and low effort using digital images, where the foreground (i.e., pigments in chromatophores) can be detected and separated from the background. Images of the brown shrimp, Crangon crangon were used to compare PiC with the traditional Chromatophore Index (CI). Results indicate that PiC outcompetes CI for pigment detection and transparency measures in terms of speed, accuracy and precision. The proposed methodology provides researchers with a useful tool to answer essential physiological, behavioural and evolutionary questions on animal colouration in a wide range of species

Comparison of E-ink and OLED screens as train seat displays : a user study

This study was designed to provide an evaluation of two types of train seat displays (OLED and E-ink), from a user-centred perspective. Numerous factors influence the decisions on which display to use, such as costs or energy use. It is also important to consider human factors aspects like readability and user preferences. To provide some real-world insights into these issues we designed a pilot study to compare both displays. Participants were asked to give their impressions and respond to questions during a semi-structured interview process, when they were presented with both displays. Results show that participants favour the OLED display overall as it is easily noticeable in different light conditions. However, some aspects of the E-ink are preferred: it is easier to read and understand. We conclude that research with real users is extremely important when designing and defining hardware to be used during the implementation of intelligent transport systems

Hide and seek : a multidisciplinary study on the ecological success of an estuarine dweller

Estuaries are dynamic systems in which biotic and abiotic conditions vary remarkably. Survival in these habitats requires flexibility in dealing with these variations, which include changes in food availability and shelter opportunities. A thorough understanding of ecological networks in these systems, therefore, relies on comprehensive information on anti-predator adaptations and trophic relationships among species. The present study focuses on two key traits of the brown shrimp Crangon crangon L. (Decapoda: Caridea), a key component of European sandy shores, namely i) its ability to conceal from predators and ii) its trophic flexibility. This shrimp is well known for its camouflage abilities and central role in the estuarine food web. Here, I applied behavioural experiments using a novel method to quantify pigment cover (PiC) to study background matching in Crangon crangon, and assessed the application of metabarcoding to define its trophic ecology in six European estuaries. Results indicate that the brown shrimp is capable of repeated fast colour adaptations and that its background matching ability is mainly influenced by presence of light and sediment colour. High levels of intra- and inter-individual variation indicated, on the other hand, a complex balance between behavioural-plasticity and environmental adaptation. Large spatial variation, on local and regional scales, in its diverse diet also confirmed the highly flexible nature of this trophic opportunist. Its diet reflected local patterns in prey item distributions, and the variation in its stomach content was evaluated as a tool for the assessment of heavy metal pollution impacts and fish biodiversity patterns in European estuaries for the first time. Overall, the results of this study yielded insights into many key factors influencing predator-prey dynamics in estuarine systems. This included the effects of environmental and behavioural factors on the evolution of animal background matching and the application of metabarcoding towards a more robust reconstruction of ecological networks

Perioperative Nerve Blockade: Clues from the Bench

Peripheral and neuraxial nerve blockades are widely used in the perioperative period. Their values to diminish acute postoperative pain are established but other important outcomes such as chronic postoperative pain, or newly, cancer recurrence, or infections could also be influenced. The long-term effects of perioperative nerve blockade are still controversial. We will review current knowledge of the effects of blocking peripheral electrical activity in different animal models of pain. We will first go over the mechanisms of pain development and evaluate which types of fibers are activated after an injury. In the light of experimental results, we will propose some hypotheses explaining the mitigated results obtained in clinical studies on chronic postoperative pain. Finally, we will discuss three major disadvantages of the current blockade: the absence of blockade of myelinated fibers, the inappropriate duration of blockade, and the existence of activity-independent mechanisms

Meningeal defects alter the tangential migration of cortical interneurons in Foxc1hith/hith mice

<p>Abstract</p> <p>Background</p> <p>Tangential migration presents the primary mode of migration of cortical interneurons translocating into the cerebral cortex from subpallial domains. This migration takes place in multiple streams with the most superficial one located in the cortical marginal zone. While a number of forebrain-expressed molecules regulating this process have emerged, it remains unclear to what extent structures outside the brain, like the forebrain meninges, are involved.</p> <p>Results</p> <p>We studied a unique <it>Foxc1 </it>hypomorph mouse model (<it>Foxc1^hith/hith</it>) with meningeal defects and impaired tangential migration of cortical interneurons. We identified a territorial correlation between meningeal defects and disruption of interneuron migration along the adjacent marginal zone in these animals, suggesting that impaired meningeal integrity might be the primary cause for the observed migration defects. Moreover, we postulate that the meningeal factor regulating tangential migration that is affected in homozygote mutants is the chemokine Cxcl12. In addition, by using chromatin immunoprecipitation analysis, we provide evidence that the <it>Cxcl12 </it>gene is a direct transcriptional target of Foxc1 in the meninges. Further, we observe migration defects of a lesser degree in Cajal-Retzius cells migrating within the cortical marginal zone, indicating a less important role for Cxcl12 in their migration. Finally, the developmental migration defects observed in <it>Foxc1^hith/hith</it>mutants do not lead to obvious differences in interneuron distribution in the adult if compared to control animals.</p> <p>Conclusions</p> <p>Our results suggest a critical role for the forebrain meninges to promote during development the tangential migration of cortical interneurons along the cortical marginal zone and Cxcl12 as the factor responsible for this property.</p

Temperature response of ex-situ greenhouse gas emissions from tropical peatlands: Interactions between forest type and peat moisture conditions

Climate warming is likely to increase carbon dioxide (CO2) and methane (CH4) emissions from tropical wetlands by stimulating microbial activity, but the magnitude of temperature response of these CO2 and CH4 emissions, as well as variation in temperature response among forest types, is poorly understood. This limits the accuracy of predictions of future ecosystem feedbacks on the climate system, which is a serious knowledge gap as these tropical wetland ecosystems represent a very large source of greenhouse gas emissions (e.g. two-thirds of CH4 emissions from natural wetlands are estimated to be from tropical systems). In this study, we experimentally manipulated temperatures and moisture conditions in peat collected from different forest types in lowland neotropical peatlands in Panama and measured how this impacted ex-situ CO2 and CH4 emissions. The greatest temperature response was found for anaerobic CH4 production (Q10 = 6.8), and CH4 consumption (mesic conditions, Q10 = 2.7), while CO2 production showed a weaker temperature response (Q10 2 production was found under flooded oxic conditions. Net emissions of CO2 and CH4 were greatest from palm forest under all moisture treatments. Furthermore, the temperature response of CH4 emissions differed among dominant vegetation types with the strongest response at palm forest sites where fluxes increased from 42 ± 25 to 2166 ± 842 ng CH4 g−1 h−1 as temperatures were raised from 20 to 35 °C. We conclude that CH4 fluxes are likely to be more strongly impacted by higher temperatures than CO2 fluxes but that responses may differ substantially among forest types. Such differences in temperature response among forest types (e.g. palm vs evergreen broad leaved forest types) need to be considered when predicting ecosystem greenhouse gas responses under future climate change scenarios