The shadow position sensors (SPS) formation flying metrology subsystem for the ESA PROBA-3 mission: present status and future developments

PROBA-3 [1] [2] is a Mission of the European Space Agency (ESA) composed of two formation-flying satellites, planned for their joint launch by the end of 2018. Its main purposes have a dual nature: scientific and technological. In particular, it is designed to observe and study the inner part of the visible solar corona, thanks to a dedicated coronagraph called ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), and to demonstrate the in-orbit formation flying (FF) and attitude control capability of its two satellites. The Coronagraph payload on-board PROBA-3 consists of the following parts: the Coronagraph Instrument (CI) with the Shadow Position Sensor (SPS) on the Coronagraph Spacecraft (CSC), the Occulter Position Sensor (OPSE) [3] [4] and the External Occulting (EO) disk on the Occulter Spacecraft (OSC). The SPS subsystem [5] is one of the main metrological devices of the Mission, adopted to control and to maintain the relative (i.e. between the two satellites) and absolute (i.e. with respect to the Sun) FF attitude. It is composed of eight micro arrays of silicon photomultipliers (SiPMs) [6] that shall be able to measure, with the required sensitivity and dynamic range as asked by ESA, the penumbral light intensity on the Coronagraph entrance pupil. With the present paper we describe the testing activities on the SPS breadboard (BB) and Development Model (DM) as well as the present status and future developments of this PROBA-3 metrological subsystem

Connectivity among wetlands matters for vulnerable amphibian populations in wetlandscapes

Wetlands have been degraded and destroyed, resulting in the decline of many wetland-dependent species populations. Many conservation efforts are based on protection of individual wetlands; however, fluxes of energy, materials and organisms between wetlands create important structural and functional connections upon which several species depend. We investigated the role of individual wetlands within a wetlandscape in sustaining an amphibian population. Wetlandscapes were represented as networks, where nodes were wetlands and links were flows of organisms described by an amphibian population model. Relationships between a wetland's connectivity to the other wetlands and the abundance of amphibians under different wetland management strategies were examined. The first finding was that wetlands within a network can be classified into sinks (where local mortality exceeds birth rate), sources (where local birth rate exceeds mortality), and pseudo-sinks (where excessive immigration maintains the population above the carrying capacity). These three wetland classes have low, medium, and high Indegree (a parameter reflecting a wetland's connectivity), respectively. The second finding was that management interventions in wetlands have different consequences according to the wetland's Indegree: wetland removal has the worst impact on amphibian populations if the wetland is a source, and wetland restoration has the best impact if the wetland is a pseudo-sink. These findings provide support for policies that managing wetlands not as independent objects but as integral parts of the wetlandscape

Safeguarding Wetlands and Their Connections within Wetlandscapes to Improve Conservation Outcomes for Threatened Amphibian Species

Wetlands should not be considered as independent objects but as dynamically connected objects, collectively known as wetlandscapes. We developed a framework that analyzes the influences of wetland suitability and connectivity on amphibian distributions. We defined two indices: a Wetland Suitability Index describing wetland quality and a Movement Permeability Index characterizing wetland connectivity for amphibian population dynamics. These indices were calculated from raster datasets and time-varying inundation estimates. The indices were used to define a wetlandscape and an amphibian model was used to simulate population dynamics within the wetlandscape. The framework was applied to the Nose Creek watershed, a highly modified wetlandscape in Alberta, Canada. Two amphibian species were selected with different habitat preferences: the Northern Leopard Frog that prefers wet habitats and has high mobility over land, and the Great Plains Toad that prefers terrestrial habitats and has low mobility over land. We found each amphibian species had a “preferred” wetlandscape, reflecting their life cycle traits and migration strategies which in turn were dependent on the hydrological and ecological connections within the wetlandscape. This study highlights the importance of investigating both individual wetlands and the wetlandscape and considering both wetland habitat quality and connectivity as non-substitutable properties that act jointly, but differently, on population dynamics

Bile secretory function in the obese Zucker rat: evidence of cholestasis and altered canalicular transport function

Background: Obese Zucker rats (ZR) have been used as an experimental model for non-alcoholic fatty liver disease and are particularly susceptible to various types of liver injury. Bile secretory function has not been assessed in ZR. Aim: To study bile secretion and expression of the main hepatobiliary transporters in ZR. Methods: Bile flow and biliary secretion of lipids and glutathione were determined in eight and 14 week old obese ZR and their lean controls. Protein mass and mRNA of the Na(+)/taurocholate cotransporting polypeptide (Ntcp), the bile salt export pump (Bsep), and the multidrug resistant associated protein 2 (Mrp2) were assessed by western and northern blot, respectively. The effects of administration of a tumour necrosis factor α inactivator (etanercept) and an insulin sensitiser (rosiglitazone) were assessed in obese ZR while leptin was given to non-obese rats to study its effect on Mrp2 expression. Results: ZR exhibited increased body weight and hyperlipidaemia. Only 14 week old obese ZR has fatty liver. Decreased bile flow and biliary lipid and glutathione secretion as well as reduced hepatic transport of both taurocholate and bromosulphthalein were found in obese ZR. Hepatic Mrp2 protein mass was markedly reduced (−70%) in obese rats while Ntcp and Bsep protein levels were similar to lean rats. Downregulation of Mrp2 seems to involve both transcriptional and post-transcriptional mechanisms probably related to insulin and leptin resistance. Conclusions: Obese ZR exhibit an impaired bile secretory function with significant functional and molecular alterations consistent with mild cholestasis. A defective hepatobiliary transport capacity may be a contributory factor in rendering the obese ZR more susceptible to liver injury

Radical oxygen species and bile secretion

Oxidative stress is a common feature in most hepatopathies. Accumulating evidences indicate that reactive oxygen species (ROS) induce a number of functional changes either deleterious or adaptive in the capability of the hepatocytes to produce bile and to secrete exogenous and endogenous compounds. This review is aimed to describe the mechanisms involved in these changes. For this purpose, we will summarize: 1. The current evidence that acutely induced oxidative stress is cholestatic, by describing the mechanisms underlying the hepatocyte secretory failure, including the disorganization of the actin cytoskeleton and its most noticeable consequences, that is, the impairment of tight-junctional structures and the endocytic internalization of canalicular transporters relevant to bile formation. 2. The role for oxidative-stress-activated signalling pathways in the pathomechanisms described above, particularly those involving Ca2+ elevation and its consequent activation via Ca2+ of “classical” and “novel” PKC isoforms. 3. The mechanisms involved in the adaptive response against oxidative stress mediated by ROS-responsive transcription factors, such as upregulation of GSH synthesis pathway, antioxidant enzymes, and hepatocellular efflux pumps. 4. The consequences on hepatocellular secretory function when this adaptive response can be surpassed by the sustained/high production of ROS. This deleterious effects include transcriptional and posttranscriptional changes in the expression of transporters relevant to bile formation, as has been shown to occur, for example, after long-term administration of aluminum to rats, in the Long-Evans Cinnamon rat (a model of chronic hepatic copper accumulation mimicking Wilson’s disease), and in ischemia-reperfusion injury.Fil: Basiglio, Cecilia Lorena. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Fisiología Experimental (IFISE‑CONICET); Argentina.Fil: Toledo, Flavia D. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Fisiología Experimental (IFISE‑CONICET); Argentina.Fil: Sánchez Pozzi, Enrique J. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Fisiología Experimental (IFISE‑CONICET); Argentina.Fil: Roma, Marcelo Gabriel. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Fisiología Experimental (IFISE‑CONICET); Argentina