Results of breadboard tests withan integrated CO2, humidity and thermal control system

Membrane gas absorption and desorption (MGA/MGD) for the removal of CO 2 in manned spacecraft or other enclosed environment is subject of study by Stork and TNO for many years. The system is based on the combination of membrane separation and gas absorption. Advantage of this technology is that the system not only can be used to remove the carbon dioxide but also to control the relative humidity and temperature. Absorption of moisture and heat is achieved by cooling the absorption liquid below the dewpoint temperature of the gas stream. From the start in 1995, the Crew Transfer Vehicle is used as a basis for the design (1,2). Compared to the planned air conditioning system, consisting of a condensing heat exchanger, LiOH cartridges and a water evaporator assembly, MGA/MGD shows advantage in volume, mass and power consumption. The absorption liquid circulates through the spacecraft thermal control loop, replacing the coolant water. The CO2 absorption capacity of the absorption liquid is restored in a desorption unit. This process is based on pervaporation. The absorption liquid is led through this membrane unit in which a reduced pressure is maintained using the space vacuum. Due to this pressure difference a driving force for water vapor and CO2 is created. The water evaporation and the CO2 desorption rate are controlled by a throttle valve in the venting duct to the vacuum source. Because the absorption liquid is used as coolant, temperature increases, a driving force for water vapor and CO2 mass transfer is created. Should additional heat rejection be required (off nominal case), it is established by dumping extra water, using the associated heat of vaporization. For the initial studies an existing laboratory set-up has been applied for the practical work. In 1999 a project started on the development of a dedicated breadboard. In this paper, the test results of this breadboard assembly will be presented. Copyright © 2003 SAE International

Food deprivation induces chronic stress and affects thyroid hormone metabolism in senegalese sole (solea senegalensis) post-larvae

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8 páginas, 4 figuras, 3 tablas.The hypothalamus-pituitary-interrenal (HPI) axis is pivotal in the endocrine stress response of fish. Hypothalamic corticotropin-releasing hormone (CRH) initiates the endocrine stress response and stimulates the release of adrenocorticotropic hormone (ACTH) from the pituitary pars distalis, which in turn activates cortisol production and release by the interrenal cells of the head kidney. CRH activity depends on the levels of a specific CRH binding protein (CRH-BP). We have characterized the cDNAs coding for CRH and CRH-BP in Senegalese sole (Solea senegalensis) and investigated their mRNA expression in juveniles that were submitted to a protocol that involved exposure to a chronic stressor (viz. increased cultivation densities) followed by an acute stressor (viz. transfer to increased ambient salinity). Juveniles were cultivated at three densities (1.9, 4.7 and 9.8 kg/m2) for 33 days, and then exposed to an osmotic challenge that involved transfer from seawater (39‰ salinity, SW) to hypersaline seawater (55‰, HSW). The highest density imposed stress as indicated by elevated cortisol levels and CRH mRNA expression compared to fish stocked at low density. Fish kept at high density differentially responded to a posterior transfer to HSW; no cortisol or CRH response was seen, but osmoregulatory and metabolic parameters were affected. No differences in CRH-BP mRNA expression levels were found at different stocking densities; transfer to HSW enhanced expression in both low and high density stocked animals, suggesting that CRH-BP acts as a modulator of the acute stress response, not so of the chronic stress response. We conclude that stocking of Senegalese sole at high density is a stressful condition that may compromise the capacity to cope with subsequent stressors.his work was partially funded by grants AGL2007-61211/ACU (Ministerio Educación y Ciencia of Spain) and Proyecto de Excelencia PO7-RNM-02843 (Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía, Spain) to J.M.M., as well as by the project AQUAGENOMICS (CSD2007-00002, Consolider-Ingenio 2010 Program, MICINN, Spain).Peer reviewe