SHARC: Space Habitat, Assembly and Repair Center

Integrated Space Systems (ISS) has taken on the task of designing a Space Habitat, Assembly and Repair Center (SHARC) in Low Earth Orbit to meet the future needs of the space program. Our goal is to meet the general requirements given by the 1991/1992 AIAA/LORAL Team Space Design competition with an emphasis on minimizing the costs of such a design. A baseline structural configuration along with preliminary designs of the major subsystems was created. Our initial mission requirements, which were set by AIAA, were that the facility be able to: support simultaneous assembly of three major vehicles; conduct assembly operations and minimal extra vehicular activity (EVA); maintain orbit indefinitely; and assemble components 30 feet long with a 10 foot diameter in a shirtsleeve environment

Bright and stable CdSe/CdS@SiO2 nanoparticles suitable for long term cell labeling

Semiconductor quantum dots (QDs) constitute very promising candidates as light emitters for numerous applications in the field of biotechnology, including cell labeling, in vivo imaging and diagnostics.[1] For such applications, semiconductor QDs represent an attractive alternative to classic organic fluorophores as they exhibit a higher brightness thanks to their large absorption cross-sections and high photoluminescence quantum yields. Nevertheless, QDs usually suffer from higly oxidative environments, such as water, which can cause a dramatic decrease of their photoluminescent quantum yield but also can result in the realease of toxic elements. In this contribution we present a new generation of QD@SiO2 nanoparticles based on newly developped core-shell QDs that mostly overcome these limitations, resulting in efficient nanoprobes for long term cell labeling. Among the numerous QDs being reported, core-shell heterostructures such as CdSe/CdS QDs with relatively thick CdS shells, are of particular interest as they offer several properties essential to biolabeling, including high photoluminescence quantum yields, low blinking behavior and robustness towards aggressive environments. We recently developed a new, fast and very efficient method for the synthesis of such QDs, denoted as ‘flash’ CdSe/CdS, which can feature up to 20 CdS monolayers after only 3 minutes of reaction.[2] They show state-of-the-art optical properties (sharp emission spectra, high photoluminescence quantum yields, low blinking behavior), and the CdS shell thickness can be easily controlled thanks to the full chemical yield of the reaction. These ‘flash’ CdSe/CdS QDs were encapsulated in silica nanoparticles through a water-in-oil microemulsion process, which allows a high control on the morphology of the resulting QD@SiO2 nanoparticles. All the nanoparticles contain one single QD located in its center (Fig. 1) and the thickness of the silica shell can be varied from only a few nanometers up to several tens of nanometers. The silica matrix provides the QDs with enhanced colloidal stability in polar solvents, but also with enhanced photo-physical and photo-chemical stability under continuous irradiation. More importantly, the QD@SiO2 nanoparticles based on ‘flash’ CdSe/CdS QDs fully retain their photoluminescence quantum yield even after a year of storage in water (Fig. 1), whereas QD@SiO2 nanoparticles based on ‘classical’ SILAR grown core-shell QDs typically lose their luminescence after a few weeks or even days. Thereafter, these ‘flash’ CdSe/CdS@SiO2 nanoparticles have proven to be very promising nanoprobes for bioimaging techniques. Indeed, the rapid uptake of high levels of these nanoparticles by live cells was evidenced by confocal fluorescence microscopy (Fig. 1). Furthermore, thanks to the high stability of their optical properties but also to their low toxicity after silica encapsulation, these nanoparticles are particularly appropriate for long term cell labeling, with up to 9 cell divisions being tracked. Thus, in this contribution we will report from the synthesis and characterization of these ‘flash’ CdSe/CdS@SiO2, all the way to the study of their toxicity and their application to cell labeling

Crossbreeding in sheep in respect to economic efficiency

International audienc

An open-source software tool for the generation of relaxation time maps in magnetic resonance imaging

BACKGROUND: In magnetic resonance (MR) imaging, T1, T2 and T2* relaxation times represent characteristic tissue properties that can be quantified with the help of specific imaging strategies. While there are basic software tools for specific pulse sequences, until now there is no universal software program available to automate pixel-wise mapping of relaxation times from various types of images or MR systems. Such a software program would allow researchers to test and compare new imaging strategies and thus would significantly facilitate research in the area of quantitative tissue characterization. RESULTS: After defining requirements for a universal MR mapping tool, a software program named MRmap was created using a high-level graphics language. Additional features include a manual registration tool for source images with motion artifacts and a tabular DICOM viewer to examine pulse sequence parameters. MRmap was successfully tested on three different computer platforms with image data from three different MR system manufacturers and five different sorts of pulse sequences: multi-image inversion recovery T1; Look-Locker/ TOMROP T1; modified Look-Locker inversion recovery (MOLLI) T1; single-echo T2/ T2*; and multi-echo T2/ T2*. Computing times varied between 2 and 113 seconds. Estimates of relaxation times compared favorably to those obtained from non-automated curve fitting. Completed maps were exported in DICOM format and could be read in standard software packages used for analysis of clinical and research MR data. CONCLUSIONS: MRmap is a flexible cross-platform research tool that enables accurate mapping of relaxation times from various pulse sequences. The software allows researchers to optimize quantitative MR strategies in a manufacturer-independent fashion. The program and its source code were made available as open-source software on the internet

The Effects Of Seasonal Changes And Irrigation Diversion On The Benthic Insect Populations Of Confederate Creek, Broadwater County, Montana

Benthic insect populations of Confederate Creek, Broadwater County, Montana, were studied during June-August, 1979. Samples were taken above and below an irrigation diversion once a month and assayed for insect number and diversity. Five orders were represented: Coleoptera, Diptera, Ephemeroptera, Plecoptera, and Trichoptera. Numbers of insects in all orders tended to increase with each sampling. The order with the greatest population density below the irrigation diversion was Diptera. The order with the greatest population density above the irrigation diversion was Ephemeroptera. One sample was taken August 19 in the altered water route used for irrigation. One insect was found in this sample, compared to 641 insects in the sample below the irrigation diversion and 152 insects in the sample above the irrigation diversion taken the same day