| 1. |
- Gnos, Edwin, et al.
(författare)
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Ash Shutbah: A possible impact structure in Saudi Arabia
- 2014
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Ingår i: Meteoritics and Planetary Science. - : Wiley. - 1086-9379. ; 49:10, s. 1902-1914
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the Ash Shutbah circular structure in central Saudi Arabia (21 degrees 37N 45 degrees 39E) using satellite imagery, field mapping, thin-section petrography, and X-ray diffraction of collected samples. The approximately 2.1km sized structure located in flat-lying Jurassic Tuwaiq Mountain Limestone has been nearly peneplained by erosional processes. Satellite and structural data show a central area consisting of Dhruma Formation sandstones with steep bedding and tight folds plunging radially outward. Open folding occurs in displaced, younger Tuwaiq Mountain Limestone Formation blocks surrounding the central area, but is absent outside the circular structure. An approximately 60cm thick, unique folded and disrupted orthoquartzitic sandstone marker bed occurring in the central area of the structure is found 140m deeper in undisturbed escarpment outcrops located a few hundred meters west of the structure. With exception of a possible concave shatter cone found in the orthoquartzite of the central area, other diagnostic shock features are lacking. Some quartz-rich sandstones from the central area show pervasive fracturing of quartz grains with common concussion fractures. This deformation was followed by an event of quartz dissolution and calcite precipitation consistent with local sea- or groundwater heating. The combination of central stratigraphic uplift of 140m, concussion features in discolored sandstone, outward-dipping concentric folds in the central area, deformation restricted to the rocks of the ring structure, a complex circular structure of 2.1km diameter that appears broadly consistent with what one would expect from an impact structure in sedimentary targets, and a possible shatter cone all point to an impact origin of the Ash Shutbah structure. In fact, the Ash Shutbah structure appears to be a textbook example of an eroded, complex impact crater located in flat-lying sedimentary rocks, where the undisturbed stratigraphic section can be studied in escarpment outcrops in the vicinity of the structure.
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| 2. |
- Khan, M. Ajmal, et al.
(författare)
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Effect of titania concentration on the grain boundary conductivity of calcium-doped ceria electrolyte
- 2014
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Ingår i: Ceramics International. - : Elsevier BV. - 0272-8842 .- 1873-3956. ; 40:7, s. 9775-9781
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Tidskriftsartikel (refereegranskat)abstract
- A solid-state technique was used to synthesize ceria-based (CDC-xT, in which x=0-1 mol%) solid electrolyte ceramics. The effects of doping the ceramic solid electrolyte (CDC) with titanium oxide were studied with regard to densification, crystal structure, morphology, electro-impedance spectroscopy and fuel cell performance. TiO2 doping afforded materials a 95% relative density at 940 degrees C, approximately 200 degrees C lower than the temperature required without titanium oxide. The addition of titanium oxide (TiO2) reduced the CDC sintering temperature and significantly improved the grain boundary conduction. The minimum grain boundary resistivity was obtained at 0.8 mol% TiO2. X-ray diffraction (XRD) results showed that the lattice parameters enhanced with increased titanium oxide concentrations up to 0.8 mol%, revealing the solubility limit for Caria's fluorite structure. The optimum doping level (0.8 mol%) is provided maximum conductivity. Conductivities were measured using EIS (Electrochemical Impedance Spectroscopy) with a two-probe method, and the activation energies were calculated using the Arrhenius plots. The maximum power density (660 mW/cm(2)) was achieved with CDC 0.8T electrolyte at 650 degrees C using LiCuZnNi oxide electrodes.
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| 3. |
- Ruifrok, Anneloes E, et al.
(författare)
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Study protocol : Differential effects of diet and physical activity based interventions in pregnancy on maternal and fetal outcomes: Individual patient data (IPD) meta-analysis and health economic evaluation
- 2014
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Ingår i: Systematic Reviews. - : Springer Science and Business Media LLC. - 2046-4053. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundPregnant women who gain excess weight are at risk of complications during pregnancy and in the long term. Interventions based on diet and physical activity minimise gestational weight gain with varied effect on clinical outcomes. The effect of interventions on varied groups of women based on body mass index, age, ethnicity, socioeconomic status, parity, and underlying medical conditions is not clear. Our individual patient data (IPD) meta-analysis of randomised trials will assess the differential effect of diet- and physical activity-based interventions on maternal weight gain and pregnancy outcomes in clinically relevant subgroups of women.Methods/designRandomised trials on diet and physical activity in pregnancy will be identified by searching the following databases: MEDLINE, EMBASE, BIOSIS, LILACS, Pascal, Science Citation Index, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Database of Abstracts of Reviews of Effects, and Health Technology Assessment Database. Primary researchers of the identified trials are invited to join the International Weight Management in Pregnancy Collaborative Network and share their individual patient data. We will reanalyse each study separately and confirm the findings with the original authors. Then, for each intervention type and outcome, we will perform as appropriate either a one-step or a two-step IPD meta-analysis to obtain summary estimates of effects and 95% confidence intervals, for all women combined and for each subgroup of interest. The primary outcomes are gestational weight gain and composite adverse maternal and fetal outcomes. The difference in effects between subgroups will be estimated and between-study heterogeneity suitably quantified and explored. The potential for publication bias and availability bias in the IPD obtained will be investigated. We will conduct a model-based economic evaluation to assess the cost effectiveness of the interventions to manage weight gain in pregnancy and undertake a value of information analysis to inform future research.
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| 4. |
- Ullah, M., et al.
(författare)
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Growth of Nitrogen-Incorporated Diamond Films Using Hot-Filament Chemical Vapor Deposition Technique
- 2013
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Ingår i: Advanced Science Letters. - : American Scientific Publishers. - 1936-6612 .- 1936-7317. ; 19:1, s. 291-295
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Tidskriftsartikel (refereegranskat)abstract
- Micro- and nanocrystalline diamond (MNCD) films were deposited on silicon substrates by hot-filament chemical vapor deposition (HF-CVD) at chamber pressure of 22.5 torr for 20 hours. The total mass flow rate was 300 sccm (3 Vol.% CH4), while the nitrogen gas flow rate was varied from 0.04 to 0.64 sccm corresponding to 0.8 to 12.8% of H2+CH4 mixture. The resulting films were characterized by X-Ray Diffraction (XRD), Raman Spectra, Scanning Electron Microscope (SEM) and four point probe van der Pauw method to analyze and measure the structure, quality, morphology and resistivity of the deposited films, respectively. Results show that the grain size increases at low concentration of nitrogen, while it decreases for high concentration of nitrogen and the fact is probably the formation of atomic nitrogen N° near filament surface and its inward diffusion on the surface of growing film. Resistivity decreases continuously due to formation of C—H bonds in a trans-polyacetylene structure along with diamond film, which leads to change surface morphology. By increasing nitrogen content enhance distortion along [111] direction of the resulting films.
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| 5. |
- Vasile, Massimiliano, et al.
(författare)
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The Suaineadh Project : a Stepping Stone Towards the Deployment of Large Flexible Structures in Space
- 2010
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Ingår i: Proceedings of the 61<sup>st</sup> International Astronautical Congress. - : the International Astronautical Federation. ; , s. IAC-10-C3.4-
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Konferensbidrag (refereegranskat)abstract
- The Suaineadh project aims at testing the controlled deployment and stabilization of space web. The deployment system is based on a simple yet ingenious control of the centrifugal force that will pull each of the four daughters sections apart. The four daughters are attached onto the four corners of a square web, and will be released from their initial stowed configuration attached to a central hub. Enclosed in the central hub is a specifically designed spinning reaction wheel that controls the rotational speed with a closed loop control fed by measurements from an onboard inertial measurement sensor. Five other such sensors located within the web and central hub provide information on the surface curvature of the web, and progression of the deployment. Suaineadh is currently at an advanced stage of development: all the components are manufactured with the subsystems integrated and are presently awaiting full integration and testing. This paper will present the current status of the Suaineadh project and the results of the most recent set of tests. In particular, the paper will cover the overall mechanical design of the system, the electrical and sensor assemblies, the communication and power systems and the spinning wheel with its control system.
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