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Amorphous TiO2 and SnO2 electron transport layers (ETLs) were deposited by low-temperature atomic layer deposition (ALD). Surface morphology and x-ray photoelectron spectroscopy (XPS) indicate uniform and pinhole free coverage of these ALD hole blocking layers. Both mesoporous and planar perovskite solar cells were fabricated based on these thin films with aperture areas of 1.04 cm2 for TiO2 and 0.09 cm2 and 0.70 cm2 for SnO2. The resulting cell performance of 18.3 % power conversion efficiency (PCE) using planar SnO2 on 0.09 cm2 and 15.3 % PCE using mesoporous TiO2 on 1.04 cm2 active areas are discussed in conjunction with the significance of growth parameters and ETL composition.
In this paper, we present preliminary results of soft X-ray diffuse background observations. We observed two particular regions of the sky in the 0.3–1.5 keV range. The detection system consisted of three independent, 1 cm diameter, cooled solid state detectors. Nearly overlapping fields of view subtended a solid angle of approximately 1/4 sr. Except for the field of view, the whole set was similar to that described in Schnopper et al. (1982) (hereafter referred to as paper 1). This system was flown on board a three-axis stalibized rocket. The flight took place at White Sands Missile Range on 1981 May 4 at 0755 UT.
Physical dormancy of Robinia pseudoacacia seeds makes it a challenge for scientists and forest managers to obtain a homogeneous germination for larger seed samples. Water imbibition of the seeds can be achieved through manual piercing of the seed coat, but this method remains time consuming and heterogeneous. We tested several ecologically friendly methods to break seed dormancy, including manual pin puncture, water soaking, oven dry-heating (two temperatures) and sanding. Sanding was performed using an automatic grinder to control shaking duration (three durations) and get a homogeneous scraping of the coat. All methods, except dry-heating, resulted in successful dormancy breaking; water soaking was the least efficient method, attaining 57% germination. Sanding proved to be as efficient as puncturing (97%) but long duration sanding (10 or 15 min) could damage cotyledons, which would impede further development of the plant. Short-time sanding (5 min) proved to be the best method to reach high total germination and healthy (undamaged cotyledon) seedlings, and was successfully applied to 500 seeds. The reference puncture method and the automatic sanding were also tested on seeds of nine Fabaceae species and proved to be efficient for some species. Automated sanding can thus be used as a standard to break physical dormancy of black locust or other Fabaceae seeds to allow further comparative studies of plant populations or genotypes.
The transformation of dry snow to firn is described by the transition between densification by deformationless restacking and densification by power-law creep. The observed decrease with temperature of the density at the snow-firn transition seems to result from the competition between grain-boundary sliding and power-law creep. These two densification processess occur concurrently in snow, although there are probably micro-regions in which sliding alone occurs. Validation of a geometrical densification model developed for ceramics has been obtained from densification data from several Antarctic and Greenland sites and from the characterization of the structure of polar firn.
The bush dog Speothos venaticus is a medium-sized Neotropical canid. It is considered to be rare and its biology and population parameters are still poorly understood. The Amazon is one of the main strongholds of this species and is important for maintaining viable populations, as the region still holds extensive tracts of pristine habitat. We gathered field data from camera-trap studies throughout the Brazilian Amazon to estimate the relative abundance of the species and gain an understanding of its rarity, and how this compares with estimates from other vegetative formations and for sympatric hypercarnivores. We focused on three pristine or partially disturbed sites and one fragmented site. The estimated relative abundance of the species was 0.060–0.185 individuals per 100 trap-days, confirming that the species is rare. The bush dog's abundance in the Amazon is equivalent to that in all other areas outside the Basin. The mean group size recorded was c. 2.5 individuals. There were no differences in group sizes between forests in the Amazon and in other regions of Central America; however, there were significant differences between forests and open habitats. A combination of competition/predation, habitat structure/integrity, and disease may be acting synergistically in determining the abundance and rarity of bush dogs.
The BBXRT observed nine supernova remnants during its nine-day flight. We present preliminary results from some of these observations, emphasizing the ability of BBXRT to perform spatially resolved spectroscopy. The improved spectral resolution and efficiency over previous instruments makes possible measurements of previously undetectable lines, and the broad bandpass allows simultaneous measurement of lines from oxygen through iron.
Thanks to an original approach based on the carburization of silicon nanowires, silicon carbide-based one dimensional nanostructures – SiC nanotubes, Si-SiC core-shell nanowires and SiC nanowires – have been synthesized. The original process, which relies on controlling the out-diffusion of Si atoms through SiC, can be monitored by the temperature, the pressure and the time of carburization. These SiC-based 1D nanostructures have been characterized by SEM, FIB-SEM and TEM microscopies and also Raman spectroscopy. Bio-nano-sensors, nano-Field-Effect-Transistors (nano-FETs) or gas sensors may be some applications for these nanostructures.
We have installed a small telescope to monitor the sky brightness around the sun at the French-Italian station Concordia at Dome C in Antarctica. Previous campaigns have been performed with the same instrument at Haleakala in Hawai and Sunspot in New Mexico. We compare here the results of the first year of the campaign at Dome C (2008) to the purest sky observed at Haleakala. We show that Dome C is an outstanding site for coronal observations. Compared to Haleaka, it appears to be more transparent, and to contain less aerosols. Its water vapour content is also significantly smaller. These results still have to be confirmed by the analysis of the 2009 and 2010 data.
In order to develop a novel proton conductive membrane for proton exchange membrane fuel cell (PEMFC), a poly(vinyl di-fluoride) (PVDF) matrix was irradiated with swift heavy ions (SHI) to obtain radically active cylindrical latent tracks in the polymer film. Styrene was then radiografted and further sulfonated into these irradiated cylindrical regions, leading to sulfonated polystyrene (PVDF-g-PSSA) domains within PVDF. The role of the grafting degree and fluence of irradiation of the PVDF matrix on PVDF-g-PSSA membranes properties (chemical composition, ion exchange capacity) was investigated. Then, a membrane-electrode assembly (MEA) was prepared and fuel cell tests have been performed. Our results clearly show that PVDF-g-PSSA membranes with a grafting degree of about 140%, obtained after irradiation at a fluence of 1010 ions/cm2, exhibit good conductivity values but their durability is limited to about 70 h. Decreasing the fluence leads to membranes with lower grafting yield but with fuel cell performances closer to those of 140% grafted PVDF-g-PSSA membrane and improved mechanical properties. Then, ion track grafting technique is a promising technique to obtain PEM with a good trade-off between proton conductivity and mechanical properties.
It is generally considered that the absorption of Mg is inversely related to the ingested dose. The objective of the present study was to determine if the mode of administration (bolus v. consumption throughout the day) could influence Mg bioavailability from Mg-rich natural mineral water comparing the same nutritional Mg amount (126 mg). Using a 2 d cross-over design, twelve healthy men were asked to drink 1·5 litres Mg-rich mineral water either as 2 × 750 ml or 7 × 212 ml throughout the day. Two stable isotopes (25Mg and 26Mg) were used to label the water in order to distinguish both regimens. Fractional apparent Mg absorption was determined by faecal monitoring and Mg retention was determined by measuring urinary excretion of Mg isotopes. Higher Mg absorption (50·7 (sd 12·7) v. 32·4 (sd 8·1) %; P = 0·0007) and retention (47·5 (sd 12·9) v. 29·0 (sd 7·5) %; P = 0·0008) from Mg-rich mineral water were observed when it was consumed in seven servings compared with larger servings. Thus, regular water consumption throughout the day is an effective way to increase Mg bioavailability from Mg-rich mineral water.
Aqueous colloidal solutions of well dispersed YVO4:Ln (Ln = Eu, Nd) nanoparticles are synthesized through precipitation reactions at room temperature. In the case of YVO4:Eu, a luminescence quantum yield of 15% is found, which is not as high as in the bulk due to the existence of residual crystalline defects and nonradiative relaxations from the hydroxylated surface. Appropriate hydrothermal annealing and deuteration of the surface allow to rise the yield up to 38%. Incorporation of the nanocrystals into a transparent silica matrix is achieved through preliminary coating of the particles with a functionnalized silicon alkoxide and further dispersion into a sol-gel precursor solution. Such sol-gel materials doped with YVO4:Nd nanocrystals are transparent and exhibit the typical emission at 1.06 μm of the Nd3+ ion.
Current models for predicting the unusual deformation characteristics of Ni3Al alloys are based upon the idea of cross-slip pinning of screw dislocation segments. These models assume an Arrhenius type framework which employs a stress-modified activation barrier for forward cross slip. Use of such models has been successful in describing the orientation, asymmetry and temperature characteristics of yielding. A limitation of current models is their inability to predict the apparent lack of a strain rate effect in Ni3Al alloys. The current model approaches the problem using both kinetic and thermodynamic arguments to describe the physical process. It is then demonstrated that the driving force for cross-slip controls the process. The model describes all aspects of deformation including apparent strain rate insensitivity. An additional feature of the model is its ability to provide analytical and physical justification for the use of Arrhenius type equations for representing experimental data.
Since the middle of the 90's, GaN epitaxy techniques have been developed, using either MOCVD or MBE growth methods. A low cost approach is presented aiming at satisfying thermal issues encountered on conventional substrates such as SiC, Sapphire and more recently Silicon. Domain of application are being covered with their associated challenges: RF and High Power applications. Stress engineering is one of the key parameters.