High resolution imaging at large telescopes

Image recovery at a resolution limited only by diffraction is now possible at large telescopes. The theory of speckle image reconstruction is explained and the current status of a video recording and digitization system for the reconstruction procedure is described. Potential applications of the process when used with very large telescopes are discussed. The constraints on telescope design imposed by these techniques are listed

The relationship between dissolved solids yield and the presence of snow cover in the periglacial basin of the Obruchev Glacier (Polar Urals) during the ablation season

Hydrochemical investigations were carried out in the periglacial basin of Obruchev Glacier (Polar Urals, Russia) in order to provide a quantitative and qualitative comparison of dissolved solids yields during the ablation season with and without snow cover taking into account the mineral composition of rocks and deposits occurring in the studied area. The concentration of dissolved solids in the waters of the investigated basin is very low (about 7.0–8.9 μS cm^{-1}). It is most of all due to harsh local climate conditions as well as the presence of minerals resistant to weathering in the parent material. Both factors contribute to the low rate of chemical weathering in the area. Results obtained indicate that a larger dissolved solids yield was transported during the period with snow cover (106 kg km^{-2} day^{-1}, on average), than at the same time of the year but without snow cover (13 kg km^{-2} day^{-1}, on average) indicating that melting snow is an important factor influencing the yield of dissolved solids in surface waters

Which Drivers Control the Suspended Sediment Flux in a High Arctic Glacierized Basin (Werenskioldbreen, Spitsbergen)?

A unique data set of suspended sediment transport from the Breelva, which drains the Werenskioldbreen (Southwestern Spitsbergen), is reported for the period 2007–2012. This basin is thoroughly described hydrologically, glaciologically, and chemically. However, until now there was a lack of full recognition of mechanical denudation. This study extends the information on quantitative suspended sediment load (SSL), amounting to 37.30–130.94 kt per year, and also underlines the importance of its modification by high discharge events, triggered by intense snowmelt or heavy rainfall. The large floods during the hydrologically active season transported even 83% of the total SSL. The variability of the SSL is controlled by glacial storage and release mechanisms. Particularly interesting is the second half of the hydrologically active season when intense rainfall events plays a key role in shaping the sediment supply pattern. The main source of fine mineral matter is the basal moraine, drained by subglacial outflows. Their higher mobilization occurs when the hydrostatic pressure increases, often as a result of rainwater supply to the glacier system. An increasing precipitation trend for Hornsund fjord region determines a positive trend predicted for sediment flux

A study of a space-station-associated multiple spacecraft Michelson spatial interferometer

One approach to Michelson spatial interferometry at optical wavelengths involves use of an array of spacecraft in which two widely-separated telescopes collect light from a star and direct it to a third, centrally-located, device which combines the beams in order to detect and measure interference fringes. The original version of a spacecraft array for Michelson spatial interferometry (SAMSI) was modified so that the system uses the fuel resupply capability of a space station. The combination of this fuel resupply capability with a method of obtaining image Fourier transform phase information, necessary for full image reconstruction, permits SAMSI to be used to synthesize images equivalent to those produced by huge apertures in space. Synthesis of apertures in the 100 to 500 meter range is discussed. Reconstruction can be performed to a visual magnitude of at least 8 for a 100 A passband in 9 hours. Data are simultaneously collected for image generation from 0.1 micron to 18 microns. In the one-dimensional mode, measurements can be made every 90 minutes (including acquisition and repointing time) for objects as faint as 19th magnitude in the visible

Treści naukowe w formie drukowanej i cyfrowej. Przegląd preferencji nadawców i odbiorców komunikatów naukowych

Praca recenzowanaW artykule omówiono wyniki i przedstawiono wnioski z przeprowadzonego badania ankietowego, którego celem było poznanie nastawienia użytkowników publikacji naukowych, głównie pracowników naukowo-dydaktycznych, wobec formy użytkowanych komunikatów. Podjęto próbę udzielenia odpowiedzi na pytanie: jak kształtują się preferencje użytkowników po około piętnastu latach obecności w bibliotekach mediów elektronicznych obok tradycyjnych

Biblioteki specjalne we Francji

Basing on the available sources of information, the article intends to define and distinguish special kinds of libraries in France, and describe their history, organization and typical activities that they conduct. Additionally, the author focuses on characterizing the libraries’ staff, the services provided and the users

Observed Characteristics of Clouds and Precipitating Systems Associated with the Tropical Circulation in Global Models and Reanalyses

This dissertation presents a series of work related to the representation of the Hadley circulation (HC) in atmospheric reanalyses and general circulation models (GCMs), with connections to the underlying tropical and subtropical cloud systems that comprise the mean meridional circulation. An intercomparison of eight atmospheric reanalyses showed that significant variability exists in the mean state for HC intensity, with less variability in HC width. Ensemble trends were broadly consistent with previous work and suggest a strengthening and widening of the tropical circulation over the last 30 years. Composite profiles of the apparent heat source and moisture sink were calculated for the International Satellite Cloud Climatology Project (ISCCP) cloud regimes using sounding observations from 10 field campaigns. Distinct heating profiles were determined for each ISCCP cloud regime, ranging from strong, upper-tropospheric heating for mesoscale convective systems to integrated cooling for populations associated with marine stratus and stratocumulus clouds. The derived profiles were generally similar over land and ocean with the notable exception of the fair-weather cumulus regime, which leads to some uncertainty in the mid- and upper-level reconstruction of subtropical heating. An instrument simulator indicated that low-latitude cloud properties from the NASA MERRA reanalysis qualitatively matched the distributions of cloud-top pressure and optical thickness in the ISCCP data, though the tallest and thickest clouds were missing from the reanalysis. Simulator results were sensitive to the choice of cloud overlap parameterization and the reanalysis consistently underpredicted the observed cloud fractions for all regimes. The vertical velocity, temperature, and moisture for each regime in MERRA largely matched observations from previous studies, suggesting that the dynamic and thermodynamic properties of the cloud regimes are well captured by the reanalysis. Finally, HC interannual variability was examined as a function of the observed frequency of the ISCCP cloud regimes. The strongest HC overturning events were attributed to an El Niño response in the central Pacific Ocean in addition to links between the intensity and position of the Pacific ITCZ. The ISCCP regime describing the most vigorous and organized convection contributed the most towards the total anomalous heating during HC extremes, despite an overall low frequency of occurrence. Idealized GCM simulations forced with the observed three-dimensional diabatic heating from ISCCP data produced too strong a HC with some improvement in other fields. Overall, much progress has been made regarding the links between low-latitude cloud systems and the HC, though future work will continue to address the upscale feedbacks of regional cloud variations upon the tropical circulation