Sapphires from Sri Lanka

A rural industry of small‐scale mining, for sapphires and a host of other gemstones, is alive and thriving at Ratnapura in Sri Lanka. The minerals are extracted from alluvial gravels and colluvium, and most are then cut and polished locally for use in jewellery.     

UV detectors for spectrographs of WSO-UV project

The WUVS (WSO-UV Ultra Violet Spectrographs) consists of two high resolution spectrographs (R=50000) covering the Far-UV range of 115–176 nm and the Near-UV range of 174–310 nm, and a long-slit spectrograph (R=1000) covering the wavelength range of 115–305 nm. Significant progress in the CCD development gives a possibility to use back-illuminated CCD detectors with anti-reflection coating for observations in the UV. These detectors are under construction by e2v company (UK) based on their heritage of detectors production for numerous space missions including those for UV- and far-UV. The main parameters of WUVS detector subsystems are described.     

Klondike Gold

In 1896, the world's greatest gold rush descended on the Klondike, in northern Canada. The hardships endured on the journey there and then in hand-mining the frozen ground are the stuff of legends. But the 'mother lode' was never found, and only recently have the origins of the gold been recognized. After the madness and the extravagance of the initial rush, mining methods evolved, and there are miners still working the Klondike today.     

Finding outlier light curves in catalogues of periodic variable stars

We present a methodology to discover outliers in catalogues of periodic light curves. We use a cross-correlation as the measure of 'similarity' between two individual light curves, and then classify light curves with lowest average 'similarity' as outliers. We performed the analysis on catalogues of periodic variable stars of known type from the MACHO and OGLE projects. This analysis was carried out in Fourier space and we established that our method correctly identifies light curves that do not belong to those catalogues as outliers. We show how an approximation to this method, carried out in real space, can scale to large data sets that will be available in the near future such as those anticipated from the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) and Large Synoptic Survey Telescope (LSST).     

Simulating zonal scale shifts in the partitioning of surface and subsurface freshwater flow in response to increasing pCO2

Freshwater discharge is one main element of the hydrological cycle that physically and biogeochemically connects the atmosphere, land surface, and ocean and directly responds to changes in pCO₂. Nevertheless, while the effect of near-future global warming on total river runoff has been intensively studied, little attention has been given to longer-term impacts and thresholds of increasing pCO₂ on changes in the partitioning of surface and subsurface flow paths across broad climate zones. These flow paths and their regional responses have a significant role for vegetation, soils, and nutrient leaching and transport. We present climate simulations for modern, near-future (850?ppm), far-future (1880?ppm), and past Late Cretaceous (1880?ppm) pCO₂ levels. The results show large zonal mean differences and the displacement of flows from the surface to the subsurface depending on the respective pCO₂ level. At modern levels the ratio of deeper subsurface to near-surface flows for tropical and high northern latitudes is 1:4.0 and 1:0.5, respectively, reflecting the contrast between permeable tropical soils and the areas of frozen ground in high latitudes. There is a trend toward increased total flow in both climate zones at 850?ppm, modeled to be increases in the total flow of 34 and 51%, respectively, with both zones also showing modest increases in the proportion of subsurface flow. Beyond 850?ppm the simulations show a distinct divergence of hydrological trends between mid- to high northern latitudes and tropical zones. While total wetting reverses in the tropics beyond 850?ppm due to reduced precipitation, with average zonal total runoff decreasing by 46% compared to the 850?ppm simulation, the high northern latitude zone becomes slightly wetter with the average zonal total runoff increasing by a further 3%. The ratio of subsurface to surface flows in the tropics remains at a level similar to the present day, but in the high northern latitude zone the ratio increases significantly to 1:1.6 due to the loss of frozen ground. The results for the high pCO₂ simulations with the same uniform soil and vegetation cover as the Cretaceous are comparable to the results for the Cretaceous simulation, with higher fractions of subsurface flow of 1:5.4 and 1:5.6, respectively for the tropics, and 1:2.2 and 1:1.6, respectively for the high northern latitudes. We suggest that these fundamental similarities between our far future and Late Cretaceous models provide a framework of possible analogous consequences for (far-) future climate change, within which the integrated human impact over the next centuries could be assessed. The results from this modeling study are consistent with climate information from the sedimentary record which highlights the crucial role of terrestrial-marine interactions during past climate change. This study points to profound consequences for soil biogeochemical cycling, with different latitudinal expressions, passing of climate thresholds at elevated pCO₂ levels, and enhanced export of nutrients to the ocean at higher pCO₂.     

Surf zone characterization from Unmanned Aerial Vehicle imagery

We investigate the issues and methods for estimating nearshore bathymetry based on wave celerity measurements obtained using time series imagery from small unmanned aircraft systems (SUAS). In contrast to time series imagery from fixed cameras or from larger aircraft, SUAS data are usually short, gappy in time, and unsteady in aim in high frequency ways that are not reflected by the filtered navigation metadata. These issues were first investigated using fixed camera proxy data that have been intentionally degraded to mimic these problems. It has been found that records as short as 50 s or less can yield good bathymetry results. Gaps in records associated with inadvertent look-away during unsteady flight would normally prevent use of the required standard Fast Fourier Transform methods. However, we found that a full Fourier Transform could be implemented on the remaining valid record segments and was effective if at least 50% of total record length remained intact. Errors in image geo-navigation were stabilized based on fixed ground fiducials within a required land portion of the image. The elements of a future method that could remove this requirement were then outlined. Two test SUAS data runs were analyzed and compared to survey ground truth data. A 54-s data run at Eglin Air Force Base on the Gulf of Mexico yielded a good bathymetry product that compared well with survey data (standard deviation of 0.51 m in depths ranging from 0 to 4 m). A shorter (30.5 s) record from Silver Strand Beach (near Coronado) on the US west coast provided a good approximation of the surveyed bathymetry but was excessively deep offshore and had larger errors (1.19 m for true depths ranging from 0 to 6 m), consistent with the short record length. Seventy-three percent of the bathymetry estimates lay within 1 m of the truth for most of the nearshore.     

Turbidity development and dissipation in paleoplacer gold deposits, southern New Zealand

Placer gold mining inevitably produces highly turbid processing waters. Five historic paleoplacer mining sites in Central Otago, New Zealand, provided 24 samples which were used in laboratory-based settling experiments. Turbidity was examined in the context of stratigraphy of paleoplacer deposits, their environments of formation, and the groundwater processes that affected the deposits as well as the underlying bedrock. Settling rates were characterised by measuring turbidity levels over time (up to 40 days) using turbidimeter and Coulter counter methods. High clay mineral (mostly kaolinite) contents of the materials were confirmed by X-ray diffraction. Grain size distributions of suspended materials were very comparable across all samples with majority of particles falling between <1.2 and 2.5 μm. The levels of turbidity produced by the auriferous sediments were partly controlled by the level of sorting and winnowing that the sediments were subjected to during transport and deposition. Debris flow material generated high turbidity [initial levels of 120–420 nephelometric turbidity units (NTU)] which settled slowly, as did eolian siltstone (1,600 NTU). Fluvial sediments generally generated lower turbidity which settled more rapidly, on the scale of hours to days. It was found that cementation of the sediment can reduce turbidity generation by limiting disaggregation of the clay minerals. On the other hand, the presence of altered lithic clasts within the sediments contributes to higher turbidity production. There was poor correlation between the level of bedrock alteration, as indicated by Chemical Index of Alteration, and the resulting turbidity. Settling rates were more rapid in experiments conducted in saline solution, as opposed to stream water, due to floc formation.