Morphological Comparison of Three Asian Native Honey Bees (Apis Cerana, a. Dorsata, a. Florea) in Northern Vietnam and Thailand

Three species of Asian native honey bees (Apis cerana, A. florea and A. dorsata) from northern Vietnam and Thailand were morphologically analyzed for investigations on their geographic variations and relations. In Vietnam, samples were collected from feral and managed colonies. In Thailand, the collections were from feral colonies or from field bees on flowers. Morphological analysis was carried out, using measurements common to honeybee taxonomy. Measured characters were done under stereomicroscope with an ocular micrometer. ANOVA program and multivariate statistical analyses were applied for treating the data. Overall, A. cerana populations in northern Vietnam are significantly morphologically different than from those in Thailand. It may be due to their different geographic locations between the Thai and Vietnamese populations of A. cerana. A. florea bees from Vietnam are generally bigger in size than those from Thailand, but the differences are uncertain. In contrast, the body size of A. dorsata populations from Thailand are bigger than those from Vietnam. However, these differences are also not significant. It is necessary to take further comparative investigations of these bee species from both countries

Constraints on cometary surface evolution derived from a statistical analysis of 67P's topography

We present a statistical analysis of the distribution of large-scale topographic features on comet 67P/Churyumov-Gerasimenko.We observe that the cumulative cliff height distribution across the surface follows a power law with a slope equal to -1.69 ± 0.02. When this distribution is studied independently for each region, we find a good correlation between the slope of the power law and the orbital erosion rate of the surface. For instance, the Northern hemisphere topography is dominated by structures on the 100 m scale, while the Southern hemisphere topography, illuminated at perihelion, is dominated by 10 m scale terrain features. Our study suggests that the current size of a cliff is controlled not only by material cohesion but also by the dominant erosional process in each region. This observation can be generalized to other comets, where we argue that primitive nuclei are characterized by the presence of large cliffs with a cumulative height-power index equal to or above -1.5, while older, eroded cometary surfaces have a power index equal to or below -2.3. In effect, our model shows that a measure of the topography provides a quantitative assessment of a comet's erosional history, that is, its evolutionary age. © 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Embedded voxel colouring with adaptive threshold selection using globally minimal surfaces

mage-based 3D reconstruction remains a competitive field of research as state-of-the-art algorithms continue to improve. This paper presents a voxel-based algorithm that adapts the earliest space-carving methods and utilises a minimal surface technique to obtain a cleaner result. Embedded Voxel Colouring is built in two stages: (a) progressive voxel carving is used to build a volume of embedded surfaces and (b) the volume is processed to obtain a surface that maximises photo-consistency data in the volume. This algorithm combines the strengths of classical carving techniques with those of minimal surface approaches. We require only a single pass through the voxel volume, this significantly reduces computation time and is the key to the speed of our approach. We also specify three requirements for volumetric reconstruction: monotonic carving order, causality of carving and water-tightness. Experimental results are presented that demonstrate the strengths of this approach