Colour dependence of zodiacal light models

Colour models of the zodiacal light in the ecliptic have been calculated for both dielectric and metallic particles in the sub-micron and micron size range. Two colour ratios were computed, a blue ratio C_b (0.40 μm, 0.53 μm) and a red ratio, either C_r (0.82 μm, 0.53 μm) or C_r' (0.71 μm, 0.53 μm). The models with a size distribution ∝s^−2.5ds generally show a colour close to the solar colour and almost independent of elongation. Especially in the blue colour ratio there is generally no significant dependence on the lower cutoff size (0.1–1 μm). The main feature of absorbing particles is a reddening at small elongations. The models for size distributions ∝s⁻⁴ds show larger departures from solar colour and more variation with model parameters. Colour measurements, including red and near infra-red, therefore are useful to distinguish between flat and steep size spectra and to verify the presence of slightly absorbing particles.     

Detrital composition of Ordovician sandstones from the Rügen boreholes: implications for the evolution of the Tornquist Ocean

The Lower Palaeozoic sequences of the Rügen boreholes are composed of pelitic-clastic sediments which range in age from the Cambro-Ordovician boundary to the Late Ordovician. Provenance studies have been carried out on Cambro-Ordovician sandstones from the Loissin borehole and on Middle-Upper Ordovician greywackes of the Rugen 5 borehole.The Loissin sandstones were deposited as turbidites and debris flows in an unstable sedimentary basin. They form immature arkoses and subarkoses with high matrix contents. Their debris derived from a polycyclic, sedimentary cratonic provenance and from a monocyclic magmatic provenance. This is reflected in the heavy mineral spectrum, which is dominated by an anhedral, coloured zircon fraction and a euhedral, transparent zircon fraction.The Middle-Upper Ordovician Rügen greywackes derived from proximal, high energy turbidites which were transported into a deep marine basin. They form homogeneous lithic arkoses and arkosic litharenites. Their debris derived from a composite provenance with an ultramafic-mafic, ophiolitic source, an acidic magmatic source and a heterogeneous sedimentary cratonic source.Although the Loissin sandstones probably originated in an intracratonic, rift-related sedimentary basin, the debris of the Rugen greywackes is regarded as derived from a heterogeneous active continental margin. Results and interpretations of the provenance study are discussed in the light of proposed Lower Palaeozoic palaeogeographic reconstructions.     

Review: Saltwater intrusion in fractured crystalline bedrock

Hydrogeology Journal - During the past few years, the number of regional and national assessments of groundwater quality in regard to saltwater intrusion in coastal aquifers has increased steadily....     

Abundance estimates of an isolated population of common bottlenose dolphins Tursiops truncatus in Walvis Bay,Namibia, 2008–2012

The coastal population of common bottlenose dolphins Tursiops truncatus found in Namibia is regionally isolated and unique. This population faces several potential anthropogenic threats, especially in Walvis Bay, including boat-based tourism, a commercial harbour undergoing expansion, and aquaculture for oysters and mussels. Between 2008 and 2012, 238 boat-based surveys were conducted, resulting in 170 encounters with bottlenose dolphins. Overall, group sizes varied from 1 to 45 individuals (mean 10.7). Encounter rates, group sizes and total numbers of animals identified were higher in winter than in summer field seasons. The number, and survival and immigration parameters, of bottlenose dolphins using Walvis Bay was investigated using robust design and Huggins closed-population mark-recapture models. The highest numbers estimated were in the first and last years of the study, with estimates of 74–82 in 2008 and 76–77 in 2012 (numbers identified and upper 95% confidence limits). The only previously available data, from an incomplete study in the early 1990s, suggested that the population was between 100 and 150 individuals at the time. Although no linear trend in population size was obvious during the current study, the clear evidence of isolation, small population size, low annual birth rate, and potential long-term decrease in numbers since the early 1990s is concerning. Further work to collect data on demographic parameters is urgently recommended with a view to obtaining increased protection for this species.     

广东东莞地区中侏罗统塘厦组凝灰质沉积物的元素地球化学特征及构造背景

东莞地区中侏罗统塘厦组为富含凝灰质的湖泊沉积。对样品进行全岩分析和ICP-MS微量元素分析,并计算Sr/Ba、B/Ga和Ca/Mg比值,其比值变化与古盐度变化成正相关,特征显示塘厦组为咸水湖泊沉积,由下至上古盐度逐渐降低,水体深度也逐渐变浅。对样品进行ICP-MS稀土元素分析,计算各样品δCe值和(La/Yb)_N比值,δCe值介于0.83 ~ 1.31之间,(La/Yb)_N值均明显大于1或小于1,其特征反映湖泊沉积物沉积速率较低,只在塘厦组底部和上部出现相对高的沉积。元素P和Sr/Cu值反映其富集与迁移,受到气候的控制。元素P平均值在0.205×10^-2; Sr/Cu平均值大于4.0×10^-6,在中晚期出现最低值1.42×10^-6,这是塘厦组以干热气候为主,中晚期出现了短暂温湿气候所造成的。塘厦组为干热气候下缓慢沉积的咸水湖泊沉积。Zr-Th、La-Th-Sc判别图解、稀土元素特征及区域构造分析,显示中侏罗世东莞地区构造背景为活动大陆边缘的弧后盆地。受伸展作用影响,本区发育弧后裂谷型湖盆。泥岩La/Yb-∑REE源岩判别图解显示,源岩为玄武岩、花岗岩和沉积岩。     

Labrador Sea convection and subpolar North Atlantic Deep Water export in the SODA assimilation model

Labrador Sea convection was most intense and reached the greatest depths in the early 1990s, followed by weaker, shallower, and more variable convection after 1995. The Simple Ocean Data Assimilation (SODA) version 2.0.2/2.0.4 assimilation model is used to explore convective activity in the North Atlantic Ocean for the period from 1992 to 2007. Hydrographic conditions, which are relatively well observed during this period, are used to compare modeled and observed winter mixed-layer depths and water mass anomalies in relation to Deep Western Boundary Current transports and meridional overturning circulation (MOC) changes at the exit of the subpolar basin. The assimilation differs markedly from local observations in the March mixed-layer depth, which represents deep convection and water mass transformation. However, mean MOC rates at the exit of the subpolar gyre, forced by stratification in the mid-latitudes, are similar to estimates based on observations and show no significant decrease during the 1992–2007 period. SODA reproduces the deep Labrador Sea Water formation in the western North Atlantic without any clear indication of significant formation in the Irminger Sea while the lighter upper Labrador Sea Water density range is reached in the Irminger Sea in the 1990s, in agreement with existing assumptions of deep convection in the Irminger Sea and also supported by computed lag correlations with the Labrador Sea. Deep Water transformation mainly takes place in the eastern North Atlantic. The introduction of CFC-11 into the SODA model as a tracer reproduces the mean and multiyear variations of observed distributions.     

Scattering of radiation by a large particle with a random rough surface

Intensity and polarization of scattered light by an absorbing spherical particle with a random rough surface and with a radius larger than the wavelength of radiation are investigated. Multiple reflections of incident light on the rough surface are treated based on the multiple scattering theory.Within the limits of our approximation the model gives good agreement with typical scattering features by irregular shaped particles derived by microwave analogue experiments and laser measurements, namely a backward enhancement of the intensity, and a reduction of magnitude of polarization.Our treatment will be provide a powerful tool for studying scattering problems of interstellar and/or interplanetary grains as well as those of asteroids and the Moon.