ALBERT

Description: SUMMARY Tsunami generated by the Late Bronze Age (LBA) eruption of Thera were simulated using synthetic tide records produced for selected nearshore (∼20 m depths) sites of northern Crete, the Cyclades Islands, SW Turkey and Sicily. Inundation distances inland were also calculated along northern Crete. Modelling was performed by incorporating fully non-linear Boussinesq wave theory with two tsunamigenic mechanisms. The first involved the entry of pyroclastic flows into the sea, assuming a thick (55 m; 30 km 3 ) flow entering the sea along the south coast of Thera in three different directions all directed towards northern Crete, then a thin pyroclastic flow (1 m; 1.2 km 3 ) entering the sea along the north coast of Thera directed towards the Cyclades Islands. Flows were modelled as a solid block that slowly decelerates along a horizontal surface. The second mechanism assumed caldera collapse, of 19 km 3 and 34 km 3 modelled as a dynamic landslide producing rapid vertical displacements. Calculated nearshore wave amplitudes varied from a few metres to 28 m along northern Crete from pyroclastic flows, and up to 19 m from caldera collapse (34 km 3 volume). Inundation distances on Crete were 250–450 m. Waves produced by pyroclastic flows were highly focused, however, as a function of sea entry direction. Smaller volume pyroclastic flows produced nearshore wave amplitudes up to 4 m in the Cyclades islands north of Thera. Wave amplitudes in the Cyclades from smaller volume caldera collapse (19 km 3 ) were up to 24 m, whereas in SW Turkey were as low as 2.1 and 0.8 m (Didim and Fethye where LBA tsunami deposits have been found). Wave amplitudes for the larger volume caldera collapse (34 km 3 ) were generally 2.5–3 times larger than those generated by the smaller volume collapse (19 km 3 ). These results provide estimates for understanding possible consequences of tsunami impact in LBA coastal zones, thus providing criteria at archaeological sites for detecting inundation damage, as well as for contemporary hazard assessment; they also provide additional criteria for deciphering homogenite layers in the abyssal stratigraphy of the Ionian and eastern Mediterranean Seas.

Description: In personal injury litigation, claimants may seek their compensation for future losses or expenses as a lump sum that is determined by the product of a multiplicand and a multiplier. The multiplicand represents the annual loss in earnings and other benefits, as assessed at the trial date, while the multiplier discounts future pecuniary values into a single present-day lump sum amount. At present, multipliers in the UK are calculated using actuarial methods and based on assumed mortality and interest rates. However, it is entirely possible that these assumptions are incorrect, and if they are, then all claimants who rely on the same set of actuarial multipliers will be affected. In this article, we investigate how the uncertainty surrounding mortality and interest rate assumptions affects the precision of actuarial multipliers. With the aid of stochastic models, we estimate the possible range of values that an actuarial multiplier can take.

Description: The Mackenzie River Delta is a lake-rich arctic floodplain that receives high inputs of dissolved organic matter (DOM) and suspended particulates from allochthonous and autochthonous sources, and may transfer carbon from dissolved to particulate phase via in situ formation of transparent exopolymer particles (TEP). TEP provides food for grazers, surfaces for bacteria, and increased potential for aggregation and sedimentation of organic matter. During open water 2006, we tracked TEP abundances in three Delta lakes representing gradients that include declining river-to-lake connection times, increasing levels of dissolved organic carbon (DOC), and declining chromophoric-DOM (CDOM). Unexpectedly, TEP abundances were highest immediately after the flood, when autochthonous autotrophic production was at a seasonal low and CDOM a seasonal high. Moreover, the lake with the strongest riverine influence and lowest levels of autochthonous autotrophic production had the highest mean TEP-carbon (TEP-C) concentrations among the lakes. The mean proportion of particulate organic carbon (POC) represented by TEP-C increased with increasing river connection time, and appears to represent a substantial proportion of POC in Mackenzie Delta Lakes. Unexpectedly, the TEP gradient was most strongly related to CDOM (river water source) rather than overall DOC. Variations in CDOM accounted for 53% of TEP-C variation among the lakes, indicating allochthonous matter was the most important source of TEP. DOC release from in situ macrophytes during periods of high photosynthesis may contribute to TEP formation in the lake with lowest riverine influence, but pH levels 〉9.5 driven by the high photosynthetic rates complicate the interpretation of results from this lake.

Description: The nearly neutral theory of molecular evolution predicts that the efficacy of both positive and purifying selection is a function of the long-term effective population size ( N e ) of a species. Under this theory, the efficacy of natural selection should increase with N e . Here, we tested this simple prediction by surveying ~1.5 to 1.8 Mb of protein coding sequence in the two subspecies of the European rabbit ( Oryctolagus cuniculus algirus and O. c. cuniculus ), a mammal species characterized by high levels of nucleotide diversity and N e estimates for each subspecies on the order of 1 x 10 6 . When the segregation of slightly deleterious mutations and demographic effects were taken into account, we inferred that 〉60% of amino acid substitutions on the autosomes were driven to fixation by positive selection. Moreover, we inferred that a small fraction of new amino acid mutations (〈4%) are effectively neutral (defined as 0 〈 N e s 〈 1) and that this fraction was negatively correlated with a gene’s expression level. Consistent with models of recurrent adaptive evolution, we detected a negative correlation between levels of synonymous site polymorphism and the rate of protein evolution, although the correlation was weak and nonsignificant. No systematic X chromosome–autosome difference was found in the efficacy of selection. For example, the proportion of adaptive substitutions was significantly higher on the X chromosome compared with the autosomes in O. c. algirus but not in O. c. cuniculus . Our findings support widespread positive and purifying selection in rabbits and add to a growing list of examples suggesting that differences in N e among taxa play a substantial role in determining rates and patterns of protein evolution.

Description: We assess the accuracy of global-gridded terrestrial water storage (TWS) estimates derived from temporal gravity field variations observed by the Gravity Recovery and Climate Experiment (GRACE) satellites. The TWS data set has been corrected for signal modification due to filtering and truncation. Simulations of terrestrial water storage variations from land-hydrology models are used to infer relationships between regional time series representing different spatial scales. These relationships, which are independent of the actual GRACE data, are used to extrapolate the GRACE TWS estimates from their effective spatial resolution (length scales of a few hundred kilometers) to finer spatial scales (∼100 km). Gridded, scaled data like these enable users who lack expertise in processing and filtering the standard GRACE spherical harmonic geopotential coefficients to estimate the time series of TWS over arbitrarily shaped regions. In addition, we provide gridded fields of leakage and GRACE measurement errors that allow users to rigorously estimate the associated regional TWS uncertainties. These fields are available for download from the GRACE project website (available at http://grace.jpl.nasa.gov). Three scaling relationships are examined: a single gain factor based on regionally averaged time series, spatially distributed (i.e., gridded) gain factors based on time series at each grid point, and gridded-gain factors estimated as a function of temporal frequency. While regional gain factors have typically been used in previously published studies, we find that comparable accuracies can be obtained from scaled time series based on gridded gain factors. In regions where different temporal modes of TWS variability have significantly different spatial scales, gain factors based on the first two methods may reduce the accuracy of the scaled time series. In these cases, gain factors estimated separately as a function of frequency may be necessary to achieve accurate results.

Description: Forty years after a similar retrospective on ozone research at Oxford by Dobson in 1968, a review and synthesis is presented of the scientific and technological advances that were possible during the period from 1970 to 2010 as a result of the deployment of a number of innovative instruments on meteorological satellites by a research group in the Atmospheric Physics department at Oxford University. Copyright © 2011 Royal Meteorological Society

Description: The effects of different inlet/outlet features and helical structures on the flow pattern and transfer performance of membrane modules were investigated with both three-dimensional computational fluid dynamics and experimental methods. In a circular flat membrane module, two types of inlet/outlet with single-port or three-port configuration were used to evaluate the influence of small differences in the opening area structure of the inlet/outlet on the flow patterns. Although the transfer regions differ, large flow swirls appear in both systems, leading to stagnation regions and causing significant back-mixing. To alleviate the swirls and improve the flow pattern, a helix clapboard was used to separate the membrane feed channel as spiral channel. Both the numerical and experimental results indicate that the helical structure can greatly enhance the transfer performance and increase the permeation rate while the increment in energy consumption is very small. Three-dimensional computational fluid dynamics simulations were performed for three membranes modules to detect the effects of structures on the membrane process. It was found that the flow patterns were dominated by the flow structures, and the spiral channel could effectively restrain the flow eddies and enhance the transfer while the increment in energy consumption was quite small.

Description: This paper shows that at solar maximum, equatorial ion densities at L = 2.5 are substantially higher at American longitudes in the December months than in the June months. This arises because the configuration of the geomagnetic field causes a longitude-dependent asymmetry in ionospheric solar illumination at conjugate points that is greatest at American longitudes. For example, at −60°E geographic longitude the L = 2.5 field line has its foot point near 65° geographic latitude in the Southern Hemisphere but near 42° latitude in the Northern Hemisphere. We investigated the consequent effects on equatorial electron and ion densities by comparing ground-based observations of ULF field line eigenoscillations with in situ measurements of electron densities (from the CRRES and IMAGE spacecraft) and He+ densities (IMAGE) for L = 2.5 at solar maximum. Near −60°E longitude the electron and ion mass densities are about 1.5 and 2.2 times larger, respectively, in the December months than in the June months. Over the Asia-Pacific region there is little difference between summer and winter densities. Plasmaspheric empirical density models should be modified accordingly. By comparing the electron, helium, and mass densities, we estimate the annual variation in H+, He+, and O+ concentrations near −3°E longitude and −74°E longitude. In each case the He+ concentration is about 5% by number, but O+ concentrations are substantially higher at −3°E longitude compared with −74° E. We speculate that this may be related to enhanced ionospheric temperatures associated with the South Atlantic anomaly.