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An artificial diet formulated for continuous rearing of the predator Arma chinensis was inferior to natural prey when evaluated using life history parameters. A transcriptome analysis identified differentially expressed genes in diet-fed and prey-fed A. chinensis that were suggestive of molecular mechanisms underlying the nutritive impact of the artificial diet. Changes in the diet formulation were made based on the transcriptome analysis and tested using life history parameters. The quantity of pig liver, chicken egg, tuna fish, biotin, nicotinamide, vitamin B6, thiamine, riboflavin, vitamin C, L-glutamine, and sucrose was reduced, and wheat germ oil, calcium pantothenate and folic acid were increased. Ecuadorian shrimp was added as a partial substitute for tuna fish. Several parameters improved over six generations, including increased egg viability, and decreased egg and adult cannibalism. Additionally, several parameters declined, including longer developmental times for 2nd–5th instars, and decreased nymphal weights. The improvements in life history parameters support the use of transcriptome analyses to help direct formulation improvements. However, the decline in some parameters suggests that additional information, e.g., proteomic data, may be useful as well to maximize diet formulations.
The Groningen field is the largest onshore gas field in Europe. Continuous production since 1963 has led to induced seismicity starting in the early 1990s. Production measures aimed at lowering the level of seismicity have been implemented since 2014. In this paper we start from an empirical relationship between the cumulative number of seismic events and cumulative gas production. We show that a better way to analyse the data is to relate the ratio of activity rate over production rate versus the cumulative production, such that the model parameters and their uncertainty can be determined. This also allows us to make predictions including the confidence intervals.
Using this model, we first performed regression analysis based on the larger seismic catalogue which includes all recorded events with a magnitude of 1.3 and larger, because we consider this value to be the magnitude of completeness since 1995. We have also performed regression analysis based on a smaller seismic catalogue consisting of all events with a magnitude of 1.5 and larger. This was done in order to be able to compare our forecast with forecasts performed by others. Our prediction for 2016, based on the seismic catalogue of all events with a magnitude of M≥1.5 (using only the events recorded before 2016), was 16±8 events. By the end of 2016, 13 such events had been recorded.
We discuss a number of factors which may influence the predictive power of the derived relationship and which require further study. For instance, we consider the delay between production and earthquakes which increases with decreasing reservoir pressure. In addition, the effect of seasonal fluctuation in Groningen production should be considered. Future work can be done to include these effects in the empirical model. We also investigated the challenges related to the applicability of the analysis to sub-regions of the Groningen field.
The Finite Element Sea-ice Ocean Model (FESOM) has been augmented by an ice-shelf component with a three-equation system for diagnostic computation of boundary layer temperature and salinity. Ice-shelf geometry and global ocean bathymetry have been derived from the RTopo-1 dataset. A global domain with a triangular mesh and a hybrid vertical coordinate is used. To evaluate sub-ice-shelf circulation and melt rates for present-day climate, the model is forced with NCEP reanalysis data. Basal mass fluxes are mostly realistic, with maximum melt rates in the deepest parts near the grounding lines and marine ice formation in the northern sectors of the Ross and Filchner–Ronne Ice Shelves, Antarctica. Total basal mass loss for the ten largest ice shelves reflects the importance of the Amundsen Sea ice shelves; the Getz Ice Shelf is shown to be a major meltwater contributor to the Southern Ocean. Despite their modest melt rates, the ‘cold water’ ice shelves in the Weddell Sea are still substantial sinks of continental ice in Antarctica. Discrepancies between the model and observations can partly be attributed to deficiencies in the forcing data or to (sometimes unavoidable) smoothing of ice-shelf and bottom topographies.
A sea-ice mass-balance monitoring study including ice extent and thickness observations was started at Kongsfjorden (79˚N, 12˚E), Svalbard, in 2003. The inner part of Kongsfjorden is usually covered by seasonal fast ice <1m thick, initially forming between December and March and persisting until June. Ice extent is visually observed from the mountain Zeppelinfjellet, and documented by ice maps and photographs several times a week. Ice and snow thickness is measured regularly at four sites from drillholes. Time series of ice extent in four areas east of Ny-Ålesund (total area 120 km2) were calculated for 2003–05. By combining extent with thickness data, ice-mass time series were calculated. As also observed earlier than 2003 in other studies, the fast ice varies interannually in extent and thickness. Among the factors which control the fast-ice evolution are physical and meteorological parameters, and the geographical setting of Kongsfjorden, with its coastline and a group of islands in its inner part having a protective effect. This study is ongoing and a major aim is to identify and quantify connections between the Kongsfjorden fast-ice evolution and climate parameters.
Sea-ice thickness is a key parameter for estimates of salt fluxes to the ocean and the contribution to global thermohaline circulation. Observations of sea-ice thickness in the Southern Ocean are sparse and difficult to collect. An exception to this data gap is time-series data from upward-looking sonars (ULS) which sample the drifting sea ice continuously. In this study we use ULS data from ten different locations over periods ranging from 9 to 25 months to compare with model data. Although these data are limited in space and time, they provide a qualitative indication of the ability of global climate models (GCMs) to adequately represent Southern Ocean sea ice. We compare the ULS data to output from four different GCMs (BCCR-BCM2.0, ECHAM5/MPI-OM, UKMO-HadCM3 and NCAR CCSM3) which were used for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. They simulate the ice thickness reasonably well, but in most cases average model ice thickness is less than thicknesses derived from ULS data. The seasonal cycle produced by the models correlates well with the ULS except for locations near Maud Rise, where in summer the ULS find a low concentration of thick ice floes. This overly thin ice will have implications for both the salt flux to the central Weddell Sea during the growth season and the freshwater flux during the melt season. Using satellite-derived ice-drift data to calculate transports in the Weddell Sea, we find that the underestimation of ice thickness results in underestimated salt fluxes.
The processes of trapping, compression, and acceleration of short electron bunches externally injected into the wakefields generated by intense femtosecond laser pulse in a plasma channel are analyzed and optimized. The influence of the laser non-linear dynamics to the longitudinal bunch compression and impact of the beam loading effect (self-action of the bunch charge) to the finite energy and the energy spread of the accelerated electrons are investigated. The limitations to the charge of accelerated electron bunch determined by the requirement of a small width of the electron energy distribution of the bunch are found.
We calculate the partial inflow of gas fuelled by stellar mass loss at an early epoch (109yr after the birth of the galaxy) during the evolution of an elliptical galaxy assuming a modified King model stellar distribution. The influence of the partial thermalization of stellar mass lost on the amount of gas which can be stored in the nucleus of a typical elliptical during the time of partial inflow is investigated. Masses up to 105M⊙ of cool (≤ 104K) material can be stored in the nucleus of the galaxy before the fast dissipation of the “kinetic bulk energy” of the nuclear gas cloud leads to “thermal” instability and subsequent collapse. A supermassive star can form. A detailed discussion of the model and the results is subject of a forthcoming paper (Kunze et al., 1986).
Variability of sea-ice and snow conditions on the scale of a few hundred meters is examined using in situ measurements collected in first-year pack ice in the European Arctic north of Svalbard. Snow thickness and surface elevation measurements were performed in the standard manner using a snow stick and a rotating laser. Altogether, 4109 m of measurement lines were surveyed. The snow loading was large, and in many locations the ice freeboard was negative (38.8% of snowline measurements), although the modal ice and snow thickness was 1.8 m. The mean of all the snow thickness measurements was 36 cm, with a standard deviation of 26 cm. The mean freeboard was only 3 cm, with a standard deviation of 23 cm. There were noticeable differences in snow thickness among the measurement sites. Over the undeformed ice areas, the mean snow thickness and freeboard were 23 and 2.4 cm, respectively. Over the ridged ice areas, the mean freeboard was only –0.3 cm due to snow accumulation on the sails of ridges (average thickness 54 cm). These findings imply that retrieval algorithms for converting freeboard to ice thickness should take account of spatial variability of snow cover.
We present sea-ice surface roughness estimates, i.e. the standard deviation of relative surface elevation, in the Arctic regions of Fram Strait and the Nansen Basin north of Svalbard acquired by an airborne laser scanner and a single-beam laser altimeter in 2010. We compare the scanner to the altimeter and compare the differences between the two survey regions. We estimate and correct sensor roll from the scanner data using the hyperbolic response of the scanner over a flat surface. Measurement surveys had to be longer than 5 km north of Svalbard and longer than 15 km in Fram Strait before the statistical distribution in surface roughness from the scanner and altimeter became similar. The shape of the surface roughness probability distributions agrees with those of airborne electromagnetic induction measurements of ice thickness. The ice in Fram Strait had a greater mean surface roughness, 0.16 m vs 0.09 m, and a wider distribution in roughness values than the ice in the Nansen Basin. An increase in surface roughness with increasing ice thickness was observed over fast ice found in Fram Strait near the coast of Greenland but not for the drift ice.
Rijpfjorden (808 N, 22° E) is a high-Arctic fjord on Nordaustlandet in the Svalbard archipelago. To monitor the thermodynamic change of sea ice in spring, an ice mass-balance buoy (IMB) was deployed for 2.5 months (10 April–26 June 2011), with accompanying in situ measurements, sea-ice sampling on three occasions and ice-core analysis. Uncertainties and sources of error in in situ measurements and IMB data are discussed. The in situ measurements, ice-core analysis and IMB data together depict the development of snow and ice in spring. Snow and ice thickness exhibited large spatial and temporal variability. After relatively stable conditions with only little change in ice thickness and accumulation of snow, a layer of superimposed ice ∼0.06 m thick formed at the snow-ice interface due to refreezing of snow meltwater in late spring. Ice thickness (except for growth of superimposed ice) did not change significantly based on in situ observations. In contrast, the under-ice sonar data from the IMB show reflections from a layer deeper than the underside of the ice during the melting phase. This can be explained as a reflection of the sonar pulses from an interface between a freshwater layer under the ice and more saline water below, or as a false-bottom formation.
Toxocara canis is an important but neglected zoonotic parasite, and is the causative agent of human toxocariasis. Chondroitin proteoglycans are biological macromolecules, widely distributed in extracellular matrices, with a great diversity of functions in mammals. However, there is limited information regarding chondroitin proteoglycans in nematode parasites. In the present study, a female-enriched chondroitin proteoglycan 2 gene of T. canis (Tc-cpg-2) was cloned and characterized. Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to measure the transcription levels of Tc-cpg-2 among tissues of male and female adult worms. A 485-amino-acid (aa) polypeptide was predicted from a continuous 1458-nuleotide open reading frame and designated as TcCPG2, which contains a 21-aa signal peptide. Conserved domain searching indicated three chitin-binding peritrophin-A (CBM_14) domains in the amino acid sequence of TcCPG2. Multiple alignment with the inferred amino acid sequences of Caenorhabditis elegans and Ascaris suum showed that CBM_14 domains were well conserved among these species. Phylogenetic analysis suggested that TcCPG2 was closely related to the sequence of chondroitin proteoglycan 2 of A. suum. Interestingly, a high level of Tc-cpg-2 was detected in female germline tissues, particularly in the oviduct, suggesting potential roles of this gene in reproduction (e.g. oogenesis and embryogenesis) of adult T. canis. The functional roles of Tc-cpg-2 in reproduction and development in this parasite and related parasitic nematodes warrant further functional studies.
Glaciological investigations were carried out on the Greenland ice sheet to help develop plans for a hydro-electric power station to supply energy to Ilulissat/Jakobshavn. The investigations required research on supraglacial and subglacial melt-water drainage in order to delineate water-drainage basins. This involved repeated detailed photogrammetric mapping, radio echo-sounding, hot-water drilling, and mathematical modelling of subglacial drainage. Repeated mappings combine to show an overall stability in the supraglacial drainage pattern, while model calculations for the subglacial conditions show a limited sensitivity in the predicted drainage areas to changes in hydraulic conditions. The investigations provide the basis for setting safer limits for planning hydro-electric power in the area, and give a general understanding of glacier hydrology for a continuous ice cover such as the Greenland ice sheet.
We calculate the present ice budget for Antarctica from measurements of accumulation minus iceberg calving, run-off and in situ melting beneath the floating ice shelves. The resulting negative mass balance of 469 Gt year−1 differs substantially from other recent estimates but some components are subject to high temporal variability and budget uncertainties of 20–50%. Annual accumulation from an earlier review is adjusted to include the Antarctic Peninsula for a total of 2144 Gt year−1. An iceberg production rate of 2016 Gt year−1 is obtained from the volume of large icebergs calculated from satellite images since 1978, and from the results of an international iceberg census project. Ice-shelf melting of 544 Gt year−1 is derived from physical and geochemical observations of meltwater outflow, glaciological field studies and modeling of the sub-ice ocean circulation. The highest melt rates occur near ice fronts and deep within sub-ice cavities. Run-off from the ice-sheet surface and from beneath the grounded ice is taken to be 53 Gt year−1. Less than half of the negative mass balance need come from the grounded ice to account for the unattributed 0.45 mm year−1 in the IPCC “best estimate” of the recent global sea-level rise.
Run-off modelling is needed in Greenland to extend the short series of measurements. However, the delineation of hydrological basins on the Greenland ice sheet is difficult because of the lack of information about surface and subglacial drainage patterns. Low Sun-angle Landsat data have been used for mapping local surface features which has led to an improvement in basin delineations and thereby run-off simulations. Work is now in progress to map subglacial topography by electromagnetic reflection (EMR) from a helicopter. This information will be used for calculating hydraulic potentials within the basin and to assess the possibilities of future changes in drainage-basin delineation.
The production of Antarctic Bottom Water is mainly influenced by Ice Shelf Water, which is formed through the modification of shelf water masses under huge ice shelves. To simulate this modification a two-dimensional thermohaline circulation model has been developed for a section perpendicular to the ice-shelf edge. Hydrographic data from the Filchner Depression enter into the model as boundary conditions. In the outflow region they also serve as a verification of model results.
The standard solution reveals two circulation cells. The dominant one transports shelf water near the bottom toward the grounding line, where it begins to ascend along the inclined ice shelf. The contact with the ice shelf causes melting with a maximum rate of 1.5 m a−1 at the grounding line. Freezing and therefore the accumulation of “sea ice” at the bottom of the ice shelf occurs at the end of the melting zone at a rate on the order of 0.1 ma−1. Both rates are comparable with values estimated or predicted by models concerning ice-shelf dynamics.
As one example of model sensitivity to changing boundary conditions, a higher sea-ice production in the southern Weddell Sea, as might be expected for a general climatic cooling event, is assumed. The resultant decrease/ increase in temperature/salinity of the inflow (Western Shelf Water) reduces the circulation under the ice shelf and therefore the outflow of Ice Shelf Water by 40%. The maximum melting and freezing rate decreases by 0.1 ma−1 and 0.01 m a−1, respectively. and the freezing zone shifts toward the grounding line by 100 km.
In general the intensity of the circulation cells, the characteristics of Ice Shelf Water, the distribution of melting and freezing zones and the melting and freezing rates differ from the standard results with changing boundary conditions. These are the temperature and salinity of the inflow, the surface temperature at the top, and the extension and morphology of the ice shelf.
Glaciological investigations have been carried out in areas proposed for local hydro-power stations in Greenland, A mapping programme was set up, to provide data for mass balance and simulation of run-off, as well as glacier dynamics.
Two types of glacier map have been produced, covering the margin of the Inland Ice: detailed photogrammetric maps, based on plotting from vertical aerial photographs and a new type of surface feature map, based on digitally-processed Landsat data. The photogrammetric maps, plotted on a scale of 1:25 000, include surface topography and surface features, such as crevasses, lakes, moraines etc. The surface feature maps, plotted on a scale of 1:100 000, show surface features related to ice and melt-water drainage, as well as subtle, topographic features, related to the subglacial topography.
The maps have so far been used for preliminary delineation of drainage areas on the Inland Ice and for planning tracks of radio echo-soundings.
Jakobshavns Isbra;, located at 69°10′ Ν on the west coast of Greenland, is the world’s fastest known glacier. Measurement of surface velocities at the calving front in July of 1964, 1976, 1978, 1985, and 1986 yielded a mean velocity of 20.6 m/d. Variation in mean velocity from year to year is less than 1 m/d. Velocity measurements 10 km behind the calving front indicated mean annual velocities of 17.1 m/d compared to mid-summer velocities of 17.6 m/d. The maximum possible decline in winter velocity is then 7%. Calculation of the volume flux into the fjord is 3.72 × 1010 m3 a−1 ± 10%. The surface balance of Jakobshavns Isbræ is 3.37 × 1010 m3 a−1 ± 12%. The agreement between these balance calculations, the long-term stability in glacier velocity, and the reasonably stable glacier front indicate that Jakobshavns Isbræ is in a state of near equilibrium, with probably a small negative balance.
As the energy spread of intense pulsed electron beams (IPEB) strongly influences the irradiation effects, it has been of great importance to characterize the IPEB energy spectrum. With the combination of Child–Langmuir law and Monte Carlo simulation, the IPEB energy spectrum has been obtained in this work by transformation from the accelerating voltage applied to the diode. To verify the accuracy of this simple algorithm, a magnetic spectrometer with an imaging plate was designed to test the IPEB energy spectrum. The measurement was completed with IPEB generated by explosive emission electron diode, the pulse duration, maximum electron energy, total beam current being 80 ns, 450 keV, and 1 kA, respectively. The results verified the reliability of the above analysis method for energy spectrum, which can avoid intercepting the beam, and at the same time significantly improved the energy resolution. Some calculation and experimental details are discussed in this paper.
The recent years have seen a clear trend in observational astronomy towards digital detectors, but they are only able to cover sky fields which are significantly smaller than what is possible with photographic plates. In consequence, there has been a tendency to concentrate on small sky areas and individual objects. Nevertheless, many large-scale structures can only be well comprehended if the observed fields are much larger than such CCD-frames. Similarly, the use of more than one passband adds important information for a better understanding of the nature of large structures. We demonstrate this by showing here a two-field composite of IC 1396 (Palomar/ESO Atlas), and a four-field composite from the ESO R-Atlas, covering an area of more than 100 square degrees around IC 4628 in Scorpius/Ara.