bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas Extraction From Polar Ice Cores: A Critical Issue For Studying The Evolution of Atmospheric CO2 and Ice-Sheet Surface Elevation
Authors: Raynaud D. , Delmas R , Ascencio J.M. , Legrand M. 
Published: September 2017

The measurement of gases enclosed in polar ice cores provides valuable Information concerning the history of the ice sheets and their environment. The extraction of gases from ice is a critical step in the experimental procedure. We found that the most efficient methods of gas extraction for 20 to 50 g samples were ice melting and controlled refreezing of the melt water for the total gas content and ice crushing far the CO2 content. These two experimental methods are described in detail.It is shown, in particular, that ice is easily contaminated by carbonate dust during sample preparation. This contamination introduces an excess of CO2 when gases are extracted using a procedure involving ice melting.
Air Content Of The Byrd Core And Past Changes In The West Antarctic Ice Sheet
Authors: Raynaud D. , Whillans I. M. 
Published: September 2017

Analyses of ice cores taken from the Antarctic ice sheet can provide information on the environmental conditions under which the ice was formed. New results from measurements of gas content and stable isotope ratios in the Byrd station ice core are discussed and interpreted in terms of past iceflow changes.165 selected ice samples from 32 different depth levels along the core were processed for total gas content V and stable isotope ratios. This large dataset is used to discuss the variability and significance of the values of V at different depths. The short term variations of V are mainly explained by heterogeneities of the pore volume when the firn pores close off.The general trends in the values of V with depth are then used to investigate the possibility of past changes in the ice sheet. They suggest near-steady flow during the past few tens of thousands of years and that a thickening of about 200 to 250 m occurred in this area of the ice sheet at the end of the last ice age. This thickening could be due to a change in the accumulation rate.
Electrical Resistivity Of George VI Ice Shelf, Antarctic Peninsula
Authors: Reynolds John M. 
Published: September 2017

A georesistivity survey was made on part of George VI Ice Shelf (71°55'S, 67°20'W). The principal objectives were to determine the electrical structure of the 1ce shelf, in particular how refrozen melt water differs in electrical behaviour from dry firn, and to Investigate the environment beneath the ice shelf.Apparent resistivity profiles using a Schlumberger electrode configuration have been interpreted using Ghosh's convolution method for vertical electrical sounding (VES), adapted for use where extreme resistivity contrasts are present.Warm, wet surface conditions tend to reduce the gross resistivity of shallow permeable layers. The electrical results indicate that the refrozen free water has affected the resistivity only indirectly; the mean density of firn is raised to about 0.915 Mg m−3 within the uppermost 10 m of the ice shelf at which point the resistivity is comparable to that of Ice of the same density but formed by compaction of firn. The apparent resistivities in the top 100 m reflect the variation of density with depth; a small range of resistivities implies that the range of density 1s narrow and that densification is affected by the percolation and refreezing of melt water.The bulk of the ice behaves as if resistivity either Is independent of temperature or has only a slight dependence (activation energy ~0.15 eV) with a basal melting rate in excess of 1 to 2 m a−1. The principal resistivities determined for two sites on George VI Ice Shelf were within 10% of those at station BC on the Ross Ice Shelf, allowing for differences in temperature. This Indicates that polar ice, I.e. non-temperate ice, has a very narrow range of resistivity. The apparent resistivity profiles are consistent with there being sea-water of oceanic salinity under the Ice shelf.
Accumulation Distribution in the IAGP Area, Antarctica: 90°E-150°E
Authors: Young N. W. , Pourchet M. , Kotlyakov V. M. , Korolev P. A. , Dyugerov M. B. 
Published: September 2017

The distribution of mean net accumulation rate over a large sector (90°E to 150°E) of the IAGP (International Antarctic Glaciological Project) area in Antarctica is presented in map form. The basic data have been compiled from direct measurements of accumulation at stake networks, and by dating horizons in the snow pack by gross β-activity measurements, on four long traverse routes. The spatial variability can be high, over 40%, for a single year, and typically about 20% for multiyear averages. Local surface topography in the form of undulations of several kilometres wavelength can account for about 35% of the variance. Averaging over Intervals of 50 km or more will give the smooth large-scale distribution pattern. But the resultant values can still deviate from the long-term average accumulation by 25% or more due to temporal variability over time scales of years to decades.A very high correlation (r = 0.97) was found for the relationship a = 1414 exp (0.060 θ10) between accumulation, a kg m−2 a−1, and 10 m depth snow temperature, θ10°C, when the data set was limited to a single large drainage basin in Wilkes Land.
Deep Geoelectric and Radar Soundings at Dome c, East Antarctica (Abstract only)
Authors: Shabtaie Sion , Thyssen Franz , Bentley Charles R. 
Published: September 2017

Deep geoelectric soundings using a Schlumberger array were carried out at Dome C, Antarctica. To penetrate the 3 500 m thick ice, electrode half spacings up to 8 km (the largest yet made on polar ice) were used. A constant-current dc transmitter with voltages up to 10 kV, resulting in constant currents of up to 10 mA, was employed; potentials were measured with an electrometer and recorded continuously on an x-y recorder.A computer program has been developed to calculate apparent resistivities on an ice sheet in which the density, temperature, and impurities, and thus the actual resistivity, vary continuously with depth. Preliminary models show that the actual resistivity at a depth of about 500 m increases downward by a factor of about three, and that elevated resistivities must persist to much greater depth. This change in resistivity appears to be linked to transition from ice-age to Holocene ice.The cause of this resistivity increase is not well understood, and may be attributed to any of several physical and chemical changes that also occur at about the same depth.
The Heat Regime of the Central Parts of the Antarctic Ice Sheet with Changing Climate (Abstract only)
Authors: Barbash V.R. , Zotikov I.A. 
Published: September 2017

The heat regime and dynamics of the Antarctic ice sheet are studied using numerical modelling for two flow lines, one of which passes Vostok station and the other Byrd station. A two-dimensional non-steady heat-transfer equation with an energy dissipation term was used. The study consists of two parts. The first is a study of velocity and temperature distributions within the glacier under steady-state conditions. The second study was performed assuming surface temperature changes intended to model palaeoclimatic changes for the last 100 ka and also to model future climate changes due to a possible "greenhouse" effect.Computer numerical modelling shows that the Antarctic ice sheet retains a record of the climatic temperature minimum 18 ka BP. Numerical modelling of the greenhouse effect assumes a temperature increasing by 10 deg within the next 100 a; its influence increases after this even if the surface temperature then remains the same for the next 20 ka. It is shown that for the next 1 ka the temperature wave will penetrate only a thin surface layer of the ice. Even in 20 ka the bottom temperature of the ice sheet will still be unchanged. Small increases of ice velocity can produce ice-sheet thinning of the order of 10 mm a−1.
Geocryological Zones Of Antarctica (Abstract only)
Authors: Vtyurin B.I. 
Published: September 2017

Criteria for the determination of geocryological zones are: (1) distribution of permafrost, (2) the mean annual temperature of permafrost, (3) thickness of the active layer, (4) types of ground ice and ice content of permafrost, (5) regularities of cryogenic structure, (6) cryogenic phenomena, and (7) types of cryogenic relief.Interpretation of the available data allows us to delineate the following geocryological zones in the Antarctic: (1) sub-Antarctic islands, (2) coastalcontinental, and (3) intercontinental. The brief general geocryological characteristic of these zones is given in the paper.The sub-Antarctic island zone features discontinuous and continuous permafrost. The mean annual temperature of the permafrost is near 0°C and the maximum thickness is several tens of metres. The seasonal thawed zone has a thickness of 0.4 to 1.2 m. There are visible ice inclusions and very small ice forms in the permafrost and seasonal frost. Frost action causes frost sorting, hill - slope forms, and thermokarst. Ice-wedges are not found in the sub-Antarctic zone.The coastal-continental zone has continuous permafrost. The mean annual temperature of the permafrost therejs -1°C in the Antarctic Peninsula and up to -5 to -7°C in East Antarctica. Maximum thickness of the permafrost is over 100 m and the active layer is 0.3 to 1 m. The ground ice is mainly pore ice but in some places there is buried glacier ice in moraine. Frost action, frost sorting, creep, nivation, and pre-glacial slope forms are developed in the coastalcontinental zone.The intercontinental zone consists of continuous permafrost only. The mean annual temperature of the permafrost there is -10°C or lower. Thickness of this permafrost is several hundreds of metres and of the active layer is 0.1 to 0.5 m. The ice content is low with only small ice forms. The cryogenic structure of the permafrost is the same as the coastal-continental zone. Because alternate freezing and thawing is infrequent in the intercontinental zone all cryogenic processes are less rapid than in the other zones. Thermokarst is not found there and 1n general the intercontinental zone is not as well studied as the two other zones.
Temperate Ice Beneath the “Polar” Taylor Glacier, Victoria Land, Antarctica (Abstract only)
Authors: Robinson P.H. 
Published: September 2017

Two interdependent lines of evidence contribute to an understanding of basal ice conditions within Taylor Glacier, from the thermal regime and from features of the englacial and basal debris. The thermal regime of the basal ice in Taylor Glacier suggests mechanisms for the entrainment and transportation of debris near the glacier sole.Assuming steady-state conditions, basal temperatures over the ablation area of Taylor Glacier were calculated from the geothermal heat in flux, the nearsurface ice temperatures, ice velocities, and the ice thickness. In over 50% of the lower ablation area the basal ice may be melting.The englacial and basal debris is incorporated by processes operating at the glacier sole. Englacial debris is incorporated by particle regelation; basal debris is incorporated by freezing block regelation. Both processes occur close to the glacier margin, where inner warm basal ice is in contact with marginal cold ice. The debris frozen to the sole here remains relatively unmodified during transport to the margin.Both lines of evidence indicate that Taylor Glacier is, and has been, capable of erosion and entrainment of debris by temperate ice at the glacier sole. Debris deposited along the margin i s similar to drift deposited beyond the glacier, implying that any recent climatic changes have had little effect on basal ice conditions within Taylor Glacier.
Radio Echo-Sounding of Riiser-Larsenisen (Abstract only)
Authors: Orheim Olav 
Published: September 2017

The Norwegian Antarctic Research Expedition 1978–79 used the Scott Polar Research Institute Mk IV radio echo-sounding system fitted in a Bell 206B helicopter to survey 620 km of Riiser-Larsenisen and 100 km across the outer part of Stancomb-Wills Ice Stream. Observed thicknesses of Riiser-Larsenisen decrease from 700 m at the grounding line to less than 200 m at the ice front. The thickness of Bllenga ice rise varied between 200 and 450 m. The ice shelf thins towards the east, and seems there to flow obliquely to the ice front (Fig.1).Step-like change in thickness of >150 m over 500 m horizontal distance i s observed in the central part of the ice shelf. The records also demonstrate undulations in ice thickness of 600 to 700 m wavelength and 50 m amplitude, and various types of rifts and crevasses. Internal layering is recorded at 250 to 300 m depth over Blåenga and i n the ice shelf up-stream of this ice rise.Observed ice thicknesses on Stancomb-Wills Ice Stream range from 130 to 220 m, with no systematic decrease towards the ice front. The records include long sections of heavy scatter from densely spaced rifts and bottom crevasses. This ice stream attains velocities > 4 km a−1, and is much more active than Riiser-Larsenisen. This high activity has resulted in extensive fracturing of the ice shelf.
Contribution to the modelling of the ice accretion process: ice density variation with the impacted surface angle
Authors: Bain M. , Gayet J. F 
Published: September 2017

Icing measurements were carried out in natural winter clouds with an instrumented wind tunnel set up at the summit of Puy de Dome (1 500 m a.s.l.). The microphysical data (liquid water content, droplet spectra) were obtained by using the particle measuring system PMS ASSP 100. The ice density was measured on a rotating cylinder and the ice deposit of the cross-section was photographed on a fixed cylinder. The density measurements ranged from 300 to 900 kg m–3 during the experioment and are in agreement with Macklin’s results (1962). The profile of the ice deposit is comparedto the profile predicted by the model of Lozowski and others (19791, which considers a fixed density.We propose to improve this model by talking into account the variation of ice density with the angle of impact on the cylinder. This calculation is based on Macklin’s results and on the determination of the local impact speed by using the result of Langrature, air speed, liquid wter content, and, especially, the droplet distribution. The improvement is not sufficiemuir and Blodgett (1960). The variation o fice density with the angle depends on various parameters: pressure, tempen to explain some observed profiles; this may be attributed to the fact that the model is not time-dependent.
Gravity Measurements in Permafrost Terrain Containing Massive Ground Ice
Authors: Kawasaki K. , Osterkamp T. E. , Jurick R.W. , Kienle J. 
Published: September 2017

Gravity measurements were made with a very sensitive gravimeter in permafrost terrain containing massive ground ice and other segregated ice. Measurements were first taken along a line over undisturbed terrain where a road cut was to be made; a second gravity profile parallel to the first profile but laterally displaced from it by about 36 m was subsequently made along the edge of the roadbed after road construction. Data from pre-construction borings and a profile of subsurface soil and ice conditions, synthesized from information obtained during cutting, were used for ground-truth information and compared with the gravity measurements. The horizontal dimensions and locations of the deposits of ground ice embedded in the soil layer correlated reasonably well with the dimensions and locations of the lows in the gravity profile. However, the second profile, taken along the roadbed, also showed significant variation even after the usual types of gravity corrections were applied, suggesting that there are significant horizontal variations in the density of the topmost layers of the underlying bedrock (schist) through which the cut was made.The density contrast of the undisturbed ice-rich soil as a function of distance along the first pro-file was estimated assuming the contrast was produced by infinitely long, transverse, rectangular blocks of given dimensions but unknown density. A set of equations dependent (to a first approximation) only on the unknown block densities was constructed from the corrected gravity data and solved by the Gauss-Seidel method. The maximum contrast for one block was found to be about 0.4 Mg m3 which gives a volumetric ice content of about 80% for the block, if the mean den-sity for all the blocks is taken to be 1.45 Mgg m3A third gravity profile was made over an artificially-constructed ice mass with dimensions of 34 × 0.69 × 3.2 m buried at a depth of 1.2 m. This profile did not show conclusively the presence of the ice mass, partly because the anomaly it produces is close to the nominal limit of detection of the gravimeter.It is concluded that large massive ground ice can be detected by means of its gravitational field using sensitive commercially-available gravimeters in conjunction with some ground-truth data. However, the application of such gravimeters to routine pre-construction investigations and terrain reconnaissance for ground ice is limited by their sensitivity and by the requirement for a stable measuring platform. At present, the gravity method and possibly impulse radar are the only non-contacting remote methods for obtaining an estimate of the excess ice in permafrost.
Experimental Studies on Snow Accretion at Subzero Temperatures
Authors: Mizuno Yukiko , Wakahama Gorow 
Published: September 2017

In order to clarify the process of snow accretion, which occurs at a temperature below the melting point of ice, experimental studies were made on the microscopic process of ice Adhesion as well as the tensile adhesive strength of snow onto various kinds of materials.For this purpose, direct observations were made of the formation of an ice bond developed at the interface between an ice particle and a plate made of a transparent material such as glass, acrylic plastic (polymethyl methacrylate (PMMA)), or ice, and measurements made of the growth rate of the real contact area.The growth rate of an ice bond formed at the interface between an ice particle and the plate of a hydrophilic material such as glass was equal to or slightly larger than that of ice sintering, while an ice bond was not formed at the interface between an ice particle and the plate of a hydrophobic material such as teflon.As for adhesive strength, with the lapse of time it increased rapidly at the former interface and slowly at the latter interface. Examinations of fracture planes revealed that at or near the interface a pure adhesive break did not take place with the exception of teflon and vinyl, and that what took place there was a cohesive break or a mixture of cohesive and adhesive breaks.
INVESTIGATION OF DISEASES OF JUVENILE CATLA FROM CULTURE POND FARMING CONDITION IN MYMENSINGH
Authors: Das D. R. , Chandra K. J. 
Published: September 2017

Investigation on health conditions and diseases of juvenile catla (Catla catla) was carried out for clinical and histopathological observations from different farms of Mymensingh region. A total of eight (8) farms, four Government (Govt.) and four Private (Pvt.) fish farms were selected for the study. The Indian major carp - catla was examined during June, 2010 to May, 2012. Monthly samplings were carried out with 5 fishes from each farm. Altogether 960 fish hosts were examined during the study period. Water quality parameters such as temperature, dissolved oxygen, pH, ammonia, hardness, alkalinity, transparency and depth of water etc. were taken and management practices were investigated fortnightly interval. These were almost similar for all experimental ponds. The risk of being infestation by parasites of catla significantly (p<0.001) increased when the water quality parameters were not maintained the optimum level. Clinical examination of fishes was also carried out for any kind of abnormalities at monthly intervals. For histopathological studies skin, muscle, gill, liver and kidney were collected, processed and stained in Haematoxylin and Eosin. Histologically, catla of different fish farms were more affected in colder months (October to January). Structures of fish organs were normal from March to July. In the months of September, minor pathologies were found to be started and in the months of February the pathological condition of fish gradually reduced. Pathological changes like necrosis, fungal granuloma, protozoan and monogenean cyst, vacuolation, melanomacrophase, haemorrhage, hypertrophy, hyperplasia and clubbing were recorded in all the investigated organs. Among them fish gills and skin were more affected followed by liver and kidney. Again when considered individual fish farm, fish of Pvt. Fish farms were more affected than others. The study showed that severity of clinically and pathologically changes were gradually increased in November to January. During the period mixed infection of protozoa, monogenea and argulus were noticed in catla of the investigated farms.
Cost-effectiveness of antibiotic treatment of uncomplicated urinary tract infection in women: a comparison of four antibiotics
Authors: Sadler Susannah , Holmes Michael , Ren Shijie , Holden Stephen , Jha Swati , Thokala Praveen 
Published: September 2017

BackgroundUrinary tract infections (UTIs) are one of the most common reasons for women to attend primary care. There are four different antibiotics currently recommended in England for treatment of uncomplicated UTI but little evidence on their comparative cost-effectiveness.AimTo assess the relative cost-effectiveness of the four antibiotics currently recommended in England for treatment of uncomplicated UTI in adult women.Design & settingA cost-effectiveness model in adult women with signs and symptoms of uncomplicated UTI in primary care in England treated with fosfomycin, nitrofurantoin, pivmecillinam, or trimethoprim.MethodA decision tree economic model of the treatment pathway encompassed up to two rounds of treatment, accounting for different resistance levels. End points included recovery, persistence, pyelonephritis, and/or hospitalisation. Prescription, primary and secondary care treatment, and diagnostic testing costs were aggregated. Cost-effectiveness was assessed as cost per UTI resolved.ResultsTrimethoprim 200 mg twice daily (for 3 or 7 days) was estimated to be the most cost-effective treatment (£70 per UTI resolved) when resistance was <30%. However, if resistance to trimethoprim was ≥30%, fosfomycin 3 g once became more cost-effective; at resistance levels of ≥35% for trimethoprim, both fosfomycin 3 g once and nitrofurantoin 100 mg twice daily for 7 days were shown to be more cost-effective.ConclusionKnowing local resistance levels is key to effective and cost-effective empirical prescribing. Recent estimates of trimethoprim resistance rates are close to 50%, in which case a single 3 g dose of fosfomycin is likely to be the most cost-effective treatment option.