bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulations of anisotropy and fabric development in polar ices
Authors: Castelnau O. , Duval P.
Published: September 2017

The preferred orientation of ice crystals in polar ice sheets developsas a result of intracrystalline slip. Polycrystalline plasticity theory has been successfully used to simulate development of fabrics in rocks. In this study, we present a simpletheory for plastic deformation and fabric evolution. Each crystal within the aggregateis assumed to deform only by basal glide, and recrystallization processes are not directly taken into account. We have adopted the uniform stress bound, that is, stress is supposed to be homogeneous in the polycrystal. Simulated fabrics in uniaxial compression and tension are similar to those observed in ice sheets. In simple shear,simulations show that c axes rotate toward the direction of the maximal compression,in contradiction to the intuitive conclusion that stable orientations correspond to the easy glide position. But, these results are in agreement with predictions of Taylor theory and self-consistent approaches. We suggest that effects of vertical compression and/or rotation recrystallization are of great importance for fabric evolution in polarice sheets. The proposed model can reproduce viscosities of anisotropic ice samples tested in compression or tension but it is not able to reproduce the low viscosity of ices with a single-maximum fabric when tested in simple shear
Modelling the Antarctic ice-sheet changes through time
Authors: Budd W.F. , Jenssen D. , Coutts B.
Published: September 2017

A new assessment is made of the possible range of responses of the Antarctic ice sheet to future global warming by performing a series of sensitivity tests to prescribed climatic forcing with an ice-sheet model. The model includes thermodynamics; it is three-dimensional, with 20 km horizontal grid spacing and 30 points in the vertical, and it treats the ice shelves explicitly. To obtain an appropriate initial present state for the ice sheet, it has been necessary to perform a series of simulations through the last glacial cycle with prescribed forcing including accumulation, sea level are less importantly climatic temperature. For the future climatic forcing, General Circulation Model simulations have been used with particular concern for the changes in the sea-ice cover and ocean warming. Effects of progressive changes have been examined with increases of basal-melt rates up to 10 m a1, surface annual mean temperatures by up to 7°C and surface-accumulation rates to double the present values. Without additional accumulation, the increased basal melt of 10 m a-1 would greatly reduce the ice shelves and contribute to sea-level rise of 0.3 m in 100 years and over 0.6 m by 500 years. The additional accumulation counteracts this to dive about zero change by 100 years and -1.2 m by 500 years.
Reconnaissance of chemical and isotopic firn properties on top of Berkner Island, Antarctica
Authors: Wagenhach D. , Graf W. , Minikin A. , Trefzer U. , Kipfstuhl J. , Oerter H. , Blindow N.
Published: September 2017

The ice cap on Berkner Island is grounded on bedrock within the Filchner-Ronne Ice Shelf and is, therefore, expected to be a well-suited place to retrieve long-term ice-core records reflecting the environmental situation of the Weddell Sea region. Shallow firn cores were drilled to 11 m at the two main summits of Berkner Island and analysed in high depth resolution for electrical d.c. conductivity(ECM), stable isotopes, chloride, sulphate, nitrate and methane-sulphonate (MSA).From the annual layering of δD and non-sea-salt (nss) sulphate, a mean annual snow accumulation of 26.6 cm water at the north dome and 17.4cm water at the south domeare obtained. As a result of ineffective wind scouring indicated by a relatively lownear-surface snow density, regular annual cycles are found for all species at least in the upper 4-5 m. Post-depositional changes are responsible for a substantial decrease o[the seasonal δD and nitrate amplitude as well as for considerable migration of the MSA signal operating below a depth of 3-4 m. The mean chemical and isotopic firn properties at the south dome correspond to the situation on the Filchner-Ronne Ice Shelf at a comparable distance to the coast, whereas the north dome is found to be much more influenced by maritime air masses. Persistent high sea-salt levels in winter snow at Berkner Island heavily obscure the determination of nss sulphate probably due to sulphate fractionation in the Antarctic sea-salt aerosol. Estimated time-scale spredict ages at 400 m depth to be ~2000 years for the north and ~3000 years for the south dome. Pleistocene ice is expected in the bottom 200 and 300 m, respectively.
Development of enhanced ice flow at the southern margin of Ice Stream D, Antarctica
Authors: Scambos Ted A. , Echelmeyer Keith A. , Fahnestock Mark A. , Bindschadler Robert A.
Published: September 2017

A combination of image-based velocity mapping techniques and finite-element modeling has been used to study a part of the southern shear margin of Ice Stream D, Antarctica. The study area is a region over which the margin shows considerable development morphologically, where a new southern margin is forming in response to an abrupt increase in ice-stream width just upstream of the study area. A series of ice-speed profiles perpendicular to the margin was determined by semiautomated displacement measurements of small ice features in sequential Landsat TM images. Transverse speed gradients ∂u/∂y of these profiles were determined by calculating the slope of a high-order polynomial fit to the speed profiles. Maximum ice speed and ∂u/∂y increase dramatically as the margin develops in the downstream direction, from 420 to 670 mal,and from 0.02 to 0.16 a, respectively. Finite-element modeling of the upstream and downstream profiles suggests that a considerable change occurs in the stiffness of the ice in the marginal zone between the two profiles, and in the stiHness or amount of sliding in the basal layer underlying the margin. Ice in the downstream profile appears to have marginal zones of softer ice in which shear strain is concentrated and uniformly low resistance to deformation in the bed. For the upstream profile, modeling suggests that the ice is not softened near the margin and that the bed is stiffer near the margin. Model-based calculations suggest that the bed shear is responsible for 69% of the resistance to flow in the upstream margin area;this value is 51 % in the downstream area.
Depositional environment of the snow cover on West Antarctic pack-ice floes
Authors: Jeffries M.O. , Veazey A.L. , Morris K. , Krouse H.R.
Published: September 2017

The depth, density, load and isotopic (δ18O) composition of the snow cover on pack-ice floes were measured in late austral summer 1992 in the eastern Ross, Amundsen and western Bellingshausen Seas. Snow-density values commonly exceeded 350 kg m-3 and some were as high as 500 kg m-3. The densification of the snow occurs quickly and is attributed to a windy environment. The high density and sometimes considerable depth of the snow on the floes accounts for loads of as much as 700 kg m-2 and resultant sea-water flooding of the underlying sea ice. Lower mean δ18O values in the Ross/Amundsen Seas snow cover suggest that the region might have a cooler climate than the Bellingshausen Sea region. Snow depths on floes in the Bellingshausen Sea region were lower than those in the Ross/Amundsen Seas region, because the Bellingshausen Sea floes were first-year ice. Possible annual units in the isotope profiles of snow, as much as 2m deep, indicate that floes in the Ross/Amundsen Seas region were 2-3 years old.
A numerical model of blowing snow around an Antarctic building
Authors: Moore I. , Mobbs S.D. , Ingham D.B. , King J.C.
Published: September 2017

The accumulation of drifting snow around buildings in regions of severe climate has important implications on their design and location. This paper studies one such building, at a station run by the British Antarctic Survey and located on the Brunt Ice Shelf at the edge of the Antarctic continent. Four previous stations have been built in the area, the buildings of which were designed to become covered in snow and all have been crushed within a few years. The current station, Halley V, consists of three buildings which are all raised from the ice shelf by means of legs. They were designed in such a way that the action of the wind blowing underneath the buildings would keep them-clear of snow.

This paper describes a model which predicts the shape and position of drift formation, and then compares the results with those observed at Halley. This model is a first attempt to address the problem and as such the paper can be considered to be a progress report; improvements arc currently being made as part of continuing research. It is found that there is some qualitative agreement and possible reasons for a few quantitative discrepancies are discussed. Both the model and the true data show clearly that the new design is very effective in prolonging the useful life of the buildings.
Validating and improving elevation data of a satellite-image map of Filchner,Ronne Ice Shelf, Antarctica, with Results from ERS-1
Authors: Sievers J. , Doake C.S.M. , Ihde J. , Mantripp D.R. , Pozdeev V.S. , Ritter B. , Schenke H.W. , Thyssen F. , Vaughan D.G.
Published: September 2017

A satellite-image map with surface-elevation contours of Filchner Ronne Ice Shelf has been published previously as a topographic map. The image map was constructed from a mosaic of 69 Landsat Multispectral Scanner (MSS) images and NOAA AVHRR data. The standard deviation in position in the central part of the mosaic is ±125m. Topographic-glaciologic features were taken from Landsat scenes and represent the best coastline of this region. Surface elevations have been calculated from airborne and ground measurements of either ice thickness (by assuming hydrostatic equilibrium) or barometric pressure. Accuracies vary from ±2 to ±7 m, Oversnow trigonometric levelling in the northeastern part of the ice shelf, tied to sea level at the ice front, has given accuracies of ± 1m. Accuracies reduce to about ±20 m in the grounded ice areas,

ERS-I radar-altimeter data over the ice shelf have been processed to give ellipsoidal heights elevation above the ellipsoid), Geoidal reductions have been used to convert these to orthometric heights (elevation above sea level). No tidal corrections have been applied. The overall accuracy of the radar-altimeter-derived elevations is estimated to be better than ±5m. There are noticeable differences from the topographic map in the central part where the radar data indicate a lower surface. However, the maps agree to within the stated error figures.
Sea-bed depths at the mouth of Rutford Ice Stream, Antarctica
Authors: Smith A. M. , Doake C. S. M.
Published: September 2017

Seismic measurements of ice- and water column thickness have been made on Rudard Ice Stream where it joins the Ronne Ice Shelf. Assuming that the ice is in hydrostatic equilibrium, these values have been used to calculate sea-bed elevations. A sea-bed trough more than 2 km below sea level along the western margin continues downstream from the grounded to the floating ice.
A comparison of satellite-altimetry and ice-thickness measurements of the Ross Ice Shelf, Antarctica
Authors: Jonathan Bamber , Charles r Bentley
Published: September 2017

The launch of ERS-l provides coverage, by satellite altimetry, of a large part of the Ross Ice Shelf ineluding areas of input from Byrd Glacier and Ice Streams D and E. Five 35 d repeats of fast-delivery data, comprising approximately 100000 height estimates, have been used to produce a Digital Elevation Model (DEM) of the Ross Icc Shelf north of 81.5° S. Careful filtering of the altimeter data, which removed about 30% of the measurements, ensured that only valid values were used. The data were grldded to produce a DEM with a cell size of 10km. Repeatability of the data was assessed from an analysis of crossing points of ascending and descending tracks. The rms cross-over difference for the ice shelf was 0.94 m. Using the five repeat tracks gave a random error of 0.30 m for an averaged height measurement. Regionally correlated errors in the orbit and geoid add a systematic long wavelength bias of approximately 2m to the final elevation estimate. Two of the latest geoid models, OSU91-A and JGMI, were compared with the available in situ data and hYdrostatic models based on ice and water densities.

The altimetry was compared with ice-thickness data from Ross Icc Shelf Geophysical and Glaciological Survey (RIGGS) stations and Scott Polar Research Institute radio-echo-sounding surveys undertaken in the 1970s. Differences between the DEM and heights calculated from ice thicknesses and a standard density -depth equation lie, in general, within the combined measurement errors. There are, however, several areas where this is not the case. Prominent north-south stripes of different ice thickness shown on a RIGGS map apparently do not exist. Low elevations are associated with high-density ice draining from East Antarctic outlet glaciers. The grounding line of Icc Streams D and E and an ice plain behind it are clearly demarcated by the break in surface slope. Grounded ice north of Steershead is also observed
The central part of the Filchner-Ronne Ice Shelf, Antarctica: internal structures revealed by 40MHz monopulse RES
Authors: Blindow N.
Published: September 2017

About 1200 km of surface-based radio-echo sounding (RES) profiles were measured during the German Antarctic field season 1989-90 on the Filchner Ronne Ice Shelf (FRIS), Antarctica, with a 40 MHz monopulse sounder developed in Münster. In the area investigated, downstream of Doake Ice Rumples and Henry Ice Rise, a basal layer of marine ice up to 400 m thick was found below the meteoric ice, which is less than 100 m thick in some places. High absorption losses and low bottom reflectivity of the basal layer prevented sounding of the total ice thickness, except for areas near the ice edge with strong melting.

From common mid-point (CMP) measurements, the velocities of electromagnetic waves in the ice shelf were determined, to obtain precise depths from travel times for airborne and surface-based soundings.

The continuous profiling yielded the total ice thickness in the northern part and a variety of internal structures, including lavers in the meteoric and the marine ice, remnants of crevasses, varying reflections of the meteoric-marine interface reflection (MMR). From these data, it is shown that the most-disturbed MMR signatures originate at grounding zones at Doake lee Rumples and at both sides of Henry Ice Rise. The status of the meteoric ice bottom is preserved by the formation of marine ice. Hence, structures remain widely unchanged over 400 km of flow. Internal features that can be correlated on parallel profiles perpendicular to the flow provide an independent means for the construction of flow lines. Even in areas with a smooth MMR, reflection amplitudes show variations by a factor of 2. Their spatial frequency is maximal on profiles prependicular to the now direction. A possible explanation for the amplitude variations is the varying salinity of the top of the marine ice.
Investigating tidal flexure on an ice shelf using kinematic GPS
Authors: Vaughan David G.
Published: September 2017

The positions of ice-stream grounding zones are uniquely sensitive to changes in the mass balance of the ice sheet. Present methods for locating groundingzone features are either imprecise or require considerable effort in interpretation and so are of little value for change studies. We present a new method which uses the kinematic GPS technique to locate the position of the limit of tidal flexure. The method involves the collection of at least two surface-elevation profiles along the same track through the grounding zone, at different times during the tidal cycle. The elevation profiles obtained coincide upstream of the: limit of flexure but diverge downstream of the limit of flexure. Subtracting the profiles produces a tidal-def1ection profile which shows directly the response of the ice shelf to the tidal forcing.

We present two examples of the use of this method, both on Rutford Ice Stream. Antarctica. The first is across the grounding zone and shows that the method is capable of measuring grounding positions to around 200 m precision. The second, taken across an active shear margin, shows a tidal-deflection profile, with an absence of steps that would indicate the presence of fracture planes penetrating from the ice base to sea level.
Studies of the grounding-line location on Ice Streams D and E, Antarctica
Authors: Jacobel Robert W. , Robinson Audrey E. , Bindschadler Robert A.
Published: September 2017

Landsat Thematic Mapper (TM) images were used prior to the 1991–92 field season to infer the position of the grounding line at the mouths of Ice Streams D and E, West Antarctica. Our field plan for mass-balance studies was based on this determination, and thus the imagery played a central role in both the scientific and logistics planning. A radar profile along the flow direction was made across the inferred grounding line at one location, and ice-thickness measurements together with surface surveying enable us to compare the hydrostatic surface and the actual topography to determine the point at which the ice becomes grounded. The profile transits from floating to grounded ice at the same location as the grounding line inferred from the imagery. Changes in the radar-echo strength also occur at this location, giving further support to this interpretation. Tilt studies of the ice flexure caused by tidal variations at locations on either side of this grounding point give additional evidence that grounding is occurring close by. The combination of these three measurements therefore confirms the grounding-line location derived from the satellite imagery and supports the use of this technique to determine grounding.
Numerical flow simulation at local parts of Filchner-Ronne Ice Shelf, Antarctica
Authors: Jonas M. , Grosfeld K. , Thyssen F.
Published: September 2017

The Munster radio-echo-sounding (RES) work in the central part of
Filchner-Ronne Ice Shelf has revealed new information. Different signatures are
discernible in the airborne RES data. Local model calculations in the area between
Henry Ice Rise and Berkner Island are used to interpret these signatures in terms of
thermal and dynamic parameters. From our airborne measurements, the shapes of the
meteoric and marine-ice layers were prepared as input data for dynamic-model
calculations. A general increase in the temperature-dependent flow parameter is
compared vvith a spatially variable flow parameter that is derived from model
calculations concerning freezing and melting processes. Velocity and strain fields were
calculated by a finite-difierence method on a local data base between Henry Ice Rise
and Berkner Island.
20th century behaviour of Drygalski Ice Tongue, Ross Sea, Antarctica
Authors: Frezzotti M. , Mabin M.C.G
Published: September 2017

Drygalski Ice Tongue is the floating seaward extension of David Glacier, a large outlet glacier draining from Talos and Circe Domes of the East Antarctic ice sheet. Several explorers mapped and described Drygalski Ice Tongue in the early years of the 20th century and, although this information does not allow detailed interpretation of ice-tongue behaviour, it is clear that from 1900–12 it was a significant feature extending 65—75 km from the coast. More detailed information has been compiled from aerial photographs and satellite images. In December 1956, the ice tongue was about 110 km long. By December 1957, a major calving event had occurred and the outer 40 km of the ice tongue had broken away. This is the only major 20th century calving event identified, and it may have occurred during a violent storm that affected the Ross Sea area in mid-June 1957. By 1960, further minor ice loss had occurred but, since that time, Drygalski Ice Tongue has maintained the same shape. In January 1993, the ice tongue was 95.8 km long and at its terminus was flowing at 880 900 m a-1. Drygalski Ice Tongue is an important regulator of the size of the Terra Nova Bay polynya. The average size of the Polynya has varied from nearly 2000 km2, in 1956, to 650 km2 in 1957. This has a. significant impact on sea-ice production in the Ross Sea. In 1956, about 115 km3,) of sea ice would have been produced, sufficient to cover 30%of the Ross Sea area with a 1 m thickness of sea ice.
Landsat TM image maps of the Shirase and Siple Coast ice streams, West Antarctica
Authors: Ferrigno Jane G. , Mullins Jerry L. , Stapleton Jo Anne , Bindschadler Robert A. , Scambos Ted A. , Bellisime Lynda B. , Bowell Jo-Ann , Acosta Alex V.
Published: September 2017

Fifteen 1: 250000 and one 1: 1000 000 scale Landsat Thematic Mapper (TM) image mosaic maps are currently being produced of the West Antarctic ice streams on the Shirase and Siple Coasts. Landsat TM images were acquired between 1984 and 1990 in an area bounded approximately by 78°-82.5°S and 120°- 160° W. Landsat TM bands 2, 3 and 4 were combined to produce a single band, thereby maximizing data content and improving the signal-to-noise ratio. The summed single band was processed with a combination of high- and low-pass filters to remove longitudinal striping and normalize solar elevation-angle effects. The images were mosaicked and transformed to a Lambert conformal conic projection using a cubic-convolution algorithm. The projection transformation was controled with ten weighted geodetic ground-control points and internal image-to-image pass points with annotation of major glaciological features. The image maps are being published in two formats: conventional printed map sheets and on a CD-ROM.
Recent advance of the grounding line of Lambert Glacier, Antarctica, deduced from satellite-radar altimetry
Authors: Herzfeld Ute C. , Lingle Craig S. , Lee Li-Her
Published: September 2017

Satellite radar-altimeter data from Seasat (1978) and the Geosat Exact Repeat Mission (1987–89) are evaluated to investigate the question of advance or retreat of Lambert Glacier, Amery Ice Shelf, East Antarctica. New maps based on a fine-scale 3 km grid arc calculated using ordinary kriging. The break in slope at the 100 m elevation contour, relative to the WGS 1984 ellipsoid, is taken as a proxy for the grounding line. Measurements indicate that the irregular grounding line, which includes shoals, advanced approximately 10km between 1978 and 1987‐89, corresponding to a mean advance rate of about 1000 m year-1.
Ice sheets and continental drift
Authors: Paltridge Garth W.
Published: September 2017

Cycles of ice-sheet loading during glacial periods of the Earth's history induce horizontal velocities in the uppermost mantle which may be of the same order as those of continental drift. Given some non-linear mechanism which ensures preferential movement in the one direction, a climatically induced component of continental drift is therefore possible during glacial periods such as the Quaternary. If so, one might expect that component of drift is intermittent on time-scales between 20 and 100 ka, i.e. on time-scales of observed ice-volume variations which, at least over the last 700 ka, have been related to the Earth's orbital variations.
Morphology and late Cenozoic (<5 Ma) glacial history of the area between David and Mawson Glaciers, Victoria Land, Antarctica
Authors: Verbers Anja L.L.M. , Damm Volkmar
Published: September 2017

Glacio-geological field work and radar ice-thickness sounding were carried out in the area between David and Mawson Glaciers. A subglacial topographic map has been compiled from radio-echo-sounding data. The northern part of this map shows that the trench of David Glacier reaches a depth of more than 1000 m below sea level. The area south of David Glacier comprises a landscape of nunatak clusters dissected by glaciated valleys with ice thicknesses as much as 800 m. Subglacial cirques occur at the outer margins of the nunatak clusters. A model for the regional glacial history is proposed. It starts with a major deglaciation in the Pliocene, which results in marine transgression in basins west of the Transantarctic Mountains. During the late Pliocene, the ice advanced towards the northeast, depositing a thin layer of (Sirius Group) till containing reworked mid-Pliocene marine diatoms. Due to accelerated mountain uplift, the ice cut iIlto the pre-Pliocene peneplain, eroding broad valleys. A period of ice-sheet retreat followed to expose a landscape of large nunataks separated by wide valleys. During this period, local cirque glaciation occurred. When the ice sheet advanced again, another phase of uplift forced the glaciers to cut deeper into the valleys. Probably since the Last Glacial Maximum the ice surface has lowered by about 100 m.
Changes and surface features of the Larsen Ice Shelf, Antarctica, derived from Landsat and Kosmos mosaics
Authors: Skvarca Pedro
Published: September 2017

Two uncontrolled mosaics were assembled at an ~1 : 1000 000 scale, covering for the first time almost the entire Larsen Ice Shelf area, using Landsat TM images of 1986-89 and the Kosmos KATE-200 photographic products of late 1975. By comparing them, it was possible to estimate the change along the 600 km north-south ice-shelfs seaward margin where substantial calving has occurred in the recent past. In overall extent, the ice shelf has decreased by ~9300km2 since 1975. The interpretation of the available satellite data also allowed estimates of the ice-shelf’s inland boundary and detection of new surface ice features, especially in the very disturbed region south of Jason Peninsula, which may help to explain the significant calving events occurring in this region. Estimates of surface velocities were derived by photographically co-registering sequential imagery in the chaotic rifted-crevassed area east of Kenyon Peninsula, where conspicuous ice features could be clearly detected even after a 10.4 year time interval. The Landsat TM mosaic, though uncontrolled, provides a basic data set for future studies of global change of the major ice shelf on the Antarctic Peninsula which is probably very sensitive to any climatic trend.
Small-Scale variability of physical properties and structural characteristics of Antarctic fast ice
Authors: Veazey A.L. , Jeffries M.O. , Morris K.
Published: September 2017

The small-scale variability of physical properties and structural characteristics of multiple pairs of fast-ice cores obtained during the austral summer of 1991-92 at two Antarctic sites, McMurdo Sound (MCM) and Pine Island Bay (PIB), are examined and discussed with respect to the growth and decay of the sea ice. The ice at the MCM site was thicker than that at the PIB site and was covered by a somewhat thinner snowpack. While mean salinity and temperature of the ice at the two sites were similar, small-scale variations in both salinity and temperature were greater at PIB than at MCM. The ice sheet at MCM was a two-layer medium consisting of congelation ice overlying platelet ice. The ice from the PIB site, however, was composed of mainly frazil ice and layers of congelation ice with occasional thin layers of snow-ice at the surface of the cores. Crystal sub-structure measurements, c-axis orientation and brine-layer spacing from the MCM cores revealed that the congelation ice had moderately aligned, horizontally oriented c axes, suggesting that east-west currents off the southwest tip of Hut Point Peninsula control crystal-growth orientation.d others: Variability of physical and structural characteristics of Antarctic fast ice
Causes and nature of ice-sheet radio-echo internal reflections estimated from the dielectric properties of ice
Authors: Fujita Shuji , Mae Shinji
Published: September 2017

The causes and nature of ice-sheet radio-echo internal reflections at deep layers in polar ice sheets are discussed, based on the dielectric properties of ice that have been measured at microwave frequency and radio frequency. The reflection coefficients of electromagnetic waves in ice sheets due to two causes the change in permittivity induced by changes in crystal-orientation fabrics with depth, and changes in conductivity induced by changes in acidity with depth - were derived respectively as a function of the frequency used in radar sounding and the temperature of ice, and both were compared quantitatively. It is shown that at single-plane boundaries the reflection coefficients due to the former cause are independent of frequency and temperature and that they are large enough to produce dominant internal reflections. In contrast, reflection coefficients due to the latter cause strongly depend on frequency and temperature. Since they are inversely proportional to the frequency, the latter cause can be dominant only when frequencies below about 60 MHz are used. Examination of previous observational data has suggested that not only changes in acidity but also changes in crystal-orientation fabrics exist at depths corresponding to the dates of earlier volcanic eruptions.
Simplified Time-Dependent Column Shortening Analysis in Special Reinforced Concrete Moment Frames
Authors: Afshari Mohammad Jalilzadeh , Kheyroddin Ali , Gholhaki Majid
Published: September 2017

Necessity for adaption of high-rise reinforced concrete structures’ design and practical steps of implementation through nonlinear staged analysis by consideration of long-term behavior of concrete have always been strongly recommended by researchers in recent years. Cumulative column shortening in conventional analyses is the most important consequence of neglecting the above issues. In this article, numerous modeling and extensive nonlinear staged analyses are carried out on structures with different geometrical characteristics and extremely simple empirical equations to estimate column shortening caused by creep, shrinkage and time changes of modulus of elasticity are provided in such a way that these relations can be independent of conventional parameters of ACI209R-92 regulations used in prediction of mentioned axial strains. Results obtained from validation of the proposed equations show high compliance of all proposed equations for up to 30 floors and also show accuracy of proposed shrinkage equation for the moment frame structures higher than the studied range.
Experimental and Analytical Analysis of Creep of Steel Fibre Reinforced Concrete
Authors: Nakov Darko
Published: September 2017

To find out the influence of different fibre dosages on the creep of SFRC (Steel fibre reinforced concrete), an experiment was carried out at the Faculty of Civil Engineering–Skopje. The experiment involved 9 specimens manufactured with concrete class C30/37 and reinforced with different amount of fibres (0, 30 and 60 kg/m3). According to the experimental results obtained up to the age of 400 days, the addition of steel fibres had an influence on the creep strains (a decrease of up to 12%). Based on the experimental results, analytical analyses of creep were performed by use of the B3 model and fib Model Code 2010. The analyses were prolonged up to the estimated age of service life of structures of 100 years. According to the B3 model, at the age of 100 years, the decrease of the creep coefficient is 11.1% in the case of the SFRC type C30/37 FL 1.5/1.5, while in the case of C30/37 FL 2.5/2.0, it is 17.8%, when compared to C30/37.
Effect of ginger extract on angiogenesis using CAM assay
Authors: Bashir Muhammad Farhan , Qadir Muhammad Imran
Published: September 2017

Angiogenesis performs a critical role in the embryonic growth and several pathological conditions in cancer. This study evaluated the anti-angiogenic properties of the ginger extract using CAM assay. Ginger extract was prepared by methanol. Window was made after 5 days of incubation of eggs and the ginger extract was applied on day 6 at different doses (20, 50, 75 and 150 µL). SPIP software was utilized to investigate the CAM region and diameter of blood vessels. Ginger extract proved anti-angiogenic consequence by decreasing the diameter of CAM of blood vessels. Comparable results were attained at dilution of 150 µL. The anti-angiogenic activity of ginger extract implicates its possible application for diseases where inhibition of blood vessel formation is desired.
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Sheltering under the Covenant: The National Covenant, Orthodoxy and the Irish Rebellion, 1638–1644
Authors: Langley Chris R.
Published: September 2017

The Irish rebellion of October 1641 drove large numbers of clerical migrants across the Irish Sea to Scotland. These ministers brought news of protestantism's plight in Ireland, petitions for charitable aid and, in many cases, requests to work as preachers in Scotland. Historians have long recognised the social and religious links between Ireland and Scotland in the mid-seventeenth century and have seen these men as part of a wider effort to establish presbyterianism across Britain and Ireland. Such an argument fails to understand the complexity of mid-seventeenth-century presbyterianism. This paper explores these petitions for work and the less-than-enthusiastic response of ecclesiastical authorities in Scotland. Rather than automatically embracing Irish ministers as fellow presbyterians, the covenanted kirk leadership was aware that the infant presbyterian congregations in Ireland had followed a very different course to their own. Rather than fellow sufferers for Christ's cause, or part of a wider covenanted network, kirk leaders needed to assess Irish ministers for their godly credentials.
SMA Observations of the Hot Molecular Core IRAS 18566+0408
Authors: Silva Andrea , Zhang Qizhou , Sanhueza Patricio , Lu Xing , Beltran Maria T. , Fallscheer Cassandra , Beuther Henrik , Sridharan T. K. , Cesaroni Riccardo
Published: September 2017

We present Submillimeter Array (SMA) observations toward the high-mass star-forming region IRAS 18566+0408. Observations at the 1.3 mm continuum and in several molecular line transitions were performed in the compact (2.″4 angular resolution) and very-extended (∼0.″4 angular resolution) configurations. The continuum emission from the compact configuration shows a dust core of 150 M
⊙, while the very-extended configuration reveals a dense (2.6 × 107 cm−3) and compact (∼4000 au) condensation of 8 M
⊙. We detect 31 molecular transitions from 14 species including CO isotopologues, SO, CH3OH, OCS, and CH3CN. Using the different k-ladders of the CH3CN line, we derive a rotational temperature at the location of the continuum peak of 240 K. The

,

, and

lines reveal a molecular outflow at PA ∼ 135° centered at the continuum peak. The extended

emission has been recovered with the IRAM 30 m telescope observations. Using the combined data set, we derive an outflow mass of 16.8 M
⊙. The chemically rich spectrum and the high rotational temperature confirm that IRAS 18566+0408 is harboring a hot molecular core. We find no clear velocity gradient that could suggest the presence of a rotational disk-like structure, even at the high-resolution observations obtained with the very-extended configuration.
Searching for a Cosmological Preferred Direction with 147 Rotationally Supported Galaxies
Authors: Zhou Yong , Zhao Zhi-Chao , Chang Zhe
Published: September 2017

It is well known that the Milgrom’s modified Newtonian dynamics (MOND) explains well the mass discrepancy problem in galaxy rotation curves. The MOND predicts a universal acceleration scale below which the Newtonian dynamics is still invalid. We get the universal acceleration scale of 1.02 × 10−10 m s−2 by using the Spitzer Photometry and Accurate Rotation Curves (SPARC) data set. Milgrom suggested that the acceleration scale may be a fingerprint of cosmology on local dynamics and related to the Hubble constant g
† ∼ cH
0. In this paper, we use the hemisphere comparison method with the SPARC data set to investigate possible spatial anisotropy on the acceleration scale. It is found that the hemisphere of the maximum acceleration scale is in the direction

,

with g
†,max = 1.10 × 10−10 m s−2, while the hemisphere of the minimum acceleration scale is in the opposite direction

,

with g
†,min = 0.76 × 10−10 m s−2. The level of anisotropy reaches up to 0.37 ± 0.04. Robust tests show that such an anisotropy cannot be reproduced by a statistically isotropic data set. We also show that the spatial anisotropy on the acceleration scale is less correlated with the non-uniform distribution of the SPARC data points in the sky. In addition, we confirm that the anisotropy of the acceleration scale does not depend significantly on other physical parameters of the SPARC galaxies. It is interesting to note that the maximum anisotropy direction found in this paper is close with other cosmological preferred directions, particularly the direction of the “Australia dipole” for the fine structure constant.
X-Ray and Radio Observations of the Magnetar SGR J1935+2154 during Its 2014, 2015, and 2016 Outbursts
Authors: Younes George , Kouveliotou Chryssa , Jaodand Amruta , Baring Matthew G. , van der Horst Alexander J. , Harding Alice K. , Hessels Jason W. T. , Gehrels Neil , Gill Ramandeep , Huppenkothen Daniela , Granot Jonathan , Göğüş Ersin , Lin Lin
Published: September 2017

We analyzed broadband X-ray and radio data of the magnetar SGR J1935+2154 taken in the aftermath of its 2014, 2015, and 2016 outbursts. The source soft X-ray spectrum <10 keV is well described with a blackbody+power-law (BB+PL) or 2BB model during all three outbursts. Nuclear Spectroscopic Telescope Array observations revealed a hard X-ray tail, with a PL photon index Γ = 0.9, extending up to 50 keV, with flux comparable to the one detected <10 keV. Imaging analysis of Chandra data did not reveal small-scale extended emission around the source. Following the outbursts, the total 0.5–10 keV flux from SGR J1935+2154 increased in concordance to its bursting activity, with the flux at activation onset increasing by a factor of ∼7 following its strongest 2016 June outburst. A Swift/X-Ray Telescope observation taken 1.5 days prior to the onset of this outburst showed a flux level consistent with quiescence. We show that the flux increase is due to the PL or hot BB component, which increased by a factor of 25 compared to quiescence, while the cold BB component kT = 0.47 keV remained more or less constant. The 2014 and 2015 outbursts decayed quasi-exponentially with timescales of ∼40 days, while the stronger 2016 May and June outbursts showed a quick short-term decay with timescales of about four days. Our Arecibo radio observations set the deepest limits on the radio emission from a magnetar, with a maximum flux density limit of 14 μJy for the 4.6 GHz observations and 7 μJy for the 1.4 GHz observations. We discuss these results in the framework of the current magnetar theoretical models.
Time Variations of Observed Hα Line Profiles and Precipitation Depths of Nonthermal Electrons in a Solar Flare
Authors: Falewicz Robert , Radziszewski Krzysztof , Rudawy Paweł , Berlicki Arkadiusz
Published: September 2017

We compare time variations of the Hα and X-ray emissions observed during the pre-impulsive and impulsive phases of the C1.1-class solar flare on 2013 June 21 with those of plasma parameters and synthesized X-ray emission from a 1D hydrodynamic numerical model of the flare. The numerical model was calculated assuming that the external energy is delivered to the flaring loop by nonthermal electrons (NTEs). The Hα spectra and images were obtained using the Multi-channel Subtractive Double Pass spectrograph with a time resolution of 50 ms. The X-ray fluxes and spectra were recorded by RHESSI. Pre-flare geometric and thermodynamic parameters of the model and the delivered energy were estimated using RHESSI data. The time variations of the X-ray light curves in various energy bands and those of the Hα intensities and line profiles were well correlated. The timescales of the observed variations agree with the calculated variations of the plasma parameters in the flaring loop footpoints, reflecting the time variations of the vertical extent of the energy deposition layer. Our result shows that the fast time variations of the Hα emission of the flaring kernels can be explained by momentary changes of the deposited energy flux and the variations of the penetration depths of the NTEs.
iCollections methodology: workflow, results and lessons learned
Authors: Blagoderov Vladimir , Penn Malcolm , Sadka Mike , Hine Adrian , Brooks Stephen , Siebert Darrell , Sleep Chris , Cafferty Steve , Cane Elisa , Martin Geoff , Toloni Flavia , Wing Peter , Chainey John , Duffell Liz , Huxley Rob , Ledger Sophie , McLaughlin Caitlin , Mazzetta Gerardo , Perera Jasmin , Crowther Robyn , Douglas Lyndsey , Durant Joanna , Honey Martin , Huertas Blanca , Howard Theresa , Carter Victoria , Albuquerque Sara , Paterson Gordon , Kitching Ian
Published: September 2017

The Natural History Museum, London (NHMUK) has embarked on an ambitious programme to digitise its collections. The first phase of this programme was to undertake a series of pilot projects to develop the workflows and infrastructure needed to support mass digitisation of very large scientific collections. This paper presents the results of one of the pilot projects – iCollections. This project digitised all the lepidopteran specimens usually considered as butterflies, 181,545 specimens representing 89 species from the British Isles and Ireland. The data digitised includes, species name, georeferenced location, collector and collection date - the what, where, who and when of specimen data. In addition, a digital image of each specimen was taken. A previous paper explained the way the data were obtained and the background to the collections that made up the project. The present paper describes the technical, logistical, and economic aspects of managing the project.
Discovery of Implementation Factors That Lead to Technology Adoption in Long-Term Care
Authors: Schoville Rhonda R.
Published: September 2017

The current exploratory, qualitative study discovered and clarified implementation factors that led to technology adoption in long-term care (LTC). The Integrated Technology Implementation model guided the study of an electronic health record used in three LTC settings. Thirty key stakeholders (i.e., directors of nursing, nurses, and certified nurse aides) participated in focus groups or interviews. Findings indicated experiences were more similar than different among groups and facilities. Five major implementation themes supported by a variety of minor themes were identified. Implications for nursing include that leaders must be knowledgeable and committed to the change and engage staff throughout the implementation process. In addition, various communication and education strategies are required. [
Journal of Gerontological Nursing, 43
(10), 21–26.]
Tectónica y procesos metalogénicos de la zona Tamajón-Campillo de Rana. Sistema Central
Authors: Monterrubio S. , Martínez Frías J. , De Vicente G. , Vindel E.
Published: September 2017

En este trabajo se analizan las características mineralógicas. texturales y estructurales de la mineralización de Tamajón-Campillo de Ranas y su relación con el yacimiento argentífero principal (Zona de Hiendelaencina). Se establece una correlación paragenética de los sulfuros y sulfosales de ámbas zonas y se plantea una formación conjunta. dentro de un mismo encuadre geotectónico.
Un modelo de mapa neotectónico en la región Nor-oriental de la provincia de Valencia (España)
Authors: Martínez Gallego J. , Goy J. L. , Zazo C.
Published: September 2017

Se realiza un modelo de mapa neotectónico en el área Nor-oriental de la provincia de Valencia. Dicha zona está sometida a una tectónica distensiva desde el Mioceno inferior-medio a la actualidad, dentro de la cual pueden ser distinguidas varias fases (Simon, 1984).
Después de los estudios realizados en el área, la última fase de fracturación importante sucede en el Pleistoceno inferior, y ésta es particularmente intensa en el área de Náquera, Casinos y Chelva.
El mapa neotectónico que aquí se elabora parte de dos mapas base, por un lado el geológico, en el que están particularmente detallados los depósitos correspondientes al Plio-Cuaternario y Cuaternario, y el geomorfológico.
La utilización de las secuencias de unidades geomorfológicas, el dispositivo geométrico de las mismas (encajamiento y/o superposición) y la representación de los rasgos geomorfológicos indicadores de neotectónica tales como: pendientes anómalas por exceso o defecto, contrapendientes, rectificación del talweg, potencias anómalas de sedimentos, etc., puede ser el único medio utilizable para inscribir los movimientos recientes dentro de una escala temporal, sobre todo en áreas donde los materiales son azoicos y las litologías semejantes.
Quizás la mayor aplicación de este mapa, sobre todo en riesgos sismotectónicos, se deba a la posibilidad de utilización del color o en su defecto caracteres alfabéticos y numéricos para indicar el último movimiento de los accidentes.
Caracterización del Sistema Kárstico de Olalde a partir del análisis del hidrograma del manantial
Authors: Cruz-Sanjulián J. J. , Morales T.
Published: September 2017

El manantial de Olalde es la principal surgencia del sistema kárstico constituido por las calizas de San Miguel de Ereñozar; el acuífero es recargado además, a través de sumideros, por la escorrentía superficial de cuencas endorreicas ocupadas parcialmente por materiales impermeables. El caudal medio del manantial es de 240 l/seg con una notable variabilidad: el caudal era de 2633 l/seg al comienzo de la decrecida estudiada en este trabajo y de 18 l/seg el último día considerado. El coeficiente de agotamiento α tiene un valor de 0.032 día-1 y la duración de la decrecida propiamente dicha es de 21,5 días. Los valores del coeficiente de velocidad de infiltración ἠ y del coeficiente del heterogeneidad ξ son, respectivamente, 0.0465 -1 día y 3,49-1 día. Los parámetros i (=0.114) y k (=0.025) indican una decrecida muy rápida y un escaso poder regulador, lo que corresponde a sistemas muy karstificados con redes de drenaje subterráneo muy desarrolladas, propias del dominio de las redes espeleológicas. Todo ello pone de manifiesto unas perspectivas de regulación del manantial poco favorables y que, en todo caso, afectarían a una pequeña fracción de las aportaciones totales.
Formas terminales de Hippidion (Mammalia, Perissodactyla) de los yacimientos del Pleistoceno Tardio-Holoceno de la Patagonia (Argentina y Chile)
Authors: Alberdi M. T. , Menegaz A. N. , Prado J. L.
Published: September 2017

El presente estudio comprende una revisión de las formas terminales de caballos sudamericanos recuperados de sitios arqueológicos de la Patagonia. Se comparan con las formas del noroeste argentino. Incluye aspectos paleoambientales y cronológicos relacionados.