bluuebunny/crossref_metadata_2025 huggingface dataset:
Team-Based Professional Development Interventions in Higher Education: A Systematic Review
Authors: Gast Inken , Schildkamp Kim , van der Veen Jan T.
Published: September 2017

Most professional development activities focus on individual teachers, such as mentoring or the use of portfolios. However, new developments in higher education require teachers to work together in teams more often. Due to these changes, there is a growing need for professional development activities focusing on teams. Therefore, this review study was conducted to provide an overview of what is known about professional development in teams in the context of higher education. A total of 18 articles were reviewed that describe the effects of professional development in teams on teacher attitudes and teacher learning. Furthermore, several factors that can either hinder or support professional development in teams are identified at the individual teacher level, at the team level, and also at the organizational level.
The Effects of Mobile-Computer-Supported Collaborative Learning: Meta-Analysis and Critical Synthesis
Authors: Sung Yao-Ting , Yang Je-Ming , Lee Han-Yueh
Published: September 2017

One of the trends in collaborative learning is using mobile devices for supporting the process and products of collaboration, which has been forming the field of mobile-computer-supported collaborative learning (mCSCL). Although mobile devices have become valuable collaborative learning tools, evaluative evidence for their substantial contributions to collaborative learning is still scarce. The present meta-analysis, which included 48 peer-reviewed journal articles and doctoral dissertations written over a 16-year period (2000–2015) involving 5,294 participants, revealed that mCSCL has produced meaningful improvements for collaborative learning, with an overall mean effect size of 0.516. Moderator variables, such as domain subject, group size, teaching method, intervention duration, and reward method were related to different effect sizes. The results provided implications for future research and practice, such as suggestions on how to appropriately use the functionalities of mobile devices, how to best leverage mCSCL through effective group learning mechanisms, and what outcome variables should be included in future studies to fully elucidate the process and products of mCSCL.
What Happens to Students Placed Into Developmental Education? A Meta-Analysis of Regression Discontinuity Studies
Authors: Valentine Jeffrey C. , Konstantopoulos Spyros , Goldrick-Rab Sara
Published: September 2017

This article reports a systematic review and meta-analysis of studies that use regression discontinuity to examine the effects of placement into developmental education. Results suggest that placement into developmental education is associated with effects that are negative, statistically significant, and substantively large for three outcomes: (a) the probability of passing the college-level course in which remediation was needed, (b) college credits earned, and (c) attainment. Several sensitivity analyses suggest these results are not a function of particular stylized studies or the choices made in assembling the meta-analytic database. Two exploratory moderator analyses suggest that the negative effects of placement into developmental education are stronger for university students than for community college students and worse for students placed in reading or writing than in math. This work can inform debate and research on postsecondary policies and on alternative mechanisms for ensuring that college students have the skills needed to meet their goals.
Effective Dementia Education and Training for the Health and Social Care Workforce: A Systematic Review of the Literature
Authors: Surr Claire A. , Gates Cara , Irving Donna , Oyebode Jan , Smith Sarah Jane , Parveen Sahdia , Drury Michelle , Dennison Alison
Published: September 2017

Ensuring an informed and effective dementia workforce is of international concern; however, there remains limited understanding of how this can be achieved. This review aimed to identify features of effective dementia educational programs. Critical interpretive synthesis underpinned by Kirkpatrick’s return on investment model was applied. One hundred and fifty-two papers of variable quality were included. Common features of more efficacious educational programs included the need for educational programs to be relevant to participants’ role and experience, involve active face-to-face participation, underpin practice-based learning with theory, be delivered by an experienced facilitator, have a total duration of at least 8 hours with individual sessions of 90 minutes or more, support application of learning in practice, and provide a structured tool or guideline to guide care practice. Further robust research is required to develop the evidence base; however, the findings of this review have relevance for all working in workforce education.
Developing, Analyzing, and Using Distractors for Multiple-Choice Tests in Education: A Comprehensive Review
Authors: Gierl Mark J. , Bulut Okan , Guo Qi , Zhang Xinxin
Published: September 2017

Multiple-choice testing is considered one of the most effective and enduring forms of educational assessment that remains in practice today. This study presents a comprehensive review of the literature on multiple-choice testing in education focused, specifically, on the development, analysis, and use of the incorrect options, which are also called the distractors. Despite a vast body of literature on multiple-choice testing, the task of creating distractors has received much less attention. In this study, we provide an overview of what is known about developing distractors for multiple-choice items and evaluating their quality. Next, we synthesize the existing guidelines on how to use distractors and summarize earlier research on the optimal number of distractors and the optimal ordering of distractors. Finally, we use this comprehensive review to provide the most up-to-date recommendations regarding distractor development, analysis, and use, and in the process, we highlight important areas where further research is needed.
Short term radiological outcome of inserting screw at fracture level in posterior short segment fixation in thoracolumbar burst fractures
Authors: Pradhan Rabindra Lal , Pandey Bimal Kumar , Khanal Krishna Raj
Published: September 2017

Background: Unstable thoracolumbar burst fractures are treated surgically by short segment fixation but may be associated with high implant failure. Supplementation of anterior column by insertion of screw at fracture site makes it more biomechanically stable.Objectives: The purpose of this prospective study was to evaluate radiological parameters in thoracolumbar fractures treated with intermediate screw fixation with a minimum follow up of two years.Methods: This prospective study was conducted from 2011 till 2012 where unstable  thoracolumbar fractures treated with short segment posterior instrumentation with screw at fracture site were evaluated. All patients (average age 34.64 were followed up for at least 24 months and were classified according to Thoracolumbar Injury Classification and Severity Score and load sharing classifi cation. Out of total 32 patients, four lost to follow up. Radiological parameters like vertebral body height and segmental kyphosis were evaluated and pain was evaluated by Visual Analogue Scale score.Results: Preoperative pain showed mean Visual Analogue Scale Score score of 8.29 that improved to 0.97 at fi nal follow up. Average preoperative loss of vertebral body height was 48.19 %, which improved to 11.4 % after surgery (p<.001). Final vertebral body collapse was 12.98 % with mean percentage loss of vertebral height at 1.57%. Average segmental kyphotic angle was 22.54 before surgery, which corrected to 5.89 immediately after surgery (p<0.001). Final segmental kyphosis was 8.46. Loss of kyphosis correction was 2.57. Two patients had implant failure, but was solidly united during implant removal in both cases.Conclusion: Excellent maintenance of reduction in thoracolumbar burst fractures with short segment fixation with intermediate screws at fracture site with limited decompression resulted in improved neurologic function and satisfactory clinical outcomes, with a low incidence of implant failure and progressive deformity.
Evaluation of mid-trimester abortion: A way forward
Authors: Padhye Saraswati M , Karki Chanda
Published: September 2017

Background: Need of second trimester abortion has been increasing because of the wide scale introduction of prenatal screening programs detecting women whose pregnancies are complicated by serious fetal abnormalities. Lack of accredited centers and skills required for mid trimester abortion have made this procedure inaccessible to rural population of Nepal.Objectives: This study was conducted to assess correlation of uterine size measured by clinical examination and that assessed by ultrasound, foetal foot length measurement post abortion, dose of misoprostol required and induction delivery interval in medical induction and dilatation and evacuation cases.Methods: This is a hospital based cross-sectional study conducted from April 2011 to July 2012. gestational age was assessed by clinical palpation and ultrasound in women undergoing mid trimester abortion. Standard protocol was followed for medical and surgical abortion. Fetal foot length was measured post abortion. Mean dose of misoprostol and induction abortion interval were noted.Results: Mean age of the patients in dilatation and evacuation group and medical induction group were similar 28 (SD= 6.2) and 27 (SD=7) respectively. The mean dose of misoprostol requiredwas 400 micrograms for dilatation and evacuation and 600 micrograms for medical induction. There was moderate degree of relationship between foot length measurement of the fetus and USG findings, high degree of positive relationship between size of the uterus and fetal foot length measurement.Conclusion: Clinical estimation of period of gestation by size of the uterus correlated well with ultrasonography findings and fetal foot length measurement post abortion. The mid trimester service can thereforebe provided in the centers where sophisticated appliances like ultrasonography is not available.
Oral pemphigus vulgaris
Authors: Sharma Mohit
Published: September 2017

Pemphigus is a group of potentially life-threatening autoimmune mucocutaneous diseases characterized by epithelial blistering affecting cutaneous and/ or mucosal surfaces. Pemphigus affects 0.1-0.5 patients per 100,000 population per year. Oral lesions of pemphigus are seen in up to 18% of patients at dermatology out-patient clinics, but despite the frequency of oral involvement, and novel therapeutic approaches, there are surprisingly few recent studies of either the oral manifestations of pemphigus or their management, and delays in diagnosis are still common. Most patients are initially misdiagnosed and improperly treated for many months or even years. Dental professionals must be sufficiently familiar with the clinical manifestations of pemphigus vulgaris to ensure early diagnosis and treatment, since this in turn determines the prognosis and course of the disease. Pemphigus has been reviewed in the oral literature in the past decade, but several advances in the understanding of the etiopathogenesis, pemphigus variants, and management warrant an update. Here, we report a case of pemphigus vulgaris that was misdiagnosed in its earliest stage. Oral ulceration may arise from a variety of causes. This case illustrates that, although rare, pemphigus vulgaris may need to be included in differential diagnosis.
Isolated gross haematuria: A rare clinical presentation in neonate with urinary tract infection
Authors: Kayastha Pawana , Basnet Rydam , Adhikari Ramesh Kant
Published: September 2017

Gross haematuria is uncommon in the fi rst month of life and etiologies of haematuria in the newborn is different from those in older children. we reported a six days old term male baby who was brought by parents with isolated complain of red colored urine for one day and his mother had culture positive urinary tract infection prior to delivery. The baby was diagnosed to have culture positive urinary tract infection. Our fi ndings suggest the diversity of clinical presentation of urinary tract infection in neonates and also some relationship between the history of urinary tract infection in mother and occurrence of urinary tract infection in neonate.
Ethics in research: Beating a dead horse
Authors: Acharya Jenash
Published: September 2017

No abstract available.
Risk factors associated with retinopathy of prematurity among neonates in a tertiary care hospital in Nepal
Authors: Shrestha Jyoti Baba , Yadav Reena , Shrestha Jeevan Kumar , Shrestha Laxman , Sah Raman Prasad
Published: September 2017

Background: Retinopathy of prematurity is a vascular retinal disease that can cause blindness in premature new born babies. Several risk factors are associated with the incidence of ROP. Information and data on risk factors associated with ROP in context to Nepalese population is scarcely documented in literature.Objectives: The purpose of this study was to evaluate the risk factors of retinopathy of prematurity in premature infants admitted in the neonatal intensive care unit of Tribhuvan University Teaching Hospital.Methods: Neonates with gestational age of 36 weeks or less and birth weight of 2000 gram or less admitted to neonatal intensive care unit (NICU), during 2013 to 2015 were screened for retinopathy of prematurity. Risk factors and severity of retinopathy of prematurity were evaluated. The initial examination was carried out at 4-6 weeks after birth by indirect ophthalmoscope and retinopathy of prematurity positive and negative infants were compared subsequently. The Chisquare and independent t-tests were used for statistical analysis. A p value less than 0.05 was considered statistically signifi cant.Results: The incidence of retinopathy of prematurity was 22.6% and severe retinopathy of prematurity requiring treatment was observed in 3.2% of 93 neonates who had eye examinations. There was a signifi cant relationship between the occurrence of ROP and birth weight (p=0.000), gestational age (p=0.000), duration of oxygen therapy (p=0.009) and sepsis (p=0.002). However, insignifi cant relationship was observed between the occurrence of retinopathy of prematurity and gender, type of delivery, multiple gestation, premature rupture of foetal membrane, respiratory distress syndrome and hyperbilirubinaemia.Conclusion: The risk factors contributing to development of retinopathy of prematurity showed signifi cant relationship with immaturity, duration of oxygen supplementation and septicaemia.Journal of Kathmandu Medical CollegeVol. 5, No. 1, Issue 15, Jan.-Mar., 2016,page: 28-33
Reconstruction of the Glacial Ice Covers of Greenland and the Canadian Arctic Islands by Three-Dimensional, Perfectly Plastic Ice-Sheet Modelling
Authors: Reeh N.
Published: September 2017

A three-dimensional perfectly plastic ice-sheet model, developed for determining the surface elevations and the flow pattern of an ice sheet with given bottom topography and ice-margin positions, is applied to the reconstruction of the glacial ice covers of Greenland and the Canadian Arctic islands. In the northern regions, two different reconstructions have been performed with ice margins along the present 600 and 200 m sea-depth contours, respectively. In central Greenland, the ice margin is considered to be at the outermost ice-margin deposits on the coastal shelf to the west, and at the present 200 m sea-depth contour to the east.

The main conclusions to be drawn from the reconstructions are: (1). The flow pattern of the glacial ice cover of Greenland shows a great resemblance to the present one, the central ice divide being displaced less than 50 km from its present position and being no more than 200 m higher than today. (2). The main ice divide of the ice sheet covering the Canadian Arctic islands (the Innuitian ice sheet) was located over the highlands of eastern Ellesmere Island with local domes positioned over the present ice caps, indicating that even the deep ice of Wisconsin age in these ice caps is of local origin. This is also the case for the Devon Island ice cap. (3). Even in the not very likely case of a rather extensive glacial ice cover in north-west Greenland, the ice-flow pattern upstream of the Camp Century deep drill site would not have changed radically compared to the present flow pattern. Thus it is concluded that even advanced ice margins in late-Wisconsin time could at most have resulted in an elevation of the deposition site of the late-Wisconsin ice at Camp Century 600 m higher than at present. The consequences of this conclusion are discussed.
Temporal Variations in the 10Be Concentration Levels Found in the Dye 3 Ice Core, Greenland
Authors: Beer J. , Oeschger H. , Andrée M. , Bonani G. , Suter M. , Wölfli W. , Langway C. C.
Published: September 2017

In order to study in some detail the variability of the 10Be concentration and its correlation with climatic parameters such as δ18O we have investigated 28 samples of the deep ice core from Dye 3, Greenland, covering the depth interval from 1 860 to 1 890 m which corresponds to the period 30 to 40 ka BP. The results show that the mean 10Be concentration during this period is higher by a factor of 1.7 than during the twentieth century and that there is a correlation between 10Be results and δ18O values. A possible explanation is that during cold periods (low δ18O values) precipitation rates are lower and therefore the number of 10Be atoms per gram of ice is higher. However, processes strongly related to δ18O values alone cannot explain the entire variability of the 10Be results.
Atmospheric CO2 Concentration During the Last Glaciation
Authors: Stauffer B. , Hofer H. , Oeschger H. , Schwander J. , Siegenthaler U.
Published: September 2017

Analyses of atmospheric air extracted from air bubbles in polar glacier ice provide a measure of past CO2 concentrations and their temporal variations. Earlier measurements have shown that the atmospheric CO2 concentration was significantly lower during the late Wisconsin stage and that the change from low to high CO2 concentration occurred in a relatively short time period.

We measured the CO2 concentration of ice samples from the deep ice core recently drilled at Dye 3 (south Greenland). The core section investigated represents ice from about 40 to 30 ka BP. The air extracted from the ice samples shows large variations of CO2 concentration which are correlated with δ18O values of the ice samples. A probable explanation of the results is that corresponding changes of the atmospheric CO2 concentration occurred during that glacial period. These changes could have had a significant influence on the climate. Possible reasons for the variations of the atmospheric CO2 concentration are discussed.
Impurities in Snow: Effects on Albedo and Snowmelt (Review)
Authors: Warren Stephen G.
Published: September 2017

Very small (ppm) amounts of soil dust in snow can significantly reduce snow albedo and thereby affect the snow-surface energy budget. Ice cores from Greenland show enhanced dust concentrations in ice from the last glacial maximum, in amounts capable of causing measurable effects on snow albedo. This enhanced dust is probably due in part to the expanded desert areas at that time.

Volcanic ash layers visible in the Byrd station core reduced the snow albedo in West Antarctica when they were on the surface. The ash is unlikely to have had a long-term effect on albedo because of the episodic nature of volcanic eruptions.

Very large amounts of dust on snow can inhibit snow-melt by insulating the snow. A debris cover probably slowed the melting of parts of the North American ice sheet during its most recent decay phase.

Snow in the Arctic Ocean is presently suffering large-scale contamination by carbon soot from anthropogenic sources. Preliminary estimates indicate that soot concentrations in Arctic snow are sufficient to reduce snow albedo measurably.
Ice-Shelf Densities from a Comparison of Radio Echo and Seismic Soundings
Authors: Doake C. S. M.
Published: September 2017

A 40 km line across George VI Ice Shelf was sounded in January 1981 by both radio echo and seismic reflection methods. Because the velocities of radio and seismic waves vary with ice density in different ways, an accurate comparison of travel times from the two methods allowed the average density of the ice shelf to be calculated.

A distinguishable echo from the base of the ice shelf was recorded at 22 out of 23 seismic stations. Continuous radio echo profiling was achieved in ice varying in thickness from about 200 to 350 m. The calculated mean densities fell into two groups, In an area where summer meltwater frequently floods the surface the average densities were around 0.915 Mg m−3, while in the drier areas the average densities were around 0.884 Mg m−3. Apart from this division, there was no apparent systematic variation of average density with position. The sounding was carried out approximately along a flowline on the ice shelf.

The variation of ice density with depth and position is difficult to allow for when modelling the deformation of ice shelves. Measured values of surface strain-rate, for example, may in some circumstances need to be corrected for effects due to the compressibility of snow.
Geothermal Effects of 18 ka BP Ice Conditions in the Swiss Plateau
Authors: Haeberli Wilfried , Rellstab Werner , Harrison William D.
Published: September 2017

Quaternary surface temperature and ice conditions have lowered today’s temperatures in the uppermost 1 to 2 km of the Earth’s crust in the Swiss plateau by about 5 to 6°C in regions of formerly temperate glacier beds, and these effects were even greater on temperatures in formerly periglacial regions. Effects of latent heat exchange during the formation and thawing of ice-rich permafrost in high-porosity sediments enhance the effects of heat diffusion in low-porosity rock. The influence of underground ice formation, however, seems to be limited. This is due both to the limited thickness of high-porosity sediments and to the fact that high post-glacial surface temperatures in the Swiss plateau shortened the thaw time of ice-rich permafrost which formed at the time of maximum glaciation (18 ka BP). The greatest effects of ice conditions in 18 ka BP may therefore be expected outside the plateau in Alpine valleys. Here, advection of cold ice through glacier flow may have cooled high-porosity sediments of considerable thickness well below 0°C.
Introduction to a New Sea-Ice Database
Authors: Knight Richard W.
Published: September 2017

An important new sea-ice database is presently being created at the National Climatic Data Center in Asheville, North Carolina, USA. The data are digitized from weekly charts prepared at the US Navy/National Oceanic and Atmospheric Administration (NOAA) Joint Polar Ice Center and converted into a digital format prescribed by the World Meteorological Organization. The data cover both the Arctic and Antarctic for a ten-year period of record. The grid points are identified by earth coordinates and have a resolution of 15 nm or better.

This paper is intended to inform potential users of sea-ice data about the availability of the new data set. Topics covered are (1) data source, (2) brief description of the processing procedures, (3) the SIGRID output format, and (4) future plans.
Late-Glacial Maximum-Holocene Atmospheric and Ice-Thickness Changes from Antarctic Ice-Core Studies
Authors: Lorius C. , Raynaud D. , Petit J.-R. , Jouzel J. , Merlivat L.
Published: September 2017

A review of Byrd, Vostok and Dome C Antarctic ice-core records indicates significant changes in atmospheric characteristics between the late glacial maximum (LGM) and the Holocene. This data is relevant to general circulation model (GCM) boundary conditions and validation of output results. Reciprocally, GCM data could help to interpret ice-core results and to extend observed high-latitude changes to a larger scale.

During the LGM, low troposphere temperatures were colder by about 5 to 7°C and surface temperatures by 8 to 10°C over the Antarctic ice sheet. There are indications that snow accumulation was slightly lower and isotopic data suggests higher relative humidity over the ocean. A large increase in continental dust (up to a factor of 20) and marine aerosols (up to a factor of 5) is observed on the high Antarctic plateau, both explained by the increased (possibly up to 1.4 to 2 times) intensity of the large-scale atmospheric circulation modulated by desert and sea-ice area extension. Ice-core results show large changes in atmospheric CO2 concentrations with LGM values around 200 ppmv and “pre-industrial” values of about 260 ppmv. Finally, determinations of total gas content suggest that central West and East Antarctica were not thicker during the LGM, in contrast with higher surface elevations inferred from coastal-ice studies.
Studies on Structures and Physical Properties of Snow on Mizuho Plateau, Antarctica
Authors: Nishimura Hiroshi , Maeno Norikazu
Published: September 2017

Relations between structures and physical properties of snow of four 30-m cores in Mizuho Plateau, Antarctica were investigated by measuring their specific areas of internal free surfaces and air permeabilities. The specific area of internal free surfaces and the air permeability decreased with increasing depth. Both of the depth profiles showed a kink at a depth of a critical density 550 kg/m3, indicating a change in the physical mechanism of densification. The drastic decrease of the specific areas above the depth of the kink was considered to be mainly caused by rounding and growth of ice particles; the gradual decreases below the kink were attributed to the development of bonding and particles.

Measured air permeability was compared with the theoretical one for randomly packed powders of uniformly sized solid particles. The discrepancy between the measured and theoretical permeabilities was explained by the change in shapes and sizes of air channels in the snow. The depth hoar formation, which was active in regions with smaller accumulation of snow, was considered to result in the favorable shapes of channels for air permeation.
Enclosure of Air During Metamorphosis of Dry Firn to Ice
Authors: Stauffer B. , Schwander J. , Oeschger H.
Published: September 2017

If cold firn has reached a density of about 0.55 Mg m-3, further densificaron occurs by a sintering process which increases the contact surface between the firn grains. The pore volume is decreasing continuously but the firn remains permeable to air up to a density of 0.82 Mg m-3. At about this density the remaining air in the pore volume is closed off in isolated bubbles. We are interested in the age and the age distribution of the air enclosed in bubbles relative to the age of the surrounding ice, and are investigating the development of the pore volume in firn.

A newly constructed measuring device allows the field measurement of the amount of air which is already enclosed in bubbles of firn samples. Measurements have been made during summer 1983 in Greenland and during winter 1983/84 at the South Pole. The results are discussed and compared with results obtained with a simplified statistical sintering model, using some results of percolation theory.
Estimation and Effects of Internal Accumulation on Five Glaciers in Alaska
Authors: Trabant D. C. , Mayo L. R.
Published: September 2017

Estimates of internal accumulation for five Alaskan glaciers in different climates suggests that internal accumulation occurs in glaciers throughout Alaska. A method of estimating the quantity of internal accumulation is based on the annual minimum temperature ?Γ the snow-firn interface. The consistency of the estimates suggests that valid approximations of internal accumulation can be made over large areas. The estimates have not been confirmed by measurements of mass change, but are believed to be accurate within 10 percent. Point balance quantities of internal accumulation range from 0.65 m a-1, which is 64% of the annual accumulation on McCall Glacier, to 0.12 m a-1, 7% of the annual accumulation on Wolverine Glacier. The amount of internal accumulation decreases rapidly from north to south in Alaska; however it should be expected worldwide where sub-freezing, porous firn is invaded by water.

Internal accumulation occurs in temperate glaciers in strongly maritime climates as well as glaciers in cold continental climates where it delays the onset of runoff, accelerates the process of converting snow into glacier ice, and explains the occurrence of temperate glaciers in permafrost areas.
Effect of Snow Cover on Time Lag of Runoff from a Watershed
Authors: Kobayashi Daiji , Motoyama Hideaki
Published: September 2017

A large scale study on the dependence of time lag of runoff on snow depth and stratigraphy was carried out in a watershed. The time lag in peak runoff was found to be increased by 1.5 - 4 h per I m increment in snow depth. Although the data were widely scattered, it was found that the time lag series converged in a line every year and that discrete layers in the snow cover composed in a warm winter, accelerated meltwater flow.

Subtracting the time of propagation through a snowcover from the total time lag, the effect of size of a watershed on a delay in runoff was rearranged, as follows:

where Tf is the time lag in min after discharge from a snow cover, A the area of a watershed in km2, Re the effective snowmelt in mm/hr. The time lag Tf increases only by 1.5 times when an area of a watershed is increased by a factor of ten.
Computer Study of Snow Avalanche Startup Dynamics
Authors: Nakamura Tsutomu , Abe Osamu , Numano Natsuo , Lang Theodore E.
Published: September 2017

The startup dynamics of three wet snow avalanches in central Japan were evaluated by computer modeling the occurrences and comparing leading edge position-time data. Results were compared between three finite difference based computer codes, which were used to model the startup transients. Two of the computer codes use equations of uniform flow hydrodynamics, the third uses transient viscous fluid mechanics. The latter two codes also incorporate a material description of snow as a locking material. Results show a general increasing of frictional and/or viscous coefficients in the avalanche startup zones in order to match the kinematics of startup. Differences in results between the codes is attributed to the shape of the startup zones, whether convex or concave. The results indicate the magnitude of perturbation of startup on total avalanche runout time, which is likely to be negligible on long-duration avalanche occurrences.
Energy Exchange and its Influence Factors on Mountain Glaciers in West China
Authors: Zhongyuan Bai , Xinzhi Yu
Published: September 2017

Heat balance studies were carried out during summer ablation periods 1960-1983 by the glacial investigation team of the Chinese Academy of Sciences. The effect of energy exchange on development of mountain glaciers was determined, based on the observation of heat exchange over the glacial surface of various mountainous regions. Relationships between energy transfer and climatic parameters under different climatic regimes and landform conditions are analyzed in detail. It was found that the most important heat source for snow-ice melting is radiation, a contribution amounting to between 59.0% and 92.1% of the total. Sensible heat contributed 8 - 36%. The sensible heat flux depends on the bulk transfer coefficient and the glacier cooling effect. The mean value is about 16.3 Ly/day.K.. With the decrease of sea influence, altitude of the snow-line is elevated, aridity of glacier climate increases, evaporation increases gradually and melting decreases, providing conditions for glacial nourishment. When the glacier is covered with a debris layer, the glacier heat balance in continental regions is altered. Finally, the authors’ investigation on the glacier No 1, at the headwater of Urumqi river, shows that differences in structure of glacier heat balance are mainly the result of the influence of the topography and albedo on net radiation. Finally, diagrams of distribution of net radiation in space and time are presented.
Temperature and Accumulation of High Altitude Firn in the Alps
Authors: Haeberli Wilfried , Alean Jürg
Published: September 2017

Data on temperature and accumulation of high altitude firn in the Alps are compiled and discussed. Firn temperature varies with incoming radiation (slope aspect) at a given altitude. The altitudinal gradient of temperature in highly permeable firn bodies appears to be about twice as high as the mean lapse rate of air temperature. “Cold infiltration” takes place above about 3500 m a.s.l. Firn temperatures on the highest peaks are around -15°C. Accumulation (net balance) also decreases with increasing altitude from about 3m H2O at 3500 m a.s.1. to around 0.5 m H2O at wind exposed sites between 4300 and 4800 m a.s.l. Probably this is strongly due to wind erosion and topographical effects. However, temperature and accumulation not only appear to be interrelated, but also seem to be positively correlated to the heat applied to the surface. Assuming the observed altitudinal gradients have remained constant in time, it can be estimated that high altitude firn bodies have become considerably warmer since the last century. CO2-induced atmospheric warming could lead to a drastic change in (he mass turnover and flow activity of high glaciers, in wind-exposed places where wind erosion of the snowpack becomes a controlling factor of accumulation.
Rate Determining Processes of Sea Ice Growth
Authors: Kuroda T.
Published: September 2017

We have derived an analytical expression for the growth rate of sea ice by taking account of the processes relevant to the growth, eg heat conduction, diffusion of salt molecules, radiation, sensible heat transport, evaporation and so on. We discuss the role of each process as rate determining processes under various environmental conditions. It is shown that because of coupling of salt diffusion and heat conduction, the growth rate feeds back to the heat flux Qw from water to ice which controls the growth rate and that Qw decreases with the thickness I of sea ice, even if the environmental conditions are kept constant.
Oceanic Heat Flux as a Component of the Heat Budget of Sea Ice
Authors: Langleben M. P.
Published: September 2017

Heat budget studies of the sea ice cover near Pond Inlet, NWT, were made using data obtained at two locations in Eclipse Sound, one about 0.5 km from shore and the other about 7.5 km from shore. The observations at intervals of one week included ice temperatures at 10 cm separation in vertical profile, salinities of adjacent 2.5 cm-thick slices from vertical ice cores, and ice thickness. The time series analysed extend from three to six months in the six data sets obtained for three winters of observations. Values of oceanic heat flux have been determined as residuals in the energy balance equation applied to the ice cover. The results show that in Eclipse Sound the oceanic heat flux is a significant component of the heat budget of the ice cover. Its value over the winter is typically about 6 W m-2 about half as large as the average rate of release of the latent heat of freezing. There does not appear to be any systematic variation in value of the 4 week-average oceanic heat flux during the season. Nor is there any apparent correlation of oceanic heat flux with rate of release of latent heat (ie ice growth rate), or with the severity of the winter as measured by the magnitude of the conductive heat flux.
Heat Exchange and Surface Conditions in North Water Northern Baffin Bay
Authors: Steffen K. , Ohmura A.
Published: September 2017

North Water is situated in the high Arctic between Greenland and Canada (74°-79°N, 70°-78°W) The sea surface of this region has no homogeneous ice cover during the winter and spring months, due to the occurrence of polynyas

The results of the heat balance and the airborne remote sensing over North Water during winter are reported The heat balance investigation was concerned with the identification of heat sources and their magnitudes The remote sensing was aimed at determining the sea surface temperature and clarifying the exact nature of the surface of North Water in winter

North Water was found to be mostly covered with new and young ice and probably devoid of first year ice until March The surface was about 20 °C warmer than that of the surrounding fast ice The warmest areas were frequently located in Smith Sound, Lady Ann Strait and around the Carey Islands Open water patches above freezing point, ranging from -1 5°C to -0 1 °C were often found along the west coast of Greenland

The surface of North Water receives heat from the sea water during winter between October and March at the rate of 15 MJm^d”1 of which 80% and 20% are from enthalpy contained in sea water and latent heat of fusion released as the surface water freezes, respectively. The basic difference in winter heat balance between North Water and other ice covered arctic seas is the magnitude of the enthalpy supplied by the seawater which is 9 MJn-2d-1 larger for the North Water This is the main heat source, which keeps the surface from becoming solidly frozen
An Arctic Iceberg Deterioration Field Study and Model Simulations
Authors: Venkatesh S. , El-Tahan M. , Mitten P. T.
Published: September 2017

This paper describes the details of a field study on the deterioration of two icebergs grounded outside St John’s harbour in Newfoundland, Canada. Observational data was collected during the period 10-25 June 1983, and included berg-related, meteorological and océanographie data. The study indicated the need for a stable observation platform to enable accurate measurements of iceberg profiles.

The observed decay of the two icebergs is compared with simulations from a model that predicts mass losses due to insolation, buoyant vertical convection, forced convection in air and water, wave erosion and calving of the resulting overhanging ice slabs. There was good agreement between observations and model simulations with the model underestimating the mass losses by about ten percent. Other salient features noted during the field study are also discussed.
On Brine Drainage Channels of Young Sea Ice
Authors: Wakatsuchi Masaaki , Saito Takashi
Published: September 2017

This paper describes characteristic features of brine channels observed both macroscopically and microscopically using samples of natural sea ice. Systematic observations of brine channels, including the effects of ice growth rate and ice thickness, provide knowledge of their spatial distribution in young sea ice.
Morphological Instability of Polyhedral Ice Crystals Growing in Air at Low Temperature
Authors: Gonda T. , Gomi H.
Published: September 2017

The morphology of snow crystals growing at a low temperature has been experimentally studied. The habit and the morphological instability of the crystals vary remarkably with air pressure. In addition, the morphological instability of the crystals depends not only on air pressure but also on supersaturation, crystal size, the ratio of growth rates and the ratio of axial lengths. It is supposed from the experimental results that long prisms with small skeletal structures forming at low supersaturation are precipitating in polar regions.
Thermal Modification of Air Moving Over Melting Snow Surfaces
Authors: Takahara Hiroshi , Hlguchi Keiji
Published: September 2017

Observations were made on thermal modification due to cooling when air flows from a grass-covered area onto a melting snow surface. To clarify the relation between such modification of air and snowmelt, the downwind variation of temperature, humidity and wind speed, together with net radiation and spatial variation of snowmelt were observed at a small snow patch measuring 70 m long and 30 m wide. When air temperature was between 10 and 20°C, with nearly neutral stratification over the upwind grass-covered area, air temperature at 0.1 m level decreased by 4 to 9°C over the downwind distance of 48 m above the snow patch, and so the sensible heat flux decreased in the downwind direction. As a result of such cooling, snowmelt in the central part of the snow patch was found to be about 25% smaller than near its edge. This value can be explained by the decrease of the total heat flux toward the snow surface due to the air modification.
Detection of an Ice-Forming Area by Radar and Satellite
Authors: Aota Masaaki , Oi Masayuki , Ishikawa Masao , Fukushi Hiroki
Published: September 2017

This paper describes a method of distinguishing between pack ice and sea clutter in radar echoes, an attempt to roughly estimate the thickness of sea ice from measurement of surface temperature by air-borne infrared radiometer, and an application of thermal images from satellite data to estimate the concentration of sea ice off the Okhotsk Sea coast of Hokkaido.
Structural Characteristics of Snow Drifts and Cornices
Authors: Naruse Renji , Nishimura Hiroshi , Maeno Norikazu
Published: September 2017

Sorting effects of snow particles during deposition were studied in field observations of snow cornices and wind-tunnel experiment of snow drifts. Grain size, density and hardness were larger at the upper part (root) of a cornice than at the lower part (scarp). Experiments with the use of a horizontal step in a wind-tunnel revealed the importance of redistribution of snow particles on the formation of drifts: at wind speed of 5 m/s, about 40% of particles fallen onto the surface behind a 0.1-m high step were removed by erosion, rebound and creep. The surface mass balance controlling the growth and shape of a drift are briefly discussed.
Internal Radio-Echo Reflections of Polar Snow Covers in Relation to Acidic Layers and Density Fluctuations
Authors: Nlshio Fumihiko , Ohmae Hirokazu
Published: September 2017

To confirm radio-echo layering due to changes in density variations and in specific conductivity in the amount of acid impurities, radio-echo sounding surveys with impulse radar technique were carried out. The continuous and strong internal layers of the snow covers were found to give good correlation with strong peaks of specific conductivity of melted samples from ice cores, rather than the differences in density fluctuations between depositional layers. Measured high conductivity due to acidity variations in ice cores may be correlated with recent volcanic eruptions in the northern hemisphere, and in the Scotia Arc and the South Sandwich Islands.
Mechanical Instability of Snowcover with Saturated Layer
Authors: Nohguchi Yasuaki
Published: September 2017

If rain falls on a new snowcover, a water saturated layer is often clearly formed in it. A snowcover with a saturated layer is sometimes unstable; the snowcover is folded and dimples appear on the snow surface. The mechanism of this instability is discussed theoretically. As a result, we find that a snowcover with a saturated layer can be unstable owing to lateral movement of water along a saturated layer and elastic deformation of the snow layer directly under it. Then the wavelength of the instability depends on the snow density; this result is consistent with field observations.
Measurement of Strains and Pressure in a Snow Cover on a Slope
Authors: Shimizu Hiromu , Akitaya Eizi , Oh’Izumi Mitsuo , Hirabayashi Yauso
Published: September 2017

Four methods of measuring strain and pressure in a snow cover on a slope are presented. The hole-mark method and short-span deformation gauge are used to measure the internal strains of snow, the long-span deformation gauge to measure the local extension/contraction of a snow cover, and snow pressure gauge to measure the pressure in a snow cover.
Errors and Corrections in Calculation of Heat Flux in Antarctic Surface Snow
Authors: Kikuchi Tokio , Wada Makoto , Yamanouchi Takashi
Published: September 2017

This paper describes errors and corrections in snow heat flux when it is calculated using the numerical differentiation and integration method. The data obtained by the 20th Japanese Antarctic Research Expedition during GARP-POLEX in 1979 are used as a test case. Four factors are considered as causes of errors: a) temperature resolution, b) integration, c) determination of snow density and d) the deepest boundary condition. Factors a) and b) are significant in short term estimation, and the total error exceeds 90% if a daily value is calculated. The errors from a) can be reduced if the temperature is averaged over a long period, while those from b) become small in long term flux calculations. The total error can be reduced to 10% in monthly flux, while the improvement is limited by c) and d). If a constant thermal diffusivity is assumed between two levels of temperature measurement, a numerical filter which compensates for the effect of b) is composed. By using running averages in deep layers (z > 0.5 m) and the numerical filter in shallow layers (z <0.5 m), hourly flux can be calculated with errors of about 30%.
Two Dimensional Solutions for a Turbulent Continuum Theory for the Atmospheric Mixture of Snow and Air
Authors: Decker Rand , Brown R. L.
Published: September 2017

The equations of motion (continuity and momentum balance) for a dispersed, negatively buoyant particulate of snow entrained in a turbulent airflow contain apparent turbulent forces or turbulent particle buoyancies. These turbulent buoyancies arise from the constitutive assumption that the turbulent fluctuations of the snow phase velocity vector U’s, and the drift snow density ρ’s, are proportional to the deviatoric mean rate of deformation tensor for the airflow.

For an established, discretized airflow regime, the momentum balance equation for the snow phase can be solved by finite difference techniques for the snow particle velocity field. The snow phase continuity equation can then be solved for the drift snow density field.

The solutions for the snow phase equations of motion for a one dimensional airflow adjacent a solid surface show that the theory can reproduce an inertia! snow particle effect. The snow particle decelerates less rapidly than the airflow, resulting in the snow particle having a positive horizontal impact velocity at the solid surface, where air velocity goes to zero.

The solutions for the snow phase equations of motion for mixture flow and subsequent wind-aided snow accumulation on the immediate lee of a model mountain slope show that the theory can reproduce the geometries typical of wind-aided snow accumulation profiles, measured on the lee of mountain slopes.
Wind-Tunnel Experiments on Blowing Snow
Authors: Maeno N. , Naruse R. , Nishimura K. , Takei I. , Ebinuma T. , Kobayabhi S. , Nlshlmura H. , Kaneda Y. , Ishida T.
Published: September 2017

Blowing snow was produced artificially in a cold wind-tunnel, and various measurements were conducted including particle diameters, concentrations, saltation lengths heat transport and electric charge. The mean diameter of blowing snow particles decreased only slightly with increasing height; in the saltation layer, standard deviation was large and velocities were scattered in a wide range, suggesting the complex dynamic process on taking-off. The mean saltation length ranged from a few cm to 40 cm increasing with wind velocity.

When wind blew without snow drifting, the static air pressure on the snow surface was smaller at higher levels, the vertical pressure gradient being negative. The pressure gradient became positive when blowing snow was initiated eg +9.6 Pa/m at 11.2 m/s and -8.3 °C. The magnitude of à downward force acting on a saltating snow partice caused by the pressure gradient was not large enough to explain the downward acceleration found from photographic analyses of particle trajectories.

Blowing snow particles were charged negatively the magnitude of charge increased with lowering temperature. Increase in vertical heat transfer was found in blowing snow by measuring the temperature of the air at various levels; the increase is reflected on that in the apparent turbulent diffusion coefficient.