scholarly journals From high friction zone to frontal collapse: dynamics of an ongoing tidewater glacier surge, Negribreen, Svalbard

2020 ◽  
Vol 66 (259) ◽  
pp. 742-754
Author(s):  
Odin Næss Haga ◽  
Robert McNabb ◽  
Christopher Nuth ◽  
Bas Altena ◽  
Thomas Schellenberger ◽  
...  
Keyword(s):  
Tidewater Glaciers ◽  
Process Stage ◽  
Quiescent Phase ◽  
Glacier System ◽  
Digital Elevation ◽  
Stage 4 ◽  
Tidewater Glacier ◽  
Stage Process ◽  
Triggering Mechanisms ◽  
Stage 1

AbstractNegribreen, a tidewater glacier located in central eastern Svalbard, began actively surging after it experienced an initial collapse in summer 2016. The surge resulted in horizontal surface velocities of more than 25 m d−1, making it one of the fastest-flowing glaciers in the archipelago. The last surge of Negribreen likely occurred in the 1930s, but due to a long quiescent phase, investigations of this glacier have been limited. As Negribreen is part of the Negribreen Glacier System, one of the largest glacier systems in Svalbard, investigating its current surge event provides important information on surge behaviour among tidewater glaciers within the region. Here, we demonstrate the surge development and discuss triggering mechanisms using time series of digital elevation models (1969–2018), surface velocities (1995–2018), crevasse patterns and glacier extents from various data sources. We find that the active surge results from a four-stage process. Stage 1 (quiescent phase) involves a long-term, gradual geometry change due to high subglacial friction towards the terminus. These changes allow the onset of Stage 2, an accelerating frontal destabilization, which ultimately results in the collapse (Stage 3) and active surge (Stage 4).

scholarly journals From ice-shelf tributary to tidewater glacier: continued rapid recession, acceleration and thinning of Röhss Glacier following the 1995 collapse of the Prince Gustav Ice Shelf, Antarctic Peninsula

2011 ◽  
Vol 57 (203) ◽  
pp. 397-406 ◽  
Author(s):  
N.F. Glasser ◽  
T.A. Scambos ◽  
J. Bohlander ◽  
M. Truffer ◽  
E. Pettit ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Satellite Image ◽  
Ice Shelf ◽  
Tidewater Glaciers ◽  
Speed Increase ◽  
Glacier System ◽  
Digital Elevation ◽  
Tidewater Glacier ◽  
Before And After ◽  
The Antarctic

AbstractWe use optical (ASTER and Landsat) and radar (ERS-1 and ERS-2) satellite imagery to document changes in the Prince Gustav Ice Shelf, Antarctic Peninsula, and its tributary glaciers before and after its January 1995 collapse. The satellite image record captures the transition from an ice-shelf glacier system to a tidewater glacial system and the subsequent rapid retreat and inferred ‘fatal’ negative mass balances that occur as lower glacier elevations lead to higher ablation and tidewater-style calving collapse. Pre-1995 images show that the central ice shelf was fed primarily by Sjögren Glacier flowing from the Antarctic Peninsula and by Röhss Glacier flowing from James Ross Island. Numerous structural discontinuities (rifts and crevasses) and melt ponds were present on the ice shelf before the collapse. After the ice shelf collapsed, Röhss Glacier retreated rapidly, becoming a tidewater glacier in 2002 and receding a total of ∼15 km between January 2001 and March 2009, losing >70% of its area. Topographic profiles of Röhss Glacier from ASTER-derived digital elevation models show a thinning of up to ∼150 m, and surface speeds increased up to ninefold (0.1–0.9 m d−1) over the same period. The rates of speed increase and elevation loss, however, are not monotonic; both rates slowed between late 2002 and 2005, accelerated in 2006 and slowed again in 2008–09. We conclude that tributary glaciers react to ice-shelf removal by rapid (if discontinuous) recession, and that the response of tidewater glaciers on the Antarctic Peninsula to ice-shelf removal occurs over timescales ranging from sub-annual to decadal.

The Containment of Disk Burst Fragments by Cylindrical Shells

1974 ◽  
Vol 96 (2) ◽  
pp. 114-123 ◽  
Author(s):  
A. C. Hagg ◽  
G. O. Sankey
Keyword(s):  
Kinetic Energy ◽  
Test Results ◽  
Process Stage ◽  
Inelastic Impact ◽  
Impact Area ◽  
Stage Process ◽  
Local Impact ◽  
Energy Dissipated ◽  
Stage 1 ◽  
Steel Cylindrical Shell

Tests and analysis show that containment of missile-like steel disk fragments by a steel cylindrical shell is a sequential two-stage process. Stage 1 involves inelastic impact and transfer of momentum to include an effective target mass. For nonperforation, the energy dissipated in plastic compression and shear strain at the local impact area must be sufficient to accommodate the loss in kinetic energy of the system. With nonperforation, the process enters stage 2, which involves dissipation of energy in plastic tension strain over extended volumes of shell material. For containment, the energy dissipated in plastic strain in stage 2 must accommodate the residual kinetic energy of the system. Criteria for nonperforation and containment are given which are in satisfactory agreement with test results.

Teaching undergraduates the process of peer review: learning by doing

2010 ◽  
Vol 34 (3) ◽  
pp. 137-144 ◽  
Author(s):  
P. K. Rangachari
Keyword(s):  
Peer Review ◽  
Review Process ◽  
Peer Review Process ◽  
Learning By Doing ◽  
Student Responses ◽  
Active Approach ◽  
Stage 4 ◽  
Stage Process ◽  
The Individual ◽  
Stage 1

An active approach allowed undergraduates in Health Sciences to learn the dynamics of peer review at first hand. A four-stage process was used. In stage 1, students formed self-selected groups to explore specific issues. In stage 2, each group posted their interim reports online on a specific date. Each student read all the other reports and prepared detailed critiques. In stage 3, each report was discussed at sessions where the lead discussant was selected at random. All students participated in the peer review process. The written critiques were collated and returned to each group, who were asked to resubmit their revised reports within 2 wk. In stage 4, final submissions accompanied by rebuttals were graded. Student responses to a questionnaire were highly positive. They recognized the individual steps in the standard peer review, appreciated the complexities involved, and got a first-hand experience of some of the inherent variabilities involved. The absence of formal presentations and the opportunity to read each other's reports permitted them to study issues in greater depth.

Alterations in the number of motoneurons containing immunoreactive calcitonin gene-related peptide(CGRP)& choline acetyltransferase(ChAT) in the cervical spinal cord of the wobbler mouse during the development of the motoneuron disease

1995 ◽  
Vol 53 ◽  
pp. 970-971
Author(s):  
L. Vacca-Galloway ◽  
Y.Q. Zhang ◽  
P. Bose ◽  
S.H. Zhang
Keyword(s):  
Spinal Cord ◽  
Early Stage ◽  
Cervical Spinal Cord ◽  
Wild Type Mouse ◽  
Reflex Response ◽  
Mouse Strains ◽  
Behavioral Tests ◽  
Wobbler Mouse ◽  
Stage 4 ◽  
Stage 1

The Wobbler mouse (wr) has been studied as a model for inherited human motoneuron diseases (MNDs). Using behavioral tests for forelimb power, walking, climbing, and the “clasp-like reflex” response, the progress of the MND can be categorized into early (Stage 1, age 21 days) and late (Stage 4, age 3 months) stages. Age-and sex-matched normal phenotype littermates (NFR/wr) were used as controls (Stage 0), as well as mice from two related wild-type mouse strains: NFR/N and a C57BI/6N. Using behavioral tests, we also detected pre-symptomatic Wobblers at postnatal ages 7 and 14 days. The mice were anesthetized and perfusion-fixed for immunocytochemical (ICC) of CGRP and ChAT in the spinal cord (C3 to C5).Using computerized morphomety (Vidas, Zeiss), the numbers of IR-CGRP labelled motoneurons were significantly lower in 14 day old Wobbler specimens compared with the controls (Fig. 1). The same trend was observed at 21 days (Stage 1) and 3 months (Stage 4). The IR-CGRP-containing motoneurons in the Wobbler specimens declined progressively with age.

Novel staging classification of primary mitral regurgitation based on the presence of cardiac damage

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
A.L Van Wijngaarden ◽  
Y.L Hiemstra ◽  
P Van Der Bijl ◽  
V Delgado ◽  
N Ajmone Marsan ◽  
...  
Keyword(s):  
Mitral Regurgitation ◽  
Kidney Function ◽  
Left Ventricular ◽  
Prognostic Impact ◽  
Cardiac Damage ◽  
Stage 4 ◽  
All Cause Mortality ◽  
Primary Mitral Regurgitation ◽  
Stage 1 ◽  
Staging Classification

Abstract Background The indication for surgery in patients with severe primary mitral regurgitation (MR) is currently based on the presence of symptoms, left ventricular (LV) dilatation and dysfunction, atrial fibrillation and pulmonary hypertension. The aim of this study was to evaluate the prognostic impact of a new staging classification based on cardiac damage including the known risk factors but also including global longitudinal strain (GLS), severe left atrial (LA) dilatation and right ventricular (RV) dysfunction. Methods In total 614 patients who underwent surgery for severe primary MR with available baseline transthoracic echocardiograms were included. Patients were classified according to the extent of cardiac damage (Figure): Stage 0-no cardiac damage, Stage 1-LV damage, Stage 2-LA damage, Stage 3-pulmonary vasculature or tricuspid valve damage and Stage 4-RV damage. Patients were followed for all-cause mortality. Results Based on the proposed classification, 172 (28%) patients were classified as Stage 0, 102 (17%) as Stage 1, 134 (21%) as Stage 2, 135 (22%) as Stage 3 and 71 (11%) as Stage 4. The more advanced the stage, the older the patients were with worse kidney function, more symptoms and higher EuroScore. Kaplan-Meier curve analysis revealed that patients with more advanced stages of cardiac damage had a significantly worse survival (log-rank chi-square 35.2; p<0.001) (Figure). On multivariable analysis, age, male, chronic obstructive pulmonary disease, kidney function, and stage of cardiac damage were independently associated with all-cause mortality. For each stage increase, a 22% higher risk for all-cause mortality was observed (95% CI: 1.064–1.395; p=0.004). Conclusion In patients with severe primary MR, a novel staging classification based on the extent of cardiac damage, may help refining risk stratification, particularly including also GLS, LA dilatation and RV dysfunction in the assessment. Funding Acknowledgement Type of funding source: None

A Description of Middle School Male Singers’ Voice Change and Voice Part Assignment

2021 ◽  
pp. 875512332110182
Author(s):  
Ryan Austin Fisher ◽  
Nancy L. Summitt ◽  
Ellen B. Koziel
Keyword(s):  
Middle School ◽  
Sixth Grade ◽  
Eighth Grade ◽  
Voice Change ◽  
Stage 4 ◽  
Public Middle School ◽  
Middle School Choir ◽  
Choral Programs ◽  
Stage 1 ◽  
The Voice

The purpose of this study was to describe the voice change and voice part assignment of male middle school choir members. Volunteers ( N = 92) were recruited from three public middle school choral programs (Grades 6-8). Participants were audio-recorded performing simple vocal tasks in order to assess vocal range and asked to share the music they were currently singing in class. Results revealed 23.91% of participants’ voices could be categorized as unchanged, 14.13% as Stage 1, 3.26% as Stage 2, 10.87% as Stage 3, 26.09% as Stage 4, and 21.74% as Stage 5. The majority of sixth-grade participants were classified as unchanged or in Stage 1 of the voice change and the majority of eighth-grade participants were classified in Stages 4 to 5 of the voice change. Of the participants labeled “tenors” in their choir, over 60% were classified as either unchanged voices or in Stage 1 of the voice change.

scholarly journals Temporal changes of quantitative CT findings from 102 patients with COVID-19 in Wuhan, China: A longitudinal study

2021 ◽  
Vol 29 ◽  
pp. 297-309
Author(s):  
Xiaohui Chen ◽  
Wenbo Sun ◽  
Dan Xu ◽  
Jiaojiao Ma ◽  
Feng Xiao ◽  
...  
Keyword(s):  
Lung Diseases ◽  
Early Stage ◽  
Temporal Changes ◽  
Time Interval ◽  
Lesion Area ◽  
Quantitative Ct ◽  
Diagnosis And Prognosis ◽  
Ct Findings ◽  
Stage 4 ◽  
Stage 1

BACKGROUND: Computed tomography (CT) imaging combined with artificial intelligence is important in the diagnosis and prognosis of lung diseases. OBJECTIVE: This study aimed to investigate temporal changes of quantitative CT findings in patients with COVID-19 in three clinic types, including moderate, severe, and non-survivors, and to predict severe cases in the early stage from the results. METHODS: One hundred and two patients with confirmed COVID-19 were included in this study. Based on the time interval between onset of symptoms and the CT scan, four stages were defined in this study: Stage-1 (0 ∼7 days); Stage-2 (8 ∼ 14 days); Stage-3 (15 ∼ 21days); Stage-4 (> 21 days). Eight parameters, the infection volume and percentage of the whole lung in four different Hounsfield (HU) ranges, ((-, -750), [-750, -300), [-300, 50) and [50, +)), were calculated and compared between different groups. RESULTS: The infection volume and percentage of four HU ranges peaked in Stage-2. The highest proportion of HU [-750, 50) was found in the infected regions in non-survivors among three groups. CONCLUSIONS: The findings indicate rapid deterioration in the first week since the onset of symptoms in non-survivors. Higher proportion of HU [-750, 50) in the lesion area might be a potential bio-marker for poor prognosis in patients with COVID-19.

scholarly journals P0828CKD STAGE DISTRIBUTION IN AN ITALIAN PROVINCE; SEVEN YEARS OF FOLLOW UP

2020 ◽  
Vol 35 (Supplement_3) ◽  
Author(s):  
Alessandro Roggeri ◽  
Daniela Paola Roggeri ◽  
Carlotta Rossi ◽  
Marco Gambera ◽  
Rossana Piccinelli ◽  
...  
Keyword(s):  
Hospital Discharge ◽  
Administrative Database ◽  
Ca Channel ◽  
Dialysis Treatment ◽  
First Choice ◽  
Stage 4 ◽  
Ckd Stage ◽  
Significant Difference ◽  
Stage 1

Abstract Background and Aims Chronic kidney disease (CKD) is a chronic illness with important implications for the health of the population and for the commitment of resources by public health services. CKD staging makes it possible to assess the severity of the disease and its distribution in the population. The distribution of the stages of CKD diagnosed through hospitalization were analyzed using administrative database of the Local Health Authority of a province with a population of about 1 million inhabitants in northern Italy. Method Patients with hospital discharge with a diagnosis of CKD (ICD9CM 5851, 5852, 5853, 5854) in 2011- 2012 years, without dialysis treatment, neither transplantation procedure nor acute renal failure were selected. Demographic characteristics, comorbidities, dialysis treatment, drugs prescription and nephrological follow-up were investigated. This cohort of patients was examined over a 7-year period (2011-2017). Stage five was not considered to avoid possible misunderstanding with five D stage. Results 1808 patients diagnosed with CKD were extracted from the 2011-2017 administrative database; of these, 1267 had a diagnosis with the CKD stage specification. The distribution of 1267 patients in the CKD stages at the first hospital discharge was as follows: 7.4% stage 1, 30.9% stage 2, 42.3% stage 3, 19.3% stage 4. The 832 patients described in the study were still alive as of Jan. 1, 2013 while 435 (34.3%) died by Dec. 31, 2012. Until Dec. 31, 2017, 503 of the 832 patients died representing the 52.8% of stage 1 patients, 62% of stage 2 patients, 58.2% of stage 3 patients, 66.4% of stage 4 patients. Males were the most prevalent gender (58.5%), without any significant difference into CKD stages. Our patients have a fairly high age as can be seen from the table 1. The presence of co-morbidities was assessed either directly for the main risk factors or by the modified Charlson index (MCI) for CKD patients. The average value of the MCI is 3.8 ± 3.1 for all patients and 3.4 ±3.0 for stage 1, 4.1 ± 3.3 for stage 2, 3.7 ± 3.1 for stage 3, 3.7 ± 2.9 for stage 4, with maximum values of 12.0, 17.0, 16.0 and 14.0 respectively. About 40% of patients had diabetes mellitus, with the highest prevalence in stage 4 (49.3%) and the lowest in stage 1 (25%). Cardiovascular disease was distributed almost equally among all patients with a value between 82% in stage 1 and 86.3% in stage 4. Cancer were present in 26.3% of patients with similar values in all stages. Just about 9% of patients underwent dialysis treatment for achieving ESRD, with a percentage of 5.6% among patients in stage 1 and 17.1% among those in stage 4. Hemodialysis represented first choice treatment (86%) compared with peritoneal one (14%). Time from the diagnosis of CKD to the first dialysis was variable with an average of 3.4 ±1.7 years; the longest interval for patients in stage 1 (5.1±1.8) and the shortest (3.0 ±1.6) for patients in stage 4. The number of nephrological visits at renal units was analyzed for an assessment of the extent of follow-up and prevention upon reaching the ESRD (table2). More than 90% of patients had prescribed drugs antagonists of the renin angiotensin system, in all stages of CKD; other antihypertensive drugs (Ca channel blockers and peripheral vasodilators) had a similar prescription level. Anemia control drugs (ESA and iron) had an incremental prescription with stages of the disease from 51.4% in stage 1 to 74% in stage 4, similarly to Ca-P metabolism control drugs ranging from 44.4% in stage 1 to 67.8% in stage 4. Conclusion Correct staging of CKD is very important to assess the prognosis of patients, but the major determinants of outcome are comorbidities and age of the patients. The cohort examined has a high mortality rate, far higher than reported in the literature for CKD. It should be noted that the sample was identified by hospitalization for cardiovascular diseases more than 50% complicated by diabetes and hypertension, so death represents the main outcome and not ESRD.

Lightbulb technique for the treatment of osteonecrosis of the femoral head

2017 ◽  
Vol 28 (3) ◽  
pp. 272-277 ◽  
Author(s):  
Cemil Yildiz ◽  
Yusuf Erdem ◽  
Kenan Koca
Keyword(s):  
Femoral Head ◽  
Disease Progression ◽  
Bone Grafting ◽  
Treatment Effectiveness ◽  
Treatment Success ◽  
Total Hip ◽  
Kaplan Meier ◽  
Grafting Technique ◽  
Stage 4 ◽  
Stage 1

Introduction: The aim of this study was to report the clinical and radiological outcomes for 21 patients (28 hips) treated for osteonecrosis of the femoral head using the lightbulb technique, a nonvascularised bone grafting technique. Methods: The study group included 14 men and 7 women, with a mean age of 33.2 (range 22-50) years, presenting with avascular necrosis of the femoral head of stage 4a or earlier, according to the Steinberg classification. Patients were treated using the nonvascularised lightbulb bone grafting technique. The primary clinical outcome was the Harris Hip Scores (HHS), while primary outcomes of treatment effectiveness and disease progression were based on radiographic evidence of disease progression and the need for total hip replacement. The rate of treatment success and failure was evaluated using the Kaplan-Meier survival analysis. Results: The mean HHS increased from 52.66 to 74.33 after treatment, with excellent-to-good outcomes obtained in 21 (75%) of the cases. Fair-to-poor results were obtained in 7 (25%) of the cases, with total hip arthroplasty subsequently required in 5 of these cases. The radiological failure rate was 50% among cases treated in Steinberg stage 1 (1/2), 42% in stage 3 (5/12), and 100% in stage 4 (2/2). Conclusions: The lightbulb technique can provide a clinically acceptable rate of successful treatment of osteonecrosis of the femoral head when used in the early stages of the disease, prior to collapse of the femoral head.

Studies of the explosive combustion of hydrocarbons by kinetic spectroscopy I. Free radical absorption spectra in acetylene combustion

1953 ◽  
Vol 216 (1125) ◽  
pp. 165-183 ◽  
Keyword(s):  
Absorption Spectra ◽  
Total Pressure ◽  
Flash Photolysis ◽  
Initial Period ◽  
Kinetic Spectroscopy ◽  
Radical Concentration ◽  
Stage 4 ◽  
Explosive Reaction ◽  
Stage 1 ◽  
Flash Spectroscopy

The explosive oxidation of acetylene, initiated homogeneously by the flash photolysis of a small quantity of nitrogen dioxide, has been investigated by flash spectroscopy. The absorption spectra of OH, CH, C 2 (singlet and triplet), C 3 , CN and NH, a number of which have not previously been observed, are described, and the relative concentrations, at all times throughout the explosion, are given. Four stages have been distinguished in the explosive reaction: 1. An initial period during which only OH appears. 2. A rapid chain branching involving all the diatomic radicals. 3. Further reaction, occurring only when oxygen is present in excess of equimolecular proportions, during which the OH concentration rises exponentially and the other radicals are totally consumed. 4. A relatively slow exponential decay of the excess radical concentration remaining after completion of stages 2 and 3. The duration of stage 1 is 0 to 3 ms. In an equimolecular mixture at 20 mm total pressure, containing 1.5 mm NO 2 , the durations of both stage 2 and stage 3 are approximately 10 -4 s and the half-life of OH in stage 4 is 0.28 ms. A preliminary interpretation of these changes and of the radical reactions is given.

Sign in / Sign up

Export Citation Format

Share Document