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Representation of sharp rifts and faults mechanics in modeling ice shelf flow dynamics: Application to Brunt/Stancomb-Wills Ice Shelf, Antarctica
Ice shelves play a major role in buttressing ice sheet flow into the ocean, hence the importance of accurate numerical modeling of their stress regime. Commonly used ice flow models assume a continuous medium and are therefore complicated by the presence of rupture features (crevasses, rifts, and faults) that significantly affect the overall flow patterns. Here we apply contact mechanics and penalty methods to develop a new ice shelf flow model that captures the impact of rifts and faults on the rheology and stress distribution of ice shelves. The model achieves a best fit solution to satellite observations of ice shelf velocities to infer the following: (1) a spatial distribution of contact and friction points along detected faults and rifts, (2) a more realistic spatial pattern of ice shelf rheology, and (3) a better representation of the stress balance in the immediate vicinity of faults and rifts. Thus, applying the model to the Brunt/Stancomb-Wills Ice Shelf, Antarctica, we quantify the state of friction inside faults and the opening rates of rifts and obtain an ice shelf rheology that remains relatively constant everywhere else on the ice shelf. We further demonstrate that better stress representation has widespread application in examining aspects affecting ice shelf structure and dynamics including the extent of ice mélange in rifts and the change in fracture configurations. All are major applications for better insight into the important question of ice shelf stability
Creep deformation and buttressing capacity of damaged ice shelves: theory and application to Larsen C ice shelf
Around the perimeter of Antarctica, much of the ice sheet discharges to the ocean through floating
ice shelves. The buttressing provided by ice shelves is critical for modulating the flux of ice
into the ocean, and the presently observed thinning of ice shelves is believed to be reducing
their buttressing capacity and contributing to the acceleration and thinning of the grounded ice
sheet. However, relatively little attention has been paid to the role that fractures play in the
ability of ice shelves to sustain and transmit buttressing stresses. Here, we present a new
framework for quantifying the role that fractures play in the creep deformation and buttressing
capacity of ice shelves. We apply principles of continuum damage mechanics to derive a new
analytical relation for the creep of an ice shelf that accounts for the softening influence of
fractures on longitudinal deformation using a state damage variable. We use this new analytical
relation, combined with a temperature calculation for the ice, to partition an inverse method
solution for ice shelf rigidity into independent solutions for softening damage and stabilizing
backstress. Using this new approach, field and remote sensing data can be utilized to monitor the
structural integrity of ice shelves, their ability to buttress the flow of ice at the grounding
line, and thus their indirect contribution to ice sheet mass balance and global sea level. We
apply this technique to the Larsen C ice shelf using remote sensing and Operation IceBridge data,
finding damage in areas with known crevasses and rifts. Backstress is highest near the grounding
line and upstream of ice rises, in agreement with patterns observed on other ice shelves. The ice
in contact with the Bawden ice rise is weakened by fractures, and additional damage or thinning in
this area could diminish the backstress transmitted upstream. We model the consequences for the
ice shelf if it loses contact with this small ice rise, finding that flow speeds would increase by
25% or more over an area the size of the former Larsen B ice shelf. Such a perturbation could
potentially destabilize the northern part of Larsen C along pre-existing lines of weakness,
highlighting the importance of the feedback between buttressing and fracturing in an ice shelf
Optimal numerical solvers for transient simulations of ice flow using the Ice Sheet System Model (ISSM versions 4.2.5 and 4.11)
Identifying fast and robust numerical solvers is a critical issue that needs to
be addressed in order to improve projections of polar ice sheets evolving in a
changing climate. This work evaluates the impact of using advanced numerical
solvers for transient ice-flow simulations conducted with the JPL–UCI Ice Sheet
System Model (ISSM). We identify optimal numerical solvers by testing a broad
suite of readily available solvers, ranging from direct sparse solvers to
preconditioned iterative methods, on the commonly used Ice Sheet Model
Intercomparison Project for Higher-Order ice sheet Models benchmark tests.
Three types of analyses are considered: mass transport, horizontal stress
balance, and incompressibility. The results of the fastest solvers for
each analysis type are ranked based on their scalability across mesh size and
basal boundary conditions. We find that the fastest iterative solvers are
∼ 1.5–100 times faster than the default direct solver used in ISSM, with
speed-ups improving rapidly with increased mesh resolution. We provide a set of
recommendations for users in search of efficient solvers to use for transient
ice-flow simulations, enabling higher-resolution meshes and faster turnaround
time. The end result will be improved transient simulations for short-term,
highly resolved forward projections (10–100 year time scale) and also improved
long-term paleo-reconstructions using higher-order representations of stresses
in the ice. This analysis will also enable a new generation of comprehensive
uncertainty quantification assessments of forward sea-level rise projections,
which rely heavily on ensemble or sampling approaches that are inherently
expensive
CosmoHub: Interactive exploration and distribution of astronomical data on Hadoop
We present CosmoHub (https://cosmohub.pic.es), a web application based on Hadoop to perform interactive exploration and distribution of massive cosmological datasets. Recent Cosmology seeks to unveil the nature of both dark matter and dark energy mapping the large-scale structure of the Universe, through the analysis of massive amounts of astronomical data, progressively increasing during the last (and future) decades with the digitization and automation of the experimental techniques. CosmoHub, hosted and developed at the Port d'Informació Científica (PIC), provides support to a worldwide community of scientists, without requiring the end user to know any Structured Query Language (SQL). It is serving data of several large international collaborations such as the Euclid space mission, the Dark Energy Survey (DES), the Physics of the Accelerating Universe Survey (PAUS) and the Marenostrum Institut de Ciències de l'Espai (MICE) numerical simulations. While originally developed as a PostgreSQL relational database web frontend, this work describes the current version of CosmoHub, built on top of Apache Hive, which facilitates scalable reading, writing and managing huge datasets. As CosmoHub's datasets are seldomly modified, Hive it is a better fit. Over 60 TiB of cataloged information and 50×10 astronomical objects can be interactively explored using an integrated visualization tool which includes 1D histogram and 2D heatmap plots. In our current implementation, online exploration of datasets of 10 objects can be done in a timescale of tens of seconds. Users can also download customized subsets of data in standard formats generated in few minutes.CosmoHub has been partially funded through projects of the Spanish national program “Programa Estatal de I + D + i” of the Spanish government. The support of the ERDF fund is gratefully acknowledged
Protocol for the CUPIDO trials; multicenter randomized controlled trials to assess the value of combining prolapse surgery and incontinence surgery in patients with genital prolapse and evident stress incontinence (CUPIDO I) and in patients with genital prolapse and occult stress incontinence (CUPIDO II)
Background: About 40% of all patients with genital prolapse report stress-incontinence. In about half of the 60% patients that do not report stress-incontinence, occult urinary stress-incontinence can be detected. In these patients stress-incontinence is masked due to kinking or compression of the urethra by the prolapse. In case surgical correction is indicated there are two strategies to manage patients with combined prolapse and (occult) stress incontinence. This strategy is either (i) a combination of prolapse surgery and stress-incontinence surgery or (ii) to correct the prolapse first and evaluate afterwards whether additional stress-incontinence surgery is indicated. The advantage of combining prolapse and stress-incontinence surgery is that only few patients report stress-incontinence following such combination. However, this combination has been associated with an increased risk on complications, of which the development of obstructive micturition symptoms, overactive bladder symptoms and bladder retention are the most important ones. Furthermore, combining two procedures may be unnecessary as performing only prolapse surgery may cure stress-incontinence In the randomized CUPIDO trials both strategies are compared in patients with prolapse and evident stress incontinence (CUPIDO I trial) and in patients with prolapse and occult stress incontinence (CUPIDO II trial). Methods/Design: The CUPIDO trials are two multicenter randomized controlled trials in which women with stress urinary incontinence (SUI) or occult stress urinary incontinence (OSUI) are randomized to prolapse surgery combined with anti incontinence surgery (concomitant surgery) or to prolapse surgery only. Patients with at least stage 2 POP are eligible, women with evident SUI are randomized in CUPIDO I. Patients without SUI are eligible for CUPIDO II and will have urodynamic evaluation or a standardized redression test. Women with OSUI are randomized, women without OSUI are followed up but not randomized. The primary outcome measure is absence of SUI twelve months after surgery. Furthermore, economic evaluations are conducted, and the effectiveness of urodynamic investigation is evaluated against a non-invasive way to determine SUI in women with POP. A total of 450 women will be included in the study
The short-term effect of swimming training load on shoulder rotational range of motion, shoulder joint position sense and pectoralis minor length
Background: Shoulder pain or injury is the most common issue facing elite competitive swimmers and the most frequent reason for missed or modified training. Literature suggests that highly repetitive upper limb loading leads to inappropriate adaptations within the shoulder complex. The most likely maladaptations to occur are variations in shoulder rotational range of motion, reduction in joint position sense and shortened pectoralis minor length. This has yet to have been confirmed in experimental studies. The aim of this study was to investigate the short-term effects of swimming training load upon internal and external rotation range of motion, joint position sense and pectoralis minor length.
Method: Sixteen elite swimmers training in the British Swimming World Class programme participated. Measures of internal and external range of motion, joint position sense error score and pectoralis minor length were taken before and after a typical 2h swimming session.
Results: Following swimming training shoulder external rotation range of motion and pectoralis minor length reduced significantly (-3.4°,p=<0.001 and -0.7cm, p=<0.001, respectively), joint position sense error increased significantly (+2.0° error angle, p=<0.001). Internal rotation range of motion demonstrated no significant change (-0.6, p=0.53).
Discussion: This study determined that elite level swimming training results in short-term maladaptive changes in shoulder performance that could potentially predispose them to injury
A systematic review of outcome and outcome-measure reporting in randomised trials evaluating surgical interventions for anterior-compartment vaginal prolapse: a call to action to develop a core outcome set
INTRODUCTION: We assessed outcome and outcome-measure reporting in randomised controlled trials evaluating surgical interventions for anterior-compartment vaginal prolapse and explored the relationships between outcome reporting quality with journal impact factor, year of publication, and methodological quality. METHODS: We searched the bibliographical databases from inception to October 2017. Two researchers independently selected studies and assessed study characteristics, methodological quality (Jadad criteria; range 1-5), and outcome reporting quality Management of Otitis Media with Effusion in Cleft Palate (MOMENT) criteria; range 1-6], and extracted relevant data. We used a multivariate linear regression to assess associations between outcome reporting quality and other variables. RESULTS: Eighty publications reporting data from 10,924 participants were included. Seventeen different surgical interventions were evaluated. One hundred different outcomes and 112 outcome measures were reported. Outcomes were inconsistently reported across trials; for example, 43 trials reported anatomical treatment success rates (12 outcome measures), 25 trials reported quality of life (15 outcome measures) and eight trials reported postoperative pain (seven outcome measures). Multivariate linear regression demonstrated a relationship between outcome reporting quality with methodological quality (β = 0.412; P = 0.018). No relationship was demonstrated between outcome reporting quality with impact factor (β = 0.078; P = 0.306), year of publication (β = 0.149; P = 0.295), study size (β = 0.008; P = 0.961) and commercial funding (β = -0.013; P = 0.918). CONCLUSIONS: Anterior-compartment vaginal prolapse trials report many different outcomes and outcome measures and often neglect to report important safety outcomes. Developing, disseminating and implementing a core outcome set will help address these issues
Biomarkers of stroke recovery: consensus-based core recommendations from the Stroke Recovery and Rehabilitation Roundtable
The most difficult clinical questions in stroke rehabilitation are ‘‘What is this patient’s potential for recovery?’’ and ‘‘What is the best rehabilitation strategy for this person, given her/his clinical profile?’’ Without answers to these questions, clinicians struggle to make decisions regarding the content and focus of therapy, and researchers design studies that inadvertently mix participants who have a high likelihood of responding with those who do not. Developing and implementing biomarkers that distinguish patient subgroups will help address these issues and unravel the factors important to the recovery process. The goal of the present paper is to provide a consensus statement regarding the current state of the evidence for stroke recovery biomarkers. Biomarkers of motor, somatosensory, cognitive and language domains across the recovery timeline post-stroke are considered; with focus on brain structure and function, and exclusion of blood markers and genetics. We provide evidence for biomarkers that are considered ready to be included in clinical trials, as well as others that are promising but not ready and so represent a developmental priority. We conclude with an example that illustrates the utility of biomarkers in recovery and rehabilitation research, demonstrating how the inclusion of a biomarker may enhance future clinical trials. In this way, we propose a way forward for when and where we can include biomarkers to advance the efficacy of the practice of, and research into, rehabilitation and recovery after stroke
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