Glaciers in Equilibrium, McMurdo Dry Valleys, Antarctica

The McMurdo Dry Valleys are a cold, dry polar desert and the alpine glaciers therein exhibit small annual and seasonal mass balances, ofte

Distributed Modeling of Ablation (1996–2011) and Climate Sensitivity on the Glaciers of Taylor Valley, Antarctica

The McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than over smooth glacier surfaces. In contrast, the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~−0.02 m w.e. K−1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed

Do Patients Taking Warfarin Experience Delays to Theatre, Longer Hospital Stay, and Poorer Survival After Hip Fracture?

BACKGROUND: Patients sustaining a fractured neck of the femur are typically of advanced age with multiple comorbidities. As a consequence, the proportion of these patients receiving warfarin therapy is approximately 10%. There are currently few studies investigating outcomes in this subset of patients. QUESTIONS/PURPOSES: The purpose of this study was to assess the association between warfarin therapy and time to surgery, length of hospital stay, and survival in patients sustaining a fractured neck of the femur. METHODS: Data for 2036 patients admitted to our center between July 2009 and July 2014 with a fractured neck of the femur were extracted from the National Hip Fracture Database. Fifty-seven patients received no surgical treatment and were excluded from analysis. Multivariable ordinary least squares regression was performed to test the association between warfarin treatment on time to surgery and length of stay, and Cox proportional hazards to test followup survival. Variables included in the regression model were age, sex, American Society of Anesthesiologists (ASA) score, admission Abbreviated Mental Test Score (AMTS), fracture type, operation type, and premorbid Work Ability Index (WAI). One hundred fifty-two of 1979 surgically treated patients (8%) were receiving warfarin therapy at the time of admission. RESULTS: After controlling for age, sex, ASA score, AMTS, fracture type, operation type, and WAI, we found that patients taking warfarin were less likely to go to surgery by 36 hours (odds ratio [OR], 0.20; 95% CI, 0.14-0.30), and less likely to go to surgery by 48 hours (OR, 0.17; 95% CI, 0.11-0.24). Patients taking warfarin had a longer length of stay (median, 15 days; interquartile range [IQR], 12-22 days) compared with patients not taking warfarin (median, 13 days; IQR, 9-20 days; p < 0.001). Survival analysis to June 2015 showed a higher mortality for patients taking warfarin (12-month survival, 66% vs 76%; hazard ratio, 1.57; 95% CI, 1.21-2.04; p < 0.001). CONCLUSIONS: After controlling for multiple prognostic factors such as age, ASA score, AMTS, and WAI, warfarin therapy at the time of injury is associated with increased time to surgery, length of stay, and decreased survival. This study highlights the need to view warfarin therapy as a 'red flag' in patients presenting with a fractured neck of the femur. Preoperatively, prompt warfarin reversal together with adequate investigation and optimization of the patient should ensure timely, safe surgery. Early involvement of the anesthesia team should ensure an appropriate level of postoperative care for these patients. LEVEL OF EVIDENCE: Level III, therapeutic study.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s11999-016-5056-

Near-Surface Internal Melting: a Substantial Mass Loss on Antarctic Dry Valley Glaciers

The McMurdo Dry Valleys, southern Victoria Land, East Antarctica, are a polar desert, and melt from glacial ice is the primary source of water to streams, lakes and associated ecosystems. Previous work found that to adequately model glacier ablation and subsurface ice temperatures with a surface energy-balance model required including the transmission of solar radiation into the ice. Here we investigate the contribution of subsurface melt to the mass balance of (and runoff from) Dry Valley glaciers by including a drainage process in the model and applying the model to three glacier sites using 13years of hourly meteorological data. Model results for the smooth glacier surfaces common to many glaciers in the Dry Valleys showed that sublimation was typically the largest component of surface lowering, with rare episodes of surface melting, consistent with anecdotal field observations. Results also showed extensive internal melting 5-15 cm below the ice surface, the drainage of which accounted for 50% of summer ablation. This is consistent with field observations of subsurface streams and formation of a weathering crust. We identify an annual cycle of weathering crust formation in summer and its removal during the 10 months of winter sublimation

External validation and recalibration of an incidental meningioma prognostic model - IMPACT: protocol for an international multicentre retrospective cohort study.

INTRODUCTION: Due to the increased use of CT and MRI, the prevalence of incidental findings on brain scans is increasing. Meningioma, the most common primary brain tumour, is a frequently encountered incidental finding, with an estimated prevalence of 3/1000. The management of incidental meningioma varies widely with active clinical-radiological monitoring being the most accepted method by clinicians. Duration of monitoring and time intervals for assessment, however, are not well defined. To this end, we have recently developed a statistical model of progression risk based on single-centre retrospective data. The model Incidental Meningioma: Prognostic Analysis Using Patient Comorbidity and MRI Tests (IMPACT) employs baseline clinical and imaging features to categorise the patient with an incidental meningioma into one of three risk groups: low, medium and high risk with a proposed active monitoring strategy based on the risk and temporal trajectory of progression, accounting for actuarial life expectancy. The primary aim of this study is to assess the external validity of this model. METHODS AND ANALYSIS: IMPACT is a retrospective multicentre study which will aim to include 1500 patients with an incidental intracranial meningioma, powered to detect a 10% progression risk. Adult patients ≥16 years diagnosed with an incidental meningioma between 1 January 2009 and 31 December 2010 will be included. Clinical and radiological data will be collected longitudinally until the patient reaches one of the study endpoints: intervention (surgery, stereotactic radiosurgery or fractionated radiotherapy), mortality or last date of follow-up. Data will be uploaded to an online Research Electronic Data Capture database with no unique identifiers. External validity of IMPACT will be tested using established statistical methods. ETHICS AND DISSEMINATION: Local institutional approval at each participating centre will be required. Results of the study will be reported through peer-reviewed articles and conferences and disseminated to participating centres, patients and the public using social media

Lateralization of mesial temporal lobe epilepsy with chronic ambulatory electrocorticography

OBJECTIVE: Patients with suspected mesial temporal lobe (MTL) epilepsy typically undergo inpatient video-electroencephalography (EEG) monitoring with scalp and/or intracranial electrodes for 1 to 2 weeks to localize and lateralize the seizure focus or foci. Chronic ambulatory electrocorticography (ECoG) in patients with MTL epilepsy may provide additional information about seizure lateralization. This analysis describes data obtained from chronic ambulatory ECoG in patients with suspected bilateral MTL epilepsy in order to assess the time required to determine the seizure lateralization and whether this information could influence treatment decisions. METHODS: Ambulatory ECoG was reviewed in patients with suspected bilateral MTL epilepsy who were among a larger cohort with intractable epilepsy participating in a randomized controlled trial of responsive neurostimulation. Subjects were implanted with bilateral MTL leads and a cranially implanted neurostimulator programmed to detect abnormal interictal and ictal ECoG activity. ECoG data stored by the neurostimulator were reviewed to determine the lateralization of electrographic seizures and the interval of time until independent bilateral MTL electrographic seizures were recorded. RESULTS: Eighty-two subjects were implanted with bilateral MTL leads and followed for 4.7 years on average (median 4.9 years). Independent bilateral MTL electrographic seizures were recorded in 84%. The average time to record bilateral electrographic seizures in the ambulatory setting was 41.6 days (median 13 days, range 0-376 days). Sixteen percent had only unilateral electrographic seizures after an average of 4.6 years of recording. SIGNIFICANCE: About one third of the subjects implanted with bilateral MTL electrodes required >1 month of chronic ambulatory ECoG before the first contralateral MTL electrographic seizure was recorded. Some patients with suspected bilateral MTL seizures had only unilateral electrographic seizures. Chronic ambulatory ECoG in patients with suspected bilateral MTL seizures provides data in a naturalistic setting, may complement data from inpatient video-EEG monitoring, and can contribute to treatment decisions