Diagonalization-based preconditioners and generalized convergence bounds for ParaOpt

The ParaOpt algorithm was recently introduced as a time-parallel solver for optimal-control problems with a terminal-cost objective, and convergence results have been presented for the linear diffusive case with implicit-Euler time integrators. We reformulate ParaOpt for tracking problems and provide generalized convergence analyses for both objectives. We focus on linear diffusive equations and prove convergence bounds that are generic in the time integrators used. For large problem dimensions, ParaOpt's performance depends crucially on having a good preconditioner to solve the arising linear systems. For the case where ParaOpt's cheap, coarse-grained propagator is linear, we introduce diagonalization-based preconditioners, inspired by recent advances in the ParaDiag family of methods. These preconditioners not only lead to a weakly-scalable ParaOpt version, but are themselves invertible in parallel, making maximal use of available concurrency. They have proven convergence properties in the linear diffusive case that are generic in the time discretization used, similarly to our ParaOpt results. Numerical results confirm that the iteration count of the iterative solvers used for ParaOpt's linear systems becomes constant in the limit of an increasing processor count. The paper is accompanied by a sequential MATLAB implementation

Geochemical, sedimentological and microbial diversity in two thermokarst lakes of far Eastern Siberia

Thermokarst lakes are important conduits for organic carbon sequestration, soil organic matter (soil-OM) decomposition and release of atmospheric greenhouse gases in the Arctic. They can be classified as either floating-ice lakes, which sustain a zone of unfrozen sediment (talik) at the lakebed year-round, or as bedfast-ice lakes, which freeze all the way to the lakebed in winter. Another key characteristic of thermokarst lakes are their eroding shorelines, depending on the surrounding landscape, they can play a major role in supplying the lakebeds with sediment and OM. These differences in winter ice regime and eroding shorelines are key factors which determine the quantity and quality of OM in thermokarst lake sediments. We used an array of physical, geochemical, and microbiological tools to identify the differences in the environmental conditions, sedimentary characteristics, carbon stocks and microbial community compositions in the sediments of a bedfast-ice and a floating-ice lake in Far East Siberia with different eroding shorelines. Our data show strong differences across most of the measured parameters between the two lakes. For example, the floating-ice lake contains considerably lower amounts of sediment organic matter and dissolved organic carbon, both of which also appear to be more degraded in comparison to the bedfast-ice lake, based on their stable carbon isotope composition (δ13C). We also document clear differences in the microbial community composition, for both archaea and bacteria. We identified the lake water depth (bedfast-ice vs. floating-ice) and shoreline erosion to be the two most likely main drivers of the sedimentary, microbial and biogeochemical diversity in thermokarst lakes. With ongoing climate warming, it is likely that an increasing number of lakes will shift from a bedfast- to a floating-ice state, and that increasing levels of shoreline erosion will supply the lakes with sediments. Yet, still little is known about the physical, biogeochemical and microbial differences in the sediments of these lake types and how different eroding shorelines impact these lake system

Reliable Alignment in Total Knee Arthroplasty by the Use of an iPod-Based Navigation System

Axial alignment is one of the main objectives in total knee arthroplasty (TKA). Computer-assisted surgery (CAS) is more accurate regarding limb alignment reconstruction compared to the conventional technique. The aim of this study was to analyse the precision of the innovative navigation system DASH® by Brainlab and to evaluate the reliability of intraoperatively acquired data. A retrospective analysis of 40 patients was performed, who underwent CAS TKA using the iPod-based navigation system DASH. Pre- and postoperative axial alignment were measured on standardized radiographs by two independent observers. These data were compared with the navigation data. Furthermore, interobserver reliability was measured. The duration of surgery was monitored. The mean difference between the preoperative mechanical axis by X-ray and the first intraoperatively measured limb axis by the navigation system was 2.4°. The postoperative X-rays showed a mean difference of 1.3° compared to the final navigation measurement. According to radiographic measurements, 88% of arthroplasties had a postoperative limb axis within ±3°. The mean additional time needed for navigation was 5 minutes. We could prove very good precision for the DASH system, which is comparable to established navigation devices with only negligible expenditure of time compared to conventional TKA

Do elderly trauma patients receive the required treatment? Epidemiology and outcome of geriatric trauma patients treated at different levels of trauma care

Purpose In an ageing society, geriatric trauma displays an increasing challenge in trauma care. Due to comorbidities and reduced physiologic reserves, these patients might benefit from an immediate specialised care. The current study aims to clarify the prevalence and outcome of geriatric trauma depending on the level of the primary trauma centre. Methods Data sets of 124,641 patients entered in the TR-DGU between 2009 and 2016 were included. Geriatric trauma was defined above 65 years and ISS >= 9. Analysing the prevalence, the age structure of all trauma cases registered in 2014 was compared to demographic data of the German Federal Statistical Office. Differences in injury pattern, in-hospital care and outcome between the primary levels of care were analysed. Results In comparison to their share of population, geriatric patients are highly overrepresented in the TR-DGU. Despite minor injury mechanisms, severe head injuries are common. A tendency to under-triage can be observed, as level II and III trauma centres receive a higher percentage of older patients. Nevertheless, there is no effect on the mortality. 10% of these patients require an early transfer to a higher levelled trauma centres mainly due to severe head and spine injuries. Surprisingly, pre-clinical available signs such as GCS or blood pressure were not altered in these patients. Conclusion Patients above the age of 65 years represent a second group with high risk for traumatic injuries besides younger adults. Despite low-energy trauma mechanisms, these patients are prone to suffer from severe injuries, which require specialised care. Current admission practice appears adequate, as pre-clinical available symptoms did not correlate with injuries that demanded an early inter-hospital transfer. Specialised geriatric triage scores might further improve admission practice

Comparison of transportation related injury mechanisms and outcome of young road users and adult road users, a retrospective analysis on 24,373 patients derived from the TraumaRegister DGU®

Background: Most young people killed in road crashes are known as vulnerable road users. A combination of physical and developmental immaturity as well as inexperience increases the risk of road traffic accidents with a high injury severity rate. Understanding injury mechanism and pattern in a group of young road users may reduce morbidity and mortality. This study analyzes injury patterns and outcomes of young road users compared to adult road users. The comparison takes into account different transportation related injury mechanisms. Methods: A retrospective analysis using data collected between 2002 and 2012 from the TraumaRegister DGU (R) was performed. Only patients with a transportation related injury mechanism (motor vehicle collision (MVC), motorbike, cyclist, and pedestrian) and an ISS >= 9 were included in our analysis. Four different groups of young road users were compared to adult trauma data depending on the transportation related injury mechanism. Results: Twenty four thousand three hundred seventy three, datasets were retrieved to compare all subgroups. The mean ISS was 23.3 +/- 13.1. The overall mortality rate was 8.61%. In the MVC, the motorbike and the cyclist group, we found young road users having more complex injury patterns with a higher AIS pelvis, AIS head, AIS abdomen and AIS of the extremities and also a lower GCS. Whereas in these three sub-groups the adult trauma group only had a higher AIS thorax. Only in the group of the adult pedestrians we found a higher AIS pelvis, AIS abdomen, AIS thorax, a higher AIS of the extremities and a lower GCS. Discussion: This study reports on the most common injuries and injury patterns in young trauma patients in comparison to an adult trauma sample. Our analysis show that in contrast to more experienced road users our young collective refers to be a vulnerable trauma group with an increased risk of a high injury severity and high mortality rate. We indicate a striking difference in terms of the region of injury and the mechanism of injury when comparing the young versus the adult trauma collectives. Conclusions: Young drivers of cars, motorbikes and bikes were shown to be on high risk to sustain a specific severe injury pattern and a high mortality rate compared to adult road users. Our data emphasize a characteristic injury pattern of young trauma patients and may be used to improve trauma care and to guide prevention strategies to decrease injury severity and mortality due to road traffic injuries

The fabella syndrome - a rare cause of posterolateral knee pain: a review of the literature and two case reports

Background: The purpose of this article was to evaluate the risks and benefits of non-operative treatment versus surgical excision of a fabella causing posterolateral knee pain. We performed a systematic review of literature and also present two case reports. Twelve publications were found in a PubMed literature review searching the word fabella syndrome. Non-operative treatment and surgical excision of the fabella has been described. Case presentation: Two patients presented to our outpatient clinic with persisting posterolateral knee pain. In both cases the presence of a fabella was identified, located in close proximity to the posterolateral femoral condyle. All other common causes of intra-and extra articular pathologies possibly causing the posterolateral knee pain were excluded. Following failure to respond to physiotherapy both patients underwent arthroscopy which excluded other possible causes for posterolateral knee pain. The decision was made to undertake surgical excision of the fabella in both cases without complication. Both patients were examined 6 month and one year after surgery with the Tegner activity score, the Visual Analogue Scale (VAS), and International Knee Documentation Committee Score (IKDC). Conclusion: Consistent posterolateral pain during exercise might indicate the presence of a fabella syndrome. Resecting the fabella can be indicated and is a minor surgical procedure with minimal risk. Despite good results in the literature posterolateral knee pain can persist and prevent return to a high level of sports. Level of evidence: IV, case reports and analysis of literature

Trauma-induced coagulopathy upon emergency room arrival: still a significant problem despite increased awareness and management?

PurposeOver the last decade, the pivotal role of trauma-induced coagulopathy has been described and principal drivers have been identified. We hypothesized that the increased knowledge on coagulopathy of trauma would translate into a more cautious treatment, and therefore, into a reduced overall incidence rate of coagulopathy upon ER admission.Patients and methodsBetween 2002 and 2013, 61,212 trauma patients derived from the TraumaRegister DGU (R) had a full record of coagulation parameters and were assessed for the presence of coagulopathy. Coagulopathy was defined by a Quick's value50), the incidence of coagulopathy was reduced by 7%. Regardless of the injury severity, the amount of pre-hospital i.v.-fluids declined during the observed period by 51%. Simultaneously, morbidity and mortality of severely injured patients were on the decrease.ConclusionDuring the 12years observed, a substantial decline of coagulopathy has been observed. This was paralleled by a significant decrease of i.v.-fluids administered in the pre-hospital treatment. The reduced presence of coagulopathy translated into decreased transfusion requirements and mortality. Nevertheless, especially in the most severely injured patients, posttraumatic coagulopathy remains a frequent and life-threatening syndrome

Prehospital volume resuscitation - Did evidence defeat the crystalloid dogma? An analysis of the TraumaRegister DGU (R) 2002-2012

Background: Various studies have shown the deleterious effect of high volume resuscitation following severe trauma promoting coagulopathy by haemodilution, acidosis and hypothermia. As the optimal resuscitation strategy during prehospital trauma care is still discussed, we raised the question if the amount and kind of fluids administered changed over the recent years. Further, if less volume was administered, fewer patients should have arrived in coagulopathic depletion in the Emergency Department resulting in less blood product transfusions. Methods: A data analysis of the 100 489 patients entered into the TraumaRegister DGU (R) (TR-DGU) between 2002 and 2012 was performed of which a total of 23512 patients (23.3 %) matched the inclusion criteria. Volume and type of fluids administered as well as outcome parameter were analysed. Results: Between 2002 and 2012, the amount of volume administered during prehospital trauma care decreased from 1790 ml in 2002 to 1039 ml in 2012. At the same time higher haemoglobin mean values, higher Quick's mean values and reduced mean aPTT can be observed. Simultaneously, more patients received catecholamines (2002: 9.2 to 2012: 13.0 %). Interestingly, the amount of volume administered decreased steadily regardless of the presence of shock. Fewer patients were in the need of blood products and the number of massive transfusions (>= 10 pRBC) more than halved. Discussion: The changes in volume therapy might have reduced haemodilution potentially resulting in an increase of the Hb value. During the period observed transfusion strategies have become more restrictiveand ratio based; the percentage of patients receiving MT halved as blood products may imply negative secondary effects. Furthermore, preventing administration of high blood product ratios result in less impairment of coagulation factors and inhibitors and an therfore improved coagulation. Conclusion: The volume administered in severely injured patients decreased considerably during the last decade possibly supporting beneficial effects such as minimizing the risk of coagulopathy and avoiding potential harmful effects caused by blood product transfusions. Despite outstanding questions in trauma resuscitation, principle evidence merges quickly into clinical practice and algorithms