Forecasting yearly geomagnetic variation through sequential estimation of core low and magnetic diffusion

Earth’s internal magnetic field is generated through motion of the electrically conductive iron-alloy fluid comprising its outer core. Temporal variability of this magnetic field, termed secular variation (SV), results from two processes: one is the interaction between core fluid motion and the magnetic field, the other is magnetic diffusion. As diffusion is widely thought to take place over relatively long, millennial time scales, it is common to disregard it when considering yearly to decadal field changes; in this frozen-flux approximation, core fluid motion may be inferred on the core–mantle boundary (CMB) using observations of SV at Earth’s surface. Such flow models have been used to forecast variation in the magnetic field. However, recent work suggests that diffusion may also contribute significantly to SV on short time scales provided that the radial length scale of the magnetic field structure within the core is sufficiently short. In this work, we introduce a hybrid method to forecast field evolution that considers a model based on both a steady flow and diffusion, in which we adopt a two-step process: first fitting the SV to a steady flow, and then fitting the residual by magnetic diffusion. We assess this approach by hindcasting the evolution for 2010–2015, based on fitting the models to CHAOS-6 using time windows prior to 2010. We find that including diffusion yields a reduction of up to 25% in the global hindcast error at Earth’s surface; at the CMB this error reduction can be in excess of 77%. We show that fitting the model over the shortest window that we consider, 2009–2010, yields the lowest hindcast error. Based on our hindcast tests, we present a candidate model for the SV over 2020–2025 for IGRF-13, fit over the time window 2018.3–2019.3. Our forecasts indicate that over the next decade the axial dipole will continue to decay, reversed-flux patches will increase in both area and intensity, and the north magnetic (dip) pole will continue to migrate towards Siberia

Endoscopic complications avoidance and management

The frequency of endoscopic complications is likely to rise owing to the increased number of indications for therapeutic procedures and also to the increased complexity of endoscopic techniques. Informed patient consent should be obtained as part of the procedure. Prevention of endoscopic adverse events is based on knowledge of the relevant risk factors and their mechanisms of occurrence. Thus, suitable training of future gastroenterologists and endoscopists is required for these complex procedures. When facing a complication, appropriate management is generally provided by an early diagnosis followed by prompt therapeutic care tailored to the situation. The most common complications of diagnostic and therapeutic upper gastrointestinal endoscopy, retrograde cholangiopancreatography, small bowel endoscopy and colonoscopy are reviewed here. Different modalities of medical, endoscopic or surgical management are also considered. © 2012 Macmillan Publishers Limited. All rights reserved.SCOPUS: re.jinfo:eu-repo/semantics/publishe