A quadratically convergent inexact SQP method for optimal control of differential algebraic equations

In this paper, we present an inexact sequential quadratic programming method in the context of a direct multiple shooting approach for differential algebraic equations. For the case that a numerical integration routine is used to compute the states of a relaxed differential algebraic equation, the computation of sensitivities, with respect to a large number of algebraic states, can become very expensive. To overcome this limitation, the inexact sequential quadratic programming method that we propose in this paper requires neither the computation of any sensitivity direction of the differential state trajectory, with respect to the algebraic states, nor the consistent initialization of the differential algebraic equation. We prove the locally quadratic convergence of the proposed method. Finally, we demonstrate the numerical performance of the method by optimizing a distillation column with 82 differential and 122 algebraic states. Copyright © 2012 John Wiley & Sons, Ltd.     

ZTE imaging with long‐T2 suppression

Three‐dimensional radial zero echo time (ZTE) imaging enables efficient direct MRI of tissues with rapid transverse relaxation. Yet, the feature of capturing signals with a wide range of T₂ and T₂* values is accompanied by a lack of contrast between the corresponding tissues. In particular, the targeted short‐T₂ tissues may not be easily identified, and various approaches have been proposed to generate T₂ contrast by reducing the long‐T₂ signal of water and/or fat. The aim of this work was to provide efficient long‐T₂ suppression for selective direct MRI of short‐T₂ tissues using the ZTE technique. For magnetization preparation, suppression pulses for water and fat were designed to provide both good T₂ selectivity and off‐resonance performance. To obtain high efficiency at short TRs, the pulses were applied in a segmented sequence scheme with minimized timing overhead, thus leading to a quasi‐steady state of magnetization. The sequence timing was adjusted for optimal tissue contrast in musculoskeletal applications by means of simulations and experiments, incorporating both T₂ and T₁ of the involved tissues. The developed technique was employed for imaging of a lamb joint sample at 4.7 T. ZTE images were obtained with effective suppression of signals from tissues with long‐T2 water, such as muscle or articular spaces, and fat. Hence, primarily short‐T₂ tissues were visible, such as bone and tendon. The MR image intensity of bone showed strong similarity with bone density imaged with micro‐computed tomography. Copyright © 2014 John Wiley & Sons, Ltd.     

Risk–benefit assessment of closed intra-abdominal drains after pancreatic surgery: a systematic review and meta-analysis assessing the current state of evidence

Background  

This systematic review aims to analyse the risk–benefit association of (1) prophylactic drains and/or (2) the time of their removal after pancreatic resection.     

Cardiac arrest caused by acute intoxication—insight from a registry

IntroductionThe aim of the study was to evaluate the epidemiology and outcome after cardiac arrest caused by intoxication.MethodsA retrospective analysis of 1991 to 2010 medical record of patients experiencing cardiac arrest caused by self-inflicted, intentional intoxication was performed. The setting was an emergency department of a tertiary care university hospital. The primary end point was the presentation of epidemiologic data in relation to favorable neurologic outcome, defined as cerebral performance categories 1 or 2 and 180-day survival. Furthermore, the patients were subdivided into a single-substance and polysubstance group, depending on the substances causing the intoxication.ResultsOf 3644 patients admitted to our department, 99 (2.7%) with a median age of 26 (interquartile range, 19-42) years (37% female) were included. Cardiac arrest was witnessed in 62 cases (63%). Eleven patients (11%) received basic life support by bystanders, and 11 (11%) had a shockable rhythm in the initial electrocardiogram. The combined end point “good survival” was achieved by 34 patients (34%). Cardiac arrest occurred out of hospital in 73 patients (74%) and in-hospital in 26 patients (26%). A single substance causing the intoxication was found in 56 patients (56%). Opiates were the leading substance, with 25 patients (25%) using them.ConclusionCardiac arrest caused by intoxication is found predominately in young patients. Overall, favorable neurologic survival was achieved in 34%. Opiate-related cardiac arrest was associated with poor survival and a high incidence of neurologic deficits.     

Separation of collagen‐bound and porous bone water transverse relaxation in mice: proposal of a multi‐step approach

The separation and quantification of collagen‐bound water (CBW) and pore water (PW) components of the cortical bone signal are important because of their different contribution to bone mechanical properties. Ultrashort TE (UTE) imaging can be used to exploit the transverse relaxation from CBW and PW, allowing their quantification. We tested, for the first time, the feasibility of UTE measurements in mice for the separation and quantification of the transverse relaxation of CBW and PW in vivo using three different approaches for T₂* determination. UTE sequences were acquired at 4.7 T in six mice with 10 different TEs (50–5000 μs). The transverse relaxation time T₂* of CBW (T₂*_cbw) and PW (T₂*_pw) and the CBW fraction (bwf) were computed using a mono‐exponential (i), a standard bi‐exponential (ii) and a new multi‐step bi‐exponential (iii) approach. Regions of interest were drawn at multiple levels of the femur and vertebral body cortical bone for each mouse. The sum of the normalized squared residuals (Res) and the homogeneity of variance were tested to compare the different methods. In the femur, approach (i) yielded mean T₂* ± standard deviation (SD) of 657 ± 234 μs. With approach (ii), T₂*_cbw, T₂*_pw and bwf were 464 ± 153 μs, 15 777 ± 10 864 μs and 57.6 ± 9.9%, respectively. For approach (iii), T₂*_cbw, T₂*_pw and bwf were 387 ± 108 μs, 7534 ± 2765 μs and 42.5 ± 6.2%, respectively. Similar values were obtained from vertebral bodies. Res with approach (ii) was lower than with the two other approaches (p < 0.007), but T₂*_pw and bwf variance was lower with approach (iii) than with approach (ii) (p < 0.048). We demonstrated that the separation and quantification of cortical bone water components with UTE sequences is feasible in vivo in mouse models. The direct bi‐exponential approach exhibited the best approximation to the measured signal curve with the lowest residuals; however, the newly proposed multi‐step algorithm resulted in substantially lower variability of the computed parameters. Copyright © 2016 John Wiley & Sons, Ltd.     

The Short-Term Impact of a Paranoid Explanation on Self-esteem: An Experimental Study

Low self-esteem and negative emotions often precede paranoid delusions. Theories have suggested that delusions might have a short term ‘stabilizing’ effect. The present pilot study tests whether a conspiracy explanation for social exclusion exerts a short-term positive effect on self-esteem and emotions compared to a self-blaming explanation but is not beneficial for the maintenance of self-esteem in the longer run. A sample from the general population (N = 60) was randomly assigned to a conspiracy, self-blaming or neutral explanation condition after being socially excluded in a virtual ball game. Self-esteem and emotions were assessed at four time-points (prior to exclusion, after exclusion, directly after and 15 min after receiving the explanation for the exclusion). There was a significant interaction of time and condition (F = 12.36, p ≤ 0.001) in support of the hypothesis that the conspiracy condition increases self-esteem more than the self-blame condition. There was a marginally significant effect for the conspiracy condition to decrease anxiety directly after receiving the explanation (F = 4.04, p = 0.05) more strongly than the self-blame condition and a trend for sadness (F = 3.17, p = 0.08). Finally, there was a trend for a stronger longer-term recovery of self-esteem in the neutral compared to the conspiracy condition (F = 3.41, p = 0.07). The results support the hypothesis that paranoid explanations lead to short-term stabilization of self-esteem.