Extremal dependence structures and bounds of Tail Value-at-Risk

Session 2Organized by The University of Hong Kong & Society of Actuaries (SOA)In quantitative risk management, we often need to deal with risk aggregation with dependence uncertainty. In this session, we examine several extremal positive and negative dependence structures. We will also discuss their relationships with upper and lower bounds of concave distortion risk measures of aggregate risks.published_or_final_versio

Characterizing mutual exclusivity as the strongest negative multivariate dependence structure

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Bounds for sums of random variables when the marginal distributions and the variance of the sum are given

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Surgical treatment of acute TB spondylitis: indications and outcomes

Introduction: Spinal tuberculosis represents a challenging disease to treat, not because of the technical expertise or the time required to cure it, but more so because of the decisions involved to treat it. The Medical Research Council (MRC) Working Party on Tuberculosis of the Spine designed trials to help address several questions. Methods: A comprehensive literature search was performed using PubMed Medline, including English articles from 1934 to 1012, which pertain to spinal tuberculosis, with special effort in tracing the 13 MRC reports. The primary focus was on disease eradication, fusion rate, and a secondary focus on both short and long-term results in terms of disease recurrence and alignment. Additional searches were made on the use of spinal implants for infection cases. Results: After reviewing MRC and non-MRC reports, it was evident that the "Hong Kong operation", which involved radical debridement and strut grafting the lesion, produced better short-, medium- and long-term results in such aspects as fusion rate, spinal deformity and relapse of abscess/sinus. Subsequent work by others demonstrated the importance of prevention of progressive kyphosis, therefore the need to identify risk factors for these and pre-emptive measures such as kyphosis correction, careful graft selection, and instrumentation. Conclusion: Improvement in quality of life is also accompanied by higher patient expectations. Though developing nations may lack the resources now, eventually patients will demand better functional and cosmetic results after being afflicted by this disfiguring and potentially disabling disease, and the "Hong Kong operation" represented the best outcome, provided resources were available. © 2012 The Author(s).published_or_final_versio

Initial motion of a rectangular object being pushed or pulled

Techniques are described for determining the location of the initial center of rotation (COR) of a rectangular bar being pushed or pulled. The initial COR is the point about which the bar first rotates when the pushing or pulling force is applied. This point characterizes the initial motion of the bar. Also investigated is how the location of the initial COR varies with the magnitude of the exerted force. The minimum effort criterion is proved to be able to predict the quasi-static centre of rotation. It is found that the initial COR always lies between the quasi-static and the impulsive CORs and that it will move towards the impulsive COR as the magnitude of the applied force increases. It is shown that there exists a point on an object such that, when the force is applied at that point, the object will start to rotate about a known point.published_or_final_versio

Investigation on semi-active control of vehicle suspension using adaptive inerter

The analysis of passive control with inerter in suspension system has been well studied in previous work by employing different configurations and optimizing the spring stiffness, damping coefficient and inertance simultaneously. In this paper, we study the suspension performance with semi-active control under the assumption that the inertance may be adjusted in real-time. The suspension system is designed to attenuate the vertical acceleration of the sprung mass. A quarter-car model is considered, and the inerter is installed parallel to the spring and damper. First, an analysis is provided on the influence of a fixed inerter to a given suspension system. Then, a state-feedback H2 controller for active suspension system is designed. The active force is approximated by an inerter with adaptive inertance. Simulation results show that comparing with the passive suspension with a fixed inerter, the designedH2 controller realized by adaptive inerter can achieve good improvement of ride comfort at the sprung mass natural frequency at the expense of a relatively small deterioration at the unsprung mass natural frequency. Copyright © (2014) by the International Institute of Acoustics & Vibration All rights reserved.postprin

Automatic boundary extraction and rectification of bony tissue in CT images using artificial intelligence techniques

A novel approach is presented for fully automated boundary extraction and rectification of bony tissue from planar CT data. The approach extracts and rectifies feature boundary in a hierarchical fashion. It consists of a fuzzy multilevel thresholding operation, followed by a small void cleanup procedure. Then a binary morphological boundary detector is applied to extract the boundary. However, defective boundaries and undesirable artifacts may still be present. Thus two innovative anatomical knowledge based algorithms are used to remove the undesired structures and refine the erroneous boundary. Results of applying the approach on lumbar CT images are presented, with a discussion of the potential for clinical application of the approach.published_or_final_versio

Antimicrobial prophylaxis to prevent surgical site infection in adolescent idiopathic scoliosis patients undergoing posterior spinal fusion: 2 doses versus antibiotics till drain removal

PURPOSE: There is much variation in the choice, timing and duration of antimicrobial prophylaxis for preventing surgical site infections (SSI) but no guideline exists for scoliosis surgery. The aim of study was to compare the efficacy of two antimicrobial prophylaxis (AMP) protocols with cephazolin in preventing SSI in adolescent idiopathic scoliosis (AIS). METHODS: A retrospective comparative analysis of two post-operative AMP protocols (two postoperative doses versus continued antibiotics till drain removal) was performed. Patient characteristics, pre-operative, intra- and post-operative risk factors for infection, drain use, generic drug name and number of doses administered were recorded from 226 patients with AIS who had undergone posterior spinal fusion. Details of superficial or deep SSI and wound healing aberrations, and serious adverse events were recorded. Analysis was performed to evaluate differences in the pre-, intra- and post-operative variables between the two groups. RESULTS: 155 patients received 2 postoperative doses of AMP and 71 patients had antibiotics till drain removal. The average follow-up was 43 months. The overall rate of SSI was 1.7 % for the spine wound and 1.3 % for the iliac crest wound. 1.9 % of patients with 2 doses of AMP and 1.4 % of patients with antibiotics till drain removal had SSI. No adverse reactions attributable to cephazolin were observed. CONCLUSIONS: This is the first study on the AMP protocol in scoliosis surgery for SSI prevention. Results suggest that two doses of AMP are as effective as continued antimicrobial use until drain removal. Cephazolin appears to be effective and safe for prophylaxis.postprin

Motivating smokers at outdoor public smoking hotspots to have a quit attempt with a nicotine replacement therapy sample: study protocol for a randomized controlled trial

© 2016 Cheung et al.Background: About half of the daily smokers in Hong Kong have never tried and have no intention to quit smoking. More than one-third (37.9 %) of daily smokers have attempted to quit but failed. Nicotine replacement therapy (NRT) is a safe and effective pharmacotherapy to increase abstinence by reducing withdrawal symptoms during the early stage of smoking abstinence. However, the prevalence of NRT use in Hong Kong is lower than in most developed countries. The proposed study aims to assess the effectiveness of providing free NRT samples to smokers on increasing quit attempts and the quit rate. Methods: Trained university undergraduate students as ambassadors will invite smokers at outdoor public smoking hotspots to participate in the randomized controlled trial, in which eligible smokers will be randomized to receive a 1-week free NRT sample and medication counselling (intervention) or advice to purchase NRT on their own (control). The primary outcome is self-reported quit attempts (no smoking for at least 24 hours) in the past 30 days at 1-month and 3-month telephone follow-up. Discussion: The findings will inform the effectiveness of delivering free NRT samples at outdoor public smoking hotspots to increase quit attempts and abstinence. The study will also provide information on smokers' adherence to the NRT sample, side effects and safety issues related to the usage. This will improve the design of a large trial to test the effect of the NRT sample. Trial registration: ClinicalTrials.gov NCT02491086. Registered on 7 July 2015.published_or_final_versio

Magnetically controlled growing rods for severe spinal curvature in young children: A prospective case series

Scoliosis in skeletally immature children is often treated by implantation of a rod to straighten the spine. Rods can be distracted (lengthened) as the spine grows, but patients need many invasive operations under general anaesthesia. Such operations are costly and associated with negative psychosocial outcomes. We assessed the eff ectiveness and safety of a new magnetically controlled growing rod (MCGR) for non-invasive outpatient distractions. Methods We implanted the MCGR in fi ve patients, two of whom have now reached 24 months' follow-up. Each patient underwent monthly outpatient distractions. We used radiography to measure the magnitude of the spinal curvature, rod distraction length, and spinal length. We assessed clinical outcome by measuring the degree of pain, function, mental health, satisfaction with treatment, and procedure-related complications. Findings In the two patients with 24 months' follow-up, the mean degree of scoliosis, measured by Cobb angle, was 67° (SD 10°) before implantation and 29° (4°) at 24 months. Length of the instrumented segment of the spine increased by a mean of 1·9 mm (0·4 mm) with each distraction. Mean predicted versus actual rod distraction lengths were 2·3 mm (1·2 mm) versus 1·4 mm (0·7 mm) for patient 1, and 2·0 mm (0·2 mm) and 2·1 mm (0·7 mm) versus 1·9 mm (0·6 mm) and 1·7 mm (0·8 mm) for patient 2's right and left rods, respectively. Throughout follow-up, both patients had no pain, had good functional outcome, and were satisfi ed with the procedure. No MCGR-related complications were noted. Interpretation The MCGR procedure can be safely and eff ectively used in outpatient settings, and minimises surgical scarring and psychological distress, improves quality of life, and is more cost-eff ective than is the traditional growing rod procedure. The technique could be used for non-invasive correction of abnormalities in other disorders.postprin