Comparing conditional hedging strategies.

The traditional approach to discriminate amongst two competing hedging strategies is to compare the sample portfolio return variance implied by each strategy. This simple approach suffers from two drawbacks. First, it is an unconditional performance measure which is theoretically not coherent with a dynamic hedging strategy that minimizes the conditional portfolio return variance. Second, estimating unconditional performance over the entire period may not be sufficcient since a strategy with a good unconditional hedging performance may not perform well at a particular point in time. In this paper, I use the Giacomini and White (2006), the Wald, and the Diebold and Mariano (1995) statistical tests in order to conditionally (and as a special case, unconditionally) compare the portfolio return variances implied by two competing hedging strategies. The attractive feature of the conditional perspective is that, in case of rejection of equal conditional hedging effectiveness among two initial strategies, it provides us with a new hedging strategy that selects at each date the initial strategy that will perform the best next period, conditional on current information. An application to several agricultural commodities illustrates the technique. For daily hedging horizons, it is found that most of the time Ederington's (1979) static strategy is superior to more elaborate dynamic strategies. This calls into question earlier results reported in the literature that were based on a much smaller database.GARCH; Hedging; Strategy; Portfolio; Variance; IT; Performance; Time; Tests; Order; Effectiveness; Information; Database;

Testing futures returns predictability : implications for hedgers.

The predictability of futures returns is investigated using a semiparametric approach where it is assumed that the expected returns depend non parametrically on a combination of predictors. We first collapse the forecasting variables into a single index variable where the weights are identified up to scale, using the average derivative estimator proposed by Stoker (1986). We then use the Nadaraya-Watson kernel estimator to calculate (and visually depict) the relation between the estimated index and the expected futures returns. An application to four agricultural commodity futures illustrates the technique. The results indicate that for each of the commodities considered, the estimated index contains statistically significant information regarding the expected futures returns. Economic implications for a non-infinitely risk averse hedger are also discussed.Average derivative estimates; futures market; Hedging; Futures; Implications; Information;

Ain\u27t You Coming Back to Old New Hampshire, Molly?

https://digitalcommons.library.umaine.edu/mmb-vp/1162/thumbnail.jp

Aggressive prevention and preemptive management of vascular complications after pediatric liver transplantation: A major impact on graft survival and long-term outcome

Vascular complications are a major cause of patient and graft loss after LTs. The aim of this study was to evaluate the effect of a multimodal perioperative strategy aimed at reducing the incidence of vascular complications. A total of 126 first isolated LTs-performed between November 2008 and December 2015-were retrospectively analyzed. A minimum follow-up period of 24 months was analyzable for 124/126 patients (98.4%). The aggressive preemptive strategy consisted of identifying and immediately managing any problem and any abnormality in the vascular flow, in any of the hepatic vessels, and at any time after the liver graft revascularization. As a result, with a median follow-up of 57 months (3-112 months), not a single graft has been lost from vascular or biliary problems. The actuarial 8-year graft survival is 96.5%. These results have shown that a combination of technical attention, medical prevention, an early diagnosis, and rapid interventions reduced the negative impact of vascular problems on the outcome of both grafts and patients

A case of Incontinentia Pigmenti associated with congenital absence of portal vein system and nodular regenerative hyperplasia

Congenital absence of portal vein system (CAPVS) is a rare condition in which portal perfusion is bypassed by portosystemic shunt leading to the development of portal hypertension (PH) or porto‐systemic encephalopathy (PSE). Visceral anomalies and liver cancer can be associated with CAPVS1.Thanks to the advances in imaging, the number of CAPVS cases detected has increased. Incontinentia Pigmenti (IP) (OMIM #308300) also represents a rare condition, characterized by skin, teeth, hair, nails, eyes and central nervous system alterations, due to mutations of NEMO/IKBKG gene. We report on the first case of IP associated with CAPVS and nodular regenerative hyperplasia (NRH) of the liver, in a patient with facial dysmorphisms and speech delay. Although rare, this finding may support the role of NEMO in liver homeostasis

Rex Shunt Preoperative Imaging: Diagnostic Capability of Imaging Modalities

The purpose of this study was to evaluate the diagnostic capability of imaging modalities used for preoperative mesenteric-left portal bypass (“Rex shunt”) planning. Twenty patients with extrahepatic portal vein thrombosis underwent 57 preoperative planning abdominal imaging studies. Two readers retrospectively reviewed these studies for an ability to confidently determine left portal vein (PV) patency, superior mesenteric vein (SMV) patency, and intrahepatic left and right PV contiguity. In this study, computed tomographic arterial portography allowed for confident characterization of left PV patency, SMV patency and left and right PV continuity in 100% of the examinations. Single phase contrast-enhanced CT, multi-phase contrast-enhanced CT, multiphase contrast-enhanced MRI, and transarterial portography answered all key diagnostic questions in 33%, 30%, 0% and 8% of the examinations, respectively. In conclusion, of the variety of imaging modalities that have been employed for Rex shunt preoperative planning, computed tomographic arterial portography most reliably allows for assessment of left PV patency, SMV patency, and left and right PV contiguity in a single study

Management of hepatic epithelioid haemangio-endothelioma in children: what option?

Hepatic epithelioid haemangio-endothelioma (HEHE) is an endothelium-derived tumour of low-to-medium grade malignancy. It is predominantly seen in adults and is unresponsive to chemotherapy. Liver transplantation is an accepted indication when the tumour is unresectable. Hepatic epithelioid haemangio-endothelioma is very rare in children and results after transplantation are not reported. The aim of this study is to review the experience of three European centres in the management of HEHE in children. A retrospective review of all paediatric patients with HEHE managed in three European centres is presented. Five children were identified. Four had unresectable tumours. The first had successful resection followed by chemotherapy and is alive, without disease 3 years after diagnosis. One child died of sepsis and one of tumour recurrence in the graft and lungs 2 and 5 months, respectively, after transplant. Two children who had progressive disease with ifosfamide-based chemotherapy have had a reduction in clinical symptoms and stabilisation of disease up to 18 and 24 months after the use of platinum-based chemotherapy. HEHE seems more aggressive in children than reported in adults and the curative role of transplantation must be questioned. Ifosfamide-based chemotherapy was not effective. Further studies are necessary to confirm if HEHE progression in children may be influenced by platinum-based chemotherapy

Old and new cluster designs in emergency field surveys: in search of a one-fits-all solution

<p>Abstract</p> <p>Introduction</p> <p>Cluster surveys are frequently used to measure key nutrition and health indicators in humanitarian emergencies. The survey design of 30 clusters of 7 children (30 × 7) was initially proposed by the World Health Organization for measuring vaccination coverage, and later a design of 30 clusters of 30 children (30 × 30) was introduced to measure acute malnutrition in emergency settings. Recently, designs of 33 clusters of 6 children (33 × 6) and 67 clusters of 3 children (67 × 3) have been proposed as alternatives that enable measurement of several key indicators with sufficient precision, while offering substantial savings in time. This paper explores expected effects of using 67 × 3, 33 × 6, or 30 × 7 designs instead of a "standard" 30 × 30 design on precision and accuracy of estimates, and on time required to complete the survey.</p> <p>Analysis</p> <p>The 67 × 3, 33 × 6, and 30 × 7 designs are expected to be more statistically efficient for measuring outcomes having high design effects (e.g., vaccination coverage, vitamin A distribution coverage, or access to safe water sources), and less efficient for measuring outcomes with more within-cluster variability, such as global acute malnutrition or anemia. Because of small sample sizes, these designs may not provide sufficient levels of precision to measure crude mortality rates. Given the small number (3 to 7) of survey subjects per cluster, it may be hard to select representative samples of subjects within clusters.</p> <p>The smaller sample size in these designs will likely result in substantial time savings. The magnitude of the savings will depend on several factors, including the average travel time between clusters. The 67 × 3 design will provide the least time savings. The 33 × 6 and 30 × 7 designs perform similarly to each other, both in terms of statistical efficiency and in terms of time required to complete the survey.</p> <p>Conclusion</p> <p>Cluster designs discussed in this paper may offer substantial time and cost savings compared to the traditional 30 × 30 design, and may provide acceptable levels of precision when measuring outcomes that have high intracluster homogeneity. Further investigation is required to determine whether these designs can consistently provide accurate point estimates for key outcomes of interest. Organizations conducting cluster surveys in emergency settings need to build their technical capacity in survey design to be able to calculate context-specific sample sizes individually for each planned survey.</p

Measles outbreaks in displaced populations: a review of transmission, morbidity and mortality associated factors

<p>Abstract</p> <p>Background</p> <p>Measles is a highly contagious infectious disease with a significant public health impact especially among displaced populations due to their characteristic mass population displacement, high population density in camps and low measles vaccination coverage among children. While the fatality rate in stable populations is generally around 2%, evidence shows that it is usually high among populations displaced by disasters. In recent years, refugees and internally displaced persons have been increasing. Our study aims to define the epidemiological characteristics and risk factors associated with measles outbreaks in displaced populations.</p> <p>Methods</p> <p>We reviewed literature in the PubMed database, and selected articles for our analysis that quantitatively described measles outbreaks.</p> <p>Results</p> <p>A total of nine articles describing 11 measles outbreak studies were selected. The outbreaks occurred between 1979 and 2005 in Asia and Africa, mostly during post-conflict situations. Seven of eight outbreaks were associated with poor vaccination status (vaccination coverage; 17-57%), while one was predominantly due to one-dose vaccine coverage. The age of cases ranged from 1 month to 39 years. Children aged 6 months to 5 years were the most common target group for vaccination; however, 1622 cases (51.0% of the total cases) were older than 5 years of age. Higher case-fatality rates (>5%) were reported for five outbreaks. Consistent factors associated with measles transmission, morbidity and mortality were vaccination status, living conditions, movements of refugees, nutritional status and effectiveness of control measures including vaccination campaigns, surveillance and security situations in affected zones. No fatalities were reported in two outbreaks during which a combination of active and passive surveillance was employed.</p> <p>Conclusion</p> <p>Measles patterns have varied over time among populations displaced by natural and man-made disasters. Appropriate risk assessment and surveillance strategies are essential approaches for reducing morbidity and mortality due to measles. Learning from past experiences of measles outbreaks in displaced populations is important for designing future strategies for measles control in such situations.</p