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;

Handbook of methods for the analysis of the various parameters of the carbon dioxide system in sea water. Version 2

The collection of extensive, reliable, oceanic carbon data is a key component of the Joint Global Ocean Flux Study (JGOFS). A portion of the US JGOFS oceanic carbon dioxide measurements will be made during the World Ocean Circulation Experiment Hydrographic Program. A science team has been formed to plan and coordinate the various activities needed to produce high quality oceanic carbon dioxide measurements under this program. This handbook was prepared at the request of, and with the active participation of, that science team. The procedures have been agreed on by the members of the science team and describe well tested methods. They are intended to provide standard operating procedures, together with an appropriate quality control plan, for measurements made as part of this survey. These are not the only measurement techniques in use for the parameters of the oceanic carbon system; however, they do represent the current state-of-the-art for ship-board measurements. In the end, the editors hope that this handbook can serve widely as a clear and unambiguous guide to other investigators who are setting up to analyze the various parameters of the carbon dioxide system in sea water

Anthropogenic carbon distribution in the eastern South Pacific Ocean

We present results of the CO(2)/carbonate system from the BIOSOPE cruise in the Eastern South Pacific Ocean, in an area not sampled previously. In particular, we present estimates of the anthropogenic carbon (C(ant)(TrOCA)) distribution in the upper 1000m of this region using the TrOCA method. The highest concentrations of C(ant)(TrOCA) found around 13 degrees S, 132 degrees W and 32 degrees S, 91 degrees W, are higher than 80 mu mol.kg(-)1 and 70 mu mol.kg(-1), respectively. The lowest concentrations are observed below 800m depth (<= 2 mu mol.kg(-1)) and within the Oxygen Minimum Zone (OMZ), mainly around 140 degrees W (< 11 mu mol.kg(-1)). As a result of the anthropogenic carbon penetration there has been decrease in pH by over 0.1 on an average in the upper 200 m. This work further improves our understanding on the penetration of anthropogenic carbon in the Eastern Pacific Ocean

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

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

Distribution of lipid biomarkers and carbon isotope fractionation in contrasting trophic environments of the South East Pacific

The distribution of lipid biomarkers and their stable carbon isotope composition was investigated on suspended particles from different contrasting trophic environments at six sites in the South East Pacific. High algal biomass with diatom-related lipids (24-methylcholesta-5,24(28)-dien-3&amp;beta;-ol, C&lt;sub&gt;25&lt;/sub&gt; HBI alkenes, C&lt;sub&gt;16:4&lt;/sub&gt; FA, C&lt;sub&gt;20:5&lt;/sub&gt; FA) was characteristic in the upwelling zone, whereas haptophyte lipids (long-chain (C&lt;sub&gt;37&lt;/sub&gt;-C&lt;sub&gt;39&lt;/sub&gt;) unsaturated ketones) were proportionally most abundant in the nutrient-poor settings of the centre of the South Pacific Gyre and on its easter edge. The dinoflagellate–sterol, 4&amp;alpha;-23,24-trimethylcholest-22(&lt;i&gt;E&lt;/i&gt;)-en-3&amp;beta;-ol, was a minor contributor in all of the studied area and the cyanobacteria-hydrocarbon, C&lt;sub&gt;17&lt;/sub&gt;&lt;i&gt;n&lt;/i&gt;-alkane, was at maximum in the high nutrient low chlorophyll regime of the subequatorial waters near the Marquesas archipelago. &lt;br&gt;&lt;br&gt; The taxonomic and spatial variability of the relationships between carbon photosynthetic fractionation and environmental conditions for four specific algal taxa (diatoms, haptophytes, dinoflagellates and cyanobacteria) was also investigated. The carbon isotope fractionation factor (&amp;epsilon;&lt;sub&gt;p&lt;/sub&gt;) of the 24-methylcholesta-5,24(28)-dien-3&amp;beta;-ol diatom marker, varied over a range of 16% along the different trophic systems. In contrast, &amp;epsilon;&lt;sub&gt;p&lt;/sub&gt; of dinoflagellate, cyanobacteria and alkenone markers varied only by 7–10&amp;permil;. The low fractionation factors and small variations between the different phytoplankton markers measured in the upwelling area likely reveals uniformly high specific growth rates within the four phytoplankton taxa, and/or that transport of inorganic carbon into phytoplankton cells may not only occur by diffusion but also by other carbon concentrating mechanisms (CCM). In contrast, in the oligotrophic zone, i.e. gyre and eastgyre, relatively high &amp;epsilon;&lt;sub&gt;p&lt;/sub&gt; values, especially for the diatom marker, indicate diffusive CO&lt;sub&gt;2&lt;/sub&gt; uptake by the eukaryotic phytoplankton. At these nutrient-poor sites, the lower &amp;epsilon;&lt;sub&gt;p&lt;/sub&gt; values for haptophytes, dinoflagellates and cyanobacteria indicate higher growth rates or major differences on the carbon uptake mechanisms compared to diatoms

Thermodynamic Forecasts of the Mediterranean Sea Acidification

Anthropogenic CO2 is a major driver of the present ocean acidification. This latter is threatening the marine ecosystems and has been identified as a major environmental and economic menace. This study aims to forecast from the thermodynamic equations, the acidification variation (ΔpH) of the Mediterranean waters over the next few decades and beyond this century. In order to do so, we calculated and fitted the theoretical values based upon the initial conditions from data of the 2013 MedSeA cruise. These estimates have been performed both for the Western and for the Eastern basins based upon their respective physical (temperature and salinity) and chemical (total alkalinity and total inorganic carbon) properties. The results allow us to point out four tipping points, including one when the Mediterranean Sea waters would become acid (pH<7). In order to provide an associated time scale to the theoretical results, we used two of the IPCC (2007) atmospheric CO2 scenarios. Under the most optimistic scenario of the “Special Report: Emissions Scenarios” (SRES) of the IPCC (2007), the results indicate that in 2100, pH may decrease down to 0.245 in the Western basin and down to 0.242 in the Eastern basin (compared to the pre-industrial pH). Whereas for the most pessimistic SRES scenario of the IPCC (2007), the results for the year 2100, forecast a pH decrease down to 0.462 and 0.457, for the Western and for the Eastern basins, respectively. Acidification, which increased unprecedentedly in recent years, will rise almost similarly in both Mediterranean basins only well after the end of this century. These results further confirm that both basins may become undersaturated (< 1) with respect to calcite and aragonite (at the base of the mixed layer depth), only in the far future (in a few centuries)

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