The formulation of the National Centers for Environmental Prediction four-dimensional variational dataassimilation (4D-Var) system is described. Results of applying 4D-Var over a one-week assimilation period, with a full set of physical parametrizations, are presented and compared with those of 3D-Var. The linearization has been performed without simplifications and, therefore, the tangent-line...

Compact chromatin structure, induction of gene silencing in position-effect variegation (PEV), and crossing-over suppression are typical features of heterochromatin. To identify genes affecting crossing-over suppression by heterochromatin we tested PEV suppressor mutations for their effects on crossing over in pericentromeric regions of Drosophila autosomes. From the 46 mutations (28 loci) stud...

A variety of methods is available to estimate a portfolio’s Value-at-Risk. Aside from the overall VaR there is an apparent need for information about marginal VaR, component VaR and incremental VaR. Expressions for these VaR metrics have been derived under the restrictive normality assumption. In this paper we investigate these VaR concepts in an elliptical world and in a general distribution-f...

Antigenic variation in the human malaria parasite Plasmodium falciparum depends on the transcriptional regulation of the var gene family. In each individual parasite, mRNA is expressed exclusively from 1 var gene out of ∼60, while the rest of the genes are transcriptionally silenced. Both modifications to chromatin structure and DNA regulatory elements associated with each var gene have been im...

Cyclopoid copepods and mosquito larvae were surveyed in southwestern Louisiana rice fields. Almost every rice field had a natural population of Mesocyclops ruttneri, Acanthocylops vernalis, or Macrocyclops albidus. Judging from the abundance of pupae, 29% of the fields were responsible for virtually all Anopheles quadrimaculatus production, apparently because larval mortality suppressed product...

Austral summer frosts in the Andean highlands are ubiquitous throughout the crop cycle, causing yield losses. In spite of the existing warming trend, climate change models forecast high variability, including freezing temperatures. As the potato center of origin, the region has a rich biodiversity which includes a set of frost resistant genotypes. Four contrasting potato genotypes--representing...

MARCH 2003 THE JOURNAL OF FIXED INCOME 81 V alue at risk modelers face difficult trade-offs in choosing between the two major VaR methodologies: historical/ Monte Carlo simulations or parametric models. The historical approach uses the recent history of the asset price (or, for derivatives, the price of the underlying), while the parametric approach imposes functional form assumptions upon the ...

After publication of the article [1], it has been brought to our attention that the original version of this Article contained a typo in the 3rd paragraph of the section 'Review process and data extraction'. It concerns the equation published as "Var(lnRR) = Var(lnR1 + lnR0)". On the right part, the "+" within the parenthesis should be "-", as defined and derived from the left part. As a result...

Expected Shortfall (ES) is the average return on a risky asset conditional on the return being below some quantile of its distribution, namely its Value-at-Risk (VaR). The Basel III Accord, which will be implemented in the years leading up to 2019, places new attention on ES, but unlike VaR, there is little existing work on modeling ES. We use recent results from statistical decision theory to ...