Rank reduction of correlation matrices by majorization

In this paper a novel method is developed for the problem of finding a low-rank correlation matrix nearest to a given correlation matrix. The method is based on majorization and therefore it is globally convergent. The method is computationally efficient, is straightforward to implement, and can handle arbitrary weights on the entries of the correlation matrix. A simulation study suggests that majorization compares favourably with competing approaches in terms of the quality of the solution within a fixed computational time. The problem of rank reduction of correlation matrices occurs when pricing a derivative dependent on a large number of assets, where the asset prices are modelled as correlated log-normal processes.correlation matrix;lognormal price processes;majorization;rank

Rassenvergelijking Regioras: Kostelijk Brabant 2013

Een belangrijke stap om kennis over zaadvermeerdering en veredeling onder telers in stand te houden is bewustzijn van raskenmerken te bevorderen, dat wil zeggen het bewustzijn dat niet alle rassen voor alle teeltsystemen geschikt zijn. Zo geldt dit met name voor biologische abonnemententelers in Brabant die op zandgrond werken. Groenteveredeling richt zich op grootschalige intensieve teelt op vruchtbare (klei) bodems. Deze rassen zijn steeds minder geschikt voor biologische abonnemententelers. De opzet van dit project was om specifiek met deze Noord‐Brabantse telers van drie gewassen een rassenvergelijking op te zetten (veldsla, boerenkool en rode biet), per gewas vijf rassen, en de kwaliteit gezamenlijk te vergelijken

Synthesis of monoalkylated calix[4]arenes via direct alkylation

A new one-step procedure for the synthesis of monoalkylated calix[4]arenes is presented. Reaction of calix[4]arene 1a or 1b with 1.2 equivalent of a weak base (K2CO3 in MeCN or CsF in DMF) and excess of alkylating agent affords the monoalkylated calix[4]arenes in moderate to good yield

Participatory plant breeding: a way to arrive at better-adapted onion varieties

The search for varieties that are better adapted to organic farming is a current topic in the organic sector. Breeding programmes specific for organic agriculture should solve this problem. Collaborating with organic farmers in such programmes, particularly in the selection process, can potentially result in varieties better adapted to their needs. Here, we assume that organic farmers' perceptive of plant health is broader than that of conventional breeders. Two organic onion farmers and one conventional onion breeder were monitored in their selection activities in 2004 and 2005 in order to verify whether and in which way this broader view on plant health contributes to improvement of organic varieties. They made selections by positive mass selection in three segregating populations under organic conditions. The monitoring showed that the organic farmers selected in the field for earliness and downy mildew and after storage for bulb characteristics. The conventional breeder selected only after storage. Farmers and breeder applied identical selection directions for bulb traits as a round shape, better hardness and skin firmness. This resulted in smaller bulbs in the breeders’ populations, while the bulbs in the farmer populations were bigger than in the original population. In 2006 and 2007 the new onion populations will be compared with each other and the original populations to determine the selection response

Buitenzorg Ayrshire Farm Breeding Diagram

A diagram of a family tree of the Ayrshire cows on Ralph LeCocq\u27s farm, with photos and descriptions.https://nwcommons.nwciowa.edu/lecocqfarm/1000/thumbnail.jp

De zaadteelt van ui (Allium cepa) - Handleiding voor zaadteelt en selectie

Deze handleiding is met name bedoeld voor telers die met zaadteelt en/of selectie aan de gang willen gaan onder Nederlandse klimaatomstandigheden. Deze handleiding is gebaseerd op veel praktische ervaring uit het veld, deels ervaring vanuit (oude)vakliteratuur, en deels door interviews met ervaren zaadtelers en selecteurs

Review of the initial validation and characterization of a chicken 3K SNP array.

In 2004 the chicken genome sequence and more than 2.8 million single nucleotide polymorphisms (SNPs) were reported. This information greatly enhanced the ability of poultry scientists to understand chicken biology, especially with respect to identification of quantitative trait loci (QTL) and genes that control simple and complex traits. To validate and address the quality of the reported SNPs, assays for 3072 SNPS were developed and used to genotype 2576 DNAs isolated from commercial and experimental birds. Over 90% of the SNPs were valid based on the criterion used for segregating, and over 88% had a minor allele frequency of 2% or greater. As the East Lansing (EL) and Wageningen University (WAU) reference panels were genotyped, 1933 SNPs were added to the chicken genetic map, which was used in the second chicken genome sequence assembly. It was also discovered that linkage disequilibrium varied considerably between commercial layers and broilers; with the latter having haplotype blocks averaging 10 to 50 kb in size. Finally, it was estimated that commercial lines have lost 70% or more of their genetic diversity, with the majority of allele loss attributable to the limited number of chicken breeds used

Cholesterol efflux pathways, inflammation, and atherosclerosis

Plasma levels of high-density lipoprotein (HDL) inversely correlate with the incidence of cardiovascular diseases (CVD). The causal relationship between plasma HDL-cholesterol levels and CVD has been called into question by Mendelian randomization studies and the majority of clinical trials not showing any benefit of plasma HDL-cholesterol raising drugs on CVD. Nonetheless, recent Mendelian randomization studies including an increased number of CVD cases compared to earlier studies have confirmed that HDL-cholesterol levels and CVD are causally linked. Moreover, several studies in large population cohorts have shown that the cholesterol efflux capacity of HDL inversely correlates with CVD. Cholesterol efflux pathways exert anti-inflammatory and antiatherogenic effects by suppressing proliferation of hematopoietic stem and progenitor cells, and inflammation and inflammasome activation in macrophages. Cholesterol efflux pathways also suppress the accumulation of cholesteryl esters in macrophages, i.e. macrophage foam cell formation. Recent single-cell RNASeq studies on atherosclerotic plaques have suggested that macrophage foam cells have lower expression of inflammatory genes than non-foam cells, probably reflecting liver X receptor activation, upregulation of ATP Binding Cassette A1 and G1 cholesterol transporters and suppression of inflammation. However, when these pathways are defective lesional foam cells may become pro-inflammatory

Computational techniques for applied econometric analysis of macroeconomic and financial processes

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