Genomic abundance is not predictive of tandem repeat localization in grass genomes.

Highly repetitive regions have historically posed a challenge when investigating sequence variation and content. High-throughput sequencing has enabled researchers to use whole-genome shotgun sequencing to estimate the abundance of repetitive sequence, and these methodologies have been recently applied to centromeres. Previous research has investigated variation in centromere repeats across eukaryotes, positing that the highest abundance tandem repeat in a genome is often the centromeric repeat. To test this assumption, we used shotgun sequencing and a bioinformatic pipeline to identify common tandem repeats across a number of grass species. We find that de novo assembly and subsequent abundance ranking of repeats can successfully identify tandem repeats with homology to known tandem repeats. Fluorescent in-situ hybridization shows that de novo assembly and ranking of repeats from non-model taxa identifies chromosome domains rich in tandem repeats both near pericentromeres and elsewhere in the genome

Precipitation and Hydrolysis of Thorium(IV) in Aqueous Solution. II. Influence of pH and Neutral Electrolytes upon the Precipi tation in the System Thorium Nitrate - Potassium Phthalate

The influence of the pH and other neutral electrolytes upon the precipitation and hydrolysis of thorium(IV) in aqueous solutions of thorium nitrate and potassium phthalate was investigated. A three-dimensional concentration tyndallogram in which turbidity has been plotted against the concentration of potassium phthalate and the pH, at constant concentration of Th(IV) 1.25 X 10-3M, shows various precipitation and dissolution regions of th e system. The following co ncentration regions were marked and discussed: the concentration region where sudden precipitation of thorium hydroxide occurs, the region of thorium hydroxide stable sols, the region of thorium phthalate sols, the region of unstable systems in which crystals appear after a few days\u27 aging and the region of stable clear solution at rathe r high pH values. The effect of neutral electrolytes upon the precipitation in the regio n of stable clear solution was investigated. It was d etermined that neutral electrolytes influence to a great extent the prec ipitation at the boundary of thorium phthalate precipitate (pH= 5)

Precipitation · and Hydrolysis of Thorium(IV) in Aqueous Solution: Thorium Nitrate - Potassium Hydroxide. I. Determination of Solubility Constants of Th(OH)4

The precipitation and h ydrolysis 0f thorium (IV) in aqueous solutions of thorium nitrate - potassium hydroxide was investigated at 20oc with a tyndallometel\u27.\u27 a nd a pH-meter. A three-dimensional precipitation diagram for a wide r ange of concentrations of both precipitating components was constructed. The concentration region of thorium hydroxide, the fast precipitation, the formation of sols and of stable clear solutions were observed. The decreased precipitation of thorium h ydroxide at pH between 9 - 10.4 is considered to be the effect of the carbonate ions present. By a very simple graphical tyndallometric method the solubility products of thorium hydroxide were directly determined as: log K so = - 45.7; log Ks2 = - 24.3 and the cumulative hydrolytic constant */3 2 = 1.029 X 10-1 was calculated. The predominant hydrolytic species of thorium-ion in aqueous solution in equilibrium with the solid phase of Th(OH) 4 were estimated. The predominant species is the free ion Th4+ for pH 3.4 and [Th(OH)22+]n for the pH between 3.5 and 4.L At values lower pH 4.1 ionic species of thorium are formed with more than two OH- ions per one thorium ion

Social defeat stress: Mechanisms underlying the increase in rewarding effects of drugs of abuse

Social interaction is known to be the main source of stress in human beings, which explains the translational importance of this research in animals. Evidence reported over the last decade has revealed that, when exposed to social defeat experiences (brief episodes of social confrontations during adolescence and adulthood), the rodent brain undergoes remodeling and functional modifications, which in turn lead to an increase in the rewarding and reinstating effects of different drugs of abuse. The mechanisms by which social stress cause changes in the brain and behavior are unknown, and so the objective of this review is to contemplate how social defeat stress induces long-lasting consequences that modify the reward system. First of all, we will describe the most characteristic results of the short- and long-term consequences of social defeat stress on the rewarding effects of drugs of abuse such as psychostimulants and alcohol. Secondly, and throughout the review, we will carefully assess the neurobiological mechanisms underlying these effects, including changes in the dopaminergic system, corticotrophin releasing factor signaling, epigenetic modifications and the neuroinflammatory response. To conclude, we will consider the advantages and disadvantages and the translational value of the social defeat stress model, and will discuss challenges and future directions

Circumstellar interaction in supernovae in dense environments - an observational perspective

In a supernova explosion, the ejecta interacting with the surrounding circumstellar medium (CSM) give rise to variety of radiation. Since CSM is created from the mass lost from the progenitor star, it carries footprints of the late time evolution of the star. This is one of the unique ways to get a handle on the nature of the progenitor star system. Here, I will focus mainly on the supernovae (SNe) exploding in dense environments, a.k.a. Type IIn SNe. Radio and X-ray emission from this class of SNe have revealed important modifications in their radiation properties, due to the presence of high density CSM. Forward shock dominance of the X-ray emission, internal free-free absorption of the radio emission, episodic or non-steady mass loss rate, asymmetry in the explosion seem to be common properties of this class of SNe.Comment: Fixed minor typos. 31 pages, 9 figures, accepted for publication in Space Science Reviews. Chapter in International Space Science Institute (ISSI) Book on "Supernovae" to be published in Space Science Reviews by Springe

Gold(I)-Catalyzed Coupling Reactions for the Synthesis of Diverse Small Molecules Using the Build/Couple/Pair Strategy

The build/couple/pair strategy has yielded small molecules with stereochemical and skeletal diversity by using short reaction sequences. Subsequent screening has shown that these compounds can achieve biological tasks considered challenging if not impossible (‘undruggable’) for small molecules. We have developed gold(I)-catalyzed cascade reactions of easily prepared propargyl propiolates as a means to achieve effective intermolecular coupling reactions for this strategy. Sequential alkyne activation of propargyl propiolates by a cationic gold(I) catalyst yields an oxocarbenium ion that we previously showed is trapped by C-based nucleophiles at an extrannular site to yield α-pyrones. Here, we report O-based nucleophiles react by ring opening to afford a novel polyfunctional product. In addition, by coupling suitable building blocks, we subsequently performed intramolecular pairing reactions that yield diverse and complex skeletons. These pairing reactions include one based on a novel aza-Wittig-6π-electrocyclization sequence and others based on ring-closing metathesis reactions.Chemistry and Chemical Biolog

Sport, War and Democracy in Classical Athens

This article concerns the paradox of athletics in classical Athens. Democracy may have opened up politics to every class of Athenian but it had little impact on sporting participation. The city’s athletes continued to drawn predominantly from the upper class. It comes as a surprise then that lower-class Athenians actually esteemed athletes above every other group in the public eye, honoured them very generously when they won, and directed a great deal of public and private money to sporting competitions and facilities. In addition athletics escaped the otherwise persistent criticism of upper-class activities in the popular culture of the democracy. The research of social scientists on sport and aggression suggests this paradox may have been due to the cultural overlap between athletics and war under the Athenian democracy. The article concludes that the practical and ideological democratization of war by classical Athens legitimized and supported upper-class sport

The genome-wide dynamics of purging during selfing in maize

Self-fertilization (also known as selfing) is an important reproductive strategy in plants and a widely applied tool for plant genetics and plant breeding. Selfing can lead to inbreeding depression by uncovering recessive deleterious variants, unless these variants are purged by selection. Here we investigated the dynamics of purging in a set of eleven maize lines that were selfed for six generations. We show that heterozygous, putatively deleterious single nucleotide polymorphisms are preferentially lost from the genome during selfing. Deleterious single nucleotide polymorphisms were lost more rapidly in regions of high recombination, presumably because recombination increases the efficacy of selection by uncoupling linked variants. Overall, heterozygosity decreased more slowly than expected, by an estimated 35% to 40% per generation instead of the expected 50%, perhaps reflecting pervasive associative overdominance. Finally, three lines exhibited marked decreases in genome size due to the purging of transposable elements. Genome loss was more likely to occur for lineages that began with larger genomes with more transposable elements and chromosomal knobs. These three lines purged an average of 398 Mb from their genomes, an amount equivalent to three Arabidopsis thaliana genomes per lineage, in only a few generations