The orientation and kinematics of inner tidal tails around dwarf galaxies orbiting the Milky Way

Using high-resolution collisionless N-body simulations we study the properties of tidal tails formed in the immediate vicinity of a two-component dwarf galaxy evolving in a static potential of the Milky Way (MW). The stellar component of the dwarf is initially in the form of a disk and the galaxy is placed on an eccentric orbit motivated by CDM-based cosmological simulations. We measure the orientation, density and velocity distribution of the stars in the tails. Due to the geometry of the orbit, in the vicinity of the dwarf, where the tails are densest and therefore most likely to be detectable, they are typically oriented towards the MW and not along the orbit. We report on an interesting phenomenon of `tidal tail flipping': on the way from the pericentre to the apocentre the old tails following the orbit are dissolved and new ones pointing towards the MW are formed over a short timescale. We also find a tight linear relation between the velocity of stars in the tidal tails and their distance from the dwarf. Using mock data sets we demonstrate that if dwarf spheroidal (dSph) galaxies in the vicinity of the MW are tidally affected their kinematic samples are very likely contaminated by tidally stripped stars which tend to artificially inflate the measured velocity dispersion. The effect is stronger for dwarfs on their way from the peri- to the apocentre due to the formation of new tidal tails after pericentre. Realistic mass estimates of dSph galaxies thus require removal of these stars from kinematic samples.Comment: 8 pages, 7 figures, accepted for publication in MNRA

Search for gamma-ray emission from magnetars with the Fermi Large Area Telescope

We report on the search for 0.1-10 GeV emission from magnetars in 17 months of Fermi Large Area Telescope (LAT) observations. No significant evidence for gamma-ray emission from any of the currently-known magnetars is found. The most stringent upper limits to date on their persistent emission in the Fermi-LAT energy range are estimated between ~10^{-12}-10^{-10} erg/s/cm2, depending on the source. We also searched for gamma-ray pulsations and possible outbursts, also with no significant detection. The upper limits derived support the presence of a cut-off at an energy below a few MeV in the persistent emission of magnetars. They also show the likely need for a revision of current models of outer gap emission from strongly magnetized pulsars, which, in some realizations, predict detectable GeV emission from magnetars at flux levels exceeding the upper limits identified here using the Fermi-LAT observations.Comment: ApJ Letters in press; Corresponding authors: Caliandro G. A., Hadasch D., Rea N., Burnett

The genome of the seagrass Zostera marina reveals angiosperm adaptation to the sea

Seagrasses colonized the sea(1) on at least three independent occasions to form the basis of one of the most productive and widespread coastal ecosystems on the planet(2). Here we report the genome of Zostera marina (L.), the first, to our knowledge, marine angiosperm to be fully sequenced. This reveals unique insights into the genomic losses and gains involved in achieving the structural and physiological adaptations required for its marine lifestyle, arguably the most severe habitat shift ever accomplished by flowering plants. Key angiosperm innovations that were lost include the entire repertoire of stomatal genes(3), genes involved in the synthesis of terpenoids and ethylene signalling, and genes for ultraviolet protection and phytochromes for far-red sensing. Seagrasses have also regained functions enabling them to adjust to full salinity. Their cell walls contain all of the polysaccharides typical of land plants, but also contain polyanionic, low-methylated pectins and sulfated galactans, a feature shared with the cell walls of all macroalgae(4) and that is important for ion homoeostasis, nutrient uptake and O-2/CO2 exchange through leaf epidermal cells. The Z. marina genome resource will markedly advance a wide range of functional ecological studies from adaptation of marine ecosystems under climate warming(5,6), to unravelling the mechanisms of osmoregulation under high salinities that may further inform our understanding of the evolution of salt tolerance in crop plants(7)

Economy and Divorces: Their Impact Over Time on the Self-Employment Rates in Spain

The paper used time-series data and examined the effect of economic and social variables on the male and female self-employment rates in Spain. We also employed cointegration analysis (with and without) structural breaks. We thus find strong evidence that long run relationships exist among the variables. More precisely, we find that the unemployment rates and the ratio of self-employment to employees’ earnings have a positive effect on self-employment, whereas, economic development and divorce rates have a negative effect. Importantly, we find that the economic variables have equal or stronger long run impact on females than males, with both groups reacting to changes in family circumstances. Finally, we show that the short run family circumstances are better predictors of self-employment choices rather than economic factors, with self-employment being a means of adjustment to new personal circumstances and economic needs

Dioxin levels in imported dairy products

De resultaten worden beschreven van een studie naar de gehalten van PCDD's en PCDF's in geimporteerde zuivelproducten. In november 1995 zijn door de Regionale Inspecties Gezondheidsbescherming monsters geimporteerde melk en kaas verzameld van verschillende producenten in Duitsland, Belgie en Frankrijk. De monstername werd uitgevoerd bij belangrijke importeurs van Franse kaas en supermarkten met een groot marktaandeel, gesitueerd in verschillende regio's verspreid over Nederland. Uit de ingezamelde melkmonsters werden zestien tijdgemiddelde mengmonsters samengesteld van melk geproduceerd door fabrieken gelegen in diverse regio's in Duitsland en Belgie. Daarnaast werd in het analyseprogramma een monster Franse schapenkaas opgenomen, alsmede een drietal mengmonsters van verschillende typen Franse kaas geproduceerd op basis van koemelk. De chemische analyse omvatte de bepaling van de zeventien 2,3,7,8-chloorgesubstitueerde PCDD- en PCDF-congeneren in de vette fractie van de monsters. Uit de congeneer-specifieke gegevens is een dioxinegehalte uitgedrukt in toxische equivalenten van 2,3,7,8-TCDD (TEQ's) afgeleid, waarbij gebruik is gemaakt van de Internationale Toxiciteits Equivalentie Factoren (i-TEF's). In alle onderzochte monsters werden dioxinegehalten aangetoond die ruim beneden de warenwetnorm van 6 pg (i)-TEQ/g vet liggen. De dioxinegehalten in melk geimporteerd uit Duitsland liepen uiteen van 0.3 tot 1.2 pg (i)-TEQ/g melkvet. De gehalten in de Belgische melkmonsters varieerden van 1.4 tot 2.7 pg (i)-TEQ/g vet, en de gehalten in de Franse kazen lagen tussen 0.5 en 1.2 pg (i)-TEQ/g vet. Als de waargenomen gehalten worden vergeleken met eerder gerapporteerde gegevens over consumptiemelk verzameld in Nederland in de periode 1992-1993, waarin de dioxinegehalten varieerden van 0.9-2.1 pg (i)-TEQ/g vet (Liem et al., 1996), suggereren de meetgegevens lagere gehalten in Duitse en hogere gehalten in Belgische melk. De representativiteit van de onderzochte monsters kent echter enige restricties. Op grond hiervan kan daarom niet worden beoordeeld in hoeverre de verschillen statistische betekenis hebben. De verschillen zijn echter gering. Daarom bestaat er op grond van de gegevens voortvloeiend uit dit onderzoek geen aanleiding om nader onderzoek uit te voeren.Results are presented from a study on the occurrence of PCDDs and PCDFs in imported dairy products. In November 1995, samples of consumer milk and cheese imported from different producers in Germany, Belgium and France have been collected by Regional Inspectorates for Health Protection at major importers and supermarkets in various regions distributed over the Netherlands. Milk samples have been aggregated into sixteen pooled samples of milk representing time-averaged samples originating from different producers located in various regions in Germany and Belgium. In addition, one sample of French sheep cheese and three composites of different types of French cheese based on cows milk have been included in the analytical programme. Chemical analyses included determinations of the 2,3,7,8-chlorine substituted PCDD and PCDF congeners in the lipid fraction of the samples. From the congener-specific data, a dioxin concentration expressed in toxic equivalents of 2,3,7,8-TCDD (TEQs) has been derived by use of the International Toxic Equivalency Factors (i-TEFs). For all samples investigated, measured dioxin levels were well below the Dutch standard of 6 pg (i)- TEQ/g fat. The study revealed dioxin levels in imported consumer milk from Germany, varying between 0.3 and 1.2 pg (i)-TEQ/g fat. Dioxin levels in milk samples from Belgium ranged between 1.4 and 2.7 pg (i)-TEQ/g fat, and dioxins in French cheese were found at levels between 0.5 and 1.2 pg (i)-TEQ/g fat. If the observed levels are compared with earlier reported levels in consumer milk collected in the Netherlands in the period 1992-1993 of 0.9-2.1 pg (i)-TEQ/g fat (Liem et al., 1996), this study suggests lower levels in imported milk from Germany and higher levels in imported milk from Belgium. Some restrictions should, however, be taken into account concerning the representativity of the investigated samples. As a consequence, the statistical significance of the observed differences can not be assessed. However, the differences are small. Hence, there is no reason to conduct supplementary studies.IG