On the Orbits of Low-mass Companions to White Dwarfs and the Fates of the Known Exoplanets

The ultimate fates of binary companions to stars (including whether the companion survives and the final orbit of the binary) are of interest in light of an increasing number of recently discovered, low-mass companions to white dwarfs (WDs). In this Letter, we study the evolution of a two-body system wherein the orbit adjusts due to structural changes in the primary, dissipation of orbital energy via tides, and mass loss during the giant phases; previous studies have not incorporated changes in the primary's spin. For companions ranging from Jupiter's mass to ~0.3 Msun and primaries ranging from 1-3 Msun, we determine the minimum initial semimajor axis required for the companion to avoid engulfment by the primary during post-main-sequence evolution, and highlight the implications for the ultimate survival of the known exoplanets. We present regions in secondary mass and orbital period space where an engulfed companion might be expected to survive the common envelope phase (CEP), and compare with known M dwarf+WD short-period binaries. Finally, we note that engulfed Earth-like planets cannot survive a CEP. Detection of a first-generation terrestrial planet in the white dwarf habitable zone requires scattering from a several-AU orbit to a high-eccentricity orbit (with a periastron of ~Rsun) from which it is damped into a circular orbit via tidal friction, possibly rendering it an uninhabitable, charred ember.Comment: Replaced with version in Journa

The formation of high-field magnetic white dwarfs from common envelopes

The origin of highly-magnetized white dwarfs has remained a mystery since their initial discovery. Recent observations indicate that the formation of high-field magnetic white dwarfs is intimately related to strong binary interactions during post-main-sequence phases of stellar evolution. If a low-mass companion, such as a planet, brown dwarf, or low-mass star is engulfed by a post-main-sequence giant, the hydrodynamic drag in the envelope of the giant leads to a reduction of the companion's orbit. Sufficiently low-mass companions in-spiral until they are shredded by the strong gravitational tides near the white dwarf core. Subsequent formation of a super-Eddington accretion disk from the disrupted companion inside a common envelope can dramatically amplify magnetic fields via a dynamo. Here, we show that these disk-generated fields are sufficiently strong to explain the observed range of magnetic field strengths for isolated, high-field magnetic white dwarfs. A higher-mass binary analogue may also contribute to the origin of magnetar fields.Comment: Accepted to Proceedings of the National Academy of Sciences. Under PNAS embargo until time of publicatio

The structure and function of DNA G-Quadruplexes

Guanine-rich DNA sequences can fold into four-stranded, non-canonical secondary structures called G-quadruplexes (G4s). G4s were initially considered a structural curiosity, but recent evidence suggests their involvement in key genome functions such as transcription, replication, genome stability, and epigenetic regulation, together with numerous connections to cancer biology. Collectively, these advances have stimulated research probing G4 mechanisms and consequent opportunities for therapeutic intervention. Here, we provide a perspective on the structure and function of G4s with an emphasis on key molecules and methodological advances that enable the study of G4 structures in human cells. We also critically examine recent mechanistic insights into G4 biology and protein interaction partners and highlight opportunities for drug discovery.The Balasubramanian laboratory is core-funded by Cancer Research UK ( C14303/A17197 ); Cancer Research UK programme ( C9681/A18618 ); S.B. is a Welcome Trust Senior Investigator ( 099232/Z/12/Z ); J.S. gratefully acknowledges funding from the EU H2020 Framework Programme ( H2020-MSCA-IF-2016 , ID: 747297-QAPs )

Quality and yield of Alicante Grenache and Semillon on various rootstocks in an arid climate

Alicante Grenache and Semillon wine grape varieties, were studied on their own roots and on seven rootstocks, for yield and quality criteria, in an arid climate. Grenache on its own roots was outstanding in yield, vigour, T.S.S. and acid content. Of the grafted rootstock combinations, 140 Ru yielded highest, followed by 110 R, 41 B MG, 1103 P. Acid content was lowest with 41 B MG. Bunch weight was lowest on ungrafted vines and highest on 140 Ru and 1103 P. Semillon had the highest yield and acid content on 41 B MG, followed by ownroot vines, 161-49 C (low vigour) and 1103 P. Highest bunch weights were observed with 140 Ru and 41 B MG, while high T.S.S. were observed with 161-49 C, own root-vines and 99 R.On 1103 P and 140 Ru, both varieties showed less decline in vigour with age, relative to other combinations.Qualitäts- und Ertragseigenschaften von Alicante Grenache und Semillon auf verschiedenen Unterlagen in einem ariden KlimaIn einem ariden Klima wurden Ertrags- und Qualitätskriterien der Keltertraubensorten Alicante Grenache und Semillon bei wurzelechtem Anbau und in Kombination mit sieben Unterlagen untersucht.Grenache zeigte bei wurzelechtem Anbau überdurchschnittliche Leistungen in Ertrag, Wüchsigkeit, löslicher Trockensubstanz und Säuregehalt. Bei den Pfropfkombinationen wirkte sich 140 Ru auf den Ertrag am vorteilhaftesten aus; es folgten 110 R, 41 B MG, 1103 P. Der Säuregehalt war in Verbindung mit 41 B MG am niedrigsten. Das Traubengewicht war bei den wurzelechten Reben am niedrigsten und auf 140 Ru und 1103 P am höchsten.Semillon hatte auf 41 B den höchsten Ertrag und Säuregehalt, gefolgt von der wurzelechten Rebe und den Kombinationen mit 161-49 C (schwache Wüchsigkeit) sowie mit 1103 P. Das höchste Traubengewicht wurde nach Pfropfung auf 140 Ru und 41 B MG gemessen, während auf 161-49 C, im wurzelechten Zustand und auf 99 R ein hoher Gehalt an löslicher Trockensubstanz beobachtet wurde.Auf 1103 P und 140 Ru ließ die Wüchsigkeit beider Sorten mit fortschreitendem Alter weniger nach als bei anderen Pfropfkombinationen

Performance of table grape cultivars on different rootstocks in an arid climate

The performance of the table grape varieties Queen of the Vineyards, Muscat of Hamburg and Dabouki on eight different rootstocks, was studied in the arid Negev, on a loess soil under irrigation.The highest yields (nine years of bearing) from Queen of the Vineyards were recorded on 161-49, followed by 1202 and 99 R; from Muscat of Hamburg on ownroot plants, 41 B and 110 R; from Dabouki on 41 B, 110 R and 161-49. Maximum vigor in Queen of the Vineyards was obtained on 1202, followed by own-root plants and 1103; in Muscat of Hamburg, on 140 R and 1202; in Dabouki, 0n 110 R and 1202.Highest relative fruitfulness (ratio of total crop per total weight of prunings) 1Jf Queen of the Vineyards was found on 161-49, followed by 41 B and 216-3; of Muscat of Hamburg, on 110 Rand 41 B; of Dabouki, on 41 B and 216-3.No correlation was noted between the ranking of stionic combinations as to vigor and their ranking as yielders. There was a marked tendency toward decreased vigor with age, except on 140 with all three varieties, on 1103 and 1202 with Muscat, on 216-3 with Dabouki, and on 1103 with Queen of the Vineyards. A comparatively large overgrowth in the Dabouki variety with some rootstocks n.id not impair performance.Great variation was noted in the performance of different varieties of V. vinifera on their own roots; high relative yields were obtained with Muscat of Hamburg, and low yield with Queen of the Vineyards. Only small differences were found in quality, cluster weight and berry weight on different rootstocks

Standard Solar models in the Light of New Helioseismic Constraints II. Mixing Below the Convective Zone

In previous work, we have shown that recent updated standard solar models cannot reproduce the radial profile of the sound speed at the base of the convective zone (CZ) and fail to predict the Li7 depletion. In parallel, helioseismology has shown that the transition from differential rotation in the CZ to almost uniform rotation in the radiative solar interior occurs in a shallow layer called the tachocline. This layer is presumably the seat of large scale circulation and of turbulent motions. Here, we introduce a macroscopic transport term in the structure equations, which is based on a hydrodynamical description of the tachocline proposed by Spiegel and Zahn, and we calculate the mixing induced within this layer. We discuss the influence of different parameters that represent the tachocline thickness, the Brunt-Vaissala frequency at the base of the CZ, and the time dependence of this mixing process along the Sun's evolution. We show that the introduction of such a process inhibits the microscopic diffusion by about 25%. Starting from models including a pre-main sequence evolution, we obtain: a) a good agreement with the observed photospheric chemical abundance of light elements such as He3, He4, Li7 and Be9, b) a smooth composition gradient at the base of the CZ, and c) a significant improvement of the sound speed square difference between the seismic sun and the models in this transition region, when we allow the phostospheric heavy element abundance to adjust, within the observational incertitude, due to the action of this mixing process. The impact on neutrino predictions is also discussed.Comment: 15 pages, 7 figures, to be published in ApJ (used emulateapj style for latex2e). New email for A. S. Brun: [email protected]

The Origin of Solar Activity in the Tachocline

Solar active regions, produced by the emergence of tubes of strong magnetic field in the photosphere, are restricted to within 35 degrees of the solar equator. The nature of the dynamo processes that create and renew these fields, and are therefore responsible for solar magnetic phenomena, are not well understood. We analyze the magneto-rotational stability of the solar tachocline for general field geometry. This thin region of strong radial and latitudinal differential rotation, between the radiative and convective zones, is unstable at latitudes above 37 degrees, yet is stable closer to the equator. We propose that small-scale magneto-rotational turbulence prevents coherent magnetic dynamo action in the tachocline except in the vicinity of the equator, thus explaining the latitudinal restriction of active regions. Tying the magnetic dynamo to the tachocline elucidates the physical conditions and processes relevant to solar magnetism.Comment: 10 pages, 1 figure, accepted for publication in ApJ

Tools to support the self assessment of the performance of Food Safety Management Systems

Changes in food supply chains, health and demographic situations, lifestyle and social situations, environmental conditions, and increased legislative requirements have led to significant efforts in the development of quality and safety management systems in agribusiness and food industry worldwide (Ropkins and Beck, 2000; Efstratiadis, Karirti, and Arvanitoyannis, 2000; Jacxsens, et al, 2009a, Luning and Marcelis, 2009a). Nowadays, companies have implemented various quality assurance (QA) guidelines and standards, such as GMP and HACCP guidelines (like General Principles of food hygiene (Codex Alimentarius 2003), GFSI guidance document (GFSI (2007), and quality assurance standards (like ISO 9001:2008 (2008), ISO22000:2005 (2005), BRC (2008), and IFS (2007) into their company own food safety management system. The performance of such systems in practice is, however, still variable. Moreover, the continuous pressure on food safety management system (FSMS) performance and the dynamic environment wherein the systems operate (such as emerging pathogens, changing consumer demands, developments in preservation techniques) require that they can be systematically analysed to determine opportunities for improvement (Wallace, et al, 2005; Manning et al, 2006; Van der Spiegel et al, 2006; Cornier et al, 2007; Luning et al, 2009a). Within the European project entitled ‘PathogenCombat- EU FOOD-CT-2005-007081’ various tools have been developed to support food companies and establishments in systematically analysing and judging their food safety management system and its microbiological performance as basis for strategic choices on interventions to improve the FSMS performance. This chapter describes briefly principles of the major tools that have been developed and some others, which are still under still under construction