Concepts in ichnotaxonomy illustrated by small round holes in shells

La clasificación de las pistas fósiles requiere un doble sistema de nomenclatura. El nombre de la pista fósil (ichnotaxon) está basado en la morfologia de la estructura, mientras que el taxon biológico  representa la posicion filogenética que se interpreta del organismo causante. Los dos sistemas de nomenclatura no se pueden intercambiar, y ambos son necesarios para la completa clasificacion dela pista. A muchas de estas pistas no les ha sido aún atribuido unichnotaxon descriptivo, pero ya que las  pistas fósiles re quieren nombres si han de ser tratadas sistemáticamente, se ofrece comunmente en tales  casos un biotaxon interpretativo en lugar del ichnotaxon que no se ha descritotodavia Este procedimiento tiende a desviar la atención de la verdadera naturaleza de la pista fósil e implica una falsa  exactitud en la determinación filogenética, lo cual conduce a conclusiones paleobiologicas poco seguras. Estos puntos quedan bien ilustrados por el ejemplo de unas perforaciones pequeíias y redondas sobre  conchas. Son pistas fósiles abundantes y, no teniendo ichnotaxon, tienden a ser relacionadas con la  accion perforante de los gasteropedos-naticidos y muricidos-sobre conchas. Sin embargo, varios grupos  más de gasteropodos producen perforaciones redondas, al igual que los cefalopodos octopodos,  turbelarios, nemátodos y braquiópodos articulados, pero su acción es poco conocida. Antes de embarcarse en tales especulaciones, como son los organismos causantes, es necesario un ichnotaxón para atraer la atención hacia estas pistas fosiles y aumentarel rigorde su tratamiento. Sólo cuando sumorfologia y distribución sean mejor conocidas estaremos en una posición mejor para discutir sus  atribuciones filogenéticas

Terrestrial Planet Formation I. The Transition from Oligarchic Growth to Chaotic Growth

We use a hybrid, multiannulus, n-body-coagulation code to investigate the growth of km-sized planetesimals at 0.4-2 AU around a solar-type star. After a short runaway growth phase, protoplanets with masses of roughly 10^26 g and larger form throughout the grid. When (i) the mass in these `oligarchs' is roughly comparable to the mass in planetesimals and (ii) the surface density in oligarchs exceeds 2-3 g/sq cm at 1 AU, strong dynamical interactions among oligarchs produce a high merger rate which leads to the formation of several terrestrial planets. In disks with lower surface density, milder interactions produce several lower mass planets. In all disks, the planet formation timescale is roughly 10-100 Myr, similar to estimates derived from the cratering record and radiometric data.Comment: Astronomical Journal, accepted; 22 pages + 15 figures in ps format; eps figures at http://cfa-www.harvard.edu/~kenyon/dl/ revised version clarifies evolution and justifies choice of promotion masse

Characteristics and Management Implications of the Spring Waterfowl Hunt in the Western Canadian Arctic, Northwest Territories

The species composition, timing of the harvest, sex, age, breeding status, and numbers of geese and swans shot during the spring hunt by residents of Tuktoyaktuk, Paulatuk, and Sachs Harbour, Northwest Territories were studied in each community hunting area for three consecutive years (1987 to 1990). Investigators visited hunters repeatedly in the field, conducting interviews and examining >=27% of the reported harvest. Snow geese (Anser caerulescens caerulescens) accounted for 70% of the harvest, followed by white-fronted geese (Anser albifrons frontalis, 19%), Canada geese (Branta canadensis hutchinsii, 5%), brant (Branta bernicla nigricans, 4%), tundra swans (Cygnus columbianus, 2%), and Ross' geese (Anser rossii, <1%). Sex ratios varied by species and community. Age ratios (yearlings per adult) also varied, and were inversely correlated with the size of the previous year's continental recreational harvest for white-fronted geese. Breeding status of geese with adult plumage varied, but was generally near 80% breeders. Average annual harvest of geese and swans were estimated at 5986 for Tuktoyaktuk, 1605 for Paulatuk, and 2790 for Sachs Harbour. Regional spring harvests, as a percent of continental harvests of regional populations, were 19% for lesser snow geese and 15% for white-fronted geese. Harvest levels require consideration in all stages of management of the resource, from local to continental. Action is required in Canada, through cooperative wildlife management mechanisms of the Inuvialuit Final Agreement and other land claims legislation, and through new regional bodies, to ensure that the spring harvest is incorporated into regional, national and international management of migratory birds.Durant trois années consécutives (de 1987 à 1990), on a étudié la composition des espèces, le moment des prélèvements, le sexe, l'âge, le statut de reproducteur et le nombre d'oies et de cygnes tués par balle au cours de la chasse printanière par les résidents de Tuktoyaktuk, de Paulatuk et de Sachs Harbour (Territoires du Nord-Ouest) dans la zone de chasse de chacune de ces communautés. Les chercheurs ont à plusieurs reprises rendu visite aux chasseurs sur le terrain, mené des entrevues et examiné >= 27 p. cent des prélèvements rapportés. L'oie des neiges (Anser caerulescens caerulescens) comptait pour 70 p. cent des prélèvements, suivie de l'oie à front blanc (Anser albifrons frontalis, 19 p. cent), de la bernache du Canada (Branta canadensis hutchinsii, 5 p. cent), de la bernache noire (Branta bernicla nigricans, 4 p. cent), du cygne siffleur (Cygnus columbianus, 2 p. cent), et de l'oie de Ross (Anser rossii, < 1 p. cent). Le taux mâle / femelle variait suivant les espèces et la communauté. Le taux entre les âges (nombre de petits d'un an par adulte) variait aussi, et était corrélé inversement pour l'oie à front blanc avec le nombre d'oiseaux prélevés au cours de la chasse sportive de l'année précédente à l'échelle du continent. Le statut de reproducteur des oies ayant un plumage d'adulte variait, mais en général, près de 80 p. cent étaient des oiseaux reproducteurs. On a évalué la moyenne des prélèvements annuels d'oies et de cygnes à 5986 pour Tuktoyaktuk, 1605 pour Paulatuk et 2790 pour Sachs Harbour. Les prélèvements printaniers régionaux, en tant que pourcentage des prélèvements de populations régionales à l'échelle du continent, étaient de 19 p. cent pour la petite oie des neiges et de 15 p. cent pour l'oie à front blanc. Il faut porter attention au niveau des prélèvements à tous les stades de la gestion des ressources, du niveau local au niveau du continent tout entier. Des mesures doivent être prises au Canada, par le biais des mécanismes de coopération de gestion de la faune contenus dans la Convention définitive des Inuvialuit et d'autres lois relatives aux revendications territoriales, ainsi que par le biais de nouvelles instances régionales, pour assurer que les prélèvements printaniers soient intégrés dans une gestion régionale, nationale et internationale des oiseaux migrateurs

Children’s Food and Drink Purchasing Behaviour ‘‘Beyond the School Gate’’ : The Development of a Survey Module

Copyright © 2013 Wendy J.Wills et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly citedMany children eat a diet which supplies a higher than recommended amount of nonmilk extrinsic sugars and saturated fatty acids. The school setting is often targeted for nutrition intervention as many children consume food at school. In Scotland, attempts have been made to improve the nutritional content of food in schools and attention has now turned to food and drink available “beyond the school gate.” This paper describes the development of a module on food and drink purchasing behaviour. The Food Purchasing Module was designed to collect data, for the first time, from a representative sample of children aged 8–16 years about food and drinks purchased on the way to/from school, during break time/free periods, and at lunchtime, from outlets around schools. Cognitive testing of the module highlighted that younger children find self-completion questionnaires problematic. Older children have fewer problems with self-completion questionnaires butmany do not follow question routing, which has implications for the delivery of future surveys. Development of this survey module adds much needed evidence about effectively involving children in surveys. Further research exploring food and drinks purchased beyond the school gate is needed to continue to improve the nutritional quality of children’s dietsPeer reviewe

The existence of a 2Po excited state for the e+Ca system

The Configuration Interaction method is used to demonstrate that there is an electronically stable state of positronic calcium with an orbital angular momentum of L=1. This prediction relies on the use of an asymptotic series to estimate the variational limit of the energy. The best estimate of the binding energy is 37 meV. A discussion of the structure of the system is also presented.Comment: 4 pages, 2 figures, in press PR

The Vanishing Sociology-Social Work Alliance: A Study in the Politics of Professionalism

The undergraduate sociology-social work alliance in sociology departments has a long tradition in American colleges despite ideological differences between the two disciplines. Recently this old alliance shows signs of disintegration. This paper argues that the recent emphasis on professionalization of undergraduate social work through the use of accrediting standards coupled with the control of Federal social work training grants have placed new pressures on the old alliance. Evidence is presented which indicates that the conflict is being resolved in the direction of greater administrative specialization and autonomy for social work

MARINE AND NORMARINE TRACE FOSSILS AND PLANT ROOTS IN A REGRESSIONAL SETTING (PLEISTOCENE, ITALY)

The sedimentary structures occurring in one of the Pleistocene marine terraces at the Ionian coast, indicate a shoaling upward trend from the shoreface of a sandy beach to nonmarine conditions. Four main facies have been recognized. Facies A consists of hummocky cross-bedded sands representing a wave-dominated nearshore environment. Physical and biological structures of facies B are suggestive of an abrupt reduction in energy level, possibly related to the establishment of shallow protected environments. Features of facies C suggest a stable environment of upper shoreface but strongly influenced by continental supplies. Upward, this facies passes into sediments deposited in continental conditions. The last facies (D) is related to moist or wet terrestrial environments. Bioturbation levels of facies A to C are in general low. Facies D, however, is well bioturbated, having an ichnofabric dominated by Taenidium isp. Sparse, vertical roots of vascular plants extended in many cases to at least 3 m below the base of facies D. Particularly unusual is the close association of large Taenidium isp. and vertical roots, where the trace fossil is clustered tightly around the plant, in some cases to more than 1 m below the water-sediment interface

Large dimension Configuration Interaction calculations of positron binding to the group II atoms

The Configuration Interaction (CI) method is applied to the calculation of the structures of a number of positron binding systems, including e+Be, e+Mg, e+Ca and e+Sr. These calculations were carried out in orbital spaces containing about 200 electron and 200 positron orbitals up to l = 12. Despite the very large dimensions, the binding energy and annihilation rate converge slowly with l, and the final values do contain an appreciable correction obtained by extrapolating the calculation to the l to infinity limit. The binding energies were 0.00317 hartree for e+Be, 0.0170 hartree for e+Mg, 0.0189 hartree for e+Ca, and 0.0131 hartree for e+Sr.Comment: 13 pages, no figs, revtex format, Submitted to PhysRev

Practical quantum metrology in noisy environments

This is the final version. Available from American Physical Society via the DOI in this recordThe problem of estimating an unknown phase φ using two-level probes in the presence of unital phase-covariant noise and using finite resources is investigated. We introduce a simple model in which the phase-imprinting operation on the probes is realized by a unitary transformation with a randomly sampled generator. We determine the optimal phase sensitivity in a sequential estimation protocol and derive a general (tight-fitting) lower bound. The sensitivity grows quadratically with the number of applications N of the phase-imprinting operation, then attains a maximum at some N opt , and eventually decays to zero. We provide an estimate of N opt in terms of accessible geometric properties of the noise and illustrate its usefulness as a guideline for optimizing the estimation protocol. The use of passive ancillas and of entangled probes in parallel to improve the phase sensitivity is also considered. We find that multiprobe entanglement may offer no practical advantage over single-probe coherence if the interrogation at the output is restricted to measuring local observables.European Research CouncilRoyal Societ

An Alternative Origin for Hypervelocity Stars

Halo stars with unusually high radial velocity ("hypervelocity" stars, or HVS) are thought to be stars unbound to the Milky Way that originate from the gravitational interaction of stellar systems with the supermassive black hole at the Galactic center. We examine the latest HVS compilation and find peculiarities that are unexpected in this black hole-ejection scenario. For example, a large fraction of HVS cluster around the constellation of Leo and share a common travel time of $\sim 100$-200 Myr. Furthermore, their velocities are not really extreme if, as suggested by recent galaxy formation models, the Milky Way is embedded within a $2.5\times 10^{12} h^{-1} M_{\odot}$ dark halo with virial velocity of $\sim 220$ km/s. In this case, the escape velocity at $\sim 50$ kpc would be $\sim 600$ km/s and very few HVS would be truly unbound. We use numerical simulations to show that disrupting dwarf galaxies may contribute halo stars with velocities up to and sometimes exceeding the nominal escape speed of the system. These stars are arranged in a thinly-collimated outgoing ``tidal tail'' stripped from the dwarf during its latest pericentric passage. We speculate that some HVS may therefore be tidal debris from a dwarf recently disrupted near the center of the Galaxy. In this interpretation, the angular clustering of HVS results because from our perspective the tail is seen nearly ``end on'', whereas the common travel time simply reflects the fact that these stars were stripped simultaneously from the dwarf during a single pericentric passage. This proposal is eminently falsifiable, since it makes a number of predictions that are distinct from the black-hole ejection mechanism and that should be testable with improved HVS datasets.Comment: 4 pages, 4 figures. Replacement to match version accepted to ApJ