817 research outputs found
Foraminiferal record and astronomical cycles: An example from the Messinian pre-evaporitic Gello Composite Section (Tuscany, Italy)
A high resolution bio-magneto and cyclostratigraphical study has been carried out for the first time on Messinian pre-evaporitic marine deposits (Gello Composite Section) from the Volterra Basin (Italy). Since the investigated deposits manifest no evident lithological cyclicity, others records have been used to recognize the vidences of an astronomical periodicity. The distribution curves of planktonic and benthic foraminifera have been used for paleoenvironmental reconstruction. yclostratigraphical analyses have been based on: i) abundance fluctuations of Bolivina and Bulimina among the benthic foraminifera, Globigerinoides, Orbulina and Turborotalita among the planktonics; ii) CaCO3 content changes; and iii) Shannon-Weaver index variations relative to benthic assemblages. As a result, 18 precession-controlled cycles have been recognized. Moreover, the recognition of the C3An.1r, C3An.1n and C3r magnetozone and some biochronohorizons,
have allowed the tuning of the studied section with the ATNTS (Astronomical Tuned Neogene Time Scale) using the Laskar 2001 (1,1.2) solution of the insolation curve. This multidisciplinary study strongly supports that the onset of evaporitic deposition in Tuscany and in other circum-Mediterranean type-successions, as the Abad Composite Section (Spain) and the Falconara Section (Sicily), was isochronous
LATE MIOCENE PALEOGEOGRAPHY OF THE MONTE SOLDANO AREA, SOUTHEASTERN PART OF VOLTERRA BASIN, TUSCANY, ITALY
Several Upper Tortonian to Lower Messinian sedimentary facies were recognized and mapped in the M.te Soldano area at the southeastern end of the extensional Basin of Volterra in the Nothern Apennines in Tuscany. They consist of (a) disorganized coarse conglomerates, ft) organized conglomerates interbedded with sandstone, (c) coarse to medium grained sandstone which is present both as interlayers within the organized conglomerares as well as turbidite layers interbedded with lacustrine clay,(d) marlstone rich in opercula of Bithynia, and (e) lacustrine clay with few sandy turbidite interlayers. The vertical and lateral distribution of these facies indicates the existence of a large alluvial fan complex. The development of such a large complex from an apparently relatively narrow sediment source area (an interbasin ridge) was possible because the feeding rivers were probably located at the intersection between a border fault and a fault associated with a transfer zone. This allowed for a much wider drainage basin
The Scaglia Toscana Formation of the Monti del Chianti: new lithostratigraphic and biostratigraphic data
The Scaglia Toscana Formation (Scisti Policromi Auctt.) is one of the most investigated formations of the Tuscan Nappe. The formation is widely exposed in the Chianti Mounts and despite the number of studies in this area, some aspects remain poorly known and debated.In this paper new litho- and bio-stratigraphic data from eight key-sections distributed over the entire area are provided and discussed in order to clarify the stratigraphic relationships among different lithostratigraphic members, as well as the depositional ages of each member. The formation was deposited in the Cretaceous-Oligo-cene time interval and it can be subdivided into five lithostratigraphic members: i) the “Argilliti di Brolio” (wine-red shales with sporadic siliceous calcilutites and rare interbedded cherts); ii) the “Marne del Sugame” (red and pink marls, calcareous marls and marly limestones
with interbedded calcarenitic beds and ruditic lens-shaped bodies including calcareous-siliceous clasts); iii) the “Argilliti di Cintoia” (grey-green to black shales, locally with manganese-rich siliceous calcilutites and cherts); iv) the “Calcareniti di Montegrossi” (thin beds of calcilutites and calcarenites with varicoloured shaly-marly interbeds); and v) the “Argilliti e Calcareniti di Dudda” (alternating thin beds of calcilutites and calcarenites with varicoloured shaly-marly interbeds). These members were deposited in a marine environment and have been interpreted as deposited in a turbiditic system, in which shaly and calcareous turbiditic members have been attributed to a basin plain below the CCD, whereas the marls and marly limestones of the Marne del Sugame Member were deposited in a slope/ramp environment above or close to the CCD. Furthermore, the combination of these new
data with structural informations coming from the literature allowed a better paleogeographic reconstruction of the paleobasin. In order to better explain these data, the paper is accompanied by two geological maps realized in the past but never distributed. The two geological maps, at the scale of 1:25,000, cover the whole area from the Cintoia (south of Florence) to the San Gusmè (north of Siena) villages
Discovery of a 0.42-s pulsar in the ultraluminous X-ray source NGC 7793 P13
NGC 7793 P13 is a variable (luminosity range ~100) ultraluminous X-ray source
(ULX) proposed to host a stellar-mass black hole of less than 15 M in
a binary system with orbital period of 64 d and a 18-23 M B9Ia
companion. Within the EXTraS project we discovered pulsations at a period of
~0.42 s in two XMM-Newton observations of NGC 7793 P13, during which the source
was detected at and erg
s (0.3-10 keV band). These findings unambiguously demonstrate that the
compact object in NGC 7793 P13 is a neutron star accreting at super-Eddington
rates. While standard accretion models face difficulties accounting for the
pulsar X-ray luminosity, the presence of a multipolar magnetic field with ~
few 10 G close to the base of the accretion column appears to
be in agreement with the properties of the system.Comment: 5 pages, 5 figures, 2 tables; Version accepted for publication in
MNRAS Letter
Circadian clock genes, ovarian development and diapause
Insects, like most organisms, have an internal circadian clock that oscillates with a daily rhythmicity, and a timing mechanism that mediates seasonal events, including diapause. In research published in BMC Biology, Ikeno et al. show that downregulation of the circadian clock genes period and cycle affects expression of ovarian diapause in the insect Riptortus pedestris. They interpret these important results as support for Erwin Bünning's (1936) hypothesis that the circadian clock constitutes the basis of photoperiodism. However, their observations could also be the result of pleiotropic effects of the individual clock genes
A Study of Time-Dependent CP-Violating Asymmetries and Flavor Oscillations in Neutral B Decays at the Upsilon(4S)
We present a measurement of time-dependent CP-violating asymmetries in
neutral B meson decays collected with the BABAR detector at the PEP-II
asymmetric-energy B Factory at the Stanford Linear Accelerator Center. The data
sample consists of 29.7 recorded at the
resonance and 3.9 off-resonance. One of the neutral B mesons,
which are produced in pairs at the , is fully reconstructed in
the CP decay modes , , , () and , or in flavor-eigenstate
modes involving and (). The flavor of the other neutral B meson is tagged at the time of
its decay, mainly with the charge of identified leptons and kaons. The proper
time elapsed between the decays is determined by measuring the distance between
the decay vertices. A maximum-likelihood fit to this flavor eigenstate sample
finds . The value of the asymmetry amplitude is determined from
a simultaneous maximum-likelihood fit to the time-difference distribution of
the flavor-eigenstate sample and about 642 tagged decays in the
CP-eigenstate modes. We find , demonstrating that CP violation exists in the neutral B meson
system. (abridged)Comment: 58 pages, 35 figures, submitted to Physical Review
Measurement of the Branching Fraction for B- --> D0 K*-
We present a measurement of the branching fraction for the decay B- --> D0
K*- using a sample of approximately 86 million BBbar pairs collected by the
BaBar detector from e+e- collisions near the Y(4S) resonance. The D0 is
detected through its decays to K- pi+, K- pi+ pi0 and K- pi+ pi- pi+, and the
K*- through its decay to K0S pi-. We measure the branching fraction to be
B.F.(B- --> D0 K*-)= (6.3 +/- 0.7(stat.) +/- 0.5(syst.)) x 10^{-4}.Comment: 7 pages, 1 postscript figure, submitted to Phys. Rev. D (Rapid
Communications
Evidence for the Rare Decay B -> K*ll and Measurement of the B -> Kll Branching Fraction
We present evidence for the flavor-changing neutral current decay and a measurement of the branching fraction for the related
process , where is either an or
pair. These decays are highly suppressed in the Standard Model,
and they are sensitive to contributions from new particles in the intermediate
state. The data sample comprises
decays collected with the Babar detector at the PEP-II storage ring.
Averaging over isospin and lepton flavor, we obtain the branching
fractions and , where the
uncertainties are statistical and systematic, respectively. The significance of
the signal is over , while for it is .Comment: 7 pages, 2 postscript figues, submitted to Phys. Rev. Let
Potential conservation of circadian clock proteins in the phylum Nematoda as revealed by bioinformatic searches
Although several circadian rhythms have been described in C. elegans, its molecular clock remains elusive. In this work we employed a novel bioinformatic approach, applying probabilistic methodologies, to search for circadian clock proteins of several of the best studied circadian model organisms of different taxa (Mus musculus, Drosophila melanogaster, Neurospora crassa, Arabidopsis thaliana and Synechoccocus elongatus) in the proteomes of C. elegans and other members of the phylum Nematoda. With this approach we found that the Nematoda contain proteins most related to the core and accessory proteins of the insect and mammalian clocks, which provide new insights into the nematode clock and the evolution of the circadian system.Fil: Romanowski, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Cronobiología; ArgentinaFil: Garavaglia, Matías Javier. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Ing.genética y Biolog.molecular y Celular. Area Virus de Insectos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Goya, María Eugenia. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Cronobiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ghiringhelli, Pablo Daniel. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Ing.genética y Biolog.molecular y Celular. Area Virus de Insectos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Golombek, Diego Andres. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Cronobiología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Study of e+e- --> pi+ pi- pi0 process using initial state radiation with BABAR
The process e+e- --> pi+ pi- pi0 gamma has been studied at a center-of-mass
energy near the Y(4S) resonance using a 89.3 fb-1 data sample collected with
the BaBar detector at the PEP-II collider. From the measured 3pi mass spectrum
we have obtained the products of branching fractions for the omega and phi
mesons, B(omega --> e+e-)B(omega --> 3pi)=(6.70 +/- 0.06 +/- 0.27)10-5 and
B(phi --> e+e-)B(phi --> 3pi)=(4.30 +/- 0.08 +/- 0.21)10-5, and evaluated the
e+e- --> pi+ pi- pi0 cross section for the e+e- center-of-mass energy range
1.05 to 3.00 GeV. About 900 e+e- --> J/psi gamma --> pi+ pi- pi0 gamma events
have been selected and the branching fraction B(J/psi --> pi+ pi- pi0)=(2.18
+/- 0.19)% has been measured.Comment: 21 pages, 37 postscript figues, submitted to Phys. Rev.
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