5,829 research outputs found
The Monterey event in the Mediterranean: A record from shelf sediments of Malta
Oligo-Miocene carbonate platform and shelf sediments outcropping on the Maltese Islands provide an excellent archive of the paleoceanography of the central Mediterranean. A sequence of shallow water limestones, than shelf limestones, and marls, followed again by shallow water limestones, reflects drowning of a carbonate platform, the establishment of a shelf environment and, in the late Miocene, renewed progradation and aggradation of shallow water carbonates. The sequence recording the deepening of the Maltese platform contains several phosphorite hardgrounds and phosphorite pebble beds. These phosphorites were dated with strontium isotopes. Major episodes of phosphogenesis occurred between 25 and 16 Ma, and they are coeval with those phosphorite events reported from Florida and North Carolina. A Miocene carbon isotope and oxygen isotope stratigraphy was established on planktic and benthic foraminifera and on bulk samples. A major carbon isotope excursion with an amplitude of up to +l‰ between 18 and 12.5 Ma can be correlated with the globally recognized Monterey carbon isotope excursion. This is the first record of this event both in shallow water sediments and in the Mediterranean. The carbon isotope excursion precedes an oxygen isotope excursion which also was recognized in deep-sea records. Major episodes of phosphogenesis and platform drowning preceded the carbon isotope excursion by up to millions of years
Segmental aging underlies the development of a Parkinson phenotype in the AS/AGU rat
There is a paucity of information on the molecular biology of aging processes in the brain. We have used biomarkers of aging (SA β-Gal, p16Ink4a, Sirt5, Sirt6, and Sirt7) to demonstrate the presence of an accelerated aging phenotype across different brain regions in the AS/AGU rat, a spontaneous Parkinsonian mutant of PKCγ derived from a parental AS strain. P16INK4a expression was significantly higher in AS/AGU animals compared to age-matched AS controls (p < 0.001) and displayed segmental expression across various brain regions. The age-related expression of sirtuins similarly showed differences between strains and between brain regions. Our data clearly show segmental aging processes within the rat brain, and that these are accelerated in the AS/AGU mutant. The accelerated aging, Parkinsonian phenotype, and disruption to dopamine signalling in the basal ganglia in AS/AGU rats, suggests that this rat strain represents a useful model for studies of development and progression of Parkinson's disease in the context of biological aging and may offer unique mechanistic insights into the biology of aging
Earth orbital teleoperator systems evaluation
The mechanical extension of the human operator to remote and specialized environments poses a series of complex operational questions. A technical and scientific team was organized to investigate these questions through conducting specific laboratory and analytical studies. The intent of the studies was to determine the human operator requirements for remotely manned systems and to determine the particular effects that various system parameters have on human operator performance. In so doing, certain design criteria based on empirically derived data concerning the ultimate control system, the human operator, were added to the Teleoperator Development Program
Relative entropy via non-sequential recursive pair substitutions
The entropy of an ergodic source is the limit of properly rescaled 1-block
entropies of sources obtained applying successive non-sequential recursive
pairs substitutions (see P. Grassberger 2002 ArXiv:physics/0207023 and D.
Benedetto, E. Caglioti and D. Gabrielli 2006 Jour. Stat. Mech. Theo. Exp. 09
doi:10.1088/1742.-5468/2006/09/P09011). In this paper we prove that the cross
entropy and the Kullback-Leibler divergence can be obtained in a similar way.Comment: 13 pages , 2 figure
Experimental position-time entanglement with degenerate single photons
We report an experiment in which two-photon interference occurs between
degenerate single photons that never meet. The two photons travel in opposite
directions through our fibre-optic interferometer and interference occurs when
the photons reach two different, spatially separated, 2-by-2 couplers at the
same time. We show that this experiment is analogous to the conventional
Franson-type entanglement experiment where the photons are entangled in
position and time. We measure wavefunction overlaps for the two photons as high
as 94 3%.Comment: Updated to published version, new fig. 4., corrected typo
Free carrier effects in gallium nitride epilayers: the valence band dispersion
The dispersion of the A-valence-band in GaN has been deduced from the
observation of high-index magneto-excitonic states in polarised interband
magneto-reflectivity and is found to be strongly non-parabolic with a mass in
the range 1.2-1.8 m_{e}. It matches the theory of Kim et al. [Phys. Rev. B 56,
7363 (1997)] extremely well, which also gives a strong k-dependent
A-valence-band mass. A strong phonon coupling leads to quenching of the
observed transitions at an LO-phonon energy above the band gap and a strong
non-parabolicity. The valence band was deduced from subtracting from the
reduced dispersion the electron contribution with a model that includes a full
treatment of the electron-phonon interaction.Comment: Revtex, 4 pages, 5 figure
Measuring Family Centred Care: Working with Children and Their Parents in a Tertiary Hospital
Rationale and aim: Family-centred care (FCC) is widely used in paediatrics, though no rigorous evidence for it exists. A growing body of qualitative research raises concerns about FCC, and health professionals’ attitudes to it. We measured attitudes to working with children and working with parents of hospitalised children held by nurses, doctors, allied health and ancillary staff at an Australian children’s hospital, using a validated questionnaire with two scores, one for working with children, one for working with parents, and demographic characteristics, and compared responses. Method: we recruited a randomized sample, and compared means of working with children and working with parents scores, using a Wilcoxon signed rank test p<0.0001. Mean differences by categories of demographics were estimated using ANOVA and median test compared the median scores.Results: respondents gave significantly more positive scores for working with children than parents. These were influenced by level of education, whether respondents were parents themselves, if they held senior positions, had worked with children for a long time, and held a paediatric qualification. Conclusions: paediatric health professionals view working with children in a more positive light than working with parents. However, if FCC was being implemented effectively, given its empahsis on the whole family as the unit of care, there would be no difference between working with children or their parents. This quantiative study supports the increasing body of qualitative research which highlights problems with this model. In addition, this study provides a way to measure FCC
The Quasar SDSS J105041.35+345631.3: Black Hole Recoil or Extreme Double-Peaked Emitter?
The quasar SDSS J105041.35+345631.3 (z = 0.272) has broad emission lines
blueshifted by 3500 km/s relative to the narrow lines and the host galaxy. Such
an object may be a candidate for a recoiling supermassive black hole, binary
black hole, a superposition of two objects, or an unusual geometry for the
broad emission-line region. The absence of narrow lines at the broad line
redshift argues against superposition. New Keck spectra of J1050+3546 place
tight constraints on the binary model. The combination of large velocity shift
and symmetrical H-beta profile, as well as aspects of the narrow line spectrum,
make J1050+3546 an interesting candidate for black hole recoil. Other aspects
of the spectrum, however, suggest that the object is most likely an extreme
case of a ``double-peaked emitter.'' We discuss possible observational tests to
determine the true nature of this exceptional object.Comment: 5 pages, 2 figures, LaTeX; substantial revision
Behavioral Interactions Between Japanese Beetle (Coleoptera: Scarabaeidae) Grubs and an Entomopathogenic Nematode (Nematoda: Heterorhabditidae) within Turf Microcosms
Distribution of Japanese beetle, Popillia japonica Newman, grubs and dispersal of an entomopathogenic nematode, Heterorhabditis bacteriophora Poinar ‘Oswego' strain (an isolate from New York state), were examined for 5 wk within soil-filled flats containing grass. Japanese beetle grubs uniformly dispersed to all sections of the flats not infested with H. bacteriophora ‘Oswego' strain. In flats infested with H. bacteriophora ‘Oswego' strain, however, greater proportions of Japanese beetle grubs were recovered in sections near the nematode release site or center sections of the flats. H. bacteriophora ‘Oswego' strain dispersed to all sections of the flats but dispersed more rapidly within the flats infested with Japanese beetle grubs than in flats not infested with Japanese beetle grub
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