387 research outputs found
Optical and structural properties of sol-gel derived materials embedded in porous anodic alumina
Structure composing a xerogel, doped with lanthanide ions (erbium, terbium and europium), embedded in porous anodic alumina (PAA) have been fabricated and their optical and electrical characterisitics have been studied. Erbium photoluminescence at 1.53 µm from titania xerogel/PAA was found to increase with the number of xerogel layers and erbium concnetration for the excitation wavelength 532 nm, matching the area of transparency of both titania xerogel and PAA. Visible green and red electroluminescence was observed for terbium- and europium-doped IN2O3 and SnO2 xerogels embedded in porous anodic alumina. The improvement of the electrical properties of the xerogel/PAA cell is discussed, taking into account the observed ability of conducting In2O3:Sn (ITO) nanoparticles to penetrate into the anodic alumina pores
A Universal Method to Generate Hyperpolarisation in Beams and Samples
Sizable hyperpolarisation, i.e. an imbalance of the occupation numbers of
nuclear spins in a sample deviating from thermal equilibrium, is needed in
various fields of science. For example, hyperpolarised tracers are utilised in
magnetic resonance imaging in medicine (MRI) and polarised beams and targets
are employed in nuclear physics to study the spin dependence of nuclear forces.
Here we show that the quantum interference of transitions induced by radio-wave
pumping with longitudinal and radial pulses are able to produce large
polarisations at small magnetic fields. This method is easier than established
methods, theoretically understood and experimentally proven for beams of
metastable hydrogen atoms in the keV energy range. It should also work for a
variety of samples at rest. Thus, this technique opens the door for a new
generation of polarised tracers, possibly low-field MRI with better spatial
resolution or the production of polarised fuel to increase the efficiency of
fusion reactors by manipulating the involved cross sections.Comment: 22 pages, 9 figures, splitted into two parts: main paper and method
Self-similar chain conformations in polymer gels
We use molecular dynamics simulations to study the swelling of randomly
end-cross-linked polymer networks in good solvent conditions. We find that the
equilibrium degree of swelling saturates at Q_eq = N_e**(3/5) for mean strand
lengths N_s exceeding the melt entanglement length N_e. The internal structure
of the network strands in the swollen state is characterized by a new exponent
nu=0.72. Our findings are in contradiction to de Gennes' c*-theorem, which
predicts Q_eq proportional N_s**(4/5) and nu=0.588. We present a simple Flory
argument for a self-similar structure of mutually interpenetrating network
strands, which yields nu=7/10 and otherwise recovers the classical Flory-Rehner
theory. In particular, Q_eq = N_e**(3/5), if N_e is used as effective strand
length.Comment: 4 pages, RevTex, 3 Figure
Childhood trauma and anger in adults with and without depressive and anxiety disorders
Stress and Psychopatholog
Aspects of the breeding biology of the southern rockhopper penguin Eudyptes c. chrysocome and new consideration on the intrinsic capacity of the A-egg
Pollution, habitat loss, fishing and climate change as critical threats to penguins
Cumulative human impacts across the world’s oceans are considerable. We therefore examined a single model taxonomic group, the penguins (Spheniscidae), to explore how marine species and communities might be at risk of decline or extinction in the southern hemisphere. We sought to determine the most important threats to penguins and to suggest means to mitigate these threats. Our review has relevance to other taxonomic groups in the southern hemisphere and in northern latitudes, where human impacts are greater. Our review was based on an expert assessment and literature review of all 18 penguin species; 49 scientists contributed to the process. For each penguin species, we considered their range and distribution, population trends, and main anthropogenic threats over the past approximately 250 years. These threats were harvesting adults for oil, skin, and feathers and as bait for crab and rock lobster fisheries; harvesting of eggs; terrestrial habitat degradation; marine pollution; fisheries bycatch and resource competition; environmental variability and climate change; and toxic algal poisoning and disease. Habitat loss, pollution, and fishing, all factors humans can readily mitigate, remain the primary threats for penguin species. Their future resilience to further climate change impacts will almost certainly depend on addressing current threats to existing habitat degradation on land and at sea. We suggest protection of breeding habitat, linked to the designation of appropriately scaled marine reserves, including in the High Seas, will be critical for the future conservation of penguins. However, large-scale conservation zones are not always practical or politically feasible and other ecosystem-based management methods that include spatial zoning, bycatch mitigation, and robust harvest control must be developed to maintain marine biodiversity and ensure that ecosystem functioning is maintained across a variety of scales.Los impactos humanos acumulativos a lo largo de los océanos del planeta son considerables. Por eso examinamos un solo modelo de grupo taxonómico, los pingüinos (Sphenischidae), para explorar cómo las especies y las comunidades marinas pueden estar en riesgo de disminuir o de extinguirse en el hemisferio sur. Buscamos determinar la amenaza más importante para los pingüinos y sugerir métodos para mitigar estas amenazas. Nuestra revisión tiene relevancia para otros grupos taxonómicos en el hemisferio sur y en las latitudes norteñas, donde los impactos humanos son mayores. Nuestra revisión se basó en una evaluación experta y una revisión de literaratura de las 18 especies de pingüinos; 49 científicos contribuyeron al proceso. Para cada especie de pingüino, consideramos su rango y distribución, tendencias poblacionales y las principales amenazas antropogénicas en aproximadamente los últimos 250 años. Estas amenazas fueron la captura de adultos para obtener aceite, piel y plumas y el uso como carnada para la pesca de cangrejos y langostas: la recolección de huevos; la degradación del hábitat terrestre; la contaminación marina; la pesca accesoria y la competencia por recursos; la variabilidad ambiental y el cambio climático; y el envenenamiento por algas tóxicas y enfermedades. La pérdida de hábitat, la contaminación y la pesca, todos factores que los humanos pueden mitigar, siguen siendo las amenazas principales para las especies de pingüinos. Su resiliencia futura a más impactos por cambio climático dependerá certeramente de que nos enfoquemos en las amenazas actuales a la degradación de hábitats existentes en tierra y en el mar. Sugerimos que la protección de hábitats de reproducción, en conjunto con la designación de reservas marinas de escala apropiada, incluyendo alta mar, será crítica para la conservación futura de los pingüinos. Sin embargo, las zonas de conservación a gran escala no son siempre prácticas o políticamente viables, y otros métodos de manejo basados en ecosistemas que incluyen la zonificación espacial, la mitigación de captura accesoria, y el control fuerte de captura deben desarrollarse para mantener la biodiversidad marina y asegurar que el funcionamiento de los ecosistemas se mantenga a lo largo de una variedad de escalas.Fil: Trathan, Phil N.. British Antartic Survey; Reino UnidoFil: Garcia Borboroglu, Jorge Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Boersma, P. Dee. University of Washington; Estados UnidosFil: Bost, Charles André. Centre d´Etudes Biologiques de Chizé; FranciaFil: Crawford, Robert J. M.. Department of Environmental Affairs; SudáfricaFil: Crossin, Glenn T.. Dalhousie University Halifax; CanadáFil: Cuthbert, Richard. Royal Society for the Protection of Birds; Reino UnidoFil: Dann, Peter. Phillip Island Nature Parks; AustraliaFil: Davis, Lloyd Spencer. University Of Otago; Nueva ZelandaFil: de la Puente, Santiago. Universidad Cayetano Heredia; PerúFil: Ellenberg, Ursula. University Of Otago; Nueva ZelandaFil: Lynch, Heather J.. Stony Brook University; Estados UnidosFil: Mattern, Thomas. University Of Otago; Nueva ZelandaFil: Pütz, Klemens. Antarctic Research Trust; AlemaniaFil: Seddon, Philip J.. University Of Otago; Nueva ZelandaFil: Trivelpiece, Wayne. Southwest Fisheries Science Center; Estados UnidosFil: Wienecke, Bárbara. Australian Antarctic Division; Australi
Evaluating the effectiveness of a large multi-use MPA in protecting Key Biodiversity Areas for marine predators
Marine protected areas can serve to regulate harvesting and conserve biodiversity. Within large multi‐use MPAs, it is often unclear to what degree critical sites of biodiversity are afforded protection against commercial activities. Addressing this issue is a prerequisite if we are to appropriately assess sites against conservation targets. We evaluated whether the management regime of a large MPA conserved sites (Key Biodiversity Areas, KBAs) supporting the global persistence of top marine predators
Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data
We present a measurement of neutrino oscillations via atmospheric muon
neutrino disappearance with three years of data of the completed IceCube
neutrino detector. DeepCore, a region of denser instrumentation, enables the
detection and reconstruction of atmospheric muon neutrinos between 10 GeV and
100 GeV, where a strong disappearance signal is expected. The detector volume
surrounding DeepCore is used as a veto region to suppress the atmospheric muon
background. Neutrino events are selected where the detected Cherenkov photons
of the secondary particles minimally scatter, and the neutrino energy and
arrival direction are reconstructed. Both variables are used to obtain the
neutrino oscillation parameters from the data, with the best fit given by
and
(normal mass hierarchy assumed). The
results are compatible and comparable in precision to those of dedicated
oscillation experiments.Comment: 10 pages, 7 figure
A combined maximum-likelihood analysis of the high-energy astrophysical neutrino flux measured with IceCube
Evidence for an extraterrestrial flux of high-energy neutrinos has now been
found in multiple searches with the IceCube detector. The first solid evidence
was provided by a search for neutrino events with deposited energies
TeV and interaction vertices inside the instrumented volume. Recent
analyses suggest that the extraterrestrial flux extends to lower energies and
is also visible with throughgoing, -induced tracks from the Northern
hemisphere. Here, we combine the results from six different IceCube searches
for astrophysical neutrinos in a maximum-likelihood analysis. The combined
event sample features high-statistics samples of shower-like and track-like
events. The data are fit in up to three observables: energy, zenith angle and
event topology. Assuming the astrophysical neutrino flux to be isotropic and to
consist of equal flavors at Earth, the all-flavor spectrum with neutrino
energies between 25 TeV and 2.8 PeV is well described by an unbroken power law
with best-fit spectral index and a flux at 100 TeV of
.
Under the same assumptions, an unbroken power law with index is disfavored
with a significance of 3.8 () with respect to the best
fit. This significance is reduced to 2.1 () if instead we
compare the best fit to a spectrum with index that has an exponential
cut-off at high energies. Allowing the electron neutrino flux to deviate from
the other two flavors, we find a fraction of at Earth.
The sole production of electron neutrinos, which would be characteristic of
neutron-decay dominated sources, is rejected with a significance of 3.6
().Comment: 16 pages, 10 figures; accepted for publication in The Astrophysical
Journal; updated one referenc
The IceCube Neutrino Observatory - Contributions to ICRC 2015 Part II: Atmospheric and Astrophysical Diffuse Neutrino Searches of All Flavors
Papers on atmospheric and astrophysical diffuse neutrino searches of all
flavors submitted to the 34th International Cosmic Ray Conference (ICRC 2015,
The Hague) by the IceCube Collaboration.Comment: 66 pages, 36 figures, Papers submitted to the 34th International
Cosmic Ray Conference, The Hague 2015, v2 has a corrected author lis
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