2,127 research outputs found
Femtosecond pulses at 50-W average power from an Yb:YAG planar waveguide amplifier seeded by an Yb:KYW oscillator
Reproducibility of species recognition in modern planktonic foraminifera and its implications for analyses of community structure
Applications of planktonic foraminifera in Quaternary palaeoceanographic and
palaeobiological studies require consistency in species identification. Yet
the degree of taxonomic consistency among the practitioners and the effects
of any potential deviations on community structure metrics have never been
quantitatively assessed. Here we present the results of an experiment in
taxonomic consistency involving 21 researchers representing a range of
experience and taxonomic schools from around the world. Participants were
asked to identify the same two sets of 300 specimens from a modern
subtropical North Atlantic sample, one sieved at > 125 µm
and one at > 150 µm. The identification was carried out
either on actual specimens (slide test) or their digital images
(digital test). The specimens were fixed so the identifications could be
directly compared. In all tests, only between one-quarter and one-eighth of
the specimens achieved absolute agreement. Therefore, the identifications
across the participants were used to determine a consensus ID for each
specimen. Since no strict consensus ( > 50 % agreement) could be
achieved for 20–30 % of the specimens, we used a soft consensus based
on the most common identification. The average percentage agreement relative
to the consensus of the slide test was 77 % in the > 150 µm
and 69 % in the > 125 µm test. These values
were 7 % lower for the digital analyses. We find that taxonomic
consistency is enhanced when researchers have been trained within a taxonomic
school and when they regularly perform community analyses. There is an almost
negligible effect of taxonomic inconsistency on sea surface temperature
estimates based on transfer function conversion of the census counts,
indicating the temperature signal in foraminiferal assemblages is correctly
represented even if only two-thirds of the assemblage is consistently
identified. The same does not apply to measures of diversity and community
structure within the assemblage, and here we advise caution in using compound
datasets for such studies. The decrease in the level of consistency when
specimens are identified from digital images is significant and
species-specific, with implications for the development of training sets for
automated identification systems.</p
Extreme Sensitivity of the Superconducting State in Thin Films
All non-interacting two-dimensional electronic systems are expected to
exhibit an insulating ground state. This conspicuous absence of the metallic
phase has been challenged only in the case of low-disorder, low density,
semiconducting systems where strong interactions dominate the electronic state.
Unexpectedly, over the last two decades, there have been multiple reports on
the observation of a state with metallic characteristics on a variety of
thin-film superconductors. To date, no theoretical explanation has been able to
fully capture the existence of such a state for the large variety of
superconductors exhibiting it. Here we show that for two very different
thin-film superconductors, amorphous indium-oxide and a single-crystal of
2H-NbSe2, this metallic state can be eliminated by filtering external
radiation. Our results show that these superconducting films are extremely
sensitive to external perturbations leading to the suppression of
superconductivity and the appearance of temperature independent, metallic like,
transport at low temperatures. We relate the extreme sensitivity to the
theoretical observation that, in two-dimensions, superconductivity is only
marginally stable.Comment: 10 pages, 6 figure
Babesia microti-like en un perro inmunocompetente
La babesiosis canina es una enfermedad infecciosa de distribución mundial causada por parásitos intraeritrocitarios transmitidos por garrapatas. Si bien ha sido tradicionalmente asumido que sólo dos de las 73 especies de babesias identificadas causan enfermedad en la especie canina, Babesia canis y Babesia gibsoni, recientes publicaciones demuestran que una tercera especie (Babesia microti-like) también puede parasitar a perros. Este último parásito, genéticamente relacionado con Babesia microti, es el origen de una enfermedad endémica entre la población canina del noroeste de España. Este trabajo presenta un caso no experimental de esta forma de Babesia microti-like en un perro cocker spaniel de 9 años, sin antecedentes de inmunodeficiencia ni de esplenectomía, que se presenta en la clínica veterinaria con signos de hipertermia, hemoglobinuria, escalofríos y apatía. Una muy intensa parasitemia (24%), junto con trombopenia y una acusada anemia hemolítica regenerativa fueron los hallazgos más caractéristicos. En la extensión de sangre periférica se visualizaron múltiples merozoitos intraeritrocitarios (parasitemia de un 24%) de pequeño tamaño (1-2 um) y presentación única en cada hematíe. Cuarenta y ocho horas después del comienzo de los síntomas, y tras tratamiento específico con dipropionato de imidocarb el perro evolucionó hacia la curación
Layered Antiferromagnetism Induces Large Negative Magnetoresistance in the van der Waals Semiconductor CrSBr
The recent discovery of magnetism within the family of exfoliatable van der
Waals (vdW) compounds has attracted considerable interest in these materials
for both fundamental research and technological applications. However current
vdW magnets are limited by their extreme sensitivity to air, low ordering
temperatures, and poor charge transport properties. Here we report the magnetic
and electronic properties of CrSBr, an air-stable vdW antiferromagnetic
semiconductor that readily cleaves perpendicular to the stacking axis. Below
its N\'{e}el temperature, K, CrSBr adopts an A-type
antiferromagnetic structure with each individual layer ferromagnetically
ordered internally and the layers coupled antiferromagnetically along the
stacking direction. Scanning tunneling spectroscopy and photoluminescence (PL)
reveal that the electronic gap is eV with a
corresponding PL peak centered at eV. Using magnetotransport
measurements, we demonstrate strong coupling between magnetic order and
transport properties in CrSBr, leading to a large negative magnetoresistance
response that is unique amongst vdW materials. These findings establish CrSBr
as a promising material platform for increasing the applicability of vdW
magnets to the field of spin-based electronics
Effects of climate-induced changes in isoprene emissions after the eruption of Mount Pinatubo
In the 1990s the rates of increase of greenhouse gas concentrations, most notably of methane, were observed to change, for reasons that have yet to be fully determined. This period included the eruption of Mt. Pinatubo and an El Nino warm event, both of which affect biogeochemical processes, by changes in temperature, precipitation and radiation. We examine the impact of these changes in climate on global isoprene emissions and the effect these climate dependent emissions have on the hydroxy radical, OH, the dominant sink for methane. We model a reduction of isoprene emissions in the early 1990s, with a maximum decrease of 40 Tg(C)/yr in late 1992 and early 1993, a change of 9%. This reduction is caused by the cooler, drier conditions following the eruption of Mt. Pinatubo. Isoprene emissions are reduced both directly, by changes in temperature and a soil moisture dependent suppression factor, and indirectly, through reductions in the total biomass. The reduction in isoprene emissions causes increases of tropospheric OH which lead to an increased sink for methane of up to 5 Tg(CH4)/year, comparable to estimated source changes over the time period studied. There remain many uncertainties in the emission and oxidation of isoprene which may affect the exact size of this effect, but its magnitude is large enough that it should remain important
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