2,946 research outputs found
Magnetic behaviour of PrPd2B2C
We have synthesized a new quaternary borocarbide PrPdBC and
measured its magnetization, electrical resistivity and specific heat. The
compound crystallizes in the LuNiBC-type tetragonal structure
(space group {\it I4/mmm}). Above 100 K the magnetic susceptibility follows
Curie-Weiss behavior with effective moment = 3.60 , which
is very close to the value expected for Pr ions. We do not find evidence
for magnetic or superconducting transition down to 0.5 K. Specific heat
exhibits a broad Schottky type anomaly with a peak at 24 K, very likely related
to crystal electric field (CEF) excitation. The magnetic properties suggest the
presence of a singlet CEF ground state leading to a Van-Vleck paramagnetic
ground state.Comment: 2 pages, 2 figure
The Ecology And Evolution Of Natal Philopatry In Migratory Songbirds Breeding In Managed Habitats
Knowledge of which cues attract natal dispersers back to natal areas is important for conservation because these cues could be used to attract breeders to source habitat or discourage breeders from settling in sink habitat. We examined the influence of intrinsic and extrinsic variables on natal philopatry using two metrics, short-distance natal dispersal and the probability of philopatry to the natal field, in two obligate grassland bird species breeding in an agricultural landscape: the Bobolink (Dolichonyx oryzivorus) and Savannah Sparrow (Passerculus sandwichensis). We also measured heritability and evolvability of morphological traits in the Savannah Sparrow. During 2002-2014 we detected 90 and 129 locally hatched Savannah Sparrows and Bobolinks breeding as adults on or near their places of origin (mean±SD dispersal distances: Savannah Sparrows 917 ± 851m; Bobolinks 1,251 ± 839m). Natal dispersal distance was genetically influenced, i.e., partially heritable for Savannah Sparrows (h2=0.153 ± 0.087), but there was no detectable heritability for Bobolinks. The probability a Savannah Sparrow was philopatric increased as fledge date increased, while the probability decreased if there was an opposite sex parent or sibling present on the natal field or the field was under a late-hay management scheme. None of the variables considered explained variation in Bobolink natal philopatry. Natal philopatry and short-distance natal dispersal in these species appear to be influenced by factors that are difficult to manage. Heritabilities varied from low to high (Bill Width: 0.160±0.182 to Tarsus: 0.651±0.155), while evolvabilities were low across all traits except mass, which was six times higher than the second highest measured in this study (Wing: 0.035±0.013 to Tarsus: 0.064±0.019; Mass: 0.399±0.280). While most of the traits examined have low evolutionary potential in our study population, body mass has relatively high potential; furthermore our previous work indicated that they may be under strong selection from agricultural management that influences mating and reproductive success
Therapeutic approaches with intravitreal injections in geographic atrophy secondary to age-related macular degeneration: current drugs and potential molecules
The present review focuses on recent clinical trials that analyze the efficacy of
intravitreal therapeutic agents for the treatment of dry age-related macular degeneration (AMD),
such as neuroprotective drugs, and complement inhibitors, also called immunomodulatory or
anti-inflammatory agents. A systematic literature search was performed to identify randomized
controlled trials published prior to January 2019. Patients affected by dry AMD treated with
intravitreal therapeutic agents were included. Changes in the correct visual acuity and reduction in
geographic atrophy progression were evaluated. Several new drugs have shown promising results,
including those targeting the complement cascade and neuroprotective agents. The potential action
of the two groups of drugs is to block complement cascade upregulation of immunomodulating
agents, and to prevent the degeneration and apoptosis of ganglion cells for the neuroprotectors,
respectively. Our analysis indicates that finding treatments for dry AMD will require continued
collaboration among researchers to identify additional molecular targets and to fully interrogate the
utility of pluripotent stem cells for personalized therapy
Insights on star formation histories and physical properties of Herschel-detected galaxies
We test the impact of using variable star forming histories (SFHs) and the
use of the IR luminosity (LIR) as a constrain on the physical parameters of
high redshift dusty star-forming galaxies. We explore in particular the stellar
properties of galaxies in relation with their location on the SFR-M* diagram.
We perform SED fitting of the UV-NIR and FIR emissions of a large sample of
GOODS-Herschel galaxies, for which rich multi-wavelength observations are
available. We test different SFHs and imposing energy conservation in the SED
fitting process, to face issues like the age-extinction degeneracy and produce
SEDs consistent with observations. Our models work well for the majority of the
sample, with the notable exception of the high LIR end, for which we have
indications that our simple energy conservation approach cannot hold true. We
find trends in the SFHs fitting our sources depending on stellar mass M* and z.
Trends also emerge in the characteristic timescales of the SED models depending
on the location on the SFR-M* diagram. We show that whilst using the same
available observational data, we can produce galaxies less star-forming than
usually inferred, if we allow declining SFHs, while properly reproducing their
observables. These sources can be post-starbursts undergoing quenching, and
their SFRs are potentially overestimated if inferred from their LIR. Fitting
without the IR constrain leads to a strong preference for declining SFHs, while
its inclusion increases the preference of rising SFHs, more so at high z, in
tentative agreement with the cosmic star formation history. Keeping in mind
that the sample is biased towards high LIR, the evolution shaped by our model
appears as both bursty (initially) and steady-lasting (later on). The global
SFH of the sample follows the cosmic SFH with a small scatter, and is
compatible with the "downsizing" scenario of galaxy evolution.Comment: 28 pages, 26 figures, one appendix, Accepted for publication in
Astronomy & Astrophysic
\u3cem\u3eRhizobium leguminosarum\u3c/em\u3e CFN42 Genetic Regions Encoding Lipopolysaccharide Structures Essential for Complete Nodule Development on Bean Plants
Eight symbiotic mutants defective in lipopolysaccharide (LPS) synthesis were isolated from Rhizobium leguminosarum biovar phaseoli CFN42. These eight strains elicited small white nodules lacking infected cells when inoculated onto bean plants. The mutants had undetectable or greatly diminished amounts of the complete LPS (LPS I), whereas amounts of an LPS lacking the O antigen (LPS II) greatly increased. Apparent LPS bands that migrated between LPS I and LPS II on sodium dodecyl sulfate-polyacrylamide gels were detected in extracts of some of the mutants. The mutant strains were complemented to wild-type LPS I content and antigenicity by DNA from a cosmid library of the wild-type genome. Most of the mutations were clustered in two genetic regions; one mutation was located in a third region. Strains complemented by DNA from two of these regions produced healthy nitrogen-fixing nodules. Strains complemented to wild-type LPS content by the other genetic region induced nodules that exhibited little or no nitrogenase activity, although nodule development was obviously enhanced by the presence of this DNA. The results support the idea that complete LPS structures, in normal amounts, are necessary for infection thread development in bean plants
Electronic structure basis for the titanic magnetoresistance in WTe
The electronic structure basis of the extremely large magnetoresistance in
layered non-magnetic tungsten ditelluride has been investigated by
angle-resolved photoelectron spectroscopy. Hole and electron pockets of
approximately the same size were found at the Fermi level, suggesting that
carrier compensation should be considered the primary source of the effect. The
material exhibits a highly anisotropic, quasi one-dimensional Fermi surface
from which the pronounced anisotropy of the magnetoresistance follows. A change
in the Fermi surface with temperature was found and a high-density-of-states
band that may take over conduction at higher temperatures and cause the
observed turn-on behavior of the magnetoresistance in WTe was identified
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