2,716 research outputs found
Extended main-sequence turnoffs in the double cluster and Persei: The complex role of stellar rotation
Using {\sl Gaia} Data Release 2 photometry, we report the detection of
extended main-sequence turnoff (eMSTO) regions in the color--magnitude diagrams
(CMDs) of the Myr-old double clusters and Persei (NGC 869
and NGC 884). We find that stars with masses below 1.3 in
both and Persei populate narrow main sequences (MSs), while more
massive stars define the eMSTO, closely mimicking observations of young
Galactic and Magellanic Cloud clusters (with ages older than 30 Myr).
Previous studies based on clusters older than 30 Myr find that rapidly
rotating MS stars are redder than slow rotators of similar luminosity,
suggesting that stellar rotation may be the main driver of the eMSTO. By
combining photometry and projected rotational velocities from the literature of
stars in and Persei, we find no obvious relation between the
rotational velocities and colors of non-emission-line eMSTO stars, in contrast
with what is observed in older clusters. Similarly to what is observed in
Magellanic Cloud clusters, most of the extremely rapidly rotating stars,
identified by their strong H emission lines, are located in the red
part of the eMSTOs. This indicates that stellar rotation plays a role in the
color and magnitude distribution of MSTO stars. By comparing the observations
with simulated CMDs, we find that a simple population composed of coeval stars
that span a wide range of rotation rates is unable to reproduce the color
spread of the clusters' MSs. We suggest that variable stars, binary
interactions, and stellar rotation affect the eMSTO morphology of these very
young clusters.Comment: 14 pages, 12 figures, ApJ accepte
Maternal exposure to angiotensin converting enzyme inhibitors in the first trimester and risk of malformations in offspring: a retrospective cohort study
OBJECTIVE: To examine a reported association between use of angiotensin converting enzyme (ACE) inhibitors during the first trimester and risk of malformations in offspring.
DESIGN: A population based, retrospective cohort study linking automated clinical and pharmacy databases including comprehensive electronic medical records.
PARTICIPANTS: Pregnant women and their live born offspring (465,754 mother-infant pairs) in the Kaiser Permanente Northern California region from 1995 to 2008.
MAIN OUTCOME MEASURE: Congenital malformation in live births.
RESULTS: The prevalence of ACE inhibitor use in the first trimester only was 0.9/1000, and the use of other antihypertensive medications was 2.4/1000. After adjustment for maternal age, ethnicity, parity, and obesity, use of ACE inhibitors during the first trimester only seemed to be associated with increased risk of congenital heart defects in offspring compared with normal controls (those with neither hypertension nor use of any antihypertensives during pregnancy) (15/381 (3.9%) v 6232/400,021 (1.6%) cases, odds ratio 1.54 (95% confidence interval 0.90 to 2.62)). A similar association was observed for use of other antihypertensives (28/1090 (2.6%) cases of congenital heart defects, odds ratio 1.52 (1.04 to 2.21)). However, compared with hypertension controls (those with a diagnosis of hypertension but without use of antihypertensives) (708/29,735 (2.4%) cases of congenital heart defects), neither use of ACE inhibitors or of other antihypertensives in the first trimester was associated with increased congenital heart defects risk (odds ratios 1.14 (0.65 to 1.98) and 1.12 (0.76 to 1.64) respectively).
CONCLUSIONS: Maternal use of ACE inhibitors in the first trimester has a risk profile similar to the use of other antihypertensives regarding malformations in live born offspring. The apparent increased risk of malformations associated with use of ACE inhibitors (and other antihypertensives) in the first trimester is likely due to the underlying hypertension rather than the medications
Atomic physics on a 50 nm scale: Realization of a bilayer system of dipolar atoms
Atomic physics has greatly advanced quantum science, mainly due to the
ability to control the position and internal quantum state of atoms with high
precision, often at the quantum limit. The dominant tool for this is laser
light, which can structure and localize atoms in space (e.g., in optical
tweezers, optical lattices, 1D tubes or 2D planes). Due to the diffraction
limit of light, the natural length scale for most experiments with atoms is on
the order of 500 nm or larger. Here we implement a new super-resolution
technique which localizes and arranges atoms on a sub-50 nm scale, without any
fundamental limit in resolution. We demonstrate this technique by creating a
bilayer of dysprosium atoms, mapping out the atomic density distribution with
sub-10 nm resolution, and observing dipolar interactions between two physically
separated layers via interlayer sympathetic cooling and coupled collective
excitations. At 50 nm, dipolar interactions are 1,000 times stronger than at
500 nm. For two atoms in optical tweezers, this should enable purely magnetic
dipolar gates with kHz speed
The topological differences between visitation and pollen transport networks: a comparison in species rich communities of the Himalaya–Hengduan Mountains
Pollination networks are usually constructed and assessed by direct field observations which commonly assume that all flower visitors are true pollinators. However, this assumption is often invalid and the use of data based on mere visitors to flowers may lead to a misunderstanding of intrinsic pollination networks. Here, using a large dataset by both sampling floral visitors and analyzing their pollen loads, we constructed 32 networks pairs (visitation versus pollen transport) across one flowering season at four elevation sites in the Himalaya–Hengduan Mountains region. Pollen analysis was conducted to determine which flower visitors acted as potential pollinators (pollen vectors) or as cheaters (those not carrying pollen of the visited plants). We tested whether there were topological differences between visitation and pollen transport networks and whether different taxonomic groups of insect visitors differed in their ability to carry pollen of the visited plants. Our results indicated that there was a significantly higher degree of specialization at both the network and species levels in the pollen transport networks in contrast to the visitation networks. Modularity was lower but nestedness was higher in the visitation networks compared to the pollen transport networks. All the cheaters were identified as peripheral species and most of them contributed positively to the nested structure. This may explain in part the differences in modularity and nestedness between the two network types. Bees carried the highest proportion of pollen of the visited plants. This was followed by Coleoptera, other Hymenoptera and Diptera. Lepidoptera carried the lowest proportion of pollen of the visited plants. Our study shows that the construction of pollen transport networks could provide a more in-depth understanding of plant–pollinator interactions. Moreover, it suggests that detecting and removing cheater interactions when studying the topology of other mutualistic networks might be also important.This study was supported by Strategic Priority Research Program of the Chinese Academy of Sciences (XDB31020000), National Key Basic Research Program of China (2014CB954100), Joint Fund of the National Natural Science Foundation of China-Yunnan Province (U1502261), Major International Joint Research Project of NSF China (31320103919), Applied Fundamental Research Foundation of Yunnan Province (2014GA003), National Natural Science Foundation of China (31700361), Yunlin Scholarship of Yunnan Province to H. Wang (YLXL20170001) and CAS ‘Light of West China’ Program to Y.H. Zhao. A. Lázaro was supported by a Ramóny Cajal contract financed by the Spanish Ministry of Economy and Competitiveness
Phenomenological Scaling of Rapidity Dependence for Anisotropic Flows in 25 MeV/nucleon Ca + Ca by Quantum Molecular Dynamics Model
Anisotropic flows (, , and ) of light fragments up till
the mass number 4 as a function of rapidity have been studied for 25
MeV/nucleon Ca + Ca at large impact parameters by Quantum
Molecular Dynamics model. A phenomenological scaling behavior of rapidity
dependent flow parameters (n = 1, 2, 3 and 4) has been found as a
function of mass number plus a constant term, which may arise from the
interplay of collective and random motions. In addition, keeps
almost independent of rapidity and remains a rough constant of 1/2 for all
light fragments.Comment: 4 pages, 5 figure
Insecticidal Activity of the Leaf and Stem Water Extract of Gelsemium elegans against Solenopsis invicta
A comprehensive green worker ants control method that can be used to replace traditional chemical synthetic insecticides. In this study, the leaves and stems of Gelsemium elegans were extracted with water as the solvent, and the bioactivity of G. elegans against worker ants was determined by the “water tube” method. The bioassay results of insecticidal activity showed that when the time was extended to the 10th day, the mortality of worker ants treated with G. elegans extract reached 55.00% (1/20 leaf extract), 46.67% (1/20 stem extract) and 45.00% (1 mg/kg koumine). And the behavioral impact test results showed that the aggregation rate was reduced to 56.67% (1/100 leaf extract), 60.00% (1/100 stem extract) and 60.00% (0.5 mg/kg koumine); the climbing rate was reduced to 60.00 % (1/100 leaf extract), 58.33% (1/100 stem extract) and 58.33% (0.5 mg/kg koumine). The effect on the walking ability of worker ants is obvious. The walking rate drops to 1.53cm/s (1/100 leaf extract), 1.60cm/s (1/100 stem extract) and 1.47cm/s (0.5 mg/kg koumine). Therefore, we conclude that the water extract of G. elegans can be used for long-term continuous control of worker ants, which can be used to replace traditional chemical synthetic insecticides
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