2,018 research outputs found
Luminescent gold(III) thiolates: Supramolecular interactions trigger and control switchable photoemissions from bimolecular excited states
A new family of cyclometallated gold(III) thiolato complexes based on pyrazine-centred pincer ligands has been prepared, (C^Npz^C)AuSR, where C^Npz^C=2,6-bis(4-ButC6H4)pyrazine dianion and R=Ph (1), C6H4tBu-4 (2), 2-pyridyl (3), 1-naphthyl (1-Np, 4), 2-Np (5), quinolinyl (Quin, 6), 4-methylcoumarinyl (Coum, 7) and 1-adamantyl (8). The complexes were isolated as yellow to red solids in high yields using mild synthetic conditions. The single-crystal X-ray structures revealed that the colour of the deep-red solids is associated with the formation of a particular type of short (3.2â3.3â
Ă
) intermolecular pyrazineâ
â
â
pyrazine Ď-interactions. In some cases, yellow and red crystal polymorphs were formed; only the latter were emissive at room temperature. Combined NMR and UV/Vis techniques showed that the supramolecular Ď-stacking interactions persist in solution and give rise to intense deep-red photoluminescence. Monomeric molecules show vibronically structured green emissions at low temperature, assigned to ligand-based 3IL(C^N^C) triplet emissions. By contrast, the unstructured red emissions correlate mainly with a 3LLCT(SRâ{(C^Npz^C)2}) charge transfer transition from the thiolate ligand to the Ďâ
â
â
Ď dimerized pyrazine. Unusually, the Ď-interactions can be influenced by sample treatment in solution, such that the emissions can switch reversibly from red to green. To our knowledge this is the first report of aggregation-enhanced emission in gold(III) chemistry
Planet Sensitivity from Combined Ground- and Space-based Microlensing Observations
To move one step forward toward a Galactic distribution of planets, we
present the first planet sensitivity analysis for microlensing events with
simultaneous observations from space and the ground. We present this analysis
for two such events, OGLE-2014-BLG-0939 and OGLE-2014-BLG-0124, which both show
substantial planet sensitivity even though neither of them reached high
magnification. This suggests that an ensemble of low to moderate magnification
events can also yield significant planet sensitivity and therefore probability
to detect planets. The implications of our results to the ongoing and future
space-based microlensing experiments to measure the Galactic distribution of
planets are discussed.Comment: 10 pages, 5 figures, 1 table; ApJ in pres
MOA-2016-BLG-227Lb: A Massive Planet Characterized by Combining Light-curve Analysis and Keck AO Imaging
We report the discovery of a microlensing planetâMOA-2016-BLG-227Lbâwith a large planet/host mass ratio of q â 9 Ă 10â3. This event was located near the K2 Campaign 9 field that was observed by a large number of telescopes. As a result, the event was in the microlensing survey area of a number of these telescopes, and this enabled good coverage of the planetary light-curve signal. High angular resolution adaptive optics images from the Keck telescope reveal excess flux at the position of the source above the flux of the source star, as indicated by the light-curve model. This excess flux could be due to the lens star, but it could also be due to a companion to the source or lens star, or even an unrelated star. We consider all these possibilities in a Bayesian analysis in the context of a standard Galactic model. Our analysis indicates that it is unlikely that a large fraction of the excess flux comes from the lens, unless solar-type stars are much more likely to host planets of this mass ratio than lower mass stars. We recommend that a method similar to the one developed in this paper be used for other events with high angular resolution follow-up observations when the follow-up observations are insufficient to measure the lensâsource relative proper motion
MOA-2011-BLG-293Lb: A test of pure survey microlensing planet detections
Because of the development of large-format, wide-field cameras, microlensing
surveys are now able to monitor millions of stars with sufficient cadence to
detect planets. These new discoveries will span the full range of significance
levels including planetary signals too small to be distinguished from the
noise. At present, we do not understand where the threshold is for detecting
planets. MOA-2011-BLG-293Lb is the first planet to be published from the new
surveys, and it also has substantial followup observations. This planet is
robustly detected in survey+followup data (Delta chi^2 ~ 5400). The planet/host
mass ratio is q=5.3+/- 0.2*10^{-3}. The best fit projected separation is
s=0.548+/- 0.005 Einstein radii. However, due to the s-->s^{-1} degeneracy,
projected separations of s^{-1} are only marginally disfavored at Delta
chi^2=3. A Bayesian estimate of the host mass gives M_L = 0.43^{+0.27}_{-0.17}
M_Sun, with a sharp upper limit of M_L < 1.2 M_Sun from upper limits on the
lens flux. Hence, the planet mass is m_p=2.4^{+1.5}_{-0.9} M_Jup, and the
physical projected separation is either r_perp = ~1.0 AU or r_perp = ~3.4 AU.
We show that survey data alone predict this solution and are able to
characterize the planet, but the Delta chi^2 is much smaller (Delta chi^2~500)
than with the followup data. The Delta chi^2 for the survey data alone is
smaller than for any other securely detected planet. This event suggests a
means to probe the detection threshold, by analyzing a large sample of events
like MOA-2011-BLG-293, which have both followup data and high cadence survey
data, to provide a guide for the interpretation of pure survey microlensing
data.Comment: 29 pages, 6 figures, Replaced 7/3/12 with the version accepted to Ap
Characterizing Low-Mass Binaries From Observation of Long Time-scale Caustic-crossing Gravitational Microlensing Events
Despite astrophysical importance of binary star systems, detections are
limited to those located in small ranges of separations, distances, and masses
and thus it is necessary to use a variety of observational techniques for a
complete view of stellar multiplicity across a broad range of physical
parameters. In this paper, we report the detections and measurements of 2
binaries discovered from observations of microlensing events MOA-2011-BLG-090
and OGLE-2011-BLG-0417. Determinations of the binary masses are possible by
simultaneously measuring the Einstein radius and the lens parallax. The
measured masses of the binary components are 0.43 and 0.39
for MOA-2011-BLG-090 and 0.57 and 0.17 for
OGLE-2011-BLG-0417 and thus both lens components of MOA-2011-BLG-090 and one
component of OGLE-2011-BLG-0417 are M dwarfs, demonstrating the usefulness of
microlensing in detecting binaries composed of low-mass components. From
modeling of the light curves considering full Keplerian motion of the lens, we
also measure the orbital parameters of the binaries. The blended light of
OGLE-2011-BLG-0417 comes very likely from the lens itself, making it possible
to check the microlensing orbital solution by follow-up radial-velocity
observation. For both events, the caustic-crossing parts of the light curves,
which are critical for determining the physical lens parameters, were resolved
by high-cadence survey observations and thus it is expected that the number of
microlensing binaries with measured physical parameters will increase in the
future.Comment: 8 pages, 5 figures, 4 table
Heat shock proteins in chronic kidney disease
Heat shock proteins (HSP) form a heterogenous, evolutionarily conserved group of molecules with high sequence homology. They mainly act as intracellular chaperones, protecting the protein structure and folding under stress conditions. The extracellular HSP, released in the course of damage or necrosis, play a pivotal role in the innate and adaptive immune responses. They also take part in many pathological processes. The aim of this review is to update the recent developments in the field of HSP in chronic kidney disease (CKD), in regard to three different aspects. The first is the assessment of the role of HSP, either positive or deleterious, in the pathogenesis of CKD and the possibilities to influence its progression. The second is the impact of dialysis, being a potentially modifiable stressor, on HSP and the attempt to assess the value of these proteins as the biocompatibility markers. The last area is that of kidney transplantation and the potential role of HSP in the induction of the immune tolerance in kidney recipients
MOA-2010-BLG-477Lb: constraining the mass of a microlensing planet from microlensing parallax, orbital motion and detection of blended light
Microlensing detections of cool planets are important for the construction of
an unbiased sample to estimate the frequency of planets beyond the snow line,
which is where giant planets are thought to form according to the core
accretion theory of planet formation. In this paper, we report the discovery of
a giant planet detected from the analysis of the light curve of a
high-magnification microlensing event MOA-2010-BLG-477. The measured
planet-star mass ratio is and the projected
separation is in units of the Einstein radius. The angular
Einstein radius is unusually large mas. Combining
this measurement with constraints on the "microlens parallax" and the lens
flux, we can only limit the host mass to the range . In
this particular case, the strong degeneracy between microlensing parallax and
planet orbital motion prevents us from measuring more accurate host and planet
masses. However, we find that adding Bayesian priors from two effects (Galactic
model and Keplerian orbit) each independently favors the upper end of this mass
range, yielding star and planet masses of
and at a distance of kpc,
and with a semi-major axis of AU. Finally, we show that the
lens mass can be determined from future high-resolution near-IR adaptive optics
observations independently from two effects, photometric and astrometric.Comment: 3 Tables, 12 Figures, accepted in Ap
Developing search strategies for clinical practice guidelines in SUMSearch and Google Scholar and assessing their retrieval performance
<p>Abstract</p> <p>Background</p> <p>Information overload, increasing time constraints, and inappropriate search strategies complicate the detection of clinical practice guidelines (CPGs). The aim of this study was to provide clinicians with recommendations for search strategies to efficiently identify relevant CPGs in SUMSearch and Google Scholar.</p> <p>Methods</p> <p>We compared the retrieval efficiency (retrieval performance) of search strategies to identify CPGs in SUMSearch and Google Scholar. For this purpose, a two-term GLAD (GuideLine And Disease) strategy was developed, combining a defined CPG term with a specific disease term (MeSH term). We used three different CPG terms and nine MeSH terms for nine selected diseases to identify the most efficient GLAD strategy for each search engine. The retrievals for the nine diseases were pooled. To compare GLAD strategies, we used a manual review of all retrievals as a reference standard. The CPGs detected had to fulfil predefined criteria, e.g., the inclusion of therapeutic recommendations. Retrieval performance was evaluated by calculating so-called diagnostic parameters (sensitivity, specificity, and "Number Needed to Read" [NNR]) for search strategies.</p> <p>Results</p> <p>The search yielded a total of 2830 retrievals; 987 (34.9%) in Google Scholar and 1843 (65.1%) in SUMSearch. Altogether, we found 119 unique and relevant guidelines for nine diseases (reference standard). Overall, the GLAD strategies showed a better retrieval performance in SUMSearch than in Google Scholar. The performance pattern between search engines was similar: search strategies including the term "guideline" yielded the highest sensitivity (SUMSearch: 81.5%; Google Scholar: 31.9%), and search strategies including the term "practice guideline" yielded the highest specificity (SUMSearch: 89.5%; Google Scholar: 95.7%), and the lowest NNR (SUMSearch: 7.0; Google Scholar: 9.3).</p> <p>Conclusion</p> <p>SUMSearch is a useful tool to swiftly gain an overview of available CPGs. Its retrieval performance is superior to that of Google Scholar, where a search is more time consuming, as substantially more retrievals have to be reviewed to detect one relevant CPG. In both search engines, the CPG term "guideline" should be used to obtain a comprehensive overview of CPGs, and the term "practice guideline" should be used if a less time consuming approach for the detection of CPGs is desired.</p
A Sex-Specific Metabolite Identified in a Marine Invertebrate Utilizing Phosphorus-31 Nuclear Magnetic Resonance
Hormone level differences are generally accepted as the primary cause for sexual dimorphism in animal and human development. Levels of low molecular weight metabolites also differ between men and women in circulating amino acids, lipids and carbohydrates and within brain tissue. While investigating the metabolism of blue crab tissues using Phosphorus-31 Nuclear Magnetic Resonance, we discovered that only the male blue crab (Callinectes sapidus) contained a phosphorus compound with a chemical shift well separated from the expected phosphate compounds. Spectra obtained from male gills were readily differentiated from female gill spectra. Analysis from six years of data from male and female crabs documented that the sex-specificity of this metabolite was normal for this species. Microscopic analysis of male and female gills found no differences in their gill anatomy or the presence of parasites or bacteria that might produce this phosphorus compound. Analysis of a rare gynandromorph blue crab (laterally, half male and half female) proved that this sex-specificity was an intrinsic biochemical process and was not caused by any variations in the diet or habitat of male versus female crabs. The existence of a sex-specific metabolite is a previously unrecognized, but potentially significant biochemical phenomenon. An entire enzyme system has been synthesized and activated only in one sex. Unless blue crabs are a unique species, sex-specific metabolites are likely to be present in other animals. Would the presence or absence of a sex-specific metabolite affect an animal's development, anatomy and biochemistry
MOA-2016-BLG-227Lb: A Massive Planet Characterized by Combining Light-curve Analysis and Keck AO Imaging
We report the discovery of a microlensing planet - MOA-2016-BLG-227Lb - with a large planet/host mass ratio of q â 9 Ă10-3. This event was located near the K2 Campaign 9 field that was observed by a large number of telescopes. As a result, the event was in the microlensing survey area of a number of these telescopes, and this enabled good coverage of the planetary light-curve signal. High angular resolution adaptive optics images from the Keck telescope reveal excess flux at the position of the source above the flux of the source star, as indicated by the light-curve model. This excess flux could be due to the lens star, but it could also be due to a companion to the source or lens star, or even an unrelated star. We consider all these possibilities in a Bayesian analysis in the context of a standard Galactic model. Our analysis indicates that it is unlikely that a large fraction of the excess flux comes from the lens, unless solar-type stars are much more likely to host planets of this mass ratio than lower mass stars. We recommend that a method similar to the one developed in this paper be used for other events with high angular resolution follow-up observations when the follow-up observations are insufficient to measure the lens-source relative proper motion
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