58 research outputs found
Egy 14. századi új Salamon: V. (Bölcs) Károly francia király
The result of in-hospital all mortality (P < 0.001; RR 3.23; 95% CI 2.28–4.57). (DOCX 54 kb
A Practical Sequential Stopping Rule for High-Dimensional Markov Chain Monte Carlo
<p>A current challenge for many Bayesian analyses is determining when to terminate high-dimensional Markov chain Monte Carlo simulations. To this end, we propose using an automated sequential stopping procedure that terminates the simulation when the computational uncertainty is small relative to the posterior uncertainty. Further, we show this stopping rule is equivalent to stopping when the effective sample size is sufficiently large. Such a stopping rule has previously been shown to work well in settings with posteriors of moderate dimension. In this article, we illustrate its utility in high-dimensional simulations while overcoming some current computational issues. As examples, we consider two complex Bayesian analyses on spatially and temporally correlated datasets. The first involves a dynamic space-time model on weather station data and the second a spatial variable selection model on fMRI brain imaging data. Our results show the sequential stopping rule is easy to implement, provides uncertainty estimates, and performs well in high-dimensional settings. Supplementary materials for this article are available online.</p
Enantioselective 2‑Alkylation of 3‑Substituted Indoles with Dual Chiral Lewis Acid/Hydrogen-Bond-Mediated Catalyst
A chiral-at-metal bis-cyclometalated
iridium complex combines electrophile
activation via metal coordination with nucleophile activation through
hydrogen bond formation. This new bifunctional chiral Lewis acid/hydrogen-bond-mediated
catalyst permits the challenging enantioselective 2-alkylation of
3-substituted indoles with α,β-unsaturated 2-acyl imidazoles
in up to 99% yield and with up to 98% enantiomeric excess at a catalyst
loading of 2 mol %. As an application, the straightforward synthesis
of a chiral pyrroloÂ[1,2-<i>a</i>]Âindole is demonstrated
Restricted Conformation of a Hydrogen Bond Mediated Catalyst Enables the Highly Efficient Enantioselective Construction of an All-Carbon Quaternary Stereocenter
A highly
active catalyst for the enantioselective Friedel–Crafts
alkylation of indoles with β,β-disubstituted nitroalkenes
is reported, allowing catalyst loadings down to 0.05 mol % for this
challenging transformation, providing useful synthetic building blocks
with an all-carbon quaternary stereocenter. The catalyst is based
on a bis-cyclometalated iridiumÂ(III) complex as a structural template,
and through the ligand sphere it forms hydrogen bonds with the two
substrates. Starting from a previous design (<i>Angew. Chem.
Int. Ed.</i> <b>2013</b>, <i>52</i>, 14021),
the catalyst was rendered <i>C</i><sub>2</sub>-symmetrical
in order to maximize the atom economy of this catalyst scaffold (two
catalytic centers per iridium complex), and, most importantly, rational
design was applied to restrict the conformational freedom of a key
hydrogen bond acceptor, being responsible for activating the indole
nucleophile and bringing it in an ideal position for the presumed
ternary transition state
Measurements of Secondary Organic Aerosol Formed from OH-initiated Photo-oxidation of Isoprene Using Online Photoionization Aerosol Mass Spectrometry
Isoprene is a significant source of atmospheric organic
aerosol;
however, the secondary organic aerosol (SOA) formation and involved
chemical reaction pathways have remained to be elucidated. Recent
works have shown that the photo-oxidation of isoprene leads to form
SOA. In this study, the chemical composition of SOA from the OH-initiated
photo-oxidation of isoprene, in the absence of seed aerosols, was
investigated through the controlled laboratory chamber experiments.
Thermal desorption/tunable vacuum-ultraviolet photoionization time-of-flight
aerosol mass spectrometry (TD-VUV-TOF-PIAMS) was used in conjunction
with the environmental chamber to study SOA formation. The mass spectra
obtained at different photon energies and the photoionization efficiency
(PIE) spectra of the SOA products can be obtained in real time. Aided
by the ionization energies (IE) either from the ab initio calculations
or the literatures, a number of SOA products were proposed. In addition
to methacrolein, methyl vinyl ketone, and 3-methyl-furan, carbonyls,
hydroxycarbonyls, nitrates, hydroxynitrates, and other oxygenated
compounds in SOA formed in laboratory photo-oxiadation experiments
were identified, some of them were investigated for the first time.
Detailed chemical identification of SOA is crucial for understanding
the photo-oxidation mechanisms of VOCs and the eventual formation
of SOA. Possible reaction mechanisms will be discussed
Asymmetric Construction of 3,3-Disubstituted Oxindoles Bearing Vicinal Quaternary–Tertiary Carbon Stereocenters Catalyzed by a Chiral-at-Rhodium Complex
A highly
diastereo- and enantioselective synthesis of 3,3-disubstituted
oxindoles bearing vicinal quaternary–tertiary carbon centers
is enabled by a chiral-at-rhodium Lewis acid catalyst starting from
isatin <i>N</i>-protected ketimines and 2-acyl imidazoles.
The excellent results with 93–99% yields, diastereoselectivities
of 43:1 to >200:1, and high enantioselectivities of 98.4 to >99%
confirm
the potential of bis-cyclometalated rhodium catalysts for the development
of effective asymmetric transformations
Media 1: Optical trapping of red blood cells in living animals with a water immersion objective
Originally published in Optics Letters on 01 December 2013 (ol-38-23-5134
Optimizing the Reinforcement of Polymer-Based Nanocomposites by Graphene
The stress transfer between the internal layers of multilayer graphene within polymer-based nanocomposites has been investigated from the stress-induced shifts of the 2D Raman band. This has been undertaken through the study of the deformation of an ideal composite system where the graphene flakes were placed upon the surface of a polymer beam and then coated with an epoxy polymer. It is found that the rate of band shift per unit strain for a monolayer graphene flake is virtually independent of whether it has one or two polymer interfaces (<i>i</i>.<i>e</i>., with or without an epoxy top coating). In contrast, the rate of band shift is lower for an uncoated bilayer specimen than a coated one, indicating relatively poor stress transfer between the graphene layers. Mapping of the strain in the coated bilayer regions has shown that there is strain continuity between adjacent monolayer and bilayer regions, indicating that they give rise to similar levels of reinforcement. Strain-induced Raman band shifts have also been evaluated for separate flakes of graphene with different numbers of layers, and it is found that the band shift rate tends to decrease with an increase in the number of layers, indicating poor stress transfer between the inner graphene layers. This behavior has been modeled in terms of the efficiency of stress transfer between the inner graphene layers. Taking into account the packing geometry of polymer-based graphene nanocomposites and the need to accommodate the polymer coils, these findings enable the optimum number of graphene layers for the best reinforcement to be determined. It is demonstrated that, in general, multilayer graphene will give rise to higher levels of reinforcement than monolayer material, with the optimum number of layers depending upon the separation of the graphene flakes in the nanocomposite
Additional file 2 of Predictive value of neutrophil to lymphocyte ratio in patients with acute ST segment elevation myocardial infarction after percutaneous coronary intervention: a meta-analysis
The result of Angina(P = 0.007; RR 1.67; 95%CI 1.15–2.41). (DOCX 41 kb
Additional file 4 of Predictive value of neutrophil to lymphocyte ratio in patients with acute ST segment elevation myocardial infarction after percutaneous coronary intervention: a meta-analysis
The result of in-stent thrombosis (P < 0.001; RR 2.72; 95%CI 1.66–4.44). (DOCX 41 kb
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