448 research outputs found
Intermolecular C-H activation with an Ir-METAMORPhos piano-stool complex: multiple reaction steps at a reactive ligand
Substrate activation by means of a reactive ligand is a topic of much interest. Herein we describe a stoichiometric anti-Markovnikov C-N bond formation involving ligand reactivity in multiple steps along the reaction coordinate, including ligand assisted substrate (de)protonation and C-N bond formation, as illustrated by a combined experimental, spectroscopic and computational study. This affords a highly unusual four-membered iridacycle bearing an exo-cyclic C=C double bond
Політичні процеси в українському суспільстві на початку ХХІ століття
У статті висвітлюються питання щодо наукового осмислення
політичних процесів розвитку українського суспільства на
початку ХХІ століття та ролі політичної науки у процесах його
функціонування.The author reviews the problems of scientific conceptualizing of
political processes of the development of Ukrainian society at the
beginning of the 21-st century and the role of political science in
processes of its functioning
PhenTAA: A Redox-Active N<sub>4</sub>-Macrocyclic Ligand Featuring Donor and Acceptor Moieties
Here, we present the development and characterization of the novel PhenTAA macrocycle as well as a series of [Ni(R2PhenTAA)]n complexes featuring two sites for ligand-centered redox-activity. These differ in the substituent R (R = H, Me, or Ph) and overall charge of the complex n (n = −2, −1, 0, +1, or +2). Electrochemical and spectroscopic techniques (CV, UV/vis-SEC, X-band EPR) reveal that all redox events of the [Ni(R2PhenTAA)] complexes are ligand-based, with accessible ligand charges of −2, −1, 0, +1, and +2. The o-phenylenediamide (OPD) group functions as the electron donor, while the imine moieties act as electron acceptors. The flanking o-aminobenzaldimine groups delocalize spin density in both the oxidized and reduced ligand states. The reduced complexes have different stabilities depending on the substituent R. For R = H, dimerization occurs upon reduction, whereas for R = Me/Ph, the reduced imine groups are stabilized. This also gives electrochemical access to a [Ni(R2PhenTAA)]2- species. DFT and TD-DFT calculations corroborate these findings and further illustrate the unique donor-acceptor properties of the respective OPD and imine moieties. The novel [Ni(R2PhenTAA)] complexes exhibit up to five different ligand-based oxidation states and are electrochemically stable in a range from −2.4 to +1.8 V for the Me/Ph complexes (vs Fc/Fc+).</p
An ultra-deep multi-band VLA survey of the faint radio sky (COSMOS-XS): New constraints on the cosmic star formation history
We make use of ultra-deep 3 GHz Karl G. Jansky Very Large Array observations
of the COSMOS field from the multi-band COSMOS-XS survey to infer radio
luminosity functions (LFs) of star-forming galaxies (SFGs). Using 1300
SFGs with redshifts out to , and fixing the faint and bright end
shape of the radio LF to the local values, we find a strong redshift trend that
can be fitted by pure luminosity evolution with the luminosity parameter given
by . We then combine the
ultra-deep COSMOS-XS data-set with the shallower VLA-COSMOS
large project data-set over the wider COSMOS field in order to fit for joint
density+luminosity evolution, finding evidence for significant density
evolution. By comparing the radio LFs to the observed far-infrared (FIR) and
ultraviolet (UV) LFs, we find evidence of a significant underestimation of the
UV LF by at high redshift (,
integrated down to ). We derive the cosmic star
formation rate density (SFRD) by integrating the fitted radio LFs and find that
the SFRD rises up to and then declines more rapidly than
previous radio-based estimates. A direct comparison between the radio SFRD and
a recent UV-based SFRD, where we integrate both LFs down to a consistent limit
(), reveals that the discrepancy between the radio and
UV LFs translates to a significant (1 dex) discrepancy in the derived
SFRD at , even assuming the latest dust corrections and without accounting
for optically dark sources.Comment: Submitted to ApJ; 27 pages, 13 figures, 4 table
Contributions of amino acid, acylcarnitine and sphingolipid profiles to type 2 diabetes risk among South-Asian Surinamese and Dutch adults
Introduction:
People of South Asian origin are at high risk of type 2 diabetes (T2D), but the underpinning mechanisms are not fully understood. We determined ethnic differences in acylcarnitine, amino acid and sphingolipid concentrations and determined the associations with T2D.
Research design and methods:
Associations between these metabolites and incident T2D among Dutch and South-Asian Surinamese were determined in participants from the Healthy Life in an Urban Setting (HELIUS) study (Amsterdam, the Netherlands) using Prentice-weighted Cox regression. The HELIUS study includes 95 incident T2D cases and a representative subcohort of 700 people from a cohort of 5977 participants with a mean follow-up of 4 years.
Results:
Concentrations of acylcarnitines were comparable between both ethnic groups. Amino acid and lactosylceramide concentrations were higher among South-Asian Surinamese than Dutch (eg, isoleucine 65.7 (SD 16.3) vs 60.7 (SD 15.6) µmol/L). Ceramide concentrations were lower among South-Asian Surinamese than Dutch (eg, Cer d18:1 8.48 (SD 2.04) vs 9.08 (SD 2.29) µmol/L). Metabolic dysregulation preceded T2D without evidence for a multiplicative interaction by ethnicity. Most amino acids and (dihydro)ceramides were associated with increased risk (eg, Cer d18:1 HR 2.38, 95% CI 1.81 to 3.12) while acylcarnitines, glycine, glutamine and lactosylceramides were associated with decreased risk for T2D (eg, LacCer d18:2 HR 0.56, 95% CI 0.42 to 0.77).
Conclusions:
Overall, these data suggest that the disturbances underlying amino acid and sphingolipid metabolism may be predictive of T2D risk in populations of both South Asian and European background. These observations may be used as starting point to unravel the underlying metabolic disturbances
Continuous monitoring of colonoscopy performance in the Netherlands: first results of a nationwide registry
Background To optimize colonoscopy quality, several performance measures have been developed. These are usually assessed without distinction between the indications for colonoscopy. This study aimed to assess the feasibility of linking two national registries (one for colonoscopy and one for adverse events of gastrointestinal endoscopies in the Netherlands), and to describe the results of colonoscopy quality per indication.Methods This retrospective study was conducted with prospectively collected data of the Dutch Gastrointestinal Endoscopy Audit (DGEA) and the Dutch Registration of Complications in Endoscopy (DRCE). Data between 01-01-2016 and 01-01-2019 were analyzed. To calculate adverse event rates, data were linked at the level of endoscopy service.Results During the 3-year study period, 266 981 colonoscopies were recorded in DGEA. Of all indications, cecal intubation rate was highest in fecal immunochemical test (FIT)-positive screening colonoscopies (97.1 %), followed by surveillance (93.2 %), diagnostic (90.7 %), and therapeutic colonoscopies (83.1 %). The highest rate of adequate bowel preparation was observed in FIT-positive screening colonoscopies (97.1 %). A total of 1540 colonoscopy-related adverse events occurred (0.58 % of all colonoscopies). Bleeding and perforation and rates were highest for therapeutic (1.56 % and 0.51 %, respectively) and FIT-positive screening (0.72 % and 0.06 %, respectively) colonoscopies. The colonoscopy-related mortality was 0.006 %.Conclusion This study describes the first results of the Dutch national colonoscopy registry, which was successfully linked to data from the national registry for adverse events of gastrointestinal endoscopies. In this large dataset, performance varied between indications. Our results emphasize the importance of defining benchmarks per indication in future guidelines.Cellular mechanisms in basic and clinical gastroenterology and hepatolog
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