We have developed a nickel-catalyzed method for the asymmetric cross-coupling of secondary electrophiles with secondary nucleophiles, specifically, stereoconvergent Negishi reactions of racemic ...benzylic bromides with achiral cycloalkylzinc reagents. In contrast to most previous studies of enantioselective Negishi cross-couplings, tridentate pybox ligands are ineffective in this process; however, a new, readily available bidentate isoquinoline–oxazoline ligand furnishes excellent ee’s and good yields. The use of acyclic alkylzinc reagents as coupling partners led to the discovery of a highly unusual isomerization that generates a significant quantity of a branched cross-coupling product from an unbranched nucleophile.
Challenging space mission scenarios include those in low altitude orbits, where the atmosphere creates significant drag to the S/C and forces their orbit to an early decay. For drag compensation, ...propulsion systems are needed, requiring propellant to be carried on-board. An atmosphere-breathing electric propulsion system (ABEP) ingests the residual atmosphere particles through an intake and uses them as propellant for an electric thruster. Theoretically applicable to any planet with atmosphere, the system might allow to orbit for unlimited time without carrying propellant. A new range of altitudes for continuous operation would become accessible, enabling new scientific missions while reducing costs. Preliminary studies have shown that the collectible propellant flow for an ion thruster (in LEO) might not be enough, and that electrode erosion due to aggressive gases, such as atomic oxygen, will limit the thruster lifetime. In this paper an inductive plasma thruster (IPT) is considered for the ABEP system. The starting point is a small scale inductively heated plasma generator IPG6-S. These devices are electrodeless and have already shown high electric-to-thermal coupling efficiencies using O2 and CO2. The system analysis is integrated with IPG6-S tests to assess mean mass-specific energies of the plasma plume and estimate exhaust velocities.
•Collect and use planet's atmosphere as propellant for an electric thruster.•Compensate drag of satellites at very low altitudes to extend life time.•Inductive plasma thruster: electrodeless device to avoid electrode erosion.•First thrust estimation using a small-scale inductively heated plasma generator.•Results show feasibility of drag compensation for such a system.
In a convenient one-pot process, easily accessed propargyl vinyl ethers and aromatic amines are effectively converted into tetra- and pentasubstituted 5-methylpyrroles which can further be ...transformed into 5-formylpyrroles via IBX-mediated oxidation. The cascade reaction proceeds through a silver(I)-catalyzed propargyl−Claisen rearrangement, an amine condensation, and a gold(I)-catalyzed 5-exo-dig heterocyclization.
In this work, we present the development and application of a convolutional neural network (CNN)-based algorithm to precisely determine the interaction position of
-quanta in large monolithic ...scintillators. Those are used as an absorber component of a Compton camera (CC) system under development for ion beam range verification via prompt-gamma imaging. We examined two scintillation crystals: LaBr
:Ce and CeBr
. Each crystal had dimensions of 50.8 mm × 50.8 mm × 30 mm and was coupled to a 64-fold segmented multi-anode photomultiplier tube (PMT) with an 8 × 8 pixel arrangement. We determined the spatial resolution for three photon energies of 662, 1.17 and 1.33 MeV obtained from 2D detector scans with tightly collimated
Cs and
Co photon sources. With the new algorithm we achieved a spatial resolution for the CeBr3 crystal below 1.11(8) mm and below 0.98(7) mm for the LaBr3:Ce detector for all investigated energies between 662 keV and 1.33 MeV. We thereby improved the performance by more than a factor of 2.5 compared to the previously used categorical average pattern algorithm, which is a variation of the well-established k-nearest neighbor algorithm. The trained CNN has a low memory footprint and enables the reconstruction of up to 10
events per second with only one GPU. Those improvements are crucial on the way to future clinical
applicability of the CC for ion beam range verification.
Au‐spicious! Under silver‐free conditions, simple 3‐silyloxy‐1,5‐enynes were converted into complex cyclopentenes by a gold(I)‐catalyzed sequence that likely proceeds through a carbocyclization ...followed by a pinacol rearrangement. For the final demetalation step, isopropyl alcohol and N‐iodosuccinimide are effectively utilized, and the resulting products are set up for a wealth of further reactions.
PtCl2‐catalyzed alkyne activation initiates a domino reaction, in which a heterocyclization is followed by a 1,2‐alkyl migration, for the construction of a variety of substituted 3(2H)‐furanones. ...This stereospecific reaction is proposed to proceed through an oxonium ion intermediate (see scheme).
A combination of gold(I) complexes and amine bases catalyzes the 5-exo-dig cyclization of formyl alkynes. This direct α-functionalization of aldehydes with unactivated alkynes does not involve the ...use of preformed enol equivalents.
To evaluate the effect of age on the clinical benefit of atrial septal defect (ASD) closure in adults.
Functional status, the presence of arrhythmias, right ventricular (RV) remodelling, and ...pulmonary artery pressure (PAP) were studied in 236 consecutive patients undergoing transcatheter ASD closure 164 females, mean age of 49 ± 18 years, 78 younger than 40 years (Group A), 84 between 40 and 60 years (Group B) and 74 older than 60 years (Group C). Defect size median 22 mm (inter-quartile range, 19, 26 mm) and shunt ratio Qp:Qs 2.2 (1.7, 2.9) did not differ among age groups. Older patients had, however, more advanced symptoms and both, PAP (r = 0.65, P < 0.0001) and RV size (r = 0.28, P < 0.0001), were significantly related to age. Post-interventionally, RV size decreased from 41 ± 7, 43 ± 7, and 45 ± 6 mm to 32 ± 5, 34 ± 5, and 37 ± 5 mm for Groups A, B, and C, respectively (P < 0.0001), and PAP decreased from 31 ± 7, 37 ± 10, and 53 ± 17 mmHg to 26 ± 5, 30 ± 6, and 43 ± 14 mmHg (P < 0.0001), respectively. Absolute changes in RV size (P = 0.80) and PAP (P = 0.24) did not significantly differ among groups. Symptoms were present in 13, 49, and 83% of the patients before and in 3, 11, and 34% after intervention in Groups A, B, and C. Functional status was related to PAP.
At any age, ASD closure is followed by symptomatic improvement and regression of PAP and RV size. However, the best outcome is achieved in patients with less functional impairment and less elevated PAP. Considering the continuous increase in symptoms, RV remodelling, and PAP with age, ASD closure must be recommended irrespective of symptoms early after diagnosis even in adults of advanced age.
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