Cobalt–chiral diphoshine catalytic systems promote intramolecular hydroacylation reactions of 2-acylbenzaldehydes and 2-alkenylbenzaldehydes to afford phthalide and indanone derivatives, ...respectively, in moderate to good yields with high enantioselectivities. The ketone hydroacylation did not exhibit a significant H/D kinetic isotope effect (KIE) with respect to the aldehyde C–H bond, indicating that C–H activation would not be involved in the rate-limiting step.
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In this paper, we are interested in the application of the ALM and the ADM for some nuclear norm involved minimization problems. When the resulting subproblems do not have closed-form solutions, we ...propose to linearize these subproblems such that closed-form solutions of these linearized subproblems can be easily derived.
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A unique cobalt(I)–diphosphine catalytic system has been identified for the coupling of salicylaldehyde (SA) and an internal alkyne affording a dehydrogenative annulation product (chromone) or a ...reductive annulation product (4‐chromanone) depending on the alkyne substituents. Distinct from related rhodium(I)‐ and rhodium(III)‐catalyzed reactions of SA and alkynes, these annulation reactions feature aldehyde C−H oxidative addition of SA and subsequent hydrometalation of the C=O bond of another SA molecule as common key steps. The reductive annulation to 4‐chromanones also involves the action of Zn as a stoichiometric reductant. In addition to these mechanistic features, the CoI catalysis described herein is complementary to the RhI‐ and RhIII‐catalyzed reactions of SA and internal alkynes, particularly in the context of chromone synthesis.
An unexpected outcome: A cobalt(I)–diphosphine catalyst has been employed for the coupling of salicylaldehyde and internal alkynes to afford, depending on the alkyne substituents, chromone or 4‐chromanone derivatives. These annulation reactions feature aldehyde C−H oxidative addition and subsequent hydrometalation of another aldehyde as key steps.
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Today's systems produce a rapidly exploding amount of data, and the data further derives more data, forming a complex data propagation network that we call the data's lineage. There are many reasons ...that users want systems to forget certain data including its lineage. From a privacy perspective, users who become concerned with new privacy risks of a system often want the system to forget their data and lineage. From a security perspective, if an attacker pollutes an anomaly detector by injecting manually crafted data into the training data set, the detector must forget the injected data to regain security. From a usability perspective, a user can remove noise and incorrect entries so that a recommendation engine gives useful recommendations. Therefore, we envision forgetting systems, capable of forgetting certain data and their lineages, completely and quickly. This paper focuses on making learning systems forget, the process of which we call machine unlearning, or simply unlearning. We present a general, efficient unlearning approach by transforming learning algorithms used by a system into a summation form. To forget a training data sample, our approach simply updates a small number of summations -- asymptotically faster than retraining from scratch. Our approach is general, because the summation form is from the statistical query learning in which many machine learning algorithms can be implemented. Our approach also applies to all stages of machine learning, including feature selection and modeling. Our evaluation, on four diverse learning systems and real-world workloads, shows that our approach is general, effective, fast, and easy to use.
We report herein cobalt-catalyzed enantioselective and chemodivergent reactions between a cyclopropanol and an oxabicyclic alkene via a cobalt homoenolate, which afford either an alkylative ...ring-opening product or a hydroalkylation product, with the counterion of the cobalt catalyst being a major chemoselectivity-controlling factor. A catalyst generated from cobalt(II) chloride and a chiral diphosphine promotes alkylative ring opening to afford 1,2-dihydronaphthalen-1-ol derivatives in good yields with high enantioselectivity. By contrast, a catalyst generated from cobalt(II) acetate and the same diphosphine ligand, with the assistance of methanol, selectively affords hydroalkylation products with retention of the bicyclic structure at a comparable level of enantioselectivity.
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In view of the problems existing in the current exam system, such as separation from the command information system and difficulty in carrying out remote group training, a scalable and extensible ...command training exam system architecture is proposed to provide technical support for integrating and invoking the relevant components of the command information system and carrying out large-scale group training. Firstly, the component integration framework of multi-system integration and the integrated exam course evaluation mode are proposed to realize the assessment of each course including command skills. Then, a multi-level server exam structure is designed. On this basis, through the application of virtualization cluster and other technologies, the rapid deployment of the system under diverse conditions and the large-scale remote group training application is realized.
Recent compressive sensing results show that it is possible to accurately reconstruct certain compressible signals from relatively few linear measurements via solving nonsmooth convex optimization ...problems. In this paper, we propose the use of the alternating direction method - a classic approach for optimization problems with separable variables (D. Gabay and B. Mercier, ¿A dual algorithm for the solution of nonlinear variational problems via finite-element approximations,¿ Computer and Mathematics with Applications, vol. 2, pp. 17-40, 1976; R. Glowinski and A. Marrocco, ¿Sur lapproximation par elements finis dordre un, et la resolution par penalisation-dualite dune classe de problemes de Dirichlet nonlineaires,¿ Rev. Francaise dAut. Inf. Rech. Oper., vol. R-2, pp. 41-76, 1975) - for signal reconstruction from partial Fourier (i.e., incomplete frequency) measurements. Signals are reconstructed as minimizers of the sum of three terms corresponding to total variation, ¿ 1 -norm of a certain transform, and least squares data fitting. Our algorithm, called RecPF and published online, runs very fast (typically in a few seconds on a laptop) because it requires a small number of iterations, each involving simple shrinkages and two fast Fourier transforms (or alternatively discrete cosine transforms when measurements are in the corresponding domain). RecPF was compared with two state-of-the-art algorithms on recovering magnetic resonance images, and the results show that it is highly efficient, stable, and robust.
Transition-metal catalyzed asymmetric cyclization of 1,6-enynes has emerged as a powerful method for the construction of carbocycles and heterocycles. However, very rare examples worked under ...electrochemical conditions. We report herein a Co-catalyzed enantioselective intramolecular reductive coupling of enynes via electrochemistry using H
O as hydride source. The products were obtained in good yields with high regio- and enantioselectivities. It represents the rare progress on the cobalt-catalyzed enantioselective transformation via electrochemistry with a general substrate scope. DFT studies explored the possible reaction pathways and revealed that the oxidative cyclization of enynes by LCo(I) is more favorable than oxidative addition of H
O or other pathways.
We propose a deep network architecture for the pan-sharpening problem called PanNet. We incorporate domain-specific knowledge to design our PanNet architecture by focusing on the two aims of the ...pan-sharpening problem: spectral and spatial preservation. For spectral preservation, we add up-sampled multispectral images to the network output, which directly propagates the spectral information to the reconstructed image. To preserve spatial structure, we train our network parameters in the high-pass filtering domain rather than the image domain. We show that the trained network generalizes well to images from different satellites without needing retraining. Experiments show significant improvement over state-of-the-art methods visually and in terms of standard quality metrics.
A cobalt–diphosphine catalyst has been found to promote a formal 3 + 2 cycloaddition reaction between a cyclopropanol and an allene via cyclopropanol ring opening, which affords a ...3-alkylidenecyclopentanol derivative with high regio- and diastereoselectivities. The reaction tolerates monosubstituted, 1,1-disubstituted, and 1,3-disubstituted allenes and various functional groups. The reaction is proposed to proceed through carbometalation of the allene with a cobalt homoenolate followed by intramolecular carbonyl allylation of the resulting allylcobalt species.
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