1,092 research outputs found
First insights into the synthesis of carbo-phospholane and carbo-phospholene oxides
Fifteen-membered ring carbo-mers of five-membered rings are considered in the heterocyclic series of the phosphole oxide and less unsaturated parents. The synthesis of the first carbo-phospholane oxides is achieved by a [14+1] two-step/one-pot macrocyclization route with 86 % yield. Reduction of the latter phosphora-[5]pericyclyne with SnClÂ2 allowed consistent 1H and 31P NMR characterization of the corresponding carbo-phospholene, produced with 11 % yield. The ultimate carbo-phosphole oxide could not be isolated, but preliminary results on alternative strategies towards this 14 pz-electron HĂĽckel carbo-aromatic are reported.
Ma pratique des conserves de fruits et légumes et de quelques autres aliments : simples recettes a l'usage des ménagéres
Deuxième éditio
End-to-End Meta-Bayesian Optimisation with Transformer Neural Processes
Meta-Bayesian optimisation (meta-BO) aims to improve the sample efficiency of
Bayesian optimisation by leveraging data from related tasks. While previous
methods successfully meta-learn either a surrogate model or an acquisition
function independently, joint training of both components remains an open
challenge. This paper proposes the first end-to-end differentiable meta-BO
framework that generalises neural processes to learn acquisition functions via
transformer architectures. We enable this end-to-end framework with
reinforcement learning (RL) to tackle the lack of labelled acquisition data.
Early on, we notice that training transformer-based neural processes from
scratch with RL is challenging due to insufficient supervision, especially when
rewards are sparse. We formalise this claim with a combinatorial analysis
showing that the widely used notion of regret as a reward signal exhibits a
logarithmic sparsity pattern in trajectory lengths. To tackle this problem, we
augment the RL objective with an auxiliary task that guides part of the
architecture to learn a valid probabilistic model as an inductive bias. We
demonstrate that our method achieves state-of-the-art regret results against
various baselines in experiments on standard hyperparameter optimisation tasks
and also outperforms others in the real-world problems of mixed-integer
programming tuning, antibody design, and logic synthesis for electronic design
automation
La religion de Constantin.
¿Cuándo se convirtió Constantino al cristianismo y por qué motivos? Los historiadores siguen discutiendo
sobre este tema. DespuĂ©s de referir brevemente las diversas opiniones, el artĂculo intenta definir la postura de
Constantino acerca de la religio, basándose en sus escritos, en concreto las cuarenta cartas y los discursos. Tras
abandonar sus principales ideas sobre el cristianismo,religio llegó a significar para Constantino únicamente el cristianismo, es decir la religión de un Dios único, omnipotente y providente, de su Hijo que por su enseñanza aporta la salvación a los hombres, de una sola Iglesia, cuya
unidad Ă©l desea y favorece.------------When did Constantine convert to Christianity,
and why? Historians are still debating these questions. After briefly reviewing the different points of view on this
subject, this article attempts to define Constantine’s attitude to religio, on the basis of his writings, in particular his
forty letters and speeches. After Constantine abandoned his previous thinking on Christianity, he came to think of
religio as meaning Christianity alone, understood as the religion which centres on a single God who is both omnipotent
and provident, on his Son, whose teachings lead human beings to salvation, and on the one true Church,whose unity he both desired and defended
Towards fluorescent indolyl-carbo-benzenes
The C18 macro-aromatic carbo-benzene core is a strong chromophoric unit resembling the porphine ring which is prone to quench the emission of fluorophoric substituents. Within the aim of preparing fluorescent carbo-benzenes (and carbo-cyclohexadiene parents) for measurement of their two-photon absorption cross-section by the TPEF method, several indole derivatives were devised and anchored to the C18 macrocycle either directly, p-phenylogously or ethynylogously. Synthesis methodology and spectroscopical measurements are presented in a comparative prospec
En route to a dianilinyl-substituted carbo-cyclohexadiene with promising electrical properties
The macro-aromatic carbo-benzene core para-disubstituted by 4-anilinyl groups is known to be an efficient single-molecule conductor, exhibiting a conductance of 106 nS measured by the scanning tunneling microscopy-break junction technique. The linear carbo-butadiene analogue bearing the same anilinyl substituents was found to be less efficient, with a conductance of 2.7 nS. The reason of this difference could be elucidated through the study of the charge transport properties of a cyclically locked carbo-butadiene core in a carbo-cyclohexadiene derivative. In this paper, advances in the synthesis of this challenging dianilinyl-substituted carbo-cyclohexadiene are presented
First example of ring carbomer of 1,4-cyclohexadiene
While a series of carbo-mers of 1,3-cyclohexadienes was reported through the use of a specifically developed synthetic strategy, no example of their 1,4-regioisomers was known. Inspired by the methodology elaborated for the preparation of the 1,3-isomers, the synthesis of the first example of carbo-mer of 1,4-cyclohexadiene is presented. Comparison of physico-chemical properties of this first representative with those of the recently described 1,4-regioisomer, especially UV-vis absorption properties, is also addressed
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