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排序方式: 共有1108条查询结果,搜索用时 24 毫秒
1.
Riccardo Adami Ugo Boscain Valentina Franceschi Dario Prandi 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2021,38(4):1095-1113
In this paper we show that, for a sub-Laplacian Δ on a 3-dimensional manifold M, no point interaction centered at a point exists. When M is complete w.r.t. the associated sub-Riemannian structure, this means that Δ acting on is essentially self-adjoint in . A particular example is the standard sub-Laplacian on the Heisenberg group. This is in stark contrast with what happens in a Riemannian manifold N, whose associated Laplace-Beltrami operator acting on is never essentially self-adjoint in , if . We then apply this result to the Schrödinger evolution of a thin molecule, i.e., with a vanishing moment of inertia, rotating around its center of mass. 相似文献
2.
Marco Carboni Dr. Andrea Giacomo Marrani Dr. Riccardo Spezia Dr. Sergio Brutti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17188-17203
The reaction thermodynamics of the 1,2‐dimethoxyethane (DME), a model solvent molecule commonly used in electrolytes for Li?O2 rechargeable batteries, has been studied by first‐principles methods to predict its degradation processes in highly oxidizing environments. In particular, the reactivity of DME towards the superoxide anion O2? in oxygen‐poor or oxygen‐rich environments is studied by density functional calculations. Solvation effects are considered by employing a self‐consistent reaction field in a continuum solvation model. The degradation of DME occurs through competitive thermodynamically driven reaction paths that end with the formation of partially oxidized final products such as formaldehyde and methoxyethene in oxygen‐poor environments and methyl oxalate, methyl formate, 1‐formate methyl acetate, methoxy ethanoic methanoic anhydride, and ethylene glycol diformate in oxygen‐rich environments. This chemical reactivity indirectly behaves as an electroactive parasitic process and therefore wastes part of the charge exchanged in Li?O2 cells upon discharge. This study is the first complete rationale to be reported about the degradation chemistry of DME due to direct interaction with O2?/O2 molecules. These findings pave the way for a rational development of new solvent molecules for Li?O2 electrolytes. 相似文献
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Philippe Schwaller Riccardo Petraglia Valerio Zullo Vishnu H. Nair Rico Andreas Haeuselmann Riccardo Pisoni Costas Bekas Anna Iuliano Teodoro Laino 《Chemical science》2020,11(12):3316
We present an extension of our Molecular Transformer model combined with a hyper-graph exploration strategy for automatic retrosynthesis route planning without human intervention. The single-step retrosynthetic model sets a new state of the art for predicting reactants as well as reagents, solvents and catalysts for each retrosynthetic step. We introduce four metrics (coverage, class diversity, round-trip accuracy and Jensen–Shannon divergence) to evaluate the single-step retrosynthetic models, using the forward prediction and a reaction classification model always based on the transformer architecture. The hypergraph is constructed on the fly, and the nodes are filtered and further expanded based on a Bayesian-like probability. We critically assessed the end-to-end framework with several retrosynthesis examples from literature and academic exams. Overall, the frameworks have an excellent performance with few weaknesses related to the training data. The use of the introduced metrics opens up the possibility to optimize entire retrosynthetic frameworks by focusing on the performance of the single-step model only.We present an extension of our Molecular Transformer model combined with a hyper-graph exploration strategy for automatic retrosynthesis route planning without human intervention. 相似文献
5.
A Quantitative Model for Alkane Nucleophilicity Based on C−H Bond Structural/Topological Descriptors
6.
Dr. Anna Notaro Marta Jakubaszek Severin Koch Dr. Riccardo Rubbiani Dr. Orsolya Dömötör Dr. Éva A. Enyedy Mazzarine Dotou Dr. Fethi Bedioui Mickaël Tharaud Dr. Bruno Goud PD Dr. Stefano Ferrari Prof. Dr. Enzo Alessio Dr. Gilles Gasser 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(22):4997-5009
Cancer is one of the main causes of death worldwide. Chemotherapy, despite its severe side effects, is to date one of the leading strategies against cancer. Metal-based drugs present several potential advantages when compared to organic compounds and they have gained trust from the scientific community after the approval on the market of the drug cisplatin. Recently, we reported the ruthenium complex ([Ru(DIP)2(sq)](PF6) (where DIP is 4,7-diphenyl-1,10-phenantroline and sq is semiquinonate) with a remarkable potential as chemotherapeutic agent against cancer, both in vitro and in vivo. In this work, we analyse a structurally similar compound, namely [Ru(DIP)2(mal)](PF6), carrying the flavour-enhancing agent approved by the FDA, maltol (mal). To possess an FDA approved ligand is crucial for a complex, whose mechanism of action might include ligand exchange. Herein, we describe the synthesis and characterisation of [Ru(DIP)2(mal)](PF6), its stability in solutions and under conditions that resemble the physiological ones, and its in-depth biological investigation. Cytotoxicity tests on different cell lines in 2D model and on HeLa MultiCellular Tumour Spheroids (MCTS) demonstrated that our compound has higher activity than cisplatin, inspiring further tests. [Ru(DIP)2(mal)](PF6) was efficiently internalised by HeLa cells through a passive transport mechanism and severely affected the mitochondrial metabolism. 相似文献
7.
Silvia Colomban Mirko De Rosso Riccardo Flamini Luciano Navarini 《Journal of mass spectrometry : JMS》2023,58(10):e4970
The present study aims to both identify and quantify trans-sinapoylquinic acid (SiQA) regioisomers in green coffee by combined UHPLC-ESI-QqTOF-MS/MS and UHPLC-ESI-QqQ-MS/MS methods. Among the various mono-acyl chlorogenic acids found in green coffee, SiQA regioisomers are the least studied despite having been indicated as unique phytochemical markers of Coffea canephora (known as Robusta). The lack of commercially available authentic standards has been bypassed by resorting to the advantages offered by high-resolution LC–MS as far as the identification is concerned. SiQA regioisomers have been identified in several samples of Robusta and Coffea arabica (known as Arabica) commercial lots from different geographical origin and, for the first time, in different samples of coffee wild species (Coffea liberica and Coffea pseudozanguebariae). Quantification (total SiQA ranging from 3 to 5 mg/100 g) let to reconsider these chlorogenic acids as unique phytochemical markers of Robusta being present in the same quantity and distribution in C. liberica as well. Gardeniae Fructus samples (fruits of Gardenia jasminoides) have additionally been characterized as this matrix is recognized as one of the few naturally occurring SiQA sources. The SiQA regioisomer content (total SiQA about 80 mg/100 mg) fully supports the proposal to use this matrix as a surrogate standard for further studies. 相似文献
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9.
Paolo Della Porta Riccardo Zanasi Guglielmo Monaco 《Journal of computational chemistry》2015,36(10):707-716
Current density plots of closed‐shell intermolecular H? H interactions characterized by a bond critical point (BCP) show two vortices separated by a saddle, a pattern which allows for a clear definition of a pair current strength. This H? H current strength turns out to be roughly related to the potential energy density at the BCP and then to the dissociation energy. The same pattern is also recognizable, at least for an azimuthal orientation of a field perpendicular to the H? H line, for the intramolecular interactions previously investigated to propose the H? H bonding. In the case of the H atoms of the bay region of polycyclic aromatic hydrocarbons, the current of the H? H delocalized diatropic vortex gives a quantitative indication of stabilization; however, on rotation of the field and the subsequent onset of a bay‐delocalized paratropic vortex (a typical signature of antiaromaticity), the diatropic vortex can be reshaped or it can even disappear, consistently with its smallness, and thus showing the effect of other more relevant interactions. © 2015 Wiley Periodicals, Inc. 相似文献