A Quantitative Comparison between Shannon and Tsallis–Havrda–Charvat Entropies Applied to Cancer Outcome Prediction

In this paper, we propose to quantitatively compare loss functions based on parameterized Tsallis–Havrda–Charvat entropy and classical Shannon entropy for the training of a deep network in the case of small datasets which are usually encountered in medical applications. Shannon cross-entropy is widely used as a loss function for most neural networks applied to the segmentation, classification and detection of images. Shannon entropy is a particular case of Tsallis–Havrda–Charvat entropy. In this work, we compare these two entropies through a medical application for predicting recurrence in patients with head–neck and lung cancers after treatment. Based on both CT images and patient information, a multitask deep neural network is proposed to perform a recurrence prediction task using cross-entropy as a loss function and an image reconstruction task. Tsallis–Havrda–Charvat cross-entropy is a parameterized cross-entropy with the parameter α . Shannon entropy is a particular case of Tsallis–Havrda–Charvat entropy for α=1 . The influence of this parameter on the final prediction results is studied. In this paper, the experiments are conducted on two datasets including in total 580 patients, of whom 434 suffered from head–neck cancers and 146 from lung cancers. The results show that Tsallis–Havrda–Charvat entropy can achieve better performance in terms of prediction accuracy with some values of α .     

Merging Grubbs second-generation catalyst with photocatalysis enables Z-selective metathesis of olefins: scope,limitations, and mechanism

Olefin cross-metathesis is a cornerstone reaction in organic synthesis where stereoselectivity is typically governed by the structure of the catalyst. In this work, we show that merging Grubbs second generation catalyst, a classical E-selective catalyst, with a readily available photocatalyst, enables the exclusive formation of the contra-thermodynamic Z-isomer. The scope and limitations of this unprecedented approach are discussed based on both computational and experimental mechanistic data.

Light is magic! The combination of Grubbs second generation catalyst, a well-known catalyst for E-selective olefin metathesis, with a photosensitizer enables efficient access to the contra-thermodynamic Z-isomers.     

Photoionization and Electron Transfer of Biphenyl within the Channels of Al-ZSM-5 Zeolites

Evidence of the photogenerated long-lived biphenyl radical and a trapped electron in the void space of aluminated nonacidic ZSM-5 zeolites has been obtained from the time-resolved UV/Vis absorption, Raman scattering, and EPR spectra. The restoration of the ground states implicates the existence of long-lived positive holes in the framework.     

What Differentiates Free Amino Acids and Aminoacyl Residues? An Exploration of Conformational and Lipophilicity Spaces

The objective of this study was to unravel the changes in property space resulting from the amino-acid-to-residue transformation. Conformation-dependent lipophilicity was chosen as the metric to assess changes in property spaces. Phe, Ala-Phe-Ala, Gln, and Ala-Gln-Ala were first submitted to a conformational search strategy using quenched molecular dynamics in order to obtain an efficient sampling of a conformational space. This search was performed for the four electrical forms of the compounds (cationic, zwitterionic, uncharged, and anionic). The virtual lipophilicity (logP) of each conformer was then calculated by the Molecular Lipophilicity Potential (MLP). Similarly, the lipophilicity increment of the Phe and Gln residues in all electrical states and conformers of Ala-Phe-Ala and Ala-Gln-Ala, respectively, were calculated by the MLP. As expected, the results showed a marked expansion in the property space of a tripeptide compared to an amino acid. However, they also revealed a marked reduction in property space resulting from the amino-acid-to-residue transformation.     

Nucleophilic Substitution of 4‐Fluoronitrobenzene with Polyvinylamine in Water Mediated by Cyclodextrins

Polyvinylamine (PVAm) can be readily functionalized by means of a nucleophilic substitution reaction with 4‐fluoro‐substituted aromatic compounds having a substituent with negative mesomeric effect in ortho and/or para position. PVAm is soluble in water only in which aromatic fluoro compounds are usually sparingly soluble. However, the solubility of aromatic compounds in water can be mediated in particular by cyclodextrin derivatives. This first report on the nucleophilic substitution reaction of 4‐fluoronitrobenzene with PVAm provides an elegant method towards the preparation of chromophoric water‐soluble polymers by means of a one‐pot procedure.     

Processing-induced chromism in thin films of polythiophene derivatives

Langmuir-Blodgett films of amphiphilic poly[3-oligo(oxyethylene)-4-methylthiophene] have been obtained. The resulting thin films are poorly conjugated, with a maximum of absorption at 405 nm which remains almost constant upon heating or cooling. In contrast, cast thin films of this polymer exhibit a maximum of absorption at 550 nm and show interesting thermochromic effects. These results to indicate that the method of preparation of thin films can have a significant influence on the conformational structure of the polymer at room temperature and, consequently, on its thermochromic behaviour.     

Mean Value Operators, Differential Operators and D'Atri Spaces

We study commutativity relations between differential operators and spherical means on Riemannian manifolds. The results show that all D'Atri spaces are ball-homogeneous. A further consequence characterizes complete nonpositively curved, simply connected D'Atri spaces by commuting mean value operators.     

Extended Thienylenevinylene Oligomers as Highly Efficient Molecular Wires

A much smaller band gap than in the parent polymer is observed for the π-conjugated hexadecamer 1 , which can be reversibly charged up to the hexacation in a small potential range.