Pd-catalyzed arylation/ring-closing metathesis approach to azabicycles

Palladium-catalyzed arylation followed by Grignard addition to imines and ring-closing metathesis, using Grubbs’ catalysts, provides a route to six-, seven-, and eight-membered azabicycles.     

First principles study of photostability within hydrogen-bonded amino acids

The photochemistry and photophysics of a two-glycine minimal model is studied at the CASPT2//CASSCF level of theory. Different photoinduced processes are discussed, on the basis of the calculated minimum energy paths and the characterization of the electronic state crossings. Two main processes could provide UV-photostability to the hydrogen-bonded peptide system: (i) forward-backward photoinduced electron/proton transfer involving the H in the hydrogen bond, (ii) singlet-singlet energy transfer between two amino acids, providing ultrafast population of the low-energy n,π* state.     

Does employee participation matter? An empirical study on the effects of participation on well-being and organizational performance

Central European Journal of Operations Research - Employability, talent and/or motivation of people can be a source of sustainable competitive advantage; difficult for competitors to imitate. The...     

Adaptative and developmental responses to stress in Aspergillus nidulan

Development in the ascomycete A. nidulans is principally determined by environmental signals. Adaptability to oxidative stimuli can derive in changes of growth patterns and /or the activation of sexual or asexual reproductive cycles but this model fungus might also respond to high osmotic or salt concentrations, the redox state, the availability and quantity of carbon or nitrogen sources and the degree or quality of illumination. Since each cell within the colony follows a single morphogenetic program at a time, all these environmental cues might be sensed and integrated into a limited number of intracellular signals which, finally, would activate the required morphogenetic program and repress the others. This signaling mainly occurs through stress response pathways. The present review aims to summarize the available knowledge on how these pathways transduce environmental stimuli to mediate morphological changes in Aspergillus nidulans.     

Intramolecular triplet-triplet energy transfer in oxa- and aza-di-pi-methane photosensitized systems

Two different mechanisms are proposed for the intramolecular triplet-triplet energy transfer in oxa- and aza-di-pi-methane systems, one thermally induced and the other photoinduced. These mechanisms involve a key structure that corresponds to an avoided crossing. The triplet sensitized photochemistry of these compounds, focusing attention in the di-pi-methane rearrangement, is discussed in light of these proposed mechanisms.     

Triplet versus singlet photoreaction mechanism in the barrelene di-pi-methane rearrangement

A detailed study of the potential energy surfaces involved in the di-pi-methane rearrangement (singlet and triplet states) reveals the factors that modulate the mechanisms (pathways) and reactivity in strained di-pi-methane systems such as bicyclo[2.2.2]octa-2,5,7-triene (barrelene). [structure: see text]     

The role of the intersection space in the photochemistry of tricyclo[3.3.0.0(2,6)]octa-3,7-diene

CASSCF and CASPT2 methods were used to study the photochemistry of tricyclo[3.3.0.0(2,6)]octa-3,7-diene (TOD). The analysis of different S1 reaction paths as well as the topology of the S1/S0 intersection space allows us to establish two novel properties associated with the photochemical behavior of this compound: (i) simple low-lying intersection space domains can mediate different photoproducts, and (ii) TOD photochemistry is probably mediated by two disconnected intersection space domains, related to the formation of cyclooctatetraene and semibulvalene in different time-scales. It is shown that these domains are chemically distinct since the first, leading to COT, mediates barrierless pericyclic reactions while the second, leading to SBV, is accessed through the formation of an excited-state biradical intermediate. To the best of our knowledge, in the domain of single molecule photochemistry, TOD represents the first example where a different chemical role of distinct low-lying intersection spaces has been computationally documented. The observed photoproducts can be rationalized in terms of branching space diagrams, constructed by determining the branching space (derivative coupling and gradient difference vectors) for each conical intersection involved in the photochemical process.     

THz Generation via Optical Rectification in Nanomaterials: Universal Modeling Approach and Effective χ¯¯(2) Description

Optical rectification (OR) at the nanoscale has attracted an increasing interest in the prospect of providing efficient ultracompact terahertz (THz) sources. Here, a universal modeling approach capable of addressing both isotropic and anisotropic all-dielectric nonlinear nanomaterials on an ultra-broad spectral range, covering the highly dispersive phonon-polariton window, and different orientations of the crystallographic axes with respect to the geometry of the structure is reported. This analysis is exemplified by considering two study cases, that is, nanopillars of AlGaAs and of LiNbO₃. A close comparison between the two cases is established in terms of THz generation efficiency from 4 to 14 THz. Phonon-polariton contributions to the OR process are disentangled from the electronic one, and a model order reduction based on the reciprocity theorem is applied and validated on both the considered configurations. These results, combined with the inspection of the THz near-field features, pave the way to the design and optimization of nonlinear metasurfaces for THz generation and detection at the nanoscale.     

Rhythm Analysis during Cardiopulmonary Resuscitation Using Convolutional Neural Networks

Chest compressions during cardiopulmonary resuscitation (CPR) induce artifacts in the ECG that may provoque inaccurate rhythm classification by the algorithm of the defibrillator. The objective of this study was to design an algorithm to produce reliable shock/no-shock decisions during CPR using convolutional neural networks (CNN). A total of 3319 ECG segments of 9 s extracted during chest compressions were used, whereof 586 were shockable and 2733 nonshockable. Chest compression artifacts were removed using a Recursive Least Squares (RLS) filter, and the filtered ECG was fed to a CNN classifier with three convolutional blocks and two fully connected layers for the shock/no-shock classification. A 5-fold cross validation architecture was adopted to train/test the algorithm, and the proccess was repeated 100 times to statistically characterize the performance. The proposed architecture was compared to the most accurate algorithms that include handcrafted ECG features and a random forest classifier (baseline model). The median (90% confidence interval) sensitivity, specificity, accuracy and balanced accuracy of the method were 95.8% (94.6–96.8), 96.1% (95.8–96.5), 96.1% (95.7–96.4) and 96.0% (95.5–96.5), respectively. The proposed algorithm outperformed the baseline model by 0.6-points in accuracy. This new approach shows the potential of deep learning methods to provide reliable diagnosis of the cardiac rhythm without interrupting chest compression therapy.