Proton‐responsive photochromic molecules are attractive for their ability to react on non‐invasive rapid optical stimuli and the importance of protonation/deprotonation processes in various fields. ...Conventionally, their acidic/basic sites are on hetero‐atoms, which are orthogonal to the photo‐active π‐center. Here, we incorporate azulene, an acid‐sensitive pure hydrocarbon, into the skeleton of a diarylethene‐type photoswitch. The latter exhibits a novel proton‐gated negative photochromic ring‐closure and its optical response upon protonation in both open and closed forms is much more pronounced than those of diarylethene photoswitches with hetero‐atom based acidic/basic moieties. The unique behavior of the new photoswitch can be attributed to direct protonation on its π‐system, supported by 1H NMR and theoretical calculations. Our results demonstrate the great potential of integrating non‐alternant hydrocarbons into photochromic systems for the development of multi‐responsive molecular switches.
Incorporation of an azulene moiety into a diarylethene photoswitch gives rise to unprecedented acid‐dependent negative photochromism. The unusual photochromic behavior can be understood by direct protonation on the photoactive π‐system due to the unique electronic structure of azulene.
A lane changing assistance system that advises drivers of safe gaps for making mandatory lane changes at lane drops is developed. Bayes classifier and decision-tree methods were applied to model lane ...changes. Detailed vehicle trajectory data from the Next Generation Simulation (NGSIM) data set were used for model development (U.S. Highway 101) and testing (Interstate 80). The model predicts driver decisions on whether to merge or not as a function of certain input variables. The best results were obtained when both Bayes and decision-tree classifiers were combined into a single classifier using a majority voting principle. The prediction accuracy was 94.3% for nonmerge events and 79.3% for merge events. In a lane change assistance system, the accuracy of nonmerge events is more critical than merge events. Misclassifying a nonmerge event as a merge event could result in a traffic crash, whereas misclassifying a merge event as a nonmerge event would only result in a lost opportunity to merge. Sensitivity analysis performed by assigning higher misclassification cost for nonmerge events resulted in even higher accuracy for nonmerge events but lower accuracy for merge events.
In this study high‐valent Cu(III) trifluoromethyl compounds in combination with DMSO is shown to be an efficient and mild oxidizing system for the conversion of alcohols to ketones (aldehydes as ...well). Trifluoromethoxylated sulfonium species is proposed to be initially formed that engages in crucial steps of alkoxy replacement at sulfonium center and deprotonative collapse of the resulting alkoxysulfonium intermediate in the presence of a base. This reaction is highly selective without over‐oxidation, and can tolerate a broad range of functional groups owing to mild oxidizing ability of the Cu(III)‐CF3/DMSO system and the inert N2 conditions. This method can be applied to the synthesis and functionalization of commercial drug compounds. This study illustrates an unusual reactivity property of high‐valent Cu(III) trifluoromethyl compounds beyond the conventional CF3 group transfer reactivity, and opens up new opportunities for developing novel reactions of Cu(III)‐CF3 compounds. The combined use of high‐valent Cu(III)‐CF3 compound and DMSO is anticipated to find more applications to develop other novel and useful oxidation reactions.
When high‐valent Cu(III)‐CF3 compounds meet DMSO, a unique platform is set up to manipulate sulfonium chemistry. A case study of oxidation of alcohols to ketones is shown herein. Crucial trifluoromethoxysulfonium is initially generated, and reacts with alcohols to give new alkoxysulfonium species via ligand exchange. Subsequent base‐promoted E2 elimination gives ketones with the release of Me2S.
Traffic Flow Forecasting for Urban Work Zones Yi Hou; Edara, Praveen; Sun, Carlos
IEEE transactions on intelligent transportation systems,
08/2015, Letnik:
16, Številka:
4
Journal Article
Recenzirano
None of numerous existing traffic flow forecasting models focus on work zones. Work zone events create conditions that are different from both normal operating conditions and incident conditions. In ...this paper, four models were developed for forecasting traffic flow for planned work zone events. The four models are random forest, regression tree, multilayer feedforward neural network, and nonparametric regression. Both long-term and short-term traffic flow forecasting applications were investigated. Long-term forecast involves forecasting 24 h in advance using historical traffic data, and short-term forecasts involves forecasting 1 h and 45, 30, and 15 min in advance using real-time temporal and spatial traffic data. Models were evaluated using data from work zone events on two types of roadways, a freeway, i.e., I-270, and a signalized arterial, i.e., MO-141, in St. Louis, MO, USA. The results showed that the random forest model yielded the most accurate long-term and short-term work zone traffic flow forecasts. For freeway data, the most influential variables were the latest interval's look-back traffic flows at the upstream, downstream, and current locations. For arterial data, the most influential variables were the traffic flows from the three look-back intervals at the current location only.
Synthesis of two dicyclopentaannelated hexa‐peri‐hexabenzocoronene (PHBC) regioisomers was carried out, using nonplanar oligoaryl precursors with fluorenyl groups: mPHBC 8 with two pentagons in the ...“meta”‐configuration was obtained as a stable molecule, while its structural isomer with the “para”‐configuration, pPHBC 16, could be generated and characterized only in situ due to its high chemical reactivity. Both PHBCs exhibit low energy gaps, as reflected by UV‐vis‐NIR absorption and electrochemical measurements. They also show open‐shell singlet ground states according to electron paramagnetic resonance (EPR) measurements and density functional theory (DFT) calculations. The use of fully benzenoid HBC as a bridging moiety leads to significant singlet biradical characters (y0) of 0.72 and 0.96 for mPHBC 8 and pPHBC 16, respectively, due to the strong rearomatization tendency of the HBC π‐system; these values are among the highest for planar carbon‐centered biradical molecules. The incorporation of fully unsaturated pentagons strongly perturbs the aromaticity of the parent HBC and makes the constituted benzene rings less aromatic or antiaromatic. These results illustrate the high impact of cyclopentaannelation on the electronic structures of fully benzenoid polycyclic aromatic hydrocarbons (PAHs) and open up a new avenue towards open‐shell PAHs with prominent singlet biradical characters.
Incorporation of two fully unsaturated pentagons to the bay positions of hexa‐peri‐hexabenzocoronene (HBC) core gives access to two dicyclopentaannelated HBC regioisomers: mPHBC and pPHBC. Both compounds show decreased energy gaps compared with the parent HBC and exhibit singlet biradical ground state with prominent biradical character.
Huntington's disease (HD) is caused by Huntingtin (Htt) gene mutation resulting in the loss of striatal GABAergic neurons and motor functional deficits. We report here an in vivo cell conversion ...technology to reprogram striatal astrocytes into GABAergic neurons in both R6/2 and YAC128 HD mouse models through AAV-mediated ectopic expression of NeuroD1 and Dlx2 transcription factors. We found that the astrocyte-to-neuron (AtN) conversion rate reached 80% in the striatum and >50% of the converted neurons were DARPP32
medium spiny neurons. The striatal astrocyte-converted neurons showed action potentials and synaptic events, and projected their axons to the targeted globus pallidus and substantia nigra in a time-dependent manner. Behavioral analyses found that NeuroD1 and Dlx2-treated R6/2 mice showed a significant extension of life span and improvement of motor functions. This study demonstrates that in vivo AtN conversion may be a disease-modifying gene therapy to treat HD and other neurodegenerative disorders.
Polarization‐sensitive photodetectors are gaining numerous attention since polarization detection is important in geological remote sensing, atmospheric monitoring, military recon, and medical ...examination. Among various reported photoactive materials for photodetectors, metal halide perovskites have outstanding advantages such as tunable band gaps, excellent optoelectronic properties, and easy fabrication. Moreover, the characteristics of crystal structure anisotropy and controllable growth orientation of perovskite crystals endow the perovskite photodetector with the ability to identify light polarization states. This review outlines the recent research progress of perovskite photodetectors on polarization‐sensitive detection. Firstly, key device parameters of polarization‐sensitive detection are introduced. Then, the recent progress of polarization‐sensitive perovskite detectors in the field of linear and circular polarization is reviewed according to the different principles of polarization response. Finally, the challenges of polarization‐sensitive perovskite photodetector are discussed.
Polarization‐sensitive photodetectors are important in geological remote sensing, atmospheric monitoring, military recon, and medical examination. The review addresses the recent research progress of perovskite photodetectors on polarization‐sensitive detection in terms of key device parameters, linear and circular polarization via different principles of polarization response.
Rare earth (RE) nanoparticles have attracted considerable attention due to their unique optical and magnetic properties associated with f‐electrons. The recent accomplishments in RE nanoparticle ...synthesis have aroused great interest of scientists to further explore their biomedical applications. This Research News summarizes recent achievements in controlled synthesis of magnetic and luminescent RE nanoparticles, surface modification, and toxicity studies of RE nanomaterials, and highlights state‐of‐the‐art in in vivo applications of RE nanoparticles.
Owing to the unique magnetic and optical properties associated with f‐electrons, rare earth (RE) nanoparticles show great potential for versatile in vivo applications, especially sensitive tumor imaging according to animal experiments. Recent achievements in the synthesis, surface modification, in vivo application, and toxicity of RE nanoparticles are summarized, and their perspectives for clinical applications are discussed.
Molecular dynamics (MD) is a widely-used tool for simulating molecular and materials properties. It is common wisdom that molecular dynamics simulations should obey physical laws and, hence, lots of ...effort is put into ensuring that molecular dynamics simulations are energy conserving. The emergence of machine learning (ML) potentials for MD leads to a growing realization that monitoring conservation of energy during simulations is of low utility because the dynamics is often unphysically dissociative. Other ML methods for MD are not based on a potential and provide only forces or trajectories which are reasonable but not necessarily energy-conserving. Here we propose to clearly distinguish between the simulation-energy and true-energy conservation and highlight that the simulations should focus on decreasing the degree of true-energy non-conservation. We introduce very simple, new criteria for evaluating the quality of molecular dynamics by estimating the degree of true-energy non-conservation and we demonstrate their practical utility on an example of infrared spectra simulations. These criteria are more important and intuitive than simply evaluating the quality of the ML potential energies and forces as is commonly done and can be applied universally,
e.g.
, even for trajectories with unknown or discontinuous potential energy. Such an approach introduces new standards for evaluating MD by focusing on the true-energy conservation and can help in developing more accurate methods for simulating molecular and materials properties.
Molecular dynamics is often simulation-energy conserving but the quality of calculations is still unsatisfactory. It is more conducive to focus on evaluating and improving the theoretical best estimate of total-energy time evolution.
Abstract
During metal additive manufacturing, the porosity of the as-built part deteriorates the mechanical property and even hinders the further application of metal additive manufacturing. ...Particularly, the mechanisms of keyhole pores associated with the keyhole fluctuation are not fully understood. To reveal the mechanisms of the keyhole pores formation, we adopt a multiphysics thermal-fluid flow model incorporating heat transfer, liquid flow, metal evaporation, Marangoni effect, and Darcy’s law to simulate the keyhole pore formation process, and the results are validated with the in situ X-ray images. The simulation results present the instant bubble formation due to the keyhole instability and motion of the instant bubble pinning on the solidification front. Furthermore, comparing the keyhole pore formation under different laser scanning speeds shows that the keyhole pore is sensitive to the manufacturing parameters. Additionally, the simulation under a low ambient pressure shows the feasibility of improving the keyhole stability to reduce and even avoid the formation of keyhole pores.
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