keyword
https://read.qxmd.com/read/38513220/photophysics-of-a-monoannulated-indigo-intra-and-intermolecular-charge-transfer
#21
JOURNAL ARTICLE
Bidyut Das, Smiti Rani Bora, Siddharth Mall Bishen, Hirdyesh Mishra, Dhruba Jyoti Kalita, Abdul Wahab
In the present work, the photoinduced charge-transfer (CT) behavior of 7-phenyl-6 H -pyrido[1,2- a :3,4- b ']diindole-6,13(12 H )-dione ( HCB ) as a function of solvent polarity is reported by UV-vis absorption, steady-state and time-resolved fluorescence, and quantum chemical calculations. Calculated excited state energies of HCB at the B3PW91/6-31+G* level in vacuo and in solvents fulfill the energy requirements for singlet fission, which is the most promising path for the generation of highly efficient solar cells...
March 21, 2024: Journal of Physical Chemistry. A
https://read.qxmd.com/read/38512639/diastereoselective-dearomatizing-cyclizations-of-5-arylpentan-2-ones-by-samarium-diiodide-a-computational-analysis
#22
JOURNAL ARTICLE
Luca Steiner, Andreas Achazi, Anne-Marie Kelterer, Beate Paulus, Hans-Ulrich Reissig
This study analyzes the samarium diiodide-promoted cyclizations of 5-arylpentan-2-ones to dearomatized bicyclic products utilizing density functional theory. The reaction involves a single electron transfer to the carbonyl group, which occurs synchronously with the rate determining cyclization event, and a second subsequent proton-coupled electron transfer. These redox reactions are accurately computed employing small core pseudo potentials explicitly involving all f-electrons of samarium. Comparison of the energies of the possible final products rules out thermodynamic control of the observed regio- and diastereoselectivities...
March 21, 2024: Chemistry: a European Journal
https://read.qxmd.com/read/38509839/total-synthesis-of-the-euphorbia-diterpenoid-pepluacetal
#23
JOURNAL ARTICLE
Meng Liu, Chuanhua Wu, Xingang Xie, Huilin Li, Xuegong She
The first total synthesis of the Euphorbia diterpenoid pepluacetal is disclosed in both racemic and chiral fashions. The synthesis strategically relies on a photo-induced Wolff rearrangement/lactonization cascade (WRLC) reaction to access the cyclobutane moiety, a ring-closing metathesis/cyclopropanation sequence to rapidly forge the 7-3 bicyclic system, and a late-stage Rh-catalyzed transannular carbenoid insertion to C(sp3)-H bond followed by a Baeyer-Villiger oxidation and ring-opening manipulations to install the side chain...
March 21, 2024: Angewandte Chemie
https://read.qxmd.com/read/38504061/solution-to-bridged-bicyclic-molecule-nmr-challenge
#24
Andrii V Kozytskyi, Andrii V Bondarenko
No abstract text is available yet for this article.
April 2024: Analytical and Bioanalytical Chemistry
https://read.qxmd.com/read/38502026/bridged-bicyclic-lactam-enables-chemically-recyclable-nylon
#25
JOURNAL ARTICLE
Wenxiu Lv, Maosheng Li, Youhua Tao
Nylon, a widely-used high-performance thermoplastic, boasts exceptional durability and resistance to various solvents and weak acids, making it indispensable across diverse applications. However, its nonbiodegradable nature has led to alarming environmental pollution in land and oceans. Chemical recycling to monomers (CRM) stands as a crucial strategy for establishing a circular plastic economy, but the CRM of nylon remains largely unexplored. Herein, we introduce the bridged bicyclic lactam 5-azabicyclo[2...
March 19, 2024: Angewandte Chemie
https://read.qxmd.com/read/38497681/metal-free-radical-bicyclization-chloroalkylarylation-of-1-6-enynes-with-chloroalkanes
#26
JOURNAL ARTICLE
Hongxun Zhou, Lijun Li, Qinqin Yan, Jinyue Ma, Ying Wang, Yongjun Gao, Zhong-Quan Liu, Zejiang Li
Free radical initiated bicyclization of 1,6-enynes with chloralkanes, is achieved via selective activation of the C(sp3 )-H bond of the chloralkane, resulting in diverse polychlorinated/chlorinated polyheterocycles. Two kinds of transformations and a scaled-up experiment were performed to test the synthetic importance of the organic chlorides. Finally, a range of radical inhibition operations and radical clock tests were explored to support the reaction process.
March 18, 2024: Chemical Communications: Chem Comm
https://read.qxmd.com/read/38497619/construction-of-seven-membered-oxacycles-using-a-rh-i-catalyzed-cascade-c-c-formation-cleavage-of-cyclobutenol-derivatives
#27
JOURNAL ARTICLE
Jin Su Ham, Mina Son, Christina G Na, Bohyun Park, Mu-Hyun Baik, Richmond Sarpong
Herein, we describe the synthesis of substituted oxepane derivatives through the skeletal remodeling of 4-hydroxy-2-cyclobutenones, which are readily prepared from commercially available dialkyl squarates upon their reaction with acrylonitrile. Mechanistically, a Rh(I)-catalyzed C-C bond formation and cleavage cascade is proposed. Specifically, a fused [3.2.0] bicycle is proposed to form from dialkyl squarate-derived cyclobutenols via an unusual Rh(I)-catalyzed intermolecular oxa-Michael addition of a tertiary alcohol with acrylonitrile, followed by an intramolecular conjugate addition/migratory insertion...
March 18, 2024: Journal of Organic Chemistry
https://read.qxmd.com/read/38494854/cycloaddition-of-phenyltriazolinedione-with-carbazole-alkynes-and-yne-carbamates-to-access-diazacyclobutenes
#28
JOURNAL ARTICLE
Brock A Miller, Chandima J Narangoda, Samuel Kwain, William T Bridges, Monireh Noori, Erin E Solomon, Alexis A Bragg, Alex T Sung, Yusuke Iwai, Lauren Ulisse, William H Schmidt, Colin D McMillen, Brian N Dominy, Daniel C Whitehead
Previously, we described the synthesis of stable, bicyclic examples of the rather rare diazacyclobutene (DCB) motif by means of a cycloaddition between triazolinediones and electron-rich thiolated alkynes. Here, we report the investigation of the cycloaddition of triazolinediones with related electron-rich yne-carbamates and carbazole-alkynes. Bicyclic DCBs arising from yne-carbamates were isolated in 8-65% yield, while those arising from carbazole-alkynes were isolated in 28-59% yield. Mechanistic studies and characterization of isolable byproducts shed light on the underlying issues leading to poor to moderate yields...
March 17, 2024: Journal of Organic Chemistry
https://read.qxmd.com/read/38491909/polyketide-trimming-shapes-dihydroxynaphthalene-melanin-and-anthraquinone-pigments
#29
JOURNAL ARTICLE
Maximilian Schmalhofer, Anna L Vagstad, Qiuqin Zhou, Helge B Bode, Michael Groll
Pigments such as anthraquinones (AQs) and melanins are antioxidants, protectants, or virulence factors. AQs from the entomopathogenic bacterium Photorhabdus laumondii are produced by a modular type II polyketide synthase system. A key enzyme involved in AQ biosynthesis is PlAntI, which catalyzes the hydrolysis of the bicyclic-intermediate-loaded acyl carrier protein, polyketide trimming, and assembly of the aromatic AQ scaffold. Here, multiple crystal structures of PlAntI in various conformations and with bound substrate surrogates or inhibitors are reported...
March 16, 2024: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
https://read.qxmd.com/read/38490942/quantitative-analysis-of-the-protective-performance-of-bicycle-helmet-with-multi-direction-impact-protection-system-in-oblique-impact-tests
#30
JOURNAL ARTICLE
Yong Han, Hao Yang, He Wu, Di Pan, Bing-Yu Wang
PURPOSE: The current study aimed to assess the protective performance of helmets equipped with a multi-directional impact protection system (MIPS) under various oblique impact loads. METHODS: Initially, a finite element model of a bicycle helmet with MIPS was developed based on the scanned geometric parameters of an actual bicycle helmet. Subsequently, the validity of model was confirmed using the KASK WG11 oblique impact test method. Three different impact angles (30°, 45°, and 60°) and 2 varying impact speeds (5 m/s and 8 m/s) were employed in oblique tests to evaluate protective performance of MIPS in helmets, focusing on injury assessment parameters such as peak linear acceleration (PLA) and peak angular acceleration (PAA) of the head...
March 7, 2024: Chinese Journal of Traumatology
https://read.qxmd.com/read/38490674/maximal-exercise-tolerance-objective-trunk-strength-and-mobility-measurements-in-axial-spondyloarthritis
#31
JOURNAL ARTICLE
Sophie De Mits, Tine Willems, Patrick Calders, Lieven Danneels, Gaëlle Varkas, Filip Van den Bosch, Dirk Elewaut, Philippe Carron
OBJECTIVE: Although exercise therapy is safe, effective and recommended within the nonpharmacological treatment in axial spondyloarthritis (axSpA), guidelines regarding type and dosage lack. Insufficient knowledge about physical and physiological parameters makes designing effective exercise programs challenging. Therefore, the goal was to simultaneously assess trunk strength, spinal mobility and the axSpA patients' cardiorespiratory fitness. METHODS: In a cross-sectional study, 58 axSpA patients (mean age:40...
March 15, 2024: Journal of Rheumatology
https://read.qxmd.com/read/38485374/evaluation-of-bicyclist-physiological-response-and-visual-attention-in-commercial-vehicle-loading-zones
#32
JOURNAL ARTICLE
Hisham Jashami, Douglas Cobb, Ivan Sinkus, Yujun Liu, Edward McCormack, Anne Goodchild, David Hurwitz
INTRODUCTION: With growing freight operations throughout the world, there is a push for transportation systems to accommodate trucks during loading and unloading operations. Currently, many urban locations do not provide loading and unloading zones, which results in trucks parking in places that obstruct bicyclist's roadway infrastructure (e.g., bicycle lanes). METHOD: To understand the implications of these truck operations, a bicycle simulation experiment was designed to evaluate the impact of commercial vehicle loading and unloading activities on safe and efficient bicycle operations in a shared urban roadway environment...
February 2024: Journal of Safety Research
https://read.qxmd.com/read/38485366/how-do-bicyclists-respond-to-vehicles-with-adaptive-headlamp-systems-a-nighttime-study-in-an-immersive-virtual-environment
#33
JOURNAL ARTICLE
Lakshmi Devi Subramanian, Rini Sherony, Joseph K Kearney, Jodie M Plumert, Elizabeth E O'Neal
INTRODUCTION: The risk of motor vehicle-bicyclist crashes and fatalities is greater during nighttime than daytime lighting conditions, even though there are fewer cyclists on roadways at night. Vehicle Adaptive Headlamp Systems (AHS) aim to increase the visibility of bicyclists for drivers by directing a spotlight to illuminate bicyclists on or near the roadway. AHS technology also serves to alert bicyclists to the approaching vehicle by illuminating the road beneath the rider and by projecting a warning icon on the roadway...
February 2024: Journal of Safety Research
https://read.qxmd.com/read/38485363/exploring-the-spatial-relationship-of-e-bike-and-motorcycle-crashes-implications-for-risk-reduction
#34
JOURNAL ARTICLE
Pei-Fen Kuo, Umroh Dian Sulistyah, I Gede Brawiswa Putra, Dominique Lord
INTRODUCTION: Electric bicycles, or e-bikes, have become very popular over the past decade. In order to reduce the risk of crashes, it is necessary to understand the contributing factors. While several researchers have examined these elements, few have considered the spatial heterogeneity between crashes and environmental variables, such as Points of Interest (POI). In addition, there is a scarcity of studies comparing the crash-related factors of e-bikes and motorcycles. Despite their differing speed and range capabilities, different POIs also tend to impact area/bandwidths differently because e-bikes cannot cover the same range that motorcycles can...
February 2024: Journal of Safety Research
https://read.qxmd.com/read/38484628/acute-and-subacute-effects-of-strenuous-exercise-on-platelet-aggregation-coagulation-and-fibrinolysis-in-patients-with-stable-coronary-artery-disease
#35
JOURNAL ARTICLE
Jacobina Kristiansen, Erik L Grove, Tórur Sjúrðarson, Magni Mohr, Steen D Kristensen, Anne-Mette Hvas
INTRODUCTION: Strenuous exercise may occasionally cause coronary thrombosis with myocardial infarction and sudden cardiac death. MATERIALS AND METHODS: Patients with stable coronary artery disease (CAD) (n = 164) and healthy individuals (n = 25) performed strenuous exercise on a bicycle ergometer. Blood was drawn at baseline, immediately after exercise and 2 h later. Platelet aggregation was measured with Multiplate® Analyzer. Thrombin generation was determined using a thrombogram and by measuring prothrombin fragment 1 + 2 (F1 + 2)...
March 5, 2024: Thrombosis Research
https://read.qxmd.com/read/38484170/high-molar-mass-polycarbonates-as-closed-loop-recyclable-thermoplastics
#36
JOURNAL ARTICLE
Gloria Rosetto, Fernando Vidal, Thomas M McGuire, Ryan W F Kerr, Charlotte K Williams
Using carbon dioxide (CO2 ) to make recyclable thermoplastics could reduce greenhouse gas emissions associated with polymer manufacturing. CO2 /cyclic epoxide ring-opening copolymerization (ROCOP) allows for >30 wt % of the polycarbonate to derive from CO2 ; so far, the field has largely focused on oligocarbonates. In contrast, efficient catalysts for high molar mass polycarbonates are underinvestigated, and the resulting thermoplastic structure-property relationships, processing, and recycling need to be elucidated...
March 14, 2024: Journal of the American Chemical Society
https://read.qxmd.com/read/38483085/asymmetric-total-synthesis-of-cryptorigidifoliol-i
#37
JOURNAL ARTICLE
Rodney A Fernandes, Dashrath Jangid
An efficient asymmetric total synthesis of cryptorigidifoliol I based on an unusual Luche reduction leading to bicyclic etherification and acid hydrolysis to a thermodynamically less stable 4-hydroxy-2,6- trans -disubstituted-THP moiety has been achieved. The easy setup of trans -2,6-substitution on the core pyran ring through bicyclic etherification would enable the synthesis of various THP and bicyclic-THP-lactone natural products.
March 14, 2024: Journal of Organic Chemistry
https://read.qxmd.com/read/38481986/design-and-optimization-of-a-high-performance-multi-barrier-ipms-motor-for-an-electric-scooter-and-bicycle
#38
JOURNAL ARTICLE
Halil Gör, Adem Dalcalı
Acknowledging the growing importance of electric vehicles (EVs) in the face of environmental concerns and increasing mobility needs, this study focuses on enhancing the performance of the electric motor, a critical component in EVs. The electric motor of these battery-powered vehicles is expected to have optimal characteristics and efficiency. This paper presents a comprehensive investigation into the design and optimization of a multi-barrier interior permanent magnet synchronous motor tailored for e-scooters and electric bicycles...
March 2024: Royal Society Open Science
https://read.qxmd.com/read/38481839/the-impact-of-street-greenery-on-active-travel-a-narrative-systematic-review
#39
Jiahua Yu, Hao Zhang, Xinyang Dong, Jing Shen
BACKGROUND: Street greenery may have a profound effect on residents' active travel (AT), a mode of transportation involving walking and cycling. This study systematically reviewed the scientific evidence on the effects of street greenery on active travel. METHODS: A comprehensive search was performed using keywords and references in PubMed, Web of Science, Scopus, and Cochrane Library. The review included studies that met the following criteria: (1) Study design: experimental studies, cross sectional studies, (2) Participants: individuals of all ages, (3) Exposure variables: street greenery, including street vegetation (e...
2024: Frontiers in Public Health
https://read.qxmd.com/read/38481219/self-reported-cycling-behavior-and-previous-history-of-traffic-accidents-of-cyclists
#40
JOURNAL ARTICLE
Enayatollah Homaie Rad, Fatemeh Kavandi, Leila Kouchakinejad-Eramsadati, Kamran Asadi, Naema Khodadadi-Hassankiadeh
BACKGROUND: Cyclists are vulnerable traffic users and studying the cycling behavior of professional and elite cyclists, their previous history of traffic accidents combined with the current knowledge on high-risk behaviors of this group can be a useful basis for further studies on ordinary cyclists. This study aimed to determine the relationship between cycling behavior and the previous history of traffic accidents among members of the Cycling Federation of Guilan province in 2022. METHODS: A descriptive-analytical study was performed in which the Bicycle Rider Behavior Questionnaire (BRBQ) constructed in the Porsline platform was distributed using the WhatsApp social network...
March 13, 2024: BMC Public Health
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