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排序方式: 共有981条查询结果,搜索用时 15 毫秒
1.
Dr. Lidia A. Maslovskaya Dr. Andrei I. Savchenko Prof. Elizabeth H. Krenske Dr. Sharon Chow Tina Holt Dr. Victoria A. Gordon Dr. Paul W. Reddell Carly J. Pierce Prof. Peter G. Parsons Prof. Glen M. Boyle Prof. Andrei G. Kutateladze Prof. Craig M. Williams 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11862-11867
Structurally unique halimanes EBC-232 and EBC-323, isolated from the Australian rainforest plant Croton insularis, proved considerably difficult to elucidate. The two diastereomers, which consist an unusual oxo-6,7-spiro ring system fused to a dihydrofuran, were solved by unification and consultation of five in silico NMR elucidation and prediction methods [i.e., ACDLabs, olefin strain energy (OSE), DP4, DU8+ and TD DFT CD]. Structure elucidation challenges of this nature are prime test case examples for empowering future AI learning in structure elucidation. 相似文献
2.
Wei Peng Jie Dong Han‐Bin Li Christine Chow Qiao‐Sheng Hu 《Journal of polymer science. Part A, Polymer chemistry》2019,57(14):1606-1611
Room temperature Suzuki cross‐coupling polymerization of aryl dibromides/diiodides with aryldiboronic acids/acid esters with t‐Bu3P‐coordinated 2‐phenylaniline‐based palladacycle complex, [2′‐(amino‐kN)[1,1′‐biphenyl]‐2‐yl‐kC]chloro(tri‐t‐butylphosphine)palladium, as a general precatalyst is described. Such room temperature Suzuki cross‐coupling polymerization is achieved by employing six equivalents or more of the base and affords polymers within an hour, with the yields and the molecular weights in general comparable to or higher than reported results that required higher reaction temperature and/or longer polymerization time. Our study provides a general catalyst system for the room temperature Suzuki cross‐coupling polymerization of aryl dibromides/diiodides with aryldiboronic acids/acid esters and paves the road for the investigation of employing other monodentate ligand‐coordinated palladacycle complexes including other electron‐rich monophosphine‐coordinated ones for room temperature cross‐coupling polymerizations. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1606–1611 相似文献
3.
Cover Picture: Mild and Low‐Pressure fac‐Ir(ppy)3‐Mediated Radical Aminocarbonylation of Unactivated Alkyl Iodides through Visible‐Light Photoredox Catalysis (Chem. Eur. J. 27/2016) 下载免费PDF全文
4.
Chun Y. Chow Hélène Bolvin Victoria E. Campbell Régis Guillot Jeff W. Kampf Wolfgang Wernsdorfer Frédéric Gendron Jochen Autschbach Vincent L. Pecoraro Talal Mallah 《Chemical science》2015,6(7):4148-4159
We report here the synthesis and the investigation of the magnetic properties of a series of binuclear lanthanide complexes belonging to the metallacrown family. The isostructural complexes have a core structure with the general formula [Ga4Ln2(shi3–)4(Hshi2–)2(H2shi–)2(C5H5N)4(CH3OH)x(H2O)x]·xC5H5N·xCH3OH·xH2O (where H3shi = salicylhydroxamic acid and Ln = GdIII1; TbIII2; DyIII3; ErIII4; YIII5; YIII0.9DyIII0.16). Apart from the Er-containing complex, all complexes exhibit an antiferromagnetic exchange coupling leading to a diamagnetic ground state. Magnetic studies, below 2 K, on a single crystal of 3 using a micro-squid array reveal an opening of the magnetic hysteresis cycle at zero field. The dynamic susceptibility studies of 3 and of the diluted DyY 6 complexes reveal the presence of two relaxation processes for 3 that are due to the excited ferromagnetic state and to the uncoupled DyIII ions. The antiferromagnetic coupling in 3 was shown to be mainly due to an exchange mechanism, which accounts for about 2/3 of the energy gap between the antiferro- and the ferromagnetic states. The overlap integrals between the Natural Spin Orbitals (NSOs) of the mononuclear fragments, which are related to the magnitude of the antiferromagnetic exchange, are one order of magnitude larger for the Dy2 than for the Er2 complex. 相似文献
5.
Mushrooms, the fruiting bodies of fungi, are known for a long time in different cultures around the world to possess medicinal properties and are used to treat various human diseases. Mushrooms that are parts of traditional medicine in Asia had been extensively studied and this has led to identification of their bioactive ingredients. North America, while home to one of the world’s largest and diverse ecological systems, has not subjected its natural resources especially its diverse array of mushroom species for bioprospecting purposes: Are mushrooms native to North America a good source for drug discovery? In this review, we compile all the published studies up to September 2020 on the bioprospecting of North American mushrooms. Out of the 79 species that have been investigated for medicinal properties, 48 species (60%) have bioactivities that have not been previously reported. For a mere 16 selected species, 17 new bioactive compounds (10 small molecules, six polysaccharides and one protein) have already been isolated. The results from our literature search suggest that mushrooms native to North America are indeed a good source for drug discovery. 相似文献
6.
Effects of Ultraviolet Radiation (UVA+UVB) and Copper on the Morphology,Ultrastructural Organization and Physiological Responses of the Red Alga Pterocladiella capillacea 下载免费PDF全文
Éder C. Schmidt Marianne Kreusch Marthiellen R. de L. Felix Debora T. Pereira Giulia B. Costa Carmen Simioni Luciane C. Ouriques Francine L. Farias‐Soares Neusa Steiner Fungyi Chow Fernanda Ramlov Marcelo Maraschin Zenilda L. Bouzon 《Photochemistry and photobiology》2015,91(2):359-370
The effect of ultraviolet (UV) radiation and copper (Cu) on apical segments of Pterocladiella capillacea was examined under two different conditions of radiation, PAR (control) and PAR+UVA+UVB (PAR+UVAB), and three copper concentrations, ranging from 0 (control) to 0.62, 1.25 and 2.50 μm . Algae were exposed in vitro to photosynthetically active radiation (PAR) at 70 μmol photons m?2 s?1, PAR + UVB at 0.35 W m?2 and PAR +UVA at 0.70 W m?2 during a 12‐h photocycle for 3 h each day for 7 days. The effects of radiation and copper on growth rates, content of photosynthetic pigments and photosynthetic performance were analyzed. In addition, samples were processed for light and transmission electron microscopy. The content of photosynthetic pigments decreased after exposure to radiation and Cu. Compared with PAR radiation and copper treatments modified the kinetics patterns of the photosynthesis/irradiance curve. The treatments also caused changes in the ultrastructure of cortical and subcortical cells, including increased cell wall thickness and accumulation of plastoglobuli, as well as changes in the organization of chloroplasts. The results indicate that the synergistic interaction between UV radiation and Cu in P. capillacea, led to the failure of protective mechanisms and causing more drastic changes and cellular imbalances. 相似文献
7.
Inside Back Cover: A Multifunctional Bimetallic Molecular Device for Ultrasensitive Detection,Naked‐Eye Recognition,and Elimination of Cyanide Ions (Chem. Eur. J. 37/2015) 下载免费PDF全文
8.
Chow JY Davids K Button C Shuttleworth R Renshaw I Araújo D 《Nonlinear dynamics, psychology, and life sciences》2006,10(1):71-103
Team sport competition can be characterized as a complex adaptive system in which concepts from nonlinear dynamics can provide a sound theoretical framework to understand emergent behavior such as movement coordination and decision making in game play. Nonlinear Pedagogy is presented as a methodology for games teaching, capturing how phenomena such as movement variability, self-organization, emergent decision making, and symmetry-breaking occur as a consequence of interactions between agent-agent and agent-environment constraints. Empirical data from studies of basketball free-throw shooting and dribbling are used as task vehicles to exemplify how nonlinear phenomena characterize game play in sport. In this paper we survey the implications of these data for Nonlinear Pedagogy, focusing particularly on the manipulation of constraints in team game settings. The data and theoretical modeling presented in this paper provide a rationale in nonlinear dynamics for the efficacy of a prominent model of game play teaching, Teaching Games for Understanding approach. 相似文献
9.
The sidewall is one of the regions where service failures occur in a pneumatic tire. Knowledge of the stresses or strains developed in the sidewall under varying service conditions is required if such pneumatic-tire failures are to be avoided. This paper describes an experimental investigation into the effect of inflation pressure, vehicle load and camber angle on the sidewall-surface strains in a radial tire. Photoelastic coating and a specially designed strain-gaging technique were used. For pure-inflation pressure, the magnitude of the measured shear strains in the sidewall is directly related to the inflation pressure. The maximum sidewall shear strains in pure inflation are located in the lower sidewall (18 mm from bead), irrespective of the magnitude of the inflation pressure. The mendional sidewall strain is predominant in the inflated but otherwise unloaded tire. The meridional strain is proportional to the square root of the inflation pressure. The maximum mendional strain is located in the mid-sidewall region. For a constant vehicle loading, there is a transition inflation pressure below or above which the circumterential shoulder strain increases sharply. This observation highlights the importance of maintaining satistactory inflation pressure in passenger-car tires as an under-inflated tire will induce severe strain development at the shoulder. In addition to the vehicle load, the introduction of camber angle produces localized change in the meridional and circumterential strains within the contact zone. The increase of camber angle up to 10 deg causes continuous increase in the meridional strain in the lower sidewall but decrease in the upper sidewall. The mid-sidewall meridional strains remain practically unchanged. The circumferential strains along the load line are, in general, lower due to the increase in camber angle. 相似文献
10.
An analysis of determining the plane stress fracture toughness based on a beam-on-elastic foundation model for compact tension specimens (CTS) covering a wide range of a/2H and d/W ratios is presented. The solution is achieved by using the Timoshenko beam theory and Pasternak foundation with alternative formulations of the foundation modulus and the shear parameter to reflect more accurately the stress-strain distributions at the crack tip.The solution applicable to a wider range of a/2H and d/W ratios becomes desirable for practical reasons. For instance, the determination of plane-strain fracture toughness from the CTS specimens at higher a/W ratios enables the reduction of loading capacity from a testing machine which may become prohibitively high for medium strength engineering materials. Maximum fatigue crack growth data to be measured from a CTS specimen also becomes possible when the validity of fracture toughness can be ensured at the extended a/W ratios.The computed fracture toughness from the present analysis are compared with those measured experimentally and found to be satisfactory not only for high a/W ratios but also for a wide range of a/2H ratios commonly used in double-cantilever beam specimens. 相似文献