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https://www.readbyqxmd.com/read/28691695/mechanical-and-biological-characterization-of-alkaline-substituted-orthophosphate-bone-substitutes-containing-meta-and-diphosphates
#1
Moritz Klein, Matthias W Laschke, Joerg H Holstein, Tina Histing, Tim Pohlemann, Michael Menger, Patric Garcia
Despite the growing knowledge on the mechanisms of fracture healing, bone defects often do not heal in a timely manner. Clinically, tricalcium phosphate (Ca-P) bone substitutes are used to fill bone defects and promote bone healing. However, the degradation rate of these implants is often too slow for sufficient bone replacement. The use of calcium phosphate material with the crystalline phase Ca10 [K/Na](PO4)7 containing different amounts of di- and metaphosphates may overcome this problem, because these materials show an accelerated degradation...
July 10, 2017: Biomedical Materials
https://www.readbyqxmd.com/read/28688396/experimental-and-theoretical-investigations-of-h2o-ar
#2
Thomas Vanfleteren, Tomas Földes, Michel Herman, Jacques Liévin, Jérôme Loreau, Laurent H Coudert
We have used continuous-wave cavity ring-down spectroscopy to record the spectrum of H2O-Ar in the 2OH excitation range of H2O. 24 sub-bands have been observed. Their rotational structure (Trot = 12 K) is analyzed and the lines are fitted separately for ortho and para species together with microwave and far infrared data from the literature, with a unitless standard deviation σ=0.98 and 1.31, respectively. Their vibrational analysis is supported by a theoretical input based on an intramolecular potential energy surface obtained through ab initio calculations and computation of the rotational energy of sub-states of the complex with the water monomer in excited vibrational states up to the first hexad...
July 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28667433/craniofacial-features-affecting-mandibular-asymmetries-in-skeletal-class-ii-patients
#3
Guilherme Thiesen, B F Gribel, M P M Freitas, D R Oliver, K B Kim
OBJECTIVES: The aim of this study was to evaluate the characteristics affecting different intensities of mandibular asymmetry in skeletal Class II adults using three-dimensional images. This study is clinically relevant since it allows professionals to evaluate the morphological components related to these deformities and more carefully obtain correct diagnosis and treatment plan for such patients. METHODS: Cone-beam computed tomography data of 120 Class II patients (40 with relative symmetry, 40 with moderate asymmetry, and 40 with severe asymmetry) were imported to SimPlant Ortho Pro(®) 2...
June 30, 2017: Journal of Orofacial Orthopedics, Fortschritte der Kieferorthopädie
https://www.readbyqxmd.com/read/28661133/enantiospecific-synthesis-of-ortho-substituted-benzylic-boronic-esters-by-a-1-2-metalate-rearrangement-1-3-borotropic-shift-sequence
#4
Stefan Aichhorn, Raphael Bigler, Eddie L Myers, Varinder K Aggarwal
Coupling reactions between benzylamines and boronic esters have been investigated. ortho-Lithiated benzylamines react with boronic esters and a N-activator to afford ortho-substituted benzylic boronic esters with formal 1,1'-benzylidene insertion into the C-B bond. The reaction occurs by a SN2' elimination and 1,2-metalate rearrangement of the N-activated boronate complex to afford a dearomatized intermediate, which undergoes a Lewis-acid catalyzed 1,3-borotropic shift to afford the boronic ester products in high yield and with excellent enantiospecificity...
July 6, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28658508/selectivity-of-c-h-vs-c-f-bond-oxygenation-by-homo-and-heterometallic-fe4-fe3mn-and-mn4-clusters
#5
Graham de Ruiter, Kurtis M Carsch, Michael K Takase, Theodor Agapie
A series of tetranuclear [LM3(HFArPz)3OM'][OTf]2 (M, M' = Fe or Mn) clusters that displays 3-(2-fluorophenyl)pyrazolate (HFArPz) as bridging ligand is reported. With these complexes manganese is demonstrated to facilitate C(sp2)-F bond oxygenation via a putative terminal metal-oxo species. Moreover, the presence of both ortho C(sp2)-H and C(sp2)-F bonds in proximity provides an opportunity to investigate the selectivity of intramolecular C(sp2)-X bond oxygenation (X = H or F) in these isostructural compounds...
June 28, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28642057/novel-multifunctional-dental-cement-to-prevent-enamel-demineralization-near-orthodontic-brackets
#6
Yansong Ma, Ning Zhang, Michael D Weir, Yuxing Bai, Hockin H K Xu
OBJECTIVES: White spot lesions due to biofilm acid-induced enamel demineralization are prevalent in orthodontic treatments. The aim of this study was to develop a novel bioactive multifunctional cement with protein-repellent, antibacterial and remineralizing capabilities, and investigate the effects on enamel hardness and lesion depth in vitro for the first time. MATERIALS AND METHODS: 2-Methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM), and nanoparticles of amorphous calcium phosphate (NACP) were incorporated into a resin-modified glass ionomer (RMGI)...
June 19, 2017: Journal of Dentistry
https://www.readbyqxmd.com/read/28621913/visible-light-promoted-generation-of-alpha-ketoradicals-from-vinyl-bromides-and-molecular-oxygen-synthesis-of-indenones-and-dihydroindeno-1-2-c-chromenes
#7
Santosh K Pagire, Peter Kreitmeuer, Oliver Reiser
Ortho-alkynylated α-bromocinnamates can be converted by a visible light mediated photocascade reaction with molecular oxygen either to indenones or to dihydroindeno[1,2-c]chromenes. The one-step process features two photochemical key steps, i.e. the activation of vinyl bromides by energy transfer giving rise to α-ketoradicals in the reaction with molecular oxygen and the α-hydroxylation of an arene moiety.
June 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28571386/glassy-dynamics-of-polymethylphenylsiloxane-in-one-and-two-dimensional-nanometric-confinement-a-comparison
#8
Wycliffe K Kipnusu, Mohamed Elsayed, Reinhard Krause-Rehberg, Friedrich Kremer
Glassy dynamics of polymethylphenylsiloxane (PMPS) is studied by broadband dielectric spectroscopy in one-dimensional (1D) and two-dimensional (2D) nanometric confinement; the former is realized in thin polymer layers having thicknesses down to 5 nm, and the latter in unidirectional (thickness 50 μm) nanopores with diameters varying between 4 and 8 nm. Based on the dielectric measurements carried out in a broad spectral range at widely varying temperatures, glassy dynamics is analyzed in detail in 1D and in 2D confinements with the following results: (i) the segmental dynamics (dynamic glass transition) of PMPS in 1D confinement down to thicknesses of 5 nm is identical to the bulk in the mean relaxation rate and the width of the relaxation time distribution function; (ii) additionally a well separated surface induced relaxation is observed, being assigned to adsorption and desorption processes of polymer segments with the solid interface; (iii) in 2D confinement with native inner pore walls, the segmental dynamics shows a confinement effect, i...
May 28, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28567460/ni-and-cu-catalyzed-one-pot-synthesis-of-unsymmetrical-1-3-di-hetero-aryl-1h-indazoles-from-hydrazine-o-chloro-hetero-benzophenones-and-hetero-aryl-bromides
#9
Carson Wiethan, Christopher M Lavoie, Andrey Borzenko, Jillian S K Clark, Helio G Bonacorso, Mark Stradiotto
The nickel-catalyzed cyclization of in situ generated ortho-chlorobenzophenone hydrazone derivatives, to afford 3-(hetero)aryl-1H-indazoles, is documented for the first time. The product 1H-indazoles can be transformed subsequently in a one-pot procedure into 1,3-di(hetero)aryl-1H-indazoles via copper-catalyzed N-arylation with (hetero)aryl bromides.
June 14, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28561101/on-the-outside-looking-in-rethinking-the-molecular-mechanism-of-1-3-dipolar-cycloadditions-from-the-perspective-of-bonding-evolution-theory-the-reaction-between-cyclic-nitrones-and-ethyl-acrylate
#10
A I Adjieufack, I M Ndassa, I Patouossa, J K Mbadcam, V S Safont, M Oliva, J Andrés
In this work we report on the progress that has been made towards gaining an understanding of the molecular mechanism of 1,3-dipolar cycloadditions using the bonding evolution theory (BET). A detailed analysis of the flow of electron density along the reaction pathway of the formal 1,3-dipolar cycloaddition reaction between cyclic nitrones (pyrroline-1-oxide and 2,3,4,5-tetrahydropyridine-1-oxide) and ethyl acrylate, as a case study, allowed the nature of the molecular mechanisms to be characterized. The present study provides a deep insight into the reaction mechanism, based on the electron density rearrangements given by the structural stability domains, and their connection with the bond breaking/forming processes along the reaction pathway...
May 31, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28511010/%C3%AF-extended-and-curved-antiaromatic-polycyclic-hydrocarbons
#11
Junzhi Liu, Ji Ma, Ke Zhang, Prince Ravat, Peter Machata, Stanislav Avdoshenko, Felix Hennersdorf, Hartmut Komber, Wojciech Pisula, Jan J Weigand, Alexey A Popov, Reinhard Berger, Klaus Müllen, Xinliang Feng
Synthesis of antiaromatic polycyclic hydrocarbons (PHs) is challenging because the high energy of their highest occupied molecular orbital and low energy of their lowest unoccupied molecular orbital cause them to be reactive and unstable. In this work, two large antiaromatic acene analogues, namely, cyclopenta[pqr]indeno[2,1,7-ijk]tetraphene (CIT, 1a) and cyclopenta[pqr]indeno[7,1,2-cde]picene (CIP, 1b), as well as a curved antiaromatic molecule with 48 π-electrons, dibenzo[a,c]diindeno[7,1,2-fgh:7',1',2'-mno]phenanthro[9,10-k]tetraphene (DPT, 1c), are synthesized on the basis of the corona of indeno[1,2-b]fluorene...
June 7, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28503205/substitution-of-fluorine-in-m-c6f5bf3-with-organolithium-compounds-distinctions-between-o-and-n-nucleophiles
#12
Anton Yu Shabalin, Nicolay Yu Adonin, Vadim V Bardin
Borates M[C6F5BF3] (M = K, Li, Bu4N) react with organolithium compounds, RLi (R = Me, Bu, Ph), in 1,2-dimethoxyethane or diglyme to give M[4-RC6F4BF3] and M[2-RC6F4BF3]. When R is Me or Bu, the nucleophilic substitution of the fluorine atom at the para position to boron is the predominant route. When R = Ph, the ratio M[4-RC6F4BF3]/M[2-RC6F4BF3] is ca. 1:1. Substitution of the fluorine atom at the ortho position to boron is solely caused by the coordination of RLi via the lithium atom with the fluorine atoms of the BF3 group...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28485602/metal-free-sequential-c-sp-2-h-oh-and-c-sp-3-h-aminations-of-nitrosoarenes-and-n-heterocycles-to-ring-fused-imidazoles
#13
Anisha Purkait, Subhra Kanti Roy, Hemant Kumar Srivastava, Chandan K Jana
Hydrogen bond assisted ortho-selective C(sp(2))-H amination of nitrosoarenes and subsequent α-C(sp(3))-H functionalization of aliphatic amines is achieved under metal-free conditions. The annulation of nitrosoarenes and 2-hydroxy-C-nitroso compounds with N-heterocycles provides a facile excess to a wide range of biologically relevant ring-fused benzimidazoles and structurally novel polycyclic imidazoles, respectively. Nucleophilic aromatic hydrogen substitution (SNArH) was found to be preferred over classical SNAr reaction during the C(sp(2))-H amination of halogenated nitrosoarenes...
May 9, 2017: Organic Letters
https://www.readbyqxmd.com/read/28443910/spin-state-variability-in-fe-2-complexes-of-substituted-2-pyridin-2-yl-1-10-phenanthroline-ligands-as-versatile-terpyridine-analogues
#14
Holm Petzold, Paul Djomgoue, Gerald Hörner, Silvio Heider, Charles Lochenie, Birgit Weber, Tobias Rüffer, Dieter Schaarschmidt
Fe(2+) spin crossover complexes [Fe(L)2](2+) (L = 2-(6-R(1)-pyridin-2-yl)-1,10-phenanthroline with R(1) = H, methoxy, bromo, -(1H-pyrazol-1-yl) or L = 2-(3-methoxy-pyridin-2-yl)-1,10-phenanthroline) were prepared. These air stable and durable complexes show SCO behaviour with very different transition temperatures T1/2 ranging from 130 K to 600 K depending on the substitution pattern. The use of (1)H NMR spectroscopy to elucidate the thermodynamics and kinetics of SCO in a solution of this series is described in detail...
May 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28441011/synthesis-characterization-and-dft-analysis-of-bis-terpyridyl-based-molecular-cobalt-complexes
#15
Safwan Aroua, Tanya K Todorova, Paul Hommes, Lise-Marie Chamoreau, Hans-Ulrich Reissig, Victor Mougel, Marc Fontecave
Terpyridine ligands are widely used in chemistry and material sciences owing to their ability to form stable molecular complexes with a large variety of metal ions. In that context, variations of the substituents on the terpyridine ligand allow modulation of the material properties. Applying the Stille cross-coupling reaction, we prepared with good yields a new series of terpyridine ligands possessing quinoline-type moieties in ortho, meta, and para positions and dimethylamino substituents at central or distal positions...
April 25, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28435723/formamidinium-iodide-crystal-structure-and-phase-transitions
#16
Andrey A Petrov, Eugene A Goodilin, Alexey B Tarasov, Vladimir A Lazarenko, Pavel V Dorovatovskii, Victor N Khrustalev
At a temperature of 100 K, CH5N2(+)·I(-) (I), crystallizes in the monoclinic space group P21/c. The formamidinium cation adopts a planar symmetrical structure [the r.m.s. deviation is 0.002 Å, and the C-N bond lengths are 1.301 (7) and 1.309 (8) Å]. The iodide anion does not lie within the cation plane, but deviates from it by 0.643 (10) Å. The cation and anion of I form a tight ionic pair by a strong N-H⋯I hydrogen bond. In the crystal of I, the tight ionic pairs form hydrogen-bonded zigzag-like chains propagating toward [20-1] via strong N-H⋯I hydrogen bonds...
April 1, 2017: Acta Crystallographica. Section E, Crystallographic Communications
https://www.readbyqxmd.com/read/28426213/role-of-mediator-and-effects-of-temperature-on-ortho-c-n-bond-fusion-reactions-of-aniline-using-ruthenium-templates-isolation-and-characterization-of-new-ruthenium-complexes-of-the-in-situ-generated-ligands
#17
Suman K Roy, Debabrata Sengupta, Santi Prasad Rath, Tanushri Saha, Subhas Samanta, Sreebrata Goswami
In this work, ortho-C-N bond fusion reactions of aniline are followed by the use of two different ruthenium mediators. Reaction of aniline with [Ru(III)(terpy)Cl3] (terpy = 2,2':6',2″-terpyridine) resulted in a trans bis-aniline ruthenium(II) complex [1](+) which upon oxidation with H2O2 produced compound [2](+) of a bidentate ligand, N-phenyl-1,2-benzoquinonediimine, due to an oxidative ortho-C-N bond fusion reaction. Complex [1](+) and aniline (neat) at 185 °C produced a bis-chelated ruthenium complex (3)...
April 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28406298/reaction-of-aniline-with-singlet-oxygen-o2-1-%C3%AE-g
#18
Jomana Al-Nu'airat, Mohammednoor Altarawneh, Xiangpeng Gao, Phillip R Westmoreland, Bogdan Z Dlugogorski
Dissolved organic matter (DOM) acts as an effective photochemical sensitizer that produces the singlet delta state of molecular oxygen (O2(1)Δg), a powerful oxidizer that removes aniline from aqueous solutions. However, the exact mode of this reaction, the p- to o-iminobenzoquinone ratio, and the selectivity of one over the other remain largely speculative. This contribution resolves these uncertainties. We report, for the first time, a comprehensive mechanistic and kinetic account of the oxidation of aniline with the singlet delta oxygen using B3LYP and M06 functionals in both gas and aqueous phases...
May 4, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28358500/molecular-mechanism-of-dioxin-formation-from-chlorophenol-based-on-electron-paramagnetic-resonance-spectroscopy
#19
Lili Yang, Guorui Liu, Minghui Zheng, Yuyang Zhao, Rong Jin, Xiaolin Wu, Yang Xu
Few studies have investigated the free radical intermediates involved in the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from chlorophenol. This study clarified the reaction pathways during thermochemical formation of PCDDs from 2,3,6-trichlorophenol (TCP) over a Cu(II)O/silica matrix, which was used to simulate fly ash, at 298-523 K. The reaction was studied using electron paramagnetic resonance (EPR) spectroscopy and theoretical calculations. In situ EPR indicated the TCP radical (TCPR) formed by hydrogen abstraction of TCP...
May 2, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28346278/effects-of-myopic-orthokeratology-on-visual-performance-and-optical-quality
#20
Guihua Liu, Zhi Chen, Feng Xue, Jing Li, Mi Tian, Xingtao Zhou, Ruihua Wei
OBJECTIVES: To analyze the changes in visual performance and optical quality after orthokeratology (ortho-k) treatment and its correlation with the magnitude of lens decentration and the diameter of treatment zone (TxZ). METHODS: A prospective study was conducted in 27 eyes of 27 patients wearing ortho-k contact lens. Area under log contrast sensitivity function (AULCSF), modulation transfer function cutoff values (MTFcutoff), Strehl ratio (SR), and objective scattering index (OSI) were measured and compared before and 1 month after ortho-k lens treatment...
March 24, 2017: Eye & Contact Lens
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