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Phosphoric acid

Benjamin List, Grigory A Shevchenko, Barry Oppelaar
The single electron oxidation of enamines is a well-established activation mode for organocatalytic enantioselective α-functionalizations of simple aldehydes and ketones.[1] Due to the intrinsic limitations of enamine catalysis, the oxidation of the corresponding α-branched ketones has so far not been reported. Herein we disclose the first direct and asymmetric α-aryloxylation of cyclic ketones via enol catalysis, using quinones as the reaction partner. Catalytic amounts of a phosphoric acid promote the exclusive formation of α,α-disubstituted ketones from the corresponding α-substituted ketones in good yields and enantioselectivities (up to 96...
May 22, 2018: Angewandte Chemie
U Daood, J K H Tsoi, P Neelakantan, J P Matinlinna, H A K Omar, M Al-Nabulsi, A S Fawzy
OBJECTIVE: Collagen fibrils aid in anchoring resin composite restorations to the dentine substrate. The aim of the study was to investigate effect of non-enzymatic glycation on bond strength and durability of demineralized dentine specimens in a modified two-step etch-and-rinse dentine adhesive. METHODS: Dentine surfaces were etched with 37% phosphoric acid, bonded with respective in vitro ethanol and acetone adhesives modified with (m/m, 0, 1%, 2% and 3% ribose), restored with restorative composite-resin, and sectioned into resin-dentine slabs and beams to be stored for 24h or 12 months in artificial saliva...
May 17, 2018: Dental Materials: Official Publication of the Academy of Dental Materials
Michael Chae, Lin Xia, Chengyong Zhu, David C Bressler
Although the improved dewaterability and digestibility of primary biosolids subjected to thermal hydrolysis has been studied for decades, there are a surprisingly small number of studies exploring the use of this thermal treatment for digested biosolids that are typically left to settle in large settling lagoons. This is likely because of the high capital and operating costs associated with thermal hydrolysis, coupled with the limited applications and value of the resulting products. However, due to the anticipated increases in the amount of generated biosolids combined with issues surrounding potential environmental release and the limited availability of land for additional lagoons, other biosolids management strategies are being explored...
May 17, 2018: Journal of Environmental Management
Chao Han, Weiguang Li, Chengyao Hua, Fengqing Sun, Pengsheng Bi, Qunqing Wang
Enzymatic saccharification of lignocellulosic biomass is increasingly applied in agricultural and industrial applications. Nevertheless, low performance in the extreme environment severely prevents the utilization of commercial enzyme preparations. To obtain cellobiohydrolases with improved catalytic activity and thermostability, structure-based rational design was performed based on a thermostable cellobiohydrolase CtCel6 from Chaetomium thermophilum. In the present study, four conserved and noncatalytic residue substitutions were generated via site-directed mutagenesis...
May 15, 2018: International Journal of Biological Macromolecules
Y Chae, M Yang, J R Kim
AIM: To investigate the release of growth factors into the root canal space after various final irrigants during regenerative endodontic procedures. The residual cytotoxic effect of final irrigants on stem cells from the apical papilla (SCAP) was also examined. METHODOLOGY: To measure the release of TGF-β1, root segments (8mm long) were irrigated with 1.5% NaOCl followed by 20 mL of final irrigants; Saline, 17% EDTA, 10% citric acid, 10% or 37% phosphoric acid...
May 17, 2018: International Endodontic Journal
Akram El Kateb, Claudio Stalder, Andres Rüggeberg, Christoph Neururer, Jorge E Spangenberg, Silvia Spezzaferri
The marine environment in the Gulf of Gabes (southern Tunisia) is severely impacted by phosphate industries. Nowadays, three localities, Sfax, Skhira and Gabes produce phosphoric acid along the coasts of this Gulf and generate a large amount of phosphogypsum as a waste product. The Gabes phosphate industry is the major cause of pollution in the Gulf because most of the waste is directly discharged into the sea without preliminary treatment. This study investigates the marine environment in the proximity of the phosphate industries of Gabes and the coastal marine environment on the eastern coast of Djerba, without phosphate industry...
2018: PloS One
Min-Hye Jeong, Dohyun Kwak, Hyun-Soo Ra, A-Young Lee, Jong-Soo Lee
Few-layer black phosphorus has shown great potential for next-generation electronics with tunable band gap and high carrier mobility. For the electronic applications, the thickness modulation of a BP flake is an essential due to its thickness-dependent electronic properties. However, controlling the precise thickness of few-layer BP is a challenge for the high-performance device applications. In this study, we demonstrate that thermal treatment under ambient condition precisely controls the thickness of BP flake...
May 17, 2018: ACS Applied Materials & Interfaces
Teerapon Pirom, Amornchai Arponwichanop, Ura Pancharoen, Tetsu Yonezawa, Soorathep Kheawhom
Yttrium (Y) is an essential lanthanide rare earth element and can be effectively extracted and purified using a hollow fiber supported liquid membrane (HFSLM) system. However, the stability of HFSLM system is a significant challenge. Pseudoemulsion-hollow fiber strip dispersion (PEHFSD) system, providing excellent stability, is attracting research attention. In this work, the recovery of Y(III) by PEHFSD system using di(2-ethylhexyl)phosphoric acid (D2EHPA) as a carrier was investigated. The effects of several operating parameters, including the initial concentration of Y(III) in the feed phase, the flow rate of feed, the stirring speed and the volumetric ratio of feed to strip on Y(III) separation were studied...
May 16, 2018: Scientific Reports
Wentong Zhao, Xiaoqing Lu, Manickam Selvaraj, Wei Wei, Zhifeng Jiang, Nabi Ullah, Jie Liu, Jimin Xie
Low-cost electrocatalysts play an important role in the hydrogen evolution reaction (HER). Particularly, transition metal phosphides (TMPs) are widely applied in the development of HER electrocatalysts. To improve the poor electrochemical reaction kinetics of HER, we introduce a facile way to synthesize carbon core-shell materials containing cobalt phosphide nanoparticles embedded in different graphene aerogels (GAs) (CoP@C-NPs/GA-x (x = 5, 10 and 20)) using seaweed biomass as precursors. The synthesized CoP@C-NPs/GA-5 exhibits efficient catalytic activity with small overpotentials of 120 and 225 mV at current densities of 10 mA cm-2, along with the low Tafel slopes of 57 and 66 mV dec-1, for HER in acidic and alkaline electrolytes, respectively...
May 15, 2018: Nanoscale
Rafael Caldas Pereira, Carla de Fátima Alves Nonato, Cicera Janaine Camilo, Henrique Douglas Melo Coutinho, Fabíola Fernandes Galvão Rodriguesa, Jianbo Xiao, José Galberto Martins da Costa
A method using high performance liquid chromatography with diode array detector (HPLC-DAD) for identification and quantification of pilocarpine in the extract of Pilocarpus microphyllus, popularly known as jaborandi. The analysis was conducted using RP-18 column (250 mm × 4.6 mm x 5 μm id) and a buffer solution composed of acidified water, phosphoric acid and triethylamine and methanol as a mobile phase in a flow rate of 1.0 mL/min and detection at 215  nm at 25 °C. Excellent linearity with r2 equal to 0...
May 10, 2018: Food and Chemical Toxicology
Chun-Yue Huang, Dan-Wei Ouyang, Li-Xin Niu, Jing Zhou, Shan Lin, Xiao Hu
The study is to establish the two-dimension HPLC fingerprints of Dihuang (Rehmannia glutinosa), by HPLC-PDA and HPLC-ELSD methods. The separations were performed on Waters Atlantis®T3(4.6 mm× 250 mm,5 μm)and Welch Ultimate®Hilic-NH₂(4.6 mm× 250 mm,5 μm)columns with the gradient elution of acetonitrile-0.01% phosphoric acid and acetonitrile-water, respectively. The chromatographic display wavelength for PDA detector was set at 203 nm. For HPLC-ELSD, the nebulizer was set as cooling mode, the drift tube temperature was set at 60 °C and the gas pressure was 35...
April 2018: Zhongguo Zhong Yao za Zhi, Zhongguo Zhongyao Zazhi, China Journal of Chinese Materia Medica
Danqing Xin, Xili Chu, Xuemei Bai, Weiwei Ma, Hongtao Yuan, Jie Qiu, Changxing Liu, Tong Li, Xin Zhou, Wenqiang Chen, Dexiang Liu, Zhen Wang
We previously reported that L-Cysteine, an H2 S donor, significantly alleviated brain injury after hypoxia-ischemic (HI) injury in neonatal mice. However, the mechanisms underlying this neuroprotective effect of L-Cysteine against HI insult remain unknown. In the present study, we tested the hypothesis that the protective effects of L-Cysteine are associated with glial responses and autophagy, and L-Cysteine attenuates synaptic injury as well as behavioral deficits resulting from HI. Consistent with our previous findings, we found that treatment with L-Cysteine after HI reduced early brain injury, improved behavioral deficits and synaptic damage, effects which were associated with an up-regulation of synaptophysin and postsynaptic density protein 95 expression in the lesioned cortex...
May 8, 2018: Brain, Behavior, and Immunity
Alesandere Ortega, Ruben Manzano, Uxue Uria, Luisa Carrillo, Efraim Reyes, Tomas Tejero, Pedro Merino, Jose L Vicario
Racemic cyclopropyl ketones undergo enantioselective rearrangement to deliver the corresponding dihydrofurans in the presence of a chiral phosphoric acid as catalyst. The reaction involves activation of the donor-acceptor cyclopropane substrate by the chiral Brønsted acid catalyst that promotes the ring-opening event driven by the release of ring strain, generating a carbocationic intermediate that subsequently undergoes cyclization. Computational studies supported by control experiments support this mechanistic pathway...
May 9, 2018: Angewandte Chemie
Wei Xiao, Shuo Ke, Nannan Quan, Limin Zhou, Jun Wang, Lijuan Zhang, Yaming Dong, Wenqing Qin, Guanzhou Qiu, Jun Hu
Dissolved air flotation (DAF) is broadly applied in wastewater treatment, especially for the recovery of organic pollution with low concentration. Yet the mechanism of interaction between nanoscale gas bubbles and nanoparticles in the process of DAF remains unclear. Here, we investigated the role of nanobubbles in the precipitation of styryl phosphoric acid (SPA)-Pb particles and recovering organic phosphine-containing in beneficiation wastewater by UV-vis (Ultraviolet-Visible) spectra, micro-flotation tests, nanoparticle tracking analysis, dynamic light scattering and Atomic Force Microscopy measurements...
May 8, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Haiming Wu, Ziyang Li, Hai Liu
In this study, polyhydric alcohols, including glycerol, erythritol, xylitol, mannitol, and inositol, were chosen as carbon precursors for preparation of carbon adsorbents via phosphoric acid activation. The thermal behaviors of phosphoric acid-treated polyhydric alcohols revealed the formation and decomposition of organic phosphates at low temperatures, which enhanced the creation of functional groups on activated carbon. In general, the activated carbons showed relative low surface area (the highest one of 509 m2 /g for AC-xylitol) due to the low activation temperature, and low yields (the highest one of 36...
April 30, 2018: Chemosphere
María de Los Angeles Moyaho-Bernal, Rosalía Contreras-Bulnes, Laura Emma Rodríguez-Vilchis, Efraín Rubio-Rosas
Innovators conditioning protocols are emerged in permanent dentin, however for deciduous dentin the information is limited; the aim of this study was to evaluate in vitro diameter of deciduous and permanent dentinal tubules after several conditioning protocols. Eighty dentin samples were distributed in sixteen groups (n = 5 p/g) and dentin surface was conditioned as follow: G1D/G1P acid etching; G2D/G2P, self-etch adhesive; G3D/G3P, G4D/G4P, Er: YAG laser irradiation at 200 mJ-25.5 J/cm2 and 300 mJ-38.2 J/cm2 , at 10 Hz under water spray respectively; G5D/G5P, G6D/G6P, G7D/G7P, and G8D/G8P were irradiated under the same energy densities followed phosphoric acid or self-etch adhesive conditioning...
May 8, 2018: Microscopy Research and Technique
Mark R Swingle, Richard Eric Honkanen
BACKGROUND: The reversible phosphorylation of proteins regulates many key functions in eukaryotic cells. Phosphorylation is catalyzed by protein kinases, with the majority of phosphorylation occurring on side chains of serine and threonine residues. The phosphomonoesters generated by protein kinases are hydrolyzed by protein phosphatases. In the absence of a phosphatase the half-time for the hydrolysis of alkyl phosphate dianions at 25º C is over 1 trillion years; knon ~2 x 10-20 sec-1...
May 7, 2018: Current Medicinal Chemistry
J Chris Slootweg
Avoiding white phosphorus: Cummins and Geeson have recently described the conversion of phosphoric acid into the novel bis(trichlorosilyl)phosphide anion, which serves as a key intermediate in the synthesis of organophosphines, hexafluorophosphate, and phosphine gas in a reaction sequence that does not rely on white phosphorus.
May 7, 2018: Angewandte Chemie
F Y Abdelmegid
Objective: The purpose of this in vitro investigation was to assess the effect of deproteinization before and after acid etching on the surface roughness of immature human enamel of permanent teeth compared to acid etching alone using noncontact three-dimensional (3D) optical profilometer. Materials and Methods: Forty-eight enamel blocks were randomly distributed into 4 groups (12 each) according to the surface treatment in the form of deproteinized with 2.5% sodium hypochlorite (NaOCl) before and after acid etching with 32% phosphoric acid (H3PO4) compared to application of H3PO4 alone...
May 2018: Nigerian Journal of Clinical Practice
Kai Jiang, Yuhui Wang, Congzhong Cai, Hengwei Lin
Stimuli-responsive optical materials have received tremendous interest in the last several decades due to their numerous promising applications. Here, fluorescence emissive polymer carbon dots (F-CDs), prepared with a simple heating treatment from ethylenediamine and phosphoric acid, are found to produce unexpected ultralong room-temperature phosphorescence (URTP), which lasts for about 10 s with a lifetime of 1.39 s. This is the first example to achieve the conversion of a fluorescence material to URTP by means of an external heating stimulus...
May 7, 2018: Advanced Materials
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