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https://www.readbyqxmd.com/read/29792667/control-of-selectivity-in-palladium-ii-catalyzed-oxidative-transformations-of-allenes
#1
Bin Yang, Youai Qiu, Jan-E Bäckvall
Oxidation reactions play a central role in organic synthesis, and it is highly desirable that these reactions are mild and occur under catalytic conditions. In Nature, oxidation reactions occur under mild conditions via cascade processes, and furthermore, they often occur in an enantioselective manner with many of them involving molecular oxygen or hydrogen peroxide as the terminal oxidant. Inspired by the reactions in Nature, we have developed a number of Pd(II)-catalyzed cascade reactions under mild oxidative conditions...
May 24, 2018: Accounts of Chemical Research
https://www.readbyqxmd.com/read/29792664/tricolor-white-light-emitting-carbon-dots-with-multiple-cores-shell-structure-for-wled-application
#2
Tianyi Zhang, Feifei Zhao, Li Li, Bin Qi, Dongxia Zhu, Jianhua Lü, Changli Lü
The past few years have witnessed the rapid development of carbon dots (CDs) due to their outstanding optical properties and a wide range of applications. However, the design and control of CDs with long-wavelength and multicolor emission are still huge challenges to be addressed for their practical use in different fields. Here, novel nitrogen doped multiple-cores@shell structured CDs with tricolor emissions of red, green and blue were constructed via one pot hydrothermal method from citric acid (CA) and 5-amino-1,10-phenanthroline (Aphen) as reactants and the growth process of CDs was monitored with the reaction time in the synthetic system...
May 24, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29792344/direct-formylation-of-2-pyridone-core-of-3-n-methylcytisine-via-duff-reaction-synthesis-of-9-enyl-9-ynyl-and-9-imino-derivatives
#3
Polina R Petrova, Alena V Koval'skaya, Alexander N Lobov, Inna P Tsypysheva
The first direct synthesis of 3-N-methyl-9-formylcytisine via electrophylic formylation is described. It is established, that Vilsmeier-Haack and Gatterman variants of this reaction are unsuccessful in the case with 3-substituted (-)-cytisine derivatives, but Duff procedure (with hexamethylenetetramine in trifluoroacetic acid) gives a possibility to obtain the target pseudo aromatic aldehyde with the 69% yield. Convenient precursors for [4 + 2]- or [3 + 2]-cycloaddition reactions are obtained by means of condensation of synthesized 3-N-methyl-9-formylcytisine with acetone, nitromethane and phosphorous ylides with yields from 70 to 87%...
May 24, 2018: Natural Product Research
https://www.readbyqxmd.com/read/29791396/effective-freeform-tir-lens-designed-for-leds-with-high-angular-color-uniformity
#4
Zhili Zhao, Honghai Zhang, Sheng Liu, Xinzhong Wang
Most LED luminaires face the problem of color nonuniformity in illumination fields, which seriously degrades their lighting quality. To address this issue, we proposed a freeform TIR lens, which could be applied to the most widely adopted phosphor-converted LEDs and multicolor LED arrays. Based on light pattern overlap and energy mapping, the novel TIR lens comprised the freeform panel and the collimator. Analysis of angular color uniformity (ACU), based on a phosphor-converted white LED model, proved that the normalized standard deviation (NSD) of the LED integrated with the freeform TIR lens significantly decreased from 0...
May 20, 2018: Applied Optics
https://www.readbyqxmd.com/read/29791129/formation-of-deep-electron-trap-by-yb-3-codoping-leads-into-super-long-persistent-luminescence-in-ce-3-doped-yttrium-aluminum-gallium-garnet-phosphors
#5
Jumpei Ueda, Shun Miyano, Setsuhisa Tanabe
The Y3 Al2 Ga3 O12 :Ce3+ -Cr3+ compound is one of the brightest persistent phosphors, but its persistent luminescence (PersL) duration is not so long due to the relatively shallow Cr3+ electron trap. Comparing the vacuum referred binding energy of the electron trapping state by Cr3+ and those by lanthanide ions, we selected Yb3+ as a deeper electron trapping center. The Y3 Al2 Ga3 O12 :Ce3+ -Yb3+ phosphors show Ce3+ :5d→4f green persistent luminescence after ceasing blue light excitation. The formation of Yb2+ was confirmed by the increased intensity of absorption at 585 nm during the charging process...
May 23, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29790556/fabricating-highly-luminescent-solid-hybrids-based-on-silicon-nanoparticles-a-simple-versatile-and-green-method
#6
Jingchun Huang, Qi Li, Zhengzhong Shao
In this work, we report a simple but novel method to transfer highly luminescent silicon nanoparticles (Si NPs) from solutions to solids without sacrificing their excellent photoluminescence (PL) properties. Hybrid Si NP/clay phosphors that glowed ultrabright and had colorful PL properties were first obtained. More importantly, large-area and flexible films with superior PL properties can be easily obtained via combining the Si NP/clay hybrids with different kinds of polymer. The Si NP-based phosphors and films from our method show high stabilities with no significant loss of PL performance after long-term storage (several months)...
May 23, 2018: Nanoscale
https://www.readbyqxmd.com/read/29790552/quantum-dot-polymer-conjugates-for-stable-luminescent-displays
#7
Sushant Ghimire, Anjali Sivadas, Ken-Ichi Yuyama, Yuta Takano, Raju Francis, Vasudevanpillai Biju
The broad absorption of light in the UV-Vis-NIR region and the size-based tunable photoluminescence color of semiconductor quantum dots make these tiny crystals one of the most attractive antennae in solar cells and phosphors in electrooptical devices. One of the primary requirements for such real-world applications of quantum dots is their stable and uniform distribution in optically transparent matrices. In this work, we prepare transparent thin films of polymer-quantum dot conjugates, where CdSe/ZnS quantum dots are uniformly distributed at high densities in a chitosan-polystyrene copolymer (CS-g-PS) matrix...
May 23, 2018: Nanoscale
https://www.readbyqxmd.com/read/29790001/enhanced-up-conversion-emission-in-al-3-co-doped-znga-2-o-4-yb-3-tm-3-powder-phosphors
#8
Yuan Cheng, Kangning Sun
Yb3+ -Tm3+ co-doped up-conversion powder phosphors using Zn(Alx Ga1-x )2 O4 (ZAGO) as the host materials were synthesized via solid-state reaction successfully. In addition, the morphology, structural characterization and up-conversion luminescent properties were all investigated by scanning electron microscope (SEM), x-ray diffraction (XRD) and fluorescence spectrophotometer (F-7000), respectively. Under the excitation of a 980 nm laser, all as-prepared powders can carry out blue emission at about 477 nm (corresponding to 1 G4  → 3 H6 transition of Tm3+ ions), and red emission at about 691 nm (attributed to 3 F3  → 3 H6 transition of Tm3+ ions)...
May 22, 2018: Journal of Fluorescence
https://www.readbyqxmd.com/read/29789883/functional-characterization-of-a-thermostable-endoglucanase-belonging-to-glycoside-hydrolase-family-45-from-fomitopsis-palustris
#9
Ju-Hee Cha, Jeong-Jun Yoon, Chang-Jun Cha
A gene encoding an endoglucanase belonging to subfamily C of glycoside hydrolase family 45 (GH45) was identified in the brown rot fungus Fomitopsis palustris and functionally expressed in Pichia pastoris. The recombinant protein displayed hydrolytic activities toward various substrates such as carboxymethyl cellulose, phosphoric acid swollen cellulose, glucomannan, lichenan, and β-glucan. In particular, the enzyme had a unique catalytic efficiency on β-1,4-glucans rather than mixed β-1,3/1,4-glucans as compared to other GH45 endoglucanases...
May 22, 2018: Applied Microbiology and Biotechnology
https://www.readbyqxmd.com/read/29789223/vitamin-d-status-in-diabetic-children-and-adolescents
#10
Tahereh Ziaei-Kajbaf, Majid Aminzadeh, Elham Fatahinezhad, Seyyed Mohammad-Hassan Aletayeb
INTRODUCTION: Besides its role in calcium homeostasis, vitamin D (VD) has an important immuno-mudulation effect. However, its role in autoimmune diseases such as type 1 diabetes is under discussion. This study designed to investigate serum VD status in children and adolescents with and without diabetes. MATERIALS AND METHODS: In a case-control study, 85 diabetic and 85 non-diabetic control (total 170) aged 1-15 yr. were enrolled. History of breast feeding and vitamin supplementation was obtained; growth indices and serum levels of Calcium, phosphorous, Alkaline-Phosphatase (ALP), Hemoglobin-A1c and VD were measured and analyzed...
March 16, 2018: Diabetes & Metabolic Syndrome
https://www.readbyqxmd.com/read/29786930/an-unexpected-%C3%AE-oxidation-of-cyclic-ketones-with-1-4-benzoquinone-via-enol-catalysis
#11
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
https://www.readbyqxmd.com/read/29786673/fabrication-flexible-and-luminescent-nanofibrillated-cellulose-films-with-modified-sral%C3%A2-o%C3%A2-eu-dy-phosphors-via-nanoscale-silica-and-aminosilane
#12
Longfei Zhang, Shaoyi Lyu, Zhilin Chen, Siqun Wang
Flexible 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized nanofibrillated cellulose (ONFC) films with long afterglow luminescence containing modified SrAl₂O₄: Eu2+ , Dy3+ (SAOED) phosphors were fabricated by a template method. Tetraethyl orthosilicate (TEOS) and (3-aminopropyl) trimethoxy-silane (APTMS) were employed cooperatively to improve the water resistance and compatibility of the SAOED particles in the ONFC suspension. The structure and morphology after modification evidenced the formation of a superior SiO₂ layer and coarse amino-compounds on the surface of the phosphors...
May 22, 2018: Nanomaterials
https://www.readbyqxmd.com/read/29785439/highly-efficient-upconversion-emission-of-er-3-in-%C3%AE-sc-4-zr-3-o-12-and-broad-range-temperature-sensing
#13
Wen Liu, Guo-Hui Pan, Zhendong Hao, Liangliang Zhang, Xia Zhang, Yongshi Luo, Haifeng Zhao, Huajun Wu, Jiahua Zhang
Developing optical temperature sensors with a wider range, higher sensitivity and repeatability based on Er3+/Yb3+ doped upconverting phosphors has always been at the forefront of temperature measurement technologies. Here, we report the intense green upconversion luminescence in Er3+/Yb3+ doped δ-Sc4Zr3O12 for the first time and its temperature sensing performance is investigated. The structure of δ-Sc4Zr3O12 is given by Rietveld refinement of XRD data and the site occupancy of Er3+ ions has been determined...
May 22, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29784461/stability-and-reactivity-of-%C3%AE-%C3%AE-ptms-silane-in-some-commercial-primer-and-adhesive-formulations
#14
Maria Dimitriadi, Angeliki Panagiotopoulou, Maria Pelecanou, Konstantina Yannakopoulou, George Eliades
OBJECTIVES: To evaluate the stability and reactivity of γ-methacryloxypropyl trimethoxysilane (MPTMS) in commercially available primers and adhesives. METHODS: Four representative primer formulations [Calibra Silane Coupling Agent/Dentsply (CLB), G-Multi Primer/GC (GMP), Kerr Silane Primer/Kerr (KSP), Monobond Plus/Ivoclar Vivadent (MBP)] and a universal adhesive [Scotchbond Universal/3M ESPE (SBU)] containing MPTMS were analyzed spectroscopically. For the stability study, the silanol content was evaluated in bulk solutions as received (reference-RE) and after aging (AG, 48°C/1month) by 1 H, 13 C, 31 P NMR and in fresh films by transmission FTIR analysis (TIR, films applied on Ge windows after solvent evaporation)...
May 18, 2018: Dental Materials: Official Publication of the Academy of Dental Materials
https://www.readbyqxmd.com/read/29783716/photovoltaic-performance-enhancement-of-silicon-solar-cells-based-on-combined-ratios-of-three-species-of-europium-doped-phosphors
#15
Wen-Jeng Ho, Bang-Jin You, Jheng-Jie Liu, Wen-Bin Bai, Hong-Jhang Syu, Ching-Fuh Lin
This paper presents a scheme for the enhancement of silicon solar cells in terms of luminescent emission band and photovoltaic performance. The proposed devices are coated with an luminescent down-shifting (LDS) layer comprising three species of europium (Eu)-doped phosphors mixed within a silicate film (SiO₂) using a spin-on film deposition. The three species of phosphor were mixed at ratios of 0.5:1:1.5, 1:1:1, or 1.5:1:0.5 in weight percentage (wt %). The total quantity of Eu-doped phosphors in the silicate solution was fixed at 3 wt %...
May 18, 2018: Materials
https://www.readbyqxmd.com/read/29781269/crystallization-of-nanocrystals-in-spherical-confinement-probed-by-in-situ-x-ray-scattering
#16
Federico Montanarella, Jaco J Geuchies, Tonnishtha Dasgupta, P Tim Prins, Carlo van Overbeek, Rajeev Dattani, Patrick Baesjou, Marjolein Dijkstra, Andrei V Petukhov, Alfons van Blaaderen, Daniël Vanmaekelbergh
We studied the formation of supraparticles from nanocrystals confined in slowly evaporating oil droplets in an oil-in-water emulsion. The nanocrystals consist of an FeO core, a CoFe2 O4 shell, and oleate capping, with an overall diameter of 12.5 nm. We performed in-situ Small- and Wide-Angle X-ray Scattering experiments during the entire period of solvent evaporation and colloidal crystallization. We observed a slow increase in the volume fraction of nanocrystals inside the oil droplets up to 20%, at which a sudden crystallization occurs...
May 21, 2018: Nano Letters
https://www.readbyqxmd.com/read/29781267/highly-regular-uniform-k-3-scf-6-mn-4-phosphors-facile-synthesis-microstructures-photo-luminescence-properties-and-application-in-led-devices
#17
Hong Ming, Shuifu Liu, Lili Liu, Jiaqing Peng, Junxiang Fu, Fu Du, Xinyu Ye
A new generation of red phosphors of complex fluoride matrices activated with Mn4+ , has gained a broad interest in getting high color rendering index (CRI), low correlated color temperature (CCT) of white light-emitting diodes(WLEDs). However, besides their instability towards moisture, the extremely irregular and nonuniform morphologies of these phosphors have limited their practical industry applications. In the present study, a novel type of K3 ScF6 :Mn4+ red phosphor with highly regular, uniform and high color purity was synthesized successfully via a facile two-step co-precipitation method under mild conditions...
May 21, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29780230/evaluation-of-bone-health-among-epileptic-patients-using-biochemical-markers-and-dexa-scan-an-egyptian-study
#18
Ebtesam Mohamed Fahmy, Laila Ahmed Rashed, Rania Shehata Ismail, Hanan Helmy, Doaa Atef Mekkawy
Background: An association between antiepileptic drugs, low bone mineral density (BMD), fractures, and abnormalities in bone metabolism has been suggested for a longer period, although conclusive evidence has not been reported. Methods: Thirty epileptic patients and 30 matched healthy subjects participated in the study. Measurements of serum levels of calcium, phosphorus, vitamin D, parathormone, and alkaline phosphatase were done for included subjects. Dual-energy X-ray absorptiometry (DEXA) scan was also performed...
2018: The Egyptian journal of neurology, psychiatry and neurosurgery
https://www.readbyqxmd.com/read/29779627/in-vitro-assessment-of-ribose-modified-two-step-etch-and-rinse-dentine-adhesive
#19
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
https://www.readbyqxmd.com/read/29778959/accelerating-settling-rates-of-biosolids-lagoons-through-thermal-hydrolysis
#20
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
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