bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved Photocatalytic Performance of the Ultra‐small Ag Nanocrystallite‐Decorated TiO2 Hollow Sphere Heterostructures
Authors: Li Qian , Zhang Caihong , Ma Jianmin , Wang Guozhong , Ng Dickon H. L. 
Published: March 2014

AbstractThe ultra‐small Ag nanocrystallite‐decorated TiO2 hollow sphere heterostructures were fabricated by using a two‐step hydrothermal method. These heterostructures demonstrated an excellent photodegradation performance of rhodamine B. The photodegradation efficiency could reach up to 100 % within 20 min under simulated sunlight irradiation. XRD, field emission SEM, TEM, scanning TEM, high‐resolution TEM coupled with energy‐dispersive X‐ray spectroscopy, UV/Vis absorption and photoluminescence spectroscopy, X‐ray photoelectron spectroscopy, Mott–Schottky analysis, and hydroxyl radical measurements were used to correlate the structure, surface property, and energy band alignment of rhodamine B to its photocatalytic activity. In these metal–semiconductor heterostructures, the Ag nanocrystallites were highly crystalline and were distributed evenly on the surface of TiO2 hollow spheres with compact interfaces. They reduced the recombination rate of charge carriers and favoured the charge transfer across the interfaces. The increased surface adsorbed oxygen facilitated the generation of hydroxyl radicals, and the reduced surface defects increased the lifetime of charge carriers upon Ag loading. The Schottky barriers between Ag and illuminated TiO2, the upward shift of the Fermi level, and increased electron density due to Ag coupling contributed to the charge transfer and increase in quantum efficiency. These key factors involved in photocatalysis are of great importance to design functional and effective photocatalysts.
Role of the Base and Control of Selectivity in the Suzuki–Miyaura Cross‐Coupling Reaction
Authors: Lima Carlos F. R. A. C. , Rodrigues Ana S. M. C. , Silva Vera L. M. , Silva Artur M. S. , Santos Luís M. N. B. F. 
Published: March 2014

AbstractThe outcome of the Suzuki–Miyaura cross‐coupling for the direct competition reaction between two boronic acids was evaluated under routine synthesis conditions. The reaction selectivity was found to depend on the amount of the base used, with fewer bases favoring the reactivity of the boronic acid with lower pKa (stronger acid). The dependence of the reaction selectivity on base stoichiometry was found to increase with the increase in the difference in the pKa values of the competing boronic acids. These results confirm a relationship between acid–base chemistry and the Suzuki–Miyaura reaction catalytic cycle. Moreover, the results indicate that under these specific conditions, the most reactive organoboron species toward transmetalation is the borate anion RB(OH)3− instead of the neutral boronic acid RB(OH)2. Hence, the main role of the base in the reaction mechanism is to increase the reactivity of the boronic acid toward the Pd–halide complex by converting it into the respective organoborate. In addition, boric acid, an important reaction byproduct, affects the selectivity in the Suzuki reaction because its gradual formation in the reaction medium disturbs the acid–base equilibrium.
NaBr/DMSO‐Induced Synthesis of 2,5‐Diformylfuran from Fructose or 5‐(Hydroxymethyl)furfural
Authors: Laugel Caroline , Estrine Boris , Le Bras Jean , Hoffmann Norbert , Marinkovic Sinisa , Muzart Jacques 
Published: March 2014

Abstract2,5‐Diformylfuran (DFF) was obtained by heating a solution of 5‐(hydroxymethyl)furfural in DMSO. The addition of acids or salts improved the selectivity, especially if bromides were employed. Good yields of DFF were obtained with HBr or NaBr as the catalyst. One‐pot procedures were developed from fructose, which led to DFF in medium yields. This transformation occurs through the formation of 5‐(bromomethyl)furan‐2‐carbaldehyde followed by a Kornblum‐type reaction. In the presence of bromide salts, the in situ formation of the catalyst involves the thermolysis of DMSO and the association of the resulting strong acids with the bromides.
First Pre‐Functionalised Polymeric Aromatic Framework from Mononitrotetrakis(iodophenyl)methane and its Applications
Authors: Verde‐Sesto Ester , Pintado‐Sierra Mercedes , Corma Avelino , Maya Eva M. , de la Campa Jose G. , Iglesias Marta , Sánchez Felix 
Published: March 2014

AbstractStarting from mononitrotetrakis(iodophenyl)methane as monomer, we report the preparation of the first pre‐functionalised porous aromatic frameworks (PAFs) and their application as supports for organometallic catalysts. Neutral coordinate imino‐pyridine Schiff base (PAF‐NPy) or chiral bis‐amino (PAF‐NPro) ligands were obtained by post‐synthetic treatment of PAF‐NH2 and treated with copper(I) or rhodium(I) to yield the corresponding supported transition‐metal catalysts. The as‐prepared PAF‐NN‐M catalysts exhibited activity and selectivity similar to that of the corresponding homogeneous catalysts and were easily removed from reaction media and recycled without loss of activity or selectivity.
The Use of a Microreactor for Rapid Screening of the Reaction Conditions and Investigation of the Photoluminescence Mechanism of Carbon Dots
Authors: Lu Yue , Zhang Ling , Lin Hengwei 
Published: March 2014

AbstractA microreactor is applied and reported, for the first time, in the field of research of carbon dots (CDs), including rapid screening of the reaction conditions and investigation of the photoluminescence (PL) mechanism. Various carbonaceous precursors and solvents were selected and hundreds of reaction conditions were screened (ca. 15 min on average per condition). Through analyzing the screened conditions, tunable PL emission maxima, from about 330 to 550 nm with respectable PL quantum yields, were achieved. Moreover, the relationship between different developmental stages of the CDs and the PL properties was explored by using the microreactor. The PL emission was observed to be independent of the composition, carbonization extent, and morphology/size of the CDs. This study unambiguously presents that a microreactor could serve as a promising tool for the research of CDs.
Synthesis of Nanoporous Carbon–Cobalt‐Oxide Hybrid Electrocatalysts by Thermal Conversion of Metal–Organic Frameworks
Authors: Chaikittisilp Watcharop , Torad Nagy L. , Li Cuiling , Imura Masataka , Suzuki Norihiro , Ishihara Shinsuke , Ariga Katsuhiko , Yamauchi Yusuke 
Published: March 2014

AbstractNanoporous carbon–cobalt‐oxide hybrid materials are prepared by a simple, two‐step, thermal conversion of a cobalt‐based metal–organic framework (zeolitic imidazolate framework‐9, ZIF‐9). ZIF‐9 is carbonized in an inert atmosphere to form nanoporous carbon–metallic‐cobalt materials, followed by the subsequent thermal oxidation in air, yielding nanoporous carbon–cobalt‐oxide hybrids. The resulting hybrid materials are evaluated as electrocatalysts for the oxygen‐reduction reaction (ORR) and the oxygen‐evolution reaction (OER) in a KOH electrolyte solution. The hybrid materials exhibit similar catalytic activity in the ORR to the benchmark, commercial, Pt/carbon black catalyst, and show better catalytic activity for the OER than the Pt‐based catalyst.
Stereochemistry and Conformation of Skyllamycin, a Non‐Ribosomally Synthesized Peptide from Streptomyces sp. Acta 2897
Authors: Schubert Vivien , Di Meo Florent , Saaidi Pierre‐Loïc , Bartoschek Stefan , Fiedler Hans‐Peter , Trouillas Patrick , Süssmuth Roderich D. 
Published: March 2014

AbstractSkyllamycin is a non‐ribosomally synthesized cyclic depsipeptide from Streptomyces sp. Acta 2897 that inhibits PDGF‐signaling. The peptide scaffold contains an N‐terminal cinnamoyl moiety, a β‐methylation of aspartic acid, three β‐hydroxylated amino acids and one rarely occurring α‐hydroxy glycine. With the exception of α‐hydroxy glycine, the stereochemistry of the amino acids was assigned by comparison to synthetic reference amino acids applying chiral GC‐MS and Marfey‐HPLC analysis. The stereochemistry of α‐hydroxy glycine, which is unstable under basic and acidic conditions, was determined by conformational analysis, employing a combination of data from NOESY‐NMR spectroscopy, simulated annealing and free MD simulations. The simulation procedures were applied for both R‐ and S‐configured α‐hydroxy glycine of the skyllamycin structure and compared to the NOESY data. Both methods, simulated annealing and free MD simulations independently support S‐configured α‐hydroxy glycine thus enabling the assignment of all stereocenters in the structure of skyllamycin and devising the role of two‐component flavin dependent monooxygenase (Sky39) as S‐selective.
Direct Olefination of Fluorinated Benzothiadiazoles: A New Entry to Optoelectronic Materials
Authors: Xiao Yu‐Lan , Zhang Bo , He Chun‐Yang , Zhang Xingang 
Published: March 2014

AbstractFluorinated olefin‐containing benzothiadiazoles have important applications in optoelectronic materials. Herein, we reported the direct olefination of fluorinated benzothiadiazoles, as catalyzed by palladium. The reaction proceeds under mild reaction conditions and shows high functional‐group compatibility. A preliminary study of the properties of the resulting symmetrical and unsymmetrical olefin‐containing fluorinated benzothiadiazoles in red‐light‐emitting dyes has also been conducted.
A Fully Synthetic Glycopeptide Antitumor Vaccine Based on Multiple Antigen Presentation on a Hyperbranched Polymer
Authors: Glaffig Markus , Palitzsch Björn , Hartmann Sebastian , Schüll Christoph , Nuhn Lutz , Gerlitzki Bastian , Schmitt Edgar , Frey Holger , Kunz Horst 
Published: March 2014

AbstractFor antitumor vaccines both the selected tumor‐associated antigen, as well as the mode of its presentation, affect the immune response. According to the principle of multiple antigen presentation, a tumor‐associated MUC1 glycopeptide combined with the immunostimulating T‐cell epitope P2 from tetanus toxoid was coupled to a multi‐functionalized hyperbranched polyglycerol by “click chemistry”. This globular polymeric carrier has a flexible dendrimer‐like structure, which allows optimal antigen presentation to the immune system. The resulting fully synthetic vaccine induced strong immune responses in mice and IgG antibodies recognizing human breast‐cancer cells.
Aerobic Double Dehydrogenative Cross Coupling between Cyclic Saturated Ketones and Simple Arenes
Authors: Gigant Nicolas , Bäckvall Jan‐E. 
Published: March 2014

AbstractThe synthesis of 3‐aryl‐2‐cyclohexenones is a topic of current interest as they are not only privileged structures in bioactive molecules, but they are also relevant feedstocks for the synthesis of substituted phenols or anilines, which are ubiquitous structural elements both in drug design and medicinal chemistry. A simple and sustainable one‐pot aerobic double dehydrogenative reaction under mild conditions for the introduction of arenes in the β‐position of cyclic ketones has been developed. Starting from the corresponding saturated ketone, this reaction sequence proceeds under relatively low Pd catalyst loading and involves catalytic amounts of electron‐transfer mediators (ETMs) under ambient oxygen pressure.
Single Enantiomer Versus Racemate: Chiral Distinction in the Proton Pump Inhibitors Omeprazole and Esomeprazole
Authors: Marom Hili , Pogodin Sergey , Agranat Israel 
Published: March 2014

ABSTRACTChiral distinction in the proton pump inhibitor drugs omeprazole and in its chiral‐switch esomeprazole magnesium was studied employing the Density Functional Theory (DFT) method. At B3LYP/6‐311G(d,p), the 6‐methoxy∙∙∙6‐methoxy and 5‐methoxy∙∙∙5‐methoxy homochiral and heterochiral dimers were calculated. The chiral distinction free energies (ΔΔG298,(RS‐SS)) between the cyclic C2‐(S,S)‐ and Ci‐(R,S)‐dimers with two intermolecular hydrogen bonds are 3.8, 1.9 (with BSSE counterpoise correction), and –6.9 (with D3 dispersion and BSSE counterpoise corrections) kJ/mol. Adding water as an implicit solvent (polarized continuum model [PCM] model) resulted in a chiral distinction energy of –3.3 kJ/mol, indicating a reversal of the order of the relative stabilities of C2‐(S,S)‐ and Ci‐(R,S)‐dimers. The chiral distinction free energies between the corresponding (less stable) C1‐dimers with one intermolecular hydrogen bond are –9.3, –5.8 (with BSSE CC), 17.6 (D3 + BSSE CC), and –3.2 (H2O) kJ/mol. The results highlight the contention that omeprazole is not just a superposition of its enantiomer constituents. They are consistent with the pharmacological evidence of enantiomer–enantiomer interactions in omeprazole versus esomeprazole and the differences between the drugs omeprazole and esomeprazole magnesium and support the lodged application for regulatory supplementary protection certificate (SPC) exclusivity for the esomeprazole‐related combination drug Vimovo. Chirality 26:214–227, 2014. © 2014 Wiley Periodicals, Inc.
Synthesis and Anti‐HCV Entry Activity Studies of β‐Cyclodextrin–Pentacyclic Triterpene Conjugates
Authors: Xiao Sulong , Wang Qi , Si Longlong , Shi Yongying , Wang Han , Yu Fei , Zhang Yongmin , Li Yingbo , Zheng Yongxiang , Zhang Chuanling , Wang Chunguang , Zhang Lihe , Zhou Demin 
Published: March 2014

AbstractIn our previous studies, oleanolic acid (OA) and echinocystic acid (EA), isolated from Dipsacus asperoides, were found to have anti‐HCV entry properties. The major issue for members of this type of triterpene is their low water solubility. In this study, a series of new water‐soluble triazole‐bridged β‐cyclodextrin (CD)–pentacyclic triterpene conjugates were synthesized via click chemistry. Thanks to the attached β‐CD moiety, all synthesized conjugates showed lower hydrophobicity (Alog P) than their parent compounds. Several conjugates exhibited moderate anti‐HCV entry activity. With the exception of per‐O‐methylated β‐CD–pentacyclic triterpene conjugates, all other conjugates showed no cytotoxicity based on an alamarBlue assay carried out with HeLa, HepG2, MDCK, and 293T cells. More interestingly, the hemolytic activity of these conjugates disappeared upon the introduction of β‐CDs. Easy access to such conjugates that combine the properties of β‐CD and pentacyclic triterpenes may provide a way to obtain a new class of anti‐HCV entry inhibitors.
An alternative RP‐HPLC method for the separation and determination of tocopherol and tocotrienol homologues as butter authenticity markers: A comparative study between two European countries
Authors: Górnaś Paweł , Siger Aleksander , Czubinski Jaroslaw , Dwiecki Krzysztof , Segliņa Dalija , Nogala‐Kalucka Malgorzata 
Published: March 2014

Eight tocochromanols (α, β, γ, and δ homologues of tocopherol and tocotrienol) naturally occurring in foods were successfully separated within a 13‐min run in the RP‐HPLC mode. Analytes were separated on the Phenomenex Luna PFP column filled with the pentafluorophenyl stationary phase (3 µm, 150 mm × 4.6 mm) using the mobile phase containing methanol:water (93:7 v/v) with an elution flow rate of 1 ml/min and column oven temperature of 40°C. The method was rapid, linear, accurate, and precise with detection limits in the range of 0.000184–0.000605 µg, preventing analyte losses due direct dissolution in 2‐propanol. The developed RP‐HPLC method in comparison with the NP‐HPLC mode had a significantly higher sensitivity, speed, and repeatability, but primarily it protected against the loss of analytes and thus reduced the risk of possible error measurements. It was found that tocopherol contents in the tested butter samples amounted to 2.00–16.92 mg/100 g for samples coming from Poland and 2.61–2.98 mg/100 g for samples from Latvia, respectively. The method is characterized by simplicity of implementation and it was successfully applied in the determination of tocochromanols in butter to verify product authenticity.Practical applications: To ensure consumers' protection, food products should be subject to continuous quality and authenticity control. One way to determine butter authenticity is to analyze native tocochromanol contents. This paper describes a simple and fast method determine plant oils added to milk fat with the use of RP‐HPLC techniques.Eight tocochromanols (α, β, γ, and δ homologues of tocopherol and tocotrienol) naturally occurring in foods were successfully separated within by RP‐HPLC. The method is rapid, linear, accurate, and precise with detection limits in the range of 0.184–0.605 μg. The method was successfully applied to determine tocochromanols in butter to verify product authenticity.
Physical properties and fatty acid composition of pomegranate seed oil microcapsules prepared by using starch derivatives/whey protein blends
Authors: Sahin‐Nadeem Hilal , Afşin Özen Murat 
Published: March 2014

Effect of different product formulation on the properties of resulting pomegranate seeds oil (PSO) microcapsules during spray drying encapsulation was studied. PSO microencapsulation was optimized using Box–Behnken's response surface methodology. Emulsion droplet size (3.01–9.21 µm) and viscosity (16–34 cP), product yield (50–76%), microencapsulation efficiency (76–88%), moisture (2.3–3.5 g/100 g dry matter), water activity (0.17–0.22), bulk density (262–522 kg/m3), hygroscopicity (14–23%), solubility (>97%), particle size (11.30–36.27 µm), and microstructure were analyzed. Three saturated and six unsaturated fatty acids were identified in the PSO; punicic acid was predominant in both unprocessed and microencapsulated ones. The ratio of saturated and unsaturated fatty acids was stable during processing, however, distribution of fatty acids – especially C18:3 isomers – changed by microencapsulation. Optimum product formula which simultaneously maximized the product yield and microencapsulation efficiency was predicted as 75.5 g/100 g emulsion dry matter (EDM) of maltodextrin/modified starch N‐LOK (70/30), 24.5 g/100 g EDM of whey protein concentrate, and 15 g oil/100 g EDM. Peroxide and p‐anisidine values of the encapsulated PSO were within acceptable range after spray drying. However, the oxidative stability decreased at high temperature (60°C) after 5 days of storage.The fatty acids composition of the unprocessed and microencapsulated PSO was same. The encapsulated PSO produced with the optimum product formula had a POV < 15 meq/kg oil, which indicates acceptable oil quality. Oxidation products reached to an unacceptable level (Totox value >30) after 5th day of storage at 60°C.
Impact of reach geometry on stream channel sensitivity to extreme floods
Authors: Buraas Eirik M. , Renshaw Carl E. , Magilligan Francis J. , Dade William B. 
Published: March 2014

ABSTRACTPredicting spatial and temporal variations in bank erosion due to extreme floods presents a long‐standing challenge in geomorphology. We develop two methodologies for rapid, regional‐scale assessments of stream reaches susceptible to channel widening. The first proposes that channel widening occurs when unit stream power exceeds a critical threshold (300 W/m2). The second is motivated by the observation that widening often occurs at channel bends. We introduce a new metric, the bend stress parameter, which is proportional to the centripetal force exerted on a concave bank. We propose that high centripetal forces generate locally high bank shear forces and enhance channel bank erosion. We test both metrics using the geomorphic signature of Tropical Storm Irene (2011) on the White and the Saxtons Rivers, Vermont. Specifically, we test if reaches where significant channel widening occurred during Irene required one or both metrics to exceed threshold values. We observe two distinct styles of channel widening. Where unit stream power and bend stress parameter are high, widening is usually due to bank retreat. Elsewhere widening is usually due to the stripping of the upstream end of mid‐channel islands. Excluding widening associated with the stripping of the heads of mid‐channel islands, almost all the widening (> 98%) occurred along reaches identified as susceptible to widening. The combined metrics identify up to one‐quarter of the reaches lacking susceptibility to channel widening. Copyright © 2014 John Wiley & Sons, Ltd.
Bt rice producing Cry1C protein does not have direct detrimental effects on the green lacewing Chrysoperla sinica (Tjeder)
Authors: Li Yunhe , Chen Xiuping , Hu Long , Romeis Jörg , Peng Yufa 
Published: March 2014

Abstract

The effects of insect-resistant genetically engineered rice producing Cry1C protein derived from Bacillus thuringiensis (Bt) on Chrysoperla sinica (Tjeder) (Neuroptera: Chrysopidae) were assessed in laboratory bioassays. Survival and development of C. sinica larvae were not adversely affected when the larvae were fed a diet containing purified Cry1C protein at 200 µg/g fresh weight, representing a worst-case exposure scenario; in contrast, C. sinica larvae were adversely affected when the diet contained avidin or potassium arsenate. Life table parameters of C. sinica adults did not differ when the adults were fed with Bt or non-Bt rice pollen together with a 2-M sucrose solution. Life table parameters of C. sinica adults also did not differ when the adults were fed an artificial diet with or without purified Cry1C protein at a nominal concentration that was approximately 20 times higher than that in rice pollen; in contrast, C. sinica adults were adversely affected when the diet contained potassium arsenate. In all bioassays with lacewings, the bioactivity and stability of the Cry1C protein in the diet and Cry1C protein uptake by the lacewings were confirmed by enzyme-linked immunosorbent assay (ELISA) and by bioassays with a Cry1C-sensitive lepidopteran. These results demonstrate that neither larvae nor adults of C. sinica are sensitive to Cry1C protein at concentrations higher than those encountered in the field, demonstrating that the growing of Bt rice producing Cry1C protein is unlikely to pose a risk to C. sinica. Environ Toxicol Chem 2014;33:1391–1397. © 2014 SETAC
Modeling selenium (IV and VI) adsorption envelopes in selected tropical soils using the constant capacitance model
Authors: Gabos Mariana Bassetto , Goldberg Sabine , Alleoni Luís Reynaldo Ferracciú 
Published: March 2014

Abstract

The adsorption of selenium (Se) on soil is important because of the relevance of Se to environmental and health issues. The adsorption of Se(IV) and Se(VI) was evaluated on soil samples from São Paulo State, Brazil, as a function of varying pH, and the experimental data were fitted to the constant capacitance model. Adsorption experiments were conducted for 15 soil samples, after the addition of 20 µmol L−1 of either Se(IV) or Se(VI), and the adjusted pH ranged between 2.5 and 10. Selenite adsorption was high for all soils, decreased with increasing pH, and was strongly correlated with Fe and Al oxide content. In contrast, Se(VI) adsorption was very low at pH values commonly found in agricultural soils, except for the highly weathered Rhodic Acrudox. The constant capacitance model fitted the Se(IV) and Se(VI) adsorption data well. Optimizations of mono- and bidentate complexation and surface protonation constants were used for the Se(IV) adsorption data. For Se(VI), optimizations for the 2 monodentate species were employed. Environ Toxicol Chem 2014;33:2197–2207. © 2014 SETAC