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https://www.readbyqxmd.com/read/28636824/bicanonical-ab-initio-molecular-dynamics-for-open-systems
#1
Johannes Frenzel, Bernd Meyer, Dominik Marx
Performing ab initio molecular dynamics simulations of open systems, where the chemical potential rather than the number of both, nuclei and electrons is fixed, still is a challenge. Here, drawing on bicanonical sampling ideas introduced two decades ago by Swope and Andersen to calculate chemical potentials of liquids and solids, an ab initio simulation technique is devised, which introduces a fictitious dynamics of two superimposed but otherwise independent periodic systems including full electronic structure, such that either the chemical potential or the average fractional particle number of a specific chemical species can be kept constant...
June 21, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28633824/ultrasound-assisted-extraction-of-polysaccharides-from-rhododendron-aganniphum-antioxidant-activity-and-rheological-properties
#2
Xiao Guo, Xiaofei Shang, Xuzheng Zhou, Baotang Zhao, Jiyu Zhang
In this study, we aimed to optimize the extraction of polysaccharides from the leaves of Rhododendron aganniphum and investigate its rheological properties and antioxidant activity. After optimizing the operating parameters using a Box-Behnken design (BBD), the results showed that the optimal ultrasound-assisted extraction conditions were as follows: extraction temperature, 55°C; liquid-solid ratio, 25:1; extraction time, 2.2h; and ultrasound treatment power, 200W. The optimized experimental yield of polysaccharides by ultrasound-assisted extraction (PUAE) was 9...
September 2017: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/28633115/occurrence-of-commonly-used-pesticides-in-personal-air-samples-and-their-associated-health-risk-among-paddy-farmers
#3
Hazwanee Hamsan, Yu Bin Ho, Siti Zulfa Zaidon, Zailina Hashim, Nazamid Saari, Ali Karami
Tanjung Karang, Selangor, is widely known for its paddy cultivation activity and hosts the third largest paddy field in Malaysia. Pesticides contamination in agriculture fields has become an unavoidable problem, as pesticides are used to increase paddy productivity and reduce plant disease. Human exposure to agrichemicals is common and could results in both acute and chronic health effects, such as acute and chronic neurotoxicity. This study aims to determine the concentrations of commonly used pesticides (azoxystrobin, buprofezin, chlorantraniliprole, difenoconazole, fipronil, imidacloprid, isoprothiolane, pretilachlor, propiconazole, pymetrozine, tebuconazole, tricyclazole, and trifloxystrobin) in personal air samples and their associated health risks among paddy farmers...
June 17, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28633099/simultaneous-and-specific-enrichment-of-several-amphenicol-antibiotics-residues-in-food-based-on-novel-aptamer-functionalized-magnetic-adsorbents-using-hplc-dad
#4
Shengfeng Huang, Ning Gan, Haibo Liu, You Zhou, Yinji Chen, Yuting Cao
In this work, a novel aptamer functionalized magnetic adsorbent was developed and combined with magnetic dispersive solid phase extraction (MDSPE) for selective enrichment of several amphenicol antibiotics residues (chloramphenicol(CAP), thiamphenicol(TAP) and florphenicol(FF)) in foodstuff then determined by High Performance Liquid Chromatography (HPLC)-Diode array detector(DAD). Firstly, a magnetic silica-coated Fe3O4 microsphere(Fe3O4@SiO2) was synthetized by sol-gel method, then it was functionalized by amino groups through 3-Aminopropyltriethoxysilane (APTES) reagent to form Fe3O4@SiO2-NH2; Thirdly, the amino group on Fe3O4@SiO2-NH2 was transferred to carboxylic group via the succinic anhydride to form Fe3O4@SiO2-COOH...
June 12, 2017: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
https://www.readbyqxmd.com/read/28629106/tannin-extraction-pretreatment-and-very-high-gravity-fermentation-of-acorn-starch-for-bioethanol-production
#5
Bin Chao, Ruiliang Liu, Xueling Zhang, Xu Zhang, Tianwei Tan
The bioethanol production from a novel non-grain feedstock, acorn starch, was studied in this work. The inhibition of tannin in strain growth was investigated, and the effect of tannin was negligible when the tannin concentration was lower than 1g/L in medium. Therefore, the extraction of tannin was performed using 40% (v/v) ethanol-water solution as the solvent for three times under the conditions of solid/liquid ratio 1:20, 60°C, 3h, by which more than 80% of tannin in acorn was extracted and the content of tannin in acorn decreased from 7...
June 8, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28628316/soft-sphere-continuum-solvation-in-electronic-structure-calculations
#6
Giuseppe Fisicaro, Luigi Genovese, Oliviero Andreussi, Sagarmoy Mandal, Nisanth N Nair, Nicola Marzari, Stefan Goedecker
We present an implicit solvation approach where the interface between the quantum-mechanical solute and the surrounding environment is described by a fully continuous permittivity built up with atomic-centered ``soft'' spheres. This approach combines many of the advantages of the self-consistent continuum solvation model in handling solutes and surfaces in contact with complex dielectric environments or electrolytes in electronic-structure calculations. In addition it is able to describe accurately both neutral and charged systems...
June 19, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28623771/liquid-electrode-plasma-optical-emission-spectrometry-combined-with-solid-phase-preconcentration-for-on-site-analysis-of-lead
#7
Suman Barua, Ismail M M Rahman, Iftakharul Alam, Maho Miyaguchi, Hikaru Sawai, Teruya Maki, Hiroshi Hasegawa
A relatively rapid and precise method is presented for the determination of lead in aqueous matrix. The method consists of analyte quantitation using the liquid electrode plasma-optical emission spectrometry (LEP-OES) coupled with selective separation/preconcentration by solid-phase extraction (SPE). The impact of operating variables on the retention of lead in SPEs such as pH, flow rate of the sample solution; type, volume, flow rate of the eluent; and matrix effects were investigated. Selective SPE-separation/preconcentration minimized the interfering effect due to manganese in solution and limitations in lead-detection in low-concentration samples by LEP-OES...
June 9, 2017: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
https://www.readbyqxmd.com/read/28623023/pyrolysis-reaction-models-of-waste-tires-application-of-master-plots-method-for-energy-conversion-via-devolatilization
#8
Dilan Irmak Aslan, Prakash Parthasarathy, Jillian L Goldfarb, Selim Ceylan
Land applied disposal of waste tires has far-reaching environmental, economic, and human health consequences. Pyrolysis represents a potential waste management solution, whereby the solid carbonaceous residue is heated in the absence of oxygen to produce liquid and gaseous fuels, and a solid char. The design of an efficient conversion unit requires information on the reaction kinetics of pyrolysis. This work is the first to probe the appropriate reaction model of waste tire pyrolysis. The average activation energy of pyrolysis was determined via iso-conversional methods over a mass fraction conversion range between 0...
June 13, 2017: Waste Management
https://www.readbyqxmd.com/read/28621780/structure-property-relationship-of-blue-solid-state-emissive-phenanthroimidazole-derivatives
#9
Agne Ivanauskaite, Ramunas Lygaitis, Steponas Raisys, Karolis Kazlauskas, Gediminas Kreiza, Dmytro Volyniuk, Dalius Gudeika, Saulius Jursenas, Juozas V Grazulevicius
Seven new derivatives of phenanthro[9,10-d]imidazole having differenet substituents at the 1st and the 2nd positions of the phenanthroimidazole moiety were synthesized and characterized. The comparative study of their properties was performed employing thermal, optical, electrochemical and photoelectrical measurements. The properties of the newly synthesized compounds were compared with those of earlier reported derivatives of phenanthroimidazole and several interesting new findings were disclosed. Density functional theory calculations accompanied by optical spectroscopy measurements have shown the possibility of tuning the emission properties (excited-stated decay rate, fluorescence quantum yield, etc...
June 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28617581/creating-an-optimal-microenvironment-within-mesoporous-silica-mcm-41-for-capture-of-tobacco-specific-nitrosamines-tsna-in-solution
#10
Shuo Hao Li, Xiaodan Sun, Yang-Zhong Wang, Zhi-Peng Wang, Wen-Bo Gu, Wei-Miao Wang, He-Ming Yao, Ying Wang, Jian Hua Zhu
To meet the requirement of capturing tobacco specific nitrosamines (TSNA) in environment protection, a unique micro-environment was carefully created inside the channel of mesoporous silica MCM-41. In situ carbonization of template micelles at 923 K combined with the excess aluminum used in one-pot synthesis of MCM-41 are adopted to tailor the tortuosity of mecsoporous channels, while loaded metal oxides (5 wt.-%) and the Al-component in framework are employed to exert the necessary electrostatic interaction towards the target carcinogens TSNA in solution...
June 15, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28613416/topical-antimicrobial-agents-for-treating-foot-ulcers-in-people-with-diabetes
#11
REVIEW
Jo C Dumville, Benjamin A Lipsky, Christopher Hoey, Mario Cruciani, Marta Fiscon, Jun Xia
BACKGROUND: People with diabetes are at high risk for developing foot ulcers, which often become infected. These wounds, especially when infected, cause substantial morbidity. Wound treatments should aim to alleviate symptoms, promote healing, and avoid adverse outcomes, especially lower extremity amputation. Topical antimicrobial therapy has been used on diabetic foot ulcers, either as a treatment for clinically infected wounds, or to prevent infection in clinically uninfected wounds...
June 14, 2017: Cochrane Database of Systematic Reviews
https://www.readbyqxmd.com/read/28612683/determination-of-26-anti-diabetic-compounds-in-dietary-supplements-using-a-validated-uplc-method
#12
Nam Sook Kim, Kyu Yeon Kim, Geum Joo Yoo, Ji Hyun Lee, Han Na Park, Sung-Kwan Park, Sun Young Baek
The purpose of this study was to validate a rapid, simple, and accurate method using ultra performance liquid chromatography (UPLC) for the simultaneous determination of 26 anti-diabetic compounds in illegally adulterated dietary supplements. The method was validated for specificity, linearity, limit of detection, limit of quantitation, precision, accuracy, recovery, and stability. All compounds were separated with a resolution of over 1.5. The limits of detection and quantitation were 0.10-1.70 and 0.30-5...
June 14, 2017: Food Additives & Contaminants. Part A, Chemistry, Analysis, Control, Exposure & Risk Assessment
https://www.readbyqxmd.com/read/28608690/conformational-plasticity-of-the-cell-penetrating-peptide-sap-as-revealed-by-solid-state-19-f-nmr-and-circular-dichroism-spectroscopies
#13
Sergii Afonin, Vladimir Kubyshkin, Pavel K Mykhailiuk, Igor V Komarov, Anne S Ulrich
The cell-penetrating peptide SAP, which was designed as an amphipathic poly-L-proline helix II (PPII), was suggested to self-assemble into regular fibrils that are relevant for its internalization. Herein we have analyzed the structure of SAP in the membrane-bound state by solid-state (19)F-NMR, which revealed other structural states, in addition to the expected surface-aligned PPII. (2S)-2-Amino-2-[3-(trifluoromethyl)bicyclo[1.1.1]pent-1-yl]ethanoic acid and two rigid isomers of trifluoromethyl-4,5-methanoprolines (CF3-MePro) were used as labels for (19)F-NMR analysis...
June 13, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28605682/a-uhplc-method-for-the-rapid-separation-and-quantification-of-anthocyanins-in-acai-berry-and-dry-blueberry-extracts
#14
Jakub Fibigr, Dalibor Šatínský, Petr Solich
The presented work describes the development and validation of a rapid UHPLC-UV method using a core-shell particle column with a pentafluorophenyl stationary phase for the separation and quantitative analysis of the six anthocyanins in acai berry and dry blueberry extracts. The anthocyanins (cyanidin-3-glucoside, cyanidin-3-rutenoside, delphinidin-3-galactoside, delphinidin-3-glucoside, delphinidin-3-rutenoside, and peonidin-3-glucoside) were separated and analyzed in 5min. The chromatographic separation was performed on a Kinetex PFP (150×2...
June 3, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28598599/generation-spectroscopic-and-chemical-characterization-of-an-octahedral-iron-v-nitrido-species-with-a-neutral-ligand-platform
#15
Gerard Sabenya, Laura Lazaro, Ilaria Gamba, Vlad Martin-Diaconescu, Erik Andris, Thomas Weyhermüller, Frank Neese, Jana Roithova, Eckhard Bill, Julio Lloret-Fillol, Miquel Costas
Iron complex [FeIII(N3)(MePy2tacn)](PF6)2 (1), containing a neutral triazacyclononane-based pentadentate ligand, and a terminally bound azide ligand has been prepared and spectroscopically and structurally characterized. Structural details, magnetic susceptibility data and Mössbauer spectra demonstrate that 1 has a low-spin state (S = 1/2) ferric center. X-Ray diffraction analysis of 1 reveals remarkably short Fe - N (1.859 Å) and long FeN - N2 (1.246 Å) distances, respectively, and the FT-IR spectra showed an unusually low N - N stretching frequency (2019 cm-1), suggesting that the FeN - N2 bond is particularly weak...
June 9, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28598428/real-time-observation-of-cation-exchange-kinetics-and-dynamics-at-the-muscovite-water-interface
#16
Sang Soo Lee, Paul Fenter, Kathryn L Nagy, Neil C Sturchio
Ion exchange at charged solid-liquid interfaces is central to a broad range of chemical and transport phenomena. Real-time observations of adsorption/desorption at the molecular-scale elucidate exchange reaction pathways. Here we report temporal variation in the distribution of Rb(+) species at the muscovite (001)-water interface during exchange with Na(+). Time-resolved resonant anomalous X-ray reflectivity measurements at 25 °C reveal that Rb(+) desorption occurs over several tens of seconds during which thermodynamically stable inner-sphere Rb(+) slowly transforms to a less stable outer-sphere Rb(+)...
June 9, 2017: Nature Communications
https://www.readbyqxmd.com/read/28596612/alignment-of-liquid-crystals-by-polymers-with-residual-amounts-of-solvents
#17
Alexander M Parshin, Victor Y Zyryanov, Vasily F Shabanov
The homogeneous nematic layers in liquid crystal cells with treated surfaces are affected by orientational transitions in the electric, magnetic, or temperature fields. The liquid crystal structures formed on solid or liquid surfaces find limited application in identifying the liquid-crystal states by the textures observed in polarized light. The use of surfaces prepared from polymer solutions makes it possible to significantly broaden the range of application of the liquid crystal structures. We investigate the structures with the continuous transformation of the nematic director orientation from radial to planar, which were formed by the polycarbonate surface in the presence of different residual solvents...
June 8, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28595415/computational-methodology-for-solubility-prediction-application-to-the-sparingly-soluble-solutes
#18
Lunna Li, Tim Totton, Daan Frenkel
The solubility of a crystalline substance in the solution can be estimated from its absolute solid free energy and excess solvation free energy. Here, we present a numerical method, which enables convenient solubility estimation of general molecular crystals at arbitrary thermodynamic conditions where solid and solution can coexist. The methodology is based on standard alchemical free energy methods, such as thermodynamic integration and free energy perturbation, and consists of two parts: (1) systematic extension of the Einstein crystal method to calculate the absolute solid free energies of molecular crystals at arbitrary temperatures and pressures and (2) a flexible cavity method that can yield accurate estimates of the excess solvation free energies...
June 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28595404/self-consistent-field-theory-of-polyelectrolyte-brushes-with-finite-chain-extensibility
#19
Inna O Lebedeva, Ekaterina B Zhulina, Oleg V Borisov
Polyelectrolyte brushes are formed by charged macromolecules tethered by the end segment to a solid-liquid interface. At low ionic strength of the solution, the intermolecular electrostatic interactions lead to strong stretching of the macromolecules that may, as a result, approach the limit of their extensibility (the contour length). Here, we present an analytical theory of polyelectrolyte brushes developed within the Poisson-Boltzmann approximation which explicitly accounts for finite extensibility of the brush-forming chains...
June 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28595391/thermodiffusion-as-a-means-to-manipulate-liquid-film-dynamics-on-chemically-patterned-surfaces
#20
Sreeram K Kalpathy, Amrita Ravi Shreyes
The model problem examined here is the stability of a thin liquid film consisting of two miscible components, resting on a chemically patterned solid substrate and heated from below. In addition to surface tension gradients, the temperature variations also induce gradients in the concentration of the film by virtue of thermodiffusion/Soret effects. We study the stability and dewetting behaviour due to the coupled interplay between thermal gradients, Soret effects, long-range van der Waals forces, and wettability gradient-driven flows...
June 7, 2017: Journal of Chemical Physics
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