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partition coefficient

Lei Huang, Hongwei Fang, Xingya Xu, Guojian He, Xuesong Zhang, Danny Reible
Phosphorus (P) fate and transport plays a crucial role in the ecology of rivers and reservoirs in which eutrophication is limited by P. A key uncertainty in models used to help manage P in such systems is the partitioning of P to suspended and bed sediments. By analyzing data from field and laboratory experiments, we stochastically characterize the variability of the partition coefficient (Kd) and derive spatio-temporal solutions for P transport in the Three Gorges Reservoir (TGR). We formulate a set of stochastic partial different equations (SPDEs) to simulate P transport by randomly sampling Kd from the measured distributions, to obtain statistical descriptions of the P concentration and retention in the TGR...
March 16, 2017: Science of the Total Environment
Juhua Yu, Shiming Ding, Jicheng Zhong, Chengxin Fan, Qiuwen Chen, Hongbin Yin, Lei Zhang, Yinlong Zhang
Sediment dredging is an effective restoration method to control the internal phosphorus (P) loading of eutrophic lakes. However, the core question is that the real mechanism of dredging responsible for sediment internal P release still remains unclear. In this study, we investigated the P exchange across the sediment-water interface (SWI) and the internal P resupply ability from the sediments after dredging. The study is based on a one-year field simulation study in Lake Taihu, China, using a Rhizon soil moisture sampler, high-resolution dialysis (HR-Peeper), ZrO-Chelex diffusive gradients in thin film (ZrO-Chelex DGT), and P fractionation and adsorption isotherm techniques...
March 16, 2017: Science of the Total Environment
Jiao Xu, Zhiyong He, Maomao Zeng, Bingbing Li, Fang Qin, Linxiang Wang, Shengfang Wu, Jie Chen
The effects of xanthan gum on the release of strawberry flavor compounds in formulated soy protein isolate (SPI) beverage were investigated by headspace gas chromatography (GC). Seven strawberry flavor compounds (limonene, ethyl hexanoate, (Z)-3-hexenyl acetate, ethyl 2-methylbutanoate, ethyl butanoate, (Z)-3-hexen-1-ol and diacetyl) could be detected by GC and hence analyzed the gas-matrix partition coefficients (K). The release of flavor compounds was restrained in SPI and/or xanthan gum solution. The retention of (Z)-3-hexen-1-ol, limonene and diacetyl significantly changed (p<0...
August 1, 2017: Food Chemistry
Karin M Rosenblatt, Heike Bunjes
When using lipid nanoparticles as drug carrier system it is important to know how much drug can be loaded to the nanoparticles. The mainly used drug loading procedure is an empirical approach dissolving the drug in the liquid lipid during preparation of the nanoparticles. This approach does not necessarily lead to the truly loadable amount, as the lipid can, e.g. be overloaded, in particular when it is processed in the heat. In this work, a different procedure, passive drug loading, was evaluated to determine the drug loading capacity of various lipid nanoparticles (supercooled trimyristin emulsion droplets, solid trimyristin nanoparticles, tristearin nanoparticles in the α-modification and cholesteryl myristate nanoparticles in the supercooled smectic as well as in the crystalline state)...
March 15, 2017: European Journal of Pharmaceutics and Biopharmaceutics
María Eugenia Parolo, Mónica Claudia Savini, Ruth Miriam Loewy
Sorption of non-ionic organic compounds to soil is usually expressed as the carbon-normalized partition coefficient (KOC) assuming that the main factor that influences the amount sorbed is the organic carbon content (OC) of the soil. However, KOC can vary across a range of soils. The influence of certain soil characteristics on the chlorpyrifos KOC values variation for 12 representative soils of the Northpatagonian Argentinian region with different physicochemical properties was investigated for this study...
March 14, 2017: Journal of Environmental Management
Liena Qin, Duc-Duy Vo, Azadeh Nakhai, C David Andersson, Mikael Elofsson
Benzofuran and 2,3-dihydrobenzofuran scaffolds are core components in a large number of biologically active natural and synthetic compounds including approved drugs. Herein, we report efficient synthetic protocols for preparation of libraries based on 3-carboxy 2-aryl benzofuran and 3-carboxy 2-aryl trans-2,3-dihydrobenzofuran scaffolds using commercially available salicylaldehydes, aryl boronic acids or halides and primary or secondary amines. The building blocks were selected to achieve variation in physicochemical properties and statistical molecular design and subsequent synthesis resulted in 54 lead-like compounds with molecular weights of 299-421 and calculated octanol/water partition coefficients of 1...
March 17, 2017: ACS Combinatorial Science
Reza Ghanbari, Salvatore Assenza, Abhijit Saha, Raffaele Mezzenga
We present an experimental investigation on the diffusion of unfolded polymers in the triply-periodic water-channel network of inverse bicontinuous cubic phases. Depending on the chain size, our results indicate the presence of two different dynamical regimes corresponding to Zimm and Rouse diffusion. We support our findings by scaling arguments based on a combination of blob and effective-medium theories, and suggest the presence of a third regime where dynamics is driven by reptation. Our experimental results also show an increasing behavior of the partition coefficient as a function of polymer molecular weight, indicative of a reduction of the conformational degrees of freedom induced by the confinement...
March 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Emil Dražević, Krešimir Košutić, Marin Svalina, Jacopo Catalano
Reverse osmosis (RO) membranes are primarily designed for removal of salts i.e. for desalination of brackish and seawater, but they have also found applications in removal of organic molecules. While it is clear that steric exclusion is the dominant removal mechanism, the fundamental explanation for how and why the separation occurs remains elusive. Until recently there was no strong microscopic evidences elucidating the structure of the active polyamide layers of RO membranes, and thus they have been conceived as "black boxes"; or as an array of straight capillaries with a distribution of radii; or as polymers with a small amount of polymer free domains...
March 9, 2017: Water Research
C Schwienheer, J Krause, G Schembecker, J Merz
In addition to the selection or adjustment of phase systems to gain a suitable partition coefficient for the target molecule, the separation efficiency in centrifugal partition chromatography (CPC) is strongly influenced by the hydrodynamic interactions of the mobile and the stationary phase in the chambers. Thus, the hydrodynamic interactions must be investigated and understood in order to enhance a CPC separation run. Different hydrodynamic effects like mass transfer, back mixing and the non-ideal behavior of stationary phase, which cannot be determined directly, are known, but quantifying these effects and their influence on separation performance is barely achieved...
March 6, 2017: Journal of Chromatography. A
Leonie van 't Hag, Sally L Gras, Charlotte E Conn, Calum J Drummond
Ordered amphiphile self-assembly materials with a tunable three-dimensional (3D) nanostructure are of fundamental interest, and crucial for progressing several biological and biomedical applications, including in meso membrane protein crystallization, as drug and medical contrast agent delivery vehicles, and as biosensors and biofuel cells. In binary systems consisting of an amphiphile and a solvent, the ability to tune the 3D cubic phase nanostructure, lipid bilayer properties and the lipid mesophase is limited...
March 10, 2017: Chemical Society Reviews
Dong-Xing Guan, Jian-Lun Zheng, Jun Luo, Hao Zhang, William Davison, Lena Q Ma
Desorption/adsorption of bisphenols (BPs) in soils affects their mobility and availability. However, the kinetics of these processes have not been well studied, due to the lack of appropriate means of measurement. Diffusive gradients in thin-films (DGT) technique can assess kinetic processes in soils and have recently been developed for measuring three BPs (BPA, BPB and BPF). DGT was deployed for 2.5h to 20 d in five soils with different soil properties. Non-linear increase in mass accumulation by DGT with time indicated poor resupply of BPs from soil solid to solution phase...
February 27, 2017: Journal of Hazardous Materials
Mylène Ghislain, Joana Beigbeder, Hervé Plaisance, Valérie Desauziers
The gas-phase concentration at the material surface (y 0 ) is pointed out in the literature as a key parameter to describe semivolatile organic compound (SVOC) emissions from materials. This is an important input data in predictive models of SVOC behavior indoors and risk exposure assessment. However, most of the existing measurement methods consist of determining emission rates and not y 0 and none allow on-site sampling. Hence, a new passive sampler was developed. It consists of a glass cell that is simply placed on the material surface until reaching equilibrium between material and air; y 0 is then determined by solid-phase microextraction (SPME) sampling and GC-MS analysis...
March 7, 2017: Analytical and Bioanalytical Chemistry
N Selvasudha, Kailasam Koumaravelou
The present study reported design and evaluation of nanoformulations of Simvastatin using different polymers. The study emphasizes upon the synergistic activity of the drug and the polymers owing to the reported anti- hyperlipidemic activity of the selected polymers. Preliminary studies advocated for chitosan formulations due to the expected particle size (543±26nm) among the three polymer formulations. Four formulations (F1-F4) were prepared varying chitosan ratio. F4 demonstrated optimal characteristics (particle size - 549±23...
May 1, 2017: Carbohydrate Polymers
Jana Tomková, Martin Švidrnoch, Vítězslav Maier, Peter Ondra
A new ultra high performance liquid chromatography with electrospray ionization time-of-flight mass spectrometry method for the selective and sensitive separation, identification and determination of selected designer benzodiazepines (namely, pyrazolam, phenazepam, etizolam, flubromazepam, diclazepam, deschloroetizolam, bentazepam, nimetazepam and flubromazolam) in human serum was developed. The separation of the studied designer benzodiazepines was achieved on C18 chromatographic column using gradient elution within 6 min without any significant matrix interferences...
March 7, 2017: Journal of Separation Science
Lalita, Anirudh P Singh, Rajeev Kr Sharma
To develop pH responsive hydrogels, N-isopropylacrylamide (NIPAM) has been grafted on to chitosan by free radical initiation method using azoisobutrylnitrile (AIBN) as an initiator. The optimum grafting conditions were worked out for grafting of NIPAM onto 1g of chitosan by varying one reaction parameter at a time and keeping all other parameters constant. Binary monomers were grafted for five different concentrations of comonomers acrylic acid (AAc), acrylamide (AAm) and acrylonitrile (AN) at optimum grafting conditions evaluated for GMA alone onto chitosan...
March 3, 2017: International Journal of Biological Macromolecules
Adrián Gutiérrez-Serpa, Priscilla Rocío-Bautista, Verónica Pino, Francisco Jiménez-Moreno, Ana I Jiménez-Abizanda
The use of solid-phase microextraction coatings based on gold nanoparticles was investigated, focusing the attention on the preparation of nanoparticles with non-classical reduction agents of HAuCl4 such as gallic acid and H2 O2 , rather than the conventional sodium citrate. All nanoparticles were characterized by diode array spectroscopy, whereas novel nanoparticles prepared with gallic acid and H2 O2 were also characterized by microscopic techniques. Solid-phase microextraction coatings were prepared with a layer-by-layer approach...
March 6, 2017: Journal of Separation Science
Parichehr Saranjampour, Emily N Vebrosky, Kevin L Armbrust
Salinity has been reported to influence the water solubility of organic chemicals entering marine ecosystems. However, there is limited data available on salinity impacts for chemicals potentially entering seawater. Impacts on water solubility would correspondingly impact chemical sorption as well as overall bioavailability and exposure estimates used in the regulatory assessment. Pesticides atrazine, fipronil, bifenthrin, cypermethrin, as well as crude oil constituents dibenzothiophene as well as 3 of its alkyl derivatives all have different polarities and were selected as model compounds to demonstrate the impact of salinity on their solubility and partitioning behavior...
March 6, 2017: Environmental Toxicology and Chemistry
Paul G Tratnyek, Eric J Bylaska, Eric J Weber
Quantitative structure-activity relationships (QSARs) have long been used in the environmental sciences. More recently, molecular modeling and chemoinformatic methods have become widespread. These methods have the potential to expand and accelerate advances in environmental chemistry because they complement observational and experimental data with "in silico" results and analysis. The opportunities and challenges that arise at the intersection between statistical and theoretical in silico methods are most apparent in the context of properties that determine the environmental fate and effects of chemical contaminants (degradation rate constants, partition coefficients, toxicities, etc...
March 6, 2017: Environmental Science. Processes & Impacts
Franziska Bezold, Maria E Weinberger, Mirjana Minceva
Tocopherols are a class of molecules with vitamin E activity. Among those, α-tocopherol is the most important vitamin E source in the human diet. The purification of tocopherols involving biphasic liquid systems can be challenging since these vitamins are poorly soluble in water. Deep eutectic solvents (DES) can be used to form water-free biphasic systems and have already proven applicable for centrifugal partition chromatography separations. In this work, a computational solvent system screening was performed using the predictive thermodynamic model COSMO-RS...
March 31, 2017: Journal of Chromatography. A
Christopher Lyndon Davey, Laurence Edmund Jones, Michael Squance, Sarah Jane Purdy, Anne Louise Maddison, Jennifer Cunniff, Iain Donnison, John Clifton-Brown
Miscanthus is a rhizomatous C4 grass of great interest as a biofuel crop because it has the potential to produce high yields over a wide geographical area with low agricultural inputs on marginal land less suitable for food production. At the moment, a clonal interspecific hybrid Miscanthus × giganteus is the most widely cultivated and studied in Europe and the United States, but breeding programmes are developing newer more productive varieties. Here, we quantified the physiological processes relating to whole season yield in a replicated plot trial in Wales, UK...
February 2017: Global Change Biology. Bioenergy
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