Surfactants are increasingly being used in an ever-expanding variety of applications for drilling fluids. In oil-based drilling fluids, the most well-known applications of surfactants are as emulsifiers and wetting agents. In water-based drilling fluids, there is a continually-growing variety of applications that include:
oil-in-water emulsification in base fluid formulations;
shale-swelling inhibitors to prevent wellbore instabilities;
detergency to prevent cuttings sticking to drill bit (adhesion of clay to metal parts);
prevention of differential sticking;
dispersants to inhibit flocculation of clay particles;
foaming additives, to generate high gas/water ratio foam used as drilling fluids for low-pressure reservoirs and hard-rock drilling;
defoaming additives to eliminate undesirable foam in water-based fluids;
surfactant-polymer complexes for enhanced properties in fluids for low-pressure reservoirs.
This review describes historical and modern applications of surfactant technology in drilling fluids, and the impact of those molecules on drilling operations. Proper selection and application of surfactants in drilling fluids have a significant economic impact, in terms of reducing the amount of lost time and potential trouble, and have a direct consequence on overall drilling performance and results. 相似文献
Abstract This work describes the problems occurring in routine determination of polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in water. On the basis of experiments carried out, sources of analyte losses in a particular step of the analytical procedure were identified and assessed. Primary attention has been paid to evaluation of the?following:
degree of adsorption of analytes from the group of PCBs and PAHs on the walls of glass vessels used during sample pretreatment and storage
influence of excess of solvent evaporation from extracts on analyte recoveries
influence of material of extraction column (glass, polyethylene) on analyte recovery during the solid extraction process.
These Recommendations expand and replace the Tentative Rules for Carbohydrate Nomenclature [1] issued in 1969 jointly by the IUPAC Commission on the Nomenclature of Organic Chemistry and the IUB-IUPAC Commission on Biochemical Nomenclature (CBN) and reprinted in [2]. They also replace other published JCBN Recommendations [3-71 that deal with specialized areas of carbohydrate terminology; however, these documents can be consulted for further examples. of relevance to the field, though not incorporated into the present document, are the following recommendations:
Nomenclature of cyclitols, 1973 [8]
Numbering of atoms in myo-inositol, 1988 [9]
Symbols for specifying the conformation of polysaccharide chains, 1981 [10]
Nomenclature of glycoproteins, glycopeptides and peptidoglycans, 1985 [11]
Nomenclature of glycolipids, in preparation [12]
The present Recommendations deal with the acyclic and cyclic forms of monosaccharides and their simple derivatives, as well as with the nomenclature of oligosaccharides and polysaccharides. They are additional to the Definitive Rules for the Nomenclature of Organic Chemistry [13,14] and are intended to govern those aspects of the nomenclature of carbohydrates not covered by those rules. 相似文献
The rates of electrodeposition of copper plates were determined by measuring cathodic limiting current in the absence and in the presence of carbohydrates (glucose, fructose, mannose, sucrose, lactose, and maltose). It is found that the rate of electrodeposition decreases in the presence of organic additives by an amount ranging from 1.89% to 35.85%, and depending on the types of additives and its concentrations. Our investigation of adsorption isotherm indicates that the inhibition fits both the Langmuir adsorption isotherm and Flory-Huggins adsorption isotherm; we found that the rate of electrodeposition decreases by increasing height and increasing CuSO4 concentrations. Thermodynamic parameters are given and show that electrodeposition process is diffusion controlled. The rate of deposition and its equations are represented:
Sh = 0.099Re0.715 Sc0.33 for glucose with average deviation: ±0.158%
Sh = 0.097Re0.715 Sc0.33 for fructose with average deviation: ±0.058%
Sh = 0.099Re0.715 Sc0.33 for mannose with average deviation: ±0.108%
Sh = 0.098Re0.713 Sc0.33 for sucrose with average deviation: ±0.003%
Sh = 0.099Re0.714 Sc0.33 for lactose with average deviation: ±0.018%
Sh = 0.099Re0.713 Sc0.33 for maltose with average deviation: ±0.097%.
A series of sample stability tests has been undertaken to support a large UK-based survey of trace substances in wastewater. This program aims to quantify the input of priority chemicals to the aquatic environment via sewage effluent. The stability tests have demonstrated that, in most cases, the proposed approach of chilling samples meets the target that sample concentrations should not change by more than 25%, provided samples are analyzed or otherwise stabilized within 3–5 d. Substances tested fall into three main classes:
Instability in effluents greater than the project-based threshold of 25% over 3–5 d can be ruled out provided samples are chilled for: DEHP (DEHA), glyphosate, AMPA, bentazone, mecoprop, ofloxacin, erythromycin, and ibuprofen;
Some indication of possible instability up to 25% provided chilled storage periods do not extend beyond 3–5 d for: mercury (note requires acid dichromate preservation on site or as soon as possible), tributyltin, bisphenol A, reactive aluminum (in effluents, note requires filtration on sampling), oxytetracycline, and propranolol; and
Clear stability problems are demonstrated for salicylic acid (effluents and influents), with indications of important instability (>25%) for bisphenol (effluents) AMPA and glyphosate (influents).
The contents of zinc, copper, lead and cadmium were measured in the dominant species (plants:Scripus triquetor andPhrgrmites australis, macrobenthos:Ilyoplax deschampsin, Helice tridens tientsinensis, Bullacta exarata and Corbicula fluminea, and migrating waders: Calidris ruficollis and C. alpina) of the ecosystem of Yangtze Estuary, China, from 1995–1998. Results show that:
(1)
Since the heavy metals stored in plants during growth seasons will be released into the environment in winter, plants are temporary stocks for metals. For the aboveground parts of reeds, about 156.6 kg·ha-1·a-1 of zinc, 369.9 kg·ha-1·a-10 of copper, 32.9 kg·ha-·a-1 of lead and 6.5 kg·ha-1·a-1 of cadmium were released.
(2)
The mollusca, especially C.fluminea, are the key species storing and transporting heavy metals on the food chain.
(3)
The temporal change in the highest trophic level was studied and found that it was significantly related with metabolic rates. The contents of heavy metals in Dunlin reach the peaks in January and October, which are wintering season and migratory season, respectively, of the bird.
(4)
Organisms often show regulation/accumulation mechanisms to different elements of heavy metals. The elements that are widely required, such as zinc and copper, are accumulated at the metabolically active parts. It is quite another thing for the other two elements. Lead was regulated well and scarcely accumulated in the bodies of macrobenthos, but cadmium was absolutely accumulated in the animals.
(5)
Heavy metals were found accumulated in some parts of the bodies of these organisms, such as shells and skeletons of macrobenthos and lives and muscles of waders.
(6)
All these four elements were accumulated higher in the bodies of waders than in the plants and macrobenthos, which showed a bio-magnification function of the food chain. Overall, besides the physical and chemical processes, biological processes of heavy metal elements in Yangtze Estuarine ecosystem play a very important role in self-purification function of the ecosystem. Measurement of heavy metal contents in plants and animals in the estuarine ecosystem is an efficient technology for monitoring the environmental quality of the estuary.
Highlights? In silico screening against a pocket formed by the Skp2-Cks1 protein interface ? Structure-based discovery of Skp2 ligase inhibitors that block p27 ubiquitylation ? Inhibition of Skp2 ligase activity stabilizes p27 protein in melanoma cells ? Inhibitor induction of p27 results in cell cycle arrest in various cancer cells 相似文献
Highlights? A highly modified nucleotide as substrate for polymerases ? The reversibility of the polymerase reaction at the template level ? Synthesis of a nucleoside with two anomeric centers 相似文献
AbstractIn last two decades, acid doped polybenzimidazole as polymer electrolyte membrane (PEM) has been widely recognized and envisioned as “ideal” proton conducting materials for application in high temperature PEM fuel cell (HT-PEMFC). The majority of research and developmental work is mainly focused on poly (2,2´-m-phenylene-5,5´-bibenzimidazole), However, it is neither easy-processed nor inexpensive component of the respective family. On the other hand, among the various members belonging to benzimidazole family, poly (2,5-benzimidazole) is unique because it possesses a cost-attractive, single-step synthesis process, high extent of doping as well as good chemical and thermal stability. In the recent years this material has proved its potency in the earlier research. Thus this review puts special emphasis on poly (2,5-benzimidazole) and epitomizes the on-going breath-taking progress and achievements on the fabrication of poly (2,5-benzimidazole) based membranes. The write-up describes the effect of blending, cross-linking, ionic liquids and incorporation organic/inorganic nano-fillers. In addition, incorporating other protonic dopants such as heteropoly acids into the chain of poly (2,5-benzimidazole) molecular skeleton is also overviewed. Moreover, the critical interpretation of different causes responsible for earlier degradation and their effect towards the fabrication of high temperature membrane electrode assembly are visualized herein.
Highlights
Current developments and existing challenges of ABPBI in PEMFC have been reviewed.
PEM Modification and addition of protonic dopants has been discussed.
Proton migration, permeability, stability and reliability are thoroughly illustrated.
Different ABPBI-based membranes and their performance are comparatively analyzed.
Highlights? Development of an assay for LF protease using a full-length protein substrate ? Lichen depsidones identified as exosite-targeting LF inhibitors ? Exosite inhibitors protect macrophages from LF cytotoxicity 相似文献
Highlights? Catalytic domain of JMJD2A (cJMJD2A) removes methyl marks in a distributive manner ? Homogeneously methylated nucleosomes were used as substrates ? Quantitative assay for nucleosome demethylation has been developed 相似文献
Highlights? Prohibitins regulate cell survival, metabolism, and inflammation ? Prohibitins act as a hub for many signaling pathways ? Prohibitin ligands are examined in cancer, Parkinson’s disease, and obesity 相似文献
The aim of this paper was to prepare composites of bacterial cellulose (BC) and collagen to evaluate both the effect of collagen on the morphological, mechanical and thermal properties of BC and the effect of BC on the thermal stability of collagen for designing composites with increased potential biomedical applications. Two series of composites were prepared, the first series by immersing BC pellicle in solutions of collagen obtained in three forms, collagen gel (CG), collagen solution (CS) and hydrolysed collagen (HC), followed by freeze drying; and the second series of composites by mixing BC powder in solutions of collagen (CG, CS and HC), also followed by freeze drying. The properties of obtained composites were evaluated by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), mechanical tests, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results revealed that BC acts as a thermal stabilizer for CS matrix, while with CG matrix it interacts synergistically leading to composites with improved properties. On the other hand, the BC sheet impregnated with collagen has a significantly improved thermal stability. Collagen (as HC, CS or CG) has also a positive influence on the mechanical properties of lyophilized BC sheet. A four times increase of modulus was observed in BC/HC and BC/CG composites. and an increase of 60 times for BC/CS. The spectacular increase of elastic modulus and tensile strength in the case of BC/CS composite was explained by the easier penetration of collagen solution in the BC network and impregnation of BC fibrils as revealed by SEM and AFM analyzes.
Summary: Carboxymethyl Konjac Glucomannan–Chitosan (CKGM‐CS) nanoparticles, which are well dispersed and stable in aqueous solution, were spontaneously prepared under very mild conditions by polyelectrolyte complexation. Investigations of the physicochemical properties of these nanoparticles were undertaken. This study showed that the nanoparticulate system driven by complex formation has potential as an advanced drug‐delivery system for water‐soluble drugs.
Preparation mechanism of CS–CKGM nanoparticles. 相似文献
Highlights? Cellular FRET biosensors for Ras, Rho, and Rab membrane anchorage were developed ? We provide evidence for Rab protein nanoclustering on cellular membranes ? Two FRET biosensors were demonstrated to be suitable for high-throughput screening ? Macrotetrolides were identified as nanoclustering and MAPK signaling disruptors 相似文献
Highlights? The natural anticancer compound rocaglamide directly binds to PHB1 and PHB2 ? Rocaglamide blocks PHB-mediated activation of CRaf-MEK-ERK pathway and cancer proliferation ? Rocaglamide may serve as a new type of anticancer agent ? Rocaglamide may serve as a new molecular tool for studying PHB-mediated cellular functions 相似文献
Highlights? Peptoid ligands for anti-AQP4 autoantibodies that drive NMO have been identified ? Some of these peptoids provide an accurate blood test for the disease 相似文献
