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1
Natarajan, N., e G. Suresh Kumar. "Numerical modelling of colloidal transport in fractured porous media with double layered fracture-skin". Journal of Geo-Engineering Sciences 1, n. 2 (2014): 83–94. http://dx.doi.org/10.3233/jgs-130016.
Testo completoAbstract (sommario):
A numerical model is developed for studying the transport of colloids in a coupled fracture-matrix system with double layer fracture-skin. The governing equations describing colloid transport along the fracture and diffusion into fracture-skin layers as well as rock-matrix, normal to the fracture axis are coupled with each other. The coupled non linear equations are solved numerically with fully implicit finite difference method. Sensitivity analysis is performed to investigate the effect of various colloid properties on the colloid concentration in the multiple porosity fractured system. Colloid remobilisation and filtration has been accounted in the model. Results suggest that the inclusion of a second fracture-skin layer has a marginal effect on the transport mechanism of colloids. As colloid velocity increases, the diffusion of colloids into the fracture-skin decreases due to the low residence time available for the colloids. High first layer fracture-skin thickness and porosity enhances the diffusion of colloids from the aqueous phase of the fracture into the skin considerably resulting in low colloidal concentration within the fracture. Variation in the porosity as well as thickness of the second layer of the fracture-skin has negligible effect on the colloidal concentration in the fracture. The colloid transport mechanism in fractured porous media is marginally affected by the multiple porosity system, or in other words additional layers of fracture skin. High filtration coefficient and low remobilisation coefficient result in low colloidal concentration within the fracture.
2
Bagalkot, Nikhil, e G. Kumar. "Colloid Transport in a Single Fracture–Matrix System: Gravity Effects, Influence of Colloid Size and Density". Water 10, n. 11 (27 ottobre 2018): 1531. http://dx.doi.org/10.3390/w10111531.
Testo completoAbstract (sommario):
A numerical model was developed to investigate the influence of gravitational force on the transport of colloids in a single horizontal fracture–matrix system. Along with major transport phenomena, prominence was given to study the mass flux at the fracture–matrix interface, and colloid penetration within the rock matrix. Results suggest that the gravitational force significantly alters and controls the velocity of colloids in the fracture. Further, it was shown that the colloid density and size play a vital part in determining the extent that gravity may influence the transport of colloids in both fracture and rock matrix. The mass flux transfer across the fracture–matrix interface is predominantly dependent on the colloidal size. As large as 80% reduction in penetration of colloids in the rock matrix was observed when the size of the colloid was increased from 50–600 nm. Similarly, the farther the density of colloid from that of the fluid in the fracture (water), then the higher the mitigation of colloids in the fracture and the rock matrix. Finally, a non-dimensional parameter “Rock Saturation Factor” has been presented in the present study, which can offer a straightforward approach for evaluating the extent of penetration of colloids within the rock matrix.
3
Klitzke, Sondra, Friederike Lang, Jason Kirby, Enzo Lombi e Rebecca Hamon. "Lead, antimony and arsenic in dissolved and colloidal fractions from an amended shooting-range soil as characterised by multi-stage tangential ultrafiltration and centrifugation". Environmental Chemistry 9, n. 5 (2012): 462. http://dx.doi.org/10.1071/en12010.
Testo completoAbstract (sommario):
Environmental context The size of soil colloids is – among other characteristics – crucial for the mobility of associated contaminants. We analysed the effect of liming on the size of colloids mobilised from strongly contaminated shooting-range soils using multi-stage tangential ultrafiltration (MTUF) for the size fractionation of dispersed soil colloids. Our results indicate the high analytical potential of MTUF and show that liming induces the aggregation of colloids, thereby decreasing the mobilisation of colloid-bound Sb and As, but increasing colloidal Pb. Abstract The size and composition of colloids are important factors controlling their relevance as carriers of metal(loid)s in soils. Liming, which is often used to reduce the effect of heavy metal contamination in soil, can alter concentrations and characteristics of colloids in soil suspension. In batch studies, we compared the influence of changing pH and cation valency on the size distribution and composition of dispersed colloids and on the concentrations of Pb, As and Sb associated with colloids and in solution following the addition of Ca(OH)2 and KOH to soil samples from a contaminated-shooting range site. Multi-stage tangential ultrafiltration (MTUF) and centrifugation were used for the size fractionation of colloids in aqueous suspension. An increase in soil pH resulted in an increase in colloid-associated Pb, with much higher concentrations in the KOH than in the Ca(OH)2 treated samples. In contrast colloid-associated Sb and As increased only in the KOH treated samples. Addition of the monovalent K-ion induced the dispersion of small (~9–220 nm) organo(-mineral) colloids, whereas the divalent Ca-ion suppressed their dispersion and led to the formation of larger colloids (220–1200 nm). Whereas centrifugation underestimated contaminants (i.e. Pb) associated with organic colloids (density <2.6 g cm–3) MTUF gave a distorted distribution of inorganic colloids (i.e. needle-shaped sesquioxides).
4
Ibrahim, Yahaya, e Saratu Abddulfatah. "PAIR INTERACTION OF ACTIVE COLLOIDS IN AN EXTERNAL CHEMICAL GRADIENT". FUDMA JOURNAL OF SCIENCES 6, n. 3 (6 luglio 2022): 271–77. http://dx.doi.org/10.33003/fjs-2022-0603-999.
Testo completoAbstract (sommario):
We study the pair interaction of chemically isotropic active colloidal particles in an externally imposed chemical gradient. Colloid particles migrate in response to a gradient of chemical solutes (i.e., via the diffusiophoresis mechanism). The particles motion induces fluid flow and distort locally the background chemical concentration field. Using the methods of images, we calculate the phoretic inter-particle interaction between two symmetric active colloids in the presence of an externally applied gradient. We highlight an interesting colloidal dipole that would arise from tuning the surface and chemical activity of the colloids. The colloidal phoretic dipoles share similar properties to the electrostatic dipoles. The inter-particle interaction we obtained is an important component for a large-scale simulation of the active colloid suspension. It may also help towards better understanding of the active systems’ emergent phenomena
5
Schmid, Günter, Andreas Lehnert, Ulrich Kreibig, Zbignew Adamczyk e Peter Belouschek. "Synthese und elektronenmikroskopische Untersuchung kontrolliert gewachsener, ligandstabilisierter Goldkolloide sowie theoretische Überlegungen zur Oberflächenbelegung durch Kolloide / Synthesis and Electron Microscopic Investigation of Controlled Grown, Ligand Stabilized Gold Colloids and Theoretical Considerations on the Covering of Surfaces by Colloids". Zeitschrift für Naturforschung B 45, n. 7 (1 luglio 1990): 989–94. http://dx.doi.org/10.1515/znb-1990-0713.
Testo completoAbstract (sommario):
18 nm Gold colloids are used as seeds for a controlled growth of 36 nm colloids which are then stabilized by P(m-C6H4SO3Na)3. These colloids can be isolated as golden leaflets and are readily soluble in water in virtually any concentration. Electron microscopic investigations prove a very small particle size distribution. X-ray powder diffraction and molecular weight determinations support the results of the electron microscopic investigations. The distance between the colloidal particles in two-dimensional layers corresponds to double-layers of phosphane ligands around each colloid, twice 1.2 nm. Isolated colloids seem to possess thicker ligand shells. A single 44 nm colloid shows a corona of about 7.2 nm thickness, corresponding to 12 phosphane layers. A quantitative description of two-dimensional packing densities is suggested using a novel theoretical model. By means of Monte Carlo simulations the two-dimensional structures are formed during the covering of supports of different geometry can be calculated.
6
Niu, Lihua, Rui Chen, Yi Li, Yamei Chen, Wenlong Zhang, Huanjun Zhang e Longfei Wang. "Colloidal Filterable Bacteria Enhance Ammonia Nitrogen Enrichment in River Colloids under Different Turbidity Conditions: Bacterial Diversity, Assembly Mechanism, and Nitrogen Transformation". Water 16, n. 7 (1 aprile 2024): 1024. http://dx.doi.org/10.3390/w16071024.
Testo completoAbstract (sommario):
Turbidity has been one of the most typical problems in urban rivers, accompanied by eutrophication. Though the colloid is a nonnegligible factor associated with turbidity and nutrient enrichment in urban rivers, the characteristics of nitrogen enrichment and bacterial communities of colloids under different turbidity conditions of urban rivers have not been well understood. In this study, colloids of low and high molecular weights (LMW, 30 kDa–0.2 μm, and HMW, 0.2–1 μm) were separately collected from the bulk water (<1 μm) of several typical urban rivers in China. Since the colloidal concentration presented the significantly highest correlation with turbidity, colloidal characteristics were further explored under three turbidity gradients with two cutoffs of 10 and 30 NTU. Results showed that colloidal organic matter in medium and high turbidity rivers was mainly sourced from the release of endogenous plankton and the proportion of colloidal organic carbon in dissolved organic carbon increased from 33% to 38% with increased turbidity. Colloidal ammonia nitrogen in medium turbidity accounted for the highest proportion (an average of 60%) in bulk water, which could be explained by the significantly positive correlation of colloidal ester groups and ammonia nitrogen (R2 = 0.47). Bulk water, HMW, and LMW colloids presented different dominant bacterial genera and LMW colloids also contained three unique dominant filterable genera: Flavobacterium, Acinetobacter, and Limnohabitans. LMW colloidal filterable bacteria under medium and high turbidities presented the greatest potential for dissimilatory nitrate reduction to ammonium, which might further enhance the enrichment of ammonia nitrogen in colloids. This study provides a primary understanding of the characteristics of colloids and colloidal bacterial communities in urban rivers from the perspective of turbidity and puts a new insight on the remediation of rivers under medium turbidity.
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Nikishina, Maria B., Evgenia V. Ivanova, Yury M. Atroschenko, Irina V. Shahkeldyan, Igor V. Blohin, Loik G. Mukhtorov, Konstantin I. Kobrakov e Georgy V. Pestsov. "Biological activity of colloidal solutions of silver, obtained by means of sálix cáprea extract". Butlerov Communications 60, n. 10 (31 ottobre 2019): 54–59. http://dx.doi.org/10.37952/roi-jbc-01/19-60-10-54.
Testo completoAbstract (sommario):
The presented publication is devoted to the study of the biological activity of silver colloids synthesized based on extracts obtained from various parts of the goat willow plant (Sálix cáprea). The ability of colloidal silver solutions of various concentrations to stimulate growth processes in wheat seeds at the germination stage is analyzed. The effect of colloidal solutions on the catalytic effect of amylase was studied. The fungicidal activity of synthesized silver particles was studied. For the study, colloidal silver particles were obtained by the "green synthesis" method. Extracts of goat willow bark, leaves and buds of varying degrees of dilution were used as a reducing agent. The analysis of sugar content and pH of solutions of plant extracts before and after colloid formation was carried out in order to establish the participation of sugars and acids in the process of silver recovery. The biological activity of colloids was analyzed on the seeds of winter wheat cultivar "Moskovskaya-39". The germination energy of wheat seeds was determined on the 3rd day after sowing by counting the germinated seeds. Amylase activity was measured in the roots and shoots of wheat plants by the amount of undecomposed starch by spectrophotometry. Fungicidal activity was studied with respect to fungi: F. moniliforme, F. oxysporum, S. sclerotiorum, V. inaequalis, R. solani, B. sorokiniana, P. ostreatus. The data obtained show that the sugars that make up the initial extracts of various parts of goat willow are completely consumed in the process of silver recovery and the formation of colloidal particles. A change in the acid content at the stage of colloid formation does not allow us to draw an unambiguous conclusion about the mechanism of participation of these compounds in the process of colloid formation. A study of the biological activity of synthesized silver colloids showed their high ability to stimulate growth processes in wheat seeds. A study of enzymatic catalysis also shows, in general, the positive effect of silver colloids on amylase activity within 1 minute of the starch hydrolysis reaction. An analysis of the data obtained in the study of fungistaticity suggests that silver colloids obtained in extracts from leaves, bark and willow inflorescences exhibit high fungicidal activity against F. moniliforme, S. sclerotiorum, P. ostreatus and B. sorokiniana.
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Joshi, Darshana, Dylan Bargteil, Alessio Caciagli, Jerome Burelbach, Zhongyang Xing, André S. Nunes, Diogo E. P. Pinto, Nuno A. M. Araújo, Jasna Brujic e Erika Eiser. "Kinetic control of the coverage of oil droplets by DNA-functionalized colloids". Science Advances 2, n. 8 (agosto 2016): e1600881. http://dx.doi.org/10.1126/sciadv.1600881.
Testo completoAbstract (sommario):
We report a study of reversible adsorption of DNA-coated colloids on complementary functionalized oil droplets. We show that it is possible to control the surface coverage of oil droplets using colloidal particles by exploiting the fact that, during slow adsorption, compositional arrest takes place well before structural arrest occurs. As a consequence, we can prepare colloid-coated oil droplets with a “frozen” degree of loading but with fully ergodic colloidal dynamics on the droplets. We illustrate the equilibrium nature of the adsorbed colloidal phase by exploring the quasi–two-dimensional phase behavior of the adsorbed colloids under the influence of depletion interactions and present simulations of a simple model that illustrates the nature of the compositional arrest and the structural ergodicity.
9
Lattuada, Marco, e Kata Dorbic. "Polymer Colloids: Moving beyond Spherical Particles". CHIMIA 76, n. 10 (26 ottobre 2022): 841. http://dx.doi.org/10.2533/chimia.2022.841.
Testo completoAbstract (sommario):
When thinking about colloidal particles, the fist image that comes into mind is that of tiny little polystyrene spheres with a narrow size distribution. While spherical polymer colloids are one of the workhorses of colloid science, scientists have been working on the development of progressively advanced strategies to move beyond particles with spherical shapes, and prepared polymer colloids with more complex morphologies. This short review aims at providing a summary of these developments, focusing primarily on methods applicable to submicron particles, with an eye towards their applications and some discussion about advantages and drawbacks of the various approaches.
10
Laabs, C., G. Amy e M. Jekel. "Organic colloids and their influence on low-pressure membrane filtration". Water Science and Technology 50, n. 12 (1 dicembre 2004): 311–16. http://dx.doi.org/10.2166/wst.2004.0728.
Testo completoAbstract (sommario):
Wastewater treatment by low-pressure membrane filtration (MF and UF) is affected to a large extent by macromolecules and colloids. In order to investigate the influence of organic colloids on the membrane filtration process, colloids were isolated from a wastewater treatment plant effluent using a rotaryevaporation pre-concentration step followed by dialysis. Stirred cell tests were carried out using redissolved colloids, with and without additional glass fiber filtration. After constant pressure membrane filtration of 190 L/m2, the initial flux had declined by 50% for colloids > 6-8 kD (glass fiber filtered) with a hydrophilic MF membrane and for colloids >12-14 kD (glass fiber filtered) with a hydrophobic MF membrane. For the non-filtered colloidal solutions, the flux decline was even steeper with the flux being below 10% of the initial flux after 190 L/m2 were passed through the membranes. As with larger particles, colloids form a filtration cake layer on top of the membrane surface when used as isolates without prior filtration. This filtration cake is easily removed during backwashing. However, polysaccharides as a macromolecular component of the colloid isolate cause severe fouling by the formation of a gel layer on the membrane surface that is difficult to remove completely.
11
Wang, Yongsheng, Haiyan Huo, Xueren Qian e Jing Shen. "Colloids, nanostructures, and supramolecular assemblies for papermaking". BioResources 15, n. 3 (1 maggio 2020): 4646–49. http://dx.doi.org/10.15376/biores.15.3.4646-4649.
Testo completoAbstract (sommario):
The dominating role of colloid science in papermaking processes, as exemplified by wet-end chemistry, is now well known. The concept of colloids dates back to about 160 years ago. In certain cases, however, the term “colloids” can have an overlapping meaning with the modern terms “nanomaterials” and “supramolecular assemblies”. The latter terms, and the scientists who have gravitated to those terms, have enriched colloid science, providing new insights into colloidal systems. It is proposed here that reconsidering papermaking in light of these multi-disciplinary sciences has potential to facilitate effective teaching and learning pertaining to universities that have pulp and paper programs. Enhanced integration of basic sciences with papermaking may further our understanding and broaden existing research areas, which is likely to create breakthroughs in basic research, applied research, and product development.
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Priyadarshini, N., M. Sampath, Shekhar Kumar, U. Kamachi Mudali e R. Natarajan. "Probing Uranium(IV) Hydrolyzed Colloids and Polymers by Light Scattering". Journal of Nuclear Chemistry 2014 (26 marzo 2014): 1–10. http://dx.doi.org/10.1155/2014/232967.
Testo completoAbstract (sommario):
Tetravalent uranium readily undergoes hydrolysis even in highly acidic aqueous solutions. In the present work, solutions ranging from 0.4 to 19 mM (total U) concentration (1<pH<4) are carefully investigated by light scattering technique with special emphasis on polymerization leading to colloid formation. The results clearly indicate that the concentration has significant effect on particle size as well as stability of colloids. With increasing concentration the size of colloids formed is smaller due to more crystalline nature of the colloids. Stability of colloids formed at lower concentration is greater than that of colloids formed at higher concentration. Weight average molecular weight of the freshly prepared and colloidal polymers aged for 3 days is determined from the Debye plot. It increases from 1,800 to 13,000 Da. 40–50 atoms of U are considered to be present in the polymer. Positive value of second virial coefficient shows that solute-solvent interaction is high leading to stable suspension. The results of this work are a clear indication that U(IV) hydrolysis does not differ from hydrolysis of Pu(IV).
13
Kunberger, T., e M. A. Gabr. "Laboratory testing and microanalysis of colloidal mobilization from a glacial till". Canadian Geotechnical Journal 48, n. 7 (luglio 2011): 1116–24. http://dx.doi.org/10.1139/t11-030.
Testo completoAbstract (sommario):
The effect of the dispersion and piping of clay fines — colloid mobilization — as a means of remediating subsurface contamination was investigated. Prior colloid mobility research has focused on mitigating colloidal movement to reduce contaminant transport or monitoring colloids to determine the extent of mobility and contamination transport. To date, limited work has been performed to evaluate remediation efficiency associated with the removal of clay-sized (colloidal) particles and related sorbed contamination. Laboratory flow-through tests were performed on a glacial till from a radioactive cesium contaminated site. Post-testing analysis comprised mass balance checks, grain-size distribution testing, and microscopic analysis of removed particles. Results showed the potential of initiating and maintaining clay dispersion and piping, thus establishing a means to mobilize colloids and subsequently remove them from the subsurface environment. Beneficial effects of hydraulic gradient and ionic strength manipulations were influenced by soil properties, such as cation exchange capacity, clay content, and average pore diameter. In general, colloid mobilization testing results found that extreme levels of mobilization typically resulted in particle trapping and an overall reduction in colloidal removal, while the effect of more moderate levels was mobilization with increased rates of removal.
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Liao, Yu Bo, Zhao Sheng Lai, Yao Yong Meng e Ping Li Zhang. "Surface-Enhanced Raman Spectroscopic Study of Calf Thymus DNA on Two Different Silver Colloids". Advanced Materials Research 781-784 (settembre 2013): 1072–75. http://dx.doi.org/10.4028/www.scientific.net/amr.781-784.1072.
Testo completoAbstract (sommario):
Two different silver colloids were produced by the reduction of AgNO3using sodium citrate (SCAg colloid) or hydroxylamine hydrochloride (HHAg colloid) as reductant. A comparative study was made on SERS spectra (λexc=514.5 nm) of the calf thymus DNA on the two silver colloids in solution of 0.06mol/L NaCl, pH7.0. With the SCAg colloid, the bands at 732, 915, 1340, and 1448 cm-1for adenine, and 800, 1180, 1590, 1625 and 1651 cm-1for thymidine are dramatically enhanced. It shows that the DNA molecules can be oriented relatively perpendicularly to the SCAg colloidal surface via the N6H2, N7 of adenine and C2=O of thymine residues. While with the HHAg colloid, most of the in-plane modes of the bases are poorly enhanced, except for some weak bands or shoulders assigned to cytosine and guanine. Thus the DNA molecules is supposed to be adsorbed on the HHAg colloid surface in a tilted mode.
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Amézaga González, María Fernanda, Jazzely Acosta Bezada, Víctor Gómez Flores, Christian Chapa González, Jose Rurik Farias Mancilla, S. J. Castillo, Carlos Avila Orta e Perla E. García-Casillas. "Effect of Physiological Fluid on the Photothermal Properties of Gold Nanostructured". International Journal of Molecular Sciences 24, n. 9 (6 maggio 2023): 8339. http://dx.doi.org/10.3390/ijms24098339.
Testo completoAbstract (sommario):
Colloidal gold particles have been extensively studied for their potential in hyperthermia treatment due to their ability to become excited in the presence of an external laser. However, their light-to-heat efficiency is affected by the physiologic environment. In this study, we aimed to evaluate the ability of gold sphere, rod, and star-shaped colloids to elevate the temperature of blood plasma and breast cancer-simulated fluid under laser stimulation. Additionally, the dependence of optical properties and colloid stability of gold nanostructures with physiological medium, particle shape, and coating was determined. The light-to-heat efficiency of the gold particle is shape-dependent. The light-to-heat conversion efficiency of a star-shaped colloid is 36% higher than that of sphere-shaped colloids. However, the raised temperature of the surrounding medium is the lowest in the star-shaped colloid. When gold nanostructures are exited with a laser stimulation in a physiological fluid, the ions/cations attach to the surface of the gold particles, resulting in colloidal instability, which limits electron oscillation and diminishes the energy generated by the plasmonic excitation. Fluorescein (Fl) and polyethylene glycol (PEG) attached to gold spheres enhances their colloidal stability and light-to-heat efficiency; post-treatment, they remand their optical properties.
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Sasamoto, Hiroshi, e Shingo Onda. "Preliminary results for natural groundwater colloids in sedimentary rocks of the Horonobe Underground Research Laboratory, Hokkaido, Japan". Geological Society, London, Special Publications 482, n. 1 (7 settembre 2018): 191–203. http://dx.doi.org/10.1144/sp482.1.
Testo completoAbstract (sommario):
AbstractColloid concentration is an important parameter in models of colloid-facilitated transport. The purpose of the present study is to characterize colloid concentrations and colloid stability in natural groundwater from the Horonobe Underground Research Laboratory (URL) in Hokkaido, Japan. The particle sizes of colloids in groundwaters from the Horonobe URL range from several nanometres to c. 500 nm, with a mode particle size of c. 120 nm. Evaluation of colloid stability by DLVO theory suggests that larger colloids (i.e. >100 nm in diameter) would be more stable than smaller colloids in some groundwaters. The estimated colloid particle concentrations when considering the results of DLVO calculations ranged from 2.33 × 106 to 1.12 × 108 particles/ml, and mass concentrations were estimated to range from 45 to 1540 µg l−1 for diameters greater than 100 nm. Colloids in Horonobe groundwaters appear to be less stable, with a moderate potential for transport, than colloids investigated in similar international studies. This reduced stability may be due to relatively higher ionic strengths and moderate dissolved organic concentrations in Horonobe groundwaters compared to their international counterparts.
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RAGALLER, MAXIMILIAN J. R., HERMANN THEILEN e THEA KOCH. "Volume Replacement in Critically Ill Patients with Acute Renal Failure". Journal of the American Society of Nephrology 12, suppl 1 (febbraio 2001): S33—S39. http://dx.doi.org/10.1681/asn.v12suppl_1s33.
Testo completoAbstract (sommario):
Abstract. Maintenance and restoration of intravascular volume are essential tasks of critical care management to achieve sufficient organ function and to avoid multiple organ failure in critically ill patients. Inadequate intravascular volume followed by impaired renal perfusion is the predominate cause of acute renal failure. Crystalloid solutions are the first choice to correct fluid and electrolyte deficits in these patients. However, in case of major hypovolemia, particularly in situations of increased capillary permeability, colloid solutions are indicated to achieve sufficient tissue perfusion. Whereas albumin should be avoided for correction of intravascular hypovolemia, synthetic colloids can restore intravascular volume and stabilize hemodynamic conditions. In addition to a faster, more effective and prolonged restoration of intravascular volume, colloid solutions are able to improve microcirculation. Of the synthetic colloids, hydroxyethyl starch (HES) solutions with a low in vivo molecular weight, such as HES 200/0.5, offer the best risk/benefit ratio. These solutions are safe with respect to effects on coagulation, platelets, reticuloendothelial system, and renal function, if used below their upper dosage limits. For patients with acute renal dysfunction, daily monitoring of renal function is necessary if colloids are required to stabilize hemodynamic conditions. In these patients, measurement of the colloidal osmotic pressure and adequate amounts of crystalloid solutions will reduce the risk of hyperoncotic renal failure. Of all colloids, gelatin and HES solutions with low in vivo molecular weight are preferred in these cases. In the very specific situation of kidney transplantation, colloid solutions should be administered in a restricted manner to organ donors and kidney recipients.
18
Chikina, Yu, e V. Shikin. "Multicharged Colloids at the Metal/Electrolyte Interface". Электрохимия 59, n. 1 (1 gennaio 2023): 56–60. http://dx.doi.org/10.31857/s0424857023010218.
Testo completoAbstract (sommario):
The electrostatic properties of multicharged colloids (the so-called DLVO complexes) at the interface of two media with different permittivities are discussed. It is shown that being quasi-neutral in the electrolyte volume, the DLVO colloids turn out to be partly charged near the z = 0 boundary that separates these media. The problem of the interaction of an individual colloid, which has a solid inoculating core R0≫a0, (a0 is the interatomic distance) and the charge Q=Ze≫e (e is elementary charge), with the metal/electrolyte interface is considered in detail. The problem has various applications in the diagnosis of DLVO complexes and the practice of dealing with solutions capable of maintaining the electrophoretic motion of colloidal assembles.
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Valverde-Alva, Miguel A., Jhenry F. Agreda-Delgado, Juan A. Vega-González, Juan C. Rodríguez-Soto, Julio C. Idrogo-Córdova, Luis M. Angelats-Silva e Claver W. Aldama-Reyna. "Effect of the magnetic field on the synthesis of colloidal silver and gold nanoparticles by laser ablation in bidestilated water". MOMENTO, n. 63 (9 luglio 2021): 1–11. http://dx.doi.org/10.15446/mo.n63.91515.
Testo completoAbstract (sommario):
The effect of magnetic field of 0.3 T on the concentration, distribution of sizes in suspension and zeta potential of colloidal gold and colloidal silver nanoparticles, obtained by considering the pulsed laser ablation in double distilled water was studied. The magnetic field was transverse to the direction of incidence of the laser radiation and parallel to the surface of a submerged target. An Nd: YAG laser was used (1064 nm in wavelength, 10 ns in duration, repetition rate of 10 Hz and 37 mJ of energy) to ablate targets. The colloids were characterized by inductively coupled plasma optical emission spectroscopy, ultraviolet-visible spectroscopy, dynamic light scattering and zeta potential. Concentration analysis suggested that applying magnetic field of 0.3 T during nanoparticle synthesis leads to higher concentration. Applying magnetic field led to an eleven percent increase in the concentration of the colloid with gold nanoparticles and a five percent increase in the concentration of the colloidal silver nanoparticles. The absorption spectra suggested the presence of spherical nanoparticles. When analyzing the effect of the magnetic field on the hydrodynamic size distribution of the nanoparticles and the zeta potential of the colloids, no significant changes were evidenced. The magnetic confinement of the plasma induced by laser ablation caused changes in the characteristics of the colloids.
20
Kashyap, Swarnima, Shashank Mishra e Shantanu K. Behera. "Aqueous Colloidal Stability of Graphene Oxide and Chemically Converted Graphene". Journal of Nanoparticles 2014 (13 novembre 2014): 1–6. http://dx.doi.org/10.1155/2014/640281.
Testo completoAbstract (sommario):
Graphene oxide (GO) was prepared by modified Hummer’s method, and chemically converted graphene (CCG) was prepared by further reduction of the aqueous GO colloid. The effect of pH on particle size, particle charge, and light absorption of the aqueous colloids of GO and CCG was studied with titration against HCl or NaOH, to find the ideal characteristics for a stable dispersion. The GO colloid was stable in the pH range of 4–11, whereas the CCG colloid gained stability at a relatively narrower pH range of 7–10. Poor stability of the colloids was observed for both GO and CCG colloids at both extremes of the pH scale. Both of the colloids exhibited average size of ~1 micron in the low pH range, whereas for higher pH the size ranged between 300 and 500 nm. The UV-Vis spectra showed absorption peak at 230 nm for GO colloids that shifted to 260 nm for the CCG colloid. Such shift can be ascribed to restoring of electronic conjugation of the C=C bonds in CCG.
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Chang, Chaur-Yang, Kuo-Hsiung Tseng, Jui-Tsun Chang, Meng-Yun Chung e Zih-Yuan Lin. "A Study of Nano-Tungsten Colloid Preparing by the Electrical Spark Discharge Method". Micromachines 13, n. 11 (18 novembre 2022): 2009. http://dx.doi.org/10.3390/mi13112009.
Testo completoAbstract (sommario):
This study developed an energy-enhanced (ee)-micro-electric discharge machining (EDM) system for preparing nano-tungsten (nano-W) colloids. This system enables spark discharge using tungsten wires immersed in deionized water, to produce nano-W colloids. Compared with the chemical preparation method, the processing environment for preparing colloids in this study prevented nanoparticle escape. Among the nano-W colloids prepared using the ee-micro-EDM system and an industrial EDM system, the colloid prepared by the ee-micro-EDM system exhibited a more favorable absorbance, suspensibility, and particle size. The colloid prepared by the ee-micro-EDM system with a pulse on time and off time of 10–10 μs had an absorbance of 0.277 at a wavelength of 315 nm, ζ potential of −64.9 mV, and an average particle size of 164.9 nm. Transmission electron microscope imaging revealed a minimum particle size of approximately 11 nm, and the X-ray diffractometer spectrum verified that the colloid contained only W2.00 and W nanoparticles. Relative to industrial EDM applications for nano-W colloid preparation, the ee-micro-EDM system boasts a lower cost and smaller size, and produces nano-W colloids with superior performance. These advantages contribute to the competitiveness of the electrical spark discharge method in the preparation of high-quality nano-W colloids.
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Tan, Yan Peng, Xiao Wen Zhang, Jun Wen Lv, Dong Shan Tang e Qin Su. "Transformation Behaviors of U(VI) on Irons Hydroxide Colloids". Advanced Materials Research 734-737 (agosto 2013): 2563–67. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.2563.
Testo completoAbstract (sommario):
The presence of the colloid will affect uranium heap leaching. The objective of this study was the examination of the ability of colloid retardation to uranium by irons hydroxide colloids simulated heap leaching process. Batch studies have been carried by observing the effects of pH, contact time, uranium concentration. Iron hydroxide colloids can exist stably at pH 1.5-3.0. The size of the colloid samples is between 20 nm and 1000 nm. The sorption equilibrium was attained at 24 h. The load uranium capacity on iron hydroxide colloids are between 2.43×10-3 and 3.84×10-3 mmol/mol. The colloid morphology of before and after loaded uranium were identified using S-4800 scanning electron microscopy (SEM/EDS). The load uranium capacity on iron hydroxide colloids is least at pH=2, it implies that the appropriate pH of uranium heap leach is 2.0 on the point of retardation of colloid to uranium migration.
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Yokoyama, Kazushige, Kieran Brown, Peter Shevlin, Jack Jenkins, Elizabeth D’Ambrosio, Nicole Ralbovsky, Jessica Battaglia, Ishan Deshmukh e Akane Ichiki. "Examination of Adsorption Orientation of Amyloidogenic Peptides Over Nano-Gold Colloidal Particle Surfaces". International Journal of Molecular Sciences 20, n. 21 (28 ottobre 2019): 5354. http://dx.doi.org/10.3390/ijms20215354.
Testo completoAbstract (sommario):
The adsorption of amyloidogenic peptides, amyloid beta 1–40 (Aβ1–40), alpha-synuclein (α-syn), and beta 2 microglobulin (β2m), was attempted over the surface of nano-gold colloidal particles, ranging from d = 10 to 100 nm in diameter (d). The spectroscopic inspection between pH 2 and pH 12 successfully extracted the critical pH point (pHo) at which the color change of the amyloidogenic peptide-coated nano-gold colloids occurred due to aggregation of the nano-gold colloids. The change in surface property caused by the degree of peptide coverage was hypothesized to reflect the ΔpHo, which is the difference in pHo between bare gold colloids and peptide coated gold colloids. The coverage ratio (Θ) for all amyloidogenic peptides over gold colloid of different sizes was extracted by assuming Θ = 0 at ΔpHo = 0. Remarkably, Θ was found to have a nano-gold colloidal size dependence, however, this nano-size dependence was not simply correlated with d. The geometric analysis and simulation of reproducing Θ was conducted by assuming a prolate shape of all amyloidogenic peptides. The simulation concluded that a spiking-out orientation of a prolate was required in order to reproduce the extracted Θ. The involvement of a secondary layer was suggested; this secondary layer was considered to be due to the networking of the peptides. An extracted average distance of networking between adjacent gold colloids supports the binding of peptides as if they are “entangled” and enclosed in an interfacial distance that was found to be approximately 2 nm. The complex nano-size dependence of Θ was explained by available spacing between adjacent prolates. When the secondary layer was formed, Aβ1–40 and α-syn possessed a higher affinity to a partially negative nano-gold colloidal surface. However, β2m peptides tend to interact with each other. This difference was explained by the difference in partial charge distribution over a monomer. Both Aβ1–40 and α-syn are considered to have a partial charge (especially δ+) distribution centering around the prolate axis. The β2m, however, possesses a distorted charge distribution. For a lower Θ (i.e., Θ <0.5), a prolate was assumed to conduct a gyration motion, maintaining the spiking-out orientation to fill in the unoccupied space with a tilting angle ranging between 5° and 58° depending on the nano-scale and peptide coated to the gold colloid.
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Kalnina, Daina, Kārlis Agris Gross, Artur Medvids e Pavels Onufrijevs. "Formation of Negatively Charged AgI Colloid Nanoparticles by Condensation". Advanced Materials Research 1117 (luglio 2015): 159–63. http://dx.doi.org/10.4028/www.scientific.net/amr.1117.159.
Testo completoAbstract (sommario):
The stability of silver halide colloids is reported to be important for the toxicological outcome. This study shows a well-suited and cheap condensation reaction to obtain negatively charged silver iodide (AgI) nanoparticles without additional stabilization agents. Charged AgI colloids were synthesized from silver nitrate and potassium iodide solutions. An excess of potassium iodide not only imparted a negative charge, but provided a narrow particle size distribution (50 ± 10 nm). The change of optical properties in the colloid was investigated by UV-VIS spectroscopy. A silver iodide exciton absorption band at peak ~421nm (2.93eV), red-shifted over time. The peak at half maximum intensity increased from 13.3nm to 14.8 nm, characterizing the dispersity of AgI colloidal particles. Colloidal particles stabilized after 33 hours. In-situ real-time UV-VIS measurements provide a tool to adjust the particle characteristics and may serve to further optimize the performance in biological applications.
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Roller, Jörg, Aleena Laganapan, Janne-Mieke Meijer, Matthias Fuchs e Andreas Zumbusch. "Observation of liquid glass in suspensions of ellipsoidal colloids". Proceedings of the National Academy of Sciences 118, n. 3 (4 gennaio 2021): e2018072118. http://dx.doi.org/10.1073/pnas.2018072118.
Testo completoAbstract (sommario):
Despite the omnipresence of colloidal suspensions, little is known about the influence of colloid shape on phase transformations, especially in nonequilibrium. To date, real-space imaging results at high concentrations have been limited to systems composed of spherical colloids. In most natural and technical systems, however, particles are nonspherical, and their structural dynamics are determined by translational and rotational degrees of freedom. Using confocal microscopy of fluorescently labeled core–shell particles, we reveal that suspensions of ellipsoidal colloids form an unexpected state of matter, a liquid glass in which rotations are frozen while translations remain fluid. Image analysis unveils hitherto unknown nematic precursors as characteristic structural elements of this state. The mutual obstruction of these ramified clusters prevents liquid crystalline order. Our results give insight into the interplay between local structures and phase transformations. This helps to guide applications such as self-assembly of colloidal superstructures and also gives evidence of the importance of shape on the glass transition in general.
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Nohé, Boris, Tanja Johannes, Jörg Reutershan, Albert Rothmund, Helene A. Haeberle, Annette Ploppa, Torsten H. Schroeder e Hans-Juergen Dieterich. "Synthetic Colloids Attenuate Leukocyte-Endothelial Interactions by Inhibition of Integrin Function". Anesthesiology 103, n. 4 (1 ottobre 2005): 759–67. http://dx.doi.org/10.1097/00000542-200510000-00014.
Testo completoAbstract (sommario):
Background It has been suspected that synthetic colloids may interfere with leukocyte adhesion by down-regulation of endothelial cell adhesion molecules. Although inhibition of endothelial inflammation might reduce leukocyte-related tissue injury, the same mechanism may be detrimental for host defense during severe infection. Regarding the widespread use of colloids, the authors performed a laboratory investigation to determine the mechanisms by which synthetic colloids interfere with leukocyte-endothelial interactions. Methods Adhesion molecule expression on native and cytokine-activated endothelium from umbilical veins was measured after pretreatment with gelatin and various preparations of dextran or hydroxyethyl starch. Inhibition of neutrophil adhesion to activated endothelium was examined in a flow chamber by perfusion of untreated and colloid-treated neutrophils over colloid-pretreated endothelium at 2 dyn/cm. Comparisons were made between untreated controls, colloid-pretreated endothelium, and colloid-cotreated neutrophils. Results Intercellular adhesion molecule 1, vascular cell adhesion molecule 1, E-selectin, and P-selectin were not attenuated by any colloid. Accordingly, colloid pretreatment of endothelium alone did not reduce neutrophil adhesion. In contrast, when neutrophils were cotreated by addition of colloids to the perfusate immediately before perfusion, adhesion decreased by 31-51% (P < 0.05) regardless of the colloid type. As indicated by the twofold increased rolling fractions, this reduction was due to an inhibition of neutrophil integrins. Conclusions This study shows that synthetic colloids inhibit neutrophil adhesion by a neutrophil-dependent mechanism rather than interfering with endothelial cell activation. This suggests that inhibition of leukocyte sequestration by volume support is a common and transient phenomenon depending on the colloid concentration in plasma.
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Majumdar, Udayan, Thrisha Alexander, Morris Waskar e Manoj V. Dagaonkar. "Effect of biofilm on colloid attachment in saturated porous media". Water Science and Technology 70, n. 2 (7 maggio 2014): 241–48. http://dx.doi.org/10.2166/wst.2014.197.
Testo completoAbstract (sommario):
Biofilm plays an important role in controlling the transport of colloids in a porous media. Biofilms are formed when micro-organisms come in contact with substrates, and are able to attach and grow with availability of nutrients. The microorganisms get embedded in a matrix of the substrate and extracellular polymeric substances which are responsible for the morphology, physico-chemical properties, structure and coherence of the biofilm. In this study, the effect of biofilm and its aging on colloid removal was studied on a glass bead column. Oocysts, polystyrene microspheres and inorganic colloids were used as colloidal particles. Pseudomonas aeruginosa was used as a model biofilm-forming microorganism. Presence of biofilm significantly enhanced colloid removal in the column. After 3 weeks, almost complete colloid removal was observed. The formation of biofilm was confirmed by various physical characterization techniques. During the extended aging study, biofilm sloughed off under shear stress. The loss of biofilm was higher during the early stage of its growth, and subsequently slowed down probably due to the formation of a more rigid biofilm. This research indicates that biofilm formation, maturation and sloughing-off play a critical role in colloid removal through porous media.
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Kurosawa, S., e S. Ueta. "Effect of colloids on radionuclide migration for performance assessment of HLW disposal in Japan". Pure and Applied Chemistry 73, n. 12 (1 gennaio 2001): 2027–37. http://dx.doi.org/10.1351/pac200173122027.
Testo completoAbstract (sommario):
Colloidal effect is one of the major factors to enhance the migration of radionuclides in groundwater. The experimental and theoretical studies of colloid mobility and colloid-facilitated radionuclide transport for the performance assessment of high-level radioactive waste (HLW) geological disposal is presented in this paper. The major aims of the study are (1) to study the filtration effect on colloids by the engineered barrier system, (2) to study bentonite colloid generation by erosion of the engineered barrier system, and (3) to calculate radionuclide migration with groundwater colloids through fractured rock systems. Alternative coagulants based on prehydrolyzed forms of aluminium or iron can be more effective than the traditional materials in many cases, but their mode of action is not completely understood, especially with regard to the role of charge neutralization and hydroxide precipitation. Basic principles of colloid stability and metal ion hydrolysis are briefly reviewed, and the action of hydrolyzing metal coagulants is then discussed, with some examples from recent experimental studies. Although it is possible to interpret results reasonably well in terms of established ideas, there are still some uncertainties that need to be resolved
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Sepehrnia, Nasrollah, Olga Fishkis, Bernd Huwe e Jörg Bachmann. "Natural colloid mobilization and leaching in wettable and water repellent soil under saturated condition". Journal of Hydrology and Hydromechanics 66, n. 3 (1 settembre 2018): 271–78. http://dx.doi.org/10.1515/johh-2017-0058.
Testo completoAbstract (sommario):
AbstractThe coupled transport of pollutants that are adsorbed to colloidal particles has always been a major topic for environmental sciences due to many unfavorable effects on soils and groundwater. This laboratory column study was conducted under saturated moisture conditions to compare the hydrophobic character of the suspended and mobilized colloids in the percolates released from a wettable subsoil and a water repellent topsoil. Both soils with different organic matter content were analyzed for wettability changes before and after leaching using sessile drop contact angles as well as water and ethanol sorptivity curves, summarized as repellency index. Hydrophobicity of the effluent suspensions was assessed using the C18 adsorption method. Water repellency level of the repellent soil decreased after leaching but remained on a lower level of water repellency, while, the wettable soil remained wettable. The leached colloids from the repellent soil were predominantly hydrophilic and the percentage of the hydrophobic colloid fraction in the effluent did not systematically changed with time. Total colloid release depended on soil carbon stock but not on soil wettability. Our results suggest that due to the respective character of transported colloids a similar co-transport mechanism for pollutants may occur which does not depend explicitly on soil wettability of the releasing horizon, but could be more affected by total SOM content. Further studies with a wider range of soils are necessary to determine if the dominant hydrophilic character of leached colloids is typical. Due to the mostly hydrophilic colloid character we conclude also that changes in wettability status, i.e. of wettable subsoil horizons due to the leachate, may not necessarily occur very fast, even when the overlaying topsoil is a repellent soil horizon with a high organic matter content.
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Liu, Iris B., Nima Sharifi-Mood e Kathleen J. Stebe. "Curvature-driven assembly in soft matter". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 374, n. 2072 (28 luglio 2016): 20150133. http://dx.doi.org/10.1098/rsta.2015.0133.
Testo completoAbstract (sommario):
Control over the spatial arrangement of colloids in soft matter hosts implies control over a wide variety of properties, ranging from the system’s rheology, optics, and catalytic activity. In directed assembly, colloids are typically manipulated using external fields to form well-defined structures at given locations. We have been developing alternative strategies based on fields that arise when a colloid is placed within soft matter to form an inclusion that generates a potential field. Such potential fields allow particles to interact with each other. If the soft matter host is deformed in some way, the potential allows the particles to interact with the global system distortion. One important example is capillary assembly of colloids on curved fluid interfaces. Upon attaching, the particle distorts that interface, with an associated energy field, given by the product of its interfacial area and the surface tension. The particle’s capillary energy depends on the local interface curvature. We explore this coupling in experiment and theory. There are important analogies in liquid crystals. Colloids in liquid crystals elicit an elastic energy response. When director fields are moulded by confinement, the imposed elastic energy field can couple to that of the colloid to define particle paths and sites for assembly. By improving our understanding of these and related systems, we seek to develop new, parallelizable routes for particle assembly to form reconfigurable systems in soft matter that go far beyond the usual close-packed colloidal structures. This article is part of the themed issue ‘Soft interfacial materials: from fundamentals to formulation’.
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Lai, Yeong Lin, Li Wei Chen e Chih Hung Chen. "Processes of Titanium-Dioxide Colloids for Working Electrodes of Dye-Sensitized Solar Cells". Applied Mechanics and Materials 865 (giugno 2017): 54–59. http://dx.doi.org/10.4028/www.scientific.net/amm.865.54.
Testo completoAbstract (sommario):
New titanium-dioxide (TiO2) colloids composed of nano-crystalline TiO2 and polydimethylsiloxane (PDMS) have been developed for use in the working electrodes of dye-sensitized solar cells (DSSCs). The surface morphology and electrical characteristics of the TiO2 colloid electrodes were studied. The analysis of the surface morphology of the TiO2 colloids was conducted by an atomic force microscope (AFM) and a field-emission scanning electron microscope (FE-SEM). The photovoltaic characteristics of the TiO2 colloids with different compositions were investigated. The TiO2 content of the colloids determined the photovoltaic conversion ability of DSSCs. Colorful colloids were implemented by adding pigments to the TiO2 colloids. The processes of the TiO2 colloids demonstrated the advantages of simple fabrication and low cost. The flexible property of the TiO2 colloids showed great potential for application in flexible optoelectronics.
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Li, Runwei, Changfu Wei, Hefa Cheng e Gang Chen. "Adhesion of Colloids and Bacteria to Porous Media: A Critical Review". Reviews of Adhesion and Adhesives 7, n. 4 (1 dicembre 2019): 417–60. http://dx.doi.org/10.7569/raa.2019.097314.
Testo completoAbstract (sommario):
Adhesion of colloids and bacteria to various surfaces is important for a variety of environmental phenomena including microbial biofouling and contamination prevention. Under saturated conditions, both colloids and bacteria have the opportunity to attach to porous medium surfaces. Under water unsaturated conditions or in the presence of the air-water interface, besides the porous medium surfaces, colloids and bacteria can also attach to the air-water interface, including the air-water-solid threephase interface. The magnitudes of adhesion of colloids and bacteria are correlated to the interactions of the colloids and bacteria with the surfaces, which are a function of their surface physicochemical properties. In this review, adhesion theories are revisited and adhesion of colloids and bacteria to porous media and the air-water interface is discussed. The interaction forces are quantified using various theoretical models including the DLVO models and used to interpret related adhesion. The impact of surfactants on colloid and bacterial adhesion is also discussed. The review also includes the implementation of the adhesion theory in interpreting colloid and bacterial fate and transport in the subsurface soil.
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Szakasits, Megan E., Keara T. Saud, Xiaoming Mao e Michael J. Solomon. "Rheological implications of embedded active matter in colloidal gels". Soft Matter 15, n. 40 (2019): 8012–21. http://dx.doi.org/10.1039/c9sm01496a.
Testo completoAbstract (sommario):
We examine the effect of embedded active colloids on the linear viscoelastic moduli of colloidal gels. We find that the autonomous, out-of-equilibrium dynamics of active colloids incorporated into the colloidal network decreases gel elasticity.
34
Leppard, G. G., M. M. West, D. T. Flannigan, J. Carson e JNA Lott. "A classification scheme for marine organic colloids in the Adriatic Sea: colloid speciation by transmission electron microscopy". Canadian Journal of Fisheries and Aquatic Sciences 54, n. 10 (1 ottobre 1997): 2334–49. http://dx.doi.org/10.1139/f97-140.
Testo completoAbstract (sommario):
Organic colloids from the Adriatic Sea, covering the full colloid size range, were characterized on a per-colloid basis by transmission electron microscopy applied to ultrathin sections of embedded colloids. To detect, assess, and minimize artifacts, a multimethod correlative approach to analysis was used. A colloid classification scheme was developed from the characterizations, with individual colloid species defined in the broad sense established by environmental analytical aquatic chemists. The basic scheme is related to derivative classification schemes in which abundant colloid species are listed according to activities known from the literature, with a focus on activities related to carbon transformations and transport. Morphological criteria show that abundant colloid species occupy broad size ranges, such that colloid fractionation protocols based on sizing alone are likely to be of questionable scientific utility. Image analysis revealed that small colloids, designated as humic substances, represented 91% of the total organic colloid burden of the bulk water during a summer period of high biological productivity. At this time, fibrils were rare in the bulk water while representing the most abundant colloid in marine snow.
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Xu, Bing, e Ren Guo Song. "Fabrication of Ag Nanoparticles Colloids by Pulsed Laser Ablation in Liquid". Advanced Materials Research 123-125 (agosto 2010): 675–78. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.675.
Testo completoAbstract (sommario):
Ag nanoparticles colloids have been fabricated by pulsed laser ablation in various liquids. The particle size, morphology and absorption spectroscopy of the obtained nanoparticles colloids were characterized by ultraviolet to visible (UV-Vis) spectrophotometer and transmission electron microscopy (TEM), the average diameter and its distribution were analyzed by Image-ProPlus software. The results showed that the Ag nanoparticles with best characterization are those produced at the repetition rate of 10Hz and laser fluence of 4.2J/cm2 by ablating for 7.5min in the distilled water, with the least average diameter(D=14.48 nm), the narrowest distribution of particles size (=25.8 nm) and more homogeneous morphologies. The effects of experimental conditions on the silver nanoparticles colloid can be explained by fragmentation and melting induced aggregation of colloidal particles by self-absorption of laser pulses.
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Kuno, Goshi, e Akikazu Matsumoto. "Easy Cell Detachment and Spheroid Formation of Induced Pluripotent Stem Cells Using Two-Dimensional Colloidal Arrays". Macromol 3, n. 2 (10 maggio 2023): 224–33. http://dx.doi.org/10.3390/macromol3020014.
Testo completoAbstract (sommario):
Induced pluripotent stem cells (iPSCs) may develop into any form of cell and are being intensively investigated. The influence on iPSCs of nanostructures generated using two-dimensional colloidal arrays was examined in this study. Colloidal arrays were formed using the following procedure. First, core–shell colloids were adsorbed onto a glass substrate using a layer-by-layer method. Second, the colloids were immobilized via thermal fusion. Third, the surface of the colloids was modified by plasma treatment. By adjusting the number density of colloids, cultured iPSCs were easily detached from the substrate without manual cell scraping. In addition to planar culture, cell aggregation of iPSCs attached to the substrate was achieved by combining hydrophilic surface patterning on the colloidal array. Multilayered cell aggregates with approximately four layers were able be cultured. These findings imply that colloidal arrays might be an effective tool for controlling the strength of cell adhesion.
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Molkova, Elena A., Vladimir I. Pustovoy, Evgenia V. Stepanova, Irina V. Gorudko, Maxim E. Astashev, Alexander V. Simakin, Ruslan M. Sarimov e Sergey V. Gudkov. "pH-Dependent HEWL-AuNPs Interactions: Optical Study". Molecules 29, n. 1 (22 dicembre 2023): 82. http://dx.doi.org/10.3390/molecules29010082.
Testo completoAbstract (sommario):
Optical methods (spectroscopy, spectrofluorometry, dynamic light scattering, and refractometry) were used to study the change in the state of hen egg-white lysozyme (HEWL), protein molecules, and gold nanoparticles (AuNPs) in aqueous colloids with changes in pH, and the interaction of protein molecules with nanoparticles was also studied. It was shown that changing pH may be the easiest way to control the protein corona on gold nanoparticles. In a colloid of nanoparticles, both in the presence and absence of protein, aggregation–deaggregation, and in a protein colloid, monomerization–dimerization–aggregation are the main processes when pH is changed. A specific point at pH 7.5, where a transition of the colloidal system from one state to another is observed, has been found using all the optical methods mentioned. It has been shown that gold nanoparticles can stabilize HEWL protein molecules at alkaline pH while maintaining enzymatic activity, which can be used in practice. The data obtained in this manuscript allow for the state of HEWL colloids and gold nanoparticles to be monitored using one or two simple and accessible optical methods.
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Ding, Xuhan, Guang Xu, Dengfei Wang, Zhenmin Luo e Tao Wang. "Effect of Synergistic Aging on Bauxite Residue Dust Reduction Performance via the Application of Colloids, an Orthogonal Design-Based Study". Polymers 13, n. 12 (17 giugno 2021): 1986. http://dx.doi.org/10.3390/polym13121986.
Testo completoAbstract (sommario):
The application of polymer colloids is a promising approach for bauxite residue dust pollution control. However, due to the existence of synergistic aging, the efficiency of colloid dynamic viscosity to predict the dust control performance of bauxite residue is unclear. Previous studies were also rarely performed under synergistic aging conditions. Thus, this paper investigates the relationship between colloids’ viscosity and dust control performance under synergistic aging modes. Results illustrated that the binary colloid achieved better dust control performance than unitary colloid for their higher viscosity and penetration resistance. For both unitary and binary colloid, higher viscosity results in better crust strength. A logarithmic relationship was found for viscosity and dust erosion resistance under unitary aging. However, Only the dynamic viscosity of colloids in solid-liquid two-phase conditions, rather than dissolved in deionized water, can effectively predict the dust control performance under synergistic aging conditions.
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Liu, Yongliang, Yud-Ren Chen, Xiangwu Nou e Kuanglin Chao. "Potential of Surface-Enhanced Raman Spectroscopy for the Rapid Identification of Escherichia Coli and Listeria Monocytogenes Cultures on Silver Colloidal Nanoparticles". Applied Spectroscopy 61, n. 8 (agosto 2007): 824–31. http://dx.doi.org/10.1366/000370207781540060.
Testo completoAbstract (sommario):
Surface-enhanced Raman (SERS) spectra of various batches of bacteria adsorbed on silver colloidal nanoparticles were collected to explore the potential of the SERS technique for rapid and routine identification of E. coli and L. monocytogenes cultures. Relative standard deviation (RSD) of SERS spectra from silver colloidal suspensions and ratios of SERS peaks from small molecules (K3PO4) were used to evaluate the reproducibility, stability, and binding effectiveness of citrate-reduced silver colloids over batch and storage processes. The results suggested consistent reproducibility of silver colloids over batch process and also stability and consistent binding effectiveness over an eight-week storage period. A variety of mixtures of E. coli/L. monocytogenes cultures with different colloidal batches revealed that, despite large variations in relative intensities and positions of SERS active bands, characteristic and unique bands at 712 and 390 cm−1 were consistently observed and were the strongest in E. coli and L. monocytogenes cultures, respectively. Two specific bands were used to develop simple algorithms in the evaluation of binding effectiveness of silver colloids over storage and further to identify E. coli and L. monocytogenes cultures with a 100% success. A single spectrum acquisition took 5∼6 min, and a minimum of 25 μL silver colloid was directly mixed with 25 μL volume of incubated bacterial culture. The short acquisition time and small volume of incubated bacterial culture make silver colloidal nanoparticle based SERS spectroscopy ideal for potential use in the routine and rapid screening of E. coli and L. monocytogenes cultures on large scales. This is the first report of the development of simple and universal algorithms for bacterial identification from the respective exclusive SERS peaks.
40
Shim, Wonmi, Chan Sik Moon, Hyeonjin Kim, Hyun Su Kim, Haoxiang Zhang, Su Kyung Kang, Pyung Soo Lee e Sanghyuk Wooh. "Tailoring the Morphology of Supraparticles by Primary Colloids with Different Shapes, Sizes and Dispersities". Crystals 11, n. 2 (21 gennaio 2021): 79. http://dx.doi.org/10.3390/cryst11020079.
Testo completoAbstract (sommario):
Surface-templated evaporation driven (STED) method is a promising method to fabricate supraparticles with various sizes, porosities, and shapes by drying colloidal dispersion drops on liquid repellent surfaces. Until now, for the method, only spherical shaped colloidal particles have been used as primary colloids. Here, we introduce six different shapes of nano-colloidal dispersions for the STED method: nanocubics, nanoplates, nanosheets, coffin-shaped nanoparticles (NPs), spherical NPs, and aggregates of NPs. It is confirmed that the shape and size of the primary colloids have little effect for drying the dispersion drop when a single component colloidal dispersion is dried. For heterogeneous supraparticles with composite material assembly, still the shape of the colloids has no influences, while the size and dispersity play roles for tuning the morphology of the supraparticles. From the results, we propose a way to fabricate homogeneous mixture, core/shell, and Janus core/shell structures of the supraparticles depending on the size and dispersity of the mixture colloidal dispersion. Indeed, knowledge on the effects of types of colloids would be of great importance for tailoring supraparticles.
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Zuo, Rui, Kexue Han, Rongtao Shi, Fei Ding, Li Liu, Jinsheng Wang, Yanguo Teng, Jie Yang e Xin Liu. "Effect of Colloidal Silicate on the Migration Behaviour of Strontium in Groundwater Environment of Geological Disposal Candidate Site". Journal of Chemistry 2019 (23 settembre 2019): 1–11. http://dx.doi.org/10.1155/2019/9606121.
Testo completoAbstract (sommario):
Various colloids are present in the natural groundwater environment, and colloids act on the processes involved when radionuclides leak from a repository in a high-level waste disposal site. This paper investigates the effect of colloidal silicate in natural groundwater environments on the migration behaviour of Sr(II). Three different experimental cases have been designed: (1) effect in the presence of colloidal silicate, (2) effect in the presence of a porous medium, and (3) effect in the presence of both colloidal silicate and porous medium (referred to as CS, PM, and PC, respectively). Batch experiments were used to study the effect of influencing factors on Sr(II) migration behaviour, such as the amount of CS, solid-to-liquid ratio, pH, contact time, and initial concentration of Sr(II). The experiments showed that the effect of PC on the migration behaviour of Sr(II) was greatest, and the presence of CS enhanced the sorption. The colloid amount, pH, and solid-to-liquid ratio significantly affected the migration behaviour. The more the colloids were added, the better the adsorption effect. The optimal pH and solid-to-liquid ratio were 6 and 20 : 1, respectively. The alkaline environment is more conductive to colloid sorption. When the solid-to-liquid ratio was 20 : 1, the sorption percentage of PC is 0.5 times larger than PM. Although the PC has a longer adsorption equilibrium time, the percentage of adsorption can be larger than that in the other two cases. The kinetics and isotherms of Sr(II) were best described by the pseudo-second-order and Langmuir models. It was inferred that strong chemical interactions and/or surface complexation contributed primarily to Sr(II) sorption, and the process was on the monolayer adsorption of the outer surface. These findings provide valuable information for the migration behaviour of strontium in groundwater environments of geological disposal site. At the same time, it provides information for the implementation of permeable reactive barrier technology to control the transport of radioactive Sr(II) and its species in natural surface and groundwater.
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Zhou, Xiang, Dongbao Yao, Wenqiang Hua, Ningdong Huang, Xiaowei Chen, Liangbin Li, Miao He et al. "Programming colloidal bonding using DNA strand-displacement circuitry". Proceedings of the National Academy of Sciences 117, n. 11 (4 marzo 2020): 5617–23. http://dx.doi.org/10.1073/pnas.1917941117.
Testo completoAbstract (sommario):
As a strategy for regulating entropy, thermal annealing is a commonly adopted approach for controlling dynamic pathways in colloid assembly. By coupling DNA strand-displacement circuits with DNA-functionalized colloid assembly, we developed an enthalpy-mediated strategy for achieving the same goal while working at a constant temperature. Using this tractable approach allows colloidal bonding to be programmed for synchronization with colloid assembly, thereby realizing the optimal programmability of DNA-functionalized colloids. We applied this strategy to conditionally activate colloid assembly and dynamically switch colloid identities by reconfiguring DNA molecular architectures, thereby achieving orderly structural transformations; leveraging the advantage of room-temperature assembly, we used this method to prepare a lattice of temperature-sensitive proteins and gold nanoparticles. This approach bridges two subfields: dynamic DNA nanotechnology and DNA-functionalized colloid programming.
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Pan, Hong Cheng, Jiang Tao Liu, Jin Ming Liang, Dun Nan Li, Jian Ping Li, Wen Yuan Zhu e Chang Jie Mao. "Preparation of Pt Colloids via a Wet-Chemical Method for Methanol Sensor". Advanced Materials Research 295-297 (luglio 2011): 527–30. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.527.
Testo completoAbstract (sommario):
Pt colloids were synthesized by a wet-chemical method. The Pt colloids were modified on the glassy carbon electrode (GCE). The electrochemical behavior and electrocatalyst for methanol of the colloidal Pt-modified electrode in H2SO4medium were investigated. The results show that the as-prepared Pt colloids are good electrocatalysts for methanol oxidation and the oxidation current increases with methanol concentration in the range of 0.002 to 0.5 M. The colloidal Pt-modified electrode is simple, easy-to-use and reusable, showing promising applications in the electrocatalyst and determination of methanol.
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Wang, Xiaolu, Martin In, Christophe Blanc, Paolo Malgaretti, Maurizio Nobili e Antonio Stocco. "Wetting and orientation of catalytic Janus colloids at the surface of water". Faraday Discussions 191 (2016): 305–24. http://dx.doi.org/10.1039/c6fd00025h.
Testo completoAbstract (sommario):
Janus colloidal particles show remarkable properties in terms of surface activity, self-assembly and wetting. Moreover they can perform autonomous motion if they can chemically react with the liquid in which they are immersed. In order to understand the self-propelled motion of catalytic Janus colloids at the air–water interface, wetting and the orientation of the catalytic surface are important properties to be investigated. Wetting plays a central role in active motion since it determines the contact between the fuel and the catalytic surface as well as the efficiency of the transduction of the chemical reaction into motion. Active motion is not expected to occur either when the catalytic face is completely out of the aqueous phase or when the Janus boundaries are parallel to the interfacial plane. The design of a Janus colloid possessing two hydrophilic faces is required to allow the catalytic face to react with the fuel (e.g. H2O2 for platinum) in water and to permit some rotational freedom of the Janus colloid in order to generate propulsion parallel to the interfacial plane. Here, we discuss some theoretical aspects that should be accounted for when studying Janus colloids at the surface of water. The free energy of ideal Janus colloidal particles at the interface is modeled as a function of the immersion depth and the particle orientation. Analytical expressions of the energy profiles are established. Energetic aspects are then discussed in relation to the particle’s ability to rotate at the interface. By introducing contact angle hysteresis we describe how the effects of contact line pinning modifies the scenario described in the ideal case. Experimental observations of the contact angle hysteresis of Janus colloids at the interface reveal the effect of pinning; and orientations of silica particles half covered with a platinum layer at the interface do not comply with the ideal scenarios. Experimental observations suggest that Janus colloids at the fluid interface behave as a kinetically driven system, where the contact line motion over the defects decorating the Janus faces rules the orientation and rotational diffusion of the particle.
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Kumar, Manoj, Anupam Singh, Benedetta Del Secco, Maksim V. Baranov, Geert van den Bogaart, Stefano Sacanna e Shashi Thutupalli. "Assembling anisotropic colloids using curvature-mediated lipid sorting". Soft Matter 18, n. 9 (2022): 1757–66. http://dx.doi.org/10.1039/d1sm01517f.
Testo completoAbstract (sommario):
Anisotropic colloidal geometry is used to drive lipid sorting in multi-component membranes along the colloids, which are then exploited to create “shape-anisotropic patchy colloids” for directed self-assembly.
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Choi, Jinseok, Seong-Gyu Park, Yeo-Jin Choi, Seung-Mun Baek, Han-Jung Kim, Yoonkap Kim, Ki-Sik Im e Sung-Jin An. "Viscosity-Controllable Graphene Oxide Colloids Using Electrophoretically Deposited Graphene Oxide Sheets". Micromachines 13, n. 12 (7 dicembre 2022): 2157. http://dx.doi.org/10.3390/mi13122157.
Testo completoAbstract (sommario):
Graphene oxide (GO) is one of the interesting ink materials owing to its fascinating properties, such as high dissolubility in water and high controllable electric properties. For versatile printing application, the viscosity of GO colloids should be controlled in order to meet the specific process requirements. Here, we report on the relatively rapid fabrication of viscosity-increased GO (VIGO) colloids mixed with electrophoretically deposited GO sheets (EPD-GO). As the GO colloid concentration, applied voltage, and deposition time increase, the viscosity of the GO colloids becomes high. The reason for the improved viscosity of GO colloids is because EPD-GO has parallel stacked GO sheets. The GO and VIGO colloids are compared and characterized using various chemical and structural analyzers. Consequently, our simple and fast method for the fabrication of GO colloids with enhanced viscosity can be used for producing inks for flexible and printed electronics.
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Homoky, William B., Tim M. Conway, Seth G. John, Daniela König, FeiFei Deng, Alessandro Tagliabue e Rachel A. Mills. "Iron colloids dominate sedimentary supply to the ocean interior". Proceedings of the National Academy of Sciences 118, n. 13 (26 marzo 2021): e2016078118. http://dx.doi.org/10.1073/pnas.2016078118.
Testo completoAbstract (sommario):
Dissolution of marine sediment is a key source of dissolved iron (Fe) that regulates the ocean carbon cycle. Currently, our prevailing understanding, encapsulated in ocean models, focuses on low-oxygen reductive supply mechanisms and neglects the emerging evidence from iron isotopes in seawater and sediment porewaters for additional nonreductive dissolution processes. Here, we combine measurements of Fe colloids and dissolved δ56Fe in shallow porewaters spanning the full depth of the South Atlantic Ocean to demonstrate that it is lithogenic colloid production that fuels sedimentary iron supply away from low-oxygen systems. Iron colloids are ubiquitous in these oxic ocean sediment porewaters and account for the lithogenic isotope signature of dissolved Fe (δ56Fe = +0.07 ± 0.07‰) within and between ocean basins. Isotope model experiments demonstrate that only lithogenic weathering in both oxic and nitrogenous zones, rather than precipitation or ligand complexation of reduced Fe species, can account for the production of these porewater Fe colloids. The broader covariance between colloidal Fe and organic carbon (OC) abundance suggests that sorption of OC may control the nanoscale stability of Fe minerals by inhibiting the loss of Fe(oxyhydr)oxides to more crystalline minerals in the sediment. Oxic ocean sediments can therefore generate a large exchangeable reservoir of organo-mineral Fe colloids at the sediment water interface (a “rusty source”) that dominates the benthic supply of dissolved Fe to the ocean interior, alongside reductive supply pathways from shallower continental margins.
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Shang, Shu Bo, e Xu Qian Li. "Study on the Co-Migration of Pb with Soil Colloids under Rainfall". Advanced Materials Research 183-185 (gennaio 2011): 437–41. http://dx.doi.org/10.4028/www.scientific.net/amr.183-185.437.
Testo completoAbstract (sommario):
In this experiment, clay loam, fine sandy loam and silty loam collected from the farmland (FL), floodplain (FP) and Loess platform (LP) in Changchun separately were chosen to study the role of rainfall on the migration of heavy metal (Pb)-colloid complexes quantitively through soil column simulation in laboratory. The purpose of this study is to illuminate the tendency for colloid-Pb co-migrating to deep soil and groundwater. The study shows whether how the mechanism between colloid and heavy metal acts, the processes exist in common. First, through some sort of adsorption, heavy metal form complexes with colloids, and co-migrate in the underground environment, which is called a co-migration mechanism. And Pb migrated out the FL, LP, and FP soil column contain 28.4%、25.7% and 22.6% complexes separately. Second, the heavy metal complexes with colloids have a certain stability and mobility. Third, in migrating process, the presence of colloids increases the migration concentration and amount of heavy metal (Pb). And the quantitative of Pb migrated out the FL, LP and FP soil column which added colloids are 1.37、1.36 and 1.25 double control columns separately. Forth, the presence of colloids reduces the reduction ability heavy metal (Pb), and shortens the consumption time for heavy metal (Pb) migrating to a certain depth of groundwater. And the time consuming of Pb migrating to groundwater with same deep is Loess horizon>floodplain horizon>farmland horizon.
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Moonrat, Chanikan, Siriwan Kittinaovarut, Supatra Jinawath e Pornapa Sujaridworakun. "The Effect of pH Values on Color Development of Silver Colloids". Key Engineering Materials 862 (settembre 2020): 17–21. http://dx.doi.org/10.4028/www.scientific.net/kem.862.17.
Testo completoAbstract (sommario):
This study aimed to investigate the effect of pH value raging from pH 4 - 8 on color development of silver colloids. Silver colloids with different colors were synthesized by chemical reduction method using NaBH4 as a reducing agent and then adjusted pH value by adding dropwise of acetic acid. These silver colloids were characterized by Transmission Electron Microscopy and UV-Vis spectrophotometer. The results showed that the colors of silver colloids ranging from blue to yellow depended on amount of NaBH4 added. Due to Localized Surface Plasmon Resonance (LSPR) properties, different shapes and sizes of silver nanoparticles resulting in different colors. It was found that the pH value also affected color development of silver colloids. By adjusting the pH value, the colors of silver colloids changed to different colors or shades, which were clarified by the changes in the center as well as intensity of the absorption spectra. Moreover, the silver colloid in an acidic condition led to aggregation of nanoparticles.
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Bouzghaia, Mohamed, Ferhat Souidi e Zakaria Larbi. "Polydisperse Colloids Two-Moment Diffusion Model Through Irreversible Thermodynamics Considerations". Journal of Non-Equilibrium Thermodynamics 46, n. 1 (18 novembre 2020): 77–90. http://dx.doi.org/10.1515/jnet-2020-0004.
Testo completoAbstract (sommario):
Abstract This study deals with the problem of diffusion for polydisperse colloids. The resolution of this complex problem usually requires computationally expensive numerical models. By considering the number of colloidal particles and their mass as independent variables, the equations of state for a dilute polydisperse colloid are derived on a statistical mechanics basis. Irreversible thermodynamics is then applied to obtain a simple two-moment diffusion model. The validity of the model is illustrated by comparing its results with those obtained by a classical size spectrum approach, in a sedimentation equilibrium problem and in an unsteady one-dimensional diffusion problem in Stokes–Einstein regime, and under the hypothesis that the size spectrum distribution is stochastic. In the first problem, the two-moment diffusion problem allows to represent rigorously the vertical size segregation induced by gravity, while in the second one, it allows a convenient description of the diffusion of polydisperse colloids by using two coupled diffusion equations, with an accuracy comparable with that of the classical size spectrum approach. The contribution of our work lies primarily in the application of a non-equilibrium thermodynamics methodology to a challenging issue of colloid modeling, namely, polydispersity, by going from statistical mechanics to the derivation of phenomenological coefficients, with the two-moment approach as a guideline.