Oxidation of Sulfides with Pyridinium Tribromide in the Presence of Hydrated Silica Gel

A variety of sulfides have been oxidized to sulfoxides utilizing pyridinium tribromide in the presence of hydrated silica gel in a non‐aqueous media. A combination of pyridinium tribromide and hydrated silica gel releases molecular bromine slowly in the reaction, affecting the oxidation. Hydrated silica gel also promotes decomposition of the bromosulfonium intermediate to the product. This procedure employs non‐aqueous media for the first time in such a reaction.     

Liesegang rings of lead chromate Part II

Faint rings of lead chromate are formed in gelatin gel when a solution of lead nitrate diffuses in gelatin gel containing potassium chromate. These rings become well defined in the presence of a coagulant like potassium nitrate. Well definedLiesegang rings of insoluble substances in gel media can be obtained if the substance can exist in the colloidal state in the media and is coagulable by the diffusing ion.     

Novel Gel with Controllable Strength for In-Depth Conformance Control: Bulk Gelation Performance and Propagation Properties in Porous Media

Polymer gel has been widely used to control excessive water production in mature oilfields. However, in view of reservoir conditions characterized by serious heterogeneous thick oil layers, high strength and in-depth propagation are required of polymer gel to achieve good treatment efficiency. Based on the concept of in-depth conformance control, a novel gel with controllable strength composed of polymer, resorcinol/hexamethylenetetramine (HMTA), acetic acid and gel strength modifier was developed. The effects of component concentrations on bulk gelation properties were investigated. The microstructures of conventional gel and novel gel at different aging time were studied by scanning electron microscopy (SEM), which can provide insight into the mechanism of controllable gel strength. Moreover, sandpack flow experiments were carried out on sandpacks (Φ2.5 × 100 cm) with multi-point pressure taps to investigate whether the novel gel can propagate in porous media. Compared with the conventional gel, SEM results showed that the three-dimensional network structure of novel gel was weakened more seriously, resulting in the decrease of gel strength. Due to decreased gel strength at different aging time, the novel gel can propagate in porous media to achieve in-depth conformance control.     

Swelling-contraction of sodium polyacrylate hydrogels in media with various pH values

The swelling kinetics of sodium polyacrylate gels has been studied in media with different pH values. The pH dependence of the degree of equilibrium swelling shows a maximum at pH 6. The degree of swelling decreases with an increase in the crosslink density, and this dependence follows an S-shaped pattern for all examined gels. When a gel swollen in media with pH 3–13 is dried in air, its contraction is reversible, while in the case of the gel swollen in acidic media at pH < 3, the process is irreversible owing to the replacement of sodium ions with protons.     

Spectrophotometric determination of boron in natural waters and rocks after specific adsorption on sephadex gel

Borate ions are adsorbed on Sephadex G-25 gel from alkaline media and desorbed reversibly into acidic media; the adsorption is ascribed to complex formation between borate and glucose units in the gel matrix. The coexistence of large amounts of salts, e.g. sodium chloride, ammonium chloride, sodium sulfate, and sodium perchlorate, has little effect on the adsorption. The effect of cations which form complexes with borate can be eliminated by the addition of EDTA. Boron present, in natural waters and rocks at lowlevels can be selectively concentrated by means of a gel column and determined spectrophotometrically by the azomethine-H method.     

Ionic liquid–modified cellulosic hydrogels for loading and sustained release of selenourea: an ensuing inhibition of tyrosinase activity

Cellulose-based hydrogel materials were prepared and modified with tannic acid and l-methionine using ionic liquid as the solvent. The gels were prepared to develop a sustained release medium for selenourea (SeU). The drug delivery characteristics of selenourea-loaded cellulose (CSeU), selenourea-loaded tannic acid-modified cellulose (CTSeU), and selenourea-loaded L-methionine-modified cellulose (CMSeU) were investigated in aqueous media and simulated gastric fluid (SGF) media. This modified gel beads have been characterized using field emission scanning electron microscope, X-ray energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, thermogravimetry–differential thermal analysis and swelling properties and compared with those of the unmodified ones. We also investigated the inhibitory effects of SeU released from these gels on the activity of mushroom tyrosinase. Out of all the gel materials, CTSeU showed maximum SeU release both in water and SGF media. However, tyrosinase inhibitory action in PBS medium was comparable for all the three gel materials.     

Highly concentrated (gel) emulsions,versatile reaction media

Highly concentrated (gel) emulsions are characterised by dispersed phase volume fractions exceeding 0.74, the critical value for the most compact packing of monodispersed undistorted spheres. Their structure consists of polyhedral droplets separated by thin films of continuous phase, a structure resembling gas–liquid foams. Their rheological properties vary from elastic to viscoelastic having a gel appearance. One of the most promising applications is their use as reaction media. The recent advances in the preparation of low-density polymeric materials (solid foams, aerogels) are reviewed and new applications are described. These include the preparation of dual meso/macroporous inorganic oxide materials and the use of gel emulsions as alternative to conventional solvent media in chemical and enzyme-catalysed reactions.     

Formation and pharmacological activity of silicon—chitosan-containing glycerohydrogels obtained by biomimetic mineralization

The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications.     

Coreflooding and Pore-Scale Visualization of Foamed Gel Flowed in Porous Network Media

To investigate the mechanisms of enhancing oil recovery and the flow behaviors of foamed gel in porous media, foamed gels with characteristics of excellent strength and viscosity were prepared with polymer, crosslinking agent, foam agent, and formation water. The breakthrough-vacuum method and a rotary viscometer were used to evaluate the strength and viscosity of foamed gel. Coreflooding and pore-level visualization experiments were performed in heterogeneous reservoir models. Laboratory results illustrate that high strength and viscosity of foamed gel can be prepared by 0.15% NJ-8, 0.2% polyacrylamide solution, and 1.5% foaming agent. The strength and viscosity of the foamed gel reached 0.06 MPa and 10,000 MPa · s, respectively. The results of coreflooding experiments in heterogeneous cores show that oil recovery can be improved by approximately 36.9% after injecting 0.3 pore volume of the foamed gel, and enhanced oil recovery is mainly attributed to the improving sweep efficiency of mid- to low-permeability layers. Images of visualization flooding demonstrate that foamed gel exhibits good oil resistance and elasticity when used with crude oil. Furthermore, the new amoeba effect, Jamin effect, fluid-diverting effect, and extruding effect between foamed gel and oil in porous media can enhance oil recovery by improving sweep efficiency.     

Silica‐Gel‐Supported Ceric Ammonium Nitrate (CAN): A Simple and Efficient Solid‐Supported Reagent for Oxidation of Oxygenated Aromatic Compounds to Quinones

A silica‐gel‐supported heterogeneous ceric ammonium nitrate (CAN) reagent has been developed for oxidizing oxygenated aromatics to quinones in nonaqueous media. The advantages of this procedure include excellent yields, mild reaction conditions, nonaqueous media, short reaction times, and easy product isolation.     

New Inexpensive and Selective Sorbent Phases for Rapid Thin Layer Chromatographic Analysis of Metal Ions

Abstract

New sorbent phases have been developed by impregnating silica gel G with different inorganic salts for the analysis of metal ions by thin layer chroma to graphy in carboxylic acids media. Thin layers prepared from silica gel G impregnated with ammonium chloride or barium nitrate show the unusual selectivity towards metal ions in comparison to the thin layers prepared from plain silica gel G or silica gel impregnated with silver nitrate or aluminium nitrate. Many qualitative separations     

Peptide separations by slab gel electrophoresis in pluronic F127 polymer liquid crystals

Proteomics and peptidomics could benefit from simple methods for high-resolution separation of oligopeptides analogous to slab gel electrophoresis of proteins. Gels of Pluronic F127 copolymer surfactant were investigated as media for slab gel electrophoresis of oligopeptides using a trypsin digest of myoglobin. Concentrated solutions of Pluronic F127 are fluid at low temperatures (相似文献   

Dynamic thickening investigation of the gelation process of PAM/PEI system at high temperature and high pressure

The gelation process of organically polymer gel was investigated by dynamic thickening measurements. Rheological measurements were used to evaluate the viscosity of the gel. During the gelation process, high temperature resulted in higher rate of crosslinking. Rigid and stable gel was formed in neutral and alkaline media, and the higher of the pH value, the faster of the gelation process. However, gel could not be formed in acid condition. Moreover, the rate of crosslinking increased with the increase of concentration of polymer and crosslinker. The addition of NH₄Cl elongated the gelation time significantly, but played a negative role in the gel strength, while a rigid gel was formed in the presence of Sodium acetate or trisodium citrate dehydrate. This paper summarizes the results and discusses how various parameters affect the gelation process of the gel.     

Self-oscillating swelling and deswelling of polymer gels

Novel gel systems demonstrating rhythmically pulsatile mechanical motion similar to that of a heartbeat were developed. Self-oscillations of swelling and deswelling for the polymer hydrogels were realized by coupling pH and temperature sensitive hydrogels with a non-linear chemical reaction in the external solution media. The novel gel dynamics exhibiting cyclic and rhythmical oscillations may establish a new concept for functional materials that work under dynamic oscillating states.     

Oxidation of Sulfides with N‐Bromosuccinimide in the Presence of Hydrated Silica Gel

An efficient and highly selective procedure for oxidation of sulfides to sulfoxides with N‐bromosuccinimide (NBS) in the presence of hydrated silica gel has been developed. Hydrated silica gel supplies the water necessary for decomposition of the intermediate bromosulfonium salt to the product, allowing the reaction to employ a nonaqueous media. Also, this procedure has increased the scope of the reaction by oxidizing a wider variety of sulfides, which was not possible until now.     

Room temperature-stable electride as a synthetic organic reagent: application to pinacol coupling reaction in aqueous media

Room temperature-stable inorganic electride [Ca(24)Al(28)O(68)](4+)4e(-) was employed for a pinacol coupling reaction in aqueous media. Ca-Al-O gel formed by the destruction of the crystal structure of an electride by water media played a key role in transferring the electron to electrophilic aldehydes. Aromatic aldehydes reacted smoothly with moderate to high yields.     

Highly concentrated emulsions as novel reaction media

Synthesis of a cationic surfactant, N^α-lauroyl arginine methyl ester hydrochloride (LAM) has been carried out in gel emulsions of the system water/C₁₄E₄/decane. The yields of LAM synthesized in gel emulsions are comparable to those obtained in conventional dimethylformamide (DMF) media. The rate of LAM formation is faster in gel emulsions at short times, the reaction taking place without mechanical energy input and at 25°C.     

Polyacrylamide gel plugs enabling 2-D microfluidic protein separations via isoelectric focusing and multiplexed sodium dodecyl sulfate gel electrophoresis

In situ photopolymerized polyacrylamide (PAAm) gel plugs are used as hydrodynamic flow control elements in a multidimensional microfluidic system combining IEF and parallel SDS gel electrophoresis for protein separations. The PAAm gel plugs offer a simple method to reduce undesirable bulk flow and limit reagent/sample crosstalk without placing unwanted constraints on the selection of separation media, and without hindering electrokinetic ion migration in the complex microchannel network. In addition to improving separation reproducibility, the discrete gel plugs integrated into critical regions of the chip enable the use of a simple pressure-driven sample injection method which avoids electrokinetic injection bias. The gel plugs also serve to greatly simplify operation of the spatially multiplexed system by eliminating the need for complex external fluidic interfaces. Using an FITC-labeled Escherichia coli cell lysate as a model system, the use of gel plugs is shown to significantly enhance separation reproducibility in a chip containing five parallel CGE channels, with an average variance in peak elution time of only 4.1%.     

Reinforced superabsorbent polyacrylamide hydrogels

The ability of linear stiff-chain poly(sodium p-phenylenesulfonate) to self-assemble in aqueous media with the formation of rodlike aggregates was used to immobilize it in a polyacrylamide network without covalent bonding. It was shown that polyelectrolyte rods impart simultaneously two useful properties to the gel: higher ability to absorb water and higher mechanical strength. The counterions of charged rods ensure the enhancement of the absorption capacity of the gel, while stiff elements strengthen the gel. This makes such systems potentially promising as superabsorbent materials.     

Simultaneous Ferguson plot analysis, using electrophoresis on a single agarose pore gradient gel, of DNA fragments contained in a mixture.

A recent study has demonstrated the feasibility of obtaining Ferguson plots in agarose gel electrophoresis, using a single pore gradient gel. We now report three remedies for defects in the previous experimental approach: (i) UV-absorbing media for density stabilization of the gel is avoided by replacing 5-(N-2,3-dihydroxypropylacetamido)-2,4,6-triiodo-N,N'-bis(2,3-dihy droxypropyl) isophthalamide (Nycodenz) with heavy water; this renders the method applicable to ethidium bromide-labeled DNA. (ii) The density stabilizing medium is kept from having an effect on field strength. (iii) Data collection by uninterrupted time-lapse photography is possible by using an apparatus with a quartz window. These three measures make the method practical for the gel electrophoretic identification and physical characterization of DNA species, potentially up to 50 kb in size.