Mullite Formation of Colloidal Matrix Hybrid Aluminosilicate Gel

A hybrid aluminosilicate gel composed of a relatively small amount of single-phase gel in a diphasic matrix forms when a diphasic gel of AlOOH and SiO₂ is heated at 700°C for 7 h. The formation of mullite from this hybrid gel is a sequential conversion process, but not of two entirely independent processes of single-phase gel and diphasic gel. The high commencement temperature (>1250°C) of mullite formation from this hybrid gel indicates that the dominant component (diphasic component) strongly affects or controls the mullite transformation behavior of the hybrid gel. The apparent activation energy for mullitization from this hybrid gel is 846 kJ/mol, which is somewhat lower than that of pure diphasic gel but much higher than that of pure single-phase gel.     

Na~+浓度对反应体系成胶特性及SiO_2凝胶粉末性能的影响

以水玻璃为原料，乙酸乙酯为潜伏酸试剂，采用溶胶—凝胶法制备超细二氧化硅凝胶粉末。研究了成胶反应过程中Ｎａ＋ 浓度对反应体系成胶特性及最终所得二氧化硅凝胶粉末性能的影响，并用透射电镜和氮气物理吸附实验手段对粉末的有关性能进行了测试表征     

Dissolvable disulphide-polyacrylamide gels for the electrophoretic analysis of chromosomal proteins and for affino-electrophoresis of thiol-proteins

A discontinous gel system is described that is composed of the dissolvable, disulphide-containing acrylamide gel developed by Hansen and the acetic acid-urea gel as introduced by Panyim and Chalkley. A cleavable SDS gel is used for the identification and an initial separation of proteins according to molecular weight; it is then solubilized by tris-mercaptoethanol and layered on the acidic gel, where it functions as a stacking gel with a pronounced concentrating capacity. The final resolution obtained by this technique permits the identification of single protein species according to the degree of enzymatic modification (acetylation and phosphorylation). Side reactions of the disulphide gel matrix with thiol proteins are discussed and other possible application are considered.     

Influence of gel content on the physical properties of unfilled and carbon black filled natural rubber vulcanizates

Recently, gel content has been considered as a standard property for evaluating commercial grade natural rubber (NR). In this study, NR containing various amounts of gel was prepared by accelerated storage hardening as a model to clarify the influence of gel content on the physical properties of both unfilled and carbon black filled vulcanizates. Furthermore, the NR samples were investigated to determine the effect of gel fraction on Mooney viscosity and the structure of the gel after mastication. The results revealed that Mooney viscosity was related to the percentage of gel fraction that has been proven to be the result of interactions between proteins and phospholipids at chain ends. After mastication, although the gel fraction of NR can be decomposed to ∼0% w/w, the interactions of proteins and phospholipids at the chain ends still existed, corresponding to the gel content of the raw rubber. In the case of unfilled vulcanizates, the gel content showed no effect on cure characteristics, crosslink density and ultimate tensile strength, whereas the upturn of stress occurred at a smaller strain when the gel content increased. However, in the case of carbon black filled vulcanizates, the gel content played a dominant role in the carbon black dispersion, which was poorer when gel content increased, contributing to a decrease of crosslink density and ultimate tensile strength.     

制备方法对Pd催化剂上丙烯选择性还原NO反应性能的影响

 采用三种不同方法制备了氧化铝负载的Pd催化剂．比表面积测定\r\n结果表明,与浸渍法相比,溶胶－凝胶加浸渍法和溶胶－凝胶法制备的\r\nPd／Al2O3样品具有较大的比表面积,但抗烧结性能不佳．其中采用溶\r\n胶－凝胶法制备的样品中,由于Pd分散于体相中,表面的活性位相对较\r\n少,造成催化剂在NO选择性还原反应中的活性较差;而将Pd浸渍于溶胶\r\n－凝胶法制得的Al2O3载体上所获得的催化剂比表面积较大,活性较好\r\n．添加CeO2的样品活性总体上比Pd／Al2O3样品高．其中采用溶胶－凝\r\n胶法制备的样品比表面积不大,并且XRD数据表明Al2O3和CeO2是高度分\r\n散并均匀地搀杂在一起的,不象在浸渍法制备的样品中那样以大晶粒的\r\n形式存在,因而CeO2的助剂作用没有充分体现出来,催化剂的活性比浸\r\n渍法制备的样品差一些．     

The Evaluation of Healing Properties of Galium verum-Based Oral Gel in Aphthous Stomatitis in Rats

Although oral ulcers represent one of the most frequent oral mucosal diseases, the available treatment is not sufficient to provide complete ulcer recovery without side-effects. Therefore, the aim of our study was to prepare a mucoadhesive oral gel based on Galium verum ethanol extract (GVL gel) and reveal its healing effects in the model of aphthous stomatitis in rats. Rats with oral ulcers were divided into the following groups: control (untreated), gel base (ulcer was treated with the gel base, three times per day for 10 days), and GVL gel group (the ulcer was treated with GVL gel in the same way as the gel base). Animals from each group were sacrificed on days 0, 3, 6, and 10 for collecting blood and ulcer tissue samples. Healing properties of oral gel were determined by clinical evaluation, as well as biochemical and histopathological examinations. Our findings suggest a significant decrease in the ulcer size in GVL gel group, with healing effects achieved through the alleviation of oxidative stress, reduction in COX-2 immunopositivity, and increase in collagen content in buccal tissue. Significant ulcer repairing potential of GVL gel highlights this oral mucoadhesive gel as a promising tool for prevention and treatment of RAS.     

Study of radiation-induced polymerization of vinyl monomers adsorbed on inorganic substances. VII. Effect of pretreatment temperature of silica gel on styrene–silica gel system

To investigate the reaction mechanism of radiation-induced polymerization of styrene adsorbed on silica gel, the effect of pretreatment temperature of silica gel was studied. Preheating of silica gel was carried out at 200, 500, and 800°C. The number of silanol groups of silica gel surface decreased as preheating temperature increased. The rate of polymerization on the silica gel preheated at 500°C was faster than that at 200°C, but the polymerization rate on the silica gel preheated at 800°C was the lowest. These results suggest that rate of polymerization on the silica gel is affected by the conditions of silica gel surface such as the number of silanol groups and the pore size. At the same monomer conversion, percent grafting decreased as preheating temperature of silica gel increased. The GPC spectra of both graft polymers and homopolymers have two peaks at all preheating temperatures. The monomer conversion of low molecular weight peaks of graft polymers decreased as preheating temperature of silica gel increased. This result suggests that there is a probability that the grafting sites of low molecular weight peaks of graft polymers somehow interact with silanol groups.     

Effect of surface character of filler particles on rheology of heat-set whey protein emulsion gels

Small-deformation and large-deformation rheological properties of heat-set whey protein emulsion gels containing active and inactive filler particles have been investigated using a controlled stress rheometer. The results suggest that the contributions to the gel network are quite different for pure protein gels and emulsion gels having similar storage moduli. An emulsion gel containing inactive filler has a larger phase angle due to the energy dissipation at the ‘slippery’ droplet surface under the influence of the applied shear stress. The large-deformation rheology of the heat-set protein gel has behaviour intermediate between that for an entropic biopolymer gel and that for a particle gel. Emulsion gels containing active or inactive fillers behave more like typical particle gel systems.     

Potential application of poly(N-isopropylacrylamide) gel containing polymeric micelles to drug delivery systems

We have investigated rapidly thermo-responsive NIPA gel containing polymer surfactant PMDP (NIPA-PMDP gel) as a potential drug carrier using (+)-l-ascorbic acid as a model drug. In the NIPA-PMDP gel system micelles of polymer surfactant PMDP are trapped by the entanglement of polymer chains inside the gel networks. Therefore, in principle the gel system tightly stores targeted drug in the micelles and rapidly releases controlled amount of the drug by switching on-off of external stimuli such as temperature or infrared laser beam. In our investigation on release profile, the NIPA-PMDP gel system showed completely different releasing behavior from that of the conventional NIPA gel. The NIPA-PMDP gel released rapidly all loaded (+)-l-ascorbic acid above the phase transition temperature (ca. 34 degrees C), while slowly released the corresponding amount of the drug below the temperature. In contrast, the conventional NIPA gel released more slowly limited amount of the drug above the phase transition temperature while similarly did to the NIPA-PMDP gel below the temperature. The release profile of the NIPA-PMDP gel seems to be governed by only kinetics of volume phase transition of the gel network but not by the hydrophobic domains of the micelles probably because of too hydrophilic nature of (+)-l-ascorbic acid.     

Crosslinked poly(N-isopropylacrylamide) gel for electrophoretic separation and recovery of substances

Crosslinked poly(N-isopropylacrylamide) gel was tested on the feasibility for a preparative electrophoretic matrix. Horse heart myoglobin and bovine hemoglobin were well separated on the gel matrix electrophoretically by molecular sieving effect of the gel network. Relative mobilities of those proteins in the gel were larger than those in a crosslinked polyacrylamide gel of the same polymer concentration. After the separation, the protein-containing portion of the gel underwent swelling at 4°C and deswelling at 37°C, alternatively. As a result of the deswelling, each protein was recovered in a discharged solution out of the gel at almost 100% yield.     

Flow of water through channels filled with deformable polymer gels

A mathematical model is developed for the flow of water through a channel impregnated with a polymer gel that is treated as an elastic and deformable porous medium. The model uses a Brinkman equation along with an experimentally observed velocity-dependent permeability. Numerical and approximate analytical solutions are given. These results show that the gel intrinsic properties, i.e., gel reference permeability and elastic index, control the water flow. First, the permeability of water flow through the gel increases with an increase of gel reference permeability. Second, the velocity of water decreases when the gel velocity exponent increases. Our theoretical results show that the velocity-dependent permeability of water flow through polymer gels is in fact an intrinsic property of the gel rather than a property of the channel or some interaction between the gel and the pore walls.     

采用一锅法制备量子点/琼脂纳米复合凝胶

以天然高分子琼脂为稳定剂,采用简单便捷的一锅法制备Mn掺杂ZnS量子点/琼脂纳米复合凝胶,琼脂不仅作为制备量子点的稳定剂,同时也是纳米复合凝胶的主要成分。对该纳米复合凝胶中量子点的化学结构和尺寸大小进行了表征,并对纳米复合凝胶的荧光性能和凝胶性能进行了研究。实验结果表明,制备得到的纳米复合凝胶均一稳定,在302 nm紫外光下呈现十分明显的橙红色荧光。在该纳米复合凝胶的透射电子显微镜（TEM）表征中可以观察到大小比较均一、粒径为3 nm左右的纳米粒子,光谱分析结果进一步证实纳米复合凝胶中存在Mn掺杂ZnS量子点。该纳米复合凝胶不仅具有良好的荧光性能,还具有温度刺激响应性可逆溶胶-凝胶转变性能,同时具有较高的溶胶转变温度和较好的温度稳定性。利用这些性能特点,可以方便地制备纳米复合凝胶小球。此外,该纳米复合凝胶还可以被潜在应用于金属离子的荧光检测分析领域。     

Study of radiation-induced polymerization of vinyl monomers adsorbed on inorganic substances. VIII. Polymerization of styrene and methyl methacrylate adsorbed on aerosil

Aerosil is silica having a purity which is very high compared with that of silica gel and having, unlike silica gel, no micropores. To investigate the effects of impurities and micropores on the radiation-induced polymerization of styrene and methyl methacrylate adsorbed on silica gel, the radiation-induced polymerization of styrene and methyl methacrylate adsorbed on Aerosil was carried out. The results of both the styrene–Aerosil 300 system and the methyl methacrylate–Aerosil 300 system were similar to those of the styrene–silica gel and methyl methacrylate–silica gel systems, respectively. This suggests that in the radiation-induced polymerization of both styrene–silica gel and methyl methacrylate–silica gel systems the impurity and the presence of micropores have almost no effects on the reaction mechanism. The effect of aluminum as an impurity was investigated on the styrene–Aerosil MOX 170 system. It was found that aluminum accelerated the cationic polymerization.     

Localization of separated protein bands in unstained electrophoresed polyacrylamide gradient slab gel.

Polyacrylamide gel electrophoresis has become the most widely used separation method in biological science. Once electrophoresis is complete the protein bands must be localized prior to excision. A zig-zag gel cutter is described which cuts a strip of gel from the side of a slab gradient gel or a gel of uniform concentration in peaks and valleys. The location of the protein of interest is determined by counting the number of peaks on the stained side strip. The portion of the unstained gel corresponding to the same count (number of valleys) is cut to recover the protein of interest from the main gel for further manipulations.     

The controlled release of a drug from biodegradable chitosan gel beads

Chitosan (CS) forms a gel in solutions with a pH above 12, and the gelation occurs at pH of about 9 in 10% amino acid solutions. In this paper, we investigated the enzymatic degradation and the drug release profile of this novel CS gel beads. The degradability of the CS gel beads was affected by the CS properties, e.g. the degree of deacetylation. The release of prednisolone (PS), as a model drug, from the CS gel beads was sustained significantly compared with the gel prepared with NaOH only. However, the release was not able to be sustained by the increment of NaOH concentration in the solution employed for the preparation of CS gel beads. We also investigated the control of drug release from CS gel beads by application of a complex formed between chondroitin sulfate (Cho) and CS. The release of PS from the CS gel beads treated with Cho was prolonged, and the release pattern was not affected by the treatment time. The time to 50% drug release was about 5 min with PS powder, about 200 min in CS gel beads with 10% glycine (Gly) (pH 9.0), and about 330 min in the CS gel beads with 10% Gly (pH 9.0) treated with Cho. Thus CS gel beads appear promising as a vehicle for sustained drug delivery, and the degradation of CS gel beads may be controlled by the degree of deacetylation of CS.     

Dynamic light scattering study of the dynamics of a gelled polymeric micellar system

The dynamics of the E(92)B(18)/water system are studied by dynamic light scattering (DLS) in the liquid, soft gel, and hard gel phases. Both the liquid and the soft gel phases are micellar phases, although the structural order is higher in the soft gel phase than in the liquid phase. The hard gel phase corresponds to a face-centered cubic arrangement of micelles. DLS results show that the dilute liquid phase is characterized by a single characteristic time tau(1) associated with the diffusion of the micelles. In addition, a second characteristic time tau(2) associated with the presence of micellar clusters in the system is identified in the concentrated liquid and in the soft gel phases. According to these results, DLS suggests that the structure of the soft gel phase comprises micellar clusters coexisting with micellar fluid, in good agreement with hypotheses from our previous work. The dynamics of the system slows down as the hard gel phase is approached and a plateau is observed in the DLS correlation function. The structure of the hard gel is "softened" upon increasing temperature and/or decreasing concentration.     

琼脂糖性质对凝胶电泳法分离金属性和半导体性单壁碳纳米管的影响

利用琼脂糖凝胶电泳分离单壁碳纳米管(SWCNTs)技术, 考察了MB, Agarose, Agarose B和LRU 4种琼脂糖对SWCNTs分离效率的影响. 紫外-可见-近红外(UV-Vis-NIR)吸收光谱研究结果表明, 不同的琼脂糖对SWCNTs中s-SWCNTs的分离效率影响较小, 而对m-SWCNTs的分离效率影响较大. 分析4种琼脂糖凝胶的凝胶强度和凝胶网孔尺寸等发现, 影响SWCNTs中m-SWCNTs分离效率的主要因素是琼脂糖的凝胶强度和琼脂糖凝胶形成的网孔尺寸, 小的凝胶网孔尺寸有利于m-SWCNTs富集, 高凝胶强度则不利于其富集.     

Laser light scattering study of polyacrylamide gels

Laser light scattering experiments with polyacrylamide gels containing diffusing bovine plasma albumin are described. Complete heterodyne beating has not been assumed, and an account is given of a novel method for finding the degree of spectral broadening by scanning angles of scatter while measuring the temporal autocorrelation function. Results obtained by this method for polyacrylamide gels and un-cross-linked solutions in the absence of diffusing protein, are compared with those of other authors. In the presence of the protein there is a complex interaction between the diffusion coefficient of the protein and the coefficient associated with the diffusing fluctuations in segment density of polyacrylamide. The diffusing protein dominates at low gel concentrations, and the gel density fluctuations dominates at high gel concentrations. It is proposed that the protein preferentially occupies the less dense regions of the gel, so that at low gel concentrations, where it diffuses faster than the gel fluctuations, it tends to cancel them out, whereas at high gel concentrations where the protein is highly impeded by the gel structure, it tends to be carried along by the gel density fluctuations.     

Preliminary investigation of a new type of propylene based gel dosimeter (DEMBIG)

Radiotherapy widely uses the polymer gel dosimeter. The advantage of polymer gel dosimetry is the mapped 3D absorbed dose distribution that other dosimeters cannot achieve. The Acrylamide (AAm) is a frequently used monomer; however, the extreme toxicity of Acrylamide (ORL-RAT LD50: 124 mg/kg) raises a concern. Therefore, this study developed a new type of Propylene acid based gel dosimeter, named DEMBIG gel. The following outlines the aim of this study: (1) using two-point formulation to find the optimal scan parameter of MRI according to the best sensitivity and linearity (correlation coefficient) of DEMBIG gel, (2) using the optimal scan parameter of MRI to observe the properties of DEMBIG gel, and (3) verifying the three-dimensional (3D) dose distributions of radiotherapy. This study obtained three major results: 1. The scan protocol of MRI was established. 2. The preliminary results of DEMBIG gel were: (1) The range of absorbed dose of DEMBIG gel: 0–20 Gy. (2) The sensitivity and correlation coefficient of DEMBIG gel at verification as slope: 0.181 sGy^?1, R ²:0.997. (3) There is no energy dependency of the DEMBIG gel. 3. The dose difference was 3% in the three-dimensional (3D) isocenter dose in clinical radiotherapy. These data show that DEMBIG gel is a potential candidate for the 3D dosimeter.     

Polyacrylamide gel method: synthesis and property of BeO nanopowders

Effects of monomer (AM) concentration, monomer/crosslinker (AM/MBAM) ratio and salt concentration on the thermal behavior of precursor gel and the properties of BeO nanopowder synthesized by polyacrylamide gel method were investigated. The decomposition process of precursor gel was also studied. The decomposition process of precursor gel is that, first, the extraction of free and crystallized water, and then the thermal degradation of polymeric network under temperature higher than 600 °C, final, the decomposition of nanoscale beryllium sulfate to BeO nanopowder. As the monomer concentration increases, the calcination temperature of precursor gel decreases due to more compact network structure of gel and thus smaller size of salt in nanocaves in gel. The average particle size of nanopowder reduces correspondingly. The AM/MBAM ratio also has significant effect on the thermal behavior of precursor gel and the average particle size of product. When the ratio of AM to MBAM is 6, the calcination temperature of precursor gel is the lowest, the average particle size of powders is the smallest, because the network structures of gel is the tightest and thus the sizes of salts in precursor gels are the smallest. As the AM/MBAM ratio deviates from this value, the network structures of gel becomes looser and thus the size of salt in precursor gel becomes larger, so the calcination temperature increases and the average particle size of powders becomes larger certainly. For the same reason, both the calcination temperature and the average particle size of powders increases with increasing the salt concentration. The synthesis conditions have no effect on the particle size distribution of the final product due to the natural random distribution of porosity in gel.