Gel Slurry Research Articles

Preparation and Rheological Properties of the PVA/CMC/Gel Composite for Mining.

A composite gel material with an interpenetrating network structure was formed using the chemical cross-linking method. The viscosity, yield stress, and thixotropy of a poly(vinyl alcohol)/carboxymethyl cellulose/gelatin (PVA/CMC/Gel) composite gel slurry with different ratios were tested using a viscometer, and the interaction between the surface of the gelling agent and the cross-linking agent was analyzed by calculating the frontline orbital energy of a single polymer material molecule. The seepage diffusion characteristics of the composite gel in a goaf were then studied through a numerical simulation. The results indicate that the PVA/CMC/Gel composite gel exhibits shear thinning behavior following the power law model and behaves as a pseudoplastic fluid. The optimal ratio for the composite gel at 30 °C is determined as follows: 30 wt % for the gelling agent (PVA/(Gel + CMC) = 20:10), 4 wt % for the cross-linking agent, 3.09 wt % for the carbide slag, 7.5 wt % for the alcohol amine solution, and 0.5% sodium dodecyl sulfonate + 0.1% alkyl glycoside for the foaming agent. Gel exhibits the lowest energy band gap (0.096 eV), indicating strong reaction activity and strong reaction with the cross-linking agent (sodium tetraborate). PVA has the largest energy band gap (0.238 eV), strong molecular stability, and weak reaction with the cross-linking agent (sodium tetraborate). When the dip angle of the goaf is 4° and the injection time is 40 min, the composite gel tends to diffuse more easily along the dip. The investigation into the rheological properties of the PVA/CMC/Gel composite gel holds significant importance in the design of coal mine pipeline transportation and understanding diffusion flow in goaf.

Description of a new laboratory evaluation method of interdental brush abrasion as a clinical hazard.

To simulate the abrasive potential of an interdental brush when applied with toothpastes and prophylactic gels/solutions in a novel laboratory brushing simulation set-up. A brushing device was customized to treat dentin samples mimicking a simplified interdental space with an interdental brush (ISO 2). The brushing, that is, 7200 strokes for 1 h, was performed with artificial saliva (control), a povidone-iodine solution, and slurries of chlorhexidine and fluoride gels as well as three toothpastes with different RDA values ranging from 29 to 100, respectively. The loss of dentin was profilometrically assessed and compared with ANOVA and Fishers LSD. While artificial saliva as control, the solution and the gel slurries showed no measurable dentin loss, toothpastes resulted in a measurable linear surface damage with respect to the actual intrinsic RDA values and ranged from 12.6 to 26.5 μm (p < 0.001). Any interdental cleaning product should be tailored and carefully instructed. Any over- and misuse should be avoided, which applies especially to the use of interdental brushes in combination with abrasive toothpastes.

Heat transfer characteristics in turbulent flow and flow patterns of PCM slurry using super-hydrophobic gel particles

An experimental study on the characteristics of heat transfer in turbulent flow and the flow patterns of an organic phase change marerial (PCM) slurry was conducted to investigate the latent heat transportation. As a PCM slurry, the particles of the super-hydrophobic marshmallow-like gel, adsorbing hexadecane on their surface, were dispersed in sodium carboxymethyl cellulose (CMC) solution. Hexadecane is a PCM with a melting point of 17.5 °C, and latent heat of 226.5 kJ·kg−1. For the heat transfer measurement, a double-tube heat exchanger with an inner tube with an inner diameter of 8 mm was used. The results demonstrated that the heat transfer of the marshmallow-like slurry with hexadecane was 1.5 times higher than that of Newtonian fluids. From the pressure drop in the test section, the heat transport efficiency was calculated, which was also higher than that of Newtonian fluids. Furthermore, the flow patterns of the marshmallow-like gel slurries were investigated by varying the CMC concentration and flow velocity. From the results, four patterns of particle dispersion in the flow were observed. The most dispersed flow pattern was observed with all CMC concentrations when the flow velocity was sufficiently high. Based on these results, it was concluded that heat transportation by the marshmallow-like gel slurry is promising.

Permeation-diffusion characteristics and air-leakage blocking mechanism for the fire-extinguishing inorganic gel flows in loose broken coal particles

• Three various stages of gel slurry transports in loose coal particles were acquired experimentally and numerically. • Investigated the influence of grouting pressure and coal voids on permeation, diffusion, and filtration of gel. • Theoretically revealed the mechanisms for permeation-diffusion and wind-plugging of gel. Fire prevention with inorganic gel is the most efficient approach to the prevention and control for spontaneous fires of loose coal piles. This work explores the impact of grouting pressures on the seepage, diffusion, and filtration of fire-extinguishing inorganic gel in loose broken coal particles with different voids. Firstly, an experimental system for investigating the filtering effect, permeation behaviors, and diffusion modes for the permeation grouting of inorganic gel in loose coal particles was developed. A 2D discrete element numerical modeling was then performed to probe the intuitive features and underlying mechanisms in the experimental observation, with the numerical modeling matching fairly well with the experimental findings. Results showed that the entire permeation-diffusion process presents obvious stage characteristics with permeation-compaction, permeation-splitting flow, compacting-splitting flow-permeation, and the diffusion distance of gel slurry front increased exponentially while the diffusion velocity decreased initially and then retained stable gradually. Meanwhile, the permeability coefficient of gel slurry showed spatial–temporal properties affected by the filtration effect. Besides, the increasing grouting pressure would promote the filtration effect of gel slurry in loose coal particles, while the decreasing coal sample voids pose an opposite tendency. Under lower grouting pressures (P ≤ 0.3 MPa), the bubble radius increased slightly, and the variation in diffusion distance was faint with the increase in grouting pressure. Under higher grouting pressures (P ≥ 0.3 MPa), the bubble radius increased obviously, and the variation in diffusion distance increased obviously with the increase in grouting pressure, demonstrating that increasing grouting pressure would increase the diffusion distance and diffusion velocity significantly. In addition, increasing the gel grouting pressure and coal voids would result in a non-linear increase in the diffusion distance and diffusion velocity of the gel slurry front, which would also shorten the time required for coal particles to reach the saturation state. Moreover, the mechanisms of seepage-diffusion and wind-plugging of gel slurry in loose coal particles were discussed theoretically. This work would assist us in interpreting and illuminating the seepage-diffusion mechanism and macro–micro characteristics of inorganic gel for high-temperature loose broken coal particles.

Comprehensive evaluation of a novel re-crosslinkable preformed particle gel for the water management of reservoir with concentrated divalent ions

As one of the most widely used technology to ameliorate the reservoir's heterogeneity, polymer gels have been applied for more than 60 years. However, how to plug fractured reservoirs with significant abnormal features, high temperature and high salinity, especially the divalent cations, is still a challenging target. This work systematically evaluated a novel salt-resistant re-crosslinkable preformed particle gel (SR-RPPG) designed for fractured reservoirs with excellent salt resistance (up to 5 % CaCl2). We evaluated the swelling kinetics, thermal stability and plugging efficiency of this SR-RPPG. We assessed the swelling kinetic and re-crosslinking behavior of the SR-RPPG through the bottle test method. High temperature-resistant glass tubes with thermally stable O-rings were employed to evaluate the long-term thermal stability of the SR-RPPG product, and the testing lasted for over 200 days. A fractured model was used to assess the plugging efficiency of the SR-RPPG product. Results showed that the SR-RPPG could swell more than 30 times its original volume in 5 % CaCl2 and a middle east formation water. Besides, the SR-RPPG gel slurry can re-crosslink to form a rubber-like elastic bulk gel at 80–100 °C, and the elastic modulus of the re-crosslinked bulk gel can reach up to 1350 Pa with a swelling ratio of 10. The SR-RPPG prepared in 1 % NaCl, 2 % KCl, middle east formation water and 5 % CaCl2 with a swelling ratio of 10 have been stable for over 200 days at 100 °C. The core flooding test demonstrated that the SR-RPPG could efficiently block the open fractures, and the water breakthrough pressure gradient reached 927.30 psi/ft (20.98 MPa/m).

Test and Microstructural Analysis of a Steel Slag Cement-Based Material Using the Response Surface Method.

In this study, the silica fume replacement rate, fly ash replacement rate, and curing temperature were regarded as the independent variables, and the compressive and flexural strengths were regarded as the response values. The response surface method was used to construct the response surface polynomial regression model and obtain the optimal preparation parameters of a steel slag cement-based gel slurry (SCGS). The univariate and multivariate effects on the SCGS’s strength were investigated via analysis of variance and a three-dimensional surface model, and the hydration products and strength development law were characterized via scanning electron microscopy and X-ray diffraction. The actual compressive strengths at 3 and 28 d of age were 31.78 and 53.94 MPa, respectively, which were close to the predicted values (32.59 and 55.81 MPa, respectively), demonstrating that the optimized strengths were accurate and reliable. Further, the hydration reaction rate of SiO2 in the silica fume and the physical filling effect of the inert components of fly ash and steel slag under the optimal parameters were the key factors for the early strength of the material. Moreover, continuous C3S hydration in steel slag and the continuous excitation of the volcanic ash properties of fly ash were important factors for the later strength.

Experimental Study and Application of LASC Foamed Concrete to Create Airtight Walls in Coal Mines

If an airtight wall in a coal mine leaks air, it may cause spontaneous combustion of residual coal in the gob and even cause a full‐blown fire or gas explosion. In this study, we developed a new type of foamed concrete, low‐alkalinity sulphoaluminate cement (LASC), to control air leakage. The performance of filling materials that were prepared by adding various dosages of foam to LASC was studied. The longer the curing period for the foam filling material of LASC, the better the crystallinity of the hydrated product. With an increasing foam dosage, the initial setting time gradually extends while the fluidity of the foam slurry decreases. The bubble rate of the filling material increases and the density decreases with increasing foam dosage. The compressive strength of the LASC filling material decreases with increasing foam dosage and increases with increasing curing time. In the LASC filling materials, the optimal volume ratio of foam dosage to gel slurry is 2. The crystallinity, initial gel time, and compressive strength of the LASC foaming materials are better than those of ordinary Portland cement (OPC) foaming materials. When the crossheading is filled with LASC foam cement, the deformation of the surrounding rock is less than 19 cm, and the air leakage prevention is better than that achieved with loess and fly‐ash‐cement foam. Thus, the proposed LASC foam material can be applied to the filling of the crossheading to efficiently prevent leakage in underground coal mines.

Influence of Hydrophobicity of Backbone Polymer in Thermo-responsive Hydrogel with Immobilized Amine on Cycle Capacity for Absorption and Recovery of CO2.

The chemisorption process with amines is the major separation and recovery method of CO2 because of its high processing capacity and simplicity. However, large energy consumption for the desorption of CO2 is also associated with the process. To develop a separation and recovery process that is capable of desorbing CO2 at low temperatures and with minimal energy consumption, polymer hydrogels with a lower critical solution temperature (LCST) polymer network and amine groups immobilized in the polymer network of the hydrogels were exploited. Thermo-responsive amine gels with a series of hydrophobicity of polymer networks were systematically synthesized, and the influence of the hydrophobicity of the gels on the CO2 desorption temperature and cycle capacity (CO2 amount that can be separated and recovered by 1 cycle of temperature swing operation) was investigated using slurries with the series of gels. A significant decrease in the CO2 desorption temperature and increase in the cycle capacity occurred simultaneously by lowering the LCST of the gels via hydrophobisation of the polymer network. Based on an equilibrium adsorption model representing the CO2 separation and a recovery system with the gel slurries, an analysis of the system dynamics was performed in order to understand the recovery mechanism in the process.

Recovery of CO2 Using Temperature‐Responsive Amine Gel Slurry

Temperature‐responsive change in pKa of tertiary amines that are immobilized in the cross‐linked LCST polymer chains (temperature‐responsive amine gels) is applied to the separation and recovery of CO2 gas. Adsorption and desorption behaviors of CO2 gas on the temperature‐responsive amine gels are experimentally investigated using a temperature‐controlled gas‐liquid contact reactor with the slurries of the gels. Based on the control of the swelling volume of the temperature‐responsive gels via temperature swing, pKa of the amines in the gels was controlled. Influences of monomer composition in the gels and solvent composition in the slurry on the performance of CO2 recovery were investigated.

Efficacy of Aloe Vera as A Pulpotomy Agent in Children Primary Teeth: Clinical and Radiographic Studies

Aim: The present study was conducted to compare effects of acemannan and formocresol as pulp-dressing agents clinically and radiographically in primary teeth. Materials and Methods: Aloe vera gel high molecular weight fractions (AHM) containing native ingredients of polysaccharide (acemannan) and glycoprotein (verectin) were obtained by using the patented hyper dry system after washing out coloured materials with running water from Aloe vera gel slurry. Thirty healthy children aged from four to eight years, they were selected from patients attending outpatient clinic of Pediatric Dentistry department. Each child had at least bilateral deep carious lower primary molar indicated for pulpotomy. Pulpotomy was done in both groups; where group I treated by AHM, acemannan, as a dressing agent while formocresol used as a dressing agent in group II. The study cases were recalled after three, six, nine and twelve months for clinical and radiographic evaluation. Results: The overall clinical success rate of acemannan group was 96.5%, while formocresol group was 89.6%. The two groups were clinically successful with no statistically significant difference between them (p = 0.148). The radiographic success rate of acemannan group was 93.1%, while for formocresol group was 86.2%. There was no statistically significant difference between the two groups (p = 0.385). Conclusion: The acemannan showed higher clinical and radiographic success rate compared to formocresol as a pulpulpotomy agent in molars. It can be considered as an acceptable biomaterial for vital pulp therapy of deep caries in primary teeth.

Experimental Study, Characterization and Application of Starch-Graft-Acrylamide Gel for Plugging

During underbalance drilling, completion and workover wells, plugging channeling, blocking preformation and plugging formation water are inevitable problems. Gel is one of the most effective and convenient method to solve the problem. In this study, modified starch gel is synthesized, investigated experimentally and improved for efficient oil and gas field applications. The gel slurry is composed of starch (3.6 wt.%), initiator (0.02 wt.%), acrylamide (14.4 wt.%), cross-linking agent (4.7 wt.%), all of the components are mixed together with water at pH 10 – 11 which viscosity is as low as 35 – 82 mPa.s and desired to form gel. Here the effects of the components, reaction temperature and pH on gelation time and gel viscosity are systematically investigated, and the results showed that the gelation can be controlled in a wide range 30 – 120 min efficiently by pH and initiator. Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) are employed to study the molecular structure and microstructure of the gel, respectively. A compact three-dimensional network structure was formed in the gel, which contribute to a good adhesion. The gel has been successfully used in shale gas field which provides a reference for sealing other similar high formation pressure under unbalanced workover treatment. DOI: http://dx.doi.org/10.5755/j01.ms.24.4.18565

Preparation and performance evaluation of silica gel/tricalcium silicate composite slurry for 3D printing

Tricalcium silicate (C3S) has excellent biocompatibility and osteoconductivity, however its use in implant scaffold manufacture is primarily achieved through hand kneading, making it difficult to accurately control the resulting size and shape. 3D printing is a rapid prototyping technology that can be used to accurately manufacture scaffolds with complex shapes. However, tricalcium silicate reacts rapidly with water, and the slurry solidifies quickly, making it impossible to use it to synthesize complex structures by 3D printing. In this study, a Tricalcium Silicate / Silica gel slurry suitable for 3D printing was prepared by combining silica gel (SG) particles and hydroxypropyl methylcellulose (HPMC) with Tricalcium Silicate (C3S). The effect of HPMC solution concentration on powder agglomeration was studied. The printability of the C3S/SG slurry was tested by measuring the printable time. The mechanical properties and in vitro degradation rate of C3S/SG and changes in composition during the degradation process, were evaluated. The C3S/SG slurry was used for printing complex scaffolds with high precision. The study of the C3S/SG slurry provides a new approach for the manufacture of tricalcium silicate implants, which can be applied as prosthetic materials in orthopedics, dentistry, and other areas of clinical medicine.

Solid-phase extraction with injection of modified silica gel slurries into ETAAS for determination of Cu(II), Hg(II), Pd(II)

Electrothermal atomic absorption spectrometry with injections of slurry samples was used to determine Cu(II), Hg(II), and Pd(II) in natural and drinking waters after solid-phase extraction with modified silica gels. The formation regularities of the analytical signals of elements in the presence of excessive sorbent solid phase were studied. The solid phase of slurries under analysis (amorphous silicon dioxide with a particle size from 40 to 60 µm) favors the formation of a high (and sometimes uncorrected) background absorption. The conditions for the correct measurements of analytical signals of analytes elements: platform atomization, slurry concentration, peak height measurements, method for calibration curve plotting, and its linearity range, were determined. The preconcentration factor calculated as the weight ratio between analytes in a graphite furnace injected as a sorbent slurry after concentration and as a starting water sample (the injection volumes were identical) was 615. The limits of detection according to the 3σ concept were 1.5 ng/dm3 for Cu, 5 ng/dm3 for Pd, and 18 ng/dm3 for Hg. The developed method was applied with success upon determination of elements in real water samples using aqueous standard solutions and the ERM CA022a “Soft Drinking Water UK Metals”-certified reference samples of drinking water.

Enantioresolution of three active pharmaceutical ingredients by different thin-layer chromatographic approaches

Enantioresolution of three active pharmaceutical ingredients (APIs), namely, atenolol, betaxolol, and orciprenaline, marketed as racemic mixture, has been achieved in a direct mode using (S)-glutamic acid as chiral additive in thin-layer chromatography. Two different approaches were adopted: (1) (S)-glutamic acid was mixed in the silica gel slurry for making thin-layer plates, or (2) it was added in the mobile phase and plain plates without any chiral additive were used. Both (1) and (2) were capable of separating enantiomers of all the three racemates, but different combinations and proportions of solvents were found successful in the two cases. Good resolution was achieved in both cases, and the results are compared for these two sets of studies among themselves and with other literature reports. Iodine was used to locate the spots of the corresponding enantiomers. The detection limits for each enantiomer were found in the range of 1.4–1.9 μg (per spot).

Acemannan and Formocresol Pulpotomies in Primary Teeth: a Comparative Histopathological Study

AIM: The present study was conducted to compare the histopathological effects of acemannan to that of formocresol as pulp-dressing agents in primary teeth underwent pulpotomy. MATERIALS AND METHODS: Aloe vera gel high molecular weight fractions (AHM) containing native ingredients of polysaccharide (acemannan) and glycoprotein (verectin) were obtained by using the patented hyper dry system after washing out coloured materials with running water from Aloe vera gel slurry. Forty-six primary first teeth from children between 6-9 years, which formerly planned for serial extraction were selected. The children were distributed into two equal groups; twelve teeth for each. Pulpotomy was done in both groups; where group I treated by AHM, acemannan, as a dressing agent while formocresol used as a dressing agent in group II. The teeth from each group were extracted at two, four, and twelve week intervals for histopathological evaluation. RESULTS: In group I (Acemannan), after twelve weeks significantly better results in pulp inflammation, incomplete dentine bridge formation, and soft tissue organization were demonstrated (p<0.05). Most of the acemannan-treated group demonstrated no pulp inflammation with only (3/12, 25%) revealed mild pulp inflammation under the exposure site and only one tooth 1/12 teeth (8.3%) showed partial dentine bridge formation. In contrast, group II (Formocresol) moderate or severe pulp inflammation (10/12, 83%), no dentine bridge formation were observed. In almost all cases (10/12, 83%) the soft tissue of the pulp was not well organized. CONCLUSION: According to these findings, AHM, acemannan may be a suitable agent for pulpotomy in primary teeth. Moreover, the inflammatory response was less severed and no necrosis was noted after pulpotomy with acemannan compared to formocresol.

Formation of Percolating Carbon Networks in Battery Processing and Their Effects on Electrode Performance

The increasing demand for energy storage has led to continual improvements in materials for battery electrodes. However, the overall processing of these materials into devices and the need for composite electrodes has remained essentially the same. Currently, the optimal processing conditions are determined through time-, labor-, and capital-intensive trial and error. Determining the fundamental particle and electrochemical physics that result in high-performance composite electrodes is so far an untapped field of potential. Our work strives to fully understand from a rheological perspective the interactions of components in electrode slurries. These insights will allow the manufacturing process of new materials to be accelerated, resulting in faster, more efficient implementation of new materials into effective electrodes. The mixing, coating, drying and calendaring of active material, conductive additive, and polymer binder in solvent affect the final battery microstructure. Although it is well-known that the electrode slurry microstructure impacts the final battery performance, there is little agreement on what constitutes a favorable microstructure [1,2]. Slurries may be broadly divided into two rheological categories, fluids and gels. In a fluid-like system, suspended particles typically interact via hydrodynamic forces. In a colloidal gel, particles form a percolating network that extends across the volume of the system through surface or depletion interactions. In this work, we study a model system of lithium nickel manganese cobalt oxide (NMC), carbon black, polyvinyldifluoride (PVDF), and 1-methyl-2-pyrrolidinone (NMP) to determine the effects of slurry microstructure on battery performance. Slurries are characterized using small-amplitude oscillatory shear (SAOS) in which a constant strain is applied at increasing angular frequencies and the viscous and elastic components of the stress are determined as a function of frequency (frequency sweep). Figure 1 compares the frequency sweeps for a fluid system and a gel system formed with micron-sized and nano-sized active material, while maintaining constant PVDF molecular weight, carbon black, and mixing parameters. A fluid system is depicted by G” larger than G’. Gel systems are typically observed when G’ dominates. Suspended micron-sized active material does not form a gel in the presence of polymer binder. However, the addition of a critical volume fraction of free nano-sized carbon additive causes the suspension to gel. We find that the critical gelation volume fraction of free carbon black (40nm) is equal to 0.5 vol%. The typical quantity used in commercial battery slurry recipes is 2 vol% [3]. The amount of free carbon is highly dependent on the commonly used dry-mixing step, where active material and conductive additive are blended together. It has been shown that dry –mixing causes conductive additive to coat the active material reducing the amount of free carbon in the suspension. In other words, in the absence of dry-mixing, all the carbon is above the critical concentration and readily forms a gel, i.e. percolating network. However, depending on the dry-mixing conditions, enough carbon is coated on the active material such that the amount of free carbon is too low to form a colloidal gel. By varying the dry mixing step of slurry preparation, a wide range of slurry microstructures can be achieved without varying the total carbon concentration. Contrary, nano-sized active material readily forms a gel due to its size and large volume fraction in the electrode slurry. Slurries with characterized microstructures are coated, dried, and calendered into electrodes in order to relate slurry microstructure to electronic conductivity, life cycle and rate capability of the processed electrodes. Measurements of the electronic conductivity and battery performance show that gel slurries form electrodes with higher initial conductivity and lower porosity. Electrodes from gel slurries also cycle longer and have higher capacities than fluid slurries. We hypothesize that the continuous carbon network is necessary to provide sufficient electronic conductivity. Future work will investigate the dependence of performance and electrode tortuosity on slurry microstructure and the effects of drying parameters on battery performance.

Nonlinear rheology and pressure wave propagation in a thixotropic elasto-viscoplastic fluids, in the context of flow restart

A new continuous nonlinear rheological model is established to quantify, correlate, and predict the thixotropic viscoelastic and visco-plastic properties of waxy crude oil gels. A complete rheological description of the gel is afforded by quantification of the maximum stress point (so called static yield stress) in conjunction with viscosity of the pristine gel and final slurry. Extraneous parameters are derived from the maximum stress condition. In order to develop an understanding of flow restart processes within gelled pipelines, direct numerical simulation of pressure propagation in weakly compressible thixotropic elasto-viscoplastic gel (Oldroyd-B fluid model) is performed using the rheological correlations. Deficiencies associated with conventional Bingham yield stress and conventional shear thinning methodologies are concomitantly revealed by the present elasto-viscoplastic model. Depending on parametric values, pressure may propagate and flow may commence for pipeline lengths larger than the critical length, Lc=ΔpR/2τy, (where Lc is the flow restart length for a yielding gel without microstructure breakage, Δp is the applied pressure, R is the pipe radius, and τy is the yield stress). Prior to attaining the critical length, the nature of the pressure wave is shown to be either inertial or viscous, depending on the initial gel viscosity. Upon approaching the critical length, the nature of the pressure wave is governed by gel degradation, except at extreme compressibility values. At high compressibility, the nature of the pressure wave is controlled by gel degradation, even prior to reaching Lc, facilitating flow commencement in long pipes via a sequential breakage process. At very low compressibility, the pressure wave propagates until the force exerted by the fluid on the wall evenly balances the applied pressure. Hence, the pressure wave may propagate beyond the critical length but sustained flow does not commence. At intermediate compressibility values, if propagation of pressure to the critical length causes mean near-wall gel deformation on a similar magnitude as the static yield strain value (γ≡χΘΔp2/2τy∼γs, where χΘ is the isothermal compressibility) then the pressure wave does not propagate substantially beyond Lc and flow does not restart in the pipeline. For intermediate compressibility when γ > >γs, then flow restarts via the high compressibility mechanism (e.g. low gel strength cases) and when γ < <γs then the pressure wave propagates without flow restart (e.g. high gel strength cases), similar to the low compressibility regime. For validation of numerical results, a case with only a viscous term is compared with literature results. Furthermore, large scale flow loop experiments were performed to measure pressure propagation. Experimental results are consistent with the mechanism of pressure propagation and flow restart determined numerically.

Resolution of Enantiomers of (RS)-Baclofen by Ligand-Exchange Thin-Layer Chromatography.

A new chromatographic method has been developed for direct enantioresolution of (RS)-baclofen by ligand-exchange thin-layer chromatography (TLC) adopting two different approaches; (A) TLC plates were prepared by mixing the ligand exchange reagents (LER) with silica gel slurry and the chromatograms were developed with different achiral solvents or solvents having no chiral additive, and (B) the LER consisting of Cu(II)-L-amino acid complex was used as chiral mobile phase additive and the plain plates of silica gel having no chiral selector were used. Cu(II) acetate and four L-amino acids (namely, L-tryptophan, L-histidine, L-proline and L-phenylalanine) were used for the preparation of LERs. Spots were located by the use of iodine vapor. Effect of temperature and the mole ratio of Cu(II)-to-amino acid on enantioresolution were also studied. The results for the two methods have been compared, and the issue of involvement of the Cu(II) cation for the best performance of the two methods has been discussed with respect to the same mobile phase. L-Trp proved to be a good ligand using a common mobile phase in each case.

Anti-oxidation properties of a BN/SiC/Si3N4–ZrO2–SiO2 multilayer coating for carbon/carbon composites

To improve the oxidation behavior of carbon/carbon composites, we developed a multilayer coating system by pack cementation and sol–gel slurry method. The coating consists of a BN–SiC inner dual-layer and a Si3N4–ZrO2–SiO2 outer barrier layer. The coating can effectively protect the C/C composites from oxidizing below 1500°C. Thermogravimetric analysis shows that the weight loss of the composites is less than 2.40wt.% after oxidizing at 1400°C for 220h. The whole temperature range oxidation resistance can be attributed to the multilayer protection design. The BN–SiC inner dual-layer can cure the cracks by producing borosilicate glass, and the Si3N4–ZrO2–SiO2 outer barrier layer can prevent the formation of cracks and seal the bubbles. The oxidation kinetics of the coated carbon/carbon composites shows that the Arrhenius curve consists of four parts, corresponding to four different oxidation processes and mechanisms in different temperature regions.

Autologous tissue patch rich in stem cells created in the subcutaneous tissue

To investigate whether we could create natural autologous tissue patches in the subcutaneous space for organ repair. We implanted the following three types of inert foreign bodies in the subcutaneous tissue of rats to produce autologous tissue patches of different geometries: (1) a large-sized polyvinyl tube (L = 25 mm, internal diameter = 7 mm) sealed at both ends by heat application for obtaining a large flat piece of tissue patch for organ repair; (2) a fine polyvinyl tubing (L = 25 mm, internal diameter = 3 mm) for creating cylindrically shaped grafts for vascular or nerve repair; and (3) a slurry of polydextran particle gel for inducing a bladder-like tissue. Implantation of inert materials was carried out by making a small incision on one or either side of the thoracic-lumbar region of rats. Subcutaneous pockets were created by blunt dissection around the incision into which the inert bodies were inserted (1 or 2 per rat). The incisions were closed with silk sutures, and the animals were allowed to recover. In case of the polydextran gel slurry 5 mL of the slurry was injected in the subcutaneous space using an 18 gauge needle. After implanting the foreign bodies a newly regenerated encapsulating tissue developed around the foreign bodies. The tissues were harvested after 4-42 d of implantation and studied by gross examination, histology, and histochemistry for organization, vascularity, and presence of mesenchymal stem cells (MSCs) (CD271+CD34+ cells). Implanting a large cylindrically shaped polyvinyl tube resulted in a large flat sheet of tissue that could be tailored to a specific size and shape for use as a tissue patch for repairing large organs. Implanting a smaller sized polyvinyl tube yielded a cylindrical tissue that could be useful for repairing nerves and blood vessels. This type of patch could be obtained in different lengths by varying the length of the implanted tube. Implanting a suspension of inert polydextran suspension gave rise to a bladder-like tissue that could be potentially used for repairing heart valves. Histologically, the three different types of tissue patches generated were organized similarly, consisting of three layers, increasing in thickness until day 14. The inner layer in contact with the inert material was avascular; a middle layer that was highly vascular and filled with matrix, and an outer layer consisting of loose connective tissue. MSCs identified as CD271+CD34+ cells were present in the medial layer and around major blood vessels at day 4 but absent at later time points. The early-harvested tissues, endowed with MSCs, could be used for tissue repair, while the later-harvested tissues, being less vascular but thicker and tougher, could be used as filler tissue for cosmetic purposes. An autologous, vascularized tissue patch of desired shape and size can be created in the subcutaneous space by implanting different types of inert bodies.