Surface Of Glass Beads Research Articles

Direct microscopic observation of particle deposition in porous media: Role of the secondary energy minimum

A flow-cell has been constructed where micrometer-sized particles flow horizontally through a single layer of packed glass beads. Deposition is viewed through a fluorescent microscope with phase contrast capabilities. This allows the visualization of particle deposition in porous media in real time and provides insight into phenomena such as secondary minimum deposition of particles and microbial pathogens during physicochemical filtration. At low ionic strengths (1–3 mM), no deposition was observed on the collector beads. As the monovalent salt concentration was raised to moderate ionic strengths (10–30 mM), the particles became trapped in the secondary minimum and translated along the glass bead surface, accumulating near the rear of the spherical collectors. At high ionic strength (100 mM), no calculated electrostatic energy barrier to deposition exists and particles deposited over the entire surface of the spherical collector. It is concluded that deposition in the secondary energy minimum is an important removal mechanism for micrometer-sized particles in flow through granular porous media.

UHMWPE as interface toughening agent in glass particle filled composites

Abstract UHMWPE was adsorbed from dilute solution onto glass beads surface modified with a copolymer of 0.5–1.2 mol% vinyltrimethoxysilane-ethylene (PE-silane). Functional methacrylate groups were introduced through treatment of the UHMWPE with octadecyltrimethoxysilane (OMS) followed by reaction with 3-methacryloxypropyltrichlorosilane (Cl-MPS). Composites were prepared with 20 vol% PE-silanated/UHMWPE glass and BisGMA/TEGDMA (60/40 wt/wt); Cl-MPS treatment did not affect the results. Toughness increased 40% compared with neat or glass-filled resin, consistent with the addition of the high toughness UHMWPE; moduli were intermediate between the neat resin and glass filled composites, consistent with the relative moduli of glass and UHMWPE; flexural strengths decreased in the order: neat resin > resin + glass beads > silanated/UHMWPE coated glass beads, suggesting that each interface negatively affected the flexural strength.

Preparation of core–shell glass bead/polysulfone microspheres with two‐step sol–gel process

AbstractCore–shell microspheres made from glass beads as the core phase and polysulfone (PSf) as the shell phase can act as an absorbent in the separation process or a supporter for chemical reactions. Based on phase‐inversion principles, a two‐step sol–gel method was developed in this work in which ether was added first and H2O was added second to a PSf‐containing dimethyformamide (DMF) solution to help PSf solidify on the surface of glass beads. The results from scanning electron microscopy, Fourier transform IR, and X‐ray photoelectron spectroscopy showed that a dense layer of PSf (thin to several microns) was coated on the glass beads and the core–shell microspheres were almost monodispersed. The utilization percentages of the glass beads and PSf were high as 100 and 80%, respectively. The thickness of the PSf membrane was calculated to be about 4.3 μm. To obtain well‐monodispersed microspheres, the practical volume ratio of ether to DMF was recommended to be larger than 4.5. The results suggested that the two‐step sol–gel method is a highly efficient process for preparation of glass bead/PSf core–shell microspheres. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3365–3369, 2006

Modeling Cr(VI) Reduction and Phenol Degradation in a Coculture Biofilm Reactor

A transient-state model was developed to simulate simultaneous Cr(VI) reduction and phenol degradation by a coculture of Cr(VI)-reducing/phenol-degrading bacteria growing on glass bead surfaces in a fixed-film bioreactor. The coculture consisted of the Cr(VI) reducers, Escherichia coli ATCC 33456, and the phenol degraders, Pseudomonas putida DMP-1. Phenol was supplied as the sole added carbon source and electron donor. The model simulated cell growth kinetics with E. coli utilizing metabolites formed from phenol degradation in P. putida as carbon sources. Substrate utilization and Cr(VI) reduction in the fixed-film bioreactor was represented by a system of (second-order) partial differential equations (PDEs). The PDE system was solved by the fourth-order Runge–Kutta method adjusted for mass transport resistance by the second-order Crank–Nicholson and backward Euler methods. A heuristic procedure, genetic search algorithm, was used to optimize the model against experimental data. The model predicted efflue...

Comment on Breakdown of Colloid Filtration Theory: Role of the Secondary Energy Minimum and Surface Charge Heterogeneities

The mechanisms and causes of deviation from the classical colloid filtration theory (CFT) in the presence of repulsive Derjaguin-Landau-Verwey-Overbeek (DLVO) interactions were investigated. The deposition behavior of uniform polystyrene latex colloids in columns packed with spherical soda-lime glass beads was systematically examined over a broad range of physicochemical conditions, whereby both the fluid-phase effluent particle concentration and the profile of retained particles were measured. Experiments conducted with three different-sized particles in a simple (1:1) electrolyte solution reveal the controlling influence of secondary minimum deposition on the deviation from CFT. In a second series of experiments, sodium dodecyl sulfate (SDS) was added to the background electrolyte solution with the intent of masking near-neutrally charged regions of particle and collector surfaces. These results indicate that the addition of a small amount of anionic surfactant is sufficient to reduce the influence of certain surface charge inhomogeneities on the deviation from CFT. To verify the validity of CFT in the absence of surface charge heterogeneities, a third set of experiments was conducted using solutions of high pH to mask the influence of metal oxide impurities on glass bead surfaces. The results demonstrate that both secondary minimum deposition and surface charge heterogeneities contribute significantly to the deviation from CFT generally observed in colloid deposition studies. It is further shown that agreement with CFT is obtained even in the presence of an energy barrier (i.e., repulsive colloidal interactions), suggesting that it is not the general existence of repulsive conditions which causes deviation but rather the combined occurrence of fast and slow particle deposition.

α-Cyclodextrin-modified infrared chemical sensing system that utilizes enzymatic reactions for the determination of glucose

A new infrared (IR) sensing system based on attenuated total reflection (ATR) to determine the levels of glucose in aqueous solutions was developed in this work. To increase the selectivity of the system, we employed glucose oxidase (GOx) to convert glucose into gluconic acid, which was the actual species detected by the IR-ATR sensor. Because gluconic acid is highly polar and was produced generally in low concentrations, the surface of the IR-ATR sensor was modified with cyclodextrin to increase the sensitivity of its detection. As a result, the sensitivity increased roughly by 100 times relative to that of the unmodified ATR. To simplify the detection system, we immobilized GOx onto the surfaces of glass beads and packed them into a column to function as an enzyme reactor. For comparison, GOx was also immobilized onto the internal surface of fused silica tubing. Glucose can be converted to gluconic acid effectively when passed through a flow system and using either packed or open tubular columns. To optimize the performance of the developed system, we investigated the effects of the pH of the sample solutions and the flow rate used to pump glucose through the system. Our results indicate that the optimal pH for the system was ca. 5; a low pH was required for high-efficiency detection of gluconic acid by the CD phase, but it lowered the efficiency of the enzymatic reactions. The flow rate exerted a small influence on the analytical signals over the examined range of flow rates because of the limited rates of the enzymatic reactions. Under the optimal conditions, the linear regression coefficients in the standard curve can be >0.99 for a concentration range of 1–50 mM and a detection time of 2 min. In addition, our developed system can be regenerated effectively using aqueous solutions at high pH.

Breakdown of Colloid Filtration Theory: Role of the Secondary Energy Minimum and Surface Charge Heterogeneities

The mechanisms and causes of deviation from the classical colloid filtration theory (CFT) in the presence of repulsive Derjaguin-Landau-Verwey-Overbeek (DLVO) interactions were investigated. The deposition behavior of uniform polystyrene latex colloids in columns packed with spherical soda-lime glass beads was systematically examined over a broad range of physicochemical conditions, whereby both the fluid-phase effluent particle concentration and the profile of retained particles were measured. Experiments conducted with three different-sized particles in a simple (1:1) electrolyte solution reveal the controlling influence of secondary minimum deposition on the deviation from CFT. In a second series of experiments, sodium dodecyl sulfate (SDS) was added to the background electrolyte solution with the intent of masking near-neutrally charged regions of particle and collector surfaces. These results indicate that the addition of a small amount of anionic surfactant is sufficient to reduce the influence of certain surface charge inhomogeneities on the deviation from CFT. To verify the validity of CFT in the absence of surface charge heterogeneities, a third set of experiments was conducted using solutions of high pH to mask the influence of metal oxide impurities on glass bead surfaces. The results demonstrate that both secondary minimum deposition and surface charge heterogeneities contribute significantly to the deviation from CFT generally observed in colloid deposition studies. It is further shown that agreement with CFT is obtained even in the presence of an energy barrier (i.e., repulsive colloidal interactions), suggesting that it is not the general existence of repulsive conditions which causes deviation but rather the combined occurrence of "fast" and "slow" particle deposition.

Effects of hyperbranched poly(ester-silane) as a coupling agent on the mechanical behavior of glass bead filled epoxy resin

Hyperbranched poly(ester-silane)s (HPE-Si, including HPE-Si4 and HPE-Si8) were synthesized for glass bead filled epoxy resins. The grafting reaction and the degree of grafting of HPE-Si onto the surface of glass beads were characterized by Fourier transform infrared photoacoustic spectroscopy (FT-IR-PAS) and thermogravimetric analysis (TGA) measurements. The degree of grafting was calculated to be in the range 1.0–4.2% for different HPE-Si treatments. The tensile strength and modulus of glass bead filled epoxy resins were found to increase with increasing filler content. Moreover, HPE-Si4 series have the highest tensile strength and modulus at the same glass bead size and volume fraction in the composites compared with HPE-Si8 series. The fracture toughness (K1c) of specimens with different glass bead sizes (4.8 and 2.0 μm) has the same trend that changes with the filler content and the modification of the surface of glass beads. The investigation of the toughening mechanism using Irwin's model through the yield stress measurements suggest that the toughening mechanism for small glass bead filled resins does not involve matrix plasticity, whereas the toughening mechanism involving matrix shear banding for large glass bead filled resins with higher filler content (up to 10 wt%) was proposed. The morphology of the filled resins studied by scanning electron microscopy (SEM) showed that the interface compatibility between the glass beads and epoxy matrix was greatly improved by the treatment with HPE-Si. Copyright © 2005 John Wiley & Sons, Ltd.

EHD-enhanced drying with multiple needle electrode

The enhancement of drying rate by corona discharge from a multiple-needle electrode has been experimentally evaluated in this study. Corona wind produced by an assembly of three needle electrodes impinges and removes moisture from the surface of uniform glass beads (with a diameter of 3 mm or 6 mm) completely wetted with water. Corona discharges with positive and negative polarities have been considered. Two sets of experiments have been conducted (one with the cross-flow of air and the other without), at 1 kV increments from the corona threshold voltage to a maximum voltage of 25 kV. To evaluate the drying enhancement, a companion experiment was carried out simultaneously for each case under the same ambient conditions but without the application of the electric field. Each experiment lasted for at least 5 h. The weight loss of water as well as the ambient temperature and humidity were measured. The results are compared with those obtained using a single needle electrode to evaluate the effectiveness of a multiple-electrode system.

Bacillus licheniformis α-amylase immobilized on glass beads and equilibrated at low moisture content: potentials as a Time–Temperature Integrator for sterilisation processes

Time–Temperature Integrator (TTI) systems based on Bacillus licheniformis α-amylase (BLA), sucrose and salts immobilized at the surface of non-porous glass beads (inert filler) and under several low moisture conditions ( a w in the range 0–0.63 after equilibrium at 4 °C) were studied. These systems showed interesting thermal stabilities in the range 100–132 °C under isothermal conditions. More precisely, the TTI system equilibrated at a w=0.48 (BLAGB48) showed capabilities, under non-isothermal conditions, for monitoring the process value z TTI=9.4 °C F 121.1 °C in the range 0–30 min with an absolute average % error of 14%. Although this error is comparable to already reported systems, this TTI showed numerous advantages over the latter: (i) The time required for the moisture equilibration of the systems was significantly reduced (2–3 days instead of 3 weeks). (ii) The aggregation of the α-amylase during heating could be overcome enhancing the solubilization of the α-amylase after heat treatment in only 1 min. (iii) Consequently, it became possible to use convenient residual activity reading method (only 5 min required) instead of a residual heat denaturation enthalpy reading (15 min required) as a response property of the system. (iv) The amount of α-amylase required per TTI was 50-fold smaller. (v) Finally, larger thermal impacts (process values up to 30 min) could be monitored.

Biofilm-specific surface properties and protein expression in oral Streptococcus sanguis

Objective: Oral streptococci are primary colonisers of the tooth surface and are abundant in dental plaque biofilms. Bacteria growing in these relatively dense, surface-associated communities are phenotypically quite distinct from their planktonic counterparts. The purpose of the present study was to develop a method to investigate biofilm-specific surface protein expression by Streptococcus sanguis to help provide a better understanding of the critical events in plaque development. Design: Biofilm cells were grown on the surface of glass beads in a biofilm device fed with mucin-containing artificial saliva. Planktonic cells were grown in continuous culture at approximately the same growth rate. Surface hydrophobicity of biofilm and planktonic cells was determined by hexadecane partitioning, and expression of streptococcal fibronectin adhesin CshA was determined in ELISA using specific antiserum. Antisera raised to glutaraldehyde-fixed whole biofilm or planktonic grown cells were used to screen an expression library of S. sanguis genomic DNA, and isolated clones were sequenced. Results: Phenotypic analysis of biofilm and planktonic cells confirmed that mode of growth affected surface properties of S. sanguis. Thus, hydrophobicity and CshA expression was significantly elevated in biofilm cells. Library screening with biofilm antiserum yielded 32 recombinant clones representing 21 different S. sanguis proteins involved in adhesion and colonisation, carbohydrate utilisation or bacterial metabolism. In differential analysis of four selected Escherichia coli clones, biofilm antiserum reacted five times stronger than planktonic antiserum with cell-free extracts of clones encoding homologues of CshA and Cna collagen adhesin of Staphylococcus aureus, suggesting that these surface proteins are up-regulated in biofilm cells. In contrast, both antisera reacted equally strongly with cell-free extracts of the remaining two clones (encoding dihydrofolate synthase and an unknown protein). Conclusions: The method described represents a useful means for determining bacterial protein expression in biofilms based on a combination of molecular and immunological techniques. Surface expression of putative fibronectin and collagen adhesins was up-regulated in biofilm cells.

Enhanced Interfacial Adhesion between PPO and Glass Beads in Composites by Surface Modification of Glass Beads via In Situ Polymerization and Copolymerization

Glass beads were modified with vinyl triethoxyl silane (VTES) followed by in situ copolymerization with styrene (St) and by direct modification with St via in situ polymerization. It was seen that the presence of glass beads did not inhibit the polymerization of St, and FT-IR spectra confirmed that the polystyrene (PS) molecules were grafted on the surfaces of glass beads. When the modified glass beads were filled in a poly(phenylene oxide) (PPO) matrix, the PS segments on the surfaces of glass beads clearly improved compatibility and enhanced interfacial adhesion between the PPO matrix and glass beads, which was responsible for the slightly increased glass transition temperature of the PPO component. Surface modifications, especially by in situ copolymerization of VTES and St, increased significantly notch impact strengths and marginal stiffness and tensile strengths of PPO/glass bead composites.

The production of anti-inflammatory cytokines in whole blood by physico-chemical induction.

Cytokines such as interleukin-1 (IL-1) play an important role in degenerative musculo-skeletal diseases, including osteoarthritis, and a multitude of inflammatory disorders. Agents that inhibit the action of such cytokines have a high therapeutic potential in such diseases. Here we describe a new method for enhancing the production of the interleukin-l receptor antagonist (IL-1Ra) and other anti-inflammatory cytokines in whole blood. Human venous blood was incubated in the presence of CrSO(4)-treated glass beads. Serum was recovered and the concentrations of IL-1Ra and other relevant cytokines were measured by ELISA. The interaction of the glass bead surface with cells in whole blood increased production of IL-1Ra and anti-inflammatory cytokines. Removal of the beads and centrifugation generated a serum preparation enriched in anti-inflammatory cytokines. This preparation is of therapeutic value in treating various inflammatory and degenerative disorders. The increased de novo production of anti-inflammatory cytokines by a direct physico-chemical induction of whole blood in the Orthokin system is feasible and offers an alternative, novel approach to treating mild to moderate OA and other orthopaedic conditions such as degenerative spine diseases.

A study of direct loading of beta-cyclodextrins on glass beads as chromatographie separators

Beta-cyclodextrin(β-CD) was successfully loaded on the surface of glass beads without spacer group or cross-linking agent. The directly loaded β-CD was stable in toluene and methanol flows but critically hurt in more polar solvent such as water and dimethylformamide. Cross-linking could stabilize the directly bonded β-CD glass beads. Pore openings of cyclodextrin can be narrowed or blocked by end-capping agent, spacer groups, and cross-linking agents. The β-CD directly bonded glass beads have a capability to form inclusion complexes with larger host molecules because this method can avoid pore narrowing and blocking problems.

Unexpected thermal destruction of dried, glass bead-immobilized microorganisms as a function of water activity.

To help us understand the factors and mechanisms implicated in the death of microorganisms or their resistance to temperature in a low water activity environment, microorganisms were dried on the surface of glass beads before being subjected to high temperatures for a short period followed by rapid cooling. Two microorganisms were studied: the yeast Saccharomyces cerevisiae and the bacterium Lactobacillus plantarum. Experiments were carried out at 150, 200, and 250 degrees C, with four durations of heat treatment and seven levels of initial water activity between 0.10 and 0.70. We observed an unexpected range of water activity, between 0.30 and 0.50, at which microorganisms were more resistant to the various treatments, with maximal viability at 0.35 for L. plantarum and 0.40 for S. cerevisiae.

The effect of compatibilizing and coupling agents on the mechanical properties of glass bead filled PP/PET blends

AbstractPP/PET blends (95/5) filled with 50% by weight of glass beads were prepared and studied at morphological and mechanical level, and compared with its analogous samples of glass bead‐filled PP. The influence of a compatibilizing agent (maleic anhydride grafted polypropylene) and different silane coupling agents was analysed. It has been found that PET embeds glass bead surface independently on the silane coupling agent employed. Addition of MAPP in PP/PET blends leaded to tensile strength values similar to those of unfilled PP, but rupture takes place in a brittle manner.

Tagless extraction-retentate chromatography: a new global protein digestion strategy for monitoring differential protein expression.

A new global protein digestion and selective peptide extraction strategy for the purpose of monitoring differential protein expression, coined as tagless extraction-retentate chromatography, is introduced. Target protein populations are firstly digested under reduced and alkylated conditions, and resultant peptides selectively extracted via covalent attachment to methionine residues by bromoacetyl reactive groups tethered to the surface of glass beads packed in small reaction vessels. After conjugation, reactive beads are stringently washed to remove nonspecifically bound peptides and then later treated with beta-mercaptoethanol to release captured methionine peptides in their nascent state, without complicating affinity tags. Recovered methionine containing peptides are profiled using the surface-enhanced laser desorption/ionization (SELDI) retentate chromatography mass spectrometry (RCMS) method. Selected peptides are further studied employing ProteinChip tandem mass spectrometry (MS/MS) analysis to identify their parent proteins. This approach has been applied to an Escherichia coli lysate model system and has demonstrated facility in reducing global digest complexity, sensitivity to low protein expression levels, and significant quantitative capability. It is envisioned that tagless extraction-RCMS will evolve to be a valuable approach for both basic research and clinical proteomics endeavors.

Surface modification of nonporous glass beads with chitosan and their adsorption property for transition metal ions

A new hybrid material that adsorbs transition metal ions was prepared by immobilizing chitosan on the surface of nonporous glass beads. The glass beads, prepared by etching in aqueous NaOH at 100°C, were first reacted with γ-aminopropyltriethoxysilane (APES) to introduce amino groups on the surface. Subsequently, the resulting aminated beads were treated with glutaraldehyde at 25°C to change the amino groups into aldehyde groups. Finally, chitosan of average molecular weight 40,000 was introduced via the aldehyde groups through a Schiff's reaction. After complete acid-hydrolysis of the immobilized chitosan, the Svennerholm method for glucosamine analysis showed that 0.3% (w/w) chitosan had been successfully introduced on the glass beads. Atomic absorption spectroscopic analysis of eluants of a column of the chitosan-modified glass beads showed that metal ions such as Cu 2+, Ag +, Pb 2+, Fe 3+, and Cd 2+ were more than 90% entrapped on a column of beads prepared in this manner.

Ultrasound-Enhanced Dissolution of UO2in Supercritical CO2Containing a CO2-Philic Complexant of Tri-n-butylphosphate and Nitric Acid

Application of ultrasound can significantly enhance the dissolution of UO2 powders placed on small glass beads in supercritical fluid CO2 using a CO2-soluble tri-n-butylphosphate (TBP)/HNO3/H2O complexant as an extractant. The amount of UO2 dissolved in CO2 for a 20-min dynamic extraction at 323 K and 15 MPa can be increased by an order of magnitude with sonification compared to experiments without sonification. The application of ultrasound probably contributes to the transfer of locally concentrated UO2(NO3)2·2TBP from the surface of glass beads into supercritical fluid CO2. This ultrasound-aided process for direct dissolution of UO2 in supercritical fluid CO2 that requires no aqueous solutions and organic solvents may have important applications for reprocessing of spent nuclear fuels and for treatment of certain nuclear wastes.

Effects of surface modification of glass beads with poly(acrylic acid)

Etched glass beads were functionalized with 3-aminopropyltriethoxysilane (APS) and glycidoxypropyltrimethoxysilane (GPS). The surface of glass beads were further modified with poly(acrylic acid) by reacting the carboxyl groups on poly(acrylic acid) with the amino groups of the grafted aminopropyltriethoxysilane. The modifications were characterized by FT-IR spectroscopy and tensiometry for contact angle and porosity measurements. Five different molecular weight PAA polymers ranging from 2,000 to 3,000,000 were grafted with less than expected increase of grafting% with molecular weight. The amount of poly(acrylic acid) (PAA) on the surface was determined from thermal gravimetric analysis and elemental analysis data. The surface properties of surface modified glass beads were determined by measuring water and hexane penetration rate and contact angle. The surface morphology was examined by scanning electron microscopy.