Dry Beads Research Articles

Porous Chitin Microbeads for More Sustainable Cosmetics

The microbead form is a material architecture that is promising for use in biomedical and cosmetic applications; however, the use of petroleum-based microbeads (i.e., plastics) has raised significant environmental concerns in recent years. Microbeads prepared from renewable polymers could represent a sustainable alternative to these synthetic microbeads. This work explores the use of chitin in preparing biodegradable, biocompatible microbeads of low toxicity. Chitin microbeads were synthesized using the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]); the IL was used to both extract chitin directly from waste shrimp shell and to prepare the porous microbeads by coagulation in polypropylene glycol (PPG). The effects of biopolymer source and bead-preparation parameters on the formation of beads were investigated, as well as the effects of the drying conditions on the dry bead structure. It was found that IL-extracted chitin could be used to prepare beads of homogeneous size distribution...

Objective measurement of isoniazid levels: practical approach for monitoring tuberculosis drug treatment adherence

Drug treatment adherence is one of the biggest issues in tuberculosis (TB) treatment. Including DOTS (Directly Observed Treatment, Short-course) program, many programs for TB cases have yielded marginal success and the new drug resistance varieties of TB persist. During the 1960s, researchers have projected naphthoquinone–mercuric chloride (N-M) test as the single most way to objectively track the presence of isoniazid (INH) in urine and hence treatment adherence. INH is metabolised by cytochrome P450s and usually cleared from body within 8 h. Hence, the typical INH levels in biological fluids are within 1–5 μg/ml. The N-M test practically works at 10–50 μg/ml and the authors developed the sodium polyacrylate (SPA) as a solid surface to improve detection limit of INH by 6–10 fold. The modification involves absorbing the reagents of N-M test on the SPA surface and lyophilised material is directly used for diagnosis. The dry beads can detect 1–2 μg/ml of INH in saliva. The test performed with spiked as well as clinical samples and the results have good correlation. This new test has a realistic chance of tracking the TB treatment adherence remotely and in that direction a system was projected for implementation.

Development of alginate gel beads with a potential use in the treatment against acute lead poisoning

The objective was to develop alginate beads that could adsorb lead ions in gastric pH, in view to preconize their use in gastric lavage following lead poisoning. The swelling measurements of both, dry and hydrated beads, were carried out in simulated gastric fluid (SGF). The sorption kinetics was examined at lead concentrations ranging from 50 to 200mg/l. Calcium released during the sorption process was investigated.The swelling rate of the dry beads increased considerably with time increase and reached the equilibrium at 736% after 240min; concerning the hydrated beads, the equilibrium swelling reached 139% after 180min. The adsorption of Pb (II) in SGF by dry beads increased with the increase of time and initial lead concentration. The adsorption kinetics of Pb ions by hydrated alginate beads indicated a rapid binding of Pb ions to the sorbent during the first 15min for all the concentrations, followed by a slow increase until the equilibrium was reached after 90min. The adsorption capacity of Pb ions increased with the increase of the storage time in water at 4°C and with the weight. The amount of Ca2+ released by the beads increased with the increase of Pb ions a rate.

横型乾式ビーズミルを用いた微粉砕および所要動力と粒子径の関係

Dry bead mills are believed to contribute significantly to the shortening of drying processes and reduction of required production space, as well as the energy costs reductions that result from these improvements. In this study, we used a dry bead mill to perform grinding test on silica sand, alumina, and activated carbon. We investigated the impact various dry bead mill conditions had on grinding, and explored the dry grinding potential of bead mills. We found a regular relationship between the median diameter and the power, and that this tended to match previous reports. We also demonstrated that within the scope of this experiment, tip speed, bead filling, and the feed rate were not factors that affected the energy efficiency.

Stick-slip behaviours of dry glass beads in triaxial compression

Consolidated undrained triaxial compression tests are conducted on standard cylindrical samples of nearly monodisperse glass beads, initially assembled in a dense state by a funnel pouring technique. Deviator stress, volumetric strain and induced pore air pressure are measured as functions of vertical strain under different confining stress and vertical strain rates. We find that in stick phase the glass beads accumulate energy and regain strength, which can lead to slow sliding in volumetric strain curve without stress drop in deviatoric stress curve for confining stress of 1000 kPa. Particularly after the previous slip event, as the deviatoric stress increases, the volume of sample repetitively compacts and then dilates before reaching the next slip events under high confining stress, which never happens at the lower. In slip phase, a stress drop coincides with a jump of volumetric strain and vertical strain, which make the pore air pressure grow sharply. The effects of confining stress and vertical strain rate on stick-slip instabilities are discussed in dry dense glass beads samples.

Experimental and numerical study of cylindrical triaxial test on mono-sized glass beads under quasi-static loading condition

This paper aims at studying the shear behavior of homogeneous granular materials by conventional triaxial test. The work is performed both in laboratory tests and by discrete element method simulations. Conventional triaxial tests are performed on glass beads packing, while a cylindrical rigid wall boundary condition based on lame formula and a series of procedures are proposed to simulate the conventional triaxial test. The experimental results on dry and saturated glass beads samples have been studied to find out the effect of saturation condition on the shear behavior. The comparisons between experimental and numerical results show that the numerical model can reproduce deviatoric curves satisfactorily in experimental conditions as long as experimental sample remains cylindrical. It correctly describes the volumetric strains of a numerical sample up to the peak value. Additionally, a parametric study on the influence of main micromechanical parameters has been carried out, which has been compared to experimental tests with glass beads of different textures. The comparison highlights the significant effect of friction coefficients and rolling resistance coefficients on global behavior of granular materials.

Alginate/bacterial cellulose nanocomposite beads prepared using Gluconacetobacter xylinus and their application in lipase immobilization

Alginate/bacterial cellulose nanocomposite beads, with well-controlled size and regular spherical shapes, were prepared in a simple manner by entrapping Gluconacetobacter xylinus in barium alginate hydrogel beads, followed by cultivation of the entrapped cells in culture media with a low sodium ion concentration. The entire surface of the alginate hydrogel beads containing the cells was covered with cellulose fibers (∼30nm) after 36h of cultivation. The cellulose crystallinity index of the alginate/bacterial cellulose beads was 0.7, which was slightly lower than that of bacterial cellulose prepared by cultivating dispersed cells. The water vapor sorption capacity of the alginate/bacterial cellulose beads increased significantly from 0.07 to 38.00 (g/g dry bead) as cultivation time increased. These results clearly indicate that alginate/bacterial cellulose beads have a much higher surface area, crystallinity, and water-holding capacity than alginate beads. The immobilization of lipase on the surface of the nanocomposite beads was also investigated as a potential application of this system. The activity and specific activity of lipase immobilized on alginate/bacterial cellulose beads were 2.6- and 3.8-fold higher, respectively, than that of lipase immobilized on cellulose beads. The alginate/bacterial cellulose nanocomposite beads prepared in this study have several potential applications in the biocatalytic, biomedical, and pharmaceutical fields because of their biocompatibility, biodegradability, high crystallinity, and large surface area.

Effects of triaxial confining pressure and strain rate on stick-slip behavior of a dry granular material

Some granular materials including spherical glass beads may suffer from stick-slip instabilities which are characterized by successive fluctuations in the stress–strain behavior. Under various loading conditions, these stick-slip failures cause a portion of the stored strain energy within the granular medium to be suddenly released. It is accompanied by a partial collapse and volumetric contraction occurring at the same time. In order to understand the factors behind the stick-slip mechanism, a series of laboratory experiments were carried out in this study. Cylindrical specimens constituted by dry loosely-packed spherical glass beads were tested in triaxial compression. The effects of confining pressure and strain rate on stick-slip behavior were investigated. The experimental results show that as the confining pressure is increased, both the deviatoric stress amplitude and the oscillation amplitude increase. On the other hand, any increase in the strain rate causes the deviatoric stress amplitude to decrease. However, the oscillation amplitude is not affected by the strain rate.

Development of a novel methodology to determine mill power draw

This paper presents an approach that has been developed to calculate the power draw of each size within a distribution of charge in a tumbling mill. Positron Emission Particle Tracking (PEPT) and the Discrete Element Method (DEM) are used to test the methodology. Experiments are conducted using dry spherical glass bead charge in a laboratory scale tumbling mill, which is mounted with a torque transducer and tachometer to provide measurements of mill power. Particle tracking information from PEPT is used to reconstruct the motion of glass beads and infer the overall charge behaviour, while DEM is employed to simulate particle motion and interaction, with collision mechanics calculated using the Hertz–Mindlin contact model. For both sets of data, the product of torque and average angular velocities in discrete cells are accumulated to obtain mill power. This method is found to be within statistical agreement with measured power for all cases investigated.

Dry ice blasting as a substitution for the conventional electroplating pre-treatments

For high quality electroplated products, surfaces must be thoroughly pre-treated. For this purpose electroplating currently needs a variety of chemical baths. The used chemicals are injurious to health and harmful to the environment. In addition, the conventional pre-treatment has a long process time which results in high costs. Dry ice blasting alone or in combination with other processes has the potential to completely substitute these conventional pre-treatment processes. Three process sequences as pre-treatment methods prior to electroplating were investigated on the aluminium alloys AlSi12 and AlMg3. The used processes are dry ice blasting, tempering during dry ice blasting and glass bead blasting followed by dry ice blasting. The influence of the parameters on the surface roughness, surface topography and surface tension of the workpieces was examined. A model to describe the correlation between the dry ice blasting parameters and surface parameters was developed. Finally, an adhesion test of electroplated specimen was conducted in order to determine the suitability of these alternative pre-treatment processes.

Discrimination of shape and size sues by day-old chicks in two one-trial learning tasks

The ability of day-old chicks (Gallus gallus domesticus) to discriminate between the shape and size of beads was investigated in two one-trial tasks, taste avoidance and sickness-conditioned learning. Previous studies determined that color is a critical classification cue for conditioned stimuli in these tasks. In taste avoidance learning, a chick pecks a bead coated with a bitter substance. In sickness-conditioned learning, chicks peck a dry bead and are injected 30min later with lithium chloride. Chicks could discriminate beads of different sizes, but not different shapes, when trained in the taste avoidance task, whereas in the sickness-conditioned learning task, chicks could discriminate shape, but not size. These results suggest that chicks use a number of classificatory cues to remember an avoidance response, and, in the absence of color cues, chicks rely on different cues for different learning tasks.

An approach for the improved immobilization of penicillin G acylase onto macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) as a potential industrial biocatalyst.

The use of penicillin G acylase (PGA) covalently linked to insoluble carrier is expected to produce major advances in pharmaceutical processing industry and the enzyme stability enhancement is still a significant challenge. The objective of this study was to improve catalytic performance of the covalently immobilized PGA on a potential industrial carrier, macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [poly(GMA-co-EGDMA)], by optimizing the copolymerization process and the enzyme attachment procedure. This synthetic copolymer could be a very promising alternative for the development of low-cost, easy-to-prepare, and stable biocatalyst compared to expensive commercially available epoxy carriers such as Eupergit or Sepabeads. The PGA immobilized on poly(GMA-co-EGDMA) in the shape of microbeads obtained by suspension copolymerization appeared to have higher activity yield compared to copolymerization in a cast. Optimal conditions for the immobilization of PGA on poly(GMA-co-EGDMA) microbeads were 1 mg/mL of PGA in 0.75 mol/L phosphate buffer pH 6.0 at 25°C for 24 h, leading to the active biocatalyst with the specific activity of 252.7 U/g dry beads. Chemical amination of the immobilized PGA could contribute to the enhanced stability of the biocatalyst by inducing secondary interactions between the enzyme and the carrier, ensuring multipoint attachment. The best balance between the activity yield (51.5%), enzyme loading (25.6 mg/g), and stability (stabilization factor 22.2) was achieved for the partially modified PGA.

Sodium Alginate/Starch Blends Loaded with Ciprofloxacin Hydrochloride as a Floating Drug Delivery System - In Vitro Evaluation

In the present study, Floating Drug Delivery Beads (FDDS) were prepared with sodium alginate/ starch blend as a matrix, sodium hydrogen carbonate as a pore forming agent, methyl cellulose as a binder and barium chloride solution as a hardening agent. In order to prepare the beads with different porosity and morphology the ratio between pore forming agent to polymer blend and ratio of the constituents of the blend were varied. Ciprofloxacin hydrochloride was used as a model drug for in-vitro studies. The swelling property of the dry beads is found to be in the range of 80% to 125% from its original dimension. The amount of drug released from the beads was measured by UV-Visible spectrometer at λmax of 278. The drug release from the floating beads can be varied from 7% to 67% by varying the ratios of composition of the blend and pore forming agents to the polymer blend. From the results it is proved that this system can be used as an oral delivery system with an ability of controlled release of drug in a sustained manner.

Observed Effects of Interparticle Friction and Particle Size on Shear Behavior of Granular Materials

AbstractThis paper presents an experimental study on the shear behavior of granular materials, focusing on the effects of interparticle friction and particle size, which are of fundamental importance but are not yet well understood. The experimental program consisted of a large number of direct shear tests on glass beads of varying sizes and interparticle friction conditions, performed under a range of packing densities and normal stress levels. Test data were interpreted in terms of the stress–dilatancy relationship and shear strength parameters. The study indicates that under otherwise similar testing conditions, oil-lubricated glass beads tend to have substantially lower shear strength as compared with water-lubricated, water-flooded, and dry glass beads. It has also been found that at similar particle size uniformity, increasing mean particle size (d50) leads to more dilatant shear response and higher shear strength. A generalized stress–dilatancy relation is proposed, which introduces a variable dila...

High-Throughput Sorting and Placement of One-Bead-One-Compound (OBOC) Libraries from Bulk to Single Wells in Organic Solvent.

One-bead-one-compound (OBOC) solid-phase combinatorial chemistry has been used extensively in drug discovery. However, a major bottleneck has been the sorting of individual beads, while still swollen in organic solvent, into individual wells of a microwell plate. To solve this problem, we have constructed an automated bead sorting system with integrated quality control that is capable of sorting and placing large numbers of beads in bulk to single wells of a 384-well plate, all in an organic solvent. The bead sorter employs a unique, reciprocating fluidic design capable of depositing 1 bead every 1.5 s, with an average accuracy of 97%. We quantified the performance of this instrument by sorting over 8500 beads, followed by cleaving the conjugated compound and confirming the chemical identity of each by liquid chromatography/mass spectrometry (LC/MS). This instrument should enable more efficient screening of combinatorial small molecule libraries without the need to dry beads or otherwise change the chemical environment.

Immobilization of thermostable nucleoside phosphorylases on MagReSyn® epoxide microspheres and their application for the synthesis of 2,6-dihalogenated purine nucleosides

Immobilization of enzymes has been considered as an efficient approach to facilitate enzyme recovery and to improve biocatalyst stability. However, multimeric nucleoside phosphorylases, useful for the synthesis of modified nucleosides, encounter several challenges to their immobilization, including requirement for high enzymatic load, and poor retention of enzyme activity. In this study, multimeric enzymes pyrimidine nucleoside phosphorylase (PyNP) and purine nucleoside phosphorylase (PNP), from Thermus thermophilus and Geobacillus thermoglucosidasius, respectively, were successfully immobilized on the magnetic beads with cross-linked polyethyleneimine and epoxide functional groups, resulting in high enzyme loading (up to 0.4 and 1.3g per g dry beads), high enzyme activity maintenance (41% and 83% under the highest enzyme loading), and improved enzyme stability. The screening of the immobilization conditions showed that binding buffer pH, enzyme loading amount, binding temperature and binding time are important factors for the immobilization yield. The application of the immobilized enzymes in the synthesis of 2,6-dihalogenated purine nucleosides achieved with high substrate conversion (78.5–85.5%) as well as high productivity (1.5–2.0gL−1h−1).

High-Strain Rate Compressive Behavior of Glass Beads Under Confinement

Glass beads are often used to examine simulation models for granular materials. The dynamic behavior of glass beads, however, has not been characterized accurately. In this paper, the dynamic behavior is characterized at high strain rates. To describe the beads used in these experiments, the size distribution was measured, and the bead-level mechanical properties were determined by nanoindentation. The dynamic compressive behavior of glass beads under confinement was characterized at strain rates near 400 s−1 using a long split Hopkinson pressure bar. The glass beads were confined inside a hollow cylinder of hardened steel and capped by cemented tungsten carbide cylindrical rods. The assembly was subjected to repeated shaking and tapping to consolidate the glass beads to attain a given bulk mass density. Experiments were conducted on dry unsorted beads at three initial mass densities (1.46, 1.54 and 1.61 g/cm3), sorted beads at three sizes (0.30, 0.212, and 0.106 mm), and partially saturated beads with average bead size of 0.212 mm at five water contents (0, 7, 14, 18 and 22 % by weight). Effect of initial mass density, bead size and water content on the dynamic volumetric and deviatoric response was investigated. The impacted beads were sorted for analysis of the particle size distribution. The compressibility was characterized in terms of the void ratio as a function of the axial pressure.

Macroporous Poly(Vinyl Acetate-Co-Divinyl Benzene) Copolymer Beads as Adsorptive Support for the Direct Immobilization of Candida antarctica Lipase B

A series of macroporous poly(vinyl acetate-co-divinyl benzene) [poly(VAc-co-DVB)] copolymer beads with varying cross-link density (CLD) were synthesized by suspension polymerization and used as support for the immobilization of Candida antarctica lipase B (CALB) with and without saponification. These copolymer beads have average pore diameter and BET (Brunauer-Emmett-Teller) surface area ranging between 69 nm to 115 nm and 89 m2/g to 204 m2/g respectively. On immobilization, non-saponified poly(VAc-co-DVB) copolymer beads with CLD 50% (PVAc-DVB-50-UH) showed higher tributyrin hydrolysis activity (2647.35 TBU/g dry beads) than that saponified beads (PVAc-DVB-50-H) (1706.54 TBU/g dry beads) indicating that direct immobilization without saponification is better for CALB immobilization. PVAc-DVB-50-UH showed 94.82% residual activity after 100 days of storage.

Pearling and arching instabilities of a granular suspension on a super-absorbing surface.

We show that a granular suspension, composed of particles immersed in a liquid, can form pearls, hooks, and arches when deposited from a nozzle onto a translating substrate that acts as a liquid super-absorber. The removal of the liquid induces a rapid pinning of the contact line leading to mechanically stable structures that are held together by capillary adhesion with shapes that depend on the relative solidification rate. Pearls or hooks form depending on whether the suspension snaps off before or after coming into contact with the substrate. A cylindrical thread with a near circular cross-section and various undulatory structures forms if solidification occurs prior to snap-off. In particular, when the jet solidifies before coming into contact with the substrate, it folds periodically, resulting in arches with a span length determined by the deposition flux and the substrate speed. Period doubling and meandering are observed leading to further structures with vertical and horizontal ripples when the deposition flux is increased.

Uptake of nickel ions from aqueous solutions using protonated dry alginate beads

Uptake of nickel ions from aqueous solutions using protonated dry alginate beads was studied. Nickel uptake increased with stirring rate, reaching values of 75·9 mg mg−1 of dry alginate at 300 rev min−1, at solution pH of 5·0 and 360 min. For a nickel concentration less than 12 mg L−1, the uptake was complete. The nickel uptake mechanism is explained by ion exchange between Ni ions and protons from the functional groups of the alginate beads. The uptake kinetics was represented by a pseudo-second order model. A rate constant value of 1·1×10−4 g mg−1 min−1 was determined. At equilibrium conditions, the experimental data were fitted to a Langmuir adsorption model, and the highest uptake values were found to be 97·6 and 131·6 mg g−1 at pH of 4·0 and 5·0, respectively, which were higher than the values reported for different sorbents used for nickel uptake in the literature. Observations obtained by SEM and cross-sectional compositions measured by EDS indicated that the surface of the alginate beads do not suffer any size variation after the experimentation; however, the roughness the surface was lost during the removal.