Bead Density Research Articles

Macroparticle-enhanced cultivation of Lentzea aerocolonigenes: Variation of mechanical stress and combination with lecithin supplementation for a significantly increased rebeccamycin production.

The actinomycete Lentzea aerocolonigenes produces the antitumor antibiotic rebeccamycin. In previous studies the rebeccamycin production was significantly increased by the addition of glass beads during cultivation in different diameters between 0.5 and 2 mm and the induced mechanical stress by the glass beads was proposed to be responsible for the increased production. Thus, this study was conducted to be a systematic investigation of different parameters for macroparticle addition, such as bead diameter, concentration, and density (glass and ceramic) as well as shaking frequency, for a better understanding of the particle-induced stress on L. aerocolonigenes. The induced stress for optimal rebeccamycin production can be estimated by a combination of stress energy and stress frequency. In addition, the macroparticle-enhanced cultivation of L. aerocolonigenes was combined with soy lecithin addition to further increase the rebeccamycin concentration. With 100 g L-1 glass beads in a diameter of 969 µm and 5 g L-1 soy lecithin a concentration of 388 mg L-1 rebeccamycin was reached after 10 days of cultivation, which corresponds to the highest rebeccamycin concentrations achieved in shake flask cultivations of L. aerocolonigenes stated in literature so far.

Ultra-Lightweight EPS Concrete: Mixing Procedure and Predictive Models for Compressive Strength

Expanded polystyrene (EPS) lightweight concrete is increasingly used in various applications due to its lightweight, excellent heat preservation, sound insulation and energy absorbing characteristics. However, due to the hydrophobic nature and very low density of EPS beads, EPS concretes are prone to segregation, poor bonding, and homogeneity issues. The properties of EPS concrete are highly dependent on the mixture proportions and mixing procedure. This study involves the development of a quality mixing procedure for Ultra-lightweight EPS concrete and the development of two predictive compressive strength models function of concrete mixture and density, respectively. An experimental program is developed to implement the mixing procedure and to calibrate and evaluate the accuracy of the models. The proposed models were found to accurately predict the strength of concrete mixtures. The corresponding standard error for the models is less than 0.3 MPa and the corresponding correlation coefficient is greater than 0.93. To ensure quality control before concrete is cast, a link between the plastic density of fresh concrete and the compressive strength was established. Furthermore, to accommodate tight construction schedules, the effects of concrete age on the compressive strength development were studied and the 28-day strength was related to strengths at early ages.

An Estimation Approach for the Effective Elastic Modulus of Lightweight Bulk Filling Material with Compressible Inclusions and Imperfect Interfaces.

In this study, an approach is developed to estimate the density and effective elastic modulus of a lightweight bulk filling material made up of expanded polystyrene (EPS) and cement-reinforced clay (matrix). First, a representative volume element (RVE) is composed of cell A (an EPS and matrix) and cell B (matrix only). Then, an elastic interface is introduced to describe the discontinuity of displacement at the interface between EPS beads and matrix. Third, an Eshelby compliance tensor is modified in cell A to include the effects of imperfect interface and the compressibility of EPS beads. Finally, the approach for the density and effective elastic modulus of the EPS beads mixed cement-reinforced clay is verified with experimental data. The compressibility ratio of lightweight clay is compared under different confining pressures and curing times. It is found that the imperfect interface has salient impacts on the effective elastic modulus with the increase of volume fraction of inclusions. The interface parameters (α and β) vary with curing time and confining pressure. At the same curing time, the parameter α is almost constant regardless of confining pressure but the parameter β changes with confining pressure. The compressibility ratio is smaller for longer curing time if the confining pressure is constant.

Traction Force Microscopy to Study B Lymphocyte Activation.

Traction force microscopy (TFM) enables the measurement of forces produced by a cell on a substrate. This technique infers traction force measurements from an experimentally observed displacement field produced by a cell pulling on an elastic substrate. Here, we adapted TFM to investigate the spatial and temporal structure of the force field exerted by B cells when activated by antigen engagement of the B cell receptor. Gel rigidity, bead density, and protein functionalization must be optimized for the study of relatively small cells (~ 6 µm) that interact with, and respond specifically to ligands for cell surface receptors.

Mechano-responsiveness of fibrillar adhesions on stiffness-gradient gels.

ABSTRACTFibrillar adhesions are important structural and adhesive components in fibroblasts, and are required for fibronectin fibrillogenesis. While nascent and focal adhesions are known to respond to mechanical cues, the mechanoresponsive nature of fibrillar adhesions remains unclear. Here, we used ratiometric analysis of paired adhesion components to determine an appropriate fibrillar adhesion marker. We found that active α5β1-integrin exhibits the most definitive fibrillar adhesion localization compared to other proteins, such as tensin-1, reported to be in fibrillar adhesions. To elucidate the mechanoresponsiveness of fibrillar adhesions, we designed a cost-effective and reproducible technique to fabricate physiologically relevant stiffness gradients on thin polyacrylamide (PA) hydrogels, embedded with fluorescently labelled beads. We generated a correlation curve between bead density and hydrogel stiffness, thus enabling a readout of stiffness without the need for specialized knowhow, such as atomic force microscopy (AFM). We find that stiffness promotes growth of fibrillar adhesions in a tensin-1-dependent manner. Thus, the formation of these extracellular matrix-depositing structures is coupled to the mechanical parameters of the cell environment and may enable cells to fine-tune their matrix environment in response to changing physical conditions.

Fluctuation-Based Super-Resolution Traction Force Microscopy.

Cellular mechanics play a crucial role in tissue homeostasis and are often misregulated in disease. Traction force microscopy is one of the key methods that has enabled researchers to study fundamental aspects of mechanobiology; however, traction force microscopy is limited by poor resolution. Here, we propose a simplified protocol and imaging strategy that enhances the output of traction force microscopy by increasing i) achievable bead density and ii) the accuracy of bead tracking. Our approach relies on super-resolution microscopy, enabled by fluorescence fluctuation analysis. Our pipeline can be used on spinning-disk confocal or widefield microscopes and is compatible with available analysis software. In addition, we demonstrate that our workflow can be used to gain biologically relevant information and is suitable for fast long-term live measurement of traction forces even in light-sensitive cells. Finally, using fluctuation-based traction force microscopy, we observe that filopodia align to the force field generated by focal adhesions.

Bayesian Cell Force Estimation Introducing Cell Shape Prior

Cell morphogenesis and migration are essential for various physiological and pathological processes. To elucidate their mechanisms, it is necessary to observe the mechanical force generated by the cells. Traction force microscopy (TFM) uses fluorescent nanobeads that are embedded in the surface layer of an elastic gel substrate. When cells cultured on the substrate generate traction force, the beads change their locations due to the force-induced deformation of the gel substrate. Various algorithms for estimating traction force from bead displacement have been proposed. Higher bead density is better for accurate force estimation. However, substrates containing high-density beads have several problems such as heterogeneous distribution of beads, fusions of condensed beads on the image, and influence on the effective Young's modulus of the substrate. Therefore, it is important to develop an algorithm to estimate accurate traction forces under the condition of a small number of beads. In this study, we proposed the traction force estimation algorithm introducing the force priors: force is more likely to occur near the edge of a cell and is directed from the edge to the center of the cell. Using synthetic condition with 3∼8 beads per one um2, we estimated traction force by employing Bayesian framework. We also estimated the minimum density of the beads against the cell size that guarantees the accuracy of force estimation. The proposed algorithm showed better performance than other regression-based methods such as Ridge regression or LASSO. Furthermore, we applied the algorithm to the traction force estimation of neuronal growth cone.

Optimization of the optical structure of thin direct-lit LED backlights for LCD applications by using micro-LEDs

The optimized optical structure of the micro-LED-based direct-lit backlight was investigated through optical simulation. The backlight consisted of only one diffuser plate and an array of micro-LEDs with a reflection film positioned on the bottom of the backlight. An additional reflector was put on top of each micro-LED to prevent the formation of bright spots. Under several number density conditions of the microbeads in the diffuser plate, stable regions were found on the gap-pitch plot, where a high Mura index of ∼1 was secured. The bead density needed to be small (around 104 mm−3) to maintain above 60% transmittance, because the transmittance of the backlight was significantly reduced at higher bead densities. Under the 104 mm−3 bead density condition, the gap can be reduced to 1.5 mm at a 3 mm pitch. The gap can be further reduced if additional optical films, such as a diffuser sheet, a prism film, and a reflective polarizer, will be adopted in the backlight. This work demonstrated that micro-LEDs are ideal light sources for realizing a thin direct-lit backlight for LCD applications.

A new approach for the shaping up of very fine and beadless UV light absorbing polycarbonate fibers by electrospinning

An innovation will be recognized as successful only if it satisfies all phases of product development; i.e. from the specification to mass production. Therefore, a cost-effective production by keeping the best possible characteristics is vital in any Industry. Large scale production of polymer fibers with ultrafine morphology is such a challenge to the field of nanotechnology. The idea proposed here utilizes the versatile electrospinning technology for the preparation of uniform, beadless and ultraviolet light absorbing polycarbonate (PC) nanofibers. The average diameter limits to 114 nm and that too by using most convenient and comparatively less toxic solvent mixture. This method is simple and so far, it is not reported elsewhere. For THF-DMF system a PC concentration of 17 w/v% and for DCM-DMF system a PC concentration of 15 w/v% was found to be the optimum polymer concentration. The average fiber diameter and bead density were very much influenced by the viscosity, conductivity and concentration of the solution used for electrospinning. The PC fibers (PC concentration of 15 w/v % in DCM-DMF system) with lowest average diameter of 114 nm shows excellent ultraviolet absorption, semicrystalline nature, enhanced glass transition temperature and thermal stability.

High-Efficiency Enzymatic Fuel Cell Via Multienzyme Cascade on DNA Scaffold

Even though enzymatic fuel cells (EFCs) are considered as a promising green alternative method of power generation, much of their research has been limited to the use of a single enzyme as biocatalyst, leading to incomplete oxidation as well as limited range of simple fuels. In this work, enzymatic fuel cell utilizing multienzyme cascade system immobilized on DNA scaffold as anodic biocatalyst as well as high-surface area, electrically conductive carbonaceous nanofibers (CNFs) as electrodes was built for the first time to accommodate a complex molecule such as cellulose as fuel. Three cellulases and cellulose-binding domain (CBD) were expressed in E.Coli, purified using elastin-like polypeptide (ELP) and then conjugated with DNA linker using a fusion partner called HaloTag. All four enzymes and commercial glucose oxidase (GOx) were site-specifically immobilized on customized DNA template via hybridization for efficient cellulose hydrolysis and subsequent glucose oxidation. Varied number of enzymes were combined on the DNA scaffold and resulting reaction rate was compared to the same number of enzymes freely suspended in solution. Successful immobilization of enzymes on the DNA template increased the reaction rate up to 10-fold compared to when they were in solution, confirming the synergistic effect of the multiple enzymes immobilized on a scaffold. Investigation of temperature and pH effect revealed imitating the enzymes’ typical habitat (i.e. 37 oC and pH5) further increased the reaction rate of the multienzyme system. Carbonaceous nanofibers (CNFs) were used as the electrodes for both anode and cathode, which were first produced as polyacrylonitrile (PAN) nanofibers via electrospinning method. Three sets of design of experiments (DOEs) were used to systematically vary the solution, electrospinning, and environmental conditions. Analyses of the effect of the conditions on nanofiber diameter and bead density allowed for minimization of PAN nanofiber diameter down to 38 ± 7 nm with negligible bead density. PAN nanofibers were then converted to CNFs via a two-step heat treatment, and their resulting molecular structure confirmed by FT-IR and XRD was graphitic. Electrical conductivity characterized by 4-point probe measurement supported that CNFs were suitable for electrode applications, ranging from 1.2 to 7.4 S/cm. Electrochemical characterization of CNF mat electrode functionalized with GOx exhibited direct electron transfer from GOx cofactor to the CNF mat electrode at E=-0.63 V vs. Ag/AgCl. Anodic performance of CNF mat electrode functionalized with multienzyme system was electrochemically characterized by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Finally, cellulolytic enzymatic fuel cell was assembled with the multienzymatic CNF anode and CNF cathode, which was functionalized with bilirubin oxidase for oxygen reduction. Figure 1. Schematic representation of the cellulolytic enzymatic fuel cell with multienzyme cascade on DNA scaffold immobilized on carbonaceous nanofiber mat electrode. Components not drawn to scale. Figure 1

Establishing an Electrostatics Paradigm for Membrane Electroporation in the Framework of Dissipative Particle Dynamics

With an exclusive aim to looking into a mechanism of membrane electroporation on mesoscopic length and time scales, we report the dissipative particle dynamics (DPD) simulation results for systems with and without electrolytes. A polarizable DPD model of water is employed for accurate modeling of long-range electrostatics near the water-lipid interfaces. A great deal of discussion on field induced change in dipole moments of water and lipids together with the special variation of electric field is made in order to understand the dielectrophoretic movement of water, initiating a pore formation via an intrusion through the bilayer core. The presence of salt alters the dipolar arrangement of lipids and water, and thereby it reduces the external field required to create a pore in the membrane. The species fluxes through the pore, distributions for bead density, electrostatic potential, stresses across the membrane, etc. are used to answer some of the key questions pertaining to mechanism of electroporation. The findings are compared with the molecular dynamics simulation results found in the literature, and the comparison successfully establishes an electrostatics paradigm for biomembrane studies using DPD simulations.

A cost effective and facile approach to prepare beadless polycarbonate nanofibers with ultrafine fiber morphology

Preparing defect free nanofibers with average diameter well below 100 nm is a challenge to researchers by electrospinning technology. In the present contribution, the electrospinning method was utilized to prepare beadless polycarbonate (PC) nanofibers with average diameter 90 nm using comparatively less toxic and suitable solvents in a convenient way. Spinning PC with pure dichloromethane (DCM) and also with 1:1 mixture of DCM and N,N dimethylformamide under the same spinning parameters with varying PC concentration has very much helped to establish the effect of solvents on fiber formation. This study also proved the impact of solution concentration, viscosity, and solution conductivity on the formation of beadless ultrafine PC fibers and subsequently on the bead density and average fiber diameter. The appropriate proportion of solvents under suitable spinning parameters has helped to minimize the quantity of PC during the formation of bead free nanofibers by electrospinning. The ultrafine, uniform, and beadless morphology of the electrospun PC fibers can be utilized for various nanotechnology advancements. POLYM. ENG. SCI., 59:1799–1809, 2019. © 2019 Society of Plastics Engineers

Fabrication of superhydrophobic surfaces with tunable water droplet adhesion force by a two-step method

Abstract In this paper, we present a convenient approach to prepare hierarchical structured superhydrophobic coatings with tunable adhesion force, composed of micro-size glass beads, nano-size SiO2 particles and epoxy resin. Surfaces of two types with different roughness were fabricated, one type is only with single-scale roughness demonstrating lotus effect with low sliding angle, the other type is hierarchically micro-nano-structured roughness exhibiting petal effect with high adhesion force. The surface roughness is pivotal for controlling the wetting behavior and regulating the contact angle including the contact angle hysteresis. Varying the density of micro-size glass beads could adjust the roughness of the surface, which means the adhesion force of the prepared surface could be easily controlled based on the proposed method. Through variation of glass beads’ amount, the surface could be designed to pin the water droplet with different adhesion force when the surface turned upside down. The surface wettability, surface morphology, adhesion force of the prepared samples are investigated and mechanism of the Cassie-to-Wenzel state transition are discussed in detail. Furthermore, the convenient method provides a possibility for controlling surface morphology, composition and corresponding surface adhesion which could be applied to various substrates such as tile, wood, steel and fabric.

Water vapor capturing using an array of traveling liquid beads for desalination and water treatment.

Growing concern over the scarcity of freshwater motivates the development of compact and economic vapor capture methods for distributed thermal desalination or harvesting of water. We report a study of water vapor condensation on cold liquid beads traveling down a massive array of vertical cotton threads that act as pseudo-superhydrophilic surfaces. These liquid beads form through intrinsic flow instability and offer localized high-curvature surfaces that enhance vapor diffusion toward the liquid surface, a critical rate-limiting step. As the liquid flow rate increases, the bead spacing decreases, whereas the bead size and speed stay nearly constant. The resulting increase in the spatial bead density leads to mass transfer conductances and hence condensation rates per volume that are almost three times higher than the best reported values. Parallel and contiguous gas flow paths also result in a substantial reduction in gas pressure drop and hence electric fan power consumption.

Hertzian elasticity and triggered swelling kinetics of poly(amino ester)-based gel beads with controlled hydrophilicity and functionality: A mild and convenient synthesis via dropwise freezing into cryogenic liquid

Poly(amino ester)-based homo- and co-polymeric gel beads were prepared via “dropwise freezing into cryogenic liquid” method and multi-responsive properties of the prepared spherical beads were confirmed by the pulsatile swelling kinetics and the stress-strain relationships based on Hertzian elasticity. Dual pH- and ionic strength-responsive homopolymeric PDMAEMA as well as copolymeric poly(hydroxyethyl methacrylate-co-dimethylaminoethyl methacrylate) P(HEMA-co-DMAEMA) gel beads crosslinked with diethyleneglycol dimethacrylate (DEGDMA) were prepared by aqueous phase crosslinking copolymerization at subzero temperature within the millimeter-sized frozen droplets in the paraffin oil as continuous phase. With this method, spherical ionic gel beads of sizes 2–5 mm could be synthesized without using a stabilizer. The successful synthesis of PDMAEMA and P(HEMA-co-DMAEMA) gel beads was confirmed by ATR-FTIR and SEM. Modulus of elasticity of cross-linked poly(amino ester)-based gel beads in swollen state was measured as a function of the bead diameter. The relationship between the compressive elastic force and corresponding deformation was obtained to compare the experimental results with theoretical-analytical formulations using the constitutive relations from Hertzian elasticity. The effective crosslink density of gel beads produced in the same synthesis batch increased as a function of increasing bead diameter, which was attributed to the formation conditions of the beads via frozen droplets of the pre-gel solution. The synthesis pathway used for the production of gel beads from methacrylate-based monomer with a polar tertiary amino group offered one-way control over material geometry to design soft and smart materials with controlled size and porosity.

Study on the degradation performance and kinetics of immobilized cells in straw-alginate beads in marine environment

In this study, two strains Halomonas and Aneurinibacillus were mixed in equal proportions as free cells that could degrade diesel and produce biosurfactant. A new type of immobilized cells, free cells immobilized in beads combined with sodium alginate and straw, was studied. The components of straw-alginate beads were optimized by Response Surface Method, and the degradation performance of immobilized cells was determined. The result indicated that the density, strength and broken rate of straw-alginate beads were 1.04 g/cm3, 216 g and 4%, respectively. The best degradation rate of immobilized cells in straw-alginate beads could be 68.68%. Lately, by analyzing the Monod model, vmax (maximum specific degradation rate of diesel) and KS (half saturation rate constant) of immobilized cells in straw-alginate beads were 1.84 d−1 and 3.23 g/L, respectively, which explained the higher degradation performance.

The Effect of Bead Shape and Texture on the Energy Loss Characteristics in a Rotating Capsule

Energy loss characteristics in a rotating bead-filled capsule are impacted by bead shape, size, surface texture, density, and capsule fill level. In this paper, the energy loss results are reported from experiments of bead-filled cylindrical capsules rolling down a ramp in a controlled manner without sliding. These experiments were motivated by the potential applications of bead-filled capsules for energy dissipation and vibration control systems, as well as for understanding energy use in rotating drum-based industrial processes. The experiment used a plexiglass cylindrical capsule filled with beads of different sizes, materials, and textures. The bead-filled capsule was rolled down an inclined ramp and came to a stop on a level ramp. The position at which the capsule stopped was recorded. As the capsule rolled down the ramp, the potential energy converted to kinetic energy. When the kinetic energy dissipated, the capsule came to a stop. The distance traveled by the capsule is controlled by the energy loss caused by the collision and the friction of the beads. The nature of the collision and friction of the beads depended on the amount, size, type, and texture of the beads in the cylinder. The data was analyzed to determine the conditions for optimal fill level, which is defined as the case for maximum energy loss. We found that the intermediate filling level had the most energy loss. This optimal filling was obtained for each bead type.The maximum energy dissipation increased with bead surface texture and bead density but decreased with bead size.

Electroporation Using Dissipative Particle Dynamics with a Novel Protocol for Applying Electric Field.

In molecular dynamics simulations of membrane electroporation, the bilayer is subjected to an electric field E either by direct addition of a force f = qE on the charge-bearing species or by imposing an ion imbalance in the salt solutions on the two sides of the bilayer. The former is believed to mimic electroporation with high fields over nanosecond pulse period, during which the membrane is almost uncharged, especially in the low salt limit. Conversely, the ion imbalance method elucidates a low electric field-induced poration over a longer period of micro- to milliseconds with a fully charged membrane. Both these methods of applying electric field have disadvantages while investigating electroporation using dissipative particle dynamics (DPD) simulations. The method involving direct addition of force fails to address the presence of a nonuniform dielectric background for ions embedded in nonpolarizable DPD water and those found in the core of the bilayer. The ion imbalance method in DPD simulations suffers from its unavoidable use of a wall potential to prevent the movement of ions across the periodic boundaries. To address the above issues, we propose a simple method for imposing a desired transmembrane potential (TMV) by placing oppositely but uniformly charged plates on either side of the bilayer. Our DPD simulations demonstrate that the profiles for bead density, mechanical stress, electrical potential, as well as the transient responses in the dipole moment and species fluxes obtained from the proposed method utilizing charged plates are quite similar to those obtained using the ion imbalance method. The proposed protocol is free from the aforementioned drawbacks of the direct force addition and ion imbalance methods.

An examination of critical parameters in hybridization-based epigenotyping using magnetic microparticles.

Gene-specific promoter methylation is involved in gene silencing and is an important cancer biomarker. Cancer-specific methylation patterns have been observed and clinically validated for numerous gene promoters, but the knowledge gleaned from this large body of work is currently under-utilized in the clinic. Methylation-specific PCR is currently the gold standard method for clinical methylation assessment, but several research groups have proposed hybridization-based techniques which could be simpler to implement and provide more accurate results. However, the sensitivity of this easier alternative must be improved dramatically in order to compete with methylation-specific PCR. Efficient sample capture is a key step in maximizing sensitivity, so here we investigate the key parameters involved in (i) maximizing the capture of gene-specific target DNA molecules at the surfaces of functionalized, magnetic microparticles and (ii) recognizing DNA methylation using an engineered methyl-CpG-binding domain (MBD) protein. The magnetic bead density, the probe concentration, and the MBD concentration were very important for maximizing detection, and other variables such as the hybridization time also impacted the target capture efficiency but had a smaller effect on the overall methylation assay. The effect of genomic DNA on the capture of the target sequence was also investigated, and model methylated vs. unmethylated target sequences could be distinguished in the presence of 1 ng/μL genomic DNA. The findings we report related to the underlying binding events involved in hybridization-based epigenotyping can be leveraged in combination with the many signal amplification and detection approaches that are currently being developed. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1589-1595, 2018.

Synthesis and characterization of orthorhombic-MoO3 nanofibers with controlled morphology and diameter

Orthorhombic molybdenum trioxide (α-MoO3) nanofibers with controlled morphology and diameter were synthesized by adjusting electrospinning and calcination conditions. Experimental design was utilized to vary several factors including solution properties, electrospinning parameters and environmental conditions to analyze their effects toward nanofiber morphology (i.e., diameter and bead density). Polyvinylpyrrolidone (PVP) content, which effects viscosity, predominated control morphology of nanofibers where low PVP content (i.e., 3.0wt.%) yielded heavily beaded nanofibers with smaller diameter. The morphology of nanofibers was also tuned by adjusting electrospinning parameters (i.e., applied voltage and feed rate), where smallest nanofibers with minimum bead density was achieved at applied voltage of 8kV with feed rate of 0.5mL/h. The as-electrospun ammonium molybdate/polyvinylpyrrolidone nanofibers were calcined to α-MoO3 nanofibers in air. The ramping rate significantly altered the morphology of α-MoO3 nanofibers where rapid thermal annealing with the ramping rate of 15°C/s yielded smoother nanofibers whereas slower ramping rate yielded platelet-like structures. BET analysis showed an increase in specific surface area with decreasing average diameter (i.e., 6.7m2/g for 125nm–86.4m2/g for 35nm).