Large Beads Research Articles

The functional significance of stereopsis.

Purpose. Development or restoration of binocular vision is one of the key goals of strabismus management; however, the functional impact of stereoacuity has largely been neglected. Methods. Subjects aged 10 to 30 years with normal, reduced, or nil stereoacuity performed three tasks: Purdue pegboard (measured how many pegs placed in 30 seconds), bead threading (with two sizes of bead, to increase the difficulty; measured time taken to thread a number of beads), and water pouring (measured both accuracy and time). All tests were undertaken both with and without occlusion of one eye. Results. One hundred forty-three subjects were recruited, 32.9% (n = 47) with a manifest deviation. Performances on the pegboard and bead tasks were significantly worse in the nil stereoacuity group when compared with that of the normal stereoacuity group. On the large and small bead tasks, those with reduced stereoacuity were better than those with nil stereoacuity (when the Preschool Randot Stereoacuity Test [Stereo Optical Co, Inc., Chicago, IL] results were used to determine stereoacuity levels). Comparison of the short-term monocular conditions (those with normal stereoacuity but occluded) with nil stereoacuity showed that, on all measures, the performance was best in the nil stereoacuity group and was statistically significant for the large and small beads task, irrespective of which test result was used to define the stereoacuity levels. Conclusions. Performance on motor skills tasks was related to stereoacuity, with subjects with normal stereoacuity performing best on all tests. This quantifiable degradation in performance on some motor skill tasks supports the need to implement management strategies to maximize development of high-grade stereoacuity.

Prediction of Hot Cracks of T-Joints in Full-Penetration Welding Process

In this study, the influence of welding conditions on the formation of a pear-shaped bead crack is examined through experiments on full-penetration welding of T-joints. These problems are analyzed using the finite element method (FEM). The formation and growth of a pear-shaped bead crack in T-joints welded by full-penetration, high-current pulsed MAG (Metal Active Gas) welding is simulated using temperature-dependent interface elements, which are introduced in the thermal-elastic-plastic FEM analysis. The experimental results show that a pear-shaped bead crack does not occur when the heat input is greater than 2 500 J/mm, or when the penetration bead is formed. However, according to commonly accepted knowledge, both large heat input and a large penetration bead (deep penetration relative to the penetration width) lead to hot crack formation. To understand these experimental results, FEM simulations are conducted and the influences of heat input and the size of the penetration bead are investigated.

Essential Analogies in Human Anatomy & Physiology

Research Article| November 01 2009 Essential Analogies in Human Anatomy & Physiology R. Bruce Sundrud, R. Bruce Sundrud Search for other works by this author on: This Site PubMed Google Scholar Kris Hueftle Kris Hueftle Search for other works by this author on: This Site PubMed Google Scholar The American Biology Teacher (2009) 71 (9): 554–557. https://doi.org/10.2307/20565380 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation R. Bruce Sundrud, Kris Hueftle; Essential Analogies in Human Anatomy & Physiology. The American Biology Teacher 1 November 2009; 71 (9): 554–557. doi: https://doi.org/10.2307/20565380 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe American Biology Teacher Search This content is only available via PDF. Copyright National Association of Biology Teachers Article PDF first page preview Close Modal You do not currently have access to this content.

Folding of electrostatically charged beads-on-a-string as an experimental realization of a theoretical model in polymer science

The "beads-on-a-string" model for folding of polymers is a cornerstone of theoretical polymer science. This communication describes a physical model of beads-on-a-string, based on the folding of flexible strings of electrostatically charged beads in two dimensions. The system comprises millimeter-scale Teflon and Nylon-6,6 (spherical or cylindrical) beads (approximately 6 mm in diameter) separated by smaller (approximately 3 mm) poly(methyl methacrylate) (PMMA) spherical beads, threaded on a flexible string. The smaller, uncharged beads define the distances between the larger beads, and control the flexibility of the string. During agitation of the sequence of beads on a planar, horizontal paper surface, tribocharging generates opposite electrostatic charges on the larger Nylon and Teflon beads, but leaves the smaller PMMA beads essentially uncharged; the resulting electrostatic interactions cause the string to fold. Examination and comparison of two models--one physical and one theoretical--may offer a new approach to understanding folding, collapse, and molecular recognition at an abstract level, with particular opportunity to explore the influence of the flexibility of the string and the shape of the beads on the pattern and rate of folding. The physical system is, thus, an analog computer, simulating the theoretical beads-on-a-string model in two dimensions; this system makes it possible to test hypotheses connecting "sequence" to "folding", rapidly and conveniently, while exploring nonlinearities and other complexities omitted from the theoretical model.

Entropic organization of interphase chromosomes

Chromosomes are not distributed randomly in nuclei. Appropriate positioning can activate (or repress) genes by bringing them closer to active (or inactive) compartments like euchromatin (or heterochromatin), and this is usually assumed to be driven by specific local forces (e.g., involving H bonds between nucleosomes or between nucleosomes and the lamina). Using Monte Carlo simulations, we demonstrate that nonspecific (entropic) forces acting alone are sufficient to position and shape self-avoiding polymers within a confining sphere in the ways seen in nuclei. We suggest that they can drive long flexible polymers (representing gene-rich chromosomes) to the interior, compact/thick ones (and heterochromatin) to the periphery, looped (but not linear) ones into appropriately shaped (ellipsoidal) territories, and polymers with large terminal beads (representing centromeric heterochromatin) into peripheral chromocenters. Flexible polymers tend to intermingle less than others, which is in accord with observations that gene-dense (and so flexible) chromosomes make poor translocation partners. Thus, entropic forces probably participate in the self-organization of chromosomes within nuclei.

Confocal Nanoscanning, Bead Picking (CONA): PickoScreen Microscopes for Automated and Quantitative Screening of One-Bead One-Compound Libraries

Solid phase combinatorial chemistry provides fast and cost-effective access to large bead based libraries with compound numbers easily exceeding tens of thousands of compounds. Incubating one-bead one-compound library beads with fluorescently labeled target proteins and identifying and isolating the beads which contain a bound target protein, potentially represents one of the most powerful generic primary high throughput screening formats. On-bead screening (OBS) based on this detection principle can be carried out with limited automation. Often hit bead detection, i.e. recognizing beads with a fluorescently labeled protein bound to the compound on the bead, relies on eye-inspection under a wide-field microscope. Using low resolution detection techniques, the identification of hit beads and their ranking is limited by a low fluorescence signal intensity and varying levels of the library beads' autofluorescence. To exploit the full potential of an OBS process, reliable methods for both automated quantitative detection of hit beads and their subsequent isolation are needed. In a joint collaborative effort with Evotec Technologies (now Perkin-Elmer Cellular Technologies Germany GmbH), we have built two confocal bead scanner and picker platforms PS02 and a high-speed variant PS04 dedicated to automated high resolution OBS. The PS0X instruments combine fully automated confocal large area scanning of a bead monolayer at the bottom of standard MTP plates with semiautomated isolation of individual hit beads via hydraulic-driven picker capillaries. The quantification of fluorescence intensities with high spatial resolution in the equatorial plane of each bead allows for a reliable discrimination between entirely bright autofluorescent beads and real hit beads which exhibit an increased fluorescence signal at the outer few micrometers of the bead. The achieved screening speed of up to 200,000 bead assayed in less than 7 h and the picking time of approximately 1 bead/min allow exploitation of one-bead one-compound libraries with high sensitivity, accuracy, and speed.

Nonlinear dynamics of superparamagnetic beads in a traveling magnetic-field wave

The nonlinear dynamic behavior of superparamagnetic beads exposed to a periodic array of micromagnets and an external rotating field is simulated as a function of the relative size of the bead with respect to the micromagnet size and the strength of the external field relative to the pole density of the substrate. For large bead sizes, it is confirmed that the motion of the beads corresponds to the dynamics of an overdamped nonlinear harmonic oscillator. For lower bead sizes, additional subharmonic locking effects are observed along with the emergence of bounded orbits. These results qualitatively support previous experimental investigations of traveling-wave magnetophoresis and provide guidelines for achieving nearly infinite separation resolution between differently sized beads.

Fast Detection of Biological Targets With Magnetic Marker and SQUID

We have been developing a SQUID system for the detection of biological targets. In this system, magnetic markers are bound to the targets, and the magnetic signal from the bound markers is detected with the SQUID. In order to realize fast detection of the targets, we developed a liquid-phase detection method. First, we used large polymer beads as material to capture the targets. Since the polymer beads are uniformly dispersed in liquid, biological targets on the surface of the polymer bead can be easily coupled to the markers, which results in the fast reaction time. Next, we detected the bound markers without using the washing process to separate the bound and unbound markers, which was realized by using the difference in the Brownian relaxation time between them. Using this procedure, we demonstrated the detection of the target called IgE, as well as biotin-coated polymer beads. We obtained a good relationship between the amount of IgE and the magnetic signal. The result was the same as that obtained using the conventional procedure. The reaction time for the coupling between the magnetic marker and the target was 4 min, which was much shorter than the conventional method. These results show the usefulness of the present method.

Dispersion of particles by spontaneous interparticle percolation through unconsolidated porous media

We have performed extensive experimental and numerical studies of spontaneous percolation of small beads through an unconsolidated porous media made with large glass beads. In this paper, an experimental setup and a fast "discrete element method" algorithm are presented to deal with large numbers of particles during our interparticle percolation phenomenon studies. In all the experimental and numerical analyses, the size ratio between the moving beads and the stable packing was chosen larger than the geometrical trapping threshold: xi_{c}=(2/sqrt[3]-1);{-1}=6.464... . We measure the longitudinal and transverse dispersion coefficients versus the height of the porous medium or the number of falling small beads. The influence of bead properties such as density, diameter, or restitution coefficients was investigated by using either steel or glass beads. The individual description of these effects and their explanations were made possible by confrontation and coupling between experimental and numerical results. Indeed, with our numerical model, individual analysis of the effects of these mechanical or geometrical parameters were made possible and carried out.

Experimental and numerical investigations of gouge formation related to blast furnace burden distribution

This paper presents an experimental and numerical study of the gouge formation related to burden distribution in a BF. Physical experiments are conducted using a simplified bell-less charging model. The results indicate that the burden distribution is affected by particle properties such as density and size, and geometry of experimental set-up such as chute angle and distance between bin and chute. The gouge area generated is related to the ratio of the input energy from the top layer to the inertial energy from the base layer for the cases with red wooden balls, large glass beads and large steel balls. Numerical experiments are performed by means of the discrete element method. It is shown that the simulation model can reproduce the experimental results well. The weight ratio distribution is found to be largely affected by the densities of materials. The force structures are also analyzed to understand the fundamentals of the formation of the burden profiles.

Axial and radial segregation of granular mixtures in a rotating spherical container

We report the formation of axial segregation patterns of bidisperse granular mixtures of glass beads in a spherical container which is rotated about a central axis. When the rotation axis is horizontal, three distinct segregation bands are formed for a broad range of geometrical and dynamical parameters. We find two distinct regimes: at low fill levels the small size beads of the mixture are collected at the poles and the large size beads in a central band. At high fill levels the pole regions are occupied by large beads, while the small beads form the central band. The critical fill level for this structural transition decreases with increasing container size. For a container with 37 mm inner diameter, containing a mixture of 0.5 and 1.5 mm beads, the transition occurs between 40% and 50% fill level. When the rotation axis is tilted, the band positions are shifted and two-band structures are formed with the smaller particles at the lower pole. In our experiments the granulate is submersed in water; this allows NMR imaging of the complete three-dimensional band structures. We compare the observed segregation structures to those in cylindrical mixers and propose a model for the qualitative explanation of the pattern formation process.

Self-Assembled Magnetic Surface Swimmers

We report studies of novel self-assembled magnetic surface swimmers (magnetic snakes) formed from a dispersion of magnetic microparticles at a liquid-air interface and energized by an alternating magnetic field. We show that under certain conditions the snakes spontaneously break the symmetry of surface flows and turn into self-propelled objects. Parameters of the driving magnetic field tune the propulsion velocity of these snakelike swimmers. We find that the symmetry of the surface flows can also be broken in a controlled fashion by attaching a large bead to a magnetic snake (bead-snake hybrid), transforming it into a self-locomoting entity. The observed phenomena have been successfully described by a phenomenological model based on the amplitude equation for surface waves coupled to a large-scale hydrodynamic mean flow equation.

Burial rates of surrogate seeds in arable fields

Westerman PR, Dixon PM & Liebman M (2009). Burial rates of surrogate seeds in arable fields. Weed Research49, 142–152.SummaryThe probability of seed consumption by surface‐dwelling predators depends on the duration of seed exposure on the soil surface. We investigated seed burial using painted ceramic beads as surrogate seeds. Fifty beads of three size classes each were applied to small arenas within crop fields and their fates were followed from August to October. New sets of beads were applied as soon as most beads had disappeared from the soil surface. Bead availability on the soil surface declined immediately after placement, and then declined steadily over time, with increased loss during rain and management practices. Smaller beads were incorporated into the soil/litter matrix more easily than larger beads. Bead burial differed considerably among crop environments, with more burial in forage crops (red clover, lucerne) than in row crops (soyabean, maize). The fact that seed availability differed among crop environments suggests that it can be manipulated to maximise predation risk.

Dynamic renormalization in the framework of nonequilibrium thermodynamics

We show how the dynamic renormalization of nonequilibrium systems can be carried out within the general framework of nonequilibrium thermodynamics. Whereas the renormalization of Hamiltonians is well known from equilibrium thermodynamics, the renormalization of dissipative brackets, or friction matrices, is the main new feature for nonequilibrium systems. Renormalization is a reduction rather than a coarse-graining technique; that is, no new dissipative processes arise in the dynamic renormalization procedure. The general ideas are illustrated for dilute polymer solutions where, in renormalizing bead-spring chain models, dissipative hydrodynamic interactions between different smaller beads contribute to the friction coefficient of a single larger bead.

A Flexible Anti-Brownian Electrokinetic (ABEL) Trap for Single-Molecule Immobilization in Solution

We demonstrate our ability to trap and probe individual fluorescent particles in solution using an improved anti-Brownian electrokinetic (ABEL) trap. Traditional single-molecule immobilization techniques include surface attachment and laser tweezers; the former technique often disrupts fragile biochemical systems, while the latter requires that molecules be conjugated to large beads. The ABEL trap circumvents these issues by tracking the motion of a particle via fluorescence, and applying electrokinetic feedback forces to cancel its Brownian motion.Our ABEL trap suppresses the Brownian motion of a fluorescent particle as follows. A laser beam is rapidly steered in a small scan pattern near the center of a microfluidic cell. An avalanche photodiode detects fluorescence photons from the molecule. A field-programmable gate array compares the precise arrival time of each photon with the known position of the laser, and generates a corresponding feedback voltage. The feedback voltages is amplified and applied to the trap. We use a broadband supercontinuum laser with an acousto-optic tunable filter to enable fluorescent tracking in any part of the visible spectrum, and we scan the laser using electro-optic deflectors that can function at up to 100 kHz. This combination of hardware enables precise spatial, temporal, and spectral control of our illumination and detection optics and can apply feedback at a latency of 2 μs, a better-than-tenfold improvement over previous trap designs. We hope that these improvements will enable us to trap single small-molecule fluorophores in solution.The flexibility of the ABEL trap makes it amenable for a wide variety of biophysical studies. Work is currently underway to apply the ABEL trap to study the dynamics of DNA in solution. In the future, we hope to apply the trap to study the kinetics of proteins such as proteorhodopsin.

Separation of protein mixtures using pH-gradient cation-exchange chromatography

Historically, separation of a protein mixture after adsorption to a cation-exchange column is effected by alteration in ionic strength. An alternative separation method using pH induced gradient in the range of 4–7.5 was studied. A cation-exchange column with large particle beads containing excessive carboxyls was employed. A pH gradient across the column was generated by a step change at the column entrance using a non-retained buffer system. Consistency and accuracy of pH values in timed intervals were demonstrated in three different batches. In development of the application, we found a correlation coefficient of >0.9 between the elution pH values of six acidic proteins and their isoelectric points. One case study showed the resolution between a monoclonal antibody and non-retained protein species from a protein A column. Another case study showed the feasibility of separating polyethylene glycol conjugated protein from native protein.

Effect of an injectable 3D scaffold for osteoblast differentiation depends on bead size

The objective of this study was to evaluate the effect of beta-tricalcium phosphate (beta-TCP) bead size on the behavior of KUSA/A1 mouse osteoblasts when the beta-TCP beads are used as the solid phase of a scaffold in which alginate was used as the gel phase. KUSA/A1 cells were loaded onto a three-dimensional (3D) scaffold fabricated from beta-TCP beads with diameters ranging from 300 to 500 microm (small beads), 500-700 microm (medium beads) and 700-850 microm (large beads); cells were cultured for 3, 7 and 14 days. Scanning electron microscope observations showed that each bead was connected in a network consisting of the alginate gel and KUSA/A1 cellular matrix that was tightly bonded to form a 3D structure. After 3 days, cells in the 3D scaffold with medium beads had a significantly higher alkaline phosphatase activity (ALP) than cells in the other scaffolds. However, by 7 and 14 days in culture there was no significant difference in DNA levels, ALP activity or osteocalcin expression. At 8 weeks, only the composite containing small beads and KUSA/A1 cells had turned completely into bone in vivo. Thus, bead size may influence the success of bone formation in this context.

温度依存型界面要素を用いたT継手完全溶け込み溶接時における梨形ビード割れの発生予測

After the experience of Hanshin-Awaji Earthquake, demands for full penetration welding joint with large plate thickness have been increased to improve the performance of bridges under severe earthquake. At the same time, the full penetrated T-joints without significant defects are required from the fatigue strength point of view. In case of conventional methods, removable backing material or back gouging are employed. When the removable backing material is used, root openings are required and assembly process becomes complicated. The gouging produces large noise and fume which are not welcome for good working environment. To achieve defect free full penetration T-joint without environmental problem, high current pulsed MAG welding is introduced as an alternative method. By using this welding method, the plate with thickness from 15 to 30 mm can be welded without back gouging. It is reported that no welding defect occurs when the plate thickness is less than 17mm1). However, when the plate thickness is over 25 mm, the pear-shaped bead cracking were sometimes generated if appropriate welding conditions are not selected. Therefore, in order to apply this welding method for the construction of bridges, it is necessary to clarify the welding conditions which can prevent the formation of pear-shaped bead cracking.In this study, the influence of the welding conditions on the formation of pear-shaped bead cracking is examined through the experiments of the full penetration welding of T-joints. And the same problems are analyzed using Finite Element Method. The formation and growth of pear-shaped bead crack in T-joints welded by full penetration high current pulsed MAG welding can be simulated using temperature dependent interface element which is introduced in the thermal-elastic-plastic FEM analysis.Results of experiments show that the pear-shaped bead cracking is not formed when the heat input is greater than 2,500 J/mm or when the penetration bead is formed. However, both large heat input and large penetration bead (deep penetration compared to the penetration width) have negative influence on hot crack formation according to the commonly accepted knowledge. To understand these experimental results, FEM simulations are conducted and influences of heat inputs and size of penetration bead are investigated.

Estimation of particle size distributions from focused beam reflectance measurements based on an optical model

A popular in situ particle characterization technique, which can be applied without dilution, is the focused beam reflectance measurement ( FBRM ® ) . The FBRM probe measures a chord length distribution (CLD) which is different from a particle size distribution (PSD). In order to compare results obtained by an FBRM probe with other measurement technologies such as laser diffraction, it is necessary to reconstruct the PSD from a measured CLD. For this reconstruction a measurement model and an inversion procedure are required. Most FBRM models presented in the literature assume that an FBRM records a geometric chord which can be deduced from a two-dimensional projection of the particle silhouette. In previous work [Kail, N., Briesen, H., Marquardt, W., 2008. Analysis of FBRM measurements by means of a 3D optical model. Powder Technology 185 (3), 211–222] it has been demonstrated that FBRM data show significant deviations from this geometric model. Consequently, an estimation of a PSD using such a geometric FBRM model will fail. A novel FBRM model is developed in this work. This model imitates the chord discrimination algorithm used in a Lasentec D600L FBRM system and takes the intensity profile of the laser beam and the optical aperture of the probe into account. The model is ideally suited for the estimation of a PSD from a measured CLD using a sequential, linear inversion routine, as proposed in this work. The novel FBRM model and the inversion procedure are evaluated using small, mono-disperse polystyrene beads, large ion-exchanger beads, and α -lactose-monohydrate particles. The applicability of the FBRM for PSD measurements is discussed on the basis of these results.

Hydrogen Peroxide Removal with Magnetically Responsive Saccharomyces cerevisiae Cells

Hydrogen peroxide (HP) is a promising chemical sanitizer for use in the food industry. Its residues have to be decomposed, usually using an enzyme process employing catalase. In order to offer an inexpensive biocatalyst and to simplify subsequent manipulation, we have prepared magnetically responsive alginate beads containing entrapped Saccharomyces cerevisiae cells and magnetite microparticles. Larger beads (2-3 mm in diameter) were prepared by dropping the mixture into calcium chloride solution, while microbeads (the diameter of majority of particles ranged between 50 and 100 microm) were prepared using the water in oil emulsification process. In general, microbeads enabled more efficient HP decomposition. The prepared microparticulate biocatalyst caused efficient decomposition of HP in water solutions (up to 2% concentration), leaving very low residual HP concentration after treatment (below 0.001% under appropriate conditions). The biocatalyst was stable; the same catalytic activity was observed after one month storage at 4 degrees C, and the microbeads could be used at least five times.