Motion Of Beads Research Articles

Phase-modulated multi-foci microscopy for rapid 3D imaging

3D imaging technology is pivotal in monitoring the functional dynamics and morphological alterations in living cells and tissues. However, conventional volumetric imaging associated with mechanical z-scanning encounters challenges in limited 3D imaging speed with inertial artifact. Here, we present a unique phase-modulated multi-foci microscopy (PM3) technique to achieve snapshot 3D imaging with the advantages of extended imaging depths and adjustable imaging intervals between each focus in a rapid fashion. To accomplish the tasks, we utilize a spatial light modulator (SLM) to encode the phases of the scattered or fluorescence light emanating from a volumetric sample and then project the multiple-depth images of the sample onto a single charge-coupled device camera for rapid 3D imaging. We demonstrate that the PM3 technique provides ∼55-fold improvement in imaging depth in polystyrene beads phantom compared to the depth of field of the objective lens used. PM3 also enables the real-time monitoring of Brownian motion of fluorescent beads in water at a 15 Hz volume rate. By precisely manipulating the phase of scattered light on the SLM, PM3 can pinpoint the specific depth information in living zebrafish and rapidly observe the 3D dynamic processes of blood flow in the zebrafish trunk. This work shows that the PM3 technique developed is robust and versatile for fast 3D dynamic imaging in biological and biomedical systems.

Granular vibration pumping system for handling and characterizing particulate materials.

A unique setup for a granular vibration pumping system was developed to ease the installation into a wide variety of granular handling processes and provide flexible options for granular physics research. Although the granular vibration pumping system can notably lift granular materials with an oscillating pipe, the climbing mechanism and related granular physics are yet to be clarified thoroughly. The new setup employs an eccentric cam mechanism as the excitation source, a linear system with dust tolerance, and a recording system, making it simple, compact, and adaptable for extending experiments. The excitation mechanism generated a clear sinusoidal vibration in the pipe, realizing better reproducibility of the climbing motions of glass beads. Moreover, the compact design facilitates the close placement of multiple pipes vibrating individually, which affects the transport performance. In addition, various types of sample cells that store particles and the imaging system allow for the detailed observation of particle motions in the pipes and even the sample cells. This developed system provides easy and accurate tuning of the existing parameters of the granular vibration pumping system, as well as new options for a further understanding of granular physics.

Experimental validation of the brachistochrone curve

We built a simple, cheap and accessible experiment to study the motion of spherical beads through three different curves, one of them being the curve of fastest descent, or brachistochrone. Despite the absence of a no-friction constraint and the rolling of the beads, our experimental findings consistently support the conclusion that the brachistochrone path remains the fastest. We perform a numerical simulation to confront with experiments and obtain that the values are in agreement, with ttheory=0.237 s, and t‾braq=0.25±0.03 s. This simple system not only serves as a practical demonstration of minimization principles but can also inspire and engage students in high schools and colleges interested in physics.

Quantitation of DNA Binding Affinity Using Tethered Particle Motion.

The binding constant is an important characteristic of a DNA-binding protein. A large number of methods exist to measure the binding constant, but many of those methods have intrinsic flaws that influence the outcome of the characterization. Tethered particle motion (TPM) is a simple, cheap, and high-throughput single-molecule method that can be used to measure binding constants of proteins binding to DNA reliably, provided that they distort DNA. In TPM, the motion of a bead tethered to a surface by DNA is tracked using light microscopy. A protein binding to the DNA will alter bead motion. This change in bead motion makes it possible to measure the DNA-binding properties of proteins. We use the bacterial protein integration host factor (IHF) and the archaeal histone HMfA as examples to show how specific binding to DNA can be measured. Moreover, we show how the end-to-end distance can provide structural insights into protein-DNA binding.

Up-and-down motion of a Belousov-Zhabotinsky bead in couple with chemical oscillation

Up-and-down motion of a Belousov-Zhabotinsky bead in couple with chemical oscillation

Rescaling invariance and anomalous energy transport in a small vertical column of grains.

It is well known that energy dissipation and finite size can deeply affect the dynamics of granular matter, often making usual hydrodynamic approaches problematic. Here we report on the experimental investigation of a small model system, made of ten beads constrained into a 1D geometry by a narrow vertical pipe and shaken at the base by a piston excited by a periodic wave. Recording the beads motion with a high frame rate camera allows to investigate in detail the microscopic dynamics and test hydrodynamic and kinetic models. Varying the energy, we explore different regimes from fully fluidized to the edge of condensation, observing good hydrodynamic behavior down to the edge of fluidization, despite the small system size. Density and temperature fields for different system energies can be collapsed by suitable space and time rescaling, and the expected constitutive equationholds very well when the particle diameter is considered. At the same time, the balance between dissipated and fed energy is not well described by commonly adopted dependence due to the up-down symmetry breaking. Our observations, supported by the measured particle velocity distributions, show a different phenomenological temperature dependence, which yields equationsolutions in agreement with experimental results.

Structural and dynamical behavior of a vibrated granular system of hard-cubes

We study experimentally and by molecular dynamics simulations a quasi-two-dimensional granular system of cubic particles, confined in a squared box and kept in a dynamic steady state via vertical oscillations. First, we compared the dynamics of a single spherical bead and a cube. Remarkably, the trajectory of the cube shows characteristics of Brownian motion induced by the particle geometry, i.e. an erratic path generated by the collisions of the vertexes and edges of the cube with the vibrated plate; in contrast to the more predicted ballistic motion of a spherical bead. Upon the addition of more cubic particles to the system, the erratic motion is enhanced by multiple collisions, leading to a rich collective behavior. As the number of particles is increased, for instance, both the radial distribution function and the mean square displacement exhibit the qualitative features of the gas, liquid and crystalline-solid phases observed in thermally driven colloidal systems. The results obtained with experiments and simulations are in good agreement and, combined, suggest that a vibrated system of granular cubic particles provides a macroscopic ideal model of Brownian motion.

Detecting DNA Loops Using Tethered Particle Motion.

The range of motion of a micron-sized bead tethered by a single polymer provides a dynamic readout of the effective length of the polymer. The excursions of the bead may reflect the intrinsic flexibility and/or topology of the polymer as well as changes due to the action activity of ligands that bind the polymer. This is a simple yet powerful experimental approach to investigate such interactions between DNA and proteins as demonstrated by experiments with the lac repressor. This protein forms a stable, tetrameric oligomer with two binding sites and can produce a loop of DNA between recognition sites separated along the length of a DNA molecule.

Quantification and modeling of macroparticle-induced mechanical stress for varying shake flask cultivation conditions.

In biotechnological processes, filamentous microorganisms are known for their broad product spectrum and complex cellular morphology. Product formation and cellular morphology are often closely linked, requiring a well-defined level of mechanical stress to achieve high product concentrations. Macroparticles were added to shake flask cultures of the filamentous actinomycete Lentzea aerocolonigenes to find these optimal cultivation conditions. However, there is currently no model concept for the dependence of the strength and frequency of the bead-induced stress on the process parameters. Therefore, shake flask simulations were performed for combinations of bead size, bead concentration, bead density and shaking frequency. Contact analysis showed that the highest shear stresses were caused by bead-bottom contacts. Based on this, a newly generated characteristic parameter, the stress area ratio (SAR), was defined, which relates the bead wall shear and normal stresses to the total shear area. Comparison of the SAR with previous cultivation results revealed an optimum pattern for product concentration and mean product-to-biomass related yield coefficient. Thus, this model is a suitable tool for future optimization, comparison and scaling up of shear-sensitive microorganism cultivation. Finally, the simulation results were validated using high-speed recordings of the bead motion on the bottom of the shake flask.

Insights into Uniaxial Tension and Relaxation of Nanorod-Filled Polymer Vitrimer Nanocomposites: A Molecular Dynamics Simulation

The mechanical properties of polymer nanocomposites (PNCs) depend sensitively on the structure (e.g., orientation, dispersion, and so on) of the incorporated nanofillers. Many studies have shown that the alignment of anisotropic nanofillers can improve the mechanical properties of PNCs. However, achieving this alignment typically requires complex preparation processes. To address this challenge, researchers have introduced dynamic covalent bonds to form reversible cross-linked polymer systems, which would lead to unique properties, such as self-healing, recyclability, and reprocessibility. In addition, inspired by the above ideas, we introduce nanorods as fillers into a linear vitrimer system to form nanorod vitrimer composites (NVCs). In NVCs, we can easily manipulate the alignment of the nanorods due to bond exchange reactions (BERs) in the vitrimer matrices. By using coarse-grained molecular dynamics (CGMD) simulations, we systematically investigate the factors affecting the nanorod orientation in NVCs. We find that the main factor affecting the nanorod orientation is the network rearrangement caused by BERs. Specifically, the BER potential barrier (ΔEsw) directly determines the probability of BERs’ occurrence. At the same time, the increase of the interfacial interaction between polymer chains and nanorods (εnp) confines the motion of the active beads, which slows down the rate of BERs. Additionally, the impact of temperature (T) and aspect ratio (ld) on the orientation of nanorods during uniaxial stretching or stress relaxation are also discussed. Finally, by combining uniaxial stretching and stress relaxation processes, we elucidate the orientation retention mechanism of NVCs and demonstrate the mechanical property enhancement phenomenon of the pre-oriented NVC systems. This work provides a simple strategy for manipulating the nanorod alignment in vitrimer matrices and uncovers guidelines for designing new functional polymer vitrimer nanocomposites at the molecular level.

DEM Simulation of a Rotary Drum with Inclined Flights Using the Response Surface Methodology

Conventional flighted rotary drums usually have flights parallel to the rotating axis, which cannot facilitate the axial motion of the materials in the drum. Here, a new type of horizontal rotary drum with inclined flights and beads was designed. Inclined flights are used to facilitate the axial movement of beads and material, while beads are used as fillers to increase the gas-liquid contact area and to crush the solid materials. We simulated the drum and studied the axial motion of fillers using the discrete element method (DEM). To improve the mass and heat transfer performance, we optimized the distribution of beads in the active phase. The effects of the rotational speed, joint angle, and inlet flow rate in the drum were investigated systematically. The individual effects were evaluated in terms of the mass of particles in the active phase (MAP) and passive phase (MPP), the percentage of the active phase occupied by the particles (OAR), and the axial speed (AS). The response surface methodology (RSM) was used to investigate the significant effects of the interaction between the parameters. The maximum MAP value can be obtained by the following parameters: a rotational speed of 37 rpm, joint angle of 139°, and inlet flow rate of 7.83 kg/s. The interaction between rotational speed and inlet flow rate is the most significant for MAP. The joint angle and inlet flow rate have a significant interactive effect on AS. Besides, the rotational speed, joint angle and inlet flow rate show an interactive effect on OAR and AS. Based on the optimization results, the effect of the inclined angle on the axial motion of beads was also evaluated. The axial motion of the beads occurs mainly in the active phase. Compared to the drum without inclined flights, the drum with inclined flights has an enhanced axial speed increased by 26%. This study will be helpful for the design and optimization of drums with inclined flights.

Anomalous Colloidal Motion under Strong Confinement.

Diffusion of biological macromolecules in the cytoplasm is a paradigm of colloidal diffusion in an environment characterized by a strong restriction of the accessible volume. This makes of the understanding of the physical rules governing colloidal diffusion under conditions mimicking the reduction in accessible volume occurring in the cell cytoplasm, a problem of a paramount importance. This work aims to study how the thermal motion of spherical colloidal beads in the inner cavity of giant unilamellar vesicles (GUVs) is modified by strong confinement conditions, and the viscoelastic character of the medium. Using single particle tracking, it is found that both the confinement and the environmental viscoelasticity lead to the emergence of anomalous motion pathways for colloidal microbeads encapsulated in the aqueous inner cavity of GUVs. This anomalous diffusion is strongly dependent on the ratio between the volume of the colloidal particle and that of the GUV under consideration as well as on the viscosity of the particle's liquid environment. Therefore, the results evidence that the reduction of the free volume accessible to colloidal motion pushes the diffusion far from a standard Brownian pathway as a result of the change in the hydrodynamic boundary conditions driving the particle motion.

Measuring DNA extension during unfolding in a centrifugal force microscope

DNA in sperm cells can form compact toroids when bound with proteins from the protamine family. To study DNA folding and toroid formation, we have built a centrifugal force microscope (CFM) to unfold DNA and observe the intermediate folding states. In a CFM, micron-sized beads tethered to the sample by a DNA strand are placed into a microscope within a desktop centrifuge. The centrifuge applies a centrifugal force (a pseudoforce caused by inertia) to our sample, unfolding the DNA. Recording and analyzing the bead motion can yield information on the extension of the DNA over time and the intermediate stages of DNA condensation. Our CFM is operational at low centrifuge speeds, but we did not have a method for measuring the extension of the DNA. Here, we will discuss our progress in creating a program that gathers and analyzes video microscopy data from the CFM to measure extension in real time. This program will be useful in collecting data on the pathway of DNA condensation and for other force spectroscopy measurements with the CFM.

Abstract A017: Polyaneuploid Cancer Cells (PACCs) as metastasis-competent cells

Abstract Metastasis is responsible for 90% of cancer deaths, yet on a cellular level, successful metastasis is rare. Barriers to metastasis exist at every step of the metastatic cascade (invasion, intravasation, survival in the circulation, extravasation, and colonization.) Modeling predicts that only one of every 1.5 billion circulating tumor cells results in clinically-detectable metastasis. Identification of the rare subset of metastasis-competent cells is the most crucial goal of cancer research. Polyanuploid Cancer Cells (PACCs) are physically enlarged, treatment-resistant cells with increased genomic content that form in response to stress. After stress-induction, PACCs exist in a non-proliferative state for many weeks before undergoing eventual depolyploidization to produce progeny of “typical” cancer cell size, morphology, and nuclear content. PACCs can be identified in both primary and metastatic patient tumor tissues. As such, we propose Polyaneuploid Cancer Cells (PACCs) are metastasis-competent cells. Single-cell tracking reveals that PACCs are more motile than nonPACCs. Additionally, we observe that PACCs exhibit increased directional migration in 2D chemotactic environments. Optical-tracking of spontaneous bead motion reveals that PACCs demonstrate increased cytoskeletal rearrangement, an observation that aligns with increased environment-sensing and directional motility. In total, this predicts successful invasion. Analyses of cellular deformability using Magnetic Twisting Cytometry and Atomic Force Microscopy jointly reveal that cells in the PACC state display hyper-elastic properties. Among these include increased peripheral deformability and maintained peri-nuclear cortical integrity, both of which predict successful intravasation and extravasation. Functional deformability of PACCs navigating through narrow channels in a chemotactic environment was confirmed using a custom microfluids device. RTqPCR, NanoString mRNA quantification, Western blot, and immunofluorescent imaging reveal that PACCs highly overexpress Vimentin, a cytoskeletal component known to confer hyper-elasticity. Notably, there is no correlation between Vimentin content and motility dynamics in PACCs, indicating that the role of Vimentin in PACCs may primarily drive increased hyper-elasticity rather than increased motility. Anoikis-resistance assays and detection of PACCs in the blood of a patient with metastatic prostate cancer using a selection-free circulating tumor cell detection platform reveal that PACCs are capable of surviving in the circulation. Our work to date reports that PACCs demonstrate increased motility, environment-sensing, hyper-elasticity, and anoikis-resistance. Taken together with the knowledge that PACCs exist in a treatment-resistant state and are capable of eventual depolyploidization (as a potential route to successful colony formation), this data suggests PACCs are a candidate rare metastasis-competent cell type worthy of further analysis. Citation Format: Mikaela M. Mallin, Nicholas Kim, Mohammad Ikbal Choudhury, SeJong Lee, Steven S. An, Sean X. Sun, Konstantinos Konstantopoulos, Sarah R. Amend, Kenneth J. Pienta. Polyaneuploid Cancer Cells (PACCs) as metastasis-competent cells [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr A017.

Space probe of the gravitational constant G

The empirical Gravitational constant G is of fundamental interest in metrology, Newtonian physics, and the field equations in General Relativity, particle physics, geophysics, and astrophysics. The precise value of G has yet to be known with the desired level of accuracy. In the 233 years since Cavendish, hundreds of experiments sought more accurate results but produced inconsistent results. Although they have had much more advanced supporting technology, past experiments have mostly stayed the same from the Cavendish approach. This paper shows that a different method is feasible to enhance the accuracy of G. A sphere made of metal with a large uniform mass density having a channel through the center with a bead oscillating back and forth in a simple-harmonic fashion. Monitoring the positions of the bead experimentally and comparing the predictions of the channel model will allow refining the value of G. The study develops a gravitational force function for the bead in a channeled sphere to provide more accuracy in the prediction of the bead's motion. This study determines that the best place to perform future gravitation constant experiments is in space far away from interfering effects. A near-perfect place is likely to be in outer space at the Sun-Earth Lagrange point L1, located about 1.5 million kilometers from the Earth on a line toward the Sun where other probes reside. It is estimated that three to six significant figures may be added to the current value of G.

Spatial Variability in the Motion of a Rolling Bead due to a Step in Bed Roughness

Spatial Variability in the Motion of a Rolling Bead due to a Step in Bed Roughness

Small Volume Microrheology to Evaluate Viscoelastic Properties of Nucleic Acid-Based Supra-Assemblies.

Particle tracking (PT) microrheology is a passive microrheological approach that characterizes material properties of soft matter. Multicomponent materials with the ability to create extensive crosslinking, such as supra-assemblies, may exhibit a complex interplay of viscous and elastic properties with a substantial contribution of liquid phase still diffusing through the system. Microrheology analyzes the motion of microscopic beads immersed in a sample, making it possible to evaluate the rheological properties of biological supra-assemblies. This method requires only a small volume of the sample and a relatively simple, inexpensive experimental setup. The objective of this chapter is to describe the experimental procedures for the observation of particle motion, calibration of an optical setup for particle tracking, preparation of imaging chambers, and the use of image analysis software for particle tracking in viscoelastic nucleic acid-based supra-assemblies.

Development and verification of a novel blood viscoelastic monitoring method based on reciprocating motion of magnetic bead.

Blood coagulation function is an essential index in clinical examination, and it is of great significance to evaluate blood coagulation function comprehensively. Based on the blood viscoelasticity theory and hydrodynamics, we proposed a method to monitor the whole blood coagulation process based on the reciprocating motion of the magnetic bead (magnetic bead method for short). We have established a mathematical model between the moment acting on the magnetic bead and the viscoelasticity of blood in the process of blood coagulation. The change of blood viscoelasticity acks on the magnetic bead in the form of moment changes, which shows that the amplitude of the motion of the magnetic bead varies with the change of blood viscoelasticity. Designed and verified a blood coagulation monitoring device based on the reciprocating movement of the magnetic bead and discussed the device's parameters through the orthogonal experiment. Lastly, the TEG5000 was used as the control group to test the thromboelasticity of four groups of thromboelastography quality control products in the same batch and 10 groups of human whole blood. It verified that our device has good repeatability, and has good consistency with TEG5000, it has particular application potential as a new blood coagulation monitoring method.

Dynamic Magnetic Excitation Detection Method for Low-Concentration Superparamagnetic Particles via Quartz Crystal Microbalance

Magnetic biomarker detection and monitoring at low concentrations are critical for the early diagnosis of many diseases and for accurately identifying specific biomolecules. Previously reported highly sensitive detection methods rely on magnetic sensors to detect the stray fields of magnetic labels (usually magnetic beads). The random noise generated by the Brownian motion of magnetic beads in solution makes it difficult to reduce further the limit of detection (LOD) of this measurement. Therefore, we propose a low-concentration magnetic beads sensor and a dynamic magnetic excitation detection method. The intensity of magnetization motion under the ac excitation magnetic field detected by the quartz crystal microbalance (QCM) realizes the measurement of the magnetic bead concentration in the solution. The experimental results show that the LOD of the proposed sensor in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.8~\mu \text{m}$ </tex-math></inline-formula> magnetic bead solution is 10 ng/mL and displays an approximate linear detection characteristic in the range of 20–100 ng/mL. The intensity of magnetization detected by QCM has an approximately linear relationship with the magnetic bead concentration. Given the wide application of magnetic-labeled biomolecule detection and its huge application prospects in early disease detection and precision medicine, this method provides an inexpensive, fast, and flexible detection technology for the general labeling analysis of magnetic labels in biomolecule detection.

High-Speed and Low-Latency 3D Fluorescence Imaging for Robotic Microscope

In this study, we propose a high-speed and low-latency 3D fluorescence imaging method for robotic microscopes. The prototype system consists of a focus-tunable lens called a TAG lens, which operates at several hundred kHz, an image intensifier (I.I.) that enhances faint light such as fluorescence, and a high-speed vision system that can transfer acquired images to the host PC in 500 Hz. The proposed method can acquire images at arbitrary focal lengths at frame rates on the order of 1 kHz by synchronizing the focal-length fluctuation of the TAG lens and the exposure timing of the I.I., whose duration is a few hundred nanoseconds. The low-latency we aim for in this paper is on the order of a few milliseconds. A prototype system was developed to validate the proposed method. High-speed 3D tracking of the Brownian motion of a fluorescent bead of 0.5 μm diameter was demonstrated to verify the feedback performance of the proposed low-latency 3D fluorescence imaging method.