Target Bead Research Articles

Cratering Experiments on Granular Targets With a Variety of Particle Sizes: Implications for Craters on Rubble‐Pile Asteroids

AbstractWe performed cratering experiments on targets composed of glass beads with a power‐law size distribution that simulated the surface of rubble‐pile asteroids, and we improved the previously studied reduction factor on the crater size scaling relationship including the armoring effect using the momentum transfer efficiency. Cratering experiments were conducted using light gas guns at Kobe University and ISAS/JAXA to control the impact velocity, , from 50 to 4,400 m s−1. Two kinds of mixed targets were prepared by mixing glass beads with diameters of 0.1, 1, 3, and 10 mm—one with the smallest diameter beads, and one without. The size ratio of the target bead to the projectile (diameter of 1–3 mm), , changed from 0.03 to 10. The crater size scaling relationships for the mixed targets were found to depend on the first contacted bead size. Notably, first contact with a 10 mm‐sized bead reduced the crater radius by 35% in maximum. The reduction factor due to this armoring effect on the crater size scaling relationship is written as follows: ; it decreased with the increase of the size ratio of the target bead to the projectile, while it increased with the increase of the impact velocity and approached unity. Our improved crater size scaling relationship that includes the reduction factor could be used to reconstruct the crater size frequency distribution on rubble‐pile asteroids such as Ryugu, and it may lead to a revision of the crater chronology of asteroids.

Geometric optimisation of electrohydrodynamic fluid flows for enhanced biosensing

The removal of non-specific binding on the sensor surface represents a major challenge for rapid and sensitive biosensing. The stimulation of an electrohydrodynamic (EHD) fluid flow in proximity to the biosensor surface can improve sensor performance. The EHD fluid flow is depending on the geometry of electrodes. Here, the effect of electrode diameter and spacing of asymmetric circular electrodes is investigated for the capability to stimulate fluid flow and capture model beads and protein biomarker. Six geometries with diameters of 30–1000μm and spacing of 200–1500μm were systematically studied. Capture of target beads in excess of non-target beads showed higher target bead capture with increase in electrode diameter. The target bead capture was 4× improved and displacement of non-target reduced by factor 2. The electrode with the highest bead capture was then used to establish an immunoassay for detection of novel cancer immunotherapy biomarker CD28 fortified in buffer and fetal bovine serum. The EHD parameters for optimal CD28 capture were different to the bead capture parameters. This indicated that, depending on the binding strength of target to affinity tag, the EHD parameters could be tailored to provide ideal capture conditions. The use of EHD significantly reduced the assay time by 92.4%, removed non-target binding by a factor of 3.5 compared to static incubation, and was sensitive to detect as low as 20pgmL−1 CD28. In a proof-of-concept study, the potential of the EHD-assisted immunoassay for point of care application was demonstrated using a simple naked eye read-out.

"Killer" Microcapsules That Can Selectively Destroy Target Microparticles in Their Vicinity.

We have developed microscale polymer capsules that are able to chemically degrade a certain type of polymeric microbead in their immediate vicinity. The inspiration here is from the body's immune system, where killer T cells selectively destroy cancerous cells or cells infected by pathogens while leaving healthy cells alone. The "killer" capsules are made from the cationic biopolymer chitosan by a combination of ionic cross-linking (using multivalent tripolyposphate anions) and subsequent covalent cross-linking (using glutaraldehyde). During capsule formation, the enzyme glucose oxidase (GOx) is encapsulated in these capsules. The target beads are made by ionic cross-linking of the biopolymer alginate using copper (Cu2+) cations. The killer capsules harvest glucose from their surroundings, which is then enzymatically converted by GOx into gluconate ions. These ions are known for their ability to chelate Cu2+ cations. Thus, when a killer capsule is next to a target alginate bead, the gluconate ions diffuse into the bead and extract the Cu2+ cross-links, causing the disintegration of the target bead. Such destruction is visualized in real-time using optical microscopy. The destruction is specific, i.e., other microparticles that do not contain Cu2+ are left undisturbed. Moreover, the destruction is localized, i.e., the targets destroyed in the short term are the ones right next to the killer beads. The time scale for destruction depends on the concentration of encapsulated enzyme in the capsules.

Depletion effect on concave microstructure upon size-specific target particle collection

The depletion effect on a concave microstructure for size-specific target particle collection was evaluated using a set of strictly size-controlled superparamagnetic hemispheres, “magcups”, with mixtures of differently sized model target microbeads in the presence of dispersed polystyrene nanoparticles (PS-NPs), which are thought to enhance entropic depletion effects to capture model target beads having the size closest to those of the hemispherical microstructures of magcups. Magcups with diameters of 10 to 50 µm were fabricated with the formation of three nickel layers (2 nm thickness) inserted between silicon dioxide layers (15 nm) on polystyrene template spheres by vapor deposition and subsequent polystyrene removal by burning. Two different diameters of model target beads (10 and 20 µm) were mixed with the magcups in order to evaluate the contribution of the depletion effect to the frequency of target bead capture by the concave microstructures of magcups of various sizes. To evaluate the depletion effect caused by the presence of dispersed PS-NPs, we compared the frequencies of target bead-magcup conjugations with and without PS-NPs in reaction solvents, and found that (i) the frequency of 10-µm-diameter bead capture increased 3.0 times on average for 15- and 20-µm-diameter magcups, and (ii) the frequencies of 10-µm-diameter beads capture increased as almost the same level with that of 20-µm bead for 30-, 40-, and 50-µm-diameter magcups. These results suggest that conjugations of target beads with magcups were encouraged by the depletion effect due to the presence of PS-NPs.

Measurement of the Organ of Corti Mechanical Responses using a New Microchamber

The mammalian cochlea is an acoustic spectrum analyzer and pressure transducer with a remarkable operating range. In the cochlear sensory epithelium called the organ of Corti (OC), cellular mechanical force is transmitted to select and amplify acoustic vibrations. However, the amplification mechanism is still unclear. Diverse experiments in cochlear research have been developed to clarify the mechanics and physiology of the OC, but most experiments share some concerns (e.g., non-physiological electrical and chemical conditions of in vitro experiments; limited means of control over the subject of in vivo tests). Furthermore, most available data of cochlear mechanics are from the basal (high frequency) region.We developed a new microchamber system to overcome the limitations. The microchamber has two ports for solution circulation, two ports for sound delivery and exit, two slits for magnetic pole tips, a port for a ground electrode, and a slit for the cochlear tissue placement. An 800 μm long sensory epithelium was harvested from young (7-11 days old postnatal) gerbil cochlea. The tissue was transplanted to the microchamber. The tissue separated two fluid spaces filled and refreshed with different ionic solutions imitating the original chemical conditions of the endolymph and the perilymph. A target bead was attached to the tectorial membrane (an acellular matrix on top of the OC). Acoustic pressure was delivered through the bottom chamber and the motion of the target bead was measured using a laser interferometer (along the optical axis) and photo-diodes (in transverse plane). The motion trajectory was analyzed with our computational model of the OC.[Supported by NSF CMMI grant]

Density-dependent separation of encapsulated cells in a microfluidic channel by using a standing surface acoustic wave

This study presents a method for density-based separation of monodisperse encapsulated cells using a standing surface acoustic wave (SSAW) in a microchannel. Even though monodisperse polymer beads can be generated by the state-of-the-art technology in microfluidics, the quantity of encapsulated cells cannot be controlled precisely. In the present study, mono-disperse alginate beads in a laminar flow can be separated based on their density using acoustophoresis. A mixture of beads of equal sizes but dissimilar densities was hydrodynamically focused at the entrance and then actively driven toward the sidewalls by a SSAW. The lateral displacement of a bead is proportional to the density of the bead, i.e., the number of encapsulated cells in an alginate bead. Under optimized conditions, the recovery rate of a target bead group (large-cell-quantity alginate beads) reached up to 97% at a rate of 2300 beads per minute. A cell viability test also confirmed that the encapsulated cells were hardly damaged by the acoustic force. Moreover, cell-encapsulating beads that were cultured for 1 day were separated in a similar manner. In conclusion, this study demonstrated that a SSAW can successfully separate monodisperse particles by their density. With the present technique for separating cell-encapsulating beads, the current cell engineering technology can be significantly advanced.

The influence of sample volume applied to the Makler sperm counting chamber upon the measured concentration of latex beads: A multi-centre study

To undertake a multi-centre study to maximize the number of Makler chambers used. A total of 15 laboratories participated with 31 Makler chambers. A suspension of latex beads was prepared to a concentration of 20 millions per milliliter, and 0.5 mL aliquots distributed to each participating laboratory. They measured the concentration on their Makler chamber(s) used for routine semen analysis by adding 3, 4, 5, 7 and 10 μL volumes of bead suspension to the chamber. There was no difference in within-chamber analysis of the bead concentration according to the volume of bead suspension applied within the range of 3–10 μL ( F 4,14 =2.634, P =0.056). However, the between-chamber effects were significantly different (F 30,124 =4.937, P =0.000), and 24/31 (77.5%) chambers tested had an average bias>10% compared to the target bead concentration. A volume of 3–10 μL added to Makler counting chambers does not influence the concentration measured of latex beads, but the between-chamber variability and positive bias seen would suggest that other sources of error are present which are yet to be identified.

Focal plane location using integrated gray-level gradient method in digital particle holography

To accurately locate the focal plane of the object in digital particle holography, the integrated gray-level gradient method is presented. This method consists of a conventional edge-sharpness [Es] method and a new method, namely, overall-sharpness [Os] method which is an efficient supplement of the former. The respective scopes of application of above criterions were discussed by using numerical simulation holograms of particles. At last, the integrated gray-level gradient method was applied to the real holograms of dot array target, calibration target and glass bead. The experiment results demonstrate that this method can effectively extract the focal plane of particle.

Development of Detection System Using Multiplex PCR and Liquid Beadarray for Stacked Genetically Modified Rice Event (LS28×Cry1Ac)

A multiplex system was developed to assess detection of stacked genetically modified (GM) rice (LS28 × Cry1Ac) based on multiplex polymerase chain reaction (PCR) and liquid beadarray, and the accuracy of the system was analyzed. Standard and specific bulging specific (SBS) primers with standard primers were used to simultaneously detect multiple targets in stacked events of rice. Five sets of primers for the stacked events were applied to amplify their targets, and were separated distinctly in agarose gel. A liquid beadarray assay for the stacked GM rice was performed using the multiplex PCR products, followed by target biotinylation and hybridization between biotinylated-tagged target and anti-tagged bead. Fluorescent signals of the hybridized target sequences were detected by the Luminex system. The signaling patterns were analyzed by their mean fluorescent intensity (MFI) value. Results showed that liquid beadarrays with standard and SBS primers were in complete agreement with the PCR data, and detection of the different target elements was found to be very specific with no cross reaction among samples. Therefore, our detection system developed for stacked GM crop using multiplex PCR and liquid beadarray can be a useful and efficient system for screening and analyzing multiple transgenes in a single tube for qualitative analysis.

Integrative Experimental and Theoretical Approach Exposes Fundamental Mechanisms of J774 Macrophage Phagocytosis

Macrophage cell lines like murine J774 cells are ideal model systems to study phagocytosis. Our unique methodology combines single-cell/single-target experiments with advanced computer simulations to elucidate the fundamental mechanisms of J774 macrophage phagocytosis. As a first step, the baseline mechanical properties of the murine macrophages were established. Micropipette-aspiration experiments were used to characterize the cortical tension and cytoplasmic viscosity of the J774 cells. Next, we used a dual-micropipette manipulation system to quantify the time courses of a number of key parameters during Fcγ-target phagocytosis. A passive cell is selected and picked up with a micropipette by partial aspiration. Another micropipette is used to bring an opsonized target bead (5-30 um diameter) into soft contact with the cell, which usually results in immediate adhesion. The target is released and images of the ensuing phagocytosis are recorded directly to a computer hard disk. Their analysis provides the time course of cell morphology, bead position, and cortical tension. Intriguingly, the macrophages maintained a constant cortical tension when engulfing targets that required a surface area expansion of up to ∼250%, indicating an extremely large membrane reservoir. The tension rose when the cells increased their surface area by an amazing ∼550%. These and other experimental observations were compared side-by-side with finite-element models of macrophage phagocytosis. This comparison allows us to assess the viability of different mechanistic models used for phagocytosis. Optimal models include a repulsion between the cytoskeleton and the free membrane (which drives protrusion), and an attraction between cytoskeleton and surface membrane newly adherent to the target (which results in thin pseudopods). Confocal inspection of the engulfment of 20 um beads by GFP-actin transfected macrophages revealed excellent agreement between the cytoskeletal density predicted by the optimal model and the observed actin distribution.

Coordination of Actin Filament and Microtubule Dynamics during Neurite Outgrowth

Although much evidence suggests that axon growth and guidance depend on well-coordinated cytoskeletal dynamics, direct characterization of the corresponding molecular events has remained a challenge. Here, we address this outstanding problem by examining neurite outgrowth stimulated by local application of cell adhesion substrates. During acute outgrowth, the advance of organelles and underlying microtubules was correlated with regions of attenuated retrograde actin network flow in the periphery. Interestingly, as adhesion sites matured, contractile actin arc structures, known to be regulated by the Rho/Rho Kinase/myosin II signaling cascade, became more robust and coordinated microtubule movements in the growth cone neck. When Rho Kinase was inhibited, although growth responses occurred with less of a delay, microtubules failed to consolidate into a single axis of growth. These results reveal a role for Rho Kinase and myosin II contractility in regulation of microtubule behavior during neuronal growth.

Genetic-Algorithm-Based Computational Models for Optimizing the Process Parameters of A-TIG Welding to Achieve Target Bead Geometry in Type 304 L(N) and 316 L(N) Stainless Steels

The weld-bead geometry in 304LN and 316LN stainless steels produced by A-TIG welding plays an important role in determining the mechanical properties of the weld and its quality. Its shape parameters such as bead width, depth of penetration, and reinforcement height are decided according to the A-TIG welding process parameters such as current, voltage, torch speed, and arc gap. Identification of a suitable combination of A-TIG process parameters to produce the desired weld-bead geometry required many experiments, and the experimental optimization of the A-TIG process was indeed time consuming and costly. Therefore it becomes necessary to develop a methodology for optimizing the A-TIG process parameters to achieve the target weld-bead geometry. In the present work, genetic algorithm (GA)-based computational models have been developed to determine the optimum/near optimum process parameters to achieve the target weld-bead geometry in 304LN and 316LN stainless steel welds produced by A-TIG welding.

Experimental verification of an interpolation algorithm for improved estimates of animal position.

This article presents experimental verification of an interpolation algorithm that was previously proposed in Jaffe [J. Acoust. Soc. Am. 105, 3168-3175 (1999)]. The goal of the algorithm is to improve estimates of both target position and target strength by minimizing a least-squares residual between noise-corrupted target measurement data and the output of a model of the sonar's amplitude response to a target at a set of known locations. Although this positional estimator was shown to be a maximum likelihood estimator, in principle, experimental verification was desired because of interest in understanding its true performance. Here, the accuracy of the algorithm is investigated by analyzing the correspondence between a target's true position and the algorithm's estimate. True target position was measured by precise translation of a small test target (bead) or from the analysis of images of fish from a coregistered optical imaging system. Results with the stationary spherical test bead in a high signal-to-noise environment indicate that a large increase in resolution is possible, while results with commercial aquarium fish indicate a smaller increase is obtainable. However, in both experiments the algorithm provides improved estimates of target position over those obtained by simply accepting the angular positions of the sonar beam with maximum output as target position. In addition, increased accuracy in target strength estimation is possible by considering the effects of the sonar beam patterns relative to the interpolated position. A benefit of the algorithm is that it can be applied "ex post facto" to existing data sets from commercial multibeam sonar systems when only the beam intensities have been stored after suitable calibration.

Striato-telencephalic and striato-tegmental circuits: relevance to learning in domestic chicks

Memory formation for a passive avoidance task in the domestic chick is likely to involve a hyperstriatum ventrale (IMHV)-archistriatum-lobus parolfactorius (LPO) arc. The present study summarises previous findings, relevant to this neural system, and is also supplemented with some recent data from our laboratory. Projections from the IMHV on the archistriatum, as well as from the archistriatum on the LPO, have been characterised using a combination of anterograde pathway tracing ( Phaseolus lectin), and post-embedding GABA and glutamate immunocytochemistry. The majority of IMHV efferents have been found to synapse with dendritic spine heads and necks of densely spiny projection neurons of the ventral archistriatum, and the ultrastructure of synapses suggested a potent excitatory input. Similar synaptic connections of the excitatory type were ultrastructurally verified between ventral archistriatal afferent terminals and dendrites or spines of the LPO, suggesting an involvement of the medium sized spiny neurons, which are typical of the striatum. Although some of the IMHV boutons terminating in the archistriatum were immunoreactive to glutamate, this was not observed in the archistriatal-LPO pathway. Tegmental connections of the basal ganglia, in particular LPO, are also likely to play a role in processing of the avoidance response. We have demonstrated reciprocal connections between the LPO and dopaminergic (TH-positive) neurons of the substantia nigra and ventral tegmentum. Dopamine D1 receptors were upregulated bilaterally in the LPO following avoidance learning and this response was not accompanied by significant changes in the level of dopamine or its metabolites (HVA, DOPAC), as revealed by HPLC chromatography of brain samples dissected from the LPO of control and trained chicks. The dopamine receptor-related phosphoprotein DARPP-32 was localised in dendritic elements of the LPO, often forming asymmetric synapses with glutamate immunoreactive axon terminals. The findings are consistent with a scenario in which the striatum acts as a suppressor of natural pecking behaviour. Learned visual association with the target (bead) occurs in the IMHV and is relayed to the basal ganglia via the limbic archistriatum (amygdala equivalent), the latter introducing a motivational element (aversion, fear). Suppression of a brainstem pecking centre is likely to involve activation of the nigrostriatal (tegmentostriatal) dopaminergic circuit.

Causes of young children's confusion of same and different

Three experiments are reported that explore 3-year-olds' and adults' understanding of the words, same and different. In the first, 3-year-olds selected a bead that was “the same color as” or “a different color from” a target bead. In the second, 3-year-olds selected a bead that was “the same in some way as” or “different in some way from” a target bead. Contrary to results reported previously, the majority of consistent responders chose a bead identical with the target in response to the different instruction in both experiments. The rates of both incorrect different responding and incorrect same responding were greater in Experiment II than in Experiment I. In Experiment III, adults chose objects that were “the same as” or “different from” a target; unlike the children, they never chose a target-identical object in response to different instructions. It is argued that children and adults treat same and different differently, and that children's task performance is influenced by three factors: semantic, pragmatic, and nonlinguistic.