Adjacent Beads Research Articles

Numerical simulation of Gaussian chains near hard surfaces

We present a coarse grain representation for Gaussian chains in the presence of hard surfaces. Whereas a Gaussian chain in the bulk can be represented by a bead-spring model with a quadratic potential between adjacent beads, the presence of a surface reduces the number of allowed chain configurations and modifies the effective potential between the beads. We derive the corrected potentials for several surface geometries: a single wall, two parallel walls (slit), and a spherical or cylindrical object (nanoparticle). Those potentials can be used in any model that includes a Gaussian chain, regardless of the simulation method. As an illustration, we consider a coarse grain model of a polymeric melt and, using Monte Carlo simulations, we compute the density profiles for (i) a melt confined in a slit and (ii) a melt in the vicinity of a nanoparticle. The case of a polymeric solution confined within a slit is also addressed, and the proposed approach is shown to yield results in qualitative agreement with those obtained with field-theoretic simulations.

The ‘string of beads’ fossil ( Horodyskia) in the mid-Proterozoic of Tasmania

Horodyskia has been found at a single Tasmanian locality, in the Cassiterite Creek Quartzite (ca. 1300–800 Ma), part of a thick Proterozoic, mildly deformed, low greenschist facies, marine shelfal siliciclastic succession known as the Rocky Cape Group. The rock hosting the fossils is thinly interbedded and interlaminated dark grey slaty shale and quartzose siltstone. The sharp-based, graded siltstone layers are interpreted as distal storm surge deposits on an outer marine shelf. The ‘strings of beads’ are mostly preserved at the base of the siltstone layers, in concave hyporelief (external moulds) on the soles of the event beds, and as convex epirelief (casts) on the tops of the underlying shale beds. The casts comprise shale identical to the underlying bed. The beads average 1.7 mm in diameter, and the gap between the borders of adjacent beads tends to be approximately equal to the bead diameter. Occasionally, the fossils are preserved within shale, as wholly flattened beads delineated by a subtle darkened halo. The Tasmanian ‘strings of beads’ have most of the morphological attributes of previously described Horodyskia, including regularity of size and spacing of beads in any one string, lack of branching, and in some instances, ‘haloes’ and casts with apical depressions. The strings on at least one bedding plane have a strong N–S preferred orientation of unknown origin. Tectonic deformation has resulted in 30% shortening in a SW–NE direction. The morphologic similarity, but differing mode of preservation of the Tasmanian Horodyskia to the two previously described Mesoproterozoic species is strong evidence for a biologic origin for the string of beads phenomenon. After morphological and morphometric comparisons with other species of Horodyskia, the Tasmanian specimens are assigned to Horodyskia williamsii.

Dynamic Microarray Devices for the Observation of Paired Different Types of Beads

In this study, we propose a dynamic microarray device that can trap two adjacent different beads in one spot. By combining a pair of microfluidic channels, we can make an array of two different types of 100 μm-sized beads in a line. We expect that this method will be useful in the continuous observation of the interaction or molecular diffusion between the beads.

Highly nonlinear solitary waves in heterogeneous periodic granular media

We use experiments, numerical simulations, and theoretical analysis to investigate the propagation of highly nonlinear solitary waves in periodic arrangements of dimer (two-mass) and trimer (three-mass) cell structures in one-dimensional granular lattices. To vary the composition of the fundamental periodic units in the granular chains, we utilize beads of different materials (stainless steel, brass, glass, nylon, polytetrafluoroethylene, and rubber). This selection allows us to tailor the response of the system based on the masses, Poisson ratios, and elastic moduli of the components. For example, we examine dimer configurations with two types of heavy particles, two types of light particles, and alternating light and heavy particles. Employing a model with Hertzian interactions between adjacent beads, we find good agreement between experiments and numerical simulations. We also find good agreement between these results and a theoretical analysis of the model in the long-wavelength regime that we derive for heterogeneous environments (dimer chains) and general bead interactions. Our analysis encompasses previously-studied examples as special cases and also provides key insights on the influence of heterogeneous lattices on the properties (width and propagation speed) of the nonlinear wave solutions of this system.

2TA5-08 異種ビーズを隣接させた状態で観察可能なダイナミックマイクロアレイ(バイオエンジニアリング,第47回日本生物物理学会年会)

2TA5-08 異種ビーズを隣接させた状態で観察可能なダイナミックマイクロアレイ(バイオエンジニアリング,第47回日本生物物理学会年会)

2P-277 異種ビーズを隣接させた状態で観察可能なダイナミックマイクロアレイ(バイオエンジニアリング,口頭発表,第47回日本生物物理学会年会)

2P-277 異種ビーズを隣接させた状態で観察可能なダイナミックマイクロアレイ(バイオエンジニアリング,口頭発表,第47回日本生物物理学会年会)

Molecular dynamics simulation of AFM studies of a single polymer chain

Single polymer chain force-extension behavior measured by Atomic Force Microscopy (AFM) was interpreted by molecular dynamics (MD) simulation performed by applying a bead-spring (coarse-graining) model in which the bond potential function between adjacent beads is described by a worm-like chain (WLC) model. Simulation results indicate that caution should be applied when interpreting experimental AFM data, because the data vary depending on the point of AFM tip-polymer chain attachment. This approach offers an effective way for eventual analysis of the mechanical behavior of complex polymer networks.

Nanometer-scaled triangular platinum islands fabricated using the bridge phenomenon of polystyrene beads

The authors optimized the fabrication of nanometer-scaled triangular platinum islands using the bridge phenomenon of polystyrene beads. Both the mixture ratio of polystyrene beads and the spin coating process were optimized to array a uniform monolayer of polystyrene beads at a high density over a large area. The length of the bridge between the adjacent polystyrene beads as well as the size of polystyrene beads could be controlled using the oxygen plasma ashing process with an adjustment in the ashing time. Platinum was deposited on the ashed polystyrene beads with the bridges as a mask, and the hexagonally arrayed triangular platinum islands were obtained through the dense and uniform triangular structures surrounded by the polystyrene bead bridges with dimensions of less than 45nm2 on the silicon substrate.

Freeform fabrication of superalloy objects by 3D micro welding

3D Micro welding (3DMW) is a newly developed rapid prototyping method for metals. It is a combination of micro tungsten inert gas (micro-TIG) welding and a layered manufacturing method. The tip of a thin metal wire is melted by a micro-TIG welder to form a small metal bead. By building up metal beads layer by layer under computer control, a 3D metal object is eventually formed. The fabrication of simple 3D objects made of Inconel alloy 600 was studied. The interface between adjacent beads had good adhesion. No cracks or pores remained in the formed objects. The tensile strength, elongation, density, and Vickers hardness were measured and compared to those of the commercial superalloy. The obtained results suggest that actual micro components or tools of refractory metals with high strength and oxidization resistance can be formed without molds by 3DMW.

Highly nonlinear solitary waves in periodic dimer granular chains

We investigate the propagation of highly nonlinear solitary waves in heterogeneous, periodic granular media using experiments, numerical simulations, and theoretical analysis. We examine periodic arrangements of particles in experiments in which stiffer and heavier beads (stainless steel) are alternated with softer and lighter ones (polytetrafluoroethylene beads). We find good agreement between experiments and numerics in a model with Hertzian interactions between adjacent beads, which in turn agrees very well with a theoretical analysis of the model in the long-wavelength regime that we derive for heterogeneous environments and general bead interactions. Our analysis encompasses previously studied examples as special cases and also provides key insights into the influence of the dimer lattice on the properties (width and propagation speed) of the highly nonlinear wave solutions.

Experimental validation of band gaps and localization in a one-dimensional diatomic phononic crystal

The propagation of compressional ultrasonic pulses through a finite one-dimensional chain of various unit cells is investigated experimentally. The chain, initially compressed by an axially applied constant force, is excited by a periodic force, which acts in line with axis of bead chain. The experimental measurements giving the eigenfrequencies of the specimen are based on a Fourier analysis of the transmitted acoustic pulse. The results are compared with the numerical calculations and it is shown that the two approaches are well correlated. A phononic band structure is observed and under certain conditions, depending on the parity of the number and on the masses of the beads in the chain, it is shown that localized modes propagating in the forbidden band are exhibited. Much attention is devoted to the existence of these localized modes according to the mass ratio between two adjacent beads constituting the unit cell.

Development of Freeform Fabrication of Metals by Three Diminsional Micro-Welding

A newly developed freeform fabrication process named 3D Micro-Welding, which is a combined system of a micro-TIG welding and a layered manufacturing method, is demonstrated. Various refractory alloys such as Inconel, stainless steel, and Invar can be freeformed besides elemental metals like titanium. Small metal beads of ~1mm in diameter are formed by emitting micro arc to the top of a thin metal wire of 0.2mm diameter. A fused bead is welded to a metal substrate or previously formed beads. By continuing this process and building up beads layer by layer under the control of CAD/CAM system, 3D objects were produced. In this study, optimization of micro-welding parameters such as the waveform of pulsed arc current and electrode materials were investigated and simple 3D objects of Inconel 600, SUS 304, Invar 42 were formed. The interfaces between adjacent beads were joined well and no crack or pore existed in the formed objects. The density and Vickers hardness of Inconel 600 objects showed comparable values to the commercial Inconel alloy, however the yield strength and Young’s modulus was about 80% and 70% of that alloy, respectively.

Influence of welding sequence on welding stress of T joint

In order to get the optimizing scheme of T type joint's welding sequence, the effect of welding sequence on welding residual stress field of T joint is simulated from the view of multibead welding, subsection welding and multilayer welding on the basis of ensuring reasonable welding heat source and establishing the finite model. For the multibead welding, the residual tensile stress appears in the weld and nearby while the maximum value appears in the weld. Moreover, the method of the different welding direction between adjacent beads during the multibead welding makes the residual tensile stress peak value minimum. The subsection welding in which the prior welding section is the two end section and the latter welding section is the middle section not only can increase the low stress region of weld, but also can effectively decrease welding residual stress of the prior welding section. Moreover, the decreasing effect of subsection welding is related to the welding direction of the latter welding section and the distance between one point of the prior welding section and the end of the latter section. In the multilayer welding process, the method of symmetry welding gets the minimum residual tensile stress.

Method used to measure interaction of proteins with dual-beam optical tweezers

In the force measurement of protein-protein interaction, proteins are usually attached to microbeads, so the coated beads serve as both handles and force transducers. Due to the short interaction distance between proteins, the beads are usually close enough to each other. When dual-beam optical tweezers and quadrant photodiode detector are used to investigate the interaction of proteins, it is found that the signal of detected beads is greatly affected by adjacent beads. Analysis reveals that the contribution of two beads to the quadrant detector signal is independent. A method for extracting the real interaction signal from a disturbed one is presented. Based on this method, interaction between microtubules and AtMAP65-1 is measured. The results show that this method is useful for measuring short-distance interaction with the precision of piconewton and nanometer scales.

Host color preferences and short‐range searching behavior of the egg parasitoid Trichogramma ostriniae

AbstractThe color of lepidopteran eggs often varies by species or egg condition, and parasitoids that attack lepidopteran eggs could therefore potentially use color to obtain information about host identity or quality. The objective of our study was to determine whether females of the egg parasitoid Trichogramma ostriniae Pang & Chen (Hymenoptera: Trichogrammatidae) showed differential responses to egg color when searching for hosts over short distances and when evaluating the suitability of encountered eggs. We examined the wasps’ host‐selection behavior in a Petri dish arena using white, yellow, green, and black clay beads as egg models presented against a green background (to mimic leaf color). In no‐choice tests, bead color had a significant effect on the proportion of tested wasps that accepted a bead for further examination, on the time it took wasps to find and begin examining a bead, and on the time that wasps spent examining the beads. However, bead color had only a marginally significant effect on the proportion of wasps attempting to drill into a bead with their ovipositors, and no significant effect on the amount of time they spent drilling. The wasps also showed significant color preferences when given a choice between two adjacent beads of different colors. The results of the no‐choice and choice trials taken together indicated a color preference ranking of yellow > white > green > black. The wasps’ higher preference for the yellow and white egg models generally corresponds to the white or yellowish‐white egg color of T. ostriniae's target host, the European corn borer moth, Ostrinia nubilalis Hübner (Lepidoptera: Crambidae). The wasps’ strong rejection of black egg models is likely to be an adaptive response that reflects the fact that eggs that are wholly or partially black are often unsuitable for parasitization due to advanced caterpillar development, damage to the egg, or previous parasitization.

Two-Point Separation in Far-Field Super-Resolution Fluorescence Microscopy Based on Two-Color Fluorescence Dip Spectroscopy, Part I: Experimental Evaluation

The two-point resolution of a novel two-color far-field super-resolution fluorescence microscopy was evaluated by measuring fluorescent beads 100 nm in diameter. This microscopy is based on a combination of two-color fluorescence dip spectroscopy and a phase-modulation technique for a laser beam. By simply introducing two-color laser light, the size of the fluorescent image of a bead was shrunk down to a diameter of 250 nm from the diffraction-limited image with a diameter of 360 nm. For two closely adjacent fluorescent beads with a separation distance of 350 nm, the two-color microscope clearly gave separated fluorescence images, while the conventional one-color fluorescence microscope could not resolve them. It has been proved that our technique breaks Rayleigh's diffraction limit.

Microtomography assessment of failure in acrylic bone cement

Micromechanical studies of fatigue and fracture processes in acrylic bone cement have been limited to surface examination techniques and indirect signal analysis. Observations may then be mechanically unrepresentative and/or affected by the presence of the free surface. To overcome such limiting factors the present study has utilised synchrotron X-ray microtomography for the observation of internal defects and failure processes that occurred within a commercial bone cement during loading. The high resolution and the edge detection capability (via phase contrast imaging) have enabled clear microstructural imaging of both strongly and weakly absorbing features, with an effective isotropic voxel size of 0.7 μm. Detailed assessment of fatigue damage processes in in vitro fatigue test specimens is also achieved. Present observations confirm a link with macroscopic failure and the presence of larger voids, at which crack initiation may be linked to the mechanical stress concentration set up by adjacent beads at pore surfaces. This study does not particularly support the suggested propensity for failure to occur via the inter-bead matrix; however crack deflections at matrix/bead interfaces and the incidence of crack arrest within beads do imply locally increased resistance to failure and potential improvements in global crack growth resistance via crack tip shielding.

Influence of a welding sequence on the welding residual stress of a thick plate

The residual stress in one-groove welding using an ellipsoidal heat source is analysed. The results show that it can ameliorate the residual stress distribution and greatly decrease the peak value of residual stress after welding if the converse welding method is adopted between adjacent layers in a multi-layer weld, or between adjacent beads in every layer. Moreover, the numerical simulation results of the double V-groove thick plate welding model show that the residual tensile stress appears on the weld and nearby, the residual compressive stress appears on the area far away from the weld and the peak value of tensile stress appears on the surface of the weld. Differences in the welding sequence influence the value and the distribution of the welding residual stress greatly, and a more suitable welding sequence can be deduced. The reliability of the numerical simulation results is proved by the experimental results.

On the solitary wave pulse in a chain of beads

We study the shape of solitary wave pulses that propagate in an infinite chain of beads initially in contact with no compression. For this system, the repulsive force between two adjacent beads is proportional to the p th power of the distance of approach of their centers with p = 3/2. It is known that solitary wave solutions exist for such a system when p > 1. We prove extremely fast, double-exponential, asymptotic decay for these wave pulses. An iterative method of solution is also proposed and is seen to work well numerically.

Process control of reactive rapid prototyping for nickel aluminides

A new freeform fabrication method for intermetallics named Reactive Rapid Prototyping (RRP), which combines combustion synthesis and rapid prototyping, has been developed. Small droplets of molten aluminum ejected onto the nickel powder bed on the moving x– y– z stage form and simultaneously join hot nickel aluminide beads eventually building up the 3-D object. The RRP is systematically controlled by computer. The process control was investigated because the formation and joining of beads are influenced by temperature and volume of aluminum droplets, time and space intervals of their ejection, thickness of the nickel powder bed, and reaction control agents. The addition of fine alumina particles to the nickel powder bed effectively controlled the spreading of the bead formation. Joinings between adjacent beads and between layers were successfully performed without cracks and pores. The boundary region between layers was composed of NiAl phase, but the interior in each layer shifted from the stoichiometric composition.