Sticky Spheres Research Articles

Multi-year evaluation of an attract-and-kill strategy for apple maggot fly (Diptera: Tephritidae) in New England commercial apple orchards.

Previously developed behavioral approaches for controlling the apple maggot fly, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), include attract-and-kill (AK) systems such as perimeter trapping using either, odor-baited red sticky spheres or odor-baited, sticky-free attracticidal spheres with contoured tops that ensure the sustained release of both insecticide and feeding stimulant. Here, over a 3-year span in 26 commercial apple orchards across Massachusetts, New Hampshire, and Maine, we evaluated the effectiveness of a novel AK strategy for R. pomonella management. Synthetic apple blend lures were deployed on perimeter-row trees to attract the pest, while perimeter-row insecticide sprays blended with 2% sugar, a known phagostimulant, served as the lethal component. Comparatively, grower standard (GS) blocks received full-block insecticide sprays devoid of sugar and lures. Monitoring revealed that red sticky spheres in AK blocks captured significantly more R. pomonella adults than unbaited monitoring spheres in GS blocks. Penetration of R. pomonella into block interiors remained consistently low and statistically similar for both AK and GS blocks. Whole-block infestation levels showed no significant difference between the 2 management approaches. Notably, insecticide application in AK blocks was reduced by 75%, 64.7%, and 64.2% in 2019, 2020, and 2021, respectively, compared with GS blocks. This grower-friendly AK approach could be integral to a reduced insecticide spray-based strategy for apple cultivation in the northeastern United States.

Complex Formation of Gold Nanoparticles with Collagen in Aqueous Media Studied by X-ray Scattering and Absorption Spectroscopy.

Small-angle X-ray scattering and UV-vis absorption measurements were performed on mixed solutions of gold nanoparticles (AuNPs) and atelocollagen (AC), triple-helical collagen without telopeptide, in acetate buffer at pH 4 under different temperature conditions, i.e., preparation temperature Tprep and measurement temperature Tmeas. Due to the significantly higher electron density of gold than that of AC, the structure factor S(q) of AuNPs is readily estimated from the scattering intensities of AuNP-only and mixed solutions. The resulting S(q) profile for the mixed solution indicated significant attractive interactions, especially for the smaller AuNPs. Therefore, the sticky sphere model was applied to analyze S(q) to determine the interaction parameters at different Tprep and Tmeas. The attractive interactions between AuNPs were higher at higher Tprep, suggesting that single-chain AC tends to make the interactions between AuNPs more attractive than those for triple-helical AC. Complex formation was also detected by the aggregation-induced surface plasmon absorption shift. More densely packed AuNPs were detected from the absorption spectra for higher AuNP content at which the ζ potential disappeared, while a split absorption band was also found, indicating that not all AuNPs can form a complex with AC at ζ = 0.

Necking and failure of a particulate gel strand: signatures of yielding on different length scales.

"Sticky" spheres with a short-ranged attraction are a basic model of a wide range of materials from the atomic to the granular length scale. Among the complex phenomena exhibited by sticky spheres is the formation of far-from-equilibrium dynamically arrested networks which comprise "strands" of densely packed particles. The aging and failure of such gels under load is a remarkably challenging problem, given the simplicity of the model, as it involves multiple length- and time-scales, making a single approach ineffective. Here we tackle this challenge by addressing the failure of a single strand with a combination of methods. We study the mechanical response of a single strand of a model gel-former to deformation, both numerically and analytically. Under elongation, the strand breaks by a necking instability. We analyse this behaviour at three different length scales: a rheological continuum model of the whole strand; a microscopic analysis of the particle structure and dynamics; and the local stress tensor. Combining these different approaches gives a coherent picture of the necking and failure. The strand has an amorphous local structure and has large residual stresses from its initialisation. We find that neck formation is associated with increased plastic flow, a reduction in the stability of the local structure, and a reduction in the residual stresses; this indicates that the system loses its solid character and starts to behave more like a viscous fluid. These results will inform the development of more detailed models that incorporate the heterogeneous network structure of particulate gels.

Particle Nonresolved DNS‐DEM Study of Flocculation Dynamics of Cohesive Sediment in Homogeneous Isotropic Turbulence

AbstractA two‐phase Euler‐Lagrangian framework was implemented to investigate the flocculation dynamics of cohesive sediment in isotropic turbulence. The primary particles are modeled as sticky soft spheres using the discrete element method (DEM). The attractive van der Waals forces are modeled by the DLVO theory and the JKR adhesive contact theory. The near steady state equilibrium floc size distribution (FSD) strongly depends on the ratio of the turbulent shear to the floc strength (or particle stickiness). When turbulence is strong, a single peak around the Kolmogorov length scale appears in the FSD, and the distribution fits the Weibull distribution well. A power‐law floc size distribution develops when the floc strength is greater than the destabilizing effect of turbulent shear. Sediment concentration does not significantly affect the shape of FSD or the average floc size. The average apparent floc settling velocity Ws increases with the average floc size. Fractal dimension of flocs decreases with the floc size following a power‐law relation for large flocs. Settling velocity of flocs as a function of floc size also follows a power‐law relation. Deviation from the power‐law relationship is found for large flocs because of their porous nature. At equilibrium stage, the construction by aggregation is balanced with the destruction by breakup, and the construction by breakup is balanced with the destruction by aggregation. The aggregation kernel by turbulent shear and power‐law breakup kernel can describe the dynamics reasonably well for the flocculation of cohesive sediment in homogeneous isotropic turbulence.

An alternative analysis of contrast-variation neutron scattering data of casein micelles in semi-deuterated milk.

Contrast-variation small-angle neutron scattering (CV-SANS) is an excellent way to determine the structure of complex, hierarchical colloids, including self-assembled biological systems. In these experiments, the scattering length density of solvents is changed (by varying the ratio of water or [Formula: see text] and heavy water or [Formula: see text]) to highlight or mask scattering from different components in the system. This approach has been used with synthetic colloids, but it is also increasingly being used in the biological and food sciences. Perhaps the most studied food colloid is the "casein micelle," a self-assembled nanometer-scale colloid of the structure-forming casein protein in milk. CV-SANS data available in the literature are typically analyzed using approximations, which may be invalid for casein micelles, as they have been shown to be sticky spheres. To assess the applicability of this approximate approach, a comprehensive set of CV-SANS data from casein micelles in diluted milk was reanalyzed using a model-based approach, where the casein micelles were formally treated as interacting spheres. In general, the conclusions of the previous study are reproduced, but this new approach makes it more straightforward to distinguish the different components in milk and can be applied to any dairy sample with known form of interparticle interactions, which offers the possibility of studying semi-deuterated milk at its native concentration.

Glassy Behavior of Sticky Spheres: What Lies beyond Experimental Timescales?

We use the swap MonteCarlo algorithm to analyze the glassy behavior of sticky spheres in equilibrium conditions at densities where conventional simulations and experiments fail to reach equilibrium, beyond predicted phase transitions and dynamic singularities. We demonstrate the existence of a unique ergodic region comprising all the distinct phases previously reported, except for a phase-separated region at strong adhesion. All structural and dynamic observables evolve gradually within this ergodic region, the physics evolving smoothly from well-known hard sphere glassy behavior at small adhesions and large densities, to a more complex glassy regime characterized by unusually broad distributions of relaxation timescales and length scales at large adhesions.

Revisiting neutron scattering data from deuterated milk

Deuterated milk (dried milk powder that has been dissolved in deuterated water, 2H2O or D2O) is a valuable material for determining the structure of dairy products by neutron scattering. This has primarily been used in the past to study the internal structure of casein micelles, and when longer length scales have been studied, interparticle interactions have been neglected. This will impact fits to the data over all length scales, which will hamper quantitative data analysis. Previously measured large length scale neutron scattering data from the literature, both ultra-small-angle neutron scattering (USANS) and spin-echo small-angle neutron scattering (SESANS) data, have been reanalyzed and improved fits have been obtained using a recently proposed model describing casein micelles as sticky spheres, rather than as hard spheres. This shows that these interactions will also be necessary for modeling neutron scattering data on deuterated milk.

Drag on Janus Sphere in a Channel: Effect of Particle Position

Abstract Potential use of Janus spheres in novel engineering applications is being explored actively in recent years. Hydrodynamics around Janus spheres is different from that around homogeneous sticky or slippery spheres. Instantaneous motion of a sphere in channel flow is governed by hydrodynamic force experienced by the sphere, which in turn depends on the particle to channel size ratio, its instantaneous position, hydrophobicity of its surface, and the particle Reynolds number. We investigate numerically the drag experienced by a Janus sphere located at different off-center positions in a square channel. Two orientations of Janus sphere consisting of a sticky and a slippery hemisphere with the boundary between them parallel to the channel midplane are studied: (1) slippery hemisphere facing the channel centerline and (2) sticky hemisphere facing the channel centerline. The flow field around Janus sphere is found to be steady (for Re ≤ 50 investigated in this work) and asymmetric. Based on the data obtained, a correlation for drag coefficient as a function of particle Reynolds number and dimensionless particle position is also proposed.

Trapping tephritid fruit flies (Diptera: Tephritidae) in citrus groves of Fujian Province of China

Abstract Certain tephritid fruit flies, such as the oriental fruit fly, Bactrocera dorsalis , the Chinese citrus fly, B. minax and the Japanese orange fly, B. tsuneonis (Diptera: Tephritidae: Dacinae), are destructive citrus pests in China. A two-year trapping study was conducted in pomelo, Citrus maxima, groves in Fujian Province of China. The objectives of this study were to investigate the species, the abundance of tephritid fruit flies in the orchards, as well as the efficacy of the selected lure traps to these flies. Four lure traps or devices, i.e. methyl eugenol + Steiner trap (ST), cuelure + ST, ammonium acetate + putrescine + ST, and sticky spheres, were deployed from June to November 2017 and April to October 2018. Six economically significant Dacini pests were trapped during the period. These flies are B. dorsalis, the melon fruit fly, Zeugodacus cucurbitae, the pumpkin fruit fly, Z. tau, the Malaysian fruit fly, B. latifrons, and other two species - B. rubigina and Z. scutellatus. B. dorsalis was the most abundant, accounting for more than 50% of the capture, followed by Z. cucurbitae. The remaining four species accounted for less than 2% of the total capture. B. minax and B. tsuneonis, two destructive citrus-damaging tephritid fruit flies in China, were not found during the trapping period. Methyl eugenol trapped the highest number of fruit flies, followed by cuelure.

Morphology Regulation of Monosodium Urate Monohydrate Crystals via Fabricated Uniform Hydrogel Slices

AbstractCrystal morphology control is a common concern for the crystal engineering and relevant applications. For example, urate crystallization is important for the study of the hyperuricemia induced gout. Herein, biomimetic hydrogel material with uniform surface and vertical structure is fabricated, which possesses hybrid pH‐temperature responsibility for high‐efficiency interfacial nucleation and concentration regulation functions. The developed hydrogel layers are prepared to slice type as a functional microplatform and then added into the uric acid dihydrate (UAD) crystal solution to induce monosodium urate monohydrate (MSUM) crystallization. With different dosage of the hydrogel slices (HGS) in the solution, diverse crystal morphologies can be obtained in an efficient manner, such as “flower,” “sphere,” “sticky spheres,” which entirely distinguishes from the one prepared via no‐HGS. This work explores a new path for revealing the relevant crystallization mechanism and developing crystal morphology control technology with hydrogel interfacial materials.

Drag on Sticky and Janus (Slip-Stick) Spheres Confined in a Channel

Abstract Flow over a sphere is a frequently occurring phenomenon in a range of industries. The sphere is confined in a channel in most of these applications. Therefore, it is important to understand the effect of confinement on the hydrodynamics of the flow around a sphere placed in a channel. These spheres can be bubbles, solid particles or droplets resulting in different boundary conditions (stick or slip) on the surface of the sphere. In recent years, Janus spheres having slip and stick boundary conditions on parts of the sphere have gained importance because of their potential applications. In this article, drag coefficient for a spherical particle fixed at the centerline of a channel of square cross-section is obtained computationally for stick, slip, and stick-slip surfaces of the sphere for a range of particle Reynolds numbers (1–80) and particle to channel size ratios (0.05–0.80). Further, the position of stick particle in the channel is varied to understand the effect of particle location on the drag coefficient. Correlations are proposed to calculate the drag coefficient for no-slip and Janus particles when the particle is at the channel center.

Casein micelles in milk as sticky spheres.

Milk is a ubiquitous foodstuff and food ingredient, and milk caseins are key to the structural properties of milk during processing and storage. Caseins self-assemble into nanometer-sized colloids, referred to as "micelles", and particles of this size are ideally suited to study by small-angle scattering (SAS). Previous SAS measurements have almost exclusively focussed on the internal structure of the micelles. While important for milk's properties, this attention to the interior of the micelles provides limited information about the structure-forming properties of milk and milk ingredients. The ultra-small-angle X-ray scattering (USAXS) measurements and analysis in this study extend to the micrometer scale, which makes it possible to characterize the interaction between the micelles. Until now, SAS studies have generally excluded a consideration of the interparticle interactions between casein micelles. This is inconsistent with these new data, and it is not possible to model the data without some interparticle attraction. If the micelles are treated as sticky spheres, excellent agreement between experimental data and model fits can be obtained over the length scales studied, from micrometers to ångströms. The stickiness of casein micelles will impact ultra-small-angle scattering and small-angle scattering measurements of casein micelles, but it particularly limits the application of simple approximations, which generally assume that particles are dilute and noninteracting. In summary, this analysis provides an approach to modelling scattering data over many orders of magnitude, which will provide better understanding of interactions between caseins and during food processing.

Evaluation of Brightness Temperature Sensitivity to Snowpack Physical Properties Using Coupled Snow Physics and Microwave Radiative Transfer Models

There are multiple existing microwave radiative transfer models (RTMs) to simulate the brightness temperature (Tb) of snowpacks. It is still challenging to have consistent Tb responses from RTMs due to individual physical formulations of the snowpack scattering process. This article examines three of the widely-used multi-layer RTMs: 1) the microwave emission model of layered snowpacks (MEMLS); 2) the dense media radiative transfer based on the quasi-crystalline approximation (QCA) of Mie scattering of densely packed sticky spheres (DMRT-QMS); and 3) the Helsinki University of Technology (HUT) model. Interestingly, these models yield slightly different Tb responses when driven by the same physical snowpack properties. Tb variations, dependent on the choice of RTMs, are then evaluated to improve the understanding of model differences in microwave emission from a snowpack. We first perform a sensitivity study of the Tb predictions from the three RTMs as a function of snow grain sizes, densities, and depths. While Tb from all three RTMs decreases with increasing snow grain sizes, it is found that a scaling factor is required to have the same amount of Tb attenuation for small grain sizes within the Rayleigh scattering regime. For larger grain sizes, however, a scaling coefficient is not enough to match the model outputs due to the different scattering assumptions of the RTMs. For a single snow layer with increasing snow depths and densities, all three RTMs exhibit Tb attenuations arising from the increase in path lengths and optical depths. Further evaluations are conducted by feeding the three RTMs with the output of a snow physics model driven by in situ weather forcing in a coupled simulation. Outputs of this coupled model include snowpack physical properties and Tbs. By using snow stratigraphy observations, another set of Tb simulation is also conducted with RTMs driven by in situ snowpit observations. The snow physics outputs from the coupled case are compared against in situ snow stratigraphy observations. And both Tb simulations are compared against ground-based microwave observations from the European Space Agency (ESA) Nordic Snow Radar Experiment (NoSREx) 2009–2012. For three consecutive years, the in situ driven Tbs have 21.0-K root-mean-squared error (RMSE) while the coupled simulations have 24.7-K RMSE. However, after isolating the dry snow period and excluding diurnal melting snow conditions, 12.2- and 6.3-K RMSEs are achieved from in situ and coupled cases, respectively, in the 2011 water year.

Self-propulsion of a sticky sphere partially covered with a surface slip velocity

Microorganisms follow various strategies to swim in a viscous medium. In an attempt to understand the swimming of ciliated microorganisms, we study low Reynolds number locomotion of a rigid slip-stick swimmer where the propulsive slip velocity is concentrated around an annular patch, which imitates the distinctive surface activity of the microorganisms. In addition, we assume the Navier slip condition at the rigid-fluid interface, which contributes to the hydrodynamic slip or stickiness across the surface. We solve for the locomotion speed and the corresponding flow fields of the swimmer in an axisymmetric unbounded medium. Our analysis reveals insights into how the choice of active slip influences the swimming velocity and the other relevant swimming characteristics. Interestingly, we find that for an optimal active slip in the annular range [π/4, 3π/4], the locomotion speed of the partially covered swimmer is enhanced by a factor of 2 compared to the standard fully covered squirmer. In addition, the corresponding swimming efficiency is enhanced by ∼2.4 times. We independently treat the influence of stickiness of the swimmer on the swimming characteristics. We find that the stickiness reduces the hydrodynamic resistance for the partially covered swimmer and further enhances the swimming speed and efficiency. These findings will be helpful to design efficient artificial swimmers in terms of higher mobility and lower power dissipation.

One-step template-free hydrothermal synthesis of partially Sr-incorporated hierarchical K-CHA zeolite microspheres

Abstract Partially Sr-incorporated hierarchical K-CHA zeolite microsphere of primary truncated bi-pyramidal crystallites was hydrothermally synthesized by one-step template-free hydrothermal process and the formation mechanism was investigated in detail. Its crystallization was accelerated by addition of strontium, and it was formed by three distinct steps: formation and aggregation of amorphous hollow nanospheres, collapse of agglomerated hollow nanospheres to multilayered disc, and rotational intergrowth into thread ball shape microsphere. The hollow nanosphere was formed by thermal expansion of Sr-coated solid silica nanoparticle, and the multilayered disc, by collapse of spherically aggregated hollow nanospheres. The collapse took place to minimize total surface energy by flattening sticky hollow spheres and oriented attachment of crystallites nucleated in the shell of hollow spheres. The multilayered disc grew finally to be thread ball shape microspheres. K-CHA zeolite microspheres displayed hierarchical character and showed excellent 298 K adsorptions for water (316 cm3 g−1), and CO2 (167.0 mg g−1 at 10 bar). The CO2/N2 adsorption selectivity was 10 due to incorporated potassium ions. Evidently, partially Sr-incorporated K-CHA zeolite microsphere was a good adsorbent for solvent dehydration and carbon capture.

Calculating the Symmetry Number of Flexible Sphere Clusters

We present a theoretical and computational framework to compute the symmetry number of a flexible sphere cluster in $\mathbb{R}^3$, using a definition of symmetry that arises naturally when calculating the equilibrium probability of a cluster of spheres in the sticky-sphere limit. We define the sticky symmetry group of the cluster as the set of permutations and inversions of the spheres which preserve adjacency and can be realized by continuous deformations of the cluster that do not change the set of contacts or cause particles to overlap. The symmetry number is the size of the sticky symmetry group. We introduce a numerical algorithm to compute the sticky symmetry group and symmetry number, and show it works well on several test cases. Furthermore we show that once the sticky symmetry group has been calculated for indistinguishable spheres, the symmetry group for partially distinguishable spheres (those with non-identical interactions) can be efficiently obtained without repeating the laborious parts of the computations. We use our algorithm to calculate the partition functions of every possible connected cluster of 6 identical sticky spheres, generating data that may be used to design interactions between spheres so they self-assemble into a desired structure.

Gregory-Newton problem for kissing sticky spheres

All possible non-isomorphic arrangements of 12 spheres kissing a central sphere (the Gregory-Newton problem) are obtained for the sticky-hard-sphere (SHS) model, and subsequently projected by geometry optimization onto a set of structures derived from an attractive Lennard-Jones (LJ) type of potential. It is shown that all 737 derived SHS contact graphs corresponding to the 12 outer spheres are (edge-induced) subgraphs of the icosahedral graph. The most widely used LJ(6,12) potential has only one minimum structure corresponding to the ideal icosahedron where the 12 outer spheres do not touch each other. The point of symmetry breaking away from the icosahedral symmetry towards the SHS limit is obtained for general LJ($a,b$) potentials with exponents $a,b\in \mathbb{R}_+$. Only if the potential becomes very repulsive in the short-range, determined by the LJ hard-sphere radius $\sigma$, symmetry broken solutions are observed.

Monte Carlo on Manifolds: Sampling Densities and Integrating Functions

AbstractWe describe and analyze some Monte Carlo methods for manifolds in euclidean space defined by equality and inequality constraints. First, we give an MCMC sampler for probability distributions defined by unnormalized densities on such manifolds. The sampler uses a specific orthogonal projection to the surface that requires only information about the tangent space to the manifold, obtainable from first derivatives of the constraint functions, hence avoiding the need for curvature information or second derivatives. Second, we use the sampler to develop a multistage algorithm to compute integrals over such manifolds. We provide single‐run error estimates that avoid the need for multiple independent runs. Computational experiments on various test problems show that the algorithms and error estimates work in practice. The method is applied to compute the entropies of different sticky hard sphere systems. These predict the temperature or interaction energy at which loops of hard sticky spheres become preferable to chains. © 2018 Wiley Periodicals, Inc.

Deposition of sticky spheres in channel flow: Modeling of surface coverage evolution requires accurate sphere-sphere collision hydrodynamics

We analyzed the role of hydrodynamic interactions in a microfluidic channel flow containing a dilute suspension of micron-scale colloidal spheres (0.03%, 0.1%, 0.3% volume fraction) engineered to adhere onto a collector patch on the channel wall at wall shear rates of 9.3–930 s−1. Particle-wall adhesion was mediated by single-stranded DNA oligomers grafted onto the spheres and the glass channel wall, producing well-defined interactions via DNA strand base pairing. Particle positions in the flow were evolved using Brownian dynamics simulations in which hydrodynamic interactions between moving particles and the channel walls and/or adhered particles were computed off-line using a series of local simulations that explicitly resolve the fluid flow at the particle scale. By systematically varying the nature of hydrodynamic interactions captured in the Brownian dynamics simulations, we find that the interactions between moving and adhered particles represents the single most important physical element in such models. Once captured sufficiently accurately, the resulting models are able to predict coarse variables such as the overall particle coverage evolution, as well as more subtle characteristics, such as the microstructural distribution of the adhered particles.

Field Evaluation of Eight Attractant Traps forBactrocera minax(Diptera: Tephritidae) in a Navel Orange Orchard in China

The Chinese citrus fly, Bactrocera minax (Enderlein) (Diptera: Tephritidae), is the most destructive pest in many citrus orchards of south central China. Methyl eugenol and cuelure, 2 potent male lures that are effective for capturing related species, are believed not to attract this species. Limited knowledge is available about the effectiveness of attractant traps for this pest. A field trial was carried out to determine the efficacy of 8 attractant traps to B. minax. The study was conducted during the adult occurrence season in an orchard of navel orange, Citrus sinensis (L.) Osbeck (Rutaceae), in Zhijiang County, Hunan Province, China, in 2016. To link the efficacy of these attractant traps with the pest population, fruit infestations in the orchard also were investigated. As expected, this study confirmed that methyl eugenol and cuelure were not attractive to B. minax. Green-colored sticky spheres trapped significantly more flies and males than methyl eugenol and cuelure-baited traps. On average, ammonium acetate putrescine trapped more females than males, but it was not statistically better than any of the other tested attractant traps. Fruit infestation rates by B. minax ranged from 0.7 to 11.1% in the replicates. Judging by the results of trapping and actual field infestation, it appears that trap effectiveness of the 8 attractant traps was low. A more potent attractant trap is needed, especially for early detection of the pest.