Dumbbell Shapes Research Articles

Influence of Silver Nanoparticle Integration on the Composition and Surface Properties of Acrylic Dental Resins Employed in Temporary Bridges

Background: Recognized widely for its irreversible effects, periodontal disease stands as one of the most prevalent conditions, particularly emphasizing the potential for permanent damage caused by gingivitis, extending to encompass the entirety of the supportive complex, including the connective tissue and alveolar bone. Patients necessitating comprehensive periodontal and prosthetic treatments require an interdisciplinary approach, involving the coordination of pre-treatment procedures and appropriate prosthetic strategies. The adoption of advanced materials and techniques can prove beneficial in addressing complex dental issues. (2) Methods: Forty specimens were prepared using the prescribed procedure, with 20 acting as controls and the other 20 integrating AgNPs. The initial step involved crafting wax patterns of distinct shapes: dumbbell shapes for tensile testing and rectangular shapes for roughness assessments. These dimensions were aligned with ASTM D-638 and ISO 527-2 standards and adjusted to match the specifications of the analysis device for mechanical properties. (3) Results: In this case, the results indicate minimal differences in heat-curing acrylic resins compared to the control samples at a 5% concentration. However, notable disparities arise at concentrations of 10% and 20%. (4) Conclusions: Temporary prosthetic constructions are essential for preventing functional imbalances and complications. Incorporating AgNPs at a 5% concentration maintains mechanical properties while providing antibacterial effects for long-term interim prosthodontic restorations. Higher nanoparticle concentrations may reduce resin mechanical properties without affecting material surface condition

Morphological, Microstructural, and In Situ Chemical Characteristics of Siderite Produced by Iron-Reducing Bacteria.

Dissimilatory iron-reducing bacteria (DIRB) oxidize organic matter or hydrogen and reduce ferric iron to form Fe(II)-bearing minerals, such as magnetite and siderite. However, compared with magnetite, which was extensively studied, the mineralization process and mechanisms of siderite remain unclear. Here, with the combination of advanced electron microscopy and synchrotron-based scanning transmission X-ray microscopy (STXM) approaches, we studied in detail the morphological, structural, and chemical features of biogenic siderite via a growth experiment with Shewanella oneidensis MR-4. Results showed that along with the growth of cells, Fe(II) ions were increasingly released into solution and reacted with CO32- to form micrometer-sized siderite minerals with spindle, rod, peanut, dumbbell, and sphere shapes. They are composed of many single-crystal siderite plates that are fanned out from the center of the particles. Additionally, STXM revealed Fh and organic molecules inside siderite. This suggests that the siderite crystals might assemble around a Fh-organic molecule core and then continue to grow radially. This study illustrates the biomineralization and assembly of siderite by a successive multistep growth process induced by DIRB, also provides evidences that the distinctive shapes and the presence of organic molecules inside might be morphological and chemical features for biogenic siderite.

Manufacturing, characterization, and macromechanical modeling of short flax/hemp fiber-hybrid reinforced polypropylene

The present work focuses on the manufacturing, mechanical characterization, and modeling of hybrid Flax/Hemp/Polypropylene (PP) composites under dry conditions. Geometric parameters of the fibers were measured both before and after the melt processing. The results indicated that the processed fibers, especially the hybrid ones, had a narrowed length distribution with an average fiber length of 0.48 mm for hybrids compared to 0.62 mm for non-hybrids. The hybrid composites were mechanically characterized using basic and loading-unloading tensile tests with various fiber combinations and weight percentages. The study also examined the effect of strain rate and cutting angle on the behaviors of the composites. The results demonstrated the significance of fiber orientation as the primary factor in explaining mechanical variations. The tensile strength and Young's Modulus of FH30 composites (PP + 15 wt% flax + 15 wt% hemp) increased by about 24.1 % and 10.9 %, respectively, when the plates were cut into dumbbell shapes at a 90° angle to the injection molding flow direction, compared to a cut at 0° The study also showed that the tensile strength is directly proportional to the mass fraction of reinforcements, with an increase in tensile strength by 7.9 % for 0° cut angle specimens between FH10 (PP + 5 wt% flax + 5 wt% hemp) and FH30 bio-composites, while the uniform strain is inversely proportional to the mass fraction of reinforcements, evidenced by a reduction in uniform strain of 30 % between FH10 and FH30 samples. Morphological observations revealed the presence of bands indicating the propagation of micro-cracks, as well as debonding or cohesive failure. Finally, a Perzyna-type elasto-viscoplastic constitutive model was applied to accurately predict the overall mechanical response of a hybrid composite material. Specifically, the model successfully captured the tension deformation behavior of hybrid natural short-fiber thermoplastic composites, including the elastic stage, yield stress, and nonlinear hardening.

Fabrication and assessment of CuO and NiO-infused MnO2 nanocomposites: Characterization, methylene blue degradation, and antibacterial efficacy

This study employed the solid combustion method to fabricate CuO and NiO-doped MnO2 nanocomposites (MnNCs). Various spectral techniques confirmed their structural integrity. The Ultraviolet-Visible (UV–Vis) spectrum of the nanocomposites revealed peaks at 466 nm, ascribed to the bandgap and enhance the visible light absorption. The crystalline structure of the nanocomposites was confirmed by X-ray diffraction method. The scanning electron microscopy (SEM) images displayed a dumbbell and spherical shapes, while Transmission Electron Microscope (TEM) showed hexagonal, octahedral, and spherical particles. The elemental composition and oxidation state of MnNCs composites were verified by Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The EDS analysis results indicate that the prepared composites contain a reasonable amount of Mn, Cu, Ni, and O atoms. Additionally, based on the XPS results, the estimated percentages of Mn, Cu, Ni, and O are 49.48%, 8.79%, 11.84%, and 22.91%, respectively. The MnNCs-2 composites exhibit superior photocatalytic activity compared to MnO2 and MnNCs-1. Within 100 min, the MnNCs-2 nanocomposites demonstrate an 89.05% efficiency in degrading MB dye. The synthesized MnNCs nanocomposites are found to be extremely toxic against Gram-positive bacteria, Staphylococcus aureus (S. aureus), Streptococcus pyogenes (S. pyogenes), and Gram-negative bacteria, Escherichia coli (E. coli), and Klebsiella pneumoniae (K. pneumoniae). This study underscores the potential of MnNCs nanocomposites as versatile photocatalysts and antibacterial agents

Influence of Blending on Mechanical Behavior of Low-Density Polyethylene, Polypropylene, Polyvinylchloride

Three thermoplastic polymers, low-density polyethylene (LDPE), polypropylene(PP), and polyvinyl chloride (PVC),were synthesized from their raw pellets.Three blends of 1:1 wt.% of low-density polyethylene/polypropylene, low-density polyethylene/polyvinylchloride, polypropylene/polyvinylchloride, and one blend of 1:1:1 wt.% of low-density polyethylene/polypropylene/polyvinylchloride were produced via compression mould method using Two-roll Mill machine and Compression Mould machine. Using the Tensile Strength Tester machine, the pristine polymer and the blends were cut into dumbbell shapes for mechanical testing. The resultsobtained are 9.8MPa and 67.5% maximum stress and strain, respectively, for LDPE, 29MPa, and 12.4% maximum stress and strain, respectively, for neat PP. 25.8MPa and 35% maximum stress and strain respectively for pristine PVC, 19.2MPa and 44% maximum stress and strain respectively for LDPE/PVC blend, 19MPa and 29% maximum stress and strain respectively for LDPE/PP blend, 27.5MPa and10.75% maximum stress and strain respectively for PP/PVC, 21MPa and 10.4% maximum stress and stain respectively for LDPE/PP/PVC blend. The force at peak and the respective peak elongation are; 85.612N and 0.008387m for pristineLDPE, 344.810N and 0.004810m for pristinePP, 264.976N and 0.005496m forpristine PVC, 188.288N and 0.005980m for LDPE/PVC blend, 174.755N and 0.005109m for LDPE/PP blend, 250.196N and0.004287m for PP/PVC blend, 275.175N and 4.009mm for LDPE/PP/PVC blend. The maximum energies expended to have maximum extension are 0.71802784J (LDPE), 2.04578339J (PP), 1.70308635J (PVC), 1.12596224J (LDPE/PVC),0.8928233J (LDPE/PP), 1.50129025J (PP/PVC) and 1.10317658J (LDPE/PP/PVC). These results show improvement in the mechanical properties of the blends when compared with those of the constituent polymers. It also indicatesthat polymeric properties modification via an immiscible polymer blend is possible and easy to achieve.

Specimen Geometry Effect on Experimental Tensile Mechanical Properties of Tough Hydrogels.

Synthetic tough hydrogels have received attention because they could mimic the mechanical properties of natural hydrogels, such as muscle, ligament, tendon, and cartilage. Many recent studies suggest various approaches to enhance the mechanical properties of tough hydrogels. However, directly comparing each hydrogel property in different reports is challenging because various testing specimen shapes/sizes were employed, affecting the experimental mechanical property values. This study demonstrates how the specimen geometry-the lengths and width of the reduced section-of a tough double-network hydrogel causes differences in experimental tensile mechanical values. In particular, the elastic modulus was systemically compared using eleven specimens of different shapes and sizes that were tensile tested, including a rectangle, ASTM D412-C and D412-D, JIS K6251-7, and seven customized dumbbell shapes with various lengths and widths of the reduced section. Unlike the rectangular specimen, which showed an inconsistent measurement of mechanical properties due to a local load concentration near the grip, dumbbell-shaped specimens exhibited a stable fracture at the reduced section. The dumbbell-shaped specimen with a shorter gauge length resulted in a smaller elastic modulus. Moreover, a relationship between the specimen dimension and measured elastic modulus value was derived, which allowed for the prediction of the experimental elastic modulus of dumbbell-shaped tough hydrogels with different dimensions. This study conveys a message that reminds the apparent experimental dependence of specimen geometry on the stress-strain measurement and the need to standardize the measurement of of numerous tough hydrogels for a fair comparison.

Slug bubble deformation and its influence on bubble breakup dynamics in microchannel

The deformation of moving slug bubbles and its influence on the bubble breakup dynamics in microchannel were studied. Three bubble morphologies were found in the experiment: slug, dumbbell and grenade shapes. The viscosity effect of continuous phase aggravates the velocity difference between the fluid near the wall and the bubble, resulting in that the continuous phase near the bubble head flows towards and squeezes the bubble tail, which causes the deformation of bubbles. Moreover, the experimental results show that the deformation of bubbles could significantly prolong the bubble breakup period at the downstream Y-junction. There exists the critical capillary number Ca Cr for the asymmetric breakup of grenade bubbles, Ca Cr increases with the rise of flow rate and viscosity of the continuous phase.

In Situ Sol-Gel Synthesis of Unique Silica Structures Using Airborne Assembly: Implications for In-Air Reactive Manufacturing.

Optical trapping enables the real-time manipulation and observation of morphological evolution of individual particles during reaction chemistry. Here, optical trapping was used in combination with Raman spectroscopy to conduct airborne assembly and kinetic experiments. Micro-droplets of alkoxysilane were levitated in air prior to undergoing either acid- or base-catalyzed sol–gel reaction chemistry to form silica particles. The evolution of the reaction was monitored in real-time; Raman and Mie spectroscopies confirmed the in situ formation of silica particles from alkoxysilane droplets as the product of successive hydrolysis and condensation reactions, with faster reaction kinetics in acid catalysis. Hydrolysis and condensation were accompanied by a reduction in droplet volume and silica formation. Two airborne particles undergoing solidification could be assembled into unique 3D structures such as dumb-bell shapes by manipulating a controlled collision. Our results provide a pipeline combining spectroscopy with optical microscopy and nanoscale FIB–SEM imaging to enable chemical and structural insights, with the opportunity to apply this methodology to probe structure formation during reactive inkjet printing.

Topological Interaction among Molecular Cluster Assemblies Affords Tunable Viscoelasticity.

In the assemblies of subnanoscale polyhedral oligomeric silsesquioxane, topological interaction makes the dominant contribution to their viscoelasticity with broad tunability. The assembly molecules are designed with dumbbell, triangular, and tetrahedral shapes, and they demonstrate an intrinsic glassy feature with neither long-range ordering nor supramolecular assembly formation in their bulk. Their viscoelasticity can be broadly tuned through the tailoring of molecular topologies, while the trimer and tetramer assemblies afford elastic moduli comparable to those of rubbers (∼0.5 MPa) even 80 K above their glass transition temperatures. Molecular dynamics studies reveal the topological constraints resulting from the topology-disrupted cooperative dynamics among the cluster assemblies, and this finally leads to the typical caging dynamics of the structural units and the elasticity of the bulk materials. Further broadband dielectric spectroscopy studies uncover the unique hierarchical relaxation dynamics, inspiring the strategy for the decoupling of mechanical strengths and toughness for the design of impact resistant materials.

Interfacial Reinitiation of Free Radicals Enables the Regeneration of Broken Polymeric Hydrogel Actuators

Interfacial Reinitiation of Free Radicals Enables the Regeneration of Broken Polymeric Hydrogel Actuators

Room temperature synthesis of lanthanum phosphates with controlled nanotexture as host for Ln(III) through the Epoxide Route

Herein, the Epoxide Route, a one-pot room temperature alkalinization method based on the reaction between a nucleophile and an epoxide, has been employed to synthesize LaPO4 in the form of a Rhabdophane phase. The intrinsic features of this synthetic approach allow the reaction to be followed by pH monitoring, making possible the identification of the different precipitation steps involved in the formation of the solid. Once demonstrated the effectiveness of this chemical methodology, the size and shape of the LaPO4 particles were controlled by varying the identity and proportion of the organic co-solvents employed to perform the reaction. By these means, crystalline particles with dumbbell, urchin and needle shapes were obtained, with sizes that ranged from less than 200 nm to more than 5 μm. Finally, luminescent materials in the form of a LnPO4Rhabdophane structure were easily obtained by the incorporation of EuIII along the whole composition range. Additionally, photophysical characterization of selected samples was performed, with a promising outcome. The results presented in this work pave the way to obtaining a wide variety of luminescent materials with sizes and morphologies adjustable on demand, by using a simple and reliable synthetic approach.The Epoxide Route has been adapted to drive the precipitation of lanthanum phosphates exhibiting high control on size and morphology through a solvent-controlled growth approach. Additionally, this synthetic scenario allows the obtaining of luminescent materials by simply incorporating Eu(III) in the whole composition range.

Deposition characteristics of debris flows in a lateral flume considering upstream entrainment

The sediment deposited by debris flows in rivers is a common cause of mountain disasters. The deposition characteristics of debris flows are strongly affected by the entrainment during the transportation process and the water depth in the river channel, but how is poorly understood. Here, the effects of the released flow volume, flow density, bed sediment and water depth on the deposition process of debris flows are investigated for a total of 22 different tests. Detailed topographic surveys of deposit lobes are conducted using a 3D laser scanner with high precision. The slopes of lobes are largely determined by the flow density and bed-sediment composition. However, the effect of released flow volume on the lobe slope is relatively limited. The lobe areas projected onto the horizontal plane display dumbbell or trapezoidal shapes depending on deposit volume, and the cross sections along the lateral flume present a Gaussian distribution for flows after bed-sediment entrainment. The lobe area is reduced and lobe height is enhanced with an increase of water depth, contributing to a steeper deposit. Partial, submersed or complete blockages occur, depending on the debris-flow volume and water depth. This study improves understanding of the deposition features and may aid future hazard assessments of debris flows.

Microscopic diffusion coefficients of dumbbell- and spherocylinder-shaped colloids and their application in simulations of crowded monolayers.

We explore the diffusion properties of colloidal particles with dumbbell and spherocylinder shapes using a hydrodynamic bead-shell approach and additional Brownian dynamics (BD) simulations. By applying the bead-shell method, we determine empirical formulas for the microscopic diffusion coefficients. A comparison of these formulas and established experimental and theoretical results shows remarkable agreement. For example, the maximum relative discrepancy found for dumbbells is less than 5%. As an application example of the empirical formulas, we perform two-dimensional (2D) BD simulations based on a single dumbbell or spherocylinder in a suspension of spheres and calculate the resulting effective long-time diffusion coefficients. The performed BD simulations can be compared to quasi-2D systems such as colloids confined at the interface of two fluids. We find that the effective diffusion coefficient of translation mostly depends on the sphere area fraction ϕ, while the effective diffusion coefficient of rotation is influenced by the aspect ratio and ϕ. Furthermore, the effective rotational diffusion constant seems to depend on the particle shape with the corresponding implementation of the interactions. In the resolution limit of our methods, the shape-dependent differences of the microscopic diffusion coefficients and the long-time diffusion constant of translation are negligible in the first approximation. The determined empirical formulas for the microscopic diffusion coefficients add to the knowledge of the diffusion of anisotropic particles, and they can be used in countless future studies.

Surface gravity of rotating dumbbell shapes

We investigate the problem of determining the shape of a rotating celestial object – e.g., a comet or an asteroid – under its own gravitational field. More specifically, we consider an object symmetric with respect to one axis – such as a dumbbell – that rotates around a second axis perpendicular to the symmetry axis. We assume that the object can be modeled as an incompressible fluid of constant mass density, which is regarded as a first approximation of an aggregate of particles.In the literature, the gravitational field of a body is often described as a multipolar expansion involving spherical coordinates (Kaula, 1966). In this work we describe the shape in terms of cylindrical coordinates, which are most naturally adapted to the symmetry of the body, and we express the gravitational potential generated by the rotating body as a simple formula in terms of elliptic integrals. An equilibrium shape occurs when the gravitational potential energy and the rotational kinetic energy at the surface of the body balance each other out. Such an equilibrium shape can be derived as a solution of an optimization problem, which can be found via the variational method. We give an example where we apply this method to a two-parameter family of dumbbell shapes, and find approximate numerical solutions to the corresponding optimization problem.

Studies of electrical and optical properties of cadmium‐doped zinc oxide for energy conversion devices

AbstractIn this modern era, energy devices have become an important part of our daily life. Various types of energy conversion devices have been developed to meet the current energy demands. Semiconductor anode (CdZnO) has been synthesized by the sol‐gel method and lattice constants and the band gap results have been compared experimentally and theoretically. XRD results show that Cd‐doped ZnO shifts the peaks toward the lower angles, increases the lattice parameters, and decreases the crystallite size (48 nm). Microstructure of Cd‐doped ZnO shows the agglomerations of particles, found in the shape of cubes, hexagons, and dumbbell shapes with diameter in the range of 2–7 µm. The experimentally obtained conductivity of CdZnO is 0.142 S/cm at 550°C. The electrochemical impedance spectroscopy shows the decreased resistance with an increase in temperature. The doped system shows a maximum open circuit voltage of 0.95 V and performance of 0.52 W/cm2 at 550°C.

Self-Assembly of Polymer End-Tethered Gold Nanorods into Two-Dimensional Arrays with Tunable Tilt Structures

We demonstrated a facile yet effective strategy for self-assembly of polymer end-tethered gold nanorods (GNRs) into tunable two-dimensional (2D) arrays with the assistance of supramolecules of hydrogen bonded poly(4-vinyl pyridine) (P4VP) and 3-n-pentadecylphenol (PDP). Well-ordered 2D arrays with micrometer size were obtained by rupturing the assembled supramolecular matrix with a selective solvent. The formation of long-range ordered 2D arrays during a drying process was observed via small-angle X-ray scattering. Interestingly, the packing structure of the ordered arrays strongly depends on the molecular weight (Mw) of the polymer ligands and the size of the GNRs. By increasing Mw of the polymer ligands, tilted arrays can be obtained. The average angle between GNRs and the surface normal direction of the layered 2D arrays changes from 0 to 37° with the increase in Mw of the polymer ligands. A mechanism for assembly behavior of dumbbell shapes with a soft shell structure has been proposed. The resulting GNR arrays with different orientations showed anisotropic surface-enhanced Raman scattering (SERS) performance. We showed that the vertically ordered GNR arrays exhibited ∼3 times higher SERS signals than the tilt ordered arrays. The results prove that the polymer end-tethered GNRs can be used as a building block for preparing the tilted 2D arrays with tunable physicochemical properties, which could have a wide range of potential applications in photonics, electronics, plasmonics, etc.

Calcimicrobes in Cambrian microbialites (Shandong, North China) and comparison with experimentally produced biomineralization precipitates

Microbialites can be important oil and gas reservoirs because of their high initial porosity and they may well be source rocks too. However, the formation mechanisms of calcimicrobes in microbialites are still not fully understood, and further research is needed. Herein, microbialites (thrombolites, dendrolites, and oncolites) from the Cambrian successions of Shandong Province, China, are examined for their microbial fabrics and comparisons are made with the results of laboratory biomineralization experiments using the modern cyanobacterium Synechocystis sp. PCC6803 and the halophilic Bacillus licheniformis SRB2. The thrombolites show mosaic, meshed, and spotted textures, each with a different microbial clot morphology, and Epiphyton is the dominant calcimicrobe. Dendrolitic buildups consist of a lower gray core dominated by the chambered Renalcis, and an upper orange part dominated by dendritic Epiphyton, suggesting a transition of the microbial community across the color change, related to an increase in iron content. Oncolites occur in beds up to 10-cm-thick with spherical to ellipsoidal oncoids containing Girvanella developed around a bioclast nucleus. Scanning electron microscopy observations distinguish the calcimicrobes with their rough, peloidal surface morphology from adjacent cement; aggregated spheroidal and or filamentous calcimicrobes can be recognized, the latter with hollow centers in some cases. The results of the laboratory biomineralization experiments show that the two modern microbes can induce the precipitation of carbonate minerals, mostly of calcite. These biominerals are commonly granular and have a complex microscopic structure including spherical and dumbbell shapes. The microbes are commonly encrusted with calcite and after decomposition of the bacteria, hollow mineral crusts are produced; these are the result of the nucleation and growth of nano-minerals on the extracellular polymeric substances (EPS) present around the microbes. The bio-precipitates induced by modern microbes in the laboratory experiments are similar in many respects to the calcimicrobes in the Cambrian microbialites; biomineralization processes clearly play an important role in the formation of carbonate minerals and lithification of microbial mats.

Ultralow effective interfacial tension between miscible molecular fluids

We exploit the deformation of drops spinning in a denser background fluid to investigate the effective interfacial tension (EIT) between miscible molecular fluids. We find that for sufficiently low interfacial tension, spinning drops develop dumbbell shapes, with two large heads connected by a thinner central body. We show that this shape depends not only on the density and viscosity contrast between the drop and background fluids, but also on the fluid molecular structure, and hence on the stresses developing at their interface due to different molecular interaction. We systematically investigate the dynamics of dumbbell-shaped drops of water-glycerol mixtures spinning in a pure glycerol reservoir. By developing a model for the deformation based on the balance of the shear stress opposing the deformation, the imposed normal stress on the drop and an effective interfacial tension, we exploit the time evolution of the drop shape to measure the EIT. Our results show that the EIT in water-glycerol systems is orders of magnitude lower than that reported in previous experimental measurements, and in excellent agreement with values calculated via the phase field model proposed in [Phys. Rev. X 6, 041057, 2016].

Shape transformation and manipulation of a vesicle by active particles.

Langevin dynamics simulations are employed to study the shape transformation of a two-dimensional vesicle induced by active particles both inside and outside. We find that the shape of the vesicle changes from circle, to capsule, and eventually to dumbbell with the enhancement of the particle activity. Under the cooperation between the inside and the outside active particles, such significant shape transformation is realized by tuning the activity in a small range. And unexpectedly, the fluctuations of the capsule and the dumbbell shapes are not completely random but mostly along the direction of the short axis. In the situation of strong activity, the inside of the dumbbell vesicle is analogous to a system of two chambers, which are connected by a narrow channel. Intriguingly, we observe the vibration of the channel width, accompanied with the exchange of active particles between the two chambers. We also find that dynamical manipulation of the vesicle shape is possible through tuning the particle activity dynamically. This work provides new ideas to the control of the vesicle morphology and new insights into the dynamics in the vesicle's shape transformation.

Anisotropic properties of phase separation in two-component dipolar Bose–Einstein condensates

Using Crank–Nicolson method, we calculate ground state wave functions of two-component dipolar Bose–Einstein condensates (BECs) and show that, due to dipole–dipole interaction (DDI), the condensate mixture displays anisotropic phase separation. The effects of DDI, inter-component s-wave scattering, strength of trap potential and particle numbers on the density profiles are investigated. Three types of two-component profiles are present, first cigar, along z-axis and concentric torus, second pancake (or blood cell), in xy-plane, and two non-uniform ellipsoid, separated by the pancake and third two dumbbell shapes.