The rectangular twisted torus is an attractive alternative to the classic torus as interconnection topology of high-performance computers. In this article, we establish the analytical expression of ...the diameter of a rectangular twisted torus with any aspect ratio and any twist slope. The result validates the optimality of a rectangular twisted torus with width-height-slope ratio 2:1:1.
Materials patterned with high‐aspect‐ratio nanostructures have features on similar length scales to cellular components. These surfaces are an extreme topography on the cellular level and have become ...useful tools for perturbing and sensing the cellular environment. Motivation comes from the ability of high‐aspect‐ratio nanostructures to deliver cargoes into cells and tissues, access the intracellular environment, and control cell behavior. These structures directly perturb cells' ability to sense and respond to external forces, influencing cell fate, and enabling new mechanistic studies. Through careful design of their nanoscale structure, these systems act as biological metamaterials, eliciting unusual biological responses. While predominantly used to interface eukaryotic cells, there is growing interest in nonanimal and prokaryotic cell interfacing. Both experimental and theoretical studies have attempted to develop a mechanistic understanding for the observed behaviors, predominantly focusing on the cell–nanostructure interface. This review considers how high‐aspect‐ratio nanostructured surfaces are used to both stimulate and sense biological systems.
High‐aspect‐ratio nanostructured surfaces trigger a wide range of biological responses and can be thought to act as biological metamaterials. Their nanoscale structuring is comparable with that of intracellular machinery, interacting directly with the cell membrane and cytoskeleton. They are used for molecular delivery, intracellular sensing, and as biomechanical cues. Different applications and open research questions are summarized.
Under an applied magnetic field, superparamagnetic Fe3O4 nanoparticles with complementary DNA strands assemble into crystalline, pseudo‐1D elongated superlattice structures. The assembly process is ...driven through a combination of DNA hybridization and particle dipolar coupling, a property dependent on particle composition, size, and interparticle distance. The DNA controls interparticle distance and crystal symmetry, while the magnetic field leads to anisotropic crystal growth. Increasing the dipole interaction between particles by increasing particle size or external field strength leads to a preference for a particular crystal morphology (e.g., rhombic dodecahedra, stacked clusters, and smooth rods). Molecular dynamics simulations show that an understanding of both DNA hybridization energetic and magnetic interactions is required to predict the resulting crystal morphology. Taken together, the data show that applied magnetic fields with magnetic nanoparticles can be deliberately used to access nanostructures beyond what is possible with DNA hybridization alone.
DNA programmable assembly in combination with applied magnetic fields is used to direct magnetite nanoparticles into high‐aspect‐ratio superlattice crystals with various morphologies. A range of field strengths, nanoparticle core diameters, particle symmetries, and DNA lengths are explored to understand the competition between hybridization and magnetic dipole–dipole coupling interactions.
Experiments on the flow around stationary circular cylinders with very low aspect ratio piercing the water free surface were carried out in a recirculating water channel. Eight different aspect ...ratios were tested, namely L/D=0.1, 0.2, 0.3, 0.5, 0.75, 1.0, 1.5 and 2.0; no end-plates were employed. Forces were measured using a six degree-of-freedom load cell and the Strouhal number was inferred through the transverse force fluctuation frequency. The range of Reynolds number covered 10000<Re<50000. PIV measurements were performed in some aspect ratio cases, namely L/D=0.3, 0.5, 1.0 and 2.0 for Reynolds number equal to 43000. The results showed a decrease in drag force coefficients with decreasing aspect ratio, as well as a decrease in Strouhal number with decreasing aspect ratio. The PIV measurements and the PSD of forces showed different behavior for cylinders with L/D≤0.5, in which cases the free-end effects were predominant. Even without von Kármán street main characteristics around the majority length of the cylinder, in the range of 0.2<L/D≤0.5, the vortex shedding around it is capable of producing alternating forces in the transverse direction. Therefore, alternating forces were not observed in the transverse direction for cylinders with L/D≤0.2.
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•Simple and precise synthesis method for homogenous ZnO nanorods and nanowires growth.•Preferred CO2 surface adsorptions at monodentate and bidentate sites on ZnO structures.•Stable, ...repetitive and high CO2 sensing response ∼80 %.
In the present research, hybrid Au-ZnO one-dimensional (1-D) nanostructures were grown on silicon substrates with an Al-doped ZnO (AZO) seed layer (Ultrasonic Spray Pyrolysis: USP grown) and no seed layer (NSL) using two different catalytic gold films of 2 nm and 4 nm, respectively. Consequently, such 1-D nanostructures growth was associated with the vapor-liquid-solid (VLS) and vapor-solid (VS) processes. Scanning electron microscopy (SEM) imaging analysis confirms that heat treatment triggered Au nanoparticles nucleation with varying diameters. The Au nanoparticles size and underneath seed layer texture strongly affect the morphology and aspect ratio of 1-D ZnO nanostructures. The seed layer (1-D USP) sample resulted in the growth of longer nanowires (NWs) with a high aspect ratio. The NSL sample showed the formation of nanorods (NRs) with a low aspect ratio mainly via VS growth process. X-ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), and photoluminescence (PL) analysis also revealed the differences in the NWs and NRs properties and confirmed VLS and VS growth mechanisms. CO2 gas sensing performance at different concentrations was demonstrated, and NWs with seed layer showed a relatively higher sensing response. In contrast, NSL samples (NRs) exhibited two times faster response. A detailed gas sensing mechanism with different CO2 adsorption modes based on properties of 1-D nanostructures has been discussed. Currently, CO2 sensing and capturing are critical topics in the green transition framework. The present work would be of high significance to the scientific field of NW growth and fulfill the urgent need for CO2 gas sensing.
The axial gap structure of a half-wave rectified variable field flux motor (AG-HVFM) has been proposed, which has a double stator structure and field winding short-circuited by a diode. Although the ...AG-HVFM can achieve a high efficiency drive in wide speed and torque range via variable field flux control, its structure deteriorates the average torque and torque ripple. In this paper, we sequentially design the core shape, aspect ratio and current control method for an AG-HVFM to improve its torque characteristics.
Graphene/noble metal substrates for surface enhanced RAMAN scattering (SERS) possess synergistically improved performance, due to the strong chemical enhancement mechanism accounted to graphene and ...the electromagnetic mechanism raised from the metal nanoparticles. However, only the effect of noble metal nanoparticles characteristics on the SERS performance was studied so far. In attempts to bring a light to the effect of quality of graphene, in this work, two different graphene oxides were selected, slightly oxidized GOS (20%) with low aspect ratio (1000) and highly oxidized (50%) GOG with high aspect ratio (14,000). GO and precursors for noble metal nanoparticles (NP) simultaneous were reduced, resulting in rGO decorated with AgNPs and AuNPs. The graphene characteristics affected the size, shape, and packing of nanoparticles. The oxygen functionalities actuated as nucleation sites for AgNPs, thus GOG was decorated with higher number and smaller size AgNPs than GOS. Oppositely, AuNPs preferred bare graphene surface, thus GOS was covered with smaller size, densely packed nanoparticles, resulting in the best SERS performance. Fluorescein in concentration of 10−7 M was detected with enhancement factor of 82 × 104. This work demonstrates that selection of graphene is additional tool toward powerful SERS substrates.
A thermodynamic based model for predicting the martensite-start temperature (Ms) of steels has been developed that accounts for variations in the austenite grain size (Dγ). This is achieved by ...introducing two additional energy terms in the physical expression of the critical driving force proposed by Ghosh and Olson. Since grain refinement leads to stronger austenite, a higher driving force and thus a lower Ms is required to initiate the shear transformation. This first mechanism is described by a Hall Petch strengthening term. Secondly, the aspect ratio of martensitic units, i.e. laths, increases when Dγ becomes lower than a critical diameter DC. This implies more stored energy and therefore a higher driving force is required which also contributes to a decrease of Ms. Model calculations show a good agreement with experimental dependencies between Ms and Dγ. Although the developed Ms model has a strong thermodynamic basis, predictions can be made without having access to thermodynamic calculation software and databases. Instead, for a certain critical driving force the corresponding Ms can be calculated using a simple composition dependent relationship that has been adequately validated with thermodynamic calculations. Model parameters have been optimized by fitting against experimental data of more than 100 alloys. Benchmarking of model predictions against calculations made with various empirical models from literature demonstrates a significant improvement in accuracy.
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The deep-injection floating-catalyst chemical vapor deposition (DI-FCCVD) technique is introduced to continuously synthesize carbon nanotubes (CNTs) with high aspect ratio (AR>17000) and high ...crystallinity (IG/ID > 60) at high production rate (>6 mg/min). In this technique all reactants are injected directly and rapidly into high-temperature reaction zone through thin alumina tube; this process leads to simultaneous thermal decomposition of well-mixed catalyst precursors (ferrocene and thiophene), and thus to formation of uniformly-sized catalyst particles. Carbon nanotube fiber (CNTF) fabricated from high-AR CNT has specific strength of 2.94 N/tex and specific modulus of 231 N/tex, which are comparable to those of the state-of-the-art carbon fiber. Both DI-FCCVD and wet spinning methods are easily scalable to mass production, so this study may enable widespread industrial application of CNTFs.
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The Colloidal Properties of Nanocellulose Benselfelt, Tobias; Kummer, Nico; Nordenström, Malin ...
ChemSusChem,
April 21, 2023, Volume:
16, Issue:
8
Journal Article
Peer reviewed
Open access
Nanocelluloses are anisotropic nanoparticles of semicrystalline assemblies of glucan polymers. They have great potential as renewable building blocks in the materials platform of a more sustainable ...society. As a result, the research on nanocellulose has grown exponentially over the last decades. To fully utilize the properties of nanocelluloses, a fundamental understanding of their colloidal behavior is necessary. As elongated particles with dimensions in a critical nanosize range, their colloidal properties are complex, with several behaviors not covered by classical theories. In this comprehensive Review, we describe the most prominent colloidal behaviors of nanocellulose by combining experimental data and theoretical descriptions. We discuss the preparation and characterization of nanocellulose dispersions, how they form networks at low concentrations, how classical theories cannot describe their behavior, and how they interact with other colloids. We then show examples of how scientists can use this fundamental knowledge to control the assembly of nanocellulose into new materials with exceptional properties. We hope aspiring and established researchers will use this Review as a guide.
Colloidal toolbox: Nanocelluloses are anisotropic nanoparticles of semicrystalline assemblies of glucan polymers with great potential as a renewable raw material for a more sustainable society. In this comprehensive overview, we describe the most prominent colloidal behaviors of nanocellulose based on classical and new theories and how controlling these colloidal interactions is a toolbox to guide the assembly of nanocellulose into new nanostructured materials.
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