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We study fractional-derivative Maxwell theory, as appears in effective descriptions of, for example, large N f QED 3 , graphene, and some types of surface defects. We argue that when the theory is realized on a lattice, monopole condensation leads to a confining phase via the Polyakov confinement mechanism.
A kinetic equation for a system of elastic hard spheres or disks confined by a hard wall of arbitrary shape is derived. It is a generalization of the modified Enskog equation in which the effects of the confinement are taken into account and it is supposed to be valid up to moderate densities. From the equation, balance equations for the hydrodynamic fields are derived, identifying the collisional transfer contributions to the pressure tensor and heat flux. A Lyapunov functional, H[f], is identified. For any solution of the kinetic equation, H decays monotonically in time until the system reaches the inhomogeneous equilibrium distribution, that is a Maxwellian distribution with a density field consistent with equilibrium statistical mechanics.
Measurements at the single-entity level provide more precise diagnosis and understanding of basic biological and chemical processes. Recent advances in the chemical measurement provide a means for ultra-sensitive analysis. Confining the single analyte and electrons near the sensing interface can greatly enhance the sensitivity and selectivity. In this work, we summarize the recent progress in single-entity electrochemistry of single molecules, single particles, single cells and even brain analysis. The benefits of confining these entities to a compatible size sensing interface are exemplified. Finally, the opportunities and challenges of single entity electrochemistry are addressed.
The effects of quantum confinement have been observed pronouncedly in the island morphology of Pb thin films. The evolution of these nano-islands on Si (111)-(7 x 7) and sapphire (001) surfaces has been studied with a new X-ray diffraction method. A charge-coupled device (CCD) camera was used to collect two- and three-dimensional (2-D and 3-D, respectively) maps of the surface X-ray diffraction in real time. Large ranges of the reflectivity curves, with rocking curves at every point on the reflectivity curves, could be measured continuously in a relatively short amount of time. The abundance of information from 2-D k-space maps reveals clear changes in the growth modes of these thin Pb films. With the 3-D extension of this method, it was possible to observe the ordering of the islands. The islands maintain a nearly uniform interisland distance but lack any angular correlation. The interisland ordering is correlated well with the development of 'magic' island heights caused by quantum confinement.
Simulating eutectic growth with convection is challenging because of the enormous computing demand resulting from the required domain size compared with the eutectic scale. In this study, a phase-field lattice-Boltzmann approach was employed to reproduce the eutectic growth with convection (both natural and forced). To enable and accelerate large-scale simulations, a parallel-adaptive mesh refinement algorithm was developed to combine with this numerical approach. The effects of the boundary conditions and the geometric confinement on the eutectic growth with convection were systematically investigated in the Al-Cu eutectic alloy. Results showed that both boundary conditions and the geometric confinement altered the eutectic evolution by affecting the distributions of the solute and velocity ahead of the eutectic solid/liquid interface. As the first attempt to explore the two factors on the eutectic growth with convection, our thorough investigation lays a foundation for modeling the coupled convection–solute eutectic evolution.
The selection of suitable materials to construct a facility for the final disposal of radioactive wastes (repository) is a challenge in materials science, since these facilities must be designed to provide confinement to the radionuclides for long periods of time. In the case of the low-level radioactive waste (LLRW) repository, the confinement of the species must be guaranteed for more than 300 years. In this context, the evaluation of the proposed materials must be performed under accelerated laboratory tests. One type of LLRW consists of ashes that result from the incineration of solid combustible radioactive waste. In Argentina, one of the proposed projects is to place these ashes inside steel drums and immobilized them by a cementation process. The issue to be resolved is whether the steel drums will undergo internal corrosion depending on the presence of certain deleterious species. The aim of the present work is to evaluate the corrosion susceptibility of steel drums containing simulated cemented incineration ashes. To this purpose, a special type of specimen was designed and the corrosion process was followed up for almost 4 years. It was found that, although the deleterious effect of chloride is undeniable, corrosion rates are not as high as to compromise the integrity of the steel drums for a design period of 300 years.
Laser-driven inertial confinement fusion creates a central hot-spot plasma by irradiating a spherical target containing a thermonuclear fuel layer of deuterium (D) and tritium (T) with temporally-shaped, high-intensity lasers or X rays. Inertial confinement fusion relies on the DT-fusion alpha particles depositing their energy in a hot-spot plasma, causing its temperature to rise sharply and a thermonuclear burn wave to propagate out through the surrounding cold, dense DT fuel, producing significantly more energy than was used to heat and compress the fuel. Alpha heating has been demonstrated and burning plasma (i.e., yield amplification due to alpha heating >3.5) is being explored with megajoule-scale lasers on the path to ignition (i.e., yield amplification due to alpha heating >20)
Here, nanopores (at least one dimension ≤100 nm and no dimension <1 nm) are commonly observed features of grain coatings and primary silicate minerals and can contribute substantially to the total surface area available for chemical reactions. Despite the ubiquity of nanopores in natural and synthetic porous media, a generalizable framework for evaluating the effects of nanopore confinement on both fluid and sorbate properties across the entire nanoscale has yet to emerge. As a result, we have a poor understanding of the effect of pore size on molecular-scale processes controlling nano-confinement phenomena in systems in which mineral surfaces are in contact with aqueous solutions.
Successful carbon capture and storage (CCS) requires secure CO 2 confinement within a geologic reservoir. If associated with a depleted hydrocarbon reservoir, the sealing capability can be determined by examination of the shallow subsurface for hydrocarbon leaks. Numerous seismic signatures have been reported to be hydrocarbon indicators. The interpretation can be advanced by using seismic diffractions, which could indicate subtle hydrocarbon accumulations not detectable by conventional techniques. In this work, we investigate the potential of seismic diffractions for use in shallow gas detection. We extract diffractions from the ultra-high-resolution 3D P-Cable seismic dataset acquired along the Gulf of Mexico inner continental shelf. Interpretation of this dataset revealed numerous seismic signatures associated with hydrocarbon accumulations (e.g., a prominent gas chimney). We analyze scattering features of the detected hydrocarbon accumulations and confirm the correlation between confidently interpreted gas accumulations and seismic diffractions. Based on that, we suggest using diffractions for confining system integrity assessment. As a result, diffraction analysis allows operating with subtle seismic signals that facilitates exploration of reliable CO 2 storage sites.
A direct numerical simulation (DNS) campaign is deployed for a series of confined downward oriented, non-isothermal turbulent impinging jet configurations. A baseline Reynolds number of 9960 is obtained through a precursor DNS pipe flow simulation (Re τ = 505). Three jet temperature configurations (confinement height to nozzle diameter of three) enter a cylindrical domain that share ambient and impingement plate temperatures (298.15 K). The range of jet temperatures are crafted such that the ratio of inlet to ambient density varies from unity to 0.52, showcasing the effect of density disparity on flow characteristics such as core collapse, radial mixing of momentum and energy, near-wall stagnation behavior, wall-jet profiles, and large-scale vortical structures. Surface quantities provided include mean radial heat flux and wall-shear stress profiles, and heat flux histograms at select radial stations. Results showcase increased radial normal stresses for higher temperature jets that support increased mixing, resulting in large-scale recirculation structures that are smaller, while retaining similar normalized radial wall profiles for shear stress, heat flux and pressure. Furthermore, radial plots for wall shear stress and Nusselt number showcase strong radial decay as compared to previous configurations that share similar jet and ambient temperatures. For the 373.15 K case, a Gaussian-like histogram for heat fluxes at the impingement plate transitions to a log-normal profile as radial distances increase. In contrast, the 573.15 K configuration displays a bi-modal heat flux characteristic at the impingement plate, and in similar manner to the moderate temperature counterpart, transitions to a log-normal profile at larger radial distances.
This paper presents a Hammir tandem mirror confinement performance analysis based on Realta Fusion’s first-of-a-kind model for axisymmetric magnetic mirror fusion performance. This model uses an integrated end plug simulation model including, heating, equilibrium and transport combined with a new formulation of the plasma operation contours (POPCONs) technique for the tandem mirror central cell. Using this model in concert with machine learning optimization techniques, it is shown that an end plug utilizing high temperature superconducting magnets and modern neutral beams enables a classical tandem mirror pilot plant producing a fusion gain Q > 5. The approach here represents an important advance in tandem mirror design. The high-fidelity end plug model enables calculations of heating and transport in the highly non-Maxwellian end plug to be made more accurately. The detailed end plug modelling performed in this work has highlighted the importance of classical radial transport and neutral beam absorption efficiency on end plug viability. The central cell POPCON technique allows consideration of a wide range of parameters in the relatively simple near-Maxwellian central cell, facilitating the selection of more optimal central cell plasmas. These advances make it possible to find more conservative classical tandem mirror fusion pilot plant operating points with lower temperatures, neutral beam energies and end plug performance requirements than designs in the literature. Despite being more conservative, it is shown that these operating points have sufficient confinement performance to serve as the basis of a viable fusion pilot plant provided that they can be stabilized against magnetohydrodynamic and trapped particle modes.
Heterogeneous advanced oxidation processes (AOPs) allow for the destruction of aqueous organic pollutants via oxidation by hydroxyl radicals ( • OH). However, practical treatment scenarios suffer from the low availability of short-lived • OH in aqueous bulk, due to both mass transfer limitations and quenching by water constituents, such as natural organic matter (NOM). In this work, we overcome these challenges by loading iron oxychloride catalysts within the pores of a ceramic ultrafiltration membrane, resulting in an internal heterogeneous Fenton reaction that can degrade organics in complex water matrices with pH up to 6.2. With • OH confined inside the nanopores (~ 20 nm), this membrane reactor completely removed various organic pollutants with water fluxes of up to 100 L m –2 h –1 (equivalent to a retention time of 10 s). This membrane, with a pore size that excludes NOM (>300 kDa), selectively exposed smaller organics to •OH within the pores under confinement and showed excellent resiliency to representative water matrices (simulated surface water and sand filtration effluent samples). Moreover, the membrane exhibited sustained AOPs (>24 h) and could be regenerated for multiple cycles. Our results suggest the feasibility of exploiting ultrafiltration membrane-based AOP platforms for organic pollutant degradation in complex water scenarios.
Many macroscopic properties such as collective chiral responses enhanced by coupled plasmonic nanoparticles require complex nanostructures. However, a key challenge is to directly assemble nanosized building blocks into functional entities with designed morphologies. For example, the DNA templated nanoparticle assembly has low scalability and requires aqueous conditions, while other approaches such as controlled drying and polymer templating access only simple 1-D, 2-D, and 3-D structures with limited assembly patterns. In this paper, we demonstrate a new self-assembly strategy that expands the diversity of 3-D nanoparticle assemblies. By subjecting supramolecular nanocomposites to cylindrical confinement, a range of new nanoparticle assemblies such as stacked rings and single and double helices can be readily obtained with a precisely defined morphology. Circular dichroism dark field scattering measurements on the single nanowire with Au helical ribbon-like assembly show chiral plasmonic response several orders of magnitude higher than that of natural chiral materials. The phase behavior of supramolecular nanocomposite under geometric constraints is quite different from that of block copolymer. Finally, it depends on the complex interplay among nanoparticle packing and phase behavior of parent block copolymers under confinement and can be governed by nanoparticle diffusion.
The optical properties of silicon nanocrystals (Si NCs) are a subject of intense study and continued debate. In particular, Si NC photoluminescence (PL) properties are known to depend strongly on the surface chemistry, resulting in electron-hole recombination pathways derived from the Si NC band-edge, surface-state defects, or combined NC-conjugated ligand hybrid states. In this Letter, we perform a comparison of three different saturated surface functional groups - alkyls, amides, and alkoxides - on nonthermal plasma-synthesized Si NCs. We find a systematic and size-dependent high-energy (blue) shift in the PL spectrum of Si NCs with amide and alkoxy functionalization relative to alkyl. Time-resolved photoluminescence and transient absorption spectroscopies reveal no change in the excited-state dynamics between Si NCs functionalized with alkyl, amide, or alkoxide ligands, showing for the first time that saturated ligands - not only surface-derived charge-transfer states or hybridization between NC and low-lying ligand orbitals - are responsible for tuning the Si NC optical properties. To explain these PL shifts we propose that the atom bound to the Si NC surface strongly interacts with the Si NC electronic wave function and modulates the Si NC quantum confinement. Furthermore, these results reveal a potentially broadly applicable correlation between the optoelectronic properties of Si NCs and related quantum-confined structures based on the interaction between NC surfaces and the ligand binding group.
High-photoluminescence quantum yield (PLQY) is required to reach optimal performance in solar cells, lasers, and light-emitting diodes (LEDs). Typically, PLQY can be increased by improving the material quality to reduce the nonradiative recombination rate. It is in principle equally effective to improve the optical design by nanostructuring a material to increase light out-coupling efficiency (OCE) and introduce quantum confinement, both of which can increase the radiative recombination rate. However, increased surface recombination typically minimizes nanostructure gains in PLQY. Here a template-guided vapor phase growth of CH 3 NH 3 PbI 3 (MAPbI 3 ) nanowire (NW) arrays with unprecedented control of NW diameter from the bulk (250 nm) to the quantum confined regime (5.7 nm) is demonstrated, while simultaneously providing a low surface recombination velocity of 18 cm s –1 . This enables a 56-fold increase in the internal PLQY, from 0.81% to 45.1%, and a 2.3-fold increase in OCEy to increase the external PLQY by a factor of 130, from 0.33% up to 42.6%, exclusively using nanophotonic design.
Here, we study the assembly of DNA-functionalized nanocubes under lateral confinement in microscale square trenches on a DNA-functionalized substrate. Microfocus small-angle X-ray scattering (SAXS) and scanning electron microscopy (SEM) are used to characterize the superlattices (SLs). The results indicate that nanocubes form simple-cubic SLs with square-prism morphology and a (100) out-of-plane orientation to maximize DNA bonding. In-plane, SLs align with the template, exposing their {100} side facets, and the degree of alignment depends on trench size. Interestingly, the distribution of in-plane orientations determined from SAXS and SEM do not agree, indicating that the internal and external structures of the SLs differ. To understand this discrepancy, X-ray ptychography is employed to image the internal structures of the SLs, revealing that SLs which appear to be single-crystalline in SEM may have subsurface grain boundaries, depending on trench size. SEM reveals that the SLs grow via nucleation and growth of randomly oriented domains, which then coalesce; this mechanism explains the observed dependence of alignment and defect structure on size. Interestingly, crystallization occurs via an unusual growth mode, whereby continuous SL layers grow on top of several misoriented islands. Overall, this work elucidates the effect of lateral confinement on the crystallization of DNA-functionalized nanoparticles and shows how X-ray ptychography can be used to gain insight into nanoparticle crystallization.
Here, borophene nanoribbons (BNRs) are one-dimensional strips of atomically thin boron expected to exhibit quantum-confined electronic properties that are not present in extended two-dimensional borophene. While the parent material borophene has been experimentally shown to possess anisotropic metallicity and diverse polymorphic structures, the atomically precise synthesis of nanometer-wide BNRs has not yet been achieved. Here, we demonstrate the synthesis of multiple BNR polymorphs with well-defined edge configurations within the nanometer-scale terraces of vicinal Ag(977). Through atomic-scale imaging, spectroscopy, and first-principles calculations, the synthesized BNR polymorphs are characterized and found to possess distinct edge structures and electronic properties. For single-phase BNRs, v 1/6 -BNRs and v 1/5 -BNRs adopt reconstructed armchair edges and sawtooth edges, respectively. In addition, the electronic properties of single-phase v 1/6 -BNRs and v 1/5 -BNRs are dominated by Friedel oscillations and striped moiré patterns, respectively. On the other hand, mixed-phase BNRs possess quantum-confined states with increasing nodes in the electronic density of states at elevated biases. Overall, the high degree of polymorphism and diverse edge topologies in borophene nanoribbons provide a rich quantum platform for studying one-dimensional electronic states.
Traditionally, photonic crystal slabs can support resonances that are strongly confined to the slab but also couple to external radiation. However, when a photonic crystal slab is placed on a substrate, the resonance modes become less confined, and as the index contrast between slab and substrate decreases, they eventually disappear. Using the scale structure of the Dione juno butterfly wing as an inspiration, we present here a low-index zigzag surface structure that supports resonance modes even without index contrast with the substrate. The zigzag structure supports resonances that are contained away from the substrate, which reduces the interaction between the resonance and the substrate. We experimentally verify the existence of substrate-independent resonances in the visible wavelength regime. Potential applications include substrate-independent structural color and light guiding.