On-site Potential Research Articles

Nanopore-assisted ELISA for ultrasensitive, portable, and on-site detection of ricin

Effective detection technologies in food safety with the merits of portable and on-site detection potential are always in pressing demand. Herein, we developed a nanopore-assisted Enzyme-linked immunosorbent assay (NELISA) platform, which innovatively introduced hairpin DNA (HP DNA) probes as reaction substrates. This innovation of substrates effectively avoided the inherent limitations of colorimetric signals (i.e., low sensitivity and inaccurate results) and greatly improved the sensitivity and accuracy of NELISA platform. The alkaline phosphatase (ALP)-modified detection antibody (ALP-Ab2) can specifically bind to ricin and hydrolyze the phosphate groups modified on the HP DNA probes. Nanopore recordings demonstrated that two states of probes produced highly distinguishable nanopore events, enabling the qualitative and quantitative detection of ricin. This NELISA platform fully combined the specificity of ELISA with the ultra-sensitivity, and unique single-molecule fingerprint recognition of nanopore, showing a great on-site detection potential. This method achieved the ultrasensitive and reliable detection of ricin down to 2.46 fg/mL, which enhanced the detection sensitivity by at least 106-fold compared to traditional ELISA. Furthermore, the proposed method was capable of accurately detecting ricin in real food samples with satisfactory recoveries.

A Clickase-Mediated Immunoassay Based on Nanopore and Bionic Signal Labels for Ultrasensitive, Portable, and On-Site Detection of Ricin.

It is of particular importance to develop an effective method that possesses several merits simultaneously of rapid, ultrasensitive, portable, and on-site detection potential for food safety detection. Herein, we propose a clickase-mediated immunoassay based on nanopore and bionic signal labels for the detection of ricin. The introduction of Cu/Cys clickase and nanopore simultaneously effectively addressed the inherent limitations of natural enzymes and colorimetric signal output, respectively. Using this method, bionic signal labels can be easily formed through DNA and Gram-positive bacterial cell wall terminal peptide fragments (labeled by alkynyl and azide, respectively) and vancomycin. Translocation of the D-P@vancomycin through the nanopore generated highly specific oscillation current traces. This method showed a great on-site detection potential and superior analytical performance owing to the combination of the specificity of antibodies, high CuAAC click reaction catalytic efficiency of clickase, ultrasensitivity of the nanopore, and high signal resolution of D-P@vancomycin. Moreover, the practical applicability of the established method was also verified, achieving a limit of detection (LOD) down to 200.9 ag/mL with a wide linear relationship under the optimized conditions. In conclusion, this method is promising for rapid, portable, ultrasensitive, and on-site food safety detection.

High-Order Topological Pumping on a Superconducting Quantum Processor.

High-order topological phases of matter refer to the systems of n-dimensional bulk with the topology of m-th order, exhibiting (n-m)-dimensional boundary modes and can be characterized by topological pumping. Here, we experimentally demonstrate two types of second-order topological pumps, forming four 0-dimensional corner localized states on a 4×4 square lattice array of 16 superconducting qubits. The initial ground state of the system at half-filling, as a product of four identical entangled 4-qubit states, is prepared using an adiabatic scheme. During the pumping procedure, we adiabatically modulate the superlattice Bose-Hubbard Hamiltonian by precisely controlling both the hopping strengths and on-site potentials. At the half pumping period, the system evolves to a corner-localized state in a quadrupole configuration. The robustness of the second-order topological pump is also investigated by introducing different on-site disorder. Our Letter studies the topological properties of high-order topological phases from the dynamical transport picture using superconducting qubits, which would inspire further research on high-order topological phases.

A nanopore-based label-free CRISPR/Cas12a system for portable and ultrasensitive detection of zearalenone

BackgroundFood safety has become a serious global concern. Therefore, there is a need for effective detection technologies in this field. Currently, the development of effective on-site detection techniques is extremely important for food safety. However, the traditional on-site detection methods currently lack effective signal amplification. Herein, the aim of this study was to construct a nanopore-based label-free CRISPR/Cas12a system for the detection of Zearalenone (ZEN). The method is expected to be highly sensitive for portable detection of ZEN in food. ResultsThe proposed strategy was mainly involved three steps, including the displacement of the target DNA, the triggering of the cleavage of hairpin DNA probes (probes 1) by the trans-cleavage of CRISPR/Cas12a, and the generation of a measurable nanopore current signal. The probes 1 and DNA after the cleavage of probes 1 (probes 2) produce different characteristic nanopore signals as they pass through the nanopore. The established method achieved a low limit of detection (LOD) of 6.52 fM for ZEN and a wide liner range under optimized conditions. Furthermore, the practical applicability of this method was verified in real maize samples and showed good recoveries (90.68–101.98 %) and low relative standard deviations (RSD) (9.21–9.72 %). Therefore, this method is a promising option for rapid and ultrasensitive detection of ZEN. Significance and noveltyThe study presented a portable nanopore-based CRISPR/Cas12a signal amplification detection system for the detection of ZEN in food, which had a low LOD and the advantages of rapid, portability, and on-site detection potential. In conclusion, the method presented a promising prospect and universal platform for the detection of ZEN and other mycotoxins, offering a novel insight into on-site food safety detection.

Effect of uncorrelated on-site scalar potential and mass disorder on transport of two-dimensional Dirac fermions

Effect of uncorrelated on-site scalar potential and mass disorder on transport of two-dimensional Dirac fermions

Topological boundary states in engineered quantum-dot molecules on the InAs(111)A surface: Odd numbers of quantum dots

Atom manipulation by scanning tunneling microscopy was used to construct quantum dots on the InAs(111)A surface. Each dot comprised six ionized indium adatoms. The positively charged adatoms create a confining potential acting on surface-state electrons, leading to the emergence of a bound state associated with the dot. By lining up the dots into N-dot chains with alternating tunnel coupling between them, quantum-dot molecules were constructed that revealed electronic boundary states as predicted by the Su-Schrieffer-Heeger (SSH) model of one-dimensional topological phases. Dot chains with odd N were constructed such that they host a single end or domain-wall state, allowing one to probe the localization of the boundary state on a given sublattice by scanning tunneling spectroscopy. We found probability density also on the forbidden sublattice together with an asymmetric energy spectrum of the chain-confined states. This deviation from the SSH model arises because the dots are charged and create a variation in on-site potential along the chain—which does not remove the boundary states but shifts their energy away from the midgap position. Our results demonstrate that topological boundary states can be created in quantum-dot arrays engineered with atomic-scale precision. Published by the American Physical Society 2024

Robust correlated magnetic moments in end-modified graphene nanoribbons

We conduct a theoretical examination of the electronic and magnetic characteristics of end-modified 7-atom wide armchair graphene nanoribbons (AGNRs). Our investigation is performed within the framework of a single-band Hubbard model, beyond a mean-field approximation. First, we carry out a comprehensive comparison of various approaches for accommodating di-hydrogenation configurations at the AGNR ends. We demonstrate that the application of an on-site potential to the modified carbon atom, coupled with the addition of an electron, replicates phenomena such as the experimentally observed reduction of the bulk-states (BS) gap. These results for the density of states (DOS) and electronic densities align closely with those obtained through a method explicitly designed to account for the orbital properties of hydrogen atoms. Furthermore, our study enables a clear differentiation between magnetic moments already described in a mean-field (MF) approach, which are spatially confined to the same sites as the topological end-states (ES), and correlation-induced magnetic moments, which exhibit localization along all edges of the AGNRs. Notably, we show the robustness of these correlation-induced magnetic moments relative to end modifications, within the scope of the method we employ.

Energy transfer in the Holstein approach for the interplay between periodic on-site and linear acoustic potentials

We study the problem of a transferring electron along a lattice of phonons, in the continuous long wave limit, holding periodic on-site and linear longitudinal interactions in Holstein’s approach. We thus find that the continuum limit of our modeling produces an effective coupling between the linear Schrödinger and sine–Gordon equations. Then, we take advantage of the existence of trapped kink–anti kink solutions in the sine–Gordon equation to variationally describe traveling localized coupled solutions. We validate our variational findings by solving numerically the full coupled system. Very reasonable agreement is found between the variational and full numerical solutions for the amplitude evolution of both profiles; the wave function and the trapped kink–anti kink. Our results show the significance of permitting longitudinal interactions in the Holstein’s approach to hold trapped localized solutions. It is actually found a critical ratio between longitudinal and on-site interactions, as depending on the velocity of propagation, from where coupled localized solutions exist.

Exact counterdiabatic driving in finite topological lattice models

Adiabatic protocols are often employed in state preparation schemes but require the system to be driven by a slowly varying Hamiltonian so that transitions between instantaneous eigenstates are exponentially suppressed. Counterdiabatic driving is a technique to speed up adiabatic protocols by including additional terms calculated from the instantaneous eigenstates that counter diabatic excitations. However, this approach requires knowledge of the full eigenspectrum meaning that the exact analytical form of counterdiabatic driving is only known for a subset of problems, e.g., the harmonic oscillator and transverse field Ising model. We extend this subset of problems to include the general family of one-dimensional noninteracting lattice models with open boundary conditions and arbitrary onsite potential, tunneling terms, and lattice size. We will derive a general analytical form for the counterdiabatic term for all states of lattice models, including bound and in-gap states which appear, e.g., in topological insulators. We also derive the general analytical form of targeted counterdiabatic driving terms which are tailored to enforce the dynamical state to remain in a specific state. As an example of the use of the derived analytical forms, we consider state transfer using the topological edge states of the Su-Schrieffer-Heeger model. The derived analytical counterdiabatic driving Hamiltonian can be utilized to inform control protocols in many-body lattice models or to probe the nonequilibrium properties of lattice models. Published by the American Physical Society 2024

Slow energy relaxation in anharmonic chains with and without on-site potentials: Roles of distinct types of discrete breathers

Slow energy relaxation has been observed in one-dimensional lattices with and without a nonlinear on-site potential; however, a comprehensive understanding of the detailed relaxation process remains elusive. Here we revisit this issue by introducing damping conditions at the free-end boundary of a thermalized lattice. We reveal that, in the long-cooling-time regime considered, for systems with a nonlinear on-site potential, energy relaxation exhibits a strong temperature-dependent behavior and with the increase of temperature, there is a crossover between decaying and non-decaying behaviors, around a crossover temperature point of Tc≃4.2. This non-decaying behavior at higher temperature is attributed to the presence of standing multi Sievers–Takeno discrete breather (DB) states. Conversely, for systems without on-site potentials, relaxation is nearly independent of temperature but dependent on interparticle potential. Notably, we observe that the cubic anharmonicity can generate moving single Page DB states that contribute to the unusual slow energy relaxation within a specific time regime. Our results provide enhanced insights into the mechanisms governing slow energy relaxation during lattice cooling.

NLS approximation for a scalar FPUT system on a 2D square lattice with a cubic nonlinearity

We consider a scalar Fermi-Pasta-Ulam-Tsingou (FPUT) system on a square 2D lattice with a cubic nonlinearity. For such systems the nonlinear Schrödinger (NLS) equation can be derived to describe the evolution of an oscillating moving wave packet of small amplitude which is slowly modulated in time and space. We show that this NLS approximation makes correct predictions about the dynamics of the original scalar FPUT system for the strain and the displacement variables. The present paper provides the first NLS approximation result for a 2D lattice in a full Galilean invariant setting without imposing an on-site potential.

Effect of squared, cubic and quartic on-site potentials on heat conduction in a nonlinear silicon lattice

This paper explains the process of heat conduction in a nonlinear silicon lattice governed by squared, cubic and quartic on-site potentials along with squared and quartic interaction potentials. The tanh method is employed to construct solutions to the resulting nonlinear equations. The results show the transfer of heat in the form of solitary waves which are presented graphically.

Environment-Driven Variability in Absolute Band Edge Positions and Work Functions of Reduced Ceria.

The absolute band edge positions and work function (Φ) are the key electronic properties of metal oxides that determine their performance in electronic devices and photocatalysis. However, experimental measurements of these properties often show notable variations, and the mechanisms underlying these discrepancies remain inadequately understood. In this work, we focus on ceria (CeO2), a material renowned for its outstanding oxygen storage capacity, and combine theoretical and experimental techniques to demonstrate environmental modifications of its ionization potential (IP) and Φ. Under O-deficient conditions, reduced ceria exhibits a decreased IP and Φ with significant sensitivity to defect distributions. In contrast, the IP and Φ are elevated in O-rich conditions due to the formation of surface peroxide species. Surface adsorbates and impurities can further augment these variabilities under realistic conditions. We rationalize the shifts in energy levels by separating the individual contributions from bulk and surface factors, using hybrid quantum mechanical/molecular mechanical (QM/MM) embedded-cluster and periodic density functional theory (DFT) calculations supported by interatomic-potential-based electrostatic analyses. Our results highlight the critical role of on-site electrostatic potentials in determining the absolute energy levels in metal oxides, implying a dynamic evolution of band edges under catalytic conditions.

Observation of reentrant metal-insulator transition in a random-dimer disordered SSH lattice

The interrelationship between localization, quantum transport, and disorder has remained a fascinating focus in scientific research. Traditionally, it has been widely accepted in the physics community that in one-dimensional systems, as disorder increases, localization intensifies, triggering a metal-insulator transition. However, a recent theoretical investigation [Phys. Rev. Lett. 126, 106803] has revealed that the interplay between dimerization and disorder leads to a reentrant localization transition, constituting a remarkable theoretical advancement in the field. Here, we present the first experimental observation of reentrant localization using an experimentally friendly model, a photonic SSH lattice with random-dimer disorder, achieved by incrementally adjusting synthetic potentials. In the presence of correlated on-site potentials, certain eigenstates exhibit extended behavior following the localization transition as the disorder continues to increase. We directly probe the wave function in disordered lattices by exciting specific lattice sites and recording the light distribution. This reentrant phenomenon is further verified by observing an anomalous peak in the normalized participation ratio. Our study enriches the understanding of transport in disordered mediums and accentuates the substantial potential of integrated photonics for the simulation of intricate condensed matter physics phenomena.

Dynamical encircling of multiple exceptional points in anti-PT symmetry system

Exceptional points (EPs) in non-Hermitian systems have turned out to be at the origin of many intriguing effects with no counterparts in Hermitian cases. A typically interesting behavior is the chiral mode switching by dynamically winding the EP. Most encircling protocols focus on the two-state or parity-time (PT) symmetry systems. Here, we propose and investigate the dynamical encircling of multiple EPs in an anti-PT-symmetric system, which is constructed based on a one-dimensional lattice with staggered lossy modulation. We reveal that dynamically encircling the multiple EPs results in the chiral dynamics via multiple non-Hermiticity-induced nonadiabatic transitions, where the output state is always on the lowest-loss energy sheet. Compared with the PT-symmetric systems that require complicated variation of the gain/loss rate or on-site potentials, our system only requires modulations of the couplings which can be readily realized in various experimental platforms. Our scheme provides a route to study non-Hermitian physics by engineering the EPs and implement novel photonic devices with unconventional functions.

Engineering multiform quantum state transfers and topological devices in a splicing Su–Schrieffer–Heeger chain

We propose to implement the various kinds of topological quantum state transfers (QSTs) in a splicing Su–Schrieffer–Heeger (SSH) chain, where the transfer forms vary with the introduction of the on-site potential and are distinguished by different output ports. The splicing SSH chain without the on-site potential shows an interface symmetry in chain configuration and supports a zero-energy gap state to realize a symmetric state transfer from the central site to the two ends with equal probabilities. After introducing the on-site potential on one end or two ends, we further obtain two asymmetric versions of the splicing SSH chain. The existence of the on-site potential leads to the transformation of the zero-energy gap state into a nonzero gap state, and the nonzero gap state exhibits different distribution characteristics in two asymmetric versions. Accordingly, three QST channels with different forms in a splicing SSH chain are designed, each of which possesses the robustness against the disorder of the couplings and the inaccuracy of the evolution time. In addition, we demonstrate the scalability of a multiform QST protocol with high fidelity. The protocol with different transfer forms is expected to realize diverse functional quantum devices, which effectively improves the utilization of a splicing SSH chain and economizes the physical resource.

Thermal conductivity in one-dimensional nonlinear disordered lattices: two kinds of scattering effects of hard-type and soft-type anharmonicities

Amorphous solids can be theoretically modeled by anharmonic disordered lattices, but most of the theoretical studies on thermal conductivity in such lattices only consider hard-type (HT) anharmonicity. In this study, we investigate the thermal conductivity κ of one-dimensional disordered lattices with both HT and soft-type (ST) anharmonic on-site potentials. Our results from molecular dynamics simulations and the quasi-harmonic Green–Kubo (QHGK) method show that while the HT model exhibits non-monotonic dependence of κ on anharmonicity, the ST model shows a monotonically increasing trend. This trend provides a novel approach to enhancing thermal conductivity in disordered systems. Additionally, the QHGK predictions for κ in the HT model are consistent with simulation results over a wide range of anharmonicity values; however, for the ST model, deviations appear as the anharmonicity becomes softer. This peculiar feature may be attributed to delocalization effects being dominant in contrast to the competing roles played by both delocalization and localization effects observed in the HT model.

Dimerized Hofstadter model in two-leg ladder quasi-crystals

We theoretically study topological features, band structure, and localization properties of a dimerized two-leg ladder with an oscillating on-site potential. The periodicity of the on-site potential can take either rational or irrational values. We consider two types of dimerized configurations; symmetric and asymmetric models. For rational values of the periodicity as long as inversion symmetry is preserved both symmetric and asymmetric ladders can host topological phases. Additionally, the energy spectrum of the models exhibits a fractal structure known as the Hofstadter butterfly spectrum, dependent on the dimerization of the hopping and the strength of the on-site potential. In the case of irrational values for the periodicity, a metal-insulator phase transition occurs with small values of the critical strength of the on-site potential in the dimerized cases. Our models incorporate the effects of lattice configuration and quasi-periodicity, paving the way for establishing platforms that host both topological and non-topological phase transitions.

Laboratory and In situ Selenium Bioaccumulation Assessment in the Benthic Macroinvertebrates Hyalella azteca and Chironomus dilutus.

Selenium (Se) bioaccumulation and toxicity in aquatic vertebrates have been thoroughly investigated. Limited information is available on Se bioaccumulation at the base of aquatic food webs. In this study, we evaluated Se bioaccumulation in two benthic macroinvertebrates (BMI), Hyalella azteca and Chironomus dilutus raised in the laboratory and caged in-situ to a Canadian boreal lake e (i.e., McClean Lake) that receives continuous low-level inputs of Se (< 1μg/L) from a uranium mill. Additional Se bioaccumulation assays were conducted in the laboratory with these BMI to (i) confirm field results, (ii) compare Se bioaccumulation in lab-read and native H. azteca populations and (iii) identify the major Se exposure pathway (surface water, top 1cm and top 2-3cm sediment layers) leading to Se bioaccumulation in H. azteca. Field and laboratory studies indicated overall comparable Se bioaccumulation and trophic transfer factors (TTFs) in co-exposed H. azteca (whole-body Se 0.9-3.1µg/g d.w; TTFs 0.6-6.3) and C. dilutus (whole-body Se at 0.7-3.2µg Se/g d.w.; TTFs 0.7-3.4). Native and lab-reared H. azteca populations exposed to sediment and periphyton from McClean Lake exhibited similar Se uptake and bioaccumulation (NLR, p = 0.003; 4.1 ± 0.8µg Se/g d.w), demonstrating that lab-reared organisms are good surrogates to assess on-site Se bioaccumulation potential. The greater Se concentrations in H. azteca exposed to the top 1-3cm sediment layer relative to waterborne exposure, corroborates the importance of the sediment-detrital pathway leading to greater Se bioaccumulation potential to higher trophic levels via BMI.

Flat Band and η-Pairing States in a One-Dimensional Moiré Hubbard Model

A Moiré system is formed when two periodic structures have a slightly mismatched period, resulting in unusual strongly correlated states in the presence of particle-particle interactions. The periodic structures can arise from the intrinsic crystalline order and periodic external field. We investigate a one-dimensional Hubbard model with periodic on-site potential of period n 0, which is commensurate to the lattice constant. For large n 0, the exact solution demonstrates that there is a midgap flat band with zero energy in the absence of Hubbard interaction. Each Moiré unit cell contributes two zero energy levels to the flat band. In the presence of Hubbard interaction, the midgap physics is demonstrated to be well described by a uniform Hubbard chain in which the effective hopping and on-site interaction strength can be controlled by the amplitude and period of the external field. Numerical simulations are performed to demonstrate the correlated behaviors in the finite-sized Moiré Hubbard system, including the existence of an η-pairing state and bound pair oscillation. This finding provides a method to enhance the correlated effect by a spatially periodic external field.