Localized States Research Articles

First Hitting Times on a Quantum Computer: Tracking vs. Local Monitoring, Topological Effects, and Dark States.

We investigate a quantum walk on a ring represented by a directed triangle graph with complex edge weights and monitored at a constant rate until the quantum walker is detected. To this end, the first hitting time statistics are recorded using unitary dynamics interspersed stroboscopically by measurements, which are implemented on IBM quantum computers with a midcircuit readout option. Unlike classical hitting times, the statistical aspect of the problem depends on the way we construct the measured path, an effect that we quantify experimentally. First, we experimentally verify the theoretical prediction that the mean return time to a target state is quantized, with abrupt discontinuities found for specific sampling times and other control parameters, which has a well-known topological interpretation. Second, depending on the initial state, system parameters, and measurement protocol, the detection probability can be less than one or even zero, which is related to dark-state physics. Both return-time quantization and the appearance of the dark states are related to degeneracies in the eigenvalues of the unitary time evolution operator. We conclude that, for the IBM quantum computer under study, the first hitting times of monitored quantum walks are resilient to noise. However, a finite number of measurements leads to broadening effects, which modify the topological quantization and chiral effects of the asymptotic theory with an infinite number of measurements.

Synergistic knowledge

Simplicial complexes are a successful model for distributed computing. They have recently been observed to provide an interesting model for epistemic multi-agent logic where the agents' local states are the main building blocks (instead of the global states). A natural generalization is to study epistemic logic on semi-simplicial sets. However, finding the appropriate modal logic for semi-simplicial models has been an open question. We answer this by introducing the logic of synergistic knowledge and establishing its soundness and completeness.

Theory-driven design of local spin-state modulation at atomically dispersed iron sites for enhanced CO2 electroreduction

Herein, density functional theory (DFT) was used to guide the systematic design of highly efficient single-atom electrocatalysts to improve the kinetics of the CO2 reduction reaction (CO2RR). We present a novel class of catalysts that exhibit magnetic-proximity-induced exchange splitting (spin polarization). The design of these catalysts involved the precise modulation of d-shell energy levels at metallic sites and the subsequent alteration of the atomic/molecular orbitals of the adsorbed intermediates. To validate the effectiveness of our design strategy, we introduced neighboring nitrogen (N) doping near the Fe-N4 coordination environment, demonstrating the successful manipulation of the local spin state of the active sites. The results of the theoretical calculations align with the experimental results, with remarkable selectivity exceeding 90 % at low potentials (<-0.5 V vs. RHE) and sustained electrocatalytic activity for over 24 h. In situ characterization further revealed that a modulated local spin state led to a decrease in the occupation of the Fe 3d spin-down electronic states below the Fermi level. Concurrently, electrons migrated to the frontier antibonding orbitals of *COOH. This dual effect resulted in a lower reaction energy (ΔG), representing a thermodynamic benefit, and accelerated proton transfer to *COOH, representing a kinetic benefit, collectively enhancing the electrocatalytic process.

Slum upgrading and participation: Insights from a marginalized neighbourhood in Buenos Aires

This paper rethinks participation in slum upgrading beyond a well-established dichotomy of “top-down” and “bottom-up” processes and instead proposes a relational and strategic approach to urban transformation. Based on qualitative research with a small informal settlement, Barrio Saldías, in Buenos Aires, that fell off the city government's agenda, this paper explores the role of participation in promoting upgrading from the margins. It argues that Saldías differs from instances of community-led upgrading due to the central role of party brokers and political representatives (especially from the local state) alongside residents, all of whom participate together in a political climate dominated by the discourses of citizen participation and slum upgrading. Rather than collapsing these experiences into the logic of clientelism, participation is centred as the articulatory logic based on a shared desire and commitment to transforming urban space, towards multiple political ends. Participatory upgrading in Saldías exceeds the narrow focus of project-centric approaches and draws on a wider trajectory of participation in Buenos Aires. It demonstrates this through an analysis of three moments of participatory upgrading in Saldías.

Regional Electron Delocalization Regulation Internalizes the Reduced‐Order‐Transformation of Polysulfides

AbstractThe step‐order or disproportionation conversion of lithium polysulfides (LiPSs) is still a blind box in LiS batteries (LSBs) system. The cation‐doped electrocatalyst (Fe‐CoS2@HCNF) is designed through modulating electron‐surrounding situation of the central atomic d‐band to promote regional electron‐directed LiPSs reduced‐order‐transformation (especially, Li2S4Li2S). Fe‐CoS2@HCNF satisfies the requirement of mass (electron/ion) transfer reaction, quantizing as multi‐osmosis‐connected transportation channels and an all‐encompassing interior space for sulfur reduction occurring. Based on experiments and DFT calculations, the introduced Fe presents a local electron deficiency state toward regulating regional electron delocalization between Fe and Co matrix, which induces the d‐band state of the metal site, strengthening the metal 3d orbital coupling interaction with S2−of LiPSs, further guiding the order‐transformation of intermediate LiPSs. Consequently, the Fe‐CoS2@HCNF electrode has excellent electrochemical properties, performing at 3.0 C with 0.064 % capacity decay per cycle, and even maintaining super cycle stability at a high sulfur loadings. In addition, the pouch cell assembled can also reach an initial specific capacity of 1070.3 mAh g−1 at 0.1 C, which can still show good long‐term cycle stability. This work provides a valuable prospect for analyzing SRR intermediate state by regional electron flow regulation of electrocatalyst in practical LSBs.

Development of an accelerometer-based wearable sensor approach for alcohol consumption detection.

Alcohol is a commonly used substance associated with significant public health consequences. Treatment is often stigmatized and limited with regard to both access and affordability, demonstrating the need for innovations in alcohol treatment. Accelerometer sensors can detect drinking without user input and are widely incorporated into wearable devices, increasing accessibility and affordability. We compared a distributional and random forest classification approach to detect and evaluate sensor-based drinking data. Data were collected at a local state fair (n = 194), where participants drank water at specified intervals interspersed with confounding behaviors (e.g., touching nose, rubbing forehead, or yawning) while wearing an Android-based smartwatch for 10 min. Participants were randomized to receive one of three drinking container shapes: pint, martini, or wine. The random forest model achieved an overall testing accuracy of 93% (sensitivity = 0.32; specificity = 0.99; positive predictive value = 0.74). The distributional algorithm achieved an overall accuracy of 95% (sensitivity = 0.76; specificity = 0.97; positive predictive value = 0.72). The distributional algorithm had a significantly greater accuracy (t(193) = 7.73, p < 0.001, d = 0.56) and sensitivity (t(193) = 24.5, p < 0.001, d = 1.76). Equivalency testing demonstrated significant equivalency to the ground truth for sip duration (tlower(193) = 16.92, p < 0.001; tupper(193) = -9.85, p < 0.001) and between-sip interval (tlower(193) = 1.72, p = 0.044; thigher(193) = -3.96, p < 0.001). However, the random forest did not have significant equivalency to the ground truth for between-sip interval (tlower(193) = 1.98, p = 0.025; thigher(193) = 0.160, p = 0.564). Overall, the results indicated that consumer-grade smartwatches can be utilized to detect and measure alcohol use behavior using machine learning and distributional algorithms. This work provides the methodological foundation for future research to analyze the behavioral pharmacology of alcohol use and develop accessible just-in-time clinical interventions.

Integration of 2D borophene into semiconducting N, P, S, and F-doped 1D carbon for energy storage and conversion devices

Innovative energy storage and high-performing conversion devices are urgently required to meet global energy issues. In this study, we synthesized and characterized a nitrogen, phosphorus, sulfur, and fluorine-doped one-dimensional carbon (NPSF@C) integrated with two-dimensional borophene (Bph) nanosheets, forming a nanocomposite (NPSF@C/Bph). The physicochemical and structural characterization confirmed borophene’s successful doping and integration into the NPSF@C matrix. Density Functional Theory (DFT) analysis indicated that the doping of heteroatoms and the integration of Bph increased the number of conduction bands in NPSF@C/Bph, effectively reducing the band gap of the material from 1.99 eV (MWCNT) and 1.43 eV (Bph) to 0.067 eV. This transformation was attributed to the introduction of localized states near the Fermi level and an enhanced density of states, resulting in a metal-like behavior for the NPSF@C/Bph composite. The NPSF@C/Bph composite demonstrated a specific surface area of 1962.78 m2/g and a pore volume of 1.2423 cm3/g, significantly enhancing its electrochemical performance. The composite showed a high specific capacitance of 837F/g at a current density of 1 A/g and retained 92.72 % of its initial capacitance after 10,000 cycles. It also exhibited a high energy density of 78.28 Wh/kg and a power density of 4545 W/kg in a symmetric supercapacitor device. Additionally, electrochemical tests revealed that the NPSF@C/Bph composite exhibited a lower overpotential and higher current density for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) compared to its counterparts. Specifically, the overpotential for OER is 283 eV, and HER is 73 mV at a current density of 10 mA/cm2. The Tafel slopes were 63 mV/dec for OER and 67 mV/dec for HER, indicating superior reaction kinetics.

Light-Induced Polaronic Crystals in Single-Layer Transition Metal Dichalcogenides.

Light-induced ordered states can emerge in materials after irradiation with ultrafast laser pulses. However, their prediction is challenging because the inverted band occupation confounds our chemical intuition. Hence, we use a recently developed constrained density functional perturbation theory approach to systematically screen single-layer transition metal dichalcogenides (TMDs) for light-induced ordered states. We demonstrate that all examined single-layer TMDs reveal similar light-induced charge orderings. The corresponding reconstructions are periodic arrangements of polarons (polaronic crystals), characterized by triangular metal clusters and having no equivalent at equilibrium conditions. The polarons are accompanied by localized midgap states in the electronic band structure, detectable by experimental methods. We assess the selenides as the most promising candidates for potential photoexcitation experiments because they transition at low critical fluences, have low transition barriers, and maintain an open band gap under photoexcitation. Our work paves the way for innovative material design approaches targeting light-induced phases.

The effect of a new 3-hydroxypyridine derivative LHT-2-20 on free radical oxidation in experimental periodontitis

Aim. To study the effect of a new complex compound LHT-2-20 (2-ethyl-6-methyl-3-hydroxypyridine-2-(3benzoyl phenyl)-propanoate) on free radical oxidation in experimental periodontitis.Materials and methods. The experimental study was performed on 195 white mongrel mice weighing 19–23 g and 137 white mongrel rats weighing 180–220 g. The effect of a new complex compound LHT-2-20 (2-ethyl-6methyl-3-hydroxypyridine-2-(3-benzoyl phenyl)-propanoate) on the intensity of free radical oxidation and the local state of periodontal tissues during a course of intragastric administration was studied on the experimental model of periodontitis. Statistical processing of the results was carried out using the SPSS Statistics 20.0 software package with the analysis of variance (ANOVA) and the parametric Tukey’s test.Results. The LHT-2-20 compound reduced elevated levels of primary and secondary lipoperoxidation products (conjugated dienes, malondialdehyde in plasma and in erythrocytes during spontaneous and iron-induced oxidation) already at the early stages of the experiment, bringing the studied parameters closer to the reference values by the end of the course of treatment. The use of the compound LHT-2-20 contributed to an increase in the activity of the main antioxidant enzymes (catalase and superoxide dismutase), normalizing them to baseline values by the end of the experiment. With the correction of free radical processes, the use of LHT-2-20 limited the local inflammatory response in periodontal tissues, which was confirmed by a decrease in gingival edema and hyperemia, bleeding, depth of periodontal pockets, and tooth mobility.Conclusion. The results of this study confirm the anti-inflammatory potential of the compound and the multiplicity of its effects due to the impact on the mechanisms of oxidative stress. The expediency of further study of the drug is justified by the prospect of creating a new drug and its subsequent wide clinical application as part of the complex therapy of periodontal inflammation.

Abnormal Relaxation Behavior of Excited Electrons in the Flat Band of Kagome Compound Nb3Cl8.

Carrier dynamics is crucial in semiconductors, and it determines their conductivity, response time, and overall functionality. In flat bands (FBs), carriers with high effective masses are predicted to host unconventional transport properties. The FBs usually overlap with other trivial energy bands, however, making it difficult to accurately distinguish their carrier dynamics. In this paper, we have investigated the flat-band carrier dynamics of excited electrons in Nb3Cl8, which hosts ideal nonoverlapping FBs near the Fermi level. The optical transition between Hubbard bands is abnormally weakened, exhibiting weak interband absorption and its related slow photoresponse with a time constant of ∼120 s, which are associated with flat-band Mottness-induced large electron effective mass and parity-forbidden transitions. Besides, the localized states created by chlorine vacancies also act as trapping centers for carriers with a time constant of ∼600 s, which are similar to those of the compact localized states of the FB, making the relaxation behavior even more extraordinary. The presence and impacts of atomic defects are confirmed experimentally and theoretically. This work has revealed the abnormal flat-band carrier dynamics of Nb3Cl8, which is essential for understanding the optical, electrical, and thermal transport properties of flat-band materials.

Atomic-Scale Mechanism of Enhanced Electron-Phonon Coupling at the Interface of MgB2 Thin Films.

In conventional Bardeen-Cooper-Schrieffer (BCS) superconductors, electron-phonon coupling is the fundamental mechanism of superconductivity. For instance, the superconductivity of magnesium diboride (MgB2) comes from the coupling between E2g modes (in-plane boron-boron bond vibrations) and self-doped charge carriers. In thin films and ceramics of BCS superconductors, interfaces with discontinuous chemical bonds may alter the local electron-phonon coupling. However, such effects remain largely unexplored. Here, we investigate the heterointerface of the MgB2 film on the SiC substrate at the atomic scale using electron microscopy and spectroscopy. We detect the presence of a thin MgO layer with a thickness of ∼1 nm between MgB2 and SiC. Atomic-level electron energy loss spectra (EELS) show MgB2-E2g mode splitting and softening near the MgB2/MgO interface, which enhances electron-phonon coupling at the interface. Our findings highlight the potential of interface engineering to enhance superconductivity via modulating local phonon states and/or electron states.

The Local Welfare State and Differences in Racialized Poverty

ABSTRACT Researchers concerned with the U.S. welfare state have documented that more localized administration allows for greater geographic variation in public policies as well as the greater potential for racial discrimination to influence policy outcomes. I explore whether key attributes of the local welfare state, capacity and spending, are associated with differences in racialized poverty across localities. I develop a conceptual framework drawing on two sociological traditions: spatial inequality framework and local welfare state theory. Spatial inequality scholarship provides a framework for interrogating why poverty varies across localities and racialized groups. Local welfare scholarship conceptualizes the processes by which local governments impact poverty and how those processes may be highly racialized. Drawing on data from the Census of Governments, I examine all local governments’ capacity and spending across counties in the U.S. and their association with poverty rates among white, Black, and Hispanic populations. I find that local governments’ capacity and spending do matter to understanding differences in racialized poverty. Specifically, racialized groups perceived as more deserving are likely to be the beneficiaries of local government interventions and policies. This study calls for greater attention to the local welfare state as a possible mechanism maintaining racial stratification.

Nonprojective Bell-state measurements

The Bell-state measurement (BSM) is the projection of two qubits onto four orthogonal maximally entangled states. Here we first propose how to appropriately define more general BSMs, which have more than four possible outcomes, and then study whether they exist in quantum theory. We observe that nonprojective BSMs can be defined in a systematic way in terms of equiangular tight frames of maximally entangled states, i.e., a set of maximally entangled states, where every pair is equally, and in a sense maximally, distinguishable. We show that there exists a five-outcome BSM through an explicit construction and find that it admits a simple geometric representation. Then we prove that there exists no larger BSM on two qubits by showing that no six-outcome BSM is possible. We also determine the most distinguishable set of six equiangular maximally entangled states and show that it falls only somewhat short of forming a valid quantum measurement. Finally, we study the nonprojective BSM in the contexts of both local state discrimination and entanglement-assisted quantum communication. Our results put forward natural forms of nonprojective joint measurements and provide insight into the geometry of entangled quantum states. Published by the American Physical Society 2024

Optical properties of CdO thin films

Cadmium Oxide thin films were deposited on glass substrate by spray pyrolysis technique at different temperatures (300,350,400, 500)oC. The optical properties of the films were studied in this work. The optical band-gap was determined from absorption spectra, it was found that the optical band-gap was within the range of (2.5-2.56)eV also width of localized states and another optical properties.

Air stability of monolayer WSi2N4 in dark and bright conditions

Two-dimensional materials with chemical formula MA2Z4 are a promising class of materials for optoelectronic applications. To exploit their potential, their stability with respect to air pollution has to be analyzed under different conditions. In a first-principle study based on density functional theory, we investigate the adsorption of three common environmental gas molecules (O2, H2O, and CO2) on monolayer WSi2N4, an established representative of the MA2Z4 family. The computed adsorption energies, charge transfer, and projected density of states of the polluted monolayer indicate a relatively weak interaction between substrate and molecules resulting in an ultrashort recovery time of the order of nanoseconds. O2 and water introduce localized states in the upper valence region but do not alter the semiconducting nature of WSi2N4 nor its band-gap size apart from a minor variation of a few tens of meV. Exploring the same scenario in the presence of photogenerated electrons and holes, we do not notice any substantial difference except for O2 chemisorption when negative charge carriers are in the system. In this case, monolayer WSi2N4 exhibits signs of irreversible oxidation, testified by an adsorption energy of -5.5 eV leading to an infinitely long recovery time, a rearrangement of the outermost atomic layer bonding with the pollutant, and n-doping of the system. Our results indicate stability of WSi2N4 against H2O and CO2 in both dark and bright conditions, suggesting the potential of this material in nanodevice applications.

Electrical conduction and optical characteristics of Li2O and Bi2O3 Co-doped zinc-phosphate glassy nanocomposites: A critical observation of mixed ionic electronic effect

In the present report, the combined effects of the co-doping of metal oxide (Bi2O3) and Lithium oxide (Li2O) into the glassy matrix with chemical composition xLi2O-(0.45-x)Bi2O3-(0.15ZnO-0.40P2O5) (x = 0.05, 0.15, 025, and 0.35 mol%) are investigated thoroughly. The FESEM and X-ray diffraction data affirm the crystalline nature of the studied glassy composites. The obtained band gap energy values are declined from (3.68–3.17) eV, while the Urbach energy values are declined from (0.38–0.27) eV. Moreover, the mechanism responsible for AC conductivity has been analyzed using Almond–West formalism and Jonscher's universal power law. The observed rise in both AC and DC conductivity in the glass samples is attributed to the mixed ionic electronic effect. In the ionic diffusion model, an increased defect site concentration improves Li+ ion migration through percolation channels. The reduction in both electrostatic binding energy and strain energy lowers the Anderson-Stuart activation energy, facilitating Li+ ion migration and enhancing conductivity. Additionally, in the small polaron hopping model, an increase in the density of defect states suggests more defect sites that facilitate electronic hopping, creating deep localized states and transitions between localized and extended states. Replacing a Bismuth atom with a Lithium atom increases the number of non-bridging oxygen, enhancing the conduction band tail, reducing the energy needed for hopping conductivity, and increasing conductivity.

Immunometabolic cues recompose and reprogram the microenvironment around implanted biomaterials.

Circulating monocytes infiltrate and coordinate immune responses in tissues surrounding implanted biomaterials and in other inflamed tissues. Here we show that immunometabolic cues in the biomaterial microenvironment govern the trafficking of immune cells, including neutrophils and monocytes, in a manner dependent on the chemokine receptor 2 (CCR2) and the C-X3-C motif chemokine receptor 1 (CX3CR1). This affects the composition and activation states of macrophage and dendritic cell populations, ultimately orchestrating the relative composition of pro-inflammatory, transitory and anti-inflammatory CCR2+, CX3CR1+ and CCR2+ CX3CR1+ immune cell populations. In amorphous polylactide implants, modifying immunometabolism by glycolytic inhibition drives a pro-regenerative microenvironment principally by myeloid cells. In crystalline polylactide implants, together with arginase-1-expressing myeloid cells, T helper 2 cells and γδ+ T cells producing interleukin-4 substantially contribute to shaping the metabolically reprogrammed pro-regenerative microenvironment. Our findings inform the premise that local metabolic states regulate inflammatory processes in the biomaterial microenvironment.

Active Sites for CO2 Hydrogenation to Methanol: Mechanistic Insights and Reaction Control.

Catalytic CO2 conversion to methanol is a promising way to extenuate the adverse effects of CO2 emission, global warming and energy shortage. Understanding the fundamental features of CO2 activation and hydrogenation at the molecular level is essential for carbon utilization and sustainable chemical production in the current climate crisis. This review explores the recent advances in understanding the design of catalysts with desired active sites, including single-atom, dual-atom, interface, defects/vacancies and promoters/dopants. We focused on the design of various catalytic systems to enhance their catalytic performances by stabilizing active metal in a catalyst, identifying the unique structure of active species, and engineering coordination environments of active sites. Mechanistic insights provided by advanced operando and in situ spectroscopies were also discussed. Moreover, the review highlights the key factors affecting active sites and reaction mechanisms, such as local environments, oxidation states, and metal-support interactions. By integrating recent advancements and relating knowledge gaps this review aims to endow an inclusive overview of the field and guide future research toward more efficient and selective catalysts for CO2 hydrogenation to methanol.

The evaluation of fine needle aspiration biopsy results in differentiating between benign and malignant thyroid nodules

Introduction: Thyroid fine-needle aspiration biopsy (FNAB) has begun playing an important role in the evaluation of thyroid nodules, in addition to physical examination and imaging techniques. The purpose of this study was to evaluate the results of patients who underwent thyroid FNAB together with their demographic data, imaging findings, and follow-up compliance. Methods: Patients who underwent thyroid FNAB procedures in our hospital’s interventional radiology unit between January 2022 and May 2024 were evaluated retrospectively. Data were retrieved from patient records. Cytological results were classified as malignant, atypia of undetermined significance, benign, and non-diagnostic material. Results: Two hundred twelve solid nodules were detected in the patients who underwent biopsy, and 59 mixed nodules with a cystic component. Non-diagnostic material was reported in 51 cases at cytological examination, benign cytology in 150, atypia of undetermined significance in 53, and malignant material in 17. The incidence of non-diagnostic results was significantly higher in hypoechoic nodules and low-volume nodules. Conclusions: Thyroid FNAB is a valuable diagnostic tool due to its ease of application and provision of useful information in benign-malignant differentiation. Once it becomes capable of application by primary physicians and local state hospitals in Türkiye it will reduce delayed diagnoses, unnecessary surgical procedures, and economic burdens on social security institutions.

Investigations on the effect of arsenic and phosphorus atomic exchange on the origin of crystal potential fluctuations in InAsP/InP epilayers

The study investigates the anion exchange mechanism between the ad-atoms of arsenic and phosphorus followed by their inter-diffusion processes, in InAsP/InP hetero-structures grown by metal organic vapor phase epitaxy technique. The energetics and kinetics of the ad-atoms like arsenic and phosphorus are governed by the growth conditions. It has been found that the percolation of arsenic and phosphorus in the epilayer depends on various factors, such as gas-phase diffusion coefficients, surface reaction rates, misfit strain energy, bond energy, segregations, and the presence of defects and dislocations. Effects of anion exchange mechanisms on generating local crystal potential states that originated due to the local crystal bonding environment are further investigated. The magnitude of these local potential states strongly depends on the strain states associated with the layer thickness. If the difference between the potential minima is small (< 25 meV), it leads to distinct “S” shaped temperature-dependent luminescence/absorption spectra. In contrast, a large difference gives rise to two distinctive luminescence/absorption peaks. Thus, by controlling the strain states associated with the energetics and kinetics of ad-atoms like arsenic/phosphorus and layer thickness, such “S” shaped behavior can be controlled.