Local Vacancy Research Articles

Mn Doping at High‐Activity Octahedral Vacancies of γ‐Fe2O3 for Oxygen Reduction Reaction Electrocatalysis in Metal‐Air Batteries

γ‐Fe2O3 with the intrinsic cation vacancies is an ideal substrate for heteroatom doping into the highly active octahedral sites in spinel oxide catalysts. However, it is still a challenge to confirm the vacancy location of γ‐Fe2O3 through experiments and obtain enhanced catalytic performance by preferential occupation of octahedral sites for heteroatom doping. Here, a Mn‐doped γ‐Fe2O3 incorporated with carbon nanotubes catalyst was developed to successfully achieve preferential doping into highly active octahedral sites by employing γ‐Fe2O3 as the precursor. Further, the vacancy in γ‐Fe2O3 was only located on octahedral sites rather than tetrahedral ones, which was first proved by direct experimental evidence through the clarification doping sites of Mn. Notably, the catalyst shows outstanding activity towards oxygen reduction reaction with the half‐wave potential of 0.82 V and 0.64 V vs. reversible hydrogen electrode in alkaline and neutral electrolytes, respectively, as well as the maximum power density of 179 mWcm−2 and 403 mWcm−2 for Mg‐air batteries and Al‐air batteries, respectively. It could be attributed to the synergistic effect of the doping Mn on octahedral sites and the substrate γ‐Fe2O3 along with the modification of the adsorption/desorption properties for ORR oxygen‐containing intermediates as well as the optimization of the reaction energy barriers.

Visualization of Anion Vacancy Defect Annihilation in CZTSe Solar Cells by Hydrogen-Assisted Selenization with In Operando X-ray Nanoprobe Studies.

The traditional sulfur selenization process in Cu2ZnSn(S,Se)4 (CZTSSe) solar cell fabrication often results in the creation of localized anion vacancies (VS and VSe). These vacancies are considered harmful defects as they can trap carriers generated by light, leading to reduced solar cell efficiency. Moreover, concrete evidence has been lacking on the extent of the impact caused by these anion vacancies. Our research introduces a novel approach: the hydrogen-assisted selenization (HAS) process, specifically designed to minimize localized anion vacancies in Cu2ZnSnSe4 (CZTSe) solar cells. Our investigation, utilizing current-voltage (I-V) and admittance spectroscopy measurements, provides clear insights. We observed notable improvements in carrier collection efficiency and a discernible reduction in defect states. Furthermore, there was a significant decrease in the activation energy required within the solar cell device, dropping from 184 to 145 meV. To delve deeper into the structural and compositional aspects, we employed synchrotron-based X-ray nanoprobes. Through nanoscale X-ray fluorescence and hard X-ray beam-induced current measurements, we can directly observe and document the relationship between the local compositional distribution and photocurrent activity in operando. These comprehensive results furnish strong evidence that mitigating anion vacancies in the CZTSe layer can substantially improve the power conversion efficiency of the CZTSe solar cells. This advancement not only sheds light on the critical role of anion vacancies in solar cell performance but also underscores the effectiveness of the HAS process in enhancing overall device efficiency.

Impact of skilled nursing facility quality on Medicare beneficiaries with dementia: Evidence from vacancies.

People living with dementia are less likely to be admitted to high-rated nursing homes than people without dementia, despite their increased care needs. We investigated the effect of admission to nursing homes with higher staffing ratings on adverse outcomes for individuals with and without dementia post-hospitalization. Among Traditional Medicare beneficiaries discharged to nursing homes between 2011 and 2017, we examined the relationship between facility staffing star-ratings and short-term readmission and mortality using an instrumental variables approach to account for selection bias. The instrumental variables were the number of nearby vacant beds in high-rated facilities. Admission to a higher-rated nursing home lowered post-discharge mortality risk at 90 days and reduced 30- and 90-day readmission. Point estimates were larger for people with dementia. Findings underscore the need for enhancing direct care staffing in nursing homes and addressing access disparities, particularly for individuals with dementia who benefit significantly from high-quality care. We assessed how admission to nursing homes with higher staffing ratings impacted outcomes for individuals with and without dementia by exploiting variation in local bed vacancies as a source of quasi-random assignment. For both persons with and without dementia, adjusted short-term mortality and readmission rates were lower among those discharged to nursing homes with higher staffing ratings. Effects were larger for persons with dementia, indicating welfare loss from inequitable access to higher-rated nursing homes. Increasing staffing in nursing homes and reducing disparities for persons with dementia is essential for enhancing both equity and value.

Mechanisms of enhanced performance in Zr4+/Ta5+ codoped rutile-TiO2 ceramics via broadband dielectric spectroscopy.

Aliovalent dopant codoped rutile-TiO2 materials have garnered attention due to their excellent performance properties, characterized by low loss tangent (tanδ), high dielectric permittivity (ε'), and stable ε' over a broad temperature range. This performance is primarily due to the electron-pinned defect-dipoles (EPDDs) of the complex defects [Formula: see text]Ti3+-[Formula: see text]Ti3+BTi. Notably, the excellent dielectric properties in ZrxTa2.5%Ti0.975-xO2 (Zr-TTO) ceramics can be achieved using the traditional mixed oxide method without the EPDDs, due to the absence of A3+ (acceptor doping ions). Instead, the existence of localized free electrons and oxygen vacancies ([Formula: see text]) in Zr-TTO structures, due to doping ions and the sintering process, was confirmed by X-ray photoelectron and Raman spectroscopies. These ceramics exhibited ε'~ 2 × 104 and tanδ < 0.03 at 1kHz and 25°C in the 2.5-10%Zr-TTO samples. Moreover, all ceramics demonstrated a maximum ε' change (∆ε') of less than ±15% over the temperature range suitable for X7R and X8R type ceramic capacitors. Significantly, the change in ε' related to relative humility was calculated to be less than ±0.5% over the range of 50-95% RH, indicating the environmental stability of the dielectric properties, which is essential for capacitor applications. Investigations suggested that at least four mechanisms contributed to this system: the intrinsic effect of ionic polarization, Ti4+ · e- -[Formula: see text]- Ti4+ · e- and Ti4+ · e- - [Formula: see text] defects, interfacial polarization at insulating grain boundaries, and non-Ohmic contact between the surface sample and the metal electrode.

Ruthenium Single-Atom Modulated Protonated Iridium Oxide for Acidic Water Oxidation in Proton Exchange Membrane Electrolysers.

Proton exchange membrane water electrolysers promise to usher in a new era of clean energy, but they remain a formidable obstacle in designing active and durable electrocatalysts for the acidic oxygen evolution reaction (OER). In this study, a protonated iridium oxide embedded with single-atom dispersed ruthenium atoms (H3.8Ir1- xRuxO4) that demonstrates exceptional activity and stability in acidic water oxidation is introduced. The single Ru dopants favorably induce localized oxygen vacancies in the Ir─O lattice, synergistically strengthening the adsorption of OOH* intermediates and enhancing the intrinsic OER activity. In addition, the preferential oxidation of Ru and the electronegativity of the oxygen vacancies significantly stabilize the Ir─O active sites, improving the OER stability. Consequently, the H3.8Ir1─ xRuxO4 catalyst shows an overpotential of 255mV at 10mA cm-2 and displays exceptional catalytic endurance in acidic electrolytes, surpassing 1100 h, representing a remarkable one-order-of-magnitude increase in stability compared to that of pristine H3.8IrO4. A proton exchange membrane electrolyser utilizing the H3.8Ir1- xRuxO4 catalyst as an anode exhibits stable performance for more than 1280 h under a high current density of 2 A cm-2.

The Impact of Carbon Corrosion Towards Oxygen Reduction Reaction Activity on Atomically Dispersed M-N-C Catalysts

Atomically dispersed Pt group metal free (PGM free) M-N-C catalysts offer a promising pathway towards a clean energy future.1 This class of materials has proven to be a viable substitute for commercial Pt/C to catalyze oxygen reduction reaction (ORR) with similar activity at only a fraction of the raw material cost.2 To gain a wider market adoption, however, M-N-C catalysts need to significantly improve its durability compared to Pt and its alloys in a real-world operating condition. Towards this end, substantial efforts have focused on making more durable M-N-C catalysts while simultaneously maintaining and improving its ORR activity.3,4 As part of the effort to understand the fundamental aspects that control M-N-C catalysts’ durability during ORR condition, we employ a combined approach using first principles density functional theory (DFT) and density functional tight binding theory (DFTB) to identify the impact of carbon corrosion occurring on M-N-C catalyst towards ORR activity. Our starting atomic representation of the ORR active site is the “C10” type local structure composed of FeN4C10 local defect5 embedded in a monolayer graphene support of varying cell size. As carbon corrosion occurs and consequently creating local carbon vacancies surrounding the active site, we then obtain a family of FeN4C11 and FeN4C12 type of local structures. Our DFT calculations of OH binding energy on these corrosion derived structures suggest that the presence of C vacancies and the subsequent H passivation on dangling C introduces elastic structural deformation to various degree that decreases the theoretical ORR limiting potential. This decrease in DFT calculated ORR limiting potential across a family of FeN4C10, FeN4C11, and FeN4C12 local structures can be attributed to a mechanical energy arising from the surface reconstructions. Reference D. A. Cullen et al., Nat Energy, 6, 462–474 (2021).G. Wu, K. L. More, C. M. Johnston, and P. Zelenay, Science, 332, 443–447 (2011).E. F. Holby, G. Wang, and P. Zelenay, ACS Catal., 10, 14527–14539 (2020).T. Patniboon and H. A. Hansen, ACS Catal., 11, 13102–13118 (2021).H. T. Chung et al., Science, 357, 479–484 (2017).

The impact of S vacancies on the modulation of the work function and Schottky barrier at the Au/MoS2 interface

The S vacancy at metal/MoS2 interface plays a much important role than the semiconductor itself. In this work, the influence of different configurations of S vacancy concentrations on the effective work function and band structure of the Au/MoS2 interface has been investigated systematically using first-principles calculations. The study specifically explores the effective work function of the Au/MoS2 interface, the deviation of interface effects from the vacuum work function, and the dipole moment caused by interface charge transfer. The results reveal that the electronic work function of Au/MoS2 increases with the increase in S vacancy concentration, but the rate of increase tends to slow down with higher S concentrations. The variation in the effective work function of the Au/MoS2 interface may be attributed to the presence of S vacancies and the exposure of Mo atoms. S vacancies lead to a reduction in the Schottky barrier, resulting in increased leakage current. The Fermi pinning caused by S vacancy concentration and location is also observed. The results obtained in this study can serve as a theoretical foundation for applications in electronic devices that rely on metal/MoS2 contact.

Unraveling the Photoluminescent Properties of Sb-Doped Cd-Based Inorganic Halides: A First-Principles Study.

Sb-doped Cd-based inorganic halides, with varying connections of CdCl6 octahedra ranging from 0D to 3D, exhibit a variety of photoluminescent properties. Single-band emission is observed in Sb-doped Rb4CdCl6 (0D) and Cs2CdCl4 (2D), while dual-band emission is seen in Sb-doped RbCdCl3 (1D) and CsCdCl3 (3D). Density-functional-based first-principles calculations were conducted. The results reveal that cation vacancies, acting as charge compensators, influence the luminescence properties of dopant centers. In CsCdCl3, the local cation vacancy VCd″ for Sb3+ at the Cd2+ site ([Sb□Cl9]6-) significantly modifies the photoluminescence property, accounting for the observed dual-band emission alongside the nonlocal compensation case. This effect is insignificant in Sb-doped Rb4CdCl6, RbCdCl3, and Cs2CdCl4, due to the large distances or high formation energies of Cd vacancies in these hosts. However, in Sb-doped RbCdCl3, two different potential energy minima, one that involves typical structure relaxation and the other that is off-center, lead to the observed dual-band emission. Furthermore, the shift of the charge transition level illustrates the different temperature dependences of the dual-band emission caused by the charge-compensating point defects. These insights not only enhance our understanding of luminescent materials based on halides containing ns2 dopants but also provide valuable guidance for the design and optimization of luminescent materials.

ФОРМИРОВАНИЕ ПРОФЕССИОНАЛЬНЫХ НАВЫКОВ СПЕЦИАЛИСТОВ ПО ЭКСПЛУАТАЦИИ ТРАНСПОРТА В СООТВЕТСТВИИ С ТРЕБОВАНИЯМИ РЫНКА ТРУДА

The article presents the experience of automated analysis of the corpus of job advertisements relevant for graduates of the training direction 23.03.03 «Operation of transport and technological machines and complexes». As part of the study, 20516 vacancies in the automotive business and related sub-sectors were collected and analyzed. The location of vacancies, the aver-age salary are determined, the most frequent requirements for applicants are identified. The results of the analysis are correlated with the main provisions of the educational program, on the basis of which conclusions are drawn about the need for systematic consideration of employers' require-ments to improve the quality of training specialists.

Pure and Sc-doped diopside (CaMgSi2O6) vibrational spectra: modelling and experiments.

We investigated the structure of pure and Sc-doped synthetic diopside (a monoclinic single-chain silicate nominally CaMgSi2O6); in Sc-doped diopside, Sc3+ substitutes Mg2+ in the structure and, to achieve charge balance, vacancies form at the expense of Ca2+. We compared the structure obtained from ab initio modelling techniques at the density functional theory (DFT) level with the structure solved by employing single crystal X-ray diffraction. Furthermore, we compared IR and Raman spectroscopy experiments with vibrational density of states (VDOS) calculated from the Fourier transform of the velocity autocorrelation function obtained using ab initio (DFT) molecular dynamics simulations. In this framework, we developed a computational tool to assign the vibrational mode associated with a specific frequency. This method consists of projecting velocities along a specific set of internal coordinates such as stretching or bending, in cases involving defects or vacancies, to calculate a partial VDOS (pVDOS) that takes into account only the vibrations associated with selected internal modes, aiding the interpretation of the total VDOS and the experimental spectra in a relevant way. The computed data were validated with the experiments and we observed that doping the diopside structure with Sc produces peak broadening and the occurrence of new peaks in the Raman spectra and that site vacancies are associated with the nearby Sc site. The present work constitutes an interesting starting point to exploit the calculated VDOS/pVDOS to characterize experimental vibrational spectra of complex systems containing local vacancies, substitutions or defects as the Sc-doped diopside.

8-Pmmn borophene: edge states in competition with Landau levels and local vacancy states.

The tight-binding method is used to investigate the electronic and magnetic properties of borophene nano-ribbons (BNRs) in the presence of a perpendicular magnetic field. Most BNRs exhibit metallic characteristics due to edge bands. Additionally, the appearance of Landau levels (LLs) is strongly influenced by the edge states, contrasting with the sheet platform which produces distinct LLs. We also investigated single atomic vacancy disorders in BNRs and observed localized vacancy states (LVSs) resulting from atomic disorder. Both LVSs and LLs are influenced by the edge states, underscoring that the electronic and magnetic properties of BNRs are strongly edge-dependent. This aspect is crucial for consideration in experimental, theoretical, and computational studies.

Electrochemical reconstruction of non-noble metal-based heterostructure nanorod arrays electrodes for highly stable anion exchange membrane seawater electrolysis

Direct seawater electrolysis for hydrogen production has been regarded as a viable route to utilize surplus renewable energy and address the climate crisis. However, the harsh electrochemical environment of seawater, particularly the presence of aggressive Cl−, has been proven to be prone to parasitic chloride ion oxidation and corrosion reactions, thus restricting seawater electrolyzer lifetime. Herein, hierarchical structure (Ni,Fe)O(OH)@NiCoS nanorod arrays (NAs) catalysts with heterointerfaces and localized oxygen vacancies were synthesized at nickel foam substrates via the combination of hydrothermal and annealing methods to boost seawater dissociation. The hierarchical nanostructure of NiCoS NAs enhanced electrode charge transfer rate and active surface area to accelerate oxygen evolution reaction (OER) and generated sulfate gradient layers to repulsive aggressive Cl−. The fabricated heterostructure and vacancies of (Ni,Fe)O(OH) tuned catalyst electronic structure into an electrophilic state to enhance the binding affinity of hydroxyl intermediates and facilitate the structural transformation into amorphous γ-NiFeOOH for promoting OER. Furthermore, through operando electrochemistry techniques, we found that the γ-NiFeOOH possessing an unsaturated coordination environment and lattice-oxygen-participated OER mechanism can minimize electrode Cl− corrosion enabled by stabilizing the adsorption of OH* intermediates, making it one of the best OER catalysts in the seawater medium reported to date. Consequently, these catalysts can deliver current densities of 100 and 500 mA cm−2 for boosting OER at minimal overpotentials of 245 and 316 mV, respectively, and thus prevent chloride ion oxidation simultaneously. Impressively, a highly stable anion exchange membrane (AEM) seawater electrolyzer based on the non-noble metal heterostructure electrodes reached a record low degradation rate under 100 μV h−1 at constant industrial current densities of 400 and 600 mA cm−2 over 300 h, which exhibits a promising future for the non-precious and stable AEMWE in the direct seawater electrolysis industry.

The Ni–P dual vacancies crystalline/amorphous bifunctional electrode with ZnO “electron pump” for urea-assisted electrolysis of water to produce hydrogen

Electrochemical urea electrolysis holds great potential for energy-efficient hydrogen production and wastewater treatment. However, developing cost-effective and highly active catalysts remains a challenge. In this study, a novel bifunctional electrocatalyst of Ni–Zn bimetallic nanosheets (ZnO–Ni2P) was synthesized on Ni foam (NF) for efficient urea decomposition in urea-containing wastewater. The results showed that inactive ZnO phase acted as an "electron pump", which facilitated electron redistribution between Ni and P atoms and created localized vacancies of Ni and P cations. This optimized electronic configuration enhanced the kinetics of both the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER). Additionally, a unique particle-porous structure with abundant grain boundaries was achieved through the utilization of the Kirkendall Effect and Ostwald Ripening. In an alkaline urea electrolysis system, the alkaline urea electrolyzer assembled with ZnO–Ni2P/NF sample as both electrodes exhibited a low driving potential of only 1.424 V to achieve a current density of 10 mA cm−2, which outperformed the commercial noble metal-based electrolyzer (RuO2||Pt/C). The results verify that incorporating an inactive phase to manipulate the electronic structure of the active phase can be an effective strategy in developing catalysts for urea electrolysis.

The Role of Vacancy Dynamics in Two‐Dimensional Memristive Devices

AbstractTwo‐dimensional layered transition metal dichalcogenides (TMDCs) are promising memristive materials for neuromorphic computing systems. Despite extensive experimental work, the underlying switching mechanisms are still not understood, impeding progress in material and device functionality. This study reveals the dominant role of defect dynamics in the switching process of 2D TMDC materials. The switching process is governed by the formation and annihilation dynamics of a local vacancy depletion zone. It explains the distinct features of the device characteristics observed experimentally, including fundamentally different device behavior previously thought to originate from multiple mechanisms. Key influence factors are identified and discussed with a fully coupled and dynamic charge transport model for electrons, holes, and ionic point defects, including image‐charge‐induced Schottky barrier lowering (SBL). Thermal effects and local Joule heating are considered by coupling the transient heat transfer equation to the electronic properties. The model is validated with hysteresis and pulse measurements for various lateral 2D MoS2‐based devices, strongly corroborating the relevance of vacancy dynamics in TMDC devices and offering a new perspective on the switching mechanisms. The insights gained from this study can be used to extend the functional behavior of 2D TMDC memristive devices in future neuromorphic computing applications.

Associations between vacant urban lands and public health outcomes in growing and shrinking cities

Vacant urban land, although not officially designated as a green space, often exhibits a semi-wild natural state due to being left open to colonization by nature. Attention to the effects of vacant urban land on human health has increased due to both rising urban vacancy rates and non-communicable diseases (NCDs). However, relationships between many vacant land characteristics (such as vegetation coverage, size, duration, and location) and NCDs have not been comprehensively examined, especially comparing shrinking (depopulating) and growing (populating) cities. This study evaluates St. Louis, MO (shrinking), and Los Angeles, CA (growing) to explore these relationships using ordinary least squares (OLS) interaction analysis with a moderator approach. Results show that associations between vacancy rate, duration, location, and NCDs differ significantly between city types. Vegetation coverage and size are associated with specific NCDs, but there are no differences between city types. Unlike the largely dilapidated vacant lands in the shrinking city, which tend to harm public health, vacant lots in the growing city were more functional green spaces that can, in some cases, even mitigate NCDs. Interestingly, In St. Louis, the shorter the average duration of the vacant land, the greater the risk of NCDs in a shrinking city. This is because vacant land can be contagious to nearby lots if not treated, leading to more newly emerged vacant lands and reducing the average duration of vacant land. In such cases, census tracts with the lower duration of vacant lands in St. Louis tend to be areas facing persistent environmental degradation and high public health threats. Regarding location, vacant lands near industrial areas were linked to negative health outcomes in the Los Angeles (growing), while those near single-family and commercial areas posed higher risks of NCDs in the St Louis (shrinking). The findings aid decision-making for land supply regulation and regeneration as well as urban green space management to promote human health and well-being.

Ca-substituted Na3ZnGaS4 with enhanced ionic conductivity and its applicability for all-solid-state sodium-ion batteries

Na3ZnGaS4 is a new class of Na + -conducting materials with a sturdy framework consisting of corner-shared super-tetrahedra. The ionic conductivity (σion) of pristine Na3ZnGaS4 is quite low, but it can be improved by introducing defects. Herein, we describe the incorporation of vacancies into Na2 sites of Na3ZnGaS4 via Ca-doping (Na3-xCaxZnGaS4; x = 0–0.2), which leads to a significant increase in σion, reaching 0.28 mS cm−1 (hot-pressed Na2.7Ca0.15ZnGaS4 pellet). The preferential residence of vacancies and Ca2+ in Na + -conducting Na2 sites is theoretically and experimentally verified. Because of simultaneous location of vacancies and Ca2+ in Na2 sites, the increase in σion with 'x' in Na3-xCaxZnGaS4 is not related to a decrease in the migration energy barrier (EA) but rather to an increase in effective hopping frequencies, compensating for the increase in EA. Na2.7Ca0.15ZnGaS4 also exhibits excellent compatibility with Na2Sn anode and TiS2 cathode. A full cell (Na2Sn│Na2.7Ca0.15ZnGaS4│TiS2) delivers a discharge capacity of over 146 mAh g−1TiS2 during 100 charge/discharge cycles at 0.12 mA cm−2 (120 mA g−1TiS2). In comparison to Na3SbS4, Na2.7Ca0.15ZnGaS4 also demonstrates inertness in various organic solvents, which is important for layer-by-layer stacking processes in the fabrication of all-solid-state batteries.

Effects of Carbon on Void Nucleation in Self-Ion–Irradiated Pure Iron

Impurities such as carbon atoms play a significant role in the void swelling of irradiated metals. The phenomenon is important to both materials designs in which impurities are intentionally introduced and accelerator-based ion irradiation testing in which impurities are introduced unintentionally as contaminants. Here, we report rate theory simulations of void nucleation in pure Fe, which are irradiated by 5-MeV Fe ions, as one typical irradiation condition used in nuclear material testing. Based on kinetics obtained previously from ab initio calculations, Multiphysics Object-Oriented Simulation Environment (MOOSE)–based numerical solvers were used to simulate defect distributions and void nucleation. Vacancy-carbon interactions increase the effective migration energies of carbon and decrease the diffusivity prefactors. The vacancy mobility reduction decreases both interstitial flux and vacancy flux. However, the vacancy flux reduction is more significant than that of interstitials, leading to reduced void nucleation in bulk. On the other hand, reduced vacancy flux toward the surface leads to local vacancy pileups, leading to locally enhanced void nucleation. These two combined effects make the void nucleation profile deviate from the displacements per atom (dpa) peak, and void swelling peaks shift to the near-surface region. The transition from deep swelling to near-surface swelling is plotted as a function of dpa rate, carbon concentration, and temperature. The study shows that the swelling peak shifting caused by the carbon effect can be avoided by either reducing dpa rates or increasing irradiation temperatures. The study is important to understand swelling behaviors and to optimize irradiation parameters for accelerator-based swelling testing.

Learning from national implementation of the Veterans Affairs Clinical Resource Hub (CRH) program for improving access to care: protocol for a six year evaluation

BackgroundThe Veterans Affairs (VA) Clinical Resource Hub (CRH) program aims to improve patient access to care by implementing time-limited, regionally based primary or mental health staffing support to cover local staffing vacancies. VA’s Office of Primary Care (OPC) designed CRH to support more than 1000 geographically disparate VA outpatient sites, many of which are in rural areas, by providing virtual contingency clinical staffing for sites experiencing primary care and mental health staffing deficits. The subsequently funded CRH evaluation, carried out by the VA Primary Care Analytics Team (PCAT), partnered with CRH program leaders and evaluation stakeholders to develop a protocol for a six-year CRH evaluation.The objectives for developing the CRH evaluation protocol were to prospectively: 1) identify the outcomes CRH aimed to achieve, and the key program elements designed to achieve them; 2) specify evaluation designs and data collection approaches for assessing CRH progress and success; and 3) guide the activities of five geographically dispersed evaluation teams.MethodsThe protocol documents a multi-method CRH program evaluation design with qualitative and quantitative elements. The evaluation’s overall goal is to assess CRH’s return on investment to the VA and Veterans at six years through synthesis of findings on program effectiveness. The evaluation includes both observational and quasi-experimental elements reflecting impacts at the national, regional, outpatient site, and patient levels. The protocol is based on program evaluation theory, implementation science frameworks, literature on contingency staffing, and iterative review and revision by both research and clinical operations partners.DiscussionHealth systems increasingly seek to use data to guide management and decision-making for newly implemented clinical programs and policies. Approaches for planning evaluations to accomplish this goal, however, are not well-established. By publishing the protocol, we aim to increase the validity and usefulness of subsequent evaluation findings. We also aim to provide an example of a program evaluation protocol developed within a learning health systems partnership.

Ab initio study of the lattice distortion and the vacancy defects in multi-anion oxycarbonitride ceramics TiCNO and TiZrCNO

Multicomponent ceramics have received much attention due to the tunning physicochemical properties and the huge compositional space, while multicomponent ceramics with the mixing of multi-anion are rarely studied. In this work, the local lattice distortion and vacancy formation energy in TiCNO and TiZrCNO are systematically investigated by density functional theory calculations combining with the special quasi-random structure model. The present results show that multi-anionic mixed oxycarbonitride ceramics exhibit obvious local lattice distortion. The quantified displacive distortions of C, N, and O in TiCNO are relatively large, being in order of C < N < O, although metallic elements Ti has larger distortion than nonmetals. Within incorporative mixing of Zr in cation sublattice, the distortions of Ti, C, N, and O increase evidently, the distortion degree for nonmetal elements is still in order of C < N < O. The distortion of Ti is still the largest, whereas Zr possesses almost the smallest distortion. The electronic structure shows a close association with the degree of distortion, the larger DOS at the Fermi level corresponds to the larger distortion. The vacancy defects are further studied. Our consequences show that the vacancy formation energies of non-metal elements with large local distortions are relatively low, suggesting that the local chemical environment profoundly affects the vacancy formation energy and defect-related properties. The present study reveals the important correlation of lattice distortion with electronic structure and vacancy generation, so it is valuable to deepen the understanding of the excellent properties of multicomponent ceramics with multi-anion mixing, and develop novel multicomponent ceramics with polyanionic structures.

Comparative analysis of low-frequency noise based resistive switching phenomenon for filamentary and interfacial RRAM devices

We investigate the low-frequency noise (LFN) characteristics of resistive switching random access memory (RRAM) devices with metal–insulator–metal structures of TiN/Ti/TiO2/TiN (filamentary) and TiN/Ti/TiO2/HfO2/TiN (interfacial). By comparing filamentary and interfacial RRAM devices, we stipulate guidelines for noise sources according to the resistance states or resistive switching mechanisms of RRAM device. In filamentary RRAM devices, the dominant noise source in the low resistance state is the localized oxygen vacancies, whereas the noise characteristics in the high resistance state represent a bulk effect. In interfacial RRAM devices, the noise characteristics in both resistance states represent the bulk effect. The physical mechanism of the multilevel cell operation is inferred by the I–V characteristics in both Icc and Vreset control modes. Specifically, the changes in the structure of the conductive filament inside the switching layer can be confirmed through LFN measurement.