Nitride materials for memristors are benefited from their high response speed and high power density. The memristive effects on 1D nitride structures has not yet been elucidated. Hence, the ...activation of the memristive capability of nanowire (NW)‐based nitride memristors using an uncomplicated fabrication as single‐step anisotropic wet etching is proposed. Among nitrides, gallium nitride, a third‐generation semiconductor, exhibits properties potentially suitable for neuromorphic applications. The wet etchant considerably alters the chemisorbed molecules and dangling bonds associated with the surface states of the nanowires. A device based on such NWs which exhibits low power consumption with no required compliance current and forming voltage for operation is demonstrated. It can integrate all memristive capabilities, including multiple state switching, nonvolatile bipolar memory, and Ca2+ dynamics‐imitating synaptic actions. The examination of the memristive process also highlights the significance of altering surfaces in the devices, in addition to the shared principles that underlie biological and artificial synapses. The operating mode of the nitride‐nanowire devices can be controlled by controlling the formation/dissolution of the oxygen‐conductive path along the nanowires. Thus, the study realizes nanowire memristors based on a nitride material framework, that is promising for application in the 1D–1D system downsizing required for the bio‐inspired artificial synapse.
A novel method, single‐step anisotropic wet etching, is developed to fabricate nanowire‐based GaN memory. The wet etchant alters the surface states of the GaN nanowires. The surface states on the nanowires are responsible for the control between different states of memristive functions. Moreover, the memristive modes of GaN nanowire memory integrate multiple‐state switching and Ca2+ dynamics‐imitating synaptic actions.
Severe distortion is one of the four core effects in single‐phase high‐entropy alloys (HEAs) and contributes significantly to the yield strength. However, the connection between the atomic‐scale ...lattice distortion and macro‐scale mechanical properties through experimental verification has yet to be fully achieved, owing to two critical challenges: 1) the difficulty in the development of homogeneous single‐phase solid‐solution HEAs and 2) the ambiguity in describing the lattice distortion and related measurements and calculations. A single‐phase body‐centered‐cubic (BCC) refractory HEA, NbTaTiVZr, using thermodynamic modeling coupled with experimental verifications, is developed. Compared to the previously developed single‐phase NbTaTiV HEA, the NbTaTiVZr HEA shows a higher yield strength and comparable plasticity. The increase in yield strength is systematically and quantitatively studied in terms of lattice distortion using a theoretical model, first‐principles calculations, synchrotron X‐ray/neutron diffraction, atom‐probe tomography, and scanning transmission electron microscopy techniques. These results demonstrate that severe lattice distortion is a core factor for developing high strengths in refractory HEAs.
The lattice distortions of the NbTaTiV and NbTaTiVZr refractory high‐entropy alloys (HEAs) are quantitatively calculated and measured by various techniques. The relationship between the lattice distortion and yield strength is clearly demonstrated by the addition of Zr elements in an NbTaTiV HEA, resulting in an enhanced yield strength due to the increased lattice distortion.
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•Single-phase binary FCC alloy with superb strength is designed through volume-misfit-maximization-strategy.•The targeted Ni80Mo20 exhibits a yield strength of ∼1.05 GPa while ...maintaining ∼40% elongation.•Unprecedented volume misfit brings a highest-ever Hall-Petch coefficient (1034 MPa·μm1/2) and a pronounced solid solution strengthening (224 MPa).•Volume misfit is a good pertinent indicator of kHP.•Screw dislocations can control the strengthening in SP-FCC alloys.
Single-phase face-centered cubic (SP-FCC) alloys normally possess low strength. Conventionally strengthening strategies inevitably cause significant ductility sacrifice. Here, a single-phase Ni-based FCC alloy with a superb yield strength of ∼1.05GPa and a good ductility of 37% is designed through maximizing the volume misfits. The misfit of the purposely targeted Ni80Mo20 alloy is severer than all existing FCC alloys, bringing the alloy a highest-ever Hall-Petch coefficient (kHP = 1034 MPa·μm1/2) and a pronounced solid solution strengthening (Δσss = 224 MPa). Current work yields two surprising and novel findings for SP-FCC alloys. First, volume misfit is a good pertinent indicator of kHP. Second, the conventional impression about the sole contribution of edge dislocations to strengthening in SP-FCC alloys may no longer hold; instead, screw dislocations can also kick in once the nonsphericity of the solute-induced stress field reaches a critical value. Altogether, this work paves a new avenue of pursuing ultimate strengthening without significant ductility sacrifice for SP-FCC alloys relying on the volume-misfit-maximization strategy.
Abstract
Energy efficiency is motivating the search for new high-temperature (high-T) metals. Some new body-centered-cubic (BCC) random multicomponent “high-entropy alloys (HEAs)” based on refractory ...elements (Cr-Mo-Nb-Ta-V-W-Hf-Ti-Zr) possess exceptional strengths at high temperatures but the physical origins of this outstanding behavior are not known. Here we show, using integrated in-situ neutron-diffraction (ND), high-resolution transmission electron microscopy (HRTEM), and recent theory, that the high strength and strength retention of a NbTaTiV alloy and a high-strength/low-density CrMoNbV alloy are attributable to edge dislocations. This finding is surprising because plastic flows in BCC elemental metals and dilute alloys are generally controlled by screw dislocations. We use the insight and theory to perform a computationally-guided search over 10
7
BCC HEAs and identify over 10
6
possible ultra-strong high-T alloy compositions for future exploration.
Background & Aims Eradication of Helicobacter pylori infection has been reported to reduce the risk of gastric cancer among asymptomatic individuals in high-risk areas. The magnitude of benefit of H ...pylori eradication in populations with different levels of gastric cancer risk and in different clinical scenarios is unclear. We performed a systematic review and meta-analysis of randomized controlled trials and observational studies to investigate the effects of H pylori eradication on the incidence of gastric cancer. Methods We searched PubMed, Cochrane Library, and ClinicalTrials.gov , reviewing titles and abstracts of studies of the effects of eradication of H pylori infection on risk of gastric cancer, through May 2015. We also searched bibliographies of included studies, related reviews, and abstracts presented at Digestive Disease Week. Twenty-four eligible studies (22 research manuscripts and 2 abstracts) were included in our meta-analysis (715 incident gastric cancers among a total of 48,064 individuals/340,255 person-years). We assessed the effects, as well as their modification by baseline gastric cancer incidence, study design (randomized trial vs observational study), clinical scenario (asymptomatic infected individuals vs individuals after endoscopic resection of early gastric cancer), demographic characteristics of patients (age and sex), and duration of follow-up. Results After adjustment for baseline gastric cancer incidence, individuals with eradication of H pylori infection had a lower incidence of gastric cancer than those who did not receive eradication therapy (pooled incidence rate ratio = 0.53; 95% confidence interval: 0.44−0.64). There was little heterogeneity among studies. Baseline gastric cancer incidence modified the benefit of H pylori eradication ( P = .037 for interaction); the incidence rate ratio of gastric cancer decreased in a nonlinear fashion with increasing baseline incidence of gastric cancer ( P = .018, in comparison with the linear model). The benefit also modestly increased with age ( P = .023 for interaction), but this might be due to correlation between age and baseline gastric cancer incidence. Eradication provided significant benefit for asymptomatic infected individuals (pooled incidence rate ratio, 0.62; 95% CI: 0.49−0.79) and individuals after endoscopic resection of gastric cancers (pooled incidence rate ratio, 0.46; 95% CI: 0.35−0.60). The benefits of H pylori eradication did not differ with study design, sex, or follow-up period. Conclusions In a systematic review and meta-analysis, we associated eradication of H pylori infection with a reduced incidence of gastric cancer. The benefits of eradication vary with baseline gastric cancer incidence, but apply to all levels of baseline risk.
Exploitation of the oxidation behaviour in an environmentally sensitive semiconductor is significant to modulate its electronic properties and develop unique applications. Here, we demonstrate a ...native oxidation-inspired InSe field-effect transistor as an artificial synapse in device level that benefits from the boosted charge trapping under ambient conditions. A thin InO
layer is confirmed under the InSe channel, which can serve as an effective charge trapping layer for information storage. The dynamic characteristic measurement is further performed to reveal the corresponding uniform charge trapping and releasing process, which coincides with its surface-effect-governed carrier fluctuations. As a result, the oxide-decorated InSe device exhibits nonvolatile memory characteristics with flexible programming/erasing operations. Furthermore, an InSe-based artificial synapse is implemented to emulate the essential synaptic functions. The pattern recognition capability of the designed artificial neural network is believed to provide an excellent paradigm for ultra-sensitive van der Waals materials to develop electric-modulated neuromorphic computation architectures.
Subjective cognitive decline (SCD) is an early stage of dementia linked to Alzheimer's disease pathology. White matter changes were found in SCD using diffusion tensor imaging, but there are known ...limitations in voxel-wise tensor-based methods. Fixel-based analysis (FBA) can help understand changes in white matter fibers and how they relate to neurodegenerative proteins and multidomain behavior data in individuals with SCD.
Healthy adults with normal cognition were recruited in the Northeastern Taiwan Community Medicine Research Cohort in 2018-2022 and divided into SCD and normal control (NC). Participants underwent evaluations to assess cognitive abilities, mental states, physical activity levels, and susceptibility to fatigue. Neurodegenerative proteins were measured using an immunomagnetic reduction technique. Multi-shell diffusion MRI data were collected and analyzed using whole-brain FBA, comparing results between groups and correlating them with multidomain assessments.
The final enrollment included 33 SCD and 46 NC participants, with no significant differences in age, sex, or education between the groups. SCD had a greater fiber-bundle cross-section than NC (pFWE < 0.05) at bilateral frontal superior longitudinal fasciculus II (SLFII). These white matter changes correlate negatively with plasma Aβ42 level (r = -0.38, p = 0.01) and positively with the AD8 score for subjective cognitive complaints (r = 0.42, p = 0.004) and the Hamilton Anxiety Rating Scale score for the degree of anxiety (Ham-A, r = 0.35, p = 0.019). The dimensional analysis of FBA metrics and blood biomarkers found positive correlations of plasma neurofilament light chain with fiber density at the splenium of corpus callosum (pFWE < 0.05) and with fiber-bundle cross-section at the right thalamus (pFWE < 0.05). Further examination of how SCD grouping interacts between the correlations of FBA metrics and multidomain assessments showed interactions between the fiber density at the corpus callosum with letter-number sequencing cognitive score (pFWE < 0.01) and with fatigue to leisure activities (pFWE < 0.05).
Based on FBA, our investigation suggests white matter structural alterations in SCD. The enlargement of SLFII's fiber cross-section is linked to plasma Aβ42 and neuropsychiatric symptoms, which suggests potential early axonal dystrophy associated with Alzheimer's pathology in SCD. The splenium of the corpus callosum is also a critical region of axonal degeneration and cognitive alteration for SCD.
Optical second harmonic generation (SHG) is known as a sensitive probe to the crystalline symmetry of few-layer transition metal dichalcogenides (TMDs). Layer-number dependent and polarization ...resolved SHG have been observed for the special case of Bernal stacked few-layer TMDs, but it remains largely unexplored for structures deviated from this ideal stacking order. Here we report on the SHG from homo- and heterostructural TMD bilayers formed by artificial stacking with an arbitrary stacking angle. The SHG from the twisted bilayers is a coherent superposition of the SH fields from the individual layers, with a phase difference depending on the stacking angle. Such an interference effect is insensitive to the constituent layered materials and thus applicable to hetero-stacked bilayers. A proof-of-concept demonstration of using the SHG to probe the domain boundary and crystal polarity of mirror twins formed in chemically grown TMDs is also presented. We show here that the SHG is an efficient, sensitive, and nondestructive characterization for the stacking orientation, crystal polarity, and domain boundary of van der Waals heterostructures made of noncentrosymmetric layered materials.
The present work discovers the unique deformation behavior of a refractory high-entropy alloy at elevated temperatures.
Single-phase solid-solution refractory high-entropy alloys (HEAs) show ...remarkable mechanical properties, such as their high yield strength and substantial softening resistance at elevated temperatures. Hence, the in-depth study of the deformation behavior for body-centered cubic (BCC) refractory HEAs is a critical issue to explore the uncovered/unique deformation mechanisms. We have investigated the elastic and plastic deformation behaviors of a single BCC NbTaTiV refractory HEA at elevated temperatures using integrated experimental efforts and theoretical calculations. The in situ neutron diffraction results reveal a temperature-dependent elastic anisotropic deformation behavior. The single-crystal elastic moduli and macroscopic Young’s, shear, and bulk moduli were determined from the in situ neutron diffraction, showing great agreement with first-principles calculations, machine learning, and resonant ultrasound spectroscopy results. Furthermore, the edge dislocation–dominant plastic deformation behaviors, which are different from conventional BCC alloys, were quantitatively described by the Williamson-Hall plot profile modeling and high-angle annular dark-field scanning transmission electron microscopy.
In this paper, we empirically investigate the relationship between the convenience yield of government bonds and the real exchange rates using monthly data from 1999 to 2018. We extend the ...conventional models, based on the present‐value relationship between the real exchange rate and economic fundamentals, while explicitly considering the role of the convenience yield. Empirical results suggest that our present‐value models can capture the dynamic properties of the real exchange rate documented in the literature, including high persistence, excess volatility and excess co‐movement compared with real interest rate differentials. We also find that the sum of expected convenience yields significantly drives real exchange rate movements. Moreover, we find that foreign exchange swap market friction also plays a role in explaining real exchange rates. Finally, we find that monetary policy at the zero lower bound may be essential in real exchange rate modelling.
Résumé
Dynamique entre le rendement de détention et les taux de change réels : une interprétation de la valeur actualisée. Dans l'article, nous étudions de façon empirique la relation entre le rendement de détention des obligations d'État et les taux de change réels à l'aide des données mensuelles de 1999 à 2018. Nous élargissons les modèles conventionnels, en fonction de la relation en valeur actualisée entre les taux de change réels et les facteurs économiques fondamentaux, tout en tenant explicitement compte du rôle du rendement de détention. Les résultats empiriques donnent à penser que nos modèles de la valeur actualisée peuvent saisir les propriétés dynamiques des taux de change réels consignés dans la littérature, notamment la persistance élevée, la volatilité excessive et la covariation excessive comparativement aux différences du taux d'intérêt réel. Nous constatons également que la somme des rendements de détention attendus stimule nettement les mouvements des taux de change réels. En outre, nous observons que les frictions sur le marché de swap de devises jouent également un rôle dans l'explication des taux de change réels. Enfin, nous constatons que la politique monétaire à la borne du zéro peut être essentielle dans la modélisation des taux de change réels.
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