A Three-Step Resolution-Reconfigurable Hazardous Multi-Gas Sensor Interface for Wireless Air-Quality Monitoring Applications

This paper presents a resolution-reconfigurable wide-range resistive sensor readout interface for wireless multi-gas monitoring applications that displays results on a smartphone. Three types of sensing resolutions were selected to minimize processing power consumption, and a dual-mode front-end structure was proposed to support the detection of a variety of hazardous gases with wide range of characteristic resistance. The readout integrated circuit (ROIC) was fabricated in a 0.18 ??m CMOS process to provide three reconfigurable data conversions that correspond to a low-power resistance-to-digital converter (RDC), a 12-bit successive approximation register (SAR) analog-to-digital converter (ADC), and a 16-bit delta-sigma modulator. For functional feasibility, a wireless sensor system prototype that included in-house microelectromechanical (MEMS) sensing devices and commercial device products was manufactured and experimentally verified to detect a variety of hazardous gases

The effect of dynamic written corrective feedback for learners of Korean

This study investigates the effectiveness of dynamic written corrective feedback (DWCF) for intermediate learners of Korean as a foreign language (KFL) compared to traditional types of written corrective feedback. DWCF is an innovative method of providing written corrective feedback on students\u27 writing that has primarily been used in English as a second language (ESL) settings. It aims to improve learners\u27 linguistic accuracy and requires multilayered interaction between teachers and students. Although DWCF has been effectively used to increase linguistic accuracy in various ESL settings, it has not yet been widely applied to other language learning settings. This study demonstrates the extent to which DWCF increases the linguistic accuracy of intermediate KFL learners and determines DWCF\u27s impact on fluency and complexity. The treatment group (n = 9) was managed with DWCF and the control group (n = 10) wrote six essays over a 12-week period. The pre- and post-test results were analyzed to determine differences in linguistic accuracy, fluency, and complexity between the two groups. A mixed-model repeated measures ANOVA revealed that the treatment group\u27s accuracy significantly increased compared to the control group, whereas there was no significant difference in fluency or complexity for either group. Limitations and suggestions for future research are discussed in the conclusion

Nanotwin governed toughening mechanism in hierarchically structured materials

As an important class of natural biocomposite materials, mollusk shells possess remarkable mechanical strength and toughness as a consequence of their hierarchical structuring of soft organic and hard mineral constituents through biomineralization. Strombus gigas, one of the toughest mollusk shell (99 wt% CaCO3, 1 wt% organic), contains high density of nanoscale {110} growth twins in its third order lamellae, the basic building block of the material [1]. Although the existence of these nanotwins has been known for decades their roles and functions in mechanical behaviors and properties of biological materials are still unrevealed because numerous studies in recent years aimed to investigate the relationship between mechanical properties and the elegant nano- and hierarchical structures[1-2]. To evaluate the actual role of these nanotwins, we performed in situ TEM deformation experiment, large scale atomistic simulations and finite element modeling. With these analytic tools, we revealed nano scale twins in conch shell provide a basis of the several orders higher toughness comparing to twin free aragonite. In terms of qualitative experiment, we observed nanotwins can hinder crack propagation effectively comparing to twin free single crystal aragonite and leaving phase transformed area near crack tip (Fig 1 a-c) by in situ TEM deformation experiment. Through large scale MD simulation, we confirmed this phase transformation as a hitherto unknown toughening mechanism governed by nanoscale twins. For the quantitative comparison in terms of toughness, we performed specially designed in situ TEM experiments additionally for conch shell and aragonite single crystal so as to assess the contributions of these nanoscale twins on toughness of conch shell (Fig 1.d). By combining in situ TEM nanoscale mechanical test and FEM simulation, we found that nanotwins in 3rd order lamellar can increase fracture energy an order magnitude higher than twin free aragonite and this effect become amplified via structural hierarchy. The unique properties and structural features of nanotwinned aragonitic conch shell are expected to provide a guide to designing and fabricating hierarchically structured biomimetic materials with high toughness and high modulus

Direct observation of dislocation plasticity in FeCrCoMnNi high-entropy alloys

In the past decade, high-entropy alloys (HEAs) have been intensively investigated not only because of fundamental scientific interests, but also their outstanding mechanical properties, for example, high ductility and fracture toughness. Among hundreds of different combinations of principal elements, the equiatomic FeCrCoMnNi alloy, the so-called Cantor alloy, has been studied as a model system, which is a single phase material with face-centered cubic (FCC) structure at room temperature and shows outstanding ductility and strain hardening especially at cryogenic temperatures. However, dislocation-based deformation mechanisms of HEAs remain elusive and require a fundamental understanding in order to tailor their mechanical properties. Several models have been suggested possible strengthening mechanisms of HEAs, for instance, the high entropy effect and the lattice distortion effect. In the case of the Cantor alloy, the main strengthening mechanism was identified as deformation twinning with critical twinning stress of 720 MPa. At room temperature, dislocation slip by full dislocations is dominant, however, at strains exceeding 20 % and high flow stresses, deformation twinning was also observed. To reveal the hardening mechanism in more detail, direct observation of dislocation plasticity and deformation dynamics is required. Here, we present a study correlating the microstructure and dislocation plasticity of a single crystalline FeCrCoMnNi FCC single phase HEA by employing in-situ transmission electron microscope (TEM) compression and tensile deformation. Moreover, an atomic-scale chemical analysis is conducted by aberration-corrected scanning TEM energy dispersive X-ray spectroscopy (STEM-EDS) and atom probe tomography to investigate chemical inhomogeneity, for example, precipitate formation or local inhomogeneity. Compression tests with sub-micron pillars with 250 and 120 nm diameter show less pronounced mechanical size effects in the alloy compared to other FCC metals as the size exponent is measured as 0.53. It suggests that relatively strong inherent hardening processes are present which attenuate the FCC reported size scaling exponent, which is typically 0.6 to 1.0 for pure FCC metals. The elemental distribution and lattice strains at the atomic scale are rather uniform without long-range ordering analyzed by high-resolution scanning TEM (STEM) and atom probe tomography. Finally, dislocation glide motion was directly observed during in situ TEM tensile tests. The local shear stress measured from gliding of individual dislocations is exceeding 400 MPa. Kink-pair-like glide behavior and periodic fluctuation in the stacking fault width suggest that local pinning points, severe lattice distortion or short-range ordering hinder dislocation motion in HEAs

The origin of jerky dislocation motion in high-entropy alloys

Dislocations in single-phase concentrated random alloys, including high-entropy alloys (HEAs), repeatedly encounter pinning during glide, resulting in jerky dislocation motion. While solute-dislocation interaction is well understood in conventional alloys, the origin of individual pinning points in concentrated random alloys is a matter of debate. In this work, we investigate the origin of dislocation pinning in the CoCrFeMnNi HEA. In-situ transmission electron microscopy studies reveal wavy dislocation lines and a jagged glide motion under external loading, even though no segregation or clustering is found around Shockley partial dislocations. Atomistic simulations reproduce the jerky dislocation motion and link the repeated pinning to local fluctuations in the Peierls friction. We demonstrate that the density of high local Peierls friction is proportional to the critical stress required for dislocation glide and the dislocation mobility

Vacancy driven surface disorder catalyzes anisotropic evaporation of ZnO (0001) polar surface

The evaporation and crystal growth rates of ZnO are highly anisotropic and are fastest on the Zn-terminated ZnO (0001) polar surface. Herein, we study this behavior by direct atomic-scale observations and simulations of the dynamic processes of the ZnO (0001) polar surface during evaporation. The evaporation of the (0001) polar surface is accelerated dramatically at around 300 °C with the spontaneous formation of a few nanometer-thick quasi-liquid layer. This structurally disordered and chemically Zn-deficient quasi-liquid is derived from the formation and inward diffusion of Zn vacancies that stabilize the (0001) polar surface. The quasi-liquid controls the dissociative evaporation of ZnO with establishing steady state reactions with Zn and O$_{2}$ vapors and the underlying ZnO crystal; while the quasi-liquid catalyzes the disordering of ZnO lattice by injecting Zn vacancies, it facilitates the desorption of O$_{2}$ molecules. This study reveals that the polarity-driven surface disorder is the key structural feature driving the fast anisotropic evaporation and crystal growth of ZnO nanostructures along the [0001] direction

The additive effect of herbal medicines on lifestyle modification in the treatment of non-alcoholic fatty liver disease: a systematic review and meta-analysis

Introduction: Non-alcoholic fatty liver disease (NAFLD) is difficult to manage because of its complex pathophysiological mechanism. There is still no effective treatment other than lifestyle modification (LM) such as dietary modifications, regular physical activity, and gradual weight loss. Herbal medicines from traditional Chinese Medicine and Korean Medicine have been shown to be effective in the treatment of NAFLD based on many randomized controlled trials. This systematic review and meta-analysis aims to evaluate the additive effects of herbal medicines on LM in the treatment of NAFLD.Methods: Two databases (PubMed and Cochrane library) were searched using keywords related to NAFLD and herbal medicines. Then the randomized controlled trials (RCTs) evaluating the therapeutic effects of herbal medicines combined with LM were selected. The pooled results were analyzed as mean difference (MD) with 95% confidence interval (CI) for continuous data, and risk ratio (RR) with 95% CI for dichotomous data.Results and Discussion: Eight RCTs with a total of 603 participants were included for this review study. Participants were administered with multi-herbal formulas (Yiqi Sanju Formula, Tiaogan Lipi Recipe, and Lingguizhugan Decoction) or single-herbal extracts (Glycyrrhiza glabra L., Magnoliae offcinalis, Trigonella Foenum-graecum L. semen, Portulaca oleracea L., and Rhus Coriaria L. fructus) along with LM for 12 weeks. The meta-analysis showed a significant improvement in ultrasoundbased liver steatosis measured by odds ratio (OR) in the herbal medicine group than those with LM alone (OR = 7.9, 95% CI 0.7 to 95.2, p < 0.1). In addition, herbal medicines decreased the levels of aspartate transferase (MD -7.5, 95% CI -13.4 to −1.7, p = 0.01) and total cholesterol (MD -16.0, 95% CI -32.7 to 0.7, p = 0.06) more than LM alone. The meta-analysis partially showed clinical evidence supporting the additive benefits of herbal medicines for NAFLD in combination with LM. Whereas, it is necessary to provide a solid basis through higher-quality studies using a specific herbal medicine

Vacancy driven surface disorder catalyzes anisotropic evaporation of ZnO (0001) polar surface

Evaporation and crystal growth occur at different rates on different surfaces. Here authors show dissociative evaporation from ZnO (0001) polar surfaces is accelerated by the formation of a Zn-deficient quasi-liquid layer derived from the formation and inward diffusion of Zn vacancies that stabilize the polar surface. The evaporation and crystal growth rates of ZnO are highly anisotropic and are fastest on the Zn-terminated ZnO (0001) polar surface. Herein, we study this behavior by direct atomic-scale observations and simulations of the dynamic processes of the ZnO (0001) polar surface during evaporation. The evaporation of the (0001) polar surface is accelerated dramatically at around 300 degrees C with the spontaneous formation of a few nanometer-thick quasi-liquid layer. This structurally disordered and chemically Zn-deficient quasi-liquid is derived from the formation and inward diffusion of Zn vacancies that stabilize the (0001) polar surface. The quasi-liquid controls the dissociative evaporation of ZnO with establishing steady state reactions with Zn and O-2 vapors and the underlying ZnO crystal; while the quasi-liquid catalyzes the disordering of ZnO lattice by injecting Zn vacancies, it facilitates the desorption of O-2 molecules. This study reveals that the polarity-driven surface disorder is the key structural feature driving the fast anisotropic evaporation and crystal growth of ZnO nanostructures along the [0001] direction