Band Model Research Articles

Inhibition of MRTF-A Ameliorates Pathological Remodeling of the Pressure-loaded Right Ventricle.

Right ventricular (RV) fibrosis is associated with RV dysfunction in a variety of RV pressure-loading conditions where RV mechanical stress is increased, but the underlying mechanisms driving RV fibrosis are incompletely understood. In pulmonary and cardiovascular diseases characterized by elevated mechanical stress and transforming growth factor - beta-1 (TGF-β1) signaling, myocardin-related transcription factor A (MRTF-A) is a mechanosensitive protein critical to driving myofibroblast transition and fibrosis. Here we investigated whether MRTF-A inhibition improves RV pro-fibrotic remodeling and function in response to a pulmonary artery banding (PAB) model of RV pressure-loading. Rats were assigned into either 1) sham or 2) PAB groups. MRTF-A inhibitor CCG-1423 was administered daily at 0.75mg/kg in a subset of PAB animals. Echocardiography and pressure-volume hemodynamics were obtained at a terminal experiment 6-weeks later. RV myocardial samples were analyzed for fibrosis, cardiomyocyte hypertrophy, and pro-fibrotic signaling. MRTF-A inhibition slightly reduced systolic dysfunction in PAB rats reflected by increased lateral tricuspid annulus peak systolic velocity, while diastolic function parameters were not significantly improved. RV remodeling was attenuated in PAB rats with MRTF-A inhibition, displaying reduced fibrosis. This was accompanied with a reduction in PAB-induced upregulation of yes-associated protein (YAP) and its paralog transcriptional co-activator with PDZ-binding motif (TAZ). We also confirmed using a second-generation MRTF-A inhibitor CCG-203971 that MRTF-A is critical in driving RV fibroblast expression of TAZ and markers of myofibroblast transition in response to TGF-β1 stress and RhoA activation. These studies identify RhoA, MRTF-A, and YAP/TAZ as interconnected regulators of pro-fibrotic signaling in RV pressure-loading, and as potential targets to improve RV pro-fibrotic remodeling.

Optimization of the thermoelectric performance of aluminum-doped zinc oxide-graphene heterojunctions under high temperature and high pressure

High-pressure effects can be used to effectively optimize the thermoelectric performance of wide-bandgap oxides. We build upon this finding to show that the synergistic effects of doping with aluminum and graphene composite give excellent thermoelectric performance under high pressure. By employing the parabolic band model, the Pisarenko curves are derived at different pressures, coupled with the band structure of Al-doped ZnO. An analysis indicates that pressure-induced narrowing of the bandgap in Al-doped ZnO reduces the electron excitation energy, thereby optimizing the electrical properties of the samples. The Debye Callaway model is also used to fit the lattice thermal conductivity of the samples, thus enabling an in-depth analysis of the phonon scattering mechanisms. Our analysis suggests that graphene composites significantly enhance point defect scattering and Umklapp scattering, thus increasing the phonon relaxation time and effectively reducing the lattice thermal conductivity of the samples. The improvement in the figure of merit (zT) of ZnO is attributed to the simultaneous enhancement of its electrical properties under high pressure and the synergistic optimization of reducing the lattice thermal conductivity through doping and composites. In this work, we consider a fixed doping ratio of Al and a constant proportion of graphene composite, and analyze the microstructure and thermoelectric properties of 0.1C–ZnAl0.04O (C–ZnAlO) samples synthesized under pressures ranging from 1 to 5 GPa, with the aim of elucidating the influence of pressure and graphene composite on the electro-acoustic transport properties of ZnO. We find that the zT value for a sample synthesized at 5 GPa is increased to 0.27 at 973 K.

Engineering the PEM Water Electrolysis Anode for Better Interfacial Electrical Conductivity

In pursuing cost-effective green hydrogen production via proton exchange membrane water electrolysis (PEMWE), the high expense of the iridium (Ir)-based oxygen evolution reaction (OER) catalysts poses a significant challenge. To overcome this issue, researchers have focused on developing active OER catalysts and catalyst layers (CLs) with minimum uses of Ir. However, they frequently encountered performance problems at the single-cell level that originate not only from the kinetic polarization but also from the ohmic polarization. In this aspect, we have focused on identifying the reasons for the poor performance of low IrOx-loaded anodes, with loadings as low as 0.10 mg cm-2. We pinpoint the cause of the poor performance of the low loaded anodes to an electron transport problem within the native oxide on the Ti porous transport layer (PTL). Our analysis, grounded in the metal-insulator band model, reveals that the primary factors contributing to electron conductivity loss in the Ti oxide are the upward band bending induced by the Schottky contact with high work function IrOx and by the pinch-off effect from the extensive ionomer contact. Based on the above understanding, we propose an anode CL composed of a one-dimensional iridium catalyst, fabricated by electrospinning and calcination processes. Our nanofiber-based CL effectively mitigates the electron transport problem of the native Ti oxide. This improvement stems from the low work function of the Ir nanofiber catalyst and the highly porous structure that reduces the ionomer contact with the Ti oxide. Furthermore, the highly porous nature of the nanofiber-based CL enhances two-phase mass transport, facilitating the high current operation. These findings underscore the critical role of the CL/PTL interface of the PEMWE anode and present the necessity of a well-structured CL to achieve efficient and cost-effective water electrolysis.

Low thermal conductivity and enhanced thermoelectric properties of Cu-substituted Bi2-xCuxSr2Co2Oy ceramics

The Bi2Sr2Co2Oy ceramic, known for its stability as a p-type thermoelectric material, has limited thermoelectric performance that necessitates enhancement. In this study, Bi2-xCuxSr2Co2Oy (x = 0, 0.025, 0.05, 0.1, 0.2) ceramic samples were synthesized using the conventional solid-state reaction method. Substitution of Cu2+ for Bi3+ in the samples increased carrier concentration, significantly reducing electrical resistivity. Utilizing the single parabolic band (SPB) model, it was determined that Cu incorporation led to an increased effective mass, thereby enhancing the Seebeck coefficient. Additionally, fine grains and lattice defects induced by Cu2+ substitution effectively scattered phonons, resulting in an ultra-low thermal conductivity of 0.59 Wm−1K−1 at 923 K for the Bi1.8Cu0.2Sr2Co2Oy sample. Consequently, Cu substitution optimized both the electrical and thermal transport properties of Bi2-xCuxSr2Co2Oy samples. The dimensionless thermoelectric figure of merit (ZT) for Bi1.95Cu0.05Sr2Co2Oy reached 0.31 at 923 K, representing a 63 % increase over the pristine Bi2Sr2Co2Oy sample.

Abstract Tu051: ROR2 Drives Right Ventricular Failure Via Proteostatic Imbalances

Background: No therapies exist to treat right ventricular failure (RVF), in part because RVF molecular drivers have been incompletely studied. We recently identified that the developmentally restricted noncanonical WNT receptor ROR2 is re-expressed in a severity-dependent manner in human RVF. Here we test in mice if, and how, the re-expression of Ror2 causes RVF. Methods/Results: We find in neonatal rat ventricular myocytes (NRVMs) that Ror2 overexpression (Ror2 OE ) both activates protein translation and reduces Hspa1a/b mRNA and Hsp70 protein, resulting in increased protein turnover, fragmented sarcomeres, intercalated disc disruption, reduced cell major axis, impairment of contractile and relaxation kinetics, and ectopy. Ror2 knockdown (Ror2 KD ) results in opposing phenotypes. Hsp70 overexpression or proteasome inhibition rescues many of the Ror2 OE phenotypes, demonstrating their causal involvement. NRVM proteomic analysis indicates that Ror2 OE activates an ERK/p90RSK/Eef2 pathway that is known to regulate translation extension. In vivo, cardiac Ror2 OE in mice causes RV dilation and dysfunction, intercalated disc disruption, reduced Hspa1b (encoding for Hsp70), proteasome activation, and reduced cardiomyocyte ubiquitin staining. The mouse pulmonary artery banding (PAB) model of RVF reveals similar Ror2 induction and proteasome activation. Ror2 KD by AAV9 in PAB reduces RV dilation and improves RV systolic and diastolic function. Finally, in cardiac samples from human RVF, we find evidence for a similar ROR2-responsive proteostatic imbalance with increased proteasome activity and ubiquitin as well as markers of increased ERK and p90RSK. Conclusions: ROR2 is induced in human and mouse RVF, and mechanistic studies in NRVMs and mice show that the induction of ROR2 causes RVF by disrupting the proteostatic balance of translation, folding, and turnover. Knockdown or suppression of ROR2 may serve as a novel RVF therapeutic target.

Critical regions in a one-dimensional flat band lattice with a quasi-periodic potential

In our previous work, the concept of critical region in a generalized Aubry–André model (Ganeshan–Pixley–Das Sarma’s model) has been established. In this work, we find that the critical region can be realized in a one-dimensional flat band lattice with a quasi-periodic potential. It is found that the above flat band lattice model can be reduced to an effective Ganeshan–Pixley–Das Sarma’s model. Depending on various parameter ranges, the effective quasi-periodic potential may be bounded or unbounded. In these two cases, the Lyapunov exponent, mobility edge, and critical indices of localized length are obtained exactly. In this flat band model, the localized-extended, localized-critical and critical-extended transitions can coexist. Furthermore, we find that near the transitions between the bound and unbounded cases, the derivative of Lyapunov exponent of localized states with respect to energy is discontinuous. At the end, the localized states in bounded and unbounded cases can be distinguished from each other by Avila’s acceleration.

Long-lived, pulse-induced transient absorption inLiNb1-x Ta x O3 (0≤x≤1) solid solutions: the case of three intrinsic defect sites for electron localization with strong coupling

Abstract Femto-/nanosecond pulse-induced, red and near-infrared absorption is studied in LiNb1-x Ta x O3 (0≤x≤1, LNT) solid solutions with the aim of studying transient optical nonlinearities associated with the formation, transport and recombination of optically generated small bound electron polarons with strong coupling to the lattice. As a result, a pronounced, long-lived transient absorption is uncovered for LNT which exceed lifetimes and starting amplitudes of LiNbO3 (LN) and LiTaO3 (LT) by a factor of up to 100 and 10, respectively. The transients reveal a stretched-exponential decay behavior and a thermally activated process which provide strong evidence for an underlying hopping transport mechanism of small bound polarons. All findings are discussed in comparison to the model systems LN and LT within the framework of appropriate band models and optical generation of polarons via two-photon excitation. To explain the significant differences, the simultaneous presence of Nb5+ Li , Ta5+ Li antisites, and Ta5+ V interstitial defects, i.e. a mixture of the intrinsic defects widely established for LN and LT, is assumed for LNT.

Evolution of thermoelectric transport properties of Sb2Te3–Sb2Se3 solid-solution alloys depending on phase formation behavior

Sb2Te3-based alloys exhibit decent thermoelectric transport properties in the mid-temperature range above 550 K. However, the study on Sb2Te3 alloys has been limited in simple doping approach. Herein, evolution in the thermoelectric transport properties associated with the phase formation of solid solution alloys of Sb2(Te1−xSex)3 (x = 0, 0.25, 0.33, 0.5, 0.75, and 1.0) compositions is investigated to widen the strategy to solid solution alloying. A single phase of the Sb2Te3 rhombohedral structure formed from x = 0 to 0.5, whereas mixed phases with an orthorhombic structure of Sb2Se3 was observed at x = 0.75. The electrical conductivity weighted mobility were gradually decreased as Se content increases to x = 0.75. Consequently, the power factor was decreased gradually and significantly to 0.076 mW/mK2 for x = 0.75 (Sb2(Te0·25Se0.75)3) compared with 2.6 mW/mK2 of the pristine sample. The total thermal conductivity of 2.0 W/mK for the Sb2Te3 was significantly reduced gradually to 0.64 W/mK for x = 0.75 owing to simultaneous decrease in electrical and lattice thermal conductivities. The reduction in lattice thermal conductivity is mainly owing to the addition point defect scattering caused by the Se addition. Nevertheless, thermoelectric figure of merit zT of Sb2Te3 is gradually decreased from 0.64 to 0.11 for x = 0.75 at 650 K due to the degradation in electrical transport properties. Furthermore, the theoretical zT was estimated for all samples with varying carrier concentration based on single parabolic band model.

Enhanced thermoelectric performance of Cr-doped ZnSb through lattice thermal conductivity reduction below the phonon glass limit

Zinc antimonide (ZnSb) is a promising thermoelectric material due to its economic viability, elemental abundance, and superior phase stability compared to other Zn-Sb compounds. However, its widespread application is hindered by a low figure-of-merit (zT). Extensive research has explored doping, alloying, and nanostructuring to improve zT. This study investigates the impact of Cr doping in CryZn1-ySb (y = 0.0 – 0.03). Cr doping with y = 0.01 significantly reduces lattice thermal conductivity below the phonon glass limit. Debye-Callaway model calculations suggest a combined effect of point defects and decreased grain size caused by Cr incorporation. This reduction translates to enhanced thermoelectric performance, with the y = 0.01 sample exhibiting a 70 % improvement in zT at 673 K, reaching ∼0.67. Exceeding the Cr substitution limit leads to the formation of a detrimental secondary CrSb2 phase, increasing thermal conductivity. The Single Parabolic Band model calculations predict further zT enhancement in y = 0.01 sample to ∼0.2 at 300 K through optimized carrier concentration (307 % improvement in zT). These findings demonstrate the potential for significant zT improvement in ZnSb via defect engineering and carrier concentration tuning.

A common gene signature of the right ventricle in failing rat and human hearts

The molecular mechanisms of progressive right heart failure are incompletely understood. In this study, we systematically examined transcriptomic changes occurring over months in isolated cardiomyocytes or whole heart tissues from failing right and left ventricles in rat models of pulmonary artery banding (PAB) or aortic banding (AOB). Detailed bioinformatics analyses resulted in the identification of gene signature, protein and transcription factor networks specific to ventricles and compensated or decompensated disease states. Proteomic and RNA-FISH analyses confirmed PAB-mediated regulation of key genes and revealed spatially heterogeneous mRNA expression in the heart. Intersection of rat PAB-specific gene sets with transcriptome datasets from human patients with chronic thromboembolic pulmonary hypertension (CTEPH) led to the identification of more than 50 genes whose expression levels correlated with the severity of right heart disease, including multiple matrix-regulating and secreted factors. These data define a conserved, differentially regulated genetic network associated with right heart failure in rats and humans.

Characterization of the p-NiO/n-GaN heterojunction and development of ultraviolet photodiode

Nickel oxide semiconductor is a good p-type material for fabricating a p-n-heterojunction with n-type GaN semiconductor. The p-NiO/n-GaN heterojunction, which produces a type II band bias, has significant prospects for creating photosensitive devices. Herein, it is shown that a selective ultraviolet photodetector can be created based on this heterojunction. p-NiO films were formed using magnetron sputtering onto n-doped GaN epitaxial layers grown by plasma assisted molecular beam epitaxy. The structural, optical, and electronic properties of the formed nickel oxide films were studied. A mechanism for reducing dislocation density and conductivity and increasing transparency due to film annealing is proposed. It has been established that the current–voltage characteristics of the p-NiO/n-GaN heterojunction are typical for diode structures and show selective sensitivity to ultraviolet radiation. The band model and sensitivity of the fabricated ultraviolet photodiode were evaluated. The photosensitivity at zero voltage was 3.11 mA/W, the quantum yield was 0.011, and the detection ability was 8.69 × 109 Jones. The work shows the potential of using the p-NiO/n-GaN heterojunction to create ultraviolet photodetectors.

Regulation of the RhoA exchange factor GEF-H1 by profibrotic stimuli through a positive feedback loop involving RhoA, MRTF, and Sp1.

RhoA and its effectors, the transcriptional coactivators myocardin-related transcription factor (MRTF) and serum response factor (SRF), control epithelial phenotype and are indispensable for profibrotic epithelial reprogramming during fibrogenesis. Context-dependent control of RhoA and fibrosis-associated changes in its regulators, however, remain incompletely characterized. We previously identified the guanine nucleotide exchange factor GEF-H1 as a central mediator of RhoA activation in renal tubular cells exposed to inflammatory or fibrotic stimuli. Here we found that GEF-H1 expression and phosphorylation were strongly elevated in two animal models of fibrosis. In the Unilateral Ureteral Obstruction mouse kidney fibrosis model, GEF-H1 was upregulated predominantly in the tubular compartment. GEF-H1 was also elevated and phosphorylated in a rat pulmonary artery banding (PAB) model of right ventricular fibrosis. Prolonged stimulation of LLC-PK1 tubular cells with tumor necrosis factor (TNF)-α or transforming growth factor (TGF)-β1 increased GEF-H1 expression and activated a luciferase-coupled GEF-H1 promoter. Knockdown and overexpression studies revealed that these effects were mediated by RhoA, cytoskeleton remodeling, and MRTF, indicative of a positive feedback cycle. Indeed, silencing endogenous GEF-H1 attenuated activation of the GEF-H1 promoter. Of importance, inhibition of MRTF using CCG-1423 prevented GEF-H1 upregulation in both animal models. MRTF-dependent increase in GEF-H1 was prevented by inhibition of the transcription factor Sp1, and mutating putative Sp1 binding sites in the GEF-H1 promoter eliminated its MRTF-dependent activation. As the GEF-H1/RhoA axis is key for fibrogenesis, this novel MRTF/Sp1-dependent regulation of GEF-H1 abundance represents a potential target for reducing renal and cardiac fibrosis.NEW & NOTEWORTHY We show that expression of the RhoA regulator GEF-H1 is upregulated in tubular cells exposed to fibrogenic cytokines and in animal models of kidney and heart fibrosis. We identify a pathway wherein GEF-H1/RhoA-dependent MRTF activation through its noncanonical partner Sp1 upregulates GEF-H1. Our data reveal the existence of a positive feedback cycle that enhances Rho signaling through control of both GEF-H1 activation and expression. This feedback loop may play an important role in organ fibrosis.

Soft robotic platform for progressive and reversible aortic constriction in a small-animal model.

Our understanding of cardiac remodeling processes due to left ventricular pressure overload derives largely from animal models of aortic banding. However, these studies fail to enable control over both disease progression and reversal, hindering their clinical relevance. Here, we describe a method for progressive and reversible aortic banding based on an implantable expandable actuator that can be finely tuned to modulate aortic banding and debanding in a rat model. Through catheterization, imaging, and histologic studies, we demonstrate that our platform can recapitulate the hemodynamic and structural changes associated with pressure overload in a controllable manner. We leveraged soft robotics to enable noninvasive aortic debanding, demonstrating that these changes can be partly reversed because of cessation of the biomechanical stimulus. By recapitulating longitudinal disease progression and reversibility, this animal model could elucidate fundamental mechanisms of cardiac remodeling and optimize timing of intervention for pressure overload.

Estimating leaf area index of Eucalyptus dunnii over the dry and wet seasons using vegetation indices and image texture derived from WorldView-3 imagery

ABSTRACT Leaf Area Index (LAI) remains one of the most important forest structural attributes, as accurate estimation of LAI is crucial for predicting the growth of different species. Using the Partial Least Squares Regression (PLS-R) algorithm, this study investigated three image processing techniques to determine the best technique for estimating LAI using WorldView-3 imagery in the Midlands, KwaZulu-Natal province of South Africa. The PLS-R texture ratios model achieved the highest accuracy of R 2 = 0.70, RMSE = 1.21 (2.32% of the mean measured LAI) and R 2 = 0.72, RMSE = 1.26 (2.41% of the mean measured LAI) for the wet and dry seasons, respectively. This was followed by the PLS-R single texture band model that produced an accuracy of R 2 = 0.65, RMSE = 1.35 (2.58% of the mean measured LAI) and R 2 = 0.67, RMSE = 1.32 (2.52% of the mean measured LAI) for the wet and dry seasons, respectively. The PLS-R model using a combination of vegetation indices had the lowest estimation accuracy of R 2 = 0.59, RMSE = 1.38 (2.64% of the mean measured LAI) and R 2 = 0.60, RMSE = 1.40 (2.67% of the mean measured LAI) for the wet and dry seasons, respectively. The results of this study provided evidence that image texture ratios can be used to estimate LAI effectively.

Estimation of Maximum <i>zT</i> in Cu<sub>3</sub>SbSe<sub>4</sub> for Different Starting Materials Content

Cu<sub>3</sub>SbSe<sub>4</sub> is considered a promising thermoelectric material because of its large effective mass and low thermal conductivity, originating from its unique lattice structure. However, Cu<sub>3</sub>SbSe<sub>4</sub> has intrinsically low carrier concentration and relatively high electric resistance which limit performance. Recently, a <i>zT</i> improvement in Cu<sub>3</sub>SbSe<sub>4</sub> was reported where doping/precipitation is controlled by changing the content of the starting materials. However, the effect of these changes in starting content on electronic band structures has not been studied. Here, we investigate how the change in starting materials content (<i>x</i> varying from 6 to 20) affects band parameters like density-of-states effective mass (<i>m<sub>d</sub></i> *), non-degenerate mobility (<i>μ<sub>0</sub></i>), weighted mobility (<i>μ<sub>W</sub></i>), and B-factor using the Single Parabolic Band (SPB) model. For <i>x</i> greater than 8, precipitation of the secondary phase (CuSe) was observed, and the band parameters changed differently for <i>x</i> greater than 8. The <i>m<sub>d</sub></i> * increases up to <i>x</i> = 8 and then rapidly decreases for <i>x</i> > 8. For <i>μ<sub>0</sub></i>, an overall decrease is observed for increasing <i>x</i>, but the rate of decrease is suppressed for <i>x</i> > 8. The <i>μ<sub>W</sub></i> reaches the maximum at <i>x</i> = 8. As <i>x</i> increases, the experimental lattice thermal conductivity also increases, especially for <i>x</i> > 8. Therefore, the B-factor, which is directly related to the theoretical maximum zT, becomes maximum at = 8. Hence the SPB model predicts a maximum <i>zT</i> of 0.0484 for <i>x</i> = 8 at 300 K, which is 15.5% higher than the experimental <i>zT</i> of 0.0419, which can be achieved by tuning the Hall carrier concentration to 4.44 × 10<sup>19</sup> cm<sup>-3</sup>.

Thermodynamic Response and Neutral Excitations in Integer and Fractional Quantum Anomalous Hall States Emerging from Correlated Flat Bands.

Integer and fractional Chern insulators have been extensively explored in correlated flat band models. Recently, the prediction and experimental observation of fractional quantum anomalous Hall (FQAH) states with spontaneous time-reversal symmetry breaking have garnered attention. While the thermodynamics of integer quantum anomalous Hall (IQAH) states have been systematically studied, our theoretical knowledge on thermodynamic properties of FQAH states has been severely limited. Here, we delve into the general thermodynamic response and collective excitations of both IQAH and FQAH states within the paradigmatic flat Chern-band model with remote band considered. Our key findings include (i)in both ν=1 IQAH and ν=1/3 FQAH states, even without spin fluctuations, the charge-neutral collective excitations would lower the onset temperature of these topological states, to a value significantly smaller than the charge gap, due to band mixing and multiparticle scattering; (ii)by employing large-scale thermodynamic simulations in FQAH states in the presence of strong interband mixing between C=±1 bands, we find that the lowest collective excitations manifest as the zero-momentum excitons in the IQAH state, whereas in the FQAH state, they take the form of magnetorotons with finite momentum; (iii)the unique charge oscillations in FQAH states are exhibited with distinct experimental signatures, which we propose to detect in future experiments.

Measuring lattice thermal conductivity of Bi1-xSbx enabled by external magnetic field

Minimizing lattice thermal conductivity (κL) is one of the most successful strategies for enhancing thermoelectrics. Existing experimental approach for κL-determination largely depend on model approximations for the electronic component (κE) with a subtraction from the measured total thermal conductivity (κ = κL+κE). However, the approximations (e.g. Wiedemann-Franz law) may not always be accurate particularly for materials with complicated band structures. Accurate κL-determination, not only characterizing the fundamental capability in heat conduction but also providing the insight of thermal functional materials, is still challenging. In this work, we utilize the magneto-thermoelectric effect under a magnetic field to suppress κE whereas κL is nearly unaffected. This allows for direct κL-measurement in materials that particularly have high carrier mobility. It is demonstrated in Bi1-xSbx single crystals that longitudinal κE can be sufficiently minimized to enable direct measurement in longitudinal κL at T < 100 K under a magnetic field of 5 T. It is revealed that the commonly used single Kane band (SKB) model approximations would lead to a 30 % overestimation in κL. The method proposed here enables a pathway of κL-determination for understanding the phonon transport in materials with complicated band structure.

A Correlated‐K Parameterization for O2 Photolysis in the Schumann‐Runge Bands

AbstractA recent study comparing ozone column depths and methane lifetimes at varied atmospheric O2 (pO2) levels calculated in the Kasting‐group 1‐D photochemical model and the Whole Atmosphere Community Climate Model version 6 (WACCM6) 3‐D model (Ji, Kasting, et al., 2023; https://doi.org/10.1098/rsos.230056) has exposed weaknesses in both models in parameterizing photolysis in the O2 Schumann‐Runge bands, 175–205 nm. WACCM6 does a good job for Earth's present atmosphere but neglects scattering, which becomes important at low pO2. The 1‐D model includes scattering but is based on an out‐of‐date band model, and it neglects the temperature dependence of photolysis at low pO2. We have revised and improved the 1‐D photochemical model by replacing the old O2 photolysis algorithm with a new correlated‐k parameterization, which improves accuracy for all O2 levels and all temperature profiles. The WACCM6 parameterization was also included in the 1‐D model for comparative purposes. The correlated‐k and WACCM6 photolysis algorithms agree well for both the present atmosphere and for an atmosphere containing 10−3 times the present O2 level, but only if multiple scattering is included at low pO2. The correlated‐k parameterization will be made available to photochemical modeling groups who might choose to adopt it.

Dominant n-type conduction and fast photoresponse in BP/MoS2 heterostructures

In recent years, van der Waals heterojunctions between two-dimensional (2D) materials have garnered significant attention for their unique electronic and optoelectronic properties and have opened avenues for innovative device architectures and applications. Among them, the heterojunction formed by black phosphorus (BP) and molybdenum disulfide (MoS2) stands out as a promising candidate for advanced optoelectronic devices. This study unravels the interplay between BP, MoS2, and Cr contacts to explain the electrical behavior of a BP/MoS2 heterojunction showing rectifying behavior with dominant n-type conduction, and a high ON/OFF current ratio around 104 at ± 20 V. The higher unexpected current observed when applying a negative bias to either MoS2 or BP side is elucidated by an energy band model incorporating a type II heterojunction at the BP/MoS2 interface with Cr forming a Schottky contact with MoS2 and an ohmic contact with BP. The BP/MoS2 heterojunction shows pronounced photoresponse, linearly dependent on the incident laser power, with a responsivity of 100 µA/W under white light at 50 µW incident power. Time-resolved photocurrent measurements reveal a relatively fast response with characteristic rise times less than 200 ms. This work demonstrates that BP/MoS2 van der Waals heterojunctions have unique electrical and photoresponse characteristics that are promising for advanced optoelectronic applications.

Exploring ZnO nanoparticles: UV–visible analysis and different size estimation methods

The study investigates several theoretical and empirical methods for determining the size of zinc oxide nanoparticles (ZnO NPs) and studies their characteristics by using solely UV–visible spectroscopy. The investigation begins with the green synthesis of three samples of ZnO NPs using three different reducing agents Aspergillus Niger fungal biomass (AN), Aloe barbadensis Mille (ABM) and Ocimum tenuiflorum (OT) leaves, respectively with Zinc Sulphate as a precursor involving precipitation method. The study analyses the UV–visible data of each sample to obtain optical bandgap, Urbach energy, refractive index, optical conductivity. and apply several methods or Models such as Effective Mass Approximation (EMA) or Brus Equation (BE), Hyperbolic Band Model (HBM), Meulenkamp's Expression (ME), Tight Binding Model (TBM) and a simplified version of EMA (SEMA) to estimate the size of ZnO NPs. The effectiveness of size-determining models was assessed using two sets of one-way analysis of variance (ANOVA) for each ZnO sample and models Followed by Tukey post-hoc analysis to identify the exact sample that is different from other samples.