High Bias Research Articles

Tibial-sided Anterolateral Ligament Injuries Are Associated With Poor Healing and Residual Pivot Shift Testing After Anterior Cruciate Ligament Reconstruction

Purpose; to investigate if tibial sided anterolateral ligament (ALL) injuries are associated with poor healing and residual pivot shift. Methods; Patients who underwent anterior cruciate ligament reconstructions within postinjury 6 weeks from January 2008 to March 2021 were included. They had concomitant ALL injury confirmed by preoperative magnetic resonance imaging (MRI) and were followed minimum 20 months. Preoperative ALL injury was graded by the Muramatsu classification and postoperative ALL healing were graded by a modification of the Lee classification (good, partial, and non-visualized). The patients were allocated to an improved group (IG) and an unimproved group (UG) based on a comparison of pre- and postoperative MRI. ALL tear site, postoperative knee stability, Lysholm score, and Tegner activity scale (PROs) were compared between the two groups. Results; 128 patients were enrolled. 94.5 % patients achieved the minimal clinically important difference (MCID) for PROs, respectively. The ALL was torn at the femoral side in 46.9% patients, at mid-substance in 31.2.%, and at tibial side in 21.9%, Preoperatively, 86 (67.2%) patients had a partial tear and 42 (32.8%) patients had a complete tear. Based on the postoperative MRI appearances, 38 (29.7%) and 90 (70.3%) patients were allocated to the IG and UG, respectively. The tibial side tears were significantly frequent in UG (p= .032). Pivot shift showed a significantly higher incidence in UG than IG (p=.004). Lachman test and PROs did not differ between the two groups. Conclusions; Tibial-sided ALL tears occurred in 18.7% of the UG compared to 3.2% of the IG, and 45.6% of the UG had a postoperative grade 1 or 2 pivot shift, compared to 15.8% of the IG. Percentages of patients with the MCID for PROs did not differ between the two groups. However, the clinical relevance is limited by a high transfer bias.

Heterojunction polarization enhancement and shielding for AlGaN-based solar-blind ultraviolet avalanche detectors.

AlGaN-based solar-blind ultraviolet avalanche detectors have huge potentials in the fields of corona discharge monitoring, biological imaging, etc. Here, we study the impact of the heterojunction polarization-related effects on the AlGaN-based solar-blind ultraviolet avalanche detectors. Our work confirms that the polarization heterojunction is beneficial to reducing avalanche bias and lifting avalanche gain by improving the electric field in the depletion region, while the polarization-induced fixed charges will lead to a redistribution of the electrons, in turn shielding the charges and weakening the electric field enhancement effect. This shielding effect will need external bias to eliminate, and that is why the polarization heterojunction cannot work at relatively low bias but has an enhancement effect at high bias. Controlling the doping level between the hetero-interface can affect the shielding effect. An unintentionally doped polarization heterojunction can effectively reduce the shielding effect, thus reducing the avalanche bias. The conclusions also hold true for the negative polarization regime. We believe our findings can provide some useful insights for the design of the AlGaN-based solar-blind ultraviolet detectors.

Investigating the comparative utility of ECMWF precipitation forecasts as an alternative to reanalysis data

ABSTRACT Many near-real-time applications require near-real-time precipitation estimates, and in the absence of reanalysis datasets due to their usually delayed release, precipitation forecasts could offer a potential alternative. This motivates the inter-comparison of forecast and reanalysis products conducted in this study investigating the statistical accuracy and hydrological utility of three precipitation datasets from European Centre for Medium-Range Weather Forecasts (ECMWF) [i.e. high-resolution (HRES) forecasts, Ensemble Mean (EM) forecasts, and ECMWF’s 5th generation reanalysis (ERA5)] over Türkiye and Germany for 2007–2018 using ground-based observed data as truth. ERA5 has higher bias than HRES and EM in both regions while HRES has the lowest daily correlations. ERA5 (EM) shows the highest hydrological utility in Germany (Türkiye). ERA5 showed improved monthly correlations compared to forecasts; the improvement over Germany (i.e. 0.02) is better than over Türkiye (~0.01). Wetness and topographical complexity of a region affect precipitation estimation uncertainty there.

Effectiveness of identity-building interventions on recovery identity and patient-reported health outcomes in chronic diseases: A meta-analysis.

This meta-analysis aimed to assess the impact of identity-building interventions on recovery identity and patient-reported health outcomes in chronic disease patients. We identified 15 relevant empirical studies (comprising 2261 patients) from 989 records through extensive keyword searches and manual screening conducted between March 2nd and March 13th, 2023. Utilizing the Cochrane tool, meta-regression, and the GRADE approach, we evaluated these studies for their characteristics, findings, and quality. The analysis revealed that identity-building interventions, encompassing recovery-oriented group, interest group, and linguistic approaches, positively influenced identity synthesis and had varying effects on health outcomes. Notably, multiple regression analysis demonstrated that identity synthesis significantly predicted health outcomes. However, the study identified mild heterogeneity, a high attrition bias risk, and insufficient data on selection and detection bias as limitations. Overall, identity-building interventions proved influential in enhancing recovery identity, a vital predictor of patient-reported health outcomes in chronic disease patients.

Field emission characteristics of AlGaN/GaN nanoscale lateral vacuum diodes

We report the design, fabrication, and measurement of the field emission (FE) characteristics of AlGaN/GaN nanoscale lateral vacuum diodes with triangular cathodes and cathode to anode spacings from 50 to 600 nm. The FE characteristics of the AlGaN/GaN diodes with metallic or AlGaN/GaN anodes show successful rectification with forward bias FE current in the range of microamperes or milliamperes, respectively, when biased within a maximum range varying from 10 to 30 V. In the forward bias mode, the measured current Im vs applied anode to cathode bias Vm are well fitted to Murphy–Good profiles associated with FE at higher biases, and an Ohmic leakage profile below the threshold for FE. Our results are the first successful demonstration of FE of electrons between the two two-dimensional electron gases (2DEGs) present on both sides of a nanogap formed by electron lithography through an AlGaN/GaN heterojunction. A qualitative explanation of the loop-type FE characteristics of both AlGaN/GaN vacuum diodes, with either metallic or AlGaN/GaN anodes, is presented.

Evaluation and comparison of MODIS and MISR aerosol products with ground-based monitoring stations in the Amazon Basin

This study evaluates the long-term accuracy of six daily aerosol optical depth (AOD) datasets derived from the Moderate Resolution Imaging Spectroradiometers (MODIS) Dark Target (DT) at 3 and 10 km resolution, Deep Blue (DB), combined DT and DB datasets (DTB) and MODIS Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithms and the Multi-angle Imaging SpectroRadiometer (MISR) Version 23, by comparing them with ground-based AOD observations in 18 Aerosol Robotic Network (AERONET) sites over the Amazon basin between 2000 and 2022. The AOD retrieval accuracy was also assessed under varying seasons, aerosol loading, particle size, elevation and land cover type. Overall results showed that Terra and Aqua-MODIS DB and MISR algorithms perform better, with about 88% of AOD retrievals within the expected error range. However, MISR presented a systematic high negative bias. MODIS DT 3 km overestimated AOD values and indicated unsatisfactory retrieval accuracy in almost all scenarios. MODIS and MISR retrievals showed improved performance under low aerosol loading, whereas Aqua-MODIS MAIAC under intermediate conditions (AOD>0.2). MISR indicated a large dependence on a coarse mode-dominated environment with considerable negative bias. Terra-MODIS MAIAC retrievals exhibited a smaller dependence for aerosol particle size distribution, while Terra-MODIS DB performed better for fine mode and Aqua-MODIS DB for coarse dominance. MAIAC also performed well under polluted scenarios in the dry season in contrast to the majority of satellite-based AOD retrievals, which showed good agreement under clean background conditions in the wet season. Almost all satellite-based retrievals showed higher uncertainty under extremely high altitudes (>3000 m) followed by non-satisfactory correlation and significant biases. Additionally, almost all satellite-based AOD retrievals indicated poor performance as vegetation coverage increases. On the contrary, MISR showed higher accuracy under forest type. In general, MODIS and MISR retrieval accuracy demonstrated distinct levels of dependencies that require further improvement in the Amazon Basin.

Applying oversampling before cross-validation will lead to high bias in radiomics

Class imbalance is often unavoidable for radiomic data collected from clinical routine. It can create problems during classifier training since the majority class could dominate the minority class. Consequently, resampling methods like oversampling or undersampling are applied to the data to class-balance the data. However, the resampling must not be applied upfront to all data because it would lead to data leakage and, therefore, to erroneous results. This study aims to measure the extent of this bias. Five-fold cross-validation with 30 repeats was performed using a set of 15 radiomic datasets to train predictive models. The training involved two scenarios: first, the models were trained correctly by applying the resampling methods during the cross-validation. Second, the models were trained incorrectly by performing the resampling on all the data before cross-validation. The bias was defined empirically as the difference between the best-performing models in both scenarios in terms of area under the receiver operating characteristic curve (AUC), sensitivity, specificity, balanced accuracy, and the Brier score. In addition, a simulation study was performed on a randomly generated dataset for verification. The results demonstrated that incorrectly applying the oversampling methods to all data resulted in a large positive bias (up to 0.34 in AUC, 0.33 in sensitivity, 0.31 in specificity, and 0.37 in balanced accuracy). The bias depended on the data balance, and approximately an increase of 0.10 in the AUC was observed for each increase in imbalance. The models also showed a bias in calibration measured using the Brier score, which differed by up to −0.18 between the correctly and incorrectly trained models. The undersampling methods were not affected significantly by bias. These results emphasize that any resampling method should be applied correctly only to the training data to avoid data leakage and, subsequently, biased model performance and calibration.

Numerical investigation on the convergence of self-consistent Schrödinger-Poisson equations in semiconductor device transport simulation

Semiconductor devices at the nanoscale with low-dimensional materials as channels exhibit quantum transport characteristics, thereby their electrical simulation relies on the self-consistent solution of the Schrödinger-Poisson equations. While the non-equilibrium Green’s function (NEGF) method is widely used for solving this quantum many-body problem, its high computational cost and convergence challenges with the Poisson equation significantly limit its applicability. In this study, we investigate the stability of the NEGF method coupled with various forms of the Poisson equation, encompassing linear, analytical nonlinear, and numerical nonlinear forms Our focus lies on simulating carbon nanotube field-effect transistors (CNTFETs) under two distinct doping scenarios: electrostatic doping and ion implantation doping. The numerical experiments reveal that nonlinear formulas outperform linear counterpart. The numerical one demonstrates superior stability, particularly evident under high bias and ion implantation doping conditions. Additionally, we investigate different approaches for presolving potential, leveraging solutions from the Laplace equation and a piecewise guessing method tailored to each doping mode. These methods effectively reduce the number of iterations required for convergence.

Robust retrieval of forest canopy structural attributes using multi‐platform airborne LiDAR

AbstractLiDAR data acquired from airplanes and helicopters – known as airborne laser scanning (ALS) – are widely regarded as the gold standard for characterizing the 3D structure of forests at scale. But in the last decade, advances in unoccupied aerial vehicle (UAV) technologies have led to a rapid rise in the use of UAV laser scanning (ULS) for mapping forest structure. As both ALS and ULS data become increasingly available, they are being used to derive an ever‐growing number of metrics designed to measure different facets of canopy structure. However, which metrics can be robustly retrieved from both ALS and ULS platforms remains unclear. To address this question, we acquired coincident, high‐density ALS and ULS scans covering 115 plots (4‐ha in size) in an open‐canopy temperate ecosystem in Western Australia. Using this unique dataset, we quantified 32 canopy structural metrics related to canopy height, openness and heterogeneity, including metrics calculated directly from the point clouds and ones measured from derived canopy height models (CHM). Overall, we found that ALS and ULS‐derived metrics were strongly correlated (r2 = 0.90). However, this high degree of correlation masked considerable systematic differences between platforms. Specifically, point cloud metrics were less strongly (r2 = 0.87) correlated and had higher bias (10.7%) compared to CHM‐derived ones (r2 = 0.98; bias = 2.5%). Similarly, metrics of canopy openness and heterogeneity were less strongly correlated (r2 = 0.84 and 0.87) and exhibited greater bias (14.4 and 7.9%) than ones relating to canopy height (r2 = 0.96; bias = 3.8%). Our results indicate that only a small subset of the 32 metrics we tested were directly comparable between ALS and ULS platforms. Consequently, future efforts to combine laser scanning data across platforms and instruments should think carefully about which metrics are most appropriate, especially when working with point cloud data.

Nanoskiving of van der Waals Materials toward Edge/Basal Plane Contact Heterojunctions for High-Performance Photodetection.

The unique features of edges in van der Waals materials may lead to edge-basal plane contacts that could provide new opportunities for electronic and optoelectronic devices. However, few studies have addressed edge/basal plane contact heterojunctions owing to the formidable challenges in integrating edges with the basal plane to form a heterojunction. Here, taking the example of black phosphorus (BP)/ReS2, a heterojunction with contact between the edge and the basal plane was successfully achieved by the introduction of a nanoskiving technique to fabricate BP edges with controlled orientation, followed by the dry transfer of a ReS2 flake. The deformation of BP during the nanoskiving process was clearly revealed, where interlayer slipping in the BP determined the formation of the edges. The edge/basal plane contact heterojunctions based on BP/ReS2 exhibited a reverse-rectifying behavior upon contact, and a high rectifying current was attributed to direct tunneling and Fowler-Nordheim tunneling in low and high bias regimes, respectively. As a photodetector, the heterojunction diode demonstrated an impressive responsivity of 65 A/W, a rapid response time (<10 ms), and polarization-sensitive detection under 532 nm illumination without gate biasing.

Multifidus atrophy and/or dysfunction following lumbar radiofrequency ablation: A systematic review.

Lumbar medial branch nerve radiofrequency ablation (LRFA) is an interventional procedure used to treat chronic lumbar facet joint pain. Because the medial branch nerves also innervate the multifidus muscle, it has been proposed that LRFA may pose a risk of multifidus atrophy and/or dysfunction. However, the quality and level of evidence to answer this clinical question have not been established. Therefore, this review aimed to systematically appraise the literature to discern whether the prevailing evidence substantiates the hypothesis in question. A systematic review compliant with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was performed to evaluate the quality and level of evidence of studies reporting functional and/or structural changes in the multifidus muscle following LRFA. Only five cohort studies met inclusion criteria. Two studies assessed changes in multifidus function following LRFA with confirmed denervation at electromyography and significant reduction in multifidus shear modulus with ultrasound shear wave elastography. Of the four studies that evaluated changes in multifidus structure with magnetic resonance imaging following LRFA, two demonstrated a decrease in cross-sectional area or an increase in fat infiltration, one demonstrated no change, and one revealed an apparent increase. Given the destructive nature attributed to LRFA, some degree of multifidus atrophy and/or dysfunction may be plausible, albeit with a very low certainty that relies on a restricted body of literature of modest quality and with a presence of high bias. There is a paucity of studies discussing the potential association between LRFA and multifidus atrophy and/or dysfunction. In light of the shortage of high-quality studies and the absence of standardized protocols to assess both changes in the structure and function of the multifidus subsequent to LRFA, there is a pressing need for more prospective studies with a high methodological rigor to comprehensively address and answer this enduring debate in clinical practice.

Multilayer Graphene/Epitaxial Silicon Near‐Infrared Self‐Quenched Avalanche Photodetectors

Abstract2D materials and their heterostructures exhibit considerable potential in the development of avalanche photodetectors (APDs) with high gain, response, and signal‐to‐noise ratio. These materials hold promise in addressing inherent technical challenges associated with APDs, such as low light absorption coefficient, elevated noise current, and substantial power consumption due to high bias resulting in only moderate current gain. In this work, a macro‐assembled graphene nanofilm (nMAG)/epitaxial silicon (epi‐Si) vertical heterostructure photodetector with a responsivity of 0.38 A W−1 and a response time of 1.4 µs is reported. The photodetectors use high‐quality nMAG as the absorption layer and a lightly‐doped epi‐Si layer as the multiplication region under the avalanche mode to provide a high responsivity (2.51 mA W−1) and detectivity (2.67 × 109 Jones) at 1550 nm, which can achieve high‐resolution imaging. In addition, the APD displays a weak noise level and an avalanche gain of M = 1123. It can work with relatively low avalanche turn‐on voltages and achieve self‐quenching by switching from illumination to dark during avalanche multiplication, with a real‐time data transfer rate of 38 Mbps in near‐infrared light communication data links. The proposed structure enables the fabrication of high‐performance APDs in the infrared range using complementary‐metal‐oxide‐semiconductor (CMOS)‐compatible processes.

A Test Method for Identifying Selection Bias Risk in Prospective Controlled Clinical Therapy Trials Using the I2 Point Estimate.

A test method is proposed for identifying potential selection bias risk in single prospective controlled clinical therapy trials that can be applied by trial reviewers. The method is described in detail and was tested on eight randomised controlled trials (RCTs) with reported negative Berger-Exner test results as negative and on eight prospective, controlled cohort studies as positive controls. All 16 studies were identified by systematic literature search. The test method yielded negative results for all RCTs and positive results for six out of the eight cohortstudies. All test results remained within the expected limits for both study types, suggesting a reasonably high accuracy for correctly identifying selection bias risk. However, the method does not provide the possibility to establish whether such bias risk has actually altered trial outcomes. Instead, a positive test result may provide an empirical basis for rating a trial as of high selection bias risk during trial appraisal.

Diagnostic accuracy of cognitive screening tools validated for older adults in Iran: a systematic review and meta-analysis

BackgroundThis systematic review aims to comprehensively assess the diagnostic accuracy of cognitive screening tools validated for older adults in Iran, providing evidence-based recommendations for clinicians and researchers.MethodsA comprehensive search in March 2023 across Web of Science, PubMed, Scopus, ScienceDirect, SID, IranMedex, and IranDoc, enhanced by hand-searching references and Google Scholar, identified cross-sectional studies on cognitive screening in Iranian seniors. We assessed diagnostic accuracy, cognitive domains, and test strengths and weaknesses. A bivariate random-effects meta-analysis provided summary estimates and 95% confidence intervals, illustrated in forest plots.ResultsOur review, derived from an initial screening of 38 articles, focused on 17 studies involving 14 cognitive screening tools and participant counts from 60 to 350, mostly from specialized clinics. The MMSE was the only tool examined in at least three studies, prompting a meta-analysis revealing its sensitivity at 0.89 and specificity at 0.77 for dementia detection, albeit amidst significant heterogeneity (I^2 > 80%). ACE-III demonstrated the highest diagnostic accuracy for MCI and dementia, while MoCA’s performance was deemed adequate for MCI and excellent for dementia. High bias risk in studies limits interpretation.ConclusionThis review identifies key cognitive tools for dementia and MCI in Iranian older adults, tailored to educational levels for use in primary and specialized care. It emphasizes the need for further validation to enhance diagnostic precision across diverse settings, within a concise framework prioritizing brevity and accuracy for clinical applicability.

Evaluation of reanalysis soil moisture products using cosmic ray neutron sensor observations across the globe

Abstract. Reanalysis soil moisture products are valuable for diverse applications, but their quality assessment is limited due to scale discrepancies when compared to traditional in situ point-scale measurements. The emergence of cosmic ray neutron sensors (CRNSs) with field-scale soil moisture estimates (∼ 250 m radius, up to 0.7 m deep) is more suitable for the product evaluation owing to their larger footprint. In this study, we perform a comprehensive evaluation of eight widely used reanalysis soil moisture products (ERA5-Land, CFSv2, MERRA2, JRA55, GLDAS-Noah, CRA40, GLEAM and SMAP L4 datasets) against 135 CRNS sites from the COSMOS-UK, COSMOS-Europe, COSMOS USA and CosmOz Australia networks. We evaluate the products using six metrics capturing different aspects of soil moisture dynamics. Results show that all reanalysis products generally exhibit good temporal correlation with the measurements, with the median temporal correlation coefficient (R) values spanning 0.69 to 0.79, though large deviations are found at sites with seasonally varying vegetation cover. Poor performance is observed across products for soil moisture anomalies time series, with R values varying from 0.46 to 0.66. The performance of reanalysis products differs greatly across regions, climate, land covers and topographic conditions. In general, all products tend to overestimate data in arid climates and underestimate data in humid regions as well as grassland. Most reanalysis products perform poorly in steep terrain. Relatively low temporal correlation and high bias are detected in some sites from the west of the UK, which might be associated with relatively low bulk density and high soil organic carbon. Overall, ERA5-Land, CRA40, CFSv2, SMAP L4 and GLEAM exhibit superior performance compared to MERRA2, GLDAS-Noah and JRA55. We recommend that ERA5-Land and CFSv2 could be used in humid climates, whereas SMAP L4 and CRA40 perform better in arid regions. SMAP L4 has good performance for cropland, while GLEAM is more effective in shrubland regions. Our findings also provide insights into directions for improvement of soil moisture products for product developers.

Generation of broadband optical chaos at mid-infrared wavelength with an interband cascade laser

Nonlinear dynamics at mid-infrared wavelength is of interest for various applications but has been mainly limited to quantum cascade lasers so far. In this article, we show that interband cascade lasers can generate complex optical chaos with bandwidth in the GHz range and this outperforms the performances of quantum cascade laser chaos. The chaos nature of our signal is confirmed by a thorough time-series analysis. Modeling of the semiconductor laser under short-cavity external optical feedback allows confirming the high bias chaos operation that we observe experimentally. These results pave the way for applications at mid-infrared wavelength, such as private free-space communication.

Suppressing the Thermal Quenching Effect via a Cluster Conformer in Copper(I)-Iodide Coordination Polymeric Phosphors for High-Power White LED Lighting.

High-power LED lighting is a crucial challenge due to the notorious thermal quenching (TQ) effect of traditional phosphors at high operating currents, which would result in poor device performance and hamper practical optoelectronic application. Herein, we demonstrate ligand engineering of a cubane- versus staircase-like [Cu4I4] conformer as a node in coordination polymers, which remarkably suppresses the TQ effect of cluster-based photoluminescence. For complex 1 (the formula [Cu4I4(bbimb)2]n) with the cubane-like [Cu4I4] conformer as a node, the metallophilicity interaction enables ultrabright triplet emission with a photoluminescence quantum yield over 82%, and the phonon-assisted detrapping process of excitons effectively suppresses the TQ effect in the wide temperature range. In contrast, the staircase-like [Cu4I4] conformer as a node in complex 2 (the formula [Cu4I4(bbtmb)2]n) exhibits a serious TQ effect over the investigated temperature. Phosphor-converted white LEDs (pc-wLEDs) were fabricated by integrating the cluster-based coordination polymers as a color converter, and their electroluminescence performances were investigated under high bias currents. The prototype pc-wLED device by incorporating the phosphor with the suppressed TQ effect exhibits a continuous rise in brightness under a high bias current of 300 mA. The results demonstrate that ligand engineering of the cluster conformer via suppressing the TQ effect proves efficient in designing an ideal color converter for high-power pc-wLED lighting.

Potassium phosphate modulation of the microstructure and its influence on the magnetic properties of FeSiAl soft magnetic composites

FeSiAl soft magnetic composites (SMCs) with phosphate-silicone resin as the insulating layer were prepared by phosphating FeSiAl powder with K3PO4 solution. The effects of K3PO4 content on the microstructure and composition of the insulation coating were investigated. Further, the soft magnetic properties of SMCs were analyzed in detail. It is revealed that the annealed inorganic coating layer which predominantly consists of Al(PO3)3, Al2O3, and P2O5 exhibits a high resistivity, high temperature resistance and thin thickness, significantly reducing the eddy current loss. The outstanding magnetic properties of a power loss of 118.6 kW/m3 (100 kHz, 0.1 T) and permeability of 63.8 were achieved for this high-quality thin insulation coating. Moreover, the magnetic loss was separated into hysteresis, eddy current and excess part, and the mechanism was analyzed in detail. The reduced total loss can be ascribed to the suppression of the eddy current. The novel SMCs coating with K3PO4 are particularly suitable for applications in high frequency and high DC bias situations for switching power supplies, photovoltaic inverter boost inductors and other applications.

Performance limiting inhomogeneities of defect states in ampere-class Ga2O3 power diodes

Impacts of spatial charge inhomogeneities on carrier transport fluctuations and premature breakdown were investigated in Schottky ampere-class Ga2O3 power diodes. Three prominent electron traps were detected in Ga2O3 epilayers by a combination of the depth-resolved capacitance spectroscopy profiling and gradual dry etching. The near-surface trap occurring at 1.06 eV below the conduction band minimum (EC), named E3, was found to be confined within a 180 nm surface region of the Ga2O3 epilayers. Two bulk traps at EC − 0.75 eV (E2*) and at EC − 0.82 eV (E2) were identified and interconnected with the VGa- and FeGa-type defects, respectively. In the framework of the impact ionization model, employing the experimental trap parameters, the TCAD simulated breakdown characteristics matched the experimental breakdown properties well, consistently with inverse proportionality to the total trap densities. In particular, the shallowest distributed E3 trap with the deepest level is responsible for higher leakage and premature breakdown. In contrast, Ga2O3 Schottky diodes without E3 trap exhibit enhanced breakdown voltages, and the leakage mechanism evolves from variable range hopping at medium reverse voltages, to the space-charge-limited conduction at high reverse biases. This work bridges the fundamental gap between spatial charge inhomogeneities and diode breakdown features, paving the way for more reliable defect engineering in high-performance Ga2O3 power devices.

Spontaneous mutations and mutational responses to penicillin treatment in the bacterial pathogen Streptococcus pneumoniae D39

Bacteria with functional DNA repair systems are expected to have low mutation rates due to strong natural selection for genomic stability. However, our study of the wild-type Streptococcus pneumoniae D39, a pathogen responsible for many common diseases, revealed a high spontaneous mutation rate of 0.02 per genome per cell division in mutation-accumulation (MA) lines. This rate is orders of magnitude higher than that of other non-mutator bacteria and is characterized by a high mutation bias in the A/T direction. The high mutation rate may have resulted from a reduction in the overall efficiency of selection, conferred by the tiny effective population size in nature. In line with this, S. pneumoniae D39 also exhibited the lowest DNA mismatch-repair (MMR) efficiency among bacteria. Treatment with the antibiotic penicillin did not elevate the mutation rate, as penicillin did not induce DNA damage and S. pneumoniae lacks a stress response pathway. Our findings suggested that the MA results are applicable to within-host scenarios and provide insights into pathogen evolution.