Browse Articles

Luminescence efficiency and temperature quenching of spontaneous and stimulated emission in ultra-low dislocation density InN

In this letter, we evaluate temperature quenching of photoluminescence in ultra-high quality epitaxial InN films to assess the internal quantum efficiency (IQE) of band-to-band light emission. Measured room-temperature carrier lifetimes of ∼10 ns in the samples with record-low dislocation density of Nd ∼ 5 × 108 cm−2 appear consistent with the diffusion-limited Shockley–Reed–Hall recombination model and lead to a maximum emission IQE of ∼1.5% at T = 300 K. For the stimulated emission (SE) regime, dislocation densities in excess of 1010 cm−2 can be actually tolerated without seriously affecting the SE threshold, and its temperature dependence is determined by a competition between radiative and Auger processes, with a crossover point around liquid-nitrogen temperature.

Vitamin D, acute respiratory infections, and Covid-19: The curse of small-size randomised trials. A critical review with meta-analysis of randomised trials

Background Randomised trials conducted from 2006 to 2021 indicated that vitamin D supplementation (VDS) was able to prevent severe COVID-19 and acute respiratory infections (ARI). However, larger randomised trials published in 2022 did not confirm the health benefits of VDS in COVID-19 patients. Objective To examine through a systematic review with meta-analysis the characteristics of randomised trials on VDS to COVID-19 patients and admission to intensive care unit (ICU), and of randomised trials on VDS for the prevention of ARI. Method A systematic search retrieved randomised trials on VDS to COVID-19 patients and admission to ICU. Data on VDS and ARI were extracted from the meta-analysis of Jolliffe et al. 2021. Groups were formed including trials with total numbers of patients below or above the median size of all trials. The associations between VDS vs no VDS, and admission to ICU were evaluated using random-effects models from which summary odds ratios (SOR) and 95% confidence intervals (CI) were obtained. Meta-analyses were done for all trials and for each group of trials, which allowed testing a possible effect modification of trial size. Publication bias was assessed using the Louis-Furuya-Kanaruori (LFK) index (no bias if index between -1 and +1) and the trim and fill method. Results Nine trials on VDS for preventing admission to ICU were identified, including 50 to 548 patients. The summary odds ratio (SOR) was 0.61 (95% CI: 0.39–0.95) for all trials, 0.34 (0.13–0.93) for trials including 50 to <106 patients and 0.88 (0.62–1.24) for trials including 106 to 548 patients (interaction p = 0.04). The LFK index was -3.79, and after trim and fill, the SOR was 0.80 (0.40–1.61). The SOR for the 37 trials on VDS for ARI prevention included 25 to 16,000 patients. The SOR was 0.92 (0.86–0.99) for all trials, 0.69 (0.57–0.83) for trials including 25 to <248 patients and 0.98 (0.94–1.03) for trials including 248 to 16,000 patients (interaction p = 0.0001). The LFK index was -3.11, and after trim and fill, the SOR was 0.96 (0.88–1.05). Conclusion Strong publication bias affected small randomised trials on VDS for the prevention of severe COVID-19 and of ARI. Systematic reviews should beware of small-size randomised trials that generally exaggerate health benefits.

Cryogenic hybrid magnonic circuits based on spalled YIG thin films

Yttrium iron garnet (YIG) magnonics has garnered significant research interest because of the unique properties of magnons (quasiparticles of collective spin excitation) for signal processing. In particular, hybrid systems based on YIG magnonics show great promise for quantum information science due to their broad frequency tunability and strong compatibility with other platforms. However, their broad applications have been severely constrained by substantial microwave loss in the gadolinium gallium garnet (GGG) substrate at cryogenic temperatures. In this study, we demonstrate that YIG thin films can be spalled from YIG/GGG samples. Our approach is validated by measuring hybrid devices comprising superconducting resonators and spalled YIG films, which exhibit anti-crossing features that indicate strong coupling between magnons and microwave photons. Such new capability of separating YIG thin films from GGG substrates via spalling and the integrated superconductor-YIG devices represent a significant advancement for integrated magnonic devices, paving the way for advanced magnon-based coherent information processing.

Efficiency of four trap types and human landing catch in the sampling of Mansonia (Diptera, Culicidae) in Porto Velho, Rondônia, Brazil

Entomological surveillance plays a crucial role in designing and implementing mosquito control measures. In this context, developing more effective collection strategies is essential to accurately estimate the entomological parameters necessary for effective control. In this study, we investigated the effectiveness of four traps: CDC light trap, MosqTent, BG-Sentinel, and SkeeterVac, compared to human landing catch (HLC) in the collection of Mansonia mosquitoes, known to cause discomfort to riverside populations along the Madeira River in the District of Jaci Paraná, Porto Velho, in Rondônia state, Brazil. Sampling was conducted, during three periods corresponding to two seasons, dry and rainy, over five consecutive days for each period. The captures using HLC and the installation of the traps took place on the grounds of five selected residences from 6 to 10 pm. Rotational exchanges between houses ensured that all traps and the HLC were used in each of the five residences, following a predetermined Latin square pattern. A total of 7,080 mosquitoes were collected, of which 90.5% belonged to the Mansonia genus, distributed in four species: Mansonia titillans (75.97%), Mansonia humeralis (18.91%), Mansonia amazonensis (1.90%), and Mansonia indubitans (1.37%). HLC captured the highest number of Mansonia mosquitoes (58.1%), followed by SkeeterVac (21.8%) and MosqTent (18.9%). CDC and BG-Sentinel showed a very low performance (0.92 and 0.23%, respectively). Although HLC performed better in capturing Mansonia, our results suggest that SkeeterVac and MosqTent can serve as valuable additional tools to entomological inventories or sentinels for detecting invasive species in areas with high epidemiological vulnerability, thereby providing evidence-based recommendations for improving mosquito control measures and entomological surveillance.

Influence of laser polarization on the laser-induced damage threshold: Comparison with photoionization theory

The influence of laser polarization on the laser-induced damage threshold of fused silica is presented. Measurements were performed using femtosecond and nanosecond laser pulse durations. The impact of laser polarization on the laser damage varies with laser wavelength. While no difference in UV laser damage was observed between linear and circular polarizations, circular polarization improved the damage resistance of fused silica to infrared and visible laser radiation in comparison with linear polarization. By measuring the femtosecond laser damage of a SiO2 thin film deposited onto a substrate, we show that the ratio between the bandgap of the sample and the photon energy causes the polarization dependent laser damage to change. These experimental findings are explained by considering the photoionization theory for solids.

Analysis of the social-epistemological dimensions of a Clinical Teaching Unit and Small Private Online Course compared to a traditional clerkship Internal Medicine

Clinical workplace learning is often suboptimal due to the dynamics of the clinical learning environment and several challenges encountered in clinical practice. At LUMC, clinical teachers introduced a novel blended learning program that included both the introduction of a Clinical Teaching Unit (CTU) and Small Private Online Course (SPOC). This study aimed to analyze the educational content and design of our educational interventions, by categorizing and comparing the dimensions of the learning program before and after the interventions. The novel blended learning program was integrated into a clerkship internal medicine, aiming to optimize clerks’ clinical workplace learning. Therefore, a traditional inpatient ward was transformed into a CTU, featuring the introduction of learning activities that promoted multidisciplinary and interprofessional learning. It included an integrated SPOC, aiming to improve clinical reasoning skills, feedback and collaboration of the clerks. The authors analyzed the clerkships’ content and design, by categorizing the social-epistemological dimensions of the teaching modes offered before (traditional clerkship) and after (including CTU and SPOC) the intervention. These dimensions consisted of individual versus group (collaborative), and objectivist versus constructive learning categories. The CTU model added eleven group activities to the clinical workplace, of which nine were characterized as constructivist-group activities. It also led to more active learning of the clerks, compared to the traditional clerkship. Analysis of the SPOC revealed 344 teaching modes in total, which included 113 objectivist–individual, 205 constructive–individual and 23 constructive–group activities. Compared to a traditional clerkship, the CTU with SPOC led to more constructivist and collaborative learning and a more diverse educational program. This study illustrates a methodology to address active and collaborative learning activities in an educational program, and offers tools to evaluate and redesign one’s teaching program. The methods and models described can be applied to clinical environments in other areas of medicine.

Lattice Boltzmann modeling of droplet actuation via temperature gradient and electrowetting

Droplet manipulation under various physical fields is crucial for microfluidics. Theoretical models are key to understand the physics. In this work, by extending the binary phase lattice Boltzmann model to fully coupled thermodynamics and electrostatics, we systematically explore the behaviors of droplet transport driven by temperature-dependent surface tension, thermocapillary, and electrowetting effects. It is shown that electrowetting enables bidirectional transport of the droplet, determined by various physical parameters such as electric voltage, wettability, viscosity, thermal conductivity, and surface tension. Specifically, the physics revealed in this work is more than simply electrowetting modified wettability. Actually, the droplet transport is controlled further by contact angle hysteresis and thermocapillary-induced temperature gradient.

In vivo imaging of mitochondrial function in normal, glaucoma suspect, and glaucoma eyes

To investigate macula and optic nerve head (ONH) mitochondrial metabolic activity using flavoprotein fluorescence (FPF) in normal, glaucoma suspect (GS), and open-angle glaucoma (OAG) eyes we performed a cross-sectional, observational study of FPF in normal, GS, and OAG eyes. The macula and ONH of each eye was scanned and analyzed with a commercially available FPF measuring device (OcuMet Beacon, OcuSciences Inc., Ann Arbor, MI). One-way analysis of variance was used to compare macula and ONH FPF scores between groups. Linear regression models investigated the correlation between FPF scores and structural and functional parameters. We included 25 normal, 16 GS, and 54 OAG eyes. The average age in years ± SD for normal, GS, and OAG groups was 60.6 ±17.4, 67.8 ± 10.3, and 67.9 ± 11.6, respectively (P = 0.064). There was no significant difference in gender, race/ethnicity, visual acuity, and intraocular pressure between groups. OAG eyes had larger cup-to-disc ratio, thinner retinal nerve fiber and macula thicknesses, and worse visual field indices compared to normal and GS eyes (P ≤ 0.018). There was no significant difference in any FPF metric between the study groups in either the macula or the ONH, despite normalizing FPF data for structural differences between groups (e.g. retinal nerve fiber layer and ganglion cell-inner plexiform layer thickness). In conclusion, no significant differences in metabolic activity as measured by FPF were found in macula and ONH FPF scores using the integrated clinician report generator between normal, GS, and OAG eyes. Further research is needed to evaluate the role of mitochondrial metabolic activity measurements in glaucoma.

Characterization and optimization of high-efficiency crystalline silicon solar cells: Impact of recombination in the space charge region and trap-assisted Auger exciton recombination

Since the photoconversion efficiency η of the silicon-based solar cells (SCs) under laboratory conditions is approaching the theoretical fundamental limit, further improvement of their performance requires theoretical modeling and/or numerical simulation to optimize the SCs parameters and design. The existing numerical approaches to modeling and optimizing the key parameters of high-efficiency solar cells based on monocrystalline silicon, the dominant material in photovoltaics, are described. It is shown that, in addition to the four usually considered recombination processes, namely, Shockley–Read-Hall, surface, radiative, and band-to-band Auger recombination mechanisms, the non-radiative exciton Auger recombination and recombination in the space charge region (SCR) have to be included. To develop the analytical SC characterization formalism, we proposed a simple expression to model the wavelength-dependent external quantum efficiency of the photocurrent near the absorption edge. Based on this parameterization, the theory developed allows for calculating and optimizing the base thickness-dependent short-circuit current, the open-circuit voltage, and the SC photoconversion efficiency. The accuracy of the approach to optimizing solar cell parameters, particularly thickness and base doping level, is demonstrated by its application to three Si solar cells reported in the literature: one with an efficiency of 26.63%, another with 26.81%, and a third with a record efficiency of 27.3%. The results show that the developed formalism enables further optimization of solar cell thickness and doping levels, leading to potential increases in efficiency.

Look-alike modelling in violence-related research: A missing data approach

Violence has been analysed in silo due to difficulties in accessing data and concerns for the safety of those exposed. While there is some literature on violence and its associations using individual datasets, analyses using combined sources of data are very limited. Ideally data from the same individuals would enable linkage and a longitudinal understanding of experiences of violence and their (health) impacts and consequences. This paper aims to provide proof of concept to create a synthetic dataset by combining data from the Crime Survey for England and Wales (CSEW) and administrative data from Rape Crisis England and Wales (RCEW), pertaining to victim-survivors of sexual violence in adulthood. Intuitively, the idea was to impute missing information from one dataset by borrowing the distribution from the other. In our analyses, we borrowed information from CSEW to impute missing data in the RCEW administrative dataset, creating a combined synthetic RCEW-CSEW dataset. Using look-alike modelling principles, we provide an innovative and cost-effective approach to exploring patterns and associations in violence-related research in a multi-sectorial setting. Methodologically, we approached data integration as a missing data problem to create a synthetic combined dataset. Multiple imputation with chained equations were employed to collate/impute data from the two different sources. To test whether this procedure was effective, we compared regressions analyses for the individual and combined synthetic datasets on binary, continuous and categorical variables. We extended our testing to an outcome measure and, finally, applied the technique to a variable fully missing in one data source. Our results show that the effect sizes for the combined dataset reflect those from the dataset used for imputation. The variance is higher, resulting in fewer statistically significant estimates. Our approach reinforces the possibility of combining administrative with survey datasets using look-alike methods to overcome existing barriers to data linkage.

PyLRO: A Python calculator for analyzing long-range structural order

We present PyLRO, an open-source Python calculator designed to detect, quantify, and display long-range order in periodic structures. The program’s design methodology, workflow, and approach to order quantification are described and demonstrated using a simple toy model. Additionally, we apply PyLRO to a series of metastable AlPO4 structural intermediates from a prior high-pressure study, demonstrating how to compute and visualize structural order in all directions on a Miller sphere. We further highlight the program’s capabilities through a high-throughput analysis of structural patterns in the pressure-induced amorphization of AlPO4, revealing atomistic insights into specific energy regions of massive amorphous structures. These results suggest that PyLRO can be a valuable tool for investigating crystal–amorphous transition in materials research.

Artificial intelligence and network science as tools to illustrate academic research evolution in interdisciplinary fields: The case of Italian design

In this paper, we explore the application of Artificial Intelligence and network science methodologies in characterizing interdisciplinary disciplines, with a specific focus on the field of Italian design, taken as a paradigmatic example. Exploratory data analysis and the study of academic collaboration networks highlight how the field is evolving towards increased collaboration. Text analysis and semantic topic modelling identified the evolution of research interest over time, defining a ranking of pairs of keywords and three prominent research topics: User-Centric Experience Design, Innovative Product Design and Sustainable Service Design. Our results revealed a significant transformation in the field, with a shift from individual to collaborative research, as evidenced by the increasing complexity and collaboration within groups. We acknowledge the limitations faced by this work, suggesting that the methodology may be primarily suitable for bibliometric and more silos-like disciplines. However, we emphasize the urgency for the scientific community to address the future of research not indexed by large open-access databases like OpenAlex.

The Peierls stress of interfacial dislocation under lattice mismatches

The dislocation motion at heterointerfaces can be quantitatively predicted by estimating the Peierls barrier using the generalized stacking-fault energy surface. A simple formula is derived for the Peierls stress of misfit dislocations within the framework of the Peierls–Nabarro mechanism. This formula clarifies the correlation between a material’s yield strength, its elastic constant, and the dislocation structure, which is crucial for understanding the stability of heterointerfaces. Using the BAs/AlN heterojunction as an example, the validity of the energy barrier at the B–Al interface is confirmed through numerical results obtained from first-principles simulations.

Impact of communication anxiety on L2 WTC of middle school students: Mediating effects of growth language mindset and language learning motivation

Previous research has shown a connection between communication anxiety and willingness to communicate (WTC) among English as a foreign/second language (L2) learners. Nonetheless, the potential mediating roles of learners’ beliefs like growth language mindset and language learning motivation have not been thoroughly investigated, particularly in the context of middle school language learners. This study aimed to explore the relationship between communication anxiety and L2 WTC by considering the mediating roles of growth language mindset and language learning motivation. To achieve this goal, an online survey was administered to 847 participants from five middle schools in eastern China. Structural equation modeling was employed to analyze the collected data. The findings revealed that L2 WTC was negatively impacted by communication anxiety and growth language mindset, while positively influenced by language learning motivation. Additionally, communication anxiety had a negative effect on both growth language mindset and language learning motivation, whereas growth language mindset exerted a positive effect on language learning motivation. Moreover, either individually or synergistically, growth language mindset and language learning motivation played mediating roles in the relationship between communication anxiety and L2 WTC. These research findings have significant implications for understanding the interrelationship among the variables, offering an innovative perspective on the mediating effects of growth language mindset and language learning motivation on communication anxiety and WTC among secondary school students. Consequently, this study provides valuable insights for language learning and instruction among middle school students and teachers.

Two-carrier model-fitting of Hall effect in semiconductors with dual-band occupation: A case study in GaN two-dimensional hole gas

We develop a two-carrier Hall effect model-fitting algorithm to analyze temperature-dependent magnetotransport measurements of a high-density (∼4×1013cm−2) polarization-induced two-dimensional hole gas (2DHG) in a GaN/AlN heterostructure. Previous transport studies in GaN 2DHGs have reported a twofold reduction in 2DHG carrier density when cooled from room to cryogenic temperature. We demonstrate that this apparent drop in carrier density is an artifact of assuming one species of charge carrier when interpreting Hall effect measurements. Using an appropriate two-carrier model, we resolve light hole (LH) and heavy hole (HH) carrier densities congruent with self-consistent Poisson-k⋅p simulations and observe an LH mobility of ∼1400 cm2/Vs and HH mobility of ∼300 cm2/Vs at 2 K. This report constitutes the first experimental signature of LH band conductivity reported in GaN.

Correction to Supporting Information for Le et al., Motor neuron disease, TDP-43 pathology, and memory deficits in mice expressing ALS–FTD-linked <i>UBQLN2</i> mutations

Exploring cooking fuel choices among Ghanaian women of reproductive age: A socio-economic analysis from a statistical mechanics perspective

Access to clean and efficient cooking fuel is crucial for promoting good health, safeguarding the environment, and driving economic growth. Despite efforts to promote the adoption of cleaner alternatives, traditional solid fuels such as charcoal and firewood remain prevalent in Ghana. In this study, we utilized a statistical mechanical model as a framework to explore the statistical relationship between socio-economic factors such as educational attainment, wealth status, place of residence, and cooking fuel choices. We analysed data from the Ghana Malaria Indicator Survey (GMIS) conducted in 2019, involving a total of 2,942 women of reproductive age. The findings revealed that 13.77% of participants preferred using LPG fuels for cooking, while 86.23% preferred non-LPG fuels for their cooking needs. The data indicated that among LPG users, 96.54% are educated women of reproductive age, and 3.46% are non-educated women of reproductive age. Among these, 95.31% are non-poor, and 4.69% are poor. Additionally, 21.73% reside in rural areas, while 78.27% live in urban areas. The data also showed that among non-LPG fuel users, 68.70% are educated women of reproductive age, and 31.30% are non-educated women of reproductive age. Among this group, 16.04% are non-poor, and 83.96% are poor. Furthermore, 67.24% reside in rural areas, and 32.76% live in urban areas. Our findings showed that in the absence of social interaction, a woman’s wealth status has a relationship to her choice of fuel for cooking. Additionally, women of reproductive age in rural areas with some education demonstrated a significant private incentive (40.12%) to use LPG, implying a positive correlation between education and the use of LPG for cooking. However, when social interactions are considered, factors such as education, wealth status, and place of residence have significant relationships with a woman’s decision about fuel choice. The interaction strength among women of reproductive age in urban areas with some education shows a negative estimate (-4.06%), suggesting that there is no significant imitative effect. The study further suggests that urban women of reproductive age who are poor exert a greater influence on their urban counterparts who are not poor when social interaction is incorporated. Women of reproductive age in rural areas with some form of education exert a greater influence on women of reproductive age in rural areas with no form of education. We recommend that the government of Ghana and its stakeholders focus on leveraging the influence of urban poor women and educated rural women through community-led programs and educational campaigns. Financial support mechanisms like microfinance and subsidies, alongside reliable LPG infrastructure, can make access easier for these target groups. Tailored communication strategies, peer-to-peer learning, and collaboration with local institutions are crucial for spreading awareness and encouraging the adoption of LPG.

High performance triboelectric nanogenerator by synchrotron x-ray assisted Ru/g-C3N4 nanostructure incorporated into PDMS matrix

The integration of metal–semiconductor nanostructures is of significant interest to the advanced technology development. However, the synthesis methods for metal–semiconductor nanostructures are complicated and require multi-stage processing, which includes the separate synthesis of metallic and semiconductor nanostructures, controlling pH, and dedicated equipments. Herein, we report a one-step in situ synthesis and simultaneous embedding of Ru nanostructures on g-C3N4 nanosheets using the synchrotron x-ray irradiation method. The results indicate that Ru nanostructures were uniformly embedded within the g-C3N4 nanosheets, leading to the formation of Ru—O, RuO2, and Ru—O—Ru chemical bonds. Moreover, three distinct types of Ru nanostructures could be achieved by adjusting the x-ray dose. High-performance triboelectric nanogenerators (TENGs) were fabricated using these three types of Ru-embedded g-C3N4 nanosheets within a PDMS matrix. The output performance of these TENG devices was compared with that of PDMS and g-C3N4/PDMS TENGs. The improved dielectric constant contributes to the high performance of the TENG. The synthesized Ru/g-C3N4 nanostructures are notably significant due to increased contact surface area, charge distribution density, and the formation of a metal–semiconductor heterostructure system. These characteristics lead to high charge transfer rates, improved charge transport, and a higher density of charge trapping centers within the insulating matrix. Thus, we achieved a high TENG peak power density of 4.86 W/m2 during the contact separation process. The practical applicability of the TENG is also demonstrated. Furthermore, a 47 μF capacitor could be charged to 7.8 V in ∼400 s and can be used to continuously drive low power electronic gadgets.

Assessing the global dynamics of Nipah infection under vaccination and treatment: A novel computational modeling approach

In biology and life sciences, fractal theory and fractional calculus have significant applications in simulating and understanding complex problems. In this paper, a compartmental model employing Caputo-type fractional and fractal-fractional operators is presented to analyze Nipah virus (NiV) dynamics and transmission. Initially, the model includes nine nonlinear ordinary differential equations that consider viral concentration, flying fox, and human populations simultaneously. The model is reconstructed using fractional calculus and fractal theory to better understand NiV transmission dynamics. We analyze the model’s existence and uniqueness in both contexts and instigate the equilibrium points. The clinical epidemiology of Bangladesh is used to estimate model parameters. The fractional model’s stability is examined using Ulam-Hyers and Ulam-Hyers-Rassias stabilities. Moreover, interpolation methods are used to construct computational techniques to simulate the NiV model in fractional and fractal-fractional cases. Simulations are performed to validate the stable behavior of the model for different fractal and fractional orders. The present findings will be beneficial in employing advanced computational approaches in modeling and control of NiV outbreaks.

Application of the Skanavi model to CaCu3Ti4O12 materials

In this paper, the optical and static permittivities of CaCu3Ti4O12 supercells are calculated based on the Skanavi model by decomposing the electric field of molecules into the electric field of ions. The results show that the Skanavi model's theoretical predictions are significantly more accurate than those of the Clausius–Mossotti equation and Born model and are in good agreement with the experimental data. In addition, the absence of ferroelectricity in CaCu3Ti4O12 is also revealed by investigating the changes in the structural coefficients of the effective electric field caused by the displacement of Ti4+ along the z-axis. Finally, by analyzing the contribution of TiO6 octahedra or CuO4 planar squares to the static permittivity, the main polarization unit in the structure of CaCu3Ti4O12 has been discovered. This study not only makes up for the insufficient research on the polarization mechanism of CaCu3Ti4O12 but also provides a new tool to explore the polarization mechanism of other materials.