Current Level Research Articles

Fast and robust multilevel optoelectronic memory based on van der Waals heterostructure

Optoelectronic memory (OEM) has attracted tremendous attention for its great potential to boost the storage capacity of memory chips and break through the von Neumann bottleneck in the post-Moore era. Two-dimensional (2D) van der Waals (vdW) heterostructures, formed by artificially stacking different 2D layered materials, offer tremendous possibilities in OEMs due to their extraordinary capability to integrate and process optical/electrical signals. However, the realization of 2D vdW OEMs with high writing speed and robust memory performance has long been challenging. Here, we report a 2D vdW OEM consisting of tungsten diselenide (WSe2) and hexagonal boron nitride, which functions based on the fast charge transfer dynamics at a 2D interface. The OEM demonstrates high writing speed reaching up to 50 μs, approximately one order of magnitude faster than those of other 2D OEMs. Moreover, the outstanding robustness of such OEM is demonstrated by long retention time exceeding 14 days, together with a broad temperature endurance window from 100 to 420 K. Additionally, through continuously switching laser pulse on the OEM, we achieve 17 distinct current levels (over 4-bit storage) with random access. Our findings envision 2D vdW heterostructure-based OEM as a potential platform to overcome the “memory wall” in the conventional von Neumann configuration and to promote a promising paradigm for big data storage.

On epistemic decentralising: infrastructuring knowledge beyond global North

ABSTRACT The history of science has shown that knowledge has tended to be concentrated in a few places. This required a set of institutions, practices and infrastructures that operated globally. These were articulated with broader trends, such as capitalist and colonial expansion. Subsequently, this concentration allowed these places to become centres of knowledge production, from which theories and conceptual frameworks often spread to all corners of the world. In recent years, such knowledge has been described (and denounced) as Eurocentric, colonial, patriarchal and classist by various currents, from feminism to post-colonialism. In doing so, scholars have opened up the possibility of a decentring of canons that has brought new and refreshing standpoints to the fore. However, for such questioning to transcend the level of ideas, curricula and mainstream currents, a decentralisation of institutions, practices and infrastructures is needed to re-integrate, but in different ways, the marginalised parts of science in a more egalitarian configuration. This article theoretically analyses these notions of epistemic decentring and decentralisation and presents two empirical cases to show the possibilities and challenges of such a process.

Preliminary assessment of environmental safety (ecosafety) of dextrin-based nanosponges for environmental applications

The ability to employ waste products, such as vegetable scraps, as raw materials for the synthesis of new promising adsorbing materials is at the base of the circular economy and end of waste concepts. Dextrin-based nanosponges (D_NS), both cyclodextrin (CD) and maltodextrin (MD), have shown remarkable adsorption abilities in the removal of toxic compounds from water and wastewater, thus representing a bio-based low-cost solution which is establishing itself in the market. Nevertheless, their environmental safety for either aquatic or terrestrial organisms has been overlooked, raising concern in terms of potential hazards to natural ecosystems. Here, the environmental safety (ecosafety) of six newly synthesized batches of D_NS was determined along with their full characterization by means of dynamic light scattering (DLS), thermogravimetric analysis (TGA), Fourier transformed infrared spectroscopy with attenuated total reflection (FTIR-ATR) and transmission electron microscopy (SEM). Ecotoxicity evaluation was performed using a battery of model organisms and ecotoxicity assays, such as the microalgae growth inhibition test using the freshwater Raphidocelis subcapitata and the marine diatom Dunaliella tertiolecta, regeneration assay using the freshwater cnidarian Hydra vulgaris and immobilization assay with the marine brine shrimp Artemia franciscana. Impact on seedling germination of a terrestrial plant of commercial interest, Cucurbita pepo was also investigated. Ecotoxicity data showed mild to low toxicity of the six batches, up to 1 mg/mL, in the following order: R. subcapitata >H. vulgaris >D. tertiolecta >A. franciscana > C. pepo. The only exception was represented by one batch (NS-Q+_BDE_(GLU2) which resulted highly toxic for both freshwater species, R. subcapitata and H. vulgaris. Those criticalities were solved with the synthesis of a fresh new batch and were hence attributed to the single synthesis and not to the specific D_NS formulation. No effect on germination of pumpkin but rather more a stimulative effect was observed. To our knowledge this is the first evaluation of the environmental safety of D_ NS. As such we emphasize that current formulations and exposure levels in the range of mg/mL do not harm aquatic and terrestrial species thus representing an ecosafe solution also for environmental applications.

Automated experimental design of safe rampdowns via probabilistic machine learning

Typically the rampdown phase of a shot consists of a decrease in current and injected power and optionally a change in shape, but there is considerable flexibility in the rate, sequencing, and duration of these changes. On the next generation of tokamaks it is essential that this is done safely as the device could be damaged by the stored thermal and electromagnetic energy present in the plasma. This works presents a procedure for automatically choosing experimental rampdown designs to rapidly converge to an effective rampdown trajectory. This procedure uses probabilistic machine learning methods paired with acquisition functions taken from Bayesian optimization. In a set of 2022 experiments at DIII-D, the rampdown designs produced by our method maintained plasma control down to substantially lower current and energy levels than are typically observed. The actions predicted by the model significantly improved as the model was able to explore over the course of the experimental campaign.

Menopause and the role of physical activity - The views and knowledge of women aged 40-65.

Menopause marks the end of female reproductive capacity. It is defined as the point after cessation of the menstrual cycle for 12months (Nursat et al., 2008). Awareness about menopause has increased over the last decade, yet studies have shown that women still lack knowledge regarding the subject. Likewise, awareness of women between the age of 40-65 on the potential role of physical activity prior to and during menopause in women is unclear. Women (n = 162) aged 40-65years completed a survey rating their knowledge, answered fact-based questions and reported their experiences of menopause. Their levels of, and beliefs on, the role physical activity on symptoms and menopause associated disease risk were also collected. Women reported their confidence in their current knowledge level at 67% reflecting 37% higher rating than an estimate of their knowledge 10years ago. Their factual knowledge score was 56%. Knowledge was primarily gained through friends and family and almost half (46%) had not spoken to a healthcare professional. Frustration was expressed with lack of knowledge and support of healthcare and others. Women using HRT (44%) had mixed attitudes towards its role. A high proportion were active and felt that physical activity can help manage symptoms and impact long-term health consequences of menopause. Menopause education strategies for women, healthcare professionals and others need to be improved. Lack of education may be causing women to struggle and feel negatively towards this life stage. Physical activity was viewed positively for the symptoms and a treatment during menopause and long-term health.

Constructing blocked-nanolayer by surface charge inversion over anion exchange membrane for improved antifouling performance

Anion exchange membranes (AEMs) with excellent antifouling property are essential for treating highly saline organic wastewater through electrodialysis (ED). In this study, we proposed a strategy of surface charge inversion to construct a blocked- nanolayer based on in-suit dopamine (DA) deposition followed by grafting negative-charged 2-acrylamide-2-methylpropanesulfonic acid (AMPS) for promoting the antifouling performance of AEM. It's indicated that the surface hydrophilicity and negative charge density was gradually enhanced with the increase of AMPS grafting density without sacrifices of ion exchange capability, swelling ratio and desalination performance. In the simulated fouling experiments, the optimal AEM-AMPS-105 membrane exhibited excellent antifouling property due to the improved surface hydrophilicity and high electrostatic repulsion against organic matter. It's highlighted that the transmembrane voltage of modified membrane after operating 200 min was reduced from 7.12 V to 4.85 V with a significant decrease of energy consumption by 55.1 % while maintaining a high current efficiency level of 85.5 %. Moreover, the modified membrane performed significantly enhanced salt/contaminant selectivity and high stability in dye wastewater treatment. We anticipated that the construction of charge-blocked nanolayer by surface charge inversion offered a practical method for improving the organic fouling-resistance of AEMs.

The role of repowering India’s ageing wind farms in achieving net-zero ambitions

India’s ambitious net-zero climate goals include plans for a four-fold increase in current levels of wind energy generation by 2030. Many existing wind farms in India occupy sites with the best wind resources nationally but use older, smaller turbines that achieve lower capacity factors compared to modern turbine designs. A strategy of replacing existing wind turbines with state-of-the-art models (termed repowering) could boost capacity factors and ensure maximal use of available wind resources. However, a nationwide assessment of the potential wind generation increases resulting from repowering is currently lacking for India. Here, we present the first validated synthetic wind generation dataset for India based on reanalysis data and show that full repowering of the existing fleet of wind turbines could boost capacity factors by 82% nationwide (from 0.19 to 0.35). Our assessment of attainable capacity factors under full repowering exceeds equivalent estimates within the National Electricity Plan of India and national decarbonisation pathways compiled by the Intergovernmental Panel on Climate Change (IPCC), suggesting less total installed capacity is required to achieve specific generation outcomes than previously estimated. Ongoing technological progress, leading to increased turbine dimensions, will drive capacity factors beyond the levels estimated here, which could further add to the generation benefits of repowering. Yet, despite the higher average output from a repowered fleet of wind generators, substantial variability in generation across timescales persists, highlighting the increasing need for power system flexibility within a decarbonised energy system.

‘Greening’ an Oil Exporting Country: A Hydrogen, Wind and Gas Turbine Case Study

In the quest for achieving decarbonisation, it is essential for different sectors of the economy to collaborate and invest significantly. This study presents an innovative approach that merges technological insights with philosophical considerations at a national scale, with the intention of shaping the national policy and practice. The aim of this research is to assist in formulating decarbonisation strategies for intricate economies. Libya, a major oil exporter that can diversify its energy revenue sources, is used as the case study. However, the principles can be applied to develop decarbonisation strategies across the globe. The decarbonisation framework evaluated in this study encompasses wind-based renewable electricity, hydrogen, and gas turbine combined cycles. A comprehensive set of both official and unofficial national data was assembled, integrated, and analysed to conduct this study. The developed analytical model considers a variety of factors, including consumption in different sectors, geographical data, weather patterns, wind potential, and consumption trends, amongst others. When gaps and inconsistencies were encountered, reasonable assumptions and projections were used to bridge them. This model is seen as a valuable foundation for developing replacement scenarios that can realistically guide production and user engagement towards decarbonisation. The aim of this model is to maintain the advantages of the current energy consumption level, assuming a 2% growth rate, and to assess changes in energy consumption in a fully green economy. While some level of speculation is present in the results, important qualitative and quantitative insights emerge, with the key takeaway being the use of hydrogen and the anticipated considerable increase in electricity demand. Two scenarios were evaluated: achieving energy self-sufficiency and replacing current oil exports with hydrogen exports on an energy content basis. This study offers, for the first time, a quantitative perspective on the wind-based infrastructure needs resulting from the evaluation of the two scenarios. In the first scenario, energy requirements were based on replacing fossil fuels with renewable sources. In contrast, the second scenario included maintaining energy exports at levels like the past, substituting oil with hydrogen. The findings clearly demonstrate that this transition will demand great changes and substantial investments. The primary requirements identified are 20,529 or 34,199 km2 of land for wind turbine installations (for self-sufficiency and exports), and 44 single-shaft 600 MW combined-cycle hydrogen-fired gas turbines. This foundational analysis represents the commencement of the research, investment, and political agenda regarding the journey to achieving decarbonisation for a country.

Threshold nonlinearities and the democracy-growth nexus

Summary This paper investigates the relationship between democracy and economic growth in the context of a linear index threshold regression model. We first introduce the baseline model with endogeneity and propose a two-step smoothed generalised method of moments estimation method. We establish the consistency and derive the asymptotic distributions of the proposed estimators. We then extend the approach to a dynamic panel context and employ the model to explore the impact of democratisation on economic growth. Our findings reveal that democratisation’s impact on growth is nonlinear and depends on the country’s current institutional quality level. Furthermore, democracy’s impact on economic growth is more pronounced in countries with higher education levels than others, suggesting that education also plays a crucial role in enhancing the positive effects of democracy. Our proposed estimator can be used in other situations that require the use of more than one threshold variable. In these cases, our hybrid estimator has less stringent data requirements than an alternative model where the thresholds would enter separately, especially when the threshold variables are correlated.

Single-grain K-feldspar luminescence dating of the late Quaternary rapid decline in the largest Lake over the Tibetan Plateau

Well-preserved shorelines, situated at elevations ranging from tens to hundreds of meters above the current lake levels, are commonly found in the lake basins across the Tibetan Plateau (TP). These shorelines offer a valuable opportunity to reconstruct past hydroclimate changes, contingent upon precise age determination of palaeoshorelines. While single-aliquot luminescence methods have been extensively employed for dating palaeoshoreline sediments, both quartz and K-feldspar fractions, the application of single-grain (SG) dating techniques has been relatively limited, particularly in the case of water-lain sediments where partial bleaching must be taken into account. In this study, we applied the single-grain K-feldspar dating technique using the post-IR IRSL (pIRIR) protocol to a selection of palaeoshorelines from Qinghai Lake, the largest lake on the TP. Our primary objectives were to investigate the behavior of single-grain K-feldspar pIRIR signals and to establish precise timing for late Quaternary lake level fluctuations based on SG data. Our findings reveal a clear correlation between the De (equivalent dose) values of single grains and their fading rates. The higher fading rates observed in dim grains constitute the primary reason for the underestimation of De values. However, it appears that the internal K content of the grains cannot explain the relationship between fading rates and grain brightness. Finally, we utilized the 30% brightest grains for SG pIRIR De determinations, allowing us to reconstruct the historical water level fluctuations of Qinghai Lake. Our results indicate a pronounced decline in lake levels during the last interglacial-glacial transition, approximately 90,000 to 75,000 years ago. This decline can be attributed to the response of regional hydroclimate patterns to global environmental changes.

One (photon), two(-dimensional crystals), a lot (of potential): a quick snapshot of a rapidly evolving field

Abstract We present a concise overview of the state of affairs in the development of single-photon sources based on two-dimensional (2D) crystals, focusing in particular on transition-metal dichalcogenides and hexagonal boron nitride. We briefly discuss the current level of advancement (i) in our understanding of the microscopic origin of the quantum emitters (QEs) identified in these two material systems, and (ii) in the characterisation of the optical properties of these emitters; then, we survey the main methods developed to enable the dynamic control of the QEs’ emission energy. Finally, we summarise the main results stemming from the coupling of QEs embedded in 2D materials with photonic and plasmonic structures.

Solidarity Economy and Cooperation in Academic Discourse and Public Practice

The authors analyze the current level of study of the problem of formation and development of solidarity economy and the role of cooperation in its structure, focus on the system-forming qualities of solidarity economy: democracy, immanence of ecologically sustainable development, justice and social mutual assistance, achievement of public benefit.

Value-based healthcare implementation in the Netherlands: a quantitative analysis of multidisciplinary team performance.

Many hospitals worldwide have set up multidisciplinary Value Improvement (VI) teams that use the Value-Based Health Care (VBHC) theory to improve patient value. However, it remains unclear what the level of VBHC implementation is within these teams. We therefore studied the current level of VBHC implementation in VI teams. A questionnaire was developed based on the strategic agenda for value transformation and real-world experiences with VBHC implementation. The questionnaire consisted of 21 questions, mapped to seven domains, and was sent out to 25 multidisciplinary VI teams. Median scores for individual questions (scale = 1-5) and average scores per domain were calculated. One hundred forty VI team members completed the questionnaire. The overall average score is 3.49. The 'culture and responsibility' domain obtained the highest average score (µ = 4.11). The domain 'measure and improve outcomes' and the domain 'multidisciplinary team' obtained average scores that are slightly higher than the overall average (µ = 3.78 and µ = 3.76 respectively), and the domains 'strategy and organizational policy,' 'collaboration and sharing,' and 'IT and data' scored a little below the overall average (µ = 3.41, µ = 3.32, and µ = 3.29 respectively). The domain 'costs and reimbursement' obtained the lowest average score (µ = 2.42) of all domains, indicating that the implementation of this particular aspect of VBHC remains lagging behind. Our results indicate activity in each of the questionnaire domains. To bring VBHC implementation to the next level, more attention should be given to the financial aspects. Our questionnaire can be used in future studies to identify improvements or differences within VI teams.

Weld-free mounting of lamellae for electrical biasing operando TEM

Recent advances in microelectromechanical systems (MEMS)-based substrates and sample holders for in situ transmission electron microscopy (TEM) are currently enabling exciting new opportunities for the nanoscale investigation of materials and devices. The ability to perform electrical testing while simultaneously capturing the wide spectrum of signals detectable in a TEM, including structural, chemical, and even electronic contrast, represents a significant milestone in the realm of nanoelectronics. In situ studies hold particular promise for the development of Metal-Insulator-Metal (MIM) devices for use in next-generation computing. However, achieving successful device operation in the TEM typically necessitates meticulous sample preparation involving focused ion beam (FIB) systems. Conducting contamination introduced during the FIB thinning process and subsequent attachment of the sample onto a MEMS-based chip remains a formidable challenge. This article delineates an improved FIB-based sample preparation methodology that results in good electrical connectivity and operational functionality across various MIM devices. To exemplify the efficacy of the sample preparation technique, we demonstrate preparation of a clean cross section extracted from a Au/Pt/BaSrTiO3/SrMoO3 tunable capacitor (varactor). The FIB-prepared TEM lamella mounted on a MEMS-based chip showed current levels in the tens of picoamperes range at 0.1 V. Furthermore, the electric response and current density of the TEM lamella device closely align with macro-scale devices. These samples exhibit comparable current densities to their macro-sized counterparts thus validating the sample preparation process and confirming device connectivity. The simultaneous operation and TEM characterization of electronic devices enabled by this process enables direct correlation between device structure and function, which could prove pivotal in the development of new MIM systems.

God is not back: the long-term effects of Soviet secularism

ABSTRACT How effective was Soviet secularization and what is its long-term legacy? This paper investigates the lasting effects of Khrushchev’s Virgin Lands Campaign (1950s) on the current level of Orthodox religiosity in eastern Russia using an original district (raion)-level dataset that combines historical and contemporary evidence. By employing various matching techniques and an instrumental variable approach, I identify significant effects of the Virgin Lands cultivation on diminishing the role of religion even 60 years later. Moreover, I demonstrate that the resettlement of Communist Youth League (Komsomol) members and the destruction of traditional social relations may have worked as key mechanisms that contributed to the legacy effects. This study offers one of the first micro-level empirical investigations into the impact of Communism-driven secularization, and contributes to the emerging inquiry into the historical legacy of communism.

A comparative study on the moderating impact of renewable energy and innovation on environmental quality

AbstractThis study explores the complex interactions between renewable energy production, innovation, economic growth, institutional quality, economic globalization, and CO2 emissions in OECD countries and emerging economies from 1996 to 2021. Results from Driscoll–Kraay standard error and feasible generalized least square reveal distinct trends: renewable energy production leads to increased CO2 emissions in emerging economies but significantly reduces emissions in OECD countries. Besides, residential and non‐residential innovation, along with total innovation, show similar effects. Notably, technology‐moderated renewable energy production effectively lowers CO2 emissions in both country groups. Similarly, economic growth enhances environmental quality in both sets of countries. However, institutional quality needs improvement in emerging economies, while current levels suffice in OECD nations to maintain environmental quality. Moreover, the study emphasizes the importance of considering globalization's impact on CO2 emissions, advocating for international agreements to leverage globalization for environmental benefits. Overall, these findings provide valuable insights for shaping renewable energy policies, fostering innovation, promoting economic growth, enhancing institutional quality, and harnessing globalization efforts to reduce CO2 emissions and enhance environmental quality.

Objective Detection of Trust in Automated Urban Air Mobility: A Deep Learning-Based ERP Analysis

Urban Air Mobility (UAM) has emerged in response to increasing traffic demands. As UAM involves commercial flights in complex urban areas, well-established automation technologies are critical to ensure a safe, accessible, and reliable flight. However, the current level of acceptance of automation is insufficient. Therefore, this study sought to objectively detect the degree of human trust toward UAM automation. Electroencephalography (EEG) signals, specifically Event-Related Potentials (ERP), were employed to analyze and detect operators’ trust towards automated UAM, providing insights into cognitive processes related to trust. A two-dimensional convolutional neural network integrated with an attention mechanism (2D-ACNN) was also established to enable the end-to-end detection of trust through EEG signals. The results revealed that our proposed 2D-ACNN outperformed other state-of-the-art methods. This work contributes to enhancing the trustworthiness and popularity of UAM automation, which is essential for the widespread adoption and advances in the UAM domain.

Universal screening and treatment towards the elimination of chronic hepatitis C in China: an economic evaluation

ObjectivesChina has the largest number of hepatitis C virus (HCV) infection in the world, but current levels of diagnosis and treatment are low. The objective of this study was to assess the cost-effectiveness of various universal HCV screening and treatment strategies in China and inform decisions on health policy. Study designA cost-effectiveness analytical study. MethodsWe developed a Markov model to investigate cost-effectiveness of different HCV screening and treatment strategies in China. We simulated several screening scenarios for Chinese people aged 18–70 years. We estimated incremental cost-effectiveness ratios (ICERs) of different intervention scenarios compared with status quo. ResultsExpanded HCV screening and treatment strategy with prioritisation for high-risk groups (Scenario S5) was the most cost-effective strategy (ICER: USD $11,667.71/quality-adjusted life-year [QALY] gained), which resulted in great reduction in HCV-related diseases and deaths, with a 67.11% reduction in cases of chronic HCV. Universal HCV screening and treatment implementation remains a cost-effective strategy when delayed until 2025 (ICER: USD $17,093.69/QALY), yet the delayed strategy is less effective in reducing HCV-related deaths. ConclusionsExpanded HCV screening and treatment strategy with prioritisation for high-risk groups is the most cost-effective strategy and has lead to a significant reduction in both HCV morbidity and mortality in China, which would essentially eliminate HCV as a public threat.

Academic Self-Efficacy and Substance Use Among Undergraduate Students of Nnamdi Azikiwe University, Awka, Anambra State

Students’ academic self-efficacy significantly affects their academic achievement and health. Students with low sense of academic self-efficacy choose to avoid challenges and academic stress, thereby resorting to substance use as the best way to relieve academic stress. This is a cross-sectional study conducted between July 2023 and October 2023 to determine the prevalence of substance use and influence of academic self-efficacy and certain socio-demographic variables on substance use among undergraduate students of Nnamdi Azikiwe University, Awka. Consecutive sampling technique was used to select 373 respondents from the four campuses and pre-tested questionnaire on substance use (QSU) and General self-efficacy scale (GSE) were used to collect data. Data were analyzed using SPSS version 25 and then summarized in tables of frequency and percentages. Mann-Whitney U test was used to determine differences in academic self -efficacy between substance and non-substance users. Chi-square was used to test the influence of age, gender, academic level of study, location of campus on substance use and binary logistic regression was used to determine the predictor effect of gender and age on substance use. Results showed high prevalence of substance use (46.5%). Alcohol was the most commonly used substance (42.2%). Substance users have low mean score (29.08) of academic self -efficacy compared to non-substance users (32.40) and this is significant (p = 0.014). Age, gender, current level of study and location of campus showed significant influence to substance use (P<0.001). Supportive academic environments which can promote students’ self-efficacy should be created by lecturers and university management.

Role of material properties on metal transfer dynamics in gas metal arc welding

In the gas metal arc welding (GMAW) process, metal transfer dynamics, influenced by wire material properties such as electrical conductivity and surface tension, serve as key sources of mass and heat for metal deposition on substrates. To elucidate the role of these material properties on metal transfer dynamics from a driving force perspective, this study examined molten droplet elongation across five distinct wires: Al, Cu, Fe, Ni, and Ti. Additionally, a unique non-transferred arc welding setup equipped with a consumable wire anode and two tungsten cathodes was introduced, allowing for observations at minimized arc lengths and preventing current concentration in molten droplets. For Al and Cu wires, while only projected-spray transfer was observed under sufficient arc length conditions, a shift to minimized arc length resulted in significant droplet elongation and a transition to streaming-spray transfer. This contrast emphasized the impact of high electrical conductivity in reducing the internal gradient of electromagnetic pressure and inhibiting the occurrence of streaming-spray transfer. Further substantiating this mechanism, Fe, Ni, and Ti wires revealed that higher electrical conductivity corresponded to an increased transition current to streaming-spray transfer. Additionally, surface tension played a crucial role in the formation of molten droplets and ensured transfer stability, with its influence varying at different current levels. These insights contribute to our comprehensive understanding of arc plasma and molten metal interactions. Our study proposes material-specific strategies to optimize metal transfer dynamics, leading to enhanced control over weld bead formation and overall mechanical properties of welded joints in the GMAW.