Low Current Levels Research Articles

Microstructure evolution and mechanical properties of pulse high current diffusion bonding γ-TiAl alloy to Ti2AlNb alloy

The development of lightweight high-temperature materials and their processing methods are receiving increasing attention as the need for improved performance and energy efficiency in aero-engines increase. In this study, the γ-TiAl alloy was successfully soundly bonded to Ti2AlNb alloy by pulsed high current (PHC) diffusion welding. The effect of different high level (HL)/low level (LL) of composite pulse current on the microstructure and mechanical properties of the joints have been studied. The representative interface microstructure of PHC-950 °C TiAl/Ti2AlNb joint was γ-TiAl substrate/diffusion bonding zone/Ti2AlNb impacted zone/Ti2AlNb substrate. The diffusion bonding zone was composed of continuous equiaxed α2 grains and a small amount of B2 and O phases. The α2 phase in the diffusion bonding zone was mainly transformed from the γ phase in γ-TiAl substrate and the B2 and O phase in Ti2AlNb substrate. The composite pulse current has a significant promoting effect on the diffusion of elements and joint formation. The diffusion coefficients of DAl and DNb in hot-pressing (HP, without current effect) diffusion welding joint at interface were 2 × 10−14 m2/s and 0.92 × 10−14 m2/s, respectively. In the representative PHC-950 °C joint with HL/LL = 12/2 cycles (single cycle duration 3.3 ms), diffusion coefficients of DAl-12/2, DNb-12/2 at interface were 19.62 × 10−14 m2/s, 13.34 × 10−14 m2/s, respectively. Increasing the duration of LL would weaken the current effect. The current waveform parameters were tuned to HL/LL = 12/4 and 12/6 cycles, the diffusion coefficients of DAl-12/4, DNb-12/4DAl-12/6 and DNb-12/6 were reduced to 15.69 × 10−14 m2/s, 12.49 × 10−14 m2/s, 15.31 × 10−14 m2/s and 10.99 × 10−14 m2/s, respectively. The PHC-950 °C joints have the highest shear strength of 257.3 MPa at HL/LL = 12/2 cycles, reaching 83.3% of the base material strength. The HP-950 °C TiAl/Ti2AlNb joint has a shear strength of 230.5 MPa, reaching 74.6% of the base material strength. The shear strength of PHC-950 °C joints at HL/LL = 12/4 and 12/6 reduced to 205.3 MPa, 195.8 MPa due to insufficient element diffusion and damages the bonding quality. This work provides a strategy that contributes to reduce the thermal damage of base metal and improve the joint forming efficiency.

Multistep InAs/InAsSb staircase nBn long-wavelength infrared detectors with enhanced charge carrier transport

Gallium-free Type-II superlattices (T2SLs) have emerged as promising candidates for high-performance long-wavelength infrared (LWIR) detectors at a high operating temperature. However, InAs/InAsSb barrier detectors suffer from the limited absorption efficiency, resulting in a trade-off between quantum efficiency (QE) and dark current. Here, a nBn LWIR detector based on multistep strain-balanced InAs/InAs0.5Sb0.5 superlattice staircase configuration is proposed. With this configuration, charge carrier transport and collection can be efficiently improved via the multistep staircase valance band, leading to an increased QE from 19.3% to 20.8% at a bias of −0.20 V. As a result, the device with multistep staircase configuration exhibits an improved performance, including a low dark current density of 4.13 × 10−5 A/cm2, high responsivity of 1.23 A/W and peak detectivity reaching 3.10 × 1011 cm·Hz1/2/W. By optimizing absorbing length of the multistep staircase absorber, the peak QE can be further boosted from 20.8% to 28.4% while maintaining a low dark current level, providing an alternative strategy to improve LWIR T2SL device performance.

First demographic insights reveal high extinction risk of an endemic raptor species: the Reunion harrier

Gathering demographic information on rare species is critical to understanding their population dynamics and implementing efficient conservation measures. Using integrated models, we jointly analyzed multiple data sets, including capture–recapture, GPS tracking and nest monitoring data collected over the last 10 years, to provide the first demographic insights for one of the world's rarest raptors, the endemic Reunion harrier Circus maillardi. We estimated key demographic rates including annual survival and breeding parameters (clutch size, hatching and fledging success), and used population projection models to assess population growth rate and quasi‐extinction risk. In order to guide future conservation actions for the population, we evaluated the effects of different management scenarios that improve survival, fecundity, or both, on population growth and quasi‐extinction risk. Comparison of the estimated annual survival (juvenile and subadult survival: 0.66; adult survival: 0.71) and breeding parameters (clutch size: 2.3; hatching success: 0.45; fledging success: 0.83) with those of other harrier species suggests that adult survival and breeding parameters of Reunion harriers are low. A small data set collected 40 years ago suggests that the probability of an egg producing a fledgling was higher and has declined to the current low level. The population models project that the Reunion harrier population is declining and faces a high risk of quasi‐extinction in the next 40 years. Only management measures that simultaneously improve adult survival and fecundity could lead to a recovery of the population. These alarming results call for immediate conservation action aimed at rapidly improving the demographic rates.

A look into our future under climate change? Adaptation and migration intentions following extreme flooding in the Netherlands

Worldwide, increased flood risk from climate change prompts adaptive behavior of households in situ or through migration. Both can be sensible adaptation responses involving tradeoffs, and understanding their drivers is important for effective climate policy. However, in-situ adaptation and migration are rarely studied in combination and research on how extreme events trigger adaptive behavior in originally low-risk areas is lacking. We analyze survey data from residents affected by the extreme summer floods of 2021 in the Netherlands to contribute to fill this research gap. Our results indicate that current low levels of flood-related migration are likely to increase under higher flood risk. Undertaken in-situ adaptation may act as a barrier for further in-situ adaptation or migration behavior. Where in-situ adaptation is mostly related to cognitive factors including risk perceptions, response efficacy and self-efficacy, migration seems to be driven by flood-related emotions. Personal flood experience, mediated by worry, is strongly associated with both types of adaptive behavior. We discuss how policymakers can use these insights to guide and anticipate household adaptation behavior.

Psychological Rest in Student-Athletes: Relationships Between Sport Demands, Mental Rest, Depressive Symptoms, and Well-Being

The purpose of this study was to explore how sport demands and psychological aspects of rest are related to depressive symptoms and well-being among female college athletes. Eccles and Kazmier (2019) proposed that physical and psychological (i.e., cognitive and emotional) demands of sport negatively affect perceptions of being mentally rested, which in turn reduce well-being and elicit depressive symptoms. They also proposed that engaging in resting experiences buffers negative effects of sport demands on perceptions of being mentally rested. These model predictions were tested in this study. Female athletes (N = 179) in NCAA Division I sports provided online responses to the Demand-Induced Strain Compensation Questionnaire for Sport (Balk et al., 2018), Center for Epidemiologic Studies Depression Scale (Radloff, 1977), and Mental Health Continuum-Short Form (Keyes et al., 2008). They also completed measures of perceptions of recent resting experiences and perceived current level of mental rest that were developed for this study. Results showed that emotional demands but not physical or cognitive demands, significantly predicted current level of mental rest. Also, recent resting experiences significantly predicted current level of mental rest but did not significantly moderate the relationship between sport demands and current level of mental rest. Finally, athletes who reported a lower current level of mental rest experienced a lower level of well-being and more depressive symptoms. Monitoring of emotional demands and engaging in key psychological resting experiences might be useful for athletes as they attempt to obtain adequate mental rest and stay healthy mentally.

Breast Cancer Literacy: Status of Peripheral Health Workers in Lucknow

Background: Every woman needs to know the facts, and the fact is, when it comes to breast cancer, every woman is at risk. India accounts for 7.2% of global cancer incidence, but in terms of mortality, the country accounts for 8.3% of global mortality. India faces a high burden of cancer with the late-stage presentation being a common feature. Early detection of cancer is an important strategy for improved survival and simple cost-effective treatment. Low levels of cancer awareness are a significant factor for delay in seeking treatment by women.Objective: The present study was conducted among Peripheral Health Workers (PHWs) in the Lucknow district to assess their perception of risk factors of breast cancer, knowledge of symptoms, early detection methods, and their availability in the district. Methods: The study was conducted from September 2017 to August 2018, among 450 female PHWs working in rural and urban areas of Lucknow. A semi-structured questionnaire was used to collect information about the awareness of PHWs regarding breast cancer. The awareness score was calculated based on their responses. Data were analyzed using SPSS version 24.0 (IBM Corporation).Results: The mean score for overall knowledge of breast cancer was statistically significantly high in BHWs in comparison to ASHAs (Accredited Social Health Activist). The mean knowledge score of signs and symptoms was significantly high among BHWs (Basic Health Workers). PHWs that had undergone training for breast cancer had about 5 times higher chances of having an above-median score. Conclusion: Current low awareness levels, scarcity of resources, and screening programs call for training and refresher pieces of training for peripheral level health workers to empower them to provide preventive health education and screening at the community level. Breastfeeding counseling sessions during home visits and VHNDs could be utilized as an opportunity to create awareness about breast cancer, especially its protective effect on breast cancer.

Persistent charge storage and memory operation of top-gate transistors solely based on two-dimensional molybdenum disulfide

We fabricate top-gate transistors on the three-layer molybdenum disulfide (MoS2) with three, two, and one layers in the source and drain regions using atomic layer etching (ALE). In the presence of ALE, the device at zero gate voltage can exhibit high and low levels of drain current under the forward and reverse gate bias, respectively. The hysteresis loop on the transfer curve of transistor indicates that two distinct charge states exist in the device within a range of gate bias. A long retention time of the charge is observed. Unlike conventional semiconductor memories with transistors and capacitors, the two-dimensional (2D) material itself plays two parts in the current conduction and charge storage. The persistent charge storage and memory operation of the multilayer MoS2 transistors with thicknesses of a few atomic layer will further expand the device application of 2D materials with reduced linewidths.

First Constraints from DAMIC-M on Sub-GeV Dark-Matter Particles Interacting with Electrons.

We report constraints on sub-GeV dark matter particles interacting with electrons from the first underground operation of DAMIC-M detectors. The search is performed with an integrated exposure of 85.23gdays, and exploits the subelectron charge resolution and low level of dark current of DAMIC-M charge-coupled devices (CCDs). Dark-matter-induced ionization signals above the detector dark current are searched for in CCD pixels with charge up to 7e^{-}. With this dataset we place limits on dark matter particles of mass between 0.53 and 1000 MeV/c^{2}, excluding unexplored regions of parameter space in the mass ranges [1.6,1000] MeV/c^{2} and [1.5,15.1] MeV/c^{2} for ultralight and heavy mediator interactions, respectively.

The link between knowledge and practices in relation to herbal supplement use: for a rapid transfer of knowledge in the field of phytovigilance and pharmacovigilance health care systems

Abstract Objectives The use of health supplements (HSs) is increasing globally. It is essential to better understand health care providers’ knowledge, attitudes and practices (KAP) regarding HS use and their associated adverse events (AEs). Thus, we conducted a cross-sectional study of health care professionals in Dubai. Methods Four hundred and twenty-seven health care professionals from hospitals, clinics (public and private) and community pharmacies completed an online questionnaire that collected demographic data and enquired about their experience with HSs. Simple descriptive statistics were used to characterise participants. Based on 10 questions, a summary score was created for the overall KAP of respondents. For each question, an affirmative response scored 1 and a negative response scored 0. A total score of 10 was therefore obtainable; logistic regression was used to identify the correlates of those scores. Key findings The results showed that 18.3% (n = 78) of respondents had good KAP concerning HS, 38.9% (n = 166) had fair KAP and 42.9% (n = 183) had poor KAP. Scores were significantly higher among non-UAE nationals compared with UAE nationals (P = 0.001), among physicians and pharmacists compared with other health care practitioners (P = 0.000), and among practitioners with more than 6 years of experience compared to those with 6 years of experience or less (0.017). No association was found between KAP scores and age, marital status, employment status or educational level. Conclusion Despite the popularity and widespread use of HS among the general population in Dubai, knowledge of HSs and their possible adverse effects is limited among health professionals. This was the first study to investigate this topic in the United Arab Emirates. Further policies are needed to reduce the potential for adverse events related to HS use. Additionally, educational programs are required for health care professionals to address current low levels of knowledge.

Impact of Mg-doping on the performance and degradation of AlGaN-based UV-C LEDs

We investigate the impact of Mg-doping on the performance and degradation kinetics of AlGaN-based UV-C light-emitting diodes (LEDs). By comparing LEDs from three wafers with different nominal doping levels [Mg/(Al+Ga) ratio: 0.15%, 0.5%, and 1% in the gas phase during epitaxy] in the AlGaN:Mg electron-blocking layer (EBL), we demonstrate the following results: (i) A higher Mg-doping in the EBL results in a higher optical power at low current levels, which is ascribed to an increased hole injection efficiency. (ii) The reduction of the optical power follows a non-exponential trend, which can be reproduced by using the Hill's formula and is ascribed to the generation/activation of defects within the quantum wells. (iii) A higher Mg-doping in the EBL mitigates the degradation rate. An interpretation of the experimental data is proposed, assuming that hydrogen, which is present in and moving from the EBL, can reduce the rate of de-hydrogenation of point defects in the active region, which is responsible for degradation.

Design, Annealing, and Electric Field Effects on Proton and Gamma Irradiated MWIR HgCdTe Focal Plane Arrays

This work presents the performance degradation under irradiation of multi pixel-designs n/p mid-wavelength infrared HgCdTe focal plane arrays (FPA). Gamma and proton irradiations are conducted to single out the effects of total ionizing dose (TID) from the damage induced by displacement damage dose (DDD). The radiation-induced degradation is analysed through the current levels evolution and the random telegraph signal (RTS) phenomenon. TID damages the silicon read-out integrated circuit (ROIC), causing low current level and RTS pixels. The influence of photodiode size and electric field on TID-induced defects is investigated. The results suggest that leakage currents in the ROIC, induced by TID, are involved. DDD impacts the HgCdTe photodetection layer: the number of pixels with high dark current and RTS is increased in the FPA. The amount of DDD-induced degradation scales with the photodiode size and the applied bias. This suggests that the defects responsible for the evolution of the dark current and RTS are located in the HgCdTe depletion region. Annealing mechanisms of these effects indicate different types of DDD-induced defects.

The effects of positive leadership on quality of work and life of family doctors: The moderated role of culture.

Quality of work and life (QWL) of family doctors is highly valued in improving access and equity of healthcare; however, the current low level of QWL in many countries and regions needs to be improved urgently. This study explored the effect of positive leadership on the QWL of family doctors, as well as the moderating role of culture, via analysis of data from 473 valid questionnaires of family doctors in China as a sample using SEM, hierarchical linear regression, and a simple slope test. The empirical results show that positive leadership promoted the QWL of family doctors by improving their achievement motivation and coordinating supportive resources. In addition, our hierarchical linear regression analysis found that the interactive items of positive leadership and culture had a positive effect on achievement motivation (β (a) = 0.192), QWL (β (b) = 0.215) and supportive resources (β (c) = 0.195). Meanwhile, culture had a moderated mediating effect on the relationship between positive leadership and QWL via the achievement motivation of family doctors and supportive resources. These findings suggest that the interaction among multiple factors, including environmental factors, individual physiological features and culture, may influence the impact of positive leadership on the QWL of family doctors. The possible reasons of these findings and theoretical and practical implications are discussed in this study.

Particulate Matter Air Pollution and Long-Term Outcomes in Patients Undergoing Percutaneous Coronary Intervention

BackgroundFine particulate matter (PM2.5) promotes atherosclerosis progression and plaque vulnerability. Consequently, patients with a high atherosclerotic burden may be at especially increased risk when exposed to air pollution. ObjectivesThe purpose of this study was to examine the relationship between chronic ambient PM2.5 exposure and adverse outcomes after percutaneous coronary interventions (PCI). MethodsBaseline clinical and procedural data from U.S. veterans undergoing elective PCI (2005-2018) were linked to annual ambient PM2.5 exposure. The association between PM2.5 exposure and major adverse cardiovascular events (MACEs) (myocardial infarction, stroke, or all-cause mortality) was determined using time-varying Cox regression models. Using flexible parametric models, we also evaluated the average life months lost for specific PM2.5 levels over the 15-year period. ResultsIn the 73,425 veterans that underwent an elective PCI, the mean annual PM2.5 exposure was 8.4 ± 1.8 μg/m3 (median follow-up 6.75 years). The incidence of MACE was 28%, 48%, and 65% at 5, 10, and 15 years, respectively. In adjusted models, each 1-μg/m3 increase in PM2.5 exposure was associated with an 8.7% (95% CI: 8.4%-8.9%; P < 0.001) increase in MACE. Compared to patients exposed to 5 μg/m3, those exposed to 10 μg/m3 lost 1.1, 3.8, and 7.6 months of life at 5, 10, and 15 years of exposure, respectively. ConclusionsVeterans undergoing elective PCI are at increased risk of MACE and significant life years lost with long-term exposure to fine particulate matter pollution, even at the current low levels in the United States. These findings emphasize the need for improved air quality standards and patient interventions to better protect vulnerable populations.

Prototypical approach for an individualized standardization process in the context of intelligent construction and automation

Strategies based on an optimal balance between standardization and individualization must be implemented to successfully overcome the current low level of automation in building construction. Project-specific adaptability can be ensured by a combination of automated machine technology and digital planning tools available today. In addition to achieving economic advantages, the focus is on improving sustainability factors, which concern both material consumption and functionality and improved use of resources and energy for building production and operation. The results of research into “lightweight aerogel concrete technology” has shown that an innovative liquid material mixture with insulating properties can be successfully implemented in an automated production process. An adaptive system for standardized wall, ceiling, and floor panels was developed, which can adapt to specific functionality needs and thus address the requirements of individual building tasks while keeping economic as well as architectural factors in mind. The advanced mono-material complies with current European regulations for insulated wall structures, considering the requirements for load-bearing capacity. Due to its homogeneous insulation effect across the entire element section, the aero lightweight concrete allows for intelligent detailing and connection principles and prevents the formation of thermal bridges. The relationship between material composition, material production, construction method, and building operation is essential for a circular planning process. Robotization as a multiple fabrication technology may facilitate these parameters in one cycle. The new technology allows for the crucial transition from research to an end-to-end construction workflow that maps the entire process chain, from concept planning to design and joining principles up to fabrication and assembly.

Counting statistics of single electron transport in bilayer graphene quantum dots

We measure telegraph noise of current fluctuations in an electrostatically defined quantum dot in bilayer graphene by real-time detection of single electron tunneling with a capacitively coupled neighboring quantum dot. Suppression of the second and third cumulant (related to shot noise) in a tunable graphene quantum dot is demonstrated experimentally. With this method we demonstrate the ability to measure very low current and noise levels. Furthermore, we use this method to investigate the first spin excited state, an essential prerequisite to measure spin relaxation.

Effects of meteorological and climatological factors on extremely high residual load and possible future changes

Under high variable renewable energy (VRE) penetration, the occurrence of low VRE production, such as dark doldrums (Dunkelflaute) and wind-solar drought, can threaten a secure and continuous energy supply owing to an imbalance between electricity demand and supply. In this study, historically reconstructed long-term VRE generation and electricity demand were used to investigate the relationship between extremely high residual load (demand minus VRE output) and weather/climate in Japan. The impact of changes in the VRE's installed capacity on this relationship was also investigated using three simple future target scenarios. The results showed that the increase in installed VRE capacity causes greater daily and weekly residual load variabilities and affects the seasonality of its peaks. To study the weather patterns associated with high residual load events, self-organizing maps were applied to atmospheric circulation fields derived from atmospheric reanalysis data. The high residual load was associated with enhanced cold surge-type weather patterns during winter at the current low VRE installation level. However, under future increased VRE penetration, the weather patterns leading to high residual load will change to cloudy-windless types typically caused by a southern coastal extratropical cyclone. There is also considerable interannual variability in the frequency of high residual load events, which changed significantly with increasing VRE capacity. It is crucial to incorporate the dependence of climatic conditions into designing power systems to maintain the stability of a power system under future conditions.

Portable Multi-Channel Electrochemical Device with Good Interaction and Wireless Connection for On-Site Testing.

It is very important to rapidly test the key indicators of water in the field to fully evaluate the quality of the regional water environment. However, a high-resolution measuring device that can generate small currents for low-concentration analytes in water samples is often bulky, complex to operate, and difficult for data sharing. This work introduces a portable multi-channel electrochemical device with a small volume, good interaction, and data-sharing capabilities called PMCED. The PMCED provides an easy-to-operate graphical interactive interface to conveniently set the parameters for cyclic voltammetry or a differential pulse method performed by the four electrode channels. At the same time, the device, with a current sensitivity of 100 nA V-1, was applied to the detection of water samples with high background current and achieved a high-resolution measurement at low current levels. The PMCED uses the Narrow Band Internet of Things (NB-IoT) to meet the needs for uploading data to the cloud in remote areas. The electrochemical signal preprocessing and chemometrics models run in the cloud, and the final results are visualized on a web page, providing a remote access channel for on-site testing results.

Fertility and ageing – actuarial perspectives

Abstract Fertility, particularly at its current low level in many developed countries and high level in some less developed countries, is a key factor driving demographic, economic, and societal changes at local, national, and global levels. Population ageing due to low fertility and increasing longevity represents one of the most significant global megatrends and risks. Many countries are already experiencing population decline and rapid growth of their elderly populations, with implications for workforce size, economic development, health and pension schemes, and social security arrangements. Actuaries are well known for their work on mortality and morbidity, but they have rarely considered fertility and its proximate determinants, despite their demographic and economic effects. This paper explores key explanations and outcomes of past and projected future fertility trends, and the implications for actuaries and for political and economic decision-makers.

Dependence of reverse leakage on the edge termination process in vertical GaN power device

The trench gate metal oxide semiconductor field effect transistor (MOSFET) represents a prominent device architecture among the Gallium Nitride (GaN) based vertical devices currently investigated for the next generation of power electronics. A low leakage current level in off-state under high drain bias is of great importance for vertical transistors since it is a crucial feature for high breakdown voltage and device reliability. The off-state drain leakage originates from different sources in the vertical trench gate MOSFET. Besides the trench gate module, the leakage paths at the dry-etched sidewall of the lateral edge termination can also significantly contribute to the off-state drain-current. In this report, the influence of each relevant process step on the drain leakage current in off-state that is related to the lateral edge termination is investigated utilizing specific test structures on high-quality GaN epitaxial material which mimic the lateral edge termination of the MOSFET. Electrical characterization reveals the sensitivity of the leakage current to plasma-related processes. A termination technology is presented that results in low leakage current while including thick dielectric layers from plasma-assisted deposition as intended for fabrication of a field plate structure over the edge termination.

High responsivity n-ZnO nanorods/p-GaN heterojunction-based UV-A photodetectors

Here, we report the fabrication of ZnO/p-GaN based high responsivity ultraviolet (UV) photodetector. Hydrothermal technique has been followed to grow ZnO nanorods; where two different types of precursors (nitrate and chloride) were used for the growth of nanorods. Interestingly, it was found that the ZnO nanorods grown using nitrate precursor are less prone to defect emission in comparison to the ZnO nanorods prepared using chloride-based precursor which resulted in low dark current levels. The photo-responsivity and photo-detectivity values of the as-fabricated device were calculated to be 350 mA W−1 and 3.5 × 1011 Jones, respectively at 360 nm excitation wavelength and ∼1.79 µW cm−2 excitation intensity. The demonstration of high responsivity UV detectors (at low excitation intensity values) using ZnO nanorods/GaN can pave the way toward the development of high-performance next generation UV photodetectors.