Mass Turnover Research Articles

Controllable Detachment of Organic Ligands on Ultrathin Amorphous Nanosheets Tailors the Electron-Aggregation for Accelerated pH-Universal Hydrogen Reaction.

Tailoring the local environment of catalyst surface has emerged as an effective strategy to enhance the reaction kinetics involving multiple intermediates. For hydrogen evolution reactions (HER), the driving factors for hydrogen aggregation and migration which are poorly understood in depth affects the reaction kinetics especially over a wide pH range. Inspired by the selectivity of the catalyst surface microenvironment for intermediates, an interfacial electrocatalyst composed of Ru ultrafine nanocatalysts anchored onto monolayer amorphous (a-WCoNiO) nanosheets with electron-rich microenvironment induced by an organic oleylamine ligand is designed to realize high-performance pH-universal HER. This Ru/a-WCoNiO possesses impressively low overpotentials of -13, -14, and -14mV at 10mA cm-2 in 0.5m H2SO4, 1m KOH and 1m PBS, respectively, ranking among the best HER catalysts reported to date. Benefiting from the electron-rich microenvironment, the Ru/a-WCoNiO exhibits record-high turnover frequency (TOF) and mass activity (MA), which is more than 47.9 times higher than that of commercial 20% Pt/C. Importantly, other precious metals are loaded on a-WCoNiO and enhancing their mass current density for pH-universal HER. It is believed that this developed approach of organic modifiers tailored local microenvironment has practical significance and advantages for designing other high-performance catalysts.

Tuning Hydrogen Binding on Ru Sites by Ni Alloying on MoO2 Enables Efficient Alkaline Hydrogen Evolution for Anion Exchange Membrane Water Electrolysis.

Ruthenium (Ru)-based electrocatalysts have shown promise for anion exchange membrane water electrolysis (AEMWE) due to their ability to facilitate water dissociation in the hydrogen evolution reaction (HER). However, their performance is limited by strong hydrogen binding, which hinders hydrogen desorption and water re-adsorption. This study reports the development of RuNi nanoalloys supported on MoO2, which optimize the hydrogen binding strength at Ru sites through modulation by adjacent Ni atoms. Theoretical simulations reveal that substituting Ni atoms for adjacent Ru atoms reduces the high hydrogen adsorption Gibbs free energy on Ru while maintaining a low energy barrier for water dissociation. As a result, the RuNi/MoO₂ catalyst shows excellent HER performance with a low overpotential of 51mV at a current density of 100mAcm⁻2, outperforming commercial Pt/C. Furthermore, RuNi/MoO₂ demonstrates high turnover frequency (7.06s-1), mass activity (13.4Amg-1), and price activity (1030.77Adollar-1). In an AEMWE cell, RuNi/MoO₂ as the cathode catalyst achieves a current density of 1Acm-2 at 60°C with just 1.7V using 1m KOH. This work highlights the potential of RuNi/MoO₂ for ultra-high mass activity in efficient AEMWE applications.

Application of the COSIAM method for muscle protein turnover and skeletal muscle mass in young females: A comparison of methods for body composition assessment

Evaluating rates of myofibrillar protein synthesis (MyoPS) and breakdown (MyoPB) is essential for understanding muscle protein turnover, which underpins changes in skeletal muscle mass (SMM). For the first time, we applied the Combined Oral Stable Isotope Assessment of Muscle (COSIAM) method in a group of young, healthy females. This protocol allows simultaneous measurement of MyoPS, MyoPB, and SMM using deuterium oxide, D3-3-methylhistidine, and methyl-D3-creatine (D3-Cr), respectively. Additionally, we evaluated the agreement between D3-Cr-derived SMM and several SMM proxies, to determine the bias of each method relative to D3-Cr-derived SMM. Using the three-day COSIAM protocol, we assessed MyoPS, MyoPB and SMM in a cohort of twenty-one healthy, females (age: 22 ± 2 years, BMI: 24.7 ± 3.5 kg/m2). Bioelectrical impedance (BIA), DXA and BodPod were used to estimate SMM, lean mass (LM), and fat-free mass (FFM), respectively. BIA, DXA, and ultrasound (US) were also used to assess appendicular lean mass (ALM), while US was additionally used to measure vastus lateralis cross-sectional area. Rates of MyoPS (1.97 ± 0.29 %/d) and MyoPB (rate constant [k] of 0.045) aligned with previous literature. DXA-derived LM, BIA-derived SMM, and BodPod-derived FFM overestimated D3-Cr-derived SMM by 20.1 ± 3.6 kg, 4.0 ± 2.2 kg, and 22.8 ± 4.1 kg, respectively. Conversely, DXA, BIA, and US-derived ALM uniformly underestimated D3-Cr-derived SMM by approximately 2.50 kg. Our findings suggest that the COSIAM method is a viable approach for assessing muscle protein turnover in young, healthy females, and provides reference values for future research. Additionally, this study reveals the degree to which commonly used proxy measures of SMM, overestimate or underestimate D3-Cr-derived SMM. These insights support the application of COSIAM in future female-focused research and advance our understanding of biases in body composition assessments for young females.

Optimal crawling: From mechanical to chemical actuation.

Taking inspiration from the crawling motion of biological cells on a substrate, we consider a physical model of self-propulsion where the spatiotemporal driving can involve both a mechanical actuation by active force couples and a chemical actuation through controlled mass turnover. When the material turnover is slow and the mechanical driving dominates, we find that the highest velocity at a given energetic cost is reached when the actuation takes the form of an active force configuration propagating as a traveling wave. As the rate of material turnover increases, and the chemical driving starts to dominate the mechanical one, such a peristalsis-type control progressively loses its efficacy, yielding to a standing-wave-type driving which involves an interplay between the mechanical and chemical actuation. Our analysis suggests a paradigm for the optimal design of crawling biomimetic robots where the conventional purely mechanical driving through distributed force actuators is complemented by a distributed chemical control of the material remodeling inside the force-transmitting machinery.

(Invited) Boosting Oxygen Evolution Reaction by Stabilization of Ultrasmall Ruthenium Nanoclusters on Thiol-Functionalized Metal-Organic Framework

Rational designing of efficient nanocatalysts plays a crucial role in catalyzing kinetically sluggish reactions like Oxygen Evolution Reaction (OER). However, the uncontrolled nucleation and growth of nanostructures poses major effectiveness and economic challenges in the implementation and commercialization of noble metal-based electrocatalysts. Functionalized Metal-Organic Frameworks (MOFs) have the properties to stabilize such unstable nanoclusters in extremely small sizes by compensating for their high surface energy and Ostwald’s ripening effect. Here, we have reported the synthesis of ultrasmall Ruthenium nanoclusters stabilized through thiol-functionalized Ni-MOF (Ru@Ni-M-SH). The stabilization of ruthenium under reduced conditions on the MOF surface was facilitated by the lower electronegativity and increased orbital overlapping effect of sulfur, resulting in an average size of 1.5 nm. A perturbed electronic structure confirmed from XPS as well as XAS studies revealed the fundamental understanding behind electronic redistribution. Backed with such a favorable electronic structure, the catalytic OER activity for Ru@Ni-M-SH outperformed the state-of-the-art RuO2 with three times higher current density (242 mA/cm2) and 143 mV reduced overpotential. With 95% Faradaic efficiency, the Turnover Frequency (TOF) and Mass activity of Ru@Ni-M-SH were found to be several orders higher as compared to RuO2. Unlike other Ru-based catalysts, Ru@Ni-M-SH showed extremely high stability with over 24 h of chronoamperometry study. With thorough in-situ analysis providing information regarding catalytically active sites and intermediates, Ru@Ni-M-SH established itself as an economically sustainable OER electrocatalyst.

Social support, psychological capital, multidimensional job burnout, and turnover intention of primary medical staff: a path analysis drawing on conservation of resources theory

BackgroundJob burnout is a prevalent and emerging challenge in the primary medical system, causing mass turnover, especially of primary medical staff. Little attention has been paid to the different dimensions of job burnout (emotional exhaustion, personality disintegration, and reduced sense of achievement), which may hinder efforts to tackle high turnover intention among primary medical staff. From the perspective of conservation of resources theory, social support and psychological capital are basic resources with potential to diminish job burnout and thus lower turnover intention. However, there is insufficient research evidence on the relationships between social support, psychological capital, and the three dimensions of job burnout within the primary medical system.ObjectivesFocusing on primary medical staff, this study conducts a path analysis to examine the correlations between two types of resources (social support and psychological capital) and the three dimensions of job burnout, and to test the impact of the latter on turnover intention. Based on the results, effective management strategies to improve the work stability of primary medical staff are proposed.MethodsMulti-stage cluster random sampling was used to select participants in Anhui Province, China. Data were collected using a self-administered questionnaire containing measures of the main variables and demographic questions. In total, 1132 valid questionnaires were returned by primary medical staff. Structural equation modeling was used for path analysis of the data.ResultsSocial support was negatively associated with emotional exhaustion (β = − 0.088, P = 0.020), personality disintegration (β = − 0.235, P < 0.001), and reduced sense of achievement (β = − 0.075, P = 0.040). Moreover, psychological capital was negatively associated with emotional exhaustion (β = − 0.079, P = 0.030), personality disintegration (β = − 0.156, P < 0.001), and reduced sense of achievement (β = − 0.432, P < 0.001). All three dimensions of job burnout positively affected turnover intention (emotional exhaustion: β = 0.246, P < 0.001; personality disintegration: β = 0.076, P = 0.040; reduced sense of achievement: β = 0.119, P = 0.001).ConclusionsThe results highlight the importance of social support and psychological capital for diminishing the three dimensions of job burnout for primary medical staff and, in turn, lowering their turnover intention. Accordingly, to alleviate job burnout and improve staff retention, material and psychological supports from leaders, colleagues, family, relatives, and friends are essential, as are measures to improve the psychological energy of primary medical staff.

Chromium-Induced High Covalent Co-O Bonds for Efficient Anodic Catalysts in PEM Electrolyzer.

The proton exchange membrane water electrolyzer (PEMWE), crucial for green hydrogen production, is challenged by the scarcity and high cost of iridium-based materials. Cobalt oxides, as ideal electrocatalysts for oxygen evolution reaction (OER), have not been extensively applied in PEMWE, due to extremely high voltage and poor stability at large current density, caused by complicated structural variations of cobalt compounds during the OER process. Thus, the authors sought to introduce chromium into a cobalt spinel (Co3O4) catalyst to regulate the electronic structure of cobalt, exhibiting a higher oxidation state and increased Co-O covalency with a stable structure. In-depth operando characterizations and theoretical calculations revealed that the activated Co-O covalency and adaptable redox behavior are crucial for facilitating its OER activity. Both turnover frequency and mass activity of Cr-doped Co3O4 (CoCr) at 1.67V (vs RHE) increased by over eight times than those of as-synthesized Co3O4. The obtained CoCr catalyst achieved 1500mA cm-2 at 2.17V and exhibited notable durability over extended operation periods - over 100h at 500 mA cm-2 and 500h at 100 mA cm-2, demonstrating promising application in the PEMWE industry.

Assessing energy fluxes and carbon use in soil as controlled by microbial activity - A thermodynamic perspective A perspective paper

Soil organic matter (SOM) plays a central role for both the C cycle and soil functions. Plants provide the input and heterotrophic (micro)organisms are essential for the turnover. Microbial metabolism links matter and energy fluxes and generates the highest energy turnover dynamics in SOM because the organisms need both energy and matter for maintenance and growth. In this perspectives paper, we evaluate the knowledge on thermodynamic approaches potentially applicable to study the turnover of organic matter in the soil system. Thermodynamics is essential for understanding organic matter turnover in soil as turnover and storage are controlled by the energy supply to, and consumption by, microbes. Instead of just comparing the heat of combustion of compounds without considering microbial anabolism, we need to apply conventional thermodynamic state variables that can be either estimated using established thermodynamic equations, or measured empirically in soil. In particular, we can follow and quantify overall changes of enthalpies by calorimetry. Here, we suggest to apply a thermodynamic concept with the related experimental approaches of calo(respiro)metry and turnover mass balances including biomass formation. This enables us to better interpret and understand the highly variable carbon use efficiency (CUE) in a multi-substrate system such as soil and to relate this to energy use efficiency (EUE). Combining the experimental measurements of the thermodynamic state variables with mass turnover data allow prediction of whether compounds can be metabolized with energy delivery to microorganisms, or be thermodynamically stabilized under the respective redox and electron acceptor conditions. Energy balancing shows how much energy is actually used and retained in the soil, how much is emitted as heat, and how much may be stabilized due to endergonic turnover reactions. Thermodynamic stabilization should therefore be considered as basic stabilization process for organic compounds in soil.

Recent Mass Balance Anomalies on the Djankuat Glacier, Northern Caucasus

A 54-year-long series of continuous instrumental measurements of mass balance and its main components has already been accumulated at the Djankuat Glacier, which is representative of the Caucasus and the most studied glacier in Russia. The anomalies of these indicators in 2017/2018–2020/2021 were evaluated against an analysis of meteorological reasons that predetermined them. Each of the four balance years under consideration represents a particular anomaly of varying severity. As for conditions of mass income, three years saw accumulation higher than average, and in one year (2018/2019) it approached the norm. As for summer ablation conditions, similarly, in one season (2019) the melting differed from the average only slightly, but in the other three it was much higher. Consequently, in one year (2020/2021) the state of the glacier was close to normal, in another (2017/2018) the budget situation was much more favorable for Djankuat, and in the other two the final losses significantly exceeded the average annual mass loss rate. At the same time, in 2019/2020, an absolute record of ablation since the beginning of monitoring in 1967/1968 was recorded (4360 mm w.e.). Nevertheless, although negative mass balance values continue to be recorded annually, signs of an inevitable slowdown in the rate of glacier degradation in the Caucasus have appeared in the last 4-year-long period: the continued growth of winter snow accumulation overlaps the ongoing intensification of summer melting. The growth of debris cover in terms of area and thickness also affects this mass loss slowdown to some extent. This inhibits ablation, exerting a heat-insulating effect. Because of this, the congruence of mass balance parameters vs. altitude curves is distorted. Also, a tendency toward increasing annual glacier mass turnover was revealed for the last half-century. This fact gradually increases the energy of glaciation and indirectly indicates a weakening of continentality in the climate of the Caucasian highlands.

Vacancy Defects Inductive Effect of Asymmetrically Coordinated Single-Atom Fe─N3 S1 Active Sites for Robust Electrocatalytic Oxygen Reduction with High Turnover Frequency and Mass Activity.

The development of facile, efficient synthesis method to construct low-cost and high-performance single-atom catalysts (SACs) for oxygen reduction reaction (ORR) is extremely important, yet still challenging. Herein, an atomically dispersed N, S co-doped carbon with abundant vacancy defects (NSC-vd) anchored Fe single atoms (SAs) is reported and a vacancy defects inductive effect is proposed for promoting electrocatalytic ORR. The optimized catalyst featured of stable Fe─N3 S1 active sites exhibits excellent ORR activity with high turnover frequency and mass activity. In situ Raman, attenuated total reflectance surface enhanced infrared absorption spectroscopy reveal the Fe─N3 S1 active sites exhibit different kinetic mechanisms in acidic and alkaline solutions. Operando X-ray absorption spectrareveal the ORR activity of Fe SAs/NSC-vd catalyst in different electrolyte is closely related to the coordination structure. Theoretical calculation reveals the upshifted d band center of Fe─N3 S1 active sites facilitates the adsorption of O2 and accelerates the kinetics process of *OH reduction. The abundant vacancy defects around the Fe─N3 S1 active sites balance the OOH* formation and *OH reduction, thus synergetically promoting the electrocatalytic ORR process.

Spatial pattern of glacier mass balance sensitivity to atmospheric forcing in High Mountain Asia

Abstract The complex topography and size of High Mountain Asia (HMA) result in large differences in glacier mass-balance variability and climate sensitivity. Current understanding of these sensitivities is limited by simplifications in past studies’ model structure. This study overcomes this limitation by using a mass-balance model to investigate the climatic mass-balance variability and climate sensitivity of 16 glaciers covering major mountain ranges in HMA. Generally, glaciers in the southeast have higher mass turnover while glaciers at the margins of HMA show higher interannual mass-balance variability. All glaciers are most sensitive to temperature perturbations in summer. The climatic mass balance of 15 glaciers is most sensitive to precipitation perturbations in summer or spring and summer, even if the seasonal accumulation peak is not in summer. Only one glacier's mass balance (Chhota Shigri Glacier) is most sensitive to precipitation perturbations in winter. Glaciers with high mass turnover and high summer-precipitation ratio are more sensitive to temperature perturbations. Sensitivity experiments reveal that besides the non-linearity of mass-balance temperature sensitivity, mass-balance precipitation sensitivity is non-linear as well. Furthermore, resolving the diurnal cycle of albedo, (re)freezing and the differentiation between liquid and solid precipitation are important to assess climate sensitivity of glaciers in HMA.

The mass-loss rates of star clusters with stellar-mass black holes: implications for the globular cluster mass function

ABSTRACT Stellar-mass black holes (BHs) can be retained in globular clusters (GCs) until the present. Simulations of GC evolution find that the relaxation driven mass-loss rate is elevated if BHs are present, especially near dissolution. We capture this behaviour in a parametrized mass-loss rate, bench marked by results from N-body simulations, and use it to evolve an initial GC mass function (GCMF), similar to that of young massive clusters in the Local Universe, to an age of 12 Gyr. Low-metallicity GCs ([Fe/H] ≲ −1.5) have the highest mass-loss rates, because of their relatively high BH masses, which combined with their more radial orbits and stronger tidal field in the past explains the high turnover mass of the GCMF ($\sim 10^5\, {\rm M}_\odot$ ) at large Galactic radii ($\gtrsim 10\, {\rm kpc}$ ). The turnover mass at smaller Galactic radii is similar because of the upper mass truncation of the initial GCMF and the lower mass-loss rate due to the higher metallicities. The density profile in the Galaxy of mass lost from massive GCs ($\gtrsim 10^{5}\, {\rm M}_\odot$ ) resembles that of nitrogen-rich stars in the halo, confirming that these stars originated from GCs. We conclude that two-body relaxation is the dominant effect in shaping the GCMF from a universal initial GCMF, because including the effect of BHs reduces the need for additional disruption mechanisms.

Nanostructured Ternary Nickel‐Based Mixed Anionic (Telluro)‐Selenide as a Superior Catalyst for Oxygen Evolution Reaction

Developing protocols for designing high‐efficiency, durable, cost‐effective electrocatalysts for oxygen evolution reaction (OER) necessitates deeper understanding of structure–property correlation as a function of composition. Herein, it has been demonstrated that incorporating tellurium into binary nickel chalcogenide (NiSe) and creating a mixed anionic phase perturbs its electronic structure and significantly enhances the OER activity. A series of nanostructured nickel chalcogenides comprising a layer‐by‐layer morphology along with mixed anionic ternary phase are grown in situ on nickel foam with varying morphological textures using simple hydrothermal synthesis route. Comprehensive X‐ray diffraction, X‐ray photoelectron spectroscopy, and in situ Raman spectroscopy analysis confirms the formation of a trigonal single‐phase nanocrystalline nickel (telluro)‐selenide (NiSeTe) as a truly mixed anionic composition. The NiSeTe electrocatalyst exhibits excellent OER performance, with a low overpotential of 300 mV at 50 mA cm−2 and a small Tafel slope of 98 mV dec−1 in 1 m KOH electrolyte. The turnover frequency and mass activity are 0.047 s−1 and 90.3 Ag−1, respectively. Detailed electrochemical measurements also reveal enhanced charge transfer properties of the NiSeTe phase compared to the mixture of binaries. Density functional theory calculations reveal favorable OH adsorption energy in the mixed anionic phase compared to the binary chalcogenides confirming superior electrocatalytic property.

Computational modeling reveals inflammation-driven dilatation of the pulmonary autograft in aortic position.

The pulmonary autograft in the Ross procedure, where the aortic valve is replaced by the patient's own pulmonary valve, is prone to failure due to dilatation. This is likely caused by tissue degradation and maladaptation, triggered by the higher experienced mechanical loads in aortic position. In order to further grasp the causes of dilatation, this study presents a model for tissue growth and remodeling of the pulmonary autograft, using the homogenized constrained mixture theory and equations for immuno- and mechano-mediated mass turnover. The model outcomes, compared to experimental data from an animal model of the pulmonary autograft in aortic position, show that inflammation likely plays an important role in the mass turnover of the tissue constituents and therefore in the autograft dilatation over time. We show a better match and prediction of long-term outcomes assuming immuno-mediated mass turnover, and show that there is no linear correlation between the stress-state of the material and mass production. Therefore, not only mechanobiological homeostatic adaption should be taken into account in the development of growth and remodeling models for arterial tissue in similar applications, but also inflammatory processes.

Transplanting Gold Active Sites into Non-Precious-Metal Nanoclusters for Efficient CO2-to-CO Electroreduction.

Electrocatalytic CO2 reduction reaction (CO2RR) is greatly facilitated by Au surfaces. However, large fractions of underlying Au atoms are generally unused during the catalytic reaction, which limits mass activity. Herein, we report a strategy for preparing efficient electrocatalysts with high mass activities by the atomic-level transplantation of Au active sites into a Ni4 nanocluster (NC). While the Ni4 NC exclusively produces H2, the Au-transplanted NC selectively produces CO over H2. The origin of the contrasting selectivity observed for this NC is investigated by combining operando and theoretical studies, which reveal that while the Ni sites are almost completely blocked by the CO intermediate in both NCs, the Au sites act as active sites for CO2-to-CO electroreduction. The Au-transplanted NC exhibits a remarkable turnover frequency and mass activity for CO production (206 molCO/molNC/s and 25,228 A/gAu, respectively, at an overpotential of 0.32 V) and high durability toward the CO2RR over 25 h.

Molybdenum Oxycarbide Supported Rh-Clusters with Modulated Interstitial C-O Microenvironments for Promoting Hydrogen Evolution.

Tuning the microenvironment and electronic structure of support materials is essential strategy to induce electron transfer between supports and active centers, which is of great importance in optimizing catalytic kinetics. In this study, the molybdenum oxycarbide supported Rh-clusters are synthesized with modulated interstitial C-O microenvironments (Rh/MoOC) for promoting efficient hydrogen evolution in water splitting. Both electronic structure characterizations and theoretical calculations uncover the apparent charge transfer from Rh to MoOC, which optimizes the d-band center, H2 O adsorption energy, and hydrogen binding energy, thus enhancing its intrinsic hydrogen-evolving activities. In addition, the co-occurrence of interstitial C and O atoms in MoOC supports plays a vital role in the dissociation reaction of water during the hydrogen-evolving process. Impressively, the Rh/MoOC exhibits excellent hydrogen-evolving activities in terms of exceptional turnover frequency values (11.4 and 39.41 H2 s-1 in alkaline and acidic media) and mass activities (21.3 and 73.87 A mg-1 in alkaline and acidic media) at an overpotential of 100mV, which is more than 40 times higher than that of the benchmark commercial Rh/C catalysts. This work sheds new light on designing water dissociation materials that surpasses most of the reported catalysts.

Work-Related Stress and Turnover Intention during Covid-19 among Nurses in Hospital Universiti Sains Malaysia

The outbreak of COVID-19 had significantly impacted the healthcare system, placing it under tremendous strain. Nurses were shown to have suffered the impact of the pandemic, suggested traumatization and estimated a mass turnover intention among nurses globally due to the pandemic [1]. The objective of this cross-sectional study is to assess the prevalence of work-related stress and turnover intention among nurses in the Hospital Universiti Sains Malaysia (Hospital USM). This hospital is a teaching hospital with 830 beds that offers various specialties recognized as Hybrid COVID Hospital in managing patients.&#x0D; &#x0D; This study utilized multi-stage sampling. The population was stratified into three strata which were, Medical-Surgical wards, Specialty wards (Pediatric, Obstetrics and Gynecology), and Critical Care wards. Next, the wards were selected through a simple random method. The nurses from the selected wards who follow inclusion criteria; nurses with grade U29 or U32 (KUP) with at least one year of working experience [2] were invited to join the study. A total of 365 nurses participated in this study by answering a self-administered questionnaire through Google Forms sent to them. The questionnaire included three parts; Part A sociodemographic data, Part B Nurse Stress Index (NSI) with scoring ranging from 30-150 and Part C Turnover Intention Scale (TIS-6) with a scoring of 9-18[3]. The NSI is categorized into four categories: 30-60= no pressure, 61-90= very little pressure, 91-120= moderate pressure and 121-150=extreme pressure[3]. As for TIS-6, a score &lt;18 indicates a desire to stay whereas ≥18 indicates a desire to leave [3].&#x0D; &#x0D; The collected data were analyzed using SPSS version 26.0. Sociodemographic characteristics, the prevalence of work-related stress and turnover intention were analyzed descriptively. Pearson correlation test was used to analyze the correlation between work-related stress and turnover intention. Nearly half of the nurses experienced little (40.8%) to moderate (42.5%) level of work-related stress however 73.3% of the nurses reported that they did not have the intention to leave (Table 1 and Table 2). The mean score of work-related stress and turnover intention showed that the nurses were in a moderate level of stress (90.78), with low turnover intention (16.42). Next, the findings showed a significant and positive correlation between work-related stress and turnover intention (r= 0.559, p&lt; 0.001) (Table 3).&#x0D; This study found that work-related stress was significant among nurses although the data were collected towards the end of the pandemic approaching endemic phase. This could be explained by the uncertainty of the disease which was among the factors that could contribute to stress among frontliners [4]. Although the stress level is significant, the nurses in this study have low intention to leave. This could be possibly due to the job security working in government sector as this study was done in a semi-government hospital where the nurses receives benefits and securities such as salary remuneration and pension scheme[5]. Findings of the study shows a positive correlation between work-related stress and turnover intention. It is known that prolonged stress causes negative impact towards the physical and mental health of nurses, subsequently being the contributing factor towards turnover intention[6].&#x0D; &#x0D; Nevertheless, this study implies that healthcare personnel should be alert regarding the issues and consequences related to work-related stress and turnover intention. Appropriate strategies or recommendations should be done to improve nurses’ satisfaction and addressing issues related that surround the nursing practice environment to improve the quality of work life among nurses and thus, improve the quality of care delivered and patient safety, thus retaining highly skilled nurses.

The main sequence of star-forming galaxies across cosmic times

ABSTRACT By compiling a comprehensive census of literature studies, we investigate the evolution of the main sequence (MS) of star-forming galaxies (SFGs) in the widest range of redshift (0 &amp;lt; z &amp;lt; 6) and stellar mass (108.5–1011.5 M⊙) ever probed. We convert all observations to a common calibration and find a remarkable consensus on the variation of the MS shape and normalization across cosmic time. The relation exhibits a curvature towards the high stellar masses at all redshifts. The best functional form is governed by two parameters: the evolution of the normalization and the turnover mass (M0(t)), which both evolve as a power law of the Universe age. The turn-over mass determines the MS shape. It marginally evolves with time, making the MS slightly steeper towards z ∼ 4–6. At stellar masses below M0(t), SFGs have a constant specific SFR (sSFR), while above M0(t) the sSFR is suppressed. We find that the MS is dominated by central galaxies. This allows to turn M0(t) into the corresponding host halo mass. This evolves as the halo mass threshold between cold and hot accretion regimes, as predicted by the theory of accretion, where the central galaxy is fed or starved of cold gas supply, respectively. We, thus, argue that the progressive MS bending as a function of the Universe age is caused by the lower availability of cold gas in haloes entering the hot accretion phase, in addition to black hole feedback. We also find qualitatively the same trend in the largest sample of star-forming galaxies provided by the IllustrisTNG simulation. Nevertheless, we still note large quantitative discrepancies with respect to observations, in particular at the high-mass end. These can not be easily ascribed to biases or systematics in the observed SFRs and the derived MS.

Defect-stabilized platinum single atoms and clusters in bilayer nitrogen-doped porous carbon nanocages for synergistic catalysis of basic hydrogen evolution

Alkaline water electrolysis is a safe and efficient method for producing hydrogen that is favored by the industry. At present, single-atom catalysts have attracted extensive attention due to their extremely high atom utilization. However, studies on the single-atom site catalytic mechanism of the Volmer step, the rate-determining step of the cathodic HER reaction, are lacking. Here, we used ZIF-8 to obtain double-layer N-doped porous carbon nanocages, and successfully achieved the co-loading of Pt single atoms and their clusters (NPCN–Pt). The turnover frequency (TOF) and mass activity of NPCN–Pt are 5 and 7.2 times higher than those of commercial Pt/C, respectively, and the former exhibits significantly better stability than Pt/C. Theoretical calculations show that Pt clusters have a lower activation energy barrier for water molecules compared to Pt single atoms, which favors the Volmer step. The ΔGH* of Pt single-atom sites is smaller than that of Pt clusters, which is more conducive to the release of H2. The study shows that Pt clusters and single atoms can synergistically catalyze the HER reaction, providing new ideas for the development of efficient HER catalysts.

The hydrogen clock to infer the upper stellar mass

ABSTRACT The most massive stars dominate the chemical enrichment, mechanical and radiative feedback, and energy budget of their host environments. Yet how massive stars initially form and how they evolve throughout their lives is ambiguous. The mass loss of the most massive stars remains a key unknown in stellar physics, with consequences for stellar feedback and populations. In this work, we compare grids of very massive star (VMS) models with masses ranging from 80 to 1000 M⊙, for a range of input physics. We include enhanced winds close to the Eddington limit as a comparison to standard O-star winds, with consequences for present-day observations of ∼50–100 M⊙ stars. We probe the relevant surface H abundances (Xs) to determine the key traits of VMS evolution compared to O stars. We find fundamental differences in the behaviour of our models with the enhanced-wind prescription, with a convergence on the stellar mass at 1.6 Myr, regardless of the initial mass. It turns out that Xs is an important tool in deciphering the initial mass due to the chemically homogeneous nature of VMS above a mass threshold. We use Xs to break the degeneracy of the initial masses of both components of a detached binary, and a sample of WNh stars in the Tarantula Nebula. We find that for some objects, the initial masses are unrestricted and, as such, even initial masses of the order 1000 M⊙ are not excluded. Coupled with the mass turnover at 1.6 Myr, Xs can be used as a ‘clock’ to determine the upper stellar mass.