Constitutive Modeling of Annealed OFHC with Wide Strain-Rate and Temperature Effects: Incorporating Dislocation Dynamics and Normalized Microstructural Size Evolution.

The flow stress of face-centered cubic (FCC) metals exhibits a rapid increase near a strain rate of 104 s-1 under fixed-strain conditions. However, many existing constitutive models either fail to capture the mechanical characteristics of this plastic deformation or use piecewise strain-rate hardening models to describe this phenomenon. Unfortunately, these piecewise models may suffer from issues such as discontinuity of physical quantities and difficulties in determining segment markers, and struggle to reflect the underlying physical mechanisms that give rise to this mutation phenomenon. In light of this, this paper proposes that the abrupt change in flow stress sensitivity to strain rate in FCC metals can be attributed to microstructural evolution characteristics. To address this, a continuous semiempirical physical constitutive model for FCC metals is established based on the microstructural size evolution proposed by Molinari and Ravichandran and the dislocation motion slip mechanism. This model effectively describes the mutation behavior of strain-rate sensitivity under fixed strain, particularly evident in an annealed OFHC. The predicted results of the model across a wide range of strain rates (10-4-106 s-1) and temperatures (77-1096 K) demonstrate relative errors generally within ±10% of the experimental values. Furthermore, the model is compared with five other models, including the mechanical threshold stress (MTS), Nemat-Nasser-Li (NNL), Preston-Tonks-Wallace (PTW), Johnson-Cook (JC), and Molinari-Ravichandran (MR) models. A comprehensive illustration of errors reveals that the proposed model outperforms the other five models in describing the plastic deformation behavior of OFHC. The error results offer valuable insights for selecting appropriate models for engineering applications and provide significant contributions to the field.

Constructing A Solar Evaporator by Stacking Exhausted Wood Sponges for Freshwater Generation and Fertilizer Recovery.

Solar water evaporation is an efficient and sustainable technology. To reduce energy consumption and improve cost efficiency, the surface modification of wood sponge by polypyrrole-glutathione (PGWS) was achieved using an in-situ synthetic method. The PGWS exhibits excellent adsorption efficiency for Hg(II) ions with adsorption capacity of 330.8 mg g-1 at 25 °C. Following Hg(II) absorption, the PGWS could be upcycled for solar steam generation. A stackable device was constructed by placing two wood sponges under a Hg(II) saturated PGWS [PGWS-Hg(II)], this system exhibited the highest water evaporation rate of 2.14 kg m-2 h-1 under 1 kW m-2 . Moreover, collecting paper was inserted between the stacked PGWS-Hg(II) and wood sponge for the collection of salts. As such salt can be successfully collected from simulated fertilizer plant effluent and then used as a nutrient for growing plants using a hydroponic system. The facile design of stackable evaporation provides an opportunity for wastewater utilization by harvesting solar energy.

Do sleep and psychological factors influence musculoskeletal pain among nurses?

BACKGROUND: The physical factors associated with musculoskeletal pain in nursing personnel have been largely investigated, although the role of sleep and psychological factors resulting in musculoskeletal pain has not been addressed thoroughly. OBJECTIVE: This study aimed to explore the prevalence of musculoskeletal pain and investigate how sleep and psychological factors influence musculoskeletal pain in a nursing group. METHODS: Nordic standard questionnaires were distributed to 230 female nurses. Chi-square tests were performed to assess the associations between sleep problems, psychological problems, and musculoskeletal pain symptoms. Binary logistic regression analysis was also conducted to identify the primary factors influencing the prevalence of musculoskeletal pain. RESULTS: The highest prevalence of pain was observed in the lower back, neck, and shoulders, whereas the lowest prevalence of pain was observed in the ankles, feet, elbows, and hips/buttocks. Chi-square analysis and binary logistic regression showed that sleep duration, sleep onset time, and sleep quality all significantly contributed to the development of neck and upper back pain. With regard to the psychological factors, only occupational pride and stress had a significant effect on pain; in contrast, family support did not show any significant influence. CONCLUSION: Compared with other body regions, musculoskeletal pain in the lower back, neck, and shoulders requires more attention and preventive interventions. Special efforts should be made to shift the workday system of the nursing group because of the strong correlation between sleep problems and pain. Incentives other than penalty mechanisms should be considered seriously in nursing to boost occupational pride and relieve job stress.

Reclaimable MoS2 Sponge Absorbent for Drinking Water Purification Driven by Solar Energy.

With the fast development of modern industries, scarcity of freshwater resources caused by heavy metal pollution (i.e., Hg2+) has become a severe issue for human beings. Herein, a 3D-MoS2 sponge as an excellent absorbent is fabricated for mercury removal due to its multidimensional adsorption pathways, which decreases the biomagnification effect of methylmercury in water bodies. Furthermore, a secondary water purification strategy is employed to harvest drinkable water with the exhausted adsorbents, thus alleviating the crisis of drinking water shortage. Compared to the conventional landfill treatment, the exhausted MoS2 sponge absorbents are further functionalized with a poly(ethylene glycol) (PEG) layer to prevent the heavy metals from leaking and enhance the hydrophilicity for photothermal conversion. The fabricated evaporator displays excellent evaporation rates of ∼1.45 kg m-2 h-1 under sunlight irradiation and produces freshwater with Hg2+ under the WHO drinking water standard at 0.001 mg L-1. These results not only assist in avoiding the biodeposition effect of mercury in water but also provide an environment-friendly strategy to recycle hazardous adsorbents for water purification.

Reduced graphene oxide/Bi4O5Br2 nanocomposite with synergetic effects on improving adsorption and photocatalytic activity for the degradation of antibiotics.

A photocatalyst based on the integration of reduced graphene oxide (rGO) with Bi4O5Br2 nanosheets was facilely prepared and was confirmed by transmission electron microscope, scanning electron microscope, X-ray diffraction and Raman spectroscopy. The integration of rGO can effectively improve the adsorption and the photocatalytic properties of Bi4O5Br2 nanosheets towards the target antibiotics under visible light irradiation. rGO/Bi4O5Br2 nanocomposite containing 1.0 wt% of rGO exhibits the optimal adsorption and photocatalytic activity towards ciprofloxacin (CIP), norfloxacin (NOR) and tetracycline (TC). The removal efficiencies of CIP, NOR and TC are 97.6%, 80.7% and 98.7%, which are higher than that obtained with Bi4O5Br2 nanosheets. The capture experiments and ESR data show that ·O2-, OH· and h+ are the main active species that participated in the photodegradation system. This work provides a simple strategy to integrate rGO with BixOyXz (X = Cl, Br, I) nanosheets to construct effective photocatalysts for the degradation of antibiotics.

Effects of molecular weight fractions and chemical properties of time-series cyanobacterial extracellular polymeric substances on the aggregation of lake colloidal particles.

Colloidal particles in lake waters interact inevitably with cyanobacterial extracellular polymeric substance (EPS), which will change their behavior and fate. Quantitative prediction of the effects of cyanobacterial EPS on colloidal behavior is difficult due to its variability and heterogeneity. To explore the effects of molecular weight (MW) fractions and chemical properties of cyanobacterial EPS on aggregation kinetics of colloidal particles, time-series cyanobacterial samples were collected in Lake Taihu, China, from April to November (during blooming and maintenance period), with the bulk EPS matrix fractionating into low MW (LMW-, <1 nm) and high MW (HMW-, 1 nm-0.45 µm) fractions. HMW-EPS was generally characterized with higher absorbance and predominant distribution of protein-like substances, while LMW-EPS contained mainly the humic- and fulvic-like substances. The absorbance, molecular size, and humification degree for each MW fraction consistently increased from April to November, showing obvious temporal variations from blooming period to maintenance period. As for the MW-dependent aggregation behaviors, the HMW-EPS provided better stability against aggregation than the LMW-EPS, and the bulk EPS matrix that consisted of HMW- and LMW-fractions exhibited the effects intermediate between that of each fraction alone. Regardless of MW fractions, the effects of EPS-induced stability enhancement were more evident in maintenance period than in blooming period. Further analysis showed that the colloidal stability was correlated positively with SUVA254 (R2 = 0.82-0.93) but negatively with Slope275-295 (R2 = 0.53-0.91) of UV-Vis absorption spectra, indicating that aromaticity and MWs were two critical parameters controlling colloidal aggregation. Therefore, cyanobacterial EPS can exhibit variable effects on colloidal stability, and characterization of MW distribution is strongly required in predicating the behavior and fate of colloidal particles in water environments.

Abundance, chemical composition and lead adsorption properties of sedimentary colloids in a eutrophic shallow lake.

Colloidal particles are omnipresent in lake sediments and substantially influence the retention, transportation, and fate of contaminants in lake ecosystems. In this study, the abundance, chemical composition and adsorption behavior of sedimentary colloids (including total and inorganic colloids) from different ecological regions, were for the first time investigated via ultrasonic extraction, spectral analysis and batch absorption experiments. Results showed that the extraction efficiencies of sedimentary colloids showed an ultrasonic energy-dependent enhancement, and the algae-dominated area contained comparable colloidal abundance with the macrophyte-dominated area (i.e., 198.5 vs. 183.3 mg/g). Despite the different ecosystems, these sedimentary colloids usually had a wide size distribution of 30-200 nm, and were characterized with montmorillonite-, kaolin-, volkonskoite-, and quartz-rich chemical compositions. Batch experiment showed that the total pristine colloids exhibited higher adsorption capacity for Pb(II) than the inorganic colloids both for the macrophyte- and algae-dominated sediments, and the adsorption process followed pseudo-second-order kinetics and Langmuir isotherm, irrespective of different colloidal types. Thus, sedimentary colloids can immobilize the heavy metals in sediment and decrease their release into the water column, which can be considered as a sink for contaminants. This study highlighted the significance of sedimentary colloids in determining the physicochemical properties of lake sediments and in evaluating the environmental behavior and fate of contaminants in lake ecosystems.

Characterization, origin and aggregation behavior of colloids in eutrophic shallow lake.

Stability of colloidal particles contributes to the turbidity in the water column, which significantly influences water quality and ecological functions in aquatic environments especially shallow lakes. Here we report characterization, origin and aggregation behavior of aquatic colloids, including natural colloidal particles (NCPs) and total inorganic colloidal particles (TICPs), in a highly turbid shallow lake, via field observations, simulation experiments, ultrafiltration, spectral and microscopic, and light scattering techniques. The colloidal particles were characterized with various shapes (spherical, polygonal and elliptical) and aluminum-, silicon-, and ferric-containing mineralogical structures, with a size range of 20-200 nm. The process of sediment re-suspension under environmentally relevant conditions contributed 78-80% of TICPs and 54-55% of NCPs in Lake Taihu, representing an important source of colloids in the water column. Both mono- and divalent electrolytes enhanced colloidal aggregation, while a reverse trend was observed in the presence of natural organic matter (NOM). The influence of NOM on colloidal stability was highly related to molecular weight (MW) properties with the high MW fraction exhibiting higher stability efficiency than the low MW counterparts. However, the MW-dependent aggregation behavior for NCPs was less significant than that for TICPs, implying that previous results on colloidal behavior using model inorganic colloids alone should be reevaluated. Further studies are needed to better understand the mobility/stability and transformation of aquatic colloids and their role in governing the fate and transport of pollutants in natural waters.