Elevated Exposure Research Articles

Effect of continuous dietary administration of the Saccharomyces cerevisiae yeast, Δmnn9, on Pacific oyster (Crassostrea gigas) juveniles: Immunological and histopathological findings after Vibrio coralliilyticus challenge

Yeast cells and their cell wall components, mainly β-glucans, are strong immunostimulants in bivalves, however, it remains unclear whether long-term administration of yeast contributes to prolonged activity of bivalve immune systems. Understanding these innate immune mechanisms is essential to establishing feeding strategies and disease prevention in hatcheries and nurseries. The present study examined the immunostimulatory effect of continuous dietary supply of the Saccharomyces cerevisiae mnn9 mutant (∆mnn9), which exhibits elevated exposure of β-glucans on the cell-wall surface, on Crassostrea gigas juveniles, and its protective effect against Vibrio coralliilyticus infections. In trial 1 the expression levels of immune-related genes were determined in oysters fed the ∆mnn9-containing diet 50A50Y (50% algae, 50% ∆mnn9; based on dry weight), compared to those fed the 100% algae-based diet (100A), after 6, 9, 12, 18, 24 h of feeding. In trial 2: the feeding period was expanded to 8 days, where the algal diet (100A) was provided every day, but substituted with 50A50Y for 0, 1, 2, 4, and 8 days (treatments 0D (control), 1D, 2D, 4D, and 8D, respectively) just before a Vibrio challenge, which was monitored for 7 days. Gene expression was measured before and 24-h after the Vibrio challenge. Histological analysis was performed on oysters on day 7 post-Vibrio challenge. Results showed that 50A50Y induced upregulation of interleukin 17–5 (CgIL17–5; 6 h), lysozyme (CgLys; 6 and 9 h), β-glucan-binding protein (CgβGBP; 18 h), and superoxide dismutase (CgSOD; 18 and 24 h) genes in juveniles (trial 1). Before the challenge, trial 2 demonstrated overexpression of CgSOD in animals from 1D, CgLys in those from 1D, 2D, and 4D, but not in oysters from 8D, compared to those from 0D. However, higher CgIL17–5 expression levels were observed in animals from 2D, 4D, and 8D, suggesting that inflammatory genes can remain inducible after 8 days of ∆mnn9 feeding. After the Vibrio challenge, a significantly higher survival was observed in animals from 1D (35.8%), 2D (45.0%), 4D (49.2%), but not 8D (25.8%), compared to the survival of animals from 0D (16.7%). These findings suggest that regulatory feedback mechanisms occurring during continuous ∆mnn9 feeding might lead to host tolerance or homeostasis. Also, we showed that V. coralliilyticus promotes overexpression of CgβGBP, C-type lectin receptor (CgCLec-3), myeloid differentiation factor 88 (CgMyD88), nuclear factor-kappa B (CgNFκB), CgLys, and CgSOD genes in oysters at 24-h post-exposure. Finally, this study provides insights into histopathological manifestations in the digestive tract, muscles, and gills of Vibrio-infected oysters.

Malnutrition and poststroke depression in patients with ischemic stroke

BackgroundIdentifying high-risk patients based on modifiable clinical characteristics, such as malnutrition, is critical to intervening with these variables to reduce the risk of post-stroke depression (PSD). The aim of this study was to investigate the effect of nutritional status on the risk of incident PSD and the trajectory of PSD risk. MethodsConsecutive patients with acute ischemic stroke were recruited in this observational cohort and followed up for 1 year. Multivariate logistic regressions and multilevel mixed-effects logistic regressions with random intercepts and slopes were used to investigate the effects of nutritional indexes [the Controlling Nutritional Status (CONUT) score, the Nutritional Risk Index (NRI), and the Prognostic Nutritional Index (PNI)] and body mass index (BMI) on the risk of incident PSD and the trajectory of PSD risk over the 12-month observation period. ResultsA total of 538 patients were included in the final analysis. Worsening CONUT [odds ratio (OR) = 1.36; confidence interval (CI): 1.15–1.61], NRI (OR = 0.91; CI: 0.87–0.96) and PNI (OR = 0.89; CI: 0.84–0.95) scores were significantly associated with an increased risk of incident PSD. Moderate and severe risk malnutrition statuses were associated with higher incidences of PSD regardless of the malnutrition index (CONUT, NRI or PNI). Additionally, PSD risk decreased over time with a significant two-way interaction between time and CONUT, NRI, and PNI, implying that patients with elevated exposure to malnutrition showed a slower decline in PSD risk. BMI had no significant effect on the occurrence and development of PSD. ConclusionMalnutrition, but not BMI, was associated with a higher probability of incident PSD and was more likely to lead to a slower rate of decline in PSD risk.

Occupational Bioaerosol Exposures Associated with Poultry Farming

ABSTRACT This study aimed to investigate occupational exposure to particulate dust, endotoxin, and (1–3)-β-D-glucan among workers involved in various poultry farming activities. A total of 298 personal samples were collected from randomly selected individuals from exposure groups based on distinct poultry farming activities comprising broiler farms, rearing, laying, hatchery, and catching activities. Aside from the inhalable particulate dust concentration that was determined, filter extracts were also analyzed for (1–3)-β-D-glucan and endotoxin using the endpoint Glucatell® and Limulus amoebocyte lysate (LAL) assays, respectively. Data were analyzed using STATA 12 and linear regression models developed. The mean (GM) dust particulate concentration was 11.04 mg/m3 (GSD = 3.87); 2298 endotoxin units (EU/m3) (GSD = 10.56) and 149 ng/m3 for (1–3)-β-D-glucan (GSD = 4.62). A modest positive correlation was observed between log-transformed endotoxin and (1–3)-β-D-glucan concentrations (Pearson r = 0.44, p < .001), whilst a moderate negative correlation was observed for inhalable dust particulate and (1–3)-β-D-glucan (Pearson r = −0.33, p < .001). However, there was a very poor correlation between inhalable dust and endotoxin (Pearson r = −0.02, p < .001). In the regression models, exposure group based on the nature of farming activity explained 50% of the variability in dust particulate and glucan levels. For dust particulate, rearing activities were significant predictors of higher dust levels compared to hatchery work, while rearing, laying, broiler and catching activities were significant predictors of higher endotoxin or glucan levels. Furthermore, working in a small broiler was a significant determinant of elevated glucan exposures. Farms using automated laying activities had significantly higher particulate levels compared to those using manual laying activities. This study revealed that workers engaged in poultry farming activities were exposed to significantly high levels of inhalable particulate dust, endotoxin, and (1–3)-β-D-glucan concentrations, posing an increased risk for adverse respiratory health effects in these farm workers.

Bond performance between FRP bars and geopolymer concrete after elevated temperature exposure

The use of geopolymer concrete structure reinforced with fiber reinforced polymer (FRP) bars is an effective approach to solve the problems of high energy consumption, large CO2 emission, and steel corrosion caused by traditional reinforced concrete structures. This paper presents an experimental study on the effect of elevated temperatures on bond performance between FRP bars and geopolymer concrete. The influence factors include exposure temperature, surface treatment of FRP bars, fiber type of FRP bars, geopolymer concrete strength and type of concrete. The test results indicate that the bond strength between FRP bar and geopolymer concrete increases first and then decreases gradually with the increase of exposure temperature. After exposure to 350 °C, the bond strength retention ranges from 56.0% to 83.3%, while after exposure to 400 °C, the residual bond strength retention is not more than 17.7%. The bond strength retention of FRP bars in geopolymer concrete is basically higher than that in ordinary concrete from 25 °C to 350 °C. Moreover, the ribbed FRP bars possess a higher bond strength retention than the sand-coated FRP bars after elevated temperature exposure. With the increase of the geopolymer concrete strength, the high temperature resistance of geopolymer concrete decreases, resulting in a corresponding decreasing in the bond strength retention. In addition, the fiber type of FRP bar has no significant effect on the interfacial bonding properties compared with surface treatment of FRP bar and concrete strength. Finally, the available equations for calculating the development length of FRP bar in geopolymer concrete after elevated temperature exposure was proposed, which may be used for the design of fire prevention and fire safety assessments.

Durability Enhancement Effect of Silica Fume on the Bond Behavior of Concrete-PCM Composites under Environmental Conditions.

The long-term performance of the concrete-polymer cement mortar (PCM) interface under environmental exposure is crucial to the safety of the PCM overlaying method as the environmental exposure of the repaired structures caused further degradation of the interface, leading to a significant reduction in intended service life. This study investigates the durability enhancement effect of silica fume of the concrete-PCM interface, considering an individual action of elevated temperature (e.g., 60 °C) [constant (short and moderate duration) and cyclic conditions] and moisture content [continuous immersion and wetting/drying (W/D) cycle]. Our previous research confirmed that the use of silica fume forms more C-S-H with strong binding force and enhances the interfacial bonding strength due to the denser microstructure at the interface, and it is expected to be utilized for durability purposes under the aforementioned exposure conditions. Under all elevated temperature exposure conditions, the reduction percentage of the interfacial performance corresponding to the respective reference specimens reduced significantly with the inclusion of silica fume with overlay material. The occurrence of interface fracture at lower load and a greater number of pure interface fracture modes observed in normal PCM specimens compared to modified PCM specimens indicates a positive influence of higher adhesion with better durability of modified PCM overlay with substrate concrete. Under both conditions of moisture content, significant reduction in interfacial strength was observed in normal PCM specimens. In all cases, the reducing ratio of interfacial strength was higher in normal PCM compared to modified PCM, indicating a positive influence of silica fume under moisture content. Furthermore, silica fume inclusion shifts the fracture mode from pure interfacial fracture to composite fracture mode, indicating a positive response of silica fume to improve the resistance of interface fracture under moisture content. Conclusively, the use of silica fume improves concrete-overlay layer adhesion and enhances the bonding durability under environmental exposure.

Weight loss relapse associated with exposure to perfluorinated alkylate substances.

The purpose of this study was to test the hypothesis that perfluorinated alkylate substance (PFAS) exposures are associated with body weight increases in a dietary intervention study. In the DioGenes trial, adults with obesity first lost at least 8% of their body weight and then completed at least 26 weeks on a specific diet. Concentrations of five major PFASs were assessed in plasma samples from study baseline. In 381 participants with complete data, plasma concentrations averaged 2.9ng/mL and 1.0ng/mL for perfluorooctanoic acid (PFOA) and perfluorohexanesulfonic acid (PFHxS), respectively. A doubling in plasma PFOA was associated with an increase in weight at 26 weeks by 1.50 kg (95% CI: 0.88-2.11),with an increase of0.91kg(95% CI: 0.54-1.27) for PFHxS, independent of diet groups and sex. Associations for other PFASs were in the same direction and significant, although not after adjustment for PFOA and PFHxS. Weight changes associated with elevated PFAS exposureswere similar to or larger than average changes ascribed to the different diet groups. Elevated plasma concentrations of PFOA and PFHxS were associated with increased weight gain that exceeded those related to the diets. Obesogenic PFASs may cause weight gain and thus contribute to the obesity pandemic.

Tissue‐like environments shape functional interactions of HIV‐1 with immature dendritic cells

Immature dendritic cells (iDCs) migrate in microenvironments with distinct cell and extracellular matrix densities in vivo and contribute to HIV‐1 dissemination and mounting of antiviral immune responses. Here, we find that, compared to standard 2D suspension cultures, 3D collagen as tissue‐like environment alters iDC properties and their response to HIV‐1 infection. iDCs adopt an elongated morphology with increased deformability in 3D collagen at unaltered activation, differentiation, cytokine secretion, or responsiveness to LPS. While 3D collagen reduces HIV‐1 particle uptake by iDCs, fusion efficiency is increased to elevate productive infection rates due to elevated cell surface exposure of the HIV‐1‐binding receptor DC‐SIGN. In contrast, 3D collagen reduces HIV transfer to CD4 T cells from iDCs. iDC adaptations to 3D collagen include increased pro‐inflammatory cytokine production and reduced antiviral gene expression in response to HIV‐1 infection. Adhesion to a 2D collagen matrix is sufficient to increase iDC deformability, DC‐SIGN exposure, and permissivity to HIV‐1 infection. Thus, mechano‐physical cues of 2D and 3D tissue‐like collagen environments regulate iDC function and shape divergent roles during HIV‐1 infection.

Airway delivery of Streptococcus salivarius is sufficient to induce experimental pulmonary hypertension in rats.

The causal relationship between altered host microbiome composition, especially the respiratory tract microbiome, and the occurrence of pulmonary hypertension (PH) has not yet been studied. An increased abundance of airway streptococci is seen in patients with PH compared with healthy individuals. This study aimed to determine the causal link between elevated airway exposure to Streptococcus and PH. The dose-, time- and bacterium-specific effects of Streptococcus salivarius (S. salivarius), a selective streptococci, on PH pathogenesis were investigated in a rat model established by intratracheal instillation. Exposure to S. salivarius successfully induced typical PH characteristics, such as elevated right ventricular systolic pressure (RVSP), right ventricular hypertrophy (Fulton's index) and pulmonary vascular remodelling, in a dose- and time-dependent manner. Moreover, the S. salivarius-induced characteristics were absent in either the inactivated S. salivarius (inactivated bacteria control) treatment group or the Bacillus subtilis (active bacteria control) treatment group. Notably, S. salivarius-induced PH is characterized by elevated inflammatory infiltration in the lungs, in a pattern different from the classic hypoxia-induced PH model. Moreover, in comparison with the SU5416/hypoxia-induced PH model (SuHx-PH), S. salivarius-induced PH causes similar histological changes (pulmonary vascular remodelling) but less severe haemodynamic changes (RVSP, Fulton's index). S. salivarius-induced PH is also associated with altered gut microbiome composition, suggesting potential communication of the lung-gut axis. This study provides the first evidence that the delivery of S. salivarius in the respiratory tract could cause experimental PH in rats.

Effect of superabsorbent polymer and polypropylene fiber on mechanical performances of alkali-activated high-calcium fly ash mortar under ambient and elevated temperatures

This study investigated the mechanical properties of alkali-activated fly ash (AAF) mortars containing superabsorbent polymers (SAPs) and polypropylene (PP) fibers before and after exposure to elevated temperatures. AAF mortars were synthesized using sodium silicate and high-calcium fly ash as the solid activator and aluminosilicate source, respectively. This procedure classified the binder as a one-part AAF mortar. The mechanical properties of the AAF mortar, including compressive and flexural strengths, were investigated considering eight mixes with varying SAP contents (0%, 0.5%, 1%, and 2% by weight of binder) and fiber contents (0 and 0.2% by volume). Moreover, physical properties including the permeability and sorptivity were examined, and physiochemical analysis was performed to evaluate the behavior of AAF mortar at room temperature, 300, 500, and 700 °C. The results show that the compressive strength of specimens at room temperature slightly decreased owing to the increased macroporosity caused by SAPs through pre-swelling, while the flexural strength was maintained via an internal curing effect. The PP fibers significantly enhanced the flexural capacity of the cement mortar, while the compressive strength initially decreased at 28 d and later exhibited a negligible effect at 90 d. The specimens produced using SAPs were effective in preserving the residual compressive and flexural strengths compared with those without SAPs after exposure to 300 °C. Meanwhile, the residual strength of PP fiber specimens diminished after elevated temperature exposure because the melted fiber led to the excessive formation of cavities.

Abstract 4223: A metabolomic investigation of serum perfluorooctane sulfonate and perfluorooctanoate

Abstract Background: Per- and polyfluoroalkyl substances (PFAS) are environmentally persistent synthetic chemicals detectable in the blood of most Americans. Elevated exposures to perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), the two most prevalent PFAS, have been associated with several health outcomes including metabolic outcomes and some cancers. To evaluate possible mechanisms related to the biological effects of these chemicals, we conducted a pooled metabolome-wide association study (MWAS) of circulating PFOS and PFOA among 3,647 participants included in one of eight nested case-control serum metabolomic profiling studies conducted in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) population. Methods: All metabolomic profiling was conducted by Metabolon Inc, using liquid-phase or gas chromatography coupled with mass spectrometry. All metabolites including PFOS and PFOA were centered (mean=0, standard deviation=1) and log-transformed. We conducted multivariable linear regression analyses to estimate study-specific associations between metabolite levels and PFOS and PFOA, adjusted for age at specimen collection, race/ethnicity, body mass index, smoking, case-control status, study center, and year of specimen collection. Sex was additionally adjusted for studies including both men and women. We then conducted combined the study-specific findings through meta-analysis using random effects models. Results: The meta-analysis results of 1,040 metabolites for PFOS and 1,103 for PFOA identified 83 and 67 metabolites, respectively, associated at Bonferroni-corrected significance thresholds (P=4.81 × 10−5 for PFOS; P=4.53 × 10−5 for PFOA). For both PFOS and PFOA, the strongest positive associations were observed for the xenobiotics 3,5-dichloro-2,6-dihydroxybenzoic acid [PFOS, summary beta coefficient =0.74, 95% confidence interval=0.67,0.80; PFOA, 0.48 (0.35,0.61)] and 3-bromo-5-chloro-2,6-dihydroxybenzoic acid [0.57 (0.43,0.72) and 0.39 (0.23,0.55)]. We also observed strong positive associations with PFOS and PFOA for metabolites related to the sphingomyelin (SM) pathway, such as hydroxypalmitoyl sphingomyelin (d18:1/16:0(OH)) [PFOS, 0.44 (0.24,0.64)] and SM (d18:1/18:0) [PFOS, 0.35 (0.24,0.46); PFOA, 0.25 (0.16,0.34)], and SM (d18:2/24:2) [PFOS, 0.32 (0.17,0.47)]. The PFOS metabolite associations remained after model adjustment for PFOA; however, the PFOA associations were greatly attenuated after controlling for PFOS. Conclusions: In this MWAS of PFAS, to our knowledge the largest to date, we observed robust positive associations with serum PFOS for several xenobiotic compounds and for metabolites related to the sphingomyelin pathway. Further investigation of these metabolites may offer insight into PFOS-related biologic effects contributing to disease development. Citation Format: Jongeun Rhee, Steven C. Moore, Demetrius Albanes, Tracy M. Layne, Erikka Loftfield, Rachael Stolzenberg-Solomon, Linda M. Liao, Mary C. Playdon, Mark P. Purdue. A metabolomic investigation of serum perfluorooctane sulfonate and perfluorooctanoate. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4223.

Abrasion resistance and hardness evaluation of FCAW-S hard-facing following elevated temperature exposure

Proprietary compositional blends were welded for hardfacing applications. The blends were subsequently heat treated at progressively increasing temperatures followed by testing using industry key performance indicators. Each blend was developed to be used as a self-shielded FCAW wire for high-amperage, high-productivity deposition. Heat treatment of each consumable was completed in three conditions: as-welded, 400 °C (750 °F), and 700 °C (1290 °F). Microstructural analysis complimented mechanical testing and included field-emission scanning electron microscopy, surface hardness (HV10kg), ASTM G65 Method A abrasion mass loss, carbide volume fraction analysis, and rotary impact testing. The results of hardness testing showed that there was a differentiated decrease in average surface hardness between the blends as the heat treatment temperature was increased. All surface hardness measurements met the stringent industry performance indicator of 600 HV10 minimum. ASTM G65 Method A abrasion testing was performed following each heat treatment. All blends had acceptable abrasion mass loss as-welded, after a 400 °C heat treatment, and after a second heat treatment at 700 °C. Rotary impact testing of the consumables was completed after high temperature exposure in accordance with the Alberta Oil Sands procedure. Microstructural comparisons of the blends showed performance-indicating variation to support the mechanical testing results.

Objectively-Assessed Ultraviolet Radiation Exposure and Sunburn Occurrence.

Ultraviolet radiation (UVR) exposure is the primary modifiable risk factor for melanoma. Wearable UVR sensors provide a means of quantifying UVR exposure objectively and with a lower burden than self-report measures used in most research. The purpose of this study was to evaluate the relationship between detected UVR exposure and reported sunburn occurrence. In this study, a UVR monitoring device was worn by 97 parent-child dyads during waking hours for 14 days to measure instantaneous and accumulated UVR exposure. The results showed that the participants' total UVR exposure was associated with reported sunburn after adjusting for Fitzpatrick skin type and geographic location. It was observed that one standard erythemal dose (SED) increase in the participants' daily total UVR exposure was associated with reported sunburn (an odds ratio (OR) of 1.26 with a 95% CI of 1.13 and 1.41, and p < 0.001 for parents and an OR of 1.28 with a 95% CI of 1.12 and 1.47, and p < 0.001 for children). A one-SED increase in the participants' UVR exposure from 10 am to 4 pm was also associated with reported sunburn (an OR of 1.31 with a 95% CI of 1.15 and 1.49, and p < 0.001 for parents and an OR of 1.33 with a 95% CI of 1.12 and 1.59, and p = 0.001 for children). We found that elevated UVR exposure recordings measured by the UVR sensor were associated with reported sunburn occurrence. Future directions for wearable UVR sensors may include their use as an intervention tool to support in-the-moment sunburn prevention.

Interaction of silica fume on flexural properties of 10 mm-thickness geopolymers based on fly ash and ladle furnace slag under the thermal conditions

Studies regarding the properties of geopolymers with silica fume addition at elevated temperature exposure were rarely reported. This paper evaluates the effect of silica fume inclusion on the flexural and thermal performance of geopolymers based on fly ash (FA) and ladle furnace slag (LFS) with thickness of merely 10 mm. Fly ash/slag (FS) geopolymer was prepared by mixing FA and LFS using a weight ratio of 60:40 with an alkali activator (sodium silicate and sodium hydroxide). Silica fume (1, 2, 3, and 4 wt%) was added to prepare FSF geopolymers. The geopolymers were then subjected to the elevated temperature up to 1100 °C after 28-days of curing. Higher flexural strength of 9.1 MPa was achieved in unexposed FSF geopolymers with 3 wt% silica fume addition as compared to unexposed FS geopolymers (7.8 MPa). Flexural strength degraded with higher silica fume content of 4 wt%. Heat treatment significantly improved the flexural strength of geopolymers. Both FS and FSF3 geopolymers had increased strength of 208.9% to 24.1 MPa at 1100 °C and 192.3% to 26.6 MPa at 1000 °C, respectively as compared to the unexposed specimen. The inclusion of silica fume with extreme fineness improved the interconnectivity of the geopolymer matrix, densifying the geopolymer structure and thus enhancing the thermal resistance of geopolymers. However, the dense matrix with low flowability of FSF3 geopolymers could not sustain the high thermal stress and caused strength degradation and crack formation at a high temperature of 1100 °C. Even so, the flexural strength of 1100 °C heat-treated FSF3 geopolymer was 13.2% higher than the unexposed specimen. This demonstrated that silica fume could be incorporated in enhancing the thermal resistance and high strength achievement in geopolymers.

Skin Physiology, Mucosal Functions, and Symptoms Are Modulated by Grass Pollen and Ozone Double Exposure in Allergic Patients

Introduction: Along with climate changes, we see an increase in allergic symptoms and the number of pollen-allergic patients in many countries. Increased allergic symptoms are associated with an elevated ozone exposure which may be linked by impaired epithelial barrier function. This study aimed to quantify the clinical effect of ozone and pollen double exposure (DE). We tested whether ozone impairs barrier-related skin physiology and mucosal functions under DE with pollen in grass pollen-allergic patients versus healthy controls. Methods: This case-control study included 8 grass pollen-allergic patients and 8 non-allergic healthy subjects exposed to grass pollen and ozone in the GA²LEN pollen chamber, comparing shorter and longer DE duration. Non-invasive skin physiological parameters were assessed, including stratum corneum hydration, skin redness, surface pH, and basal transepidermal water loss as a parameter for epidermal barrier function. The subjects’ general well-being, bronchial, nasal, and ocular symptoms were documented. Results: Skin physiology tests revealed that DE in allergic patients deteriorates the epidermal barrier function and increases the surface pH and skin redness. DE significantly induced nasal secretion in pollen-allergic versus healthy subjects, which was more pronounced with longer DE. The general well-being was significantly impaired under DE versus pollen or ozone alone, with a negative influence of DE duration. No relevant bronchial symptoms were recorded. Conclusion: Skin physiology and nasal mucosal symptoms are negatively affected by ozone and grass pollen DE in allergic patients. The negative effects showed, in some parameters, a dose (time)-response relationship. The pH can be regarded as a possible modulatory mechanism.

Effect of Er and Si co-microalloying on mechanical properties and microstructures of AlCuMg alloys

The effect of Er and Si on the evolution of precipitates in Al–Cu–Mg alloys during elevated temperature exposure was investigated. The Er segregation in θ′-Al2Cu precipitates and Si/Mg co-segregation at the interfaces of θ'/Al matrix are experimentally observed in Al–Cu–Mg–Si–Er alloy, which finally contributes to the heat resistance of the Al–Cu–Mg–Si–Er alloy. Si enhances formation of the Q″ phases as nucleation sites for the θ′ phases, resulting in a refined distribution of θ′ phases. Al–Cu–Mg alloy with high strength as well as high thermal stability is obtained by co-adding Er and Si. The high-temperature yield strength (YS) of Al–Cu–Mg–Si–Er alloy at 225 °C are increased by 37 MPa compared with that of Al–Cu–Mg alloy. Simultaneously, the addition of Er significantly increases the elongation of Al–Cu–Mg–Si–Er alloy.

Post-fire flexural behaviour and performance of unrestrained cold-formed steel built-up section beams: Experimental and numerical investigation

Cold-formed steel (CFS) sections are light gauge materials widely used to construct industrial structures. CFS construction is gaining more interest among researchers, construction industries, and structural engineers due to its lightweight and cost-effective design. Fire safety in the building is a significant factor to be considered in the design and construction practices. However, limited studies are reported on experimental and finite element modelling (FEM) of back-to-back built-up channel sections under flexure with unrestrained conditions. Nine back-to-back built-up CFS sections were considered for the experiment. CFS test specimens were exposed to elevated temperatures following the ISO 834 standard fire curve for durations of 30 min (821 ℃), 60 min (925 ℃), 90 min (986 ℃), and 120 min (1029 ℃). After the temperature exposure, air- and water-cooling methods were adopted to cool the CFS specimens. The influence of temperature exposure and cooling affects CFS sections' residual load-carrying capacity and failure behaviour. A detailed physical observation was made after cooling conditions to observe the failure behaviour of CFS specimens. Experiments were performed to evaluate the influence of elevated temperature exposure on the ultimate flexural capacity, moment-deformation behaviour, load-strain behaviour and stiffness of CFS. The moment of resistance results obtained from FEM and the Direct Strength Method (DSM) were validated with experimental results. The experimental results showed that, while increasing the temperature exposure and heating duration, the CFS's load-carrying capacity decreases drastically. In the case of cooling conditions, air-cooled specimens exhibited a higher residual strength capacity, about 10–15%, compared to the water-cooled specimens. A good correlation was noted between the experiment and FEM results in failure modes.

Influence of elevated temperature exposure on the interfacial shear strength capacity of binary blended high strength self-compacting geopolymer concrete

The development of sustainable infrastructure is a serious issue faced by modern society. Portland cement is one of the common ingredients in concrete, which influences construction activities. The major issue with the employment of cement in civil-based works is that it is responsible for carbon dioxide emission (CO2-e), the primary greenhouse gas responsible for global warming. Alternative to cement-based concrete, geopolymer concrete (GPC) employs zero cement for concrete production, leading to a reduction in CO2-e. In the case of mass concreting, interface/joints are developed, which are found to be the possible failure spots of brittle fracture. Concrete with different grades (strength) may interface, or other building materials, such as reinforcing materials. The interfacial bond strength has to be examined to ensure the homogeneity of the composite structures. The employment of shear ties at the interface ensures homogeneous behaviour. Moreover, a higher number of shear ties in the shear zone increases the cost of production. The interfacial shear strength (ISS) parameters will be miserably damaged in the concrete structures subjected to fire accidents, which might depend on the intensity of temperature exposure and its duration. The current study investigates the ISS of the High Strength Self-compacting geopolymer concrete (HSGC) in the interface of push-off samples. SCGC was made using binary blended composites, which comprised Fly Ash (FA), Metakaolin (MK), and Ground Granulated Blast Furnace Slag (GGBFS) as precursor materials. The work highlights the need to comprehend the reduction in shear strength of SCGC subjected to high temperatures. The fresh properties of the SCGC composites strictly adhered to the EFNARC guidelines. The SCGC composites, after their curing period, were exposed to 821 ℃, 925 ℃, 986 ℃, and 1029 ℃ following ISO 834 guidelines. Residual mechanical properties were examined after being cooled to room temperature.

NIR-II xanthene dyes with structure-inherent bacterial targeting for efficient photothermal and broad-spectrum antibacterial therapy.

Development of novel broad-spectrum sterilization is an efficient strategy that can overcome drug resistance and avoid antibiotics abuse toward bacterial-infected diseases. Photothermal therapy (PTT) in the second near-infrared (NIR-II) therapeutic window with an increased tissue penetration and elevated maximal permissible exposure has attracted considerable attention in antibacterial applications. However, the lack of bacterial-targeted photothermal agents limits their further development. Herein, we developed three xanthene derivatives (CNs) with intense light harvesting ability around 1180 nm. Their bulky planar conformations facilitated the formation of H-aggregates with outstanding photothermal conversion ability and good photostability in the NIR-II therapeutic bio window. By manipulating side chains of CNs, their liposomes exhibited different surface charges, ranging from negative to positive. Remarkably, the intermolecular hydrogen bonding of CN3 dimer drived the positively charged xanthene skeleton exposed to the periphery, which endowed it natural bacterial targeting potency. Therefore, CN3 possessed a good NIR-II photothermal and broad-spectrum sterilization against Gram-positive and Gram-negative bacteria. The photothermal antibacterial activities for S. aureus and E. coli were 99.4% and 99.2%, respectively, promoting significant wound healing in bacteria-infected mice with superior biocompatibility. This structure-inherent bacterial targeting strategy as a proof-of-concept shows an efficient broad-spectrum bacterial inactivation, indicating more encouraging NIR-II photothermal antibacterial therapy. STATEMENT OF SIGNIFICANCE: Photothermal therapy (PTT) in the second near-infrared region (NIR-II, 1000-1700 nm) enables the treatment of deep inflammation more satisfactory due to higher tissue penetration depth. In this work, three new NIR-II xanthene derivatives (CNs) with intense light harvesting ability around 1180 nm were developed. CNs showed typical H-aggregated performance with bulky planar conformations and outstanding photothermal conversion ability. Density functional theory calculations revealed that the intermolecular hydrogen bonding of CN3 dimer drived the exposure of positively charged xanthene skeleton to periphery of dimer. Therefore, CN3 NPs possessed natural bacterial targeting potency and excellent NIR-II photothermal and broad-spectrum sterilization, and so as to significantly promote the wound healing of Gram-positive / negative bacteria infected mice.

Parameters for health risk assessment associated with chronic exposure to hydrogen sulphide in ambient air

High levels of chemical pollution in ambient air due to industrial emissions can facilitate development of functional disorders in various organs and systems. They are a significant component to be considered when assessing health risks under expo-sure to combined multi-factorial pollution. However, the issue of methodical approaches to assessing possible effects on health under exposure to combinations of chemicals has not been studied enough as regards public health risk assessment. Given that, we suggest a trend to develop the methodology that involves revising and substantiating indicators applied in health risk assessment. This should be done as new research data on influence exerted by chemicals on health (including exposure to levels higher than reference ones) become available. We have substantiated a system of quantitative indicators (including additional reference concentrations) for health risk assessment under chronic exposure to hydrogen sulphide in ambient air (including its elevated levels). Points of departure and modifying factors were established by analyzing studies on effects produced on health by hydrogen sulphide. On their basis, we developed parameters for non-carcinogenic health risk assessment. The reference concentration equaled 0.002 mg/m3 (the critical systems were respiratory organs and the nervous system). The additional reference concentration for risk assessment under elevated exposure to hydrogen sulphide was substantiated as equal 0.07 mg/m3 (impaired development being the critical system in the case). The suggested system of quantitative indicators enhances and specifies parameters for health risk assessment. This makes it possible to perform more adequate assessment of health risks under combined exposure to chemicals in ambient air including those contained in levels higher than reference ones. The suggested system of quantitative indicators was tested properly; as a result, the system was established to give an opportunity to obtain more comprehensive and accurate results of health risk assessment under combined exposure to chemical pollutants.

Параметры для оценки риска, связанного с хронической аэрогенной экспозицией сероводорода

High levels of chemical pollution in ambient air due to industrial emissions can facilitate development of functional disorders in various organs and systems. They are a significant component to be considered when assessing health risks under expo-sure to combined multi-factorial pollution. However, the issue of methodical approaches to assessing possible effects on health under exposure to combinations of chemicals has not been studied enough as regards public health risk assessment. Given that, we suggest a trend to develop the methodology that involves revising and substantiating indicators applied in health risk assessment. This should be done as new research data on influence exerted by chemicals on health (including exposure to levels higher than reference ones) become available. We have substantiated a system of quantitative indicators (including additional reference concentrations) for health risk assessment under chronic exposure to hydrogen sulphide in ambient air (including its elevated levels). Points of departure and modifying factors were established by analyzing studies on effects produced on health by hydrogen sulphide. On their basis, we developed parameters for non-carcinogenic health risk assessment. The reference concentration equaled 0.002 mg/m3 (the critical systems were respiratory organs and the nervous system). The additional reference concentration for risk assessment under elevated exposure to hydrogen sulphide was substantiated as equal 0.07 mg/m3 (impaired development being the critical system in the case). The suggested system of quantitative indicators enhances and specifies parameters for health risk assessment. This makes it possible to perform more adequate assessment of health risks under combined exposure to chemicals in ambient air including those contained in levels higher than reference ones. The suggested system of quantitative indicators was tested properly; as a result, the system was established to give an opportunity to obtain more comprehensive and accurate results of health risk assessment under combined exposure to chemical pollutants.