This research study evaluates the impact of the Covid 19 pandemics on the downside risk-return volatilities across the four stock markets of the USA, UK, China, and Pakistan. The pandemic results in severe economic and financial consequences both at micro and macro levels as well as across the stock markets of various countries. The selected stock markets of the USA, UK, Pakistan, and China are significantly affected in terms of both investor risk and return during the pandemic time. The entire period distribution of the risk exhibited the downside risk behavior of both markets and investors’ serious concern regarding their investment strategies. Using high-frequency data from January 2020 to April 2021, the findings of the study reveal more of the downside abnormal returns across both markets. The impact is larger and high in developed markets of USA and UK compared to the emerging markets of China and Pakistan. The outcomes of the various value-at-risk models disclose the higher downside risk implications for all markets, larger for developed countries. Similarly, the three stock markets of the USA, UK, and China were found to be significantly connected during a pandemic. Investors’ reactions were positive and high in case of positive news outbreaks and dwindling in case of negative news and downside impact. The outcomes of the study are useful for investors, portfolio managers, investment advisors, and others to understand the dynamics of the pandemic situation and devise effective strategies to overcome the severities of downside risk.

Cefazolin (CFZ) is a ubiquitous antibiotic in hospital settings and has been recognized as an emerging contaminant due to its ecotoxicity. Despite the growing concern around this compound, the literature addressing feasible advanced techniques for CFZ uptake from aqueous matrices is still scarce. Thus, the objective of this work was to evaluate the adsorption of cefazolin on Spectrogel® organoclay in a batch system as an efficient remediation method. The optimization of experimental conditions was determined by a central composite rotational design. A pH study, as well as equilibrium, kinetic, and thermodynamic assays, was performed to assess the adsorption of CFZ on Spectrogel®. The kinetic and equilibrium models that best described the system were the external mass transfer resistance and Sips models, respectively. A removal efficiency above 80% was achieved, and the maximum adsorption capacity at 25 °C was 398.6 mg g⁻¹. The post-process contaminated organoclay was thermally regenerated. The outcomes of this work indicate that Spectrogel® is an environmentally friendly adsorbent for the removal of cefazolin from wastewater.

The increasing rare earth elements’ (REE) demand to meet the market request and the current political scenario show that it is essential to find good solutions to recover these elements from waste (both industrial and mining). Zeolites are microporous materials with high cation exchange capacity, up to now only little investigated for REE recycle. Here, we propose the use of NH₄⁺-exchanged zeolite L for Ce recovery from a very diluted solution (0.002 M), mimicking the Ce³⁺ concentration of the liquors deriving from the leaching of spent catalysts. The aim of this work is twofold: (i) to investigate the exploitability of zeolite L as cation exchanger in the Ce recovery; and (ii) to determine the best working conditions. The investigated process consists of a coupled cation exchange: (1) in the first exchange the NH₄⁺ cations — present in the zeolite porosities — are exchanged with the Ce³⁺ ions in the solution; and (2) in the second experiment, the Ce³⁺ trapped into the zeolite is recovered through a further exchange with NH₄. The best working conditions for Ce³⁺ exchange of NH₄-zeolite L are: batch system, liquid/solid ratio equal to 90 mL/g and 180 mL/g, 24 h of contact at 25 °C. The resulting Ce adsorption capacity (qₜ) is equal to ~25 mg/g and ~39 mg/g and the removal efficiency 100% and 77% for the two tested liquid/solid ratios, respectively. The kinetics was proved to be fast and consistent with industrial timing; no energy cost for temperature setting is required; and the acid pH (~4) of the solutions does not affect the zeolite structure stability and its exchange performance. It has been demonstrated that the zeolite framework is not affected by the exchange so that the same absorbent material can be employed many times.

In the present work, an outdoor experimental investigation for solar air heater with arc-shape apex upstream flow by the use of circular cross-sectional wires as roughness elements has been carried out. The roughness elements have been expressed in non-dimensionalizing geometric parameters as relative roughness pitch (P/e), relative roughness height (e/D), and flow attack angle (α/60), and the range of these parameters varies from 8 to 15, 0.0454, and 0.75 to 1.25, respectively. For evaluation of performance of the roughened SAH, a novel parameter has been proposed and introduced in the present investigation which is thermo-hydraulic improvement parameter (THIP). With the use of present roughness geometry, considerably, Nusselt number enhancement ratio (NNER) and friction factor enhancement ratio (FFER) have been observed. The maximum NNER and FFER values obtained experimentally are about 2.83 and 1.79 times, respectively, while the maximum THIP obtained is 157.49% higher than the smooth SAH. Using the experimental results, correlations for the output parameters (Nusselt number and friction factor) as a function of input parameters (flow and roughness) have been developed.

Although the solar distillers are one of the economic solutions for addressing the freshwater shortage problem around the world, these devices suffer from low productivity. In this paper, a simple and inexpensive modification was made in the tubular solar still (TSS) to improve its productivity. The adjustment is to tilt the glass cylinder, something to help the droplets move down and collect them as a distillate. The modified inclined TSS was abbreviated by ITSS. Then, three different inclination angles were investigated (2°, 4°, and 6°), and the performance of ITSS with these inclination angles was compared with that of TSS without inclination angle (0°). Moreover, to obtain additional productivity for ITSS, the basin was painted with a mixture of matte black paint with nanomaterials. Three types of nanomaterials were studied (copper oxide nanoparticles, titanium oxide nanoparticles, and silver nanoparticles). For further improvement in ITSS productivity, Ag nanoparticles mixed with phase change material (PCM) were employed beneath the ITSS base to work as thermal energy storage material. Experimental results revealed that the highest average daily productivity rise for ITSS over TSS was observed when tilting ITSS by 6°, where the daily productivity rise and thermal efficiency reached 24% and 37.6%, respectively. Besides, the average increase in daily distillate of ITSS was 34%, 30%, and 28.5% when using Ag, CuO, and TiO₂, respectively, compared to that of TSS. Moreover, ITSS with Ag provided the best thermal efficiency compared to the other operating cases, where it was 39.1%. In addition, ITSS-PCM-Ag showed a daily productivity of 62.5% more than that of TSS and a thermal efficiency of 43.5%.

The aquatic ecological health status was focused on the Huai River Basin (HRB) from the aspects of water quantity, water quality, water ecology, river connectivity, and riparian habitat environment. Ten monitoring sections were set up in the middle and upper reaches of HRB, and 5 experiments of each section were conducted in July and December from 2012 to 2014. Thus, relevant data on the species, the density of phytoplankton, zooplankton and benthic animals, the concentration of water physicochemical variables, and riparian habitat quality were obtained. Eleven key impact factors were chosen using frequency statistics, theoretical analysis, and correlation analysis methods, forming the evaluation index system of aquatic ecological health. Then, the indicator weight value was determined by the combined weight method, and the health degree was evaluated by the comprehensive index method. On the whole, the aquatic ecological health degree of the upper sections (D1 ~ D3) of the Shaying River ranges from 0.334 to 0.927, which is generally in a “sub-healthy” state. The aquatic ecological health degree of the main section of the Huai River (D8 ~ D10) ranges from 0.362 to 0.777, which is in the “critical” or “sub-healthy” state. The Huaidian Sluice (D5) and Fuyang Sluice (D6) in the middle and lower reaches of the Shaying River had the worst aquatic ecological health. Its water ecological health range is 0.283–0.523, and most of them are under “sub-pathologic.” The research results have important theoretical and practical significance. They can enrich the evaluation theories and methods of river aquatic ecological health, help to grasp the aquatic ecological health status in HRB, and provide basic support for aquatic ecological protection and water pollution control in sluice-controlled rivers.

In this study, we optimized and explored the effect of the conditions for synthesizing Fe-loaded food waste biochar (Fe@FWB) for Cr(VI) removal using the response surface methodology (RSM) and artificial neural network (ANN). The pyrolysis time, temperature, and Fe concentration were selected as the independent variables, and the Cr(VI) adsorption capacity of Fe@FWB was maximized. RSM analysis showed that the p-values of pyrolysis temperature and Fe concentration were less than 0.05, indicating that those variables were statically significant, while pyrolysis time was less significant due to its high p-value (0.2830). However, the ANN model results showed that the effect of pyrolysis time was more significant on Cr(VI) adsorption capacity than Fe concentration. The optimal conditions, determined by the RSM analysis with a lower sum of squared error than ANN analysis, were used to synthesize the optimized Fe@FWB (Fe@FWB-OPT) for Cr(VI) removal. From the equilibrium model fitting, the Langmuir model showed a better fit than the Freundlich model, while the Redlich–Peterson isotherm model overlapped. The Cr(VI) sorption capacity of Fe@FWB-OPT calculated from the Langmuir model was 377.71 mg/g, high enough to be competitive to other adsorbents. The kinetic Cr(VI) adsorption was well described by the pseudo-second-order and Elovich models. The XPS results showed that Cr adsorbed on the surface of Fe-FWB-OPT was present not only as Cr(VI) but also as Cr(III) by the reduction of Cr(VI). The results of Cr(VI) adsorption by varying the pH indicate that electrostatic attraction is a key adsorption mechanism.

In this study, the risk of Aspergillus (Asp.) positivity and its respiratory health impacts on wastewater treatment plant (WWTP) workers were studied. In addition, it identified the geno-susceptibility role of mannose-binding lectin 2 (MBL2) gene polymorphisms and the mannose-binding lectin (MBL) serum levels on the pulmonary functions of the Asp.-positive workers. Pulmonary function tests (PFTs) were performed for 89 workers from a selected WWTP, after exclusion of the smokers. Molecular identification of Asp. blood positivity was done by 18S rRNA sequencing. Determination of MBL2 gene polymorphism and estimation of MBL serum levels were done. PFTs revealed abnormalities in 49.2% of the workers. Asp. was positive in 42.5% of the workers with different species. Among the Asp.-positive workers, 6.5% of the workers were with obstructive PFTs, 12.9% with restriction, and 22.6% with combined PFT abnormalities. MBL2 genotyping showed that wild genotype AA was common (68.5%) among Asp.-positive workers compared to the other genotypes. This allele, whether homozygous or heterozygous, was significantly associated with decline in PFTs of the exposed workers. MBL serum levels were significantly lower in workers with obstructive, restrictive, and combined PFT abnormalities compared to those with normal PFTs, and in the workers with Asp.-positive species than the Asp.-negative workers. Moreover, it was significantly lower in workers with Asp. fumigatus compared to that in the workers with other Asp. species, and in the Asp.-positive workers with homozygous or heterozygous A allele compared to that in the Asp.-positive workers with homozygous B allele. Working in a WWTP can be associated with impaired PFTs due to exposure to airborne fungi. MBL2 genotyping showed that Asp.-positive workers with homozygous or heterozygous A allele were at risk to develop decline in their PFTs.

CdS-AgO@g-C₃N₄ nanocomposites were successfully synthesized and characterized by XRD, N₂ physical adsorption, XPS, SEM, TEM, EDX, and UV–Vis DRS (various technical means). The adsorption light range of as-prepared materials could extend to the whole visible light region with the addition of Ag. Silver can act as a bridge to facilitate the separation of electrons and holes, thereby greatly enhancing the photocatalytic activity of CdS-AgO@g-C₃N₄, enabling the maximum degradation efficiency of salicylic acid in water to reach 92.8% under visible light. Peroxy radical is the most important radical in the photocatalytic reaction process, followed by electron and hole, while hydroxyl radical has almost no effect. In addition, the mechanism of photocatalytic process was also explored.

Assessment of contaminated food through the dietary intake is essential for human health. To investigate the health risk of rare earth element (REE) exposure to fruits and vegetables in mining areas in China, we collected 288 fruit samples and 942 vegetable samples from four representative mining points (Bayan Obo in Inner Mongolia, Weishan in Shandong, Maoming in Guangdong, Longnan in Jiangxi) and their control areas. The content of REEs was determined by inductively coupled plasma-mass spectrometry (ICP-MS). The total REEs in fruits from mining and control areas were 12.90 μg kg⁻¹ and 11.89 μg kg⁻¹, and in vegetables were 92.90 μg kg⁻¹ and 62.38 μg kg⁻¹, and the difference was statistically significant in vegetables (P = 0.048). The drupes had more REE concentration in fruits (68.41 μg kg⁻¹, 16.90 μg kg⁻¹ in mining and control areas, respectively) (P < 0.01), and the leafy vegetables had more REE concentration in vegetables (245.81 μg kg⁻¹, 123.51 μg kg⁻¹ in mining and control areas, respectively) (P < 0.01). With the enrichment of light rare earth elements (LREE), the REE distribution patterns coincided in mining and control areas and different types of fruits and vegetables. The health risk assessment indicated that the estimated daily intakes (0.02–0.06 μg kg⁻¹ day⁻¹, 0.53–1.22 μg kg⁻¹ day⁻¹ for fruits and vegetables, respectively) were lower than the allowable daily intake value (60.4 μg kg⁻¹ day⁻¹). In mining areas, REEs obtained from fruits and vegetables were insufficient to cause health damage to human beings. However, sustained exposure to low REEs, especially for children, still needs attention.