A two-stage treatment system that included vertical flow (VF) and free-water surface (FWS) constructed wetlands was investigated for the dual purposes of sewage treatment and reuse. The VF included ...four layers (biochar, sand, gravel, and sandy soil), and the FWS was installed after the VF and used as a polishing tank. Two types of local plants, namely Colocasia esculenta and Canna indica, were planted in the VF and FWS, respectively. The system operated for approximately six months, and the experimental period was categorized into four stages that corresponded to changes in the hydraulic loading rate (HLR) (0.02–0.12 m/d). The removal efficiencies for total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD5), ammonia (NH4-N), and total coliform (Tcol) were 71 ± 11%, 73 ± 13%, 79 ± 11%, 91 ± 3%, and 70 ± 20%, respectively. At HLRs of 0.04–0.06 m/d, the COD and BOD5 levels satisfied Vietnam's irrigation standards, with removable rates of 64% and 88%, respectively, and the TSS and Tcol levels satisfied Vietnam's standards for potable water. Furthermore, the NO3-N levels satisfied the reuse limits, whereas the NH4-N levels exceeded the reuse standards. At high HLRs (e.g., 0.12 m/d), all the effluent parameters, except Tcol and NO3-N, exceeded the standards.
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•A sewage treatment system with biochar and a constructed wetland was studied.•The COD and BOD5 levels of the system effluents met the irrigation standards.•All indicators except NH4-N satisfied the Vietnamese water supply standards.•The system most optimally processes water for irrigation at an HLR of 0.04–0.06 m/d.•Biochar is a promising medium for soil-based wastewater treatment systems.
In this research, the numerical calculation for elastic and nonlinear strains of Fe metal and FeC alloy under different pressures has been performed by the statistical moment method SMM with ...Mie–-Lennard–Jones potential (MLJ) and Embedded-Jones potential Atom Method (EAM). The analysis reveals that an enhancement in the concentration (cC) from 0 to 5% causes a decrement in the Young’s modulus (E) at room temperature (T = 300 K) for FeC. These calculated results are consistent with the experimental results. In addition, the obtained stress-strain curves for Fe are in perfect agreement with the experimental curves. Besides, increasing the cC for a continuous strain decreases the stress, showing that adding C to Fe to form FeC steel will increase strength and hardness, but decrease elasticity and hardness. The results obtained will be very useful not only for experimental studies but also for theoretical studies of metals and their interstitial alloys.
This study evaluated and compared the performance of two vertical flow constructed wetlands (VF) using expanded clay (VF1) and biochar (VF2), of which both are low-cost, eco-friendly, and exhibit ...potentially high adsorption as compared to conventional filter layers. Both VFs achieved relatively high removal for organic matters (i.e. Biological oxygen demand during 5 days, BOD5) and nitrogen, accounting for 9.5 – 10.5 g.BOD5.m−2.d−1 and 3.5 – 3.6 g.NH4-N.m−2.d−1, respectively. The different filter materials did not exert any significant discrepancy to effluent quality in terms of suspended solids, organic matters and NO3-N (P > 0.05), but they did influence NH4-N effluent as evidenced by the removal rate of that by VF1 and VF2 being of 82.4 ± 5.7 and 84.6 ± 6.4%, respectively (P < 0.05). The results obtained from the designed systems were further subject to machine learning to clarify the effecting factors and predict the effluents. The optimal algorithms were random forest, generalized linear model, and support vector machine. The values of the coefficient of determination (R2) and the root mean square error (RMSE) of whole fitting data achieved 74.0% and 5.0 mg.L−1, 80.0% and 0.3 mg.L−1, 90.1% and 2.9 mg.L−1, and 48.5% and 0.5 mg.L−1 for BOD5_VF1, NH4-N_VF1, BOD5_VF2, and NH4-N_VF2, respectively
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•Vertical flow packed biochar exposed the promising potential for absorbing nitrogen.•Different filters do not significantly influence effluents, except for NH4-N.•Random forest, Generalized linear model, and Support vector machines selected.•Low difference between RMSE and the range of experimental effluents (BOD5 and NH4-N).
•Nanoporous α-Fe2O3 nanoparticles were prepared by a facile hydrothermal method.•The Fe2O3 was effectively used for benzylation of benzene and aromatic compounds.•The dispersion and the porous ...structure affect the catalytic sites of the Fe2O3.•The Fe2O3 are potential catalyst for benzylation to synthesize diphenylmethane.
The catalytic benzylation of benzene and other aromatic compounds is one of the most important reactions in the synthesis of pharmaceutical compounds. In this study, we report the synthesis of nanoporous α-Fe2O3 nanoparticles via a hydrothermal method and their application in the catalytic benzylation of benzene and benzyl chloride in the fabrication of diphenylmethane. Crystal structure and morphology characterization results demonstrated that the hydrothermal method enabled the fabrication of highly dispersed α-Fe2O3 nanoparticles with spherical shape and an average size of 100nm. The α-Fe2O3 nanoparticles have nanopores of less than 10nm that are randomly distributed inside the nanoparticles. The catalytic benzylation of benzene and benzyl chloride was conducted over the synthesized α-Fe2O3 nanoparticles. The results demonstrated that the synthesized α-Fe2O3 nanoparticles are effective catalysts for the benzylation of benzene and benzyl chloride with high activity and selectivity.
In this study, we used both silk fibroin nanofibers (nSFs) and rice husk silica nanoparticles as epoxy (EP) resin reinforcement materials to improve the modes I and II interlaminar fracture toughness ...of EP-filled carbon fiber-based (CF/EP) composites. The nSFs were obtained by electrospinning, while the rice husk silica nanoparticles were obtained via acidic and thermal treatments. The results showed that the interfacial shear strength, GIC, and GIIC of the CF/EP composites improved by 25, 36, and 30%, respectively, by adding 0.2 wt% nSF and 20 wt% silica nanoparticles.
Nowadays, estuarial areas have been strongly affected by the construction of electrical power dams from upstream, downstream urbanization and many types of hazards along the coastal regions. It has ...resulted in significant changes in estuarine wetland ecosystems between rainy and dry seasons. To avoid estuary vulnerability, monitoring and evaluation of the estuarine ecosystems are very critical tasks. The main goal of this research is to propose and implement a novel deep learning method in monitoring various ecosystems in estuarine regions. The processing speed and accuracy of common neural networks is improved more than ten times through spatial and context paths integrated into a novel Bilateral Segmentation Network (BiSeNet). The multi-sensor and multi-temporal satellite images (including Sentinel-2, ALOS-DEM, and NOAA-DEM images) served as input data. As a result, four BiSeNet models out of 20 trained models achieved a greater than 90% accuracy, especially for interpreting estuarine waters, intertidal forested wetlands, and aquacultural lands in subtidal regions. These models outperformed Random Forest and Support Vector Machine approaches. The best one was used to map estuarine ecosystems from 12 satellite images over a five-year period in the largest estuary in northern Vietnam. The ecosystem changes between dry and rainy seasons were analyzed in detail to assess the ecological succession in estuaries. Furthermore, this model can potentially update new estuarine ecosystem types in other estuarine areas across the world, making possible real-time monitoring and assessing estuarine ecological conditions for sustainable management of wetland ecosystem.
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•Deep learning models can be applied to monitoring estuarine wetland ecosystems.•The BiSeNet model using Nadam optimizer was chosen in 48 trained models.•The best model for classification of estuarine wetland ecosystem achieved accuracy of 94%.•The estuarine ecosystems were monitored through 20 S-2 images using the BiSe-Nadam model.
The synthesis of reduced graphene oxide modified by magnetic iron oxide (Fe3O4/rGO) and its application for heavy metals removal were demonstrated. The obtained samples were characterized by X-ray ...diffraction (XRD), nitrogen adsorption/desorption isotherms, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and magnetic measurement. The results showed that the obtained graphene oxide (GO) contains a small part of initial graphite as well as reduced oxide graphene. GO exhibits very high surface area in comparison with initial graphite. The morphology of Fe3O4/rGO consists of very fine spherical iron nanooxide particles in nanoscale. The formal kinetics and adsorption isotherms of As(V), Ni(II), and Pb(II) over obtained Fe3O4/rGO have been investigated. Fe3O4/rGO exhibits excellent heavy metal ions adsorption indicating that it is a potential adsorbent for water sources contaminated by heavy metals.
Evaluating the prognosis of patients with aneurysmal subarachnoid hemorrhage (aSAH) who may be at risk of poor outcomes using grading systems is one way to make a better decision on treatment for ...these patients. This study aimed to compare the accuracy of the modified World Federation of Neurosurgical Societies (WFNS), WFNS, and Hunt and Hess (H&H) Grading Scales in predicting the outcomes of patients with aSAH. From August 2019 to June 2021, we conducted a multicenter prospective cohort study on adult patients with aSAH in three central hospitals in Hanoi, Vietnam. The primary outcome was the 90-day poor outcome, measured by a score of 4 (moderately severe disability) to 6 (death) on the modified Rankin Scale (mRS). We calculated the areas under the receiver operator characteristic (ROC) curve (AUROCs) to determine how well the grading scales could predict patient prognosis upon admission. We also used ROC curve analysis to find the best cut-off value for each scale. We compared AUROCs using Z-statistics and compared 90-day mean mRS scores among intergrades using the pairwise multiple-comparison test. Finally, we used logistic regression to identify factors associated with the 90-day poor outcome. Of 415 patients, 32% had a 90-day poor outcome. The modified WFNS (AUROC: 0.839 95% confidence interval, CI: 0.795-0.883; cut-off valuegreater than or equal to2.50; P.sub.AUROC <0.001), WFNS (AUROC: 0.837 95% CI: 0.793-0.881; cut-off valuegreater than or equal to3.5; P.sub.AUROC <0.001), and H&H scales (AUROC: 0.836 95% CI: 0.791-0.881; cut-off valuegreater than or equal to3.5; P.sub.AUROC <0.001) were all good at predicting patient prognosis on day 90.sup.th after ictus. However, there were no significant differences between the AUROCs of these scales. Only grades IV and V of the modified WFNS (3.75 standard deviation, SD: 2.46 vs 5.24 SD: 1.68, p = 0.026, respectively), WFNS (3.75 SD: 2.46 vs 5.24 SD: 1.68, p = 0.026, respectively), and H&H scales (2.96 SD: 2.60 vs 4.97 SD: 1.87, p<0.001, respectively) showed a significant difference in the 90-day mean mRS scores. In multivariable models, with the same set of confounding variables, the modified WFNS grade of III to V (adjusted odds ratio, AOR: 9.090; 95% CI: 3.494-23.648; P<0.001) was more strongly associated with the increased risk of the 90-day poor outcome compared to the WFNS grade of IV to V (AOR: 6.383; 95% CI: 2.661-15.310; P<0.001) or the H&H grade of IV to V (AOR: 6.146; 95% CI: 2.584-14.620; P<0.001). In this study, the modified WFNS, WFNS, and H&H scales all had good discriminatory abilities for the prognosis of patients with aSAH. Because of the better effect size in predicting poor outcomes, the modified WFNS scale seems preferable to the WFNS and H&H scales.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Chemical bonding of the 3d transition metal-doped germanium Ge
2
M (M = Sc–Zn) clusters is investigated by using quantum chemical calculations combined with the analyses of natural atomic orbital ...(NAO), natural bond orbital (NBO) and natural resonance theory (NRT). All of the clusters have ground state structure of isosceles triangle whose chemical bonding can be described by orbital overlaps and electron transfers between M atom and Ge
2
unit. Among the series, Ge
2
Ti is found to be the most stable cluster due to the best electron pairing between AO-4
s
and AOs-3
d
of Ti atom and the three bonding orbitals of the Ge
2
unit, whereas Ge
2
Zn is the least stable thanks to the only overlap between AO–4
s
(Zn) and MO-π
y
of the Ge
2
unit. While the Ge–Ge bond is of most covalent character, the Ge–M bond is of half-half covalent and ionic character. The double Ge=Ge bond of Ge
2
is either enhanced (M = Cr, Mn, Cu and Zn) or depleted (M = Sc–Ti, Fe–Ni) upon interacting with the transition metal atom due to the electron transfer between the metal atom and the Ge
2
unit. Finally, the 3d shell of the dopant atoms remains most of their own character in these clusters, especially magnetic moment, which is very interesting for potential magnetic materials.
Small and medium-sized firms, particularly startups, are highly vulnerable to the COVID-19 pandemic because of their financial instability. Using a sample of listed startups across four countries, we ...investigate whether a startup's built-up capacity pre-COVID-19 can stimulate corporate immunity to endure the impact of the COVID-19 pandemic, reflected via stock performance. We find that the increase in the accumulated COVID-19 confirmed cases worsens stock returns and that the negative effect is alleviated if startups are greater in size as well as have low debt, large board size and CEO duality. Moreover, national cultural dimensions significantly moderate the relationship between stock returns and COVID-19. The COVID-19 negative impact is relieved in societies where people are more collectivistic and cooperative, less tolerant towards uncertainty, and more long-term oriented. Overall, our results support the consolidation of corporate capacities and suggest policymakers consider national culture when formulating COVID-19 or similar infectious pandemic strategies.
•We examine whether a startup's built-up capacity helps stimulate corporate immunity.•Accumulated COVID-19 confirmed cases worsens stock returns of listed startups.•Negative effect is alleviated if startups have low debt, larger board, and CEO duality.•Larger startups are less affected.•National cultural dimensions significantly moderate the return-COVID relationship.
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