This work studies the Pb(II) removal onto bentonite clay modified by hexadecyl trimethyl ammonium bromide (HDTMA). Characterizations of the unmodified and modified materials were performed by using ...XRD, SEM, TG-DSC, FT-IR, and BET surface area analyses. Factors influencing the uptake of Pb(II) from aqueous solution, such as pHsolution, ion strength, uptake time, adsorbent dosage, and initial Pb(II) concentration, were examined. The obtained results showed that bentonite clay was successfully modified by HDTMA, resulting in an increase in its surface area by about 70 %. The Pb(II) adsorption onto modified bentonite clay reached equilibrium at pH = 5.0 after 120 min. Studies within the isotherm and kinetic models demonstrated that the adsorption followed the Sips isotherm and pseudo-second-order kinetic models. The maximum monolayer adsorption capacity calculated from the Langmuir model at 30 °C was 25.8 mg/g, which is much higher than that obtained for the unmodified sample (18.9 mg/g). The FT-IR and TG-DSC analyses indicated that the formation of inner-sphere complexes plays a fundamental role in the mechanism of Pb(II) uptake onto HDTMA-bentonite clay. This mechanism of Pb(II) adsorption was further investigated, for the first time, by using the positron annihilation lifetime (PAL) and electron momentum (EMD) measurements. The PAL and EMD analyses indicated that the existence of Al and Si mono-vacancies in the HDTMA-bentonite should have essential contributions to the adsorption mechanism. In particular, we found a very interesting mechanism that the Pb(II) adsorption should occur inside the interlayer spaces of the HDTMA-bentonite.
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•Bentonite clay was modified by HDTMA to enhance the Pb(II) removal.•The Langmuir monolayer adsorption capacity of HDTMA-modified bentonite was 25.8 mg/g.•The mechanisms of Pb(II) adsorption were studied via different analytical methods.•The formation of inner-sphere complexes played a major mechanism in the Pb(II) uptake.
A simple design of a broadband multifunctional polarization converter using an anisotropic metasurface for X-band application is proposed. The proposed polarization converter consists of a periodic ...array of the two-corner-cut square patch resonators based on the FR-4 substrate that achieves both cross-polarization and linear-to-circular polarization conversions. The simulated results show that the polarization converter displays the linear cross-polarization conversion in the frequency range from 8 to 12 GHz with the polarization conversion efficiency above 90%. The efficiency is kept higher than 80% with wide incident angle up to 45°. Moreover, the proposed design achieves the linear-to-circular polarization conversion at two frequency bands of 7.42-7.6 GHz and 13-13.56 GHz. A prototype of the proposed polarization converter is fabricated and measured, showing a good agreement between the measured and simulated results. The proposed polarization converter exhibits excellent performances such as simple structure, multifunctional property, and large cost-efficient bandwidth and wide incident angle insensitivity in the linear cross polarization conversion, which can be useful for X-band applications. Furthermore, this structure can be extended to design broadband polarization converters in other frequency bands.
Data on breakthrough SARS-CoV-2 Delta variant infections in vaccinated individuals are limited.
We studied breakthrough infections among Oxford-AstraZeneca vaccinated healthcare workers in an ...infectious diseases hospital in Vietnam. We collected demographic and clinical data alongside serial PCR testing, measurement of SARS-CoV-2 antibodies, and viral whole-genome sequencing.
Between 11th–25th June 2021 (7-8 weeks after the second dose), 69 staff tested positive for SARS-CoV-2. 62 participated in the study. Most were asymptomatic or mildly symptomatic and all recovered. Twenty-two complete-genome sequences were obtained; all were Delta variant and were phylogenetically distinct from contemporary viruses obtained from the community or from hospital patients admitted prior to the outbreak. Viral loads inferred from Ct values were 251 times higher than in cases infected with the original strain in March/April 2020. Median time from diagnosis to negative PCR was 21 days (range 8–33). Neutralizing antibodies (expressed as percentage of inhibition) measured after the second vaccine dose, or at diagnosis, were lower in cases than in uninfected, fully vaccinated controls (median (IQR): 69.4 (50.7-89.1) vs. 91.3 (79.6-94.9), p=0.005 and 59.4 (32.5-73.1) vs. 91.1 (77.3-94.2), p=0.043). There was no correlation between vaccine-induced neutralizing antibody levels and peak viral loads or the development of symptoms.
Breakthrough Delta variant infections following Oxford-AstraZeneca vaccination may cause asymptomatic or mild disease, but are associated with high viral loads, prolonged PCR positivity and low levels of vaccine-induced neutralizing antibodies. Epidemiological and sequence data suggested ongoing transmission had occurred between fully vaccinated individuals.
Wellcome and NIH/NIAID
Two new cycloartanes, combretic acid C (1) and combretanone I (3), were isolated from the leaves of Combretum quadrangulare Kurz, together with the previously-reported combretic acids A-B (2 and 5) ...and combretanone A (4). An extensive set of spectroscopic methods were used to elucidate the structures of these compounds. Cytotoxicity against the K562 cancer cell line was evaluated. Compound 1 showed strong activity, with an IC
50
value of 9.7 µM. The other compounds showed moderate activity. Alpha-glucosidase inhibition was also evaluated. The isolated compounds showed moderate inhibition, with IC
50
values in the range 102.2-194.7 µM.
In this report, the adsorption of Cr(VI) onto MnO2/CS nanocomposite material from aqueous solution is investigated. All the factors, which affect the adsorption, such as pH, adsorption time, Cr(VI) ...initial concentration and adsorbent dosage, are also examined. The results obtained show that the Cr(VI) uptake is strongly affected by pH and ion strength. Analysis within the nonlinear isotherm models indicates that the Sips isotherm combining with the Langmuir and Freundlich models offer the best fit to the experimental data due to the obtained highest R2 and smallest RMSE and χ2 values. The calculated Langmuir monolayer adsorption capacity is 61.56 mg g−1 at pH of 2.0 and adsorption time of 120 min. Moreover, the mechanism studies by combining theoretical models with analytical spectroscopies reveal that the electrostatic attraction plays the important role to the uptake of Cr(VI) onto MnO2/CS nanocomposite. Therefore, the present nanocomposite material can be applied to remove total Cr from wastewater produced by the galvanized manufacturing factory with a relatively high efficiency.
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•MnO2/CS nanocomposite was used as an adsorbent to remove Cr(VI) from aqueous solution.•The Langmuir monolayer adsorption capacity is 61.56 mg g−1.•The primary mechanism of the uptake of Cr(VI) onto MnO2/CS was proposed.•MnO2/CS was applied to remove total Cr in effluent with the high removal of 94.21%.
Channel catfish (Ictalurus punctatus) are one of the most commercially important fish species cultured in Vietnam, and has been a major driver of Vietnam's rise to become a leading country for ...fisheries exports in the world. Since 2016, there have been several outbreaks of a contagious disease which in channel catfish has resulted in severe levels of economic loss. In this study, bacterial isolates from diseased fish were sampled and analyzed from 22 farms in four Northern Vietnam provinces experiencing outbreaks. Isolates were identified as Aeromonas veronii based on their bacteriological characteristics, 16S rRNA sequence analysis, and presence of Aeromonas veronii specific rpoB gene by PCR examinations. Subsequently, A. veronii isolates were tested for their virulence to fish via an experimental infection challenge, and their susceptibility to 21 antibiotics was also assessed. Results showed that A. veronii is pathogenic and has probably contributed to the mass mortality of this channel catfish species in Vietnam. Notably, A. veronii also exhibited resistance to four common antibiotics including amoxicillin, bicozamycin, lincomycin, and vancomycin. To our knowledge, this is the first report of outbreaks associated with A. veronii infection in channel catfish in a Southeast Asian country. This report could be used to alert aquaculture farmers and managers in this region to develop an appropriate biosecurity strategy for protecting catfish and other vulnerable species to A. veronii infection, and find alternative solutions to help mitigate occurences of the disease.
•Aeromonas veronii caused disease and mortality among farmed channel catfish.•Aeromonas veronii exhibited their pathogenic nature towards channel catfish and showed resistance to several common antibiotics used in aquaculture.•The first report of A. veronii infection in channel catfish from Southeast Asian countries.
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