The purpose of this research is the elaboration of cadmium telluride nanoparticles by using the chemical bath deposition technique. The formulation procedure consists of preparing tellurium ions (Te
...−2
) and combination of tellurium ion solution with deionized water, cadmium chloride, and polyethyleneimine (PEI). The nanoparticles were synthesized at three different concentrations denoted C1, C2, and C3. Furthermore, for each CdTe, nanoparticles were obtained with absorption edges at 404.02 nm, 428 nm and 452.66 nm related to C1, C2, and C3, respectively. Also, the direct energy gaps of CdTe nanoparticle semiconductors were: Eg(C1) = 3.07 eV, Eg(C2) = 2.9 eV, and Eg(C3) = 2.74 eV. Transmission electron microscopy (TEM) indicated three different average diameter sizes of a single nanoparticle: D(C1) = 3.23 nm, D(C2) = 6.46 nm, and D(C3) = 7.73 nm with average sizes of 6.11 nm, 5.29 nm, and 9.76 nm, respectively. The fast Fourier transform of TEM contrast micrographs corresponded with a hexagonal structure. The presence of Cd, Te, and TeO
2
was identified by x-ray photoelectron spectroscopy. Raman spectroscopy was used to identify three peaks at 122 cm
−1
, 140 cm
−1
and 165 cm
−1
that proved the formation of CdTe nanoparticles.
The goal of this paper is to present a stable and new formulation route for the synthesis of silver sulfide nanoparticles with stoichiometric Ag
2
S composition in aqueous solution. The structural, ...optical, and morphological properties of Ag
2
S nanoparticles were studied by using characterization techniques such as ultraviolet–visible spectroscopy (UV–Vis), transmission electron microscopy and x-ray photoelectron spectroscopy (XPS). From the UV–Vis spectrum, the direct and indirect energy gap values of 3.56 and 1.89 eV were calculated, related to direct and indirect transitions of electrons, as an estimation of bandgaps. Also, an optical band gap shift with respect to bulk bandgap is observed reported in the literature and is related to nanoparticle size decrease. Furthermore, from the high-resolution transmission electron microscopy micrograph an orthorhombic crystallographic structure was determined with lattice parameters 4.77 × 6.92 × 6.88 Å and the nanoparticle surface showed a honeycomb-like interference pattern. Finally, the expected chemical composition was proved by the low- and high-resolution XPS spectra.
Irgarol and Diuron are the most representative "organic booster biocides" that replaced organotin compounds in antifouling paints. It cannot be assumed beforehand that their use will have no ...environmental impact: more ecotoxicological data and a significant environmental monitoring are required. Spermio and embryotoxicities of the biocides Irgarol and Diuron were investigated on Paracentrotus lividus, the dominant echinoid species of the Mediterranean Sea. Spermiotoxicity was studied by assessing the effects of sperm exposure on fertilization rate as well as on the induction of transmissible damages to the offspring. Embryotoxicity was studied by assessing the developmental defects in the exposed larvae. The experimental results show a Diuron EC50 of 2.39 (+/- 0.21) mg/L with a NOEL of 0.25 mg/L for embryos, and of 5.09 (+/- 0.45) mg/L with a NOEL of 0.5 mg/L for sperms, respectively. Data obtained from the embryotoxicity test on Irgarol EC50 0.99 (+/- 0.69) mg/L are of the same order of magnitude as the literature data about Japanese urchins. Spermiotoxicity tests show an Irgarol EC50 of 9.04 (+/- 0.45) mg/L with a NOEL of 0.1 mg/L. These data show the different sensitivities of the two tests: embryos are more sensitive than sperms for both the tested chemicals and Diuron seems to be the less toxic one. Moreover, as a major output of the experimental work, tested herbicides exert transmissible damage to spermatozoa evidenced by larval malformations in the offspring, mainly P1 type (skeletal alterations). The comparison of the endpoints results offers an interesting indication of a probable different mode of action (Irgarol seems to interact with calcium homeostasis) of the two biocides.
Sea urchin embryotoxicity tests are widely used for evaluating the biological effects of contaminants in marine environments. The currently used traditional and standardized protocols are quite slow ...and laborious. The present work shows a modified bioassay (new embryotoxicity test; NET) in an attempt to speed up laboratory work using a limited number of fertilized eggs. Several experiments have been conducted both with a traditional bioassay and with the NET, using the same test conditions, in order to evaluate the reliability of the proposed simplified bioassay. Adult
Paracentrotus lividus (Lamark) were collected from the Tyrrenian Sea (Bay of Naples) and embryos, reared in filtered seawater, were exposed to increasing potassium dichromate and copper sulfate concentrations. Then the EC
50 was calculated. The analysis of the results evidenced good repeatability. The confidence limits in all tests overlapped; moreover, data correlation analysis between the results of both tests showed a high significant accordance (chromium,
R
2=0.93,
P<0.01; copper,
R
2=0.86,
P<0.05). In conclusion, the NET seems to be a good alternative to the traditional tests; it could be a first step toward a new routine ecotoxicological kit for seawater.
Gluconacetobacter diazotrophicus stands out among the acetic acid bacteria as it fixes dinitrogen and is a true endophyte. It has a set of constitutive enzymes to oxidize ethanol and acetaldehyde ...which is upregulated during N2-dependent growth. The membrane-bound alcohol dehydrogenase (ADH) is a heterodimer (subunit I ≈ 72 kDa, subunit II ≈ 44 kDa) and constitutes an important component of this organism. ADH of Ga. diazotrophicus is a typical quinohemoprotein with one pyrroloquinoline quinone (PQQ) and four c-type cytochromes. For the first time, a 2Fe-2S cluster has been identified by EPR spectroscopy in this type of enzyme. This finding is supported by quantitative chemical analysis, revealing 5.90 ± 0.15 Fe and 2.06 ± 0.10 acid-labile sulfurs per ADH heterodimer. The X-band EPR spectrum of ADH (as isolated in the presence of dioxygen, 20 K) showed three broad resonances at g 2.007, 1.941, and 1.920 (g av 1.956), as well as an intense narrow line centered at g = 2.0034. The latter signal, which was still detected at 100 K, was attributed to the PQQ semiquinone radical (PQQsq). The broad resonances observed at lower temperature were assigned to the 2Fe-2S cluster in the one-electron reduced state. The oxidation−reduction potentials E m (pH 6.0 vs SHE) of the four c-type cytochromes were estimated to E m1 = −64 (±2) mV, E m2 = −8 (±2) mV, E m3 = +185 (±15) mV, and E m4 = +210 (±10) mV (spectroelectrochemistry), E mFeS = −250 (±5) mV for the 2Fe-2S cluster, and E mPQQ = −210 (±5) mV for the PQQ/PQQH2 couple (EPR spectroscopy). We propose a model for the membrane-bound ADH of Ga. diazotrophicus showing hypothetical intra- and intermolecular electron pathways. Subunit I binds the PQQ cofactor, the 2Fe-2S cluster, and one c-type cytochrome. Subunit II harbors three c-type cytochromes, thus providing an efficient electron transfer route to quinones located in the cytoplasmic membrane.
In this work, the synthesis of manganese oxide nanoparticles was achieved by one-step spray pyrolysis method. The nanoparticles were synthesized just from MnCl2 aqueous solution. The solution was ...nebulized to a Si substrate placed at 400 °C for 1, 5 10 and 20 min and transported at a 0.1 L /min rate in a Nitrogen flux. The X-ray diffraction confirms tetragonal Mn3O4 as the unique phase in the whole sample. The scanning electron microscopy images proved the achievement of irregular nanoparticles with an average diameter of 280 nm experimentally determined by dynamic light scattering. Energy dispersive X-ray and Raman spectroscopy confirmed that the nanoparticles were obtained with Mn3O4 single-phase and the employed methodology prevented any contamination. The nanoparticles proved to induce temperature enhancement on artificial breast tissue by exposition to microwave radiation by achieving an increase in temperature around 8 %.
Although the biodegradability of compostable bioplastic bags (CBBs) is well ascertained, concerns arise about the possibility of treating a massive quantity of compostable materials in composting ...facilities of all sizes and configurations. These concerns are even greater in small-scale composting where the biodegrading conditions may be milder that those in industrial composting. In this work, 7–15 lightweight CBBs were disposed of, together with organic food waste, in an electromechanical composter (EMC), every day for about 2 months. For the bulking agent, fragments and twigs of golden wattle wood were used instead of the recommended wood pellets. The composting process was carried out for 3 months in the EMC, and for further 4 months in a heap, in order to complete the maturation. During the process, critical issues in general, and any due to the presence of the CBBs, were reported: high temperatures, up to 72 °C, were constantly reached both in the ECM and in the heap, while critical anaerobic pockets were not detected. After 7 months, when the temperature and pH of the heap were equal to the ambient temperature and to 7.4, respectively, and were constant over time, the process was stopped and the compost produced underwent chemical, physical and biological analysis, in order to evaluate its quality. The CBBs did not produce any visual contamination of the final compost with bioplastic residues. Finally, all the stability, environmental and agronomic parameters were in compliance with the reference values established by law. This work shows how lightweight CBBs are perfectly managed by the EMC, at least with a CBB/organic waste mass ratio that is consistent with a normal use of CBBs as the collector of organic waste.
Graphical abstract
The COVID-19 pandemic forced the scientific community and the pharmaceutical industry to develop new vaccines, in an attempt to reach herd immunity and stop the SARS-CoV-2 from spreading. However, to ...ensure vaccination among the general population, COVID-19 vaccine intention must be measured. So far, no studies have focused on rural residents in Latin America, which represent approximately 20% of the population of this geographical region. In this study, we present the validation of a self-developed questionnaire, which was validated in a pilot study with 40 Spanish-speaking Mexican rural residents in the state of Guerrero, Mexico. In this study, we describe the chronological validation of the questionnaire, including the assessment of its internal consistency and temporal reliability, which we measured with the Cronbach’s alpha and Spearman’s rank correlation coefficient, respectively. After the psychometrical analysis, we were able to validate a 20-item questionnaire, which intends to assess vaccine intention among the rural population. Aiming to develop a comprehensive policy and vaccination strategies, we hope this instrument provides valuable insight regarding COVID-19 vaccination willingness across rural communities in Mexico and Latin America. Finally, if we want to reach worldwide herd immunity, it is important to understand rural residents’ position towards COVID-19 vaccination.
The aim of this work was to investigate the mixture toxicity of Irgarol (2-methylthio-4-t-butylamino-6-cyclopropylamino-s-triazine), Diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea), and copper upon ...the sea urchin Paracentrotus lividus and to compare the observed data with the predictions derived from approaches of Concentration Addition (CA) and Independent Action (IA). Copper spermiotoxicity was more sensitive (EC50 = 0.018 mg/L) than embryotoxicity (EC50 = 0.046 mg/L). The offspring malformations were mainly P1 type (skeletal alterations) in both cases, probably because copper competes to fix Ca²⁺. Irgarol and Diuron toxicity has been previously investigated. EC50 mixture embryotoxicity showed an EC50 of 1.79 mg/L, whereas spermiotoxicity mixture effects were lower than 11%. Both CA and IA modeling approaches failed to predict accurately mixture toxicity. For embryotoxicity, the IA model overestimated the mixture toxicity at effect levels of <80%. CA does not represent the worst-case approach showing values lower than IA (embryotoxicity) or similar (spermiotoxicity).
Improving detection of pediatric tuberculosis (TB) is critical to reducing morbidity and mortality among children.
We conducted a systematic review to estimate the number of children needed to screen ...(NNS) to detect a single case of active TB using different active case finding (ACF) screening approaches and across different settings.
We searched 4 databases (PubMed, Embase, Scopus, and the Cochrane Library) for articles published from November 2010 to February 2020.
We included studies of TB ACF in children using symptom-based screening, clinical indicators, chest x-ray, and Xpert.
We indirectly estimated the weighted mean NNS for a given modality, location, and population using the inverse of the weighted prevalence. We assessed risk of bias using a modified AXIS tool.
We screened 27 221 titles and abstracts, of which we included 31 studies of ACF in children < 15 years old. Symptom-based screening was the most common screening modality (weighted mean NNS: 257 range, 5-undefined, 19 studies). The weighted mean NNS was lower in both inpatient (216 18-241) and outpatient (67 5-undefined) settings (107 5-undefined) compared with community (1117 28-5146) and school settings (464 118-665). Risk of bias was low.
Heterogeneity in the screening modalities and populations make it difficult to draw conclusions.
We identified a potential opportunity to increase TB detection by screening children presenting in health care settings. Pediatric TB case finding interventions should incorporate evidence-based interventions and local contextual information in an effort to detect as many children with TB as possible.
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