Levels of Cu,Zn, Pb,and Cd in the leaves of the tea plant (Camellia sinensis) and in the soil of Gilan and Mazandaran farms of Iran

Tea is known as an inevitable and important part of a healthy and balanced diet. However, it might be contaminated by heavy metals via many ways, including irrigation by sewage water, industrial effluents, sewage sludge, vehicular emissions, industrial wastes, and atmospheric deposition. The concentrations of Cu, Zn, Cd, and Pb elements in the leaves and soil samples of the tea farms in North Iran were determined by using flame and graphite furnace atomic absorption spectrometry. The samples were digested with the concentrated nitric acid and perchloric acid. The descending sequence of the mean metal levels in the tea leaves is as follows: Zn > Cu > Pb > Cd. The content of heavy metals in the tea samples were found and are provided in the following ranges: 6.07–15.24, 55.35–127.22, 0.03–0.64, and 0.06–0.38 µg/g for Cu, Zn, Pb, and Cd, respectively. According to the Institute of Standards and Industrial Research of Iran (ISIRI), the tolerance limits have been adjusted only for copper, cadmium, and lead. However, the present database can be employed for fixing the tolerance limit of zinc in tea. The contents of copper and lead in tea were significantly lower than the permissible limit under the ISIRI act. In contrast, the cadmium concentration was significantly above the permissible limit (P < 0.05). In the conclusion, the comparisonis made between the research results and the literature values.     

The efficacy of nisin can drastically vary when produced in situ in model cheeses

Nisin, a bacteriocin produced by strains of Lactococcus lactis, has a broad inhibitory effect against Gram-positive bacteria. This study investigated the efficacy of nisin Z against Lactobacillus sakei when produced by a nisin-producing strain L. lactis in model cheeses manufactured with ultrafiltrated milk. These cheeses, containing 0, 4 or 10% of gelatin in their dry matter, were inoculated with both strains. Measurement of Lb. sakei loss of viability was an indirect indicator of nisin in situ efficacy. After 24 h, the loss of viability of Lb. sakei was from 0.73 ± 0.14 to 3.30 ± 0.60 log₁₀ cfu g⁻¹ in the cheeses with 0 and 10% of gelatin, respectively, indicating a better in situ efficacy of nisin when gelatin was incorporated. However, the concentration of nisin produced by Lactococcus was similar (3.5 μg g⁻¹) in all model cheeses when measured using an enzyme-linked immune sorbent assay (ELISA). The growth of Lactococcus was slightly improved when gelatin was incorporated, leading to a higher lactate concentration, which is one of the factors explaining the increased nisin efficacy. These results reinforced previous observations that prediction of nisin efficacy in complex food systems remains difficult.     

Screening of arsenic in tubewell water with field test kits: evaluation of the method from public health perspective

There is an urgent need for Bangladesh to identify the arsenic (As) contaminated tubewells (TWs) in order to assess the health risks and initiate appropriate mitigation measures. This will involve testing water in millions of TWs and raising community awareness about the health problems related to chronic As exposure from drinking water. Field test kits offer the only practical tool within the time frame and financial resources available for screening and assessment of the As contaminated TWs as well as their monitoring than that of the laboratory measurement. A comparison of field test kit and laboratory measurements by AAS as "gold standard" for As in water of 12,532 TWs in Matlab Upazila in Bangladesh, indicates that the field kit correctly determined the status of 91% of the As levels compared to the Bangladesh Drinking Water Standard (BDWS) of 50 microg/L, and 87% of the WHO guideline value of 10 microg/L. Nevertheless, due to analytical and human errors during the determination of As by the field test kits, some misclassification of wells is inevitable. Cross-checking of the field test kit results, both by Field Supervisor and by the laboratory analyses reveal considerable discrepancies in the correct screening mainly at As concentration ranges of 10-24.9 microg/L and 50-99.9 microg/L, critical from a public health point of view. The uncertainties of misclassification of these two groups of TWs have severe public health implications due to As exposure from drinking water sources. This can be reduced through proper training of the field personnel, cross verification of the field test kit results with laboratory analyses and further development of the field test kits to determine As at low concentrations.     

Electrochemically Induced Conformational Change of Di-Boronic Acid-Functionalized Ferrocene for Direct Solid-State Monitoring of Aqueous Fluoride Ions

While fluoride ions (F⁻) are abundant across environmental and biological systems, common procedures and potentiometric sensors for quantifying aqueous F⁻ are inefficient, time-consuming, and suffer from poor pH resiliency and high detection limits. Herein, this work reports a new di-boronic acid-functionalized ferrocene (FDBA) molecular receptor for noncovalent F⁻ recognition, toward the development of a solid-state miniaturized voltammetric fluoride sensor capable of direct and reversible F⁻ detection in drinking water (DW) (pH 6) and community water (pH 7.6–9.1) over the µg L⁻¹–mg L⁻¹ range. The associated sensing mechanism is enabled by the conformational change of FDBA from the open (charge-repelled) to closed (π-dimerized) conformation, which is facilitated by the unique linkage of two electron-accepting phenylboronic acid moieties with the electron-donating ferrocene moiety using rigid conjugated amide linkers. The square wave voltammetric (SWV) oxidation current response of the FDBA-based fluoride sensor is spectroscopically investigated, suggesting a combination of electrooxidation-triggered conformational change of FDBA on a nanocarbon-modified electrode, F⁻ anion–π interactions, and resulting electron transfer between F⁻ and FDBA. The performance of the voltammetric fluoride sensor is compared to that of a commercial liquid junction-based fluoride ion-selective electrode (F-ISE), and of a solid-contact (SC) F-ISE sensor chip, demonstrating significant advantages versus traditional potentiometric F-ISEs.     

Correction: Novel Surface Topography and Microhardness Characterization of Laser Clad Layer on TC4 Titanium Alloy Using Laser-Induced Breakdown Spectroscopy and Machine Learning

Metallurgical and Materials Transactions A -     

SARS-CoV-2 Viral Entry Proteins in Hyperandrogenemic Female Mice: Implications for Women with PCOS and COVID-19

SARS-CoV-2, the causative agent of COVID-19, infects host cells using the angiotensin I converting enzyme 2 (ACE2) as its receptor after priming by host proteases, including TMPRSS2. COVID-19 affects multiple organ systems, and male patients suffer increased severity and mortality. Polycystic Ovary Syndrome (PCOS) is the most common endocrine disorder in reproductive-age women and is characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovarian morphology. PCOS is associated with obesity and cardiometabolic comorbidities, both being risk factors associated with severe COVID-19 pathology. We hypothesize that elevated androgens in PCOS regulate SARS-CoV-2 entry proteins in multiple tissues increasing the risk for this population. Female mice were treated with dihydrotestosterone (DHT) for 90 days. Body composition was measured by EchoMRI. Fasting glucose was determined by an enzymatic method. mRNA and protein levels of ACE2, Tmprss2, Cathepsin L, Furin, Tmprss4, and Adam17 were quantified by RT-qPCR, Western-blot, or ELISA in tissues, serum, and urine. DHT treatment increased body weight, fat and lean mass, and fasting glucose. Ace2 mRNA was upregulated in the lung, cecum, heart, and kidney, while downregulated in the brain by DHT. ACE2 protein was upregulated by DHT in the small intestine, heart, and kidney. The SARS-CoV-2 priming proteases Tmprss2, Cathepsin L, and Furin mRNA were upregulated by DHT in the kidney. ACE2 sheddase Adam17 mRNA was upregulated by DHT in the kidney, which corresponded with increased urinary ACE2 in DHT treated mice. Our results highlight the potential for increased cardiac, renal, and gastrointestinal dysfunction in PCOS women with COVID-19.     

Synthesis and characterization of nanocrystalline Barium Strontium Titanate powder via sol-gel processing

Barium Strontium Titanate (BST) solid solution is a strong candidate material for application in tunable ferroelectric devices. In this research, we have synthesized and characterized nanocrystalline BST (Ba_0.7Sr_0.3TiO₃) powder with average particle-diameter of 15 nm through a simple sol-gel process, using barium acetate, strontium acetate and titanium isopropoxide as the precursors. In this process, stoichiometric proportions of barium acetate and strontium acetate were dissolved in acetic acid followed by refluxing, and addition of titanium (IV) isopropoxide to form BST gel. The gel was analyzed using Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA). The as-formed gel was dried at 200 °C and then calcined in the temperature range of 400 to 800 °C for crystallization. Phase evolution during calcination was studied using X-ray diffraction (XRD) technique. Particle size, morphology and the lattice fringes of the calcined powder were characterized by high-resolution transmission electron microscopy (HR-TEM). To study the effects of sintering on BST nanopowder, green ceramic specimens were prepared by uniaxial compaction and then sintered at 950–1,100 °C under atmospheric conditions. Sintered specimens were analyzed for phase composition, grain size and geometric bulk density.     

New Biodegradable Nonionic-Anionic Surfactants Based on Different Fatty Alcohols as Corrosion Inhibitors for Aluminum in Acidic Medium

Two series of eco-friendly nonionic anionic surfactants based on itaconic acid and 1, 6 hexane diol were synthesized. The chemical structures of the prepared surfactant were confirmed by FTIR and ¹H NMR spectroscopy. The prepared surfactants were evaluated to prevent the corrosion of aluminum in 1.0 M HCl solution by electrochemical and chemical methods. The data obtained showed that the prepared compounds have good inhibition efficiency (IE%) even at 10⁻⁵ M concentrations and act as mixed-type inhibitors, they do not affect the mechanism of the electrode processes, as well as the IE% increase by increasing the concentrations of the inhibitors, immersion time, and hydrophilic chain length. The high inhibition efficiency is due to the adsorption of the inhibitors molecules on the metal surface and the formation of a protective film. The surface activities of these compounds were also investigated and were correlated to their inhibition efficiencies and chemical structure. Through studying biodegradability of the synthesized surfactants we find that they are readily biodegradable in the environment and thus they are considered as eco-friendly corrosion inhibitors. Finally, the effect of the addition of these compounds on the aluminum surface was identified by atomic force microscopy (AFM) technique.