Pb Ratios Research Articles

Charm hadronisation measurements with the ALICE experiment

Charm quarks are produced in hard scatterings at the early stages of the hadronic collisions due to the heavy mass of the quark. The production cross section of charm can be described by pQCD calculations based on the factorisation approach. This description traditionally assumes universal fragmentation functions of charm into hadrons among different collision systems. The ALICE experiment measured charmed-baryon production in pp collisions for different baryon species, observing a significant enhancement of the charm baryon-to-meson yield ratios, for pT < 10–12 GeV/c, with respect to measurements performed at e+e− and ep colliders. Measurements of charmed baryon production in pp collisions also provide a fundamental reference for heavy-ion collisions, in which an enhancement of the baryon-to-meson ratio could be due to an additional hadronisation mechanism via coalescence of charm quarks with lighter quarks in a deconfined medium. This contribution discusses the latest measurements of charm production performed by the ALICE Collaboration in pp collisions at the LHC via D mesons, Λc+, Σc0,+,++, Ξc0,+, and Ωc0 baryons at midrapidity at √s = 5.02 and 13 TeV. The most recent measurements of the Λc+/D0 ratio in Pb–Pb collisions at √sNN = 5.02 are also presented, together with the first measurement of the charm fragmentation fraction into hadrons in pp and p–Pb collisions at the same energy.

ПРОСТРАНСТВЕННО-ВРЕМЕННАЯ СМЕНА ГЛУБИННЫХ ИСТОЧНИКОВ КАЙНОЗОЙСКИХ ВУЛКАНИЧЕСКИХ ПОРОД ВОСТОКА КОРЯКСКОГО НАГОРЬЯ

A spatiotemporal analysis of the trace element ratios and the isotopic composition of Sr, Nd and Pb in Cenozoic post-accretionary volcanic rocks in the east of the Koryak Highlands (Northeastern Russia) has been carried out. The Early Paleogene volcanic complex is shown to be represented by moderately Ti-rich aluminous tholeiites with elevated contents of high field strength elements (HFSE) (except for Ta and Nb), which makes them similar to E-MORBs. Low (La/Yb)n and high Zr/Nb (25–35) ratios characterize one of the source components as depleted and similar to MORBs. At the same time, low ratios of Nb/Ta, Ce/Pb, Nb/La with a high ratio of K/Nb were determined in basalts, which indicates the presence of a subduction component in the source. Low Zr/Hf and (Dy/Yb)n ratios indicate melting of the garnet-free substratum. The second (Miocene) stage is represented by the subalkaline basalt flows and dacite extrusions and dikes forming a bimodal series. Basalts are characterized by low concentrations of large ion lithophile elements (LILE), enrichment in HFSE, and fractionated distribution of REE, with (La/Yb)n ratios varying from the values characteristic of E-MORBs to the values corresponding to intraplate tholeiites. The Nb/Ta, Ce/Pb, La/Ta, and Hf/Th ratios tend to exhibit compositions of intraplate tholeiites. The (Dy/Yb)n and (La/Yb)pm - Ybpm ratios indicate the formation of Miocene basalts during the selective melting of garnet peridotite with varying garnet contents in the source. Dikes of dacites, in comparison with effusive facies, differ in calc-alkaline differentiation trends and other absolute concentrations of a number of elements. Early Quaternary alkaline olivine basalts and basanites of the Navarin area are high in HFSE, LILE, and REE and are compositionally similar to intraplate volcanics of oceanic islands and continental rifts. Data points of these rocks plotted on discriminant diagrams are confined to the field of the garnet-rich intraplate source with low degrees of partial melting. The initial isotopic ratios of Sr, Nd, and Pb in the Cenozoic basaltoids characterize the deep sources of Cenozoic rocks in the eastern part of the Koryak Highlands as depleted. The similarity of isotope ratios in the basalts of the Miocene and Early Quaternary stages of volcanism suggests that the mantle region was isotopically homogenized as a result of local convection.

Determination of the Heavy Metal Contents and the Benefit/Cost Analysis of Hypericum salsugineum in the Vicinity of Salt Lake

In this study, Hypericum salsugineum, an endemic halophytic plant growing around Salt Lake, was analyzed to determine the heavy metals (chromium, lead, copper, zinc and nickel) on it and on the soil it grew. The phytoremediation potential of H. salsugineum was evaluated. In addition, the benefit cost (B/C) analysis was performed for its potential use in phytoremediation. The plant and soil samples were collected from Eskil and Cihanbeyli between May and September in 2016. A total of 300 soil and plant samples were analysed for heavy metal content. Statistical and standard benefit/cost analyses were performed for assessment. The capacity of accumulating the aforementioned heavy metals was found to be high in H. salsugineum. It was found that Ni and Pb ratio exceeded optimum values in its habitat, and H. salsugineum accumulated available Ni and Pb. When the plant was evaluated in terms of benefit/cost, B/C ratio was greater than 1 during the useful life of the study. This conclusion increases the ecological and economical values of H. Salsugineum, effecting its potential use in phytoremediation.

Hydrophobic modified poly(l‐glutamic acid) graft copolymer micelles with ultrahigh drug loading capacity for anticancer drug delivery

AbstractSelf‐assembled polymeric nanoparticle (NP) drug carriers are capable of encapsulated and controlled delivery, facilitating improvements in the therapeutic efficiency of drugs. Here we report a series of poly(l‐glutamic acid)‐g‐methoxy poly(ethylene glycol)/4‐phenylbutyl ester (PLG‐g‐mPEG/PB) copolymers, which were synthesized by esterification of 4‐phenylbutanol (PB) and PLG‐g‐mPEG in different feed ratios. The copolymers obtained form into nano‐sized micelles in aqueous solution by a self‐assembly process, with lower critical micelle concentration value for higher PB ratio in the copolymers. Variable temperature infrared spectroscopy and circular dichroism were used to prove the breaking of intermolecular hydrogen bonds after PB modification. Podophyllotoxin (PPT), an effective anticancer agent, was incorporated into the inner core of the micelle system by physical entrapment through hydrophobic interaction between the drug and the PB‐modified copolymers. Both the drug loading content and the loading efficiency increased with PB content in the PLG‐g‐mPEG/PB copolymers and reached an ultrahigh value of 28.2 wt% and 94%, respectively. The PPT‐encapsulated micelles (PPT‐NPs) were stable at pH 7.4 but dissociated and released 80% of loaded PPT in a weak acidic environment (pH 5.0). The in vitro proliferation of non‐small‐cell lung cancer cells (A549) was significantly inhibited by PPT‐NPs in a cytotoxicity assay. These results demonstrate that hydrophobic modification is an efficient route for tuning the self‐assembly behaviour and drug encapsulation of PLG‐g‐mPEG copolymers, and our PLG‐g‐mPEG/PB will serve as a promising carrier for hydrophobic anticancer drug delivery. © 2021 Society of Industrial Chemistry.

Praseodymium-doped triple-cation perovskite layer for enhanced photovoltaic performance

Doping a hybrid perovskite semiconductor with metal elements offers an effective means of adjusting its photoelectric properties. To give one example, it has been found that adding lanthanide elements such as Europium (Eu) and Samarium (Sm) into a perovskite layer enhances the photovoltaic performance and photothermal stability of perovskite solar cells. In this study, we therefore added different Praseodymium (Pr)/Lead (Pb) ratios from 0% to 1% to perovskite films in a precursor solution of tri-cation perovskite. We found the photoelectric properties and device performance of perovskite solar cells doped with 0.25% Praseodymium ion (Pr3+) to be significantly improved, with a champion power conversion efficiency (PCE) of 18.56% obtained. Furthermore, the stability of perovskite solar cells (PSCs) with 0.25% Pr3+ doping improved effectively. Overall, with Pr3+ doping, the carrier mobility was dramatically enhanced, and the carrier recombination effectively hindered. These results therefore indicate that Pr3+ doping causes the perovskite to produce lattice shrinkage. As such, the findings shed light on a fresh dopant engineering tactic for fabricating high performance perovskite solar cells.

An extensive study of depth dose distribution and projectile fragmentation cross-section for shielding materials using Geant4

Geant4 Monte Carlo simulation was executed for 16O beam in various elemental and hydrogenous materials for assessment of ion characteristics and shielding efficacy. In the energy-dependent comparison, at energies 200–594 MeV/n, the peak to entrance ratio decrement up to 78.6% in water target validates the substantial increase in fragmentation factor. Further, hydrogenous materials and low Z elements (C, Al) demonstrate a low peak-to-entrance ratio (0.92–1.66) compared to heavy element (Cu, Sn, Pb) ratio (2.73–3.54), at 594 MeV/n, indicating the high fragmentation properties of hydrogenous and low Z elements. Accordingly, the depth dose reduction percentage was found to be significantly higher for hydrogenous materials (0.92–1.72%) having 4.20–14.37 H wt.% than non-hydrogenous targets (0.09–0.82%). LiH was found to exhibit the lowest peak-to-entrance ratio and highest depth dose reduction. The high shielding effectiveness of LiH (12.59%) irrespective of having a low H fraction compared to polyethylene (14.37%) which is widely used shielding material, suggests the contribution of low Z element Li (87.41 wt%) over the C (85.63 wt%) element in the material. Also, simulated results of fragmentation for high Z materials were compared with the experimental data for the reliability of Geant4. Finally, the comparison of these properties recommends the use of hydrogenous materials with low Z elements for effective space radiation shielding.

Enhanced desorption of cationic and anionic metals/metalloids from co-contaminated soil by tetrapolyphosphate washing and followed by ferrous sulfide treatment

In this study, a novel approach was employed for the remediation of cationic and anionic metals/metalloids co-contaminated soil by tetrapolyphosphate enhanced soil washing coupled with ferrous sulfide treatment. Tetrapolyphosphate could simultaneously enhance the desorption of cationic metals (Pb and Zn) and anionic metal/metalloid (Cr and As) from the contaminated soil in the whole tested pH range of 2–10. With addition of 0.15 mol/L tetrapolyphosphate at pH 7.0, the removal ratio of Pb, Zn, As and Cr could achieve 83.1%, 70.4%, 75.7% and 66.4% respectively. The fractionation analysis of heavy metals/metalloids demonstrated the release of exchangeable and Fe/Mn bound forms contributed to most desorption of Pb and Zn. The decreases of non-specifically sorbed form and amorphous and poorly-crystalline hydrous oxides of Fe and Al bound form were responsible for most removal of As. The comparison with other common washing agents (EDTA, oxalate and phosphate) under their respective optimal dosage could confirm that tetrapolyphosphate was superior to simultaneously desorb the cationic and anionic metals/metalloids with higher efficiency. After 12 h, applying 150 mg/L FeS at pH 3.5 could totally remove Pb, Zn, As and Cr from the washing effluent by sulfide precipitation, reduction and adsorption processes. Higher pH would inhibit the removal of As and Cr by FeS. Meanwhile, the residual of tetrapolyphosphate could be totally recovered from the washing effluent by employing anion exchange resin. This study suggests tetrapolyphosphate enhanced soil washing coupled with ferrous sulfide treatment is a promising approach for remediation of cationic and anionic metals/metalloids co-contaminated soil in view of its high efficiency and simple operation.

Alloyed Palladium–Lead Nanosheet Assemblies for Electrocatalytic Ethanol Oxidation

Synthesizing alloyed bimetallic electrocatalysts with a three-dimensional (3D) structure assembly have arouse great interests in electrocatalysis. We synthesized a class of alloyed Pd3Pb/Pd nanosheet assemblies (NSAs) composed of a two-dimensional (2D) sheet structure with adjustable compositions via an oil bath approach at a low temperature. Both the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal the successful formation of the nanosheet structure, where the morphology of Pd3Pb/Pd NSAs can be regulated by adjusting the atomic mole ratio of Pb and Pb metal precursors. The power X-ray diffraction (XRD) pattern shows that Pd3Pb/Pd NSA catalysts are homogeneously alloyed. Electrochemical analysis and the density functional theory (DFT) method demonstrate that the electrocatalytic activity of the alloyed Pd3Pb/Pd NSAs can be improved by the doping of the Pb element. As a result of the addition of element Pb and change of the electron structure, the electrocatalytic activity toward ethanol oxidation of alloyed Pd3Pb/Pd-15 NSA can reach up to 2886 mA mg-1, which is approximately 2.8 times that of the pure Pd NSA counterpart (1020 mA mg-1). The Pd3Pb/Pd NSAs are favorable in a high catalytic temperature, high KOH concentration, and high ethanol concentration.

Estimation of Pulmonary Arterial Wave Reflection by Echo-Doppler: A Preliminary Study in Dogs With Experimentally-Induced Acute Pulmonary Embolism.

Background: Pulmonary arterial (PA) wave reflection provides additional information for assessing right ventricular afterload, but its applications is hampered by the need for invasive pressure and flow measurements. We tested the hypothesis that PA pressure and flow waveforms estimated by Doppler echocardiography could be used to quantify PA wave reflection.Methods: Doppler echocardiographic images of tricuspid regurgitation and right ventricular outflow tract flow used to estimate PA pressure and flow waveforms were acquired simultaneously with direct measurements with a dual sensor-tipped catheter under various hemodynamic conditions in a canine model of pulmonary hypertension (n = 8). Wave separation analysis was performed on echo-Doppler derived as well as catheter derived waveforms to separate PA pressure into forward (Pf) and backward (Pb) pressures and derive wave reflection coefficient (RC) defined as the ratio of peak Pb to peak Pf.Results: Wave reflection indices by echo-Doppler agreed well with corresponding indices by catheter (Pb: mean difference = 0.4 mmHg, 95% limits of agreement = −4.3 to 5.0 mmHg; RC: bias = 0.13, 95% limits of agreement = −0.25 to 0.26). RC correlated negatively with PA compliance.Conclusion: This echo-Doppler method yields reasonable measurement of reflected wave in the pulmonary circulation, paving the way to a more integrative assessment of pulmonary hemodynamics in the clinical setting.

Measurement of Pulmonary Artery Wave Reflection Before and After Mitral Valvuloplasty in Canine Patients With Pulmonary Hypertension Caused by Myxomatous Mitral Valve Disease.

Background: Pulmonary arterial wave reflection provides novel information about pulmonary artery hemodynamics in pulmonary hypertension (PH). PH is common in dogs with myxomatous mitral valve disease (MMVD), though research examining the relationship between pulmonary arterial wave reflection and MMVD with PH is lacking.Hypothesis/Objective: This study investigated conventional echocardiographic parameters and pulmonary artery wave reflection parameters before and after mitral valvuloplasty in canine patients with PH due to MMVD. The parameters were backward pressure (Pb), forward pressure (Pf), and the reflection coefficient calculated as the ratio of peak Pb to peak Pf (RC).Animals: The study subjects were 10 client-owned dogs receiving mitral valvuloplasty for MMVD with PH.Methods: Conventional echocardiographic parameters and pulmonary artery wave reflection parameters were measured before and after mitral valvuloplasty. The relationships between pulmonary artery wave reflection parameters and echocardiographic parameters, estimation of pulmonary artery systolic pressure, and right atrium pressure (RAP) gained by catheter in mitral valvuloplasty were also investigated. Post-operative echocardiography and the measurement of pulmonary arterial wave reflection were performed 2 weeks after mitral valvuloplasty.Results: The parameters of normalized left ventricular internal diameter at end-diastole (LVIDDN), E velocity, and the estimation of pulmonary artery systolic pressure were significantly reduced post-operatively compared with baseline measurements (p < 0.05). Post-operative Pb decreased significantly compared with pre-operative measurements (8.8 ± 5.9 to 5.0 ± 3.2 mmHg, p = 0.037) as did RC (0.37 ± 0.15 to 0.22 ± 0.11, p < 0.01). A statistically significant positive correlation existed between wave reflection parameters and RAP, an estimation of pulmonary artery systolic pressure.Conclusions: Results demonstrate that mitral valvuloplasty can be used to treat secondary PH caused by MMVD, resulting in the improvement of post-operative echocardiographic and wave reflection parameters and a decrease in the right afterload. In some patients, some degree of vascular admittance mismatch persisted, despite the improvement of left atrial pressure. This may be indicative of residual pulmonary arterial disease, which may continue to adversely affect interactions between the right ventricle and the vasculature.

Determination of Sr–Nd–Pb Isotopic Ratios of Rock Reference Materials Using Column Separation Techniques and TIMS

Thermal ionization mass spectrometry (TIMS) can provide highly accurate strontium (Sr), neodymium (Nd), and lead (Pb) isotope measurements for geological and environmental samples. Traces of these isotopes are useful for understanding crustal reworking and growth. In this study, we conducted a sequential separation of Sr, Nd, and Pb and subsequently measured the 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 13 widely used rock certified reference materials (CRMs), namely BCR-2, BHVO-2, GSP-2, JG-1a, HISS-1, JLk-1, JSd-1, JSd-2, JSd-3, LKSD-1, MAG-1, SGR-1, and 4353A, using TIMS. In particular, we reported the first isotopic ratios of Sr, Nd, and Pb in 4353A, Sr and Nd in HISS-1 and SGR-1, and Sr in JLk-1, JSd-2, JSd-3, and LKSD-1. The Sr–Nd–Pb isotopic compositions of most in-house CRMs were indistinguishable from previously reported values, although the Sr and Pb isotopic ratios of GSP-2, JSd-2, JSd-3, and LKSD-1 obtained in different aliquots and/or batches varied slightly. Hence, these rock reference materials can be used for monitoring the sample accuracy and assessing the quality of Sr–Nd–Pb isotope analyses.

Argon Plasma Treated Phosphatic Clays for Efficient Heavy Metal Pb(II) Immobilization

Phosphatic clays, one type of phosphorite industry wastes, could induce environmental issues and geological disasters when they are piled in the open air. Previous research demonstrated that phosphatic clays usually exhibit poor performance in heavy metal immobilization mostly due to low phosphate content. Thus, phosphatic clays could not be applied in practical heavy metal remediation without pretreatment. If the adsorption performance of phosphatic clays could be improved, employing phosphatic clays for heavy metal immobilization may act as an eco-friendly, economic way to not only reutilize phosphorite industry wastes but also remedy environmental heavy metal pollution at the same time. In this study, we propose an argon plasma treatment approach to remarkably improve the effectiveness of phosphatic clay performances in heavy metal immobilization. The optimal Pb(II) sorption capacity of 66.7mgg-1 can be obtained at pH 6 and 25°C by using 15-min argon plasma treated phosphatic clays, which is two times as large as those of the untreated phosphatic clays and almost reaches those of raw apatite minerals. Moreover, the Pb(II) desorption ratios of Pb(II)-adsorbed phosphatic clays are also reduced by 30%-60% at different pH conditions. Therefore, applying argon-plasma technique to transform waste phosphatic clays into efficient heavy-metal sorbents is a promising road to phosphorite waste reclamation and environmental remediation.

Enhanced Electrocatalytic Activity of Alloyed Palladium-Lead Nanoparticles toward Electrooxidation of Ethanol.

Although many researchers have made great efforts to pursue promising high-efficiency electrocatalysts, a formidable challenge remains for designing excellent palladium-based electrocatalysts for commercializing direct liquid fuel cells. This study reports the synthesis of bimetallic PdPb nanoparticles (NPs) via a mixed solution containing cetyl trimethyl ammonium bromide as the capping agent. Alloyed PdPb NPs are formed, where the size of the NPs increases as Pb atoms are introduced gradually. However, Pd3Pb NPs are obtained with the same molar ratio of Pd and Pb in the raw systems. Among all of the as-made NPs, Pd9Pb1 NPs exhibit superior catalytic activity (2620 mA mg-1) toward ethanol electrooxidation, 4.3 times higher than commercial Pd/C catalysts (613 mA mg-1). The overall rate of the EOR for PdPb NPs is determined, demonstrating that the electrocatalytic activity of the PdPb NPs increases at high catalytic temperatures, in high pH environments, and/or at high ethanol concentrations.

Release of the additive metals from 3 commonly used plastics during the degradation under the treatment of UV irradiation.

Additive metals are continuously released into the environment during the photo-degradation of plastics into microplastics, but this phenomenon has not been reported by many studies. Herein, we investigated the surface morphology changes along with the release of additive metals (Cr, Mn, Fe, Co, Cu, Zn, and Pb) during the degradation of three types of plastics, i.e., polypropylene (PP), polyethylene terephthalate (PET) and polyvinyl chloride (PVC), under UV light irradiation. FTIR results showed that 168 days of UV-irradiation led to the primary degradation of each plastic sample. The metal release could be found after 70 days UV-irradiation. The rate of metal release for the three plastics showed the following order: PP > PET ≈ PVC. In addition, the distribution and concentrations of the metals in the plastic could influence the release characteristics of each metal. Low release rate of Fe symbolized by the total metal release in the range of 4.28 ~10.27% as evident from the results of the primary degradation experiment, indicated the release of Fe occurring in the late stage of the plastic degradation or even in the microplastics-formation stage. As for the release of Co from PP, it was far lower than that of the other elements (0.35%), showing the same release characteristics as that of Fe. On the contrary, the release ratio of Pb from PP was 78.89% and was mainly concentrated in the early stage of the plastic degradation. The results help understanding the release behavior of the additive metals during the degradation of typical plastics under ultraviolet light irradiation.

Genesis of the early mesozoic granitoids at the Hardat Tolgoi Ag-Pb-Zn deposit in East Ujimqin Banner, Inner Mongolia, NE China: Insights from whole-rock geochemistry, zircon U-Pb-Hf isotopes, and Pb-Si systematics

The Hardat Tolgoi Ag-Pb-Zn deposit is located in the Erenhot-East Ujimqin polymetallic metallogenic belt, on the western part of the Great Xing’an Range, Inner Mongolia, northeast China. The Ag-Pb-Zn veins are mainly hosted by the argillaceous siltstone and feldspar quartz sandstone of Aobaotinghundi Formation, which show close genetic relationship with the granitoids at Hardat Tolgoi (i.e., biotite granite, syenogranite, and monzogranite). New LA-ICP-MS zircon U-Pb dating yielded the emplacement ages of 196.1 ± 5.8 Ma for biotite granite, 192.3 ± 6.0 Ma for syenogranite, and 194.8 ± 1.7 Ma for monzogranite, respectively, indicating that they were formed in the Early Jurassic. Geochemically, these granitoids are characterized by high SiO2, Na2O + K2O, and low MgO and TiO2 concentrations, belonging to high-K calc-alkaline series. They exhibit relatively flat REE patterns, with pronounced negative Eu anomalies (EuN/EuN* = 0.004–0.015), enriched in LREEs and LILEs (e.g., Rb, U, and Pb), and depleted in Ba, Sr, Nb, P, and Ti. Zircon in situ Hf isotopic analyses yield positive εHf(t) values ranging from + 5.7 to + 11.8, corresponding relatively young Hf isotopic crustal model ages of 452 to 843 Ma. The granitoid samples have the 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of 18.950 to 19.444, 15. 573 to 15.615, and 38.487 to 38.789, corresponding to initial Pb ratios of 18.483 to 18.960, 15.552 to 15.662, and 37.905 to 38.193, respectively, and yield the δ30Si values between − 0.4 and − 0.1‰, similar to the quartz separates (−0.7 to − 0.1‰). The available geochemical and isotopic data imply that the source magma at Hardat Tolgoi was most likely derived from partial melting of juvenile lower crust. Combined our whole-rock geochemical and Hf − Pb − Si isotopic data with regional tectono-magmatic evolution, it is proposed that the Early Jurassic magmatism at Hardat Tolgoi was probably attributed to the southeastward subduction of the Mongol − Okhotsk oceanic plate beneath the Erguna massif, and their generation was favorable to the Hardat Tolgoi Ag-Pb-Zn ore formation.

Mechanism of zero-valent lead reduction for removing high concentration of arsenic from waste acid of lead smelting system

Lead metal smelting waste acid containing high concentrations of arsenic and sulfuric acid threaten human health and pose huge potential environmental risks due to its possible leakages during storage and disposal. In order to remove arsenic in smelting waste acid, a new method for arsenic removal by adding zero-valent lead and CuSO4 is proposed. The substitution reaction between zero-valent lead and CuSO4 to generate Cu0, and form a Pb-Cu galvanic cell system with zero-valent lead. Through the reduction of zero-valent lead, As(III) was reduced to As(0) and reacted with Cu0 to produce Cu3As precipitation. As the pH of waste acid changed, AsO2- will produce As2O3. When the molar ratio of Pb to As (Pb/As) was 6, CuSO4 concentration was 7 g/L, 25 °C, and 240 min, the arsenic concentration sharp decreased from 4706.4 mg/L to 35.21 mg/L, arsenic removal efficiency reached 99.25%. The arsenic removal process could be described by the shrinking core model which was controlled by a diffusion process. XRD, SEM-EDS, and XPS were used to characterize the phase, morphology, and elemental valence of the arsenic-containing precipitates. Based on the above analysis and combined with thermodynamic analysis, the mechanism of arsenic removal by zero-valent lead combined with CuSO4 was revealed.

Continuous On-Line Leaching To Evaluate The Effect Of Toasting On Bioaccessibility, And Pb Source Apportionment Of Alternative Breads

Laser-induced with the increasing popularity of alternative breads, investigating their health benefits and risks is vitally important. The bioaccessibility of potentially toxic elements in these breads could indicate a potential risk to consumers. The continuous online leaching method (COLM) involves the sequential leaching of a mini-column of food by artificial saliva, gastric juice, and intestinal fluid with real time monitoring of elements being released. Because the dissolution equilibrium is shifted to the right from continuous exposure to fresh reagent, it assesses bioaccessibility in three gastrointestinal matrices in less than 30 min and includes valuable kinetic extraction information. In this study, a gluten-free (GF) and a rye bread were analyzed for As, Cd, and Pb before and after toasting. Toasting lowered all PTE concentrations by a factor of 1.5 (As in rye bread) to 2.5 (Cd in rye bread). Most of the PTEs present were bioaccessible whether the bread was toasted or not. In the case of As, a significant portion is in the form of As(III) and As(V). COLM analysis allowed for Pb sourcing, revealing two potential sources of Pb being released separately in gastric juice from rye bread based on their significantly different 206Pb/207Pb and 208Pb/206Pb isotope ratios. Comparison with Pb ratios reported in previous literature revealed that some of the gastric-mobile Pb in rye bread came from the Pb historically added to gasoline in North America. This source completely vanished upon toasting rye bread.

Thermal stability, mechanical properties, and gamma radiation shielding performance of polyvinyl chloride/Pb(NO3)2 composites

Abstract Radiation shielding composites based on polyvinyl chloride (PVC) reinforced with different weight ratios of Pb(NO3)2 (5, 10, and 20 wt%) were prepared using the solution-casting technique. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy, and tensile testing method were used to characterize the PVC composite films. FTIR and XRD investigations illustrate the structural change and modification of the as-prepared PVC composites. The morphological analysis of the composite revealed that Pb(NO3)2 was dispersed uniformly within PVC polymer matrix. TGA revealed that the incorporation of Pb(NO3)2 improved the thermal stability of the investigated composites, whereas adding Pb(NO3)2 to the polymer matrix worsened its tensile properties. The as-prepared composite films were investigated for radiation-shielding of gamma-rays radioactive point sources (241Am, 133Ba, 137Cs, and 60Co). Linear attenuation coefficient (μ, cm−1), mass attenuation coefficient (μ/ρ, cm2/g), and half-value layer (HVL, cm) have been estimated from the obtained data using the MicroShield program. Reasonable agreement was attended between theoretical and experimental results. The deviation between the experiment and theoretical values of mass attenuation coefficient is being to be lower than 9%, and this can be correlated to the good distribution of Pb(NO3)2. The results revealed that adding Pb(NO3)2 to PVC polymer composites improved their mass attenuation coefficient.

An Isotopic Study of Bio-accessible Lead in Wheat, Miswak Toothbrush and Miswak Fruit Using the Continuous On-line Leaching Method with Inductively Coupled Plasma Mass Spectrometry

In this study, sources of Pb are investigated using the 206Pb/207Pb isotopic ratio measured by inductively coupled plasma quadrupole mass spectrometry in the bio-accessible fractions from wheat, Miswak toothbrush (also used as chewing stick) and Miswak fruit. These samples were obtained for the in vitro batch and on-line leaching methods that mimic the human gastrointestinal tract by sequentially using artificial saliva, gastric juice and intestinal fluid for extraction. The two methods provided similar results according to a Student’s t-test at the 95% confidence level. Significant (p &lt; 0.05) differences in 206Pb/207Pb were noted at the 95% confidence level in different artificial body fluids. Except for unpolluted Miswak toothbrush and Miswak fruit, which only contained geogenic Pb, the samples contained a mixture of geogenic and anthropogenic Pb, with bio-accessible Pb in saliva being mainly from a geogenic source, whereas bio-accessible Pb in the stomach and intestinal fluids was mainly from anthropogenic sources. Despite the fact that leaded petrol was phased out in Saudi Arabia in 2001, a Miswak toothbrush collected on the side of a busy road after exposure for only a few days and Safeer wheat were still being contaminated with Pb and had an isotopic composition matching that of Pb added to petrol. The 208Pb/206Pb isotopic ratio for gastric bio-accessible Pb also matched that reported in tetraethyllead. The 206Pb/207Pb isotopic ratios of intestinal bio-accessible Pb from Qassim wheat and Safeer wheat point to coal combustion as the source. Overall, these results highlight the need for continued Pb monitoring and the value of examining bio-accessible fractions periodically to identify Pb sources.

Charge Transport in 2D Layered Mixed Sn–Pb Perovskite Thin Films for Field‐Effect Transistors

AbstractThe optoelectronic characteristics of organic–inorganic perovskites can be tailored by mixing different metal cations with various ratios. 2D layered organic–inorganic perovskites with charge transport anisotropy are considered as promising channel materials for field‐effect transistors. However, there are few reports about 2D Pb‐based perovskite thin film transistors although their Sn counterparts have been extensively investigated for use in this field. Herein, the synthesis and tuning of the physical properties of 2D layered Sn–Pb perovskite solid solutions based on phenylethylammonium tin and lead iodide perovskites ((PEA)2SnxPb1−xI4 (x = 0, 0.3, 0.5, 0.7, 1)) are reported. A thermally activated semiconducting behavior is confirmed in this series of perovskite thin films. The electronic band structure, conductivity, and in‐plane ion migration are found to be largely affected by the Sn–Pb ratio, which is important for transistor performance. Furthermore, the 2D layered mixed Sn–Pb perovskite field‐effect transistors constructed on cheap and commercially available polymer dielectrics and a signature of field‐effect characteristics in the (PEA)2PbI4 film are demonstrated for the first time. The (PEA)2Sn0.7Pb0.3I4 transistor operating at room temperature in air exhibits a hole mobility of 0.02 cm2 V−1 s−1. This work can improve the understanding of the influence mechanisms of ion migration in 2D layered perovskite field‐effect transistors.