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Epikarst springs are the main source of water used by the community in the western part of Gunungsewu Karst Area. One of the springs found in Gunungsewu karst area is Guntur Spring, with a catchment area that functions as agricultural land and settlements. Guntur Spring has connectivity between swallow holes and karst windows, so the spring can easily be polluted; therefore, a temporal study is needed regarding the water quality. The methods used were analysis of water quality standards, Schoeller diagrams, triangular Piper diagrams, and scatter plots. The results of the analysis of water quality standards showed that only Ca2+ and HCO3- ions and a small portion of Na+ exceeded WHO standards. The results of the Schoeller diagram analysis showed that the dominant ions were Ca2+ and HCO3-. The results of the Piper diagram analysis showed that the Guntur Spring is included in the classification of types I, J, and M, indicating the spring is not polluted. The results of the Piper diagrams showed that Guntur Spring is included in the dominant types of types C, A, G, D, and F, indicating the springs are not included in the polluted category. The scatter plot analysis of the Ca2+ + Mg2+ versus HCO3- + SO42- showed that the dominant ion in the Guntur Spring came from the dissolving of limestone. The scatter plot analysis of HCO3 - versus Na+ indicated that the main process that forms Guntur Spring ions is not the dissolving process of silicates. The scatter plot analysis of Cl- - SO42- versus Na+ indicated that the main process that forms Guntur Spring ions is not the dissolving process of sodium/sodium sulfate and halite. There was one sample in the Cl- versus Na+ scatter plot analysis that showed an indication of an anthropogenic pollution. However, the overall analysis showed that anthropogenic activities in the study area do have a major impact on the water quality of the epikarst springs at the study site. [ABSTRACT FROM AUTHOR]

The objective of the present study was to assess the effect of monolithic and bilayer restorations considering heat-pressed and milled/CAD/CAM reinforced lithium disilicate ceramic veneers, on the flexural strength after cementation. Method and materials: Thirty-five specimens were divided into five groups (n = 7), according to the restorative solution: 2-mm thickness composite resin (CR2); heat-pressed monolithic ceramic 0.6 mm (HPM), CAD/CAM monolithic ceramics 0.6 mm (CCM); heat-pressed monolithic ceramic 0.4 mm + 0.2 mm glass-ceramic (HPB); CAD/CAM monolithic ceramic 0.4 mm + 0.2 glass-ceramic (CCB). Specimens were cemented on composite resin bars and submitted to a threepoint bending test on a Universal Testing Machine, until fracture. Fractured samples were analyzed under stereomicroscope and SEM. Flexural strength data were analyzed by one-way ANOVA and Tukey test. Results: The control group showed the highest flexural strength results (119.57 ± 19.49 MPa), with values similar to groups HPM (98 ± 25.62 MPa) and CCM (96.14 ± 20.60 MPa). Groups HPB and CCB showed lower values when compared with the other groups. Fracture started from the base on monolithic groups and from ceramic on bilayer groups. Conclusion: Both ceramic systems (CAD/ CAM and heat-pressed) have similar fracture strength, although bilayer restorations present lower strength when compared with monolithic ceramics. [ABSTRACT FROM AUTHOR]

Oceanic anoxic events (OAEs) are historical intervals of global-scale ocean deoxygenation associated with hyperthermal climate states and biological crises 1,2 . Massive volcanic carbon dioxide (CO 2 ) emissions frequently associated with these events are thought to be a common driver of ocean deoxygenation through several climate-warming-related mechanisms 1,3,4 . The Early Cretaceous OAE1a is one of the most intense ocean deoxygenation events, persisting for more than 1 Myr (refs.  5,6 ). However, existing records of marine chemistry and climate across OAE1a are insufficient to fully resolve the timing and dynamics of the underlying processes, thus obscuring cause-and-effect relationships between climate forcing and ocean oxygenation states. Here we show that rapid ocean deoxygenation during OAE1a is linked to volcanic CO 2 emissions and the crossing of an associated climate threshold, after which the sluggish pace of the silicate-weathering feedback and climate recovery delayed reoxygenation for >1 Myr. At the end of OAE1a, recrossing this threshold allowed for ocean reoxygenation. Following OAE1a, however, the Earth system remained sufficiently warm such that orbitally forced climate dynamics led to continued cyclic ocean deoxygenation on approximately 100-kyr timescales for another 1 Myr. Our results thus imply a tight coupling between volcanism, weathering and ocean oxygen content that is characterized by a climate threshold., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

A method for aerosol chemical analysis using handheld Raman spectrometer has been developed and its application to measurement of crystalline silica concentration in workplace atmosphere is described. The approach involves collecting aerosol as a spot sample using a wearable optical aerosol monitor, followed by direct-on-filter quantitative analysis of the spot sample for crystalline silica using handheld Raman spectrometer. The filter cassette of a commercially available optical aerosol monitor (designed to collect aerosol for post-shift analysis) was modified to collect 1.5-mm-diameter spot sample, which provided adequate detection limits for short-term measurements over a few tens of minutes or hours. The method was calibrated using aerosolized α-quartz standard reference material in the laboratory. Two Raman spectrometers were evaluated, one a handheld unit (weighing less than 410 g) and the other a larger probe-based field-portable unit (weighing about 5 kg). The lowest limit of quantification for α-quartz of 16.6 μg m−3 was obtained using the handheld Raman unit at a sample collection time of 1 h at 0.4 l min−1. Short-term measurement capability and sensitivity of the Raman method were demonstrated using a transient simulated workplace aerosol. Workplace air and personal breathing zone concentrations of crystalline silica of workers at a hydraulic fracturing worksite were measured using the Raman method. The measurements showed good agreement with the co-located samples analyzed using the standard X-ray powder diffraction (XRD) method, agreeing within 0.15–23.2% of each other. This magnitude of difference was comparable to the inter- and intra-laboratory analytical precision of established XRD and infrared methods. The pilot study shows that for silica-containing materials studied in this work it is possible to obtain quantitative measurements with good analytical figures of merit using handheld or portable Raman spectrometers. Further studies will be needed to assess matrix interferences and measurement uncertainty for several other types of particle matrices to assess the broader applicability of the method. [ABSTRACT FROM AUTHOR]

We studied the effective net charge density (Qeff) of strontium silicate (SrxSiOx+2, x = 1, 2, 3) films grown on silicon (Si) (100) substrates. The SrxSiOx+2 layers were deposited from a Sr2SiO4 polycrystalline target by pulsed laser deposition, and then annealed at 400–600 °C in an oxygen atmosphere with a tube furnace. The Qeff values of the SrxSiOx+2/Si (100) samples were obtained from the shift in the voltage of the flat band state in their capacitance–voltage curves. The SrxSiOx+2/ Si (100) samples with a thickness of 15 nm annealed at 400 °C showed the maximum Qeff/q value of 1.03 × 1013 cm-2, where q is the elementary charge. With increasing annealing temperature, the SrxSiOx+2 layer penetrated into the Si (100) substrate. This penetration may degrade the interfacial properties and decrease the Qeff value of the layers. For all the samples, the charges concentrated near the SrxSiOx+2/Si (100) interface. Our results suggest that anion and cation migration plays an important role in charge generation at the SrxSiOx+2/Si (100) interface, consistent with the findings of a previously reported molecular dynamics calculation. [ABSTRACT FROM AUTHOR]

This study is aimed at evaluating five mineral oxides (5MO), mineral trioxide aggregate repair high plasticity (MTA HP), and mineral trioxide aggregate (MTA) in relation to the antimicrobial action over Porphyromonas gingivalis, Porphyromonas endodontalis, Parvimonas micra, Fusobacterium nucleatum, and Prevotella intermedia; the genotoxicity over mouse macrophage (RAW 264.7) and osteoblast (Mg-63) cultures; and the morphological analysis using scanning electron microscopy (SEM) analysis (50 k and ×100 k). Sodium hypochlorite (NaOCl), calcium hydroxide, and saline solution were used as control groups in the different analysis. All data were submitted to a normality test and then analyzed with one-way ANOVA, Tukey, and Kruskal-Wallis and Dunn tests, considering α ≤ 0.05 significance level. It was found that over P. gingivalis and P. endodontalis, there was no a significant difference between the calcium silicate-based cements (CSC) and the control group of saline solution, and only 5MO was similar to the NaOCl group. However, over P. micra, all groups were effective and showed a statistically significant difference compared to the saline solution group. Conversely, none of the groups were effective over F. nucleatum and P. intermedia, except of the NaOCl group. There was a significant difference between 5MO and MTA groups in comparison with NaOCl and MTA HP over osteoblasts and macrophages after 24 hours. SEM images showed small irregular particles interspersed with some elongated needle-like particles and small irregular particles with some larger particles as well as elongated particles. It was concluded that 5MO, MTA, and MTA HP have effective antimicrobial action over P. micra. However, only 5MO is effective over P. gingivalis and P. endodontalis. Besides, 5MO and MTA are not genotoxic over mouse macrophage (RAW 264.7) and osteoblast (Mg-63) cultures. [ABSTRACT FROM AUTHOR]

The complete dissolution of silicate-containing materials, often necessary for elemental determination, is generally performed by microwave-assisted digestion involving the forced use of hydrofluoric acid (HF). Although highly efficient in dissolving silicates, this acid exhibits many detrimental effects (e.g., formation of precipitates, corrosiveness to glassware) that make its removal after digestion essential. The displacement of HF is normally achieved by evaporation in open-vessel systems: atmospheric contamination or loss of analytes can occur when fuming-off HF owing to the non-ultraclean conditions necessarily adopted for safety reasons. This aspect strongly hinders determination at the ultra-trace level. To overcome this issue, we propose a clean and safe microwave-assisted procedure to induce the evaporative migration of HF inside a sealed "vessel-inside-vessel" system: up to 99.9% of HF can be removed by performing two additional microwave cycles after sample dissolution. HF migrates from the digestion solution to a scavenger (ultrapure H2O) via a simple physical mechanism, and then, it can be safely dismissed/recycled. The procedure was validated by a soil reference material (NIST 2710), and no external or cross-contamination was observed for the 27 trace elements studied. The results demonstrate the suitability of this protocol for ultra-trace analysis when the utilization of HF is mandatory. [ABSTRACT FROM AUTHOR]

Background: Mica drugs, a group of herbo-metallic traditional preparations comprising biotite mica as the major mineral ingredient, are prescribed for skin disorders and respiratory ailments and other chronic conditions in South Asian countries, particularly India and Sri Lanka. Mica-based drugs (Abhrak drugs) are subjected to unique and varied preparation procedures and the bioactivity of the drugs can be affected by drug-processing conditions, the ingredients used and the mica composition. The current study aimed to evaluate and compare, on the basis of their physical and chemical characteristics, the antimicrobial potential of two commercial mica drugs AbBb (Abhrak bhashma) and AbCh (Abhrak Chenhuram) and two mica drugs ABL1 (Abhrak Bhasma Laboratory Prepared 1) and ABL2 (Abhrak Bhasma Laboratory Prepared 2) prepared in the laboratory under different conditions. Methods: Antimicrobial activity of all four drugs was assessed at 10 mg/ml concentration against Pseudomonas aeruginosa, Escherischia coli, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA) and Candida albicans using well diffusion assay, agar dilution assay and Miles and Misra method. Major and trace metal constituents of the drug samples were measured using atomic absorption spectrometry. Mineralogical properties, bacteria-mineral interactions, morphological changes in microbes and the surface characteristics of the drugs were determined using X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Results: The drugs ABL1, ABL2 and AbBh exhibited antimicrobial activity against only Gram-positive organisms (S. aureus and MRSA) when tested with Miles and Misra method (broth method). Mineralogical studies (XRD) revealed that biotite mica was altered into secondary clay minerals and iron oxides in the commercial drug AbCh while the other three drugs had altered mica and iron oxide phases. The essential elements (Na, K, Ca and Mg) required for microbial functions were present in varying extents in all four drugs while they were present in exceedingly high amounts in AbCh having comparatively high cation-exchange capacity, consistent with the observation that AbCh was inactive against all the microbes tested. The three drugs (ABL1, ABL2 and AbBh) showing antimicrobial activity contained comparatively high amounts of Fe, Zn and Cu that are known to display antimicrobial properties at high concentrations. SEM studies revealed that the drug particles adhered and entrapped the bacterial species, presumably modifying the physiochemical characteristics of the bacteria and eventually causing lethality. Conclusion: Three of the four mica drugs inhibited the tested Gram-negative bacteria and the antibacterial activity of the mica drugs depends on their constituents and the methods of preparation. [ABSTRACT FROM AUTHOR]

Riverine phytoplankton takes up phosphate, dissolved silicate, and nitrate. We investigated which nutrients are depleted during a Lagrangian sampling in the free-flowing part of the River Elbe in 2023. As part of this study, we tested the hypotheses that nutrient depletion might be caused by (1) above-average phytoplankton biomass or by (2) decreased nutrient load of the river during previous years. Phytoplankton biomass increased up to 350 km in rivers and stopped increasing exactly when soluble reactive phosphorus had been completely consumed, and molar carbon to phosphorus ratios of seston indicated the beginning phosphorus limitation. The concentrations of dissolved silicate and nitrate dropped below the detection limit as well. In contrast to the results from eight previous longitudinal samplings taken in 2018-2022, nitrate exhaustion was detected for the first time in 2023 within the transect. This was caused neither by an above-average phytoplankton biomass nor by a declined overall nutrient load of the river in 2018-2023. Instead, denitrification appears to be the most plausible explanation for the downstream decrease of nitrate and the loss of total nitrogen which was supported by enrichment of nitrate stable isotopes and a decreasing ratio of nitrate 15 N/ 18 O., (© 2024. The Author(s).)

Objective: To evaluate the effect of surface treatments on optical, colorimetric, and surface characteristics of lithium disilicate glass–ceramic. Materials and Methods: Specimens (n = 5, IPS e.max CAD) were randomly allocated to the following treatments: mirror‐polished: SiC papers; as‐cut: mimicking CAD‐CAM milling; ground: 90‐120 μm‐grit diamond bur; ground polished: ground, finished (46‐30 μm‐grit diamond bur), polished (diamond cups, brush and diamond paste); ground glazed: ground, glazed; ground polished glazed: association of methods. CIELAB color coordinates were obtained by a spectrophotometer. CIEDE2000 color differences (ΔE00) and the translucency parameter (TP00) were calculated. Light transmittance was assessed with a colorimeter. Surface characteristics (topography and roughness) were analyzed. Statistical differences for each condition and outcome were detected using one‐way ANOVA with Tukey's post‐hoc test (α = 0.05). Results: TP00 data show statistical reduction after grinding (p < 0.05), which was only restored with polishing (solely or with glazing). ΔE00 shows that grinding results in perceptible variations in color (above 0.81), which were restored after all post‐processing protocols (exception to only glaze application in contact with a black background). Light transmittance data corroborated such performance. Polishing and glazing reduced roughness and improved surface topography. Conclusion: Grinding statistically increased roughness, reduced translucency, light transmittance through the ceramic, and resulted on color differences. On contrary, polishing (followed or not by glazing) reduced roughness and enhanced ceramic translucency and light transmittance. Glaze also reduced roughness, but it still presented reduced translucency. The positioning (facing up or down) of the ceramic treated surface influenced the considered outcomes. Clinical Significance: Grinding with diamond burs results in a deleterious impact to the optical, colorimetric and surface characteristics of lithium disilicate ceramic. Thus, polishing (followed or not by glazing) is recommended for optical and topographical enhancements when lithium disilicate monolithic restorations require occlusal adjustments. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this in vitro study was to compare the effect of simulated endodontic access preparation on the failure loads of lithium disilicate crowns and resin‐matrix ceramic (RMC) crowns. Materials and methods: Eighty maxillary first premolar crowns were manufactured by using four different CAD/CAM blocks (n = 20): lithium disilicate (LD; IPS e.max CAD), resin nanoceramic (RNC; Lava Ultimate), flexible nanaoceramic (FNC; GC Cerasmart), and polymer‐infiltrated ceramic (PIC; VITA Enamic). Half of each group was accessed and repaired to simulate endodontic treatment. After cyclic loading, all specimens were loaded to failure. Data were analyzed with two‐way ANOVA followed by Tukey‐HSD test (α =.05). Results: The load to failure results showed significant differences for material types (P <.001), but not for endodontic access simulation (P =.09). The highest and lowest mean failure loads were obtained for LD (1546 N) and PIC (843 N), respectively. Conclusion: The endodontic access preparation was not found to affect the fracture strength of LD and RMC crowns. The LD showed higher fracture strength than RMC crowns. Even though significant differences were noted for failure loads regarding different crown materials, all could reasonably withstand masticatory forces. Clinical Significance: The endodontic access preparation through a restoration is known to be a common challenge in clinical practice. Maintaining a repaired LD or RMC crown is feasible and replacement may not be necessary. [ABSTRACT FROM AUTHOR]

The reported advantage of new dual-cured adhesive agents is that they do not require light curing, resulting in a reduced film thickness and improved seating of bonded all-ceramic restorations. The purpose of this study was to determine the effect of dual-cured adhesives on the bond strength of dual-cured resin cement to dentin under different polymerization conditions: with or without light curing of the dual-cured adhesive as well as with or without light curing of the dual-cured resin cement through a lithium disilicate ceramic material. Human molars were sectioned to remove the coronal tooth structure and randomly divided into 3 adhesive groups: Clearfil SE Bond 2, ExciTE F DSC, and Universal Primer. The adhesive agents were applied to the dentin surface with or without light activation. A dual-cured resin cement was applied, and discs of lithium disilicate were cemented to the dentin surface. Half of the discs were light cured from the top surface, and the other half were allowed to self-cure. Shear bond strength was tested after storage in distilled water for 24 hours. The effect of light curing of the adhesive or cement on the shear bond strength of the lithium disilicate discs to dentin was product dependent. Clearfil SE Bond 2 performed significantly better with light curing of both the adhesive and cement. Less significant effects of the various light-curing and self- curing combinations were observed with ExciTE F DSC or Universal Primer. When neither the adhesive nor the cement was light cured, all 3 adhesives performed poorly and had a significant loss in bond strength. [ABSTRACT FROM AUTHOR]

Background: One-visit apexification is a treatment of choice in necrotic immature open apex teeth. Calcium silicate base materials are suitable for this method. The purpose of this study was to investigate and compare the sealing efficiency of Biodentine, mineral trioxide aggregate (MTA) ProRoot, and calcium-enriched mixture (CEM) cement orthograde apical plug using bacterial leakage method. Materials and Methods: In this in vitro study a total of 70 extracted maxillary incisors were cleaned and shaped. A 1.1-mm standardized artificially open apex was created in all samples. The teeth were randomly divided into three experimental groups of 20, and two negative and positive control groups of 5. In experimental groups, 4-mm thick apical plugs of ProRoot MTA, CEM cement, or Biodentine were placed in an orthograde manner. Negative control samples were completely filled with MTA while positive control samples were left unfilled. Sealing efficiency was measured by bacterial leakage method, and results were analyzed by Kaplan–Meier and Chi-square tests. The level of significance was set at 0.05. Results: The highest number of turbidity was recorded for ProRoot MTA samples, while the lowest for Biodentine. There was a significant difference in the number of turbidity between ProRoot MTA and Biodentine groups (P < 0.001), but there was no significant difference between CEM cement and Biodentine (P = 0.133) and ProRoot MTA (P = 0.055). Conclusion: Within the limitation of this in vitro study, Biodentine showed promising results as a substance with good-sealing efficiency. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the dentine bond strength of a novel fast‐setting calcium silicate cement (Protooth) versus a calcium hydroxide‐based cement (Dycal), a calcium silicate cement (ProRoot MTA), and a glass ionomer cement (Ketac‐Molar). Mid‐root dentine slices of 1 mm thickness were obtained from human maxillary incisors. After enlarging the lumen of the canal to 1.3 mm, the cavities were randomly filled with test materials. Samples were immersed in physiological‐like solution. The push‐out bond strength was tested on days 1, 28, and 180 (n = 12). Failure types of bonding were determined using a stereomicroscope. We analysed the data using linear regression. Dycal and day 1 were considered as reference for cement type and assessment time, respectively. Protooth, Ketac‐Molar, and ProRoot MTA demonstrated higher push‐out bond strength than Dycal. The push‐out bond strength in the Protooth group increased on day 28 and 180. The bond strength of Ketac‐Molar was significantly reduced on day 28. Dycal showed a significant decrease in bond strength on day 180 compared with that on day 1 and 28. Mixed failure was the dominant failure type. Protooth bonding to dentine was increased with time, in contrast to that of ProRoot MTA, Dycal, and Ketac‐Molar, as a function of time. [ABSTRACT FROM AUTHOR]

Tongling is a significant non-ferrous metal mining city in China, which produces waste that negatively impacts the area's water environment. It is essential to comprehend the hydrochemical properties and formation processes of groundwater to safeguard and utilize it efficiently. We explored major ions, strontium, and its isotopes in water and river-bottom samples from the northern (i.e., A-A' section) and southern (i.e., B-B' section) areas. The hydrochemical facies show the mining activities have a greater impact on surface water than on groundwater. Groundwater hydrochemical formation results from several factors, with water-rock interaction and ion exchange being primary. Additionally, the dissolution of calcite, dolomite, and feldspar, oxidation of pyrite, and hydrolysis of carbonate minerals also impact the formation of groundwater chemistry. Our analysis of strontium and its isotopes indicates that carbonate dissolution primarily occurred in the recharge area; the runoff from the recharge to the discharge area results in the dissolution of certain silicate rocks; calcite dissolution sources account for > 70% contribution in both surface water and groundwater water-rock interactions, whereas silicate rock dissolution sources and dolomite dissolution sources account for < 30%. Due to changed order of dissolved carbonate and silicate minerals during groundwater flow, the distribution of strontium and its isotopes in the A-A' section is opposite to that in the B-B' section. The findings provide a basis for developing, utilizing, managing, and protecting groundwater resources, especially in similar mining areas., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The present study investigated the formation and fixation of silicate deposits during steam sterilization. First, transfer of silicic acid from the feed water into the sterilization steam onto the sterile supplies was analysed in theory by comparing the process parameters of all substeps of a typical steam sterilization process with a solubility diagram for silicic acid in water and in steam. Next, in furnace tests silicate deposits were selectively deposited onto test specimen made of non-rusting steel and with instrument-like surfaces. Deposit formation was visualized through digital photography and differential interference contrast (DIC) microscopy. In addition, topography images were obtained with atomic force microscopy (AFM) and the chemical composition of surfaces was determined with X-ray fluorescence analysis. Theoretical considerations supported the notion of a pressure- and temperature-dependent solubility of silicic acid in steam which, based on the steam sterilization process parameters, led to extensive entrainment of silicic acid into, and little removal from, the autoclave. Furthermore, experimental findings demonstrated that entrainment of silicic acid compounds gave rise to high, interlocking silicate margins on the test specimen, with a thin flat configuration within the dried drops. By combining the theoretical considerations and experimental findings, it was possible for the first time to add to the literature repository an explanation for the transfer of silicic acid to the sterile supplies and for the mechanism underling the transformation into visible deposits. [ABSTRACT FROM AUTHOR]

Techniques for the separation of Cerium (Ce) from silicate matrices and for the analysis of radiogenic (ε138Ce) and mass dependent (δ142Ce) Ce isotope variations by Thermal Ionisation Mass Spectrometry (TIMS) are presented in this study. We developed a static acquisition method associated with 1013 Ω amplifiers that allows (i) the precise determination of the 140Ce peak tailing effect on the lighter Ce isotopes and (ii) the reduction of the counting time necessary to obtain a high precision isotopic composition. The long-term reproducibility obtained for our Ce reference material (CeLMV) on the 138Ce/142Ce ratio is 0.02257053 ± 0.00000061 (27 ppm, 2 s.d., n = 48). The new CeLMV has been calibrated against the commonly used AMES reference material (0.02257426 ± 0.00000068 (30 ppm, 2 s.d., n = 25)). The static cup configuration also allows a more stable determination of the tailing effect from the 140Ce isotope peak onto 136Ce and 138Ce. Finally, the 1013 Ω amplifiers permit a better determination of the tailing effect during low voltage measurements. A new method to measure mass dependent Ce isotope variations based on the double spike method has also been developed. Uncertainty propagation calculations demonstrate that the best spike mixture is a 136Ce–138Ce–140Ce triple spike. We have calibrated an in-house triple spike used to correct for the instrumental mass bias effect and fractionation of Ce isotopes during Ce separation. Numerical simulations demonstrate the effect of potential isobaric interferences from Ba, Nd and La and highlight the need for an efficient chemical separation. Two loading techniques were tested for triple spike measurements (oxide and metal). The best reproducibility for δ142Ce is obtained for the metal runs and is about ±0.028‰. Although this technique has been developed for silicate matrices, the mass spectrometry method can be applied to other matrices such as carbonates. The newly calibrated Ce reference material is available to the community upon request. [ABSTRACT FROM AUTHOR]

Monolithic and powdered Biosilicate®, produced by conventional glass‐ceramic technology, have been widely recognized as excellent materials for bone tissue engineering applications. In the current research, we focus on an alternative processing route for this material, consisting of the thermal treatment of silicone polymers containing micro‐sized oxide fillers, which offers a unique integration between materials synthesis and shaping. In particular, the new method allows obtaining highly porous Biosilicate® glass‐ceramics, in the form of 3D printed scaffolds and foams. 3D scaffolds were successfully fabricated by direct writing using an ink based on a silicone polymer and active inorganic fillers, followed by firing in air at 1000°C. The products showed regular geometries, large open porosity (~60 vol%) and still high compressive strength (~7 MPa). Open‐cellular foams with porosity up to ∼80 vol% were also prepared from liquid silicones mixed with several fillers, including hydrated sodium phosphate. This specific filler acted both as a foaming agent, because of the gas release by dehydration occurring at low temperature, and as a provider of liquid phase upon firing in air, again at 1000°C. [ABSTRACT FROM AUTHOR]

Abstract Hypersaline tidal flats (HTF) are transitional ecosystems which play an important role over Si biogeochemistry in wetlands. Sources and sinks of Si in these ecosystems are directly dependent on pedogenesis and are strongly influenced by the readily soluble Si components, such as dissolved Si, adsorbed Si, and amorphous silicates. The aim of this study was to identify and assess the distribution of readily soluble Si pool in two HTFs on the Brazilian coast. We based our studies on sequential extractions of iron and silicon, modeling of the soil aqueous phase, and X-ray diffraction of the fine clay fraction. Our results show that mobile Si and adsorbed Si are present at very low levels in HTF soils, comprising <3% of the readily soluble Si pool. Silicon associated with Fe oxyhydroxides is the second largest component of the readily soluble Si pool, making up 8.7–40.8% of the Si extractions. The correlation between the ferrihydrite fraction and Si associated with Fe oxyhydroxides indicates a large control of Si by ferrihydrite. Amorphous Si makes up the dominant fraction, comprising 59–90% of the Si extractions. SEM images show the presence of diatoms, sponges, and phytoliths in the soils. Precipitation of pedogenic opal seems to occur in the soils due to a dry season at both sites. The clay assemblages are composed of the mixed-layer kaolinite-smectite (K-S), kaolinite-illite (K-I), and illite-smectite (I-S), and lesser amounts of kaolinite (K) and smectite (S) end-members. The presence of these clays indicates that HTF soils are conducive to the formation of mixed-layer minerals, which partially control Si dynamics. Our data indicate that HTF soils tend to accumulate Si by adsorption, (co)precipitation, and reactions involving clay minerals. [ABSTRACT FROM AUTHOR]

Limited by the sluggish kinetics of conversion‐type anodes from huge diffusion‐controlled phase transformation and unsatisfactory capacities of intercalation/alloy‐type anodes, the performances of lithium‐based dual ion batteries (LDIBs) remain to be promoted. Herein, for the first time, ultra‐small manganese silicate (MS) nanosheets anchored on reduced graphene oxides (MSR) with enhanced diffusion kinetics are constructed, realizing the construction of high performance LDIBs on the basis of conversion‐type anodes. The ion diffusion rate of MSR is promoted by in situ coating Li4SiO4 ionic conductor on the electrode surface during lithiation process. Simultaneously, the ion diffusion pathways are shortened by partially converting the diffusion‐controlled bulk reaction to surface reaction with massive pseudocapacitive contribution. Consequently, the MSR‐based LDIB exhibits superior electrochemical performances with discharge capacities of 191 mA h g−1 at 0.5 C and 128 mA h g−1 at 2 C after 150 cycles, exceeding to those of reported LDIBs and benefiting the future electrode design of LDIBs. Conversion‐type ultra‐small Mn7O8(SiO4) nanosheet/reduced graphene oxide anodes with enhanced diffusion kinetics are constructed for Li‐dual ion batteries (LDIBs) for the first time. The in situ formed Li4SiO4 ionic conductor and the pseudocapacitive contribution endow them with 191 mA h g−1 at 0.5 C and 128 mA h g−1 at 2 C after 150 cycles, realizing the construction of high‐performance LDIBs. [ABSTRACT FROM AUTHOR]

Abstract We have determined the chemical speciation of dissolved sulfur and the sulfur concentration at fixed oxygen and sulfur fugacities for a wide range of silicate melt compositions (from Fe-rich basalt to dacite). Each melt was equilibrated at 1300 °C and 1-atmosphere pressure at oxygen fugacities (f O 2) between −1.67 and +1.6 log units relative to the Fayalite–Magnetite–Quartz (FMQ) buffer and absolute sulfur fugacities between −5.1 and −1.2 log units. The f O 2 and f S 2 of the experiments were controlled by using gas mixtures of CO–CO 2 –SO 2. The speciation of sulfur in the quenched glasses was determined using both X-ray Absorption Near-Edge Spectroscopy (XANES), and from the dependence of equilibrium sulfur concentration on the f S 2 / f O 2 ratio measured by secondary-ion mass spectrometry (SIMS) and electron microprobe. The speciation of dissolved sulfur in each melt undergoes an abrupt transformation from S2− to S6+ with increasing f O 2 , and this transition is shifted ∼0.5 log units higher in f O 2 as melt FeO concentration increases from ∼5 wt% to ∼18 wt%. Since sulfide concentrations at constant f O 2 and f S 2 are consistently greater for more FeO-rich melts, the compositional effect on speciation may be explained by the well-known sensitivity of the sulfide capacity (C S 2 − ) of the melt to FeO concentration. S6+/S2− ratios for the glasses exhibit a linear relationship with Fe3+/Fe2+, indicating that the redox couples for iron and sulfur can be directly related to one another. We used thermodynamic data to model the interrelationship between Fe and S oxidation states in terms of the equilibrium FeS + 8 FeO 1.5 = 8 FeO + FeSO 4 Fitting the data to our experiments at 1300 °C we obtained the following expression for the temperature-dependence of speciation: log ⁡ ( S 6 + S 2 − ) = 8 log ⁡ ( Fe 3 + Fe 2 + ) + 8.7436 × 10 6 T 2 − 27703 T + 20.273 This equation fits the data for all our compositions and is also consistent with earlier results at 1050 °C and 950 °C. We used the interdependence of S and Fe oxidation states to infer electron transfer between Fe2+ and S6+ during quenching of glasses from Mauna Kea, Hawaii. The effect is sufficient to cause significant overestimation of equilibrium Fe3+/ Σ Fe in natural glasses and corresponding overestimate of f O 2 by about 0.8 log units. Glasses equilibrated under the most oxidizing conditions (containing S6+ only) have equilibrium S concentrations that are negatively correlated with their mole fractions of tetrahedral (Si + Ti) cations. Highlights • Measurements of S6+/S2− in 6 silicate melts varying from Martian basalt to terrestrial dacite. • The change in S6+/S2− of a silicate melts with f O 2 follows the thermodynamically predicted trend. • S6+/S2− and Fe3+/Fe2+ ratios of silicate melts are quantitatively linked. • Electron exchange between Fe2+ and S6+ during quench may modify Fe3+/Fe2+ in natural glasses. [ABSTRACT FROM AUTHOR]

Water is one of the most abundant molecules in the form of solid ice phase in the different regions of the interstellar medium (ISM). This large abundance cannot be properly explained by using only traditional low-temperature gas-phase reactions. Thus, surface chemical reactions are believed to be major synthetic channels for the formation of interstellar water ice. Among the different proposals, hydrogenation of atomic O (i.e. 2H  + O → H2O) is a chemically 'simple' and plausible reaction toward water formation occurring on the surfaces of interstellar grains. Here, novel theoretical results concerning the formation of water adopting this mechanism on the crystalline (010) Mg2SiO4 surface (a unequivocally identified interstellar silicate) are presented. The investigated reaction aims to simulate the formation of the first water ice layer covering the silicate core of dust grains. Adsorption of the atomic O as a first step of the reaction has been computed, results indicating that a peroxo (O |$^{2-}_{2}$|⁠) group is formed. The following steps involve the adsorption, diffusion, and reaction of two successive H atoms with the adsorbed O atom. Results indicate that H diffusion on the surface has barriers of 4–6 kcal mol−1, while actual formation of OH and H2O present energy barriers of 22–23 kcal mol−1. Kinetic study results show that tunneling is crucial for the occurrence of the reactions and that formation of OH and H2O are the bottlenecks of the overall process. Several astrophysical implications derived from the theoretical results are provided as concluding remarks. [ABSTRACT FROM AUTHOR]

Abstract Two sets of activating solutions with increasing sodium hydroxide contents were prepared either with or without silicates. Their buffer capacities, i.e. their ability to resist changes in pH, were determined and compared using the Hammett acidity function, a measure of acidity appropriate for concentrated solutions. This is the first time the Hammett acidity function of sodium silicate solutions has been measured. The effects of the buffer capacity and of the initial Hammett acidity function on the reactivity of metakaolin-based pastes were assessed using isothermal conduction micro-calorimetry. The reactivity of metakaolin in sodium hydroxide solutions is shown to be directly related to the initial Hammett acidity function, whereas for sodium silicate mixtures, the buffer capacity is a more pertinent parameter. The mechanism deduced for the role of hydroxide ions during geopolymerization also highlights the role of silicate species as a hydroxide reservoir that nurtures the dissolution process. [ABSTRACT FROM AUTHOR]

Geological and environmental silicate samples, such as soils and sediments, often contain high total carbon (carbonaceous) that poses difficulty in the precise analysis by certain XRF techniques. The presence of carbon in the matrix in excess of c. 2-3% results in pronounced enhancements of fluorescent X-ray intensities of analytes leading to overestimation by as much as >5% depending upon carbon content of the sample. In order to quantify this overestimation and its matrix dependence, XRF measurements were performed on reference silicate standards by doping with varying amounts (2-20%) of carbon. Precise measurement of carbon X-rays is commonly not used in routine analysis of silicate rock samples, which limits the use of internal matrix correction for carbon. The enhancement effect is found to be more serious on high-Z elements compared to lighter elements. The error of estimation exhibits a linear correlation with the carbon content of the sample. External correction factors, therefore, derived from this linear relationship were applied to the test samples that reasonably improved the accuracies of estimation to within an acceptable limit. [ABSTRACT FROM AUTHOR]

Abstract The analysis of iron, manganese and antimony in silicate glass is of great interest in chemistry, materials science, earth sciences and archaeological sciences. Yet, conclusions from different fields appear to be contradictory and many questions about redox reactions in glass remain. The purpose of this study is thus to discuss whether and how these multivalent elements interact in glass. Soda-lime silicate melts containing iron along with manganese and/or antimony have been analysed at different high temperatures under argon atmosphere. Using in-situ XANES at the Fe K-edge, redox thermodynamics, kinetics and diffusivities have been assessed for the different compositions. The data obtained show that antimony is more efficient at oxidising iron compared to manganese at all temperatures. The oxidising power trend would thus be Sb > Sb + Mn > Mn. Furthermore, hypotheses on the formation of Fe-Mn complexes are also reported in glasses with stoichiometric proportions of iron and manganese. Based on the determination of redox diffusivities, it appears that presence of other multivalent elements does not significantly affect the iron redox mechanisms and that diffusivity is essentially controlled by the mobility of calcium. Highlights • In-situ XANES is used to study how Fe, Mn and Sb interact in silicate melts. • The oxidising power trend is Sb > Sb + Mn > Mn. • We hypothesize that Mn Fe clusters can form and impede Fe oxidation. • Mechanisms and kinetics are not significantly affected by the presence of multivalent elements. [ABSTRACT FROM AUTHOR]

Groundwater from shallow and deep aquifers are widely used for drinking, agricultural and industrial use in Kabul, the capital of Afghanistan. However, unplanned urbanization and rapid population growth has led to the installation of numerous unlicensed wells to meet the public demand. This has caused to extraction of huge amounts of groundwater from the subsurface and further deterioration of groundwater quality. Therefore, understanding the hydrogeochemical characteristics of groundwater in shallow aquifers and deep aquifers is imperative for sustainable management of the groundwater resource in Kabul Plain. Thus, in this study, we used a multi-parameter approach, involving hydrochemical and environmental isotopes to understand the geochemical evolution of entire groundwater system of the Kabul Plain including river and dam water. The results of this study show that shallow and deep aquifers are dominantly of Mg-(Ca)-HCO 3 and Na-Cl water type, respectively. We observed that (1) water-rock interaction is the major contributing factor to the chemical compositions of groundwater in the Kabul Plain; (2) groundwater in deep aquifer is mainly influenced by silicate weathering, and dissolution of evaporitic and carbonate minerals and reverse cation exchange; (3) dissolution of carbonates and silicate weathering plays a pivotal role in the groundwater chemistry of shallow aquifer; (4) the stable isotopes of groundwater display that the shallow aquifer is principally recharged by river water and local precipitation; (5) the tritium analysis exhibited that groundwater of shallow aquifer was primarily recharged recently, whereas groundwater of deep aquifer is the mixture of pre 1953 with post 1953 groundwater. This study revealed that there are hydraulic interactions between the two aquifers and the deep aquifer is recharged through shallow aquifer. The findings of this study would be useful for Afghanistan's water authorities to develop an effective strategy for sustainable water resources management in the Kabul Basin., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Abstract Katoite-bearing rock was revealed in the Hatrurim Basin, Israel. The rock formed by hydration of pyrometamorphic calc-silicate assemblages at temperatures higher than 200 °C. The likely age of the hydration process is Miocene, about 6.2 Ma. The main phases of katoite-bearing rock are minerals of the katoite-grossular series, calcium hydrosilicates, fluorapatite and carbonate. Chemistry and mineralogy of katoite-bearing rock resembles belite sulfoaluminate concrete. Studied samples show two sets of porosities, which are low and high, between 22 and 28% and between 29 and 39%, respectively. Increased porosity characterizes non-weathered katoite-bearing samples, whereas decreased porosity is linked to carbonation during weathering. Katoite remained stable in spite of natural alkaline leaching. Although high porosity samples display decreasing strength parameters, most observed rock mechanic characteristics are comparable to modern-day concrete. We suggest that obtained data on natural katoite-bearing rock can simulate the longevity and durability of belite sulfoaluminate concrete. Graphical abstract Image 1 Highlights • Katoite-bearing rock genesis is related to hydration of pyrometamorphic calc-silicate assemblages. • Rock forming minerals are katoite-grossular, fluorapatite, several calcium hydrosilicates, carbonate, and magnesioferrite. • Katoite-bearing rock is a natural analogue of belite sulfoaluminate that survived in nature for a few million years. • Most of measured rock mechanic parameters are in the range typical for modern-day concretes. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Thin film form of microporous titanosilicate (ETS-10, (Na,K) 2 TiSi 5 O 13), microporous vanadosilicate (AM-6, (Na,K) 2 VSi 5 O 13), and silver nanoparticle (Ag0) incorporated vanadosilicate AM-6 were investigated as photocatalysts for the photocatalytic decomposition of methylene blue (MB). • The effect of V5+ cation present in the structure of AM-6 on the photocatalytic sensitivity of the photocatalyst under visible light irradiation were investigated. • It was found that AM-6 with higher amounts of V5+ cation showed photocatalytic activity under visible light irradiation. • The effect of noble metal nanoparticles on the photocatalytic activity of the photocatalyst were investigated by incorporating silver nanoparticles into AM-6. Abstract In the current study, a new photocatalyst in thin film form exhibiting photocatalytic activity under visible light range was introduced. For that purpose, microporous vanadosilicate (AM-6, (Na,K) 2 VSi 5 O 13) and silver nanoparticle (Ag0) incorporated vanadosilicate AM-6 thin films were investigated as photocatalysts for the photocatalytic decomposition of methylene blue (MB). To create different oxidation states of vanadium cation present in the ⋯V O V O V⋯ quantum wires within the framework of AM-6, two different molar compositions were used for thin film formation of vanadosilicate AM-6. The vanadosilicate AM-6 thin films demonstrated photocatalytic activity under ultraviolet (UV) and visible light irradiation. The microporous titanosilicate (ETS-10, (Na,K) 2 TiSi 5 O 13) thin films, isomorph of vanadosilicate AM-6, were also used as photocatalysts for the degradation of MB for the comparison of photocatalytic effectiveness. When visible light irradiation is used for the photocatalytic decomposition of MB, the photocatalytic activity of AM-6 was significantly different with respect to ETS-10. The narrower band gap of AM-6 with respect to the band gap of ETS-10 and the presence of V5+ cations in the structure of AM-6 provided photocatalytic activity under visible light irradiation. It was found that, vanadosilicate AM-6 films with higher amount of V5+ ions possess better photocatalytic activity under visible light irradiation for the degradation of MB, which can be attributed to the presence of V5+ cations within the framework of AM-6. The presence of both V4+ and V5+ cations was characterized by XPS and Raman spectroscopy in the vanadosilicate AM-6 thin films. To enhance the photocatalytic activity of AM-6 thin films, Na+ and K+ ions of the as-synthesized AM-6 thin films were ion-exchanged with Ag+ ions and then reduced to Ag0 nanoparticles (NP) by using sodium borohydride (NaBH 4) solution. The results showed that Ag0 NP incorporated AM-6 thin films showed an increased photocatalytic activity due to various reasons such as the role of metal nanoparticles as electron traps, surface plasmon resonance effect, and band-gap narrowing. [ABSTRACT FROM AUTHOR]

Dicalcium silicate finds applications in different fields (cement, bio-ceramics, refractories). In the case of Portland cement, its interest is its lower sintering temperature compared to tricalcium silicate and therefore an interesting compound for low CO 2 cements. Dicalcium silicate goes through different polymorphic forms, namely α, α' H , α' L , β and γ, as the temperature decreases. In theory, only the γ-phase is stable at room temperature. In a polycrystalline material, the different polymorphs can co-exist depending on several factors (sintering conditions, presence of impurities, grain size) and the interpretations given in the literature are sometimes contradictory. For cement applications, only the α, α' or β polymorphs react with water to give hydrates while γ does not. Therefore, this paper focuses specifically on the effect of grain size on the β to γ transformation. We also propose that the transformation is semi-reconstructive and not martensitic as suggested by some authors. [ABSTRACT FROM AUTHOR]

In this study, novel in-house synthesized hybrid polyacrylamide-grafted nanoparticles (Hy-PAM) were used to enhance the recovery of phosphorus bearing minerals from plant tailing by the froth flotation process. Characterization assays, including X-ray diffraction (XRD) and mineral liberation analysis (MLA) indicated that apatite, fluorapatite and quartz are the major crystalline phases in the tailing sample. Flotation experiments were performed using a bench scale Denver flotation cell with 1 L capacity in the presence of sodium oleate, which was used as a collector. Several influencing parameters such as polymer dosage, pH, and the flotation time were investigated to optimize the flotation outcomes in terms of recovery and grade of phosphorus pentoxide (P 2 O 5 ). Results indicated that the P 2 O 5 content in the plant tailings can be enriched from 21.6% to 28.6% at a recovery value of 80.5% in the first 4 min of flotation without the need to add a pH modifier. Moreover, flotation kinetics was investigated using classical first order kinetic model which was evaluated based on the flotation rate constant, the ultimate phosphorous recovery and the correlation coefficients obtained by non-linear regression analysis. Results indicated that the ultimate recoveries and the flotation rate constant values were affected by the change of the pulp’s pH. [ABSTRACT FROM AUTHOR]

Chondritic meteorites preserve extreme intra-sample 15 N/ 14 N variations, which exceed, in some cases, the range of nitrogen isotope ratios observed at the Solar System scale. These observations are based on in situ analyses of CN − molecular ions by secondary ionization mass spectrometry (SIMS) in carbon-rich phases. The distribution of nitrogen and its isotopes in silicate minerals and glasses has not been investigated to this date due to the lack of an appropriate analytical protocol, as well as of suitable N-bearing standards. In order to improve our knowledge of the nitrogen signature of both extraterrestrial and terrestrial silicate samples, we have developed a protocol for determining precise and accurate nitrogen abundances (and isotope ratios) in basaltic glasses using high mass resolution SIMS. Twelve (C-)N-bearing synthetic basaltic glasses, containing between <1 and 18,443 ± 966 ppm N, form the suite of reference materials for this study. By targeting the CN − , NO − , AlN − , and SiN − secondary molecular ions, nitrogen abundances can be detected down to the ppm level in both carbon-bearing and carbon-free glasses. The analytical precision and reproducibility of isotope ratios in the form of 15 N 16 O − / 14 N 16 O − is on the order of 11‰ and 10 to 17‰ (2σ), respectively, for reference glasses containing ≥100 ppm N. Thus, nitrogen isotope ratios can be determined with an uncertainty that is small enough to resolve nitrogen isotope variations in extraterrestrial silicates. The study of four chondrules of the ordinary chondrite Semarkona (LL3.0) reveals that the nitrogen distribution in the mesostasis is highly heterogeneous, with concentrations ranging from 0 to 1099 ± 168 ppm. The δ 15 N values in mesostasis, olivine, and pyroxene vary between −36 ± 50‰ and +55 ± 72‰, indicating that silicate phases in chondrules do not host particularly 15 N-poor nitrogen. [ABSTRACT FROM AUTHOR]

Bi can exist in a variety of chemical states (with varying ionic charges) and the microstructure of the glass surrounding the ions can be engineered to manipulate the chemical state. In this work, efficient enhancement of Ho3+ emission is observed with the change in local glass environment around Bi by adding Al2O3 to multi-component germanosilicate glass. In this multi-component glass, Al3+ can form tetrahedral AlO4 by accepting the non-bridging oxygen (NBO) and then, the addition of the AlO4-tetrahedron to the glass network facilitates the diffusion of alkali metals. Hence, Al2O3 decreases the Ba2+-rich domain and is conducive to the existence of Bi ions that are at low valence state. Moreover, the emission spectra indicate high efficiency energy transfer (ET) derived from NIR emission centers (Bi0/Bi+) located in close proximity to the Ho3+ ions. These results indicate that the optimized fluorescence of Ho3+ for optical fiber laser can be achieved by adjusting the local structure of the host glass. [ABSTRACT FROM AUTHOR]

Lignin is a renewable resource that can generate a variety of value-added benzene derivatives during hydrothermal and/or chemical hydrolysis treatment; the crucial task is to separate the targeted derivatives from the hydrolysate. This study aims to investigate the adsorption kinetics of lignin-derived benzene derivatives onto silicalite-1 crystal in an aqueous-phase system to examine the potential applicability of silicalite-1 to aqueous-phase kinetic separation. Functional groups substituted to benzene include –OH, –CH 3 , –CH 2 –CH 3 , –OCH 3 , –CHO, –COOH, and –CH 2 =CH 2 –COOH. First, the corrected diffusivity was compared among cresol isomers. Critical diameter of the isomers was found to be a key parameter, giving rise to significant differences in diffusivity. Interestingly, we also discovered a considerable difference (maximum over 4 orders of magnitude) in corrected diffusivity, even among mono - and para -substituted derivatives, although these sorbates have the same critical diameter. In particular, the carboxylic derivatives tended to exhibit extremely low diffusivities and to show S-shaped isotherms. The diffusivities were strongly affected by the melting point of the sorbates. These results indicate a strong sorbate-sorbate interaction (e.g., hydrogen-bonding between carboxylic groups) that considerably limits molecular mobility in the narrow channel. Our findings are relevant to research on silicalite-1 to aqueous-phase kinetic separation. [ABSTRACT FROM AUTHOR]

Because of the tunability of properties demonstrated by organic-inorganic hybrid materials, they have attracted considerable attention in recent years. However, despite luminescence being one of the major research topics involving hybrids, SiO2-poly(methyl methacrylate) (PMMA) systems have been poorly explored. In this paper, Eu3+:SiO2-PMMA samples were prepared with different Eu3+/Si molar ratios in order to determine Eu3+ local coordination, the potential interferences of these ions on synthesis reactions and the optimized lanthanide concentration for improved luminescence output. Careful analysis of FTIR spectra showed the presence of Eu3+ ions coordinated to carbonyl groups in the hybrid matrix, while TG results, allied to FTIR, indicate dopant influence on the mechanisms of formation of polymeric chains. Photoluminescence results showed that, at higher lanthanide contents, the position of the 5D0 → 7F0 band and spectroscopic parameters are modified, a clear signal of the formation of lanthanide clusters, which results in concentration quenching of luminescence. [ABSTRACT FROM AUTHOR]

Knowledge of the structure and properties of silicate magma under extreme pressure plays an important role in understanding the nature and evolution of Earth's deep interior. Here we report the structure of MgSiO3 glass, considered an analog of silicate melts, up to 111 GPa. The first (r1) and second (r2) neighbor distances in the pair distribution function change rapidly, with r1 increasing and r2 decreasing with pressure. At 53-62 GPa, the observed r1 and r2 distances are similar to the Si-O and Si-Si distances, respectively, of crystalline MgSiO3 akimotoite with edge-sharing SiO6 structural motifs. Above 62 GPa, r1 decreases and r2 remains constant, with increasing pressure until 88 GPa. Above this pressure, r1 remains more or less constant and r2 begins decreasing again. These observations suggest an ultrahighpressure structural change around 88 GPa. The structure above 88 GPa is interpreted as having the closest edge-shared SiO6 structural motifs similar to those of the crystalline postperovskite, with densely packed oxygen atoms. The pressure of the structural change is broadly consistent with or slightly lower than that of the bridgmanite-to-postperovskite transition in crystalline MgSiO3. These results suggest that a structural change may occur in MgSiO3 melt under pressure conditions corresponding to the deep lower mantle. [ABSTRACT FROM AUTHOR]

The bulk solubility and speciation of H 2 O in silicate melts of virtually any composition is predicted from first principles with a satisfactory precision. The solubility of molecular water is first predicted from the Scaling Particle Theory (SPT) coupled with an ab initio assessment of the electronic, dispersive and repulsive energy terms based on the Polarized Continuum Model (PCM). The Silver-Stolper ideal homogeneous speciation model is then applied to compute the fractional molar amount of neutral hydroxyl functionals [OH] 0 in the melt and the computed [OH] 0 amount is added to the molecular form [OH 2 ]. The Hydrogen Bonding (HB) electrostatic contributions to the stabilization of molecular water [OH 2 ] in solution are then resolved through an inverse non-linear minimization procedure on the basis of an extended dataset (970 samples) of experiments concerning the H 2 O saturation hyper-surface carried out in the last half century. The Gibbs free energy of solution ΔG S , the ΔG HB contributions and the energy terms involved in the homogeneous speciation reaction are shown to be consistent with first principles. The procedure is fully predictive (i.e. no need of an initial hint about approximate bulk amounts of H 2 O in solution) and sufficiently accurate to be proposed as an exploratory tool (mean absolute accuracy of ~2.1 kJ/mol in terms of energy and ~1.7% in terms of fractional molar amount X H2O per unit mole of liquid). [ABSTRACT FROM AUTHOR]

BACKGROUND Bio-treated coking wastewater is difficult to treat further, mainly due to the bio-refractory organic content. Coal gangue is the largest solid waste in China and it contains large amounts of aluminum, iron and silicon. This study attempts to recover the waste in coal gangue as a novel poly-silicic metal coagulant for bio-treated coking wastewater treatment. RESULTS The poly-silicic metal coagulant was synthesized from coal gangue under different conditions. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy confirmed that both amorphous and crystalline phases were present in the samples and new chemical bonds such as Si-O-Al and Si-O-Fe were formed. The results show that the composite coagulant was effective for organic removal from the bio-treated coking wastewater and the optimal Al/Fe/Si molar ratios were Al/Fe = 3 and (Al + Fe)/Si = 13. The removal of organics exhibits a parabolic curve as the coagulant dosage increases. However, the optimal dosage (125 mg L-1) for organic removal was not equal to the isoelectric point (100 mg L-1). Furthermore, SEM images showed that the flocs start to disintegrate at a dosage of 150 mg L-1, leading to deteriorating sludge settling. CONCLUSIONS It is feasible to fabricate poly-silicic metal coagulants for coking wastewater treatment by using coal gangue as the raw material. The removal of the bio-refractory organics by the composite coagulant was attributed to the combined effects of charge neutralization, bridge adsorption and the net capturing. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A transition-metal-free catalytic hydrodefluorination (HDF) reaction of polyfluoroarenes is described. The reaction involves direct hydride transfer from a hydrosilicate as the key intermediate, which is generated from a hydrosilane and a fluoride salt. The eliminated fluoride regenerates the hydrosilicate to complete the catalytic cycle. Dispersion-corrected DFT calculations indicated that the HDF reaction proceeds through a concerted nucleophilic aromatic substitution (CSNAr) process. [ABSTRACT FROM AUTHOR]

The reaction of Ca(CO3) with H3BO3 in oleum (20 % SO3) yielded colorless single-crystals of CaB2S4O16 (monoclinic, P21/ c, a=5.5188(2), b=15.1288(6), c=13.2660(6) Å, β=92.88(1)°, V=1106.22(8) Å3). X-ray single-crystal structure analysis revealed a phyllosilicate-analogue anionic sub-structure, forming 2D infinite anionic layers, which exhibit an unprecedented arrangement of condensed twelve-membered ( zwölfer) and four-membered ( vierer) rings of corner-shared (SO4) and (BO4) tetrahedra. Charge compensation is achieved by Ca2+ cations, residing exclusively above the centers of the twelve-membered rings. DFT investigations on the solid-state structure corroborate the experimental findings and allow for a detailed valuation of charge distribution within the anionic network and an assignment of vibrational frequencies. [ABSTRACT FROM AUTHOR]

Inorganic polymers can be introduced in a variety of undergraduate courses to discuss concepts related to polymer chemistry. Inorganic polymers such as silicates and polysiloxanes are simple materials that can be incorporated into an introductory or descriptive inorganic course. Polymers based on inorganic carbon, including diamond and graphite, can likewise be used to introduce concepts related to structure-property relationships. Diamond and graphite can be discussed in more detail in an upper-division inorganic chemistry course as well as an introduction to coordination polymers and semiconducting organic polymers. Herein, these materials are briefly discussed in terms of how they can be merged into relevant coursework. [ABSTRACT FROM AUTHOR]

This study has led to a new technique for the separation of Cr from small silicate samples (0.3–2 mg) and determination of stable Cr isotopes in silicates by double spike thermal ionization mass spectrometry (DS-TIMS). Based on our recent two-step exchange resin scheme (Li et al., JAAS, 2016, 31, 2375), we further significantly reduced the procedural blank and improved Cr recovery (94.7–97.5%) from a range of complex silicate rocks varying in composition from andesite to ultra-mafic, and carbonates as well. The key improvement is that KMnO4 was employed to replace conventional (NH4)2S2O8 as the oxidizing reagent, which reduces the procedural blank from 1–20 ng in previous studies to 0.15 ± 0.04 ng (n = 8). In addition, the inhibition effect on the Cr signal caused by residual SO42− in the Cr fraction using the conventional method has been completely eliminated during TIMS measurements. This permits the high precision determination of Cr isotopic ratios from geological samples as small as ∼46 ng. This chemical procedure was verified using a variety of silicate rocks in the size range of 0.3–2 mg. A series of analyses demonstrated that it is possible to attain internal precisions (2 SE) of ±0.03 to 0.06‰. Replicate digestions and analyses of basalt standard BIR-1 with a sample size of 0.3 mg (δ53Cr = −0.158 ± 0.052‰, 2 SD) demonstrated that good intermediate precision is obtainable for extremely small silicate samples. [ABSTRACT FROM AUTHOR]

The unidentified mineral (F78) occurs very sparingly as soft, grayish-brown coatings a few mm thick in the centers of quartz and blue amphibole seams that cut the metamorphosed peralkaline granite of Fountain Quarry, Pitt County, NC. The habit is always fibrous, but the enclosing minerals show no evidence for shearing. F78 has low 1st order interference colors and refractive indices slightly greater than 1.700. No optic figures could be obtained, but the fibers exhibit parallel extinction and are length slow. F78 is a hydrous Fe-Ti-Mn silicate (in wt%; 19.2 Fe2O3, 11.8 FeO, 9.3 TiO2, 6.8 MnO, and 35.1 SiO2) with small percentages of Zr, F, Na, K, Mg, Ca, and Al. Fe3+/Fet has been measured (0.595) by Mossbauer spectrometry and the XANES spectrum shows the Mn to be Mn2+. Molecular water exhibits a prominent peak in the IR spectrum and the analysis deficit (10.8%) is probably entirely due to hydrous components. X-ray diffraction (XRD) scans included powders and various arrangements of fibers mounted on a no-background Si plate. Accompanying minerals include quartz, blue amphibole, albite, microcline, and barite. Results of 29 XRD scans utilizing Cu radiation (3° to 73° 2-theta for most scans) show 11 peaks not matched by any of the accompanying minerals nor were any combinations of these peaks matched to any pattern in an extensive mineral data base. These 11 peaks were assigned to F78. The strongest two peaks are 11.47Å and 3.290Å. The F78 peaks exhibit unusually large FWHMs (full peakwidths at half maximum intensity values in degrees 2 theta). This fact and the known dspacings of possible accompanying minerals (AMs) were used to identify 14 additional F78 peaks possibly overlapped by AM peaks. Peaks (25) with smaller FWHM values were assigned to one or more of the accompanying minerals. In cases where narrow and wide peaks with the same d-spacings appeared in different scans, the wider peaks were assigned to F78, the narrower to an accompanying mineral. The wide peaks suggest that the F78 crystallites exhibit some degree of structural disorder and/or are very small. The unit cell parameters need to be determined, however, only a very small quantity of this material, all fibrous, is available for further studies. [ABSTRACT FROM AUTHOR]

Background: The eruptions of Eyjafjallajökull (2010) and Grímsvötn (2011), Iceland, triggered immediate, international consideration of the respiratory health hazard of inhaling volcanic ash, and prompted the need to estimate the potential hazard posed by future eruptions of Iceland's volcanoes to Icelandic and Northern European populations.Methods: A physicochemical characterization and toxicological assessment was conducted on a suite of archived ash samples spanning the spectrum of past eruptions (basaltic to rhyolitic magmatic composition) of Icelandic volcanoes following a protocol specifically designed by the International Volcanic Health Hazard Network.Results: Icelandic ash can be of a respirable size (up to 11.3 vol.% < 4 μm), but the samples did not display physicochemical characteristics of pathogenic particulate in terms of composition or morphology. Ash particles were generally angular, being composed of fragmented glass and crystals. Few fiber-like particles were observed, but those present comprised glass or sodium oxides, and are not related to pathogenic natural fibers, like asbestos or fibrous zeolites, thereby limiting concern of associated respiratory diseases. None of the samples contained cristobalite or tridymite, and only one sample contained quartz, minerals of interest due to the potential to cause silicosis. Sample surface areas are low, ranging from 0.4 to 1.6 m2 g-1, which aligns with analyses on ash from other eruptions worldwide. All samples generated a low level of hydroxyl radicals (HO•), a measure of surface reactivity, through the iron-catalyzed Fenton reaction compared to concurrently analyzed comparative samples. However, radical generation increased after 'refreshing' sample surfaces, indicating that newly erupted samples may display higher reactivity. A composition-dependent range of available surface iron was measured after a 7-day incubation, from 22.5 to 315.7 μmol m-2, with mafic samples releasing more iron than silicic samples. All samples were non-reactive in a test of red blood cell-membrane damage.Conclusions: The primary particle-specific concern is the potential for future eruptions of Iceland's volcanoes to generate fine, respirable material and, thus, to increase ambient PM concentrations. This particularly applies to highly explosive silicic eruptions, but can also hold true for explosive basaltic eruptions or discrete events associated with basaltic fissure eruptions. [ABSTRACT FROM AUTHOR]

Purpose Mechanical and chemical properties of acrylic-melamine automotive clear coat in the presence of different percentages of well dispersed nano-layered sodium montmorillonite (Na-MMT) silicate particles were investigated. For this purpose, prepared dry clear coat film samples were subjected to the entire standard test series, usually carried out in automotive coating industry.Design/methodology/approach Effects of adding different percentages of nano-layered silicate on mechanical and chemical properties of acrylic-melamine automotive clear coat were investigated. To increase the compatibility of nanoclays with polymer matrix of clear coat, the surface of nanoclays was modified by benzalkonium chloride as a cationic surfactant. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used for characterization and comparison between clays before and after modification, and also after dispersion in coating. Prepared dry clear coat film samples subjected to the test series are usually carried out in automotive coating industry.Findings The results indicated that incorporation of 1 and 2 Wt.% of nano-layered silicate caused desired improvement in chemical and physical properties of the acrylic-melamine clear coat. Increasing the percentage of nanoclay to over 2 Wt.% caused damage in some properties such as hardness, cupping and gloss.Research limitations/implications All materials and methods were used in this research are industrial grade. Therefore, the introduced modified clear coat sample has potential for commercial production as an automotive clear coat.Originality/value As far as it was searched in the literature, effects of adding nanoclay particles on mechanical and physical properties of different clear coats, such as epoxy clear coat, have been investigated in a few researches, but in this research, common and special tests which are necessary in automotive coating industry have been ignored. In the present study for the first time, acrylic-melamine clear coat was subjected to modification using nano-clay, and also, the most common industrial test methods were used for investigation of mechanical and chemical properties. [ABSTRACT FROM AUTHOR]

Recent developments in X-ray optics have allowed the development of a range of commercially available benchtop micro-XRF (μ-XRF) instruments that can produce X-ray spot sizes of 20-30 μm on the sample, allowing major- and trace-element analysis on a range of sample types and sizes with minimal sample preparation. Such instruments offer quantitative analysis using fundamental parameter based 'standardless' quantification algorithms. The accuracy and precision of this quantitative analysis on geological materials, and application of micro-XRF to wider geological problems is assessed using a single benchtop micro-XRF instrument. Quantitative analysis of internal reference materials and international standards shows that such instruments can provide highly reproducible data but that, for many silicate materials, standardless quantification is not accurate.Accuracy can be improved, however, by using a simple type-calibration against a reference material of similar matrix and composition. Qualitative analysis with micro-XRF can simplify and streamline sample characterization and processing for subsequent geochemical and isotopic analysis. [ABSTRACT FROM AUTHOR]

A suite of fifteen peridotite xenoliths from the Bakony-Balaton Highland Volcanic Field (BBHVF, Pannonian Basin, Central Europe) that show abundant petrographic evidence of fluid and melt percolation were studied in order to decipher the formation of their melt pockets and veins. The suite mainly consists of “fertile” lherzolites (5.8–19.9 vol.% clinopyroxene) and a few harzburgites (1.9–5.4 vol.% clinopyroxene) from well-known localities (Szentbékkálla, Szigliget) and two previously unreported localities (Füzes-tó and Mindszentkálla). Major and trace element data indicate that most of the peridotites record variable degrees of partial melt extraction, up to > 15% for the harzburgites. Subsequently, the xenoliths experienced at least two stages of metasomatic modification. The first stage was associated with percolation of a volatile-bearing silicate melt and resulted in crystallization of amphibole, enrichment in the most incompatible trace elements (Ba, Th, U, Sr), and development of negative Nb-Ta anomalies in clinopyroxene. The second and last metasomatic event, widespread beneath the BBHVF, is associated with the formation of silicate melt pockets, physically connected to a network of melt veins, with large and abundant CO 2 vesicles. The glass in these veins has sub-alkaline trachy-andesitic composition and displays an OIB-like trace element signature. Its composition attests to the migration through a supra-subduction zone mantle wedge of silicic melt highly enriched in volatiles (CO 2 , H 2 O, Cl, F), LILE, REE and HFSE and consistent with compositions of natural and experimental examples of slab melting-derived magma. In the present case, however, melt was likely derived from melting of oceanic crust and carbonated sediments under conditions where Nb-rich mineral phases were not stable in the residue. A likely scenario for the origin such melts involves melting after subduction ceased as the slab thermally equilibrated with the asthenosphere. Melt-rock reactions due to ascent of hot, CO 2 -rich, siliceous melt to near-Moho depths triggered destabilization of amphibole and primary clinopyroxene, spinel, and possibly olivine. The resulting andesitic glass in melt pockets evolved to more mafic compositions due to mantle mineral assimilation but has heterogeneous trace element signatures mostly inherited from preexisting amphibole. The present example of melt-rock reactions between highly volatile-enriched siliceous slab-derived melt and peridotite from the upper part of the lithospheric mantle ultimately produced derivative melt with major element composition akin to calc-alkaline basaltic andesite, with generally low trace elements concentrations but selective pronounced enrichments in LILE's such as Ba, Sr, Pb. [ABSTRACT FROM AUTHOR]

This study explored the sorption behavior and mechanism of U(VI) on sericite. The surface properties of sericite were investigated, and the effects of several environmental factors on U(VI) sorption to sericite were evaluated. The experimental data were simulated by different isotherm models and kinetic models. Humic acids affects U(VI) sorption obviously while silicate promotes the process in the whole pH range. The sorption-desorption hysteresis suggests an irreversible sorption process. Spectroscopic analyses indicate that the −OH groups have an important effect in the U(VI) sorption. [ABSTRACT FROM AUTHOR]

Terrestrial chemical weathering of silicate minerals is a fundamental component of the global cycle of carbon and other elements. Past changes in temperature, rainfall, ice cover, sea-level and physical erosion are thought to affect weathering but the relative impact of these controls through time remains poorly constrained. This problem could be addressed if the nature of past weathering could be constrained at individual sites. In this study, we investigate the use of speleothems as local recorders of the silicate weathering proxy, Li isotopes. We analysed δ 7 Li and [Li] in speleothems that formed during the past 200 ka in two well-studied Israeli caves (Soreq and Tzavoa), as well as in the overlying soils and rocks. Leaching and mass balance of these soils and rocks show that Li is dominantly sourced from weathering of the overlying aeolian silicate soils. Speleothem δ 7 Li values are ubiquitously higher during glacials (∼23‰) than during interglacials (∼10‰), implying more congruent silicate weathering during interglacials (where “congruent” means a high ratio of primary mineral dissolution to secondary mineral formation). These records provide information on the processes controlling weathering in Israel. Consideration of possible processes causing this change of weathering congruency indicates a primary role for temperature, with higher temperatures causing more congruent weathering (lower δ 7 Li speleo ). The strong relationship observed between speleothem δ 7 Li and climate at these locations suggests that Li isotopes may be a powerful tool with which to understand the local controls on weathering at other sites, and could be used to assess the distribution of weathering changes accompanying climate change, such as that of Pleistocene glacial cycles. [ABSTRACT FROM AUTHOR]

Results of assessment of the stability and homogeneity of the Be−Mg−Al−silicate glass synthesized by the authors and possibilities of its use as a quality control material (QCM) in the X-ray electron probe microanalysis (EPMA) of Be-bearing silicate materials, i.e., crystals and quenched melts (glasses), and also silicates and oxides are presented. The homogeneity of the samples was studied at the macro- (10-100 μm) and microlevels (1-10 μm) and assessed according to the scheme of dispersion analysis. A possibility of using the Be-silicate glass as a certified reference material for the determination of the concentrations of Mg, Al, Si was estimated using international reference materials of glasses and QCM of minerals of the known composition. The metrological performance of the experimental data obtained suggest that the studied glass can be used as a QCM in the EPMA of Be-bearing silicate materials, silicates, and oxides. The use of the Be-silicate glass as a certified reference material of composition in EPMA ensures acquisition of satisfactory data on the composition of minerals including cordierite and beryllium cordierite, beryllium indialite, beryl and also of metastable phases of chrysoberyl and compounds with the structure of β-quartz and petalite. [ABSTRACT FROM AUTHOR]

Objectives: Hammer drills are used extensively in commercial construction for drilling into concrete for tasks including rebar installation for structural upgrades and anchor bolt installation. This drilling task can expose workers to respirable silica dust and noise. The aim of this pilot study was to evaluate the effects of bit wear on respirable silica dust, noise, and drilling productivity. Method: Test bits were worn to three states by drilling consecutive holes to different cumulative drilling depths: 0, 780, and 1560 cm. Each state of bit wear was evaluated by three trials (nine trials total). For each trial, an automated laboratory test bench system drilled 41 holes 1.3 cm diameter, and 10 cm deep into concrete block at a rate of one hole per minute using a commercially available hammer drill and masonry bits. During each trial, dust was continuously captured by two respirable and one inhalable sampling trains and noise was sampled with a noise dosimeter. The room was thoroughly cleaned between trials. Results: When comparing results for the sharp (0 cm) versus dull bit (1560 cm), the mean respirable silica increased from 0.41 to 0.74 mg m-3 in sampler 1 (P = 0.012) and from 0.41 to 0.89 mg m-3 in sampler 2 (P = 0.024); levels above the NIOSH recommended exposure limit of 0.05 mg m-3. Likewise, mean noise levels increased from 112.8 to 114.4 dBA (P < 0.00001). Drilling productivity declined with increasing wear from 10.16 to 7.76 mm s-1 (P < 0.00001). Discussion: Increasing bit wear was associated with increasing respirable silica dust and noise and reduced drilling productivity. The levels of dust and noise produced by these experimental conditions would require dust capture, hearing protection, and possibly respiratory protection. The findings support the adoption of a bit replacement program by construction contractors. [ABSTRACT FROM AUTHOR]