Sulfur Peak Research Articles

Atomistic insights into salicylic acid treatment on human keratinized skin by XPS combined with argon gas cluster sputtering: A pilot study

Stratum corneum is the skin's outermost layer, whose main constituent is keratin. The treatment of dermatological diseases showing hyperkeratosis is a serious problem in dermatology and cosmetics seriously affecting the population showing increasing prevalence. One of the treatment is a peeling agent like salicylic acid (SA), categorized as a keratolytic agent, however its mode of action is not fully understood. X-ray photoelectron spectroscopy (XPS) is a method for monitoring the changes of surface composition at atomistic level in 5–10 nm depth. The development of argon cluster sputtering enabled the investigation of deeper regions (nanometric level) even for biomaterials. In this pilot study, the mode of action of SA has been studied at atomistic level for the first time. Different concentrations of SA (3, 5, 10 wt%) in different time frames (1 day, 1 week, 1 month) was applied on human keratinized skin. The carbon, nitrogen and oxygen peak have not shown changes during the treatment, not showing the suggested desmolytic mechanism of SA. However, significant changes were observed in the sulfur peak, with increasing time and concentration the rate of sulfonate and sulfate was increased compared to thiol group indicating the break of sulfide bonds between the polypeptide chains in keratin, indicating that keratolysis happens at nanometric level. Already a 1 week-10 wt% SA treatment resulted in higher rate of sulfate compared to sulfonate indicating further oxidation of the keratolytic product. However, 1 month-10 wt% treatment resulted in the same surface composition as 3 wt%-1-month treatment indicating that enough time with low concentration can exert the same effect as higher concentrations. These findings have relevance in the design of future SA-based dermatologic therapies.

Petroleum evolution and its genetic relationship with the associated Jinding Pb[sbnd]Zn deposit in Lanping Basin, Southwest China

The spatial association of hydrocarbons with metalliferous ore deposits is found worldwide and is particularly common to MVT PbZn deposits. Heavy oil and bitumen are found in the Jinding PbZn deposit within the Lanping Basin, South China. However, the temporal and genetic associations between hydrocarbons and the deposit are still controversial. To this end, integrating Raman analysis, ReOs geochronology and transmission electron microscopy analysis of the bitumen and in situ S isotope analyses of the sulfide, the petroleum evolution of the Jinding reservoir and its genetic relationship with the PbZn deposits were discussed. Bitumen ReOs data from this study and published works indicate that the late Triassic shales underwent two distinct oil-generation events before mineralisation (∼25 Ma), with initial oil generation occurring during the early Cretaceous (∼116 Ma) and the second during the early Paleogene (ca. 68–59 Ma). These two ages agree with the modelled thermal history of the Jinding reservoir. Combining the oil-before-ore timing sequence, high metal abundance of the bitumen, two negative sulfur isotope peaks of the sulfide and high S/C atomic ratio of the bitumen from the Jinding deposit, the oil-containing aqueous solutions were considered as one metal carrier during the hydrocarbon migration and accumulation; further, bacterial sulfate reduction and thermo-chemically induced sulfate reduction processes could have participated in the supply of reduced sulfur for the PbZn deposit precipitation.

Measurement of prompt neutron capture gamma coming from iron and chlorine

Prompt gamma radiation mostly comes from neutron reactions, thus naturally accompanying neutron transport. Therefore, it is an important part of the gamma field in nuclear installations, which accompanies neutrons leaking from the system. This also implies that good knowledge of the prompt gamma description of iron is essential in reactor dosimetry, especially as part of gamma heating and related issues. As the prompt gamma has a discrete character, it can be efficiently used in nuclear forensics for the identification of various isotopes. Prompt gamma rays from neutron capture on iron and chlorine were measured using HPGe and stilbene detector. Iron (as FeSO4) and chlorine (as NaCl) were dissolved in water to maximize the thermalization process of 252Cf(s.f.) neutrons emitted from acentrally positioned neutron source in the solution tank. Not only iron and chlorine peaks were found in the HPGe spectra, but six sulfur peaks from ferrous sulphate were identified as well. The experiments were simulated with the MCNP6.2 code using the ENDF/B-VIII.0, JEFF-3.3 and JENDL-5 libraries. Peak comparisons using HPGe results were generally discrepant in all libraries. Astudy of prompt gammas from thermal neutron capture reveals significant differences between the libraries studied. The comparison of whole spectra using stilbene results shows discrepancies in the gamma production data for chlorine in all libraries. Calculations with FeSO4 give quite good results for JENDL-5 and ENDF/B-VIII.0 and discrepant results for JEFF-3.3.

Adsorptive Desulfurization of Condensate Contains Aromatic Compounds Using a Commercial Molecular Sieve.

This study is undertaken to evaluate the potential of a commercial molecular sieve to remove diverse sulfur compounds from condensate with high aromatic on an industrial scale. For the first part of this study, the adsorbent is characterized in detail using inductively coupled plasma optical emission spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, and Brunauer-Emmett-Teller analysis. For the second part, dynamic breakthrough experiments on an industrial scale are performed to assess the dynamic adsorption performance of a commercial molecular sieve. Dynamic experiments show that the adsorbent effectively removes the sulfur compound from condensate that has approximately 900 ppmw S. In more detail, this commercial molecular sieve selectively desulfurizes condensate to about 12 ppmw S, and this is achieved when the concentration of non-sulfur aromatic is greater than 15 times higher than the total sulfur. As regeneration is a crucial part of the continuous adsorption-regeneration cycling process, the final part of this study is focused on finding a desorption method to avoid a sulfur concentration peak in tail gas.

Synergetic effects of Mo2C sphere/SCN nanocatalysts interface for nanomolar detection of uric acid and folic acid in presence of interferences

Till to date, the application of sulfur-doped graphitic carbon nitride supported transition metal carbide interface for electrochemical sensor fabrication was less explored. In this work, we designed a simple synthesis of molybdenum carbide sphere embedded sulfur doped graphitic carbon nitride (Mo2C/SCN) catalyst for the nanomolar electrochemical sensor application. The synthesized Mo2C/SCN nanocatalyst was systematically characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with elemental mapping. The SEM images show that the porous SCN network adhered uniformly on Mo2C, causing a loss of crystallinity in the diffractogram. The corresponding elemental mapping of Mo2C/SCN shows distinct peaks for carbon (41.47%), nitrogen (32.54%), sulfur (1.37%), and molybdenum (24.62%) with no additional impurity peaks, reflecting the successful synthesis. Later, the glassy carbon electrode (GCE) was modified by Mo2C/SCN nanocatalyst for simultaneous sensing of uric acid (UA) and folic acid (FA). The fabricated Mo2C/SCN/GCE is capable of simultaneous and interference free electrochemical detection of UA and FA in a binary mixture. The limit of detection (LOD) calculated at Mo2C/SCN/GCE for UA and FA was 21.5 nM (0.09 – 47.0 μM) and 14.7 nM (0.09 – 167.25 μM) respectively by differential pulse voltammetric (DPV) technique. The presence of interferons has no significant effect on the sensor’s performance, making it suitable for real sample analysis. The present method can be extended to fabricate an electrochemical sensor for various molecules.

Mechanism and Kinetics of Stibnite Dissolution in H2SO4-NaCl-Fe(SO4)1.5-O2

This paper is concerned with the kinetics of stibnite (Sb2S3) dissolution in H2SO4-NaCl-Fe(SO4)1.5-O2 solutions. The experimental results of our study showed a positive effect from ferric ions on stibnite dissolution of up to 0.05 M. An increase in H2SO4 concentration from 0.8 to 3 M and NaCl concentration from 0 to 3 M NaCl improved the stibnite dissolution. In solutions without ferric ions, the leaching occurs by the acid dissolution reaction producing H2S without forming elemental sulfur, as we confirmed by the X-ray diffraction (XRD) analysis of leach residues. In this case, the kinetic data was analyzed using a shrinking core model controlled by a chemical reaction, and the calculated activation energy was 54.6 kJ/mol. Conversely, in the presence of ferric ions, the XRD patterns of the leach residues showed large peaks for elemental sulfur, confirming that the stibnite was oxidized and formed a sulfur porous layer. The mechanism in the presence of ferric ions involved an acid dissolution reaction, with the diffusion of the reactant/product species through the porous product layer, followed by the oxidation of H2S by ferric ions. The kinetic data were analyzed using a diffusion-controlled model, and the activation energy was 123.8 kJ/mol. This high activation value is consistent with the proposed mechanism.

Climatic, weather, and socio-economic conditions corresponding to the mid-17th-century eruption cluster

Abstract. The mid-17th century is characterized by a cluster of explosive volcanic eruptions in the 1630s and 1640s, climatic conditions culminating in the Maunder Minimum, and political instability and famine in regions of western and northern Europe as well as China and Japan. This contribution investigates the sources of the eruptions of the 1630s and 1640s and their possible impact on contemporary climate using ice core, tree-ring, and historical evidence but will also look into the socio-political context in which they occurred and the human responses they may have triggered. Three distinct sulfur peaks are found in the Greenland ice core record in 1637, 1641–1642, and 1646. In Antarctica, only one unambiguous sulfate spike is recorded, peaking in 1642. The resulting bipolar sulfur peak in 1641–1642 can likely be ascribed to the eruption of Mount Parker (6∘ N, Philippines) on 26 December 1640, but sulfate emitted from Komaga-take (42∘ N, Japan) volcano on 31 July 1641 has potentially also contributed to the sulfate concentrations observed in Greenland at this time. The smaller peaks in 1637 and 1646 can be potentially attributed to the eruptions of Hekla (63∘ N, Iceland) and Shiveluch (56∘ N, Russia), respectively. To date, however, none of the candidate volcanoes for the mid-17th century sulfate peaks have been confirmed with tephra preserved in ice cores. Tree-ring and written sources point to cold conditions in the late 1630s and early 1640s in various parts of Europe and to poor harvests. Yet the early 17th century was also characterized by widespread warfare across Europe – and in particular the Thirty Years' War (1618–1648) – rendering any attribution of socio-economic crisis to volcanism challenging. In China and Japan, historical sources point to extreme droughts and famines starting in 1638 (China) and 1640 (Japan), thereby preceding the eruptions of Komaga-take (31 July 1640) and Mount Parker (4 January 1641). The case of the eruption cluster between 1637 and 1646 and the climatic and societal conditions recorded in its aftermath thus offer a textbook example of difficulties in (i) unambiguously distinguishing volcanically induced cooling, wetting, or drying from natural climate variability and (ii) attributing political instability, harvest failure, and famines solely to volcanic climatic impacts. This example shows that while the impacts of past volcanism must always be studied within the contemporary socio-economic contexts, it is also time to move past reductive framings and sometimes reactionary oppositional stances in which climate (and environment more broadly) either is or is not deemed an important contributor to major historical events.

Synthesis of the S/AgBr nano/micropowder in DMSO-water system

A new synthesis method of S/AgBr nano/micropowder based on sulfur and silver halide was developed. The nano/micropowder was obtained in the DMSO-water system, in two stages. Initially, sulfur was dissolved in DMSO at 120°C. The resulting solution was cooled to room temperature and separated from sulfur by filtration. Then, pre-prepared water solutions of AgNO3 and NaBr were introduced drop by drop into a sulfur solution in DMSO, at room temperature. The phase composition and structure of the precipitated powdery sediment were studied by X-ray diffraction analysis (XRD) and Raman spectroscopy. Scanning electron microscopy (SEM) was used to study the morphology and particle size. XRD showed the presence of the crystalline phase of AgBr, while the Raman spectra were characterized by the presence of sulfur and AgBr peaks. The SEM results showed that the S/AgBr is represented by oval, spherical and triangular particles of a homogeneous structure; the particle size was in the range from 300 to 800 nm.

Impact of DBDS and Silver Sulfide on the Performance of Thermally Aged Mineral oil Impregnated Pressboard Material

The corrosive sulfur compounds present in the mineral oil causes the formation of dibenzyl disulfide (DBDS) complex and it can also erode the on-load tap changing selector contacts leading to generation of silver sulfide (AgS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ).The present work reports the effect of DBDS and Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S concentrations in mineral oil on thermally aged pressboard material. The results demonstrate that surface discharge inception voltage (SDIV) is higher for the aged pressboard specimen. The higher concentrations of DBDS showed a reduction of more than 50% in the magnitude of SDIV compared to its effect with the addition of Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S. The surface potential analysis indicates a higher initial potential for the aged specimens with an increased half lifetime. In addition, only deep traps observed on the aged specimens with a slight right shift in its trap energy level. The mechanical strength of aged pressboard specimens with DBDS and Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S is understood using tensile testing and simultaneous analysis is captured using Digital Image Correlation (DIC) technique to understand its strain percentage at different areas on the pressboard material during its elongation. The laser induced breakdown spectroscopy (LIBS) analysis is performed to identify the elements responsible for thermal ageing such as carbon, copper and sulfur on the surface of pressboard material. The plasma temperature calculated from sulfur peaks is higher for DBDS aged specimen compared to AgS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and a linear correlation is observed on the LIBS intensity with ageing duration. Further, the Principal Component Analysis (PCA) is used for its classification on the degradation of pressboard due to the diffusion of both copper and silver sulfide from the mineral oil. The two principal components (PC1 and PC2) provided a higher variance of 99.8% with a clear classification observed between the unaged and aged pressboard specimens due to the addition of both DBDS and Ag <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S in mineral oil.

Rapid Degradation of the Electrical Properties of 2D MoS2 Thin Films under Long-Term Ambient Exposure.

The MoS2 thin film has attracted a lot of attention due to its potential applications in flexible electronics, sensors, catalysis, and heterostructures. Understanding the effect of long-term ambient exposure on the electrical properties of the thin film is important for achieving many overreaching goals of this material. Here, we report for the first time a systematic study of electrical property variation and stability of MoS2 thin films under ambient exposure of up to a year. The MoS2 thin films were grown via the sulfurization of 6 nm thick molybdenum films. We found that the resistance of the samples increases by 114% just in 4 weeks and 430% in 4 months and they become fully insulated in a year of ambient exposure. The dual-sweep current–voltage (I–V) characteristic shows hysteretic behavior for a 4-month-old sample which further exhibits pronounced nonlinear I–V curves and hysteretic behavior after 8 months. The X-ray photoelectron spectroscopy measurements show that the MoS2 thin film gradually oxidizes and 13.1% of MoO3 and 11.8% oxide of sulfur were formed in 4 months, which further increased to 23.1 and 12.7% in a year, respectively. The oxide of the sulfur peak was not reported in any previous stability studies of exfoliated and chemical vapor deposition-grown MoS2, suggesting that the origin of this peak is related to the distinct crystallinity of the MoS2 thin film due to its smaller grain sizes, abundant grain boundaries, and exposed edges. Raman studies show the broadening of E2g1 and A1g peaks with increasing exposure time, suggesting an increase in the disorder in MoS2. It is also found that coating the MoS2 thin film with polymethylmethacrylate can effectively prevent the electrical property degradation, showing only a 6% increase in resistance in 4 months and 40% over a year of ambient exposure.

Investigating the Effects of Surface Adsorbates on Gold and Palladium Deposition on Carbon

Surface functional groups have a strong influence on the deposition and final state of nanoparticles adsorbed on to the surface, a role discussed by Professor Spencer in his work. This tribute to Spencer explores the formation of hydroxyls, thiosulfates, sulfites and sulfur atoms on carbon (HOPG) surfaces and their effect on the deposition of gold and palladium from aqueous solutions. Hydroxyls formed from ammonium hydroxide treatment have identical behaviour to those formed by acid treatment, and gold adsorption from Au3+ solutions gives Au0 initially, with Au3+ formed at higher concentrations on these surfaces. In contrast, palladium adsorption is hindered by the presence of the hydroxyls and there is no indication of any reduction to the metallic state. Ammonium thiosulfate adsorbs dissociatively from aqueous solutions on HOPG if the surface is pre-activated by the presence of surface hydroxyls. At low concentrations of ammonium thiosulfate, adsorbed sulfite and sulfur are formed in equimolar concentrations whereas adsorption of high concentrations of ammonium thiosulfate gives some degree of molecular adsorption, with evidence in XP spectra for an ammonium ion and a sulfur 2p peak at 282.9 eV attributed to the undissociated thiosulfate ion. Both sulfur and the sulfite are stable at the surface in neutral solutions but the sulfite desorbs when treated with acidified solutions (~ pH ≤ 6). These two groups are also stable at 373 K but begin to desorb by 473 K. Exposure to a weak chloroauric acid solution causes the desorption of the sulfite and formation of a gold species with an XP binding energy of 84.6 eV; we cannot determine from the present data whether this peak is due to a Au(I) state or very small nanoparticles of Au(0).Graphic

The Effect of Crystalline Waterproofing Materials on Accelerated Corrosion of Steel Reinforcement in Concrete

This research aimed to investigate the effects of two types of crystalline waterproofing materials (CWPM): surface coating and admixture mixing type, on the corrosion behavior of reinforced concrete. For the first type, the effects of curing and different degrees of the defective coating (0.1 and 2% of the area) were investigated. For the second type, different dosages of crystalline waterproofing material admixtures (0.5, 0.8, 1, and 2% of cement content by weight) were studied. Impressed voltage was used to accelerate the steel corrosion. Compressive strength, time to initiate the observed first crack, and rust stain and corrosion extent of steel were studied. The results showed that while both crystalline types yielded improved compressive strength, both short- and long-term strength of mixing type specimens were significantly higher than those of the coated specimens. The benefit increased with the increase in dosage and age. In terms of steel corrosion, the mixing type seemed to indicate improved corrosion resistance. The 2% addition provided the most advantageous effects by delaying the onset of corrosion in reinforced concrete. However, the coated concrete slightly improved the corrosion resistance. The corrosions of steel in all specimens were similar regardless of the defects on coated areas and the curing condition. The mixing type revealed better performance for steel corrosion prevention than those of the coating type. Before and after immersion into NaCl solution, needle-like crystal structures of both the mixing and coating type specimens were observed. Some needle-like crystal in concrete with CWPM showed a high sulfur peak was similar to ettringite crystals in control concrete.

Evaluation of Interaction between Phosphate Ion and Metal Complex-layered Hydroxide

A nickel-aluminium-zirconium complex-layered hydroxide (NAZ), which was synthesized using each inorganic sulfate mixing ratio of 0.9 : 1.0 : 0.1, was prepared and calcined at different temperatures. The physicochemical properties of the NAZ were analyzed by scanning electron microscopy, specific surface area, number of hydroxyl groups, and pore volume. The specific surface area, number of hydroxyl groups, and pore volume of NAZ was 51.9 m2/g, 1.08 mmol/g, and 0.27 μL/g, respectively. The amount of phosphate ion adsorbed onto NAZ was higher than that onto calcined NAZ at different temperatures. Therefore, the interaction between phosphate ions and NAZ was assessed using the elemental distribution analysis and the binding energy. After adsorption, the intensity of phosphorus atoms increased, indicating that the phosphate ions were adsorbed onto the NAZ surface. Additionally, phosphorus peaks (189 eV for 2s and 130 eV for 2p), which were not detected before adsorption, were clearly detected after adsorption. On the other hand, the intensity of the sulfur peak (165 eV for 2p) decreased after adsorption. Thus, we evaluated the ion exchange between phosphate ion and sulfate ion in the interlayer space of the NAZ. As a result, the correlation coefficient between the amount of phosphate ion adsorbed and the amount of sulfate ion released was positively correlated (r=0.960). Therefore, it can be clearly stated that one of the adsorption mechanisms of phosphate ions was related to ion exchange in the interlayer space of the NAZ. These findings are useful for preventing the eutrophication and recovery of phosphate ion in water environments.

Smoking guns and volcanic ash: the importance of sparse tephras in Greenland ice cores

Volcanic ash (fine-grained tephra) within Greenland ice cores can complement the understanding of past volcanism and its environmental and societal impacts. The presence of ash in sparse concentrations in the ice raises questions about whether such material represents primary ashfall in Greenland or resuspended (remobilized) material from continental areas. In this article, we investigate this issue by examining tephra content in quasi-annual samples from two Greenland ice cores during a period of ca. 20 years and considering their relationships with sulphur and particulate data from the same cores. We focus on the interval 815–835 CE as it encompasses a phase (818–822 CE) of heightened volcanogenic sulphur previously ascribed to an eruption of Katla, Iceland. We find that tephra is a frequent but not continuous feature within the ice, unlike similarly sized particulate matter. A solitary ash shard whose major element geochemistry is consistent with Katla corroborates the attribution of the 822±1 CE sulphur peak to this source, clearly showing that a single shard can signify primary ashfall. Other tephras are present in similarly low abundances, but their geochemistries are less certainly attributable to specific sources. Although these tephra shards tend to coincide with elevated sulphur and fine (&lt;10 µm) particulates, they are not associated with increased coarse (&gt;10 µm) particle concentrations that might be expected if the shards had been transported by dust storms. We conclude that the sparse shards derive from primary ashfall, and we argue that low tephra concentrations should not be dismissed as insignificant.

X-Ray Emission from Jupiter’s Galilean Moons: A Tool for Determining Their Surface Composition and Particle Environment

Abstract We analyze archival Chandra X-ray Observatory observations of Jupiter to search for emission from the Galilean moons. X-ray emission has previously been reported from Io and Europa using a subset of these data. We confirm this detection, and marginally detect X-ray emission from both Ganymede and Callisto as well. The X-ray spectrum of Europa is strongly peaked around the neutral oxygen fluorescence line (525 eV), while Io’s has peaks at both oxygen and sulfur (2308 eV) plus a broad continuum between 350 and 5000 eV. Ganymede’s spectrum is similar to Io’s, but without the sulfur peak. A few events, mostly clustered around the oxygen line, are detected from Callisto. Using measurements by the Galileo mission of the specific intensity of ambient protons and electrons, we model the X-ray spectra and flux of the moons from two processes: particle-induced X-ray emission (PIXE) from the impact of energetic protons and X-ray emission from electron bremsstrahlung. With uncertainties of a factor of a few, the electron bremsstrahlung and PIXE models overestimate the X-ray flux from Europa, preventing us from making a definitive statement about the origin of the X-ray emission. The PIXE model of Io predicts emission lines at O and S similar to those observed, but underestimates their flux by nearly two orders of magnitude. Based on this discrepancy in the PIXE flux, combined with the detected broadband continuum in the spectrum, we conclude that the X-ray emission from Io is due to electron bremsstrahlung. Likewise, because of Ganymede’s broad continuum, we tentatively conclude that its X-ray emission is also due to electron bremsstrahlung. Callisto is too faint in the X-rays to draw any conclusion. Obtaining in situ X-ray observations of the moons would provide a direct measurement of their elemental composition.

Chromatographic detection of low-molecular-mass metal complexes in the cytosol of Saccharomyces cerevisiae.

Fluorescence-based chelators are commonly used to probe labile low-molecular-mass (LMM) metal pools in the cytosol of eukaryotic cells, but such chelators destroy the complexes of interest during detection. The objective of this study was to use chromatography to directly detect such complexes. Towards this end, 47 batches of cytosol were isolated from fermenting S. cerevisiae yeast cells and passed through a 10 kDa cut-off membrane. The metal contents of the cytosol and resulting flow-through solution (FTS) were determined. FTSs were applied to a size-exclusion LC column located in an anaerobic refrigerated glove box. The LC system was coupled to an online inductively-coupled-plasma mass spectrometer (ICP-MS) for detection of individual metals. Iron-detected chromatograms of cytosolic FTSs from WT cells exhibited 2-4 major species with apparent masses between 500-1300 Da. Increasing the iron concentration in the growth medium 40-fold increased the overall intensity of these peaks. Approximately 3 LMM cytosolic copper complexes with apparent masses between 300-1300 Da were also detected; their LC intensities were weak, but these increased with increasing concentrations of copper in the growth medium. Observed higher-mass copper-detected peaks were tentatively assigned to copper-bound metallothioneins Cup1 and Crs5. FTSs from strains in which Cup1 or the Cox17 copper chaperone were deleted altered the distribution of LMM copper complexes. LMM zinc- and manganese-detected species were also present in cytosol, albeit at low concentrations. Supplementing the growth medium with zinc increased the intensity of the zinc peak assigned to Crs5 but the intensities of LMM zinc complexes were unaffected. Phosphorus-detected chromatograms were dominated by peaks at apparent masses 400-800 Da, with minor peaks at 1000-1500 Da in some batches. Sulfur chromatograms contained a low-intensity peak that comigrated with a glutathione standard; quantification suggested a GSH concentration in the cytosol of ca. 13 mM. A second LMM sulfur peak that migrated at an apparent mass of 100 Da was also evident.

Investigation of crosslink structure of natural rubber during vulcanization using X-ray absorption near edge spectroscopy

The X-ray absorption near edge spectroscopy technique (XANES) has been applied to determine the crosslinking structure of natural rubber (NR) during sulfur vulcanization process. The NR samples were prepared using DCBS as an accelerator at different sulfur to DCBS ratios (from 0.26 to 6.67). The results showed that with increasing cure time from tc50 to tc70, tc90 and tc100 the position of sulfur peak shifted to higher energy. This implied that the amount of polysulfidic crosslink gradually decreased with increasing cure time. This result supported the crosslinking mechanism proposed in the literature at which the polysulfidic crosslink is dominating at initial curing stage. Moreover, when rubber was over-cured for 20 min, the amount of polysulfidic crosslink further decreased indicating by shifting of sulfur peak to high energy. The effect of sulfur to accelerator ratio on the crosslink structure was also elucidated by XANES. The results showed that the position of sulfur peak passed through the lowest energy with the increasing of the sulfur to DCBS ratios. It means that the amount of polysulfidic crosslink was not simply correlated with the sulfur to accelerator ratios. It passed through maximum with increasing sulfur to accelerator ratio. This caused the reversion resistance of rubber no longer directly proportional to the sulfur to accelerator ratio. The result from this study indicated that XANES technique is a prospective tool to investigate the crosslink structure of sulfur cured rubber.

Inventive Microstructural and Durability Investigation of Cementitious Composites Involving Crystalline Waterproofing Admixtures and Portland Limestone Cement.

The durability of a cement-based material is mainly dependent on its permeability. Modifications of porosity, pore-structure and pore-connectivity could have significant impacts on permeability improvement, which eventually leads to more durable materials. One of the most efficient solutions in this regard is to use permeability reducing admixtures (PRA). Among these admixtures for those structures exposed to hydro-static pressure, crystalline waterproofing admixtures (CWA) have been serving in the construction industries for decades and according to ACI 212—chemical admixtures’ report, it has proven its capability in permeability reduction and durability-enhancement. However, there is substantial research being done on its durability properties at the macro level but very limited information available regarding its microstructural features and chemical characteristics at the micro level. Hence, this paper presents one of the first reported attempts to characterize microstructural and chemical elements of hydration products for cementitious composites with CWA called K, P and X using Scanning Electron Microscopy (SEM). Backscattered SEM images taken from a polished-section of one CWA type—K—admixture were analyzed in ImageJ to obtain paste matrix porosity, indicating a lower value for the CWA-K mixture. X-ray analysis and SEM micrographs of polished sections were examined to identify chemical compositions based on atomic ratio plots and brightness differences in backscatter-SEM images. To detect chemical elements and the nature of formed crystals, the fractured surfaces of three different CWA mixtures were examined. Cementitious composites with K admixture indicated needle-like crystal formation—though different from ettringite; X and P admixtures showed sulfur peaks in Energy Dispersive Spectrum (EDS) spectra, like ettringite. SEM images and X-ray analyses of mixtures incorporating Portland Limestone Cement (PLC) indicated lower-than-average porosity but showed different Si/Ca and Al/Ca atomic ratios.

Characterization and Phosphate Adsorption Capability of Novel Nickel-Aluminum-Zirconium Complex Hydroxide.

In this study, the adsorption capability of phosphate ion using a novel tri-metals complex hydroxide was evaluated for preventing the eutrophication in water environment. A nickel-aluminum-zirconium complex hydroxide (NAZ) was synthesized using each inorganic sulfate mixing ratio of 0.9 : 1.0 : 0.1 and was calcined at different temperatures. The characteristics of the NAZ were analyzed by scanning electron microscopy images, X-ray diffraction analysis, elemental distribution, and binding energy. Moreover, the amount adsorbed of phosphate ion onto uncalcined and calcined NAZ was measured. That of phosphate ions onto the uncalcined was the largest of all. These results suggested that the adsorption of phosphate ions tends to depend on the physicochemical properties (e.g., amount of hydroxyl groups, pore volumes, and pH) of the adsorbents. Moreover, the adsorption mechanism of phosphate ions was evaluated on the basis of binding energy and elemental analysis. After adsorption, the binding energy of phosphorus P (2s and 2p) peaked and the sulfur peak intensity S(2s) reduced. This result indicated that the adsorption mechanism of phosphate would be exchanged with sulfate ions.

Linear Sulfur–Nylon Composites: Structure, Morphology, and Antibacterial Activity

Stabilization of sulfur in its linear form is highly challenging but recently developed inverse vulcanization method succeeded by reacting polysulfur terminals groups with organic cross-linkers. In present work, linear sulfur chains were stabilized in nylon matrix by forming amine-polysulfur complex. Composites were prepared by coextruding nylon with various amount of sulfur (2.5 to 30 wt %) under inert gas environment. Polysulfur chains produced under extrusion condition reacts with terminal amine groups of nylon in molten state and form polysulfur-amine complex. The color of these composites change from translucent to dark brown; which is due to formation of sulfur-amide complex based on FTIR spectroscopy. Furthermore the presence of NH3+ and sulfur anion peaks in XPS spectra confirms the formation of this complex. Disappearance of sulfur crystalline peak and absence of sulfur melt transition in XRD and DSC respectively suggests the conversion of crystalline sulfur into randomly arranged amorphous polys...