Similar Compositional Changes Research Articles

Geochemical insights into secular changes in the depositional environment of ferromanganese nodules in the western North Pacific

Understanding Earth's surface dynamics and biological evolution requires deciphering past marine environmental changes. Hydrogenetic ferromanganese nodules formed by the direct precipitation of Fe–Mn oxide/hydroxide from seawater could record the marine environment at the time of deposition, as in the case of ferromanganese crusts. In this study, petrological and geochemical analyses were conducted on ferromanganese nodules collected from the Japanese Exclusive Economic Zone around Minamitorishima Island in the western North Pacific Ocean. Additionally, the results were compared with those of ferromanganese crusts distributed in the same area to elucidate the secular changes in the depositional environment. The mineralogical features (consisting solely of Fe-vernadite with an absence of 10 Å Mn oxide) and the geochemical characteristics (including positive Ce-anomaly and negative Y-anomaly in rare-earth element patterns, high Co contents, and low Cu and Ni contents) of the nodules suggest that the studied nodules are of a hydrogenetic origin. From the inside to the outside of the nodule, the Mn/Fe and Y/Ho ratios decrease while the Th/U ratio increases, indicating a changing depositional environment over time. A similar trend was observed in ferromanganese crusts from the nearby Takuyo-Daigo Seamount. Furthermore, similar compositional changes were observed on the surfaces of the crust samples (uppermost 1–3 mm), which correlated with depth-related changes in seawater oxygen concentrations. Therefore, the observed cross-sectional changes in the chemical compositions of the nodules and crusts may reflect changes in seawater-dissolved oxygen concentrations over time. The Mn/Fe and Y/Ho trends indicate a shift towards a less oxic environment with increasing age while maintaining the current depth profile, implying an expansion of the oxygen minimum zone (OMZ). Moreover, the observed Ni and Cu enrichment, together with the changes in the Mn/Fe and Y/Ho ratios, suggest that the expansion of the OMZ was caused by increased surface ocean productivity.

Increase of tocopherols, phytosterols, and carotenoids in high‐oil subtropical maize after recurrent selection

AbstractBackground and ObjectivesSubtropical high‐oil maize (HOM) genotypes have been successfully developed, but further evaluation of the content of liposoluble nutraceuticals is essential. The aim of this study was to determine the concentration and profile of tocopherols, phytosterols, and carotenoids in HOM and the effects of high‐oil selection in white and yellow subtropical populations.FindingsResults indicated that recurrent selection increase of germ proportion (9%–12%) in the total kernel had a direct effect on the oil content and increased the contents of carotenoids, tocopherols, and phytosterols. In particular, carotenoids improved only in yellow populations, with an improvement in total carotenoid (from 13 to 17 mg/kg dry weight [dw]), provitamin A, β‐carotenes, and β‐cryptoxanthin. α‐ and γ‐Tocopherols showed an overall increase in the total content (up to 39 mg/kg dw). Total phytosterols increased significantly in both populations, with similar changes in composition (up to 374 mg/kg dw). β‐Sitosterol was the predominant phytosterol associated with HOM.ConclusionsRecurrent selection for high oil in subtropical maize effectively altered the liposoluble nutraceuticals compounds of improved kernels in terms of carotenoids, tocopherols, and phytosterols, with modifications in their profiles.Significance and NoveltyThis research demonstrated that recurrent selection is an effective traditional breeding tool that improves oil, tocopherols, phytosterols, and carotenoids in subtropical maize. This investigation represents a first step toward understanding how the improvement of oil content affects the lipophilic nutraceutical content.

Phylotype resolved spatial variation and association patterns of planktonic Thaumarchaeota in eastern Chinese marginal seas

The majority of marine ammonia oxidizers belong to Thaumarchaeota, a phylum of Archaea, which is distributed throughout the water column. Marine surface waters contain distinct thaumarchaeotal phylotypes compared to the deeper ocean, but spatial dynamics of the surface-associated lineages are largely unsolved. This study of 120 seawater samples from the eastern Chinese marginal seas identified contrasting distribution and association patterns among thaumarchaeotal phylotypes across different dimensions. Horizontally, Nitrosopumilus-like and Nitrosopelagicus-like phylotypes dominated the surface water (3 m) of the Yellow Sea (YS) and East China Sea (ECS), respectively, along with increased abundance of total free-living Thaumarchaeota in ECS. Similar compositional changes were observed in the surface microlayer. The spatial heterogeneity of particle-attached Thaumarchaeota was less clear in surface microlayers than in surface waters. Vertically, the Nitrosopelagicus-like phylotype increased in abundance from surface to 90 m in ECS, which led to an increase in the proportion of Thaumarchaeota relative to total prokaryotes. This occurred mainly in the free-living fraction. These results indicate a clear size-fractionated niche partitioning, which is more pronounced at lower depths than in the surface water/surface microlayer. In addition, associations of Thaumarchaeota with other microbial taxa varied between phylotypes and size fractions. Our results show that a phylotype-resolved and size-fractionated spatial heterogeneity of the thaumarchaeotal community is present in surface oceanic waters and a vertical variation of the Nitrosopelagicus-like phylotype is present in shallow shelf waters.

Convection-induced bridging during alloy solidification

In this work, the effect of solute expansion coefficient on the natural convection and freezing front propagation is investigated by performing three-side cooled solidification experiments. Four different aqueous salt solutions, and different compositions thereof, were employed for experimentation. The mixtures were solidified to analyze the effect of solute expansion coefficients on the convection currents and the composition distribution in the bulk. The initial compositions were chosen such that all cases have the same primary solid fraction at eutectic temperature, for obtaining similar compositional changes in the bulk liquid at various stages. Similar cooling conditions were also maintained to ensure that the variation in convection strength is primarily caused by different solute expansion coefficients. A distinct observation of the free surface freezing before the bulk, termed bridging, is reported in certain cases. Further analysis revealed that the bridging could be attributed to a difference in solute convection caused by the solute expansion coefficient. Numerical simulations were performed to further ascertain the plausible initiation mechanisms for bridging. The predicted compositional and solid fraction distribution revealed lesser solute accumulation near the surface, for the lower solute expansion cases, and the resulting increase in the tendency of freezing at the top. An upper limit for the ratio of solutal to thermal Rayleigh numbers in the experimental conditions has been identified for the occurrence of bridging in high Prandtl number fluids.

Changes in the Composition of Oral and Intestinal Microbiota After Sleeve Gastrectomy and Roux-En-Y Gastric Bypass and Their Impact on Outcomes of Bariatric Surgery

BackgroundWe aimed to assess the changes in composition of bacterial microbiota at two levels of the digestive tract: oral cavity and large intestine in patients 6 months after bariatric surgery.MethodsThis was a prospective cohort study including patients undergoing bariatric surgery. Before surgery and 6 months after the procedure, oral swabs were obtained and stool samples were provided. Our endpoint was the analysis of the differences in compositions of oral and fecal microbiota prior and after the surgical treatment of obesity.ResultsBacteria from phylum Bacteroidetes seemed to increase in abundance in both the oral cavity and the large intestine 6 months after surgery among patients undergoing bariatric surgery. The subgroup analysis we conducted based on the volume of weight-loss revealed that patients achieving at least 50% of excess weight loss present similar results to the entire study group. Patients with less favorable outcomes presented an increase in the population of bacteria from phylum Fusobacteria and a decrease of phylum Firmicutes in oral cavity.ConclusionIntestinal microbiota among these patients underwent similar changes in composition to the rest of the study group. Bariatric surgery introduces a significant change in composition of oral and intestinal microbiota.Graphical abstract

Effects of domestication on the gut microbiota parallel those of human industrialization.

Domesticated animals experienced profound changes in diet, environment, and social interactions that likely shaped their gut microbiota and were potentially analogous to ecological changes experienced by humans during industrialization. Comparing the gut microbiota of wild and domesticated mammals plus chimpanzees and humans, we found a strong signal of domestication in overall gut microbial community composition and similar changes in composition with domestication and industrialization. Reciprocal diet switches within mouse and canid dyads demonstrated the critical role of diet in shaping the domesticated gut microbiota. Notably, we succeeded in recovering wild-like microbiota in domesticated mice through experimental colonization. Although fundamentally different processes, we conclude that domestication and industrialization have impacted the gut microbiota in related ways, likely through shared ecological change. Our findings highlight the utility, and limitations, of domesticated animal models for human research and the importance of studying wild animals and non-industrialized humans for interrogating signals of host-microbial coevolution.

Raman microspectroscopic analysis of the tissue-specific composition of the human osteochondral junction in osteoarthritis: A pilot study

This study investigates the influence of osteoarthritis (OA) disease severity on the bio-composition of the osteochondral junction at the human tibial plateau using Raman microspectroscopy. We specifically aim to analyze the spatial composition of mineralized osteochondral tissues, i.e., calcified cartilage (CC) and subchondral bone plate (SBP) from unfixed, hydrated specimens. We hypothesize that the mineralization of CC and SBP decreases in advanced OA. Twenty-eight cylindrical osteochondral samples (d = 4 mm) from tibial plateaus of seven cadaveric donors were harvested and sorted into three groups following histopathological grading: healthy (n = 5), early OA (n = 8), and advanced OA (n = 15). Raman spectra were subjected to multivariate cluster analyses to identify different tissues. Finally, the tissue-specific composition was analyzed, and the impact of OA was statistically evaluated with linear mixed models. Cluster analyses of Raman spectra successfully distinguished CC and SBP as well as a tidemark region and uncalcified cartilage. CC was found to be more mineralized and the mineral was more crystalline compared with SBP. Both tissues exhibited similar compositional changes as a function of histopathological OA severity. In early OA, the mineralization tends to increase, and the mineral contains fewer carbonate substitutions. Compared with early OA, mineral crystals are rich in carbonate while the overall mineralization decreases in advanced OA. This Raman spectroscopic study advances the methodology for investigating the complex osteochondral junction from native tissue. The developed methodology can be used to elucidate detailed tissue-specific changes in the chemical composition with advancing OA. Statement of SignificanceIn this study, Raman microspectroscopy was utilized to investigate the influence of osteoarthritic degeneration on the tissue-specific biochemical composition of the human osteochondral junction. Multivariate cluster analyses allowed us to characterize subtle compositional changes in the calcified cartilage and subchondral bone plate as well as in the tidemark region. The compositional differences found between the calcified cartilage and subchondral bone plate in both organic and mineral phases will serve as critical benchmark parameters when designing biomaterials for osteochondral repair. We found tissue-specific changes in the mineralization and carbonate substitution as a function of histopathological OA severity. Our developed methodology can be used to investigate the metabolic changes in the osteochondral junction associated with osteoarthritis.

Raman Micro-Spectroscopic Analysis of the Tissue-Specific Composition of the Human Osteochondral Junction in Osteoarthritis

This study investigates the influence of osteoarthritis (OA) disease severity on the bio-compositional properties of the osteochondral junction at human tibial plateau using Raman micro-spectroscopy. We specifically aimed to analyze the spatial composition of mineralized osteochondral tissues, i.e. calcified cartilage (CC) and subchondral bone plate (SBP). We hypothesize that the mineralization of CC and SBP decreases in OA. Twenty-eight cylindrical osteochondral samples (d=4mm) from tibial plateaus of cadaveric donors (N=7) were harvested and sorted into three groups following histopathological grading: healthy (n=5), early OA (n=8), and advanced OA (n=15). Raman spectra were subjected to multivariate cluster analyses to identify different tissue types. Finally, the tissue-specific composition was analyzed, and the impact of OA was statistically evaluated with linear mixed models. Cluster analyses of Raman spectra successfully distinguished CC and SBP as well as a tidemark region and uncalcified cartilage. CC was found to be more mineralized and the mineral was more crystalline compared to SBP. Both tissues exhibited similar compositional changes with OA progression. In early OA, the degree of mineralization increases, and the mineral contains fewer carbonate substitutions. Compared to early OA, mineral crystals are rich in carbonate while the overall mineralization decreases in advanced stages. This study provides insight into both mineral and organic phases of the osteochondral junction with OA progression in human tissue. The results show that the mineralization is altered already from the early OA in this biomechanically crucial junction, which advances our understanding of the initiation of OA.

Susceptibility of low-density lipoprotein particles to aggregate depends on particle lipidome, is modifiable, and associates with future cardiovascular deaths.

AimsLow-density lipoprotein (LDL) particles cause atherosclerotic cardiovascular disease (ASCVD) through their retention, modification, and accumulation within the arterial intima. High plasma concentrations of LDL drive this disease, but LDL quality may also contribute. Here, we focused on the intrinsic propensity of LDL to aggregate upon modification. We examined whether inter-individual differences in this quality are linked with LDL lipid composition and coronary artery disease (CAD) death, and basic mechanisms for plaque growth and destabilization.Methods and resultsWe developed a novel, reproducible method to assess the susceptibility of LDL particles to aggregate during lipolysis induced ex vivo by human recombinant secretory sphingomyelinase. Among patients with an established CAD, we found that the presence of aggregation-prone LDL was predictive of future cardiovascular deaths, independently of conventional risk factors. Aggregation-prone LDL contained more sphingolipids and less phosphatidylcholines than did aggregation-resistant LDL. Three interventions in animal models to rationally alter LDL composition lowered its susceptibility to aggregate and slowed atherosclerosis. Similar compositional changes induced in humans by PCSK9 inhibition or healthy diet also lowered LDL aggregation susceptibility. Aggregated LDL in vitro activated macrophages and T cells, two key cell types involved in plaque progression and rupture.ConclusionOur results identify the susceptibility of LDL to aggregate as a novel measurable and modifiable factor in the progression of human ASCVD.

Microwave radiation and conventional roasting in conjunction with hulling on the oxidative state and physicochemical properties of rapeseed oil

The purpose of the present study was to extend knowledge concerning the effect of rapeseeds pre‐processing methods on the changes in oxidative state, alterations within fatty acids contents, and color of oil. Thermal pre‐treatment of non‐hulled and hulled rapeseeds by microwave radiation (2–10 min, 800 W, 2450 MHz) was studied in comparison with conventional roasting (20–100 min, 165°C). As rapeseeds were thermally pre‐treated, with longer time a significant increase (p < 0.05) in the amounts of total carotenoids, chlorophylls, and phenolics in the oils pressed from microwaved and roasted seeds was found. Oils pressed from hulled seeds (HRO) were characterized by significantly lighter yellow hue than non‐hulled (NHRO) ones; however, the microwaving and roasting time significantly affected color change of both types of oils. Although induction period increased with longer seeds microwaving and roasting, oils pressed from thermally pre‐treated seeds exhibited higher level of primary and secondary oxidation. Additionally, prolonged seeds heating resulted in unsaturated fatty acids degradation as detected by GC‐FID. Based on the results obtained by applying principal component analysis (PCA), it can be concluded that within much shorter rapeseed exposition to microwaves similar compositional changes and degree of oxidation of oils was achieved as during conventional roasting.Practical applications:Color of edible oil is an important commercial parameter, whereas oxidative stability need to be monitored to ensure high quality of the finished product. Thermal pre‐treatment is currently being used in oilseeds pre‐processing, but very little researches studied its effect on color change and oxidative state of oil. Although rapeseed thermal pre‐treatment can cause a number of positive quality changes, such as an increase of bioactive compounds, the results should be interpreted with caution since application of too harsh heating conditions may result in unsaturated fatty acids degradation, lipid oxidation, or undesirable color change.Thermal pre‐treatment is currently being used in oilseeds pre‐processing, but very little researches studied its effect on color change and oxidative state of oil. Although rapeseed thermal pre‐treatment can cause a number of positive quality changes, such as an increase of bioactive compounds, the results should be interpreted with caution since application of too harsh heating conditions may result in unsaturated fatty acids degradation, lipid oxidation, or undesirable color change.

Mt. Etna plumbing system revealed by combined textural, compositional, and thermobarometric studies in clinopyroxenes

Coupled textural and in situ geochemical studies of clinopyroxene (cpx) phenocrysts, from both historical and recent eruptions of Mt. Etna volcano, provide a means to investigate the processes occurring in the deepest portion of the feeding system (>10 km depth). Five distinct textures were recognized: (1) normal oscillatory zoning, (2) normal zoning with Fe-rich rim, (3) sieve-textured core, (4) reverse oscillatory zoning, and (5) dusty rim. Electron microprobe analyses indicate an almost constant diopside–augite composition, with a slight enrichment in the enstatite for more recent erupted cpx. Core-to-rim compositional profiles, performed along the cpx, reveal distinct compositional characteristics. Normal oscillatory zoning is often characterized by a sharp increase in FeO (Δ ~ 2 wt%) accompanied by a drop in Al2O3 on the outermost 30 μm. Reverse oscillatory zoning, by contrast, exhibits a drop in FeO, Al2O3 (Δ ~ 2 wt%), and a remarkable crystal rim increase in MgO (up to 5 wt%). Similar compositional changes are evident in dusty-textured rims, which are characterized by dissolution edges and overgrowth containing glass pockets and channels. No significant compositional variations have been observed across crystals with sieve-textured cores. Trace element concentrations show enrichments in Sr, La, Zr, and REE, together with a decreasing La/Yb ratio (from ~7 to ~4) in rims of normally zoned crystals. Cpx with reverse zoning and dusty rims has low Sr, La, Zr, and REE contents toward crystal rims. Thermometers and barometers, based on equilibrium cpx-melt pairs, suggest that cpx cores start nucleating at 720 MPa, with the majority of them forming between 600 and 400 MPa but continuing to crystallize until very shallow depths (<100 MPa). Normal oscillatory-zoned phenocrysts surrounded by rims form at pressures shallower than 400 MPa, while reverse zoning and dusty rims occur between 400 and 500 MPa. Coupled petrologic and thermobarometric studies on both clinopyroxenes and plagioclases, associated with detailed textural and in situ geochemical analyses, are promising tools to reconstruct the entire magma ascent path beneath open-system volcanoes. At Mt. Etna, two distinct processes could account for the observed textures: Fe-rich rims in normal oscillatory-zoned crystals can be related to decompression-induced crystallization, while reverse zoning and dusty rims can be produced by mixing with a more basic magma at 400–500 MPa (i.e., ~10 km). Textural features are not restricted to a particular evolutionary phase of the volcano, which suggest that the deep feeding system has not changed significantly since the first alkaline volcanic phase.

Structural and superconducting features of Tl-1223 prepared at ambient pressure

This study provides an account of the bulk preparation of TlBa2Ca2Cu3O9−δ (Tl-1223) superconductor at ambient pressure, and the critical temperature (Tc) features under thermal-annealing conditions. The ‘as-prepared’ Tl-1223 (Tc = 106 K) presents a significantly higher Tc = 125 K after annealing the polycrystalline material in either flowing Ar + 4% H2, or N2 gases. In order to understand the fundamental reasons for a particular Tc, we refined the average bulk structures using powder x-ray diffraction data. Although Ar + 4%H2 annealed Tl-1223 shows an increased ‘c’ lattice parameter, it shrinks by 0.03% (approximately unchanged) upon N2 anneal. Due to such indeterminate conclusions on the average structural changes, local structures were investigated at using aberration-corrected scanning-transmission electron microscopy technique. Similar compositional changes in the atomic arrangements of both annealed-samples of Tl-1223 were detected in which the plane containing a Ca atomic layer gives a non-uniform contrast, due to substitution of some heavier Tl. In this report, extensive bulk properties are summarized through temperature-dependent resistivity, and shielding and Meissner fractions of magnetic susceptibility results; the bulk and local structures are investigated to correlate to properties.

Determining the baking isotherm temperature of Söderberg electrodes and associated structural changes

One of the most commonly employed electrode systems in industrial metal smelting applications is continuous self-baking electrodes, i.e. the Söderberg electrode system. In this system, the temperature at which transition from a liquid/soft paste to a solid carbonaceous electrode takes place is termed the baking isotherm temperature. This temperature is extremely important within the context of electrode management. In this paper, thermo mechanical analysis (TMA) was used to measure the dimensional changes that take place in coal tar pitch in the temperature range relevant to the determination of the baking isotherm temperature. It was found that the baking isotherm temperature of coal tar pitches was between 450 and 475°C, irrespective of the initial chemical composition and physical characteristics of the coal tar pitch. Subsequent Fourier Transform Infra-Red (FTIR) analyses indicated that all coal tar pitches underwent similar compositional changes during the transition from a molten/liquid coal tar pitch to a solid carbonaceous material.

Age-related changes in intramuscular and subcutaneous fat content and fatty acid composition in growing pigs using longitudinal data

The evolution of intramuscular fat (IMF) and subcutaneous backfat (SB) content and fatty acid composition with age was investigated. A repeated sampling scheme (n=517) for longissimus dorsi (LM) and SB specimens was performed from 160 to 220days on 216 purebred Duroc barrows. IMF content increased linearly with age at a rate of 0.05%/day, with major compositional changes occurring in C18:1 and C18.2, which increased and decreased by around 4%, respectively. Backfat thickness increase rate declined with age, showing similar compositional changes to IMF but halved in magnitude. Fat content itself also influenced fat composition. At a fixed age, both saturated (SFA) (C16:0) and monounsaturated (MUFA) (C18:1) increased with IMF but only SFA (C16:0 and C18:0) with SB. Aging mostly affected MUFA while fatness SFA. A delay in age at slaughter will enhance IMF and C18:1 in relation to overall fatness but at expense of decreasing body and loin growth rate.

Viscosity effect of titanium pickup by mould fluxes for stainless steel

Mould flux samples from an operating continuous caster showed a steady state increase in titanium oxide content of 3–4% for a titanium stabilised ferritic stainless steel and about 6% for a titanium stabilised austenitic stainless steel. Owing to the reduction of silica the flux basicity increased from 0.8 to 0.9, and from 0.95 to 1.2, for the ferritic and austenitic steels, respectively. Similar changes in composition were found for mould shims, which had been recovered from the mould after casting the ferritic steel. The increased titanium oxide content caused a decrease in the flux viscosity, for the original basicity. However, when the flux basicity was increased from 0.95 to 1.2, the apparent viscosity of the mould flux of the austenitic steel increased markedly, for 10% TiO2 and temperatures of 1250°C and below. Precipitation of perovskite was found to be responsible for the higher apparent viscosity.

Contributions of restructuring and oxidation to the aging of the surface of plasma polymers containing heteroatoms

The properties and composition of plasma polymer surfaces stored in air can change considerably over time, especially as a result of oxidative reactions. When plasma polymers contain an element other than O, it is possible to probe for mechanisms in addition to oxidation that contribute to the aging of the surface. Plasma polymers containing N were fabricated from either 1,3-diaminopropane (DAP),n-heptylamine (nHA), or allylamine (AA), and studied by X-ray photo-electron spectroscopy (XPS) and air/water contact angles (CA). For each of the plasma polymers, a multiexponential increase in the O/C ratio was observed over time using XPS. The N/C ratios remained constant (AA) or decreased somewhat (nHA and DAP). In contrast, the trends in CA values differed, declining for the nHA surfaces, rising for the AA, and changing little for the DAP. Surface roughness, assessed by scanning tunnelling or atomic force microscopy, did not change over time. The diverse adjustments in the polarity of each surface and the similar compositional changes between them are reconcilable if the aging of the plasma polymer surface is a manifestation of the superposition of concurrent oxidative reactions and partial surface reorientation; the former introduce polar groups and the latter transports then from the surface to deeper regions beyond the CA probe depth but within the XPS analysis depth. These processes vary between different plasma polymers. Data for the alkylamine plasma polymers is also compared with that for two plasma polymers fabricated from methanol. The change in composition, but not polarity, of the DAP surface after 4 days of storage demonstrates the importance of using multiple techniques to characterize the aging of plasma polymer surfaces.

Concentrations of organic contaminants in Mytilus edulis from the Hudson-Raritan Estuary and Long Island Sound

In this paper, we present the findings of 2-, 3-, 4-, and 5-ring polynuclear aromatic hydrocarbons (PAH), selected polychlorinated biphenyl (PCB) congeners, the pesticide DDT and its degradation products, and the marine paint antifouling agent tributyltin (TBT), in the tissues of Mytilus edulis collected from 10 sites in the Hudson-Raritan Estuary and 10 sites in Long Island Sound. In the estuary, contaminant concentrations were highest in the Upper Bay, and systematically decreased moving south and east into the New York Bight. Near equal distributions of tetra-, penta-, and hexa-chlorinated PCBs in the Upper Bay systematically shifted to a composition dominated by more heavily chlorinated PCBs in the New York Bight. In Long Island Sound, contaminant concentrations were highest in the heavily populated southwest region of the Sound, while the lowest bivalve contaminant levels were observed near the eastern-most tip of Long Island. PAH distributions generally were reminiscent of complex mixtures of combustion products and refined fuel products. PCB congener distributions exhibited similar changes in composition as those observed in the Hudson-Raritan Estuary.

Concentrations of organic contaminants in Mytilus edulis from the Hudson-Raritan Estuary and Long Island Sound

In this paper, we present the findings of 2-, 3-, 4-, and 5-ring polynuclear aromatic hydrocarbons (PAH), selected polychlorinated biphenyl (PCB) congeners, the pesticide DDT and its degradation products, and the marine paint antifouling agent tributyltin (TBT), in the tissues of Mytilus edulis collected from 10 sites in the Hudson-Raritan Estuary and 10 sites in Long Island Sound. In the estuary, contaminant concentrations were highest in the Upper Bay, and systematically decreased moving south and east into the New York Bight. Near equal distributions of tetra-, penta-, and hexa-chlorinated PCBs in the Upper Bay systematically shifted to a composition dominated by more heavily chlorinated PCBs in the New York Bight. In Long Island Sound, contaminant concentrations were highest in the heavily populated southwest region of the Sound, while the lowest bivalve contaminant levels were observed near the eastern-most tip of Long Island. PAH distributions generally were reminiscent of complex mixtures of combustion products and refined fuel products. PCB congener distributions exhibited similar changes in composition as those observed in the Hudson-Raritan Estuary.

Eruption of rhyolite at the Honeycomb Hills, Utah: Cyclical tapping of a zoned silicic magma reservoir

The Honeycomb Hills volcanic complex, erupted at 4.7 Ma in west central Utah, consists of a 12.5‐m‐thick tephra deposit that is predominantly fallout tuff, overlain by a 0.15 km3 dome of rhyolitic lava. The Honeycomb Hills rhyolite contains unusually high fluorine (up to 3.4 wt %) and lithophile trace elements (Rb to 1900 ppm). The dominantly fallout tephra deposit has been examined in detail, quantifying textural and compositional parameters. Three distinct eruption phases produced the tephra deposit. Phases I and II display similar changes in clast size, clast speciation, crystal content, pumice vesicularity, bedding style, and glass and mineral composition. The final phase of eruption, phase III, exhibits similar compositional changes while texturally recording the transition from explosive to effusive eruption style. Two‐feldspar temperatures yield an average temperature of 570°C with a weakly developed gradient from 550 to 600°C upward through the tephra. ƒH2O/ƒHF increases upsection from 560 near the base of the tuff to a maximum of 2400 in the vitrophyre at the top of the pyroclastic section. A corresponding increase exists in the ƒHCl/ƒHF ratio from 0.17 to 5.85. The mineral assemblage topaz‐anorthite‐annite‐fluorite‐quartz yields fugacities of ƒH2O from 250 to 1200 bars and ƒHF from 0.2 to 0.8 bars. Fugacity ratios, as well as major and minor elements in glass and biotite, exhibit cyclic variation within each eruptive phase whose boundaries are defined by physical parameters. The cyclicity is attributed to dynamic relaxation of the magma reservoir during brief pauses between eruptive phases. The patterns of varying eruption energy are most strongly correlated with vent widening, crystal content, and gas fugacity ratios. Initially, increasing vent radius and tapping of deeper, higher ƒH2O regions strongly increased eruption vigor, evident in phases I and II. During phase III, continuing crystallization, loss of volatiles, increasing viscosity, and growing conduit size from vent erosion led to the transition from explosive to effusive eruption, culminating in the extrusion of the lava dome.

EDS investigation of solute-precipitate interactions in ferritic steels under irradiation

The local composition at exactly the same position of the specimen is measured before and after irradiation by energy-dispersive X-ray spectrometer (EDS) in a Fe-10 Cr-2 Mo ferritic/martensitic steel. Microchemical charges are especially analyzed at precipitates and at the nearby matrix (25 nm from boundaries). The precipitates are identified, beforehand, to be Cr-rich ( M 23 C 6), Mo-rich (mostly M 6C), and Nb-rich (MC). The combination of EDS and microdiffraction techniques has made it possible to identify precipitates with the size of less than 20 nm in infoil conditions. After irradiation to 20 dpa by 1.25 MeV electrons at 500°C, enrichment of Si and depletion of Cr are observed at all precipitates and nearby matrices. By irradiation at 300°C, however, only significant enrichment of Si is observed. Since similar compositional changes are observed at grain boundaries irradiated at 500°C, the above decomposition is expected to be caused by defect-solute interactions. The present results extend our understanding of the mechanisms of precipitate rearrangements during irradiation.