Role Of Volatiles Research Articles

The role of an oxidized lithospheric mantle in gold mobilization.

Phanerozoic orogenic gold mineralization at craton margins is related to the metasomatism of the lithospheric mantle by crustal material. Slab subduction transfers Au from the crust to the metasomatized mantle and oxidizes the latter to facilitate the mobilization of Au into mantle melts. The role of volatiles in the mobilization of Au in the mantle is unclear because of the absence of direct geochemical evidence relating the mantle source of Au to Au mineralization in the overlying crust. This study uses lithium isotopes from a large suite of lamprophyres to characterize the mantle beneath the eastern North China Craton, which hosts giant Mesozoic gold deposits. Our results indicate a strong genetic link between carbonate metasomatism in the mantle and Au mineralization in the overlying crust. Although pre-enrichment of Au in the mantle is critical for forming giant Au provinces, the oxidation of the lithospheric mantle controls the mobilization of Au.

Role of volatility and thermal properties in droplet spreading: a generalisation to Tanner's law

Droplet spreading is ubiquitous and plays a significant role in liquid-based energy systems, thermal management devices and microfluidics. While the spreading of non-volatile droplets is quantitatively understood, the spreading and flow transition in volatile droplets remains elusive due to the complexity added by interfacial phase change and non-equilibrium thermal transport. Here we show, using both mathematical modelling and experiments, that the wetting dynamics of volatile droplets can be scaled by the spatial–temporal interplay between capillary, evaporation and thermal Marangoni effects. We elucidate and quantify these complex interactions using phase diagrams based on systematic theoretical and experimental investigations. A spreading law of evaporative droplets is derived by extending Tanner's law (valid for non-volatile liquids) to a full range of liquids with saturation vapour pressure spanning from $10^1$ to $10^4$ Pa and on substrates with thermal conductivity from $10^{-1}$ to $10^3\ {\rm W}\ {\rm m}^{-1}\ {\rm K}^{-1}$ . In addition to its importance in fluid-based industries, the conclusions also enable a unifying explanation to a series of individual works including the criterion of flow reversal and the state of dynamic wetting, making it possible to control liquid transport in diverse application scenarios.

Automating methods for estimating metabolite volatility.

The volatility of metabolites can influence their biological roles and inform optimal methods for their detection. Yet, volatility information is not readily available for the large number of described metabolites, limiting the exploration of volatility as a fundamental trait of metabolites. Here, we adapted methods to estimate vapor pressure from the functional group composition of individual molecules (SIMPOL.1) to predict the gas-phase partitioning of compounds in different environments. We implemented these methods in a new open pipeline called volcalc that uses chemoinformatic tools to automate these volatility estimates for all metabolites in an extensive and continuously updated pathway database: the Kyoto Encyclopedia of Genes and Genomes (KEGG) that connects metabolites, organisms, and reactions. We first benchmark the automated pipeline against a manually curated data set and show that the same category of volatility (e.g., nonvolatile, low, moderate, high) is predicted for 93% of compounds. We then demonstrate how volcalc might be used to generate and test hypotheses about the role of volatility in biological systems and organisms. Specifically, we estimate that 3.4 and 26.6% of compounds in KEGG have high volatility depending on the environment (soil vs. clean atmosphere, respectively) and that a core set of volatiles is shared among all domains of life (30%) with the largest proportion of kingdom-specific volatiles identified in bacteria. With volcalc, we lay a foundation for uncovering the role of the volatilome using an approach that is easily integrated with other bioinformatic pipelines and can be continually refined to consider additional dimensions to volatility. The volcalc package is an accessible tool to help design and test hypotheses on volatile metabolites and their unique roles in biological systems.

Role of volatiles in highly explosive basaltic eruptions

Water and carbon dioxide are the most abundant volatile components in terrestrial magmas. As they exsolve into magmatic vapour, they promote magma buoyancy, accelerating ascent and modulating eruptive dynamics. It is commonly thought that an increase in pre-eruptive volatile content produces an increase in eruption intensity. Using a conduit model for basaltic eruptions, covering the upper 6 km of conduit, we show that for the same chamber conditions mass eruption rate is not affected by CO2 content, whereas an increase in H2O up to 10 wt.% produces an increase in eruption rate of an order of magnitude. It is only when CO2 is injected in the magma reservoir from an external source that the resulting pressurisation will generate a strong increase in eruption rate. Results also show that ascent velocity and fragmentation depth are strongly affected by pre-eruptive volatile contents demonstrating a link between volatile content and eruptive style.

Role of Volatiles in the Evolution of a Carbonatitic Melt in Peridotitic Mantle: Experimental Constraints at 6.3 GPa and 1200–1450 °C

Reconstruction of the mechanisms of carbonatitic melt evolution is extremely important for understanding metasomatic processes at the base of the continental lithospheric mantle (CLM). We have studied the interaction between garnet lherzolite and a carbonatitic melt rich in molecular CO2 and H2O in experiments at 6.3 GPa and 1200–1450 °C. The interaction with garnet lherzolite and H2O-bearing carbonatite melt leads to wehrlitization of lherzolite, without its carbonation. Introduction of molecular CO2 and H2O initiates carbonation of olivine and clinopyroxene with the formation of orthopyroxene and magnesite. Partial carbonation leads to the formation of carbonate–silicate melts that are multiphase saturated with garnet harzburgite. Upon complete carbonation of olivine already at 1200 °C, melts with 27–31 wt% SiO2 and MgO/CaO ≈ 1 are formed. At 1350–1450 °C, the interaction leads to an increase in the melt fraction and the MgO/CaO ratio to 2–4 and a decrease in the SiO2 concentration. Thus, at conditions of a thermally undisturbed CLM base, molecular CO2 and H2O dissolved in metasomatic agents, due to local carbonation of peridotite, can provide the evolution of agent composition from carbonatitic to hydrous silicic, i.e., similar to the trends reconstructed for diamond-forming high density fluids (HDFs) and genetically related proto-kimberlite melts.

Role of gas coal in sulfur regulation from the release behavior and mass transfer condition of volatiles

There were new restrictions on sulfur regulation of high organic-sulfur coal (HOSC: A) brought by the differences in the pyrolysis characteristics of different gas coals (GC: B and C) and the mass transfer conditions of their volatiles. Firstly, the role of volatiles from GC in the sulfur regulation along vertical and horizontal directions was revealed by designing two stacking modes in a cylindrical crucible and using the parallel and cylindrical baffles to block the volatiles’ migration. Secondly, the different performances of volatiles from two different GC on the sulfur regulation were associated with their volatiles’ release behaviors. And finally, the effect of mass transfer conditions of volatiles on the sulfur regulation was discussed and reflected in the sulfur spatial distribution in chars. Contrast experiments with or without parallel and cylindrical baffles indicated that the monodirectional migration of volatiles from GC helped reduce the sulfur contents along both vertical and horizontal directions. The maximum distances of effective sulfur removal by volatiles from GC along vertical and horizontal directions varied respectively within 5 ∼ 15 and 8 ∼ 15 mm as changing GC. The performance of different GC in sulfur removal depended on the good match of its intensive volatiles release to the high permeability of HOSC and the continuous supply of hydrogen-rich volatiles. The effective distance of bi-directional vertical migration of volatiles was shortened to 3 ∼ 6 mm. It was promising to use the effective distance of sulfur removal by volatiles migrating vertically to evaluate the potential of GC as a sulfur regulator. The bi-directional migration of volatiles from GC helped extend the effective distance in the horizontal direction (>15 mm), which was related to the temperature gradient. The proper temperature gradient helped the volatiles of GC spontaneously or forcedly complement the hydrogen-rich volatiles in the HOSC layer. The temperature gradient is promising to maximize the potential of GC as a sulfur regulator and break the limits on sulfur removal by GC’s volatiles.

The role of volatile in the evolution of high silicic magma: Insights from the Late Cretaceous granitoids in the coastal area of southeastern China

东南沿海分布大面积的白垩纪晚期侵入岩。这些岩石可分为两期：其中115~100Ma以钙碱性系列岩石为主，岩石组合为辉长岩-闪长岩-花岗闪长岩-二长花岗岩-碱性长石花岗岩；而100~86Ma的岩石为碱性系列，岩石组合为石英二长斑岩-正长斑岩-碱性长石花岗岩。115~100Ma的辉长岩以角闪辉长岩为主，具有极高的CaO、MgO和Al₂O₃含量，具有极低的SiO₂(42.9%~53.8%)、全碱(K₂O+Na₂O: 0.86%~5.28%)、Ba、Nb、Th、Rb和Zr含量，也具有极低的FeO^T/MgO、La/Yb和Zr/Hf比值，较高的Eu/Eu^*、Sr/Y比值和Sr含量，为基性-超基性堆晶岩。与辉长岩同期的闪长岩和细粒暗色包体具有较高的SiO₂(50.34%~63.68%)，较低的CaO、P₂O₅、MgO、Al₂O₃含量，相对低的Eu/Eu^*和Sr/Y比值，变化较大的La/Yb和Zr/Hf比值，代表了从基性岩浆储库中抽取的富硅熔体。115~100Ma的花岗闪长岩和二长花岗岩类岩石为准铝质岩石，SiO₂含量变化较大(61.7%~75.3%)，具有较低的FeO^T/MgO、Ga/Al比值和Nb、Zr及Nb+Zr+Ce+Y元素含量，显示出典型I型花岗岩的特征。这些花岗岩具有相对高的La/Yb、Eu/Eu^*和Zr/Hf比值和高的Sr、Ba和Zr含量。结合岩相学特征，这些花岗岩为堆晶花岗岩。而115~100Ma的碱性长石花岗岩具有极高的SiO₂含量(大于75%)，低的Eu/Eu^*、La/Yb、Zr/Hf和Sr/Y比值，具有低的Ba、Sr和Zr含量和高的Rb、Nb、Y和Th含量和Rb/Sr比值，表明这些花岗岩是由富硅岩浆储库中抽离的高硅熔体侵入地壳形成。100~86Ma期间形成的二长斑岩和正长斑岩具有极高的全碱含量，可以达到8%~12%，其SiO₂主要集中在60%~70%，具有极高的Zr、Sr和Ba含量和Eu/Eu^*、La/Yb和Sr/Y比值，显示出堆晶花岗岩的特征。而100~86Ma期间形成的大部分碱性长石花岗岩具有极高的SiO₂含量(大于75%)，并显示出A型花岗岩的特征，具有高的Rb/Sr比值和高的Rb、Y和Th和低的Ba、Sr含量和低的Zr/Hf、La/Yb、Eu/Eu^*和Sr/Y比值，表明它们是由富硅岩浆储库抽离的高硅熔体侵入浅部地壳形成。东南沿海高硅花岗岩的形成和穿地壳岩浆系统密切相关，高硅花岗岩是由浅部地壳内晶体-熔体分异产生的熔体侵入地壳所形成，而高硅花岗岩的地球化学特征与岩浆储库的水及挥发份含量密切相关。115~100Ma期间，从富水的岩浆储库抽离的熔体形成具有低高场强元素含量和低Rb/Sr比值的高硅花岗岩，这一过程与古太平洋板块俯冲有关；100~86Ma期间，从富挥发份的岩浆储库抽离的熔体形成碱性特征、富含高场强元素和具有高的Rb/Sr比值的高硅花岗岩，这一过程和古太平洋板块回撤软流圈上涌有关。

KREDİ DERECELENDİRME KURULUŞLARININ VE EKONOMİ İLE İLGİLİ HABERLERİN HİSSE SENEDİ PİYASASINDA YARATTIĞI VOLATİLİTE

The study aims to identify volatility in the banking sector and general market related to some different types of announcements. Totally 103 announcements are clustered considering their sentiment and source. Daily closing values of banking and market indices, XBANK and BIST100, are included in the dataset which spans from the beginning of January 2018 to the end of March 2019. Findings indicate that the banking sector is not affected by the announcements released by the government. Announcements of credit rating agencies carry an informative value and play an important role in volatility. Furthermore, the relationship between economic indicators and volatility exists for the national market. As an interesting finding, investors tend to react 2 days before to the announcements belonging to Standard & Poor’s and Fitch.

A parasitoid's dilemma between food and host resources: the role of volatiles from nectar-providing marigolds and host-infested plants attracting Aphidius platensis.

The use of nectar-producing companion plants in crops is a well-known strategy of conserving natural enemies in biological control. However, the role of floral volatiles in attracting parasitoids and effects on host location via herbivore-induced plant volatiles is poorly known. Here, we examined the role of floral volatiles from marigold (Tagetes erecta), alone or in combination with volatiles from sweet pepper plant (Capsicum annuum), in recruiting Aphidius platensis, an important parasitoid of the green peach aphid Myzus persicae. We also investigated whether marigold floral volatiles are more attractive to the parasitoid than those emitted by sweet pepper plants infested by M. persicae. Olfactometry assays indicated that floral volatiles attracted A. platensis to the marigold plant and are more attractive than sweet pepper plant volatiles. However, volatiles emitted by aphid-infested sweet pepper were as attractive to the parasitoid as those of uninfested or aphid-infested blooming marigold. The composition of volatile blends released by uninfested and aphid-infested plants differed between both blooming marigold and sweet pepper, but the parasitoid did not discriminate aphid-infested from uninfested blooming marigold. Volatile released from blooming marigold and sweet pepper shared several compounds, but that of blooming marigold contained larger amounts of fatty-acid derivatives and a different composition of terpenes. We discuss the potential implications of the aphid parasitoid attraction in a diversified crop management strategy.

Amplification of early drought responses caused by volatile cues emitted from neighboring tea plants

Plants have developed sophisticated mechanisms to survive in dynamic environments. Plants can communicate via volatile organic compounds (VOCs) to warn neighboring plants of threats. In most cases, VOCs act as positive regulators of plant defense. However, the communication and role of volatiles in response to drought stress are poorly understood. Here, we showed that tea plants release numerous VOCs. Among them, methyl salicylate (MeSA), benzyl alcohol, and phenethyl alcohol markedly increased under drought stress. Interestingly, further experiments revealed that drought-induced MeSA lowered the abscisic acid (ABA) content in neighboring plants by reducing 9-cis-epoxycarotenoid dioxygenase (NCED) gene expression, resulting in inhibition of stomatal closure and ultimately decreasing early drought tolerance in neighboring plants. Exogenous application of ABA reduced the wilting of tea plants caused by MeSA exposure. Exposure of Nicotiana benthamiana to MeSA also led to severe wilting, indicating that the ability of drought-induced MeSA to reduce early drought tolerance in neighboring plants may be conserved in other plant species. Taken together, these results provide evidence that drought-induced volatiles can reduce early drought tolerance in neighboring plants and lay a novel theoretical foundation for optimizing plant density and spacing.

Volatiles inheriting from Crossostephium chinense act as repellent weapons against aphids in Chrysanthemum lavandulifolium cultivars

Chrysanthemum lavandulifolium is a kind of medicinal plant with large industrial scale and widely cultivated in southern China. Chrysanthemum aphids (Macrosiphoniella sanborni) seriously restricted the development of C. lavandulifolium industry. In this study, in order to breed aphid resistant cultivars, we introduced a potential aphid resistant germplasm Crossostephium chinense to participate in breeding, and the role of volatiles in this process was analyzed. Nine true hybrids were obtained by distant hybridization combined with embryo rescue. The aphid resistance and behavioral effects of their volatiles on aphids were tested. All hybrids behaved stronger resistance and repellency than C. lavandulifolium. The repellency of H1, H2 and H11 was significantly higher than other hybrids. Forty-seven major volatiles were detected in the parent and hybrid leaves by using solid phase micro extraction-gas chromatography-mass spectrometry (SPME-GC–MS). H1, H2 and H11 can be separated from other plant materials by PCA analysis, 15 volatiles such as 1, 2-Oxidolinalool were identified as their characteristic difference compounds. Methacrolein was demonstrated to be a repellent compound to aphids by using standard chemical. These findings may lead to novel control strategies against M. sanborni of C. lavandulifolium and its relative species.

Role of Volatiles from the Endophytic Fungus Trichoderma asperelloides PSU-P1 in Biocontrol Potential and in Promoting the Plant Growth of Arabidopsis thaliana.

Fungal volatile organic compounds (VOCs) emitted by Trichoderma species interact with a plant host and display multifaceted mechanisms. In this study, we investigated the antifungal activity of VOCs emitted by Trichoderma asperelloides PSU-P1 against fungal pathogens, as well as the ability of VOCs to activate defense responses and to promote plant growth in Arabidopsis thaliana. The strain’s VOCs had remarkable antifungal activity against fungal pathogens, with an inhibition range of 15.92–84.95% in a volatile antifungal bioassay. The VOCs of T. asperelloides PSU-P1 promoted the plant growth of A. thaliana, thereby increasing the fresh weight, root length, and chlorophyll content in the VOC-treated A. thaliana relative to those of the control. High expression levels of the chitinase (CHI) and β-1,3-glucanase (GLU) genes were found in the VOC-treated A. thaliana by quantitative reverse transcription polymerase chain reaction (RT-PCR). The VOC-treated A. thaliana had higher defense-related enzyme (peroxidase (POD)) and cell wall-degrading enzyme (chitinase and β-1,3-glucanase) activity than in the control. The headspace VOCs produced by PSU-P1, trapped with solid phase microextraction, and tentatively identified by gas chromatography–mass spectrometry, included 2-methyl-1-butanol, 2-pentylfuran, acetic acid, and 6-pentyl-2H-pyran-2-one (6-PP). The results suggest that T. asperelloides PSU-P1 emits VOCs responsible for antifungal activity, for promoting plant growth, and for inducing defense responses in A. thaliana.

To act or not to act. Debating the climate change agenda in the United States Congress

ABSTRACT Most climate change actions take place in the international context in terms of multilateral negotiations and accords or in bilateral agreements between heads of the state. Parliaments or legislatures such as the United States Congress are in a crucial position when it comes to converting agreements or aims to action in domestic politics. The United States has played a volatile role in international negotiations on climate change. From categorically rejecting the Kyoto protocol during the George W. Bush administration, President Barack Obama announced that the United States would join the Paris Climate Accord prior to President Donald J. Trump's announcement of the withdrawal of the United States from the Paris Accord. In domestic politics, too, efforts to address climate change have likewise varied. This article explores the complexity of climate change as a political question in the United States and considers the problematic issue that explains why the United States Congress has not have similar momentum to address climate change since the House of Representatives passed cap and trade legislation in 2009. The focus will be on theoretical discussions on congressional inaction and the United States Congress members' views on how and to what extent that institution should play a role in addressing climate change.

Do plant volatiles confuse rather than guide foraging behavior of the aphid hyperparasitoid Dendrocerus aphidum?

Many species of parasitoid wasps use plant volatiles to locate their herbivorous hosts. These volatiles are reliable indicators of host presence when their emission in plants is induced by herbivory. Hyperparasitoids may also use information from lower trophic levels to locate their parasitoid hosts but little is known about the role of volatiles from the plant–host complex in the foraging behavior of hyperparasitoids. Here, we studied how Dendrocerus aphidum (Megaspilidae) responds to plant and host volatiles in a series of experiments. This hyperparasitoid uses aphid mummies as its host and hampers biological control of aphids by parasitoids in greenhouse horticulture. We found that D. aphidum females were strongly attracted to volatiles from mummy-infested sweet pepper plants, but only when clean air was offered as an alternative odor source in the Y-tube olfactometer. Hyperparasitoid females did not have a preference for mummy-infested plants when volatiles from aphid-infested or healthy pepper plants were presented as an alternative. These olfactory responses of D. aphidum were mostly independent of prior experience. Volatiles from the host itself were also highly attractive to D. aphidum, but again hyperparasitoid females only had a preference in the absence of plant volatiles. Our findings suggest that plant volatiles may confuse, rather than guide the foraging behavior of D. aphidum. Mummy hyperparasitoids, such as D. aphidum, can use a wide variety of mummies and are thus extreme generalists at the lower trophic levels, which may explain the limited role of (induced) plant volatiles in their host searching behavior.

Credit spread and employment growth – a time-varying relationship?

ABSTRACT In this article, I explore time variation in the relationship between the credit spread and employment growth. Using a Bayesian VAR framework and formal model selection, it is concluded that the relationship is best modelled with constant parameters, but that heteroscedasticity needs to be taken into account. An interesting change in the dynamics is uncovered, where volatility in employment shocks induces more of the dynamics earlier in the sample and the role of volatility in credit-spread shocks is more pronounced in the latter parts.

Volatile-mediated antagonism of soil bacterial communities against fungi.

SummaryCompetition is a major type of interaction between fungi and bacteria in soil and is also an important factor in suppression of plant diseases caused by soil‐borne fungal pathogens. There is increasing attention for the possible role of volatiles in competitive interactions between bacteria and fungi. However, knowledge on the actual role of bacterial volatiles in interactions with fungi within soil microbial communities is lacking. Here, we examined colonization of sterile agricultural soils by fungi and bacteria from non‐sterile soil inoculums during exposure to volatiles emitted by soil‐derived bacterial communities. We found that colonization of soil by fungi was negatively affected by exposure to volatiles emitted by bacterial communities whereas that of bacteria was barely changed. Furthermore, there were strong effects of bacterial community volatiles on the assembly of fungal soil colonizers. Identification of volatile composition produced by bacterial communities revealed several compounds with known fungistatic activity. Our results are the first to reveal a collective volatile‐mediated antagonism of soil bacteria against fungi. Given the better exploration abilities of filamentous fungi in unsaturated soils, this may be an important strategy for bacteria to defend occupied nutrient patches against invading fungi. Another implication of our research is that bacterial volatiles in soil atmospheres can have a major contribution to soil fungistasis.

The role of volatiles in Rhizobium tolerance to cadmium: Effects of aldehydes and alcohols on growth and biochemical endpoints

Rhizobia have a significant agronomic and environmental role and are eminent contributors to soil fertility. However, this group of microorganisms are affected by various environmental stresses, such as Cd contamination. High Cd concentrations change bacterial metabolism. During this metabolic shift, bacteria alter their volatilome (the set of volatile metabolites synthesized by an organism). In the presence of Cd, peak areas of saturated aldehydes and alcohols were previously reported to increase, and the consequences of this increase to cells are poorly known. In this study, Rhizobium sp. strain E20-8 cells were exposed to Cd and aldehydes or their conjugated alcohols. Exposure to Cd (100 μM) inhibited cell growth and induced several biomarkers of oxidative stress. The present study also evidenced the higher toxicity of most aldehydes relatively to the corresponding alcohol in the presence of Cd, suggesting that reduction of aldehydes into alcohols may be an effective mechanism to restrain aldehydes toxicity in Rhizobium cells under Cd toxicity. Nonetheless, the protective effect was dependent on the pair aldehyde-respective alcohol considered and it differed between Cd stressed and non-stressed cells. Differences in the ability to convert aldehydes to alcohols may emerge as a new feature helping explain the oxidative tolerance variability among bacteria.

Hyperspectral imaging of drill core from the Steen River impact structure, Canada: Implications for hydrothermal activity and formation of suevite‐like breccias

AbstractHyperspectral imaging can be used to rapidly identify and map the spatial distributions of many minerals. Here, hyperspectral mapping in three wavelength regions (visible and near‐infrared, shortwave infrared, and thermal infrared) was applied to drill cores (ST001, ST002, and ST003) penetrating a continuous sequence of crater‐fill breccias from the Steen River impact structure in Alberta, Canada. The combined data sets reveal distinct mineralogical layering, with breccias derived predominantly from sedimentary rocks overlying those derived from granitic basement. This stratigraphy demonstrates that the breccias were not appreciably disturbed following deposition, which is inconsistent with formation models of similar breccias (suevites) by explosive impact melt–fluid interaction. At Steen River, volatiles from sedimentary target rocks were an inherent part of forming these enigmatic breccias. Approximately three quarters of terrestrial impact structures contain sedimentary target rocks; therefore, the role of volatiles in producing so‐called suevitic breccias may be more widespread than previously realized. The hyperspectral maps, specifically within the SWIR wavelength region, also delineate minerals associated with postimpact hydrothermal activity, including ammoniated clay and feldspar minerals not detectable using traditional techniques. These nitrogen‐bearing minerals may have originated from microbial processes, associated with oil‐ and gas‐producing units in the crater vicinity. Such minerals may have important implications for the production of habitable environments by impact‐induced hydrothermal activity on Earth and Mars.

The role of volatiles in plant communication.

SummaryVolatiles mediate the interaction of plants with pollinators, herbivores and their natural enemies, other plants and micro‐organisms. With increasing knowledge about these interactions the underlying mechanisms turn out to be increasingly complex. The mechanisms of biosynthesis and perception of volatiles are slowly being uncovered. The increasing scientific knowledge can be used to design and apply volatile‐based agricultural strategies.

Asymmetric linkages among precious metals, global equity and bond yields: The role of volatility and business cycle factors

Asymmetric linkages among precious metals, global equity and bond yields: The role of volatility and business cycle factors