143 research outputs found
Li Isotope Analysis And Experiments To Understand Fluid Exchange During Bay of Islands Ophiolitic Crust Formation And Dynamic Metamorphism Of Its Sole
No full textThree Li isotopic studies were conducted to understand: 1) hydrothermal alteration of crustal levels of the Bay of Islands Ophiolite (BOIC), 2) Li alteration during dynamic metamorphism of protoliths in the welded metamorphic sole, and 3) Li partitioning and isotope fractionation factors at 150 °C and 300 °C in basalt and gabbro during hydrothermal reaction. Compared to unaltered MORB (Li = 6.1 ug/g, d7Li = 3.4 ‰), the upper pillow lava and dike section (Li = 1.24 - 40.66 ug/g, d7Li = -2.97 – 20.69 ‰) and lower plutonic section (Li = 0.087 - 8.16 mg/g, d7Li = 0.79 - 18.83 ‰) show extensive hydrothermal alteration. Hydrothermal fluid penetration appears limited to ~2km depth in the region above axial magma chamber but circulates as brine fluids off-axis to deep levels that create a hybrid system of magma chamber cooling.
The HT-LP metamorphic sole subcreted to the base of BOIC ophiolite during subduction consists of 3 primary protoliths: sedimentary, altered basaltic, and altered gabbroic rocks. Amphibolite to granulite metabasites exhibit a high Li (10.55 -57.33 ug/g) and light d7Li (-1.39 - +2.80 ‰) compared with altered oceanic crust (AOC, Li = 14 ug/g, d7Li = 7.5 ‰). Metasediments have enriched Li (53.86 - 66.24 ug/g) but low d7Li (0.81 - 1.52 ‰), compared with Global Subducting Sediments (GLOSS- II, Li = 45 ug/g, d7Li = 2.42 ‰). Two-stage process during subduction and formation of BOIC sole includes: (1) dehydration of protoliths during subduction resulting in initial depletion of both Li and d7Li followed by (2) metasomatism by later retrograde Li-rich fluids derived from metasediments subducted and dehydrated at deeper levels of subduction interface resulting in Li enrichment and slight increase of d7Li compared to dehydrated values.
Laboratory hydrothermal experiments yielded new Li partitioning coefficients (Kd) and Li isotopic fractionation factors (a) to aid models presented. Gabbroic samples show higher Kd (12.41) and lower a (0.9816) compared to basaltic glass (Kd = 6.08, a = 0.9863) at 150 °C but show lower values of Kd = 1.53 and a = 0.9964 compared to basaltic glass which has Kd = 2.79 and a = 0.9908 at 300 °C.Earth and Atmospheric Sciences, Department o
Crustal Lithium Isotopic Profile through the Bay of Islands Ophiolite: The Implications for the Extent of Hydrothermal Cooling of the Lower Oceanic Crust
No full textA bulk rock Li isotope, immobile and mobile trace element traverses through the crustal section of the Bay of Islands Ophiolite Complex (BIOC) in Western Newfoundland, Canada was analyzed to understand the extent of hydrothermal alteration at different pseudo-stratigraphic levels in the oceanic crust. Lithium systematics together with previously obtained Strontium isotope and Oxygen isotope data (Casey et al., in prep) were incorporated to give a better understanding of alteration extent. Of key importance are mylonite zones discovered that penetrate to the lower gabbroic crust which may provide strain localization zones and permeable fluid pathways. Trace element analysis was conducted by QQQ-ICP-MS and Li isotopic composition was analyzed by MC-ICP-MS at the University of Houston.
The bulk rocks from BOIC have a wide range of 7Li values from -5.80 ‰ to +19.00 ‰, reflecting water/rock interaction at various temperature and water/rock (w/r) ratios. Generally, alteration temperatures increase with depth close to the ridge axis. The York Harbor Mine Basalts were collected in 630 to 680 m depths in the basaltic section. They have the most negative 7Li values between -5.80 ‰ to -1.43 ‰ as well as very high Li contents with 13.9 g/g to 51 g/g, suggest an upwelling zone of high temperature hydrothermal fluids. Mylonitic zones from 2500 m to 2710 m show slightly enriched 7Li value with +3.31 ‰ to +7.42 ‰ compared to fresh MORB (+3.4 ‰±1.4 ‰, (Tomascak et al., 2008)) reflecting the reaction temperature for late stage of alteration between 200 °C to 400 °C based on modeling results. Most mylonitic plutonic rocks, however have higher temperature (480 °C-800 °C) amphibolite facies, indicating retrograde metamorphic alteration effects likely occurred off axis at lower temperatures. The layered gabbroic rock (2915 m to 4307 m) have both depleted and enriched 18O values from +4.08 ‰ to +7 ‰ (Casey et al., in prep) relative to unaltered MORB (+5.7 ‰±0.3 ‰) (Harmon and Hoefs, 1995), reflecting a relatively low temperatures (200 °C-250 °C) hydrothermal alteration. All the observations indicated that the lower oceanic crust at this location may have been constructed by hybrid model and cooled by hydrothermal fluids/seawater circulation at both on-axis and off-axis locations.Earth and Atmospheric Sciences, Department o
Investigations of barley powdery mildew effectors (CSEPs) in the non-host plant wheat and host plant barley
No full textBlumeria graminis f. sp. hordei is a biotrophic obligate fungus that can survive and cause powdery mildew disease exclusively on living barley plants. Over 500 Candidate Secreted Effector Proteins (CSEPs), which are considered to be secreted by the fungal feeding structure haustoria, have been identified. Some of the CSEPs, such as CSEP0064 and CSEP0264, were found to contribute to the pathogen virulence.
Wheat is resistant to Blumeria graminis f. sp. hordei-This is a form of non-host resistance. Recently, a Pseudomonas fluorescens based effector-to host analyser strain (EtHAn) was developed as a modified T3SS, which can deliver foreign effectors into plants. In this study, I used the EtHAn strain to deliver CSEP0064 and CSEP0264 into wheat, and screened for effector-triggered responses in a mapping population of wheat (WAGTAIL). Although the bacterium itself induced pattern-triggered immunity (PTI) in wheat, three cultivars (Rialto, Abbot and Madrigal) were capable of consistently recognizing and differentiating introduced CSEP0064 or CSEP0264, leading to an enhancement of EtHAn-triggered PTI.
Subsequently, I tested whether the recognition of EtHAn-delivered effectors in these three lines can affect the susceptibility of wheat to subsequent fungal infection. The results showed that the recognition of introduced CSEPs triggered systemic resistance in Rialto and Madrigal, whereas induced systemic susceptibility in Abbot, to the adapted pathogen Blumeria graminis f. sp. tritici. Delivered CSEPs did not affect systemic wheat immunity to sebsequent infection of the non-adapted pathogen Blumeria graminis f. sp. hordei. These results suggest that either wheat host resistance and non-host resistance are controlled by different systemic signalling pathways or basal plant immunity is sufficient to restrict non-host pathogen invasion and additional up-regulation of systemic immunity does not provide any additional advantage.
In parallel, the expression of CSEP0064 in host plant barley was also investigated. In this study, I observed that CSEP0064 is detectable by western blotting in heavily infected barley leaves and isolated haustoria. Unexpectedly, a protein with an apparent molecular mass around 200 kDa was recognized by the anti-CSEP0064 antibody on western blots. Here, I refer to this protein as ‘Big CSEP’. This ‘Big CSEP’ was detected in fungal structure-containing materials only. TFMS-mediated deglycosylation successfully removed this ‘Big CSEP’ signal, suggesting that the ‘Big CSEP’ may be a hyper/O-glycosylated CSEP0064, or a glycosylated complex containing CSEP0064.
Large-scale shotgun proteomics have been performed on Blumeria graminis f. sp. hordei, leading to the identification of some haustoria-exclusive effectors including CSEP0064. Here, MRM-MS was used to detect and quantify CSEP0064 in different fractions of infected barley leaf. An enzymatic method was conducted to isolate haustoria from infected barley epidermis. GAPDH (Blumeria graminis f. sp. hordei) and GAPDH (H. vulgare) were used as reference for fungal and plant proteins. CSEP0064 was more abundant than GAPDH (Blumeria graminis f. sp. hordei) in isolated haustoria and the plant cytoplasm fractions. Moreover, CSEP0064 was four times more abundant than GAPDH (H. vulgare) in the plant cytoplasm fraction. Finally, the results demonstrate the secreation of CSEP0064 from haustoria and the uptake of CSEP0064 by the host cell.Open Acces
Expression profiling of the barley powdery mildew Effector (CSEP) superfamily
No full textImperial Users onl
A Green function characterization of uniformly rectifiable sets of any codimension
No full textIn this paper, we obtain a unified characterization of uniformly rectifiable
sets of {\it any codimension} in terms of a Carleson estimate on the second
derivatives of the Green function. When restricted to domains with boundaries
of codimension 1, our result generalizes a previous result of Azzam for the
Laplacian to more general elliptic operators. For domains with boundaries of
codimension greater than 1, our result is completely new.Comment: Made corrections to some typos and minor mistakes in the first
version. 38 pages. To appear in Adv.Mat
The Poisson-Neumann problem and its relation to the Neumann problem
No full textWe introduce the Poisson-Neumann problem for an uniformly elliptic operator in divergence form in a bounded 1-sided Chord Arc Domain , which considers solutions to in with zero Neumann data on the boundary for and in some tent spaces. We give different characterizations of solvability of the Poisson-Neumann problem and its weaker variants, and in particular, we show that solvability of the weak Poisson-Neumann probelm is equivalent to a weak reverse Hölder inequality. We show that the Poisson-Neumman problem is closely related to the Neumann problem, whose solvability is a long-standing open problem. We are able to improve the extrapolation of the Neumann problem from Kenig and Pipher by obtaining an extrapolation result on the Poisson-Neumann problem.49 page
Multi-objective optimal path finding in stochastic time-dependent transportation networks considering timeliness reliability and travel expense
No full textPredicting Habitat Suitability and Adaptation Strategies of an Endangered Endemic Species, Camellia luteoflora Li ex Chang (Ericales: Theaceae) under Future Climate Change
No full textCamellia luteoflora Li ex Chang is an endangered plant endemic to the East Asian flora with high ornamental value as well as phylogenetic and floristic research value. Predicting the impact of climate change on its distribution and suitable habitat is crucial until scientific conservation measures are implemented. Based on seven environmental variables and 17 occurrence records, this study optimized the MaxEnt model using the kuenm data package to obtain the optimal parameter combinations (RM = 1.3, FC = LPT) and predicted the potential distribution pattern of C. luteoflora in various future periods. The results revealed that the mean diurnal range, temperature annual range, and precipitation of the wettest month were the influential factors determining the distribution pattern of C. luteoflora, contributing 60.2%, 14.4%, and 12.3% of the variability in the data, respectively. Under the current conditions, the area of suitable habitats for C. luteoflora was only about 21.9 × 104 km2. Overall, the suitable area around the C. luteoflora distribution points will shrink in a circular pattern in response to future global warming, but some potentially suitable distribution areas will expand and migrate to higher latitudes and the Hengduan Mountains region, representing a survival strategy for coping with climate change. It is hypothesized that the future climate refugia will be the highly suitable area and the Hengduan Mountains region. Furthermore, a retrospective validation method was employed to assess the reliability of the predictions and estimate the model’s predictive performance in the future. This study proposes a survival strategy and adaptation measures for C. luteoflora in response to climate change, and the proposed measures can be generalized for application in conservation planning and restoration processes. We also recommend that future studies incorporate factors such as the anthropogenic disturbances and associated socio-economic activities related to C. luteoflora into the model and to further predict the distribution pattern for C. luteoflora in response to historical climatic changes, tracing the evolutionary history of its population
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