scholarly journals The effect of lithology on the relationship between denudation rate and chemical weathering pathways

2021 ◽  
Author(s):  
Aaron Bufe ◽  
Kristen L. Cook ◽  
Albert Galy ◽  
Hella Wittmann ◽  
Niels Hovius
Keyword(s):  
Chemical Weathering ◽  
Sulfide Oxidation ◽  
Metamorphic Rocks ◽  
Silicate Weathering ◽  
Low Grade ◽  
Carbonate Dissolution ◽  
High Grade ◽  
Denudation Rate ◽  
Denudation Rates ◽  
The Impact

Abstract. The denudation of rocks in mountain belts exposes a range of fresh minerals to the surface of the Earth that are chemically weathered by acidic and oxygenated fluids. The impact of the resulting coupling between denudation and weathering rates fundamentally depends on the types of minerals that are weathering. Whereas silicate weathering sequesters CO2, the combination of sulfide oxidation and carbonate dissolution emits CO2 to the atmosphere. Here, we combine the concentrations of dissolved major elements in stream waters with 10Be basin-wide denudation rates from 35 small catchments in eastern Tibet to elucidate the importance of lithology in modulating the relationships between denudation rate, chemical weathering pathways, and CO2 consumption or release. Our catchments span three orders of magnitude in denudation rate in low-grade flysch, high grade metapelites, and granitoid rocks. For each stream, we estimate the concentrations of solutes sourced from silicate weathering, carbonate dissolution, and sulfide oxidation using a mixing model. We find that for all lithologies, cation concentrations from silicate weathering are largely independent of denudation rate, but solute concentrations from carbonates and, where present, sulfides increase with increasing denudation rate. With increasing denudation rates, weathering may, therefore, shift from consuming to releasing CO2 in both (meta)sedimentary and granitoid lithologies. We find that catchments draining high grade metamorphic rocks have systematically higher concentrations of sulfate from sulfide weathering than catchments containing weakly metamorphosed sediments. Moreover, our data provide tentative evidence that sulfate concentrations in these catchments are potentially more sensitive to denudation rate. We propose that changes in the sulfur oxidation state during prograde metamorphism of pelites in the mid-crust could lead to sulfate reduction that is even more complete than in low-grade sediments and provides a larger sulfide source for oxidation upon re-exposure of the rocks. In this case, the elevated concentration of sulfate in catchments draining high-grade metapelites would suggest that exposure of an increasing fraction of metamorphic rocks during orogenesis could lead to a boost in the release of CO2 that is independent of denudation rate.

scholarly journals Intense Chemical Weathering at Glacial Meltwater-Dominated Hailuogou Basin in the Southeastern Tibetan Plateau

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1209 ◽  
Author(s):  
Xiangying Li ◽  
Yongjian Ding ◽  
Qiao Liu ◽  
Yong Zhang ◽  
Tianding Han ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
River Water ◽  
River Discharge ◽  
Chemical Weathering ◽  
Sulfide Oxidation ◽  
Solute Flux ◽  
The Tibetan Plateau ◽  
Denudation Rate ◽  
Weathering Processes ◽  
The Impact

Climate warming has caused rapid shrinkage of glaciers in the Tibetan Plateau (TP), but the impact of glacier retreat on the chemical denudation rate remains largely unknown at the temperate glacial basins. The chemical weathering processes were examined at a temperate glacial basin (HLG) in the southeastern TP based on comprehensive data from the supraglacial meltwater, proglacial river water, precipitation and groundwater over two glacier melt seasons in 2008 and 2013. The concentrations of major ions and suspended sediments in river water exhibit a pronounced seasonality and display a close relationship with river discharge, suggesting a strong hydrological control on the chemical and physical weathering processes. Runoff chemistry is dominated by carbonate weathering and sulfide oxidation. HCO3−, Ca2+, and/or SO42− are the dominant ions in meltwater, river water, precipitation and groundwater. For river water, HCO3− and Ca2+ primarily come from calcite weathering, and SO42− is mainly derived from pyrite oxidation. Both solute and sediment fluxes are positively related to river discharge (r = 0.69, p < 0.01 for sediments). The solute flux and yields are 18,095–19,435 t·year−1 and 225–241 t·km−2·year−1, and the sediment load and yields are 126,390 t·year−1 and 1570 t·km−2·year−1, respectively. The solute yields, cationic denudation rate (CDR; 2850–3108 Σ*meq+ m−2·year−1) and chemical weathering intensity (CWI; 616–711 Σ*meq+ m−3·year−1) at HLG are higher than those at most basins irrespective of the lithology, suggesting more intense weathering in the TP in comparison to other glacial basins worldwide.

scholarly journals Impact of Pathological Stratification on the Clinical Outcomes of Advanced Well-Differentiated/Dedifferentiated Liposarcoma Treated with Trabectedin

Cancers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1453
Author(s):  
Chiara Fabbroni ◽  
Giovanni Fucà ◽  
Francesca Ligorio ◽  
Elena Fumagalli ◽  
Marta Barisella ◽  
...  
Keyword(s):  
Clinical Outcomes ◽  
Proportional Hazards ◽  
Case Series ◽  
Progression Free Survival ◽  
Cox Proportional Hazards ◽  
Low Grade ◽  
High Grade ◽  
Retrospective Case ◽  
Well Differentiated ◽  
The Impact

Background. We previously showed that grading can prognosticate the outcome of retroperitoneal liposarcoma (LPS). In the present study, we aimed to explore the impact of pathological stratification using grading on the clinical outcomes of patients with advanced well-differentiated LPS (WDLPS) and dedifferentiated LPS (DDLPS) treated with trabectedin. Patients: We included patients with advanced WDLPS and DDLPS treated with trabectedin at the Fondazione IRCCS Istituto Nazionale dei Tumori between April 2003 and November 2019. Tumors were categorized in WDLPS, low-grade DDLPS, and high-grade DDLPS according to the 2020 WHO classification. Patients were divided in two cohorts: Low-grade (WDLPS/low-grade DDLPS) and high-grade (high-grade DDLPS). Results: A total of 49 patients were included: 17 (35%) in the low-grade cohort and 32 (65%) in the high-grade cohort. Response rate was 47% in the low-grade cohort versus 9.4% in the high-grade cohort (logistic regression p = 0.006). Median progression-free survival (PFS) was 13.7 months in the low-grade cohort and 3.2 months in the high-grade cohort. Grading was confirmed as an independent predictor of PFS in the Cox proportional-hazards regression multivariable model (adjusted hazard ratio low-grade vs. high-grade: 0.45, 95% confidence interval: 0.22–0.94; adjusted p = 0.035). Conclusions: In this retrospective case series, sensitivity to trabectedin was higher in WDLPS/low-grade DDLPS than in high-grade DDLPS. If confirmed in larger series, grading could represent an effective tool to personalize the treatment with trabectedin in patients with advanced LPS.

Zircon ages and the distribution of Archaean and Proterozoic rocks in the Rauer Islands

1993 ◽  
Vol 5 (2) ◽  
pp. 193-206 ◽  
Author(s):  
P. D. Kinny ◽  
L. P. Black ◽  
J. W. Sheraton
Keyword(s):  
Granulite Facies ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
High Grade ◽  
Ion Microprobe ◽  
Rock Interaction ◽  
Mafic Rocks ◽  
Grade Fluid ◽  
Vestfold Hills ◽  
Intrusive Suite

The application of zircon U-Pb geochronology using the SHRIMP ion microprobe to the Precambrian high-grade metamorphic rocks of the Rauer Islands on the Prydz Bay coast of East Antarctica, has resulted in major revisions to the interpreted geological history. Large tracts of granitic orthogneisses, previously considered to be mostly Proterozoic in age, are shown here to be Archaean, with crystallization ages of 3270 Ma and 2800 Ma. These rocks and associated granulite-facies mafic rocks and paragneisses account for up to 50% of exposures in the Rauer Islands. Unlike the 2500 Ma rocks in the nearby Vestfold Hills which were cratonized soon after formation, the Rauer Islands rocks were reworked at about 1000 Ma under granulite to amphibolite facies conditions, and mixed with newly generated felsic crust. Dating of components of this felsic intrusive suite indicates that this Proterozoic reworking was accomplished in about 30–40 million years. Low-grade retrogression at 500 Ma was accompanied by brittle shearing, pegmatite injection, partial resetting of U-Pb geochronometers and growth of new zircons. Minor underformed lamprophyre dykes intruded Hop and nearby islands later in the Phanerozoic. Thus, the geology of the Rauer Islands reflects reworking and juxtaposition of unrelated rocks in a Proterozoic orogenic belt, and illustrates the important influence of relatively low-grade fluid-rock interaction on zircon U-Pb systematics in high-grade terranes.

Endoscopic Surveillance Practice for Barrett's Oesophagus in Scotland and Early Experience in Implementing Local Guidelines

2003 ◽  
Vol 48 (2) ◽  
pp. 43-45 ◽  
Author(s):  
E F Shen ◽  
S Gladstone ◽  
G Milne ◽  
S Paterson-Brown ◽  
I D Penman
Keyword(s):  
Early Experience ◽  
High Grade Dysplasia ◽  
Low Grade ◽  
High Grade ◽  
Wide Variability ◽  
Low Grade Dysplasia ◽  
Surveillance Practice ◽  
Four Quadrant ◽  
The Impact

Management of columnar lined oesophagus (CLO; Barrett s oesophagus) is controversial. We prospectively audited surveillance practices in Scotland and prospectively assessed the impact of introducing local guidelines for Barrett s surveillance in Edinburgh. Most respondents were gastroenterologists. The majority take random, not four quadrant, biopsies from the CLO. In Edinburgh during 2000, 80 patients underwent surveillance. The guideline protocol was not followed in 30 (37.5%) patients. Follow up of patients without dysplasia generally conformed to the guidelines. Follow up of patients with low grade dysplasia was highly variable while management of those with high grade dysplasia followed the guidelines. Overall we found a wide variability in the management and surveillance of CLO. Early experience suggests that implementation of guidelines is helpful but there is still variation in practice.

scholarly journals <sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

2017 ◽  
Author(s):  
Maarten Lupker ◽  
Jérôme Lavé ◽  
Christian France-Lanord ◽  
Marcus Christl ◽  
Didier Bourlès ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Sediment Flux ◽  
Coarse Grained ◽  
The Tibetan Plateau ◽  
Data Set ◽  
Denudation Rate ◽  
Cosmogenic Nuclide ◽  
Denudation Rates ◽  
The Impact ◽  
Eastern Himalayan Syntaxis

Abstract. The Tsangpo-Brahmaputra River drains the eastern part of the Himalayan range, flowing from the Tibetan Plateau through the eastern Himalayan syntaxis and downstream to the Indo-Gangetic floodplain. As such it is a unique natural laboratory to study how denudation and sediment production processes are transferred to river detrital signals. In this study, we present a new 10Be data set to constrain denudation rates across the catchment and to quantify the impact of rapid erosion within the syntaxis region on cosmogenic nuclide budgets and signals. 10Be denudation rates span around two orders of magnitude across the catchments (ranging from 0.03 mm/yr to > 4 mm/yr) and sharply increase as the Tsangpo-Brahmaputra flows across the eastern Himalaya. The increase in denudation rates however occurs ~ 150 km downstream of the Namche Barwa-Gyala Peri massif (NBGPm), an area which has been previously characterized by extremely high erosion and exhumation rates. We suggest that this downstream lag is mainly due to the physical abrasion of coarse grained, low 10Be concentration, landslide material produced within the syntaxis that dilutes the upstream high concentration 10Be flux from the Tibetan Plateau only after abrasion has transferred sediment to the studied sand fraction. A simple abrasion model produces typical lag distances of 50 to 150 km compatible with our observations. Abrasion effects reduce the spatial resolution over which denudation can be constrained in the eastern Himalayan syntaxis. In addition, we also highlight that denudation rate estimates are dependent on the sediment connectivity, storage and quartz content of the upstream Tibetan Plateau part of the catchment which tends to lead to an overestimation of downstream denudations rates. Taking these effects into account we estimate a denudation rates of ca. 2 to 5 mm/yr for the entire syntaxis and ca. 4 to 28 mm/yr for the NBGPm, which is significantly higher than other to other large catchments. Overall, 10Be concentrations measured at the outlet of the Tsangpo-Brahmaputra in Bangladesh suggest a sediment flux between 780 and 1430 Mt/yr equivalent to a denudation rate between 0.7 and 1.2 mm/yr for the entire catchment.

Applying the Paris System for Reporting Urine Cytology Increases the Rate of Atypical Urothelial Cells in Benign Cases: A Need for Patient Management Recommendations

2016 ◽  
Vol 61 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Rosario Granados ◽  
Joanny A. Duarte ◽  
Teresa Corrales ◽  
Encarnación Camarmo ◽  
Paloma Bajo
Keyword(s):  
False Positive Rate ◽  
Urine Cytology ◽  
Urinary Cytology ◽  
Low Grade ◽  
High Grade ◽  
Abnormal Cytology ◽  
Positive Rate ◽  
High Grade Carcinoma ◽  
Management Recommendations ◽  
The Impact

The Paris System (TPS) for reporting urinary cytology attempts to unify the terminology in this field. Objectives: To analyze the impact of adopting TPS by measuring nomenclature agreement and cytohistological correlation. Materials and Methods: Voided urine liquid-based cytology samples corresponding to 149 biopsy-proven cases (76 high-grade carcinomas, 40 low-grade carcinomas, and 33 benign lesions), were reclassified by the same pathologist using TPS. Diagnostic agreement and sensitivity for both nomenclature systems was measured. Results: When using TPS, the rate of atypical samples increased 8 times (from 3 to 24.2%) in benign cases, 10 times (from 2.5 to 25%) in low-grade carcinomas, and 2.4 times (from 6.6 to 15.8%) in high-grade carcinomas. The false-positive rate (abnormal cytology in negative or low-grade carcinoma cases) increased from 11 to 34.2%. Sensitivity was higher (63 vs. 49%) with TPS at the expense of a lower specificity (73 vs. 91%). The agreement between both nomenclatures was moderate for negative and high-grade carcinoma cases (k = 0.42 and 0.56, respectively) and weak for low-grade tumors (k = 0.35). Conclusions: Adopting TPS for reporting urine cytology results in a considerable increase in atypical diagnoses, improving sensitivity but lowering specificity. Appropriate management recommendations for patients with an atypical cytological diagnosis are required.

Significance of “gneissic” rocks in the Liscomb Complex, Nova Scotia

2010 ◽  
Vol 47 (6) ◽  
pp. 927-940 ◽  
Author(s):  
J. V. Owen ◽  
R. Corney ◽  
J. Dostal ◽  
A. Vaughan
Keyword(s):  
Igneous Rocks ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
High Grade ◽  
Peraluminous Granite ◽  
Isotopic Signatures ◽  
Conventional View ◽  
Basement Rocks ◽  
Mineral Assemblages ◽  
Intrusive Rocks

The Liscomb Complex comprises Late Devonian intrusive rocks (principally peraluminous granite) and medium- to high-grade metamorphic rocks (“gneisses”) that collectively are hosted by low-grade (greenschist facies) metasediments of the Cambro-Ordovician Meguma Group. The conventional view that these “gneisses” contain high-grade mineral assemblages and represent basement rocks has recently been challenged, and indeed, some of the rocks previously mapped as gneisses, particularly metapelites, have isotopic compositions resembling the Meguma Group. Amphibole-bearing enclaves in the Liscomb plutons, however, are isotopically distinct and in this regard resemble xenoliths of basement gneisses in the Popes Harbour lamprophyre dyke, south of the Liscomb area. Metasedimentary enclaves with Meguma isotopic signatures can contain garnets with unzoned cores (implying high temperatures) that host high-grade minerals (prismatic sillimanite, spinel, and (or) corundum) and are enclosed by retrograde-zoned rims. These features are interpreted here as having formed during and following the attainment of peak temperatures related to Liscomb magmatism. The amphibole-bearing meta-igneous rocks described here contain cummingtonite or hornblendic amphibole and occur as enclaves in granodioritic to tonalitic plutons. They are mineralogically, texturally, and isotopically distinct from Meguma metasediments and at least some of the plutonic rocks that enclose them, so remain the most likely candidate for basement rocks in the Liscomb Complex.

Morbidity profile following aggressive resection of parietal lobe gliomas

2012 ◽  
Vol 116 (6) ◽  
pp. 1182-1186 ◽  
Author(s):  
Nader Sanai ◽  
Juan Martino ◽  
Mitchel S. Berger
Keyword(s):  
Classification System ◽  
Tumor Volume ◽  
Parietal Lobe ◽  
Tumor Resection ◽  
High Rate ◽  
Low Grade ◽  
High Grade ◽  
Language Pathways ◽  
The Impact ◽  
Glioma Classification

Object The impact of parietal lobe gliomas is typically studied in the context of parietal lobe syndromes. However, critical language pathways traverse the parietal lobe and are susceptible during tumor resection. The authors of this study reviewed their experience with parietal gliomas to characterize the impact of resection and the morbidity associated with language. Methods The study population included adults who had undergone resection of parietal gliomas of all grades. Tumor location was identified according to a proposed classification system for parietal region gliomas. Low- and high-grade tumors were volumetrically analyzed using FLAIR and T1-weighted contrast-enhanced MR imaging. Results One hundred nineteen patients with parietal gliomas were identified—34 with low-grade gliomas and 85 with high-grade gliomas. The median patient age was 45 years, and most patients (53) presented with seizures, whereas only 4 patients had an appreciable parietal lobe syndrome. The median preoperative tumor volume was 31.3 cm3, the median extent of resection was 96%, and the median postoperative tumor volume was 0.9 cm3. Surprisingly, the most common early postoperative neurological deficit was dysphasia (16 patients), not weakness (12 patients), sensory deficits (14 patients), or parietal lobe syndrome (10 patients). A proposed parietal glioma classification system, based on surgical anatomy, was predictive of language deficits. Conclusions This is the largest reported experience with parietal lobe gliomas. The findings suggested that parietal language pathways are compromised at a surprisingly high rate. The proposed parietal glioma classification system is predictive of postoperative morbidity associated with language and can assist with preoperative planning. Taken together, these data emphasize the value of identifying language pathways when operating within the parietal lobe.

scholarly journals The Impact of Blastocyst Grade on Singleton Birthweight in Fresh Transplanted Cycles

2021 ◽  
Author(s):  
Qiongyao Shi ◽  
Senlin Shi ◽  
Wenyan Song ◽  
Feifei Zhao ◽  
Haixia Jin ◽  
...  
Keyword(s):  
Birth Weight ◽  
Live Birth ◽  
Cell Mass ◽  
The Other ◽  
Low Grade ◽  
High Grade ◽  
Significant Difference ◽  
Group A ◽  
Grade 3 ◽  
The Impact

Abstract Background: A retrospectively cohort study was performed to compare the birth weight of different blastocyst grades in fresh transplantation cycle and explore the related factors affecting the birth weight. Methods: The 1301 fresh cycles of single blastocyst transplantation and single live birth profile were analyzed,four groups were divided according to the grade of transplanted blastocyst. There are 170 cycles in group A with AA blastocyst grade, 312 cycles in group B with AB/BA blastocyst grade, 559 cycles in group C with BB/CA/AC blastocyst grade and 260 cycles in group D with BC/CB blastocyst grade. Comparison were made among four groups of birth weight, general conditions, fertilization rate, embryo rate, cleavage rate and D5,D6 blastocyst formation rate and other laboratory indicators. And then comparison were performed among the birth weight of different groups which were divided by the degree of blastocyst expansion, and the classification of inner cell mass(ICM) and the trophectoderm(TE). Results: The study shows that the birth weight of group A is significantly higher than that of the other three groups (P < 0.05). And the high quality embryo rate and blastocyst rate of group A are significantly higher than those of the other three groups (P < 0.05). What’s more, the clinical pregnancy rate, implantation rate and live birth rate of high grade blastocyst are higher, but there are no significant difference in abortion rate. The birth weight of the degree of blastocyst expansion in grade 3 and below is significantly lower than that of those with grade 3 and above (P < 0.05). The birth weight of grade A of ICM is significantly higher than that of grade B (P < 0.05). The birth weight of grade B of TE is significantly heavier than that of grade C (P < 0.05). Conclusions: Our results indicate that high grade blastocyst transplantation can achieve better pregnancy outcome. Different blastocyst grades affect birth weight, and low grade blastocyst transplantation is associated with a single birth weight loss.

Weathering profiles, mass-balance analysis, and rates of solute loss: Linkages between weathering and erosion in a small, steep catchment

2002 ◽  
Vol 114 (9) ◽  
pp. 1143-1158 ◽  
Author(s):  
Suzanne Prestrud Anderson ◽  
William E. Dietrich ◽  
George H Brimhall
Keyword(s):  
Chemical Weathering ◽  
Dynamic Equilibrium ◽  
Solid Phase ◽  
Water Flux ◽  
Solute Flux ◽  
Denudation Rate ◽  
Rock Fragments ◽  
Denudation Rates ◽  
Uplift Rates ◽  
Balance Analysis

Abstract In a headwater catchment in the Oregon Coast Range, we find that solid-phase mass losses due to chemical weathering are equivalent in the bedrock and the soil. However, the long-term rate of mass loss per unit volume of parent rock is greater in the soil than in the rock. We attribute this finding to the effects of biotic processes in the soil and to hydrologic conditions that maximize contact time and water flux through the mineral matrix in the soil. This result stems both from earlier work in which we demonstrated that rock and soil contribute equally to the solute flux and from arguments presented here that the basin is in dynamic equilibrium with respect to erosion and uplift. The silica flux of 10.7 ± 7.1 t·km−2·yr−1 from the basin is several times larger than the flux from older soils elsewhere, but comparable to the flux from sites with similar physical erosion rates. This result argues that physical denudation or uplift rates play an important role in setting the chemical denudation rate. Physical processes appear to influence chemical-weathering rates in several ways. First, they limit chemical evolution by removing material, thus setting the residence time within the weathered rock and the soil. Second, bioturbation mixes rock fragments into the more reactive soil and maintains high soil porosity, allowing free circulation of water. Because the weathering in the soil is more intense than in the rock, we argue that the chemical denudation rate will diminish where uplift rates—and, hence, physical-denudation rates—are great enough to lead to a bedrock-dominated landscape. Chemical denudation rates will increase with physical-denudation rates, but only as long as the landscape remains mantled by soil.

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