Cosmogenic nuclide and solute flux data from central Cuba emphasize the importance of both physical and chemical denudation in highly weathered landscapes

Abstract. We consider measurements of both in situ produced cosmogenic nuclides and dissolved load flux to characterize the processes and pace of landscape change in central Cuba. The tropical landscape of Cuba is losing mass in multiple ways, making it difficult to quantify total denudation rates and thus to assess the impact of agricultural practices on rates of contemporary landscape change. Long-term sediment generation rates inferred from 26Al and 10Be concentrations in quartz extracted from central Cuban river sand range from 3.7–182 tons km−2 yr−1 (mean = 62, median = 57). Rock dissolution rates (24–154 tons km−2 yr−1; mean = 84, median = 78) inferred from stream solute loads exceed measured cosmogenic nuclide-derived sediment generation rates in 15 of 22 basins, indicating significant landscape-scale mass loss not reflected in the cosmogenic nuclide measurements. 26Al / 10Be ratios lower than that of surface production are consistent with the presence of a deep, mixed, regolith layer in the five basins that have the greatest disagreement between rock dissolution rates (high) and sediment generation rates inferred from cosmogenic nuclide concentrations (low). Our data show that accounting for the contribution of mineral dissolution at depth in calculations of total denudation is particularly important in the humid tropics, where dissolved load fluxes are high, and where mineral dissolution can occur many meters below the surface, beyond the penetration depth of most cosmic rays and thus the production of most cosmogenic nuclides. Relying on cosmogenic nuclide data or stream solute fluxes alone would both lead to underestimates of total landscape denudation in the central Cuba, emphasizing the importance of combining these approaches to fully capture mass loss in tropical landscapes.

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Introduction to geomicrobiology

10.1093/oso/9780198789406.003.0013 ◽

2018 ◽

Author(s):

David L. Kirchman

Keyword(s):

Fossil Fuels ◽

Solid Phase ◽

Direct Reduction ◽

Iron Oxidation ◽

Mineral Dissolution ◽

Precipitation Process ◽

Soluble Ions ◽

Chemolithoautotrophic Bacteria ◽

The Impact

Geomicrobiology, the marriage of geology and microbiology, is about the impact of microbes on Earth materials in terrestrial systems and sediments. Many geomicrobiological processes occur over long timescales. Even the slow growth and low activity of microbes, however, have big effects when added up over millennia. After reviewing the basics of bacteria–surface interactions, the chapter moves on to discussing biomineralization, which is the microbially mediated formation of solid minerals from soluble ions. The role of microbes can vary from merely providing passive surfaces for mineral formation, to active control of the entire precipitation process. The formation of carbonate-containing minerals by coccolithophorids and other marine organisms is especially important because of the role of these minerals in the carbon cycle. Iron minerals can be formed by chemolithoautotrophic bacteria, which gain a small amount of energy from iron oxidation. Similarly, manganese-rich minerals are formed during manganese oxidation, although how this reaction benefits microbes is unclear. These minerals and others give geologists and geomicrobiologists clues about early life on Earth. In addition to forming minerals, microbes help to dissolve them, a process called weathering. Microbes contribute to weathering and mineral dissolution through several mechanisms: production of protons (acidity) or hydroxides that dissolve minerals; production of ligands that chelate metals in minerals thereby breaking up the solid phase; and direct reduction of mineral-bound metals to more soluble forms. The chapter ends with some comments about the role of microbes in degrading oil and other fossil fuels.

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Claudin Tight Junction Proteins: Novel Aspects in Paracellular Transport

Peritoneal Dialysis International ◽

10.1177/089686080802800605 ◽

2008 ◽

Vol 28 (6) ◽

pp. 577-584 ◽

Cited By ~ 32

Author(s):

Constanze Will ◽

Michael Fromm ◽

Dominik Müller

Keyword(s):

Tight Junction ◽

Solute Transport ◽

Molecular Mechanisms ◽

Family Members ◽

Transport Processes ◽

Paracellular Transport ◽

Solute Flux ◽

Solute Fluxes ◽

Essential Components ◽

Renal Tubular

Claudins are essential components of the intercellular tight junction and major determinants of paracellular solute fluxes across epithelia and endothelia. Many members of this family display a distinct charge or size specificity, whereas others render the epithelium impermeable to transport. Due to intercellular localization, claudin-mediated transport processes are passive and driven by an electrochemical gradient. In epithelial tissues, claudins exhibit a temporal–spatial expression pattern corresponding with regional and local solute transport profiles. Whereas paracellular transport mechanisms in organs such as intestine and kidney have been extensively investigated, little is known about the molecular mechanisms determining solute transport in the peritoneum, and thus the determinants of peritoneal dialysis. Given the ubiquitous expression of claudins in endothelia and epithelia, it is predictable that claudins also contribute to pore formation and determination in the peritoneum, and that they are involved in solute flux. Therefore, we review the basic characteristics of claudin family members and their function as exemplified in renal tubular transport and give an outlook to what extent claudin family members might be of importance for solute reabsorption across the peritoneal membrane.

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Windblown Sand-Induced Degradation of Glass Panels in Curtain Walls

Materials ◽

10.3390/ma14030607 ◽

2021 ◽

Vol 14 (3) ◽

pp. 607

Author(s):

Yuxi Zhao ◽

Rongcheng Liu ◽

Fan Yan ◽

Dawei Zhang ◽

Junjin Liu

Keyword(s):

Visible Light ◽

Mass Loss ◽

Effective Area ◽

Area Ratio ◽

Light Transmittance ◽

Relative Mass ◽

Impact Time ◽

Windblown Sand ◽

Glass Panels ◽

The Impact

The windblown sand-induced degradation of glass panels influences the serviceability and safety of these panels. In this study, the degradation of glass panels subject to windblown sand with different impact velocities and impact angles was studied based on a sandblasting test simulating a sandstorm. After the glass panels were degraded by windblown sand, the surface morphology of the damaged glass panels was observed using scanning electron microscopy, and three damage modes were found: a cutting mode, smash mode, and plastic deformation mode. The mass loss, visible light transmittance, and effective area ratio values of the glass samples were then measured to evaluate the effects of the windblown sand on the panels. The results indicate that, at high abrasive feed rates, the relative mass loss of the glass samples decreases initially and then remains steady with increases in impact time, whereas it increases first and then decreases with an increase in impact angle such as that for ductile materials. Both visible light transmittance and effective area ratio decrease with increases in the impact time and velocities. There exists a positive linear relationship between the visible light transmittance and effective area ratio.

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Effect of Storage Conditions on Storability and Antioxidant Potential of Pears cv. ‘Conference’

Agriculture ◽

10.3390/agriculture11060545 ◽

2021 ◽

Vol 11 (6) ◽

pp. 545

Author(s):

Grzegorz P. Łysiak ◽

Krzysztof Rutkowski ◽

Dorota Walkowiak-Tomczak

Keyword(s):

Mass Loss ◽

Strong Influence ◽

Storage Conditions ◽

Quality Parameters ◽

Soluble Solids ◽

Controlled Atmosphere ◽

Postharvest Diseases ◽

Market Prices ◽

Long Period ◽

The Impact

Late pear cultivars, such as ‘Conference’, can be stored for a long period if kept in good storage conditions. A three-year study (2011–2013) compared the impact of six-month storage using four technologies—normal atmosphere, normal atmosphere + 1-methylcyclopropene (1-MCP), controlled atmosphere, and controlled atmosphere + 1-MCP—on the quality parameters of ‘Conference’ pears, such as mass loss, firmness, total soluble solids, acidity, antioxidant capacity, and the incidence of diseases and disorders. Additionally, the study analysed different storage conditions in terms of profitability, based on the market prices for pears in the seasons during which the pears were stored. The storage conditions had a very strong influence on the fruit quality parameters, and were found to affect most visibly the mass loss and the incidence of postharvest diseases and disorders. The storage of ‘Conference’ pears for 180 days in normal atmosphere is not economically viable, even if the fruit is subjected to 1-MCP treatment; at the same time, it is profitable to store ‘Conference’ pears in controlled atmosphere for the same period, no matter whether 1-MCP was applied or not.

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The effect of heat treatment and impact angle on the erosion behavior of nickel-tungsten carbide cold spray coating using response surface methodology

Emergent Materials ◽

10.1007/s42247-021-00274-7 ◽

2021 ◽

Author(s):

Marios Kazasidis ◽

Elisa Verna ◽

Shuo Yin ◽

Rocco Lupoi

Keyword(s):

Heat Treatment ◽

Response Surface Methodology ◽

Mass Loss ◽

Tungsten Carbide ◽

Response Surface ◽

Spray Coating ◽

Impact Angle ◽

Control Factors ◽

Heat Treated ◽

The Impact

AbstractThis study elucidates the performance of cold-sprayed tungsten carbide-nickel coating against solid particle impingement erosion using alumina (corundum) particles. After the coating fabrication, part of the specimens followed two different annealing heat treatment cycles with peak temperatures of 600 °C and 800 °C. The coatings were examined in terms of microstructure in the as-sprayed (AS) and the two heat-treated conditions (HT1, HT2). Subsequently, the erosion tests were carried out using design of experiments with two control factors and two replicate measurements in each case. The effect of the heat treatment on the mass loss of the coatings was investigated at the three levels (AS, HT1, HT2), as well as the impact angle of the erodents (30°, 60°, 90°). Finally, the response surface methodology (RSM) was applied to analyze and optimize the results, building the mathematical models that relate the significant variables and their interactions to the output response (mass loss) for each coating condition. The obtained results demonstrated that erosion minimization was achieved when the coating was heat treated at 600 °C and the angle was 90°.

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Temporal and Spatial Heterogeneity of Mineral Dissolution Rates in Fractured Media

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2021.08.008 ◽

2021 ◽

Author(s):

Elizabeth Andrews ◽

Alexis Navarre-Sitchler

Keyword(s):

Spatial Heterogeneity ◽

Fractured Media ◽

Mineral Dissolution ◽

Dissolution Rates ◽

Temporal And Spatial ◽

Temporal And Spatial Heterogeneity

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ENHANCED MASS LOSS RATES IN RED SUPERGIANTS AND THEIR IMPACT ON THE CIRCUMSTELLAR MEDIUM

Revista Mexicana de Astronomía y Astrofísica ◽

10.22201/ia.01851101p.2019.55.02.04 ◽

2019 ◽

Vol 55 (2) ◽

pp. 161-175

Author(s):

L. Hernández-Cervantes ◽

B. Pérez-Rendón ◽

A. Santillán ◽

G. García-Segura ◽

C. Rodríguez-Ibarra

Keyword(s):

Mass Loss ◽

Stellar Evolution ◽

Gas Dynamics ◽

Numerical Experiments ◽

Evolutionary Models ◽

Solar Composition ◽

Red Supergiants ◽

The Impact ◽

Circumstellar Medium ◽

Loss Rates

In this work, we present models of massive stars between 15 and 23 M⊙ , with enhanced mass loss rates during the red supergiant phase. Our aim is to explore the impact of extreme red supergiant mass-loss on stellar evolution and on their circumstellar medium. We computed a set of numerical experiments, on the evolution of single stars with initial masses of 15, 18, 20 and, 23 M⊙ , and solar composition (Z = 0.014), using the numerical stellar code BEC. From these evolutionary models, we obtained time-dependent stellar wind parameters, that were used explicitly as inner boundary conditions in the hydrodynamical code ZEUS-3D, which simulates the gas dynamics in the circumstellar medium (CSM), thus coupling the stellar evolution to the dynamics of the CSM. We found that stars with extreme mass loss in the RSG phase behave as a larger mass stars.

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Significant submarine ice loss from the Getz Ice Shelf, Antarctica

10.5194/tc-2018-163 ◽

2018 ◽

Author(s):

David M. Rippin

Keyword(s):

Mass Loss ◽

West Antarctica ◽

Ice Shelf ◽

Ice Streams ◽

Ice Shelves ◽

Warming Climate ◽

Circulation Patterns ◽

Direct Measurements ◽

Radio Echo Sounding ◽

The Impact

Abstract. We present the first direct measurements of changes taking place at the base of the Getz Ice Shelf (GzIS) in West Antarctica. Our analysis is based on repeated airborne radio-echo sounding (RES) survey lines gathered in 2010 and 2014. We reveal that while there is significant variability in ice shelf behaviour, the vast majority of the ice shelf (where data is available) is undergoing basal thinning at a mean rate of nearly 13 m a−1, which is several times greater than recent modelling estimates. In regions of faster flowing ice close to where ice streams and outlet glaciers join the ice shelf, significantly greater rates of mass loss occurred. Since thinning is more pronounced close to faster-flowing ice, we propose that dynamic thinning processes may also contribute to mass loss here. Intricate sub-ice circulation patterns exist beneath the GzIS because of its complex sub-ice topography and the fact that it is fed by numerous ice streams and outlet glaciers. It is this complexity which we suggest is also responsible for the spatially variable patterns of ice-shelf change that we observe. The large changes observed here are also important when considering the likelihood and timing of any potential future collapse of the ice shelf, and the impact this would have on the flow rates of feeder ice streams and glaciers, that transmit ice from inland Antarctica to the coast. We propose that as the ice shelf continues to thin in response to warming ocean waters and climate, the response of the ice shelf will be spatially diverse. Given that these measurements represent changes that are significantly greater than modelling outputs, it is also clear that we still do not fully understand how ice shelves respond to warming ocean waters. As a result, ongoing direct measurements of ice shelf change are vital for understanding the future response of ice shelves under a warming climate.

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