Repeated Measurements of In Situ Soil Stiffness with Permanently Embedded Geophones

Simultaneous measurements of photocurrent and outer segment Ca2+ were made from isolated salamander cone photoreceptors. While recording the photocurrent from the inner segment, which was drawn into a suction pipette, a laser spot confocal technique was employed to evoke fluorescence from the outer segment of a cone loaded with the Ca2+ indicator fluo-3. When a dark-adapted cone was exposed to the intense illumination of the laser, the circulating current was completely suppressed and fluo-3 fluorescence rapidly declined. In the more numerous red-sensitive cones this light-induced decay in fluo-3 fluorescence was best fitted as the sum of two decaying exponentials with time constants of 43 ± 2.4 and 640 ± 55 ms (mean ± SEM, n = 25) and unequal amplitudes: the faster component was 1.7-fold larger than the slower. In blue-sensitive cones, the decay in fluorescence was slower, with time constants of 140 ± 30 and 1,400 ± 300 ms, and nearly equal amplitudes. Calibration of fluo-3 fluorescence in situ from red-sensitive cones allowed the calculation of the free-Ca2+ concentration, yielding values of 410 ± 37 nM in the dark-adapted outer segment and 5.5 ± 2.4 nM after saturating illumination (mean ± SEM, n = 8). Photopigment bleaching by the laser resulted in a considerable reduction in light sensitivity and a maintained decrease in outer segment Ca2+ concentration. When the photopigment was regenerated by applying exogenous 11-cis-retinal, both the light sensitivity and fluo-3 fluorescence recovered rapidly to near dark-adapted levels. Regeneration of the photopigment allowed repeated measurements of fluo-3 fluorescence to be made from a single red-sensitive cone during adaptation to steady light over a range of intensities. These measurements demonstrated that the outer segment Ca2+ concentration declines in a graded manner during adaptation to background light, varying linearly with the magnitude of the circulating current.

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Effects of Seagrass Wasting Disease on Eelgrass Growth and Belowground Sugar in Natural Meadows

Frontiers in Marine Science ◽

10.3389/fmars.2021.768668 ◽

2021 ◽

Vol 8 ◽

Author(s):

Olivia J. Graham ◽

Lillian R. Aoki ◽

Tiffany Stephens ◽

Joshua Stokes ◽

Sukanya Dayal ◽

...

Keyword(s):

Disease Severity ◽

Negative Impact ◽

Sugar Content ◽

Severe Disease ◽

Disease Outbreaks ◽

Repeated Measurements ◽

Carbon Accumulation ◽

Wasting Disease ◽

Seagrass Meadows

Seagrass meadows provide valuable ecosystem benefits but are at risk from disease. Eelgrass (Zostera marina) is a temperate species threatened by seagrass wasting disease (SWD), caused by the protist Labyrinthula zosterae. The pathogen is sensitive to warming ocean temperatures, prompting a need for greater understanding of the impacts on host health under climate change. Previous work demonstrates pathogen cultures grow faster under warmer laboratory conditions and documents positive correlations between warmer ocean temperatures and disease levels in nature. However, the consequences of disease outbreaks on eelgrass growth remain poorly understood. Here, we examined the effect of disease on eelgrass productivity in the field. We coupled in situ shoot marking with high-resolution imagery of eelgrass blades and used an artificial intelligence application to determine disease prevalence and severity from digital images. Comparisons of eelgrass growth and disease metrics showed that SWD impaired eelgrass growth and accumulation of non-structural carbon in the field. Blades with more severe disease had reduced growth rates, indicating that disease severity can limit plant growth. Disease severity and rhizome sugar content were also inversely related, suggesting that disease reduced belowground carbon accumulation. Finally, repeated measurements of diseased blades indicated that lesions can grow faster than healthy tissue in situ. This is the first study to demonstrate the negative impact of wasting disease on eelgrass health in a natural meadow. These results emphasize the importance of considering disease alongside other stressors to better predict the health and functioning of seagrass meadows in the Anthropocene.

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In-situ basal melt rate distribution of the floating tongue of 79°N Glacier, Greenland

10.5194/egusphere-egu2020-14759 ◽

2020 ◽

Author(s):

Ole Zeising ◽

Daniel Steinhage ◽

Niklas Neckel ◽

Julia Christmann ◽

Veit Helm ◽

...

Keyword(s):

Greenland Ice Sheet ◽

Repeated Measurements ◽

Ultra Wideband ◽

North East ◽

The North ◽

Dense Grid ◽

Phase Sensitive ◽

Hinge Zone ◽

Wideband Radar

<p>The 79&#176;N Glacier (79NG) in northeast Greenland, one of the last glaciers in Greenland with a floating ice tongue, plays a crucial role for buttressing the North-East Greenland Ice Stream (NEGIS). Remote-sensing studies indicate high basal melt rates (> 50 m/a) near the grounding line but these methods are limited by the hinge zone, where the floating ice is not in hydrostatic equilibrium. As part of the Greenland Ice Sheet Ocean Interaction (GROCE) project, we have performed a dense grid of repeated measurements with a phase-sensitive radio echo sounder (pRES) accompanied with autonomous pRES (ApRES) stations to estimate basal melt rates focusing on the hinge zone of 79NG. For analysing the pRES measurements, we additionally used ice thickness information derived from AWI&#8217;s ultra-wideband radar (UWB) revealing steep channels at the base. The estimated basal melt rates downstream the hinge zone are approximately the same as satellite-derived melt rates. In the hinge zone we found by far larger basal melt rates exceeding 100 m/a next to basal channels.</p>

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Determination of p-y curves for offshore piles based on in-situ soil investigations

MATEC Web of Conferences ◽

10.1051/matecconf/201821905003 ◽

2018 ◽

Vol 219 ◽

pp. 05003

Author(s):

Kamila Międlarz ◽

Lech Bałachowski

Keyword(s):

Field Tests ◽

Soil Parameters ◽

Lateral Loads ◽

Cohesionless Soils ◽

In Situ Tests ◽

Soil Stiffness ◽

Soil Response ◽

Direct Design ◽

Offshore Piles

Offshore piles are subjected to complex loads with considerable lateral component. The pile-soil response to lateral loads can be described with the p-y method. For a given depth the load–deflection relationship is built to simulate the surrounding soil stiffness. This state-of-art paper presents a brief discussion of determination methods for the p-y curves using a standard approach based on the soil parameters derived from laboratory and in-situ tests or directly from field tests. The basic relationships for both cohesive and cohesionless soils are discussed. The advantage of direct design methods to describe the p-y curve relies in the reduction of necessary laboratory tests.

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Temperature Gradient Daily Dynamics Area and Time Zoning for Local Analysis of Air-Water Interaction

10.21203/rs.3.rs-155562/v1 ◽

2021 ◽

Author(s):

Christophil S. Medellu ◽

Alfrits Komansilan

Keyword(s):

Temperature Gradient ◽

Fresh Water ◽

Coastal Waters ◽

Water Surface ◽

Repeated Measurements ◽

Local Analysis ◽

Thermal Interaction ◽

Water Interaction ◽

Water Measurement

Abstract This article describes the results of the application of time zoning for air-water thermal interaction, and the temperature gradient daily dynamics area (TGDDA) parameters at six locations with different ecological conditions. The research locations consisted of two locations in lakes, two locations in coastal waters which were affected by fresh water and two locations in coastal waters which were not affected by fresh water. Measurement of air and water temperature was carried out in situ at several vertical positions with logarithmic distances to the water surface. The results of the analysis show that the analysis and modeling of the TGDDA parameters produce the time zoning of thermal interaction and TGDDA that vary between research locations. Repeated measurements on two consecutive days at the same location, resulted in almost the same TGDDA and time zoning duration of air-water thermal interaction. These results suggest that these parameters can be used to characterize air-water interactions. The results of this study serve as references to the chemical analysis of water and biota which is interactive or influenced by the dynamics of air-water thermal interactions.

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Mixed nonlinear models in ruminal in situ degradability trials

Ciência Animal Brasileira ◽

10.1590/1809-6891v21e-57596 ◽

2020 ◽

Vol 21 ◽

Author(s):

Simone Daniela Sartorio de Medeiros ◽

César Gonçalves de Lima ◽

Taciana Villela Savian ◽

Euclides Braga Malheiros ◽

Simone Silmara Werner

Keyword(s):

Degradation Kinetics ◽

Nonlinear Models ◽

Repeated Measurements ◽

Experimental Unit ◽

Model Parameters ◽

Estimation Of Parameters ◽

Nutritional Qualities ◽

Ruminal Degradation ◽

Two Phases

Abstract Classical methods of analysis of nonlinear models are widely used in studies of ruminal degradation kinetics. As this type of study involves repeated measurements in the same experimental unit, the use of mixed nonlinear models (MNLM) is proposed, in order to solve problems of heterogeneity of variances of the responses, correlation among repeated measurements and consequent lack of sphericity in the covariance matrix. The aims of this work are to present an evaluation of the applicability of MNLM in the estimation of parameters to describe the in situ ruminal degradation kinetics of the dry matter of Tifton 85 hay and to compare the results with those obtained from the usual analysis in two-phases. The steers used in the trial were fed diets composed of three different combinations of roughage and concentrate and two hays with different nutritional qualities. The proposed approach was proven as effective as the traditional one for estimating model parameters. However, it adequately models the correlation among the longitudinal data, which can affect the estimates obtained, the standard error associated with them and potentially change the results of the inferences. It is quite attractive when the research seeks to understand the behavior of the process of food degradation throughout the incubation times.

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