scholarly journals Mercury Methylation Upon Coastal Sediment Resuspension: A Worst-case Approach Under Dark Conditions

2021 ◽  
Author(s):  
Christiane Monte ◽  
Ana Paula Rodrigues ◽  
Petrus Galvão ◽  
Gabriela Pontes ◽  
Olaf Malm ◽  
...  
Keyword(s):  
Temporal Variability ◽  
Total Mercury ◽  
Sediment Resuspension ◽  
River Estuary ◽  
Guanabara Bay ◽  
Experimental Conditions ◽  
Worst Case ◽  
Fine Grained ◽  
Concentration Changes ◽  
Worst Case Approach

Abstract Mercury behavior upon resuspension of sediments from two impacted areas of Guanabara Bay was evaluated to assess worst-case methylmercury (MeHg) responses, under dark experimental conditions. Total mercury (THg) and MeHg concentrations were determined along 24 hours experiments of sediment resuspension in the bay water. Fine-grained Meriti River estuary (MR) sediments had 8-times higher MeHg initial concentrations than sandy Rio the Janeiro Harbor (RJH) sediments (3.4 ± 0.29 vs. 0.41 ± 0.1 ng g− 1, respectively).THg contents were uncorrelated with resuspension time, while correlations of resuspension time with MeHg (r2 = 0.66) and %MeHg in relation to THg (r2 = 0.75) were observed only for RJH sediments. These findings correspond to a 2.8-times MeHg concentration increase (ΔMeHg = 0.75 ng g− 1) and 4.4-times increase in %MeHg (Δ%MeHg = 1.0%) for station RJH.This suggests that assessments of MeHg spatial-temporal variability can be limited if concentration changes due to sediment resuspension are not considered.

Statistical Safe Braking Analysis

2011 ◽  
Author(s):  
David F. Thurston
Keyword(s):  
Control Systems ◽  
System Capacity ◽  
Worst Case ◽  
Stopping Distance ◽  
Train Control ◽  
Classic Theory ◽  
Braking Distance ◽  
Prime Determinant ◽  
Worst Case Approach

The main objective in optimizing train control is to eliminate the waist associated with classical design where train separation is determined through the use of “worst case” assumptions that are invariant to the system. In fact, the worst case approach has been in place since the beginning of train control systems. Worst case takes the most conservative approach to the determination of train stopping distance, which is the basis for design of virtually all train control. This leads to stopping distances that could be far more that actually required under the circumstances at the time the train is attempting to brake. Modern train control systems are designed to separate trains in order to provide safety of operation while increasing throughput. Calculations for the minimum distance that separates trains have traditionally been based on the sum of a series of worst case scenarios. The implication was that no train could ever exceed this distance in stopping. This distance is called Safe Braking Distance (SBD). SBD has always been calculated by static parameters that were assumed to be invariant. This is, however, not the case. Parameters such as adhesion, acceleration, weight, and reaction vary over time, location or velocity. Since the worst case is always used in the calculation, inefficiencies result in this methodology which causes degradation in capacity and throughput. This is also true when mixed traffic with different stopping characteristics are present at the same time. The classic theory in train control utilizes a SBD model to describe the characteristics of a stopping train. Since knowledge of these conditions is not known, poor conditions are assumed. A new concept in train control utilizes statistical analysis and estimation to provide knowledge of the conditions. Trains operating along the line utilize these techniques to understand inputs into their SBD calculation. This provides for a SBD calculation on board the train that is the shortest possible that maintains the required level of safety. The new SBD is a prime determinant in systems capacity. Therefore by optimizing SBD as describes, system capacity is also optimized. The system continuously adjusts to changing conditions.

scholarly journals A role for adenosine in metabolic depression in the marine invertebrate Sipunculus nudus

1997 ◽  
Vol 272 (1) ◽  
pp. R350-R356 ◽  
Author(s):  
A. Reipschlager ◽  
G. E. Nilsson ◽  
H. O. Portner
Keyword(s):  
Body Wall ◽  
Marine Invertebrate ◽  
Coelomic Fluid ◽  
Metabolic Depression ◽  
O2 Consumption ◽  
Experimental Conditions ◽  
Indwelling Catheter ◽  
Sipunculus Nudus ◽  
Body Wall Musculature ◽  
Concentration Changes

Involvement of neurotransmitters in metabolic depression under hypoxia and hypercapnia was examined in Sipunculus nudus. Concentration changes of several putative neurotransmitters in nervous tissue during anoxic or hypercapnic exposure or during combined anoxia and hypercapnia were determined. Among amino acids (gamma-aminobutyric acid, glutamate, glycine, taurine, serine, and aspartate) and monoamines (serotonin, dopamine, and norepinephrine), some changes were significant, but none were consistent with metabolic depression under all experimental conditions applied. Only the neuromodulator adenosine displayed concentration changes in accordance with metabolic depression under all experimental conditions. Levels increased during anoxia, during hypercapnia, and to an even greater extent during anoxic hypercapnia. Adenosine infusions into coelomic fluid via an indwelling catheter induced a significant depression of the normocapnic rate of O2 consumption from 0.36 +/- 0.04 to a minimum of 0.24 +/- 0.02 (SE) mumol.g-1.h-1 after 90 min (n = 6). Application of the adenosine antagonist theophylline caused a transient rise in O2 consumption 30 min after infusion during hypercapnia but not during normocapnia. Effects of adenosine and theophylline were observed in intact individuals but not in isolated body wall musculature. The results provide evidence for a role of adenosine in inducing metabolic depression in S. nudus, probably through the established effects of decreasing neuronal excitability and neurotransmitter release. In consideration of our previous finding that metabolic depression in isolated body wall musculature was elicited by extracellular acidosis, it is concluded that central and cellular mechanisms combine to contribute to the overall reduction in metabolic rate in S. nudus.

Home-Canned Smoked Fish: A New Processing Recommendation

1993 ◽  
Vol 56 (7) ◽  
pp. 619-621 ◽  
Author(s):  
CAROLYN A. RAAB ◽  
KENNETH S. HILDERBRAND
Keyword(s):  
Chum Salmon ◽  
Moisture Loss ◽  
Process Time ◽  
Case Scenario ◽  
Experimental Conditions ◽  
Worst Case ◽  
Smoked Fish ◽  
Heat Penetration ◽  
Penetration Data ◽  
New Processing

Smoked fish often varies in moisture content. To kill Clostridium-botulinum spores, recommendations for home canning in glass jars must take this and the fill of the jar into account. Pale chum salmon were smoked to three levels of moisture loss (10, 20, 30%) and canned using household techniques. Heat penetration data from thermocouples showed that the slowest heating jars were more likely to be drier smoked fish that was packed tightly. To take this “worst-case scenario” into account, a process time of 110 min was established as the new recommendation for home canning smoked fish in pint jars at sea level under the experimental conditions which are outlined.

scholarly journals Dredging Activities Carried Out in a Brazilian Estuary Affect Mercury Levels in Swimming Crabs

2020 ◽  
Vol 17 (12) ◽  
pp. 4396
Author(s):  
Paloma de Almeida Rodrigues ◽  
Rafaela Gomes Ferrari ◽  
Rachel Ann Hauser-Davis ◽  
Luciano Neves dos Santos ◽  
Carlos Adam Conte-Junior
Keyword(s):  
Total Mercury ◽  
Abiotic Factors ◽  
Human Consumption ◽  
Consumer Health ◽  
Swimming Crab ◽  
Health Issues ◽  
Guanabara Bay ◽  
Direct Mercury Analyzer ◽  
Mercury Analyzer

(1) Although suffers from intense pollution inputs, Guanabara Bay, the most socioeconomically and environmentally important estuary in Rio de Janeiro, Brazil, is still home to a diverse fauna, including several fish and crab species consumed by humans. The bay presents high sedimentation rates and sediment contamination, further aggravated by dredging processes carried out in recent years. In this context, this study aimed to verify the effect of the dredging process on total mercury (THg) concentrations at Guanabara Bay through swimming crab assessments sampled before (2016), during (2017), and after (2018) the dredging process, and mainly, if the detected concentrations can be harmful to consumer health; (2) Methods: Swimming crab samplings were carried out at the same time and sampling points in 2016, 2017 and 2018 and the total Hg was determined using a Direct Mercury Analyzer (DMA-80, Milestone, Bergamo, Italy); (3) Results: Increased Hg concentrations were observed during the dredging process, decreasing to lower values, close to the initial concentrations, at the end of the process. Some of the investigated abiotic factors favor Hg dynamics in the aquatic environment, while others were positively altered at some of the assessed sampling areas at the end of the dredging process; (4) Conclusions: Although crab Hg levels were below maximum permissible limits for human consumption, it is important to note that these animals are significantly consumed around Guanabara Bay, which may lead to public health issues in the long term.

scholarly journals Worst-case energy consumption minimization based on interference analysis and bank mapping in multicore systems

2017 ◽  
Vol 13 (2) ◽  
pp. 155014771668696
Author(s):  
Zhihua Gan ◽  
Zhimin Gu ◽  
Hai Tan ◽  
Mingquan Zhang ◽  
Jizan Zhang
Keyword(s):  
Energy Consumption ◽  
Real Time ◽  
Multicore Systems ◽  
Worst Case ◽  
Mapping Algorithm ◽  
Fine Grained ◽  
Energy Consumption Reduction ◽  
Deadline Constraints ◽  
Core Mapping ◽  
The Impact

Energy is a scarce resource in real-time embedded systems due to the fact that most of them run on batteries. Hence, the designers should ensure that the energy constraints are satisfied in addition to the deadline constraints. This necessitates the consideration of the impact of the interference due to shared, low-level hardware resources such as the cache on the worst-case energy consumption of the tasks. Toward this aim, this article proposes a fine-grained approach to analyze the bank-level interference (bank conflict and bus access interference) on real-time multicore systems, which can reasonably estimate runtime interferences in shared cache and yield tighter worst-case energy consumption. In addition, we develop a bank-to-core mapping algorithm for reducing bank-level interference and improving the worst-case energy consumption. The experimental results demonstrate that our approach can improve the tightness of worst-case energy consumption by 14.25% on average compared to upper-bound delay approach. The bank-to-core mapping provides significant benefits in worst-case energy consumption reduction with 7.23%.

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