572 research outputs found
The issue of outwelling in the Guadiana River estuary (Portugal): some findings and research suggestions in the context of recent evidence
Abstract The ‘‘Outwelling Theory’’ states that salt marshes play a major role in exporting production to adjacent estuarine and coastal ecosystems.
However, it has been found that some marshes act as net importers instead of net exporters of organic matter and nutrients. Once we include mangroves and refine the analysis to comprehend bacterioplankton,
organic and stable isotope tracers, the
picture became, more complex, making room for a revival of the outwelling idea. The exchanges between the Castro Marim salt marsh and the main estuary were tentatively established determining periodically, in a selected cross-section, the concentrations
of TSS, FSS, VSS, NH4, NO2, NO3, NKjeldhal, SiO4, PO4, TDP, Chlorophyll a and Pheopigments, measuring their fluxes along tidal cycles and computing the corresponding budgets.
Apparently, the sedimentary behaviour of the
marsh will be close to equilibrium during the period of study. However, it will import mainly inert matter and export mainly organic matter in the same period. Moreover, extrapolating these results to the entire Guadiana salt marshes, the exchanges
of sediment do not seem to be significant. Particularly, the marshes will not trap a significantly amount sediment transported by the main river (0.5%). It also seems to follow, that in a general way, the Guadiana salt marshes might have a more significant role than was anticipated in the system
economy ofOMand nutrients and their outwelling to coastal waters, assuring outputs that could amount to something like 6% of the river load of N, 1.2% of the river load of P, and 20-57% of the river load of TOC, for an average year, and 42% of the river load of Nand 35% of the river load of P in a dry year. These findings suggest that a more detailed investigation, over an extended period of time, is certainly worthwhile
Recommended from our members
Session D7: Is CFD an Efficient Tool ao Develop Pool Type Fishways?
Abstract:
Rivers longitudinal connectivity is compromised by man-made obstacles, such as dams and weirs, which affect fish movements, leading to populations decrease and genetic deterioration. Properly designed fishways re-establish connectivity, allowing for fish migration. The aim of our work is to contribute to a more fast and efficient development of pool-type fishways using hydrodynamic modelling, based on fish behaviour experiments. Modelling free surface flows in hydraulic structures with complex geometry, like pooltype fishways, with aerated and complex flow patterns, represents a significant research challenge. Knowledge already acquired in an experimental full scale indoor pool-type fishway in previous studies is used. A 1:2.5 scaled fishway of this facility was built and used to characterize velocity and turbulence in a pool-type fishway with cross-walls equipped with bottom orifices. An offset orifice configuration was used with consecutive orifices positioned on opposite sides of the cross-walls, creating a sinusoidal flow path. The measurements of velocity fields were made using Particle Image Velocimetry (PIV) and Acoustic Doppler Velocimetry (ADV). Velocity maps were obtained at several positions, for planes parallel to the bottom and parallel to the sidewalls. Parameters that influence fishways efficiency like velocity fields, turbulent kinetic energy and Reynolds shear stresses were determined. A 3D computational fluid dynamics (CFD) model of the fishway was developed using a commercial software FLOW-3D. Velocity fields, turbulent kinetic energy and Reynolds shear stresses were compared with the ones determined from PIV measurements and ADV measurements and results deviations between experimental and numerical data were analyzed. The use of FLOW 3D to simulate mean velocity patterns and flow turbulence in pooltype fishways and its use as design tool for new fishway geometries are discussed
Recommended from our members
Assessing multi slot versus single slot pool-type fishways suitability for potamodromous cyprinids: An experimental approach using numerical modelling and fish
Developing new fishway designs that provide suitable hydrodynamic conditions for multiple native freshwater fish species is paramount to mitigate the negative effects of anthropogenic barriers in rivers. This poses an increased challenge in Mediterranean regions, where water availability is limited and issue of conflicting demands. Vertical slot fishways (VSF) are considered one of the best types of technical fishways for potamodromous fish species. However, they generally require a greater amount of water to operate relatively to other type of facilities. The present study used 3D numerical modelling to compare the hydrodynamics and assess the hydraulic suitability for multiple fish species, of a widely used VSF and of two multi slot fishway (MSF) configurations. The MSF configuration requires a lower discharge to operate (\u3e 20% less discharge) than the VSF, while keeping similar flow depths. With the reduction in discharge, the velocity, turbulent kinetic energy and Reynolds shear stress values for MSF are also much lower than the values for VSF (c. 20 – 40% less). Hence, besides requiring smaller discharges than similar VSF design, the MSF seems to be less selective for fish species, particularly smaller-sized individuals, and individuals with weaker swimming capacities. Passage performance of the Iberian barbel, Luciobarbus bocagei (Steindachner, 1864) was subsequently assessed when negotiating a VSF and a MSF in an indoor full scale experimental model. Results showed that the Iberian barbel performed a significantly higher number of movements in the MSF when compared to the VSF. On the other hand, no differences were found in the entrance time, entry efficiency and overall fish performance between configurations. This study shows that numerical modelling complemented with laboratory fish experiments can be an important tool to develop cost-effective fishways
Development of Non-Linear Equations for Predicting Electrical Conductivity in Silicates
Electrical conductivity is of fundamental importance in electric arc furnaces
(EAF) and the interaction of this phenomenon with the process slag results in
energy losses and low optimization. As mathematical modeling helps in
understanding the behavior of phenomena and it was used to predict the
electrical conductivity of EAF slags through artificial neural networks. The
best artificial neural network had 100 neurons in the hidden layer, with 6
predictor variables and the predicted variable, electrical conductivity. Mean
absolute error and standard deviation of absolute error were calculated, and
sensitivity analysis was performed to correlate the effect of each predictor
variable with the predicted variable.Comment: 8 pages, 6 figures, 1 table (AISTech 2023 - Presented and Accepted
VARICELLA-RELATED HOSPITALIZATIONS IN CHILDREN – CASE SERIES IN A SECONDARY HOSPITAL
Introdução: A varicela é uma doença infeciosa frequente na infância. Embora considerada geralmente uma doença benigna e autolimitada, pode cursar com complicações graves. O objetivo deste trabalho foi caracterizar os internamentos por varicela e suas complicações.
Métodos: Análise retrospetiva dos processos clÃnicos das crianças com internamento no Serviço de Pediatria por varicela entre 01.01.2000 e 31.12.2012.
Resultados: Foram internadas 105 crianças por varicela, nos 13 anos avaliados, com idades entre um dia e os dez anos (mediana: 22 meses), sendo 51,4% do género feminino. A maior incidência sazonal foi de Abril a Junho. Nenhuma criança tinha a vacina antivÃrus varicela-zoster. Complicações associadas à varicela foram o motivo de internamento mais frequente (76%), incluindo infeções cutâneas (56,8%), complicações respiratórias (14,8%) e neurológicas (14,8%). As restantes crianças foram internadas, pela presença de fatores de risco (idade, varicela congénita, imunossupressão) ou pela gravidade da sintomatologia. Efetuaram aciclovir 68 crianças (65%), das quais, 20 tinham iniciado terapêutica antes da hospitalização. A duração média do internamento foi de 4,5 dias. Foram transferidas três crianças para hospital terciário, uma por sÃndrome de pele escaldada, uma por otomastoidite com indicação cirúrgica e outra por pneumonia com derrame pleural. Uma criança com encefalite desenvolveu sequelas.
Discussão: A varicela pode originar complicações graves sobretudo em crianças com fatores de risco. No perÃodo referido foi responsável por 0,7% dos internamentos. As complicações mais frequentes foram as cutâneas, o que está de acordo com outros estudos. Este trabalho permitiu rever as práticas do serviço, nomeadamente questionar critérios de internamento no grupo com fatores de risco, mas sem complicações da doença
Linear Modeling of the Glass Transition Temperature of the system SiO2-Na2O-CaO
This work aimed to mathematically model the glass transition temperature
(Tg), one of the most important parameters regarding the behavior of slag,
responsible for the sudden change in thermomechanical properties of
non-crystalline materials, by the chemical composition of the SiO2-Na2O-CaO
system, widely applicable in the production of glasses and constituent of iron,
magnesium and aluminum metallurgy slags. The SciGlass database was used to
provide data for mathematical modeling through the Python programming language,
using the method of least squares. A new equation was established, called P
Model, and it presented a lower mean absolute error and lower standard
deviation of absolute errors in relation to 3 equations in the literature. The
raised equation provides significant results in the mathematical modeling of Tg
by the chemical system SiO2-Na2O-CaO, valid for the limits of the data used in
the mathematical modeling.Comment: 5 pages, 3 figures, 2 table
Liquidus temperature nonlinear modeling of silicates
The liquidus temperature is an important parameter in understanding the
crystalline behavior of materials and in the operation of blast furnaces. Its
modeling can be carried out by linear and nonlinear methods through data,
considering the artificial neural network a modeling method with high
efficiency because it presents the theorem of universal approximation and with
that better performances and possibility of greater oscillations. The best
linear model and the best nonlinear model were modeled by structural parameters
and presented a good numerical approximation, thus demonstrating that
mathematical modeling can be performed using structural arguments and also
showing a dimensionality reduction method for modeling a thermophysical
property of the materials.Comment: 11 pages, 8 figures, 3 table
The technical challenge of Functional 18F-FDG-PET Brain imaging in paediatric epilepsy
Epilepsy is a chronic brain disease, characterized by the appearance of crisis (whit or without convulsions), caused by abnormal electric activity on brain cells. Neuroimaging might be necessary in the work-up of epilepsy for localisation of the seizure focus for possible surgical cure.
In our department, we started performing inter-ictal 18F-2-deoxyglucose (FDG)-PET/TC Brain imaging in 2009, in paediatric patients, following EANM procedure guidelines.
Aim: the aim of the study was to retrospectively review all the performed inter-ictal 18F-FDG-PET/TC brain imaging, to assess the difficulties found during these procedures and the deviation according to guideline recommendations. We also intend to focus on the major importance of an optimal cooperation with other departments, such as anaesthesiology and neurophysiology.
Material and Methods: between 2009 and 2012, eleven patients (pt) were referred for an 18F-FDG-PET-TC brain study, with ages between 10 months - 18 years old all with medically intractable epilepsy. The exams were performed with different conditions according to the needs of each patient, because we know that exceptional procedures call for special conditions.
Results: All files were review for pt information pertinent to performance of the procedure, pt pre-arrival preparation, pt pre-injection preparation, pt monitoring for ictal crises before injection (EEG), pt sedation, variability of radiopharmaceutical administration and data acquisition parameters. 8 of the pt were performed with anaesthesia while 3 without since the pediatric patient were cooperative. All of the pt were monitored under parental surveillance, one with additional movie recording and other with EEG.
Conclusion: We found that this process of retrospective review of this pool of paediatric patients with epilepsy enhanced the learning curve in this very specific procedure.
We also found it critical to request the collaboration of the departments of anaesthesiology and neurophysiology
Recommended from our members
Can vertical slot fishways (VSF) operate with less water without compromising effectiveness
- …