Modelling phloem transport within a pruned dwarf bean: a 2-source-3-sink system

2011 ◽  
Vol 38 (2) ◽  
pp. 127 ◽  
Author(s):  
Michael R. Thorpe ◽  
André Lacointe ◽  
Peter E. H. Minchin
Keyword(s):  
Mechanistic Model ◽  
Phloem Transport ◽  
Phaseolus Vulgaris L ◽  
Model Predictions ◽  
Complex Architectures ◽  
Treatment Responses ◽  
Model Platform ◽  
Bidirectional Flow ◽  
Source And Sink ◽  
Dwarf Bean

A mechanistic model of carbon partitioning, based on the Münch hypothesis of phloem transport and implemented with PIAF-Münch modelling platform (Lacointe and Minchin 2008), was tested for an architecture more complex than any tested previously. Using 11C to label photosynthate, responses in transport of photosynthate within a heavily pruned dwarf bean plant (Phaseolus vulgaris L.) to changes in source and sink activities were compared with model predictions. The observed treatment responses were successfully predicted. However, the observations could not be completely explained if the modelled stem contained only one phloem pathway: tracer from a labelled leaf was always detected in both shoot apex and root, whichever of the two leaves was labelled. This shows that bidirectional flow occurred within the stem, with solute moving simultaneously in both directions. Nevertheless, a model architecture with very little more complexity could incorporate such bidirectional flow. We concluded that the model could explain the observations, and that the PIAF-Münch model platform can be expected to describe partitioning in even more complex architectures.

Applicability of Choking Flow Models for Subcooled Flashing Flow Through Tube Cracks

2011 ◽  
Author(s):  
Brian Wolf ◽  
Shripad T. Revankar ◽  
Jovica R. Riznic
Keyword(s):  
Mechanistic Model ◽  
Channel Length ◽  
Two Phase ◽  
Experimental Conditions ◽  
Flow Rates ◽  
Flow Models ◽  
Model Predictions ◽  
Flow Through ◽  
The Difference ◽  
Non Equilibrium

Recently there is some database available on choking flow through cracks relevant to steam generator (SG) tubes to model the critical flow. These data are used in assessing the key choking flow models. Based on this assessment a mechanistic choking model is developed. The model is used to predict the choking flow rates for various experimental conditions for subcooled flashing flow through narrow slits with L/D varying from small values (∼5) to large values (100). Results are presented on the effects of thermal and mechanical non-equilibrium on the choking flow for small L/D channels. A mechanistic model was developed to model two-phase choking flow through slits. A comparison of model results to experimental data shows that the homogeneous equilibrium based models markedly under predict choking flow rates in such geometries. As subcooling increases, and channel length decreases the non-equilibrium effects play a greater role in the choking phenomenon, therefore the difference in model predictions and experimental results increases.

scholarly journals Consideration of Latent Infections Improves the Prediction of Botrytis Bunch Rot Severity in Vineyards

Plant Disease ◽  
2020 ◽  
Vol 104 (5) ◽  
pp. 1291-1297 ◽  
Author(s):  
Giorgia Fedele ◽  
Elisa González-Domínguez ◽  
Laurent Delière ◽  
Ana M. Díez-Navajas ◽  
Vittorio Rossi
Keyword(s):  
Decision Making ◽  
Mechanistic Model ◽  
False Negative ◽  
Growing Season ◽  
Weather Data ◽  
Growth Stages ◽  
Latent Infections ◽  
Vine Growth ◽  
Model Predictions ◽  
Bunch Rot

The current study validated a mechanistic model for Botrytis cinerea on grapevine with data from 23 independent Botrytis bunch rot (BBR) epidemics (combinations of vineyards × year) that occurred between 1997 and 2018 in Italy, France, and Spain. The model was operated for each vineyard by using weather data and vine growth stages to anticipate, at any day of the vine-growing season, the disease severity (DS) at harvest (severe, DS ≥ 15%; intermediate, 5 < DS < 15%; and mild, DS ≤ 5%). To determine the ability of the model to account for latent infections, postharvest incubation assays were also conducted using mature berries without symptoms or signs of BBR. The model correctly classified the severity of 15 of 23 epidemics (65% of epidemics) when the classification was based on field assessments of BBR severity; when the model was operated to include BBR severity after incubation assays, its ability to correctly predict BBR severity increased from 65% to >87%. This result showed that the model correctly accounts for latent infections, which is important because latent infections can substantially increase DS. The model was sensitive and specific, with the false-positive and false-negative proportion of model predictions equal to 0.24 and 0, respectively. Therefore, the model may be considered a reliable tool for decision-making for BBR control in vineyards.

Modeling of Axial-Symmetric Flow Structure in Gas–Solids Risers

2015 ◽  
Vol 138 (4) ◽  
Author(s):  
Pengfei He ◽  
Dawei Wang ◽  
Rajesh Patel ◽  
Chao Zhu
Keyword(s):  
Flow Structure ◽  
Mechanistic Model ◽  
Turbulent Convection ◽  
Nonuniform Flow ◽  
Symmetric Flow ◽  
Radial Transport ◽  
The Core ◽  
Interparticle Collision ◽  
Model Predictions ◽  
Back Mixing

Pneumatic transport of solids in a riser has a unique nonuniform flow structure, characterized by the core solids acceleration and the wall solids deceleration along the riser, which causes the down-flow of solids and hence back mixing. To predict this nonuniform flow structure, this paper presents a mechanistic model that includes two controlling mechanisms: the interparticle collision damping for axial transport of solids and the effects of collision-induced diffusion and turbulent convection for radial transport of solids. The model predictions are partially validated against available measurements, such as axial and radial distributions of concentration and velocity of solids.

scholarly journals Computational simulation of flocculent sedimentation based on experimental results

2012 ◽  
Vol 65 (6) ◽  
pp. 1007-1013 ◽  
Author(s):  
Mafeni S. Ramatsoma ◽  
Evans M. N. Chirwa
Keyword(s):  
Empirical Model ◽  
Mechanistic Model ◽  
Computational Simulation ◽  
Data Sets ◽  
Random Errors ◽  
Wide Range ◽  
Model Predictions ◽  
Sedimentation Basins ◽  
Semi Empirical ◽  
Better Than

Computerised interpolation algorithms as well as the empirical model for analysing the flocculent settling data were developed. A mechanistic semi-empirical model developed from fundamental physical principles of a falling particle in a viscous fluid was tested against actual flocculation column data. The accuracy of the mechanistic model was evaluated using the sum of the squared errors between the interpolated values (real values) and the model predictions. Its fitting capabilities were compared with Özer's model using nine flocculent data sets of which four were obtained from literature and the rest were actual data from the performed experiments. The developed model consistently simulated the flocculation behaviour of particles in settling columns better than Özer's model in eight of the nine data sets considered. It is recommended that the model's performance be further compared with other models like the Rule based and San's model. The errors due to the use of interpolated values when determining the performance of the empirical models need to be investigated. Furthermore, a three-way rather than two-way interpolation should now be achievable using the interpolation algorithm developed in this study thereby reducing the effects of interpolation bias. The above work opens the way to full automation of design of flocculation sedimentation basins and other gravitational particle separation systems which at present are designed manually and are susceptible to a wide range of human and random errors.

A Simple Mechanistic Model of Phloem Transport which Explains Sink Priority

1993 ◽  
Vol 44 (5) ◽  
pp. 947-955 ◽  
Author(s):  
P. E. H. MINCHIN ◽  
M. R. THORPE ◽  
J. F FARRAR
Keyword(s):  
Mechanistic Model ◽  
Phloem Transport

scholarly journals Testing the Münch hypothesis of long distance phloem transport in plants

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Michael Knoblauch ◽  
Jan Knoblauch ◽  
Daniel L Mullendore ◽  
Jessica A Savage ◽  
Benjamin A Babst ◽  
...  
Keyword(s):  
Strong Support ◽  
Sieve Tube ◽  
Phloem Transport ◽  
Plant Tissues ◽  
Long Distance ◽  
Pressure Flow ◽  
Long Distance Transport ◽  
Sieve Tubes ◽  
Distance Transport ◽  
Source And Sink

Long distance transport in plants occurs in sieve tubes of the phloem. The pressure flow hypothesis introduced by Ernst Münch in 1930 describes a mechanism of osmotically generated pressure differentials that are supposed to drive the movement of sugars and other solutes in the phloem, but this hypothesis has long faced major challenges. The key issue is whether the conductance of sieve tubes, including sieve plate pores, is sufficient to allow pressure flow. We show that with increasing distance between source and sink, sieve tube conductivity and turgor increases dramatically in Ipomoea nil. Our results provide strong support for the Münch hypothesis, while providing new tools for the investigation of one of the least understood plant tissues.

scholarly journals Detecting the impact of temperature on transmission of Zika, dengue and chikungunya using mechanistic models

2016 ◽  
Author(s):  
Erin A. Mordecai ◽  
Jeremy M. Cohen ◽  
Michelle V. Evans ◽  
Prithvi Gudapati ◽  
Leah R. Johnson ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Mechanistic Model ◽  
The United States ◽  
Human Case ◽  
Mosquito Vector ◽  
Temperature Dependent ◽  
Model Predictions ◽  
Incidence Risk ◽  
The Impact ◽  
Case Data

AbstractRecent epidemics of Zika, dengue, and chikungunya have heightened the need to understand the seasonal and geographic range of transmission by Aedes aegypti and Ae. albopictus mosquitoes. We use mechanistic transmission models to derive predictions for how the probability and magnitude of transmission for Zika, chikungunya, and dengue change with mean temperature, and we show that these predictions are well matched by human case data. Across all three viruses, models and human case data both show that transmission occurs between 18-34°C with maximal transmission occurring in a range from 26-29°C. Controlling for population size and two socioeconomic factors, temperature-dependent transmission based on our mechanistic model is an important predictor of human transmission occurrence and incidence. Risk maps indicate that tropical and subtropical regions are suitable for extended seasonal or year-round transmission, but transmission in temperate areas is limited to at most three months per year even if vectors are present. Such brief transmission windows limit the likelihood of major epidemics following disease introduction in temperate zones.Author SummaryUnderstanding the drivers of recent Zika, dengue, and chikungunya epidemics is a major public health priority. Temperature may play an important role because it affects mosquito transmission, affecting mosquito development, survival, reproduction, and biting rates as well as the rate at which they acquire and transmit viruses. Here, we measure the impact of temperature on transmission by two of the most common mosquito vector species for these viruses, Aedes aegypti and Ae. albopictus. We integrate data from several laboratory experiments into a mathematical model of temperature-dependent transmission, and find that transmission peaks at 26-29°C and can occur between 18-34°C. Statistically comparing model predictions with recent observed human cases of dengue, chikungunya, and Zika across the Americas suggests an important role for temperature, and supports model predictions. Using the model, we predict that most of the tropics and subtropics are suitable for transmission in many or all months of the year, but that temperate areas like most of the United States are only suitable for transmission for a few months during the summer (even if the mosquito vector is present).

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