Applying Ecological Input-Output Flow Analysis to Material Flows in Industrial Systems

This article, continuing with the themes of the companion article, expounds the capabilities of input-output techniques as applied to material flows in industrial systems. Material flows are the primary focus because of their role in directly linking natural and industrial systems and thereby being fundamental components of environmental issues in industrial economies. The specific topic in this article concerns several material flow metrics used to characterize system behavior that are derived from the ecological development of input-output techniques; most notable of these metrics are several measures of material cycling and a measure of the number of processes visited by material while in a system. These metrics are shown to be useful in analyzing the state of material flow systems. Further-more, the metrics are shown to be a central link in connecting input-output flow analysis to synthesis (i.e., the process of using measurements of system behavior to design changes to that system). By connecting the flow metrics to both environmental objectives and controllable aspects of flow models, changes to existing flow systems are synthesized to generate improved system behavior. To bring this pair of articles to a close, several limitations of input-output flow analysis are summarized with the goal of stimulating further interest and research.     

Applying Ecological Input-Output Flow Analysis to Material Flows in Industrial Systems: Part I: Tracing Flows

Input-output mathematics, which allows a modeler to fully consider direct and indirect relationships among conserved flows in a system, has a long history in economics with prominent use dating to Leontief in the 1930s. Nearly all previous industrial applications of input-output analysis have been grounded in the monetary flows of an economy. Here however, because of the central nature of physical flows in the environmental impact of industry, we consider physical flows to be a fundamental component of an industrial economy. Hence, we propose an input-output based approach for modeling physical flows in industry independent of their monetary implications.
In this first part of a two-part article, a framework for using input-output mathematics to model material and energy flows is constructed from a foundation laid by previous research in nutrient and energy cycling in natural ecosystems. The mathematics of input-output flow analysis is presented from an ecological perspective, culminating in two core capabilities: tracing of flows with environs (investigated in this article) and characterizing system behavior with flow metrics (presented in the second article). We assert that environ analysis is an effective means for tracing flows through industrial systems while fully considering direct and indirect flow paths. We explore material flows of aluminum and five other metals in depth using environ analysis in this article.     

A Hybrid Analytical/Numerical Model for the Characterization of Preferential Flow Path with Non-Darcy Flow

Due to the long-term fluid-solid interactions in waterflooding, the tremendous variation of oil reservoir formation parameters will lead to the widespread evolution of preferential flow paths, thereby preventing the further enhancement of recovery efficiency because of unstable fingering and premature breakthrough. To improve oil recovery, the characterization of preferential flow paths is essential and imperative. In efforts that have been previously documented, fluid flow characteristics within preferential paths are assumed to obey Darcy''s equation. However, the occurrence of non-Darcy flow behavior has been increasingly suggested. To examine this conjecture, the Forchheimer number with the inertial coefficient estimated from different empirical formulas is applied as the criterion. Considering a 10% non-Darcy effect, the fluid flow in a preferential path may do experience non-Darcy behavior. With the objective of characterizing the preferential path with non-Darcy flow, a hybrid analytical/numerical model has been developed to investigate the pressure transient response, which dynamically couples a numerical model describing the non-Darcy effect of a preferential flow path with an analytical reservoir model. The characteristics of the pressure transient behavior and the sensitivities of corresponding parameters have also been discussed. In addition, an interpretation approach for pressure transient testing is also proposed, in which the Gravitational Search Algorithm is employed as a non-linear regression technology to match measured pressure with this hybrid model. Examples of applications from different oilfields are also presented to illustrate this method. This cost-effective approach provides more accurate characterization of a preferential flow path with non-Darcy flow, which will lay a solid foundation for the design and operation of conformance control treatments, as well as several other Enhanced Oil Recovery projects.     

Cluster Structure of Anaerobic Aggregates of an Expanded Granular Sludge Bed Reactor

The metabolic properties and ultrastructure of mesophilic aggregates from a full-scale expanded granular sludge bed reactor treating brewery wastewater are described. The aggregates had a very high methanogenic activity on acetate (17.19 mmol of CH₄/g of volatile suspended solids [VSS]·day or 1.1 g of CH₄ chemical oxygen demand/g of VSS·day). Fluorescent in situ hybridization using 16S rRNA probes of crushed granules showed that 70 and 30% of the cells belonged to the archaebacterial and eubacterial domains, respectively. The spherical aggregates were black but contained numerous whitish spots on their surfaces. Cross-sectioning these aggregates revealed that the white spots appeared to be white clusters embedded in a black matrix. The white clusters were found to develop simultaneously with the increase in diameter. Energy-dispersed X-ray analysis and back-scattered electron microscopy showed that the whitish clusters contained mainly organic matter and no inorganic calcium precipitates. The white clusters had a higher density than the black matrix, as evidenced by the denser cell arrangement observed by high-magnification electron microscopy and the significantly higher effective diffusion coefficient determined by nuclear magnetic resonance imaging. High-magnification electron microscopy indicated a segregation of acetate-utilizing methanogens (Methanosaeta spp.) in the white clusters from syntrophic species and hydrogenotrophic methanogens (Methanobacterium-like and Methanospirillum-like organisms) in the black matrix. A number of physical and microbial ecology reasons for the observed structure are proposed, including the advantage of segregation for high-rate degradation of syntrophic substrates.     

Characterization of Granular Particles Isolated from Postsynaptic Densities

Abstract: We describe here the isolation and biochemical characterization of a population of protein aggregates from the postsynaptic density (PSD) prepared from pig cerebral cortex. The protein constituents of these aggregates are linked together primarily by disulfide bonds. Negative staining electron microscopy revealed that the isolated protein aggregates were granular objects with an average outside diameter of ∼21 nm and with small protrusions on their surface. The major constituents of the isolated granular aggregates consist of tubulin and an unidentified protein of 70 kDa in size. Small amounts of the α subunit of calcium/calmodulin-dependent protein kinase II and subunits of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and NMDA subtypes of glutamate receptors were also detected by immunoblotting. Actin, however, was not found in these granular aggregates. We propose that these granular protein aggregates correspond to the ∼20-nm-diameter granular particles of the PSD on the basis of their biochemical and morphological characteristics. The spatial arrangement of these granular aggregates relative to other components of the postsynaptic terminal is also postulated here.     

颈动脉瘤个体化模型血流数值分析

动脉瘤日益受到广泛关注,介入术成为动脉瘤的理想化治疗方法,但现实临床实践缺少理论支撑,所以数值模拟成为研究动脉瘤血流动力学参数的关键技术。为了研究动脉瘤的血液动力特性,进而探讨不同参数对动脉瘤的血液动力学特性影响因素,本研究基于1例个体化动脉瘤的影像数据,通过影像提取的方法建立了个体化动脉瘤模型,并根据双向流固耦合的方法进行血流场分析(流线,壁面变形分布,壁面剪切力分布)。通过数值分析结果表明,在一个心动周期的不同时刻动脉瘤瘤腔内的涡流强度先增强再减弱并在0.1 s达到最强。动脉瘤壁面的壁面切应力(wall shear stress, WSS)的分布也随着时间的变化,同样在0.1 s时刻壁面WSS分布梯度较大,到0.22 s时刻以及后各个时刻达到均匀无梯度分布。而从壁面变形来看,一个心动周期前0.3 s时刻动脉瘤壁的最大变形位置均为瘤顶处并呈现由小到大再到小的变化(0.1 s时刻达到最大变形量),0.3 s时刻的最大变形量位置发生改变,为瘤颈中间部位,但变形量很小为0.01 mm。     

Contact Angle Measurement and Cell Hydrophobicity of Granular Sludge from Upflow Anaerobic Sludge Bed Reactors

The contact angle, which is generally used to evaluate the hydrophobicities of pure bacterial strains and solid surfaces, was used to study mixed cell cultures of bacteria involved in anaerobic digestion. Previously published data and data from this study showed that most acidogens are hydrophilic (contact angle, <45(deg)) but most of the acetogens and methanogens isolated from granular sludge are hydrophobic (contact angle, >45(deg)). The hydrophobicities of mixtures of hydrophilic and hydrophobic cells were found to be linearly correlated with the cell mixing ratio. The hydrophobicities of cells present in effluents from upflow anaerobic sludge bed reactors which were treating different types of substrates were different depending on the reactor conditions. When the reactor liquid had a high surface tension, cells sloughing off from sludge granules, as well as cells present on the outer surfaces of the granules, were hydrophobic. Short-term batch enrichment cultures revealed that proteins selected for highly hydrophilic cells. Long-term in-reactor enrichment cultures revealed that sugars selected for hydrophilic acidogens on the surfaces of the granules, while fatty acids tended to enrich for hydrophobic methanogens. When linear alkylbenzenesulfonate was added, the cells on the surfaces of granules became more hydrophilic. Control tests performed with pure cultures revealed that there was no change in the surface properties due to linear alkylbenzenesulfonate; hence, the changes in the wash-out observed probably reflect changes in the species composition of the microbial association. A surface layer with moderate hydrophobicity, a middle layer with extremely high hydrophobicity, and a core with high hydrophobicity could be distinguished in the grey granules which we studied.     

Numerical Simulation of Supersonic Gap Flow

Various gaps in the surface of the supersonic aircraft have a significant effect on airflows. In order to predict the effects of attack angle, Mach number and width-to-depth ratio of gap on the local aerodynamic heating environment of supersonic flow, two-dimensional compressible Navier-Stokes equations are solved by the finite volume method, where convective flux of space term adopts the Roe format, and discretization of time term is achieved by 5-step Runge-Kutta algorithm. The numerical results reveal that the heat flux ratio is U-shaped distribution on the gap wall and maximum at the windward corner of the gap. The heat flux ratio decreases as the gap depth and Mach number increase, however, it increases as the attack angle increases. In addition, it is important to find that chamfer in the windward corner can effectively reduce gap effect coefficient. The study will be helpful for the design of the thermal protection system in reentry vehicles.     

Diffusional Properties of Methanogenic Granular Sludge: 1H NMR Characterization

The diffusive properties of anaerobic methanogenic and sulfidogenic aggregates present in wastewater treatment bioreactors were studied using diffusion analysis by relaxation time-separated pulsed-field gradient nuclear magnetic resonance (NMR) spectroscopy and NMR imaging. NMR spectroscopy measurements were performed at 22°C with 10 ml of granular sludge at a magnetic field strength of 0.5 T (20 MHz resonance frequency for protons). Self-diffusion coefficients of H₂O in the investigated series of mesophilic aggregates were found to be 51 to 78% lower than the self-diffusion coefficient of free water. Interestingly, self-diffusion coefficients of H₂O were independent of the aggregate size for the size fractions investigated. Diffusional transport occurred faster in aggregates growing under nutrient-rich conditions (e.g., the bottom of a reactor) or at high (55°C) temperatures than in aggregates cultivated in nutrient-poor conditions or at low (10°C) temperatures. Exposure of aggregates to 2.5% glutaraldehyde or heat (70 or 90°C for 30 min) modified the diffusional transport up to 20%. In contrast, deactivation of aggregates by HgCl₂ did not affect the H₂O self-diffusion coefficient in aggregates. Analysis of NMR images of a single aggregate shows that methanogenic aggregates possess a spin-spin relaxation time and self-diffusion coefficient distribution, which are due to both physical (porosity) and chemical (metal sulfide precipitates) factors.     

A Numerical Study of Local Variations in Tidal Regime of Tagus Estuary,Portugal

Tidal dynamics of shallow estuaries and lagoons is a complex matter that has attracted the attention of a large number of researchers over the last few decades. The main purpose of the present work is to study the intricate tidal dynamics of the Tagus estuary, which states as the largest estuary of the Iberian Peninsula and one of the most important wetlands in Portugal and Europe. Tagus has large areas of low depth and a remarkable geomorphology, both determining the complex propagation of tidal waves along the estuary of unknown manner. A non-linear two-dimensional vertically integrated hydrodynamic model was considered to be adequate to simulate its hydrodynamics and an application developed from the SIMSYS2D model was applied to study the tidal propagation along the estuary. The implementation and calibration of this model revealed its accuracy to predict tidal properties along the entire system. Several model runs enabled the analysis of the local variations in tidal dynamics, through the interpretation of amplitude and phase patterns of the main tidal constituents, tidal asymmetry, tidal ellipses, form factor and tidal dissipation. Results show that Tagus estuary tidal dynamics is extremely dependent on an estuarine resonance mode for the semi-diurnal constituents that induce important tidal characteristics. Besides, the estuarine coastline features and topography determines the changes in tidal propagation along the estuary, which therefore result essentially from a balance between convergence/divergence and friction and advection effects, besides the resonance effects.     

Three-Dimensional Numerical Simulations of Biofilm Dynamics with Quorum Sensing in a Flow Cell

We develop a multiphasic hydrodynamic theory for biofilms taking into account interactions among various bacterial phenotypes, extracellular polymeric substance (EPS), quorum sensing (QS) molecules, solvent, and antibiotics. In the model, bacteria are classified into down-regulated QS, up-regulated QS, and non-QS cells based on their QS ability. The model is first benchmarked against an experiment yielding an excellent fit to experimental measurements on the concentration of QS molecules and the cell density during biofilm development. It is then applied to study development of heterogeneous structures in biofilms due to interactions of QS regulation, hydrodynamics, and antimicrobial treatment. Our 3D numerical simulations have confirmed that (i). QS is beneficial for biofilm development in a long run by building a robust EPS population to protect the biofilm; (ii). biofilms located upstream can induce QS downstream when the colonies are close enough spatially; (iii). QS induction may not be fully operational and can even be compromised in strong laminar flows; (v). the hydrodynamic stress alters the biofilm morphology. Through further numerical investigations, our model suggests that (i). QS-regulated EPS production contributes to the structural formation of heterogeneous biofilms; (ii) QS down-regulated cells tend to grow at the surface of the biofilm while QS up-regulated ones tend to grow in the bulk; (iii) when nutrient supply is sufficient, QS induction might be more effective upstream than downstream; (iv) QS may be of little benefit in a short timescale in term of fighting against invading strain/species; (v) the material properties of biomass (bacteria and EPS) have strong impact on the dilution of QS molecules under strong shear flow. In addition, with this modeling framework, hydrodynamic details and rheological quantities associated with biofilm formation under QS regulation can be resolved.     

Regime shifts in a social-ecological system

Ecological regime shifts are rarely purely ecological. Not only is the regime shift frequently triggered by human activity, but the responses of relevant actors to ecological dynamics are often crucial to the development and even existence of the regime shift. Here, we show that the dynamics of human behaviour in response to ecological changes can be crucial in determining the overall dynamics of the system. We find a social–ecological regime shift in a model of harvesters of a common-pool resource who avoid over-exploitation of the resource by social ostracism of non-complying harvesters. The regime shift, which can be triggered by several different drivers individually or also in combination, consists of a breakdown of the social norm, sudden collapse of co-operation and an over-exploitation of the resource. We use the approach of generalized modeling to study the robustness of the regime shift to uncertainty over the specific forms of model components such as the ostracism norm and the resource dynamics. Importantly, the regime shift in our model does not occur if the dynamics of harvester behaviour are not included in the model. Finally, we sketch some possible early warning signals for the social–ecological regime shifts we observe in the models.     

Numerical Modeling of Interstitial Fluid Flow Coupled with Blood Flow through a Remodeled Solid Tumor Microvascular Network

Modeling of interstitial fluid flow involves processes such as fluid diffusion, convective transport in extracellular matrix, and extravasation from blood vessels. To date, majority of microvascular flow modeling has been done at different levels and scales mostly on simple tumor shapes with their capillaries. However, with our proposed numerical model, more complex and realistic tumor shapes and capillary networks can be studied. Both blood flow through a capillary network, which is induced by a solid tumor, and fluid flow in tumor’s surrounding tissue are formulated. First, governing equations of angiogenesis are implemented to specify the different domains for the network and interstitium. Then, governing equations for flow modeling are introduced for different domains. The conservation laws for mass and momentum (including continuity equation, Darcy’s law for tissue, and simplified Navier–Stokes equation for blood flow through capillaries) are used for simulating interstitial and intravascular flows and Starling’s law is used for closing this system of equations and coupling the intravascular and extravascular flows. This is the first study of flow modeling in solid tumors to naturalistically couple intravascular and extravascular flow through a network. This network is generated by sprouting angiogenesis and consisting of one parent vessel connected to the network while taking into account the non-continuous behavior of blood, adaptability of capillary diameter to hemodynamics and metabolic stimuli, non-Newtonian blood flow, and phase separation of blood flow in capillary bifurcation. The incorporation of the outlined components beyond the previous models provides a more realistic prediction of interstitial fluid flow pattern in solid tumors and surrounding tissues. Results predict higher interstitial pressure, almost two times, for realistic model compared to the simplified model.     

Analysis and Modeling of Lithium Flows in Porous Materials

One of the primary conditions necessary for the success of magnetic fusion reactors is the ability to mitigate damage to the first wall during ELMs and plasma disruptions. A potential solution involves the use of flowing liquid metals such as lithium as a first wall, but ensuring its stability under the extreme environments in the reactor would be imperative. The conditions leading to instabilities on the free surface of flowing liquid lithium (LL) layers on a substrate and in a porous material are investigated using both analytical methods and computational modeling, with consideration for the effects of LL velocity, LL layer thickness, substrate porosity, LL permeability, and hydrogen (H) plasma velocity. Linear stability analysis is used to predict the critical velocity and wavelength-dependence of wave growth, as well as the onset of instability. The modeling of LL flows is performed on a flat substrate and in a porous material for various LL thicknesses, LL and H plasma velocities to analyze the conditions leading to droplet formation and ejection.     

Energy Nonequipartition in a Sheared Granular Mixture

The kinetic granular temperatures of a binary granular mixture in simple shear flow are calculated by means of the Direct Simulation Monte Carlo method. The results show that the temperature ratio is clearly different from unity (as may be expected since the system is out of equilibrium) and strongly depends on the restitution coefficients as well as on the parameters of the mixture. The influence of the temperature differences on the rheological properties is also discussed. The results are compared with the theoretical predictions obtained from the Boltzmann kinetic theory by using a Sonine polynomial expansion. The comparison shows an excellent agreement over the range of parameters investigated.     

Characterization and quantification of diadenosine hexaphosphate in chromaffin cells: Granular storage and secretagogue-induced release

The presence of diadenosine hexaphosphate (Ap6A) in chromaffin cells is described. The characterization of Ap6A has been accomplished by HPLC techniques, using three different elution conditions, rechromatography, and coelution with standards. Treatment with phosphodiesterase from Crotalus durissus produced AMP and adenosine pentaphosphate. The HPLC techniques described allowed the quantification of Ap6A in the picomole range. Chromaffin granules store Ap6A in a quantity of 48.5 +/- 9.7 nmol/mg protein, with a molar ratio ATP/Ap6A of 27. In chromaffin cells the Ap6A value was 1.46 +/- 0.32 nmol/10(6) cells. Diadenosine hexaphosphate was released from chromaffin cells by the action of carbachol and a value of 64 +/- 15 pmol/10(6) cells was obtained, which represents 4-5% of the total cellular content.     

Mechanical Characterization of Protein L in the Low-Force Regime by Electromagnetic Tweezers/Evanescent Nanometry

Mechanical manipulation at the single molecule level of proteins exhibiting mechanical stability poses a technical challenge that has been almost exclusively approached by atomic force microscopy (AFM) techniques. However, due to mechanical drift limitations, AFM techniques are restricted to experimental recordings that last less than a minute in the high-force regime. Here we demonstrate a novel combination of electromagnetic tweezers and evanescent nanometry that readily captures the forced unfolding trajectories of protein L at pulling forces as low as 10 ∼ 15 pN. Using this approach, we monitor unfolding and refolding cycles of the same polyprotein for a period of time longer than 30 min. From such long-lasting recordings, we obtain ensemble averages of unfolding step sizes and rates that are consistent with single-molecule AFM data obtained at higher stretching forces. The unfolding kinetics of protein L at low stretching forces confirms and extends the observations that the mechanical unfolding rate is exponentially dependent on the pulling force within a wide range of stretching forces spanning from 13 pN up to 120 pN. Our experiments demonstrate a novel approach for the mechanical manipulation of single proteins for extended periods of time in the low-force regime.     

Compartment Analysis of Nitrogen Flows through Mature Leaves

Nitrogen flows in mature leaves of rice, sunflower and cornwere analyzed by multicompartment analyses of data from ¹⁵Ntracer experiments. The fourcompartment model fit the measureddata better than the two- or three-compartment models. Rateconstants of the nitrogen flows, transfers with or without proteinturnover and flow through a storage pool of soluble-N, werederived from a least-squares fit between the mathematical expressionsand the corresponding measured data. Results of computations indicated the following: The flow ofnitrogen through the protein pool was larger than the directflow in recently matured leaves, whereas the reverse was truein senescent leaves. The presence of a temporary storage poolof soluble N was suggested, and the half-life of the N exchangein that pool was estimated to be roughly the amount of the insolubleN present in three of the four cases examined. The half-livesof insoluble N (protein) pools were 35 to 150 h. The pool forthe N efflux from the leaves was small with the shortest half-lives(most less than 2 h) of N turnover. Some recycling of N duringprotein turnover was suggested in sunflower leaves, but theextent in the leaves of rice seedlings was estimated to be little. (Received April 28, 1983; Accepted October 6, 1983)     

Hydrology-Driven Regime Shifts in a Shallow Tropical Lake

Shifts between alternative stable states have become a focus of research in temperate shallow lakes. Here we show that sharp transitions between a clear, macrophyte-dominated state and a turbid state without submerged plants can also occur in tropical floodplain lakes, albeit driven by a largely different set of mechanisms. We show how a shallow lake in the Pantanal becomes covered by an exploding population of the submerged macrophyte Egeria najas Planchon as the water level rises during the annual high-water period. Water clarity increases spectacularly in this period due to flushing with river water that has lost most of its suspended matter during its slow flow over the flooded vegetated plains. A few months later when the water level drops again, the submerged plant beds die and decompose rapidly, triggering a phase of increasing turbidity. During this period an increase in dissolved organic matter, suspended matter, and phytoplankton biomass results in a sharp deterioration in water clarity. The concomitant water level decrease largely counteracts the effects on the underwater light climate, so that the amount of light at the bottom may not differ in comparison with the high-water period. Therefore, changes in light climate seem unlikely to be the sole driver of the vegetation shifts, and other mechanisms may prevent recovery of the submerged vegetation until the next high-water episode. Also, contrary to what is found in temperate lakes, there is no evidence for top-down control of phytoplankton biomass associated with the macrophyte-dominated state in our tropical lake. Author Contributions  Simoni Maria Loverde-Oliveira, Vera Lúcia Moraes Huszar—conceived the study, Simoni Maria Loverde-Oliveira—performed research and analyzed data, Simoni Maria Loverde-Oliveira, Vera Lúcia Moraes Huszar, Nestor Mazzeo, Marten Scheffer—wrote the paper.