A video imaging method for time-dependent measurements of molecular mass transfer and biofilm dynamics in microchannels

MRS Advances ◽  
2016 ◽  
Vol 1 (29) ◽  
pp. 2099-2106 ◽  
Author(s):  
M. Parvinzadeh Gashti ◽  
M. Zarabadi ◽  
J. Greener
Keyword(s):  
Biomass Accumulation ◽  
Structural Heterogeneity ◽  
Displacement Velocity ◽  
Imaging Method ◽  
Shear Forces ◽  
Growth Environment ◽  
Biofilm Thickness ◽  
Loading Rates ◽  
Local Shear ◽  
Growth Approach

ABSTRACTThe biomass accumulation and movement of biofilms in a microchannel is monitored by optical microscopy. First, the average optical density of the biofilm is monitored in time as a measure of biofilm thickness and structural heterogeneity. These results are used as inputs to calculate changing flow velocities due to resulting excluded volume. Next the displacement velocity of moving biofilm segments was recorded in different places in the microchannel. Quantitative analysis by a particle tracking routine showed differences in displacement velocity near and far from the microchannel corner, which is believed to be related to the local shear forces which vary depending on the height of the biofilm segment and its position in the microchannel. The effect of changing biofilm thickness and different hydrodynamic environments in the microchannel are then discussed in terms of their effects on molecular loading rates. Finally, a demonstration of a flow-templated growth approach as a means to homogenize the growth environment.

Two-dimensional cellular automaton model for mixed-culture biofilm

2004 ◽  
Vol 49 (11-12) ◽  
pp. 193-198 ◽  
Author(s):  
G.E. Pizarro ◽  
C. Garcia ◽  
R. Moreno ◽  
M. E. Sepulveda
Keyword(s):  
Steady State ◽  
Structural Heterogeneity ◽  
Constant Thickness ◽  
Two Dimensional ◽  
Active Biomass ◽  
Biofilm Thickness ◽  
Biofilm Model ◽  
Systems Models ◽  
Microbial Mass

Structural and microbial heterogeneity occurs in almost any type of biofilm system. General approaches for the design of biofilm systems consider biofilms as homogeneous and of constant thickness. In order to improve the design of biofilms systems, models need to incorporate structural heterogeneity and the effect of inert microbial mass. We have improved a 2D biofilm model based on cellular automata (CA) and used it to simulate multidimensional biofilms with active and inert biomass including a self-organizing development. Results indicate that the presence of inert biomass within biofilm structures does not change considerably the substrate flux into the biofilm because the active biomass is located at the surface of the biofilm. Long-term simulations revealed that although the biofilm system is highly heterogeneous and the microstructure is continuously changing, the biofilm reaches a dynamic steady-state with prediction of biofilm thickness and substrate flux stabilizing on a delimited range.

scholarly journals The Dinaric Mountains versus the Western Carpathians: Is structural heterogeneity similar in close-to-primeval Abies–Picea–Fagus forests?

2020 ◽  
Author(s):  
J. Paluch ◽  
S. Keren ◽  
Z. Govedar
Keyword(s):  
Spatial Scale ◽  
Structural Complexity ◽  
Abies Alba ◽  
Basal Area ◽  
Biomass Accumulation ◽  
European Beech ◽  
Structural Heterogeneity ◽  
Western Carpathians ◽  
Silver Fir ◽  
Canopy Trees

Abstract In this study, we analysed patterns of spatial variation in the basal area of live and dead trees and structural complexity in close-to-primeval forests in the Dinaric Mts. The results were compared with an analogous study conducted in the Western Carpathians. The research was carried out in the Janj, Lom and Perucića forest reserves (Bosnia and Herzegovina) in mixed-species stands of silver fir Abies alba Mill., European beech Fagus sylvatica L. and Norway spruce Picea abies (L.) H. Karst. In the core zones of the reserves, concentric sample plots (154 and 708 m2) were set in a regular 20 × 20 m grid covering approximately 10 ha. The analyses revealed varying distribution patterns of live canopy trees, suggesting that these characteristics may fluctuate to some extent at the regional level. At the spatial scale of 708 m2, attractive associations between dead canopy trees were found, but this tendency disappeared with increasing area. Although stands in the Dinaric Mts. are characterized by an almost twofold greater biomass accumulation compared to those from the Western Carpathians, the study revealed analogous bell-shaped distributions of stand basal areas of live trees and a very similar trend of decreasing variation in stand basal area and structural heterogeneity with increasing spatial scale. Nonetheless, the higher growing stocks, lower ratios of dead to live tree basal area and lower proportion of homogeneous structure types found in the Dinaric Mts. may suggest a less severe disturbance history over recent decades in this region compared to the Western Carpathians.

Feasibility Study of Force Measurement for Multi-digit Unconstrained Grasping via Fingernail Imaging and Visual Servoing

2020 ◽  
Vol 1 (2) ◽  
Author(s):  
Navid Fallahinia ◽  
Stephen A. Mascaro
Keyword(s):  
Visual Servoing ◽  
Degrees Of Freedom ◽  
Force Measurement ◽  
Field Of View ◽  
Imaging Method ◽  
Shear Forces ◽  
Maximum Value ◽  
6 Degrees Of Freedom ◽  
Finger Pad ◽  
Rms Errors

Abstract A fingernail imaging has been shown to be effective in estimating the finger pad forces along all three directions simultaneously in previous works. However, this method has never been used for the purpose of force measurement during a grasping task with multiple fingers. The objective of this paper is to demonstrate the grasp force-sensing capabilities of the fingernail imaging method integrated with a visual servoing robotic system. In this study, the fingernail imaging method has been used in both constrained and unconstrained multi-digit grasping studies. Visual servoing has been employed to solve the issue of keeping fingernail images in the field of view of the camera during grasping motions. Two grasping experiments have been designed and conducted to show the performance and accuracy of the fingernail imaging method to be used in grasping studies. The maximum value of root-mean-square (RMS) errors for estimated normal and shear forces during constrained grasping has been found to be 0.58 N (5.7%) and 0.49 N (9.2%), respectively. Moreover, a visual servoing system implemented on a 6-degrees-of-freedom (DOF) robot has been devised to ensure that all of the fingers remain in the camera frame at all times. Comparing unconstrained and constrained forces has shown that force collaboration among fingers could change based on the grasping condition.

Fluidized bed reactor operation for groundwater denitrification

1994 ◽  
Vol 29 (10-11) ◽  
pp. 509-515 ◽  
Author(s):  
M. Green ◽  
M. Shnitzer ◽  
S. Tarre ◽  
B. Bogdan ◽  
G. Shelef ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Loading Rate ◽  
Fluidized Bed Reactor ◽  
Reactor Operation ◽  
Biofilm Thickness ◽  
Loading Rates ◽  
Nitrite Removal ◽  
Sand Particles ◽  
Nitrate And Nitrite ◽  
Very High

Groundwater denitrification was carried out in a laboratory scale fluidized bed reactor using sand particles as the biomass carrier. This paper is concentrated on the fluidized bed reactor operation at very high nitrate loading rates (between 30 to 100 kg.NO3/m3 reactor/day) with corresponding short retention times (5 to 1.5 minutes). The effects of nitrate loading rate on nitrate and nitrite removal, as well as on reactor biomass profiles and biofilm characteristics, are presented in this article. The results of the present study indicate that this type of reactor can operate efficiently at retention times shorter than 3 minutes and at nitrate loading rates higher than 70 kg.NO3/m3/day. However, this system requires careful control of the biofilm thickness to achieve a reliable reactor operation.

Synergistic Effect Based on Enhanced Local Shear Forces in PVDF/TiO2/CNT Ternary Composites

2020 ◽  
Vol 59 (42) ◽  
pp. 18887-18897
Author(s):  
Huanhuan Zhang ◽  
Mingliang Zhao ◽  
Zhao-Xia Huang ◽  
Jin-Ping Qu
Keyword(s):  
Synergistic Effect ◽  
Shear Forces ◽  
Local Shear

Flow-induced detachment of adherent platelets from fibrinogen-coated surface

1996 ◽  
Vol 270 (1) ◽  
pp. H160-H166 ◽  
Author(s):  
C. J. Jen ◽  
H. M. Li ◽  
J. S. Wang ◽  
H. I. Chen ◽  
S. Usami
Keyword(s):  
Shear Stress ◽  
Shape Change ◽  
Electron Microscopic Observation ◽  
Flow Chamber ◽  
Metabolic Energy ◽  
Shear Forces ◽  
Electron Microscopic ◽  
Local Shear ◽  
Coated Surface ◽  
Different Levels

A study of the shear forces under which adherent platelets of different morphologies can be detached from surfaces was carried out using a newly designed tapered flow chamber, which covered the entire shear range of physiological circulation. Platelets that naturally settled on a fibrinogen-coated surface were exposed to shear flow and were subsequently processed for scanning electron microscopic observation. We found that 1) the density of platelets remaining after flow exposure decreased with local shear stress, 2) adherent platelets of different morphologies withstood different levels of shear stress: most round cells and 40% of the cells that had a few short pseudopods were detached at < 10 dyn/cm2, whereas most spread cells could withstand 50 dyn/cm2, 3) pulsatile flow was more effective in removing adherent platelets than equivalent steady flow, 4) cytochalasin D and colchicine retarded platelet shape change and made them more easily detached by shear forces, and 5) metabolic energy-depleted platelets spread readily and formed shear-resistant clumps. Our observations indicated that adherent platelets of different morphologies on a fibrinogen-coated surface could withstand different levels of flow shear stress.

Role of shear forces and adhesion molecule distribution on P-selectin-mediated leukocyte rolling in postcapillary venules

2004 ◽  
Vol 287 (6) ◽  
pp. H2705-H2711 ◽  
Author(s):  
Michael B. Kim ◽  
Ingrid H. Sarelius
Keyword(s):  
Adhesion Molecule ◽  
Expression Patterns ◽  
Local Variation ◽  
Early Event ◽  
High Temporal Resolution ◽  
Leukocyte Rolling ◽  
Shear Forces ◽  
Rolling Velocity ◽  
Local Shear

Rolling on the venular endothelium is a critical step in the recruitment of leukocytes during the inflammatory response. P-selectin is a key mediator of leukocyte rolling, which is an early event in the inflammatory cascade; this rolling is likely to be directly regulated by both local fluid shear forces and P-selectin site densities in the microvasculature. However, neither the spatial pattern of P-selectin expression in postcapillary venules nor the effect of local expression patterns on rolling behavior in intact functional venules is known. We investigated the influence of local shear forces and the spatial distribution of endothelial P-selectin in intact blood perfused post capillary venules in anesthetized mice using intravital confocal microscopy, high temporal resolution particle tracking, and immunofluorescent labeling. We demonstrated a shear-dependent increase in average leukocyte rolling velocity that was attributable to a shear-dependent increase in the occurrence of transient leukocyte detachments from the endothelial surface: translational velocity during leukocyte contact with the vessel wall remained constant. P-selectin expression was not different in venules with characteristically different shear rates or diameters but varied significantly within individual venules. In postcapillary venules, regions of high P-selectin expression correlated with regions of slow leukocyte rolling. Thus the characteristically variable leukocyte rolling in vivo is a function of the spatial heterogeneity in P-selectin expression. The study shows how the local hydrodynamic forces and the nonuniform pattern of P-selectin expression affect the behavior of interacting leukocytes, providing direct evidence for the local variation of adhesion molecule expression as a mechanism for the regulation of leukocyte recruitment.

scholarly journals Simultaneous organic matter removal and nitrification of an inert self-supporting immersed media to upgrade aerated lagoons

2017 ◽  
Vol 77 (1) ◽  
pp. 51-59 ◽  
Author(s):  
E. Boutet ◽  
S. Baillargeon ◽  
B. Patry ◽  
P. Lessard
Keyword(s):  
Organic Matter ◽  
Freezing Point ◽  
Nitrification Rate ◽  
Test Results ◽  
Organic Matter Removal ◽  
Biofilm Thickness ◽  
Effluent Quality ◽  
Loading Rates ◽  
Organic Removal ◽  
Fixed Film

Abstract A pilot study was performed to evaluate the potential of an inert self-supported immersed fixed film media to upgrade aerated lagoons. Simultaneous organic matter removal and nitrification was assessed under different loading rates and temperatures (near 0 °C) using 12 laboratory-scale reactors operated in parallel. Test results showed that both the temperature and the load have an influence on organic matter effluent concentrations. Effluent quality seemed related to the observed biofilm thickness. Thicker biofilm is believed to have contributed to biomass detachment and increased particulate organic matter concentrations in the effluent. Simultaneous organic removal and nitrification was obtained at loads above 5 g CBOD5/m2·d. The highest nitrification rate at 0.4 °C was obtained for the smallest load, which showed a nitrification limitation close to freezing point.

Toward an operational dynamic model for tertiary nitrification by submerged biofiltration

2007 ◽  
Vol 55 (8-9) ◽  
pp. 301-308 ◽  
Author(s):  
E. Vigne ◽  
J.M. Choubert ◽  
J.P. Canler ◽  
A. Héduit ◽  
P. Lessard
Keyword(s):  
Loading Rate ◽  
Experimental Tests ◽  
Calibration Procedure ◽  
Biofilm Thickness ◽  
Loading Rates ◽  
Total Head ◽  
Model Predictions ◽  
Reduction Coefficient ◽  
The Mean ◽  
Set Up

This work deals with the methodology put in place to fit and validate the parameters of a biofiltration model (BAF) in tertiary nitrification treatment and dynamic conditions. For an average loading rate of 0.65 kg NH4-N/m3 media/d, different time loading rates are applied inside a filtration-backwash run using a semi-industrial pilot. Comparisons between predicted and observed values on the NH4-N, NO3-N and TSS in treated water and the total head loss ΔP are carried out firstly using default values of BAF parameters. Model predictions overestimate values measured but trends are well reproduced. A sensitivity analysis is carried out and the hierarchy of BAF parameters has been set up classifying them into strong and low influence on the effluent concentrations. Among parameters revealing the strongest influence are those of the filtration module and the mean density of biofilm for the TSS effluent and the total ΔP, the specific autotrophic growth rate, the maximum biofilm thickness and the reduction coefficient of diffusivity in the biofilm for the NH4-N, NO3-N effluent. Finally, this classification leads to setting a calibration procedure, thanks to specific experimental tests directly measuring some BAF parameters.

scholarly journals Enriching and aggregating purple non-sulfur bacteria in an anaerobic sequencing-batch photobioreactor for nutrient capture from wastewater

2020 ◽  
Author(s):  
Marta Cerruti ◽  
Berber Stevens ◽  
Sirous Ebrahimi ◽  
Abbas Alloul ◽  
Siegfried E. Vlaeminck ◽  
...  
Keyword(s):  
Mixed Culture ◽  
Municipal Wastewater ◽  
Biomass Accumulation ◽  
Amplicon Sequencing ◽  
Stirred Tank ◽  
List Type ◽  
Organic Loading ◽  
Loading Rates ◽  
Sulfur Bacteria ◽  
Ir Light

AbstractPurple non-sulfur bacteria (PNSB), a guild of anoxygenic photomixotrophic organisms, rise interest to capture nutrients from wastewater in mixed-culture bioprocesses. One challenge targets the aggregation of PNSB biomass through gravitational separation from the treated water to facilitate its retention and accumulation, while avoiding the need for membranes. We aimed to produce an enriched, concentrated, well-settling, nutrient-removing PNSB biomass using sequencing batch regimes (SBR) in an anaerobic photobioreactor. The stirred tank was fed with a synthetic influent mimicking loaded municipal wastewater (430-860 mg CODAc LInf-1, COD:N:P ratio of 100:36:4-100:11:2 m/m/m), operated at 30°C and pH 7, and continuously irradiated with infrared (IR) light (>700 nm) at 375 W m-2. After inoculation with activated sludge at 0.1 g VSS L-1, PNSB were rapidly enriched in a first batch of 24 h: the genus Rhodobacter reached 54% of amplicon sequencing read counts. SBR operations at volume exchange ratio of 50% with decreasing hydraulic retention times (48 to 16 h; 1 to 3 cycles d-1) and increasing volumetric organic loading rates (0.2 to 1.3 kg COD m-3 d-1) stimulated the aggregation (compact granules of 50-150 μm), settling (sedimentation G-flux of 4.7 kg h-1 m-2), and accumulation (as high as 3.8 g VSS L-1) of biomass. The sludge retention time (SRT) increased freely from 2.5 to 11 d without controlled sludge wasting. Acetate, ammonium, and orthophosphate were removed simultaneously (up to 96% at a rate of 1.1 kg COD m-3 d-1, 77% at 113 g N m-3 d-1, and 73% at 15 g P m-3 d-1) with a COD:N:P assimilation ratio of 100:6.7:0.9 (m/m/m). Competition for substrate and photons occurred in the PNSB guild. SBR regime shifts sequentially selected for Rhodobacter (90%) under shorter SRT and non-limiting acetate concentrations during reaction phases, Rhodopseudomonas (70%) under longer SRT and acetate limitation, and Blastochloris (10%) under higher biomass concentrations. We highlighted the benefits of a PNSB-based SBR process for biomass accumulation and simultaneous nutrient capture at substantial rates, and its underlying microbial ecology.Graphical abstractHighlightsPNSB were highly enriched (90%) in an anaerobic stirred-tank photobioreactor.The mixed-culture SBR process fostered PNSB biomass aggregation and accumulation.PNSB sludge reached 3.8 g VSS L-1 and a sedimentation G-flux of 4.7 kg h-1 m-2.PNSB enabled a high simultaneous removal of COD (96%), N (77%), and P (73%).Rhodobacter, Rhodopseudomonas, and Blastochloris competed for acetate and photons.

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