scholarly journals The Porous Surface Model, a Novel Experimental System for Online Quantitative Observation of Microbial Processes under Unsaturated Conditions

2008 ◽  
Vol 74 (16) ◽  
pp. 5195-5200 ◽  
Author(s):  
Arnaud Dechesne ◽  
Dani Or ◽  
Gamze Gülez ◽  
Barth F. Smets
Keyword(s):  
Liquid Film ◽  
Liquid Medium ◽  
Real Time ◽  
Single Cells ◽  
Liquid Films ◽  
Microbial Processes ◽  
Porous Surface ◽  
Surface Model ◽  
Ceramic Plate ◽  
Matric Potential

ABSTRACT Water is arguably the most important constituent of microbial microhabitats due to its control of physical and physiological processes critical to microbial activity. In natural environments, bacteria often live on unsaturated surfaces, in thin (micrometric) liquid films. Nevertheless, no experimental systems are available that allow real-time observation of bacterial processes in liquid films of controlled thickness. We propose a novel, inexpensive, easily operated experimental platform, termed the porous surface model (PSM) that enables quantitative real-time microscopic observations of bacterial growth and activity under controlled unsaturated conditions. Bacteria are inoculated on a porous ceramic plate, wetted by a liquid medium. The thickness of the liquid film at the surface of the plate is set by imposing suction, corresponding to soil matric potential, to the liquid medium. The utility of the PSM was demonstrated using Pseudomonas putida KT2440 tagged with gfp as a model bacterium. Single cells were inoculated at the surface of the PSM, and the rate at which colonies expanded laterally was measured for three matric potentials (−0.5, −1.2, and −3.6 kPa). The matric potential exerted significant influence on colony expansion rates, with a faster rate of spreading at −0.5 than at −1.2 or −3.6 kPa (diameter increase rate, ca. 1,000, 200, and 17 μm h−1, respectively). These differences can be attributed to cell motility, strongly limited under the most negative matric potential. The PSM constitutes a tool uniquely adapted to study the influence of liquid film geometry on microbial processes. It should therefore contribute to uncovering mechanisms of microbial adaptation to unsaturated environments.

scholarly journals Transcriptome Dynamics of Pseudomonas putida KT2440 under Water Stress

2011 ◽  
Vol 78 (3) ◽  
pp. 676-683 ◽  
Author(s):  
Gamze Gülez ◽  
Arnaud Dechesne ◽  
Christopher T. Workman ◽  
Barth F. Smets
Keyword(s):  
Gene Expression ◽  
Pseudomonas Putida ◽  
Unsaturated Soils ◽  
Water Deprivation ◽  
Expression Profiles ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Surface Model ◽  
Matric Potential ◽  
Peg 8000

ABSTRACTWater deprivation can be a major stressor to microbial life in surface and subsurface soil. In unsaturated soils, the matric potential (Ψm) is often the main component of the water potential, which measures the thermodynamic availability of water. A low matric potential usually translates into water forming thin liquid films in the soil pores. Little is known of how bacteria respond to such conditions, where, in addition to facing water deprivation that might impair their metabolism, they have to adapt their dispersal strategy as swimming motility may be compromised. Using the pressurized porous surface model (PPSM), which allows creation of thin liquid films by controlling Ψm, we examined the transcriptome dynamics ofPseudomonas putidaKT2440. We identified the differentially expressed genes in cells exposed to a mild matric stress (−0.4 MPa) for 4, 24, or 72 h. The major response was detected at 4 h before gradually disappearing. Upregulation of alginate genes was notable in this early response. Flagellar genes were not downregulated, and the microarray data even suggested increasing expression as the stress prolonged. Moreover, we tested the effect of polyethylene glycol 8000 (PEG 8000), a nonpermeating solute often used to simulate Ψm, on the gene expression profile and detected a different profile than that observed by directly imposing Ψm. This study is the first transcriptome profiling of KT2440 under directly controlled Ψmand also the first to show the difference in gene expression profiles between a PEG 8000-simulated and a directly controlled Ψm.

scholarly journals Visualization of Surface Acoustic Waves in Thin Liquid Films

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
R. W. Rambach ◽  
J. Taiber ◽  
C. M. L. Scheck ◽  
C. Meyer ◽  
J. Reboud ◽  
...  
Keyword(s):  
Liquid Film ◽  
Acoustic Waves ◽  
Low Cost ◽  
Thin Liquid Film ◽  
Surface Acoustic Waves ◽  
Liquid Films ◽  
Theoretical Description ◽  
Propagation Path ◽  
Microfluidic Channels ◽  
Potential Applications

Abstract We demonstrate that the propagation path of a surface acoustic wave (SAW), excited with an interdigitated transducer (IDT), can be visualized using a thin liquid film dispensed onto a lithium niobate (LiNbO3) substrate. The practical advantages of this visualization method are its rapid and simple implementation, with many potential applications including in characterising acoustic pumping within microfluidic channels. It also enables low-cost characterisation of IDT designs thereby allowing the determination of anisotropy and orientation of the piezoelectric substrate without the requirement for sophisticated and expensive equipment. Here, we show that the optical visibility of the sound path critically depends on the physical properties of the liquid film and identify heptane and methanol as most contrast rich solvents for visualization of SAW. We also provide a detailed theoretical description of this effect.

Dynamics of Developing Laminar Non-Newtonian Falling Liquid Films With Free Surface

1978 ◽  
Vol 45 (1) ◽  
pp. 19-24 ◽  
Author(s):  
V. Narayanamurthy ◽  
P. K. Sarma
Keyword(s):  
Liquid Film ◽  
Power Law ◽  
Mathematical Formulation ◽  
Liquid Films ◽  
Interfacial Shear ◽  
Newtonian Liquid ◽  
Power Law Model ◽  
Falling Liquid Film ◽  
Falling Liquid Films ◽  
Special Case

The dynamics of accelerating, laminar non-Newtonian falling liquid film is analytically solved taking into account the interfacial shear offered by the quiescent gas adjacent to the liquid film under adiabatic conditions of both the phases. The results indicate that the thickness of the liquid film for the assumed power law model of the shear deformation versus the shear stress is influenced by the index n, the modified form of (Fr/Re). The mathematical formulation of the present analysis enables to treat the problem as a general type from which the special case for Newtonian liquid films can be derived by equating the index in the power law to unity.

Study of the Fluid Dynamics of Thin Liquid Films Flowing Down a Vertical String With Counterflow of Gas

2015 ◽  
Author(s):  
Zezhi Zeng ◽  
Gopinath Warrier ◽  
Y. Sungtaek Ju
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Film Thickness ◽  
Liquid Film ◽  
Direct Contact ◽  
High Speed ◽  
Small Diameter ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Liquid Coolant

Direct-contact heat transfer between a falling liquid film and a gas stream yield high heat transfer rates and as such it is routinely used in several industrial applications. This concept has been incorporated by us into the proposed design of a novel heat exchanger for indirect cooling of steam in power plants. The DILSHE (Direct-contact Liquid-on-String Heat Exchangers) module consists of an array of small diameter (∼ 1 mm) vertical strings with hot liquid coolant flowing down them due to gravity. A low- or near-zero vapor pressure liquid coolant is essential to minimize/eliminate coolant loss. Consequently, liquids such as Ionic Liquids and Silicone oils are ideal candidates for the coolant. The liquid film thickness is of the order of 1 mm. Gas (ambient air) flowing upwards cools the hot liquid coolant. Onset of fluid instabilities (Rayleigh-Plateau and/or Kapitza instabilities) result in the formation of a liquid beads, which enhance heat transfer due to additional mixing. The key to successfully designing and operating DILSHE is understanding the fundamentals of the liquid film fluid dynamics and heat transfer and developing an operational performance map. As a first step towards achieving these goals, we have undertaken a parametric experimental and numerical study to investigate the fluid dynamics of thin liquid films flowing down small diameter strings. Silicone oil and air are the working fluids in the experiments. The experiments were performed with a single nylon sting (fishing line) of diameter = 0.61 mm and height = 1.6 m. The inlet temperature of both liquid and air were constant (∼ 20 °C). In the present set of experiments the variables that were parametrically varied were: (i) liquid mass flow rate (0.05 to 0.23 g/s) and (ii) average air velocity (0 to 2.7 m/s). Visualization of the liquid flow was performed using a high-speed camera. Parameters such as base liquid film thickness, liquid bead shape and size, velocity (and hence frequency) of beads were measured from the high-speed video recordings. The effect of gas velocity on the dynamics of the liquid beads was compared to data available in the open literature. Within the range of gas velocities used in the experiments, the occurrence of liquid hold up and/or liquid blow over, if any, were also identified. Numerical simulations of the two-phase flow are currently being performed. The experimental results will be invaluable in validation/refinement of the numerical simulations and development of the operational map.

A Deformable Surface Model for Real-Time Water Drop Animation

2012 ◽  
Vol 18 (8) ◽  
pp. 1281-1289 ◽  
Author(s):  
Yizhong Zhang ◽  
Huamin Wang ◽  
Shuai Wang ◽  
Yiying Tong ◽  
Kun Zhou
Keyword(s):  
Real Time ◽  
Water Drop ◽  
Surface Model ◽  
Deformable Surface ◽  
Deformable Surface Model

scholarly journals Liquid Films Falling Down a Vertical Fiber: Modeling, Simulations and Experiments

Fluids ◽  
2021 ◽  
Vol 6 (8) ◽  
pp. 281
Author(s):  
Yadong Ruan ◽  
Ali Nadim ◽  
Lekha Duvvoori ◽  
Marina Chugunova
Keyword(s):  
Velocity Profile ◽  
Liquid Film ◽  
Control Volume ◽  
Plug Flow ◽  
Traveling Wave Solutions ◽  
Liquid Films ◽  
Physical Experiments ◽  
Theoretical Predictions ◽  
Viscous Liquid Film ◽  
Linear Drag

We provide a new framework for analyzing the flow of an axisymmetric liquid film flowing down a vertical fiber, applicable to fiber coating flows and those in similar geometries in heat exchangers, water treatment, and desalination processes. The problem considered is that of a viscous liquid film falling under the influence of gravity and surface tension on a solid cylindrical fiber. Our approach is different from existing ones in that we derive our mathematical model by using a control-volume approach to express the conservation of mass and axial momentum in simple and intuitively appealing forms, resulting in a pair of equations that are reminiscent of the Saint-Venant shallow-water equations. Two versions of the model are obtained, one assuming a plug-flow velocity profile with a linear drag force expression, and the other using the fully-developed laminar velocity profile for a locally uniform film to approximate the drag. These can, respectively, model high- and low-Reynolds number regimes of flow. Linear stability analyses and fully nonlinear numerical simulations are presented that show the emergence of traveling wave solutions representing chains of identical droplets falling down the fiber. Physical experiments with safflower oil on a fishing line are also undertaken and match the theoretical predictions from the laminar flow model well when machine learning methods are used to estimate the parameters.

scholarly journals Construction of micro-nano electrochemical sensing interfaces for real-time monitoring of single cells

2020 ◽  
Vol 51 (3) ◽  
pp. 359-373
Author(s):  
Yu-Ting Qi ◽  
Fu-Li Zhang ◽  
Si-Yu Tian ◽  
Xiao-Ke Yang ◽  
Yan-Ling Liu ◽  
...  
Keyword(s):  
Real Time ◽  
Single Cells ◽  
Electrochemical Sensing ◽  
Real Time Monitoring
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