Can gel concentration gradients improve two-dimensional DNA displays?

2014 ◽  
Vol 35 (5) ◽  
pp. 736-745
Author(s):  
David Sean ◽  
Yixuan E. Wang ◽  
Gary W. Slater
Keyword(s):  
Two Dimensional ◽  
Concentration Gradients

Finite Element Study of Oxygen Diffusion in the Intervertebral Disc

2000 ◽  
Author(s):  
E. Sélard ◽  
A. Shirazi-Adl ◽  
J. P. G. Urban
Keyword(s):  
Intervertebral Disc ◽  
Blood Supply ◽  
Oxygen Diffusion ◽  
Consumption Rate ◽  
The Body ◽  
Cellular Viability ◽  
Two Dimensional ◽  
Concentration Gradients ◽  
Exchange Area ◽  
The Matrix

Abstract The intervertebral disc consists of a water-rich extra-cellular matrix which is synthesized and maintained by its cells. The disc is the largest avascular tissue in the body with its cells lying as much as 8mm away from the blood supply. Nutrients, essential for maintaining cellular viability, diffuse through the matrix from blood supply under a concentration gradient arising from cellular demand. The oxygen concentration gradients in the intervertebral disc are investigated to examine the effects of exchange area and disc thickness on oxygen flux in the disc. The concentration gradients are computed using the two-dimensional Poisson’s equation and measured values for oxygen consumption rate and oxygen diffusion.

Field measurement and modelling of two-dimensional river mixing

2001 ◽  
Vol 1 (2) ◽  
pp. 57-65 ◽  
Author(s):  
G. Putz ◽  
D.W. Smith
Keyword(s):  
Water Quality ◽  
Computer Modelling ◽  
Water Quality Management ◽  
Water Quality Monitoring ◽  
Two Dimensional ◽  
Concentration Gradients ◽  
Athabasca River ◽  
Transverse Mixing ◽  
Treatment Facilities ◽  
Receiving Stream

Wastewater treatment facilities commonly discharge effluent to large receiving streams. An effluent plume may easily extend for many tens of kilometres downstream of a discharge point. A characteristic of the effluent plume is the existence of significant transverse concentration gradients in the river as the discharged effluent slowly mixes with the river water. Within this two-dimensional, transverse mixing zone accurate delineation of the effluent plume is essential for water quality monitoring and for management of the receiving stream. The capability to mathematically model two-dimensional river mixing and to predict effluent plume concentrations is a valuable tool for water quality management. An overview of two-dimensional river mixing theory is presented. Tracer methods for delineating effluent plumes resulting from continuous or transient input to rivers are described, and the results of tracer studies conducted on the Athabasca River in western Canada are presented. A computer modelling procedure for simulating two-dimensional river mixing is described. Application of the model is explained and comparison of model output to measured tracer concentrations is presented.

scholarly journals Facile Fabrication of “Dual Click” One- and Two-Dimensional Orthogonal Peptide Concentration Gradients

2013 ◽  
Vol 14 (3) ◽  
pp. 665-671 ◽  
Author(s):  
Yanrui Ma ◽  
Jukuan Zheng ◽  
Emily F. Amond ◽  
Christopher M. Stafford ◽  
Matthew L. Becker
Keyword(s):  
Two Dimensional ◽  
Concentration Gradients ◽  
Peptide Concentration ◽  
Facile Fabrication

scholarly journals NUMERICAL MODELLING OF SUSPENDED SEDIMENT

1974 ◽  
Vol 1 (14) ◽  
pp. 65
Author(s):  
Brian A. O'Connor ◽  
Samir Zein
Keyword(s):  
Suspended Sediment ◽  
Eddy Diffusion ◽  
Suspended Sediment Transport ◽  
Physical Parameters ◽  
Advection Equation ◽  
Two Dimensional ◽  
Concentration Gradients ◽  
Vertical Diffusion ◽  
Fall Velocity ◽  
Time Step

The present paper describes the application of a two-dimensional numerical suspended sediment model to problems having analytical solutions, as well as to laboratory and field situations. The model is based upon an implicit finite-difference solution to a two-* dimensional (longitudinal and vertical) diffusion-advection equation for suspended sediment transport. Horizontal eddy diffusion is neglected in comparison with vertical diffusion and vertical water motion is assumed negligible in comparison with the sediment fall velocity. The various applications indicate that the greatest errors in the model are due to large spatial concentration gradients and that errors can be controlled by a suitable choice of space and time step. In addition, it is considered that the model has great flexibility and seems to have an acceptable level of accuracy, at least in the field situations tested, provided the physical parameters of the model can also be determined accurately.

Two-dimensional effects in double-diffusive convection

1974 ◽  
Vol 63 (3) ◽  
pp. 577-592 ◽  
Author(s):  
J. S. Turner ◽  
C. F. Chen
Keyword(s):  
Two Dimensional ◽  
Double Diffusive Convection ◽  
Mechanism Of Formation ◽  
Concentration Gradients ◽  
One Dimensional ◽  
Horizontal Gradients ◽  
Diffusive Convection ◽  
Similar Density ◽  
Double Diffusive ◽  
Vertical Gradients

The limitations of existing one-dimensional experiments on double-diffusive convection are discussed, and a variety of new two-dimensional phenomena are described. We have used the sugar-salt system and shadowgraph photography to make exploratory studies of motions which can arise in a fluid with two smooth, opposing, vertical concentration gradients, with and without horizontal gradients. Many different effects have been observed, the most important of which are the following, (a) In the ‘finger’ case, local disturbances can propagate rapidly as wave motions, which cause a simultaneous breakdown to convection over large horizontal distances. (b) Layers formed in the’ diffusive’ sense overturn locally to produce fingers, but propagate more slowly, as convective rather than wave motions, (c) A series of layers, separated by diffusive interfaces, can become unstable, in the sense that successive layers merge in time as their densities become equal, (d) The presence of horizontally separated sources of water of similar density but differentT,Scharacteristics can lead to the development of strong vertical gradients and extensive quasi-horizontal layering.Most of our results are qualitative, but it is hoped that they will stimulate further quantitive work on each of the new processes described. It is already clear that much more needs to be done before the mechanism of formation of layers observed in the ocean can be regarded as properly understood.

Growth of microorganisms in two-dimensional steady-state diffusion gradients

1973 ◽  
Vol 19 (1) ◽  
pp. 53-58 ◽  
Author(s):  
D. E. Caldwell ◽  
P. Hirsch
Keyword(s):  
Steady State ◽  
Gradient System ◽  
Two Dimensional ◽  
Concentration Gradients ◽  
Differential Growth ◽  
Waste Products ◽  
State Diffusion ◽  
Test Organisms ◽  
Rhodomicrobium Vannielii ◽  
Steady State Diffusion

A two-dimensional, steady-state diffusion system has been devised for growth of microorganisms in nutrient concentration gradients. Two reservoirs continually supply substrates, while unused substrates and waste products are washed into a third reservoir. Substrates are supplied in the form of a steady-state gradient within an agar sheet which contains the test organisms. Microbial populations can thus be exposed to all values and combinations of two test variables. The system was tested with Escherichia coli grown in glucose and bicarbonate gradients. Hyphomicrobium sp., Rhodomicrobium vannielii, and Thiopedia sp. in a mixed population were segregated by use of a gradient system of methylamine and sodium sulfide. Exposure of natural aquatic populations to a gradient of pond mud and acetate resulted in differential growth of Bacillus sp. and rod-shaped bacteria with terminal endospores. Thus the potential value of gradients in predicting the response of natural microbial communities to nutrients or toxicants and in enriching for specific organisms has been demonstrated qualitatively.

Instabilities induced by concentration gradients in dusty gases

2001 ◽  
Vol 435 ◽  
pp. 247-260 ◽  
Author(s):  
JUAN A. HERNÁNDEZ
Keyword(s):  
Mass Fraction ◽  
Fluidized Beds ◽  
Physical Mechanism ◽  
Volume Fraction ◽  
Numerical Code ◽  
Two Dimensional ◽  
Concentration Gradients ◽  
Low Volume ◽  
The Stability ◽  
Small Disturbances

This paper deals with the stability of suspensions modelled as dusty gases for non-uniform profiles of mass fraction of particles. It is known that a stationary uniform fluidized bed may be unstable to small disturbances which grow until a secondary instability develops forming bubbles that rise through the bed. Interactions between particles are difficult to model and this makes it necessary to close the model with some assumptions. However, in dilute fluidized beds which are characterized by a low volume fraction of particles, interactions between particles are negligible and this motivates the study of instabilities of suspensions by means of the dusty gas equations, avoiding the problem of particular closures.We show in this work that suspensions blown to regions of higher concentration are unstable to two-dimensional disturbances. An equation which governs this instability is obtained. A physical mechanism is proposed to explain this instability and it is related to the Rayleigh–Taylor one in the limit of long characteristic lengthscales associated with the concentration profile. Finally, the evolution of this instability is followed using a fully nonlinear numerical code showing the formation of streamers and clusters of particles.

Conversion Enhancement of Fixed-Bed Reactors Using Two-Dimensional Hollow Cylindrical Catalyst Pellet

2013 ◽  
Vol 11 (1) ◽  
pp. 159-168 ◽  
Author(s):  
Mohammad Asif
Keyword(s):  
Pressure Drop ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Two Dimensional ◽  
Concentration Gradients ◽  
Fixed Bed Reactors ◽  
Catalyst Pellet ◽  
Conversion Level ◽  
Catalyst Pellets ◽  
Rigorous Model

Abstract The key challenge in the operation of any industrial fixed-bed heterogeneous reactor is to enhance the conversion level while keeping the pressure-drop low. Towards this end, the use of finite hollow cylindrical catalyst pellets instead of spherical ones is proposed here. The absence of the pellet core helps to lower the effect of the internal mass transport resistance besides providing a greater surface area. Another equally important advantage is a lower pressure-drop due to the higher bed void fraction associated with hollow pellets. A rigorous model of the heterogeneous fixed-bed reactor containing finite hollow cylindrical catalyst pellet is presented here accounting for the concentration gradients both in the axial as well as the radial directions, thus, resulting in a two-dimensional partial differential equation for the solid catalytic phase.

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