Horizontal jets and vortex dipoles in a stratified fluid

1991 ◽  
Vol 227 ◽  
pp. 543-566 ◽  
Author(s):  
S. I. Voropayev ◽  
Ya. D. Afanasyev ◽  
I. A. Filippov
Keyword(s):  
Fluid Flows ◽  
Stratified Fluid ◽  
Theoretical Explanation ◽  
Thymol Blue ◽  
High Concentration ◽  
Governing Parameter ◽  
Aluminium Powder ◽  
Density Distributions ◽  
Vortex Dipoles ◽  
Short Period

When a horizontal force is applied locally to some volume of a viscous densitystratified fluid, flows with high concentration of vertically oriented vorticity (vortex dipoles) are generated. The processes of generation and evolution with time of these unsteady flows in a stratified fluid are studied. A convenient way to produce and study these flows in the laboratory is to use a submerged horizontal jet as a ‘point’ source of momentum. The main governing parameter (the ‘force’) is easily controlled in this case. Two regimes were studied: starting jets with dipolar vortex fronts (the force acts continuously) and impulsive vortex dipoles (the force acts for a short period of time). A conductivity microprobe, aluminium powder, shadowgraph, thymol-blue and other techniques have been used to measure the velocity and density distributions in the flows. It is found that in both regimes the flows are self-similar: the lengthscale of the flows increases with time as t½ for starting jets and as t1/3 for vortex dipoles. Detailed information about the generation mechanism, kinematics and dynamics of the flows is obtained. On the basis of similarity principles a theoretical explanation of the experimental results is given. The theory is in good agreement with the results obtained.

Factors Affecting Gelation of Lidocaine Hydrochloride-Loaded Polyelectrolyte Complex Thermosensitivity Gel for Dry Socket Treatment

2021 ◽  
Vol 901 ◽  
pp. 111-116
Author(s):  
Nuttawut Supachawaroj ◽  
Sucharat Limsitthichaikoon
Keyword(s):  
Polyelectrolyte Complex ◽  
Gelation Time ◽  
Lidocaine Hydrochloride ◽  
Gelation Temperature ◽  
High Concentration ◽  
Preparation Methods ◽  
Factors Affecting ◽  
Dry Socket ◽  
Short Period ◽  
Gel Preparation

Dry socket disease, a pocket wound caused by the tooth extraction that resulted in severe acute pain which requires a topical analgesic with rapidly pain reduction and suppress the pain until the wound healed. This study aimed to investigate factors affecting gelation temperature and gelation time of lidocaine hydrochloride (LH)-loaded polyelectrolyte complex (PEC) thermosensitivity gel for treating dry socket wound. The first factor was investigated the effects of the ratio of three different types of polymers as chitosan (CS), hyaluronic acid (HA) and poloxamer407 (P407) on the phase transition caused by temperature. The second factor was examined the effects of gel preparation methods. The results showed that increasing concentration of the cationic polymer as CS induced the separation of the solution to gel (sol-to-gel) system due to the charge of CS and the charge of PEC. The ratio of HA:P407 affected the gel forming which high concentration of P407 reduced the gelation temperature while low concentration of HA disturbed the sol-to-gel state causing coagulation. The viscosity, spreadability, and swelling were significantly increased due to the concomitant increased in each polymer, HA and P407. The particle of the formulation observed under microscope was found to be less than 1 µm. Phase inversion from sol-to-gel was found after a min at 23°C. Since gelation temperature of the purposed formula is supposed to form gel below 37°C within a short period of injection. The results of the study indicate the suitable sol-to-gel forming in the appropriate temperature and time which should be used for further investigation in the efficacy and safety.

scholarly journals Induction of Somatic Embryogenesis in Vulnerable Medicinal Plant Hedychium spicatum Buch-Ham ex Smith

2014 ◽  
Vol 23 (2) ◽  
pp. 147-155 ◽  
Author(s):  
Dinesh Giri ◽  
Sushma Tamta
Keyword(s):  
Somatic Embryogenesis ◽  
Medicinal Plant ◽  
Somatic Embryos ◽  
Synthetic Seeds ◽  
Ex Situ ◽  
Secondary Embryogenesis ◽  
Zygotic Embryos ◽  
High Concentration ◽  
Cotyledon Explants ◽  
Short Period

This protocol has been developed for somatic embryogenesis in Hedychium spicatum. Simultaneously, a method has also been developed for the production of synthetic seeds by using somatic embryos. Direct somatic embryos were developed on cotyledon explants of zygotic embryos on MS supplemented with high concentration of NAA (20.0 µM). Induction of secondary embryogenesis was best in 2,4-D supplemented medium fortified with activated charcoal. Germination of somatic embryos was enhanced by using GA3. Besides this, round and semi-hard beads of somatic embryos (synthetic seeds) could be produced by using 2% Na-alginate and 100 mM calcium chloride and more than 30% germination of synthetic seeds was achieved in MS. Well acclimated plants produced via somatic embryogenesis and/or synthetic seeds were transferred to field where more than 60% survived. This simple study enabled us to obtain a number of plantlets throughout the year each cycle requiring a short period of time. Besides propagation, this study provided an ex situ method for conservation of this vulnerable Himalayan species.D. O. I.http://dx.doi.org/10.3329/ptcb.v23i2.17506Plant Tissue Cult. & Biotech. 23(2): 147-155, 2013  (December)

The hydraulics of a stratified fluid flowing through a contraction

1993 ◽  
Vol 251 ◽  
pp. 355-375 ◽  
Author(s):  
Laurence Armi ◽  
Richard Williams
Keyword(s):  
Flow Rate ◽  
Fluid Flows ◽  
Stratified Fluid ◽  
Wave Mode ◽  
Similar Solution ◽  
Constant Density ◽  
Self Similar Solution ◽  
Hydraulic Theory ◽  
Self Similar

The steady hydraulics of a continuously stratified fluid flowing from a stagnant reservoir through a horizontal contraction was studied experimentally and theoretically. As the channel narrows, the flow accelerates through a succession of virtual controls, at each of which the flow passes from sub-critical to supercritical with respect to a particular wave mode. When the narrowest section acts as a control, the flow is asymmetric about the narrowest section, supercritical in the divergent section and self- similar throughout the channel. With increased flow rate a new enclosed self-similar solution was found with level isopycnals and velocity uniform with depth. This flow is only symmetric in the immediate neighbourhood of the narrowest section, and in the divergent section remains supercritical with respect to higher internal modes, has separation isopycnals and splits into one or more jets separated by regions of stagnant, constant-density fluid. Flows which are subcritical with respect to lowest modes can also be asymmetric about the narrowest section for higher internal modes. The experiments are interpreted using steady, inviscid hydraulic theory. Solutions require separation isopycnals and regions of stationary, constant-density fluid in the divergent section.

Controlling factors in localised corrosion morphologies observed for magnesium immersed in chloride containing electrolyte

2015 ◽  
Vol 180 ◽  
pp. 313-330 ◽  
Author(s):  
Geraint Williams ◽  
Nick Birbilis ◽  
H. Neil McMurray
Keyword(s):  
Current Density ◽  
Radial Growth ◽  
Cathodic Current Density ◽  
Nacl Solution ◽  
High Concentration ◽  
Cathodic Current ◽  
Density Distributions ◽  
Filiform Corrosion ◽  
Density Values ◽  
Current Densities

The early stages of localised corrosion affecting magnesium (Mg) surfaces when immersed in aqueous sodium chloride (NaCl) solutions involves the propagation of dark regions, within which both anodic metal dissolution and cathodic hydrogen evolution occur. For nominally “pure” Mg, these dark areas can either take the form of discs which expand radially with time, or filiform-like tracks which lengthen with time. For Mg surfaces which display disc-form corrosion features in concentrated NaCl electrolyte, a transition to filiform corrosion (FFC) is observed as the concentration is decreased, indicating ohmic constraints on radial propagation. A similar effect is observed when Mg specimens of different iron impurity are immersed in a fixed, high concentration NaCl solution, where disc-form corrosion is observed on samples having ≥280 ppm Fe, but FFC predominates at ≤80 ppm Fe. An in situ scanning vibrating electrode technique (SVET) is used to determine current density distributions within the propagating corrosion features. Cathodic current density values of between −100 and −150 A m−2 measured in central areas of disc-like features are sufficient to sustain the radial growth of a local anode at the perimeter of the discs. However, for high purity Mg specimens (≤80 ppm Fe), cathodic current densities of −10 A m−2 or less are measured over FFC affected regions, indicating that linear propagation arises when there is insufficient cathodic current produced on the corroded surface to sustain radial growth. The results are consistent with surface control of localised corrosion propagation in concentrated electrolyte, but ohmic control in dilute, lower conductivity NaCl solution.

Growth and Physiological Effects of Model Acid Rain and Lead Contamination to Tall Fescue Seedlings

2014 ◽  
Vol 665 ◽  
pp. 543-546
Author(s):  
Hui Qin Liu ◽  
Gao Feng Shen ◽  
Yi Liu ◽  
Qin Xu ◽  
Hui Ping Liu ◽  
...  
Keyword(s):  
Tall Fescue ◽  
Total Concentration ◽  
Sugar Content ◽  
Soluble Sugar ◽  
High Stress ◽  
Lead Contamination ◽  
Stress Concentrations ◽  
High Concentration ◽  
Short Period ◽  
Stress Changes

In order to explore phytoremediation and physiological effect of plant to heavy metal, physiological and biochemical changes of tall fescue seedlings were comparatively analyzed when they were contaminated by lead at different times and concentrations. The results showed that: At three lead concentrations, superoxide dismutase (SOD) and peroxidase (POD) activity in tall fescue increased initially and then decreased overall with stress times. Change of POD is slower. It indicated that lead can rapid induce tall fescue protecting enzyme activity at low concentrations or in a short period. Malondialdehyde (MDA) contents were positively correlated with stress time and stress concentrations, which indicated that with the increase of stress concentration and time, membrane lipid peroxidation strengthen. Changes of chlorophyll total concentration increased first and then decreased at low concentration (500 and 1000 mg·L-1), and continued to decline at high concentration. It indicated tall fescue may adapt low lead stress by increasing chlorophyll to, and lose regulation at high concentrations.Proline content decreased initially and then increased with time at 500,1000 mg·L-1, however, it was opposite at 1500 mg·L-1. They were higher than controls, indicating that osmotic adjustment ability enhanced after lead stress. Changes of soluble sugar content were down - up - down with times at three concentrations, eventually they reduced significantly. Therefore, in the process of lead stress, changes of physiological characteristics in tall fescue showed their actively adapt and resistance at low stress, and tolerance and injury at high stress.

Effect of anoxia on intracellular and extracellular potassium activity in hypoglossal neurons in vitro

1991 ◽  
Vol 66 (1) ◽  
pp. 103-111 ◽  
Author(s):  
C. Jiang ◽  
G. G. Haddad
Keyword(s):  
Brain Slice ◽  
Neuronal Response ◽  
Extracellular Potassium ◽  
Intracellular Recordings ◽  
High Concentration ◽  
Slice Preparation ◽  
Adult Rats ◽  
Short Period ◽  
Brain Slice Preparation

1. A brain slice preparation was used to study the hypoglossal (XII) neuronal response to anoxia. Both intra- and extracellular potassium activities (K+i,K+o) were measured by the use of ion-selective microelectrodes, and K+ flux was assessed by the use of pharmacologic blockers. 2. Extracellular recordings showed that a short period of anoxia (4 min) induced an increase in K+o of 26.4 +/- 7.5 mM (mean +/- SD, n = 20) in the XII nucleus of adult rats. 3. Intracellular recordings (n = 31) in XII neurons showed a substantial decrease in K+i during anoxia. Fourteen neurons were analyzed in detail and these showed that XII neurons depolarized to -25.3 +/- 7.7 mV, whereas K+i dropped from 93.6 +/- 14.9 to 32 +/- 9.0 mM. These results strongly suggested that K+ is lost from XII neurons during anoxia. 4. Although the extracellular space (ECS) shrank by approximately 50% during anoxia, the possibility that the increase in K+o and decrease in K+i were mainly caused by shrinkage of the ECS and swelling of intraneuronal space was excluded to a great degree because the changes in K+i and K+o during anoxia were relatively very large. 5. To study the mechanisms by which K+ is lost from XII neurons, we used several pharmacologic blockers. High concentration of ouabain (10 mM) and strophanthidin (80 microM) increased K+o from baseline (3-4 mM) to 40.9 +/- 2.5 mM (n = 6) but did not abolish an additional anoxia-induced increase in K+o, suggesting that mechanisms other than Na(+)-K(+)-adenosine triphosphatase inhibition were also responsible for the anoxia-induced K+ leakage.(ABSTRACT TRUNCATED AT 250 WORDS)

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