Effect of urea concentration on human plaque pH levels in situ

1967 ◽  
Vol 12 (12) ◽  
pp. 1475-1484 ◽  
Author(s):  
I. Kleinberg
Keyword(s):  
Urea Concentration ◽  
Plaque Ph

Urea permeability of alveolar membrane; hemodynamic effects of liquid in the alveolar spaces

1960 ◽  
Vol 198 (5) ◽  
pp. 1029-1031 ◽  
Author(s):  
Cecil E. Cross ◽  
P. Andre Rieben ◽  
Peter F. Salisbury
Keyword(s):  
Urea Concentration ◽  
Hemodynamic Parameters ◽  
Hemodynamic Effects ◽  
Endotracheal Tubes ◽  
Closed Chest ◽  
Lobar Bronchus ◽  
Flow Through ◽  
Isolated Lungs ◽  
Lavage Solution

The blood flow through isolated lungs, excised or in situ, was measured while air or isotonic lavage solution was injected into and withdrawn from the lobar bronchus under variable pressures. Lavage of isolated lobes, intubated via the lobar bronchus with cuffed endotracheal tubes, was also performed in closed-chest experiments while certain hemodynamic parameters were recorded. Urea equilibration between the blood and the alveolar fluid could be expressed as an asymptotic line; the urea concentration of the alveolar fluid reached 30% and 55% of the blood urea concentration when the lavage solution remained in the alveoli for 5 and 15 minutes, respectively. Regardless of the presence or absence of liquid in the alveoli, vascular resistance in the isolated lobe was determined by airway pressure. In closed-chest experiments the hemodynamic effects of pulmonary lavage were minimal as long as low positive and negative pressures were used to inject and withdraw the lavage solution.

Role of Models in Assessing New Agents for Caries Prevention-Non-Fluoride Systems: Reaction Paper

1995 ◽  
Vol 9 (3) ◽  
pp. 312-314
Author(s):  
R.G. Quivey ◽  
A.J. Smith
Keyword(s):  
Quantitative Methods ◽  
Model Systems ◽  
New Agents ◽  
Ph Values ◽  
Plaque Ph ◽  
Micro Organisms ◽  
Over Time ◽  
Do So

Several important issues have been raised concerning the need for consideration of alternatives to fluoride. The principle reason to do so has been the lack of comprehensive effectiveness of fluoride, which in turn reveals incomplete understanding of the caries process. Included among the topics required for clarification of caries initiation would be quantitative methods for relating plaque pH values to the formation of caries. Thus, methods for assessing the activity of anticaries agents over time would be of considerable assistance in monitoring the effects of these test compounds on bacteria. The use of recombinant oral micro-organisms containing genetic fusions, to provide information on the effects of agents on bacteria growing in model systems, is discussed as a possible means of obtaining relevant data in situ.

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

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