Diffusion Cells for Integrating Temperature and Humidity Over Long Periods of Time

1988 ◽  
Vol 125 ◽  
Author(s):  
Fred Trembour ◽  
Franklin L. Smith ◽  
Irving Friedman
Keyword(s):  
Vapor Pressure ◽  
Pressure Gradient ◽  
Pure Water ◽  
Volcanic Glass ◽  
Saturated Solution ◽  
Rubber Stopper ◽  
Centrifuge Tube ◽  
Final Design ◽  
One Year ◽  
Vapor Pressure Gradient

ABSTRACTThe rate of many processes, including the diffusion of water into rhyolitic volcanic glass (obsidian), as well as the racemization of amino acids is temperature dependent, and a knowledge of temperatures integrated over time periods of at least a year is necessary to quantify these processes. The construction and properties of simple devices consisting of small plastic containers that change weight at a rate that is a function of temperature and the activity of water will be described. The cells function because water diffuses through the plastic across a constant vapor-pressure gradient. This vapor-pressure gradient is maintained constant between the substances within the cell and the materials outside the cell. The plastic cells are usually filled with water and surrounded by a dehydrating agent, such as silica gel. A better arrangement is to fill the cell with a mixture of solid sodium chloride (NaCl) and a saturated solution of NaCl, and to surround the cell with pure water. A number of plastics have been investigated, including polycarbonate, polystyrene, tefzel, polyallomer, and methacrylate. The cells have been sealed by various methods including screw caps, room-temperature vulcanizing silicone rubber sealant, and rubber stoppers. The final design consists of a small cell made of a polycarbonate plastic centrifuge tube containing solid NaCl plus NaCl-saturated solution sealed with a rubber stopper and placed in a polypropylene tube containing pure water. Our aim has been to develop cells that are sufficiently sensitive to yield a precision of ±0.2°C when exposed for one year at temperatures that range from 0° to 40°, and that will fit into metal fittings that can be screwed into standard 3/4-inch plastic water pipe (approximately 1 inch outside diameter).

Diffusion Cells for Integrating Temperature and Humidity Over Long Periods of Time

1988 ◽  
Vol 123 ◽  
Author(s):  
Fred Trembour ◽  
Franklin L. Smith ◽  
Irving Friedman
Keyword(s):  
Vapor Pressure ◽  
Pressure Gradient ◽  
Pure Water ◽  
Volcanic Glass ◽  
Saturated Solution ◽  
Rubber Stopper ◽  
Centrifuge Tube ◽  
Final Design ◽  
One Year ◽  
Vapor Pressure Gradient

AbstractThe rate of many processes, including the diffusion of water into rhyolitic volcanic glass (obsidian), as well as the racemization of amino acids is temperature dependent, and a knowledge of temperatures integrated over time periods of at least a year is necessary to quantify these processes. The construction and properties of simple devices consisting of small plastic containers that change weight at a rate that is a function of temperature and the activity of water will be described. The cells function because water diffuses through the plastic across a constant vapor-pressure gradient. This vapor-pressure gradient is maintained constant between the substances within the cell and the materials outside the cell. The plastic cells are usually filled with water and surrounded by a dehydrating agent, such as silica gel. A better arrangement is to fill the cell with a mixture of solid sodium chloride (NaCl) and a saturated solution of NaCl, and to surround the cell with pure water. A number of plastics have been investigated, including polycarbonate, polystyrene, tefzel, polyallomer, and methacrylate. The cells have been sealed by various methods including screw caps, room-temperature vulcanizingsilicone rubber sealant, and rubber stoppers. The final design consists of a small cell made of a polycarbonate plastic centrifuge tube containing solid NaCl plus NaCl-saturated solution sealed with a rubber stopper and placed in a polypropylene tube containing pure water. Our aim has been to develop cells that are sufficiently sensitive to yield a precision of ±0.2° C when exposed for one year at temperatures that range from 0° to 40°, and that will fit into metal fittings that can be screwed into standard 3/4-inch plastic water pipe (approximately 1 inch outside diameter).

scholarly journals EXPERIMENTAL STUDY OF OSMOSIS THROUGH A COLLODION MEMBRANE

1958 ◽  
Vol 42 (2) ◽  
pp. 429-444 ◽  
Author(s):  
Giacomo Meschia ◽  
Ivo Setnikar
Keyword(s):  
Experimental Study ◽  
Hydrostatic Pressure ◽  
Vapor Pressure ◽  
Pressure Gradient ◽  
Molecular Volume ◽  
Experimental Demonstration ◽  
Vapor Pressure Gradient ◽  
Net Transfer

Experiments were carried out on a collodion membrane in order to study the factors that determine direction and magnitude of net flow of water across a membrane permeable to the solvent and to some of the solutes present. The solutes used were all non-ionic. When only one solute was present and there was no difference of hydrostatic pressure across the membrane, water flowed toward the side where its vapor pressure was lower, but the rate of transfer depended upon the nature of the solute: for a given difference in osmolality across the membrane, the rate increased with the molecular volume of the solute and reached its maximum with the solute to which the membrane was impermeable. These results led to the experimental demonstration that in the presence of two or more solutes of different molecular volumes, of which one at least can diffuse through the barrier, the net transfer of water can take place against its vapor pressure gradient. Some of the physicochemical and physiological implications of the data are discussed.

The stomatal response of red alder and black cottonwood to changing water status

1982 ◽  
Vol 12 (4) ◽  
pp. 761-771 ◽  
Author(s):  
S. R. Pezeshki ◽  
T. M. Hinckley
Keyword(s):  
Stomatal Conductance ◽  
Vapor Pressure ◽  
Pressure Gradient ◽  
Soil Water Potential ◽  
Black Cottonwood ◽  
Pressure Potential ◽  
Red Alder ◽  
Xylem Pressure ◽  
Xylem Pressure Potential ◽  
Vapor Pressure Gradient

Response of stomata of newly planted red alder (Alnusrubra Bong.) and black cottonwood (Populustrichocarpa Torr. & Gray) to periods of water stress and changes in light intensity, vapor pressure gradient, and xylem pressure potential were studied in the field and in controlled environments. The results indicated that soil drought had a pronounced effect, reducing stomatal conductance in both species. Lower predawn xylem pressure potential values at the beginning of the day resulted in lower stomatal conductance irrespective of vapor pressure gradient in both species. Under field conditions of high soil water potential, stomatal conductance decreased as xylem pressure potential decreased below −1.0 MPa in black cottonwood and −1.1 MPa in red alder. As soil water potential decreased to −0.13 MPa, the threshold value of xylem pressure potential resulting in stomatal closure shifted from −1.0 to −0.5 MPa in cottonwood; it did not change in alder. Laboratory experiments indicated that cottonwood had greater rates of net photosynthesis on a per-unit leaf-area basis as compared with red alder. The mean maximum photosynthetic rates were 0.46 mg CO2•m−2•s−1 in black cottonwood and 0.25 mg CO2•m−2•s−1 in red alder. Net CO2 uptake also had a temperature optimum around 20 °C when the corresponding relative humidity was about 50%. Both species, when compared with other deciduous hardwoods, could be ranked as relatively drought sensitive.

The effect of minimal differences in the skin-to-air vapor pressure gradient at various dry-bulb temperatures on self-paced exercise performance

2021 ◽  
Author(s):  
Felicity M. Bright ◽  
Brad Clark ◽  
Ollie Jay ◽  
Julien D. Periard
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Relative Humidity ◽  
Vapor Pressure ◽  
Pressure Gradient ◽  
Rectal Temperature ◽  
Exercise Performance ◽  
Perceived Exertion ◽  
Ratings Of Perceived Exertion ◽  
Vapor Pressure Gradient

The effects of dry-bulb temperature on self-paced exercise performance, along with thermal, cardiovascular and perceptual responses, were investigated by minimizing differences in the skin-to-air vapor pressure gradient (Psk,sat-Pa) between temperatures. Fourteen trained male cyclists performed 30-km time trials in 13˚C and 44% relative humidity (RH), 20˚C and 70% RH, 28˚C and 78% RH, and 36˚C and 72% RH. Power output was similar in 13˚C (275±31 W; mean and SD) and 20˚C (272±28 W; P=1.00), lower in 36˚C (228±36 W) than 13˚C, 20˚C and 28˚C (262±27 W; P<0.001) and lower in 28˚C than 13˚C and 20˚C (P<0.001). Peak rectal temperature was higher in 36˚C (39.6±0.4˚C) than all conditions (P<0.001) and higher in 28˚C (39.1±0.4˚C) than 13˚C (38.7±0.3˚C; P<0.001) and 20˚C (38.8˚C±0.3˚C; P<0.01). Heart rate was higher in 36˚C (163±14 beats·min-1) than all conditions (P<0.001) and higher in 20˚C (156±11 beats·min-1; P=0.009) and 28˚C (159±11 beats·min-1; P<0.001) than 13˚C (153±11 beats·min-1). Cardiac output was lower in 36˚C (16.8±2.5 l·min-1) than all conditions (P<0.001) and lower in 28˚C (18.6±1.6 l·min-1) than 20˚C (19.4±2.0 l·min-1; P=0.004). Ratings of perceived exertion were higher in 36˚C than all conditions (P<0.001) and higher in 28˚C than 20˚C (P<0.04). Self-paced exercise performance was maintained in 13˚C and 20˚C at a matched evaporative potential, impaired in 28˚C and further compromised in 36˚C in association with a moderately lower evaporative potential and marked elevations in thermal, cardiovascular and perceptual strain.

Hydration Chamber for Jeolco 200 Kv Microscope

1970 ◽  
Vol 28 ◽  
pp. 542-543
Author(s):  
V. R. Matricardi ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Electron Microscope ◽  
Water Vapor ◽  
Vapor Pressure ◽  
Pressure Gradient ◽  
Room Temperature ◽  
List Type ◽  
Type Number ◽  
Equilibrium Vapor Pressure

In order to observe room temperature hydrated specimens in an electron microscope, the following conditions should be satisfied: The specimen should be surrounded by water vapor as close as possible to the equilibrium vapor pressure corresponding to the temperature of the specimen.The specimen grid should be inserted, focused and photo graphed in the shortest possible time in order to minimize dehydration.The full area of the specimen grid should be visible in order to minimize the number of changes of specimen required.There should be no pressure gradient across the grid so that specimens can be straddled across holes.Leakage of water vapor to the column should be minimized.

Porous Hydroxyapatite with Tailored Crystal Surface Prepared by Hydrothermal Method

2005 ◽  
Vol 284-286 ◽  
pp. 353-356 ◽  
Author(s):  
Koji Ioku ◽  
Giichiro Kawachi ◽  
Nakamichi Yamasaki ◽  
Hirotaka Fujimori ◽  
Seishi Goto
Keyword(s):  
Aspect Ratio ◽  
Vapor Pressure ◽  
Hydrothermal Method ◽  
Saturated Vapor Pressure ◽  
Crystal Surface ◽  
Saturated Vapor ◽  
Pure Water ◽  
Porous Hydroxyapatite ◽  
Exposure Method ◽  
The Mean

Porous plates of hydroxyapatite (Ca10(PO4)6(OH)2; HA) with about 0.5 to 5 mm in thickness and porous HA granules of about 40 µm to 1 mm in size with tailored crystal surface were prepared by the hydrothermal vapor exposure method at the temperatures above 105 °C under saturated vapor pressure of pure water. Porous HA plates with about 75 % porosity prepared at 120 °C were composed of rod-shaped crystals of about 20 µm in length. Porous HA granules prepared at 160 °C were also composed of rod-shaped crystals of about 20 µm in length with the mean aspect ratio of 30. These crystals were elongated along the c-axis. Rod-shaped HA crystals were locked together to make micro-pores of about 0.1 to 0.5 µm in size. Both of materials were nonstoichiometric HA with calcium deficient composition. These materials must have the advantage of adsorptive activity, because they had large specific crystal surface and much micro-pores.

Addressing the siphoning effect in new shunt designs by decoupling the activation pressure and the pressure gradient across the valve

2013 ◽  
Vol 11 (2) ◽  
pp. 181-187 ◽  
Author(s):  
Tobias A. Mattei ◽  
Martin Morris ◽  
Kathleen Nowak ◽  
Daniel Smith ◽  
Jeremy Yee ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Flow Rate ◽  
Fluid Velocity ◽  
Component System ◽  
The Past ◽  
Benchmark Tests ◽  
Final Design ◽  
Actual Flow Rate ◽  
Actual Flow ◽  
Labview Program

Object Although several improvements have been observed in the past few years in shunt technology, currently available systems still present several associated problems. Among these, overdrainage along with its complications remains one of the great challenges for new shunt designs. To address the so-called siphoning effect, the authors provide a practical example of how it is possible to decouple the activation pressure and the pressure gradient across the valve through a 3–key component system. In this new shunt design, the flow is expected to depend only on the intracranial pressure and not on the pressure gradient across the valve, thus avoiding the so-called siphoning effect. Methods The authors used computer models to theoretically evaluate the mechanical variables involved in the operation of the newly designed valve, such as the fluid's Reynolds number, proximal pressure, distal pressure, pressure gradient, actual flow rate, and expected flow rate. After fabrication of the first superscaled model, the authors performed benchmark tests to analyze the performance of the new shunt prototype, and the obtained data were compared with the results predicted by the previous mathematical models. Results The final design of the new paddle wheel valve with the 3–key component antisiphoning system was tested in the hydrodynamics laboratory to prove that the siphoning effect did not occur. According to the calculations obtained using the LabVIEW program during the experiments, each time the distal pressure decreased without an increase in the proximal pressure (despite the range of the pressure gradient), the pin blocked the spinning of the paddle wheels, and the calculated fluid velocity through the system tended to zero. Such a situation was significantly different from the expected flow rate for such a pressure gradient in a siphoning situation without the new antisiphon system. Conclusions The design of this new prototype with a 3–key component antisiphoning system demonstrated that it is possible to decouple the activation pressure and the pressure gradient across the valve, avoiding the siphoning effect. Although further developments are necessary to provide a model compatible to clinical use, the authors believe that this new prototype illustrates the possibility of successfully addressing the siphoning effect by using a simple 3–key component system that is able to decouple the activation pressure and the pressure gradient across the valve by using a separate pressure chamber. It is expected that such proof of concept may significantly contribute to future shunt designs attempting to address the problem of overdrainage due to the siphoning effect.

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