Ultra-rapid flow-through polymerase chain reaction microfluidics using vapor pressure

A novel flow-through polymerase chain reaction (PCR) microfluidic system using vapor pressure was developed that can achieve ultra-rapid, small-volume DNA amplification on a chip. The 40-cycle amplification can be completed in as little as 120 s, making this device the fastest PCR system in the world. The chip device is made of a pressure-sensitive polyolefin (PSP) film and cyclo-olefin polymer (COP) substrate which was processed by cutting-work to fabricate the microchannel. The enclosed structure of the microchannel was fabricated solely by weighing the PSP film on the COP substrate, resulting in superior practical application. The vapor pressure in the denaturation zone of the destabilizing flow source was applied to the flow force, and ultra-rapid, efficient amplification was accomplished with a minimal amount of PCR reagents for detection. The flowing rhythm created by vapor pressure minimized the residual PCR products, leading to highly efficient amplification. For field test analysis, airborne dust was collected from a public place and tested for the presence of anthrax. The PCR chip had sufficient sensitivity for anthrax identification. The fastest time from aerosol sampling to detection was theoretically estimated as 8 min.     

A vapor pressure deficit effect on crop canopy photosynthesis

Canopy CO₂-exchange rates (CER), air temperatures, and dew points were measured throughout ten days during the 1987 growing season for cotton (Gossypium hirsutum L.), grain sorghum [Sorghum bicolor (L) Moench], and five soybean [Glycine max (L) Merr.] cultivars, and throughout seven days in 1988, on maize (Zea maize L.). The objective was to determine if the decline in CER per unit light during the afternoon is associated with a vapor pressure deficit (VPD) increase. Some of the soybean and maize plots were kept as dry as possible. A VPD term significantly contributed (P0.05) to a canopy CER regression model in 54 of 80 data sets in 1987. Grain sorghum was less sensitive than the well-watered soybean genotypes to an increasing VPD (P0.05) on three of the ten measurement days and less sensitive than cotton (P0.05) on only one day. Cotton demonstrated less VPD sensitivity than soybean (P0.05) on one day. The moisture stressed soybean plots showed a greater CER sensitivity to VPD (P0.05) than the well-watered soybean plots. In 1988, the frequently irrigated maize plots were less sensitive to VPD (P0.05) than the rain-fed plots early in the season, before the rain-fed plots were excessively damaged by moisture stress. These results indicate that the afternoon declines in canopy CER found in a number of different species are associated with increases in the VPD; recent work of others suggests that this may be due to partial stomatal closure.Abbreviations CER carbon dioxide exchange rate - VPD vapor pressure deficit - PPFD photosynthetic photon flux density - DAP days after planning     

The effect of high pressure sodium vapor lamps on the rat

The effect of high pressure sodium vapor lamps and daylight-simulating fluorescent lights on the growth, hematology, and behavior of Sprague-Dawley rats has been investigated. Rats weaned under the sodium vapor lamps had slightly heavier adrenals than those exposed to the daylight lamps when the two lighting systems were equalized either for total irradiance or for scotopic illuminance. However, no differences were observed in the tail-flick response, hot plate response, or swimming endurance of rats housed under the two lighting conditions. No consistent differences were seen in the hemoglobin, red and white cell count, hematocrit, and mean cell volume between rats weaned under the high pressure sodium vapor lamps and daylight-simulating fluorescent lights.     

New expressions to describe solution nonideal osmotic pressure, freezing point depression, and vapor pressure.

New empirical expressions for osmotic pressure, freezing point depression, and vapor pressure are proposed based on the concepts of volume occupancy and (or) hydration force. These expressions are in general inverse relationships in comparison to the standard ideal expressions for the same properties. The slopes of the new equations are determined by the molecular weight of the solute and known constants. The accuracy and precision of the molecular weights calculated from the slope are identical and approximately 1% for the experiments reported here. The nonideality of all three colligative expressions is described by a dimensionless constant called the solute-solvent interaction parameter I. The results on sucrose have the same I = 0.26 for all three solution properties. The nonideality parameter I increased from 0.26 on sucrose to 1.7 on hemoglobin to successfully describe the well-known nonideal response of macromolecules.     

High vapor pressure perfluorocarbons cause vesicle fusion and changes in membrane packing

Perfluorocarbons (PFCs) hold great promise for biomedical applications. However, relatively little is known about the impact of these chemicals on membranes. We used unilamellar vesicles to explore the effects of PFCs on membrane packing and vesicle stability. Four clinically relevant PFCs with varying vapor pressures (PP1, 294 mbar; PP2, 141 mbar; PP4, 9.6 mbar; and PP9, 2.9 mbar) were examined. Microscopy imaging and spectroscopic measurements suggest that PFCs, especially those with high vapor pressures, lead to vesicle fusion within hours. Upon exposure to PP1 and PP2 for 72 h, vesicles retained a spherical shape, but the size changed from ∼200 nm to ∼20-40 μm. In addition, membrane packing underwent marked changes during this timeframe. A significant decrease in water content in the lipid polar headgroup regions occurred during the first 1-2-h exposure to PFCs, followed by a steady increase in water content over time. Possible mechanisms were proposed to explain these dramatic structural changes. The finding that chemically inert PFCs exhibited fusogenic activity and marked changes in membrane surface packing is novel, and should be considered when using PFCs for biomedical applications.     

Stomatal response of populus clones to light intensity and vapor pressure deficit

Responses of stomata of clones of Populus candicans Ait. × P. berolinensis Dipp. and Populus deltoides Bartr. × P. caudina (Ten.) Bugala to two levels of light intensity and vapor pressure deficit were studied in controlled environments. Significant stomatal responses to light and vapor pressure deficit were observed. Interactive effects of low light intensity and high vapor pressure deficit elicited greater stomatal closure than was obtained under low light or high vapor pressure deficit alone, indicating adaptation for increased water use efficiency under conditions unfavorable for photosynthesis relative to transpiration. Adaxial stomata of both clones were more sensitive than abaxial stomata to changing vapor pressure deficit and light intensity. Stomatal response to vapor pressure deficit appeared to be independent of bulk leaf water status. Stomata of P. candicans × P. berolinensis were more sensitive than stomata of P. deltoides × P. caudina to a change in vapor pressure deficit and less sensitive to a change in light intensity. The sensitivity of stomata of P. candicans × P. berolinensis to vapor pressure deficit may be related to drought resistance in its parentage (P. berolinensis).     

Continuum reaction field calculation of dielectric constant and vapor pressures for water and carbon disulfide.

Continuum reaction field theory is applied to calculations of dielectric constant, contribution of intermolecular interactions to the free energy of a liquid, and heat of vaporization. Introduction of repulsive interactions and the use of one adjustable parameter, the free volume, enables prediction of vapor pressures. The calculations are illustrated for a simple nonpolar liquid, carbon disulfide, and for liquid water. It is shown that when Onsager's equation is rearranged to a quadratic equation, and a recently found value of the polarizability is employed, its solutions for liquid water yield good agreement with experimental values throughout the whole temperature range. The decrease of the dielectric constant with temperature is essentially linear with the inverse of absolute temperature, but there is additional significant decrease due to the decrease of density with temperature. The relatively high value of the heat of vaporization of liquid water is expressed in terms of large dipolar interaction of a water molecule with the environment, which is due to polarization effects.     

Effect of water vapor pressure on the thermal decomposition of 2-chloroethylphosphonic Acid

Decomposition of 2-chloroethylphosphonic acid (Ethephon) was studied in dried films at various water vapor pressures (0.6 to 86.9 millimeters Hg, 3.2 to 93.9% relative humidity) and temperatures (20, 30, 40, and 50 C) at pH 6.3 and 7.0. The rate of decomposition could be determined equally well by [¹⁴C]Ethephon or ethylene measurements. The rate increases at increasing water vapor pressures at a constant temperature and pH, up to an optimum. The optimum vapor pressure for decomposition approximately doubles for each 10 C increase. The activation energy for the decomposition reaction in water vapor pressures of 3.2 to 12 millimeters Hg is 8.7 and 14.3 kilocalories per mole at pH 6.3 and 7.0, respectively.