SUMMARY / RELATED TOPICS

Vapor pressure

Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system. The equilibrium vapor pressure is an indication of a liquid's evaporation rate, it relates to the tendency of particles to escape from the liquid. A substance with a high vapor pressure at normal temperatures is referred to as volatile; the pressure exhibited by vapor present above a liquid surface is known as vapor pressure. As the temperature of a liquid increases, the kinetic energy of its molecules increases; as the kinetic energy of the molecules increases, the number of molecules transitioning into a vapor increases, thereby increasing the vapor pressure. The vapor pressure of any substance increases non-linearly with temperature according to the Clausius–Clapeyron relation; the atmospheric pressure boiling point of a liquid is the temperature at which the vapor pressure equals the ambient atmospheric pressure.

With any incremental increase in that temperature, the vapor pressure becomes sufficient to overcome atmospheric pressure and lift the liquid to form vapor bubbles inside the bulk of the substance. Bubble formation deeper in the liquid requires a higher temperature due to the higher fluid pressure, because fluid pressure increases above the atmospheric pressure as the depth increases. More important at shallow depths is the higher temperature required to start bubble formation; the surface tension of the bubble wall leads to an overpressure in the small, initial bubbles. Thus, thermometer calibration should not rely on the temperature in boiling water; the vapor pressure that a single component in a mixture contributes to the total pressure in the system is called partial pressure. For example, air at sea level, saturated with water vapor at 20 °C, has partial pressures of about 2.3 kPa of water, 78 kPa of nitrogen, 21 kPa of oxygen and 0.9 kPa of argon, totaling 102.2 kPa, making the basis for standard atmospheric pressure.

Vapor pressure is measured in the standard units of pressure. The International System of Units recognizes pressure as a derived unit with the dimension of force per area and designates the pascal as its standard unit. One pascal is one newton per square meter. Experimental measurement of vapor pressure is a simple procedure for common pressures between 1 and 200 kPa. Most accurate results are obtained near the boiling point of substances and large errors result for measurements smaller than 1kPa. Procedures consist of purifying the test substance, isolating it in a container, evacuating any foreign gas measuring the equilibrium pressure of the gaseous phase of the substance in the container at different temperatures. Better accuracy is achieved when care is taken to ensure that the entire substance and its vapor are at the prescribed temperature; this is done, as with the use of an isoteniscope, by submerging the containment area in a liquid bath. Low vapor pressures of solids can be measured using the Knudsen effusion cell method.

In a medical context, vapor pressure is sometimes expressed in other units millimeters of mercury. This is important for volatile anesthetics, most of which are liquids at body temperature, but with a high vapor pressure. Anesthetics with a higher vapor pressure at body temperature will be excreted more as they are exhaled from the lungs; the Antoine equation is a pragmatic mathematical expression of the relation between the vapor pressure and the temperature of pure liquid or solid substances. It is obtained by curve-fitting and is adapted to the fact that vapor pressure is increasing and concasve as a function of temperature; the basic form of the equation is: log ⁡ P = A − B C + T and it can be transformed into this temperature-explicit form: T = B A − log ⁡ P − C where: P is the absolute vapor pressure of a substance T is the temperature of the substance A, B and C are substance-specific coefficients log is either log 10 or log e A simpler form of the equation with only two coefficients is sometimes used: log ⁡ P = A − B T which can be transformed to: T = B A − log ⁡ P Sublimations and vaporizations of the same substance have separate sets of Antoine coefficients, as do components in mixtures.

Each parameter set for a specific compound is only applicable over a specified temperature range. Temperature ranges are chosen to maintain the equation's accuracy of a few up to 8–10 percent. For many volatile substances, several different sets of parameters are available and used for different temperature ranges; the Antoine equation has poor accuracy with any single parameter set when used from a compound's melting point to its critical temperature. Accuracy

Tony DeLap

Tony DeLap was a West Coast artist, known for his abstract sculpture utilizing illusionist techniques and meticulous craftsmanship. As a pioneer of West Coast minimalism and Op Art, DeLap's oeuvre is a testament to his willingness to continuously challenge the viewer's perception of reality. Born in 1927 in Oakland, DeLap grew up in the Bay Area and studied art and graphic design at several Bay Area colleges, including the San Francisco Academy of Art, he attended the Claremont Colleges in Southern California, he returned to the Bay Area, where he taught at the California College of Arts and Crafts, the San Francisco Art Institute and at UC Davis until he secured a teaching position at the newly founded campus of the University of California, Irvine. Bruce Nauman, James Turrell and John McCracken studied with DeLap. Along with artists such as Ellsworth Kelly, DeLap followed a path of Geometric abstraction and Minimal art embracing the principles of limited color, precise craftsmanship, intellectual rigor.

Since the early 1960s, he was associated with an emerging movement of West Coast minimalism referred to as "finish fetish," along with several other artists including Craig Kauffman, Larry Bell, DeWain Valentine. DeLap's work has been exhibited both nationally and internationally. Along with numerous solo exhibitions, DeLap was included in several important group exhibitions of the 1960s including, he died on May 29, 2019 at the age of 91. DeLap's work is including the San Jose Museum of Art. Interview of Delap, part of Los Angeles Art Community - Group Portrait interview series, Center for Oral History Research, UCLA Library Special Collections, University of California, Los Angeles

Glenn Wilson (tennis)

Glenn Wilson is a former professional tennis player from New Zealand. Wilson is from the small farming town of Rai Valley in Marlborough, he and his brother would practice on a floodlit asphalt court their parents had installed on their property. In 1987 to played collegiate tennis for three and a half years, he began playing professionally in the early 1990s and specialised in doubles, in which he reached 160 in the world. His only main draw appearance as a singles player came at the 1994 Tel Aviv Open, where he made it through qualifying, before losing to Andrei Cherkasov in the first round, he had his best year on the doubles circuit in 1995 when he won the Prostějov Challenger with Andrei Pavel and reached the quarter-finals at the ATP Auckland Open, one of four main draw appearances he made in that tournament. In 1997 he represented New Zealand in a Davis Cup tie against Indonesia in Jakarta. Wilson, aged 29, debuted in the reverse singles, a dead rubber which he won in straight sets over Suwandi Suwandi.

This remained his only Davis Cup court appearance. From 2000 to 2003 he acted as non playing captain of New Zealand's Davis Cup team. List of New Zealand Davis Cup team representatives Glenn Wilson at the Association of Tennis Professionals Glenn Wilson at the Davis Cup Glenn Wilson at the International Tennis Federation