Pirani

With the rotary and diffusion pumps in tandem, aided by a liquid-nitrogen trap, a vacuum of 10 Torr became readily attainable between the wars by degrees, as oils and vacuum greases improved, this was inched up towards 10 Torr (a hundred-billionth of atmospheric pressure), but there it stuck. These low pressures were beyond the range of the McLeod gauge and even beyond the Pirani gauge based on heat conduction from a hot filament (limit Torr), and it was necessary to... 

Effect of Different Motivational Schemes on Use of PPE (adapted from Pirani and Reynolds, 1976)... 

Pirani, M., Reynolds, J. (1976). Gearing Up for Safety. Personnel Management, February, 25-29. 

Barbero S, Bajetto A, Bonavia R, Porcile C, Piccioli P, Pirani P, Ravetti JL, Zona G, Spaziante R, Florio T, Schettini G (2002) Expression of the chemokine receptor CXCR4 and its ligand stromal cell-derived factor 1 in human brain tumors and their involvement in glial proliferation in vitro. Ann NY Acad Sci 973 60-69... 

Blaustein MP, Golovina VA (2001) Structural complexity and functional diversity of endoplasmic reticulum Ca(2-i-) stores. Trends Neurosci 24 602-608 Bonavia R, Bajetto A, Barbero S, Pirani P, Florio T, Schettini G (2003) Chemokines and then-receptors in the CNS expression of CXCL12/SDF-1 and CXCR4 and their role in astrocyte proliferation. Toxicol Lett 139 181-189... 

Pirani gage is similar here the change in temperature of the wire is measured by the variation of the wire electrical resistance. The lowest measurable pressure is around 10-3 torr. The calibration (usually for dry air) is a function of the heat conductivity of the gas. Figure 1.30 shows a typical correction to be introduced for different gases. 

Fig. 1.30. Typical pressure correction for a Pirani gage for different gas species (courtesy of Alcatel).

Molecular dynamic studies used in the interpretation of experiments, such as collision processes, require reliable potential energy surfaces (PES) of polyatomic molecules. Ab initio calculations are often not able to provide such PES, at least not for the whole range of nuclear configurations. On the other hand, these surfaces can be constructed to sufficiently good accuracy with semi-empirical models built from carefully chosen diatomic quantities. The electric dipole polarizability tensor is one of the crucial parameters for the construction of such potential energy curves (PEC) or surfaces [23-25]. The dependence of static dipole properties on the internuclear distance in diatomic molecules can be predicted from semi-empirical models [25,26]. However, the results of ab initio calculations for selected values of the internuclear distance are still needed in order to test and justify the reliability of the models. Actually, this work was initiated by F. Pirani, who pointed out the need for ab initio curves of the static dipole polarizability of diatomic molecules for a wide range of internuclear distances. 

Fig. 3. Schematic drawing of the high pressure electron spectrometer. A, Argon ion gun D, differentially pumped region EL, electron lens G, gas cell HSEA, hemispherical electron analyzer LO, two-grid LEED optics LV, leak valve M, long travel rotatable manipulator P, pirani gauge S, sample TSP titanium sublimation pump W, window X, twin anode x-ray source.

It is vital to maintain clean contacts on the connection fitting of the Pirani gauge, because it is very sensitive to resistivity changes due to tarnishing or dust. 

The adsorption of carbon dioxide or oxygen on praseodymium samples was measured by a constant-volume method using a calibrated Pirani vacuum gauge. Praseodymium oxide was heated in oxygen (4 kPa) at 775°C for 1 h, then evacuated at 750°C for 0.5 h just before the measurement. The sample of praseodymium oxychloride was prepared from praseodymium chloride by heating under oxygen flow... 

Thermocouple gauges work on a similar principle but have a thermocouple as sensor connected to a heated platinum filament. The e.m.f. of the thermocouple is measured with a galvanometer or potentiometer. Such gauges have a normal working range from 10 to 10" Torr, but otherwise have characteristics similar to Pirani gauges. 

Hendricks and Ross (1941) Pirani (1963) Wise and Eugster (1964) Glauconites... 

Alterations of basic or intermediate composition eruptive rocks giving celadonite and related minerals (Peyrone, et al , 1965 Pirani,... 

PIRANI (R.), 1963. Sul fillosilicato dei livelli eruttivi di Monte Bonifato di alcamo e di Monte Barbaro di Segesta e sulla validita di uso della nomenclatura binomica Glauconite-celadonite. Min. Petr. Acta , 31-78. 

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