Problem: Hydrostatic gauges (such as the mercury column manometer) consist of a vertical column of liquid in a tube whose ends are exposed to different pressures. The column will rise or fall until its weight is in equilibrium with the pressure differential between the two ends of the tube. The simplest design is a closed-end U-shaped tube, one side of which is connected to the region of interest. Any fluid can be used, but mercury is preferred for its high density and low vapour pressure. Simple hydrostatic gauges can measure pressures ranging from 1 torr (100 Pa) to above atmospheric. An important variation is the McLeod gauge which isolates a known volume of vacuum and compresses it to multiply the height variation of the liquid column. The McLeod gauge can measure vacuums as high as 10−6 torr (0.1 mPa), which is the lowest direct measurement of pressure that is possible with current technology. Other vacuum gauges can measure lower pressures, but only indirectly by measurement of other pressure-controlled properties. These indirect measurements must be calibrated via a direct measurement, most commonly a McLeod gauge.
What is the density level of mercury in the air?
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Answer: unanswerable


Problem: The City of Tucson, Pima County, the State of Arizona, and the private sector have all made commitments to create a growing, healthy economy[citation needed] with advanced technology industry sectors as its foundation. Raytheon Missile Systems (formerly Hughes Aircraft Co.), Texas Instruments, IBM, Intuit Inc., Universal Avionics, Honeywell Aerospace, Sunquest Information Systems, Sanofi-Aventis, Ventana Medical Systems, Inc., and Bombardier Aerospace all have a significant presence in Tucson. Roughly 150 Tucson companies are involved in the design and manufacture of optics and optoelectronics systems, earning Tucson the nickname "Optics Valley".
How many optics-related companies are in Tucson?
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Answer: 150


Problem: The majority of British Jews live in London, with significant Jewish communities in Stamford Hill, Stanmore, Golders Green, Finchley, Hampstead, Hendon and Edgware in North London. Bevis Marks Synagogue in the City of London is affiliated to London's historic Sephardic Jewish community. It is the only synagogue in Europe which has held regular services continuously for over 300 years. Stanmore and Canons Park Synagogue has the largest membership of any single Orthodox synagogue in the whole of Europe, overtaking Ilford synagogue (also in London) in 1998. The community set up the London Jewish Forum in 2006 in response to the growing significance of devolved London Government.
When was the London Jewish Forum established?
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Answer:
2006