SPECIAL menu

The 'Special' menu contains several utility functions, calculators, and converters.

  •   Simple math calculator This is a basic calculator with some additional keys that are specific to data acquisition.  Along with standard math operations, it contains keys for a number of surface and volume conversions frequently used by physiologists and other scientists.  

    The calculator has an RPN function with addition, subtraction, multiplication, and division (which should be familiar to users of HP desk calculators).   Note that you should use the underline key (_) instead of the minus key (-) for subtraction (this is because the minus key is assumed to indicate a negative number, not subtraction).

  •    The STP adjustment calculator lets you correct for the effects of temperature and pressure on measured flow rates.  'STP' means Standard Temperature and Pressure; by convention this is 760 torr (sea level atmospheric pressure) and 0 degrees C.   The calculator functions for both continuous flow measurement devices and volume measurements (i.e., volume by time), and can account for differential internal pressure in the measurement device.

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  •    ALTITUDE & PRESSURE...     Computes the relationship between pressure and altitude, based on standard meteorological data (Smithsonian tables).  This does not adjust for any effects of weather on local pressure.

    Note that due to rounding errors, the calculations are not 100% reversible (e.g. computing the pressure at a given altitude and then using that computed pressure to calculate altitude will not yield the identical initial altitude -- but it will be very close).

  •       ALTITUDE SIMULATION...     This calculator will compute the appropriate gas concentration to simulate one altitude at the barometric pressure of another altitude.  For example, you might want to use a custom mixture of oxygen and nitrogen in a lab at sea level to simulate the partial pressure of oxygen at high altitude (say, 4000 meters).  Oxygen is the most likely gas of interest but the calculator will also work with other gases.

        

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  •   pO2 ESTIMATION... You can use this calculator to determine the partial pressure of oxygen (pO2) -- or any other gas species in a mixture -- from ambient temperature, ambient pressure (in the gas phase), fractional concentration of the gas species of interest in a dry gas mix, and the percent saturation of water vapor (i.e., relative humidity) in the gas phase. Oxygen (or other gases) are diluted by water vapor, and the degree of that dilution depends on RH and temperature.

    In the example at right, pressure is sea level standard atmospheric pressure(760 torr), temperature is the typical mammalian body temperature (37 °C), etc. Note that at this temperature the saturation vapor pressure of water is about 47.6 torr (this is not affected by the total pressure in the system).

    Other considerations for this calculator:

    • The calculated pO2 value is applicable for the gas phase, and also for dissolved oxygen, as long as the solution is fully saturated with O2
    • The default pressure (torr or kilopascals, kPa) is obtained from the current data file; the default temperature is 37 °C, and the default fractional gas concentration is .2095 (20.95%, the normal oxygen content of dry atmospheric air). 

  •   DISSOLVED OXYGEN... This calculator determines the amount of oxygen dissolved in a given volume water, as a function of partial pressure, temperature, and salinity (dissolved solutes).

    In the example at right, pressure is sea level standard atmospheric pressure (760 torr), temperature 10 °C, the water is fully saturated with oxygen, and there are 2 parts/thousand of dissolved solutes (reasonable for fairly fresh water). The calculator provides the dissolved oxygen per unit volume, and for the total volume.

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  •    METABOLIC ALLOMETRY....     You can use this calculator to estimate metabolic rates and the necessary flow rate (in air or water) for respirometry, based on the maximum tolerable change in oxygen concentration and the size, taxa, and activity of the animal under study.

           The initial popup menu contains some very generalized equations, and also allows you to switch to submenus for specific taxa (arthropods, fish, birds, mammals, etc.).  For most taxa, several different equations are available from different literature sources.  You can also pick an approximate level of activity (resting, moderately active, etc.) -- but be aware that these are estimates based on the allometry of resting metabolism.  The effects of temperature can be included with the Q10 value and body temperature data (see next section for more detail).

  •   Q10 ADJUSTMENT…     This calculates the effect of temperature (Q10) on the rate of reactions or functions -- speed, power, metabolism, etc.   To do that, enter a base temperature and an adjusted temperature, the base value of the rate function, and the Q10 (the default is 2.2), and click the 'compute adjusted value' button.   Alternately, enter the base and adjusted temperatures and the base and adjusted rate values, and compute Q10 by clicking the 'compute Q10. button.   Q10 is the factorial change in rate across a 10 °C temperature change.   The temperature difference (base temperature to adjusted temperature) can be positive or negative.

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  •    CLOSED SYSTEM RESPIROMETRY...     This calculator computes rates of oxygen consumption (VO2) and/or carbon dioxide production (VCO2) in air or other breathable gas mixture in a closed system (i.e, the animal is sealed in an air-tight chamber for some time and metabolism is computed by the change in concentration of O2 and CO2 between initial and final gas samples). You need to enter:
    • chamber temperature, pressure, and relative humidity (when sealed, not at the end of measurements).
    • chamber volume
    • elapsed time (between taking the initial and final gas samples)
    • initial fractional concentrations of O2 (FiO2) and CO2 (FiCO2)
    • the change in concentration (in percent) of oxygen and/or CO2, and the respiratory quotient (RQ)
    If you measure only one of these two gas species, the program will use RQ to estimate the other. If you measure both O2 and CO2 concentration changes, the program will optionally use O2 in the calculation of VCO2. NOTE: it is assumed that sample gas is dried before measurement, and the default settings are:
    • Initial O2 concentration (FiO2) = .2095
    • Initial CO2 concentration (FiCO2) = .0004
    • CO2 is absorbed prior to O2 measurement
    • VCO2 is computed from VO2, if oxygen is measured, or from RQ otherwise

    Equations notes:
    • STP = standard temperature and pressure (0°C, 760 torr)
    • Δ[O2] = fractional change in O2 concentration
    • Δ[CO2] = fractional change in CO2 concentration
    • FeO2 = FiO2 - Δ[O2]
    • FeCO2 = FiCO2 + Δ[CO2]
    VO2 equations:
    • CO2 is absorbed: VO2 = STP volume * Δ[O2] /(1 - FeO2)
    • CO2 NOT absorbed, compute from Δ[CO2]: VO2 = STP volume * (Δ[O2] - (FeO2 * Δ[CO2])/(1 - FeO2)
    • CO2 NOT absorbed, compute from RQ: VO2 = STP volume * (Δ[O2] /(1 - FeO2 * (1-RQ))
    VCO2 equations: NOTE: at typical Δ[CO2], different equations have little effect on calculated VCO2
    • from RQ: VCO2 = STP volume * Δ[CO2]/(1 - FeCO2 * (1-(1/RQ)))
    • from VO2: VCO2 = STP volume * (Δ[CO2] - (FeCO2 * VO2))/(1 - FeCO2)
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  •    DAY OF THE YEAR...     This simple calculator will provide the Julian date (days since December 31) for a combination of date, month, and year.   It should account for leap years.

  •    SUNRISE, SUNSET...     This utility uses the well-known ‘Sunrise equation’ to compute the approximate times of sunrise and sunset from date (month, day, year) and location (degrees latitude and longitude).   You need to select North or South latitude, and East or West longitude relative to the Prime Meridian.
             NOTE: The program expects latitude and longitude in fractional degrees, not degrees and minutes. Thus 27° 30’ north should be entered as ’27.5’ (i.e., halfway between 27° N and 28° N).

    Sun time estimates are approximate for several reasons:

    • Sunrise and sunset times are based on local solar noon (i.e., when the sun is at its zenith (highest above the horizon) from the perspective of the observer’s position.   This is likely to be slightly different from local time.   As defined by people, time zones are arbitrary, and since they are roughly 15 ° of longitude wide and often do not run strictly north and south, sunrise and sunset times can vary by an hour or more with a single time zone.

    • The calculator has no allowance for elevation above sea level (which makes rise times earlier and set times later, if the horizon is at sea level).   It also has no allowance for local topography — for example, if the observer is in a deep valley, the visual horizon is elevated above the ‘real’ horizon, and rise times will be later and set times will be earlier than shown here.

    • The precise times of sunrise and sunset are of concern to astronomers and the like, but for most purposes they are rather ‘fuzzy’ due to the angular diameter of the solar disc (about 32 minutes of arc or 0.53 degrees), atmospheric refraction, etc.

    NOTE: The U.S. Naval Observatory hosts a web page (USNO Sun and Moon Data) that permits very accurate calculations of solar and lunar data.  It incorporates ‘fixes’ for many of the issues described above, and — if you are connected to the internet — can be accessed with the ‘Naval Observatory Website’ button.

    • The 'Get Latitude and Longitude From World Map' button opens a window with a world map (d'oh!) in Mercator projection.   Move the cursor to the desired location and hit either the spacebar or return keys to select that position; as you move the cursor the latitude and longitude boxes at upper left update continuously.   If you want to select a position on a higher-resolution 'regional' map, click the Zoom in X5 button, a rectangular cursor appears; move it until it encloses your area of interest and hit either the spacebar or return keys to enlarge that region.   Then use the cursor and keys to select a position as described above.

    Location data are accurate only to 0.33 degree of longitude and 0.25 degree of latitude on the world map and 0.11 degrees of longitude and latitude on the regional maps, but that should be accurate enough for most sunrise-sunset calculations.

    As geographic references, the maps show the equator (yellow), the Prime or Greenwich Meridian (zero degrees of longitude), the Arctic and Antarctic Circles (~ 66.5 degrees N and S), and the Tropics of Cancer and Capricorn (~ 23.3 degrees N and S). Only a few of these will be visible on the enlarged regional maps.

    Of course, if you want higher-resolution position data (and you are connected to the Internet), use Google Earth.

    • The 'Annual Plot' button will compute and display an entire year's day length cycle, based on latitude-longitude position.   The 'Print Data to Spreadsheet' button makes a tab-delineated .xls spreadsheet containing the annual cycle (date, sunrise time, sunset time, and day length).   This example shows a Polar-region cycle, with complete darkness in winter and 24-hour sunlight in summer:

  •    UNIT CONVERSIONS...     This calculator will convert many commonly-used units into other units. The conversions are arranged by type, selected with the radio buttons on the right of the window. This utility will also estimate certain biophysical and meteorological data. In the example below, solar radiation intensity is estimated as a function of how far the sun is above the horizon.


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