![]() |
SPECIAL menu
|
The SPECIAL menu contains several utility routines useful in respirometry
(STP conversion, altitude and pressure calculations, a metabolism estimates
routine, a routine to compute ventilation) and a simple calculator. For convenience they can be activated from the main plot window by typing specific keys, indicated by ‘key’ on the menu.
• Mathematically impossible operations (such as attempting to take the square root of a negative number) will generate a warning notice (this calculator only deals with real numbers).
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 default salinity value (2 parts/thousand) is reasonable for freshwater. For seawater, use a value of 35 parts/thousand, and for typical physiological saline, use 9 parts/thousand. 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.
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, which are described in the 'help' field to the right). You can also pick the desired output units. The energy equivalence of metabolism (joules per ml of oxygen consumed) can be set with the 'O2 heat equivalence' selection in the "Respirometry" submenu (EDIT menu); the default value is 20.1 joules/ml. The mass coefficient in the allometric equation ('a' value) is adjusted to reflect whatever output unit is in use. Results can be stored for later use. ![]() metabolism = a Mb (where a is the mass coefficient, M is mass, and b is the mass exponent)
This example shows an estimate of the resting metabolic rate (RMR) of
a 37.3 g bird, in units of ml O2/min.
The equation was derived from a paper published by Andrew Mckechnie and
Blair Wolf (Click here for a list of the references from which allometric equations were obtained.). The 'Store' button 'remembers' the computed metabolism for later use (for example in other calculators). The 'Save' button, if present, lets you save the current mass coefficient and mass exponent values for future use, accessed as 'Custom coefficent and exponent' option in the Taxon popup. The 'Save' button is accessible only if the units are set to ml O2 /min. NOTE: you will have to click the 'Save Current Preferences' button in the Preferences window if you want to have your custom values available the next time you run the program.
![]() This window calculates the washout rates of theoretical perfectly-mixed chambers as a function of volume and flow rate. The computed value is the time for X% of intial gas volume to be replaced -- akin to the 'half-life' concept for radioactive decay and related phenomena.
![]() 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:
Equations notes:
To support these calculations -- which are largely based on the small pressure fluctuations induced by the warming and wetting of tidal air -- you need to provide a number of variables. Several of these are self-explanatory (at least if you know something about respiratory physiology). Abbreviations for some of the more obscure ones are:
You can use the 'waveform analysis' routines in the ANALYSIS menu to obtain breathing frequeny, calibration volts, and sample volts from recorded breathing records.
In this fairly typical example, the animal (a mouse) breathed about 6.3
times per second (not unusual for a small mammal in cold conditions) and
had a tidal volume of 0.256 ml and a minute volume of about 97 ml/min. The
oxygen extraction was about 25.7%. 1. For temperature data, the program's default 'assumption' is that a value of zero = bad data (or no data). If your temperatures include real values of zero, then use .001 (or some other small but non-zero number) instead of zero.
2. The program will attempt to find the highest 6 and 12-h readings, so the implicit assumption is that your climate data are sampled at least once per hour (higher sampling rates are OK).
For each point in the data file, the necessary metabolic rate is computed according to the following rules: When Te < LCT in the inactive part of the daily cycle, if the animal can use torpor (selected in the 'options' window), one of two calculations are performed:
-- if Te is at or above 1 °C less than a minimal (defended) Tb, the metabolic rate is reduced from BMR in proportion to how close Te is to minimum Tb.
Flowcharts (decision trees) for calculations of environmental temperature and thermoregulatory costs are at the end of this page.
|
Program output includes:
mean metabolic rate (watts)
factorial increase of mean metabolic rate above BMR
highest single metabolic rate (watts)
factorial increase of highest metabolic rate above BMR
percent of total samples for which metabolic rate = BMR (i.e., Te > LCT)
mean metabolic rate for all samples where Te < LCT
factorial increase above BMR for mean metabolic rate for all samples where Te < LCT
maximum daily average (watts), and expressed as factorial increase above BMR
maxima over 6 and 12 hours (watts), and expressed as factorial increase above BMR
mean metabolic rate while in torpor (watts), and expressed as factorial change from BMR
percent of time spent in torpor
NOTE: For nightime data, if a value for shade temperature is missing, the program will attempt to use the sun temperature value instead. This substitution does not occur for daytime data.
These thermal calculations are performed in one of two ways:
One individual at a time (click the 'compute costs' button): The user enters the animal's thermal parameters in edit fields in the main program window, selects the time, sun, and shade temperature channels, and then starts calculations. Results are shown after all Te data are processed:
Multiple individuals (species) in a spreadsheet
Optionally, the computed costs for each entry in the main data file can be saved in a new channel (if the file has < 40 channels).
an indicator (yes, no, y, n, 1, 0) of whether the animal can 'use' sunlight to warm itself. If true, the calculations use the 'sunshine' value in the main data file of temperature data. body temperature, in degrees C minimum thermal conductance, in watts/degree C (here, degrees C is the gradient between body temperature and environmental temperature). the Lower Critical Temperature (LCT) in degrees C. Basal Metabolic Rate (BMR); the units are either watts or ml O2/min (selected in the 'options' window). an indicator (yes, no, y, n, 1, 0) of whether the animal can use torpor to save energy during the inactive phase (night or day) of its daily cycle. the minimum body temperature (Tb; degrees C) that the animal will tolerate in torpor. The lowest environmental temperature at which this is achieved without increasing metabolism is assumed to be 1 °C lower than minimum Tb. At lower Te, the animal will increase metabolic heat production to maintain Tb at the minimum value. The program uses the thermal conductance value (Cth) to calculate this metabolic rate. an indicator (yes, no, y, n, 1, 0, D, d, N, n) of whether the animal's active phase is during the day (diurnal) or at night (nocturnal). A 'yes' or '1' value or equivalent means the animal is diurnal.
![]()
For both methods, the 'options' button opens a window where you can select a number of alternate ways of handling data and calculations, including:
For each spreadsheet entry, the program runs through the Te channels from the main data file. The combined results can be saved, along with the raw data from the 'source' .csv file, in a user-selected spreadsheet file.
The program always saves a column containing the mean thermoregulatory cost in watts.
Other thermoregulatory data columns to be placed in the spreadsheet are selected from the window at right:
Note that if you elect to NOT allow torpor use, that restriction will apply globally to all entries in a .csv file. If you DO allow torpor use, each entry in a .csv file will indicate whether or not torpor is applicable to that entry. |
Times are computed using the ‘Sunrise equation’; this example shows an annual day length cycle for a tropical latitude (~ 14 ° south).
This flowchart shows how Te, time, and physiological parameters are used to compute thermoregulatory energy costs:
Sun time estimates are approximate for several reasons:
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.
- Sunrise and sunset times are based on local solar noon, defined as the time when the sun is at its zenith (highest above the horizon) as seen from the observer’s position. Times based on solar noon are likely to be somewhat different from local time. As defined by people, time zones are arbitrary, and since they are roughly 15 degrees of longitude wide and often do not run strictly north and south, sunrise and sunset times can vary by an hour or more within a single time zone. Due to the arbitrary positioning of time zones, local times of sunrise and sunset can also be an hour different (sometimes more) from results of this calculator; these differences are typically greater a high latitudes.
- The calculator has no allowance for an observer's 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. Also, there are differing concepts of sunrise and sunset (e.g., the first or last glimpse of the solar disk above the horizon, vs. the time when the sun's equator at the horizon, and so forth).
• 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 click the mouse to select that position (you can also hit either the spacebar or return keys); 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 select a position on the enlarged map 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 0.067 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:
Other links: |