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- adding unit 'u' (synonym for amu)
- adding units to the help file

\label{Physical_Units}
\section*{Physical Units Accepted by LON-CAPA}
The following subsections show the physical units that LON-CAPA accepts. 
The symbols must be used when entering the units, for example {}``35 kg''.
\subsection*{Base Units}
\begin{verbatim}
# name      symbol     comment

meter           m      # length
kilogram        kg     # mass
second          s      # time
ampere          A      # electric current
kelvin          K      # thermodynamic temperature
mole            mol    # amount of substance
candela         cd     # luminous intensity
\end{verbatim}
\subsection*{Prefixes}
\begin{verbatim}
#   Prefix     symbol     factor

yotta            Y         10^{24}
zetta            Z         10^{21}
exa              E         10^{18}
peta             P         10^{15}
tera             T         10^{12}
giga             G         10^9
mega             M         10^6
kilo             k         10^3
hecto            h         10^2

deci             d         10^-1
centi            c         10^-2
milli            m         10^-3
micro            u         10^-6
nano             n         10^-9
pico             p         10^{-12}
femto            f         10^{-15}
atto             a         10^{-18}
zepto            z         10^{-21}
yocto            y         10^{-24}
\end{verbatim}
\subsection*{Derived Units}
\begin{verbatim}
# Derived Unit
# name       symbol    comment

gram            g      # mass
hour            hr     # time
minute          min    # time
day             day    # time
year            yr     # time
pound           lb     # mass
ounce           oz     # mass
inch            in     # length
foot            ft     # length
mile            mi     # length
yard            yd     # length
nautical_mile   n_mi   # length, nautical mile (UK)
rood            rood   # area, rood
acre            acre   # area, acre
hertz           Hz     # frequency
litre           L      # volume
newton          N      # force
pound_force     lbf    # force
dyne            dyn    # force
pascal          Pa     # pressure, stress
bar             bar    # pressure
mmHg            mmHg   # pressure, millimeter of mercury
torr            torr   # pressure
atm             atm    # standard atmosphere
joule           J      # energy, work, heat
electronvolt    eV     # energy
calorie         cal    # energy
Btu             Btu    # energy
watt            W      # power, radiant flux
coulomb         C      # electric charge
volt            V      # electric potential, electromotive force
ohm             ohm    # electric resistance, use this in /ANS
ohm             ohms   # electric resistance
ohm             Ohm    # electric resistance
ohm             Ohms   # electric resistance
siemens         S      # electric conductance
farad           F      # electric capacitance
tesla           T      # magnetic flux density
weber           Wb     # magnetic flux
henry           H      # inductance
radian          rad    # plane angle
degree          deg    # plane angle (Pi rad=180 deg)
steradian       sr     # solid angle
lumen           lm     # luminous flux
lux             lx     # illuminance
becquerel       Bq     # activity (radioactive)
gray            Gy     # absorbed dose (of radiation)
sievert         Sv     # dose equivalent (dose equivalent index)
astroUnit       AU     # mean distance earth to sun
celcius         degC   # multiplicatively OK
farenheight     degF   # multiplicatively OK
molarity        M      # chemisty
amu             amu    # atomic mass unit
amu             u      # atomic mass unit
\end{verbatim}
\subsection*{Interpretation}
The coded units are interpreted in the order of basic unit, 
derived unit, then prefix. For example, ``T'' will be matched against 
``tesla'' instead of considered the prefix ``T''. Another example is that 
``min'' will match
``minutes'' instead of treated  as a combination of the prefix ``m'' and units.