Hâgard, from hâ- prefix denoting "reversal; to," sometimes creating nuance
[Dehxodâ], + gard present stem of gardidan, gaštan
"to change; to turn;" Mid.Pers. vartitan;
Av. varət- "to turn, revolve;" cf.
Skt. vrt- "to turn, roll," vartate "it turns round, rolls;"
L. vertere "to turn;" O.H.G. werden "to become;"
PIE base *wer- "to turn, bend."

conversion factor

کروند ِ هاگرد

karvand-e hâgard

Fr.: facteur de conversion

1) A numerical factor that, by multiplication or division, translates one
unit or value into another.
2) In → molecular cloud studies, a factor used to convert
the → carbon monoxide (CO) line intensity to
→ molecular hydrogen (H_{2})
→ column density; usually denoted
X_{CO} = I(CO) / N(H_{2}). This useful factor relates
the observed CO intensity to the cloud mass. A general method to derive X_{CO}
is to compare the → virial mass
and the ^{12}CO (J = 1-0) luminosity of a cloud.
The basic assumptions are that the CO and H_{2} clouds are co-extensive, and
molecular clouds obey the → virial theorem.
However, if the molecular cloud is subject to ultraviolet radiation,
selective → photodissociation may take place, which will change
the situation. Moreover, molecular clouds may not be in
→ virial equilibrium.
To be in virial equilibrium molecular clouds must have enough mass, greater than
about 10^{5} solar masses.
The way → metallicity affects
X_{CO} is a matter of debate, and there is no clear correlation
between X_{CO} and metallicity. Although lower metallicity brings about
higher ultraviolet fields than in the solar vicinity, other factors appear to be
as important as metallicity for the determination of X_{CO}.
In the case of the → Magellanic Clouds,
X_{CO}(SMC) =
14 ± 3 × 10^{20} cm^{-2} (K km s^{-1})^{-1}, which is
larger than X_{CO} (LMC) = 7 ± 2 × 10^{20} cm^{-2}
(K km s^{-1})^{-1}.
An independent method to derive X_{CO} is to make use of the
gamma ray emission from a cloud. The flow of → cosmic ray
protons interacts with interstellar low-energy hydrogen nuclei in clouds creating neutral
→ pions. These pions quickly decay into two gamma rays. It is therefore
possible to estimate the number of hydrogen nuclei and hence the cloud mass
from the gamma ray counts. Such a gamma-ray based conversion factor is estimated to be
2.0 × 10^{20} cm^{-2} (K km s^{-1})^{-1}
for Galactic clouds, in good agreement with the result obtained from the
virial method. However, the gamma ray flux is not well known in general, so this
method is uncertain as well. See, e.g., Fukui & Kawamura, 2010 (ARAA 48, 547).

Deriving the → wavelength of an undulatory phenomenon from
its → frequency, and vice versa.
1) For → electromagnetic waves:
λ = c / f, where λ is the wavelength,
c is the → speed of light in
→ meters per second
and f the frequency in → hertz. It can be written as:
λ (m) = 2.998 × 10^{8} / f (Hz).
2) For → sound waves: λ = C / f,
where C is the → sound speed. For air at
temperature 0°C, λ (m) = 332 / f (Hz).

A → radiationless relaxation process in which a molecule
in some excited → electronic state
converts to a state of the same → multiplicity
but of lower electronic energy and in
which the lost electronic energy is converted initially into vibrational energy.

The conversion of a → number system
with a given → base to another system with a
different base; such as the conversion of a → decimal number
(base 10) to a → binary number system
(base 2).
In order to convert a number into its representation in a different
number base, we have to express the number in terms of powers of the other base.
For example, to convert the decimal number 100 to base 3, we must figure out how to
express 100 as the sum of powers of 3. We proceed as follows:
1: Divide the decimal number to be converted (100) by the value of the new base
(3).
2: Get the remainder from Step 1 (that is 1) as the rightmost digit (least
significant digit) of new base number.
3: Divide the quotient of the previous divide (33) by the new base.
4: Record the remainder from Step 3 (0) as the next digit (to the left) of the new base number.
Repeat Steps 3 and 4, getting remainders from right to left, until the
quotient becomes zero in Step 3 (2 and 0).
The last remainder thus obtained (1) will be the most significant digit of the new base number.
Therefore, 100_{10} = 10201_{3}.
Conversely, to convert from another base to decimal we must:
1: Determine the column (positional) value of each digit.
2: Multiply the obtained column values (in Step 1) by the digits in the corresponding columns.
3: Sum the products calculated in Step 2. The total is the equivalent value in decimal.
For example, the binary number 1100100 is determined by computing the place
value of each of the digits of the number:
(1 × 2^{6}) + (1 × 2^{5}) + (0 × 2^{4}) +
(0 × 2^{3}) + (1 × 2^{2}) + (0 × 2^{1}) +
(0 × 2^{0}) = 64 + 32 + 0 + 0 + 4 + 0 + 0 = 100.

A chemical process converting the → yellowcake
to → uranium hexafluoride.
The uranium
hexafluoride is heated to become a gas and loaded into
cylinders. When it cools, it condenses into a solid.