Page 145 -

αβδ βδ αβ αβ αδ βδ
wW = γ − γ where γ , γ , and γ are the surface ten-
sions between two bulk phases α, β; α, δ and
where γ αβ and γ βδ are the surface ten- β, δ, respectively.
sions between two bulk phases α, β and β, δ, The work of adhesion as defined above, and
respectively. traditionally used, may be called the work of
separation.
White’s formula A closed DNA molecule
modeled as a ribbon has a twist (Tw) with respect
work of cohesion per unit area Of a single
to its central line (the line of centroids) and α
pure liquid or solid phase α, w is the work done
C
a writhe (Wr) which represents the contortion
on the system when a column α of unit area is
of the central line in space. It was shown by split, reversibly, normal to the axis of the column
J.H. White, that Tw + Wr = linking number, a
to form two new surfaces each of unit area in
topological invariant. White’s formula relates
contact with the equilibrium gas phase.
DNA structure to knot theory (see also DNA
supercoil; cf. J.H. White, Am. J. Math., 91, 693 w = 2γ α
α
C
(1969)).
α
where γ is the surface tension between phase α
wind rose A diagram designed to show the and its equilibrium vapor or a dilute gas phase.
distribution of wind direction experienced at a
given location over a considerable period of time. work softening The application of a finite
Usually shown in polar coordinates (distance shear to a system after a long rest may result
from the origin being proportional to the prob- in a decrease of viscosity or consistency. If the
ability of the wind direction being at the given decrease persists when the shear is discontinued,
angle usually measured from the north). Similar this behavior is called work softening (or shear
diagrams are sometimes used to summarize the breakdown), whereas if the original viscosity or
average concentrations of a given pollutant seen consistency is recovered this behavior is called
over a considerable period of time as a function thixotropy.
of direction from a given site (sometimes called
a pollution rose). working electrode An electrode that serves
asatransducerrespondingtotheexcitationsignal
wood horn A mechanical device that acts by and the concentration of the substance of interest
absorption as a perfect photon trap. in the solution being investigated, and that per-
mits the flow of current sufficiently large to effect
wood lamp A term used to describe a low- appreciable changes of bulk composition within
pressure mercury arc. See lamp.
the ordinary duration of a measurement.

work, w w w, W W W Scalar produce of force, F, and
working set Constraints believed to be
position change, d r,w = F × d r.
active at a solution.
work hardening Opposite of work soft-
wormlike chain (in polymers) A hypo-
ening, in which shear results in a permanent
thetical linear macromolecule consisting of an
increase of viscosity or consistency with time.
infinitely thin chain of continuous curvature; the
direction of a curvature at any point is ran-
work of adhesion The work of adhesion per
αβδ dom. The model describes the whole spectrum
unit area, w , is the work done on the system
A of chains with different degrees of chain stiffness
when two condensed phases α and β, forming
from rigid rods to random coils, and is particu-
an interface of unit area, are separated reversibly
larly useful for representing stiff chains. In the
to form unit areas of each of the αδ- and βδ-
literature this chain is sometimes referred to as a
interfaces.
Porod-Kratky chain. Synonymous with continu-
αβδ αδ βδ αβ
w = γ + γ − γ ously curved chain.
A

© 2003 by CRC Press LLC
© 2003 by CRC Press LLC