deletions | additions       diff --git a/When_a_laser_beam_of__1.tex b/When_a_laser_beam_of__1.tex  index 609c025..ef33eec 100644  --- a/When_a_laser_beam_of__1.tex  +++ b/When_a_laser_beam_of__1.tex 
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\end{equation}  where $c_k$ the thermal wave speed (usually taken as equal to the compression wave speed), $\rho$ the density, $\kappa$ the thermal diffusivity and $C$ the heat capacity.  The thermal diffusion path, equal to $\sqrt{4kt}$, where $k$ is ..., is equal to 0.01 $\mu$m.  The propagation of the heat is slow compared to the duration of the heating (10 ns) and the thermal expansion duration (), so that the phenomenon can be considered as adiabatic.  %$\kappa$ is approximately equal to 10${^6}$ m$^2$.s$^{-1}$ for water, the main component of biological tissues; for a 10 ns laser pulse, the thermal diffusion path is then equal to 0.01 to 0.1 $\mu$m. $\gamma^{-1}$ of water is equal to 0.1 m, which is a million times higher; even for melanin and haemoglobin, highly absorbing at 532 nm, $\gamma^{-1}$ is respectively equal to 10 and 100 $\mu$m, far higher than the thermal diffusion path. The thermal conductivity effects are consequently negligible, and increase of temperature lies in laser absorption zone. 
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