  A sufficient condition is derived for a finite-time $L_2$ singularity of the
3d incompressible Euler equations, making appropriate assumptions on
eigenvalues of the Hessian of pressure. Under this condition $\lim_{t \to T_*}
\sup | \frac{D \o} {Dt} |_{L_2(\vO)} = \infty$, where $~ \vO \subset \R3$ moves
with the fluid. In particular, $|{\o}|$, $|\S_{ij}| , and $|\P_{ij}|$ all
become unbounded at one point $(x_1,T_1)$, $T_1$ being the first blow-up time
in $L_2$.
