  The regions of existence are established for a class of two point nonlinear
diffusion type boundary value problems (NDBVP) \begin{eqnarray*}
&&\label{abst-intr-1} -s''(x)-ns'(x)-\frac{m}{x}s'(x)=f(x,s), \qquad m>0,~n\in
\mathbb{R},\qquad x\in(0,1),\\ &&\label{abst-intr-2} s'(0)=0, \qquad
a_{1}s(1)+a_{2}s'(1)=C, \end{eqnarray*} where $a_{1}>0,$ $a_{2}\geq0,~
C\in\mathbb{R}$. These problems arise very frequently in many branches of
engineering, applied mathematics, astronomy, biological system and modern
science (see \cite{Gatica1989, GRAY1980, Baxley1991, Chandershekhar1939,
Duggan1986, Chambre1952}). By using the concept of upper and lower solutions
with monotone constructive technique, we derive some sufficient conditions for
existence in the regions where $\frac{\partial f}{\partial s}\geq0$ and
$\frac{\partial f}{\partial s}\leq0$. Theoretical methods are applied for a set
of problems which arise in real life.
