In the first note we show for a strongly continuous family of operators ${\left(T\left(t\right)\right)}_{t\ge 0}$ that if every orbit $t\mapsto T\left(t\right)x$ is differentiable for $t>t_x$, then all orbits are differentiable for $t>t_0$ with $t_0$ independent of $x$. In the second note we give an example of an eventually differentiable semigroup which is not differentiable on the same interval in the operator norm topology.

In the paper a sufficient condition for all solutions of the differential equation with $p$-Laplacian to be proper. Examples of super-half-linear and sub-half-linear equations $\left(\right|y^{\text{'}}{|}^{p-1}{y}^{\text{'}}{)}^{\text{'}}+r\left(t\right){\left|y\right|}^{\lambda }sgny=0$, $r>0$ are given for which singular solutions exist (for any $p>0$, $\lambda >0$, $p\ne \lambda$).

Let $E={\bigcup }_{n=1}^{\infty }{I}_n$ be the union of infinitely many disjoint closed intervals where $I_n=[a_n$, $b_n]$, $0<a_1<b_1<a_2<b_2<\cdots <b_n<\cdots$, ${lim}_{n\to \infty }{b}_n=\infty .$ Let $\alpha \left(t\right)$ be a nonnegative function and ${\left\{{\lambda }_n\right\}}_{n=1}^{\infty }$ a sequence of distinct complex numbers. In this paper, a theorem on the completeness of the system $\left\{t^{{\lambda }_n}{log}^{m_n}t\right\}$ in $C_0\left(E\right)$ is obtained where $C_0\left(E\right)$ is the weighted Banach space consists of complex functions continuous on $E$ with $f\left(t\right){\mathrm{e}}^{-\alpha \left(t\right)}$ vanishing at infinity.

Suppose that the function $q\left(t\right)$ in the differential equation (1) $y^{\text{'}\text{'}}+q\left(t\right)y=0$ is decreasing on $(b,\infty )$ where $b\ge 0$. We give conditions on $q$ which ensure that (1) has a pair of solutions $y_1\left(t\right),y_2\left(t\right)$ such that the $n$-th derivative ($n\ge 1$) of the function $p\left(t\right)=y_1^2\left(t\right)+y_2^2\left(t\right)$ has the sign ${(-1)}^{n+1}$ for sufficiently large $t$ and that the higher differences of a sequence related to the zeros of solutions of (1) are ultimately regular in sign.