Let the crown $C_{13}$ be linear $3$-graph on $9$ vertices $\{a,b,c,d,e,f,g,h,i\}$ with edges $$E = \{\{a,b,c\}, \{a, d,e\}, \{b, f, g\}, \{c, h,i\}\}.$$ Proving a conjecture of Gyárfás et. al., we show that for any crown-free $G$ $n$ vertices, its number satisfy $$\lvert E(G) \rvert \leq \frac{3(n - s)}{2}$$ where $s$ is in degree at least $6$. This result, combined previous work, essentially ...

the aim of this work was to develop a new and simple coacervative extraction method for the preconcentration and spectrophotometric determination of cu(ii) in water samples. dithizone was used as the chelating agent while an anionic surfactant, namely sodium dodecyl sulfate (sds), was used as extracting agent at room temperature. central composite design (ccd) based on response surface methodol...

Vertex-connectivity and edge-connectivity represent the extent to which a graph is connected. Study of these key properties of graphs plays an important role in varieties of computer science applications. Recent years have witnessed a number of linear time 3-edge-connectivity algorithms with increasing simplicity. In contrast, the state-of-the-art algorithm for 3-vertex-connectivity due to Hopc...