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Junli Hu

Publications and source records attributed to Junli Hu.

4 recordsLinked to original sources
arXiv2024

Effects of degumming conditions on the structure of the regenerated silk fibroin and the properties of its film

The traditional degumming method using sodium carbonate solution severely damages the structure of silk fibroin and results in low molecular weight, which limits the properties and applications of silk materials. In this study, we report a modified degumming method and compared it with the traditional one. The results indicate that compared with the traditional degumming method, the modified degumming method produces silk fibroin with higher \b{eta}-sheet content (53.43% vs 46.68%), higher crystallinity (44.92% vs 42.72%), and more concentrated molecular weight (100 ~ 300 kDa vs 72 ~ 300 kDa), while allowing for the same full removal of sericin. Correspondingly, the film of the silk fibroin prepared with the modified degumming method exhibits higher \b{eta}-sheet content (35.22% vs 32.82%), higher crystallinity (26.96% vs 25.53%), and higher tensile strength (87.91 MPa vs 72.62 MPa). This work provides a degumming method superior to the traditional one and lays a foundation for the development of high-performance silk materials.

physics.bio-ph↗
arXiv2023

Extremal spectral radius of weighted adjacency matrices of bicyclic graphs

The weighted adjacency matrix $A_{f}(G)$ of a simple graph $G=(V,E)$ is the $|V|\times|V|$ matrix whose $ij$-entry equals $f(d_{i},d_j)$, where $f(x,y)$ is a symmetric function such that $f(d_i,d_j)>0$ if $ij\in E$ and $f(d_i,d_j)=0$ if $ij\notin E$ and $d_i$ is the degree of the vertex $i$. In this paper, we determine the unique graph having the largest spectral radius of $A_{f}(G)$ among all the bicyclic graphs under the assumption that $f(x,y)$ is increasing and convex in $x$ and $f(x_1,y_1)\geq f(x_2,y_2)$ when $|x_1-y_1|>|x_2-y_2|$ and $x_1+y_1=x_2+y_2$. Moreover, we determine the unique graph having the second largest spectral radius of $A_{f}(G)$ among all the bicyclic graphs when $f(x,y)=x+y$, $(x+y)^2$ or $x^2+y^2$, which corresponds to the well-known first Zagreb index, first hyper-Zagreb index, and forgotten index, respectively. In addition, we also characterize the bicyclic graphs with the first two largest spectral radii of $A_{f}(G)$ when $f(x,y)=\frac{1}{2}(x/y+y/x)$, corresponding to the extended index.

math.CO↗
arXiv2021

On trees with extremal extended spectral radius

Let G be a simple connected graph with n vertices, and let d_i be the degree of the vertex v_i in G. The extended adjacency matrix of G is defined so that the ij-entry is 1/2(d_i/d_j+d_j/d_i) if the vertices v_i and v_j are adjacent in G, and 0 otherwise. This matrix was originally introduced for developing novel topological indices used in the QSPR/QSAR studies. In this paper, we consider extremal problems of the largest eigenvalue of the extended adjacency matrix (also known as the extended spectral radius) of trees. We show that among all trees of order n>= 5, the path Pn(resp., the star Sn) uniquely minimizes (resp., maximizes) the extended spectral radius. We also determine the first five trees with the maximal extended spectral radius.

math.CO↗