Cacti with Extremal PI Index

The vertex PI index $PI(G) = \sum_{xy \in E(G)} [n_{xy}(x) + n_{xy}(y)]$ is a distance-based molecular structure descriptor, where $n_{xy}(x)$ denotes the number of vertices which are closer to the vertex $x$ than to the vertex $y$ and which has been the considerable research in computational chemistry dating back to Harold Wiener in 1947. A connected graph is a cactus if any two of its cycles have at most one common vertex. In this paper, we completely determine the extremal graphs with the largest and smallest vertex PI indices among all the cacti. As a consequence, we obtain the sharp bounds with corresponding extremal cacti and extend a known result.Comment: Accepted by Transactions on Combinatorics, 201

Evaluating Alzheimer's Disease Progression by Modeling Crosstalk Network Disruption

Aβ, tau and P-tau have been widely accepted as reliable markers for Alzheimer’s disease (AD). The crosstalk between these markers forms a complex network. AD may induce the integral variation and disruption of the network. The aim of this study was to develop a novel mathematic model based on a simplified crosstalk network to evaluate the disease progression of AD. The integral variation of the network is measured by three integral disruption parameters. The robustness of network is evaluated by network disruption probability. Presented results show that network disruption probability has a good linear relationship with Mini Mental State Examination (MMSE). The proposed model combined with Support vector machine (SVM) achieves a relative high 10-fold cross-validated performance in classification of AD vs normal and mild cognitive impairment (MCI) vs normal (95% accuracy, 95% sensitivity, 95% specificity for AD vs normal; 90% accuracy, 94% sensitivity, 83% specificity for MCI vs normal). This research evaluates the progression of AD and facilitates AD early diagnosis

On the Aα-spectral radii of cactus graphs

© 2020 by the authors. Let A(G) be the adjacent matrix and D(G) the diagonal matrix of the degrees of a graph G, respectively. For 0 ≤ α ≤ 1, the Aα-matrix is the general adjacency and signless Laplacian spectral matrix having the form of Aα(G) = αD(G) + (1-α)A(G). Clearly, A0(G) is the adjacent matrix and 2A1/2 is the signless Laplacian matrix. A cactus is a connected graph such that any two of its cycles have at most one common vertex, that is an extension of the tree. The Aα-spectral radius of a cactus graph with n vertices and k cycles is explored. The outcomes obtained in this paper can imply some previous bounds from trees to cacti. In addition, the corresponding extremal graphs are determined. Furthermore, we proposed all eigenvalues of such extremal cacti. Our results extended and enriched previous known results

Fabrication and magnetic properties of Sm2Co17 and Sm2Co17/Fe7Co3 magnetic nanowires via AAO templates

AbstractThe Sm2Co17 single-phase and Sm2Co17/Fe7Co3 double-phase nanowire arrays with smaller diameter (around 50nm) have been fabricated into the anodic aluminum oxide (AAO) templates by direct-current electrodeposition. The crystal structure and micrograph of these nanowire arrays were characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy (TEM). It is found that the as-deposited Sm2Co17 nanowires have the amorphous microstructure. The magnetic hysteresis loops obtained by vibrating sample magnetometer (VSM) show that the easily magnetized direction of the Sm2Co17 single-phase and Sm2Co17/Fe7Co3 double-phase nanowire arrays is parallel to the nanowire arrays and the exchange coupling interaction in nanocomposite Sm2Co17/Fe7Co3 is discussed. The study of the Sm2Co17 single-phase and Sm2Co17/Fe7Co3 double-phase nanowires with small diameter may open up new opportunities for the design and control of nanostructures such as the fabrication of magnetic recording devices

Postseismic Restoration of the Ecological Environment in the Wenchuan Region Using Satellite Data

Using Landsat remote-sensing data combined with geological information extracted from ALOS and Sentinel-1A radar data, the ecological environment was evaluated in the years 2007, 2008, 2013, and 2017 through gray correlation analysis on the basis of the construction of the pressure-state-response model. The main objective of this research was to assess the ecological environment changes in Wenchuan County before and after the earthquake, and to provide reference for future social development and policy implementation. The grading map of the ecological environment was obtained for every year, and the ecological restoration status of Wenchuan County after the earthquake was evaluated. The results showed that the maximum area cover at a “safe” ecological level was over 46.4% in 2007. After the 2008 earthquake, the proportion of “unsafe” and “very unsafe” ecological levels was 40.0%, especially around the Lancang River and the western mountain area in Wenchuan County. After five years of restoration, ecological conditions were improved, up to 48.0% in the region. The areas at “critically safe” and above recovered to 85.5% in 2017 within nine years after the deadly Wenchuan earthquake of May 12, 2008. In this paper, we discuss the results of detailed analysis of ecological improvements and correlation with the degrees of pressure, state, and response layers of the Pressure-State-Response (PSR) model

Land-Use/Land-Cover Changes and Their Influence on the Ecosystem in Chengdu City, China during the Period of 1992–2018

Due to urban expansion, economic development, and rapid population growth, land use/land cover (LULC) is changing in major cities around the globe. Quantitative analysis of LULC change is important for studying the corresponding impact on the ecosystem service value (ESV) that helps in decision-making and ecosystem conservation. Based on LULC data retrieved from remote-sensing interpretation, we computed the changes of ESV associated with the LULC dynamics using the benefits transfer method and geographic information system (GIS) technologies during the period of 1992–2018 following self-modified coefficients which were corrected by net primary productivity (NPP). This improved approach aimed to establish a regional value coefficients table for facilitating the reliable evaluation of ESV. The main objective of this research was to clarify the trend and spatial patterns of LULC changes and their influence on ecosystem service values and functions. Our results show a continuous reduction in total ESV from United States (US) $1476.25 million in 1992, to US$1410.17, $1335.10, and$1190.56 million in 2001, 2009, and 2018, respectively; such changes are attributed to a notable loss of farmland and forest land from 1992–2018. The elasticity of ESV in response to changes in LULC shows that 1% of land transition may have caused average changes of 0.28%, 0.34%, and 0.50% during the periods of 1992–2001, 2001–2009, and 2009–2018, respectively. This study provides important information useful for land resource management and for developing strategies to address the reduction of ESV