Negative thermal expansion in NbF_3 and NbOF_2:A comparative theoretical study

Thermal expansion control is always an obstructive factor and challenging in high precision engineering field. Here,the negative thermal expansion of Nb F_3 and Nb OF_2 was predicted by first-principles calculation with density functional theory and the quasi-harmonic approximation(QHA). We studied the total charge density, thermal vibration, and lattice dynamic to investigate the thermal expansion mechanism. We found that the presence of O induced the relatively strong covalent bond in Nb OF_2, thus weakening the transverse vibration of F and O in Nb OF_2, compared with the case of Nb F_3.In this study, we proposed a way to tailor negative thermal expansion of metal fluorides by introducing the oxygen atoms.The present work not only predicts two NTE compounds, but also provides an insight on thermal expansion control by designing chemical bond type.     

Discrete element modelling of large soil deformations under heavy vehicles

This paper addresses the challenges of creating realistic models of soil for simulations of heavy vehicles on weak terrain. We modelled dense soils using the discrete element method with variable parameters for surface friction, normal cohesion, and rolling resistance. To find out what type of soils can be represented, we measured the internal friction and bulk cohesion of over 100 different virtual samples. To test the model, we simulated rut formation from a heavy vehicle with different loads and soil strengths. We conclude that the relevant space of dense frictional and frictional-cohesive soils can be represented and that the model is applicable for simulation of large deformations induced by heavy vehicles on weak terrain.     

Treatment activity of a mixed-ligand coordination polymer on gastric carcinoma

Reaction of 4,4′,4″-nitrilotribenzoic acid (H₃L), a C₃-symmetric ligand, with the divalent Co(II) salt Co(NO₃)₂·6H₂O in the present of the N-donor ligand 1,2-di(4-pyridyl)ethylene (DPE) affords a new mixed-ligand coordination polymer with the chemical formula of [Co₃(TNB)(DPE)₂]·2H₂O·DMF (1). In this study, CCK-8 assay was used to determine the effect of novel compound on proliferation of gastric cancer cells. The VEGF signaling pathway in gastric cancer cells was determined through employing real-time PCR after treatment of the above complex. Further, molecular docking simulation confirmed that the biological activity was coming from the carboxyl groups through the hydrogen bonding interactions with the receptor protein, the pyridine group only bonded with the Co ion for the formation of the Co complex.     

Negative thermal expansion: Mechanisms and materials

Negative thermal expansion (NTE) of materials is an intriguing phenomenon challenging the concept of traditional lattice dynamics and of importance for a variety of applications. Progresses in this field develop markedly and update continuously our knowledge on the NTE behavior of materials. In this article, we review the most recent understandings on the underlying mechanisms (anharmonic phonon vibration, magnetovolume effect, ferroelectrorestriction and charge transfer) of thermal shrinkage and the development of NTE materials under each mechanism from both the theoretical and experimental aspects. Besides the low frequency optical phonons which are usually accepted as the origins of NTE in framework structures, NTE driven by acoustic phonons and the interplay between anisotropic elasticity and phonons are stressed. Based on the data documented, some problems affecting applications of NTE materials are discussed and strategies for discovering and design novel framework structured NET materials are also presented.     

Performance evaluation of functionalized ordered mesoporous silica for VOCs adsorption by molecular dynamics simulation

Volatile organic compounds (VOCs) are growing pollutants now that cause the serious environmental pollution and threaten human health. The functionalized ordered mesoporous silica (FOMS) has attracted considerable attention in adsorbing VOCs. In this paper, the molecular dynamics simulation was used to simulate the adsorption performance of FOMS on VOCs (acetone, ethyl acetate and toluene). After simulating different pore sizes (2 nm, 3 nm and 4 nm) adsorption performances of ordered mesoporous silica (OMS) on VOCs, OMS with a pore size of 4 nm was selected to further study the influence of functional groups (vinyl, methyl, and phenyl). The following law was obtained: the saturated adsorption capacities of vinyl-functionalized OMS (V-FOMS) to acetone, ethyl acetate and toluene were 3.045 mmol.g^?1, 2.568 mmol.g^?1 and 1.976 mmol.g^?1 respectively; the saturated adsorption capacities of methyl-functionalized OMS (M-FOMS) to acetone, ethyl acetate and toluene were 2.798 mmol.g^?1, 2.312 mmol.g^?1 and 1.698 mmol.g^?1 respectively; the saturated adsorption capacities of phenyl-functionalized OMS (P-FOMS) to acetone, ethyl acetate and toluene were 2.124 mmol.g^?1, 1.941 mmol.g^?1 and 1.539 mmol.g^?1 respectively. These results show that the adsorption ability of FOMS for different adsorbates follows the sequence of acetone > ethyl acetate > toluene. Furthermore, the interaction between functional groups (vinyl, methyl and phenyl) in FOMS and VOCs was explored. It is found that the interaction between different functional groups and adsorbates is different (interaction energy effect). This interaction energy effect promotes FOMS to better adsorb VOCs. This work would provide fundamental understanding and guidance for the development of novel adsorption materials for the adsorption of VOCs.     

The Picone identity: A device to get optimal uniqueness results and global dynamics in Population Dynamics

This paper infers from a generalized Picone identity the uniqueness of the stable positive solution for a class of semilinear equations of superlinear indefinite type, as well as the uniqueness and global attractivity of the coexistence state in two generalized diffusive prototypes of the symbiotic and competing species models of Lotka–Volterra. The optimality of these uniqueness theorems reveals the tremendous strength of the Picone identity.     

Design,synthesis and evaluation of novel dehydroabietic acid-dithiocarbamate hybrids as potential multi-targeted compounds for tumor cytotoxicity

In the present study, novel representatives of the important group of biologically-active, dehydroabietic acid-bearing dithiocarbamate moiety, were synthesized and characterized by ¹H NMR, ¹³C NMR, HR-MS. The in vitro antiproliferative activity evaluation (MTT) indicated that these compounds exhibited potent inhibitory activities in various cancer cell lines (HepG-2, MCF-7, HeLa, T-24, MGC-803). Particularly, compound III-b possessed extraordinary cytotoxicity with low micromolar IC₅₀ values ranging from 4.07 to 38.84 µM against tested cancer cell lines, while displayed weak cytotoxicity on two normal cell lines (LO-2 and HEK 293 T). Subsequently, the potential mechanisms of representative compound III-b were elementarily investigated by Transwell experiment, which showed III-b can inhibit cancer cells migration. Annexin-V/PI dual staining showed that the compound can induce HepG-2 cells apoptosis in a dose-dependent manner. Meanwhile this apoptosis may be related to the upregulated protein expression of cleaved-caspase 3, cleaved-caspase 9, Bax and downregulated of Bcl-2 indicated by Western Blot. Later study further confirmed that ROS levels in HepG-2 cells increased significantly with the rise of concentrations. In addition, through the network pharmacology data analyzing, the core targets and signaling pathways of compound III-b for treatment of liver neoplasms were forecasted. Molecular docking model showed that compound III-b had high affinity with hub targets (CASP3, EGFR, HSP90AA1, MAPK1, ERBB2, MDM2), suggesting that compound III-b might target the hub protein to modulate signaling activity. Taken together, these data indicated that dehydroabietic acid structural modification following the “Molecular hybridization” principle is a feasible way to discover the potential multi-targeted antitumor compounds.