Unstable Property Research Articles

Mechanical Assessment of Denture Polymers Processing Technologies.

Removable prostheses have seen a fundamental change recently because of advances in polymer materials, allowing improved durability and performance. Despite these advancements, notable differences still occur amongst various polymer materials and processing technologies, requiring a thorough grasp of their mechanical, physical, and therapeutic implications. The compressive strength of dentures manufactured using various technologies will be investigated. Traditional, injection molding, and additive and subtractive CAD/CAM processing techniques, all utilizing Polymethyl methacrylate (PMMA) as the main material, were used to construct complete dentures. The specimens underwent a compressive mechanical test, which reveals the differences in compressive strength. All the specimens broke under the influence of a certain force, rather than yielding through flow, as is characteristic for plastic materials. For each specimen, the maximum force (N) was recorded, as well as the breaking energy. The mean force required to break the dentures for each processing technology is as follows: 4.54 kN for traditional packing-press technique, 17.92 kN for the injection molding technique, 1.51 kN for the additive CAD/CAM dentures, and 5.9 kN for the subtractive CAD/CAM dentures. The best results were obtained in the case of the thermoplastic injection system and the worst results were recorded in the case of 3D printed samples. Another important aspect depicted is the standard deviation for each group, which reveal a relatively unstable property for the thermoplastic injected dentures. Good results here in terms of absolute property and stability of the property can be conferred to CAD/CAM milled group.

Turning waste into wealth: Li2CO3 impurity conversion into ionic conductive and lithiophlic interphase for garnet-based solid-state lithium batteries

Garnet-type solid-state electrolytes (SSEs) show great potential because of high ionic conductivity and steadiness against metallic Li. However, the unstable property of garnet in air and poor interface contact with Li metal dramatically influence the electrochemical performance. In this manuscript, TiO2 gel is coated on the surface of Li6.75La3Zr1.75Ta0.25O12 (LLZTO) pellets by a spin coating process, to remove the surface impurity and in-situ construct an air-stable and lithiophilic LixTiyOz (LTO) layer on the garnet electrolyte surface. The LTO interface layer can enhance interface contact, improve ionic transport and suppress Li dendrite growth. The low interfacial resistance (18.40 Ω cm2) in Li|LTO@LLZTO|Li symmetric cells manifests good wettability. Density functional theory (DFT) calculation results indicate that the modification layer owns higher work of adhesion and interfacial energy, suggesting excellent stability and inhibition in Li dendrite growth. Specifically, the Li symmetric cells with LTO-modified electrolyte show an enhanced critical current density of 0.9 mA cm−2 and outstanding capability to survive long cycling over 5000 h at 0.1 mA cm−2. The assembled LiFePO4-based full cell displays both high reversible capacity and cycling capability. This work provides a promising strategy to take advantage of interfacial Li2CO3 impurities on the garnet electrolytes.

Functional Lignin‐based Polymers: Isolation, Synthetic Methods and High‐valued Applications

AbstractAs a major component of lignocellulosic biomass, lignin has lots of fascinating properties, such as regeneration, biocompatibility, antioxidant, hydrophilicity, unique aromatic structure, and various functional groups, which make them become interesting natural polymer raw material, and attracted more and more attention. In particular, the rich functional groups of lignin can be easily functionalized through various synthesis methods, which can endow lignin‐based polymers with new structure and function. These functional lignin‐based polymers are widely used in environmental remediation, smart hydrogel materials, catalysis, biomedical, etc. However, its various sources and types, the complex structure, relatively weak chemical reactivity, the unstable processing property, and few high value‐added products limited their practical applications. With the development of lignin varieties, modified reagent, synthesis methods, and polymerization process, many works had been published for the synthesis and application of lignin‐based polymers. In this review, the lignin isolation, modification strategies, polymerization method and process, and the promising applications were summarized and analyzed in recent years. Specially, the recent advances in the preparation of high excellent adsorbents from deconstructed lignin products are highlighted from the synthesis methods and adsorption mechanism perspective. Finally, we discussed these challenges in the green and controllable synthesis of lignin‐based polymers, and prospected their functional applications.

First-principles investigation of stable lead-free halide perovskite materials CsSnCl x Br y I3−x−y for solar cell applications

Perovskite solar cells based on hybrid organic–inorganic lead halide materials have attracted immense interest in recent years due to their enhanced power conversion efficiency. However, the toxic lead element and unstable property of the material limit their applications. With first-principles calculations based on density functional theory, we studied a series of ten lead-free perovskite materials made of cesium, tin, and halogen elements, chlorine (Cl), bromine (Br), and iodine (I). We found that the relative concentrations of the halogen atoms determine the crystal structures and the relative stability of the halide perovskites. Chlorine tends to increase the structural stability, while iodine plays the role of reducing the band gaps of the mixed halide perovskites. Considering the stability and the requirement of suitable band gaps, we identify that, among the ten lead-free halide perovskites, CsSnCl2I, CsSnBr2I, CsSnClBrI, CsSnClI2, CsSnBrI2, and CsSnI3 are the appropriate choices for solar cell applications.

Dynamic modeling and analysis on planar free vibration of long-span arch bridges during construction

The cantilever construction model, which consists of the arch, towers and cables, can be regarded as a cable-stayed system and is widely applied in constructing long-span arch bridges. The vibration induced by this temporary structure's unstable property has a safety risk and deserves to be concerned. Thus, a fully analytical beam-spring-arch model is presented for the cantilever and closure construction states of long-span arch bridges. Subsequently, based on the boundary and continuity conditions, the governing differential equations for in-plane free vibration are derived according to the Hamilton principle and solved using the transfer matrix method to determine frequencies and mode shapes of the system. Meanwhile, the results calculated by the proposed method are verified with the finite element method. Finally, the effects of structural parameter variations during construction on in-plane vibration properties are investigated. The results show that as the length of the erected arch rib gets longer, the system's first six-order frequencies and mode shapes are significantly affected. Moreover, the veering phenomenon is observed. The cables can increase the frequencies of the system to a certain extent. The model that neglects the tower's vibration would overestimate the stiffness of the erection system unless the tower's stiffness is much bigger than the arch.

The asymptotic solutions of two-term linear fractional differential equations via Laplace transform

In this paper, the asymptotic solutions about the origin and infinity are formulated via Laplace transform for a two-term linear Caputo fractional differential equation. The asymptotic expansion about the origin describes the complete singular information of the solution, which is also a good approximation of the solution near the origin. The expansion at infinity exhibits the structure of the solution, as well as the stable or unstable property of the solution, which becomes more accurate as the variable tends to larger. Based on the asymptotic solution about the origin, a singularity-separation Legendre collocation method is designed to validate the methods in this paper. Numerical examples show the easy calculation and high accuracy of the truncated expansions and their Padé approximations when the variable is suitably small or sufficiently large. As an application, the method is used to solve the initial value problem of the Bagley–Torvik equation, and the oscillatory property of the solution is displayed.

Preliminary Structural Characterization of Selenium Nanoparticle Composites Modified by Astragalus Polysaccharide and the Cytotoxicity Mechanism on Liver Cancer Cells.

Astragalus alcohol soluble polysaccharide (AASP) could present superior water solubility and antitumor activity with high concentration. Selenium nanoparticles (SeNPs) have received growing attention in various fields, but their unstable property increases the application difficulties. In the present study, functionalized nano-composites (AASP-SeNPs) were synthesized through SeNPs using AASP (average molecular weight of 2.1 × 103 Da) as a surface modifier, and the preliminary structural characteristics and inhibitory mechanism on liver cancer (HepG2) cells were investigated. Results showed that AASP-SeNPs prepared under a sodium selenite/AASP mass ratio of 1/20 (w/w) were uniformly spherical with a mean grain size of 49.80 nm and exhibited superior dispersivity and stability in water solution. Moreover, the composites could dose-dependently inhibit HepG2 cell proliferation and induce apoptosis through effectively regulating mitochondria-relevant indicators including ΔΨm depletion stimulation, intracellular ROS accumulation, Bax/Bcl-2 ratio improvement, and Cytochrome c liberation promotion. These results provide scientific references for future applications in functional food and drug industries.

Molecular fluorescent probes for imaging and evaluation of peroxynitrite fluctuations in living cells and in vivo under hypoxic stress

Hypoxia stress causes cell damage and apoptosis by producing excessive reactive oxygen species (ROS), which is a universal concern in biology and medicine. Peroxynitrite (ONOO-) plays a vital part in the oxidative injury of tissue proteins in the pathogenic mechanism of many disorders, which is a one of ROS. Thus, excessive production of ONOO- may be one of the crucial factors leading to hypoxia stress injury. However, due to the unstable chemical property and strong reactivity of ONOO-, most of the existing detection ways cannot image and detect its level in real time. Herein, in order to selectively imaging and detecting ONOO- in living cells and in vivo, we synthesized a fluorescent probe Cy-CF3 (our fluorescent probe for detection of ONOO-). Cy-CF3 was capable of monitoring ONOO- with excellent sensitivity and selectivity. Using Cy-CF3, the relationship between hypoxia stress and ONOO- was evaluated. The probe was also employed to sense the change of ONOO- in zebrafish under hypoxia conditions as well as determine ONOO- in living mice with acute liver ischemia. Taken together, the proposed probe maybe a powerful chemical tool for the study of ONOO- in biological mechanisms.

Property rights and market participation: evidence from the land titling program in rural China

The incomplete and unstable property rights of farmland in rural China hinder the development of the nation’s farmland rental market. The Chinese government implemented a land titling program in 2008 and conducted several pilot programs in various provinces to remove the barriers resulting from ambiguous property rights. Using data from the China Health and Retirement Longitudinal Study, this paper investigates the effects of rural land titling on market participation in rural China. First, we provide novel evidence regarding the impact of land titling on land market participation and investigate the heterogeneous wealth effects and geographic locations of land rental decisions. Second, we examine the endogeneity of land titling program implementation through empirical analysis. Our results indicate that clear and well-defined farmland property rights increase land rental activities and raise rental prices. We also find a significantly negative wealth effect in land transfer decisions, indicating that land titling encourages poorer farmers to rent out farmland. Land titling is found to promote land transfer, with the strongest effect in central China, and raise rental rates, with the largest increase in western China.

Construction of Jaffe reaction-based SERS chip for determination of trace picric acid

Picric acid (PA) has a severe environmental risk and security problem owing to its unstable property and high toxic. On-field selective and sensitive detection of trace PA is also a challenging task. PA molecules due to poor affinity to surface of noble metal nanoparticles are hardly detectable by surface-enhanced Raman scattering (SERS) method. In this work, silver shell and gold core nanoparticles with inositol hexaphosphate inner gap (Au@IP6@AgNPs) is prepared and then two-dimension (2D) substrate at the ITO surface (designated as ITO-Au@IP6@Ag) is formed via self-assembly. For capturing PA, we firstly modify creatinine (CRN) molecules onto the ITO-Au@IP6@Ag designated as ITO-Au@IP6@Ag@CRN to construct a specific SERS chip for PA, taking advantage of Jaffe reaction between PA and CRN. The generated Jaffe Complex has the greater Raman scattering section with respect to PA. Therefore, such chip-based SERS array for PA shows a good sensitivity and selectivity and the limit of detection at 3.9 × 10−11 mol/L could be reached. As real applications, the ITO-Au@IP6@Ag@CRN chips have been used for identification of PA in environmental samples such as clothing, envelope, and luggage, and determination of trace PA (~10−7 mol/L) in lake water. It demonstrates a promising perspective for on-site detection of the explosive for public security.

Preparation of PAA/PAM/MXene/TA hydrogel with antioxidant, healable ability as strain sensor

Conductive hydrogels based on MXene have gained more attention due to the excellent conductive property and biocompatibility. At present, they have great potential in electronic skins, personally healthcare monitoring and human motion sensing. However, MXene are prone to be oxidized due to the abundant hydroxyls, which results in the unstable conductive property of hydrogel. To improve the shortcoming, conductive PAA/PAM/MXene/TA hydrogel was prepared, in which the introduction of TA can prevent MXene from oxidation owing to the great deal of pyrogallol groups. Mechanical tests showed that the tensile strength, toughness and elongation at break of PAA/PAM/MXene/TA hydrogel are 0.251 ± 0.05 MPa, 0.895 ± 0.16 MJ/m3 and 560.82 ± 19.56%, respectively, indicating the hydrogel possess good stretchability. In addition, the MXene and TA were introduced into hydrogel through hydrogen bonds, which endow the hydrogel with good restorability and self-healing property. Resistance variation-strain curves demonstrated that the introduction of MXene endue the hydrogel with appreciable sensing performances. Moreover, in vitro cytotoxicity assay indicated that the hydrogel has good biocompatibility. In conclusion, PAA/PAM/MXene/TA hydrogel has great potential in flexible wearable sensor field.

Below the Land Deals: The Making of Mineral Property in Ga-Mphahlele, South Africa, 1880–1994

AbstractThis article examines the transformation of mineral matter into mineral property from the vantage point of Ga-Mphahlele, a section of northern South Africa's platinum belt in which minerals are particularly complex to access. Building on Thomas Sikor and Christian Lund's work, I show that the demands of mining capital played a key role in facilitating a co-constitutive relationship between political authority and mineral property. Because of the geological difficulties accessing Ga-Mphahlele's platinum, mining companies have only shown an intermittent interest in the area's minerals, resulting in a volatile relationship between mineral property and political authority. In turn, this has meant that minerals have often been a relatively unstable property form. By adding the role of capital to Lund and Sikor's analytic lens for studying property and authority, this article tracks the relationship between chiefly authority, African land purchasing, platinum companies, and the emergence of mineral rights.

Encapsulation of Curcumin in a Ternary Nanocomplex Prepared with Carboxymethyl Short Linear Glucan-Sodium-Caseinate-Pectin Via Electrostatic Interactions.

This work chemically modified short linear glucan (SLG) by introducing a surface carboxymethyl group to obtain carboxymethylated SLG (CMSLG), then prepared CMSLG-based ternary nanocomplex particles based on electrostatic interactions with sodium-caseinate (NaCas) and pectin. These nanocomplex particles are homogeneous, generally exhibiting sizes of<200nm with spherical shape and negative surface charge. In addition, the results showed the increase in both the mass ratio of CMSLG and NaCas and the synthesis temperature can improve the colloidal stability of nanocomplex particles when they are exposed to simulated gastrointestinal fluids containing digestive enzymes. Moreover, nanocomplex particles have an exceptional capability to encapsulate curcumin, and this encapsulation efficiency increased as the mass ratios of CMSLG and NaCas were increased. The study also investigated the antioxidant activity and in vitro release properties of curcumin encapsulated by nanocomplex particles and found that CMSLG/NaCas/pectin had improved higher ABTS radical scavenging capacity and allowed for the controlled, sustained release of curcumin in simulated gastrointestinal fluid within 6hours. Thus, this study provides new insights into the design of a CMSLG-based ternary nanocomplex and its use as a potential oral delivery system for lipophilic bioactive compounds. PRACTICAL APPLICATION: Curcumin, as a sort of natural polyphenolic compound, has many physiologic functions such as anti-oxidation, anticancer, and prevention of Alzheimer's disease. However, the application of the curcumin has been limited by its poor water solubility and unstable physicochemical property. To solve this problem, the nanotechnology has been used to prepare the nano-delivery carriers for curcumin. This work prepared a ternary nanoparticle based on the carboxymethyl short linear glucan, sodium-caseinate, and pectin. The ternary nanoparticle can achieve a higher encapsulation efficiency for curcumin. In addition, the ternary nanoparticle can enhance the ABTS radical scavenging capacity and provided control and sustained release of curcumin in the simulated gastrointestinal fluid.

On a terminal value problem for parabolic reaction–diffusion systems with nonlocal coupled diffusivity terms

In this article, we are interested in investigating the nonlocal nonlinear reaction–diffusion system with final conditions. This problem is called backward in time problem, or terminal value problem which is understood as redefining the previous distributions when the distribution data at the terminal observation are known. There are three main goals presented in this paper. First, we prove that the problem is ill-posed (often called as unstable property) in the sense of Hadamard. Our next propose is to provide a modified quasi-reversibility model to stabilize the ill-posed problem. Using some techniques and tools of Faedo–Galerkin method, we prove the existence of the unique weak solution of the regularized problem. Further, we investigate error estimates between the sought solution and the regularized solution in L2(Ω)− and H1(Ω)− norms. The final aim of this paper is to give some numerical results to demonstrate that our method is useful and effective.

Ultraviolet waveband vector beams generation assisted by the nonlinear frequency conversion

Vector beams with a nonseparable polarization distribution are almost thoroughly studied from their generation to application in infrared and visible regimes. Until now, the nonlinear generation of ultraviolet vector beams is only focused on the nonlinear optical processes of gas molecules, which seriously impacts its further applications due to the unstable property. Here, we present a study on the generation of ultraviolet vector beams assisted by the nonlinear frequency conversion processes in potassium dihydrogen phosphate crystals. The vectorial properties of the generated ultraviolet waveband vector beams are characterized in both theoretical and experimental environments. The proposed method paves the way for the generation of extreme ultraviolet vector beams with solid-state nonlinear crystal, which is a more compact and stable way compared with the gas nonlinear method. This work also opens a route for photolithographic techniques and laser processing based on ultraviolet waveband vector beams.

Electrochemical oxidation of π-π coupling organic cathode for enhanced zinc ion storage

Organic materials typically present low rate performance and limited cycling durability due to the structural destruction and dissolution during electrochemical processes, which greatly hinders their application as promising cathodes for aqueous rechargeable zinc-ion batteries (ZIBs). Here, a strategy of in situ electrochemical oxidation with π-π interaction coupling between graphene and 2,3,6,7,10,11-Hexahydroxytriphenylene (HHTP) stabilizes the composite structure, rendering it a very promising organic composite cathode (named as GH) for ZIBs. More explicitly, the hydroxyl groups of HHTP are in-situ electrochemically transformed into carbonyl groups to form the redox-active sites, in which π-π interactions with graphene urges the highly reversible coordination/incoordination between zinc ions and the GH cathode. Further, such a GH cathode shows a specific capacity of 225 mAh g−1 at 0.05 A g−1 with a high capacity retention of 90% at 10 A g−1 after 7000 cycles, demonstrating high rate and cycle stability are achieved during the discharge/charge process. Thereby, this work provides a novel strategy for engineering an organic composite cathode which corrects the low rate and unstable cycling property for effective use in ZIBs.

Discrete Gaussian Curvature Flow for Piecewise Constant Gaussian Curvature Surface

A method is presented for generating a discrete piecewise constant Gaussian curvature (CGC) surface. An energy functional is first formulated so that its stationary point is the linear Weingarten (LW) surface, which has a property such that the weighted sum of mean and Gaussian curvatures is constant. The CGC surface is obtained using the gradient derived from the first variation of a special type of the energy functional of the LW surface and updating the surface shape based on the Gaussian curvature flow. A filtering method is incorporated to prevent oscillation and divergence due to unstable property of the discretized Gaussian curvature flow. Two techniques are proposed to generate a discrete piecewise CGC surface with preassigned internal boundaries. The step length of Gaussian curvature flow is adjusted by introducing a line search algorithm to minimize the energy functional. The effectiveness of the proposed method is demonstrated through numerical examples of generating various shapes of CGC surfaces.

The improved anticancer effects of Bortezomib-loaded hollow mesoporous silica nanospheres on lymphoma development

As the first clinical proteasome inhibitor, Bortezomib (BTZ) has been reported to improve the outcome of lymphoma. However, due to the unstable property, low bioavailability, and hydrophobic properties of BTZ, it is needed to develop effective drug delivery systems to deliver BTZ into targeted cells or organs. Here we developed a bortezomib (BTZ)-loaded HMSNs (BTZ@HMSNs) system, which can sustain the release of BTZ in targeted tissues. In vitro assays showed that BTZ@HMSNs limited cell proliferation and augmented apoptosis of lymphoma SNK-1 cells. Moreover, BTZ@HMSNs significantly diminished migration and invasion of SNK-1 cells as compared with BTZ. In contrast to the upregulation of SHP-1, BTZ@HMSNs decreased the mRNA levels of c-Kit, NF-κB, and JAK1, which elicit oncogenic role in lymphoma development. Importantly, lymphoma mice model showed that BTZ@HMSNs significantly activated p53 signaling and reduced tumor volume and weight compared with free BTZ. Our data thus demonstrate that BTZ@HMSNs manifests improved tumor-suppressing effect in vitro and in vivo compared to free BTZ. We believe that HMSNs is a promising strategy for delivering therapeutic agents for cancer treatment.

VEGF-PLGA controlled-release microspheres enhanced angiogenesis in encephalomyosynangiosis-based chronic cerebral hypoperfusion

Treatments enhancing angiogenesis for chronic cerebral hypoperfusion (CCH) are still in the research stage. Although encephalomyosynangiosis (EMS) is a common indirect anastomosis for the treatment of CCH, the effectiveness to promote angiogenesis is not satisfactory. Vascular endothelial growth factors (VEGF) is a cytokine found to specifically act directly on vascular endothelial cells, promote neovascularization, and enhance capillary permeability. However, the short half life and unstable property of VEGF underlies the need to explore available delivery system. In this study, poly (lactide-co-glycolide) (PLGA) was used to prepare VEGF controlled-release microspheres. In vitro and in vivo analysis of release kinetics showed that the microspheres could release VEGF continuously within 30 days. Then, modified chronic cerebral hypoperfusion rat model was established by ligation of bilateral internal carotid artery and one vertebral artery. At 14 days after ischemia, the EMS and the VEGF microspheres injection were performed. At 30 days after the injection, the result of Morris water maze displayed that combinating VEGF microspheres and EMS significantly ameliorated cognitive deficit after ischemia. We observed that combinating VEGF microspheres and EMS could further significantly increase cerebral blood flow. We speculated that this enhancement of cerebral blood flow was attributed to more angiogenesis induced by combination of VEGF microspheres and EMS, which verified by more collateral circulation with cerebral angiography and higher expression of CD31 or α-SMA. Our study demonstrated that combinating VEGF-PLGA controlled-release microspheres could significantly promote angiogenesis in EMS-based CCH rats model, providing new ideas for clinical treatment of CCH.

Study on triaxial creep behavior and the damage constitutive model of red sandstone containing a single ice-filled flaw

The freezing method is widely used in the construction of vertical shafts in water-rich strata. The formed frozen rock wall is often involved in the creep process, and in particular, the creep behavior of frozen fissured rock mass poses a great threat to construction safety. To better understand the creep instability law of ice-filled, fractured red sandstone under freezing and triaxial stress conditions, a series of triaxial creep tests on frozen red sandstone specimens containing a single, pre-existing flaw at −10°C and under a confining pressure of 4 MPa were carried out with a self-developed DRTS-500 subzero rock triaxial testing system. The multistage loading creep curves were obtained, and the evolution laws of deformation and damage for the frozen specimens in the primary (instantaneous), secondary (steady-state) and tertiary (accelerating) phases were analyzed. The nonlinear visco-elastoplastic constitutive model of red sandstone with a single ice-filled flaw was established according to the fractional calculus theory and the Kachanov damage theory. The results show that the initial creep property, unstable creep property and creep failure mode of frozen single-flaw red sandstone are significantly affected by the flaw dip angle. The proposed creep damage model can accurately describe the complete creep curves of frozen red sandstone with a single ice-filled flaw, especially in the unstable creep stage. The influences of the stress level and flaw dip angle on the creep parameters were analyzed, and sensitivity analyses of the characteristic creep parameters were carried out to verify the reliability and rationality of our creep model. This research can be applied to the assessment of collapse, cracking and other long-term failures and hence can be used as a theoretical basis of design in the freezing engineering of coal mine shafts.