A Novel Approach for Prediction of Monthly Ground Water Level Using a Hybrid Wavelet and Non-Tuned Self-Adaptive Machine Learning Model

Water Resources Management - In recent decades, due to groundwater withdrawal in the Kabodarahang region, Iran, Hamadan, hazardous events such as sinkholes, droughts, water scarcity, etc., have...     

An experimental study on the spray characteristics of pressure nozzle in a fluid bed granulation

The particles with a narrow size distribution are proper products in a fluid bed granulation and coating. As well, the process efficiency is one of the most important parameters, and the wall deposition of sprayed liquid reduces it. The modality of spray volume distribution is a key parameter in the definition of particle size distribution and process efficiency. This work is done in two steps: In the first step, an experimental study on spray characteristics including spray flux distribution, spray cone angle, and discharge coefficient is conducted. Based on the experimental data, the curves of liquid volume flux versus nozzle pressure and height are obtained. The results indicate that the flux distribution changes significantly with even small pressure and height changes. In the second step, the granulation process is carried out in a semi-industrial conical fluid bed, and the particles size distribution curves and the deposited mass on the bed wall are obtained. The results show that the precise determination of the spray flux distribution is an appropriate way to predict the well-advised nozzle pressure/height in order to achieve the narrow particle size distribution and high efficiency of the process.     

Dynamic model of online information quality perceptions and impacts: a literature review

This paper reviews the literature related to the concept of information quality (IQ) in the context of the online environment to understand how it has been conceptualised in the Information Systems (IS) literature, to identify gaps in the literature, and to make recommendations for future research. This study also extends the Information Processing Model (IPM) and proposes a novel dynamic model of online IQ perceptions and impacts. To understand the online IQ construct, an in-depth review of the literature is conducted. Overall, we reviewed 508 journal articles published between 1995 and 2016. This study found that there is a substantial gap in the IS literature in regards to a full understanding of the online IQ construct and its relation with the IPM. More research is needed to understand the way individuals process and respond to online information. Further, although the importance of context in theory development has been emphasised in the literature, very few empirical articles have explored the impact of contextual factors on the IPM as well as perceived online IQ. The findings provide online vendors with important guidelines that should be considered to motivate individuals to acquire more information from their websites that could lead to more satisfied and loyal users.     

Harnessing Normal and Engineered Mesenchymal Stem Cells Derived Exosomes for Cancer Therapy: Opportunity and Challenges

There remains a vital necessity for new therapeutic approaches to combat metastatic cancers, which cause globally over 8 million deaths per year. Mesenchymal stem cells (MSCs) display aptitude as new therapeutic choices for cancer treatment. Exosomes, the most important mediator of MSCs, regulate tumor progression. The potential of harnessing exosomes from MSCs (MSCs-Exo) in cancer therapy is now being documented. MSCs-Exo can promote tumor progression by affecting tumor growth, metastasis, immunity, angiogenesis, and drug resistance. However, contradictory evidence has suggested that MSCs-Exo suppress tumors through several mechanisms. Therefore, the exact association between MSCs-Exo and tumors remains controversial. Accordingly, the applications of MSCs-Exo as novel drug delivery systems and standalone therapeutics are being extensively explored. In addition, engineering MSCs-Exo for targeting tumor cells has opened a new avenue for improving the efficiency of antitumor therapy. However, effective implementation in the clinical trials will need the establishment of standards for MSCs-Exo isolation and characterization as well as loading and engineering methods. The studies outlined in this review highlight the pivotal roles of MSCs-Exo in tumor progression and the promising potential of MSCs-Exo as therapeutic drug delivery vehicles for cancer treatment.     

A comparative study of ethylene polymerization by bis(aminotropone) Ti catalysts

A series of titanium aminotropone complexes bearing a pair of chelating [O–N] ligands have been synthesized and used for polymerization of ethylene successfully. Ethylene polymerization reactions were carried out at different conditions using the prepared catalysts. The activities for ethylene polymerization were significantly dependent on the catalyst structure. The polymerization activity increased with increasing of the both monomer pressure and [MAO]:[Ti] ratio. The highest activity of the catalysts was obtained at about 30–40 °C. It was demonstrated that unlike the high performance Ti–FI catalysts, bis(aminotropone) Ti catalysts do not require the presence of steric bulk in close proximity to the oxygen moiety. Introduction of the bulky alkyl substitution next to the oxygen moiety decreased the activity of the catalysts. Density Functional Theory (DFT) studies reveal that the active species derived from these catalysts normally possess higher electrophilicity nature compared with those produced using bis(phenoxy-imine) Ti catalysts (Ti–FI catalysts). Hydrogen was used as the chain transfer agent. The activities of the catalysts were increased with hydrogen concentration to some extent, but the M _v values of the obtained polymers were decreased. Crystallinity and melting point of the obtained polymer were between 42–62% and 102–124 °C, respectively. Higher pressure increased both the crystallinity and the M _v values of the resulting polymers. The catalyst 8a also produced PE with almost narrow polydispersities (1.10–2.55) as is typical for single-site catalysts. However, PDI was broadened by time.     

Crystallinity of biodegradable polymers reinforced with functionalized carbon nanotubes

Well-dispersed multiwall carbon nanotubes (MWCNTs) were prepared by grafting poly(L-lactide-co-ε-caprolactone) (PLACL) biodegradable copolymer onto the sidewall of hydroxylated MWCNTs using oligomeric L-lactide (LA) and ε-caprolactone (CL). After preparation of MWCNT/PLACL composites, the effect of functionalized MWCNTs on crystallinity of PLACL was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and polarized light optical microscopy (POM). The surface functionalization effectively improved the dispersion and adhesion of MWCNTs which acted as reinforcing filler in the PLACL polymer matrix and hence improved the physical and thermomechanical properties of the nanocomposites. The glass transition temperature (T _g) and the crystallinity of nanocomposites decreased in comparison with those of neat PLACL when the concentration of functionalized MWCNTs in nanocomposites was 0.5 wt%. With further increment in concentration of functionalized MWCNTs, the T _g of composites increased until the T _g of neat PLACL, and also the crystallinity of composites increased. The functionalized MWCNTs have no significant effect on the melting point of nanocomposites. The MWCNTs acted as heterogeneous nucleation points and increased the lamella size and therefore the crystallinity of PLACL. Furthermore, the larger agglomerated clusters of both kinds of MWCNTs (i.e., MWCNT-grafted-PLACL and pristine MWCNTs) are more effective than small clusters as nucleation points for growing the spherulites.     

Thermal decomposition kinetics of dynamically vulcanized polyamide 6–acrylonitrile butadiene rubber–halloysite nanotube nanocomposites

Thermally stable thermoplastic elastomer nanocomposites based on polyamide 6 (PA6), acrylonitrile butadiene rubber (NBR), and halloysite nanotubes (HNTs) were dynamically vulcanized, and their nonisothermal decomposition kinetics were examined. The Friedman, Kissinger–Akahira–Sunose (KAS), Ozawa–Wall–Flynn (FWO), and modified Coats–Redfern (m-CR) isoconversional models were used to obtain information about the kinetics of the thermal decomposition of PA6–NBR–HNTs in terms of the activation energy per partial mass loss monitored through thermogravimetric analyses performed at different heating rates. An erratic trend was due to the Friedman model, especially for systems having higher HNT loadings, whereas the KAS, FWO, and m-CR models revealed very similar meaningful thermal decomposition kinetics. A relatively high activation energy corroborating a reliable thermal stability was obtained by the addition of HNTs to PA6–NBR, and the resistance against decomposition was higher for systems containing more HNT. This signified the role of the HNTs as thermal stability modifiers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47483.     

Effects of various barium precursors and promoters on catalytic activity of Ba-Ti perovskite catalysts for oxidative coupling of methane

The influences of barium precursor and promoter type on the catalytic performance of perovskite catalysts in OCM reaction were studied. Catalysts (BaTiPO₃, P: promoter) were prepared by carbonate, hydroxide and propionate precursors of barium and SnCl₂ and CeO₂ as promoters by sol-gel method, tested in a fixed-bed microreactor and characterized by XRD, BET, CO₂-TPD, FT-IR and UV-Visible analysis. The experiment results showed that based on the extent of effect upon catalyst efficiency, the barium anions can be ranked as; propionate > carbonate > hydroxide, and the CeO₂ promoted catalysts were more active than the SnCl₂ promoted ones. The characterization results showed that the substitution of metal precursors caused formation of different phases with different particle sizes, influenced the basicity of the catalysts, resulted in the appearance of the peaks corresponding to different groups in IR spectroscopy, and shifted the absorption peaks in UV-Visible spectra. These results suggested that OCM reaction over perovskite catalysts is structure sensitive and depended on the type of used precursor and promoter.     

Biodegradable metals for cardiovascular stent application: interests and new opportunities

During the last decade, biodegradable metallic stents have been developed and investigated as alternatives for the currently-used permanent cardiovascular stents. Degradable metallic materials could potentially replace corrosion-resistant metals currently used for stent application as it has been shown that the role of stenting is temporary and limited to a period of 6-12 months after implantation during which arterial remodeling and healing occur. Although corrosion is generally considered as a failure in metallurgy, the corrodibility of certain metals can be an advantage for their application as degradable implants. The candidate materials for such application should have mechanical properties ideally close to those of 316L stainless steel which is the gold standard material for stent application in order to provide mechanical support to diseased arteries. Non-toxicity of the metal itself and its degradation products is another requirement as the material is absorbed by blood and cells. Based on the mentioned requirements, iron-based and magnesium-based alloys have been the investigated candidates for biodegradable stents. This article reviews the recent developments in the design and evaluation of metallic materials for biodegradable stents. It also introduces the new metallurgical processes which could be applied for the production of metallic biodegradable stents and their effect on the properties of the produced metals.     

Theoretical and practical investigations of copper ion selective electrode with polymeric membrane based on N,N′-(2,2-dimethylpropane-1,3-diyl)-bis(dihydroxyacetophenone)

A novel ion-selective poly(vinyl chloride) (PVC) membrane sensor for Cu²⁺ ions based on N,N′-(2,2-dimethylpropane-1,3-diyl)-bis(dihydroxyacetophenone) (NDHA) as a new ionophore was prepared and studied. The best performance was observed for the membrane composition, including 30:65:1:4 (wt%) = PVC:DBP:KTpClPB:NDHA. The electrode showed a good Nernstian slope of 30.0 ± 0.5 mV/decade in a wide linear range activity of 3.0 × 10⁻⁷ to 1.0 × 10⁻² mol dm⁻³ Cu(NO₃)₂ with limit of detection 2.5 × 10⁻⁷. Sensor exhibited a fast response time (t_95% < 10 s) and could be used for about 4 months in the pH range of 3.0–7.4. The proposed potentiometric sensor was found to work satisfactorily in partially non-aqueous media up to 30 (vol%) content of methanol, ethanol and acetone. Applications of this electrode for the determination of copper in real samples, and as an indicator electrode for potentiometric titration of Cu²⁺ ion using EDTA, were reported. In order to predict the extraction ability of NDHA for different metallic ions, the complexes [M(NDHA)] and [M(H₂O)₆] (where M = Cu²⁺, Co²⁺, Hg²⁺, Pb²⁺, Ag⁺, Mg²⁺, Ca²⁺, Mn²⁺, Zn²⁺, Cd²⁺, K⁺ and Al³⁺) were investigated using ab initio theoretical calculations. The metal binding capability was evaluated using the binding energy. Results of our study could be useful for prediction of the extraction power of this Schiff base and could play a guiding role in planning experiments.