Reduction and oxidation kinetics of Mn3O4/Mg-ZrO2 oxygen carrier particles for chemical-looping combustion

The kinetics of reduction with methane and oxidation with oxygen of Mn₃O₄ supported on Mg-ZrO₂ prepared by freeze granulation has been investigated. The reactivity experiments were performed in a thermogravimetric analyzer (TGA) using different reacting gas concentrations and temperatures in the range of 1073-1223 K. The oxygen carrier particles showed high reactivity during both reduction and oxidation at all investigated temperatures. An empirical reaction model, which assumes a linear relation between time and conversion, was used to determine the kinetic parameters for reduction and oxidation, with chemical reaction being the main resistance to the reaction. The order of reaction found was 1 with respect to CH₄ and 0.65 with respect to O₂. The activation energy for the reduction reaction was 119 and for the oxidation reaction. The reactivity data and kinetic parameters were used to estimate the solid inventory in the air and fuel reactor of a CLC system. The optimum solid inventory obtained was at a value of ΔX_s=0.4. At these conditions, the recirculation rate of oxygen carrier between air and fuel reactor was per MW of fuel, which could be accomplished in an industrial reactor. The high reactivity of the Mn₃O₄/Mg-ZrO₂ with both methane and oxygen showed that this is a very promising oxygen carrier for CLC.     

Tubular Expansion in Irregularly Shaped Boreholes—Computer Simulation and Field Measurement

Abstract

Abstract Recently, field engineers have tried to use a new technique using expandable tubular with elastomers to seal the annulus. Ultrasonic down-hole measurements carried out for evaluation of zonal isolation revealed that the tubular expanded to an oval x-section instead of the desired circular x-section at certain locations. This is a phenomenon previously unknown. It is believed to occur due to expansion in irregularly shaped boreholes. The ovalization of expanded tubular was studied to avoid such problems in future. The finite element method was used to predict tubular ovality and compare it to measured values. Results were then used to develop ready-to-use design curves in making decisions for running a completion tool in expanded tubular.     

Soot sheet dimensions in turbulent nonpremixed flames

A method is presented to automate the generation of the statistics of the characteristic length (L) and width (W) of the 2-D slices through 3-D soot sheets in turbulent nonpremixed flames. The method employs the simplified approximation of fitting an equivalent ellipse. The effectiveness of the method is first evaluated by comparison with two types of manual assessment. It is then applied to assess the evolution of the soot sheet dimensions in two turbulent nonpremixed propane flames. These two flames, had the same fuel flow rates but different global mixing rates, were produced by a precessing jet (PJ) and a simple jet (SJ) burner. The global mixing rate of the flames was observed to affect the shape of probability density functions (PDFs) of soot sheets L and W. The shapes of the PDFs of the flames reveal that burnout of the soot sheets in the PJ and SJ flame proceeded predominantly through the reduction of the soot sheet dimensions, and the number of soot sheets, respectively. Finally, a convenient way to estimate the actual maximum width of the single-branched soot sheets is proposed, and this value is estimated to be ∼20 mm for both flames.     

Stress Driven Discovery of Natural Products From Actinobacteria with Anti-Oxidant and Cytotoxic Activities Including Docking and ADMET Properties

Elicitation through abiotic stress, including chemical elicitors like heavy metals, is a new technique for drug discovery. In this research, the effect of heavy metals on actinobacteria Streptomyces sp. SH-1312 for secondary metabolite production, with strong pharmacological activity, along with pharmacokinetics profile, was firstly investigated. The optimum metal stress conditions consisted of actinobacteria strain Streptomyces sp. SH-1312 with addition of mix metals (Co²⁺ + Zn²⁺) ions at 0.5 mM in Gause’s medium. Under these conditions, the stress metabolite anhydromevalonolactone (MVL) was produced, which was absent in the normal culture of strain and other metals combinations. Furthermore, the stress metabolite was also evaluated for its anti-oxidant and cytotoxic activities. The compound exhibited remarkable anti-oxidant activities, recording the IC₅₀ value of 19.65 ± 5.7 µg/mL in DPPH, IC₅₀ of 15.49 ± 4.8 against NO free radicals, the IC₅₀ value of 19.65 ± 5.22 µg/mL against scavenging ability, and IC₅₀ value of 19.38 ± 7.11 µg/mL for iron chelation capacity and the cytotoxic activities against PC3 cell lines were recorded with IC₅₀ values of 35.81 ± 4.2 µg/mL after 24 h, 23.29 ± 3.8 µg/mL at 48 h, and 16.25 ± 6.5 µg/mL after 72 h. Further mechanistic studies have revealed that the compound MVL has shown its pharmacological efficacy by upregulation of P53 and BAX while downregulation of BCL-2 expression, indicating that MVL is following apoptosis in varying degrees. To better understand the pharmacological properties of MVL, in this work, the absorption, distribution, metabolism, excretion, and toxicity (ADMET) were also evaluated. During ADMET predictions, MVL has displayed a safer profile in case of hepatotoxicity, cytochrome inhibition and also displayed as non-cardiotoxic. The compound MVL showed good binding energy in the molecular docking studies, and the results revealed that MVL bind in the active region of the target protein of P53 and BAX. This work triumphantly announced a prodigious effect of heavy metals on actinobacteria with fringe benefits as a key tool of MVL production with a strong pharmacological and pharmacokinetic profile.     

Foliar epidermal anatomy of some selected wild edible fruits of Pakistan using light microscopy and scanning electron microscopy

The present study is focused on the detailed foliar epidermal anatomy of some selected wild edible fruits (WEFs) from Pakistan using light microscopy (LM) and scanning electron microscopy (SEM). The studied species are Ficus racemosa L., Solanum nigrum L., Capparis spinosa L., Physalis divaricata D.Don, Rosa moschata Herrm. and Ribes orientale Desf. collected from various localities of Pakistan. The objective of the present study is to investigate qualitative and quantitative anatomical characters for the identification and differentiation of collected wild edible fruits. The characters studied are shape and size of epidermal cells, anticlinal wall pattern, trichome type and shape, average number of stomata, length and width of stomata and pore. The detailed microscopic investigation and variations in the characters recorded have a key role in the determination and authentication of wild edible fruits. This study possesses great potential for plant taxonomists to further evaluate the species at molecular and genetic levels.     

Study on brittleness templates for shale gas reservoirs-A case study of Longmaxi shale in Sichuan Basin,southern China

Differentiating brittle zones from ductile zones in low permeability shale formations is imperative for efficient hydraulic fracturing stimulation.The brittlene...     

Synthesis of yttrium and cerium doped ZnO nanoparticles as highly inexpensive and stable photocatalysts for hydrogen evolution

Yttrium and cerium co-doped ZnO nanoparticles were synthesized by combustion route and characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),UV-visible diffuse reflectance spectroscopy(UV-vis DRS),photoluminescence(PL)and electrochemical impedance spectroscopy(EIS)techniques.The introduction of yttrium ions has efficiently increased the relative percentage of Ce³⁺ions in ZnO.Yttrium and cerium co-doped ZnO shows efficient photo activity for hydrogen evolution(10.61 mmol/((g·h))higher than previously reported optimal value for rare earth codoped ZnO photocatalysts.This remarkably increased hydrogen evolution can be ascribed to the synergy between electronic anchoring effect of Y³⁺/Y²⁺and Ce⁴⁺/Ce³⁺redox couples.This report presents new idea for the synthesis of efficient photocatalyst using economical route and ion anchoring effect.The hydrogen evolution was also tested using Na₂S and Na₂SO₃as electron donors under visible light illumination.The synthesized photocatalysts also exhibit high stability.     

Rainfall Extremes: a Novel Modeling Approach for Regionalization

The rainfall events of extreme magnitude over the past few decades have caused destructive damages to lives and properties, especially in the subcontinent (e.g. Pakistan, India, Bangladesh etc). Rainfall hazard maps for these areas can be of great practical and theoretical interests. In our work, we used extreme value analysis and spatial interpolation techniques to provide such maps through a combination of the Tropical Rainfall Measuring Mission Precipitation (TRMM) 3B42 product and raingauge data. This mixed approach takes advantage of both the long time series available at a limited number of stations, and the large spatial coverage of the satellite data which, instead, has a poor temporal extent. The methodology is implemented by (1) creating a unique growth curve for the homogeneous region by utilizing in-situ rainfall data and (2) mapping the parameters of intensity-duration functions for the entire length of the study area by using TRMM 3B42 product. The regional results obtained by using mixed approach and TRMM 3B42 are compared with the estimates obtained by using in-situ data. The comparison showed that the overall output of mixed approach is more consistent with what transpired by in-situ data for a pre-defined return period.