Transverse Transport of Polymeric Nanofluid under Pure Internal Heating: Keller Box Algorithm

The present work aims to investigate transverse Oldroyd-B nanofluid flow on a stretched panel with consideration of internal heat generation. Buongiorno model is utilized to study influence of thermophoresis and Brownian motion effects. A numerical procedure known as Keller box algorithm is used to solve the governed physical model. Graphically velocity, temperature and concentration of nanoparticles are expressed. Also, concerned physical measures such as heat and mass transfer are investigated numerically. The simulations performed revealed that fluid parameters play a significant role in heat transfer under Brownian motion and thermophoresis effects. Local heat flux is elevated while local mass flux is suppressed with enhancing Brownian motion parameter. Streamlines pattern exhibits that flow is more inclined in the presence of Deborah number effects. To the best of our knowledge, transverse flow of an Oldroyd-B type fluid which incorporates the thermal relaxation effects has never been reported before in the presence of Brownian motion and internal heating phenomenon. Therefore we intend to discuss these features in detail. The obtained results are a novel contribution, which can be benchmark for further relevant academic research related to polymer industry.     

The effect of high dose of gamma-irradiation on residual radicals concentration in ultra-high molecular weight polyethylene (UHMWPE) in the presence of vitamin E

Powder samples of UHMWPE (GUR 1020) containing 0.1% by wt. vitamin E (??-tocopherol, ??-T) were irradiated at room temperature in air for doses of 30-kGy, 65-kGy or 100-kGy (⁶⁰Co). After irradiation, they were stored at ?78.5°C (dry ice temperature) for one year and then opened to air at room temperature. Following the decay of the primary alkyl and allyl radicals (at room temperature in air), growth of the carbon-centered polyenyl R1 (?^·CH?CH=CH?, m ?? 3), and the oxygen-centered dior tri-enyl R2 (?^·OCH?CH=CH? _m , m ?? 3) residual radicals were measured for eight weeks. An X-band electron spin resonance (ESR) spectrometer was used for radical measurements. The initial relative radical concentrations (R2/R1) were found to be 10.13, 4.6 and 3.7 for the 65-kGy, 30-kGy and 100-kGy samples, respectively. R1 and R2 were both found to grow significantly in the 65-kGy samples while they grew only slightly in the 30-kGy and 100-kGy samples. In 65-kGy sample, R1 grew faster than R2 and the relative concentration R2/R1 was reduced from 10.13 to 2.9 for the 65-kGy sample while that for the 30-kGy and 100-kGy samples reduced only slightly, from 4.6 to 3.5 and 3.7 to 3.2, respectively. The behavior of the residual radicals can be explained by Raman spectroscopic data which suggest that the 65-kGy samples had a higher percentage of amorphous regions when compared to the 30-kGy or 100-kGy (21.7% compared to 15.7% or 17.9%) and also suggest a lower percentage of inter-phase regions (16.4% compared to 25.6% or 17.5%) and a lower level of structural disorder (0.26% compared to 0.44% or 0.27%).     

Design and development of an optical beam splitter assembly and high precision colinearity measurements of laser beams

Laser beams with extremely high colinearity are often required where precision position monitoring is important. In order to achieve the said objective, a special type of Laser Beam Splitter Assembly (BSA) has been designed and fabricated in a very small volume due to space constraints. The main features and details of such a system are described here. This type of beam splitter assembly coupled with a diode laser through fibers can be remotely used for alignment or position monitoring of different medium to large size structures with a reconstruction accuracy of 10 μm. In this way, BSA generates two counter propagating laser beams from a single diode laser coupled to an optical fiber. In the present work, the colinearity between two beams within 1 mrad with the variation of 50 μrad has been achieved. The laser's power in the two arms may be controlled precisely, which is an important feature of this BSA. The BSA has been tested to work over a temperature range between ?20 °C to +40 °C. It has also been exposed to 1.0 MeV neutrons at a flux of ～5.0×10¹⁰ n/cm²/s and found compatible.     

Synthesis and Structural Characterization of Bioactive Ferrocenyl Substituted Hydrazones

Russian Journal of Coordination Chemistry - A series of ferrocenyl substituted hydrazones (I–VII) derived from ferrocene carboxaldehyde and substituted hydrazides have been prepared and...     

Development and Characterization of Novel Biopolymer Derived from Abelmoschus esculentus L. Extract and Its Antidiabetic Potential

Abelmoschus esculentus (Okra) is an important vegetable crop, widely cultivated around the world due to its high nutritional significance along with several health benefits. Different parts of okra including its mucilage have been currently studied for its role in various therapeutic applications. Therefore, we aimed to develop and characterize the okra mucilage biopolymer (OMB) for its physicochemical properties as well as to evaluate its in vitro antidiabetic activity. The characterization of OMB using Fourier-transform infrared spectroscopy (FT-IR) revealed that okra mucilage containing polysaccharides lies in the bandwidth of 3279 and 1030 cm⁻¹, which constitutes the fingerprint region of the spectrum. In addition, physicochemical parameters such as percentage yield, percentage solubility, and swelling index were found to be 2.66%, 96.9%, and 5, respectively. A mineral analysis of newly developed biopolymers showed a substantial amount of calcium (412 mg/100 g), potassium (418 mg/100 g), phosphorus (60 mg/100 g), iron (47 mg/100 g), zinc (16 mg/100 g), and sodium (9 mg/100 g). The significant antidiabetic potential of OMB was demonstrated using α-amylase and α-glucosidase enzyme inhibitory assay. Further investigations are required to explore the newly developed biopolymer for its toxicity, efficacy, and its possible utilization in food, nutraceutical, as well as pharmaceutical industries.     

Synthesis of Starch-Grafted Polymethyl Methacrylate via Free Radical Polymerization Reaction and Its Application for the Uptake of Methylene Blue

In this research, a new biodegradable and eco-friendly adsorbent, starch-grafted polymethyl methacrylate (St-g-PMMA) was synthesized. The St-g-PMMA was synthesized by a free radical polymerization reaction in which methyl methacrylate (MMA) was grafted onto a starch polymer chain. The reaction was performed in water in the presence of a potassium persulfate (KPS) initiator. The structure and different properties of the St-g-PMMA was explored by FT-IR, 1H NMR, TGA, SEM and XRD. After characterization, the St-g-PMMA was used for the removal of MB dye. Different adsorption parameters, such as effect of adsorbent dose, effect of pH, effect of initial concentration of dye solution, effect of contact time and comparative adsorption study were investigated. The St-g-PMMA showed a maximum removal percentage (R%) of 97% towards MB. The other parameters, such as the isothermal and kinetic models, were fitted to the experimental data. The results showed that the Langmuir adsorption and pseudo second order kinetic models were best fitted to experimental data with a regression coefficient of R² = 0.93 and 0.99, respectively.     

p-Substituted Tris(2-pyridylmethyl)amines as Ligands for Highly Active ATRP Catalysts: Facile Synthesis and Characterization

A facile and efficient two-step synthesis of p-substituted tris(2-pyridylmethyl)amine (TPMA) ligands to form Cu complexes with the highest activity to date in atom transfer radical polymerization (ATRP) is presented. In the divergent synthesis, p-Cl substituents in tris(4-chloro-2-pyridylmethyl)amine (TPMA^3Cl) were replaced in one step and high yield by electron-donating cyclic amines (pyrrolidine (TPMA^PYR), piperidine (TPMA^PIP), and morpholine (TPMA^MOR)) by nucleophilic aromatic substitution. The [Cu^II(TPMA^NR2)Br]⁺ complexes exhibited larger energy gaps between frontier molecular orbitals and >0.2 V more negative reduction potentials than [Cu^II(TPMA)Br]⁺, indicating >3 orders of magnitude higher ATRP activity. [Cu^I(TPMA^PYR)]⁺ exhibited the highest reported activity for Br-capped acrylate chain ends in DMF, and moderate activity toward C−F bonds at room temperature. ATRP of n-butyl acrylate using only 10–25 part per million loadings of [Cu^II(TPMA^NR2)Br]⁺ exhibited excellent control.     

Chemical sensing of Benzo[a]pyrene using Corchorus depressus fluorescent flavonoids

Plant phytochemicals, such as flavonoids are in use for the development of optical biosensor. Benzo[a]pyrene (B[a]P), is a pervasive environmental and dietary carcinogen. A fluorescent assay is developed using plant isolated flavonoid for the detection of B[a]P. High content saponins are excluded from the flavonoid-containing methanolic extract of Corchorus depressus by implying reduction of silver ions by saponins resulting in formation of silver nanoparticles. Isolated plant flavonoids are used to develop a spectrofluorometric assay for the detection of B[a]P. Decrease in the flavonoid fluorescence intensity by B[a]P is found to be based on both static and dynamic quenching. Specificity of the assay for B[a]P was tested for other carcinogens belonging to different classes of compounds. Flavonoids-mediated sensing can be implied for the development of new generation of nanoparticle-based biosensors that can be more sensitive and less susceptible to external factors, such as temperature and humidity.     

Photoluminescence emission behavior on the reduced band gap of Fe doping in CeO2-SiO2 nanocomposite and photophysical properties

Fe/CeO₂-SiO₂ nanocomposite was synthesized via hydrothermal method. Bond length of nanocomposite was determined through FTIR analysis, while Raman analysis showed lattice relaxation of CeO₂ phase in Fe/CeO₂-SiO₂. TEM, XRD and DLS-PSA revealed an increase in size of Fe/CeO₂-SiO₂ as compared to CeO₂-SiO₂ which was attributed to have more oxygen vacancies in CeO₂ after doping of iron. Lattice contraction was also observed in some phases of CeO₂ in Fe/CeO₂-SiO₂ nanocomposite as compared to CeO₂-SiO₂ nanocomposite. This contraction was used for determination of Fe content incorporated in CeO₂ [1 1 1] phase. The band gap values of Fe/CeO₂-SiO₂ nanocomposite were found reduced after doping of Fe by factors of 0.62 and 0.55 eV, respectively. Photoluminescence study of the materials was carried out to study the different type of transitions occurring after absorption of electromagnetic radiation. Photoluminescence intensity at 2.12 eV was found enhanced after doping of Fe due to increased oxygen vacancy. Photocatalytic activity of the nanocomposites was studied with the degradation of chlorpyrifos pesticide.