Effect of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> phases on the enhancement of thermal conductivity and viscosity of nanofluids in engine oil

Thermal conductivity of α-Al₂O₃ was measured using hot wire method. α-Al₂O₃ (20 nm in size) was synthesized by microwave method for which, the results were compared with commercially available γ-Al₂O₃. Thermal conductivity of nanofluids was investigated considering, it is dependency on Al₂O₃ phase. It was observed that by adding 3 wt% of nano γ-Al₂O₃ and α-Al₂O₃ to the engine oil, thermal conductivity increases by 37 and 31%, respectively. The corresponding viscosity increase for the same amount of nano γ-Al₂O₃ and α-Al₂O₃ were 36 and 38%, respectively. It was concluded that the differences in thermal conductivity originate from higher specific surface area of γ-Al₂O₃ compared to the α-Al₂O₃ which is the result of porosity difference, obtained during the synthesis process.     

Control of Protonated Schiff Base Excited State Decay within Visual Protein Mimics: A Unified Model for Retinal Chromophores

Artificial biomimetic chromophore-protein complexes inspired by natural visual pigments can feature color tunability across the full visible spectrum. However, control of excited state dynamics of the retinal chromophore, which is of paramount importance for technological applications, is lacking due to its complex and subtle photophysics/photochemistry. Here, ultrafast transient absorption spectroscopy and quantum mechanics/molecular mechanics simulations are combined for the study of highly tunable rhodopsin mimics, as compared to retinal chromophores in solution. Conical intersections and transient fluorescent intermediates are identified with atomistic resolution, providing unambiguous assignment of their ultrafast excited state absorption features. The results point out that the electrostatic environment of the chromophore, modified by protein point mutations, affects its excited state properties allowing control of its photophysics with same power of chemical modifications of the chromophore. The complex nature of such fine control is a fundamental knowledge for the design of bio-mimetic opto-electronic and photonic devices.     

Synthesis,structural characterization and anticancer properties of p-cymene Ru(II) complexes with 2-(N-methyl-1H-1,2,4-triazol-3-yl)pyridines

Transition Metal Chemistry - The structures of new p-cymene Ru(II) complexes with 2-(1-methyl-1H-1,2,4-triazol-3-yl)pyridine and 2-(1-methyl-1H-1,2,4-triazol-5-yl)pyridine were established based on...     

Structures,g-tensors,and hyperfine coupling constants of L-α-alanine radicals in radiation dosimetry: An ab initio molecular dynamics simulation study

Alanine is used as a transfer standard dosimeter for gamma ray and electron beam calibration. An important factor affecting its dosimetric response is humidity which can lead to errors in absorbed dose calculations. Ab initio molecular dynamics calculations were performed to determine the environmental effects on the electron paramagnetic resonance (EPR) parameters of L-α-alanine radicals in acidic and alkaline solutions. A new result, not dissimilar to the closed-shell amino acid molecule alanine, is that the non-zwitterionic form of the alanine radical is the stable form in the gas phase while the zwitterionic neutral alanine radical is not a stable structure in the gas phase. Geometric and EPR parameters of radicals in both gas and solution phases are found to be dependent on hydrogen bonding of water molecules with the polar groups and on dynamic solvation. Calculations on the optimized free radicals in the gas phase revealed that for the neutral radical, hydrogen bonding to water molecules drives a decrease in the magnitudes of g-tensor components g _xx and g _yy without affecting neither g _zz component nor the hyperfine coupling constants (HFCCs). The transfer from the gas to solution phase of the alanine radical anion is accompanied with an increase in the spin density on the carboxylic group's oxygen atoms. However, for the neutral radical, this transfer from gas to solution phase is accompanied with the decrease in the spin density on oxygen atoms. Calculated isotropic HFCCs and g-tensor of all radicals are in good agreement with experiment in both acidic and alkaline solutions.     

Interior and interfacial aqueous solvation of benzene dicarboxylate dianions and their methylated analogues: A combined molecular dynamics and photoelectron spectroscopy study

Aqueous solvation of benzene dicarboxylate dianions (BCD(2-)) was studied by means of photoelectron spectroscopy and molecular dynamics simulations. Photoelectron spectra of hydrated o- and p-BCD(2-) with up to 25 water molecules were obtained. An even-odd effect was observed for the p-BCD(2-) system as a result of the alternate solvation of the two negative charges. However, the high polarizability of the benzene ring makes the two carboxylate groups interact with each other in p-BCD(2-), suppressing the strength of this even-odd effect compared with the linear dicarboxylate dianions linked by an aliphatic chain. No even-odd effect was observed for the o-BCD(2-) system, because each solvent molecule can interact with the two carboxylate groups at the same time due to their proximity. For large solvated clusters, the spectral features of the solute decreased while the solvent features became dominant, suggesting that both o- and p-BCD(2-) are situated in the center of the solvated clusters. Molecular dynamics simulations with both nonpolarizable and polarizable force fields confirmed that all three isomers (o-, m-, and p-BCD(2-)) solvate in the aqueous bulk. However, upon methylation the hydrophobic forces overwhelm electrostatic interactions and, as a result, the calculations predict that the tetramethyl-o-BCD(2-) is located at the water surface with the carboxylate groups anchored in the liquid and the methylated benzene ring tilted away from the aqueous phase.     

First-passage Monte Carlo algorithm: diffusion without all the hops

We present a novel Monte Carlo algorithm for N diffusing finite particles that react on collisions. Using the theory of first-passage processes and time dependent Green's functions, we break the difficult N-body problem into independent single- and two-body propagations circumventing numerous diffusion hops used in standard Monte Carlo simulations. The new algorithm is exact, extremely efficient, and applicable to many important physical situations in arbitrary integer dimensions.     

Design of a highly efficient and water-tolerant sulfonic acid nanoreactor based on tunable ordered porous silica for the von Pechmann reaction

Among a number of different sulfonic acid nanoreactors prepared, 5 having both acidic sites and phenyl groups located inside the mesochannels of SBA-15 was shown to be the most active and reusable catalyst in the von Pechmann reaction. The mesochannels, and covalently anchored organic groups, provide a synergistic means of an efficient approach of the reactants to acidic sites, enough space for the subsequent cyclization, and suitable hydrophobicity to drive out the water byproduct.     

Fabrication of poly(ϵ-caprolactone)/paclitaxel (core)/chitosan/zein/multi-walled carbon nanotubes/doxorubicin (shell) nanofibers against MCF-7 breast cancer

In the present study, paclitaxel (PTX), multi-walled carbon nanotubes (MWCNTs), and doxorubicin (DOX) have been simultaneously doped into the poly(ϵ-caprolactone) (PCL)/chitosan/zein core-shell nanofibers to increase its cytotoxicity for MCF-7 breast cancers killing. The physico-chemical properties of synthesized nanofibers were determined by scanning electron microscope, Fourier-transform infrared spectroscopy, tensile strength, and degradation rate determinations. The in vitro release studies demonstrated the sustained release of drugs from core-shell nanofibrous scaffold. The cytotoxicity and compatibility of core-shell nanofibers were investigated by their treating with MCF-7 breast cancer cells and L929 normal cells, respectively. PCL/PTX/chitosan/zein/MWCNTs/DOX core-shell nanofibers containing 1 wt% MWCNTs, 100 μg ml⁻¹ DOX and 100 μg ml⁻¹ PTX had a high biocompatibility with a 84% MCF-7 cancer cells killing. The in vivo studies revealed the synergic effects of MWCNTs and anticancer drugs on the tumor inhibition. This method could be considered as a new way for developing of MWCNTs loaded-nanofibers for cancer treatment in future.     

Targeted Delivery of Anticancer Drug Loaded Charged PLGA Polymeric Nanoparticles Using Electrostatic Field

Pure positive electrostatic charges (PPECs) show suppressive effect on the proliferation and metabolism of invasive cancer cells without affecting normal tissues. PPECs are used for the delivery of drug-loaded polymeric nanoparticles (DLNs) capped with negatively charged poly(lactide-co-glycolide) (PLGA) and Poly(vinyl-alcohol) PVA into the tumor site of mouse models. The charged patch is installed on top of the skin in the mouse models' tumor region, and the controlled selective release of the drug is assayed by biochemical, radiological, and histological experiments on both tumorized models and normal rats' livers. It is found that DLNs synthesized by PLGA show great attraction to PPECs due to their stable negative charges, which would not degrade immediately in blood. The burst and drug release after less than 48h of this synthesized DLNs are 10% and 50%, respectively. These compounds can deliver the loaded-drug into the tumor site with the assistance of PPECs, and the targeted-retarded release will take place. Hence, local therapy can be achieved with much lower drug concentration (conventional chemotherapy [2 mg kg⁻¹] versus DLNs-based chemotherapy [0.75 mg kg⁻¹]) with negligible side effects in non-targeted organs. PPECs have many potential clinical applications for advanced-targeted chemotherapy with the lowest discernible side effects.