Entropy generation of graphene–platinum hybrid nanofluid flow through a wavy cylindrical microchannel solar receiver by using neural networks

Journal of Thermal Analysis and Calorimetry - Analyzing microchannel heat sinks (MCHS) in terms of the second thermodynamic law is useful, and it is necessary to examine MCHSs in terms of...     

Poly (L-phenylalanine-paired ionic liquid) as halogen-free heterogeneous nanocatalyst toward regiospecific 1,3-dipolar cycloaddition reaction

Although amino acid-paired ionic liquids (IL [AA]) have attracted considerable attention due to their environmental-friendly nature and providing abundant catalytic active sites, polymerized eco-friendly ILs have been rarely reported. Herein, we introduce a novel polymerized L-phenylalanine-paired ionic liquid (PIL [Phe]), synthesized in a new smart manner, as a promising heterogeneous nanocatalyst for regiospecific 1,3-dipolar cycloaddition reaction. For this purpose, new polymerizable ionic liquid (3-(3-aminopropyl)-1-vinylimidazolium (L)-2-amino-3-phenylpropanoate ([AVIm][Phe])) was designed and constructed as a halogen-free multifunctional monomer. The successful fabrication of chiral IL was approved by different techniques including ¹H NMR, FT-IR, and elemental analysis. Next, a green precipitation polymerization approach was applied using a water-soluble initiator under mild conditions. Co₃O₄@PIL [Phe] was synthesized by in situ copolymerization of the [AVIm][Phe] with ethyleneglycoldimethacrylate (EGDMA) (as non-ionic cross-linker) supported on magnetic Co₃O₄@MPS. The obtained data reveal that the supported polymerized form of [AVIm][Phe] is more efficient due to the formation of a porous structure with high-specific surface area (235.5 m²/ g) and a cross-linked network with high thermal stability (35% weight loss around 600 °C). In the following, the proposed Co₃O₄@PIL [Phe] nanostructure was applied as a magnetic catalyst toward the preparation of new and reported pyrrolidinyldispirooxindoles; and it displayed accelerated mass transfer due to its large pore volume (0.85 cm³/ g), and numerous accessible active sites. Consequently, a range of pharmaceutical dispirobisoxindole scaffolds with broad structural diversity were readily obtained in excellent yields (>92%) and high regioselectivity under environmental conditions.     

Numerical investigation of serrated fins on natural convection from concentric and eccentric annuli with different cross sections

Journal of Thermal Analysis and Calorimetry - In this paper, the effect of internal serrated fins and eccentricity on natural convection heat transfer between annular spaces with the equivalent...     

A smoothed particle hydrodynamics approach for numerical simulation of nano-fluid flows

Journal of Thermal Analysis and Calorimetry - Nano-fluidic flow and heat transfer around a horizontal cylinder at Reynolds numbers up to 250 are investigated by using weakly compressible smoothed...     

Effects of H-bonding and structural constituents on the acidity and potential "anticancer activity" of D-mandelonitrile-β-D-glucuronic acid by density functional theory

Research on Chemical Intermediates - Laetrile (D-mandelonitrile-β-D-glucuronic acid, 1COOH) is being promoted, more and more, as an alternate cancer treatment, in many countries. Here we show...     

Melting entropy of nanocrystals: an approach from statistical physics

Considering size effect on the equations obtained from statistical mechanical theories for the entropy of crystal and liquid phases, a new model has been developed for the melting entropy of nanocrystals, including the effects of the quasi-harmonic, anharmonic and electronic components of the overall melting entropy. Then with the use of our suggested new proportionality between the melting point and the entropy temperature (θ(0)), the melting entropy of nanocrystals has been obtained in terms of their melting point. Moreover, for the first time, the size-dependency of the electronic component of the overall melting entropy, arising from the change in the electronic ground-state of the nanocrystal upon melting, has been taken into account to calculate the melting entropy of nanocrystals. Through neglecting the effect of the electronic component, the present model can corroborate the previous model for size-dependent melting entropy of crystals represented by Jiang and Shi. The present model has been validated by the available computer simulation results for Ag and V nanoparticles. Moreover, a fairly constant function has been introduced which couples the melting temperature, the entropy temperature and the atomic density of elements to each other.     

Highly Efficient Synthesis of Substituted Benzenes in the Presence of B(HSO4)3 as a New and Reusable Catalyst Under Solvent-Free Conditions

A highly efficient and simple procedure for the synthesis of substituted benzenes is described. A broad range of ketones (alkyl–aryl ketones and cyclic ketones) were condensed via a cyclotrimerization reaction in the presence of catalytic amounts of boron sulfonic acid [B(HSO₄)₃], a new, highly efficient, and reusable catalyst, under solvent-free conditions. All reactions completed in short times without formation of any by-products. The catalyst was recovered and reused successfully for 15 cycles of the reaction.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

A study on the binding of two water-soluble tetrapyridinoporphyrazinato copper(II) complexes to DNA

Interaction of N,N′,N″,N-tetramethyltetra-2,3-pyridinoporphyrazinatocopper(II), ([Cu(2,3-tmtppa)]⁴⁺) and N,N′,N″,N-tetramethyltetra-3,4-pyridinoporphyrazinatocopper(II), ([Cu(3,4-tmtppa)]⁴⁺) with calf thymus DNA was studied in 1 mM phosphate buffer and low ionic strength (5 mM NaCl) at various temperatures by UV-visible and circular dichroism (CD) spectroscopies and viscometric method. The binding constants were determined from the changes in the visible part of porphyrazine complexes spectra using SQUAD software. The values of K have been obtained (7.9±0.4)×10⁴ and (2.2±0.1)×10⁵ M⁻¹ for [Cu(2,3-tmtppa)]⁴⁺ and [Cu(3,4-tmtppa)]⁴⁺, respectively at 27 °C. The higher affinity of 3,4-isomer of Cu complex towards DNA with respect to the 2,3-isomer was attributed to favorable external positioning of the cationic charges in former, which enables superior interaction with the DNA duplex. The thermodynamic parameters (ΔG°, ΔH°, ΔS°) were calculated by van't Hoff equation. The enthalpy and entropy changes were determined, +34.2±3.6 kJ mol⁻¹ and +207.8±12.70 J mol⁻¹ K⁻¹ for [Cu(2,3-tmtppa)]⁴⁺ and +49.7±2.1 kJ mol⁻¹ and +267.8±7.9 J mol⁻¹ K⁻¹ for [Cu(3,4-tmtppa)]⁴⁺. The existence of extensive hypochromicity, large red shift and negative CD in the visible part of [Cu(3,4-tmtppa)]⁴⁺ spectra suggested an intercalation binding mode. Analysis of the moderate hypochromicity, red shift and bisignate CD in the Q-band absorption region of [Cu(2,3-tmtppa)]⁴⁺ spectra possibly led us to the coexistence of intercalation and outside binding modes. The influence of the ionic strength on the binding parameters and binding modes was investigated. The results show that increase in ionic strength causes the decrease in the binding constants. It was also concluded that increase in ionic strength affects the binding characteristics of positively charged complexes with DNA.

The increase in DNA viscosity in the presence of Cu–tmtppa complexes is attributed to the lengthening of DNA helix due to the intercalation. This result is consistent with conclusions obtained from the spectroscopic techniques.