Heterotrinuclear manganese(II) and vanadium(IV) Schiff base complexes as epoxidation catalysts

The catalytic epoxidation of styrene using urea-hydrogen peroxide and heterotrinuclear Cu(II) complexes with general formula (ML ⁿ )₂Cu(acac)₂, where n = 1–3 and M = VO²⁺ or Mn²⁺ is reported. Schiff base complexes ML ⁿ involving a 3,4-diaminopyridine bridge with free coordination site were used as the ligand, where (Lⁿ)²⁻ is [(5-x-Sal)₂Py]² and x = H, Br or NO₂. The complexes were characterized by physico-chemical and spectroscopic methods. The electrochemical properties of M were modified upon trinuclear complex formation. The trinuclear complexes show high catalytic activity, with up to 86% conversion and 93% selectivity, while no catalytic properties were observed for the monomeric complexes. The catalyst could be reused with some loss of activity.     

Collective behavior of cortico-thalamic circuits: Logic gates as the thalamus and a dynamical neuronal network as the cortex

This paper introduces a two-layer network to investigate the effects of cortico-thalamic circuits on the cortex's collective behavior. In the brain, different parts of the cortex collaborate to process information. One of the main parts, which is the path of different cortex contacts, is the thalamus whose circuit is referred to as the "vertical" cortico-thalamic connectivity. Thalamus subnuclei can participate in the processing of the information that passes through them. It has been shown that they play the functional role of logic gates (AND, OR and XOR). To study how these thalamus circuits affect the cortical neuron behavior, a two-layer network is proposed wherein the cortex layer is composed of Hindmarsh-Rose models and the thalamus layer is constructed with logic gates. Results show that considering these logic gates can lead the network towards different synchronization, asynchronization, chimera and solitary patterns. It is revealed that for AND-gate and OR-gate, increasing the number of gates or their outputs can increase and decrease the network's coherency in excitatory and inhibitory cases, respectively. However, considering XOR-gates always results in the chimera state.     

Green synthesis and biological activity investigation of new derivatives of spiroisatins

In this research, the synthesis of novel derivatives of spiroisatins in high yields was investigated. These new compounds were synthesized using a multicomponent reaction (MCR) of isatin, malononitrile, acetophenone derivatives, diethyl oxalate, primary amines, and Et₃N in aqueous media. Under similar conditions, spiropyrroloisatins were prepared using MCRs of synthesized spiroistins. The antioxidant activity of newly synthesized spiroisatins is due to having an NH group which was evaluated by two procedures. Also, the antimicrobial activity of newly generated spiroisatins was evaluated by a disk distribution process utilizing two kinds of Gram-negative bacteria and Gram-positive bacteria and bacterial growth was stopped using these compounds. The advantages of this method are short reaction times, high yields of products, and the easy separation of catalyst and product using simple procedures.     

Synthesis of a New Class of Highly Functionalized Phosphorus Ylides Containing Heterocyclic Compounds

The zwitterionic intermediate generated from the reaction of triphenylphosphine with electron deficient acetylenic compounds was trapped by various NH acids. The synthesis resulted in a new class of highly functionalized heterocyclic compounds. Some of the reactions produced E and Z isomers. And the stability and transformation of them were studied by dynamic ¹H NMR and density functional theory (DFT) calculations.     

Stereoselective synthesis of functionalised carbocyclic amides: construction of the syn-(4aS,10bS)-phenanthridone skeleton

A new synthetic approach has been developed for the preparation of 7-deoxypancratistatin analogues bearing a syn-(4aS,10bS)-phenanthridone ring junction. A one-pot tandem process involving a substrate-directed Overman rearrangement and ring closing metathesis reaction was developed for the stereoselective synthesis of a carbocyclic allylic trichloroacetamide. Conversion to a 6-bromopiperonyl amide, followed by a Heck reaction generated a homoallylic alcohol and completed the syn-(4aS,10bS)-phenanthridone carbon skeleton. Stereoselective epoxidation and dihydroxylation of the syn-(4aS,10bS)-phenanthridone framework was then investigated leading to the preparation of new analogues of 7-deoxypancratistatin.     

EPR Study of γ-Irradiated UHMWPE Doped with Vitamin E: Assessment of Thermal Effects on the Organic Radicals During Vitamin E Diffusion

Thermal effects on ultra-high-molecular-weight polyethylene (UHMWPE) residual radicals during the vitamin E diffusion process were studied in detail. Electron paramagnetic resonance (EPR) technique showed a significant reduction in concentrations of radiation-induced primary (alkyl (–CH₂– ^?CH–CH₂–), allyl (–CH₂–^?CH=CH–CH–CH₂–) and polyenyl (–^?CH–[CH=CH–] _m –) with m > 3) radicals for both control and vitamin E-doped samples. The concentrations of radiation-induced primary radicals (RIPRs) were found to decrease proportionally with the heat/diffusion time. While the EPR spectra of the control samples showed only polyethylene (PE) radicals, the spectra of vitamin E-doped samples were found to exhibit vitamin E radicals in addition to PE radicals. Of particular interest, the heat involved during vitamin E diffusion plays a significant role in reducing the radiation-induced primary radicals of UHMWPE. For 120 min of heat/diffusion time, the available quantity of primary radicals in control samples were found to be ~7.5 % of initial radicals. The leftover amounts of these primary radicals for vitamin E-doped samples were approximately ~10.0 %. In addition to this, EPR power saturation techniques were also used to assess the effects of initial heat/diffusion treatment on the oxygen-induced residual radicals (OIRRs): R₁ (–^?CH–[CH=CH–] _m –) with m > 3 and R₂ (^?OCH–[CH=CH–] _m –) with m = 2 or 3. It was found that the concentration of OIRRs also decreases proportionally with initial heat/diffusion time. The remaining amount of OIRRs relative to leftover RIPRs after heat/diffusion was found to be approximately 4.0 % in controls and was still found to be 10.0 % in vitamin E-doped UHMWPE. This may indicate that vitamin E slows down the oxidation processes, which may contribute to the strong oxidation resistance of vitamin E-doped UHMWPE.     

An efficient scheme for digital watermarking using chaotic map

This paper presents the new digital watermarking algorithm based on the chaotic map. Data can easily be hidden in images by using the least significant bits. In the anticipated algorithm, the logistic map is employed for locating embedding positions of chaotic watermark generation and a novel watermarking scheme is proposed. Simulation results reveal that the proposed technique is feasible and watermarks are indiscernible. The results illustrate that mean of energy, correlation, contrast, and homogeneity analyses of the proposed algorithm are quite optimal.     

First-principles study of vibrational properties of TiSiO4 clusters

First-principles calculations were performed to investigate the vibrational properties of monomers and dimers of titania, silica, and titania-silica hybrid clusters. Density functional theory-based formulism was employed to optimize the geometry at the B3LYP level and calculate the infrared and Raman spectra of the clusters by using the GGA-PBE exchange-correlation functional. It was found that the vibrational spectra of Ti₂O₄, Si₂O₄, and TiSiO₄ hybrid clusters provide fingerprint information about structures and structural transitions during the formation of cluster structures. In the case of Si₂O₄ the mode at 410 cm⁻¹ exhibited the largest vibration of Si atoms, whereas in the case of Ti₂O₄ the mode at 442 cm⁻¹ exhibited the largest vibration of Ti atoms. The hybrid cluster TiSiO₄ was structured using two different methods to explore the effects of starting geometry on the structures and vibrational modes of the clusters. The structural properties of the clusters remained unchanged but vibrational modes were found to be different. It is found that Si shows notable vibrations, but the metal atom Ti merely shows any vibration in the case of TiSiO₄ hybrid clusters. The low and intermediate frequency modes were stiffened, whereas the three highest frequency modes were softened when the starting geometry of the hybrid clusters was changed from Si₂O₄ to Ti₂O₄.