Functionalization of Cubanes and Homocubanes via Oxidative Displacement of Iodine Using Hypervalent Iodine

The iodo group in 4-iodo-1-carbomethoxycubane (1) can be replaced by mesyloxy, tosyloxy and chloro by oxidative displacement with C₆H₅I(OH)OMs, C₆H₅I(OH)OTs and C₆H₅ICl₂, respectively. Similarly, the iodo group in the homocubyl compound 4-iodo-1-bromopentacyclo[4.3.0.0^2,5.0^3,8.0^4,7]nonane-9-one ethylene acetal (2) was analogously replaced by mesyloxy, tosyloxy and chloro. Possible pathways for these reactions are discussed.     

Effects of additives on the structure of rhamnolipid (biosurfactant): a small-angle neutron scattering (SANS) study

Pollution of soils and sediments by heavy metals is an environmental concern. Among the remedial techniques, soil washing is proving to be reliable. Biosurfactant rhamnolipid has shown its potential as a washing agent. In this research, small angle neutron scattering (SANS) was employed to investigate the size and morphology of rhamnolipid aggregates and micelle structure in the presence of heavy metals Cu, Zn, and Ni. The results indicate the importance of the pH of the system in the morphology of the aggregates in the rhamnolipid solution. Creation of a basic condition by addition of 1% NaOH led to the formation of large aggregates (>2000 A) + micelles with RG approximately 17 A while in the acidic environment with 1% NaCl, large polydisperse vesicles with a radius about 550-600 A were formed. The size of the aggregates in both acidic and basic condition is fine enough to ease the flow of the rhamnolipid solution through the porous media with the pore sizes as small as 200 nm.     

Local Clique Covering of Claw‐Free Graphs

A clique covering of a simple graph G is a collection of cliques of G covering all the edges of G such that each vertex is contained in at most k cliques. The smallest k for which G admits a clique covering is called the local clique cover number of G and is denoted by lcc(G). Local clique cover number can be viewed as the local counterpart of the clique cover number that is equal to the minimum total number of cliques covering all edges. In this article, several aspects of the local clique covering problem are studied and its relationships to other well‐known problems are discussed. In particular, it is proved that the local clique cover number of every claw‐free graph is at most , where Δ is the maximum degree of the graph and c is a constant. It is also shown that the bound is tight, up to a constant factor. Moreover, regarding a conjecture by Chen et al. (Clique covering the edges of a locally cobipartite graph, Discrete Math 219(1–3)(2000), 17–26), we prove that the clique cover number of every connected claw‐free graph on n vertices with the minimum degree δ, is at most , where c is a constant.     

Metal-Chelate Immobilization of Lipase onto Polyethylenimine Coated MCM-41 for Apple Flavor Synthesis

An enzyme immobilized on a mesoporous silica nanoparticle can serve as a multiple catalyst for the synthesis of industrially useful chemicals. In this work, MCM-41 nanoparticles were coated with polyethylenimine (MCM-41@PEI) and further modified by chelation of divalent metal ions (M = Co²⁺, Cu²⁺, or Pd²⁺) to produce metal-chelated silica nanoparticles (MCM-41@PEI-M). Thermomyces lanuginosa lipase (TLL) was immobilized onto MCM-41, MCM-41@PEI, and MCM-41@PEI-M by physical adsorption. Maximum immobilization yield and efficiency of 75 ± 3.5 and 65 ± 2.7% were obtained for MCM@PEI-Co, respectively. The highest biocatalytic activity at extremely acidic and basic pH (pH = 3 and 10) values were achieved for MCM-PEI-Co and MCM-PEI-Cu, respectively. Optimum enzymatic activity was observed for MCM-41@PEI-Co at 75 °C, while immobilized lipase on the Co-chelated support retained 70% of its initial activity after 14 days of storage at room temperature. Due to its efficient catalytic performance, MCM-41@PEI-Co was selected for the synthesis of ethyl valerate in the presence of valeric acid and ethanol. The enzymatic esterification yield for immobilized lipase onto MCM-41@PEI-Co was 60 and 53%, respectively, after 24 h of incubation in n-hexane and dimethyl sulfoxide media.

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Graphical Abstract Divalent metal chelated polyethylenimine coated MCM-41 (MCM-41@PEI-M) was used for immobilization of Thermomyces lanuginosa lipase catalyzing green apple flavor preparation

     

Patient-specific model of lung deformation using spatially dependent constitutive parameters

Breathing-induced spatially dependent lung deformation is predicted using patient-specific elastic properties with the contact–impact analysis model. The lung geometry is derived from 4D CT scan data of real patients. The spatially varying Young’s modulus for the patient is obtained from a previous study that used inverse deformation of the lung. The compact–impact analysis is implemented using the finite element method. The predicted lung deformation is compared with the results based on linear elasticity. The results are consistent with physiology, indicating large deformations near the diaphragm and smaller values at remote locations on the lobe. The effect of non-linearity of elastic property is most significant at the remote locations where the diaphragm-induced deformation is significantly attenuated.     

Ligand-mediated formation of Cu/metal oxide hybrid nanocrystals with tunable number of interfaces

Combining domains of different chemical nature within the same hybrid material through the formation of heterojunctions provides the opportunity to exploit the properties of each individual component within the same nano-object; furthermore, new synergistic properties will often arise as a result of unique interface interactions. However, synthetic strategies enabling precise control over the final architecture of multicomponent objects still remain scarce for certain classes of materials. Herein, we report on the formation of Cu/MO_x (M = Ce, Zn and Zr) hybrid nanocrystals with a tunable number of interfaces between the two domains. We demonstrate that the organic ligands employed during the synthesis play a key role in regulating the final configuration. Finally, we show that the synthesized nanocrystals serve as materials platforms to investigate the impact of the Cu/metal oxide interfaces in applications by focusing on the electrochemical CO₂ reduction reaction as one representative example.

We report on the formation of Cu/metal oxide hybrid nanocrystals with a tunable number of interfaces between the two domains. We demonstrate that the organic ligands employed during the synthesis play a key role in regulating the final configuration.     

Solvohyperiodination. A comparison with solvothallation

C₆H₅IO/CH₃OH and a catalyst such as FSO₃H , CF₃SO₃H or BF₃-Et₂O as well as C₆H₅(OH)OTs-CH₃OH,react with chalcones, acetophenones and styrenes to yield rearranged products. The overall course of these reactions is analogous to that of Tl(NO₃)₃-CH₃OH in reaction with the same compounds.     

Binding Effect of Common Ions to Human Serum Albumin in the Presence of Norfloxacin: Investigation with Spectroscopic and Zeta Potential Approaches

In this work, the toxic influence of metallic ions (Al³⁺, Cu²⁺, Mg²⁺, Pb²⁺) on human serum albumin (HSA) in the absence and presence of norfloxacin (NRF) was studied by spectroscopic approaches [fluorescence quenching, synchronous fluorescence, three-dimensional fluorescence, circular dichroism, resonance light scattering (RLS) and zeta potential techniques] under simulated physiological conditions. Fluorescence spectroscopy revealed that these metallic ions and NRF can quench the HSA fluorescence, and this quenching effect became more significant when both ion and drug are present together. The binding constants and binding sites of metal ions with HSA in the absence and presence of NRF were determined, based on the fluorescence quenching results. Ion aggregation gives rise to an enhancement of the RLS intensity for HSA and the critical induced aggregation concentration (C _CIAC) of the ions, causing HSA aggregation for binary and ternary systems. The zeta potential measurements indicate a combination of electrostatic and hydrophobic interactions between ion, NRF and HSA and the formed micelle-like clusters. These data illustrated that NRF has an effect on the interaction between HSA and metal ions, with relevance for various toxicological and therapeutic processes.     

Synthesis and kinetics of graft polymerization of methyl methacrylate from the RAFT coordinated surface of nano‐TiO2

Polymer chains of PMMA were grown from nano titania (n‐TiO₂) by the reversible addition‐fragmentation chain transfer polymerization process. The mechanism and kinetics of MMA polymerization from both solution and “grafted from” n‐TiO₂ were studied. The RAFT agent, 4‐cyano‐4‐(dodecylsulfanylthiocarbonyl) sulfanyl pentanoic acid, with an available carboxyl group was used to anchor onto the n‐TiO₂ surface, with the S?C(SC₁₂H₂₅) moiety used for subsequent RAFT polymerization of MMA to form n‐TiO₂/PMMA nanocomposites. The functionalization of n‐TiO₂ was determined by FTIR, XPS, partitioning studies, and thermal analysis. The livingness of the polymerization was verified using NMR and GPC, while the dispersion of the inorganic filler in the polymer was studied using electron microscopy, FTIR, and thermal analysis. The monomer conversion and molecular weight kinetics were explored for the living RAFT polymerization, both in solution and grafted from n‐TiO₂, with first‐order kinetics being observed in both cases. Increased graft density on n‐TiO₂ led to a lower rate of polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3926–3937, 2008