A similarity theory of approximate deconvolution models of turbulence

We apply the phenomenology of homogeneous, isotropic turbulence to the family of approximate deconvolution models proposed by Stolz and Adams. In particular, we establish that the models themselves have an energy cascade with two asymptotically different inertial ranges. Delineation of these gives insight into the resolution requirements of using approximate deconvolution models. The approximate deconvolution model's energy balance contains both an enhanced energy dissipation and a modification to the model's kinetic energy. The modification of the model's kinetic energy induces a secondary energy cascade which accelerates scale truncation. The enhanced energy dissipation completes the scale truncation by reducing the model's micro-scale from the Kolmogorov micro-scale.     

Multielement analysis and antioxidant capacity of Merlot wine clones developed in Montenegro

The overall aim of this paper was to compare the multielement composition and antioxidant capacity of two Montenegrin Merlot wines obtained from specific vine clones (VCR1 and VCR 101) along with commercial Merlot wine throughout the consecutive vintages in 2010 and 2011. Elemental composition was analysed using inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS). Additionally, antioxidant capacity was assessed by cyclic voltammetry. VCR 1 wine from 2011 stood out for its elemental composition. On the other hand, antioxidant capacity of VCR 101 wines was the highest one for the both vintages. According to the experimental data obtained, all three wines are good source of essential elements and products with a significant antioxidant activity and specific geographical origin.     

Self-assembled diisocyanide monolayer films on gold and palladium

Self-assembled monolayers (SAMs) of the aromatic diisocyanides, 1,4-phenylenediisocyanide, 2,3,5,6-tetramethyl-1,4-phenylenediisocyanide, 4,4'-biphenyldiisocyanide, 3,3',5,5'-tetramethyl-4,4'-biphenyldiisocyanide, and 4,4' '-p-terphenyldiisocyanide, were prepared on gold and palladium surfaces. The SAMs were characterized by ellipsometry, polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), and grazing-angle attenuated total reflectance infrared spectroscopy (GATR). Based on the position of the metal-coordinated isocyanide stretching band, the SAMs on gold were found to bind in the terminal (eta(1)) geometry, while the SAMs on palladium prefer a different geometry which is possibly a triply bridging (mu(3)-eta(1)) geometry. A side-reaction of the unbound isocyanide in the SAM was identified as oxidation to an isocyanate group.     

Synthesis of the new, weakly coordinating anions [RB(C6F5)3]- (R = CH2Me, CHMe2, CH2CMe3); utilization of [HNMe2Ph][Me3CCH2B(C6F5)3] to activate zirconocene catalysts for propylene polymerization

The compound [HNMe2Ph][NpB(C6F5)3](Np =(CH3)3CCH2) reacts with dimethylzirconocenes to give active propylene polymerization catalysts which are significantly more active and give higher molecular weight polypropylene than do the catalysts obtained using B(C6F5)3; the [NpB(C6F5)3]- anion is for steric reasons more weakly coordinating than is [MeB(C6F5)3]-.     

Mono‐ and Binuclear Rhodium and Platinum Complexes of 1, 3, 5‐Trimethyl‐1, 3, 5‐triaza‐2σ3λ3‐phosphorin‐4, 6‐dionyloxy‐substituted Calix[4]arenes

The reaction behaviour of 1, 3, 5‐triaza‐2σ³λ³‐phosphorin‐4, 6‐dionyloxy‐substituted calix[4]arenes towards mono‐ and binuclear rhodium and platinum complexes was investigated. Special attention was directed to structure and dynamic behaviour of the products in solution and in the solid state. Depending on the molar ratio of the reactands, the reaction of the tetrakis(triazaphosphorindionyloxy)‐substituted calix[4]arene ( 4 ) and its tert‐butyl‐derivative ( 1 ) with [(cod)RhCl]₂ yielded the mono‐ and disubstituted binuclear rhodium complexes 2 , 3 , and 5 . In all cases, a C₂‐symmetrical structure was proved in solution, apparently caused by a fast intramolecular exchange process between cone conformation and 1, 3‐alternating conformation. The X‐ray crystal structure determination of 5 confirmed [(calixarene)RhCl]₂‐coordination through two opposite phosphorus atoms with a P ⃜P separation of 345 pm. The complex displays crystallographic inversion symmetry, and the Rh₂Cl₂ core is thus exactly planar. Reaction of 1 and of the bis(triazaphosphorindionyloxy)‐bis(methoxy)‐substituted tert‐butyl‐calix‐[4]arene ( 7 ) with (cod)Rh(acac) in equimolar ratio and subsequent reaction with HBF₄ led to the expected cationic monorhodium complexes 5 and 8 , involving 1, 3‐alternating P‐Rh‐P‐coordination. The cone conformation in solution was proved by NMR spectroscopy and characteristic values of the ¹J(PRh) coupling constants in the ³¹P‐NMR‐spectra. Reaction of equimolar amounts of 4 with (cod)Rh(acac) or (nbd)Rh(acac) led, by substitution of the labile coordinated acetylacetonato and after addition of HBF₄, to the corresponding mononuclear cationic complexes 9 and 10 . Only two of the four phosphorus atoms in 9 and 10 are coordinated to the central metal atom. Displacement of either cycloocta‐1, 5‐diene or norbornadiene was not observed. For both compounds, the cone conformation was proved by NMR spectroscopy. Reaction of 4 with (cod)PtCl₂ led to the PtCl₂‐complex ( 11 ). As for all compounds mentioned above, only two phosphorus atoms of the ligand coordinate to platinum, while two phosphorus atoms remain uncoordinated (proved by δ³¹P and characteristic values of ¹J(PPt)). NMR‐spectroscopic evidence was found for the existence of the cone conformation in the cis‐configuration of 11 .     

Characterization of thermally sensitive interactions in aqueous mixtures of hydrophobically modified hydroxyethylcellulose and cyclodextrins

Effects of beta-cyclodextrin (beta-CD) or hydroxypropyl-beta-cyclodextrin (HP-beta-CD) addition and temperature on thermodynamic, rheological, and structural features of semidilute solutions of hydroxyethylcellulose (HEC) and its hydrophobically modified analogue (HM-HEC) are reported. Differential scanning calorimetric (DSC) measurements revealed a thermally induced crystal melting transition of beta-CD at high concentrations in solutions of HEC and HM-HEC. No transition with HP-beta-CD was observed in aqueous solution. Viscosity results indicated that at a cosolute concentration of 2 mm, the beta-CD units are threaded onto hydrophobic tails of HM-HEC (C16 groups) to form columnar structures. This arrangement is more effective in the encapsulation of the hydrophobic chains than the monomer hydrophobic deactivation accomplished by the HP-beta-CD units. At cosolute concentrations above 8 mm, no further decoupling of the hydrophobic interactions occurs for any of the cosolutes. Small-angle neutron scattering (SANS) experiments on HM-HEC/beta-CD mixtures suggest that the large-scale association structures in HM-HEC/D(2)O solutions are reduced upon addition of beta-CD, and an interesting temperature effect is observed at 2 mm beta-CD addition. At high beta-CD concentrations and low temperatures, the formation of large beta-CD clusters or crystallites generates cross-links in the HEC and HM-HEC networks, resulting in a viscosity enhancement of several orders of magnitude. This strong temperature effect is not reflected in the structural features probed by SANS.     

以方沸石负载Ni(II)催化剂修饰的电极电氧化甲醇Seyed Naser Azizi,Shahram Ghasemi,Neda Salek Gilani简

There is a high overvoltage in the oxidation of methanol in fuel cells, and so modified electrodes are used to decrease it. A modified electrode that used Ni(Ⅱ) loaded analcime zeolite to catalyze the electrooxidation of methanol in alkaline solution was proposed. Analcime zeolite was synthesized by hydrothermal synthesis, and Ni(Ⅱ) ions were incorporated into the analcime structure, which was then mixed with carbon paste to prepare modified electrode. The electrocatalytic oxidation of methanol on the surface of the modified electrode in alkaline solution was investigated by cyclic voltammetry and chronoamperometry. The effects of the scan rate of the potential, concentration of methanol, and amount of zeolite were investigated. The rate constant for the catalytic reaction of methanol was 6×10³ cm³ mol^-1 s^-1 from measurements using chronoamperometry. The proposed electrode significantly improved the electron transfer rate and decreased the overpotential for methanol oxidation.     

Nanoscale co-organization of quantum dots and conjugated polymers using polymeric micelles as templates

Hierarchical organization of light-absorbing molecules is integral to natural light harvesting complexes and has been mimicked by elegant chemical systems. A challenge is to attain such spatial organization among nanoscale systems. Interactions between nanoscale systems, e.g., conjugated polymers, carbon nanotubes, quantum dots, and so on, are of interest for basic and applied reasons. However, typically the excited-state interactions and dynamics are examined in rather complex blends, such as cast films. A model system with complexity intermediate between a film and a supramolecular system would yield helpful insights into electronic energy and charge transfer. Here, we report a simple and versatile approach to achieving spatially defined organization of colloidal CdSe, CdSe/ZnS core/shell, or PbS nanocrystals (quantum dots) with poly(3-hexylthiophenes) (P3HTs) using micelles of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) as the main structural motif. We compare the characteristics of this system to those of natural light-harvesting complexes. Bulk heterojunction films (and related systems) are characterized by electronic interactions, and therefore dynamics of charge and energy transfer, at interfaces rather than between specific donor-acceptor molecules. Owing to structural disorder, such systems are inherently complex. Therefore, we expect that the spatially defined organization of the active components in the present system provides new opportunities for studying the complicated photophysics intrinsic to blends of nanoscale systems, such as bulk heterojunctions by establishing simplified and better controlled interfaces.     

Phenolic compounds in field horsetail (Equisetum arvense L.) as natural antioxidants

In this paper, the study of antioxidant activity and phenolic composition of three different extracts (EtOAc, n-BuOH and H(2)O) of field horsetail (Equisetum arvense L.) is presented. The antioxidant activity has been evaluated measuring the total reducing power (expressed by Ascorbate Equivalent Antioxidant Capacity - AEAC), inhibition of lipid peroxidation, and free radical scavenging capacity (RSC) towards 2,2-diphenyl-1-picrylhydrazyl (DPPH radical) and nitric oxide (NO), respectively. In addition, the total flavonoid content (TFC) and phenolic constituents of each extract have been determined. The results obtained show that the highest RSC regarding both DPPH and NO radicals is expressed by EtOAc extract (EC(50)=2.37 microg/mL and EC(50)=90.07 microg/mL, respectively), and the lowest by H(2)O extract (EC(50)=37.2 microg/mL and EC(50)>333.33 microg/mL, respectively). n-BuOH extract showed the highest total reducing power (AEAC=13.40 microg/mL). Differences in the phenolic composition of examined extracts are found comparing the HPLC chemical profiles. Although, isoquercitrin is the main flavonoid in both EtOAc and n-BuOH extracts, a considerable amount of di-E-caffeoyl-meso-tartaric acid was presented in the n-BuOH extract. In H(2)O extract high content of phenolic acids and low percentage of flavonoids were detected.     

Electrochemical synthesis of 6-amino-5-(3,4-dihydroxyphenyl) pyrimidine

Electrochemical oxidation of several catechols is studied in the presence of 4(6)-aminouracil (3a) and 6-amino-1,3-dimethyl uracil (3b) as nucleophiles in aqueous solution using cyclic voltammetry and controlled-potential coulometry. The results reveal that quinones derived from catechols participate in Michael additions with 3a and 3b to give the corresponding catecholamine derivatives via an electron transfer followed by chemical reaction (EC) mechanistic pathway in good yields and purities.