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The process of soot formation is one of the most complex combustion phenomena. However, the most important stage of soot formation is the poorly studied stage of nucleation, where young soot particles are formed from gas phase molecules. Revealing the process of soot nucleation will subsequently lead to the creation of kinetic mechanisms that describe the formation of soot in the smoking flame. Given the above, the study of the mechanisms of nucleation of soot is an urgent task. It is currently considered that the most likely mechanism for the particles nucleation is the nucleation through the formation of a strong chemical bond. The results of a theoretical study by A. Mebel and M. Frenklach, obtained by modern methods of computational chemistry, showed that the interaction of acepyrene and a pyrenyl radical leads to the formation of a PAH dimer via a so-called E-bridge bond, where the E-bridge bond is one common edge for the five-membered rings of two monomers. In this paper, we consider the formation of an E-bridge bond between the molecules of aceanthracene and anthracene. The geometry of the reactants, products, transition states, and intermediates were optimized at the DFT B3LYP theory level with the 6-31G** basis set. For the aceanthracene-anthracene system, dimerization due to the formation of an E-bridge bond can have several similar paths that differ in the position of the benzene rings in the starting monomers relative to each other. The formation of two main products is possible, each of which can be present in a cis and a trans configuration. Moreover, four possible paths practically do not differ in terms of the energies of the intermediates and transition states. [ABSTRACT FROM AUTHOR]

The kinetics of the ethylene to propylene process was studied in a laboratory reactor. Ethylene dimerization was shown to be the limiting stage of the process. By means of calculations using a non-isothermal model, it was found that the adiabatic heating of the bed in the reactor is 350 °C and more, which requires the use of an isothermal reactor. The contact time providing the maximum propylene yield is 6 s at WHSV 1 h-1 and 50° C. [ABSTRACT FROM AUTHOR]

The iodoaniline malonamide dimer, prepared by double acylation of iodoaniline failed to yield the stilbene dimer by the Heck protocol. By contrast formation of the amino stilbene by a modified Heck procedure followed by double acylation provided in good yield. [ABSTRACT FROM AUTHOR]

Peroxidase enzyme was used to catalyze the dimerization process of gallic acid. The structure of the dimerization product was characterized by 1H NMR and LC-MS-MS. The mechanism of gallic acid dimerization was also discussed. It was proposed that ellagic acid was formed through an oxidative coupling mechanism that lead to the formation of a C-C bond and followed by an intramolecular Fischer esterification mechanism that lead to the formation of two C-O bonds. Moreover, the antioxidant activity of gallic acid and ellagic acid were also studied. Gallic acid and ellagic acid exhibited the DPPH radical scavenging activity with IC50 values of 13.2 /iM and 15.9 /iM, respectively. [ABSTRACT FROM AUTHOR]

Clove oil has been found to possess antibacterial, antifungal, antiviral, antitumor, antioxidant and insecticidal properties. The major compound of clove oil is eugenol about 49-87%. Eugenol as phenolic compounds exhibits antioxidant and antimicrobial activities. The derivative compound of eugenol, dieugenol, show antioxidant potency better than parent eugenol. A series of TiO2-ZrO2 mixed oxides (TZ) with various titanium contents from 0 to 100wt%, prepared by using sol gel method were tested their catalytic activity for dimerization eugenol, Their catalytic activity show that these catalysts resulted a low yield of dimer eugenol, dieugenol, about 2-9 % and the purity is more than 50%. [ABSTRACT FROM AUTHOR]

Recently, large uncertainties in amine nucleation thermodynamics associated with the description of interactions of H2SO4, the key atmospheric nucleation precursor, with pre-nucleation clusters have been revealed. Here we investigate the formation of (H2SO4)2(H2O)n (n=0-5) clusters via H2O-induced dimerization using conventional RIMP2 and PW91PW91 methods and recently developed multistep BRIMP2 and B3RICC2 methods widely used in nucleation studies and compare the obtained results with measurements for equilibrium constants of H2O-induced dimerization. Variations in Kp and Gibbs free energies predicted by different methods were found to be unexpectedly large, several times of those in hydration free energies commonly used to benchmark computational quantum methods. This means that the common hydration benchmarks are not fully representative of nucleation and that the validation of quantum methods to be recommended for use in nucleation studies is impossible without a thorough assessment of H2SO4 - H2SO4 interactions. We show clearly that only conventional RI-MP2 and PW91PW91 methods are consistent with experiments and that a thorough validation of theoretical predictions against experimental data on H2SO4 clustering is needed prior to recommending a quantum-chemical method for use in nucleation research. We also shows that conclusions about the role of Amine-Enhanced Ternary Homogeneous Nucleation (ATHN) in atmospheric nucleation may be affected by the large uncertainties in nucleation thermodynamics associated with the application of B3RICC2 and BRIMP2 methods and may need a thorough revision. [ABSTRACT FROM AUTHOR]

We synthesized very pure dimer phase of coronene by simple heat-treatment and subsequent sublimation purification. It was found that the dimer phase emits very bright red light under the irradiation of low energy ultra-violet light. [ABSTRACT FROM AUTHOR]

Modification of eugenol into its derivative compounds is an alternative way to enhance the economic value of clove oil, e.g. isoeugenol, [2 metoxy 4 (1 propeny])phenol] has higher economic value than eugenol, [2 metoxy 4 (2 propenyl)phenol|. This isomerization of eugenol is generally carried out in a homogeneous medium using strong alkaline or transition metals as catalysts in a relatively high temperature. Since homogeneous catalytic reactions have some environmentally disadvantages regarding green process, this study on catalytic modification of eugenol was conducted using solid catalyst Na/Na0H/y-Al203. This heterogeneous superbase catalyst Na/Na0H/γ-Al203 was prepared by first preparing y-Alumina, in which an industrial waste in the form of aluminium scrap was used. This catalyst was then applied to produce the derivative compounds of eugenol at room temperature. Since the OH-phenol of eugenol is very reactive towards oxidative coupling reaction, even at low temperature, methyl eugenol was used to compare the catalytic selectivity of Na/Na0H/y-Al203 catalyst. Using methyl eugenol as the catalytic substrate, Na/Na0H/y-Al203 has the activity to shift the double bond of 1-propenyl into 2-propenyl for 95.23% yield and 100% selectivity at room temperature for 2 h. Meanwhile, eugenol was transformed into 14.3% isoeugenol and 50.6% dehydrodieugenol over Na/Na0H/y-Al203 under the same condition. Dimerization of eugenol occurs at the same time competitively with the generation of isoeugenol. The dimerization of eugenol identified by H-NMR and l3C-NMR spectra is evidence that the superbase catalyst may act as an oxidizing agent for eugenol continued by radical mechanism. [ABSTRACT FROM AUTHOR]

Many cellular signaling processes are initiated by dimerization or oligomerization of membrane proteins. However, since the spatial scale of these interactions is below the diffraction limit of the light microscope, the dynamics of these interactions have been difficult to study on living cells. We have developed a novel high-speed hyperspectral microscope (HSM) to perform single particle tracking of up to 8 spectrally distinct species of quantum dots (QDs) at 30 frames per second. The distinct emission spectra of the QDs allows localization with ~ 10 nm precision even when the probes are clustered at spatial scales below the diffraction limit. The capabilities of the HSM are demonstrated by application of multi-color single particle tracking to observe membrane protein behavior, including: 1) resolving antigen induced aggregation of the high affinity IgE receptor, FceR1 ; 2) dynamic formation and dissociation of Epidermal Growth Factor Receptor dimers; 3) four color QD tracking while simultaneously visualizing GFP-actin; and 4) high-density tracking for fast viscosity mapping of the cell membrane. [ABSTRACT FROM AUTHOR]

Dimer induced reconstruction and metallicity of Ge(001) surface has been studied using SIESTA. Using slab model, we modeled our surface starting with symmetric dimerization of the surface atoms, which on optimization goes over to asymmetric(buckled) dimerization. It is found that there is a substantial decrease in the total energy of the slab. Calculated PDOS for dimer atoms on comparison with bulk density of states shows metallic states introduced around the Fermi energy. [ABSTRACT FROM AUTHOR]

We measured the anomaly in the specific heat due to the dimerization transition in ethyl and butyl phenalenyl-based neutral radical molecular conductors. A micro-calorimetric technique was used to measure samples in the hundred-microgram scale, in magnetic fields up to 15 T. Different field-dependence was found in the two compounds. In the ethyl-substituted radical, the entropy associated with the transition appears to be essentially field-independent. In the butyl-substituted radical, the entropy at zero field is appreciably reduced in an applied field of 15 T. The different entropy recovered at the transition may also be related to the significantly different transition temperatures. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

G Protein Coupled Receptors (GPCRs) can form dimeric or higher ordered oligomeric complexes, which can remarkably influence the signalling of these receptors. Bioluminsecent Resonance Energy Transfer (BRET) titration experiments are the gold standards to prove the physical interaction between the protomers of a presumed dimer. In this method the energy transfer (BRET signal) is measured between a luminescent (energy donor) and a fluorescent (energy acceptor) labelled receptor. BRET signal can increase not only due to a specific interaction (dimerization) but due to the random, non-specific interactions between donor and acceptor. To distinguish between the specific and non-specific interaction, BRET signal is measured using fixed amount of donor and varying amount of acceptor labelled receptors, and BRET signal values are plotted as a function of acceptor/donor ratio. In the case of specific interaction this plot shows a saturation curve, while in the case of non-specific interactions it shows a lineal relationship. Maintaining constant amount of donor labelled receptors is strictly required to the correct interpretation of BRET titration experiments, but it is very hard to achieve in a transient transfection system. In our work, we analysed the effects of changing donor levels on BRET titration curves, and set up a system, where it is possible to distinguish between specific and non-specific interaction even in the case of changing donor amount. To analyse the effects of changing donor levels on BRET titration curves, we performed Monte Carlo simulations. The results showed, that in the case of non-specific interaction, the BRET signal is only dependent on the amount of acceptor, while in the case of specific interaction it depends on the acceptor/donor ratio. Our simulations also showed, that in the case of changing donor levels, even non-specific interaction can lead to saturation BRET titration curves, which can lead to false interpretation of experimental results. We tested our simulation results in an inducible dimerization system, where the non-specific interaction between FKBP labelled donor and FRB labelled acceptor molecules could artificial changed with the addition of rapamycin into a specific interaction. Our experimental results verified our simulations. With these new analysis methods, we examined the dimerization between various GPCRs (type I and II angiotensin receptor, V2 vasopressin receptor, β2 adrenergic receptor, calcium sensing receptor, CB1 cannabinoid receptor). [ABSTRACT FROM AUTHOR]