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New Julolidine substituted phthalocyanine dyes developed in this work exhibit being cost-effective and simple to produce. FTIR, MALDI-TOF, UV-visible, and NMR analysis verified the structural properties of the dyes. The dyes did not clump and were soluble in a wide range of organic solvents. The dyes ZnPc, NiPc, CoPc and CuPc are completely transparent in solution. The dye’s thermal stability and transmittance were measured using thermogravimetric analysis (TGA) and UV-visible spectroscopy. Among the other produced dyes, ZnPc (17%) spin-coated films had the lowest light scattering process and the maximum transmittance (83%) in the blue area. Finally, the combined results revealed that ZnPc dye might be employed as an LCD color filter.

A series of 4-(polyfluoroalkoxy)phthalonitriles have been prepared in high yield by nucleophilic substitution of the nitro group in 4-nitrophthalonitrile on polyfluoroalkoxy groups at room temperature. These dinitriles have been cyclotetramerized in the presence of cobalt or copper salts into the corresponding phthalocyanine complexes. The spectral properties and coordination chemistry of some of them have been studied.

The dimerization and tendency to form higher aggregates of two isomeric metal-free phthalocyanine compounds with tetracumylphenoxy peripheral substitution at the alpha (1 or 4, 5 or 8, 9 or 12, 13 or 16) and beta (2 or 3, 6 or 7, 10 or 11, 14 or 15) positions has been analysed by spectroscopic measurements. The dimerization constants in chloroform solution are 1.3 × 10¹M⁻¹ and 7.0 × 10³M⁻¹ respectively. At concentrations greater than 10⁻³M, the beta phthalocyanine isomer forms a spectroscopically resolvable higher aggregate. Q-band spectra of the dimer of each isomer and of the aggregate of the beta isomer in chloroform solution were generated. Comparison of these spectra with the corresponding thin film spectra of each isomer indicates that the stronger tendency toward aggregation of the beta isomer extends into the solid state. The difference in aggregating tendency of the two isomers was attributed to a steric constraint of the alpha isomer that restricts conformational freedom and, consequently, hinders formation of dimer and higher order complexes.

The formation of micelles of cetyltrimethylammonium bromide (CTAB) in CH₂Cl₂ solution has been reported for the first time. The critical micelle concentrations (cmc) of CTAB in CH₂Cl₂ solution were determined using conductivity and fluorescence techniques in both the absence and presence of 1,3,5,7-tetramethyl-2,4,6,8-tetra(2,4,6-triisopropylphenyl)porphyrin (TMTIP). The cmc values obtained by conductivity and fluorescence methods were found to be 75 and 78 mM, respectively. The aggregation numbers (N) of CTAB and porphyrin–CTAB in CH₂Cl₂ solution were determined using pyrene and N-cetylpyridinium chloride (CPC) as the fluoroprobe and quencher, respectively. The N of CTAB in CH₂Cl₂ solution was also determined using the porphyrin (in lieu of pyrene) as the fluoroprobe and CPC as the quencher. The N of CTAB obtained by these probes was found to be 134 ± 3 and 140 ± 5, respectively. This suggests that the porphyrin could be used as an excellent fluoroprobe for determination of the aggregation number of CTAB micelles. The results of both cmc and aggregation number suggest that the micelle formation of CTAB in CH₂Cl₂ solution is favored in the presence of the porphyrin. The standard free energy change for micelle formation of CTAB in CH₂Cl₂ solution was calculated using a biphasic model. The standard free energy transfer of CTAB micelles from CH₂Cl₂ to porphyrin environment has been found to be −1.0 kJ mol⁻¹ at 25 °C, suggesting that the above transfer is difficult. However, the reverse situation, i.e. binding of the porphyrin to CTAB micelles, is more probable. The Langmuir–Blodgett (LB) film formation of the porphyrin and metalloporphyrins (Fe, Co, Cu, Zn) has also been studied and the UV-vis spectra of these films have been analyzed.

Electronic absorption spectroscopy was used to measure the molecular association of copper phthalocyanine tetrasulfonate in micellar solutions, a microemulsion made with cationic surfactant, and homogeneous solvents. Analysis of absorbance versus concentration data using a multiple-aggregation model and non-linear regression analysis gave values of association constants, molar absorptivities and estimates of average aggregation number. Microemulsions and aqueous micellar solutions made with alkylammonium surfactants inhibited aggregation, probably because of interactions between the phthalocyanine sulfonate groups and the cationic surfactant head groups at interfacial surfaces. Similar aggregation behavior was observed previously in multiple-bilayer films of cationic surfactants. Water and aqueous solutions containing tetraethylammonium bromide or anionic SDS micelles provide environments facilitating extensive aggregation of Cu^IIPcTS⁴⁻. The major species are dimers in water and acetonitrile/water, but the formation of higher aggregates is promoted by addition of SDS or TEAB. Aprotic organic solvents provide environments intermediate between these two extremes, giving relatively large aggregation numbers (i.e. five to seven) but smaller association constants than aqueous media not containing cationic surfactants.

Soluble metal-free and Cu-, Ni- and Co-substituted 3,4-tetrapyridinoporphyrazines (Tpps)5–8 have been synthesized. Poly(methyl methacrylate) (PMMA) spin coated and Langmuir–Blodgett (LB) films containing these compounds have been prepared. Third-harmonic generation (THG) was used to measure the third-order-non-linear optical susceptibility of both types of films at 1.064 μm. For the spin-coated samples a strong enhancement of the THG response was found on increasing the Tpp concentration of the chlorobenzene solution used to prepare the samples. The enhancement was associated with the formation of molecular aggregates in the solution which were ‘frozen’ into the films. In order to facilitate comparison, the final Tpp concentration in the PMMA films was kept approximately constant in all cases. Metal incorporation (particularly Co) in the macrocycle strongly enhances the THG susceptibility of the films prepared using concentrated solutions, whereas the effect is efficiently inhibited in those obtained from less concentrated solutions. We conclude that the enhancement in the THG response occurs via the influence of the metal on the Tpp aggregation process in the solution. For the LB films the THG results are more comparable with those of the spin-coated samples prepared using low-concentration solutions. This indicates that dimers, previously identified in the LB films, and possibly other small-size oligomers are formed in the low-concentration Tpp solutions. On the other hand, larger aggregates should be formed in the spin-coated samples prepared from high-concentration solutions.

Phthalocyanine (Pc) derivatives in which substituents hold the Pc units in isolation from one another in the solid state are potentially useful materials. Three synthetic approaches to achieve this goal are described: the construction of a dendrimer about a Pc core; the incorporation of alkyl side chains which are forced to lie out of the plane of the macrocycle; and the synthesis of sterically crowded hexadeca-substituted derivatives. The effectiveness of each of these strategies is readily measured by comparing the visible absorption spectrum of a spin-coated film with that obtained from the non-aggregated Pc in dilute solution. These studies show that the size of the substituents is of secondary importance for their efficiency in inducing Pc isolation. Of more importance is the substituents' adopted position relative to the Pc ring.

A series of methyl-terminated oligooxyethylene (CH₃(OCH₂CH₂)_nO, n = 8.8)-substituted phthalocyanines with peripheral substitution at four β positions, at four α positions and at the eight α positions was synthesized and structurally characterized. These compounds are isotropic liquids above 10 °C. Non-linear optical properties of the tetra-α- and tetra-β-substituted compounds were examined. Both are reverse saturable absorbers in the visible region of the spectrum, but the tetra-α-substituted compound has the larger non-linear absorption coefficient and can be a useful optical limiter in cases where a non-volatile liquid is desirable.

The synthesis of metal-free and metallo derivatives (Ni, Zn) of tetrasubstituted phthalocyanines (Pcs) obtained from 4-[methyleneoxy(15-crown-5)]phthalonitrile is described. The new compounds have been characterized by elemental analyses, IR, ¹H and ¹³CNMR, MS and UV-vis. The thermal stabilities of the compounds were determined by thermogravimetric analysis. The alkali metal ions bound to crown ether groups force dimerization of the phthalocyanine units in solution, as observed in the electronic spectra by the broadening of the Q band transition at 675 nm. The highest affinity for potassium ion was observed in the case of the NiPc derivative in solvent extraction experiments.

New metal-free 5 and metallophthalocyanines 6-11(M = Cu, Ni, Co, Pb, Zn) fused in peripheral positions with four 24-membered tetraoxatetraaza macrocycles were prepared by cyclotetramerization of 24,25-dicyano-4,10,13,17-tetra(toluene-p-sulfonyl)-1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22-didicontinehydrobenzo[y][3,9,12,18]tetraaza[1,7,16,22]tetraoxatetradicontine in the presence of the corresponding metal salt or a strong organic base. While the N-tosylated derivatives of the phthalocyanines are soluble in common organic solvents, the detosylated derivative of copper phthalocyaninate is soluble in water. The aggregation properties of the phthalocyanines were also investigated as a function of concentration, solvent and oxidative medium. The new compounds are characterized by a combination of elemental analysis and ¹H NMR, ¹³C NMR, IR, UV-vis and MS spectral data.

The synthesis and characterization of a soluble metal-free polyethyleneoxide-capped phthalocyanine and the corresponding lead compound are described. This phthalocyanine was designed to allow the formation of dimers but to inhibit formation of higher aggregates. The monomer/dimer equilibrium constant in chloroform solutions is 750 ± 20 l mol^-1. No evidence for higher aggregates was found. The molecular extinction coefficient of the metal-free polyethyleneoxide-capped phthalocyanine in chloroform is one of the lowest known (2.5 × 104 l mol^-1cm^-1). The lead-substituted material was demonstrated to be a reverse saturable absorber from 532 nm to about 610 nm. It possesses a large nonlinear absorption coefficient in the visible and is a promising optical limiter material.

Aggregation of 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (m-THPC) is observed not to occur in methanol or in ethanol:polyethyleneglycol 300:water = 2:3:5 (v/v) in the concentration range of 0.46–73.4 × 10^-5M and 0.92–29.4 × 10^-5M, respectively. However, aggregation occurs for 4.59 × 10^-5M solutions in methanol–water mixtures for compositions >50% water (v/v). The Soret band broadens and ε_max decreases; λ_max shows a red shift, consistent with a J-type structure. Possible aggregate structures are considered based on the known hydrogen bonding patterns in crystalline solvates of the closely related 5,10,15,20-tetrakis(3,5-dihydroxyphenyl)porphyrin. Spectrophotometric titration of m-THPC in methanol–buffer mixtures gives apparent pK_a values of pK₃ = 3.45 and pK₄ = 1.45. The phenolic groups have pK_a = 10.0. Comparisons are made with the corresponding porphyrin and with literature values on related systems. Singlet oxygen chemistry. The photobleaching of bilirubin is shown to be accelerated fivefold in the presence of a 0.05 mol proportion of m-THPC. The accelerated reaction is slowed down in the presence of 2,5-dimethylfuran and of β-carotene, providing further evidence by chemical reaction for the ability of m-THPC to photogenerate singlet oxygen. The relevance of these observations to clinical usage is discussed briefly.

Two main issues for event-related potential (ERP) classification in brain–computer interface (BCI) application are curse-of-dimensionality and bias-variance tradeoff, which may deteriorate classification performance, especially with insufficient training samples resulted from limited calibration time. This study introduces an aggregation of sparse linear discriminant analyses (ASLDA) to overcome these problems. In the ASLDA, multiple sparse discriminant vectors are learned from differently l₁-regularized least-squares regressions by exploiting the equivalence between LDA and least-squares regression, and are subsequently aggregated to form an ensemble classifier, which could not only implement automatic feature selection for dimensionality reduction to alleviate curse-of-dimensionality, but also decrease the variance to improve generalization capacity for new test samples. Extensive investigation and comparison are carried out among the ASLDA, the ordinary LDA and other competing ERP classification algorithms, based on different three ERP datasets. Experimental results indicate that the ASLDA yields better overall performance for single-trial ERP classification when insufficient training samples are available. This suggests the proposed ASLDA is promising for ERP classification in small sample size scenario to improve the practicability of BCI.

This paper presents an analysis of the growth of towns in the Tel Aviv metropolis. It indicates a similarity in the variation of populations so that the population functions can be scaled and superposed one onto the other. This is a strong indication that the growth mechanism for all these towns is the same. Two different models are presented to interpret the population growth: one is an analytic model while the other is a computer simulation. In the dynamic analytic model, we introduced the concept of characteristic time. The growth has two parts: in the first, the derivative is an increasing function, the town is very attractive and there is short delay between decision to build and complete realization of the process. At this time, there is no shortage of land. However, around a specific time, the delay begins to increase and there is lack of available land. The rate of the population variation decreases until saturation. The two models give a good quantitative description.

In order to provide insights into the misfolding mechanism and the subsequent aggregate formation which cause what are known as the neurodegenerative polyglutamine diseases, we have simulated a 10-residue polyglutamine (poly-Q) chain in vacuum and in solvent by multicanonical method, which enabled us to study the system in a wide temperature range and discuss thermodynamic properties. It is understood that the system in vacuum shows two phase transitions, first of them occur at high temperature that is the well-known helix-coil transition and the second one is a solid-solid transition. However, the poly-Q chain in solvent is in a random coil state at higher temperatures, goes through a conformational change at T = 200 K and assumes predominantly a mixture of anti-parallel β-sheet and α-helix structures at low temperatures. One-residue glutamine dipeptide is also simulated and low-energy stable conformations are identified.

We examine the segregation and mixing dynamics of a dilute bidisperse suspension of particles in a fluid subjected to a temperature gradient. Configurations corresponding to varying uniform bottom wall temperatures, as well as various bottom wall temperature profiles, are examined. Measures of spatial segregation and aggregation are discussed and used to analyze the suspension's dynamics. The results show that the difference in mass lead to transient segregation at short time scales, together with long-term intermixing and aggregation. Comparison of the segregation and aggregation among different configurations reveal that the strength of the temperature gradient is the primary influence on both segregation and aggregation. The particles are driven the fastest into the long – term steady state in the uniform and Gaussian bottom temperature profiles. In addition, the qualitative features of transient segregation do not change if the difference in mass is varied. The results suggest that a fluid undergoing thermal convection can be used to segregate particles, but only at short times, as fluid reaches its steady state. Keeping a fluid indefinitely in a transient state may improve the duration of segregation.

This paper deals with the molecular dynamics simulation (MDS) of nanofluid under Poiseuille flow in a model nanochannel. The nanofluid is created by exerting four solid nanoparticles dispersed in Argon (Ar), as base fluid, between two parallel solid walls. The flow is simulated by molecules with the Lennard-Jones (LJ) intermolecular potential function. Different simulations are done with two different types of solid particles and two cut-off radii. In each case, Copper (Cu) and Platinum (Pt) LJ parameters are applied for the nanoparticles and solid walls particles with cut-off ratios of 2.2σ and 2.5σ. The microstructure of the system at different time steps is investigated to describe the aggregation kinetics of nanofluid on Poiseuille flow. When a few nanoparticles or a cluster of them reach each other, they stick together and the interaction surface of the solid–fluid interface reduces, so the potential energy of the system decreases at these time steps. Therefore, the system enthalpy reduces at the aggregation time steps. Results show that the simulations with cut-off radius 2.5σ indicate minimum clustering effect at the same time. Based on the obtained results, the system with Cu nanoparticles makes it to aggregate later than that of Pt nanoparticles which is due to differences in potential interaction of two materials. The new simulation results enhance our understanding of cluster morphology and aggregation mechanisms.

The present paper develops a weighted least-square dissimilarity approach to address the Multiple Criteria ABC inventory classification problem, when the different criteria ranking makes impossible to achieve a group consensus. The proposed approach effectively eliminates drawbacks regarding subjective judgements of multiple decision makers on the criteria importance, and comprehensively aggregates all rankings of the criteria importance to provide a more reasonable and effective classification mechanism. The common weights associated with all rankings are determined. An illustrative example is presented to compare the performance of our approach with the existing studies.

A growth mechanism of ramified aggregates on nonlattice substrates with fixed impurities is studied systematically. Based on the experimental observations of Au atomic aggregates on molten glass surfaces, an Improved Restricted Cluster-Cluster Aggregation (IRCCA) model is established. In this model, fixed impurities are distributed randomly on a nonlattice substrate, and all the aggregates with different sizes are allowed to diffuse and rotate. The influence of the liquid substrate and impurity on the structure of the ramified aggregates is studied systematically. The simulation results are in good agreement with the experimental findings.

A new chemical adsorbent for fluoride, phosphate and chromium removals for use in a high magnetic filtration process was produced by applying a novel nanomagnetite aggregation process through the generating procedure of an iron oxide hydroxide. The experimental work to produce the new adsorbent can be divided into two sequential steps: (1) the formation of nanomagnetite particles by means of a chemical precipitation and (2) embedding the nanomagnetite particles, in a solute state, into an iron oxyhydroxide crystal aggregates, before crystallization, to form the new adsorbent. The experimental results obtained from VSM, zeta potential, adsorption trials and SEM pictures obviously reveal a great alteration in the main properties of the new adsorbent comparing to the base iron component material. The new adsorbent not only has a much higher ions adsorption capacity but also can effectively comes to work with a magnetically assisted water treating system due to its enhanced magnetic susceptibility.