How patchy can one get and still condense? The role of dissimilar patches in the interactions of colloidal particles

We investigate the influence of strong directional, or bonding, interactions on the phase diagram of complex fluids, and in particular on the liquid-vapour critical point. To this end we revisit a simple model and theory for associating fluids which consist of spherical particles having a hard-core repulsion, complemented by three short-ranged attractive sites on the surface (sticky spots). Two of the spots are of type A and one is of type B; the interactions between each pair of spots have strengths [image omitted], [image omitted] and [image omitted]. The theory is applied over the whole range of bonding strengths and results are interpreted in terms of the equilibrium cluster structures of the coexisting phases. In systems where unlike sites do not interact (i.e. where [image omitted]), the critical point exists all the way to [image omitted]. By contrast, when [image omitted], there is no critical point below a certain finite value of [image omitted]. These somewhat surprising results are rationalised in terms of the different network structures of the two systems: two long AA chains are linked by one BB bond (X-junction) in the former case, and by one AB bond (Y-junction) in the latter. The vapour-liquid transition may then be viewed as the condensation of these junctions and we find that X-junctions condense for any attractive [image omitted] (i.e. for any fraction of BB bonds), whereas condensation of the Y-junctions requires that [image omitted] be above a finite threshold (i.e. there must be a finite fraction of AB bonds).

Criticality of colloids with distinct interaction patches: The limits of linear chains, hyperbranched polymers, and dimers

We use a simple model of associating fluids which consists of spherical particles having a hard-core repulsion, complemented by three short-ranged attractive sites on the surface (sticky spots). Two of the spots are of type A and one is of type B; the bonding interactions between each pair of spots have strengths epsilon(AA), epsilon(BB), and epsilon(AB). The theory is applied over the whole range of bonding strengths and the results are interpreted in terms of the equilibrium cluster structures of the phases. In addition to our numerical results, we derive asymptotic expansions for the free energy in the limits for which there is no liquid-vapor critical point: linear chains (epsilon(AA)not equal 0, epsilon(AB)=epsilon(BB)=0), hyperbranched polymers (epsilon(AB)not equal 0, epsilon(AA)=epsilon(BB)=0), and dimers (epsilon(BB)not equal 0, epsilon(AA)=epsilon(AB)=0). These expansions also allow us to calculate the structure of the critical fluid by perturbing around the above limits, yielding three different types of condensation: of linear chains (AA clusters connected by a few AB or BB bonds); of hyperbranched polymers (AB clusters connected by AA bonds); or of dimers (BB clusters connected by AA bonds). Interestingly, there is no critical point when epsilon(AA) vanishes despite the fact that AA bonds alone cannot drive condensation.

Copper, nickel and zinc removal by peanut hulls: batch and column studies in mono, tri-component systems and with real effluent

The main goal of this research study was the removal of Cu(II), Ni(II) and Zn(II) from aqueous solutions using peanut hulls. This work was mainly focused on the following aspects: chemical characterization of the biosorbent, kinetic studies, study of the pH influence in mono-component systems, equilibrium isotherms and column studies, both in mono and tri-component systems, and with a real industrial effluent from the electroplating industry. The chemical characterization of peanut hulls showed a high cellulose (44.8%) and lignin (36.1%) content, which favours biosorption of metal cations. The kinetic studies performed indicate that most of the sorption occurs in the first 30 min for all systems. In general, a pseudo-second order kinetics was followed, both in mono and tri-component systems. The equilibrium isotherms were better described by Freundlich model in all systems. Peanut hulls showed higher affinity for copper than for nickel and zinc when they are both present. The pH value between 5 and 6 was the most favourable for all systems. The sorbent capacity in column was 0.028 and 0.025 mmol g-1 for copper, respectively in mono and tri-component systems. A decrease of capacity for copper (50%) was observed when dealing with the real effluent. The Yoon-Nelson, Thomas and Yan’s models were fitted to the experimental data, being the latter the best fit.

Projecto e concepção de instalação frigorífica a NH3, para uma unidade de congelação de frangos em contínuo, na Venezuela

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Mecânica

Characterizing the fungal and bacterial microflora and concentrations in fitness centres

Fitness centres are special places where conditions for microbiological proliferation should be considered. Moisture due to human perspiration and water condensation as a result of human physical activities are prevalent in this type of buildings. Exposure to microbial contaminants is clinically associated with respiratory disorders and people who work out in polluted environments would be susceptible to contaminants. This work studied the indoor air contamination in three gymnasiums in Lisbon. The sampling was performed at two periods: at the opening (morning) and closing (night) of the three gymnasiums. The airborne bacterial and fungal populations were sampled by impaction directly onto Tryptic Soy Agar (for bacteria) and Malt Extract Agar (for fungi) plates, using a Merck MAS-100 air sampler. Higher bacterial concentrations were found at night as compared to the morning but the same behaviour was not found for fungal concentrations. Gram-negative catalase positive cocci were the dominant bacteria in indoor air samples of the studied gymnasiums. In this study, 21 genera/species of fungal colonies were identified. Chrysosporium sp., Chrysonilia sp., Neoscytalidium hialinum, Sepedonium sp. and Penicillium sp. were the most prevalent species identified in the morning, while Cladosporium sp., Penicillium sp., Chrysosporium sp., Acremonium sp. and Chrysonilia sp. were more prevalent at night. A well-designed sanitation and maintenance program for gymnasiums is needed to ensure healthier space for indoor physical activity.

Aliphatic bio-oils from corks: a Py-Gc/MS study

Cork samples from Betula pendula, Quercus suber and Quercus cerris were submitted to Py-GC-MS/FID at temperatures between 550 degrees C and 900 degrees C and the pyrolysis-derived compounds (py-products) were identified and quantified. Corks were compared with wood samples. Py-products include suberin, lignin and carbohydrates derivatives. Suberin py-products are dominated by unsaturated aliphatics. Corks pyrolysis yield and composition were dramatically influenced by temperature in contrast to wood that showed stable results across temperatures. At 850-900 degrees C the peaks area of cork pyrograms were approximately two times higher than at 550 degrees C, for which yield was about half of the woods, and cork py-products were dominated by suberin-derived short chain aliphatics, namely 1-alkenes, while at 550 degrees C composition was dominated by lignin derivatives. Lignin and carbohydrate derived products decreased dramatically over 750 degrees C while the opposite was observed for unsaturated aliphatics. Cork materials show a high potential as feedstock for production of aliphatic-rich pyrolytic biofuels or as a source of olefins. (C) 2014 Elsevier B.V. All rights reserved.

Dinuclear Mn (II,II) complexes: magnetic properties and microwave assisted oxidation of alcohols

A series of six new mixed-ligand dinuclear Mn(II, II) complexes of three different hydrazone Schiff bases (H3L1, H3L2 and H3L3), derived from condensation of the aromatic acid hydrazides benzohydrazide, 2-aminobenzohydrazide or 2-hydroxybenzohydrazide, with 2,3-dihydroxy benzaldehyde, respectively, is reported. Reactions of Mn(NO3)(2) center dot 4H(2)O with the H3L1-3 compounds, in the presence of pyridine (1 : 1 : 1 mole ratio), in methanol at room temperature, yield [Mn(H2L1)(py)(H2O)](2)(NO3)(2) center dot 2H(2)O (1 center dot 2H(2)O), [Mn(H2L2)(py)(CH3OH)](2)(NO3)(2) center dot 4H(2)O (2 center dot 4H(2)O) and [Mn(H2L3)(py)(H2O)](2)(NO3)(2) (3) respectively, whereas the use of excess pyridine yields complexes with two axially coordinated pyridine molecules at each Mn(II) centre, viz. [Mn(H2L1)(py)(2)] 2(NO3)(2) center dot H2O (4 center dot H2O), [Mn(H2L2)(py) H-O (6 center dot 2CH(3)OH), respectively. In all the complexes, the (H2L1-3)-ligand coordinates in the keto form. Complexes 1 center dot 2H(2)O, 2 center dot 4H(2)O, 4 center dot H2O, 5 center dot 2H(2)O and 6 center dot 2CH(3)OH are characterized by single crystal X-ray diffraction analysis. The complexes 1, 2 and 6, having different coordination environments, have been selected for variable temperature magnetic susceptibility measurements to examine the nature of magnetic interaction between magnetically coupled Mn(II) centres and also for exploration of the catalytic activity towards microwave assisted oxidation of alcohols. A yield of 81% (acetophenone) is obtained using a maximum of 0.4% molar ratio of catalyst relative to the substrate in the presence of TEMPO and in aqueous basic solution, under mild conditions.

Halogen-bonded tris (2,4-Bis(trichloromethyl)-1,3,5,triazapentadienato)-M(III) [M = Mn, Fe, Co] complexes and their catalytic activity in the peroxidative oxidation of 1-phenylethanol to acetophenone

One-pot template condensation of CCl3C=N with ammonia on a metal source [MnCl2 center dot 4H(2)O, FeCl3 center dot 6H(2)O or Co(CH3COO)(2)center dot 4H(2)O] in DMSO led to the formation of tris(2,4-bis(trichloromethyl)-1,3,5-triazapentadienato)-M(III) complexes, [M(NH=C(CCl3)NC(CCl3)=-NH}(3)]center dot n(CH3)(2)SO [M = Mn, n = 1 (1); M = Fe, n = 2 (2); M = Co, n = 2 (3)1, which were characterized using elemental analysis, and IR, ESI-MS and single-crystal X-ray analysis. The role of inter- and intramolecular non-covalent halogen and hydrogen bonds in the synthesis of 1-3 is discussed. It is shown that the crystal ionic radii of the metal ions [68.5 (Co) < 69 (Fe) < 72 (Mn), pm] are related to the corresponding Cl center dot center dot center dot Cl distances [3.178 (3) > 3.155 (2) > 3.133 (1) Al. Compounds 1-3 and the related di(triazapentadienato)-Cu(v) complex [Cu(NH=C(CCl3)NC(CCl3)=NH}2]center dot 2(CH3)(2)SO (4) act as catalyst precursors for the additive-free microwave (MW) assisted homogeneous oxidation of 1-phenylethanol with tert-butylhydroperoxide (TBHP), leading to the formation of acetophenone with yields up to 99% and TONs up to 5.0 x 10(3) after 1 h of low power (10 W) MW irradiation.

Tetranuclear COPPER(II) complexes with macrocyclic and open-chain disiloxane ligands as catalyst precursors for hydrocarboxylation and oxidation of alkanes and 1-phenylethanol

Two new tetranuclear complexes [Cu-4(mu-O)(L-1)-Cl-4] and [Cu-4(mu(4)-O)(L-2)(2)Cl-4] (2), where H2L1 is a macrocyclic ligand resulting from [2+2] condensation of 2,6-diformy1-4-methylphanol (DFF) and 1,3-bis(aminopropy1)tetramethyldisiloxane, and HL2 is a 1:2 condensation product: of DFF with trimethylsilyl p-aminobenzoate, have been prepared. The structures of the products were established by Xray diffraction. The complexes have been characterised by FTIR, UV/Vis spectroscopy, ES1 mass-spectrometry and magnetic susceptibility measurements. The latter revealed that the letrftriuclear complexes can be descr bed as two ferromagnetically coupled dinuclear units, in which the two copper(II) ions interact antiferromacinetically. The ccimpi.iunds act as homogeneous catalyst precursors for a number of single-pot reactions, including (I) hydrocarbaxylation, with CO, H2O and K2S2O8, of a variety of linear and cyclic (n = 5-8) alkanes into the corresponding Cn+1 carboxylic acids, (ii) peroxidative oxidation of cyclohexane, and (iii) solvent-free microwave-assisted oxidation of 1-phenyletha.nol.

Methyl syringate: An efficient phenolic mediator for bacterial and fungal laccases

The aim of the present work is to provide insight into the mechanism of laccase reactions using syringyl-type mediators. We studied the pH dependence and the kinetics of oxidation of syringyl-type phenolics using the low CotA and the high redox potential TvL laccases. Additionally, the efficiency of these compounds as redox mediators for the oxidation of non-phenolic lignin units was tested at different pH values and increasing mediator/non-phenolic ratios. Finally, the intermediates and products of reactions were identified by LC-MS and H-1 NMR. These approaches allow concluding on the (1) mechanism involved in the oxidation of phenolics by bacterial laccases, (2) importance of the chemical nature and properties of phenolic mediators, (3) apparent independence of the enzyme's properties on the yields of non-phenolics conversion, (4) competitive routes involved in the catalytic cycle of the laccase-mediator system with several new C-O coupling type structures being proposed.

Production, purification and characterization of laccase from pleurottus ostreatus grown on tomato pomace

A strain of Pleurotus ostreatus was grown in tomato pomace as sole carbon source for production of laccase. The culture of P. ostreatus revealed a peak of laccase activity (147 U/L of fermentation broth) on the 4th day of culture with a specific activity of 2.8 U/mg protein. Differential chromatographic behaviour of laccase was investigated on affinity chromatographic matrices containing either urea, acetamide, ethanolamine or IDA as affinity ligands. Laccase exhibited retention on such affinity matrices and it was purified on a Sepharose 6B-BDGE-urea column with final enzyme recoveries of about 60%, specific activity of 6.0 and 18.0 U/mg protein and purification factors in the range of 14-46. It was also possible to demonstrate that metal-free laccase did not adsorb to Sepharose 6B-BDGE-urea column which suggests that adsorption of native laccase on this affinity matrix was apparently due to the specific interaction of carbonyl groups available on the matrix with the active site Cu (II) ions of laccase. The kinetic parameters (V (max), K (m) , K (cat), and K (cat)/K (m) ) of the purified enzyme for several substrates were determined as well as laccase stability and optimum pH and temperature of enzyme activity. This is the first report describing the production of laccase from P. ostreatus grown on tomato pomace and purification of this enzyme based on affinity matrix containing urea as affinity ligand.

Study of thermochemical treatments of cork in the 150-400ºC range using colour analysis and Ftir spectroscopy

A study of chemical transformations of cork during heat treatments was made using colour variation and FTIR analysis. The cork enriched fractions from Quercus cerris bark were subjected to isothermal heating in the temperature range 150–400 ◦C and treatment time from 5 to 90 min. Mass loss ranged from 3% (90 min at 150 ◦C) to 71% (60 min at 350 ◦C). FTIR showed that hemicelluloses were thermally degraded first while suberin remained as the most heat resistant component. The change of CIE-Lab parameters was rapid for low intensity treatments where no significant mass loss occurred (at 150 ◦C L* decreased from the initial 51.5 to 37.3 after 20 min). The decrease in all colour parameters continued with temperature until they remained substantially constant with over 40% mass loss. Modelling of the thermally induced mass loss could be made using colour analysis. This is applicable to monitoring the production of heat expanded insulation agglomerates.

Three-Dimensional patchy lattice model for empty fluids

The phase diagram of a simple model with two patches of type A and ten patches of type B (2A10B) on the face centred cubic lattice has been calculated by simulations and theory. Assuming that there is no interaction between the B patches the behavior of the system can be described in terms of the ratio of the AB and AA interactions, r. Our results show that, similarly to what happens for related off-lattice and two-dimensional lattice models, the liquid-vapor phase equilibria exhibit reentrant behavior for some values of the interaction parameters. However, for the model studied here the liquid-vapor phase equilibria occur for values of r lower than 1/3, a threshold value which was previously thought to be universal for 2AnB models. In addition, the theory predicts that below r = 1/3 (and above a new condensation threshold which is < 1/3) the reentrant liquid-vapor equilibria are so extreme that it exhibits a closed loop with a lower critical point, a very unusual behavior in single-component systems. An order-disorder transition is also observed at higher densities than the liquid-vapor equilibria, which shows that the liquid-vapor reentrancy occurs in an equilibrium region of the phase diagram. These findings may have implications in the understanding of the condensation of dipolar hard spheres given the analogy between that system and the 2AnB models considered here.

Reabilitação termo-higrométrica de edifícios de estabelecimentos de ensino construídos entre a década de 60 e 90

Em consequência da elevada permanência das pessoas em espaços interiores de edifícios, surge actualmente uma maior preocupação com o conforto térmico e qualidade do ar no seu interior. Apesar da grande evolução tecnológica dos sistemas de conservação de energia térmica e controle da qualidade do ar interior (QAI) na construção, os edifícios existentes acabam por não acompanhar essa evolução, apresentando um comportamento térmico e higrométrico que por vezes podem comprometer quer o conforto, quer a saúde e actividades dos seus utilizadores. Nos estabelecimentos de ensino, o comportamento termo-higrométrico assume um papel importante face à permanência diária de um grande número de crianças e jovens no seu interior. Com este estudo pretende-se caracterizar a qualidade do ambiente no interior de oito escolas, através de uma análise aos principais parâmetros de natureza higrotérmica de oito salas de aulas, tais como: a temperatura (ambiente e superficial), a humidade relativa (do ambiente e da superfície da envolvente exterior opaca), bem como o nível de escoamento do ar interior. Neste trabalho são apresentados os resultados das medições efectuadas em oito salas de aula que permitiram a comparação de características termo-higrométricas entre as respectivas escolas. É ainda apresentada a estimativa do nível de conforto térmico face às condições ambientais registadas, bem como a análise do risco de ocorrência de condensações interiores.

A stratigraphic framework for the Miocene from the lower Tagus Basin (Lisbon, Setúbal Península, Portugal) Depositional sequences, biostratigraphy and isotopic ages

Rev. Soc. Geol. España, 12(1), ano 1999