Dimensional change of two addition silicones

Poster apresentado no XXIV Congresso da Ordem dos Médicos Dentistas. Lisboa, 12-14 Novembro 2015

Platinum–rhodium–tin/carbon electrocatalysts for ethanol oxidation in acid media: effect of the precursor addition order and the amount of tin

Carbon-supported Pt x –Rh y –Sn z catalysts (x:y:z = 3:1:4, 6:2:4, 9:3:4) are prepared by Pt, Rh, and Sn precursors reduction in different addition order. The materials are characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy techniques and are evaluated for the electrooxidation of ethanol in acidic media by cyclic voltammetry, chronoamperometry, and anode potentiostatic polarization. The influence of both the order in which the precursors are added and the composition of metals in the catalysts on the electrocatalytic activity and physico-chemical characteristics of Pt x –Rh y –Sn z /C catalysts is evaluated. Oxidized Rh species prevail on the surface of catalysts synthesized by simultaneous co-precipitation, thus demonstrating the influence of synthesis method on the oxidation state of catalysts. Furthermore, high amounts of Sn in composites synthesized by co-precipitation result in very active catalysts at low potentials (bifunctional effect), while medium Sn load is needed for sequentially deposited catalysts when the electronic effect is most important (high potentials), since more exposed Pt and Rh sites are needed on the catalyst surface to alcohol oxidation. The Pt3–Rh1–Sn4/C catalyst prepared by co-precipitation is the most active at potentials lower than 0.55 V (related to bifunctional effect), while the Pt6–Rh2–Sn4/C catalyst, prepared by sequential precipitation (first Rh and, after drying, Pt + Sn), is the most active above 0.55 V.

Mechanisms of Chloroperoxidase-catalyzed Enantioselective Reactions as Probed by Site-directed Mutagenesis and Isotopic Labeling

Chloroperoxidase (CPO) is a heme-containing glycoprotein secreted by the marine fungus Caldariomyces fumago. Chloroperoxidase contains one ferriprotoporphyrin IX prosthetic group per molecule and catalyzes a variety of reactions, such as halogenation, peroxidation and epoxidation. The versatile catalytic activities of CPO coupled with the increasing demands for chiral synthesis have attracted an escalating interest in understanding the mechanistic and structural properties of this enzyme. In order to better understand the mechanisms of CPO-catalyzed enantioselective reactions and to fine-tune the catalytic properties of chloroperoxidase, asparagine 74 (N74) located in the narrow substrate access channel of CPO was replaced by a bulky, nonpolar valine and a polar glutamine using site-directed mutagenesis. The CPO N74 mutants displayed significantly enhanced activity toward nonpolar substrates compared to wild-type CPO as a result of changes in space and polarity of the heme distal environment. More interestingly, N74 mutants showed dramatically decreased chlorination and catalase activity but significantly enhanced epoxidation activity as a consequence of improved kinetic perfection introduced by the mutation as reflected by the favorable changes in kcat and kcat/KM of these reactions. It is also noted that the N74V mutant is capable of decomposing cyanide, the most notorious poison for many hemoproteins, as judged by the unique binding behavior of N74V with potassium cyanide. Histidine 105 (H105) was replaced by a nonpolar amino acid alanine using site-directed mutagenesis. The CPO H105 mutant (H105A) displayed dramatically decreased chlorination and catalase activity possibly because of the decreased polarity in the heme distal environment and loss of the hydrogen bonds between histidine 105 and glutamic acid 183. However, significantly increased enantioselectivity was observed for the epoxidation of bulky styrene derivatives. Furthermore, my study provides strong evidence for the proposed histidine/cysteine ligand switch in chloroperoxidase, providing experimental support for the structure of the 420-nm absorption maximum for a number of carbon monoxide complexes of heme-thiolate proteins. For the NMR study, [dCPO(heme)] was produced using 90% deuterated growth medium with excess heme precursors and [dCPO(Phe)] was grown in the same highly deuterated medium that had been supplemented with excess natural phenylalanine. To make complete heme proton assignments, NMR spectroscopy has been performed for high-resolution structural characterization of [dCPO(heme)] and [dCPO(Phe)] to achieve unambiguous and complete heme proton assignments, which also allows important amino acids close to the heme active center to be determined.

Effects of solid poly (ethylene glycols) addition to the solutions of aniline or N,N-dimethylaniline with water:experimental measurements and modelling

In this work, the liquid-liquid and solid-liquid phase behaviour of ten aqueous pseudo-binary and three binary systems containing polyethylene glycol (PEG) 2050, polyethylene glycol 35000, aniline, N,N-dimethylaniline and water, in the temperature range 298.15-350.15 K and at ambient pressure of 0.1 MPa, was studied. The obtained temperature-composition phase diagrams showed that the only functional co-solvent was PEG2050 for aniline in water, while PEG35000 even showed a clear anti-solvent effect in the N,N-dimethylaniline aqueous system. The experimental solid-liquid equilibria (SLE) data have been correlated by the non-random two-liquid (NRTL) model, and the correlation results are in accordance with the experimental results.

Influence of kaolin addition on the dynamics of oxygen mass transport in polyvinyl alcohol dispersion coatings

The permeability of dispersion barriers produced from polyvinyl alcohol (PVOH) and kaolin clay blends coated onto polymeric supports has been studied by employing two different measurement methods: the oxygen transmission rate (OTR) and the ambient oxygen ingress rate (AOIR). Coatings with different thicknesses and kaolin contents were studied. Structural information of the dispersion-barrier coatings was obtained by Fourier transform infrared spectroscopy (FTIR) spectroscopy and scanning electron microscopy (SEM). These results showed that the kaolin content influences both the orientation of the kaolin and the degree of crystallinity of the PVOH coating. Increased kaolin content increased the alignment of the kaolin platelets to the basal plane of the coating. Higher kaolin content was accompanied by higher degree of crystallinity of the PVOH. The barrier thickness proved to be less important in the early stages of the mass transport process, whereas it had a significant influence on the steady-state permeability. The results from this study demonstrate the need for better understanding of how permeability is influenced by (chemical and physical) structure.

ADDITION OF VINEGAR TO EXTEND THE SHELF-LIFE OF CABEÇA DE XARA

Cabeça de xara is a ready-to-eat meat product, whose production is very characteristic in Alentejo, a particular region of Portugal. It is a galantine usually moulded into parallelepiped shape made with various meats obtained from the Alentejano pig breed reared in the same region, namely deboned pork heads, tongue and connective tissue to which a number of condiments like salt, parsley, wine and pepper, are added. This work intended to test the feasibility of adding vinegar in order to increase the shelf-life of cabeça de xara, by reducing the contaminating microbiota responsible for spoilage, as well as controlling the pathogen Listeria monocytogenes. Three independent batches were produced and proximate composition, pH, aw, microbiological parameters and biogenic amines content evaluated. A sensory analysis was also performed throughout the storage period. No significant differences between control and vinegar samples was found regarding the proximate composition of cabeça de xara. As expected, pH is lower in the vinegar samples, however no differences in aw were observed between the two treatments. L. monocytogenes was present from the first month on only in one batch in the control treatment. However, it is inhibited by the addition of vinegar until the third month of storage, where L. monocytogenes is present but below the limit established in the 2073/2005 regulation. The presence of vinegar significantly decreased the content in biogenic amines, particularly cadaverine, putrescine and tyramine, throughout the storage period. Concerning sensory evaluation, no vinegar taste was reported by the panellists in a depreciating way.

Near-infrared spectroscopic study of basic aluminum sulfate and nitrate

The tridecameric Al-polymer [AlO4Al12(OH)24(H2O)12]7+ was prepared by forced hydrolysis of Al3+ up to an OH/Al molar ratio of 2.2. Under slow evaporation crystals were formed of Al13-nitrate. Upon addition of sulfate the tridecamer crystallised as the monoclinic Al13-sulfate. These crystals have been studied using near-infrared spectroscopy and compared to Al2(SO4)3.16H2O. Although the near-infrared spectra of the Al13-sulfate and nitrate are very similar indicating similar crystal structures, there are minor differences related to the strength with which the crystal water molecules are bonded to the salt groups. The interaction between crystal water and nitrate is stronger than with the sulfate as reflected by the shift of the crystal water band positions from 6213, 4874 and 4553 cm–1 for the Al13 sulfate towards 5925, 4848 and 4532 cm–1 for the nitrate. A reversed shift from 5079 and 5037 cm–1 for the sulfate towards 5238 and 5040 cm–1 for the nitrate for the water molecules in the Al13 indicate that the nitrate-Al13 bond is weakened due to the influence of the crystal water on the nitrate. The Al-OH bond in the Al13 complex is not influenced by changing the salt group due to the shielding by the water molecules of the Al13 complex.

How do customers of a financial services institution judge its communications

Communications are important for relationships within a marketing channel from both a theoretical and managerial perspective. Yet it is a problematic area for scholars. Thus, this research addresses the problem of how do customers of a financial services institution perceive communications with an ideal institution? This study's case research methodology used in-depth interviews with 34 carefully selected customers of a building society. The factors that make up customers' attitudes about corporate communications for an ideal financial services institution were identified and actual perceptions were compared against that ideal. The findings confirmed the importance of communications for customers in a relationship with a financial services provider and suggested communication priorities for customers in this context. In addition, the findings suggested sources of communication dissatisfaction for customers. These findings build upon the literature that speculates about customer perceptions of communications with organizations but provides little evidence to support hypotheses. The contributions arose from the emphasis on the customers' own attitudes and the patterns found within them.

Hydrazine-hydrate intercalated halloysite under controlled-rate thermal analysis conditions

The thermal behaviour of halloysite fully expanded with hydrazine-hydrate has been investigated in nitrogen atmosphere under dynamic heating and at a constant, pre-set decomposition rate of 0.15 mg min-1. Under controlled-rate thermal analysis (CRTA) conditions it was possible to resolve the closely overlapping decomposition stages and to distinguish between adsorbed and bonded reagent. Three types of bonded reagent could be identified. The loosely bonded reagent amounting to 0.20 mol hydrazine-hydrate per mol inner surface hydroxyl is connected to the internal and external surfaces of the expanded mineral and is present as a space filler between the sheets of the delaminated mineral. The strongly bonded (intercalated) hydrazine-hydrate is connected to the kaolinite inner surface OH groups by the formation of hydrogen bonds. Based on the thermoanalytical results two different types of bonded reagent could be distinguished in the complex. Type 1 reagent (approx. 0.06 mol hydrazine-hydrate/mol inner surface OH) is liberated between 77 and 103°C. Type 2 reagent is lost between 103 and 227°C, corresponding to a quantity of 0.36 mol hydrazine/mol inner surface OH. When heating the complex to 77°C under CRTA conditions a new reflection appears in the XRD pattern with a d-value of 9.6 Å, in addition to the 10.2 Ĺ reflection. This new reflection disappears in contact with moist air and the complex re-expands to the original d-value of 10.2 Å in a few h. The appearance of the 9.6 Å reflection is interpreted as the expansion of kaolinite with hydrazine alone, while the 10.2 Å one is due to expansion with hydrazine-hydrate. FTIR (DRIFT) spectroscopic results showed that the treated mineral after intercalation/deintercalation and heat treatment to 300°C is slightly more ordered than the original (untreated) clay.

The mechanical strength of phosphates under friction-induced cross-linking

Purpose: In the present study, we consider mechanical properties of phosphate glasses under high temperatureinduced and under friction-induced cross-linking, which enhance the modulus of elasticity. Design/methodology/approach: Two nanomechanical properties are evaluated, the first parameter is the modulus of elasticity (E) (or Young's modulus) and the second parameter is the hardness (H). Zinc meta-, pyro - and orthophosphates were recognized as amorphous-colloidal nanoparticles were synthesized under laboratory conditions and showed antiwear properties in engine oil. Findings: Young's modulus of the phosphate glasses formed under high temperature was in the 60-89 GPa range. For phosphate tribofilm formed under friction hardness and the Young's modulus were in the range of 2-10 GPa and 40-215 GPa, respectively. The degree of cross-linking during friction is provided by internal pressure of about 600 MPa and temperature close to 1000°C enhancing mechanical properties by factor of 3 (see Fig 1). Research limitations/implications: The addition of iron or aluminum ions to phosphate glasses under high temperature - and friction-induced amorphization of zinc metaphosphate and pyrophosphate tends to provide more cross-linking and mechanically stronger structures. Iron and aluminum (FeO4 or AlO4 units), incorporated into phosphate structure as network formers, contribute to the anion network bonding by converting the P=O bonds into bridging oxygen. Future work should consider on development of new of materials prepared by solgel processes, eg., zinc (II)-silicic acid. Originality/value: This paper analyses the friction pressure-induced and temperature–induced the two factors lead phosphate tribofilm glasses to chemically advanced glass structures, which may enhance the wear inhibition. Adding the coordinating ions alters the pressure at which cross-linking occurs and increases the antiwear properties of the surface material significantly.

Influence of host plant structure and microclimate on the abundance and behaviour of Tephritid fly

Microclimate and host plant architecture significantly influence the abundance and behavior of insects. However, most research in this field has focused at the invertebrate assemblage level, with few studies at the single-species level. Using wild Solanum mauritianum plants, we evaluated the influence of plant structure (number of leaves and branches and height of plant) and microclimate (temperature, relative humidity, and light intensity) on the abundance and behavior of a single insect species, the monophagous tephritid fly Bactrocera cacuminata (Hering). Abundance and oviposition behavior were signficantly influenced by the host structure (density of foliage) and associated microclimate. Resting behavior of both sexes was influenced positively by foliage density, while temperature positively influenced the numbers of resting females. The number of ovipositing females was positively influenced by temperature and negatively by relative humidity. Feeding behavior was rare on the host plant, as was mating. The relatively low explanatory power of the measured variables suggests that, in addition to host plant architecture and associated microclimate, other cues (e.g., olfactory or visual) could affect visitation and use of the larval host plant by adult fruit flies. For 12 plants observed at dusk (the time of fly mating), mating pairs were observed on only one tree. Principal component analyses of the plant and microclimate factors associated with these plants revealed that the plant on which mating was observed had specific characteristics (intermediate light intensity, greater height, and greater quantity of fruit) that may have influenced its selection as a mating site.

Components of learning and assessment in linear algebra

Linear algebra provides theory and technology that are the cornerstones of a range of cutting edge mathematical applications, from designing computer games to complex industrial problems, as well as more traditional applications in statistics and mathematical modelling. Once past introductions to matrices and vectors, the challenges of balancing theory, applications and computational work across mathematical and statistical topics and problems are considerable, particularly given the diversity of abilities and interests in typical cohorts. This paper considers two such cohorts in a second level linear algebra course in different years. The course objectives and materials were almost the same, but some changes were made in the assessment package. In addition to considering effects of these changes, the links with achievement in first year courses are analysed, together with achievement in a following computational mathematics course. Some results that may initially appear surprising provide insight into the components of student learning in linear algebra.

Assessing health risk associated with airborne polycyclic aromatic hydrocarbons by chemometrics and toxic equivalency factors

Some polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in air and have been implicated as carcinogenic materials. Therefore, literature is replete with studies that are focused on their occurrence and profiles in indoor and outdoor air samples. However, because the relative potency of individual PAHs vary widely, health risks associated with the presence of PAHs in a particular environment cannot be extrapolated directly from the concentrations of individual PAHs in that environment. In addition, database on the potency of PAH mixtures is currently limited. In this paper, we have utilized multi-criteria decision making methods (MCDMs) to simultaneously correlate PAH-related health risk in some microenvironments to the concentration levels, ethoxyresorufin-O-deethylase (EROD) activity induction equivalency factors and toxic equivalency factors (TEFs) of PAHs found in those microenvironments. The results showed that the relative risk associated with PAHs in different air samples depends on the index used. Nevertheless, this approach offers a promising tool that could help identify microenvironments of concern and assist the prioritisation of control strategies.

Why the “Big Deal” continues to persist

The advantages of bundling e-journals together into publisher collections include increased access to information for the subscribing institution’s clients, purchasing cost-effectiveness and streamlined workflows. Whilst cataloguing a consortial e-journal collection has its advantages, there are also various pitfalls and the author outlines efforts by the CAUL (Council of Australian University Libraries) Consortium libraries to further streamline this process, working in conjunction with major publishers. Despite the advantages that publisher collections provide, pressures to unbundle existing packages continue to build, fuelled by an ever-increasing selection of available electronic resources; decreases in, and competing demands upon, library budgets; the impact of currency fluctuations; and poor usage for an alarmingly high proportion of collection titles. Consortial perspectives on bundling and unbundling titles are discussed, including options for managing the addition of new titles to the bundle and why customising consortial collections currently does not work. Unbundling analyses carried out at Queensland University of Technology during 2006 to 2008 prior to the renewal of several major publisher collections are presented as further case studies which illustrate why the “big deal” continues to persist.

Passive solar systems for heating, daylighting and ventilation for rooms without an equator-facing facade

Spaces without northerly orientations have an impact on the ‘energy behaviour’ of a building. This paper outlines possible energy savings and better performance achieved by different zenithal solar passive strategies (skylights, roof monitors and clerestory roof windows) and element arrangements across the roof in zones of cold to temperate climates typical of the central and central-southern Argentina. Analyses were undertaken considering daylighting, thermal and ventilation performances of the different strategies. The results indicate that heating,ventilation and lighting loads in spaces without an equator-facing facade can be significantly reduced by implementing solar passive strategies. In the thermal aspect, the solar saving fraction reached for the different strategies were averaged 43.16% for clerestories, 41.4% for roof monitors and 38.86% for skylights for a glass area of 9% to the floor area. The results also indicate average illuminance levels above 500 lux for the different clerestory and monitor arrangements, uniformity ratios of 0.66–0.82 for the most distributed arrangements and day-lighting factors between 11.78 and 20.30% for clear sky conditions, depending on the strategy. In addition, minimum air changes rates of 4 were reached for the most extreme conditions.