Laurdan Spectrum Decomposition as a Tool for the Analysis of Surface Bilayer Structure and Polarity: a Study with DMPG, Peptides and Cholesterol

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A theoretical analysis on electronic structure of the (110) surface of TiO2-SnO2 mixed oxide

Mixed oxide compounds, such as TiO2-SnO2 system are widely used as gas sensors and should also provide varistor properties modifying the TiO2 surface. Therefore, a theoretical investigation has been carried out characterizing the effect of SnO2 on TiO2 addition on the electronic structure by means of ab initio SCF-LCAO calculations using all electrons. In order to take into account the finite size of the cluster, we have used the point charge model for the (TiO2)(15) cluster to study the effect on electronic structure of doping the TiO2 (110) Surface. The contracted basis set for titanium (4322/42/3), oxygen (33/3) and tin (43333/4333/43) atoms were used. The charge distributions, dipole moments, and density of states of doping TiO2 and vacancy formation are reported and analysed. (C) 2003 Elsevier B.V. All rights reserved.

Correlation between the surface morphology and structure and the photoluminescence of amorphous PbTiO3 thin films obtained by the chemical route

A polymeric precursor method was used to synthesis PbTiO3 amorphous thin film processed at low temperature. The luminescence spectra of PbTiO3 amorphous thin films at room temperature revealed an intense single-emission band in the visible region, the visible emission band was found to be dependent on the thermal treatment history, Photoluminescence properties Versus different annealing temperatures were investigated. The experimental results (XRD, AFM, FL) indicate that the nature of photoluminescence (PL) must be related to the disordered structure of PbTiO3 amorphous thin films, Copyright (C) 2000 John Wiley & Sons, Ltd.

Chemical structure, surface properties and biological activities of the biosurfactant produced by Pseudomonas aeruginosa LBI from soapstock

Pseudomonas aeruginosa LBI isolated from petroleum-contaminated soil produced rhamnolipids (RLLBI) when cultivated on soapstock as the sole carbon source. HPLC-MS analysis of the purified culture supernatant identified 6 RL homologues (%): R-2 C-10 C-10 28.9; R-2 C-10 C-12:1 23.0; R-1 C-10 C-10 23.4; R-2 C-10 C-12 11.3; R-2 C-10 C-12 7.9; R-2 C-10 C-12 C-12 5.5. To assess the potential antimicrobial activity of the new rhamnolipid product, RLLBI, its physicochemical properties were studied. RLLBI had a surface tension of 24 mN m(-1) and an interfacial tension 1.31 mN m(-1); the cmc was 120 mg l(-1). RLLBI produced stable emulsions with hydrocarbons and vegetable oils. This product showed good antimicrobial behaviour against bacteria: MIC for Bacillus subtilis, Staphylococcus aureus and Proteus vulgaris was 8 mg l(-1), for Streptococcus faecalis 4 mg l(-1), and for Pseudomonas aeruginosa 32 mg l(-1). RLLBI was active against phytopathogenic fungal species, MIC values of 32 mg l(-1) being found against Penicillium, Alternaria, Gliocadium virens and Chaetonium globosum. Due to its physicochemical properties and antimicrobial behaviour, RLLBI could be used in bioremediation treatment and in the food, cosmetic and pharmaceutical industries.

Local structure and near-infrared emission features of neodymium-based amine functionalized organic/inorganic hybrids

Nd3+-based organic/inorganic hybrids have potential application in the field of integrated optics. Attractive sol-gel derived di-urea and di-urethane cross-linked poly (oxyethylene) (POE)/siloxane hybrids (di-ureasils and di-urethanesils, respectively) doped with neodymium triflate (Nd(CF3SO3)(3)) were examined by Fourier transform mid-infrared (FT-IR), Raman (FT-Raman), Si-29 magic-angle spinning (MAS) nuclear magnetic resonance (NMR) and photoluminescence spectroscopies, and small-angle X-ray scattering (SAXS). The goals of this work were to determine which cation coordinating site of the host matrix (ether oxygen atoms or carbonyl oxygen atoms) is active in each of the materials analyzed, its influence on the nanostructure of the samples and its relation with the photoluminescence properties. The main conclusion derived from this study is that the hydrogen-bonded associations formed throughout the materials play a major role in the hybrids nanostructure and photoluminescence properties.

The influence of hydrogen plasma pre-treatment on the structure of BDND electrode surface applied for phenol detection

The surface properties of boron-doped nanocrystalline diamond films treated with H(2) plasma was investigated in regard to their electrochemical response for phenol oxidation. The surface of these films is relatively flat formed by crystallites with sizes of about 40 nm. X-ray photoelectron spectroscopy analyses showed that electrode surface has a high amount of C-H bonds. This behavior is in agreement with Mott-Schottky plot measurements concerning the flat band potential that presented a value as expected for hydrogenated diamond surface. This electrode presented the phenol detection limit of 0.08 mg L(-1) for low phenol concentrations from 40 to 250 mu mol L(-1).

Electrochemistry of organometallic compounds. Part III. Oxidations of methyl derivatives of organocobalt(III) complexes with delocalized electronic structure in dimethylformamide

The influence of the equatorial ligand on the electrochemical oxidation of the compounds [H3CCo(chel)B], where chel is bis (dimethylglyoximato), (DH)2; bis(salicylaldehyde)ethylenediimine, salen; bis(salicylaldehyde) o-phenylenediimine, salophen; bis(salicylaldehyde)cyclohexylenediimine, salcn; bis(acetylacetone) ethylenediimine, bae; and where B is pyridine when chel is (DH2), and dimethylformamide (DMF) when chel represents a Schiff base (salen, salcn, salophen and bae), was studied by means of cyclic voltammetry in DMF, 0.2 M in tetraethylammonium perchlorate, between 25 and -25°C, with a platinum disk working electrode. Absorption spectra in the visible and near ultraviolet regions for these compounds in DMF at 25°C were obtained. The complexes exhibit a reversible one-electron oxidation, at -20°C with scan rates >0.5 V s-; chemical reactions following electron transfer are not detected under these conditions. At slower potential or higher temperatures, the oxidized product decomposes chemically in a solvent-assisted (or nucleophile-assisted) reaction, yielding products which are electroactive in the applied potential range. The behavior of the [H3CCo (DH2)py] derivative is better described as a quasi-reversible charge transfer followed by an irreversible chemical reaction. Experimental evidence suggests that in the case of the [H3CCo(bae)] derivative at -20°C, the reactive -species is pentacoordinated and weakly adsorbed at the electrode surface. The value of E 1 2 and the energies of the first two absorption bands in the visible spectra reveal the ability of the studied complexes to donate and to delocalize electronic charge. © 1982.

Structure of cobalt (II) perchlorate adsorbed on silica gel surface chemically modified with benzimidazole molecule

Covalently attached benzimidazole molecules on silica gel surface, ≡SiL (where L = N-propyl-benzimidazole), adsorbs Co(ClO4)2 from non-aqueous solvent by forming a surface complex according to the reaction: m ≡SiL + Co(ClO4)2 → (≡SiL)mCo(ClO4)2. The equilibrium constant and the adsorption capacity, determined by applying the Langmuir equation were b = 3.0 × 103 L mol-1 and Ns= 0.098 × 10-3 mol g-1, respectively. The metal is bonded through the nitrogen atom and the perchlorate ion is not coordinated. The ESR study indicated that the complex has essentially an octahedral geometry with tetragonal distortion, with the electrons of the four nitrogen atoms interacting with the cobalt central metal ion in the equatorial plane. Only one complex species was detected on the surface.

Adsorption and structure of copper(II) complexes on a silica gel surface chemically modified with 2-aminothiazole

The isotherms of adsorption of CuX2 (X=Cl-, Br-, ClO- 4) by silica gel chemically modified with 2-aminothiazole were studied in acetone and EtOH solutions, at 25°C. The 2-aminothiazole molecule, covalently bond to the silica gel surface, adsorbs CuX2 from solvent by forming a surface complex. At low loading, the electronic and E.S.R. spectral parameters indicate that the Cu2+ complexes have a distorted tetragonal symmetry. The d-d eletronic transition spectra show that for ClO- 4 complex, the peak of absorption do not change for any degree of metal loading whilst for Cl- and Br- complexes, the peak maxima shift to higher energy with lower metal loading. © Elsevier Science Ltd.

Local and regional features of surface radiation fluxes over the tropical Atlantic ocean near Sao Pedro and Sao Paulo archipelago: Evidence of small scale upwelling

To properly describe the interactions between the ocean and atmosphere, it is necessary to assess a variety of time and spatial scales phenomena. Here, high resolution oceanographic and meteorological data collected during an observational campaign carried out aboard a ship in the tropical Atlantic Ocean, on May 15-24, 2002, is used to describe the radiation balance at the ocean interface. Data collected by two PIRATA buoys, along the equator at 23°W and 35°W and satellite and climate data are compared with the data obtained during the observational campaign. Comparison indicates remarkable similarity for daily and hourly values of radiation fluxes components as consequence of the temporal and spatial consistence presented by the air and water temperatures measured in situ and estimated from large scale information. The discrepancy, mainly in the Sao Pedro and Sao Paulo Archipelago area, seems to be associated to the local upwelling of cold water, which is not detected in all other estimates investigated here. More in situ data are necessary to clarify whether this upwelling flow has a larger scale effect and what are the meteorological and oceanographic implications of the local upwelling area on the tropical waters at the Brazilian coast.

Structure, characterization and near-infrared emission of a novel 6-connected uninodal 3D network of Nd(III) containing 2,5-thiophenedicarboxylate anion

The novel coordination polymer with the formula {[Nd2(2,5-tdc)3(dmf)2(H2O)2].dmf.H2O}n (2,5-tdc2-=2,5-thiophedicarboxylate anion and dmf=dimethylformamide) has been synthesized and characterized by thermal analysis (TG/DTA), vibrational spectroscopy (FTIR) and single crystal X-ray diffraction analysis (XRD). Structure analysis reveals that Nd(III) ions show dicapped trigonal prism coordination geometry. The 2,5-tdc2- ligands connect four Nd(III) centers, adopting (κ1 - κ1) - (κ1 - κ1) - μ4 coordination mode, generating an interesting 6-connected uninodal 3D network. Photophysical properties were studied using diffuse reflectance spectroscopy (DR) and excitation/emission spectra. The photoluminescence data show the near infrared emission (NIR) with the characteristic 4F3/2→4IJ (J=9/2, 11/2 and 13/2) transitions of Nd(III) ion, indicating that 2,5-tdc2- is able to act as a sensitizer for emission in NIR region. © 2013 Elsevier B.V.

Structure of copper complexes adsorbed on a silica gel surface chemically modified with benzimidazole

Silica gel having a particle size between 0.2 and 0.05 mm and a specific surface area, S BET = 473 m 2 g -1, was chemically modified with benzimidazole. Adsorption isotherms of CuX 2 (X = Cl, Br or ClO 4) from ethanol and acetone solutions were studied at 298 K. The metal is bonded to the surface through the free nitrogen atom of the attached benzimidazole. The average number of ligands co-ordinated to the central metal ion was shown to depend on the solid surface loading by the solute. At low loading the electronic and ESR spectral parameters indicated that the copper ion is in a distorted-tetragonal symmetry field.

Impact of the Manaus urban plume on trace gas mixing ratios near the surface in the Amazon Basin: Implications for the NO-NO2-O-3 photostationary state and peroxy radical levels

We measured the mixing ratios of NO, NO2, O-3, and volatile organic carbon as well as the aerosol light-scattering coefficient on a boat platform cruising on rivers downwind of the city of Manaus (Amazonas State, Brazil) in July 2001 (Large-Scale Biosphere-Atmosphere Experiment in Amazonia-Cooperative LBA Airborne Regional Experiment-2001). The dispersion and impact of the Manaus plume was investigated by a combined analysis of ground-based (boat platform) and airborne trace gas and aerosol measurements as well as by meteorological measurements complemented by dispersion calculations (Hybrid Single-Particle Lagrangian Integrated Trajectory model). For the cases with the least anthropogenic influence (including a location in a so far unexplored region similar to 150 km west of Manaus on the Rio Manacapuru), the aerosol scattering coefficient, sigma(s), was below 11 Mm(-1), NOx mixing ratios remained below 0.6 ppb, daytime O-3 mixing ratios were mostly below 20 ppb and maximal isoprene mixing ratios were about 3 ppb in the afternoon. The photostationary state (PSS) was not established for these cases, as indicated by values of the Leighton ratio, Phi, well above unity. Due to the influence of river breeze systems and other thermally driven mesoscale circulations, a change of the synoptic wind direction from east-northeast to south-southeast in the afternoon often caused a substantial increase of ss and trace gas mixing ratios (about threefold for sigma(s), fivefold for NOx, and twofold for O-3), which was associated with the arrival of the Manaus pollution plume at the boat location. The ratio F reached unity within its uncertainty range at NOx mixing ratios of about 3 ppb, indicating "steady-state" conditions in cases when radiation variations, dry deposition, emissions, and reactions mostly involving peroxy radicals (XO2) played a minor role. The median midday/afternoon XO2 mixing ratios estimated using the PSS method range from 90 to 120 parts per trillion (ppt) for the remote cases (sigma(s) < 11 Mm(-1) and NOx < 0.6 ppb), while for the polluted cases our estimates are 15 to 60 ppt. These values are within the range of XO2 estimated by an atmospheric chemistry box model (Chemistry As A Box model Application-Module Efficiently Calculating the Chemistry of the Atmosphere (CAABA/MECCA)-3.0).

The Role of Dyslipidemia on Ocular Surface, Lacrimal and Meibomian Gland Structure and Function

Purpose: Dyslipidemia is characterized by high lipid blood levels that are risk factors for cardiovascular diseases, which are leading causes of death. However, it is unclear whether dyslipidemia is a cause of the dry eye syndrome (DES). Therefore we determined in transgenic mice models of dyslipidemia, whether there is an association with DES development. Methods: Dyslipidemic models included male and female adult mice overexpressing apolipoprotein CIII (Apo CIII), LDL receptor knockout (LDLR-KO) and ApoE knockout (ApoE-KO). They were compared with age-and gender-matched C57BL/6 mice. Ocular health was evaluated based on corneal slit lamp assessment, phenol red thread test (PRT) and impression cytology. Blood lipid profiles and histology of meibomian and lacrimal glands were also evaluated. Effects of high-fat diet and aging were observed in LDLR-KO and ApoCIII strains, respectively. Results: Body weight and lacrimal gland weight were significantly higher in male mice compared to females of the same strain (P < 0.05). Body weight was significantly lower in LDLRKO mice receiving high lipid diet compared to their controls (P = 0.0043). ApoE-KO were hypercholesterolemic and ApoCIII hypertriglyceridemic while LDLR-KO showed increases in both parameters. The PRT test was lower in male LDLR-KO mice with high-fat diet than control mice with standard diet (P = 0.0273). Aging did not affect lacrimal structural or functional parameters of ApoCIII strain. Conclusions: DES development is not solely dependent on dyslipidemia in relevant mice models promoting this condition. On the other hand, lacrimal gland structure and function are differentially impacted by lipid profile changes in male and female mice. This dissociation suggests that other factors beside dyslipidemia impact on tear film dysfunction and DES development.

A Galactic ring of minimum stellar density near the solar orbit radius

We analyse the secular effects of a long-lived Galactic spiral structure on the stellar orbits with mean radii close to the corotation resonance. By test-particle simulations and different spiral potential models with parameters constrained on observations, we verified the formation of a minimum with amplitude ∼30–40 per cent of the background disc stellar density at corotation. Such a minimum is formed by the secular angular momentum transfer between stars and the spiral density wave on both sides of corotation. We demonstrate that the secular loss (gain) of angular momentum and decrease (increase) of mean orbital radius of stars just inside (outside) corotation can counterbalance the opposite trend of exchange of angular momentum shown by stars orbiting the librational points L4/5 at the corotation circle. Such secular processes actually allow steady spiral waves to promote radial migration across corotation. We propose some pieces of observational evidence for the minimum stellar density in the Galactic disc, such as its direct relation to the minimum in the observed rotation curve of the Galaxy at the radius r ∼ 9 kpc (for R0 = 7.5 kpc), as well as its association with a minimum in the distribution of Galactic radii of a sample of open clusters older than 1Gyr. The closeness of the solar orbit adius to the corotation resonance implies that the solar orbit lies inside a ring of minimum surface density (stellar + gas). This also implies a correction to larger values for the estimated total mass of the Galactic disc, and consequently, a greater contribution of the disc componente to the inner rotation curve of the Galaxy.