Characterizing air particulate matter composition and sources in Lisbon,Portugal

The goal of this research is to determine trends and sources of airborne particulates in the centre of Lisbon, by using speciated particulate-matter data and back-trajectory analyses. Results showed that, in 2007, the annual PM_2.5 concentration exceeded the World Health Organization recommended levels. PM_2.5 diurnal variability and the ratio between weekdays’ and weekends’ concentrations indicated that traffic contributed highly to decreasing air quality. Air back-trajectory analysis showed that maritime air mass transport had a significant role on air quality in Lisbon, promoting the decrease of anthropogenic aerosol concentrations.     

Characterisation of the seasonal exposure to air pollutants for a respiratory epidemiological study

In 2006, elementary schools of inner-city Lisbon, Portugal were given questionnaires to identify respiratory problems. In 1,175 children aged 5–10 years, 27.7% reported rhinitis, 2.5% reported hay fever and 25.9% reported asthma symptoms. April and August were the months with higher incidence of rhinitis, with a considerable difference nonetheless (10.5% and 2.3%, respectively.). The former trends are addressed here by using meteorological data, PM_2.5, and its elemental speciation. Mann-Whitney U-tests were applied to the data sets. Significantly higher values were found for humidity, K⁺, NH₄ ⁺, Sb and Zn in April, and for temperature, Cl⁻, Mg²⁺ and Na⁺ in August. Commuter and heavy-duty traffic may contribute to rhinitis episodes.     

Evaluating children exposure to air pollutants for an epidemiological study

Recent health studies evidence that epidemiological studies must be combined with accurate analyses of the physico-chemical properties of the particles in order to determine the effects of atmospheric aerosols on human health. The project “Atmospheric Aerosol Impacts on Human Health” focuses on the chemical characterization of PM2.5 aerosols with the aim to analyze the health risks associated with exposure to aerosols and understand how their chemical composition contributes to the toxicity and human health problems traditionally associated with fine particles. During one year, PM2.5 was collected daily, with a Partisol sampler, in the centre of Lisbon. The aerosols were analyzed by Neutron Activation Analysis and Ion Chromatography in order to determine their chemical composition. In parallel the clinical situation of students from the schools situated around the sampler was followed. The incidence of asthma and rhinitis episodes was registered. Results showed that students were exposed to PM2.5 concentrations that exceed the World Health Organization recommended levels. A marked sea influence in the aerosol characteristics was identified by the use of air masses trajectories and by the concentrations of chloride, sodium and magnesium.     

Fragmentation of mycosporine-like amino acids by hydrogen/deuterium exchange and electrospray ionisation tandem mass spectrometry

The determination and identification of mycosporine-like amino acids (MAAs) from algae remain a major challenge due to the low concentration. Mass spectrometry (MS) can make an invaluable contribution in the search and identification of MAAs because of its high sensitivity, possibility of coupling with liquid chromatography, and the availability of powerful tandem mass spectrometric techniques. However, the unequivocal determination of the presence and location of important functional groups present on the basic skeleton of the MAAs is often elusive due to their inherent instability under MS conditions. In this study, the use of hydrogen/deuterium (H/D) exchange and electrospray ionisation tandem mass spectrometry (ESI-MS/MS) for characterisation of four MAAs (palythine, asterina, palythinol and shinorine) isolated from the macroalgae Gracilaria tenuistipitata Chang et Xia was investigated. The accurate-mass confirmation of the protonated molecules was performed on a Q-TOF instrument. We demonstrate that employing deuterium labelling in ESI-MS/MS analysis provides a convenient tool for the determination of new MAAs. Although the fragmentation patterns of MAAs were discussed earlier, to our knowledge, this is the first time that mechanisms are proposed.     

Guanine-rich RNAs and DNAs that bind heme robustly catalyze oxygen transfer reactions

Diverse guanine-rich RNAs and DNAs that fold to form guanine quadruplexes are known to form tight complexes with Fe(III) heme. We show here that a wide variety of such complexes robustly catalyze two-electron oxidations, transferring oxygen from hydrogen peroxide to thioanisole, indole, and styrene substrates. Use of (18)O-labeled hydrogen peroxide reveals the source of the oxygen transferred to form thioanisole sulfoxide and styrene oxide to be the activated ferryl moiety within these systems. Hammett analysis of the kinetics of thioanisole sulfoxide formation is unable to distinguish between a one-step, direct oxygen transfer and a two-step, oxygen rebound mechanism for this catalysis. Oxygen transfer to indole produces a range of products, including indigo and related dyes. Docking of heme onto a high-resolution structure of the G-quadruplex fold of Bcl-2 promoter DNA, which both binds heme and transfers oxygen, suggests a relatively open active site for this class of ribozymes and deoxyribozymes. That heme-dependent catalysis of oxygen transfer is a property of many RNAs and DNAs has ramifications for primordial evolution, enzyme design, cellular oxidative disease, and anticancer therapeutics.     

Equations of motion for nuclear particle-particle excitations and the interacting boson model

Equations of motion for correlated nucleon pairs are derived and then applied to some even lead isotopes. The connection with the interacting boson model is pointed out.     

Determination of saccharides in atmospheric aerosol using anion-exchange high-performance liquid chromatography and pulsed-amperometric detection

An improved method is described for the quantification of primary sugars, sugar alcohols and anhydrosugars in atmospheric aerosols, making use of separation by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD). Quartz fibre filters from high-volume samplers were extracted with water and the extract injected directly. Repeatability is typically 4% RSD, for e.g. levoglucosan at 50 ng m(-3) in air, better for winter levels around 700 ng m(-3). Limits of detection for individual sugars are in the range 0.02-0.05 microg mL(-1) in solution, corresponding to 2-5 ng m(-3) from a 20 m(3) air sample. The overlap of arabitol and levogluocosan is overcome by using a Dionex PA-1 column, with appropriate control of eluent composition, and peak deconvolution software, allowing quantification of both sugars in difficult summer samples containing low-levels of levoglucosan. Analysis of a set of ambient aerosol samples by both GC-flame ionization detection and HPAEC-PAD shows good agreement. The new method has the advantage of requiring no sample pretreatment or derivatization and is thus well suited to handling large numbers of samples.     

Rigid-rod liquid crystalline polyesters based on n-alkoxyterephthalic acid and 4,4′-dihydroxybiphenyl

The synthesis and the characterization of a set of polymers obtained by polycondensation of n-alkoxyterephthalic acid (n = 1, 3, 5, 7) and 4,4′-dihydroxybiphenyl are reported. The n-alkoxy insertion promotes the processability of the material by lowering the melting temperature. All polymers show the nematic phase at about 300°C, almost independently of the length of lateral substituent. The isotropization is not observed up to 450°C, where thermal decomposition occurs. The temperature of glass transition decreases with increasing n, ranging from 170°C (n = 5) to 220°C (n = 1). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 263–267, 1998