No abstract

Nafion® membranes were developed by DuPont, a perfluorosulfonic acid/polytetrafluoroethylene copolymer. These membranes are hydrophilic and the water is preferentially sorbed into the clusters due to the hydrophobic character of fluorocarbon matrix. The sulfonic acid groups are chemically active and fixed within the Teflon polymer matrix. Thus, this first synthetic ionic polymer is chemically resistant and durable, making it useful for Proton Exchange Membrane fuel cells. In order to monitoring the groups -OH of the Nafion®, we used the Photoacoustic Spectroscopy phases. The optical absorption spectrum was determined for wavelengths of 800 to 2600 nm. The procedure was to measure the samples in different hydration times. Using the Phase-Resolved Photoacoustic method, it was possible to separate the contribution of –OH, of C=O and of methylene group. The phase lag as a water function behaviors found may be associated with structural changes induced by membrane hydration.

Tank bromeliads may act enhancing local biodiversity providing an important habitat for varied species. We aimed to evaluate the effect of a conservation unit and anthropic threatens on the macroinvertebrate communities associated with Aechmea distichantha (Bromeliaceae) as a model to access local ecosystems studies. The survey was conducted in the Vila Velha State Park, without severe anthropic influences and at Vila Velha Farm with the presence of Pinus spp. (an exotic/invasive species), crop plantations and a road (Ponta Grossa, Paraná, Brazil). The living organisms and bromeliad parameters were evaluated from 20 bromeliads. Total abundance was higher at anthropized area and driven by the larger size of those bromeliads. Species richness also tended to be higher at the anthropized area, although the conservation unit presented higher values when rare species were excluded. The results pointed out that bromeliads from conservation unit were under minor anthropic influences, being the presence of pines considered the main disturb in the anthropized site, which may have influenced the quality and amount of detritus resulting in distinct species composition and dominance of more tolerant taxa (Chironomidae and Ceratopogonidae). So, bromeliad mesocosm may be well suited for surveys considering anthropic influences on local ecosystems.

Parodia carambeiensis is a rupicolous, small-sized species, with globose cladode and showy flowers, and is the only endemic Cactaceae species in Paraná State (Brazil). Changes in natural landscapes and fragmentation isolate populations, increasing their vulnerability to local extinctions. Our aim was to verify the spatial distribution of P. carambeiensis, reviewing its conservation status and main threats in the distribution area. Expeditions were carried out in the Campos Gerais region to record the abundance, density and spatial distribution of P. carambeiensis populations. Local landscape and climatic variables as well as the joint effect of these with geographical distance, were analyzed. Our findings highlighted that population density differs among the studied sites and was driven by distinct levels of anthropic threats such as livestock, tourism, wildfires and their proximity to highways, along with the climatic variables evaluated (temperature range and precipitation). The models jointly explained 56% of the variation in the population density, which was mostly influence by climatic factors. Parodia carambeiensis is currently classified as (LC) least concern, however, our results provide strong evidence in favor of updating its status to (EN) endangered due to the elevated extinction risk of natural populations.

The Nafion membranes are widely used in electrochemical applications such as fuel cells, chlor-alkali cells, and actuators-sensors. In this work, the thermal-optical characterization of Nafion in acid form was performed by photoacoustic spectroscopy, thermogravimetry, and differential scanning calorimetry. In the experimental procedure three distinct hydration levels were considered: (1) pristine membrane (λ ≅ HO/-SOH ≅ 5.6); (2) swelling process (λ ≅ 17.4); and (3) drying at controlled room temperature after swelling process (λ ≅ 6.5). The discovered behaviors showed significant irreversible structural changes induced by water retention in the membrane. These structural changes depend on the water population present in the clusters and also affect the directional thermal diffusivity of the membrane irreversibly.