386 research outputs found
Titanium phosphate for Fuel Cell Proton Conduction Membranes
Environmental issues due to increases in emissions of air pollutants and greenhouse gases are driving the development of clean energy delivery technologies such as fuel cells. Low temperature Proton Exchange Membrane Fuel Cells (PEMFC) use hydrogen as a fuel and their only emission is water. While significant advances have been made in recent years, a major limitation of the current technology is the cost and materials limitations of the proton conduction membrane. The proton exchange membrane performs three critical functions in the PEMFC membrane electrode assembly (MEA): (i) conduction of protons with minimal resistance from the anode (where they are generated from hydrogen) to the cathode (where they combine with oxygen and electrons, from the external circuit or load), (ii) providing electrical insulation between the anode and cathode to prevent shorting, and (iii) providing a gas impermeable barrier to prevent mixing of the fuel (hydrogen) and oxidant. The PFSA (perfluorosulphonic acid) family of membranes is currently the best developed proton conduction membrane commercially available, but these materials are limited to operation below 100oC (typically 80oC, or lower) due to the thermochemical limitations of this polymer. For both mobile and stationary applications, fuel cell companies require more durable, cost effective membrane technologies capable of delivering enhanced performance at higher temperatures (typically 120oC, or higher. This is driving research into a wide range of novel organic and inorganic materials with the potential to be good proton conductors and form coherent membranes. There are several research efforts recently reported in the literature employing inorganic nanomaterials. These include functionalised silica phosphates [1,2], fullerene [3] titania phosphates [4], zirconium pyrophosphate [5]. This work addresses the functionalisation of titania particles with phosphoric acid. Proton conductivity measurements are given together with structural properties
Modelling metallothionein induction in the liver of sparus aurata exposed to metal-contaminated sediments
Metallothionein (MT) in the liver of gilthead seabreams (Sparus aurata L., 1758) exposed to Sado estuary (Portugal) sediments was
quantified to assess the MT induction potential as a biomarker of sediment-based contamination by copper (Cu), cadmium (Cd), lead
(Pb) and arsenic (As). Sediments were collected from two control sites and four sites with different levels of contamination. Sediment Cu,
Cd, Pb, As, total organic matter (TOM) and fine fraction (FF) levels were determined. Generalized linear models (GLM) allowed
integration of sediment parameters with liver Cu, Cd, Pb, As and MT concentrations. Although sediment metal levels were lower than
expected, we relate MT with liver Cd and also with interactions between liver and sediment Cu and between liver Cu and TOM. We
suggest integrating biomarkers and environmental parameters using statistical models such as GLM as a more sensitive and reliable
technique for sediment risk assessment than traditional isolated biomarker approaches.info:eu-repo/semantics/publishedVersio
Histological biomarkers in liver and gills of juvenile Solea senegalensis exposed
Young juvenile Solea senegalensis were exposed to three sediments with distinct contamination profiles
collected from a Portuguese estuary subjected to anthropogenic sources of contamination (the Sado estuary,
western Portugal). Sedimentswere surveyed formetals (cadmium, chromium, copper, nickel, lead and
zinc), ametalloid (arsenic) and organic contaminants (polycyclic aromatic hydrocarbons, polychlorinated
biphenyls and a pesticide, dichloro-diphenyl-trichloroethane plus itsmetabolites), aswell as total organic
matter, redox potential and particle fine fraction. The fish were exposed to freshly collected sediments
in a 28-day laboratorial assay and collected for histological analyses at days 0 (T0), 14 (T14) and 28 (T28).
Individual weighted histopathological indices were obtained, based on presence/absence data of eight
and nine liver and gill pathologies, respectively, and on their biological significance. Although livers sustained
more severe lesions, the sediments essentially contaminated by organic substances caused more
damage to both organs than the sediments contaminated by both metallic and organic contaminants,
suggesting a possible synergistic effect. Correlation analyses showed that some alterations are linked,
forming distinctive histopathological patterns that are in accordance with the severity of lesions and
sediment characteristics. The presence of large eosinophilic bodies in liver and degeneration of mucous
cells in gills (a first-time described alteration)were some of the most noticeable alterations observed and
were related to sediment organic contaminants. Body size has been found to be negatively correlated
with histopathological damage in livers following longer term exposures. It is concluded that histopathological
indices provide reliable and discriminatory data even when biomonitoring as complex media as
natural sediments. It is also concluded that the effects of contamination may result not only from toxicant
concentrations but also from their interactions, relative potency and sediment characteristics that
ultimately determine bioavailability.peerreviewe
Biochemical endpoints on juvenile Solea senegalensis exposed
Juvenile Solea senegalensis were exposed to
fresh sediments from three stations of the Sado estuary
(Portugal) in 28-day laboratory assays. Sediments revealed
distinct levels of total organic matter, fine fraction, redox
potential, trace elements (arsenic, cadmium, chromium,
copper, nickel, lead and zinc) and organic contaminants
(polycyclic aromatic hydrocarbons, polychlorinated
biphenyls and a pesticide: dichloro diphenyl trichloroethane).
Organisms were surveyed for contaminant bioaccumulation
and induction of two hepatic biochemical
biomarkers: metallothionein (MT) and cytochrome P450
(CYP1A), as potential indicators of exposure to metallic
and organic contaminants, respectively. Using an integrative
approach it was established that, although bioaccumulation
is in general accordance with sediment
contamination, lethality and biomarker responses are not
linearly dependent of the cumulative concentrations of
sediment contaminants but rather of their bioavailability
and synergistic effects in organisms. It is concluded that
metals and organic contaminants modulate both MT and
CYP1A induction and it is suggested that reactive oxygen
species may be the link between responses and effects of
toxicity.peerreviewe
A description of chloride cell and kidney tubule alterations in the flatfish Solea senegalensis exposed to moderately contaminated sediments from the Sado estuary (Portugal)
The effects of sediment-bound contaminants on kidney and gill chloride cells were surveyed in juvenile Solea
senegalensis exposed to fresh sediments collected from three distinct sites of the Sado Estuary (Portugal) in a
28-day laboratorial assay. Sediments were analyzed for metallic contaminants, polycyclic aromatic
hydrocarbons and organochlorines as well as for total organic matter, redox potential and fine fraction.
The potential for causing adverse biological effects of each surveyed sediment was assessed by comparison of
contaminant levels to available guidelines for coastal sediments, namely the Threshold Effects Level (TEL)
and the Probable Effects Level (PEL). The Sediment Quality Guideline Quotient indices (SQGQ) were
calculated to compare the overall contamination levels of the three stations. A qualitative approach was
employed to analyze the histo/cytopathological traits in gill chloride cells and body kidney of fish exposed to
each tested sediment for 0, 14 and 28 days. The results showed that sediment contamination can be
considered low to moderate and that the least contaminated sediment (from a reference site, with the lowest
SQGQ) caused lesser changes in the surveyed organs. However, the most contaminated sediment (by both
metallic and organic xenobiotics, with highest SQGQ) was neither responsible for the highest mortality nor
for the most pronounced lesions. Exposure to the sediment presenting an intermediate SQGQ, essentially
contaminated by organic compounds, caused the highest mortality (48%) and the most severe damage to
kidneys, up to full renal necrosis. Chloride cell alterations were similar in fish exposed to the two most
contaminated sediments and consisted of a pronounced cellular hypertrophy, likely involving fluid retention
and loss of mitochondria. It can be concluded that sediment contamination considered to be low or moderate
may be responsible for severe injury to cells and parenchyma involved in the maintenance of osmotic
balance, contributing for the high mortality levels observed. The results suggest that sediment-bound
organic contaminants such as PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated
biphenyls) may be very toxic to the analyzed organs, especially the kidney, even when present in lowrisk concentrations.info:eu-repo/semantics/publishedVersio
Doença inflamatória pélvica: um desfecho inesperado
Pelvic inflammatory disease is a polymicrobial infection of the upper genital tract, representing the most common complication of sexually transmitted diseases. Multiple agents are frequently involved, although some unusual agents have also been reported. The presentation is frequently sub-clinical, but may assume an acute form. We report a clinical case of a 39-year-old woman with recurrent pelvic inflammatory disease, resistant to systemic antibiotics, submitted to an exploratory surgery, with a histologic finding of tubal cysticercosis
Efeito do inseticida ciromazina sobre parasitoides idiobiontes da mosca-minadora em plantas de meloeiro.
O presente trabalho objetivou verificar o efeito do inseticida, ciromazina, sobre os parasitoides idiobiontes da mosca-minadora em meloeiro
Accuracy of three depression screening scales to diagnose major depressive episodes in older adults without neurocognitive disorders
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