The hydrogen crossover current is obtained by best-fitting the initial part of the experimental polarization curve. This can result in a simpler experimental approach to the investigation of PEMFC ...degradation.
It is well known that the membrane electrode assembly (MEA) of proton exchange membrane fuel cells (PEMFCs) can undergo deterioration, during long term operation, of both the electrode materials and the membrane. Hydrogen crossover, i.e., the undesired diffusion of the gas from the anode to the cathode through the membrane, has been ascribed as one of the main causes of deterioration of perfluorinated ionomer membranes, normally employed in PEMFCs. One of the effects of the hydrogen permeation across the membrane is the decrease of the cell's open circuit voltage (OCV), due to the reaction between the fuel and the oxidant at the cathode surface. Such reaction can lead to the production of peroxide radicals, causing the degradation of both the PEM and the catalyst layer. Hydrogen crossover increases when temperature, pressure and humidity of the cell rise. The hydrogen permeation rate through a very thin PEM is typically lower than 1
mA
cm
−2 for a new MEA, but it can exceed 10–20
mA
cm
−2 after long term operation. Various methods have been proposed to measure the rate of hydrogen crossover, mainly based on electrochemical tests on a single FC with a flow of nitrogen at the cathode, so that the steady state current corresponds to the oxidation of crossed hydrogen. Hydrogen crossover has been also determined indirectly by assuming that the changes in the OCV values are due to the passage of fuel from the anode to the cathode.
In this paper, a simplified mathematical model for the direct determination of hydrogen crossover permeation rate is presented. Such a model is based on analytical expressions of the polarization terms and it is employed to determine the hydrogen crossover rate. The main results show that the hydrogen crossover current densities increased from 0.12 to 0.32
mA
cm
−2, by decreasing the thickness of the membranes and increasing the operating cell temperature. Moreover, the hydrogen crossover determined for a fresh MEA was compared with that of a degraded one, exposed to repetitive freezing/thawing cycles. It was found that the hydrogen crossover for the degraded MEA was more than twice the value obtained with the fresh one at the same temperature.
Breast cancer is the most common type of malignancy diagnosed in women. In the metastatic setting this disease is still uncurable. Taxanes represent an important class of antitumor agents which have ...proven to be fundamental in the treatment of advanced and early-stage breast cancer, but the clinical advances of taxanes have been limited by their highly hydrophobic molecular status. To overcome this poor water solubility, lipid-based solvents have been used as a vehicle, and new systemic formulations have been developed, mostly for paclitaxel, which are Cremophor-free and increase the circulation time of the drug. ABI-007 is a novel, albumin-bound, 130-nm particle formulation of paclitaxel, free from any kind of solvent. It has been demonstrated to be superior to an equitoxic dose of standard paclitaxel with a significantly lower incidence of toxicities in a large, international, randomized phase III trial. The availability of new drugs, such as Abraxane, in association with other traditional and non-traditional drugs (new antineoplastic agents and targeted molecules), will give the oncologist many different effective treatment options for patients in this setting.
•Specific criteria are proposed to identify different longitudinal crack types.•Top-down cracking (TDC) can affect up to 20–30 % of the slow traffic lane.•TDC mainly affects open-graded friction ...courses, not dense-graded wearing layers.•Due to frequent surface maintenance, TDC severity is generally low or medium.•The concentration of cracks due to tire blowout is even higher than TDC.
Top-down cracking (TDC) is a distress affecting asphalt pavements and consists of longitudinal cracks that initiate on the pavement surface and propagate downwards. In general, TDC is more critical in the case of thick pavements with open-graded friction course (OGFC), which are the typical characteristics of Italian motorway pavements. Recent surveys showed the presence of many longitudinal cracks potentially ascribable to TDC on Italian motorways. Within this context, this study has two main objectives: 1) to define reliable identification criteria allowing to distinguish between TDC and the other types of longitudinal cracks observed and 2) based on the developed criteria, to quantify TDC in Italian motorway pavements. In this regard, a 200 km long trial network (400 km considering both directions) was studied, taking into account the effect of several variables (e.g. geometric characteristics, traffic level, wearing layer type and climate). For this purpose, images of the trial network acquired during pavement monitoring were visually analysed and some control cores were taken. Specific criteria (which can be used in a pavement management system, PMS) were developed to distinguish between the main types of longitudinal cracks observed on the trial network, i.e. TDC, cracks due to heavy vehicles tire blowout and construction joints, based on their geometric features on the pavement surface. It was found that TDC can affect up to 20–30 % of the slow traffic lane. Specifically, the highest TDC concentrations were observed for high traffic levels and OGFC, whereas TDC was absent in the case of a dense-graded wearing layer. Finally, surprisingly the concentration of tire blowout cracks was even higher than TDC. This study provides evidence on the fact that, for thick pavements with OGFC, TDC has to be considered a priority problem to be addressed in both pavement design and maintenance.
▶ Nafion membranes with carbon nanotubes provide for mixed proton and electron conductivity. ▶ Electron conductivity is reduced in wet membranes. ▶ Proton conductivity is greatly enhanced in wet ...membranes.
Carbon nanotubes (CNTs) exhibit extraordinary mechanical, electronic and thermal properties, because of which they have been used in several applications like mechanical reinforcement of polymers, electrocatalysis, sensors, electronics, batteries, etc. Nafion is a sulfonated fluoropolymer that has become standard material in fuel cell applications for its excellent proton conducting property, and for its thermal and mechanical stability.
Recently, Nafion/CNTs composites with CNT amounts less than the percolation threshold have been used to increase the mechanical stability and decrease methanol permeation of nafion, with very little effect on proton conductivity and avoiding short circuit risks. Above the percolation threshold, such membranes show the potentialities to allow a separate proton/electron conduction paths within the membrane. This aspect opens new ways for applications in selective membranes for artificial innovative devices capable of using sunlight to produce hydrogen from water splitting.
Nafion
+
multi-walled CNTs (MWCNTs) nanocomposite films with varying amounts of filler were fabricated and their proton/electron transport behaviors were characterized. Samples were prepared by recasting Nafion with MWCNTs and conditions were optimized to obtain freestanding films of thickness around 100
μm. After ultrasonication, we observed a uniform dispersion of the carbon fillers inside the matrix, with a good affinity between the two materials without the need of CNT surface functionalization. Membranes were characterized by Scanning Electron Microscopy, Electrochemical Impedance Spectroscopy and Electronic Conductivity tests.
Platinum catalyst supported on mesoporous carbon for PEMFC Ambrosio, Elisa Paola; Francia, Carlotta; Manzoli, Maela ...
International journal of hydrogen energy,
06/2008, Letnik:
33, Številka:
12
Journal Article, Conference Proceeding
Recenzirano
Ordered mesoporous carbon (OMC) was used as catalyst (Pt) support in polymer electrolyte membrane fuel cells (PEMFC) with the aim of increasing its effectiveness towards the oxygen reduction reaction ...(ORR). The mesoporous carbon (CMK3 type) was synthesized as inverse replica of a silica template (SBA-15). Platinization was achieved by impregnation with chloroplatinic acid hexahydrate, H2PtCl6, followed by a reduction in H2 flow at 573K. Samples containing 20wt% in Pt were prepared and characterized by ICP, XRD and HRTEM analysis. Structural and morphological analyses of the samples showed that the typical ordered mesoporous structure of CMK3 carbons is maintained after Pt insertion. The HRTEM analysis of the samples showed a homogeneous dispersion of platinum particles. The electro-catalyst performance was evaluated by manufacturing membrane electrodes assemblies (MEAs) containing the catalyst under study at the cathode (Pt load: 0.5mg/cm2). Tests were performed in a single fuel cell with an electrode surface area of 5cm2. The results were also compared to the performances of a commercial catalyst tested in the same way.
Regorafenib, targeting a broad range of receptor tyrosine kinases (RTKs), is an oral multikinase inhibitor which improves the progression-free survival (PFS) and overall survival (OS) of patients ...diagnosed with chemorefractory metastatic colorectal cancer (mCRC), making an immunosuppressive tumour microenvironment. The correlation between PD-1/PD-L1 expression and RTKs inhibition has been studied in several tumour types but has not been analyzed extensively in mCRC in the era of regorafenib. In this study, using liquid biopsy, we evaluated the opportunity to reveal if PD-L1 expression on circulating tumour cells (CTCs) could serve as a predictive biomarker of response and clinical benefit in patients treated with regorafenib as the third line of treatment. We analyzed a cohort of forty chemorefractory metastatic colorectal cancer patients, of whom twenty-six
mutated, treated with regorafenib, all as the third line of treatment. Blood samples were collected from patients prior to treatment and longitudinally four and eight weeks after initiation of therapy. CTCs were identified using multiparametric flow cytometry; therefore, PD-L1 expression was evaluated. Objective responses were defined following the RECIST criteria v.1.1. Moreover, focusing on peripheral blood biomarkers, we found that high platelet-to-lymphocyte ratio (PLR) was an independent prognostic indicator of poor OS. For the first time, our study showed the usefulness of sequential assessments of CTCs as a non-invasive real-time biopsy to evaluate PD-L1 expression in patients diagnosed with mCRC and treated with regorafenib. Our analysis suggests that by assessing PD-L1 expression on CTCs, we could predict who will benefit from regorafenib, offering highly individualized treatment plans.
To assess the clinical and endoscopic presentation of primary gastric lymphoma.
Remission rate and long-term survival in patients with gastric lymphoma mainly depend on disease stage at diagnosis. ...Series reporting clinical and endoscopic presentation of gastric lymphoma are generally small and heterogeneous.
Systematic review with pooled-data analysis assessing clinical and endoscopic presentation of primary gastric lymphoma.
Data regarding 2000 patients were collected. Overall, males were slightly more prevalent, alarm symptoms were absent in near half of the patients, lymphoma was diagnosed in a stage >I in one-third of the patients, and Helicobacter pylori infection was present in 88.8% of considered patients. At endoscopy, the ulcerative type was the most frequent presentation, although low-grade lymphoma was diagnosed on normal/hyperemic gastric mucosa in 9% of cases. Patients with high-grade lymphoma presented alarm symptoms (anemia and/or melena and/or hemorrhage, persistent vomiting, weight loss), an exophytic or ulcerative lesion, a stage III-IV, and a H. pylori negative status more frequently than low-grade lymphoma cases.
Our pooled-data analysis showed that gastric lymphoma is still disappointingly diagnosed in an advanced stage in a large number of patients. This is probably due to presence of nonspecific symptoms at initial clinical presentation and/or a normal appearing mucosa at endoscopic observation in the early stages.
Regorafenib (REG) and trifluridine/tipiracil (FTD/TPI) have have been shown to improve overall survival in patients with refractory metastatic colorectal cancer. The aim of our study was to evaluate ...the efficacy and safety profiles of these agents administered in sequence in real world practice.
Clinical data of patients treated beyond the 2°line with REG or FTD/TPI between January 2016 and August 2020, were retrospectively collected from eight institutes in the Lazio Region.
We included 49 patients treated with both drug sequences. A total of 28 G3/G4 toxicity events (53.8%) were recorded in the FTD/TPI-to-REG sequence vs. 24 (46.1%) in the reverse sequence. Median overall survival for the patients included in the FTP/TPI-to-REG group was 20 months (95%CI=16.7-23.3) vs. 27 months in the reverse group (95%CI=17.8-36.2). The disease control rate was 45.0% for patients treated with the REG-to-FTD/TPI sequence vs. 24.1% in those treated with the FTD/TPI-to-REG sequence (p=0.18).
The sequence REG-to-FTD/TPI and vice versa can extend survival, whereas only REG-to-FTD/TPI stabilizes cancer growth.
Network approach in liquidomics landscape Santini, Daniele; Botticelli, Andrea; Galvano, Antonio ...
Journal of experimental & clinical cancer research,
08/2023, Letnik:
42, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Tissue-based biopsy is the present main tool to explore the molecular landscape of cancer, but it also has many limits to be frequently executed, being too invasive with the risk of side effects. ...These limits and the ability of cancer to constantly evolve its genomic profile, have recently led to the need of a less invasive and more accurate alternative, such as liquid biopsy. By searching Circulating Tumor Cells and residues of their nucleic acids or other tumor products in body fluids, especially in blood, but also in urine, stools and saliva, liquid biopsy is becoming the future of clinical oncology. Despite the current lack of a standardization for its workflows, that makes it hard to be reproduced, liquid biopsy has already obtained promising results for cancer screening, diagnosis, prognosis, and risk of recurrence.Through a more accessible molecular profiling of tumors, it could become easier to identify biomarkers predictive of response to treatment, such as EGFR mutations in non-small cell lung cancer and KRAS mutations in colorectal cancer, or Microsatellite Instability and Mismatch Repair as predictive markers of pembrolizumab response.By monitoring circulating tumor DNA in longitudinal repeated sampling of blood we could also predict Minimal Residual Disease and the risk of recurrence in already radically resected patients.In this review we will discuss about the current knowledge of limitations and strengths of the different forms of liquid biopsies for its inclusion in normal cancer management, with a brief nod to their newest biomarkers and its future implications.
A remote-sensing technique based on microwave interferometry is applied to dynamic testing of wind turbine towers for power generation. A high-speed interferometric radar is able to sample the ...structure at a rate high enough for modal and transient analysis. An experimental campaign is reported carried out on wind turbine towers of a power plant in north Sardinia, Italy.
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