Effect of the relationship between particle size, inter-particle distance, and metal loading of carbon supported fuel cell catalysts on their catalytic activity

The effect of the relationship between particle size (d), inter-particle distance (x(i)), and metal loading (y) of carbon supported fuel cell Pt or PtRu catalysts on their catalytic activity, based on the optimum d (2.5-3 nm) and x(i)/d (>5) values, was evaluated. It was found that for y < 30 wt%, the optimum values of both d and x(i)/d can be always obtained. For y >= 30 wt%, instead, the positive effect of a thinner catalyst layer of the fuel cell electrode than that using catalysts with y < 30 wt% is concomitant to a decrease of the effective catalyst surface area due to an increase of d and/or a decrease of x(i)/d compared to their optimum values, with in turns gives rise to a decrease in the catalytic activity. The effect of the x(i)/d ratio has been successfully verified by experimental results on ethanol oxidation on PtRu/C catalysts with same particle size and same degree of alloying but different metal loading. Tests in direct ethanol fuel cells showed that, compared to 20 wt% PtRu/C, the negative effect of the lower x(i)/d on the catalytic activity of 30 and 40 wt% PtRu/C catalysts was superior to the positive effect of the thinner catalyst layer.

The effect of acute magnesium loading on the maximal exercise performance of stable chronic obstructive pulmonary disease patients

OBJECTIVE: The potential influence of magnesium on exercise performance is a subject of increasing interest. Magnesium has been shown to have bronchodilatatory properties in asthma and chronic obstructive pulmonary disease patients. The aim of this study was to investigate the effects of acute magnesium IV loading on the aerobic exercise performance of stable chronic obstructive pulmonary disease patients. METHODS: Twenty male chronic obstructive pulmonary disease patients (66.2 +/- 8.3 years old, FEV1: 49.3 +/- 19.8%) received an IV infusion of 2 g of either magnesium sulfate or saline on two randomly assigned occasions approximately two days apart. Spirometry was performed both before and 45 minutes after the infusions. A symptom-limited incremental maximal cardiopulmonary test was performed on a cycle ergometer at approximately 100 minutes after the end of the infusion. ClinicalTrials.gov: NCT00500864 RESULTS: Magnesium infusion was associated with significant reductions in the functional residual capacity (-0.41 l) and residual volume (-0.47 l), the mean arterial blood pressure (-5.6 mmHg) and the cardiac double product (734.8 mmHg.bpm) at rest. Magnesium treatment led to significant increases in the maximal load reached (+8 w) and the respiratory exchange ratio (0.06) at peak exercise. The subgroup of patients who showed increases in the work load equal to or greater than 5 w also exhibited significantly greater improvements in inspiratory capacity (0.29 l). CONCLUSIONS: The acute IV loading of magnesium promotes a reduction in static lung hyperinflation and improves the exercise performance in stable chronic obstructive pulmonary disease patients. Improvements in respiratory mechanics appear to be responsible for the latter finding.

The effect of CCL3 and CCR1 in bone remodeling induced by mechanical loading during orthodontic tooth movement in mice

Bone remodeling is affected by mechanical loading and inflammatory mediators, including chemokines. The chemokine (C–C motif) ligand 3 (CCL3) is involved in bone remodeling by binding to C–C chemokine receptors 1 and 5 (CCR1 and CCR5) expressed on osteoclasts and osteoblasts. Our group has previously demonstrated that CCR5 down-regulates mechanical loading-induced bone resorption. Thus, the present study aimed to investigate the role of CCR1 and CCL3 in bone remodeling induced by mechanical loading during orthodontic tooth movement in mice. Our results showed that bone remodeling was significantly decreased in CCL3−/− and CCR1−/− mice and in animals treated with Met-RANTES (an antagonist of CCR5 and CCR1). mRNA levels of receptor activator of nuclear factor kappa-B (RANK), its ligand RANKL, tumor necrosis factor alpha (TNF-α) and RANKL/osteoprotegerin (OPG) ratio were diminished in the periodontium of CCL3−/− mice and in the group treated with Met-RANTES. Met-RANTES treatment also reduced the levels of cathepsin K and metalloproteinase 13 (MMP13). The expression of the osteoblast markers runt-related transcription factor 2 (RUNX2) and periostin was decreased, while osteocalcin (OCN) was augmented in CCL3−/− and Met-RANTES-treated mice. Altogether, these findings show that CCR1 is pivotal for bone remodeling induced by mechanical loading during orthodontic tooth movement and these actions depend, at least in part, on CCL3.

PtSnIr/C Anode Electrocatalysts: Promoting Effect in Direct Ethanol Fuel Cells

This study investigates the promoting effect of PtSnIr/C (1:1:1) electrocatalyst anode, prepared by polymeric precursor method, on the ethanol oxidation reaction in a direct ethanol fuel cell (DEFC). All of the materials used were 20% metal m/m on carbon. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of Pt, PtOH2, PtO2, SnO2 and IrO2 at the electrocatalyst surface, indicating a possible decorated particle structure. X-ray diffractometry (XRD) analysis indicated metallic Pt and Ir as well as the formation of an alloy with Sn. Using the PtSnIr/C electrocatalyst prepared here with two times lower loading of Pt than PtSn/C E-tek electrocatalyst, it was possible to obtain the same maximum power density found for the commercial material. The main reaction product was acetic acid probably due to the presence of oxides, in this point the bifunctional mechanism is predominant, but an electronic effect should not be discarded.

Joint loading decreased by inexpensive and minimalist footwear in elderly women with knee osteoarthritis during stair descent

Objective Previous studies indicate that flexible footwear, which mimics the biomechanics of walking barefoot, results in decreased knee loads in patients with knee osteoarthritis (OA) during walking. However, the effect of flexible footwear on other activities of daily living, such as descending stairs, remains unclear. Our objective was to evaluate the influence of inexpensive and minimalist footwear (Moleca) on knee adduction moment (KAM) during stair descent of elderly women with and without knee OA. Methods. Thirty-four elderly women were equally divided into an OA group and a control group (CG). Stair descent was evaluated in barefoot condition, while wearing the Moleca, and while wearing heeled shoes. Kinematics and ground reaction forces were measured to calculate KAM by using inverse dynamics. Results. The OA group experienced a higher KAM during midstance under the barefoot condition (233.3%; P = 0.028), the Moleca (379.2%; P = 0.004), and heeled shoes (217.6%; P = 0.007). The OA group had a similar knee load during early, mid, and late stance with the Moleca compared with the barefoot condition. Heeled shoes increased the knee loads during the early-stance (versus barefoot [16.7%; P < 0.001] and versus the Moleca [15.5%; P < 0.001]), midstance (versus barefoot [8.6%; P = 0.014] and versus the Moleca [9.5%; P = 0.010]), and late-stance phase (versus barefoot [10.6%; P = 0.003] and versus the Moleca [9.2%; P < 0.001]). In the CG, the Moleca produced a knee load similar to the barefoot condition only during the early-stance phase. Conclusion. Besides the general foot protection, the inexpensive and minimalist footwear contributes to decreasing knee loads in elderly women with OA during stair descent. The loads are similar to the barefoot condition and effectively decreased when compared with heeled shoes.

PtSnIr/C anode electrocatalysts: promoting effect in direct ethanol fuel cells

This study investigates the promoting effect of PtSnIr/C (1:1:1) electrocatalyst anode, prepared by polymeric precursor method, on the ethanol oxidation reaction in a direct ethanol fuel cell (DEFC). All of the materials used were 20% metal m/m on carbon. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of Pt, PtOH2, PtO2, SnO2 and IrO2 at the electrocatalyst surface, indicating a possible decorated particle structure. X-ray diffractometry (XRD) analysis indicated metallic Pt and Ir as well as the formation of an alloy with Sn. Using the PtSnIr/C electrocatalyst prepared here with two times lower loading of Pt than PtSn/C E-tek electrocatalyst, it was possible to obtain the same maximum power density found for the commercial material. The main reaction product was acetic acid probably due to the presence of oxides, in this point the bifunctional mechanism is predominant, but an electronic effect should not be discarded.