SR Load Research Articles

Performance improvement of a direct carbon solid oxide fuel cell via strontium-catalyzed carbon gasification

As a new way of power generation, direct carbon solid oxide fuel cells (DC-SOFCs) exhibit great potential in solution of energy crisis and environmental pollution. According to the working principle, the cell operation is a kinetically controlled process, and the reverse Boudouard reaction is the rate-determining step of the whole system. In this study, a Sr-based catalyst is successfully introduced to accelerate carbon gasification and thus enhance cell performance of DC-SOFCs. The electrochemical performance of DC-SOFCs operated on coconut active charcoal with various Sr loading contents (3 wt%–10 wt%), are studied and compared with that of DC-SOFCs with traditional Fe-catalyzed carbon fuel. Experimental results demonstrate that the best output of 316 mW cm−2 is achieved from the single cell powered with 5 wt% Sr-loaded coconut active charcoal at 850 °C, higher than those of DC-SOFCs fueled by pure and 5 wt% Fe-loaded active charcoal. The superiority of the Sr-based catalyst is also demonstrated by the operation stability of the corresponding DC-SOFC, which displays a relatively long operation time of 22.68 h at 0.25 A cm−2 with the fuel utilization of 18.3%. The SEM/EDX results indicate that the Sr-based catalyst exhibits good stability without agglomeration during cell operation at high temperature. In addition, the carbon gasification mechanism catalyzed by Sr-based catalyst is also proposed on the basis of these properties. This study indicates that the designed Sr-loaded coconut active charcoal is expected to be an alternative carbon fuel for DC-SOFCs.

Osteoclast and osteoblast response to strontium-doped struvite coatings on titanium for improved bone integration.

To develop implants with improved bone ingrowth, titanium substrates were coated with homogeneous and dense struvite (MgNH4PO4·6H2O) layers by means of electrochemically assisted deposition. Strontium nitrate was added to the coating electrolyte in various concentrations, in order to fabricate Sr-doped struvite coatings with Sr loading ranging from 10.6 to 115μg/cm2. It was expected and observed that osteoclast activity surrounding the implant was inhibited. The cytocompatibility of the coatings and the effect of Sr-ions in different concentrations on osteoclast formation were analyzed in vitro. Osteoclast differentiation was elucidated on morphological, biochemical as well as on gene expression level. It could be shown that moderate concentrations of Sr2+ had an inhibitory effect on osteoclast formation, while the growth of osteoblastic cells was not negatively influenced compared to pure struvite surfaces. In summary, the electrochemically deposited Sr-doped struvite coatings are a promising approach to improve bone implant ingrowth.

Non-RyR Calcium Leak of the Sarcoplasmic Reticulum is Governed by TRPC1 in Cardiomyocytes

Sarcoplasmic calcium leak in cardiomyocytes has been explained by spontaneous sparks from ryanodine receptors (RyRs), non-spark-mediated RyR leak and non-RyR leak. Ion channels underlying non-RyR leak are currently ill defined. Here, we test the hypothesis that transient receptor potential cation (TRPC) 1 channels contribute to non-RyR leak. We investigated neonatal rat ventricular myocytes (NRVMs) infected with adenoviral eGFP, TRPC1-eGFP, shRNA-TRPC1-eGFP and scrambled RNA-eGFP constructs. NRVMs were studied 4-5 days after infection. NRVMs were fixed and labeled for TRPC1 and sarco/endoplasmic reticulum Ca2+ ATPase 2 (SERCA2). Three-dimensional image stacks of NRVMs were acquired using a confocal microscope (Leica SP8 TCS). Protein colocalization was measured using the Pearson correlation coefficient (Rr). We also investigated SR calcium load in Rhod-3 loaded NRVMs. In short, NRVMs were paced and then superfused with 0 sodium/0 calcium solution for 2 min. Subsequently caffeine (20 mM) was applied to trigger sarcoplasmic calcium release. Fluorescence signals were acquired using a Leica SP8 TCS microscope and analysed after noise reduction and self-ratioing. We found a mid-level degree of colocalization of SERCA2 and TRPC1 for NRVMs infected with with eGFP (Rr=0.46±0.03), TRPC1-eGFP (0.41±0.03) and shRNA-TRPC1-eGFP (0.47±0.03). Colocalization of eGFP with SERCA2 was higher for TRPC1-eGFP (0.41±0.04) than for eGFP (0.26±0.02) and shRNA-TRPC1-eGFP infected NRVMs (0.22±0.04). We measured decreased and increased sarcoplasmic calcium content in NRVMs infected with TRPC1-eGFP (1.64±0.21) and shRNA-TRPC1-eGFP (4.30±0.49), respectively, versus eGFP (3.18±0.23). Differences between calcium content in eGFP and scrambled RNA-eGFP infected NRVMs were not significant. The investigations support our hypothesis that TRPC1 channels contribute to non-RyR sarcoplasmic calcium leak in cardiomyocytes. Structural data indicate that TRPC1 is located in the sarcoplasmic membrane. We suggest that expression and activity of TRPC1 channels modulate the concentration of sarcoplasmic and cytosolic calcium in cardiac myocytes.

Effect of a biomimetic titania mesoporous coating doped with Sr on the osteogenic activity

Fabrication of titanium (Ti)-based biomedical implants with appropriate topography as well as capacity for drug delivery is highly pursued in the field of orthopedic and dental implants. In this study, a biomimetic mesoporous coating imbedded with strontium (MPs-Sr) is prepared by the high current anodization (HCA) and hydrothermal treatment (HT). This coating provides a more stable mechanical performance than the conventional nanotube arrays. The Sr loading is regulated by the HT reaction time and the Sr is released in a controllable manner from the MPs-Sr surface. The hydrophilic performance of MPs-Sr are significantly improved. Furthermore, it is showed that the attachment and spreading of preosteoblast MC3T3-E1 cells are significantly up-regulated by the nanoscale topology of MPs and the doped Sr. The improved collagen secretion and matrix mineralization levels of cells are closely related with the Sr release. The excellent osteogenic properties of MPs-Sr samples highlight their promising potential for use in clinical application.

Chemical Looping Tar reforming with Fe,Sr-doped La2Zr2O7 pyrochlore supported on ZrO2

Chemical Looping Reforming (CLR) has been proposed as a new technology for tar removal from hot raw gas derived from biomass gasification. In this two-reactor fluidized bed process at atmospheric pressure, the bed material is circulating between a reformer, in which the bed material is in contact with the raw synthesis gas, and a regenerator, in which the bed material is regenerated by oxidizing coke deposits and sulfides with air. In this study Fe,Sr-doped La2Zr2O7 pyrochlores supported on ZrO2 with different Fe and Sr loadings were investigated for their use as a catalyst in CLR. By decreasing the Fe loading to Fe/La=0.25 the benzene-to-syngas conversion could be improved by about 50% at T=800°C in comparison with the reference material with Fe/La=1.25. With this material, benzene and ethylene conversion could be further improved by co-feeding O2 with the gasification gas, achieving a benzene conversion of up to 80% and an ethylene conversion of about 95% at a temperature of 850°C and a Gas Hourly Space Velocity of 6800h−1. The performance of the bed material was found stable over at least 3 redox cycles. Considering the expected lower costs and non-toxicity of this material compared to precious metal- and Nickel-containing catalysts, normally used in fixed-bed systems, it is a promising material for a fluidized CLR system for tar removal.

Effect of Hamstring Harvest in the Setting of ACL and MCL Concurrent Injury

Objectives:Hamstrings autograft is commonly used to reconstruct an isolated ACL tear, however, there is evidence to suggest that the tendons harvested may contribute to medial knee stability. We tested the hypothesis that the gracilis (G) and semitendinosus (St) tendons significantly contribute to sagittal, coronal and/or rotational knee stability in the setting of an ACL reconstruction with concurrent partial MCL injury.Methods:Twelve human cadaveric knees were subject to a static anteriorly-directed force and moments in varus, valgus, internal and external rotation at the tibia while the femur was held stationary in order to quantify laxity at 0, 30, 60, and 90 degrees of flexion. Testing was performed on each leg in following ligament conditions: (1) ACL-intact/MCL-intact, (2) ACL-deficient/MCL-intact, (3) ACL-deficient/ MCL-partial injury, and (4) ACL-reconstruction, MCL-partial injury (chart 1). To quantify the effect of muscle loads the quadriceps, semimembranosus, biceps femoris, sartorius (Sr), St and G muscles were sutured and physiologically loaded. Quadriceps were loaded to 200 N and semimembranosus and biceps femoris were loaded to 40 N and held constant for all test conditions. The G and St were attached to a 40N load which was removed during test conditions in order to simulate hamstring graft harvest. Similarly, a Sr load of 20N was added and removed to determine its role in contributing to knee stability. For each ligament condition, the response to loading was determined with either (A) St/G muscles loaded and Sr unloaded; (B) St/G loaded, Sr loaded; (C) St/G unloaded, Sr unloaded; and (D) St/G unloaded, Sr loaded (chart 1). Three-dimensional positional data of the tibia relative to the femur was recorded to determine displacement and rotation across the knee.Results:ACL reconstruction restored anterior stability regardless of whether or not G/St and/or Sr loads were applied. A partial tear of the MCL significantly increased external rotation when the G/St were unloaded and approached significance (p<0.06) when the G/St load was applied. When an internal rotation load was applied all conditions tested were significantly less stable than intact. No differences were demonstrated during varus loading. When specimens were loaded with a valgus moment there was no significant increase in motion after ACL transection. However, when a partial MCL tear was added to the ACL injury there was a significant increase in valgus rotation regardless of whether or not the G/St and Sr muscles forces were applied. ACL reconstruction only restored valgus stability when the G/St muscles were loaded, Figure 1. However, there was no difference in valgus stability when comparing testing conditions 4A (G/St loaded) and 4D (G/St unloaded, Sr loaded, Figure 1).Conclusion:Absence of load on the G and St, as would be the case when harvested for hamstrings autograft, did not lead to increased anterior translation of the tibia in ACL reconstructed knees with partial MCL injury. Although the absence of an applied G and St muscle force did lead to increased valgus rotation after ACL reconstruction, there was no difference between the G/St loaded state compared to the G/St unloaded state once a Sr load was applied. This may have clinical implications for surgeons with regard to post-operative bracing and ACL reconstruction graft recommendations. Figure 1:Valgus rotation with application of 10N-m valgus stress

Fatty acid methyl ester (FAME) production from soybean oil under ambient conditions using strontium loaded bovine bone

Energy- and cost efficient processes are desirable for the large scale production of fatty acid methyl ester (FAME) for fuel applications. This work reports the utilization of Sr loaded bovine bone as effective and reusable catalyst for FAME production at low temperatures (30–65 °C), in high yields (>90%). Loading of Sr(NO3)2 into bovine bone (as a porous support) followed by calcination (500–1100 °C) affords a series of catalytically active materials. Material calcined at 750 °C (denoted as SrC750) gives optimum performance, with very high FAME yields (96.5%) after 1 h at 65 °C, and can be reused up to 10 times without yield decrease or need for regeneration. High yields of FAME (>93%) are also achieved at ambient temperature (30 °C) using SrC750, with products meeting ASTM 6751 and EN 14214 requirements suggesting their applicability as fuels in diesel engines.

Cardiac Fatty Acid Binding Protein (FABP3) Depletes SR Calcium Load in Ventricular Myocytes

Rationale: Cardiac fatty acid-binding protein (FABP3) is a cardiac-specific member of lipid-binding protein family and its expression level is often reduced in patients with diabetic heart diseases. Recent evidence suggests that FABP3 suppresses calcium transient and shortening of isolated rat cardiomyocytes. However, the underlying mechanisms are largely elusive. Objective: To determine the role of FABP3 in regulating SR calcium release. Results: In STZ-induced type I diabetes mouse model (DM), protein expression level of FABP3 was elevated, cardiac function was reduced and negatively correlated with FABP3 expression level. Amplitudes of cell shortening and calcium transient are both impaired in DM cardiomyocytes, which can be mimicked by applying FABP3 at pathological concentration to control cardiomyocytes. FABP3 reduces calcium transient amplitude of cardiomyocytes in a dose dependent manner (EC50 = 0.052 nmol/L). SR calcium content is reduced in DM cardiomyocytes and FABP3 depletes SR calcium content in cardiomyocytes. FABP3 colocalizes with SERCA, inhibits SERCA activity with a greater EC50 (0.49 nmol/L). Co-immunoprecipitation study suggests elevated FABP3 promotes binding between SERCA and phospholamban. FABP3 also colocalizes with RyR2, binds to RyR2 and promotes RyR2-mediated SR calcium leak. Conclusion: Increased FABP3 expression level in DM mice compromises cardiac function by reducing SR calcium load via two independent approaches: (A) to reduce SERCA activity by promoting PLB-SERCA interaction and (B) to enhance RyR2-mediated SR calcium leak.

Cesium and strontium loads into a combined sewer system from rainwater runoff

In this study, combined sewage samples were taken with time in several rain events and sanitary sewage samples were taken with time in dry weather to calculate Cs and Sr loads to sewers from rainwater runoff. Cs and Sr in rainwater were present as particulate forms at first flush and the particulate Cs and Sr were mainly bound with inorganic suspended solids such as clay minerals in combined sewage samples. In addition, multiple linear regression analysis showed Cs and Sr loads from rainwater runoff could be estimated by the total amount of rainfall and antecedent dry weather days. The variation of the Sr load from rainwater to sewers was more sensitive to total amount of rainfall and antecedent dry weather days than that of the Cs load.

Effect of Sr content on hydrogen production by steam reforming of ethanol over Ni-Sr/Al2O3-ZrO2 xerogel catalysts

A series of Ni-Sr/Al2O3-ZrO2 (15Ni-XSr/AZ) xerogel catalysts with different strontium content (X, wt%) were prepared by an epoxide-driven sol-gel method followed by a co-impregnation method. Un-promoted Ni/Al2O3-ZrO2 (15Ni/AZ) xerogel catalyst was also prepared according to the similar methods for comparison. Surface area of the catalysts decreased with increasing strontium content. Excess amount of impregnated strontium on the catalyst led to weakened metal-support interaction, inducing formation of large nickel particles in the reduced catalysts with high Sr loading. Introduction of strontium promoter reduced acidity of the catalysts, leading to a more favorable reaction pathway during the ethanol steam reforming reaction. Promotion with strontium generally had a positive effect on the catalytic activity due to enhanced nickel dispersion and suppressed acidity. Nickel surface area and ethanol adsorption capacity exhibited volcano-shaped trends with respect to strontium content. Hydrogen yield increased with increasing nickel surface area and with increasing ethanol adsorption capacity of the catalyst. Among the catalysts tested, 15Ni-6Sr/AZ, which retained the highest nickel surface area and the largest ethanol adsorption capacity, showed the highest hydrogen yield in the steam reforming of ethanol. It was concluded that an optimal amount of strontium promoter was required to achieve the best catalytic performance.

Inteplay of Trigger CA2+ Waves and CA2+ Transient Alternans in Atrial Myocytes

We previously documented triggered calcium (Ca) wave (TCW) development in atrial myocytes from large animals during rapid pacing. The goal of this study was to investigate the relationship between Ca transient (CaT) alternans and TCWs in atrial myocytes from normal and failing hearts. Ca cycling was measured via confocal microscopy in atrial myocytes isolated from normal and failing canine hearts then loaded with Ca-sensitive fluorescent dyes. Normal atrial myocytes (NAMs; n = 84) or heart failure atrial myocytes (HFAMs; n = 162) were stimulated at increasingly rapid rates leading to TCW development at rates ≥ 3Hz in ∼54% of NAMs, but often at lower rates and with greater incidence in ∼88% HFAMs. TCW development was contingent on retaining high SR load with diastolic Ca rising 10-20% above that at basal pacing (1Hz) and fractional Ca-release (FCR) being ≈ 0.5 early during rapid pacing epochs. TCWs failed to develop if such FCR was or became ≪ 0.5. However, if such FCR was or became ≫ 0.5, typically few if any TCWs developed or previously developed TCWs ceased, and either larger magnitude TCW-negative CaTs or CaT alternans developed. Overall, CaT alternans developed in ∼29% of NAMs and ∼24% of HFAMs. Additionally, large TCWs often exhibited a periodicity of about 1 per 4-5 pacing cycles, thus manifesting as large slow-rate CaTs superimposed on small rapid-rate CaTs. In summary, atrial myocytes are predisposed to TCW formation during rapid pacing. Significantly increasing FCR is effective in abrogating TCWs, but often leads to the development of CaT alternans in their stead. Our data suggest that TCWs could cause early afterdepolarizations and, along with Ca alternans, could promote dispersion of repolarization, thus promoting atrial arrhythmogenesis (such as atrial fibrillation) particularly in the setting of heart failure.

Strontium (Sr) and silver (Ag) loaded nanotubular structures with combined osteoinductive and antimicrobial activities

Two frequent problems are associated with the titanium surfaces of bone/dental implants: lack of native tissue integration and associated infection. These problems have prompted a significant body of research regarding the modification of these surfaces. The present study describes a hydrothermal treatment for the fabrication of strontium (Sr) and silver (Ag) loaded nanotubular structures with different tube diameters on titanium surfaces. The Sr loading from a Sr(OH)2 solution was regulated by the size of the inner diameter of the titanium nanotubes (NT) (30nm or 80nm, formed at 10V or 40V, respectively). The quantity of Ag was adjusted by immersing the samples in 1.5 or 2.0M AgNO3 solutions. Sr and Ag were released in a controllable and prolonged matter from the NT–Ag.Sr samples, with negligible cytotoxicity. Prominent antibacterial activity was observed due to the release of Ag. Sr incorporation enhanced the initial cell adhesion, migration, and proliferation of preosteoblast MC3T3-E1 cells. Sr release also up-regulated the expression of osteogenic genes and induced mineralization, as suggested by the presence of more mineralized calcium nodules in cells cultured on NT–Ag.Sr surfaces. In vivo experiments showed that the Sr-loaded samples accelerated the formation of new bone in both osteoporosis and bone defect models, as confirmed by X-ray, Micro-CT evaluation, and histomorphometric analysis of rats implanted with NT–Ag.Sr samples. The antibacterial activity and outstanding osteogenic properties of NT–Ag.Sr samples highlight their excellent potential for use in clinical applications. Statement of SignificanceTwo frequent problems associated with Ti surfaces, widely used in orthopedic and dental arenas, are their lack of native tissue integration and risk of infection.We describe a novel approach for the fabrication of strontium (Sr) and silver (Ag) loaded nanotubular structures on titanium surfaces. A relevant aspect of this work is the demonstration of long-lasting and controllable Ag release, leading to excellent antibacterial and anti-adherent properties against methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative bacteria such as Escherichia coli. The extended release of Sr accelerates the filling of bone defects by improving the repair of damaged cortical bone and increasing trabecular bone microarchitecture. Our results highlight the potential of Sr and Ag loaded nanotubular structures for use in clinical applications.

Functional response of the isolated, perfused normoxic heart to pyruvate dehydrogenase activation by dichloroacetate and pyruvate.

Dichloroacetate (DCA) and pyruvate activate pyruvate dehydrogenase (PDH), a key enzyme that modulates glucose oxidation and mitochondrial NADH production. Both compounds improve recovery after ischemia in isolated hearts. However, the action of DCA and pyruvate in normoxic myocardium is incompletely understood. We measured the effect of DCA and pyruvate on contraction, mitochondrial redox state, and intracellular calcium cycling in isolated rat hearts during normoxic perfusion. Normalized epicardial NADH fluorescence (nNADH) and left ventricular developed pressure (LVDP) were measured before and after administering DCA (5mM) or pyruvate (5mM). Optical mapping of Rhod-2AM was used to measure cytosolic calcium kinetics. DCA maximally activated PDH, increasing the ratio of active to total PDH from 0.48 ± 0.03 to 1.03 ± 0.03. Pyruvate sub-maximally activated PDH to a ratio of 0.75 ± 0.02. DCA and pyruvate increased LVDP. When glucose was the only exogenous fuel, pyruvate increased nNADH by 21.4 ± 2.9% while DCA reduced nNADH by 21.4 ± 6.1% and elevated the incidence of premature ventricular contractions (PVCs). When lactate, pyruvate, and glucose were provided together as exogenous fuels, nNADH increased with DCA, indicating that PDH activation with glucose as the only exogenous fuel depletes PDH substrate. Calcium transient time-to-peak was shortened by DCA and pyruvate and SR calcium re-uptake was 30% longer. DCA and pyruvate increased SR calcium load in myocyte monolayers. Overall, during normoxia when glucose is the only exogenous fuel, DCA elevates SR calcium, increases LVDP and contractility, and diminishes mitochondrial NADH. Administering DCA with plasma levels of lactate and pyruvate mitigates the drop in mitochondrial NADH and prevents PVCs.

Effect of core and shell compositions on MeOx@LaySr1−yFeO3 core–shell redox catalysts for chemical looping reforming of methane

The chemical looping reforming (CLR) process converts methane into syngas through cyclic redox reactions of an active lattice oxygen (O2−) containing redox catalyst. In CLR, methane is partially oxidized to CO and H2 using the active lattice oxygen of a redox catalyst. In a subsequent step, the oxygen-deprived redox catalyst is regenerated by air. Such a process can eliminate the need for steam and/or oxygen in reforming, thereby improving methane conversion efficiency. A number of perovskite-structured mixed metal oxides are known to be active for CLR. However, the oxygen storage capacity of perovskites tends to be low, limiting their practical application in chemical looping. In contrast reducible metal oxides such as cobalt and iron oxides can store up to 30wt.% lattice oxygen but are less selective for syngas generation. We explore oxygen carriers that utilize the advantages of both perovskites and first-row transition metal oxides by integrating a transition metal oxide core with a mixed ionic–electronic conductive (MIEC) perovskite support/shell. MIEC perovskites facilitate countercurrent conduction of O2− and electrons, allowing facile O2− transport though the solid. It is proposed that this conduction allows rapid oxygen transport to and from the transition metal oxide cores irrespective of the porosity of the redox catalyst. In this work, we show that MeOx@LaySr1−yFeO3 can be an excellent model catalyst system for CLR. The activity, selectivity, and coke resistance of the core–shell system can be tuned by changing the ratio of La to Sr in the perovskite shell and the type of transition metal oxide in the core. Our studies indicate that lower Sr loadings can improve activity and selectivity of the catalyst for methane partial oxidation, but make the LSF shell less resistant to decomposition during the reduction step.

Effects of Advanced Glycation End Products on Calcium Handling in Cardiomyocytes

Background and Aims: Advanced glycation end products (AGEs) accumulate in diabetes and the engagement of receptor for AGE (RAGE) by AGEs contributes to the pathogenesis of diabetic cardiomyopathy. This study aims to investigate the effects of AGE/RAGE on ryanodine receptor (RyR) activity and Ca²⁺ handling in cardiomyocytes to elucidate the possible mechanism underlying cardiac dysfunction in diabetic cardiomypathy. Methods and Results: Confocal imaging Ca²⁺ spark, the elementary Ca²⁺ release event reflecting RyR activity in intact cell, as well as SR Ca²⁺ content and systolic Ca²⁺ transient were performed in cultured neonatal rat ventricular myocytes. The results show that 50 mg/ml AGE increased the frequency of Ca²⁺ sparks by 160%, while 150 mg/ml AGE increased it by 53%. AGE decreased the amplitude, width and duration of Ca²⁺ sparks. Blocking RAGE with anti-RAGE IgG completely abolished the alteration of Ca²⁺ sparks. The SR Ca²⁺ content indicated by the amplitude (ΔF/F0) of 20 m<smlcap>M</smlcap> caffeine-elicited Ca²⁺ transient was significantly decreased by 150 mg/ml AGE. In parallel, the amplitude of systolic Ca²⁺ transient evoked by 1 Hz-field stimulation was remarkably decreased by 150 mg/ml AGE. The anti-RAGE antibody completely restored the impaired SR load and systolic Ca²⁺ transient. Conclusion: AGE/RAGE signal enhanced Ca²⁺ spark-mediated SR Ca²⁺ leak, causing partial depletion of SR Ca²⁺ content and consequently decreasing systolic Ca²⁺ transient, which may contribute to contractile dysfunction in diabetic cardiomyopathy.

Strontium adsorption and desorption reactions in model drinking water distribution systems

Divalent cationic strontium (Sr 2+ ) adsorption to and desorption from iron corrosion products were examined in two model drinking water distribution systems (DWDS). One system was maintained with chlorine-disinfected drinking water and the other with the same water with secondary chloramine disinfection. Flow conditions simulated primary transmission lines (constant flow) and residential mains (periods of stagnation). Accumulation of Sr 2+ to iron corrosion products in model DWDS was independent of disinfection type. Adsorption and desorption mechanisms are discussed. X-ray adsorption near edge structure (XANES) spectroscopy and linear combination fitting determined Sr 2+ was primarily associated with iron oxyhydroxide corrosion products. At the end of the desorption study, the amount of Sr 2+ remaining in iron corrosion products equilibrated to approximate levels observed at the end of the constant flow adsorption experiments. These results suggest that enhanced iron corrosion product loading of Sr 2+ during stagnation could be short lived under constant flow conditions. Differences between adsorption and desorption based on disinfection type (chlorine versus chlorine plus chloramine) cannot be used to control Sr 2+ desorption.

Calcium Handling is Altered in the Actc E99K Transgenic Mouse Model of Hypertrophic Cardiomyopathy

The ACTC (cardiac actin) E99K transgenic (TG) mouse reproduces many aspects of hypertrophic cardiomyopathy (HCM) seen in humans. The most striking characteristic is the high probability of sudden cardiac death (SCD) in young mice (28-45 days old) probably due to arrhythmias, but how this arises from a myofilament mutation remains unknown. Previous studies demonstrated that the primary effect of this mutation is increased myofilament Ca2+ sensitivity. We hypothesise that increased sensitivity will disturb intracellular Ca2+ homeostasis and trigger afterdepolarisations.Ventricular myocytes, enzymatically dissociated from E99K TG and non-transgenic (NTG) mice aged 8-12 weeks old were externally stimulated. Myocytes from TG animals showed prolonged relaxation (R50=0.079±0.003s vs 0.062±0.003s, P < 0.001) with no differences in maximum sarcomere shortening. Loaded with Fura-2AM, TG cells had smaller Ca2+ transients (Ratio=0.417±0.023 vs 0.519 ± 0.022, P < 0.01) and SR load than their NTG littermates (R=1.087±0.071 vs 1.380±0.0661, P < 0.01). We repeated these studies using cells isolated from mice aged 25-45 days old. Cells from TG mice had greater sarcomere shortening (0.097±0.004µm vs 0.070 ± 0.003µm, P < 0.001) and faster relaxation than their NTG littermates (R50 = 0.064±0.002s vs 0.072±0.002s, P < 0.05). Ca2+ transient amplitude was greater in TG cells (R=0.641±0.035 vs 0.389±0.015, P < 0.001) however there were no differences in SR load. Calcium wave frequency after 5Hz stimulation was increased in TG cells (0.285±0.018s−1 vs 0.175± 0.014s−1, P < 0.001). In both age groups, cells from TG mice displayed reduced diastolic [Ca2+], slower efflux of Ca2+ via the Na+/Ca2+ exchanger and no differences in SR Ca2+-ATPase function.These data show the cardiomyocytes from young TG mice are hypercontractile with increased Ca2+ transient amplitude which, coupled with increased propensity for spontaneous Ca2+ release, could lead to the formation of afterdepolarisations, predisposing the heart to potentially fatal arrhythmias.

Serca Stimulation Increases Intra-Sr Ca2+Threshold for Ca2+ Waves in Cadiomyocytes

In cardiac muscle, stimulation of β-adrenergic receptors leads to activation of PKA via the second messenger cAMP. PKA-dependent phosphorylation of several targets subsequently amplifies the L-type Ca2+ current, relieves the SERCA inhibition by PLB and is proposed to increase the Ca2+ sensitivity of the RyRs (by phosphorylation at serine 2808). Together, these mechanisms account for positive inotropy, but can also be arrhythmogenic via facilitation of spontaneous Ca2+ waves. Unexpectedly, the level of Ca2+ inside the SR ([Ca2+]SR) needed to initiate such waves has been reported to increase upon β-adrenergic stimulation, an observation which cannot be easily reconciled with elevated Ca2+ sensitivity of the RyRs. We tested the hypothesis that this change of Ca2+ wave threshold could occur indirectly, subsequent to SERCA disinhibition. Cytosolic and intra-SR Ca2+ waves were simultaneously recorded with confocal line-scans in permeabilized mouse cardiomyocytes with rhod-2 and fluo-5-N, respectively. We analyzed changes of SR Ca2+ content and several Ca2+ wave parameters. Ochratoxin A (OTA) was used to specifically stimulate the SERCA and the findings were compared to those in the presence of cAMP, which besides SERCA stimulation also leads to RyR phosphorylation. While cAMP resulted in a modest increase of Ca2+ wave thresholds (F/F0 9%±3.5%), OTA lead to a substantial increase (30±5.1%). Both compounds resulted in an acceleration of SR refilling (OTA earlier than cAMP), confirming SERCA stimulation. While cAMP provoked in the occurrence of Ca2+ sparks and mini waves, possibly accounting for the less pronounced SR loading, this was not observed in OTA. Together these results suggest that SERCA stimulation alone can elevate the intra-SR threshold for the generation of Ca2+ waves, independently of RyR phosphorylation. Supported by SNF.

Characterization and activity of alkaline earth metals loaded CeO2–MOx (M = Mn, Fe) mixed oxides in catalytic reduction of NO

Nanocrystalline CeO2–MOx mixed oxides (M = Mn, Fe) with different M/(M + Ce) molar ratio are prepared by sol–gel combustion method. X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Temperature Programmed Reduction with H2 (H2-TPR) and N2-adsorption (BET) analyses are conducted to characterize the physical–chemical properties of the catalysts. The activity of catalysts for reduction of NOx with ammonia has been evaluated. The CeO2–MnOx catalysts showed better low temperature activity than CeO2–FeOx. The superior activity of CeO2–MnOx with Mn/(Mn + Ce) molar ratio of 0.25 respect to other catalysts (with 83% NO conversion and 68% N2 yield at 200 °C) is associated to nanocrystalline structure, reducibility at low temperature and synergistic effect between Ce and Mn that are observed by XRD, TEM and H2-TPR. The CeO2–FeOx catalysts were found to be active at high temperature, being Ce–Fe the best catalyst yielded 82% NO conversion at 300 °C. The effect of alkaline earth metals (Ca, Mg, Sr and Ba) loading on the structure and catalytic activity of cerium mixed oxides are also investigated. Loading of Ba enhanced the NO reduction activity of mixed oxides due to the increase of number of basic sites. Highest performance with 91% NO conversion and 80% N2 yield attained over CeO2–MnOx (0.25)-Ba (7%) catalyst at 200 °C.

Effect of Sr loading on oxydehydrogenation of propane to propylene over Al2O3-supported V-Mo catalysts

Incorporation of strontium into V-Mo alumina-supported catalyst enhanced its performance (increased conversion and selectivity, decreased reducibility and improved stability) in propane oxydehydrogenation to propylene. 12.5% Sr loading was shown to be the optimum content to the V-Mo catalyst. The results were supported by various characterization techniques, namely, BET, XRD, SEM, FTIR and TPD.