Effect of carbonation on bulk resistivity of cement/carbon nanofiber composites

The conductivity of cement/carbon nanofiber (CNF) composite materials has previously been shown to be affected by parameters such as e.g. CNF content or water to cement (w/c) ratios, water saturation and temperature. However, whether and to what extent chemical processes like cement carbonation can affect the electrical conductivity of cement/CNF materials remains unexplored. To investigate this the resistivity changes upon carbonation of Portland G cement/CNF composites were followed for more than 4 months. An increase in resistivity was observed within the first weeks of carbonation followed by a plateau and a subsequent decrease after 4 months. The changes in resistivity were correlated with the progress of the carbonation front followed using X-ray tomography. The magnitude of the resistivity changes was found to be related to w/c ratio. Volumetric changes affecting the connectivity between the CNFs can explain the resistivity changes.publishedVersio

Effect of Field Caprock Shale Exposure to CO2 on Its Mechanical Properties—A Comparison of Experimental Techniques

Laboratory tests were performed on the Draupne shale formation, which may serve as a seal over CO2 storage sites. Different techniques were used to assess the integrity and mechanical properties of the shale, with the main objective of investigating whether exposure to CO2 would in any manner alter these properties. The laboratory methods used encompass traditional triaxial tests; however, with fluid substitution prior to increasing axial stress to failure. These tests were conducted on smaller cylindrical plugs than standard, taking advantage of the finer grained nature of the shale. Another set of experiments used the low-frequency technique, whereby small amplitude, cyclic axial strains are applied on the specimen, allowing a direct measurement of stiffness. Long exposure, with change of fluid from brine to CO2 , allowed for quantifying small changes in stiffness, thanks to the many repeated cycles of non-destructive testing. In a final experimental technique, the punch test, shear strength of the same material was obtained by cutting a central disk from a larger intact shale disk, while measuring the shear force needed to perform the cut.publishedVersio

Conductive epoxy/carbon nanofiber coatings for scale control

Calcium carbonate (CaCO3) is one of the most widespread scaling minerals and has been a long-standing problem within many industrial sectors. Scaling of calcium carbonate on conductive surfaces can be prevented electrochemically by anodic polarization. Anodic polarization, however, cannot be applied directly to metal surfaces like e.g., steel that will suffer from corrosion when polarized anodically in an aqueous environment. Thus, in this paper it is proposed to apply a conductive coating to a metal surface to allow anodic polarization and inhibit surface scaling, without corrosion of the underlying metal surface taking place. To this end an epoxy/carbon nanofiber conductive coating was developed and deposited at steel surfaces. The coating showed good adhesion to the surface and the bulk and surface resistivities were in the order of 52.80 kΩcm and 31.87 kΩ/cm2, respectively. The anti-scaling performance of the coating without- and under anodic polarization was tested upon exposure to 1.5 wt % CaCl2 solution being in contact with CO2. The coating has been tested at several different potentials to find optimal conditions for scale inhibition. Potentials above +3 VOCP caused a degradation of the coating due to oxygen evolution at the anode, as well as evolution of chlorine gas. At +1.5 and +2 VOCP the coating remained intact and the precipitation of CaCO3 was limited. On the other hand, cathodic polarization of the coating surface enhanced scaling and no coating degradation was observed at cathodic polarization even at potentials as high as -5 VOCP. The coating has thus proven a good solution to control surface scale deposition. Both anodic scale inhibition and cathodic scale acceleration have been achieved at the coating surfaces.publishedVersio

Field testing for toxic algae with a microarray: initial results from the MIDTAL project

One of the key tasks in MIDTAL (MIcroarrays for the Detection of Toxic ALgae) is to demonstrate the applicability of microarrays to monitor harmful algae across a broad range of ecological niches and toxic species responsible for harmful algal events. Water samples are collected from a series of sites used in national phytoplankton and biotoxin monitoring across Europe. The samples are filtered; rRNA is extracted, labelled with a fluorescent dye and applied to a microarray chip. The signal intensity from >120 probes previously spotted on the chip is measured and analysed. Preliminary results comparing microarray signal intensities with actual field counts are presented.Versión del edito

Earlier sea-ice melt extends the oligotrophic summer period in the Barents Sea with low algal biomass and associated low vertical flux

The decrease in Arctic sea-ice extent and thickness as a result of global warming will impact the timing, duration, magnitude and composition of phytoplankton production with cascading effects on Arctic marine food-webs and biogeochemical cycles. Here, we elucidate the environmental drivers shaping the composition, abundance, biomass, trophic state and vertical flux of protists (unicellular eukaryotes), including phytoplankton, in the Barents Sea in late August 2018 and 2019. The two years were characterized by contrasting sea-ice conditions. In August 2018, the sea-ice edge had retreated well beyond the shelf break into the Nansen Basin (>82°N), while in 2019, extensive areas of the northwestern Barents Sea shelf (>79°N) were still ice-covered. These contrasting sea-ice conditions resulted in marked interannual differences in the pelagic protist community structure in this area. In August 2018, the protist community was in a post-bloom stage of seasonal succession characterized by oligotrophic surface waters and dominance of small-sized phytoplankton and heterotrophic protists (predominantly flagellates and ciliates) at most stations. In 2019, a higher contribution of autotrophs and large-celled phytoplankton, particularly diatoms, to total protist biomass compared to 2018 was reflected in higher chlorophyll a concentrations and suggested that the protist community was still in a late bloom stage at some stations. It is noteworthy that particularly diatoms contributed a considerably higher proportion to the protist biomass at the ice-covered stations in both years compared to the open-water stations. This pattern was also evident in the higher vertical protist biomass flux in 2019, dominated by dinoflagellates and diatoms, compared to 2018. Our results suggest that the predicted transition toward an ice-free Barents Sea will lengthen the oligotrophic summer period with low algal biomass and associated low vertical flux.publishedVersio

Plasma CCN2/connective tissue growth factor is associated with right ventricular dysfunction in patients with neuroendocrine tumors

<p>Abstract</p> <p>Background</p> <p>Carcinoid heart disease, a known complication of neuroendocrine tumors, is characterized by right heart fibrotic lesions. Carcinoid heart disease has traditionally been defined by the degree of valvular involvement. Right ventricular (RV) dysfunction due to mural involvement may also be a manifestation. Connective tissue growth factor (CCN2) is elevated in many fibrotic disorders. Its role in carcinoid heart disease is unknown. We sought to investigate the relationship between plasma CCN2 and valvular and mural involvement in carcinoid heart disease.</p> <p>Methods</p> <p>Echocardiography was performed in 69 patients with neuroendocrine tumors. RV function was assessed using tissue Doppler analysis of myocardial systolic strain. Plasma CCN2 was analyzed using an enzyme-linked immunosorbent assay. Mann-Whitney U, Kruskal-Wallis, Chi-squared and Fisher's exact tests were used to compare groups where appropriate. Linear regression was used to evaluate correlation.</p> <p>Results</p> <p>Mean strain was -21% ± 5. Thirty-three patients had reduced RV function (strain > -20%, mean -16% ± 3). Of these, 8 had no or minimal tricuspid and/or pulmonary regurgitation (TR/PR). Thirty-six patients had normal or mildly reduced RV function (strain ≤ -20%, mean -25% ± 3). There was a significant inverse correlation between RV function and plasma CCN2 levels (r = 0.47, p < 0.001). Patients with reduced RV function had higher plasma CCN2 levels than those with normal or mildly reduced RV function (p < 0.001). Plasma CCN2 ≥ 77 μg/L was an independent predictor of reduced RV function (odds ratio 15.36 [95% CI 4.15;56.86]) and had 88% sensitivity and 69% specificity for its detection (p < 0.001). Plasma CCN2 was elevated in patients with mild or greater TR/PR compared to those with no or minimal TR/PR (p = 0.008), with the highest levels seen in moderate to severe TR/PR (p = 0.03).</p> <p>Conclusions</p> <p>Elevated plasma CCN2 levels are associated with RV dysfunction and valvular regurgitation in NET patients. CCN2 may play a role in neuroendocrine tumor-related cardiac fibrosis and may serve as a marker of its earliest stages.</p

Multicentric Atrial Strain COmparison between Two Different Modalities: MASCOT HIT Study

Two methods are currently available for left atrial (LA) strain measurement by speckle tracking echocardiography, with two different reference timings for starting the analysis: QRS (QRS-LASr) and P wave (P-LASr). The aim of MASCOT HIT study was to define which of the two was more reproducible, more feasible, and less time consuming. In 26 expert centers, LA strain was analyzed by two different echocardiographers (young vs senior) in a blinded fashion. The study population included: healthy subjects, patients with arterial hypertension or aortic stenosis (LA pressure overload, group 2) and patients with mitral regurgitation or heart failure (LA volume–pressure overload, group 3). Difference between the inter-correlation coefficient (ICC) by the two echocardiographers using the two techniques, feasibility and analysis time of both methods were analyzed. A total of 938 subjects were included: 309 controls, 333 patients in group 2, and 296 patients in group 3. The ICC was comparable between QRS-LASr (0.93) and P-LASr (0.90). The young echocardiographers calculated QRS-LASr in 90% of cases, the expert ones in 95%. The feasibility of P-LASr was 85% by young echocardiographers and 88% by senior ones. QRS-LASr young median time was 110 s (interquartile range, IR, 78-149) vs senior 110 s (IR 78-155); for P-LASr, 120 s (IR 80-165) and 120 s (IR 90-161), respectively. LA strain was feasible in the majority of patients with similar reproducibility for both methods. QRS complex guaranteed a slightly higher feasibility and a lower time wasting compared to the use of P wave as the reference

The Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP): illuminating the functional diversity of eukaryotic life in the oceans through transcriptome sequencing

International audienceCurrent sampling of genomic sequence data from eukaryotes is relatively poor, biased, and inadequate to address important questions about their biology, evolution, and ecology; this Community Page describes a resource of 700 transcriptomes from marine microbial eukaryotes to help understand their role in the world's oceans

Calculations of Resistivity Coefficients and Mass Flux in a Two-Phase Binary Lennard-Jones/spline System Using Non-Equilibrium Thermodynamics and Molecular Dynamics

Fresh water has a vital role in our everyday life. However, it is also increasingly scarce and it is important to obtain better understanding of water purification processes to secure global access to clean water. There exist many processes for water purification. In this study, the purification process membrane distillation was investigated. The aim of this study was to use non-equilibrium thermodynamics to create a model to find the resistivity coefficients present due to a thermal and chemical potential driving force. These coefficients can provide accurate information about the mass transport through the membrane. A two-phase system containing two different Lennard-Jones/spline fluids, pure liquid and mixture, separated by a hydrophobic pore was modelled to calculate these coefficients. Lennard-Jones/spline particles were used to simplify the system. It was first constructed a simple two-component system to find optimal conditions for the mixture in the pore system. For this simple system, a phase diagram was created. Then, four different systems were constructed to find the total and local resistivity coefficients. The total resistivity coefficients were rqq=13+-3, rqu=-20+-2 and ruu=35+-2. The local resistivity coefficients include the coefficients for the surface between mixture and vapor (r(s,l)), the vapor coefficient (r(vapor)), and for the surface between vapor and pure liquid (r(s,r)). These were found to be rqq(s,l)=23+-2, rqu(s,l)=-15+-1, ruu(s,l)=11+-2, rqq(vapor)=7+-1, rqu(vapor)=-0.5+-0.7, ruu(vapor)=0.05+-0.04 and rqq(s,r)=13.6+-0.8, rqu(s,r)=-8+-2, ruu(s,r)=13+-1. It was seen that the surfaces had resistivity coefficients that were significantly different from the bulk coefficients. This indicate that surface resistivity coefficients have a crucial role when it comes to providing accurate information regarding the mass flux. Simulations were also conducted to investigate how mass transport was influenced by temperature and pore diameter. A linear correlation between temperature and mass flux was found, where the mass flux increased with increasing temperature gradient. The greatest mass flux was obtained for the smallest pore investigated (pore diameter equal 10 molecular diameters). This result implied that a membrane with a greater number of pores with diameter 10 molecular diameters would provide a greater mass transport compared to a membrane with fewer, larger pores

Electrochemical enhancement and inhibition of calcium carbonate deposition

Calcium carbonate is by far the most widespread scaling material. Its deposition in pipes and flowlines has been a long-standing problem for many industries. Hence, a lot of research is devoted to scale inhibition. One of the calcium carbonate scale management methods relies on removal of calcium ions from scaling solution by electrochemically enhanced deposition. Application of potential between two electrodes may result in oxygen reduction and water electrolysis. Both processes change the local pH in close proximity to the electrodes. Solution close to the anode is becoming acidic while that close to the cathode alkaline. Solubility of calcium carbonate is pH dependent. The alkaline pH in the vicinity of the cathode promotes precipitation of calcium carbonate. On the other hand, the acidic environment near the anode prevents anode from scaling. In this paper we show how the cathodic and anodic processes, respectively, accelerate and prevent scale deposition on graphite electrode surfaces. The growth of calcium carbonate at different calcium ion concentrations and different voltage magnitudes applied were followed using X-ray computed tomography. The morphology of the deposited calcium carbonate was studied using the scanning electron microscopy. The polymorphic forms of calcium carbonate deposited at different voltage magnitudes were identified using X-ray powder diffraction. A strong correlation between the scaling rate, the average crystallite size and the voltage applied was observed.publishedVersio