Search

In the last decade, growing awareness about CO2 emissions is supporting the authorities in a more sustainable society. The proposed solutions embrace different topics, such as renewable energy implementation, lower waste production, and carbon capture and storage technologies (CCS). The latter is based upon the best available knowledge about the thermophysical properties of CO2, which are not always satisfactory for its complete characterization. In this work, it is investigated the interaction of the CO2 in solid phase (dry-ice) with sandy soil, a phenomenon that can potentially occur following pipeline ruptures. An experimental setup and a numerical model have been developed to measure and validate the temperature profiles beneath the dry-ice bank at steady-state conditions. The model has been validated with the experimental data by defining a suitable range of the thermal conductivity at the solid phase (0.25–0.30 W m−1 K−1) that led to the best match (deviation of 7.81%). Finally, the overall heat transfer coefficient (85.56–86.35 W m−2 K−1) has been numerically calculated. [ABSTRACT FROM AUTHOR]

This study aims to reduce 1% of the annual emissions in the city of Izmir. In line with this target, this study worked on the integration of a liquid solvent-based DACS system within Izmir. Primarily, the emissions within the city boundaries were calculated based on the calculation method of each sector. For the mentioned target, each component's energy requirement of the KOH solvent-based DACS system was calculated in detail. According to these calculations, the system's total energy requirement, economic, and area calculations were obtained. As a result, the total emission amount was calculated as 11,809,362 tCO2. Total needed energy, area, and cost for DACS system resulted to be 1,169 kJ kg−1, 12,527 m2, and $136.6 million, respectively. In addition to numerical results, DACS is the most logical solution apart from increasing environmental awareness for creating a better, stronger, and environmentally friendly city for the near future. [ABSTRACT FROM AUTHOR]

Background and Aims: Robotic surgery is increasingly prevalent as an advancement in care. Steep head-down positions in pelvic surgery can increase the ventilation-perfusion mismatch and increase ventilatory requirements to offset carbon dioxide (CO2) increases consequent to pneumoperitoneum. The primary objective was to assess the impact of two ventilatory strategies, volume versus pressure-controlled ventilation on the arterial to end-tidal carbon dioxide gradient P (a-ET)CO2 in patients undergoing robotic surgery in the Trendelenburg position. The effects on alveolar to arterial oxygen gradient P (A-a)O2,peak airway pressure (Paw), dynamic compliance (Cdyn) and haemodynamics were also assessed. Methods: Fifty-one patients, 18-75 y, American Society of Anesthesiologists I-III undergoing robotic surgery in Trendelenburg position were randomised to volume-controlled ventilation (Group VCV) or pressure-controlled ventilation (Group PCV). The P (a-ET)CO2 was measured at baseline T0, 10 min after Trendelenburg position T1, 2 h of surgery T2, 4 h T3 and at Te, 10 min after deflation. The P (A-a) O2, Paw, Cdyn, heart rate and blood pressure were also measured at the same time. Results: The P (a-ET)CO2 at T1, T2, T3 and at Te was lower in Group PCV versus Group VCV. The Paw was lower at T1, T2, and T3 and Cdyn higher at T3 and Te in Group PCV at comparable minute ventilation. Haemodynamics and P (A-a)O2 were comparable between the groups. Conclusion: Pressure-controlled ventilation reduces P (a-ET)CO2 gradient, Paw and improves Cdyn but does not affect P (A-a) O2 or haemodynamics in comparison to volume-controlled ventilation in robotic surgeries in the Trendelenburg position. [ABSTRACT FROM AUTHOR]

This study is aimed at improving the recovery of Natural Gas Condensate from a Niger-Delta Reservoir in Nigeria, with 35.1 million stock tank barrel (MMSTB) and a 6879 pounds per square inch (psi) reservoir pressure. ECLIPSE 300, a compositional reservoir simulator, was employed to simulate (mimic) the candidate reservoir conditions so as to understand the performance of Carbon-dioxide (CO2) as the injecting fluid, while enhancing the recovery of the natural gas condensate from the reservoir. Nine case studies with different CO2 injection rates were considered to determine the optimum CO2 injection rate. These were compared with the recovery from the natural energy drive of the reservoir. Using the natural energy (drive) of the reservoir, only 11.04MMSTB of natural gas condensates was recovered, which indicated a 32% recovery factor for the natural drive system. Case 6 with CO2 injection rate of 4000 stock tank barrel per day (STB/D) recorded the optimum recovery factor for this natural gas condensate reservoir. This case 6 yielded an ultimate recovery of 21.65MMSTB with a recovery factor of 62%. This simulation results, precisely considering the reservoir conditions, indicated that CO2 can be used to enhance natural gas condensate recovery from NigerDelta reservoirs as demonstrated in this study. Another significance of this study is that CO2 with its adverse effects to the atmosphere and environment can be gainfully used for enhanced natural gas recovery as well as stored in hydrocarbon reservoirs so as to reduce its volume in the atmosphere. [ABSTRACT FROM AUTHOR]

Abstract In previous work, Soh et al., 2014 [1] obtained >98% conversion of triolein to biodiesel (a fatty acid methyl ester) using temperatures of 95 °C, a methanol to triglyceride ratio of 5:1, and carbon dioxide as a co-solvent that enhanced the miscibility of the oil and methanol reactants. To try to determine the most advantageous conditions to operate such reactions where CO 2 is employed as a benign co-solvent, the PC-SAFT theory has been employed to model the phase behavior of the associated mixtures (including alcohols, CO 2 , fatty esters, and glycerol) that one would encounter throughout the reaction. Modelling results achieved accurate phase behavior representations for pure components, plus binary and ternary mixtures that include carbon dioxide by using a polar version of PC-SAFT. Group contribution methods were employed to predict pure component parameters for a range of fatty acid methyl- and ethyl-esters, simplifying the modelling while minimizing the number of parameters. Small errors were obtained using very low values of binary interaction coefficients (below 0.07) for the binary mixtures. Successful modelling for liquid-liquid and vapor-liquid regimes of binary and ternary systems suggest the possibility to determine process conditions for transesterification performed in multiphasic reactors in presence of CO 2. Highlights • Parametrizing glycerol using PPC-SAFT to be used with CO 2 containing systems. • Calculating binary coefficients for biodiesel alcohols with PPC-SAFT. • Generalizing binary coefficients for biodiesel, alcohols and CO 2 with PPC-SAFT. • Building a predictive model for PE of biodiesel related systems with CO 2 as cosolvent. [ABSTRACT FROM AUTHOR]

Carbon dioxide emitted from fossil fuel burning processes is quantitatively the most contributor to global warming. It is believed that climate change could be mitigated by means of Carbon Capture and Storage (CCS). CO 2 physical adsorption separation has the potential of capture carbon dioxide with minimum energy costs. A special type of metal organic frameworks named Mg-MOF-74 is an exceptional adsorbent amongst other porous materials with high CO 2 uptake at flue gas conditions. Temperature swing adsorption (TSA) composed of 4 steps (feed, rinse, heating, and cooling), for separating CO 2 from CO 2 /N 2 mixture using Mg-MOF-74; has been mathematically modeled. A computer model implementation was developed employing User-Defined-Functions linked to Ansys-Fluent software. The CFD two- and three-dimensional models have been validated against adsorption breakthrough experimental data obtained by the authors, at ambient temperature, and against published experimental data for high temperature conditions. The regeneration (heating and cooling) time has been tuned to explore the performance improvement for the TSA process. The TSA optimal key performance indices in terms of CO 2 purity, recovery, productivity, and process power consumption have been found to be 96.22%, 86.5%, 0.279 kg of CO 2 per hour per kg of Mg-MOF-74, and 663.8 kWh per ton of CO 2 captured, respectively. These productivity and power consumption values showed a substantial enhancement in the CO 2 adsorption separation compared to those reported in the literature, especially when the heating process is used for the desorption part of the process. [ABSTRACT FROM AUTHOR]

Carbon dioxide produced from carbon capture technologies could efficiently be stored into adsorbent materials. Certain types of metal organic frameworks called MOF-5 and MOF-177 are distinguished adsorbents amongst other porous materials owing to their high CO 2 uptake at medium storage pressure (10–50 bars). CO 2 adsorptive storage and energy-consumption analysis at pressures between 5 and 50 bar were numerically investigated using MOF-5 and MOF-177. An experimentally validated model was developed using User Defined-Function (written in C) linked to ANSYS Fluent program. The CFD two and three dimensional models have been validated against experimental data for adsorption storage characteristics of hydrogen on activated carbon. The developed model is feasible to accurately simulate and represent gas adsorptive systems. The results of the multidimensional modeling showed that the 2D model is properly adequate to present the adsorptive storage processes. The results obtained from CO 2 adsorptive storage using MOF-5 and MOF-177 emphasized that MOF-5 is a good choice for CO 2 storage applications at pressure less than 5 bar, while MOF-177 is a superior storage medium for the same purposes at higher pressures (≥10 bar). The optimal storage pressure for both adsorbents may be taken as 30 bar with CO 2 uptake and energy consumption about 21.07 mmol g −1 (0.93 kg_CO 2 kg_MOF −1 ) and 231 kJ tonne_CO 2 −1 for MOF-5, and about 32.5 mmol g −1 (1.43 kg_CO 2 kg_MOF −1 ) and 233 kJ tonne_CO 2 −1 for MOF-177, respectively. Importantly, the CO 2 storage is the next step after its separation from a flue gas using any separation method, and the first step prior to underground geological sequestration. The CO 2 adsorptive storage using MOF-177 showed an efficient method to store much more CO 2 quantity with lower energy-consumption than those of traditional storage systems (gas cylinders – without MOFs). [ABSTRACT FROM AUTHOR]

Limiting the air exchange of passenger vehicles by closing windows and recirculating cabin air (RC) restricts the influx of roadway pollutants and reduces in-vehicle particulate concentrations. However, the carbon dioxide (CO 2 ) exhaled by the occupants can accumulate under these conditions to reach high concentrations. We characterized the factors (ventilation setting, vehicle age, speed, cabin volume, trip duration, and number of occupants) that allow CO 2 accumulation to reach concentration thresholds found in other studies to produce cognitive or physiological effects of concern such as fatigue or difficulty concentrating. Ventilation setting was the primary determinant of CO 2 accumulation; only the RC setting (and not outside-air intake) ever allows CO 2 accumulations to exceed thresholds of concern. Longer trips with multiple occupants are a particular concern. Even so, under RC setting, a 2500 ppm threshold—the threshold consistently linked to detrimental cognitive effects—would not be exceeded for most one- or even two-occupant average-duration commutes (twenty-six minutes in the U.S.). For multiple passenger commutes and/or longer trips, RC ventilation should be periodically interrupted or partially mixed with outside air to keep CO 2 concentrations below 2500 ppm. [ABSTRACT FROM AUTHOR]

Quantitatively, carbon dioxide is the main gas emitted from the burning of fossil fuels; thus, it is the primary contributor to global warming. However, climate change could be mitigated using “carbon capture and storage” (CCS) methods. CO 2 separation by physical adsorption is a promising technology to achieve CO 2 capture with minimum energy costs. Mg-MOF-74 is a distinguished adsorbent amongst porous materials owing to its high CO 2 uptake under flue gas conditions. In this study, a vacuum pressure swing adsorption (VPSA) process composed of five steps (pressurization, feed, rinse, blowdown, and purge) for separating CO 2 from a CO 2 /N 2 mixture using Mg-MOF-74 was mathematically modeled. Two- and three-dimensional computational fluid dynamics (CFD) models were developed using a user-defined-function (UDF, written in C) linked to the ANSYS Fluent program. The models have been validated against published pressure swing adsorption experimental data. The regeneration (blowdown and purge) time has been tuned to explore the performance improvement for the VPSA process. The key optimum performance indices for VPSA in terms of CO 2 purity, recovery, productivity, and process power consumption were found to be 95.3%, 94.8%, 0.50 kg_CO 2 h −1 kg_MOF −1 , and 68.71 kW h tonne_CO 2 −1 , respectively. The corresponding operating carbon capture cost has been evaluated as $6.87 tonne_CO 2 −1 for a 500-MW post-combustion power plant. These CO 2 productivity and power consumption performances represent a significant enhancement in CO 2 separation using physical adsorption technology compared to those reported in the literature. [ABSTRACT FROM AUTHOR]

Background Revascularization appears to be beneficial only in patients with high levels of ischemia. This study examined the utility of gas analysis during the recovery phase of cardiopulmonary exercise testing (CPET) in predicting coronary artery disease (CAD) severity and prognosis. Methods 40 Caucasian patients (21.2% females), mean age 63.5 ± 7.6 with significant coronary artery lesions (≥ 50%) were studied. Within two months of coronary angiography, CPET on a treadmill (TM) and recumbent ergometer (RE) were performed on two visits 2–4 days apart; subjects were subsequently followed 32 ± 10 months. Myocardial wall motion was recorded by echocardiography at rest and peak exercise. Ischemia was quantified by the wall motion score index (WMSI). Results Mean ejection fraction was 56.7 ± 9.6%. Patients with 1–2 stenotic coronary arteries (SCA) showed a poorer CPET response during the recovery phase than patients with 3-SCA. ROC analysis revealed the change of carbon-dioxide output (∆ VCO 2 ) recovery/peak (area under ROC curve 0.77, p = 0.02, Sn = 87.5%, Sp = 70.4%) and oxygen uptake (∆ VO 2 ) recovery/peak during TM CPET (area under ROC curve 0.76, p = 0.03, Sn 75.0%, Sp 77.8%) were significant in distinguishing between 1-2-SCA and 3-SCA. The same variables predicted ΔWMSI peak/rest on univariate analysis (p < 0.05). Multivariate Cox analysis revealed a high predictive value of ∆ VO 2 recovery/peak obtained during TM CPET for composite endpoint of cumulative cardiac events (HR = 1.27, CI = 1.07–1.51, p = 0.008). Conclusions The current study suggests CPET parameters in recovery hold predictive value for CAD severity and prognosis. TM testing seems to be a better approach in the assessment of CAD severity and prognosis. [ABSTRACT FROM AUTHOR]

A two-dimensional transient numerical study of the adsorption of CO 2 /N 2 and CO 2 /H 2 mixtures on activated carbon and MOF-177 in a fixed bed is presented. Because most of the commercial CFD codes are not capable of simulating adsorption processes in a straightforward fashion, we developed an additional code to solve for the different species transport including adsorption and diffusion and used Fluent to simulate the adsorption process, fluid flow, heat and, mass transfer. We simulated the adsorption process at high temperature-low pressure and low temperature-high pressure conditions as well as the pressure swing adsorption. For adsorption of CO 2 /N 2 and CO 2 /H 2 mixtures, Toth and Viral models are used calculate equilibrium isotherms. The breakthrough curves obtained from the simulations compare well with the experimental data. Moreover, the effects of aspect ratio and geometric shapes were studied. The results show that varying the bed aspect ratio from 7.77 to 2 has an insignificant effect on the adsorption capacity and performance. [ABSTRACT FROM AUTHOR]

The rheological properties of a long chain branched polypropylene (LCB-PP) were investigated at the processing conditions of foam extrusion, namely high pressure, gas loading and high shear rates, as well as in elongational deformation. For measuring the rheological properties of PP at moderate and high deformation rates, an in-line rheometer was used. Comparison of the results to standard rotational rheometry showed good agreement. The effect of the processing parameters was quantified using shift factors for temperature, pressure and gas concentration. The influence of pressure on the shear viscosity was found to be of minor importance. In contrast, the shear viscosity was distinctly affected by CO concentration, reducing it to one third of its gas-free value at a concentration of 6 wt% at a specific shear rate. The change of viscosity by a variation of temperature is similar in magnitude compared to the variation due to dissolved blowing agent. Furthermore, thermo-rheological complex behaviour was observed. In the foaming process, thermo-rheological complexity could contribute to a better morphology control of long chain branched polymers compared to linear ones. The elongational viscosity was measured using both a hyperbolic die and a film stretching tool (UXF) for comparison. It is almost three decades higher than the shear viscosity in the non-linear region, due to pronounced strain hardening of the melt. [ABSTRACT FROM AUTHOR]

The emission reduction benefits of EVs are dependent on the time and location of charging. An analysis of battery electric and plug-in hybrid vehicles under four charging scenarios and five electricity grid profiles shows that CO 2 emissions are highly dependent on the percentage of fossil fuels in the grid mix. Availability of workplace charging generally results in lower emissions, while restricting charging to off-peak hours results in higher total emissions. [ABSTRACT FROM AUTHOR]

Growth of Spirulina sp. (MCRC-A0003), a cyanobacterium, was evaluated under different concentrations of carbon-dioxide (CO) (4-50 %) in a closed glass photobioreactor. Although significant CO utilization by the cyanobacterial strain was observed up to 50 % concentration, complete utilization was observed only at 4, 10 and 20 % concentrations on 3rd, 6th and 8th day respectively. However, considerable reduction was witnessed in reactors containing 30-50 % CO only between 6th and 9th day. A corresponding increase in the biomass and primary metabolites like chlorophyll- a, carbohydrate and protein were observed. Biomass productivity of Spirulina in reactors sparged with 4, 10 and 20 % CO were 13.7, 43 and 44 % more than that in control reactor without CO. While CO increased the levels of primary metabolites in the cyanobacterial cells, it was quite prominent in 10 % CO concentration with the chlorophyll- a, carbohydrate and protein contents were 64, 183 and 626 mg g respectively. While 10 and 6.6 % increase were noticed in chlorophyll- a and protein, 17 % increase in carbohydrate levels was observed in Spirulina cells, which could be attributed to the conversion of CO to carbohydrate by the cyanobacterium. [ABSTRACT FROM AUTHOR]

Highlights: [•] Encroachment of woody biomass in rangelands and grasslands of central Texas. [•] Torrefaction as viable pretreatment option for Mesquite and Juniper. [•] Effect of carbon dioxide as medium for torrefaction. [•] Increased weight loss and improved grindability on using CO2 for torrefaction. [ABSTRACT FROM AUTHOR]

Abstract: The variability of CO2 concentrations and fluxes in dense urban environments is high due to the inherent heterogeneity of these complex areas and their spatio-temporally variable anthropogenic sources. With a focus on micro- to local-scale CO2-exchange processes, measurements were conducted in a street canyon in the city of Basel, Switzerland in 2010. CO2 fluxes were sampled at the top of the canyon (19 m) and at 39 m while vertical CO2 concentration profiles were measured in the center and at a wall of the canyon. CO2 concentration distributions in the street canyon and exchange processes with the layers above show, apart from expected general diurnal patterns due mixing layer heights, a strong dependence on wind direction relative to the canyon. As a consequence of the resulting corkscrew-like canyon vortex, accumulation of CO2 inside the canyon is modulated with distinct distribution patterns. The evaluation of diurnal traffic data provides good explanations for the vertical and horizontal differences in CO2-distribution inside the canyon. Diurnal flux characteristics at the top of the canyon can almost solely be explained with traffic density expressed by the strong linear dependence. Even the diurnal course of the flux at 39 m shows a remarkable relationship to traffic density for east wind conditions while, for west wind situations, a change toward source areas with lower emissions leads to a reduced flux. [Copyright &y& Elsevier]

In this study, a power cycle using carbon-dioxide as working fluid was designed. Thermodynamic analysis of a power generation system driven by a geothermal energy source was performed over the cyle. In the operation of cycle, geothermal energy was directly transferred to the working fluid and the applicability of the system proposed was investigated cycling the carbon-dioxide in the super-critical region. The results of the system were compared with those of a similar system present in the literature for verification. In addition to this, the results of the system which was designed assuming that thermosiphon effect would be sufficiently high to be able to cycle the working fluid were compared with the ones that were obtained using pump. [ABSTRACT FROM AUTHOR]

Abstract: An open top chamber (OTC) study was conducted with two replications to investigate the impact of elevated CO2 (580ppm) on canopy radiation interception and its use in relation to yield components of two pigeon pea (Cajanus cajan L.) cultivars Pusa-992 and PS-2009. Two OTCs with ambient CO2 of 380ppm were used as control. The LAI and above ground biomass were significantly higher during most of the growth stages for plants exposed to higher CO2 concentration. The canopy radiation extinction coefficient (k) values for both the cultivars were lower for plants exposed to elevated CO2 than for control plants, indicating a more erect structure of these plants. However, the radiation use efficiency (RUE) was 52.3% higher for plants grown under elevated CO2 than for plants grown under ambient CO2 for both the cultivars. The canopy temperature of plants grown under elevated CO2 was found to be lower throughout the growing period. Correspondingly, these plants were supported by higher soil moisture depletion from deeper soil layers. In cultivar Pusa-992, seed yield increased by 12.0% under elevated CO2 because of increase in pod numbers and weight. But in this cultivar, the significant increase (40.6%) in biomass under elevated CO2 did not translate into a corresponding increase in seed yield due to lower harvest index and less numbers of seed per pod. Under elevated CO2, the other cultivar PS-2009 became indeterminate and did not mature, resulting in undeveloped pods. Hence in PS-2009, elevated CO2 resulted in poor seed yield, pod numbers and pod weight even though the biomass produced was higher. Elevated CO2 in the future may result in higher biomass production and higher RUE in pigeon pea due to carbon fertilization, but may not cause a corresponding gain in grain yield because it may lower harvest index. [Copyright &y& Elsevier]

Abstract: Modeled carbon-dioxide (CO2) emissions from an urban area are validated against direct eddy-covariance flux measurements. Detailed maps of modeled local carbon-dioxide emissions for a 4 km2 residential neighborhood in Vancouver, BC, Canada are produced. Inputs to the emission model include urban object classifications (buildings, trees, land-cover) automatically derived from Light Detection and Ranging (LiDAR) and optical remote sensing in combination with census, assessment, traffic and measured radiation and climate data. Different sub-models for buildings, transportation, human respiration, soils and vegetation were aggregated. Annual and monthly CO2 emissions were modeled on a spatial grid of 50 m for the entire study area. The study area overlaps with the source area of a micrometeorological flux tower for which continuous CO2 flux data (net exchange) were available for a two-year period. The measured annual total was 6.71 kg C m−2 yr−1with significant seasonal differences (16.0 g C m−2 day−1 in Aug vs. 22.1 g C m−2 day−1 in Dec correlated with the demand for space heating) and weekday-weekend differences (25% lower emissions on weekends attributed to traffic volume differences). Model results were weighted using the long-term turbulent source areas of the tower. Annual total modeled (7.42 kg C m−2 yr−1) and measured emissions agreed within 11%, but show more substantial differences in wind sectors dominated by traffic emissions. Over the year, agreement was better in summer (5% overestimation by model) vs. winter (15% overestimation), which is partially attributed to climate differences unaccounted for in the building energy models. The study shows that direct CO2 flux measurements based on the EC approach - if sites are carefully chosen - are a promising method to validate fine-scale emission inventories/models at the block or neighborhood scale and can inform further model improvements. [Copyright &y& Elsevier]

In-silico amine screening is a fast, low-cost and promising way of efficiently evaluating new amine molecules which are proposed for carbon-dioxide capture purposes. In order to implement the screening environment, reliable and robust absorber models are required. This contribution presents the modeling and validation results of a CO2 capture pilot absorber operated with monoethanolamine (MEA), as the first step of the in-silico solvent screening framework. The simulation results have shown that the outlet amine loading can be predicted with a 10% deviation from the experimental values for one column, with larger deviations for the second. In addition the model was extended to include the calculation of the overall mass transfer coefficient from laboratory based wetted-wall experiments completed at CSIRO Newcastle, Australia. This further improved the overall model prediction and significantly reduced the amine loading prediction error for the column 1. Note that no parameter fitting was performed on the pilot plant experimental data, other than to include a heat loss to the atmosphere term, and the model relies entirely on engineering and property correlations available in the scientific literature. [ABSTRACT FROM AUTHOR]

This paper deals with the technological and economic (cost) parameters of the release, capture and storage of the carbon dioxide in the flue gases of fossil fuel (coal, natural gas) fired power plants. It makes comparisons and generalisations through processing a wide range of data quoted from the literature. As the first step, the topicality of the issue is justified by illustrating the role of fossil fuels in the energy supply of the more remote future with forecast data. During the technological development of power plants in the last 50 years, block capacity has increased considerably, 5-8 times, with thermal capacity increasing by 50- 60%, as a result of which specific carbon dioxide release has decreased by 30-40%. The paper briefly refers to the theoretical possibility of the sequestration of the carbon dioxide captured from flue gases in geological formations. The enhancing effects of the implementation of CO2 capture on investment costs and its reducing effect on net power plant output and utilization (thermal) efficiency are also analysed in the paper. The efficiency of CO2 capture and the parameters of atmospheric carbon dioxide emission are also given attached to fuel types and technological solutions. As a parameter of the technological solutions, it is indicated what specific cost (USD/tCO2) is demanded for CO2 capture or avoidance, and to what extent it raises the costs of electricity production. [ABSTRACT FROM AUTHOR]

Due to an increase in demand for energy and the mobility of the human population as well as in order to keep sustainable development, there is a major need to utilize alternative energy sources. The use of biogases as a source of renewable energy could provide an effective and alternative way to fulfil a remarkable part of this demand for energy. As biogases have high inert content, their heating value is low. The energetic utilization of these low heating value renewable gaseous fuels is not fully worked out yet because their combustion characteristics significantly differ from the liquid fuels that are used nowadays in transportation, and in this way, they are not usable or their utilization is limited in devices with conventional equipment. Thus, theoretical and experimental analysis was made to investigate the usability of biogases. [ABSTRACT FROM AUTHOR]

Abstract: Anxiety sensitivity (AS) is a well-researched risk factor for the development of anxiety psychopathology. AS is typically measured using the anxiety sensitivity index (ASI) but limitations have led to the creation of second generation measures of AS including the anxiety sensitivity profile (ASP). The ASP has not been used very extensively, however, and we believe this may be due to two important issues: (1) the ASP is lengthy, and (2) the predictive validity of the ASP is unexplored in relation to critical outcomes such as anxiety psychopathology. The purpose of the present report was to address these two issues. We evaluated whether an abbreviated form of the ASP was viable and also conducted tests of the scale''s predictive validity. Findings suggest that a 22-item version of the ASP (i.e., ASP-22) is comparable to the original 60-item ASP. Moreover, the ASP-22 was predictive of anxious responding to a CO2 challenge. In fact, the ASP-22 outperformed the ASI as a predictor of CO2 reactivity. Also, the ASP-22 was a significant longitudinal predictor of incidence of Axis I diagnoses. In regard to predictive validity, the ASP-22 was comparable to the original ASP. In summary, the ASP-22 appears to represent a viable measure of AS that may complement the ASI. [Copyright &y& Elsevier]

Abstract: Experimental data are presented which illustrate heat transfer characteristics of the turbulent supercritical flow in vertical circular/non-circular channels. The working fluid was carbon-dioxide operating at a constant pressure of 8MPa. Experiments were conducted at various conditions with inlet bulk fluid temperatures ranging from 15 to 32°C, imposed heat fluxes from 3 to 180kW/m2, and mass fluxes from 209 to 1230kg/m2 s. The corresponding Reynolds numbers were within the range of 3×104 to 1.4×105. Wall temperatures are presented for the three channels with different cross-sectional shapes. These were measured by thermocouples installed on the outer surface of the heating section, and are compared with each other at the same heat flux and mass flux conditions. [Copyright &y& Elsevier]

Better quantification of isotope ratios of atmosphere-ecosystem exchange of CO 2 could substantially improve our ability to probe underlying physiological and ecological mechanisms controlling ecosystem carbon exchange, but the ability to make long-term continuous measurements of isotope ratios of exchange fluxes has been limited by measurement difficulties. In particular, direct eddy covariance methods have not yet been used for measuring the isotopic composition of ecosystem fluxes. In this article, we explore the feasibility of such measurements by (a) proposing a general criterion for judging whether a sensor’s performance is sufficient for making such measurements (the criterion is met when the contribution of sensor error to the flux measurement error is comparable to or less than the contribution of meteorological noise inherently associated with turbulence flux measurements); (b) using data-based numerical simulations to quantify the level of sensor precision and stability required to meet this criterion for making direct eddy covariance measurements of the 13 C/ 12 C ratio of CO 2 fluxes above a specific ecosystem (a mid-latitude temperate forest in central Massachusetts, USA); (c) testing whether the performance of a new sensor—a prototype pulsed quantum cascade laser (QCL) based isotope-ratio absorption spectrometer (and plausible improvements thereon)—is sufficient for meeting the criterion in this ecosystem. We found that the error contribution from a prototype sensor (&nvsim;0.2 ‰, 1 SD of 10 s integrations) to total isoflux measurement error was comparable to (1.5 to 2×) the irreducible ‘meteorological’ noise inherently associated with turbulent flux measurements above this ecosystem (daytime measurement error SD of &nvsim;60 % of flux versus meteorological noise of 30–40 % for instantaneous half-hour fluxes). Our analysis also shows that plausible instrument improvements (increase of sensor precision to &nvsim;0.1 ‰, 1 SD of 10 s integrations, and increased sensor stability during the half-hour needed to integrate eddy covariance measurements) should decrease the contribution of sensor error to the point where it is less than the contribution from meteorological noise. This suggests that new sensors using QCL-based isotope ratio absorption spectroscopy should make continuous long-term observations of the isotopic composition of CO 2 fluxes via eddy covariance methods feasible. [ABSTRACT FROM AUTHOR]

The current conventional approach to determining the primary energy associated with non-combustible renewable energy (RE) sources such as wind energy and hydro power is to equate the electricity generated from these sources with the primary energy supply. This paper compares this with an approach that was formerly used by the IEA, in which the primary energy equivalent attributed to renewable energy was equated with the fossil fuel energy it displaces. Difficulties with implementing this approach in a meaningful way for international comparisons lead to most international organisations abandoning the primary energy equivalent methodology. It has recently re-emerged in prominence however, as efforts grow to develop baseline procedures for quantifying the greenhouse gas (GHG) emissions avoided by renewable energy within the context of the Kyoto Protocol credit trading mechanisms. This paper discusses the primary energy equivalent approach and in particular the distinctions between displacing fossil fuel energy in existing plant or in new plant. The approach is then extended provide insight into future primary energy displacement by renewable energy and to quantify the amount of CO 2 emissions avoided by renewable energy. The usefulness of this approach in quantifying the benefits of renewable energy is also discussed in an energy policy context, with regard to increasing security of energy supply as well as reducing energy-related GHG (and other) emissions. The approach is applied in a national context and Ireland is case study country selected for this research. The choice of Ireland is interesting in two respects. The first relates to the high proportion of electricity only fossil fuel plants in Ireland resulting in a significant variation between primary energy and primary energy equivalent. The second concerns Ireland's poor performance to date in limiting GHG emissions in line with its Kyoto target and points to the need for techniques to quantify the potential contribution of renewable energy in achieving the target set. [ABSTRACT FROM AUTHOR]

ABSTRACT Internal transport of gases is crucial for vascular plants inhabiting aquatic, wetland or flood-prone environments. Diffusivity of gases in water is approximately 10 000 times slower than in air; thus direct exchange of gases between submerged tissues and the environment is strongly impeded. Aerenchyma provides a low-resistance internal pathway for gas transport between shoot and root extremities. By this pathway, O2 is supplied to the roots and rhizosphere, while CO2 , ethylene, and methane move from the soil to the shoots and atmosphere. Diffusion is the mechanism by which gases move within roots of all plant species, but significant pressurized through-flow occurs in stems and rhizomes of several emergent and floating-leaved wetland plants. Through-flows can raise O2 concentrations in the rhizomes close to ambient levels. In general, rates of flow are determined by plant characteristics such as capacity to generate positive pressures in shoot tissues, and resistance to flow in the aerenchyma, as well as environmental conditions affecting leaf-to-air gradients in humidity and temperature. O2 diffusion in roots is influenced by anatomical, morphological and physiological characteristics, and environmental conditions. Roots of many (but not all) wetland species contain large volumes of aerenchyma (e.g. root porosity can reach 55%), while a barrier impermeable to radial O2 loss (ROL) often occurs in basal zones. These traits act synergistically to enhance the amount of O2 diffusing to the root apex and enable the development of an aerobic rhizosphere around the root tip, which enhances root penetration into anaerobic substrates. The barrier to ROL in roots of some species is induced by growth in stagnant conditions, whereas it is constitutive in others. An inducible change in the resistance to O2 across the hypodermis/exodermis is hypothesized to be of adaptive significance to... [ABSTRACT FROM AUTHOR]

Objective and Design: A retrospective study of the incidence of contrast-medium-induced nephropathy (CMN) in patients with renal insufficiency.Subjects: All angiographies with and without endovascular therapeutic procedures (n = 2400) performed at the hospital during 1 year were evaluated. A total of 139 patients were found to have a preangiographic serum-creatinine (s-Cr) of 150 micromol L(-1) or above. Postprocedural serial s-Cr values were present in 118 patients and these were included in the study.Results: Amongst patients receiving only iodinated contrast media (CM) 8% demonstrated a 25% rise in s-Cr. The corresponding figure was 11 and 12.5% amongst patients who were given either iodinated CM together with carbon dioxide (CO2) or CO2 as sole contrast medium. After exclusion of other explanations of impaired renal function all together only seven of 114 patients (6%) were considered to have developed CMN. Four of the seven patients restituted renal function completely, whilst it remained decreased in three. No patient required dialysis. The percentage of diabetic patients were not found to be different in patients with and without signs of CMN.Conclusions: The present retrospective study indicate that the risk of CMN in connection with angiography is low when modern low-osmolality CM and contrast saving angiographic technique including CO2 is used combined with proper hydration. Patients with diabetes mellitus were not found more frequently in the groups with CMN. [ABSTRACT FROM AUTHOR]

• Method to hinder degrading electrical properties of Indium tin oxide transparent electrode. • Carbon-dioxide as an efficient annealing ambient. • Proposed ambient suppress formation of oxygen interstitials and reduce vacancy. In practical applications of indium-tin-oxide (ITO), annealing at temperatures ~400 °C without degrading its electrical and optical properties is an important challenge. In the present work, commercial Indium-tin oxide (ITO) coated on glass was subjected to post-annealing treatment in the range of 200–400 °C at different annealing atmospheres; oxygen, nitrogen and carbon-dioxide. The annealed samples were characterized by X-ray diffraction, UV–visible spectroscopy and Hall measurements to evaluate the structural, optical and electrical properties. Both oxygen and nitrogen treated samples demonstrate degradation in structural, optical and conducting properties of ITO, while carbon-dioxide atmosphere inhibits the degradation of ITO at 400 °C. The obtained results suggest that carbon-dioxide can be well utilized as annealing ambient to retain opto-electronic and structural properties of ITO and thereby improve the efficiency of ITO based solar cells. [ABSTRACT FROM AUTHOR]

This paper presents the mathematical models describing the diffusion of carbon-dioxide in concrete with considering the effect of concrete carbonation. The effect of concrete carbonation on carbon-dioxide diffusion is modelled by using a sink term added in the diffusion equation. It is shown that, when the carbonation reaction is much faster than the diffusion process, the diffusion of carbon-dioxide in carbonated concrete can be treated as the diffusion problem with a moving boundary, representing the diffusion front or the carbonation depth. An analytical solution is also derived for the diffusion problem with moving boundary. [ABSTRACT FROM AUTHOR]

• Terrestrial carbon remineralization reduces aragonite-saturation and increases pCO 2. • Export production and terrestrial CaCO 3 dissolution offset remineralization effects. • Changes in marine pCO 2 and Ω Ar depend on watershed geology and organic matter C:N. Recent research has focused on the changing ability of oceans to absorb atmospheric CO 2 and the consequences for ocean acidification, with Arctic shelf seas being among the most sensitive regions. Hudson Bay is a large shelf sea in northern Canada whose location at the margin of the cryosphere places it in the vanguard of global climate change. Here, we develop a four-compartment box-model and carbon budget using published and recently collected measurements to estimate carbon inputs, transformations, and losses within Hudson Bay. We estimate the annual effects of terrestrial carbon remineralization on aragonite saturation (Ω Ar , a proxy for ocean acidification) and on the partial pressure of CO 2 (pCO 2 , a proxy for air-sea CO 2 flux) within each compartment, as well as the effects of marine primary production, marine organic carbon remineralization, and terrestrial calcium carbonate dissolution. We find that the remineralization of terrestrial dissolved organic carbon is the main driver of CO 2 accumulation and aragonite under-saturation in coastal surface waters, but this is largely offset by marine primary production. Below the surface mixed layer, marine organic carbon remineralization is the largest contributor to CO 2 accumulation and aragonite under-saturation, and is partially offset by terrestrial CaCO 3 dissolution. Overall, the annual delivery and processing of carbon reduces Ω Ar of water flowing through HB by up to 0.17 units and raises pCO 2 by up to 165 µatm. The similarities between Hudson Bay and other Arctic shelf seas suggest these areas are also significantly influenced by terrestrial carbon inputs and transformation. [ABSTRACT FROM AUTHOR]

Attachment of bacteria to abiotic surfaces is the initial phase of attachment process which enables pathogens to persist in food processing environments. The objective of this study was to assess the antimicrobial efficacy of pressurized particulate carbon dioxide (PPCD) against cells of Salmonella Typhimurium and Listeria monocytogenes allowed to attach to stainless steel for 24 h. Model cell attachment systems were produced on stainless steel coupons and treated with PPCD for variable durations up to 10 s and employing multiple blast treatments. The reduction in attached cells recovered by surface swabbing was significantly affected by interaction of bacterium × treatment (p < 0.01). Blasts of 1 s duration and 2 blasts of 1 s separated by 30 s resulted in approximately 1 log10 CFU/coupon reduction. Average reduction (2 log10 CFU/coupon) in Salmonella cells was significant (p < 0.01) for 4 s blasting treatment. Longer blast durations of 7 s and 10 s provided approximately 3 log10 CFU/coupon reduction for both the bacteria. These results demonstrate the antimicrobial effect of pressurized particulate carbon dioxide against attached cells of pathogenic bacteria and suggest a scope for further improving this technology. • Biofilm formation enables pathogens to persist in food processing environments. • Assess antimicrobial efficacy of pressurized particulate carbon dioxide. • Pressurized carbon dioxide significantly reduced attached bacterial cells. • CO 2 blast of 7 s and 10 s provided 3 log 10 CFU/coupon reduction for the bacteria. • Study suggest strong potentials for pressurized carbon dioxide as sanitizing agent. [ABSTRACT FROM AUTHOR]

Soh et al. [1] showed that one can achieve high conversion (98%) of triglycerides to fatty acid methyl esters at 95 °C when carbon dioxide (CO 2) is used as a co-solvent to enhance mixing of the immiscible alcohol and triglyceride. Soh's results demonstrated the benefits of using CO 2 as a co-solvent yet did not provide information on the evolution of the phase behavior during the reaction. The PC-SAFT equation of state has been employed to understand and predict the phase behavior of the various biodiesel components versus temperature and pressure in the presence of CO 2. In previous work [2] the interaction between alkyl-esters and low molecular weight alcohols, glycerol, and CO 2 were investigated. Polar PC-SAFT and the Group Contribution PPC-SAFT EoS were used to model phase equilibria amongst the various multicomponent systems. The same approach is extended here, specifically applied to mixtures containing tri-, di- and monoglycerides plus low molecular weight alcohols and CO 2. Data for different types of glycerides are scarce and in general the phase boundary curves in CO 2 -based mixtures are only weakly dependent on CO 2 concentration, creating curves with very high slopes in P-T space that accumulate larger prediction errors compared to the previously investigated alkyl-ester systems. Nonetheless, it was found that one could generate a general correlation for binary interaction coefficient that depends only on carbon chain length and degree of unsaturation for description of triglyceride-CO 2 mixtures. Binary interaction parameters as low as 12% were obtained for all glyceride-methanol systems and binary interaction coefficient below 3.5% are sufficient to correctly capture CO 2 – glyceride vapor-liquid and liquid-liquid phase equilibria. [ABSTRACT FROM AUTHOR]