Search

This study investigated the environmental sustainability of economic growth: a Panel data analysis in East Africa for the period 1990-2020 And we use of OLS estimation, Fully Modified Least Squares (FMOLS), and the outcome of Descriptive statistics reveal the typical magnitudes, standard deviations, and ranges of variables such as ecological footprint (EF), carbon dioxide (CO2), biocapacity (BC), foreign direct investment (FDI), gross domestic product (GDP), and population. EF has an average of 17.15 with a low standard deviation, suggesting proximity to the mean. CO2 exhibits higher variability, with a range from -3.330 to 11.691. Similar patterns are observed for BC, FDI, GDP, and population. Correlation analysis reveals relationships, with positive correlations between EF and CO2, EF and population, CO2 and population, and BC and EF. Negative correlations exist between EF and GDP and CO2 and GDP, suggesting potential trends in the associations between ecological impact, economic development, and population dynamics. The Kao Residual Cointegration Test indicates that the variables in the analysis may be stationary after differencing, a crucial condition for cointegration. The p-values associated with residual V and HAC V are both less than 0.05, providing statistical significance and evidence against the null hypothesis of no cointegration. The overall low p-value (0.0004) for the Kao test further supports the rejection of the null hypothesis, suggesting the presence of cointegration among the variables. For biocapacity (BC) and foreign direct investment (FDI), individual intercept and trend co-integration tests show significant evidence. [ABSTRACT FROM AUTHOR]

During the recent 40 years, the quantity of energy sources globally has been reduced, and the consequence of this situation that the oil in the world becomes more expensive. Many manufacturers have been forced to initiate the development of completely new concepts of developing commercial aircraft which would be more rational regarding fuel consumption by completely retaining the best quality of passenger services. A continuous uptrend of the propellant cost globally since 1990s has forced not only smaller companies but also the most powerful enterprises in aviation industry, such as the “General Electric”, to return to the research and development programs of Turbo Prop engines. In the case of the aircraft DHC Dash 8 Q 400, the engineering preparation of the flight for calculating the changes of travel propellant while the switch of the flight altitude was being done. By analyzing nine various levels of flight, the conclusion has been indisputably reached that regardless of the vast altitudes of a flight and the horizontal distance covered during climb and descent, the fuel consumption is significantly lower than while flying at much lower altitudes with much lower horizontal distance in climb and descent. All the indicators that have been reached undeniably confirm the fact that a flight at great altitudes enables lower consumption of fuel and less necessary time of the flights. By such analysis and setting sustainable aircraft fuels into equations, numerous improvements in the world of aviation, which directly influence the quality of life on the global level, are achieved. Likewise, it will indicate the possibility of substitution of classical hydrocarbon (fossil) fuels with biofuels which, while burning, release much lower emission of exhaust gases.

During the recent 40 years, the quantity of energy sources globally has been reduced, and the consequence of this situation that the oil in the world becomes more expensive. Many manufacturers have been forced to initiate the development of completely new concepts of developing commercial aircraft which would be more rational regarding fuel consumption by completely retaining the best quality of passenger services. A continuous uptrend of the propellant cost globally since 1990s has forced not only smaller companies but also the most powerful enterprises in aviation industry, such as the "General Electric", to return to the research and development programs of Turbo Prop engines. In the case of the aircraft DHC Dash 8 Q 400, the engineering preparation of the flight for calculating the changes of travel propellant while the switch of the flight altitude was being done. By analyzing nine various levels of flight, the conclusion has been indisputably reached that regardless of the vast altitudes of a flight and the horizontal distance covered during climb and descent, the fuel consumption is significantly lower than while flying at much lower altitudes with much lower horizontal distance in climb and descent. All the indicators that have been reached undeniably confirm the fact that a flight at great altitudes enables lower consumption of fuel and less necessary time of the flights. By such analysis and setting sustainable aircraft fuels into equations, numerous improvements in the world of aviation, which directly influence the quality of life on the global level, are achieved. Likewise, it will indicate the possibility of substitution of classical hydrocarbon (fossil) fuels with biofuels which, while burning, release much lower emission of exhaust gases. [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.

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]

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.

In this work, agricultural biomass waste (maize) was used as raw material in a pyrolysis-gasification process with the presence of nickel-loaded zeolites, CaO and Al 2 O 3. Henceforward, the reusability and the deteriorating effect of the catalysts are important to be analysed, therefore the catalysts were reused for ten regeneration cycles. During the measurements, the effect of temperature, catalysts and the regeneration cycles of catalysts were also investigated, as well as the components of the gaseous product. At first, the proper temperature was determined in the 1st (200–800 °C) and the 2nd (500–700°) reactor zone, where 400 °C and 700 °C, while for the regeneration 800 °C was chosen. Throughout the regeneration cycles in case of Ni/ZSM-5 lighter hydrocarbons was increased while that of the carbon monoxide and carbon dioxide was decreased. In the presence of Ni/CaO the amount of carbon dioxide decreased until the 3rd regeneration cycle, while carbon monoxide and hydrogen was decreased till the 10th cycle. Regarding the Ni/Al 2 O 3 , the amount of CO 2 and CO was significantly decreased at each cycles, while in case of Ni/Clinoptilolite reduction was observed in hydrogen and carbon dioxide, however not only the amount of carbon monoxide but the syngas yield increased remarkably. Due to the mentioned results, the Ni/Clinoptilolite has an effective syngas enhancing and carbon dioxide capturing effect, even with low pyrolysis temperature. •Nickel supported ZSM-5, Al 2 O 3 , CaO, Clinoptilolite were used for biomass gasification. •In case of Ni/Al 2 O 3 mostly the temperature had an effect on the product yield. •Ni/CaO can be sintered during the regeneration. •The highest syngas yield was found in case of Ni/Clinoptilolite. •The syngas yield increased till the 6th regeneration cycle of Ni/Clinoptilolite. [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]

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.

In this paper, measurements of CO2 rate and its relation to temperature, humidity and wind speed were carried out at 13 different locations in Erbil city during March [ 2017 to 2018], it was found that CO2 rate is the same as global level (418ppm) for outdoor. Measurements of CO2 rates for indoor environment showed that using kerosene heaters (during winter season) caused a rapid increase of CO2 rate in a short time, which has harmful side effect on human health.

The effects of climate change such as dry spells, floods and erosion heavily impact agriculture especially smallholder systems on the Northwestern Loess Plateau of China. Nonetheless agriculture also contributes to global warming through the emission of greenhouse gases such as CO2, CH4 and N2O. Yet this complex conundrum can be alleviated and mitigated through sound soil and water management practices. Despite considerable literature on Conservation Agriculture (CA) as a strategy to improve the resilience and mitigation capacity of agroecosystems, there is still paucity of information on the impacts of CA on crop production and environmental quality on the Plateau. In order to fill this gap this study examined the effects of no-till and straw mulch on crop productivity and greenhouse gas fluxes in agroecosystems on the Plateau where farmers’ common practice of conventional tillage (CT) was tested against three CA practices: conventional tillage with straw mulch (CTS), no-till (NT) and no-till with straw mulch (NTS). The results indicated that all three CA practices (CTS, NT and NTS) markedly increased soil water content (SWC), soil organic carbon (SOC) and soil total nitrogen (STN) but reduced soil temperature (ST). Average grain yields were 854.46 ± 76.51, 699.30 ± 133.52 and 908.18±38.64 kg ha-1 respectively under CTS, NT and NTS indicating an increase by approximately 33%, 9% and 41% respectively compared with CT (644.61 ± 76.98 kg ha−1). There were significant (p

The effects of climate change such as dry spells, floods and erosion heavily impact agriculture especially smallholder systems on the Northwestern Loess Plateau of China. Nonetheless agriculture also contributes to global warming through the emission of greenhouse gases such as CO2, CH4 and N2O. Yet this complex conundrum can be alleviated and mitigated through sound soil and water management practices. Despite considerable literature on Conservation Agriculture (CA) as a strategy to improve the resilience and mitigation capacity of agroecosystems, there is still paucity of information on the impacts of CA on crop production and environmental quality on the Plateau. In order to fill this gap this study examined the effects of no-till and straw mulch on crop productivity and greenhouse gas fluxes in agroecosystems on the Plateau where farmers' common practice of conventional tillage (CT) was tested against three CA practices: conventional tillage with straw mulch (CTS), no-till (NT) and no-till with straw mulch (NTS). The results indicated that all three CA practices (CTS, NT and NTS) markedly increased soil water content (SWC), soil organic carbon (SOC) and soil total nitrogen (STN) but reduced soil temperature (ST). Average grain yields were 854.46 ± 76.51, 699.30 ± 133.52 and 908.18±38.64 kg ha-1 respectively under CTS, NT and NTS indicating an increase by approximately 33%, 9% and 41% respectively compared with CT (644.61 ± 76.98 kg ha-¹). There were significant (p < 0:05) reductions of Net CO2 emissions under NT (7.37 ± 0.89 tCO2e ha-¹y-¹) and NTS (6.65 ± 0.73 tCO2e ha-1y-1) compared with CTS (10.65 ± 0.18 tCO2e ha-¹y-¹) and CT (11.14 ± 0.58 tCO2e ha-¹y-¹). All the treatments served as sinks of CH4but NTS had the highest absorption capacity (-0.27 ± 0.024 tCO2e ha-¹y-¹) and increased absorption significantly (p<0:05) compared with CT (-0.21 ± 0.017 tCO2e ha-¹y-¹); however, CA did not reduce emissions of N2O. These had an influence on Global warming potential (GWP) as NT and NTS resulted in significant reduction in net GWP. Grain yield was significantly correlated positively with SOC and STN (p<0:05); ecosystem respiration was also significantly correlated withSWCand ST whileCH4 flux was highly correlated with ST (p<0:001). Crop yield and GHG responses to CA were controlled by soil hydrothermal and nutrient changes, thus improving these conditions through adoption of sustainable soil moisture improvement practices such as no-till, straw mulch, green manuring, contour ploughing and terracing can improve crop resilience to climate change and reduce GHG emissions in arid and semi-arid regions. [ABSTRACT FROM AUTHOR]

Clean room facilities are becoming more popular in both academic and industry settings, including low-and middle-income countries. This has led to an increased demand for cost-effective gas sensors to monitor air quality. Here we have developed a gas sensor using CoNiO 2 nanoparticles through combustion method. The sensitivity and selectivity of the sensor towards CO 2 were influenced by the structure of the nanoparticles, which were affected by the reducing agent (biofuels) used during synthesis. Among all reducing agents, urea found to yield highly crystalline and uniformly distributed CoNiO 2 nanoparticles, which when developed into sensors showed high sensitivity and selectivity for the detection of CO 2 gas in the presence of common interfering volatile organic compounds observed in cleanroom facilities including ammonia, formaldehyde, acetone, toluene, ethanol, isopropanol and methanol. In addition, the urea-mediated nanoparticle-based sensors exhibited room temperature operation, high stability, prompt response and recovery rates, and excellent reproducibility. Consequently, the synthesis approach to nanoparticle-based, energy efficient and affordable sensors represent a benchmark for CO 2 sensing in cleanroom settings., (Creative Commons Attribution license.)

The global ocean has taken up a large fraction of the CO2 released by human activities since the industrial revolution. Quantifying the oceanic anthropogenic carbon (Cant) inventory and its variability is important for predicting the future global carbon cycle. The detailed comparison of data-based and model-based estimates is essential for the validation and continued improvement of our prediction capabilities. So far, three global estimates of oceanic Cant inventory that are "data-based" and independent of global ocean circulation models have been produced: one based on the Δ C* method, and two that are based on constraining surface-to-interior transport of tracers, the TTD method and a maximum entropy inversion method (GF). The GF method, in particular, is capable of reconstructing the history of Cant inventory through the industrial era. In the present study we use forward model simulations of the Community Climate System Model (CCSM3.1) to estimate the Cant inventory and compare the results with the data-based estimates. We also use the simulations to test several assumptions of the GF method, including the assumption of constant climate and circulation, which is common to all the data-based estimates. Though the integrated estimates of global Cant inventories are consistent with each other, the regional estimates show discrepancies up to 50 %. The CCSM3 model underestimates the total Cant inventory, in part due to weak mixing and ventilation in the North Atlantic and Southern Ocean. Analyses of different simulation results suggest that key assumptions about ocean circulation and air-sea disequilibrium in the GF method are generally valid on the global scale, but may introduce errors in Cant estimates on regional scales. The GF method should also be used with caution when predicting future oceanic anthropogenic carbon uptake.

Nitrous oxide (N2O) is a powerful greenhouse gas increasing in atmospheric mixing ratio and linked to increasing amounts of reactive N in the environment, particularly fertilizer use in agriculture. The consequences of urbanization of agricultural land for global and regional N2O emissions are unclear, due to high spatial and temporal variability of fluxes from different ecosystems and relatively few studies of urban ecosystems. We measured fluxes and the stable isotope composition (δ 15N and δ 18O) of N2O over 1 year in urban (ornamental lawns and athletic fields) and agricultural (corn and vegetable fields) ecosystems near Los Angeles, California, United States. We found that urban landscapes (lawns and athletic fields) have annual N2O fluxes equal to or greater than agricultural fields. Fertilization rates of urban landscapes were equal to or greater than agricultural fields, with comparable N2O emissions factors. δ 15N and δ 18O of N2O varied widely in all ecosystems, and were not consistent with ecosystem type, season, soil moisture, or temperature. There was, however, a consistent response of δ 15N-N2O to pulses of N2O emission following fertilization, with an initial depletion in δ 15N relative to prefertilization values, then gradual enrichment to background values within about 1 week. Preliminary scaling calculations indicated that N2O emissions from urban landscapes are approximately equal to or greater than agricultural emissions in urbanized areas of southern California, which further implies that current estimates of regional N2O emissions (based on agricultural land area) may be too low.

Desert dust perturbs climate by directly and indirectly interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were increasing or decreasing desert dust in the global average. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere) over the 20th century to be −0.14 ± 0.11 W/m2 (1990–1999 vs. 1905–1914). The estimated radiative change due to dust is especially strong between the heavily loaded 1980–1989 and the less heavily loaded 1955–1964 time periods (−0.57 ± 0.46 W/m2), which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 °C. Model simulations also indicate strong regional shifts in precipitation and temperature from desert dust changes, causing 6 ppm (12 PgC) reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 PgC) of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and biogeochemistry, and our understanding of these changes and their impacts should continue to be refined.

Recent studies have revealed the qualitative and quantitative importance of the free gas emanations from aqueous environments and from soil surfaces in Romania. Interesting mixing zones of different gases can be observed on the boundary between the Miocene sedimentary deposits and Late Miocene volcaniclastics. This study presents the results of investigations of free carbondioxide and methane made in Corund area (Harghita County), at Dealul Melcului geological reserve, where a presumed methane seepage was described in the past. Measurements were performed using a closed chamber method. Our observations and result show the lack of methane emanations, while the maximum value for carbon-dioxide emanation was 458 g/m2/day.

Recent upward revisions in key sink/source terms for fixed nitrogen (N) in the oceans imply a short residence time and strong negative feedbacks involving denitrification and N fixation to prevent large swings in the ocean N inventory over timescales of a few centuries. We tested the strength of these feedbacks in a global biogeochemical elemental cycling (BEC) ocean model that includes water column denitrification and an explicit N fixing phytoplankton group. In the northern Indian Ocean and over longer timescales in the tropical Atlantic, we find strong stabilizing feedbacks that minimize changes in marine N inventory over timescales of ∼30–200 years. In these regions high atmospheric dust/iron inputs lead to phosphorus limitation of diazotrophs, and thus a tight link between N fixation and surface water N/P ratios. Maintenance of the oxygen minimum zones in these basins depends on N fixation driven export. The stabilizing feedbacks in other regions are significant but weaker owing to iron limitation of the diazotrophs. Thus Fe limitation appears to restrict the ability of N fixation to compensate for changes in denitrification in the current climate, perhaps leading the oceans to lose fixed N. We suggest that iron is the ultimate limiting nutrient leading to nitrogen being the proximate limiting nutrient over wide regions today. Iron stress was at least partially alleviated during more dusty, glacial times, leading to a higher marine N inventory, increased export production, and perhaps widespread phosphorus limitation of the phytoplankton community. The increased efficiency of the biological pump would have contributed to the glacial drawdown in atmospheric CO2.

Satellite remote sensing estimates of surface chlorophyll, temperature, wind speed, and sea ice cover are examined in the region of the Southern Ocean Iron Experiment (SOFeX). Our objectives are to place SOFeX into a regional context and highlight regional mesoscale spatial and monthly temporal variability. SOFeX fertilized two patches with iron, one south of the Antarctic Polar Front (PF) and one north of the PF but south of the Subantarctic Front (SAF). Satellite-observable phytoplankton blooms developed in both patches. The spring sea ice retreat near the south patch site was delayed in the 2001–2002 season, in turn delaying the naturally occurring, modest spring bloom in this region. Ambient surface chlorophyll concentrations for the area surrounding the southern patch during January 2002 are low (mean 0.26 mg/m3) compared with climatological January values (0.42 mg/m3). Regions east and west at similar latitudes exhibited higher mean chlorophyll concentrations (0.79 and 0.74 mg/m3, respectively). These modest phytoplankton blooms were likely stimulated by melting sea ice via changes in the light-mixing regime and release of iron and were smaller in magnitude than the iron-induced bloom within the SOFeX southern patch (>3 mg/m3). Iron inputs from melting ice may drive much of the natural spatial and temporal variability within the seasonal ice zone. Mean chlorophyll concentrations surrounding the SOFeX northern patch site were similar to climatological values during the SOFeX season. The northern patch was stretched into a long, thin filament along the southern boundary of the SAF, likely increasing the mixing/dilution rate with surrounding waters.

Effects of gas temperature and oxygen concentration on the soot formation of the axial jet laminar diffusion flame have been studied experimentally for the ambient gas mixtures of carbon-dioxide and oxygen. These data were compared to those for the ambient gas mixture of nitrogen and oxygen of 21%. The experiments showed that the flame heights for the mixture of carbon-dioxide and oxygen of 21% and that of nitrogen and oxygen 21% were about same and decreased with the increase of gas temperature. When the oxygen concentration was 21% in the ambient gas mixtures, the total soot volume for the ambient gas of nitrogen and oxygen were higher than that of carbon-dioxide and oxygen and increased with the increase of the gas temperature. When the ambient gases were the carbon-dioxide and oxygen mixtures, the total soot volume increased with the gas temperature for the fixed values of the oxygen concentration in the ambient gases. But, for the fixed ambient gas temperatures, the total soot volume increased with the increase of the oxygen concentration in the ambient gas and reached to a maximum, and then decreased slightly with the increase of the oxygen concentration. The variations of total soot volume were discussed by using the adiabatic flame temperatures for the experimental conditions. The plots of logarithm of the total soot volume for the inverse value of the adiabatic flame temperature show that the oxygen concentration has the strong effect on the total soot volume compared to the effect of the adiabatic flame temperature.

Copyright of Journal of University of Anbar for Pure Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]