Low CO2 Levels Research Articles

Accumulation of CO and other fuel impurities in the anode recirculation loop of a fuel cell: A zero dimensional transient model

The use of impure hydrogen in polymer electrolyte fuel cells could potentially improve the economics of their implementation. Here, a zero-dimensional transient model is formulated to simulate the operational effects of fuel impurities such as CH4 and CO within an anode recirculation loop with a continuous small bleed. Inert impurities are observed to accumulate until a steady state concentration is reached where entry and exit rates are balanced, for instance resulting in a 20-fold increase in concentration with a 5% bleed rate. With CO, electro-oxidation of adsorbed CO also contributes to CO removal in addition to that lost by bleed. The overall energy conversion efficiency is found to be limited to ~60% of the pure hydrogen value without further mitigation for CO impurity levels of 10–80 ppm. If pulsed oxidation is used as a mitigation method, the efficiency can be improved to ~90% of the pure hydrogen value. When air bleed is used as a mitigation method, accumulation of nitrogen limits the efficiency to about 80% of pure hydrogen. While oxygen cross-over from the cathode can prevent CO accumulation when the fuel contains low levels of CO (~1 ppm), it has minimal effect at higher CO concentrations (>10 ppm).

Effect of modified atmosphere packaging materials on physicochemical and selected enzyme activities of Agaricus bernardii

AbstractAgaricus bernardii was a typical mushroom in Inner Mongolia, China, with high metabolic rate, respiration rate and dehydration. The storage time of A. bernardii was very short. It was necessary to prolong postharvest storage. This study was to determine the physicochemical and selected enzyme activities of A. bernardii packed with different barrier packaging materials. The materials concluded low‐density polyethylene (PE), poly(butylene adipate‐co‐terephthalate)/poly(l‐lactic acid) (PBAT/PLLA), PBAT/PLLA/hydrophobic silica (0.5S SiO2) and polyamide/PE, respectively. The performance analysis of the materials, gas composition, sensory quality, physicochemical properties, nutritional quality, and index of senility of the mushrooms were measured. The results indicated that the low O2 (<1%) and moderate CO2 levels (4–7%) in 0.5S SiO2 film maintained a high level of soluble protein, soluble sugar, ascorbic acid, and phenolic contents, inhibited the increase of malondialdehyde, increased the antioxidant enzymes activities of peroxidase and decreased the enzymes activities of polyphenol oxidase. The quality index of the mushroom packed in the 0.5S SiO2 film remained a good condition and kept the market value after 15 days of storage.Practical applicationsThe biodegradable poly(butylene adipate‐co‐terephthalate)/poly(l‐lactic acid) (PBAT/PLLA/SiO2) film has a suitable water vapor permeability and CO2/O2 permeability radio, which could establish a suitable steady‐state inner atmosphere and maintain quality of mushrooms. Compared with the other films, PBAT/PLLA/SiO2 film kept the market value after 15 days of storage and the application of 0.5S SiO2 film could have potential on maintaining the quality of postharvest of Agaricus bernardii. Moreover, expected to replace the nondegradable food packaging material.

The Influence of Elite Networks on Green Policy Making

This article analyzes the relationship between the policy networks and the success of renewable energy and emission reduction policies. Arguing that strong connections between typologically different groups of elites are essential for good policies, the analysis looks at the Twitter community structure of the ministers in 34 countries. The results of the network study indicate that the success of renewable energy and CO2 emission reduction policy implementation is strongly related to the community structure in social networks of ministers. Looser network structures within policy communities and an abundance of relatively stronger connections between them are associated with higher renewable energy consumption and also lower CO2 levels, thus possibly with better policies. A case study on seven Nordic and Northern European countries complements and reinforces the theoretical expectations about deliberative policy making.Related ArticlesSabag‐Ben Porat, Chen, Azi Lev‐On, and Sam Lehman‐Wilzig. 2020. “Silent Partners: How Politicians' Facebook Communication with Constituents is Mediated.” Politics & Policy 48 (3): 550‐569. https://doi.org/10.1111/polp.12352Rowe, Andrew D., and David E. Pitfield. 2019. “The Challenge of Social Media Incorporation: A Case Study of HACAN Clearskies.” Politics & Policy 47 (4): 775‐806. https://doi.org/10.1111/polp.12319Tanaka, Yugo, Andrew Chapman, Tetsuo Tezuka, and Shigeki Sakurai. 2020. “Multiple Streams and Power Sector Policy Change: Evidence from the Feed‐In Tariff Policy Process in Japan.” Politics & Policy 48 (3): 464‐489. https://doi.org/10.1111/polp.12357[Correction added on December 17, 2020 after first online publication: The citation “Ben‐Porat, Chen Sabag, Azi Lev‐On, and Sam Lehman‐Wilzig. 2020” was edited to “Sabag‐Ben Porat, Chen, Azi Lev‐On, and Sam Lehman‐Wilzig. 2020“ to reflect correct spelling.]

Effect of controlled atmosphere storage on the quality attributes and volatile organic compounds profile of dragon fruit (Hylocereus undatus)

Abstract The short shelf-life of dragon fruit is one of the inhibiting factors for the export of Vietnamese dragon fruit to distant markets. This study aimed at finding an optimal controlled atmosphere (CA) storage condition for dragon fruit by studying the effect of CA storage on fruit quality and its volatile organic compounds profile. Dragon fruit were stored at 4 different CA conditions and at ambient air as a control treatment. At harvest and at day 10, 20, 30, 40 and 50, different fruit quality attributes were measured, including scale color, firmness, electrolyte leakage, soluble solids content, total acidity, respiration rate, and disease score. Sensory evaluation and aroma analysis were also performed. The results revealed that CA storage significantly reduced the yellowing of the scales and maintained fruit acidity. The CA condition of 2 kPa O2 + 5 kPa CO2 at 6 °C seemed to be optimal for dragon fruit storage. Normal senescence caused the loss of many volatiles, while low O2 and high CO2 level had an opposite impact on the concentration of fermentation products. However, these volatile changes did not significantly impact on the sensory quality of the fruit during storage.

Abstract 318: Association Carbon Dioxide Level During Cardiopulmonary Resuscitation with Neurological Outcome After Out-of-hospital Cardiac Arrests

Background: Little evidence exists to guide appropriate ventilation strategies during CPR. We aimed to investigate the association between carbon dioxide (CO2) pressure measured on hospital arrival from those who were receiving ongoing resuscitation and neurological outcome after out-of-hospital cardiac arrest (OHCA). Method: This nationwide hospital-based prospective observational study (The JAAM-OHCA registry) carried out between June, 2014 and December, 2017 in Japan. From this registry, we included adult OHCA patients aged ≥18 years with blood gas sampled on hospital arrival during CPR. The main exposure was CO2 level in blood gas analysis during CPR. Based on the CO2 level on hospital arrival, included patients were classified into four quartiles (Q1-Q4) defined as Q1 (<66.0 mmHg), Q2 (66.1-87.2 mmHg), Q3 (87.3-113.5 mmHg), and Q4 (≥113.6 mmHg). The primary outcome of this study was one-month survival with favorable neurological outcome defined by cerebral performance category 1 or 2. We adjusted for potential confounders with multivariable logistic regression analysis. Results: During the study period, a total of 21,137 patients were included in our analysis. The overall proportion of favorable neurological outcome was 1.0% (207/21137). The highest proportion of favorable neurological outcome was observed in the Q1 group (2.4% [140/5244]), followed by Q2 (0.7% [37/5284]), Q3 (0.4% [21/5296]), and Q4 (0.2% [9/5313]). In the multivariable logistic regression analysis, we found that the Q4 group had the significantly lower proportion of favorable neurological outcome than the Q1 group (adjusted odds ratio 0.25; 95% confidence interval 0.16-0.55). The adjusted probability of favorable neurological outcome decreased in a stepwise fashion across increasing quartiles (P<0.001). Conclusion: This study observed the association between lower CO2 level on hospital arrival and favorable neurological outcome after OHCA in a dose-dependent manner.

Modelling the effects of CO2 on C3 and C4 grass competition during the mid-Pleistocene transition in South Africa

Palaeoenvironmental reconstructions of the interior of South Africa show a wetter environment than today and a non-analogous vegetation structure in the Early Pleistocene. This includes the presence of grasses following both C3 and C4 photosynthetic pathways, whereas C3 grasses decline after the mid-Pleistocene transition (MPT, c. 1.2–0.8 Ma). However, the local terrestrial proxy record cannot distinguish between the potential drivers of these vegetation changes. In this study we show that low glacial CO2 levels, similar to those at the MPT, lead to the local decline of C3 grasses under conditions of decreased water availability, using a vegetation model (LPX) driven by Atmosphere–Ocean coupled General Climate Model climate reconstructions. We modelled vegetation for glacial climates under different levels of CO2 and fire regimes and find evidence that a combination of low CO2 and changed seasonality is driving the changes in grass cover, whereas fire has little influence on the ratio of C3:C4 grasses. Our results suggest the prevalence of a less vegetated landscape with limited, seasonal water availability, which could potentially explain the much sparser mid-Pleistocene archaeological record in the southern Kalahari.

Implementation of a free smoking-cessation program in a Lebanese academic medical center

INTRODUCTIONDespite the exceptionally high prevalence of tobacco use in Lebanon, few cessation programs exist. The American University of Beirut (AUB) developed one of the first smoking-cessation programs in the country in 2015, and the program became free-of-charge to patients in 2018. The program offers initial visit(s) with a primary care provider, in-person and/or telephone counseling, acupuncture, and medications.METHODSWe assessed patient characteristics, treatments used, and patient outcomes in the first year of implementing the free smoking-cessation program, compared to the original program. We compared 87 smokers who initiated treatment in the free program with 47 patients in the original program.RESULTSAt baseline, smokers in the free program were younger, smoked fewer cigarettes per day, and had lower CO levels than smokers in the original program. At 1 month follow-up, 72.9% were abstinent in the free program, compared with 42.2% in the original program (p<0.001). Smokers who had ≥2 primary care visits and those who had ≥1 acupuncture visits had higher rates of abstinence at 1 month and those who were prescribed bupropion had higher rates of abstinence at 12 months.CONCLUSIONSImplementation of the free smoking cessation program demonstrates preliminary efficacy, with telephone support offering potential for scalability.

Role of C4 carbon fixation in Ulva prolifera, the macroalga responsible for the world\u2019s largest green tides

Most marine algae preferentially assimilate CO2 via the Calvin-Benson Cycle (C3) and catalyze HCO3− dehydration via carbonic anhydrase (CA) as a CO2-compensatory mechanism, but certain species utilize the Hatch-Slack Cycle (C4) to enhance photosynthesis. The occurrence and importance of the C4 pathway remains uncertain, however. Here, we demonstrate that carbon fixation in Ulva prolifera, a species responsible for massive green tides, involves a combination of C3 and C4 pathways, and a CA-supported HCO3− mechanism. Analysis of CA and key C3 and C4 enzymes, and subsequent analysis of δ13C photosynthetic products showed that the species assimilates CO2 predominately via the C3 pathway, uses HCO3− via the CA mechanism at low CO2 levels, and takes advantage of high irradiance using the C4 pathway. This active and multi-faceted carbon acquisition strategy is advantageous for the formation of massive blooms, as thick floating mats are subject to intense surface irradiance and CO2 limitation.

Potential of Anthill Soil as a Pozzolan in Concrete

Cement is the most utilised construction material and the second most consumed commodity in the world after water. It has been reported that the heavily energy-intensive processes that are involved in its production account for about 7 to 10 % of the total global anthropogenic carbon dioxide (CO2), which is the main cause of climate change; and are also expensive economically. Energy and cost efficiency can however be achieved by reducing on the amount of clinker, and in its place utilising pozzolans, which require less process heating and emit lower levels of CO2. This research aimed to provide an original contribution to the body of knowledge by investigating Anthill Soil (AHS) for pozzolanic properties. Cement was replaced in concrete with AHS by weight using 5% increments by weight, from 0 to 30% at the point of need. Durability was investigated using the water absorption and sulfate tests. Results of the chemical analysis by X-Ray Diffraction (XRD) showed that AHS contained the chemical composition required for pozzolans, and the compressive strengths achieved were for classes that are listed by standards as being durable and suitable for structural applications. The behaviour of AHS in workability, density, gain in compressive strength over time, water absorption and sulfate tests were also consistent with the characteristics of pozzolans, leading to a conclusion that it may be suitable for use as a pozzolan to improve the properties of concrete, reduce on the harmful effects of cement production to the environment and lower the overall cost of concrete, allowing for the construction of low cost buildings.

Effects of CO2 dilution on partially premixed CH4-air flames in swirl and bluff body stabilized combustor

The effect of CO2 dilution on the flame characteristics and pollutant emission of a partially premixed CH4-air flame in a confined bluff body and swirl influenced flowfield is investigated using optical and laser diagnostic methods. The non-premixed burner produced a converging-diverging flowfield at the burner exit and a lifted flame is produced at all test cases, with an upstream movement of the flame with decreasing global equivalence ratios (ϕg). Based on variations in ϕg, two flame stabilization modes – bluff body influenced and swirl stabilized – with a transition mode in-between is observed for the cases with (flame FB) and without dilution (flame FM). The characteristics of the heat release zone are influenced by dilution, with the FB flames being longer and also less intense when compared to FM flames. Pollutant measurement at 30 mm downstream from the combustor exit highlighted the ultra-low NOx capability of the IIST-GS2 burner. CO2 dilution leads to a reduction in NOx emission due to both thermal and chemical effects. For ϕg ≥ 0.7 extreme low levels of CO and unburned hydrocarbons (UHC) are observed for both cases. For ϕg ≤ 0.6 the dramatic increase of both CO and UHC maybe due to the lower flame temperatures and shorter flame zone residence times, respectively.

Interactive effects of increased temperature, elevated pCO2 and different nitrogen sources on the coccolithophore Gephyrocapsaoceanica.

As a widespread phytoplankton species, the coccolithophore Gephyrocapsaoceanica has a significant impact on the global biogeochemical cycle through calcium carbonate precipitation and photosynthesis. As global change continues, marine phytoplankton will experience alterations in multiple parameters, including temperature, pH, CO2, and nitrogen sources, and the interactive effects of these variables should be examined to understand how marine organisms will respond to global change. Here, we show that the specific growth rate of G. oceanica is reduced by elevated CO2 (1000 μatm) in -grown cells, while it is increased by high CO2 in -grown ones. This difference was related to intracellular metabolic regulation, with decreased cellular particulate organic carbon and particulate organic nitrogen (PON) content in the and high CO2 condition compared to the low CO2 condition. In contrast, no significant difference was found between the high and low CO2 levels in cultures (p > 0.05). The temperature increase from 20°C to 25°C increased the PON production rate, and the enhancement was more prominent in cultures. Enhanced or inhibited particulate inorganic carbon production rate in cells supplied with relative to was observed, depending on the temperature and CO2 condition. These results suggest that a greater disruption of the organic carbon pump can be expected in response to the combined effects of increased / ratio, temperature, and CO2 level in the oceans of the future. Additional experiments conducted under nutrient limitation conditions are needed before we can extrapolate our findings to the global oceans.

Aridity-driven decoupling of δ13C between pedogenic carbonate and soil organic matter

Abstract Pedogenic carbonate is an invaluable archive for reconstructing continental paleoclimate and paleoecology. The δ13C of pedogenic carbonate (δ13Cc) has been widely used to document the rise and expansion of C4 plants over the Cenozoic. This application requires a fundamental presumption that in soil pores, soil-respired CO2 dominates over atmospheric CO2 during the formation of pedogenic carbonates. However, the decoupling between δ13Cc and δ13C of soil organic matter (δ13CSOM) have been observed, particularly in arid regions, suggesting that this presumption is not always valid. To evaluate the influence of atmospheric CO2 on soil δ13Cc, here we performed systematic δ13C analyses of paleosols across the Chinese Loess Plateau, with the sample ages spanning three intervals: the Holocene, the Late Pleistocene, and the mid-Pliocene warm period. Our paired δ13Cc and δ13CSOM data reveal broadly divergent trending patterns. Using a two-component CO2-mixing model, we show substantial incorporations of atmospheric CO2 (up to 60%) into soil pore space during carbonate precipitation. This result readily explains the enrichment of δ13Cc and its divergence from δ13CSOM. As a consequence, δ13C of pedogenic carbonates formed under semiarid and/or arid conditions are largely driven by regional aridity through its control on soil CO2 composition, and thus cannot be used to evaluate the relative abundance of C3 versus C4 plants. Nonetheless, these carbonates can be applied for atmospheric CO2 reconstructions, even for periods with low CO2 levels.

Optimal ventilator settings after return of spontaneous circulation.

To describe current practice, recent advances in knowledge and future directions for research related to the post return of spontaneous circulation (ROSC) ventilatory management of cardiac arrest patients. Out-of-hospital cardiac arrest (OHCA) is a major public health problem with an estimated incidence of approximately one per 1000 persons per year. A priority of intensive care management of resuscitated OHCA patients is to reduce secondary reperfusion injury. Most OHCA patients are mechanically ventilated. Most of these require mechanical ventilation as they are unconscious and for oxygen (O2) management and carbon dioxide (CO2) control. Low levels of O2 and CO2 following OHCA is associated with poor outcome. Recently, very high fraction of inspired oxygen has been associated with poor outcomes and elevated CO2 levels have been associated with improved neurological outcomes. Moreover, it is increasingly being appreciated that the ventilator may be a tool to adjust physiological parameters to enhance the chances of favourable outcomes. Finally, ventilator settings themselves and the adoption of protective ventilation strategies may affect lung-brain interactions and are being explored as other avenues for therapeutic benefit. Current evidence supports the targeting of normal arterial O2 and CO2 tensions during mechanical ventilation following ROSC after cardiac arrest. Use of protective lung strategies during mechanical ventilation in resuscitated cardiac arrest patients is advocated. The potential therapeutic benefits of conservative O2 therapy, mild hypercapnia and the optimal ventilator settings to use post-ROSC period will be confirmed or refuted in clinical trials.

Linking the Dynamic Response of the Carbon Dioxide-Concentrating Mechanism to Carbon Assimilation Behavior in Fremyella diplosiphon.

Cyanobacteria use a carbon dioxide (CO2)-concentrating mechanism (CCM) that enhances their carbon fixation efficiency and is regulated by many environmental factors that impact photosynthesis, including carbon availability, light levels, and nutrient access. Efforts to connect the regulation of the CCM by these factors to functional effects on carbon assimilation rates have been complicated by the aqueous nature of cyanobacteria. Here, we describe the use of cyanobacteria in a semiwet state on glass fiber filtration discs-cyanobacterial discs-to establish dynamic carbon assimilation behavior using gas exchange analysis. In combination with quantitative PCR (qPCR) and transmission electron microscopy (TEM) analyses, we linked the regulation of CCM components to corresponding carbon assimilation behavior in the freshwater, filamentous cyanobacterium Fremyella diplosiphon Inorganic carbon (Ci) levels, light quantity, and light quality have all been shown to influence carbon assimilation behavior in F. diplosiphon Our results suggest a biphasic model of cyanobacterial carbon fixation. While behavior at low levels of CO2 is driven mainly by the Ci uptake ability of the cyanobacterium, at higher CO2 levels, carbon assimilation behavior is multifaceted and depends on Ci availability, carboxysome morphology, linear electron flow, and cell shape. Carbon response curves (CRCs) generated via gas exchange analysis enable rapid examination of CO2 assimilation behavior in cyanobacteria and can be used for cells grown under distinct conditions to provide insight into how CO2 assimilation correlates with the regulation of critical cellular functions, such as the environmental control of the CCM and downstream photosynthetic capacity.IMPORTANCE Environmental regulation of photosynthesis in cyanobacteria enhances organismal fitness, light capture, and associated carbon fixation under dynamic conditions. Concentration of carbon dioxide (CO2) near the carbon-fixing enzyme RubisCO occurs via the CO2-concentrating mechanism (CCM). The CCM is also tuned in response to carbon availability, light quality or levels, or nutrient access-cues that also impact photosynthesis. We adapted dynamic gas exchange methods generally used with plants to investigate environmental regulation of the CCM and carbon fixation capacity using glass fiber-filtered cells of the cyanobacterium Fremyella diplosiphon We describe a breakthrough in measuring real-time carbon uptake and associated assimilation capacity for cells grown in distinct conditions (i.e., light quality, light quantity, or carbon status). These measurements demonstrate that the CCM modulates carbon uptake and assimilation under low-Ci conditions and that light-dependent regulation of pigmentation, cell shape, and downstream stages of carbon fixation are critical for tuning carbon uptake and assimilation.

CO2 drawdown and cooling at the onset of the Great Oxidation Event recorded in 2.45 Ga paleoweathering crust

The Archean atmosphere is thought to have been devoid of oxygen but, instead, containing high concentrations of greenhouse gases, such as CO2 and possibly CH4, that were required to keep the Earth surface environments warm enough for maintenance of liquid water under faint-young-Sun conditions. Earlier studies have suggested that the CO2 concentrations must have been as high as over 1000 times present atmospheric levels (PAL) to overcome the effects of weaker solar luminosity. However, more recent studies of Precambrian paleosols imply existence of at least tenfold-lower, but still high pCO2 levels. The appearance of minute amounts of atmospheric O2 at the transition of Archean and Proterozoic is well documented, however, the bulk composition of the atmosphere and its dynamics at this crucial time is still widely debated. Different paleoclimate proxies of the ~2.45 Ga Kuksha paleoweathering crust suggest its formation in a cool, temperate climate. Paleoatmospheric pCO2 estimates by geochemical and isotopic mass-balance models suggest remarkably low paleoatmospheric CO2 levels, with the best guess estimates of atmospheric CO2 between 1 and 10 PAL. We speculate that the Kuksha paleoweathering crust either predates, or partly overlaps with, the onset of Huronian glaciation and corresponds to a time interval of low CO2 level during the first recorded large glaciation in Earth history.

Variability in yeast invertase activity determines the extent of fructan hydrolysis during wheat dough fermentation and final FODMAP levels in bread

Consumption of fructan-containing cereal products is considered beneficial for most people, but not for those suffering from irritable bowel syndrome (IBS), as they should avoid the consumption of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (acronym: FODMAP). Controlling fructan levels in cereal products is not trivial. However, controlling yeast invertase-mediated hydrolysis of fructan during dough fermentation might offer a handle to modulate fructan concentrations. In this work, the variability in invertase activity and substrate specificity in an extensive set of industrial Saccharomyces cerevisiae strains is investigated. Analysis showed a high variability in the capacity of these strains to hydrolyse sucrose and fructo-oligosaccharides. Industrial yeast strains with a high activity towards fructo-oligosaccharides efficiently reduced wheat grain fructans during dough fermentation to a final fructan level of 0.3% dm, whereas strains with a low invertase activity yielded fructan levels around 0.6% dm. The non-bakery strains produced lower levels of CO2 in fermenting dough resulting in lower loaf volumes. However, CO2 production and loaf volume could be increased by the addition of 3% glucose. In conclusion, this study shows that variation in yeast invertase activity and specificity can be used to modulate the fructan content in bread, allowing the production of low FODMAP breads, or alternatively, breads with a higher soluble dietary fibre content.

New Insight Into Pathogenicity and Secondary Metabolism of the Plant Pathogen Penicillium expansum Through Deletion of the Epigenetic Reader SntB.

Penicillium expansum is one of the most harmful post-harvest pathogens of pomaceous fruits and the causal agent of blue rot disease. During infection, P. expansum produces the toxic secondary metabolites patulin and citrinin that can impact virulence and, further, render the fruit inedible. Several studies have shown that epigenetic machinery controls synthesis of secondary metabolites in fungi. In this regard, the epigenetic reader, SntB, has been reported to govern the production of multiple toxins in Aspergillus species, and impact virulence of plant pathogenic fungi. Here we show that deletion of sntB in P. expansum results in several phenotypic changes in the fungus including stunted vegetative growth, reduced conidiation, but enhanced germination rates as well as decreased virulence on Golden Delicious apples. In addition, a decrease in both patulin and citrinin biosynthesis in vitro and patulin in apples, was observed. SntB positively regulates expression of three global regulators of virulence and secondary metabolism (LaeA, CreA, and PacC) which may explain in part some of the phenotypic and virulence defects of the PeΔsntB strain. Lastly, results from this study revealed that the controlled environmental factors (low temperatures and high CO2 levels) to which P. expansum is commonly exposed during fruit storage, resulted in a significant reduction of sntB expression and consequent patulin and citrinin reduction. These data identify the epigenetic reader SntB as critical factor regulated in post-harvest pathogens under storage conditions and a potential target to control fungal colonization and decaying of stored fruit.

Involvement of abscisic acid, ABI5, and PPC2 in plant acclimation to low CO2.

Phosphoenolpyruvate carboxylase (PEPC) plays a pivotal role in the photosynthetic CO2 fixation of C4 plants. However, the functions of PEPCs in C3 plants are less well characterized, particularly in relation to low atmospheric CO2 levels. Of the four genes encoding PEPC in Arabidopsis, PPC2 is considered as the major leaf PEPC gene. Here we show that the ppc2 mutants suffered a growth arrest when transferred to low atmospheric CO2 conditions, together with decreases in the maximum efficiency of PSII (Fv/Fm) and lower levels of leaf abscisic acid (ABA) and carbohydrates. The application of sucrose, malate, or ABA greatly rescued the growth of ppc2 lines under low CO2 conditions. Metabolite profiling analysis revealed that the levels of glycine and serine were increased in ppc2 leaves, while the abundance of photosynthetic metabolites was decreased under these conditions. The transcript levels of encoding enzymes involved in glycine or serine metabolism was decreased in ppc2 in an ABI5-dependent manner. Like the ppc2 mutants, abi5-1 mutants had lower photosynthetic rates and Fv/Fm compared with the wild type under photorespiratory conditions (i.e. low CO2 availability). However, the growth of these mutants was similar to that of the wild type under non-photorespiratory (low O2) conditions. The constitutive expression of ABI5 prevented the growth arrest of ppc2 lines under low CO2 conditions. These findings demonstrate that PPC2 plays an important role in the acclimation of Arabidopsis plants to low CO2 availability by linking photorespiratory metabolism to primary metabolism, and that this is mediated, at least in part, through ABA- and ABI5-dependent processes.

TEPA impregnation of electrospun carbon nanofibers for enhanced low-level CO2 adsorption

The CO2 adsorption selectivity of plain activated carbon nanofibers (ANF) is generally low. For enhancement, nitrogen functionalities favorable for CO2 adsorption are usually tethered to the ANF. In the current study, we adopted chemical impregnation using 0.5 wt% tetraethylenepentamine (TEPA) solution as an impregnant. To enhance the impregnation of TEPA further, preliminary oxidation of the nanofibers with 70% HNO3 was conducted. The effects of HNO3 and TEPA treatments on the modified ANFs were investigated for physical (using N2 monosorb, thermogravimetric analyzer, scanning electron microscopy) and chemical (X-ray photoelectron spectrometer) changes. From the results, we found that although TEPA impregnation reduced the specific surface area and pore volume of the ANFs (from 673.7 and 15.61 to 278.8 m2/g and 0.284 cm3/g, respectively), whereas the HNO3 pre-oxidation increased the number of carboxylic groups on the ANF. Upon TEPA loading, pyridinic nitrogen was tethered and further enhanced by pre-oxidation. The surface treatment cumulatively increased the amine content from 5.81% to 13.31%. Consequently, the final adsorption capacity for low (0.3%) and pure CO2 levels were enhanced from 0.20 and 1.89 to 0.33 and 2.96 mmol/g, respectively. Hence, the two-step pre-oxidation and TEPA treatments were efficient for improved CO2 affinity.

Assessment of Air Pollutants Using Time Series Models in Some Selected Locations of Bauchi Metropolis, Bauchi State, Nigeria.

Gaseous samples were collected from Nov.2019 – Feb. 2020 from three (3) sampling points designated New GRA (NGRA), Railway Market (RM), and Nasarawa Jahum Street (NJS), 2km – 4 km apart in Bauchi metropolis. Control samples were also collected from Alkaleri town about 62 kilometres away from the study area. Samplings were carried out in cold and dry seasons using the Gasman detectors to assess the pollutants under investigation. Out of the four criteria air pollutants analysed (CO2, CO, NO2, and SO2) Carbon (ii) oxide had the highest concentration 1.69 ppm (±0.02).While Carbon (iv) oxide had the lowest concentration 0.05 ppm (±0.01). However, CO2, and CO are within the permissible limits of FEPA (2001) and USEPA (2008), The results obtained were subjected to statistical analysis to test the strength of the relationship between the variables with Pearson or product – moment correlation and at 95% confidence level or p – value 0.05, a very strong linear correlation exist between these variables as r - value ranged from 0.985 – 0.988. Predictive Time-Series models were developed using Minitab computer – installed software, for the pollutants concentrations obtained from datasets collected from the sampling sites. Fitted Time-Series models were obtained and expressed as Y = a + b A— T (Linear Trend Model). The locations with high and low concentration levels of CO2 and CO are 0.289ppm and 0.408ppm NGRA, 0.289ppm and 0.510ppm RM and 0.425ppm and 4.930ppm Streets respectively were all found to be simple linear trend with time.