196,065 research outputs found
Changes of gas metabolism, gas homeostasis and tissue respiration in rats during prolonged hypokinesia
The oxygen uptake and tissue gas homeostasis of restrained albinic rats remained relatively constant during a 60 day experiment. The gas metabolism in some tissues changed, and O2 consumption increased in the liver and decreased in the myocardium. Capacity for physical work was reduced by five times. Hypokinesia for 60 days resulted in a delay in the animals growth
Enhanced toluene removal using granular activated carbon and a yeast strain candida tropicalis in bubble-column bioreactors
The yeast strain Candida tropicalis was used for the biodegradation of gaseous toluene. Toluene was effectively treated by a liquid culture of C. tropicalis in abubble-column bioreactor, and the tolueneremoval efficiency increased with decreasing gas flow rate. However, toluene mass transfer from the gas-to-liquid phase was a major limitation for the uptake of toluene by C. tropicalis. The tolueneremoval efficiency was enhanced when granularactivatedcarbon (GAC) was added as a fluidized material. The GAC fluidized bioreactor demonstrated tolueneremoval efficiencies ranging from 50 to 82% when the inlet toluene loading was varied between 13.1 and 26.9 g/m3/h. The yield value of C. tropicalis ranged from 0.11 to 0.21 g-biomass/g-toluene, which was substantially lower than yield values for bacteria reported in the literature. The maximum elimination capacity determined in the GAC fluidized bioreactor was 172 g/m3/h at atoluene loading of 291 g/m3/h. Transient loading experiments revealed that approximately 50% of the toluene introduced was initially adsorbed onto the GAC during an increased loading period, and then slowly desorbed and became available to the yeast culture. Hence, the fluidized GAC mediated in improving the gas-to-liquid mass transfer of toluene, resulting in a high tolueneremoval capacity. Consequently, the GAC bubble-column bioreactor using the culture of C. tropicalis can be successfully applied for the removal of gaseous toluene
Does Leaf Position within a Canopy Affect Acclimation of Photosynthesis to Elevated CO2? . Analysis of a Wheat Crop under Free-Air CO2 Enrichment
Previous studies of photosynthetic acclimation to elevated CO2 have focused on the most recently expanded, sunlit leaves in the canopy. We examined acclimation in a vertical profile of leaves through a canopy of wheat (Triticum aestivum L.). The crop was grown at an elevated CO2 partial pressure of 55 Pa within a replicated field experiment using free-air CO2 enrichment. Gas exchange was used to estimate in vivo carboxylation capacity and the maximum rate of ribulose-1,5-bisphosphate-limited photosynthesis. Net photosynthetic CO2 uptake was measured for leaves in situ within the canopy. Leaf contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), light-harvesting-complex (LHC) proteins, and total N were determined. Elevated CO2 did not affect carboxylation capacity in the most recently expanded leaves but led to a decrease in lower, shaded leaves during grain development. Despite this acclimation, in situ photosynthetic CO2 uptake remained higher under elevated CO2. Acclimation at elevated CO2 was accompanied by decreases in both Rubisco and total leaf N contents and an increase in LHC content. Elevated CO2 led to a larger increase in LHC/Rubisco in lower canopy leaves than in the uppermost leaf. Acclimation of leaf photosynthesis to elevated CO2 therefore depended on both vertical position within the canopy and the developmental stage
High yield and high packing density porous carbon for unprecedented CO2 capture from the first attempt at activation of air-carbonized biomass
The first attempt at activation of air-carbonized carbon reveals unusual resistance to activation and unprecedentedly high yields (32â80 wt%) of high packing density (0.7â1.14 g cmâ3) microporous carbon dominated by 5.5â7 Ă
pores, which are just right for CO2 uptake (up to 5.0 mmol gâ1) at 1 bar and 25 °C. The high gravimetric uptake and packing density offer exceptional volumetric storage, and unprecedented performance for low pressure swing adsorption (PSA) with working capacity of 6â9 mmol gâ1 for a pure CO2 stream (6 to 1 bar) and 3â4 mmol gâ1 for flue gas (1.2 to 0.2 bar). The working capacity for vacuum swing adsorption (VSA) is attractive at 5.0â5.4 mmol gâ1 under pure CO2 (1.5 to 0.05 bar), and 1.8â2.2 mmol gâ1 for flue gas (0.3 to 0.01 bar). The pure CO2 volumetric working capacity breaks new ground at 246â309 g lâ1 (PSA) and 179â233 g lâ1 (VSA). For flue gas conditions, the working capacity is 120 to 160 g lâ1 (PSA). The performance of the activated air-carbonized carbons is higher than the best carbons and benchmark zeolites or MOFs
Microporous frameworks with conjugated Ï-electron skeletons for enhanced gas and organic vapor capture
Novel conjugated microporous frameworks based on adamantane (CMF-Ads) have been successfully synthesized under mild conditions. Eight-arm tetraphenyl âknotsâ and a conjugated Ï-electron skeleton endowed the target CMF-Ads with ultra-high thermal stability (up to 500âŻÂ°C), high surface area (up to 907âŻm2âŻgâ1), excellent CO2 uptake capacity of 15.13âŻwt % at 273âŻK and 1âŻbar, as well as superior organic vapor (benzene, hexane) adsorption. The ultra-high gas uptake capacity and selectivity of these CMF-Ads herein exceeds most conjugated microporous frameworks reported to date, highlighting their potential as materials for clean energy application
Metal-organic and covalent organic frameworks (MOFs and COFs) as adsorbents for environmentally significant gases (H2, CO2, and CH4)
A series of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) possessing
various functionalities, pore structures, and surface areas were evaluated for sorption and storage
properties of environmentally significant gases (H_2, CO_2, and CH_4). It was concluded that the gas
sorption behavior follows a general trend that materials with high surface area show enhanced gas
uptake performance. For example, MOF-177 (SA = 5200 m^2/g) captures 7.2 wt% of H_2 at 77 K and 19
wt% of CH_4 at 298 K. In addition, MOF-177 exhibits exceptionally high gravimetric CO_2 uptake up to
120 wt% at 298 K. Similarly, the gas storage capacity for COFs seems to follow the same trend and it is
determined by the apparent surface area. The architectural stability of both COFs and MOFs upon high
pressure H_2 and CH_4 gas sorption measurements were manifested by isotherms which reach saturation
without significant hysteresis
Development of Covalent Organic Polymer for Carbon Dioxide Capture
Natural gas has transformed to become one of the most important energy source globally surpassing w4orldâs oil demand due to the increase in energy demand and decreasing of conventional energy. With this increasing in energy demand, the oil and gas industry are forced to reevaluate previous reserve that seems economically unfeasible for processing. These reserves are abandoned due to high carbon dioxide content. Motivation towards conducting this study is due the unfeasibility of current conventional method for carbon dioxide capture in natural gas stream where they are unable to cater the high CO2 content from CO2 rich natural gas reservoirs. Therefore, the development of new alternative materials and technology is needed to overcome this problem.
The objective of this study is to synthesis and characterize covalent organic polymer (COP-1) for CO2 capture in natural gas stream. Development of COP-1 was chosen as the material due to its high CO2 uptake and its ability to withstand harsh hydrothermal conditions. However, current studies for COP-1 development are mainly focused towards removal of CO2 from flue gases. There are lack of information on its application in natural gas stream. Therefore, this study is focused on filling the gap for COP-1 application in natural gas industry.
Synthesis of COP-1in this study is done on a laboratory scale apparatus where the main raw materials for formation of COP-1 is by using Cyanuric chloride and Piperazine. Qualitative characterization of COP-1 conducted in this study is FTIR, XRD, and FESEM while the quantitative analysis includes the thermogravimetric analysis, BET surface area measurement, CO2 and CH4 uptake capacity and the hydrothermal stability.
Findings from this study shows promising outcome for the application of COP-1 in removal of CO2 from natural gas stream. Itâs significantly high CO2 uptake capacity and high stable under harsh hydrothermal conditions shows potential as alternative of current conventional method for CO2 removal from natural gas stream
The impact of post-synthetic linker functionalization of MOFs on methane storage: The role of defects
Natural gas is increasingly being viewed as one of the most viable alternatives to gasoline. However, its vehicular application will only be widespread if safe and high-capacity methane stores are developed. In this work, we report an over 33% increase in methane uptake on a post-synthetically modified metalâorganic framework. The underlying mechanism for this dramatic increase is due to lattice defects formed upon post-synthetic modification. This method may open new approaches to natural gas storage
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Energy prices, production
This paper investigates economic incentives influencing the adoption of energy saving technology by industry, namely, CHP in UK and Dutch manufacturing sectors. The empirical analysis is based on a cross sectional time series econometric model, and examines how industrial output and historical increases in the price of electricity relative to gas prices, spark the diffusion of CHP. Production and price elasticities are estimated across heterogeneous industrial groups. Using data for 13 manufacturing sectors the model shows that fuel cost savings and industry output impact significantly on CHP uptake. Model outcomes are found to differ depending on the period of estimation and the estimation period is key in determining the impact of gas price and purchased power prices on adoption of CHP
IMPACT OF TEMPERATURE AND FLUE GAS COMPONENTS ON MERCURY SPECIATION AND UPTAKE BY ACTIVATED CARBON SORBENTS
An experimental setup was built to simulate flue gas representative of coal fired power plants burning sub-bituminious powder river basin (PRB) coal. The impact of different flue gas constituents and bed temperature on mercury uptake capacity and mercury speciation were evaluated using a fixed bed epxerimental system. Two activated carbons were selected for the study: FGD activated carbon (Norit America Inc.) and a novel activated carbon manufactured by Corning Inc. After the experimental setup was tested and validated, evalauation of sorbents' performance was conducted using simulated PRB coal flue gas.A susbstantial increase in the mercury uptake capacity of both sorbents was observed in the absence of SO2 from the flue gas. Temeprature programed desorption (TPD) test on spent FGD sorbent revealed that mercury present on the surface of the spent sorbent was mostly in the elemental form. An instant breakthrough of mercury was observed with both sorbents when HCl was removed from the flue gas. This led to a significant decrease in the mercury adsorption capacity of both sorbents. Absence of water from the flue gas caused an increase in mercury uptake capacity and a decrease in mercury oxidation with both the sorbents. Removal of NO and NO2 had variable impact on different sorbent. Removal of NO or NO2 from the flue gas caused an increase in mercury uptake capacity of FGD sorbent. Removal of NO from the flue gas also led to an increase in mercury oxidation catalyzed by FGD sorbent. On the other hand, removal of NO or NO2 from PRB gas not only caused a decrease in the mercury uptake capacity of the Corning sorbent, but also led to a significant decrease in mercury oxidation catalyzed by this sorbent. A 100 °C increase in bed temperature (from 140 °C to 240 °C) caused an instant breakthrough of mercury with both sorbents under simulated PRB coal flue gas conditions. It also caused a significant decrease in the oxidation of mercury. Based on the findings of the study, a simplistic model explaining the mechanism for mercury uptake and oxidation by activated carbon through competition between Cl and SO2 for active sites on the surface of the activated carbon is proposed
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