Dioxide Ratio Research Articles

Comparison of solvent⿿wetted and kneaded l-sulpiride⿿loaded solid dispersions: Powder characterization and in vivo evaluation

The purpose of this study was to compare the powder properties, solubility, dissolution and oral absorption of solvent⿿wetted (SWSD) and kneaded (KNSD) l-sulpiride⿿loaded solid dispersions. The SWSD and KNSD were prepared with silicon dioxide, sodium laurylsulfate and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) using a spray dryer and high shear mixer, respectively. Their powder properties, solubility, dissolution and oral absorption were assessed compared to l-sulpiride powder. The drug in SWSD was in the amorphous state; however, in KNSD, it existed in the crystalline state. The SWSD with a drug/sodium laurylsulphate/TPGS/silicon dioxide ratio of 5/1/2/12 gave the higher drug solubility and dissolution compared to the KNSD with the same composition. The oral absorption of drug in the SWSD was 1.4 fold higher than the KNSD and 3.0 fold higher than the l-sulpiride powder (p<0.05) owing to better solubility and reduced crystallinity. Furthermore, the SWSD at the half dose was bioequivalent of commercial l-sulpiride⿿loaded product in rats. Thus, the SWSD with more improved oral absorption would be recommended as an alternative for the l-sulpiride⿿loaded oral administration.

Biogas upgrading and utilization from ICEs towards stationary molten carbonate fuel cell systems

ABSTRACTBiogas production from anaerobic digestion has increased rapidly in the last years, in many parts of the world, mainly due to its local scale disposition and to its potential on greenhouse gases (GHG) emissions mitigation. Biogas can be used as fuel for combined heat and power systems (CHP), in particular for internal combustion engines (ICEs). In recent investigations, fuel cells have been considered as alternative CHP systems. In the present article, two different energy conversion systems are compared: a 1.4 MW class MCFC system, running on pipeline natural gas, and an in situ ICE, running on biogas. In the first case, biogas is considered as a source fuel to obtain upgraded gas to be injected in the natural gas grid. In such scenario, the location of the fuel cell power plant is no longer strictly connected to the anaerobic digester site. Several energy balances are evaluated, considering different upgrading techniques and different biogas methane/carbon dioxide ratios.

Acute Responses of Functional Electrical Stimulation Cycling on the Ventilation-to-CO2 Production Ratio and Substrate Utilization After Spinal Cord Injury

BackgroundVentilation-to-carbon dioxide ratio is comparable with peak oxygen uptake in the prognosis of cardiovascular disorders. Currently, there are no established indices to determine the submaximal effects of functional electrical stimulation on cardiovascular performance in persons with spinal cord injury. ObjectiveTo determine the effects of an acute bout of functional electrical stimulation-lower extremity cycling on ventilation, carbon dioxide production, ventilation-to-carbon dioxide ratio, and substrate utilization in people with motor complete spinal cord injury. DesignObservational cross-sectional design. SettingClinical laboratory setting. ParticipantsTen individuals with motor complete spinal cord injury. MethodsParticipants were allowed to cycle until fatigue. The effects of functional electrical stimulation on ventilation, carbon dioxide production, ventilation-to-carbon dioxide ratio, and substrate utilization were measured with a portable metabolic cart (COSMED K4b2). Body composition was determined with bioelectrical impedance. ResultsResting and warm-up ventilation were 8.15 ± 3.5 L/min and 8.15 ± 2.8 L/min, respectively. Functional electrical stimulation increased ventilation significantly (14.5 ± 6.4 L/min), which remained significantly elevated (13.3 ± 4.3 L/min) during the recovery period. During resting and warm-up phases, the ventilation-to-carbon dioxide ratios were 41 ± 4.8 and 38 ± 5.4, respectively. Functional electrical stimulation decreased the ventilation-to-carbon dioxide ratio significantly to 31.5 ± 4, which remained significantly reduced during the recovery period (34.4 ± 3). Functional electrical stimulation relied primarily on carbohydrate utilization (188 ± 160 g/day to 574 ± 324 g/day; P = .001) with no changes in fat utilization (77.5 ± 28 g/day to 93.5 ± 133.6 g/day; P = .7) from resting to exercise periods. Significant relationships were noted between carbohydrate utilization during functional electrical stimulation and carbon dioxide (r = 0.98; P = .00010) production. The percentage whole body fat-free mass was negatively related to the exercise ventilation-to-carbon ratio (r = −0.66; P = .045). ConclusionsAn acute bout of functional electrical stimulation resulted in a significant drop in the ventilation-to-carbon ratio, accompanied with a reliance on carbohydrate utilization and a diminished capacity to utilize fat as a substrate. Fat-free mass may be associated with a decrease in ventilation to carbon dioxide ratio and an increase in carbohydrate utilization in persons with spinal cord injury.

High-Pressure Phase Behavior of Poly(l-lactic acid), Trichloromethane, and Carbon Dioxide Ternary Mixture Systems

In this study, the phase behavior of a poly(l-lactic acid) (M = 312 000, polydispersity 2.189)–trichloromethane–carbon dioxide ternary system was measured using a variable volume view cell at pressures up to 34.0 MPa and temperatures between (313.15 K and 363.15) K at an interval of 10 K. Bubble and cloud point pressures were determined as functions of the trichlomethane-to-carbon dioxide ratio, concentration of poly(l-lactic acid) (1.0, 2.0, and 3.0 wt %), and temperature. The hybrid equation of state for the supercritical CO2-polymer system combined with the van der Waals one-fluid mixing rule was used for correlation of the experimental results. The three binary parameters of this system were optimized by the simplex method algorithm.

Sulfur dioxide disproportionation for sulfur based thermochemical energy storage

Sulfur dioxide disproportionation is one of three reaction steps that make up the sulfur based thermochemical cycle used for thermal energy storage of concentrated solar power. The characteristics of this reaction were studied using thermodynamic modeling and laboratory measurements. Modeling results showed full disproportionation can only be achieved at pressure. The reaction driving force is enhanced by system pressure but declines with increasing temperature. Appropriate water to sulfur dioxide ratio also drives disproportionation. Batch experiments showed that reaction rate increases with temperature. A catalyst survey identified homogenous iodides as catalysts that can improve the reaction rate by up to twenty times while increasing the apparent extent of disproportionation. The dependence of disproportionation rate on sulfuric acid concentration was established via constant pressure experiments. Means to recover the iodide catalyst from sulfuric acid and molten sulfur for reuse were demonstrated. Modeling and test results were used to establish a design concept for a sulfur dioxide disproportionation reactor system capable of rapidly generating sulfur as required for the sulfur based thermochemical energy storage technology.

Carbon dioxide emission standards for U.S. power plants: An efficiency analysis perspective

On June 25, 2013, President Obama announced his plan to introduce carbon dioxide emission standards for electricity generation. This paper proposes an efficiency analysis approach that addresses which emission rates (and standards) would be feasible if the existing generating units adopt best practices. A new efficiency measure is introduced and further decomposed to identify different sources' contributions to emission rate improvements. Estimating two Data Envelopment Analysis (DEA) models – the well-known joint production model and the new materials balance model – on a dataset consisting of 160 bituminous-fired generating units, we find that the average generating unit's electricity-to-carbon dioxide ratio is 15.3% below the corresponding best-practice ratio. Further examinations reveal that this discrepancy can largely be attributed to non-discretionary factors and not to managerial inefficiency. Moreover, even if the best practice ratios could be implemented, the generating units would not be able to comply with the EPA's recently proposed carbon dioxide standard.

Production of sustainable methane from renewable energy and captured carbon dioxide with the use of Solid Oxide Electrolyzer: A thermodynamic assessment

A possible pathway for renewable and sustainable methane production from captured carbon dioxide, water (or seawater) and renewable electricity is proposed and analysed. The proposed system includes Solid Oxide Electrolyzer Cell combined with ex-situ methane synthesis reactor comprising Sabatier, Methanation and Water-Gas Shift reactions. A well validated electrochemical model is used to describe the behaviour of the electrolyzer for steam/carbon dioxide co-electrolysis. The methane synthesis reactor is modelled by a set of equations based on thermodynamic equilibrium reaction constants. Effects of current density, temperature, pressure and initial steam to carbon dioxide ratio on system performance are analysed and their effects are discussed. It is found that a simple, single-pass system without heat recuperation could achieve a maximum overall energy efficiency of 60.87% (based on lower heating value), a maximum electrical energy efficiency of 81.08% (based on lower heating value), and a maximum amount of methane production of ∼1.52 Nm3 h−1 m−2 of electrolyzer. It is also found that conversion of ∼100% captured carbon dioxide is possible in the proposed system.

Elevated carbon monoxide to carbon dioxide ratio in the exhaled breath of mice treated with a single dose of lipopolysaccharide.

Analysis of volatile organic chemicals in breath holds promise for noninvasive diagnosis and monitoring of patients, but investigation of this in experimental mouse models has been limited. Of particular interest is endogenous production of carbon monoxide as a biomarker of inflammation and, more particularly, during sepsis. Using a nose-only collection procedure for unanesthetized individual adult mice and sensitive gas chromatography of carbon monoxide (CO) and carbon dioxide (CO2) of sampled breath, we investigated the responses of mice to one-time injections with different doses of purified Escherichia coli lipopolysaccharide. Two strains of mice were examined: BALB/c and C3H, including an endotoxin-resistant mutant (HeJ) as well as the wild type (HOuJ). The CO to CO2 ratio increased in a dose-responsive manner within hours in treated BALC/c mice but not control mice. The CO/CO2 values declined to the range of control mice within 48-72 h after the injection of lipopolysaccharide. Breath CO/CO2 values correlated with systemic inflammation biomarkers in serum and heme oxygenase-1 gene expression in blood. C3H/HOuJ mice, but not the HeJ mice, had similar increases of the CO/CO2 ratio in response to the endotoxin. Carbon monoxide concentrations in exhaled breath of at least 2 strains of mice increase in response to single injections of endotoxin. The magnitude of increase was similar to what was observed with a bacteremia model. These findings with an experimental model provide a rationale for further studies of normalized CO concentrations in human breath as an informative biomarker for staging and monitoring of sepsis.

Comparison of ambient airborne PM2.5, PM2.5 absorbance and nitrogen dioxide ratios measured in 1999 and 2009 in three areas in Europe

Epidemiological studies often use nitrogen dioxide (NO2) or proximity to roads to characterize exposure to more health-relevant pollutants (e.g., fine particles or black carbon aerosol) in vehicle exhaust. Due to the introduction of diesel-soot filters, particle-to-NO2 ratios may have decreased, but little information is available about these ratios over time. Our study aim was to evaluate the change in particle-to-NO2 ratios between 1999 and 2009. We compared data collected during measurement campaigns in 1999 and 2009 from Munich, the Netherlands, and Stockholm. Traffic-impacted and urban and regional background sites were studied during each campaign. The same pollutants were measured in each campaign (mass concentration of particles ≤2.5 microns in diameter (PM2.5), PM2.5 absorbance (a marker for black carbon), and NO2) using the same methods except for NO2: Palmes tubes were used in 1999 and Ogawa badges in 2009. Both NO2 methods were validated against side-by-side chemiluminescence measurements. The levels of PM2.5 absorbance and PM2.5 were significantly lower (p<0.05) in 2009 at traffic and urban background sites in Stockholm, but only slightly lower in Munich and the Netherlands. In contrast, NO2 levels were not significantly different in the three areas in 2009 compared to 1999. Statistically-significant decreases between 1999 and 2009 pollutant ratios in the Netherlands (PM2.5 absorbance/NO2 and PM2.5/NO2) and in Stockholm (PM2.5 absorbance/NO2 and PM2.5 absorbance/PM2.5) were observed. Smaller decreases in these ratios were observed in Munich. The contrast between traffic and urban background locations was larger in 2009 than 1999 for NO2, whereas it was smaller for PM2.5 absorbance and PM2.5. The lower PM2.5 absorbance/NO2 and PM2.5/NO2 ratios in 2009 is likely explained by the introduction of oxidative particle filters for diesel vehicles that reduce particles but produce NO2. The changed contrasts may affect estimates of health effects related to NO2 as a marker of proximity to roads.

Reduction Characteristics of Carbon Dioxide Using a Plasmatron

To decompose carbon dioxide, which is a representative greenhouse gas, a 3-phase gliding arc plasmatron device was designed and manufactured to examine the decomposition of CO2, either alone or in the presence of methane with and without water vapour. The changes in the amount of carbon dioxide feed rate, the methane to carbon dioxide ratio, the steam to carbon dioxide ratio, and the methane to steam ratio were used as the parameters. The carbon dioxide conversion rate, energy decomposition efficiency (EDE), carbon monoxide and hydrogen selectivity, and produced gas concentration were also investigated. The maximum values of the carbon dioxide conversion rate, which is a key indicator of carbon dioxide decomposition, in different cases were compared. The maximum carbon dioxide conversion rate was 12.3 % when pure carbon dioxide was supplied; 34.5 % when methane was injected as a reforming additive; 7.8 % when steam was injected as a reforming additive; and 43 % when methane and steam were injected together. Therefore, this could be explained that the methane-and-steam injection showed the highest carbon dioxide decomposition, showing low EDE as 0.01 L/min W. Furthermore, the plasma produced carbon-black was compared with commercial carbon-black chemicals through Raman spectroscopy, surface area measurement and scanning electron microscopy. It was found that the carbon-black that was produced in this study has the high conductivity and large specific surface area. Our product makes it suitable for special electric materials and secondary battery materials applications.

Carbon black/manganese dioxide composites synthesized by sonochemistry method for electrochemical supercapacitors

Carbon black (CB)/manganese dioxide (MnO2) composites are prepared by a sonochemical method from an aqueous solution of potassium bromate and manganese sulfate. The morphology, structure, physical properties and specific surface area of samples are examined by scanning electron microscopy (SEM), transition electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) method. Electrochemical properties of the synthesized composites with different carbon to manganese dioxide ratios are studied by cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS). Electrochemical data for the composites obtained in the 0.5M Na2SO4 solutions show the capacitive behavior in the voltage window of 0–1.0V versus Ag/AgCl. When the mass ratio of MnO2 composite material is 65wt% the specific capacitance of CB–MnO2 composite calculated from the CV curves is 313Fg−1 at the scan rate of 5mVs−1 whereas specific capacitance for pure γ-MnO2 prepared in the same conditions is 257Fg−1 at the scan rate of 5mVs−1. The CB–MnO2 composites show higher energy density than pure γ-MnO2. Also, they show a long cycle life in the potential range of 0–1.0V and retain 78.3% of initial capacitance over 1000 cycles.

Bromine monoxide / sulphur dioxide ratios in relation to volcanological observations at Mt. Etna 2006–2009

Abstract. Over a 3-yr period, from 2006 to 2009, frequent scattered sunlight DOAS measurements were conducted at Mt. Etna at a distance of around 6 km downwind from the summit craters. During the same period and in addition to these measurements, volcanic observations were made by regularly visiting various parts of Mt. Etna. Here, results from these measurements and observations are presented and their relation is discussed. The focus of the investigation is the bromine monoxide/sulphur dioxide (BrO / SO2) ratio, and its variability in relation to volcanic processes. That the halogen/sulphur ratio can serve as a precursor or indicator for the onset of eruptive activity was already proposed by earlier works (e.g. Noguchi and Kamiya 1963; Menyailov, 1975; Pennisi and Cloarec, 1998; Aiuppa et al., 2002). However, there is still a limited understanding today because of the complexity with which halogens are released, depending on magma composition and degassing conditions. Our understanding of these processes is far from complete, for example of the rate and mechanism of bubble nucleation, growth and ascent in silicate melts (Carroll and Holloway, 1994), the halogen vapour-melt partitioning and the volatile diffusivity in the melt (Aiuppa et al., 2009). With this study we aim to add one more piece to the puzzle of what halogen/sulphur ratios might tell about volcanic activities. Our data set shows an increase of the BrO / SO2 ratio several weeks prior to an eruption, followed by a decline before and during the initial phase of eruptive activities. Towards the end of activity or shortly thereafter, the ratio increases to baseline values again and remains more or less constant during quiet phases. To explain the observed evolution of the BrO / SO2 ratio, a first empirical model is proposed. This model suggests that bromine, unlike chlorine and fluorine, is less soluble in the magmatic melt than sulphur. By using the DOAS method to determine SO2, we actually observe most of the emitted sulphur of Mt.~Etna. Regarding bromine, however, we are aware that by determining only the bromine monoxide (BrO) radical we might just observe a small or even a variable fraction of the total emitted bromine, which is most probable originally in the form of HBr. Therefore, we present first studies to justify the assumption that, despite the disadvantage just mentioned, the BrO / SO2 ratio can nevertheless serve as a new parameter to indicate the state of a volcano, when measurements are conducted under certain, but rather convenient, conditions.

Analysis of redox responses during TNT transformation by Clostridium acetobutylicum ATCC 824 and mutants exhibiting altered metabolism

The transformation of trinitrotoluene (TNT) by several mutant strains of Clostridium acetobutylicum has been examined to analyze the maximal rate of initial transformation, determine the effects of metabolic mutations of the host on transformation rate, and to assess the cell metabolic changes brought about during TNT transformation. Little difference in the maximal rate of TNT degradation in early acid phase cultures was found between the parental ATCC 824 strain and strains altered in the acid forming pathways (phosphotransacetylase, or butyrate kinase) or in a high-solvent-producing strain (mutant B). This result is in agreement with the previous findings of a similar degradation rate in a degenerate strain (M5) that had lost the ability to produce solvent. A series of antisense constructs were made that reduced the expression of hydA, encoding the Fe-hydrogenase, or hydE and hydF, genes encoding hydrogenase maturating proteins. While the antisense hydA strain had only ∼30 % of the activity of wild type, the antisense hydE strain exhibited a TNT degradation rate around 70 % that of the parent. Overexpression of hydA modestly increased the TNT degradation rate in acid phase cells, suggesting the amount of reductant flowing into hydrogenase rather than the hydrogenase level itself was a limiting factor in many situations. The redox potential, hydrogen evolution, and organic acid metabolites produced during rapid TNT transformation in early log phase cultures were measured. The redox potential of the acid-producing culture decreased from -370 to -200 mV immediately after addition of TNT and the hydrogen evolution rate decreased, lowering the hydrogen to carbon dioxide ratio from 1.4 to around 1.1 for 15 min. During the time of TNT transformation, the treated acidogenic cells produced less acetate and more butyrate. The results show that during TNT transformation, the cells shift metabolism away from hydrogen formation to reduction of TNT and the resulting effects on cell redox cofactors generate a higher proportion of butyrate.

Interrelation of anode and cathode processes in electrochemical carbon oxidation in a fuel cell with molten carbonate electrolyte

The object to be investigated is a fuel cell with a free molten carbonate electrolyte, which ensures direct electrochemical oxidation of solid hydrocarbons. The polarization characteristics of anode and cathode fuel cell assemblies, and also composition and gas release rate of gaseous products of anode reactions are studied. It is shown that the maximum voltages in the open cell circuit are obtained when the oxygen-carbon dioxide ratio in the cathode gas mixture corresponds to stoichiometric reaction coefficients that ensure replenishment of ions in electrolyte. However, the maximum current density values were obtained with a low carbon dioxide content. It is found that at high current values, anode potential fluctuations are observed. It is shown that carbon monoxide is the product of anode processes, along with carbon dioxide. The carbon monoxide content grows with temperature. The carbon dioxide content grows with increasing current in the fuel cell and with growing carbon dioxide content in cathode gases. The release rate of carbon oxidation products nonlinearly depends on the current value in the fuel cell. It is concluded that there is interrelation between the mass-exchange processes in the fuel cell, which is determined by the balance between cathode gas incoming into the reaction zone, the number of molecules generated during fuel oxidation, molecule dissolution and diffusion into the cathode region, and also the amount of gas released in the form of bubbles.

Effect of O2:CO2 ratio on the primary metabolism of Chlamydomonas reinhardtii

High oxygen:carbon dioxide ratios may have a negative effect on growth and productivity of microalgae. To investigate the effect of O₂ and CO₂ concentrations and the ratio between these on the metabolism of Chlamydomonas reinhardtii we performed turbidostat experiments at different O₂:CO₂ ratios. These experiments showed that elevated O₂ concentrations and the corresponding increase in the ratio of O₂:CO₂ common in photobioreactors led to a reduction of growth and biomass yield on light with 20-30%. This is most probably related to the oxygenase activity of Rubisco and the resulting process of photorespiration. Using metabolic flux modeling with measured rates for each experiment we were able to quantify the ratio of the oxygenase reaction to the carboxylase reaction of Rubisco and could demonstrate that photorespiration indeed can cause the reduction in biomass yield on light. The calculated ratio of the oxygenase reaction to the carboxylase reaction was 16.6% and 20.5% for air with 2% CO₂ and 1% CO₂, respectively. Thus photorespiration has a significant impact on the biomass yield on light already at conditions common in photobioreactors (air with 2% CO₂).

Registro de la relación isotópica de carbono en la paleoflora de la Formación Ischigualasto (Triásico Superior), noroeste Argentino: implicaciones paleoatmosféricas

FLORAL CARBON ISOTOPIC RECORD, ISCHIGUALASTO FORMATION (UPPER TRIASSIC), NORTHWEST OF ARGENTINA: PALEOATMOSPHERIC IMPLICATIONS. The Upper Triassic Ischigualasto Formation carries a well-preserved flora in the mid-upper portion (~225 Ma Carnian). This contribution is the first detailed study of the isotopic ratios (i.e. 13 Carbon vs. Carbon 12 δ 13 C) and the ratio of carbon and nitrogen (C/N) applied to Argentinean Triassic flora. The aim of this study is to chemically characterize this Triassic flora and provide data for this portion of the Pangea to be used in chemostratigraphic correlation as well as to analyze changes in the global carbon cycle. A total of 97 samples were analyzed, mainly of cuticle. The isotopic values of the samples indicate minimal diagenetic or taphonomic alteration, validating the interpretations reached. A detailed analysis of the isotopic values of this paleoflora documents minor variation in δ 13 C characteristic of differences in levels of local water-stress and of floral composition variations. Discarding minor variations, a mean value of the carbon isotope ratio of paleoflora Ischigualasto Formation of - 25.4‰ was obtained within a range from -27.4 to -23.7‰, according to the average values of C3 plants. This value is consistent with the δ 13 C values reported for terrestrial plant fossils from other Upper Triassic successions worldwide, however is enriched by about 3 ‰ with respect to the Middle Triassic plants. This migration towards more positive values of δ 13 C coincide with those observed in marine carbonates and paleosols during the same time-interval, indicating a possible disturbance in the carbon cycle during Early Mesozoic. Finally, a paleo-atmosphere isotopic composition of -6.1‰ was estimated, which differs by ~ 0.5 ‰ from that inferred using the marine carbonate proxy for the ocean-reservoir. This difference can be the response of the oxygen to carbon dioxide ratio in the paleo-atmosphere, which produces differences in the plant isotopic fractionation, diagenesis in the marine carbonates or hydric-stress alteration of the Ischigualasto flora.

Specific characteristics of molten carbonate fuel cell in realization of electrochemical coal oxidation

The test object was a fuel cell with free molten carbonate electrolyte providing realization of direct electrochemical oxidation of solid hydrocarbons. This study involved the effect of the fuel type and dispersion as well as cathode reagent gas mixture composition to the fuel cell functional parameters. The used fuels were dispersed and monolithic graphite, anthracite, and jet coal specimens. The effect of oxygen/carbon dioxide ratio on the mixture fed to cathode to the open circuit cell voltage and achieved current density levels was studied with respect to interrelation of the processes taking place in the cathode and anode units of the fuel cell. A correlation was noted between the specific fuel cell characteristics and hydrogen content in the fuel material. The highest level of current density and specific power was recorded for jet coal characterized with high hydrogen content. The different characteristics of monolithic and dispersed fuel specimens were accounted for by the effect of losses at contacts between particles. Achievement of high current density and specific power was demonstrated by using dispersed coal fuel.

Methane and carbon dioxide ratio in excreted air for quantification of the methane production from ruminants

This technical note presents a simple, fast, reliable and cheap method to estimate the methane (CH 4) production from animals by using the CH 4 and carbon dioxide (CO 2) concentrations in air near the animals combined with an estimation of the total CO 2 production from information on intake of metabolizable energy or heat producing units. By using portable equipment to analyse the air in stables or near individual animals it is possible to calculate the proportion of the carbon that is not metabolized to CO 2, but excreted as the greenhouse gas CH 4. The CH 4/CO 2 proportion in itself gives useful information and can be seen on the spot when measuring. A more detailed use of the data in combination with feedstuff analysis can be used to estimate the quantitative CH 4 production from the animals as the CO 2 excretion can be calculated from the intake of metabolizable energy minus the energy in the weight gain or milk produced, as there is close relation between heat production and CO 2 excretion. Moreover, data from air analysis in livestock buildings shows a close relation between CO 2 production and the amount of heat producing units (HPU) in a stable, which also in this situation makes CO 2 a good marker for the quantitative excretion of gases and thereby a marker to be used for the calculation of the quantitative CH 4 production from livestock.

Optimization of fluid bed formulations of metoprolol granules and tablets using an experimental design

Background: The granulation process of a metoprolol tartrate (very difficult to process active pharmaceutical ingredient) formulation in laboratory scale fluid bed equipment was studied. Aim: To study the influence of two formulation factors and three process parameters on the characteristics of the granules and subsequently of the tablets, in the case of fluid bed granulating of a powder mix containing metoprolol tartrate. Method: In order to study the influence of formulation factors (binder solution concentration and the silicon dioxide ratio) and process factors (atomizing pressure, the length of the final drying phase, and the inlet air temperature) on the technological and pharmaceutical properties of granules and tablets, a fractional factorial experimental design resolution V+ with five factors and two levels was used. Results: A high atomizing pressure allows us to obtain fine granules with large poly-dispersion index and granules with high tapped and untapped density, tablets with short disintegration time, short mean dissolution time, and a high percentage metoprolol tartrate release in the first 15 minutes. A lower concentration of binder solution allows us to obtain granules with very good flow properties, tablets which have no tendency to stick on the set punch of tabletting machine and no capping. The final drying time of granules has an influence only on the granule's relative humidity and tapped and untapped density, without any influence on the granules flow properties. Conclusions: The practical experimental results from the formulation processed in optimal working conditions were close to the predicted ones by Modde 6.0 software.

Simulation of CO 2 absorption into aqueous DEA using a hollow fiber membrane contactor: Evaluation of contactor performance

The absorption of carbon dioxide from a carbon dioxide/nitrogen mixture into an aqueous diethanolamine solution (as an example of a typical amine solution) using a hollow fiber contactor is simulated to obtain the effect of several operational variables (liquid velocity, fiber length, lean carbon dioxide loading, and amine concentration) on productivity and amine solution to carbon dioxide ratio. The model employed is based on the ones commonly used in the literature for this process, but it was significantly improved as some simplifications usually considered (irreversible reaction, low carbon dioxide loading, constant partition coefficient of molecular carbon dioxide between liquid and gas phases, absence of bicarbonate and carbonate anions) have been removed. The effect of these simplifications on the simulated results is quite important. A simple performance parameter study is proposed to evaluate the contactor's performance, keeping the feed gas concentration and the fraction of carbon dioxide removal constant. This procedure leads to optimum values of the liquid velocity and lean carbon dioxide loading, while the performance parameter improves with amine concentration.