Total Mole Fraction Research Articles

Characteristics of greenhouse gas concentrations derived from ground-based FTS spectra at Anmyeondo, South Korea

Abstract. Since the late 1990s, the meteorological observatory established in Anmyeondo (36.5382° N, 126.3311° E, and 30 m above mean sea level) has been monitoring several greenhouse gases such as CO2, CH4, N2O, CFCs, and SF6 as a part of the Global Atmosphere Watch (GAW) Program. A high resolution ground-based (g-b) Fourier transform spectrometer (FTS) was installed at this observation site in 2013 and has been operated within the frame work of the Total Carbon Column Observing Network (TCCON) since August 2014. The solar spectra recorded by the g-b FTS cover the spectral range 3800 to 16 000 cm−1 at a resolution of 0.02 cm−1. In this work, the GGG2014 version of the TCCON standard retrieval algorithm was used to retrieve total column average CO2 and CH4 dry mole fractions (XCO2, XCH4) and from the FTS spectra. Spectral bands of CO2 (at 6220.0 and 6339.5 cm−1 center wavenumbers, CH4 at 6002 cm−1 wavenumber, and O2 near 7880 cm−1 ) were used to derive the XCO2 and XCH4. In this paper, we provide comparisons of XCO2 and XCH4 between the aircraft observations and g-b FTS over Anmyeondo station. A comparison of 13 coincident observations of XCO2 between g-b FTS and OCO-2 (Orbiting Carbon Observatory) satellite measurements are also presented for the measurement period between February 2014 and November 2017. OCO-2 observations are highly correlated with the g-b FTS measurements (r2 = 0.884) and exhibited a small positive bias (0.189 ppm). Both data set capture seasonal variations of the target species with maximum and minimum values in spring and late summer, respectively. In the future, it is planned to further utilize the FTS measurements for the evaluation of satellite observations such as Greenhouse Gases Observing Satellite (GOSAT, GOSAT-2). This is the first report of the g-b FTS observations of XCO2 species over the Anmyeondo station.

Thermo-physicochemical investigation of molecular interactions in binary combination (dimethyl carbonate + methyl benzoate)

To probe the nature of interaction and its deeds with temperature in the binary combination (dimethyl carbonate + methyl benzoate), the density (ρ)/speed of sound (u) be established for the total mole fraction array at T = (308.15, 313.15 and 318.15) K and at atmospheric pressure. Sign with magnitude of evaluated excess molar volume ( $$V_{\text{m}}^{\text{E}}$$ ) was inspected and comprehensive analysis elucidated not only pervasiveness of strong molecular interactions between molecules but also its transform with temperature. Additional, strong interactions are properly hold up by partial and excess partial molar volume ( $$\overline{V}_{\text{m}}$$ , $$\overline{V}_{\text{m}}^{\text{E}}$$ , $$\overline{V}_{\text{m}}^{{{\text{E}},\infty }}$$ ). Additionally, relative association (R A ), Lennard-Jones repulsive power (n), excess isentropic compressibility ( $$\kappa_{\text{s}}^{\text{E}}$$ ), partial and their excess partial molar isentropic compressibility ( $$\overline{K}_{\text{m}}$$ , $$\overline{K}_{\text{m}}^{\text{E}}$$ ), excess values of isobaric thermal expansion coefficient ( $$\alpha_{\text{P}}^{\text{E}}$$ ), isothermal compressibility ( $$k_{\text{T}}^{\text{E}}$$ ), intermolecular free length ( $$L_{\text{f}}^{\text{E}}$$ ), acoustic impedance (Z E), ultrasonic speed (u E) were evaluated and confirmed the deductions of $$V_{\text{m}}^{\text{E}}$$ . By Redlich–Kister equation, standard deviations are computed through coefficients for excess parameters. At T = 308.15 K, $$V_{\text{m}}^{\text{E}}$$ is correlated by theories of Prigogine–Flory–Patterson (PFP)/topology/Soave–Redlich–Kwong (SRK)/Peng–Robinson (PR) cubic equation of states; prophesied first-order derivatives of thermodynamic potentials; using semi-empirical equations, excess chemical potential/activity coefficients/theoretical speeds are estimated and correlated. Further, microscopic molecular properties are assessed at all temperatures by Sehgal’s equations on nonlinear relations.

CO2 capture in lignin-derived and nitrogen-doped hierarchical porous carbons

Nitrogen-doped and hierarchical porous carbons were synthesized from lignin precursor by KOH and NH3 activation with BET surface area of 1631–2922 m2/g. X-ray photoelectron spectroscopy (XPS) revealed 5.6–7.1 at.% nitrogen with predominantly pyridinic, amino and pyrrolic/pyridonic type of functionality. Maximum CO2 adsorption capacity at 298 K and 273 K and pressure upto 760 torr (1 bar) was found to be 5.48 and 8.6 mmol/g respectively, which is higher than that of majority of nitrogen-doped carbons, reported in literature. Ideal Adsorbed Solution Theory (IAST)-based selectivity for CO2/N2 revealed that selectivity increases with the increase in nitrogen content. IAST calculations were also employed to calculate the binary adsorption isotherms to simulate mixed gas adsorption for CO2 and N2 as a function of total pressure and mole fraction of CO2 in the gas mixture. Continuous CO2 adsorption-desorption studies for 10 cycles revealed that all the nitrogen-doped carbons retained its working capacity at the end of the cycles. Finally, a breakthrough study for (10/90) CO2/N2 mixture in a dynamic column experiment confirmed a physical separation of the two components. The overall results suggest that nitrogen-doped carbons from lignin can be used as potential adsorbents for CO2 capture purposes.

Global methane emission estimates for 2000–2012 from CarbonTracker Europe-CH<sub>4</sub> v1.0

Abstract. We present a global distribution of surface methane (CH4) emission estimates for 2000–2012 derived using the CarbonTracker Europe-CH4 (CTE-CH4) data assimilation system. In CTE-CH4, anthropogenic and biospheric CH4 emissions are simultaneously estimated based on constraints of global atmospheric in situ CH4 observations. The system was configured to either estimate only anthropogenic or biospheric sources per region, or to estimate both categories simultaneously. The latter increased the number of optimizable parameters from 62 to 78. In addition, the differences between two numerical schemes available to perform turbulent vertical mixing in the atmospheric transport model TM5 were examined. Together, the system configurations encompass important axes of uncertainty in inversions and allow us to examine the robustness of the flux estimates. The posterior emission estimates are further evaluated by comparing simulated atmospheric CH4 to surface in situ observations, vertical profiles of CH4 made by aircraft, remotely sensed dry-air total column-averaged mole fraction (XCH4) from the Total Carbon Column Observing Network (TCCON), and XCH4 from the Greenhouse gases Observing Satellite (GOSAT). The evaluation with non-assimilated observations shows that posterior XCH4 is better matched with the retrievals when the vertical mixing scheme with faster interhemispheric exchange is used. Estimated posterior mean total global emissions during 2000–2012 are 516 ± 51 Tg CH4 yr−1, with an increase of 18 Tg CH4 yr−1 from 2000–2006 to 2007–2012. The increase is mainly driven by an increase in emissions from South American temperate, Asian temperate and Asian tropical TransCom regions. In addition, the increase is hardly sensitive to different model configurations ( < 2 Tg CH4 yr−1 difference), and much smaller than suggested by EDGAR v4.2 FT2010 inventory (33 Tg CH4 yr−1), which was used for prior anthropogenic emission estimates. The result is in good agreement with other published estimates from inverse modelling studies (16–20 Tg CH4 yr−1). However, this study could not conclusively separate a small trend in biospheric emissions (−5 to +6.9 Tg CH4 yr−1) from the much larger trend in anthropogenic emissions (15–27 Tg CH4 yr−1). Finally, we find that the global and North American CH4 balance could be closed over this time period without the previously suggested need to strongly increase anthropogenic CH4 emissions in the United States. With further developments, especially on the treatment of the atmospheric CH4 sink, we expect the data assimilation system presented here will be able to contribute to the ongoing interpretation of changes in this important greenhouse gas budget.

Thermodynamic Properties of Iron Melts with Titanium, Zirconium, and Hafnium

The literature data on the enthalpies of mixing and thermodynamic activities of Fe–Ti, Fe–Zr, and Fe–Hf liquid alloys are summarized. It is shown that the thermodynamic properties of these systems are characterized by significant negative deviations from the ideal behavior. In the framework of the associated solution model, the composition and temperature dependences of the thermodynamic functions of mixing for the Fe–Ti, Fe–Zr, and Fe–Hf systems are described. The temperature dependence of the thermodynamic properties of the considered systems is characterized by increase in negative deviations from the ideality with decreasing temperature and increasing thermodynamic stability of supercooled melts. Analysis of the degree of short-range order in the system melts, estimated as the total mole fraction of associates Σxass at the glass transition temperature, allows us to successfully interpret the known composition ranges of glass transition for the Fe–Zr and Fe–Hf melts and predict the composition range of glass transition for the Fe–Ti melts.

Theoretical Investigation on the Properties of R744/R290 Mixtures

At present, an interesting research is to find promising environmentally-friendly refrigerants in auto-cascade refrigeration cycle. This paper proposed a refrigerant mixture of R744 and R290 due to its zero ozone depletion potential and negligible global warming potential. The properties of R744, R290 and the mixtures refrigerant were analyzed. And performances comparisons between R744, R290, R22 and R134a were investigated based on the simulation data. Then, the vapor-liquid phase equilibrium properties of mixture were calculated. And the conversion relations of total mole fraction, vapor phase mole fraction, liquid phase mole fraction, quality, equilibrium temperature and pressure were systematically analyzed. The results show that R744 and R290 are potential refrigerant. But each pure refrigerant has obvious disadvantage, it is a good choice that R744 and R290 are mixed together into non-azeotropic mixture, which is suitable for auto-cascade refrigeration cycle due to a large temperature glide during the phase changing.

Seasonal variability of stratospheric methane: implications for constraining tropospheric methane budgets using total column observations

Abstract. Global and regional methane budgets are markedly uncertain. Conventionally, estimates of methane sources are derived by bridging emissions inventories with atmospheric observations employing chemical transport models. The accuracy of this approach requires correctly simulating advection and chemical loss such that modeled methane concentrations scale with surface fluxes. When total column measurements are assimilated into this framework, modeled stratospheric methane introduces additional potential for error. To evaluate the impact of such errors, we compare Total Carbon Column Observing Network (TCCON) and GEOS-Chem total and tropospheric column-averaged dry-air mole fractions of methane. We find that the model's stratospheric contribution to the total column is insensitive to perturbations to the seasonality or distribution of tropospheric emissions or loss. In the Northern Hemisphere, we identify disagreement between the measured and modeled stratospheric contribution, which increases as the tropopause altitude decreases, and a temporal phase lag in the model's tropospheric seasonality driven by transport errors. Within the context of GEOS-Chem, we find that the errors in tropospheric advection partially compensate for the stratospheric methane errors, masking inconsistencies between the modeled and measured tropospheric methane. These seasonally varying errors alias into source attributions resulting from model inversions. In particular, we suggest that the tropospheric phase lag error leads to large misdiagnoses of wetland emissions in the high latitudes of the Northern Hemisphere.

Evaluation of the carbon isotopic effects of NDIR and CRDS analyzers on atmospheric CO2 measurements

Non-dispersive infrared (NDIR) and cavity ring-down spectroscopy (CRDS) CO2 analyzers use 12CO2 isotopologue absorption lines and are insensitive to all or part of other CO2-related isotopologues. This may produce biases in CO2 mole fraction measurements of a sample if its carbon isotopic composition deviates from that of the standard gases being used. To evaluate and compare the effects of carbon isotopic composition on NDIR and CRDS CO2 analyzers, we prepared three test sample air cylinders with varying carbon isotopic abundances and calibrated them against five standard cylinders with ambient carbon isotopic composition using CRDS and NDIR systems. We found that the CO2 mole fractions of the sample cylinders measured by G1301 (CRDS) were in good agreement with those measured by LoFlo (NDIR). The CO2 values measured by both instruments were higher than that of a CO2 isotope measured by G2201i (CRDS) analyzer for a test cylinder with depleted carbon isotopic composition δ13C =-36.828‰, whereas no obvious difference was found for other two test cylinders with δ13C=-8.630‰ and δ13C=-15.380‰, respectively. According to the theoretical and experimental results, we concluded that the total CO2 mole fractions of samples with depleted isotopic compositions can be corrected on the basis of their 12CO2 values calibrated by standard gases using LoFlo and G1301 if the δ13C and δ18O values are known.

Dissociation Temperatures of Mixed Semiclathrate Hydrates Formed with Tetrabutylammonium Bromide Plus Tetrabutylammonium Chloride

Dissociation temperatures of mixed tetrabutylammonium bromide (TBAB) + tetrabutylammonium chloride (TBAC) semiclathrate hydrates were determined by using the DSC technique. The system was measured in five groups with a fixed total mole fraction (x = 0.0100, 0.0200, and 0.0337), TBAB mole fraction (xTBAB = 0.0370) or TBAC mole fraction (xTBAC = 0.0337). The obtained results demonstrated that at a given x, the dissociation temperatures of mixed (TBAB + TBAC) semiclathrate hydrates were all higher than that of pure TBAB hydrate, and the maximum dissociation temperature appeared at xTBAB/x = 0.25 instead of xTBAB/x = 0 or 1 (corresponding to pure TBAC or TBAB hydrate). In addition, for systems with fixed xTBAB or xTBAC, TBAC gained the control of forming TBAC semiclathrate hydrate preferentially.

Thermodynamic properties of α-terpineol over the range from T → (0 to 345) K

In the present research, the temperature dependence of heat capacity \( C_{{\text{p}\text{,m}}}^{\text{o}} = f\left( T \right) \) of α-terpineol has been measured for the first time between T = (6 and 345) K in the precision adiabatic vacuum calorimeter. The temperature and enthalpy of fusion of α-terpineol and the total mole fraction of impurities have been determined. The experimental results have been used to calculate the standard thermodynamic functions \( C_{{\text {p}\text{,m}}}^{\text{o}} /R,\;\Delta_{\text{0}}^{\text {T}} H_{\text{m}}^{\text{o}} /RT,\Delta_{\text{0}}^{\text {T}} S_{\text{m}}^{\text{o}} /R\;{\text{and}}\;\Phi_{\text{m}}^{\text{o}} /R = \Delta_{\text{0}}^{\text T} S_{\text{m}}^{\text{o}} /R{-}\Delta_{\text{0}}^{\text T} H_{\text{m}}^{\text{o}} /RT \) (where R is the universal gas constant) of α-terpineol over the range from T → (0 to 345) K. The standard entropy of formation of the compound (cr) under study at T = 298.15 K has been calculated.

Catanionic surfactant formation from the interaction of the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) and the ionic liquid 1-butyl-3-methylimidazolium octyl sulfate (bmim-octyl SO4) in aqueous solution

Abstract The interaction between the cationic surfactant Hexadecyltrimethylammonium bromide (CTAB) and the ionic liquid 1-butyl-3-methylimidazolium octyl sulfate (bmim-octylSO4) in aqueous solution has been investigated at two total concentrations (0.5 and 10 mM) and different CTAB mole fractions (αCTAB). Samples of different physical appearance were obtained depending on αCTAB suggesting different kind of aggregates. Bluish solutions (αCTAB from 0.1 to 0.6) were assigned to vesicles of the catanionic surfactant formed (CTA-octylSO4), whereas clear and isotropic solutions (αCTAB > 0.6) corresponded to mixed micelles. Surface tension, electrical conductivity, absorbance and dynamic light scattering (DLS) measurements were performed with the aim of correlating properties changes with the aggregation structures. The critical aggregation concentration (cac) and the surface tension value at the cac (γcac) were much lower for the mixtures than for the individual components. This finding reveals the exceptional surface activity of these mixtures, attributable to the formation of the CTA-octylSO4 catanionic surfactant. Once the catanionic surfactant is formed it makes no sense to consider anymore the initial CTAB/bmim-octylSO4 binary system but a new one composed by CTA-octylSO4 and the excess of bmim-octylSO4 or CTAB. On the basis of this consideration the surface activity parameters have been recalculated.

Microstructure and mechanical properties of Mg, Ag and Zn multi-microalloyed Al–(3.2–3.8)Cu–(1.0–1.4)Li alloys

To develop super-high strength Al–Li alloy, the microstructures and mechanical properties of Mg, Ag and Zn micro-alloyed Al–(3.2–3.8)Cu–(1.0–1.4)Li alloys (mass fraction) with T8 temper were studied. The results showed that 1% of lower Li content restricted the strengthening effect of increasing Cu content, while simultaneous increase in Cu and Li contents contributed effectively to the enhancement of strength. The alloys were mainly strengthened by plenty of fine and well dispersed T1(Al2CuLi) precipitates. There were also some minor precipitates of θ ′(Al2Cu) and δ′(Al3Li), which became less in number density, even disappeared during the aging process. Meanwhile, higher Li content favored the formation θ ′ and δ ′ and a small amount of S′(Al2CuMg) phases. In addition, strengthening effect and microstructure variation were analyzed through total non-solution mole fraction of Cu and Li and their mole ratio. To obtain Al–Li alloy with super-high strength, the total mole fractions of Cu and Li should be increased, and their mole ratios should also be kept at a certain high level.

Steady-State Attainment Period for Fischer–Tropsch Products

In studying the mechanism of the Fischer–Tropsch (FT) reaction, deuterium tracer techniques have been widely used and several important conclusions have been reported. A novel combination of experiment and modelling to quantify the residence times of long chain hydrocarbons using deuterium tracing has been devised. In this study, the effect of variation of residence time with carbon number on the olefin to paraffin ratio is investigated and also the time required for each hydrocarbon to reach steady state is determined. The results show that the olefin to paraffin ratio decreases with increasing carbon number which is consistent with olefin readsorption but not necessarily diffusion enhanced olefin readsorption. Therefore, chain length-dependent solubility in the liquid phase should be the predominant cause for chain length-dependencies of secondary olefin reactions in FT synthesis. Furthermore, the results show that it takes around 100 h for the overall/total mole fractions to reach steady state. Therefore, actual compositions (mole fractions) equilibrate faster even though actual flows (moles/h) might still be changing. Hence, for practical purposes the total mole fraction can be used as a guide to establish steady state.

Work of adhesion and activity of aqueous solutions of ternary mixtures of hydrocarbon and fluorocarbon nonionic surfactants at the water–air and polymer–water interfaces

The values of the surface tension and contact angle on the polytetrafluoroethylene surface (PTFE) of aqueous solutions of the ternary mixtures of hydrocarbon surfactants, TX100 and TX165, and fluorocarbon FSN100 at different mole fractions of surfactants in the bulk phase were applied for the studies of the correlation between the adsorption of surfactants at the solution–air and polymer–solution interfaces, the work of adhesion determined from the Young–Dupree equation, the parameter of the intermolecular interactions and the spreading coefficient of aqueous solutions of the studied mixtures on the PTFE surface. For this purpose the values of the total mole fraction and activity of surfactants at the polymer–solution interface obtained from the Sprow and Prausnitz equation were compared to those at the solution–air one. Also on the basis of the mole fraction of the particular surfactants at the PTFE–solution and water–air interface and on the assumption of the additivity of the adhesion work, the work of adhesion of the fluorocarbon tail to the PTFE surface as well as the Lifshitz–van der Waals component of the PTFE surface tension were calculated.

Miniaturized laser heterodyne radiometer for measurements of CO2 in the atmospheric column

We have developed a low-cost, miniaturized laser heterodyne radiometer for highly sensitive measurements of carbon dioxide (CO2) in the atmospheric column. In this passive design, sunlight that has undergone absorption by CO2 in the atmosphere is collected and mixed with continuous wave laser light that is step-scanned across the absorption feature centered at 1,573.6 nm. The resulting radio frequency beat signal is collected as a function of laser wavelength, from which the total column mole fraction can be de-convolved. We are expanding this technique to include methane (CH4) and carbon monoxide (CO), and with minor modifications, this technique can be expanded to include species such as water vapor (H2O) and nitrous oxide (N2O).

Simulations of column-averaged CO<sub>2</sub> and CH<sub>4</sub> using the NIES TM with a hybrid sigma-isentropic (σ-θ) vertical coordinate

Abstract. We have developed an improved version of the National Institute for Environmental Studies (NIES) three-dimensional chemical transport model (TM) designed for accurate tracer transport simulations in the stratosphere, using a hybrid sigma-isentropic (σ-θ) vertical coordinate that employs both terrain-following and isentropic parts switched smoothly around the tropopause. The air-ascending rate was derived from the effective heating rate and was used to simulate vertical motion in the isentropic part of the grid (above level 350 K), which was adjusted to fit to the observed age of the air in the stratosphere. Multi-annual simulations were conducted using the NIES TM to evaluate vertical profiles and dry-air column-averaged mole fractions of CO2 and CH4. Comparisons with balloon-borne observations over Sanriku (Japan) in 2000–2007 revealed that the tracer transport simulations in the upper troposphere and lower stratosphere are performed with accuracies of ~5% for CH4 and SF6, and ~1% for CO2 compared with the observed volume-mixing ratios. The simulated column-averaged dry air mole fractions of atmospheric carbon dioxide (XCO2) and methane (XCH4) were evaluated against daily ground-based high-resolution Fourier Transform Spectrometer (FTS) observations measured at twelve sites of the Total Carbon Column Observing Network (TCCON) (Bialystok, Bremen, Darwin, Garmisch, Izaña, Lamont, Lauder, Orleans, Park Falls, Sodankylä, Tsukuba, and Wollongong) between January 2009 and January 2011. The comparison shows the model's ability to reproduce the site-dependent seasonal cycles as observed by TCCON, with correlation coefficients typically on the order 0.8–0.9 and 0.4–0.8 for XCO2 and XCH4, respectively, and mean model biases of ±0.2% and ±0.5%, excluding Sodankylä, where strong biases are found. The ability of the model to capture the tracer total column mole fractions is strongly dependent on the model's ability to reproduce seasonal variations in tracer concentrations in the planetary boundary layer (PBL). We found a marked difference in the model's ability to reproduce near-surface concentrations at sites located some distance from multiple emission sources and where high emissions play a notable role in the tracer's budget. Comparisons with aircraft observations over Surgut (West Siberia), in an area with high emissions of methane from wetlands, show contrasting model performance in the PBL and in the free troposphere. Thus, the PBL is another critical region for simulating the tracer total column mole fractions.

Incomplete Elongation of the Chondroitin Sulfate Linkage Region on Aggrecan and Response to Interleukin-1β

Aggrecan is the prominent proteoglycan in cartilage and is modified with approximately 100 chondroitin sulfate (CS) chains through a tetrasaccharide linkage structure. In osteoarthritis (OA), the viscoelastic properties of cartilage are compromised on both the quantity and integrity of aggrecan core protein expressed as well as reduced overall CS chain length. Herein, we postulated that chronic low-level inflammation may also contribute to OA progression by promoting regulatory mechanisms in early CS biosynthesis that yield incomplete linkage structures on aggrecan. To test this idea, chondrocytes extracted from human tali were cultured in alginate beads and challenged with 5 ng/mL IL-1β as a model for chronic inflammation leading to OA progression. Novel mass spectrometry-based methods were devised to detect and quantify partially elongated linkage structures relative to control cultures. The total mole fraction of unelongated xylose residues per aggrecan was significantly less (p = 0.03) after IL-1β treatment compared to control cultures, with unelongated xylose residues constituting between 6% and 12% of the fraction of total CS measured. A portion (<1%) of the partially elongated linkage structures was found to be either phosphorylated or sulfated. These results establish quantitative mass spectrometry as a very sensitive and effective platform for evaluating truncated proteoglycan linkage structures. Our observations using this method suggest a possible role for aberrant linkage structure elongation in OA progression.

Separation of CO2–CH4 mixtures on defective single walled carbon nanohorns – tip does matter

Using realistic models of single-walled carbon nanohorns and their single-walled carbon nanotube counterparts, we study the equilibrium separation of CO2-CH4 mixtures near ambient operating conditions by using molecular simulations. We show that regardless of the studied operating conditions (i.e., total CO2-CH4 mixture pressures and mole fractions of mixture components in the bulk phase), single-walled carbon nanohorns maximize the CO2-CH4 equilibrium separation factor. Optimized samples of single-walled carbon nanohorns consisting of narrow tubular parts capped with horn-shaped tips show highly selective adsorption of CO2 over the CH4 mixture component, with the CO2-CH4 equilibrium separation factor of ~8-12. A large surface-to-volume ratio (i.e., enhanced surface forces) and unique defective morphology (i.e., packing of adsorbed molecules in quasi-one/quasi-zero dimensional nanospaces) of single-walled carbon nanohorns are their key structural properties responsible for the excellent separation performance. Our theoretical simulation results are in quantitative agreement with a recent experimental/theoretical study of the CO2-CH4 adsorption and separation on oxidized single-walled carbon nanohorns [Ohba et al., Chem. Lett., 40, 2011, 1089]. Both experiment and theory showed that the CO2-CH4 equilibrium separation factor of oxidized samples of single-walled nanohorns measured near ambient operating conditions is ~2-5. This reduction in the separation efficiency as compared to optimized samples of single-walled carbon nanohorns is theoretically justified by their lower surface-to-volume ratio (i.e., larger diameters of tubular parts and horn-shaped tips).

Unsaturation of Mitochondrial Membrane Lipids is Related to Palmitate Oxidation in Subsarcolemmal and Intermyofibrillar Mitochondria

Membrane lipid composition is thought to influence the function of integral membrane proteins; however, the potential for lipid composition to influence overall mitochondrial long-chain fatty acids (LCFA) oxidation is currently unknown. Therefore, the naturally occurring variability of LCFA oxidation rates within subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria in muscles with varying oxidative potentials (heart→red→white) was utilized to examine this relationship. To this end, SS and IMF mitochondria were isolated and palmitate oxidation rates were compared to membrane phospholipid composition. Among tissues, rates of palmitate oxidation in mitochondria displayed a 2.5-fold range, creating the required range to determine potential relationships with membrane lipid composition. In general, the percent mole fraction of phospholipid head groups and major fatty acid subclasses were similar in all mitochondria studied. However, rates of palmitate oxidation were positively correlated with both the unsaturation index and relative abundance of cardiolipin within mitochondria (r=0.57 and 0.49, respectively; p<0.05). Thus, these results suggest that mitochondrial LCFA oxidation may be significantly influenced by the total unsaturation and percent mole fraction of cardiolipin of the mitochondrial membrane, whereas other indices of membrane structure (e.g., percent mole fraction of other predominant membrane phospholipids, chain length, and ratio of phosphatidylcholine to phosphatidylethanolamine) were not significantly correlated.

Thermodynamic properties of neopentylbenzene over the range from T → (0 to 350) K

In the present research, the temperature dependence of heat capacity Cp,m∘=f(T) of neopentylbenzene C6H5–C5H11 has been measured between T=(6 and 350)K in the precision adiabatic vacuum calorimeter and reported for the first time. The temperature and enthalpy of fusion of neopentylbenzene and the total mole fraction of impurities have been determined. The experimental results have been used to calculate the standard (р°=0.1MPa) thermodynamic functions Cp,m∘/R,Δ0THm∘/RT,Δ0TSm∘/R and Φm∘/R=Δ0TSm∘/R-Δ0THm∘/RT (where R is the universal gas constant) of neopentylbenzene over the range from T→(0 to 350)K. The standard entropy of formation of the compound under study at T=298.15K has been calculated.