Electronic Spectra and Crystal-Field Analysis of Europium in Hexanitritolanthanate Systems

The luminescence spectra of Eu³⁺ at a <i>T</i>_<i>h</i> point-group site in the hexanitritolanthanate systems Cs₂NaEu­(¹⁴NO₂)₆, Cs₂NaEu­(¹⁵NO₂)₆, Rb₂NaEu­(¹⁴NO₂)₆, Cs₂LiEu­(¹⁴NO₂)₆, and Cs₂NaY­(¹⁴NO₂)₆:Eu³⁺ have been recorded between 19 500 and 10 500 cm^–1 at temperatures down to 3 K. The spectra comprise magnetic-dipole-allowed zero phonon lines, odd-parity metal–ligand vibrations, internal anion vibrations, and lattice modes, with some weak vibrational progressions based upon vibronic origins. With the aid of density functional theory calculations, the vibrational modes in the vibronic sidebands of transitions have been assigned. The two-center transitions involving NO₂^– stretching and scissoring modes are most prominent for the ⁵D₀ → ⁷F₂ hypersensitive transition. The onset of NO₂^– triplet absorption above 20 000 cm^–1 restricts the derived Eu³⁺ energy-level data set to the ⁷F_<i>J</i> (<i>J</i> = 0–6) and ⁵D_0,1 multiplets. A total of 21 levels have been included in crystal-field energy-level calculations of Eu³⁺ in Cs₂NaEu­(NO₂)₆, using seven adjustable parameters, resulting in a mean deviation of ∼20 cm^–1. The comparison of our results is made with Eu³⁺ in the double nitrate salt. In both cases, the fourth-rank crystal field is comparatively weaker than that in europium hexahaloelpasolites

An Optimized Methane Reaction Model for Oxyfuel Combustion

Pressurized oxyfuel combustion technology is a potential solution for reducing greenhouse gas emissions by carbon capture and storage while burning hydrocarbon fuels. Numerous experiments on CH4 ignition delay times and laminar flame propagation velocities at high pressures and CO2 atmosphere dilution have been reported, contributing to the improvement of current CH4 combustion kinetic models. However, existing mainstream models produce significantly larger prediction errors for syngas ignition delay time data, especially under oxyfuel combustion conditions. Motivated by the observation, an optimized CH4 model was developed based on a comprehensive set of experimental data, including 2205 ignition delay time, 3344 laminar flame speed, and 200 species profile measurements and balanced the predicted performance of the syngas. A novel sampling strategy was developed and embedded in the optimization algorithm to improve the computational efficiency. The optimized rate constants fall reasonably within the estimated uncertainty range. Prediction performance of the optimized model was evaluated and compared to four well-established models. The optimized model showed considerably improved results, providing a better balance between the prediction of ignition delay time and laminar flame speed data. The kinetic reasons for the improved performance were examined and discussed

An Optimized Methane Reaction Model for Oxyfuel Combustion

Pressurized oxyfuel combustion technology is a potential solution for reducing greenhouse gas emissions by carbon capture and storage while burning hydrocarbon fuels. Numerous experiments on CH4 ignition delay times and laminar flame propagation velocities at high pressures and CO2 atmosphere dilution have been reported, contributing to the improvement of current CH4 combustion kinetic models. However, existing mainstream models produce significantly larger prediction errors for syngas ignition delay time data, especially under oxyfuel combustion conditions. Motivated by the observation, an optimized CH4 model was developed based on a comprehensive set of experimental data, including 2205 ignition delay time, 3344 laminar flame speed, and 200 species profile measurements and balanced the predicted performance of the syngas. A novel sampling strategy was developed and embedded in the optimization algorithm to improve the computational efficiency. The optimized rate constants fall reasonably within the estimated uncertainty range. Prediction performance of the optimized model was evaluated and compared to four well-established models. The optimized model showed considerably improved results, providing a better balance between the prediction of ignition delay time and laminar flame speed data. The kinetic reasons for the improved performance were examined and discussed

Nonequilibrium Catalyst Materials Stabilized by the Aerogel Effect: Solvent Free and Continuous Synthesis of Gamma-Alumina with Hierarchical Porosity

Heterogeneous catalysis can be understood as a phenomenon which strongly relies on the occurrence of thermodynamically less favorable surface motifs like defects or high-energy planes. Because it is very difficult to control such parameters, an interesting approach is to explore metastable polymorphs of the respective solids. The latter is not an easy task as well because the emergence of polymorphs is dictated by kinetic control and materials with high surface area are required. Further, an inherent problem is that high temperatures required for many catalytic reactions can also induce the transformation to the thermodynamically stable modification. Alumina (Al₂O₃) was selected for the current study as it exists not only in the stable α-form but also as the metastable γ-polymorph. Kinetic control was realized by combining an aerosol-based synthesis approach and a highly reactive, volatile precursor (AlMe₃). Monolithic flakes of Al₂O₃ with a highly porous, hierarchical structure (micro-, meso-, and macropores connected to each other) resemble so-called aerogels, which are normally known only from wet sol–gel routes. Monolothic aerogel flakes can be separated from the gas phase without supercritical drying, which in principle allows for a continuous preparation of the materials. Process parameters can be adjusted so the material is composed exclusively of the desired γ-modification. The γ-Al₂O₃ aerogels were much more stable than they should be, and even after extended (80 h) high-temperature (1200 °C) treatment only an insignificant part has converted to the thermodynamically stable α-phase. The latter phenomenon was assigned to the extraordinary thermal insulation properties of aerogels. Finally, the material was tested concerning the catalytic dehydration of 1-hexanol. Comparison to other Al₂O₃ materials with the same surface area demonstrates that the γ-Al₂O₃ are superior in activity and selectivity regarding the formation of the desired product 1-hexene

Plasma ketone bodies, non-esterified fatty acids (NEFA), glycerol and hepatic lipid oxidation target expression in DIO mice treated with DualAG.

<p>After fasting for 2 hrs, mice were injected vehicle, Liraglutide (25nmol/kg) or DualAG (25nmol/kg) subcutaneously. <b>A.</b> Plasma β-hydroxybutyrate (βHBA) levels in mice after 6 hrs of treatment injection. <b>B.</b> βHBA levels monitored over the period of 6 hrs after treatment with DualAG. <b>C.</b> Plasma NEFA levels after 6 hrs; <b>D.</b> Plasma NEFA levels from 0 to 6hrs and <b>E.</b> Plasma glycerol levels after 6 hrs of treatment. Hepatic mRNA expression of peroxisome proliferator activated receptor (Ppar) α <b>(F)</b>, acyl CoA oxidase (Acox) 1 <b>(G)</b>, carnitine palmitoyl transferase (Cpt) 1α <b>(H)</b>. Cpt2 <b>(I)</b> determined by RT-PCR.</p

DualAG decreases VLDL secretion and associated hepatic gene/ protein expression in DIO mice.

<p><b>A.</b> Plasma TG levels, as a measure of VLDL secretion. DIO mice were injected with poloxamer, followed by vehicle, Liraglutide or DualAG injection. The plasma was collected at 1, 2, and 4 hrs post treatment, and TG levels were determined. <b>B.</b> Hepatic protein levels of ATP-binding cassette transporters Abca1, Abcg1, and Abcg5 by western blot, after 6 hrs of treatment with vehicle, Liraglutide (25nmol/kg) or DualAG (25nmol/kg). <b>C.</b> Western blots for Abca1, Abcg1, Abcg5 were quantified and plotted after normalizing to tubulin expression. <b>D.</b> Hepatic mRNA expression of Abcg5, Abcg8 and Abcg4 determined by RT-PCR.</p

Glp1/Gcgr dual agonist (DualAG) improved glucose and insulin levels in DIO mice.

<p>Mice were fasted for 2hrs followed by injection of vehicle, Liraglutide (25nmol/kg) or DualAG (25nmol/kg). <b>A.</b> Blood glucose levels after 6 hrs of treatment injection. <b>B.</b> DualAG induced blood glucose level decrease over the course of 6 hrs after injection. <b>C.</b> Plasma insulin levels after 6 hrs of treatment injection. <b>D.</b> Plasma insulin levels monitored at multiple time-points for vehicle and DualAG treated groups. <b>E.</b> Bioavailability of the DualAG peptide during the course of the study.</p

DualAG reduced <i>de novo</i> lipogenesis in DIO mice.

<p><b>A.</b> Timeline for <i>de novo</i> lipogenesis experiments. After fasting for 2 hrs, mice were injected with 20ml/kg i.p. deuterated water (D₂O), simultaneously with s.c. injection of vehicle, Liraglutide (25nmol/kg) or DualAG (25nmol/kg). After 6 hrs, the plasma and tissues were collected for tracer analysis. <b>B.</b> <i>De novo</i> palmitate synthesis as determined from plasma fraction. <b>C.</b> <i>De novo</i> palmitate synthesis as determined from liver tissue. <b>D.</b> <i>De novo</i> synthesized cholesterol in plasma. <b>E.</b> <i>De novo</i> synthesized cholesterol in liver tissue.</p

DualAG decreased TG synthesis in DIO mice.

<p><b>A.</b> Monoacylglycerol acyltransferase (Mgat) enzyme activity. Recombinant human Mgat2 was used as a positive control, and ratio of C¹⁴-diacylglycerol to TG was normalized to protein content from the livers of DIO mice treated with vehicle, Liraglutide (25nmol/kg) or DualAG (25nmol/kg). <b>B.</b> Diacylglycerol acyltransferase (Dgat) enzyme activity. Recombinant human Dgat1 was used as a positive control, and amount of C¹⁴-TG was normalized to protein content from the livers of DIO mice treated with vehicle, Liraglutide (25nmol/kg) or DualAG (25nmol/kg). <b>C.</b> Timeline for <i>de novo</i> TG synthesis and dynamic TG metabolism experiments. DIO mice were injected with vehicle, Recombinant human Mgat2 was used as a positive control, and ratio of C¹⁴-diacylglycerol to TG was normalized to protein content from the livers of DIO mice treated with vehicle, Liraglutide (25nmol/kg) or DualAG (25nmol/kg) s.c., followed by oral administration of Dgat2 and Mtp inhibitors. After one hour, mice were injected with intravenous ¹³C₁₈-oleate in intralipids, which was followed by blood collection at 5, 10, 20 and 30 mins (n = 4/ time point). <b>D.</b> Plasma concentration of newly made TG that incorporated ¹³C₁₈-oleate, which is an indicator of <i>de novo</i> TG synthesis and TG release from liver to blood. <b>E.</b> Overall ¹³C₁₈-oleate enrichment in plasma monoacyl glycerol, diacylglycerol and TG, indicator of <i>de novo</i> synthesis. The percentage enrichment of 13C18-oleate tracer in plasma TG 52:2 was calculated as the ratio of labeled isotopologues (M18 = TG52:2 incorporating 1 equivalent of 13C18 and M36 = TG 52:2 incorporating 2 equivalents of 13C18) to total TG 52:2 (sum of all isotopologues, M0, M18 and M36). <b>F.</b> Plasma TG levels over 30 minutes of experiment, suggesting clearance of unlabeled TG.</p

DualAG suppressed mRNA expression of key lipogenic transcription factors and enzymes in livers of DIO mice.

<p>Sterol regulatory element binding protein (Srebp) 1c, Srebp2, monoacylglycerol acyltransferase (Mgat) 1, Mgat 2, glycerol-3-phosphate acetyltransferase (Gpat), peroxisome proliferator activated receptor (Ppar) γ, liver-X-receptor (Lxr) α, and Lxrβ mRNA expression was analyzed by quantitative real-time PCR (RT-PCR).</p