13 research outputs found
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Solvent effects on catalytic activity and selectivity in amine-catalyzed D-fructose isomerization
Rational catalyst design and optimal solvent selection are key to advancing biorefining. Here, we explored the organocatalytic isomerization of D-fructose to a valuable rare monosaccharide, D-allulose, as a function of solvent. The isomerization of D-fructose to D-allulose competes with its isomerization to D-glucose and sugar degradation. In both water and DMF, the catalytic activity of amines towards D-fructose is correlated with their basicity. Solvents impact the selectivity significantly by altering the tautomeric distribution of D-fructose. Our results suggest that the furanose tautomer of D-fructose is isomerized to D-allulose, and the fractional abundance of this tautomer increases as follows: water < MeOH < DMF â DMSO. Reaction rates are also higher in aprotic than in protic solvents. The best D-allulose yield, 14 %, was obtained in DMF with 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the catalyst. The reaction kinetics and mechanism were explored using operando NMR spectroscopy
Anionic Extraction for Efficient Recovery of Biobased 2,3-Butanediol-A Platform for Bulk and Fine Chemicals
A model of HIV/AIDS population dynamics including ARV treatment and pre-exposure prophylaxis
Antiretroviral treatment (ART) and oral pre-exposure prophylaxis (PrEP) have recently
been used efficiently in management of HIV infection. Pre-exposure prophylaxis
consists in the use of an antiretroviral medication to prevent the acquisition of HIV
infection by uninfected individuals. We propose a new model for the transmission of
HIV/AIDS including ART and PrEP. Our model can be used to test the effects of ART
and of the uptake of PrEP in a given population, as we demonstrate through
simulations. The model can also be used to estimate future projections of HIV
prevalence. We prove global stability of the disease-free equilibrium. We also prove
global stability of the endemic equilibrium for the most general case of the model, i.e.,
which allows for PrEP individuals to default. We include insightful simulations based
on recently published South-African data
Identification of High-Yielding Iron-Biofortified Open-Pollinated Varieties of Pearl Millet in West Africa
Pearl millet is a predominant food and fodder crop in West Africa. This study was
carried out to test the newly developed open-pollinated varieties (OPVs) for field
performance and stability for grain yield, grain iron (Fe), and grain zinc (Zn) contents
across 10 locations in West Africa (i.e., Niger, Nigeria, Mali, Burkina Faso, Senegal, and
Ghana). The test material consisted of 30 OPVs, of which 8 are Fe/Zn biofortified. The
experiment was conducted in a randomized complete block design in three replications.
ANOVA revealed highly significant variability for grain yield and micronutrient traits. The
presence of genotype x environment (G x E) indicated that the expressions of traits are
significantly influenced by both genetic and G x E factors, for grain Fe and Zn contents.
Days to 50% flowering and plant height showed less G x E, suggesting these traits are
largely under genetic control. The genotypes CHAKTI (46 days), ICTP 8203 (46 days),
ICMV 177002 (50 days), ICMV 177003 (48 days), and Moro (53 days) had exhibited
early flowering across locations leading to early physiological maturity. CHAKTI (1.42 t/ha
yield; 62.24 mg/kg of grain Fe, 47.29 mg/kg of grain Zn) and ICMP 177002 (1.19 t/ha
yield, 62.62 mg/kg of grain Fe, 46.62 mg/kg of grain Zn) have performed well for grain
yield and also for micronutrients, across locations, compared with the check. Additive
Main Effect and Multiplicative Interaction (AMMI) ANOVA revealed the highly significant
genotypic differences, the mean sum of squares of environment, and its interaction with
the genotypes. Based on the AMMI stability value (ASV), the most stable genotype is
SOSAT-C88 (ASV = 0.04) for grain yield and resistance to downy mildew; mean grain
yield and stability rankings (YSI) revealed that the genotypes CHAKTI, SOSAT-C88, and
ICMV IS 99001 were high yielding and expressed stability across regions. The strong
correlation (r = 0.98**) of grain Fe and Zn contents that merits Fe-based selection
is highly rewarding. CHAKTI outperformed over other genotypes for grain yield (71% higher), especially with early maturing varieties in West Africa, such as GB 8735, LCIC
9702, and Jirani, and for grain Fe (16.11% higher) and Zn (7% higher) contents across
locations, and made a candidate of high-iron variety to be promoted for combating the
micronutrient malnutrition in West and Central Africa (WCA)
Corrigendum to âPrecipitating non-aqueous amine systems for absorption of carbon dioxide using 2-amino-2-methyl-1-propanolâ [Int. J. Greenh. Gas Con. 88 (2019) 460-468]
Precipitating non-aqueous amine systems for absorption of carbon dioxide using 2-amino-2-methyl-1-propanol
The aim of this study was to find a solvent to replace N-methyl-2-pyrrolidone (NMP) in CO2 absorption systems containing the amine 2-amino-2-methyl-1-propanol (AMP), in order to reduce the health risks associated with handling, as NMP is reproductively toxic. Seven organic solvents were investigated: dimethyl sulfoxide (DMSO), 3-(dimethylamino)propionitrile (3DMAPN), 1-pentanol (1 P), propylene carbonate (PC), 4-heptanone (4 H), 1-methylimidazole (1MIMI) and cyclohexanol (CH). Henry's constant, the CO2 solubility and the differential heat of absorption were determined for the pure solvents, and in solvent mixtures containing 25 wt% AMP, at 25 °C and 40 °C. Three of the solvents were found to have promising absorption properties: DMSO, 3DMAPN and 1 P. In mixtures with AMP, precipitation was formed at both 25 and 40 °C, and the CO2 absorption capacity was similar to that in the AMPâNMP system, in terms of the CO2 loading for a given partial pressure of CO2. The results also indicated that the reaction of AMP and CO2 in these solvents can be described by the zwitterion reaction mechanism