X-ray fluorescence analysis of selected micronutrients in ten African indigenous leafy vegetables cultivated in Nairobi, Kenya.

INTRODUCTION: There is a growing interest on vital roles of micronutrients in the maintenance of good health and enhancement of the immune system for prevention of diseases. METHODS: Energy dispersive X-Ray fluorescence (EDXRF) spectrometer was used for qualitative and quantitative analysis of selected micronutrients Zinc (Zn), Iron (Fe), Magnesium (Mg), Calcium (Ca) and Potassium (K) in ten African indigenous leafy vegetables (AILVs) (Corchorus olitorius, Cucurbita moschata, Amaranthus blitum, Brassica carinata , Cleome gynandra, Solanum scabrum , Crotalaria ochroleuca, Urticadioica, Manihot esculenta, Vigna unguiculata) which are cultivated, marketed and consumed in Kenya and across East and West Africa. RESULTS: In this study, the highest levels of Calcium, Zinc and Iron were found in Urticadioica leaves (75.0 mg/g), Manihot esculenta leaves (0.1 mg/g) and Cucurbita moschata leaves (1.0 mg/g). Amaranthus blitum leaves exhibited the highest content of Magnesium (9.5 mg/g) and Potassium (36.5 mg/g) respectively. This study demonstrated that based on weight and bioavailabilty, 10 g of Cucurbita moschata (dried weight) provides between 57% to 136% daily value of iron for children age between 7 and 10 years old and can provide up to 41%, 81% and 27% daily value of iron for female aged 18+, lactating females aged 18+ and males aged 18+ respectively. A 10 g portion of Urticadioica leaves (dried weight) will provide 75% or 58% of the daily value of calcium based on the North American or western European recommendation respectively while the same amount of Amaranthus leaves provides between 37% to 50 % of daily value of magnesium for adults of nineteen years and older based on their weight. The daily value of zinc despite its dependency with age, weight and Zinc bioavailability can be supplied by 10 g of Manihot esculenta leaves (dried weight) at a percentage ranged from 8% to 39%. Based on the 3510 mg daily recommendation, 10 g of Amaranthus, Brassica carinata, Cleome gynandra and Cucurbita moschata (dried weight) will provide 10.4%, 10.0%, 9.8% and 9.3% daily value for potassium respectively. CONCLUSION: The research findings are scientific evidences of the nutritional contribution of African indigenous leafy vegetables.

Upper limits for undetected trace species in the stratosphere of Titan.

In this paper we describe the first quantitative search for several molecules in Titan's stratosphere in Cassini CIRS infrared spectra. These are: ammonia (NH3), methanol (CH3OH), formaldehyde (H2CO), and acetonitrile (CH3CN), all of which are predicted by photochemical models but only the last of which has been observed, and not in the infrared. We find non-detections in all cases, but derive upper limits on the abundances from low-noise observations at 25 degrees S and 75 degrees N. Comparing these constraints to model predictions, we conclude that CIRS is highly unlikely to see NH3 or CH3OH emissions. However, CH3CN and H2CO are closer to CIRS detectability, and we suggest ways in which the sensitivity threshold may be lowered towards this goal.

The case of the weak N-X bond: Ab initio, semi-experimental, and experimental equilibrium structures of XNO (X = H, F, Cl, OH) and FNO2.

The equilibrium structures of FNO, ClNO, HONO, and FNO2 have been determined using three different, somewhat complementary methods: a completely experimental, a semi-experimental (where the equilibrium rotational constants are derived from the experimental effective ground-state rotational constants and an ab initio cubic force field), and an ab initio, where geometry optimizations are usually performed at the coupled cluster level of nonrelativistic electronic structure theory using small to very large Gaussian basis sets. For the sake of comparison, the equilibrium structures of HNO and N2O have also been redetermined, confirming and extending earlier results. The semi-experimental method gives structural parameters in good agreement with the reliable experimental results for each compound investigated. Because of inadequate treatment of electron correlation, the single-reference CCSD(T) method gives N-X (X[double bond]F, Cl, OH) bonds that are too strong and associate bond lengths that are significantly too short. The discrepancy increases with increase in the size of the basis set. A much more elaborate treatment of electron correlation at the CCSDTQ level solves this problem and results in increased bond lengths, correctly representing the weakness of the N-X bond in these XNO and XNO2 species. The equilibrium structures determined are accurate to better than 0.001 A and 0.1 degrees .