The role of the Ca vacancy in the determination of the europium position in the energy gap, its valence state and spectroscopic properties in KCa(PO3)3.

A new very promising red phosphor KCa1-xEux(PO3)3 (x = 1-5%) has been grown by the solid state method. Its luminescent quantum efficiency is close to 100% and the emission is stable over a wide temperature range i.e. 90% and 60% of the room temperature emission intensity remains at 200 °C and at 600 °C, respectively. The chromaticity coordinates were calculated as being x = 0.63, y = 0.37. The IR and Raman spectra were measured, and the maximum phonon energy of KCa1-xEux(PO3)3 is 1276 cm(-1). In the measured emission and excitation spectra of all samples only Eu(3+) ion emission was observed, emission of Eu(2+) is not present. Quantum mechanical calculations showed that in a perfect crystal the 5d levels of Eu(2+) are embedded in the conduction band. Consequently, neither absorption nor emission assigned to the Eu(2+) ions could be observed. The presence of a calcium vacancy is crucial for the explanation of the observed spectrum. The existence of a Ca(2+) vacancy compensates for the charge of Eu(3+) and results in the creation of the magnetic moment which moves the 4f levels to the valence band. Thus, transitions to the Eu(3+) excited levels located in the energy band gap are observed.

Impact of exercise and dietary fatty acid composition from a high-fat diet on markers of hunger and satiety.

To compare the effects of both dietary fatty acid composition and exercise vs. sedentary conditions on circulating levels of hunger and satiety hormones. Eight healthy males were randomized in a 2 × 2 crossover design. The four treatments were 3 days of HF diets (50% of energy) containing high saturated fat (22% of energy) with exercise (SE) or sedentary (SS) conditions, and high monounsaturated fat (30% of energy) with exercise (UE) or sedentary (US) conditions. Cycling exercise was completed at 45% of VO(2)max for 2h daily. On the third HF day, 20 blood samples were drawn over a 24h period for each hormone (leptin, insulin, ghrelin, and peptide YY (PYY)). A visual analog scale (VAS) was completed hourly between 0800 and 2200. Average 24h leptin and insulin levels were lower while 24h PYY was higher during exercise vs. sedentary conditions. FA composition did not differentially affect 24h hormone values. VAS scores for hunger and fullness did not differ between any treatment but did correlate with ghrelin, leptin, and insulin. High saturated or unsaturated fat diets did not differ with respect to markers of hunger or satiety. Exercise decreased 24h leptin and insulin while increasing PYY regardless of FA composition.

Influence of dietary fatty acid composition and exercise on changes in fat oxidation from a high-fat diet.

Acute high-fat (HF) diets can lead to short-term positive fat balances until the body increases fat oxidation to match intake. The purpose of this study was to examine the effects of a HF diet, rich in either mono-unsaturated or saturated fatty acids (FAs) and exercise, on the rate at which the body adapts to a HF diet.(13)C-labeled oleate and (2)H-labeled palmitate were also given to determine the contribution of exogenous vs. global fat oxidation. Eight healthy men (age of 18-45 yr; body mass index of 22 ± 3 kg/m(2)) were randomized in a 2 × 2 crossover design. The four treatments were a high saturated fat diet with exercise (SE) or sedentary (SS) conditions and a high monounsaturated fat diet with exercise (UE) or sedentary (US) conditions. Subjects stayed for 5 days in a metabolic chamber. All meals were provided. On day 1, 30% of energy intake was from fat, whereas days 2-5 had 50% of energy as fat. Subjects exercised on a stationary cycle at 45% of maximal oxygen uptake for 2 h each day. Respiratory gases and urinary nitrogen were collected to calculate fat oxidation. Change from day 1 to day 5 showed both exercise treatments increased fat oxidation (SE: 76 ± 30 g, P = 0.001; UE: 118 ± 31 g, P < 0.001), whereas neither sedentary condition changed fat oxidation (SS: -10 ± 33 g, P = not significant; US: 41 ± 14 g, P = 0.07). No differences for dietary FA composition were found. Exercise led to a faster adaptation to a HF diet by increasing fat oxidation and achieving fat balance by day 5. Dietary FA composition did not differentially affect 24-h fat oxidation.

The role of conjugated linoleic acid in reducing body fat and preventing holiday weight gain.

OBJECTIVE: The incidence of obesity and overweight in the US has increased considerably during the past two decades and currently affects 65% of the adult population. Research has indicated that small, yet irreversible, gains during the holiday season contribute to increases in weight during adulthood. Conjugated linoleic acid (CLA), a naturally occurring dietary fatty acid, has been found to reduce weight gain and dramatically decrease fat mass in animals. Although research in humans has shown inconsistent results, most studies have been of insufficient duration or have utilized body composition methods that are less accurate than the currently accepted criterion. DESIGN: Randomized, double-blind, placebo-controlled study of 3.2 g/day CLA for 6 months. SUBJECTS: Forty healthy, overweight subjects (age: 18-44 years; body mass index: 25-30 kg/m(2)). MEASUREMENTS: Body composition by the four-compartment model, resting metabolic rate (RMR) by indirect calorimetry, self-reported physical activity and dietary intake, and blood chemistries were determined at baseline and after 6 months. Body weight was measured monthly during the pre-holiday season (August-October), holiday season (November-December) and post-holiday season (January-March). Adverse events were assessed monthly. RESULTS: Compared to CLA, the placebo group showed a greater rate of weight gain during the holiday season (P=0.01). Within the placebo group, holiday weight change was significantly greater compared to the pre-holiday period (August-October) (P=0.03). Six-month change in body composition was improved with CLA compared to placebo (P=0.02), and body fat was significantly reduced within the CLA group (-1.0+/-2.2 kg, P=0.05). CLA had no effect on RMR, physical activity or dietary intake. The rate of reported negative emotions decreased significantly with CLA, although there was no difference in any other category of adverse event. In comparison to the placebo, CLA did not affect insulin resistance, blood lipids and markers of liver function or markers of inflammation, with the exception of a significant decrease in a biomarker of endothelial dysfunction. CONCLUSION: CLA supplementation among overweight adults significantly reduced body fat over 6 months and prevented weight gain during the holiday season. Although no adverse effects were seen, additional studies should evaluate the effect of prolonged use of CLA.