Characterization of low pressure chemical vapor deposited silicon dioxide thin films

LPCVD deposited amorphous silicon dioxide SiO2 thin films from a new chemical vapor source, diethylsilane (DES), were characterized. This work is focused on evaluation of SiO2 films prepared by varies deposition temperatures and flow rates series. SiO2 thin films were evaluated for density, porosity, and refractive index. Techniques for evaluation of the above mentioned parameters for this work included the use of infrared absorption spectroscopy, preferential etch procedures, optical measurement of refractive index and thickness, and thermal annealing of CVD films. The densification in vacuum ambient has been carried out at the temperature of 600 °, 750 °, and 900 °C, respectively. The P-etch rates of SiO2 thin films, produced using DES as a silicon source, were found to be in the range of 846 A/min. to 930 A/min. for a deposition temperatures between 375 ° and 475 °C; while the etch rates were constant (about 900 A/min.) for SiO2 films produced by varing diethylsilane flow rates between 20 and 150 sccm. In the infrared absorption spectra, the strong Si-O-Si stretching band at the frequency 1070 cm -1 shifted about 0 to 15 cm -1 to high frequency, after annealing. The degree of shifting depends on the original deposition and the annealing temperature. Shiftings were also observed at the Si-O-Si bending and rocking bands at 800 and 450 cm -1 respectively. The ellipsometric measurement indicated the index of refraction for SiO2 thin film to be 1.45 with no significant difference for samples with different deposition conditions

Cyanobacteria Predominance in Alberta\u27s Eutrophic Lakes Linked to Iron Scavenging Strategy That Uses Siderophores and Toxins

The role of the micronutrient iron in the regulation of cyanobacteria dominance and cyanotoxicity is poorly understood. Iron is required for important metabolic pathways, including both phosphorus (P) and nitrogen (N) assimilation, and low levels of this element may influence the assimilation of the macronutrients. The hypothesis tested was that cyanobacteria produce and utilize siderophores and toxins in low iron conditions to scavenge iron, when P and N are not limiting algal growth, providing some cyanobacteria with a competitive advantage over other algal species. Among the naturally eutrophic lakes studied, cyanobacteria were dominant at low iron (\u3epFe19) concentrations (Spearman r = 0.73, p=0.004). Under these low iron conditions, the concentration of hydroxamate siderophores was significantly related to cyanobacteria biomass (r2=0.81, p\u3c0.001), and the concentrations of extracellular microcystin were significantly correlated to the concentrations of hydroxamate siderophores (r2=0.98, p\u3c0.001). These findings provide support for iron regulation of cyanobacteria harmful algal blooms (cyanoHABs). Lake management programs can work to mitigate and prevent future cyanoHAB occurrences through the regulation of iron in naturally eutrophic lakes

Development of Kefir Products Using Aronia or Elderberries and the Impacts of Fermentation on the Health-promoting Characteristics of Aronia Polyphenols

Diabetes is a global health problem. The consumption of dietary polyphenols may help to decrease the risk of type 2 diabetes and slow the progression of diabetic complications. Aronia (Aronia melanocarpa) and elderberry (Sambucus nigra L. ssp. canadensis) fruits are rich in polyphenols and exhibit health-promoting properties, but they are underutilized. Aronia and elderberries are rarely consumed raw due to the astringent mouth feel. New food products are needed to increase their consumption. Kefir, a fermented dairy beverage, was chosen to be the matrix for incorporating berries due to: 1) the protein matrix can help mask the astringency; 2) an acidic environment is beneficial for the stability of phenolic compounds; 3) fermentative microorganisms may be able to increase the bioavailability of polyphenols. The first objective of this research was to develop new palatable products using underutilized berries and different sweeteners (sucrose, stevia and monk fruit extracts). Sensory evaluations were conducted to assess consumer acceptability of berry-containing kefirs. The results showed that aronia and elderberry kefirs sweetened with stevia or sucrose were all accepted by consumers where sucrose was the best-accepted sweetener. The second objective was to assess the health-promoting characteristics of the berry-containing kefirs. Aronia kefirs contained high levels of total phenolics and anthocyanins. Elderberry kefirs were moderate in total phenolics. All kefirs exhibited antioxidant capacity. The third objective was to evaluate the diabetes-beneficial properties of aronia kefir using an in-vitro digestion model. The impacts of fermentation on aronia polyphenols were also assessed. The results showed that the levels of bioaccessible polyphenols were elevated during digestion and the antioxidant capacity increased. Fermentation enhanced the inhibitory activity of aronia kefir on α-glucosidase but did not alter its weak inhibition on pancreatic α-amylase. Specific inhibition of α-glucosidase may decrease the absorption of carbohydrates and contribute to blood glucose control without side effects compared to pharmaceutical agents, such as acarbose. In conclusion, new berry-containing kefirs were well-accepted by the consumers and the consumption of berry-containing kefirs may help to reduce oxidative stress and aid in blood glucose control. In addition, fermentation may be a good strategy to increase the bioavailability of dietary polyphenols