Aqueous foam stabilized by tricephalic Amphiphilic surfactants

Aqueous foams can be described as a close packing of gas bubbles stabilized by surface active molecules. Their complex and diverse properties make them attractive for many chemical and physical applications where foaming, emulsifying or coating processes are needed. The recent synthesis of multi-cephalic and multi-tailed amphiphilic molecules have reportedly enhanced their antibacterial activity in connection with tail length and nature of the head group. This report covers the foamability of two triple head, double tail cationic surfactants (M-1,14,14, M-P,14,14) and a triple head single tail cationic surfactant (M-1,1,14) and compares them with commercially available single headed, single tailed anionic and cationic surfactants (SDS, CTAB and DTAB). Additionally, a longer tailed variant (M-1,16,16) was also tested. The results show that bubble rupture rate decreases with the length of the carbon chain, irrespective of head structure. For the longer tailed variant (M-1,16,16) foam was difficult to produce leaving it untestable. The growth rate of bubbles with short tailed surfactants (SDS) and longer, single tailed tricationic surfactants (M-1,1,14) was shown to be twice as high as those with longer tailed surfactants (CTAB, M-P,14,14, M-1,14,14). This fact was related to the size variation of bubbles, where the foams made with short tail surfactants exhibited higher polydispersity than those with short tails. This suggests that foams with tricationic amphiphilics are closely linked to their tail length and generally insensitive to their head structure

Ecology and food quality of fishes in coastal rivers of the far north of Ontario

The Far North of Ontario is home to over 24 000 people in 31 communities, and many of these people rely heavily on wild fish as part of their diet. Six of these communities are situated on the lower reaches of large river systems near the coast of Hudson and James Bays. These large rivers, as well as numerous smaller rivers along the coast, are home to a variety of fish species, including some presumed anadromous (migrating between fresh and salt water) populations, that support important subsistence fisheries. However, little research has been carried out on fish resources of these river systems, and basic information is generally lacking. I examined fish populations from the lower reaches of 14 of these rivers in terms of growth, trophic ecology, life history, and their suitability for human consumption based on mercury and fatty acid content. Stable isotope and fatty acid compositions indicative of predation on marine food sources were most evident in the presumed anadromous species - Brook Trout, Lake Whitefish and Cisco. Compared to inland lakes of the same drainage basins, coastal river populations of Northern Pike and Walleye grew faster and occupied broader trophic niches, suggestive of an indirect marine influence on their diet. In contrast, Lake Whitefish tended to grow more slowly in coastal rivers than in inland lakes. Fish mercury concentrations in coastal rivers have not changed appreciably over the last ~ 30 years. Current fish mercury concentrations did not vary latitudinally among coastal rivers, but were significantly higher than in inland lakes for Walleye, Lake Whitefish and White Sucker. Fillet lipid and essential fatty acid (EPA+DHA) content decreased with increasing latitude in Northern Pike, but not in other species. Both mercury and essential fatty acid concentrations of fish muscle varied among rivers but there did not appear to be spatial concordance between them. Presumed anadromous species - Brook Trout, Lake Whitefish, Cisco – tended to have both the greatest concentrations of essential fatty acids and among the lowest mercury concentrations, making them an especially high quality food source. Walleye generally had the highest muscle mercury concentration and relatively low essential fatty acid content.Master of Science (MSc) in Biolog

SMARTPHONE MEASUREMENT: DO PEOPLE USE MOBILE APPLICATIONS AS THEY SAY THEY DO?

Designing viable mobile services requires in-depth understanding of how people deal with their mobile phones on a daily basis. Most studies on the use of mobile phones are based on surveys that ask people how often they think they use mobile applications. While such survey studies have provided numerous insights, they also pose issues of recall, accuracy and common method bias. Fortunately, smartphones enable more direct ways of collecting usage data by installing a background application that logs all user activities. Such smartphone measurement approach has only been applied in a handful of studies, typically limited to Nokia handsets. This paper scrutinizes the reliability of surveybased measures on the perceived use of mobile services by contrasting them with log data obtained in a smartphone measurement study. We analyze the results of a smartphone measurement study carried out in the Netherlands among 129 users of iPhone, Blackberry and Android phones. Users appear moderately accurate in assessing the use of mainstream services like SMS, email and browsing, but not regarding navigation and weather information services. The findings suggest that traditional survey approaches should be complemented with smartphone measurement in order to really understand how users deal with mobile services

Natural selection on the regulation of foraging in harvester ants

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Imaging Hyperpolarized Pyruvate and Lactate after Blood-Brain Barrier Disruption with Focused Ultrasound

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