Development of an algorithm for tip-related artifacts identification in AFM biological film imaging

One major drawback identified in atomic force microscopy imaging is the dependence of the image's precision on the shape of the probe tip. In this paper a simple algorithm is proposed to provide artifact identification signaling in-situ tip features in atomic force microscopy images. The base of the identifications lied when the angle formed between two scanned points was kept the same as the tip sweeps a certain length of the sample. The potential of the described method was illustrated on a chitosan polysaccharide film. The images produced were compared to evaluate tip-artifact regions. This algorithm showed promise as a tool in the measurement and characterization fields to separate true images from artificial images in probe microscopy.<br>Um aspecto limitante a plena interpretação de imagens geradas por microscopia de força atômica é a interação entre a superfie varrida e ponta de varredura do sistema gerando artefatos de imagens. Para a identificação desses artefatos, propomos neste texto, um algoritmo simples capaz de assinalar esse tipo de irregularidade de imagem. A medida tem por princípio a identificação de ângulos similares formados entre dois pontos sobre a espécie varrida. O potencial de aplicação do método proposto é aqui ilustrado sobre um filme de polissacarídeo quitosana. As imagens geradas são comparadas entre si, indicando regiões de artefatos típicos gerados pela ponta de varredura. Este algoritmo apresenta-se como uma ferramenta útil a cientistas e usuários, permitindo a separação de aspectos reais e artificiais, que são fundamentais para uma melhor caracterização e medida

The effect of the dietary supplement, Chitosan, on body weight: a randomised controlled trial in 250 overweight and obese adults

CONTEXT: Chitosan, a deacetylated chitin, is a widely available dietary supplement purported to decrease body weight and serum lipids through gastrointestinal fat binding. Although evaluated in a number of trials, its efficacy remains in dispute. OBJECTIVE: To evaluate the efficacy of chitosan for weight loss in overweight and obese adults. DESIGN AND SETTING: A 24-week randomised, double-blind, placebo-controlled trial, conducted at the University of Auckland between November 2001 and December 2002. PARTICIPANTS: A total of 250 participants (82% women; mean (s.d.) body mass index, 35.5 (5.1) kg/m(2); mean age, 48 (12) y). INTERVENTIONS: Participants were randomly assigned to receive 3 g chitosan/day (n = 125) or placebo (n = 125). All participants received standardised dietary and lifestyle advice for weight loss. Adherence was monitored by capsule counts. MAIN OUTCOME MEASURES: The primary outcome measure was change in body weight. Secondary outcomes included changes in body mass index, waist circumference, body fat percentage, blood pressure, serum lipids, plasma glucose, fat-soluble vitamins, faecal fat, and health-related quality of life. RESULTS: In an intention-to-treat analysis with the last observation carried forward, the chitosan group lost more body weight than the placebo group (mean (s.e.), -0.4 (0.2) kg (0.4% loss) vs +0.2 (0.2) kg (0.2% gain), P = 0.03) during the 24-week intervention, but effects were small. Similar small changes occurred in circulating total and LDL cholesterol, and glucose (P < 0.01). There were no significant differences between groups for any of the other measured outcomes. CONCLUSION: In this 24-week trial, chitosan treatment did not result in a clinically significant loss of body weight compared with placebo