Highly sensitive alkane odour sensors based on functionalised gold nanoparticles

We deposit dense, ordered, thin films of Au-dodecanethiol core/shell nanoparticles by the Langmuir-Schafer (LS) printing method, and find that their resistance at ambient temperature responds selectively and sensitively to alkane odours. Response is a rapid resistance increase due to swelling, and is strongest for alkane odours where the alkane chain is similar in length to the dodecane shell. For decane odours, we find a response to concentrations as low as 15 ppm, about 600 times below the lower explosive limit. Response is weaker, but still significant, to aromatic odours (e.g. Toluene, Xylene), while potential interferants such as polar and/or hydrogen-bonding odours (e.g. alcohols, ketones, water vapour) are somewhat rejected. Resistance is weakly dependent on temperature, and recovers rapidly and completely to its original value within the error margin of measurement. (C) 2011 Elsevier B.V. All rights reserved

Inclusion of dietary fibre in model liquid and solid systems using chemistry and structure to probe potential functionality

Oat grain, being one of the major cereals in Australia, contains various macromolecules and microconstituents including protein, lipid, dietary fibre and phytochemicals that are beneficial to human health. Despite its advantageous attributes, inclusion of sufficient amount of finely milled oat powder in commercial food formulations is still limited due to undesirable organoleptic properties that might develop during storage prior to consumption. Therefore, the objective of this study is to probe the influence of oat in model liquid and solid systems through an armoury of analytical and physicochemical techniques, i.e. chromatography, spectroscopy, rheology, calorimetry, microscopy and sensory evaluation. The first experimental chapter deals with the development of various analytical protocols to probe the presence of microconstituents in model liquid oat systems following UHT processing and subsequent storage. Compounds of interest included phenolic acids (ferulic and para-coumaric acids), avenanthramides, free fatty acids and volatile lipid oxidation products. Sample preparation involved a UHT treatment at 145 °C for 5 s followed by a twelve-week storage at 22 and 30 °C. Soluble and insoluble dietary fibre fractions (SDF and IDF, respectively) were extracted from defatted oat samples through sequential enzymatic digestion. In order to extract ester bound phenolic acids, alkaline hydrolysis and liquid–liquid partitioning steps were applied to SDF and IDF. Moderate enzymatic digestion temperature (50 °C) and saponification (2M NaOH for 6 hr) were found to produce the best separation of phenolic compounds analysed by high performance liquid chromatography (HPLC). Chromatograms showed prominent ferulic and para-coumaric acids in both fractions, which were located mainly in IDF, and that was confirmed by the total phenolic content results obtained from Folin-Ciocalteau assay. Alkaline based extraction with methanol and an HPLC method were developed to analyse the avenanthramide content in oat samples. Results demonstrated that the protocols were able to detect the primary avenanthramides, i.e. A, B and C. In addition to phenolic compounds, the work examined oat lipids and their oxidation products which are the main culprit of rancid flavour in liquid oat systems. Free fatty acid determination involved fatty acid methyl ester (FAME) analysis coupled with a comprehensive gas chromatography (GC×GC) technique. Chromatograms recorded three main fatty acids, i.e. palmitic, linoleic and oleic acids, which accounted for nearly 98% of the total free fatty acids. In the case of secondary lipid oxidation compounds, head space solid phase micro-extraction (SPME) coupled with gas chromatography-mass spectroscopy (GC-MS) analysis was developed to detect the presence of volatiles, which are predominantly hexanal and 2-pentyl furan. Once the required analytical protocols were established, the focus in this work turned to the evolution of the aforementioned microconstituents during extended storage at 22 and 30 °C. It was observed that ferulic acid decreases over time at both temperatures while para-coumaric acid remains more or less stable but at a much lower content. Reduction in ferulic acid suggested conversion into another compound called paravinyl guaiacol (PVG), and this is known as the process of thermal decarboxylation. The content of avenanthramides also remained unchanged over time at both experimental temperatures. In the case of free fatty acids, unsaturated moieties (oleic and linoleic acids) decreased with temperature indicating the occurrence of lipid oxidation. That was confirmed by an increase in the levels of volatiles (hexanal and 2-pentyl furan) during storage, with the oxidation process being enhanced with increasing storage temperature. The second experimental chapter looked at off-flavour producing compounds, in particular PVG and hexanal, in relation to the sensory quality of model UHT liquid systems enriched with wholegrain oat during storage. In doing so, finely milled oat powder was mixed with skim milk powder and sucrose followed by UHT treatment and storage at ambient temperature. It was found that trained panellists were capable of differentiating the odours generated by the two compounds and identifying their intensity in the UHT samples as a function of storage time. Furthermore, a 9-point hedonic test was conducted with semi-trained panellists to assess the acceptability levels of both odours in the UHT samples. Results suggest that hexanal is the main contributor to off-flavour development in oat based liquid systems, hence arguing for the importance of avoiding lipid oxidation in these materials. Following the study on model UHT liquid systems, the third experimental chapter focuses on UHT beverage formulations that closely resemble commercial oat products. Results unveil the importance of the particle size distribution of oat fibre on the overall acceptability of liquid foods, as well as on their consistency. Increasing the particle size distribution and concentration of these particles yields higher steady shear viscosity. Furthermore, prolonged storage at 22 °C enhanced the beverages’ viscosity, whereas storage at 30 °C produces the opposite trend. The former event is attributed to the swelling of fibre particles, whereas the latter is due to the hydration of starch molecules, which dissolve into the beverage matrix (particle erosion beyond swelling), hence being unable to suspend in solution the insoluble parts of the oat particle. Given the above effect of oat-particle addition on the consistency of beverages as a major ingredient in formulations, the study was expanded into a model solid system containing gelatin as the supporting matrix. Protein concentration was fixed at 2% (w/w), with the level of oat particles varying from 0 to 4% (w/w). Findings demonstrate phase separated systems, with gelatin and oat particles serving as the continuous and dispersed phases, respectively. Incorporation of oat particles weakened the mechanical strength of the protein gels, which is a new finding in the field of hydrocolloid gels. Besides concentration, the work explores the effect of different size distribution of oat particles on the composite gels and argues that smaller particles are able to disrupt swiftly the protein network compared to the larger counterparts. Outcomes from this PhD thesis provide valuable knowledge in understanding the causes of sensory and textural profiles that might be experienced in oat based food systems. Hence, the research can be used as a basis to develop palatable processed foods, over prolonged storage, which are enriched with high levels of wholegrain powders

The Contribution of the Means of Communication and Media in Building the Saudi National Identity

The aim of the research is to study the contribution of modern means of communication and media in building and shaping the national identity among the members of the Saudi society by adopting the quantitative approach to measure the extent of the contribution of the means of communication and media in building the national identity from the point of view of the recipient: male and female Saudis. By preparing, distributing and analyzing the results of a questionnaire that was directed electronically to a sample of members of Saudi society and the qualitative approach, to determine the implications of the demographic characteristics of the audience groups, the characteristics of the means of communication and media, and the forms of exposure of the public to the means of communication and media on the role played by the various means of communication and media in building the national identity in the Kingdom of Saudi Arabia. The study reached a set of results and conclusions, the most important of which are: Only a third of the study sample considers the means of communication, the media and social networking sites contribute to the formation of the national identity and that most of them are female. Public exposure to media and communication

Aboriginal and Non-Aboriginal Students Learn About Natural Health Products from Different Information Sources

Natural health products (NHPs) include naturally derived botanical and nonbotanical products. Past research indicates a high prevalence of NHPs use amongst adults in the United States and Canada but does not clearly characterize NHPs use amongst students, ethnic variations of such use, or how users learn about NHPs. We hypothesize that there is a difference between Aboriginal and non-Aboriginal students in how they learn about NHPs. To investigate this question, we conducted a cross-sectional study at First Nations University of Canada and the University of Regina, Saskatchewan, Canada, during the fall of 2011. Aboriginal (n=214) and non-Aboriginal (n=749) students participated in the 28 question survey. Our results indicate that Aboriginal students who use NHPs are found in all age groups, are mostly female, are smokers and nonsmokers, and learn about NHPs from Elders and healers. Compared to nonAboriginal students, Aboriginal students rely significantly less on alternative and conventional health providers, electronic media, print media, and advertising as their sources of information about NHPs. Thus, Aboriginal students use Elders or healers as a primary source of information to learn about NHPs, as compared to non-Aboriginal students. Future work should investigate the role of Elder traditional educators to convey NHPs information directed specifically to Aboriginal university students

Water-gated transistor using ion exchange resin for potentiometric fluoride sensing

We introduce fluoride-selective anion exchange resin sorbents as sensitisers into membranes for water-gated field effect transistors (WGTFTs). Sorbents were prepared via metal (La or Al)-loading of a commercial macroporous aminophosphonic acid resin, PurometTM MTS9501, and were filled into a plasticised poly(vinyl chloride) (PVC) phase transfer membrane. We found a potentiometric response (membrane potential leading to WGTFT threshold shift) to fluoride following a Langmuir–Freundlich (LF) adsorption isotherm with saturated membrane potential up to ~480 mV, extremely low characteristic concentration c1/2 = 1/K, and picomolar limit of detection (LoD), even though ion exchange did not build up charge on the resin. La-loading gave a superior response compared to Al-loading. Membrane potential characteristics were distinctly different from charge accumulating sensitisers (e.g., organic macrocycles) but similar to the Cs+ (cation) selective ion-exchanging zeolite mineral ‘mordenite’. We propose a mechanism for the observed threshold shift and investigate interference from co-solutes. Strong interference from carbonate was brought under control by ‘diluting’ metal loading in the resin. This work sets a template for future studies using an entirely new ‘family’ of sensitisers in applications where very low limit of detection is essential such as for ions of arsenic, mercury, copper, palladium, and gold

Fundamental investigation into tool wear and surface quality in high-speed machining of Ti6Al4V alloy

This paper reports a fundamental investigation consisting of systematic trials into the response of Ti6Al4V alloy to high-speed machining using carbide inserts. It is a useful extension to work previously published, and aims at assessing the impact of the process parameters, depth of cut, cutting speed and feed rate in addition to cutting length, and their interrelations, on observed crater and flank wear and roughness of the machined surface. The results showed that abrasion was the most important flank wear mechanism at high speed. It also showed that increased cutting length accelerated crater wear more than exhibited flank wear and had considerable effect on surface roughness. In particular, crater wear increased by over 150% (on average), and flank wear increased by 40% (on average) when increasing cutting length from 40 to 120 mm. However, cutting the same length increased surface roughness by 50%, which helps explain how progression of tool wear leads to deteriorated surface quality. ANOVA was used to perform statistical analyses of the measured data and revealed that cutting length and depth of cut had the greatest effect on both crater and flank wear of the cutting tool. These results confirm that high-speed machining of Ti6Al4V alloy is a reliable process, with cutting speed identified as having a relatively small influence on the tool wear and resultant roughness of the machined surface relative to other parameters

A Phytochemical Analysis, Microbial Evaluation and Molecular Interaction of Major Compounds of Centaurea bruguieriana Using HPLC-Spectrophotometric Analysis and Molecular Docking

Centaurea is one of the most important genera within the family Asteraceae. An investigation of the phytochemical composition of Centaurea bruguieriana using Gas-Chromatography coupled to Mass spectrometry (GC-MS) was performed. Antimicrobial activity was evaluated using the minimum inhibitory concentration method (MIC) and validated by molecular docking for the major compounds of the most active fraction (1,10-di-epi-cubenol and methyl 8-oxooctanoate) of C. bruguieriana against three bacterial receptors (TyrRS, DNA gyrase, and dihydrofolate reductase (DHFR)). Evaluation of antioxidant activity was conducted using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. High-performance liquid chromatography (HPLC) was used to identify and quantify the contents of major compounds from ethyl acetate fraction (luteolin 7-O-glucoside, chlorogenic acid, kaempferol and isorhamnetin). The antimicrobial activity test showed that the chloroform fraction was more active against all microbial strains. The results of the molecular docking of two major compounds from chloroform fraction showed that good affinities were made between 1,10-di-epi-cubenol and the three selected receptors (TyrRs: −6.0 Kcal/mol against −8.2 Kcal/mol obtained with clorobiocin (standard); DNA gyrase: −6.6 Kcal/mol against −9.1 Kcal/mole obtained with clorobiocin; DHFR: −7.4 Kcal/mol against −6.3 Kcal/mol obtained with SCHEMBL2181345 Standard). Antioxidant evaluation showed that the ethyl acetate fraction was the most active fraction in DPPH (IC50 49.4 µg/mL) and ABTS (IC50 52.8 µg/mL) models. HPLC results showed the contents of luteolin 7-O-glucoside (7.4 µg/mg), and chlorogenic acid (3.2 µg/mg). Our study demonstrated that C. bruguierana is a promising source of bioactive compounds

A Phytochemical Analysis, Microbial Evaluation and Molecular Interaction of Major Compounds of Centaurea bruguieriana Using HPLC-Spectrophotometric Analysis and Molecular Docking

Centaurea is one of the most important genera within the family Asteraceae. An investigation of the phytochemical composition of Centaurea bruguieriana using Gas-Chromatography coupled to Mass spectrometry (GC-MS) was performed. Antimicrobial activity was evaluated using the minimum inhibitory concentration method (MIC) and validated by molecular docking for the major compounds of the most active fraction (1,10-di-epi-cubenol and methyl 8-oxooctanoate) of C. bruguieriana against three bacterial receptors (TyrRS, DNA gyrase, and dihydrofolate reductase (DHFR)). Evaluation of antioxidant activity was conducted using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. High-performance liquid chromatography (HPLC) was used to identify and quantify the contents of major compounds from ethyl acetate fraction (luteolin 7-O-glucoside, chlorogenic acid, kaempferol and isorhamnetin). The antimicrobial activity test showed that the chloroform fraction was more active against all microbial strains. The results of the molecular docking of two major compounds from chloroform fraction showed that good affinities were made between 1,10-di-epi-cubenol and the three selected receptors (TyrRs: −6.0 Kcal/mol against −8.2 Kcal/mol obtained with clorobiocin (standard); DNA gyrase: −6.6 Kcal/mol against −9.1 Kcal/mole obtained with clorobiocin; DHFR: −7.4 Kcal/mol against −6.3 Kcal/mol obtained with SCHEMBL2181345 Standard). Antioxidant evaluation showed that the ethyl acetate fraction was the most active fraction in DPPH (IC50 49.4 µg/mL) and ABTS (IC50 52.8 µg/mL) models. HPLC results showed the contents of luteolin 7-O-glucoside (7.4 µg/mg), and chlorogenic acid (3.2 µg/mg). Our study demonstrated that C. bruguierana is a promising source of bioactive compounds

Design and manufacture of functional catalyst-carrier structures for the bioorthogonal activation of anticancer agents

Novel palladium (Pd)-loaded titanium (Ti) devices with high biocompatibility and catalytic activity were prepared using a range of fabrication methods such as powder metallurgy (i.e. sintering with and without space-holder), sputtering, pulsed laser deposition and supersonic cluster beam deposition. The surface of the Ti-[Pd] devices were physico-chemically characterised to confirm the non-alloyed state of the Pd coating onto the titanium substrate. The Pd thickness was optimised to achieve maximum surface area (i.e. maximum catalytic effect) using the minimum amount of material in each method for cost effective production. The catalytic response of the different Ti-[Pd] devices was evaluated under biocompatible conditions by employing an off-on Pd-activatable fluorescent probe. The most robust coating of Pd was produced by an optimised magnetron sputtering method. The sputtered Ti-[Pd] devices were selected to induce the bioorthogonal uncaging of the anticancer drug Vorinostat from a pharmacologically-inactive Pd-activatable precursor in cancer cell culture, demonstrating the capacity of these devices to mediate a local anti-tumour effect via in-situ release of a clinically approved drug. This approach is the first step towards surgically implantable devices that could facilitate targeting affected areas with high spatial selectivity, improving pharmacological activity and reducing systemic side effects through localised treatment directly at the cancer site

Internet risks for children: Parents' perceptions and attitudes: An investigative study of the Saudi Context

Internet has become a part of our children’s daily activities at home and at school. The benefits of the Internet for children are huge and include education and entertainment. However, the same technologies also pose some risks that parents need to identify and guard against. A lack of awareness can cause children to encounter serious danger and become victims of Internet criminals. To the best of the authors’ knowledge, no previous research has been conducted in Saudi Arabia on parent’s awareness of the risks of Internet use to their children and how Saudi’s parents seek to mitigate those risks. This paper investigates the associations and correlations between what parents do and what children say about online risks. It compares and contrasts parents’ mediation strategies and their children’s online habits with the aim of investigating which parental mediation strategy has taken place to reduce the risk of online activity against children. The findings indicate a substantial gap between what children do online and what their parents know. The majority of parents are interested in monitoring their children’s online activities and collaborating with their children on those activities, but most parents also do not have a strategy for accomplishing this. The survey indicated an absence of collaboration between parents and children to ensure online safety. This is not a result of a lack of interest, but rather a result of a shortage of resources due to time constraints, and poor knowledge of the Internet, or lifestyle choices