288 research outputs found
A Novel TiO2 / PVC Layer for Use in a Photoelectrochemical Cell
A novel method of coating titanium dioxide on a glassy carbon electrode as a polyvinylchloride composite , is described. On illumination , there is an enhanced voltammetric current at this TiO2/PVC composite in aqueous formic acid solution. This electrode is used as the basis of a formic acid fuel cell where oxygen is reduced at a platinum cathode. The system yields 100 cm-2 for 0.01 mol dm-3 HCOOH in 0.1 mol dm-3 NaOH under illumination from a 150 W xenon lamp. The current without illumination is 0.5 cm-2
Use of Confocal Raman Microscopy to Characterise Ethyl Cyanoacrylate Adhesive Depth Curing
In situ spatial temporal measurement of monomer conversion during adhesive bondline curing remains a challenging area. The aim of this work was to demonstrate the effectiveness of using confocal Raman microscopy in a specially configured experimental set-up, as a versatile tool for measuring monomer concentration changes as a function of both time and adhesive bond depth during ethyl cyanoacrylate polymerisation. This also allowed monitoring of the extent of polymerisation at the adhesive substrate interface independently of the bulk bondline polymerisation region. Key kinetic parameters such as inhibition time tlag, rate of reaction Rmax and extent of reaction [at]max were obtained by fitting the experimental data to sigmoidal growth curves using simple piecewise regression models. A systematic characterisation of a polymerisation reaction was conducted using different sample substrate types (copper alloy (red brass), aluminium, aluminium alloy, stainless steel and borosilicate glass) and at various reaction temperatures. Reaction rates were found to decrease further away from the substrate interface in the bulk volume region. The fastest kinetics occurred in the vicinity of nucleophilic hydroxyl rich surfaces such as at the copper alloy (red brass). In addition to substrate surface chemistry, surface roughness was also a factor, with the highest reaction rates occurring with a grit blasted (roughened) aluminium alloy (2024 T3) surface. An approximately linear dependence of the ln Rmax vs. 1/T (Arrhenius) plot was recorded within the temperature range of 291â328 K. A better fit was obtained however through the use of two separate linear slopes, possibly indicative of a change of polymerisation reaction mechanism taking place at elevated temperatures with two distinct activation energies. Further work conducted using a larger number of temperatures would be useful to verify this finding. This work confirmed that differences in the rates of interfacial and bulk polymerisation processes could be readily measured in situ using confocal Raman microscopy which is a powerful technique for investigating such surface-confined and bulk polymerisation reaction
A simple microcalorimetry system to determine the adsorption behaviour of acids in large adhesive bond gaps using base-initiated solution polymerisation of ethyl-2-cyanoacrylate
This work presents the use of a simple microcalorimetry cyanoacrylate (CA) polymerisation system for investigating aspects of CA adhesive cure through gap and adsorption of adhesive acid stabiliser by a range of metal and glass substrates. It is well established that strong acid induced inhibition periods (IPs) are almost directly proportional to the acid concentration in weak base initiated polymerisations of alkyl CAs in tetrahydrofuran (THF). Ethyl cyanoacrylate (ECA) polymerisation IP measurements were used to determine the adsorption of methanesulfonic acid (MSA) in THF or ECA solutions by a range of metal, glass and polypropylene (PP) lap shears surfaces. The extent of substrate acid sorption was found to decrease in the order: Copper- zinc alloy (C23000) \u3e grit blasted mild steel \u3e aluminium alloy 2024T3 \u3e mild steel \u3e glass \u3e aluminium \u3e stainless steel alloy 304 \u3e PP. Differences in the extent of acid sorption were accounted for in terms of two effects: surface acidity/basicity and surface area (roughness). The decrease in MSA concentration following lap shear immersion in an MSA solution was related to the reactivity of the substrates for catalysing bond line polymerisations as described in a recently reported confocal Raman spectroscopic study of ECA /substrate reactivity
Analysis of copper(II) using the ascorbate/oxygen system â a valuable undergraduate resource
In deionised water, ascorbic acid (AHâ), through oxidation by oxygen in the presence of copper(II), was found to degrade with zero-order kinetics. The magnitude of the reaction rate varied directly with the copper(II) concentration. At a higher pH (7.4), the same reaction was found to be pseudo-first order. Once again, the magnitude of the rate increased linearly with copper(II) concentration at a micromolar level. Dissolved oxygen levels, in excess AHâ and trace copper(II), displayed similar kinetics under both conditions. Monitoring of either AHâ levels or dissolved oxygen concentration was found to be a useful novel undergraduate practical laboratory for trace copper(II) determination. Students can measure the kinetics for standards and their unknown copper solution and quantitate the unknown copper
La co-conception pour engager collÚgues et étudiants dans les pédagogies actives en physique
Affiche prĂ©sentĂ©e dans le cadre du colloque de l'ARC «Favoriser lâaccĂšs et le partage par la crĂ©ation dâun observatoire» lors du 86e CongrĂšs de l'Acfas Ă l' UniversitĂ© du QuĂ©bec Ă Chicoutimi (UQAC), les 7 et 8 mai 2018.La pĂ©dagogie active (PA) amĂ©liore nettement lâapprentissage des Ă©lĂšves. Cependant, plusieurs professeurs ont de la difficultĂ© Ă la mettre en oeuvre efficacement. Sans persĂ©vĂ©rance ou conseils, ils se dĂ©couragent et reviennent Ă un style d'enseignement plus traditionnel. Nous prĂ©sentons comment la co-conception d'activitĂ©s a permis lâengagement dâun plus grand nombre de professeurs dans la mise en oeuvre de la PA. La co-conception d'activitĂ©s fait rĂ©fĂ©rence Ă la collaboration entre chercheurs en pĂ©dagogie et professeurs dans la conception de nouvelles PA. Lâobjectif est de maximiser l'engagement et l'apprentissage des Ă©tudiants, tout en considĂ©rant lâimportance de la prĂ©paration et de la rĂ©flexion Ă l'apprentissage. Des activitĂ©s en plusieurs Ă©tapes (avant, pendant et aprĂšs le cours) ont Ă©tĂ© dĂ©veloppĂ©es. Elles utilisent les plateformes numĂ©riques, l'enseignement par les pairs et lâapproche de classe inversĂ©e. Nous avons observĂ© 9 professeurs de physique (15 groupes dâenviron 25-30 Ă©tudiants) Ă plusieurs reprises. Les donnĂ©es qualitatives dĂ©montrent lâadaptabilitĂ© des activitĂ©s : les professeurs enseignant dans diffĂ©rentes salles de cours (traditionnelles ou interactives) ainsi que ceux qui souhaitent utiliser moins de technologies numĂ©riques peuvent tout autant accomplir les activitĂ©s. Nous comparons les diffĂ©rentes mises en oeuvre utilisĂ©es par les professeurs lors de lâexĂ©cution de ces nouvelles activitĂ©s et nous examinons l'Ă©volution des rĂ©alisations Ă©tudiantes
Adsorption of 5-Fluorouracil on Au(111) and Cu(111) surfaces
The adsorption of 5-Fluorouracil (5FU) on Au(111) and Cu(111) surfaces as a function of molecular coverage and temperature has been studied, using x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. The nature of 5-Fluorouracil bonding with the two substrates is remarkably different. The Cu substrate forms a chemisorbed complex with 5-FU while the Au substrate shows only physisorption. NEXAFS data at the C, N and O K-edge show a strong angular dependence, indicating that 5-FU lies nearly parallel on the inert Au(111) surface, and at a steep angle on the Cu(111) surface. 5-FU is a biomolecule used for cancer treatment and the results are relevant for those using metal surfaces to prepare 5-FU for applications such as drug delivery.The adsorption of 5-Fluorouracil (5FU) on Au(111) and Cu(111) surfaces as a function of molecular coverage and temperature has been studied, using x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. The nature of 5-Fluorouracil bonding with the two substrates is remarkably different. The Cu substrate forms a chemisorbed complex with 5-FU while the Au substrate shows only physisorption. NEXAFS data at the C, N and O K-edge show a strong angular dependence, indicating that 5-FU lies nearly parallel on the inert Au(111) surface, and at a steep angle on the Cu(111) surface. 5-FU is a biomolecule used for cancer treatment and the results are relevant for those using metal surfaces to prepare 5-FU for applications such as drug delivery
Muddying the waters: Impacts of a bogflow on carbon transport and water quality
Landslides of peat have been recorded throughout Britain and Ireland for centuries. Whilst these events are not uncommon, land degradation can amplify their magnitude and frequency and, crucially, their immediate impacts are rarely documented. A 20,000Â m3 bogflow event that occurred on land undergoing development in the Irish border area in November 2020 was monitored at high frequency in the major receiving river system (384Â km2). Samples collected every seven hours over a 28Â day period at a site 37Â km downstream were analysed for suspended sediment (SS), particulate organic carbon (POC) and dissolved organic carbon (DOC and UV-derived fractions), synchronous with hydrometeorological data and turbidity. There was no impact of the bogflow on DOC concentrations or loads. However, concentrations of SS and POC in the first samples after the bogflow were 825Â mg/L and 346Â mg C/L, respectively, and fish kill was estimated at 100Â %. Analysis of detrended SS and POC loads suggested the main impacts of the bogflow on water quality lasted just eight days. Over this period, an additional 1318Â t of SS and 608Â t of POC were transported as far as the monitoring point, equating to 325Â % more SS and 925Â % more POC than would have been expected otherwise under the same river flow conditions. The carbon loss and water quality impacts were short lived, but nevertheless severe, and highlight the vulnerability of peatlands and the risks when these environments are inappropriately managed
Distinguishing Tuberculosis from Nontuberculous Mycobacteria Lung Disease, Oregon, USA
To determine whether tuberculosis (TB) and nontuberculous mycobacteria (NTM) infection patients could be distinguished from one another with limited information, we compared pulmonary TB and NTM patients during 2005â2006. Our finding that age, birthplace, and presence of chronic obstructive pulmonary disease could differentiate TB and NTM disease could assist tuberculosis control efforts
Identifying the metabolomic fingerprint of high and low flavonoid consumers
High flavonoid consumption can improve vascular health. Exploring flavonoidâmetabolome relationships in population-based settings is challenging, as: (i) there are numerous confounders of the flavonoidâmetabolome relationship; and (ii) the set of dependent metabolite variables are inter-related, highly variable and multidimensional. The Metabolite Fingerprint Score has been developed as a means of approaching such data. This study aims to compare its performance with that of more traditional methods, in identifying the metabolomic fingerprint of high and low flavonoid consumers. This study did not aim to identify biomarkers of intake, but rather to explore how systemic metabolism differs in high and low flavonoid consumers. Using liquid chromatographyâtandem MS, 174 circulating plasma metabolites were profiled in 584 men and women who had complete flavonoid intake assessment. Participants were randomised to one of two datasets: (a) training dataset, to determine the models for the discrimination variables (n 399); and (b) validation dataset, to test the capacity of the variables to differentiate higher from lower total flavonoid consumers (n 185). The stepwise and full canonical variables did not discriminate in the validation dataset. The Metabolite Fingerprint Score successfully identified a unique pattern of metabolites that discriminated high from low flavonoid consumers in the validation dataset in a multivariate-adjusted setting, and provides insight into the relationship of flavonoids with systemic lipid metabolism. Given increasing use of metabolomics data in dietary association studies, and the difficulty in validating findings using untargeted metabolomics, this paper is of timely importance to the field of nutrition. However, further validation studies are required
Higher habitual flavonoid intakes are associated with a lower risk of peripheral artery disease hospitalizations
Background
The role of nutrition in the primary prevention of peripheral artery disease (PAD), the third leading cause of atherosclerotic cardiovascular disease, is undetermined. Flavonoids may attenuate atherosclerosis and therefore persons who consume flavonoid-rich foods may have a lower risk of developing PAD.
Objectives
We aimed to examine the association between flavonoid intake and PAD hospitalizations and investigate if the association differs according to established risk factors for PAD.
Methods
Baseline data from 55,647 participants of the Danish Diet, Cancer, and Health Study without PAD, recruited from 1993 to 1997, were cross-linked with Danish nationwide registries. Flavonoid intake was calculated from FFQs using the Phenol-Explorer database. Associations were examined using multivariable-adjusted restricted cubic splines based on Cox proportional hazards models.
Results
After a median [IQR] follow-up time of 21 [20â22] y, 2131 participants had been hospitalized for any PAD. The association between total flavonoid intake and total PAD hospitalizations was nonlinear, reaching a plateau at âŒ750â1000 mg/d. Compared with the median flavonoid intake in quintile 1 (174 mg/d), an intake of 1000 mg/d was associated with a 32% lower risk of any PAD hospitalization (HR: 0.68; 95% CI: 0.60, 0.77), a 26% lower risk of atherosclerosis (HR: 0.74; 95% CI: 0.62, 0.88), a 28% lower risk of an aneurysm (HR: 0.72; 95% CI: 0.59, 0.88), and a 47% lower risk of a hospitalization for other peripheral vascular disease (HR: 0.53; 95% CI: 0.42, 0.67). A higher total flavonoid intake was also significantly associated with a lower incidence of revascularization or endovascular surgery and lower extremity amputation. The association between total flavonoid intake and PAD hospitalizations differed according to baseline smoking status, alcohol intake, BMI, and diabetes status.
Conclusions
Ensuring the adequate consumption of flavonoid-rich foods, particularly in subpopulations prone to the development of atherosclerosis, may be a key strategy to lower the risk of PAD
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