Microfabricated Reference Electrodes and their Biosensing Applications

Over the past two decades, there has been an increasing trend towards miniaturization of both biological and chemical sensors and their integration with miniaturized sample pre-processing and analysis systems. These miniaturized lab-on-chip devices have several functional advantages including low cost, their ability to analyze smaller samples, faster analysis time, suitability for automation, and increased reliability and repeatability. Electrical based sensing methods that transduce biological or chemical signals into the electrical domain are a dominant part of the lab-on-chip devices. A vital part of any electrochemical sensing system is the reference electrode, which is a probe that is capable of measuring the potential on the solution side of an electrochemical interface. Research on miniaturization of this crucial component and analysis of the parameters that affect its performance, stability and lifetime, is sparse. In this paper, we present the basic electrochemistry and thermodynamics of these reference electrodes and illustrate the uses of reference electrodes in electrochemical and biological measurements. Different electrochemical systems that are used as reference electrodes will be presented, and an overview of some contemporary advances in electrode miniaturization and their performance will be provided

Improved search for invisible modes of nucleon decay in water with the SNO+ detector

This paper reports results from a search for single and multi-nucleon disappearance from the $^{16}$O nucleus in water within the \snoplus{} detector using all of the available data. These so-called "invisible" decays do not directly deposit energy within the detector but are instead detected through their subsequent nuclear de-excitation and gamma-ray emission. New limits are given for the partial lifetimes: $\tau(n\rightarrow inv) > 9.0\times10^{29}$ years, $\tau(p\rightarrow inv) > 9.6\times10^{29}$ years, $\tau(nn\rightarrow inv) > 1.5\times10^{28}$ years, $\tau(np\rightarrow inv) > 6.0\times10^{28}$ years, and $\tau(pp\rightarrow inv) > 1.1\times10^{29}$ years at 90\% Bayesian credibility level (with a prior uniform in rate). All but the ($nn\rightarrow inv$) results improve on existing limits by a factor of about 3.info:eu-repo/semantics/publishedVersio

Observation of Antineutrinos from Distant Reactors using Pure Water at SNO+

The SNO+ collaboration reports the first observation of reactor antineutrinos in a Cherenkov detector. The nearest nuclear reactors are located 240 km away in Ontario, Canada. This analysis used events with energies lower than in any previous analysis with a large water Cherenkov detector. Two analytical methods were used to distinguish reactor antineutrinos from background events in 190 days of data and yielded consistent observations of antineutrinos with a combined significance of 3.5 $\sigma$.Comment: v2: add missing author, add link to supplemental materia

Measurement of neutron-proton capture in the SNO+ water phase

The SNO+ experiment collected data as a low-threshold water Cherenkov detector from September 2017 to July 2019. Measurements of the 2.2-MeV $\gamma$ produced by neutron capture on hydrogen have been made using an Am-Be calibration source, for which a large fraction of emitted neutrons are produced simultaneously with a 4.4-MeV $\gamma$. Analysis of the delayed coincidence between the 4.4-MeV $\gamma$ and the 2.2-MeV capture $\gamma$ revealed a neutron detection efficiency that is centered around 50% and varies at the level of 1% across the inner region of the detector, which to our knowledge is the highest efficiency achieved among pure water Cherenkov detectors. In addition, the neutron capture time constant was measured and converted to a thermal neutron-proton capture cross section of $336.3^{+1.2}_{-1.5}$ mb

Development, characterisation, and deployment of the SNO+ liquid scintillator

A liquid scintillator consisting of linear alkylbenzene as the solvent and 2,5-diphenyloxazole as the fluor was developed for the SNO+ experiment. This mixture was chosen as it is compatible with acrylic and has a competitive light yield to pre-existing liquid scintillators while conferring other advantages including longer attenuation lengths, superior safety characteristics, chemical simplicity, ease of handling, and logistical availability. Its properties have been extensively characterized and are presented here. This liquid scintillator is now used in several neutrino physics experiments in addition to SNO+

Educational Studies Examining Knowledge of Substance Use Disorders and Career Aspirations among Medical Trainees in an Inner-City Hospital

Objectives: Gaps in addiction medicine training are a reason for poor substance use care in North America. Hospital addiction medicine consult services (AMCS) provide critical medical services, including screening and treatment of substance use disorders (SUD). While these programs often feature an educational component for medical learners, the impact of AMCS teaching on objective knowledge and career aspirations in addiction medicine has not been well described. Methods: We report findings from two sequential studies conducted at a large academic hospital in Vancouver, Canada. The first study assessed the impact of an AMCS clinical rotation on medical trainee addiction medicine objective knowledge using an online survey of six true/false questions before and after the rotation. The second study examined the impact of an AMCS rotation on career aspirations using four seven-point Likert-type questions. One-sample t-tests on mean differences (MD) with Benjamini-Hochberg adjustment for multiple comparisons were employed for statistical analyses. Results: Between May 2017 – June 2018, knowledge scores were significantly higher postrotation (MD = 4.78, standard deviation [SD] = 19.5, p = 0.034) among 115 medical trainees. Between July 2018 – July 2019, aspirations to practice addiction medicine were significantly more favourable post-rotation (MD = 3.48, SD = 3.15, p < 0.001) among 101 medical trainees. Conclusions: AMCS rotations appear to improve addiction medicine knowledge and aspirations to practice addiction medicine among medical trainees. Larger-scale evaluations and outcomes research on integrating SUD teaching in these settings will help move the discipline forward.Medicine, Faculty ofNon UBCFamily Practice, Department ofMedicine, Department ofReviewedFacultyResearcherGraduat

Slender and stumpy bloodstream forms of Trypanosoma brucei display a differential response to extracellular acidic and proteolytic stress.

Natural infections of mammals with African trypanosomes, such as Trypanosoma brucei, are generally pleomorphic, the population consisting of different forms, termed slender and stumpy forms, that vary in number as the parasitaemia develops. We show that the differentiation of slender into stumpy forms is characterized by the acquisition by the parasite of the ability to regulate its internal pH, even in the face of a large, inwardly directed gradient of H+, as well as a tolerance towards external proteolytic stress. These adaptations effectively abbrogate cellular stress-activated signalling pathways involving adenylate cyclase and glycosylphosphoinositol-specific phospholipase-C mediated release of the surface coat. Although in metabolic terms stumpy forms of the parasite are considered to be preadapted to life in the arthropod vector, these data clearly demonstrate that these forms also possess additional cellular adaptations designed to deal with the immediate and potentially harmful changes in the extracellular environment that occur upon ingestion of a bloodmeal by the tsetse fly vector.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe