Physical Sciences and Mathematics Commons^™

Advancements In Fractal Plasmonics: Structures, Optical Properties, And Applications., Gregory Q Wallace, Francois Lagugne-Labarthet

Chemistry Publications

The structural characteristics of plasmonic nanostructures directly influence their plasmonic properties, and therefore, their potential role in applications ranging from sensing and catalysis to light- and energy-harvesting. For a structure to be compatible with a selected application, it is critical to accurately tune the plasmonic properties over a specific spectral range. Fabricating structures that meet these stringent requirements remains a significant challenge as plasmon resonances are generally narrow with respect to the considered selected spectral range. Adapted from their well-established role in GHz applications, plasmonic fractal structures have emerged as architectures of interest due to their ability to support multiple …

Near-Infrared Photoluminescence And Electrochemiluminescence From An Exceptionally Simple Boron Difluoride Formazanate Dye, Ryan R. Maar, Ruizhong Zhang, David G. Stephens, Zhifeng Ding, Joe Gilroy

Chemistry Publications

Electrochemiluminescence involves the generation of light via electrochemical reactions and has recently shown utility for single-cell imaging. To further develop this novel imaging platform, it is necessary to produce readily available dyes that photoluminesce and electrochemiluminesce in the near-infrared region to limit absorption by biological tissue. To address this need, we prepared a boron difluoride formazanate dye that exhibits near-infrared photoluminescence and electrochemiluminescence in two straightforward synthetic steps. Examination of its solid-state structure suggests that the N-aryl substituents have significant quinoidal character, which narrows the S₁-S₀ energy gap and leads to near-infrared absorption and photoluminescence. Electrochemical …

Evidence For A Partially Stalled Γ Rotor In F, Angela Murcia Rios, Siavash Vahidi, Stanley D Dunn, Lars Konermann

Chemistry Publications

F₁-ATPase uses ATP hydrolysis to drive rotation of the γ subunit. The γ C-terminal helix constitutes the rotor tip that is seated in an apical bearing formed by α₃β₃. It remains uncertain to what extent the γ conformation during rotation differs from that seen in rigid crystal structures. Existing models assume that the entire γ subunit participates in every rotation. Here we interrogated E. coli F₁-ATPase by hydrogen-deuterium exchange (HDX) mass spectrometry. Rotation of γ caused greatly enhanced deuteration in the γ C-terminal helix. The HDX kinetics implied that most F_{1 …}

Trends In Obesity And Multimorbidity In Canada., Michael Lebenbaum, Gregory S Zaric, Amardeep Thind, Sisira Sarma

Epidemiology and Biostatistics Publications

Very few studies have examined trends in multimorbidity over time and even fewer have examined trends over time across different body mass index (BMI) groups. Given a general decline in death rates but increased cardiovascular risk factors among individuals with obesity, the trend in the association between obesity and multimorbidity is hypothesized to be increasing over time. The data for our study came from the 1996-97 National Population Health Survey and the 2005 and 2012-13 Canadian Community Health Surveys (N = 277,366 across all 3 surveys). We examined trends in the association between BMI groups and multimorbidity using a logistic …

Rates Of Planimetric Change In A Proglacial Gravel-Bed Braided River: Field Measurement And Physical Modeling, Lara Middleton, Peter Ashmore, Pauline Leduc, Darren Sjogren

Geography & Environment Publications

Planimetric change was measured on daily hydrographs over two meltwater seasons using time-lapse images of the proglacial, gravel, braided, Sunwapta River, Canada. Significant planimetric change occurred on 10-15 days per year. Area of planimetric change correlated with peak and total daily meltwater hydrograph discharge. A clear threshold discharge can be identified below which no planform activity occurs, an intermediate range over which change occurs conditionally, and a peak flow range at which significant change always occurs. Field conditions were reproduced in a physical model in a laboratory flume. Photogrammetric DEMs of bed morphology and measurements of bedload output were made …

Phosphonium Hydrogels For Controlled Release Of Ionic Cargo., Tristan D Harrison, Paul J Ragogna, Elizabeth R Gillies

Chemistry Publications

We describe the synthesis of three different phosphonium salts and their reaction with poly(ethylene glycol) dimethacrylate to create cationic hydrogels. The hydrogels were loaded with an anionic dye and an anionic anti-inflammatory drug through ionic interactions and compared with an analogous ammonium gel. The release rates of these anions depended on their structure and pKa values, as well as the pH and ionic strength of the release medium.

Computer Games Are Serious Business And So Is Their Quality: Particularities Of Software Testing In Game Development From The Perspective Of Practitioners, Ronnie Santos, Cleyton Magalhaes, Luiz Fernando Capretz, Jorge Correia-Neto, Fabio Q. B. Silva Dr., Abdelrahman Saher

Electrical and Computer Engineering Publications

Over the last several decades, computer games started to have a significant impact on society. However, although a computer game is a type of software, the process to conceptualize, produce and deliver a game could involve unusual features. In software testing, for instance, studies demonstrated the hesitance of professionals to use automated testing techniques with games, due to the constant changes in requirements and design, and pointed out the need for creating testing tools that take into account the flexibility required for the game development process. Goal. This study aims to improve the current body of knowledge regarding software …

Substance Use Patterns Among Women Living With Hiv Compared With The General Female Population Of Canada, Mostafa Shokoohi, Greta R Bauer, Angela Kaida, Ashley Lacombe-Duncan, Mina Kazemi, Brenda Gagnier, Alexandra De Pokomandy, Mona Loutfy

Epidemiology and Biostatistics Publications

BACKGROUND: HIV infection and substance use synergistically impact health outcomes of people with HIV. In this study, we assessed the prevalence of substance use among women living with HIV (WLWH) and compared them with expected values from general data.

METHODS: Cigarette smoking, frequency of alcohol consumption, last-month non-prescribed cannabis use (vs. last-year use), and last 3 months regular (≥once/week) and occasional (

RESULTS: Compared to expected estimates from general population women, a higher proportion of WLWH reported daily cigarette smoking (SPD: 26.8% [95% CI: 23.9, 29.7]), smoking ≥20 cigarettes/day (SPD: 11.6% [9.8, 13.6]), regular non-prescribed cannabis use (SPD: 8.0% [4.1, …

Family Physician Remuneration Schemes And Specialist Referrals: Quasi-Experimental Evidence From Ontario, Canada., Sisira Sarma, Nirav Mehta, Rose Anne Devlin, Koffi Ahoto Kpelitse, Lihua Li

Epidemiology and Biostatistics Publications

Understanding how family physicians respond to incentives from remuneration schemes is a central theme in the literature. One understudied aspect is referrals to specialists. Although the theoretical literature has suggested that capitation increases referrals to specialists, the empirical evidence is mixed. We push forward the empirical research on this question by studying family physicians who switched from blended fee-for-service to blended capitation in Ontario, Canada. Using several health administrative databases from 2005 to 2013, we rely on inverse probability weighting with fixed-effects regression models to account for observed and unobserved differences between the switchers and nonswitchers. Switching from blended fee-for-service …

Surprising Antibacterial Activity And Selectivity Of Hydrophilic Polyphosphoniums Featuring Sugar And Hydroxy Substituents., Tyler J Cuthbert, Benjamin Hisey, Tristan D Harrison, John F Trant, Elizabeth R Gillies, Paul J Ragogna

Chemistry Publications

There is currently an urgent need for the development of new antibacterial agents to combat the spread of antibiotic-resistant bacteria. We explored the synthesis and antibacterial activities of novel, sugar-functionalized phosphonium polymers. While these compounds exhibited antibacterial activity, we unexpectedly found that the control polymer poly(tris(hydroxypropyl)vinylbenzylphosphonium chloride) showed very high activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus and very low haemolytic activity against red blood cells. These results challenge the conventional wisdom in the field that lipophilic alkyl substituents are required for high antibacterial activity and opens prospects for new classes of antibacterial polymers.

Evolution Of Grain Size Distributions And Bed Mobility During Hydrographs In Gravel-Bed Braided Rivers, Sarah Peirce, Peter Ashmore, Pauline Leduc

Geography & Environment Publications

Evolution of bed material mobility and bedload grain size distributions under a range of discharges is rarely observed in braiding in gravel-bed rivers. Yet, the changing of bedload grain size distributions with discharge is expected to be different from laterally stable, threshold, channels on which most gravel bedload theory and observation are based. Here, simultaneous observations of flow, bedload transport rate, and morphological change were made in a physical model of a gravel-bed braided river to document the evolution of grain size distributions and bed mobility over three experimental event hydrographs. Bedload transport rate and grain size distributions were measured …

Hpc For Predictive Models In Healthcare, Luiz Fernando Capretz

Electrical and Computer Engineering Publications

Increasingly we are faced with complex health data, thus researchers are limited in their capacity to mine data in a way that accounts for the complex inter-relationships between health variables of interest. This research tackles the challenge of producing accurate health prediction models in order to overcome the limitations of simple multivariate regression techniques and the assumption of linear association, also known as algorithmic models, by combining it with a soft computing approach. Predictive models develop methods to enable healthcare researchers and professionals to predict the likelihood of an individual's proclivity to a disease and the likely effectiveness of possible …

Effectiveness Of 4-Aminopyridine For The Management Of Spasticity In Spinal Cord Injury: A Systematic Review, Joshua Weiner, Jane Hsieh, Amanda Mcintyre, Robert Teasell

Epidemiology and Biostatistics Publications

Background: Spasticity is a common secondary complication of spinal cord injury (SCI), which can severely impact functional independence and quality of life. 4-Aminopyridine (4-AP) is a potassium channel blocker that has been studied as an intervention for spasticity in individuals with SCI. Objective: To conduct a systematic review of the available evidence regarding the effectiveness of 4-AP for the management of spasticity in individuals with SCI. Methods: A comprehensive literature search was conducted on five electronic databases for articles published in English up to January 2017. Studies were included if (1) the sample size was three or more subjects, (2) …

Multi-Stimuli-Responsive Self-Immolative Polymer Assemblies, Rebecca E. Yardley, Elizabeth R. Gillies

Chemistry Publications

Self-immolative polymers (SIPs) undergo depolymerization in response to the cleavage of stimuli-responsive end-caps from their termini. Some classes of SIPs, including polycarbamates, have depolymerization rates that depend on environmental factors such as solvent and pH. In previous work, hydrophobic SIPs have been incorporated into amphiphilic block copolymers and used to prepare nanoassemblies. However, stimuli-responsive hydrophilic blocks have not previously been incorporated. In the current work, we synthesized amphiphilic copolymers composed of a hydrophobic polycarbamate SIP block and a hydrophilic poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) block connected by a UV light-responsive linker end-cap. It was hypothesized that after assembly of the block copolymers …

Electrospray Ionization Of Polypropylene Glycol: Rayleigh-Charged Droplets, Competing Pathways, And Charge State-Dependent Conformations., Quentin Duez, Haidy Metwally, Lars Konermann

Chemistry Publications

Recent molecular dynamics (MD) simulations from various laboratories have advanced the general understanding of electrospray ionization (ESI)-related processes. Unfortunately, computational cost has limited most of those previous endeavors to ESI droplets with radii of ∼3 nm or less, which represent the low end of the size distribution in the ESI plume. The current work extends this range by conducting simulations on aqueous ESI droplets with radii of 5.5 nm (∼23 000 water molecules). Considering that computational cost increases with r⁶, this is a significant step forward. We focused on the ESI process for polypropylene glycol (PPG) which is …

Chain Ejection Model For Electrospray Ionization Of Unfolded Proteins: Evidence From Atomistic Simulations And Ion Mobility Spectrometry., Haidy Metwally, Quentin Duez, Lars Konermann

Chemistry Publications

The ion evaporation model (IEM) and the charged residue model (CRM) represent cornerstones of any discussion related to the mechanism of electrospray ionization (ESI). Molecular dynamics (MD) simulations have confirmed that small ions such as Na⁺ are ejected from the surface of aqueous ESI droplets (IEM), while folded proteins in native ESI are released by water evaporation to dryness (CRM). ESI of unfolded proteins yields [M + zH] ^z+ ions that are much more highly charged than their folded counterparts. A chain ejection model (CEM) has been proposed to account for the protein ESI behavior under such non-native conditions …

Imaging The Surface Of A Hand-Colored 19th Century Daguerreotype., Madalena S Kozachuk, Maria O Avilés, Ronald R Martin, Brianne Potts, Tsun-Kong Sham, François Lagugné-Labarthet

Chemistry Publications

Daguerreotypes are valued artifacts that constitute a unique historical photographic memory of the 19th century. Understanding their surface chemistry is important in order to conserve and, when necessary, to restore them. Colored highlights were often added by hand to emphasize different features on the daguerreotype's subjects. In the present work, we report on a daguerreotype that was hand-colored with a red pigment that was added to the cheeks of the two individuals. A series of experiments using micro-Raman and micro-Fourier transform infrared spectroscopy and synchrotron-based X-ray fluorescence microscopy and absorption spectroscopy are used to analyze the surface and to determine …

Controlled Polymerization Of Ethyl Glyoxylate Using Alkyllithium And Alkoxide Initiators, Amir Rabiee Kenaree, Elizabeth R. Gillies

Chemistry Publications

The synthesis of poly(ethyl glyoxylate)s (PEtGs) by anionic polymerization was explored. PEtGs are a subclass of stimuli-responsive self-immolative polymers with promising properties for applications as coatings, sensors, and drug delivery vehicles. In this report, a new purification procedure for the preparation of highly pure ethyl glyoxylate (EtG), suitable for anionic polymerization reactions, and the first successful examples of controlled polymerization of EtG are described. n-BuLi, PhLi, and t-BuLi were employed as initiators under different experimental conditions and their behavior was examined using NMR spectroscopy, size exclusion chromatography, and thermal analysis to develop an optimized procedure. As functional alkoxide …

How To Run Molecular Dynamics Simulations On Electrospray Droplets And Gas Phase Proteins: Basic Guidelines And Selected Applications., Lars Konermann, Haidy Metwally, Robert G Mcallister, Vlad Popa

Chemistry Publications

The ability to transfer intact proteins and protein complexes into the gas phase by electrospray ionization (ESI) has opened up numerous mass spectrometry (MS)-based avenues for exploring biomolecular structure and function. However, many details regarding the ESI process and the properties of gaseous analyte ions are difficult to decipher when relying solely on experimental data. Molecular dynamics (MD) simulations can provide additional insights into the behavior of ESI droplets and protein ions. This review is geared primarily towards experimentalists who wish to adopt MD simulations as a complementary research tool. We touch on basic points such as force fields, the …

Searching For Relevant Lessons Learned Using Hybrid Information Retrieval Classifiers: A Case Study In Software Engineering, Tamer Mohamed Abdellatif Mohamed, Luiz Fernando Capretz, Danny Ho

Electrical and Computer Engineering Publications

The lessons learned (LL) repository is one of the most valuable sources of knowledge for a software organization. It can provide distinctive guidance regarding previous working solutions for historical software management problems, or former success stories to be followed. However, the unstructured format of the LL repository makes it difficult to search using general queries, which are manually inputted by project managers (PMs). For this reason, this repository may often be overlooked despite the valuable information it provides. Since the LL repository targets PMs, the search method should be domain specific rather than generic as in the case of general …

A Mapping Review Of Randomized Controlled Trials In The Spinal Cord Injury Research Literature, Amanda Mcintyre, Brooke Benton, Shannon Janzen, Jerome Iruthayarajah, Joshua Weiner, Janice J. Eng, Robert Teasell, Spinal Cord Injury Research Evidence Team

Epidemiology and Biostatistics Publications

Study design

Mapping Review.

Objective

The objective of this study was to map out and characterize the quantity and quality of all published spinal cord injury (SCI) randomized controlled trials (RCTs) with respect to number, sample size, and methodological quality between January 1970 and December 2016.

Setting

Not applicable.

Methods

A literature search of multiple research databases was conducted. Studies adhering to the following criteria were included: the research design was an RCT; written in English; participants were >18 years; and the sample was >50% SCI. Data were extracted pertaining to author(s), year of publication, country of origin, initial and …

Effects Of Dispersion Corrections And Nonlocality On Density Functional Predictions Of Pressure-Induced Polymorphic Transitions Of Crystalline Diborane, Angela M. Murcia Rios, Darya N. Komsa, Viktor N. Staroverov

Chemistry Publications

The role of dispersion interactions in density functional calculations of the relative enthalpies of compressed BH3 polymorphs was investigated using plane-wave and Gaussian basis set codes. Addition of semiempirical atom-pairwise dispersion corrections to generalized gradient approximations (GGAs) was found to have little effect on the relative enthalpies of various boron hydride structures. By contrast, the stability ranking obtained with the nonlocal van der Waals density functional (vdW-DF) of Dion and co-workers was substantially more realistic than the rankings predicted by plain and dispersion-corrected GGAs. Of the functionals tested, only vdW-DF correctly predicts that compressed diborane does not leave the B2H6 …

Formazanate Complexes Of Hypervalent Group‐14 Elements As Precursors To Electronically Stabilized Radicals, Ryan R. Maar, Sara D. Catingan, Viktor N. Staroverov, Joe Gilroy

Chemistry Publications

The stability of molecular radicals containing main‐group elements usually hinges on the presence of bulky substituents that shield the reactive radical center. We describe a family of group‐14 formazanate complexes whose chemical reduction allows access to radicals that are stabilized instead by geometric and electron‐delocalization effects, specifically by the square‐pyramidal geometry adopted by the group‐14 atom (Si, Ge, Sn) within the framework of the heteroatom‐rich formazanate ligands. The reduction potentials of the Si, Ge, and Sn complexes as determined by cyclic voltammetry become more negative in that order. Examination of the solid‐state structures of these complexes suggested that their electron‐accepting …

Analysing Popularity Of Software Testing Careers In Canada, Luiz Fernando Capretz, Pradeep Waychal, Sachin Pardeshi

Electrical and Computer Engineering Publications

Software testing is critical to prevent software failures. Therefore, research has been carried out in testing but that is largely limited to the processand technology dimensions and has not sufficiently addressed the human dimension. Even though there are reports about inadequacies of testing professionals and their skills, only a few studies have tackled the problem. Therefore, we decided to explore the human dimension. We started with the basic problem that plagues the testing profession, the shortage of talent, by asking why do students and professionals are reluctant to consider testing careers, what can be done about that, and is the …

Controlling The Hydrophilicity And Cohesion During Deposition Of Highly Oriented Type I Collagen Films: An Approach For Biomedical Applications, Karina Ambrock, Bernd Grohe, Silvia Mittler

Physics and Astronomy Publications

Using the Langmuir-Blodgett (LB) technology we have pioneered a straightforward and low-cost approach to fabricate highly oriented collagen in thin film format (thickness: ~20 nm, surface areas: 2.5 x ~6.0 cm). An important factor for the use of these films is their cohesion under various conditions. Film formation was studied by coating hydrophilic or hydrophobic glass substrates. The fresh or aged (2 ½ years, -18°C.) collagen solutions used for this purpose either contained collagen network-stabilizing agents (n-propanol or phosphate ions) or were prepared without these stabilizers. Film formation on the air/water interface was analyzed by pressure-area isotherms. Maximum surface pressures …

A Π-Conjugated Inorganic Polymer Constructed From Boron Difluoride Formazanates And Platinum(Ii) Diynes, Jasveer S. Dhindsa, Ryan R. Maar, Stephanie M. Barbon, Maria Olivia Avilés, Zachary K. Powell, Francois Lagugné-Labarthet, Joe Gilroy

Chemistry Publications

The first example of a π-conjugated polymer incorporating boron difluoride (BF₂) formazanates is introduced. The film-forming properties, controllable reduction chemistry, and low optical band gap (ca. 1.4 eV) of the polymer make it an excellent candidate for use as a light-harvesting n-type semiconductor in organic electronics. Comparison of the polymer to model compounds confirmed that its unique optoelectronic properties can be directly attributed to the presence of the BF₂ formazanate repeat unit and that the [Pt(PBu₃)₂]²⁺ unit must also be present to achieve the narrow band gaps observed.

Depolymerization Of Trityl End-Capped Poly(Ethyl Glyoxylate): Potential Applications In Smart Packaging, Bo Fan, Romulo Salazar, Elizabeth R. Gillies

Chemistry Publications

The temperature-dependent depolymerization of self-immolative poly(ethyl glyoxylate) (PEtG) capped with triphenylmethyl (trityl) groups was studied and its potential application for smart packaging was explored. PEtGs with four different trityl end-caps were prepared and found to undergo depolymerization to volatile products from the solid state at different rates depending on temperature and the electron-donating substituents on the trityl aromatic rings. Through the incorporation of hydrophobic dyes including Nile red and IR-780, the depolymerization was visualized as a color change of the dye as it changed from a dispersed to aggregated state. The ability of this platform to provide information on thermal …

Plasmon-Mediated Drilling In Thin Metallic Nanostructures, Francois Lagugne-Labarthet, D. M. Mrae, K. Jeon

Chemistry Publications

Thin and ultraflat conductive surfaces are of particular interest to use as substrates for tip-enhanced spectroscopy applications. Tip-enhanced spectroscopy exploits the excitation of a localized surface plasmon resonance mode at the apex of a metallized atomic force microscope tip, confining and enhancing the local electromagnetic field by several orders of magnitude. This allows for nanoscale mapping of the surface with high spatial resolution and surface sensitivity, as demonstrated when coupled to local Raman measurements. In gap-mode tip-enhanced spectroscopy, the specimen of interest is deposited onto a flat metallic surface and probed by a metallic tip, allowing for further electromagnetic confinement …

The Variability In The Morphological Active Width: Results From Physical Models Of Gravel‐Bed Braided Rivers, Sarah Peirce, Pauline Leduc, Peter Ashmore

Geography & Environment Publications

The morphological active width, defined as the lateral extent of bed-material displacement over time, is a fundamental parameter in multi-threaded gravel-bed rivers, linking complex channel dynamics to bedload transport. Here, results are presented from 5 constant discharge experiments, and three event hydrographs, covering a range of flow strengths and channel configurations for which morphological change, bedload transport rates, and stream power were measured in a physical model. Changes in channel morphology were determined via differencing of photogrammetrically-derived digital elevation models (DEMs) of the model surface generated at regular intervals over the course of ~115 hours of experimental runs. Independent measures …

Tuning The Hydrophobic Cores Of Self-Immolative Polyglyoxylate Assemblies, Bo Fan, Rebecca E. Yardley, John F. Trant, Aneta Borecki, Elizabeth R. Gillies

Chemistry Publications

Polyglyoxylates are a recently-introduced class of self-immolative polymers, that depolymerize to small molecules upon the cleavage of a stimuli-responsive end-cap from the polymer terminus. The incorporation of different pendant ester groups or other aldehyde monomers offers the potential to tune the polymer properties, but this remains largely unexplored. With the goal of tuning the self-assembly and drug-loading properties of polyglyoxylate block copolymers, we explored the polymerization and copolymerization of n-butyl glyoxylate, L-menthyl glyoxylate, and chloral with ethyl glyoxylate to form UV light-responsive polyglyoxylates. The resulting polymers were coupled to poly(ethylene glycol) to afford amphiphilic block copolymers. Self-assembly of the …