Vibrational density of states of silicon nanoparticles

The vibrational density of states of silicon nanoparticles in the range from 2.3 to 10.3 nm is studied with the help of molecular-dynamics simulations. From these simulations the vibrational density of states and frequencies of bulk-like vibrational modes at high-symmetry points of the Brillouin-zone have been derived. The results show an increase of the density of states at low frequencies and a transfer of modes from the high-frequency end of the spectrum to the intermediate range. At the same time the peak of transverse optical modes is shifted to higher frequencies. These observations are in line with previous simulation studies of metallic nanoparticles and they provide an explanation for a previously observed discrepancy between experimental and theoretical data [C. Meier et al., Physica E, 32, 155 (2006)].Comment: 7 pages, 5 figure; accepted for publication in Phys. Rev.

Efficient Parallelization of Short-Range Molecular Dynamics Simulations on Many-Core Systems

This article introduces a highly parallel algorithm for molecular dynamics simulations with short-range forces on single node multi- and many-core systems. The algorithm is designed to achieve high parallel speedups for strongly inhomogeneous systems like nanodevices or nanostructured materials. In the proposed scheme the calculation of the forces and the generation of neighbor lists is divided into small tasks. The tasks are then executed by a thread pool according to a dependent task schedule. This schedule is constructed in such a way that a particle is never accessed by two threads at the same time.Benchmark simulations on a typical 12 core machine show that the described algorithm achieves excellent parallel efficiencies above 80 % for different kinds of systems and all numbers of cores. For inhomogeneous systems the speedups are strongly superior to those obtained with spatial decomposition. Further benchmarks were performed on an Intel Xeon Phi coprocessor. These simulations demonstrate that the algorithm scales well to large numbers of cores.Comment: 12 pages, 8 figure

Numerical study of critical properties and hidden orders in dimerized spin ladders

Dimerized antiferromagnetic spin-1/2 ladders are known to exhibit a quantum critical phase transition in the ground state, the existence or absence of which is dependent on the dimerization pattern of the ladder. The gapped phases cannot be distinguished by the conventional Landau long-range order parameter. However, they possess a non-local (hidden) string order parameter, which is non-zero in one phase and vanishes in the other. We use an exact diagonalization technique to calculate ground state energies, energy gaps and string order parameters of dimerized two- and three-leg Heisenberg ladders, as well as a critical scaling analysis to yield estimates of the critical exponents nu and beta.Comment: 7 pages, 14 figures. V.2: Extended version to appear in PR

Efficient, robust surface functionalization and stabilization of gold nanorods with quaternary ammonium-containing ionomers as multidentate macromolecular ligands

Surface functionalization of gold nanorods (GNRs) is critical to their applications in various fields. While there are several existing strategies, we report in this article a new general strategy for the surface functionalization of GNRs with quaternary ammonium-containing ionomers as a novel class of multidentate macromolecular surface ligands. A range of tetralkylammoniumcontaining hyperbranched polyethylene- and linear poly(n-butyl acrylate)-based ionomers has been specifically designed and employed in the strategy. Acting as multidentate macromolecular analogues of cetyltrimethylammonium bromide (CTAB), the ionomers have been demonstrated to bind onto the GNR surface by displacing the surface-bound CTAB species via ligand exchange to render CTAB-free ionomer-modified GNRs. By properly designing the enabling ionomers, we have shown that the modified GNRs can be endowed with some desired properties, such as excellent dispersibility in various organic solvents, robust stability under multiple rounds (up to 12 investigated) of high-speed centrifugation in organic solvents, amphiphilicity with dispersibility in both aqueous and organic media, fluorescence, and capability in carrying hydrophobic guest species. This strategy thus provides potential new ways for the construction of novel multifunctional GNR nanocomposites

Les mauvais traitements envers les personnes âgées : Une enquête bibliographique

Over the past few months, I have been assembling a bibliography on elder abuse that will soon be published on the Web site of the Ontario Network for the Prevention of Elder Abuse (www.onpea.org). I brought to this inquiry the tools I developed a decade ago during a sabbatical I spent developing subject-literature expertise in gerontology. That study was focussed exclusively on the print literature. Today, however, no bibliography would be complete without addressing the multifaceted nature of communication. Not only is there the traditional “hard copy” bibliography, there are videos, the Internet, and even the telephone. (Phone Busters, operated by the Ontario Provincial Police, does research on telemarketing scams and seniors.) I should emphasize this bibliography is not meant to be comprehensive, but a “brief bibliography” along the lines of the excellent series published by the Association for Gerontology in Higher Education.Au cours des quelques derniers mois j’ai recueilli une bibliographie sur les mauvais traitements envers les personnes âgées qui sera publiée sous peu sur les site Web du Réseau ontarien de prévention des mauvais traitements à l'égard des personnes âgées (www.onpea.org). Dans cette investigation, j’ai utilisé les instruments que j’avais élaborés voilà dix ans pendant un congé sabbatique durant lequel j’ai acquis le savoir-faire relatif à la littérature-thématique en gérontologie. L’étude était exclusivement axée sur la littérature imprimée. Toutefoirs, aujourd’hui, aucune bibliographie ne serait complète sans aborder la nature diverse de la communication. À part la bibliographie traditionnelle « sur papier », il y a les vidéos, l’Internet et même le téléphone. (Phone Busters, géré par la Police provinciale de l’Ontario, fait des recherches sur le télémarketing frauduleux et les personnes âgées.) Je dois souligner que cette bibliographie n’est pas exhaustive, ce n’est qu’une «courte bibliographie » dans la tradition de l’excellente série publiée par la Association for Gerontology in Higher Education

Biochemical adaptations in pseudomonas fluorescens exposed to nitric oxide, an endogenous antibacterial agent

Nitric oxide (NO), a free radical released by macrophages (a subset of white blood cells) as a response to infection, is noxious to organisms due to its ability to disable crucial biomolecules such as lipids, proteins and DNA. Although normally effective at eradicating invading bacteria, several pathogens have developed mechanisms to detoxify NO and its toxic by-products, reactive nitrogen species (RNS). While some of these detoxification processes have been characterized, very little is known about the metabolic changes that enable microbes to survive this deleterious environment. Investigations into the effects of RNS on microbial physiology have shown that these harmful radicals inactivate the citric acid cycle and oxidative phosphorylation, the series of reactions responsible for making energy aerobically. The central aim of this thesis was to determine how the organism counteracts the detrimental effects of RNS, while bypassing the ineffective central metabolic pathways. The findings presented herein show that P. fluorescens engineers an elaborate metabolic network to generate ATP whilst withstanding the injurious effects of nitrosative stress. Crucial to this adaptation is the ability to produce energy via substrate level phosphorylation, a necessity that arises out of the cells’ inability to produce a substantial amount of ATP using the electron transport chain (ETC). The up-regulation of the enzymes citrate lyase (CL), phosphoenolpyruvate carboxylase (PEPC) and pyruvate, phosphate dikinase (PPDK) helps the organism accomplish this feat. Blue native polyacrylamide gel electrophoresis (BN-PAGE), high performance liquid chromatography (HPLC) as well as co-immunoprecipitation (CO-IP) studies were applied to demonstrate that these proteins form a metabolon, a transient complex of enzymes that ensures citrate is converted into its desired end products, pyruvate and ATP. In order to gauge the individual contributions iv of phosphoenolpyruvate-dependent kinases, a novel in-gel activity assay was developed to probe these enzymes under disparate conditions. These results suggest that the organism switches from an ATP-dependent metabolism to one based on the utilization of pyrophosphate (PPi). The rationale for this appears to be energy efficiency, as pyrophosphate-dependent glycolysis can theoretically produce five ATP rather than the two yielded by Embden-Meyerhof glycolysis. Additionally, the up-regulation in activity of the enzymes adenylate kinase, nucleoside diphosphate kinase and acetate kinase seem to ensure that ATP generated by PPDK is properly shuttled and stored when aerobic metabolism is defective. The lower activity of inorganic pyrophosphatase likely ensures an adequate supply of pyrophosphate for the activity of PPDK. Taken together, this research reveals the critical role metabolism plays in the survival of microbes under the onslaught of NO and RNS. As several of these enzymes are absent in mammalian systems, they present themselves as novel targets for the development of new antibacterial agents. A comprehensive awareness of bacterial defense systems in response to NO may lay the groundwork to developing more effective treatments to impede microbial infections.Doctor of Philosophy (PhD) in Biomolecular Science

An EPR and DFT investigation of the products formed in the reaction of group 11 metal atoms with three-membered heterocyclic compounds

Transition metals have been shown to be efficient catalysts in a variety of organic reactions. In particular, Group 11 metals have emerged as essential components in the carboxylation or metal-catalyzed ring expansion of three-membered heterocyclic compounds. Previous reports have speculated the presence of short-lived metal-substrate complexes and metallacyclic intermediates along the reaction path, yet to date there is no direct evidence for their existence. Using cryogenic matrix isolation EPR spectroscopy, we were able to characterize several highly reactive intermediates formed in the reactions of Group 11 metal atoms, Cu, Ag, and Au, with small, strained, heterocyclic compounds, namely, oxiranes, thiiranes, and aziridines. Experimental data indicates that the major products formed are mononuclear metal complexes, M-XCH2CH2 (X = O, S or NH). In addition, reaction mixtures containing Cu atoms and oxiranes or thiirane yield novel metallacycles, i.e., cupraoxetane and cuprathietane, respectively. DFT calculations were also used to support the structural assignments of the M-XCH2CH2 complexes.Master of Science (MSc) in Chemical Science

Factors contributing to the non-urgent use of the emergency department by Canadian triage and acuity scale IV and V patient in Sudbury, Ontario

In Canada, it is estimated that 57% of all emergency department (ED) visits are for less-urgent or non-urgent care needs (Hodgins & Wuest, 2007). Factors that contribute to the non-urgent use of ED services include lack of resources, insufficient access to care, and lack of awareness regarding available health care options (Fieldston, Alpern, Nadel, Shea & Alessandrini, 2012). The goal of this quantitative descriptive design study was to determine the relationship between having access to a primary health care provider, utilizing community based health care supports, and the patient’s perception of illness, with the adult patient’s decisions for presenting to the ED with nonurgent care needs. Of the 119 respondents, 71.3% had access to a primary health care provider. A majority of the respondents (70.1%) perceived the threat of their illness as moderate. Those without registration with a primary care provider had a significantly higher perceived threat of illness than those with a primary care provider. Results indicate that 72.6% of respondents presented to the ED because of a perceived urgency of need for care, and 48.7% of participants came to the ED because they thought they required ED services. Identifying why people present to the ED with non-urgent care needs can assist health care providers and decision makers to enhance their understanding of the patient’s expectations of health care services and their perception of illness.Master of Science (MScN) in Nursin

Monitoring landscape and spatial behavioural outcomes of large scale forest management for boreal caribou (Rangifer tarandus caribou) in upland and lowland forests of Ontario, Canada

Habitat management is a key tool used to support species conservation and sustainable timber harvest on managed forests; however assessments of long-term management outcomes are rare. My study is a qualitative assessment of the outcomes of over 15 years of large scale forest management for boreal caribou in two unique Ontario, Canada landscapes: the northwestern Boreal Shield and the northeastern James Bay Lowlands. I assessed: (1) the realized outcomes of forest management direction with respect to the landscape scale structure and configuration of caribou habitat and harvested areas, and (2) changes in caribou spatial behaviour in response to forest management. I found patterns opposite to those predicted based on management recommendations in terms of harvest configuration and size, and observed no detectable changes in caribou habitat continuity or area that could be related to management application. Similarly, I observed behavioural patterns suggestive of maladaptive behavioural response to management outcomes, which could be potentially detrimental to caribou population viability. Overall, these results suggest that further investigation into the management of habitat for boreal caribou in Ontario is required. Moreover, these results highlight the importance of long-term monitoring for management practices in order to ensure management success.Master of Science (MSc) in Biolog

The therapeutic benefits of yelling

Yelling has been used as a form of healing in Indigenous cultures (Nabigon, 2010). Research suggests benefits to therapies that incorporate yelling (Karle, Corriere, & Hart, 1973). However, the physiological impact of yelling has not been investigated. The current study explores EEG measurements of yelling as compared to its derivatives (deep breathing and a vocal control). Ten participants from Laurentian University were recruited. Results of relative spectral power analysis provide evidence of a significant increase in relative gamma power following the yelling condition only (F(14,98) = 2.87, p=.001, ŋ2=.291). POMS scores confirm that there was a significant total mood disturbance reduction following the yelling condition only (t(9)=3.68, p=.005). Findings support strategies designed to enhance health and well-being.Honours Bachelor of Science in Psycholog