Heuristics for the Critical Node Detection Problem in Large Complex Networks

Complex networks have recently attracted a significant amount of research attention due to their ability to model real world phenomena. One important problem often encountered is to limit diffusive processes spread over the network, for example mitigating pandemic disease or computer virus spread. A number of problem formulations have been proposed that aim to solve such problems based on desired network characteristics, such as maintaining the largest network component after node removal. The recently formulated critical node detection problem aims to remove a small subset of vertices from the network such that the residual network has minimum pairwise connectivity. Unfortunately, the problem is NP-hard and also the number of constraints is cubic in number of vertices, making very large scale problems impossible to solve with traditional mathematical programming techniques. Even many approximation algorithm strategies such as dynamic programming, evolutionary algorithms, etc. all are unusable for networks that contain thousands to millions of vertices. A computationally efficient and simple approach is required in such circumstances, but none currently exist. In this thesis, such an algorithm is proposed. The methodology is based on a depth-first search traversal of the network, and a specially designed ranking function that considers information local to each vertex. Due to the variety of network structures, a number of characteristics must be taken into consideration and combined into a single rank that measures the utility of removing each vertex. Since removing a vertex in sequential fashion impacts the network structure, an efficient post-processing algorithm is also proposed to quickly re-rank vertices. Experiments on a range of common complex network models with varying number of vertices are considered, in addition to real world networks. The proposed algorithm, DFSH, is shown to be highly competitive and often outperforms existing strategies such as Google PageRank for minimizing pairwise connectivity.

A research capacity strengthening project for infectious diseases in Honduras: experience and lessons learned

Background: In Honduras, research capacity strengthening (RCS) has not received sufficient attention, but an increase in research competencies would enable local scientists to advance knowledge and contribute to national priorities, including the Millennium Development Goals (MDGs). Objective: This project aimed at strengthening research capacity in infectious diseases in Honduras, focusing on the School of Microbiology of the National Autonomous University of Honduras (UNAH). The primary objective was the creation of a research-based graduate program for the continued training of researchers. Parallel objectives included institutional strengthening and the facilitation of partnerships and networks. Methods: Based on a multi-stakeholder consultation, an RCS workplan was designed and undertaken from 2007 to 2012. Due to unexpected adverse circumstances, the first 2 years were heavily dedicated to implementing the project's flagship, an MSc program in infectious and zoonotic diseases (MEIZ). In addition, infrastructure improvements and demand-driven continuing education opportunities were facilitated; biosafety and research ethics knowledge and practices were enhanced, and networks fostering collaborative work were created or expanded. Results: The project coincided with the peak of UNAH's radical administrative reform and an unprecedented constitutional crisis. Challenges notwithstanding, in September 2009, MEIZ admitted the first cohort of students, all of whom undertook MDG-related projects graduating successfully by 2012. Importantly, MEIZ has been helpful in expanding the School of Microbiology's traditional etiology-based, disciplinary model to infectious disease teaching and research. By fulfilling its objectives, the project contributed to a stronger research culture upholding safety and ethical values at the university. Conclusions: The resources and strategic vision afforded by the project enhanced UNAH's overall research capacity and its potential contribution to the MDGs. Furthermore, increased research activity and the ensuing improvement in performance indicators at the prime Honduran research institution invoke the need for a national research system in Honduras.

Investigating the role of apoptosis regulator EndoG on exogenous DNA uptake, stability, replication and recombination

Endonuclease G (EndoG) is a well conserved mitochondrial nuclease with dual lethal and vital roles in the cell. It non-specifically cleaves endogenous DNA following apoptosis induction, but is also active in non-apoptotic cells for mitochondrial DNA (mtDNA) replication and may also be important for replication, repair and recombination of genomic DNA. The aim of our study was to examine whether EndoG exerts similar activities on exogenous DNA substrates such as plasmid DNA (pDNA) and viral DNA vectors, considering their importance in gene therapy applications. The effects of EndoG knockdown on pDNA stability and levels of encoded reporter gene expression were evaluated in the cervical carcinoma HeLa cells. Transfection of pDNA vectors encoding short-hairpin RNAs (shRNAs) reduced levels of EndoG mRNA and nuclease activity in HeLa cells. In physiological circumstances, EndoG knockdown did not have an effect on the stability of pDNA or the levels of encoded transgene expression as measured over a four day time-course. However, when endogenous expression of EndoG was induced by an extrinsic stimulus (a cationic liposome transfection reagent), targeting of EndoG by shRNA improved the perceived stability and transgene expression of pDNA vectors. Therefore, EndoG is not a mediator of exogenous DNA clearance, but in non-physiological circumstances it may non-specifically cleave intracellular DNA regardless of its origin. To investigate possible effects of EndoG on viral DNA vectors, we constructed and evaluated AdsiEndoG, a first generation adenovirus (Ad5 ΔE1) vector encoding a shRNA directed against EndoG mRNA, along with appropriate Ad5 ΔE1 controls. Infection of HeLa cells with AdsiEndoG at a multiplicity of infection (MOI) of 10 p.f.u./cell resulted in an early cell proliferation defect, absent from cells infected at equivalent MOI with control Ad5 ΔE1 vectors. Replication of Ad5 ΔE1 DNA was detected for all vectors, but AdsiEndoG DNA accumulated to levels that were 50 fold higher than initially, four days after infection, compared to 14 fold for the next highest control Ad5 ΔE1 vector. Deregulation of the cell cycle by EndoG depletion, which is characterized by an accumulation of cells in the G2/M transition, is the most likely reason for the observed cell proliferation defect. The enhanced replication of AdsiEndoG is consistent with this conclusion, as Ad5 ΔE1 DNA replication is intimately related to cell cycling and prolongation or delay in G2/M greatly enhances this process. Furthermore, infection of HeLa with AdsiEndoG at MOI of 50 p.f.u./cell resulted in an almost complete disappearance of viable, adherent tumour cells from culture, whereas almost a third of the cells were still adherent after infection with control Ad5 ΔE1 vectors, relative to the non-infected control. Therefore, targeting of EndoG by RNAi is a viable strategy for improving the oncolytic properties of first generation adenovirus vectors. In addition, AdsiEndoG-mediated knockdown of EndoG reduced homologous recombination between pDNA substrates in HeLa cells. The effect was modest but, nevertheless demonstrated that the proposed role of EndoG in homologous recombination of cellular DNA also extends to exogenous DNA substrates.

Mindfulness: An Ancient Wisdom for the Reconceptualisation of Modern Education in the Complex World

Exploring the new science of emergence allows us to create a very different classroom than how the modern classroom has been conceptualised under the mentality of efficiency and output. Working on the whole person, and not just the mind, we see a shift from the epistemic pillars of truth to more ontological concerns as regards student achievement in our post-Modern and critical discourses. It is important to understand these shifts and how we are to transition our own perception and mentality not only in our research methodologies but also our approach to conceptualisations of issues in education and sustainability. We can no longer think linearly to approach complex problems or advocate for education and disregard our interconnectedness insofar as it enhances our children’s education. We must, therefore, contemplate and transition to a world that is ecological and not mechanical, complex and not complicated—in essence, we must work to link mind-body with self-environment and transcend these in order to bring about an integration toward a sustainable future. A fundamental shift in consciousness and perception may implicate our nature of creating dichotomous entities in our own microcosms, yet postmodern theorists assume, a priori, that these dualities can be bridged in naturalism alone. I, on the other hand, embrace metaphysics to understand the implicated modern classroom in a hierarchical context and ask: is not the very omission of metaphysics in postmodern discourse a symptom from an education whose foundation was built in its absence? The very dereliction of ancient wisdom in education is very peculiar indeed. Western mindfulness may play a vital component in consummating pragmatic idealism, but only under circumstances admitting metaphysics can we truly transcend our limitations, thereby placing Eastern Mindfulness not as an ecological component, but as an ecological and metaphysical foundation.

Educational Qualification Without Suitable Employment: Exploring Immigrant Engineers' Personal Narratives

This qualitative study investigated the experiences of immigrant professional engineers in Canada, 81% of whom are unable to secure employment in their field despite arriving under the auspices of the Canadian government’s skilled workers program. The study sought to identify factors that impede such qualified engineers’ opportunities within the Canadian job market. Because global economic competition demands that qualified professionals contribute to technological innovation, Canada must develop transitional programs that acknowledge credentials and prior work experience in order to address the underutilization of these qualified professionals and allow immigrant engineers to gain employment within their field. To this end, the study examined personal narratives of immigrant engineers who have experienced unemployment despite high levels of educational attainment, and circumstances that contribute to immigrant engineers’ unemployed status. The paper presents a discussion and recommendations for future research in the area of qualification without suitable employment.  

Geographical Applications for Sound Walks

Geography has long been a predominantly visual discipline, but recent work in geography has sought to explore the multisensory, embodied, emotional and affective dimensions of people’s relations with places. One way to engage this type of exploration is through the use of sound walks: walks along a specified route accompanied by a soundtrack (on headphones or stationary speakers) that conveys information, enacts a story, produces an ambience or atmosphere, or illuminates certain aspects of the environment through which the listener is walking. This thesis aims to show how geographers can benefit from using sound walks as thinking tools, representational tools and teaching tools. Drawing on my own experiences producing sound walks, I first examine the ways that sound walk production processes help generate productive geographical thinking for those producing sound walks (Chapter Two). The various stages of producing a sound walk require different skill sets, pose different challenges, and require different sorts of environmental awareness, and therefore present novel opportunities for developing geographical insights about specific places or spatial relations. Second, I focus on four experientially-oriented aspects of sound walks – using multiple senses, walking, contingency, and moments of interaction – to argue that sound walks can be useful representational tools for geographers, whether those creating sound walks subscribe to a representational or non-representational theory of knowledge (Chapter Three). The value of sound walks as representational tools is in the experience of ‘doing’ them. That is, audiences discover for themselves through interaction what is being represented, rather than having it delivered to them. The experiential elements of ‘doing’ sound walks recommend them as potentially helpful representational tools for geographers. Third, by examining the work of a small sample of fourth year “Advanced Geography of Music” students, I develop the argument that sound walks can be effective tools for teaching students and for creating circumstances for students to learn independently (Chapter Four). Sound walks have potential to be effective pedagogical tools because they are commensurate with several key pedagogical schools of thought that emphasise the importance of requiring students to engage actively with their environment using a combination of senses. The thesis demonstrates that sound walks are a worthwhile resource for geographers to use theoretically, representationally and pedagogically in their work. The next step is for geographers to put them into practice and realize this potential.

Interrogation of Prisoner - Heaquarters 1st Division, American Expeditionary Forces, 27 May 1918

A prisoner interrogation report dated 27 May 1918. The report reads: "I. PRISONER X. 1st. Battalion, 272 Res. Rogt., 82d Res. 1. CIRCUMSTANCES OF CAPTURE; Captured, while attempting to raid our trenches, at point 1719 at about 7A.M. 2. INFORMATION OBTAINED FROM PRISONER (a) Between point 1814 and point 175242 the German trenches appear to be held by three companies, each numbering 3 platoons, each platoon numbering about 40 men. Each company has 4 light machine guns in the first lines, these machine guns distributed along the first trench (one of them in particular is located at bond in hostile trench at point 17215 and another at about 17245. Each company, furthermore, has one platoon (weak in numbers) in support in the ravine north of Cantigny. These platoons are in dugouts dug into the side of the hill approximately between points 28215 and 2223. Each of these support platoons has two light machine guns at its disposal. Company commanders dugout is at some point along the line of dugouts occupied by the support platoons. Another company commander's dugout (Co.3) is at point 1815 about 15 meters behind the German trench which runs along the edge of the town of Cantigny. There is a communication trench between the cemetery at 2018 and the front line at 18179. It is believed that there is a machine gun at point 17245 kept in a dugout dug under the road. The reserve battalion is believed to be at a fairly great distance from the front (near Bouillancourt). The prisoner, on the other hand, states that it may have been moved up."

Meeting Minutes July 7th, 1972

The first "business arising out of the minutes" is a protest made by Mr. W.R. Barnes concerning action taken at a previous meeting by the Directors. In the meeting in February, he had been replaced as Vice-President after 20 years in the role and 38 years as a Director. His record of attendance was called into question and would be discussed and shown at the next meeting. The second issue discussed is the "proposal with respect to purchasing the assets of the Corporation". A letter was received from F.L. Laundry Real Estate Limited with interest from a Central European client in "acquiring the assets of the Corporation, and indicating that if the circumstances warranted, a figure of 3.5 millions would not be beyond their capabilities". The offer would be explored by the solicitor. The next agenda item discusses was the Sault Ste. Marie store. Another issue discussed was the "Withdrawal from Valley Rouge Wines Limited".

Percy Carruthers Band fonds, 1857-2005, n.d. (non-inclusive)

Percy Carruthers Band was born on November 27, 1892 in Toronto, Ontario to Charles Walter Band, a grain merchant and Jessie Camp Shaw Band. He graduated from Upper Canada College and became a broker. He worked at the Dominion Bank and then at Maple Leaf Milling Company. He was stationed at Port Colborne for a while. Before leaving for the front, he was with Bankers Bond Company of Toronto and is also listed as working with the firm of Bailey, Wood and Cross. Lieutenant Band received a Certificate of Military Qualifications on Dec. 24th, 1914. He received his Certificate of Military Instruction on Nov. 30, 1915. He received these certificates while with the 48th Regiment (Highlanders). He enlisted in 1914 and went overseas in August of 1915 as an officer in the 35th Battalion. By August 26, 1915, he is listed as being with the 23rd Reserve Battalion. A year later, in August of 1916 Lieutenant Band arrived in France and was posted to the 2nd Battalion – “The Second Iron”. In 1916, Band was the victim of shell shock received during a charge. He was wounded in April of 1917 at Vimy Ridge yet he remained on duty. At this time he received a gunshot wound to his right jaw. He earned a promotion to Captain on September 16th, 1917. He was wounded again in November of 1917 at Passchendaele where he suffered a gunshot wound to the ear. For his courage and determination Percy Band received the Military Cross on February 18, 1918. He led his company under difficult circumstances even though he was wounded. He was awarded a bar to the Military Cross for gallantry during a successful attack on two villages on December 2nd, 1918. During this attack he led his company against enemy machine guns. It is said that he displayed exceptional leadership qualities and skill during this time. On the 30th of August in 1918, he made a daring reconnaissance to the front under heavy fire in an attack on Upton Wood. He was also commended on his gallantry during attacks on Cagnicourt and the Canal du Nord in September of 1918. He was awarded the second bar to the Military Cross on February 1, 1919. The award of the Croix de Guerre was conferred on Captain Percy Carruthers Band by the President of the French Republic on December 15th, 1918 for distinguished service rendered during the course of the campaign. His general demobilization took place on April 25, 1919. Percy Band married Margaret Julia Woodruff on November 25, 1919, and they had three children: Charles Woodruff Band (1921), Margaret Elizabeth Band (1924) and Robert DeVeaux Woodruff Band (1927). After the war, Mr. Band was a manager at Geo. Weston Bread and Cakes Limited, St. Catharines. Percy Band was also an avid collector. His collections included antique toys and art. He died suddenly on May 19, 1961. The Toronto Telegram published this about him: “Captain Percy Carruthers Band, M.C. with two Bars, Croix de Guerre with Palm – was an officer whose buoyant spirit and gallantry mirrored the vibrant soul of the Battalion. Blythe of heart, yet endowed with a fine sense of responsibility, he gave inspired leadership of No. 3 Company.”