The purpose of this study was to investigate the influence an increase in strand strength and the effect the as-cast vertical location had on transfer length, development length, and flexural strength and to resolve the discrepancies regarding the definition of the top-bar/strand effect. Two types of test specimens were fabricated and tested investigating each respective item. The increase in strand strength was found to influence transfer length, development length, and flexural strength, while the as-cast vertical location was only found to influence transfer length, and in turn development length. Contrary to the historical definition, the top-bar/strand effect was found to be more dependent on the amount of concrete cast above the strand than the amount below it, with transfer lengths showing a steady increase with a decrease in the amount of concrete cast above the strand. As a result of the findings of this study, a new transfer length equation was proposed and a previously proposed flexural bond length equation was recommended for use in lieu of the current code provisions. The current equations for flexural strength were found to give adequate estimates for flexural strength, although a decrease in ductility was noted. / Ph. D.

No / The comet assay or single-cell gel electrophoresis assay is a relatively simple and sensitive technique for quantitatively measuring DNA damage and repair at the single-cell level in all types of tissue where a single-cell suspension can be obtained. Isolated cells are mixed with agarose, positioned on a glass slide, and then lysed in a high-salt solution which removes all cell contents except the nuclear matrix and DNA, which is finally subjected to electrophoresis. Damaged DNA is electrophoresed from the nuclear matrix into the agarose gel, resembling the appearance of a comet, while undamaged DNA remains largely within the proximity of the nuclear matrix. By choosing different pH conditions for electrophoresis, different damage types and levels of sensitivity are produced: a neutral (pH 8–9) electrophoresis mainly detects DNA double-strand breaks, while alkaline (pH ≥ 13) conditions detect double- and single-strand breaks as well as alkali-labile sites. This protocol describes a standard comet assay study for the analysis of DNA damage and outlines important variations of this protocol.

Thesis (MSc (Geography and Environmental Studies))--University of Stellenbosch, 2004. / 103 Leaves printed on single pages, preliminary pages i- viii and numbered pages 1-94.I ncludes bibliography, ADDENDUM A: Questionnaire document used in the research; list of tables and figures. / Digitized at 330 dpi black and white PDF format (OCR), using KODAK i 1220 PLUS scanner. / ENGLISH ABSTRACT: The subject of waste management is one that evokes a variety of debates due to the overwhelming implications on the environment and on health that are associated with the management of waste. In developing urban areas associated with informal settlements, environmental problems emanating from household solid waste management predicaments such as illegal dumping, littering and overfilling of skips have become a permanent feature. This is also the case in Lwandle a developing township in Helderberg Municipality, Western Cape. This study looks into the waste management system in Lwandle with the aim to investigate institutional settings, related socio-economic factors and resultant community perceptions, and avenues for the use of environmental education and community participation. The results show waste collection to be the responsibility of the Helderberg Municipality, but the collection operation is undertaken by a private contractor. The nature of waste collection under these arrangements is mainly determined by the nature of housing and associated accessibility. Consequently, three main methods of waste collection are used: kerbside collection; communal collection where there is use of bins and communal collection where there is use of skips. These have varying efficiency among the nine housing areas. Socioeconomic conditions, which were marked by a high level of unemployment and low incomes, determine societal attitudes. These underpin finer variations and detailed conditions of waste collection. These, in tum, establish the framework for suitable environmental education and community participation. The latter was found to be minimal. Thus, a holistic approach to the improvement of waste management that first acknowledges inherent broader societal problems such as housing and unemployment is proposed as part of the recommendations. This approach then concentrates on finer aspects such as contracts for waste collection, aspects of waste collection dependent on waste stream nature of housing areas, appropriate environmental education and community participation. / AFRIKAANSE OPSOMMING: Afvalbestuur is 'n onderwerp wat 'n verskeidenheid van debatte uitlok vanwee die geweldige implikasies vir die omgewing en vir gesondheid wat met afvalbestuur geassosieer word. In ontwikkelende stedelike gebiede wat met informele behuising geassosieer word, het omgewingsprobleme soos onwettige storting, die strooi van rommel en oorvol stortbakke wat verband hou met die hantering van vaste afval uit huise 'n permanente kenmerk geword. Dit is ook die geval by Lwandle, 'n ontwikkelende dorpsgebied te Helderberg, in die Wes-Kaap. Hierdie studie beskou die afvalbestuursisteem in Lwandle met die doel om institusionele omgewings, verwante sosio-ekonomiese faktore en die persepsies van die gemeenskap wat daaruit ontwikkel, asook moontlikhede vir die gebruik van omgewingsopvoeding en gemeenskapsbetrokkenheid, te ondersoek. Die resultate van die ondersoek toon dat die Helderberg Munisipaliteit verantwoordelik is vir die insameling van afval, maar dat die insameling deur 'n private kontrakteur uitgevoer word. Onder sulke omstandighede word die aard van afvalinsameling hoofsaaklik deur die aard van die behuising en die verwante toeganklikheid bepaal. Daarvolgens is daar drie hoofmetodes van insameling, wat deur verskillende grade van effektiwiteit gekenmerk word, vir die nege behuisingsgebiede: sypaadjie versameling; kommunale versameling in dromme; en kommunale versameling in stortbakke. Sosio-ekonomiese omstandighede, wat gekenmerk word deur 'n hoe mate van werkloosheid en lae inkomstes, bepaal gemeenskapshoudings wat deur die verskillende maniere van afvalverwydering tot stand kom en ondersteun fyner variasies en gedetailleerde omstandighede van afvalinsameling. Dit bepaal weer die raamwerk vir gepaste omgewingsopvoeding en die deelname van die gemeenskap. Die studie het getoon dat laasgenoemde minimaal is. 'n Holistiese benadering tot die verbetering van afvalbestuur, wat eerstens inherente breer gemeenskapsprobleme soos behuising en werkloosheid erken, word dus as deel van die aanbevelings voorgestel. Hierdie benadering konsentreer vervolgens op die fynere aspekte, soos kontrakte vir afvalinsameling, aspekte van afvalinsameling, gepaste omgewingsopvoeding en gemeenskapsdeelname.

Syftet med den här uppsatsen är att undersöka hållbarhetsbegreppet samt hur detta implementeras i bygget av den nya stadsdelen Storsjö Strand i Östersund. För att avgränsa studien läggs fokus på två centrala delar i kommunens klimatpåverkan, hållbar mobilitet och hållbart boende. Studien består av en kvalitativ textanalys av planeringsdokument hämtade ur olika stadier av planeringsarbetet. Textanalysen kompletteras med intervjuer med personer med olika insyn i planeringsarbetet för att skapa en djupare förståelse. I arbetet med studien har det framkommit tvivel mot innebörden av hållbarhetsbegreppet. Begreppet delas in i tre centrala beståndsdelar, ekologisk-, ekonomisk- och social hållbarhet, som alla ska ha lika stor inverkan i beslutsfattande för att hållbarhet ska uppnås. Istället verkar det som att begreppet används som en ursäkt för att bibehålla den västerländska livsstilen. Detta trots att forskningen är överens om att densamma är ohållbar. Detta visar sig i arbetet med Storsjö Strand, där planer som lagts fram tidigt i planeringsarbete för att ge goda möjligheter till stora ekologiska vinster inte genomförs på grund av eventuella ekonomiska förluster. Till synes förnuftiga idéer som, enligt forskningen, på sikt ger vinst i samtliga tre perspektiv genomförs inte eller skjuts på framtiden.

Many security protocols are built as the composition of an application-layer protocol and a secure transport protocol, such as TLS. There are many approaches to proving the correctness of such protocols. One popular approach is verification by abstraction, in which the correctness of the application-layer protocol is proven under the assumption that the transport layer satisfies certain properties, such as confidentiality. Following this approach, we adapt the strand spaces model in order to analyse application-layer protocols that depend on an underlying secure transport layer, including unilaterally authenticating secure transport protocols, such as unilateral TLS. Further, we develop proof rules that enable us to prove the correctness of application-layer protocols that use either unilateral or bilateral secure transport protocols. We then illustrate these rules by proving the correctness of WebAuth, a single-sign-on protocol that makes extensive use of unilateral TLS. In this thesis we also present a full proof of the model's soundness. In particular, we prove that, subject to a suitable independence assumption, if there is an attack against the application-layer protocol when layered on top of a particular secure transport protocol, then there is an attack against the abstracted model of the application-layer protocol. In contrast to existing work in this area, the independence assumption consists of eight statically-checkable conditions, meaning that it can be checked statically, rather than having to consider all possible runs of the protocol. Lastly, we extend the model to allow protocols that consist of an arbitrary number of layers to be proven correct. In this case, we prove the correctness of the intermediate layers using the high-level strand spaces model, by abstracting away from the underlying transport-layers. Further, we extend the above soundness results in order to prove that the multi-layer approach is sound. We illustrate the effectiveness of our technique by proving the correctness of a couple of simple multi-layer protocols.

Thesis (MPA)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Apart from meeting basic customer needs, small and medium enterprises in the townships are a source of employment and livelihood for many. Businesses in the townships of the Strand have mushroomed from a formerly neglected area, like others in various townships throughout South Africa. Yet very little is known about them and their owners. What are their characteristics? What traits distinguish those that make higher revenues from the rest? Many of these small businesses have emerged without government assistance, even though such support is often seen as a non-factor in determining the rate of an enterprise’s growth. Entrepreneurship, as literature often explains, is a dynamic endeavour which requires a business founder to display both determination and skill. Yet very few businesses normally survive the early stages. Many aspects of entrepreneurship need to be practically learned to enable the business to overcome many prevalent obstacles, and thus enable the enterprise to grow and contribute to job-creation. Not all entrepreneurs are alike in their capability to spot an opportunity. Also, entrepreneurs differ in their ability to either steer or set up systems to take an enterprise through its various transitions. Yet still, the financial strategic decisions made at inception stage often influence the rate at which businesses will generate revenues later in existence. Government, both local and national, has a responsibility to provide an enabling environment for businesses to thrive. Using a study of spaza and informal trade done in the past by Unisa and by Bojanala Platinum District Municipality as a baseline, this study surveyed 60.6 percent of businesses in the Strand townships that were identified through the database of both Khanyolwethu School and Sinobulumko Business Association. The main areas of focus were – the socio-economic and demographic profile, the physical characteristics, financing, relationship with suppliers, transport, income/turnover and traits that distinguish higher-revenue businesses from others. Analyses through the Mann-Whitney U, the Spearman's rank correlation coefficient, the chi-square and the Kruskal-Wallis test then showed that the businesses that tend to make larger monthly revenues are those that are owned by males, using cheque accounts for the business, and those whose main suppliers deliver merchandise to their premises. The businesses that make larger daily revenues were shown to be those that are owned by males, registered with CIPRO, using cheque accounts for the business and those whose owners have Grade 7 to 9 qualifications and above. For government, the results of this study call for a further refining of the criteria used for loaning to businesses in townships, as well as to make the public more aware of the assistance provided by government’s business support agencies. For banks, the study calls for the designing of a ‘Spaza Account’, tailored to the needs and skills level of businesses owners in the townships. Socially, the study calls for the tearing down of all the walls that make it difficult for open trade to take place / AFRIKAANSE OPSOMMING: Klein besighede in informele nedersettings spreek die behoefte aan van kliënte en genereer ‘n tipe inkomste, maar daar is min kennis oor eienaars se belange. Besighede in die Strand se informele nedersettings was gestig in minderbevooregte gebiede, soos baie ander regdeur Suid Afrika. Watter karaktereienskappe beskik hierdie eienaars om ‘n beter inkomste te genereer as die res van die inwoners? Baie van hierdie besighede het ontstaan sonder enige hulp van regering instansies ten spyte van ondersteuningsdienste wat aan hulle beskikbaar was. Afhangende van die groei van die besigheidseienaar word dit in elk geval nie in ag geneem nie. Entrepreneurskap verduidelik letterlik dat die besigheids eienaar uithouvermoe en vaardighede kan uitbeeld. Baie min van hierdie besighede oorleef hulle eerste fase vanuit die staanspoor. Baie aspekte van die besigheid moet prakties aangeleer word om daaglikse uitdagings te oorkom. Op hierdie wyse groei die mark en sodoende word werksgeleenthede geskep. Nie alle besighede is sodanig op hoogte van sake om geleenthede raak te sien nie. Dikwels verskil bestuurstyle van besighede om sisteme in plek te stel wat verandering kan meebring. Finansiële besluite wat geneem is aan die begin stadium het ‘n impak op inkomste wat op ‘n later stadium in die besigheid gegenereer word. Beide die nasionale en plaaslike regering het die verantwoordelikheid om ‘n goedgegewe besigheids omgewing te skep vir besigheidsgroei. ‘n Vorige studie van ‘n spaza en oor informele handel deur Unisa en Bojanala Platinum Distriksmunisipaliteit was as basis gebruik. Die studie het bewys dat 60.6 persent van besighede in informele nedersettings in die Strand geidentifiseer is deur gebruik te maak van die databasisse van beide plaaslike skole en besigheidsvereningings. Die hoof fokus areas was die sosio-ekonomiese en demografiese profiele, die fisiese karaktereienskappe, finansiering, verhoudinge met verskaffers, vervoer, inkomste en kenmerke wat die hoër – inkomste genererende besigheide van die ander skei. Analises deur die Mann-Whitney, die Spearman rank korrelasie, die Chi-square en die Kruskal-Wallis toetse bewys dat besighede met ‘n hoër maandelikse inkomste deur mans besit word wat hulle besigheide vanaf hulle eiendomme bestuur en gebruik maak van tjekrekeninge. Die besighede wat ‘n daaglikse hoër inkomste genereer is ook daardie wat deur mans besit word, geregistreer is by CIPRO, gebruik maak van tjek rekeninge vir die besigheid en daardie van wie se eienaars kwalifikasies van graad 7 tot 9 en hoër het. Asgevolg van die uitkoms van hierdie studie, soos van toepassing op die regering, moet vereistes vir lenings aan besighede in informele nedersettings hersien word. Die publiek moet ook meer bewus gemaak word oor die ondersteuning wat deur die regering beskikbaar gestel word. Ten opsigte van banke het die studie uitgelig dat daar ‘n spesiale ‘Spaza rekening’ geskep moet word wat voldoen aan die behoeftes en vaardighede van besigheidseienaars in die informele nedersettings. Op ‘n sosiale vlak vra die studie aan dat die ‘mure’ wat dit moeilik en onmoontlik maak vir ope mark besigheids geleenthede om plaas te vind, afgebreek moet word.

<p>Nucleic Acid hairpins have been a subject of study for the last four decades. They are composed of single strand that is </p><p>hybridized to itself, and the central section forming an unhybridized loop. In nature, they stabilize single stranded RNA, serve as nucleation</p><p>sites for RNA folding, protein recognition signals, mRNA localization and regulation of mRNA degradation. On the other hand, </p><p>DNA hairpins in biological contexts have been studied with respect to forming cruciform structures that can regulate gene expression.</p><p>The use of DNA hairpins as fuel for synthetic molecular devices, including locomotion, was proposed and experimental demonstrated in 2003. They</p><p>were interesting because they bring to the table an on-demand energy/information supply mechanism. </p><p>The energy/information is hidden (from hybridization) in the hairpin’s loop, until required.</p><p>The energy/information is harnessed by opening the stem region, and exposing the single stranded loop section.</p><p>The loop region is now free for possible hybridization and help move the system into a thermodynamically favourable state.</p><p>The hidden energy and information coupled with </p><p>programmability provides another functionality, of selectively choosing what reactions to hide and </p><p>what reactions to allow to proceed, that helps develop a topological sequence of events. </p><p>Hairpins have been utilized as a source of fuel for many different DNA devices. In this thesis, we program four different </p><p>molecular devices using DNA hairpins, and experimentally validate them in the</p><p>laboratory. 1) The first device: A </p><p>novel enzyme-free autocatalytic self-replicating system composed entirely of DNA that operates isothermally. 2) The second</p><p>device: Time-Responsive Circuits using DNA have two properties: a) asynchronous: the final output is always correct </p><p>regardless of differences in the arrival time of different inputs.</p><p>b) renewable circuits which can be used multiple times without major degradation of the gate motifs </p><p>(so if the inputs change over time, the DNA-based circuit can re-compute the output correctly based on the new inputs).</p><p>3) The third device: Activatable tiles are a theoretical extension to the Tile assembly model that enhances </p><p>its robustness by protecting the sticky sides of tiles until a tile is partially incorporated into a growing assembly. </p><p>4) The fourth device: Controlled Amplification of DNA catalytic system: a device such that the amplification</p><p>of the system does not run uncontrollably until the system runs out of fuel, but instead achieves a finite</p><p>amount of gain.</p><p>Nucleic acid circuits with the ability </p><p>to perform complex logic operations have many potential practical applications, for example the ability to achieve point of care diagnostics.</p><p>We discuss the designs of our DNA Hairpin molecular devices, the results we have obtained, and the challenges we have overcome</p><p>to make these truly functional.</p> / Dissertation

Den här uppsatsen studerar vad Gävle kommun haft för målsättningar och hur de har arbetat med att implementera en social blandning och en blandad bostadsstruktur i den nya stadsdelen Gävle Strand. Metodiskt görs textanalys av kommunala dokument såsom översiktsplaner, detaljplaner och bostadsförsörjningsprogram, intervjuer med utvalda nyckelpersoner samt bearbetning av sekundärdata hämtat ur databasen Geosweden. Studien fokuserar på de uttalade ambitionerna i de kommunala dokumenten och i vilken utsträckning dessa mål har uppnåtts och huruvida de är att anse som realistiska. Av studiens resultat framgår att Gävle Strand inte är att anse som en socialt blandad stadsdel, trots att målsättningen med en blandad bostadsstruktur kan anses som uppnått. Uppsatsen visar också att marknadsekonomiska faktorer i hög utsträckning styrt lokaliseringen av olika upplåtelseformer inom stadsdelen, samt att det är förknippat med svårigheter att uppnå en social blandning i nyproducerade bostäder på grund av det höga kostnadsläget. Den ställer också frågan om det inte är så att en ny stadsdel riskerar öka den befintliga boendesegregationen.

Maintaining genomic integrity is crucial for cell survival. In Escherichia coli, Rec-Amediated homologous recombination (HR) plays an essential role in the repair of DNA double-strand breaks (DSB) and the SOS response through a series of highly dynamic interactions with the chromosome. A greater understanding of the mechanism of homologous recombination requires quantitative analysis of genomic studies in live cells. The aim of this thesis was to investigate the dynamics of the RecA-DNA interactions in vivo following the induction of a site-specific DSB in the chromosome of E. coli. This DSB is caused by the cleavage of a DNA hairpin by the hairpin-specific endonuclease, SbcCD. The DNA hairpin is formed only on the lagging strand template of replication by a 246 bp-interrupted palindrome. As a result cleavage only occurs on one sister chromosome, leaving one unbroken chromosome to serve as a template for repair by HR. Here, this system has been used as a basis to develop a method that combines chromatin immunoprecipitation with quantitative PCR (ChIP-qPCR) and next-generation sequencing (ChIP-Seq) to quantify RecA protein binding during the active repair of a single chromosomal DSB. This study reports that DSB-dependent RecA binding is stimulated in response to the eight base DNA sequence Chi (5’-GCTGGTGG-3’). Increasing the number of Chi sites close to the DSB stimulates more RecA loading to DNA, with ChIP-Seq analysis also revealing a role for subsequent Chi sites in RecA binding during DSBR. If the Chi sites close to the DSB are removed then Chi-dependent RecA binding to DNA can be observed at distances greater than 100 kb from the DSB, suggesting that these subsequent Chi sites can be engaged in DSBR. Through collaboration, these in vivo data were combined with stochastic modeling to determine that, in vivo, Chi is recognised by the RecBCD complex with an efficiency of 20- 35%. The genomic analysis also revealed two unexpected aspects of RecA protein binding. First, ChIP-Seq analyses identified that following a DSB at lacZ there is RecA enrichment detected in the terminus region of the E. coli chromosome. This RecA binding is Chi-dependent, indicating a role for HR. Second, DSB-independent binding was observed at the RNA encoding genes dispersed throughout the chromosome. A temporal analysis of RecA dynamics was also performed. These analyses revealed that RecA binding to DNA near the DSB is extremely dynamic, cycling between periods of high RecA enrichment and periods of low RecA enrichment. This is the first in vivo study of DSB-dependent RecA-DNA distribution and dynamics in recombination proficient E. coli cells.

DNA double strand break (DSB) repair is critical to maintain genomic integrity and cell viability. DSBs can occur during the course of cell cycle during replication or transcription, or by exogenous agents such as chemicals or ionizing radiation. For my thesis, I studied homologous recombination (HR), which has two sub-pathways: Homology Directed Repair (HDR) and Single Strand Annealing (SSA). HDR involves strand invasion of a homologous template to prime DNA synthesis; SSA involves annealing of homologous segments flanking a DSB. Background data showed that depletion of XAB2 protein by RNA interference reduced both HDR and SSA events. XAB2 protein contains 15 tetratricopeptide repeat (TPR) motifs, which likely enable protein-protein interactions. While XAB2 is speculated to have a role in transcription coupled repair and pre-mRNA splicing, its role in HR pathway is uncertain. The overall hypothesis for my thesis is that XAB2 mediates a specific step of HR (5’-3’ end resection), and the TPR motifs present in XAB2 enable the protein to function in a complex during HR. By using an end resection assay and cell biology analysis, I found that XAB2 is essential for 5’ – 3’ end resection, an intermediate step common to both HDR and SSA pathways. With a functional complementation assay I developed, I have shown that specific TPR regions are critical for XAB2 functions in HR. Overall, my research demonstrates that XAB2 protein has a key role in the 5’-3’ end resection step of HR, and its function in HR requires specific sets of its TPR regions.