Cette thèse aborde le problème de la surcharge des réseaux des données des opérateurs mobiles. La croissance des abonnements au haut débit mobile engendre aujourd'hui de nombreux goulots d'étranglement dans ces réseaux. Plus particulièrement, la disponibilité de la bande passante sur les stations de bases est de plus en plus réduite. Pour faire face à cette problématique, les opérateurs mobiles essaient de décharger le trafic des données de leurs infrastructures en déployant des réseaux de substitution à petites cellules, tels que les femtocells ou réseaux WiFi publics. Ces réseaux restent néanmoins très localisés et ne résolvent donc que très partiellement le problème. Ainsi, plus récemment, nous voyons l'émergence des réseaux opportunistes qui visent à transmettent les données en ne se basant que sur les dispositifs mobiles, c-à-d, de dispositif à dispositif. Cette thèse vise à évaluer la faisabilité de décharger le trafic de données mobile à l'aide des hotspots WiFi en étendant leur champs de couverture par l'utilisation des réseaux opportunistes. Pour ce faire, cette thèse propose un cadre pour le déchargement (offloading) de données de façon opportuniste et un mécanisme d'incitation pour encourager la coopération des utilisateurs des dispositifs mobiles. Dans une première partie de cette thèse, nous avons tracé la couverture 3G et WiFi à travers plusieurs lignes de bus à Paris afin d'évaluer la façon dont les utilisateurs et les opérateurs mobiles peuvent bénéficier des réseaux WiFi existants pour le déchargement des données. Nos résultats indiquent que les points d'accès WiFi déployés par les fournisseurs de service Internet peuvent décharger une partie non négligeable du trafic de données, cependant des restrictions telles que le temps de l'association et le processus d'authentification peuvent diminuer la quantité de données transmises. Dans une tentative d'offrir une nouvelle approche pour le déchargement mobile, nous proposons dans un second temps un cadre décisionnel multi-critères, appelé OppLite, pour décharger les données des réseaux de mobiles 3G grâce à des communications dispositif à dispositif opportunistes. Nous avons montré par des simulations qu'un tel déchargement mobile opportuniste peut étendre la couverture et l'efficacité des réseaux cellulaires, permettant un déchargement pouvant aller jusqu'à 36% des données dans certains scénarios. L'efficacité du déchargement mobile par les réseaux opportunistes dépend principalement de la tolérance au délai par l'application et de la coopération des utilisateurs mobiles. Le déchargement opportuniste dépend de la volonté de l'utilisateur d'offrir ses ressources aux autres. Nous avons donc proposé, dans un troisième temps, un mécanisme d'incitation, appelé MINEIRO, qui calcul un rang de réputation basée sur la source des messages reçus par les nœuds intermédiaires. MINEIRO permet à des réseaux composés d'un pourcentage important, allant jusqu'à 60%, de nœuds avec un comportement égoïste sans dégradation des performances dans un scénario de mobilité aléatoire. Au delà de ce pourcentage, MINEIRO permet maintenir un taux de livraison et des délais de livraison constants / This thesis addresses the overload problem of the Wireless Internet service Providers' (WISP) network. The growth of mobile broadband subscription has been leading several bottlenecks to WISPs, such as, bandwidth availability and resource sharing of over a single cellular cell. WISPs can move off data traffic from its infrastructure by deploying small cells, such as femtocells, to public WiFi networks or, more recently, to device-to-device opportunistic networks. This work evaluates the feasibility to offload mobile data traffic using WiFi hotspots, proposes a framework to opportunistic data offloading and an incentive mechanism to encourage users cooperation. We mapped 3G and WiFi coverage through several bus routes in Paris in order to evaluate how users and WISPs can benefit from the existing infrastructure. Our results indicate that the deployed WISPs access points can offload part of the data traffic, however restrictions such as association time and the authentication process may reduce the amount of offloaded data. We propose a multi-criteria decision-making framework, called OppLite, to offload data from 3G networks using opportunistic device-to-device communications. Trace-driven simulations showed that opportunistic mobile offloading can expand coverage and network efficiency, offloading up to 36% of data in certain scenarios. Thus, the effectiveness of opportunistic mobile offloading depends mainly of the delay tolerance of the applications and whether the user cooperates. Since opportunistic offloading depends on the user's willingness to offer his/her resources to others, we propose a message-based incentive mechanism that builds a reputation rank based on the source of messages received by the forwarding nodes, called MINEIRO. The network supports up to 60% of nodes with selfish behavior without performance degradation in a random mobility scenario. After this threshold, MINEIRO kept the delivery rate and the delay constant. Meanwhile, in a scenario with social-based mobility, selfish behavior degrades the network performance quickly

This research focuses on the lives of migrant mine labourers in the Free State Gold mines of Welkom. After a lengthy absence from home, away from home, some of the migrant mine labourers contact the deadly disease of HIV/AIDS. As they become weaker to work at the mines, some are relegated work at the surface, some are sent to the local hospice whilst some are left to die alone without anyone caring for them. The local community of Welkom regarded these miners as the carriers and transporters of this deadly disease due to their perceived slackness in morality by using the services of the local ladies of the night (commercial sex workers). On the basis of the above painted scenario, the migrant mine labourers were thus subjected to discrimination and stigmatisation by the local community, who regarded them as foreigners even in their country of birth. The research, therefore, aimed to pastorally journey with the infected mine labourers through their trauma of being infected by HIV/AIDS AND of being discriminated and rejected by the community which is supposed to support them in their hour of need and despair. Since the spread of HIV/AIDS is largely through sexual contact, the research, therefore, examined both the community and the church’s attitude towards sex, stigma and discrimination. A participatory observation approach was used and the analysis of the concepts that were at play during the trauma of the infected mine labourers were examined. In this research, the local community was viewed as the fertile ground of hostility against the infected migrant mine labourers. In this regard, the study powered the infected mining community with the challenges posed by HIV/AIDS and therefore sought ways and means of forming a support base for those infected and affected. This was done by breaking the conspiracy of silence around the issue of HIV/AIDS both at the community and the church level. Finally, the study concluded with ways of empowering the pastoral care-giver on how to journey with someone who has been diagnosed with HIV in order to close one’s last chapter of life in honour and dignity. New approaches based on relevant literature and affirmation of God’s power and healing were suggested. / Dissertation (MA(Theol))--University of Pretoria, 2011. / Practical Theology / unrestricted

Pocket Switched Networks (PSNs) offer a means of infrastructureless inter-human communication by utilising Delay and Disruption Tolerant Networking (DTN) technology. However, creating PSNs involves solving challenges which were not encountered in the Deep Space Internet for which DTN technology was originally intended.End-to-end communication over multiple hops in PSNs is a product of short range opportunistic wireless communication between personal mobile wireless devices carried by humans. Opportunistic data delivery in PSNs is far less predictable than in the Deep Space Internet because human movement patterns are harder to predict than the orbital motion of satellites. Furthermore, PSNs require some scheme for efficient neighbour discovery in order to save energy and because mobile devices in PSNs may be unaware of when their next encounter will take place.This thesis offers novel solutions for neighbour discovery and opportunistic data delivery in PSNs that make practical use of dynamic inter-human encounter patterns.The first contribution is a novel neighbour discovery algorithm for PSNs called PISTONS which relies on a new inter-probe time calculation (IPC) and the bursty encounter patterns of humans to set the time between neighbour discovery scans. The IPC equations and PISTONS also give participants the ability to easily specify their required level of connectivity and energy saving with a single variable.This thesis also contains novel distributed spatio-temporal clustering and opportunistic data delivery algorithms for PSNs which can be used to deliver data over multiple hops. The spatio-temporal clustering algorimths are also used to analyse the social networks and transient groups which are formed when humans interact.

Orientador: Altair Antoninha Del Bel Cury / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-26T14:52:55Z (GMT). No. of bitstreams: 1 Bertolini_MartinnadeMendoncae_D.pdf: 3303888 bytes, checksum: 17ca780a99a3e63d87bcf4ed94370ffc (MD5) Previous issue date: 2015 / Resumo: O patógeno oportunista Candida albicans e Streptococcus do grupo Mitis formam comunidades complexas em múltiplos sítios da cavidade oral, nos quais o ambiente e a disponibilidade de nutrientes sofrem mudanças constantes. Objetivou-se estudar as características estruturais e de virulência de biofilmes de Candida albicans na presença e ausência de S. oralis crescendo sobre um modelo tri dimensional de mucosa oral humana, em diferentes condições: (1) umidade da superfície mucosa (molhada ou semi seca), (2) disponibilidade de nutrientes (suplementação do meio de cultura com BHI) e (3) morfotipo da hifa (hifa ou pseudo hifa). Para isso foram utilizados modelos tri dimensionais de mucosa oral humana formado por queratinócitos imortalizados (linhagens celulares OKF6-TERT2 ou SCC15) sobre uma matriz colágena com fibroblastos para o crescimento dos biofilmes. Estes foram infectados por Streptococcus oralis 34, e/ou Candida albicans, sendo uma cepa de referência e cepas mutantes para a formação de pseudo-hifas, pela deleção dos genes ndt80 ou tup1. A determinação do biovolume e estrutura do biofilme foram realizadas por microscopia confocal a laser, com os biofilmes sendo corados por imunofluorescência com anticorpo especifico para C. albicans e sonda para Streptococcus. Como determinante de virlência secções de tecido com 5 ?m de espessura foram coradas da mesma maneira anterior ou por hematoxilina e eosina, com o intuito de se detectar a invasão de microorganismos. O dano tecidual também foi mensurado pela liberação de lactato desicrogenase no meio de cultura. Os dados foram avaliados por análises de variâncias (ANOVA) e os procedimentos para comparações múltiplas pareadas por Bonferroni t-test, com ? = 5%. Em condições úmidas C. albicans estendeu hifas longas e entrelaçadas, formando um biofilme de superfície homogênea. Biofilmes mistos apresentaram uma estrutura estratificada, com S. oralis crescendo em contato com a mucosa e a C. albicans cobrindo a superfície bacteriana. Em condições de semi-secas a C. albicans formou densos focos de crescimento localizados a partir dos quais as hifas estenderam-se radialmente para se entrelaçarem com hifas de focos adjacentes. Em biofilmes mistos este fenômeno provocou o acúmulo focal de S. oralis co-localizado com os focos de C. albicans. Embora o biovolume do biofilme de C. albicans tenha sido significativamente maior em condições úmidas (P<0,001), houve uma invasão tecidual mínima em comparação com as condições semi-secas, na qual a barreira epitelial foi completamente destruída. A suplementação do meio de cultura, em condições semi-secas não alterou a arquitetura do biofilme, mas intensificaram o crescimento, o biovolume e a invasão/dano tecidual (P<0,001), proporcionalmente as concentrações testadas. Mutantes para a formação de pseudo-hifas formaram biofilmes defeituosos, nos quais a maioria dos S. oralis estava em contato com a superfície epitelial, abaixo das pseudo-hifas. A presença de S. oralis promoveu invasão e dano tecidual em todas as condições. Conclui-se que a umidade, a disponibilidade de nutrientes, o morfotipo da Candida e a presença de S. oralis afetam fortemente a arquitetura e virulência de biofilmes de C. albicans crescidos sobre nas mucosas / Abstract: The opportunistic pathogen Candida albicans and streptococci of the Mitis group form complex communities in multiple oral sites, where the environment and nutrient availability change constantly. We aimed to study structural and virulence characteristics of Candida albicans biofilms in the presence or absence of S. oralis, growing on a three-dimensional model of human oral mucosa, under different conditions: (1) moisture of mucosal surface (wet or semi dry), (2) nutrient availability (BHI supplementation on culture media) and (3) hyphal morphotype (hyphae or pseudohyphae). For this it was used a three-dimensional model of the human oral mucosa formed by immortalized oral keratinocytes (OKF6-TERT2 or SCC15 cell lines) on a fibroblast-embedded collagenous matrix to grow biofilms. Infections were carried out using Streptococcus oralis 34, a C. albicans reference strain and pseudohyphal mutants with a homozygous deletion of the ndt80, or tup1 gene. Determination of biofilm biovolume and structure was done by confocal scanning laser microscopy with biofilms stained by immunofluorescence using an anti-Candida antibody and a Streptococcus probe. As determinant of virulence, 5-?m-thick tissue sections were stained same way or with hematoxylin and eosin in order to detect invasion of microorganisms. Also tissue damage was measured by lactate dehydrogenase release in the culture media. Statistical analyses were performed using SigmaPlot 12 software at 5% significance level. Data were evaluated by analysis of variance (ANOVA) and when statistical significances were found, all pairwise multiple comparison procedures were performed with Bonferroni t-test, with ? = 5%. Under wet conditions C. albicans extended long intertwined hyphae, forming a homogeneous surface biofilm. Mixed biofilms had a stratified structure, with S. oralis growing in close contact to the mucosa and C. albicans growing on the bacterial surface. Under semi-dry conditions, C. albicans formed localized foci of dense growth from which hyphae extended radially to intertwine with hyphae from adjacent foci. In mixed biofilms this promoted focal growth of S. oralis co-localizing with C. albicans. Although Candida biofilm biovolume was significantly greater under wet conditions (P<0.001), there was minimal tissue invasion compared to semidry conditions where the epithelial barrier was completely destroyed. Supplementing the infection medium with nutrients under semidry conditions did not change the biofilm architecture but intensified focal growth and increased biofilm biovolume and tissue invasion/damage (P<0.001), proportionally to the tested concentrations. Pseudohyphal mutants formed defective mixed biofilms, with most S. oralis in contact with the epithelial surface, below the pseudohyphal mass. Interestingly, the presence of S. oralis promoted fungal invasion and tissue damage under all conditions. Moisture, nutrient availability, hyphal morphotype and presence of S. oralis strongly affect architecture and virulence of mucosal fungal biofilms / Doutorado / Protese Dental / Doutora em Clínica Odontológica

Orientadores: Francisco Hideo Aoki, Ângela Maria de Assis / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-28T00:12:52Z (GMT). No. of bitstreams: 1 Santos_CristinaRodrigues_M.pdf: 1833064 bytes, checksum: 4087a171a36bf726cff1abdcd0bd4cf8 (MD5) Previous issue date: 2015 / Resumo: O Pneumocystis jirovecii é um fungo ascomiceto que pode causar pneumonia (PPC) em indivíduos imunossuprimidos e eventualmente em imunocompetentes. Os métodos laboratoriais de baixo custo para detecção ainda é a coloração em lâmina. Os métodos moleculares são considerados mais eficientes e tem oferecido alternativas para o entendimento da biologia e da doença causada por esse microrganismo. O objetivo desse estudo foi detectar a presença de Pneumocystis jirovecii em pacientes com doença pulmonar. O método adotado foi a técnica de coloração de lâmina com azul de toluidina para detecção de cistos, PCR para detecção do fragmento mitocondrial pAZ102-H/E, Nested PCR com primers internos pAZ102-X/Y e sequenciamento pelo método de Sanger para detecção de alterações moleculares na região genômica estudada. Foram coletadas 139 amostras, sendo 102 de lavado broncoalveolar (LBA), 7 de escarro, 10 amostras de sangue periférico (fracionadas em hemácias/leucócitos e plasma) e 10 amostras de soro. Nos resultados da coloração pela técnica de azul de toluidina, 2 amostras de escarro e 1 de LBA foram positivas. Através dos métodos moleculares, 6 amostras foram positivas na primeira PCR e 91 amostras foram positivas pela Nested PCR. Os fragmentos pAZ102-X de 51 amostras foram sequenciadas, 18 amostras apresentaram mutação nos seguintes códon/posição 4406/13217, 4419/13257, 4431/13294, 4439/13316, 4440/13321, 4446/13338, 4452/13357, 4456/13367 e 4457/13371. Os pacientes que apresentaram essas alterações tinham um perfil com doenças pulmonares ou fatores de risco associados à infecção por P. jirovecii. Como a detecção de P. jirovecii, diagnóstico e prevenção de PPC são ligadas a história clínica do paciente, os avanços moleculares podem ser um caminho para diagnóstico de PPC, diferenciando essa pneumonia dos casos de colonização por esse fungo / Abstract: Pneumocystis jirovecii is an ascomycete fungus that can cause pneumonia (PCP) in immunocompromised individuals and possibly in immunocompetent. The low cost of laboratory methods for detection is with conventional staining methods. Molecular methods are considered more efficient and have offered alternatives to the understanding of biology and disease caused by this organism. The aim of this study was to detect the target DNA fragment (mtLSUrRNA) of P. jirovecii in patients with lung disease. We compared the staining technique with molecular methods using toluidine blue for microscopy and "in house" DNA extraction, PCR and Nested PCR for molecular detection and sequencing by the Sanger method to detect molecular alterations in the genomic region studied. It was analyzed 139 samples, such as, 102 bronchoalveolar lavage (BAL), 7 sputum, 10 samples of peripheral blood (fractionated in red blood cells / leukocytes and plasma) and 10 serum samples. The results of the toluidine blue staining technique, two sputum samples and 1 BAL were positive. Through molecular methods, 6 samples were positive in the first PCR and 91 samples were positive by Nested PCR. The pAZ102-X fragments of 51 samples were sequenced, 18 samples had mutations in codon/position 4406/13217, 4419/13257, 4431/13294, 4439/13316, 4440/13321, 4446/13338, 4452/13357, 4456 / 13367 and 4457/13371. Patients who presented these alterations had a profile with lung diseases or risk factors associated with infection by P. jirovecii. As the detection of P. jirovecii, diagnosis and prevention of PCP are linked to clinical history, molecular advances can be a way for diagnosis of PCP, differentiating this pneumonia cases of colonization by the fungus. OBSERVAÇÃOPor favor manter essa palavra em itálico: Pneumocystis jirovecii / Mestrado / Clinica Medica / Mestra em Ciências

The recent addition of Karoo Lamb to South Africa’s repertoire of products with a regional identity attracted extensive publicity. The news headlines that spoke of challenges to protect the geographical name, discrepancies among supply chain stakeholders and the outright opportunism and exploitation of the geographical name made Karoo Lamb a particularly interesting case study to examine. Regrettably, the niche product “Karoo Lamb” has not yet come to its own. In an effort to support the development of this initiative, the thesis sets out to address the central question; “How do we increase farmer participation in differentiated product supply chains, whilst discouraging opportunistic behaviour so that the performance of these chains can be optimised?” The overarching question, mentioned above, is addressed in four independent but related research papers by using the differentiated Karoo Lamb supply chain as a case study. The specific questions considered in these papers are:  What are the claims most vulnerable to opportunistic behaviour?  What drives a farmer’s tendency to behave opportunistically, and how can these drivers be used to prevent opportunistic behaviour?  What factors encourage a farmer to participate in a differentiated supply chain?  What enforcement mechanisms are best suited to prevent the opportunistic behaviour of farmers?  What governance mechanisms are currently employed to govern the supply chain?  Are the governance and enforcement mechanisms properly aligned to guarantee the authenticity of the differentiated product? The thesis employed the principals of agency theory, transaction cost economics, and contract theory to address the practical problems faced by the Karoo Meat of Origin certification scheme. The thesis combined quantitative and qualitative research methods to analyse the data collected from four primary stakeholders involved in the Karoo Lamb supply chain. From the total population of 209 certified Karoo Lamb farmers, 73 farmers were interviewed on their farms in the Karoo region. In addition to the farmers, five abattoirs, two processors and/or packers and five retail outlets were interviewed. Results supported the expectation that a farmer’s decision to invest in the collective reputational capital of a product is shaped by his/her relationship with the abattoir, and the ease with which business is conducted. The easier it is for the farmer to do business with the abattoir the more likely the farmer is to invest in the Karoo Lamb initiative. Other, more personal attributes, such as the farmer’s risk profile, education and his/her network also proved to influence his/her willingness to invest in the collective reputation. The efforts to increase the membership base of Karoo Lamb contributes to the success story of Karoo Lamb. The success of the initiative, however, remains threatened by opportunism. The investigation revealed the “from the Karoo” and “free range” claims as the most vulnerable to opportunistic behaviour specifically during times of droughts. The study further revealed a lack of information exchange between the farmers and abattoirs, specifically regarding droughts, feeding practices and disease treatments, as the leading driver for opportunistic behaviour. An increase in information sharing, within the farmer network, and with the abattoir, is therefore recommended. This is the main strategy to reduce or eradicate the opportunistic behaviour of farmers. In addition to broadening farmer investments in the reputational capital of Karoo Lamb and to preventing the opportunistic behaviour of farmers, the success of the Karoo Lamb initiative also requires an alignment between the enforcement and governance mechanisms. The investigation supported the notion that the State-appointed third party is relatively unsuccessful when it specifically comes to the monitoring of the Karoo farmers for compliance with production standards. Due to the failure of the third party, the thesis made an attempt to explore alternative monitoring and enforcement mechanisms. The results indicate that the majority of the Karoo Lamb stakeholders preferred monitoring and enforcement mechanisms that include more frequent monitoring and stricter prosecution strategies to deal with non-compliant stakeholders. Owing to many years of commodity style operations throughout the supply chain, the correct vehicle for ensuring the proper implementation of the enforcement mechanisms remains a challenge. The assessment of the Karoo Lamb supply chain reveals non-contractual arrangements with qualified partners as being the most frequently utilised governance mechanism. However, this mechanism is not sufficient when the third party fails to monitor and enforce the production standards accurately. Therefore, with a view to ensuring the credibility of Karoo Lamb, a move to toward more hierarchical arrangements, are expected, which would provide a stronger focus on private or mutual enforcement mechanisms. This means that the stakeholders in the supply chain would be jointly responsible for the credibility of the product and therefore jointly responsible for the enforcement of quality and origin standards. / Thesis (PhD)--University of Pretoria, 2017. / Red Meat Research and Development SA / Bill and Melinda Gates Foundation / Agricultural Economics, Extension and Rural Development / PhD / Unrestricted

Le tube digestif est la première barrière contre les agresseurs présents dans la nourriture (virus, bactéries, produits chimiques, pesticides etc...). Il doit donc maintenir au mieux son intégrité structurale et fonctionnelle tout au long de la vie de l'individu. Bien que l'impact délétère d'une intoxication aiguë puisse être surmonté par la capacité de défense et de régénération de la muqueuse digestive, une agression prolongée ou répétée peut compromettre l'équilibre physiologique (l'homéostasie) du tube digestif. Parmi les agresseurs pouvant être ingérés avec la nourriture, on trouve la bactérie Bacillus thuringiensis (Bt) et représente 70% des ventes de bioinsecticides. Bt est une bactérie Gram+ sporulante qui produit, pendant la sporulation, des toxines nommées Cry. Parmi les différentes souches de Bt, certaines ont été sélectionnées pour la spécificité d'action de leurs toxines Cry contre des nuisibles et sont commercialisées sous forme de sporanges. Certaines de ces souches sont utilisées en agriculture biologique en France et l'accroissement de leur utilisation fait qu'elles sont de plus en plus présentes dans la nourriture, source de contamination potentielle pour l'homme et l’environnement. La question qui se pose maintenant est de savoir si un tel accroissement de l’utilisation de Bt peut avoir des impacts sur des espèces non cibles. Mon projet de thèse a consisté en l’étude des conséquences de l'ingestion de Bt (sous forme végétative ou de sporanges) sur la physiologie intestinale de la drosophile (animal non sensible à Bt en termes de toxicité aigüe / The digestive tract is continuously subjected to multiple aggressions through virus, bacteria, toxins and chemicals mixed in the feed. Therefore the gut lining has established a mechanism of replenishment in order to maintain the physiological function of the organ called the gut homeostasis. Although the deleterious impact of acute poisoning can be overcome by the defense capacity and regeneration of the gut mucosa, prolonged or repeated intoxication can impair its homeostasis. Among the aggressors hidden in the feed, there is the bacterium Bacillus thuringiensis (Bt). Bt is worldwide used as bioinsecticide. Indeed the multitude of Bt strains produces a broad range of crystalline toxins, named Cry toxins, which certain have been selected in organic farming owing to their lethal properties against specific pests. Because of incentive programs for sustainable development, the use of Bt bioinsecticides as an alternative to chemical pesticides will further increase in the next decades. Although the specificity of the acute toxicity of Cry toxins has been proved since many years, data are scarce on adverse effects that could result from chronic exposure. The question now is how far non-target organisms will be potentially impacted by the resulting augmentation of the Bt bacterium and its Cry toxins in the environment. To answer this challenge, I used Drosophila (a non-target organism) to study the impacts of Bt bioinsecticides on the gut physiology because 1/ the digestive tract is the main entrance for feed contaminated by Bt bioinsecticides and 2/ Bt and its toxins are known to impair the gut epithelium of sensitive pests

This thesis tackles problems on IEEE 802.11 MAC layer, network layer and application layer, to further push the performance of wireless P2P applications in a holistic way. It contributes to the better understanding and utilization of two major IEEE 802.11 MAC features, frame aggregation and block acknowledgement, to the design and implementation of opportunistic networks on off-the-shelf hardware and proposes a document exchange protocol, including document recommendation. First, this thesis contributes a measurement study of the A-MPDU frame aggregation behavior of IEEE 802.11n in a real-world, multi-hop, indoor mesh testbed. Furthermore, this thesis presents MPDU payload adaptation (MPA) to utilize A-MPDU subframes to increase the overall throughput under bad channel conditions. MPA adapts the size of MAC protocol data units to channel conditions, to increase the throughput and lower the delay in error-prone channels. The results suggest that under erroneous conditions throughput can be maximized by limiting the MPDU size. As second major contribution, this thesis introduces Neighborhood-aware OPPortunistic networking on Smartphones (NOPPoS). NOPPoS creates an opportunistic, pocket-switched network using current generation, off-the-shelf mobile devices. As main novel feature, NOPPoS is highly responsive to node mobility due to periodic, low-energy scans of its environment, using Bluetooth Low Energy advertisements. The last major contribution is the Neighborhood Document Sharing (NDS) protocol. NDS enables users to discover and retrieve arbitrary documents shared by other users in their proximity, i.e. in the communication range of their IEEE 802.11 interface. However, IEEE 802.11 connections are only used on-demand during file transfers and indexing of files in the proximity of the user. Simulations show that NDS interconnects over 90 \% of all devices in communication range. Finally, NDS is extended by the content recommendation system User Preference-based Probability Spreading (UPPS), a graph-based approach. It integrates user-item scoring into a graph-based tag-aware item recommender system. UPPS utilizes novel formulas for affinity and similarity scoring, taking into account user-item preference in the mass diffusion of the recommender system. The presented results show that UPPS is a significant improvement to previous approaches.

This thesis investigates the difficulty in making accurate forecasts on opportunistic commercial real estate investments. The purpose is to quantify the differences between unlevered cash flows from underwriting estimates and actual outcomes, analyse them and arrive at conclusions about the difficulty in producing forecasts on opportunistic investments. The data used in this thesis comes from two opportunistic real estate portfolios previously owned by the private equity firm Niam. Both portfolios comprised Swedish office properties. The results from analysing Niam’s investments shows that operating cash flows on individual properties are most difficult to forecast since the strategy for the assets constantly needs to be updated in order to adjust for current events like for example change in demand of office properties. This can have great impact on the profit allocation between property cash flows and exit cash flows in comparison to underwriting. Furthermore the results show of an increased need of diversification for opportunistic investments, since individual investments have high volatility. Also, analysing investments on unlevered level has limitations. On an unlevered level an investment can have actual outcomes worse than in the underwriting, but when adding effects from financial leverage and currency movements the same asset can outperform the underwriting.

This thesis investigates the difficulty in making accurate forecasts on opportunistic commercial real estate investments. The purpose is to quantify the differences between unlevered cash flows from underwriting estimates and actual outcomes, analyse them and arrive at conclusions about the difficulty in producing forecasts on opportunistic investments. The data used in this thesis comes from two opportunistic real estate portfolios previously owned by the private equity firm Niam. Both portfolios comprised Swedish office properties. The results from analysing Niam’s investments shows that operating cash flows on individual properties are most difficult to forecast since the strategy for the assets constantly needs to be updated in order to adjust for current events like for example change in demand of office properties. This can have great impact on the profit allocation between property cash flows and exit cash flows in comparison to underwriting. Furthermore the results show of an increased need of diversification for opportunistic investments, since individual investments have high volatility. Also, analysing investments on unlevered level has limitations. On an unlevered level an investment can have actual outcomes worse than in the underwriting, but when adding effects from financial leverage and currency movements the same asset can outperform the underwriting.