Material Evaluation of an Elastomer, Epoxy and Lightweight Concrete Rail Attachment System for Direct Fixation Light Rail Applications

Thesis (Master's)--University of Washington, 2016-08

Fixation du prix de vente des exploitations agricoles québécoises: comparaison entre fermes laitières et autres types de production

L’écart croissant entre les valeurs marchande et économique des exploitations agricoles québécoises complexifie le processus de transfert des fermes à la prochaine génération. La capacité de payer limitée des repreneurs et les besoins de retraite des cédants restreignent la marge de manoeuvre nécessaire afin de déterminer un prix de vente de l’entreprise adéquat. La présente étude vise à analyser les déterminants du prix de vente des fermes et montre que dans notre échantillon, le prix est significativement corrélé avec les besoins de retraite nets des cédants et de façon moins significative, avec la valeur économique des fonds propres de l’entreprise. Les considérations financières semblent éclipser les aspects humains et d’importants compromis sont réalisés des deux côtés de la transaction en vue d’assurer la continuité de l’entreprise. L’influence d’intervenants externes à l’entreprise entre également en ligne de compte dans la fixation du prix, ce qui implique que la décision ne découle pas uniquement d’une négociation entre cédants et repreneurs. De façon générale, les fermes laitières semblent confrontées aux mêmes défis que les autres types de production quant à la fixation de leur prix de vente, ce qui suggère que la problématique soit davantage une question de gestion plutôt qu’une question spécifique au secteur. À moins d’un rétrécissement de l’écart entre la valeur marchande des actifs et leurs capacités à générer des revenus, la fixation du prix de vente de plusieurs fermes du Québec risque d’être encore plus contraignante à l’avenir.

Competition and fixation of cohorts of adaptive mutations under Fisher geometrical model

One of the simplest models of adaptation to a new environment is Fisher's Geometric Model (FGM), in which populations move on a multidimensional landscape defined by the traits under selection. The predictions of this model have been found to be consistent with current observations of patterns of fitness increase in experimentally evolved populations. Recent studies investigated the dynamics of allele frequency change along adaptation of microbes to simple laboratory conditions and unveiled a dramatic pattern of competition between cohorts of mutations, i.e., multiple mutations simultaneously segregating and ultimately reaching fixation. Here, using simulations, we study the dynamics of phenotypic and genetic change as asexual populations under clonal interference climb a Fisherian landscape, and ask about the conditions under which FGM can display the simultaneous increase and fixation of multiple mutations-mutation cohorts-along the adaptive walk. We find that FGM under clonal interference, and with varying levels of pleiotropy, can reproduce the experimentally observed competition between different cohorts of mutations, some of which have a high probability of fixation along the adaptive walk. Overall, our results show that the surprising dynamics of mutation cohorts recently observed during experimental adaptation of microbial populations can be expected under one of the oldest and simplest theoretical models of adaptation-FGM.

Complications associated with operative fixation of acute midshaft clavicle fractures

The aim of this study was to review the complication rate and profile associated with surgical fixation of acute midshaft clavicle fracture in a large cohort of patients treated in a level I trauma centre.Patients and methods: We identified all patients who underwent surgical treatment of acute midshaft clavicle fracture between 2002 and 2010. The study group consisted of 138 fractures (134 patients). There were 107 males (78%) and 31 females (22%) and median age of 35 years (IQR 24-45). The most common mechanism of injury was a road traffic accident (78%). Sixty percent (n = 83) had an injury severity score of ≥ 15 indicating major trauma. The most common fracture type (75%) was simple or wedge comminuted (2B1) according to the Edinburgh classification. The median interval between the injury and operation was 3 days (IQR 1-6). Plate fixation was performed in 110 fractures (80%) and intramedullary fixation was performed in 28 fractures (20%). There were 85 males and 25 females in the plate fixation group with median age of 35 years (IQR: 25-45) There were 22 males and 6 females in intramedullary fixation group with median age of 31 years (IQR 24-42 years). Statistical analysis was performed using Independent sample t-test, Mann-Whitney test, and Chi-square test. Significant P-value was < 0.05.Results: The overall incidence of complication was 14.5% (n = 20). The overall nonunion rate 6%. Post operative wound infection occurred in 3.6% of cases. The incidence of complication associated with plate fixation was 10% (11 of 110 cases) compared to 32% associated with intramedullary fixation (9 of 28 cases) (P = 0.003). Thirty five percent of complications were related to inadequate surgical technique and potentially avoidable. Symptomatic hardware requiring removal occurred in 23% (n = 31) of patients. Symptomatic metalware was more frequent after plate fixation compared to intramedullary fixation (26% vs 7%, P = 0.03).Conclusions: Intramedullary fixation of midshaft clavicle fracture is associated with higher incidence of complications. Plate fixation is associated with a higher rate of symptomatic metalware requiring removal compared to intramedullary fixation. Approximately one in three complications may be avoided by attention to adequate surgical technique.

Rigid removable cover for dorsal wound protection and tube fixation in pigs

Objective To report the design and benefits of a rigid polyethylenecover ‘shell’ for the protection of dorsal torso wounds andtube fixation in pigs.

Methods Open C-shaped polyethylene shells were designed toprotect wounds and dressings on the dorsum of pigs used inresearch into negative pressure dressing-assisted wound healing.The shells were designed to resist trauma and contamination, tobe comfortable and expansible, and to facilitate tube fixation andmanagement. Strap fixation was optimised during experimentation. Efficacy was assessed by direct observation of dressing andwound protection, tube integrity and by macroscopic and microscopicassessments of wound healing.

Results The shells effectively protected the wounds againstblunt and sharp trauma, were simple to remove and reapply, were well tolerated and allowed for growth of the pigs. Circumferentia lneck straps attached by lateral straps to the shells provedcritical. There was no wound infection or inflammation underlyingthe shells. Porting tubing via mid-dorsal holes in the shells andaffixing the tubing just cranial to these holes prevented tubedamage and traction, permitted tube management from outsidethe cages and allowed the pigs to move freely without becomingentangled.

Conclusion These shells effectively protected dorsal skinwounds and dressings, prevented tube damage and facilitatedtube management in pigs. Similar systems may be useful forother production animals for wound management and for tubemanagement with negative pressure wound healing, drain tubesor the delivery of nutrition, fluids or medications.

Biological nitrogen fixation and nutrient release from litter of the guachapele leguminous tree under pure and mixed plantation with eucalyptus.

A Pseudosamanea guachapele (guachapele), leguminosa arbórea fixadora de nitrogênio, é uma alternativa para plantios florestais mistos nos trópicos. Como são escassas as informações sobre a espécie em plantios mistos de eucalipto em condições edafoclimáticas brasileiras, foi conduzido um experimento no qual objetivou-se avaliar a contribuição da fixação biológica de nitrogênio para a guachapele e a velocidade de decomposição e de liberação de nutrientes de folhas senescentes de eucalipto e guachapele (oriundas dos plantios puros e consorciado). A porcentagem de N derivado da atmosfera (% Ndfa) foi estimada comparando-se a abundância natural de 15N ( 15N, ) nos tecidos da guachapele com a observada nos tecidos do Eucalyptus grandis, espécie não fixadora, ambas com sete anos de idade. A constante de decomposição (k) e a meia-vida (t1/2) de serapilheira foram estimadas utilizando-se o modelo exponencial aplicado aos dados oriundos de coletas de litterbags. A estimativa da %Ndfa para guachapele, em condições de plantio puro, variou de 17 a 36%, enquanto que, em condições de plantio consorciado, foi de 35 a 60 %. A concentração de N nas folhas senescentes estava positivamente relacionada com a taxa de decomposição, sendo essa decrescente da guachapele para o eucalipto. A t1/2 dos resíduos diferiu significativamente (p < 0.05), sendo de 148, 185 e 218 dias para as folhas de guachapele, mistura das duas espécies e eucalipto, respectivamente. A liberação dos nutrientes (principalmente N, K e Mg) das folhas seguiu a mesma ordem da t1/2 devido à qualidade inicial das mesmas. Os resultados indicam que a guachapele pode beneficiar o plantio misto pela adição de N e por meio da intensificação da decomposição da serapilheira.

Mitigating surgical risk in patients undergoing hip arthroplasty for fractures of the proximal femur

Recently the National Patient Safety Agency in the United Kingdom published a report entitled "Mitigating surgical risk in patients undergoing hip arthroplasty for fractures of the proximal femur". A total of 26 deaths had been reported to them when cement was used at hemiarthroplasty between October 2003 and October 2008. This paper considers the evidence for using cement fixation of a hemiarthroplasty in the treatment of hip fractures.

The effect of insertion time on the axial pullout strength of anterior vertebral body screws

Top screw pullout occurs when the screw is under too much axial force to remain secure in the vertebral body. In vitro biomechanical pullout tests are commonly done to find the maximum fixation strength of anterior vertebral body screws. Typically, pullout tests are done instantaneously where the screw is inserted and then pulled out immediately after insertion. However, bone is a viscoelastic material so it shows a time dependent stress and strain response. Because of this property, it was hypothesised that creep occurs in the vertebral trabecular bone due to the stress caused by the screw. The objective of this study was therefore to determine whether the axial pullout strength of anterior vertebral body screws used for scoliosis correction surgery changes with time after insertion. This study found that there is a possible relationship between pullout strength and time; however more testing is required as the sample numbers were quite small. The design of the screw is made with the knowledge of the strength it must obtain. This is important to prevent such occurrences as top screw pullout. If the pullout strength is indeed decreased due to creep, the design of the screw may need to be changed to withstand greater forces.

Simulation of the nutrient supply in fracture healing

The healing process for bone fractures is sensitive to mechanical stability and blood supply at the fracture site. Most currently available mechanobiological algorithms of bone healing are based solely on mechanical stimuli, while the explicit analysis of revascularization and its influences on the healing process have not been thoroughly investigated in the literature. In this paper, revascularization was described by two separate processes: angiogenesis and nutrition supply. The mathematical models for angiogenesis and nutrition supply have been proposed and integrated into an existing fuzzy algorithm of fracture healing. The computational algorithm of fracture healing, consisting of stress analysis, analyses of angiogenesis and nutrient supply, and tissue differentiation, has been tested on and compared with animal experimental results published previously. The simulation results showed that, for a small and medium-sized fracture gap, the nutrient supply is sufficient for bone healing, for a large fracture gap, non-union may be induced either by deficient nutrient supply or inadequate mechanical conditions. The comparisons with experimental results demonstrated that the improved computational algorithm is able to simulate a broad spectrum of fracture healing cases and to predict and explain delayed unions and non-union induced by large gap sizes and different mechanical conditions. The new algorithm will allow the simulation of more realistic clinical fracture healing cases with various fracture gaps and geometries and may be helpful to optimise implants and methods for fracture fixation.