Im Rahmen der Untersuchungen wurde die N-Rhizodeposition verschiedener Futter- und Körnerleguminosen mittels Split-Root-Technik und kontinuierlicher 15N-Anreicherung quantifiziert. Anteilig an der gesamtpflanzlichen N-Menge unterschieden sich die durch Rhizodeposition abgegebenen N-Mengen zwischen den geprüften Leguminosenarten weder im Gewächshaus noch im Feld signifikant voneinander, so dass der Einflussfaktor Pflanzenart und –sorte auf die Höhe der spezifischen N-Rhizodeposition als eher gering einzuschätzen ist. Der Einfluss der Umwelt (Gewächshaus versus Freiland) auf die untersuchten Kenngrößen der Trockenmassen und N-Akkumulationen sowie der N-Rhizodeposition fiel hingegen sehr viel deutlicher aus. Die Untersuchungen zeigten zudem positive Zusammenhänge zwischen den N-Rhizodepositionsmengen und den Trockenmasseerträgen bzw. akkumulierten N-Mengen der Leguminosen.

Studies have shown that significant amounts of nitrate-N is leached beyond root zones of annual crops while small amounts of nitrate-N is leached beyond the root zones of perennial forage grasses. This study investigated short-term ammonium-N persistence and root nitrogen content of annual crop and perennial forage grasses following application of pig manure to a sandy loam soil at Carman, Manitoba. Results showed that ammonium-N in liquid pig manure (LPM) amended treatment peaked four days after manure application (DAM) in perennial cropping system (PCS; 50 - 74 kg ha-1) and annual cropping system (ACS; 18 - 29 kg ha-1) in 2014 and 2015. Ammonium-N persisted up to 7 DAM in LPM amended PCS, but did not persist beyond 4 DAM in LPM amended ACS. Ammonium-N measured in solid pig manure (SPM) amended ACS and PCS was low throughout the sampling days in both years. There was a greater percentage increase in accumulation of nitrate-N at 15 - 30 cm soil depth of LPM and SPM amended ACS than PCS. In both years, dry weight below-ground plant biomass ranged from 5,258 to 9,627 kg ha-1 at 0 - 60 cm depth in PCS while that of ACS ranged from 1,088 to 1,456 kg ha-1. Also, root N content in PCS ranged from 43 to 118 kg N ha-1 in both years while that of ACS ranged from 9 to 20 kg N ha-1. In conclusion, ammonium-N persisted longer in PCS than ACS in the short-term and total plant N was greater in PCS than ACS. Greater total plant N in PCS than ACS was mainly due to its greater root N content rather than above-ground N uptake. The order of magnitude of the difference in root N content (34 to 98 kg N ha-1) between ACS and PCS was sufficient to account for the 20 to 60 kg N/ha of nitrate-N leached in ACS in previous study at the same site. / October 2016

The objective of this study was to compare the time to final set and compressive strength of the white mineral trioxide aggregate (MTA) formulation to the original grey MTA. To test compressive strength, each MTA formulation was placed into Teflon split molds for four hours at 37° Celsius (C) and 100% humidity. Compressive strength of both MTA formulations was measured at 24 hours (n=12) and 21 days (n=19) using an Instron Testing Machine. For determination of time to final set, each MTA formulation (n=6) was placed into a metal mold and maintained at 37° C and 100% humidity while setting. At five-minute time intervals, an indenter needle was lowered onto the surface of the MTA material and allowed to remain in place for five seconds before it was removed from the specimen surface. This process was repeated until the needle failed to make a complete circular indentation in the MTA specimen. Results of a two-way ANOVA indicate that white MTA had a significantly higher compressive strength (mean=32.7 MPa) than grey MTA (mean=25.2 MPa) at 24 hours and no statistically significant differences at 21 days (white mean=38.6 MPa and grey mean=38.0 MPa). Using one-way ANOVA, results indicate that grey MTA had a significantly longer time to final setting time (mean=296 min) compared to white MTA (mean=276 min). Based on this study, the results suggest that white MTA is an effective substitute for grey MTA.

No description available.

Endodontic or root canal treatment is one of the most important dental procedures employed in modern dentistry. Although there have been many results in surgical simulation in the past two decades, little work has been done on endodontics. The objective of this thesis is to explore critical issues for simulating root canal procedures effectively and efficiently, and to develop an interactive virtual environment featured with both visual and haptic feedback to facilitate endodontic training, which opens new roads to the research of root canal simulation and endodontic training. Beyond endodontics, the results of this work can be extended and applied to other kinds of medical simulation and biomechanical modeling, especially the simulations featured with interactions between soft tissue and solid tool objects. / This work covers both theories and methodologies related to the interactive endodontic simulation and validation, including dynamic modeling, visual and haptic display, model validation and statistical learning. We focus on the simulation of the most critical step in the entire endodontic procedure---shaping root canal with endodontic files. There are four major contributions of this thesis. First, we propose a dynamic model to simulate endodontic shaping operations, which is a smoothed particle based dynamic model derived for the pulpal tissue coupled with a finite element model for the endodontic files. This approach effectively characterizes the special properties and constraints associated with both the pulpal tissue and the endodontic files. Second, we implement the derived dynamic model and build up the virtual environment for endodontic simulation with both graphic and haptic interfaces. Third, we design a novel Robotic Endodontic Measurement System to acquire real haptic data of interactions between root canal and endodontic files during endodontic shaping, and propose an experimental validation method to evaluate the performance of derived dynamic model. Finally, we propose a support vector regression model to accurately characterize the input-output haptic mapping for endodontic shaping operation. The optimized parameters of this model can be learned from robotic endodontic measurements with RBF kernel. / Li Min. / "December 2005." / Adviser: Yun-Hui Liu. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6554. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 108-116). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Orientador: Cláudio Antonio Talge Carvalho / Coorientador: Carlos Rocha Gomes Torres / Banca: César Rogério Pucci / Banca: Flávia Goulart da Rosa Cardoso / Resumo: Este estudo analisou a interface de união e a força de adesão dos pinos de fibra de vidro Rebilda Post (RP) (VOCO) e Rebilda Post GT (GT) (VOCO) após cimentação em dentes com Reabsorção Radicular Interna (RRI) simulada. Quarenta e cinco raízes de pré-molares inferiores humanos foram padronizadas em 16 mm e incluídas em resina acrílica. Os canais radiculares (CR) foram preparados biomecanicamente, as raízes foram seccionadas em sua metade e a RRI foi simulada. Os segmentos foram retornados à posição original com auxílio de parafusos. Uma pasta de Ca(OH)2 permaneceu como MIC por 15 dias. A remoção foi feita por PUI e a qualidade da limpeza foi avaliada por estereomicroscopia. Os CR das amostras foram obturados e o preparo foi feito de forma padronizada. Os espécimes foram divididos em 2 grupos (n=20), de acordo com o tipo de pino cimentado. A resistência de união foi avaliada aos níveis cervical e da RRI pelo teste push-out. Para a análise estatística só foram incluídas falhas adesivas e predominantemente adesivas. Os resultados foram submetidos ao teste de Kruskal-Wallis, Mann Whitney e teste de Dunn (α = 0,05). Foi realizada MEV para análise da interface de união entre cimento e dentina radicular (n=1) e análise por microtomografia computadorizada (micro-CT) do pino GT (n=3). PUI não foi capaz de limpar completamente a maioria das RRI (62,5%). Houve alteração da resistência adesiva entre todos os grupos (p <0,05). Os valores de resistência de união para ambos os grupos na reg... (Resumo completo, clicar acesso eletrônico abaixo) / ABSTRACT : This study analyzed the adhesion interface and bond strength of Rebilda Post (RP) (VOCO) and Rebilda Post GT (GT) (VOCO) glass fibers after cementation in teeth with simulated Internal Root Resorption (IRR). Forty-five roots of lower human premolars were standardized at 16 mm and included in acrylic resin.The root canals (RC) were prepared biomechanically, the roots were sectioned and the IRR was simulated.The segments were returned to original position with the aid of screws. A Ca(OH)2 paste remained as MIC for 15 days.The removal was done by PUI and the quality of the cleaning was evaluated by stereomicroscopy. The RC of the samples were filled and the preparation was done in standardized way. The specimens were divided into 2 groups (n=20), according to the type of cemented post. The bond strength was evaluated at the cervical and RRI levels by the push-out test. For the statistical analysis only adhesive and predominantly adhesive failures were included. The results were submitted to Kruskal-Wallis test, Mann Whitney test and Dunn test (α =.05). SEM was used to analyze the bond interface between cement and dentin root (n=1) and Microcomputed tomography (micro-CT) analysis of the GT post (n=3). PUI was not able to clear completely the majority of RRI (62.5%). There was alteration of the adhesive resistance between all groups (p <.05). The values of bond strength for both groups in the cervical region were higher in relation to the groups in the RRI region.The SEM showed formation of resin tags at the bond interface between resin cement and root dentin for both groups. In micro-CT analysis, the presence of bubbles in the cement and spaces in the bond interface between cement are visible. The adhesion of both posts was affected negatively by the level of cementation, post adaptation in the root canal and presence of IRR. Rebilda Post presented better ...(Complete abstract click electronic access below) / Mestre

Root exudates include important chelating compounds and can change the rhizosphere pH by several units. These changes are essential for nutrient uptake and can also alter solubility of soil contaminants and increase plant uptake. Mild root-zone stress may increase exudation and more severe stress can damage membranes and increase root turnover, all of which increase root-zone carbon. Increased carbon from this rhizodeposition can increase microbial activity, which might help degrade contaminants. We studied the effect of three types of stress on root exudation of crested wheatgrass (Agropyron cristatum): low K+, drought, and flooding. These stresses were compared to two types of controls: 100% NO3- and high NH4+:NO3- ratio. We developed an improved axenic system to keep plants microbe-free for 70 days while analyzing exudates for total organic carbon (TOC) and organic acids. Axenic conditions were confirmed by plate counts of the leachate and microscopic observations of the leachate and roots. Optimal conditions for plant growth were maintained by monitoring temperature, light, humidity, water, O2, CO2, nutrient availability, and root-zone pH. Plants were grown in Ottawa sand that was layered by size to optimize water availability. Total organic carbon released over the 70-day growth period in mg per gram dry plant was 2.6 in the control, 2.3 in the NH4+ treatment, 3.7 in the flood and K+ stress treatments, and 4.4 in the drought treatment, which was the only treatment significantly higher than controls (p = 0.05). TOC and organic acid levels in the exudates peaked before the end of the study. The peak TOC levels, expressed as mg TOC per gram new dry plant mass, were 1.9 in the control, 3.0 in the NH4+ treatment, 2.9 in the flood, and 5.8 in the drought and K+ stress treatments. Organic acids were measured by gas chromatography-mass spectrometry (GC-MS). Malic acid was the predominant organic acid, and accounted for the majority of the TOC in the drought treatment. Oxalic, succinic, fumaric, and malonic acids accounted for less than 10% of the TOC. These data indicate that stress may enhance phytoremediation by changing root-zone exudate composition.

<p>I detta 10-poängsarbete går jag igenom hur min egenhändigt producerade kvadratrotsalgoritm fungerar praktiskt och teoretiskt. Med denna algoritm kan man för hand räkna ut kvadratrötter som innehåller 50-60 värdesiffror. Med de tidigare kända algoritmerna för kvadratrötter kan man räkna ut 5-6 värdesiffror. </p><p>Min algoritm fungerar inte på samma sätt som de tidigare använda kvadratrotsalgoritmerna men den är lika korrekt. Stor tyngdvikt i arbetet har därför lagts på att visa på att det finns flera olika korrekta algoritmer för våra vanliga räknesätt. </p><p>Arbetet innehåller också en kort skildring av den pågående debatten huruvida algoritmräkning i grundskolan hämmar elevernas matematiska tänkande eller inte.</p>

I detta 10-poängsarbete går jag igenom hur min egenhändigt producerade kvadratrotsalgoritm fungerar praktiskt och teoretiskt. Med denna algoritm kan man för hand räkna ut kvadratrötter som innehåller 50-60 värdesiffror. Med de tidigare kända algoritmerna för kvadratrötter kan man räkna ut 5-6 värdesiffror. Min algoritm fungerar inte på samma sätt som de tidigare använda kvadratrotsalgoritmerna men den är lika korrekt. Stor tyngdvikt i arbetet har därför lagts på att visa på att det finns flera olika korrekta algoritmer för våra vanliga räknesätt. Arbetet innehåller också en kort skildring av den pågående debatten huruvida algoritmräkning i grundskolan hämmar elevernas matematiska tänkande eller inte.

Phytoremediation systems for petroleum hydrocarbons rely on a synergistic relationship between plants and their root-associated microbial communities. Plants exude organic compounds through their roots, which increase the density, diversity and activity of plant-associated microorganisms, which in turn degrade hydrocarbons. Understanding the mechanisms driving this relationship poses one of the more intriguing challenges in phytoremediation research. This study was designed to address that challenge. Plant-microbe interactions in a weathered-hydrocarbon contaminated soil were examined under controlled growth chamber, and field conditions. In both environments single-species grass treatments initially facilitated greater total petroleum hydrocarbon (TPH) degradation than <i> Medicago sativa </i> (alfalfa), mixed species, or control treatments. In growth chamber studies increased degradation was linked to increased aliphatic-hydrocarbon degrader populations within the rhizosphere. Under field conditions, specific recruitment of endophytic aliphatic-hydrocarbon degraders in response to high TPH levels may have facilitated increased degradation by the grass <i> Elymus angustus</i>(Altai wild rye, AWR). AWR stably maintained these communities during times of local drought, enabling them to act as subsequent source populations for rhizosphere communities. The broad phylogenetic diversity of AWR endophytes, compared to the <i> Pseudomonas</i>-dominated communities of other plants, contributed to the observed stability. The relative composition of exudates released by plants also impacted both degradation activity and potential. Alfalfa released higher concentrations of malonate, which hindered degradation by decreasing metabolic activity and concomitantly inhibiting catabolic plasmid transfer. In contrast, AWR exudates contained high levels of succinate, which was linked to increased catabolic gene expression and plasmid transfer. A reciprocal relationship between exudation patterns and endophytic community structure likely exists, and both parameters have a specific influence on rhizosphere degradation capacity. In this study, grasses were more successful in maintaining the specific balance of all parameters required for the transfer, preservation, and stimulation of hydrocarbon catabolic competency.