1,721,165 research outputs found
An in-vitro study investigating the effect of air-abrasion bioactive glasses on dental adhesion, cytotoxicity and odontogenic gene expression
No full textObjective
To assess the microtensile bond strength (MTBS) and interfacial characteristics of universal adhesives applied on dentine air-abraded using different powders. The analysis includes the cytotoxicity of the powders and their effect on odontogenic gene expression.
Methods
Sound human dentine specimens were air-abraded using bioglass 45S5 (BAG), polycarboxylated zinc-doped bioglass (SEL), alumina (AL) and submitted to SEM analysis. Resin composite was bonded to air-abraded or smear layer-covered dentine (SML) using an experimental (EXP) or a commercial adhesive (ABU) in etch&rinse (ER) or self-etch (SE) modes. Specimens were stored in artificial saliva (AS) and subjected to MTBS testing after 24 h and 10 months. Interfacial nanoleakage assessment was accomplished using confocal microscopy. The cytotoxicity of the powders was assessed, also the total RNA was extracted and the expression of odontogenic genes was evaluated through RT-PCR.
Results
After prolonged AS storage, specimens in the control (SML) and AL groups showed a significant drop in MTBS (p > 0.05), with degradation evident within the bonding interface. Specimens in BAG or SEL air-abraded dentine groups showed no significant difference, with resin-dentine interfaces devoid of important degradation. The metabolic activity of pulp stem cells was not affected by the tested powders. SEL and BAG had no effect on the expression of odontoblast differentiation markers. However, AL particles interfered with the expression of the odontogenic markers.
Significance
The use of bioactive glass air-abrasion may prevent severe degradation at the resin-dentine interface. Unlike alumina, bioactive glasses do not interfere with the normal metabolic activity of pulp stem cells and their differentiation to odontoblasts
From 'ICDAS' to 'cariescare international': the 20-year journey building international consensus to take caries evidence into clinical practice
No full textEste documento traza el viaje de colaboración de 20 años realizado por equipos internacionales de investigadores, educadores y profesionales de la odontología. Tras el desarrollo inicial del Sistema Internacional de Evaluación y Detección de Caries (ICDAS) en 2002, el Sistema Internacional de Clasificación y Manejo de Caries (ICCMS) se desarrolló en colaboración entre 2010-2017 con varias organizaciones de investigación y práctica dental, e influenciado por la mejor evidencia juzgada a través de Metodología SIGN, el Tratado de Minamata del PNUMA (y la eliminación progresiva de las amalgamas dentales vinculadas), tres laboratorios de políticas dentales y un movimiento internacional en odontología operativa para avanzar hacia la odontología mínimamente invasiva. La Federación Dental Mundial de la FDI publicitó y abogó por el ICCMS en 2019, cuando se publicó la Guía de consenso 'CariesCare International' y el sistema de manejo de caries 4D para ayudar a poner en práctica el ICCMS. Este sistema, que está diseñado para ayudar a los médicos a brindar una atención óptima de la caries a los pacientes, ahora se está adaptando internacionalmente para su uso pospandémico en el estudio 'Caries OUT'. También se está utilizando como un vehículo para implementar la actualización Brindar una mejor guía de salud oral sobre la caries, como parte del marco de atención médica oral de intervención mínima en el Reino Unido.This paper charts the 20-year collaborative journey made by international teams of dental researchers, educators and practitioners. Following the initial development of the International Caries Detection and Assessment System (ICDAS) in 2002, the International Caries Classification and Management System (ICCMS) was collaboratively developed between 2010-2017 with several dental research and practice organisations, and influenced by best evidence judged via SIGN methodology, the UNEP Minamata Treaty (and linked phasing down of dental amalgam), three Dental Policy Labs and an international movement in operative dentistry to move towards minimally invasive dentistry. The FDI World Dental Federation publicised and advocated the ICCMS in 2019, when the 'CariesCare International' Consensus Guide and 4D caries management system was published to aid the delivery of ICCMS into practice. This system, which is designed to help practitioners deliver optimal caries care for patients, is now being adapted internationally for post-pandemic use in the 'Caries OUT' study. It is also being used as a vehicle for implementing the updated Delivering better oral health guidance on caries, as part of the minimum intervention oral healthcare delivery framework in the UK
Analysis of an inventory system with product perishability and substitution: a simulation-optimization approach
Full text linkThis thesis focuses on some inventory management policies for substitutable and perishable items under demand uncertainty. A set of perishable products with fixed shelf lives is considered under an (R,Si) system of inventory control where demand for a preferred product can be satisfied by a substitute product with a known probability, in the event of a stockout of the preferred product. While taking demand substitution and product expiration into account, the retailer is faced with the decision of determining the order-up-to level, Si, for each product i which maximizes expected total profit, given a common review period, R, determined exogenously.Under demand uncertainty, the problem detailed in this thesis involves stochastic optimization. An exact closed form expression, however, for expected profits becomes difficult for certain parameter values involving product shelf-life, product substitution, and lead time. As an alternative approach, order replenishment, demand consumption, substitution, and product expiration can be effectively modeled using discrete-event simulation. Through a discrete-event simulation model, each realization of the profit function can be evaluated for a selected value of Si, and a mean profit value can be estimated after a number of replications of a simulation run. In order to find the best Si solution, the technique of simulation-optimization is used.This thesis also examines the impact of key parameters such as substitution characteristics, shelf-life, cost structure, lead time, and number of products on the choice of inventory issuing policy on both the optimal Si levels and corresponding mean profit values. Through a factorial experimental design, the effects of these parameters on system performance are analyzed. In addition, heuristics are proposed and tested in order to provide managers with a convenient set of rules for determining near-optimal Si values in practice.Ph.D., Decision Sciences -- Drexel University, 200
A two-location lateral transshipment problem with customer switching
No full textLateral transshipments in multi-echelon stochastic inventory systems imply that locations at the same echelon of a supply chain share inventories in some way, in order to deal with local uncertainties in demands. While the structure of a transshipment policy will depend on many important factors, a commonly observed phenomenon at the retail level, called “customer switching”, may be of some significance. Under such a phenomenon, a customer, who cannot obtain a desired product at a specific location, may visit one or more other retail locations in search of the item. We consider the inventory replenishment and transshipment decisions in the presence of such stochastic “customer switching” behavior, for two firms which are either under centralized control, or operate independently.The first model adopted in this study considers two retailers that sell the same product to retail customers. After demand is realized, transshipments occur if only one location has insufficient inventory. Under this circumstance, a random fraction of the unfulfilled demand from the stocked out firm (which we refer to as the “shortage firm”) may switch to the other firm with surplus inventory (which we refer to as the “surplus firm”). We examine the impact of such customer switching behavior on the firms’ inventory decisions. We identify situations when the firm with surplus inventory is willing to (1) transship the entire quantity requested (“complete pooling policy”), (2) transship a portion of the amount requested (“inventory keeping policy”), or (3) transship nothing (“no-shipping policy”) to the shortage firm. We demonstrate that a unique pair of optimal order quantities exist if the two firms are centeredly coordinated. When the firms operate independently, we derive a sufficient condition for the existence of a unique equilibrium replenishment order quantity pair.We also explore the optimal shortage or excess reporting policy when inventory information is asymmetric. Since the firm with a surplus makes a transshipment decision based on the magnitude of the shortage at the other location, it is possible that the shortage firm reports to the surplus firm some desired shortage quantity, instead of the real shortage. We prove that there is a possibility that the underreporting situation exists.Ph.D., Business Administration -- Drexel University, 201
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Hierarchical decision making with supply chain applications
Full text linkHierarchical decision making is a decision system, where multiple decision makers are involved and the process has a structure on the order of levels. It gains interest not only from a theoretical point of view but also from real practice. Its wide applications in supply chain management are the main focus of this dissertation.The first part of the work discusses an application of continuous bilevel programming in a remanufacturing system. Under intense competitive pressures to lower production costs, coupled with increasing environmental concerns, used products can often be collected via customer returns to retailers in supply chains and remanufactured by producers, in orderto bring them back into “as-new” condition for resale. In this part, hierarchical models are developed to determine optimal decisions involving inventory replenishment, retail pricingand collection price for returns. Based on the simplified assumption of a single manufacturer and a single retailer dealing with a single recoverable item under deterministic conditions,all of these decisions are examined in an integrated manner. Models depicting decentralized, as well as centralized policies are explored. Analytical results are derived and detailed sensitivity analysis is performed via an extensive set of numerical computations.In the second part of this dissertation, a discrete bilevel problem is illustrated by investigating a biofuel production problem. The issues of governmental incentives, industry decisions of price, and farm management of land are incorporated. While fixed costs are natural components of decision making in operations management, such discrete phenomena have not received sufficient research attention in the current literature on bilevel programming, due to a variety of theoretical and algorithmic difficulties. When such costs are taken into account, it is not easy to derive optimality conditions and explore convergence properties due to discontinuities and the combinatorial nature of this problem, which is NP-hard. In order to solve this problem, a derivative-free search technique is used to arrive at a solution to this bilevel problem. A new heuristic methodology is developed, which integrates sensitivity analysis and warm-starts to improve the efficiency of the algorithm.Ph.D., Decision Sciences -- Drexel University, 201
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