970 resultados para root-end filling material


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Upward long-distance mobile silencing has been shown to be phloem mediated in several different solanaceous species. We show that the Arabidopsis (Arabidopsis thaliana) seedling grafting system and a counterpart inducible system generate upwardly spreading long-distance silencing that travels not in the phloem but by template-dependent reiterated short-distance cell-to-cell spread through the cells of the central stele. Examining the movement of the silencing front revealed a largely unrecognized zone of tissue, below the apical meristem, that is resistant to the silencing signal and that may provide a gating or protective barrier against small RNA signals. Using a range of auxin and actin transport inhibitors revealed that, in this zone, alteration of vesicular transport together with cytoskeleton dynamics prevented or retarded the spread of the silencing signal. This suggests that small RNAs are transported from cell to cell via plasmodesmata rather than diffusing from their source in the phloem.

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Building distributed leadership for effective supervision of creative practice higher research degrees is an Office for Learning and Teaching (OLT) funded project, conducted in partnership between Queensland University of Technology, The University of Melbourne, Auckland University of Technology, University of New South Wales and University of Western Sydney. The project was initiated to develop a cooperative approach to establishing an understanding of the contextual frameworks of the emergent field of creative practice higher degrees by research (HDRs); capturing early insights of administrators and supervisors; gathering exemplars of good practices; and establishing an in-common understanding of effective approaches to supervision. To this end, the project has produced: • A literature review, to provide a research foundation for creative practice higher research degree supervision (Chapter 3). • A contextual review of disciplinary frameworks for HDR programs, produced through surveys of postgraduate research administrators (Section 4.1), and an analysis of institutional materials and academic development programs for supervisors (Section 4.2). • A National Symposium, Effective Supervision of Creative Arts Research Degrees (ESCARD), at QUT in Brisbane in February 2013, with 62 delegates from 20 Australasian Universities, at which project findings were disseminated, and delegates presented case studies and position papers, and participated in discussions on key issues for supervisors (Appendix 1). • Resources, including a booklet for supervisors: 12 Principles for the Effective Supervision of Creative Practice Higher Research Degrees, which encapsulates attitudes, insights and good practices of experienced and new supervisors. It was produced through a content analysis of interviews with twenty-five supervisors in creative disciplines (visual and performing arts, music, new media, creative writing and design) (Printed booklet, PDF, Appendix 3). • A project website to disseminate project outcomes , which holds project findings, relevant references, and a repository of case studies and position papers by supervisors and program administrators. • A call for papers for a special issue ‘Supervising Practice: Perspectives on the Supervision of Creative Practice Research Higher Degrees’ of ACCESS Journal: Critical Perspectives on Communication, Cultural & Policy Studies (ERA ranked A quality) in 2014 (Appendix 2). • A community of supervisory practice initiated through project partnerships, a national symposium where supervisors from across Australasia met in dialogue for the first time, resource sharing, and joint publishing opportunities. • A set of recommendations for supervision capacity building and academic development, produced through the triangulation of literature and contextual reviews, analysis of institutional frameworks, interviews with supervisors and national dialogues. It is anticipated that the project’s outcomes will support experienced and new supervisors in this emergent field, and so benefit HDR students, and will enable creative disciplines to build supervision capacity, and so to accommodate growth in postgraduate enrolments. Funded as a pilot project, the project set out to establish a robust research base to provide a foundation for future work involving sharing good practices, resource building, and designing effective approaches to academic development for supervisors. Recommendations that were produced out of this project include the need to extend beyond generic, formal training for supervisors to academic development that harnesses and extends distributed leadership; focuses on local, disciplinary contexts; has a strong emphasis on case studies; provides diverse resources; and facilitates dialogue between supervisors. Recommendations also include developing frameworks for mentoring new supervisors and building a national network to facilitate cross-institutional discourse, disseminate good practices, and share insights into the management of risk factors, ethical issues, and preparing candidates for examination. As a pilot investigation, the outcomes of this project lay the ground for this future work.

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A major challenge for robot localization and mapping systems is maintaining reliable operation in a changing environment. Vision-based systems in particular are susceptible to changes in illumination and weather, and the same location at another time of day may appear radically different to a system using a feature-based visual localization system. One approach for mapping changing environments is to create and maintain maps that contain multiple representations of each physical location in a topological framework or manifold. However, this requires the system to be able to correctly link two or more appearance representations to the same spatial location, even though the representations may appear quite dissimilar. This paper proposes a method of linking visual representations from the same location without requiring a visual match, thereby allowing vision-based localization systems to create multiple appearance representations of physical locations. The most likely position on the robot path is determined using particle filter methods based on dead reckoning data and recent visual loop closures. In order to avoid erroneous loop closures, the odometry-based inferences are only accepted when the inferred path's end point is confirmed as correct by the visual matching system. Algorithm performance is demonstrated using an indoor robot dataset and a large outdoor camera dataset.

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For industrial wireless sensor networks, maintaining the routing path for a high packet delivery ratio is one of the key objectives in network operations. It is important to both provide the high data delivery rate at the sink node and guarantee a timely delivery of the data packet at the sink node. Most proactive routing protocols for sensor networks are based on simple periodic updates to distribute the routing information. A faulty link causes packet loss and retransmission at the source until periodic route update packets are issued and the link has been identified as broken. We propose a new proactive route maintenance process where periodic update is backed-up with a secondary layer of local updates repeating with shorter periods for timely discovery of broken links. Proposed route maintenance scheme improves reliability of the network by decreasing the packet loss due to delayed identification of broken links. We show by simulation that proposed mechanism behaves better than the existing popular routing protocols (AODV, AOMDV and DSDV) in terms of end-to-end delay, routing overhead, packet reception ratio.

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Fire incident in buildings is common, so the fire safety design of the framed structure is imperative, especially for the unprotected or partly protected bare steel frames. However, software for structural fire analysis is not widely available. As a result, the performance-based structural fire design is urged on the basis of using user-friendly and conventional nonlinear computer analysis programs so that engineers do not need to acquire new structural analysis software for structural fire analysis and design. The tool is desired to have the capacity of simulating the different fire scenarios and associated detrimental effects efficiently, which includes second-order P-D and P-d effects and material yielding. Also the nonlinear behaviour of large-scale structure becomes complicated when under fire, and thus its simulation relies on an efficient and effective numerical analysis to cope with intricate nonlinear effects due to fire. To this end, the present fire study utilizes a second order elastic/plastic analysis software NIDA to predict structural behaviour of bare steel framed structures at elevated temperatures. This fire study considers thermal expansion and material degradation due to heating. Degradation of material strength with increasing temperature is included by a set of temperature-stress-strain curves according to BS5950 Part 8 mainly, which implicitly allows for creep deformation. This finite element stiffness formulation of beam-column elements is derived from the fifth-order PEP element which facilitates the computer modeling by one member per element. The Newton-Raphson method is used in the nonlinear solution procedure in order to trace the nonlinear equilibrium path at specified elevated temperatures. Several numerical and experimental verifications of framed structures are presented and compared against solutions in literature. The proposed method permits engineers to adopt the performance-based structural fire analysis and design using typical second-order nonlinear structural analysis software.

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Material yielding is typically modeled either by plastic zone or plastic hinge methods under the context of geometric and material nonlinear finite element methods. In fire analysis of steel structures, the plastic zone method is widely used, but it requires extensively more computational efforts. The objective of this paper is to develop the nonlinear material model allowing for interaction of both axial force and bending moment, which relies on the plastic hinge method to achieve numerical efficiency and reduce computational effort. The biggest advantage of the plastic-hinge approach is its computational efficiency and easy verification by the design code formulae of the axial force–moment interaction yield criterion for beam–column members. Further, the method is reliable and robust when used in analysis of practical and large structures. In order to allow for the effect of catenary action, axial thermal expansion is considered in the axial restraint equations. The yield function for material yielding incorporated in the stiffness formulation, which allows for both axial force and bending moment effects, is more accurate and rational to predict the behaviour of the frames under fire. In the present fire analysis, the mechanical properties at elevated temperatures follow mainly the Eurocode 3 [Design of steel structures, Part 1.2: Structural fire design. European Committee for Standisation; 2003]. Example of a tension member at a steady state heating condition is modeled to verify the proposed spring formulation and to compare with results by others. The behaviour of a heated member in a highly redundant structure is also studied by the present approach.

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This paper emphasizes material nonlinear effects on composite beams with recourse to the plastic hinge method. Numerous combinations of steel and concrete sections form arbitrary composite sections. Secondly, the material properties of composite beams vary remarkably across its section from ductile steel to brittle concrete. Thirdly, concrete is weak in tension, so composite section changes are dependent on load distribution. To this end, the plastic zone approach is convenient for inelastic analysis of composite sections that can evaluate member resistance, including material nonlinearities, by routine numerical integration with respect to every fiber across the composite section. As a result, many researchers usually adopt the plastic zone approach for numerical inelastic analyses of composite structures. On the other hand, the plastic hinge method describes nonlinear material behaviour of an overall composite section integrally. Consequently, proper section properties for use in plastic hinge spring stiffness are required to represent the material behaviour across the arbitrary whole composite section. In view of numerical efficiency and convergence, the plastic hinge method is superior to the plastic zone method. Therefore, based on the plastic hinge approach, how to incorporate the material nonlinearities of the arbitrary composite section into the plastic hinge stiffness formulation becomes a prime objective of the present paper. The partial shear connection in this paper is by virtue of the effective flexural rigidity as AISC 1993 [American Institute of Steel Construction (AISC). Load and resistance factor design specifications. 2nd ed., Chicago; 1993]. Nonlinear behaviour of different kinds of composite beam is investigated in this paper, including two simply supported composite beams, a cantilever and a two span continuous composite beam.

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This paper explores how the amalgamated wisdom of East and West can instigate a wisdombased renaissance of humanistic epistemology (Rooney & McKenna, 2005) to provide a platform of harmony in managing knowledge-worker productivity, one of the biggest management challenges of the 21st century (Drucker, 1999). The paper invites further discussions from the social and business research communities on the significance of "interpretation realism" technique in comprehending philosophies of Lao Tzu Confucius and Sun Tzu (Lao/Confucius/Sun] written in "Classical Chinese." This paper concludes with a call to build prudent, responsible practices in management which affects the daily lives of many (Rooney & McKenna, 2005) in today's knowledgebased economy. Interpretation Realism will be applied to an analysis of three Chinese classics of Lao/Confucius/Sun which have been embodied in the Chinese culture for over 2,500 years. Comprehending Lao/Confucius/Sun's philosophies is the first step towards understanding Classical Chinese culture. However, interpreting Chinese subtlety in language and the yin and yang circular synthesis in their mode of thinking is very different to understanding Western thought with its open communication and its linear, analytical pattern of Aristotelian/Platonic wisdom (Zuo, 2012). Furthermore, Eastern ways of communication are relatively indirect and mediatory in culture. Western ways of communication are relatively direct and litigious in culture (Goh, 2002). Furthermore, Lao/Confucius/Sun's philosophies are difficult to comprehend as there are four written Chinese formats and over 250 dialects: Pre-classical Chinese Classical Chinese Literary Chinese and modern Vernacular Chinese Because Classical Chinese is poetic, comprehension requires a mixed approach of interpretation realism combining logical reasoning behind "word splitting word occurrences", "empathetic metaphor" and "poetic appreciation of word.

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Most research virtually ignores the important role of a blood clot in supporting bone healing. In this study, we investigated the effects of surface functional groups carboxyl and alkyl on whole blood coagulation, complement activation and blood clot formation. We synthesised and tested a series of materials with different ratios of carboxyl (–COOH) and alkyl (–CH3, –CH2CH3 and –(CH2)3CH3) groups. We found that surfaces with –COOH/–(CH2)3CH3 induced a faster coagulation activation than those with –COOH/– CH3 and –CH2CH3, regardless of the –COOH ratios. An increase in –COOH ratios on –COOH/–CH3 and –CH2CH3 surfaces decreased the rate of coagulation activation. The pattern of complement activation was entirely similar to that of surface-induced coagulation. All material coated surfaces resulted in clots with thicker fibrin in a denser network at the clot/material interface and a significantly slower initial fibrinolysis when compared to uncoated glass surfaces. The amounts of platelet-derived growth factor-AB (PDGF-AB) and transforming growth factor-b (TGF-b1) released from an intact clot were higher than a lysed clot. The release of PDGF-AB was found to be correlated with the fibrin density. This study demonstrated that surface chemistry can significantly influence the activation of blood coagulation and complement system, resultant clot structure, susceptibility to fibrinolysis as well as release of growth factors, which are important factors determining the bone healing process.

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This paper presents the response of pile foundations to ground shocks induced by surface explosion using fully coupled and non-linear dynamic computer simulation techniques together with different material models for the explosive, air, soil and pile. It uses the Arbitrary Lagrange Euler coupling formulation with proper state material parameters and equations. Blast wave propagation in soil, horizontal pile deformation and pile damage are presented to facilitate failure evaluation of piles. Effects of end restraint of pile head and the number and spacing of piles within a group on their blast response and potential failure are investigated. The techniques developed and applied in this paper and its findings provide valuable information on the blast response and failure evaluation of piles and will provide guidance in their future analysis and design.