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- Athanassiadis, Tuija, 1971-, et al.
(författare)
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Identification of c-Fos immunoreactive brainstem neurons activated during fictive mastication in the rabbit
- 2005
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 165:4, s. 478-489
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Tidskriftsartikel (refereegranskat)abstract
- In the present study we used the expression of the c-Fos-like protein as a "functional marker" to map populations of brainstem neurons involved in the generation of mastication. Experiments were conducted on urethane-anesthetized and paralyzed rabbits. In five animals (experimental group), rhythmical bouts of fictive masticatory-like motoneuron activity (cumulative duration 60-130 min) were induced by electrical stimulation of the left cortical "masticatory area" and recorded from the right digastric motoneuron pool. A control group of five animals (non-masticatory) were treated in the same way as the experimental animals with regard to surgical procedures, anesthesia, paralysis, and survival time. To detect the c-Fos-like protein, the animals were perfused, and the brainstems were cryosectioned and processed immunocytochemically. In the experimental group, the number of c-Fos-like immunoreactive neurons increased significantly in several brainstem areas. In rostral and lateral areas, increments occurred bilaterally in the borderzones surrounding the trigeminal motor nucleus (Regio h); the rostrodorsomedial half of the trigeminal main sensory nucleus; subnucleus oralis-gamma of the spinal trigeminal tract; nuclei reticularis parvocellularis pars alpha and nucleus reticularis pontis caudalis (RPc) pars alpha. Further caudally-enhanced labeling occurred bilaterally in nucleus reticularis parvocellularis and nucleus reticularis gigantocellularis (Rgc) including its pars-alpha. Our results provide a detailed anatomical record of neuronal populations that are correlated with the generation of the masticatory motor behavior.
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- Athanassiadis, Tuija, 1971-, et al.
(författare)
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Physiological characterization, localization and synaptic inputs of bursting and nonbursting neurons in the trigeminal principal sensory nucleus of the rat
- 2005
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 22:12, s. 3099-3110
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Tidskriftsartikel (refereegranskat)abstract
- A population of neurons in the trigeminal principal sensory nucleus (NVsnpr) fire rhythmically during fictive mastication induced in the in vivo rabbit. To elucidate whether these neurons form part of the central pattern generator (CPG) for mastication, we performed intracellular recordings in brainstem slices taken from young rats. Two cell types were defined, nonbursting (63%) and bursting (37%). In response to membrane depolarization, bursting cells, which dominated in the dorsal part of the NVsnpr, fired an initial burst followed by single spikes or recurring bursts. Non-bursting neurons, scattered throughout the nucleus, fired single action potentials. Microstimulation applied to the trigeminal motor nucleus (NVmt), the reticular border zone surrounding the NVmt, the parvocellular reticular formation or the nucleus reticularis pontis caudalis (NPontc) elicited a postsynaptic potential in 81% of the neurons tested for synaptic inputs. Responses obtained were predominately excitatory and sensitive to glutamatergic antagonists DNQX and/or APV. Some inhibitory and biphasic responses were also evoked. Bicuculline methiodide or strychnine blocked the IPSPs indicating that they were mediated by GABA(A) or glycinergic receptors. About one-third of the stimulations activated both types of neurons antidromically, mostly from the masseteric motoneuron pool of NVmt and dorsal part of NPontc. In conclusion, our new findings show that some neurons in the dorsal NVsnpr display both firing properties and axonal connections which support the hypothesis that they may participate in masticatory pattern generation. Thus, the present data provide an extended basis for further studies on the organization of the masticatory CPG network.
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- Olsson, Karl-Gunnar, 1955
(författare)
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Strukturmekanik & arkitektur Om strukturmekanisk förståelse i gestaltningsprocessen
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organizing material to produce space and a load-carrying structure are central tasks in the architectural design process. In trying out and examining design ideas, use of language and tools appropriate to the purpose is fundamental.The thesis begins with reflections on the different processes that utilize knowledge of structural mechanics, how that subject is commonly presented,and how the presentation of it is affected by various tacit aims. There are two main tasks of the structural engineer: description and analysis of structural behaviour through mathematical modelling, and evaluation of safety and reliability as expressed in design codes. These tasks are comparedwith those of the architect in developing load-carrying structures that interact in a logical and meaningful way with spatial functions and with the needs and aims of architectural expression.The thesis, which takes as its point of departure Structural Mechanical traditions, considers concepts and approaches that help provide a better qualitative understanding of compound and complex structural behaviour. Alongside the concept of equilibrium, that of stiffness is examined as a means of achieving structural mechanical understanding.A new design conception, that of canonical stiffness, is proposed as a means of gaining insight into the static behaviour of structures, allowing patterns (modes) of deformation for which a structure is weak to be determinedon the basis of the stiffness of its various parts. From these patterns, the static load cases that produce the largest deformations of the structure can also be determined. Computational tools are proposed that can support a dialog between the architect and the engineer at early stages of the design process. Three computer codes ForcePAD, pointSketch and CALFEM are presented and discussed as examples of proposals initiated and/or developed within the spirit of the thesis.
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- Thelin, Carl, 1974, et al.
(författare)
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Horizontal support of historic roof structures: Design and structural efficiency
- 2008
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Ingår i: Journal of Architectural Engineering. - 1076-0431. ; 14:1, s. 18-24
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Tidskriftsartikel (refereegranskat)abstract
- In historic buildings, a variety of different types of timber roof structures reflecting different building traditions and different ideals for the inner space are found. In Sweden, damage to historic roof structures due to a lack of support for horizontal thrust is common. Knowledge of the relation between structurally efficient horizontal support and the extension of a structure in space is essential for obtaining an adequate understanding of the development of building techniques and for making sound decisions concerning restoration. An approach that involves a classification of horizontal supporting structures, together with a mechanical model that defines and distinguishes between inner and outer support, is introduced, with the aim of offering a tool for comparison of different roof-truss designs with focus on the occupation in space. Comparison of the efficiency of different designs is carried out by comparing horizontal stiffness. Eleven different designs divided into four spatial groups have been analyzed. © 2008 ASCE.
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- Thelin, Carl, 1974, et al.
(författare)
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Investigating causes of damages to historical timber structures by use of FEM
- 2005
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Ingår i: Structural analysis of historical constructions: possiblities of numerical and experimental techniques / edited by Claudio Modena, Paulo B. Lourenco, Pere Roca. - 0415363799 ; 2, s. 1429-
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Konferensbidrag (refereegranskat)abstract
- Historical timber structures are often complex, their static behaviour being difficult to grasp. Such structures are usually statically indeterminate. To determine how a statically indeterminate structure carries the load it supports, the stiffness of its separate parts needs to be taken into account. Knowledge of the static behaviour and of the factors that influence it is important when investigating the causes of damages. The damage analyses suggested involve several steps. First, a thorough investigation of the structure is needed, aimed at collecting the basic facts required for obtaining sufficient background information for creating the computational model. The next step is to create a computational model based on the Finite Elements Method. Having access to an appropriate computational model allows possible causes of damages to readily be simu-lated. The roof structure of the medieval Swedish castle of Glimmingehus was selected as an example of how such an analysis can be performed.
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- Thelin, Carl, 1974, et al.
(författare)
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Static Behaviour of a Historic Roof Structure
- 2005
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Ingår i: Journal of Architectural Engineering. - 1076-0431. ; 11:2, s. 39-49
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Tidskriftsartikel (refereegranskat)abstract
- Historic roof structures of large monumental buildings are often complex with static behavior that is difficult to grasp. Yet, understanding their static behavior is necessary to adequately preserve and maintain them. The aim of this paper is twofold. The more general aim is to develop use of the finite element method in combination with visualization and to demonstrate its potential both for providing an understanding of historic structures and their static behavior and for supporting a dialogue regarding these matters. The more specific aim is to examine the static behavior of one particular roof structure and the damages to it that occurred. The roof structure selected was that of the medieval Swedish castle of Glimmingehus. A detailed computational model of the roof truss was developed, in terms of which a set of possible causes of the damages observed was simulated. Reliable causes were found and three-dimensional visualizations were carried out to demonstrate their respective influence on the overall structural behavior. As expected, use of visualization in the analysis was found to be very helpful for interpreting the relationship between the computational model and the computed results.
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