Emerging insights into the genesis of cerebral ischaemia and stroke

Stroke is a global problem with increasing significance because of the ageing population. Except for age, hypertensionisbyfar themostimportantriskfactorfor stroke. Hypertensionpredisposes toanumberof intracerebral and extracerebral vascular lesions which may cause cerebrovascular events by different mechanisms. The high metabolic need and low energy reserve make the braiavery vulnerable to ischaemia. During the last decade a number of experimental studies - supported by PET studies in man - suggest the presence of a therapeutic window, i.e. the time during which the neurons can be saved. The penumbra is the zone surrounding the core of the infarct where the flow is decreased and the neurons are lethargic and may be electrically silent but still viable. The presumed role of calcium, excitatory amino acids, free radicals, platelet-activating factor, acidosis and brain temperature in the process of neuronal death is briefly reviewed.peer-reviewe

Labour Supply Effects of a Subsidised Old-Age Part-Time Scheme in Austria

In this paper we evaluate the impact of the old-age part-time scheme (OAPT) on the Austrian labour market which was a policy to allow flexible retirement options for the elderly with an aim to increase labour supply. According to our matching estimates employment probability increases slightly, especially in the first two years after entrance into the programme. Furthermore, the programme seems to reduce the measured unemployment risk. However, the total number of hours worked is significantly reduced by OAPT. While the policy is meant to reduce early exit from the labour force by allowing part-time work, our analysis indicates that most workers substitute part-time work for full-time work and thus the overall effect is rather negative.evaluation of labour market programmes, labour supply of the elderly, nearest neighbour matching

Malignant infarction in cats following prolonged middle cerebral artery occlusion : volumes of severe blood flow reduction predict fatal outcome

Severity and duration of cerebral blood flow (CBF) reduction are main determinants of injury in core and penumbra zones of focal brain ischemia. To study the putative role and predictive significance of the volume of these zones for induction of a malignant course due to edema formation in large hemispheric stroke, we examined reduction of CBF and oxygen metabolism (CMRO2) by sequential positron emission tomography (PET) in a transient ischemia model in cats that is susceptible to secondary deterioration after reperfusion.peer-reviewe

No secondary elevation of extracellular adenosine in malignant edema formation following transient MCA occlusion

Malignant edema is a relevant, serious complication in various clinical situations including large hemispheric stroke. To date, the roles of purine catabolites and amino acids in the course of malignant edema formation remain obscure. We examined the correlation between secondary perfusional disturbance and elevation of extracellular purine catabolites and amino acids in a transient focal ischemia model in cats that is prone to develop malignant edema and thereby secondary ischemia during reperfusionpeer-reviewe

Glutamate and purine catabolites in relation to free radical production during focal ischemia-reperfusion : an in vivo study in cats

The in-vivo interrelation between excitotoxicity and oxidative stress following cerebral ischemia in cats was investigated. To elucidate the role of this mechanism in cerebral ischemia, the study presented herein sought to investigate the spatial and temporal features of the free radical response to elevations of glutamate and purine catabolites in a reproducible model of in vivo focal ischemia/reperfusion. The time course of neurochemical and Reactive Oxygen Species (ROS) were simultaneously conducted in ischemic focus and perifocal region of the brain.peer-reviewe

Extracellular glutamate accumulates only in final, ischemic stage of progressive epidural mass lesion in cats

Epidural mass lesions may cause ischemia due to progressive intracranial hypertension. In order to 1) investigate the impact of intracranial pressure (ICP) on accumulation of neuroactive substances, and 2) test the significance of neurochemical monitoring for early prediction of fatal outcome, we gradually raised ICP in cats by inflation of an epidural balloon: We assessed extracellular substrate alterations in the contralateral cortex in relation to changes of ICP, cerebral perfusion pressure (CPP) and mean arterial blood pressure (MABP). In a complementary experiment, regional cerebral blood flow was assessed by sequential positron emission tomography (PET).peer-reviewe

Stratigraphie und Morphogenese von frühpleistozänen Ablagerungen zwischen Bodensee und Klettgau

Anhand von Feldaufnahmen, sedimentpetrographischen Untersuchungen sowie einer systematischen Auswertung von Literaturangaben und Bohraufnahmen wurde eine Neubearbeitung von Stratigrafie und Paläogeografie der Deckenschotter des Bodensee-Rheingletschersystems im Raum zwischen Bodensee und Schaffhausen sowie im Klettgau vorgenommen. Es konnten drei morphostratigraphischen Einheiten unterschieden werden: (a) Höhere Deckenschotter, (b) Tiefere Deckenschotter sowie (c) Tiefere Deckenschotter, unteres Niveau. Die Höheren Deckenschotter können lithostratigrafisch nicht weiter gegliedert werden. Die Tieferen Deckenschotter umfassen Ablagerungen aus mindestens zwei kaltzeitlichen Sedimentationsphasen. Es gibt Hinweise, dass zwischen den Sedimentationsphasen temperierte Verhältnisse herrschten. Die jüngste Einheit, „Tieferen Deckenschotter, unteres Niveau“, entstand nach einer markanten erosiven Umgestaltung des regionalen Entwässerungsnetzes, in einer einzigen Phase. Eine Analyse der tektonischen Verhältnisse im Untersuchungsgebiet ergab, dass die Höhenlagen der einzelnen Deckenschottervorkommen keine wesentlichen Verfälschungen durch neotektonische Vorgänge aufweisen. Einzig die östlich der Immensee-Verwerfung gelegenen Vorkommen im Hegau könnten eine relative tektonische Verstellung erfahren haben, da sie im Vergleich zu den talwärtigen Korrelaten topographisch ungewöhnlich hoch liegen. Die vorgeschlagene morphostratigraphische Gliederung wird dadurch jedoch nicht in Frage gestellt. Die Kontrolle des Vorflutniveaus und damit der morphogenetischen Entwicklung des Untersuchungsgebietes erfolgte dominant durch tektonische Vorgänge im Oberrheingrabensystem (Absenkung). Dies gilt auch für die Deckenschotter der zentralen Nordschweiz, weshalb die morphostratigraphischen Einheiten dieser beiden Gebiete miteinander korreliert werden können, wenngleich die Zahl der unterscheidbaren lithostratigraphischen Einheiten nicht übereinstimmt. Für die Höheren Deckenschotter kann das entweder auf eine unvollständige Überlieferung im Untersuchungsgebiet bzw. eine mangelnde Datendichte zurückzuführen sein; es könnte aber auch darauf hindeuten, dass die Verbindung Bodensee–Oberrheingraben später als die Verbindung Walenseetal–Oberrheingraben installiert wurde. Eine Korrelation mit den auf das Donau-System ausgerichteten frühpleistozänen Ablagerungen des süddeutschen Alpenvorlandes ist anhand von morpho- und lithostratigraphischen Kriterien allein nicht möglich.researc

Process Stabilization at welding Copper by Laser Power Modulation

AbstractDue to their material properties such as high electrical and thermal conductivity, copper materials are more and more demanded for industrial applications. The same material properties make laser welding of copper a challenging task. Laser welds often suffer from defective weld seams with ejections, pores and a large fluctuation in the penetration depth. In this paper the influence of laser power modulation during copper welding on weld imperfections is discussed. It is shown that a sinusoidal power modulation leads to a strong reduction of melt ejections and also to an increase in penetration depth

Identification, simulation and optimal control of heat transfer in cooling line of hot strip rolling mill

The numerical simulation of mechanical properties of hot-rolled products has a major significance for material characterisation as well as material development. The basis for these is the knowledge about the material-specific phase transformations in combination with the initial microstructure from the deformation steps before entering into the cooling line. Additionally, the technological conditions in the run-out table (ROT) are essentially for transformation kinetics. In order to simulate these processes, the plant-specific heat transfer coefficient must be measured. Therefore, steel samples with thermocouples inside are transported with defined velocities through the cooling line of the continuous pilot plant at the Institute of Metal Forming in Freiberg. Furthermore, the material and its movement must be taken into account as characteristics of the ROT (e.g. amount and distribution of the cooling medium, the streaming situation in several segments, the nozzle geometry and, as a consequence, the water jet shape, and the impact pressure of the cooling medium on the surface of the rolled material) as influencing parameters. This paper describes the possibilities for determining and simulating the heat transfer in the cooling line with industrial conditions. Moreover, this paper discusses the optimal control of the cooling line to achieve the desired temperature and phase distribution on the run-out table. The resulting information contributes to new technology and material developments at the pilot plant, as well as for the transfer of results into the industry