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Search Results: 1 - 10 of 1106 matches for " Wilhelm Behringer "
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Hypothermia in the operating theatre
Andreas Gruber, Wilhelm Behringer, Engelbert Knosp
Critical Care , 2012, DOI: 10.1186/cc11275
Abstract: Cerebral ischaemia results from a reduction or complete loss of cerebral blood flow (CBF) and lack of cerebral oxygenation, followed by depletion of ATP, dysfunction of ATP-dependent membrane pumps and subsequently occurrence of anoxic depolarisation. A large amount of glutamate is released from the intracellular space into the extracellular space, causing excitotoxic injury by stimulating N-methyl-D-aspartate (NMDA) receptors and triggering calcium influx. Increased intracellular calcium levels per se amplify injury by increasing calcium permeability and glutamate release via second messenger mechanisms. These acute cascades lead to necrotic neuronal death by interfering with the mitochondrial respiratory chain. Ischaemia and reperfusion further enhance excitotoxicity by providing oxygen as a substrate for several enzymatic oxidation reactions, thereby generating products of reactive oxygen species in large quantities. These free radicals enhance protein oxidation and lipid membrane disintegration and in conjunction with blood-brain barrier (BBB) disruption further contribute to ischaemic necrosis. Apoptosis also occurs in cerebral ischemia, with antiapoptotic proteins being selectively upregulated in surviving neurons and proapoptotic proteins being highly expressed in dying cells.The first controlled attempts to cool the human brain were undertaken by the neurosurgeon Temple Fay in 1938 [1]. Irrigating the brain directly with ice water and sometimes achieving solid parenchymal freezing, he claimed 'extremely gratifying results' in a paper on 'local and generalized refrigeration of the human brain'. Over time, many mechanisms have been proposed regarding the neuroprotective effect of hypothermia. First, hypothermia results in a temperature-dependent decrease of oxygen and glucose metabolism; that is, a 10°C decrease in temperature reduces ATP consumption and the cerebral metabolic rate (CMR) of oxygen, glucose, and lactate twofold to fourfold [2]. Second, intra-is
Out-of-hospital therapeutic hypothermia in cardiac arrest victims
Wilhelm Behringer, Jasmin Arrich, Michael Holzer, Fritz Sterz
Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine , 2009, DOI: 10.1186/1757-7241-17-52
Abstract: Sudden cardiac arrest remains a major unresolved public health problem. In Europe and the USA, approximately 425.000 people suffer of sudden cardiac death with very poor survival, usually less than 10% [1,2]. After cardiac arrest and brain ischemia, reperfusion initiates multiple independent chemical cascades and fatal pathways, resulting in neuronal death due to necrosis and apoptosis [3]. Because of the multi-factorial pathogenesis of post-arrest neuronal death, a multifaceted treatment strategy is required to achieve survival without brain damage. Hypothermia, a re-discovered promising treatment strategy, exerts its beneficial effects on brain ischemia by various mechanisms, and perfectly fulfils the requirements of a multifaceted treatment strategy [4].In therapeutic hypothermia, different degrees of cooling can be differentiated, though definition of these temperature levels may differ slightly between authors: mild (34 to 32°C), moderate (31 to 28°C), deep (27 to 11°C), profound (10 to 6°C), and ultra-profound (5 to 0°C) hypothermia. Protective hypothermia, induced before cardiac arrest, has to be differentiated from preservative hypothermia, induced during cardiac arrest treatment, and from resuscitative hypothermia, induced after successful resuscitation. Protective hypothermia is used in cardiac surgery and neurosurgery, but is clinically unrealistic in sudden cardiac death. This review will focus on a) preservative mild hypothermia during cardiac arrest treatment and b) resuscitative mild hypothermia after successful resuscitation in respect to its clinical application in the out-of-hospital setting.Preservative hypothermia can further be differentiated into the induction of hypothermia during ischemia (before initiation of resuscitation - or before reperfusion) and the induction of hypothermia during resuscitation.Research in myocytes showed that injury to cells not only occurs during ischemia itself, but mainly with reperfusion by initiating several casc
Product Repositioning in the UK Newspaper Industry  [PDF]
Stefan Behringer
Theoretical Economics Letters (TEL) , 2016, DOI: 10.4236/tel.2016.65099
Abstract: This paper investigates the alleged predatory behaviour in the UK quality newspaper industry in the 1990s in terms of product repositioning using a horizontal differentiation model and industry data. It supports the call for an effects based approach to competition law by showing that non-price conduct can be a critical and less visible, complementary means to achieve a predatory goal than mere price cuts.
Surface cooling for induction of mild hypothermia in conscious healthy volunteers - a feasibility trial
Christoph Testori, Fritz Sterz, Wilhelm Behringer, Alexander Spiel, Christa Firbas, Bernd Jilma
Critical Care , 2011, DOI: 10.1186/cc10506
Abstract: The trial was set at a clinical research ward in a tertiary care center, and included 16 healthy male volunteers 18 to 70 years old. Surface cooling was established by a novel non-invasive cooling pad with an esophageal target temperature of 32 to 34°C and maintenance for six hours. Shivering-control was achieved with meperidine and buspirone and additional administration of magnesium in eight subjects.The primary endpoint to reach a target temperature of 32 to 34°C was only reached in 6 of the 16 participating subjects. Temperatures below 35°C were reached after a median cooling time of 53 minutes (38 to 102 minutes). Cooling rate was 1.1°C/h (0.7 to 1.8°C). Additional administration of magnesium had no influence on cooling rate. At no time during the cooling procedure did the participants report uncomfortable conditions for which termination of cooling had to be considered. No severe skin damage was reported.Cooling to body temperature below 35°C by the use of non-invasive surface cooling is feasible and safe in conscious healthy volunteers. Further studies are needed to investigate an altered cooling protocol to achieve temperatures below 35°C.ISRCTN: ISRCTN50530495Therapeutic hypothermia improves neurological outcome and reduces the risk of death in patients after cardiac arrest [1,2]. In recent years, growing evidence in animal and human studies have documented or suggested the beneficial outcome effects of mild hypothermia also for stroke [3-11], for acute myocardial infarction [12-16], and for cardiogenic shock [17]. Rather than interacting on a particular pathway of post-ischemic reperfusion damage hypothermia influences multiple reactions leading to cell death [18-20].So far, the majority of therapeutic hypothermia research has involved cardiac arrest patients, in whom the induction and maintenance of mild hypothermia is facilitated by post-anoxic coma, anesthesia and paralysis to avoid shivering. The typical patient presenting to an emergency department wi
Relationship between time to target temperature and outcome in patients treated with therapeutic hypothermia after cardiac arrest
Moritz Haugk, Christoph Testori, Fritz Sterz, Maximilian Uranitsch, Michael Holzer, Wilhelm Behringer, Harald Herkner, the Time to Target Temperature Study Group
Critical Care , 2011, DOI: 10.1186/cc10116
Abstract: Temperature data between April 1995 and June 2008 were collected from 588 patients and analyzed in a retrospective cohort study by observers blinded to outcome. The time needed to achieve an esophageal temperature of less than 34°C was recorded. Survival and neurological outcomes were determined within six months after cardiac arrest.The median time from restoration of spontaneous circulation to reaching a temperature of less than 34°C was 209 minutes (interquartile range [IQR]: 130-302) in patients with favorable neurological outcomes compared to 158 min (IQR: 101-230) (P < 0.01) in patients with unfavorable neurological outcomes. The adjusted odds ratio for a favorable neurological outcome with a longer time to target temperature was 1.86 (95% CI 1.03 to 3.38, P = 0.04).In comatose cardiac arrest patients treated with therapeutic hypothermia after return of spontaneous circulation, a faster decline in body temperature to the 34°C target appears to predict an unfavorable neurologic outcome.For patients who have been successfully resuscitated after cardiac arrest, therapeutic mild hypothermia increases the rate of a favorable outcome in comparison with standard life support. Randomized controlled trials, however, have not shown evidence of whether the time to target temperature correlates with neurological outcome [1-4]. Registries about the practical use of therapeutic hypothermia have also not found a significant association between the timing of therapeutic hypothermia and final outcome [5-7]. We expected a strong relationship between the time to target temperature (<34°C) and neurological outcome. Furthermore, we hypothesized that earlier achievement of target temperature would not necessarily improve outcome.The study was designed as a single-center retrospective cohort study on temperature data extracted from patients' charts by observers blinded to outcome. The protocol and consent procedures were approved by the ethics committee of the Medical University of
Qualitative Picture of Scaling in the Entropy Formalism
Hans Behringer
Entropy , 2008, DOI: 10.3390/entropy-e10030224
Abstract: The properties of an infinite system at a continuous phase transition are characterised by non-trivial critical exponents. These non-trivial exponents are related to scaling relations of the thermodynamic potential. The scaling properties of the singular part of the specific entropy of infinite systems are deduced starting from the well-established scaling relations of the Gibbs free energy. Moreover, it turns out that the corrections to scaling are suppressed in the microcanonical ensemble compared to the corresponding corrections in the canonical ensemble.
Microcanonical entropy for small magnetisations
Hans Behringer
Mathematics , 2003, DOI: 10.1088/0305-4470/37/4/026
Abstract: Physical quantities obtained from the microcanonical entropy surfaces of classical spin systems show typical features of phase transitions already in finite systems. It is demonstrated that the singular behaviour of the microcanonically defined order parameter and susceptibility can be understood from a Taylor expansion of the entropy surface. The general form of the expansion is determined from the symmetry properties of the microcanonical entropy function with respect to the order parameter. The general findings are investigated for the four-state vector Potts model as an example of a classical spin system.
Symmetries of microcanonical entropy surfaces
Hans Behringer
Mathematics , 2003, DOI: 10.1088/0305-4470/36/33/302
Abstract: Symmetry properties of the microcanonical entropy surface as a function of the energy and the order parameter are deduced from the invariance group of the Hamiltonian of the physical system. The consequences of these symmetries for the microcanonical order parameter in the high energy and in the low energy phases are investigated. In particular the breaking of the symmetry of the microcanonical entropy in the low energy regime is considered. The general statements are corroborated by investigations of various examples of classical spin systems.
Critical properties of the spherical model in the microcanonical formalism
Hans Behringer
Statistics , 2005, DOI: 10.1088/1742-5468/2005/06/P06014
Abstract: Due to the equivalence of the statistical ensembles thermostatic properties of physical systems with short-range interactions can be calculated in different ensembles leading to the same physics. In particular, the ensemble equivalence holds for systems that undergo a continuous phase transition in the infinite volume limit so that the properties of the transition can also be investigated in the microcanonical approach. Considering as example the spherical model the ensemble equivalence is explicitly demonstrated by calculating the critical properties in the microcanonical ensemble and comparing them to the well-known canonical results.
Formalization of Federated Schema Architectural Style Variability  [PDF]
Wilhelm Hasselbring
Journal of Software Engineering and Applications (JSEA) , 2015, DOI: 10.4236/jsea.2015.82009
Abstract: Data integration requires managing heterogeneous schema information. A federated database system integrates heterogeneous, autonomous database systems on the schema level, whereby both local applications and global applications accessing multiple component database systems are supported. Such a federated database system is a complex system of systems which requires a well-designed organization at the system and software architecture level. A specific challenge that federated database systems face is the organization of schemas into a schema architecture. This paper provides a detailed, formal investigation of variability in the family of schema architectures, which are central components in the architecture of federated database systems. It is shown how the variability of specific architectures can be compared to the reference architecture and to each other. To achieve this, we combine the semi-formal object-oriented modeling language UML with the formal object-oriented specification language Object-Z. Appropriate use of inheritance in the formal specification, as enabled by Object-Z, greatly supports specifying and analyzing the variability among the studied schema architectures. The investigation also serves to illustrate the employed specification techniques for analyzing and comparing software architecture specifications.
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