Evaluation of the stability of human erythropoietin in samples for radioimmunoassay

Radioimmunoassays for erythropoietin are limited so far to a few specialized laboratories and this requires transport and storage of samples. We therefore tested the stability of immunoreactive erythropoietin in serum and plasma samples obtained from a uremic and a nonuremic anemic patient. No significant change in the concentration of immunoreactive erythropoietin was found in either serum or plasma samples for up to 14 days of storage. This type of stability was observed no matter whether the samples were stored at room temperature, 4 degrees C, or -20 degrees C. There was no difference between the estimates of erythropoietin in serum and heparinized plasma. Validity of the radioimmunoassay used in this study was demonstrated by parallelism of dilution curves of test specimens and the 2nd International Reference Preparation for erythropoietin and by a close correlation between the immunoreactivity and the bioactivity of the hormone, as assessed in the same samples by the exhypoxic polycythemic mouse bioassay. In conclusion the data obtained clearly indicate that the necessity of storage and transport of clinical samples does not limit the practicability of the radioimmunoassay for erythropoietin

Reachability Analysis on Timed Graph Transformation Systems

In recent years, software increasingly exhibits self-* properties like selfoptimization or self-healing. Such properties require reconfiguration at runtime in order to react to changing environments or detected defects. A reconfiguration might add or delete components as well as it might change the communication topology of the system. Considering communication protocols between an arbitrary number of participants, reconfiguration and state-based protocol behavior are no longer independent from each other and need to be verified based on a common formalism. Additionally, such protocols often contain timing constraints to model real-time properties. These are of integral importance for the safety of the modeled system and thus need to be considered during the verification of the protocol. In current approaches either reconfigurations or timing constraints are not considered. Existing approaches for the verification of timed graph transformation systems lack important constructs needed for the verification of state-based real-time protocol behaviors. As a first step towards a solution to this problem, we introduced Timed Story Driven Modeling [HHH10] as a common formalism integrating state-based real-time protocol behaviors and system reconfigurations based on graph transformations. In this paper, we introduce a framework allowing to perform reachability analysis based on Timed Story Driven Modeling. The framework allows to compute the reachable timed graph transition system based on an initial graph and a set of timed transformation and invariant rules

Entwicklung einer aktiven 238Uran(VI)-fluorid-Detektor-Kammer für Präzisionsexperimente in der photoneninduzierten Spaltung am S-DALINAC

Der am S-DALINAC installierte Injektor spinpolarisierter Elektronen SPIN ermöglicht den Einsatz zirkular polarisierter Bremsstrahlung mit einem hohen Polarisationsgrad in der Nähe der Endpunktsenergie für die Suche nach paritätsverletzenden Effekten in der Vorwärts-Rückwärts-Asymmetrie des leichten und schweren Spaltfragmentes der photoneninduzierten Spaltung an 238U. Zur Steigerung der Luminosität wurde im Rahmen dieser Arbeit eine aktive 238Uran(VI)-fluorid-Detektor-Kammer nach dem Prinzip einer einfachen Frisch-Gitter-Ionisationskammer entwickelt, um die Eigenschaften eines 238Uran(VI)-fluorid/Argon-Gemisches zu untersuchen und höhere 238Uran-Flächendichten zu ermöglichen. Die aktive 238Uran(VI)-fluorid-Detektor-Kammer wurde unter Verwendung von Massenflussreglern mit Argon und 238Uran(VI)-fluorid befüllt. Bei verschiedensten Einstellungen wurden Daten aufgenommen und interpretiert. Im Anschluss an die Befüllung mit 238Uran(VI)-fluorid brechen Anoden- und Kathodensignal ein und erholen sich nur langsam. Vermutlich agiert das 238Uran(VI)-fluorid ob seiner Komplexität und des hohen Fluoranteiles und dessen Elektronegativität als sehr effizienter Elektronenkollektor. Im Verlauf der Zeit reduziert sich der Anteil gasförmigen 238Uran(VI)-fluorides, mehrere Prozesse sind zur Erklärung dieses Effektes denkbar. In der derzeitigen Konfiguration der aktiven 238Uran(VI)-fluorid-Detektor-Kammer können quantitative Aussagen über die Eigenschaften eines 238Uran(VI)-fluorid/Argon-Gemisches nicht getroffen werden. Die Steigerung der Luminosität für Präzisionsexperimente in der photoneninduzierten Spaltung am S-DALINAC durch eine aktive 238Uran(VI)-fluorid-Detektor-Kammer erscheint zum jetzigen Zeitpunkt als nicht möglich

Scattering theory for Klein-Gordon equations with non-positive energy

We study the scattering theory for charged Klein-Gordon equations: \{{array}{l} (\p_{t}- \i v(x))^{2}\phi(t,x) \epsilon^{2}(x, D_{x})\phi(t,x)=0,[2mm] \phi(0, x)= f_{0}, [2mm] \i^{-1} \p_{t}\phi(0, x)= f_{1}, {array}. where: \epsilon^{2}(x, D_{x})= \sum_{1\leq j, k\leq n}(\p_{x_{j}} \i b_{j}(x))A^{jk}(x)(\p_{x_{k}} \i b_{k}(x))+ m^{2}(x), describing a Klein-Gordon field minimally coupled to an external electromagnetic field described by the electric potential $v(x)$ and magnetic potential $\vec{b}(x)$. The flow of the Klein-Gordon equation preserves the energy: h[f, f]:= \int_{\rr^{n}}\bar{f}_{1}(x) f_{1}(x)+ \bar{f}_{0}(x)\epsilon^{2}(x, D_{x})f_{0}(x) - \bar{f}_{0}(x) v^{2}(x) f_{0}(x) \d x. We consider the situation when the energy is not positive. In this case the flow cannot be written as a unitary group on a Hilbert space, and the Klein-Gordon equation may have complex eigenfrequencies. Using the theory of definitizable operators on Krein spaces and time-dependent methods, we prove the existence and completeness of wave operators, both in the short- and long-range cases. The range of the wave operators are characterized in terms of the spectral theory of the generator, as in the usual Hilbert space case

Simulation based draping of dry carbon fibre textiles with cooperating robots

Carbon fibre-reinforced plastic (CFRP) is a promising material for aircraft and other lightweight applications. To be competitive with low-cost metal based solutions highly effective and flexible production technologies are required. For this purpose production systems comprising automated fibre placement or automated tape laying technology are on the market for several years and widely spread. However, there is still a lack of automated systems capable of producing preforms efficiently and flexibly from textile semi-finished goods. Non-crimp fabrics (NCF) and weaves have to undergo considerable shear and reshaping during the layup of 3D-curved preforms in order to properly fit the 2D cut pieces to the moulds. At the Center for Lightweight Production Technology (ZLP) a digital and automated process for the easy draping of large NCF and weave cut pieces with several robots according to the previous draping simulation has been set up and tested in a robotic work cell. The details of converting the draping simulation into correct and easy to setup motions for cooperating robots and how to execute the entire process autonomously, i.e. without teaching the robots, are described. On the basis of preliminary tests the system’s capabilities on a large scale demonstrator part resembling an airplane’s rear pressure bulkhead are evaluated. An overview of the system’s architecture from simulation based planning to detecting, correct gripping, collision free autonomous transport and laydown of the cut pieces is also given

Divergent electrophysiologic action of dapagliflozin and empagliflozin on ventricular and atrial tachyarrhythmias in isolated rabbit hearts

BackgroundThe use of SGLT-2 inhibitors has revolutionized heart failure therapy. Evidence suggests a reduced incidence of ventricular and atrial arrhythmias in patients with dapagliflozin or empagliflozin treatment. It is unclear to what extent the reduced arrhythmia burden is due to direct effects of the SGLT2 inhibitors or is solely a marker of improved cardiac function.MethodsOne hundred five rabbit hearts were allocated to eight groups and retrogradely perfused, employing a Langendorff setup. Action potential duration at 90% of repolarization (APD90), QT intervals, effective refractory periods, conduction velocity, and dispersion of repolarization were obtained with monophasic action potential catheters. A model for tachyarrhythmias was established with the IKr blocker erythromycin for QT prolongation associated proarrhythmia as well as the potassium channel opener pinacidil for a short-QT model. An atrial fibrillation (AF) model was created with isoproterenol and acetylcholine. With increasing concentrations of both SGLT2 inhibitors, reductions in QT intervals and APD90 were observed, accompanied by a slight increase in ventricular arrhythmia episodes. During drug-induced proarrhythmia, empagliflozin succeeded in decreasing QT intervals, APD90, and VT burden whereas dapagliflozin demonstrated no significant effects. In the presence of pinacidil induced arrhythmogenicity, neither SGLT2 inhibitor had a significant impact on cardiac electrophysiology. In the AF setting, perfusion with dapagliflozin showed significant suppression of AF in the course of restitution of electrophysiological parameters whereas empagliflozin showed no significant effect on atrial fibrillation incidence.ConclusionIn this model, empagliflozin and dapagliflozin demonstrated opposite antiarrhythmic properties. Empagliflozin reduced ventricular tachyarrhythmias whereas dapagliflozin showed effective suppression of atrial arrhythmias

Análise de timol em cera de abelha por micro-extracção em fase sólida (SPME)

A aplicação contínua de acaricídas lipofílicos sintéticos no tratamento das abelhas conduz a uma acumulação que depende da frequência, lipofilicidade e quantidade de princípio activo utilizada. Este efeito é mais acentuado na cera de abelha que no mel, no entanto, e porque a persistência destes resíduos é elevada, provoca o aparecimento de resistências e a perda do seu efeito acaricida.[1] Esta razão levou à pesquisa de outros compostos alternativos não tóxicos e não persistentes, com efeito sobre o ácaro das abelhas, Varroa Jacobsoni. Entre estes compostos encontra-se o timol, um composto fenólico, volátil, presente no tomilho. Dos diversos componentes dos óleos essenciais este é sem dúvida o que demonstrou maior efeito acaricida, utilizando-se no tratamento das abelhas directamente ou como componente de diversas formulações.[2] Em Portugal, foi introduzido muito recentemente sob a forma comercial de APIGUARD: um gel, à base de timol, que controla termicamente a libertação do princípio activo. O controlo dos resíduos de timol na cera de abelha e no mel é assim um desafio actual quer do ponto de vista sanitário quer de qualidade alimentar. A micro-extracção em fase sólida (SPME) é uma técnica de preparação de amostras que se baseia na sorção de analítos no revestimento de uma fibra de sílica fundida e posterior desorção térmica no injector de um cromatógrafo em fase gasosa (GC). Para além de combinar num único processo etapas de extracção, purificação e concentração dos analitos, a técnica de SPME apresenta uma série de vantagens relativamente às técnicas de extracção convencionais, como a extracção líquido-líquido e extracção em fase sólida, nomeadamente a sua relativa simplicidade e rapidez, reduzido custo e não utilização de solventes para a extracção de analitos, para além de permitir a extracção por imersão directa na amostra gasosa ou líquida e extracção por amostragem do espaço-de-cabeça da amostra líquida ou sólida.[3] Ao contrário das técnicas tradicionais, que permitem uma extracção quantitativa dos analitos, a técnica de SPME baseia-se num equilíbrio de partição do analito. Esta particularidade torna a técnica de SPME bastante sensível a parâmetros experimentais que possam afectar os coeficientes de partição dos analitos e, consequentemente, a sensibilidade e reprodutibilidade dos resultados.[4] O objectivo deste trabalho é o desenvolvimento de uma metodologia para a análise de timol em ceras contaminadas, utilizando como padrão interno a benzofenona. Em primeiro lugar, procedeu-se à optimização da técnica através da determinação da quantidade de cera, temperatura de análise e período de contacto da fibra com o espaço-de-cabeça da amostra mais adequados para o caso em estudo. Numa segunda fase, procedeu-se à análise de diversas lâminas de cera contaminadas propositadamente com timol e sujeitas a diferentes condições de armazenamento: em frio, ao ar e em estufa. Finalmente, procedeu-se à construção da curva de calibração e quantificação do timol presente nas diversas amostras de cera analisadas. Considerando-se os resultados, para os níveis de contaminação avaliados, as condições analíticas mais adequadas ocorrem com a utilização de 1 g de cera, mantendo-se a fibra em contacto com o espaço-de-cabeça durante 40 minutos a uma temperatura de 60 ºC. Nestas condições experimentais foi possível obter uma boa correlação linear (r2=0,990) no intervalo de concentrações [3,5-14 mg/g]. A quantidade de timol encontrada nas amostras é significativamente inferior à colocada durante o processo de fabrico das lâminas, pelo que o processo de conservação não é o mais adequado, sendo evidente uma menor quantidade de timol quando a lâmina de cera é colocada na estufa