Induzierte Domänenbewegung in magnetischen Tunnelkontakten mit sinusförmiger Kleinfeldmodulation

First measurements on Barkhausen - noise from magnetic tunnel junctions arepresented. A low frequency magnetic field was applied to the magnetic thin film layers andthen the temporary changes in the voltage signal of the junction were measured as spectralnoise density. The alternativg magnetic field causes a temporary change of themagnetization in the ferromagnetic layers. These changes influence the behavior of theresistance directly and the TMR - effect, respectively. With this method it was possible todraw conclusions on the switching behavior of the magnetic domains in each magneticlayer.Magnetic tunnel junctions with a tri-layer system made of Co/Al$_{2}$O$_{3}$/NiFe have beenfabricated. The aluminum oxide barrier was fabricated using a mercury - low pressurelamp which was able to produce oxygen radicals as well as ozone from pure oxygen gas.This successful preparation method is concerned to be an alternative to the commonly usedplasma oxidation. All of the tunnel junctions showed a clear tunneling behavior based onthe nonlinear current - voltage characteristics. The tunneling magnetoresistance effect ofthe junctions made with the UV-light were in the range of 10 - 20 % at room temperature.The magnetic switching fields have been measured to 0,5 and 2 kA/m for the soft- andhard magnetic layers respectively.In order to characterize the tunnel barrier, noise measurements at different appliedmagnetic fields were made. No significant changes were observed in the spectra of the UV- light oxidized and the plasma oxidized tunnel junctions.The surface roughness of Co and Al were also studied by X-ray diffraction andscanning force microscopy measurements. These showed clearly that a low Ar pressureduring sputtering is responsible for the excellent smoothness. An rms - roughness wasfound which was less than 0,2 nm.TMR ratios of the UV - light oxidized barriers were investigated depending on thebias - voltage and temperature.Furthermore, the oxygen pressure was varied which was applied during the one houroxidation procedure of the aluminum. An optimal condition could be found at p = 10 mbarO$_{2}$. Using this value the maximum TMR- ratios were received

Probabilistic Analysis of LCF Crack Initiation Life of a Turbine Blade under Thermomechanical Loading

An accurate assessment for fatigue damage as a function of activation and deactivation cycles is vital for the design of many engineering parts. In this paper we extend the probabilistic and local approach to this problem proposed in [1,2] and [3] to the case of non-constant temperature fields and thermomechanical loading. The method has been implemented as a finite element postprocessor and applied to an example case of a gas-turbine blade which is made of a conventionally cast nickel base superalloy.Comment: 8 pages, 3 figure

A Probabilistic Model for LCF

Fatigue life of components or test specimens often exhibit a significant scatter. Furthermore, size effects have a non-negligible influence on fatigue life of parts with different geometries. We present a new probabilistic model for low-cycle fatigue (LCF) in the context of polycrystalline metal. The model takes size effects and inhomogeneous strain fields into account by means of the Poisson point process (PPP). This approach is based on the assumption of independently occurring LCF cracks and the Coffin-Manson-Basquin (CMB) equation. Within the probabilistic model, we give a new and more physical interpretation of the CMB parameters which are in the original approach no material parameters in a strict sense, as they depend on the specimen geometry. Calibration and validation of the proposed model is performed using results of strain controlled LCF tests of specimens with different surface areas. The test specimens are made of the nickel base superalloy RENE 80.Comment: 20 pages, 6 figure

Negative interactions and virulence differences drive the dynamics in multispecies bacterial infections

Bacterial infections are often polymicrobial, leading to intricate pathogen–pathogen and pathogen–host interactions. There is increasing interest in studying the molecular basis of pathogen interactions and how such mechanisms impact host morbidity. However, much less is known about the ecological dynamics between pathogens and how they affect virulence and host survival. Here we address these open issues by co-infecting larvae of the insect model host Galleria mellonella with one, two, three or four bacterial species, all of which are opportunistic human pathogens. We found that host mortality was always determined by the most virulent species regardless of the number of species and pathogen combinations injected. In certain combinations, the more virulent pathogen simply outgrew the less virulent pathogen. In other combinations, we found evidence for negative interactions between pathogens inside the host, whereby the more virulent pathogen typically won a competition. Taken together, our findings reveal positive associations between a pathogen's growth inside the host, its competitiveness towards other pathogens and its virulence. Beyond being generalizable across species combinations, our findings predict that treatments against polymicrobial infections should first target the most virulent species to reduce host morbidity, a prediction we validated experimentally

Утилизация отходов биологического производства

В статье рассматривается проблема утилизации отходов, так как в год Экологии это тема стала актуальной. На каждом предприятии и в каждом доме увеличилось количество мусора и от этого страдает экологическая обстановка в каждом городе. В статье подробно узучена тема биологического производства. К биологическим отходам относятся ткани и органы, образующиеся в результате медицинской и ветеринарной оперативной практики, медико-биологических экспериментов, гибели скота, других животных и птиц, и другие отходы, получаемые при переработке пищевого и непищевого сырья животного происхождения, а также отходы биотехнологической промышленности.The article deals with the problem of waste disposal as in the year of the Environment this issue has become topical. Every enterprise and every household increased the amount of debris and suffers the environmental situation in each city. The article Azucena the theme of biological production. Biodegradable waste includes tissues and organs resulting from operational medical and veterinary practice, medical and biological experiments, loss of livestock, other animals and birds, and other waste obtained in the processing of food and non-food raw materials of animal origin and waste products of the biotechnology industry

Wiki-based Collaborative Learning Experience in a Foreign Language Blended Course

The article emphasizes the educational potential of wikis for learning foreign languages. It focuses on students’ collaboration based on integration of different types of activities within a highly motivating blended learning environment where learners can interact and share their ideas. The study aims to understand if wikis could enhance online collaboration and positively affect students’ attitudes to group work. It tries to explore the level of participation and contribution of students in wiki-based activities, as well as their attitude to this type of online collaboration