Deformation behavior of bulk metallic glasses produced via Severe Plastic Deformation and the influence of a second phase

Over the last years bulk metallic glasses (BMG) have been strongly investigated as their mechanical properties are very promising especially in terms of their high yield strength and high elastic strain. However, a major drawback is their complicated production depending strongly on dimensions and chemistry. A promising technique to overcome these drawbacks is using a severe plastic deformation process, e.g. high pressure torsion (HPT), where the production can be started with metallic glass powders, which are generally much easier to fabricate. For this route, the powder is consolidated and then the powder particles are welded together by applying a high shear deformation. The produced specimen remain fully amorphous and no porosity is detectable after sufficient deformation [1]. To improve the mechanical properties of the BMG, the used Zr-based metallic glass powder is mixed with a crystalline Cu-powder or a Ni-based metallic glass powder to achieve a metal/metallic glass composite or a metallic glass/ metallic glass composite, respectively. Due to the small amounts of produced material, conventional macroscopic characterization methods, like compression or tension tests can hardly be used to analyze the overall mechanical properties. Therefore, in this work different micromechanical testing methods, such as nanoindentation, in-situ SEM micropillar compression, and finally in situ TEM picoindentation were carried out to investigate the deformation behavior under ambient but also non-ambient conditions. Using nanoindentation, the hardness and the Young’s Modulus was determined for two HPT-deformed BMGs with different composition. Additionally, high temperature nanoindentation experiments up to 350 °C were conducted to determine not only the temperature dependent hardness and the Young’s modulus but also to study the change in thermally activated processes during deformation via nanoindentation strain rate jump tests. It was found, that nanoindentation hardness is in good accordance to the macroscopic Vickers results. Increasing the temperature, hardness decreases slightly, while the modulus increases. The shear band formation is also dependent on the deformation temperature, since the extent of stair case formation in the load-displacement curves changes. Overcoming 300°C, the material becomes extremely ductile showing a strong strain rate sensitivity. Further, the uniaxial mechanical response of Zr-based BMG was examined in-situ in SEM using FIB prepared micropillars. The microcompression experiments revealed a strength of more than 2 GPa. Steps in the stress-strain curve suggest shear band formation, which could also be confirmed by the in-situ recorded SEM images Finally the influence of the second materials phase was investigated via TEM in-situ picoindentation, where a wedge shaped indenter was pressed in a TEM lamella. The load-displacement curve show a similar stair case behavior as seen during nanoindention and microcompression, indicating shear band formation. The shear band formation could be also observed in the TEM micrographs

Bulk metallic glass composites: microstructural influences on mechanical properties

Bulk metallic glasses (BMGs) have been strongly investigated as they show on the one hand interesting mechanical properties as high strength and good wear resistance but on the other hand limited ductile deformability. Bulk metallic glass composites (BMGCs) are very promising to overcome and improve the properties by clever combination of different phases. However, a major drawback is the limited choices of phase combinations in common fabrication routes and lack of major microstructure adjustability. A promising technique to overcome these drawbacks is severe plastic deformation process, e.g. high pressure torsion (HPT), where the production can be started with metallic glass powders. For this route, the powder is consolidated and deformed by applying a high shear deformation to bulk samples. Therefore, it is possible to produce fully amorphous specimens [1], but also composites containing two different amorphous phases or an amorphous and a crystalline one [2]. Please click Additional Files below to see the full abstract

Functional genomics of pH homeostasis in Corynebacterium glutamicum revealed novel links between pH response, oxidative stress, iron homeostasis and methionine synthesis

Follmann M, Ochrombel I, Kraemer R, et al. Functional genomics of pH homeostasis in Corynebacterium glutamicum revealed novel links between pH response, oxidative stress, iron homeostasis and methionine synthesis. BMC Genomics. 2009;10(1):621.Background: The maintenance of internal pH in bacterial cells is challenged by natural stress conditions, during host infection or in biotechnological production processes. Comprehensive transcriptomic and proteomic analyses has been conducted in several bacterial model systems, yet questions remain as to the mechanisms of pH homeostasis. Results: Here we present the comprehensive analysis of pH homeostasis in C. glutamicum, a bacterium of industrial importance. At pH values between 6 and 9 effective maintenance of the internal pH at 7.5 +/- 0.5 pH units was found. By DNA microarray analyses differential mRNA patterns were identified. The expression profiles were validated and extended by 1D-LC-ESI-MS/MS based quantification of soluble and membrane proteins. Regulators involved were identified and thereby participation of numerous signaling modules in pH response was found. The functional analysis revealed for the first time the occurrence of oxidative stress in C. glutamicum cells at neutral and low pH conditions accompanied by activation of the iron starvation response. Intracellular metabolite pool analysis unraveled inhibition of the TCA and other pathways at low pH. Methionine and cysteine synthesis were found to be activated via the McbR regulator, cysteine accumulation was observed and addition of cysteine was shown to be toxic under acidic conditions. Conclusions: Novel limitations for C. glutamicum at non-optimal pH values were identified by a comprehensive analysis on the level of the transcriptome, proteome, and metabolome indicating a functional link between pH acclimatization, oxidative stress, iron homeostasis, and metabolic alterations. The results offer new insights into bacterial stress physiology and new starting points for bacterial strain design or pathogen defense

Filariasis of the Axilla in a Patient Returning from Travel Abroad: A Case Report

Background: The term filariasis comprises a group of parasitic infections caused by helminths belonging to different genera in the superfamily Filaroidea. The human parasites occur mainly in tropical and subtropical regions, but filariae are also found in temperate climates, where they can infect wild and domestic animals. Humans are rarely infected by these zoonotic parasites. Patients and Methods: A 55-year-old patient presented with a new-onset, subcutaneous, non-tender palpable mass in the right axilla. Ultrasonography showed a 1.3-cm, solid, singular encapsulated node. Sonography of the breast on both sides, axilla and lymphatic drainage on the left side, lymphatic drainage on the right side, and mammography on both sides were without pathological findings. The node was excised under local anesthesia as the patient refused minimal invasive biopsy. Results: On histopathological examination, the tail of a parasite of the group of filariae was found. The patient revealed that she had stayed in Africa and Malaysia for professional reasons. 6 months before the time of diagnosis, she had also suffered from a fever and poor general condition after a trip abroad. The patient was referred for further treatment to the Institute for Tropical Medicine at the University of Dusseldorf, where a treatment with ivermectin was conducted on the basis of positive staining with antibodies against filariae. Conclusion: Our case demonstrates the importance of interdisciplinary collaboration between breast center, pathology, and other specialties such as microbiology and tropical medicine

Ascorbate-induced oxidative stress mediates TRP channel activation and cytotoxicity in human etoposide-sensitive and -resistant retinoblastoma cells

There are indications that pharmacological doses of ascorbate (Asc) used as an adjuvant improve the chemotherapeutic management of cancer. This favorable outcome stems from its cytotoxic effects due to prooxidative mechanisms. Since regulation of intracellular Ca2+ levels contributes to the maintenance of cell viability, we hypothesized that one of the effects of Asc includes disrupting regulation of intracellular Ca2+ homeostasis. Accordingly, we determined if Asc induced intracellular Ca2+ influx through activation of pertussis sensitive Gi/o-coupled GPCR which in turn activated transient receptor potential (TRP) channels in both etoposide-resistant and -sensitive retinoblastoma (WERI-Rb1) tumor cells. Ca2+ imaging, whole-cell patch-clamping, and quantitative real-time PCR (qRT-PCR) were performed in parallel with measurements of RB cell survival using Trypan Blue cell dye exclusion. TRPM7 gene expression levels were similar in both cell lines whereas TRPV1, TRPM2, TRPA1, TRPC5, TRPV4, and TRPM8 gene expression levels were downregulated in the etoposide-resistant WERI-Rb1 cells. In the presence of extracellular Ca2+, 1 mM Asc induced larger intracellular Ca2+ transients in the etoposide-resistant WERI-Rb1 than in their etoposide-sensitive counterpart. With either 100 µM CPZ, 500 µM La3+, 10 mM NAC, or 100 µM 2-APB, these Ca2+ transients were markedly diminished. These inhibitors also had corresponding inhibitory effects on Asc-induced rises in whole-cell currents. Pertussis toxin (PTX) preincubation blocked rises in Ca2+ influx. Microscopic analyses showed that after 4 days of exposure to 1 mM Asc cell viability fell by nearly 100% in both RB cell lines. Taken together, one of the effects underlying oxidative mediated Asc-induced WERI-Rb1 cytotoxicity stems from its promotion of Gi/o coupled GPCR mediated increases in intracellular Ca2+ influx through TRP channels. Therefore, designing drugs targeting TRP channel modulation may be a viable approach to increase the efficacy of chemotherapeutic treatment of RB. Furthermore, Asc may be indicated as a possible supportive agent in anti-cancer therapies

Representativeness of the European social partner organisations : Sea fisheries sector

Aquesta publicació s'elabora a partir de les contribucions de cadascú dels membres nacionals que integren la Network of Eufound Correspondent. Pel cas d'Espanya la contribució ha estat realitzada per l'Alejandro GodinoThis study provides information allowing for an assessment of the representativeness of the actors involved in the European sectoral social dialogue committee for the sea fisheries sector. Their relative representativeness legitimises their right to be consulted, their role and effective participation in the European sectoral social dialogue and their capacity to negotiate agreements. The aim of Eurofound's representativeness studies is to identify the relevant national and European social partner organisations. This study identified the Association of National Organisations of Fishing Enterprises in the European Union (Europêche) (representing employers) and European Transport Workers' Federation (ETF) (representing employees) as the most representative European level social partner organisations in the sea fisheries sector. COPA-COGECA, representing employers in the primary sector, has also some representativeness in the sector

Representativeness of the European social partner organisations : Industrial cleaning sector

Aquesta publicació s'elabora a partir de les contribucions de cadascú dels membres nacionals que integren la Network of Eufound Correspondent. Pel cas d'Espanya la contribució ha estat realitzada per l'Alejandro GodinoThis study provides information to allow for an assessment of the representativeness of the actors involved in the European sectoral social dialogue committee for the industrial cleaning sector. Their relative representativeness legitimises their right to be consulted, their role and effective participation in the European sectoral social dialogue, and their capacity to negotiate agreements. The aim of Eurofound's representativeness studies is to identify the relevant national and European social partner organisations in the field of industrial relations in selected sectors in the EU Member States. This study identified the European Cleaning and Facility Services Industry (EFCI) (representing employers) and UNI Europa (representing employees) as the most representative European-level social partner organisations in the industrial cleaning sector

Representativeness of the European social partner organisations : human health sector

Aquesta publicació s'elabora a partir de les contribucions de cadascú dels membres nacionals que integren la Network of Eufound Correspondent. Pel cas d'Espanya la contribució ha estat realitzada per l'Oscar MolinaThis study provides information allowing for an assessment of the representativeness of the actors involved in the European sectoral social dialogue committee for the human health sector. Their relative representativeness legitimises their right to be consulted, their role and effective participation in the European sectoral social dialogue, and their capacity to negotiate agreements. The aim of Eurofound's studies on representativeness is to identify the relevant national and European social partner organisations in the field of industrial relations in the EU Member States. This study identified the European Federation of Public Service Unions (EPSU) - representing employees - and the European Hospital and Healthcare Employers' Association (HOSPEEM) - representing employers - as the most representative European-level social partner organisations in the human health sector. The member organisations of the European Confederation of Independent Trade Unions (CESI) and UNI Europa also organise employees in the sector in several Member States

Representativeness of the European social partner organisations : private security sector

Aquesta publicació s'elabora a partir de les contribucions de cadascú dels membres nacionals que integren la Network of Eufound Correspondent. Pel cas d'Espanya la contribució ha estat realitzada per l'Oscar MolinaThis study provides information allowing for an assessment of the representativeness of the actors involved in the European sectoral social dialogue committee for the private security sector. Their relative representativeness legitimises their right to be consulted, their role and effective participation in the European sectoral social dialogue and their capacity to negotiate agreements. The aim of Eurofound's representativeness studies is to identify the relevant national and European social partner organisations in the field of industrial relations in the EU Member States. This study identified the Confederation of European of Security Services (CoESS) (representing employers) and UNI Europa Private Security (representing employees) as the most representative European-level social partner organisations in the private security sector

Representativeness of the European social partner organisations : live performance sector

Aquesta publicació s'elabora a partir de les contribucions de cadascú dels membres nacionals que integren la Network of Eufound Correspondent. Pel cas d'Espanya la contribució ha estat realitzada per l'Alejandro GodinoThis study provides information allowing for an assessment of the representativeness of the actors involved in the European sectoral social dialogue committee for the live performance sector. Their relative representativeness legitimises their right to be consulted, their role and effective participation in the European sectoral social dialogue and their capacity to negotiate agreements. The aim of Eurofound's studies on representativeness is to identify the relevant national and European social partner organisations in the EU Member States. This study identified EURO-MEI, FIA and FIM - representing employees - and PEARLE* - representing employers - as the representative European-level social partner organisations in the live performance sector