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

Acute cardiorespiratory responses to inspiratory pressure threshold loading

This is a non-final version of an article (under the working title "Acute cardiovascular and ventilatory responses to inspiratory pressure threshold loading") published in final form in Medicine & Science in Sports & Exercise, 42(9), 1696-1703, 2010 .Purpose: We tested the acute responses to differing pressure threshold inspiratory loading intensities in well-trained rowers. The purpose of this study was to evaluate 1) how the magnitude of inspiratory pressure threshold loading influences repetition maximum (RM), tidal volume (VT), and external work undertaken by the inspiratory muscle; and 2) whether the inspiratory muscle metaboreflex is activated during acute inspiratory pressure threshold loading. Methods: Eight males participated in seven trials. Baseline measurements of maximal inspiratory pressure (PImax), resting tidal volume (VT), and forced vital capacity (FVC) were made. During the remaining sessions, participants undertook a series of resistive inspiratory breathing tasks at loads corresponding to 50%, 60%, 70%, 80%, and 90% of PImax using a pressure threshold inspiratory muscle trainer. The number of repetitions completed at each load, VT, heart rate (fc), and measures of arterial blood pressure was assessed continuously during each trial. Results: A standardized cutoff of 10% FVC was used to define the RM, which decreased as loading intensity increased (P < 0.05). This response was nonlinear, with an abrupt decrease in RM occurring at loads ≥70% of PImax. The most commonly used inspiratory muscle training regimen of 30RM corresponded to 62.5% ± 4.6% of PImax and also resulted in the highest external work output. Tidal volume (VT) decreased significantly over time at 60%, 70%, and 80% of PImax (P < 0.05), as did the amount of external work completed (P<0.05). Conclusions: Although all loads elicited a sustained increase in fc, only the 60% load elicited a sustained rise in mean arterial blood pressure (P = 0.016), diastolic blood pressure (P = 0.015), and systolic blood pressure (P = 0.002), providing evidence for a metaboreflex response at this load

Coral reef fish larvae show no evidence for map-based navigation after physical displacement

Millions of minute, newly hatched coral reef fish larvae get carried into the open ocean by highly complex and variable currents. To survive, they must return to a suitable reef habitat within a species-specific time. Strikingly, previous studies have demonstrated that return to home reefs is much more frequent than would be expected by chance. It has been shown that magnetic and sun compass orientation can help cardinalfish maintain their innate swimming direction but do they also have a navigational map to cope with unexpected displacements? If displaced settling-stage cardinalfish Ostorhinchus doederleini use positional information during their pelagic dispersal, we would expect them to re-orient toward their home reef. However, after physical displacement by 180 km, the fish showed a swimming direction indistinguishable from original directions near the capture site. This suggests that the tested fish rely on innate or learned compass directions and show no evidence for map-based navigation

The Oncological Emergency Case: Paraneoplastic Hypoglycemia in Metastatic Breast Cancer - Case Report and Brief Review of the Literature

Background: Paraneoplastic hypoglycemia is a rare syndrome amoungtumorous diseases. It is often associated with a paraneoplasticsecretion of ‘big’ insulin-like growth factor-II. Methods: We describethis syndrome in a 60-year-old patient with advanced breast cancer 8years after primary diagnosis. Results and Conclusion: This non-isletcell tumor-induced hypoglycemia may be the only evidence for anotherwise clinically occult disease progression. Fast diagnosis andappropriate acute and causal treatment concepts should be part ofoncological management

The Swift BAT-detected Seyfert 1 Galaxies: X-ray Broadband Properties and Warm Absorbers

We present results from an analysis of the broad-band, 0.3-195 keV, X-ray spectra of 48 Seyfert 1-1.5 sources detected in the very hard X-rays with the Swift Burst Alert Telescope (BAT). This sample is selected in an all-sky survey conducted in the 14-195 keV band. Therefore, our sources are largely unbiased towards both obscuration and host galaxy properties. Our detailed and uniform model fits to Suzaku/BAT and XMM-Newton/BAT spectra include the neutral absorption, direct power-law, reflected emission, soft excess, warm absorption, and narrow Fe K-alpha emission properties for the entire sample. We significantly detect O VII and O VIII edges in 52% of our sample. The strength of these detections are strongly correlated with the neutral column density measured in the spectrum. Among the strongest detections, X-ray grating and UV observations, where available, indicate outflowing material. The ionized column densities of sources with O VII and O VIII detections are clustered in a narrow range with N$_{\rm warm} \sim 10^{21}$\,cm$^{-2}$, while sources without strong detections have column densities of ionized gas an order of magnitude lower. Therefore, we note that sources without strong detections likely have warm ionized outflows present but at low column densities that are not easily probed with current X-ray observations. Sources with strong complex absorption have a strong soft excess, which may or may not be due to difficulties in modeling the complex spectra of these sources. Still, the detection of a flat Gamma ~ 1 and a strong soft excess may allow us to infer the presence of strong absorption in low signal-to-noise AGN spectra. Additionally, we include a useful correction from the Swift BAT luminosity to bolometric luminosity, based on a comparison of our spectral fitting results with published spectral energy distribution fits from 33 of our sources.Comment: 60 pages (pre-print format), 14 figures, accepted to Ap

Itaconic acid indicates cellular but not systemic immune system activation

Itaconic acid is produced by mammalian leukocytes upon pro-inflammatory activation. It appears to inhibit bacterial growth and to rewire the metabolism of the host cell by inhibiting succinate dehydrogenase. Yet, it is unknown whether itaconic acid acts only intracellularly, locally in a paracrine fashion, or whether it is even secreted from the inflammatory cells at meaningful levels in peripheral blood of patients with severe inflammation or sepsis. The aim of this study was to determine the release rate of itaconic acid from pro-inflammatory activated macrophages in vitro and to test for the abundance of itaconic acid in bodyfluids of patients suffering from acute inflammation. We demonstrate that excretion of itaconic acid happens at a low rate and that it cannot be detected in significant amounts in plasma or urine of septic patients or in liquid from bronchial lavage of patients with pulmonary inflammation. We conclude that itaconic acid may serve as a pro-inflammatory marker in immune cells but that it does not qualify as a biomarker in the tested body fluids