Multiple cracking events in metal bi-layers on polymer substrates

Metal films on polymer substrates are used in a variety of applications such as flexible electronics, sensors, medical devices and aerospace including multilayer insulators and surface mirrors on satellites. A common way to assess the mechanical behavior of metal-polymer systems is with fragmentation testing, which strains the system under uniaxial tension. During straining cracks or localized deformation (necks) develop perpendicular to the loading direction and buckle delaminations occur parallel to the loading. From the crack spacing the fracture behavior can be determined and the interface adhesion energy can be measured from the buckles. Fragmentation testing has been used on single and multilayer films and has shown that brittle adhesion layers next to the substrate, can cause brittle cracking of normally ductile overlying films. A similar fracture behavior was observed here for the Inconel-Ag-Teflon system, but in this system, the top 30 nm Inconel film is the brittle layer inducing brittle cracking of the underlying 150 nm Ag film. Inconel acts as a corrosion protection for the Ag layer in surface mirrors on satellites in low earth orbit, where the material should not develop cracks upon mechanical loading. Observation of the Inconel surface during in-situ tensile straining revealed crack formation in the Inconel layer at less than 1% strain, which continues with increasing strain (primary cracks). At approximately 3% strain, the primary cracks in the Inconel overcoat act as stress concentrators and generate through thickness cracks in the Ag film (secondary cracks). The primary Inconel cracks had a saturation spacing of 1.5 µm, while the secondary Inconel-Ag saturation crack spacing was much larger at 12 µm. In-situ fragmentation experiments performed through the transparent Teflon substrate revealed only the secondary through thickness cracks and cross-sectional focused ion beam characterization provides further evidence for the two-stage cracking behavior. Using the shear lag model the interfacial shear stresses of the Inconel and Inconel-Ag layers were determined from the saturation crack spacings and observed fracture strains. These results further illustrate that brittle layers at any position are detrimental to the functionality of multi-layered metal-polymer systems and should be carefully considered for any application. Please click Additional Files below to see the full abstract

Electroencephalography (EEG) as a Research Tool in the Information Systems Discipline: Foundations, Measurement, and Applications

The concept of neuro-information systems (neuroIS) has emerged in the IS discipline recently. Since the neuroIS field’s genesis, several neuroIS papers have been published. Investigating empirical papers published in scientific journals and conference proceedings reveals that electroencephalography (EEG) is a widely used tool. Thus, considering its relevance in contemporary research and the fact that it will also play a major role in future neuroIS research, we describe EEG from a layman’s perspective. Because previous EEG descriptions in the neuroIS literature have only scantily outlined theoretical and methodological aspects related to this tool, we urgently need a more thorough one. As such, we inform IS scholars about the fundamentals of EEG in a compact way and discuss EEG’s potential for IS research. Based on the knowledge base provided in this paper, IS researchers can make an informed decision about whether EEG could, or should, become part of their toolbox

Analyzing and Decoding Natural Reach-and-Grasp Actions Using Gel, Water and Dry EEG Systems

Reaching and grasping is an essential part of everybody’s life, it allows meaningful interaction with the environment and is key to independent lifestyle. Recent electroencephalogram (EEG)-based studies have already shown that neural correlates of natural reach-and-grasp actions can be identified in the EEG. However, it is still in question whether these results obtained in a laboratory environment can make the transition to mobile applicable EEG systems for home use. In the current study, we investigated whether EEG-based correlates of natural reach-and-grasp actions can be successfully identified and decoded using mobile EEG systems, namely the water-based EEG-VersatileTM system and the dry-electrodes EEG-HeroTM headset. In addition, we also analyzed gel-based recordings obtained in a laboratory environment (g.USBamp/g.Ladybird, gold standard), which followed the same experimental parameters. For each recording system, 15 study participants performed 80 self-initiated reach-and-grasp actions toward a glass (palmar grasp) and a spoon (lateral grasp). Our results confirmed that EEG-based correlates of reach-and-grasp actions can be successfully identified using these mobile systems. In a single-trial multiclass-based decoding approach, which incorporated both movement conditions and rest, we could show that the low frequency time domain (LFTD) correlates were also decodable. Grand average peak accuracy calculated on unseen test data yielded for the water-based electrode system 62.3% (9.2% STD), whereas for the dry-electrodes headset reached 56.4% (8% STD). For the gel-based electrode system 61.3% (8.6% STD) could be achieved. To foster and promote further investigations in the field of EEG-based movement decoding, as well as to allow the interested community to make their own conclusions, we provide all datasets publicly available in the BNCI Horizon 2020 database (http://bnci-horizon-2020.eu/database/data-sets)

Combining brain-computer interfaces and assistive technologies: state-of-the-art and challenges

In recent years, new research has brought the field of EEG-based Brain-Computer Interfacing (BCI) out of its infancy and into a phase of relative maturity through many demonstrated prototypes such as brain-controlled wheelchairs, keyboards, and computer games. With this proof-of-concept phase in the past, the time is now ripe to focus on the development of practical BCI technologies that can be brought out of the lab and into real-world applications. In particular, we focus on the prospect of improving the lives of countless disabled individuals through a combination of BCI technology with existing assistive technologies (AT). In pursuit of more practical BCIs for use outside of the lab, in this paper, we identify four application areas where disabled individuals could greatly benefit from advancements in BCI technology, namely,“Communication and Control”, “Motor Substitution”, “Entertainment”, and “Motor Recovery”. We review the current state of the art and possible future developments, while discussing the main research issues in these four areas. In particular, we expect the most progress in the development of technologies such as hybrid BCI architectures, user-machine adaptation algorithms, the exploitation of users’ mental states for BCI reliability and confidence measures, the incorporation of principles in human-computer interaction (HCI) to improve BCI usability, and the development of novel BCI technology including better EEG devices

Does low-energy sweetener consumption affect energy intake and body weight? A systematic review, including meta-analyses, of the evidence from human and animal studies

By reducing energy density, low-energy sweeteners (LES) might be expected to reduce energy intake (EI) and body weight (BW). To assess the totality of the evidence testing the null hypothesis that LES exposure (versus sugars or unsweetened alternatives) has no effect on EI or BW, we conducted a systematic review of relevant studies in animals and humans consuming LES with ad libitum access to food energy. In 62 of 90 animal studies exposure to LES did not affect or decreased BW. Of 28 reporting increased BW, 19 compared LES with glucose exposure using a specific ‘learning’ paradigm. Twelve prospective cohort studies in humans reported inconsistent associations between LES use and Body Mass Index (-0.002 kg/m2/year, 95%CI -0.009 to 0.005). Meta-analysis of short- term randomized controlled trials (RCTs, 129 comparisons) showed reduced total EI for LES- versus sugar-sweetened food or beverage consumption before an ad libitum meal (-94 kcal, 95%CI -122 to -66), with no difference versus water (-2 kcal, 95%CI -30 to 26). This was consistent with EI results from sustained intervention RCTs (10 comparisons). Meta-analysis of sustained intervention RCTs (4 weeks to 40 months) showed that consumption of LES versus sugar led to relatively reduced BW (nine comparisons; -1.35 kg, 95%CI –2.28 to - 0.42), and a similar relative reduction in BW versus water (three comparisons; -1.24 kg, 95%CI –2.22 to -0.26). Most animal studies did not mimic LES consumption by humans, and reverse causation may influence the results of prospective cohort studies. The preponderance of evidence from all human RCTs indicates that LES do not increase EI or BW, whether compared with caloric or non-caloric (e.g., water) control conditions. Overall, the balance of evidence indicates that use of LES in place of sugar, in children and adults, leads to reduced EI and BW, and possibly also when compared with water

Short time sports exercise boosts motor imagery patterns: implications of mental practice in rehabilitation programs

Motor imagery (MI) is a commonly used paradigm for the study of motor learning or cognitive aspects of action control. The rationale for using MI training to promote the relearning of motor function arises from research on the functional correlates that MI shares with the execution of physical movements. While most of the previous studies investigating MI were based on simple movements in the present study a more attractive mental practice was used to investigate cortical activation during MI. We measured cerebral responses with functional magnetic resonance imaging (fMRI) in twenty three healthy volunteers as they imagined playing soccer or tennis before and after a short physical sports exercise. Our results demonstrated that only 10 minutes of training are enough to boost motor imagery patterns in motor related brain regions including premotor cortex and supplementary motor area (SMA) but also fronto-parietal and subcortical structures. This supports previous findings that motor imagery has beneficial effects especially in combination with motor execution when used in motor rehabilitation or motor learning processes. We conclude that sports MI combined with an interactive game environment could be a promising additional tool in future rehabilitation programs aiming to improve upper or lower limb functions or support neuroplasticity