Effects of gas hydrates dissociation on clays and submarine slope stability

Gas hydrate dissociation is often considered as a precursor or triggering factor for submarine slope failures occurring in relatively deep waters where the bulk of the gas hydrate is found in fine-grained sediments. However, there are actually relatively few studies that focus on the effect of gas hydrate dissociation on the behavior of clays, and very few on what physically happens to clay during and after the dissociation process and how gas hydrate dissociation affects the geotechnical properties of clays. In this paper, we illustrate the effects of hydrate dissociation in clays from laboratory strength tests (direct simple shear) combined with visualization including very-high-resolution 3D imaging (computed tomography), using R11 as the hydrate forming fluid in both laponite and Onsøy clay. The test results reveal that the hydrate dissociation creates bubbles in the surrounding clay matrix and around pipe/well models. In addition, we use CO₂-saturated water as the pore fluid in soft clay, and test results show that cracks may develop, allowing gas migration to take place after reducing back pressure in an oedometer cell. Direct simple shear tests show that the undrained shear strength decreases by up to ～15% due to this process. The test results were then implemented in a 2D finite element model to assess the influence of hydrate dissociation on submarine slope stability. We chose a slope segment west of Svalvard—an area where methane gas bubbles escape from the seabed. The gas bubbling in this area is likely due to climate-controlled hydrate-dissociation (warming of bottom water masses). In the finite-element model, we include the change of methane hydrate stability zone (MHSZ) with time as well as the hydrate-dissociation-induced failure zone, which may be a potential leakage pathway. The numerical study indicates that the hydrate dissociation caused by bottom water warming is unlikely to be the main cause generating a leakage pathway or failure plane. However, the hydrate dissociation causing the reduction in shear strength facilitates a potentially unstable condition. The results imply that the hydrate dissociation may contribute to slope failure as a secondary driver, but are unlikely the main driving force. The aim of this study was to improve our understanding of the physical processes of gas expansion, migration and effect of hydrate dissociation through visualization and a finite element model. In addition, this study discussed methods to detect gas hydrate through a case study, and it was found possible to predict average gas hydrate saturation at sites where the sulfate-methane transition depth is known.     

Receptive Field Sizes of Nyxnob Mouse Retinal Ganglion Cells

Patients with congenital nystagmus, involuntary eye movements, often have a reduced visual acuity. Some of these patients have a retinal-specific mutation in the protein nyctalopin, which is also present in the Nyx^nob mouse. In these mice, retinal ganglion cells (RGCs) have oscillatory activity, which leads to expanded axonal projections towards the dLGN and consequently to a desegregation of retinal projections to the brain. In this study, we investigate whether the receptive fields of Nyx^nob RGCs have also expanded by measuring the size of their receptive fields using MEA recordings. Contrary to our expectation, relative to wild-type (WT) mice we found receptive field sizes in the Nyx^nob retina had not increased but instead had decreased for green-light preferring RGCs. Additionally, we also found the receptive fields of UV-light preferring RGCs are larger than green-light preferring RGCs in both WT and Nyx^nob mice.     

Commensurability between Element Symmetry and the Number of Skyrmions Governing Skyrmion Diffusion in Confined Geometries

Magnetic skyrmions are topological magnetic structures, which exhibit quasi-particle properties and can show enhanced stability against perturbation from thermal noise. Recently, thermal Brownian diffusion of these quasi-particles has been found in continuous films, and unconventional computing applications have received significant attention, requiring structured elements. Thus, as the next necessary step, skyrmion diffusion in confined geometries is studied, and it is found to be qualitatively different: The diffusion is governed by the interplay between the total number of skyrmions and the structure geometry. In particular, the effect of circular and triangular geometrical confinement is ascertained. It is found that for triangular geometries, the behavior is drastically different for the cases when the number of skyrmions in the element is either commensurate or incommensurate with a symmetric filling of the element. This influence of commensurability is corroborated by simulations of a quasi-particle model.     

Beer quality screening by FT-IR spectrometry: Impact of measurement strategies, data pre-processings and variable selection algorithms

In the presented research three measurement strategies of Fourier transform infrared (FT-IR) spectrometry (horizontal- and micro-attenuated total reflection (HATR and μATR, respectively) and a novel high throughput transmission (HTT)) in combination with extensive chemometric approach have been applied for analysis of beer. Fifty Belgian beer samples were analyzed: lager and white beers, dark and blonde ales, lambic and Trappist beers. Partial least square (PLS) regression was used for prediction of different physicochemical parameters of beer based on mid-IR data, modified with different spectral preprocessing and variable selection algorithms for higher prediction performance. It was found that HATR and μATR have the same prediction capability with a slight advantage of μATR and excellent correlations between spectra and reference values were demonstrated for original (R² 0.95), apparent (R² 0.89) and real (R² 0.95) extracts, real and apparent degrees of fermentation (R² 0.91 and 0.89), alcohol content (R² 0.94) and energetic value (R² 0.95). Good results (R² 0.83) were obtained from the HTT experiments for prediction of real extract and allow measurement of large sample numbers in short time (1 sample/minute) with further potential increase in a sample throughput and has the possibility for automation. The obtained results indicate that mid-IR spectrometry in combination with advanced pre-processing and variable selection methods is a valuable analytical tool for high throughput measurement of beer quality attributes and thus has potential for use in product development and quality control.     

Toward quantifying metrics for rail-system resilience: identification and analysis of performance weak resilience signals

This paper aims to enhance tangibility of the resilience engineering concept by facilitating understanding and operationalization of weak resilience signals (WRSs) in the rail sector. Within complex socio-technical systems, accidents can be seen as unwanted outcomes emerging from uncontrolled sources of entropy (functional resonance). Various theoretical models exist to determine the variability of system interactions, the resilience state and the organization’s intrinsic abilities to reorganize and manage their functioning and adaptive capacity to cope with unexpected and unforeseen disruptions. However, operationalizing and measuring concrete and reliable manifestations of resilience and assessing their impact at a system level have proved to be a challenge. A multi-method, ethnographic observation and resilience questionnaire, were used to determine resilience baseline conditions at an operational rail traffic control post. This paper describes the development, implementation and initial validation of WRSs identified and modeled around a ‘performance system boundary.’ In addition, a WRS analysis function is introduced to interpret underlying factors of the performance WRSs and serves as a method to reveal potential sources of future resonance that could comprise system resilience. Results indicate that performance WRSs can successfully be implemented to accentuate relative deviations from resilience baseline conditions. A WRS analysis function can help to interpret these divergences and could be used to reveal (creeping) change processes and unnoticed initiating events that facilitate emergence that degrades rail-system resilience. Establishing relevant change signals in advance can contribute to anticipation and awareness, enhance organizational learning and stimulate resilient courses of action and adaptive behavior that ensures rail operation reliability.     

Efficient Synthesis of Peptide and Protein Functionalized Pyrrole-Imidazole Polyamides Using Native Chemical Ligation

The advancement of DNA-based bionanotechnology requires efficient strategies to functionalize DNA nanostructures in a specific manner with other biomolecules, most importantly peptides and proteins. Common DNA-functionalization methods rely on laborious and covalent conjugation between DNA and proteins or peptides. Pyrrole-imidazole (Py–Im) polyamides, based on natural minor groove DNA-binding small molecules, can bind to DNA in a sequence specific fashion. In this study, we explore the use of Py–Im polyamides for addressing proteins and peptides to DNA in a sequence specific and non-covalent manner. A generic synthetic approach based on native chemical ligation was established that allows efficient conjugation of both peptides and recombinant proteins to Py–Im polyamides. The effect of Py–Im polyamide conjugation on DNA binding was investigated by Surface Plasmon Resonance (SPR). Although the synthesis of different protein-Py–Im-polyamide conjugates was successful, attenuation of DNA affinity was observed, in particular for the protein-Py–Im-polyamide conjugates. The practical use of protein-Py–Im-polyamide conjugates for addressing DNA structures in an orthogonal but non-covalent manner, therefore, remains to be established.     

Graceful extensibility in asset management: extending the capacity to adapt in managing cyber-physical railway systems

Cognition, Technology & Work - Graceful extensibility has been recently introduced and can be defined as the ability of a system to extend its capacity to adapt when surprise events challenge...     

Urban renewal without displacement? Belgium’s ‘housing contract experiment’ and the risks of gentrification

Gentrification has become part and parcel of urban policies throughout the world. Critics have argued against those policies but they have not yet developed concrete and comprehensive alternatives. This paper seeks to remedy this omission by investigating the Belgian ‘housing contract’ experiment (2005–2007). Quite exceptionally, Belgium’s ‘housing contract’ experiment was based on the premise that housing policies should improve the quality of life in deprived urban neighborhoods without displacing the poor. We investigate both the philosophy of the housing contract experiment as well as its effects. On the basis of this evaluation, we sketch the contours of a housing policy that incorporates rent gap theory and counters the negative effects arising from disinvestment and gentrification.