Synthesis, characterisation, and utilisation of copper nanoflower for biocementation for ground improvement applications

Microbially-induced calcium carbonate precipitation (MICP) has recently emerged as a sustainable ground improvement method. Nevertheless, the technique’s applicability in soils with narrow pore throats has been queried. To overcome these challenges, the use of enzymes (including bacterially produced enzymes) was proposed for these soils. However, the use of free enzymes entails many challenges linked predominantly to the limited enzyme supply, the poor stability of the enzyme once released into the soil, and the poor reusability of the enzyme. This paper studies the use of nano enzymes with a high biocementation efficacy for carbonic anhydrase (CA) enzyme delivery as one possible way to overcome potentially these challenges. CA enzyme was used because it has the potential to be an environmentally sustainable biocementation pathway due to its ability to sequester CO2 for biocement production. The paper presents the synthesis, characterisation, and utilisation of CA-enwrapped copper phosphate-based inorganic hybrid nanoflowers for innovative delivery and enzyme stabilisation due to the enhanced thermal and enzyme activity efficiency and due to their reusability, if recovered at the end of the treatment. The results from this study show that the bovine carbonic anhydrase enzyme enhanced the CO2 hydration reaction, resulting in a bioprecipitation reaction and the production of calcium carbonate and increased strength of treated soil with 500kPa for free CA and approximately 1000kPa for the hybrid CA-Cu. The material analysis confirmed calcite as the primary precipitate formed, which would act as a bonding agent between soil particles for ground improvement applications

Biocementation mediated by native Carbonic Anhydrase-producing microbes.

This study investigated the feasibility of biocementing a fine-grained foundation soil from the East Anglia railway network via the carbonic anhydrase (CA) pathway. This pathway is a promising way of improving the mechanical properties of soils by biocementation while sequestering CO2 during the process. To achieve the aim of this research, forty CA-producing bacterial isolates from soil layers below a railway embankment in East Anglia, UK, were screened and selected using a qualitative CA activity assay. Three of these bacteria expressed high and stable CA enzyme activity and were further characterised by their morphological, molecular, and enzyme profile characteristics. Bioaugmentation was then employed to biocement the soil from the site using the native CA-producing bacteria isolated from the soil. The unconfined compressive strength and calcite content of the treated soil were determined. Preliminary results showed a substantial increase in soil unconfined compressive strength upon biocementation treatment. Although further geotechnical testing is the subject of future work, the unconfined compressive strength and calcite content results obtained so far proved biocementation of the fine-grained soil and showed promise that the CA biocementation route can be further developed as a successful and environmentally friendly soil stabilization technique, with the added advantage of sequestering CO2 from the atmosphere or using captured waste CO2, during the biocementation process

Concurrent Carbon Capture and Biocementation through the Carbonic Anhydrase (CA) activity of microorganisms ‑ a review and outlook

Biocementation, i.e., the production of biomimetic cement through the metabolic activity of microorganisms, offers exciting new prospects for various civil and environmental engineering applications. This paper presents a systematic literature review on a biocementation pathway, which uses the carbonic anhydrase (CA) activity of microorganisms that sequester CO2 to produce biocement. The aim is the future development of this technique for civil and (geo-)environmental engineering applications towards CO2-neutral or negative processes. After screening 248 potentially relevant peer-reviewed journal papers published between 2002 and 2023, 38 publications studying CA-biocementation were considered in the review. Some of these studies used pure CA enzyme rather than bacteria-produced CA. Of these studies, 7 used biocementation for self-healing concrete, 6 for CO2 sequestration, 10 for geotechnical applications, and 15 for (geo-)environmental applications. A total of 34 bacterial strains were studied, and optimal conditions for their growth and enzymatic activity were identified. The review concluded that the topic is little researched; more studies are required both in the laboratory and field (particularly long-term field experiments, which are totally lacking). No studies on the numerical modelling of CA-biocementation and the required kinetic parameters were found. The paper thus consulted the more widely researched field of CO2 sequestration using the CA-pathway, to identify other microorganisms recommended for further research and reaction kinetic parameters for numerical modelling. Finally, challenges to be addressed and future research needs were discussed

Towards the Development of Sustainable Ground Improvement Techniques —Biocementation Study of an Organic Soil

Ongoing research effort is dedicated to the development of innovative, superior and cost-effective ground improvement techniques to mitigate natural and man-made hazards while minimising waste and other environmental impacts. In this context, the nature-based process of biocementation of soils has been proposed as a potentially more sustainable technique than conventional chemical ground improvement practices. This paper focuses on the biocementation of an organic soil of the UK railway network. Having recently proven the feasibility of biocementing this soil using indigenous ureolytic bacteria, in this paper, the authors perform a parametric study to identify treatments successful in increasing the strength of the soil. Selected treatments are then applied to the soil to assess its volume change during consolidation, secondary compression and shrinkage upon drying. The results show that, depending on the treatments used, biocementation has increased the unconfined compressive strength by up to 81% compared to that of the control samples. For selected treatments and the range of water contents tested (55–33%), shrinkage upon drying reduced by 16%, while the volumetric strains of the soil upon 1-D compression reduced by 32–47%. This was reflected in the values of the coefficient of volume compressibility and the coefficient of secondary compression (the latter either reduced by up to an order of magnitude or secondary compression was not observed altogether in the testing period). Overall, the results proved that biocementation improved considerably the mechanical properties of the organic soil, which gives promise for addressing the settlement problems of this soil

The evolution of galaxy groups and of galaxies therein

Properties of groups of galaxies depend sensitively on the algorithm for group selection, and even the most recent catalogs of groups built from redshift-space selection should suffer from projections and infalling galaxies. The cosmo-dynamical evolution of groups from initial Hubble expansion to collapse and virialization leads to a fundamental track (FT) in virial-theorem-M/L vs crossing time. The increased rates of mergers, both direct and after dynamical friction, in groups relative to clusters, explain the higher fraction of elliptical galaxies at given local number density in X-ray selected groups, relative to clusters, even when the hierarchical evolution of groups is considered. Galaxies falling into groups and clusters should later travel outwards to typically 2 virial radii, which is somewhat less than the outermost radius where observed galaxy star formation efficiencies are enhanced relative to field galaxies of same morphological type. An ongoing analysis of the internal kinematics of X-ray selected groups suggests that the radial profiles of line of sight velocity dispersion are consistent with isotropic NFW distributions for the total mass density, with higher (lower) concentrations than LambdaCDM predictions in groups of high (low) mass. The critical mass, at M200 ~ 10^13 M_sun is consistent with possible breaks in the X-ray luminosity-temperature and Fundamental Plane relations. The internal kinematics of groups indicate that the M-T relation of groups should agree with that extrapolated from clusters with no break at the group scale. The analyses of observed velocity dispersion profiles and of the FT both suggest that low velocity dispersion groups (compact and loose, X-ray emitting or undetected) are quite contaminated by chance projections.Comment: Invited review, ESO workshop "Groups of Galaxies in the Nearby Universe", held in Santiago, Chile, 5-9 December 2005, ed. I. Saviane, V. Ivanov & J. Borissova, 16 page

Dynamic Evolution of a Quasi-Spherical General Polytropic Magnetofluid with Self-Gravity

In various astrophysical contexts, we analyze self-similar behaviours of magnetohydrodynamic (MHD) evolution of a quasi-spherical polytropic magnetized gas under self-gravity with the specific entropy conserved along streamlines. In particular, this MHD model analysis frees the scaling parameter $n$ in the conventional polytropic self-similar transformation from the constraint of $n+\gamma=2$ with $\gamma$ being the polytropic index and therefore substantially generalizes earlier analysis results on polytropic gas dynamics that has a constant specific entropy everywhere in space at all time. On the basis of the self-similar nonlinear MHD ordinary differential equations, we examine behaviours of the magnetosonic critical curves, the MHD shock conditions, and various asymptotic solutions. We then construct global semi-complete self-similar MHD solutions using a combination of analytical and numerical means and indicate plausible astrophysical applications of these magnetized flow solutions with or without MHD shocks.Comment: 21 pages, 7 figures, accepted for publication in APS

New values of time and reliability in passenger transport in The Netherlands

We have established new values of time (VOTs) and values of travel time reliability (VORs) for use in cost-benefit analysis (CBA) of transport projects in The Netherlands. This was the first national study in The Netherlands (and one of the first world-wide) to investigate these topics empirically in a joint framework. Stated preference (SP) questionnaires were designed for interviewing travellers, where the hypothetical alternatives were described in terms of travel time, travel costs and travel time reliability, the latter being presented to the respondents in the form of five possible travel times having equal probability. For passenger transport, we first collected interviews using an existing internet panel. Additional data collection recruitment was done by asking travellers at petrol stations/service areas, parking garages, stations, bus stops, airports and ports to participate in the survey. One important conclusion is that the SP survey using members of this internet panel leads to substantially lower VOTs than the SP survey with en-route recruitment, probably because of self-selection bias in the internet panel. We estimated discrete choice models in which the values of time differ between trips with different time and costs levels, different time and costs changes offered in the SP, and different observed characteristics of the respondents (e.g. education, income, age, household composition). By using a panel latent class model, we also account for unobserved differences between respondents in the value of time and for repeated measurements/panel effects. The reference values of time and the reference reliability ratios were estimated on the 2011 sample only, but the effect of time and cost level, time and cost changes offered and socio-economic attributes was estimated on both the 2009 and 2011 samples

Human Embryonic Stem Cell Technology: Large Scale Cell Amplification and Differentiation

Embryonic stem cells (ESC) hold the promise of overcoming many diseases as potential sources of, for example, dopaminergic neural cells for Parkinson’s Disease to pancreatic islets to relieve diabetic patients of their daily insulin injections. While an embryo has the innate capacity to develop fully functional differentiated tissues; biologists are finding that it is much more complex to derive singular, pure populations of primary cells from the highly versatile ESC from this embryonic parent. Thus, a substantial investment in developing the technologies to expand and differentiate these cells is required in the next decade to move this promise into reality. In this review we document the current standard assays for characterising human ESC (hESC), the status of ‘defined’ feeder-free culture conditions for undifferentiated hESC growth, examine the quality controls that will be required to be established for monitoring their growth, review current methods for expansion and differentiation, and speculate on the possible routes of scaling up the differentiation of hESC to therapeutic quantities