Computational Modelling of Electrical Properties of Thyroid and Parathyroid Tissue

Parathyroid gland identification is an important consideration in order to decrease the inci- dence of post-surgical complications associated with thyroid surgeries. Electrical Impedance Spectroscopy (EIS) based tissue differentiation recently emerged as a promising non-invasive technique that could enhance the tissues separation, and parathyroid preservation in a surgery setting. The aim of the work presented in this thesis is to implement a computational modelling approach in order to elucidate the differences between healthy thyroid and parathyroid tissue impedance spectra which could permit their differentiation during surgery. Multiscale finite element thyroid and parathyroid models have been constructed with the main objective to investigate the impact of morphology and composition on the bulk electrical behaviour of both tissues. The multiscale pipeline represents the hierarchical tissue structure from cellu- lar to tissue scale including a novel mesoscale for the thyroid follicular arrangements. A comprehensive inter- and intracompartmental sensitivity study provided an insight into the impact of the variations in geometrical and electrical properties of tissue structures on electrical impedance spectra of both tissue types suggesting a successful separability between the computed thyroid and parathyroid impedance spectra indices. Moreover, the modelled results obtained through the variation of geometrical parameters demonstrating the natural variability in tissue morphology provided a good agreement with the in vivo measured data acquired and published by Hillary et al. In addition, the verification of selected homogeneity assumptions and the exploration of measurement accuracy and di↵erent probe configurations provided further recommendations for future work concerning computational modelling, experimental data collection and EIS device design improvements. In particular, the outcomes of this computational study re- vealed the importance of additional experimental work concerning the electrical properties measurements of biological tissue materials, and the significance of tissue preparation and measurement accuracy in obtaining thyroid and parathyroid measurements with a tetrapolar EIS probe

The use of virtual tissue constructs that include morphological variability to assess the potential of electrical impedance spectroscopy to differentiate between thyroid and parathyroid tissues during surgery

Electrical impedance spectroscopy (EIS) has been proposed as a promising noninvasive method to differentiate healthy thyroid from parathyroid tissues during thyroidectomy. However, previously reported similarities in the in vivo measured spectra of these tissues during a pilot study suggest that this separation may not be straightforward. We utilise computational modelling as a method to elucidate the distinguishing characteristics in the EIS signal and explore the features of the tissue that contribute to the observed electrical behaviour. Firstly, multiscale finite element models (or ‘virtual tissue constructs’) of thyroid and parathyroid tissues were developed and verified against in vivo tissue measurements. A global sensitivity analysis was performed to investigate the impact of physiological micro-, meso- and macroscale tissue morphological features of both tissue types on the computed macroscale EIS spectra and explore the separability of the two tissue types. Our results suggest that the presence of a surface fascia layer could obstruct tissue differentiation, but an analysis of the separability of simulated spectra without the surface fascia layer suggests that differentiation of the two tissue types should be possible if this layer is completely removed by the surgeon. Comprehensive in vivo measurements are required to fully determine the potential for EIS as a method in distinguishing between thyroid and parathyroid tissues

Synthesis of prebiotic galactooligosaccharides from lactose using bifidobacterial β-galactosidase (BbgIV) immobilised on DEAE-Cellulose, Q-Sepharose and amino-ethyl agarose

The bifidobacterial β-galactosidase BbgIV was immobilised on DEAE-Cellulose and Q-Sepharose via ionic binding and on amino-ethyl- and glyoxal-agarose via covalent attachment, and was then used to catalyse the synthesis of galactooligosaccharides (GOS). The immobilisation yield exceeded 90 % using ionic binding, while it was low using aminoethyl agarose (25 – 28 %) and very low using glyoxal agarose (< 3 %). This was due to the mild conditions and absence of chemical reagents in ionic binding, compared to covalent attachment. The maximum GOS yield obtained using DEAE-Cellulose and Q-Sepharose was similar to that obtained using free BbgIV (49 – 53 %), indicating the absence of diffusion limitation and mass transfer issues. For amino-ethyl agarose, however, the GOS yield obtained was lower (42 – 44 %) compared to that obtained using free BbgIV. All the supports tried significantly (P < 0.05) increased the BbgIV operational stability and the GOS synthesis productivity up to 55 °C. Besides, six successive GOS synthesis batches were performed using BbgIV immobilised on Q-Sepharose; all resulted in similar GOS yields, indicating the possibility of developing a robust synthesis process. Overall, the GOS synthesis operation performance using BbgIV was improved by immobilising the enzyme onto solid supports, in particular on Q-Sepharos

Integrating hydrological modelling and ecosystem functioning for environmental flows in climate change scenarios in the Zambezi River (Zambezi Region, Namibia)

The Zambezi-Chobe wetlands in Namibia are of great international importance for trans-boundary water management because of their remarkable ecological characteristics and the variety and magnitude of the ecosystem services provided. The main objective of this study is to establish the hydro-ecological baseline for the application of environmental flow regimes (EFR). The specific objectives are: (i) the assessment of environmental flow components (EFC) in the current near-natural hydrological conditions; (ii) the generation of future scenarios for climatic and socioeconomic changes; (iii) the estimation of the area duration curves and estimated annual habitat during the inundation of the critical habitats for fisheries (mulapos), under the existing conditions and future scenarios; and (iv) to provide a framework for the future application of EFRs, based on hydrological and ecological processes. To make a sound analysis of the ecological implications, first we develop a conceptual framework of the linkages between the hydrological and biological processes concerning fish communities, because of the critical role of fisheries in the region. The EFCs in near-natural hydrological conditions provide the basis for developing interim EFRs in the region, within the framework of an adaptive management of water resources. The future scenarios indicate a mitigation of the flow variability; and, in the worst-case scenario, the reduction of the maximum flow and inundated area of the mulapos would result in a reduction of the estimated annual habitat of 22%. This means a reduction in the spawning habitats for quiet-water species, in the food resources for fry and juvenile fish and a consequent reduction in fish stocks. Furthermore, the habitat loss during low events is similar and greater under both scenarios, at ca. 35%. Here we corroborate that the EFCs and their variability may become the building blocks of flow-ecology models that lead to environmental flow recommendations, monitoring and research programmes and flow protection activities.This research was part of the research project CERPA (Certification of Protected Areas), funded by the German Federal Ministry of Education and Research (BMBF), and focused on the evaluation of new market-based instruments for biodiversity conservation and their socioeconomic implications. The authors also thank two anonymous reviewers who provided substantial input that improved the manuscript. The study has been partially funded by the national research project IMPADAPT (CGL2013-48424-C2-1-R), with MINECO (Spanish Ministry of Economy) and FEDER funds.Martinez-Capel, F.; García López, L.; Beyer, M. (2017). Integrating hydrological modelling and ecosystem functioning for environmental flows in climate change scenarios in the Zambezi River (Zambezi Region, Namibia). River Research and Applications. 33(2):258-275. https://doi.org/10.1002/rra.3058S25827533

Galacto-Oligosaccharides : production, properties, applications, and significance as prebiotics

Galacto-oligosaccharides (GOS) have now been definitely established as prebiotic ingredients after in vitro and animal and human in vivo studies. Currently, GOS are produced by glycoside hydrolases (GH) using lactose as substrate. Converting lactose into GOS by GH results in mixtures containing GOS of different degrees of polymerization (DP), unreacted lactose, and monomeric sugars (glucose and galactose). Recent and future developments in the production of GOS aim at delivering purer and more efficient mixtures. To produce high-GOS-content mixtures, GH should not only have good ability to catalyze the transgalactosylation reaction relative to hydrolysis, but also have low affinity for the GOS formed relative to the affinity for lactose. In this article, several microbial GH, proposed for the synthesis of GOS, are hierarchized according to the referred performance indicators. In addition, strategies for process improvement are discussed. Besides the differences in purity of GOS mixtures, differences in the position of the glycosidic linkages occur, because different enzymes have different regiochemical selectivity. Depending on oligosaccharide composition, GOS products will vary in terms of prebiotic activity, as well as other physiological effects. This review focuses on GOS production from synthesis to purification processes. Physicochemical characteristics, physiological effects, and applications of these prebiotic ingredients are summarized. Regulatory aspects of GOS-containing food products are also highlighted with emphasis on the current process of health claims evaluation in Europe.Agência da Inovação-Progama IDEIA (Portugal)Fundação para a Ciência e a Tecnologia (FCT

Floodplain restoration planning for a changing climate: Coupling flow dynamics with ecosystem benefits

This dissertation addresses the role that dynamic flow characteristics play in shaping the potential for significant ecosystem benefits from floodplain restoration. Mediterranean-climate river systems present challenges for restoring healthy floodplains because of the inter and intra-annual variability in stream flow, which has been dramatically reduced in an effort to control flooding and to provide a more consistent year-round water supply for human use. Habitat restoration efforts require that this reduced stream flow be altered in order to recover more naturally dynamic flow patterns and reconnect floodplains. This thesis defines and takes advantage of an eco-hydrology modeling framework to reveal how the ecological returns of different hydrologic alterations or restoration scenarios—including changes to the physical landscape and flow dynamics—influence habitat connectivity for freshwater biota. A method for quantifying benefits of expanding floodplain connectivity can highlight actions that might simultaneously reduce flood risk and restore ecological functions, such as supporting fish habitat benefits, food web productivity, and riparian vegetation establishment

Floodplain restoration planning for a changing climate: Coupling flow dynamics with ecosystem benefits

This dissertation addresses the role that dynamic flow characteristics play in shaping the potential for significant ecosystem benefits from floodplain restoration. Mediterranean-climate river systems present challenges for restoring healthy floodplains because of the inter and intra-annual variability in stream flow, which has been dramatically reduced in an effort to control flooding and to provide a more consistent year-round water supply for human use. Habitat restoration efforts require that this reduced stream flow be altered in order to recover more naturally dynamic flow patterns and reconnect floodplains. This thesis defines and takes advantage of an eco-hydrology modeling framework to reveal how the ecological returns of different hydrologic alterations or restoration scenarios--including changes to the physical landscape and flow dynamics--influence habitat connectivity for freshwater biota. A method for quantifying benefits of expanding floodplain connectivity can highlight actions that might simultaneously reduce flood risk and restore ecological functions, such as supporting fish habitat benefits, food web productivity, and riparian vegetation establishment. Pending climate change increases the uncertainty of restoration treatment outcomes yet must be addressed as part of the restoration planning process. An ecologically-oriented assessment of the current and potential future stream flow characteristics of selected Central Valley rivers makes it clear that climate change will affect future floodplain habitat function. Findings show that the low emissions (warm-wet) climate change scenario allows for higher flows at longer durations compared to the historical post-dam record and the high emissions (hot-dry) scenario. In fact, the low-emissions scenario flows might be more similar to pre-dam flow regimes--peak magnitudes in particular--than to the current regulated flow regime. The high emissions scenario can serve as a measure for the lower bounds of functional floodplain area for ecological benefit. Planning for potential impacts of climate change on flow dynamics will be essential if restoration managers are to minimize negative consequences of climate change and maximize the potential benefits that it may offer for species recovery. Efforts to plan and evaluate floodplain reconnection projects for ecological benefits have been hindered by a lack of metrics that allow for comparisons among alternative restoration sites with respect to the type and quality of dynamic habitat potential. This dissertation presents a framework for quantifying the benefits of floodplain restoration projects by coupling the spatial and temporal characteristics of floodplains to express the functional habitat they create. First, habitat was quantified using Area-Duration-Frequency (ADF) curves for several durations and across multiple frequencies of flood occurrence. From these data, a value was then generated for expected annual habitat (EAH). The method has advantages in framing the potential restored area in terms of probabilities based on dynamics of flow timing, durations, and frequencies. The EAH metric captures a comprehensive picture of the likelihood of flooded areas appearing in any given year. This method can be used to design projects to meet specific and measurable habitat objectives. These methods and new metrics provide a transparent and replicable means to examine the effects and relative importance of policy decisions and river restoration projects. To illustrate this modeling method, statistical flow characteristics needed to support floodplain benefit for species were coupled with topographic alteration scenarios for increasing beneficial habitat along the Vernalis to Mossdale corridor on the San Joaquin River, California. Findings for a suite of species that span a range of necessary flow requirements exemplify a wide array of impacts associated with flow scenarios for the San Joaquin River system. Most importantly, the modeled results predict significant declines in the availability of required flow related habitat conditions for splittail spawning and rearing and Chinook salmon rearing in the future under two climate change scenarios. Physical habitat restoration must be paired with additional in-stream flows to meet frequency, duration, and seasonal requirements for these species. Thus, restoration treatment considerations for floodplain habitat should not only include physical alterations for additional channel floodplain connectivity, but also restore a more natural flow regime to increase habitat area and frequency of inundation. Restoration planning often fails to follow strategies based on assessments of ecological benefit outcomes and cost effectiveness. A hydro-ecological approach was applied to multiple modeled floodplain restoration sites along California's Sacramento River and was integrated with socio-economic considerations into a prioritization scheme. The new EAH and ADF metrics were used to assess probabilities for ecological outcomes for increased salmon rearing habitat and combined with land value cost for parcels in the restoration areas. The model was used to assess individual and cumulative benefits of 26 floodplain rehabilitation options involving levee setbacks and examine the consequences of changing topography and climate for floodplain habitat along a large expanse of the Sacramento River. Cumulative effects of projects implemented concurrently showed only small changes in functional floodplain habitat creation. Climate change flow scenarios for this section of the Sacramento River indicate that the functional EAH habitat under a low emissions (warm-wet) regime overlaps with that created for restoration sites under the current flow regime. However, the high emissions (hot-dry) regime will create less functional habitat and serves as a good lower bound of expectations for any restoration plan. By adding to ecological outcome measures and integrating environmental benefits into a cost effectiveness ratio, some projects' priority rankings shift. Thus, cost effectiveness is relevant for informing decisions about restoration site priorities and could improve the way funds are allocated to restoration options. This study advances mitigation planning at a local and regional scale by providing tools for quantitative estimates of potential habitat that could be restored, for assessing projects individually and cumulatively, and for comparing and prioritizing sites using an analytical cost effectiveness approach.In sum, this dissertation presents a modeling framework and new quantitative metrics that can be used to plan and evaluate floodplain restoration projects that address connectivity and dynamic flows, whether they are the result of climate change or prescribed reservoir release flows. Restoration options for multiple locations in California's Central Valley were investigated to demonstrate the utility of this approach. The method has advantages in estimating the potential restored area in terms of probabilities based on dynamics of flow timing, durations, and frequencies. Ultimately, using integrative hydro-ecological models offers support for decision makers considering where to rehabilitate floodplain processes upon which biological and social benefits depend