Now showing items 1-20 of 514

• #### Modelling the effects of glucagon during glucose tolerance testing.

BACKGROUND:Glucose tolerance testing is a tool used to estimate glucose effectiveness and insulin sensitivity in diabetic patients. The importance of such tests has prompted the development and utilisation of mathematical models that describe glucose kinetics as a function of insulin activity. The hormone glucagon, also plays a fundamental role in systemic plasma glucose regulation and is secreted reciprocally to insulin, stimulating catabolic glucose utilisation. However, regulation of glucagon secretion by α-cells is impaired in type-1 and type-2 diabetes through pancreatic islet dysfunction. Despite this, inclusion of glucagon activity when modelling the glucose kinetics during glucose tolerance testing is often overlooked. This study presents two mathematical models of a glucose tolerance test that incorporate glucose-insulin-glucagon dynamics. The first model describes a non-linear relationship between glucagon and glucose, whereas the second model assumes a linear relationship. RESULTS:Both models are validated against insulin-modified and glucose infusion intravenous glucose tolerance test (IVGTT) data, as well as insulin infusion data, and are capable of estimating patient glucose effectiveness (sG) and insulin sensitivity (sI). Inclusion of glucagon dynamics proves to provide a more detailed representation of the metabolic portrait, enabling estimation of two new diagnostic parameters: glucagon effectiveness (sE) and glucagon sensitivity (δ). CONCLUSIONS:The models are used to investigate how different degrees of pax'tient glucagon sensitivity and effectiveness affect the concentration of blood glucose and plasma glucagon during IVGTT and insulin infusion tests, providing a platform from which the role of glucagon dynamics during a glucose tolerance test may be investigated and predicted.
• #### Developing A High-performance Liquid Chromatography Method for Simultaneous Determination of Loratadine and its Metabolite Desloratadine in Human Plasma.

Allergic diseases are considered among the major burdons of public health with increased prevalence globally. Histamine H1-receptor antagonists are the foremost commonly used drugs in the treatment of allergic disorders. Our target drug is one of this class, loratadine and its biometabolite desloratadine which is also a non sedating H1 receptor antagonist with anti-histaminic action of 2.5 to 4 times greater than loratadine. To develop and validate a novel isocratic reversed-phase high performance liquid chromatography (RP-HPLC) method for rapid and simultaneous separation and determination of loratadine and its metabolite, desloratadine in human plasma. The drug extraction method from plasma was based on protein precipitation technique. The separation was carried out on a Thermo Scientific BDS Hypersil C18 column (5µm, 250 x 4.60 mm) using a mobile phase of MeOH : 0.025M KH2PO4 adjusted to pH 3.50 using orthophosphoric acid (85 : 15, v/v) at ambient temperature. The flow rate was maintained at 1 mL/min and maximum absorption was measured using PDA detector at 248 nm. The retention times of loratadine and desloratadine in plasma samples were recorded to be 4.10 and 5.08 minutes respectively, indicating a short analysis time. Limits of detection were found to be 1.80 and 1.97 ng/mL for loratadine and desloratadine, respectively, showing a high degree of method sensitivity. The method was then validated according to FDA guidelines for the determination of the two analytes in human plasma. The results obtained indicate that the proposed method is rapid, sensitive in the nanogram range, accurate, selective, robust and reproducible compared to other reported methods. [Abstract copyright: Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.]
• #### De-smokeGCN: Generative Cooperative Networks for Joint Surgical Smoke Detection and Removal

Surgical smoke removal algorithms can improve the quality of intra-operative imaging and reduce hazards in image-guided surgery, a highly desirable post-process for many clinical applications. These algorithms also enable effective computer vision tasks for future robotic surgery. In this paper, we present a new unsupervised learning framework for high-quality pixel-wise smoke detection and removal. One of the well recognized grand challenges in using convolutional neural networks (CNNs) for medical image processing is to obtain intra-operative medical imaging datasets for network training and validation, but availability and quality of these datasets are scarce. Our novel training framework does not require ground-truth image pairs. Instead, it learns purely from computer-generated simulation images. This approach opens up new avenues and bridges a substantial gap between conventional non-learning based methods and which requiring prior knowledge gained from extensive training datasets. Inspired by the Generative Adversarial Network (GAN), we have developed a novel generative-collaborative learning scheme that decomposes the de-smoke process into two separate tasks: smoke detection and smoke removal. The detection network is used as prior knowledge, and also as a loss function to maximize its support for training of the smoke removal network. Quantitative and qualitative studies show that the proposed training framework outperforms the state-of-the-art de-smoking approaches including the latest GAN framework (such as PIX2PIX). Although trained on synthetic images, experimental results on clinical images have proved the effectiveness of the proposed network for detecting and removing surgical smoke on both simulated and real-world laparoscopic images.
• #### Towards sustainable methanol from industrial CO2 sources

This chapter discusses the opportunity of using CO2 from industrial sources to produce sustainable methanol. Some important industrial sectors that could be seen as potential sources of CO2 are reviewed: ammonia, steel, ethanol, ethylene, natural gas, cement and power industries. In most cases, despite a promising potential for CO2 re-use, only few projects have been identified and methanol production from CO2 is still marginal. A model for the CO2-to-methanol process is presented based on CO2-rich gas coming from ammonia production process. This model takes into account the different steps from the CO2 capture to the methanol purification, and heat integration is performed in order to determine the reduction of heat consumption achievable for the global process. Even if the economic relevance of the CO2 re-use into methanol still has to be qualified, it offers an estimation of the process efficiency.
• #### A discrete mutualism model: analysis and exploration of a financial application

We perform a stability analysis on a discrete analogue of a known, continuous model of mutualism. We illustrate how the introduction of delays affects the asymptotic stability of the system’s positive nontrivial equilibrium point. In the second part of the paper we explore the insights that the model can provide when it is used in relation to interacting financial markets. We also note the limitations of such an approach.
• #### Assisting Serious Games Level Design with an Augmented Reality Application and Workflow

With the rise in popularity of serious games there is an increasing demand for virtual environments based on real-world locations. Emergency evacuation or fire safety training are prime examples of serious games that would benefit from accurate location depiction together with any application involving personal space. However, creating digital indoor models of real-world spaces is a difficult task and the results obtained by applying current techniques are often not suitable for use in real-time virtual environments. To address this problem, we have developed an application called LevelEd AR that makes indoor modelling accessible by utilizing consumer grade technology in the form of Apple’s ARKit and a smartphone. We compared our system to that of a tape measure and a system based on an infra-red depth sensor and application. We evaluated the accuracy and efficiency of each system over four different measuring tasks of increasing complexity. Our results suggest that our application is more accurate than the depth sensor system and as accurate and more time efficient as the tape measure over several tasks. Participants also showed a preference to our LevelEd AR application over the depth sensor system regarding usability. Finally, we carried out a preliminary case study that demonstrates how LevelEd AR can be successfully used as part of current industry workflows for serious games level design.
• #### Evaluating LevelEd AR: An Indoor Modelling Application for Serious Games Level Design

We developed an application that makes indoor modelling accessible by utilizing consumer grade technology in the form of Apple’s ARKit and a smartphone to assist with serious games level design. We compared our system to that of a tape measure and a system based on an infra-red depth sensor and application. We evaluated the accuracy and efficiency of each system over four different measuring tasks of increasing complexity. Our results suggest that our application is more accurate than the depth sensor system and as accurate and more time efficient as the tape measure over several tasks. Participants also showed a preference to our LevelEd AR application over the depth sensor system regarding usability.
• #### Virtual Reality Environment for the Cognitive Rehabilitation of Stroke Patients

We present ongoing work to develop a virtual reality environment for the cognitive rehabilitation of patients as a part of their recovery from a stroke. A stroke causes damage to the brain and problem solving, memory and task sequencing are commonly affected. The brain can recover to some extent, however, and stroke patients have to relearn to carry out activities of daily learning. We have created an application called VIRTUE to enable such activities to be practiced using immersive virtual reality. Gamification techniques enhance the motivation of patients such as by making the level of difficulty of a task increase over time. The design and implementation of VIRTUE is presented together with the results of a small acceptability study.
• #### Training Powered Wheelchair Manoeuvres in Mixed Reality

We describe a mixed reality environment that has been designed as an aid for training driving skills for a powered wheelchair. Our motivation is to provide an improvement on a previous virtual reality wheelchair driving simulator, with a particular aim to remove any cybersickness effects. The results of a validation test are presented that involved 35 able bodied volunteers divided into three groups: mixed reality trained, virtual reality trained, and a control group. No significant differences in improvement was found between the groups but there is a notable trend that both the mixed reality and virtual reality groups improved more than the control group. Whereas the virtual reality group experienced discomfort (as measured using a simulator sickness questionnaire), the mixed reality group experienced no side effects.
• #### The early stages of biofilm formation by Staphylococcus epidermidis studied by XPS and AFM

Staphylococcus epidermidis is an opportunistic bacteria which forms pathogenic biofilms in medical implant environment. Biofilm formation is a complex multistage process within which the initial stages of adhesion are deemed the most critical target for preventing biofilms. This research involves the characterisation of S. epidermidis (ATCC35984 and NCTC13360) by using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) on model substrates including glass, muscovite mica, silicon (111) wafer, sputter-coated titanium and sputter-coated silver, focusing on the effect of chemical properties of the material on adhesion by using surfaces with minimal roughness. AFM was used to image the surface, from which bacterial coverage can be estimated. AFM was also used to probe adhesion forces and local mechanical properties of all samples through the use of force-distance curves. AFM images were also used to estimate the bacterial coverage. XPS was used to investigate the surface chemistry from the layer thicknesses, the percentage coverage and potential composition of the overlayer. The combination of these techniques allow the relationships between the surface chemistry of the substrate and the bacteria to be correlated with changes in coverage and properties of bacterial films. Data on incubated bacterial samples were compared with those from the reference substrates, both before and after autoclaving, and from samples prepared using protein rich growth medium (tryptic soy broth) in the absence of bacteria as well as a pure bacterial pellet in an assumed non-biofilm forming state. The research indicates the potential differences between biofilm and non-biofilm former strains, with both strains being covered by an organic layer with little influence of the growth media used to incubate the bacteria. This research also shows how XPS and AFM data can be combined and applied to bacterial adhesion.
• #### New Self-Dual and Formally Self-Dual Codes from Group Ring Constructions

In this work, we study construction methods for self-dual and formally self-dual codes from group rings, arising from the cyclic group, the dihedral group, the dicyclic group and the semi-dihedral group. Using these constructions over the rings $_F2 +uF_2$ and $F_4 + uF_4$, we obtain 9 new extremal binary self-dual codes of length 68 and 25 even formally self-dual codes with parameters [72,36,14].
• #### Evaporation of liquid nitrogen droplets in superheated immiscible liquids

Liquid nitrogen or other cryogenic liquids have the potential to replace or augment current energy sources in cooling and power applications. This can be done by the rapid evaporation and expansion processes that occur when liquid nitrogen is injected into hotter fluids in mechanical expander systems. In this study, the evaporation process of single liquid nitrogen droplets when submerged into n-propanol, methanol, n-hexane, and n-pentane maintained at 294 K has been investigated experimentally and numerically. The evaporation process is quantified by tracking the growth rate of the resulting nitrogen vapour bubble that has an interface with the bulk liquid. The experimental data suggest that the bubble volume growth is proportional to the time and the bubble growth rate is mainly determined by the initial droplet size. A comparison between the four different bulk liquids indicates that the evaporation rate in n-pentane is the highest, possibly due to its low surface tension. A scaling law based on the pure diffusion-controlled evaporation of droplet in open air environment has been successfully implemented to scale the experimental data. The deviation between the scaling law predictions and the experimental data for 2-propanol, methanol and n-hexane vary between 4% and 30% and the deviation for n-pentane was between 24% and 65%. The more detailed bubble growth rates have been modelled by a heuristic one-dimensional, spherically symmetric quasi-steady-state confined model, which can predict the growth trend well but consistently underestimate the growth rate. A fixed effective thermal conductivity is then introduced to account for the complex dynamics of the droplet inside the bubble and the subsequent convective processes in the surrounding vapour, which leads to a satisfactory quantitative prediction of the growth rate.
• #### Isolation of a Ferroelectric Intermediate Phase in Antiferroelectric Dense Sodium Niobate Ceramics

Switchable ferroelectric/antiferroelectric ceramics are of significant interest for high power energy storage applications. Grain size control of this switching is an interesting approach to controlling polarization and hence dielectric properties. However, the use of this approach in technologically relevant ceramics is hindered by difficulty in fabricating dense ceramics with small grain sizes. Here an intermediate polar ferroelectric phase (P21ma) has been isolated in dense bulk sodium niobate ceramics by grain size control through spark plasma sintering methods. Our findings, supported by XRD, DSC, P-E (I-E) loops and dielectric characterization, provide evidence that the phase transition from the antiferroelectric (AFE) R-phase, in space group Pnmm, above 300 C, to the AFE P-phase, in space group Pbma, at room temperature, always involves the polar intermediate P21ma phase and that the P21ma to Pbma transition can be suppressed by reducing grain size.
• #### Self-assembled nanostructures in ionic liquids facilitate charge storage at electrified interfaces

Driven by the potential applications of ionic liquids (ILs) in many emerging electrochemical technologies, recent research efforts have been directed at understanding the complex ion ordering in these systems, to uncover novel energy storage mechanisms at IL–electrode interfaces. Here, we discover that surface-active ILs (SAILs), which contain amphiphilic structures inducing self-assembly, exhibit enhanced charge storage performance at electrified surfaces. Unlike conventional non amphiphilic ILs, for which ion distribution is dominated by Coulombic interactions, SAILs exhibit significant and competing van der Waals interactions owing to the non-polar surfactant tails, leading to unusual interfacial ion distributions. We reveal that, at an intermediate degree of electrode polarization, SAILs display optimum performance, because the low-charge-density alkyl tails are effectively excluded from the electrode surfaces, whereas the formation of non-polar domains along the surface suppresses undesired overscreening effects. This work represents a crucial step towards understanding the unique interfacial behaviour and electrochemical properties of amphiphilic liquid systems showing long-range ordering, and offers insights into the design principles for high-energy-density electrolytes based on spontaneous self-assembly behaviour.
• #### An Altered Four Circulant Construction for Self-Dual Codes from Group Rings and New Extremal Binary Self-dual Codes I

We introduce an altered version of the four circulant construction over group rings for self-dual codes. We consider this construction over the binary field, the rings F2 + uF2 and F4 + uF4; using groups of order 4 and 8. Through these constructions and their extensions, we find binary self-dual codes of lengths 16, 32, 48, 64 and 68, many of which are extremal. In particular, we find forty new extremal binary self-dual codes of length 68, including twelve new codes with \gamma=5 in W68,2, which is the first instance of such a value in the literature.
• #### Aging and Cholesterol Metabolism

The role cholesterol metabolism has to play in health span is clear, and monitoring the parameters of cholesterol metabolism is key to aging successfully. The aim of this chapter is to provide a brief overview of the mechanisms which regulate cholesterol in the body, secondly to discuss how aging effects cholesterol metabolism, and thirdly to unveil how systems biology is leading to an improved understanding of the intersection between aging and the dysregulation of cholesterol metabolism.
• #### On the behavior of the solutions for linear autonomous mixed type difference equation

A class of linear autonomous mixed type difference equations is considered, and some new results on the asymptotic behavior and the stability are given, via a positive root of the corresponding characteristic equation.
• #### Numerical methods for solving space fractional partial differential equations by using Hadamard finite-part integral approach

We introduce a novel numerical method for solving two-sided space fractional partial differential equation in two dimensional case. The approximation of the space fractional Riemann-Liouville derivative is based on the approximation of the Hadamard finite-part integral which has the convergence order $O(h^{3- \alpha})$, where $h$ is the space step size and $\alpha\in (1, 2)$ is the order of Riemann-Liouville fractional derivative. Based on this scheme, we introduce a shifted finite difference method for solving space fractional partial differential equation. We obtained the error estimates with the convergence orders $O(\tau +h^{3-\alpha}+ h^{\beta})$, where $\tau$ is the time step size and $\beta >0$ is a parameter which measures the smoothness of the fractional derivatives of the solution of the equation. Unlike the numerical methods for solving space fractional partial differential equation constructed by using the standard shifted Gr\"unwald-Letnikov formula or higher order Lubich'e methods which require the solution of the equation satisfies the homogeneous Dirichlet boundary condition in order to get the first order convergence, the numerical method for solving space fractional partial differential equation constructed by using Hadamard finite-part integral approach does not require the solution of the equation satisfies the Dirichlet homogeneous boundary condition. Numerical results show that the experimentally determined convergence order obtained by using the Hadamard finite-part integral approach for solving space fractional partial differential equation with non-homogeneous Dirichlet boundary conditions is indeed higher than the convergence order obtained by using the numerical methods constructed with the standard shifted Gr\"unwald-Letnikov formula or Lubich's higer order approximation schemes.
• #### Factors for successful Agile collaboration between UX designers and software developers in a complex organisation

User Centred Design (UCD) and Agile Software Development (ASD) processes have been two extremely successful methods for software development in recent years. However, both have been repeatedly described as frequently putting contradictory demands on people working with the respective processes. The current research addresses this point by focussing on the crucial relationship between a User Experience (UX) designer and a software developer. In-depth interviews, an online survey, a contextual inquiry and a diary study are described from a sample of over 100 designers, developers and their stakeholders (managers) in a large media organisation exploring factors for success in Agile development cycles. The findings from the survey show that organisational separation is challenge for agile collaboration between the two roles and while designers and developers have similar levels of (moderately positive) satisfaction with Agile processes, there are differences between the two roles. While developers are happier with the wider teamwork but want more access to and close collaboration with designers, particularly in an environment set up for Agile practices, the designers’ concern was the quality of the wider teamwork. The respondent’s comments also identified that the two roles saw a close – and ideally co-located – cooperation as essential for improving communication, reducing inefficiencies, and avoiding bad products being released. These results reflected the findings from the in-depth interviews with stakeholders. In particular, it was perceived that co-located pairing helped understanding different role-dependent demands and skills, increased efficiency of prototyping and implementing changes, and enabling localised decision-making. However, organisational processes, the setup of work-environment, and managerial traditions meant that this close collaboration and localised decision-making was often not possible to maintain over extended periods. Despite this, the studies conducted between pairs of designers and developers, found that successful collaboration between designers and developers can be found in a complex organisational setting. From the analysis of the empirical studies, six contributing factors emerged that support this. These factors are 1) Close proximity, 2) Early and frequent communication, 3) Shared ideation and problem solving, 4) Crossover of knowledge and skills, 5) Co-creation and prototyping and 6) Making joint decisions. These factors are crucially determined and empowered by the support from the organisational setting and 3 teams where practitioners work. Specifically, by overcoming key challenges to enable integration between UCD and ASD and thus encouraging close collaboration between UX designers and software developers, these challenges are: 1) Organisational structure and team culture, 2) Location and environmental setup and 3) Decision-making. These challenges along with the six factors that enable successful Agile collaboration between designers and developers provide the main contributions of this research. These contributions can be applied within large complex organisations by adopting the suggested ‘Paired Collaboration Manifesto’ to improve the integration between UCD and ASD. Beyond this, more empirical studies can take place, further extending improvements to the collaborative practices between the design and development roles and their surrounding teams.
• #### Magnetic cationic liposomal nanocarriers for the efficient drug delivery of a curcumin-based vanadium complex with anticancer potential

In this work novel magnetic cationic liposomal nanoformulations were synthesized for the encapsulation of a crystallographically defined ternary V(IV)-curcumin-bipyridine (VCur) complex with proven bioactivity, as potential anticancer agents. The liposomal vesicles were produced via the thin film hydration method employing N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium (DOTAP) and egg phosphatidylcholine lipids and were magnetized through the addition of citric acid surface-modified monodispersed magnetite colloidal magnetic nanoparticles. The obtained nanoformulations were evaluated for their structural and textural properties and shown to have exceptional stability and enhanced solubility in physiological media, demonstrated by the entrapment efficiency and loading capacity results and the in vitro release studies of their cargo. Furthermore, the generated liposomal formulations preserved the superparamagnetic behavior of the employed magnetic core maintaining the physicochemical and morphological requirements for targeted drug delivery applications. The novel nanomaterials were further biologically evaluated for their DNA interaction potential and were found to act as intercalators. The findings suggest that the positively charged magnetic liposomal nanoformulations can generate increased concentration of their cargo at the DNA site, offering a further dimension in the importance of cationic liposomes as nanocarriers of hydrophobic anticancer metal ion complexes for the development of new multifunctional pharmaceutical nanomaterials with enhanced bioavailability and targeted antitumor activity.