Correction: Analysis of the transient response of a dual-fed RC transmission line

This is an Erratum for Analysis of the transient response of a dual-fed RC transmission line. PLoS One 10(3):e0116993-1-e0116993-11 Article number 2 2015. DOI: http://doi.org/10.1371/journal.pone.0116993.The transient analysis of a uniform transmission line of finite length is considered in this paper. For the first time this paper provides an analytical expression for the time-domain response of an RC transmission line, which is stimulated by a step function that is fed into both ends of the transmission line. In particular, we find an analytical expression for the step response at the center of the transmission line, in order to determine the worst-case rise time. This is of interest, for example, in large charge-coupled device (CCD) arrays, where long polysilicon lines are dual-fed in order to mitigate degradation in rise time. The analytical expressions for the RC transmission line are supported by computer-simulated lumped RC models.Mohsen Dorraki, Gregory K. Cambrell, Derek Abbot

Parameter identification using moment of velocity

Many physical systems can be adequately modelled using a second-order approximation. Thus, the problem of system identification often reduces to the problem of estimating the position of a single pair of complex–conjugate poles. This paper presents a convenient but approximate technique for the estimation of the position of a single pair of complex–conjugate poles, using the moment of velocity (MoV). The MoV is a Hilbert transform based signal processing tool that addresses the shortcomings of instantaneous frequency. We demonstrate that the MoV can be employed for parameter identification of a dynamical system. We estimate the damping coefficient and oscillation frequency via MoV of the impulse response.M. Dorraki, M.S. Islam, A. Allison and D. Abbot

Hip osteoarthritis: A novel network analysis of subchondral trabecular bone structures

Hip osteoarthritis (HOA) is a degenerative joint disease that leads to the progressive destruction of subchondral bone and cartilage at the hip joint. Development of effective treatments for HOA remains an open problem, primarily due to the lack of knowledge of its pathogenesis and a typically late-stage diagnosis.We describe a novel network analysis methodology for microcomputed tomography (micro-CT) images of human trabecular bone.We explored differences between the trabecular bone microstructure of femoral heads with and without HOA. Large-scale automated extraction of the network formed by trabecular bone revealed significant network properties not previously reported for bone. Profound differences were discovered, particularly in the proximal third of the femoral head, where HOA networks demonstrated elevated numbers of edges, vertices, and graph components. When further differentiating healthy joint and HOA networks, the latter showed fewer small-world network properties, due to decreased clustering coefficient and increased characteristic path length. Furthermore,we found that HOA networks had reduced length of edges, indicating the formation of compressed trabecular structures. In order to assess our network approach,we developed a deep learningmodel for classifying HOA and control cases, and we fed it with two separate inputs: (i) micro-CT images of the trabecular bone, and (ii) the network extracted from them. The model with plain micro-CT images achieves 74.6% overall accuracy while the trained model with extracted networks attains 96.5% accuracy. We anticipate our findings to be a starting point for a novel description of bone microstructure in HOA, by considering the phenomenon from a graph theory viewpoint.Mohsen Dorraki, Dzenita Muratovic, Anahita Fouladzadeh, Johan W. Verjans, Andrew Allison, David M. Findlay and Derek Abbot

On moment of velocity for signal analysis

The instantaneous frequency (IF) of a signal is a well-defined quantity that is widely used for analysing non-stationary signals. However, often in practice, IF as a function of time can possess large spikes and negative values. Moreover, IF is very sensitive to noise, limiting its range of practical application. Due to these deficiencies, we introduce the concept of moment of velocity (MoV) for signal analysis. As a case study, we compare the performance of MoV to a standard Hilbert transform-based approach for R-wave identification in human electrocardiogram signals, demonstrating that our approach is more robust to noise. We examine characteristic heartbeats obtained from the MIT-BIH Arrhythmia database. A detection error rate of 0.07%, a positive predictive value of 99.97%, and a sensitivity of 99.95% are achieved against analysis results from the database.M. Dorraki, A. Fouladzadeh, A. Allison, B. R. Davis and D. Abbot

Low loss and low dispersion hybrid core photonic crystal fiber for terahertz propagation

In this paper, a hybrid-core circular cladded photonic crystal fiber is designed and analyzed for application in the terahertz frequency range. We introduce a rectangular structure in addition to a conventional hexagonal structure in the core to reduce the material absorption loss. The modal characteristics of the fiber have been investigated using full vector finite element method. Simulated results exhibit an ultra-low effective material loss of 0.035 cm−1 and ultra-flattened dispersion of 0.07 ps/THz/cm. Some other important fiber characteristics suitable for terahertz signal transmission including confinement loss, core power fraction, effective area and single-mode conditions of the fiber have also been investigated. In order to simplify design and facilitate fabrication, only circular shaped air holes have been employed. Due to its promising characteristics, the proposed waveguide may provide efficient transmission of broadband terahertz signals.Md. Saiful Islam, Jakeya Sultana, Mohsen Dorraki, Javid Atai, Mohammad Rakibul Islam, Alex Dinovitser, Brian Wai-Him Ng, Derek Abbot

The development of tumour vascular networks

The growth of solid tumours relies on an ever-increasing supply of oxygen and nutrients that are delivered via vascular networks. Tumour vasculature includes endothelial cell lined angiogenesis and the less common cancer cell lined vasculogenic mimicry (VM). To study and compare the development of vascular networks formed during angiogenesis and VM (represented here by breast cancer and pancreatic cancer cell lines) a number of in vitro assays were utilised. From live cell imaging, we performed a large-scale automated extraction of network parameters and identified properties not previously reported. We show that for both angiogenesis and VM, the characteristic network path length reduces over time; however, only endothelial cells increase network clustering coefficients thus maintaining smallworld network properties as they develop. When compared to angiogenesis, the VM network efficiency is improved by decreasing the number of edges and vertices, and also by increasing edge length. Furthermore, our results demonstrate that angiogenic and VM networks appear to display similar properties to road traffic networks and are also subject to the well-known Braess paradox. This quantitative measurement framework opens up new avenues to potentially evaluate the impact of anti-cancer drugs and anti-vascular therapies.Anahita Fouladzadeh, Mohsen Dorraki, Kay Khine Myo Min, Michaelia P. Cockshell, Emma J. Thompson, Johan W. Verjans, Andrew Allison, Claudine S. Bonder and Derek Abbot

A Hi-Bi ultra-sensitive surface plasmon resonance fiber sensor

In this paper, a simple, miniature, and highly sensitive photonic crystal fiber (PCF)-based surface plasmon resonance (SPR) sensor is proposed. The target analyte and the plasmonic material are at the outer surface of the fiber making practical applications feasible. A 30-nm gold (Au) layer supports surface plasmons. A thin titanium dioxide (TiO 2 ) layer is used to assist adhesion of Au on the glass fiber. The fiber cross section is formed purely by circular-shaped holes simplifying the preform manufacturing process. A high-birefringence (hi-bi) fiber is obtained by means of an array of air holes at the center of the fiber. A finite element method (FEM) is employed to analyze the surface plasmon properties of the proposed PCF-SPR sensor. By optimizing the geometric parameters, a maximum wavelength sensitivity (WS) of 25 000 nm/RIU and an amplitude sensitivity (AS) of 1411 RIU -1 for a dielectric refractive index (RI) range of 1.33-1.38 are obtained. Moreover, an estimated maximum resolution of 4 × 10 -6 and a figure of merit (FOM) of 502 are obtained that ensures high detection accuracy of small refractive index (RI) changes. Owing to its sensitivity and simple architecture, the proposed sensor has potential application in a range of sensing application, including biosensing.Saiful Islam, Cristiano M. B. Cordeiro, Jakeya Sultana, Rifat Ahmmed Aoni, Shilun Feng, Rajib Ahmed, Mohsen Dorraki, Alex Dinovitser, Brian Wai-Him Ng, Derek Abbot