An Optimal Dimensionality Sampling Scheme on the Sphere for Antipodal Signals In Diffusion Magnetic Resonance Imaging

We propose a sampling scheme on the sphere and develop a corresponding spherical harmonic transform (SHT) for the accurate reconstruction of the diffusion signal in diffusion magnetic resonance imaging (dMRI). By exploiting the antipodal symmetry, we design a sampling scheme that requires the optimal number of samples on the sphere, equal to the degrees of freedom required to represent the antipodally symmetric band-limited diffusion signal in the spectral (spherical harmonic) domain. Compared with existing sampling schemes on the sphere that allow for the accurate reconstruction of the diffusion signal, the proposed sampling scheme reduces the number of samples required by a factor of two or more. We analyse the numerical accuracy of the proposed SHT and show through experiments that the proposed sampling allows for the accurate and rotationally invariant computation of the SHT to near machine precision accuracy.Comment: Will be published in the proceedings of the International Conference Acoustics, Speech and Signal Processing 2015 (ICASSP'2015

An Optimal Dimensionality Multi-shell Sampling Scheme with Accurate and Efficient Transforms for Diffusion MRI

This paper proposes a multi-shell sampling scheme and corresponding transforms for the accurate reconstruction of the diffusion signal in diffusion MRI by expansion in the spherical polar Fourier (SPF) basis. The sampling scheme uses an optimal number of samples, equal to the degrees of freedom of the band-limited diffusion signal in the SPF domain, and allows for computationally efficient reconstruction. We use synthetic data sets to demonstrate that the proposed scheme allows for greater reconstruction accuracy of the diffusion signal than the multi-shell sampling schemes obtained using the generalised electrostatic energy minimisation (gEEM) method used in the Human Connectome Project. We also demonstrate that the proposed sampling scheme allows for increased angular discrimination and improved rotational invariance of reconstruction accuracy than the gEEM schemes.Comment: 4 pages, 4 figures presented at ISBI 201

Increased platelet reactivity in idiopathic pulmonary fibrosis is mediated by a plasma factor

Introduction Idiopathic Pulmonary Fibrosis (IPF) is a progressive, incurable fibrotic interstitial lung disease with a prognosis worse than many cancers. Its pathogenesis is poorly understood. Activated platelets can release pro-fibrotic mediators that have the potential to contribute to lung fibrosis. We determine platelet reactivity in subjects with IPF compared to age-matched controls. Methods Whole blood flow cytometry was used to measure platelet-monocyte aggregate formation, platelet P-selectin expression and platelet fibrinogen binding at basal levels and following stimulation with platelet agonists. A plasma swap approach was used to assess the effect of IPF plasma on control platelets. Results Subjects with IPF showed greater platelet reactivity than controls. Platelet P-selectin expression was significantly greater in IPF patients than controls following stimulation with 0.1 µM ADP (1.9% positive ±0.5 (mean ± SEM) versus 0.7%±0.1; p = 0.03), 1 µM ADP (9.8%±1.3 versus 3.3%±0.8; p<0.01) and 10 µM ADP (41.3%±4.2 versus 22.5%±2.6; p<0.01). Platelet fibrinogen binding was also increased, and platelet activation resulted in increased platelet-monocyte aggregate formation in IPF patients. Re-suspension of control platelets in plasma taken from subjects with IPF resulted in increased platelet activation compared to control plasma. Conclusions IPF patients exhibit increased platelet reactivity compared with controls. This hyperactivity may result from the plasma environment since control platelets exhibit increased activation when exposed to IPF plasma

Monolithically integrated InAsSb-based nBnBn heterostructure on GaAs for infrared detection

High operating temperature i nfrared photo detectors with multi -color function that are capable of monolithic integration are of increasing importance in developing the next generation of mid -IR imag e sensors. Applications of these sensors include defense, medical diagnosis, environmental and astronomical observations. We have investigated a novel InAsSb -based nBnBn heterostructure that combines a state -of-art InAsSb nBn detector with an InAsSb/GaSb heterojuncti on detector . At room temperature, r educti on in the dark current density of more than an order of magnitude was achieved compared to previously investigated InAsSb/GaSb heterojunction dete ctors . Electrical characterization from cryogenic temperatures to roo m temperature confirmed that the nBnBn device was diffusion limited for temperature s above 150K. O ptical measurements demonstrated that the nBnBn detector was sensitive in both the SWIR and MWIR wavelength range at room temperature . The specific detectivity (D*) of the competed nBnBn devices was calculated to be 8.6 × 10 8 cm · Hz 1/2 W -1 at 300K and approximately 1.0 × 10 10 cm · Hz 1/2 W -1 when cooled down to 200K (with 0.3V reverse bias and 1550nm illumination ). In addition, all photodetector layers were grown monolithically on GaAs active layers u sing the interfacial misfit array growth mode . Our results therefore pave the way for the development of new active pixel designs for monolithically integrated mid -IR imaging arrays

Acdmcp: An adaptive and completely distributed multi-hop clustering protocol for wireless sensor networks

Clustering is a very popular network structuring technique which mainly addresses the issue of scalability in large scale Wireless Sensor Networks. Additionally, it has been shown to improve the energy efficiency and prolong the life of the network. The suggested protocols mostly base their clustering criteria on some grouping attribute(s) of the nodes. One important attribute that is largely ignored by most of the existing multi-hop clustering protocols is the reliability of the communication links between the nodes. In this paper, we suggest an adaptive and completely distributed multi-hop clustering protocol that incorporates different notions of reliability of the communication links, among other things, into a composite metric and uses it in all phases of the clustering process. The joining criteria for the nodes, which lie at one hop from the elected cluster heads, to a particular cluster not only consider the reliability of their communication link with their cluster head but also other important attributes. The nodes that lie outside the communication range of cluster heads become cluster members transitively through existing cluster members utilizing the end-to-end notion of link reliability, between the nodes and the cluster heads, along with other important attributes. Similarly, inter-cluster communication paths are selected using a set of criteria that includes the end-to-end communication link reliability with the sink node along with other important node and network attributes. We believe that incorporating link reliability in all phases of clustering process results in an efficient multi-hop communication hierarchy that has the potential of bringing down the total communication costs in the network

Perfect single-photon sources

We introduce the "gapped coherent state" in the form of a single-photon source (SPS) that consists of uncorrelated photons as a background, except that we demand that no two photons can be closer in time than a time gap $t_\mathrm{G}$. While no obvious quantum mechanism is yet identified to produce exactly such a photon stream, a numerical simulation is easily achieved by first generating an uncorrelated (Poissonian) signal and then for each photon in the list, either adding such a time gap or removing all successive photons that are closer in time from any photon that is kept than $t_\mathrm{G}$. We study the statistical properties of such a hypothetical signal, which exhibits counter-intuitive features. This provides a neat and natural connection between continuous-wave (stationary) and pulsed single-photon sources, with also a bearing on what it means for such sources to be perfect in terms of single-photon emission

Rising Power Clusters and the Challenges of Local and Global Standards

__Abstract__ This paper explores the intersection between three processes associated with globalisation. First, the rise of emerging economies like China, Brazil and India, the so-called ‘Rising Powers’, and their potential to define the contours of globalisation, global production arrangements and global governance in the twenty-first century. Second, the importance of corporate social responsibility (CSR) goals in the shaping of global trade rules and industrial practices. Third, the significance of small firm clusters as critical sites of industrial competitiveness. Some of the most significant examples of successful, innovative and internationally competitive small firm clusters from the developing world are located in the ‘Rising Powers’ and cluster promotion is a core element of national industrial policy in some of these countries. There is also evidence of engagement by clustered actors with corporate social responsibility goals around labour and environmental impacts. While these three processes have been separately studied there has been no attempt to explore their intersections. This paper addresses this gap through a comparative analysis of secondary data, and a detailed reading of the literature, on CSR and clusters in Brazil, China and India. It assesses the evidence on small firm clusters in the Rising Power economies and considers how these Rising Power clusters engage with CSR goals pertaining to labour, social and environmental standards. It argues for a greater focus on the formal and informal institutional context, termed the ‘social contract’, in explaining divergent experiences and practices observed across these countries. This raises important questions for future academic and policy research on clusters, CSR and the Rising Powers. The paper concludes by outlining a research agenda to explore the local and global consequences of the relationship between Rising Power clusters and international labour and environmental standards