Exploring barriers of m-commerce adoption in SMEs in the UK: Developing a framework using ISM

YesIn the modern business era, mobile commerce (m-commerce) is changing the way the business is conducted using the Internet. However, the prominence of m-commerce among small and medium-sized enterprises (SMEs) in the UK is minimal. The purpose of this study is to evaluate the existing literature and to extend the research surrounding the barriers that prevent the adoption of m-commerce amongst SMEs. The study uses an Interpretive Structural Modelling (ISM) and MICMAC approach for guiding and helping managers of SMEs. Data was collected from an expert participant group each of whom had extensive knowledge of m-commerce. The findings represent the unstable nature of variables in the context of their impact on each other, their relationships, and themselves. The listed factors in the proposed framework and the interrelationships between them highlight the multi-dimensional element of m-commerce adoption prevention. This observation proves criticality of analysing data as a collective entity rather than viewing the barriers in isolation. The findings also indicated ‘perceived risk’ being a key barrier that demonstrates how personal opinions of the concept of adoption can have a great significance on the outcome and whether other variables will come into effect

Sweetpotato weevil resistance in sub-saharan Africa: A viable mechanism for reducing Cylas damage.

Sweetpotato (Ipomoea batatas, L) is the third most important crop in Sub-Saharan Africa contributing significantly to food security, nutrition and income. Weevils, Cylas spp., are the most important insect pest of the crop. The weevils damage both vines and roots, causing unacceptable odour, discoloration, and bitter taste making them unfit for consumption. Depending on conditions, weevils can cause complete losses of the harvestable crop. Host plant resistance seems to be the only viable option for management of the pest. Studies in Uganda reveal existence of active resistance in some sweetpotato genotypes. Field and laboratory experiments show that clones HMA 519, ARA 230, LIR 302, APA 356, ARA 228, RAK 865 (local), and New Kawogo (improved), have varying levels of resistance compared to the susceptible varieties NASPOT1, Kakamega, and Tanzania. The resistant clones were evaluated for field resistance against the susceptible checks; root and vine damage was less in the resistant clones. No-choice bioassays using roots conducted in the laboratory to show that feeding and oviposition was less on the resistant clones indicating that the observed field resistance was not simply escape. The resistance has been linked to some hydroxycinnamic acid esters which occur in higher concentrations in the roots of resistant compared to the susceptible clones. The compounds were extracted from the roots, analysed and synthetic derivatives used to conduct toxicity & deterrence tests. Different concentrations (0.001, 0.01, 0.1mg/ml) of synthetic derivatives of the compounds were applied to the root surfaces of the susceptible variety (NASPOT 1) and showed that weevil species from both Uganda and Malawi fed less and laid fewer eggs on the treated roots compared to the untreated ones confirming the activity of the compounds against weevils. Preliminary studies indicate that the compounds have an additive effect with Cry7a proteins which are the target for the development of clones transformed with the Bt toxin. The findings have important implications for the breeding program in Uganda and will be used to map QTLs in segregating populations from a cross between the US variety Beauregard and the Ugandan variety New Kawogo

Multidimensional relativistic MHD simulations of Pulsar Wind Nebulae: dynamics and emission

Pulsar Wind Nebulae, and the Crab nebula in particular, are the best cosmic laboratories to investigate the dynamics of magnetized relativistic outflows and particle acceleration up to PeV energies. Multidimensional MHD modeling by means of numerical simulations has been very successful at reproducing, to the very finest details, the innermost structure of these synchrotron emitting nebulae, as observed in the X-rays. Therefore, the comparison between the simulated source and observations can be used as a powerful diagnostic tool to probe the physical conditions in pulsar winds, like their composition, magnetization, and degree of anisotropy. However, in spite of the wealth of observations and of the accuracy of current MHD models, the precise mechanisms for magnetic field dissipation and for the acceleration of the non-thermal emitting particles are mysteries still puzzling theorists to date. Here we review the methodologies of the computational approach to the modeling of Pulsar Wind Nebulae, discussing the most relevant results and the recent progresses achieved in this fascinating field of high-energy astrophysics.Comment: 29 pages review, preliminary version. To appear in the book "Modelling Nebulae" edited by D. Torres for Springer, based on the invited contributions to the workshop held in Sant Cugat (Barcelona), June 14-17, 201

Faraday effect : a field theoretical point of view

We analyze the structure of the vacuum polarization tensor in the presence of a background electromagnetic field in a medium. We use various discrete symmetries and crossing symmetry to constrain the form factors obtained for the most general case. From these symmetry arguments, we show why the vacuum polarization tensor has to be even in the background field when there is no background medium. Taking then the background field to be purely magnetic, we evaluate the vacuum polarization to linear order in it. The result shows the phenomenon of Faraday rotation, i.e., the rotation of the plane of polarization of a plane polarized light passing through this background. We find that the usual expression for Faraday rotation, which is derived for a non-degenerate plasma in the non-relativistic approximation, undergoes substantial modification if the background is degenerate and/or relativistic. We give explicit expressions for Faraday rotation in completely degenerate and ultra-relativistic media.Comment: 20 pages, Latex, uses axodraw.st

Magnetic fields in cosmic particle acceleration sources

We review here some magnetic phenomena in astrophysical particle accelerators associated with collisionless shocks in supernova remnants, radio galaxies and clusters of galaxies. A specific feature is that the accelerated particles can play an important role in magnetic field evolution in the objects. We discuss a number of CR-driven, magnetic field amplification processes that are likely to operate when diffusive shock acceleration (DSA) becomes efficient and nonlinear. The turbulent magnetic fields produced by these processes determine the maximum energies of accelerated particles and result in specific features in the observed photon radiation of the sources. Equally important, magnetic field amplification by the CR currents and pressure anisotropies may affect the shocked gas temperatures and compression, both in the shock precursor and in the downstream flow, if the shock is an efficient CR accelerator. Strong fluctuations of the magnetic field on scales above the radiation formation length in the shock vicinity result in intermittent structures observable in synchrotron emission images. Resonant and non-resonant CR streaming instabilities in the shock precursor can generate mesoscale magnetic fields with scale-sizes comparable to supernova remnants and even superbubbles. This opens the possibility that magnetic fields in the earliest galaxies were produced by the first generation Population III supernova remnants and by clustered supernovae in star forming regions.Comment: 30 pages, Space Science Review

Relativistic Mass Ejecta from Phase-transition-induced Collapse of Neutron Stars

We study the dynamical evolution of a phase-transition-induced collapse neutron star to a hybrid star, which consists of a mixture of hadronic matter and strange quark matter. The collapse is triggered by a sudden change of equation of state, which result in a large amplitude stellar oscillation. The evolution of the system is simulated by using a 3D Newtonian hydrodynamic code with a high resolution shock capture scheme. We find that both the temperature and the density at the neutrinosphere are oscillating with acoustic frequency. However, they are nearly 180$^{\circ}$ out of phase. Consequently, extremely intense, pulsating neutrino/antineutrino fluxes will be emitted periodically. Since the energy and density of neutrinos at the peaks of the pulsating fluxes are much higher than the non-oscillating case, the electron/positron pair creation rate can be enhanced dramatically. Some mass layers on the stellar surface can be ejected by absorbing energy of neutrinos and pairs. These mass ejecta can be further accelerated to relativistic speeds by absorbing electron/positron pairs, created by the neutrino and antineutrino annihilation outside the stellar surface. The possible connection between this process and the cosmological Gamma-ray Bursts is discussed.Comment: 40 pages, 11 figures, accepted for publication in JCA

Jet disc coupling in black hole binaries

In the last decade multi-wavelength observations have demonstrated the importance of jets in the energy output of accreting black hole binaries. The observed correlations between the presence of a jet and the state of the accretion flow provide important information on the coupling between accretion and ejection processes. After a brief review of the properties of black hole binaries, I illustrate the connection between accretion and ejection through two particularly interesting examples. First, an INTEGRAL observation of Cygnus X-1 during a 'mini-' state transition reveals disc jet coupling on time scales of orders of hours. Second, the black hole XTEJ1118+480 shows complex correlations between the X-ray and optical emission. Those correlations are interpreted in terms of coupling between disc and jet on time scales of seconds or less. Those observations are discussed in the framework of current models.Comment: Invited talk at the Fifth Stromlo Symposium: Disks, Winds & Jets - from Planets to Quasars. Accepted for publication in Astrophysics & Space Scienc

ZFOURGE catalogue of AGN candidates: an enhancement of 160-μm-derived star formation rates in active galaxies to z = 3.2

We investigate active galactic nuclei (AGN) candidates within the FourStar Galaxy Evolution Survey (ZFOURGE) to determine the impact they have on star formation in their host galaxies. We first identify a population of radio, X-ray, and infrared-selected AGN by cross-matching the deep Ks-band imaging of ZFOURGE with overlapping multiwavelength data. From this, we construct a mass-complete (log(M∗/M⊙M∗/M⊙) ≥9.75), AGN luminosity limited sample of 235 AGN hosts over z = 0.2–3.2. We compare the rest-frame U − V versus V − J (UVJ) colours and specific star formation rates (sSFRs) of the AGN hosts to a mass-matched control sample of inactive (non-AGN) galaxies. UVJ diagnostics reveal AGN tend to be hosted in a lower fraction of quiescent galaxies and a higher fraction of dusty galaxies than the control sample. Using 160 μm Herschel PACS data, we find the mean specific star formation rate of AGN hosts to be elevated by 0.34 ± 0.07 dex with respect to the control sample across all redshifts. This offset is primarily driven by infrared-selected AGN, where the mean sSFR is found to be elevated by as much as a factor of ∼5. The remaining population, comprised predominantly of X-ray AGN hosts, is found mostly consistent with inactive galaxies, exhibiting only a marginal elevation. We discuss scenarios that may explain these findings and postulate that AGN are less likely to be a dominant mechanism for moderating galaxy growth via quenching than has previously been suggested