Does Africa trade less than it should, and if so, why?: The role of market access and domestic factors

"This paper addresses the question of whether Africa is an undertrading continent. We answer this question using a much-improved data set for obtaining predicted trade and by employing methods that correct for bias in estimates of undertrading. Our results indicate that globally Africa is an underexporter in our preferred Heckman specification. This result is robust to the addition of various controls and the application of variants of the gravity model of trade. We also looked for explanations for Africa's undertrading. We found that accounting for transport and communication infrastructure reduced the undertrading effect for Africa, and in some specifications of the gravity model, the under-trading effect vanished altogether. Results from a semiparametric model provided evidence of significant nonlinear impacts from infrastructure, and the effects for a large number of African countries was significant and compared favorably with the marginal effects of infrastructure in countries on other continents and in comparable income brackets. Using this model we also found evidence of complementarity across transport and communication infrastructure, implying that much greater impacts will be likely if the infrastructure are developed jointly rather than in isolation." from Author's AbstractGravity model, Undertrading, Trade related infrastructure, Market access,

Channels Reallocation In Cognitive Radio Networks Based On DNA Sequence Alignment

Nowadays, It has been shown that spectrum scarcity increased due to tremendous growth of new players in wireless base system by the evolution of the radio communication. Resent survey found that there are many areas of the radio spectrum that are occupied by authorized user/primary user (PU), which are not fully utilized. Cognitive radios (CR) prove to next generation wireless communication system that proposed as a way to reuse this under-utilised spectrum in an opportunistic and non-interfering basis. A CR is a self-directed entity in a wireless communications environment that senses its environment, tracks changes, and reacts upon its findings and frequently exchanges information with the networks for secondary user (SU). However, CR facing collision problem with tracks changes i.e. reallocating of other empty channels for SU while PU arrives. In this paper, channels reallocation technique based on DNA sequence alignment algorithm for CR networks has been proposed.Comment: 12 page

Cross Layer Aware Adaptive MAC based on Knowledge Based Reasoning for Cognitive Radio Computer Networks

In this paper we are proposing a new concept in MAC layer protocol design for Cognitive radio by combining information held by physical layer and MAC layer with analytical engine based on knowledge based reasoning approach. In the proposed system a cross layer information regarding signal to interference and noise ratio (SINR) and received power are analyzed with help of knowledge based reasoning system to determine minimum power to transmit and size of contention window, to minimize backoff, collision, save power and drop packets. The performance analysis of the proposed protocol indicates improvement in power saving, lowering backoff and significant decrease in number of drop packets. The simulation environment was implement using OMNET++ discrete simulation tool with Mobilty framework and MiXiM simulation library.Comment: 8 page

Development of nanostructured, stress-free Co-rich CoPtP films for magnetic microelectromechanical system applications

Co-rich CoPtP alloys have been electrodeposited using direct current (dc) and pulse-reverse (PR) plating techniques. The surface morphology, crystalline structure, grain size, and magnetic properties of the plated films have been compared. The x-ray analysis and magnetic measurements reveal the presence of Co hcp hard magnetic phase with c axis perpendicular to the substrate for dc and in plane for PR plated films. The dc plated films have a granular structure in the micron scale with large cracks, which are manifestation of stress in the film. Only by using a combination of optimized PR plating conditions and stress relieving additive, we are able to produce 1-6 mu m thick (for 1 hour of plating), stress-free, and nanostructured (similar to 20 nm) Co-rich CoPtP single hcp phase at room temperature, with an intrinsic coercivity of 1500 Oe

Erase/restorable asymmetric magnetization reversal in polycrystalline ferromagnetic films

Asymmetric hysteresis loops are generally found in exchange-coupled ferromagnetic/antiferromagnetic layers or composite. Once the film is deposited the magnetization reversal behaviour becomes certain due to the fixed anisotropy of the film. We report an asymmetric magnetization reversal, which is erase/restorable in polycrystalline soft magnetic film. When the film is pre-saturated at a high field in the induced uniaxial easy direction, the asymmetric hysteresis loops with one branch governed by "coherent rotation" and another branch with kink induced by mixed reversal mechanism of "coherent rotation" and "rotation/180 degrees-domain-wall-motion/rotation" are obtained. If the film is presaturated in the induced hard axis, the kink disappears and "normal" hysteresis behaviour is observed instead. Such asymmetric magnetization curve can be restored if the film is pre-saturated in the easy axis again. The observed phenomenon is originated from an embedded second magnetically hard phase which tunes the anisotropy in the film. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4765652

Molecular identification of hookworm isolates in humans, dogs and soil in a tribal area in Tamil Nadu, India

Background : Hookworms (Necator americanus and Ancylostoma duodenale) remain a major public health problem worldwide. Infections with hookworms (e.g., A. caninum, A. ceylanicum and A. braziliense) are also prevalent in dogs, but the role of dogs as a reservoir for zoonotic hookworm infections in humans needs to be further explored. Methodology/Principal Findings : As part of an open-label community based cluster-randomized trial in a tribal area in Tamil Nadu (India; 2013-2015), a total of 143 isolates of hookworm eggs from human stool were speciated based on a previously described PCR-RFLP methodology. The presence of hookworm DNA was confirmed in 119 of 143 human samples. N. americanus (100%) was the most prevalent species, followed by A. caninum (16.8%) and A. duodenale (8.4%). Because of the high prevalence of A. caninum in humans, dog samples were also collected to assess the prevalence of A. caninum in dogs. In 68 out of 77 canine stool samples the presence of hookworms was confirmed using PCR-RFLP. In dogs, both A. caninum (76.4%) and A. ceylanicum (27.9%) were identified. Additionally, to determine the contamination of soil with zoonotic hookworm larvae, topsoil was collected from defecating areas. Hookworm DNA was detected in 72 out of 78 soil samples that revealed presence of hook-worm-like nematode larvae. In soil, different hookworm species were identified, with animal hookworms being more prevalent (A. ceylanicum: 60.2%, A. caninum: 29.4%, A. duodenale: 16.6%, N. americanus: 1.4%, A. braziliense: 1.4%). Conclusions/Significance : In our study we regularly detected the presence of A. caninum DNA in the stool of humans. Whether this is the result of infection is currently unknown but it does warrant a closer look at dogs as a potential reservoir

Shape-independent permeability model for uniaxially-anisotropic ferromagnetic thin films

A permeability model based on the three-dimensional shape demagnetization effect is developed to estimate the permeability of any uniaxially-anisotropic ferromagnetic thin-film for integrated micromagnetic structures. The model is validated by comparison to measured ferromagnetic thin films (NiFe and CoPRe) with different anisotropies and saturation magnetizations. The dependence of permeability on film-thickness is modeled as a function of the demagnetization effect and verified against fabricated samples of varying thicknesses. (C) 2010 American Institute of Physics. (doi: 10.1063/1.3430061

Precessional dynamics of Ni45Fe55 thin films for ultrahigh frequency integrated magnetics

Future monolithic point of load switched mode power supplies will be expected to meet the energy requirements of miniaturized, high functionality electronic devices. Recently, Ni45Fe55 has emerged as a potentially important material choice for use as a soft magnetic core material within high frequency integrated passive magnetic components. The operating frequency range of the integrated passives which form a key part of the point of load power supply must increase to allow for inductor/transformer miniaturization to become monolithic with power integrated circuits. In this work, an analysis of the high frequency permeability spectra of an electroplated Ni45Fe55 thin film has been carried out to quantitatively analyze the material's high frequency performance. Complex permeability spectra of the film have been investigated at frequencies up to 9 GHz to identify both the film's spectroscopic splitting factor (g) and its effective dimensionless damping parameter (alpha). The Kittel equation is utilized to identify g as 2.128, while alpha is determined to be approximately 0.045. The critically damped condition for the film is also examined to extract alpha in the critically damped case under a range of externally applied bias fields. It is concluded that for monolithic power inductors, improved device performance can be achieved when the ferromagnetic core is in an underdamped state up to a critical frequency

PwrSoC (integration of micro-magnetic inductors/transformers with active semiconductors) for more than Moore technologies

This paper introduces the concept of power supply on chip (PwrSoC) which will enable the development of next-generation, functionally integrated, power management platforms with applications in dc-dc conversion, gate drives, isolated power transmission and ultimately, high granularity, on-chip, power management for mixed-signal, SOC chips. PwrSoC will integrate power passives with the power management IC, in a 3D stacked or monolithic form factor, thereby delivering the performance of a high-efficiency dc-dc converter within the footprint of a low-efficiency linear regulator. A central element of the PwrSoC concept is the fabrication of power micro-magnetics on silicon to deliver micro-inductors and micro-transformers. The paper details the magnetics on silicon process which combines thin film magnetic core technology with electroplated copper conductors. Measured data for micro-inductors show inductance operation up to 20 MHz, footprints down to 0.5 mm(2), efficiencies up to 93% and dc current carrying capability up to 600 mA. Measurements on micro-transformers show voltage gain of approximately - 1 dB at between 10 MHz and 30 MHz