The Generalized Uncertainty Principle and Quantum Gravity Phenomenology

In this article we examine a Generalized Uncertainty Principle which differs from the Heisenberg Uncertainty Principle by terms linear and quadratic in particle momenta, as proposed by the authors in an earlier paper. We show that this affects all Hamiltonians, and in particular those which describe low energy experiments. We discuss possible observational consequences. Further, we also show that this indicates that space may be discrete at the fundamental level.Comment: 3 pages. Talk given by SD at the 12th Marcel Grossmann conference (Paris, July, 2009

Linear and Quadratic GUP, Liouville Theorem, Cosmological Constant, and Brick Wall Entropy

Motivated by the works on Equivalence Principle in the context of linear Generalized Uncertainty Principle and, independently, in the context of quadratic Generalized Uncertainty Principle, we expand these endeavors in the context of Generalized Uncertainty Principle when both linear and quadratic terms in momentum are include. We demonstrate how the definitions of equations of motion change upon that expansion. We also show how to obtain an analogue of Liouville theorem in the presence of linear and quadratic Generalized Uncertainty Principle. We employ the corresponding modified invariant unit volume of phase space to discuss the resulting density of states, the problem of cosmological constant, the black body radiation in curved spacetime, the concurrent energy and consequent no Brick Wall entropy.Comment: v1: 10 pages, RevTex, 7 figures; v2: references updated, one footnote added; v3: two footnotes and references added, no change in physics, to appear in EPJ

Orthopedic and Major Limb Trauma at the Tikur Anbessa University Hospital, Addis Ababa - Ethiopia

Background: In Ethiopia, Injuries constitute around half of all surgical emergencies, and are the primary reason for an emergency hospital visit in Addis Ababa, Ethiopia. The aim of this study was to determine the frequency and pattern of major limb traumatic injuries and orthopedic conditions treated as emergency at Tikur Anbessa University Hospital (TAUH).Methods: A three-year retrospective descriptive audit of all the orthopedic and major limb trauma patients who attended the ‘surgical’ emergency department of TAUH in the three-year period between December 2001 and November 2004, and who received treatment necessitating at least one further visit.Results: A total of 7317 patients presented to the orthopaedic emergency service at Tikur Anbessa Hospital (TAUH) during the study period. Their median age was 25 years. Males: Female ratio of 3:1. A total of 7151 (98%) had suffered one or more severe limb injuries. Polytrauma was noted in 516 (7%) of the cases. Road Traffic Injuries (RTI’s) accounted for 2793 (39%) patients of whom 88% were pedestrians who had been ‘hit by a car’. Hand injuries accounted for 841 (12%), and of these 162 (20%) lost either a part of or all of the hand. Ninety nine (61%) of these ‘hand’ amputations followed a machine injury. Only 740 patients were admitted to TAUH out of 2372 whose condition required urgent inpatient care. One hundred and sixty five patients (2% of total) arrived with an acute orthopedic infection, 120 were children (73%) and 109 (90%) of these arrived ‘late’.Conclusion: It is suggested that a reduction in the number of RTA’s together with appropriate education of the public would reduce the number of patients currently being injured in Addis Ababa. Finally we believe that this study recording the relative incidence of fractures and joint injuries by site will provide a base line for further studies

A two-stage game theoretical approach for interference mitigation in Body-to-Body Networks

International audienceIn this paper, we identify and exploit opportunities for cooperation between a group of mobile Wireless Body Area Networks (WBANs), forming a Body-to-Body Network (BBN), through inter-body interference detection and subsequent mitigation. Thus, we consider a dynamic system composed of several BBNs and we analyze the joint mutual and cross-technology interference problem due to the utilization of a limited number of channels by different transmission technologies (i.e., ZigBee and WiFi) sharing the same radio spectrum. To this end, we propose a game theoretical approach to address the problem of Socially-aware Interference Mitigation (SIM) in BBNs, where WBANs are " social " and interact with each other. Our approach considers a two-stage channel allocation scheme: a BBN-stage for inter-WBANs' communications and a WBAN-stage for intra-WBAN communications. We demonstrate that the proposed BBN-stage and WBAN-stage games admit exact potential functions, and we develop a Best-Response (BR-SIM) algorithm that converges to Nash equilibrium points. A second algorithm, named Sub-Optimal Randomized Trials (SORT-SIM), is then proposed and compared to BR-SIM in terms of efficiency and computation time. We further compare the BR-SIM and SORT-SIM algorithms to two power control algorithms in terms of signal-to-interference ratio and aggregate interference, and show that they outperform the power control schemes in several cases. Numerical results, obtained in several realistic mobile scenarios, show that the proposed schemes are indeed efficient in optimizing the channel allocation in medium-to-large-scale BBNs

A reliable design of Wireless Body Area Networks

International audienceIn this paper, we propose a reliable topology design and provisioning approach for Wireless Body Area Networks (named RTDP-WBAN) that takes into account the mobility of the patient while guaranteeing a reliable data delivery required to support healthcare applications' needs. To do so, we first propose a 3D coordinate system able to calculate the coordinates of relay-sensor nodes in different body postures and movements. This system uses a 3D-model of a standard human body and a specific set of node positions with stable communication links, forming a virtual backbone. Next, we investigate the optimal relay nodes positioning jointly with the reliable and cost-effective data routing for different body postures and movements. Therefore, we use an Integer Linear Programming (ILP) model, that is able to find the optimal number and locations of relay nodes and calculate the optimal data routing from sensors and relays towards the sink, minimizing both the network setup cost and the energy consumption. We solve the model in dynamic WBAN (Stand, Sit and Walk) scenarios, and compare its performance to other relaying approaches. Experiment results showed that our realistic and dynamic WBAN design approach significantly improves results obtained in the literature, in terms of reliability, energy-consumption and number of relays deployed on the body

Business Model Innovation: A Review and Research Agenda

Purpose – The aim of this paper is to review and synthesise the recent advancements in the business model literature and explore how firms approach business model innovation. Design/methodology/approach – A systematic review of business model innovation literature was carried out by analysing 219 papers published between 2010 and 2016. Findings – Evidence reviewed suggests that rather than taking either an evolutionary process of continuous revision, adaptation and fine-tuning of the existing business model or a revolutionary process of replacing the existing business model, firms can explore alternative business models through experimentation, open and disruptive innovations. It was also found that changing business models encompasses modifying a single element, altering multiple elements simultaneously and/or changing the interactions between elements in four areas of innovation: value proposition, operational value, human capital and financial value. Research limitations/implications – Although this review highlights the different avenues to business model innovation, the mechanisms by which firms can change their business models and the external factors associated with such change remain unexplored. Practical implications – The business model innovation framework can be used by practitioners as a “navigation map” to determine where and how to change their existing business models. Originality/value – Because conflicting approaches exist in the literature on how firms change their business models, the review synthesises these approaches and provides a clear guidance as to the ways through which business model innovation can be undertaken

Evaluation of Vibration Amplitude Stepping and Welding Performance of 20 kHz and 40 kHz Ultrasonic Power of Metal Welding

Today ultrasonic power technique is consider a mandatory technique which is always entered in many processes such as in metal and plastic welding to overcomes many issues, with aided of applying force (pressure) and supplied high frequency vibration, a solid-state weld can be generated by ultrasonic metal welding technique. That gives a technique the ability to join not only a small component, whereas also to join thicker specimens, which depends on a proper control of matching welding conditions. Therefore a welding performance can be studied and compared after designed welding horn to resonance at frequencies of 20 kHz and 40 kHz. The analyses of the designed horn are completed through use a vibration mathematical expressions, modal and harmonic analyses to ensure the weldability due to applying ultrasonic power to the working area and also to compare the performance of joint at using two resonance frequencies of 20 kHz and 40 kHz. The dimensions of the horns were determined to match the selected resonance frequencies, which the lengths were calculated as 132 mm and 66 mm respectively. The analysis of the exciting model indicates that the axial vibration modes of 19,584 Hz and 39,794 Hz are obtained in 10th mode, while the two frequency values are recorded 19,600 Hz and 39,800 Hz from the frequency response of the two horns. The weld strength between Al and Cu specimens with a thickness 0.5 mm was evaluated using a tensile test, which the analyses were obtained under using different welding pressure and varied amplitudes. The results were recorded within exciting a horn with two different resonance frequencies, show the enhancement of weld strength and quality through control of stepping amplitude, the enhancement means obtain good strength of the weld, reduce sticking horn to specimen, and lower specimen marking

A proposal for testing Quantum Gravity in the lab

Attempts to formulate a quantum theory of gravitation are collectively known as {\it quantum gravity}. Various approaches to quantum gravity such as string theory and loop quantum gravity, as well as black hole physics and doubly special relativity theories predict a minimum measurable length, or a maximum observable momentum, and related modifications of the Heisenberg Uncertainty Principle to a so-called generalized uncertainty principle (GUP). We have proposed a GUP consistent with string theory, black hole physics and doubly special relativity theories and have showed that this modifies all quantum mechanical Hamiltonians. When applied to an elementary particle, it suggests that the space that confines it must be quantized, and in fact that all measurable lengths are quantized in units of a fundamental length (which can be the Planck length). On the one hand, this may signal the breakdown of the spacetime continuum picture near that scale, and on the other hand, it can predict an upper bound on the quantum gravity parameter in the GUP, from current observations. Furthermore, such fundamental discreteness of space may have observable consequences at length scales much larger than the Planck scale. Because this influences all the quantum Hamiltonians in an universal way, it predicts quantum gravity corrections to various quantum phenomena. Therefore, in the present work we compute these corrections to the Lamb shift, simple harmonic oscillator, Landau levels, and the tunneling current in a scanning tunneling microscope.Comment: v1: 10 pages, REVTeX 4, no figures; v2: minor typos corrected and a reference added. arXiv admin note: has substantial overlap with arXiv:0906.5396 , published in a different journa

Ecrime threats on Egovernment – the case of Maldives

EGovernment implementations are nowadays common even amongst the smallest and countries around the world. The challenge of building such systems is even greater for developing countries, in particular those who are struggling against considerable penetration of the Digital Divide in their society. This paper proposes a theoretical framework for implementing eGovernment in the Maldives, a small country aiming to overcome the difficulties of offering twentyfirst century services to a small by widely dispersed population. The particular interest in the case of the Maldives is that the technological infrastructure is sensitive and dependent on external condition, while there is wide chasm in society due to the effects of the Digital Divide