Joint physical-MAC layer design of the broadcast channel protocol in adhoc networks

Broadcast transmission mode in ad hoc networks is critical to manage multihop routing or providing medium accesscontrol (MAC)-layer fairness. In this paper, it is shown that ahigher capacity to exchange information among neighbors may beobtained through a physical-MAC cross-layer design of the broadcastprotocol exploiting signal separation principles. Coherentdetection and separation of contending nodes is possible throughtraining sequences which are selected at random from a reducedset. Guidelines for the design of this set are derived for a lowimpact on the network performance and the receiver complexity.

Rehabilitation of atrophic maxilla: a review of 101 zygomatic implants

Introduction: Zygomatic implants are a good rehabilitation alternative for upper maxilla with severe bone reabsorption. These implants reduce the need for onlay-type bone grafting in the posterior sectors and for maxillary sinus lift procedures - limiting the use of bone grafts to the anterior zone of the upper jaw in those cases where grafting is considered necessary. Objective: To evaluate the survival of 101 zygomatic implants placed in upper maxilla presenting important bone reabsorption, with a follow-up of 1-72 months. Patients and methods: A retrospective study was made of 101 Zygoma® implants (Nobel Biocare, Göteborg, Sweden) placed in 54 patients with totally edentulous and atrophic upper maxilla, in the period between 1998-2004. There were 35 women and 19 men, subjected to rehabilitation in the form of fixed prostheses and overdentures using 1-2 zygomatic implants and 2-7 implants in the anterior maxillary zone. The principal study variables were smoking, a history of sinusitis, the degree of bone reabsorption, and peri-implant bone loss, among others. Results: The descriptive analysis of the 101 zygomatic implants placed in 54 patients with a mean age of 56 years (range 38-75) yielded a percentage survival of 96.04%, with four failed implants that were removed (two before and two after prosthetic loading). Nine patients were smokers, and none of the 54 subjects reported a history of sinus disorders. Discussion and conclusions: Zygomatic implants are designed for use in compromised upper maxilla. They allow the clinician to shorten the treatment time, affording an interesting alternative for fixed prosthetic rehabilitation. This study confirms that zygomatic bone offers predictable anchorage and acceptable support function for prostheses in atrophic jaws. However, these implants are not without complications. Longer-term evaluations are needed of zygomatic implant survival in order to establish a correct clinical prognosis

WiBed, A Platform for Commodity Wireless Testbeds

Testbeds are a stage between the simulation and the production stages. To this end they must be as close as possible to production environments (i.e. real hardware, on the field deployments) while also keeping the traits of experimentation facilities (i.e. fault tolerance, ease of deployment, testing and data collection). This paper presents WiBed, a FOSS platform for WiFi testbeds based on OpenWRT Linux made to run oncommodity IEEE802.11 WiFi routers part of the Community-lab.net project, a global testbed for Community networks. WiBedhas been designed to support realistic low layer network exper-iments (according to the OSI model). This work recolects thedetails of the architecture, design and implementation of WiBed consolidated during its operation as a testbed. In addition to a set of routing experimentation results obtained during the Wireless Battlemesh v7 where WiBed was used as testbed platform.

Periodontal health and esthetic results in impacted teeth exposed by apically positioned flap technique

Objectives: This study evaluates the periodontal health status and the esthetic results of teeth subjected to orthodontic traction, after their exposure by an apically positioned flap. Study design: Fifteen patients were included in the study, ages between 11 and 28 years old. The fenestrated teeth and their homologous contralateral normally erupted teeth, used as control, were evaluated. Results: Statistically significant differences were found in the position of the gingival margin (p = 0.005), with an average distance between cemento-enamel junction (CEJ) and gingival margin of 2.47 mm (SD 1.19) in control teeth and of 1 mm (SD 1.31) in the operated teeth, and in the depth of palatal probing (p = 0.031), with 2.1 mm (SD 0.9) for the experimental teeth and 1.7 mm (SD 0.8) for the control teeth. The gingival index, the bleeding during probing and the probing depth did not show statistically significant differences. The patient"s subjective esthetic evaluation was more favorable for the control teeth in most of the cases. Conclusions: The surgical approach for the impacted teeth by means of the apically positioned flap resulted to be a predictable technique allowing the maintenance of the periodontal health on a long-term basis.

Complications of guided surgery and immediate loading in oral implantology: a report of 12 cases

Objectives: The growing interest in minimally invasive surgery, together with the possibility of fitting prostheses with immediate function, have led to the development of software capable of planning and manufacturing a surgical guide and prosthesis that can be placed upon conclusion of the implant surgery step. The present study evaluates the surgical and prosthetic complications of implant treatment with the guided surgery technique, together with patient comfort during and after treatment. Patients and methods: A retrospective observational study was made of 19 patients with partially or totally edentulous upper and/or lower maxillae, involving the placement of a total of 122 implants. All cases were planned and operated upon with the guided surgery technique. Results: A total of 122 implants were placed in 14 males and 5 females. The intraoperative surgical complications comprised a lack of primary stability, while the postoperative complications consisted of infections and a lack of implant osteointegration. Ten implants failed. The prosthetic complications in turn comprised loosening of the provisional prosthesis screws, prosthesis tooth fracture, and a lack of passive fit of the immediate prosthesis. The degree of patient satisfaction was evaluated using a verbal scale. Conclusions: Implant restoration with the guided surgery technique and immediate functional loading is a predictable procedure, provided patient selection and the surgical technique are adequate, affording lesser postoperative morbidity and increased patient satisfaction thanks to the immediate restoration of esthetics and function

World Polarization in carbon emissions, potential conflict and groups: an updated revision

Typically, conflicts in world environmental negotiations are related, amongst other aspects, to the level of polarization of the countries in groups with conflicting interests. Given the predictable relationship between polarization and conflict, it would seem logical to evaluate the degree to which the distribution of countries – for example, in terms of their CO2 emissions per capita – would be structured through groups which in themselves are antagonistic, as well as their evolution over time. This paper takes the concept of polarization to explore this distribution for the period 1992-2010, looking at different analytic approaches related to the concept. Specifically, it makes a comparative evaluation of the results associated with endogenous multi-polarization measures (i.e. EGR and DER indices), exogenous measures (i.e. Z-K or multidimensional index) and strict bipolarization measures (i.e. Wolfson’s measure). Indeed, the interest lies not only in evaluating the global situation of polarization by comparing the different approaches and their temporal patterns, but also in examining the explanatory capacity of the different proxy groups used as a possible reference for designing global environmental policy from a group premise. JEL codes: D39; Q43; Q56. Key words: polarization; carbon emissions; conflict;

Experimental evaluation of anonymous protocols under the JXTA middleware

JXTA is a peer-to-peer (P2P) middleware whichhas undergone successive iterations through its 10 years of history, slowly incorporating a security baseline that may cater to different applications and services. However, in order to appeal to a broader set of secure scenarios, it would be interesting to take into consideration more advanced capabilities, such as anonymity.There are several proposals on anonymous protocols that can be applied in the context of a P2P network, but it is necessary to be able to choose the right one given each application¿s needs. In this paper, we provide an experimental evaluation of two relevant protocols, each one belonging to a different category of approaches to anonymity: unimessage and split message. Webase our analysis on two scenarios, with stable and non-stable peers, and three metrics: round trip-time (RTT), node processing time and reliability.

Mediterranean-climate streams and rivers: geographically separated but ecologically comparable freshwater systems

Streams and rivers in mediterranean-climate regions (med-rivers in med-regions) are ecologically unique, with flow regimes reflecting precipitation patterns. Although timing of drying and flooding is predictable, seasonal and annual intensity of these events is not. Sequential flooding and drying, coupled with anthropogenic influences make these med-rivers among the most stressed riverine habitat worldwide. Med-rivers are hotspots for biodiversity in all med-regions. Species in med-rivers require different, often opposing adaptive mechanisms to survive drought and flood conditions or recover from them. Thus, metacommunities undergo seasonal differences, reflecting cycles of river fragmentation and connectivity, which also affect ecosystem functioning. River conservation and management is challenging, and trade-offs between environmental and human uses are complex, especially under future climate change scenarios. This overview of a Special Issue on med-rivers synthesizes information presented in 21 articles covering the five med-regions worldwide: Mediterranean Basin, coastal California, central Chile, Cape region of South Africa, and southwest and southern Australia. Research programs to increase basic knowledge in less-developed med-regions should be prioritized to achieve increased abilities to better manage med-rivers.

Trace me if you can: the use of intrinsic biogeochemical markers in marine top predators

Human activities have serious impacts on marine apex predators. Inadequate knowledge of the spatial and trophic ecology of these marine animals ultimately compromises the viability of their populations and impedes our ability to use them as environmental biomonitors. Intrinsic biogeochemical markers, such as stable isotopes, fatty acids, trace elements, and chemical pollutants, are increasingly being used to trace the spatial and trophic ecology of marine top predators. Notable advances include the emergence of the first oceanographic"isoscapes" (isotopic geographic gradients), the advent of compound-specific isotopic analyses, improvements in diet reconstruction through Bayesian statistics, and tissue analysis of tracked animals to ground-truth biogeochemical profiles. However, most researchers still focus on only a few tracers. Moreover, insufficient knowledge of the biogeochemical integration in tissues, fractionation and routing processes, and geographic and temporal variability in baseline levels continue to hamper the resolution and potential of these markers in studying the spatial and feeding ecology of top predators.

Optimal Traffic Grooming in WDM using Lighttours

Recent developments in optical communications have allowed simpler optical devices to improve network resource utilization. As such, we propose adding a lambda-monitoring device to a wavelength-routing switch (WRS) allowing better performance when traffic is routed and groomed. This device may allow a WRS to aggregate traffic over optical routes without incurring in optical-electrical-optical conversion for the existing traffic. In other words, optical routes can be taken partially to route demands creating a sort of "lighttours". In this paper, we compare the number of OEO conversions needed to route a complete given traffic matrix using either lighttours or lightpaths

Operational Cost Reduction in WDM Networks using Lighttours

Wavelength division multiplexing (WDM) networks have been adopted as a near-future solution for the broadband Internet. In previous work we proposed a new architecture, named enhanced grooming (G+), that extends the capabilities of traditional optical routes (lightpaths). In this paper, we compare the operational expenditures incurred by routing a set of demands using lightpaths with that of lighttours. The comparison is done by solving an integer linear programming (ILP) problem based on a path formulation. Results show that, under the assumption of single-hop routing, almost 15% of the operational cost can be reduced with our architecture. In multi-hop routing the operation cost is reduced in 7.1% and at the same time the ratio of operational cost to number of optical-electro-optical conversions is reduced for our architecture. This means that ISPs could provide the same satisfaction in terms of delay to the end-user with a lower investment in the network architecture

G+: Enhanced Traffic Grooming in WDM Mesh Networks using Lighttours

In this article, a new technique for grooming low-speed traffic demands into high-speed optical routes is proposed. This enhancement allows a transparent wavelength-routing switch (WRS) to aggregate traffic en route over existing optical routes without incurring expensive optical-electrical-optical (OEO) conversions. This implies that: a) an optical route may be considered as having more than one ingress node (all inline) and, b) traffic demands can partially use optical routes to reach their destination. The proposed optical routes are named "lighttours" since the traffic originating from different sources can be forwarded together in a single optical route, i.e., as taking a "tour" over different sources towards the same destination. The possibility of creating lighttours is the consequence of a novel WRS architecture proposed in this article, named "enhanced grooming" (G+). The ability to groom more traffic in the middle of a lighttour is achieved with the support of a simple optical device named lambda-monitor (previously introduced in the RingO project). In this article, we present the new WRS architecture and its advantages. To compare the advantages of lighttours with respect to classical lightpaths, an integer linear programming (ILP) model is proposed for the well-known multilayer problem: traffic grooming, routing and wavelength assignment The ILP model may be used for several objectives. However, this article focuses on two objectives: maximizing the network throughput, and minimizing the number of optical-electro-optical conversions used. Experiments show that G+ can route all the traffic using only half of the total OEO conversions needed by classical grooming. An heuristic is also proposed, aiming at achieving near optimal results in polynomial time

Estudi i implementació pràctica d'una xarxa Wifi Mesh

En el projecte ens centrarem en el funcionament de les Xarxes mallades sense fils, es fa una breu explicació de les xarxes Ad-hoc, ja que aquestes formen un part important dintre d’una xarxa Mesh. S’explicaran diversos protocols d’enrutament com ara BATMAN, AODV, 802.11s i OLSR. Aquest últim és el que utilitzarem per a la configuració de la xarxa que realitzarem. S’explicarà el tipus de paquets que s’envien entre els nodes perquè el funcionament de la xarxa sigui òptim i tots els clients puguin tenir-hi accés i estiguin connectats entre ells. Al finalitzar l’estudi teòric d’aquest tipus de xarxa i veure les seves avantatges i desavantatges respecte altres tipus de xarxes sense fils, es muntaran dos petites xarxa. Per a muntar-les utilitzarem de Punts d’Accés els nodes Ubuquiti Nanoestation LocoM2. Una de les xarxes serà al poble Bellcaire d’Urgell, on és connectaran tres cases, on només una te accés a Internet i els nodes estaran connectats en línia, es a dir, del Node1 – Node2 – Node3. La segona serà a una casa de Barcelona on mitjançant els tres nodes obtindrem una connexió d’Internet a tota la casa, en aquest cas els tres nodes estaran connectats els tres formant un cercle, es a dir, Node1-Node2-Node3-Node1. Finalment, és mirarà una proposta de futur, on es parlaria amb l’Ajuntament del poble on s’ha fet la primera proba per realitzar una Xarxa mallada sense fils a tots els llocs públics del poble.