Search results for "LESS"
showing 10 items of 2452 documents
Endograft connector technique to treat popliteal artery aneurysm in a morbid obese patient.
2015
Surgical repair of popliteal artery aneurysm in morbid obese patients poses additional challenges. We report a morbid obese patient who had a 59 mm right popliteal artery aneurysm which was successfully treated with the endograft connector technique. This technique was used to perform the distal anastomosis of the below-knee femoro-popliteal bypass. A 10 mm Dacron graft was used as a main graft bypass and an 11 mm/10 cm stentgraft as endograft connector. Following the respective tunnel of the Dacron graft, an end-to-side proximal anastomosis was performed at distal femoral artery. The aneurysm exclusion was obtained through a proximal and a distal ligation. Postoperative duplex showed adeq…
Is It Possible to Create a “Mechanical” Arteriovenous Fistula in Hemodialysis Patients?
2010
Manual suturing still remains the best technique for the creation of vascular anastomoses on uremic patients with excellent results, despite being time consuming, difficult to perform with small vessels, and associated with a significant learning curve. We created a full mechanical arteriovenous fistula on a 65-year-old uremic patient with a new device already used in cardiac bypass surgery. The fistula was created automatically and rapidly, without the need for temporary occlusion of the artery, reducing the risk of blood clotting. We believe that mechanical devices may be useful to produce precise and fast anastomoses requiring minimal training for the surgeon.
Demand for and Pricing of Mobile Internet: Evidence from a Real-World Pricing Experiment
2006
Commercialization of innovations frequently stumbles. A prominent recent example are the early (i.e. pre3G)mobile phone-enabled Internet services, whose European takeup was slower than expected. To determine why, we build a structural model of demand for such services and estimate it using consumerlevel panel data from a real world pricing experiment. The experiment allows for a decomposition of the number of wireless connections into the number of needs instances where a consumer would establish a connection if the price were zero and the conditional probability of establishing a connection. We find that needs were plenty and potential consumer surplus several magnitudes higher than that a…
Closing the sensing-reasoning-actuating loop in resource-constrained WSANs through distributed symbolic processing
2015
Many issues in creating complex applications for pervasive environments are primarily due to the effort required to integrate perception, reasoning and actuating tasks in an efficient and homogeneous way, especially when the underlying infrastructure consists of wirelessly networked embedded devices. To mitigate the complexity of the actual implementation, satisfactory programming paradigms supporting the integration and coordination among heterogeneous devices are required. In this paper we show how a distributed symbolic processing approach that is particularly suited for resource constrained devices, such as the nodes of a Wireless Sensor and Actuator Network (WSAN), may be apt to the pu…
Energy Harvesting Powered Packet Transmissions in Duty-Cycled WSNs: A DTMC Analysis
2017
Energy harvesting (EH) promises an extended lifetime for wireless sensor networks (WSNs), supplying sensor nodes with accumulated energy from natural sources. Different from battery powered sensors, nodes in EH-enabled WSNs are equipped with an energy harvesting accessory in order to extract energy from surrounding sources. Based upon the harvested energy, sensor nodes perform data exchange activities. In this paper, we develop two discrete time Markov chain (DTMC) models to analyze the performance of packet transmissions in such a WSN while employing a generic synchronous medium access control (MAC) protocol. Using the proposed DTMC models, we investigate the effect of EH over a specific s…
Collision Avoidance in Wake-Up Radio Enabled WSNs: Protocol and Performance Evaluation
2018
In wake-up radio (WuR) enabled wireless sensor networks (WSNs), the envisaged application scenarios are primarily targeted at low traffic load conditions. When applying WuR to medium or heavy traffic load scenarios, however, collisions among wake-up calls (WuCs) may happen, resulting in a lower packet delivery ratio (PDR). In this paper, we propose a media access control protocol for WuR- enabled WSN that is capable of avoiding WuC collisions by activating a contention-based collision avoidance mechanism for WuC transmissions. The performance of the proposed protocol is evaluated by a Markov chain based mathematical model and is compared with a WuR protocol that performs only clear channel as…
Event-Triggered Sleeping for Synchronous DC MAC IN WSNs: Mechanism and DTMC Modeling
2016
Overhearing and idle listening are two primary sources for unnecessary energy consumption in wireless sensor networks. Although introducing duty cycling in medium access control (MAC) reduces idle listening, it cannot avoid overhearing in a network with multiple contending nodes. In this paper, we propose an event-triggered sleeping (ETS) mechanism for synchronous duty-cycled (DC) MAC protocols in order to avoid overhearing when a node is not active. This ETS mechanism applies to any synchronous DC MAC protocols and makes them more energy efficient. Furthermore, we develop a two dimensional discrete time Markov chain model to evaluate the performance of the proposed ETS mechanism by integra…
Energy Efficient Consecutive Packet Transmissions in Receiver-Initiated Wake-Up Radio Enabled WSNs
2018
In wake-up radio (WuR)-enabled wireless sensor networks, data communication among nodes is triggered in an on-demand manner, by either a sender or a receiver. For receiver-initiated WuR (RI-WuR), a receiving node wakes up sending nodes through a wake-up call. Correspondingly sending nodes transmit packets in a traditional way by competing with one another multiple times in a single operational cycle. In this paper, we propose a receiver-initiated consecutive packet transmission WuR (RI-CPT-WuR) medium access control (MAC) protocol, which eliminates multiple competitions to achieve higher energy efficiency. Furthermore, we develop two associated discrete time Markov chains (DTMCs) for evalua…
Modelling mass transfer properties in a biotrickling filter for the removal of isopropanol
2014
Abstract A study was carried out to model mass transfer properties in biotrickling filters, treating isopropanol as the target pollutant. This study was extended to the mass transfer of oxygen related to the fact that the treatment of hydrophilic compounds by biotrickling filtration is often limited by oxygen. A simple method for each compound was developed based on their physical properties. The influence of temperature on Henry’s law constant of isopropanol was determined. An increase of 1.8 per 10 °C for the dimensionless Henry’s law constant was obtained. The determination of the overall mass transfer coefficients of isopropanol (KGa) was carried out, obtaining values between 500 and 18…
Neutrino masses, Majorons, and muon decay
1987
5 páginas, 3 figuras.