1,431 research outputs found

    Performance study of end-to-end traffic-aware routing

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    There has been a lot research effort on developing reactive routing algorithms for mobile ad hoc networks (MANETs) over the past few years. Most of these algorithms consider finding the shortest path from source to destination in building a route. However, this can lead to some network nodes being more overloaded than the others. In MANETs resources, such as node power and channel bandwidth are often at a premium and, therefore, it is important to optimise their use as much as possible. Consequently, a traffic-aware technique to distribute the load is very desirable in order to make good utilisation of nodes' resources. A number of traffic aware techniques have recently been proposed and can be classified into two categories: end-to-end and on-the-spot. The performance merits of the existing end-to-end traffic aware techniques have been analysed and compared against traditional routing algorithms. There has also been a performance comparison among the existing on-the-spot techniques. However, there has so far been no similar study that evaluates and compares the relative performance merits of end-to-end techniques. In this paper, we describe an extensive performance evaluation of two end-to-end techniques, based on degree of nodal activity and traffic density, using measures based on throughput, end-to-end delay and routing overhead

    RRS Discovery Cruise DY032, 20 Jun - 07 Jul 2014. Cruise to the Porcupine Abyssal Plain sustained observatory

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    The Porcupine Abyssal Plain Observatory is a sustained, multidisciplinary observatory in the North Atlantic coordinated by the National Oceanography Centre, Southampton. For over 20 years the observatory has provided key time-series datasets for analysing the effect of climate change on the open ocean and deep-sea ecosystems. As is normally the case during cruises which are needed to refurbish the observatory, a wide range of other activities were carried out during the cruise. The main mooring Ocean Data Acquisition System (ODAS) buoy had ceased transmitting data in March 2015, so a high priority was to recover the buoy and its stored data and this was successfully achieved. In addition, we recovered a set of sediment traps which had been collecting sinking material in the lower part of the water column for the previous 12 months and deployed a new set. These are the autonomous systems, but as is usually the case with our trips to PAP, we carried out various other activities and in this case we investigated the degradation of particles as they sink. Our colleagues from MIO in France carry out sophisticated interrogation using radiolabelling. The Bathysnap time-lapse camera system which had been taking photos of the seabed at 4800m was recovered to give an assessment of the behaviour of the benthic animals and how the seabed appearance changes in response to deposition of material. A new module was deployed. Temporal variability of the water column and seabed fauna - a task which is difficult or impossible to do autonomously was assessed using nets and cores

    RRS James Cook Cruise 87, 31 May - 18 Jun 2013. The Twilight Cruise to the Porcupine Abyssal Plain Sustained Observatory

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    The Twilight Zone is that depth zone in the ocean between 100 and 1000m depth where a tremendous amount of activity takes place. Much of the material containing carbon which sinks out of the upper sunlit or "Euphotic" zone is broken down in the twilight zone and then mixes back up to the surface in the winter. If it manages to sink further, this carbon is lost for periods of centuries. The main factor that affects this sedimentation process and the rate of destruction of the sinking particles is the structure and function of the biological community living near the sea surface and in the twilight zone beneath. This is because the planktonic plants and animals living there both generate and destroy particles. The Porcupine Abyssal Plain sustained observatory (PAP) is a heavily instrumented area of the open ocean 350 miles southwest of Ireland and in a water depth of 4800m. The instruments measure a wide variety of properties of the environment above the water, within it and on the seabed and much of the data is transmitted in real time to land via satellite

    RV Meteor Cruise 108, 06 - 24 Jul 2014. Cruise to the Porcupine Abyssal Plain sustained observatory

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    The Porcupine Abyssal Plain Observatory is a sustained, multidisciplinary observatory in the North Atlantic coordinated by the National Oceanography Centre, Southampton. For over 20 years the observatory has provided key time-series datasets for analysing the effect of climate change on the open ocean and deep-sea ecosystems. As is normally the case during cruises which are needed to refurbish the observatory, a wide range of other activities were carried out during the cruise. The main mooring of the observatory broke in December 2013 during the horrendous winter storms which destroyed a number of Met Office moorings around the UK. However we were fortunate that the break occurred just below the main sensor frame and as a result we were able to recover it along with the massive Ocean Data Acquisition System (ODAS) buoy after it had drifted towards Ireland. We were therefore able to recover all of the sensors and, most importantly, the data stored in them. Prior to Meteor cruise 108 they were all refurbished and were deployed during M108 along with some additional sensors. In addition we recovered a set of sediment traps which had been collecting sinking material in the lower part of the water column for the previous 12 months and a new set was deployed. Furthermore some entirely novel research was carried out on the distribution and characteristics of marine snow particles in the top few hundred meters of the water column. These are inanimate particles which are the principle vehicles by which material sinks out of the upper sunlit zone down to the abyss, taking carbon down with them and out of contact with the atmosphere for centuries. We used optical methods to characterise their distribution and collected samples using the Marine Snow catcher thereby providing material for a variety of experiments with colleagues from Bremen. The Bathysnap time-lapse camera system which had been taking photos of the seabed at 4800m was recovered to give an assessment of the behaviour of the benthic animals and how the seabed appearance changes in response to deposition of material. A new module was deployed. Temporal variability of the water column and seabed fauna - a task which is difficult or impossible to do autonomously was assessed using nets and cores

    RRS Discovery Cruise DY077, 14 Apr - 01 May 2017. Cruise to the Porcupine Abyssal Plain sustained observatory

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    The Discovery slipped moorings in Southampton at 0830h GMT on Friday 14th April 2017 after an uneventful mobilisation apart from the discovery that on opening one of the sealed boxes of mooring rope for the PAP#1 mooring, it was found to be empty. Discovery arrived at PAP at 2005h for our first station, a CTD rosette cast to 100m. The Discovery left the site at 1645h on Friday 28th April, somewhat earlier than expected due to a predicted storm which did indeed cause some difficulties for the ship during the return to the UK coming alongside at Portland at 1100h on Monday 1st May to exchange personnel and equipment. Moorings were slipped at 0800h on 2nd May followed by equipment trials and a final docking at Southampton NOC at 2000h on 2nd May. The Porcupine Abyssal Plain Observatory is a sustained, multidisciplinary observatory in the North Atlantic coordinated by the National Oceanography Centre, Southampton. For over 20 years the observatory has provided key time-series datasets for analysing the effect of climate change on the open ocean and deep-sea ecosystems. More information on PAP can be found in NOCs website at: http://projects.noc.ac.uk/pap/ where the most current data can be found: http://projects.noc.ac.uk/pap/pap-april-2017 PAP is one of the 23 fixed-point open ocean observatories included in the Europe-funded project FixO3, coordinated by Professor Richard Lampitt at NOC: http://www.fixo3.eu/ This 4-year project started in September 2013 with the aim to integrate the open ocean observatories operated by European organizations and is a collaboration of 29 partners from 10 different countries

    Hybrid dual mode sensor for simultaneous detection of two serum metabolites

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    Metabolites are the ultimate readout of disease phenotype that plays a significant role in the study of human disease. Multiple metabolites sometimes serve as biomarkers for a single metabolic disease. Therefore, simultaneous detection and analysis of those metabolites facilitate early diagnostics of the disease. Conventional approaches to detect and quantify metabolites include mass spectrometry and nuclear magnetic resonance that require bulky and expensive equipment. Here, we present a disposable sensing platform that is based on complementary metal–oxide–semiconductor process. It contains two sensors: an ion sensitive field-effect transistor and photodiode that can work independently for detection of pH and color change produced during the metabolite-enzyme reaction. Serum glucose and cholesterol have been detected and quantified simultaneously with the new platform, which shows good sensitivity within the physiological range. Low cost and easy manipulation make our device a prime candidate for personal metabolome sensing diagnostics

    Impact of oxidative stress on pregnancy outcome in albino rats

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    Accumulative reports documented that oxidative stress is implicated in many human and animal diseases. However, the reports concerning the effect of oxidative stress on pregnancy outcome are limited and scarce. The objective of this study was to determine the impact of oxidative stress on pregnancy outcome and to assess the antioxidant effect of vitamin C and E on oxidative stress parameters in blood and placental tissue samples in experimental pregnant animals model exposed to oxidative stress. Wister Albino rats were used in this work to investigate the effects of oxidative stress exposure (addition of H2O2 to the drinking water) on pregnancy outcome. Rats were divided into 5 groups, as follows: Group I (included 7 normal pregnant rats which served as control group). Group II (exposed to 1 % H2O2) included 7 pregnant rats, the rats were allowed to become pregnant and received (1% H2O2) in drinking water from day 7th till the day 19th of pregnancy. Group III (exposed to 3% H2O2) included 8 pregnant rats. Same as group 2, but the rats were exposed to a higher concentration of H2O2 (3%) in drinking water. Group IV (included 8 pregnant rats). Pregnant rats received vitamins C and E without induction of oxidative stress. Group V (included 8 pregnant rats).induction of oxidative stress by 1% H2O2 with vitamins supplementation in the pregnant rats. Serum total antioxidants capacity (TAC), serum and placental tissue oxidative stress biomarker; 8-iso prostaglandin F2α (8-Isoprostane) were measured using specific ELISA kits. Also placental tissues of pregnant rats were isolated and put directly in 10% formalin prepared for histopathological examination. Results revealed a significant decrease in the median values of the body weight and total serum antioxidants capacity (TAC) in groups II and III of rats compared with the control group. A significant higher median value of TAC obtained in the groups IV and V when compared with the control group. Significant higher levels of serum and tissue Isoprostane observed in both groups II and III compared with control group. Histopathological, oxidative stress induced macroscopically degenerative with microscopical appearance of vasculitis and hemorrhage within decidua. Data of the present study demonstrated that imbalance oxidative stress status in pregnant rats occurred due to exposure to oxidant, which played an important role in the pathogenesis of abnormal pregnancy outcome. In addition antioxidants supplementation (vitamins E and C) were valuable in reducing this stress

    Hydrogenation of toluene on Ni-Co-Mo supported zeolite catalysts

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    Mixed oxides of Ni, Co and Mo supported on five zeolites -ZSM-5-a, ZSM-5-b, HY-a, HY-b and Mordenite were prepared and characterized using many techniques for use as hydrotreating catalysts. In a preliminary investigation, toluene was employed as model compound to test the catalysts in hydrogenation, as a major upgrading reaction. TGA/DSC analysis showed that the impregnation of the metals slightly affected the thermal stability of the zeolites with all catalytic samples displaying good stability up to 730oC.The XRD patterns for all the catalytic samples showed that the framework of the zeolites were retained after impregnation. XRD and TPR results confirmed the presence of molybdenum trioxide on the zeolites with NiCoMo/HY-b displaying high metal-support interaction due to low reduction temperatures. The activity results showed that toluene conversion of almost 100% and selectivity to mainly methyl-cyclohexane was achieved. The catalysts activity test showed that the zeolite support textural properties particularly surface area, pore volume and pore diameter affect the performance of the catalysts. NiCoMo/HY-b displayed the best performance after the few minutes of the reaction due to its high surface area, pore volume and average pore diameter.Keywords: Hydro treating catalysts; Hydrogenation; Toluene conversion; Surface area; Pore diamete

    Low Noise and High Photodetection Probability SPAD in 180 nm Standard CMOS Technology

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    A square shaped, low noise and high photo-response single photon avalanche diode suitable for circuit integration, implemented in a standard CMOS 180 nm high voltage technology, is presented. In this work, a p+ to shallow n-well junction was engineered with a very smooth electric field profile guard ring to attain a photo detection probability peak higher than 50% with a median dark count rate lower than 2 Hz/μm2 when operated at an excess bias of 4 V. The reported timing jitter full width at half maximum is below 300 ps for 640 nm laser pulses

    Hybrid Amperometric and Potentiometric Sensing Based on a CMOS ISFET Array

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    Potentiometry and amperometry are some of the most important techniques for electroanalytical applications. Integrating these two techniques on a single chip using CMOS technology paves the way for more analysis and measurement of chemical solutions. In this paper, we describe the integration of electrode transducers (amperometry) on an ion imager based on an ISFET array (potentiometry). In particular, this integration enables the spatial representation of the potential distribution of active electrodes in a chemical solution under investigation
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