44,813 research outputs found
Plasma needle : exploring biomedical applications of non-thermal plasmas
No full textThe plasma needle is a novel design of a radio-frequency discharge in helium/air mixtures at atmospheric pressure. The discharge contains neutral, excited and ionized particles, and emits ultraviolet (UV) light. It operates at low electric power and close to ambient temperature; it combines chemical activity with non-destructive character. Therefore it is expected that the plasma needle will be used in future in (micro) surgery, e.g. in wound healing and in controlled tissue removal through cell detachment or apoptosis, avoiding necrosis and in°ammation reactions. Focus of this study is both on optimization of needle design and on assessment of effects of plasma activity on living cells. This work is a pio- neering study of the effects of non-thermal plasma on biological samples. The design of the plasma needle was adjusted in such a way that instead of operating in a closed reactor, now the treatments could be performed in open air. Thus, larger samples could be treated and handling times were reduced. Then, a characterization of the needle was performed using electrical as well as optical diagnostics (Chapter 3). It was found that the needle operated at voltages of 140 Vrms and higher. A model was made to determine the resistance of the plasma and from this an estimation of the electron density could be made. The latter can be regarded as an indirect measure for plasma reactivity. Results from optical emission spectroscopy showed that reactive oxygen species, such as O¢ and OH¢, were produced in the plasma. Furthermore, UV emission was detected. Both the radicals and the UV are known to interact with cells and tissues. For applications, the amount of radicals that reach the sample or that are generated in the sample is important. For this reason, radicals were detected in liquid that was treated with plasma using a chemical technique (Chapter 4). It involved a fluorescent probe: the probe was dissolved in liquid and after reaction with specific radicals it became fluorescent. Radical density in the liquid depended on plasma conditions, treatment time, and amount of liquid used, but it was always in the micromolar range. These concentrations were found to be comparable with physiological concentrations that were stated in literature. Basic cell reactions after plasma treatment were determined by experiments on cultured Chinese hamster ovarian (CHO K1) cells (Chapter 5). One of these reactions was cell detachment: cells detached from their environment but remained alive after treatment. Other reactions included a small percentage of apoptosis and, when high plasma powers were used, necrosis. A comparison with the effect of UV light from UV lamps was made (Chapter 7). The main effect of UV treatment was necrosis, but only above a certain threshold value. For mammalian cells, this threshold was reasonably high. Thus, the ef- fects of plasma treatment could not be explained by the action of the UV light from the plasma. Quantitative experiments were performed on cultured bovine aortic endothelial cells (BAEC) and rat smooth muscle cells (A7r5) (Chapter 6). These two cell types constitute walls of blood vessels. It was shown that treatment times of less than one minute cause detachment of the cells if the layer thickness of the liquid that covered the cells was low (around 0.1 mm). This suggests that at short treatment times, the penetration depth of the plasma into the sample is limited. The percentage of necrotic cells was low after treatment. No difference was found in the detachment behavior of both cell types. Finally, pilot experiments were performed on carotid arteries of C57BL/6 and Swiss mice ex vivo (Chapter 8). They were studied using a two-photon laser scanning microscope (TPLSM). Cell nuclei, elastin bands, and collagen could be visualized. Preliminary results indicate that induced changes are not strongly dependent on applied energy if no heating e®ects are induced. Apparent effects were limited to the adventitia, probably due to a low penetration depth of active plasma species. In conclusion, we can state that the plasma needle is a non-destructive tool that can be ap- plied with precision. It has a superficial action and causes little damage to the tissue. The level of damage can be controlled to achieve a desired therapeutic effect. Both on cultured cells and on ex vivo arteries interesting effects were found that confirm the hypothesis that the plasma needle will have a future in surgery
Application of the domain-integrated field relations method to the solution of large scale static and stationary magnetic field problems
No full textAuthor accepted manuscript of: “Application of the domain-integrated field relations method to the solution of large scale static and stationary magnetic field problems” IEEE Transactions on Magnetics, vol. 38, no. 2, pp. 465-468, Mar., 2002Electrical Engineering, Mathematics and Computer Scienc
Doelpuntdetectie met behulp van radartechnologie
No full textMaxad is een onlangs opgericht bedrijf dat begin 2009 op de markt zal komen met een systeem dat de reclameopbrengsten bij voetbalwedstrijden aanzienlijk zal verhogen. Het systeem is in staat om accuraat en snel doelpunten te detecteren. Bij de detectie van een doelpunt, worden alle elektronische reclameborden op elkaar afgestemd. Het op dat moment vertoonde item geniet dan exclusief alle aandacht. Derhalve wordt voor adverteerders een meerwaarde gecreëerd, met alle voordelen van dien. Het systeem combineert radartechnologie met beeldverwerking. De radars worden gebruikt om de positie van de bal te bepalen. Zodra de bal zich dicht bij het doel bevindt, zal een signaal worden afgeven aan het beeldverwerkingsysteem. Dit systeem zal bepalen of de bal de doellijn is gepasseerd. Maxad heeft onder andere het adviesbureau MaxRadar in het leven geroepen, dat als specialist in radartechnologie het radarsysteem zal ontwerpen. Overige adviesbureaus aangesteld door Maxad zijn MaxSoft en MaxImage, verantwoordelijk voor respectievelijk de software van het radarsysteem en het beeldverwerkingsysteem. In dit rapport zijn de verrichtingen weergegeven van MaxRadar. Er wordt beschreven hoe het ontwerp van de radaropstelling tot stand is gekomen. Tevens zijn de overwegingen weergegeven voor de bepalende onderdelen van een dergelijke opstelling. Het ontwerp van de verschillende onderdelen neemt veel tijd in beslag. Gezien de korte looptijd van het project, is de keuze gemaakt het ontwerpproces van één onderdeel specifiek uit te werken: de microstrip patch-antenne. In dit rapport wordt kort gekeken naar de verschillende methodes die beschikbaar zijn om de bal beter zichtbaar te maken voor de radar. Vervolgens wordt de evaluatie van het gebouwde prototype behandeld. Tot slot wordt een conclusie getrokken over het eindontwerp en er worden aanbevelingen gegeven voor verder onderzoek naar doelpuntendetectiesystemen met radartechnologie. Verschillende radaropstellingen zijn bedacht en geëvalueerd aan de hand van het programma van eisen. Uit de bestudering van de verscheidene opstellingen, is bepaald dat per doel drie radars nodig zijn, hetgeen het totaal aantal radars per stadion op zes brengt. Gekozen is voor de frequency modulated continuous wave (FMCW) radar. FMCW wordt hedendaags veel gebruikt en leent zich uitstekend voor afstandsbepaling met hoge resolutie. Bovendien is de productie van FMCW relatief goedkoop, omdat het ook volop wordt gebruikt in de auto-industrie. Voor de antenne zijn verschillende alternatieven beschikbaar. Deze antennes zijn beoordeeld aan de hand van een aantal specifieke eisen. De conclusie luidt dat microstrip patch-antennes het meest bruikbaar zijn. Deze antenne heeft de vereiste brede bundel. Bovendien zijn patch-antennes goedkoop, robuust en onderhoudsarm. Er zijn een aantal mogelijkheden om de bal beter zichtbaar te maken voor de radar. Een eerste mogelijkheid is om de bal inwendig te bekleden met reflectieverhogende materialen, zoals een laag aluminiumfolie. Uit metingen is gebleken dat deze methode de reflecties van de bal aanzienlijk vergroot. Door het materiaal een bepaald profiel te geven, kan de reflectiviteit nog verder worden verhoogd. Ook kan gebruik worden gemaakt van een verborgen eigenschap van golven, te weten de polarisatie. Tevens bestaat de optie om RFID technologie toe te passen.Electrical Engineering, Mathematics and Computer Scienc
ChildFinder Hardware: Technologiekeuzes, ontwerp en conceptdemonstratie
No full textThis bachelor thesis is written for the bachelorproject 'Where is my baby?'. This is one of the three thesis for the project, describing the technology choices, hardware design and concept demonstration of the ChildFinder. The ChildFinder is device that keeps an eye on children.TelecommunicationsElectrical Engineering, Mathematics and Computer Scienc
Emulation of a Photovoltaic System with Simulink
No full textNew research on the impact of home batteries, such as the Tesla Powerwall, on the electricity grid needs photovoltaic emulators, enabling to test independent of weather conditions. However, current PV emulators give little flexibility, are hard to implement, or very expensive. Current models are mostly focused on qualitative analysis, and not so much on quantitative analysis, for when one would like to simulate a full day. In this thesis, we describe how we have built a photovoltaic emulator that is digitally controlled by a Simulink model. The model contains the typical characteristics of a PV array and is optimized with Maximum Power Point Tracking (MPPT) and a Buck-Boost converter. The output signals of this model will communicate via the Modbus communication protocol to a programmable AC/DC-converter. This converter will provide a configurable power output to the household grid, simulating realistic day-to-day conditions of a typical PV panel. This enables a flexible and easy to use solution for future research topics like smart-grids and DC-grids.Electrical Engineering, Mathematics and Computer ScienceMicroelectronic
Efficient implementation of the domain-integrated field relations method for quasi-static magnetic fields
No full textAuthor accepted manuscript of the 17th Annual Review of Progress in Applied Computational Electromagnetics, Monterey, pp. 337-344, 19 Mar 2001 → 23 Mar 2001Electrical Engineering, Mathematics and Computer Scienc
The Time-Domain Optical Theorem in Antenna Theory
No full textA special form of the time-domain optical theorem related to a general receiving antenna system is rigorously derived. It is shown that the total energies dissipated in the antenna load and in the antenna system itself can be directly related to the electromagnetic energy of the scattered field and its time-domain far-fieldcharacteristics. A practical implication of the result in optimizing antenna scattering properties with regard to the maximum energy dissipated in the antenna loading is discussed.Accepted Author ManuscriptTera-Hertz Sensin
Signal Integrity in Pulse-train Excited Array Antennas in Time and Space - A Full TD Analysis
No full textSignal integrity in the far-field radiation from pulse-train excited array antennas is studied via full timedomain instruments. The disturbance in the received signal is related to the fidelity factor. At any point in our analysis, the disturbance is evaluated based on a reduced, well defined set of parameters: pulse parameters and pulse repetition rate – temporal dependence, and elementary radiator location – spatial dependence. Their effect is examined by means of illustrative numerical experiments. These results are expedient for enhancing the detectability of the signals radiated by pulse-train excited array antennas, as needed in wireless digital transfer.Accepted author manuscriptEEMS - GeneralTera-Hertz Sensin
A defence of Mr. Garrick, in answer to the letter-writer. With remarks upon plays and players, and the present state of the stage. By a dramatic author [electronic resource].
No full textThe letter-writer = H. W., i.e. Edward Purdon, author of 'A letter to David Garrick, Esq; on opening the Theatre' published 13 October, 1759.Price from imprint: price One-Shilling.Electronic reproduction.English Short Title Catalog,Reproduction of original from British Library
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