Printed low-voltage organic transistors on plastics and paper

The main advantage of organic electronics over the more widespread inorganic counterparts lies not in the electrical performance, but rather in the solution processability that opens up for low-cost flexible electronics (e.g. displays, sensors and smart tags) fabricated by using printing techniques. Replacing the commonly used laboratory-scale fabrication techniques with mass-printing techniques is, however, truly challenging, especially when low-voltage operation is required. In this thesis it is, nevertheless, demonstrated that low-voltage organic transistors can be fully printed with a similar performance to that of transistors made by laboratory scale techniques. The use of an ion-modulated type of organic field effect transistor (OFET) not only enabled low-voltage operation and printability, but was also found to result in low sensitivity to the surface roughness of the substrate. This allows not only the use of low-cost plastic substrates, but even the use of paper as a substrate. However, while absorption into the porous paper surface is advantageous in a graphical printing process, by reducing the spreading and the coffee-stain effect and by improving the adhesion, it provides great challenges when applying thin electrically active layers. In spite of these difficulties we were able to demonstrate the first low-voltage OFET to be fabricated on paper. We have also shown that low-cost incandescent lamps can be used for sintering printed metal-nanoparticles, and that the process was especially suitable on paper and compatible with a roll-to-roll manufacturing process.

Techno-Economic Feasibility of Novel On-Line Condition Monitoring Methods in Low Voltage Distribution Networks

The focus in this thesis is to study both technical and economical possibilities of novel on-line condition monitoring techniques in underground low voltage distribution cable networks. This thesis consists of literature study about fault progression mechanisms in modern low voltage cables, laboratory measurements to determine the base and restrictions of novel on-line condition monitoring methods, and economic evaluation, based on fault statistics and information gathered from Finnish distribution system operators. This thesis is closely related to master’s thesis “Channel Estimation and On-line Diagnosis of LV Distribution Cabling”, which focuses more on the actual condition monitoring methods and signal theory behind them.

Keskijänniteverkon maakaapeloinnin kannattavuus

Tämän työn tavoitteena oli löytää tekijöitä jotka vaikuttavat keskijänniteverkon maakaapeloinnin kannattavuuteen. 1950–1970 luvuilla verkkoa rakennettiin halvimmalla mahdollisella tavalla, eikä sähkönjakelun luotettavuuteen kiinnitetty huomiota. Tämä tuo verkkoyhtiöille haasteen vanhoja verkkoja saneerattaessa, sillä keskeytyskustannusten arvostus on noussut merkittävään asemaan. Työssä tarkoituksena oli vertailla avojohdon sekä maakaapeloinnin elinkaarikustannuksia kahden erilaisen johtolähdön avulla. Toisella johtolähdöllä oli suuri julkinen kuorma ja toinen johtolähtö oli pitkä maaseutulähtö jolla esiintyi paljon vikoja. Työssä tarkastellaan myös sähkönjakeluverkon käyttövarmuutta ja maakaapeloinnin ominaisuuksia. Elinkaarikustannuksiin vaikuttavia tekijöitä olivat investointikustannukset, keskeytyskustannukset sekä ylläpitokustannukset. Tuloksista voidaan huomata, että keskeytyskustannuksilla voi olla joissain tapauksissa hyvinkin suuri vaikutus johtolähdön elinkaareen. Pitkillä ja pienitehoisilla johtolähdöillä keskeytyskustannusten merkitys pienenee, eikä kaapeloinnilla saavuteta yhtä suurta hyötyä kuin suuritehoisemmilla lähdöillä.

Tasasähköverkon modulaarisen vaihtosuuntaajan rakenne- ja kustannusanalyysi

Diplomityössä tarkastellaan tapausta, jossa tasasähköverkon vaihtosuuntaaja toteutetaan kolmella yksivaiheisella suuntaajalla yhden kolmivaiheisen sijaan. Modulaarinen rakenne mahdollistaa sen, että osa vaiheista voitaisiin sammuttaa kun kuormitus on erittäin pientä eikä kuorma ole kolmivaiheista. Galvaaninen erotus oletetaan tehtävän erottavalla DC-DC -konvertterilla, joka mahdollistaa samalla vaihtosuuntaajan DC-syöttöjännitteen muuttamisen. Työssä tutkitaan, mitkä tekijät vaikuttavat DC-syöttöjännitteen valintaan sekä tehdään valinta kyseisen jännitteen arvolle. Valittua jännitetasoa käytetään vaihtosuuntaajan suunnittelemiseen. Vaihtosuuntaajan rakennetta tarkastellaan vaihtosuuntaussillan kytkinkomponenttien sekä lähtöjännitteen suotimen osalta. Yksivaiheiselle moduulille määritetään optimaalinen teholuokka investointi- ja käyttökustannusten kannalta. Tarkastelu pitää sisällään erilaisten transistoritekniikkojen, kytkentätaajuuksien sekä kahden suodintyypin vaikutuksen kustannustehokkuuteen.

Análise interactômica da VDAC (voltage-dependent anion selective channel) nos cérebros aviar, bovino e murino

A VDAC é a proteína mais abundante na membrana mitocondrial externa. Exerce o controle da atividade desta organela através da regulação da troca de metabólitos e tem função crucial no mecanismo de apoptose. Em nosso caso, os estudos dos complexos protéicos, das interações entre a VDAC e outras proteínas presentes no interior do neurônio que auxiliam na manutenção das funções das organelas e da célula, fazem parte da chamada interactômica. O presente estudo determinou o interactoma do complexo protéico Hexoquinase-VDAC-ANT presente em cérebros murino, bovino e aviar. Nosso objetivo foi identificar se as expressões diferenciadas da VDAC1 e VDAC2 verificadas nos cérebros murino, aviar e bovino, estão associadas a diferenças nos interactomas dessas proteínas. Este estudo revelou que as espécies aviar e bovina apresentaram o maior número de complexos protéicos contendo VDACs (5) quando comparadas com os neurônios de rato (1), o que é indicativo de uma cinética diferencial de montagem ou desmontagem do complexo. Além disso, a VDAC mitocondrial neuronal aviar também interage com mais proteínas em relação à VDAC mitocondrial neuronal bovina, o que é resultado de uma composição de subunidades diferenciada. Tais resultados indicam diferenças significativas quanto ao metabolismo energético e apoptótico no cérebro aviar, bovino e murino, existindo interações diferenciais da VDAC no cérebro aviar.

Eri MAG-hitsausprosessien ja -parametrien vaikutus suurlujuusteräksestä valmistetun otsapienahitsin äärikestävyyteen, muodonmuutoskykyyn ja vauriomuotoon

Työssä tutkittiin Ruukki Oyj:n suorasammutetusta S960QC-teräksestä valmistetun kuormaakantavan levyjen ristiliitoksen pienahitsien lujuutta, muodonmuutoskykyä ja vaurioitumismekanismia laajaan kokeelliseen aineistoon perustuen. Tärkeimpänä muuttujana koematriisissa olivat eri MAG-hitsausprosessit. Perinteisen kuumakaarihitsauksen vertailukohteena oli Kemppi Oy:n uusi adaptiivinen valokaaren pituutta säätävä WiseFusion-hitsaustoiminto kuuma- ja pulssikaarihitsauksessa. Näiden kolmen hitsausprosessin rinnalla varioitiin erisuuruisia a-mittoja, eri hitsauslisäaineita ja hitsin erikylkisyyttä. Lisäksi juuritunkeuman estämisen vaikutusta hitsien käyttäytymiseen tutkittiin täydentävällä koesarjalla, jossa tunkeuman muodostuminen estettiin levyjen väliin asetetulla volframilevyllä. Työn perimmäisenä tavoitteena oli selvittää syy aiemmassa tutkimuksessa havaitulle pienahitsien vaurioitumiselle leikkautumalla sularajaa pitkin. Sularajan suhteellista pituutta saadaan kasvatettua estämällä hitsin juuritunkeuma ja absoluuttista pituutta saadaan lisää kateettipoikkeaman avulla. Lisäksi tutkimuksessa oli tarkoitus tuoda esille suurlujuusteräksisen liitoksen eri mitoituslähtökohdat (mm. lämmöntuonnin kontrollointi). Tämän vuoksi hitsausparametrit mitattiin jännitteen ja virran hetkellisiin arvoihin perustuen, jolloin kuuma- ja pulssikaarihitsauksen laskennalliset hitsaustehot ovat vertailukelpoisia. Koehitseistä valmistettiin hieet hitsien tarkan geometrian määrittämiseksi ja liitoksen mekaaniset ominaisuudet tutkittiin vetokokeella. Tulosten perusteella sularajavaurio aktivoituu pulssikaarella hitsatuissa koekappaleissa. Tämä aiheutunee pulssi- ja kuumakaarihitsauksen sularajan mikrorakenteiden eroavaisuudesta. Sularajavaurio näyttää huonontavan hitsien muodonmuutoskykyä, mutta jatkokokeita tuloksen verifioimiseksi on tehtävä. S960QC-teräkselle ominaisen pehmenneen vyöhykkeen vaurio ei aktivoitunut, vaikka Ruukin antamat jäähtymisaikasuositukset ylitettiin reilusti.

Long-term nutrient load management and lake restoration: Case of Säkylän Pyhäjärvi (SW Finland)

Eutrophication caused by anthropogenic nutrient pollution has become one of the most severe threats to water bodies. Nutrients enter water bodies from atmospheric precipitation, industrial and domestic wastewaters and surface runoff from agricultural and forest areas. As point pollution has been significantly reduced in developed countries in recent decades, agricultural non-point sources have been increasingly identified as the largest source of nutrient loading in water bodies. In this study, Lake Säkylän Pyhäjärvi and its catchment are studied as an example of a long-term, voluntary-based, co-operative model of lake and catchment management. Lake Pyhäjärvi is located in the centre of an intensive agricultural area in southwestern Finland. More than 20 professional fishermen operate in the lake area, and the lake is used as a drinking water source and for various recreational activities. Lake Pyhäjärvi is a good example of a large and shallow lake that suffers from eutrophication and is subject to measures to improve this undesired state under changing conditions. Climate change is one of the most important challenges faced by Lake Pyhäjärvi and other water bodies. The results show that climatic variation affects the amounts of runoff and nutrient loading and their timing during the year. The findings from the study area concerning warm winters and their influences on nutrient loading are in accordance with the IPCC scenarios of future climate change. In addition to nutrient reduction measures, the restoration of food chains (biomanipulation) is a key method in water quality management. The food-web structure in Lake Pyhäjärvi has, however, become disturbed due to mild winters, short ice cover and low fish catch. Ice cover that enables winter seining is extremely important to the water quality and ecosystem of Lake Pyhäjärvi, as the vendace stock is one of the key factors affecting the food web and the state of the lake. New methods for the reduction of nutrient loading and the treatment of runoff waters from agriculture, such as sand filters, were tested in field conditions. The results confirm that the filter technique is an applicable method for nutrient reduction, but further development is needed. The ability of sand filters to absorb nutrients can be improved with nutrient binding compounds, such as lime. Long-term hydrological, chemical and biological research and monitoring data on Lake Pyhäjärvi and its catchment provide a basis for water protection measures and improve our understanding of the complicated physical, chemical and biological interactions between the terrestrial and aquatic realms. In addition to measurements carried out in field conditions, Lake Pyhäjärvi and its catchment were studied using various modelling methods. In the calibration and validation of models, long-term and wide-ranging time series data proved to be valuable. Collaboration between researchers, modellers and local water managers further improves the reliability and usefulness of models. Lake Pyhäjärvi and its catchment can also be regarded as a good research laboratory from the point of view of the Baltic Sea. The main problem in both of them is eutrophication caused by excess nutrients, and nutrient loading has to be reduced – especially from agriculture. Mitigation measures are also similar in both cases.

Aktiivisen verkkosillan tuottaman yhteismuotoisen jännitteen vaimentaminen kaksitasoisessa, jännitevälipiirillisessä, taajuusmuuttajatopologiassa

Pulssinleveysmoduloidun vaihtosuuntaajan hyötysuhteen parantaminen ja kytkentätaajuuden suurentaminen ovat johtaneet lähtöjännitteen suuritaajuiseen taajuussisältöön kaksitasoisessa, jännitevälipiirillisessä taajuusmuuttajatopologiassa. Kasvava tarve siirtää tehoa myös verkkoon päin on lisännyt aktiivisen verkkosillan käyttöä. Kaksitasoisen aktiivisen verkkosillan vaikutuksesta DC-välipiirin keskipisteen ja kolmivaiheisen kuorman tähtipisteen välinen jännite on nollasta poikkeava aiheuttaen suurentuneen yhteismuotoisen jännitteen taajuusmuuttajan lähtöön ja verkon puolelle. Lisäksi yhteismuotoisten jännitteiden aiheuttamat kytkentätaajuiset häiriövirrat voivat aiheuttaa vikavirtasuojien tahatonta laukeamista, vaikeuttaa EMC-standardien vaatimusten täyttämistä, lisätä moottorin käämieristyksien rasitusta ja mahdollisuutta moottorin laakerivaurioille. Diplomityössä tutkitaan aktiivisen ja passiivisen verkkosillan tuottamaa yhteismuotoista jännitettä simuloinneilla. Esitellään aikaisempaa tutkimustietoa yhteismuotoisen jännitteen ja virran vaimennusratkaisuista aktiivista verkkosiltaa käytettäessä. Tutkimustiedon pohjalta suunnitellaan koelaitteistolle soveltuva suodin. Suotimen toiminta testataan simuloinnein sekä kokeellisin mittauksin. Tehdyt mittaukset osoittavat, että suunniteltu suodin vaimentaa yhteismuotoista jännitettä noin 20 dB verkkosillan kytkentätaajuudella ja tämän jälkeen yli 20 dB/dekadi taajuuteen 100 kHz asti. Lisäksi yhteismuotoisen virran suuruus syöttökaapelin kautta pieneni ehdotetun suotimen vaikutuksesta.

Power semiconductor nonlinearities in active du/dt output filtering

This doctoral thesis introduces an improved control principle for active du/dt output filtering in variable-speed AC drives, together with performance comparisons with previous filtering methods. The effects of power semiconductor nonlinearities on the output filtering performance are investigated. The nonlinearities include the timing deviation and the voltage pulse waveform distortion in the variable-speed AC drive output bridge. Active du/dt output filtering (ADUDT) is a method to mitigate motor overvoltages in variable-speed AC drives with long motor cables. It is a quite recent addition to the du/dt reduction methods available. This thesis improves on the existing control method for the filter, and concentrates on the lowvoltage (below 1 kV AC) two-level voltage-source inverter implementation of the method. The ADUDT uses narrow voltage pulses having a duration in the order of a microsecond from an IGBT (insulated gate bipolar transistor) inverter to control the output voltage of a tuned LC filter circuit. The filter output voltage has thus increased slope transition times at the rising and falling edges, with an opportunity of no overshoot. The effect of the longer slope transition times is a reduction in the du/dt of the voltage fed to the motor cable. Lower du/dt values result in a reduction in the overvoltage effects on the motor terminals. Compared with traditional output filtering methods to accomplish this task, the active du/dt filtering provides lower inductance values and a smaller physical size of the filter itself. The filter circuit weight can also be reduced. However, the power semiconductor nonlinearities skew the filter control pulse pattern, resulting in control deviation. This deviation introduces unwanted overshoot and resonance in the filter. The controlmethod proposed in this thesis is able to directly compensate for the dead time-induced zero-current clamping (ZCC) effect in the pulse pattern. It gives more flexibility to the pattern structure, which could help in the timing deviation compensation design. Previous studies have shown that when a motor load current flows in the filter circuit and the inverter, the phase leg blanking times distort the voltage pulse sequence fed to the filter input. These blanking times are caused by excessively large dead time values between the IGBT control pulses. Moreover, the various switching timing distortions, present in realworld electronics when operating with a microsecond timescale, bring additional skew to the control. Left uncompensated, this results in distortion of the filter input voltage and a filter self-induced overvoltage in the form of an overshoot. This overshoot adds to the voltage appearing at the motor terminals, thus increasing the transient voltage amplitude at the motor. This doctoral thesis investigates the magnitude of such timing deviation effects. If the motor load current is left uncompensated in the control, the filter output voltage can overshoot up to double the input voltage amplitude. IGBT nonlinearities were observed to cause a smaller overshoot, in the order of 30%. This thesis introduces an improved ADUDT control method that is able to compensate for phase leg blanking times, giving flexibility to the pulse pattern structure and dead times. The control method is still sensitive to timing deviations, and their effect is investigated. A simple approach of using a fixed delay compensation value was tried in the test setup measurements. The ADUDT method with the new control algorithm was found to work in an actual motor drive application. Judging by the simulation results, with the delay compensation, the method should ultimately enable an output voltage performance and a du/dt reduction that are free from residual overshoot effects. The proposed control algorithm is not strictly required for successful ADUDT operation: It is possible to precalculate the pulse patterns by iteration and then for instance store them into a look-up table inside the control electronics. Rather, the newly developed control method is a mathematical tool for solving the ADUDT control pulses. It does not contain the timing deviation compensation (from the logic-level command to the phase leg output voltage), and as such is not able to remove the timing deviation effects that cause error and overshoot in the filter. When the timing deviation compensation has to be tuned-in in the control pattern, the precalculated iteration method could prove simpler and equally good (or even better) compared with the mathematical solution with a separate timing compensation module. One of the key findings in this thesis is the conclusion that the correctness of the pulse pattern structure, in the sense of ZCC and predicted pulse timings, cannot be separated from the timing deviations. The usefulness of the correctly calculated pattern is reduced by the voltage edge timing errors. The doctoral thesis provides an introductory background chapter on variable-speed AC drives and the problem of motor overvoltages and takes a look at traditional solutions for overvoltage mitigation. Previous results related to the active du/dt filtering are discussed. The basic operation principle and design of the filter have been studied previously. The effect of load current in the filter and the basic idea of compensation have been presented in the past. However, there was no direct way of including the dead time in the control (except for solving the pulse pattern manually by iteration), and the magnitude of nonlinearity effects had not been investigated. The enhanced control principle with the dead time handling capability and a case study of the test setup timing deviations are the main contributions of this doctoral thesis. The simulation and experimental setup results show that the proposed control method can be used in an actual drive. Loss measurements and a comparison of active du/dt output filtering with traditional output filtering methods are also presented in the work. Two different ADUDT filter designs are included, with ferrite core and air core inductors. Other filters included in the tests were a passive du/dtfilter and a passive sine filter. The loss measurements incorporated a silicon carbide diode-equipped IGBT module, and the results show lower losses with these new device technologies. The new control principle was measured in a 43 A load current motor drive system and was able to bring the filter output peak voltage from 980 V (the previous control principle) down to 680 V in a 540 V average DC link voltage variable-speed drive. A 200 m motor cable was used, and the filter losses for the active du/dt methods were 111W–126 W versus 184 W for the passive du/dt. In terms of inverter and filter losses, the active du/dt filtering method had a 1.82-fold increase in losses compared with an all-passive traditional du/dt output filter. The filter mass with the active du/dt method was 17% (2.4 kg, air-core inductors) compared with 14 kg of the passive du/dt method filter. Silicon carbide freewheeling diodes were found to reduce the inverter losses in the active du/dt filtering by 18% compared with the same IGBT module with silicon diodes. For a 200 m cable length, the average peak voltage at the motor terminals was 1050 V with no filter, 960 V for the all-passive du/dt filter, and 700 V for the active du/dt filtering applying the new control principle.

LVDC power distribution system: computational modelling

In the doctoral dissertation, low-voltage direct current (LVDC) distribution system stability, supply security and power quality are evaluated by computational modelling and measurements on an LVDC research platform. Computational models for the LVDC network analysis are developed. Time-domain simulation models are implemented in the time-domain simulation environment PSCAD/EMTDC. The PSCAD/EMTDC models of the LVDC network are applied to the transient behaviour and power quality studies. The LVDC network power loss model is developed in a MATLAB environment and is capable of fast estimation of the network and component power losses. The model integrates analytical equations that describe the power loss mechanism of the network components with power flow calculations. For an LVDC network research platform, a monitoring and control software solution is developed. The solution is used to deliver measurement data for verification of the developed models and analysis of the modelling results. In the work, the power loss mechanism of the LVDC network components and its main dependencies are described. Energy loss distribution of the LVDC network components is presented. Power quality measurements and current spectra are provided and harmonic pollution on the DC network is analysed. The transient behaviour of the network is verified through time-domain simulations. DC capacitor guidelines for an LVDC power distribution network are introduced. The power loss analysis results show that one of the main optimisation targets for an LVDC power distribution network should be reduction of the no-load losses and efficiency improvement of converters at partial loads. Low-frequency spectra of the network voltages and currents are shown, and harmonic propagation is analysed. Power quality in the LVDC network point of common coupling (PCC) is discussed. Power quality standard requirements are shown to be met by the LVDC network. The network behaviour during transients is analysed by time-domain simulations. The network is shown to be transient stable during large-scale disturbances. Measurement results on the LVDC research platform proving this are presented in the work.

Fast and slow voltage modulation of apical Cl- permeability in toad skin at high [K+]

The influence of voltage on the conductance of toad skin was studied to identify the time course of the activation/deactivation dynamics of voltage-dependent Cl- channels located in the apical membrane of mitochondrion-rich cells in this tissue. Positive apical voltage induced an important conductance inhibition which took a few seconds to fully develop and was instantaneously released by pulse inversion to negative voltage, indicating a short-duration memory of the inhibiting factors. Sinusoidal stimulation at 23.4 mM [Cl-] showed hysteresis in the current versus voltage curves, even at very low frequency, suggesting that the rate of voltage application was also relevant for the inhibition/releasing effect to develop. We conclude that the voltage modulation of apical Cl- permeability is essentially a fast process and the apparent slow components of activation/deactivation obtained in the whole skin are a consequence of a gradual voltage build-up across the apical membrane due to voltage sharing between apical and basolateral membranes

An optically coupled power stimulus isolation unit with high voltage and fast rise time output

Recent technological developments have created new devices that could improve and simplify the construction of stimulus isolators. HEXFET transistors can switch large currents and hundreds of volts in nanoseconds. The newer opto-isolators can give a pulse rise time of a few nanoseconds, with output compatible with MOSFET devices, in which delays are reduced to nanoseconds. Integrated DC/DC converters are now available. Using these new resources we developed a new electrical stimulus isolator circuit with selectable constant-current and constant-voltage modes, which are precise and easy to construct. The circuit works like a regulated power supply in both modes with output switched to zero or to free mode through an opto-isolator device. The isolator analyses showed good practical performance. The output to ground resistance was 1011 ohms and capacitance 35 picofarads. The rise time and fall time were identical (5 µs) and constant. The selectable voltage or current output mode made it very convenient to use. The current mode, with higher output resistance values in low current ranges, permits intracellular stimulation even with tip resistances close to 100 megaohms. The high compliance of 200 V guarantees the value of the current stimulus. The very low output resistance in the voltage mode made the device highly suitable for extracellular stimulation with low impedance electrodes. Most importantly, these characteristics were achieved with a circuit that was easy to build and modify and assembled with components available in Brazil.

Monitoring human cytomegalovirus viral load in peripheral blood leukocytes of renal transplant recipients by a simple limiting dilution-PCR assay

To assess the clinical relevance of a semi-quantitative measurement of human cytomegalovirus (HCMV) DNA in renal transplant recipients within the typical clinical context of a developing country where virtually 100% of both receptors and donors are seropositive for this virus, we have undertaken HCMV DNA quantification using a simple, semi-quantitative, limiting dilution polymerase chain reaction (PCR). We evaluated this assay prospectively in 52 renal transplant patients from whom a total of 495 serial blood samples were collected. The samples scored HCMV positive by qualitative PCR had the levels of HCMV DNA determined by end-point dilution-PCR. All patients were HCMV DNA positive during the monitoring period and a diagnosis of symptomatic infection was made for 4 of 52 patients. In symptomatic patients the geometric mean of the highest level of HCMV DNAemia was 152,000 copies per 106 leukocytes, while for the asymptomatic group this value was 12,050. Symptomatic patients showed high, protracted HCMV DNA levels, whereas asymptomatic patients demonstrated intermittent low or moderate levels. Using a cut-off value of 100,000 copies per 106 leukocytes, the limiting dilution assay had sensitivity of 100%, specificity of 92%, a positive predictive value of 43% and a negative predictive value of 100% for HCMV disease. In this patient group, there was universal HCMV infection but relatively infrequent symptomatic HCMV disease. The two patient groups were readily distinguished by monitoring with the limiting dilution assay, an extremely simple technology immediately applicable in any clinical laboratory with PCR capability.

Yliopiston sähköverkon mallintaminen

Lappeenrannan teknillinen yliopisto tutkii älykkäiden sähköverkkojen kehittämistä. Yliopisto on hankkinut sähköverkkoonsa tuuliturbiinin ja aurinkopaneeleita, joilla pystytään tuottamaan sähköenergiaa sähköverkkoon. Näitä tuotantoja voidaan käyttää myös tutkimuksessa. Tässä työssä luodaan simulaatiomalli yliopiston sähköverkosta Matlab® Simulink® -ohjelmalla. Simulaatiomalliin mallinnetaan yliopiston sisäinen keskijänniteverkko ja osa pienjänniteverkosta. Simulaatiomalli toteutetaan ohjelman valmiilla komponenteilla, joihin lasketaan tarvittavat parametrit. Tuuliturbiinin ja aurinkopaneelien sähköntuotantotehot määritetään säätiladatojen avulla. Verkon komponenteille lasketaan arvot komponenttien tyyppitietojen perusteella ja asetetaan simulaatiomallin parametreiksi. Simulaatiomalli luodaan yliopiston sisäisen verkon tehonjaon tarkastelemiseksi. Työssä selvitetään myös mahdollisuuksia luodun simulaatiomallin käyttämiseen vikatilanteiden tarkastelussa.

Bradykinin enhances membrane electrical activity of pancreatic beta cells in the presence of low glucose concentrations

In most of cells bradykinin (BK) induces intracellular calcium mobilization. In pancreatic beta cells intracellular calcium is a major signal for insulin secretion. In these cells, glucose metabolism yields intracellular ATP which blocks membrane potassium channels. The membrane depolarizes, voltage-dependent Ca2+ channels are activated and the intracellular calcium load allows insulin secretion. Repolarization occurs due to activation of the Ca2+-dependent K+ channel. The insulin secretion depends on the integrity of this oscillatory process (bursts). Therefore, we decided to determine whether BK (100 nM) induces bursts in the presence of a non-stimulatory glucose concentration (5.6 mM). During continuous membrane voltage recording, our results showed that bursts were obtained with 11 mM glucose, blocked with 5.6 mM glucose and recovered with 5.6 mM glucose plus 100 nM BK. Thus, the stimulatory process obtained in the presence of BK and of a non-stimulatory concentration of glucose in the present study suggests that BK may facilitate the action of glucose on beta cell secretion.