732 research outputs found
A calculable impulse voltage calibrator
This thesis describes the principle, design, construction, and uncertainty analysis of a calculable impulse voltage calibrator. The calibrator can be used as a primary reference for impulse voltage measurements. The calibrator generates lightning impulses (LI) with known peak value (UP), front time (T1), and time to half value (T2); or switching impulses (SI) with known peak value (UP), time to peak (TP), and time to half value (T2). The peak voltages of the constructed devices range from 50Â mV to 1000Â V.
The calibration of impulse voltage measuring equipment is required both by high voltage and quality standards, and the gap between the best measurement accuracy available at National Metrology Institutes; the accuracy that is required in high voltage testing has been very narrow. The only way to improve the situation is to lower the measurement uncertainty levels in the National Metrology Institutes.
In this work, the traceability of the peak and time parameter values is based on the modelling of the circuit, and the calculation of these parameters according to network theory. This calculation is based on the calibrated component (resistor and capacitor) values of the impulse circuit. The uncertainty in the peak values is low, as the peak value is not sensitive to changes in the component values of the circuit.
The estimated uncertainties for lightning impulse calibrators are 0,05% for peak value, 0,5% for front time, and 0,3% for time to half value. For switching impulses the corresponding uncertainties are 0,1%, 0,4% and 0,3%.
The calibrators based on this work have been used for calibration work at Helsinki University of Technology, and as a transfer reference in an ongoing worldwide round-robin test.reviewe
GaAS-pohjaisten valosÀhkökemiallisten kennojen simuloinnit ja mittaukset
The photoelectrochemical cell offers a way to use solar power to efficiently split water into hydrogen and oxygen. A semiconductor electrode is used to generate electrical power from sunlight and drive the hydrogen and oxygen evolution reactions in aqueous environment. The work in this thesis aims to improve the understanding of the dynamics of the semiconductor electrode in a photoelectrochemical cell by implementing a numerical model of the system. The model is used to solve the carrier densities during the operation, when the charge carriers in the semiconductor are not in thermal equilibrium due to the incident radiation generating electron-hole pairs. The simulated results are compared to experimental study of different GaAs-based photoelectrodes.
For the experimental study both p- and n-type GaAs photoelectrodes were fabricated. In addition, a sample with a thin epitaxial n-type layer on a p-type substrate was studied. Chopped light voltammetry and electrochemical impedance spectroscopy measurements were used to characterize the samples. The results show that p-type GaAs is not effective as a photoelectrode due to large overpotential required before any photocurrent was observed. The n--type layer was found to slightly improve the results. The current from the n-type sample was observed to be significantly better, but this is likely to be attributed to dissolving of the sample instead of water splitting reaction. The implementation of the numerical model was successful, but the accuracy of the simulated results leaves room for improvement. The implementation of drift-diffusion model used for the simulation cannot explain all of the measured results, and a more sophisticated model would be required for predictive simulations. Based on the results, key issues are identified and future development ideas suggested.ValosÀhkökemiallinen kenno tarjoaa keinon kÀyttÀÀ aurinkoenergiaa tehokkaasti hajottamaan vettÀ vedyksi ja hapeksi. Puolijohde--elektrodi generoi sÀhkövirtaa auringon valon avulla sekÀ ajaa vedyn ja hapen kehitysreaktioita vesipitoisessa ympÀristössÀ. TÀmÀn diplomityön tavoitteena on tutkia puolijohde--elektrodin dynamiikkaa valosÀhkökemiallisessa kennossa kehittÀmÀllÀ numeerinen malli. Mallin avulla voidaan laskea varauskuljettajien tiheydet kennon toiminnan aikana, jolloin elektronit ja aukot eivÀt ole termisessÀ tasapainotilassa valaistuksen luomien varauskuljettajaparien vuoksi. Simuloituja tuloksia verrataan kokeelliseen työhön, jossa kÀytettiin erilaisia GaAs-pohjaisia elektrodeja.
Kokeellista työtÀ varten valmistettiin sekÀ p- ettÀ n-tyypin GaAs-elektrodit. LisÀksi valmistettiin p-tyypin nÀyte, jonka pÀÀlle kasvatettiin ohut n--tyypin kerros. NÀytteistÀ mitattiin virta-jÀnnite -kÀyrÀ katkotulla valaistuksella sekÀ sÀhkökemiallinen impedanssispektri. Tulokset osoittavat, ettÀ p-tyypin GaAs ei ole tehokas elektrodi veden hajottamiseen, sillÀ se vaatii korkean ylijÀnnitteen ennen kuin valon tuottama virta on havaittavissa. Kasvatetun n-tyypin kerroksen havaittiin parantavan tuloksia. N-tyypin nÀytteen tuottama virta havaittiin huomattavasti paremmaksi, mutta todennÀköisesti kyse on nÀytteen hajoamisreaktiosta veden hajottamisen sijaan. Tulosten perusteella numeerisen mallin tarkkuuden parantamiseksi esitetÀÀn jatkotoimia, sillÀ simulaation taustalla oleva fysikaalinen malli ei kykene selittÀmÀÀn aivan kaikkia mitattuja tuloksia
De inveniendo maximo vel minimo valore functionis: y = Aa [... kaava], dissertatio; quam consentiente ampl. fac. phil. Reg. Acad. Aboënsis, praeside mag. Gust. Gabr. HÀllström, physices profess. reg. et ordin. atque Reg. Societ. Oecon. Fenn. membro. Pro gradu philosophico publico examini offert Ericus Gabriel Melartin, stipend. Arckenholtz. Wiburgensis. In auditorio majori die [ ] Maji MDCCCII. Horis p. m. consuetis
Arkit: 1 arkintunnukseton lehti, A4 B1.Painovuosi nimekkeestÀ
Dissertatio physica, de interpolatione pro determinanda: vitri dilatatione a calorico, quam consent. ampl. fac. philos. Reg. Acad. Aboënsis, praeside mag. Gust. Gabr. HÀllström, physices profess. reg. et ordin. atque Reg. Societ. Oecon. Fenn. membro, pro gradu philosophico p. d. Petr. Christ. Snellman, Ostrobotniensis. In auditorio minori die XVI Dec. MDCCCI, horis a. m. consuetis
Dedicatio: Johannes Snellman.Arkit: 1 arkintunnukseton lehti, A4 B2.Painovuosi nimekkeestÀ
De variationibus declinationis magneticae diurnis: Dissertatio, consensu ampliss. facult. philos. Aboënsis, praeside mag. Gustavo Gabr. HÀllström, phys. prof. reg. [et] ordin., atque Reg. Soc. Oecon. Fenn. membro, et respondente Stephano Snellman, Austro-Fennone. Publice ventilanda in audit. Maj. die XXX Nov. 1803, horis a. m. consvetis
Dedicatio: Anders Ringbom [ruots. pr.], Eva Johanna Ringbom s. Rungia [ruots. pr.].Arkit: 1 arkintunnukseton lehti, A4 B3.Painovuosi nimekkeestÀ
âTollarsjukaâ : the outcome from a natural selection?
Hundrasen Nova Scotia Duck Tolling Retriever (Tollare), en apporterande ras med ursprung i Kanada, var i början pÄ 1900-talet nÀra att utrotas pÄ grund av tvÄ epidemier av valpsjuka som hÀrjade i landet. I dag har rasen rapporterats vara predisponerad för vissa immunmedierade
sjukdomar dÀribland s.k. tollarsjuka. Tollarsjuka anvÀnds i dagligt tal och Àr egentligen ett samlingsbegrepp för tvÄ olika immunmedierade sjukdomar: en SLE (systemisk lupus
erythematosus)-liknande reumatisk sjukdom samt en aseptisk meningit. Vid den reumatismliknande sjukdomen ses stelhet i leder och vandrande hÀlta som gÄr i skov. Hos drabbade hundar kan man ofta pÄvisa antinukleÀra antikroppar (ANA) vilket Àr karaktÀristiskt för autoimmuna sjukdomar av SLE-karaktÀr. Vid den aseptiska meningiten visar drabbade
hundar smÀrta frÄn nacken, nedsatt allmÀntillstÄnd, feber och anorexi. BÄda sjukdomsformerna kan behandlas med kortikosteroider men resultatet varierar.
Sjukdomskomplexet anses vara av multifaktoriell och multigenetisk karaktÀr.
Predisponeringen kan vara ett resultat av att rasen hÀrstammar frÄn de fÄ individer som överlevde epidemierna. Förmodligen hade de en gynnsam uppsÀttning av gener som bidrog till deras överlevnad. Syftet med denna litteraturstudie Àr att sammanstÀlla den kliniska bilden
vid tollarsjuka, vilka genetiska riskfaktorer som identifierats och om det finns en koppling mellan epidemierna och predisponeringen för autoimmuna sjukdomar.
Flera genetiska studier har utförts för att identifiera genuppsÀttningar som kan vara kopplade till sjukdomen. En studie identifierade en dog leukocyte antigen (DLA) klass II-haplotyp (DLA-DRB1*00601/DQA1*005011/DQB1*02001) med stark association till sjukdomsutveckling för den reumatismliknande sjukdomen. Ingen koppling mellan DLA
klass II och meningitformen kunde ses. Avelsrekommendationer efter DLA-haplotyp Àr dock inte aktuellt dÄ DLA klass II bara Àr en av flera riskfaktorer involverad i denna komplexa multifaktoriella sjukdom. En genom-wide association study (GWAS) utfördes dÀr ytterligare
fem riskloci med association till sjukdomskomplexet identifierades. Totalt ansÄgs fem gener (PPP3CA, HOMER2, PTPN3, DAPP1 och BANK1) extra intressanta baserat pÄ deras
biologiska funktion. De identifierade kandidatgenerna kodar för proteiner med koppling till immunförsvaret. Flera av dessa Àr involverade i NFAT pathway som visats spela en stor roll bÄde för T-cells aktivering och för utveckling av perifer tolerans. FörÀndringar i dessa gener skulle kunna leda till ett starkare immunsvar vilket Àr en trolig förklaring till den höga prevalensen av autoimmunitet inom rasen men Àven en förklaring till varför vissa tollare
överlevde infektionerna med valpsjukevirus.
Mer forskning behövs inom omrÄdet för att bÀttre förstÄ sjukdomsförloppet. FörÀndringarna i riskgener behöver identifieras, det immunologiska svaret studeras och samspelet mellan riskfaktorer, sÄvÀl genetiska som miljöfaktorer behöver hittas.The Nova Scotia Duck Tolling Retriever (Toller) is a retrieving dog breed from Canada. Early in the 20th century, two epidemics of the Canine Distemper Virus (CDV) almost destroyed the whole breed and only a few survived. The breed is today predisposed to some autoimmune
diseases, for example a disease complex called âTollarsjukaâ. The disease complex involves
steroid responsive meningitis arteritis (SRMA) and a SLE (systemic lupus erythematosus)- related disease named immune-mediated rheumatic disease (IMRD). The disease complex is considered being both multifactorial and multigenetic, and is the most common in the
population of Scandinavian Tollers. Dogs with IMRD show chronic stiffness and pain from joints and lameness. They often display antinuclear antibodies (ANA). Characteristics for the aseptic meningitis are pain from the neck, depression, fever and anorexia. The disease can be treated with corticosteroids but it does not always work. The autoimmune diseases can be a consequence from the few individuals that survived the epidemics; they probably survived due to genes that resulted in a more effective anti-viral immune response. The aim of this literature report is to summarize the clinical manifestations of disease complex, the identified genetic risk factors associated with the disease and search for a possible connection between the epidemics and the autoimmune diseases.
Genetic studies have identified risk factors. One study shows that a DLA class II-haplotype (DLA-DRB1*00601/DQA1*005011/DQB1*02001) is strongly associated with the rheumatic disease. No association between DLA class II and SRMA was found. It is not yet possible to give breeding recommendation about which dogs to use based on the DLA class II, this is because there exist multiple risk factors involved in the pathogenesis of this disease. In another study a genome-wide association mapping (GWAM) was performed and five risk loci with association to the disease were identified. Five genes (PPP3CA, HOMER2, PTPN3, DAPP1 and BANK1) on these loci were very interesting based on their biological function.
The identified candidate genes all have some connection to the immune system. Many of them are involved in the NFAT pathway, which plays a crucial role in the activation of Tcells and the development of peripheral tolerance. Many of these genes are already identified as risk factors for development of human SLE. Changes in these could result in a stronger immune response and explain the high prevalence of autoimmune diseases in the breed. It also could explain why some dogs survived the epidemics back in the 20th century. More research is needed to better understand the disease and how it develops
Handling of canine urine samples after collection : effects on bacterial growth
Infection in the urinary tract is common in dogs. Diagnosis and treatment are based on clinical signs, and on results from urine analysis, which includes bacterial culture and identification of bacteriuria. Several national and international guidelines are available that recommend how the urine sample should be collected and handled to assure reliable results. However, there are few published studies that have investigated possible associations between bacterial growth (quantity and species) and handling of urine samples.
The aim of this study was to investigate in what way handling of urine samples, immediately after collection, affects bacterial growth regarding bacterial species and quantity. The aim of the present study was also to investigate whether or not results of urine culture using UricultÂź Trio changed, if stored at room temperature after cultivation. To investigate this, urine samples were handled in different ways to simulate differing clinical scenarios. In this study, urine samples were analysed, according to standard quantitative cultures, on blood- and CLED-agar or on UricultÂź Trio.
A total of 37 urine samples were collected in this study; 13 samples were collected by cystocentesis, two samples by catheter and 22 samples by midstream voiding. Several interesting observations were made. Growth of a different potentially pathogenic bacterial species (compared to initial culture results) in a urine sample that is stored before cultivation is small, but the quantity of bacteria (CFU/ml) changes to a greater extent. Urine samples stored in refrigerators were only minimally different and were considered to give the most reliable results. Results of the present study indicate that UricultŸ Trio is a good and reliable medium for identifying bacteriuria but slightly less reliable for identification of mixed growth with several bacterial species. However, the sample size in this study was too small to make significant conclusions, and similar studies with larger sample sizes are necessary.Infektioner i urinvÀgarna Àr vanligt förekommande hos hund. Diagnos och behandling baseras i stor utstrÀckning pÄ resultat frÄn analys av urinprov, vilket inkluderar bakteriologisk odling och identifiering av bakteriuri. BÄde nationella och internationella rekommendationer finns kring vilken provtagningsmetod som anses bÀst och hur urinprovet ska hanteras efter provtagning för mest tillförlitligt resultat. Trots flertalet rekommendationer finns endast ett fÄtal publicerade studier som har undersökt eventuellt samband mellan vÀxt av bakterier och hantering av urinprovet.
Syftet med denna studie var att undersöka hur hantering av urinprov under tiden nÀrmast efter provtagningstillfÀllet pÄverkar den bakteriella vÀxten avseende vilka bakterier som förekommer samt mÀngden av bakterier. Syftet var Àven att undersöka om vÀxt pÄ UricultŸ Trio Àndrades vid förvaring i rumstemperatur efter odling. För att undersöka detta simulerades olika sÀtt ett urinprov kan hanteras under kliniska förhÄllanden innan det analyseras. I studien analyserades urinprov enligt standardmetod pÄ odling pÄ blod- och CLED-agar eller pÄ UricultŸ Trio.
Totalt insamlades 37 urinprover, 13 prover insamlades via cystocentes, tvÄ prover via kateter och 22 prover var spontankastade. Flera intressanta observationer gjordes i studien. Risken för skillnad i förekomsten av potentiellt patogena bakterier ett urinprov som förvaras i sterilt provrör innan odling anses lÄg men mÀngden bakterier med avseende pÄ CFU/ml förÀndras i stor utstrÀckning. De urinprov som förvarades i kylskÄp förÀndrades i minst utstrÀckning och ansÄgs ge mest tillförlitliga resultat. Resultaten av studien indikerar att UricultŸ Trio Àr att bra och tillförlitligt medium för att identifiera bakteriuri men inte lika bra pÄ att identifiera arter nÀr det finns tvÄ eller fler bakteriearter i samma prov. UricultŸ Trio anses dock som ett bra alternativ nÀr odling pÄ blod- och CLED-agar inte Àr möjlig. Materialet i denna studie var dock litet och liknande studier med större material Àr nödvÀndigt för att kunna dra nÄgra sÀkra slutsatser
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