984 resultados para super-orbital re-entry
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Kartta kuuluu A. E. Nordenskioldin kokoelmaan
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Kartta kuuluu A. E. Nordenskioldin kokoelmaan
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Kartta kuuluu A. E. Nordenskioldin kokoelmaan
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Nowadays, the re-refining of the used lube oils has gained worldwide a lot of attention due to the necessity for added environmental protection and increasingly stringent environmental legislation. One of the parameters determining the quality of the produced base oils is the composition of feedstock. Estimation of the chemical composition of the used oil collected from several European locations showed that the hydrocarbon structure of the motor oil is changed insignificantly during its operation and the major part of the changes is accounted for with depleted oil additives. In the lube oil re-refining industry silicon, coming mainly from antifoaming agents, is recognized to be a contaminant generating undesired solid deposits in various locations in the re-refining units. In this thesis, a particular attention was paid to the mechanism of solid product formation during the alkali treatment process of silicon-containing used lube oils. The transformations of a model siloxane, tetramethyldisiloxane (TMDS), were studied in a batch reactor at industrially relevant alkali treatment conditions (low temperature, short reaction time) using different alkali agents. The reaction mechanism involving solid alkali metal silanolates was proposed. The experimental data obtained demonstrated that the solids were dominant products at low temperature and short reaction time. The liquid products in the low temperature reactions were represented mainly by linear siloxanes. The prolongation of reaction time resulted in reduction of solids, whereas both temperature and time increase led to dominance of cyclic products in the reaction mixture. Experiments with the varied reaction time demonstrated that the concentration of cyclic trimer being the dominant in the beginning of the reaction diminished with time, whereas the cyclic tetramer tended to increase. Experiments with lower sodium hydroxide concentration showed the same effect. In addition, a decrease of alkali agent concentration in the initial reaction mixture accelerated TMDS transformation reactions resulting in solely liquid cyclic siloxanes yields. Comparison of sodium and potassium hydroxides applied as an alkali agent demonstrated that potassium hydroxide was more efficient, since the activation energy in KOH presence was almost 2-fold lower than that for sodium hydroxide containing reaction mixture. Application of potassium hydroxide for TMDS transformation at 100 C with 3 hours reaction time resulted in 20 % decrease of solid yields compared to NaOH-containing mixture. Moreover, TMDS transformations in the presence of sodium silanolate applied as an alkali agent led to formation of only liquid products without formation of the undesired solids. On the basis of experimental data and the proposed reaction mechanism, a kinetic model was developed, which provided a satisfactory description of the experimental results. Suitability of the selected siloxane as a relevant model of industrial silicon-containing compounds was verified by investigation of the commercially available antifoam agent in base-catalyzed conditions.
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Bioenergi ses som en viktig del av det nu- och framtida sortimentet av inhemsk energi. Svartlut, bark och skogsavfall tcker mer n en femtedel av den inhemska energianvndningen. Produktionsanlggningar kan fungera ofullstndigt och en mngd gas-, partikelutslpp och tjra produceras samtidigt och kan leda till belggningsbildning och korrosion. Orsaken till dessa problem r ofta obalans i processen: vissa freningar anrikas i processen och superjmviktstillstnd r bildas. I denna doktorsavhandling presenteras en ny berkningsmetod, med vilken man kan beskriva superjmviktstillstndet, de viktigaste kemiska reaktionerna, processens vrmeproduktion och tillstndsstorheter samtidigt. Berkningsmetoden grundar sig p en unik frienergimetod med bivillkor som har utvecklats vid VTT. Den hr s kallade CFE-metoden har tidigare utnyttjats i pappers-, metall- och kemiindustrin. Applikationer fr bioenergi, vilka r demonstrerade i doktorsavhandlingen, r ett nytt anvndingsomrde fr metoden. Studien visade att berkningsmetoden r vl lmpad fr hgtemperaturenergiprocesser. Superjmviktstillstnden kan uppst i dessa processer och det kemiska systemet kan definieras med ngra bivillkor. Typiska tillmpningar r frbrnning av biomassa och svartlut, frgasning av biomassa och uppkomsten av kvveoxider. Ocks olika stt att definiera superjmviktstillstnd presenterades i doktorsavhandlingen: empiriska konstanter, empiriska hastighetsuttryck eller reaktionsmekanismer kan anvndas. Resultaten av doktorsavhandlingen kan utnyttjas i framtiden i processplaneringen och i underskning av nya tekniska lsningar fr frgasning, frbrnningsteknik och biobrnslen. Den presenterade metoden r ett bra alternativ till de traditionella mekanistiska och fenomenmodeller och kombinerar de bsta delarna av bde. --------------------------------------------------------------- Bioenergia on trke osa nykyist ja tulevaa kotimaista energiapalettia. Mustalipe, kuori ja metsthteet kattavat yli viidenneksen kotimaisesta energian kulutuksesta. Tuotantolaitokset eivt kuitenkaan aina toimi tydellisesti ja niiden prosesseissa syntyy erilaisia kaasu- ja hiukkaspstj, tervoja sek prosessilaitteita kuluttavia saostumia ja ruostumista. Usein syy nihin ongelmiin on prosessissa esiintyv eptasapainotila: tietyt yhdisteet rikastuvat prosessissa ja muodostavat supertasapainotiloja. Vitstyss kehitettiin uusi laskentamenetelm, jolla voidaan kuvata nm supertasapainotilat, trkeimmt niihin liittyvt kemialliset reaktiot, prosessin lmmntuotanto ja tilansuureet yht aikaa. Laskentamenetelm perustuu VTT:ll kehitettyyn ainutlaatuiseen rajoitettuun vapaaenergiamenetelmn. Tt niin kutsuttua CFE-menetelm on aiemmin sovelluttu onnistuneesti muun muassa paperi-, metalli- ja kemianteollisuudessa. Vitstyss esitetyt bioenergiasovellukset ovat uusi sovellusalue menetelmlle. Ty osoitti laskentatavan soveltuvan hyvin korkealmpisiin energiatekniikan prosesseihin, joissa kemiallista systeemi rajoittavia tekijit oli rajallinen mr ja siten super-tasapainotila saattoi muodostua prosessin aikana. Tyypillisi sovelluskohteita ovat biomassan ja mustalipen poltto, biomassan kaasutus ja typpioksidipstt. Tyn aikana arvioitiin mys erilaisia tapoja mritell super-tasapainojen muodostumista rajoittavat tekijt. Rajoitukset voitiin tehd teollisiin mittauksiin pohjautuen, kokeellisia malleja hydynten tai mekanistiseen reaktiokinetiikkaan perustuen. Tulevaisuudessa vitstyn tuloksia voidaan hydynt prosessisuunnittelussa ja tutkittaessa uusia teknisi ratkaisuja kaasutus- ja polttotekniikoissa sek biopolttoaineiden tutkimuksessa. Kehitetty menetelm tarjoaa hyvn vaihtoehdon perinteisille mekanistisille ja ilmimalleille yhdisten niden parhaita puolia.
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Store-operated Ca2+ entry plays an important role in Ca2+ homeostasis in cells but the mechanisms of control of these channels are not completely understood. We describe an investigation of the role of the CD38-cyclic-ADP-ribose (cADPR)-ryanodine-channel (RyR) signaling pathway in store-operated Ca2+ entry in human smooth muscle. We observed that human myometrial cells have a functional store-operated Ca2+ entry mechanism. Furthermore, we observed the presence of transient receptor potential 1, 3, 4, 5, and 6 ion channels in human myometrial cells. Store-operated Ca2+ transient was inhibited by at least 50-70% by several inhibitors of the RyR, including ryanodine (10 M), dantrolene (10 M), and ruthenium red (10 M). Furthermore, the cell permeable inhibitor of the cADPR-system, 8-Br-cADPR (100 M), is a potent inhibitor of the store-operated entry, decreasing the store operated entry by 80%. Pre-incubation of cells with 100 M cADPR and the hydrolysis-resistant cADPR analog 3-deaza-cADPR (50 M), but not with ADP-ribose (ADPR) leads to a 1.6-fold increase in the store-operated Ca2+ transient. In addition, we observed that nicotinamide (1-10 mM), an inhibitor of cADPR synthesis, also leads to inhibition of the store-operated Ca2+ transient by 50-80%. Finally, we observed that the transient receptor potential channels, RyR, and CD38 can be co-immunoprecipitated, indicating that they interact in vivo. Our observations clearly implicate the CD38-cADPR-ryanodine signaling pathway in the regulation of store-operated Ca2+ entry in human smooth muscle cells.
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[N. 1:875000].
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Perustuu Joseph Nicolas Delislen laatimaan ja Johann Elias Grimmelin kaivertamaan vastaavaan karttaan vuodelta 1741.
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The effects of L-histidine (LH) on anxiety and memory retrieval were investigated in adult male Swiss Albino mice (weight 30-35 g) using the elevated plus-maze. The test was performed on two consecutive days: trial 1 (T1) and trial 2 (T2). In T1, mice received an intraperitoneal injection of saline (SAL) or LH before the test and were then injected again and retested 24 h later. LH had no effect on anxiety at the dose of 200 mg/kg since there was no difference between the SAL-SAL and LH-LH groups at T1 regarding open-arm entries (OAE) and open-arm time (OAT) (mean SEM; OAE: 4.0 0.71, 4.80 1.05; OAT: 40.55 9.90, 51.55 12.10, respectively; P > 0.05, Kruskal-Wallis test), or at the dose of 500 mg/kg (OAE: 5.27 0.73, 4.87 0.66; OAT: 63.93 11.72, 63.58 10.22; P > 0.05, Fisher LSD test). At T2, LH-LH animals did not reduce open-arm activity (OAE and OAT) at the dose of 200 mg/kg (T1: 4.87 0.66, T2: 5.47 1.05; T1: 63.58 10.22; T2: 49.01 8.43 for OAE and OAT, respectively; P > 0.05, Wilcoxon test) or at the dose of 500 mg/kg (T1: 4.80 1.60, T2: 4.70 1.04; T1: 51.55 12.10, T2: 43.88 10.64 for OAE and OAT, respectively; P > 0.05, Fisher LSD test), showing an inability to evoke memory 24 h later. These data suggest that LH does not act on anxiety but does induce a state-dependent memory retrieval deficit in mice.
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Painovuosi nimekkeest.
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Painovuosi nimekkeest.
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Invokaatio: Cum Deo.
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Variantti A.
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Highly efficient mechanisms regulate intracellular calcium (Ca2+) levels. The recent discovery of new components linking intracellular Ca2+ stores to plasma membrane Ca2+ entry channels has brought new insight into the understanding of Ca2+ homeostasis. Stromal interaction molecule 1 (STIM1) was identified as a Ca2+ sensor essential for Ca2+ store depletion-triggered Ca2+ influx. Orai1 was recognized as being an essential component for the Ca2+ release-activated Ca2+ (CRAC) channel. Together, these proteins participate in store-operated Ca2+ channel function. Defective regulation of intracellular Ca2+ is a hallmark of several diseases. In this review, we focus on Ca2+ regulation by the STIM1/Orai1 pathway and review evidence that implicates STIM1/Orai1 in several pathological conditions including cardiovascular and pulmonary diseases, among others.
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Dedikaatio: Ericus Lindskild, Nicolaus von Preutz.
