The role of surface vertical mixing in phytoplankton distribution in a stratified reservoir

We investigated convection caused by surface cooling and mixing attributable to wind shear stress and their roles as agents for the transport of phytoplankton cells in the water column by carrying out two daily surveys during the stratified period of the Sau reservoir. Green algae, diatoms, and cryptophyceae were the dominant phytoplankton communities during the surveys carried out in the middle (July) and end (September) of the stratified period. We show that a system with a linear stratification and that is subject to weak surface forcing, with weak winds , < 4 m S (-1) and low energy dissipation rate values of the order of 1028 m2 s23 or lower, enables the formation of thin phytoplankton layers. These layers quickly disappear when water parcels mix because there is a medium external forcing (convection) induced by the night surface cooling, which is characterized by energy dissipation rates on the order of , 5x10(-8)m2s(-3). During both surveys the wind generated internal waves during the entire diurnal cycle. During the day, and because of the weak winds, phytoplankton layers rise in the water column up to a depth determined by both solar heating and internal waves. In contrast, during the night phytoplankton mixes down to a depth determined by both convection and internal waves. These internal waves, together with the wind-driven current generated at the surface, seem to be the agents responsible for the horizontal transport of phytoplankton across the reservoir.

The Ionotropic receptors IR21a and IR25a mediate cool sensing in Drosophila.

Animals rely on highly sensitive thermoreceptors to seek out optimal temperatures, but the molecular mechanisms of thermosensing are not well understood. The Dorsal Organ Cool Cells (DOCCs) of the Drosophila larva are a set of exceptionally thermosensitive neurons critical for larval cool avoidance. Here, we show that DOCC cool-sensing is mediated by Ionotropic Receptors (IRs), a family of sensory receptors widely studied in invertebrate chemical sensing. We find that two IRs, IR21a and IR25a, are required to mediate DOCC responses to cooling and are required for cool avoidance behavior. Furthermore, we find that ectopic expression of IR21a can confer cool-responsiveness in an Ir25a-dependent manner, suggesting an instructive role for IR21a in thermosensing. Together, these data show that IR family receptors can function together to mediate thermosensation of exquisite sensitivity.

Construção de equipamentos de refrigeração que permitem trabalhar com temperaturas de -40ºC ou -60ºC

In this article we describe the construction of two cooling systems with an immersion probe which will allow one to work at temperatures of either -40ºC or -60ºC. The two systems were constructed with readily available components and have been used daily for the last year in our laboratory to carry out reactions at low temperature or to cool down traps of vacuum pumps, reducing our need of dry-ice or liquid nitrogen.

Fischer-Tropsch Slurry Bubble Column Reactor Modeling

The literature part of the work reviews overall Fischer-Tropsch process, Fischer-Tropsch reactors and catalysts. Fundamentals of Fischer-Tropsch modeling are also presented. The emphasis is on the reactor unit. Comparison of the reactors and the catalysts is carried out to choose the suitable reactor setup for the modeling work. The effects of the operation conditions are also investigated. Slurry bubble column reactor model operating with cobalt catalyst is developed by taking into account the mass transfer of the reacting components (CO and H2) and the consumption of the reactants in the liquid phase. The effect of hydrostatic pressure and the change in total mole flow rate in gas phase are taken into account in calculation of the solubilities. The hydrodynamics, reaction kinetics and product composition are determined according to literature. The cooling system and furthermore the required heat transfer area and number of cooling tubes are also determined. The model is implemented in Matlab software. Commercial scale reactor setup is modeled and the behavior of the model is investigated. The possible inaccuraries are evaluated and the suggestions for the future work are presented. The model is also integrated to Aspen Plus process simulation software, which enables the usage of the model in more extensive Fischer-Tropsch process simulations. Commercial scale reactor of diameter of 7 m and height of 30 m was modeled. The capacity of the reactor was calculated to be about 9 800 barrels/day with CO conversion of 75 %. The behavior of the model was realistic and results were in the right range. The highest uncertainty to model was estimated to be caused by the determination of the kinetic rate.

Ydinreaktorin painesäiliön ulkoisen jäähdytyksen lämmönsiirtokokeita

The purpose of this work was to design and carry out thermal-hydraulic experiments dealing with overcooling transients of a VVER-440-type nuclear reactor pressure vessel. Sudden overcooling accident could have negative effect on the mechanical strength of the pressure vessel. If part of the pressure vessel is compromised, the intense pressure inside a pressurized water reactor could cause the wall to fracture. Information on the heat transfer along the outside of the pressure vessel wall is necessary for stress analysis. Basic knowledge of the overcooling accident and heat transfer types on the outside of the pressure vessel is presented as background information. Test facility was designed and built based to study and measure heat transfer during specific overcooling scenarios. Two test series were conducted with the first one concentrating on the very beginning of the transient and the second one concentrating on steady state heat transfer. Heat transfer coefficients are calculated from the test data using an inverse method, which yields better results in fast transients than direct calculation from the measurement results. The results show that heat transfer rate varies considerably during the transient, being very high in the beginning and dropping to steady state in a few minutes. The test results show that appropriate correlations can be used in future analysis.

Ciência de espumas - aplicação na extinção de incêndios

The structural characteristics of foams are responsible for a broad range of applications of this system. Foams produced by aqueous solutions of surfactant concentrates are used in fire-fighting due to their special properties as extinguishing agents. In the present paper we discuss the main aspects involved in fire-fighting, based on some properties of foams. Thermal and chemical stability, good wetting of surfaces, cooling effect by water drained from the bubbles, isolation of the air from the burning surface and suppression of flammable vapors are some of the factors involved in the extinguishment of fire by foams.

Liiketoimintastrategisten vaatimusten syntyminen ja niiden toteutumisen arviointi keskisuurten yritysten toiminnanohjausjärjestelmähankkeissa. Tapaustutkimus kolmesta teollisuusyrityksestä ja aineistolähtöinen teoria

Tietojärjestelmien strateginen kehittäminen on ollut niin liike-elämän kiinnostuksen kuin akateemisen tutkimuksenkin kohteena jo pitkään. Aihe on edelleen ajankohtainen, eikä ajankohtaisuus osoita laantumisen merkkejä. Valtaosa tutkimuksesta on kohdistunut suuryrityksiin ja jonkin verran pk-yrityksiin yhtenä ryhmänä. Tutkimus on kohdistunut aiheeseen tarkastelemalla onko tietojärjestelmien ja liiketoimintastrategian välillä yhteyttä, ja jos, onko sillä merkitystä yrityksen menestykselle. Tämän tutkimuksen tavoitteena oli pureutua syvemmälle siihen tapaan, jolla yritys kytkee liiketoimintastrategiansa tietojärjestelmähankintaan. Kohdetietojärjestelmäksi tutkimuksessa valittiin toiminnanohjausjärjestelmät ja yrityskooksi keskisuuret yritykset. Toiminnanohjausjärjestelmän valintaa voidaan perustella sen kattavuudella yrityksen toiminnassa eri sidosryhmien suunnasta katsottaessa. Keskisuuret yritykset valittiin osittain sen vuoksi, koska niistä ei ole paljoakaan omaa tutkimusta, osittain sen vuoksi, että niiden luonne kehityspolun epäjatkumokohdassa haluttiin nostaa esille. Tutkimuksen empiirinen osa pohjautuu kolmeen tutkimustapaukseen, kolmen keskisuuren yrityksen toiminnanohjaushankkeeseen. Tapausyritysten liiketoiminta- ja ITjohtoa haastateltiin, ja lisäksi käytettiin kaikkea saataville ollutta kirjallista arkistoaineistoa. Tutkimuksen päämenetelmä oli Grounded Theory (GT). Tutkimustavassa ei, poiketen useista muista laadullisista tutkimustavoista, ole ennalta määrättyä viitekehystä, vaan tutkimus lähtee liikkeelle ns. puhtaalta pöydältä ilman esioletuksia luoden tutkimusprosessin kuluessa uutta teoriaa. Tutkimustavan etuna voidaan pitää ennakkoluulottomuutta. Aikaisemman tutkimuksen rooli tässä tutkimuksessa oli ensinnäkin kartoittaa tutkimusaluetta ja olla johdantona tutkimukselle, toisaalta tuloksia vertailtiin aikaisempaan tutkimukseen. Tutkimusaineisto analysoitiin tarkasti. Ensin aineisto käytiin läpi koodaamalla se aineistosta esille nousseiden käsitteiden alle. Seuraavaksi saatu tulos luokiteltiin aineistosta nousseisiin luokkiin sekä muodostettiin käsitteiden ja luokkien väliset yhteydet. Lopuksi muodostumassa oleva teoria konkretisoitiin 18 hypoteesin ja hypoteesit yhdistävän mallin avulla. Tutkimuksessa saatiin uutta tietoa siitä, miten vaatimusprosessi etenee ja miten keskisuuren yrityksen ominaispiirteet vaikuttavat vaatimusprosessiin. Lisäksi saatiin uutta tietoa siitä, mitkä ovat kriittisiä menestystekijöitä keskisuuren yrityksen toiminnanohjaushankkeessa. Keskisuuretyritykset näyttävät tämän tutkimuksen aineiston perusteella osaavan asettaa vaatimuksia toiminnanohjausjärjestelmälle liiketoimintastrategian, prosessikuvausten ja toiminnanohjausjärjestelmien tarjoamien mahdollisuuksien suunnista. Vaatimusten toteutumisenarviointi on keskisuurilla yrityksillä epäsystemaattista, kuten aikaisemmassa tutkimuksessa on todettu olevan myös suurilla yrityksillä. Resurssivaje vaikeuttaa toiminnanohjausjärjestelmän liiketoimintastrategisten vaatimusten toteutumista. Tutkimusaineiston perusteella voidaan päätellä, että keskisuurissa yrityksissä – huolimatta siitä, että niissä on olemassa prosessikuvaukset – ei ole varsinaista prosessiajattelua tai prosessijohtamista. Keskisuuret yritykset eivät tämän tutkimuksen aineiston perusteella näytä muodostavan poikkeusta, vaan mittariston käyttö on epäkypsää, eikä mittaristoa pystytä hyödyntämään tietojärjestelmähankkeen tukena. Tulosten pohjalta voidaan arvioida, että strategisen johtamisen komponentit ovat keskisuuressa yrityksessä toisistaan irrallisia. Vaikka toiminnanohjaushankkeen vaatimuksia asetettaessa liiketoimintastrategia on vahvasti mukana, jää vaatimuksenasettelu karkealle tasolle, eikä konkretisoidu prosesseihin ja mittarointiin. Sen seurauksena toiminnanohjausjärjestelmästä ei saada kaikkea sitä hyötyä ja tukea liiketoimintastrategialle, mikä olisi mahdollista. Tutkimuksessa tuli myös esille resurssi- ja osaamispuutteen haittavaikutuksia keskisuurten yritysten toiminnanohjaushankkeiden vaatimusprosessissa. Puutteet yhdistettynä hajallaan oleviin strategisen johtamisen komponentteihin muodostavat yhdessä vaikean lähtökohdan strategiselle toiminnanohjaushankkeelle.

Influence of elastic anisotropy on structural nanoscale textures

We study the influence of elastic anisotropy on nanoscale precursor textures that exist in some shape-memory alloys and show that tweed occurs in the limit of high elastic anisotropy while a nanocluster phase-separated state occurs for values of anisotropy inhibiting the formation of martensite. These results are consistent with specific heat data, elastic constant measurements, and zero-field cooling or field cooling experiments in nonstoichiometric NiTi alloys.

Metodologia para o crescimento de esferas monocristalinas de metais nobres

This paper describes in detail a technique employed to grow quasi-spherical single crystals of noble metals for electrochemical applications, using platinum as an example. The metal beads were formed by melting the extremity of a wire in an oxygen / butane flame. X-ray techniques were used to check the crystallization and to determine the orientation of the crystals. Treatment with a pure hydrogen flame followed by a cooling procedure in a hydrogen / argon atmosphere were used for conditioning the well-defined platinum single crystal surfaces. Finally, electrochemical characterization of the Pt(111), Pt(110) and Pt(100) surfaces was done in diluted sulfuric acid solution in the hydrogen adsorption / desorption potential region.

Jäähdytysnestekierron optimointi tuuliturbiinin konvertterikaapistoon

Diplomityössä perehdytään tuuliturbiinin konvertterikaapiston nestekierron tarkasteluun ja mittausten suunnitteluun sitä varten. Tarkastelun tulokset ovat yhdistettävissä konvertterikaapiston ilmapuolen jäähdytykseen, jolloin koko jäähdytysjärjestelmä on katettu. Työn alkupuolella perehdytään lyhyesti nykyhetken tuulivoimaan. Tämän jälkeen tarkastellaan itse konvertterikaapistoa, sen toimintaa sekä nestejäähdytyksen toteutusta komponentteineen. Työn keskimmäisessä osassa konvertterille tehtiin virtaustekninen malli aiempaa mittausdataa hyväksi käyttäen. Tällä mallilla suoritettiin herkkyystarkasteluja ja simuloitiin konvertterikaapiston nestekierron käyttäytymistä yhden tai useamman haaran tukkeutuessa osittain tai kokonaan. Lisäksi suunniteltiin uusi nestekierto. Lopuksi selvitetään mittauksissa tarvittava laitteisto, perehdytään kunkin laitteen toimintaperiaatteeseen sekä selvennetään suositeltavat asennuspaikat ja suojaetäisyydet.

Um banho termostático de baixo custo (temperatura ambiente até 0ºC)

Thermal baths to decrease ambient temperature are an indispensable tool for most research and teaching laboratories, especially those in tropical or equatorial regions. A simple and inexpensive thermal bath has been developed based on a scratched compressor. It has three possible setups for cooling: sample immersed into the bath, sample flowing through the bath, and cooling liquid flowing in a jacket around the sample. It has been tested for 40 months. The temperature ranges from room temperature to 0 °C, when using water. The repeatability is better than 3% and the precision varies from 0.5% to 2%.

Cristalização e taxa crítica de resfriamento para vitrificação do poli(sebacato de decametileno)

We synthesized Poly(decamethylene sebacate) - P10MS - and studied its overall crystallization rates in a range of temperatures using Differential Scanning Calorimetry in isothermal conditions, which enabled us to identify the crystallization mechanism by means of the Johnson-Mehl-Avrami-Kolmogorov equation. The critical cooling rate (Rc) to vitrify the P10MS was determined using a non-isothermal method proposed by Barandiarán & Colmenero (BC). The value of Rc is around 50-250 K/s, which confirms the experimentally observed difficulty to vitrify this polymer.

Thermal-Hydraulic Studies on the Safety Of VVER-440 Type Nuclear Power Plants

This thesis includes several thermal hydraulic analyses related to the Loviisa WER 440 nuclear power plant units. The work consists of experimental studies, analysis of the experiments, analysis of some plant transits and development of a calculational model for calculation of boric acid concentrations in the reactor. In the first part of the thesis, in the case of won of boric acid solution behaviour during long term cooling period of LOCAs, experiments were performed in scaled down test facilities. The experimental data together with the results of RELAPS/MOD3 simulations were used to develop a model for calculations of boric acid concentrations in the reactor during LOCAs. The results of calculations showed that margins to critical concentrations that would lead to boric acid crystallization were large, both in the reactor core and in the lower plenum. This was mainly caused by the fact that water in the primary cooling circuit includes borax (Na)BsO,.IOHZO), which enters the reactor when ECC water is taken from the sump and greatly increases boric acid solubility in water. In the second part, in the case of simulation of horizontal steam generators, experiments were performed with PACTEL integral test loop to simulate loss of feedwater transients. The PACTEL experiments, as well as earlier REWET III natural circulation tests, were analyzed with RELAPS/MOD3 Version Sm5 code. The analysis showed that the code was capable of simulating the main events during the experiments. However, in the case of loss of secondary side feedwater the code was not completely capable to simulate steam superheating in the secondary side of the steam generators. The third part of the work consists of simulations of Loviisa VVER reactor pump trip transients with RELAPSlMODI Eur, RELAPS/MOD3 and CATHARE codes. All three codes were capable to simulate the two selected pump trip transients and no significant differences were found between the results of different codes. Comparison of the calculated results with the data measured in the Loviisa plant also showed good agreement.

The age of the"Grande Coupure" mammal turnover: New constraints from the Eocene Oligocene record of the Eastern Ebro Basin (NE Spain.)

The Grande Coupure represents a major terrestrial faunal turnover recorded in Eurasia associated with the overall climate shift at the Eocene-Oligocene transition. During this event, a large number of European Eocene endemic mammals became extinct and new Asian immigrants appeared. The absolute age of the Grande Coupure, however, has remained controversial for decades. The Late Eocene-Oligocene continental record of the Eastern Ebro Basin (NE Spain) constitutes a unique opportunity to build a robust magnetostratigraphy- based chronostratigraphy which can contribute with independent age constraints for this important turnover. This study presents new magnetostratigraphic data of a 495-m-thick section (Moià-Santpedor) that ranges from 36.1 Ma to 33.3 Ma. The integration of the new results with previous litho- bio- and magnetostratigraphic records of the Ebro Basin yields accurate ages for the immediately pre- and post-Grand Coupure mammal fossil assemblages found in the study area, bracketing the Grande Coupure to an age embracing the Eocene-Oligocene transition, with a maximum allowable lag of 0.5 Myr with respect to this boundary. The shift to drier conditions that accompanied the global cooling at the Eocene-Oligocene transition probably determined the sedimentary trends in the Eastern Ebro Basin. The occurrence and expansion of an amalgamated-channel sandstone unit is interpreted as the forced response of the fluvial fan system to the transient retraction of the central-basin lake systems. The new results from the Ebro Basin allow us to revisit correlations for the controversial Eocene-Oligocene record of the Hampshire Basin (Isle of Wight, UK), and their implications for the calibration of the Mammal Palaeogene reference levels MP18 to MP21.