Heat transfer in superheaters of the bubbling fluidized bed boiler conversions

It is often reasonable to convert old boiler to bubbling fluidized bed boiler instead of building a new one. Converted boiler consists of old and new heat surfaces which must be fitted to operate together. Prediction of heat transfer in not so ideal conditions sets challenges for designers. Two converted boilers situated in Poland were studied on the grounds of acceptance tests and further studies. Calculation of boiler process was performed with boiler design program. Main interest was heat transfer in superheaters and factors affecting it. Theory for heat transfer is presented according to information found from literature. Results obtained from experimental studies and calculations have been compared. With correct definitions calculated parameters corresponded well to measured data at boiler maximum design load. However overload situations revealed to be difficult to model at least without considering changes in the combustion process which requires readjustments to the design program input values.

Haja-asutusalueiden sähkönjakelujärjestelmien kehittäminen – erityisesti 1000 V jakelujännitteen käyttömahdollisuudet

Yhteiskunnan riippuvuus sähköstä on lisääntynyt voimakkaasti viime vuosikymmenien aikana. Sähkönjakelussa esiintyneet lyhyet ja pitkät keskeytykset ovat osoittaneet yhteiskunnan haavoittuvuuden ja yhteiskunta kestää entistä vähemmän sähkönjakelussa tapahtuvia häiriöitä. Keskeytyksistä aiheutuneiden haittojen arvostus on kasvanut ja tämä on luonut taloudelliset perusteet sähkön laatua parantaville investoinneille. Haja-asutusalueiden keskijänniteverkon johdot on rakennettu avojohtoina ja siten ne ovat alttiita sääolosuhteista johtuville myrsky- ja lumikuormavaurioille. Ilmastomuutoksen ennustetaan lisäävän tuulisuutta ja siten ongelmat sähkönjakelussa mahdollisesti lisääntyvät. Taajamissa käytetään enemmän kaapeleita ja johtolähdöt ovat lyhyitä, joten myrskyistä aiheutuvia keskeytyksiä on vähemmän kuin haja-asutusalueella. Olemassa olevat jakeluverkot ovat käytössä vielä vuosikymmeniä, joten uuden tekniikan kehittämisen rinnalla on kehitettävä myös olemassa olevaa jakeluverkkoa ja sen ylläpitoa. Ylläpidon tavoitteena on käyttövarmuuden parantamisen lisäksi huolehtia siitä, että jakeluverkkoihin sitoutunut omaisuus säilyttää arvonsa mahdollisimman hyvin pitoajan loppuun saakka. Jakeluverkkoihin investoitiin paljon 1950–70-luvuilla. Tältä ajalta on yhä käytössä puupylväitä, joiden ikääntymisen takia korvausinvestointien tarve kasvaa. Hyvänä puolena tässä on että käyttövarmuuden parantamiseksi olemassa olevaa jakeluverkkoa ei tarvitse uusia ennenaikaisesti. Tutkimuksessa päähuomio on haja-asutusalueiden 20 kV keskijänniteverkon kehittämisessä, sillä yli 90 % asiakkaiden kokemista keskeytyksistä johtuu keskijänniteverkon vioista. Erityisesti johtorakenteisiin ja johtojen sijoittamiseen on kiinnitettävä huomiota. Käyttövarmuuden lisäksi jakeluverkkojen kehittämistä ohjaavia tekijöitä ovat taloudellisuus, ympäristön huomioiminen, viranomaisvalvonta sekä asiakkaiden ja omistajien odotukset. Haja-asutusalueilla taloudelliset haasteet ovat suuret vakituisen väestön vähenemisen ja mahdollisesti sähköntarpeen pienenemisen takia. Taloudellisuus korostuu ja riskit kasvavat, kun tuottojen määrä supistuu tarvittaviin jakeluverkon investointeihin ja ylläpitokustannuksiin verrattuna. Ristiriitaa aiheuttaa se, että asiakkaat odottavat sähkönjakelulta parempaa luotettavuutta, mutta paremmasta sähkönlaadusta ei olla valmiita maksamaan juurikaan nykyistä enempää. Jakeluverkkojen kehittämistä voi hidastaa myös viranomaisvalvonta, jos tuottoja ei voida lisätä investointien lisätarpeiden suhteessa. Tutkimuksessa on analysoitu yleisellä tasolla kaapeloinnin lisäämistä, korkeiden pylväiden käyttämistä, leveitä johtokatuja, edullisten ja yksinkertaisten sähköasemien rakentamista haja-asutusalueille ja automaatioasemien lisäämistä keskijänniteverkon solmupisteisiin. Erityisesti tutkimuksessa on analysoitu uutena tekniikkana 1000 V jännitteen käyttömahdollisuutta jakeluverkkojen kehittämisessä. Sähköjohtojen siirtäminen teiden varsiin parantaa käyttövarmuutta, vaikka johdot rakennetaan samalla tekniikalla kuin olemassa olevat johdot. Hajaasutusalueille rakennettavilla sähköasemilla pitkät syöttöjohdot voidaan jakaa pienemmiksi syöttöalueiksi, jolloin keskeytyksistä aiheutuvat haitat koskettavat kerrallaan pienempää asiakasmäärää. Samaan tulokseen päästään oikein sijoitetuilla ja toteutetuilla automaatioasemilla. Tutkimuksen mukaan lupaavaksi tekniikaksi jakeluverkkojen kehittämisessä on osoittautumassa 1000 V jänniteportaan ottaminen 400 V pienjännitteen lisäksi. 1000 V verkoilla voidaan korvata häiriöherkkiä 20 kV keskijänniteverkon lyhyitä, alle viiden kilometrin pituisia haarajohtoja ja haarajohtojen jatkeita, missä siirrettävät tehot ovat pieniä. Uudessa jakelujärjestelmässä sähkö tuodaan 1000 V jännitteellä lähelle asiakasta, jossa jännite muunnetaan normaaliksi asiakkaille soveltuvaksi 400/230 V jännitteeksi. Edullisuus perustuu siihen, että rakentamisessa käytetään samoja pienjännitejohtoja kuin asiakkaille menevässä 400 V pienjänniteverkossa. 1000 V jakelutekniikassa sekä investointikustannukset että ylläpitokustannukset ovat pienemmät kuin perinteisessä 20 kV ilmajohtotekniikassa. 1000 V johdot säästävät maisemaa, sillä ne eivät tarvitse leveää johtokatua kuten 20 kV keskijännitejohdot. 1000 V verkkojen käyttö soveltuukin erityisesti vapaa-ajanasuntojen sähköistykseen herkissä ranta- ja järvimaisemissa. 1000 V verkot mahdollistavat kaapeliauraamisen lisäämisen ja näin voidaan vähentää ympäristöä haittaavien kyllästettyjen pylväiden käyttöä. 1000 V jakeluverkkojen osalta tutkimustyön tuloksia on sovellettu suomalaisessa Suur-Savon Sähkö Oy:ssä. Käytännön kokemuksia 1000 V jakelujärjestelmästä on useista kymmenistä kohteista. Tutkimustulokset osoittavat, ettei keskijänniteverkon maakaapelointi hajaasutusalueilla ole taloudellisesti kannattavaa nykyisillä keskeytyksistä aiheutuvilla haitta-arvoilla, mutta jos keskeytyskustannusten arvostus kasvaa, tulee kaapelointi kannattavaksi monissa paikoissa. Myös myrskyisyyden ja myrskyistä aiheutuvien jakelukeskeytysten lisääntyminen tekisi kaapeloinnista kannattavan. Tulevaisuudessa jakeluverkkojen rakentaminen on entistä monimuotoisempi tehtävä, jossa taloudellisuuden ja käyttövarmuuden lisäksi on huomioitava asiakkaat, omistajat, viranomaiset ja ympäristö. Tutkimusta jakelutekniikan kehittämiseksi tarvitaan edelleen. Tulevaisuuden osalta haja-asutusalueiden jakeluverkkojen kehittämiseen liittyy paljon epävarmuuksia. Hajautetun kiinteistökohtaisen sähköntuotannon lisääntyminen voi tehdä jakeluverkoista nykyistä tarpeettomampia, mutta esimerkiksi liikenteen sähköistyminen voi kasvattaa jakeluverkkojen merkitystä. Tästä syystä jakeluverkkojen rakentamisessa tarvitaan joustavuutta, jotta tarvittaessa voidaan helposti sopeutua erilaisiin kehityssuuntiin.

Imposicions estructurals en el drenatge de la conca del riu Onyar (Girona)

The Onyar River basin is situated in the depression of la Selva. His origins are related to tectonic activity during Neogen in this region. In his evolution, we note a slowly and continuous downfall which directs the morphodinamical behaviour. In this sense, the drainage network has a directional trend towards the north, as consecuence of fault systems, and specially the N-S oriented one. A fault of this system has an important influence in the basin morphology, directs the drainage towards the north and avoids a closely drainage in the basin

Geomorphological mapping of granite zones in the province of Girona (Catalunya, Spain)

Since 1978, the unity of Geodynamics of the University of Girona has been publishing a series of detailed geological and geomorphological maps of different municipal terms of the Province of Girona, mainly on the scale of 1:10.000, situated for the major part in the Littoral and Prelittoral mountain ranges of the Cadena Costera Catalana. These mountain ranges are constituted of materials belonging to the palaeozoic era, basically metamorphous and igneous rocks (plutomc and hypoabyssal rocks)

Effects of artisanal fisheries on the scorpaenids (Scorpaena spp.) reproduction in the marine protected area of Cap de Creus (NW Mediterranean)

Rockfish species are considered important to the ecology of rocky-reef communities which constitute a key habitat in many coastal marine protected areas (MPAs). These species, which are commercially valuable for artisanal fisheries in the Mediterranean, display particular biological traits that could render them vulnerable to fishing. In this study we monitored the artisanal fisheries of scorpaenids (Scorpaena spp.) in the MPA of Cap de Creus (northwestern Mediterranean) in order to estimate the status of their populations, to link captures with the reproduction of these species, and to evaluate the potential impact that artisanal fishing may have on them. Data from onboard sampling with artisanal fishermen and from fisheries statistics (total landings) were used. Total landings and catch per unit of effort (CPUE) follow a clearly seasonal cycle, with a prominent peak during the summer months coinciding with their spawning season, which may be due to mating behavior prior to fertilization. Although maximum sizes are bigger inside the MPA than in non-protected areas situated close by, a significant percentage of individuals caught inside the MPA are below their size at sexual maturity. Although rockfish seem to be favored by the partial protection of the MPA, the allowed artisanal fisheries are probably impacting the reproduction of these species

La Palma - Nova Classis: a Publius Cornelius Scipio Africanus encampment during the Second Punic War in Iberia

This paper presents the discovery of the oldest Roman camp on the Iberian Peninsula, a camp from the Second Punic War situated in La Palma (Tarragona, Spain), by the mouth of the River Ebro. Although no structural remains have been found, the site's strategic in- terest along with many coins, arms and fragments of amphoras and other objects indicate that a military camp was established here between 218 and 209 BC. Written sources, mainly Polybius and Livy, suggest that La Palma was where the legions of Publius Cornelius Scipio gathered before the attack on Carthago Nova in 209 BC. The paper ends by suggesting that La Palma may be the Roman camp of Nova Classis mentioned by Livy during the events of the war in 217 BC.

Ewing sarcoma of the rib: respiratory tract infection as initial symptoms in a 14-year-old boy. Functional medical imaging findings

Ewing sarcoma or primitive neuroectodermal tumor (PNET) of bone is the second most common pediatric malignant bone tumor. The median age at diagnosis is 15 years and there is a male predilection of 1.5/1. The authors present the case of a 14-year-old boy with Ewing sarcoma situated on the left ninth rib which was being investigated for respiratory tract infection. Pleurisy is the most common misdiagnosis. Our case illustrates the importance of recognizing exceptional features when interpreting FDG PET or scintigraphy to prevent the misinterpretation of metastases as other etiologies, such as infection.

Development of a microprocessor controlled energy harvester using a Peltier element

Nowadays it is necessary to research other types of energy alternatives and find the way to supply and save the energy we waste. The aim of the project consist of programming a microprocessor to measure if an oven radiates heat to the exterior, for the measure It is used a Peltier element that generates a voltage depending of the temperature difference between the oven and the air of the place where the oven is situated; The energy generated by the oven will be recollected in a condensor. A sensor will be used to know the exact measure. The second part of the project the main propose, is the development of a harvester. The microprocessor will use the voltage produced by the Peltier element to supply the electricity that it needs to work. A low power circuit and the appropriate software are needed to save the voltage generated.

Vedenlaadun parantamismahdollisuudet virtausohjauksen avulla läntisen Pien-Saimaan tapauksessa

Läntisen Pien-Saimaan vesistön alueella on ilmennyt voimakasta sinileväkukintaa vuosina 2006 - 2009. Yksi tehokas keino vähentää sinilevien määrää ja parantaa vedenlaatua, onravinnepitoisuuksien alentaminen virtausohjauksen avulla. Tästä on 70 vuoden kokemus Pien- Saimaan itäosissa, joissa Vehkataipaleen pumppaamon virta on pitänyt vedenlaadun hyvänä huolimatta vesialuetta raskaasti rasittavasta puunjalostusteollisuudesta. Diplomityössä selvitetään mahdollisuuksia toteuttaa virtauksenohjausta myös läntisen Pien-Saimaan puolella, jolloin tavoitteena on vedenlaadun paraneminen. Vedenlaadun parantamista edellyttää myös Euroopan unionin vesipuitedirektiivi. Selvityksessä tarkasteltiin virtauksenohjauksen eri toteutusvaihtoehtoja ja arvioitiin näiden vaikutuksia eri alueiden vedenlaatuun. Tämän lisäksi kartoitettiin ja arvioitiin eri vaihtoehdoista aiheutuvia riskejä. Näiden tietojen pohjalta päädyttiin suositeltaviin virtauksenohjauksen toteutusvaihtoehtoihin, joita ovat Kolhonlahti – Kolinlahti välillä toteutettu pumppaus ja mahdollisen Kutilan kanavan rakentamisen yhteydessä Kopinsalmen pumppaamo. Kolhonlahti – Kolinlahti sijaitsee Pien-Saimaan koillisosassa lähellä Rehulaa. Muista tarkastelluista kohteista saatiin yhdistelemällä suositeltavaksi vaihtoehdoksi myös Vehkataipaleen pumppaamon virran kasvattaminen yhdistettynä Kirjamoinsalmen tai Kopinsalmen pumppaamoon. Tämän lisäksi eri vaihtoehdoille laadittiin alustava kustannustarkastelu. Selvityksessä käytettyjä menetelmiä ja tuloksia voidaan soveltaa myös muihin vastaavan tyyppisiin vesistöjen kunnostushankkeisiin. Työssä on lisäksi koottu yhteen yleistietoja Pien-Saimaasta ja sen tunnetuista virtauksista.

Conceitos de química dos ingressantes nos cursos de graduação do Instituto de Química da Universidade de São Paulo

A diagnostic instrument was developed to evaluate the basic chemistry concepts held by freshmen students of the three Chemistry undergraduate courses offered by the University of São Paulo. The instrument minimizes the use of algorithms or memorization by students and values high-order cognitive skills. Analysis of the students' performances reveals systematic use of "displacement reaction" as an algorithm and a mechanical use of Le Chatelier's Principle. Failure in comprehending the chemical equation and chemical language drives students to alternative models for chemical reactions in aqueous solution. For instance, reaction would occur between "ionic pairs" and/or between species situated in separate compartments.

Distribution and role of macrophytes in coastal lagoons : implications of critical shifts

Crossroads, crucibles and refuges are three words that may describe natural coastal lagoon environments. The words refer to the complex mix of marine and terrestrial influences, prolonged dilution due to the semi-enclosed nature and the function of a habitat for highly diverse plant and animal communities, some of which are endangered. To attain a realistic picture of the present situation, high vulnerability to anthropogenic impact should be added to the description. As the sea floor in coastal lagoons is usually entirely photic, macrophyte primary production is accentuated compared with open sea environments. There is, however, a lack of proper knowledge on the importance of vegetation for the general functioning of coastal lagoon ecosystems. The aim of this thesis is to assess the role of macrophyte diversity, cover and species identity over temporal and spatial scales for lagoon functions, and to determine which steering factors primarily restrict the qualitative and quantitative composition of vegetation in coastal lagoons. The results are linked to patterns of related trophic levels and the indicative potential of vegetation for assessment of general conditions in coastal lagoons is evaluated. This thesis includes five field studies conducted in flads and glo-flads in the brackish water northern Baltic Sea. Flads and glo-flads are defined as a Baltic variety of coastal lagoons, which due to an inlet threshold and post-glacial landuplift slowly will be isolated from the open sea. This process shrinks inlet size, increases exposure and water retention, and is called habitat isolation. The studied coastal lagoons are situated in the archipelago areas of the eastern coast of Sweden, the Åland Islands and the south-west mainland of Finland, where land-uplift amounts to ca. 5 mm/ per year. Out of 400 evaluated sites, a total of 70 lagoons varying in inlet size, archipelago position and anthropogenic influence to cover for essential environmental variation were chosen for further inventory. Vegetation composition, cover and richness were measured together with several hydrographic and morphometric variables in the lagoons both seasonally and inter-annually to cover for general regional, local and temporal patterns influencing lagoon and vegetation development. On smaller species-level scale, the effects of macrophyte species identity and richness for the fish habitat function were studied by examining the influence of plant interaction on juvenile fish diversity. Thus, the active election of plant monoand polycultures by fish and the diversity of fish in the respective culture were examined and related to plant height and water depth. The lagoons and vegetation composition were found to experience a regime shift initiated by increased habitat isolation along with land-uplift. Vegetation composition altered, richness decreased and cover increased forming a less isolated and more isolated regime, named the vascular plant regime and charophyte regime, respectively according to the dominant vegetation. As total phosphorus in the water, turbidity and the impact of regional influences decreased in parallel, the dominance of charophytes and increasing cover seemed to buffer and stabilize conditions in the charophyte regime and indicated an increased functional role of vegetation for the lagoon ecosystem. The regime pattern was unaffected by geographical differences, while strong anthropogenic impact seemed to distort the pattern due to loss of especially Chara tomentosa L. in the charophyte regime. The regimes were further found unperturbed by short-time temporal fluctuations. In fact the seasonal and inter-annual dynamics reinforced the functional difference between the regimes by the increasing role of vegetation along habitat isolation and the resemblance to lake environments for the charophyte regime. For instance, greater total phosphorus and chlorophyll a concentrations in the water in the beginning of the season in the charophyte regime compared with the vascular plant regime presented a steeper reduction to even lower values than in the vascular plant regime along the season. Despite a regional importance and positive relationship of macrophyte diversity in relation to trophic diversity, species identity was underlined in the results of this thesis, especially with decreasing spatial scale. This result was supported partly by the increased role of charophytes in the functioning of the charophyte regime, but even more explicitly by the species-specific preference of juvenile fish for tall macrophyte monocultures. On a smaller species-level scale, tall plant species in monoculture seemed to be able to increase their length, indicating that negative selection forms preferred habitat structures, which increase fish diversity. This negative relationship between plant and fish diversity suggest a shift in diversity patterns among trohic levels on smaller scale. Thus, as diversity patterns seem complex and diverge among spatial scales, it might be ambiguous to extend the understanding of diversity relationships from one trophic level to the other. All together, the regime shift described here presents similarities to the regime development in marine lagoon environments and shallow lakes subjected to nutrient enrichment. However, due to nutrient buffering by vegetation with increased isolation and water retention as a consequence of the inlet threshold, the development seems opposite to the course along an eutrophication gradient described in marine lagoons lacking an inlet threshold, where the role of vegetation decreases. Thus, the results imply devastating consequences of inlet dredging (decreasing isolation) in terms of vegetation loss and nutrient release, and call for increased conservational supervision. Especially the red listed charophytes would suffer negatively from such interference and the consequences are likely to also deteriorate juvenile fish production. The fact that a new species to Finland, Chara connivens Salzm. Ex. Braun 1835 was discovered during this study further indicates a potential of the lagoons serving as refuges for rare species.

Curriculum innovation in teacher education : exploring conceptions among Tanzanian teacher educators

The focus of the study is to understand curriculum innovation from the perspective of Tanzanian teacher educators. It is argued that the deterioration of quality of education in schools is partly to be attributed to the way in which teachers are educated. Curriculum innovation is considered as an essential strategy for bringing about improvement in teacher education. Therefore, in 2000 a new curriculum was introduced; however, right from the inception the curriculum was criticised by teacher educators. The overall aim of the study is to investigate teacher educators’ conceptions of curriculum innovation. In the theoretical framework the main focus is on discussion about different curriculum approaches for teacher education and innovation. In order to achieve the aim of the study, a phenomenographic approach is employed. This approach is used in order to identify similarities and variation in educators’ conceptions of curriculum innovation. The empirical basis of the study consists of interviews with thirty teacher educators working in eight teachers’ colleges situated in various parts of Tanzania. The findings, in brief, reveal variation in teacher educators’ conceptions of the dominant domains of innovation. Two broad conceptions of teaching with six aspects are identified. Conceptions of educational studies are presented in four broad categories of description with four aspects. Similarly, in methodology subjects two conceptions are described with four aspects. On the integration of subject matter studies and subject methods, two broad conceptions are presented with six aspects. Conceptions of textbook prescription policy are characterised in two broad categories of description with four aspects. With the use of modules two broad conceptions are identified with six aspects. In addition, the study identifies four broad conceptions of future curriculum approaches with eight aspects. Looking across the categories of description, the results indicate that educators cope with innovation individually. Three character types of teacher educators are presented: loyal, creative and critical. Furthermore, four types of phenomena suggesting critical areas about teacher educators’ conceptions of innovation are described: educators’ prior educational background, technical factors, student teachers’ factors and shifting from teaching to learning. On the whole, educators express a number of frame factors in the process of change towards the aim of curriculum innovation. This indicates that the new curriculum (2000) is not implemented as intended by curriculum developers. Constraints to the implementation are presented and discussed in detail. From these findings, two models of educators’ stance towards curriculum innovation are presented and can be used as a framework for planning successful curriculum innovations and analysing practice in teachers’ colleges.

Beyond the obvious : three acts in educational drama

Researching research is not a common theme in educational drama. Nor is the educational drama process from a participant perspective a typical focus of research, at least not if the participants are disabled. Yet this is the theme of this thesis, a drama in three acts. The aim of this thesis is to describe, analyse, and discuss both the ways in which research within educational drama can be carried out and represented, and the experiences of the participants of the educational drama process. The theoretical framework that steers the research process is built up of two pairs of frames, each of them, like Russian nesting dolls, containing further frames. The first frame, relating to the outcomes of conducting research in educational drama, comprises philosophical, representational, and personal theories. As the second question asks what educational drama is, the subject related frame is built up of pedagogical, drama educational, and aesthetic theories. The study in its entirety follows the structure of the researcher’s hermeneutical learning process and takes the form of a journey starting from what is familiar, stretching towards what is new and different, and finally returning back to the beginning with a new view on what was there at the start. The thesis consists of two separate but related studies. The first, a familiar study conducted earlier, Alpha in Act I, was carried out among upper secondary school pupils. In the second, the new and therefore unfamiliar study, Omega in Act III, the participants are adult individuals who are physically and communicatively disabled. In between these two Acts an element of “Verfremdung” where the Alpha study is systematically scrutinized as the purpose is to teach and to manage the reader to think. Meta-discussions on the philosophical issues of the study are conducted throughout the text, parallel to the empirical parts. The outcomes of the first research question show that philosophical, methodical, and representational consistency is crucial for research. While this may sound like stating the obvious, this has nevertheless not always been considered fact, especially not within qualitative research. The outcomes further stress that representational issues are also to be recognized when presenting non-rational aspects of educational drama. By wording the world, through the use of visualising language, the surplus of meanings of educational drama can be, as they are within this study, made visible, sensible, and almost tangible, not only cognitively understandable. The outcomes of the second question point to the different foci of the studies, with Alpha focusing on the rationally retold experiences and Omega focusing on nonrational experiences. The outcomes expose educational drama as a learning process comprising doing, reflecting, and being. The doing aspect communicates the concrete efforts in creating a piece of theatre, while the being aspect relates experiences of being as situated, embodied and sensuous, reciprocal, empowering, aesthetic and artistic, and existential. Reflection is the twine that runs throughout the process and connects both doing and being. In summary, the outcomes could be formulated as “learning from learning how to make theatre”.

Ja vet int va de heter på svenska : interaktion mellan tvåspråkiga elever och deras lärare i en enspråkig klassrumsdiskurs

This is a study about language and learning aspects in the interaction between pupils and teachers in classrooms, where the majority of the pupils are bilingual. The aim of the dissertation is to develop the understanding of interactional learning possibilities and constraints in relation to a bilingual context. Language related learning is used as an overall conception which covers learning related to classroom discourse, language and subject. The empirical study has been made in a Swedish speaking school in a strongly Finnish dominated environment in the south of Finland. In the material, mainly consisting of video recorded lessons in forms one to three, the interaction between the pupils and the teachers is analysed. Building on a social constructionist perspective, where learning is regarded as a social phenomenon, situated and visible in changing participation, sequences where pupils or teachers make the language relevant are emphasised. The sequences are analysed in line with the conversation analytic (CA) approach. A fundamental result is an understanding of a monolingual classroom discourse, jointly constructed by teachers and pupils and visible in the pupils' interactionally problematized code-switching. This means that the pupils are not victims of a top-driven language policy; they are active co-constructors of the monolingual discourse. Through different repair initiations the pupils are doing interactional work in positioning themselves correctly in the monolingual discourse, which they simultaneously maintain. This work has a price in relation to time, knowledge and exactness. The pupils' problematized code-switching is often directly and shortly repaired by the teachers. This kind of repair promotes the pupils' participation and is not, as opposed to the results of research in everyday talk, dispreferred in pupil-teacher talk. When the pupils use the possibility to, in a comparatively easy way, participate and thus express their knowledge through codeswitching, and simultaneously talk a monolingual discourse into being, the teacher can, through direct repair, show an understanding in regard to the content, facilitate language learning and simultaneously confirm the pupils as competent speakers and bilingual individuals. Furthermore, significant results show that the monolingual norm has a function of a contrasting background which gives the pupils and the teachers a possibility to use language alternation as a functional and meaningful activity. The pupils use codeswitching as a way of protesting or expressing non-participation in the classroom talk. By making the pupils' bilingualism relevant, the teachers express understanding and empathy and encourage the pupils' participation in the classroom talk. Bilingualism is a nonpreferred, but functioning, resource in the interaction between pupils and teachers.

Contexts, non-specificity, and minimalism

Atlas (2007) argues that semantic minimalism (as defended by Cappelen & Lepore 2005) fails because it cannot deal with semantic non-specificity. I argue that thereis a plausible version of minimalism-viz., situated minimalism-which doesn't succumb to the non-specificity charge insofar as non-specificity can be dealt with at a postsemantic level. Thus, pragmatics plays no rolewhen it comes to determining the (minimal) proposition expressed. Instead, pragmatic and other extra-semantic considerations enter the scene in characterizing the situation vis-à-vis which the proposition is evaluated. For this reason a plausible form of minimalism must embrace a form of truth-relativism: a proposition is not universally true/false, but true/false only relative to a situation. I show how the position defended is not only (i) more cognitively plausible than either (semantic) minimalism as proposed by Cappelen & Lepore or the positions appealing to pragmaticintrusion into the proposition expressed, but is also (ii) in accordance with ordinary people's intuitions.