Switching studies and the effect of irradiation on ferroelectric properties of TAAP and DTAAP

Polarization switching processes in TAAP and DTAAP have been studied by the Merz method. The switching process in DTAAP is slower than in TAAP. The temperature dependence of switching time indicates that the crystal might contain groups of domain nuclei with different activation energies. X-ray irradiation causes an increase in the threshold field below which switching could not occur and decrease in the mobility of domain walls. Irradiation decreases the peak value of dielectric constant, Tc and increases the value of coercive field. Domain structure studies on TAAP crystals have shown that the crystals grow as both predominantly single domain and multi domains, depending on which the internal bias increases or remains unaffected upon irradiation.

Museo yhteiskunnan peilinä? - pääkaupunkiseudulle perustetut kulttuurihistorialliset museot 1875-2010

Tässä pro gradu –tutkielmassa tarkastellaan museoita osana yhteiskunnan historiakulttuuria; niitä tapoja joiden pohjalta käsityksiä menneestä tuotetaan ja käytetään. Aihetta lähestytään kysymällä millaisia kulttuurihistoriallisia museoita pääkaupunkiseudulle on perustettu ja millaiset teemat eivät ole olleet museon arvoisia. Tutkielmassa selvitetään onko pääkaupunkiseudulle perustetuissa kulttuurihistoriallisissa museoissa havaittavissa ajallista aaltoa sen suhteen millaisille aiheille on perustettu oma museo. Lopuksi pohditaan esimerkkitapausten valossa sitä, miten erilaisia teemoja edustavien museoiden perustamistarvetta on perusteltu omana aikanaan. Etsimällä vastauksia tutkimuskysymyksiin pyritään samalla hahmotetaan sitä, millaista yhteiskunnallista historiakulttuuria museot ovat olleet osa. Työn ensimmäisessä vaiheessa kartoitettiin millaisia kulttuurihistoriallisia museoita pääkaupunkiseudulla on ollut. Museoviraston ja Suomen museoliiton aineistojen avulla on listattu kooste vuosien 1875-2010 välillä pääkaupunkiseudulla olleista museoista. Museoiden perustamiseen ja museokentältä katoamiseen liittyvää koostetta on täydennetty Helsingin matkailuyhdistyksen julkaisujen tiedoilla sekä museoiden omilla tiedonannoilla. Tutkielman museot on luokiteltu edustamiensa teemojen mukaan. Tarkoituksena on ollut hahmotella miten pääkaupunkiseudun kulttuurihistoriallisten museoiden kenttä on muuttunut 135 vuoden aikana. Työn toisessa vaiheessa tarkasteltiin neljän esimerkkitapauksen kautta museokentän ajallista muutosta ja sitä millaisia perusteluita museoiden perustamiselle on annettu sekä millaista keskustelua museon perustamisesta on omana aikanaan käyty. Esimerkkitapausten tarkastelun lähteinä käytettiin arkistomateriaalia, aikakauden lehdissä museoista käytyä keskustelua ja museoista kirjoitettuja historiikkeja. Pääkaupunkiseudun kulttuurihistoriallisissa museoissa on tutkielman mukaan havaittavissa löyhä ajallinen muutos. Kulttuurihistoriallisten museoiden edustamat historian kertomukset ovat muuttuneet ja pirstaloituneet 135 vuoden aikana virallisesta, kansallisesta historian kertomuksesta kohti useita pienempiä historian kertomuksia ja erilaisten ryhmien omaa historiaa. 1800-1900-lukujen taitteessa perustettiin pääosin valtiollisia ja instituutioiden historiaan keskittyneitä museoita sekä suurmiehille omistettuja henkilöhistoriallisia museoita. Valtiolliset ja henkilöhistorialliset teemat näkyvät museoissa läpi koko tutkielman tarkasteluajanjakson. Kansallisen historian katse suuntasi paikalliseen 1900-luvun alussa ja 1980-luvulla, jolloin perustettiin erityisen paljon paikallishistoriallisia ja alueellisia museoita. 1970-1990-luvuilla museokenttää hallitsivat monet tekniikkaan, teollisuuteen ja yrityshistoriaan keskittyneet museot. Tultaessa 2000-luvulle museot edustivat lapsiin, nuoriin, koulutukseen ja monikulttuurisuuteen liittyviä teemoja. Tutkielman toisen vaiheen esimerkkitapausten tarkastelu osoitti, että erilaisia teemoja edustavien museoiden perustamistarvetta perustellaan hyvin samankaltaisesti. Niin 1800-luvun lopussa kuin 1900-luvun lopussa museoiden tarvetta perusteltiin kasvatus- ja sivistystyöllä ja aihealueen arvostuksen kasvulla. Museon perustamisen koettiin osoittavan Suomen kuuluvan osaksi länsimaisia sivistysyhteiskuntia. Museoiden perustamisen taustalla on usein ollut asiaa ajanut yhdistys. Kuitenkin museohanke on ollut vuosikausien projekti ja konkretisoitunut usein vasta kun museon tiloihin ja talouteen liittyvät kysymykset on saatu kuntoon. Tutkielman loppupäätelmien myötä hahmottui monia historiantutkimuksellisen lisätarkastelun arvoisia aiheita museoista osana yhteiskunnan historiakulttuuria. Avainsanat – Nyckelord – Keywords kulttuurihistorialliset museot, historiakulttuuri, historiankäyttö, yhteiskunta

Conformation of substituted polyacetylenes in solution : relationship between electronic properties and local order

A study of the chain conformation in solutions of polyphenylacetylene and poly(2-octyne) has been performed. The two polymers differ in many ways : polyphenylacetylene gives a red solution while poly(2-octyne) is transparent and, a marked difference on the chain rigidity is observed : the statistical length are 45 Å and 135 Å respectively. From the study of these two systems, one deduces that curvature fluctuations play a minor role on the π electrons localization, and that the torsion between monomer units is the pertinent parameter to understand the chain conformation and the π electrons localization.

Detection of a CpA methylase in an insect system: characterization and substrate specificity

A cytosine-specific DNA methyltransferase (EC 2.1.1.37) has been purified to near homogeneity from a mealybug (Planococcus lilacinus). The enzyme can methylate cytosine residues in CpG sequences as well as CpA sequences. The apparent molecular weight of the enzyme was estimated as 135,000 daltons by FPLC. The enzyme exhibits a processive mode of action and a salt dependance similar to mammalian methylases. Mealybug methylase exhibits a preference for denatured DNA substrates.

Do the Hydrolysis Products, Methylamine and N,N'-Dimethylurea, Play any Role in the Methyl Isocyanate-Induced Haematological and Biochemical Changes in Rabbits?

The subcutaneous administration of methyl isocyanate (MIC) to female rabbits, resulted in significant increases in haemoglobin concentration, erythrocyte volume fraction and leucocyte number in blood, as well as plasma total proteins, and urea. The present study was designed to investigate whether the hydrolytic products of MIC, methylamine (MA) and N,N'-dimethylurea (DMU) play any role in eliciting these changes. Both MA and DMU administered subcutaneously in an equimolar dose to that of 1.0 LD50 MIC, 2.2 mmol kg-1, had no influence on these parameters, although there was a marginal increase in the plasma urea level shortly after the administration of DMU. This study establishes that the observed haematological and biochemical changes induced by MIC intoxication in rabbits are mostly due to MIC.

Reaction of spironaphthalenones with hydroxylamine: Part III. A novel mechanism for the formation of products and trapping of an intermediate.

A mechanism involving the intermediacy of nitrene 5, formed from the oxime of spironaphthalenone 1 by acid catalysed dehydration, has been proposed to explain the formation of pyrrolotropones/pyrrolo esters from spironaphthalenones. The initially formed nitrene rearranges to the isopyrrole 6, which either undergoes sigmatropic migration to the pyrrolotropone 2 or adds alcohol to form the pyrrolo ester depending on substitution at 1′ position. The isopyrrole intermediate 6 has been trapped as a Diels-Alder adduct 8.

Swellability properties of polyelectrolyte complexes of polyaniline

Polyelectrolyte complexes of polyaniline with both strong and weak anionic polyelectrolytes have been prepared. It has been found that the swellability of the complexes depends on the charge content of polyaniline, i.e., on the intercrosslinking between polyaniline (which is a polyacation) and polyanions. It has also been observed that polyaniline in the polyaniline-polystresulfonic acid complex exists in the conducting state when equilibrated with basic pH in aqueous media of moderately high ionic strength.

An automatic parallelization framework for multicomputers

Several researchers have looked into various issues related to automatic parallelization of sequential programs for multicomputers. But there is a need for a coherent framework which encompasses all these issues. In this paper we present a such a framework which takes best advantage of the multicomputer architecture. We resort to tiling transformation for iteration space partitioning and propose a scheme of automatic data partitioning and dynamic data distribution. We have tried a simple implementation of our scheme on a transputer based multicomputer [1] and the results are encouraging.

A New Era for Chemical Superconductors

A review of the development of ceramic superconductors and the steady increase in the superconducting transition temperature which currently stands at 135 K or about 164 K under pressure.

Fracture Analysis of Concrete Structural Components Accounting for Tension Softening Effect

This paper presents methodologies for fracture analysis of concrete structural components with and without considering tension softening effect. Stress intensity factor (SIF) is computed by using analytical approach and finite element analysis. In the analytical approach, SW accounting for tension softening effect has been obtained as the difference of SIP obtained using linear elastic fracture mechanics (LEFM) principles and SIP due to closing pressure. Superposition principle has been used by accounting for non-linearity in incremental form. SW due to crack closing force applied on the effective crack face inside the process zone has been computed using Green's function approach. In finite element analysis, the domain integral method has been used for computation of SIR The domain integral method is used to calculate the strain energy release rate and SIF when a crack grows. Numerical studies have been conducted on notched 3-point bending concrete specimen with and without considering the cohesive stresses. It is observed from the studies that SW obtained from the finite element analysis with and without considering the cohesive stresses is in good agreement with the corresponding analytical value. The effect of cohesive stress on SW decreases with increase of crack length. Further, studies have been conducted on geometrically similar structures and observed that (i) the effect of cohesive stress on SW is significant with increase of load for a particular crack length and (iii) SW values decreases with increase of tensile strength for a particular crack length and load.

A large conductance Ca2+-activated K+ channel in alpha T3-1 pituitary gonadotrophs

The Ca2+-activated K+ channel in endocrine cells is responsible for membrane hyperpolarization and rhythmic firing of action potentials. The probability of opening of this channel is sensitive to intracellular-free Ca2+ concentration. In this study we have identified one such large conductance Ca2+-activated K+ channel in alpha T3-1 pituitary gonadotroph cell. This channel is ohmic with a unit conductance of 170 pS in symmetrical KCl (135 mM) and its current reverses near zero millivolts. When more than one channel is present in the patch membrane they open and close independent of each other, exhibiting no cooperativity between them as expected of a binomial distribution. The regulatory mechanism of this channel in modulating hormone secretion from alpha T3-1 gonadotroph cells is indicated.