Diffusion Studies in A(3)B Compounds with A15 Structure

There is a constant effort to understand the defect structure and diffusion behavior in intermetallic compounds with the A15 structure. Diffusion of elements in intermetallic compounds depends mainly on antisites and vacancies on different sublattices. In this article, we shall discuss the diffusion of elements in A(3)B compounds with the A15 structure.

Suomen suuriruhtinaskunnan virkamiehistön yksityiskirjastot ja sensuurin kieltämä kirjallisuus niissä 1800-luvun alkuvuosikymmeninä

Tutkimus luotaa 1800-luvun alkuvuosikymmenten Suomen suuriruhtinaskunnan virkamiehistön poliittisia asenteita sensuuri-ja painovapauskysymysten valossa. Sadan virkamiehistöön kuuluneen henkilön yksityiskirjastot ja niiden sisältämät mahdolliset sensuurin kieltämät nimikkeet on seulottu Kansalliskirjaston kokoelmissa olevista 1800- luvun kirjahuutokauppaluetteloista vertailemalla niitä Kansallisarkistossa säilytettäviin sensuuriviranomaisten kiellettyjen teosten listoihin. Tutkimuksen keskeisimmiksi teemoiksi nousevat näin poliittis- sekä kirjahistorialliset, kirjallista kulttuuria koskettelevat ulottuvuudet. Virkamiehistön yksityiskirjastot mahdollisine kiellettyine nimikkeineen on esitelty tilastollisen taulukoinnin avulla kirjastojen koon, virkamiehistön hallintoalan, rankiluokan sekä alueellisen identiteetin mukaan jaoteltuina. Vaikka lähdeaineiston perusteella on tämänkaltaisen poliittisväritteisen kirjallisen kulttuurin tavoittaminen osaksi ongelmallista, ovat huutokauppaluettelot systemaattisesta ja säännöllisestä luonteestaan johtuen merkittävää ja satunnaisten inventaarioluetteloiden ohella lähestulkoon ainoaa käsillä olevaa yksityiskirjastoja koskevaa lähdeaineistoa. Suomen 1800-luvun valtiolliseen asemaan liittyviä historiantulkintoja on tutkimuksen edetessä pyritty kuljettamaan rinnakkain; niitä ovat toisaalta suomalaisten käsitykset maansa perustuslaillisesta asemasta ja toisaalta venäläisten viranomaisten tulkinnat Suomen asemasta yleisvaltakunnallisessa viitekehyksessä. Tämän ohella tutkimusaihetta on lähestytty sen ajalliseeen kontekstiin olennaisesti kytkeytyvien yhteiskunta-ja historianfilosofisten teorioiden avulla. Ne ovat olleet myös tutkimuksen kohteena olleille aikalaisille relevantti henkinen ulottuvuus. Tämä on perusteltua, koska filosofista ja valtiotieteellistä kirjallisuutta on ollut kirjastoissa paljon. Etiikasta ja moraalista lähtevä vapauden ongelma on ollut yksi tämänkaltainen yhteiskuntafilosofinen kysymys. Tutkimuksessa aika ajoin esiin nouseva aatteellinen vertailu muiden Euroopan maiden oloihin laajentaa tutkimuksen historiallisen viitekehyksen osaksi 1800-luvun eurooppalaisen henkisen aatemaailman maisemaa. Tutkimuksen varovaiset johtopäätökset juontuvat erilaisista näkökulmista. Kiellettyjä nimikkeitä löytyi hieman yli 30 % kaikista virkamiehistön yksityiskirjastoista, mutta kiellettyjen nimikkeiden määrät osoittautuivat kirjastokohtaisesti laskettuna pienehköiksi. Ilmiön voi näin väittää olleen toisaalta marginaalista, mutta toisaalta konkreettinen osoitus poliittiseen vakaumukseen viittaavasta asennoitumisesta; sensuuria esimerkiksi saatettiin tulkita perustuslaillisuutta ja Aleksanteri I:n antaman hallitsijanvakuutuksen taustaa vasten. Kielletyn kirjallisuuden hankkiminen sensuurilaeista piittaamatta saattoi myös olla kamppailua hyvänä pidetyn yhteiskuntajärjestyksen puolesta järjestelmän epäkohtia vastaan. Keisaria kohtaan tunnettiin lojaalisuutta, mutta hänen hallitsemaansa järjestelmää edustavia sensuuriviranomaisia kohtaan välttämättä ei. Tässä kohdin Suomen tilanteella oli vastaavuutta Saksan oloihin, j o s s a nuorhegeliläiset halusivat muuttaa yhteiskuntaa ideaalimpaan suuntaan. Venäjän keisarikuntaan kuuluminen toi mukanaan maallista hyvää, mutta henkisen kulttuurin puolella orientoiduttiin pääasiassa länteen, ja pitäydyttiin Ruotsin ajan luomassa perinnössä. Yksi keskeinen tästä kummunnut valistusaatteen traditionaalinen arvo oli itsensä vapaa kehittäminen, joten sensuurikysymyksissä ajauduttiin väistämättä törmäyskurssille valtiopoliittisen ja kulttuurisen identiteetin ristipaineessa. Vaikka valtiopoliittinen identiteetti vaihtui vuoden 1809 jälkeen, ei kulttuurisen identiteetin kohdalla näin käynyt. Tätä kautta vahvistuu kokonaiskuva 1700-luvun historian ja Ruotsin ajan perinnön tärkeydestä 1800-luvun henkiselle kehitykselle etenkin kirjallisen kulttuurin saralla.

Interruptions of (CG)n sequences by GG, TG and CA need not prevent B to Z transition in solution

Oligonucleotides containing alternating purines-pyrimidines with AT base pairs have been shown to exist in the Z-form preferably in solid state. We report that oligodeoxyribonucleotides with GG, TG and CA interruptions in their alternating CG sequences can undergo B to Z transition in solution in the absence of any chemical modification or topological constraint. The sequences, d(CGCGCGGCGCGC) and d(CGTGCGCACG) have been synthesised and shown to adopt Z- conformation in presence of millimolar concentrations of Ni2+ under low water activity conditions. Significance of GG, TG and CA interruptions in the B to Z transition is discussed.

Thermodynamic measurements of b.c.c. Cr-Mn solid solutions at 1373 K

Thermodynamics of Cr-Mn alloys have been studied by Eremenko et al (l) using a fused salt e.m.f.technique. Their results indicate positive deviations from ideality at 1023 K. Kaufman (2) has independently estimated negative enthaipy and excess entropy for the b.c.c. Cr-Mn alloys, such that at high temperatures, the entropy term predominates over the enthalpy term giving positive deviations from ideality. Recently the thermodynamic properties of the alloys have been measured by 3acob (3) using a Knudsen cell technique in the temperature range of 1200 to 1500 K. The results indicate mild negative deviations from ideality over the entire composition range. Because of the differences in the reported results and Mn being a volatile component in the alloys which leads to surface depletion under a dynamic set up, an isopiestic technique is used to measure the properties of the alloys.

Measurement of the ttbar production cross section with an in situ calibration of b-jet identification efficiency

A measurement of the top-quark pair-production cross section in ppbar collisions at sqrt{s}=1.96 TeV using data corresponding to an integrated luminosity of 1.12/fb collected with the Collider Detector at Fermilab is presented. Decays of top-quark pairs into the final states e nu + jets and mu nu + jets are selected, and the cross section and the b-jet identification efficiency are determined using a new measurement technique which requires that the measured cross sections with exactly one and multiple identified b-quarks from the top-quark decays agree. Assuming a top-quark mass of 175 GeV/c^2, a cross section of 8.5+/-0.6(stat.)+/-0.7(syst.) pb is measured.

Total syntheses of the fungal metabolites (+/-)-acremines A, B and I

A concise and diversity-oriented approach, incorporating elements of regio- and stereocontrol, to the recently isolated bioactive polyoxygenated cyclohexanoid natural products acremines A. B and I. from commercially accessible building blocks, is outlined. (c) 2010 Elsevier Ltd. All rights reserved.

Synthetic studies toward the PPAP natural products, prolifenones A and B and hyperforin: an Effenberger cyclization approach

A synthetic approach toward the geranylated PPAP natural products, prolifenones A and B. employing Effenberger cyclization as the key step, is delineated. The efficacy of this approach is further expanded through access to an advanced precursor of hyperforin. (C) 2010 Elsevier Ltd. All rights reserved.

Peptide models for b-turns.A circular dichroism study

The circular dichroism spectra of four 0-turn model peptides, Z-Aib-Pro-Aib-Pro- OMe (l), Piv-Pro-Aib-NHMe (2), Piv-Pro-D-Ala-NHMe (3) and Piv-Pro-Val-NHMe (4) have been examined under a wide range of solvent conditions, using methanol, hexafluoroisopropanol and cyclohexane. Type I and Type I1 0-turns have been observed for peptides 1 and 2 respectively, in the solid state, while the Pro-D-Ala sequence adopts a Type I1 Sturn in a related peptide crystal structure. A class C spectrum is observed for 1 in various solvents, suggesting a variant of a Type I(II1) structure. The Type I1 f3-turn is characterized by a CD spectrum having two positive CD bands at - 230 nm and - 202 nm, a feature observed in Piv-Pro- D-Ala-NHMe in cyclohexane and methanol and for Piv-Pro-Aib-NHMe in methanol. Peptide 2 exhibits solvent dependent CD spectra, which may be rationalized by considering Type 11, I11 and V reverse turn structures. Piv-Pro- Val-NHMe adopts nonaturn structures in polar solvents, but exhibits a class B spectrum in cyclohexane suggesting a population of Type I &turns.

Differences in the climatic adaptation of silver birch (Betula pendula) and downy birch (B. pubescens) in Finland based on male flowering phenology.

Male flowering was studied at the canopy level in 10 silver birch (Betula pendula Roth) stands from 8 localities and in 14 downy birch (B. pubescens Ehrh.) stands from 10 localities in Finland from 1963 to 1973. Distributions of cumulative pollen catches were compared to the normal Gaussian distribution. The basis for the timing of flowering was the 50 per cent point of the anthesis-fitted normal distribution. To eliminate effects of background pollen, only the central, normally distributed part of the cumulative distribution was used. Development up to the median point of the distribution was measured and tested in calendar days, in degree days (> 5 °C) and in period units. The count of each parameter began on and included March 19. Male flowering in silver birch occurred from late April to late June depending on latitude, and flowering in downy birch took place from early May to early July. The heat sums needed for male flowering varied in downy birch stands latitudinally but there was practically no latitudinal variation in heat sums needed for silver birch flowering. The amount of male flowering in stands of both birch species were found to have a large annual variation but without any clear periodicity. The between years pollen catch variation in stands of either birch species did not show any significant latitudinal correlation in contrast to Norway spruce stands. The period unit heat sum gave the most accurate forecast of the timing of flowering for 60 per cent of the silver birch stands and for 78.6 per cent of the for downy birch stands. Calendar days, however, gave the best forecast for silver birch in 25 per cent of the cases, while degree days gave the best forecast for downy birch in 21.4 per cent of the cases. Silver birch seems to have a local inclination for a more fixed flowering date compared to downy birch, which could mean a considerable photoperiodic influence on flowering time of silver birch. Silver birch and downy birch had different geographical correlations. Frequent hybridization of birch species occurs more often in northern Finland in than in more southern latitudes. The different timing in flowering caused increasing scatter in flowering times in the north, especially in the case of downy birch. The chance of simultaneous flowering of silver birch and downy birch so increased northwards due to a more variable climate and also higher altitudinal variations. Compared with conifers, the reproduction cycles of both birch species were found to be well protected from damage by frost.

High-Temperature (1023 K to 1273 K 750 degrees C to 1000 degrees C]) Plastic Deformation Behavior of B-Modified Ti-6Al-4V Alloys: Temperature and Strain Rate Effects

A minor addition of B to the Ti-6Al-4V alloy, by similar to 0.1 wt pct, reduces its as-cast prior beta grain size by an order of magnitude, whereas higher B content leads to the presence of in situ formed TiB needles in significant amounts. An experimental investigation into the role played by these microstructural modifications on the high-temperature deformation behavior of Ti-6Al-4V-xB alloys, with x varying between 0 wt pct and 0.55 wt pct, was conducted. Uniaxial compression tests were performed in the temperature range of 1023 K to 1273 K (750 degrees C to 1000 degrees C) and in the strain rate range of 10(-3) to 10(+1) s(-1). True stress-true strain responses of all alloys exhibit flow softening at lower strain rates and oscillations at higher strain rates. The flow softening is aided by the occurrence of dynamic recrystallization through lath globularization in high temperature (1173 K to 1273 K 900 degrees C to 1000 degrees C]) and a lower strain rate (10(-2) to 10(-3) s(-1)) regime. The grain size refinement with the B addition to Ti64, despite being marked, had no significant effect on this. Oscillations in the flow curve at a higher strain rate (10(0) to 10(+1) s(-1)), however, are associated with microstructural instabilities such as bending of laths, breaking of lath boundaries, generation of cavities, and breakage of TiB needles. The presence of TiB needles affected the instability regime. Microstructural evidence suggests that the matrix cavitation is aided by the easy fracture of TiB needles.

b-Turn conformations in crystal structures of model peptides containing a,a-di-n-propylglycine (Dpg) and a,a-di-n-butyl-glycine (Dbg).

The crystal state conformations of three peptides containing the a,a-dialkylated residues, a,adi n-propylglycine (Dpg) and a,@-di-n-butylglycine (Dbg), have been established by x-ray diffraction. Boc-Ala-Dpg-Ala-OMe ( I ) and Boc-Ala-Dbg-Ala-OMe (III) adopt distorted type II @-turn conformations with Ala ( I ) and Dpg/Dbg (2) as the corner residues. In both peptides the conformational angles at the Dxg residue (I: 4 = 66.23 J/ = 19.3'; III: 4 = 66S0, J. = 21 .la)deviate appreciablyfrom ideal values for the i + 2 residue in a type II @-turn. In both peptides the observed(N. 0) distances between the Boc CO andAla(3) NHgroups are far too long (I:3.44 k; III: 3.63 k) for an intramolecular 4 + 1 hydrogen bond. Boc-Ala-Dpg-Ala-NHMe (II)crystallizes with two independent molecules in the asymmetric unit. Both molecules IIA and IIB adopt consecutive @-turn (type III-III in IIA and type III-I in IIB) or incipient 3,,,-helical structures, stabilized by two intramolecular 4 --t I hydrogen bonds. In all four molecules the bond angle N-C"-C' ( T ) at the Dxg residues are 2 1109 The observation of conformational angles in the helical region of 4,J/ space at these residues is consistent with theoretical predictions