Segregation, precipitation, and \alpha-\alpha' phase separation in Fe-Cr alloys: a multi-scale modelling approach

Segregation, precipitation, and phase separation in Fe-Cr systems is investigated. Monte Carlo simulations using semiempirical interatomic potential, first-principles total energy calculations, and experimental spectroscopy are used. In order to obtain a general picture of the relation of the atomic interactions and properties of Fe-Cr alloys in bulk, surface, and interface regions several complementary methods has to be used. Using Exact Muffin-Tin Orbitals method the effective chemical potential as a function of Cr content (0-15 at.% Cr) is calculated for a surface, second atomic layer and bulk. At ~10 at.% Cr in the alloy the reversal of the driving force of a Cr atom to occupy either bulk or surface sites is obtained. The Cr containing surfaces are expected when the Cr content exceeds ~10 at.%. The second atomic layer forms about 0.3 eV barrier for the migration of Cr atoms between bulk and surface atomic layer. To get information on Fe-Cr in larger scales we use semiempirical methods. Using combined Monte Carlo molecular dynamics simulations, based on semiempirical potential, the precipitation of Cr into isolated pockets in bulk Fe-Cr and the upper limit of the solubility of Cr into Fe layers in Fe/Cr layer system is studied. The theoretical predictions are tested using spectroscopic measurements. Hard X-ray photoelectron spectroscopy and Auger electron spectroscopy investigations were carried out to explore Cr segregation and precipitation in Fe/Cr double layer and Fe_0.95Cr_0.05 and Fe_0.85Cr_0.15 alloys. Initial oxidation of Fe-Cr was investigated experimentally at 10^-8 Torr pressure of the spectrometers showing intense Cr_2O_3 signal. Cr segregation and the formation of Cr rich precipitates were traced by analysing the experimental spectral intensities with respect to annealing time, Cr content, and kinetic energy of the exited electron.Comment: 16 pages, 14 figures, 52 reference

Liikuntaharrastuksen merkitys sijaishuollossa olevilla nuorilla

Tiivistelmä. Tämä pro gradu -tutkielma käsittelee liikuntaharrastuksen merkitystä sijaishuollossa olevilla nuorilla. Tutkielmassamme käsiteltävät aiheet ovat ajankohtaisia ja erityisesti nuoria koskevaa syrjäytymiskeskustelua on käyty runsaasti viime vuosina. Tutkimuksen tavoitteena on selvittää millainen merkitys liikunnalla on sijaishuollossa oleville nuorille. Tutkimuskysymyksiä oli kaksi: 1) Millainen merkitys ohjatun liikunnan harrastamisella on sijaishuollon piirissä olevalle nuorelle? 2) Miksi nuori harrastaa liikuntaa? Tutkimuskysymyksiin pyrittiin saamaan vastauksia tutkimalla ilmiöitä monipuolisesti. Tästä johtuen tutkimusaihetta lähestyttiin nuorten, nuorten sijaishuollon ohjaajien ja sosiaalialan asiantuntijoiden näkökulmista. Tutkimus rakentui kolmen pääteeman ympärille, joita olivat liikuntaharrastus, syrjäytyminen ja sijaishuolto. Tutkimus toteutettiin fenomenografisena tapaustutkimuksena. Tutkimuksessa käytetty aineisto kerättiin haastattelemalla sijaishuollossa olevia, liikuntaharrastuksen omaavia alle 18-vuotiaita nuoria, nuorten omaohjaajia sekä asiantuntijoita. Nuorilta tutkimusaiheeseen liittyen kerättiin myös vapaamuotoinen kirjoitelma. Kaiken kaikkiaan tutkimusaineisto sisälsi 11 haastattelua sekä nuorten tuottamat kirjoitelmat. Aineiston analyysi suoritettiin kahdessa osassa pääpainon ollessa nuorten näkemyksissä ja kokemuksissa. Tästä johtuen nuorten ja aikuisten aineistot analysoitiin erikseen. Aikuisten aineisto oli tutkimuksessa toissijainen ja toimi nuorten aineistoa tukevana vertailupohjana. Analyysin tuloksena nuorten aineistosta muodostettiin tulosavaruus, jossa oli kolme liikunnan ulottuvuutta kuvaavaa kuvauskategoriaa ja niiden alla 16 liikunnan merkityksiä ja syitä kuvaavaa merkityskategoriaa. Aikuisten aineiston osalta analyysi tehtiin ainoastaan merkityskategoriatasolla tasolla. Aikuisten aineistosta merkityskategorioita muodostettiin kuusi kappaletta. Tulosten pohjalta pystyimme muodostamaan kaksi selkeää johtopäätöstä. Ensimmäinen johtopäätös oli se, että liikunnalla on merkittävä rooli nuorten minäkuvan kehittäjänä. Toiseksi johtopäätökseksi muodostui liikunnan suuri merkitys nuorten elämänhallinnan vahvistajana. Molempien johtopäätösten kannalta oli kuitenkin huomattava, että valmentajilla, sijaishuollolla ja erityisesti nuoren omaohjaajalla oli tärkeä rooli liikuntaharrastuksen ohjaajana sekä tukijana. Näitä johtopäätöksiä tukivat niin aikuisilta kuin nuorilta kerätyt aineistot.Abstract. The goal of the research was to find out what kind of meaning doing sports has for adolescents in foster care. There were two research questions: 1) What is the meaning of participation in physical exercise for an adolescent in foster care? 2) Why does an adolescent take part in sports? For answers to the research questions, the phenomenon was studied from any different angles. The research topic was therefore approached from the perspectives of the adolescents, foster care instructors and social work experts. The study was built on three major themes: sports participation, social exclusion and foster care. The research was implemented as a phenomenographic case study. The data used in the study was collected by interviewing foster care adolescents aged 18 who participated in sports activities, their personal foster care instructors and social work experts. Each adolescent was also invited to write an informal essay on the research topic. All in all, the research data included 11 interviews and the essays produced by the adolescents. The data analysis was performed in two parts, with the primary focus on the views and experiences of the adolescents. The data provided by the ado- lescents and adults was therefore analysed separately. In this study the data supplied by the adults was used as a secondary data source to provide a comparative basis to support the data collected from the adolescents. As a result of the analysis, an outcome space was formed from the adolescents’ data including three different description categories that represented the different dimensions of sports: physical, mental and social. 16 categories were constructed under the description categories to illustrate the meanings and reasons for doing sports. In the case of the adult data set, the analysis was only carried out at the level of the categories of meaning. Six different categories were formed on the basis of this secondary source of data. Two obvious conclusions could be drawn from the results: firstly, participation in sports has a significant role as a developer of the adolescents’ self-image. Secondly, sports participation has a great impact in strengthening their life skills. Considering both of these conclusions, it needs to be noted, however, that the coaches, foster care and especially the personal foster care instructors had a crucial role in guiding and supporting the adolescents in their physical pursuits

Formation and destabilization of Ga interstitials in GaAsN: Experiment and theory

Using first-principles total energy calculations we have found complex defects induced by N incorporation in GaAsN. The formation energy of the Ga interstitial atom is very significantly decreased due to local effects within the defect complex. The stability of the Ga interstitials is further increased at surfaces. The present results suggest that the energetically favorable Ga interstitial atoms are much more abundant in GaAsN than the previously considered N defects, which have relatively large formation energies. Our synchrotron radiation core-level photoemission measurements support the computational results. The formation of harmful Ga interstitials should be reduced by incorporating large group IV B atoms in GaAsN

Towards virtual histology with X-ray grating interferometry

Breast cancer is the most common type of cancer worldwide. Diagnosing breast cancer relies on clinical examination, imaging and biopsy. A core-needle biopsy enables a morphological and biochemical characterization of the cancer and is considered the gold standard for breast cancer diagnosis. A histopathological examination uses high-resolution microscopes with outstanding contrast in the 2D plane, but the spatial resolution in the third, Z-direction, is reduced. In the present paper, we propose two high-resolution table-top systems for phase-contrast X-ray tomography of soft-tissue samples. The first system implements a classical Talbot-Lau interferometer and allows to perform ex-vivo imaging of human breast samples with a voxel size of 5.57 μm. The second system with a comparable voxel size relies on a Sigray MAAST X-ray source with structured anode. For the first time, we demonstrate the applicability of the latter to perform X-ray imaging of human breast specimens with ductal carcinoma in-situ. We assessed image quality of both setups and compared it to histology. We showed that both setups made it possible to target internal features of breast specimens with better resolution and contrast than previously achieved, demonstrating that grating-based phase-contrast X-ray CT could be a complementary tool for clinical histopathology

Line shape and composition of the In 3d5/2 core-level photoemission for the interface analysis of In-containing III-V semiconductors

The In 3d5/2 photoelectron spectroscopy peak has been widely used to determine the interface structures of In-containing III-V device materials (e.g., oxidation states). However, an unclear parameter affecting the determination of the energy shifts and number of the core-level components, and therefore, the interpreted interface structure and composition, is still the intrinsic In 3d5/2 peak line shape. It is undecided whether the line shape is naturally symmetric or asymmetric for pure In-containing III-V compounds. By using high-resolution photoelectron spectroscopy, we show that the In 3d5/2 asymmetry arising from the emission at high binding-energy tail is not an intrinsic property of InAs, InP, InSb and InGaAs. Furthermore, it is shown that asymmetry of In 3d5/2 peaks of pure III-V&rsquo;s originates from the natural surface reconstructions which cause the coexistence of slightly shifted In 3d5/2 &nbsp;components with the symmetric peak shape and dominant Lorentzian broadening.</p

Segregation, precipitation, and α-α' phase separation in Fe-Cr alloys

Iron-chromium alloys, the base components of various stainless steel grades, have numerous technologically and scientifically interesting properties. However, these features are not yet sufficiently understood to allow their full exploitation in technological applications. In this work, we investigate segregation, precipitation, and phase separation in Fe-Cr systems analyzing the physical mechanisms behind the observed phenomena. To get a comprehensive picture of Fe-Cr alloys as a function of composition, temperature, and time the present investigation combines Monte Carlo simulations using semiempirical interatomic potential, first-principles total energy calculations, and experimental spectroscopy. In order to obtain a general picture of the relation of the atomic interactions and properties of Fe-Cr alloys in bulk, surface, and interface regions several complementary methods have to be used. Using the exact muffin-tin orbitals method with the coherent potential approximation (CPA-EMTO) the effective chemical potential as a function of Cr content (0–15 at. % Cr) is calculated for a surface, second atomic layer, and bulk. At ∼10 at. % Cr in the alloy the reversal of the driving force of a Cr atom to occupy either bulk or surface sites is obtained. The Cr-containing surfaces are expected when the Cr content exceeds ∼10 at. %. The second atomic layer forms about a 0.3 eV barrier for the migration of Cr atoms between the bulk and surface atomic layer. To get information on Fe-Cr in larger scales we use semiempirical methods. However, for Cr concentration regions less than 10 at. %, the ab initio (CPA-EMTO) result of the important role of the second atomic layer to the surface is not reproducible from the large-scale Monte Carlo molecular dynamics (MCMD) simulation. On the other hand, for the nominal concentration of Cr larger than 10 at. % the MCMDsimulations show the precipitation of Cr into isolated pockets in bulk Fe-Cr and the existence of the upper limit of the solubility of Cr into Fe layers in Fe/Cr layer systems. For high Cr concentration alloys the performed spectroscopic measurements support the MCMD simulations. Hard x-ray photoelectron spectroscopy and Auger electron spectroscopy investigations were carried out to explore Cr segregation and precipitation in the Fe/Cr double layer and Fe0.95Cr0.05 and Fe0.85Cr0.15 alloys. Initial oxidation of Fe-Cr was investigated experimentally at 10−8 Torr pressure of the spectrometers showing intense Cr2O3 signal. Cr segregation and the formation of Cr-rich precipitates were traced by analyzing the experimental atomic concentrations and chemical shifts with respect to annealing time, Cr content, and kinetic energy of the exited electron.</p

PIM1 accelerates prostate cancer cell motility by phosphorylating actin capping proteins

Background: The PIM family kinases promote cancer cell survival and motility as well as metastatic growth in various types of cancer. We have previously identified several PIM substrates, which support cancer cell migration and invasiveness. However, none of them are known to regulate cellular movements by directly interacting with the actin cytoskeleton. Here we have studied the phosphorylation-dependent effects of PIM1 on actin capping proteins, which bind as heterodimers to the fast-growing actin filament ends and stabilize them. Methods: Based on a phosphoproteomics screen for novel PIM substrates, we have used kinase assays and fluorescence-based imaging techniques to validate actin capping proteins as PIM1 substrates and interaction partners. We have analysed the functional consequences of capping protein phosphorylation on cell migration and adhesion by using wound healing and real-time impedance-based assays. We have also investigated phosphorylation-dependent effects on actin polymerization by analysing the protective role of capping protein phosphomutants in actin disassembly assays. Results: We have identified capping proteins CAPZA1 and CAPZB2 as PIM1 substrates, and shown that phosphorylation of either of them leads to increased adhesion and migration of human prostate cancer cells. Phosphorylation also reduces the ability of the capping proteins to protect polymerized actin from disassembly. </p