White dwarfs and Galactic dark matter

We discuss the recent discovery by Oppenheimer et al (2001) of old, cool white dwarf stars, which may be the first direct detection of Galactic halo dark matter. We argue here that the contribution of more mundane white dwarfs of the stellar halo and thick disk would contribute sufficiently to explain the new high velocity white dwarfs without invoking putative white dwarfs of the dark halo. This by no means rules out that the dark matter has been found, but it does constrain the overall contribution by white dwarfs brighter than M_V ~ 16 to significantly less than 1% of the Galactic dark matter. This work confirms a similar study by Reyle et al (2001).Comment: 8 pages, 8 figures. MNRAS style fil

Damage stability study of passenger ferries with new safety regulations

Kansainvälinen merenkulkujärjestö IMO käynnisti prosessin vuotovakavuussäännön kehittämiseksi sillä Euroopan meriturvallisuusviranomaisen EMSA:n vuonna 2008 teettämässä tutkimuksessa oli havaittu vakavia turvallisuuspuutteita voimaan tulevassa Solas 2009 vuotovakavuussäännössä. Tämän jälkeen matkustaja-autolauttojen vuotovakavuutta on tutkittu laajasti ja vuotovakavuussäännön muuttamiseksi on esitetty useita eri vaihtoehtoja. Näistä ehdotuksista ei kuitenkaan päästy yksimielisyyteen, joten IMO:n SDC-alakomitean työryhmä laati kompromissiehdotuksen R- ja A-indeksien muuttamiseksi. IMO:n jäsenvaltiot pystyivät hyväksymään Solas 2020:nä tunnetun sääntömuutoksen. Muutos kohottaisi merkittävästi alusten turvallisuustasoa vuotoon johtavassa yhteentörmäystilanteessa. Toisaalta aluksen suunnittelusta ja rakentamisesta tulisi aikaisempaa haastavampaa, mikä taas kasvattaisi kustannustasoa. Tässä työssä tarkastellaan tapaustutkimuksena sääntömuutoksen vaikutusta nykyaikaisen, Itämerellä operoivan matkustaja-autolautan vesitiiviin osastoinnin suunnitteluun. Työn tarkoituksena on selvittää, onko meriturvallisuuskomitean hyväksymä sääntömuutos riittävän vaativa, jotta sillä voidaan korvata matkustaja-autolautoille nykyisin voimassa oleva Tukholman sopimus, direktiivi 2003/25/EC, jolla käsitellään alustyypille ominainen, vettä kannella –tilanne. Tutkimusten tuloksena havaittiin, että Tukholman sopimus on edelleen määräävin vuotovakavuussääntö, joka tulee asettamaan rajoitukset matkustaja-autolautan vesitiiviin osastoinnin suunnittelulle.International Maritime Organization (IMO) started a development process with its damage stability regulations. Research study in year 2008 tendered by European Maritime Safety Agency EMSA found significant defects in Solas 2009 damage stability rules. Since then damage stability of passenger ferries has been widely studied and variety of proposals on how the damage stability rule should be updated have been given. Because none of the proposals were unanimously accepted by IMO member states, SDC sub-committee’s working group drafted a compromise proposal for updated R- and A-indices. This SDC proposal, which is known as Solas 2020, is widely accepted between IMO member states. This update to damage stability regulation would significantly increase the safety level of passenger ships in collision accidents. On the other hand, design and building of new vessels can be more challenging than before, which will affect cost level. Effect of the updated damage stability regulation to design requirements of the watertight compartmentation of modern Baltic ro-ro-passenger ferry is studied in this thesis. Goal of this study is to find out if safety level this updated damage stability rule high enough that current Stockholm Agreement, directive 2003/25/EC, which takes into account ferry specific ‘Water-on-Deck’ situation, can be withdrawn. As a result it was found that Stockholm Agreement is still the most governing damage stability rule, which will set requirements for design of watertight compartmentation of ro-ro passenger ferries

[”I’m there to support, ask questions and walk beside” : School officials’ experinces on the transitions of children with an ommigrant background to secondary education

Tässä artikkelissa analysoimme, millaisia rakenteellisia mahdollisuuksia ja esteitä, toimijuutta ja ajallisia ulottuvuuksia koulutussiirtymiä ohjaavat ja hallinnoivat asiantuntijat hahmottavat maahanmuuttajataustaisten nuorten siirtymissä perusopetuksesta toisen asteen koulutukseen. Tutkimuksen aineistona oli kymmenen teemahaastattelua, jotka tehtiin opinto-ohjaajille, rehtoreille ja kunnallisille virkamiehille. Aineisto analysoitiin fenomenografisesti. Viitekehyksenä on suomalainen universalistinen siirtymäjärjestelmä, jossa yksilölliset koulutuspolut ovat mahdollisia ja jossa ohjaus on institutionalisoitunut osaksi koulutusta. Tulosten mukaan siirtymäjärjestelmän eri tahot ohjaavat siirtymiä usein omista lähtökohdistaan käsin, eikä kokonaisuutta ole mietitty. Siirtymän rakenteelliset piirteet perustuvat olettamukselle, että nuorilla on suomalaisen peruskoulun tuottamat valmiudet. Maahanmuuttajien valintoja voivat kuitenkin rajoittaa esimerkiksi riittämätön koulutusjärjestelmän tuntemus tai suomen kielen taito. Lisäksi ohjaus painottuu lyhyeen nivelvaiheeseen, ja sen jatkumo katkeaa perus- ja toisen asteen välissä. Jotta maahanmuuttajataustaisten nuorten koulutuspolut tulisivat aiempaa sujuvammiksi, tulisi heidän monimuotoiset tarpeensa huomioida systemaattisemmin siirtymäjärjestelmän rakenteissa, sen tarjoamissa mahdollisuuksissa sekä siihen kytkeytyvässä aikaperspektiivissä.The educational transitions of immigrant youth are considered challenging. In this article we analyze how school officials view the structural possibilities and obstacles, agency, and time perspective that frame the transitions of children with an immigrant background to secondary education. The study is based on ten thematic interviews with study counsellors, principals and education administration officials, which were analyzed using a phenomenographic approach. The theoretical setting consists of the concept of the Finnish universalistic transition regime, where individual educational paths are possible and study counselling is an institutionalized part of education. According to the results, different actors often guide the transitions from their own perspective, and the transition as a whole has not been thoroughly considered. The structural elements of the transitions rely on the assumption that students have attained the skills that the Finnish comprehensive school is expected to provide. Immigrant students' choices can, however, be restricted by their insufficient knowledge of the Finnish education system or limited proficiency in the Finnish language, for example. Furthermore, the counselling is focused around the short phase between the comprehensive school and upper secondary education, and is not built as a continuum from one institution to another. In order to enable smoother and more accessible educational pathways for immigrant youth, a more systematic consideration of their diverse needs is required in terms of the structures of the transition system as well as the possibilities and time perspectives involved.Peer reviewe

Avohakkuiden vaikutus maassa pesivien lintujen pesäpredaatioon – koepesätutkimus

Summary: Effect of forest clear-cutting areas on nests depredation of ground nesting birds – an artificial nest experiment. Nest predation is one of the most important factor affecting bird’s offspring production. However, nest predation is not very well studied, and the real role of different predator species predating ground nesting birds’ nests is still widely unclear. We especially need more information of nest predation and predators in different habitat types, such as boreal forests. The need is especially urgent, because there has been a fast increase of alien predator populations in Finland and Europe during the past decades. Alien predators pose a potential enhanced risk to many native bird species, such as forest grouses. Here, we study the nest depredation of ground nesting birds in barren coniferous forests, which are relatively far away from human settlements and fields. There are also only small number of lakes and ponds in our study area. The area is situated in the middle part of Finland in Suomenselkä region. We created 156 artificial nests with four pheasant eggs in low densities in 2018 and monitored them for seven days after construction using wildlife cameras to record whether nest predators visit and prey upon the nests. From the 156 artificial nest 26 (17 %) were depredated: in clear-cutting area 10 (19 %), forest edge 9 (17 %) and 7 (13 %) inside forests. The most common nest visitors were avian predators, which took 19 nets (raven Corvus corax 10, great tit Parus major 5, jay Garrulus glandarius 3 and great spotted woodpecker Dendrocopos major 1 nest). Mammals depredated only 2 nest (red fox Vulpes vulpes 1 and moose Alges alges 1 nest. In five nest depredation cases we did not succeeded to identify nest predators because of camera failure. All in all, nets depredation rate on barren coniferous forest seem to be relatively low. We used GLMM (Generalised linear mixed model) to find explanatory fosters explaining nest depredation risk in two different landscape scale (250 m and 500 m wide radius around nets). Results indicate that 250 wide buffer area around nest may explain better nest depredation risk, but results were not statistically significant. In our best model small forest road and electric power line areas explain best nest depredation risk (250 m radius). The size of the clear-cut did not affect the nest probability to become depredated. Even though we have relative big number of artificial nest, only few were depredated and thus the sample size was too low to find significant results. Therefore, more data is needed to find more precise depredation risk level of ground nesting birds in barren forests. Absence of raccoon dog was a bit surprising, because it is the most common nest predator in an agricultural–forest landscape and near lakes and ponds. Our results suggest that nest depredation risk is low in forests far from human settlements and fields.Peer reviewe

Drastic demographic events triggered the Uralic spread

The widespread Uralic family offers several advantages for tracing prehistory: a firm absolute chronological anchor point in an ancient contact episode with well-dated Indo-Iranian; other points of intersection or diagnostic non-intersection with early Indo-European (the Late Proto-Indo-European-speaking Yamnaya culture of the western steppe, the Afanasievo culture of the upper Yenisei, and the Fatyanovo culture of the middle Volga); lexical and morphological reconstruction sufficient to establish critical absences of sharings and contacts. We add information on climate, linguistic geography, typology, and cognate frequency distributions to reconstruct the Uralic origin and spread. We argue that the Uralic homeland was east of the Urals and initially out of contact with Indo-European. The spread was rapid and without widespread shared substratal effects. We reconstruct its cause as the interconnected reactions of early Uralic and Indo-European populations to a catastrophic climate change episode and interregionalization opportunities which advantaged riverine hunter-fishers over herders.Peer reviewe

Photometric Properties of White Dwarf Dominated Halos

Using stellar population synthesis techniques, we explore the photometric signatures of white dwarf progenitor dominated galactic halos, in order to constrain the fraction of halo mass that may be locked-up in white dwarf stellar remnants. We first construct a 10^9 M_sun stellar halo using the canonical Salpeter initial stellar mass distribution, and then allow for an additional component of low- and intermediate-mass stars, which ultimately give rise to white dwarf remnants. Microlensing observations towards the Large Magellanic Cloud, coupled with several ground-based proper motion surveys, have led to claims that in excess of 20% of the dynamical mass of the halo (10^12 M_sun) might be found in white dwarfs. Our results indicate that (1) even if only 1% of the dynamical mass of the dark halo today could be attributed to white dwarfs, their main sequence progenitors at high redshift (z ~ 3) would have resulted in halos more than 100 times more luminous than those expected from conventional initial mass functions alone, and (2) any putative halo white dwarf progenitor dominated initial mass function component, regardless of its dynamical importance, would be virtually impossible to detect at the present-day, due to its extremely faint surface brightness.Comment: 4 pages, Refereed contribution to the 5th Galactic Chemodynamics conference held in Swinburne, July 2003. Accepted for publication in PAS

An analytical model of surface mass densities of cold dark matter haloes - with an application to MACHO microlensing optical depths

The cold dark matter (CDM) scenario generically predicts the existence of triaxial dark matter haloes which contain notable amounts of substructure. However, analytical halo models with smooth, spherically symmetric density profiles are routinely adopted in the modelling of light propagation effects through such objects. In this paper, we address the biases introduced by this procedure by comparing the surface mass densities of actual N-body haloes against the widely used analytical model suggested by Navarro, Frenk and White (1996) (NFW). We conduct our analysis in the redshift range of 0.0 - 1.5. In cluster sized haloes, we find that triaxiality can cause scatter in the surface mass density of the haloes up to sigma_+ = +60% and sigma_- = -70%, where the 1-sigma limits are relative to the analytical NFW model given value. Subhaloes can increase this scatter to sigma_+ = +70% and sigma_- = -80%. In galaxy sized haloes, the triaxial scatter can be as high as sigma_+ = +80% and sigma_- = -70%, and with subhaloes the values can change to sigma_+ = +40% and sigma_- = -80%. We present an analytical model for the surface mass density scatter as a function of distance to the halo centre, halo redshift and halo mass. The analytical description enables one to investigate the reliability of results obtained with simplified halo models. Additionally, it provides the means to add simulated surface density scatter to analytical density profiles. As an example, we discuss the impact of our results on the calculation of microlensing optical depths for MACHOs in CDM haloes.Comment: 10 pages, 6 figures and 4 tables, accepted to MNRAS October 11th 200