Paradoxical reflection in quantum mechanics

This article concerns a phenomenon of elementary quantum mechanics that is quite counter-intuitive, very non-classical, and apparently not widely known: a quantum particle can get reflected at a downward potential step. In contrast, classical particles get reflected only at upward steps. The conditions for this effect are that the wave length is much greater than the width of the potential step and the kinetic energy of the particle is much smaller than the depth of the potential step. This phenomenon is suggested by non-normalizable solutions to the time-independent Schroedinger equation, and we present evidence, numerical and mathematical, that it is also indeed predicted by the time-dependent Schroedinger equation. Furthermore, this paradoxical reflection effect suggests, and we confirm mathematically, that a quantum particle can be trapped for a long time (though not forever) in a region surrounded by downward potential steps, that is, on a plateau.

Arabidopsis GRI is involved in the regulation of cell death induced by extracellular ROS

Reactive oxygen species (ROS) have important functions in plant stress responses and development. In plants, ozone and pathogen infection induce an extracellular oxidative burst that is involved in the regulation of cell death. However, very little is known about how plants can perceive ROS and regulate the initiation and the containment of cell death. We have identified an Arabidopsis thaliana protein, GRIM REAPER (GRI), that is involved in the regulation of cell death induced by extracellular ROS. Plants with an insertion in GRI display an ozone-sensitive phenotype. GRI is an Arabidopsis ortholog of the tobacco flower-specific Stig1 gene. The GRI protein appears to be processed in leaves with a release of an N-terminal fragment of the protein. Infiltration of the N-terminal fragment of the GRI protein into leaves caused cell death in a superoxide-and salicylic acid-dependent manner. Analysis of the extracellular GRI protein yields information on how plants can initiate ROS-induced cell death during stress response and development.

Nature of chemistry in the national frame curricula for upper secondary education in Finland, Norway and Sweden

The aim of this study was to discover how current chemistry syllabi in the frame curricula for up- per secondary education in three Nordic countries (Finland, Norway, and Sweden) take into account topics related to the nature of chemistry. By qualitative content analysis, the statements related to the nature of chemistry were divided into categories. Conclusions and implications for improving the frame curricula under study were made by comparing results with research into the nature of science. Chemistry syllabi from the Nordic frame curricula analyzed take into account the aims related to the nature of chemistry in a very similar manner. The ideas that should be made more explicit in all of the analyzed curricula are: i) the limits of the chemical models and theories, ii) the relationship between chemistry and other natural sciences, iii) the importance of creativity in chemical research, iv) the concepts of evidence in science texts, v) the social nature of chemical research, and vi) chemistry as a technological practice.

The many ways to delimit species: hairs, genes and surface chemistry

Species identification forms the basis for understanding the diversity of the living world, but it is also a prerequisite for understanding many evolutionary patterns and processes. The most promising approach for correctly delimiting and identifying species is to integrate many types of information in the same study. Our aim was to test how cuticular hydro- carbons, traditional morphometrics, genetic polymorphisms in nuclear markers (allozymes and DNA microsatellites) and DNA barcoding (partial mitochondrial COI gene) perform in delimiting species. As an example, we used two closely related Formica ants, F. fusca and F. lemani, sampled from a sympatric population in the northern part of their distribu- tion. Morphological characters vary and overlap in different parts of their distribution areas, but cuticular hydrocarbons include a strong taxonomic signal and our aim is to test the degree to which morphological and genetic data correspond to the chemical data. In the morphological analysis, species were best separated by the combined number of hairs on pro- notum and mesonotum, but individual workers overlapped in hair numbers, as previously noted by several authors. Nests of the two species were separated but not clustered according to species in a Principal Component Analysis made on nuclear genetic data. However, model-based Bayesian clustering resulted in perfect separation of the species and gave no indication of hybridization. Furthermore, F. lemani and F. fusca did not share any mitochondrial haplotypes, and the species were perfectly separated in a phylogenetic tree. We conclude that F. fusca and F. lemani are valid species that can be separated in our study area relatively well with all methods employed. However, the unusually small genetic differen- tiation in nuclear markers (FST = 0.12) shows that they are closely related, and occasional hybridization between F. fusca and F. lemani cannot be ruled out.

Koulu, digitaalinen teknologia ja toimivat käytännöt

Artikkelissa tarkastellaan sitä, mitkä seikat liittyvät teknologian innovatiiviseen hyödyntämiseen koulun toiminnassa ja pedagogisissa käytännöissä sekä yleensä koulun kehittymiseen. Tutkimuksen viitekehyksenä toimii ”Innovatiivisen, kehittyvän koulun malli” ja sen teoreettiset lähtökohdat. Aineisto on koottu kuudesta koulusta, ja se koostuu opettajien ja rehtoreiden haastatteluista sekä oppituntien videoinneista. Artikkeliin on koottu parhaita esimerkkejä koulumallin kuvaamien ilmiöiden käytännöistä, jotka aikaisemman tutkimuksen perusteella edistävät koulun kehittämistä ja pedagogisten innovaatioiden leviämistä kouluyhteisössä. Koulujen välillä on suuria eroja yhteisöllisessä kehittämiskulttuurissa, mikä heijastuu myös pedagogisiin käytäntöihin. Uusia ilmiöitä näyttävät olevan koulun tietokäytännöt uuden teknologian keinoin ja oppilaiden informaalin oppimisen kautta opittujen taitojen käyttäminen hyväksi koulussa sekä oppilaiden osallistaminen koulutyöhön muutenkin kuin oppijan roolissa.

Kuinka kauas vääryyksien varjot ulottuvat?

Suomessa on viime vuosina keskusteltu 1900-luvun historiamme eräiden vaiheiden moraalisesta (uudelleen)arvioinnista. Tällöin on myös väitelty siitä, pitäisikö jonkin tahon esimerkiksi pyytää anteeksi mahdollisia tehtyjä vääryyksiä. Tässä artikkelissa tarkastellaan suomalaisnuorten ajatuksia historiallisista hyvityksistä, tulkitaan niitä suhteessa suomalaisnuorten historiatietoisuutta koskevaan aiempaan tutkimukseen sekä pohditaan lyhyesti havaintojen historiandidaktisia implikaatioita.

Magnetorotational instability driven dynamos at low magnetic Prandtl numbers

Numerical simulations of the magnetorotational instability (MRI) with zero initial net flux in a non-stratified isothermal cubic domain are used to demonstrate the importance of magnetic boundary conditions. In fully periodic systems the level of turbulence generated by the MRI strongly decreases as the magnetic Prandtl number (Pm), which is the ratio of kinematic viscosity and magnetic diffusion, is decreased. No MRI or dynamo action below Pm=1 is found, agreeing with earlier investigations. Using vertical field conditions, which allow magnetic helicity fluxes out of the system, the MRI is found to be excited in the range 0.1