Study of attosecond delays using perturbation diagrams and exterior complex scaling

We describe in detail how attosecond delays in laser-assisted photoionization can be computed using perturbation theory based on two-photon matrix elements. Special emphasis is laid on above-threshold ionization, where the electron interacts with an infrared field after photoionization by an extreme ultraviolet field. Correlation effects are introduced using diagrammatic many-body theory to the level of the random-phase approximation with exchange (RPAE). Our aim is to provide an ab initio route to correlated multi-photon processes that are required for an accurate description of experiments on the attosecond time scale. Here, our results are focused on photoionization of the M -shell of argon atoms, where experiments have been carried out using the so-called RABITT technique. An influence of autoionizing resonances in attosecond delay measurements is observed. Further, it is shown that the delay depends on both detection angle of the photoelectron and energy of the probe photon.Comment: 36 pages, 10 figure

The Multi-Configurational Hartree-Fock close-coupling ansatz: application to Argon photoionization cross section and delays

We present a robust, ab initio method for addressing atom-light interactions and apply it to photoionization of argon. We use a close-coupling ansatz constructed on a multi-configurational Hartree-Fock description of localized states and B-spline expansions of the electron radial wave functions. In this implementation, the general many-electron problem can be tackled thanks to the use of the ATSP2K libraries [CPC 176 (2007) 559]. In the present contribution, we combine this method with exterior complex scaling, thereby allowing for the computation of the complex partial amplitudes that encode the whole dynamics of the photoionization process. The method is validated on the 3s3p6np series of resonances converging to the 3s extraction. Then, it is used for computing the energy dependent differential atomic delay between 3p and 3s photoemission, and agreement is found with the measurements of Gu\'enot et al. [PRA 85 (2012) 053424]. The effect of the presence of resonances in the one-photon spectrum on photoionization delay measurements is studied.Comment: 15 pages, 8 figures, 4 table

Photoionization in the time and frequency domain

Ultrafast processes in matter, such as the electron emission following light absorption, can now be studied using ultrashort light pulses of attosecond duration ($10^{-18}$s) in the extreme ultraviolet spectral range. The lack of spectral resolution due to the use of short light pulses may raise serious issues in the interpretation of the experimental results and the comparison with detailed theoretical calculations. Here, we determine photoionization time delays in neon atoms over a 40 eV energy range with an interferometric technique combining high temporal and spectral resolution. We spectrally disentangle direct ionization from ionization with shake up, where a second electron is left in an excited state, thus obtaining excellent agreement with theoretical calculations and thereby solving a puzzle raised by seven-year-old measurements. Our experimental approach does not have conceptual limits, allowing us to foresee, with the help of upcoming laser technology, ultra-high resolution time-frequency studies from the visible to the x-ray range.Comment: 5 pages, 4 figure

Luokanopettajien näkemyksiä opetuksen eriyttämisestä ja kaikille yhteisestä koulusta

Tiivistelmä. Tämän pro gradu -tutkielman tarkoituksena on selvittää, miten alakoulun luokanopettajat eriyttävät opetustaan sekä minkälaisia asenteita heillä on eriyttämistä ja kaikille yhteistä koulua kohtaan. Tutkielmassa selvitetään myös onko opetuksen eriyttämisen menetelmien ja asenteiden välillä yhteyksiä. Aineisto on kerätty kvantitatiivisella survey-kyselylomakkeella vuoden 2015 kevään ja syksyn aikana. Tutkimukseen osallistui 53 alakoulun luokanopettajaa Pohjanmaalta ja Pohjois-Pohjanmaalta. Aineisto on käsitelty IBM SPSS Statistics -tilastojenkäsittelyohjelmalla. Tämän tutkielman teoriaosuudessa selvitetään mitä inkluusio ja opetuksen eriyttäminen tarkoittaa, missä muodoissa sitä voidaan toteuttaa ja millaisia tuloksia aiemmista tutkimuksista on saatu. Aihe on ajankohtainen ja tärkeä, sillä suomalaisessa yhteiskunnassa on viime vuosina korostunut inklusiivinen ajattelutapa ja kaikille yhteisen koulun tavoittelu. Selkeä harppaus inklusiivisen koulun tavoittelussa otettiin vuonna 2011, kun muutettiin esi- ja perusopetuksen toimintamalleja vastaamaan paremmin kaikille yhteisen koulun ihanteita. Inkluusion taustalla vaikuttaa voimakkaasti vuonna 1994 julkistettu Salamancan sopimus. Inkluusion tavoittelu on muuttanut yleisopetuksen oppilasjoukkoa heterogeenisemmäksi ja siten lisännyt eriyttämisen tarvetta. Tällä hetkellä eletään vaiheessa, jossa täytyy todella miettiä miten inkluusion periaatteet saadaan toteutumaan käytännön opetuksessa ja annetaan opettajille työvälineitä oppilaiden yksilöllisten tarpeiden huomioimiseksi. Syksyllä 2016 käyttöön otettava valtakunnallinen perusopetuksen opetussuunnitelma tulee olemaan isossa roolissa tässä kehityksessä. Tutkimuksen tuloksista saadaan selville, että opettajat käyttävät opetuksen eriyttämisen keinoja monipuolisesti ja yleisopetuksen eriyttämistä pidetään erittäin tärkeänä. Eriyttämisen ajatellaan kuitenkin vievän ylimääräistä aikaa ja etenkin oppilasryhmän suuruus vaikuttaa koettuun resurssien määrään. Vastaajien mielestä opetusta eriyttämällä koko opetusryhmä saavuttaa parempia oppimistuloksia, mutta oppitunneilla on vain harvoin riittävästi aikaa antaa tukea sitä tarvitseville. Yleisopetuksen ei kuitenkaan koeta selkeästi olevan paras vaihtoehto kaikkien oppilaiden oppimiselle. Tutkimustulokset osoittavat, että eriyttävän opetuksen toteuttaminen ja asenteet ovat vahvasti yhteydessä toisiinsa. Tuloksista selviää myös, että mitä kokeneempi ja iäkkäämpi opettaja, sitä tärkeämpänä hän pitää ylöspäin eriyttämistä. Kyselylomakkeen viimeisessä osiossa kysyttiin lisäksi ratkaisuehdotuksia opetuksen eriyttämisen helpottamiseksi. Suosituimpia ratkaisuehdotuksia olivat resurssien ja yhteistyön lisääminen sekä huomion kiinnittäminen oppilasryhmien suuruuteen.Abstract. The purpose of the current Master’s thesis is to find out how primary teachers differentiate their teaching and what their attitudes towards differentiation and a school for all are. The study also discusses if there are connections between the methods of and attitudes towards differentiated instruction. The data was collected using a quantitative survey questionnaire in the spring and autumn of 2015. The study was taken part in by 53 primary teachers from Ostrobothnia and Northern Ostrobothnia. The data was processed with the IBM SPSS Statistics software. The theoretical part of this thesis explains what inclusion and differentiated instruction means, in which forms it can be implemented, and what kind of results have been obtained in earlier studies. The topic is current and important, as Finnish society put an emphasis on the inclusive way of thinking and aspirations for a school for all in recent years. A major leap in the aspiration for an inclusive school took place in 2011, at which time the policies in preprimary and primary education were modified to be better in line with the ideals of a school for all. The Salamanca Statement adopted in 1994 is having a major influence on inclusion. Aspirations for inclusion have made the ranks of pupils in mainstream education more heterogeneous, thus adding to the need for differentiation. At this time we are living at a stage where we really need to think about the ways to fulfil the principles of inclusion in practical teaching, and how to give the teachers tools to take into account the pupils’ individual needs. The national basic education curriculum to be introduced in the autumn of 2016 will be playing a major role in this development. The results of this study show that the teachers use methods of differentiated instruction in various ways, and that differentiation of mainstream education is considered highly important. They think, however, that differentiation takes extra time, and it is the size of the group of pupils in particular that has an effect on how they experience the need for resources. The respondents think that the entire group being taught achieves improved learning results through differentiation, but there is only seldom time enough in the lessons to give support to those needing it. However, they do not feel that mainstream teaching is clearly the best alternative for all the pupils to learn. The research results indicate that the implementation of and attitudes towards differentiated instruction are strongly interconnected. The results also show that the more experienced and aged the teacher is, the more important he or she considers upwards differentiation to be. In the last section of the questionnaire, solutions were also sought to make it easier to differentiate instruction. The most popular proposals included increased resources and cooperation, and paying attention to the size of the groups of pupils

Drug-resistant genotypes and multi-clonality in Plasmodium falciparum analysed by direct genome sequencing from peripheral blood of malaria patients.

Naturally acquired blood-stage infections of the malaria parasite Plasmodium falciparum typically harbour multiple haploid clones. The apparent number of clones observed in any single infection depends on the diversity of the polymorphic markers used for the analysis, and the relative abundance of rare clones, which frequently fail to be detected among PCR products derived from numerically dominant clones. However, minority clones are of clinical interest as they may harbour genes conferring drug resistance, leading to enhanced survival after treatment and the possibility of subsequent therapeutic failure. We deployed new generation sequencing to derive genome data for five non-propagated parasite isolates taken directly from 4 different patients treated for clinical malaria in a UK hospital. Analysis of depth of coverage and length of sequence intervals between paired reads identified both previously described and novel gene deletions and amplifications. Full-length sequence data was extracted for 6 loci considered to be under selection by antimalarial drugs, and both known and previously unknown amino acid substitutions were identified. Full mitochondrial genomes were extracted from the sequencing data for each isolate, and these are compared against a panel of polymorphic sites derived from published or unpublished but publicly available data. Finally, genome-wide analysis of clone multiplicity was performed, and the number of infecting parasite clones estimated for each isolate. Each patient harboured at least 3 clones of P. falciparum by this analysis, consistent with results obtained with conventional PCR analysis of polymorphic merozoite antigen loci. We conclude that genome sequencing of peripheral blood P. falciparum taken directly from malaria patients provides high quality data useful for drug resistance studies, genomic structural analyses and population genetics, and also robustly represents clonal multiplicity

Plasmodium falciparum population dynamics during the early phase of anti-malarial drug treatment in Tanzanian children with acute uncomplicated malaria

BACKGROUND\ud \ud This study aimed to explore Plasmodium falciparum population dynamics during the early phase of anti-malarial drug treatment with artemisinin-based combination therapy in children with clinical malaria in a high transmission area in Africa.\ud \ud METHODS\ud \ud A total of 50 children aged 1-10 years with acute uncomplicated P. falciparum malaria in Bagamoyo District, Tanzania, were enrolled. Participants were hospitalized and received supervised standard treatment with artemether-lumefantrine according to body weight in six doses over 3 days. Blood samples were collected 11 times, i.e. at time of diagnosis (-2 h) and 0, 2, 4, 8, 16, 24, 36, 48, 60 and 72 h after initiation of treatment. Parasite population dynamics were assessed using nested polymerase chain reaction (PCR)-genotyping of merozoite surface protein (msp) 1 and 2.\ud \ud RESULTS\ud \ud PCR-analyses from nine sequential blood samples collected after initiation of treatment identified 20 and 21 additional genotypes in 15/50 (30%) and 14/50 (28%) children with msp1 and msp2, respectively, non-detectable in the pre-treatment samples (-2 and 0 h combined). Some 15/20 (75%) and 14/21 (67%) of these genotypes were identified within 24 h, whereas 17/20 (85%) and 19/21 (90%) within 48 h for msp1 and msp2, respectively. The genotype profile was diverse, and varied considerably over time both within and between patients, molecular markers and their respective families.\ud \ud CONCLUSION\ud \ud PCR analyses from multiple blood samples collected during the early treatment phase revealed a complex picture of parasite sub-populations. This underlines the importance of interpreting PCR-outcomes with caution and suggests that the present use of PCR-adjustment from paired blood samples in anti-malarial drug trials may overestimate assessment of drug efficacy in high transmission areas in Africa.The study is registered at http://www.clinicaltrials.gov with identifier NCT00336375

Interpreting Attoclock Measurements of Tunnelling Times

Resolving in time the dynamics of light absorption by atoms and molecules, and the electronic rearrangement this induces, is among the most challenging goals of attosecond spectroscopy. The attoclock is an elegant approach to this problem, which encodes ionization times in the strong-field regime. However, the accurate reconstruction of these times from experimental data presents a formidable theoretical challenge. Here, we solve this problem by combining analytical theory with ab-initio numerical simulations. We apply our theory to numerical attoclock experiments on the hydrogen atom to extract ionization time delays and analyse their nature. Strong field ionization is often viewed as optical tunnelling through the barrier created by the field and the core potential. We show that, in the hydrogen atom, optical tunnelling is instantaneous. By calibrating the attoclock using the hydrogen atom, our method opens the way to identify possible delays associated with multielectron dynamics during strong-field ionization.Comment: 33 pages, 10 figures, 3 appendixe