Search results for "Fysiikka"
showing 10 items of 1348 documents
Direct and correlated responses to bi-directional selection on pre-adult development time in Drosophila montana.
2019
Selection experiments offer an efficient way to study the evolvability of traits that play an important role in insects’ reproduction and/or survival and to trace correlations and trade-offs between them. We have exercised bi-directional selection on Drosophila montana flies’ pre-adult development time under constant light and temperature conditions for 10 generations and traced the indirect effects of this selection on females’ diapause induction under different day lengths, as well as on the body weight and cold tolerance of both sexes. Overall, selection was successful towards slow, but not towards fast development. However, all fast selection line replicates showed at the end of selecti…
Lignin Inter-Diffusion Underlying Improved Mechanical Performance of Hot-Pressed Paper Webs
2021
Broader use of bio-based fibres in packaging becomes possible when the mechanical properties of fibre materials exceed those of conventional paperboard. Hot-pressing provides an efficient method to improve both the wet and dry strength of lignin-containing paper webs. Here we study varied pressing conditions for webs formed with thermomechanical pulp (TMP). The results are compared against similar data for a wide range of other fibre types. In addition to standard strength and structural measurements, we characterise the induced structural changes with X-ray microtomography and scanning electron microscopy. The wet strength generally increases monotonously up to a very high pressing tempera…
Chlorophyll a fluorescence illuminates a path connecting plant molecular biology to Earth-system science
2021
Remote sensing methods enable detection of solar-induced chlorophyll a fluorescence. However, to unleash the full potential of this signal, intensive cross-disciplinary work is required to harmonize biophysical and ecophysiological studies. For decades, the dynamic nature of chlorophyll a fluorescence (ChlaF) has provided insight into the biophysics and ecophysiology of the light reactions of photosynthesis from the subcellular to leaf scales. Recent advances in remote sensing methods enable detection of ChlaF induced by sunlight across a range of larger scales, from using instruments mounted on towers above plant canopies to Earth-orbiting satellites. This signal is referred to as solar-in…
Low-Power, Subthreshold Reference Circuits for the Space Environment : Evaluated with -rays, X-rays, Protons and Heavy Ions
2019
The radiation tolerance of subthreshold reference circuits for space microelectronics is presented. The assessment is supported by measured results of total ionization dose and single event transient radiation-induced effects under &gamma
Quenching of gA deduced from the β-spectrum shape of 113Cd measured with the COBRA experiment
2020
A dedicated study of the quenching of the weak axial-vector coupling strength gA in nuclear processes has been performed by the COBRA collaboration. This investigation is driven by nuclear model calculations which show that the β-spectrum shape of the fourfold forbidden non-unique decay of 113Cd strongly depends on the effective value of gA. Using an array of CdZnTe semiconductor detectors, 45 independent 113Cd spectra were obtained and interpreted in the context of three nuclear models. The resulting effective mean values are g‾A(ISM)=0.915±0.007, g‾A(MQPM)=0.911±0.013 and g‾A(IBFM-2)=0.955±0.022. These values agree well within the determined uncertainties and deviate significantly from th…
Katsaus Suomen varhaiseen atomihistoriaan
2022
Nykyisellä ydinteknologialla on lähinnä kaksi haaraa joita ovat ydinenergia ja lääketieteellinen isotooppitekniikka. Ensin mainitun lähtölaukauksena Suomessa pidetään nk. energiakomitean perustamista vuonna 1955. Tämän historian tutkimuksen painopiste on ollut 1960-ja 1970-luvun tapahtumissa, jotka liittyvät nykyisten ydinvoimalaitosten hankintakuvioihin. Professori Lennart Simons aloitti vakavasti otettavan ydinfysiikan tutkimuksen Suomessa ja oli alan ykkösnimi 1940- ja 1950-luvuilla kun koko länsimaailman yli pyyhkäisi atomiteknologian huuma, jota ehkä voi sanoa ensimmäiseksi teknologiahypeksi modernissa mielessä. Kirjan tarkoituksena on antaa lisävalaistusta suomalaisen ydinteknologian …
Offline commissioning of a new gas cell for the MARA Low-Energy Branch
2023
Results of offline commissioning tests for a new dedicated gas cell for the Mass Analysing Recoil Apparatus (MARA) Low-Energy Branch are reported. Evacuation time, ion survival and transport efficiency in helium buffer gas were characterized with a radioactive 223Ra 𝛼-recoil source. Suppression of the ion signal, originating from non-neutralized species in the gas cell, was explored with 219Rn ions, the daughter recoil of 223Ra, as a function of voltage applied to one of the ion-collector electrodes. Two-step laser resonance ionization of stable tin isotopes produced inside the gas cell from a heated bronze filament was demonstrated, and broadening of the atomic resonances in argon buffer …
Variation of fundamental constants and 229Th
2017
The first excited state of the nucleus229Th has an exceptionally small excitation energy of7.8 eV, which is expected to be very sensitive to changes in the fine structure constant α.A small difference in the Coulomb energies of the two states, which both are of the order109eV, would amplify variations in α into large variations of the transition frequency.Hartree-Fock and Hartree-Fock-Bogoliubov calculations are performed to compute theCoulomb energies of the two states. The kinetic energies are also calculated which reflecta possible variation in the nucleon or quark masses or local Lorentz invariance violation. peerReviewed
Population of lead isotopes in binary reactions using a Rb 94 radioactive beam
2020
8 pags., 9 figs.
Lifetimes of core-excited states in semi-magic $^{95}$Rh
2020
Lifetimes of negative-parity states have been determined in the neutron deficient semi-magic (N = 50) nucleus 95Rh. The fusion-evaporation reaction 58Ni(40Ca,3p) was used to populate high-spin states in 95Rh at the Grand Accélérateur National d’Ions Lourds (GANIL) accelerator facility. The results were obtained using the Doppler Shift Attenuation Method (DSAM) based on the Doppler broadened line shapes produced during the slowing down process of the residual nuclei in a thick 6mg/cm2 metallic target. B(M1) and B(E2) reduced transition strengths are compared with predictions from large-scale shell-model calculations. peerReviewed