University of Jyväskylä

About: University of Jyväskylä is a education organization based out in Jyvaskyla, Finland. It is known for research contribution in the topics: Population & Neutron. The organization has 8066 authors who have published 25168 publications receiving 725033 citations. The organization is also known as: Jyväskylän yliopisto & Kasvatusopillinen korkeakoulu.

The reaction 48Ca + 238U → 286112* studied at the GSI-SHIP

Abstract: The synthesis of element 116 in fusion-evaporation reactions of a 48Ca beam with radioactive 248Cm targets was studied at the velocity filter SHIP of GSI in Darmstadt. At excitation energies of the compound nuclei of 40.9MeV, four decay chains were measured, which were assigned to the isotope 292116, and one chain, which was assigned to 293116. Measured cross-sections of (3.4−1.6+2.7) pb and (0.9−0.7+2.1), respectively, and decay data of the chains agree with data measured previously at the Flerov Laboratory of Nuclear Reactions in Dubna. As a new result, one α-decay chain was measured, which terminates after four α decays by spontaneous fission. The α energies of the second-to-fourth decay are considerably higher than those measured for the α decays of 289114, 285Cn, and 281Ds and the spontaneous fission half-life is significantly longer than that of 277Hs measured in previous experiments. A possible assignment is discussed in the frame of excited quasiparticle states of nuclei populated in the decay chain from 293116. Also other possible assignments were considered and are discussed. At an excitation energy of 45.0MeV no events were observed resulting in a one-event cross-section limit of 1.6 pb. The technical aspects related with the use of radioactive target material at SHIP are described in detail. The experience gained in this experiment will serve as a basis for future experiments aiming to study still heavier elements at the velocity filter SHIP.

Sexy to die for? Sexual selection and the risk of extinction

Abstract: Sexual selection is a field with a strong focus on the 'costs' of traits. However, whether such costs have an influence on the demography of the population is very rarely discussed. Here we present various processes through which sexual selection might have an impact on population viability and thus increase or decrease the risk of extinction. We argue that evolutionary 'suicide' - as sometimes suggested e.g. to have caused the extinction of the Irish elk - is unlikely in deterministic environments, except if costs are not paid by the same individual that bears the trait. Thus, intra- or inter-locus sexual conflict could in principle drive a population extinct, and we do not know why this does not frequently happen. Whether sexual selection increases or decreases extinction risks when populations face variable or unforeseen environmental conditions is likewise unknown, and we outline mechanisms that could account for either pattern. Inbreeding is another factor that could either increase or decrease population viability in sexually selected species. Inbreeding may be caused by a high mating skew, but it could also be reduced if females adaptively choose mates to avoid inbred offspring. Finally, when intraspecific competition for resources is taken into account, it is unclear how individual viabilities translate to extinction risks faced by the population. We show an example where greater mortality of males due to sexual dimorphism improves the carrying capacity of the environment, and thus presumably population viability.

International Perspectives on the Effectiveness of Geography Fieldwork for Learning

Abstract: This paper seeks to address assumptions on the effectiveness of fieldwork as a mode of learning in geography. This is approached from an international perspective, both in review of available evidence, which demonstrates a need for rigorous research into the issue, and in providing preliminary findings of research into the value of fieldwork from universities across three continents. Common themes to emerge concern the effectiveness of fieldwork in terms of learning and understanding of the subject: providing first-hand experience of the real world, whichever part of the world the students are in; skills development (transferable and technical); and social benefits. The extent to which fieldwork develops transferable skills depends on the context in which the fieldwork is undertaken. The paper points to avenues of future research to be investigated to deepen our understanding of the role fieldwork plays in student learning and to address the question, ‘how effective is fieldwork in improving learning?’

An Updated Guideline for Assessing Discriminant Validity

Abstract: Discriminant validity was originally presented as a set of empirical criteria that can be assessed from multitrait-multimethod (MTMM) matrices. Because datasets used by applied researchers rarely l...

Revised rates for the stellar triple-alpha process from measurement of C-12 nuclear resonances

Abstract: In the centres of stars where the temperature is high enough, three alpha-particles (helium nuclei) are able to combine to form C-12 because of a resonant reaction leading to a nuclear excited state(1). (Stars with masses greater than similar to0.5 times that of the Sun will at some point in their lives have a central temperature high enough for this reaction to proceed.) Although the reaction rate is of critical significance for determining elemental abundances in the Universe(1), and for determining the size of the iron core of a star just before it goes supernova(2), it has hitherto been insufficiently determined(2). Here we report a measurement of the inverse process, where a C-12 nucleus decays to three alpha-particles. We find a dominant resonance at an energy of similar to11 MeV, but do not confirm the presence of a resonance at 9.1 MeV (ref. 3). We show that interference between two resonances has important effects on our measured spectrum. Using these data, we calculate the triple-a rate for temperatures from 10(7) K to 10(10) K and find significant deviations from the standard rates(3). Our rate below similar to5 x 10(7) K is higher than the previous standard, implying that the critical amounts of carbon that catalysed hydrogen burning in the first stars are produced twice as fast as previously believed(4). At temperatures above 10(9) K, our rate is much less, which modifies predicted nucleosynthesis in supernovae(5,6).