Lattice benchmarking of deterministic, Monte Carlo and hybrid Monte Carlo reactor physics codes for the soluble-boron-free SMR cores

Since the use of deterministic transport code WIMS can significantly reduce the computational time compared to the Monte Carlo (MC) code Serpent and hybrid MC code MONK, one of the major objectives of this study is to observe whether deterministic code WIMS can provide accuracy in reactor physics calculations while comparing Serpent and MONK. Therefore, numerical benchmark calculations for a soluble-boron-free (SBF) small modular reactor (SMR) assembly have been performed using the WIMS, Serpent and MONK. Although computationally different in nature, these codes can solve the neutronic transport equations and calculate the required neutronic parameters. A comparison in neutronic parameters between the three codes has been carried out using two types of candidate fuels: 15%235U enriched homogeneously mixed all-UO2 fuel and 18%235U enriched micro-heterogeneous ThO2-UO2 duplex fuel in a 2D fuel assembly model using a 13×13 arrangement. The eigenvalue/reactivity (k∞) and 2D assembly pin power distribution at different burnup states in the assembly depletion are compared using three candidate nuclear data files: ENDF/B- VII, JEF2.2 and JEF3.1. A good agreement in k∞ values was observed among the codes for both the candidate fuels. The differences in k∞ between the codes are ∼200 pcm when cross-sections based on the same nuclear data file are used. A higher difference (up to ∼450 pcm) in the k∞ values is observed among the codes using cross-sections based on different data files. Finally, it can be concluded from this study that the good agreement in the results between the codes found provides enhanced confidence that modeling of SBF, SMR propulsion core systems with micro-heterogeneous duplex fuel can be performed reliably using deterministic neutronics code WIMS, offering the advantage of less expensive computation than that of the MC Serpent and hybrid MC MONK codes

Obstructive sleep apnoea-related respiratory events and desaturation severity are associated with the cardiac response

Obstructive sleep apnoea (OSA) causes, among other things, intermittent blood oxygen desaturations, increasing the sympathetic tone. Yet the effect of desaturations on heart rate variability (HRV), a simple and noninvasive method for assessing sympathovagal balance, has not been comprehensively studied. We aimed to study whether desaturation severity affects the immediate HRV.MethodsWe retrospectively analysed the electrocardiography signals in 5-min segments (n=39 132) recorded during clinical polysomnographies of 642 patients with suspected OSA. HRV parameters were calculated for each segment. The segments were pooled into severity groups based on the desaturation severity (i.e.the integrated area under the blood oxygen saturation curve) and the respiratory event rate within the segment. Covariate-adjusted regression analyses were performed to investigate possible confounding effects.ResultsWith increasing respiratory event rate, the normalised high-frequency band power (HFNU) decreased from 0.517 to 0.364 (p<0.01), the normalised low-frequency band power (LFNU) increased from 0.483 to 0.636 (p<0.01) and the mean RR interval decreased from 915 to 869 ms (p<0.01). Similarly, with increasing desaturation severity, the HFNUdecreased from 0.499 to 0.364 (p<0.01), the LFNUincreased from 0.501 to 0.636 (p<0.01) and the mean RR interval decreased from 952 to 854 ms (p<0.01). Desaturation severity-related findings were confirmed by considering the confounding factors in the regression analyses.ConclusionThe short-term HRV response differs based on the desaturation severity and the respiratory event rate in patients with suspected OSA. Therefore, a more detailed analysis of HRV and desaturation characteristics could enhance OSA severity estimation

The analysis of freshwater pearl mussel shells using mu-XRF (micro-x-ray fluorescence) and the applicability for environmental reconstruction

Freshwater pearl mussel is a highly threatened species, and many populations are currently on the brink of local extinction. For example, in south Finland, only two populations are currently viable. Even though the reasons for the mussels' demise are relatively well known, the long-term impacts of water quality are not completely resolved. Here, mu-XRF analysis and historical records were used to evaluate whether the differences in water chemistry or past environmental changes in three rivers in southern Finland are visible in mussel shell chemistry. The results show that the cracks inside mussel shells, invisible to the naked eye, may greatly affect the elemental composition results. Further, anomalies which could be related to inclusion of detrital matter inside the shells were detected. Manganese (Mn) seems to be related to mussel growth dynamics, especially in the nacreous layer, while high values of iron (Fe) and Mn are also present at the top sections of the prismatic layer. Line scan analysis revealed high variation between replicates. The mu-XRF method could be used as prescreening method in mussel sclerochemistry studies, but more studies are needed to clarify the ability of FPM shells to reliably record the environmental conditions

Brain Source Correlates of Speech Perception and Reading Processes in Children With and Without Reading Difficulties

Neural correlates in reading and speech processing have been addressed extensively in the literature. While reading skills and speech perception have been shown to be associated with each other, their relationship remains debatable. In this study, we investigated reading skills, speech perception, reading, and their correlates with brain source activity in auditory and visual modalities. We used high-density event-related potentials (ERPs), fixation-related potentials (FRPs), and the source reconstruction method. The analysis was conducted on 12–13-year-old schoolchildren who had different reading levels. Brain ERP source indices were computed from frequently repeated Finnish speech stimuli presented in an auditory oddball paradigm. Brain FRP source indices were also computed for words within sentences presented in a reading task. The results showed significant correlations between speech ERP sources and reading scores at the P100 (P1) time range in the left hemisphere and the N250 time range in both hemispheres, and a weaker correlation for visual word processing N170 FRP source(s) in the posterior occipital areas, in the vicinity of the visual word form areas (VWFA). Furthermore, significant brain-to-brain correlations were found between the two modalities, where the speech brain sources of the P1 and N250 responses correlated with the reading N170 response. The results suggest that speech processes are linked to reading fluency and that brain activations to speech are linked to visual brain processes of reading. These results indicate that a relationship between language and reading systems is present even after several years of exposure to print

PUHEEN HAVAINTO, KUULOJÄRJESTELMÄ JA AIVOJEN RYTMIT DYSLEKSIASSA

Dysleksia on kehityksellinen pulma lukemaan ja kirjoittamaan oppimisessa ja lukutaidon sujuvoitumisessa. Dysleksiaan liittyy myös muita pulmia esimerkiksi äänne- eli fonologisessa tietoisuudessa, kielellisessä muistissa, kyvyssä nimetä nopeasti tuttuja asioita ja kuulohavainnossa. Tämä katsausartikkeli keskittyy kuulohavainnon ja dysleksian välisiin yhteyksiin. Kuulotiedon käsittelyyn liittyvät pulmat ja lukihäiriö ovat olleet vilkkaan keskustelun aiheena jo pitkään johtuen melko ristiriitaisista löydöksistä. Meta-analyysi kuitenkin osoittaa, että jopa puolella heikoista lukijoista saattaa olla pulmaa äänen keston ja nousuaikojen havaitsemisessa sekä vähäisemmässä määrin taajuuksienhavainnossa. Vastaavasti äänen voimakkuuden havainnossa pulmiaei juurikaan esiinny. Kuulojärjestelmässä esiintyvien pulmien taustalla oleva mekanismi on edelleen selvittämättä. Uusi näkökulma mahdolliseen mekanismiin on auennut aivojen rytmien kautta. Aivojen aktiivisuus seuraa puheen tavutason rytmiä ja siten muokkaa aikaikkunoita, joissa havaitseminen on erityisen tarkkaa. Henkilöillä, joilla on dysleksia, aivojen aktivaatio saattaa seurata puhetta ja puheen rytmiä eri tavalla kuin tyypillisillä lukijoilla ja siten olla yhtenä tekijänä puheen havaitsemisen ja fonologisten pulmien taustalla.Avainsanat: aivot, dysleksia, kuulohavainto, puheKeywords: auditory perception, brain, dyslexia, speec

Infant event-related potentials to speech are associated with prelinguistic development

Neural auditory processing and prelinguistic communication build the foundation for later language development, but how these two are associated is not well known. The current study investigated how neural speech processing is associated with the level and development of prelinguistic skills in 102 infants. We recorded event-related potentials (ERPs) in 6-months-olds to assess the neural detection of a pseudoword (obligatory responses), as well as the neural discrimination of changes in the pseudoword (mismatch responses, MMRs). Prelinguistic skills were assessed at 6 and 12 months of age with a parental questionnaire (Infant-Toddler Checklist). The association between the ERPs and prelinguistic skills was examined using latent change score models, a method specifically constructed for longitudinal analyses and explicitly modeling intra-individual change. The results show that a large obligatory P1 at 6 months of age predicted strong improvement in prelinguistic skills between 6 and 12 months of age. The MMR to a frequency change was associated with the concurrent level of prelinguistic skills, but not with the improvement of the skills. Overall, our results highlight the strong association between ERPs and prelinguistic skills, possibly offering opportunities for early detection of atypical linguistic and communicative development.Peer reviewe

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