Elektronispektrometrin kalibrointi

Tämä pro gradu -tutkielma käsittelee BepiColombo-luotaimen SIXS-instrumentin testaamisessa käytettävän elektronispektrometrin kalibrointia. Tarkoitus on pienillä parannuksilla luoda jo olemassaolevasta spektrometristä paremmin tarkoitusta vastaavaja valmis mittalaitteisto. Kalibraatiossa käytetään hyväksi 90Sr -isotooppia, joka hajoaa beta-hajoamisella ja tuottaa näin ollen elektroneja. Säteilylähteen ja työssä käytettävän pintaesteilmaisimen välistä kulmaa vaihdellaan ja tarkastellaan ilmaisimeen osuvien elektronien energioiden käyttäytymistä kulman funktiona. Kulman muuttamiseen tarvitaan askelmoottoria, jonka aiheuttama virhe kulmassa on mitattava ennen spektrometrimittauksia. Tulokset osoittavat virheen olevan 0,12 astetta täyttä 360 asteen ympyrää kohden. Jotta tyhjiökammiossa sijaitsevan spektrometrin lähteen ja ilmaisimen välinen kulma voidaan tietää tarkasti, on kammiossa oltava jokin kalibrointipiste, jonka absoluuttinen kulma on tarkasti tiedossa. Tällaisen pisteen määrittämisessä käytetään hyväksi Hallin ilmiötä. Menetelmällä kalibrointipiste voidaan määritellä 0,4 asteen tarkkuudella. Elektronit kulkeutuvat lähteestä ilmaisimeen magneettikentän kautta, jossa ne taipuvat energiasta riippuvan kaarevuussäteen mukaisesti. Ratojen luonteen selvittämiseksi kentän profiili mitattiin, jolloin selvisi, että vuontiheys kentässä vaihtelee keskipisteestä mitatun etäisyyden funktiona. Profiilista voidaan erottaa kaksi pääosaa: lähellä keskipistettä kentän vuontiheyden muutos on lineaarista, kun taas kauempana kenttä on käytännössä homogeeninen. Elektronien ratoja on suhteellisen helppo laskea homogeenisessa kentässä, kun taas lineaarisesti muuttuvassa kentässä tilanne on paljon mutkikkaampi. Siksi tutkielmassa tyydytään vain toteamaan, että elektronien energian on oltava yli 200 keV, jotta ne kulkisivat myös heterogeenisen kentän kautta. Voidaan osoittaa, että ilmaisimen ja säteilylähteen välinen kulma on tällöin noin 100 astetta. Kulmakalibraatiomittaukset suoritettiin välillä 80-160 astetta kymmenen asteen välein. Työn tuloksena syntyi käsitys elektronien energian kulmariippuvuudesta spektrometrissä. Kulmakalibraatiomittaussarja voidaan tulevaisuudessa uusia esimerkiksi uudella ilmaisimen ja magneettikenttärakenteen etäisyyden arvolla.Siirretty Doriast

Large differences in catch per unit of effort between two minnow trap models

Background Little is known about variation in catch per unit of effort (CPUE) in stickleback fisheries, or the factors explaining this variation. We investigated how nine-spined stickleback (Pungitius pungitius) CPUE was influenced by trap model by comparing the CPUEs of two very similar minnow trap models fished side-by-side in a paired experimental design. Results The galvanized trap type (mean CPUE = 1.31 fish h–1) out-fished the black trap type (mean CPUE = 0.20 fish h–1) consistently, and yielded on average 81% more fish. Conclusions The results demonstrate that small differences in trap appearance can have large impacts on CPUE. This has implications for studies designed to investigate abundance and occurrence of fish using minnow traps.Peer reviewe

The impact on global magnetohydrodynamic simulations from varying initialisation methods : results from GUMICS-4

We investigate the effects of different initialisation methods of the GUMICS-4 global magnetohydrodynamic (MHD) simulation to the dynamics in different parts of the Earth's magnetosphere and hence compare five 12 h simulation runs that were initiated by 3 h of synthetic data and followed by 9 h of solar wind measurements using the OMNI data as input. As a reference, we use a simulation run that includes nearly 60 h of OMNI data as input prior to the 9 h interval examined with different initialisations. The selected interval is a high-speed stream event during a 10-day interval (12-22 June 2007). The synthetic initialisations include stepwise, linear and sinusoidal functions of the interplanetary magnetic field with constant density and velocity values. The results show that the solutions converge within 1 h to give a good agreement in both the bow shock and the magnetopause position. However, the different initialisation methods lead to local differences which should be taken into consideration when comparing model results to satellite measurements.Peer reviewe

GUMICS-4 analysis of interplanetary coronal mass ejection impact on Earth during low and typical Mach number solar winds

We study the response of the Earth's magnetosphere to fluctuating solar wind conditions during interplanetary coronal mass ejections (ICMEs) using the Grand Unified Magnetosphere-Ionosphere Coupling Simulation (GUMICS-4). The two ICME events occurred on 15-16 July 2012 and 29-30 April 2014. During the strong 2012 event, the solar wind upstream values reached up to 35 particles cm(-3), speeds of up to 694 km s(-1), and an interplanetary magnetic field of up to 22 nT, giving a Mach number of 2.3. The 2014 event was a moderate one, with the corresponding upstream values of 30 particles cm(-3), 320 km s(-1) and 10 nT, indicating a Mach number of 5.8. We examine how the Earth's space environment dynamics evolves during both ICME events from both global and local perspectives, using well-established empirical models and in situ measurements as references. We show that on the large scale, and during moderate driving, the GUMICS-4 results are in good agreement with the reference values. However, the local values, especially during high driving, show more variation: such extreme conditions do not reproduce local measurements made deep inside the magnetosphere. The same appeared to be true when the event was run with another global simulation. The cross-polar cap potential (CPCP) saturation is shown to depend on the Alfven-Mach number of the upstream solar wind. However, care must be taken in interpreting these results, as the CPCP is also sensitive to the simulation resolution.Peer reviewe

A principal component meta-analysis on multiple anthropometric traits identifies novel loci for body shape

Large consortia have revealed hundreds of genetic loci associated with anthropometric traits, one trait at a time. We examined whether genetic variants affect body shape as a composite phenotype that is represented by a combination of anthropometric traits. We developed an approach that calculates averaged PCs (AvPCs) representing body shape derived from six anthropometric traits (body mass index, height, weight, waist and hip circumference, waist-to-hip ratio). The first four AvPCs explain >99% of the variability, are heritable, and associate with cardiometabolic outcomes. We performed genome-wide association analyses for each body shape composite phenotype across 65 studies and meta-analysed summary statistics. We identify six novel loci: LEMD2 and CD47 for AvPC1, RPS6KA5/C14orf159 and GANAB for AvPC3, and ARL15 and ANP32 for AvPC4. Our findings highlight the value of using multiple traits to define complex phenotypes for discovery, which are not captured by single-trait analyses, and may shed light onto new pathways

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

Publisher Correction: Sex-dimorphic genetic effects and novel loci for fasting glucose and insulin variability.

A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-21276-3</jats:p

Sex-stratified Genome-wide Association Studies Including 270,000 Individuals Show Sexual Dimorphism in Genetic Loci for Anthropometric Traits

Peer reviewe

A principal component meta-analysis on multiple anthropometric traits identifies novel loci for body shape

Large consortia have revealed hundreds of genetic loci associated with anthropometric traits, one trait at a time. We examined whether genetic variants affect body shape as a composite phenotype that is represented by a combination of anthropometric traits. We developed an approach that calculates averaged PCs (AvPCs) representing body shape derived from six anthropometric traits (body mass index, height, weight, waist and hip circumference, waist-to-hip ratio). The first four AvPCs explain >99% of the variability, are heritable, and associate with cardiometabolic outcomes. We performed genome-wide association analyses for each body shape composite phenotype across 65 studies and meta-analysed summary statistics. We identify six novel loci: LEMD2 and CD47 for AvPC1, RPS6KA5/C14orf159 and GANAB for AvPC3, and ARL15 and ANP32 for AvPC4. Our findings highlight the value of using multiple traits to define complex phenotypes for discovery, which are not captured by single-trait analyses, and may shed light onto new pathways.Peer reviewe