Exchange of impact-generated dust between the Galilean moons

Abstract. The dust environment of Jupiter consists of various dynamically different parts: tenuous dust rings around the planet, dust streams emanating from the volcanic plumes of Io, impact-generated dust clouds around the Galilean moons, and dilute populations of dust in the outer parts of the Jupiter system. The main source of dust material in the jovian system is impact ejection from the surface of (especially the smaller) moons, caused by high-velocity micrometeoroid impacts. The dust particles are relatively short-lived, and their orbital evolution is influenced by various different forces, including gravitational forces, solar radiation forces, electromagnetic forces and drag due to plasma in the system. In the vicinity of the Galilean moons there exists a faint ring, consisting of dust material ejected from the surface of Galilean moons by micrometeoroid impacts. In contrast to the dust detached from the small moons in the inner Jupiter system, most of the material ejected from the Galilean moons moves on ballistic trajectories and re-impacts the surface of the moons. From the dust material ejected from the surface of the Galilean moons, only a small fraction manages to escape into circumjovian orbits. These escaped grains form a broad, but extremely faint ring, concentrated between the orbits of Io and Europa. Historically, a good majority of research in the Jovian dust environment has focused on the dynamics of the ring system, whereas dust in the vicinity of the Galilean satellites has attracted less attention. However, the measurements in this region by the Galileo dust instrument and the detection of impact-generated clouds have stipulated new interest, especially in view of the forthcoming missions to the Jupiter system, like the Jupiter Icy Moons Explorer by the European Space Administration, and the Europa Clipper -mission by the National Aeronautics and Space Administration, both planned for launch in the 2020s. The goal of the thesis was to derive the fluxes of dust on the surfaces of each of the Galilean moons, using the results on the dust environment of the moons from the Jovian Meteoroid Environment Model (JMEM). To this end, a program using the software Interactive Data Language was created, that directly employs functions from JMEM and then constructs the fluxes on a given surface element of a moon. To visualize the final results, contour plots of the flux distributions on the surface of the four moons were produced, explaining the effect of different parameters for the dust configuration. To support the interpretation of the final dustmap results in terms of orbital motion and evolution of dust, a simple analytical model using a fixed semimajor axis and a model distribution of eccentricities for the simulated orbits of dust, was used to produce a theoretical distribution of impact angles of dust on the surface of the Galilean moons. Through the created contour plots, leading-trailing asymmetries for the flux of dust impacting on the surface of the moons were identified and interpreted in light of this analytical model

Estimation of inbreeding depression on female fertility in the Finnish Ayrshire population

Single nucleotide polymorphism (SNP) data enable the estimation of inbreeding at the genome level. In this study, we estimated inbreeding levels for 19,075 Finnish Ayrshire cows genotyped with a low-density SNP panel (8K). The genotypes were imputed to 50K density, and after quality control, 39,144 SNPs remained for the analysis. Inbreeding coefficients were estimated for each animal based on the percentage of homozygous SNPs (F-PH), runs of homozygosity (F-ROH) and pedigree (F-PED). Phenotypic records were available for 13,712 animals including non-return rate (NRR), number of inseminations (AIS) and interval from first to last insemination (IFL) for heifers and up to three parities for cows, as well as interval from calving to first insemination (ICF) for cows. Average F-PED was 0.02, F-ROH 0.06 and F-PH 0.63. A correlation of 0.71 was found between F-PED and F-ROH, 0.66 between F-PED and F-PH and 0.94 between F-ROH and F-PH. Pedigree-based inbreeding coefficients did not show inbreeding depression in any of the traits. However, when F-ROH or F-PH was used as a covariate, significant inbreeding depression was observed; a 10% increase in F-ROH was associated with 5days longer IFL0 and IFL1, 2weeks longer IFL3 and 3days longer ICF2 compared to non-inbred cows.Peer reviewe

Characterization of TiAlSiN/TiAlSiON/SiO2 optical stack designed by modelling calculations for solar selective applications

Preparation and characterization of TiAlSiN/TiAlSiON/SiO2 solar selective absorber is reported in this contribution. All layers were deposited in a continuous mode using a industrial equipment, the nitride and oxynitride were prepared by reactive magnetron sputtering and the SiO2 layer by Plasma Enhanced Chemical Vapour Deposition. The optical constants of individual layers were calculated by modelling of spectral transmittance and reflectance of the individual layers. The three layer stack absorber was then designed using those optical properties. The thickness of the individual layers was optimized until a solar absorptance of 96% was obtained resulting in a total thickness of about 200 nm, deposited in copper and extruded aluminium absorbers. An emissivity of 5 % for an absorber temperature of 100 ºC was obtained by analyzing the measuring data from a FTIR spectrometer with integrating sphere. After test duration of 600 h, the samples subjected to a thermal annealing at 278 ºC in air showed a performance criterion (PC) below 4% for, while the samples in the humidity tests showed a PC below 2 %.Savo Sola

Optical characterization of TiAlN/TiAlON/SiO2 absorber for solar selective applications

Characterization of a TiAlN/TiAlON/SiO2 tandem absorber is reported in this contribution. The first two layers were deposited by magnetron sputtering and the third layer was prepared by plasma enhanced chemical vapour deposition (PECVD). The optimization was performed by determining the optical constants of individual layers by first measuring spectral transmittance and reflectance of the individual layers. Subsequently the measuring spectra were fitted using the SCOUT software and dielectric function of each layer was determined. The three layer stack absorber on copper was then designed using those optical properties. The thickness of the individual layers was optimized until a solar absorptance of 95.5% was obtained resulting in a total thickness of about 215 nm (65 nm/51 nm/100 nm for the individual layers, respectively). A thermal emittance of 5% for an absorber temperature of 100 °C was obtained by analyzing the measuring data from a FTIR spectrometer with integrating sphere. During continuous thermal annealing at 278 °C for 600 h the absorptance decreased by 0.4%Savo Sola

Extracting Conditionally Heteroskedastic Components using Independent Component Analysis

In the independent component model, the multivariate data are assumed to be a mixture of mutually independent latent components. The independent component analysis (ICA) then aims at estimating these latent components. In this article, we study an ICA method which combines the use of linear and quadratic autocorrelations to enable efficient estimation of various kinds of stationary time series. Statistical properties of the estimator are studied by finding its limiting distribution under general conditions, and the asymptotic variances are derived in the case of ARMA-GARCH model. We use the asymptotic results and a finite sample simulation study to compare different choices of a weight coefficient. As it is often of interest to identify all those components which exhibit stochastic volatility features we suggest a test statistic for this problem. We also show that a slightly modified version of the principal volatility component analysis can be seen as an ICA method. Finally, we apply the estimators in analysing a data set which consists of time series of exchange rates of seven currencies to US dollar. Supporting information including proofs of the theorems is available online

Sliced average variance estimation for multivariate time series

Supervised dimension reduction for time series is challenging as there may be temporal dependence between the response y and the predictors . Recently a time series version of sliced inverse regression, TSIR, was suggested, which applies approximate joint diagonalization of several supervised lagged covariance matrices to consider the temporal nature of the data. In this paper, we develop this concept further and propose a time series version of sliced average variance estimation, TSAVE. As both TSIR and TSAVE have their own advantages and disadvantages, we consider furthermore a hybrid version of TSIR and TSAVE. Based on examples and simulations we demonstrate and evaluate the differences between the three methods and show also that they are superior to apply their iid counterparts to when also using lagged values of the explaining variables as predictors

A design of selective solar absorber for high temperature applications

This study presents a design of multilayer solar selective absorber for high temperature applications. The optical stack of this absorber is composed of four layers deposited by magnetron sputtering on stainless steel substrates. The first is a back-reflector tungsten layer, which is followed by two absorption layers based on CrAlSiNx/ CrAlSiOyNx structure for phase interference. The final layer is an antireflection layer of SiAlOx. The design was theoretically modelled with SCOUT software using transmittance and reflectance curves of individual thin layers, which were deposited on glass substrates. The final design shows simultaneously high solar absorbance = 95.2 % and low emissivity ε= 9.8% (at 400 ºC) together with high thermal stability at 400 ºC, in air, and 600 ºC in vacuum for 650 h.The authors acknowledge the support of FCT in the framework of the Strategic Funding UID/FIS/04650/2013 and the financial support of FCT, POCI and PORL operational programs through the project POCI-01-0145- FEDER-016907 (PTDC/CTM-ENE/2882/2014), co-financed by European community fund FEDER.info:eu-repo/semantics/publishedVersio

Solar selective absorbers based on Al2O3:W cermets and AlSiN/AlSiON layers

Solar selective coatings based on double Al2O3:W cermet layers and AlSiN/AlSiON bilayer structures were prepared by magnetron sputtering. Both were deposited on stainless steel substrates using a metallic tungsten (W) layer as back reflector. The coating stacks were completed by an antireflection (AR) layer composed of Al2O3, SiO2, or AlSiOx. Spectrophotometer measurements, X-Ray diffraction, Scanning electron microscopy, Energy Dispersive X-Ray Spectroscopy and Rutherford Backscattering Spectrometry were used to characterize the optical properties, crystalline structure, morphology and composition of these coatings. The spectral optical constants of the single layers were calculated from the reflectance and transmittance measurements and used to design the optical stack. The coatings exhibit a solar absorptance of 93%-95% and an emissivity of 7%-10% (at 400 ºC). The coatings also exhibit excellent thermal stability, with small changes in the optical properties of the coating during heat-treatments at 400 ºC in air for 2500 h and at 580 ºC in vacuum for 850 h. The coating based on the AlSiN/AlSiON bilayer structure was obtained with an Al:Si ratio of 2.5:1. These coatings revealed similar performance as the one obtained with coatings based on Al2O3:W cermet layers.The authors acknowledge the funding from the Finnish Funding Agency for Technology and Innovation, Tekes, and from FEDER funds through the “Programa Operacional Factores de Competitividade – COMPETE” and from national funds by FCT- “Fundação para a Ciência e a Tecnologia”, under project no. PEst-C/FIS/UI0607/2011.info:eu-repo/semantics/publishedVersio

Birth cohort effects on the quantity and heritability of alcohol consumption in adulthood : a Finnish longitudinal twin study

Aims To estimate birth cohort effects on alcohol consumption and abstinence in Finland and to test differences between birth cohorts in genetic and environmental sources of variation in Finnish adult alcohol use. Design The Older Finnish Twin Cohort longitudinal survey study 1975-2011. Setting Finland. Participants A total of 26 121 same-sex twins aged 18-95 years (full twin pairs at baseline n = 11 608). Measurements Outcome variables were the quantity of alcohol consumption (g/month) and abstinence (drinking zero g/month). Predictor variables were 10-year birth cohort categories and socio-demographic covariates. In quantitative genetic models, two larger cohorts (born 1901-20 and 1945-57) were compared. Findings Multi-level models in both sexes indicated higher levels of alcohol consumption in more recent birth cohorts and lower levels in earlier cohorts, compared with twins born 1921-30 (all P < 0.003). Similarly, compared with twins born 1921-30, abstaining was more common in earlier and less common in more recent cohorts (all P < 0.05), with the exception of men born 1911-20. Birth cohort differences in the genetic and environmental variance components in alcohol consumption were found: heritability was 21% [95% confidence interval (CI) = 0-56%] in the earlier-born cohort of women [mean age 62.8, standard deviation (SD) = 5.3] and 51% (95% CI = 36-56%) in a more recent cohort (mean age 60.2, SD = 3.7) at the age of 54-74. For men, heritability was 39% (95% CI = 27-45%) in both cohorts. In alcohol abstinence, environmental influences shared between co-twins explained a large proportion of variation in the earlier-born cohort (43%, 95% CI = 23-63%), whereas non-shared environmental (54%, 95% CI = 39-72%) and additive genetic influences (40%, 95% CI = 13-61%) were more important among more recent cohorts of men and women. Conclusion The contribution of genetic and environmental variability to variability in alcohol consumption in the Finnish population appears to vary by birth cohort.Peer reviewe