Stochastic Acceleration in Relativistic Parallel Shocks

(abridged) We present results of test-particle simulations on both the first and the second order Fermi acceleration at relativistic parallel shock waves. We consider two scenarios for particle injection: (i) particles injected at the shock front, then accelerated at the shock by the first order mechanism and subsequently by the stochastic process in the downstream region; and (ii) particles injected uniformly throughout the downstream region to the stochastic process. We show that regardless of the injection scenario, depending on the magnetic field strength, plasma composition, and the employed turbulence model, the stochastic mechanism can have considerable effects on the particle spectrum on temporal and spatial scales too short to be resolved in extragalactic jets. Stochastic acceleration is shown to be able to produce spectra that are significantly flatter than the limiting case of particle energy spectral index -1 of the first order mechanism. Our study also reveals a possibility of re-acceleration of the stochastically accelerated spectrum at the shock, as particles at high energies become more and more mobile as their mean free path increases with energy. Our findings suggest that the role of the second order mechanism in the turbulent downstream of a relativistic shock with respect to the first order mechanism at the shock front has been underestimated in the past, and that the second order mechanism may have significant effects on the form of the particle spectra and its evolution.Comment: 14 pages, 11 figures (9 black/white and 2 color postscripts). To be published in the ApJ (accepted 6 Nov 2004

Apex avian species as sentinels for legacy and emerging contaminants in northern Baltic Sea coastal food webs

Anthropogenic contamination is a wide-spread environmental problem. In addition to persistent, bioaccumulative and toxic legacy contaminants, emerging contaminants with unknown environmental behaviour are causing concern. Many contaminants biomagnify in food webs, meaning that highest concentrations of contaminants are found in the apex species. Trophic dynamics of contaminants may differ depending on the properties of the contaminant, environment, and species composing a particular food web. In this thesis, I examine the current state of metal and organohalogen contamination in the Finnish Baltic coastal food webs, focussing on three avian sentinel species: the white-tailed eagle (Haliaeetus albicilla), the great cormorant (Phalacrocorax carbo), and the common eider (Somateria mollissima). In Chapter I, I investigate whether nestlings of white-tailed eagles and great cormorants act as sentinels for metal contamination associated with acidic sulphate soils. Compared to the control areas, I find higher concentrations of aluminium and cobalt in white-tailed eagles and of copper and manganese in great cormorants from the acidic sulphate soil areas. These results indicate that acidic sulphate soils are a source of certain metals for white-tailed eagle and great cormorant nestlings; there are, however, differences in metal exposure between these species. In Chapter II, I study the trophic transfer of mercury (Hg) between the benthic and pelagic food chains of the Archipelago Sea food web. The rate of trophic magnification of Hg was higher in the pelagic food chain than in the benthic food chain when the homeotherm birds were excluded from statistical models. In Chapter III, I investigate organohalogen contamination in the Archipelago Sea food web. I find that several organohalogen compounds biomagnify in the food web. Concentrations were generally highest in bird species, particularly the white-tailed eagle. As with the Hg models, statistical fit of the trophic magnification models of organohalogen compounds increased when removing birds from the data. In addition to the legacy contaminants, I also found emerging contaminant perfluoroethylcyclohexane sulfonate in the white-tailed eagle, great cormorant, and two fish species. This thesis demonstrates that different ecological and ecophysiological traits of the species play a role in the contaminant exposure and food web dynamics of the contaminants.Ravintoverkkojen huippulajit haitta-aineiden ilmentäjinä Suomen rannikolla Ympäristön kemiallinen saastuminen on vakava maailmanlaajuinen ongelma. Pysyvien, eliöihin kertyvien ja myrkyllisten, laajalle levinneiden haitta-aineiden lisäksi huolta aiheuttavat uudet haitta-aineet, joiden käyttäytymistä ympäristössä ei vielä tunneta. Monet haitta-aineet rikastuvat ravintoverkossa, jolloin korkeimmat pitoisuudet löytyvät ravintoverkon huipulla olevista lajeista. Haitta-aineiden käyttäytyminen ravintoverkossa riippuu aineen kemiallisista ominaisuuksista sekä ympäristön ja kyseisen ravintoverkon koostavien lajien piirteistä. Tässä väitöskirjassa tutkin metallien ja orgaanisten halogeeniyhdisteiden aiheuttamaa saastumista Suomen rannikon ravintoverkoissa keskittyen kolmeen ilmentäjälajiin: merikotkaan (Haliaeetus albicilla), merimetsoon (Phalacrocorax carbo) ja haahkaan (Somateria mollissima). Luvussa I tutkin ilmentävätkö merikotkan ja merimetson pesäpoikaset happamista sulfaattimaista peräisin olevia metallipäästöjä. Merikotkan poikasissa alumiinin ja koboltin pitoisuudet, ja merimetson poikasissa kuparin ja mangaanin pitoisuudet olivat koholla happamien sulfaattimaiden läheisyydessä syntyneissä ja kasvaneissa poikasissa verrattuna kontrollialueiden poikasiin. Tulokset osoittavat, että happamat sulfaattimaat ovat joidenkin metallien lähde merikotkan ja merimetson poikasille. Metalleille altistumisessa oli kuitenkin eroa lajien välillä. Luvussa II tutkin elohopean kulkeutumista Saaristomeren ravintoverkon benttisessä ja pelagisessa ravintoketjussa. Elohopea rikastui nopeammin trofiatasoa kohden pelagisessa ravintoketjussa verrattuna benttiseen ravintoketjuun, kun tasalämpöisiä lintuja ei sisällytetty mukaan rikastumismalleihin. Luvussa III tutkin orgaanisia halogeeniyhdisteitä Saaristomeren ravintoverkossa. Useat tutkituista aineista rikastuivat ravintoverkossa. Useimpien aineiden pitoisuudet olivat korkeimmat linnuissa, etenkin merikotkassa. Samoin kuin elohopean rikastumismalleissa, halogeeniyhdisteiden rikastumismallien selitysaste parani, kun lintuja ei sisällytetty malleihin. Tavanomaisten, Itämeren ympäristössä jo vuosia esiintyneiden haitta-aineiden lisäksi löysin perfluorietyylisykloheksaani sulfonaattia merikotkista, merimetsoista ja kahdesta kalalajista. Väitöskirja korostaa eri ekologisten ja ekofysiologisten ominaisuuksien roolia lajien haittaainealtistuksessa ja haitta-aineiden käyttäytymisessä ravintoverkoissa

Determination of starch by iodine colorimetry

In the iodine colorimetric method of Paloheimo gently dextrinized solutions are prepared of pure starch and of the analysis sample. One of the optical cells (A) of the comparator is provided with a solution made of pure starch and the other (B) with the solution to be analysed. Both solutions have the same iodine concentration. The solution in B must have a intensive colour than that in A. Solution B is then diluted with an iodinewater solution of the same iodine concentration as in the solutions A and B. When these solutions have attained the same colour it is concluded that also the starch concentration is the same and the starch content of the sample can be calculated. The results obtained by this method are compared with those obtained with the amyloglucosidase method of Salo. Table 1 shows that the two methods give very similar results. Different circumstances which might possibly interfere with the colorimetric starch determinations are studied. It was observed that attention must be paid to the intensity of boiling when the 0.05-N H2SO4 dextrinizing solutions are boiled. If the intensity is very different in the comparison solution and the solution to be analysed, considerable errors may occur. If the sample contains added chalk the neutralizing power of the sample should be determined beforehand and the normality of the solution adjusted to 0.05. If the sample contains acid it should be extracted beforehand with 80-% ethanol. —Cellulose and sugars have no influence on the results, nor have plant proteins or proteins of milk. However, if greater amounts of protein were added, a casein preparation intended for laboratory animals showed an obvious disturbing effect, as did gelatin and meat protein. – Faeces did not appear to have an interfering influence in colorimetric starch determination. The iodine colorimetric sensitiveness of starch solutions was also studied. It appeared that 0.18 mg of dextrinized potato starch already deepened the colour of 100 ml dilute iodine solution in room temperature. For wheat starch the corresponding minimum concentration was 0.27 mg/100 ml. In 3° the concentration limit was even lower, 0.05—0.09 mg/100 ml. In all the above mentioned studies the author has used as comparator essential parts of a Pulfrich photometer. A proper comparator (Fig. 1) can also be made by any skilled optician

Midwives as expert witnesses in the 18th-century Finnish courts of justice

In this article, I will explore how legalized Finnish midwives acted as expert witnesses in court hearings before 1809, how they worded the statements they gave in court, on what grounds they decided a woman was pregnant or had given birth, and what signs they considered as indicating a miscarriage or the birth of a full-term infant. Their work as expert witnesses relied on their midwifery training as well as their learned knowledge of the anatomy of the female body and the physiology of birth. Ultimately, their knowledge was supported by contemporary guidebooks on midwifery and forensic medicine. As expert witnesses, the trained and legalized midwives of the eighteenth century can be seen as having been legally literate women, who had a duty to provide oral or written evidence to the court and other instances who demanded it. Midwives were capable of using understandable medical and legal terminology in terms of the processing of the court case in their testimony. The forensic examinations carried out by legalized midwives and the expert witness statements they gave also demonstrate the professional skills and expertise of these women.. Their testimonies also show that they were familiar with the characteristics of infanticide referred to in the Swedish medical and forensic literature

Surface expression, peptide repertoire, and thermostability of chicken class I molecules correlate with peptide transporter specificity.

The chicken major histocompatibility complex (MHC) has strong genetic associations with resistance and susceptibility to certain infectious pathogens. The cell surface expression level of MHC class I molecules varies as much as 10-fold between chicken haplotypes and is inversely correlated with diversity of peptide repertoire and with resistance to Marek's disease caused by an oncogenic herpesvirus. Here we show that the average thermostability of class I molecules isolated from cells also varies, being higher for high-expressing MHC haplotypes. However, we find roughly the same amount of class I protein synthesized by high- and low-expressing MHC haplotypes, with movement to the cell surface responsible for the difference in expression. Previous data show that chicken TAP genes have high allelic polymorphism, with peptide translocation specific for each MHC haplotype. Here we use assembly assays with peptide libraries to show that high-expressing B15 class I molecules can bind a much wider variety of peptides than are found on the cell surface, with the B15 TAPs restricting the peptides available. In contrast, the translocation specificity of TAPs from the low-expressing B21 haplotype is even more permissive than the promiscuous binding shown by the dominantly expressed class I molecule. B15/B21 heterozygote cells show much greater expression of B15 class I molecules than B15/B15 homozygote cells, presumably as a result of receiving additional peptides from the B21 TAPs. Thus, chicken MHC haplotypes vary in several correlated attributes, with the most obvious candidate linking all these properties being molecular interactions within the peptide-loading complex (PLC).This work was originally supported by core funding to the Basel Institute for Immunology (which was founded and supported by F. Hoffmann-La Roche & Co. Ltd., CH-4005 Basel, Switzerland), then by core funding to the Institute for Animal Health [now re-branded the Pirbright Institute, sponsored by the Biotechnology and Biological Sciences Research Council (BBSRC) of the UK] and finally by programme grant 089305 from the Wellcome Trust to JK.This is the author accepted manuscript. The final version is available from PNAS via http://dx.doi.org/10.1073/pnas.151185911

Solar interacting protons versus interplanetary protons in the core plus halo model of diffusive shock acceleration and stochastic re-acceleration

With the first observations of solar γ-rays from the decay of pions, the relationship of protons producing ground level enhancements (GLEs) on the Earth to those of similar energies producing the γ-rays on the Sun has been debated. These two populations may be either independent and simply coincident in large flares, or they may be, in fact, the same population stemming from a single accelerating agent and jointly distributed at the Sun and also in space. Assuming the latter, we model a scenario in which particles are accelerated near the Sun in a shock wave with a fraction transported back to the solar surface to radiate, while the remainder is detected at Earth in the form of a GLE. Interplanetary ions versus ions interacting at the Sun are studied for a spherical shock wave propagating in a radial magnetic field through a highly turbulent radial ray (the acceleration core) and surrounding weakly turbulent sector in which the accelerated particles can propagate toward or away from the Sun. The model presented here accounts for both the first-order Fermi acceleration at the shock front and the second-order, stochastic re-acceleration by the turbulence enhanced behind the shock. We find that the re-acceleration is important in generating the γ-radiation and we also find that up to 10% of the particle population can find its way to the Sun as compared to particles escaping to the interplanetary space