Quantification of the expected residual dispersion of the MICADO Near-IR imaging instrument

MICADO, a near-infrared imager for the Extremely Large Telescope, is being designed to deliver diffraction limited imaging and 50 micro arcsecond (${\mu}$as) astrometric accuracy. MICADO employs an atmospheric dispersion corrector (ADC) to keep the chromatic elongation of the point spread function (PSF) under control. We must understand the dispersion and residuals after correction to reach the optimum performance. Therefore, we identified several sources of chromatic dispersion that need to be considered for the MICADO ADC. First, we compared common models of atmospheric dispersion to investigate whether these models remain suitable for MICADO. We showed that the differential dispersion between common atmospheric models and integration over the full atmosphere is less than 10 ${\mu}$as for most observations in H-band. We then performed an error propagation analysis to understand the uncertainty in the atmospheric dispersion as a function of atmospheric conditions. In addition, we investigated the impact of photometric color on the astrometric performance. While the differential refraction between stars within the same field of view can be significant, the inclusion of an ADC rendered this effect negligible. For MICADO specifically, we found that the current optomechanical design dominates the residual dispersion budget of 0.4 milli arcseconds (mas), with a contribution of 0.31 mas due to the positioning accuracy of the prisms and up to 0.15 mas due to a mismatch between the dispersive properties of the glass and the atmosphere. We found no showstoppers in the design of the MICADO ADC for achieving 50 ${\mu}$as relative astrometric accuracy.Comment: Submitted to Monthly Notices of the Royal Astronomical Society. Contains 11 pages and 12 figure

Demonstration of an imaging technique for the measurement of PSF elongation caused by Atmospheric Dispersion

Elongation of the point spread function due to atmospheric dispersion becomes a severe problem for high resolution imaging instruments, if an atmospheric dispersion corrector is not present. In this work we report on a novel technique to measure this elongation, corrected or uncorrected, from imaging data. By employing a simple diffraction mask it is possible to magnify the chromatic elongation caused by the atmosphere and thus make it easier to measure. We discuss the theory and design of such a mask and report on two proof of concept observations using the 40 cm Gratama telescope at the University of Groningen. We evaluate the acquired images using a geometric approach, a forward modelling approach and from a direct measurement of the length of the point spread function. For the first two methods we report measurements consistent with atmospheric dispersion models to within 0.5 arcsec. Direct measurements of the elongation do not prove suitable for the characterisation of atmospheric dispersion. We conclude that the addition of this type of diffraction mask can be valuable for measurements of PSF elongation. This can enable high precision correction of atmospheric dispersion on future instruments.Comment: Accepted for publication in the Monthly Notices of the Royal Astronomical Society. Contains 11 pages, 11 figures, 2 table

LVU och Europakonventionen - om lagligheten av att omhänderta unga över 18 år med stöd av LVU

Care provided by the Swedish social services shall, as a starting point, always be based on voluntary participation. Each person’s autonomy and integrity must be respected. However, interventions of these rights may be justified under certain circumstances. By applying the Act containing Special Provisions on the Care of Young Persons (hereinafter LVU), a child may be committed to compulsory care on account of his or her home environment, or because of his or her behaviour. LVU complements the Social Services Act (hereinafter SoL), which regulates voluntary care. Although LVU is primarily applicable in relation to children, young persons between 18 and 20 years may, under certain circumstances, be committed to compulsory care. 3 § LVU sets out the conditions for compulsory care on account of a person’s behaviour. It is on this ground that persons over the age of 18 may be committed to care. Such care may continue until that person’s 21st birthday. The compulsory care, as provided for by LVU, constitutes a significant intervention in a person’s life. The care may be provided in a family home or in an institutionalised accommodation. There are also certain accommodations, in which the young person is put under particular supervision. This form of accommodation may be used for the care of persons over 18 years. The European Convention on Human Rights was incorporated with Swedish law in 1995. Article 5 of the Convention contains the right to liberty and security. The article provides an exhaustive list of exceptions to the prohibition of depravation of liberty. The two categories that are particularly relevant to examine for the purpose of this thesis are, detention of minors, and detention for medical or social reasons, of drug addicts or alcoholics. The purpose of this thesis is to examine the legality of committing persons over the age of 18 to compulsory care in accordance with LVU, in relation to article 5 of the European Convention on Human Rights.Som utgångspunkt skall vården genom Socialtjänsten grundas på frivillighet, med respekt för varje människas självbestämmanderätt och integritet. Trots det avsteg från frivillighet, och det ingrepp i en persons såväl integritet, som självbestämmanderätt ett tvångsomhändertagande innebär, anses sådana ingripanden ändå vara försvarliga under vissa omständigheter. Genom tillämpning av lag (1990:52) med särskilda bestämmelser om vård av unga, kan barn tvångsvis omhändertas på grund av sin hemmiljö, alternativt på grund av barnets eget beteende. Trots att LVU i första hand är tillämplig i förhållande till barn, kan även unga över 18 år, som ännu ej har fyllt 20 år, bli föremål för ett tvångsomhändertagande. Det är 3 § LVU som reglerar möjligheten att omhänderta en person på grund av dennes eget beteende, och det är denna grund som kan aktualisera vård av personer över 18 år. Sådan vård får som längst fortgå fram till dess att den unge fyller 21 år. Den vård som ges i enlighet med LVU innebär en mycket ingripande åtgärd i den omhändertagne personens liv. Vården kan ges i ett familjehem, eller i ett hem för vård eller boende. Det finns även hem med särskild tillsyn, som kan aktualiseras för personer som har beretts vård på grund av sitt eget beteende. Lagen (1994:1219) om den europeiska konventionen angående skydd för de mänskliga rättigheterna och de grundläggande friheterna, trädde i kraft den 1 januari 1995, genom vilken Europakonventionen inkorporerades med svensk rätt. Sedan dess gäller konventionen som lag här i landet. Artikel 5 i Europakonventionen reglerar rätten till frihet och personlig säkerhet. I en uttömmande lista framgår de kategorier under vilka ett frihetsberövande kan anses vara konventionsenligt. De två grunder som är mest relevanta för detta arbete är den som behandlar möjligheten att frihetsberöva underåriga för att de skall undergå skyddsuppfostran, samt grunden för frihetsberövande av missbrukare av alkohol eller droger. Arbetet syftar till att undersöka huruvida svensk lagstiftning i LVU gällande omhändertaganden av unga över 18 år, är förenlig med artikel 5 i Europakonventionen

RNA structures regulating nidovirus RNA synthesis

Viruses depend on their host cell for the production of their progeny. The genetic information that is required to regulate this process is contained in the viral genome. In the case of plus-stranded RNA viruses, like nidoviruses, the RNA genome is directly involved in translation (resulting in the synthesis of viral enzymes), replication, transcription and encapsidation into progeny virions. The multifunctional nature of these viral RNA genomes requires the tight control of all these processes for which they are equipped with RNA sequence motifs and higher order RNA structures. At 25-32 kilobases, nidoviruses possess the largest known RNA genomes. One characteristic of nidoviruses is that in infected cells they produce a nested set of subgenomic (sg) mRNAs. The sg mRNAs of two nidovirus families, arteri- and coronaviruses, consist of two RNA stretches that are noncontiguous in the genome. It was demonstrated that primary and higher order RNA structures play a crucial role during the synthesis of these special sg mRNAs. The obtained knowledge of arterivirus RNA synthesis, formed the basis for an virus inhibitor study in which regulatory RNA sequences were targeted in an attempt to block virus replication in cell culture using phosphorodiamidate morpholino oligomers (P-PMOs).Leiden University Medical HospitalNWO-CW 99-010Moleculaire basis van virus pathogenese en antivirale strategiee