Radiokemian relevanssi : Tulevien radiokemistien käsityksiä

Radiokemi står inför en väldokumenterad utbildning och rekryteringskris. Äldre radiokemister går i pension och färre unga studerar radiokemi. I sin tur leder detta till brist på nyutbildade radiokemister, såväl som förlust av historisk kunskap (eftersom kunskap ofta inte förmedlas). Här analyserade vi relevansen av studien av radiokemi i högre utbildning genom framtida radiokemists uppfattningar. Vårt mål var att ge inblick i framtida radiokemisternas tänkande och ge några tydliga exempel på hur man stöder relevans. En kvalitativ studie genomfördes genom en forskningsfråga: Vilka uppfattningar om relevans upplever framtida radiokemister om radiokemistudier och radiokemi som fält? Vi använde relevansmodellen av Stuckey et al. (2013) som ram för relevans. Detta valdes eftersom det erbjuder en omfattande definition av relevans inklusive individuella, samhälleliga och yrkesmässiga dimensioner. Uppgifterna samlades in från forskarstudenter i radiokemi (magister- och doktorsexamen) genom användning av ett kvalitativt frågeformulär som utformades med den valda relevansramen. Totalt deltog 15 framtida radiokemister i studien. Uppgifterna analyserades genom teoribaserad innehållsanalys med användning av det valda relevansramverket. Enligt våra uppgifter upplever framtida radiokemister att deras universitetsstudier och kemifältet är mycket relevanta. De upplevde att ämnen för radiokemi är intressanta (individuell relevans), fältet har stor samhällseffekt genom radiofarmaceutika, energilösningar och miljöproblemlösning (samhällsrelevans) och att deras professionella framtid var tydlig, till exempel ett jobb inom kärnkraftsområdet industri (yrkesrelevans). Dessa resultat kan användas för studentrekrytering och för att utveckla radiokemiundervisning mot en mer relevant inriktning.Radiokemialla on koulutus- ja rekrytointikriisi. Vanhemmat radiokemistit siirtyvät eläkkeelle, ja yhä vähemmän nuoria valitsee radiokemiaa opiskelualakseen. Asetelman vuoksi on pulaa pätevistä radiokemisteistä, ja hiljaista tietoa häviää. Tässä tutkimuksessa selvitetään tulevien radiokemistien kokemuksia radiokemian relevanssista. Tavoitteena on selvittää, miksi radiokemiaa valinneet opiskelijat ovat alan valinneet. Tutkimus oli luonteeltaan laadullinen tutkimus. Aineisto kerättiin sähköpostikyselyillä sisältäen kaksi aineistonkeruusykliä. Ainesot analysoitiin teoriapohjaisella sisällnöanalyysillä tunnetun Stuckeyn et al. (2013) relevanssia hyödyntäen. Tutkimuksen mukaan tulevat radiokemistit kokivat alan erittäin relevanssiksi. He kokivat, että radiokemian olevan mielenkiintoista (henkilökohtainen relevanssi), radiokemian yhteiskunnallisen merkityksen olevan suuri esim. lääke- ja energiateollisuuden kautta (yhteiskunnallinen relevanssi) ja heillä oli selkeä kuva tulevaisuuden työllistymisestä (ammatillinen relevanssi). Tutkimuksen tuloksia voidaan käyttää opiskelijoiden rekrytointiin ja radiokemian opetuksen relevanssin vahvistamiseen.Radiochemistry faces a well-documented training and recruitment crisis. Older radiochemists are retiring, and fewer young people are studying radiochemistry. In turn, this is leading to a shortage in newly qualified radiochemists, as well as a loss of historical knowledge (as know-how is often not passed-on). Here, we analyzed the relevance of the study of radiochemistry in higher education through future radiochemists’ perceptions. Our objective was to provide insights into future radiochemists’ thinking and provide some clear examples on how to support relevance. A qualitative study was conducted through a research question: What perceptions of relevance do future radiochemists experience about radiochemistry studies and radiochemistry as a field? We used the relevance model of Stuckey et al. (2013) as the relevance framework. This was selected because it offers a comprehensive definition of relevance including individual, societal, and vocational dimensions. The data were gathered from postgraduate radiochemistry students (masters and Ph.D. level) through use of a qualitative questionnaire that was designed using the selected relevance framework. In total, 15 future radiochemists participated in the study. The data were analyzed through theory-based content analysis using the selected relevance framework. According to our data, future radiochemists experience their university study and the chemistry field as being highly relevant. They experienced that radiochemistry topics are interesting (individual relevance), the field has great societal impact through radiopharmaceuticals, energy solutions, and environmental problem-solving (societal relevance), and that their professional future was clear, for example, a job in the nuclear industry (vocational relevance). These results can be used in student recruitment and in developing radiochemistry teaching toward a more relevance-oriented direction.Peer reviewe

The role of E+A and post-starburst galaxies – II. Spectral energy distributions and comparison with observations

‘The definitive version is available at www3.interscience.wiley.com '. Copyright Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2009.15036.xIn a previous paper, we have shown that the classical definition of E+A galaxies excludes a significant number of post-starburst galaxies. We suggested that analysing broad-band spectral energy distributions (SEDs) is a more comprehensive method to select and distinguish post-starburst galaxies than the classical definition of measuring equivalent widths of (Hδ) and [O ii] lines. In this paper, we will carefully investigate this new method and evaluate it by comparing our model grid of post-starburst galaxies to observed E+A galaxies from the MORPHS catalogue. In the first part, we investigate the UV-optical-NIR (near-infrared) SEDs of a large variety in terms of progenitor galaxies, burst strengths and time-scales of post-starburst models and compare them to undisturbed spiral, S0 and E galaxies as well as to galaxies in their starburst phase. In the second part, we compare our post-starburst models with the observed E+A galaxies in terms of Lick indices, luminosities and colours. We then use the new method of comparing the model SEDs with SEDs of the observed E+A galaxies. We find that the post-starburst models can be distinguished from undisturbed spiral, S0 and E galaxies and galaxies in their starburst phase on the basis of their SEDs. It is even possible to distinguish most of the different post-starbursts by their SEDs. From the comparison with observations, we find that all observed E+A galaxies from the MORPHS catalogue can be matched by our models. However, only models with short decline time-scales for the star formation rate are possible scenarios for the observed E+A galaxies in agreement with our results from the first paper.Peer reviewe

AGN Jet-induced Feedback in Galaxies. II. Galaxy colours from a multicloud simulation

We study the feedback from an AGN on stellar formation within its host galaxy, mainly using one high resolution numerical simulation of the jet propagation within the interstellar medium of an early-type galaxy. In particular, we show that in a realistic simulation where the jet propagates into a two-phase ISM, star formation can initially be slightly enhanced and then, on timescales of few million years, rapidly quenched, as a consequence both of the high temperatures attained and of the reduction of cloud mass (mainly due to Kelvin-Helmholtz instabilities). We then introduce a model of (prevalently) {\em negative} AGN feedback, where an exponentially declining star formation is quenched, on a very short time scale, at a time t_AGN, due to AGN feedback. Using the Bruzual & Charlot (2003) population synthesis model and our star formation history, we predict galaxy colours from this model and match them to a sample of nearby early-type galaxies showing signs of recent episodes of star formation (Kaviraj et al. 2007). We find that the quantity t_gal - t_AGN, where t_gal is the galaxy age, is an excellent indicator of the presence of feedback processes, and peaks significantly around t_gal - t_AGN \approx 0.85 Gyr for our sample, consistent with feedback from recent energy injection by AGNs in relatively bright (M_{B} \lsim -19) and massive nearby early-type galaxies. Galaxies that have experienced this recent feedback show an enhancement of 3 magnitudes in NUV(GALEX)-g, with respect to the unperturbed, no-feedback evolution. Hence they can be easily identified in large combined near UV-optical surveys.Comment: 18 pages, 16 figures, accepted for publication on MNRAS. This version includes revisions after the referee's repor

Cholesterol-loaded nanoparticles ameliorate synaptic and cognitive function in Huntington's disease mice

Brain cholesterol biosynthesis and cholesterol levels are reduced in mouse models of Huntington's disease (HD), suggesting that locally synthesized, newly formed cholesterol is less available to neurons. This may be detrimental for neuronal function, especially given that locally synthesized cholesterol is implicated in synapse integrity and remodeling. Here, we used biodegradable and biocompatible polymeric nanoparticles (NPs) modified with glycopeptides (g7) and loaded with cholesterol (g7-NPs-Chol), which per se is not blood-brain barrier (BBB) permeable, to obtain high-rate cholesterol delivery into the brain after intraperitoneal injection in HD mice. We report that g7-NPs, in contrast to unmodified NPs, efficiently crossed the BBB and localized in glial and neuronal cells in different brain regions. We also found that repeated systemic delivery of g7-NPs-Chol rescued synaptic and cognitive dysfunction and partially improved global activity in HD mice. These results demonstrate that cholesterol supplementation to the HD brain reverses functional alterations associated with HD and highlight the potential of this new drug-administration route to the diseased brain

Isothermal Microcalorimetry, a New Tool to Monitor Drug Action against Trypanosoma brucei and Plasmodium falciparum

Isothermal microcalorimetry is an established tool to measure heat flow of physical, chemical or biological processes. The metabolism of viable cells produces heat, and if sufficient cells are present, their heat production can be assessed by this method. In this study, we investigated the heat flow of two medically important protozoans, Trypanosoma brucei rhodesiense and Plasmodium falciparum. Heat flow signals obtained for these pathogens allowed us to monitor parasite growth on a real-time basis as the signals correlated with the number of viable cells. To showcase the potential of microcalorimetry for measuring drug action on pathogenic organisms, we tested the method with three antitrypanosomal drugs, melarsoprol, suramin and pentamidine and three antiplasmodial drugs, chloroquine, artemether and dihydroartemisinin, each at two concentrations on the respective parasite. With the real time measurement, inhibition was observed immediately by a reduced heat flow compared to that in untreated control samples. The onset of drug action, the degree of inhibition and the time to death of the parasite culture could conveniently be monitored over several days. Microcalorimetry is a valuable element to be added to the toolbox for drug discovery for protozoal diseases such as human African trypanosomiasis and malaria. The method could probably be adapted to other protozoan parasites, especially those growing extracellularly

Gravitationally lensed high redshift galaxies in the field of 1E0657-56

We present images and long-slit spectra obtained with FORS1 at UT1 of the VLT centered on the gravitational arc of the galaxy cluster 1E0657-56 (z = 0.296). The cluster is one of the hottest, most massive clusters known so far and acts as a powerful gravitational telescope, amplifying the flux of background sources by up to a factor of 17. We present photometric results together with the spectra of the gravitational arc (z = 3.24) and four additional amplified high redshift objects (z = 2.34 to 3.08) that were also included in the slit by chance coincidence. A magnification map has been obtained from a lens model derived from the multiple image systems. We compare our observed spectra with models and briefly discuss the stellar contents of these galaxies. Furthermore we measured the equivalent widths of the CIV 1550 and SiIV 1400 absorption lines for the objects behind 1E0657-56 studied here, as well as for some additional starburst galaxies (nearby and at high z). For CIV we find an increasing absorption equivalent width with decreasing redshift. We discuss whether this correlation could be related to the increase of metallicity with the age of the universe.Comment: accepted to be published in A&A, 10 pages, 9 figures Latex2e using aa.cls; Fig. 1 available with better resolution at http://www.lsw.uni-heidelberg.de/~dmehlert/publications.htm

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Limited response of NK92 cells to Plasmodium falciparum-infected erythrocytes

<p>Abstract</p> <p>Background</p> <p>Mechanisms by which anti-malarial immune responses occur are still not fully clear. Natural killer (NK) cells are thought to play a pivotal role in innate responses against <it>Plasmodium falciparum</it>. In this study, the suitability of NK92 cells as models for the NK mechanisms involved in the immune response against malaria was investigated.</p> <p>Methods</p> <p>NK92 cells were assessed for several signs of activation and cytotoxicity due to contact to parasites and were as well examined by oligonucleotide microarrays for an insight on the impact <it>P. falciparum</it>-infected erythrocytes have on their transcriptome. To address the parasite side of such interaction, growth inhibition assays were performed including non-NK cells as controls.</p> <p>Results</p> <p>By performing microarrays with NK92 cells, the impact of parasites on a transcriptional level was observed. The findings show that, although not evidently activated by iRBCs, NK92 cells show transcriptional signs of priming and proliferation. In addition, decreased parasitaemia was observed due to co-incubation with NK92 cells. However, such effect might not be NK-specific since irrelevant cells also affected parasite growth <it>in vitro</it>.</p> <p>Conclusions</p> <p>Although NK92 cells are here shown to behave as poor models for the NK immune response against parasites, the results obtained in this study may be of use for future investigations regarding host-parasites interactions in malaria.</p

Chemically consistent evolution of galaxies: II. Spectrophotometric evolution from zero to high redshift

We present a new generation of chemically consistent evolutionary synthesis models for galaxies of various spectral types from E through Sd. The models follow the chemical enrichment of the ISM and take into account the increasing initial metallicity of successive stellar generations using recently published metallicity dependent stellar evolutionary isochrones, spectra and yields. Our first set of closed-box 1-zone models does not include any spatial resolution or dynamics. For a Salpeter initial mass function (IMF) the star formation rate(SFR) and its time evolution are shown to successfully parameterise spectral galaxy types E, ..., Sd. We show how the stellar metallicity distribution in various galaxy types build up with time to yield after $\sim 12$ Gyr agreement with stellar metallicity distributions observed in our and other local galaxies. The models give integrated galaxy spectra over a wide wavelength range (90.9\AA - 160$\mu$m), which for ages of $\sim 12$ Gyr are in good agreement not only with observed broad band colours but also with template spectra for the respective galaxy types. Using filter functions for Johnson-Cousins, as well as for HST broad band filters in the optical and Bessel & Brett's NIR filter system, we calculate the luminosity and colour evolution of model galaxies over a Hubble time. Including a standard cosmological model and the attenuation by intergalactic hydrogen we present evolutionary and cosmological corrections as well as apparent luminosities in various filters over the redshift range from z $\sim 5$ to the present for our galaxy types and compare to earlier models using single (=solar) metallicity input physics only. We also present a first comparison of our cc models to HDF data.(Abridged abstract)Comment: 13 pages, accepted for publication in Astronomy and Astrophysic

<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties

Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues – a realisation of the Tycho-Gaia Astrometric Solution (TGAS) – and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr−1 for the proper motions. A systematic component of ∼0.3 mas should be added to the parallax uncertainties. For the subset of ∼94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr−1. For the secondary astrometric data set, the typical uncertainty of the positions is ∼10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼0.03 mag over the magnitude range 5 to 20.7. Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data