The Mirror Alignment and Control System for CT5 of the H.E.S.S. experiment

The High Energy Stereoscopic System (H.E.S.S.) experiment is one of the largest observatories for gamma-ray astronomy. It consists of four telescopes with a reflecting dish diameter of 12m (CT1 to CT4) and a newer large telescope (CT5) with a reflecting dish diameter of 28m. On CT5 876 mirror facets are mounted, all of them equipped with a computerised system for their alignment. The design of the mirror alignment and control system and the performance of the hardware installed to the telescope are presented. Furthermore the achieved point spread function of the telescope over the full operational elevation range as well as the stability of the alignment over an extended period of time are shown

Functional analysis of epialleles in diploid and tetraploid Arabidopsis thaliana

Polyploidie, die Multiplikation des diploiden Chromosomensatzes, tritt bei Pflanzen häufig auf. Die Entstehung polyploider Pflanzen ist oft mit Änderungen ihrer Genom- als auch ihrer Epigenomorganisation verbunden. Die transkriptionelle Geninaktivierung (transcriptional gene silencing, TGS) führt zu kompletten und erblichen Verlust der Expression vorher aktiver Gene. Durch TGS können Epiallele entstehen, die in ihrer DNA Sequenz übereinstimmen, aber unterschiedlich exprimiert werden. Das inaktive Epiallel kann durch epigenetische Wechselwirkungen die aktive Form in trans beeinflussen, was zu einer epigenetischen Angleichung der beiden Epiallele führt. Dieser Erbgang folgt nicht den Mendelschen Regeln und ähnelt der Paramutation. Da epigenetische Diversität direkten Einfluss auf die phänotypische Vielfalt und den Wachstumserfolg von Pflanzen hat, sind die zugrundeliegenden, regulatorischen Mechanismen von großer Bedeutung für natürliche Evolution und Pflanzenzüchtung. Die vorliegende Arbeit beschäftigt sich mit Prinzipien der polyploidie-assoziierten transkriptionellen Geninaktivierung (polyploidy-associated transcriptional gene silencing, paTGS) eines transgenen Resistenzgens (Hygromycinphosphotransferase, HPT), das in aktiven oder inaktiven Epiallel-Varianten in Arabidopsis thaliana auftritt. Um den paTGS-Mechanismus und die allelische Interaktion zu analysieren, habe ich die genetischen und epigenetischen Merkmale der Epiallele in diploidem und tetraploidem Hintergrund und nach Mutagenese charakterisiert. Die genetische Struktur der Epiallele wurde in Linien mit aktiven, inaktiven und strukturell veränderten HPT Genen untersucht. Ich konnte spezifische epigenetische Modifikationen (DNA-Methylierung und Histonmodifikationen) der Epiallele nachweisen. Da Paramutation in Mais im funktionellen Zusammenhang mit regulatorischen RNAs (small RNAs) steht, analysierte ich die Fähigkeit des Transgens, solche RNAs oder Antisense-Transkripte zu generieren. Zusätzlich wurde der Einfluss vieler epigenetischer Mutanten auf das inaktive Epiallel untersucht. In dieser Arbeit habe ich gezeigt, dass sich die beiden Epiallelformen in ihrer epigenetischen Zusammensetzung entsprechend ihrer Expressionsmuster, unterscheiden. Small RNAs oder Antisense-Transkripte dürften bei der Regulation der Epiallele keine Rolle spielen. Verschiedene strukturelle Änderungen im inaktiven Epiallel führten zur Reaktivierung der HPT Expression, was auf einen starken Einfluss der DNA Sequenz, vermutlich über die Chromatinorganisation hindeutet.Polyploidy, a condition of containing more than two sets of homologous chromosomes, is frequent among higher plants. The formation of polyploids is often associated with genomic rearrangements and epigenetic changes, such as transcriptional gene silencing (TGS), resulting in heritable loss of gene expression from previously active genes. TGS can lead to the formation of epialleles, which are identical in DNA sequence, but differ in expression states. Silent epialleles can exert non-Mendelian behavior in a paramutation-like interaction, silencing their expressed counterpart in trans and thereby leading to functional epigenetic homozygosity. Since epigenetic diversity may create phenotypic diversity and determine plant performance, these regulatory mechanisms are likely important for natural evolution and plant breeding. In the experimental work for this thesis I investigated the principles of polyploidy-associated transcriptional gene silencing (paTGS) in a model system based on transgenic Arabidopsis thaliana lines, containing a resistance marker gene (hygromycin phosphotransferase, HPT) in active or inactive epiallelic state. I characterized genetic and epigenetic features of the epialleles in diploid, tetraploid and mutant lines, aiming to identify the mechanisms of paTGS and the allelic interaction. The structure of the epialleles is investigated in expressing and non-expressing lines, as well as in mutant lines with structural rearrangements of the epialleles. I was able to portray the epigenetic state of epialleles including DNA methylation and several histone modifications. Since paramutation in maize is functionally linked with enzymatic amplification of small RNAs, I analyzed the role of the transgene and the RNA features for their ability to produce small RNAs or antisense transcripts. Numerous Arabidopsis mutants affecting well-defined elements of epigenetic regulation allowed further mechanistic investigations of epigenetic phenomena in polyploids. In summary, I was able to show that the epialleles differ in their chromatin modification according to the differences in their expression states. No evidence for an involvement of small RNAs or antisense transcripts in silencing was observed. However, structural changes within the silent epiallele led to reactivation of the inactive HPT gene, indicating strong impact of the sequence composition on epiallelic gene regulation

Sensitivity of the Goldfish Motion Detection System Revealed by Incoherent Random Dot Stimuli: Comparison of Behavioural and Neuronal Data

Global motion detection is one of the most important abilities in the animal kingdom to navigate through a 3-dimensional environment. In the visual system of teleost fish direction-selective neurons in the pretectal area (APT) are most important for global motion detection. As in all other vertebrates these neurons are involved in the control of slow phase eye movements during gaze stabilization. In contrast to mammals cortical pathways that might influence motion detection abilities of the optokinetic system are missing in teleost fish.To test global motion detection in goldfish we first measured the coherence threshold of random dot patterns to elicit horizontal slow phase eye movements. In addition, the coherence threshold of the optomotor response was determined by the same random dot patterns. In a second approach the coherence threshold to elicit a direction selective response in neurons of the APT was assessed from a neurometric function. Behavioural thresholds and neuronal thresholds to elicit slow phase eye movements were very similar, and ranged between 10% and 20% coherence. In contrast to these low thresholds for the optokinetic reaction and APT neurons the optomotor response could only be elicited by random dot patterns with coherences above 40%.Our findings suggest a high sensitivity for global motion in the goldfish optokinetic system. Comparison of neuronal and behavioural thresholds implies a nearly one-to-one transformation of visual neuron performance to the visuo-motor output. In addition, we assume that the optomotor response is not mediated by the optokinetic system, but instead by other motion detection systems with higher coherence thresholds

The CO2 SINK Boreholes for Geological Storage Testing

Europe’s first onshore scientific carbon dioxide storage testing project CO2SINK (CO2 Storage by Injection into a Natural saline aquifer at Ketzin) is performed in a saline aquifer in NE Germany. The major objectives of CO2SINK are the advancement of the science and practical processes for underground storage of carbon dioxide, and the provision of operational field results to aid in the development of standards for CO2 geological storage. Three boreholes (one injection well and two observation wells) have been drilled in2007, each to a depth of about 800 m. The wells are completed as “smart” wells containing a variety of permanent downhole sensing equipment, which has proven its functionality during its baseline surveys. The injection of CO2 is scheduled for spring 2008 and is intended to last up to two years to allow for monitoring of migration and fate of the injected gas through a combination of downhole monitoring with surface geophysical surveys. This report summarizeswell design, drilling, coring, and completion operations

Preliminary hydrogeological interpretation of the Aigion area from the AIG10 borehole data

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Direct Observation and Analysis of Spin Dependent Transport of Single Atoms in a 1D Optical Lattice

We have directly observed spin-dependent transport of single cesium atoms in a 1D optical lattice. A superposition of two circularly polarized standing waves is generated from two counter propagating, linearly polarized laser beams. Rotation of one of the polarizations by $\pi$ causes displacement of the $\sigma^{+}$- and $\sigma^{-}$-lattices by one lattice site. Unidirectional transport over several lattice sites is achieved by rotating the polarization back and forth and flipping the spin after each transport step. We have analyzed the transport efficiency over 10 and more lattice sites, and discussed and quantified relevant error sources.Comment: 5 pages, 4 figure

CCL17 protects against viral myocarditis by suppressing the recruitment of regulatory T cells

Background Viral myocarditis is characterized by leukocyte infiltration of the heart and cardiomyocyte death. We recently identified C-C chemokine ligand (CCL) 17 as a proinflammatory effector of C-C chemokine receptor 2-positive macrophages and dendritic cells that are recruited to the heart and contribute to adverse left ventricular remodeling following myocardial infarction and pressure overload. Methods and Results Mouse encephalomyocarditis virus was used to investigate the function of CCL17 in a viral myocarditis model

Echtzeitdetektion von Punktmutationen mit DNA-Chips am Beispiel des SULT1A1*213-SNP

Der Identifizierung von Punktmutationen im menschlichen Genom kommt eine hohe Bedeutung zu. Die Entdeckung einer Vielzahl von SNPs ('single nucleotide polymorphisms'), also Mutationen einzelner Basen, die definitionsgemäß bei mehr als 1% der Bevölkerung auftreten, und die Erkenntnis, dass SNPs die Nebenwirkungen von Medikamenten determinieren können, führte zu der Vision einer 'personalisierten Medizin': Der Patient erhält nach einer Genotypisierung das für ihn verträglichste Medikament verschrieben. Notwendige Bedingung für das neue Paradigma ist eine schnelle und hochdurchsatzfähige DNA-Analytik. Da bis zu 3 Millionen von SNPs beim Menschen vermutet werden (www.snp.cshl.org), ist das etablierte Verfahren mittels PCR-Amplifikation, Restriktionsenzymverdau und Elektrophorese nicht praktikabel. Neben den zum Massenscreening geeigneten, spezialisierten MALDI- (z.B. Sequenom ®) und Primer-Extension-Verfahren (z.B. Orchid Biocomputer ®) wird insbesondere die DNA-Chip-Technologie als vielversprechende Methode für mittlere bis hohe Durchsätze und Vor-Ort-Anwendungen angesehen. Der Einsatz dieses Verfahrens zum SNP-Screening wird am Beispiel des SULT1A1*213-SNPs demonstriert. Das SULT1A1-Gen beim Menschen kodiert für eine cytosolische, thermostabile Phenol-Sulfotransferase (P-PST, EC 2.8.2.1), die in der Leber durch Sulfonierung von phenolischen Substraten Biosynthese und Entgiftungsfunktionen ausübt. Bisher wurden drei Punktmutationen in diesem Gen entdeckt (Raftogianis 1997). Die Variation *213Arginin nach *213Histidin, die bei ca. 37% der (kaukasischen) Bevölkerung auftritt, führt zu einem deutlich verschiedenen Phänotyp (geringere Aktivität, geringere Thermostabilität, Engelke 2000) und wird mit Übergewicht in Zusammenhang gebracht