[en] The decay of the radioisotope ¹²⁵I into ¹²⁵Te is typically followed by the emission of two groups of approximately 10 electrons each. In deoxyribonucleic acid (DNA) with ¹²⁵I incorporated, these electrons produce various types of damage to DNA, e.g. single and double strand breaks. They occur through direct actions of physical tracks, or indirect actions of radicals produced in water. Among the direct actions one should consider not only the excitation and ionization of DNA by electrons but also the neutralization of highly charged ^125mTe ions with electrons from neighboring molecules. The present work begins with a detailed description of electron tracks with the use of the PARTRAC code, compares results with recent experiments, and concludes with a firm assessment of the contribution to the strand break yields from the neutralization effect. (orig.)

No abstract available

[en] ATLAS is a general purpose detector presently under construction for the Large Hadron Collider (LHC) at CERN. In the first few years of operation, LHC will run at low luminosity (10³³ cm^-2s^-1) which is optimal for B-physics study. This thesis is concerned with the design of the second level B-physics trigger. The B-physics trigger relies on the partial reconstruction of B decays in order to select semi-exclusively channels of interest. After the tagged muon from one of bb-bar pair is confirmed, track reconstruction in the inner detector will be performed to search for the interesting decays of the second b quark. This thesis presents applications of a tree algorithm to search for tracks in the precision detector. The tracking algorithm constructs tracks from locally related space points. The algorithm has been implemented in C++. There are two applications which are initialised by the pixel full-scan and TRT full-scan. The performance of track reconstruction has been studied and optimised including efficiency, resolution, execution time, etc, for seeding from either the inner pixel or outer continuous tracking detectors. After tracks have been reconstructed using the tree algorithm, B-physics event selection is performed. The trigger selection for the B_d⁰ → π⁺π^- channel has been studied. The efficiency and trigger rate for this channel have been evaluated. This thesis also contains a study of the data preparation process for track reconstruction. This includes implementation of a recursive clustering algorithm in the pixel detector and development of a data pre-selection algorithm. These two algorithms are shown to be efficient and fast. The Readout Buffer (ROB) is an important part of the trigger and DAQ system. Parts of the Buffer, the ROB-in and the PCI bus, have been modelled using the Ptolemy modelling tool. Comparisons with measurements of PCI bus performance are given. (author)

[en] The harmonic superspace formalism has been used to construct the consistent chiral anomaly in N = 1, d = 6 supersymmetric Yang-Mills thoery. The expressions of the gauge anomaly Δ/sub s//sup phi/ and of the supersymmetric anomaly Δ/sub SUSY//sup phi/ are given together with the consistent condition. 7 refs

[en] DNA strand breakage induced by decay of ¹²⁵I incorporated into the pyrimidine of a small piece of DNA with a specific base pair sequence has been investigated theoretically and experimentally (Lobachevsky and Martin 2000a, 2000b; Nikjoo et al., 1996; Pomplun and Terrissol, 1994; Charlton and Humm, 1988). Recently an attempt was made to analyse the DNA kinks in a CAP-DNA complex with ¹²⁵I induced DNA strand breakage (Karamychev et al., 1999). This method could be used as a so called radioprobing for such DNa distortions like other chemical and biological assays, provided that it has been tested and confirmed in a corresponding theoretical simulation. In the measurement, the distribution of the first breaks on the DNA strands starting from their labeled end can be determined. Based on such first breakage distributions, the simulation calculation could then be used to derive information on the structure of a given DNA-protein complex. The biophysical model PARTRAC has been applied successfully in simulating DNA damage induced by irradiation (Friedland et al., 1998; 1999). In the present study PARTRAC is adapted to a DNA-protein complex in which a specific sequence of 30 base pairs of DNA is connected with the catabolite gene activator protein (CAP). This report presents the first step of the analysis in which the CAP-DNA model used in NIH is overlaid with electron track structures in liquid water and the strand breaks due to direct ionization and due to radical attack are simulated. The second step will be to take into account the neutralization of the heavily charged tellurium and the protective effect of the CAP protein against radical attack. (orig.)

[en] Measurements of the field and temperature dependence of the frequency-dependent susceptibility χ(ω) the thermoremanent magnetization (TRM) and the isothermal remanent magnetization (IRM) have been performed on a series of mixed ruthenates with chemical formula Ca_xSr_1-xRuO₃. The susceptibility data are analysed within the framework of a static scaling theory. Estimates for the critical exponents γ, β, and δ are consistent with a second-order transition from a paramagnetic to a ferromagnetic state, with exchange bond disorder. The remanence data are analysed within the framework of a Preisach model, which incorporates an explicit reference to the critical temperature T_C. The analysis shows that, under certain conditions, the TRM and the IRM yield independent scans of the Preisach distribution along two orthogonal directions in the Preisach plane, the TRM along the bias field axis H_s and the IRM along the dissipation field axis H_d

[en] Atoms and ions confined with electric and optical fields form the basis of many current quantum simulation and computing platforms. When excited to high-lying Rydberg states, long-ranged dipole interactions emerge which strongly couple the electronic and vibrational degrees of freedom through state-dependent forces. This vibronic coupling and the ensuing hybridization of internal and external degrees of freedom manifest through clear signatures in the many-body spectrum. In this talk, we briefly discuss the recent results in Ref. [1] wherein we consider the case of two trapped Rydberg ions that realize a quantum Rabi model due to the interaction between the relative vibration and Rydberg states. We proceed to demonstrate that this hybridization can be probed by radio frequency spectroscopy and discuss observable spectral signatures at finite temperatures and for larger ion crystals. [1]. J. W. P. Wilkinson, W. Li, and I. Lesanovsky, Spectral signatures of vibronic coupling in trapped cold atomic Rydberg systems, arXiv:2311.16998 (2023)

[en] Semiconductor detectors can provide better spectroscopic performance than scintillation or gas-filled detectors because of the small ionization energy required to generate each electron-hole pair. Indeed, cryogenically cooled high-purity germanium detectors have played the dominant role whenever the best gamma-ray spectroscopy is required. A decades-long search for other semiconductor detectors that could provide higher stopping power and could operate at room temperature has been ongoing. Wide-band-gap semiconductors, such as CdTe, CdZnTe, and HgI₂, have captured the most attention. However, the use of these semiconductors in detectors has been hindered primarily by problems of charge trapping and material nonuniformity. Introduced in 1994, single-polarity charge sensing on semiconductor detectors has shown great promise in avoiding the hole-trapping problem, and the newly demonstrated three-dimensional position-sensing technique can significantly mitigate the degradation of energy resolution due to the nonuniformity of detector material. In addition, three-dimensional position sensitivity will provide unique imaging capabilities of these gamma-ray spectrometers. These devices are of interest for nuclear nonproliferation, medical imaging, gamma-ray astronomy, and high-energy physics applications. This paper reports the latest results using second-generation three-dimensional position-sensitive semiconductor spectrometers. The improvements over the first generation devices include: (1) Larger volume; (2) Improved anode design; (3) More reliable connections; (4) Enhanced electronic capability; and (5) Measurement of electron drift times. The new detectors and readout electronics (from IDE AS) are being assembled and tested

[en] Carbon nanotube junctions are of great interest in the fundamental research and nanoelectronic applications. Identical carbon nanotube Y junctions have been successfully synthesized by pyrolysis of methane over cobalt supported on magnesium oxide. The Y junctions have very straight arms with uniform diameters, and the angles between the three arms are close to 120^o. Based on the analysis on the structure of the Y junctions the growth mechanism has been discussed. The fact that all the Y junctions grow in a similar way may be very important in the development of nanoelectronic devices

[en] The E. coli catabolite gene activator protein (CAP)-DNA complex with ¹²⁵I located at the position of the H5 atom of the cytosine near the centre was incorporated into the PARTRAC track structure code. DNA strand breaks due to irradiation were calculated by track structure and radical attack simulations: strand breaks due to neutralisation of the highly charged ¹²⁵Te ion were derived from a semi-empirical distribution. According to the calculations, the neutralisation effect dominates the strand breakage frequency at 2 bases away from the ¹²⁵I decay site on both strands. The first breakage distribution counted from a ³²P labelled end on the strand with ¹²⁵I agreed well with experimental data, but on the opposite strand, the calculated distribution is more concentrated around the decay site and its yield is about 20% larger than the measured data. (author)