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Some of the best compression ratios for text compression are provided by the PPM (prediction by partial matching) class of algorithms. These algorithms are based on arithmetic coding using a fixed-depth Markov chain model of the source, i.e., the subsequence of symbols generated in any state s of the source is assumed to be the output of a memoryless subsource w=w(s). One of the most crucial steps
We present a coding theoretic approach to the problem the initial state recovery of a linear feedback shift register when a noisy output sequence is given. Our work is focused on the investigation of the asymptotical behaviour of the recovery process. We give two algorithms which will work for shift registers with arbitrary feedback polynomial. Furthermore, the number of required given noisy symbo
We present an analysis of some known cartesian authentication codes and their modification into authentication codes with secrecy, with transmission rate R = r/n, where n = 2, 3, …, and 1 ≤ r ≤ n - 1 using (n - r)(r + 1) q-ary key digits. For this purpose we use a grouping technique. Essentially the same key grouping technique is used for the construction of codes that withstand spoofing attacks o
Heterogeneous catalyst surfaces are dynamic entities that respond rapidly to changes in their local gas environment, and the dynamics of the response is a decisive factor for the catalysts’ action and activity. Few probes are able to map catalyst structure and local gas environment simultaneously under reaction conditions at the timescales of the dynamic changes. Here we use the CO oxidation react
Scaling down material synthesis to crystalline structures only few atoms in size and precisely positioned in device configurations remains highly challenging, but is crucial for new applications e.g., in quantum computing. We propose to use the sidewall facets of larger III–V semiconductor nanowires (NWs), with controllable axial stacking of different crystal phases, as templates for site-selectiv
Free-electron lasers (FELs) can produce radiation in the short wavelength range extending from the extreme ultraviolet (XUV) to the X-rays with a few to a few tens of femtoseconds pulse duration. These facilities have enabled significant breakthroughs in the field of atomic, molecular, and optical physics, implementing different schemes based on two-color photoionization mechanisms. In this articl
”Conflict in Colours” är en avhandling som fokuserar på historiska narrativs roll i att legitimera och bibehålla konflikter, samt hur dessa narrativ påverkar den begynnande fredsprocessen. Genom att studera det inneboende kulturella våldet i dessa narrativ har jag visat hur kulturellt våld är en essentiell del i att legitimera, påverka och bibehålla det antagonistiska förhållandet mellan parterna Conflict in Colours is a book about the role of cultural violence in maintaining and transferring conflict situations by investigating republican and loyalist murals in Belfast during the Troubles and the Northern Irish peace process. During several decades, the people of Northern Ireland have endured warlike situations before the peace agreement in 1998. This doctoral thesis examines the ways/ho
The effect of two different pair correlation functions, used to model multiple scattering in a slab filled with randomly located spherical particles, is investigated. Specifically, the Percus-Yevick approximation is employed and a comparison with the simple hole correction is made. The kernel entries of the hole correction have an analytic solution, which makes the numerical solution of the integr
Polycyclic aromatic hydrocarbons (PAHs) play an important role in interstellar chemistry and are subject to high energy photons that can induce excitation, ionization, and fragmentation. Previous studies have demonstrated electronic relaxation of parent PAH monocations over 10–100 femtoseconds as a result of beyond-Born-Oppenheimer coupling between the electronic and nuclear dynamics. Here, we inv
Specific heat and small-angle neutron scattering measurements have been performed on the superconductor β-PdBi2. Whereas models with a uniform gap do not yield an adequate description of the temperature-dependent specific heat and the temperature and magnetic field dependence of the SANS intensity, fits to a heuristic model with two gap parameters agree well with both data sets. The fact that two
Nonlinear pulse post-compression, mainly enabled by self-phase modulation (SPM), opens new avenues towards high peak power laser pulses at high average power while bypassing the need for a gain medium with large bandwidth. However, SPM-induced spectral broadening typically introduces spectral amplitude modulations as well as a chirp of third and higher orders, limiting the temporal contrast of the
High-average power Ytterbium (Yb) laser systems are playing an increasingly important role in ultrafast science e.g. as pump lasers for optical parametric amplifiers or directly as ultrafast sources. The gain bandwidth of Yb limits the pulse duration to a few 100 fs up to about 1 ps. However, many applications, such as attosecond physics or X-ray Free Electron Laser (FEL) science, would greatly be
The power of attosecond pump-probe spectroscopy combined with advanced detection schemes, such as photoelectron/ion coincidence spectrometers and time-resolved photoelectron emission microscopy (PEEM), can be unleashed by properly accounting for the repetition rate of the source. In this work, we present a high-repetition rate (200 kHz) attosecond pulse source that opens up for exploring phenomena
The gut microbiome is increasingly recognized for its impact on host fitness, but it remains poorly understood how naturally variable environments influence gut microbiome diversity and composition. We studied changes in the gut microbiome of ten genotypes of water fleas Daphnia magna in submerged mesocosm enclosures in a eutrophic lake over a period of 16 weeks, from early summer to autumn. The m
