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A detailed flammability evaluation of different materials used in the nuclear power industry is presented as an example of how important are physical observation and detailed analysis in the interpretation of test data. The objective is to provide different criteria that could allow the use of standard test data in fire modeling. So far most fire test data has only been used as an element for rank

We report on cross-sectional scanning tunnelling microscopy (XSTM) measurements on vertically stacked InAs quantum dots in InP barriers. We have investigated two-, five- and tenfold stacked quantum dot structures,grown by low-pressure metal-organic vapour phase epitaxy. The XSTM images reveal that the quantum dots are generally vertically well aligned, and have a truncated pyramidal shape in agree

We have calculated redox potentials of the two metal clusters in Mo-nitrogenase with quantum mechanical (QM) calculations. We employ an approach calibrated for iron–sulfur clusters with 1–4 Fe ions, involving QM-cluster calculations in continuum solvent and large QM systems (400–500 atoms), based on structures from combined QM and molecular mechanics (QM/MM) geometry optimisations. Calculations on

The unification of quantum mechanics and general relativity has long been elusive. Only recently have empirical predictions of various possible theories of quantum gravity been put to test, where a clear signal of quantum properties of gravity is still missing. The dawn of multi-messenger high-energy astrophysics has been tremendously beneficial, as it allows us to study particles with much higher

A new quantum chemical definition is proposed of the full atomic valence, VA, taking into account both the covalent and ionic parts of the chemical bonds formed by atoms in molecules and crystals. The full atomic valencies, covalencies, and charges on atoms are calculated for nickel–oxygen crystalline compounds in the CNDO band theory approximation. A comparison of the chemical bonding in nickel a

Ultracold clouds of dimeric molecules can dissociate into quantum mechanically correlated constituent atoms that are either both bosons or both fermions. We theoretically model the dissociation of two-dimensional anisotropic molecular condensates for which this difference manifests as complementary geometric structures of the dissociated atoms. Atomic bosons are preferentially emitted along the lo

We report on low-temperature transport measurements on single and double quantum dots defined using local gates to electrostatically deplete InAs nanowires grown by chemical beam epitaxy. This technique allows us to define multiple quantum dots along a semiconducting nanowire and tune the coupling between them.

We have calculated the electronic structure of InAs quantum dots embedded in InP as a function of size, using strain dependent eight-band k.p theory in the envelope function approximation. A realistic three-dimensional shape was used for the simulations and the piezoelectric polarization of the system was included. In order to avoid spurious solutions, an extra term was added to the Hamiltonian. P

GaSb/GaAs quantum dot systems are fabricated using MBE under various growth modes. The as-grown samples are studied with in situ synchrotron radiation XPS covering the As 3d, Sb 4d and Ga 3d core levels and the valence band region. The XPS spectra show dramatic changes with the growth modes, reflecting changes in the local electronic structure and chemical environments of the surface and interface

In the case of a quantum-noise limited detector, signal detection theory suggests that stereoradiographic images can be acquired with one half of the per-image dose needed for a standard radiographic projection, as information from the two stereo images can be combined. Previously, film-screen stereoradiography has been performed using the same per-image dose as in projection radiography, i.e., do

X-ray crystallography is the main source of atomistic information on the structure of proteins. Normal crystal structures are obtained as a compromise between the X-ray scattering data and a set of empirical restraints that ensure chemically reasonable bond lengths and angles. However, such restraints are not always available or accurate for nonstandard parts of the structure, for example substrat

Popular Abstract in Swedish En indikator-jon för en kvantdator Ända sedan transistorn uppfanns 1948 har datorer blivit allt mer kraftfulla. Trots den enorma utveckling som skett finns det fortfarande problem som är för svåra för en dator att lösa. Ett exempel är simulering av stora molekyler, t.ex. proteiner, vilket skulle vara användbart inom medicin och biologi, bland annat för att förutsäga hRare-earth ions doped into a transparent crystal can have optically excited states with coherence times of milliseconds and hyperfine levels with coherence times of hours when cooled down to liquid helium temperatures. This makes them attractive for developing quantum computing hardware. A quantum transistor can be implemented in a rare-earth-ion-doped crystal by utilizing a dipole blockade effe

Energy- and angle-resolved photoionization spectra of He irradiated by linearly polarized intense 810 nm laser radiation and several of its XUV odd harmonics are investigated. The angular distribution of the odd-order peaks, produced by single-photon ionization by one harmonic, is, surprisingly, broadened by the IR field. The even-order ones, due to two-colour, two-photon ionization, show at 90° l

We investigate the validity of thermodynamic uncertainty relations (TURs) in a strongly correlated quantum dot system operating in the Kondo regime. TURs place fundamental bounds on the trade-off between precision and dissipation in non-equilibrium systems, and while these bounds are rigorously proven for classical stochastic dynamics, they are not guaranteed to hold in quantum-coherent, strongly

An emerging research topic in quantum thermodynamics is the study of entangled quantum heat engines, where the working medium consists of an entangled quantum system. These engines offer exciting platforms for exploring fundamental aspects of quantum thermodynamics, its intersection with quantum information theory and the nature of entanglement in general. In this bachelor’s thesis, the performanc