Dynamic programming approach to structural optimization problem – numerical algorithm

In this paper a new shape optimization algorithm is presented. As a model application we consider state problems related to fluid mechanics, namely the Navier-Stokes equations for viscous incompressible fluids. The general approach to the problem is described. Next, transformations to classical optimal control problems are presented. Then, the dynamic programming approach is used and sufficient conditions for the shape optimization problem are given. A new numerical method to find the approximate value function is developed

Picture of Jan Kochanowski by Teofil Lenartowicz

Zadanie pt. „Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki” nr 885/P-DUN/2014 zostało dofinansowane ze środków MNiSW w ramach działalności upowszechniającej nauk

Investigating magneto-chemical interactions at molecule-substrate interfaces by X-ray photo-emission electron microscopy

The magneto-chemical interaction of spin-bearing molecules with substrates is interesting from a coordination chemistry point of view and relevant for spintronics. Unprecedented insight is provided by X-ray photo-emission electron microscopy combined with X-ray magnetic circular dichroism spectroscopy. Here the coupling of a Mn-porphyrin ad-layer to the ferromagnetic Co substrate through suitably modified interfaces is analyzed with this technique

Roles of the microRNA pathway in cortical development

Dicer endoribonuclease catalyzes the maturation of microRNAs (miRNAs) from double stranded precursors. Studies conditionally inactivating Dicer in the mouse embryonic forebrain continue to shed light on the spectrum of biological processes subject to miRNA regulation. This study looked at defects of brain development following a widespread ablation of Dicer in the early forebrain. The neuroepithelial stem cells failed to specify the radial glia appropriately around the time when the first postmitotic neurons begin to be generated in the neuroepithelium. Ablation of Dicer in only a subset of radial glia was not accompanied by the early apoptosis observed in all other models of Dicer ablation in the cortex. This allowed the study of the role of miRNAs in regulating cell numbers in the cortex. The study revealed that generation of cortical cells is increased during postnatal development. Finally, the study identified a miRNA which is able to negatively regulate the development of neuronal precursor cells of the developing cortex by targeting Tbox transcription factor 2. Together the results presented in this Thesis contribute to the understanding of the roles of endogenous RNA interference in the development of the brain

Exploring chemistry and magnetism in adlayers at surfaces

The goal of my thesis was to understand, design and modify the properties of surfaces as a whole, as well as of surface-supported atoms and molecules. This way I discovered exciting differences and similarities between two- and three-dimensional systems, i.e. between the surface and the bulk, which came as a natural consequence in the pursuit of this aim. I have observed physicochemical phenomena that strictly require the specific characteristics of surfaces and also a number of effects that proceed in a very similar fashion when compared to the gas or the liquid phase. One thesis is, however, not enough to study all of the interesting phenomena in surface science, i.e. the field concerned with effects occurring when the dimensionality of the arrangement of atoms is decreased below three. Therefore I focused on exploring on-surface chemistry and magnetism – phenomena that are closely related, as they both depend on the interaction of atoms’ valence electrons with the surroundings. The first example of how one can tune the properties of a surface is provided by adding a one-atom-thick layer of adsorbates – specifically O, N and Cl on Cu(001). During my work I discovered that this simple modification can drastically alter the reactivity of a surface, as studied using the self-metalation reaction of porphyrins, in which a metal atom is taken from the substrate and embedded in the molecule. Interestingly, this approach also allowed studying the interactions between the molecules, visualised in the formation of molecular self-assembled islands and clusters. In the second studied system I investigated a surface covered by only single ad-atoms, not by a full layer of adsorbates. In this project I was interested in the influence of a substrate on the magnetic properties of single transition metal atoms. Isolated single atoms, due to their spherical symmetry, cannot possess any magnetic anisotropy – i.e. directional dependence of magnetic properties. The interaction with a surface can, however, induce such directional dependence, which in the case of Cr atoms deposited on a Bi substrate is found to reach the theoretically possible limit. It is, to the best of my knowledge, the first observation of such a giant magnetic anisotropy on a non-insulating substrate. Due to the very limited nature of the periodic table of elements, it is desirable to change the properties of paramagnetic atoms even before depositing them on a surface. Due to the vast possibilities given by organic chemistry, inserting an atom in easily modifiable molecule is a simple way to achieve that. In this thesis I show that such an organic ‘cage’ around an atom can additionally modify the magnetic interaction between the paramagnetic ion and the underlying substrate. I was able to tune the molecule-substrate magnetic exchange coupling energy by using molecules with different functional groups. Interestingly, molecule-surface magnetic interactions can also be used to study molecular motion. I also discuss the use of X-ray Magnetic Circular Dichroism for detecting out-of-plane molecular rearrangement in a model case, in which two phthalocyanines, MnPc and FePc, showed different adsorption energies with the former being able to push the latter away from the substrate. During this thesis I also developed a method for creating a supramolecular chessboard-like arrangement built from two different molecules, namely MnPc and FeFPc. This approach has been successfully used by me and my colleagues in many projects that strictly required a surface-supported, alternating arrangement of molecules. Fascinating properties of this low-dimensional magnetic layer were controlled by chemical ligation as well as by the choice of the underlying substrate – Au(111), Ag(111) or ferromagnetic O-covered Co(001). Those different supports enabled studying different magnetic coupling interactions that are strong on ferromagnetic supports, while weak on diamagnetic. This thesis expands the range of tuneable surface properties. This was achieved by the use of on-surface supramolecular engineering, an approach combining the design and modifications of molecules and surfaces, as well as the interactions between them

Towards Exascale Computing Architecture and Its Prototype: Services and Infrastructure

This paper presents the design and implementation of a scalable compute platform for processing large data sets in the scope of the EU H2020 project PROCESS. We are presenting requirements of the platform, related works, infrastructure with focus on the compute components and finally results of our work

Magnetic exchange coupling of a synthetic Co(II)-complex to a ferromagnetic Ni substrate

On-surface assembly of a spin-bearing and non-aromatic porphyrin-related synthetic Co(II)-complex on a ferromagnetic Ni thin film substrate and subsequent magnetic exchange interaction across the interface were studied by scanning tunnelling microscopy (STM), X-ray absorption spectroscopy (XAS), X-ray magnetic circular dichroism (XMCD) and density functional theory +U (DFT + U) calculations

Charge Transfer to Solvent Dynamics at the Ambient Water/Air Interface

Electron-transfer reactions at ambient aqueous interfaces represent one of the most fundamental and ubiquitous chemical reactions. Here the dynamics of the charge transfer to solvent (CTTS) reaction from iodide was probed at the ambient water/air interface by phase-sensitive transient second-harmonic generation. Using the three allowed polarization combinations, distinctive dynamics assigned to the CTTS state evolution and to the subsequent solvating electron-iodine contact pair have been resolved. The CTTS state is asymmetrically solvated in the plane of the surface, while the subsequent electron solvation dynamics are very similar to those observed in the bulk, although slightly faster. Between 3 and 30 ps, a small phase shift distinguishes an electron bound in a contact pair with iodine and a free hydrated electron at the water/air interface. Our results suggest that the hydrated electron is fully solvated in a region of reduced water density at the interface