Diagnostic features of EPR spectra of superoxide intermediates on catalytic surfaces and molecular interpretation of their g and A tensors

The use of electron paramagnetic resonance spectroscopy to study the superoxide intermediates, generated by end-on and side-on adsorption of the naturally abundant and 17O-enriched dioxygen on catalytic surfaces is discussed. Basic mechanisms of O2 − radical formation via a cationic redox mechanism, an anionic redox mechanism, and an electroprotic mechanism are illustrated with selected oxide-based systems of catalytic relevance. Representative experimental spectra of various complexities are analyzed and their diagnostic features have been identified and interpreted. The molecular nature of the g and A tensors of the electrostatic and covalent superoxide adducts is discussed in detail within the classic and density functional theory based approaches

Functionalization of graphite with oxidative plasma

Surface-modified graphite is studied as an electrode material, an adsorbent, and a membrane component, among other applications. Modifying the graphite with plasma can be used to create relevant surface functionalities, in particular, various oxygen groups. The application of surface-oxidized graphite often requires its use in an aqueous environment. The application in an aqueous environment is not an issue for acid-oxidized carbons, but a discrepancy in the structure–activity relationship may arise because plasma-oxidized carbons show a time-dependent decrease in the degree of functionalization and related properties. Moreover, plasma-oxidized materials are often characterized in terms of their chemical and physical properties, most notably their degree of functionalization after plasma treatment, without contact with water. In this study, we used low-temperature plasma oxidation with pure oxygen and carbon dioxide and sample-washing with concentrated nitric and sulfuric acids. To evaluate the electronic properties of modified graphite, the work function changes and surface oxygen content were measured just after plasma modification and after water immersion. We show that water immersion drastically decreases the work function of plasma-treated samples, which is accompanied by a decrease in the number of radicals introduced by plasma. Our results demonstrate that the increase in stable work function as a result of plasma treatment, brought about by an increase in the surface oxygen species concentration, can be realized most effectively for the acid-washed graphite

Fast Fitting of the Dynamic Memdiode Model to the Conduction Characteristics of RRAM Devices Using Convolutional Neural Networks

In this paper, the use of Artificial Neural Networks (ANNs) in the form of Convolutional Neural Networks (AlexNET) for the fast and energy-efficient fitting of the Dynamic Memdiode Model (DMM) to the conduction characteristics of bipolar-type resistive switching (RS) devices is investigated. Despite an initial computationally intensive training phase the ANNs allow obtaining a mapping between the experimental Current-Voltage (I-V) curve and the corresponding DMM parameters without incurring a costly iterative process as typically considered in error minimization-based optimization algorithms. In order to demonstrate the fitting capabilities of the proposed approach, a complete set of I-Vs obtained from Y₂O₃-based RRAM devices, fabricated with different oxidation conditions and measured with different current compliances, is considered. In this way, in addition to the intrinsic RS variability, extrinsic variation is achieved by means of external factors (oxygen content and damage control during the set process). We show that the reported method provides a significant reduction of the fitting time (one order of magnitude), especially in the case of large data sets. This issue is crucial when the extraction of the model parameters and their statistical characterization are required

The cytotoxic effect of copper (II) complexes with halogenated 1,3-disubstituted arylthioureas on cancer and bacterial cells

A series of eight copper (II) complexes with 3-(4-chloro-3-nitrophenyl)thiourea were designed and synthesized. The cytotoxic activity of all compounds was assessed in three human cancer cell lines (SW480, SW620, PC3) and human normal keratinocytes (HaCaT). The complexes 1, 3, 5, 7 and 8 were cytotoxic to the studied tumor cells in the low micromolar range, without affecting the normal cells. The complexes 1, 3, 7 and 8 induced lactate dehydrogenase (LDH) release in all cancer cell lines, but not in the HaCaT cells. They provoked early apoptosis in pathological cells, especially in SW480 and PC3 cells. The ability of compounds 1, 3, 7 and 8 to diminish interleukin-6 (IL-6) concentration in a cell was established. For the first time, the influence of the most promising Cu (II) complexes on intensities of detoxifying and reactive oxygen species (ROS) scavenging the enzymes of tumor cells was studied. The cytotoxic effect of all copper (II) conjugates against standard and hospital bacterial strains was also proved

Extraction of audio features specific to speech production for multimodal speaker detection

A method that exploits an information theoretic framework to extract optimized audio features using video information is presented. A simple measure of mutual information (MI) between the resulting audio and video features allows the detection of the active speaker among different candidates. This method involves the optimization of an MI-based objective function. No approximation is needed to solve this optimization problem, neither for the estimation of the probability density functions (pdf) of the features, nor for the cost function itself. The pdf are estimated from the samples using a non-parametric approach. The challenging optimization problem is solved using a global method: the Differential Evolution algorithm. Two information theoretic optimization criteria are compared and their ability to extract audio features specific to speech is discussed. Using these specific speech audio features, candidates video features are then classified as membership of the "speaker" or "non-speaker" class, resulting in a speaker detection scheme. As a result, our method achieves a speaker detection rate of 100% on home- grown test sequences, and of 85% on most commonly used sequences

Extraction of Audio Features Specific to Speech using Information Theory and Differential Evolution

We present a method that exploits an information theoretic framework to extract optimized audio features using the video information. A simple measure of mutual information (MI) between the resulting audio features and the video ones allows to detect the active speaker among different candidates. Our method involves the optimization of an MI-based objective function. No approximation is introduced to solve this optimization problem, neither concerning the estimation of the probability density functions (pdf) of the features, nor the cost function itself. The pdf are estimated from the samples using a non-parametric approach. As far as concern the optimization process itself, three different optimization methods (one local and two globals) are compared in this paper. The Differential Evolution algorithm is shown to be outstanding performant for our problem and is threrefore eventually retains. Two information theoretic optimization criteria are compared and their ability to extract audio features specific to speeh is discussed. As a result, our method achieves a speaker detection rate of 100% on our test sequences, and of 95% on a state-of-the-art sequence

Numerical Analysis in Nonlinear Least Squares Methods and Applications

The approximate greatest descent (AGD) method and a two-phase AGD method (AGDN) are proposed as new methods for a nonlinear least squares problem. Numerical experiments show that these methods outperform existing methods including the Levenberg-Marquardt method. However, the AGDN method outperforms the AGD method with a faster convergence. If the AGDN method fails due to singularity of the Hessian matrix, the AGD method should be used

Integrate approach to the study of chelating agents for the effects of toxic metal ions

Metals are an integral part of many structural and functional components in the body, and the interest on their role in physiological processes, environment and medicine is increasing. Many metal complex are used as metal drugs such as cis-platin for cancer treatment, paramagnetic metal complex as contrast agents for magnetic resonance imaging (MRI); many metal are toxic and metal toxicity may occur due to essential metal overload or exposure to heavy metals from various sources interfering with functions of various organ systems like the central nervous system (CNS), the haematopoietic system, liver, kidneys, etc. New therapeutic strategies, such as chelation therapy, have been developed based on restoring the normal healthy physiology of the body either by direct administration of essential metals, or by chelating out excess or toxic metals, or using them as carriers for targeted drug delivery, or for tagging biomolecules for diagnostics. Thermodynamic studies in the characterization of ligands of biomedical interest are crucial in the design of a new drugs. This thesis is focused on the studies of new molecules that have long been recognized as privileged chelating structures for the design of metal chelating drugs, especially towards hard metal ions, in view of their involvement in metal overload disorders. The approach has been multi-variated, from the chemistry to the biochemistry and biology, which has been possible due to the time spent in others research groups and to the other ones that used to collaborate with us. Because of my stay (research master thesis) in organic chemistry group at Instituto Superior Tecnico of Lisbon guided by Prof. M. Amelia Santos, three hydroxypyridinones ligands have been synthetized, whose biodistribution studies performed at Centro de Ciencias e Tecnologias Nucleares (C2TN) of Lisbon as well. In the Research Group of Chemistry and Stereochemistry of Peptides and Protein headed by Prof. Zbigniew Szewczuk at the University of Wroclaw new strategies of synthesis have been developed involving mimosine peptides derivatives. As opposite to hydroxypyridinones, whose solution equilibria studies have been possible, peptides have been mainly characterized by DFT and biological ones in collaboration with the University of San Sebastian and Cagliari. In the end, three months of my last year of PhD have been spent in the Medicinal Inorganic Chemistry group at the University of British Columbia (Vancouver) under supervision of Prof. Chris Orvig working on solution studies of radiometal complexes of bisphosphonate-picolinic acid derivatives. It needs to be tightened up with regard to PhD that it has industrial characterization under that a collaboration with industry is scheduled. At Innovative Materials I could learn about biology field and how to work with cells, particularly our idea was to test hydroxypyrones ligands on proliferation and differentiation of stamina cells. The study is still uncompleted and results about are not shown in the following chapters This thesis is divided in three chapters: • Chapter 1 – An overview of chelation It describes general aspects of chelation therapy, the rule of metal ions in human body and in human diseases. • Chapter 2 – Ligands It describes structural and chemical properties of a families of ligands studied and shows NTA(PrHP)3, KC18, KC21, SC and six mimosine-peptides derivatives under focus of this thesis. • Chapter 3 – Experimental methods It describes experimental procedures and techniques applied for thesis’s studies