Quantum transition state theory and solving a first order master equation for complex reactions numerically

The field of chemical kinetics is an exciting and active field. The prevailing theories make a number of simplifying assumptions that do not always hold in actual cases. Another current problem concerns a development of efficient numerical algorithms for solving the master equations that arise in the description of complex reactions. The objective of the present work is to furnish a completely general and exact theory of reaction rates, in a form reminiscent of transition state theory, valid for all fluid phases and also to develop a computer program that can solve complex reactions by finding the concentrations of all participating substances as a function of time. To do so, the full quantum scattering theory is used for deriving the exact rate law, and then the resulting cumulative reaction probability is put into several equivalent forms that take into account all relativistic effects if applicable, including one that is strongly reminiscent of transition state theory, but includes corrections from scattering theory. Then two programs, one for solving complex reactions, the other for solving first order linear kinetic master equations to solve them, have been developed and tested for simple applications.

Solid-state synthesis of embedded single-crystal metal oxide and phosphate nanoparticles and in situ crystallization

A new solid state organometallic route to embedded nanoparticle-containing inorganic materials is shown, through pyrolysis of metal-containing derivatives of cyclotriphosphazenes. Pyrolysis in air and at 800 °C of new molecular precursors gives individual single-crystal nanoparticles of SiP2O7, TiO2, P4O7, WP2O7 and SiO2, depending on the precursor used. High resolution transmission electron microscopy investigations reveal, in most cases, perfect single crystals of metal oxides and the first nanostructures of negative thermal expansion metal phosphates with diameters in the range 2–6 nm for all products. While all nanoparticles are new by this method, WP2O7 and SiP2O7 nanoparticles are reported for the first time. In situ recrystallization formation of nanocrystals of SiP2O7 was also observed due to electron beam induced reactions during measurements of the nanoparticulate pyrolytic products SiO2 and P4O7. The possible mechanism for the formation of the nanoparticles at much lower temperatures than their bulk counterparts in both cases is discussed. Degrees of stabilization from the formation of P4O7 affects the nanocrystalline products: nanoparticles are observed for WP2O7, with coalescing crystallization occurring for the amorphous host in which SiP2O7 crystals form as a solid within a solid. The approach allows the simple formation of multimetallic, monometallic, metal-oxide and metal phosphate nanocrystals embedded in an amorphous dielectric. The method and can be extended to nearly any metal capable of successful coordination as an organometallic to allow embedded nanoparticle layers and features to be deposited or written on surfaces for application as high mobility pyrophosphate lithium–ion cathode materials, catalysis and nanocrystal embedded dielectric layers.

Lead: Inorganic Chemistry

The article covers basic inorganic chemistry of lead. As an introduction, the properties and historical uses of metallic lead are discussed, followed by aspects of lead toxicity, including the toxicity origins and effects of lead poisoning. Properties of lead as a heavy p-block element are discussed, with emphasis on the modern view of the so-called “inert pair effect”, including its origin, the influence on stability of lead oxidation states, and on the coordination chemistry of lead(II), viz., “sterically active lone pair”. This is followed by an overview of lead inorganic compounds, including halides, pseudohalides, oxides and chalcogenides, hydroxides and their chalcogenide analogs, alkoxides, oxoacids, O-donors, S- and Se-donors, Group 15 donors, compounds with lead-transition metal bonds, and finally metallic clusters (Zintl phases). This is by no means a comprehensive review, rather compounds representative for each class were presented. In most sections, structural aspects of each class of compounds are discussed, followed by applications, with the focus on modern uses in material science.

The Great Transition:Climate, disease and society in the late-medieval world

In the fourteenth century the Old World witnessed a series of profound and abrupt changes in the trajectory of long-established historical trends. Trans-continental networks of exchange fractured and an era of economic contraction and demographic decline dawned from which Latin Christendom would not begin to emerge until its voyages of discovery at the end of the fifteenth century. In a major new study of this 'Great Transition', assessment is made of the contributions of commercial recession, war, climate change,and eruption of the Black Death to a far-reaching reversal of fortunes which spared no part of Eurasia. A wealth of new historical, palaeoecological and biological evidence are synthesised, including estimates of national income, reconstructions of past climates. and genetic analysis of DNA extracted from the teeth of plague victims, to provide a fresh account of the creation, collapse and realignment of western Europe's late-medieval commercial economy.

Lightweight metal halide and hydride fast Li ion conductors

This work was motivated by the extensive research on lithium solid state materials, which have attracted increasing interest for potential applications in hydrogen storage and/or lithium ion batteries due to their extraordinary properties. In this thesis, LiBH4-derived materials, LiInBr4 and complex phases based on lithium ammonia borane with potential use as solid state electrolytes were successfully synthesised and characterised.

Small polarons in spin-orbit coupled osmates

Small polarons (SP) have been thoroughly investigated in 3d transition metal oxides and they have been found to play a crucial role in physical phenomena such as charge transport, colossal magnetoresistance and surface reactivity. However, our knowledge about these quasi-particles in 5d systems remains very limited, since the more delocalised nature of the 5d orbitals reduces the strength of the Electronic Correlation (EC), making SP formation in these compounds rather unexpected. Nevertheless, the Spin-Orbit coupled Dirac-Mott insulator Ba2NaOsO6 (BNOO) represents a good candidate for enabling polaron formation in a relativistic background, due to the relatively large EC (U ∼ 3 eV) and Jahn-Teller activity. Moreover, anomalous peaks in Nuclear Magnetic Resonance (NMR) spectroscopy experiments suggest the presence of thermally activated SP dynamics when BNOO is doped with Ca atoms. We investigate SP formation in BNOO both from an electronic and structural point of view by means of fully relativistic first principles calculations. Our numerical simulations predict a stable SP ground state and agree on the value of 810 K for the dynamical process peak found by NMR experiments.

Kissing stenting of aortic bifurcation for aorto-iliac obstructive disease: a comparison between bare metal stents and covered stents

INTRODUCTION Aim of this multicentric study:to compare the short-and mid-term results of bare metal stents(BMS)and covered stents(CS)in the Kissing Stent(KS)technique. METHODS Patients undertaking a KS with BMS or CS between January 2017-August 2021 included. Morphological features of plaques were classified as per the extension of calcifications and thrombosis. Every endpoint and outcome was compared in relation to BMS or CS. All patients included received dual anti-platelets DAPT)for at least one month. RESULTS Thirty-four patients enrolled,17 treated with BMS and 17 with CS. Average age 66 years. The 80% of patients were part of TASC C-D categories. DAPT was administered to 82.4%(28/34)of patients with a mean duration of 4.4±1.6 months. Mean follow-up 32.1±17.8 months. Technical Success was 100%. Immediate Clinical Success was reached in 29 cases(85.3%). Immediate and 30-day Clinical Success was higher in CS(64.7% vs 100%, p=.01). Overall Clinical Success at 1-year follow-up was 91.2%,and resulted significantly higher in CS(82.4% vs 100%,p .04). Overall Primary Patency,Assisted Patency,and Secondary Patency at 30 days were 97.1%,97.1%,and 100%,without differences between BMS and CS(94.1% vs 100%,94.1% vs 100%,and 100% vs 100%;p =.7). Two cases(5.9%)of thrombosis were registered,and both occurred within 3 months after the procedure and both in the BMS,without statistical differences with the CS group(11.8% vs 0%,p .48). Both cases of thrombosis occurred in patients who were not treated with dual antiplatelet therapy(33.3% vs 0%,p .027). Survival statistically differed only at the mean follow-up in favour of CS(70.6% and 100%,p .04). CONCLUSIONS The endovascular approach is currently safe and effective in the treatment of AIOD,and KS offers excellent results in particular if performed with CS; however,no statistically significant differences emerged between the two types of stents in terms of patency,reintervention,and complications. DAPT seems to warrant the best results in terms of patency,although there is still no consensus about the ideal duration of administration.

Ultracold Bose-Fermi mixtures with pairing: quantum phase transition, mechanical stability, and trap confinement

Ultracold dilute gases occupy an important role in modern physics and they are employed to verify fundamental quantum theories in most branches of theoretical physics. The scope of this thesis work is the study of Bose-Fermi (BF) mixtures at zero temperature with a tunable pairing between bosons and fermions. The mixtures are treated with diagrammatic quantum many-body methods based on the so-called T-matrix formalism. Starting from the Fermi-polaron limit, I will explore various values of relative concentrations up to mixtures with a majority of bosons, a case barely considered in previous works. An unexpected quantum phase transition is found to occur in a certain range of BF coupling for mixture with a slight majority of bosons. The mechanical stability of mixtures has been analysed, when the boson-fermion interaction is changed from weak to strong values, in the light of experimental results recently obtained for a double-degenerate Bose-Fermi mixture of 23 Na - 40 K. A possible improvement in the description of the boson-boson repulsion based on Popov's theory is proposed. Finally, the effects of a harmonic trapping potential are described, with a comparison with the experimental data for the condensate fraction recently obtained for a trapped 23 Na - 40 K mixture.

Nanostructured diamond-like carbon films characterization

In this work, we have studied the influence of the substrate surface condition on the roughness and the structure of the nanostructured DLC films deposited by high-density plasma chemical vapor deposition Four methods were used to modify the silicon wafers surface before starting the deposition processes of the nanostructured DLC films. micro-diamond powder dispersion, micro-graphite powder dispersion, and roughness generation by wet chemical etching and roughness generation by plasma etching. The reference wafer was only submitted to a chemical cleaning. It was possible to see that the final roughness and the sp(3) hybridization degree (that is related with the structure and chemical composition) strongly depend on the substrate surface conditions The surface roughness was observed by AFM and SEM and the hybridization degree of the DLC films was analyzed by Raman Spectroscopy Thus, the effects of the substrate surface on the DLC film structure were confirmed. These phenomena can be explained by the fact that the locally higher surface energy and the sharp edges may induce local defects promoting the nanostructured characteristics in the DLC films. (C) 2009 Elsevier B.V. All rights reserved.

PbO-GeO(2) rib waveguides for photonic applications

This work presents for the first time to our knowledge the fabrication and characterization of rib waveguides produced with PbO-GeO(2) (PGO) thin films. The target was manufactured using pure oxides ( 60 PbO-40 GeO(2), in wt%) and amorphous thin films were produced with the RF sputtering technique. PGO thin films present small absorption in the visible and in the near infrared and refractive index of similar to 2.0. The definition of the rib waveguide structure was made using conventional optical lithography followed by plasma etching, performed in a Reactive Ion Etching (RIE) reactor. Light propagation mode in the waveguide structure was analyzed using integrated optic simulation software. Optical loss measurements were performed to determine the propagation loss at 633 nm, for ribs with height of 70 nm and width of 3-5 mu m; experimental values around 2 dB/cm were found for the propagation loss and confirmed the theoretical calculations. The results obtained demonstrate that PGO thin films are potential candidates for application in integrated optics. Published by Elsevier B.V.

Study of polycrystalline Cu2ZnSnS4 films by Raman scattering

Cu2ZnSnS4 (CZTS) is a p-type semiconductor that has been seen as a possible low-cost replacement for Cu(In,Ga)Se2 in thin film solar cells. So far compound has presented difficulties in its growth, mainly, because of the formation of secondary phases like ZnS, CuxSnSx+1, SnxSy, Cu2−xS and MoS2. X-ray diffraction analysis (XRD), which is mostly used for phase identification cannot resolve some of these phases from the kesterite/stannite CZTS and thus the use of a complementary technique is needed. Raman scattering analysis can help distinguishing these phases not only laterally but also in depth. Knowing the absorption coefficient and using different excitation wavelengths in Raman scattering analysis, one is capable of profiling the different phases present in multi-phase CZTS thin films. This work describes in a concise form the methods used to grow chalcogenide compounds, such as, CZTS, CuxSnSx+1, SnxSy and cubic ZnS based on the sulphurization of stacked metallic precursors. The results of the films’ characterization by XRD, electron backscatter diffraction and scanning electron microscopy/energy dispersive spectroscopy techniques are presented for the CZTS phase. The limitation of XRD to identify some of the possible phases that can remain after the sulphurization process are investigated. The results of the Raman analysis of the phases formed in this growth method and the advantage of using this technique in identifying them are presented. Using different excitation wavelengths it is also analysed the CZTS film in depth showing that this technique can be used as non destructive methods to detect secondary phases.

The ruthenium-tin system

The Ru-Sn liquid-solid and some solid-solid equilibria have been completely revised by means of differential thermal analysis, X-ray powder diffraction and microprobe investigations. The existence of two intermetallic phases has been clearly established: Ru(0.4)Sn(0.6)decomposed by a peritectic reaction at 1266(+/-4)degrees C and Ru0.3Sn0.7 congruently melting at 1257(+/-2)degrees C.