Time evolution of natural orbitals in ab initio molecular dynamics.

This work combines for the first time ab initio molecular dynamics (AIMD) within the Born-Oppenheimer approximation with a global natural orbital functional (GNOF), an approximate functional of the one-particle reduced density matrix. The most prominent feature of GNOF-AIMD is its ability to display the real-time evolution of natural orbitals, providing detailed information on the time-dependent electronic structure of complex systems and processes, including reactive collisions. The quartet ground-state reaction N(4S) + H2(1Σ) → NH(3Σ) + H(2S) is taken as a validation test. Collision energy influences on integral cross sections for different initial rovibrational states of H2 and rotational-state distributions of the NH product are discussed, showing a good agreement with previous high-quality theoretical results.

High-Dimensional Atomistic Neural Network Potential to Study the Alignment-Resolved O2 Scattering from Highly Oriented Pyrolytic Graphite.

A high dimensional and accurate atomistic neural network potential energy surface (ANN-PES) that describes the interaction between one O2 molecule and a highly oriented pyrolytic graphite (HOPG) surface has been constructed using the open-source package (aenet). The validation of the PES is performed by paying attention to static characteristics as well as by testing its performance in reproducing previous ab initio molecular dynamics simulation results. Subsequently, the ANN-PES is used to perform quasi-classical molecular dynamics calculations of the alignment-dependent scattering of O2 from HOPG. The results are obtained for 200 meV O2 molecules with different initial alignments impinging with a polar incidence angle with respect to the surface normal of 22.5° on a thermalized (110 and 300 K) graphite surface. The choice of these initial conditions in our simulations is made to perform comparisons to recent experimental results on this system. Our results show that the scattering of O2 from the HOPG surface is a rather direct process, that the angular distributions are alignment dependent, and that the final translational energy of end-on molecules is around 20% lower than that of side-on molecules. Upon collision with the surface, the molecules that are initially aligned perpendicular to the surface become highly rotationally excited, whereas a very small change in the rotational state of the scattered molecules is observed for the initial parallel alignments. The latter confirms the energy transfer dependence on the stereodynamics for the present system. The results of our simulations are in overall agreement with the experimental observations regarding the shape of the angular distributions and the alignment dependence of the in-plane reflected molecules.

The Intricate Dynamics of the Si(3P) + OH(X2Π) Reaction.

The dynamics of the Si(3P) + OH(X2Π) → SiO(X1Σ+,v',j') + H(2S) reaction is investigated by means of the quasi-classical trajectory method on the electronic ground state X2A' potential energy surface in the 10-2-1 eV collision energy range. Although the reaction involves the formation of a long-lived intermediate complex, a high probability for back-dissociation to the reactants is found because of inefficient intravibrational redistribution of energy among the complex modes. At low collision energies, the reactive events are governed by a dynamics with mixed direct/indirect features. As the collision energy increases, the intermediate complex lifetime increases and final state distributions are found to be in reasonable agreement with statistical predictions obtained using the mean potential phase space theory, thus highlighting the indirect character of the process. These rich and puzzling dynamical features are in line with what has been previously observed for the S(3P) + OH(X2Π) reaction.

Time-Dependent Quantum Wave Packet Study of the Si + OH → SiO + H Reaction: Cross Sections and Rate Constants.

The dynamics of the Si(3P) + OH(X2Π) → SiO(X1Σ+) + H(2S) reaction is investigated by means of the time-dependent wave packet (TDWP) approach using an ab initio potential energy surface recently developed by Dayou et al. ( J. Chem. Phys. 2013 , 139 , 204305 ) for the ground X2A' electronic state. Total reaction probabilities have been calculated for the first 15 rotational states j = 0-14 of OH(v=0,j) at a total angular momentum J = 0 up to a collision energy of 1 eV. Integral cross sections and state-selected rate constants for the temperature range 10-500 K were obtained within the J-shifting approximation. The reaction probabilities display highly oscillatory structures indicating the contribution of long-lived quasibound states supported by the deep SiOH/HSiO wells. The cross sections behave with collision energies as expected for a barrierless reaction and are slightly sensitive to the initial rotational excitation of OH. The thermal rate constants show a marked temperature dependence below 200 K with a maximum value around 15 K. The TDWP results globally agree with the results of earlier quasi-classical trajectory (QCT) calculations carried out by Rivero-Santamaria et al. ( Chem. Phys. Lett. 2014 , 610-611 , 335 - 340 ) with the same potential energy surface. In particular, the thermal rate constants display a similar temperature dependence, with TDWP values smaller than the QCT ones over the whole temperature range.

A global ab initio potential energy surface for the X2A' ground state of the Si + OH → SiO + H reaction.

We report the first global potential energy surface (PES) for the X(2)A' ground electronic state of the Si((3)P) + OH(X(2)Π) → SiO(X(1)Σg(+)) + H((2)S) reaction. The PES is based on a large number of ab initio energies obtained from multireference configuration interaction calculations plus Davidson correction (MRCI+Q) using basis sets of quadruple zeta quality. Corrections were applied to the ab initio energies in the reactant channel allowing a proper description of long-range interactions between Si((3)P) and OH(X(2)Π). An analytical representation of the global PES has been developed by means of the reproducing kernel Hilbert space method. The reaction is found barrierless. Two minima, corresponding to the SiOH and HSiO isomers, and six saddle points, among which the isomerization transition state, have been characterized on the PES. The vibrational spectra of the SiOH/HSiO radicals have been computed from second-order perturbation theory and quantum dynamics methods. The structural, energetic, and spectroscopic properties of the two isomers are in good agreement with experimental data and previous high quality calculations.

Caracterización de la formulación de -Macroagregados de albúmina / Characterization of - macroaggregates formulation

RESUMEN En este trabajo se realizó la caracterización del proceso de formación y marcaje de los macroagregados de albúmina (MAA) con . Con este fin se efectuaron estudios comparativos para establecer el papel de la desnaturalización en presencia del durante la formulación de -Sn-MAA, para ello se utilizaron tres formulaciones. Se realizó un análisis estructural cualitativo de la albúmina sérica humana para describir el sistema a través de un modelo gráfico. Los resultados mostraron diferencias importantes en el comportamiento radioquímico de las tres formulaciones. La formulación de -Sn-MAA (A) mostró un comportamiento superior, con purezas radioquímicas cercanas a 95% en los tiempos estudiados y una disociación inferior al 20% en 24 h.El modelo gráfico permitió explicar, a través de sencillas representaciones, los procesos involucrados en el sistema estudiado, permitiendo una mejor comprensión de este.

ABSTRACT The aim of this paper was to study the formation and radiolabelling of 99m Tcalbumin macroaggregates. Comparatives studies of three formulations to establish the role of denaturalization and in the formulation of -Sn-MAA were carried out. A qualitative structural analysis of human serum albumin was performed in order to give a description of the studied system using a graph model. The results showed important differences in the radiochemical behavior of the three formulations. -Sn-MAA (A) formulation had the best behavior, with radiochemical purity close to 95% and dissociation below 20% after 24 h of being radiolabeled. The graph model explained with simple representations the process involved in the studied system;thus allowing a better knowledge of it.

Formulación de -Macroagregados de albúmina para estudios de perfusión pulmonar / Preparation of -macroaggregated albumin for lung perfusion studies

RESUMEN En este trabajo, se realizó el diseño, optimización, control de calidad de pureza radioquímica, cualidad biológica y estudios de estabilidad en el tiempo de una formulación de macroagregados de albúmina a partir de la desnaturalización controlada de la ASH. Se realizó un diseño experimental con un plan factorial para determinar las condiciones ideales de la formulación. Los resultados mostraron que la concentración de albúmina en el intervalo 515 mg/mL es irrelevante, sin embargo, el pH final de la mezcla y la velocidad de agitación sí fueron relevantes, así como todas las variables de interacción. Con las condiciones seleccionadas en el diseño experimental, se obtuvieron formulaciones con tamaño de partículas con diámetros comprendidos entre 11 y 80 µ, que cumplieron los criterios de pureza radioquímica establecidos internacionalmente, así como la condición de esterilidad y apirogenicidad. La biodistribución en animales de experimentación mostró imágenes pulmonares de buena calidad. Los lotes producidos mantuvieron estabilidad física, radioquímica, biológica y microbiológica durante 90 días de conservación a 4°C.

ABSTRACT The present paper shows the design, optimization, quality control for testing radiochemical purity, biological quality and realtime stability studies of a preparation of macroaggregated albumin from the controlled denaturation of HSA. An experimental design with a factorial plan was carried out in order to determine the ideal conditions for the preparation. The results showed that variations of albumin concentrations within the range of 515 mg/mL were irrelevant, however, the final pH of the mixture and the stirring speed were significant variables, as well as their interaction. Formulations with particles of diameter between 11 and 80 µ were obtained with the conditions selected in the experimental design which met the internationally established criteria for radiochemical purity, sterility and apyrogenicity. The biodistribution in experimental animals showed good quality lung images. The produced lots maintained physical, radiochemical, biological and microbiological stability during 90 days of storage at 4°C.

Aplicaciones de las técnicas nucleares en la medicina: examen de respiración del carbono 13 o 14 (13o14C) / Applications of the nuclear Techniques in medicine: 13o14C respiration tests

Los examenes o tests de respiración del carbono 13 o 14 (13o14C) han sido aplicados para el estudio de procesos metabólicos y procesos infecciosos, pero la mayoría de ellos aun no han entrado en la etapa de la práctica clínica. En este trabajo daremos una panorámica acerca del presente y futuro de los tests de respiración y como estos están tomando y tomaran parte en el futuro en el diagnostico de forma no invasiva de diversas patologías(AU)

The 14C or 13C respiration tests have been applied to the study of metabolic and infectious processes, but most of them have not entered yet the clinical practice stage. In this paper, it is offered an overview of the present and future of respiration tests and how they are taking part and will take part in a future in the non-invasive diagnosis of diverse pathologies(AU)

Aplicaciones de las técnicas nucleares en la medicina: examen de respiración del carbono 13 o 14 (13o14C) / Applications of the nuclear Techniques in medicine: 13o14C respiration tests

Los examenes o tests de respiración del carbono 13 o 14 (13o14C) han sido aplicados para el estudio de procesos metabólicos y procesos infecciosos, pero la mayoría de ellos aun no han entrado en la etapa de la práctica clínica. En este trabajo daremos una panorámica acerca del presente y futuro de los tests de respiración y como estos están tomando y tomaran parte en el futuro en el diagnostico de forma no invasiva de diversas patologías.

The 14C or 13C respiration tests have been applied to the study of metabolic and infectious processes, but most of them have not entered yet the clinical practice stage. In this paper, it is offered an overview of the present and future of respiration tests and how they are taking part and will take part in a future in the non-invasive diagnosis of diverse pathologies.