Singlet vs. triplet interelectronic repulsion in confined atoms

Hund’s multiplicity rule invariably holds for the ground configurations of few-electron atoms as well as those of multi-electron quantum dots. However, the ordering of the corresponding interelectronic repulsions exhibits a reversal in the former but not in the latter system, upon varying the system parameters. Here, we investigate the transition between these two types of behaviour by studying few-electron atoms confined in spherical cavities. “Counter-intuitive” ordering of the interelectronic repulsions is confirmed when the nuclear charge is low enough and the cavity radius is large enough

Cost utility of fractional exhaled nitric oxide monitoring for the management of children asthma

Introduction Fractional exhaled nitric oxide is a simple, non-invasive measurement of airway inflammation with minimal discomfort to the patient and with results available within a few minutes. This study aimed to evaluate the cost-effectiveness of asthma management using fractional exhaled nitric oxide monitoring in patients between 4 and 18 years of age. Methods A Markov model was used to estimate the cost-utility of asthma management using fractional exhaled nitric oxide monitoring versus asthma management without using fractional exhaled nitric oxide monitoring (standard therapy) in patients between 4 and 18 years of age. Cost data were obtained from a retrospective study on asthma from a tertiary center, in Medellin, Colombia, while probabilities of the Markov model and utilities were obtained from the systematic review of published randomized clinical trials. The analysis was carried out from a societal perspective. Results The model showed that fractional exhaled nitric oxide monitoring was associated with a lower total cost than standard therapy (US $1333 vs. US$1452 average cost per patient) and higher QALYs (0.93 vs. 0.92 average per patient). The probability that fractional exhaled nitric oxide monitoring provides a more cost-effective use of resources compared with standard therapy exceeds 99% for all willingness-to-pay thresholds. Conclusion Asthma management using fractional exhaled nitric oxide monitoring was cost-effective for treating patients between 4 and 18 years of age with mild to moderate allergic asthma. Our study suggests evidence that could be used by decision-makers to improve clinical practice guidelines, but this should be replicated in different clinical settings

Parameterized optimized effective potential for the ground state of the atoms He through Xe

Parameterized orbitals expressed in Slater-type basis obtained within the optimized effective potential framework as well as the parameterization of the potential are reported for the ground state of the atoms He through Xe. The total, kinetic, exchange and single particle energies are given for each atom.Comment: 47 pages, 1 figur

Analysis of Undergraduate Dermatology Syllabi at Spanish Universities: Does the Weight of Theoretical Content Match the Skin Conditions Seen in Primary Care and General Dermatology Practices?

Introduction: Undergraduate dermatology courses vary in the nearly 50 Spanish medical faculties that teach the subject. This study aimed to describe the characteristics of these courses and to analyze whether the weight assigned to dermatology topics reflects the caseloads of primary care physicians and general dermatologists in the Spanish national health system. Material and methods: Cross-sectional study of syllabi used in Spanish medical faculties during the 2021---2022 academic year. We determined the number of teaching hours in public and private university curricula and compared the weight of dermatology topics covered to the dermatology caseloads of primary care physicians and general dermatologists as reported in published studies. Results: Most medical faculties taught dermatology for one semester. The median number of credits offered was 4.5. On average, lectures covered 24 theoretical topics, and seminars and workshops covered 9 topics. We identified a clear disparity between the percentage of time devoted to dermatology topics in course lectures and the skin conditions usually managed in primary care and general dermatology practices

Méthode numérique appliquée aux modèles analogiques quantifiables

La dinámica molecular de los polímeros puede explicarse utilizando sistemas construidos a partir de muelles y émbolos. Uno de los modelos más sustentables es el modelo de Vangheluwe y sus constantes paramétricas se determinan por los métodos método gráfico, método iterativo Marquardt, método del hiperplano. Así mismo otro modelo importante es el modelo de Zurek que determina sus constantes paramétricas usando un método gráfico e iterativo Marquardt. En este trabajo se aplica la técnica de mínimos cuadrados para evaluar las constantes numéricas de ambos modelos. La tecnica de mínimos cuadrados conduce a un sistema de ecuaciones no lineales que se resolvió por el método de Newton-Raphson. El resultado en ambos modelos fue sensiblemente mejor a los métodos disponibles.The molecular dynamics of polymers can be explained by means of systems constructed on the bases of springs and pistons. One of the most valid models is the Vangheluwe model and its parametric constants are determined by the graphic method1, the Marquardt iterative method, and the hyperplane method. Another important model is the Zurek model, whose parametric constants are determined using a graphic method and the iterative Marquardt method. In this paper, we apply the least squares technique to evaluate the numerical constants of both models. The least squares technique leads to a system of non-linear equations that were solved using the Newton-Raphson method. The results of both models were noticeably better than the available methods.La dynamique moléculaire des polymères peut s'expliquer en utilisant des systèmes construits avec des ressorts et des pistons. L'un des modèles les plus abordables est celiu de Vangheluwe et ses constantes paramétriques sont déterminées par les méthodes suivantes: méthode graphique, méthode itérative Marquardt, méthode de l'hyperplan. De même, un autre modèle important est celiu de Zurek qui détermine ses constantes paramétriques en utilisant une méhtode graphique et itérative Marquardt. Dans cette étude, la méthode des minimums carrés a été appliquée pour évaluer les constantes numériques des deux modèles. La technique des minimums carrés conduit à un système d'équations non linéaires qui est résolu par la méthode de Newton-Raphson. Dans les deux cas, le résultat a été sensiblement meilleur que celiu des méthodes disponibles

Response of a Model of CO Oxidation with CO Desorption and Diffusion to a Periodic External CO Pressure

We present a study of the dynamical behavior of a Ziff-Gulari-Barshad model with CO desorption and lateral diffusion. Depending on the values of the desorption and diffusion parameters, the system presents a discontinuous phase transition between low and high CO coverage phases. We calculate several points on the coexistence curve between these phases. Inclusion of the diffusion term produces a significant increase in the CO_2 production rate. We further applied a square-wave periodic pressure variation of the partial CO pressure with parameters that can be tuned to modify the catalytic activity. Contrary to the diffusion-free case, this driven system does not present a further enhancement of the catalytic activity, beyond the increase induced by the diffusion under constant CO pressure.Comment: 5 pages, RevTe

Projected multicluster model with Jastrow and linear state dependent correlations for 12≤A≤1612 \leq A \leq 16 nuclei

Variational wave functions based on a Margenau-Brink cluster model with short range and state dependent correlations, and angular momentum projection are obtained for some nuclei with $12 \leq A \leq 16$. The calculations have been carried out starting from the nucleon-nucleon interaction by using the Variational Monte Carlo method. The configuration used consists of three alpha clusters located at the apexes of an equilateral triangle, and an additional cluster, not necessarily of alpha type, forming a tetrahedron. This cluster is located at the top of its height. Short-range and state dependent correlations are included by means of a central Jastrow factor and a linear operatorial correlation factor respectively. Angular momentum projection is performed by using the Peierls-Yoccoz operators. Optimal structures are obtained for all the nuclei studied. Some aspects of our methodology have been tested by comparing with previous calculations carried out without short range correlations. The binding energy, the root mean square radius, and the one- and two-body densities are reported. The effects of correlations on both the energy and the nucleon distribution are analyzed systematically.Comment: 19 pages, 6 figure

Decay of metastable phases in a model for the catalytic oxidation of CO

We study by kinetic Monte Carlo simulations the dynamic behavior of a Ziff-Gulari-Barshad model with CO desorption for the reaction CO + O $\to$ CO$_2$ on a catalytic surface. Finite-size scaling analysis of the fluctuations and the fourth-order order-parameter cumulant show that below a critical CO desorption rate, the model exhibits a nonequilibrium first-order phase transition between low and high CO coverage phases. We calculate several points on the coexistence curve. We also measure the metastable lifetimes associated with the transition from the low CO coverage phase to the high CO coverage phase, and {\it vice versa}. Our results indicate that the transition process follows a mechanism very similar to the decay of metastable phases associated with {\it equilibrium} first-order phase transitions and can be described by the classic Kolmogorov-Johnson-Mehl-Avrami theory of phase transformation by nucleation and growth. In the present case, the desorption parameter plays the role of temperature, and the distance to the coexistence curve plays the role of an external field or supersaturation. We identify two distinct regimes, depending on whether the system is far from or close to the coexistence curve, in which the statistical properties and the system-size dependence of the lifetimes are different, corresponding to multidroplet or single-droplet decay, respectively. The crossover between the two regimes approaches the coexistence curve logarithmically with system size, analogous to the behavior of the crossover between multidroplet and single-droplet metastable decay near an equilibrium first-order phase transition.Comment: 27 pages, 22 figures, accepted by Physical Review