On First-Passage Times and Sojourn Times in Finite QBD Processes and Their Applications in Epidemics

In this paper, we revisit level-dependent quasi-birth-death processes with finitely many possible values of the level and phase variables by complementing the work of Gaver, Jacobs, and Latouche (Adv. Appl. Probab. 1984), where the emphasis is upon obtaining numerical methods for evaluating stationary probabilities and moments of first-passage times to higher and lower levels. We provide a matrix-analytic scheme for numerically computing hitting probabilities, the number of upcrossings, sojourn time analysis, and the random area under the level trajectory. Our algorithmic solution is inspired from Gaussian elimination, which is applicable in all our descriptors since the underlying rate matrices have a block-structured form. Using the results obtained, numerical examples are given in the context of varicella-zoster virus infections

A Comparison of Distributed Spatial Data Management Systems for Processing Distance Join Queries

Due to the ubiquitous use of spatial data applications and the large amounts of spatial data that these applications generate, the processing of large-scale distance joins in distributed systems is becoming increasingly popular. Two of the most studied distance join queries are the K Closest Pair Query (KCPQ) and the ε Distance Join Query (εDJQ). The KCPQ finds the K closest pairs of points from two datasets and the εDJQ finds all the possible pairs of points from two datasets, that are within a distance threshold ε of each other. Distributed cluster-based computing systems can be classified in Hadoop-based and Spark-based systems. Based on this classification, in this paper, we compare two of the most current and leading distributed spatial data management systems, namely SpatialHadoop and LocationSpark, by evaluating the performance of existing and newly proposed parallel and distributed distance join query algorithms in different situations with big real-world datasets. As a general conclusion, while SpatialHadoop is more mature and robust system, LocationSpark is the winner with respect to the total execution time

Caracteres geoquímicos y mineralógicos del yacimiento de Sn y Au de Montejo (Salamanca)

[Resumen] El yacimiento situado al S. E. de la Provincia de Salamanca está constituido por una serie de filones de cuarzo brechificado de dirección E-W, subverticales y encajados en materiales pertenecientes al Complejo Esquistograuváquico (Formación Monterrubio, dominando en esta zona esquistos, grauvacas y microconglomerados). Fue explotado durante los años 40 y 50 para Sn y esporádicamente para Au. Se han estudiado al microscopio 80 preparaciones pulidas y transparentes seleccionadas en cuatro sondeos de 250 metros, calicatas y antiguas escombreras, con el fin de caracterizar paragénesis, sucesión de la mineralización y alteraciones hidrotermales relacionadas. También se ha realizado un muestréo en las zonas mineralizadas y con alteración hidrotermal para su estudio geoquímico. Se han analizado: Au, As, Sb, Bi, Cu, Pb, Zn, Sn, Rb, Sr y Ba en 40 muestras. Las relaciones intereleme~ntales más evidentes son: Au-Sn-Bi y Cu-Sb. Por otro lado, se correlacionan los resultados geoquímicos con los diversos tipos de alteraciones hidrotermales.[Abstract] This tin-gold deposit is located in the SE Salamanca province. Mineralization is associated with several quartz-veins and breccias in metamorphic terrains of Precambrian-Cambrian ages (<<Complejo Esquistograuváquico»). Were studied microscopically 80 samples of four drillings (250 m deep) and other surface sampIes. It is presented mineral paragenesis and wall-rocks alterations relationed with mineralization. The geochemical stady include determinations of Au, As, Sb, Bi, Cu, Pb, Zn, Sn, Rb, Sr and Ba. A factor analysis on the geochemical data stablished the fo11owing associations: Au-Sn-Bi and Cu-Sb

Perturbation analysis in finite LD‐QBD processes and applications to epidemic models

In this paper, our interest is in the perturbation analysis of level‐dependent quasi‐birth‐and‐death (LD‐QBD) processes, which constitute a wide class of structured Markov chains. An LD‐QBD process has the special feature that its space of states can be structured by levels (groups of states), so that a tridiagonal‐by‐blocks structure is obtained for its infinitesimal generator. For these processes, a number of algorithmic procedures exist in the literature in order to compute several performance measures while exploiting the underlying matrix structure; among others, these measures are related to first‐passage times to a certain level L(0) and hitting probabilities at this level, the maximum level visited by the process before reaching states of level L(0), and the stationary distribution. For the case of a finite number of states, our aim here is to develop analogous algorithms to the ones analyzing these measures, for their perturbation analysis. This approach uses matrix calculus and exploits the specific structure of the infinitesimal generator, which allows us to obtain additional information during the perturbation analysis of the LD‐QBD process by dealing with specific matrices carrying probabilistic insights of the dynamics of the process. We illustrate the approach by means of applying multitype versions of the susceptible‐infective (SI) and susceptible‐infective‐susceptible (SIS) epidemic models to the spread of antibiotic‐sensitive and antibiotic‐resistant bacterial strains in a hospital ward

A Markov chain model to investigate the spread of antibiotic-resistant bacteria in hospitals

Ordinary differential equation (ODE) models used in mathematical epidemiology assume explicitly or implicitly large populations. For the study of infections in a hospital this is an extremely restrictive assumption as typically a hospital ward has a few dozen, or even fewer, patients. This work reframes a well-known model used in the study of the spread of antibiotic-resistant bacteria in hospitals, to consider the pathogen transmission dynamics in small populations. In this vein, this paper proposes a Markov chain model to describe the spread of a single bacterial species in a hospital ward where patients may be free of bacteria or may carry bacterial strains that are either sensitive or resistant to antimicrobial agents. We determine the probability law of the \emph{exact} reproduction number ${\cal R}_{exact,0}$, which is here defined as the random number of secondary infections generated by those patients who are accommodated in a predetermined bed before a patient who is free of bacteria is accommodated in this bed for the first time. Specifically, we decompose the exact reproduction number ${\cal R}_{exact,0}$ into two contributions allowing us to distinguish between infections due to the sensitive and the resistant bacterial strains. Our methodology is mainly based on structured Markov chains and the use of related matrix-analytic methods. This guarantees the compatibility of the new, finite-population model, with large population models present in the literature and takes full advantage, in its mathematical analysis, of the intrinsic stochasticity.Comment: 30 pages, 9 figure

Capillary glucose concentration during oral glucose tolerance test for the diagnosis of gestational diabetes

Objective: To assess concordance between two point-of-care testing (POCT) devices and the standard laboratory method in screening for gestational diabetes mellitus (GDM) in Huesca. Methods: Pregnant women who met criteria for an oral glucose tolerance test (OGTT) and attended the laboratory between October 2017 and November 2018 were recruited in this prospective observational study. Glucose was measured in venous (laboratory) and capillary blood (Accu-Chek or Contour Next glucometers). GDM was diagnosed attending to NDDG criteria for venous samples or capillary-specific cut-off. Linear regression, Passing–Bablok, Bland–Altman, and the kappa coefficient were used to study concordance between POCT and laboratory method. Results: Data from 109 women were analyzed (57 for Accu-Chek, 52 for Contour Next). Statistical analyses showed good agreement between both POCT and laboratory method. There were no statistical differences in fasting glucose measurements between capillary and venous samples and both POCT devices meet the ISO 15197 standard. Accu-Chek showed good agreement (k=0.629) regarding the laboratory method in classifying GDM, with an acceptable inter-evaluator bias of 3.5% (P<0.001). Conclusion: POCT can be used to obtain fasting values and reduce overall waiting times for patients. Additionally, Accu-Chek can be used to diagnose GDM in remote areas applying specific cut-off values

Lifetime and reproduction of a marked individual in a two-species competition process

The interest is in a stochastic model for the competition of two species, which was first introduced by Reuter [18] and Iglehart [11], and then analyzed by Ridler-Rowe [19]. The model is related to the two-species autonomous competitive model (Zeeman [24]), where individuals compete either directly or indirectly for a limited food supply and, consequently, birth and death rates depend on the population size of one or both of the species. The aim is to complement the treatment of the model we started in [8,9] by focusing here on probabilistic descriptors that are inherently linked to an individual: its residual lifetime and the number of direct descendants. We present an approximating model based on the maximum size distribution, and we discuss on various models defined in terms of the underlying killing and reproductive strategies. Numerical examples are presented to show the effects of the killing and reproductive strategies on the behavior of an individual, and how the impact of these strategies on the descriptors vanishes in highly competitive ecosystems

Adquisición de datos digitales con protocolo VME sobre FPGA

En este artículo se presenta la realización sobre FPGA de un circuito con 16 filtros digitales. Un cambio en la entrada es validado cada vez que tres muestras consecutivas toman el mismo valor. El dato muestreado es accesible mediante protocolo VME estándar, incluyendo daisy-cbain para la gestión de interrupciones. El circuito de acceso VME se ha descrito en lenguaje de comportamiento VERILOG-XL, y sintetizado usando SYNERGY. El resto del circuito ha sido capturado y simulado empleando el entorno de diseño Framework II de Cadence. El circuito ha sido programado en una FPGA 1020A de Texas Instrument. Como resultado se ha obtenido una tarjeta de adquisición de datos con una densidad de componentes muy baja, y que está siendo actualmente empleada en sistemas de control industriales

An Optical Engine Used as a Physical Model for Studies of the Combustion Process Applying a Two-Color Pyrometry Technique

[EN] This work describes an experimental installation for the investigation of the combustion and injection processes. This installation is based on a two-stroke direct injection diesel engine with a total displacement of 3 L and a cylinder head equipped with three quartz windows. The windows are optical accesses that allow studying the process of injection, the atomization and evaporation of the fuel jet in an inert atmosphere (nitrogen), and the combustion process in a reactive atmosphere (ambient air). Additionally, the application of a two-color pyrometry technique to measure soot formation in this facility is presented. A methodological study is carried out regarding the influence of the dynamic range of the detectors and the wavelengths used. Maps of KL2C, flame temperature, and error probability are presented. The use of cameras with high dynamic range provides better results since the system seems to be less sensitive to measurement noise, and fewer points are obtained with a non-physical solution. Moreover, an appropriate combination of interference filters can improve the reliability of the solution. The greater the difference between the wavelengths of both interference filters, the fewer points with a non-physical solution, which improves the reliability of results.This research was funded by Castilla-La Mancha Government to the project grant number ASUAV Ref. SBPLY/19/180501/000116.Corral-Gómez, L.; Armas, O.; Soriano, JA.; Pastor, JV.; García-Oliver, JM.; Micó, C. (2022). An Optical Engine Used as a Physical Model for Studies of the Combustion Process Applying a Two-Color Pyrometry Technique. Energies. 15(13):1-17. https://doi.org/10.3390/en15134717117151

Rotura del tendón distal del bíceps braquial

Objetivo: presentar nuestra experiencia en el tratamiento de las roturas del tendón del bíceps braquial en trabajadores manuales. Material y métodos: Hemos intervenido a 9 pacientes con una edad media de 47 años, realizando en 8 ocasiones una reinserción transósea del tendón en la tuberosidad bicipital del radio por medio de una doble vía de abordaje. El seguimiento medio ha sido de 13 meses. Resultados: fueron excelentes, recuperando en todos los casos la fuerza muscular previa y una movilidad media final completa para la flexión y extensión, 85º de supinación y 86º de pronación. Todos se han reincorporado a su puesto de trabajo en un período entre los 3 y 4 meses. Conclusiones: Esta técnica se ha mostrado muy eficaz en el tratamiento de este tipo de patología, recomendándose siempre la cirugía en pacientes activos.Objective: to present our experience in the treatment of ruptures of the distal biceps braquialis tendon in hand workers. Methods: 9 patients, middle age 47, went under surgery, 8 of them with a transoseus reinsertion of the tendon in the bicipital tuberosity of the radius with a double surgical approach. The average follow-up was 13 months. Results: excellent results were achieved in all of the 9 patients, recovering previous muscle strength, with full range of flexion-extension, 85º of supination and 86º of pronation. All 9 patients return to work in a period of 3 to 4 months. Conclusion: this technique is effective in the treatment of this injury, and it is recommended in active patients