Interpreting the Hours-Technology time-varying relationship

We investigate the time varying relation between hours and technology shocks using a structural business cycle model. We propose an RBC model with a Constant Elasticity of Substitution (CES) production function that allows for capital- and labor-augmenting technology shocks. We estimate the model with Bayesian techniques. In the full sample, we find (i) evidence in favor of a less than unitary elasticity of substitution (rejecting Cobb-Douglas) and (ii) a sizable role for capital augmenting shock for business cycles fluctuations. In rolling sub-samples, we document that the transmission of technology shocks to hours worked has been varying over time. We argue that this change is due to the increase of the elasticity of factor substitution. That is, labor and capital became less complementary throughout the sample inducing a change in the sign and size of the response of hours. We conjecture that this change may have been induced by a change in the skill composition of the labor input.Hours Worked and Business Cycles, Bayesian Methods.

The role of building information modeling in a project-based course for integration of design and construction at WPI [2010]

En el entorno competitivo de la actualidad, la Arquitectura, Ingeniería, e Industria de la construcción (A / E / C por sus siglas en inglés: Architecture, Engineering, and Construction), los servicios profesionales que compiten en el mercado para satisfacer las necesidades de los propietarios en cuanto a calidad, eficiencia, costos, y control horario. Para satisfacer estas necesidades, la industria está experimentando cambios fundamentales basados en la integración de las funciones realizadas por las empresas. Para atender las necesidades educativas derivadas de una mayor integración en la industria, en 1993 el Departamento de Ingeniería Civil y Ambiental en el Instituto Politécnico de Worcester (WPI) implementó el Programa Maestro de obras. Un curso de postgrado a nivel de la CE 535 Integración de Diseño y Construcción se desarrolló y se ofreció por primera vez durante el semestre de otoño de 1995 como parte del Programa del Master Builder. Con los años, los dos instructores de clase se han adaptado a los principios de la ingeniería de valor como un modelo pedagógico para entregar el material del curso y establecer un marco formal para apoyar el análisis racional y la toma de decisiones para la integración de diseño, construcción y planificación financiera. Ahora que los estudiantes IPM son cada vez más expuestos al uso de software 3D-OOP programación orientada a objetos y al concepto Building Information Modeling (BIM); el CE 535 se está revisando para exigir a los estudiantes a la utilización de las herramientas BIM y conceptos como parte integral de su desarrollo del proyecto. Para lograr esto, una parte de los laboratorios se dedicarán ahora a facilitar el aprendizaje de los estudiantes de esos elementos BIM que son necesarios para el desarrollo de su proyecto a largo plazo. Este artículo presenta la elaboración de un tutorial que es desarrollado principalmente por el tercer autor durante el verano del 2010. Este tutorial tiene por objeto guiar a los estudiantes en el uso de Autodesk Revit en su proyecto a largo plazo, ya que poco a poco aplicara su experiencia, respondiendo a una solicitud de propuesta para el diseño y construcción de un estacionamiento situado en Lexington Street, Worcester, MA

The spectral type of CHS7797 - an intriguing very low mass periodic variable in the Orion Nebula Cluster

We present the spectroscopic characterization of the unusual high-amplitude very low mass pre-main-sequence periodic variable CHS7797. This study is based on optical medium-resolution (R=2200) spectroscopy in the 6450-8600 A range, carried out with GMOS-GEMINI-S in March 2011. Observations of CHS7797 have been carried out at two distinct phases of the 17.8d period, namely at maximum and four days before maximum. Four different spectral indices were used for the spectral classification at these two phases, all of them well-suited for spectral classification of young and obscured late M dwarfs. In addition, the gravity-sensitive NaI (8183/8195 A) and KI (7665/7699 A) doublet lines were used to confirm the young age of CHS7797. From the spectrum obtained at maximum light we derived a spectral type (SpT) of M6.05, while for the spectrum taken four days before maximum the derived SpT is M5.75. The derived SpTs confirm that CHS7797 has a mass in the stellar-substellar boundary mass range. In addition, the small differences in the derived SpTs at the two observed phases may provide indirect hints that CHS7797 is a binary system of similar mass components surrounded by a tilted circumbinary disk, a system similar to KH15D.Comment: 6 pages, accepted for publication A&

Observational epidemiological study to identify the clinical profile of naïve patients starting antiretroviral (ARV) therapy in Spain

Purpose of the study: To identify the proportion of patients starting ARV treatment with NNRTIs or with a PI/r and to explore and compare their clinical profile establishing different factors whereby physicians select the initial ARV treatment in a Spanish clinical setting. Methods: An observational study was conducted in two different phases. In Phase I a cross-sectional registration was conducted for patients who initiated ARV treatment in a 6-month period in 65 Spanish hospitals. In Phase II clinical and social-demographic features were collected retrospectively of patients who visited HIV clinics between August and November 2010 who had started ARV treatment containing an NNRTIs or a PI/r in Phase I. Summary of results: In Phase I, 1,687 subjects who initiated ARV treatment were registered, of which 53% started with an NNRTI-based regimen whereas 42% started with a PI/r-based regimen. Two percent of the treatment initiations occurred in a clinical trial. In Phase II, 642 patients were paired consecutively and retrospectively. The group of patients was composed of predominantly male subjects (81% vs 19%). The median time between diagnosis and the start of ARV treatment was 3.6±5.3 years. At the initiation of treatment, 72% of patients had a CD4 count below 350 cells/µl. Although treatment based on NNRTIs in naïve patients is the most frequent option in Spain, the analysis of clinical profiles shows that PI/r-based therapy is more often used than NNRTIs with statistical significance in patients with high viral load, Fig. A (≥100.000 copies/ml) (58% vs 42%; OR:1,75; 95% CI: 1,26–2,43; p<0,01), with CD4 cell counts <200 cells/µl, Fig. B (68% vs 31%; OR: 2,92; 95% CI: 1,99–4,27; p<0,01), and in patients at CDC stage C (65% vs 35%; OR: 2,05; CI: 1,27–3,31; p<0,01). Conclusions: In Spain, HIV is still diagnosed late (as measured by CD4 count<350 cells/µl). Treatment based on NNRTIs are more frequently used in naïve patients, although PIs/r-based regimens play an important role being the preferred option in patients with high viral load (≥100.000 copies/ml) and low CD4 cell count (<200 cells/µl)

Mutation and SARS-CoV-2 strain competition under vaccination in a modified SIR model

The crisis caused by the COVID-19 outbreak around the globe raised an increasing concern about the ongoing emergence of variants of SARS-CoV-2 that may evade the immune response provided by vaccines. New variants appear due to mutation, and as the cases accumulate, the probability of the emergence of a variant of concern increases. In this article, we propose a modified SIR model with waning immunity that captures the competition of two strain classes of an infectious disease under the effect of vaccination with a highly contagious and deadly strain class emerging from a prior strain due to mutation. When these strains compete for a limited supply of susceptible individuals, changes in the efficiency of vaccines may affect the behaviour of the disease in a non-trivial way, resulting in complex outcomes. We characterise the parameter space including intrinsic parameters of the disease, and using the vaccine efficiencies as control variables. We find different types of transcritical bifurcations between endemic fixed points and a disease-free equilibrium and identify a region of strain competition where the two strain classes coexist during a transient period. We show that a strain can be extinguished either due to strain competition or vaccination, and we obtain the critical values of the efficiency of vaccines to eradicate the disease. Numerical studies using parameters estimated from publicly reported data agree with our theoretical results. Our mathematical model could be a tool to assess quantitatively the vaccination policies of competing and emerging strains using the dynamics in epidemics of infectious diseases.Comment: 28 pages, 8 figure

Non-traumatic chronic shoulder pain is not associated with changes in rotator cuff interval tendon thickness

To determine whether the thickness of the rotator interval tendons is different when comparing both symptomatic and non-symptomatic sides in people with chronic shoulder pain, and to those free of pain. Furthermore, to calculate the level of association between the rotator interval tendon thicknesses and perceived shoulder pain-function. A cross-sectional, observational study. The supraspinatus, subscapularis and biceps brachii tendon thickness of sixty two patients with chronic shoulder pain were determined from standardized ultrasonography measures performed on both shoulders, whereas only the dominant arm was measured for the control subjects. Supraspinatus, subscapularis and biceps brachii tendon thickness was comparable between sides in the symptomatic group and was also comparable between the symptomatic and asymptomatic participants. In addition, the correlation between the tendon thickness and shoulder pain-function was non-significant. Tendon thickness was unaltered in people with chronic shoulder pain. These findings do not rule out the possibility that other changes in the tendon are present such as changes in the elastic properties and cell population and this should be explored in future studies

The role of building information modeling in a project-based course for integration of design and construction at WPI [2018]

En el entorno competitivo de la actualidad, la Arquitectura, Ingeniería, e Industria de la construcción (A / E / C por sus siglas en inglés: Architecture, Engineering, and Construction), los servicios profesionales que compiten en el mercado para satisfacer las necesidades de los propietarios en cuanto a calidad, eficiencia, costos, y control horario. Para satisfacer estas necesidades, la industria está experimentando cambios fundamentales basados en la integración de las funciones realizadas por las empresas. Para atender las necesidades educativas derivadas de una mayor integración en la industria, en 1993 el Departamento de Ingeniería Civil y Ambiental en el Instituto Politécnico de Worcester (WPI) implementó el Programa Maestro de obras. Un curso de postgrado a nivel de la CE 535 Integración de Diseño y Construcción se desarrolló y se ofreció por primera vez durante el semestre de otoño de 1995 como parte del Programa del Master Builder. Con los años, los dos instructores de clase se han adaptado a los principios de la ingeniería de valor como un modelo pedagógico para entregar el material del curso y establecer un marco formal para apoyar el análisis racional y la toma de decisiones para la integración de diseño, construcción y planificación financiera. Ahora que los estudiantes IPM son cada vez más expuestos al uso de software 3D-OOP programación orientada a objetos y al concepto Building Information Modeling (BIM); el CE 535 se está revisando para exigir a los estudiantes a la utilización de las herramientas BIM y conceptos como parte integral de su desarrollo del proyecto. Para lograr esto, una parte de los laboratorios se dedicarán ahora a facilitar el aprendizaje de los estudiantes de esos elementos BIM que son necesarios para el desarrollo de su proyecto a largo plazo. Este artículo presenta la elaboración de un tutorial que es desarrollado principalmente por el tercer autor durante el verano del 2010. Este tutorial tiene por objeto guiar a los estudiantes en el uso de Autodesk Revit en su proyecto a largo plazo, ya que poco a poco aplicara su experiencia, respondiendo a una solicitud de propuesta para el diseño y construcción de un estacionamiento situado en Lexington Street, Worcester, MA

Voltage dip generator for testing wind turbines connected to electrical networks

This paper describes a new voltage dip generator that allows the shape of the time profile of the voltage generated to be configured. The use of this device as a tool to test the fault ride-through capability of wind turbines connected to the electricity grid can provide some remarkable benefits: First, this system offers the possibility of adapting the main features of the time–voltage profile generated (dip depth, dip duration, the ramp slope during the recovery process after clearing fault, etc.) to the specific requirements set forth by the grid operation codes, in accordance with different network electrical systems standards. Second, another remarkable ability of this system is to provide sinusoidal voltage and current wave forms during the overall testing process without the presence of harmonic components. This is made possible by the absence of electronic converters. Finally, the paper includes results and a discussion on the experimental data obtained with the use of a reduced size laboratory prototype that was constructed to validate the operating features of this new device

Interplay between internal structure and optical properties of thermosensitive nanogels

The structural and optical properties of thermosensitive particles, nanogels, are studied by light scattering and refractometry as a function of temperature. Nanogels are composed of poly- N-Isopropopylacrylamide, a polymer that shrinks at temperatures higher than its lower critical solution temperature, 33 °C. The internal nanogel structure obtained by light scattering is well modeled by assuming a constant radial mass density profile convoluted with a Gaussian function. Moreover, we introduce a simple method that allows us to describe the measured temperature-dependent index of refraction of these complex nanoparticles by using their structural information, core dimension and external radius