An elliptic property of parabolic trajectories

The curve joining the points of maximum height in the parabolas of ideal projectile motion is shown to be an ellipse. Some features of the motion are illustrated with the help of such ellipse.Comment: 4 pages, 1 figure. A shorter version of this typescript is scheduled to be published in the Am. J. Phys. probably in May 200

Sphere rolling on the surface of a cone

We analyse the motion of a sphere that rolls without slipping on a conical surface having its axis in the direction of the constant gravitational field of the Earth. This nonholonomic system admits a solution in terms of quadratures. We exhibit that the only circular of the system orbit is stable and furthermore show that all its solutions can be found using an analogy with central force problems. We also discuss the case of motion with no gravitational field, that is, of motion on a freely falling cone.Comment: 12 pages, 2 figures, to be published in Eur J Phy

Análisis bibliométrico de la producción científica peruana en cardiología y medicina cardiovascular

Objective. To determine the characteristics and trend of the articles published on cardiology and cardiovascular medicine in the Peruvian context, and to understand how it has changed over the years. Materials and methods. A bibliometric study of original articles published up to 2020 by Peruvian authors in journals indexed under the category “Cardiac & Cardiovascular Systems” in Web of Science (WOS) was performed. The articles were included according to the selection criteria in the Rayyan web application and the bibliometric analysis was performed using the Bibliometrix package in the R programming language and VOSviewer. Results. A total of 159 published articles were included, and an increase in the number of publications since 2015 was observed. The most cited article was a clinical trial by Fitchett et al. and published in 2016. Miranda JJ was the Peruvian author with the highest number of published articles followed by Hernández AV and Málaga G. The institutional affiliation with the highest number of original articles was Universidad Peruana Cayetano Heredia. Regarding the terms or keywords, it was found that most of the published studies had terms related to epidemiology, while in the most recent articles, the terms were related to outcomes or specific interventions that are used in clinical studies. Conclusions. In the last five years, there has been an increase in the scientific production on cardiology and cardiovascular medicine by authors with Peruvian institutional affiliation, with a greater production from the Universidad Peruana Cayetano Heredia. The journal with the highest number of publications by authors with Peruvian institutional affiliation on cardiology and cardiovascular medicine was Circulation, where two of the most cited articles with Peruvian institutional affiliation were also found.Objetivo. Determinar las características y la tendencia de los artículos publicados sobre cardiología y medicina cardiovascular en el contexto peruano, y comprender cómo ha cambiado a lo largo de los años. Materiales y métodos. Se realizó un estudio bibliométrico de artículos originales publicados hasta el año 2020 por autores peruanos en revistas indexadas bajo la categoría «Cardiac & Cardiovascular Systems» en Web of Science (WOS). Se incluyeron los artículos según los criterios de selección en el aplicativo web Rayyan y se realizó el análisis bibliométrico mediante el paquete Bibliometrix en el lenguaje de programación R y VOSviewer. Resultados. Se incluyeron 159 artículos publicados, y se observó un incremento del número de publicaciones desde 2015. El artículo más citado fue un ensayo clínico realizado por Fitchett et al. y publicado en 2016. Miranda JJ fue el autor peruano con mayor número artículos publicados seguido de Hernández AV y Málaga G. La filiación institucional con mayor número de artículos originales fue la Universidad Peruana Cayetano Heredia. En cuanto a los términos o palabras clave, se encontró que la mayor cantidad de estudios publicados contaban con términos relacionados con la epidemiología, mientras que en los artículos más recientes, los términos se relacionaron con desenlaces o intervenciones específicas que son utilizados en estudios clínicos. Conclusiones. Se encontró un incremento en los últimos cinco años en la producción científica sobre cardiología y medicina cardiovascular de autores con filiación institucional peruana, con una mayor producción de la Universidad Peruana Cayetano Heredia. La revista con mayores publicaciones de autores con filiación institucional peruana sobre cardiología y medicina cardiovascular fue Circulation, donde también se encontraron dos de los artículos con filiación institucional peruana más citados

Modeling of the Influence of Operational Parameters on Tire Lateral Dynamics

Tires play a critical role in vehicle safety. Proper modeling of tire–road interaction is essential for optimal performance of active safety systems. This work studies the influence of temperature, longitudinal vehicle speed, steering frequency, vertical load, and inflation pressure on lateral tire dynamics. To this end, a tire test bench that allows the accurate control of these parameters and the measurement of the variables of interest was used. The obtained results made it possible to propose a simple model that allowed the determination of relaxation length as a function of tire vertical load and vehicle linear speed, and the determination of a representative tread temperature. Additionally, a model has been proposed to determine the lateral friction coefficient from the aforementioned temperature. Finally, results also showed that some variables had little influence on the parameters that characterize lateral dynamicsThis work is partly supported partly by the Spanish Ministry of Science and Innovation under grant PID2019-105572RB-I00, partly by the Economy, Knowledge, Enterprise and Universities Council of the Andalusian Regional Government under grant UMA18-FEDERJA-109, partly by the Spanish Ministry of Education, Culture and Sport under grant FPU18/00450, and partly by the University of Malaga.Partial funding for open access charge: Universidad de Málag

The Lysholm score: Cross cultural validation and evaluation of psychometric properties of the Spanish version

This study aims at assessing the validity and reliability of the Spanish version of the Lysholm score, a widely used instrument for assessing knee function and activity level after ligament injuries. Ninety-five participants (67.4% male, 22±5 years) completed the questionnaire twice within 7 days and a subsample of 42 participants completed a test-retest reliability. Reliability, validity and feasibility psychometric properties were studied. The validity of the questionnaire was analysed using ceiling and floor effects. Factor structure and construct validity were analysed with the SF-36, the Hip and Knee Questionnaire (HKQ) and one leg jump test (OLJT). Criterion validity with the SF-36 Physical State was moderate (r = 0.50 and p<0.01), poor and inverse relationship (r = -0.31, p<0.01) with HKQ and positive moderate (r = 0.59, p<0.01) with OLJT. Measurement error from MDC90 was 3.9%. Exploratory factor analysis demonstrated a one-factor solution explaining 51.5% of total variance. The x2 test for the one-factor model was significant (x2 = 29.58, df = 20, p < 0.08). Test-retest reliability level was high (ICC2.1 = 0.92, p<0.01) and also the internal consistency (α = 0.77). The Spanish Lysholm score demonstrated that it is a reliable and valid instrument that can be used to assess knee function after ligament injuries.This study takes place thanks to the additional funding from the University of Granada, Plan Propio de Investigación 2016, Excellence actions: Units of Excellence; Unit of Excellence on Exercise and Health (UCEES)

Late myocardial reperfusion in ST-elevation myocardial infarction: Protocol for a systematic review and meta-analysis

Introduction ST-segment elevation myocardial infarction (STEMI) is the most severe clinical form of acute myocardial infarction, for which the current treatment consists of effective and timely myocardial reperfusion (within 12 hours of symptom onset). However, between 10% and 15% of patients with STEMI arrive at hospital facilities 12 hours after the onset of symptoms (late presentation). Therefore, the objective of the present study will be to determine if late revascularisation (12-72 hours after the onset of symptoms) affects the indicators of cardiovascular mortality, reinfarction, recurrent infarction, hospitalisation for heart failure and post infarction angina compared with no late revascularisation in patients with STEMI. Methods and analysis A systematic literature search of PubMed, The Cochrane Library, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science, Scopus and Global Health will be conducted. Publications in English, Portuguese or Spanish that report the clinical results of primary percutaneous revascularisation (primary PCI) in adult patients with STEMI 12-72 hours after the onset of symptoms will be included. Studies with participants with a diagnosis other than STEMI or patients with STEMI of >12 hours complicated by heart failure, cardiogenic shock or ventricular arrhythmias, and studies of combined interventions (pharmacoinvasive strategy) were excluded. Two independent authors will identify the relevant publications, and discrepancies will be adjudicated by a third author. Data extraction will be performed by two independent authors and verified by a third author. Risk of bias of studies will be assessed using the Cochrane risk of bias' tool (RoB 2) or Risk Of Bias In Non-randomised Studies - of Interventions (ROBINS-I) tool. If appropriate, a meta-analysis will be performed in order to examine the effect of late revascularisation in clinical outcomes of interest. Ethics and discussion This study will use published data only, thus, ethical approval will not be required. The results will be disseminated through peer-reviewed publication and conference presentations. PROSPERO registration number CRD42021283429.Revisión por pare

Broadband active differential array for the mid-frequency SKA band

This paper presents the design and characterization process of an active array demonstrator for the mid-frequency range (i.e., 300 MHz-1000 MHz) of the future Square Kilometre Array (SKA) radio telescope. This demonstrator, called FIDA3 (FG-IGN: Fundación General Instituto Geográfico Nacional - Differential Active Antenna Array), is part of the Spanish contribution for the SKA project. The main advantages provided by this design include the use of a dielectric-free structure, and the use of a fully-differential receiver in which differential low-noise amplifiers (LNAs) are directly connected to the balanced tapered-slot antennas (TSAs). First, the radiating structure and the differential low-noise amplifiers were separately designed and measured, obtaining good results (antenna elements with low voltage standing-wave ratios, array scanning capabilities up to 45°, and noise temperatures better than 52 K with low-noise amplifiers at room temperature). The potential problems due to the differential nature of the proposed solution are discussed, so some effective methods to overcome such limitations are proposed. Second, the complete active antenna array receiving system was assembled, and a 1 m2 active antenna array tile was characterized

ODS ferritic steels obtained from gas atomized powders through the STARS processing route: Reactive synthesis as an alternative to mechanical alloying

Oxide Dispersion Strengthened Ferritic Stainless Steels (ODS FS) are candidate materials for structural components in fusion reactors. Their ultrafine microstructure and the presence of a very stable dispersion of Y-Ti-O nanoclusters provide reasonable fracture toughness, high mechanical and creep strength, and resistance to radiation damage at the operation temperature, up to about 750 °C. An innovative route to produce ODS FS with composition Fe-14Cr-2W-0.3Ti-0.3Y2O3 (wt.%), named STARS (Surface Treatment of gas Atomized powder followed by Reactive Synthesis), is presented. This route avoids the mechanical alloying (MA) of the elemental or prealloyed powders with yttria to dissolve the yttrium in the ferritic matrix. In this study, starting powders containing Ti and Y are obtained by gas atomization at laboratory and industrial scale. Then, a metastable Cr- and Fe- rich oxide layer is formed on the surface of the powder particles. During consolidation by HIP the metastable oxide layer at Prior Particle Boundaries (PPBs) dissociates, the oxygen diffuses towards saturated solutions or metallic Ti- and Y-rich particles, and Y-Ti-O nano-oxides (mainly Y2TiO5) precipitate in the ferritic matrix. Detailed Microstructural characterization by X-ray Photoelectron Spectroscopy (XPS), X-ray Absorption Spectroscopy (XAS), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) of powders and consolidated materials is presented and correlated with mechanical behaviour

The Imaging Magnetograph eXperiment (IMaX) for the Sunrise balloon-borne solar observatory

The Imaging Magnetograph eXperiment (IMaX) is a spectropolarimeter built by four institutions in Spain that flew on board the Sunrise balloon-borne telesocope in June 2009 for almost six days over the Arctic Circle. As a polarimeter IMaX uses fast polarization modulation (based on the use of two liquid crystal retarders), real-time image accumulation, and dual beam polarimetry to reach polarization sensitivities of 0.1%. As a spectrograph, the instrument uses a LiNbO3 etalon in double pass and a narrow band pre-filter to achieve a spectral resolution of 85 mAA. IMaX uses the high Zeeman sensitive line of Fe I at 5250.2 AA and observes all four Stokes parameters at various points inside the spectral line. This allows vector magnetograms, Dopplergrams, and intensity frames to be produced that, after reconstruction, reach spatial resolutions in the 0.15-0.18 arcsec range over a 50x50 arcsec FOV. Time cadences vary between ten and 33 seconds, although the shortest one only includes longitudinal polarimetry. The spectral line is sampled in various ways depending on the applied observing mode, from just two points inside the line to 11 of them. All observing modes include one extra wavelength point in the nearby continuum. Gauss equivalent sensitivities are four Gauss for longitudinal fields and 80 Gauss for transverse fields per wavelength sample. The LOS velocities are estimated with statistical errors of the order of 5-40 m/s. The design, calibration and integration phases of the instrument, together with the implemented data reduction scheme are described in some detail.Comment: 17 figure