Selective beat averaging to evaluate ventricular repolarization adaptation to deconditioning after 5 days of head-down bed rest

The study of QT/RR relationship is important for the clinical evaluation of possible risk of ventricular tachyarrhythmia. Our aim was to assess the effects of 5-days of head-down (-6 degrees) bed-rest (HDBR) on ventricular repolarization. High fidelity 12-leads Holter ECG was acquired before (PRE), the last day of HDBR (HDT5), and five days after its conclusion (POST). X, Y, Z leads were derived (inverse Dower matrix) and vectorcardiogram computed. Selective beat averaging applied to the night period resulted in averages preceded by the same stable heart rate (for each 10 msec bin amplitude, in the range 900-1200 msec). For each template (i.e., one for each bin), T-wave maximum amplitude (Tmax), T wave area, R-Tapex and R-Tend were computed. Results (in 8 male volunteers) showed that, compared to PRE, at HDT5 both R-Tapex and R-Tend resulted significantly shortened (-5% and -3%, respectively), together with a decrease in T-wave area (-7%), while Tmax was unchanged. At POST, duration parameters showed a trend towards their control values (-1.5% and -3%, respectively) while amplitude parameters resulted restored. Despite the short-term BR, cardiac adaptation to deconditioning affected ventricular repolarization during the night period. © 2012 CCAL

Orographic and convective gravity waves above the Alps and Andes Mountains during GPS radio occultation events – a case study

Gravity waves (GWs) and convective systems play a fundamental role in atmospheric circulation, weather, and climate. Two usual main sources of GWs are orographic effects triggering mountain waves and convective activity. In addition, GW generation by fronts and geostrophic adjustment must also be considered. The utility of Global Positioning System (GPS) radio occultation (RO) observations for the detection of convective systems is tested. A collocation database between RO events and convective systems over subtropical to midlatitude mountain regions close to the Alps and Andes is built. From the observation of large-amplitude GW structures in the absence of jets and fronts, subsets of RO profiles are sampled. A representative case study among those considered at each region is selected and analyzed. The case studies are investigated using mesoscale Weather Research and Forecasting (WRF) simulations, ERA-Interim reanalysis data, and measured RO temperature profiles. The absence of fronts or jets during both case studies reveals similar relevant GW features (main parameters, generation, and propagation). Orographic and convective activity generates the observed GWs. Mountain waves above the Alps reach higher altitudes than close to the Andes. In the Andes case, a critical layer prevents the propagation of GW packets up to stratospheric heights. The case studies are selected also because they illustrate how the observational window for GW observations through RO profiles admits a misleading interpretation of structures at different altitude ranges. From recent results, the distortion introduced in the measured atmospheric vertical wavelengths by one of the RO events is discussed as an illustration. In the analysis, both the elevation angle of the sounding path (line of tangent points) and the gravity wave aspect ratio estimated from the simulations and the line of sight are taken into account. In both case studies, a considerable distortion, over- and underestimation of the vertical wavelengths measured by RO, may be expected

A method to improve the determination of wave perturbations close to the tropopause by using a digital filter

GPS radio occultation satellite data allowed to analyze in the last decade for the first time a large amount of atmospheric temperature profiles including both the troposphere and the stratosphere all over the globe. Wave amplitude enhancements have been systematically observed around tropopause levels, which are apparently due to artifacts generated by any digital filter used to isolate the wave components from these data. We present a new filtering method which can be equally applied to temperature or refractivity profiles. It was tested with synthetic temperature data based on NCEP reanalyes and observed wave climatologies and it was also statistically validated with GPS radio occultation profiles from the COSMIC mission. The suggested technique significantly reduces artificial enhancements around the tropopause, mainly at low latitudes, where a sharp lapse rate change usually exists. This represents an improvement in comparison to previous applications of standard filters. In addition it would allow the study of longer vertical wavelengths than previously done with other filtering procedures

Temperature Profiles From Two Close Lidars and a Satellite to Infer the Structure of a Dominant Gravity Wave

Gravity waves (GW) are a crucial coupling mechanism for the exchange of energy and momentum flux (MF) between the lower, middle, and upper layers of the atmosphere. Among the remote instruments used to study them, there has been a continuous increment in the last years in the installation and use of lidars (light detection and ranging) all over the globe. Two of them, which are only night operating, are located in Río Gallegos (−69.3◦ W, −51.6◦ S) and Río Grande (−67.8◦ W, −53.8◦ S), in the neighborhood of the austral tip of South America. This is a well-known GWhot spot from late autumn to early spring. Neither the source for this intense activity nor the extent of its effects have been yet fully elucidated. In the last years, different methods that combine diverse retrieval techniques have been presented in order to describe the three-dimensional (3-D) structure of observed GW, their propagation direction, their energy, and the MF that they carry. Assuming the presence of a dominant GWin the covered region, we develop here a technique that uses the temperature profiles from two simultaneously working close lidars to infer the vertical wavelength, ground-based frequency, and horizontal wavelength along the direction joining both instruments. If in addition within the time and spatial frame of both lidars there is also a retrieval from a satellite like SABER (Sounding of the Atmosphere using Broadband Emission Radiometry), then we show that it is possible to infer also the second horizontal wavelength and therefore reproduce the full 3-D GWstructure. Our method becomes verified with an example that includes tests that corroborate that both lidars and the satellite are sampling the same GW. The improvement of the Río Gallegos lidar performance could lead in the future to the observation of a wealth of cases during the GWhigh season. Between 8 and 14 hr (depending on the month) of continuous nighttime data could be obtained in the stratosphere and mesosphere in simultaneous soundings from both ground-based lidars.Facultad de Ciencias Astronómicas y GeofísicasConsejo Nacional de Investigaciones Científicas y Técnica

Tropospheric Products from High-Level GNSS Processing in Latin America

ARTÍCULO PUBLICADO EN REVISTA EXTERNA. The present geodetic reference frame in Latin America and the Caribbean is given by a network of about 400 continuously operating GNSS stations. These stations are routinely processed by ten Analysis Centres following the guidelines and standards set up by the International Earth Rotation and Reference Systems Service (IERS) and International GNSS Service (IGS). The Analysis Centres estimate daily and weekly station positions and station zenith tropospheric path delays (ZTD) with an hourly sampling rate. This contribution presents some attempts aiming at combining the individual ZTD estimations to generate consistent troposphere solutions over the entire region and to provide reliable time series of troposphere parameters, to be used as a reference. The study covers ZTD and IWV series for a time-span of 5 years (2014–2018). In addition to the combination of the individual solutions, some advances based on the precise point positioning technique using BNC software (BKG NTRIP Client) and Bernese GNSS Software V.5.2 are presented. Results are validated using the IGS ZTD products and radiosonde IWV data. The agreement was evaluated in terms of mean bias and rms of the ZTD differences w.r.t IGS products (mean bias 1.5 mm and mean rms 6.8 mm) and w.r.t ZTD from radiosonde data (mean bias 2 mm and mean rms 7.5 mm). IWV differences w.r.t radiosonde IWV data (mean bias 0.41 kg/m2 and mean rms 3.5 kg/m2).Sitio de la revista: https://link.springer.com/chapter/10.1007/1345_2020_12

A gravity waves study close to the Andes mountains in Patagonia and Antarctica with GPS radio occultation observations

We first study the seasonal and geographical behavior of gravity wave activity in the lower stratosphere over the southernmost Andes mountains and their prolongation in the Antarctic Peninsula by global positioning system (GPS) radio occultation (RO) temperature profiles, obtained between years 2002 and 2005 by the CHAllenging Minisatellite Payload (CHAMP) mission. The observed features complement observations in the same zone by other satellite passive remote sensing instruments, which are able to detect different height regions and other spectral intervals of the wave spectrum. Comparisons with previous GPS RO studies in smaller areas than the one covered in our analysis are also established. Significant seasonal variation of wave activity is observed in our work, in agreement with results from other instruments. The locations of significant cases indicate that topography is an important source. Some strong wave activity is also found over open ocean. Critical level filtering is shown to have an attenuation effect, implying that a large fraction of the observed activity can be considered to be an outcome of mountain waves. The studied region has a significant advantage as compared to other regions of our planet: it generates wavefronts nearly aligned with the North-South direction (almost parallel to the mountains), whereby this geometry favors the wave detection by the nearly meridional line of sight characterizing most of the GPS RO observations used. A distribution of the observed gravity waves in terms of amplitudes and wavelengths is also presented

A new approach to global gravity wave momentum flux determination from GPS radio occultation data

Cilj je rada analizirati 116 nadimaka engleskih nogometnih klubova iz pet liga, i to prema dva različita načela. Prvo se načelo odnosi na pozadinu koja je bila osnova davanja svakoga od analiziranih nadimaka, a drugo načelo promatra izričaj, odnosno što se u samome nadimku nalazi. U sklopu analize se, osim učestalosti kategorija na svakome od dva načela i njihove međusobne interakcije, nastojalo pokazati postoje li razlike među pet engleskih nogometnih liga s obzirom na pozadinu nadimka, kao i na to koji se sadržaj u nadimku nalazi. Na taj način bi se preko žargona, komunikacijskog aspekta unutar ponašanja, donijeli zaključci vezani za moguće obrasce vezane za taj aspekt kao dio ukupne organizacijske kulture nogometnih klubova u Engleskoj. Upravo činjenica da su nadimci engleskih nogometnih klubova nastali interakcijom među klubovima, njihovih navijača i različitih vanjskih faktora koji su usko povezani sa nogometnom aktivnošću (npr., novinari koji pišu o klubu, suparnički navijači, zajednica u okolici kluba itd.) čini nadimke nogometnih klubova u Engleskoj jedinstvenom odrednicom njihova identiteta. Nogometni su nadimci u Engleskoj kao dio žargona postali bitan dio identiteta kako kluba tako i samih navijača. Bez obzira na razlike u njihovom podrijetlu i njihovom značenju primarna svrha nadimaka je približavanje kluba navijačima koji su glavni smisao postojanja svakoga kluba. Iz podataka koji su se prikupili moguće je identificirati pojedine obrasce pojavljivanje određenih vrsta nadimaka u svakoj od pet engleskih nogometnih liga. Analizirano je podrijetlo tih nadimaka, odnosno što je dovelo do njihovih stvaranja, kao i njihova značenja koja su klubovi i navijači na direktne ili indirektne načine koristili.The aim of the paper was to analyse 116 nicknames of English football clubs from five leagues according to two different principles. The first principle referred to the background that served as the basis for the assignment of each of the nicknames analysed, while the second principle regarded the expression, that is, the content of the nickname itself. Apart from the frequency of the categories on each of the two variables and their interactions, the analysis sought to show whether there were differences between the five English football leagues with respect to the background of the nickname, as well as to its content. In this way, with the help of jargon, a communication aspect within behaviour, conclusions were drawn regarding possible patterns related to this particular aspect as part of the overall organizational culture of football clubs in England. The fact that the nicknames of English football clubs are the result of the interaction among the clubs, their fans and the various external factors closely related to football activity (e.g., journalists writing about the club, rival fans, the community around the club...) is what makes nicknames a unique marker of clubs’ identity. Football nicknames in England as a part of jargon have become an essential part of the identity of both the clubs and the fans themselves. Regardless of the differences in their origin and their meaning, the primary purpose of nicknames is to bring the clubs closer to fans, who are the main reason for their existence. From the collected data it was possible to identify some patterns in the occurrence of certain types of nicknames in each of the five English football leagues. The origin of these nicknames, that is, what led to their creation, as well as their meanings used by clubs and fans in direct or indirect ways were analysed