Analyzing dependence between point processes in time using IndTestPP

The need to analyze the dependence between two or more point processes in time appears in many modeling problems related to the occurrence of events, such as the occurrence of climate events at different spatial locations or synchrony detection in spike train analysis. The package IndTestPP provides a general framework for all the steps in this type of analysis, and one of its main features is the implementation of three families of tests to study independence given the intensities of the processes, which are not only useful to assess independence but also to identify factors causing dependence. The package also includes functions for generating different types of dependent point processes, and implements computational statistical inference tools using them. An application to characterize the dependence between the occurrence of extreme heat events in three Spanish locations using the package is shown

Modeling and projecting the occurrence of bivariate extreme heat events using a non-homogeneous common Poisson shock process

A joint model is proposed for analyzing and predicting the occurrence of extreme heat events in two temperature series, these being daily maximum and minimum temperatures. Extreme heat events are defined using a threshold approach and the suggested model, a non-homogeneous common Poisson shock process, accounts for the mutual dependence between the extreme events in the two series. This model is used to study the time evolution of the occurrence of extreme events and its relationship with temperature predictors. A wide range of tools for validating the model is provided, including influence analysis. The main application of this model is to obtain medium-term local projections of the occurrence of extreme heat events in a climate change scenario. Future temperature trajectories from general circulation models, conveniently downscaled, are used as predictors of the model. These trajectories show a generalized increase in temperatures, which may lead to extrapolation errors when the model is used to obtain projections. Various solutions for dealing with this problem are suggested. The results of the fitted model for the temperature series in Barcelona in 1951–2005 and future projections of extreme heat events for the period 2031–2060 are discussed, using three global circulation model trajectories under the SRES A1B scenario

NHPoisson: An R package for fitting and validating nonhomogeneous Poisson processes

NHPoisson is an R package for the modeling of nonhomogeneous Poisson processes in one dimension. It includes functions for data preparation, maximum likelihood estimation, covariate selection and inference based on asymptotic distributions and simulation methods. It also provides specific methods for the estimation of Poisson processes resulting from a peak over threshold approach. In addition, the package supports a wide range of model validation tools and functions for generating nonhomogenous Poisson process trajectories. This paper is a description of the package and aims to help those interested in modeling data using nonhomogeneous Poisson processes

Dynamic regression model for hourly river level forecasting under risk situations: An application to the Ebro River

This work proposes a new statistical modelling approach to forecast the hourly river level at a gauging station, under potential flood risk situations and over a medium-term prediction horizon (around three days). For that aim we introduce a new model, the switching regression model with ARMA errors, which takes into account the serial correlation structure of the hourly level series, and the changing time delay between them. A whole modelling approach is developed, including a two-step estimation, which improves the medium-term prediction performance of the model, and uncertainty measures of the predictions. The proposed model not only provides predictions for longer periods than other statistical models, but also helps to understand the physics of the river, by characterizing the relationship between the river level in a gauging station and its influential factors. This approach is applied to forecast the Ebro River level at Zaragoza (Spain), using as input the series at Tudela. The approach has shown to be useful and the resulting model provides satisfactory hourly predictions, which can be fast and easily updated, together with their confidence intervals. The fitted model outperforms the predictions from other statistical and numerical models, specially in long prediction horizons

Surface mechanomyography and electromyography provide non-invasive indices of inspiratory muscle force and activation in healthy subjects

The current gold standard assessment of human inspiratory muscle function involves using invasive measures of transdiaphragmatic pressure (Pdi) or crural diaphragm electromyography (oesEMGdi). Mechanomyography is a non-invasive measure of muscle vibration associated with muscle contraction. Surface electromyogram and mechanomyogram, recorded transcutaneously using sensors placed over the lower intercostal spaces (sEMGlic and sMMGlic respectively), have been proposed to provide non-invasive indices of inspiratory muscle activation, but have not been directly compared to gold standard Pdi and oesEMGdi measures during voluntary respiratory manoeuvres. To validate the non-invasive techniques, the relationships between Pdi and sMMGlic, and between oesEMGdi and sEMGlic were measured simultaneously in 12 healthy subjects during an incremental inspiratory threshold loading protocol. Myographic signals were analysed using fixed sample entropy (fSampEn), which is less influenced by cardiac artefacts than conventional root mean square. Strong correlations were observed between: mean Pdi and mean fSampEn |sMMGlic| (left, 0.76; right, 0.81), the time-integrals of the Pdi and fSampEn |sMMGlic| (left, 0.78; right, 0.83), and mean fSampEn oesEMGdi and mean fSampEn sEMGlic (left, 0.84; right, 0.83). These findings suggest that sMMGlic and sEMGlic could provide useful non-invasive alternatives to Pdi and oesEMGdi for the assessment of inspiratory muscle function in health and disease.Peer ReviewedPostprint (published version

Sarpa salpa herbivory on shallow reaches of Posidonia oceanica beds

El herbivorismo de Sarpa salpa en los tramos someros de los lechos de Posidonia oceanica En el presente artículo analizamos la variabilidad temporal y espacial en pequeña escala de la actividad de alimentación del pez herbívoro Sarpa salpa en los lechos someros de la pradera submarina de clima templado Posidonia oceanica. La intensidad del herbivorismo expresada como el porcentaje de superficie foliar mordida por el pez fue superior en septiembre de 2006 que en febrero de 2007, y a una profundidad de 0,5 m que de 1,5 m durante los dos períodos de muestreo. Todos los individuos de S. salpa que se alimentaban en las zonas someras estudiadas eran juveniles y el tamaño de mordedura se situaba entre 0,03 y 0,62 cm2. Los juveniles que se alimentaban a 1,5 m de profundidad fueron más grandes en febrero de 2007 que en septiembre de 2006, tal como ponen de relieve las diferencias significativas existentes en el tamaño medio de mordedura por haz. No obstante, los juveniles más grandes que se alimentaban a 1,5 m de profundidad en febrero de 2007 no parecían alimentarse con tanta frecuencia como los juveniles comparativamente más pequeños, que lo hacían a la misma profundidad en septiembre de 2006, tal como sugieren las diferencias significativas halladas en el número de mordeduras por haz. Asimismo, el número de mordeduras por haz fue inferior a 1,5 m de profundidad que a 0,5 m en febrero de 2007, si bien el tamaño medio de las mordeduras no difería en medida significativa entre las dos profundidades en aquel período de muestreo. En general, los juveniles de S. salpa no elegían un intervalo de edad concreto de las hojas a la hora de alimentarse en los lugares del estudio, a pesar de que los juveniles que se alimentaban a 1,5 m de profundidad en septiembre de 2006 parecían elegir hojas de edad mediana. Los peces no mostraron preferencia por las hojas con mayor cobertura de epífitos. Estos resultados muestran que la actividad de alimentación de los juveniles de S. salpa en los tramos someros de las praderas de P. oceanica puede variar con el tiempo y con pequeños cambios de profundidad, lo que a su vez puede afectar a la intensidad general del herbivorismo sobre las praderas submarinas.Here, we examined the temporal and small–scale spatial variability of grazing by the herbivorous fish Sarpa salpa on shallow beds of the temperate seagrass Posidonia oceanica. Herbivory intensity expressed as the percent of leaf area taken by fish bites was higher in September 2006 than in February 2007, and at 0.5 m than at 1.5 m during both sampling times. All S. salpa feeding at the shallow locations studied were juveniles, with bite sizes ranging from 0.03 to 0.62 cm2. Juveniles feeding at 1.5 m were larger in February 2007 than in September 2006, as evidenced by significant differences in mean bite size per shoot. However, the larger juveniles feeding at 1.5 m in February 2007 did not appear to feed as frequently as the comparatively smaller juveniles feeding at the same depth in September 2006, as suggested by significant differences in number of bites per shoot. The number of bites per shoot was also lower at 1.5 m than at 0.5 m in February 2007, although mean bite size did not differ significantly between the two depths at that sampling time. In general S. salpa juveniles did not select a particular range of leaf ages when feeding in the study locations, although the juveniles feeding at 1.5 m in September 2006 appeared to select mid–aged leaves. Fish did not show a preference for more epiphytized leaves. These results show that grazing activity by S. salpa juveniles in shallow reaches of P. oceanica meadows may vary temporally and across small changes in depth, which in turn may affect the overall intensity of herbivory on the seagrass.El herbivorismo de Sarpa salpa en los tramos someros de los lechos de Posidonia oceanica En el presente artículo analizamos la variabilidad temporal y espacial en pequeña escala de la actividad de alimentación del pez herbívoro Sarpa salpa en los lechos someros de la pradera submarina de clima templado Posidonia oceanica. La intensidad del herbivorismo expresada como el porcentaje de superficie foliar mordida por el pez fue superior en septiembre de 2006 que en febrero de 2007, y a una profundidad de 0,5 m que de 1,5 m durante los dos períodos de muestreo. Todos los individuos de S. salpa que se alimentaban en las zonas someras estudiadas eran juveniles y el tamaño de mordedura se situaba entre 0,03 y 0,62 cm2. Los juveniles que se alimentaban a 1,5 m de profundidad fueron más grandes en febrero de 2007 que en septiembre de 2006, tal como ponen de relieve las diferencias significativas existentes en el tamaño medio de mordedura por haz. No obstante, los juveniles más grandes que se alimentaban a 1,5 m de profundidad en febrero de 2007 no parecían alimentarse con tanta frecuencia como los juveniles comparativamente más pequeños, que lo hacían a la misma profundidad en septiembre de 2006, tal como sugieren las diferencias significativas halladas en el número de mordeduras por haz. Asimismo, el número de mordeduras por haz fue inferior a 1,5 m de profundidad que a 0,5 m en febrero de 2007, si bien el tamaño medio de las mordeduras no difería en medida significativa entre las dos profundidades en aquel período de muestreo. En general, los juveniles de S. salpa no elegían un intervalo de edad concreto de las hojas a la hora de alimentarse en los lugares del estudio, a pesar de que los juveniles que se alimentaban a 1,5 m de profundidad en septiembre de 2006 parecían elegir hojas de edad mediana. Los peces no mostraron preferencia por las hojas con mayor cobertura de epífitos. Estos resultados muestran que la actividad de alimentación de los juveniles de S. salpa en los tramos someros de las praderas de P. oceanica puede variar con el tiempo y con pequeños cambios de profundidad, lo que a su vez puede afectar a la intensidad general del herbivorismo sobre las praderas submarinas

Mythographus homericus : estudi i edició comentada /

Consultable des del TDXTítol obtingut de la portada digitalitzadaSota la denominació de Mythographus Homericus la literatura papirològica especialitzada ha anat aplegant una sèrie de fragments papiracis que coincideixen parcialment amb segments de text d'alguns escolis a Homer, principalment del corpus dels escolis menors (Scholia Minora), també anomenats escolis D arran de l'atribució errònia al gramàtic tardohel·lenístic Dídim. Aquesta col·lecció de testimonis presenta un seguit de característiques formals i de contingut que els confereixen una innegable coherència i unitat. Abans de la publicació de tots aquests testimonis papiracis ja Johannes Panzer va postular la pertinença de tot o bona part del material mitogràfic, les anomenades historiae fabulares que es detecten en els escolis D i altres corpora escoliogràfics, a una única obra perduda. Fou precisament Panzer qui encunyà la denominació de Mythographus Homericus per a aquest arquètip. La idea fou recuperada per Pfeiffer els anys trenta del segle passat, qui posà en relació la tesi de Panzer amb la col·lecció de papirs mitogràfics dependents de lemmata homèrics, i consagrà la denominació de Mythographus Homericus per a tots aquells fragments papiracis que presenten les mateixes característiques i que ofereixen coincidències irrefutables amb les parts mitogràfiques dels escolis menors a Homer. La tesi de Panzer fou, doncs, confirmada per la papirologia: la part mitogràfica dels escolis menors a Homer circulà entre els segles I i V de la nostra era de forma independent. El manuscrit més antic dels escolis menors és del s. IX: deduïm, doncs, que el text del Mythographus Homericus fou interpolat entre tot aquest material en època bizantina. El Mythographus Homericus és, doncs, una obra mitogràfica redactada sota la forma d'un hypomnema o comentari sota lemmata; aquests lemmata són citacions homèriques que suscitaren expansions narratives per part de l'eventual redactor. Aquesta obra s'ha perdut, però ha deixat prou traces com per a intentar-ne una reconstrucció, ni que sigui parcial, a partir d'una tasca de buidat dels corpora escoliogràfics i el seu acarament amb els testimonis sobre papir. Aquest treball de tesi parteix, doncs, d'aquest buidat i acarament, i té com a finalitat la reconstrucció, fins a la mesura del que ens permet el material de què disposem, de l'obra arquetípica. Una compilació de la totalitat del material i un estudi sistemàtic fonamentat en la crítica interna han possibilitat l'edició del text. El comentari mitogràfic complementa l'estudi i l'edició des d'una òptica de crítica externa. Com a resultat de tot aquest estudi sistemàtic fet sobre el text restituït podem oferir unes conclusions que constitueixen el punt fonamental de la nostra tesi: En primer lloc, el corpus aplegat i analitzat no sembla obra d'un únic autor, ateses algunes incoherències i repeticions. Ara bé, això no significa que sigui fruit d'un al·luvió fortuït d'aportacions capricioses de les múltiples mans per les quals ha anat passant el text. Molts elements certifiquen una clara unitat del corpus; si bé l'autoria sembla múltiple, els objectius i mètodes són únics i compartits. Hi ha, doncs, una innegable voluntat de coherència interna que, sens dubte, delata una tasca col·legial. En segon lloc, i arran d'una lectura més en profunditat, hom pot afirmar que el corpus en el seu conjunt és fruit d'una fusió entre dues tradicions: són les que hem denominat tradició A (Mythographus Homericus I) i B (Mythographus Homericus II). El criteri per a l'adscripció de cada historia fabularis a una o altra tradició ha estat fonamentalment la diferència d'objectius: si bé la tradició més antiga sembla contenir un element indubtablement exegètic i té per objecte aclarir determinats passatges homèrics, la tradició adventícia i superposada és una mera floritura erudita. La tradició A presenta una vinculació força estreta entre el lemma homèric i la historia narrada, condicionada per l'afany exegètic; la tradició B empra el lemma com a pur pretext per a introduir llegendes fundacionals, etiologies i etimologies basades en mites; és, doncs, una obra mitogràfica stricto sensu que s'adiu plenament als gustos tardohel·lenístics decadents. Mentre que la tradició A no s'entén si no és com a lectura paral·lela al text homèric, la tradició B sembla destinada a una lectura independent del text homèric, amb un interès per se. Els lemmata homèrics hi apareixen com un simple recurs compilatori que s'empra com a criteri per a aplegar i juxtaposar mites ben diversos.Recent papyrology han been collecting a few fragments under the name Mythographus Homericus. These textual relics give evidence of the circulation of an ancient mythographical work wich is clearly related to the homeric Scholia Minora or D-Scholia. This collection of fragments offers an amount of formal characteristics and contents wich give an undoubted unity to the corpus. All this papyrus fragments have been published independently along the XXth. Century. Nevertheless, in 1891 Johannes Panzer had already payed attention to the mythographic D-Scholia (the interpolated corpus called historiae fabulares) and pointed to one and only archetype, introducing the name Mythographus Homericus for all this interpolated material. The coincidences between these historiae fabulares and the mythographic papyrus related to the Iliad and the Odyssey led Pfeiffer into inferring a narrow relationship between the two different corpora. He stablished the denomination Mythographus Homericus for the papyrus collection mentioned; so, Panzer's thesis seemed to be confirmed by papyrological research. There is no doubt that a mythographic work was circulating independently at least from Ist. to Vth. centuries a. D. It was much later, in Byzantine times, that the historiae fabulares narrated by the Mythographus Homericus where interpolated in the corpus of the D-Scholia to Homer. The Mythographus Homericus is formally an hypomnema, a commentary to some lemmata from the homeric poems; under each lemma we can read a summarized myth. Some of them are closely related to the lemma mentioned, but some other doesn't seem to show any thematic link. This duality has led us to infer the previous existence of two different works in origin: a former commentary to Homer on a myhological basis and a later erudite compilation. The second one kept the same formal scheme, the hypomnema, and the final result was the fusion of both works into a new encyclopaedic mythological compendium related to homeric lemmata. In my work of thesis I offer an edition of all the mythographic material related to the Iliad, with an individual apparatus criticus to each historia fabularis. This edition leans on a complete reading of all the scholia to Homer, and a gathering of all the mythographic material that seems to fit with the characteristics mentioned, as an attempt to reconstruct an archetypical text of the Mythographus Homericus or, at least, of the extant we have nowadays in an altered status of the text due to the manuscript transmission. I join an introduction with a systematic study of the textual tradition, and a commentary to the text. As an annex I join the collection related to the Odyssey excerpted from the Dindorf edition of the Scholia

Trend analysis of water quality series based on regression models with correlated errors

This work proposes a methodology for characterizing the time evolution of water quality time series taking into consideration the inherent problems that often appear in this type of data such as non-linear trends, series having missing data, outliers, irregular measurement patterns, seasonal behavior, and serial correlation. The suggested approach, based on regression models with a Gaussian autoregressive moving average (ARMA) error, provides a framework where those problems can be dealt with simultaneously. Also the model takes into account the effect of influential factors, such as river flows, water temperature, and rainfall. The proposed approach is general and can be applied to different types of water quality series. We applied the modeling framework to four monthly conductivity series recorded at the Ebro river basin (Spain). The results show that the model fits the data reasonably well, that time evolution of the conductivity series is non-homogeneous over the year and, in some cases, non-monotonic. In addition, the results compared favorably over those obtained using simple linear regression, pre-whitening, and trend-free-pre-whitening techniques

Tratamiento conservador de las fracturas diafisarias de tibia en adultos

Se ha revisado la evolución y los resultados finales de 148 fracturas diafisarias de tibia cerradas (94 casos) y abiertas (54 casos) tratadas de forma conservadora. Las etiologías más frecuentes fueron los accidentes de tráfico (58%) y las caídas casuales (33%). Se constató un predominio de las fracturas espiroideas (26%), seguidas de las transversas (22%) y oblicuas cortas (22%), siendo la loralización más frecuente a nivel del tercio distal de la diálisis (48%). El período de consolidación medio fue de 15 semanas; la consolidación fue precoz en 36 casos (24%), normal en 88 (59%) y retardada en 24 (16%), observándose la presencia de pseudoartrosis en 10 pacientes (7%). Los resultados clínicos fueron satisfactorios en el 84% de los casos y los radiológicos en el 88%.The follow-up and final results of 148 diaphyseal tibial fractures (54 open and 94 closed) treated conservatively were reviewed. The most frequent causes were road traffic accident (58%) and casual falls (33%). We found predominantly spiroid fractures (26%), transverse fractures (22%) and oblicues fractures (22%). The most frequent location was the distal third of the diaphysis (48%). The average period of consolidation was 15 weeks. This was shorter in 6 cases (24%), normal in 88 (59%) and prolonged in 24 (16%). Pseudoarthrosis was present in 10 patients (7%). The results were satisfactory clinically in 84% of cases and radiologically in 88% of patients

Noninvasive assessment of inspiratory muscle neuromechanical coupling during inspiratory threshold loading

Diaphragm neuromechanical coupling (NMC), which reflects the efficiency of conversion of neural activation to transdiaphragmatic pressure (Pdi), is increasingly recognized to be a useful clinical index of diaphragm function and respiratory mechanics in neuromuscular weakness and cardiorespiratory disease. However, the current gold standard assessment of diaphragm NMC requires invasive measurements of Pdi and crural diaphragm electromyography (oesEMGdi), which complicates the measurement of diaphragm NMC in clinical practice. This is the first study to compare invasive measurements of diaphragm NMC (iNMC) using the relationship between Pdi and oesEMGdi, with noninvasive assessment of NMC (nNMC) using surface mechanomyography (sMMGlic) and electromyography (sEMGlic) of lower chest wall inspiratory muscles. Both invasive and noninvasive measurements were recorded in twelve healthy adult subjects during an inspiratory threshold loading protocol. A linear relationship between noninvasive sMMGlic and sEMGlic measurements was found, resulting in little change in nNMC with increasing inspiratory load. By contrast, a curvilinear relationship between invasive Pdi and oesEMGdi measurements was observed, such that there was a progressive increase in iNMC with increasing inspiratory threshold load. Progressive recruitment of lower ribcage muscles, serving to enhance the mechanical advantage of the diaphragm, may explain the more linear relationship between sMMGlic and sEMGlic (both representing lower intercostal plus costal diaphragm activity) than between Pdi and crural oesEMGdi. Noninvasive indices of NMC derived from sEMGlic and sMMGlic may prove to be useful indices of lower chest wall inspiratory muscle NMC, particularly in settings that do not have access to invasive measures of diaphragm function.Peer ReviewedPostprint (published version