Influencia de las fugas intencionales en la monitorización del volumen tidal en ventilación mecànica no invasiva

La modalitat més utilitzada en ventilació mecànica no invasiva es la pressió de suport (Ps) amb tubuladura única i sistemes de fuita controlada mitjançant una vàlvula espiratòria. En el nostre estudi avaluem la influència que l’increment d’aquestes fuites pot tenir en el càlcul del volum tidal (VT) per part del software dels ventiladors comercials. Els resultats mostren que el software dels ventiladors infravalora el VT real que rep el pacient. Aixó pot comportar que, almenys en alguns casos, en la pràctica clínica s’utilitzin valors de Ps superiors als necessaris quina cosa podria comportar un cert grau d’hiperinsuflació pulmonar.

High tidal volume ventilation affects neuronal activation in mechanically ventilated rats

Els malalts crítics presenten sovint seqüeles cognitives a llarg termini, l’aplicació de ventilació mecànica (VM) pot contribuir al seu desenvolupament. El principal objectiu del nostre estudi fou investigar l’efecte de dos patrons de ventilació (volum corrent elevat/baix) en l’activació neuronal (expressió de c-fos) en determinades àrees cerebrals en un model en rates. Després de 3 hores sota VM, es va trobar activació neuronal; la seva intensitat va ser superior al grup de volum corrent elevat, suggerint un efecte iatrogènic de la VM al cervell. Aquests resultats suggereixen que cal aprofundir en l’estudi del crosstalk cervell-pulmó en malalts crítics sota VM.

Dynamics of turing patterns under spatiotemporal forcing

We study, both theoretically and experimentally, the dynamical response of Turing patterns to a spatiotemporal forcing in the form of a traveling-wave modulation of a control parameter. We show that from strictly spatial resonance, it is possible to induce new, generic dynamical behaviors, including temporally modulated traveling waves and localized traveling solitonlike solutions. The latter make contact with the soliton solutions of Coullet [Phys. Rev. Lett. 56, 724 (1986)] and generalize them. The stability diagram for the different propagating modes in the Lengyel-Epstein model is determined numerically. Direct observations of the predicted solutions in experiments carried out with light modulations in the photosensitive chlorine dioxide-iodine-malonic acid reaction are also reported.

Travelling-stripe forcing generates hexagonal patterns

We study the response of Turing stripe patterns to a simple spatiotemporal forcing. This forcing has the form of a traveling wave and is spatially resonant with the characteristic Turing wavelength. Experiments conducted with the photosensitive chlorine dioxide-iodine-malonic acid reaction reveal a striking symmetry-breaking phenomenon of the intrinsic striped patterns giving rise to hexagonal lattices for intermediate values of the forcing velocity. The phenomenon is understood in the framework of the corresponding amplitude equations, which unveils a complex scenario of dynamical behaviors.

Dynamics of domain walls in pattern formation under traveling-wave forcing

We study dynamics of domain walls in pattern forming systems that are externally forced by a moving space-periodic modulation close to 2:1 spatial resonance. The motion of the forcing induces nongradient dynamics, while the wave number mismatch breaks explicitly the chiral symmetry of the domain walls. The combination of both effects yields an imperfect nonequilibrium Ising-Bloch bifurcation, where all kinks (including the Ising-like one) drift. Kink velocities and interactions are studied within the generic amplitude equation. For nonzero mismatch, a transition to traveling bound kink-antikink pairs and chaotic wave trains occurs.

Experiments of periodic forcing of Saffman-Taylor fingers

We report on an experimental study of long normal Saffman-Taylor fingers subject to periodic forcing. The sides of the finger develop a low amplitude, long wavelength instability. We discuss the finger response in stationary and nonstationary situations, as well as the dynamics towards the stationary states. The response frequency of the instability increases with forcing frequency at low forcing frequencies, while, remarkably, it becomes independent of forcing frequency at large forcing frequencies. This implies a process of wavelength selection. These observations are in good agreement with previous numerical results reported in [Ledesma-Aguilar et al., Phys. Rev. E 71, 016312 (2005)]. We also study the average value of the finger width, and its fluctuations, as a function of forcing frequency. The average finger width is always smaller than the width of the steady-state finger. Fluctuations have a nonmonotonic behavior with a maximum at a particular frequency.

Periodic forcing of scroll rings and control of Winfree turbulence in excitable media

By simulations of the Barkley model, action of uniform periodic nonresonant forcing on scroll rings and wave turbulence in three-dimensional excitable media is investigated. Sufficiently strong rapid forcing converts expanding scroll rings into the collapsing ones and suppresses the Winfree turbulence caused by the negative tension of wave filaments. Slow strong forcing has an opposite effect, leading to expansion of scroll rings and induction of the turbulence. These effects are explained in the framework of the phenomenological kinematic theory of scroll waves.

Dynamics of turing patterns under spatiotemporal forcing

We study, both theoretically and experimentally, the dynamical response of Turing patterns to a spatiotemporal forcing in the form of a traveling-wave modulation of a control parameter. We show that from strictly spatial resonance, it is possible to induce new, generic dynamical behaviors, including temporally modulated traveling waves and localized traveling solitonlike solutions. The latter make contact with the soliton solutions of Coullet [Phys. Rev. Lett. 56, 724 (1986)] and generalize them. The stability diagram for the different propagating modes in the Lengyel-Epstein model is determined numerically. Direct observations of the predicted solutions in experiments carried out with light modulations in the photosensitive chlorine dioxide-iodine-malonic acid reaction are also reported.

Travelling-stripe forcing generates hexagonal patterns

We study the response of Turing stripe patterns to a simple spatiotemporal forcing. This forcing has the form of a traveling wave and is spatially resonant with the characteristic Turing wavelength. Experiments conducted with the photosensitive chlorine dioxide-iodine-malonic acid reaction reveal a striking symmetry-breaking phenomenon of the intrinsic striped patterns giving rise to hexagonal lattices for intermediate values of the forcing velocity. The phenomenon is understood in the framework of the corresponding amplitude equations, which unveils a complex scenario of dynamical behaviors.

Tectonic-palaeoenvironmental forcing of clay-mineral assemblages in nonmarine settings: the Oligocene-Miocene As Pontes Basin (Spain)

Two small, alluvial-lacustrine subbasins developed during the early restraining overstep stages of the Oligocene-Miocene As Pontes strike-slip Basin (NW Spain). Later, the basin evolved into a restraining bend stage and an alluvial-swamp-dominated depositional framework developed. The palaeobiological record demonstrates that the Oligocene-Miocene palaeoclimate in NW Spain was subtropical, warm and humid to subhumid.

Augment de la resolució en la reconstrucció de les temperatures de l'aigua i de l'aire del llac Baikal (Sibèria) dels últims 60.000 anys

Aquest estudi consisteix en l’augment de la resolució en la reconstrucció de la temperatura de l’aigua i l’aire del llac Baikal durant els últims 60.000 anys mitjançant l’ús de les proxies de reconstrucció de la temperatura TEX86 i MAAT, i la d’aportació de matèria orgànica d’origen terrestre, el BIT. L’objectiu general d’aquesta investigació és incrementar la resolució temporal en el mostreig del testimoni CON-01-603-02 per tal de millorar el registre de dades obtingudes i d’aquesta manera poder contrastar la hipòtesi de la interconnexió climàtica global, així com identificar esdeveniments climàtics sobtats, tals com els Heinrich events i els esdeveniments D-O. Un cop obtinguts els resultats s’ha realitzat l’anàlisi de la qualitat i fiabilitat de les dades a les resolucions de 5, 10 i 20 Kanys, i es conclou que existeixen diferències globals estadísticament significatives amb els resultats realitzats per Escala et al., (r.n.p [resultats no publicats]), la resolució dels quals es volia augmentar. S’han tractat d’anular aquestes diferències restant o bé sumant la diferència mitjana obtinguda entre les dues mostres en cada un dels intervals de 5 Kanys en què s’han donat aquestes. Els resultats integrats d’Escala et al.,(r.n.p) i els d’aquest estudi, aporten dades que recolzen l’hipòtesi de la interconnexió climàtica global, ja que al comparar-los amb els registres climàtics de Grenlàndia (GRIP2) i l’Antàrtica (Vostok) mostren respostes similars tant per les forces de Milankovitch com per les de subMilankovitch.

Real time GPS precise positioning of LEO satellites

Report for the scientific sojourn at the German Aerospace Center (DLR) , Germany, during June and July 2006. The main objective of the two months stay has been to apply the techniques of LEO (Low Earth Orbiters) satellites GPS navigation which DLR currently uses in real time navigation. These techniques comprise the use of a dynamical model which takes into account the precise earth gravity field and models to account for the effects which perturb the LEO’s motion (such as drag forces due to earth’s atmosphere, solar pressure, due to the solar radiation impacting on the spacecraft, luni-solar gravity, due to the perturbation of the gravity field for the sun and moon attraction, and tidal forces, due to the ocean and solid tides). A high parameterized software was produced in the first part of work, which has been used to asses which accuracy could be reached exploring different models and complexities. The objective was to study the accuracy vs complexity, taking into account that LEOs at different heights have different behaviors. In this frame, several LEOs have been selected in a wide range of altitudes, and several approaches with different complexity have been chosen. Complexity is a very important issue, because processors onboard spacecrafts have very limited computing and memory resources, so it is mandatory to keep the algorithms simple enough to let the satellite process it by itself.

Response of photosynthetic organisms to global change: an approach based on marker pigments

Report for the scientific sojourn carried out at the Department of Freshwater Ecology, National Environmetal Research Institute, Denmark, from 2006 to 2008. The main objective of the project was to reconstruct photosynthetic organism community composition using pigmentbased methods and to study their response to natural (e.g. climate) or anthropogenic (e.g. eutrophication) perturbations that took place in the system over time. We performed a study in different locations and at different temporal scales. We analysed the pigment composition in a short sediment record (46 cm sediment depth) of a volcanic lake (Lake Furnas) in the Azores Archipelago (Portugal). The lake has been affected during the last century by successive fish introductions. The specific objective was to reconstruct the lake’s trophic state history and to assess the role of land-use, climate and fish introductions in structuring the lake community. Results obtained suggested that whereas trophic cascade and changes in nutrient concentrations have some clear effects on algal and microbial assemblages, interpreting the effects of changes in climate are not straightforward. This is probably related with the rather constant precipitation in the Azores Islands during the studied period. We also analysed the pigment composition in a long sediment record (1800 cm sediment depth) of Lake Aborre (Denmark) covering ca. 8kyr of lake history. The specific objective was to describe changes in lake primary production and lake trophic state over the Holocene and to determine the photosynthetic organisms involved. Results suggested that external forcing (i.e. land use changes) was responsible of erosion and nutrient run off to the lake that contributed to the reported changes in lake primary production along most of the Holocene.

Inflation dynamics and the New Keynesian Phillips curve in EU-4

The paper seeks to shed light on inflation dynamics of four new EU member states: the Czech Republic, Hungary, Poland and Slovakia. To this end, the New Keynesian Phillips curve augmented for open economies is estimated and additional statistical tests applied. We find the following. (1) The claim of New Keynesians that the real marginal cost is the main inflation-forcing variable is fragile. (2) Inflation seems to be driven by external factors. (3) Although inflation holds a forward-looking component, the backward-looking component is substantial. An intuitive explanation for higher inflation persistence may be rather adaptive than rational price setting of local firms.