University of Lleida

About: University of Lleida is a education organization based out in Lleida, Spain. It is known for research contribution in the topics: Population & Pregnancy. The organization has 2939 authors who have published 5853 publications receiving 148417 citations. The organization is also known as: Escola Superior Politècnica & Universitat de Lleida.

Semiempirical modeling of abiotic and biotic factors controlling ecosystem respiration across eddy covariance sites

Abstract: In this study we examined ecosystem respiration (R-ECO) data from 104 sites belonging to FLUXNET, the global network of eddy covariance flux measurements. The goal was to identify the main factors involved in the variability of R-ECO: temporally and between sites as affected by climate, vegetation structure and plant functional type (PFT) (evergreen needleleaf, grasslands, etc.). We demonstrated that a model using only climate drivers as predictors of R-ECO failed to describe part of the temporal variability in the data and that the dependency on gross primary production (GPP) needed to be included as an additional driver of R-ECO. The maximum seasonal leaf area index (LAI(MAX)) had an additional effect that explained the spatial variability of reference respiration (the respiration at reference temperature T-ref=15 degrees C, without stimulation introduced by photosynthetic activity and without water limitations), with a statistically significant linear relationship (r2=0.52, P 70% of the variance for most vegetation types. Exceptions include tropical and Mediterranean broadleaf forests and deciduous broadleaf forests. Part of the variability in respiration that could not be described by our model may be attributed to a series of factors, including phenology in deciduous broadleaf forests and management practices in grasslands and croplands.

Carotenoid and flavanone content during refrigerated storage of orange juice processed by high-pressure, pulsed electric fields and low pasteurization

Abstract: The impact of different processing technologies, including non-thermal technologies, on bioactive compounds of orange juice was investigated. Freshly squeezed orange juice was treated by high pressure (HP) (400 MPa/40 °C/1 min), pulsed electric fields (PEF) (35 kV cm−1/750 μs) and low pasteurization (LPT) (70 °C/30 s). The stability of main carotenoids and flavanones was studied just after treatment and during 40 days of refrigerated storage at 4 °C. Just after treatment, HP juice showed a significant increase on total carotenoid and flavanone content extracted (45.19 and 15.46%, respectively) and on vitamin A value (30.89%) with regard untreated juice, whereas no significant changes were observed for PEF and LPT juices. For all treated orange juices, flavanone content decreased significantly (around 50%) during the first 20 days of storage at 4 °C while carotenoid content showed a moderate decrease (less than 11%) that took place during the last 20 days. In general, during refrigerated storage, carotenoids and flavanones remained higher in HP juice than in LPT and PEF juices. Hence, HP and PEF technologies were as effective o even more than LPT to preserve bioactive compounds in orange juice during refrigerated storage.

Systolic ventricular filling.

Abstract: Summary The evidence of the ventricular myocardial band (VMB) has revealed unavoidable coherence and mutual coupling of form and function in the ventricular myocardium, making it possible to understand the principles governing electrical, mechanical and energetical events within the human heart From the earliest Erasistratus’ observations, principal mechanisms responsible for the ventricular filling have still remained obscured Contemporary experimental and clinical investigations unequivocally support the attitude that only powerful suction force, developed by the normal ventricles, would be able to produce an efficient filling of the ventricular cavities The true origin and the precise time frame for generating such force are still controversial Elastic recoil and muscular contraction were the most commonly mentioned, but yet, still not clearly explained mechanisms involved in the ventricular suction Classical concepts about timing of successive mechanical events during the cardiac cycle, also do not offer understandable insight into the mechanism of the ventricular filling The net result is the current state of insufficient knowledge of systolic and particularly diastolic function of normal and diseased heart Here we summarize experimental evidence and theoretical backgrounds, which could be useful in understanding the phenomenon of the ventricular filling Anatomy of the VMB, and recent proofs for its segmental electrical and mechanical activation, undoubtedly indicates that ventricular filling is the consequence of an active muscular contraction Contraction of the ascendent segment of the VMB, with simultaneous shortening and rectifying of its fibers, produces the paradoxical increase of the ventricular volume and lengthening of its long axis Specific spatial arrangement of the ascendent segment fibers, their interaction with adjacent descendent segment fibers, elastic elements and intracavitary blood volume (hemoskeleton), explain the physical principles involved in this action This contraction occurs during the last part of classical systole and the first part of diastole Therefore, the most important part of ventricular diastole (ie the rapid filling phase), in which it receives 70% of the stroke volume, belongs to the active muscular contraction of the ascendent segment We hope that these facts will give rise to new understanding of the principal mechanisms involved in normal and abnormal diastolic heart function

The long way down—are carbon and oxygen isotope signals in the tree ring uncoupled from canopy physiological processes?

Abstract: The carbon (δ(13)C) and oxygen (δ(18)O) stable isotope composition is widely used to obtain information on the linkages between environmental drivers and tree physiology over various time scales. The tree-ring archive can especially be exploited to reconstruct inter- and intra-annual variation of both climate and physiology. There is, however, a lack of information on the processes potentially affecting δ(13)C and δ(18)O on their way from assimilation in the leaf to the tree ring. As a consequence, the aim of this study was to trace the isotope signals in European beech (Fagus sylvatica L.) from leaf water (δ(18)O) and leaf assimilates (δ(13)C and δ(18)O) to tree-ring wood via phloem-transported compounds over a whole growing season. Phloem and leaf samples for δ(13)C and δ(18)O analyses as well as soil water, xylem water, leaf water and atmospheric water vapour samples for δ(18)O analysis were taken approximately every 2 weeks during the growing season of 2007. The δ(13)C and δ(18)O samples from the tree rings were dated intra-annually by monitoring the tree growth with dendrometers. δ(18)O in the phloem organic matter and tree-ring whole wood was not positively related to leaf water evaporative enrichment and δ(18)O of canopy organic matter pools. This finding implies a partial uncoupling of the tree-ring oxygen isotopic signal from canopy physiology. At the same time, internal carbon storage and remobilization physiology most likely prevented δ(13)C in tree-ring whole wood from being closely related to intra-annual variation in environmental drivers. Taking into account the post-photosynthetic isotope fractionation processes resulting in alterations of δ(13)C and δ(18)O not only in the tree ring but also in phloem carbohydrates, as well as the intra-annual timing of changes in the tree internal physiology, might help to better understand the meaning of the tree-ring isotope signal not only intra- but also inter-annually.