Intra-annual density fluctuations in tree rings are proxies of air temperature across Europe

Intra-Annual Density Fluctuations (IADFs) are an important wood functional trait that determine trees' ability to adapt to climatic changes. Here, we use a large tree-ring database of 11 species from 89 sites across eight European countries, covering a climatic gradient from the Mediterranean to northern Europe, to analyze how climate variations drive IADF formation. We found that IADF occurrence increases nonlinearly with ring width in both gymnosperms and angiosperms and decreases with altitude and age. Recently recorded higher mean annual temperatures facilitate the formation of IADFs in almost all the studied species. Precipitation plays a significant role in inducing IADFs in species that exhibit drought tolerance capability, and a growth pattern known as bimodal growth. Our findings suggest that species with bimodal growth patterns growing in western and southern Europe will form IADFs more frequently, as an adaptation to increasing temperatures and droughts.

P3360Quantitative assessment of tricuspid regurgitation using right and left ventricular stroke volumes obtained from tomographic equilibrium radionuclide ventriculography

Background

Quantitative assessment of valve regurgitation using volumetric method by comparing right and left ventricular stroke volumes is still under investigations.

Aims

To investigate the accuracy of tomographic equilibrium radionuclide ventriculography (t-ERV) for the quantification of tricuspid regurgitation (TR).

Methods and results

Sixty-one patients (44 men; mean age 59±12 years) who underwent both t-ERV and transthoracic echocardiography (TTE) studies within 2 weeks for right ventricular systolic function assessment were eligible for inclusion. A sub-group of 22 patients underwent both t-ERV and CMR. Patients with mitral/aortic regurgitation by TTE were excluded of the study. TR regurgitant volume (RVol) was calculated using the proximal isovelocity surface area (PISA) method from TTE and the volumetric method (right ventricular stroke volume minus left ventricular stroke volume) from t-ERV. RVol tended to be higher using the ERV volumetric method as compared to PISA method (43±35 and 35±33 ml, respectively; P<0.0001). There was a significant correlation between RVol as assess by ERV and by TTE (R=0.95, P<0.0001). Intraclass correlation coefficient between TTE and ERV for TR quantification was 0.95 (P<0.0001). Among patients who underwent CMR, the correlation between RVol obtained by TTE and by t-ERV and CMR were R=0.81 and R=0.75, respectively (all P<0.0001), without difference between the two correlations (P=0.263).

Linear regression (left) and Bland-Altma

Conclusion

TR assessment using the t-ERV correlates well with PISA from TTE in patients referred for right ventricular systolic function assessment.

Phase-field model for the morphology of monolayer lipid domains

Phase-separated domains exist in multicomponent lipid monolayers and bilayers. We present here a phase-field model that takes into account the competition between lipid dipole-dipole interactions and line tension to define the domain morphology. A dynamic equation for the phase-field is solved numerically showing stationary non-circular shapes like starfish shapes. This phase-field model could be applied to study the dynamic properties of complex problems like phase segregation in pulmonary surfactant membranes and films.

Constricting force of filamentary protein rings evaluated from experimental results

We present a model of Z -ring constriction in bacteria based on different experimental in vitro results. The forces produced by the Z ring due to lateral attraction of its constituent parts, estimated in previous studies that were based on FtsZ filaments observed by atomic force microscopy, are in good agreement with an estimation of the force required for recently found deformations in liposomes caused by FtsZ. These forces are calculated within the usual Helfrich energy formalism. In this context, we also explain the apparent attraction of multiple Z rings in the liposomes initially separated by small distances, as well as the stable distribution of rings separated by distances greater than approximately twice the diameter of the cylindrical liposomes. We adapted the model to the in vivo conditions imposed by the bacterial cell wall, concluding that the proposed mechanism gives a qualitative explanation for the force generation during bacterial division.

Polymer-induced tubulation in lipid vesicles

A mechanism of extraction of tubular membranes from a lipid vesicle is presented. A concentration gradient of anchoring amphiphilic polymers generates tubes from budlike vesicle protrusions. We explain this mechanism in the framework of the Canham-Helfrich model. The energy profile is analytically calculated and a tube with a fixed length, corresponding to an energy minimum, is obtained in a certain regime of parameters. Further, using a phase-field model, we corroborate these results numerically. We obtain the growth of tubes when a polymer source is added, and the budlike shape after removal of the polymer source, in accordance with recent experimental results.

Model for curvature-driven pearling instability in membranes

A phase-field model for dealing with dynamic instabilities in membranes is presented. We use it to study curvature-driven pearling instability in vesicles induced by the anchorage of amphiphilic polymers on the membrane. Within this model, we obtain the morphological changes reported in recent experiments. The formation of a homogeneous pearled structure is achieved by consequent pearling of an initial cylindrical tube from the tip. For high enough concentration of anchors, we show theoretically that the homogeneous pearled shape is energetically less favorable than an inhomogeneous one, with a large sphere connected to an array of smaller spheres.

Dynamic model and stationary shapes of fluid vesicles

A phase-field model that takes into account the bending energy of fluid vesicles is presented. The Canham-Helfrich model is derived in the sharp-interface limit. A dynamic equation for the phase-field has been solved numerically to find stationary shapes of vesicles with different topologies and the dynamic evolution towards them. The results are in agreement with those found by minimization of the Canham-Helfrich free energy. This fact shows that our phase-field model could be applied to more complex problems of instabilities.