The Formica rufa group comprises several ant species which are collectively referred to as “red wood ants” (hereafter RWA). These species have key roles in forest ecosystems, where they are ...ecologically dominant and greatly influence the dynamics of the habitat they colonise. Various studies have shown how their trophic activity may affect other organisms, which include both other invertebrates and plants. We can therefore hypothesize that their presence could affect the taxonomic and functional composition of epiphytes, despite clear information on such an effect is lacking. This study aimed to fill this research gap by evaluating whether the presence of red wood ants could affect the structure and composition of lichen communities. We selected two sites on the Apennine Mountains in Italy, where the red wood ant F. paralugubris was introduced from the Alps more than 50 years ago. In each site, lichen assemblages on Abies alba trees located within the colonised areas were compared to those from nearby, non-occupied areas. The results allowed for the identification of significant effects of F. paralugubris on the structure of lichen communities. Although there was no detectable impact on lichen species richness, a significant difference in their community composition between colonised and control sites was detected. Furthermore, ant presence seemed to be associated with specific lichen functional traits such as asexual reproduction. We argue that RWA could affect the lichen community either directly, e.g., by actively dispersing the species capable of asexual reproduction through their movements on trees (ant-mediated dispersion), or indirectly through herbivore exclusion. Finally, we also observed differences in β-diversity among the colonised and non-colonised sites.
Data from power analysis of the human EEG were processed statistically, and an area within the power spectrum was identified, limited by the abscissa and by an exponential curve, the parameters of ...which could be defined by a moving linear regression after logarithmic transform of the spectral data. The EEG signal of normal subjects and epileptics with borderline EEG tracings was studied before and after administration of neuroactive compounds. The exponential curve was found to be negative in all subjects; its parameters were symmetrical and were not modified by the drugs administered, though these were active on the spectral profile. The area limited by the curve was used as a reference for the standardization of the power values with respect to a constant to the signal. The method allowed a better definition of the spectral profile than it is obtained by normalization vs. the total power value.
The photosensitivity of metal complexes has been known for a long time. Early studies on ligand photosubstitution and photoredox decomposition reactions of metal complexes of simple inorganic ligands ...(e.g. NH
3, CN
−) have been followed by accurate investigations on the photophysical behavior (luminescence quantum yields and lifetimes) and on the use of metal complexes in bimolecular processes (energy and electron transfer). A large number of complexes, stable towards photodecomposition, but capable of undergoing excited state redox processes, have been used for interconverting light and chemical energy. More recently, combination of supramolecular chemistry and photochemistry has led to the design and construction of multicomponent systems capable of performing light induced functions. In this field, luminescent and/or photoredox reactive metal complexes are presently used as essential components for a bottom-up approach to the construction of molecular devices and machines. Examples of molecular devices for processing light signals and of molecular machines powered by light energy, based on coordination compounds, are illustrated.
The main goal of this contribution is to provide a simple method for constructing transversely isotropic polyconvex functions suitable for the description of biological soft tissues. The advantage of ...our approach is that only a few parameters are necessary to approximate a variety of stress–strain curves and to satisfy the condition of a stress-free reference configuration a priori in the framework of polyconvexity. The proposed polyconvex stored energies are embedded into the concept of structural tensors and the representation theorems for isotropic tensor functions are utilized. As an example, the medial layer of a human abdominal aorta is investigated, modeled by some of the proposed polyconvex functions and compared with experimental data. Hereby, the economic fitting to experimental data, and hence the easy handling of the functions is shown.
Light-harvesting dendrimers Balzani, Vincenzo; Ceroni, Paola; Maestri, Mauro ...
Current opinion in chemical biology,
12/2003, Volume:
7, Issue:
6
Journal Article
Peer reviewed
Dendrimers are well-defined, tree-like macromolecules, with a high degree of order and the possibility to contain selected chemical units in predetermined sites of their structure. Dendrimers are ...currently attracting the interest of many scientists because of their unusual chemical and physical properties and the wide range of potential applications. It is possible to design and synthesize dendrimers containing a variety of chromophoric groups organized in the dimensions of time, energy and space so as to obtain efficient light-harvesting devices that can be useful for solar energy conversion and other purposes.
Recent inve-stigations have shown that coupling luminescence with dendrimer chemistry can lead to systems capable of exhibiting quite unusual and interesting properties. In this trend article we ...focus on: (i) interactions of luminescent units within a dendrimer, (ii) quenching of dendrimer luminescence by external species, (iii) sensitization of luminescent metal ions, and (iv) sensitization and quenching of dye luminescence. Several examples of dendrimers are discussed, including compounds capable of: (a) performing excimer and/or exciplex emission, (b) exploiting energy transfer for harvesting light, (c) undergoing electron transfer processes, (d) protecting with their branches the luminescence of the core, (e) down and up converting light frequency, (f) playing the role of ligands for luminescent and non-luminescent metal ions, and (g) performing as hosts for luminescent dyes.
In this work we propose an anisotropic stored energy function which satisfies a priori the Legendre–Hadamard condition, which is strongly related to the material stability of the constitutive ...equations. In the linearized case this condition implies positive wave speeds. The Legendre–Hadamard condition plays also an important role for the (local) existence of solutions in the neighborhood of stationary points. We apply the proposed hyperelastic energies to soft tissues and compare the formulation with existing models which have been used for the calculation of medial collateral ligament and arterial walls. In our numerical and analytical investigations we discuss the distribution of wave speeds for a sequence of deformation states containing some essential stress–strain characteristics of the compared models.
A unique methodology to measure gas fluxes of SO2 and NO2 from ships using optical remote sensing is described and demonstrated in a feasibility study. The measurement system is based on Differential ...Optical Absorption Spectroscopy using reflected skylight from the water surface as light source. A grating spectrometer records spectra around 311 nm and 440 nm, respectively, with the telescope pointed downward at a 30° angle from the horizon. The mass column values of SO2 and NO2 are retrieved from each spectrum and integrated across the plume. A simple geometric approximation is used to calculate the optical path. To obtain the total emission in kg h-1 the resulting total mass across the plume is multiplied with the apparent wind, i.e. a dilution factor corresponding to the vector between the wind and the ship speed. The system was tested in two feasibility studies in the Baltic Sea and Kattegat, from a CASA-212 airplane in 2008 and in the North Sea outside Rotterdam from a Dauphin helicopter in an EU campaign in 2009. In the Baltic Sea the average SO2 emission out of 22 ships was (54 ± 13) kg h-1 , and the average NO2 emission was (33 ± 8) kg h-1 , out of 13 ships. In the North Sea the average SO2 emission out of 21 ships was (42 ± 11) kg h-1 , NO2 was not measured here. The detection limit of the system made it possible to detect SO2 in the ship plumes in 60% of the measurements when the described method was used. A comparison exercise was carried out by conducting airborne optical measurements on a passenger ferry in parallel with onboard measurements. The comparison shows agreement of (-30 ± 14)% and (-41 ± 11)%, respectively, for two days, with equal measurement precision of about 20%. This gives an idea of the measurement uncertainty caused by errors in the simple geometric approximation for the optical light path neglecting scattering of the light in ocean waves and direct and multiple scattering in the exhaust plume under various conditions. A tentative error budget indicates uncertainties within 30-45% but for a reliable error analysis the optical light path needs to be modelled. A ship emission model, FMI-STEAM, has been compared to the optical measurements showing an 18% overestimation and a correlation coefficient (R2 ) of 0.6. It is shown that a combination of the optical method with modelled power consumption can estimate the sulphur fuel content within 40%, which would be sufficient to detect the difference between ships running at 1% and at 0.1%, limits applicable within the IMO regulated areas.
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