Subset currents on free groups

We introduce and study the space of \emph{subset currents} on the free group $F_N$. A subset current on $F_N$ is a positive $F_N$-invariant locally finite Borel measure on the space $\mathfrak C_N$ of all closed subsets of $\partial F_N$ consisting of at least two points. While ordinary geodesic currents generalize conjugacy classes of nontrivial group elements, a subset current is a measure-theoretic generalization of the conjugacy class of a nontrivial finitely generated subgroup in $F_N$, and, more generally, in a word-hyperbolic group. The concept of a subset current is related to the notion of an "invariant random subgroup" with respect to some conjugacy-invariant probability measure on the space of closed subgroups of a topological group. If we fix a free basis $A$ of $F_N$, a subset current may also be viewed as an $F_N$-invariant measure on a "branching" analog of the geodesic flow space for $F_N$, whose elements are infinite subtrees (rather than just geodesic lines) of the Cayley graph of $F_N$ with respect to $A$.Comment: updated version; to appear in Geometriae Dedicat

Load along the tibial shaft during activities of daily living

External load at the tibia during activities of daily living provides baseline measures for the improvement of the design of the bone-implant interface for relevant internal and external prostheses. A motion analysis system was used together with an established protocol with skin markers to estimate three-dimensional forces and moments acting on ten equidistant points along the tibial shaft. Twenty young and able-bodied volunteers were analysed while performing three repetitions of the following tasks: level walking at three different speeds, in a straight-line and with sudden changes of direction to the right and to the left, stair ascending and descending, squatting, rising from a chair and sitting down. Moment and force patterns were normalised to the percentage of body weight per height and body weight, respectively, and then averaged over all subjects for each point, about the three tibial anatomical axes, and for each task. Load patterns were found to be consistent over subjects, but different among the anatomical axes, tasks and points. Generally, moments were higher in the medio/lateral axis and influenced by walking speed. In all five walking tasks and in ascending stairs with alternating feet, the more proximal the point was the smaller the mean moment was. For the remaining tasks the opposite trend was observed. The overall largest value was observed in the medio/lateral direction at the ankle centre in level walking at high speed (9.1% body weight * height on average), nearly three times larger than that of the anterior/posterior axis (2.9) during level walking with a sidestep turn. The present results should be of value also for in-vitro mechanical tests and finite element models

Next-generation sequencing for microbial characterization of biovermiculations from a sulfuric acid cave in Apulia (Italy)

Sulfuric acid cave systems host abundant microbial communities that can colonize several environments displaying a variety of morphologies, i.e. white filamentous mats floating on the water surface, white creamy moonmilk deposits on the walls, and biovermiculations. Up to date, only few reports have described the microbiological aspects behind biovermiculation geomicrobiology of Italian sulfuric acid caves despite their overall abundance. Here, we present the first characterization of biovermiculation microbial populations from the Santa Cesarea Terme (Apulia, Italy) using next-generation sequencing and field emission scanning electron microscopy (FESEM) approaches. We focused our analysis on biovermiculations from Fetida Cave located along the Adriatic Sea coastline. This cave is at sea level, and moving from the entrance to its inner part, it is possible to observe a decrease of marine influence accompanied by a corresponding increase in the acidic effect of the upwelling waters. Biovermiculations are copiously observed covering the ceiling and walls mainly in the inner and middle environments of the cave, while they are absent near the entrance. Biovermiculations have a widespread range of colors going from grey to dark brown with an overall slimy appearance; dendritic morphologies alternate to very dense wall-covering sheets. Total DNA was extracted from each sample and 16S rDNA sequences were analyzed through Ilumina MiSeq platform. The main lineages found in all the samples included Gammaproteobacteria, Betaproteobacteria, Alphaproteobacteria, Bacteroidetes, Planctomycetes, Actinobacteria and Acidobacteria. In particular, the samples from the inner part of the cave had the highest abundance of Acidobacteria and showed the presence of Epsilonproteobacteria that can be related to bacterial sulfuroxidizing activity. FESEM images revealed microbial mats composed of filamentous cells including Actinobacteria and reticulated filaments of unknown origin, as well as prosthecate bacteria. This study shows that the biovermiculation microbial communities from Fetida cave is in accordance with previous data reported in acidic caves from Italy and support the role of Epsilonproteobacteria typically occurring in sulfidic environments

On and Off: Epigenetic Regulation of C. albicans Morphological Switches

The human fungal pathogen Candida albicans is a dimorphic opportunistic pathogen that colonises most of the human population without creating any harm. However, this fungus can also cause life-threatening infections in immunocompromised individuals. The ability to successfully colonise different host niches is critical for establishing infections and pathogenesis. C. albicans can live and divide in various morphological forms critical for its survival in the host. Indeed, C. albicans can grow as both yeast and hyphae and can form biofilms containing hyphae. The transcriptional regulatory network governing the switching between these different forms is complex but well understood. In contrast, non-DNA based epigenetic modulation is emerging as a crucial but still poorly studied regulatory mechanism of morphological transition. This review explores our current understanding of chromatin-mediated epigenetic regulation of the yeast to hyphae switch and biofilm formation. We highlight how modification of chromatin structure and non-coding RNAs contribute to these morphological transitions