10,714 research outputs found
The genus of the configuration spaces for Artin groups of affine type
Let be a Coxeter system, finite, and let be the
associated Artin group. One has configuration spaces where
and a natural -covering The
Schwarz genus is a natural topological invariant to consider. In
this paper we generalize this result by computing the Schwarz genus for a class
of Artin groups, which includes the affine-type Artin groups. Let be
the simplicial scheme of all subsets such that the parabolic group
is finite. We introduce the class of groups for which equals
the homological dimension of and we show that is always the
maximum possible for such class of groups. For affine Artin groups, such
maximum reduces to the rank of the group. In general, it is given by
where is a well-known -complex
which has the same homotopy type as Comment: To appear in Atti Accad. Naz. Lincei Rend. Lincei Mat. App
Phase diagram of soft-core bosons in two dimensions
The low temperature phase diagram of Bose soft disks in two dimensions is
studied by numerical simulations. It is shown that a supersolid cluster phase
exists, within a range of the model parameters, analogous to that recently
observed for a system of aligned dipoles interacting via a softened potential
at short distance. These findings indicate that a long-range tail of the
interaction is unneeded to obtain such a phase, and that the soft-core
repulsive interaction is the minimal model for supersolidity
C/O white dwarfs of very low mass: 0.33-0.5 Mo
The standard lower limit for the mass of white dwarfs (WDs) with a C/O core
is roughly 0.5 Mo. In the present work we investigated the possibility to form
C/O WDs with mass as low as 0.33 Mo. Both the pre-WD and the cooling evolution
of such nonstandard models will be described.Comment: Submitted to the "Proceedings of the 16th European White Dwarf
Workshop" (to be published JPCS). 7 pages including 13 figure
The Dilemma of Renin Angiotensin System Blockers in Coronavirus Disease (Covid-19): Insights on the Lung Fluid Handling and Gas Exchange in Heart Failure Patients
Combining technologies to create bioactive hybrid scaffolds for bone tissue engineering
Combining technologies to engineer scaffolds that can offer physical and chemical cues to cells is an attractive approach in tissue engineering and regenerative medicine. In this study, we have fabricated polymer-ceramic hybrid scaffolds for bone regeneration by combining rapid prototyping (RP), electrospinning (ESP) and a biomimetic coating method in order to provide mechanical support and a physico-chemical environment mimicking both the organic and inorganic phases of bone extracellular matrix (ECM). Poly(ethylene oxide terephthalate)-poly(buthylene terephthalate) (PEOT/PBT) block copolymer was used to produce three dimensional scaffolds by combining 3D fiber (3DF) deposition, and ESP, and these constructs were then coated with a Ca-P layer in a simulated physiological solution. Scaffold morphology and composition were studied using scanning electron microscopy (SEM) coupled to energy dispersive X-ray analyzer (EDX) and Fourier Tranform Infrared Spectroscopy (FTIR). Bone marrow derived human mesenchymal stromal cells (hMSCs) were cultured on coated and uncoated 3DF and 3DF + ESP scaffolds for up to 21 d in basic and mineralization medium and cell attachment, proliferation, and expression of genes related to osteogenesis were assessed. Cells attached, proliferated and secreted ECM on all the scaffolds. There were no significant differences in metabolic activity among the different groups on days 7 and 21. Coated 3DF scaffolds showed a significantly higher DNA amount in basic medium at 21 d compared with the coated 3DF + ESP scaffolds, whereas in mineralization medium, the presence of coating in 3DF+ESP scaffolds led to a significant decrease in the amount of DNA. An effect of combining different scaffolding technologies and material types on expression of a number of osteogenic markers (cbfa1, BMP-2, OP, OC and ON) was observed, suggesting the potential use of this approach in bone tissue engineerin
Controlled surface initiated polymerization of N-isopropylacrylamide from polycaprolactone substrates for regulating cell attachment and detachment
Poly(ε-caprolactone) (PCL) substrates were modified with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) brushes to direct and control cellular attachment and detachment. Prior to brush growth, the surface of PCL was activated by a diamine to allow for initiator coupling. Infrared spectra taken before and after cell culturing demonstrated the covalently attached nature of the PNIPAM brushes. PCL is a biocompatible polymer and to prove that the modifications described above did not change this characteristic property, a cell attachment/detachment study was carried out. The modified substrates showed a lower cell attachment when compared to PCL alone and to PCL films modified with the initiator. The possibility to detach the cells in the form of a sheet was proved using PNIPAM-modified PCL films by lowering the temperature to 25 °C. No relevant detachment was shown by the unmodified or by the initiator modified surfaces. This confirmed that the detachment was temperature dependent and not connected to other factors such as polymer swelling. These functionalized polymeric films can find applications as smart cell culture systems in regenerative medicine applications
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