A New Source of Stem Cells in Amniotic Fluid and Placenta in 1st Trimester of Pregnancy

Mesenchymal stromal cells (MSC) are multipotent cells found in fetal, neonatal and adult tissues. Fetal MSC have advantageous characteristics over their adult counterparts, and the regenerative potential of fetal blood MSC has recently been shown in a model of skeletal dysplasia and renal failure. Although fetal blood MSC can be isolated during ongoing pregnancy, the clinical effectiveness of using fetal blood-derived MSC for prenatal fetal cell therapy is constrained by the invasive nature of blood sampling procedure. With amniocentesis and chorionic villus sampling (CVS), fetal MSC can be obtained with minimal invasion. The aim of this study was to characterise stem cells from 1st trimester amniotic fluid (AF) and placenta by comparing their phenotype with MSC from 1st trimester bone marrow and 2nd trimester AF. Cells from all sources have similar immunophenotype, express pluripotency markers and telomerase, but 1st trimester AF stem cells have higher kinetics. The cells can differentiate into 3 lineages (bone, fat and cartilage), form embryoid bodies (EB) in vitro and can be transfected with high efficiency using non-viral methods. The migration potential of fetal MSC was also investigated using in vitro migration assays, to recapitulate the in vivo mechanisms involved in donor cell recruitment to various tissues and delineate the pathways involved. Fetal blood MSC and AF stem cells were shown to express CXCR4, the stromal cell-derived factor-1 (SDF-1) receptor, intracellularly but not on the cell membrane and migrate to SDF-1 gradients and to osteoblast cultures derived from the Osteogenesis Imperfecta mouse (oim), but not wild type bones. Pre-stimulation with oim plasma up-regulated CXCR4 and increased chemotaxis to SDF-1 and oim bone. Conclusively, 1st trimester AF and placenta are a new source of stem cells with great potential for future cell therapy applications. Also, initial experiments indicate the importance of the SDF-1/CXCR4 axis for stem cell recruitment to the site of injury

Classes of Measures Generated by Capacities

We introduce classes of measures in the half-space $\mathbf{R}^{n+1}_+,$ generated by Riesz, or Bessel, or Besov capacities in $\mathbf{R}^n$, and give a geometric characterization as Carleson-type measures

A self-organized criticality model for ion temperature gradient (ITG) mode driven turbulence in confined plasma

A new Self-Organized Criticality (SOC) model is introduced in the form of a Cellular Automaton (CA) for ion temperature gradient (ITG) mode driven turbulence in fusion plasmas. Main characteristics of the model are that it is constructed in terms of the actual physical variable, the ion temperature, and that the temporal evolution of the CA, which necessarily is in the form of rules, mimics actual physical processes as they are considered to be active in the system, i.e. a heating process and a local diffusive process that sets on if a threshold in the normalized ion temperature gradient R/L_T is exceeded. The model reaches the SOC state and yields ion temperature profiles of exponential shape, which exhibit very high stiffness, in that they basically are independent of the loading pattern applied. This implies that there is anomalous heat transport present in the system, despite the fact that diffusion at the local level is imposed to be of a normal kind. The distributions of the heat fluxes in the system and of the heat out-fluxes are of power-law shape. The basic properties of the model are in good qualitative agreement with experimental results.Comment: In press at Physics of Plasmas, July 2010; 11 pages, 5 figure

Status Report of the CAST Experiment

This report describes the activities in the CAST experiment since the previous SPSC in April 2008

Spontaneously quenched gamma-ray spectra from compact sources

We study a mechanism for producing intrinsic broken power-law gamma-ray spectra in compact sources. This is based on the principles of automatic photon quenching, according to which, gamma-rays are being absorbed on spontaneously produced soft photons, whenever the injected luminosity in gamma-rays lies above a certain critical value. We derive an analytical expression for the critical gamma-ray compactness in the case of power-law injection. For the case where automatic photon quenching is relevant, we calculate analytically the emergent steady-state gamma-ray spectra. We perform also numerical calculations in order to back up our analytical results. We show that a spontaneously quenched power-law gamma-ray spectrum obtains a photon index 3{\Gamma}/2, where {\Gamma} is the photon index of the power-law at injection. Thus, large spectral breaks of the gamma-ray photon spectrum, e.g. $\Delta \Gamma \gtrsim 1$, can be obtained by this mechanism. We also discuss additional features of this mechanism that can be tested observationally. Finally, we fit the multiwavelength spectrum of a newly discovered blazar (PKS 0447-439) by using such parameters, as to explain the break in the gamma-ray spectrum by means of spontaneous photon quenching, under the assumption that its redshift lies in the range 0.1<z<0.24.Comment: 14 pages, 9 figures, 2 tables, accepted for publication in A&

Αξιολόγηση μεθόδων εκτίμησης των περιβαλλοντικών ροών με συνδυασμένη χρήση υδρολογικών, υδραυλικών και βιοτικών δεδομένων

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Περιβάλλον και Ανάπτυξη

Διερεύνηση γεωχωρικών ικανοτήτων κατά την πλοήγηση σε άγνωστο περιβάλλον

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Γεωπληροφορική

Solar X-rays from Axions: Rest-Mass Dependent Signatures

The spectral shape of solar X-rays is a power law. The more active the Sun is, the less steep the distribution. This behaviour can be explained by axion regeneration to X-rays occurring ~400km deep into the photosphere. Their down-comptonization reproduces the measured spectral shape, pointing at axions with rest mass m_a~17 meV/c2, without contradicting astrophysical-laboratory limits. Directly measured soft X-ray spectra from the extremely quiet Sun during 2009 (SphinX mission), though hitherto overlooked, fitt the axion scenario.Comment: To appear in Proceedings of the 5th Patras Axion Workshop, Durham 200