BMP signaling in skeletal muscle and bone

Since their discovery as bone inducers, Bone Morphogenetic Proteins (BMPs) have been demonstrated to control multiple functions during embryogenesis as well as postnatally. BMPs are acting as morphogenes, i.e. they can induce various cell fates at different concentrations. There are multiple regulatory mechanisms to control BMP signaling and dysregulated BMP signaling is pathologically linked with multiple diseases. This thesis presents novel studies regarding the role of elevated BMP signaling on the progression of two different genetic diseases, i.e. Fibrodysplasia Ossificans Progressiva (FOP) and Duchenne Muscular Dystrophy (DMD). Besides that, BMP signaling is tightly regulated on different levels; the activity of BMP signaling can also be modulated by other signaling pathways, such as the TGF_ and Wnt signaling pathways. In Chapter 2, we investigated the molecular mechanisms underlying TGF_ and BMP-induced conversion of endothelial cells into osteoblasts. In Chapter 3, using the BMP antagonist Noggin, we studied the role of BMP signaling in the progression of DMD disease. In Chapter 4, we described that Id3 is activated by canonical Wnt signaling in C2C12 cells, and mediates Wnt-induced myoblast proliferation and osteoblast differentiation. In Chapter 5, we showed that BMP6, in contrary to BMP7, BMP2 and BMP4, cannot be inhibited by Noggin, and identified the crucial amino acid that endows BMP6 resistance to Noggin inhibition. These findings make it possible to engineer BMPs with superior agonist activity through amino acid substitution. In Chapter 6, using exon skipping technology, we obtained an antisense oligonucleotide (AON) that specifically targets BMP type I receptor activin receptor-like kinase (ALK) 2. The ALK2 AON was shown to decrease ALK2 expression and reduced BMP6 induced osteoblast differentiation in vitro. Finally in Chapter 7, the results presented in the thesis were discussed and suggestions for future research were provided.UBL - phd migration 201

Ground state properties and excitation spectra of non-Galilean invariant interacting Bose systems

We study the ground state properties and the excitation spectrum of bosons which, in addition to a short-range repulsive two body potential, interact through the exchange of some dispersionless bosonic modes. The latter induces a time dependent (retarded) boson-boson interaction which is attractive in the static limit. Moreover the coupling with dispersionless modes introduces a reference frame for the moving boson system and hence breaks the Galilean invariance of this system. The ground state of such a system is depleted {\it linearly} in the boson density due to the zero point fluctuations driven by the retarded part of the interaction. Both quasiparticle (microscopic) and compressional (macroscopic) sound velocities of the system are studied. The microscopic sound velocity is calculated up the second order in the effective two body interaction in a perturbative treatment, similar to that of Beliaev for the dilute weakly interacting Bose gas. The hydrodynamic equations are used to obtain the macroscopic sound velocity. We show that these velocities are identical within our perturbative approach. We present analytical results for them in terms of two dimensional parameters -- an effective interaction strength and an adiabaticity parameter -- which characterize the system. We find that due the presence of several competing effects, which determine the speed of the sound of the system, three qualitatively different regimes can be in principle realized in the parameter space and discuss them on physical grounds.Comment: 6 pages, 2 figures, to appear in Phys. Rev.

Three-Neutrino Mixing and Combined Vacuum Oscillations and MSW Transitions of Solar Neutrinos

Assuming three flavour neutrino mixing takes place in vacuum, we investigate the possibility that the solar nu_e take part in MSW transitions in the Sun due to Delta m^2_{31} from 10^{-7} eV^2 to 10^{-4} eV^2, followed by long wave length vacuum oscillations on the way to the Earth, triggered by Delta m^2_{21} (or Delta m^2_{32}) from 10^{-12} eV^2 to 10^{-10} eV^2, Delta m^2_{31} and Delta m^2_{21} (Delta m^2_{32}) being the corresponding neutrino mass squared differences. The solar nu_e survival probability is shown to be described in this case by a simple analytic expression. Depending on whether the vacuum oscillations are due to Delta m^2_{21} or Delta m^2_{32} there are two very different types of interplay between the MSW transitions and the vacuum oscillations of the solar nu_e. Performing an analysis of the most recently published solar neutrino data we have found several qualitatively new solutions of the solar neutrino problem of the hybrid MSW transitions + vacuum oscillations type. The solutions differ in the way the pp, 7Be and 8B neutrino fluxes are affected by the transitions in the Sun and the oscillations in vacuum. The specific features of the new solutions are discussed.Comment: 37 pages Latex, 16 Postscript Figure

Persistent global power fluctuations near a dynamic transition in electroconvection

This is a study of the global fluctuations in power dissipation and light transmission through a liquid crystal just above the onset of electroconvection. The source of the fluctuations is found to be the creation and annihilation of defects. They are spatially uncorrelated and yet temporally correlated. The temporal correlation is seen to persist for extremely long times. There seems to be an especially close relation between defect creation/annihilat ion in electroconvection and thermal plumes in Rayleigh-B\'enard convection

Existence of Ricci flows of incomplete surfaces

We prove a general existence result for instantaneously complete Ricci flows starting at an arbitrary Riemannian surface which may be incomplete and may have unbounded curvature. We give an explicit formula for the maximal existence time, and describe the asymptotic behaviour in most cases.Comment: 20 pages; updated to reflect galley proof correction

Neutrinoless Double Beta Decay and the Solar Neutrino Problem

The MSW or vacuum oscillation solution of the solar neutrino problem can be reconciled with possible existence of the $(\beta\beta)_{0\nu}$ decay with a half-life corresponding to an effective Majorana mass of the electron neutrino $|m_{ee}| \cong (0.1 - 1.0)~$eV. The phenomenological consequences of such a possibility are analyzed and the implications for the mechanisms of neutrino mass generation are considered.Comment: 17 pages (2 figures available upon request), LaTeX, SISSA 113/93/EP and IC/93/360 (the word BETA inserted in the title

Simultaneous generation and routing of millimetre-wave signals exploiting optical frequency multiplication

Exploiting an integrated micro-ring resonator, the simultaneous generation and routing of millimetre-wave signals by optical frequency multiplication is demonstrated for in-building networks. Error Vector Magnitude <5% is achieved for up to 120Mb/s 64-QAM at 39.6 GHz carrier frequency

Quasi-energy-independent solar neutrino transitions

Current solar, atmospheric, and reactor neutrino data still allow oscillation scenarios where the squared mass differences are all close to 10^-3 eV^2, rather than being hierarchically separated. For solar neutrinos, this situation (realized in the upper part of the so-called large-mixing angle solution) implies adiabatic transitions which depend weakly on the neutrino energy and on the matter density, as well as on the ``atmospheric'' squared mass difference. In such a regime of ``quasi-energy-independent'' (QEI) transitions, intermediate between the more familiar ``Mikheyev-Smirnov-Wolfenstein'' (MSW) and energy-independent (EI) regimes, we first perform analytical calculations of the solar nu_e survival probability at first order in the matter density, beyond the usual hierarchical approximations. We then provide accurate, generalized expressions for the solar neutrino mixing angles in matter, which reduce to those valid in the MSW, QEI and EI regimes in appropriate limits. Finally, a representative QEI scenario is discussed in some detail.Comment: Title changed; text and acronyms revised; results unchanged. To appear in PR

Damping of phase fluctuations in superfluid Bose gases

Using Popov's hydrodynamic approach we derive an effective Euclidean action for the long-wavelength phase fluctuations of superfluid Bose gases in D dimensions. We then use this action to calculate the damping of phase fluctuations at zero temperature as a function of D. For D >1 and wavevectors | k | << 2 mc (where m is the mass of the bosons and c is the sound velocity) we find that the damping in units of the phonon energy E_k = c | k | is to leading order gamma_k / E_k = A_D (k_0^D / 2 pi rho) (| k | / k_0)^{2 D -2}, where rho is the boson density and k_0 =2 mc is the inverse healing length. For D -> 1 the numerical coefficient A_D vanishes and the damping is proportional to an additional power of |k | /k_0; a self-consistent calculation yields in this case gamma_k / E_k = 1.32 (k_0 / 2 pi rho)^{1/2} |k | / k_0. In one dimension, we also calculate the entire spectral function of phase fluctuations.Comment: 6 pages, 4 figures, published versio

Enhancement of Sm3+emission by SnO2nanocrystals in the silica matrix

Silica xerogels containing Sm3+ions and SnO2nanocrystals were prepared in a sol–gel process. The image of transmission electron microscopy (TEM) shows that the SnO2nanocrystals are dispersed in the silica matrix. The X-ray diffraction (XRD) of the sample confirms the tetragonal phase of SnO2. The xerogels containing SnO2nanocrystals and Sm3+ions display the characteristic emission of Sm3+ions (4G5/2 → 6HJ(J = 5/2, 7/2, 9/2)) at the excitation of 335 nm which energy corresponds to the energy gap of the SnO2nanocrystals, while no emission of Sm3+ions can be observed for the samples containing Sm3+ions. The enhancement of the Sm3+emission is probably due to the energy transfer from SnO2nanocrystals to Sm3+ions