A 4-neutrino model with a Higgs triplet

We take as a starting point the Gelmini -- Roncadelli model enlarged by a term with explicit lepton number violation in the Higgs potential and add a neutrino singlet field coupled via a scalar doublet to the usual leptons. This scenario allows us to take into account all three present indications in favour of neutrino oscillations provided by the solar, atmospheric and LSND neutrino oscillation experiments. Furthermore, it suggests a model which reproduces naturally one of the two 4-neutrino mass spectra favoured by the data. In this model the solar neutrino problem is solved by large mixing MSW \nu_e\to\nu_\tau transitions and the atmospheric neutrino problem by transitions of \nu_\mu into a sterile neutrino.Comment: Latex, 14 pages, no figure

A socio-economic analysis of youth disconnectedness

According to our research, some 12% of young people in Germany between the ages of 17 and 19 are disconnected, i.e. not in school, unemployed, and not living with a partner. The percentage of disconnected youths has been on the rise since 2002. There is evidence that an adverse family environment is the most important variable for being disconnected. Early life adversity influences the development of cognitive and noncognitive skills as well as school and labour market outcomes. Macroeconomic factors also contribute to disconnectedness. Recessions are followed by an increase in the number of disconnected youth. --Disconnected youth,unemployment,school failure,life adversity

A Socio-Economic Analysis of Youth Disconnectedness

Disconnectedness among youth can have several dimensions. From a socio-economic viewpoint, failure in school, unemployment and the lack of an intimate relationship are among the most important ones. In our samples from SOEP youth questionnaires, approximately 13% of young people in Germany between the ages of 17 and 19 are disconnected. The percentage of disconnected youths has been on the rise since 2001. There is evidence that an adverse family background is the most important variable for being disconnected in young adulthood. Macroeconomic factors also contribute to disconnectedness. Recessions are followed by increases in the number of disconnected youth.Disconnected youth, unemployment, school failure, life adversity

A Socio-economic Analysis of Youth Disconnectedness

Disconnectedness among youth can have several dimensions. From a socio-economic viewpoint, failure in school, unemployment and the lack of an intimate relationship are among the most important ones. In our samples from SOEP youth questionnaires, approximately 13% of young people in Germany between the ages of 17 and 19 are disconnected. The percentage of disconnected youths has been on the rise since 2001. There is evidence that an adverse family background is the most important variable for being disconnected in young adulthood. Macroeconomic factors also contribute to disconnectedness. Recessions are followed by increases in the number of disconnected youth.disconnected youth, unemployment, school failure, life adversity

Degenerate states of narrow semiconductor rings in the presence of spin orbit coupling: Role of time-reversal and large gauge transformations

The electron Hamiltonian of narrow semiconductor rings with the Rashba and Dresselhaus spin orbit terms is invariant under time-reversal operation followed by a large gauge transformation. We find that all the eigenstates are doubly degenerate when integer or half-integer quantum fluxes thread the quantum ring. The wavefunctions of a degenerate pair are related to each other by the symmetry operation. These results are valid even in the presence of a disorder potential. When the Zeeman term is present only some of these degenerate levels anticross

Direct innervation of capillary endothelial cells in the lamina propria of the ferret stomach

Direct innervation of capillary endothelial cells in lamina propria of ferret stomac

Higher Gauge Theory and Gravity in (2+1) Dimensions

Non-abelian higher gauge theory has recently emerged as a generalization of standard gauge theory to higher dimensional (2-dimensional in the present context) connection forms, and as such, it has been successfully applied to the non-abelian generalizations of the Yang-Mills theory and 2-form electrodynamics. (2+1)-dimensional gravity, on the other hand, has been a fertile testing ground for many concepts related to classical and quantum gravity, and it is therefore only natural to investigate whether we can find an application of higher gauge theory in this latter context. In the present paper we investigate the possibility of applying the formalism of higher gauge theory to gravity in (2+1) dimensions, and we show that a nontrivial model of (2+1)-dimensional gravity coupled to scalar and tensorial matter fields - the $\Sigma\Phi EA$ model - can be formulated both as a standard gauge theory and as a higher gauge theory. Since the model has a very rich structure - it admits as solutions black-hole BTZ-like geometries, particle-like geometries as well as Robertson-Friedman-Walker cosmological-like expanding geometries - this opens a wide perspective for higher gauge theory to be tested and understood in a relevant gravitational context. Additionally, it offers the possibility of studying gravity in (2+1) dimensions coupled to matter in an entirely new framework.Comment: 22 page

Imaging Transport Resonances in the Quantum Hall Effect

We use a scanning capacitance probe to image transport in the quantum Hall system. Applying a DC bias voltage to the tip induces a ring-shaped incompressible strip (IS) in the 2D electron system (2DES) that moves with the tip. At certain tip positions, short-range disorder in the 2DES creates a quantum dot island in the IS. These islands enable resonant tunneling across the IS, enhancing its conductance by more than four orders of magnitude. The images provide a quantitative measure of disorder and suggest resonant tunneling as the primary mechanism for transport across ISs.Comment: 4 pages, 4 figures, submitted to PRL. For movies and additional infomation, see http://electron.mit.edu/scanning/; Added scale bars to images, revised discussion of figure 3, other minor change

Universal temperature dependence of optical excitation life-time and band-gap in chirality assigned semiconducting single-wall carbon nanotubes

The temperature dependence of optical excitation life-time, Gamma, and transition energies, E_ii, were measured for bucky-papers of single-wall carbon nanotubes (SWCNTs) and inner tubes in double-wall carbon nanotubes (DWCNTs) using resonant Raman scattering. The temperature dependence of Gamma and E_ii is the same for both types of samples and is independent of tube chirality. The data proves that electron-phonon interaction is responsible for temperature dependence of E_ii(T). The temperature independent inhomogeneous contribution to Gamma is much larger in the SWCNT samples, which is explained by the different SWCNT environment in the two types of samples. Gamma of the inner tubes for the bucky-paper DWCNT sample is as low as \sim 30 meV, which is comparable to that found for individual SWCNTs