Red electroluminescence from ZnGaS:Mn thin films

We demonstrate color shifting from the yellow to the red in the electroluminescence from (ZnGa)S:Mn films. We observe threshold voltages down to about 35 V, extremely low for such devices. We discuss the materials characteristics of the phosphor films, and the potential for improvement of the luminous intensity of the devices

Diverse topics in crystalline beams

Equations of motion are presented, appropriate to interacting charged particles of diverse charge and mass, subject to the external forces produced by various kinds of magnetic fields and radio-frequency (rf) electric fields in storage rings. These equations are employed in the molecular dynamics simulations to study the properties of crystalline beams. The two necessary conditions for the formation and maintenance of crystalline beams are summarized. The transition from ID to 2D, and from 2D to 3D is explored, and the scaling behavior of the heating rates is discussed especially in the high temperature limit. The effectiveness of various cooling techniques in achieving crystalline states has been investigated. Crystalline beams made of two different species of ions via sympathetic cooling are presented, as well as circulating ``crystal balls`` bunched in all directions by magnetic focusing and rf field. By numerically reconstructing the original experimental conditions of the NAP-M ring, it is found that only at extremely low beam intensities, outside of the range of the original measurement, proton particles can form occasionally-passing disks. The proposed New ASTRID ring is shown to be suitable for the formation and maintenance of crystalline beams of all dimensions

p-type conductivity in CuCr₁₋ₓMgₓO₂ films and powders

CuCr₁₋ₓMgₓO₂, a wide band gap semiconductor with the delafossite structure, has been synthesized in bulk and thin-film form. Bulk undoped CuCrO₂ is almost black and has moderate conductivity with p-type carriers. Upon doping with 5% Mg, the conductivity increases by a factor of 1000. In films, the best p-type conductivity is 220 S cm⁻¹ in CuCr₀.₉₅Mg₀.₀₅O₂, a factor of 7 higher than previously reported for Cu-based p-type delafossites. Undoped films have a conductivity of order 1 S cm⁻¹. Films are usually polycrystalline on amorphous substrates, but undoped films can be c-axis oriented if deposited at or above 650 °C. Optical and ultraviolet transmission data indicate a direct band gap of 3.1 eV.This is the publisher’s final pdf. The published article is copyrighted by the American Institute of Physics and can be found at: http://scitation.aip.org/content/aip/journal/jap. Article Copyright (2001) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics

Econometric Modelling based on Pattern recognition via the Fuzzy c-Means Clustering Algorithm

In this paper we consider the use of fuzzy modelling in the context of econometric analysis of both time-series and cross-section data. We discuss and demonstrate a semi-parametric methodology for model identification and estimation that is based on the Fuzzy c-Means algorithm that is widely used in the context of pattern recognition, and the Takagi-Sugeno approach to modelling fuzzy systems. This methodology is exceptionally flexible and provides a computationally tractable method of dealing with non-linear models in high dimensions. In this respect it has distinct theoretical advantages over non-parametric kernel regression, and we find that these advantages also hold empirically in terms of goodness-of-fit in a selection of economic applications.Fuzzy logic, fuzzy sets, fuzzy c-means algorithm, pattern recognition, semi-parametric modelling, curse of dimensionality.

CD19-independent instruction of murine marginal zone B-cell development by constitutive Notch2 signaling.

B cell-specific gene ablation of Notch2 results in the loss of the Marginal Zone (MZ) B cell lineage. To analyze the effects of constitutive Notch2 signaling in B cells, we have generated a transgenic mouse strain allowing the conditional expression of a constitutively active, intracellular form of Notch2 (Notch2IC). Expression of Notch2IC at the earliest developmental stages of the B cell lineage completely abolished B cell generation and led to the development of ectopic T cells in the bone marrow, showing that Notch2IC is acting redundantly with Notch1IC in driving ectopic T cell differentiation. In B cells clearly committed to the B cell lineage induction of Notch2IC drove all cells towards the MZ B cell compartment at the expense of Follicular B cells. Notch2IC-expressing B cells reflected the phenotype of wild type MZ B cells with respect to their localization in the MZ, the expression of characteristic surface markers, their enhanced proliferation after stimulation and increased basal activity of Akt, Erk and Jnk. Notch2IC-driven MZ B cell generation in the spleen was achieved even in the absence of CD19. Our results implicate that a constitutive Notch2 signal in T1 B cells is sufficient to drive MZ B cell differentiation