Class I dependence of the development of CD4+ CD8- NK1.1+ thymocytes.

A small subset of functionally active CD4+ CD8- thymocytes express the NK1.1 marker, as do most CD4-CD8- NK1.1+ thymocytes. Previous studies have failed to implicate a role for major histocompatibility complex (MHC) or related molecules in the selection of the CD4+ CD8- NK1.1+ subset. We report here that the development of most of these cells is sharply reduced in class I-deficient mice, but not in class II-deficient mice. Hence, some CD4+ T cells are class I dependent and not class II dependent. Unlike conventional T cells, however, the development of NK1.1+ thymocytes in both the CD4+ CD8- and CD4- CD8- subsets is dependent on class I MHC expression by hematopoietic cells and not thymic epithelial cells. We propose that these populations are selected by nonpolymorphic class Ib or CD1 molecules

Positive selection of V beta 8+ CD4-8- thymocytes by class I molecules expressed by hematopoietic cells.

A small subset of T cells of mature phenotype express the alpha/beta T cell receptor, but not CD4 and CD8 coreceptors (alpha/beta double-negative [DN] cells). The repertoire of V beta usage of alpha/beta DN cells is strongly biased towards V beta 8 expression, suggesting that the formation of the population is subject to selection. We now report that deficiency of class I expression leads to a strongly depressed frequency of V beta 8+ DN cells, but has little effect on V beta 8- DN cells. Studies of hematopoietic chimeras between class I+ and class I- mice demonstrated that expression of class I molecules by hematopoietic cells is necessary and sufficient for selection of most V beta 8 DN cells. The lack of a role for class I expression by thymic epithelial cells suggests that the mechanism of selection of these cells by class I differs significantly from the mechanism of selection of conventional T cells. Models to explain the selection of these cells as well as their possible function in vivo are discussed

Defective development of gamma/delta T cells in interleukin 7 receptor-deficient mice is due to impaired expression of T cell receptor gamma genes.

Mice lacking the interleukin 7 receptor (IL-7R) generate alpha/beta T cells at a detectable but greatly reduced rate, but gamma/delta T cells are completely absent. The special role of IL-7R signaling in gamma/delta T cell development has remained unclear. IL-7Ralpha(-/-) mice exhibit a paucity of gamma gene rearrangements. This striking observation can be explained by a defect in T cell receptor (TCR)-gamma gene rearrangement, a defect in TCR-gamma gene transcription leading to death of gamma/delta lineage cells, and/or a requirement for IL-7R in commitment of cells to the gamma/delta lineage. To determine the role of IL-7R signaling in gamma/delta T cell development, we examined transcription of a prerearranged TCR-gamma transgene in IL-7Ralpha(-/-) mice, as well as the effects of IL-7 on transcription of endogenous, rearranged TCR-gamma genes in alpha/beta lineage cells. The results demonstrate that IL-7R-mediated signals are necessary for the normal expression of rearranged TCR-gamma genes. Equally significant, the results show that the poor expression of TCR-gamma genes in IL-7Ralpha(-/-) mice is responsible for the selective deficit in gamma/delta cells in these mice, since a high copy TCR-gamma transgene exhibited sufficient residual expression in IL-7Ralpha(-/-) mice to drive gamma/delta cell development. The results indicate that the absence of gamma/delta T cells in IL-7Ralpha(-/-) mice is due to insufficient TCR-gamma gene expression

ITERA: IDL Tool for Emission-line Ratio Analysis

We present a new software tool to enable astronomers to easily compare observations of emission line ratios with those determined by photoionization and shock models, ITERA, the IDL Tool for Emission-line Ratio Analysis. This tool can plot ratios of emission lines predicted by models and allows for comparison of observed line ratios against grids of these models selected from model libraries associated with the tool. We provide details of the libraries of standard photoionization and shock models available with ITERA, and, in addition, present three example emission line ratio diagrams covering a range of wavelengths to demonstrate the capabilities of ITERA. ITERA, and associated libraries, is available from \url{http://www.brentgroves.net/itera.html}Comment: Accepted for New Astronomy, 3 figures. ITERA tool available to download from http://www.brentgroves.net/itera.htm

Scholars Forum: A New Model For Scholarly Communication

Scholarly journals have flourished for over 300 years because they successfully address a broad range of authors' needs: to communicate findings to colleagues, to establish precedence of their work, to gain validation through peer review, to establish their reputation, to know the final version of their work is secure, and to know their work will be accessible by future scholars. Eventually, the development of comprehensive paper and then electronic indexes allowed past work to be readily identified and cited. Just as postal service made it possible to share scholarly work regularly and among a broad readership, the Internet now provides a distribution channel with the power to reduce publication time and to expand traditional print formats by supporting multi-media options and threaded discourse. Despite widespread acceptance of the web by the academic and research community, the incorporation of advanced network technology into a new paradigm for scholarly communication by the publishers of print journals has not materialized. Nor have journal publishers used the lower cost of distribution on the web to make online versions of journals available at lower prices than print versions. It is becoming increasingly clear to the scholarly community that we must envision and develop for ourselves a new, affordable model for disseminating and preserving results, that synthesizes digital technology and the ongoing needs of scholars. In March 1997, with support from the Engineering Information Foundation, Caltech sponsored a Conference on Scholarly Communication to open a dialogue around key issues and to consider the feasibility of alternative undertakings. A general consensus emerged recognizing that the certification of scholarly articles through peer review could be "decoupled" from the rest of the publishing process, and that the peer review process is already supported by the universities whose faculty serve as editors, members of editorial boards, and referees. In the meantime, pressure to enact regressive copyright legislation has added another important element. The ease with which electronic files may be copied and forwarded has encouraged publishers and other owners of copyrighted material to seek means for denying access to anything they own in digital form to all but active subscribers or licensees. Furthermore, should publishers retain the only version of a publication in a digital form, there is a significant risk that this material may eventually be lost through culling little-used or unprofitable back-files, through not investing in conversion expense as technology evolves, through changes in ownership, or through catastrophic physical events. Such a scenario presents an intolerable threat to the future of scholarship

Cosmological Parameter Determination in Free-Form Strong Gravitational Lens Modeling

We develop a novel statistical strong lensing approach to probe the cosmological parameters by exploiting multiple redshift image systems behind galaxies or galaxy clusters. The method relies on free-form mass inversion of strong lenses and does not need any additional information other than gravitational lensing. Since in free-form lensing the solution space is a high-dimensional convex polytope, we consider Bayesian model comparison analysis to infer the cosmological parameters. The volume of the solution space is taken as a tracer of the probability of the underlying cosmological assumption. In contrast to parametric mass inversions, our method accounts for the mass-sheet degeneracy, which implies a degeneracy between the steepness of the profile and the cosmological parameters. Parametric models typically break this degeneracy, introducing hidden priors to the analysis that contaminate the inference of the parameters. We test our method with synthetic lenses, showing that it is able to infer the assumed cosmological parameters. Applied to the CLASH clusters, the method might be competitive with other probes.Comment: 11 pages, 5 figures. Accepted for publication in MNRA

Entanglement between living bacteria and quantized light witnessed by Rabi splitting

We model recent experiments on living sulphur bacteria interacting with quantised light, using the Dicke model. The strong coupling achieved between the bacteria and the light indicates that during the experiment the bacteria (treated as dipoles) and the quantized light are entangled. The vacuum Rabi splitting, which was measured in the experiment for a range of different parameters, can be used as an entanglement witness

Effects of Foreground Contamination on the Cosmic Microwave Background Anisotropy Measured by MAP

We study the effects of diffuse Galactic, far-infrared extragalactic source, and radio point source emission on the cosmic microwave background (CMB) anisotropy data anticipated from the MAP experiment. We focus on the correlation function and genus statistics measured from mock MAP foreground-contaminated CMB anisotropy maps generated in a spatially-flat cosmological constant dominated cosmological model. Analyses of the simulated MAP data at 90 GHz (0.3 deg FWHM resolution smoothed) show that foreground effects on the correlation function are small compared with cosmic variance. However, the Galactic emission, even just from the region with |b| > 20 deg, significantly affects the topology of CMB anisotropy, causing a negative genus shift non-Gaussianity signal. Given the expected level of cosmic variance, this effect can be effectively reduced by subtracting existing Galactic foreground emission models from the observed data. IRAS and DIRBE far-infrared extragalactic sources have little effect on the CMB anisotropy. Radio point sources raise the amplitude of the correlation function considerably on scales below 0.5 deg. Removal of bright radio sources above a 5 \sigma detection limit effectively eliminates this effect. Radio sources also result in a positive genus curve asymmetry (significant at 2 \sigma) on 0.5 deg scales. Accurate radio point source data is essential for an unambiguous detection of CMB anisotropy non-Gaussianity on these scales. Non-Gaussianity of cosmological origin can be detected from the foreground-subtracted CMB anisotropy map at the 2 \sigma level if the measured genus shift parameter |\Delta\nu| >= 0.02 (0.04) or if the measured genus asymmetry parameter |\Delta g| >= 0.03 (0.08) on a 0.3 (1.0) deg FWHM scale.Comment: 26 pages, 7 figures, Accepted for Publication in Astrophysical Journal (Some sentences and figures modified