Ultra-compact structure in intermediate-luminosity radio quasars: building a sample of standard cosmological rulers and improving the dark energy constraints up to z∼3z\sim 3

In this paper, we present a new compiled milliarcsecond compact radio data set of 120 intermediate-luminosity quasars in the redshift range $0.46< z <2.76$. These quasars show negligible dependence on redshifts and intrinsic luminosity, and thus represents, in the standard model of cosmology, a fixed comoving-length of standard ruler. We implement a new cosmology-independent technique to calibrate the linear size of of this standard ruler as $l_m= 11.03\pm0.25$ pc, which is the typical radius at which AGN jets become opaque at the observed frequency $\nu\sim 2$ GHz. In the framework of flat $\Lambda$CDM model, we find a high value of the matter density parameter, $\Omega_m=0.322^{+0.244}_{-0.141}$, and a low value of the Hubble constant, $H_0=67.6^{+7.8}_{-7.4}\; \rm{kms}^{-1}\rm{Mpc}^{-1}$, which is in excellent agreement with the CMB anisotropy measurements by \textit{Planck}. We obtain ${\Omega_m}=0.309^{+0.215}_{-0.151}$, $w=-0.970^{+0.500}_{-1.730}$ at 68.3% CL for the constant $w$ of a dynamical dark-energy model, which demonstrates no significant deviation from the concordance $\Lambda$CDM model. Consistent fitting results are also obtained for other cosmological models explaining the cosmic acceleration, like Ricci dark energy (RDE) or Dvali-Gabadadze-Porrati (DGP) brane-world scenario. While no significant change in $w$ with redshift is detected, there is still considerable room for evolution in $w$ and the transition redshift at which $w$ departing from -1 is located at $z\sim 2.0$. Our results demonstrate that the method extensively investigated in our work on observational radio quasar data can be used to effectively derive cosmological information. Finally, we find the combination of high-redshift quasars and low-redshift clusters may provide an important source of angular diameter distances, considering the redshift coverage of these two astrophysical probes.Comment: 36 pages, 5 tables, 16 figures, A&A, in pres

Destabilizing the autoinhibitory conformation of Zap70 induces up-regulation of inhibitory receptors and T cell unresponsiveness.

Zap70 plays a critical role in normal T cell development and T cell function. However, little is known about how perturbation of allosteric autoinhibitory mechanisms in Zap70 impacts T cell biology. Here, we analyze mice with a hypermorphic Zap70 mutation, W131A, which destabilizes the autoinhibitory conformation of Zap70, rendering the kinase in a semiactive state. W131A mutant mice with wild-type T cell receptor (TCR) repertoires exhibited relatively normal T cell development. However, crossing the W131A mutant mice to OTII TCR transgenic mice resulted in increased negative selection of OTII+ thymocytes and in increased thymic and peripheral T regulatory cells. Strikingly, increased basal TCR signaling was associated with a marked increase in inhibitory receptor expression and with T cells that were relatively refractory to TCR stimulation. PD-1 inhibitory receptor blockade partially reversed T cell unresponsiveness. Collectively, disruption of normal Zap70 autoinhibition engaged negative feedback mechanisms by which negative selection and inhibitory receptors restrain TCR signaling to enforce both central and peripheral tolerance