Positron beam lifetime spectroscopy at Lawrence Livermore National Laboratory

Defect analysis is needed for samples ranging in thickness from thin films to large engineering parts. We are meeting that need with two positron beam lifetime spectrometers: on on a 3 MeV electrostatic accelerator and the second on our high current linac beam. The high energy beam spectrometer performs positron lifetime analysis on thick samples which can be encapsulated for containment or for in situ measurements in controlled environments. At our high current beam, we are developing a low energy, microscopically focused, pulsed positron beam to enable positron annihilation lifetime spectroscopy for defect specific, 3-D maps with sub-micron location resolution. The data from these instruments with the aid of first principles calculations of defect specific positron lifetimes

Normal levels of p27Xic1 are necessary for somite segmentation and determining pronephric organ size

The Xenopus laevis cyclin dependent kinase inhibitor p27Xic1 has been shown to be involved in exit from the cell cycle and differentiation of cells into a quiescent state in the nervous system, muscle tissue, heart and retina. We show that p27Xic1 is expressed in the developing kidney in the nephrostomal regions. Using over-expression and morpholino oligonucleotide (MO) knock-down approaches we show normal levels of p27Xic1 regulate pronephros organ size by regulating cell cycle exit. Knock-down of p27Xic1 expression using a MO prevented myogenesis, as previously reported; an effect that subsequently inhibits pronephrogenesis. Furthermore, we show that normal levels of p27Xic1 are required for somite segmentation also through its cell cycle control function. Finally, we provide evidence to suggest correct paraxial mesoderm segmentation is not necessary for pronephric induction in the intermediate mesoderm. These results indicate novel developmental roles for p27Xic1, and reveal its differentiation function is not universally utilised in all developing tissues

The formation history of massive cluster galaxies as revealed by CARLA

We use a sample of 37 of the densest clusters and protoclusters across 1.3 ≤ z ≤ 3.2 from the Clusters Around Radio-Loud AGN (CARLA) survey to study the formation of massive cluster galaxies. We use optical i′-band and infrared 3.6 and 4.5 μm images to statistically select sources within these protoclusters and measure their median observed colours; 〈i′ − [3.6]〉. We find the abundance of massive galaxies within the protoclusters increases with decreasing redshift, suggesting these objects may form an evolutionary sequence, with the lower redshift clusters in the sample having similar properties to the descendants of the high-redshift protoclusters. We find that the protocluster galaxies have an approximately unevolving observed-frame i′ − [3.6] colour across the examined redshift range. We compare the evolution of the 〈i′ − [3.6]〉 colour of massive cluster galaxies with simplistic galaxy formation models. Taking the full cluster population into account, we show that the formation of stars within the majority of massive cluster galaxies occurs over at least 2 Gyr, and peaks at z ∼ 2–3. From the median i′ − [3.6] colours, we cannot determine the star formation histories of individual galaxies, but their star formation must have been rapidly terminated to produce the observed red colours. Finally, we show that massive galaxies at z > 2 must have assembled within 0.5 Gyr of them forming a significant fraction of their stars. This means that few massive galaxies in z > 2 protoclusters could have formed via dry mergers

Large scale structures around radio galaxies at z~1.5

We explore the environments of two radio galaxies at z~1.5, 7C1751+6809 and 7C1756+6520, using deep optical and near-infrared imaging. Our data cover 15'x15' fields around the radio galaxies. We develop and apply BzK color criteria to select cluster member candidates around the radio galaxies and find no evidence of an overdensity of red galaxies within 2Mpc of 7C1751+6809. In contrast, 7C1756+6520 shows a significant overdensity of red galaxies within 2Mpc of the radio galaxy, by a factor of 3.1 +/- 0.8 relative to the four MUSYC fields. At small separation (r<6''), this radio galaxy also has one z~1.4 evolved galaxy candidate, one z~1.4 star-forming galaxy candidate, and an AGN candidate (at indeterminate redshift). This is suggestive of several close-by companions. Several concentrations of red galaxies are also noticed in the full 7C1756+6520 field, forming a possible large-scale structure of evolved galaxies with a NW-SE orientation. We construct the color-magnitude diagram of red galaxies found near (r<2Mpc) 7C1756+6520, and find a clear red sequence that is truncated at Ks~21.5 (AB). We also find an overdensity of mid-IR selected AGN in the surroundings of 7C1756+6520. These results are suggestive of a proto-cluster at high redshift.Comment: 21 pages, 12 figures, 6 tables, accepted for publication in A&

Why z > 1 radio-loud galaxies are commonly located in protoclusters

Distant powerful radio-loud active galactic nuclei (RLAGN) tend to reside in dense environments and are commonly found in protoclusters at z > 1.3. We examine whether this occurs because RLAGN are hosted by massive galaxies, which preferentially reside in rich environments. We compare the environments of powerful RLAGN at 1.3 1014M cluster having experienced powerful radio-loud feedback of duration ~60 Myr during 1.3<z<3.2. This feedback could heat the intracluster medium to the extent of 0.5–1 keV per gas particle, which could limit the amount of gas available for further star formation in the protocluster galaxies

Improved constraints on the expansion rate of the Universe up to z~1.1 from the spectroscopic evolution of cosmic chronometers

We present new improved constraints on the Hubble parameter H(z) in the redshift range 0.15 < z < 1.1, obtained from the differential spectroscopic evolution of early-type galaxies as a function of redshift. We extract a large sample of early-type galaxies (\sim11000) from several spectroscopic surveys, spanning almost 8 billion years of cosmic lookback time (0.15 < z < 1.42). We select the most massive, red elliptical galaxies, passively evolving and without signature of ongoing star formation. Those galaxies can be used as standard cosmic chronometers, as firstly proposed by Jimenez & Loeb (2002), whose differential age evolution as a function of cosmic time directly probes H(z). We analyze the 4000 {\AA} break (D4000) as a function of redshift, use stellar population synthesis models to theoretically calibrate the dependence of the differential age evolution on the differential D4000, and estimate the Hubble parameter taking into account both statistical and systematical errors. We provide 8 new measurements of H(z) (see Tab. 4), and determine its change in H(z) to a precision of 5-12% mapping homogeneously the redshift range up to z \sim 1.1; for the first time, we place a constraint on H(z) at z \neq 0 with a precision comparable with the one achieved for the Hubble constant (about 5-6% at z \sim 0.2), and covered a redshift range (0.5 < z < 0.8) which is crucial to distinguish many different quintessence cosmologies. These measurements have been tested to best match a \Lambda CDM model, clearly providing a statistically robust indication that the Universe is undergoing an accelerated expansion. This method shows the potentiality to open a new avenue in constrain a variety of alternative cosmologies, especially when future surveys (e.g. Euclid) will open the possibility to extend it up to z \sim 2.Comment: 34 pages, 15 figures, 6 tables, published in JCAP. It is a companion to Moresco et al. (2012b, http://arxiv.org/abs/1201.6658) and Jimenez et al. (2012, http://arxiv.org/abs/1201.3608). The H(z) data can be downloaded at http://www.physics-astronomy.unibo.it/en/research/areas/astrophysics/cosmology-with-cosmic-chronometer

The angular clustering of infrared-selected obscured and unobscured quasars

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2014 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.Recent studies of luminous infrared-selected active galactic nuclei (AGN) suggest that the reddest, most obscured objects display a higher angular clustering amplitude, and thus reside in higher mass darkmatter haloes. This is a direct contradiction to the prediction of the simplest unification-by-orientation models of AGN and quasars. However, clustering measurements depend strongly on the 'mask' that removes low-quality data and describes the sky and selection function.We find that applying a robust, conservative mask to WISE-selected quasars yields a weaker but still significant difference in the bias between obscured and unobscured quasars. These findings are consistent with results from previous Spitzer surveys, and removes any scale dependence of the bias. For obscured quasars with =0.99, we measure a bias of bq = 2.67 ± 0.16, corresponding to a halo mass of log(Mh/M⊙h-1) = 13.3 ± 0.1, while for unobscured sources with = 1.04 we find bq = 2.04 ± 0.17 with a halo mass log(Mh/M⊙h-1) = 12.8 ± 0.1. This improved measurement indicates that WISE-selected obscured quasars reside in haloes only a few times more massive than the haloes of their unobscured counterparts, a reduction in the factor of ∼10 larger halo mass as has been previously reported using WISE-selected samples. Additionally, an abundance matching analysis yields lifetimes for both obscured and unobscured quasar phases on the order of a few 100 Myr (∼1 per cent of the Hubble time) - however, the obscured phase lasts roughly twice as long, in tension with many model predictions.Peer reviewe

4MOST complete calibration of the colour-redshift relation (4C3R2)

Galaxie

Staged decline of neuronal function in vivo in an animal model of Alzheimer's disease

The accumulation of amyloid-β in the brain is an essential feature of Alzheimer's disease. However, the impact of amyloid-β-accumulation on neuronal dysfunction on the single cell level in vivo is poorly understood. Here we investigate the progression of amyloid-β load in relation to neuronal dysfunction in the visual system of the APP23×PS45 mouse model of Alzheimer's disease. Using in vivo two-photon calcium imaging in the visual cortex, we demonstrate that a progressive deterioration of neuronal tuning for the orientation of visual stimuli occurs in parallel with the age-dependent increase of the amyloid-β load. Importantly, we find this deterioration only in neurons that are hyperactive during spontaneous activity. This impairment of visual cortical circuit function also correlates with pronounced deficits in visual-pattern discrimination. Together, our results identify distinct stages of decline in sensory cortical performance in vivo as a function of the increased amyloid-β-load

Sex Pheromone Evolution Is Associated with Differential Regulation of the Same Desaturase Gene in Two Genera of Leafroller Moths

Chemical signals are prevalent in sexual communication systems. Mate recognition has been extensively studied within the Lepidoptera, where the production and recognition of species-specific sex pheromone signals are typically the defining character. While the specific blend of compounds that makes up the sex pheromones of many species has been characterized, the molecular mechanisms underpinning the evolution of pheromone-based mate recognition systems remain largely unknown. We have focused on two sets of sibling species within the leafroller moth genera Ctenopseustis and Planotortrix that have rapidly evolved the use of distinct sex pheromone blends. The compounds within these blends differ almost exclusively in the relative position of double bonds that are introduced by desaturase enzymes. Of the six desaturase orthologs isolated from all four species, functional analyses in yeast and gene expression in pheromone glands implicate three in pheromone biosynthesis, two Δ9-desaturases, and a Δ10-desaturase, while the remaining three desaturases include a Δ6-desaturase, a terminal desaturase, and a non-functional desaturase. Comparative quantitative real-time PCR reveals that the Δ10-desaturase is differentially expressed in the pheromone glands of the two sets of sibling species, consistent with differences in the pheromone blend in both species pairs. In the pheromone glands of species that utilize (Z)-8-tetradecenyl acetate as sex pheromone component (Ctenopseustis obliquana and Planotortrix octo), the expression levels of the Δ10-desaturase are significantly higher than in the pheromone glands of their respective sibling species (C. herana and P. excessana). Our results demonstrate that interspecific sex pheromone differences are associated with differential regulation of the same desaturase gene in two genera of moths. We suggest that differential gene regulation among members of a multigene family may be an important mechanism of molecular innovation in sex pheromone evolution and speciation