17 research outputs found
Evidence for Widespread AGN Activity among Massive Quiescent Galaxies at z ~ 2
We quantify the presence of Active Galactic nuclei (AGN) in a mass-complete
(M_* >5e10 M_sun) sample of 123 star-forming and quiescent galaxies at 1.5 < z
< 2.5, using X-ray data from the 4 Ms Chandra Deep Field-South (CDF-S) survey.
41+/-7% of the galaxies are detected directly in X-rays, 22+/-5% with
rest-frame 0.5-8 keV luminosities consistent with hosting luminous AGN
(L_0.5-8keV > 3e42 ergs/s). The latter fraction is similar for star-forming and
quiescent galaxies, and does not depend on galaxy stellar mass, suggesting that
perhaps luminous AGN are triggered by external effects such as mergers. We
detect significant mean X-ray signals in stacked images for both the
individually non-detected star-forming and quiescent galaxies, with spectra
consistent with star formation only and/or a low luminosity AGN in both cases.
Comparing star formation rates inferred from the 2-10 keV luminosities to those
from rest-frame IR+UV emission, we find evidence for an X-ray excess indicative
of low-luminosity AGN. Among the quiescent galaxies, the excess suggests that
as many as 70-100% of these contain low- or high-luminosity AGN, while the
corresponding fraction is lower among star-forming galaxies (43-65%). The
ubiquitous presence of AGN in massive, quiescent z ~ 2 galaxies that we find
provides observational support for the importance of AGN in impeding star
formation during galaxy evolution.Comment: 9 pages, 3 figures, 3 tables; Accepted for publication in ApJ. Minor
editing changes and a few references added. Matches published versio
The Danish National Prescription Registry.
Abstract Introduction: Individual-level data on all prescription drugs sold in Danish community pharmacies has since 1994 been recorded in the Register of Medicinal Products Statistics of the Danish Medicines Agency. Content: The register subset, termed the Danish National Prescription Registry (DNPR), contains information on dispensed prescriptions, including variables at the level of the drug user, the prescriber, and the pharmacy. Validity and coverage: Reimbursement-driven record keeping, with automated bar-code-based data entry provides data of high quality, including detailed information on the dispensed drug. Conclusion: The possibility of linkage with many other nationwide individual-level data sources renders the DNPR a very powerful pharmacoepidemiological tool
Grain boundary-induced variability of charge transport in hydrogenated polycrystalline graphene
Chemical functionalization has proven to be a promising means of tailoring
the unique properties of graphene. For example, hydrogenation can yield a
variety of interesting effects, including a metal-insulator transition or the
formation of localized magnetic moments. Meanwhile, graphene grown by chemical
vapor deposition is the most suitable for large-scale production, but the
resulting material tends to be polycrystalline. Up to now there has been
relatively little focus on how chemical functionalization, and hydrogenation in
particular, impacts the properties of polycrystalline graphene. In this work,
we use numerical simulations to study the electrical properties of hydrogenated
polycrystalline graphene. We find a strong correlation between the spatial
distribution of the hydrogen adsorbates and the charge transport properties.
Charge transport is weakly sensitive to hydrogenation when adsorbates are
confined to the grain boundaries, while a uniform distribution of hydrogen
degrades the electronic mobility. This difference stems from the formation of
the hydrogen-induced resonant impurity states, which are inhibited when the
honeycomb symmetry is locally broken by the grain boundaries. These findings
suggest a tunability of electrical transport of polycrystalline graphene
through selective hydrogen functionalization, and also have implications for
hydrogen-induced magnetization and spin lifetime of this material
Localized electronic states at grain boundaries on the surface of graphene and graphite
Recent advances in large-scale synthesis of graphene and other 2D materials
have underscored the importance of local defects such as dislocations and grain
boundaries (GBs), and especially their tendency to alter the electronic
properties of the material. Understanding how the polycrystalline morphology
affects the electronic properties is crucial for the development of
applications such as flexible electronics, energy harvesting devices or
sensors. We here report on atomic scale characterization of several GBs and on
the structural-dependence of the localized electronic states in their vicinity.
Using low temperature scanning tunneling microscopy (STM) and spectroscopy
(STS), together with tight binding and ab initio numerical simulations we
explore GBs on the surface of graphite and elucidate the interconnection
between the local density of states (LDOS) and their atomic structure. We show
that the electronic fingerprints of these GBs consist of pronounced resonances
which, depending on the relative orientation of the adjacent crystallites,
appear either on the electron side of the spectrum or as an electron-hole
symmetric doublet close to the charge neutrality point. These two types of
spectral features will impact very differently the transport properties
allowing, in the asymmetric case to introduce transport anisotropy which could
be utilized to design novel growth and fabrication strategies to control device
performance
Endotoxemia Is Associated with Altered Innate and Adaptive Immune Responses in Untreated HIV-1 Infected Individuals
BACKGROUND: Microbial translocation may contribute to the immunopathogenesis in HIV infection. We investigated if microbial translocation and inflammation were associated with innate and adaptive immune responses in adults with HIV. METHODOLOGY/PRINCIPAL FINDINGS: This was an observational cohort study. Sera from HIV-infected and HIV-uninfected individuals were analyzed for microbial translocation (soluble CD14, lipopolysaccharides [LPS], endotoxin core antibody, and anti-α-galactosyl antibodies) and inflammatory markers (high sensitivity C-reactive protein, IL-6, IL-1 receptor antagonist, soluble tumor necrosis factor receptor II, and IL-10) with enzyme-linked immunosorbent assays. Peripheral blood mononuclear cells (PBMC) from HIV-infected persons and healthy controls (primed with single-stranded HIV-1-derived RNA) were stimulated with LPS, and cytokine production was measured. Finally, HIV-infected patients were immunized with Prevnar 7vPnC±CpG 7909 followed by Pneumo Novum PPV-23. Effects of microbial translocation and inflammation on immunization were analyzed in a predictive regression model. We included 96 HIV-infected individuals, 76 on highly active antiretroviral therapy (HAART), 20 HAART-naive, and 50 healthy controls. Microbial translocation and inflammatory markers were higher among HIV-infected persons than controls. Cytokine levels following LPS stimulation were increased in PBMCs from HAART-naive compared to HAART-treated HIV-infected persons. Further, RNA-priming of PBMCs from controls acted synergistically with LPS to augment cytokine responses. Finally, high serum LPS levels predicted poor vaccine responses among HAART-naive, but not among HAART-treated HIV-infected individuals. CONCLUSIONS/SIGNIFICANCE: LPS acts synergistically with HIV RNA to stimulate innate immune responses in vitro and increasing serum LPS levels seem to predict poor antibody responses after vaccination among HAART-naive HIV-infected persons. Thus, our results suggest that microbial translocation may be associated with innate and adaptive immune dysfunction in untreated HIV infection
The Danish National Prescription Registry.
Abstract Introduction: Individual-level data on all prescription drugs sold in Danish community pharmacies has since 1994 been recorded in the Register of Medicinal Products Statistics of the Danish Medicines Agency. Content: The register subset, termed the Danish National Prescription Registry (DNPR), contains information on dispensed prescriptions, including variables at the level of the drug user, the prescriber, and the pharmacy. Validity and coverage: Reimbursement-driven record keeping, with automated bar-code-based data entry provides data of high quality, including detailed information on the dispensed drug. Conclusion: The possibility of linkage with many other nationwide individual-level data sources renders the DNPR a very powerful pharmacoepidemiological tool