A multi-method approach to radial-velocity measurement for single-object spectra

The derivation of radial velocities from large numbers of spectra that typically result from survey work, requires automation. However, except for the classical cases of slowly rotating late-type spectra, existing methods of measuring Doppler shifts require fine-tuning to avoid a loss of accuracy due to the idiosyncrasies of individual spectra. The radial velocity spectrometer (RVS) on the Gaia mission, which will start operating very soon, prompted a new attempt at creating a measurement pipeline to handle a wide variety of spectral types. The present paper describes the theoretical background on which this software is based. However, apart from the assumption that only synthetic templates are used, we do not rely on any of the characteristics of this instrument, so our results should be relevant for most telescope-detector combinations. We propose an approach based on the simultaneous use of several alternative measurement methods, each having its own merits and drawbacks, and conveying the spectral information in a different way, leading to different values for the measurement. A comparison or a combination of the various results either leads to a "best estimate" or indicates to the user that the observed spectrum is problematic and should be analysed manually. We selected three methods and analysed the relationships and differences between them from a unified point of view; with each method an appropriate estimator for the individual random error is chosen. We also develop a procedure for tackling the problem of template mismatch in a systematic way. Furthermore, we propose several tests for studying and comparing the performance of the various methods as a function of the atmospheric parameters of the observed objects. Finally, we describe a procedure for obtaining a knowledge-based combination of the various Doppler-shift measurements.Comment: 16 pages, 4 figure

Nods, Nalps and Naip: intracellular regulators of bacterial-induced inflammation

The innate immune system is the most ancestral and ubiquitous system of defence against microbial infection. The microbial sensing proteins involved in innate immunity recognize conserved and often structural components of microorganisms. One class of these pattern-recognition molecules, the Toll-like receptors (TLRs), are involved in detection of microbes in the extracellular compartment whereas a newly discovered family of proteins, the NBS-LRR proteins (for nucleotide-binding site and leucine-rich repeat), are involved in intracellular recognition of microbes and their products. NBS-LRR proteins are characterized by three structural domains: a C-terminal leucine-rich repeat (LRR) domain able to sense a microbial motif, an intermediary nucleotide binding site (NBS) essential for the oligomerization of the molecule that is necessary for the signal transduction induced by different N-terminal effector motifs, such as a pyrin domain (PYD), a caspase-activating and recruitment domain (CARD) or a baculovirus inhibitor of apoptosis protein repeat (BIR) domain. Two of these family members, Nod1 and Nod2, play a role in the regulation of pro-inflammatory pathways through NF-κB induced by bacterial ligands. Recently, it was shown that Nod2 recognizes a specific peptidoglycan motif from bacteria, muramyl dipeptide (MDP). A surprising number of human genetic disorders have been linked to NBS-LRR proteins. For example, mutations in Nod2, which render the molecule insensitive to MDP and unable to induce NF-κB activation when stimulated, are associated with susceptibility to a chronic intestinal inflammatory disorder, Crohn's disease. Conversely, mutations in the NBS region of Nod2 induce a constitutive activation of NF-κB and are responsible for Blau syndrome, another auto-inflammatory disease. Nalp3, which is an NBS-LRR protein with an N-terminal Pyrin domain, is also implicated in rare auto-inflammatory disorders. In conclusion, NBS-LRR molecules appear as a new family of intracellular receptors of innate immunity able to detect specific bacterial compounds and induce inflammatory response; the dysregulation of these processes due to mutations in the genes encoding these proteins is involved in numerous auto-inflammatory disorders.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75732/1/j.1462-5822.2003.00304.x.pd

Multi--Pressure Polytropes as Models for the Structure and Stability of Molecular Clouds. I. Theory

Molecular clouds are supported by thermal pressure, magnetic pressure, and turbulent pressure. Each of these can be modeled with a polytropic equation of state, so that overall the total pressure is the sum of the individual components. We model the turbulent pressure as being due to a superposition of Alfven waves. The theory of polytropes is generalized to allow for the flow of entropy in response to a perturbation, as expected for the entropy associated with wave pressure. The equation of state of molecular clouds is "soft", so that the properties of the clouds are generally governed by the conditions at the surface. In general, the polytropes are not isentropic, and this permits large density and pressure drops to occur between the center and the edge of the polytropes, as is observed.Comment: Submitted to ApJ with 10 figure

CN and HCN in Dense Interstellar Clouds

We present a theoretical investigation of CN and HCN molecule formation in dense interstellar clouds. We study the gas-phase CN and HCN production efficiencies from the outer photon-dominated regions (PDRs) into the opaque cosmic-ray dominated cores. We calculate the equilibrium densities of CN and HCN, and of the associated species C+, C, and CO, as functions of the far-ultraviolet (FUV) optical depth. We consider isothermal gas at 50 K, with hydrogen particle densities from 10^2 to 10^6 cm^-3. We study clouds that are exposed to FUV fields with intensities 20 to 2*10^5 times the mean interstellar FUV intensity. We assume cosmic-ray H2 ionization rates ranging from 5*10^-17 s^-1, to an enhanced value of 5*10^-16 s^-1. We also examine the sensitivity of the density profiles to the gas-phase sulfur abundance.Comment: Accepted for publication in ApJ, 33 pages, 8 figure

Experimental investigation on camera calibration for 3D photogrammetric scanning of micro-features for micrometric resolution

[EN] Recently, it has been demonstrated that photogrammetry can be used for the measurement of small objects with micro-features, with good results and lower cost, compared to other established techniques such as interferometry, conoscopic holography, and 3D microscopy. Calibration is a critical step in photogrammetry and the classical pinhole camera model has been tested for magnifications lower than 2×. At higher magnification levels, because of the reduction of the depth of field (DOF), images can lead to calibration data with low reprojection errors. However, this could lead to bad results in the 3D reconstruction. With the aim of verifying the possibility of applying the camera model to magnifications higher than 2×, experiments have been conducted using reflex cameras with 60 mm macro lens, equipped with the combination of three extension tubes, corresponding to 2.06, 2.23, and 2.4 magnification levels, respectively. Experiments consisted of repeating calibration five times for each configuration and testing each calibration model, measuring two artifacts with different geometrical complexity. The calibration results have shown good repeatability of a subset of the internal calibration parameters. Despite the differences in the calibration reprojection error (RE), the quality of the photogrammetric 3D models retrieved was stable and satisfying. The experiment demonstrated the possibilities of the photogrammetric system presented, equipped to very high magnification levels, to retrieve accurate 3D reconstruction of micro-features with uncertainties of few micrometers, comparable with industry s expensive state-of-the-art technologies.Percoco, G.; Guerra, MG.; Sánchez Salmerón, AJ.; Galantucci, LM. (2017). Experimental investigation on camera calibration for 3D photogrammetric scanning of micro-features for micrometric resolution. 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Radio Recombination Lines in Galactic HII Regions

We report radio recombination line (RRL) and continuum observations of a sample of 106 Galactic HII regions made with the NRAO 140 Foot radio telescope in Green Bank, WV. We believe this to be the most sensitive RRL survey ever made for a sample this large. Most of our source integration times range between 6 and 90 hours which yield typical r.m.s. noise levels of 1.0--3.5 milliKelvins. Our data result from two different experiments performed, calibrated, and analyzed in similar ways. A CII survey was made at 3.5 cm wavelength to obtain accurate measurements of carbon radio recombination lines. When combined with atomic (CI) and molecular (CO) data, these measurements will constrain the composition, structure, kinematics, and physical properties of the photodissociation regions that lie on the edges of HII regions. A second survey was made at 3.5 cm wavelength to determine the abundance of 3He in the interstellar medium of the Milky Way. Together with measurements of the 3He+ hyperfine line we get high precision RRL parameters for H, 4He, and C. Here we discuss significant improvements in these data, with both longer integrations and newly observed sources.Comment: LaTeX, 50 pages with 11 figures. Accepted for publication in The Astrophysical Journal Supplement Serie

Cerebrospinal fluid HIV-1 escape in patients with neurocognitive symptoms: pooled data from a neuro-HIV platform and the NAMACO study.

BACKGROUND Despite modern antiretroviral therapy, HIV-1 RNA escape into the cerebrospinal fluid (CSF) may occur. We examined the prevalence of and factors associated with CSF HIV-1 escape among people living with HIV (PLWH) in Switzerland. SETTING The Neurocognitive Assessment in the Metabolic and Aging Cohort (NAMACO) study is an ongoing, prospective, longitudinal, multicenter study within the Swiss HIV Cohort Study. The neuro-HIV platform is a multi-disciplinary, single-day outpatient consultation at Lausanne University Hospital. METHODS We pooled data from the NAMACO study and the neuro-HIV platform participants who underwent lumbar puncture (LP) between 2011 and 2019. Both patient groups had neurocognitive symptoms. CSF HIV-1 escape was defined as the presence of quantifiable CSF HIV-1 RNA when plasma HIV-1 RNA was suppressed or CSF HIV-1 RNA greater than plasma HIV-1 RNA when the latter was detectable. RESULTS Of 1166 PLWH assessed, 288 underwent LP. CSF HIV-1 escape was observed in 25 PLWH (8.7%) of whom 19 (76%) had supressed plasma HIV-1 RNA. Characteristics of PLWH were comparable whether they had CSF HIV-1 escape or not, including comorbidities, time since HIV diagnosis (15 vs 16 years, p=0.9), median CD4 nadir (158.5/mm3 vs 171/mm3, p=0.6), antiretroviral CSF-Penetration-Effectiveness score (7 vs 7 points, p=0.8), neurocognitive diagnosis based on Frascati criteria and radiological findings. CONCLUSIONS In this large pooled sample of PLWH with neurocognitive symptoms, CSF HIV-1 escape occurred in 8.7% of PLWH. PLWH with CSF HIV-1 escape presented no distinctive clinical or paraclinical characteristics. We conclude that LP is unavoidable in confirming CSF HIV-1 escape

GYES, a multifibre spectrograph for the CFHT

We have chosen the name of GYES, one of the mythological giants with one hundred arms, offspring of Gaia and Uranus, for our instrument study of a multifibre spectrograph for the prime focus of the Canada-France-Hawaii Telescope. Such an instrument could provide an excellent ground-based complement for the Gaia mission and a northern complement to the HERMES project on the AAT. The CFHT is well known for providing a stable prime focus environment, with a large field of view, which has hosted several imaging instruments, but has never hosted a multifibre spectrograph. Building upon the experience gained at GEPI with FLAMES-Giraffe and X-Shooter, we are investigating the feasibility of a high multiplex spectrograph (about 500 fibres) over a field of view 1 degree in diameter. We are investigating an instrument with resolution in the range 15000 to 30000, which should provide accurate chemical abundances for stars down to 16th magnitude and radial velocities, accurate to 1 km/s for fainter stars. The study is led by GEPI-Observatoire de Paris with a contribution from Oxford for the study of the positioner. The financing for the study comes from INSU CSAA and Observatoire de Paris. The conceptual study will be delivered to CFHT for review by October 1st 2010.Comment: Contributed talk at the Gaia ELSA conference 2010, S\`evres 7-11 June 2010, to be published on the EAS Series, Editors: C. Turon, F. Arenou & F. Meynadie

Very Cold Gas and Dark Matter

We have recently proposed a new candidate for baryonic dark matter: very cold molecular gas, in near-isothermal equilibrium with the cosmic background radiation at 2.73 K. The cold gas, of quasi-primordial abundances, is condensed in a fractal structure, resembling the hierarchical structure of the detected interstellar medium. We present some perspectives of detecting this very cold gas, either directly or indirectly. The H$_2$ molecule has an "ultrafine" structure, due to the interaction between the rotation-induced magnetic moment and the nuclear spins. But the lines fall in the km domain, and are very weak. The best opportunity might be the UV absorption of H$_2$ in front of quasars. The unexpected cold dust component, revealed by the COBE/FIRAS submillimetric results, could also be due to this very cold H$_2$ gas, through collision-induced radiation, or solid H$_2$ grains or snowflakes. The $\gamma$-ray distribution, much more radially extended than the supernovae at the origin of cosmic rays acceleration, also points towards and extended gas distribution.Comment: 16 pages, Latex pages, crckapb macro, 3 postscript figures, uuencoded compressed tar file. To be published in the proceeedings of the "Dust-Morphology" conference, Johannesburg, 22-26 January, 1996, D. Block (ed.), (Kluwer Dordrecht