685 research outputs found
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-ÎșB 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-ÎșB 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-ÎșB 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 2Ă. 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 2Ă, 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.; SĂĄnchez SalmerĂłn, AJ.; Galantucci, LM. (2017). Experimental investigation on camera calibration for 3D photogrammetric scanning of micro-features for micrometric resolution. The International Journal of Advanced Manufacturing Technology. 91(9-12):2935-2947. https://doi.org/10.1007/s00170-016-9949-6S29352947919-12Uhlmann E, Mullany B, Biermann D, Rajurkar KP, Hausotte T, Brinksmeier E (2016) Process chains for high-precision components with micro-scale features. CIRP Ann - Manuf Technol 65:549â572. doi: 10.1016/j.cirp.2016.05.001Savio E, De Chiffre L, Schmitt R (2007) Metrology of freeform shaped parts. CIRP Ann - Manuf Technol 56:810â835. doi: 10.1016/j.cirp.2007.10.008RodrĂguez-martĂn M, LagĂŒela S, GonzĂĄlez-aguilera D, RodrĂguez-gonzĂĄlvez P (2015) Optics & Laser Technology Procedure for quality inspection of welds based on macro-photogrammetric three-dimensional reconstruction;73:54â62Xu Z, Toncich D, Stefani S (1999) Vision-based measurement of three-dimensional geometric workpiece properties. Int J Adv Manuf Technol 15:322â331. doi: 10.1007/s001700050074Galantucci LM, Lavecchia F, Percoco G (2013) Multistack close range photogrammetry for low cost submillimeter metrology. J Comput Inf Sci Eng 13:44501. doi: 10.1115/1.4024973MatĂ© GonzĂĄlez, M.T., Yravedra, J., GonzĂĄlez-Aguilera, D., Palomeque-GonzĂĄlez, J.F., DomĂnguez-Rodrigo, M. Micro-photogrammetric characterization of cut marks on bones (2015) Journal of Archaeological Science, 62, pp. 128-142. doi: 10.1016/j.jas.2015.08.006Brown DC (1971) Close-range camera calibration. Photogramm Eng 37:855â866 doi:10.1.1.14.6358Tang R, Fritsch D (2013) Correlation analysis of camera self-calibration in close range photogrammetry. Photogramm Rec 28:86â95. doi: 10.1111/phor.12009Agisoft LLC (2011) Agisoft PhotoScan User Manual :37.Jcgm JCFGIM (2008) Evaluation of measurement dataâguide to the expression of uncertainty in measurement- annex B "general metrological terms"- B.2.14. Int Organ Stand Geneva ISBN 50:134. doi: 10.1373/clinchem.2003.030528Yanagi, H., Chikatsu, H. Performance evaluation of macro lens in digital close range photogrammetry (2009) Proceedings of SPIE - The International Society for Optical Engineering, 7447, art. no. 74470J, doi: 10.1117/12.825817Galantucci LM, Pesce M, Lavecchia F (2015) A stereo photogrammetry scanning methodology, for precise and accurate 3D digitization of small parts with sub-millimeter sized features. CIRP Ann - Manuf Technol 64:507â510. doi: 10.1016/j.cirp.2015.04.016Galantucci LM, Pesce M, Lavecchia F (2015) A powerful scanning methodology for 3D measurements of small parts with complex surfaces and sub millimeter-sized features, based on close range photogrammetry. Precis Eng. doi: 10.1016/j.precisioneng.2015.07.010Percoco G, SĂĄnchez SalmerĂłn AJ (2015) Photogrammetric measurement of 3D freeform millimetre-sized objects with micro features: an experimental validation of the close-range camera calibration model for narrow angles of view. Meas Sci Technol 26:95203. doi: 10.1088/0957-0233/26/9/095203Gallo A, Muzzupappa M, Bruno F (2014) 3D reconstruction of small sized objects from a sequence of multi-focused images. J Cult Herit 15:173â182. doi: 10.1016/j.culher.2013.04.009Stamatopoulos C, Fraser CS, Cronk S (2010) On the self-calibration of long focal length lenses. Int Arch Photogramm Remote Sens Spat Inf Sci Newcastle upon Tyne, UK 2010 XXXVIII:560â564Atkinson KB (1996) Close range photogrammetry and machine vision. Whittles PublishingLuhmann T, Fraser C, Maas HG (2016) Sensor modelling and camera calibration for close-range photogrammetry. ISPRS J Photogramm Remote Sens 115:37â46. doi: 10.1016/j.isprsjprs.2015.10.006Tsai RY (1986) An efficient and accurate camera calibration technique for 3D machine vision. Proc IEEE Conf Comput Vis Pattern Recognition 1986Ricolfe-Viala C, Sanchez-Salmeron A-J (2011) Camera calibration under optimal conditions. Opt Express 19:10769â10775. doi: 10.1364/OE.19.010769Wang L, Wang W, Shen C, Duan F (2016) A convex relaxation optimization algorithm for multi-camera calibration with 1D objects. NeurocomputingRicolfe-Viala C, Sanchez-Salmeron A. Lens distortion models evaluation. Appl Opt 2010;49:5914â5928.Percoco G, Lavecchia F, SalmerĂłn AJS (2015) Preliminary study on the 3D digitization of millimeter scale products by means of photogrammetry. Procedia CIRP 33:257â262. doi: 10.1016/j.procir.2015.06.046Bradski G (2000) The OpenCV Library. Dr Dobbâs J Softw ToolsRicolfe-Viala C, Sanchez-Salmeron A-J (2011) Optimal conditions for camera calibration using a planar template. 2011 18th IEEE. Int Conf Image Process, IEEE 2011:853â856. doi: 10.1109/ICIP.2011.6116691Lowe DG (1999) Object recognition from local scale-invariant features. Proc Seventh IEEE Int Conf Comput Vis 2:1150â1157. doi: 10.1109/ICCV.1999.790410Triggs B, Mclauchlan P, Hartley R, Fitzgibbon A, Triggs B, Mclauchlan P, et al. (2010) Bundle adjustmentâa modern synthesis to cite this version: bundle adjustmentâa modern synthesisCignoni P, Callieri M, Corsini M, Dellepiane M, Ganovelli F, Ranzuglia G (2008) Meshlab: an open-source mesh processing tool. Eurographics Ital Chapter Conf 2008:129â136Besl P, McKay N (1992) A method for registration of 3-D shapes. IEEE Trans Pattern Anal Mach Intell 14:239â256. doi: 10.1109/34.12179
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 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 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 gas, through collision-induced radiation, or
solid H grains or snowflakes. The -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
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