893 research outputs found
Infrared Ellipsometry Analysis of Heritage Photographic Prints
[EN] Focusing on the photographic archive of Julian Carrillo (Mexico), we study and characterize the photographic processes of a set of 13 photographs dated between 1884 and 1925. By using infrared spectroscopic ellipsometry, we classified a selected set of photographs according to its kind of binder. Thus, we recognized for each photograph, the presence of proteins, and therefore, the particular photographic process. Furthermore, we have identified the presence of baryta layer, the use of plasticizer, and the eventual coating utilized to protect the photograph, whose composition was based in natural organic components, mainly shellac, beeswax, or camphorNieto-Villena, A.; Martinez, JR.; Flores-Camacho, JM.; Lastras-Martinez, A.; De La Cruz-Mendoza, JA.; Ortega-Zarzosa, G.; Valcarcel AndrĂ©s, JC.... (2018). Infrared Ellipsometry Analysis of Heritage Photographic Prints. Studies in Conservation. 63(8):466-476. https://doi.org/10.1080/00393630.2018.1476962S466476638Brambilla, L., Riedo, C., Baraldi, C., Nevin, A., Gamberini, M. C., DâAndrea, C., ⊠Toniolo, L. (2011). Characterization of fresh and aged natural ingredients used in historical ointments by molecular spectroscopic techniques: IR, Raman and fluorescence. Analytical and Bioanalytical Chemistry, 401(6), 1827-1837. doi:10.1007/s00216-011-5168-zCasoli, A., & Fornaciari, S. (2014). An analytical study on an early twentieth-century Italian photographs collection by means of microscopic and spectroscopic techniques. Microchemical Journal, 116, 24-30. doi:10.1016/j.microc.2014.04.003Cattaneo, B., Chelazzi, D., Giorgi, R., Serena, T., Merlo, C., & Baglioni, P. (2008). Physico-chemical characterization and conservation issues of photographs dated between 1890 and 1910. Journal of Cultural Heritage, 9(3), 277-284. doi:10.1016/j.culher.2008.01.004Daher, C., Paris, C., Le HĂŽ, A.-S., Bellot-Gurlet, L., & Ăchard, J.-P. (2010). A joint use of Raman and infrared spectroscopies for the identification of natural organic media used in ancient varnishes. Journal of Raman Spectroscopy, 41(11), 1494-1499. doi:10.1002/jrs.2693Edwards, H. G. M., Farwell, D. W., & Daffner, L. (1996). Fourier-transform Raman spectroscopic study of natural waxes and resins. I. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 52(12), 1639-1648. doi:10.1016/0584-8539(96)01730-8Fujiwara, H. (2007). Spectroscopic Ellipsometry. doi:10.1002/9780470060193Hendriks, K., & Ross, L. (1988). Chemical Treatments of Discoloured Photographic Prints: Image Manipulation or Legitimate Restoration? The Journal of Photographic Science, 36(3), 132-132. doi:10.1080/00223638.1988.11736990MallĂ©gol, J., Gardette, J.-L., & Lemaire, J. (2000). Long-term behavior of oil-based varnishes and paints. Photo- and thermooxidation of cured linseed oil. Journal of the American Oil Chemistsâ Society, 77(3), 257-263. doi:10.1007/s11746-000-0042-4Nieto-Villena, A., MartĂnez, J. R., de la Cruz-Mendoza, J. A., ValcĂĄrcel-AndrĂ©s, J. C., Ortega-Zarzosa, G., Solbes-GarcĂa, Ă., & VĂĄzquez-MartĂnez, E. (2018). Atomic force microscopy as a tool for binder identification in ancient photographic processes. Surface and Interface Analysis, 50(4), 496-505. doi:10.1002/sia.6408Ostroff, Eugene. 1966. âRestoration of Photographs by Neutron Activation.â Science 154 (3745): 119â123. http://science.sciencemag.org/content/154/3745/119.Othmer, Kirk, ed. 2005. Encyclopedia of Chemical Technology. Vol. 17, 5th ed. New York: Wiley.Ricci, C., Bloxham, S., & Kazarian, S. G. (2007). ATR-FTIR imaging of albumen photographic prints. Journal of Cultural Heritage, 8(4), 387-395. doi:10.1016/j.culher.2007.07.002Sifontes, Ă. B., Cañizales, E., Toro-Mendoza, J., Ăvila, E., HernĂĄndez, P., Delgado, B. A., ⊠Cruz-Barrios, E. (2015). Obtaining Highly Crystalline Barium Sulphate Nanoparticles via Chemical Precipitation and Quenching in Absence of Polymer Stabilizers. Journal of Nanomaterials, 2015, 1-8. doi:10.1155/2015/510376Stulik, Dusan, Herant Khanjian, Alberto de Tagle, and Alexandra M. Botelho. 2002. âInvestigation of Jean-Louis-Marie-Eugene Durieuâs Toning and Varnishing Experiments: A Non-Destructive Approach.â ICOM Committee for Conservation 13th Triennial Meeting, RĂo de Janeiro, 658â663.Price, Beth A., and Boris Pretzel, eds. 2009. Infrared and Raman Users Group Spectral Database. 2007 ed. Vol. 1 & 2. Philadelphia: IRUG. Accessed June 20, 2014. http://www.irug.org/.Vila, A., & Centeno, S. A. (2013). FTIR, Raman and XRF identification of the image materials in turn of the 20th century pigment-based photographs. Microchemical Journal, 106, 255-262. doi:10.1016/j.microc.2012.07.01
The Sensitivity of HAWC to High-Mass Dark Matter Annihilations
The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view
detector sensitive to gamma rays of 100 GeV to a few hundred TeV. Located in
central Mexico at 19 degrees North latitude and 4100 m above sea level, HAWC
will observe gamma rays and cosmic rays with an array of water Cherenkov
detectors. The full HAWC array is scheduled to be operational in Spring 2015.
In this paper, we study the HAWC sensitivity to the gamma-ray signatures of
high-mass (multi- TeV) dark matter annihilation. The HAWC observatory will be
sensitive to diverse searches for dark matter annihilation, including
annihilation from extended dark matter sources, the diffuse gamma-ray emission
from dark matter annihilation, and gamma-ray emission from non-luminous dark
matter subhalos. Here we consider the HAWC sensitivity to a subset of these
sources, including dwarf galaxies, the M31 galaxy, the Virgo cluster, and the
Galactic center. We simulate the HAWC response to gamma rays from these sources
in several well-motivated dark matter annihilation channels. If no gamma-ray
excess is observed, we show the limits HAWC can place on the dark matter
cross-section from these sources. In particular, in the case of dark matter
annihilation into gauge bosons, HAWC will be able to detect a narrow range of
dark matter masses to cross-sections below thermal. HAWC should also be
sensitive to non-thermal cross-sections for masses up to nearly 1000 TeV. The
constraints placed by HAWC on the dark matter cross-section from known sources
should be competitive with current limits in the mass range where HAWC has
similar sensitivity. HAWC can additionally explore higher dark matter masses
than are currently constrained.Comment: 15 pages, 4 figures, version to be published in PR
VAMOS: a Pathfinder for the HAWC Gamma-Ray Observatory
VAMOS was a prototype detector built in 2011 at an altitude of 4100m a.s.l.
in the state of Puebla, Mexico. The aim of VAMOS was to finalize the design,
construction techniques and data acquisition system of the HAWC observatory.
HAWC is an air-shower array currently under construction at the same site of
VAMOS with the purpose to study the TeV sky. The VAMOS setup included six water
Cherenkov detectors and two different data acquisition systems. It was in
operation between October 2011 and May 2012 with an average live time of 30%.
Besides the scientific verification purposes, the eight months of data were
used to obtain the results presented in this paper: the detector response to
the Forbush decrease of March 2012, and the analysis of possible emission, at
energies above 30 GeV, for long gamma-ray bursts GRB111016B and GRB120328B.Comment: Accepted for pubblication in Astroparticle Physics Journal (20 pages,
10 figures). Corresponding authors: A.Marinelli and D.Zaboro
f(R) theories
Over the past decade, f(R) theories have been extensively studied as one of
the simplest modifications to General Relativity. In this article we review
various applications of f(R) theories to cosmology and gravity - such as
inflation, dark energy, local gravity constraints, cosmological perturbations,
and spherically symmetric solutions in weak and strong gravitational
backgrounds. We present a number of ways to distinguish those theories from
General Relativity observationally and experimentally. We also discuss the
extension to other modified gravity theories such as Brans-Dicke theory and
Gauss-Bonnet gravity, and address models that can satisfy both cosmological and
local gravity constraints.Comment: 156 pages, 14 figures, Invited review article in Living Reviews in
Relativity, Published version, Comments are welcom
Measurement of the t-channel single top quark production cross section
The D0 collaboration reports direct evidence for electroweak production of
single top quarks through the t-channel exchange of a virtual W boson. This is
the first analysis to isolate an individual single top quark production
channel. We select events containing an isolated electron or muon, missing
transverse energy, and two, three or four jets from 2.3 fb^-1 of ppbar
collisions at the Fermilab Tevatron Collider. One or two of the jets are
identified as containing a b hadron. We combine three multivariate techniques
optimized for the t-channel process to measure the t- and s-channel cross
sections simultaneously. We measure cross sections of 3.14 +0.94 -0.80 pb for
the t-channel and 1.05 +-0.81 pb for the s-channel. The measured t-channel
result is found to have a significance of 4.8 standard deviations and is
consistent with the standard model prediction.Comment: 7 pages, 6 figure
Dependence of the production cross section on the transverse momentum of the top quark
We present a measurement of the differential cross section for
events produced in collisions at TeV as a function
of the transverse momentum () of the top quark. The selected events
contain a high- lepton (), four or more jets, and a large imbalance
in , and correspond to 1 fb of integrated luminosity recorded
with the D0 detector. Each event must have at least one candidate for a
jet. Objects in the event are associated through a constrained kinematic fit to
the process. Results
from next-to-leading-order perturbative QCD calculations agree with the
measured differential cross section. Comparisons are also provided to
predictions from Monte Carlo event generators using QCD calculations at
different levels of precision.Comment: 8 pages, 6 figures, 4 tables, updated to reflect the published
versio
Measurement of trilinear gauge boson couplings from WW + WZ to lnu jj events in pp-bar collisions at sqrt{s}=1.96 TeV
We present a direct measurement of trilinear gauge boson couplings at gammaWW
and ZWW vertices in WW and WZ events produced in pp-bar collisions at
sqrt{s}=1.96 TeV. We consider events with one electron or muon, missing
transverse energy, and at least two jets. The data were collected using the D0
detector and correspond to 1.1/fb of integrated luminosity. Considering two
different relations between the couplings at the gammaWW and ZWW vertices, we
measure these couplings at 68% C.L. to be kappa_{gamma}=1.07^{+0.26}_{-0.29},
lambda =0.00^{+0.06}_{-0.06} and g_{1}^{Z}=1.04^{+0.09}_{-0.09} in a scenario
respecting SU(2)_L x U(1)_Y gauge symmetry and kappa =1.04^{+0.11}_{-0.11} and
lambda=0.00^{+0.06}_{-0.06} in an "equal couplings" scenario.Comment: 14 pages, 7 figures, published in Phys. Rev. D, updated to published
versio
Search for dark photons from supersymmetric hidden valleys
We search for a new light gauge boson, a dark photon, with the D0 experiment.
In the model we consider, supersymmetric partners are pair produced and cascade
to lightest neutralinos that can decay into the hidden sector state plus either
a photon or a dark photon. The dark photon decays through its mixing with a
photon into fermion pairs. We therefore investigate a previously unexplored
final state that contains a photon, two spatially close leptons, and large
missing transverse energy. We do not observe any evidence for dark photons and
set a limit on their production.Comment: submitted to PR
Measurement of the W boson mass
We present a measurement of the W boson mass in W -> ev decays using 1 fb^-1
of data collected with the D0 detector during Run II of the Fermilab Tevatron
collider. With a sample of 499830 W -> ev candidate events, we measure M_W =
80.401 +- 0.043 GeV. This is the most precise measurement from a single
experiment.Comment: As published in PR
Search for CP violation in semileptonic Bs decays
We have performed a search for CP violation in a sample of Bs -> Ds mu X
decays corresponding to ~fb of proton-antiproton collisions collected
by the D0 detector in Run~II at the Fermilab Tevatron Collider. New physics in
mixing could contribute a significant CP violating weak phase, which
would be observed as a difference in the decay-time distribution for oscillated states versus that for . A fit
to the decay-time distributions of the candidates yields
the flavor-specific asymmetry , which
excludes CP violation due to new physics within the experimental sensitivity.Comment: published in Phys. Rev.
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