Gravitational waves from inspiralling compact binaries: Energy flux to third post-Newtonian order

The multipolar-post-Minkowskian approach to gravitational radiation is applied to the problem of the generation of waves by the compact binary inspiral. We investigate specifically the third post-Newtonian (3PN) approximation in the total energy flux. The new results are the computation of the mass quadrupole moment of the binary to the 3PN order, and the current quadrupole and mass octupole to the 2PN order. Wave tails and tails of tails in the far zone are included up to the 3.5PN order. The recently derived 3PN equations of binary motion are used to compute the time-derivatives of the moments. We find perfect agreement to the 3.5PN order with perturbation calculations of black holes in the test-mass limit for one body. Technical inputs in our computation include a model of point particles for describing the compact objects, and the Hadamard self-field regularization. Because of a physical incompleteness of the Hadamard regularization at the 3PN order, the energy flux depends on one unknown physical parameter, which is a combination of a parameter \lambda in the equations of motion, and a new parameter \theta coming from the quadrupole moment.Comment: 69 pages, version which includes the correction of an Erratum to be published in Phys. Rev. D (2005

In situ elaboration of a binary Ti–26Nb alloy by selective laser melting of elemental titanium and niobium mixed powders

Ti–Nb alloys are excellent candidates for biomedical applications such as implantology and joint replacement because of their very low elastic modulus, their excellent biocompatibility and their high strength. A low elastic modulus, close to that of the cortical bone minimizes the stress shielding effect that appears subsequent to the insertion of an implant. The objective of this study is to investigate the microstructural and mechanical properties of a Ti–Nb alloy elaborated by selective laser melting on powder bed of a mixture of Ti and Nb elemental powders (26 at.%). The influence of operating parameters on porosity of manufactured samples and on efficacy of dissolving Nb particles in Ti was studied. The results obtained by optical microscopy, SEM analysis and X-ray microtomography show that the laser energy has a significant effect on the compactness and homogeneity of the manufactured parts. Homogeneous and compact samples were obtained for high energy levels. Microstructure of these samples has been further characterized. Their mechanical properties were assessed by ultrasonic measures and the Young's modulus found is close to that of classically elaborated Ti–26Nb ingot

Spectral characteristics of water megamaser galaxies II: ESO 103-G035, TXS 2226-184, and IC 1481

Long-slit optical emission-line spectra of the H2O megamaser galaxies ESO 103-G03, TXS 2226-184, and IC 1481 are evaluated in order to look for characteristics typical for water-megamaser galaxies. We present rotation curves, line ratios, electron densities, temperatures, and Hbeta luminosities. The successful line-profile decompositions rest on d-Lorentzians with an additional parameter d to adjust the wings, rather than Gaussians or Lorentzians as basic functions. No significant velocity gradient is found along the major axis in the innermost 2 kpc of TXS 2226-184. IC 1481 reveals a spectrum suggestive of a vigorous starburst in the central kiloparsec 10^8 years ago. None of the three galaxies shows any hints for outflows nor special features which could give clues to the presence of H2O megamaser emission. The galaxies are of normal Seyfert-2 (ESO 103-G035) or LINER (TXS 2226-184, IC 1481) type.Comment: 12 pages, 14 figures, accepted for publication in A&A, corrected typo

Synthesis and characterization of Ti-27.5Nb alloy made by CLAD® additive manufacturing process for biomedical applications

Biocompatible beta-titanium alloys such as Ti-27.5(at.%)Nb are good candidates for implantology and arthroplasty applications as their particular mechanical properties, including low Young’s modulus, could significantly reduce the stress-shielding phenomenon usually occurring after surgery. The CLAD® process is a powder blown additive manufacturing process that allows the manufacture of patient specific (i.e. custom) implants. Thus, the use of Ti-27.5(at.%)Nb alloy formed by CLAD® process for biomedical applications as a mean to increase cytocompatibility and mechanical biocompatibility was investigated in this study. The microstructural properties of the CLAD-deposited alloy were studied with optical microscopy and electron back-scattered diffraction (EBSD) analysis. The conservation of the mechanical properties of the Ti-27.5Nb material after the transformation steps (ingot-powder atomisation-CLAD) were verified with tensile tests and appear to remain close to those of reference material. Cytocompatibility of the material and subsequent cell viability tests showed that no cytotoxic elements are released in the medium and that viable cells proliferated well

Stellar population analysis on local infrared-selected galaxies

To study the stellar population of local infrared galaxies, which contain star-forming galaxies, composite galaxies, LINERs, and Seyfert 2s. We also want to find whether infrared luminosity and spectral class have any effects on their stellar populations. The sample galaxies are selected from the main galaxy sample of SDSS-DR4 and then cross-correlated with the IRAS-PSCz catalog. We fit our spectra (stellar absorption lines and continua) using the spectral synthesis code STARLIGHT on the base of the templates of Simple Stellar Population and the spectra of star clusters.Among the 4 spectral classes, LINERs present the oldest stellar populations, and the other 3 sub-samples all present substantial young and intermediate age populations and very few old populations. The importance of young populations decreases from star-forming, composite, Seyfert 2 to LINER. As to different infrared luminosity bins, ULIGs & LIGs (log($L_{IR}/L_{\odot})\geq$11) present younger populations than starbursts and normal galaxies. However, the dominant contributors to mass are old populations in all sample galaxies. The fittings by using the spectra of star clusters with different ages and metallicities as templates also give consistent results. The dominated populations in star-forming and composite galaxies are those with metallicity $Z=0.2Z_\odot$, while LINERs and Seyfert 2s are more metal-rich. The normal galaxies are more metal-rich than the ULIGs & LIGs and starbursts for the star-forming galaxies within different infrared luminosity bins. Additionally, we also compare some synthesis results with other parameters obtained from the MPA/JHU catalog.Comment: 13 pages, 11 figures, accepted for publication by A&

Gravitational-Wave Inspiral of Compact Binary Systems to 7/2 Post-Newtonian Order

The inspiral of compact binaries, driven by gravitational-radiation reaction, is investigated through 7/2 post-Newtonian (3.5PN) order beyond the quadrupole radiation. We outline the derivation of the 3.5PN-accurate binary's center-of-mass energy and emitted gravitational flux. The analysis consistently includes the relativistic effects in the binary's equations of motion and multipole moments, as well as the contributions of tails, and tails of tails, in the wave zone. However the result is not fully determined because of some physical incompleteness, present at the 3PN order, of the model of point-particle and the associated Hadamard-type self-field regularization. The orbital phase, whose prior knowledge is crucial for searching and analyzing the inspiral signal, is computed from the standard energy balance argument.Comment: 12 pages, version which includes the correction of an Erratum to be published in Phys. Rev. D (2005

Probing the near infrared stellar population of Seyfert galaxies

We employ IRTF SpeX NIR (0.8-2.4 microns) spectra to investigate the stellar population (SP), active galactic nuclei (AGN) featureless continuum (FC) and hot dust properties in 9 Sy 1 and 15 Sy 2 galaxies. Both the starlight code and the hot dust as an additional base element were used for the first time in this spectral range. We found evidence of correlation among the equivalent widths (W) Si I 1.59 microns x Mg I 1.58 microns, equally for both kinds of activity. Part of the W{Na I 2.21 microns} and W {CO 2.3 microns} strengths may be related to galaxy inclination. Our synthesis shows significant differences between Sy 1 and Sy 2 galaxies: the hot dust component is required to fit the K-band spectra of ~90% of the Sy 1 galaxies, and only of ~25% of the Sy 2; about 50 % of the Sy 2 galaxies require a $FC$ component contribution >20%, while this fraction increases to 60% in the Sy 1; also, in about 50 % of the Sy2, the combined FC and young components contribute with more than 20%, while this occurs in 90% of the Sy1, suggesting recent star formation in the central region. The central few hundred parsecs of our galaxy sample contain a substantial fraction of intermediate-age SPs with a mean metallicity near solar. Our SP synthesis confirms that the 1.1 micron CN band can be used as a tracer of intermediate-age SPs. The simultaneous fitting of SP, FC and hot dust components increased in ~150% the number of AGNs with hot dust detected and the mass estimated. The NIR emerges as an excellent window to study the stellar population of Sy 1 galaxies, as opposed to the usually heavily attenuated optical range. Our approach opens a new way to investigate and quantify the individual contribution of the three most important NIR continuum components observed in AGNs.Comment: The paper contains 14 figures and 5 tables. Accepted for publication in MNRA

Seyfert galaxies in UZC-Compact Groups

We present results concerning the occurrence of Seyfert galaxies in a new automatically selected sample of nearby Compact Groups of galaxies (UZC-CGs). Seventeen Seyferts are found, constituting ~3% of the UZC-CG galaxy population. CGs hosting and non-hosting a Seyfert member exhibit no significant differences, except that a relevant number of Sy2 is found in unusual CGs, all presenting large velocity dispersion (sigma > 400 km/s), many neighbours and a high number of ellipticals. We also find that the fraction of Seyferts in CGs is 3 times as large as that among UZC-single-galaxies, and results from an excess of Sy2s. CG-Seyferts are not more likely than other CG galaxies to present major interaction patterns, nor to display a bar. Our results indirectly support the minor-merging fueling mechanism.Comment: 12 pages, 5 figures, A&A, accepte

Synthesis and biological evaluation of novel flexible nucleoside analogues that inhibit flavivirus replication in vitro

Flaviviruses, such as Dengue (DENV) and Zika (ZIKV) viruses, represent a severe health burden. There are currently no FDA-approved treatments, and vaccines against most flaviviruses are still lacking. We have developed several flexible analogues (“fleximers”) of the FDA-approved nucleoside Acyclovir that exhibit activity against various RNA viruses, demonstrating their broad-spectrum potential. The current study reports activity against DENV and YFV, particularly for compound 1. Studies to elucidate the mechanism of action suggest the flex-analogue triphosphates, especially 1-TP, inhibit DENV and ZIKV methyltransferases. The results of these studies are reported herein