The expected performance of stellar parametrization with Gaia spectrophotometry

Gaia will obtain astrometry and spectrophotometry for essentially all sources in the sky down to a broad band magnitude limit of G=20, an expected yield of 10^9 stars. Its main scientific objective is to reveal the formation and evolution of our Galaxy through chemo-dynamical analysis. In addition to inferring positions, parallaxes and proper motions from the astrometry, we must also infer the astrophysical parameters of the stars from the spectrophotometry, the BP/RP spectrum. Here we investigate the performance of three different algorithms (SVM, ILIUM, Aeneas) for estimating the effective temperature, line-of-sight interstellar extinction, metallicity and surface gravity of A-M stars over a wide range of these parameters and over the full magnitude range Gaia will observe (G=6-20mag). One of the algorithms, Aeneas, infers the posterior probability density function over all parameters, and can optionally take into account the parallax and the Hertzsprung-Russell diagram to improve the estimates. For all algorithms the accuracy of estimation depends on G and on the value of the parameters themselves, so a broad summary of performance is only approximate. For stars at G=15 with less than two magnitudes extinction, we expect to be able to estimate Teff to within 1%, logg to 0.1-0.2dex, and [Fe/H] (for FGKM stars) to 0.1-0.2dex, just using the BP/RP spectrum (mean absolute error statistics are quoted). Performance degrades at larger extinctions, but not always by a large amount. Extinction can be estimated to an accuracy of 0.05-0.2mag for stars across the full parameter range with a priori unknown extinction between 0 and 10mag. Performance degrades at fainter magnitudes, but even at G=19 we can estimate logg to better than 0.2dex for all spectral types, and [Fe/H] to within 0.35dex for FGKM stars, for extinctions below 1mag

Carbon footprint of geopolymeric mortar: Study of the contribution of the alkaline activating solution and assessment of an alternative route

[EN] CO2 emissions associated with geopolymeric mortar prepared using spent fluid catalytic cracking catalyst (FCC) were compared to those calculated for plain ordinary Portland cement (OPC) mortar. Commercial waterglass used for preparing the alkaline activating solution for geopolymeric mortar was the main contributing component related to CO2 emission. An alternative route for formulating alkaline activating solution in the preparation of the geopolymeric binder was proposed: refluxing of rice husk ash (RHA) in NaOH solution. Geopolymeric mortar using rice hull ash-derived waterglass led to reduced CO2 emission by 63% compared to the OPC mortar. The new alternative route led to a 50% reduction in CO2 emission compared to geopolymer prepared with commercial waterglass. Replacement of commercial waterglass by rice hull ash- derived waterglass in the preparation of the geopolymer did not cause a significant decrease in the mechanical strength of the mortar. CO2 intensity performance indicators (Ci) for geopolymeric mortars were lower than that found for OPC mortar, indicating that the new route for activating solution led to the lowest C-i valueThe authors are grateful to the Spanish Ministry of Economy and Competitiveness (Project GEOCEDEM BIA 2011-26947), and to Generalitat Valenciana (Project 3018/2009) and 'Centro de Cooperacion al Desarrollo' of the Universitat Politecnica de Valencia (ADSIDEO COOPERACIO, Project COMBURES) for supporting this study, and to DACSA S. A. for supplying RHA samples.Mellado Romero, AM.; Catalan, C.; Bouzón, N.; Borrachero Rosado, MV.; Monzó Balbuena, JM.; Paya Bernabeu, JJ. (2014). Carbon footprint of geopolymeric mortar: Study of the contribution of the alkaline activating solution and assessment of an alternative route. RSC Advances. 4(45):23846-23852. doi:10.1039/C4RA03375BS2384623852445Phair, J. W. (2006). Green chemistry for sustainable cement production and use. Green Chemistry, 8(9), 763. doi:10.1039/b603997aParvulescu, A., Rossi, M., Pina, C. D., Ciriminna, R., & Pagliaro, M. (2011). Investigation of glycerol polymerization in the clinker grinding process. Green Chem., 13(1), 143-148. doi:10.1039/c0gc00107dMymrin, V., de Araújo Ponte, H., Ferreira Lopes, O., & Vazquez Vaamonde, A. (2003). Environment-friendly method of high alkaline bauxite’s Red Mud and Ferrous Slag utilization as an example of green chemistry. Green Chem., 5(3), 357-360. doi:10.1039/b300495nFernández Bertos, M., Li, X., Simons, S. J. R., Hills, C. D., & Carey, P. J. (2004). Investigation of accelerated carbonation for the stabilisation of MSW incinerator ashes and the sequestration of CO2. Green Chem., 6(8), 428-436. doi:10.1039/b401872aJ. L. Provis and J. S. J.van Deventer, Geopolymers. Structure, processing, properties and industrial applications, Woodhead Publishing Limited and CRC Press LLC, UK, 2009F. Pacheco-Torgal and S.Jalali, Eco-efficient Construction and Building Materials, Springer, London, 2011Pacheco-Torgal, F., Castro-Gomes, J., & Jalali, S. (2008). Alkali-activated binders: A review. Construction and Building Materials, 22(7), 1305-1314. doi:10.1016/j.conbuildmat.2007.10.015Pacheco-Torgal, F., Castro-Gomes, J., & Jalali, S. (2008). Alkali-activated binders: A review. Part 2. About materials and binders manufacture. Construction and Building Materials, 22(7), 1315-1322. doi:10.1016/j.conbuildmat.2007.03.019Komnitsas, K., & Zaharaki, D. (2007). Geopolymerisation: A review and prospects for the minerals industry. Minerals Engineering, 20(14), 1261-1277. doi:10.1016/j.mineng.2007.07.011Duxson, P., Fernández-Jiménez, A., Provis, J. L., Lukey, G. C., Palomo, A., & van Deventer, J. S. J. (2006). Geopolymer technology: the current state of the art. Journal of Materials Science, 42(9), 2917-2933. doi:10.1007/s10853-006-0637-zTashima, M. M., Akasaki, J. L., Castaldelli, V. N., Soriano, L., Monzó, J., Payá, J., & Borrachero, M. V. (2012). New geopolymeric binder based on fluid catalytic cracking catalyst residue (FCC). Materials Letters, 80, 50-52. doi:10.1016/j.matlet.2012.04.051Rodríguez, E. D., Bernal, S. A., Provis, J. L., Gehman, J. D., Monzó, J. M., Payá, J., & Borrachero, M. V. (2013). Geopolymers based on spent catalyst residue from a fluid catalytic cracking (FCC) process. Fuel, 109, 493-502. doi:10.1016/j.fuel.2013.02.053Tashima, M. M., Soriano, L., Monzó, J., Borrachero, M. V., & Payá, J. (2013). Novel geopolymeric material cured at room temperature. Advances in Applied Ceramics, 112(4), 179-183. doi:10.1179/1743676112y.0000000056Tashima, M. M., Akasaki, J. L., Melges, J. L. P., Soriano, L., Monzó, J., Payá, J., & Borrachero, M. V. (2013). Alkali activated materials based on fluid catalytic cracking catalyst residue (FCC): Influence of SiO2/Na2O and H2O/FCC ratio on mechanical strength and microstructure. Fuel, 108, 833-839. doi:10.1016/j.fuel.2013.02.052Duxson, P., Provis, J. L., Lukey, G. C., & van Deventer, J. S. J. (2007). The role of inorganic polymer technology in the development of ‘green concrete’. Cement and Concrete Research, 37(12), 1590-1597. doi:10.1016/j.cemconres.2007.08.018Habert, G., d’ Espinose de Lacaillerie, J. B., & Roussel, N. (2011). An environmental evaluation of geopolymer based concrete production: reviewing current research trends. Journal of Cleaner Production, 19(11), 1229-1238. doi:10.1016/j.jclepro.2011.03.012Turner, L. K., & Collins, F. G. (2013). Carbon dioxide equivalent (CO2-e) emissions: A comparison between geopolymer and OPC cement concrete. Construction and Building Materials, 43, 125-130. doi:10.1016/j.conbuildmat.2013.01.023M. Weil , K.Dombroswski and A.Buchwald, in Geopolymers. Structure, processing, properties and industrial applications, ed. J. L. Provis and J. S. J. van Deventer, Woodhead Publishing Limited and CRC Press LLC, UK, 2009, pp. 194–210Salas, A., Delvasto, S., de Gutierrez, R. M., & Lange, D. (2009). Comparison of two processes for treating rice husk ash for use in high performance concrete. Cement and Concrete Research, 39(9), 773-778. doi:10.1016/j.cemconres.2009.05.006Payá, J., Monzó, J., Borrachero, M. ., Mellado, A., & Ordoñez, L. . (2001). Determination of amorphous silica in rice husk ash by a rapid analytical method. Cement and Concrete Research, 31(2), 227-231. doi:10.1016/s0008-8846(00)00466-xJ. Bejarano , C.Garzón, R.Mejía de Gutiérrez, S.Delvasto and M.Gordillo, in II Simposio Aprovechamiento de residuos agro-industriales como fuente sostenible de materiales de construcción, Valencia, Spain, 2010, pp. 409–418Bouzón, N., Payá, J., Borrachero, M. V., Soriano, L., Tashima, M. M., & Monzó, J. (2014). Refluxed rice husk ash/NaOH suspension for preparing alkali activated binders. Materials Letters, 115, 72-74. doi:10.1016/j.matlet.2013.10.001IPCC , Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories, Greenhouse Gas Inventory Reference Manual, Workbook, 1997, vol. 2V. Årskog , S.Fossdal and O. E.Gjørv, in Proceedings of the International Workshop on Sustainable Development and Concrete Technology, Beijing, China, 2004, pp. 193–200Peris Mora, E. (2007). Life cycle, sustainability and the transcendent quality of building materials. Building and Environment, 42(3), 1329-1334. doi:10.1016/j.buildenv.2005.11.004Damineli, B. L., Kemeid, F. M., Aguiar, P. S., & John, V. M. (2010). Measuring the eco-efficiency of cement use. Cement and Concrete Composites, 32(8), 555-562. doi:10.1016/j.cemconcomp.2010.07.009J. Davidovits , in Geopolymer, Green Chemistry and Sustainable Development Solutions World Congress Proc., 2005, pp. 9–15McLellan, B. C., Williams, R. P., Lay, J., van Riessen, A., & Corder, G. D. (2011). Costs and carbon emissions for geopolymer pastes in comparison to ordinary portland cement. Journal of Cleaner Production, 19(9-10), 1080-1090. doi:10.1016/j.jclepro.2011.02.010IDAE Instituto para la Diversificación y Ahorro de la Energía, http://www.idae.es/index.php, Ministerio de Industria, Energía y Turismo, Secretaría de Estado de Energía, Madrid, EspañaPAS 2050 , Specification for the assessment of the life cycle greenhouse gas emissions of goods and services, British Standards Institution, UK, 2011Yang, K.-H., Song, J.-K., & Song, K.-I. (2013). Assessment of CO2 reduction of alkali-activated concrete. Journal of Cleaner Production, 39, 265-272. doi:10.1016/j.jclepro.2012.08.00

The expected performance of stellar parametrization with Gaia spectrophotometry

Gaia will obtain astrometry and spectrophotometry for essentially all sources in the sky down to a broad band magnitude limit of G=20, an expected yield of 10^9 stars. Its main scientific objective is to reveal the formation and evolution of our Galaxy through chemo-dynamical analysis. In addition to inferring positions, parallaxes and proper motions from the astrometry, we must also infer the astrophysical parameters of the stars from the spectrophotometry, the BP/RP spectrum. Here we investigate the performance of three different algorithms (SVM, ILIUM, Aeneas) for estimating the effective temperature, line-of-sight interstellar extinction, metallicity and surface gravity of A-M stars over a wide range of these parameters and over the full magnitude range Gaia will observe (G=6-20mag). One of the algorithms, Aeneas, infers the posterior probability density function over all parameters, and can optionally take into account the parallax and the Hertzsprung-Russell diagram to improve the estimates. For all algorithms the accuracy of estimation depends on G and on the value of the parameters themselves, so a broad summary of performance is only approximate. For stars at G=15 with less than two magnitudes extinction, we expect to be able to estimate Teff to within 1%, logg to 0.1-0.2dex, and [Fe/H] (for FGKM stars) to 0.1-0.2dex, just using the BP/RP spectrum (mean absolute error statistics are quoted). Performance degrades at larger extinctions, but not always by a large amount. Extinction can be estimated to an accuracy of 0.05-0.2mag for stars across the full parameter range with a priori unknown extinction between 0 and 10mag. Performance degrades at fainter magnitudes, but even at G=19 we can estimate logg to better than 0.2dex for all spectral types, and [Fe/H] to within 0.35dex for FGKM stars, for extinctions below 1mag.Comment: MNRAS, in press. Minor corrections made in v

Multimodal analysis of GRC ageing process using Nonlinear Impact Resonance acoustic Spectroscopy

Glass fibre Reinforced Cement (GRC) is a composite material composed of Portland cement mortar with low w/c (water/cement) ratio and high proportion of glass fibres. This material suffers from the ageing process by losing its strength with time because of its exposure to severe weather conditions. Ageing process damages the fibre surface and decreases the mechanical properties of the structural components made of this material. It reduces the elastic modulus and toughness of GRC. Fracture toughness is traditionally measured by four point bending tests. In a previous study by the authors it was observed that ageing related deterioration or damage of GRC could be monitored by Non Destructive Testing (NDT) techniques such as Non-linear Impact Resonance Acoustic Spectroscopy (NIRAS) and other ultrasonic techniques. The scope of this paper is to corroborate previous investigations and offer early damage detection capability by generating more experimental data points by optimizing location of the point of strike and thus generating more resonance vibration modes in NIRAS tests.The authors acknowledge the financial support of the Ministerio de Ciencia e Innovacion MICINN, Spain, and FEDER funding (Ondacem Project: BIA 2010-19933).Genovés Gómez, V.; Riestra García-San Miguel, C.; Borrachero Rosado, MV.; Eiras Fernández, JN.; Kundu, T.; Paya Bernabeu, JJ. (2015). Multimodal analysis of GRC ageing process using Nonlinear Impact Resonance acoustic Spectroscopy. Composites Part B: Engineering. 76:105-111. https://doi.org/10.1016/j.compositesb.2015.02.020S1051117

Evaluation of electric properties of cement mortars containing pozzolans

[ES] En este trabajo se analiza la microestructura de morteros de cemento Portland, mediante medidas de impedancia eléctrica. Se comparan morteros de cemento sin y con dos sustituciones puzolánicas: residuo de catalizador de craqueo catalítico (FCC) y metacaolín (MK). Se describe el método de medida y se desarrolla el modelo de análisis de los espectros de impedancia eléctrica. Se definen tres parámetros eléctricos: resistividad eléctrica, exponente capacitivo y factor capacitivo. Se observa un aumento importante de la resistividad de los morteros con puzolana a partir de los 7 días de curado, sobre todo en morteros con MK. Este aumento está correlacionado con la fijación de cal de las puzolanas. Las propiedades capacitivas son diferentes a edad temprana, pero se igualan a los 148 días. Los resultados eléctricos y mineralógicos muestran que la evolución microestructural comienza antes en los morteros con MK que con FCC y que la microestructura final es diferente.[EN] In this paper the evolution of the microstructure of Portland cement mortar is analyzed, by using electrical impedance measurements. Cement mortars are compared without and with two pozzolanic substitutions: spent fluid catalytic cracking catalyst (FCC) and metakaolin (MK). The measurement method is described and the model for analyzing the electrical impedance spectra is developed. Three electrical parameters are defined: electrical resistivity, capacitance exponent, and capacitive factor. The results show a significant increase in resistivity of the mortars with pozzolans after 7 days of curing, especially in mortars with MK. This increase is correlated with lime-fixing by the pozzolans. The capacitive properties evolve differently at early age, but reach the same values after 148 days. The electrical and mineralogical data show that the evolution of the microstructure in the mortar with MK starts before it does in the mortars with FCC and that the final microstructure becomes different.Authors thank to Ministerio de Educacion (Spanish research plan) the financial support to the projects BIA 2006-15188-C03-02 y BIA 2004-00520, with FEDER co-financing. Also thank to Universidad Politecnica de Valencia (Vicerrectorado de Investigacion) the research grant for L.F. Lalinde (PPI-01-04 ref 5939) and financial support to the project PAID-05-09 ref 4302.Cruz González, JM.; Paya Bernabeu, JJ.; Lalinde Castrillón, LF.; Fita Fernández, IC. (2011). Evaluación de las propiedades eléctricas de morteros de cemento con puzolanas. Materiales de Construcción. 61(301):7-26. doi:10.3989/mc.2010.53709S7266130

Mineralogical evolution of cement pastes at early ages based on thermogravimetric analysis (TGA)

[EN] Ordinary thermogravimetric analysis (TG) and high-resolution TG tests were carried out on three different Portland cement pastes to study the phases present during the first day of hydration. Tests were run at 1, 6, 12 and 24 h of hydration, in order to determine the phases at these ages. High-resolution TG tests were used to separate decompositions presented in the 100¿200 C interval. The non-evaporable water determined by TG was used to determine hydration degree for the different ages. The effect of particle size distribution (PSD) on mineralogical evolution was established, as well as the addition of calcite as mineralogical filler. Finer PSD and calcite addition accelerate the hydration process, increasing the hydration degree on the first day of eaction between water and cement. According to high-resolution TG results, it was demonstrated that ettringite was the only decomposed phase in the 100¿200 C interval during the first 6 h of hydration for all studied cements. C-S-H phase starts to appear in all cements after 12 h of hydration.Funding was provided by Colciencias (Grant No. Convocatoria 567-2012).Gaviria, X.; Borrachero Rosado, MV.; Paya Bernabeu, JJ.; Monzó Balbuena, JM.; Tobón, J. (2018). Mineralogical evolution of cement pastes at early ages based on thermogravimetric analysis (TGA). Journal of Thermal Analysis and Calorimetry. 132(1):39-46. https://doi.org/10.1007/s10973-017-6905-0S39461321Benboudjema F, Meftah JM, Torernti F. Interaction between drying, shrinkage, creep and cracking phenomena in concrete. Eng Struct. 2005;27:239–50.Holt E. Contribution of mixture design to chemical and autogenous shrinkage of concrete at early ages. Cem Concr Res. 2005;35:464–72.Darquennes A, Staquet S, Delplancke-Ogletree MP, Espion B. Effect of autogenous deformation on the cracking risk of slag cement concretes. Cem Concr Compos. 2011;33:368–79.Slowik V, Schmidt M, Fritzsch R. Capillary pressure in fresh cement-based materials and identification of the air entry value. Cem Concr Compos. 2008;30(7):557–65.Evju C, Hansen S. Expansive properties of ettringite in a mixture of calcium aluminate cement, Portland cement and ß-calcium sulfate hemihydrates. Cem Concr Res. 2001;31:257–61.Bentz DP, Jensen OM, Hansen KK. Olesen, Stang, H. Haecker, C.J. Influence of cement particle-size distribution on early age autogenous strain and stresses in cement-based materials. J Am Ceram Soc. 2001;84(1):129–35.Barcelo L, Moranville M, Clavaud B. Autogenous shrinkage of concrete: a balance between autogenous swelling and self-desiccation. Cem Concr Res. 2005;35(1):177–83.Bouasker M, Mounanga P, Turcry P, Loukili A, Khelidj A. Chemical shrinkage of cement pastes and mortars at very early age: effect of limestone filler and granular inclusions. Cem Concr Compos. 2008;30(1):13–22.Bentz DP. A review of early-age properties of cement-based materials. Cem Concr Res. 2008;38(2):196–204.Ozawa T. Controlled rate thermogravimetry. New usefulness of controlled rate thermogravimetry revealed by decomposition of polyimide. J Therm Anal Calorim. 2000;59:375–84.Ramachandran VS, Paroli RM, Beaudoin JJ, Delgado AH. Thermal analysis of construction materials. Building materials series. New York: Noyes Publications; 2003.Zanier A. High-resolution TG for the characterization of diesel fuel additives. J Therm Anal Calorim. 2001;64:377–84.Tobón JI, Payá J, Borrachero MV, Restrepo OJ. Mineralogical evolution of Portland cement blended with silica nanoparticles and its effect on mechanical strength. Constr Build Mater. 2012;36:736–42.Singh M, Waghmare S, Kumar V. Characterization of lime plasters used in 16th century Mughal Monument. J Archeol Sci. 2014;42:430–4.Majchrzak-Kuçeba I. Thermogravimetry applied to characterization of fly ash-based MCM-41 mesoporous materials. J Therm Anal Calorim. 2012;107:911–21.Silva ACM, Gálico DA, Guerra RB, Legendre AO, Rinaldo D, Galhiane MS, Bannach G. Study of some volatile compounds evolved from the thermal decomposition of atenolol. J Therm Anal Calorim. 2014;115:2517–20.Rios-Fachal M, Gracia-Fernández C, López-Beceiro J, Gómez-Barreiro S, Tarrío-Saavedra J, Ponton A, Artiaga R. Effect of nanotubes on the thermal stability of polystyrene. J Therm Anal Calorim. 2013;113:481–7.Yamarte L, Paxman D, Begum S, Sarkar P, Chambers A. TG measurement of reactivity of candidate oxygen carrier materials. J Therm Anal Calorim. 2014;116:1301–7.Borrachero MV, Payá J, Bonilla M, Monzó J. The use of thermogravimetric analysis technique for the characterization of construction materials. The gypsum case. J Therm Anal Calorim. 2008;91(2):503–9.Tobón JI, Payá J, Borrachero MV, Soriano L, Restrepo OJ. Determination of the optimum parameters in the high resolution thermogravimetric analysis (HRTG) for cementitious materials. J Therm Anal Calorim. 2012;107:233–9.Kuzielova E, Žemlička M, Másilko, J, Palou, M.T. Effect of additives on the performance of Dyckerhoff cement, Class G, submitted to simulated hydrothermal curing. J Therm Anal Calorim. Accepted 29 Oct 2017Genc M, Genc ZK. Microencapsulated myristic acid–fly ash with TiO2 shell as a novel phase change material for building application. J Therm Anal Calorim. Accepted 24 Oct 2017.Singh M, Kumar SV, Waghmare SA. The composition and technology of the 3–4th century CE decorative earthen plaster of Pithalkhora caves, India. J Archeol Sci. 2016;7:224–37.Liu L, Liu Q, Cao Y, Pan WP. The isothermal studies of char-CO2 gasification using the high-pressure thermo-gravimetric method. J Therm Anal Calorim. 2015;120:1877–82.Majchrzak-Kuce I, Bukalak-Gaik D. Regeneration performance of metal–organic frameworks TG-vacuum tests. J Therm Anal Calorim. 2016;125:1461–6.Ion RM, Radovici C, Fierascu RC, Fierascu I. Thermal and mineralogical investigations of iron archaeological Materials. J Therm Anal Calorim. 2015;121:1247–53.Rupasinghe M, San Nicolas R, Mendis P, Sofi M, Ngo T. Investigation of strength and hydration characteristics in nano-silica incorporated cement paste. Cem Concr Compos. 2017;80:17–30.Esteves PL. On the hydration of water-entrained cement–silica systems: combined SEM, XRD and thermal analysis in cement pastes. Thermochim Acta. 2011;518:27–35.Riesen R. Adjustment of heating rate for maximum resolution in TG and TMA (MaxRes). J Therm Anal. 1998;53:365–74.Lim S, Mondal P. Micro- and nano-scale characterization to study the thermal degradation of cement-based materials. Mater Charact. 2014;92:15–25.Gill PS, Sauerbrunn SR, Crowe BS. High resolution thermogravimetry. J Therm Anal. 1992;38:255–66.Mounanga P, Khelidj A, Loukili A, Baroghel-Bouny V. Predicting Ca(OH)2 content and chemical shrinkage of hydrating cement pastes using analytical approach. Cem Concr Res. 2004;34:255–65.Zeng Q, Li K, Fen-chong T, Dangla P. Determination of cement hydration and pozzolanic reaction extents for fly-ash cement pastes. Constr Build Mater. 2012;27:560–9.Parrott LP, Geiker M, Gutteridge WA, Killoh D. Monitoring Portland cement hydration: Comparison of methods. Cem Concr Res. 1990;20:919–26.Hewlett PC. Lea’s chemistry of cement and concrete. 4th ed. Oxford: Elsevier Science & Technology Books; 2004.ASTM C305 Standard practice for mechanical mixing of hydraulic cement pastes and mortars of plastic consistency. ASTM International, West Conshohocken, PA; 2012.Taylor HF. Cement chemistry. 2nd ed. Westminster: Thomas Telford; 1997.Nadelman EI, Freas DJ, Kurtis KE. Nano- and microstructural characterization of Portland limestone cement paste. In: Nanotechnology in construction. Proceedings of NICOM 5. 2015. p. 87–92

<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties

Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release. Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues – a realisation of the Tycho-Gaia Astrometric Solution (TGAS) – and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr−1 for the proper motions. A systematic component of ∼0.3 mas should be added to the parallax uncertainties. For the subset of ∼94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr−1. For the secondary astrometric data set, the typical uncertainty of the positions is ∼10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼0.03 mag over the magnitude range 5 to 20.7. Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data

Effect of curing time on the microstructure and mechanical strength development of alkali activated binders based on vitreous calcium aluminosilicate (VCAS)

The aim of this paper is to study the influence of curing time on the microstructure and mechanical strength development of alkali activated binders based on vitreous calcium aluminosilicate (VCAS). Mechanical strength of alkali activated mortars cured at 65 °C was assessed for different curing times (4¿168 h) using 10 molal NaOH solution as alkaline activator. Compressive strength values around 77 MPa after three days of curing at 65 °C were obtained. 1·68 MPa/h compressive strength gain rate was observed in the first 12 h, decreasing to 0·95 MPa/h for the period of 12¿72 h. The progress of geopolymeric reaction was monitored by means of TGA and, electrical conductivity and pH measurements in an aqueous suspension. Significant decrease in pH and electrical conductivity were observed in the 4¿72 h period, demonstrating the geopolymerization process. Furthermore, SEM images showed an important amount of (N, C)ASH gel and low porosity of the developed matrix.To the Ministerio de Ciencia e Innovacion (MICINN) of the Spanish Government (BIA2011-26947) and also to FEDER for funding and to Vitrominerals company for supplying VCAS samples.Mitsuuchi Tashima, M.; Soriano Martínez, L.; Borrachero Rosado, MV.; Monzó Balbuena, JM.; Paya Bernabeu, JJ. (2013). Effect of curing time on the microstructure and mechanical strength development of alkali activated binders based on vitreous calcium aluminosilicate (VCAS). Bulletin of Materials Science. 36:245-249. https://doi.org/10.1007/s12034-013-0466-zS24524936Bernal S A, Gutiérrez R M, Pedraza A L, Provis J L, Rodriguez E D and Delvasto S 2011 Cem. Concr. Res. 41 1Criado M, Fernández-Jiménez A, Sobrados I, Palomo A and Sanz J 2011 J. Eur. Ceram. Soc. avaiable onlineDavidovits J 2008 Geopolymer chemistry and applications Institute Geopolymere, Saint-Quentin, FranceDuxson P, Fernández-Jiménez A, Provis J L, Lukey G C, Palomo A and van Deventer J S J 2007 J. Mater. Sci. 47 2917Fernández-Jiménez A, Palomo A and Criado M 2005 Cem. Concr. Res. 35 1204Hossain A B, Shrazi S A, Persun J and Neithalath N 2008 J. Transp. Res. Board 2070 32Komnitsas K and Zaharaki D 2007 Miner. Eng. 20 1261Lampris C, Lupo R and Cheeseman C R 2009 Waste Manage. 29 368Lin T, Jia D, Wang M, He P and Liang D 2009 Bull. Mater. Sci. 32 77Lloyd R R, Provis J L and van Deventer J S J 2009 J. Mater. Sci. 44 608Marín-López C, Reyes Araiza J L, Manzano-Ramírez A, Rubio Avalos J C, Perez-Bueno J J, Muñiz-Villareal M S, Ventura-Ramos E and Vorobiev Y 2009 Inorg. Mater. 45 1429Najafi Kani E, Allahverdi A and Provis J L 2012 Cem. Concr. Comp. 34 25Neithalath N, Persun J and Hossain A 2009 Cem. Concr. Res. 39 473Pacheco-Torgal F, Castro-Gomes J and Jalali S 2008a Constr. Build. Mater. 22 1315Pacheco-Torgal F, Castro-Gomex J and Jalali S 2008b Constr. Build. Mater. 22 1201Pacheco-Torgal F, Castro-Gomex J and Jalali S 2008c Constr. Build. Mater. 22 2212Payá J, Borrachero M V, Monzó J, Soriano L and Tashima M M 2012 Mater. Lett. 74 223Puertas F, Martínez-Ramírez S, Alonso S and Vázquez T 2000 Cem. Concr. Res. 30 1625Puertas F, Barba A, Gazulla M F, Gómez M P, Palacios M and Martínez-Ramírez S 2006 Mater. Construc. 56 73Reig L, Tashima M M, Borrachero M V, Monzó J and Payá J 2010 II Simposio aprovechamiento de residuos agro-industriales como fuente sostenible de materiales de construcción p. 83Rodriguez E D, Bernal S A, Provis J, Payá J, Monzó J and Borrachero M V 2012 Cem. Concr. Comp. (submitted)Tashima M M, Borrachero M V, Monzó J, Soriano L and Payá J 2009 COMATCOMP09 p.421Tashima M M, Akasaki J L, Castaldelli V N, Soriano L, Monzó J, Payá J and Borrachero M V 2012 Mater. Lett. 80 50Xu H and van Deventer J S J 2000 Int. J. Miner. Process. 59 247Yao X, Zhang Z, Zhu H and Chen Y 2009 Thermochim. Acta 493 49Zivica V 2004 Bull. Mater. Sci. 27 179Zivica V, Balkovic S and Drabik M 2011 Constr. Build. Mater. 25 220

Gaia Data Release 1: Testing parallaxes with local Cepheids and RR Lyrae stars

Context. Parallaxes for 331 classical Cepheids, 31 Type II Cepheids, and 364 RR Lyrae stars in common between Gaia and the Hipparcos and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS). Aims. In order to test these first parallax measurements of the primary standard candles of the cosmological distance ladder, which involve astrometry collected by Gaia during the initial 14 months of science operation, we compared them with literature estimates and derived new period-luminosity (PL), period-Wesenheit (PW) relations for classical and Type II Cepheids and infrared PL, PL-metallicity (PLZ), and optical luminosity-metallicity (M V -[Fe/H]) relations for the RR Lyrae stars, with zero points based on TGAS. Methods. Classical Cepheids were carefully selected in order to discard known or suspected binary systems. The final sample comprises 102 fundamental mode pulsators with periods ranging from 1.68 to 51.66 days (of which 33 with σ Ω /Ω < 0.5). The Type II Cepheids include a total of 26 W Virginis and BL Herculis stars spanning the period range from 1.16 to 30.00 days (of which only 7 with σ Ω /Ω < 0.5). The RR Lyrae stars include 200 sources with pulsation period ranging from 0.27 to 0.80 days (of which 112 with σ Ω /Ω < 0.5). The new relations were computed using multi-band (V,I,J,K s ) photometry and spectroscopic metal abundances available in the literature, and by applying three alternative approaches: (i) linear least-squares fitting of the absolute magnitudes inferred from direct transformation of the TGAS parallaxes; (ii) adopting astrometry-based luminosities; and (iii) using a Bayesian fitting approach. The last two methods work in parallax space where parallaxes are used directly, thus maintaining symmetrical errors and allowing negative parallaxes to be used. The TGAS-based PL,PW,PLZ, and M V - [Fe/H] relations are discussed by comparing the distance to the Large Magellanic Cloud provided by different types of pulsating stars and alternative fitting methods. Results. Good agreement is found from direct comparison of the parallaxes of RR Lyrae stars for which both TGAS and HST measurements are available. Similarly, very good agreement is found between the TGAS values and the parallaxes inferred from the absolute magnitudes of Cepheids and RR Lyrae stars analysed with the Baade-Wesselink method. TGAS values also compare favourably with the parallaxes inferred by theoretical model fitting of the multi-band light curves for two of the three classical Cepheids and one RR Lyrae star, which were analysed with this technique in our samples. The K-band PL relations show the significant improvement of the TGAS parallaxes for Cepheids and RR Lyrae stars with respect to the Hipparcos measurements. This is particularly true for the RR Lyrae stars for which improvement in quality and statistics is impressive. Conclusions. TGAS parallaxes bring a significant added value to the previous Hipparcos estimates. The relations presented in this paper represent the first Gaia-calibrated relations and form a work-in-progress milestone report in the wait for Gaia-only parallaxes of which a first solution will become available with Gaia Data Release 2 (DR2) in 2018. © ESO, 2017

Gaia Data Release 2 Mapping the Milky Way disc kinematics

Context. The second Gaia data release (Gaia DR2) contains high-precision positions, parallaxes, and proper motions for 1.3 billion sources as well as line-of-sight velocities for 7.2 million stars brighter than G(RVS) = 12 mag. Both samples provide a full sky coverage. Aims. To illustrate the potential of Gaia DR2, we provide a first look at the kinematics of the Milky Way disc, within a radius of several kiloparsecs around the Sun. Methods. We benefit for the first time from a sample of 6.4 million F-G-K stars with full 6D phase-space coordinates, precise parallaxes (sigma((omega) over bar)/(omega) over bar Results. Gaia DR2 allows us to draw 3D maps of the Galactocentric median velocities and velocity dispersions with unprecedented accuracy, precision, and spatial resolution. The maps show the complexity and richness of the velocity field of the galactic disc. We observe streaming motions in all the components of the velocities as well as patterns in the velocity dispersions. For example, we confirm the previously reported negative and positive galactocentric radial velocity gradients in the inner and outer disc, respectively. Here, we see them as part of a non-axisymmetric kinematic oscillation, and we map its azimuthal and vertical behaviour. We also witness a new global arrangement of stars in the velocity plane of the solar neighbourhood and in distant regions in which stars are organised in thin substructures with the shape of circular arches that are oriented approximately along the horizontal direction in the U - V plane. Moreover, in distant regions, we see variations in the velocity substructures more clearly than ever before, in particular, variations in the velocity of the Hercules stream. Conclusions. Gaia DR2 provides the largest existing full 6D phase-space coordinates catalogue. It also vastly increases the number of available distances and transverse velocities with respect to Gaia DR1. Gaia DR2 offers a great wealth of information on the Milky Way and reveals clear non-axisymmetric kinematic signatures within the Galactic disc, for instance. It is now up to the astronomical community to explore its full potential.Peer reviewe