Guide For Recommended Practices To Perform Crack Tip Opening Displacement Tests In High Strength Low Alloy Steels

Fracture mechanics approach is important for all mechanical and civil projects that might involve cracks in metallic materials, and especially for those using welding as a structural joining process. This methodology can enhance not only the design but also the service life of the structures being constructed. This paper includes detailed consideration of several practical issues related to the experimental procedures to assess the fracture toughness in high strength low alloy steels (HSLA) using the crack tip opening displacement (CTOD) parameter, specifically pipeline steels for oil and gas transportation. These considerations are important for engineers who are new in the field, or for those looking for guidelines performing different procedures during the experimentation, which usually are difficult to understand from the conventional standards. We discuss on topics including geometry selection, number of replicate tests, fatigue precracking, test procedure selection and realization, reports of results and other aspects.213290302Colciencias [512]PetrobrasLNNano/CNPE

Discontinuous roughage delivery on digestion, rumen metabolism, feed efficiency and liveweight gain of beef steers fed a concentrate diet

Two experiments were carried out to study the effect of feeding a total mixed ration (TMR) compared to feeding the roughage portion of the diet once every two days and separated of the daily delivered concentrate mixture on dry matter intake, nutrient digestibility, ruminal metabolism, feed efficiency and liveweight gain. In Trial 1, thirty beef steers (Braford and Braford × Criollo; initial BW = 259 ± 27 kg) were used in a 69-d feeding trial. Treatments were: total mixed ration (TMR), and the same proportion of ingredients for the ration but roughage offered once every 2-d and separated from the daily delivered concentrate portion of the diet (REOD). Treatments were arranged in a completely randomized design (three pens/ treatment). In both treatments, daily offered ration had on dry matter basis 90% concentrate and 10% grass hay (Setaria italica). Average daily gain (ADG) did not differ among treatment (1013 vs. 1080 g/d for TMR vs. REOD respectively; SEM = 95 g/d). Dry matter intake was greater in TMR compared to REOD (P < 0.01). Gain to feed ratio tended to be better for REOD than TMR (P = 0.07). In Trial 2, four rumen cannulated steers (Braford) were used in an experiment with a crossover design. Treatments were arranged as a 2*2 factorial design, where the first factor consisted of roughage level (RL): (R14) 14% roughage: 86% concentrate and (R7) 7% roughage: 93% concentrate. The second factor was roughage delivery system (RDS; as it was described for Trial 1): TMR and REOD. There were no RL*RDS interactions for intake and digestion (OM, CP, NDF and starch). Both RL were similar for intake and digestion. Roughage delivery system did not significantly affect intake and digestion of OM, CP, NDF, and starch measured by total fecal collection. Total organic acids (TOA), acetate to propionate ratio (A:P), pH, and rumen ammonia concentrations were not affected by RL and RDS. In conclusion, under the conditions of these trials, steers fed a separated roughage source once every 2-d had similar ADG, and tended to be more efficient compared with TMR. Total tract digestibility and rumen environment traits (pH, VFA, and ammonia) were not affected in response to discontinuous roughage delivery.Fil: Arroquy, Jose Ignacio. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santiago del Estero. Universidad Nacional de Santiago del Estero. Centro de Investigaciones y Transferencia de Santiago del Estero; ArgentinaFil: Nazareno, Mónica Azucena. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Santiago del Estero. Universidad Nacional de Santiago del Estero. Centro de Investigaciones y Transferencia de Santiago del Estero; ArgentinaFil: Avila, M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; ArgentinaFil: Garcia, M.. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: Cervetto, J.. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: Distel, Roberto Alejandro. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; ArgentinaFil: Saravia, J. J.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; Argentin

The Primeval Populations of the Ultra-Faint Dwarf Galaxies

We present new constraints on the star formation histories of the ultra-faint dwarf (UFD) galaxies, using deep photometry obtained with the Hubble Space Telescope (HST). A galaxy class recently discovered in the Sloan Digital Sky Survey, the UFDs appear to be an extension of the classical dwarf spheroidals to low luminosities, offering a new front in efforts to understand the missing satellite problem. They are the least luminous, most dark-matter dominated, and least chemically-evolved galaxies known. Our HST survey of six UFDs seeks to determine if these galaxies are true fossils from the early universe. We present here the preliminary analysis of three UFD galaxies: Hercules, Leo IV, and Ursa Major I. Classical dwarf spheroidals of the Local Group exhibit extended star formation histories, but these three Milky Way satellites are at least as old as the ancient globular cluster M92, with no evidence for intermediate-age populations. Their ages also appear to be synchronized to within ~1 Gyr of each other, as might be expected if their star formation was truncated by a global event, such as reionization.Comment: Accepted for publication in The Astrophysical Journal Letters. Latex, 5 pages, 2 color figures, 1 tabl

Effect of discontinuous roughage delivery on digestion, rumen metabolism, feed efficiency and live weight gain of beef steers fed a concentrate diet

Two experiments were carried out to study the effect of feeding a total mixed ration (TMR) compared to feeding the roughage portion of the diet once every two days and separated of the daily delivered concentrate mixture on dry matter intake, nutrient digestibility, ruminal metabolism, feed efficiency and liveweight gain. In Trial 1, thirty beef steers (Braford and Braford × Criollo; initial BW = 259 ± 27 kg) were used in a 69-d feeding trial. Treatments were: total mixed ration (TMR), and the same proportion of ingredients for the ration but roughage offered once every 2-d and separated from the daily delivered concentrate portion of the diet (REOD). Treatments were arranged in a completely randomized design (three pens/ treatment). In both treatments, daily offered ration had on dry matter basis 90% concentrate and 10% grass hay (Setaria italica). Average daily gain (ADG) did not differ among treatment (1013 vs. 1080 g/d for TMR vs. REOD respectively; SEM = 95 g/d). Dry matter intake was greater in TMR compared to REOD (P < 0.01). Gain to feed ratio tended to be better for REOD than TMR (P = 0.07). In Trial 2, four rumen cannulated steers (Braford) were used in an experiment with a crossover design. Treatments were arranged as a 2*2 factorial design, where the first factor consisted of roughage level (RL): (R14) 14% roughage: 86% concentrate and (R7) 7% roughage: 93% concentrate. The second factor was roughage delivery system (RDS; as it was described for Trial 1): TMR and REOD. There were no RL*RDS interactions for intake and digestion (OM, CP, NDF and starch). Both RL were similar for intake and digestion. Roughage delivery system did not significantly affect intake and digestion of OM, CP, NDF, and starch measured by total fecal collection. Total organic acids (TOA), acetate to propionate ratio (A:P), pH, and rumen ammonia concentrations were not affected by RL and RDS. In conclusion, under the conditions of these trials, steers fed a separated roughage source once every 2-d had similar ADG, and tended to be more efficient compared with TMR. Total tract digestibility and rumen environment traits (pH, VFA, and ammonia) were not affected in response to discontinuous roughage delivery.Fil: Arroquy, Jose Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: Nazareno, Mónica Azucena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias. Instituto de Ciencias Químicas; ArgentinaFil: García, Elisa Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias. Instituto de Ciencias Químicas; ArgentinaFil: Cervetto, Juan Jose. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: Avila, M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; ArgentinaFil: Saravia, J. J.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Tucumán-Santiago del Estero; ArgentinaFil: Distel, Roberto Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; Argentin

Stellar Properties of z ~ 8 Galaxies in the Reionization Lensing Cluster Survey

Measurements of stellar properties of galaxies when the universe was less than one billion years old yield some of the only observational constraints of the onset of star formation. We present here the inclusion of \textit{Spitzer}/IRAC imaging in the spectral energy distribution fitting of the seven highest-redshift galaxy candidates selected from the \emph{Hubble Space Telescope} imaging of the Reionization Lensing Cluster Survey (RELICS). We find that for 6/8 \textit{HST}-selected $z\gtrsim8$ sources, the $z\gtrsim8$ solutions are still strongly preferred over $z\sim$1-2 solutions after the inclusion of \textit{Spitzer} fluxes, and two prefer a $z\sim 7$ solution, which we defer to a later analysis. We find a wide range of intrinsic stellar masses ($5\times10^6 M_{\odot}$ -- $4\times10^9$ $M_{\odot}$), star formation rates (0.2-14 $M_{\odot}\rm yr^{-1}$), and ages (30-600 Myr) among our sample. Of particular interest is Abell1763-1434, which shows evidence of an evolved stellar population at $z\sim8$, implying its first generation of star formation occurred just $< 100$ Myr after the Big Bang. SPT0615-JD, a spatially resolved $z\sim10$ candidate, remains at its high redshift, supported by deep \textit{Spitzer}/IRAC data, and also shows some evidence for an evolved stellar population. Even with the lensed, bright apparent magnitudes of these $z \gtrsim 8$ candidates (H = 26.1-27.8 AB mag), only the \textit{James Webb Space Telescope} will be able further confirm the presence of evolved stellar populations early in the universe.Comment: 8 pages, 3 figures, 2 table