Magnetic Field Amplification in Galaxy Clusters and its Simulation

We review the present theoretical and numerical understanding of magnetic field amplification in cosmic large-scale structure, on length scales of galaxy clusters and beyond. Structure formation drives compression and turbulence, which amplify tiny magnetic seed fields to the microGauss values that are observed in the intracluster medium. This process is intimately connected to the properties of turbulence and the microphysics of the intra-cluster medium. Additional roles are played by merger induced shocks that sweep through the intra-cluster medium and motions induced by sloshing cool cores. The accurate simulation of magnetic field amplification in clusters still poses a serious challenge for simulations of cosmological structure formation. We review the current literature on cosmological simulations that include magnetic fields and outline theoretical as well as numerical challenges.Comment: 60 pages, 19 Figure

Effects of feeding three types of corn-milling coproducts on milk production and ruminal fermentation of lactating Holstein cattle

Two experiments were conducted to determine the effects of feeding 3 corn-milling coproducts on intake, milk production, ruminal fermentation, and digestibility of lactating Holstein cows. In experiment 1, three corn-milling coproducts were fed at 15% of the diet dry matter (DM) to 28 Holstein cows averaging (±SD) 625 ± 81 kg of body weight and 116 ± 33 d in milk to determine effects on DM intake and milk production. In experiment 2, the same rations were fed to 4 ruminally fistulated, multiparous Holstein cows averaging 677 ± 41 kg of body weight and 144 ± 5 d in milk to determine the effects on ruminal fermentation and digestibility. In both experiments, cows and treatments were assigned randomly in 4 × 4 Latin squares over four 21-d periods. Treatments were formulated by replacing portions of forage and concentrate feeds with 15% coproduct and included 1) 0% coproduct (control), 2) dried distillers grains plus solubles (DDGS), 3) dehydrated corn germ meal (germ), and 4) high-protein dried distillers grains (HPDDG). Feed intake was recorded daily, and milk samples were collected on d 19 to 21 of each period for analysis of major components. Rumen fluid was collected at 10 time points over 24 h post feeding on d 21 of experiment 2. In experiment 1, DM intake was greater for the germ (24.3 kg/d) and DDGS treatments (23.8 kg/d), but DDGS was not different from the control (22.9 kg/d) and HPDDG treatments (22.4 kg/d). Milk production paralleled DM intake and tended to be greater for the germ (32.1 kg/d) and DDGS treatments (30.9 kg/d), but the DDGS treatment was not different from the control (30.6 kg/d) and HPDDG treatments (30.3 kg/d). However, yields of milk fat, milk protein, and 3.5% FCM were similar and averaged (±SEM) 1.1 ± 0.1, 0.9 ± 0.03, and 31.7 ± 1.3 kg/d. Milk urea nitrogen was greater for the HPDDG (15.9 mg/dL) and germ treatments (15.5 mg/dL) than for the control (15.0 mg/dL) and DDGS treatments (14.9 mg/dL). In experiment 2, DM intake and milk production were not different across treatments and averaged 26.1 ± 2.3 and 28.3 ± 3.9 kg/d. Ruminal pH (6.26 ± 0.08) and total concentration of volatile fatty acids (125.3 ± 4.2 mM) were similar. Acetate concentration was higher for the control treatment than the DDGS, germ, and HPDDG treatments (81.7 vs. 75.8, 75.0, and 78.4 mM). Concentrations of propionate and butyrate were not different and averaged 27.8 ± 1.2 and 14.3 ± 0.9 mM across treatments. The acetate:propionate ratios for the control, germ, and HPDDG treatments were greater than for the DDGS treatment (3.02, 2.88, and 2.91 vs. 2.62). Dry matter, organic matter, and neutral detergent fiber digestibilities were similar across treatments and averaged 63.5 ± 2.7, 67.3 ± 2.2, and 43.5 ± 4.2%. Milk production followed DM intake in experiment 1, and yield of major milk components was not affected. Results of these experiments indicate that dairy rations can be successfully formulated to include 15% of diet DM as corn-milling coproducts while maintaining or increasing DM intakes and yields of milk and milk components

Rendimento e composição químico-bromatológica de fenos triturados de gramíneas tropicais Yield and chemical composition of chopped tropical grass hays

A pesquisa foi conduzida objetivando avaliar o rendimento, a composição químico-bromatológica e as perdas de fenos triturados de milheto, sorgo sudanense, capim-elefante e sorgos forrageiros (SF-25 e IPA-467-4-2). Os materiais foram colhidos quando atingiram 30% de inflorescências, com exceção do capim-elefante, colhido aos 60 dias. Utilizou-se delineamento de blocos completos casualizados, com cinco tratamentos e quatro repetições. Houve diferenças significativas, com maiores produções de feno para os sorgos IPA-467-4-2 (10,85 t/ha/corte) e SF-25 (10,65 t/ha/corte), que foram superiores ao capim-elefante, sorgo sudanense e milheto, com, respectivamente, 6,94; 6,69 e 4,93 t/ha/corte. Os percentuais de perdas na fenação não diferiram entre os tratamentos, com níveis variando de 17,33 a 20,17%. Os fenos de milheto e sorgo sudanense tiveram as maiores concentrações de PB (10,56 e 8,80%), superiores às do capim-elefante (6,76%) e dos sorgos SF-25 (5,62%) e IPA-467-4-2 (5,50%). Os valores de FDN foram, na maioria, superiores a 70,0%. As menores concentrações de NIDN foram observadas nos cultivares de sorgo (0,42 e 0,40% da MS). As concentrações de NIDA variaram de 0,06 a 0,30% na MS. As maiores concentrações de lignina (%MS) dos fenos foram obtidas no milheto (6,52%) e no sorgo IPA-467-4-2 (6,17%). As concentrações de nutrientes digestíveis totais estimadas (NDTe) dos fenos diferiram significativamente, com o maior valor para o sorgo sudanense (53,35%). Os fenos triturados das gramíneas tropicais avaliadas apresentaram rendimentos elevados e composição químico-bromatológica dentro dos padrões mínimos recomendáveis para nutrição de ruminantes.<br>The research was carried out to evaluate yield, chemical composition and losses of chopped tropical grass hays with the following forages: pearl millet (Pennisetum americanum), sudangrass (Sorghum sudanense), elephantgrass (Pennisetum purpureum) and two cultivars of forage sorghum (SF-25 and IPA-467-4-2) (Sorghum bicolor). The materials were harvested at 30% flowering, except for elephantgrass (60 days). The experiment was conducted according to a complete randomized block design, with five treatments and four replications. There were significant differences among hay productions with sorghum cultivars IPA-467-4-2 and SF-25 reaching the highest yields (10.85 and 10.65 t/ha/cut). Production of elephantgrass, sudangrass and pearl millet hays were respectively of 6.94, 6.69, and 4.93 t/ha/cut. Percentage of hay losses were not different among all treatments and varied from 17.33 to 20.17%. Pearl millet and sudangrass hays had the highest CP concentrations (10.56 and 8.80%), which were superior to elephantgrass (6.76%) and sorghum cultivars (5.62 and 5.50%). Most of the NDF values were superior to 70.0%. Sorghum cultivars exhibited the lowest NDIN concentration (0.42 and 0.40% of DM). The ADIN concentration ranged from 0.06 to 0.30% of DM. The highest lignin (%DM) concentration was observed for pearl millet (6.52%) and sorghum IPA-467-4-2 (6.17%) hays. Estimated TDN of the hays showed significant differences and sudangrass reached the highest value (53.35%). Production of chopped tropical grass hays showed high yields and chemical composition according to the minimum standards for ruminant nutrition

Substituição total do farelo de soja por uréia ou amiréia, em dietas com alto teor de concentrado, sobre a amônia ruminal, os parâmetros sangüíneos e o metabolismo do nitrogênio em bovinos de corte Total replacement of soybean meal by urea or starea in high grain diets on nitrogen metabolism, ruminal ammonia-N concentration and blood parameters in beef cattle

Seis novilhos da raça Nelore, não castrados, com peso médio inicial de 420 kg, distribuídos em delineamento em quadrado latino 3x3 duplicado, foram utilizados para avaliar a substituição total de uma fonte de proteína verdadeira (farelo de soja), em uma dieta deficiente em proteína degradável no rúmen (PDR), por uréia ou amiréia (fontes de nitrogênio não protéico), ambas em uma dieta adequada em PDR. As dietas foram isoprotéicas (13,0%) utilizando-se o bagaço de cana-de-açúcar in natura (BIN) como única fonte de volumoso (20% da MS). Foram avaliados: a concentração de amônia ruminal, nitrogênio uréico plasmático, glicose plasmática e o metabolismo do nitrogênio. Os tratamentos foram: 1) farelo de soja (FS); 2) uréia e 3) amiréia (A-150S). A concentração de nitrogênio amoniacal no fluido ruminal foi superior no tratamento com uréia, comparado ao tratamento com farelo de soja, sendo que o tratamento com amiréia não diferiu dos demais. O tratamento com amiréia apresentou maior perda de N urinário. A retenção de N (g/d e % do consumido) e o valor biológico da proteína (N retido, % do N digerido) foram superiores para o tratamento com uréia, comparado aos demais. A concentração de nitrogênio uréico no plasma e a concentração de glicose plasmática foram similares entre os tratamentos. A substituição total do farelo de soja por uréia, ajustando a PDR na dieta de bovinos de corte, demonstrou ser viável. A uréia na forma convencional apresentou vantagens em relação à amiréia.<br>Six Nellore bulls, with initial body weight of 420 kg, were assigned to a duplicated 3x3 Latin square design to evaluate the effects of replacing a true protein source (soybean meal), of high biological value, in a rumen degradable protein (RDP) deficient diet, by urea or starea (a supposedly slow release nonprotein nitrogen source), both in a RDP adjusted diet. In natura sugarcane bagasse as the only source of forage (20% of DM). Evaluated parameters were: rumen ammonia-N concentration, plasma urea-N, glucose and nitrogen balance. Experimental treatments were: 1) soybean meal (SBM); 2) urea and 3) starea (A-150S). Diets were isonitrogen (13% CP). The rumen ammonia-N concentration was higher in the treatment with urea, compared to the treatment with SBM, and starea showed no difference compared to the others. Starea had higher loss of urinary N. N retention (g/d and % of consumed) and protein biological value (N retention, % of N digestible) were higher for urea treatment, compared to the others. There was no difference on plasma urea-N and glucose concentration among treatments. Total replacement of SBM by urea, adjusting PDR in diets for growing beef cattle, demonstrated to be viable. Conventional urea showed advantage compared to starea

Multi-messenger Observations of a Binary Neutron Star Merger

International audienceOn 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 $\,{M}_{\odot }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim 40\,{\rm{Mpc}}$) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position $\sim 9$ and $\sim 16$ days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta