Upper limits on the 21 cm power spectrum from the epoch of reionization

In this Thesis work, we analyse 21cm line observations taken with the Precision Array to Probe the Epoch of Reionization (PAPER) in the 120-180MHz range (6<z<10). We focus on the power spectrum estimate of the Epoch of Reionization (EoR) signal at four different redshift intervals from 8 hours of data. The analysis of PAPER data is unconventional: the array is constituted by 128 dipoles arranged in a redundant configuration in order to maximize the power spectrum sensitivity on a limited number of k-modes. For this reason, PAPER observations are not ideal to image and model foreground emission: we instead adopted a strategy that relies on avoidance, isolating the power spectrum region where the foreground emission is expected to be fainter than the EoR signal. We estimated the power spectrum from PAPER observations using only 30m baselines, the most numerous one. After an initial data selection, we developed a pipeline to estimate the power spectrum of the 21cm signal. The pipeline averages calibrated data over the duration of the observation, Fourier ("delay") transforms them along the frequency axis and then calculate cross-products between different baselines of the same length. The resulting cross-spectra are averaged to obtain a final estimate for each redshift interval. The delay transform separates the foregrounds, that are confined to the low k-modes. Higher k-modes are consistent with the noise power spectrum that we derived from the data themselves. We, therefore, estimated upper limits on the 21cm power spectrum. Finally, using a simple, analytic model of the 21cm signal, we calculated a lower limit on the IGM temperature at z=7.48

Processi di scattering in astrofisica

Lo scattering è il processo in cui un’onda elettromagnetica interagisce con la materia, tipicamente un elettrone libero. In tale interazione l’onda cambia direzione e può modificare la propria energia. Se lo scattering produce solo un cambio di direzione, si parla di scattering Thomson, che risulta particolarmente importante per la definizione di sezione d’urto classica. Quando invece la radiazione perde energia e la trasferisce all’elettrone, si ha lo scattering Compton, viceversa, quando la radiazione guadagna energia sottraendola all’elettrone, si ha l’inverse Compton. Questi ultimi due processi producono una modifica nello spettro energetico (SED) di alcune regioni, fenomeno noto come Comptonizzazione. Nel caso in cui la Comptonizzazione agisca sullo spettro della radiazione cosmica di fondo (CMB), si ha l’effetto Sunyaev-Zel’dovich. In particolare, questo si suddivide in un effetto termico, dovuto agli elettroni liberi molto energetici di una regione che fanno inverse Compton sui fotoni della CMB, e in un effetto cinetico, dovuto al moto relativo della regione rispetto alla CMB. Nel presente scritto si focalizzerà l’attenzione su come si può misurare l’evoluzione della temperatura della CMB fino a redshift z = 1, che è un’applicazione del Sunyaev-Zel’dovich termico, e sul calcolo dell’effetto cinetico nell’alone di gas del Gruppo Locale

Fish health and fillet quality following substitution of fishmeal (FM) and fish oil (FO) with vegetable meal (VM) and oil (VO) in the modern aquaculture.

Plant proteins in vegetable meals (VM) and oils are used in an increasing percentage in diets for carnivorous fish to replace fish meal (FM) and fish oil (FO) in order to reduce production costs and to face the limitation of marine resources and to be sustainable in respect to the protection of oceanic biodiversity. However, several studies report that fish respond to such replacements by reducing growth rate, feed conversion and fillet quality. It may be due to a deficiency or poor availability in VM ingredients of some essential amino acids, but also to the occurrence of anti-nutritionals and inflammatory compounds acting on the fish intestine. This can lead to economic losses for fish farmers, increased fish diseases occurrence, and negative environmental impact. This study focuses on European sea bass and Rainbow trout, as two among the most commercially important fish species in Italy. Aims of the study are to improve feed formulation and optimize feed additives such taurine, as well as butyrate, salt of a short chain fatty acid (SCFA), to protect fish intestine and evaluate the effects on fish fillet quality of the modern commercial diets where FM is partially substitute with VM. In that context, our experimental study investigated butyrate and taurine in the diet, as nutraceutics able to reduce or minimize the negative effects of VM inclusion in fish performances and health. After improvement of analytical methods for butyrate titration in fecal samples, the possibility that a butyric fermentation occurs in fish intestine has been experimentally evaluated. The protective effect of butyrate on fish intestine has been studied by following approaches including histology with light and electronic microscopy, then a molecular approach to study inflammatory cytokines, as well as the epigenetic action of this SCFA. In spite, dietary butyrate showed no significant differences in weight gain or SGR (specific growth rate) of sea bass, the protective effect on the intestine walls was highlighted, together with its epigenetic effects on hiperacetylation histone H4 at lysine 8, while no effects has been found on the histone H3 at Lys9. A butyrate effect on the liver, as an increased transcriptional expression of the genes Dicer1, ehmt2, and hdac11 and il-10 have been assessed, suggesting an anti-inflammatory as well as an antiviral role of butyrate in seabass receiving a 2% of Na-butyrate as diet supplement. The effect of a dietary supplementation of the sulphonic aminoacid taurine, almost absent in the VM, was studied on seabass growth performances and on its potential role as antioxidant. Seabass fed with 1.5% taurine addition showed an increase of the fish growth performance and a marked reduction of the ROS production under resting conditions that was enhanced following forced swimming performances. The synergistic effect of butyrate and taurine as feed additives was also explored in seabass feeding diet containing an elevate concentration of a soy protein. Different cytological protective mechanisms have been observed, indicating the existence of a synergistic action of the two nutraceutical compounds. The quality of fish fillet in trout fed with 6 different commercial feed where FM was differently substituted by VM, has been studied by assessing the fillet lipidograms. Trout was utilized in this study as is know for the capacity to elongate and desaturate the n-3 long chain fatty acid EPA in DHA. The EPA/DHA ratio in feed and in fillet were expected to be modified by the fish, with an increased restitution of DHA as consequence of a reduction in EPA. Actually, such a dynamic was observed in fish fed with only 4 of the challenged commercial feed and that was supposed to be due to an effect on the fatty acids metabolism, following an unbalancement of the essential aminoacids in the diets where higher substitution of FM with VM was operated. In conclusion, a number of the expected negative effects due the FM substitution with VM have been actually assessed. On the same time, the possibility to mitigate such negative performances with diet manipulation have been documented as well. Beside some practical results immediately applicable by the fish farming industry, indications for further researches are emerging from this study

Fish health and fillet quality following substitution of fishmeal (FM) and fish oil (FO) with vegetable meal (VM) and oil (VO) in the modern aquaculture.

Plant proteins in vegetable meals (VM) and oils are used in an increasing percentage in diets for carnivorous fish to replace fish meal (FM) and fish oil (FO) in order to reduce production costs and to face the limitation of marine resources and to be sustainable in respect to the protection of oceanic biodiversity. However, several studies report that fish respond to such replacements by reducing growth rate, feed conversion and fillet quality. It may be due to a deficiency or poor availability in VM ingredients of some essential amino acids, but also to the occurrence of anti-nutritionals and inflammatory compounds acting on the fish intestine. This can lead to economic losses for fish farmers, increased fish diseases occurrence, and negative environmental impact. This study focuses on European sea bass and Rainbow trout, as two among the most commercially important fish species in Italy. Aims of the study are to improve feed formulation and optimize feed additives such taurine, as well as butyrate, salt of a short chain fatty acid (SCFA), to protect fish intestine and evaluate the effects on fish fillet quality of the modern commercial diets where FM is partially substitute with VM. In that context, our experimental study investigated butyrate and taurine in the diet, as nutraceutics able to reduce or minimize the negative effects of VM inclusion in fish performances and health. After improvement of analytical methods for butyrate titration in fecal samples, the possibility that a butyric fermentation occurs in fish intestine has been experimentally evaluated. The protective effect of butyrate on fish intestine has been studied by following approaches including histology with light and electronic microscopy, then a molecular approach to study inflammatory cytokines, as well as the epigenetic action of this SCFA. In spite, dietary butyrate showed no significant differences in weight gain or SGR (specific growth rate) of sea bass, the protective effect on the intestine walls was highlighted, together with its epigenetic effects on hiperacetylation histone H4 at lysine 8, while no effects has been found on the histone H3 at Lys9. A butyrate effect on the liver, as an increased transcriptional expression of the genes Dicer1, ehmt2, and hdac11 and il-10 have been assessed, suggesting an anti-inflammatory as well as an antiviral role of butyrate in seabass receiving a 2% of Na-butyrate as diet supplement. The effect of a dietary supplementation of the sulphonic aminoacid taurine, almost absent in the VM, was studied on seabass growth performances and on its potential role as antioxidant. Seabass fed with 1.5% taurine addition showed an increase of the fish growth performance and a marked reduction of the ROS production under resting conditions that was enhanced following forced swimming performances. The synergistic effect of butyrate and taurine as feed additives was also explored in seabass feeding diet containing an elevate concentration of a soy protein. Different cytological protective mechanisms have been observed, indicating the existence of a synergistic action of the two nutraceutical compounds. The quality of fish fillet in trout fed with 6 different commercial feed where FM was differently substituted by VM, has been studied by assessing the fillet lipidograms. Trout was utilized in this study as is know for the capacity to elongate and desaturate the n-3 long chain fatty acid EPA in DHA. The EPA/DHA ratio in feed and in fillet were expected to be modified by the fish, with an increased restitution of DHA as consequence of a reduction in EPA. Actually, such a dynamic was observed in fish fed with only 4 of the challenged commercial feed and that was supposed to be due to an effect on the fatty acids metabolism, following an unbalancement of the essential aminoacids in the diets where higher substitution of FM with VM was operated. In conclusion, a number of the expected negative effects due the FM substitution with VM have been actually assessed. On the same time, the possibility to mitigate such negative performances with diet manipulation have been documented as well. Beside some practical results immediately applicable by the fish farming industry, indications for further researches are emerging from this study

Forme latine in Orazio e Gadda - Tabella di confronto

No abstract availabl

LAB-CEG - Gadda, un autore al microscopio

No abstract availabl

Cooccorrenze Statistiche di

No abstract availabl

Electronic Archive of the Works by Emilio Gadda: from Compilers to users of a textual database

No abstract availabl