203 research outputs found
Component separation for all-sky CMB temperature maps
No full textThe work described in this Thesis is related to the PLANCK mission, scheduled for launch in 2008, which will observe the microwave sky with unprecedent resolution and sensitivity. The PLANCK collaboration involves hundreds of scientists and profits from the contributions of research groups in many countries. Among them, an Italian collaboration has a key role on component separation. This is a crucial step of the data reduction process, aimed at disentangling the Cosmic Microwave Background (CMB) and all the astrophysical components which are mixed in the nine observational channels of PLANCK The most important diffuse components are, besides the CMB, synchrotron, free-free and thermal dust emissions due to our own Galaxy. Moreover, the PLANCK maps will contain radio and infrared extragalactic sources as well as the Sunyaev-Zel'dovich effects from clusters of galaxies. All the components which mix with the CMB are referred to as ``foregrounds'', as they are placed between the CMB and the observer.
The main goal of component separation is to provide a map of the CMB, from which the relevant cosmological information will be derived, clean from foreground contamination. On the other hand, maps of astrophysical components are of great interest per se. The accuracy of the component separation process will ultimately set that of the final results PLANCK will provide.
Our work was mainly focused on the development and testing of a new method for the separation of diffuse foregrounds, the Correlated Component Analysis (CCA), proposed by Bedini et al. (2005). This technique exploits second-order statistics to estimate the ``mixing matrix'', which contains the frequency behavior of the components mixed in the data. It is necessary to adopt a model for such components, i.e. to parametrize their frequency scaling in a suitable way. Our approach is to estimate the mixing matrix separately in different regions of the sky, where the spectral dependencies of foregrounds can be assumed to be constant.
Once the mixing matrix is known, several methods are available to perform component separation, such as Wiener Filtering (WF), Maximum Entropy Method (MEM) or other Bayesian inversion techniques.
After having suitably implemented the CCA method, we tested its performances on simulated PLANCK data.
In Bonaldi et al. (2006) we applied the method to different sets of simulated PLANCK channels and estimated the errors on the mixing matrix with a Monte Carlo approach. The simulations included realistic diffuse foregrounds, with spatially varying spectral properties, and Gaussian noise at the nominal level for the PLANCK satellite.
This test showed that the method is efficient and that the errors on the mixing matrix estimation produce a minor contribution to the errors on the CMB power spectrum.
We then partecipated in a blind comparative test of component separation methods coordinated by the PLANCK working group on ``component separation''.
The test used a more sophisticated simulation of PLANCK data, which included, besides diffuse foreground emissions, also point sources and extragalactic background and a more realistic treatment of the noise. On these data, we tested CCA combined with harmonic Wiener Filtering. We focused on the reconstruction of the CMB map and on the power spectrum estimation, and obtained in both cases very good results, highly competitive with those provided with the best methods developed so far. We also got satisfactory reconstructions of Galactic dust emission, which is the dominant foreground in the highest resolution (high frequency) PLANCK channels.
In Bonaldi et al. (2007b) we tested the same strategy on real data i.e. the first three years of WMAP data. Our results are generally compatible with the result published by the WMAP team. We investigated the presence in the data of the so-called "microwave anomalous emission", an additional foreground component which could dominate in the lowest frequency WMAP channel (23 GHz). This component, revealed by cross correlations of microwave data with IR maps, appears to be correlated with thermal dust emission and has been interpreted as emission due to spinning dust grains (Draine & Lazarian 1998) or, alternatively, as synchrotron emission from dusty active star-forming regions (Hinshaw et al. 2006). We adopted various models for the frequency scaling of such component, whose properties are still poorly known.
We then applied several quality tests to the maps reconstructed for each model and selected a subset of models having a good compatibility with the data. We also managed to get the first, albeit preliminary, template of the anomalous emission over about 90% of the sky.
We then estimated how our imperfect knowledge of the foreground components affects the CMB power spectrum. To this end we compared the CMB power spectra obtained adopting different foreground models that passed our quality tests. A significant spread has been found for the largest scales, where anomalies of the WMAP power spectrum compared to the expectations from the best fit cosmological model have been reported. Taking into account modelization errors, we find no large scale power spectrum anomalies significant at > 1.5 sigma, except for the excess power at l=40,
which is significant at around the 4 sigma level.
A minor part of this Thesis was devoted to the study of the Sunyaev-Zel'dovich (SZ) effect, due to inverse Compton scattering of CMB photons by hot electrons in the astrophysical plasmas bound to the cosmic structures. PLANCK is expected to provide a big sample of galaxy clusters observed through the SZ effect. One exploitation of the PLANCK cluster sample is related to the study of the physics of the intra-cluster (IC) gas. In Bonaldi et al. (2007a) we investigated
the observable effects of different modeling of the physics of the IC gas.
Another research field related to the SZ effect concerns the study of the Large Scale Structure of the Universe. In Dolag et al. (2006) we analysed the SZ emission due to the so-called cosmic web, the network of filamentary structures which is now believed to connect galaxy clusters. The signal is too weak to be detected but its presence may bias the observed properties of galaxy clusters both in the X-ray band and in the microwaves
EoR imaging with the SKA: the challenge of foreground removal
No full textAbstract21-cm observations of the Cosmic dawn (CD) and Epoch of Reionization (EoR) are one of the high priority science objectives for SKA Low. One of the most difficult aspects of the 21-cm measurement is the presence of foreground emission, due to our Galaxy and extragalactic sources, which is about four orders of magnitude brighter than the cosmological signal. While end-to-end simulations are being produced to investigate in details the foreground subtraction strategy, it is useful to complement this thorough but time-consuming approach with simpler, quicker ways to evaluate performance and identify possible critical steps. In this work, I present a forecast method, based on Bonaldi et al. (2015), Bonaldi & Ricciardi (2011), to understand the level of residual contamination after a component separation step, and its impact on our ability to investigate CD and EoR.</jats:p
Active feedback cooling of a SiN membrane resonator by electrostatic actuation
No full textFeedback-based control techniques are useful tools in precision measurements as they allow us to actively shape the mechanical response of high quality factor oscillators used in force detection measurements. In this paper, we implement a feedback technique on a high-stress low-loss SiN membrane resonator, exploiting the charges trapped on the dielectric membrane. A properly delayed feedback force (dissipative feedback) enables the narrowing of the thermomechanical displacement variance in a similar manner to the cooling of the normal mechanical mode down to an effective temperature Teff. In the experiment reported here, we started from room temperature and gradually increasing the feedback gain, we were able to cool down the first normal mode of the resonator to a minimum temperature of about 124mK. This limit is imposed by our experimental setup and, in particular, by the injection of the read-out noise into the feedback. We discuss the implementation details and possible improvements to the technique.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and MaterialsEKL Equipmen
Sunyaev–Zel'dovich profiles and scaling relations: modelling effects and observational biases
No full textWe use high-resolution hydrodynamic resimulations to investigate the
properties of the thermal Sunyaev-Zel'dovich (SZ) effect from galaxy
clusters. We compare results obtained using different physical models
for the intracluster medium (ICM), and show how they modify the SZ
emission in terms of cluster profiles and scaling relations. We also
produce realistic mock observations to verify whether the results from
hydrodynamic simulations can be confirmed. We find that SZ profiles
depend marginally on the modelled physical processes, while they exhibit
a strong dependence on cluster mass. The central and total SZ emission
strongly correlates with the cluster X-ray luminosity and temperature.
The logarithmic slopes of these scaling relations differ from the
self-similar predictions by less than 0.2; the normalization of the
relations is lower for simulations including radiative cooling. The
observational test suggests that SZ cluster profiles are unlikely to be
able to probe the ICM physics. The total SZ decrement appears to be an
observable much more robust than the central intensity, and we suggest
using the former to investigate scaling relations
A novel strategy for syngas production through the oxy-gasification of pulp and paper mill sludge
No full textPulp and paper mill sludge (PPMS) is the main organic residual generated from the wastewater treatments of the pulp and paper industry. It is generally divided into primary sludge, characterised by cellulosic-rich fibre and ash, and secondary sludge, primarily composed of organic matter with a high microbial content. Due to the huge production of the paper-making industry, around 400 million wet tons of PPMS are produced annually. Nowadays, the management and disposal of PPMS are landfilling and/or incineration, incurring economic, environmental and social costs. The present work concerns the use of the gasification process as a promising valorisation method of primary and secondary PPMS, with the goal of the production of syngas. The syngas obtained by gasification is generally composed by CO, CO2, H2 and CH4, and it is commonly used as feedstock for the synthesis of key molecules within the chemical industry, such as methanol and hydrocarbons, or for plant energy recovery (heat or electricity generation). The composition of PPMS depends on several factors, however, due to the biological activity of secondary PPMS, only primary PPMS has been characterised, highlighting a total amount of 70 wt% of CaCO3 and 25 wt% of cellulosic fibre. The experimental activity has mainly focused on an oxy-gasification strategy. Initially, fir pellets were used as a benchmark, followed by experimentation with a blend of PPMS and wood pellets in a 1:4 wt/wt ratio. The gasification attempts have been conducted in a downdraft fixed bed reactor (≈100 KwTH) by adopting a mixture of O2/H2O as a gasifying agent. Notably, the co-gasification with both primary and secondary PPMS resulted in obtaining nitrogen-free syngas characterized by a high H2 content (40 mol%) and CO (21 mol%). However, only the syngas composition derived from primary PPMS has shown to be stable over time, displaying high values (≈80%) of Cold Gas Efficiency (CGE), which is an indicator of gasification effectiveness. Finally, the characterization of the side products, such as ash and tar (condensable hydrocarbon and aromatic molecules) has been also performed. In particular, FT-IR analysis revealed that the primary PPMS ash predominantly consisted of CaO. In conclusion, this work proposes the integrated valorization of PPMS through gasification, leading to a promising syngas composition for energy recovery and a high CaO content in gasification ash primary PPMS, which opened up possible strategies for its recovery and recycling
Chemical and thermochemical approaches for sustainable energy production starting from waste biomasses
No full textThe present work aims the valorisation of low-cost lignocellulosic feedstocks, as natural (Posidonia Oceanica) or industrial (paper mill sludge) wastes, for bio-fuel production respectively through chemical and thermochemical processes. In particular, Posidonia Oceanica has been chemically converted through a one-pot alcoholysis reaction for the production of alkyl levulinates, on the other hand, the paper mill sludge, one of the most abundant waste produced by the paper industry, was investigated as possible feedstock for syngas production through the gasification process. In conclusion, this work proposes the valorization of natural lignocellulosic residues and industrial wastes as low-value feedstock
Gasification of paper mill waste: a low-value feedstock for sustainable energy production
No full textIn the papermaking industry billions of tonnes of paper mill waste are globally produced every year. In the present work, the preliminary compositional analysis of the paper mill sludge has been carried out highlighting a high content of CaCO3 (70 wt%) and a minor amount of cellulosic fibre (30 wt%).Due to its features, the thermochemical treatment of paper mill sludge through gasification for syngas production could represent an innovative and strategic valorisation route. The gasification was carried out in a fixed bed (downdraft) reactor (≈100 kWTH), employing a mixture of O2/H2O or air as gasifying agents. Moreover, the characterization of the side products, as ash and tar, which is a mixture of condensable hydrocarbon and aromatic molecules, has been also performed. In conclusion, for the first time, this work proposes the integrated valorization of paper mill waste through the gasification process producing both the syngas for energetic purposes and ash that can be valorized recycling it within the same papermaking process
Urinary Incontinence and Other Pelvic Floor Dysfunctions as Underestimated Problems in People under Forty Years: What Is Their Relationship with Sport?
No full textUrinary incontinence is still an underestimated problem due to its anatomical complexity and social taboo. Most of the time, it is believed to affect predominantly the elderly female population, and the literature still lacks data on its presence in the younger and male populations. Its relationship with other pelvic floor dysfunctions (PFDs) and sport activity remains an open topic. Thus, the present study surveyed 342 subjects of both genders, ranging from 18 to 39 y/o and with different sport activity levels, to understand the prevalence of PFDs (such as haemorrhoids, anal fissures, involuntary urinary/faecal leakage, and urgency). The results also showed a significative prevalence in younger, sporty, and male people. Approximately one third of the population had urinary incontinence mostly during stress activities (sport activity: 17%, cough/sneeze: 13%). The statistical analysis confirmed a higher prevalence in the cases of a light (32%) and intense (41%) sport activity level and a protective role of sport if practiced between 5 and 10 h/week, with bodybuilding/CrossFit and running seeming to be the riskiest sports. The relationship with the other PFDs showed a statistically significant dependence with most of them, confirming that urinary incontinence cannot be considered a separate problem from the other PFDs
Frequency-noise cancellation in optomechanical systems for ponderomotive squeezing
No full textPonderomotive squeezing of the output light of an optical cavity has been recently observed in the megahertz range in two different cavity optomechanical devices. Quadrature squeezing becomes particularly useful at lower spectral frequencies, for example, in gravitational wave interferometers, despite being more sensitive to excess phase and frequency noise. Here we show a phase and frequency-noise cancellation mechanism due to destructive interference which can facilitate the production of ponderomotive squeezing in the kilohertz range and we demonstrate it experimentally in an optomechanical system formed by a Fabry-P´erot cavity with a micromechanical mirror.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc
Multivariate approach for the optimization of sucrose ethanolysis: Paving the way to the exploitation of sucrose-rich by-products
No full textThe depletion of fossil resources is making the synthesis of renewable compounds urgent. Ethyl levulinate (EL) represents a strategic compound within the biorefinery process, being a valuable intermediate, solvent and biofuel additive of renewable origin. The one-pot ethanolysis is the preferred route for its synthesis, but the proper optimization of the reaction conditions to maximize the EL yield and minimize the critical by-products formation, diethyl ether (DEE) and humins, is still a challenge. In this regard, the present work aims at the optimization of sucrose ethanolysis through the multivariate approach, adopting H2SO4 as catalyst and following the high gravity approach (10.5 wt% sucrose loading), which allows the obtaining of concentrated EL streams, increasing productivity and making downstream operations easier and cheaper. The optimization allowed a compromise between the highest EL yield and the lowest DEE production, thus simplifying EL purification and consuming less solvent that can be recycled in the following run. Under these conditions, the humins formation was also kept low and, for the first time, not only the solid humins were characterized, proving to be suitable as solid fuel turning into a co-product of the process, but also the chemical structure of the soluble ones was investigated. For the first time, a preliminary study regarding the ethanolysis of thick juice was also performed, thus opening the way to the employment of low-cost sucrose-rich feedstocks as substrate for the synthesis of EL. Thus, this work contributes to making the synthesis of a strategic renewable compound as EL more sustainable
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