Spectral filtering for the resolution of the Gibbs phenomenon in MPI applications

open3Polynomial interpolation on the node points of Lissajous curves using Chebyshev series is an e effective way for a fast image reconstruction in Magnetic Particle Imaging. Due to the nature of spectral methods, a Gibbs phenomenon occurs in the reconstructed image if the underlying function has discontinuities. A possible solution for this problem are spectral filtering methods acting on the coefficients of the interpolating polynomial. In this work, after a description of the Gibbs phenomenon in two dimensions, we present an adaptive spectral filtering process for the resolution of this phenomenon and for an improved approximation of the underlying function or image. In this adaptive filtering technique, the spectral filter depends on the distance of a spatial point to the nearest discontinuity. We show the effectiveness of this filtering approach in theory, in numerical simulations as well as in the application in Magnetic Particle Imaging.openDe Marchi, Stefano; Erb, Wolfgang; Marchetti, Francesco.DE MARCHI, Stefano; Erb, Wolfgang; Marchetti, Francesc

Spectral filtering for the reduction of the Gibbs phenomenon of polynomial approximation methods on Lissajous curves with applications in MPI

Polynomial interpolation and approximation methods on sampling points along Lissajous curves using Chebyshev series is an effective way for a fast image reconstruction in Magnetic Particle Imaging. Due to the nature of spectral methods, a Gibbs phenomenon occurs in the reconstructed image if the underlying function has discontinuities. A possible solution for this problem are spectral filtering methods acting on the coefficients of the approximating polynomial. In this work, after a description of the Gibbs phenomenon and classical filtering techniques in one and several dimensions, we present an adaptive spectral filtering process for the resolution of this phenomenon and for an improved approximation of the underlying function or image. In this adaptive filtering technique, the spectral filter depends on the distance of a spatial point to the nearest discontinuity. We show the effectiveness of this filtering approach in theory, in numerical simulations as well as in the application in Magnetic Particle Imaging

Structural adjustment, ownership transformation, and size in Polish industry

The authors argue that significant adjustment took place in Polish industry after Poland's 1990 reforms. They analyze data on two- and three-digit manufacturing industries, disaggregated by firm ownership and size. By applying a statistical model to labor productivity growth, they try to disentangle structural determinants of the recovery from cyclical determinants. They contend that structural determinants outweigh cyclical ones. They find that the productive response of state enterprises was markedly different from that of private firms--private firms outperformed state enterprises (just as anecdotal evidence suggested). Size also matters, at least among private firms. Generally, there seem to be increasing returns to scale for private firms, except for very large enterprises (many of which were previously state-owned and may need further restructuring). The fact that size does not appear to matter among public enterprises suggests that several of them have not yet adopted optimal technologies and production processes.Banks&Banking Reform,Municipal Financial Management,Labor Policies,Environmental Economics&Policies,Economic Theory&Research,Environmental Economics&Policies,Banks&Banking Reform,Municipal Financial Management,Economic Theory&Research,Health Monitoring&Evaluation

Integrating Survey and Administrative Data on Local Social Protection

Welfare systems can be observed according to two different perspectives. The former deals with the supply of social protection, i.e. with the funding and provision of social benefits and the production of social services and goods. The latter focuses on the demand of social protection, and particularly on the characteristics of people benefiting from social protection or asking for it. Typically, data on the supply of social benefits have an administrative nature (registers and budgets data) whereas data on beneficiaries come from sample surveys. In theory, administrative data, being census data, can be detailed by territory. On the contrary, sample surveys are usually planned to provide accurate estimates at the national level or for large sub-national areas. This chapter provides an example on the use of different data sets for the Old age and Family/children functions at the province level (LAU 1 in the EU nomenclature). Data on the supply of benefits derive from the SISSIM (Istat Survey on Interventions and Social Services of Individual and associated Municipalities) and from municipalities' budgets. Data on the demand of social protection come from EU-SILC (European Union - Statistics on Income and Living Conditions), a survey that is annually conducted by Istat in a comparable European framework. Earned benefits are estimated applying small area estimation methods, given that the sample size of the EU-SILC survey at the province level is small, so the traditional design-based estimators usually are unreliable. Results are analysed to understand whether administrative and sample survey data can be used to to compose a coherent picture of social protection delivered at the provincial level

The reactivity of niobium and tantalum pentahalides with imines

The reactivity of NbCl5, NbF5 and TaCl5 with a selection of commercial imines was investigated for the first time by using dichloromethane as reaction medium. NbCl5 reacted with Ph2C=NH, in 1:2 molar ratio, affording [Ph2C=NH2][NbCl5(N=CPh2)], 1, in 55% yield, as result of imine self-protonation. The iminium salt [PhCH=NHtBu][NbCl6], 2, was isolated in 52% yield from NbCl5 and PhCH=NtBu (1:1 molar ratio), while a low yield of [tBu2C=NH2][NbCl6], 3, was identified from NbCl5/tBu2C=NH. The 1:1 reactions of NbF5 with Ph2C=NH and PhCH=NtBu were accompanied by electron interchange and led to the isolation of the salts [Ph2C=NH2][NbF6], 4, and [PhCH=NHtBu][NbF6], 5, respectively, in ca. 50% yields. Few crystals of [Ph2C=NH2]2[Ta2Cl10O], 6, were recovered from TaCl5/Ph2C=NH, the anion being probably generated by the action of adventitious water. Compounds 1-6 were characterized by elemental analysis, IR and NMR spectroscopy. The structures of 1, 4 and 6 were ascertained by X-ray diffraction studies

The use of Twitter data to improve small area estimates of households’ share of food consumption expenditure in Italy

The use of big data in many socio-economic studies has received a growing interest in the last few years. In this work we use emotional data coming from Twitter as auxiliary variable in a small area model to estimate Italian households’ share of food consumption expenditure (the proportion of food consumption expenditure on the total consumption expenditure) at provincial level. We show that the use of Twitter data has a potential in predicting our target variable. Moreover, the use of these data as auxiliary variable in the small area working model reduces the estimated mean squared error in comparison with what obtained by the same working model without the Twitter data

The reactivity of MoCl5 with molecules containing the alcohol functionality

The 1:1 M reaction of MoCl5 with Cl(CH2)2OH, in dichloromethane at room temperature, proceeded with chlorine–oxygen interchange and HCl release to give MoOCl3 in 65% yield. The analogous reactions involving iPrOH, MeOH, L-menthol and H2O gave impure MoOCl3. MoCl5 reacted with Me2N(CH2)2OH in 1:1 M ratio affording the 2-chloroammonium salt [Me2NH(CH2)2Cl]2[Mo2O2Cl8], 1. The reaction of MoCl5 with MeO(CH2)2OH afforded a mixture of [Mo(O(CH2)2OMe)2Cl2][Mo2O2Cl7], 2a, and [Mo(O(CH2)2OMe)2Cl2][MoOCl4], 2b. The products 1, 2a and 2b were characterized by analytical and spectroscopic techniques, and by X-ray diffractometry. The X-ray structure of 2b shows weak anion–anion interactions, therefore 2b might be alternatively viewed as a [Mo2O2Cl8]2- salt

METODI DI STIMA PER PICCOLE AREE APPLICATI ALLE INDAGINI CORRENTI IN AGRICOLTURA IN ITALIA

La tesi tratta della stima per piccoli domini usando dati campionari riferiti all'intero dominio utilizzando il modello lineare ad effetti misti e l'autocorrelazione spaziale. Si presentano in questo lavoro i metodi di stima per piccole aree, con particolare attenzione agli stimatori noti some EBLUP e EBLUP Spaziale (Spatial EBLUP), un caso di simulazione per testare l'efficienza degli stimatori e un'applicazione a dati reali, relativi all'indagine sulla struttura e produzione delle aziende agricole in toscana