188,385 research outputs found
Simulation and optimization of power-programmed sdfff: Applications for fractionating and characterizing submicrometer particulate matter in river water
No full textThe submicrometer fraction of the particulate matter suspended in river water is characterized by decay- programmed sedimentation field-flow fractionation (SdFFF). The power program was chosen because of its ability to yield a homogeneous fractionating power with respect to the analysis of broadly dispersed particulate samples. An appropriate search for the optimum power program setup is performed by numerical simulation. Comparison between simulated and experimental fractograms proves to be feasible in establishing the physical features of the sample (i.e., number of components, their relative dimensions, polydispersity, and absolute amount). A method is presented coupling SdFFF with electron microscopy (EM) techniques. Both the separation achieved and the sample model on which SdFFF simulation has been based are then verified using this coupled approach. Examples of EM morphological characterization on SdFFF-fractionated samples of river-borne particulate matter are reported. Under optimized power programming conditions, some effects of particulate sample treatments on SdFFF fractograms are presented. Chemical oxidation and sample aging are shown to influence the SdFFF- based, dimensional distribution of the particles. © Oxford University Press 1992
Atlas Of Pediatric Ocular Oncology
No full textThis atlas-book was conceived in the dark evenings during the Covid pandemic to keep the
mind busy, not only mine but also the young residents of our clinic.
The images that enrich each chapter are part of a life of over 30 years dedicated to ocular
oncology, mainly of the pediatric age.
A passion and commitment transmitted by my mentor Prof. Frezzotti who treated the first
retinoblastoma in 1959.
So here, I find myself collecting the most significant images of hundreds of clinical cases
faced, diagnosed and treated over the years.
Retinoblastoma is obviously the largest part of this atlas due to the over 900 cases observed
and treated in Siena.
It took almost 3 years...because unfortunately the time left to write, study and publish is
the evening hours after long and tiring days of clinical care activities.
My long friendship, collaboration and growth together with Paolo Galluzzi has allowed us
to add to each chapter MRI notions useful in the differential diagnosis of various pathologies.
My friend Rana’a helped correct some chapters and give his contribution on ocular mela-
noma in pediatric age.
Good friends and colleagues have been added among the collaborators for sending unu-
sual and rare cases.
I thank Tero Kivela, Sonia De Francesco, Tommaso Bacci, Marco Mazza, Mattia Pasti,
Alfonso Cerase, Lucia Monti, Mario Fruschelli and Cristina Menicacci for their precious
contributions.
An affectionate thought goes to all the young residents who, with great enthusiasm, em-
braced the topics assigned to them and carried out the various chapters with curiosity and
interest.
The drawings were all done by the talented resident Dimitris Pollalis who gave a truly
artistic touch to this atlas.
This book is dedicated to all ophthalmologists, of all ages, who are passionate, curious and
fascinated by their work with the hope that the hundreds of images can help to recognize
unusual and complex cases
Fourier analysis of multicomponent chromatograms. Numerical evaluation of statistical parameters
No full textA procedure based on the power spectrum (PS) model of a multicomponent chromatogram is introduced by which the number m of detectable components (or single-component peaks) and the parameters of the single-component peak such as standard deviation and asymmetry factor can be evaluated. In essence, when fitted to theoretical models, the experimental PS-expressing the chromatographic response variance dependence on the time distance-provides the Information necessary to accept or reject the model and to give the necessary parameter estimations. The procedure is tested by using computer-generated multicomponent chromatograms with Poissonian retention time distribution and random and uncorrelated peak heights, in which density, asymmetry and height distribution are widely varied. How to obtain unbiased PS numerical determination by windowing is also discussed. It Is shown that unbiased parameter estimations are obtained, the only procedure limitation being the approximation made In the evaluation of the single-component peak height dispersion. An example Is given of how a retention time distribution other than the Poissonian can be detected. © 1990, American Chemical Society. All rights reserved
Location of pharmaceuticals adsorbed from water on Y organophilic zeolite by neutron powder diffraction
No full textIn the last decade, it was demonstrated that domestic wastewaters contain a variety of organic contaminants such as pharmaceuticals and personal care products. Most of these compounds undergo both incomplete removal in wastewater treatment plants and slow natural degradation, consequently they are found in surface waters receiving effluent from treatment plants [1]. Pharmaceuticals can also be found in surface waters due to their veterinary use, in such cases they enter the environment via manure dispersion and animal excretion onto soils [2]. Studies on conventional biological drinking-water treatment processes such as biofiltration have shown that they are largely ineffective in removing pharmaceuticals [3].
In literature, several works focused on advantages of zeolites as adsorbents, such as high selectivity, rapid kinetics, reduced interference from salt and humic substances [4], excellent resistance to chemical, biological, mechanical and thermal stress [5-7 and references therein]. Even if zeolites are more expensive with respect to other adsorbents, they offer the possibility to be regenerated without loss of performances at relatively low temperatures [8-10].
In this work, the removal of three different pharmaceuticals (atenolol C14H22N2O3, ketoprofen C16H14O3, diclofenac C14H11Cl2NO2) from water by high-silica organophilic zeolite Y (with a SiO2/Al2O3 ratio equal to 200) will be investigated. All selected drugs differ in chemical properties and molecular dimensions and are ubiquitous contaminants in the sewage waters, while not being effectively removed by conventional activated sludge treatment and membrane bioreactors (MBRs).
Despite the large effort devoted to these studies, up to now, a limited number of investigations on drugs-loaded zeolites have been carried out by X-ray or neutron diffraction to obtain the location and population of atoms sites [4-7, 9-10]. The present study is designed to determine the contribution of hydrogen bonding, hydration and dynamics to the thermostability of selected pharmaceuticals adsorbed onto zeolites from water. Neutron diffraction has been shown to be a powerful technique for locating light atoms even at medium resolution. By using the deuterated forms of the target pharmaceuticals almost all accessible labile H atoms (i.e., most of those in O-H and N-H groups) will been replaced by D atoms thus increasing the overall scattering power of the crystal for neutrons and cancelling the negative scattering density of H atoms which tends to reduce the positive density of other atoms. Additionally, deuteration also reduces the incoherent scattering from hydrogen in the sample as well as the background scattering thus increasing the diffraction signal. Finally, the extent of H/D exchange in the OH/COOH groups, as determined in neutron Fourier maps, directly reflects local dynamics in the drugs structure.
This experimental technique has already been used by our group to determine the population and location of hydroxyls in deuterated and calcined D-ferrierite [11-12], mordenite [13] and heulandite [14] and very recently zeolite L (proposal 5-22-744 ) by using the data collected at D2B beamline (ILL, Grenoble).
The aim of this proposal is to determine the number and location of adsorbed-drugs sites in zeolite Y, the synthetic counterpart of natural faujasite, via powder neutron diffraction. Zeolite Y is a large pore material which crystallizes in the cubic space group Fd-3m, with a lattice constant ranging from about 24.2 to 25.1 A, depending on the framework aluminium concentration, cations, and state of hydration. The pore structure is characterized by approximately 12A diameter cages, linked through access windows ( 7.0A×7.1A in diameter) and thus permitting quite large molecules to enter, making this structure potentially useful in the adsorption of thedrugs under study. The sample to be used in this project is a synthetic commercial zeolite Y (code HSZ-390HUA) with a 200 SiO2/Al2O3 (mol/mol) ratio, purchased in its protonated form from the Tosoh Corporation (Japan). We plan to collect three samples of zeolite Y powders (Atenolol-Y, diclofenac-Y and ketoprofen-YL, respectively). In particular, all samples will be obtained by the ion exchanging the as-synthesized form with deuterated drugs in aqueous solution for ≈140 h at room temperature and then washed with D2O. All samples will be packed in our laboratory in an argon-flushed glove-bag into a vanadium container sealed with a rubber gasket to ensure humidity-free transport to the neutron source. Powder diffraction data will be preferentially collected at the D2B beamline, with satisfactory counting statistics in order to allow full Rietveld refinements of all datasets. The powder data will be processed using the GSAS package. The location of extraframework species will be carried out by a combination of least squares and Difference Fourier map techniques.
To achieve these results high resolution at high-q is mandatory to obtain powder diffraction data for accurate Rietveld refinement. The proposed D2B instrument will dramatically expand the knowledge of drugs adsorption on zeolites, allowing large chemical complexes and a range of pharmaceuticals to be studied.
References
[1] Martucci, A., Braschi, I., Marchese, L., & Quartieri, S. (2014) Mineral. Mag., 78(5), 1115. [2] Figueroa R.A., Leonard A., MacKay A.A. (2004) Environ. Sci. Technol. 38, 476. [3] Ternes T.A., Meisenheimer M., McDowell D., Sacher F., Brauch H.J., Haist- Gulde B., Preuss G., Wilme U., Zulei-Seibert N. (2002) Environ. Sci. Technol. 36, 3855. [4] Braschi I., Martucci A., Blasioli S., Mzini L. L., Ciavatta C., & Cossi M. (2016) Chemosphere, 155, 444. [5] Martucci A., Pasti L., Marchetti N., Cavazzini A., Dondi F., Alberti A. (2012) Micro. Meso. Mater. 148, 174. [6] Pasti L., Sarti E., Cavazzini A., Marchetti N., Dondi F., Martucci, A. (2013) J. Sep. Sci. 36, 1604.[7] Braschi I., Blasioli S., Gigli L., Gessa C.E., Alberti A., Martucci A. (2010) J. Hazard. Mater. 17, 218. [8] Rodeghero E., Martucci A., Cruciani G., Bagatin R., Sarti E., Bosi V., Pasti L. (2016) Catal. Today 227, 118. [9] Martucci A., Rodeghero E., Pasti L., Bosi V., Cruciani G. (2015) Micro. Meso. Mater. 215, 175. [10] Braschi I., Blasioli S., Buscaroli E., Montecchio D., & Martucci A. (2016). J. Env. Sciences, 43, 302. [11] Martucci A., Alberti A., Cruciani G., Radaelli P., Ciambelli P., Rapacciuolo M., (1999) Micro. Meso. Mater., 30, 95. [12] Alberti A. and Martucci A. (2010) J. Phys. Chem. C 114, 7767. [13] Martucci A., Cruciani G., Alberti A., Ritter C., Ciambelli P., Rapacciuolo M., (2000) Micro. Meso. Mater. 35–36, 405. [14] Martucci A., Parodi I., Simoncic P., Armbruster T., Alberti A. (2009), Micro. Meso. Mater. 123, 15
SIMULATION OF FRACTOGRAMS OF FAT EMULSIONS IN POWER-PROGRAMMED SEDIMENTATION FIELD-FLOW FRACTIONATION (SDFFF)
No full textA quasi-empirical approach to the simulation of fractograms was examined to verify that the elution behavior of emulsions in power-based field programmed sedimentation field-flow fractionation (SdFFF) is consistent and predictable. The approach was applied to Intralipid, a commercial soybean emulsion and to an investigational medium chain triglyceride emulsion. The simulations predicted the fractograms that were obtained under various conditions of field strength, field decay and velocity of the suspending fluid, using distribution parameters obtained from one preliminary measurement of size distribution profile. Predicted fractograms were compared to experimental ones, under various fractionating powers. Good agreement was observed in most cases, in which interference of the secondary relaxation effects was not effective. The agreement confirmed the applicability of the approach to emulsions and that the simulations can be used instead of actual experiments for the optimization of their characterization by power-programmed SdFFF. © 1995
L’educazione ambientale: un percorso scolastico quinquennale finalizzato allo studio delle trasformazioni dovute al cambiamento globale ed alle pressioni antropiche in ecosistemi di transizione
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Optimization of signal denoising in discrete wavelet transform
No full textA method to optimize the parameters used in signal denoising in the wavelet domain is presented. The method, which is based on cross-validation CV.procedure, permits to select the best decomposition level and the best wavelet filter function to denoise a signal in the discrete wavelet domain. The procedure was validated by using computer generated signals to which white noise was added. Signals having different features and a range of signal to noise ratios were explored. The method was shown to give reliable results for all cases studied. The proposed method was applied to experimental gravitation field flow fractionation records, and the results were compared with classical low pass filtering in the Fourier domain
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