171,471 research outputs found
New TiO2 based photocatalysts for the degradation of organic pollutants in water
No full textIn the last years a new category of TiO2 based composites prepared by impregnation of bare polycrystalline TiO2 powders with different sensitizers (i.e. phthalocyanines, porphyrins) permitted the improvement of the photocatalytic degradation of 4-nitrophenol (4-NP) under UV1-3 as well as under visible light irradiation.4 On the other hand growing interest devoted to the photodegradation of organic pollutants in water solutions by means of economically advantageous and environmental friendly processes are regarding this topic.
Continuing our research in this area, we report here our recent results concerning: i) the preparation of new TiO2 and TiO2 based photocatalysts containing Fe and Cu species; ii) improvement of the photodegradation processes and conditions.
1. Mele, G.; Del Sole, R.; Vasapollo, G.; García-López, E.; Palmisano, L.; Schiavello, M. J. Catal. 2003, 217, 334. 2. Mele, G. ; Del Sole, R.; Vasapollo, G.; Marcì, G.; Garcìa-Lòpez, E.; Palmisano, L.; Coronado, J. M.; Hernández-Alonso, M. D.; Malitesta, C.; Guascito, R. J. Phys Chem. B 2005, 109, 12347. 3. Mele, G.; García-López, E.; Palmisano, L.; Dyrda, G.; Słota, R. J. Phys. Chem. C, 2007, 111, 6581. 4. Wang, C.; Li, J.; Mele, G.; Yang, G. M.; Zhang, F. X.; Palmisano, L.; Vasapollo, G. Appl. Catal. B: Environ. 2007, 76, 218
Special needs and characteristic features of (photo)catalytic reactors with a review of the proposed Solutions
No full textIn the present chapter, the analogies between photocatalytic systems and the systems where the more common thermally activated reactions take place are highlighted. The objective is to propose a unified approach for the analysis and the design, which, however, must take into account how and why photocatalytic reactors differ from reactors with thermal reactions. The necessity of absorbing photons to activate the photocatalytic process adds complexity to the system, but some approaches are presented to simplify the problems and make easier their solution
A Fourier optics approach to the dynamical theory of X-ray diffraction – continuously deformed crystals
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DINAMICA DELL’ACQUA SULLA SUPERFICIE DI UN BIOSSIDO DI TITANIO NANOSTRUTTURATO SINTETIZZATO IN LABORATORIO
No full textUn campione biossido di titanio sintetizzato in laboratorio è stato ottenuto mediante idrolisi di TiCl4
in acqua deionizzata (rapporto in volume 1:10) a temperatura ambiente. Dopo 12 h di agitazione la
soluzione trasparente è stata portata all’ebollizione per 0.5 h per ottenere la sospensione finale.
La sospensione è stata quindi seccata alla temperatura di 50°C per ottenere il catalizzatore in
polvere. Successivamente, la polvere così ottenuta è stata lavata e centrifugata diverse volte allo
scopo di ridurre fino a valori trascurabili la concentrazione di ioni cloruro nell’acqua di lavaggio. Il
catalizzatore così ottenuto è stato denominato HP0.5 (Home Prepared bollito per 0.5 h) [1].
Un grammo di tale prodotto è stato sospeso in 3 mL di acqua e sottoposto a sonicazione per 10
minuti. Dopo sedimentazione notturna, la componente solida, non separata dalla fase acquosa, è
stata sottoposta ad analisi in rilassometria NMR a ciclo di campo a 4 diverse temperature: 25, 40, 60
e 70°C [2].
I profili ottenuti si possono dividere in due parti. La prima parte, nell’intervallo di frequenze di
Larmor protoniche compreso tra 10 e 0.9 MHz, mostra un andamento lineare la cui pendenza non
viene influenzata dalle variazioni di temperatura. Questo comportamento è tipico di acqua
fortemente legata alla superficie di un mezzo poroso. Per effetto della forte i nterazione con la
superficie del biossido di titanio, la dinamica dell’acqua non risente di fluttuazioni nel range di
temperature utilizzato.
Nell’intervallo di frequenze di Larmor protoniche 0.8-0.01 MHz si osserva un andamento del
profilo di tipo Lorentziano in cui i valori delle velocità di rilassamento in funzione della
temperatura indicano una dinamica dell’acqua ascrivibile ad un regime di moto veloce.
Il comportamento rilassometrico dell’acqua sulla superficie del biossido di titanio nanostrutturato
preparato in laboratorio in funzione della temperatura, consente di ipotizzare che esistono due strati
di acqua intorno alla superficie del TiO
2
. Il primo è uno strato di acqua immobilizzata, circondato
da un secondo strato di acqua mobile. E’ proprio la presenza di acqua fortemente legata e
difficilmente rimovibile nell’intervallo di temperature investigato che rende conto della scarsa resa
cinetica del catalizzatore in esame rispetto ad anatase cristallino.
Riferimenti bibliografici
[1] M. Addamo, V. Augugliaro, A. Di Paola, E. García-López, V. Loddo, G. Marcì, R. Molinari,
L. Palmisano, M. Schiavello, Preparation, characterization and photoactivity of
polycrystalline nanostructured TiO
2
catalysts, J. Phys. Chem. B, 108 (2004) 3303-3310.
[2] P. Conte, V. Loddo, C. De Pasquale, V. Marsala, G. Alonzo, L. Palmisano, Nature of
interactions at the interface of two water-saturated commercial TiO
2
polymorphs, J. Phys.
Chem. C, 117 (2013) 5269-5273
An easily applicable method to analyse the ankle-foot power absorption and production during walking
No full textBackground: Power and work at the ankle joint during gait are usually computed considering the foot as a rigid body [1–6] (Ankle Joint method, AJ). The foot is instead a deformable structure and can absorb and produce work by pronation/supination, foot arch deformation and other intrinsic movements. A different approach, named “the Distal Shank method (DS)” [7–12] considers all these aspects without increasing the complexity of the protocol, and thus it seems promising for clinical applications [12]. Research questions: a) To characterize the differences in power and work computed using the two mentioned methods for a relatively large number of subjects walking at different velocities, barefoot and with different shoes; b) To assess the practical feasibility of the DS method for clinical applications. Materials and methods: Eighteen healthy subjects were evaluated while walking barefoot at slow, natural and fast velocity. Shod walking was analysed at natural velocity. Four subjects were also analysed while walking in high-heel shoes. The power at the ankle joint was computed with both the AJ and the DS methods. We then compared the obtained results. Results: The DS method showed a consistent negative peak of power absorption during the load acceptance phase, barely visible with the AJ method. The maximum power production calculated with the DS method was significantly lower. The work at the end of the stride cycle was lower with the DS method, and in most conditions even negative, thus indicating higher energy dissipation. Significance: We confirmed on a large cohort of healthy subjects and in different walking conditions that neglecting foot deformations during gait leads to underestimate power absorption and overestimate power production. The DS method does not require a complex gait analysis protocol, nor additional time for the analysis, and can provide information of clinical interest, related to foot mechanical alterations
Optimization of statistical methods for HpGe gamma-ray spectrometer used in wide count rate ranges
No full textThe need to perform gamma-ray measurements with HpGe detectors is a common technique in many fields such as nuclear physics, radiochemistry, nuclear medicine and neutron activation analysis. The use of HpGe detectors is chosen in situations where isotope identification is needed because of their excellent resolution. Our challenge is to obtain the "best" spectroscopy data possible in every measurement situation. "Best" is a combination of statistical (number of counts) and spectral quality (peak, width and position) over a wide range of counting rates. In this framework, we applied Bayesian methods and the Ellipsoidal Nested Sampling (a multidimensional integration technique) to study the most likely distribution for the shape of HpGe spectra. In treating these experiments, the prior information suggests to model the likelihood function with a product of Poisson distributions. We present the efforts that have been done in order to optimize the statistical methods to HpGe detector outputs with the aim to evaluate to a better order of precision the detector efficiency, the absolute measured activity and the spectra background.Reaching a more precise knowledge of statistical and systematic uncertainties for the measured physical observables is the final goal of this research project. (C) 2015 Elsevier B.V. All rights reserved
GC-MS identification of a novel N3-methylated metabolite of 5’-deoxy-5-fluorouridine in serum of cancer patients under chemotherapy J.Pharm.Biom.Anal. 14 (1996) 1521-28
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