Determination of the geographical origin of green coffee beans using NIR spectroscopy and multivariate data analysis

In this work, near infrared (NIR) spectroscopy and multivariate data analysis were investigated as a fast and non disruptive method to classify green coffee beans on continents and countries bases. FT-NIR spectra of 191 coffee samples, origin from 2 continents and 9 countries, were acquired by two different laboratories. Laboratory-independent Partial Least Square-Discriminant Analysis and interval PIS-DA models were developed by following a hierarchical approach, i.e. considering at first the continent and then the country of origin as discrimination rule. The best continent-based classification model was able to identify correctly more than 98% in prediction, whereas 100% of them were correctly predicted by the best country-based classification model. The inter-laboratory reliability of the proposed method was confirmed by McNemar test, since no significant differences (P > 0.05) were found. Furthermore, a validation was performed predicting the spectral test set of a laboratory using the model developed by the other one

Optical response with threefold symmetry axis on oriented microdomains of opal photonic crystals

The paper deals with three-dimensional photonic crystals known as artificial opals, namely, fcc lattices of dielectric spheres: such systems have been the subject of numerous investigations. Opal photonic crystals viewed along the [111] direction of the fcc structure have a threefold symmetry axis; however this microscopic symmetry is difficult to observe in optical measurements performed on macroscopic areas containing microdomains with different orientations. In this work polarized transmittance measurements on [111]-stacked silica opals with single oriented microdomains, identified by field-emission scanning electron microscopy and laser-scanning confocal microscopy, demonstrate different optical response of twin structures with the two possible vertical stacking sequences. A detailed comparison with theory shows that microtransmittance experiments probe the photonic band structure along the Gamma-L-K and Gamma-L-U orientations of the Brillouin zone, respectively, thus giving conclusive evidence for macroscopic optical response related to the presence of a threefold (instead of a sixfold) symmetry axis in the photonic microstructure. The paper arises from a collaboration between the University of Pavia and the Politecnico di Torino

Electrical Properties of Meso-Porous Silicon: from a surface effect to Coulomb Blockade and more

Abstract: since the Volker Lehmann's paper "Resistivity of Porous Silicon: a surface effect" published in 1995 [1], a great deal of efforts has been produced in understanding the basic mechanisms ruling the electron transport in Si mesostructures and how these phenomena are affected by external environment. After more than 10 years, new experimental evidences and physical insights have been obtained, like gas sensitivity [2], chemisorption phenomena [3], Coulomb blockade [4] and glassy dynamics In the first half of the '90s, the most studied porous silicon morphology was from high resistivity p-type wafers, because of the high luminescence efficiency. The Lehmann's paper on electrical properties of porous silicon from p+ doped wafers, addressed few unanswered crucial questions regarding resistivity, impurity role, carrier freeze out and surface conditioning proposing a microscopic model of transport in mesoPS, in analogy to submicron channels of CMOS devices, whose figures of telegraph noise are affected by single charge trapping at the oxide-semiconductor interface. In 1999, the first report of strong interaction between mesoporous p+ silicon was announced in Strasbourg, EMRS by our group The successive years were so devoted to a fundamental study of mesoporous silicon in interaction with gas, by means of IR spectroscopy, ESR, NMR and ab-initio calculations Since the former paper of 1999 other groups contributed to study the phenomenon of NO 2 interaction with detailed papers on IR spectroscopy and Drude effect due to free carriers restored by nitrogen dioxid

Monitoraggio on-line del processo di tostatura del caffè mediante spettroscopia NIR

La principale trasformazione del caffè prima della commercializzazione è rappresentata dalla tostatura, processo che influenza pesantemente le caratteristiche organolettiche della bevanda. A livello industriale, per soddisfare le aspettative dei consumatori legate ad una qualità costante, il processo richiede un controllo molto attento. Il monitoraggio del colore del caffè durante la tostatura potrebbe costituire uno strumento molto importante per valutare in tempo reale le performance del processo e garantirne la riproducibilità. In questo lavoro viene descritta l’applicazione di un sistema on-line per il monitoraggio del processo di tostatura del caffè, eseguito su un tostino da laboratorio. Il controllo di processo è realizzato utilizzando una sonda nel vicino infrarosso (Bruker Optics, Germania) posta all’interno del tostino (Probat, Germania). E’ stata esaminata l’influenza sul colore di diverse variabili sperimentali: la varietà di caffè (Arabica, Robusta e miscele 50/50 p/p), la temperatura (sono stati considerati 4 diversi valori), e l’umidità iniziale dei chicchi; sono stati acquisiti un totale di 800 spettri durante 65 esperimenti di tostatura. Per ottenere il modello di predizione sul colore di tostatura viene utilizzata la Partial Least Square; sono stati utilizzati i parametri Hotelling T2 e i residui Q per valutare la presenza di campioni outliers. Il modello ottenuto presenta una buona capacità predittiva per la determinazione del colore di tostatura con un RMSECV pari all'1,5 U.A. (in Fig. 1 è riportato il grafico del valore predetto vs. reale del colore). Questo studio conferma l’applicabilità della spettroscopia NIR per il monitoraggio on-line del processo di tostatura del caffè. Dopo un’ottimizzazione del metodo si prospetta l’implementazione di questa tecnologia su scala industriale per automatizzare il controllo dei parametri del processo

Monitoring Harvesting degree of red ‘Scarlet’ Apples using DR-UV–Vis and NIR Spectroscopy

The identification of the harvest date has a fundamental role in the agro food chain as the quality of fruits depends primarily on the right harvesting time and storage conditions in post-harvest period. The marked need and the importance of rapid, reliable and non destructive tools for the determination of the ripeness level become apparent. This work is focused on the study of red apples ripening (Scarlet cv), with the aim of better identifying harvest date characterizing each stage of fruit ripening on trees using classical analysis and non destructive analysis. Non destructive NIR analysis has been applied to starch and sugar content and firmness, while UV-Vis analysis was applied to monitor variation of chlorophyll concentration in the skin of red apples. A further approach was tested considering UV-Vis and NIR data together, and using GA-PLS algorithm to elaborate a multivariate model based on the difference (in days) between every sampling and the harvest

Solid state equilibria in the system Al2O3-La2O3-Cr2O3: Reactivity catalyst/support LaCrO3/Al2O3

The zone of the ternary system Al2O3-La2O3-Cr2O3 delimited by LaCrO3, LaAlO3, Al2O3 and Cr2O3 has been examined. The existence of an extended field of mixed crystals with rhombohedral symmetry LaAl1-xCrxO3 (0≤x≤0·85) has been verified. On the other hand, for x>0·85, the solids show XR diffraction spectrograms typical of the orthorhombic phase LaCrO3. It has been found a small isomorphous substitution of Al3+ by Cr3+ in the β-alumina type phase, leading to the formation of the LaAl11-x CrxO18 series (0≤x≤0·75); moreover, the existence of Al2-xCrxO3 (0≤x≤2) mixed crystals field has been confirmed. Finally it has been experimentally verified that catalytic systems formed by mechanical mixtures of LaCrO3 and Al2O3 prepared anyhow (LaCrO3 dispersed or supported on Al2O3) result thermodynamically unstable whatever the composition