Dimensionality and Construct Validity of the Romanian Self-Report Strengths and Difficulties Questionnaire (SDQ)

The Strengths and Difficulties Questionnaire (SDQ) is one of the most widely utilised measures of behavioural and emotional difficulties among children and young people. Previous research has raised concerns about the psychometric properties of the measure, particularly the internal consistency of the CP and PP subscales. Confirmatory factor analysis (CFA) has generally supported a five-factor solution that is consistent with Goodman’s (1997) original conceptualisation of the SDQ, but alternative factor structures have been validated including models with internalising and externalising factors, and a total difficulties factor. This was the first study to examine the dimensionality, construct validity and internal consistency of the Romanian self-report version of the SDQ. Based on data collected from 1,086 school children aged 9-17 years old, six alternative factor models were specified and tested using conventional CFA techniques and a confirmatory bifactor modelling approach. The five-factor model provided a better fit for the data than alternative factor structures, but was still unacceptable according to a range of overall model fit indices and individual item loadings. Model fit statistics for the five-factor solution were also notably poorer among boys than girls. Internal consistency was low for the CP, H and PP subscales among the total sample and girls only; and for the EP, CP, H and PP subscales among boys only. Results are discussed in terms of the appropriate interpretation of the Romanian SDQ

Development of a maximum entropy approach for the thermomecanical modelling of the rotary friction welding process

A multi-physics modelling of rotary friction welding process based on a Maximum Entropy approach is proposed. This approach will be able to solve coupled thermomechanical problems. Because strains are very high locally around the welded area, the remeshing time in a classical finite element method is very important. The use of this meshless method should reduce simulations time and the numerical diffusion phenomena

Fast exploration and classification of large hyperspectral image datasets for early bruise detection on apples

Hyperspectral imaging allows to easily acquire tens of thousands of spectra for a single sample in few seconds; though valuable, this data-richness poses many problems due to the difficulty of handling a representative amount of samples altogether. For this reason, we recently proposed an approach based on the idea of reducing each image into a one-dimensional signal, named hyperspectrogram, which accounts both for spatial and for spectral information. In this manner, a dataset of hyperspectral images can be easily and quickly converted into a set of signals (2D data matrix), which in turn can be analyzed using classical chemometric techniques. In this work, the hyperspectrograms obtained from a dataset of 800 NIR-hyperspectral images of two different apple varieties were used to discriminate bruised from sound apples using iPLS-DA as variable selection algorithm, which allowed to efficiently detect the presence of bruises. Moreover, the reconstruction as images of the selected variables confirmed that the automated procedure led to the exact identification of the spatial features related to the onset and to the subsequent evolution with time of the bruise defect

Colourgrams GUI: A graphical user-friendly interface for the analysis of large datasets of RGB images

Colourgrams GUI is a graphical user-friendly interface developed in order to facilitate the analysis of large datasets of RGB images through the colourgrams approach. Briefly, the colourgrams approach consists in converting a dataset of RGB images into a matrix of one-dimensional signals, the colourgrams, each one codifying the colour content of the corresponding original image. This matrix of signals can be in turn analysed by means of common multivariate statistical methods, such as Principal Component Analysis (PCA) for exploratory analysis of the image dataset, or Partial Least Squares (PLS) regression for the quantification of colour-related properties of interest. Colourgrams GUI allows to easily convert the dataset of RGB images into the colourgrams matrix, to interactively visualize the signals coloured according to qualitative and/or quantitative properties of the corresponding samples and to visualize the colour features corresponding to selected colourgram regions into the image domain. In addition, the software also allows to analyse the colourgrams matrix by means of PCA and PLS

Investigations of ultrafast photoisomerization of photochromic molecular switches by fs-time-resolved transient absorption spectroscopy

The photoinduced isomerization of trans- and cis- azobenzene and the cis-trans photoisomerization of the furylfulgide were studied with a pump-probe setup. The detection of the ultrafast transient absorption was realized using supercontinuum (SC) broadband probe pulses generated in sapphire or CaF2. A study of the cross-phase modulation showed that the SC could be described as linearly chirped pulses. Stimulated Raman amplification contribution was used to find the best setting for the pulse compression for the NOPA pump pulses. The photoinduced isomerization of azobenzene in CCl4 and ethanol at room temperature was studied after excitation at 466 nm and 387 nm. In the first case (466 nm), two wavelength-independent decay components of tau1 = 0.52(2) ps and tau2 = 3.22(2) ps were found, in agreement with previous work. The shortest time constant was interpreted as very fast motion of the excited state wavepacket out of the Franck-Condon region and ultrafast conversion to the S0 state via a conical intersection (CI), the second component was attributed to molecules that do not take the direct path. A much weaker third component of tau3 = 18 ps only found at lambda = 510 nm was assigned to the relaxation of vibrationally hot molecules in the S0 state. For excitation at 387 nm leading to S2 state, three decay components with tau1 = 0.08(5) ps, tau2 = 0.4(3) ps and tau3 = 13(3) ps were found. The fastest component (tau1) could be related to the conversion from the S2 to the S1 state. The second decay time (tau2) was attributed to motion in the S1 state towards the S1/S0-CI and the slowest component was assigned to cooling of vibrationally hot molecules in S0 state. It is not clear why, in contrast to literature, no tau ~ 3 ps component was observed. The photoisomerization of the furylfulgide Z-ACR 540 was studied after excitation at lambda = 387 nm in toluene and ethanol. In toluene, a short-lived component only present within the first 0.3 ps and a long lived second component were found. The latter had a rise time of tau = 16 ps and did not decay within 136 ps. That component was also observed in pure toluene and was assigned to the photoinduced formation of toluene excimers. In ethanol only one single fast decay component of tau = 248(2) fs was found. The time scale of the process could be interpreted as motion from the S1 state to the S0 state via a CI

Macropores in Si: fundamental study and prospective applications

This work is to a great extent multidisciplinary. It covers such areas as: simulations and modelling of fundamental electrochemical processes at the Si-HF interface, in particular the oscillatory behaviour of the Si electrode; investigation of the pore growth phenomenology in n-Si; development of novel optical elements based on Photonic Crystals (PCs) as well as concepts for new generation of metamaterials, i.e. Negative Index Materials (NIM). A detailed analysis of the electrochemical current and potential oscillations at the Si–HF interface is presented. Calculations and simulations are based on the current burst model, which was extended to the simulation of various oscillatory phenomena at the Si–HF interface. Apart from a detailed analysis of current oscillations in various modes, potential oscillations could be simulated for the first time, too. Much progress has been made towards a better understanding of the macropore growth phenomenology by using the input from the CBM and results from a newly introduced in-situ characterization technique – Fast Fourier Transformed impedance spectroscopy. For the first time a completely new impedance spectroscopy mode is proposed – (backside) photo impedance. In particular, the pore quality could be quantified for the first time in-situ, especially by extracting the valence of the ongoing process. The study paves the way towards an automatized etching system where the pore etching parameters are adjusted in-situ during the pores etching process. A new type of NIM is proposed and tested. Very good focusing properties of plane plate lenses, based on this material, could be obtained. Another topic addressed in this thesis was PCs with unusual index of refraction, i.e. neff < 1, were investigated, and optical components with a wide range of functionality based on this class of PCs are designed and tested. Envisioned uses included lenses, filters, beam splitters, antennas, etc

Mixture design and multivariate image analysis to monitor the colour of strawberry yoghurt purée

Food colour is a commercial added value, since it represents the first appealing factor for consumers. In this context, this study was aimed at evaluating the effect of strawberry yoghurt purée (SYP) formulation on the corresponding colour and on its variation over time, which is mainly due to degradation and browning phenomena. To this aim, a combined approach was used that included mixture design and multivariate analysis of RGB images. Strawberry purée, sugar, lemon juice and two types of thickener were mixed in different proportions by I-optimal mixture design to obtain 44 SYP formulations. The samples were subjected to light and temperature stress conditions for five weeks; during this time the RGB images of the samples were acquired using a flatbed scanner, along with the images of the corresponding control samples. The dimensionality of the acquired images was reduced by two different approaches: i) the conversion of images into signals, namely colourgrams, which can be seen as the colour fingerprint of the imaged samples, and ii) the calculation of the median values of various colour-related parameters. The colourgrams dataset was then subjected to exploratory data analysis using Principal Component Analysis, while the median values of colour-related parameters were analysed using Response Surface Methodology and Partial Least Squares-Discriminant Analysis. The aim of data analysis was both to find the best colour parameters to describe colour variability over time, and to investigate the cause-effect relationship between mixture proportions and colour response. The results highlighted that, among the considered colour parameters, relative green (i.e., the ratio of green to lightness) and red could be used to monitor colour changes. Colour variation due to stress conditions was more pronounced for samples with a high percentage of strawberry purée, and the type of thickener also affected the colour degradation kinetics

Exploring the potential of NIR hyperspectral imaging for automated quantification of rind amount in grated Parmigiano Reggiano cheese

Parmigiano Reggiano (P-R) is one of the most important Italian food products labelled with Protected Designation of Origin (PDO). The PDO denomination is applied also to grated P-R cheese products meeting the requirements regulated by the Specifications of Parmigiano Reggiano Cheese. Different quality parameters are monitored, including the percentage of rind, which is edible and should not exceed the limit of 18% (w/w). The present study aims at evaluating the possibility of using near infrared hyperspectral imaging (NIR-HSI) to quantify the rind percentage in grated Parmigiano Reggiano cheese samples in a fast and non-destructive manner. Indeed, NIR-HSI allows the simultaneous acquisition of both spatial and spectral information from a sample, which is more suitable than classical single-point spectroscopy for the analysis of heterogeneous samples like grated cheese. Hyperspectral images of grated P-R cheese samples containing increasing levels of rind were acquired in the 900–1700 nm spectral range. Each hyperspectral image was firstly converted into a one-dimensional signal, named hyperspectrogram, which codifies the relevant information contained in the image. Then, the matrix of hyperspectrograms was used to calculate a calibration model for the prediction of the rind percentage using Partial Least Squares (PLS) regression. The calibration model was validated considering two external test sets of samples, confirming the effectiveness of the proposed approach