197,244 research outputs found
Multichannel wavelength conversion of 40 Gbit/s NRZ DPSK signals in a highly nonlinear dispersion flattened lead silicate fibre
No full textWe experimentally demonstrate the wavelength conversion of three wavelength multiplexed 40 Gbit/s Differential Phase Shift Keyed (DPSK) signals in a 2.2m length of highly nonlinear, dispersion tailored W-type lead-silicate optical fibre
New optical fibre based technologies and their application in highly nonlinear systems
No full textThis thesis investigates new fibre technologies and their application in nonlinear optical systems, designed mainly for telecommunications. The thesis includes a study of two different directions in achieving a high nonlinearity in a fibre system, namely holey fibres filled with nonlinear liquids and soft glass, small core microstructured fibres. The challenges arising from the development of liquid-filled structures have made soft glass microstructured fibres the technology of choice for the realisation of highly nonlinear systems.Amongst the various soft glasses, commercially available lead-silicate glasses are identified as the material for the development of highly nonlinear fibres. Small-core, leadsilicate fibres with different designs are considered within this thesis. A solid core holey fibre design as well as two all-solid designs, a multi-ring cladding and a simpler W-index profile, are characterised. The measurements confirm the advantages of the all-solid designs over the holey structures and reveal the possibility to achieve simultaneously a high nonlinear coefficient and a novel dispersion profile in such fibres. Some of the presented fibres are employed in all-optical wavelength conversion schemes based on four-wave-mixing. Numerical simulations and experimental results are combined to study the performance of the fibres and demonstrate their use in wavelength conversion devices. In particular, a lead-silicate W-index profile fibre, showing a high nonlinear coefficient of 820W-1km-1 with a near zero dispersion profile at telecoms wavelengths, is employed to demonstrate a flat conversion gain in the whole C-band. The same fibre is then employed in FWM-based systems to demonstrate multi-channel wavelength conversion, generation of high repetition rate pulses and all-optical demultiplexing. The experiments presented in this thesis clearly reveal the potential of small-core soft-glass fibres for nonlinear applications.The use of soft glass microstructured fibres in the mid-IR is also investigated. Tellurite holey fibres with different core sizes and hole arrangements are employed in a supercontinuum generation scheme
Wavelength conversion in a short length of a solid lead-silicate fibre
No full textWe experimentally demonstrate a four-wave-mixing-based wavelength conversion scheme at 1.55 µm using a 1.1-m length of highly nonlinear, dispersion tailored W-type lead–silicate optical fibe
Il sogno di Eva. Sesso e destino in Paradise Lost.
No full textL'articolo analizza il rapporto tra il sogno di Eva nel Libro V del Paradise Lost e la scena della tentazione e della caduta del Libro IX. La tesi dell'articolo è che il sogno sensuale di Eva indotto dal Serpente prefigura le motivazioni fondamentalmente sessuali ed erotiche della caduta, aprendo così una inaspettata possibilità che Milton concordi con l'interpretazione agostiniana del peccato originale come impossibilità degli uomini di controllare liberamente la propria sessualità
Monitoring Aging Effects in Graphite Bisulfates by Means of Raman Spectroscopy
No full textGraphite bisulfate (GBS) compounds consist of graphite layers intercalated by HSO4− ions and H2SO4 molecules. Owing to electrostatic interactions with the graphene plane, HSO4− ions cause point defects in the graphite’s crystalline structure, while H2SO4 molecules are free to move via diffusion in the spaces between the adjacent graphite sheets and segregate to form linear defects. In the present work, we report the results of our investigation using Raman spectroscopy on the temporal evolution of such defects on selected GBS samples over 84 months. Two characteristic lengths correlated with the average distance between defects have been estimated and their evolution with aging was investigated. The results show a decrease in the density of point-like defects after aging, regardless of the pristine structural configuration of the GBS samples, revealing a structural instability. This study can provide significant information for the technological development of industrial processes aimed to produce expanded graphite based on GBS precursors, where the aging of GBS is known to influence the efficiency and quality
Choosing the duration of continuous glucose monitoring for reliable assessment of time in range: A new analytical approach to overcome the limitations of correlation-based methods
No full textAims: Reliable estimation of the time spent in different glycaemic ranges (time-in-ranges) requires sufficiently long continuous glucose monitoring. In a 2019 paper (Battelino et al., Clinical targets for continuous glucose monitoring data interpretation: recommendations from the international consensus on time in range. Diabetes Care. 2019;42:1593-1603), an international panel of experts suggested using a correlation-based approach to obtain the minimum number of days for reliable time-in-ranges estimates. More recently (in Camerlingo et al., Design of clinical trials to assess diabetes treatment: minimum duration of continuous glucose monitoring data to estimate time-in-ranges with the desired precision. Diabetes Obes Metab. 2021;23:2446-2454) we presented a mathematical equation linking the number of monitoring days to the uncertainty around time-in-ranges estimates. In this work, we compare these two approaches, mainly focusing on time spent in (70-180) mg/dL range (TIR). Methods: The first 100 and 150 days of data were extracted from study A (148 subjects, ~180 days), and the first 100, 150, 200, 250 and 300 days of data from study B (45 subjects, ~365 days). For each of these data windows, the minimum monitoring duration was computed using correlation-based and equation-based approaches. The suggestions were compared for the windows of different durations extracted from the same study, and for the windows of equal duration extracted from different studies. Results: When changing the dataset duration, the correlation-based approach produces inconsistent results, ranging from 23 to 64 days, for TIR. The equation-based approach was found to be robust versus this issue, as it is affected only by the characteristics of the population being monitored. Indeed, to grant a confidence interval of 5% around TIR, it suggests 18 days for windows from study A, and 17 days for windows from study B. Similar considerations hold for other time-in-ranges. Conclusions: The equation-based approach offers advantages for the design of clinical trials having time-in-ranges as final end points, with focus on trial duration
Surface-enhanced raman spectroscopy for monitoring extravirgin olive oil bioactive components
No full textOlive oil is the main fat source of the Mediterranean diet. This seasoning ingredient is highly appreciated for its unique taste, functional properties, and positive impact on human health. The determination of chemical composition is a demanding task in order to fully characterize this precious food product, ensure its quality, and prevent fraudulent practices. Among innovative techniques proposed for the oil analysis, surface-enhanced Raman spectroscopy (SERS) can be an extremely useful tool for olive oil characterization. In this frame, we have investigated five noncommercial olive oils produced in different parts of South Italy by using a commercial Raman microspectroscopy apparatus and home-made signal-enhancing SERS substrates. A wavelet-based data analysis has allowed us to efficiently remove the background and the noise from the acquired spectra. The analysis of these SERS spectra has enabled the quantification of the relative contents of carotene, oleic acid, and phenols. These relative contents differ in the examined samples. In addition, SERS response in the lipid region has indicated differences in the relative abundance of saturated fatty acids. The present results confirm the validity of the SERS technique as a rapid, nondestructive, and reliable analytical technique for identifying olive oil bioactive components
Monitoring biochemical and structural changes in human periodontal ligaments during orthodontic treatment by means of micro-raman spectroscopy
No full textThe aim of the study was to examine the biochemical and structural changes occurring in the periodontal ligament (PDL) during orthodontic-force application using micro-Raman spectroscopy (μ-RS). Adolescent and young patients who needed orthodontic treatment with first premolar extractions were recruited. Before extractions, orthodontic forces were applied using a closed-coil spring that was positioned between the molar and premolar. Patients were randomly divided into three groups, whose extractions were performed after 2, 7, and 14 days of force application. From the extracted premolars, PDL samples were obtained, and a fixation procedure with paraformaldehyde was adopted. Raman spectra were acquired for each PDL sample in the range of 1000–3200 cm−1 and the more relevant vibrational modes of proteins (Amide I and Amide III bands) and CH2 and CH3 modes were shown. Analysis indicated that the protein structure in the PDL samples after different time points of orthodontic-force application was modified. In addition, changes were observed in the CH2 and CH3 high wavenumber region due to local hypoxia and mechanical force transduction. The reported results indicated that μ-RS provides a valuable tool for investigating molecular interchain interactions and conformational modifications in periodontal fibers after orthodontic tooth movement, providing quantitative insight of time occurring for PDL molecular readjustment
Changes in periodontal ligament (PDL) by orthodontic forces: a micro-raman analysis of amide I and lipid contribution.
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