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Auto e cross trasformate tempo - frequenza per l'analisi e la sintesi di brani di segnale EMG
No full textProduzione di composti ad alto valore aggiunto da sottoprodotti rinnovabili mediante un sistema multienzimatico a cascata
Full text linkThe efficient valorization of the lignocellulosic biomass components, and in particular the lignin fraction, could serve as a starting point for the establishment of a circular bioeconomy model aimed at the recycling and reutilization of industrial by-products over the exploitation of virgin feedstock. From lignocellulosic biomass both fermentable carbohydrate and aromatics can be obtained, which can be used for the production of biofuels and bioplastics thus reducing the dependence on petroleum-based feedstocks. The present Ph.D. thesis focuses on the development of novel biotechnological processes aimed at the extraction of aromatics from lignocellulosic by-products and their conversion to value-added products using whole-cell biocatalytic approaches.
Firstly, I developed an efficient and green process to produce ccMA from renewable feedstocks (i.e. kraft lignin and wheat bran) based on: a) the optimization of the extraction procedures of vanillin from lignin and of ferulic acid from wheat bran; b) the genetic engineering of an E. coli strain to modulate the expression of up to seven recombinant enzymes. In detail, vanillin was recovered from kraft lignin (4.5 mg vanillin/g kraft lignin) by an enzymatic treatment using the recombinant Bacillus licheniformis laccase, and ferulic acid from wheat bran (3.0 mg ferulic acid/g wheat bran) by a thermo-enzymatic method using the Ultraflo®XL commercial enzyme. The whole-cell biocatalyst used to convert vanillin into ccMA expresses the dehydrogenase LigV, the demethylase VanAB, the decarboxylase AroY and the dioxygenase C12O; meanwhile the whole-cell biocatalyst to convert ferulic acid to ccMA expresses all the above-mentioned enzymes plus the decarboxylase Fdc and the dioxygenase Ado. The engineered strains converted >95% of lignin-derived vanillin in 30 minutes, obtaining the production of 4.2 mg ccMA/g of kraft lignin. Starting from the wheat bran-derived ferulic acid, ccMA was produced with a >95% conversion yield in 10 hours, corresponding to 0.73 g ccMA/g ferulic acid, and 2.2 mg ccMA/g wheat bran biomass.
To further evaluate the capabilities of the whole-cell biocatlyst, the scaled-up production of ccMA from vanillin using the engineered E. coli growing cells was studied. The bioconversion reaction was carried out in a fermenter, providing improved control of the reaction conditions such as pH, dissolved oxygen and substrate pulse-feed rate, streamlining the biocatalytic process and enhancing scalability. The optimized growth medium composition (0.5 g/L glucose and 2 g/L lactose) and substrate addition strategy (1 mmol/h pulse-feed) enabled the engineered strain to produce 5.2 ± 0.36 g/L of ccMA in 48 hours, corresponding to 0.86 g ccMA/g vanillin. The purification of the produced ccMA from the fermentation broth was achieved through crystallization, yielding 2.58 ± 0.07 g per liter of broth, corresponding to a ≈50% purification yield.
Lastly, a preliminary analysis of a one-pot process for the production of 4-vinylguaiacol from wheat bran was conducted. The process involves the extraction of ferulic acid from the wheat bran using the three-step thermo-enzymatic protocol utilized previously and the simultaneous conversion of ferulic acid into 4-vinylguaicol using an engineered E. coli strain expressing the decarboxylase Fdc. The novelty of this process arises from the employment of the wheat bran crude extract as an auto-inducing growth medium, based on the presence of several fermentable carbohydrates and the utilization of a hybrid phenol-inducible promoter for the induction of Fdc expression, making the wheat bran-derived ferulic acid both the inducer and the substrate of the enzyme. The unoptimized process produced 1.8 mg 4-vinylguaiacol per gram of wheat bran, which correspond to the conversion of ≈75% of the ferulic acid extracted using the thermo-enzymatic method and ≈64% of the alkaline extractable ferulic acid present in the wheat bran
A Vision-Based Technique for Lay Length Measurement of Metallic Wire Ropes
Full text linkThe lay length of metallic wire ropes is an important dimensional quantity whose analysis is useful to highlight rope deformations due to distributed damages. This paper describes a measurement system that is based on a video camera and on an offline processing algorithm. The camera acquires an image sequence of the running rope; then, an image processing algorithm extracts the rope contour and measures both the distance among rope strands and the whole distance covered by the rope during the test. A mathematical model of the rope contour has been developed and employed to test the proposed algorithm with simulated data. Field tests have been carried out with the proposed system on a working aerial cableway using a general-purpose camer
Assessment of Muscle Fatigue During Biking
No full textThe analysis of the surface myoelectric signal recorded while a muscle is performing a sustained contraction is a valuable tool for assessing the progression of localized fatigue. It is well known that the modifications of the spectral content of the myoelectric signal are mainly related to changes in the interstitial fluid pH, which, in turn, affect the membrane excitability of the active muscle fibers. This paper describes the effects of muscle fatigue on the surface myoelectric signal recorded from three thigh and leg muscles during biking, on a population consisting of 22 young healthy volunteers. The purpose of this study was to obtain normative data relative to an exercise protocol mild enough to be applicable, in the future, to pathological subjects as well. Each subject was asked to exercise 30 min on a cycloergometer at a constant velocity and against a constant torque. While subjects were biking, the surface myoelectric signal was recorded from the rectus femoris, the biceps femoris, and the gastrocnemius muscles. In this study, we considered two different aspects of muscle fatigue: first, the localized muscle fatigue as shown by the decrement of the instantaneous frequency of the myoelectric signal during the exercise; second, the modifications of the muscle ON-OFF timing, which could be explained as a strategy for increasing endurance by modifying the role of different muscles during the exercise. The first aspect was studied by obtaining the spectral characteristics of the signals by means of bilinear time-frequency transforms and by applying an original estimator of the instantaneous frequency of stochastic processes based on cross time-frequency transforms. Our results demonstrated that none of the subjects showed significant signs of localized muscle fatigue, since the decrement of the instantaneous frequency during the exercise was always lower than 5% of its initial value. Muscle ON-OFF timing was obtained by applying to the raw myoelectric signal a double threshold statistical detector to identify the time intervals during which the observed muscles were active. This demonstrated that the subjective feeling of fatigue each subject reported during the exercise did not cause a change of the activation strategy of the observed muscles. It is concluded that the experimental protocol herein described and the signal processing procedures adopted are appropriate for monitoring different effects of muscle fatigue during biking. Moreover, data obtained from our sample population can be considered as a reference for studying the manifestations of muscle fatigue in pathological subjects asked to follow a similar experimental protocol
Intima-Media Thickness: Setting a Standard for a Completely Automated Method of Ultrasound Measurement
Full text linkThe intima – media thickness (IMT) of the common carotid artery is a widely used clinical marker of severe cardiovascular diseases. IMT is usually manually measured on longitudinal B-Mode ultrasound images. Many computer-based techniques for IMT measurement have been proposed to overcome the limits of manual segmentation. Most of these, however, require a certain degree of user interaction.
In this paper we describe a new completely automated layers extraction (CALEXia) technique for the segmentation and IMT measurement of carotid wall in ultrasound images. CALEXia is based on an integrated approach consisting of feature extraction, line fitting, and classification that enables the automated tracing of the carotid adventitial walls. IMT is then measured by relying on a fuzzy K-means classifier. We tested CALEXia on a database of 200 images. We compared CALEXia performances to those of a previously developed methodology that was based on signal analysis (CULEXsa). Three trained operators manually segmented the images and the average profiles were considered as the ground truth. The average error from CALEXia for lumen – intima (LI) and media – adventitia (MA) interface tracings were 1.46 ± 1.51 pixel (0.091 ± 0.093 mm) and 0.40 ± 0.87 pixel (0.025 ± 0.055 mm), respectively. The corresponding errors for CULEXsa were 0.55 ± 0.51 pixels (0.035 ± 0.032 mm) and 0.59 ± 0.46 pixels (0.037 ± 0.029 mm). The IMT measurement error was equal to 0.87 ± 0.56 pixel (0.054 ± 0.035 mm) for CALEXia and 0.12 ± 0.14 pixel (0.01 ± 0.01 mm) for CULEXsa. Thus, CALEXia showed limited performance in segmenting the LI interface, but outperformed CULEXsa in the MA interface and in the number of images correctly processed (10 for CALEXia and 16 for CULEXsa). Based on two complementary strategies, we anticipate fusing them for further IMT improvements
Greedy Technique and Its Validation for Fusion of Two Segmentation Paradigms Leads to an Accurate Intima-Media Thickness Measure in Plaque Carotid Arterial Ultrasound
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An integrated approach to computer-based automated tracing and its validation for 200 common carotid arterial wall ultrasound images: a new technique.
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