322,937 research outputs found
Digital Signal Processing Methodologies for Audio System Modeling and Audio Output Enhancement
No full textThis chapter summarizes some of the main results I obtained during my Ph.D. studies at Politecnico di Milano, under the supervision of Professor Augusto Sarti and Professor Alberto Bernardini. Audio systems have become, nowadays, pervasive in many different market sectors, such as that of consumer electronics and biomedical devices. To accurately represent, digitally replicate, and process the signals of such complex systems, it is crucial to develop multiphysics models that capture their nonlinear behaviors. In this chapter, I introduce novel multiphysics models of audio systems together with innovative digital signal processing techniques with the ultimate goal of improving their acoustic response. By leveraging the efficiency and accuracy of Wave Digital Filters, I propose novel modeling methods to incorporate the various physical domains involved in audio systems. I introduce iterative methods for streamlined emulation and parallel implementation, addressing, at the same time, complex nonlinearities such as magnetic saturation and hysteresis. I present new linearization and virtualization algorithms to manipulate the audio device behavior leveraging on the newly introduced multiphysics models. Finally, I combine psychoacoustic methodologies with deep-learning models to tackle operating conditions affected by very strict physical constraints. With this investigation, I cover diverse audio signal processing tasks, offering fresh insights and practical solutions across various application scenarios
Nonlinear elastic tomography using sparse array measurements
No full textLiterature offers a quantitative number of diagnostic imaging methods that can continuously provide a detailed image of the material defects in aerospace and civil applications. This paper presents a nonlinear Structural Health Monitoring (SHM) imaging method, based on nonlinear elastic wave tomography (NEWT), for the detection of the nonlinear signature in damaged isotropic structures. The proposed technique, based on a combination of higher order statistics (HOS) and radial basis function (RBF) interpolation, is applied to a number of waveforms containing the nonlinear responses of the medium. HOS such as bispectral analysis and bicoherence was used to characterize the second order nonlinearity of the structure due to corrosion, whilst RBF interpolation was applied to a number of signals acquired from a sparse array of sensors, in order to obtain an image of the defect. Compared to standard linear ultrasonic imaging techniques, the robustness of this nonlinear tomography sensing system was experimentally demonstrated. Moreover, this methodology does not require any baseline with the undamaged structure for the detection of the nonlinear source as well as a priori knowledge of the mechanical properties of the medium. Finally, the use of HOS makes NEWT a valid alternative to traditional nonlinear elastic wave spectroscopy (NEWS) methods for materials showing either classical or non-classical nonlinear behaviour
Headspace solid-phase microextraction for the determination of benzene, toluene, ethylbenzene and xylenes in urine
No full textA method for the determination of benzene, toluene, ethylbenzene and xylenes (BTEX) in urine of people exposed to these airborne pollutants present in the living environment, has been described. Solid-phase microextraction has been used for sampling BTEX from the headspace of urine and gas chromatography-mass spectrometry has been applied for the selective analysis of chemicals. The method has the following features: small volume of urine (2 ml) needed, linearity in the range of interest (from the limit of detection up to 5000 ng/l) with coefficient of correlation > or =0.998, limit of detection in the range 12-34 ng/l, good repeatability (coefficient of variation 2-7%), high specificity. The stability of the urine sample during storage (-20 degrees C) was evaluated: BTEX remained stable for up to 2 months. The assay has been successfully applied to the biological monitoring of two subjects environmentally exposed to airborne BTEX in an urban area
Biological and environmental monitoring of exposure to airborne benzene and other aromatic hydrocarbons in Milan traffic wardens
No full textEnvironmental and biological monitoring of airborne aromatic hydrocarbons has been performed in 20 policemen working as traffic wardens exposed to motor vehicle exhausts and in 19 peers employed as clerks. Airborne benzene, toluene, ethylbenzene and xylene concentrations, measured during the workshift, resulted in significantly higher outdoor than indoor concentrations (benzene and related aromatic hydrocarbons mean values, respectively of 53 and 350 micrograms/m3 vs. 29 and 180 micrograms/m3). Blood benzene, toluene, ethylbenzene and xylene concentrations did not differ significantly between indoor and outdoor workers; no differences were found between values obtained at the beginning (07:30 h) and the end of shift (00:30) in either group. Blood hydrocarbon concentrations seem to reflect airborne pollution, whilst the blood benzene concentration determined after the workshift poorly reflects airborne benzene morning peaks. Endshift blood benzene mean concentration in smokers (462 ng/l, n = 9) differs significantly from non-smokers (292 ng/l, n = 39)
High-precision biomedical binary relation extraction system
No full textThe system is designed to extract highly precise relational information from input texts. Our approach to relation extraction includes two stages: 1) text preprocessing, in which a sequence of natural language processing modules are applied to texts. 2) relation extraction, in which relationships between entities are identified and classified.
The system is available as a docker image, thus is platform independent.
It allows users to: - extract entities in custom texts (providing input texts and input dictionaries); - extract relations in custom texts (providing input texts and input dictionaries); - replicate the results in gold standard corpor
Biological monitoring of exposure to solven : a method for the gas-chromatographic determination of aromatic hydrocarbons in the blood and urine
No full textA gas chromatographic procedure with dynamic head-space purge and trap preconcentration (HSGC) and FID detection for blood and urinary benzene, toluene, ethylbenzene and xylenes (BTEX) determination at low level exposure is described. Critical steps (sample collection, calibration, HSGC conditions, contamination control) are discussed. The calibration curve is linear in the range 50 ng/l-500 micrograms/l; the calculated detection limit is 50 ng/l for all the considered aromatic hydrocarbons (AH) both in blood and urine; the within-day precision, calculated as variation coefficient (CV) at 400 ng/l and 40 micrograms/l (n = 6) was respectively CV = 13% and CV = 6% for all the studied analytes. The recovery rate was in the range 29-70%, depending on the hydrocarbon and matrix (blood or urine) considered. The procedure was applied to the biological monitoring of 151 workers occupationally or environmentally exposed to BTEX. Occupationally exposed subjects showed blood AH levels of 2-4 order of magnitude higher than environmentally exposed subjects. In white-collar workers exposed to BTEX urban pollution a significant difference in blood and urine levels of AH was observed between nonsmokers and smokers. Nonsmokers showed blood AH median values of respectively benzene = 241 ng/l, toluene = 759 ng/l, ethylbenzene = 140 ng/l, xylenes = 604 ng/l. Significatively higher BTEX blood values were observed in smokers after a median consumption of 5 cigarettes in 5 hours; observed median values were respectively: benzene = 365 ng/l toluene = 1327 ng/l, ethylbenzene = 233 ng/l, xylenes = 794 ng/l.A gas chromatographic procedure with dynamic head-space purge and trap preconcentration (HSGC) and FID detection for blood and urinary benzene, toluene, ethylbenzene and xylenes (BTEX) determination at low level exposure is described. Critical steps (sample collection, calibration, HSGC conditions, contamination control) are discussed. The calibration curve is linear in the range 50 ng/l - 500 μg/l; the calculated detection limit is 50 ng/l for all the considered aromatic hydrocarbons (AH) both in blood and urine; the within-day precision, calculated as variation coefficient (CV) at 400 ng/l and 40 μg/l (n = 6) was respectively CV = 13% and CV = 6% for all the studied analytes. The recovery rate was in the range 29-70%, depending on the hydrocarbon and the matrix (blood or urine) considered. The procedure was applied to the biological monitoring of 151 workers occupationally or environmentally exposed to BTEX. Occupationally exposed subjects showed blood AH levels of 2-4 orders of magnitude higher than environmentally exposed subjects. In white-collar workers exposed to BTEX urban pollution a significant difference in blood and urine levels of AH was observed between nonsmokers and smokers. Nonsmokers showed blood AH median values of respectively benzene = 241 ng/l, toluene = 759 ng/l, ethylbenzene = 140 ng/l, xylenes = 604 ng/l. Significatively higher BTEX blood values were observed in smokers after a median consumption of 5 cigarettes in 5 hours; observed median values were respectively: benzene = 365 ng/l, toluene = 1327 ng/l, ethylbenzene = 233 ng/l, xylenes = 794 ng/l
High-Precision Biomedical Relation Extraction for Reducing Human Curation Efforts in Industrial Applications
No full textThe body of biomedical literature is growing at an unprecedented rate, exceeding the ability of researchers to make effective use of this knowledge-rich amount of information. This growth has created interest in biomedical relation extraction approaches to extract domain-specific knowledge for diverse applications. Despite the great progress in the techniques, the retrieved evidence still needs to undergo a time-consuming manual curation process to be truly useful. Most relation extraction systems have been conceived in the context of Shared Tasks, with the goal of maximizing the F1 score on restricted, domain-specific test sets. However, in industrial applications relations typically serve as input to a pipeline of biologically driven analyses; as a result, highly precise extractions are central for cutting down the manual curation effort, thus to translate the research evidence into practice smoothly and reliably. In this paper, we present a highly precise relation extraction system designed to reduce human curation efforts. The engine is made up of sophisticated rules that leverage linguistic aspects of the texts rather than sticking on application-specific training data. As a result, the system could be applied to diverse needs. Experiments on gold-standard corpora show that the system achieves the highest precision compared with previous rule-based, kernel-based, and neural approaches, while maintaining a F1 score comparable or superior to other methods. To show the usefulness of our approach in industrial scenarios, we finally present a case study on the mTOR pathway, showing how it could be applied on a large-scale
Characterization of the disulfides of bio-thiols by electrospray ionization and triple-quadrupole tandem mass spectrometry
No full textGlutathione and other intracellular low molecular mass thiols act both as the major endogenous antioxidant and redox buffer system and, as recently highlighted, as an important regulator of cellular homeostasis. Such cellular functions are mediated by protein thiolation, a newly recognized post-translational modification which involves the formation of mixed disulfides between GSH and key disulfide-linked Cys residues in the native protein structure. It is also well known that thiol-seeking heavy metals, such as mercury, cadmium and lead, may interfere in this regulatory system, thus disrupting the cellular functioning. To identify such mixed disulfides in order to investigate their biological role, 15 homo- and heterodimeric disulfides were prepared by air oxidation of binary mixtures containing cysteine, homocysteine, penicillamine, N-acetylcysteine, N-acetylpenicillamine and glutathione and their protonated molecules were characterized by mass spectrometry. Collisionally activated unimolecular decomposition of protonated homo- and heterodimeric disulfides generated by electrospray ionization gives rise to fission of the disulfide system both between the two sulfur atoms and across the C--S bonds, to yield structurally specific fragments which allow one to define the structure of the compounds and to discriminate between isomeric compounds. Fission between the sulfur atoms yields a pair of R--S(+) ions and, in some cases, also the complementary fragments corresponding to the protonated amino acids. Fission across the C--S bonds mainly occurs in the disulfides of N-acetylcysteine and N-acetylpenicillamine and gives rise to non-S-containing fragments formally similar to those obtained from some mercapturic acids. The complementary fragments, formally connected as R--S--S(+) ions are also observed. Fragmentation of glutathione disulfides mainly shows the characteristic loss of the terminal gamma-linked glutamic acid and little, if any, fragmentation of the disulfide system
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Recording cortico-cortical evoked potentials of the human arcuate fasciculus under general anaesthesia
No full textObjective: We examined the feasibility of using cortico-cortical evoked potentials (CCEPs) to monitor the major cortical white matter tract involved in language, the arcuate fasciculus (AF), during surgery under general anaesthesia. Methods: We prospectively recruited nine patients undergoing surgery for lesions in the left peri-sylvian cortex, for whom awake surgery was not indicated. High angular resolution diffusion imaging (HARDI) tractography was used to localise frontal and temporal AF terminations, which guided intraoperative cortical strip placement. Results: CCEPs were successfully evoked in 5/9 patients, showing a positive potential (P1) at 12 ms and a negative component (N1) at 21 ms when stimulating from the frontal lobe and recording in the temporal lobe. CCEP responses peaked in the posterior middle temporal gyrus. No CCEPs were evoked when stimulating temporal sites and recording from frontal contacts. Conclusion: For the first time, we show that CCEPs can be evoked from the peri-sylvian cortices also in adult patients who are not candidates for awake procedures. Our results are akin to those described in the awake setting and suggest the recorded activity is conveyed by the arcuate fasciculus. Significance: This intraoperative approach may have promising implications in reducing deficits in patients that require surgery in language areas under general anesthesia
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