323,649 research outputs found
Lucretia as a Figure of Mary in Machiavelli’s Mandragola
No full textWhen studied in political and ideological contexts, the numerous references to the Virgin Mary in Machiavelli’s comedic masterpiece Mandragola enable us to see how the author not only parodies a sacred play, but also deftly repurposes Christological and Mariological symbolism to celebrate his work’s unnamed referent: the first Medici pope, Leo X
Calculations of band-filling optical nonlinearities in extrinsic semiconductors beyond the low injection limit
No full textThe calculations regarding band-filling optical nonlinearities in direct band-gap extrinsic semiconductors were carried out. The process was based on the self-consistant determination of pseudochemical potential and it improved with other calculations. These calculations also enabled direct calculation of the non-linear optical suceptibility and fixing of photogenerated electron-hole density as a parameter was not needed. The study showed that the code can easily be extended to calculate the non-linear response of multilayered structures
Nonresonant Kerr effect in microporous silicon: Nonbulk dispersive behavior of below band gap χ (3)(ω)
No full textAlthough in recent years resonant optical nonlinearities in quantum confined silicon generated significant interest, no experimental work has been dedicated to the nonresonant regime, which is the range of interest for optical switching applications. In this article we report a systematic investigation on the different types of optical nonlinearities which can be activated in quantum-sized silicon. In particular, original measurements of nonresonant nonlinear refraction (Kerr effect) are reported at different wavelengths, spanning the infrared middle-gap range. The dispersive scaling rule and values of the nonlinear refractive index are clearly incompatible with those of three-dimensional semiconductors. Hence the quantum confined density of states plays a key role in determining the frequency dispersion of the nonresonant third-order susceptivity χ (3)(ω). Also, this suggests the need of further investigation of the influence of quantum-size effects (and related density of states modifications) on below-gap χ (3). © 2002 American Institute of Physics
Non-resonant Kerr Effect in Microporous Silicon: Non-bulk Dispersive Behaviour of Below Band-gap chi(3)(w)
No full textNon-resonant Kerr Effect in Microporous Silicon: Non-bulk Dispersive Behaviour of Below Band-gap chi(3)(w)
No full textFluorescently Tagged Poly(methyl methacrylate)s
No full textPlastic pollution is a global problem affecting the environment and, consequently, people's well-being. Careful and timely end-of-life plastic recycling is certainly a way, albeit a partial one, to remedy the problem. The immediate identification and selection of the different types of plastic materials in the recycling process certainly facilitate its recovery and reuse, allowing the damage caused by plastic emission into the environment to be limited. Recently, new technologies for automatic sorting of plastics based upon fluorescent tagging have been considered. This article reports the synthesis and characterization of fluorescent copolymers of poly(methyl methacrylate) (PMMA) that could be potentially used as fluorescent markers of commercial PMMA. Poly(methylmetacrylate-co-2-(9-carbazolyl)ethyl methacrylate) (P(MMA-co-CEMA)) and poly(methylmetacrylate-co-7-methacryloyloxycoumarin) (P(MMA-co-MAOC)) samples containing a small number of fluorescent units (<4%) were synthesized by free-radical polymerization. All copolymer samples show chemico-physical properties like those of pure PMMA and produce fluorescence emission under 290 nm wavelength excitation. P(MMA-co-CEMA)s and P(MMA-co-MAOC)s were also tested as fluorescent dyes for PMMA identification. The experimental results demonstrate that PMMA/P(MMA-co-CEMA) and PMMA/P(MMA-co-MAOC) blends prepared using 1% by weight of fluorescent copolymer show a homogeneous morphology completely similar to pure PMMA and are still optically active
An Investigation of Condensation Effects in Supercritical Carbon Dioxide Compressors
No full textSupercritical CO[subscript 2](S-CO[subscript 2]) power cycles have demonstrated significant performance improvements in concentrated solar and nuclear applications. These cycles promise an increase in thermal-to-electric conversion efficiency of up to 50% over conventional gas turbines (Wright, S., 2012, "Overview of S-CO[subscript 2] Power Cycles," Mech. Eng., 134(1), pp. 40-43), and have become a priority for research, development, and deployment. In these applications the CO[subscript 2] is compressed to pressures above the critical value using radial compressors. The thermodynamic state change of the working fluid is close to the critical point and near the vapor-liquid equilibrium region where phase change effects are important. This paper presents a systematic assessment of condensation on the performance and stability of centrifugal compressors operating in S-CO[subscript 2]. The approach combines numerical simulations with experimental tests. The objectives are to assess the relative importance of two-phase effects on the internal flow behavior and to define the implications for radial turbomachinery design. The condensation onset is investigated in a systematic manner approaching the critical point. A nondimensional criterion is established that determines whether condensation might occur. This criterion relates the time required for stable liquid droplets to form, which depends on the expansion through the vapor-pressure curve, and the residence time of the flow under saturated conditions. Two-phase flow effects can be considered negligible when the ratio of the two time scales is much smaller than unity. The study shows that condensation is not a concern away from the critical point. Numerical two-phase calculations supported by experimental data indicate that the timescale associated with nucleation is much longer than the residence time of the flow in the saturated region, leaving little opportunity for the fluid to condense. Pressure measurements in a converging diverging nozzle show that condensation cannot occur at the level of subcooling characteristic of radial compressors away from the critical point. The implications are not limited to S-CO[subscript 2] power cycles but extend to applications of radial machines for dense, saturated gases. In the immediate vicinity of the critical point, two-phase effects are expected to become more prominent due to longer residence times. However, the singular behavior of thermodynamic properties at the critical point prevents the numerical schemes from capturing important gas dynamic effects. These limitations require experimental assessment, which is the focus of ongoing and future research.Mitsubishi Heavy Industries Takasago R&D Cente
Use of health apps and wearable devices : Survey among Italian associations for patient advocacy
No full textBackground: Technological tools such as Web-based social networks, telemedicine, apps, or wearable devices are becoming more widespread in health care like elsewhere. Although patients are the main users, for example, to monitor symptoms and clinical parameters or to communicate with the doctor, their perspective is seldom analyzed, and to the best of our knowledge, no one has focused on the patients’ health care advocacy associations’ point of view. Objective: The objective of this study was to assess patients’ health care advocacy associations’ opinions about the use, usefulness, obstacles, negative aspects, and impact of health apps and wearable devices through a Web-based survey. Methods: We conducted a Web-based survey through SurveyMonkey over nearly 3 months. Participants were contacted via an email explaining the aims of the survey and providing a link to complete the Web-based questionnaire. All the 20 items were mandatory, and the anonymized data were collected automatically into a database. Only fully completed questionnaires were considered for analysis. Results: We contacted 1998 patients’ health care advocacy associations; a total of 258 questionnaires were received back (response rate 12.91%), and 227 of the received questionnaires were fully completed (completion rate 88.0%). Informative apps, hospital apps for viewing medical reports or booking visits, and those for monitoring physical activity are the most used. They are considered especially useful to improve patients’ engagement and compliance with treatment. Wearable devices to check physical activity and glycemia are the most widespread considering, again, their benefits in increasing patients’ involvement and treatment compliance. For health apps and wearable devices, the main obstacles to their use are personal and technical reasons; the risk of overmedicalization is considered the most negative aspect of their constant use, while privacy and confidentiality of data are not rated a limitation. No statistical difference was found on stratifying the answers by responders’ technological level (P=.30), age (P=.10), and the composition of the association’s advisory board (P=.15). Conclusions: According to responders, health apps and wearable devices are sufficiently known and used and are considered potential supports for greater involvement in health management. However, there are still obstacles to their adoption, and the developers need to work to make them more accessible and more useful. The involvement of patients and their associations in planning services and products based on these technologies (as well as others) would be desirable to overcome these barriers and boost awareness about privacy and the confidentiality of data
Unconventional use of mixed-phase TiO2 as optical gauge of molecular oxygen with ratiometric-enhanced responsivity
No full textWe show that mixed-phase (MP) titanium dioxide (TiO2) can be effectively employed as an unconventional, inorganic, dual-emitting and ratiometric optical sensor of O2. Thanks to the peculiar “anti-correlated” photoluminescence of the two TiO2 crystal phases, MP-TiO2 exhibits an unusual ratiometric-enhanced responsivity. Simultaneous availability of rutile and anatase TiO2 PL allows using their ratio as measurement parameter associated to O2 concentration, leading to larger experimental responsivity compared to the one obtainable for single-phase PL detection. A proof of this concept is given, showing a two-fold enhancement of the optical responsivity. Additional characteristics of mixed phase TiO2 can be envisaged as favorable for O2 optical probing, namely: (a) low production costs, (b) absence of heterogeneous components, (c) self-supporting properties. These characteristics promote testing mixed phase TiO2 use for applications requiring high indicator quantities at competitive price, possibly also tackling the need to develop supporting matrixes that carry the luminescent probes and avoiding issues related to the use of different components for ratiometric sensing
Social Return on Investment of a robotic exoskeleton for upper limb rehabilitation after stroke
No full textA stroke is a medical situation characterized by acute deterioration of brain functions lasting more than 24 hours. Worldwide, it is the third leading cause of death and disability together. One of the most common consequences for stroke survivors is upper limb impairment; this can have a significant impact on patients’ quality of life, and an appropriate rehabilitation strategy is needed to improve their status. Repetitive and monitored movements typical of robotic rehabilitation, whose market has grown rapidly in recent years, have the potential to enhance functional recovery.
A team of researchers at Politecnico di Milano has developed an exoskeleton for upper limb rehabilitation, called AGREE, at the stage gate between translational research and clinical validation. Since the cost of this device is particularly high, the present study aimed to provide a framework for assessing its value. The Social Return On Investment (SROI) method, which unlike other economic analyses is able to grasp the economic, social and environmental impact of an activity, was applied. The stakeholders considered were patients, hospitals, physiotherapists, caregivers, and employers of stroke patients.
Expert opinions of a pool of clinical engineers and healthcare professionals from different Italian hospitals were used to obtain information. Inputs and outcomes were identified and monetized for the stakeholders. Attribution, deadweight, and drop-off were then estimated to calculate the final SROI value. This was done with a 5-year time horizon for both a single exoskeleton and a number of exoskeletons sold estimated by the authors. Environmental impacts were estimated through Life Cycle Assessment (LCA) and expressed in terms of CO2 emissions; once monetized, they were incorporated into the outcomes of the analysis. The SROI for a single exoskeleton was 3.75 and that for multiple exoskeletons was 2.868.
In summary, the SROI value for multiple exoskeletons is lower than that for a single exoskeleton, because the higher the number of exoskeletons sold, the higher the outcomes but also the associated inputs. Moreover, the environmental result did not have a large influence on the SROI, as the technology has a much greater social impact. This study provides a model for combining economic, social and environmental outcomes that, besides contributing to theory, could be useful for decision-making. Future research should focus on reducing the subjectivity and uncertainty of this study, by a higher involvement of stakeholders
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