1,354,278 research outputs found
Self-propagating frontal copolymerization
No full textThe application of self-propagating frontal polymerization (FP) to synthesize copolymers has been investigated. Frontal copolymerizations of methyl methacrylate and methacrylic acid(MMA-MAA), acrylic acid and methacrylic acid (AA-MAA), and styrene and methacrylic acid(STY-MAA) with benzoyl peroxide (BPO) as initiator have been performed. The measured front velocities have been compared with the results of a suitably developed model. This is based on the pseudokinetic approach, accounts for the depropagation reaction, and is fully predictive; i.e., it does not include any adjustable parameter (although one had to be used for the specific experimental setup used in this work). An explicit, simplified solution of the model has been obtained using the constant pattern approximation. The microstructures of copolymers produced in bulk and by FP have been analyzed by differential scanning calorimetry. Their comparison indicates that self-propagating frontal copolymerization provides a substantial improvement in the uniformity of the chain composition distribution. (C) 1998 John Wiley & Sons, Inc
INTEGRATED THERMAL ENERGY STORAGE SYSTEM - ROLE OF MANAGEMENT STRATEGY IN DESIGN OF A STORAGE TANK
No full textIn recent years, our society has experienced an important energy transition that is becoming a central aspect in geopolitical choices in several countries around the world. However, several issues arise from these scenarios, in which an increasing number of RES power plants are installed and connected to electrical grids. In fact, most renewable sources, such as wind and solar, are characterised by a fluctuating and unpredictable behaviour that causes a decrease in the quality of the energy transmitted through the grid and leads to a more difficult management of the grid itself. To mitigate and reduce these negative aspects, it is important to install devices, such as storage systems, capable of facilitating the correct management of electrical grids, meeting, at the same time, the electrical demand of the users and the energy produced in RES-based power plants. Although several technologies have been proposed over the years, Carnot batteries seem to guarantee adequate performances without stringent geographical constraints and represent a promising solution. Among them, integrated thermal energy storage systems (IT-ESS) can be easily installed and coupled with existing power plants. The central element of such technology is represented by a sensible heat-thermal energy storage device, consisting of a packed bed. The literature is still lacking accurate design methods for the storage tank, and this is the leading aspect that led the authors to develop an innovative procedure to determine the size of the storage device, based on the necessity of producing energy during the night, while the accumulation phase occurs during the day. In this phase, the power of a photovoltaic plant is exploited: the plant is described through curves that reproduce the power generated in a typical day for each month of the year. An algorithm built in the MATLAB environment had been used to determine the volume of the storage device, with the goal of being able to cover the hours in which the PV is not producing energy. The results of the analysis have underlined the need to consider in a proper way both the user needs and the characteristics of the renewable power plants, to correctly evaluate the volume of the storage tank to be installed in the system
Street-crossing behavior of people with disabilities
No full textPhysical disability is as a multifaceted phenomenon, whose manifestations may be difficult to realize and properly address when designing or improving urban built environments. The mere application of technical requirements cannot account for designing accessible public spaces and infrastructures for pedestrian mobility. In this perspective, unsignalized crosswalks are emblematic. Design recommendations for them are prevalently focused on purely technical aspects, such as pedestrian walking speed and visibility problems. Apprehension and nervousness experienced by pedestrians when attempting to traverse the roadway is usually neglected, but this uneasinesses may weaken the autonomy and comfort of pedestrians with disabilities. Interaction with approaching drivers is a decisive factor. It is known that unimpaired pedestrians attempt hazardous crossings if they realize that drivers do not observe their right-of-way. The question arises of investigating street-crossing behavior of people with different impairments and their interaction with drivers. Field surveys was carried out wherein people with different disabilities were requested to traverse the roadway using unsignalized crosswalks. Survival analyses were then applied on gathered waiting times at the curbside to ascertain the way in which disability status and other characteristics influence the interaction between drivers and pedestrians. However, given the complexity of the examined phenomenon, the analytical approach must act in synergy with qualitative observations and people's concerns for acquiring the most possible complete framework. Street crossing was particularly arduous for people in wheelchairs, while individuals with hearing impairments revealed unexpected versatility against a hostile urban environment. © 2015 American Society of Civil Engineers
Optimization and assessment method to approach industrial site decarbonization: A case study of a light industry
No full textThe industrial sector includes a wide range of industries and processes for which a single approach or universal strategies for decarbonization can hardly be identified. In general, the most efficient way to decarbonize building sites consists of two phases: (i) reduce the energy demand and (ii) replace the fossil-based power generation units with renewable energy sources, possibly working on the management of HVAC systems to reduce the required peak power. Literature provides general rules and schemes, but no specific works on the energy retrofit of industrial buildings have been found in literature so far. The present study investigates an existing industrial district, using dynamic energy models of buildings tuned with the current conditions and compared with seven decarbonization scenarios. A neutral water loop exchanging heat with the ground has been studied, representing a widely replicable solution due to the higher heat exchange efficiency and the modular installation, which can be expanded within the site. The significant energy savings (28%) and CO2 emission reduction (up to 70%) obtained are representative of the potential achievable for many industrial sites in mild European climates, where decarbonization should achieve optimal cost-benefit results while minimizing the impact on the production through modular approaches
Concanavalin A-Rose Bengal bioconjugate for targeted Gram-negative antimicrobial photodynamic therapy
No full textPhotodynamic therapy (PDT) is considered a very promising therapeutic modality for antimicrobial therapy. Although several studies have demonstrated that Gram-positive bacteria are very sensitive to PDT, Gram-negative bacteria are more resistant to photodynamic action. This difference is due to a different cell wall structure. Gram-negative bacteria have an outer cell membrane containing lipopolysaccharides (LPS) that hinder the binding of photosensitizer molecules, protecting the bacterial cells from chemical attacks. Combination of the lipopolysaccharides-binding activity of Concanavalin A (ConA) with the photodynamic properties of Rose Bengal (RB) holds the potential of an innovative protein platform for targeted photodynamic therapy against Gram-negative bacteria. A ConA-RB bioconjugate was synthesized and characterized. Approximately 2.4 RB molecules were conjugated per ConA monomer. The conjugation of RB to ConA determines a decrease of the singlet oxygen generation and an increase of superoxide and peroxide production. The photokilling efficacy of the ConA-RB bioconjugate was demonstrated in a planktonic culture of E. coli. Irradiation with white light from a LED lamp produced a dose-dependent photokilling of bacteria. ConA-RB conjugates exhibited a consistent improvement over RB (up to 117-fold). The improved uptake of the photosensitizer explains the enhanced PDT effect accompanying increased membrane damages induced by the ConA-RB conjugate. The approach can be readily generalized (i) using different photo/sonosensitizers, (ii) to target other pathogens characterized by cell membranes containing lipopolysaccharides (LPS)
Polymer blends by self-propagating frontal polymerization
No full textThe use of self-propagating frontal polymerization to produce polymer blends has been investigated. A homogeneous solution of monomer, polymer (of a second monomer), and initiator is initially heated at a specific location to start a polymerization front that propagates along the system. The obtained polymerization reaction is very fast compared with diffusion, sea that the two types of macromolecules remain homogeneously distributed, as in the original monomer/polymer solution. In the case of two incompatible polymers, the system has no time to reach the equilibrium condition where phase separation occurs and a polymer blend is obtained in the form of a metastable solution. Applications to two incompatible pairs (methyl methacrylate-styrene and methyl methacrylate-methacrylic acid) are discussed. Moreover, it has been found that the presence of inert polymer in the initial mixture improves the process performance, leading to more stable propagation fronts, lower front temperatures, and higher monomer conversions. (C) 1998 John Wiley & Sons, Inc
Influence of hybrid lactose-permeate standardisation on the physicochemical and functional properties of skim milk and concentrates
No full textStandardisation of protein content is important in ensuring consistent composition and functionality of dairy powders, especially those made from a seasonal milk supply. This study investigated the effects of hybrid standardisation media, composed of lactose and permeate mixtures, on the physicochemical and functional properties of skim milk concentrates. The protein content target was 3.5 %, using five different permeate:lactose (P:L) ratios: 100P, 75P:25L, 50P:50L, 25P:75L, and 100L (at 8 % total solids (TS)), followed by evaporation to 52 % TS. Results showed that higher P:L ratios led to higher viscosity of skim milk concentrates and enhanced the heat stability of protein-standardised milk at pH in the ranges 6.4–6.7 and 7.0–7.2. Mineral analysis reflected higher concentrations of calcium, phosphorous, and trace minerals for higher P:L ratios, contributing to higher buffering capacity, increased micellar hydration and larger particle size post-evaporation. These findings demonstrate the potential of hybrid standardisation media to optimise processing conditions in milk powder production, balancing enhanced heat stability and viscosity development of milk concentrates
Stump appendicitis: a rare and unusual complication after appendectomy. Case report and review of the literature
No full textI NTRODUCTION : Stump appendicitis is a rare but important complication that can occour after an open or laparoscop-
ic appendectomy. Although it represents a recognized serious condition that should not be overlooked, it is not often con-
sidered by surgeons within the differential diagnoses faced with a patient presenting right iliac fossa abdominal pain,
particularly those who present a previous history of appendectomy.
M ATERIAL OF S TUDY : A comprehensive review of English literature was performed and 87 cases of stump appendicitis
were identified. Each case was charted based on 10 variables and data were analyzed. One original case of stump appen-
dicitis after open appendectomy treated at our institution is also described and taken as a model.
D ISCUSSION : Several factors may contribute to the etiology of stump appendicitis, mainly related to the length of the
residual tissue after appendectomy. A delay in diagnosis, possibly misled by a previous history of appendectomy, represents
a risk of complications and possible stump perforation. The imaging studies, especially CT scan, seem to be helpful tools
in getting the earliest possible diagnosis.
C ONCLUSION : Surgeons should be aware of the occurrence of this rare but dangerous entity, in order to avoid a delay
in diagnosis and in the appropriate therapeutic choice. We want to emphasize also the technical recommendations to be
respected in course of appendectomy
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