Cyclodextrin Insulation Prevents Static Quenching of Conjugated Polymer Fluorescence at the Single Molecule Level

Conjugated polymers (CPs) are promising materials for fluorescence imaging application. However, a significant problem in this field is the unexplained abnormally low fluorescence brightness (or number of fluorescence photons detected per one excitation photon) exhibited by most of CP single chains in solid polymer hosts. Here it is shown that this detrimental effect can be fully avoided for short chains of polyfluorene‐bis‐vinylphenylene (PFBV) embedded in a host polymer matrix of PMMA, if the conjugated backbone is insulated by cyclodextrin rings to form a polyrotaxane (PFBV‐Rtx). Fluorescence kinetics and quantum yields are measured for the polymers in liquid solutions, pristine films, and solid PMMA blends. The fluorescence brightness of PFBV‐Rtx single chains dispersed in a solid PMMA is very close to that expected for a chain with 100% fluorescence quantum yield, while the unprotected PFBV chains of the same length possess 4 times lower brightness. Despite this, the fluorescence decay kinetics are the same for both polymers, suggesting the presence of static or ultrafast fluorescence quenching in the unprotected polymer. About 80% of an unprotected PFBV chain is estimated to be completely quenched. The hypothesis is that the cyclodextrin rings prevent the quenching by working as ‘bumpers’ reducing the mechanical forces applied by the host polymer to the conjugated backbone and help retaining its conformational freedom. While providing a recipe for making CP fluorescence bright at the single‐molecule level, these results identify a lack of fundamental understanding in the community of the influence of the environment on excited states in conjugated materials.     

Large Scale Probabilistic Drought Characterization Over Europe

A reliable assessment of drought return periods is essential to help decision makers in setting effective drought preparedness and mitigation measures. However, often an inferential approach is unsuitable to model the marginal or joint probability distributions of drought characteristics, such as drought duration and accumulated deficit, due to the relatively limited number of drought events that can be observed in the historical records of the hydrological variables of interest. As an alternative, the marginal and multivariate probability cdf’s of drought characteristics can be derived as functions of the parameters of the cdf of the underlying variable (e.g. precipitation), whose sample series is usually long enough to obtain trustworthy estimates in a statistical sense. In this study, the latter methodology is applied to investigate space-time variability of drought occurrences over Europe by using the CRU TS3.10.01 precipitation dataset for the period 1901–2009. In particular, a methodology able to take into account autocorrelation in the underlying precipitation series is adopted. First, a spatial analysis of historical droughts at European level is carried out. Then, the joint probability distributions of drought duration and accumulated deficit are derived for each cell, with reference to both historical and design drought events. Finally, the corresponding bivariate drought return periods are computed, as the expected values of the interarrival time between consecutive critical droughts.Results show that several heavy drought episodes have widely affected the continent. Among the most recent events, drought occurred during the period 1985–1995 was the worst in terms of extent of the regions characterized by return periods greater than 250 years. Besides Euro-Mediterranean regions, North Western and Central Eastern regions appear more drought prone than the rest of Europe, in terms of low values of return periods.     

A general framework for modeling long-term behavior of earth and concrete dams

Many problems are linked with the long-term behavior of both earthdams and concrete dams. They range from hydraulic fracturing to alkali-silica reaction (ASR) and to repair work in concrete dams, from seismic behavior to secondary consolidation in earthdams. A common framework for the simulation of such systems is shown, based on the mechanics of multiphase porous media. The general model is particularized to specific situations and several examples are shown.     

Energy retrofit of historical buildings: theoretical and experimental investigations for the modelling of reliable performance scenarios

The paper suggests a multi-criteria approach for the energy refurbishment of historical buildings, proposing methodologies for the performance analysis, coupling several experimental and numerical studies. The target consisted in a rigorous evaluation procedure, in order to guarantee the necessary reliability of a numerical model of the system “building envelope/technical plants”, on which testing the technical and economical convenience of energy retrofit solutions.The paper collects the long work carried out by several Institutions during the last years, on Building “Palazzo dell’Aquila Bosco-Lucarelli”, a historical building located in Benevento (Southern Italy), currently analyzed in order to define the technical adoption of possible improving actions.The carried out studies, beyond the proposition of an operational methodology, are aimed to evidence a best-practice specified for the Italian territorial context, which has several historical buildings needing restoration.Carefully applied investigations, based on various methodologies and through several instrumentations, allowed the definition of a numerical model correspondent to the real building, defined also comparing the results with the historical requests of gas and electricity. Moreover, dynamic energy simulations tested the effectiveness, singularly and coupled, of several solutions for the building energy optimization. A significant potentiality of energy and economic optimization has been demonstrated.     

Thermoreversible and remendable glass-polymer interface for fiber-reinforced composites

Adhesion of the reinforcement to the polymer matrix is essential for load transfer from the polymer matrix to the reinforcement material in fiber-reinforced composites. The reversible Diels-Alder reaction between a furan-functionalized epoxy-amine thermosetting matrix with a maleimide-functionalized glass fiber was used to impart remendability at the polymer-glass interface for potential application in glass fiber-reinforced composites. At room temperature the Diels-Alder adduct is formed spontaneously and above 90 °C the adduct breaks apart to reform the original furan and maleimide moieties. Healing of the interface was investigated with single fiber microdroplet pull-out testing. Following complete failure of this interface, significant healing was observed, with some specimens recovering over 100% of the initial properties. Healing efficiency was not affected by the distance of displacement, with an overall average of 41% healing efficiency. Up to five healing cycles were successfully achieved. It is expected that a glass fiber-reinforced composite of maleimide-sized glass within a furan-functionalized network will demonstrate extension of fatigue life.     

A Comparative Life Cycle Assessment of Disposable and Reusable Packaging for the Distribution of Italian Fruit and Vegetables

Each year in Italy, millions of tons of fruits and vegetables are harvested, packed and transported to national and foreign retail outlets. Packaging is an essential component of this system, but what is its environmental impact? This study takes into consideration the delivery from the field to the retail outlet of 12 types of fruits and vegetables grown and harvested in Italy and sold in Italy and Europe. The study compares two different packaging and distribution systems: one‐way with corrugated boxes and reusable with plastic containers. A number of different scenarios were generated by combining the most diffused packaging sizes with the most important production and selling locations for each type of fruit and vegetable and by considering the specific route required to perform the transportation with each distribution system. The environmental impact of each system in each scenario has then been analysed using the life cycle assessment methodology. Two algorithms and a number of coefficients were derived to simplify data collection and impact analysis for all scenarios. This provides an easy tool to evaluate the potential environmental burden of the two alternative distribution systems in a specific scenario by taking into consideration only a few variables (such as size of packaging and transportation distance). These algorithms and coefficients are presented in the work, along with the process that led to their generation and with considerations about the main critical environmental aspects for both distribution systems. The work aims to suggest possible design solutions that can make each system more sustainable. Copyright © 2011 John Wiley & Sons, Ltd.     

Fabrication of miniaturized Si-based electrocatalytic membranes

The increasing interest for lightweight and portable electronic systems, cellphones and small digital devices is driving technological research towards integrated regenerating power sources with small dimensions and great autonomy. Conventional batteries are already unable to deliver power in ever smaller volumes while maintaining the requirements of long duration and light weight. A possible solution to overcome these limits is the use of miniaturized fuel cells. The fuel cell offers a greater gravimetric energy density compared to conventional batteries. The micromachining technology of silicon is an important tool to reduce the fuel cell structure to micron sizes. The use of silicon also gives the opportunity to integrate the power source and the electronic circuits controlling the fuel cell on the same structure. This article reports preliminary results concerning the micromachining process for fabricating a silicon-based electrocatalytic membrane for miniaturized Si-based proton-exchange membrane (PEM) fuel cells.     

Editorial for the special issue on recent advances in adaptive methods for frequency estimation with applications

The Special Issue presents results of current research on adaptive methods designed for periodic signals with unknown frequency. The first group of papers presents new methods for parameter estimation, while the second group focuses on practical applications involving active noise and vibration control problems. These papers are compiled in a special virtual issue of the journal at the journal homepage. To access all of the papers please follow the following link http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-1115/homepage/virtual_issue_-_recent_advances_in_adaptive_methods_for_frequency_estimation_wit.htm . ? ? Correction added on 3 October 2016, after first online publication: Reference to the virtual issue was added.
Copyright © 2016 John Wiley & Sons, Ltd.     

Comparison of traditional and reductive winemaking: influence on some fixed components and sensorial characteristics

An explorative study to verify the applicability of reductive winemaking (RW) on two cultivars was carried out. To this purpose, traditional winemaking (TW) and RW were carried out on a semi-aromatic white grape (Sauvignon blanc) and a white neutral one (Trebbiano romagnolo). All phenolic parameters were higher in RW wines, while other substances such as alcohol, reducing sugars, acids, and volatile acidity acids were less affected by the different winemaking technique. A deeper yellow color (OD 420) was a direct consequence of the higher phenolic content of RW wines, while OD 320 was strictly related to caftaric acid integrity. Analyses showed a modification of the RW wines, also in the case of a neutral cultivar. Principal component analysis (PCA) was applied to the data set, and the first two PCs explained almost 85% of the total variability and divided TW and RW wines in two groups to demonstrate that the effect of winemaking overwhelmed maturation differences. Panelists preferred RW wines, which were characterized by a richer and more delicate aroma. The study demonstrated that a careful exclusion of air combined with an effective oxidation prevention yields to more characterized and pleasant wines.