117,301 research outputs found
Effects of glutathione on the luminescent behavior of CdSe-nanocrystals
No full textThe luminescent behavior of semiconductor nanocrystals is a sensitive reporter of their electronic properties and of the impact of surface passivation on the excitonic state. In this work, CdSe nanocrystals (CdSe-Nc) are prepared in microemulsions and the effects of tripeptide Glutathione (GSH) as a stabilizing ligand, are examined. The CdSe samples are investigated by steady-state and time-resolved luminescence methods. The luminescent properties of CdSe without GSH spectrally evolve over time, and a dramatic reduction of luminescence intensity and decay times are observed. This behavior suggests that although the colloids are in microemulsion media, they undergo progressive aging that ruins their luminescent properties. The presence of GSH in the microemulsions at the beginning of the synthesis stops the nanocrystal aging, thus acting as an efficient stabilizing agent, freezing the luminescence properties of CdSe nanocrystals. The effects of GSH on the colloids are also documented by a detailed analysis of luminescence decay times, carried out through the Maximum Entropy Method. Interestingly, the addition of GSH on aged CdSe colloids is able to not only stabilize the structures but also recover the luminescent efficiency leading to an attractive “brightening” effect
On kids' environmental wellbeing and their access to nature in urban heat islands: Hyperlocal microclimate analysis via surveys, modelling, and wearable sensing in urban playgrounds
No full textThe aim of this research is to investigate the environmental wellbeing of children in urban outdoor environments by developing and testing a new wearable device called the Baby c-air. Children are particularly vulnerable to environmental discomfort due to their physiological characteristics and lack of awareness about their own adaptation capabilities. This vulnerability can lead to childhood diseases and health issues, especially when exposed to overheating or continuous pollutants. Portable monitoring devices, such as the Baby c-air, can assess children's environmental exposure and provide timely information to limit their health risks.The study involved testing two prototypes of the Baby c-air under laboratory and in-field conditions to verify the accuracy of the device in collecting data. An experimental campaign involving 122 children was conducted in Italy during the summer, across four playgrounds. The option of integrating the COMFA-kid model for thermal comfort assessment was evaluated. The results indicated that microclimate peculiarities underline the importance of a human-centric approach for properly addressing environmental exposure. The discrepancies between thermal sensations provided by interviewed parents/tutors and predicted thermal sensations derived by the COMFA-kid model suggest that adults are generally weakly aware of children's thermal conditions.The Baby c-air can support children's adaptation potential and drive accompanying persons towards implementing conscious behaviors or moving to those areas with better environmental quality. The outcomes of this study can contribute towards urban outdoor design guidelines to improve children's well-being
AFM Measurements to Investigate Particulates and Their Interactions with Biological Macromolecules
No full textEvaluation of cytotoxicity effects of nanoparticles present in working environments: preliminary results.
No full textPhotophysical properties of halo-derivatives of angelicins
No full textThe properties of the lowest excited singlet and triplet state of four halo-angelicins (HA) have been investigated by steady-state and time-resolved spectrometric techniques. The study has been performed in solvents with different polarity and proticity: cyclohexane, dioxane, acetonitrile, ethanol and 2,2,2-trifluoroethanol. Absorption and emission spectra showed that the nature of lowest singlet state is mainly pi,pi* and the transitions are allowed or partially allowed. Absorption coefficients, fluorescence quantum efficiency and lifetimes are also presented. Flash photolysis investigations have indicated the presence of a unique transient assignable to the lowest triplet state T-1. The triplet state has been characterized in terms of absorption spectra, decay kinetics, molar absorption coefficients and formation quantum yields. The racing of both intersystem crossing and fluorescence quantum yields going from a non-polar to a highly polar-protic solvent indicates the presence of a S-2 state, n,pi* in nature, close lying to the pi,pi* one. The quantum yields of the singlet decay pathways (fluorescence, intersystem crossing and internal conversion) depends markedly on the energy gap between S-1 and S-2 states in agreement with the manifestation of the "proximity effect". In fact in cyclohexane HA decay mainly through S-1 -> S-0 internal conversion, while in trifluoroethanol their fluorescence and intersystem crossing increase significantly.
Singlet-oxygen quantum yields have been also determined in order to understand the possible application of the investigated drugs in photodynamic therapy. The absence of photochemical pathways allowed the indirect evaluation of the internal conversion decay bringing to the achievement of a complete decay pathways picture
Engineering Biodegradable Polymers to Control Their Degradation and Optimize Their Use as Delivery and Theranostic Systems
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Spectrophotometric analysis of nickel colloid performances as catalysts for hydrogenation of nitro-phenol: Influence of the stabilizing agents
No full textNickel nanoparticles are prepared through thermolysis or polyol procedures and they are fully characterized through TEM and XRD. The catalytic efficiencies are tested toward the hydrogenation reaction of 4-nitrophenol, which was spectrophotometrically detected. A significant improvement of the reaction rate and turnover number (TON) and frequency (TOF) is observed using alkyl amine-stabilized nanoparticles, likely due to their reduced surface steric hindrance. However, the polymer stabilized-nanocatalysts show a better selectivity for product formation, since only hydrogenation products are observed, while azo-benzene derivatives are detected when alkyl amine-stabilized nanoparticles are used. The findings indicate an important impact of surface properties of colloids on the catalysed reaction
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