382 research outputs found
NOVEL PT(II) AND IR(III) COMPLEXES WITH NON-LINEAR OPTICAL AND LUMINESCENT PROPERTIES.
No full textMy PhD project has been focused on the synthesis of novel Pt(II) and Ir(III) complexes with nonlinear optical (NLO) and luminescent properties.
Metal complexes with nonlinear optical properties:
It is known that molecules formed by donor (D) and acceptor (A) groups linked with an unsaturated bridge having polarizable π-electrons are particularly NLO-efficient. Compared to organic compounds, metal complexes can offer further flexibility due to the presence of NLO-active charge transfer transitions between the metal and the ligands, usually at relatively low energy and of high intensity, tunable by virtue of the nature, oxidation state and coordination sphere of the metal center.[1] Based on the fact that metal alkynyl fragments are good donors in NLO-active systems, the idea of a hybrid with a C60-fullerene is highly intriguing because C60 is an electron deficient compound that can act as a good electron acceptor. For this reason, novel Pt-fullerene-alkynyl complexes were prepared and studied during the first part of my thesis.
We applied the EFISH (Electric-field induced second harmonic generation) method to study their NLO response in solution.
The huge values of μβEFISH observed for the fullerene platinum alkynyl derivatives are remarkable for neutral metal complexes. Indeed, to our knowledge, one of the complexes is characterized by the highest absolute value of μβEFISH reported for a platinum alkynyl complex. In order to evaluate also the solid state NLO properties (Second Harmonic Generation, SHG), composite films of some complexes dispersed both in polymethylmethacrylate (PMMA) and polystyrene were prepared. The preliminary data confirm the important role of the matrix whose specific functionalities can lead to host-guest interactions and affect the stability of the organized NLO molecules.
During the thesis, various cyclometallated anionic Ir(III) complexes were also prepared in order to study their second-order NLO properties, by using the EFISH technique.
To our knowledge EFISH studies on anionic metal complexes have never been performed. Preliminary results show that the prepared novel anionic iridium complexes are characterized by a good NLO response in CHCl3 solution.
In parallel, some multifunctional cyclometallated neutral Ir(III) complexes were prepared, some of which resulted to provide good μβEFISH values.
Metal complexes with luminescent properties:
In the second part of my thesis, the luminescent properties of the prepared neutral Ir(III) complexes were investigated. Some of them turned out to be of interest for electroluminescent devices and biomedical application, showing a deep blue emission in degassed CH2Cl2. With such complexes OLED devices were fabricated. To our knowledge, they led to the bluest and best-performing iridium-based OLED reported so far (EQEmax = 13.4%).[2]
Further, for some complexes the effect given by the addition of EWG elements on the ligand mojety was investigated. The most promising of complexes were used to fabricate an OLED devices.
It turned out that one of above mentioned Ir(III) neutral complexes resulted to have also a remarkable cytotoxic activity. Besides, the internalization, cytotoxicity and photocytotoxicity were studied in collaboration with Dr. Simona Polo in the IFOM Institute in Milan. This complex appears to be a very promising photosensitizer for combined photodynamic therapy and cellular imaging. It has several desirable properties for the purpose: (i) it is highly phosphorescent and soluble; (ii) it easily enters into cells where it is concentrated in mitochondria, even at limited concentration; (iii) it is highly phototoxic upon irradiation with suitable light, but not cytotoxic in the dark.[3]
In conclusion, during this thesis various novel Pt(II) and Ir(III) complexes were prepared and well characterized. Some of them show interesting second-order NLO properties whereas others are good candidates for the preparation of OLEDs. One of the complexes may offer interesting future potential for phototherapeutic applications in combination with emission imaging microscopy.
References:
[1] See for instance: Di Bella, S. et al. In Topics in Organometallic Chemistry 28. Molecular Organometallic Materials for Optics; Eds: Le Bozec, H. et al. Springer, 2010, 28, 1. [2] Pal A. K., Krotkus S., Fontani M., Mackenzie C. F. R., Cordes D. B., Slawin A. M., Samuel I. D. W., Zysman-Colman E. Accepted by Advanced Materials. [3] Colombo, A., Fontani, M. , Dragonetti, C., Roberto, D. , Williams, J.A.G., Scotto di Perrotolo, R., Casagrande, F., Barozzi, S., and Polo, S. submitted to Chem. Eur. J.
A Note on Relative Efficiency of Axiom Systems
No full textWe introduce a notion of relative efficiency for axiom systems. Given an axiom system A_eta for a theory T consistent with S^1_2, we show that the problem of deciding whether an axiom system A_alpha for the same theory is more efficient than A_eta is Pi_2-hard. Several possibilities of speed-up of proofs are examined in relation to pairs of axiom systems A_alpha, A_eta, with A_alpha including A_eta, both in the case of A_alpha, A_eta having the same language, and in the case of the language of A_alpha extending that of A_eta: in the latter case, letting Pr_alpha, Pr_eta denote the theories axiomatized by A_alpha, A_eta, respectively, and assuming Pr_alpha to be a conservative extension of Pr_eta, we show that if A_alpha-A_eta contains no nonlogical axioms, then A_alpha can only be a linear speed-up of A_eta; otherwise, given any recursive function g and any A_eta, there exists a finite extension A_alpha of A_eta such that A_alpha is a speed-up of A_eta with respect to g
Sezione 321040, Foglio 321 Abbadia S. Salvatore, Carta Geologica Regionale, Scala 1:10.000, Regione Toscana
No full textMetadati Carta Geologica Regione Toscana scala 1:10.000. http://159.213.57.103/geoweb/listmet/lista_metadati_10k.ht
Different effects of ACTH fragments on hippocampal EEG and behavior
No full textThe hippocampal electrical activity and behavior of rabbits have been studied in the presence of novel and emotional stimuli. The effects of these stimuli have been recorded in controls and in groups of animals treated with ACTH (4-10)(10 micrograms/100 g, i.m.) and ACTH (1-24) (10 micrograms/100 g, i.m.). Recordings were made immediately and 30 min after injection. ACTH (4-10) injection failed to evoke any significant behavioral or electrical response. Rabbits recorded 30 min after ACTH (1-24) injection showed a reduction of hippocampal RSA (rhythmic slow activity) frequency and behavioral activity. In particular, reduction of exploration, self-grooming, motor activity and approaches to the new object have been observed. Since ACTH is characterized by a corticotropic action these results can be due to corticosteroid stimulation
Effect of Omega-3 and Policosanol supplementation on attention and reactivity in athletes
No full textOBJECTIVE: The purpose of this study was to determine the effect of omega-3 fatty acids and policosanol supplementation on the cognitive processes involved in the control of reactivity in karateka engaged in attention tests.
METHODS: Eighteen karateka were randomly assigned to 2 groups. One group (10 subjects) took the supplement of omega-3 fatty acids (2.25 g) plus policosanol (10 mg) (O3 + P) for 21 days, and the other group was supplemented with placebo (oleic sunflower oil). Subjects were tested at the beginning of the experiment (Test 1), after 21 days (Test 2), and after 42 days (Test 3). The experimental procedure consisted of an Alert and a Sustained Attention (SA) reaction time test: the subject had to react by pressing a key of a computer keyboard in Alert and a sequence of 3 keys in SA in response to stimuli, activating a complex go/no-go paradigm. For each test, we recorded the reaction time and the event-related potentials by electroencephalogram and electromyography (EMG) of the forefinger flexor muscle. The Profile of Mood States (POMS) test was also administered.
RESULTS: After 21 days of supplementation, subjects who received O3 + P showed a reduced reaction time and increased vigor sensation associated with a reduction of the negative states measured with the POMS test. Analysis of the event-related brain potentials showed a reduced latency of the movement-related brain macropotentials. In particular, the potentials recorded in the premotor period and motor period occurred earlier and the latency of EMG activation was reduced. In the third test, 21 days after the last O3 + P supplementation, the positive effects on the mood state persisted, while the reaction time, EMG, and brain potential latencies increased, although their values remained lower than in the first test. The placebo group did not show any significant differences in Tests 2 and 3 compared to Test 1 for either POMS or reactivity and brain potentials.
CONCLUSIONS: Supplementation with O3 + P may be effective in improving mood state and reactivity. The reaction time reduction appears to be due to a central nervous system effect, as shown by the reduced latency of movement-related brain macropotentials and EMG activation. These results are in line with previous experiments
Analysis of single phase natural circulation experiments with Cathare v1.3u and Relap5/mod3.2 codes
No full textDuring the period 1993 -2004, D’Auria had the opportunity to cooperate with the University of Genova (noticeably Prof. Misale). This cooperation brought to a valuable contribution to the scientific community based on the characterization of the single phase instabilities in a simple atmospheric pressure ‘glass’ loop previously available by UNIGE and upgraded within the framework of the cooperation with UNIPI. The characterization was made with the help of system thermal-hydraulic codes and confirmed some early investigation results by Velander 1968.
The present document deals with the application of both RELAP and CATHARE to the analysis of unstable experimental data in the UNIGE loop and was performed in the framework of a cooperation with the Argentinean government institution CNEA (Commission for Nuclear Energy in Buenos Aires)
Changes in biodeterioration patterns of mural paintings: Multi-temporal mapping for a preventive conservation strategy in the Crypt of the Original Sin (Matera, Italy)
No full textMulti-temporal investigation of biodeterioration patterns (BPs)in cultural heritage sites is crucial for the development of effective management plans. Here, microscopy and biomolecular methods were employed to analyze the BPs, which took place in the Crypt of the Original Sin (Italy)over a wide temporal scale, i.e., from 2001 to 2017. Before restoration interventions, performed in 2002–2003, a variety of BPs was observed, including green patinas (Chlorophyceae), brown-black patinas (Cyanobacteria), rosy discolorations (Actinobacteria)and some colonization by lichens, mosses and ferns. Restoration included biocide treatments as well as structural interventions causing environmental modifications of the site. To interpret the ecological relationships between environmental factors and temporal changes, we combined the analysis of ecological information on the various BPs with the results of a multivariate statistical analysis. Using BPs as bioindicators, humidity maps of the plasters were generated and water infiltration paths reconstructed. Several years after biocide application, a significant reduction of BPs was observed, together with limited colonization by dematiaceous and meristematic fungi. Our observations demonstrate the usefulness of combining structural and environmental interventions for an effective restoration strategy; these interventions reduced the moisture levels of the walls, consequently reducing biological colonization. Moreover, our findings suggest that monitoring BPs during time can be of guidance in the long-term maintenance of cultural heritage, and provide an evidence-based model for preventive interventions and biocide treatments
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