117,415 research outputs found
Simulation of EPR and Time Resolved EPR lineshapes in partially ordered phases
No full textSimulation of magnetic resonance spectra of probes in partially ordered glasses requires in principle a numerical integration on the full set of three Euler angles Ohm=(alpha beta gamma) from a laboratory fixed to a molecule fixed reference frame. It is shown that it is possible to manage efficiently this problem by using the algebraic properties of the Wigner matrix elements. This analysis is applied to time resolved EPR (TREPR) spectra of a series of bis-adducts of C-60 in the ordered glass of a nematic liquid crystal solvent. A paramagnetic triplet state is created by light excitation and TREPR spectra are obtained with the external magnetic field set parallel or perpendicular to the director n of the mesophase. The preferred orientation in the mesophase of the triplet state zero field tensor is determined
Intermolecular electron transfer in merocyanine aggregates studied by optical and transient EPR methods
No full textExcited states of two merocyanine chromophores have been studied by means of optical and magnetic resonance techniques. The dye molecules were dissolved in solvents of different polarity and cast in thin films on quartz surfaces. The optical absorption and emission spectra of both molecules indicate a little charge-transfer character in the S-0-S-1 transition. The cast films contain monomers and H type aggregates. EPR spectra have been obtained by time resolved techniques at low temperature after illumination of the sample. EPR spectra of isolated molecules in frozen solutions are typical of triplet excited states generated by spin-orbit promoted intersystem crossing. Two signals are observed in EPR spectra of the cast films, with a narrow line in emission superimposed on a very weak molecular triplet lineshape. The polarization and lineshape analysis suggest that a radical ion pair with a lifetime of the order of microseconds is formed by intermolecular charge migration following the photoinduced electron-transfer reaction between the donor and acceptor moieties of the chromophore
Micellar aggregation of alkyltrimethylammonium bromide surfactants studied by electron paramagnetic resonance of an anionic nitroxide
No full textThe self-aggregation process of five alkyltrimethylammonium bromide surfactants [CH3(CH2)n_1N(CH3)3Br (n = 6,8,10,12,16), CnTAB] in aqueous solution at pH = 7 has been studied by electron paramagnetic resonance (EPR) spectroscopy by employing 3-carboxy-PROXYL in its deprotonated form [2,2,5,5- tetramethyl-3-carboxypyrrolidinyloxy sodium salt, CP_] as a spin probe. In all the considered systems, the nitrogen isotropic hyperfine coupling constant of CP_, hANi, decreases and the correlation time, tC , increases with increasing surfactant molality. Concerning the surfactants with long hydrophobic tails (n 1⁄4 8,10,12,16), both hANi and tC present a slope change corresponding to the critical micellar composition, c.m.c. In these cases the tC increase can be interpreted in terms of a reduction of the spin probe mobility determined by the strong electrostatic interaction between the CP_ charge and the cationic micelles’ surface. Particularly, the tC values show that the microviscosity experienced by CP_ in C16TAB micelles is much higher in respect to that found in the other micellar systems, thus suggesting a different structural organization of the aggregates ’ surface. The hANi decrease can be ascribed to a partial embedding of the NO moiety of CP_ in the outer part of the micellar hydrophobic core. The CP_ affinity for the micellar pseudo-phase has been estimated by evaluating the distribution coefficient, Kd , of the spin probe between the micelles and the aqueous medium. The Kd value increases with the length of the surfactant hydrophobic chain. Because of the short hydrophobic tail, the C6TAB aqueous mixtures exhibit a peculiar behaviour: hANi smoothly decreases and tC of CP_ increases with increasing surfactant molality without any abrupt slope change. This experimental evidence suggests that C6TAB association can be described in terms of a gradual change, with increasing surfactant molality, from solvent-mediate to direct surfactant–surfactant interactions
The mastro ecosystem: Ontology-based data management from theory to practice
No full textOntology Based Data Management (OBDM) is the paradigm that enables accessing existing data by means of a comprehensible and semantically rich representation of the application domain expressed by an ontology. In this demonstration we present the Mastro Ecosystem, a suite of tools providing solutions for OBDM covering a vast array of features ranging from ontology design, data access and querying, data quality analysis, open data creation and publishing, and many more
CONVENTIONAL AND UNCONVENTIONAL EPR TECHNIQUES FOR THE STUDY OF POLYMER-FULLERENE MATERIALS FOR BHJ PHOTOVOLTAIC CELLS
No full textA granular activated carbon (GAC) packed-bed reactor for a more efficient anaerobic treatment and valorization (via methane production) of olive mill wastewaters
No full textChondrosarcoma: New Molecular Insights, Challenges in Near-Patient Preclinical Modeling, and Therapeutic Approaches
No full textChondrosarcoma (CS), the second most common malignant bone tumor after osteosarcoma, accounts for 20-30% of all malignant bone tumors. It mainly affects adults, middle-aged, and elderly people. The CS family includes various entities displaying peculiar biological, genetic, and epigenetic characteristics and clinical behaviors. Conventional CS is the most common subtype. High-grade, dedifferentiated, and mesenchymal CS, as well as unresectable and metastatic CS, exhibit poor prognoses due to their intrinsic resistance to radiotherapy and chemotherapy, underscoring the urgent need for novel therapeutic strategies. CS research is dealing with several challenges. Experimental studies can rely on animal and patient-derived models, but the paucity of representative near-patient preclinical models has hampered predictive drug screening research. This review describes the main clinical and molecular features of CS subtypes, discussing recent data on the genetic alterations and molecular mechanisms involved in CS pathogenesis and progression. The review provides an overview of the current in vitro and in vivo CS models, discusses their advantages and limitations, and highlights the recent efforts in the development of new targeted therapies against CS dependencies, including IDH1/2 mutations, NAD+ dependency, and SIRT1-HIF-2 alpha axis, or exploring DR5 targeting, antiangiogenic therapies, epigenetic drugs, and immunological approaches. All such strategies, in combination with advanced preclinical modeling and personalized multi-omic profiling, hold promise for improving the survival of patients with advanced CS
Preferential Orientation of Fulleropyrrolidine Bisadducts in E7 Liquid Crystal: a Time Resolved EPR Study
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