Chaos in free electron laser oscillators

The chaotic nature of a storage-ring free electron laser (FEL) is investigated. The derivation of a low embedding dimension for the dynamics allows the low-dimensionality of this complex system to be observed, whereas its unpredictability is demonstrated, in some ranges of parameters, by a positive Lyapounov exponent. The route to chaos is then explored by tuning a single control parameter, and a period-doubling cascade is evidenced, as well as intermittence.     

Physico-chemical and pharmaceutical characterization of sulindac–proglumide binary system

Journal of Thermal Analysis and Calorimetry - Sulindac is a nonsteroidal anti-inflammatory drug with poor water solubility. This study presents a way to increase its dissolution rate while reducing...     

Synthesis of cns potentially active bicyclic and tricyclic derivatives of pyrazolo[1,5-a][1,3]diazepines

Reaction of 5-ethylamino-3-phenylpyrazole with dicarboxylic acid anhydrides in tetrahydrofuran in the presence of 1,3-dicyclohexylcarbodiimide, afforded bicyclic and tricyclic derivatives of pyrazolo[1,5-a][1,3]-diazepines. The tricyclic derivatives constitute a new class of compounds. Characterisation of these products was effected with ir, pmr, and ¹³C nmr spectral data.     

Molecular associations of hydrazones of heterocyclic systems. XI

Complexes of hydrazones of heterocyclic compounds with organic acceptors are investigated through the evaluation of spectroscopic and thermodynamic properties. Values of the formation constants and comparison between uv-visible and ft-ir determinations on liquid and solid phases indicate these systems are weak complexes. Contributions from hydrogen bonding and the effects of π?π* or n?π* transitions on the spectroscopic and thermodynamic properties of the complexes are discussed.     

Nitroxide and anion radicals derived from isatogen and related indole derivatives

Neutral indolic nitroxides were obtained by oxidation of 1-hydroxyindoles with lead dioxide. Anion indolic nitroxides were obtained by reduction of indoline-N-oxides in DMSO/t-BuOK (reducing agent being the CH₃SOCH₂^? anion). In both cases an a^N of about 6 gauss was found. This value, which differs from values previously reported, is justified in the course of the work. Some other anion radicals derived from bi-indolic derivatives are also reported and their structures discussed on the basis of MO calculations or by comparison with analogous examples.     

Terpyridine Zn (II), Ru (III) and Ir (III) complexex as new asymmetric chromophores for nonlinear optics: first evidence for a shift from positive to negative value of the quadratic hyperpolarizability of a ligand carrying an electron donor substituent upon coordination to different metal centres

The synthesis of 4'-(C6H4-p-NBU2)-2,2':6',2" -terpyridine and the strongly enhanced second-order NLO response of its Zn(II), Ru(III) and Ir(III)complexes are reported, evidencing for the first time a shift from positive to negative value of the ligand quadratic hyperpolarizability by varying the nature of the metal centre. .     

Structure and dynamics of water confined in silica hydrogels: X-ray scattering and dielectric spectroscopy studies

We have used a sol-gel technique to obtain optically transparent hydrogels in which water is confined within a 3D silica matrix. In this work we report X-ray scattering and dielectric spectroscopy measurements on samples having different aging times and compare them with previously obtained results with near-infrared (NIR) absorption spectroscopy. X-ray scattering at room temperature enables to characterize the structure and size of the matrix pores and the non-uniform distribution of water inside the hydrogel. Broad band dielectric spectroscopy in the temperature range 130-280 K enables to study water dynamics. In aged hydrogels two relaxations are clearly evident and show characteristic temperature dependence. The faster relaxation has an Arrhenius behavior in the whole temperature range investigated with an activation enthalpy of approximately 50 kJ/mol; it is attributed to water molecules strongly interacting with the silica matrix. The slower relaxation has a markedly non-Arrhenius behavior which can be fitted with a Vogel-Fulcher-Tamman (VFT) relation with critical temperature of approximately 100 K and activation enthalpies of 35 and 95 kJ/mol at 300 and 170 K respectively; it is attributed to water molecules within the pores that do not interact strongly with the matrix and behave collectively. The VFT temperature dependence of the dielectric relaxation time suggests that this water does not crystallize, in agreement with previous results from NIR spectroscopy.     

Electrochemical and ESR studies on the reduction of 3-arylimino-3H-indole-N,N′-dioxides

3-Arylimino-3H-indole-N,N′-dioxides have been reduced in DMF to the corresponding radical anions, and studied using polarographic and controlled potential electrolysis, as well as UV and ESR spectrometry. A multistep scheme has been suggested in order to explain the various experimental results. ESR spectra were explained in terms of HFSC evaluation and theoretically reconstructed in order to check the validity of the attributions. The same radicals were obtained with DMSO/t-BuOK as reducing agent.     

Superoxide Dismutase Administration: A Review of Proposed Human Uses

Superoxide dismutases (SODs) are metalloenzymes that play a major role in antioxidant defense against oxidative stress in the body. SOD supplementation may therefore trigger the endogenous antioxidant machinery for the neutralization of free-radical excess and be used in a variety of pathological settings. This paper aimed to provide an extensive review of the possible uses of SODs in a range of pathological settings, as well as describe the current pitfalls and the delivery strategies that are in development to solve bioavailability issues. We carried out a PubMed query, using the keywords “SOD”, “SOD mimetics”, “SOD supplementation”, which included papers published in the English language, between 2012 and 2020, on the potential therapeutic applications of SODs, including detoxification strategies. As highlighted in this paper, it can be argued that the generic antioxidant effects of SODs are beneficial under all tested conditions, from ocular and cardiovascular diseases to neurodegenerative disorders and metabolic diseases, including diabetes and its complications and obesity. However, it must be underlined that clinical evidence for its efficacy is limited and consequently, this efficacy is currently far from being demonstrated.     

Perturbation of water structure due to monovalent ions in solution

The ion induced modification to the tetrahedral structure of water is a topic of much current interest. We address this question by interpreting neutron diffraction data from monovalent ionic solutions of NaCl and KCl using a computer assisted structural modeling technique. We investigate the effect that these ions have on the water-water O-O, O-H and H-H radial distribution functions as a function of ionic concentration. It is found that the O-H and H-H functions are only marginally affected by ionic composition, signaling that hydrogen bonding between water molecules remains largely intact, even at the highest concentrations. On the other hand the O-O functions are strongly modified by the ions. In particular the position of the second peak in g(OO)(r), is found to move inwards with increasing salt concentration, in a manner closely analogous to what happens in pure water under pressure. Furthermore by recalculating g(OO)(r) after excluding all the water molecules in the first hydration shell of each ion, we show that this structural perturbation exists outside the first hydration shell of the ions.