Search

Layer-by-layer thin films of arylenediimides were grown on phosphonate-primed silicon and quartz substrates by the zirconium phosphonate method. The method consists in depositing alternated organic/inorganic layers, where the organic layer was a phosphonate-substituted arylenediimide and the inorganic layer was Zr4+. Heterogeneous films with up to 50 layers, containing different imides, were produced. The building blocks were N,N′-bis(2-phosphonoethyl)pyromellitimide (PPMI), N,N′-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (PNDI) and N,N′-bis(2-phosphonoethyl)-3,4,9,10-perylenediimide (PPDI). Thin films with the sequence PPDI/PNDI, PPDI/PPMI, PNDI/PPMI and PPDI/PNDI/PPMI were produced. Organized film growth was observed by UV–visible–NIR spectroscopy (quartz substrates) and ellipsometry (silicon substrates). AFM images showed that the surface of the films was smooth and uniform. The imides in the films were reduced using sodium dithionite as a reducing agent, generating stable radical anions and dianions of the imides. The following species were detected in the absorption spectra of the reduced films: PPDI−∙, PPDI2−, PNDI−∙, and PNDI2−. Reduction of the imides in the films was rather slow, as compared to homogeneous solutions. When the reduced films were exposed to atmospheric oxygen, reoxidation took place, which was also much slower than in homogeneous solutions. In conclusion, a mix of aromatic imide reduced species, absorbing through the whole visible range, was produced and stabilized in thin films.

Radial and longitudinal strain assessment in the carotid artery wall using speckle tracking

Fluorescence spectroscopy was used to characterize inclusion compounds between 4-amino-1,8-naphthalimides (ANI) derivatives and different cyclodextrins (CDs). The ANI derivatives employed were N-(12-aminododecyl)-4-amino-1,8-naphthalimide (mono-C12ANI) and N,N′-(1,12-dodecanediyl)bis-4-amino-1,8-naphthalimide (bis-C12ANI). The CDs used here were α-CD, β-CD, γ-CD, HP-α-CD, HP-β-CD and HP-γ-CD. The presence of CDs resulted in pronounced blue-shifts in the emission spectra of the ANI derivatives, with increases in emission intensity. This behavior was parallel to that observed for the dyes in apolar solvents, indicating that inclusion complexes were formed between the ANI and the CDs. Mono-C12ANI formed inclusion complexes of 1:1 stoichiometry with all the CDs studied. Complexes with the larger CDs (HP-β-CD, HP-γ-CD and γ-CD) were formed by inclusion of the chromophoric ANI ring system, whereas the smaller CDs (α-CD, HP-α-CD and β-CD) formed complexes with mono-C12ANI by inclusion of the dodecyl chain. Bis-C12ANI formed inclusion complexes of 1:2 stoichiometry with HP-β-CD, HP-γ-CD and γ-CD, but did not form inclusion complexes with α-CD, HP-α-CD and β-CD. The data were treated in the case of the large CDs using a Benesi-Hildebrand like equation, giving the following equilibrium constants: mono-C12ANI:HP-β-CD (K11 = 50 M−1), mono-C12ANI:HP-γ-CD (K11 = 180 M−1), bis-C12ANI:HP-β-CD (K12 = 146 M−2), bis-C12ANI:HP-γ-CD (K12 = 280 M−2).

The synthesis of three novel phosphonate-substituted aromatic diimides is described: N,N′ -bis(2-phosphonoethyl)pyromellitimide (PPMI), N,N′ -bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (PNDI) and N,N′ -bis(2-phosphonoethyl)-3,4,9,10-perylenediimide (PPDI). The imides are water-soluble, allowing spectroscopical studies to be performed in water. PPMI and PNDI exist in the monomeric form in water, but PPDI formed dimers. Self-assembled thin films of the three compounds were grown on phosphonate-primed silicon and quartz substrates by the zirconium phosphonate method. Film growth was followed by ellipsometry (silicon) and ultraviolet/visible absorption spectroscopy (quartz). The films obtained were highly thermally and solvolitically stable for all the three imides, making them excellent candidates for applications in nanotechnological devices.

Aqueous solutions of N,N'-bis(2-phosphonoethyl)-3,4,9,10-perylenediimide (PPDI) were titrated with sodium dithionite, generating radical anions (PPDI(-*)) and dianions (PPDI(2-)). In aqueous ethanol (1:1 v/v), PPDI existed as monomers and remained in the monomeric form in all reduced states. In water, on the other hand, PPDI formed dimers, which were transformed into a pi-stacked aggregated form upon one-electron reduction to PPDI(-*). Addition of a second electron, however, resulted in dissociation of the aggregates, giving the dianion PPDI(2-) in the monomeric form. The presence of CTAB micelles prevented the aggregation of PPDI(-*) in water, indicating that the radical anions were incorporated into the micellar phase. Reduction of PPDI in ethanol solution, where the dye was aggregated, resulted in the formation of soluble mixed stacks containing both PPDI(-*) and PPDI(2-). These mixed stacks stabilized the radical anion form, preventing further reduction to the dianion.

Self-assembled thin films of 3,4,9,10-perylenediimides (PDIs) containing up to 50 PDI layers were grown on quartz slides using the zirconium phosphonate technique. When the films were immersed in aqueous solutions of the sodium dithionite reducing agent, in situ reduction of the dye was observed, generating a purple film containing PDI radical anions. The PDI radical anions formed within the films were rather stable, persisting for several minutes in the presence of atmospheric oxygen. Atomic force microscopy (AFM) images showed that the film surface was rather smooth and pinhole-free.

Supraventricular arrhythmias are considered to be benign when the ventricular rate is slowed and treated by anticoagulants. The aim of this study was to determine the possible influence of these arrhythmias in resuscitated cardiac arrest. Between 1980 and 2002, 151 patients were admitted after a cardiac arrest. Supraventricular arrhythrmias were identified as a possible cause of the cardiac arrest in 21 patients. They underwent echocardiography, exercise stress test, Holter ECG monitoring , coronary angiography and electrophysiological investigation. After these investigations, three patients had a malignant form of the Wolff-Parkinson-White syndrome, two were asymptomatic and, in the third patient, ventricular fibrillation was induced by treatment with diltiazem. In 8 patients, a rapid supraventricular arrhythmia was considered to be the cause of cardiac arrest by cardiogenic shock; 2 patients had hypertrophic cardiomyopathy, 5 had severe dilated cardiomyopathy which regressed in one patient. In ten patients, cardiac arrest due to ventricular tachycardia or fibrillation was provoked by a rapid (220 beats/min) supraventricular arrhythmia; two patients had no apparent underlying cardiac pathology. In the others, myocardial ischaemia or acute cardiac failure were considered to be the cause of the cardiac arrest. The authors conclude that rapid supraventricular arrhythmias may cause cardiac arrest either by cardiogenic shock or degenerescence to ventricular tachycardia or fibrillation. Usually, this event occurs in patients with severe cardiac disease but it may occur in subjects without cardiac disease or by an arrhythmia-induced cardiomyopathy.

The properties of N,N'-bis(2-phosphonoethyl)-3,4,9,10-perylenetetracarboxylic diimide (PPDI), a water-soluble perylene dye, have been studied in solution and in thin films. Absorption spectra showed that PPDI exists in the monomeric form in water/ethanol (1:1) and water/dimethyl sulfoxide (DMSO) (3:7) mixtures, but forms dimers in water and higher aggregates in ethanol. The PPDI monomer is highly fluorescent, in contrast to the dimers and aggregates, which are nonfluorescent. The monomer/dimer equilibrium was conveniently followed in a water/ethanol (7:3) mixture by varying the dye concentration. An equilibrium constant of K = 1.25 x 10(5) M(-1) was estimated for the dimerization process in this solvent mixture. The addition of cetyl trimethylammonium bromide (CTAB), a cationic surfactant, to aqueous solutions of PPDI resulted in the dissociation of the dimers, showing that the dye was incorporated into the micellar phase. Self-assembled thin films of PPDI were grown on both silica gel particles and flat surfaces, using zirconium phosphonate chemistry. The growth of multilayered films on flat surfaces was monitored by ellipsometry (silicon substrates) and UV/Vis spectroscopy (quartz slides), and was linear with the number of deposition cycles. No fluorescence was detected from the PPDI films, and the absorption spectra of the films were quite similar to the spectrum of the compound in ethanol, indicating that the dye molecules were stacked in the films. Mixed monolayers containing PPDI and N,N'-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (PNDI) on quartz were also prepared. Monolayers obtained by codeposition from solutions containing both PPDI and PNDI were richer in PPDI, even when the solution contained a large excess of the naphthalene derivative, showing that pi-stacking of PPDI is an important driving force in the formation of the films.

N -dodecyl- N ′-(2-phosphonoethyl)-1,4,5,8-naphthalenetetracarboxylic diimide (DNDI) is a novel naphthalenic diimide with amphiphilic character. DNDI was synthesized through the sequential reaction of 1,4,5,8-naphthalenetetracarboxylic dianhydride, first with dodecylamine and then with 2-aminoethylphosphonic acid. Fluorescence measurements showed that DNDI forms excimers in water at sufficiently high concentrations. The fluorescence quantum yield of DNDI in diluted solutions is sensitive to the polarity of the microenvironment, decreasing as going from water to less polar solvents. This property allowed to monitor the incorporation of DNDI into cetyl trimethyl ammonium bromide (CTAB) micelles, with a binding constant of 1.2 × 10 4 M −1 . UV irradiation (365 nm) of solutions containing DNDI and the redox protein cytochrome c (cyt c ) resulted in the reduction of the heme iron from the Fe(III) to the Fe(II) state, a reaction that was inhibited by the incorporation of DNDI into CTAB micelles. DNDI formed host–guest complexes with α-cyclodextrin (α-CD) through the inclusion of the dodecyl group, resulting in an increased aqueous solubility of the compound.

UnlabelledThe objective of this study was to verify self-care guidelines together with lower limb home exercises alter ankle and foot plantar pressure and alignment in patient with Type 2 Diabetes Mellitus (DM) measuring health and sociodemographic factors. The health factors analyzed were sensitivity and circulation aspects, risk rating, and neuropathy symptom score, ankle and foot alignment (photogrammetry), plantar pressures, and postural stability (baropodometry) before and after administering these guidelines and home exercises in 97 patients type 2 DM during 10 months. The self-care guidelines and exercises changed the forefoot alignment (Right Foot - Initial vs Final, p = 0.04; Left Foot, PTrial registrationThe Brazilian Clinical Trials Registry RBR-8854CD.

Microperoxidases (MP) as water-soluble models attract interest to studying the reaction mechanism of peroxidases because these heme peptides are able to form the same enzyme intermediates during the reaction with peroxides. In this work we have demonstrated that the association of Fe(III)MP-9 and Fe(III)MP-11 with CTAB micelles (MP-9/CTAB and MP11/CTAB) provides a microenvironment with an alkaline interface and a hydrophobic core that exhibits peroxidase behavior. This microenvironment shifts positively the redox potential of microperoxidases by approximately 100 mV. tert-Butylhydroperoxide (t-BuOOH) when added to the medium, converted Fe(III)MP-9/CTAB to MP-9/CTAB Compound II, a high valence oxidized intermediate of the heme peptide. Subsequent addition of diphenylacetaldehyde (DPAA) to MP-9/CTAB Compound II regenerated the native form of the enzyme, Fe(III)MP-9/CTAB, what characterizes the occurrence of a peroxidase cycle. Fe(III)MP-9/CTAB regenerated during the peroxidase cycle reacted with residual DPAA in the medium to form Fe(II)MP-9/CTAB, which indicates that both Fe(III)MP-9/CTAB and its oxyferryl form can use aldehydes as reducing agents. According to the determined reduction potential, Fe(III)MP-9 and Fe(III)MP-9/CTAB should be able to oxidize DPAA (reduction potential -630 mV). The reaction of MP-9/CTAB with DPAA produced benzophenone as final product, detected by infrared spectroscopy and mass spectrometry. Interestingly, a significant difference was observed in the benzophenone yield according to the micelle/MP-9 molar ratio.