The biological basis of the aging process

El procés biològic bàsic subjacent de l’envelliment va ésser avançat per la teoria de l’envelliment basada en els radicals lliures l’any 1954: la reacció dels radicals lliures actius, produïts fisiològicament en l’organisme, amb els constituents cel·lulars inicia els canvis associats a l’envelliment. La implicació dels radicals lliures en l’envelliment està relacionada amb el seu paper clau en l’origen i l’evolució de la vida. La informació disponible avui en dia ens mostra que la composició específica de les macromolècules cel·lulars (proteïnes, àcids nucleics, lípids i carbohidrats) en les espècies animals longeves tenen intrínsicament una resistència elevada a la modificació oxidativa, la qual cosa probablement contribueix a la longevitat superior d’aquestes espècies. Les espècies longeves també mostren unes taxes reduïdes de producció de radicals lliures i de lesió oxidativa. D’altra banda, la restricció dietària disminueix la producció de radicals lliures i la lesió molecular oxidativa. Aquests canvis estan directament associats a la reducció de la ingesta de proteïnes dels animals sotmesos a restricció, que alhora sembla que són deguts específicament a la reducció de la ingesta de metionina. En aquesta revisió s’emfatitza que una taxa baixa de generació de lesió endògena i una resistència intrínsecament elevada a la modificació de les macromolècules cel·lulars són trets clau de la longevitat de les espècies animals.

Between Cratylism and Positivism: the Old Poem and What Alice Found There

En aquest article em referiré molt sumàriament a la fi lologia del dinou, mirant de relacionar-la amb tot el joc de paraules en Lewis Carrol, per tal d'establir-hi una trama correcta de (dis)continuïtats. El meu objectiu és considerar el Jabberwocky de Humpty Dumpty en el context de la feina i les descobertes de la moderna fi lologia. F. A. Wolf i J. Grimm condensen bona cosa dels experiments radicals i les troballes que tingueren lloc en aquells moments, que podríem contrastar amb les aventures textuals d'Alícia a l'altra banda de l'espill. Els llibres de l'altra banda necessiten intèrprets i cerquen la versió correcta, original, de la mateixa manera que la interpretació dels mots depèn d'un mètode fi able. Segurament Lewis Carroll com a jove fi lòleg era capaç de jugar bé amb aquelles troballes, entre un món que s'acabava i un altre que començava.

Studies on grain boundaries in nanocrystalline silicon grown by Hot-Wire CVD

The use of a tantalum wire in hot-wire chemical vapour deposition (HWCVD) has allowed the deposition of dense nanocrystalline silicon at low filament temperatures (1550 °C). A transition in the crystalline preferential orientation from (2 2 0) to (1 1 1) was observed around 1700 °C. Transmission electron microscopy (TEM) images, together with secondary ion mass spectrometry (SIMS) measurements, suggested that no oxidation occurred in materials obtained at low filament temperature due to the high density of the tissue surrounding grain boundaries. A greater concentration of SiH 3 radicals formed at these temperatures seemed to be responsible for the higher density.

Correlation of the EPR properties of perchlorotriphenylmethyl radical and their efficiency as DNP polarizers

Water soluble perchlorinated trityl (PTM) radicals were found to be effective 95 GHz DNP (dynamic nuclear polarization) polarizers in ex situ (dissolution) 13C DNP (Gabellieri et al., Angew Chem., Int. Ed. 2010, 49, 3360). The degree of the nuclear polarization obtained was reported to be dependent on the position of the chlorine substituents on the trityl skeleton. In addition, on the basis of the DNP frequency sweeps it was suggested that the 13C NMR signal enhancement is mediated by the Cl nuclei. To understand the DNP mechanism of the PTM radicals we have explored the 95 GHz EPR characteristics of these radicals that are relevant to their performance as DNP polarizers. The EPR spectra of the radicals revealed axially symmetric g-tensors. A comparison of the spectra with the 13C DNP frequency sweeps showed that although the solid effect mechanism is operational the DNP frequency sweeps reveal some extra width suggesting that contributions from EPR forbidden transitions involving 35,37Cl nuclear flips are likely. This was substantiated experimentally by ELDOR (electron-electron double resonance) detected NMR measurements, which map the EPR forbidden transitions, and ELDOR experiments that follow the depolarization of the electron spin upon irradiation of the forbidden EPR transitions. DFT (density functional theory) calculations helped to assign the observed transitions and provided the relevant spin Hamiltonian parameters. These results show that the 35,37Cl hyperfine and nuclear quadrupolar interactions cause a considerable nuclear state mixing at 95 GHz thus facilitating the polarization of the Cl nuclei upon microwave irradiation. Overlap of Cl nuclear frequencies and the 13C Larmor frequency further facilitates the polarization of the 13C nuclei by spin diffusion. Calculation of the 13C DNP frequency sweep based on the Cl nuclear polarization showed that it does lead to an increase in the width of the spectra, improving the agreement with the experimental sweeps, thus supporting the existence of a new heteronuclear assisted DNP mechanism.

Hot wire configuration for depositing device grade nano-crystalline silicon at high deposition rate

The University of Barcelona is developing a pilot-scale hot wire chemical vapor deposition (HW-CVD) set up for the deposition of nano-crystalline silicon (nc-Si:H) on 10 cm × 10 cm glass substrate at high deposition rate. The system manages 12 thin wires of 0.15-0.2 mm diameter in a very dense configuration. This permits depositing very uniform films, with inhomogeneities lower than 2.5%, at high deposition rate (1.5-3 nm/s), and maintaining the substrate temperature relatively low (250 °C). The wire configuration design, based on radicals' diffusion simulation, is exposed and the predicted homogeneity is validated with optical transmission scanning measurements of the deposited samples. Different deposition series were carried out by varying the substrate temperature, the silane to hydrogen dilution and the deposition pressure. By means of Fourier transform infrared spectroscopy (FTIR), the evolution in time of the nc-Si:H vibrational modes was monitored. Particular importance has been given to the study of the material stability against post-deposition oxidation.

Oxidative Stress and Antioxidant Activity in Hypothermia and Rewarming. Can RONS Modulate the Beneficial Effects of Therapeutic Hypothermia?

Hypothermia is a condition in which core temperature drops below the level necessary to maintain bodily functions. The decrease in temperature may disrupt some physiological systems of the body, including alterations in microcirculation and reduction of oxygen supply to tissues. The lack of oxygen can induce the generation of reactive oxygen and nitrogen free radicals (RONS), followed by oxidative stress, and finally, apoptosis and/or necrosis. Furthermore, since the hypothermia is inevitably followed by a rewarming process, we should also consider its effects. Despite hypothermia and rewarming inducing injury, many benefits of hypothermia have been demonstrated when used to preserve brain, cardiac, hepatic, and intestinal function against ischemic injury. This review gives an overview of the effects of hypothermia and rewarming on the oxidant/antioxidant balance and provides hypothesis for the role of reactive oxygen species in therapeutic hypothermia.

Influence of EfOM on the oxidation of micropollutants by Ozone and UV/H2O2 in secondary effluents

The aim of this work was to study the influence of effluent organic matter (EfOM) on micropollutants removal by ozone and UV/H2O2. To perform the experiments, deionized water and municipal secondary effluents (SE) were artificially contaminated with atrazine (ATZ) and treated by the two proposed methods. ATZ concentration, COD and TOC were recorded along the reaction time and used to evaluate EfOM effect on the system efficiency. Results demonstrate that the presence of EfOM can significantly reduce the micropollutant removal rate due to competition of EfOM components to react with radicals and/or molecular ozone. The hydroxyl radical scavenging caused by EfOM was quantified as well as the contribution of molecular ozone and �OH radicals during the ozonation of SE. EfOM components promoted higher inhibition of ATZ oxidation by hydroxyl radicals than by molecular ozone.