Comportamento de busca da informação: uma comparação de dois modelos

Starting from a literature review on concepts related to information-seeking behaviour, the paper presents and compares two models of information seeking: a behavioural model, developed by David Ellis from a study on Social Scientist, and a model of a process, developed by Carol Kuhlthau from a study of undergraduate students. It concludes that both models offer valid theoretical background, even though Ellis´s model appears to be more appropriate for the study of information seeking in scientific contexts

Electrostatic Control of Spin Exchange Between Mobile Spin-Correlated Radical Pairs Created in Micellar Solutions

A series of photoinduced H-atom abstraction reactions between anthraquinone-2,6,-disulfonate, disodium salt (AQDS) and differently charged micellar substrates is presented. After a 248 nm excimer laser flash, the first excited triplet state of AQDS is rapidly formed and then quenched by abstraction of a hydrogen atom from the alkyl chain of the micelle surfactant, leading to a spin-correlated radical pair (SCRP). The SCRP is detected 500 ns after the laser flash using time-resolved (direct detection) electron paramagnetic resonance (TREPR) spectroscopy at X-band (9.5 GHz). By changing the charge on the surfactant headgroup from negative (sodium dodecyl sulfate, SDS) to positive (dodecyltrimethylammonium chloride, DTAC), TREPR spectra with different degrees of antiphase structure (APS) in their line shape were observed. The first derivative-like APS line shape is the signature of an SCRP experiencing an electron spin exchange interaction between the radical centers, which was clearly observable in DTAC micelles and absent in SDS micellar solutions. Solutions with surfactant concentrations well below the critical micelle concentration (cmc) or solutions where micellar formation had been disrupted (1:1 v/v CH3CN/H2O) also showed no APS line shapes in their TREPR spectra. These results support the conclusion that electrostatic forces between the sensitizer (AQDS) charge and the substrate (surfactant) headgroup charge are responsible for the observed effects. The results represent a new example of electrostatic control of a spin exchange interaction in mobile radical pairs

Pianificazione preoperatoria al computer per la simulazione di interventi chirurgici plastico ricostruttivi

A correct and accurate preoperative planning is fundamental for reconstructive and plastic procedures in order to obtain functional and esthetic results. The aim of this study is to describe a prototype of a software dedicated to the visualization of a 3D model from one single patient. This kind of model, generated by the manipulation of MR images, can be used to simulate both the demolitive and reconstructive phase of the surgical procedures planned