Observation of anomalous behaviour of the nuclear moment of inertia at large rotational frequencies in Yb and Hf

The (α, 8n) reaction has been used to produce high-spin states in ¹⁶⁴Yb and ¹⁶⁸Hf. In both cases a sharp increase of the moment of inertia as a function of rotational frequency was observed at I = 12.     

Exchange dipole optical transition in the manganese aluminosilicate glass: An insulating spin glass

We report on the absorption spectra of amorphous Mn²⁺ aluminosilicates which may be considered as insulating spin glasses at low temperature. The two bands localized around 4 180 Å and 3 550 Å were assigned respectively to the ⁶A₁ → ⁴E^a, ⁴A₁ (⁴G) and ⁶A₁ → ⁴E^b(⁴D) electric dipole exchange transitions. The temperature dependence of their intensity and position are related to the static two spin correlation functions of nearest ions. This gives informations on the magnetic ordering in such a spin glass.     

Beitrag zur titrimetrischen Schnellbestimmung des Gesamtschwefels in Kiesen, Abbr?nden und Flugst?uben mit Benzidin

Zusammenfassung Es wird eine Analysenmethode beschrieben, die es erlaubt, in Ergänzung der bisher bekannten Vorschläge mit Hilfe von Benzidin den Gesamtschwefelgehalt von Kiesen, Abbränden und Flugstäuben mit genügender Genauigkeit bei geringem Zeitaufwand titrimetrisch zu bestimmen. Gleichzeitig wird eine Arbeitsvorschrift zur Rückgewinnung des verwendeten Benzidins mitgeteilt.     

Ablation of silicon suboxide thin layers

We investigate the ablation of SiO _x thin films on fused silica substrates using single-pulse exposures at 193 nm and 248 nm. Two ablation modes are considered: front side (the surface of a film is irradiated from above) and rear side (a film is irradiated through its supporting substrate). Fluence is varied from below 200 mJ/cm² to above 3 J/cm². SiO _x films of thickness 200 nm, 400 nm, and 600 nm are ablated. In the case of rear-side illumination, at moderate fluences (around 0.5 mJ/cm²) the ablation depth corresponds roughly to the film thickness, above 1 J/cm² part of the substrate is ablated as well. In the case of front-side ablation the single-pulse ablation depth is limited for all film thicknesses to less than 200 nm even at fluences up to 4 J/cm². Experimental results are discussed in relation to film thickness, fluence, and ablation mode. Simple numerical calculations are performed to clarify the influence of heat transport on the ablation process.     

Digital technologies and the challenge of constructing an inclusive school mathematics

This article addresses research related to the use of digital technologies in the teaching and learning of mathematics in Brazil. Its scope is limited to the context of school mathematics and, more specifically, to an ongoing research programme which involves the development of collaborative research partnerships with teachers of mathematics. The paper begins with a brief presentation of the introduction of computers into the Brazilian educational scenario in the 1980s, highlighting how computer technology was heralded as a key to permitting new pedagogical approaches appropriate to the constructivist philosophy of that time. It goes on to consider recent developments in the theoretical frameworks used to interpret mathematics learning in the presence of digital technologies and the importance of focusing on the learning system as a whole, considering epistemological, cognitive and pedagogic dimensions concomitantly. In this vein, it is argued that for any real integration to take place, the mathematical practices afforded by digital tools must be considered legitimate by all the actors in this process and, perhaps most notably, by teachers. The rest of the paper focuses on our approaches to involve teachers in making decisions about technology use in their own classrooms. The strategy used was based on the realisation of research activities underpinned by the idea of the collaborative design of learning situations and the goal of including the wide diversity of learners that characterises Brazilian mathematics classrooms.     

Beyond prostaglandins--chemistry and biology of cyclic oxygenated metabolites formed by free-radical pathways from polyunsaturated fatty acids

Polyunsaturated fatty acids (PUFAs) are important constituents in all organisms. They fulfil many functions, ranging from modulating the structure of membranes to acting as precursors of physiologically important molecules, such as the prostaglandins, which for a long time were the most prominent cyclic PUFA metabolites. However, since the beginning of the 1990s a large variety of cyclic metabolites have been discovered that form under autoxidative conditions in vivo to a much larger extent than do prostaglandins. These compounds--isoprostanes, neuroprostanes, phytoprostanes, and isofurans--proved subsequently to be ubiquitous in nature. They display a wide range of biological activities, and isoprostanes have become the currently most reliable indicators of oxidative stress in humans. In a relatively short time, the structural variety, properties, and applications of the autoxidatively formed cyclic PUFA derivatives have been uncovered.