Circularly Polarized Photoluminescence as a Probe of Density of States in GaAs/AlGaAs Quantum Hall Bilayers

Polarized magnetophotoluminescence is employed to study the energies and occupancies of four lowest Landau levels in a couple quantum Hall GaAs/AlGaAs double quantum well. As a result, a magnetic field-induced redistribution of charge over the Landau levels manifesting to the continuous formation of the charge density wave and direct evidence for the symmetric-antisymmetric gap shrinkage at v = 3 are found. The observed interlayer charge exchange causes depolarization of the ferromagnetic ground state.

Conservative approach to restore the first molar with extensive destruction: a 30-month follow-up

The available options for restoring multiple surface cavities are: amalgam, composite resin, or indirect restorations. Adhesive system and intradentinal pin-retained composite resin restorations should have a similar performance to pin-retained amalgam, regarding resistance to support occlusal forces. Polymerization shrinkage is a major concern when performing direct posterior composite resin restorations and the incremental insertion technique can provide less stress and outstanding margin behavior. Intradentinal pins can potentially enhance composite resin's retention, while reducing gaps caused by polymerization shrinkage. This article reports a clinical case involving an extensive restoration on a posterior tooth with cusp loss that was successfully treated using an intradentinal pin and direct nano-hybrid composite resin restoration.

Exploring anorganic bovine bone granules as osteoblast carriers for bone bioengineering: a study in rat critical-size calvarial defects

It is known that current trends on bone bioengineering seek ideal scaffolds and explore innovative methods to restore tissue function. In this way, the objective of this study was to evaluate the behavior of anorganic bovine bone as osteoblast carrier in critical-size calvarial defects. MC3T3-E1 osteoblast cells (1x10(5) cells/well) were cultured on granules of anorganic bovine bone in 24-well plates and after 24 h these granules were implanted into rat critical-size calvarial defects (group Biomaterial + Cells). In addition, other groups were established with different fillings of the defect: Blood Clot (negative control); Autogenous Bone (positive control); Biomaterial (only granules) and Cells (only MC3T3-E1 cells). After 30 days, the animals were euthanized and the calvaria were technically processed in order to allow histological and morphometric analysis. It was possible to detect blood vessels, connective tissue and newly formed bone in all groups. Particularly in the Biomaterial + Cells group, it was possible to observe a profile of biological events between the positive control group (autogenous bone) and the group in which only anorganic bovine granules were implanted. Altogether, the results of the present study showed that granules of anorganic bovine bone can be used as carrier to osteoblasts and that adding growth factors at the moment of implantation should maximize these results.

Performance estimation for concretes made with recycled aggregates of construction and demolition waste of some Brazilian cities

The aim of this paper is to verify the influence of composition variability of recycled aggregates (RA) of construction and demolition wastes (CDW) on the performance of concretes. Performance was evaluated building mathematical models for compressive strength, modulus of elasticity and drying shrinkage. To obtain such models, an experimental program comprising 50 concrete mixtures was carried out. Specimens were casted, tested and results for compressive strength, modulus of elasticity and drying shrinkage were statistically analyzed. Models inputs are CDW composition observed at seven Brazilian cities. Results confirm that using RA from CDW for concrete building is quite feasible, independently of its composition, once compressive strength and modulus of elasticity still reached considerable values. We concluded the variability presented by recycled aggregates of CDW does not compromise their use for concrete building. However, this information must be used with caution, and experimental tests should always be performed to certify concrete properties.