Statistical physics of two-temperature rotational energy distributions in stationary plasmas.

Two-temperature rotational energy distributions from rarefied diatomic molecules are very often observed in laboratory plasmas. There has been much debate over the years about the physical meaning of this kind of rotational energy distributions and the associated statistical physics. We show here that under certain reasonable assumptions and constraints the condition of Shannon-Jaynes entropy maximization may produce a two-temperature distribution.

Characterization of low-shrinkage dental composites containing methacrylethyl-polyhedral oligomeric silsesquioxane (ME-POSS).

The aim of this study was to characterize low-shrinkage dental composites containing methacrylethyl-polyhedral oligomeric silsesquioxane (ME-POSS). Four experimental composites were manufactured, two of which contained organic matrixes of BisGMA-TEGDMA (70/30 wt% - BGC) and BisEMA-TEGDMA (80/20 wt% - BEC). The two other experimental composites replaced BisGMA and BisEMA with 25 wt% of ME-POSS (BGP and BEP).

The diffusion kinetics of a nanofilled and a midifilled resin composite immersed in distilled water, artificial saliva, and lactic acid.

This study investigated the diffusion kinetics of a nanofilled (Filtek Z350) and a midifill (Filtek P60) resin composite immersed in distilled water, artificial saliva and lactic acid. Resin composite specimens were desiccated, immersed in the media, weighed at suitable time intervals until they reached sorption equilibrium and were then desiccated again. Sorption and solubility (µg/mm(3)) were calculated based on ISO 4049:2000(E).

Influence of light polymerization modes on degree of conversion and crosslink density of dental composites.

This study analyzed the influence of light polymerization modes on crosslink density (CD) and the degree of conversion (DC) of dental composites. A minifilled hybrid and a nanofilled dental composite were photoactivated with two light polymerization modes: Conventional-850 mW/cm2 for 20 s and Gradual-50 up to 1,000 mW/cm2 for 10 s+1,000 mW/cm2 for 10 s. DC was determined by the use of FT-Raman-spectrometer.

Composite depth of cure obtained with QTH and LED units assessed by microhardness and micro-Raman spectroscopy.

This study analyzed the depth of cure of a composite assessed by microhardness and the degree of conversion as a function of the light cure unit (LCU) used. Two light cure units, one LED (Ultraled-Dabi Atlante) and one quartz-tungsten-halogen (QTH, Optilux 401-Demetron) unit were used to cure 4.0 x 4.