Multi-scale approach to assess total porosity and pore size in four different kinds of carbonate rocks.

Petroleum is, at present, still the main energy source in the world. Most of it is stored in carbonate rock reservoirs with complex inner structures and pores ranging from nanometers to dozens of meters. Knowing the rock's entire pore network is indispensable to perform an effective petroleum extraction. X-ray microtomography, a technique that generates images from samples' inner structure and a powerful tool to evaluate the 3D pore network, was employed in this scientific research to scan four kinds of carbonate rocks (Dolomite, Desert Pink, Indiana, and Winterset) in five different pore scales (90 µm, 13 µm, 5.5 µm, 1.0 µm, and 65 nm). A multi-scale approach based on the number of pores was applied to integrate different pore scale data and assess the total porosity as well as each sample pore size distribution. The results were compared to classical Mercury Injection Capillary Pressure (MICP) results, demonstrating a fair agreement in total porosity in the two samples. Multi-scale porosity of the Dolomite sample was 17.7% against (18.9 ± 2.1)% of the MICP porosity. The Winterset sample had multi-scale porosity of 26.2%, while MICP porosity was (31.2 ± 0.6)%. Pore size distribution results were rather satisfactory, especially when overlapping regions in different scales were compared. In general, the multi-scale approach showed good potential. It still needs further evaluation to fine-tune some procedures and fluid flow simulation tests but might become a useful tool to study reservoir rocks with a wide range of pore sizes, such as carbonate rocks.

Microporosity and polymerization contraction as function of depth in dental resin cements by X-ray computed microtomography.

This research aimed to obtain the depth dependence of polymerization contraction and microporosity from irradiated dental resin cements by X-ray computed microtomography (µCT). Samples (n = 5) of commercial Relyx U200 (RU) and AllCem Core (AC) dual-cure resin cements were injected in a cylindrical Teflon sampler (25 mm3 ) and separated according to polymerization mechanism: self-cured (not irradiated) and dual-cured (irradiated from the top surface with a LED device). The cement's volume was scanned with the µCT scanning conditions kept constant. To assess the depth dependence of polymerization contraction, it was measured the displacement of the cement mass from the sample holder at 30 vertical cuts (0.1 mm distant). To probe the microporosity, the percentage of area with presence of porosity by slice was obtained. All data were statistically treated. It was observed a positive linear correlation between depth and polymerization contraction in the irradiated groups. In the other hand, the concentration of micropores decreased with increasing depth. Furthermore, the composition of the resin cement was determinant for the correlation's coefficients of these physical properties with depth. The µCT technique showed to be useful to probe physical properties of dental restorative materials that influence in the clinical outcomes, revealing that, for thin specimens, when light cured the RU cement presented mechanical behavior more favorable for clinical applications.

Higher Speed and No Glide Path: A New Protocol to Increase the Efficiency of XP Shaper in Curved Canals-An In Vitro Study.

INTRODUCTION: This in vitro study compared the performance of the XP-endo Shaper (XP; FKG, La Chaux-de-Fonds, Switzerland) in curved canals when used with a higher speed (3000 rpm) without a glide path with the manufacturer's protocol. METHODS: Twenty extracted mandibular molars with separate mesial curved canals were matched to obtain 2 standardized groups (n = 20). For the XP 1000 group, a glide path up to a size 15 hand file was performed followed by rotary instrumentation with the XP shaper at 1000 rpm, following the manufacturer's recommendations. For the canals in the XP 3000 group, the file was rotated at 3000 rpm after only negotiation the canal with a size 8 hand file (patency file). The operating time and the number of strokes taken to reach the working length (WL) and fit a 30/.04 gutta-percha cone to the WL were recorded. The shaping abilities were evaluated by micro-computed tomographic imaging and file deformation by scanning electron microscopy. Data were analyzed using analysis of variance and chi-square tests at a 5% significance level. RESULTS: The XP 3000 group required less time and strokes to reach the WL (P < .05) and resulted in a higher percentage of adequate cone fit (P < .05). No difference was found between groups regarding the micro-CT parameters, except for the taper, which was larger in the XP 3000 group in the apical and middle thirds (P < .05). No difference was found regarding file deformation between the 2 groups. CONCLUSIONS: The suggested protocol for the use of the XP (3000 rpm without a glide path) appears to be more efficient than the manufacturer's recommended protocol to prepare curved canals in vitro.

Morphological study of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) eggs by X-ray computed microtomography.

Aedes aegypti and Aedes albopictus are vectors of several arboviruses responsible for causing dengue, chikungunya, Zika, and yellow fever viruses and microcephaly, resulting in a public health problem in several countries worldwide. Even in this scenario, studies on the morphology of mosquito eggs are still lacking. In this paper, X-ray microtomography was used to study mosquito egg morphology. Several parameters such as length, surface area, volume, area-by-volume ratio, eccentricity and center of mass of the eggs were determined. The results obtained showed that micro-CT is an efficient technique for the morphological study of insect eggs and provides information that cannot be obtained with other techniques.

Polymerization shrinkage and porosity profile of dual cure dental resin cements with different adhesion to dentin mechanisms.

This research aims to probe the porosity profile and polymerization shrinkage of two different dual cure resin cements with different dentin bonding systems. The self-adhesive resin cement RelyX U200 (named RU) and the conventional Allcem Core (named AC) were analyzed by x-ray microtomography (µCT) and Scanning Electron Microscopy (SEM). Each cement was divided into two groups (n = 5): dual-cured (RUD and ACD) and self-cured (RUC and ACC). µCT demonstrated that the method of polymerization does not influence the porosity profile but the polymerization shrinkage. Fewer concentration of pores was observed for the conventional resin cement (AC), independently the method used for curing the sample. In addition, SEM showed that AC has more uniform surface and smaller particle size. The method of polymerization influenced the polymerization shrinkage, since no contraction for both RUC and ACC was observed, in contrast with results from dual-cured samples. For RUD and ACD the polymerization shrinkage was greater in the lower third of the sample and minor in the upper third. This mechanical behavior is attributed to the polymerization toward the light. µCT showed to be a reliable technique to probe porosity and contraction due to polymerization of dental cements.

Determining chemical composition of materials through micro-CT images.

X-ray microtomography is a 3D non-destructive method which, through digital images, enables a view of the internal structure of samples. Recently, researchers have been extensively performing various methods in the attempt to determine the chemical composition of materials. This paper brings further insight into this matter and proposes a new experimental method for determining the internal chemical composition of samples. Using a set of standard samples, calibration curves can be created that allow to relate the average gray scale of a sample obtained through microtomographic images to the value of ρZeff(m). In this model, ρZeff(m) is the parameter that chemically characterizes a material. The exponent m is obtained by the average value obtained with standard samples, which were titanium dioxide (TiO2), calcium chloride (CaCl2), calcium hydroxide (Ca(OH)2), and calcium nitrate (Ca(NO3)2). For the samples scanning process, a Bruker SkyScan 1172 microCT was used for testing rocks, nylon, graphite, calcium carbonate (CaCO3) and aluminum samples. The experimental results achieved by this method were consistent with the theoretical values.