Effect Of Core Diameter Research Articles

Effect of Core Diameter, Surface Coating, and PEG Chain Length on the Biodistribution of Persistent Luminescence Nanoparticles in Mice

A growing insight toward optical sensors has led to several major improvements in the development of convenient probes for in vivo imaging. Efficient optical detection using quantum dots (QDs) as well as near-infrared organic dyes relies on several key driving principles: the ability to lower background absorption or autofluorescence from tissue, a good photostability of the probe, and a high quantum yield. In this article, we report the real-time biodistribution monitoring of lanthanide-doped persistent luminescence nanoparticles (PLNP), emitting in the near-infrared window, in healthy and tumor-bearing mice. We focused on the influence of hydrodynamic diameter, ranging from 80 to 180 nm, and polyethylene glycol (PEG) surface coating on the behavior of our probes. Tissue distribution was found to be highly dependent on surface coverage as well as core diameter. The amount of PLNP in the blood was highly increased for small (d < 80 nm) and stealth particles. On the opposite, PEG shield molecular weight, ranging from 5 to 20 kDa, had only negligible influence on the in vivo biodistribution of our silicate-based material.

Some Factors Influencing Effect of Core Diameter on Measured Concrete Compressive Strength

Various concrete mixtures were produced using crushed limestone and river gravels with four different maximum sizes of 10, 15, 22, and 30 mm (0.39, 0.59, 0.87, and 1.18 in.). The 28-day cube strength of concrete mixtures ranged between 28 and 43 MPa (4061 and 6236.6 psi). Beam specimens were cast by these concrete mixtures and cores were drilled from the beams. Compressive strength tests were performed at the ages of 7, 28, and 90 days on a total of 2268 core and cube specimens and the effect of core diameter on concrete core strength was examined. The strength correction factors were determined to convert the strength of a core with a diameter of 144, 69, or 46 mm (5.67, 2.72, or 1.81 in.) to that of a core having a diameter of 94 mm (3.70 in.). As the maximum aggregate size increased, the strength of the core decreased and, consequently, the correction factors increased. The effect was more pronounced for smaller diameter cores. The correction factors were somewhat higher for cores drilled from river gravel concrete. The age of the concrete was found to be an important factor in the strength correction of different diameter cores, that is, the older the concrete, the lower the correction factor. It should be noted, however, that it is very difficult to use age-versus-correction factor relation in practical terms. Additionally, test results showed that the length-to-diameter ratio of the specimen is more significant for small-diameter cores.

Effect of Core Diameter and Surface Treatment on the Retention of Resin Composite Cores to Prefabricated Endodontic Posts

With advances in adhesive dentistry and current emphasis on esthetic restorations, dowel systems have been developed to take advantage of these new techniques. Of interest when using these systems is the interaction between core materials and post materials. This investigation compared the tensile retentive force of two resin composite core materials to two metallic and one non-metallic prefabricated endodontic posts. Two dimensions of core build-up and two post-surface treatments were tested. One hundred twenty posts (stainless steel, titanium alloy, and glass fiber-impregnated resin) were secured in a jig with 4 mm of the post extending into a cylindrical matrix. The matrix formed cylinders with diameters of 3 and 5 mm into which resin composite was inserted. The posts were treated or not treated with a bonding agent. After storage for 24 hours at 100% humidity, five specimens per condition were tested in an Instron testing machine at a crosshead speed of 0.5 mm/min. Failure loads were recorded in kilograms and failure modes were observed under light microscopy (40 x). Four-way analysis of variance and multiple comparison testing were used to compare means at the 0.05 level of significance. The means and standard deviations of tensile loads were calculated. All variables were significant in either main effects or interactions ( p<0.05). Fisher's PLSD intervals for post, core, treatment, and diameter were 2.0, 1.6, 1.6, and 1.6 kg, respectively. In most cases, the retentive force recorded for metallic posts was higher than that of glass fiber posts. Titanium posts had higher retentive forces than did the stainless steel posts. For metallic posts, 5-mm cores provided higher forces than 3-mm cores. In the glass fiber group, core diameter was not significant. For core materials, Build-It gave higher results with stainless steel posts, and FluoroCore gave higher results with the titanium ones. The surface treatment results were mixed. In the metallic post groups the adhesive failure data ranged between 80% and 100%, whereas in the glass fiber post groups, adhesive failures ranged between 60% and 70%. Within the limitations of this study, the metallic post groups always provided higher tensile retentive forces, with the titanium post groups showing higher retentive forces than the stainless steel ones. In the glass fiber post groups, different core diameters did not affect retention values.