Prevalence of Color Vision Deficiency among Dental Practitioners and its Effect on Shade Matching Ability

Objective: Shade selection is a crucial step in achieving aesthetically-pleasing restorations, and it is affected by the dentist’s ability to match the shade of the patient’s teeth. Color Deficiency Disease (CVD) has been thought to be a potential factor affecting color perception. The study aims to find the prevalence of CVD between dentists and dental students and to evaluate its effect on shade matching ability. Methods: A sample of 319 dentists and dental students in the College of Dentistry at Ajman University, Ajman, UAE was examined with the Ishihara test to find the prevalence of CVD. Then participants with CVD were tested for shade matching ability, and were compared to participants with normal color vision with the same gender and qualification level. They were asked to match 10 random composite samples with different shades to a custom shade guide made from the same composite material. A score was calculated, representing the number of correct answers they achieved. Results: The results showed that 8 out of 143 males (5.6%) had CVD, and 0 out of 176 females had CVD. There was no significant difference in the score of shade matching test between participants with CVD and participants with normal color vision (p=0.075). Conclusion: Males showed a higher prevalence of color vision deficiency than females. CVD had no significant effect on shade matching ability.

Fabrication of multilayer tubular scaffolds with aligned nanofibers to guide the growth of endothelial cells

Aligned electrospun fibers used for the fabrication of tubular scaffolds possess the ability to regulate cellular alignment and relevant functional expression, with applications in tissue engineering. Despite significant progress in the fabrication of small-diameter vascular grafts (SDVGs) over the past decade, several challenges remain; one of the most problematic of these is the fabrication of aligned nanofibers for multilayer SDVGs. Furthermore, delamination between each layer is difficult to avoid during the fabrication of multilayer structures. This study introduces a new fabrication method for minute delamination four-layer tubular scaffolds (FLTSs) that consist of an interior layer with highly longitudinal aligned nanofibers, two middle layers composed of electrospun sloped and circumferentially aligned fibers, and an exterior layer comprising random fibers. These FLTSs are used to simulate the structures and functions of native blood vessels. Here, thermoplastic polyurethane (TPU)/polycaprolactone (PCL)/polyethylene glycol (PEG) were electrospun to fabricate FLTSs or tubular scaffolds with completely random fibers layer (RLTSs). The surface wettability of the TPU/PCL/PEG tubular scaffold was tested by water contact angle analysis. In particular, compared with RLTSs, FLTSs showed excellent mechanical properties, with higher circumferential and longitudinal tensile properties. Furthermore, the high viability of the human umbilical vein endothelial cells (HUVECs) on the FLTSs indicated the biocompatibility of the tubular scaffolds comparing to RLTSs. The aligned and random composite structure of the FLTSs are conducive to promoting the growth of HUVECs, and the cell adhesion and proliferation on these scaffolds was found to be superior to that on RLTSs. These results demonstrate that the fabricated FLTSs have the potential for application in vascular tissue regeneration and clinical arterial replacements.

Transmission and reflection at the boundary of a random two-component composite

A half-space x 2 > 0 is occupied by a two-component statistically uniform random composite with specified volume fractions and two-point correlation. It is bonded to a uniform half-space x 2 < 0 from which a plane wave is incident. The transmitted and reflected mean waves are calculated via a variational formulation that makes optimal use of the given statistical information. The problem requires the specification of the properties of three media: those of the two constituents of the composite and those of the homogeneous half-space. The complexity of the problem is minimized by considering a model acoustic-wave problem in which the three media have the same modulus but different densities. It is formulated as a problem of Wiener–Hopf type which is solved explicitly in the particular case of an exponentially decaying correlation function. Possible generalizations are discussed in a brief concluding section.

Unlabelled Gibbs partitions

We study random composite structures considered up to symmetry that are sampled according to weights on the inner and outer structures. This model may be viewed as an unlabelled version of Gibbs partitions and encompasses multisets of weighted combinatorial objects. We describe a general setting characterized by the formation of a giant component. The collection of small fragments is shown to converge in total variation toward a limit object following a Pólya–Boltzmann distribution.

From statics of composites to acoustic metamaterials

The Hashin–Shtrikman formalism for the static response of a composite is first summarized, in a form applicable to anisotropic media and arbitrary two-point correlations. Its extension to dynamic response is then explained and in particular the extra coupling, for stress with velocity as well as strain, and momentum density with strain as well as velocity that inevitably follows, is highlighted. The more recent dynamical formulations which incorporate extra flexibility through the use of a weighted mean displacement also receive mention. The article is concluded with an explicit analysis of a simple model random composite and some lessons are drawn from the solution, which exposes at least one clear gap in existing knowledge and requires further research. This article is part of the theme issue ‘Modelling of dynamic phenomena and localization in structured media (part 1)’.

Electrospinning of Cellulose Nanocrystal-Filled Poly (Vinyl Alcohol) Solutions: Material Property Assessment

Poly (vinyl alcohol) (PVA) and cellulose nanocrystals (CNC) random composite mats were prepared using the electrospinning method. PVA/CNC mats were reinforced with weight concentrations of 0, 20 and 50% CNC (w/w) relative to PVA. Scanning electron microscopy was used to measure the fiber diameter, which ranged from 377 to 416 nm. Thermogravimetric analysis (TGA) confirmed the presence of CNC fibers in the mat fibers which were not visible by scanning electron microscope (SEM). Mechanical testing was conducted using ASTM D 638 on each sample group at 10 mm min−1. Neat PVA and PVA/CNC mats were heat treated at 170 °C for 2h hours, and the morphological structure was maintained with some fiber diameter reduction. Mechanical property results after heat treatment showed a decrease in tensile strength, an increase in tensile stiffness and a decrease in strain to yield (%). This effect was attributable to enhanced diffusion bonding of the mat fiber intersections. The CNC fibers also increased mat stiffness, and reduced strain to yield in non-treated mats. The use of CNCs show potential for compounding into bulk polymer composites as a reinforcement filler, and also show promise for chemical crosslinking attributable to the –OH groups on both the PVA, in addition to esterification of the vinyl group, and CNC.

The prevalence and audience reach of food and beverage advertising on Chilean television according to marketing tactics and nutritional quality of products

ObjectiveIn the light of Chile’s comprehensive new restriction on unhealthy food marketing, we analyse food advertising on Chilean television prior to the first and final phases of implementation of the restriction.DesignContent analysis of marketing strategies of 6976 advertisements, based on products’ nutritional quality. Statistical analysis of total and child audience reached using television ratings data.SettingAdvertising from television aired between 06.00 and 00.00 hours during two random composite weeks across April–May 2016 from the four broadcast and four cable channels with the largest youth audiences.ResultsFood ads represented 16 % of all advertising; 34 % of food ads featured a product high in energy, saturated fats, sugars and/or salt (HEFSS), as defined by the initial regulation. HEFSS ads were seen by more children and contained more child-directed marketing strategies than ads without HEFSS foods. If HEFSS advertising was restricted only in programmes where 20 % are children aged 4–12 years, 31 % of children’s and 8 % of the general audience’s HEFSS advertising exposure would be reduced. The newest 06.00–22.00 hours restriction captures 80 % of all audience exposure.ConclusionsHEFSS advertising was seen by a large proportion of children before Chile’s regulation. Chile’s first implementation based on audience composition should reduce a third of this exposure and its second restriction across the television day should eliminate most of the exposure. The current study is a crucial first step in evaluating how Chile’s regulation efforts will impact children’s diets and obesity prevalence.