3,813 research outputs found
Comparison Between Radiotracer and Surface Profile Methods for the Determination of Dentifrice
poster abstractIntroduction: ISO11609 states that a surface profile (Sp) method can be used to determine dentifrice
abrasivity in relation to dentin (RDA) as an alternative to the traditional radiotracer method (Rt). A
comparison between both methods was performed in this study.
Methods: Specimens from human root dentin were prepared for each method and randomly assigned to 8
dentifrice/abrasive groups (n=8), which represented a wide abrasivity range. Aqueous dentifrice slurries
or abrasive suspensions in a solution containing 0.5% carboxymethylcellulose and 10% glycerin were
used to brush specimens in a custom-made V-8 cross-brushing machine. Two independent studies (Sp,
Rt) were carried out. For Rt, the specimen preparation, study design, analysis and calculation of the
abrasive level (RDA) followed the ISO11609/Annex A guidelines. Similarly for Sp, the ISO11609/Annex
B recommendations were followed, except by the number of brushing strokes, which was pre-determined
to be 2000 strokes (instead of 10000) in a preliminary test. Data were analyzed using ANOVA and Tukey
tests, with significance level set at 5%. The correlation between methods was also investigated.
Results: Overall, higher variation and RDA values were observed for the Sp method compared to Rt.
While good correlation was found between methods (R2=0.841), group ranking was dissimilar and better
statistical differentiation among groups was observed in Rt.
Conclusions: The Rt method showed to be a more standardized and robust method compared to Sp for the
determination of RDA values of dentifrices/abrasives. Sp needs to be further developed before being
considered as an equivalent test method for RDA. The determination of the abrasive levels of toothpastes
using standard testing methods is important to guide oral care professionals and patients on the prevention
of toothbrushing abrasive wear
Cosmology and Astrophysics from Relaxed Galaxy Clusters II: Cosmological Constraints
We present cosmological constraints from measurements of the gas mass
fraction, , for massive, dynamically relaxed galaxy clusters. Our data
set consists of Chandra observations of 40 such clusters, identified in a
comprehensive search of the Chandra archive, as well as high-quality weak
gravitational lensing data for a subset of these clusters. Incorporating a
robust gravitational lensing calibration of the X-ray mass estimates, and
restricting our measurements to the most self-similar and accurately measured
regions of clusters, significantly reduces systematic uncertainties compared to
previous work. Our data for the first time constrain the intrinsic scatter in
, % in a spherical shell at radii 0.8-1.2 ,
consistent with the expected variation in gas depletion and non-thermal
pressure for relaxed clusters. From the lowest-redshift data in our sample we
obtain a constraint on a combination of the Hubble parameter and cosmic baryon
fraction, , that is insensitive to the
nature of dark energy. Combined with standard priors on and ,
this provides a tight constraint on the cosmic matter density,
, which is similarly insensitive to dark energy. Using
the entire cluster sample, extending to , we obtain consistent results for
and interesting constraints on dark energy:
for non-flat CDM models, and
for flat constant- models. Our results are both competitive
and consistent with those from recent CMB, SNIa and BAO data. We present
constraints on models of evolving dark energy from the combination of
data with these external data sets, and comment on the possibilities for
improved constraints using current and next-generation X-ray
observatories and lensing data. (Abridged)Comment: 25 pages, 14 figures, 8 tables. Accepted by MNRAS. Code and data can
be downloaded from http://www.slac.stanford.edu/~amantz/work/fgas14/ . v2:
minor fix to table 1, updated bibliograph
Recommended from our members
Dissecting a complex chemical stress: chemogenomic profiling of plant hydrolysates.
The efficient production of biofuels from cellulosic feedstocks will require the efficient fermentation of the sugars in hydrolyzed plant material. Unfortunately, plant hydrolysates also contain many compounds that inhibit microbial growth and fermentation. We used DNA-barcoded mutant libraries to identify genes that are important for hydrolysate tolerance in both Zymomonas mobilis (44 genes) and Saccharomyces cerevisiae (99 genes). Overexpression of a Z. mobilis tolerance gene of unknown function (ZMO1875) improved its specific ethanol productivity 2.4-fold in the presence of miscanthus hydrolysate. However, a mixture of 37 hydrolysate-derived inhibitors was not sufficient to explain the fitness profile of plant hydrolysate. To deconstruct the fitness profile of hydrolysate, we profiled the 37 inhibitors against a library of Z. mobilis mutants and we modeled fitness in hydrolysate as a mixture of fitness in its components. By examining outliers in this model, we identified methylglyoxal as a previously unknown component of hydrolysate. Our work provides a general strategy to dissect how microbes respond to a complex chemical stress and should enable further engineering of hydrolysate tolerance
3D-Image Analysis of the Impact of Toothpaste Abrasivity on the Progression of Simulated Non-Carious Cervical Lesions
Objectives
To investigate the effect of toothpaste abrasive level on the progression of non-carious cervical lesions (NCCLs) using 3D-image subtraction.
Methods
Upper first premolars were allocated into seven groups (n = 16) of toothpaste/abrasive slurries: A-Zeodent113/5%, B-Zeodent124/10%, C-Zeodent103/15%, D-Sensodyne Pronamel, E-Crest Cavity-Protection, F-Crest Pro-Health-Whitening, and G-Deionized water (DIW). Teeth were mounted on acrylic blocks, and their root surfaces covered with acrylic resin, except for 2-mm near the cemento-enamel junction that was exposed to toothbrushing. Specimens were brushed with the slurries for 5000-, 15,000-, 35,000- and 65,000-strokes. Impressions were taken at baseline and after each brushing time, and then scanned by a 3D optical profilometer. Dentine volume loss was calculated by image subtraction software and subjected to mixed-model ANOVA and multiple comparison tests (α = 0.05).
Results
No significant differences among slurries were observed at 5000 and 15,000. At 35,000, F showed higher loss than all other groups except C, which did not differ from the others. At 65,000, F (4.19 ± 3.29 mm3) showed the highest loss, followed by C (2.33 ± 1.47 mm3), which differed from all the other groups except B (1.85 ± 0.91 mm3). Groups B, A (1.35 ± 0.65 mm3), D (1.17 ± 0.48 mm3), E (1.40 ± 0.68 mm3) and G (1.12 ± 0.73 mm3) did not differ from each other. Groups F and C showed significant increase of volume loss starting at 35,000, while B, A, D and E only at 65,000; no increase loss was observed for G.
Conclusions
3D-image subtraction was able to quantify and differentiate tooth loss, but only at advanced stages. The progression of NCCLs was more evident and faster for highly abrasive slurries.
Clinical significance
Upon root dentin exposure, brushing with lower abrasive dentifrices is advisable to reduce the risk for NCCLs development
Defining “elite” status in sport: from chaos to clarity
The past two decades have seen a rapid rise in attention towards talent identification, athlete development and skill acquisition. However, there are important limitations to the evidentiary foundations of this field of research. For instance, variability in describing the performance levels of individuals has made it challenging to draw inferences about inter- and intrapopulation differences. More specifically, recent reviews on high performers in sport have noted considerable variation in how terms such as “elite” are used. This may be particularly concerning for researchers in high-performance disciplines, since they regularly struggle with small sample sizes and rely on research synthesis approaches (i.e. meta-analyses and systematic reviews) to inform evidence-based decisions. In this discussion piece, we (a) highlight issues with the application of current terminology, (b) discuss challenges in conceptualizing an improved framework and (c) provide several recommendations for researchers and practitioners working in this area
Human pluripotent stem cell-derived striatal interneurons: differentiation and maturation in vitro and in the rat brain
Striatal interneurons are born in the medial and caudal ganglionic eminences (MGE and CGE) and play an important role in human striatal function and dysfunction in Huntington's disease and dystonia. MGE/CGE-like neural progenitors have been generated from human pluripotent stem cells (hPSCs) for studying cortical interneuron development and cell therapy for epilepsy and other neurodevelopmental disorders. Here, we report the capacity of hPSC-derived MGE/CGE-like progenitors to differentiate into functional striatal interneurons. In vitro, these hPSC neuronal derivatives expressed cortical and striatal interneuron markers at the mRNA and protein level and displayed maturing electrophysiological properties. Following transplantation into neonatal rat striatum, progenitors differentiated into striatal interneuron subtypes and were consistently found in the nearby septum and hippocampus. These findings highlight the potential for hPSC-derived striatal interneurons as an invaluable tool in modeling striatal development and function in vitro or as a source of cells for regenerative medicine
Language games and blurry terminology: Can clarity enhance athlete development?
This perspective focuses on the need for researchers and practitioners to carefully consider the clarity and consistency of their language in the context of athlete development. Evidence supporting a lack of congruency in the way certain terms and expressions are defined, understood, and operationalized continues to accumulate, highlighting the importance of this area for sport stakeholders and the potential looming crises. In systems that regularly rely on precision and accuracy, it will be critical that all involved in the co-creation of knowledge generation and application carefully consider terms that may further complicate athlete development practices. We highlight some potentially blurry terms and draw attention to potential avenues for future research
- …