Completely depolarizing channels are often regarded as the prototype of physical processes that are useless for communication: any message that passes through them along a well-defined trajectory is ...completely erased. When two such channels are used in a quantum superposition of two alternative orders, they become able to transmit some amount of classical information, but still no quantum information can pass through them. Here, we show that the ability to place N completely depolarizing channels in a superposition of N alternative causal orders enables a high-fidelity heralded transmission of quantum information with error vanishing as 1 / N . This phenomenon highlights a fundamental difference with the N = 2 case, where completely depolarizing channels are unable to transmit quantum data, even when placed in a superposition of causal orders. The ability to place quantum channels in a superposition of orders also leads to an increase of the classical communication capacity with N , which we rigorously prove by deriving an exact single-letter expression. Our results highlight the more complex patterns of correlations arising from multiple causal orders, which are similar to the more complex patterns of entanglement arising in multipartite quantum systems.
Using ab initio simulations we investigate whether water ice is stable in the cores of giant planets, or whether it dissolves into the layer of metallic hydrogen above. By Gibbs free energy ...calculations we find that for pressures between 10 and 40 Mbar the ice-hydrogen interface is thermodynamically unstable at temperatures above approximately 3000 K, far below the temperature of the core-mantle boundaries in Jupiter and Saturn. This implies that the dissolution of core material into the fluid layers of giant planets is thermodynamically favored, and that further modeling of the extent of core erosion is warranted.
The aim of this study was to review patterns of restoration placement and replacement. A previous study had been carried out in the late 1990s and this study sought to update the literature in this ...important aspect of dental practice.
Studies based on the protocol of Mjör (1981) were selected. Such studies involved participating dentists completing a proforma each time a patient presented for a new or replacement restoration.
Twenty-five papers were included in this study, of which 12 were included in the original review. The pre-1998 review reported on the placement of 32,697 restorations, of which 14,391 (44%) were initial placements and 18,306 (56%) were replacements. The new studies included in the post-1998 review reported on an additional 54,023 restorations, of which 22,625 (41.9%) were initial placements and 31,398 (58.1%) were replacements. Therefore, across all studies considered, information is available on 86,720 restorations, of which 37,016 (42.7%) were new placements and 49,704 (57.3%) were replacements. Comparing review periods, there was a reduction in the placement of amalgam restorations from 56.7% (pre-1998 review) to 31.2% (post-1998 review), with a corresponding increase in the placement of resin composites from 36.7% to 48.5%. The most common use of amalgam was seen in Nigeria (71% of restorations), Jordan (59% of restorations) and the UK (47% of restorations). The most frequent use of resin composite was seen in Australia (55% of restorations), Iceland (53% of restorations) and Scandinavia (52% of restorations). Secondary caries was the most common reason for replacing restorations (up to 59% of replacement restorations).
In the years subsequent to the initial review, replacement of restorations still accounts for more than half of restorations placed by dentists, and the proportion of replacement restorations continues to increase. Trends towards the increased use of resin composites is noted in recent years.
Further research is required in this area to investigate changes in the approaches to the restoration of teeth, especially with increased understanding of the concept of restoration repair as an alternate to replacement.
Charcoal-containing dentifrices Greenwall, Linda H; Greenwall-Cohen, Joseph; Wilson, Nairn H F
British dental journal,
05/2019, Letnik:
226, Številka:
9
Journal Article
Recenzirano
Charcoal toothpastes and powders are fashionable oral hygiene products, intended for toothbrushing, extrinsic stain removal and, it is claimed, 'tooth whitening'. The popularity of charcoal ...toothpastes is believed to be increasing in many countries across the world, including the UK, US, Japan, India, Thailand, Lithuania, Australia, Hong Kong, China, Korea and Switzerland, where charcoal-based toothpastes have been reported to be produced. It is understood that many patients ask members of their dental team for advice on the use and benefits of charcoal toothpastes and powders, and that such advice is often empirical. The purpose of this article is to provide an overview of the current knowledge and understanding of charcoal toothpastes and powders, including consideration of the strength of the evidence to support claims made by the manufacturers of these products.
Abstract There have been many developments in operative dentistry in recent years, including a progressive shift to the use of resin composites, rather than dental amalgam, in the restoration of ...posterior teeth. This shift allows the adoption of minimal intervention approaches, thereby helping to conserve and preserve remaining tooth tissues and structures. This paper presents the position of the Academy of Operative Dentistry European Section (AODES) in relation to posterior resin composites. The AODES considers adhesively bonded resin composites of suitable composition and properties to be the “material of choice” for use in direct minimal intervention approaches to the restoration of posterior teeth. In so doing, the AODES emphasises the importance of the practice of evidence-based minimal intervention dentistry, including the use of refurbishment and repair techniques to extend the longevity of restorations. Guidance, based on best available evidence, has been made in relation to certain aspects of resin composite placement techniques in posterior teeth.
The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 gamma-ray bursts (GRBs) since it began science operations in 2008 July. We use a subset of over 300 GRBs localized by instruments such ...as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the InterPlanetary Network, to analyze the accuracy of GBM GRB localizations. We find that the reported statistical uncertainties on GBM localizations, which can be as small as 1degrees, underestimate the distance of the GBM positions to the true GRB locations and we attribute this to systematic uncertainties. The distribution of systematic uncertainties is well represented (68% confidence level) by a 3degrees.7 Gaussian with a non-Gaussian tail that contains about 10% of GBM-detected GRBs and extends to approximately 14degrees. A more complex model suggests that there is a dependence of the systematic uncertainty on the position of the GRB in spacecraft coordinates, with GRBs in the quadrants on the Y axis better localized than those on the X axis.
Given the many, different challenges which are anticipated to face academic dentistry in the foreseeable future, high quality leadership is a ‘must’ if academic dentistry is to realise its potential ...in healthcare education, training and research, let alone help effect much-needed improvements in oral health and ensure the rightful place of oral healthcare in future general health and social care provision. Furthermore, the vision of leaders in academic dentistry must be increasingly all-inclusive and global, if the individuals and groups they lead are to succeed and be effective in meeting future multicultural and otherwise diverse needs and expectations. Special thanks are extended to Chris Lynch in his role as Editor-in-Chief of the Journal of Dentistry for agreeing to publish a special issue on leadership in academic dentistry, and to the Journal of Dentistry production team at Elsevier for their invaluable help and support.
A major challenge in nanoscience and nanotechnology is the rational assembly of nanoscale objects. Here we report that gold nanorods, aspect ratio 18, can be functionalized with a biotin disulfide, ...and subsequent addition of streptavidin links the rods together in an end-to-end manner much more often than expected.
To investigate current teaching and operative techniques for posterior composite resin restorations in dental schools in Austria, Germany, and Switzerland.
Data on teaching, including operative ...techniques applied in the placement of posterior composites, were collected by means of a 25-item validated questionnaire sent to the Heads of Department of Operative/Restorative Dentistry at all 38 dental schools in Austria, Germany, and Switzerland. Responses were compiled in Excel and analysed.
Thirty-three schools responded to the survey, resulting in a response rate of 87 %. All dental schools indicated teaching of 2- and 3-surface posterior composite restorations. About one third only of the preclinical teaching is assigned to teaching posterior composite restorations, while the vast majority of posterior restorations placed by students in their clinical instruction are composite (89.6 ± 9.3 %). Most dental schools teach few contraindications to posterior composites, except for adverse reactions such as allergies. All dental schools consider moisture control to be important, while approaches to the management of exposed dentine differ.
The teaching of the placement of posterior composite restorations is common to all the dental schools in Austria, Germany, and Switzerland which participated in the present study. Most aspects of the teaching were found to be consistent amongst the schools. However, marked variations were observed in respect of operative techniques for the placement of posterior composites.
Graduates from dental schools in Austria, Germany, and Switzerland may be found to have received theoretical, preclinical, and clinical instruction in posterior composites, but do show some variation in approach to the management of exposed dentine.
The aim of this study was to evaluate theeffects of different finishing and polishing techniques on the surface roughness of microhybrid and nanofilled resin composites.
The resin composites included ...were Filtek Z250 (a universal microhybrid resin composite) and Filtek Supreme XTE (a universal nanofill resin composite). Ninety cylindrical-shaped specimens were prepared for each composite resin material. The polishing methods used included tungsten carbide bur (TC); diamond bur (Db); Sof-Lex discs (S); Enhance PoGo discs (PG); TC + S; Db + S; TC + PG; Db + PG. Polymerisation against a Mylar strip without finishing and polishing acted as the control group. Surface roughness was measured using a 3D contact optical profilometer and surface morphology was examined by scanning electron microscope examination.
The results showed that the Mylar-formed surfaces were smoothest for both composites. Finishing with the 20 μm diamond finishing bur caused significantly greater surface irregularity (P < 0.0001) and damage than finishing with the tungsten carbide finishing bur. The Enhance PoGo polishing system produced smoother surfaces than the Sof-Lex disc polishing system; this difference was statistically highly significant (P < 0.0001).
For both composites, the Mylar-formed surfaces were smoothest. Where indicated clinically, finishing is better conducted using a tungsten carbide bur- rather than a diamond finishing bur. The Enhance PoGo system was found to produce a smoother surface finish than the Sof-Lex system.
If finishing and polishing is required the use a tungsten carbide finishing bur followed by Enhance PoGo polishing may be found to result in the smoothest surface finish.
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