Asymptotic density and the Ershov hierarchy

We classify the asymptotic densities of the $\Delta^0_2$ sets according to their level in the Ershov hierarchy. In particular, it is shown that for $n \geq 2$, a real $r \in [0,1]$ is the density of an $n$-c.e.\ set if and only if it is a difference of left-$\Pi_2^0$ reals. Further, we show that the densities of the $\omega$-c.e.\ sets coincide with the densities of the $\Delta^0_2$ sets, and there are $\omega$-c.e.\ sets whose density is not the density of an $n$-c.e. set for any $n \in \omega$.Comment: To appear in Mathematical Logic Quarterl

If you build it, they may not come: Why Australian university students do not take part in outbound mobility experiences.

Universities around the world seek to internalise students to prepare them for an increasingly globalised world. Outbound mobility experiences (OMEs) are recognised as one of the most effective ways to foster independent thinking, cultural sensitivity, and a sense of 'worldmindedness'. This article takes a case study from an Australian university and explores efforts to increase student participation rates in OMEs

Survival analysis of metal crowns versus restorations in primary mandibular molars

Background The effectiveness of stainless steel crowns (SSCs) versus direct restorations when placed in primary mandibular molars (teeth nos. L and S) is uncertain. The authors evaluated effectiveness by gauging longevity of treatment. Methods The authors obtained private dental insurance claims (2004-2016) from a national dental data warehouse. Paid insurance claims records (n = 1,323,489) included type of treating dentist, treatment placed, and patient age. Results Dentist specialty, type of treatment, and patient age were significant in predicting failure after the first restoration. The authors found high survival rates for all treatments (> 90%) after 5 years; however, as soon as within 3 years after treatment, SCCs had approximately 6% better survival. Conclusions Teeth nos. L and S first treated with SSCs lasted longer without new treatment compared with teeth first treated with direct restorations; the difference was small. Teeth treated by pediatric dentists had better survival rates. Practical Implications Primary mandibular first molars initially treated with SSCs lasted longer without new treatment compared with direct restorations. Overall dental care costs of the former were considerably higher

Characteristics of 0.8- and 0.2-microns gate length In(x)Ga(1-x) As/In(0.52)Al(0.48)As/InP (0.53 less than or equal to x less than or equal to 0.70) modulation-doped field-effect transistors at cryogenic temperatures

The performance characteristics of InP-based In(x)Ga(1-x)As/In(0.52)Al(0.48)As (0.53 is less than or equal to x is less than or equal to 0.70) pseudomorphic modulation-doped field-effect transistors (MODFET's) as a function of strain in the channel, gate, length, and temperature were investigated analytically and experimentally. The strain in the channel was varied by varying the In composition x. The temperature was varied in the range of 40-300 K and the devices have gate lengths L(sub g) of 0.8 and 0.2 microns. Analysis of the device was done using a one-dimensional self consistent solution of the Poisson and Schroedinger equations in the channel, a two-dimensional Poisson solver to obtain the channel electric field, and a Monte Carlo simulation to estimate the carrier transit times in the channel. An increase in the value of the cutoff frequency is predicted for an increase in In composition, a decrease in temperature, and a decrease in gate length. The improvements seen with decreasing temperature, decreasing gate length, and increased In composition were smaller than those predicted by analysis. The experimental results on pseudomorphic InGaAs/InAlAs MODFET's showed that there is a 15-30 percent improvement in cutoff frequency in both the 0.8- and 0.2-micron gate length devices when the temperature is lowered from 300 to 40 K

Structure of anhydrotetracycline-bound Tet(X6) reveals the mechanism for inhibition of type 1 tetracycline destructases

Inactivation of tetracycline antibiotics by tetracycline destructases (TDases) remains a clinical and agricultural threat. TDases can be classified as type 1 Tet(X)-like TDases and type 2 soil-derived TDases. Type 1 TDases are widely identified in clinical pathogens. A combination therapy of tetracycline and a TDase inhibitor is much needed to rescue the clinical efficacy of tetracyclines. Anhydrotetracycline is a pan-TDase inhibitor that inhibits both type 1 and type 2 TDases. Here, we present structural, biochemical, and phenotypic evidence that anhydrotetracycline binds in a substrate-like orientation and competitively inhibits the type 1 TDase Tet(X6) to rescue tetracycline antibiotic activity as a sacrificial substrate. Anhydrotetracycline interacting residues of Tet(X6) are conserved within type 1 TDases, indicating a conserved binding mode and mechanism of inhibition. This mode of binding and inhibition is distinct from anhydrotetracycline\u27s inhibition of type 2 TDases. This study forms the framework for development of next-generation therapies to counteract enzymatic tetracycline resistance

Utilization of Silver Diamine Fluoride by Dentists in the United States: A Dental Claims Review

Purpose: A Current Dental Terminology (CDT) code, D1354, for silver diamine fluoride was made effective on January 1, 2016. The purpose of this study was to investigate the utilization of silver diamine fluoride (SDF) by pediatric dentists (PDs) and general dentists (GDs) in the United States. Methods: Data were obtained from a commercial dental insurance claims warehouse in the United States. Deidentified data for CDT code D1354 were collected from January 2016 to July 2019. Descriptive statistics and chi-square tests were used. Results: A total of 321,726 D1354 claims were found. Data showed that SDF use measured by average monthly claims, unique number of dentists, and percent of paid claims increased each year. Patients zero to nine years old were the most likely to receive SDF treatment. SDF was significantly more likely to be placed on posterior teeth and in children zero to eight years old (P<0.001). PDs were more likely than GDs to submit claims for SDF in children (P<0.001). Conclusions: Silver diamine fluoride use is increasing, especially in patients age zero to nine years. Pediatric dentists are more likely to use SDF in children than general dentists. Posterior teeth receive the majority of SDF treatment

Trends in dental insurance claims in the United States before and during the SARS-CoV-2 pandemic in 2020

Objectives: The SARS-CoV-2 pandemic disrupted health care services. Previous reports estimated reductions in demand and supply of dental care services, but actual changes have not been reported. The present report depicts a perspective of trends in claims from private dental practice in the United States during 2019 and 2020. Methods: Private dental insurance paid claims data from a data warehouse (encompassing 66+ carriers in the United States) were obtained for children and adults (treatments identified by their American Dental Association Code of Dental Procedures and Nomenclature [CDT]), encompassing a 5% random sample of all records between January 2019 and December 2020. A market-based treatment classification placed CDT codes into one of four categories based on the likelihood of being associated with urgent/emergency care. Results: Claims for 3.8 million patients constituted the 5% random sample for analyses. Substantial drops in the provision of treatment items were quantified for a large segment of private dental insurance plans at a national level, showing differential impacts in dental care categories. Conclusions: Week-by-week, detailed descriptions of demand/availability changes in dental care throughout the first year of the 2020 SARS-CoV-2 pandemic were obtained through contrasting perspectives in 2019. Provision of dental care and associated impacts fluctuated over time subject to treatment urgency, but also modified as the weeks/months of dental office lockdowns ebbed in and out of the dental market

Jafari and Transformation: A Model to enhance short-term overseas study tours

This paper promotes a reconstructed Jafari (1987) tourism model as a framework to understand the various components of the student and staff travel experience while participating in an outbound mobility experience (OME), especially short-term overseas study trips. Working through each of the components of the Jafari model allows recognition of the changing needs and requirements of both students and staff throughout an OME and the tensions that accompany this relationship

Reducing Baylisascaris procyonis Roundworm Larvae in Raccoon Latrines

Baylisascaris procyonis roundworms, a parasite of raccoons, can infect humans, sometimes fatally. Parasite eggs can remain viable in raccoon latrines for years. To develop a management technique for parasite eggs, we tested anthelmintic baiting. The prevalence of eggs decreased at latrines, and larval infections decreased among intermediate hosts, indicating that baiting is effective

"Pathogen Eradication" and "Emerging Pathogens": Difficult Definitions in Cystic Fibrosis.

Infection is a common complication of cystic fibrosis (CF) airway disease. Current treatment approaches include early intervention with the intent to eradicate pathogens in the hope of delaying the development of chronic infection and the chronic use of aerosolized antibiotics to suppress infection. The use of molecules that help restore CFTR (cystic fibrosis transmembrane conductance regulator) function, modulate pulmonary inflammation, or improve pulmonary clearance may also influence the microbial communities in the airways. As the pipeline of these new entities continues to expand, it is important to define when key pathogens are eradicated from the lungs of CF patients and, equally important, when new pathogens might emerge as a result of these novel therapies