Surface properties of polyetheretherketone after different laboratory and chairside polishing protocols

STATEMENT OF PROBLEM Polyetheretherketone (PEEK) can be used as a framework material for fixed dental prostheses. However, information about laboratory and chairside polishing methods is still scarce. PURPOSE The purpose of this in vitro study was to determine the effects of laboratory and chairside polishing methods on the surface roughness (SR) and surface free energy (SFE) of PEEK, an autopolymerizing poly(methyl methacrylate), and a veneering composite resin. MATERIAL AND METHODS For each of the 3 materials, 80 specimens were prepared (N=240) and divided into 7 polishing groups and 1 control group (n=10). The 7 groups were split into 4 laboratory protocols: polishing paste (Abraso), a second polishing paste (Opal L), silicone polisher (Ceragum), and diamond grinder (Diagen-Turbo grinder). The other 3 groups were chairside protocols: rainbow technique (Super-Snap kit), polishing paste (Prisma gloss), and a polishing system (Enhance finishing). Machine polishing with SiC P4000 served as the control treatment. The protocols' average SRs and SFEs were measured, and their surface topographies were evaluated with scanning electron microscopy (SEM). The logarithmically transformed data were analyzed using covariance analysis, 2-way and 1-way ANOVA, and partial correlation (α=.05). RESULTS The polishing protocol exerted the highest influence on SR and SFE values (P<.001; SR: partial eta squared ηP(2)=.970; SFE: ηP(2)=.450), followed by material group (P<.001, SR: ηP(2)=.319; SFE: ηP(2)=.429). The interaction effect of the binary combinations of the 2 independent parameters (polishing protocol and material group) was also significant (P<.001, SR: ηP(2)=.681; SFE: ηP(2)=.365). CONCLUSIONS Chairside methods presented lower SR values than laboratory methods, and specimens polished using the 2-body mode showed higher SR than did specimens polished using the 3-body mode

The Retail FX Trader: Random Trading and the Negative Sum Game

With the internet boom of early 2000 making access to trading the Foreign Exchange (FX) market far simpler for members of the general public, the growth of 'retail' FX trading continues, with daily transaction volumes as high as $200 billion. Potential new entrants to the retail FX trading world may come from the recent UK pension deregulations, further increasing the volumes. The attraction of FX trading is that it offers high returns and whilst it has been understood that it is high-risk in nature, the rewards are seen as being commensurately high for the 'skilled and knowledgeable' trader who has an edge over other market participants. This paper analyses a number of independent sources of data and previous research, to examine the profitability of the Retail FX trader and compares the results with that of a simulated random trading models. This paper finds evidence to suggest that whilst approximately 20% of traders can expect to end up with a profitable account, around 40% might expect their account to be subject to a margin call. This paper finds a strong correlation between the overall profitability of traders and impact of the cost of the bid-ask spread, whilst finding little if any evidence that retail FX traders, when viewed as a group, are achieving results better than that from random trading

Effect of active immunization against growth hormone releasing factor on concentrations of somatotropin and insulin-like growth factor I in lactating beef cows

Two experiments were conducted to determine the effects of immunoneutralization of growth hormone-releasing factor [GRF(1–29)-NH2] on concentrations of somatotropin (ST) and insulin-like growth factor I (IGF-I) in lactating beef cows. In Experiment 1, multiparous Hereford cows were immunized against 2 mg GRF(1–29)-(Gly)4-Cys-NH2 conjugated to human serum albumin (GRFi, n=3) or 2 mg human serum albumin (HSAi, n=3) at 52 ± 1 d prior to parturition. Boosters (1 mg) were administered on days 12, 40 and 114 postpartum (pp). Serum samples were collected at 15-min intervals for 5 hr on days 18, 46 and 120 pp, followed by administration (IV) of an opioid agonist (FK33-824; 10 μg/kg) and an antagonist (naloxone; .5 mg/kg) at hours 5 and 7, respectively. A GRF-analog ([desamino-Tyr1, D-Ala2, Ala15] GRF (1–29)-NH2; 3.5 μg/kg) and arginine (.5 g/kg) were administered at hour 10 on days 47 and 121, respectively. Percentage binding of [125I]GRF (1:100 dilution of serum) 28 d after primary immunization was greater in GRFi (14.3 ± 4.9) than in HSAi (.7 ± .3) cows. Binding increased to 29.3 ± 6.5% after first booster in GRFi cows. Episodic release of ST was abolished by immunization against GRF; concentration and frequency of release of ST were lower (P125I]GRF, absence of pulsatile release of ST, low concentrations of ST and IGF-I and failure of ST to increase after IV opioid agonist or arginine

Integer polyhedra for program analysis

Polyhedra are widely used in model checking and abstract interpretation. Polyhedral analysis is effective when the relationships between variables are linear, but suffers from imprecision when it is necessary to take into account the integrality of the represented space. Imprecision also arises when non-linear constraints occur. Moreover, in terms of tractability, even a space defined by linear constraints can become unmanageable owing to the excessive number of inequalities. Thus it is useful to identify those inequalities whose omission has least impact on the represented space. This paper shows how these issues can be addressed in a novel way by growing the integer hull of the space and approximating the number of integral points within a bounded polyhedron

Secondary syringe exchange as a model for HIV prevention programs in the Russian Federation

Effective prevention of syringe-borne transmission of HIV and the hepatitis viruses can be undermined if contact between injection drug users and the staff of prevention programs is impeded by police harassment, limited program resources, and the absence of an open "drug scene." All these are commonplace in the Russian Federation. In response, "Project Renewal," the harm reduction program of the AIDS Prevention and Control Center of the Tatarstan Ministry of Health in Kazan, has created a hybrid syringe exchange program that as its primary focus recruited and trained volunteers to provide secondary syringe exchange. To compensate for operational barriers, the program staff identified private venues and trained responsible individuals to work through their own and related networks of injectors to provide clean syringes, other harm reduction supplies, and educational materials, while facilitating the collection and removal of used and potentially contaminated syringes. Program staff developed a detailed set of tracking instruments to monitor, on a daily and weekly basis, the locations and types of contacts and the dissemination of trainings and materials to ensure that the secondary distribution network reaches its target audience. Data show that these secondary exchange sites have proven more productive than the primary mobile and fixed-site syringe exchanges in Kazan. Beginning in 2001, Project Renewal has trained other harm reduction programs in the Russian Federation to use this model of reaching injectors, identifying and training volunteers, and monitoring results of secondary syringe exchange. Copyright © 2006 Taylor & Francis Group, LLC

Differences in risk behaviours and HIV status between primary amphetamines and opioid injectors in Estonia and Russia

Background and objective People who inject drugs (PWID) account for over half of new HIV infections in Eastern Europe and central Asia, where opioids continue to be the dominant illicit drugs injected. Stimulants including amphetamines (ATS) have been associated with HIV infection risk in several settings. We sought to examine whether primary ATS injection was associated with greater HIV risk, compared to opioid injection in two European locales with significant HIV epidemics. Methods PWID in Kohtla-Järve and St. Petersburg were recruited using respondent-driven sampling in 2012–2013. Survey data on demographic characteristics, service use, injecting and sexual risk behaviours and HIV-status (and HCV in Kohtla-Järve) were compared between primary opioid and ATS injectors using logistic regression models. Results Of 591 injectors recruited in Kohtla-Järve and 811 in St. Petersburg, 195 (33%) and 27 (4%) primarily injected ATS in each city. In both cities, ATS injectors were younger than opioid injectors, initiated injection later, injected less frequently and were more likely to have been paid for sex. In both cities, PWID had high levels of multiple sex partners. In Kohtla-Järve, ATS-injectors had lower odds of back-loading and greater odds of polydrug use than opioid-injectors. In St. Petersburg, where over half of PWID reported unsafe sharing practices, ATS-injectors were less likely to report these practices. ATS-injection was negatively associated with being HIV positive in Kohtla-Järve (aOR = 0.6; 95%CI: 0.5–0.8) and St. Petersburg (aOR = 0.3; 95%CI: 0.1–0.7). ATS-injection was negatively associated with HCV-reactivity in Kohtla-Järve (aOR = 0.5; 95%CI: 0.3–0.6). Conclusions In both locations, primary ATS injection was associated with lower injecting risk behaviours, lower odds of HIV and being paid for sex compared to opioid injection. Interventions targeting the characteristics and needs of ATS injectors are needed to increase contact with services and reduce sexual and injecting risk. Harm reduction services, including sexual risk reduction, need to be expanded for all PWID in St. Petersburg