Use of different concentrations of carbamide peroxide for bleaching teeth: an in vitro study

OBJECTIVE: This in vitro study compared the shade changes in extracted teeth during 2 weeks' whitening with 5%, 10%, or 16% carbamide peroxide. METHOD AND MATERIALS: After color calibration, the sole examiner selected 110 extracted unrestored, noncarious teeth, shade A3 or darker on a value-oriented guide. The teeth were randomly distributed into equal color groups. The control group (11 teeth) was treated with 0.9% saline, while the experimental groups (33 teeth each) were treated with 5%, 10%, or 16% carbamide peroxide. The solutions remained on the teeth for 8 hours. The teeth and tray were rinsed with tap water for 2 minutes, then rehydrated in 0.9% saline for 16 hours in the humidifier. The shade was assessed, and the process was repeated daily for 2 weeks. RESULTS: Repeated-measures analysis of variance indicated a significant difference in overall shade values between the control and all carbamide peroxide-treated groups at days 8 and 15. A Kaplan-Meier Survival Analysis indicated a quicker two-tab color change for the 10% and 16% groups than the 5% group. However, continuation of the 5% treatment to 3 weeks resulted in shades that approached the 2-week 10% and 16% values. CONCLUSION: Lower concentrations of carbamide peroxide take longer to whitening teeth but eventually achieve the same result as higher concentrations. Higher concentrations may cause increased sensitivity.     

Asymmetric Sequential Michael Addition–N–Heterocyclization Reactions Involving Chiral Imines

The reaction of chiral imines ent- 14, 27 , and 31 with α-chloroacrylonitrile 6 , maleic anhydride 9 , and citraconic anhydride 35 has been investigated. Addition of imine 27 to 6 furnished, after NaBH₃CN-reduction of the crude product, the bicyclic derivative 28 as a single isomer. When the same protocol was applied to imine ent- 14 , a mixture of adducts 29 and 30 was obtained. Addition of imine 31 to 6 gave the annulated pyrrole 32. Condensation of imine 27 with maleic anhydride 9 afforded compound 33 as a single isomer. Addition of imine ent- 14 to citraconic anhydride 35 led, after esterification of the crude product with CH₂N₂, to a mixture of adducts 36 and 37. The mechanism of these aza-annulations was discussed on the basis of the regio- and stereoselectivities observed.     

Graduate education in psychology.

Reviews some of the previous major conferences on graduate education in psychology since the 1st conference was held in 1949 in Boulder, Colorado. Planning for the 1987 conference in Salt Lake City, Utah, is described, including selection of issues, selection of participants, and structure of the conference. The themes of unity, diversity, quality, and humanity are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of mother-father perceptions of their child's self-management of diabetes

This study compared mothers' and fathers' perceptions of their children's self-management of diabetes. Participants included a subsample of 29 paired parents of children and youth with diabetes, ages 8-14, who attended a diabetes camp in the Midwest. Parents completed a self-report structured questionnaire that included content specific to self-management. Results showed high ratings for child responsibility for self-management, style of care delivery, and mother-father self-efficacy in managing specific tasks of diabetes self-management. Although overall ratings were similar, in the majority of measures mothers' ratings were higher than fathers' ratings. Areas of similarity and significant differences in perceptions are identified with implications for practice stated.     

A generalized Forney formula for algebraic-geometric codes

This correspondence contains a straightforward generalization of decoding of BCH codes to the decoding of algebraic-geometric codes, couched in terms of varieties, ideals, and Grobner bases. This consists of 1) a Berlekamp-Massey-type lattice-shifting row-reduction algorithm with majority voting similar to algorithms in the current literature, 2) a realization that it produces a minimal Grobner basis B for the error-locator ideal I(V) relative to a particular weighted total degree monomial ordering, 3) a factoring of that basis into several minimal PLEX bases, that facilitates finding the variety V of error positions, and 4) a direct generalization of Forney's formula to calculate error magnitudes using functions σp, which are by-products of this factoring     

Investigations into the cumene hydroperoxide-based cure chemistry of anaerobic adhesives

Anaerobic adhesives polymerise rapidly, by a free radical mechanisms, when confined between two closely fitting metal surfaces to form tough solvent and heat resistant material. Anaerobic adhesives are typically based on methacrylate monomers and are predominantly used for the sealing and retaining of metallic objects. Transition metal ions on the substrate surface play a key role in the cure chemistry, catalytically decomposing hydroperoxides, such as cumene hydroperoxide, present in the adhesive to generate free radicals capable of initiating polymerisation. This study investigates the ability of lower and higher oxidation states of copper and iron to decompose cumene hydroperoxide, and also investigates the influence of saccharin, maleic acid and adhesive accelerators on this process.     

Poor social performance of lonely people: Lacking a skill or adopting a role?

The authors hypothesize that the adoption of passive interpersonal roles predisposes lonely people to exhibit inadequate social performance. In order to test this hypothesis, lonely and nonlonely subjects were assigned to one of two roles: They either listened (Condition Li) to an interaction partner describe a personal problem or they themselves described a personal problem (Condition Pr) to their partner. The subjects' interpersonal role produced a substantial effect on their social behavior. Subjects who listened to their partner describe a problem generated more solutions to a set of hypothetical situations, attended to their partners more adequately, and conversed longer than did subjects who described a personal problem. In contrast, lonely subjects did not differ from nonlonely subjects in their social performance within each particular role. Lonely and nonlonely subjects did differ, however, in their subjective evaluations of themselves and of their performance. These results illustrate the need for research to address both the interpersonal and the intrapersonal bases of social performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Achieving cost savings through collaborative seismic testing

Seismic qualification of nuclear power plant equipment through testing has been perceived by utility personnel as a costly and complicated process. Certainly, some equipment types may only be qualified by test due to the complexity of the item and/or the inability to represent the item in a quantitative analysis. Other factors also influence the reluctance by some to resort to seismic testing. These include cost, dealing with test failures, lack of understanding of the testing process, and greater reliance on new analytical techniques. A group of utilities have allied themselves to address these issues and have formed the Seismic Qualification Reporting and Testing Standardization (SQURTS) group. SQURTS has implemented a program whereby testing is performed at a low cost, often lower than a comparable analytical solution. Testing is conducted at generic seismic levels using generic test procedures, which broadens the applicability of results. Test reports are published in a standard format which shortens the process of review and approval. Testing is no longer just a requirement, but a cost-effective option.     

Waveguide devices based on active metallic photonic crystals

We present a detailed analysis of waveguide devices patterned in two- and three-dimensional metallic photonic crystals. Tuning of guiding properties of electromagnetic waves is induced by a reflectivity modulation of waveguide walls by means of active electronic devices inserted in the 2D lattice. Such an active waveguide acts as a phase shifter in monomode operation as a consequence of the tunable capacitive coupling afforded by the 3D lattice. On this basis, various operating modes of multiport waveguide devices are investigated: (i) a switching operation in a T-shaped structure, (ii) highly directional lateral transfers in a multimode branch line coupler.