Nondestructive estimation of the strength of dental ceramic materials.

OBJECTIVES: The aim of this study was to prove a nondestructive method to evaluate the strength of dental ceramic materials with respect to its potentiality and limitations. METHODS: The Young's moduli of 13 dental ceramic materials were determined by the resonance frequency method. Additionally, the flexural strengths of eight of these materials were evaluated by the four-point bending test. Strength values for the other five ceramic materials were taken from the literature. The Young's moduli were correlated with the strength values by Hook's law, respectively. RESULTS: Young's modulus for ceramics can be determined using a resonance frequency method. Fracture strain values of the ceramic materials tested (with the exception of Empress 2) have fracture strain values between 0.08 and 0.15%. A mean strain can be calculated (0.11%) and used with the value of Young's modulus to estimate fracture strength of ceramics. For the materials evaluated, predicted strength was within 39% of the measured values. SIGNIFICANCE: A non-destructive method to estimate strength of dental ceramic materials is possible, even though the accuracy of the predicted values is not very high. Nevertheless, the method permits new materials proposed for dental ceramic restorations to be screened for probable clinical success. Expensive and time-consuming testing would only need to be done on those materials which pass this initial criterion.     

Does repeated and heavy exercise impair blood rheology in carriers of sickle cell trait?

OBJECTIVE: To determine if the time courses of hemorheologic parameters are different between carriers of sickle cell trait (SCT) and subjects with normal hemoglobin in response to exercise. DESIGN: Observational and comparative study. SETTING: Testing was conducted in a laboratory of exercise physiology. PARTICIPANTS: Nine carriers of sickle cell trait (SCT group) and 7 subjects with normal hemoglobin (CONT group) performed an exercise protocol of the repetition of 3 successive maximal ramp exercise tests. INTERVENTIONS: Blood was sampled at rest (TR), at the end of each of the 3 tests (T1, T2, T3), and during the immediate (T2h) and late (T24h, T48h) recovery periods. MAIN OUTCOME MEASUREMENTS: Blood and plasma viscosity (etab and etap, respectively), hematocrit (Hct), and red blood cell (RBC) rigidity (Tk and k indexes) were determined. RESULTS: In both groups, etab significantly increased in response to exercise but the SCT group had significantly higher etab at T3 and T2h. etab then returned to baseline value at T2h in the CONT group and at T24h in the SCT group. Tk and k were not changed by exercise but significantly increased above baseline value in both groups at T24h and T48h. The increase in Tk and k during late recovery was higher in the SCT group than in the CONT group, indicating that SCT carriers had significantly higher RBC rigidity than the CONT group at that time. CONCLUSIONS: The hemorheologic changes induced by exercise in the SCT carriers could trigger microcirculatory disorders during the recovery.     

Double blind study of tiapride versus haloperidol and placebo in agitation and aggressiveness in elderly patients with cognitive impairment

Objective: The aim of the present study was to compare the efficacy and safety of tiapride versus haloperidol and placebo in the treatment of agitation and aggressiveness in elderly patients with mild or moderate mental impairment. Method: This international, multicentre, randomized, double blind, three parallel groups study compared efficacy and safety of a 21-day regimen of tiapride 100–300 mg/day versus haloperidol 2– 6 mg/day and placebo in 306 elderly patients with mild or moderate dementia according to DSM III R and behavioural troubles with the Multidimensional Observation Scale for the Elderly Subjects (MOSES) irritability/aggressiveness subscore ranging from 16 to 30. Results: The percentage of responders (defined as patients with at least a 25% MOSES irritability/aggressiveness subscore decrease between the inclusion and the end of the treatment) was significantly greater in the tiapride (63%, P=0.04) and haloperidol (69%, P=0.004) groups than in the placebo group (49%), with no significant difference between the active drugs. Similar results were observed for the mean MOSES irritability/aggressiveness subscores on D₇, D₂₁ and at D_end which were significantly smaller in the tiapride and haloperidol groups than in the placebo group. The decrease between D₀ and D_end was significantly greater in the tiapride (6.57, P=0.009) and haloperidol groups (6.75, P=0.005) than in the placebo group (4.71). The global improvement CGI was significantly better in the tiapride and haloperidol groups than in the placebo group (P=0.03 and P=0.02). No significant difference was observed between the two active drugs or among the three treatment groups for the Folstein’s Mini Mental Status scale (MMS) total score, and there was no notable change during treatment. The number of patients with adverse events, assessed on the Udvalg Kliniske Undersogelser scale (UKU), and the number of UKU symptoms were smaller in the tiapride group (62 patients, 61%, 212 events) than in the haloperidol group (77 patients, 76%, 305 events) and identical to that observed in the placebo group (69 patients, 67%, 234 events). Of interest, the number of patients with at least one extrapyramidal symptom was significantly lower (P=0.003) in the tiapride group (16 patients, 16%) than in the haloperidol group (34 patients, 34%) and similar to that of the placebo group (18 patients, 17%); the difference observed between the haloperidol and placebo groups was significant (P=0.008). Conclusion: Tiapride is not different from haloperidol in the treatment of agitation and aggressiveness in elderly patients and better tolerated, in particular with significantly fewer extrapyramidal symptoms. Received: 17 February 1999 / Final version: 1 October 1999     

Structure-activity studies of orexin a and orexin B at the human orexin 1 and orexin 2 receptors led to orexin 2 receptor selective and orexin 1 receptor preferring ligands

The neuropeptides orexin A and B (also known as hypocretins) play an important role in many physiological and behavioral activities. Orexins are ligands of two closely related G-protein-coupled receptors, that are the named orexin 1 and orexin 2 receptors. To clearly identify the minimal ligand sequences required for receptor activation, we synthesized and analyzed different centrally, C- and N-terminally truncated analogues of orexins A and B. Furthermore, we used the shortest active analogue to screen for important amino acid residues by l-alanine and l-proline replacement scans. For orexin A, only full-length peptides were able to show the same activity as orexin A, but interestingly, reduced orexin A and natural orexin A, which contains the two disulfide bonds, had the same activity. The shortest highly active orexin B analogue was orexin B 6-28. In addition, we identified orexin A 2-33 as the first analogue with orexin 1 receptor preference and orexin B 10-28, [A27]orexin B 6-28, and [P11]orexin B 6-28 as being highly potent orexin 2 receptor selective (>1000-fold) peptides.     

The determinants of successful collaboration: a review of theoretical and empirical studies

Successful collaboration in health care teams can be attributed to numerous elements, including processes at work in interpersonal relationships within the team (the interactional determinants), conditions within the organization (the organizational determinants), and the organization's environment (the systemic determinants). Through a review of the literature, this article presents a tabulated compilation of each of these determinant types as identified by empirical research and identifies the main characteristics of these determinants according to the conceptual work. We then present a "showcase" of recent Canadian policy initiatives--The Canadian Health Transition Fund (HTF)--to illustrate how the various categories of determinants can be mobilized. The literature review reveals that very little of the empirical work has dealt with determinants of interprofessional collaboration in health, particularly its organizational and systemic determinants. Furthermore, our overview of experience at the Canadian HTF suggests that a systemic approach should be adopted in evaluative research on the determinants of effective collaborative practice.     

The conceptual basis for interprofessional collaboration: core concepts and theoretical frameworks

Interprofessional collaboration is a key factor in initiatives designed to increase the effectiveness of health services currently offered to the public. It is important that the concept of collaboration be well understood, because although the increasingly complex health problems faced by health professionals are creating more interdependencies among them, we still have limited knowledge of the complexity of interprofessional relationships. The goal of this literature review was to identify conceptual frameworks that could improve our understanding of this important aspect of health organizations. To this end, we have identified and taken into consideration: (A) the various definitions proposed in the literature and the various concepts associated with collaboration, and (B) the various theoretical frameworks of collaboration. Our results demonstrate that: (1) the concept of collaboration is commonly defined through five underlying concepts: sharing, partnership, power, interdependency and process; (2) the most complete models of collaboration seem to be those based on a strong theoretical background, either in organizational theory or in organizational sociology and on empirical data; (3) there is a significant amount of diversity in the way the various authors conceptualized collaboration and in the factors influencing collaboration; (4) these frameworks do not establish clear links between the elements in the models and the outputs; and (5) the literature does not provide a serious attempt to determine how patients could be integrated into the health care team, despite the fact that patients are recognized as the ultimate justification for providing collaborative care.     

Regression of CD8+ pseudolymphoma after HIV antiviral triple therapy

To our knowledge, we report the first case of improvement of HIV-associated cutaneous CD8(+) pseudolymphoma with highly active antiretroviral therapy. This favors the hypothesis of a reactive cutaneous infiltration by HIV-specific cytotoxic T cells in this disease.     

Response of Polyelectrolyte Complexes to Subsequent Addition of Sodium Chloride: Time‐Dependent Static Light Scattering Studies

Summary: The applications of polyelectrolyte complexes range from large‐scale industrial products to special uses in biotechnology and medicine, yet one significant problem is their instability against changes in their environmental conditions, particularly the addition of salts. This concerns the colloidal stability as well as the stability of ionic bindings. Previous work on the effect of sodium chloride revealed that not only additional aggregation, but also complete dissolution may occur, depending on the nature of the polyelectrolyte components used. In these studies, the systems required up to one hour to become stable. Multi‐angle static light scattering was used to investigate the processes taking place after the addition of NaCl to polyelectrolyte complexes (PEC) formed in pure water. PECs were prepared with polymethacrylate as polyanion and poly(diallyldimethylammonium chloride) and a copolymer of this polycation with 53 mol‐% of acrylamide. These systems were chosen because of their interesting behavior: secondary aggregation, swelling, and dissolution at a critical salt concentration. The time‐dependence of these effects was studied in detail by static light scattering.

Aggregation and swelling demonstrated by changes in particle mass, radius, and structure density of the PEC.