Experimental clean combustor program, phase 1

A program of screening three low emission combustors for conventional takeoff and landing, by testing and analyzing thirty-two configurations is presented. Configurations were tested that met the emission goals at idle operating conditions for carbon monoxide and for unburned hydrocarbons (emission index values of 20 and 4, respectively). Configurations were also tested that met a smoke number goal of 15 at sea-level take-off conditions. None of the configurations met the goal for oxides of nitrogen emissions at sea-level take-off conditions. The best configurations demonstrated oxide of nitrogen emission levels that were approximately 61 percent lower than those produced by the JT9D-7 engine, but these levels were still approximately 24 percent above the goal of an emission index level of 10. Additional combustor performance characteristics, including lean blowout, exit temperature pattern factor and radial profile, pressure loss, altitude stability, and altitude relight characteristics were documented. The results indicate the need for significant improvement in the altitude stability and relight characteristics. In addition to the basic program for current aircraft engine combustors, seventeen combustor configurations were evaluated for advanced supersonic technology applications. The configurations were tested at cruise conditions, and a conceptual design was evolved

Experimental clean combustor program, phase 2

The alternate fuels investigation objective was to experimentally determine the impacts, if any, on exhaust emissions, performance, and durability characteristics of the hybrid and vorbix low pollution combustor concepts when operated on test fuels which simulate composition and property changes which might result from future broadened aviation turbine fuel specifications or use of synthetically derived crude feedstocks. Results of the program indicate a significant increase in CO and small NOX increase in emissions at idle for both combustor concepts, and an increase in THC for the vorbix concept. Minimal impact was observed on gaseous emissions at high power. The vorbix concept exhibited significant increase in exhaust smoke with increasing fuel aromatic content. Altitude stability was not affected for the vorbix combustor, but was substantially reduced for the hybrid concept. Severe carbon deposition was observed in both combustors following limited endurance testing with No. 2 home heat fuel. Liner temperature levels were insensitive to variations in aromatic content over the range of conditions investigated

La física de la fuerza impresa y sus implicaciones para la enseñanza de la mecánica

When exarnining learners' understanding of questions involving the movement of projectiles one notices, in general, that their common sense is far away from making any reference to aristotelian antiperistasis. The causes for a 'violent' or forced movement are seen as located in the body itself, following from the projectile-projector interaction. This is essentially the concept of impressed force, introduced by astronomer Hipparcus (second century BC) and adopted by Philoponus (sixth century), among others. The notion of impressed force has an interesting historical development.It may have been a reference for the establishment of the impetus theory by Buridan in the fourteenth century, and was part of the debate that took place from the twelfth century onwards about the possible movement of a projectile in the void. This work explores historically this concept, making use of it in problem situations that are both well familiar to the students and relevant for the development of mechanics. From the point of view of teaching that takes into consideration the learners' ideas, this theme has great didactic potential for the development of strategies to help the reformulation of their conceptions, turning them more consistent with what is accepted as scientific today

Signature region within the 16S rDNA sequences of Aeromonas popoffii

To identify a group of eight Aeromonas strains of our collection showing ribotyping patterns similar to those described for the species Aeromonas popoffii, 16S rRNA gene sequence analysis was performed. Results were in agreement with the DNA binding values, and allowed the identification of a ‘signature region' differentiating the A. popoffii strains from all other members of the genus Aeromona

Anti-Hypertensive Medications and Cardiovascular Events in Older Adults with Multiple Chronic Conditions

Importance Randomized trials of anti-hypertensive treatment demonstrating reduced risk of cardiovascular events in older adults included participants with less comorbidity than clinical populations. Whether these results generalize to all older adults, most of whom have multiple chronic conditions, is uncertain. Objective: To determine the association between anti-hypertensive medications and CV events and mortality in a nationally representative population of older adults. Design: Competing risk analysis with propensity score adjustment and matching in the Medicare Current Beneficiary Survey cohort over three-year follow-up through 2010. Participants and Setting 4,961 community-living participants with hypertension. Exposure Anti-hypertensive medication intensity, based on standardized daily dose for each anti-hypertensive medication class participants used. Main Outcomes and Measures Cardiovascular events (myocardial infarction, unstable angina, cardiac revascularization, stroke, and hospitalizations for heart failure) and mortality. Results: Of 4,961 participants, 14.1% received no anti-hypertensives; 54.6% received moderate, and 31.3% received high, anti-hypertensive intensity. During follow-up, 1,247 participants (25.1%) experienced cardiovascular events; 837 participants (16.9%) died. Of deaths, 430 (51.4%) occurred in participants who experienced cardiovascular events during follow-up. In the propensity score adjusted cohort, after adjusting for propensity score and other covariates, neither moderate (adjusted hazard ratio, 1.08 [95% CI, 0.89–1.32]) nor high (1.16 [0.94–1.43]) anti-hypertensive intensity was associated with experiencing cardiovascular events. The hazard ratio for death among all participants was 0.79 [0.65–0.97] in the moderate, and 0.72 [0.58–0.91] in the high intensity groups compared with those receiving no anti-hypertensives. Among participants who experienced cardiovascular events, the hazard ratio for death was 0.65 [0.48–0.87] and 0.58 [0.42–0.80] in the moderate and high intensity groups, respectively. Results were similar in the propensity score-matched subcohort. Conclusions and Relevance In this nationally representative cohort of older adults, anti-hypertensive treatment was associated with reduced mortality but not cardiovascular events. Whether RCT results generalize to older adults with multiple chronic conditions remains uncertain

Combining estimates of interest in prognostic modelling studies after multiple imputation: current practice and guidelines

Background: Multiple imputation (MI) provides an effective approach to handle missing covariate data within prognostic modelling studies, as it can properly account for the missing data uncertainty. The multiply imputed datasets are each analysed using standard prognostic modelling techniques to obtain the estimates of interest. The estimates from each imputed dataset are then combined into one overall estimate and variance, incorporating both the within and between imputation variability. Rubin's rules for combining these multiply imputed estimates are based on asymptotic theory. The resulting combined estimates may be more accurate if the posterior distribution of the population parameter of interest is better approximated by the normal distribution. However, the normality assumption may not be appropriate for all the parameters of interest when analysing prognostic modelling studies, such as predicted survival probabilities and model performance measures. Methods: Guidelines for combining the estimates of interest when analysing prognostic modelling studies are provided. A literature review is performed to identify current practice for combining such estimates in prognostic modelling studies. Results: Methods for combining all reported estimates after MI were not well reported in the current literature. Rubin's rules without applying any transformations were the standard approach used, when any method was stated. Conclusion: The proposed simple guidelines for combining estimates after MI may lead to a wider and more appropriate use of MI in future prognostic modelling studies

Teamwork in nursing: restricted to nursing professionals or an interprofessional collaboration?

Abstract OBJECTIVE To understand the nursing professionals' conceptions of teamwork and their elements. METHOD A qualitative study conducted in an oncological hospital using a semi-structured interview with 21 nursing professionals. RESULTS Two conceptions emerged from the accounts: teamwork restricted to nursing professionals and teamwork with interprofessional collaboration with particular importance for interactive dimensions: communication, trust and professional bonds, mutual respect and recognition of the other's work, collaboration, and conflict, with this last subcategory considered as an obstacle to teamwork. CONCLUSION Nursing conceives teamwork as an interprofessional practice, which is a result of the quality of interaction among professionals from different areas and involves the recognition and handling of conflicts

Contributions of team climate in the study of interprofessional collaboration: a conceptual analysis

The concept of team climate is widely used to understand and evaluate working environments. It shares some important features with Interprofessional Collaboration (IPC). The four-factor theory of climate for work group innovation, which underpins team climate, could provide a better basis for understanding both teamwork and IPC. This article examines in detail the common ground between team climate and IPC, and assesses the relevance of team climate as a theoretical approach to understanding IPC. There are important potential areas of overlap between team climate and IPC that we have grouped under four headings: (1) interaction and communication between team members; (2) common objectives around which collective work is organised; (3) responsibility for performing work to a high standard; and (4) promoting innovation in working practices. These overlapping areas suggest common characteristics that could provide elements of a framework for considering the contribution of team climate to collaborative working, both from a conceptual perspective and, potentially, in operational terms as, for example, a diagnostic tool