An investigation of combustion instability in aircraft-engine reheat systems

The principal objective of this study was to examine experimentally the effects of upstream temperature, velocity, gutter blockage, tailpipe length, and main and pilot fuel flows, on the form of combustion instability encountered in aircraft reheat systems which is sometimes referred to as 'buzz'. Tests were carried out at atmospheric pressure for upstream temperatures of between 200 and 500°C, and upstream velocities ranging from 140 to 200 ft/sec. Three values of stabilizer blockage were employed, namely 25, 30 and 35%. The tailpipe length was varied between 9 and 45 inches. Auto-correlation techniques were used in the frequency analysis of the buzz waveforms. It was found that a certain minimum tailpipe length is necessary in order to produce buzz which is then strengthened as the tailpipe length is increased. Buzz also becomes more pronounced with an increase in gas velocity but stabilizer blockage appears to have no discernible effect … [cont.]

Analysis of relative navigation architectures for formation flying spacecrafts

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006.Includes bibliographical references (p. 191-194).Many future space missions will involve fleets with a large number of satellites flying in formation. Indeed, such fleets provably offer more reliability, redundancy, scalability and repeatability. However, large fleets also represent a challenge, especially for the navigation algorithms, which must provide an accurate estimate of the state of the fleet, with minimum requirements. Furthermore, as the number of satellites in the fleet increases, the computations to be performed increase dramatically, as well as the synchronization and communication requirements, making the design of efficient algorithms a difficult challenge. Based on previous studies, Decentralized Algorithms were designed to spread the computational task. Hierarchic Algorithms were also studied in order to reduce the synchronization requirements. This thesis presents both analytical and numerical comparisons of these algorithms in terms of accuracy, computational complexity, synchronization, and communication. The Decentralized and Hierarchic Algorithms were shown to have good performance in terms of accuracy, while involving far fewer computations than the Centralized Algorithm. As a result, they can be used as scalable algorithms for large formation flying fleets.(cont.) The thesis investigated two additional problems often associated with navigation filters. The first study considers the problem of processing delayed measurements. Three strategies are analyzed, and compared in terms of the accuracy of the estimate they perform, and the memory and computations they require. One of these approach is shown to be efficient, being accurate without requiring heavy computations nor memory. The second study analyzes a particular instability of the Extended Kalman Filter, encountered when two sensors have very different accuracies. The instability is explained and a method to fix it is proposed. In the example analyzed the method proves to be efficient in addressing the instability.by Henry Jacques Lefebvre de Plinval-Salgues.S.M

Short-term prospective memory deficits in chronic back pain patients

Objective: Chronic pain, particularly low back pain, is widespread. Although a great deal is known about the impact that this has on quality of life and physical activity, relatively little has been established regarding the more cognitive effects of pain. This study aims to find out whether individuals with chronic pain experience memory deficits in prospective memory (PM), the process of remembering to do things at some future point in time. Examples of PM include remembering to keep an appointment, such as a visit to a clinic, or to perform a particular task, such as paying a bill on time. Methods: The PM of 50 participants with chronic pain was compared with 50 pain-free participants. Each participant completed the Prospective Memory Questionnaire, which assesses three aspects of prospective memory (short-term habitual, long-term episodic, and internally cued), and records the use of strategies to aid remembering. Results: In comparison to those not in pain, participants with chronic pain had significantly impaired short-term prospective memory, an effect which was evident even after co-varying use of analgesics and other drugs. Conclusions: These findings provide new insights into prospective memory dysfunction in people with chronic pain. Possible mechanisms for this dysfunction are discussed and suggestions for future research given

Clostridium difficile in Retail Ground Meat, Canada

Clostridium difficile was isolated from 12 (20%) of 60 retail ground meat samples purchased over a 10-month period in 2005 in Canada. Eleven isolates were toxigenic, and 8 (67%) were classified as toxinotype III. The human health implications of this finding are unclear, but with the virulence of toxinotype III strains further studies are required

Identification of a Prg4‐Expressing Articular Cartilage Progenitor Cell Population in Mice

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111178/1/art39030.pd

Deep learning of chest X‑rays can predict mechanical ventilation outcome in ICU‑admitted COVID‑19 patients

The COVID-19 pandemic repeatedly overwhelms healthcare systems capacity and forced the development and implementation of triage guidelines in ICU for scarce resources (e.g. mechanical ventilation). These guidelines were often based on known risk factors for COVID-19. It is proposed that image data, specifically bedside computed X-ray (CXR), provide additional predictive information on mortality following mechanical ventilation that can be incorporated in the guidelines. Deep transfer learning was used to extract convolutional features from a systematically collected, multi-institutional dataset of COVID-19 ICU patients. A model predicting outcome of mechanical ventilation (remission or mortality) was trained on the extracted features and compared to a model based on known, aggregated risk factors. The model reached a 0.702 area under the curve (95% CI 0.707-0.694) at predicting mechanical ventilation outcome from pre-intubation CXRs, higher than the risk factor model. Combining imaging data and risk factors increased model performance to 0.743 AUC (95% CI 0.746-0.732). Additionally, a post-hoc analysis showed an increase performance on high-quality than low-quality CXRs, suggesting that using only high-quality images would result in an even stronger model

Re-Treatment Tuberculosis Cases Categorised as “Other”: Are They Properly Managed?

BACKGROUND: Although the World Health Organization (WHO) provides information on the number of TB patients categorised as "other", there is limited information on treatment regimens or treatment outcomes for "other". Such information is important, as inappropriate treatment can lead to patients remaining infectious and becoming a potential source of drug resistance. Therefore, using a cohort of TB patients from a large registration centre in Lilongwe, Malawi, our study determined the proportion of all TB re-treatment patients who were registered as "other", and described their characteristics and treatment outcomes. METHODS: This retrospective observational study used routine program data to determine the proportion of all TB re-treatment patients who were registered as "other" and describe their characteristics and treatment outcomes between January 2006 and December 2008. RESULTS: 1,384 (12%) of 11,663 TB cases were registered as re-treatment cases. Of these, 898 (65%) were categorised as "other": 707 (79%) had sputum smear-negative pulmonary TB and 191 (21%) had extra pulmonary TB. Compared to the smear-positive relapse, re-treatment after default (RAD) and failure cases, smear-negative "other" cases were older than 34 years and less likely to have their HIV status ascertained. Among those with known HIV status, "other" TB cases were more likely to be HIV positive. Of TB patients categorised as "other", 462 (51%) were managed on the first-line regimen with a treatment success rate of 63%. CONCLUSION: A large proportion of re-treatment patients were categorised as "other". Many of these patients were HIV-infected and over half were treated with a first-line regimen, contrary to national guidelines. Treatment success was low. More attention to recording, diagnosis and management of these patients is warranted as incorrect treatment regimen and poor outcomes could lead to the development of drug resistant forms of TB

Antibiotics for acute bronchitis.

BACKGROUND: The benefits and risks of antibiotics for acute bronchitis remain unclear despite it being one of the most common illnesses seen in primary care. OBJECTIVES: To assess the effects of antibiotics in improving outcomes and assess adverse effects of antibiotic therapy for patients with a clinical diagnosis of acute bronchitis. SEARCH METHODS: We searched CENTRAL 2013, Issue 12, MEDLINE (1966 to January week 1, 2014), EMBASE (1974 to January 2014) and LILACS (1982 to January 2014). SELECTION CRITERIA: Randomised controlled trials (RCTs) comparing any antibiotic therapy with placebo or no treatment in acute bronchitis or acute productive cough, in patients without underlying pulmonary disease. DATA COLLECTION AND ANALYSIS: At least two review authors extracted data and assessed trial quality. MAIN RESULTS: Seventeen trials with 3936 participants were included in the primary analysis. The quality of trials was generally good. There was limited evidence to support the use of antibiotics in acute bronchitis. At follow-up, there was no difference in participants described as being clinically improved between antibiotic and placebo groups (11 studies with 3841 participants, risk ratio (RR) 1.07, 95% confidence interval (CI) 0.99 to 1.15; number needed to treat for an additional beneficial outcome (NNTB) 22. Participants given antibiotics were less likely to have a cough (four studies with 275 participants, RR 0.64, 95% CI 0.49 to 0.85; NNTB 6); have a night cough (four studies with 538 participants, RR 0.67, 95% CI 0.54 to 0.83; NNTB 7) and a shorter mean cough duration (seven studies with 2776 participants, mean difference (MD) -0.46 days, 95% CI -0.87 to -0.04). The differences in presence of a productive cough at follow-up and MD of productive cough did not reach statistical significance.Antibiotic-treated patients were more likely to be unimproved according to clinician\u27s global assessment (six studies with 891 participants, RR 0.61, 95% CI 0.48 to 0.79; NNTB 25); have an abnormal lung exam (five studies with 613 participants, RR 0.54, 95% CI 0.41 to 0.70; NNTB 6); have a reduction in days feeling ill (five studies with 809 participants, MD -0.64 days, 95% CI -1.16 to -0.13) and a reduction in days with limited activity (six studies with 767 participants MD -0.49 days, 95% CI -0.94 to -0.04). The differences in proportions with activity limitations at follow-up did not reach statistical significance. There was a significant trend towards an increase in adverse effects in the antibiotic group (12 studies with 3496 participants) (RR 1.20, 95% CI 1.05 to 1.36; NNT for an additional adverse effect 5). AUTHORS\u27 CONCLUSIONS: There is limited evidence to support the use of antibiotics in acute bronchitis. Antibiotics may have a modest beneficial effect in some patients such as frail, elderly people with multimorbidity who may not have been included in trials to date. However, the magnitude of this benefit needs to be considered in the broader context of potential side effects, medicalisation for a self-limiting condition, increased resistance to respiratory pathogens and cost of antibiotic treatment

A value-based comparison of the management of ambulatory respiratory diseases in walk-in clinics, primary care practices, and emergency departments : protocol for a multicenter prospective cohort study

Background: In Canada, 30%-60% of patients presenting to emergency departments are ambulatory. This category has been labeled as a source of emergency department overuse. Acting on the presumption that primary care practices and walk-in clinics offer equivalent care at a lower cost, governments have invested massively in improving access to these alternative settings in the hope that patients would present there instead when possible, thereby reducing the load on emergency departments. Data in support of this approach remain scarce and equivocal. Objective: The aim of this study is to compare the value of care received in emergency departments, walk-in clinics, and primary care practices by ambulatory patients with upper respiratory tract infection, sinusitis, otitis media, tonsillitis, pharyngitis, bronchitis, influenza-like illness, pneumonia, acute asthma, or acute exacerbation of chronic obstructive pulmonary disease. Methods: A multicenter prospective cohort study will be performed in Ontario and Québec. In phase 1, a time-driven activity-based costing method will be applied at each of the 15 study sites. This method uses time as a cost driver to allocate direct costs (eg, medication), consumable expenditures (eg, needles), overhead costs (eg, building maintenance), and physician charges to patient care. Thus, the cost of a care episode will be proportional to the time spent receiving the care. At the end of this phase, a list of care process costs will be generated and used to calculate the cost of each consultation during phase 2, in which a prospective cohort of patients will be monitored to compare the care received in each setting. Patients aged 18 years and older, ambulatory throughout the care episode, and discharged to home with one of the aforementioned targeted diagnoses will be considered. The estimated sample size is 1485 patients. The 3 types of care settings will be compared on the basis of primary outcomes in terms of the proportion of return visits to any site 3 and 7 days after the initial visit and the mean cost of care. The secondary outcomes measured will include scores on patient-reported outcome and experience measures and mean costs borne wholly by patients. We will use multilevel generalized linear models to compare the care settings and an overlap weights approach to adjust for confounding factors related to age, sex, gender, ethnicity, comorbidities, registration with a family physician, socioeconomic status, and severity of illness. Results: Phase 1 will begin in 2021 and phase 2, in 2023. The results will be available in 2025. Conclusions: The end point of our program will be for deciders, patients, and care providers to be able to determine the most appropriate care setting for the management of ambulatory emergency respiratory conditions, based on the quality and cost of care associated with each alternative