Design of a controllable pitch underwater thruster system

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1993Control systems for underwater vehicles have reached the level of sophistication where they are limited by the dynamic performance of the thrust actuators. Standard fixed-pitch propellers have been shown to have very poor dynamic characteristics, particularly at low thrust levels The dynamic response of a fixed-pitch propeller is dependent upon highly non-linear transients encountered while the shaft speed approaches its steady-state value. This thesis proposes the use of a controllable pitch propeller system to address this problem. A controllable pitch propeller varies the amount of thrust produced by varying the pitch angle of the blades at a constant shaft speed. The bandwidth of this type of thrust actuator would be dependent primarily on the speed at which the pitch angle of the blades are changed. A variable pitch propeller system suitable for retrofit into an ROV is designed and built. The system is designed for maximal pitch angle bandwidth with low actuator power consumption

Using Social Construction Theory as a Foundation for Macro-Level Interventions in Communities Impacted by HIV and Addictions

Many professionals working with people living with HIV and alcohol and other drug addictions rely heavily on micro and mezzo-level interventions. The authors argue that although these approaches are effective for helping people living with some social problems they are too narrow for working effectively with HIV-positive and alcohol and other drug-addicted individuals. The authors use social construction theory to analyze the social problems of HIV/AIDS and addictions and make recommendations for macro-level interventions that may help curtail the dual problems of HIV and addictions

Clinical trials of potential cognitive-enhancing drugs in schizophrenia: what have we learned so far?

In light of the number of studies conducted to examine the treatment of cognitive impairment associated with schizophrenia (CIAS), we critically reviewed recent CIAS trials. Trials were identified through searches of the website "www.clinicaltrials.gov" using the terms "schizophrenia AND cognition," "schizophrenia AND neurocognition," "schizophrenia AND neurocognitive tests," "schizophrenia AND MATRICS," "schizophrenia AND MCCB," "schizophrenia AND BACS," "schizophrenia AND COGSTATE," and "schizophrenia AND CANTAB" and "first-episode schizophrenia AND cognition." The cutoff date was 20 April 2011. Included trials were conducted in people with schizophrenia, the effects on cognition were either a primary or secondary outcome, and the effect of a pharmacologically active substance was examined. Drug challenge, pharmacokinetic, pharmacodynamic, or prodrome of psychosis studies were excluded. We identified 118 trials, with 62% using an add-on parallel group design. The large majority of completed trials were underpowered to detect moderate effect sizes, had ≤8 weeks duration, and were performed in samples of participants with chronic stable schizophrenia. The ongoing add-on trials are longer, have larger sample sizes (with a number of them being adequately powered to detect moderate effect sizes), and are more likely to use a widely accepted standardized cognitive battery (eg, the MATRICS Consensus Cognitive Battery) and MATRICS guidelines. Ongoing studies performed in subjects with recent onset schizophrenia may help elucidate which subjects are most likely to show an effect in cognition. New insights into the demands of CIAS trial design and methodology may help increase the probability of identifying treatments with beneficial effect on cognitive impairment in schizophrenia

A framework for a maintenance management system for Massachusetts.

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Dept. of Civil Engineering.Includes bibliographical references.M.S

Cognitive impairment in schizophrenia: aetiology, pathophysiology, and treatment

Cognitive deficits are a core feature of schizophrenia, account for much of the impaired functioning associated with the disorder and are not responsive to existing treatments. In this review, we first describe the clinical presentation and natural history of these deficits. We then consider aetiological factors, highlighting how a range of similar genetic and environmental factors are associated with both cognitive function and schizophrenia. We then review the pathophysiological mechanisms thought to underlie cognitive symptoms, including the role of dopamine, cholinergic signalling and the balance between GABAergic interneurons and glutamatergic pyramidal cells. Finally, we review the clinical management of cognitive impairments and candidate novel treatments

Deconstructing cognitive impairment in psychosis with a machine learning approach

Importance: Cognitive functioning is associated with various factors, such as age, sex, education, and childhood adversity, and is impaired in people with psychosis. In addition to specific effects of the disorder, cognitive impairments may reflect a greater exposure to general risk factors for poor cognition. Objective: To determine the extent that impairments in cognition in psychosis reflect risk factor exposures. Design, Setting, and Participants: This cross-sectional study examined the relationship between exposures and cognitive function using data from the Bipolar-Schizophrenia Network on Intermediate Phenotypes studies 1 and 2 across 6 sites. Participants included healthy controls; patients with schizophrenia, schizoaffective disorder, or bipolar I disorder with psychosis; and relatives of patients. Predictive modeling was performed using extreme gradient boosting regression to train a composite cognitive score prediction model with nested cross-validation. Shapley additive explanations values were used to examine the relationship between exposures and cognitive function. Exposure: Exposures were chosen based on associations with cognition previously identified: age, sex, race and ethnicity, childhood adversity, education, parental education, parental socioeconomic status, parental age at birth, substance use, antipsychotic dose, and diagnosis. Main Outcomes and Measures: Cognition was assessed using the Brief Assessment of Cognition in Schizophrenia. Results: A total of 3370 participants were included: 840 healthy controls, 709 patients with schizophrenia, 541 with schizoaffective disorder, 457 with bipolar I disorder with psychosis, and 823 relatives of patients. The mean (SD) age was 37.9 (13.3) years; 1887 were female (56%) and 1483 male (44%). The model predicted cognitive scores with high accuracy: out-of-sample Pearson correlation between predicted and observed cognitive composite score was r = 0.72 (SD = 0.03). Individuals with schizophrenia (z = −1.4), schizoaffective disorder (z = −1.2), and bipolar I disorder with psychosis (z = −0.5) all had significantly worse cognitive composite scores than controls. Factors other than diagnosis and medication accounted for much of this impairment (schizophrenia z = −0.73, schizoaffective disorder z = −0.64, bipolar I disorder with psychosis z = −0.13). Diagnosis accounted for a lesser proportion of this deficit (schizophrenia z = −0.29, schizoaffective disorder z = −0.15, bipolar I disorder with psychosis z = −0.13), and antipsychotic use accounted for a similar deficit across diagnostic groups (schizophrenia z = −0.37, schizoaffective disorder z = −0.33, bipolar I disorder with psychosis z = −0.26). Conclusions and Relevance: This study found that transdiagnostic factors accounted for a meaningful share of the variance in cognitive functioning in psychosis. A significant proportion of the cognitive impairment in psychosis may reflect factors relevant to cognitive functioning in the general population. When considering interventions, a diagnosis-agnostic, symptom-targeted approach may therefore be appropriate

Postpartum Depression Among Low-Income Mothers of Color: A Womanist Perspective

The ideals of “good mothering” are constructed by various social policies and institutions. Many mothers from traditionally oppressed groups may find them difficult to achieve. The intersections of multiple forms of oppression create harsh circumstances for mothers from minority groups that can contribute to postpartum depression (PPD). Left untreated, PPD can have long-lasting negative effects on the mothers’ and their children’s well-being. Despite the growing research on PPD that finds striking disparities in prevalence by race, ethnicity, and socio-economic class, virtually all of the research has focused on mothers from privileged backgrounds and none has used a well-established theory to explain PPD among mothers from minority groups. To address this gap in the literature, this article uses Womanism as a theory to examine PPD among low-income mothers of color as a way to help sociologists and social workers take action to address PPD through theory, research, and practice

The Devil is in the Details: Inland Northwest Stakeholders’ Views on Three Forest-Based Bioenergy Scenarios

Public and private initiatives are actively exploring a range of forest-based bioenergy development options in the Inland Northwest of the United States. These efforts are motivated in part by the potential to generate renewable energy while creating a market for forest residues that would facilitate hazardous fuels reduction and provide economic opportunities. Understanding stakeholders’ perspectives is critical to the feasibility and long-term viability of bioenergy projects. This study presents stakeholder perspectives on forest-based bioenergy development strategies for communities in the forested areas of Idaho, western Montana, eastern Washington, and eastern Oregon. We developed three scenarios based on bioenergy initiatives currently being explored in the region: a decentralized mobile biochar and drop-in fuel scenario, a centralized bioaviation fuel scenario, and a centralized wood pellet scenario. We then asked a range of stakeholders to identify and assess the tradeoffs they associated with each scenario during in-depth interviews. Participants were generally supportive of any viable scenario that supports forest restoration and economic development, but many favored small-scale, locally oriented bioenergy development similar to what has occurred in some rural communities related to local food systems

Pain Coping Skills Training for Patients Who Catastrophize About Pain Prior to Knee Arthroplasty: A Multisite Randomized Clinical Trial

BACKGROUND: Pain catastrophizing has been identified as a prognostic indicator of poor outcome following knee arthroplasty. Interventions to address pain catastrophizing, to our knowledge, have not been tested in patients undergoing knee arthroplasty. The purpose of this study was to determine whether pain coping skills training in persons with moderate to high pain catastrophizing undergoing knee arthroplasty improves outcomes 12 months postoperatively compared with usual care or arthritis education. METHODS: A multicenter, 3-arm, single-blinded, randomized comparative effectiveness trial was performed involving 5 university-based medical centers in the United States. There were 402 randomized participants. The primary outcome was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain Scale, measured at baseline, 2 months, 6 months, and 12 months following the surgical procedure. RESULTS: Participants were recruited from January 2013 to June 2016. In 402 participants, 66% were women and the mean age of the participants (and standard deviation) was 63.2 ± 8.0 years. Three hundred and forty-six participants (90% of those who underwent a surgical procedure) completed a 12-month follow-up. All 3 treatment groups had large improvements in 12-month WOMAC pain scores with no significant differences (p > 0.05) among the 3 treatment arms. No differences were found between WOMAC pain scores at 12 months for the pain coping skills and arthritis education groups (adjusted mean difference, 0.3 [95% confidence interval (CI), -0.9 to 1.5]) or between the pain coping and usual-care groups (adjusted mean difference, 0.4 [95% CI, -0.7 to 1.5]). Secondary outcomes also showed no significant differences (p > 0.05) among the 3 groups. CONCLUSIONS: Among adults with pain catastrophizing undergoing knee arthroplasty, cognitive behaviorally based pain coping skills training did not confer pain or functional benefit beyond the large improvements achieved with usual surgical and postoperative care. Future research should develop interventions for the approximately 20% of patients undergoing knee arthroplasty who experience persistent function-limiting pain. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence