Modeling and characterization of a voice coil motor

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 45-46).This thesis describes the development of a voice-coil motor that will allow viscous fluids to be delivered via a portable needle-free injection device. The chosen motor design features opposing magnets whose flux is channeled across the air gap by a center radial magnet, thus creating a higher flux density in the gap compared to a one-magnet design. An analytical model is developed which gives the force of the motor based on the material properties and geometry. An optimized geometry is modeled using finite element analysis, which predicts a motor constant of 11.02 N/[the square root of]W. The motor is fabricated and characterization reveals it to have a motor constant of 8.43 N/[the square root of]W. Althought the motor constant is less than expected, it is a large improvement over the current motor used in needle-free injection, which has a motor constant of 3.21 N/[the square root of]W.by Ashley Brown.S.B

Acid-Suppressing Agents and Risk for Clostridium difficile Infection in Pediatric Patients

Background. Acid-suppressing agents have been associated with increased Clostridium difficile infection (CDI) in adults. The objective of this study was to evaluate the association of acid-suppressing therapy with the development of CDI in the pediatric population. Methods. This was a retrospective case-control study. Children aged 1 through 17 years with a positive C difficile polymerase chain reaction (PCR) result obtained between June 1, 2008, and June 1, 2012, were randomly matched to a control population selected from patients with negative PCR. Results. A total of 458 children were included. No difference was observed in acid-suppressive therapy prior to PCR in CDI-positive versus -negative patients (n = 131 [57.2%] vs n = 121 [52.8%], P = .348). Among patients receiving acid-suppressing therapy prior to obtaining a PCR, no difference was observed in proton pump inhibitor use (45% vs 46.3%, P = .843), but histamine-2 receptor antagonist (H2RA) use was greater in the CDI-positive patients (32.8% vs 14.9%, P = .001). Logistic regression analysis demonstrated that H2RA therapy at home (odds ratio = 4.6; 95% confidence interval = 1.5-14.5) was an independent CDI predictor. Conclusion. In this pediatric population, CDI risk in children receiving home acid-suppressive therapy with H2RAs is nearly 4.5 times greater than that of children not receiving H2RA therapy. These results suggest the need for continued monitoring and study of H2RA therapy in children

A Wide-Field CCD Survey for Centaurs and Kuiper Belt Objects

A modified Baker-Nunn camera was used to conduct a wide-field survey of 1428 square degrees of sky near the ecliptic in search of bright Kuiper Belt objects and Centaurs. This area is an order of magnitude larger than any previously published CCD survey for Centaurs and Kuiper Belt Objects. No new objects brighter than red magnitude m=18.8 and moving at a rate 1"/hr to 20"/hr were discovered, although one previously discovered Centaur 1997 CU26 Chariklo was serendipitously detected. The parameters of the survey were characterized using both visual and automated techniques. From this survey the empirical projected surface density of Centaurs was found to be SigmaCentaur(m<18.8)=7.8(+16.0 -6.6)x10^-4 per square degree and we found a projected surface density 3sigma upper confidence limit for Kuiper Belt objects of SigmaKBO(m< 18.8)<4.1x10^-3 per square degree. We discuss the current state of the cumulative luminosity functions of both Centaurs and Kuiper Belt objects. Through a Monte Carlo simulation we show that the size distribution of Centaurs is consistent with a q=4 differential power law, similar to the size distribution of the parent Kuiper Belt Objects. The Centaur population is of order 10^7 (radius > 1 km) assuming a geometric albedo of 0.04. About 100 Centaurs are larger than 50 km in radius, of which only 4 are presently known. The current total mass of the Centaurs is 10^-4 Earth Masses. No dust clouds were detected resulting from Kuiper Belt object collisions, placing a 3sigma upper limit <600 collisionally produced clouds of m<18.8 per year.Comment: 13 pages, 5 figures, Accepted for Publication in A

Hidden links: Trait anxiety and the hostile attribution bias

The hostile attribution bias (HAB) is a tendency to interpret malevolent intentions when confronted by ambiguous actions of others. This project examines the relationship between HAB and trait anxiety and whether a metacognitive manipulation reduces HAB. In Study 1, our results showed that trait anxiety and HAB had a positive correlation using both methods of detecting hostility, even when negative affect was accounted for. In Study 2, overall analyses revealed that compared to a true control condition, the metacognition manipulation reduced the link between trait anxiety and HAB. This study needs to be replicated before we can definitively draw conclusions, but still guides us to a potential new method for reducing HAB in anxious individuals

Evaluating the Sensitivity and Specificity of Siemens Clinitest Lateral Flow Test and the Simple AMplification-Based Assay (SAMBA)-2 PCR Test for SARS-CoV-2 Infection.

Introduction Accurate point-of-care testing for SARS-CoV-2 could quickly identify which patients need to be isolated and improve flow for patients being admitted as an emergency to the hospital. We evaluated two diagnostic tests with shorter turnaround times, the Siemens Clinitest Lateral Flow (Siemens Healthineers AG, Erlangen, Germany) and the Simple AMplification-Based Assay (SAMBA)-2 PCR test against a standard laboratory PCR test. Methods We conducted a prospective diagnostic cohort study in a single English emergency department. Adult participants underwent three swabs: the Siemens Clinitest Lateral Flow Test, the SAMBA-2 and a standard laboratory PCR test. Results A total of 212 participants were recruited. The sensitivity and specificity of the Siemens Clinitest Lateral Flow Test against the laboratory PCR test was 55.6% (95% CI 30.8-78.5) and 100% (95% CI 98.1-100) respectively. The sensitivity and specificity of the SAMBA-2 PCR test against the laboratory PCR test was 60.0% (95% CI 32.3-83.7) and 100% (95% CI 97.9-100) respectively. Conclusion Neither the Siemens Clinitest Lateral Flow Test nor the SAMBA-2 PCR test demonstrated sufficient sensitivity to rule out active SARS-CoV-2 infection. Both tests demonstrated high specificity

Glaucoma surgery calculator: limited additive IOP effect of phacoemulsification on Ab Interno Trabeculectomy

Purpose: To compare reduction of intraocular pressure (IOP) after Trabectome in pseudophakic patients and Trabectome combined with phacoemulsification (Trabectome-phaco) in phakic patients. Methods: Cases were excluded if patients were followed for less than 12 months, diagnosed with neovascular glaucoma, or required additional glaucoma surgery within 12 months after Trabectome or Trabectome-phaco. Missing data such as type of glaucoma, gender, or age was imputed by generating 5 similar but non-identical datasets. Groups were matched using Coarsened Exact Matching based on age, gender, type of glaucoma, race, preoperative number of glaucoma medications and baseline IOP. Linear regression was used to examine IOP reduction after surgery. Results: A total of 612 cases were included in the study with 248 Trabectome cases and 364 Trabectome-phaco cases. Baseline IOP was found to be statistically significant. An average of 0.73±0.03 mmHg IOP reduction is associated with an increment of 1 mmHg in baseline IOP. Type of surgery was not statistically significant after adjusting for baseline IOP, age, baseline number of glaucoma medications and type of glaucoma. Conclusion: Patients with higher baseline IOP are expected to have a greater IOP reduction

Sleep and Military Members: Emerging Issues and Nonpharmacological Intervention

Background. Many individuals who work in the military experience sleep deficiency which presents a significant problem given the nature of their work. The cause of their sleep problems is likely multifactorial, stemming from the interplay between their personal health, habits and lifestyle juxtaposed with the stress of their military work such as emotional and physical trauma experienced in service. Objective. To present an overview of sleep deficiency in military members (MMs) and review of nonpharmacological treatment options. Discussion. Although there are a number of promising nonpharmacological treatment options available for people working in the military who experience problems sleeping, testing interventions within the context of the military are still in the early stages. Further research utilizing rigorous design and standardized, context appropriate outcome measures is needed to help treat this burgeoning problem

Are We Giving Them a Fair Chance? Racial Stereotypes and the Juvenile Justice System

Prior research indicates that there are racial disparities throughout the criminal justice system and that decision-makers may use stereotypes when determining guilt and deciding on sentences for juveniles. This study looked at sentence disparities between White and Latinx juveniles, as well as potential stereotypes that could be used in decision-making. There were no differences in sentence length and severity between the White and Latinx offender. Additionally, the likelihood of the offender receiving a lesser or greater sentence as an adult did not differ among conditions. Our results also showed that participants with prior juror experience used less stereotypical language in their sentence explanations. This research highlights the presence of sentence disparities in prior studies and generates avenues for future research