Feasibility study of rapid prototyping using the uniform droplet spray process

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998.Includes bibliographical references (leaf 29).This work studied the feasibility of rapid prototyping using the Uniform Droplet Spray (UDS) process. Straight and stable liquid metal jets are crucial requirements in the application of UDS to rapid prototyping. Methods to maintain the jet straight and stable were developed. Hardware improvements include an auxiliary orifice mounting fixture and a new crucible bottom with a tightly-fitting orifice-pocket. A droplet trajectory controller, including deflection plates and a pulse provider to a charging plate, was developed to precisely deliver droplets for deposition. The degree of separation between deflected and undetected streams of droplets was modeled and the prediction was compared with experimental results. This comparison revealed that the degree of actual deflection was approximately twice as high as the predicted value. Using the trajectory controller, deposition was conducted using pure tin (Sn) with droplet impact conditions of velocity and liquid fraction of 45 m/s and 97%, respectively. The deposition frequency was varied in the experiment to study its effects on deposit shapes. A low frequency deposition at 57Hz produced a vertical pillar, whereas a high frequency deposition at 574Hz resulted in a large drop.by Jennifer Hyunjong Shin.S.B

Dynamics and statics of actin assemblies

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 95-101).The conversion of chemical energy into mechanical forces that powers cell movements is a ubiquitous theme across biology. The acrosome reaction of Limulus sperm is a simple example of such a dynamical transformation where a 60 [mu]m-long crystalline bundle of actin filaments, tightly cross-linked by actin bundling protein scruin, straightens from a coiled conformation and extends from the cell in five seconds. This spring-like mechanism represents a third type of actin-based motility that is distinctly different from the better known polymerization or myosin-driven processes. To identify the basis and mechanism for this movement, we examine the possible sources of chemical and mechanical energy and show that the stored elastic energy alone is sufficient to drive the reaction. We also provide an estimate of the maximum force generated during the uncoiling by stalling the bundle using an agarose gel. Finally, we provide a simple mathematical model that rationalizes the dynamics of uncoiling. Motivated by the very stiff cross-linking in the bundle induced by scruin, we next turn to a model system of scruin mediated cross-linked actin networks where the elastic response is dominated by the properties of actin. While the biological significance of the actin cross-linking proteins is well documented, little is known about how bundling and cross-linking quantitatively affects the microstructure and mechanical properties of actin networks. We quantify the effect of scruin on actin networks using imaging techniques, co-sedimentation assays. multi-particle tracking (MPT), and bulk rheology and demonstrate how a simple entropic elasticity model for a semi-flexible polymer network explains the linear elastic regime of the actin-scruin network.by Jennifer Hyunjong Shin.Ph.D

Quantitatively Controlled Fabrication of Uniaxially Aligned Nanofibrous Scaffold for Cell Adhesion

In light of tissue engineering, development of a functional and controllable scaffold which can promote cell proliferation and differentiation is crucial. In this study, we introduce a controllable collection method of the electrospinning process for regularly-distributed and uniaxially oriented nanofiber scaffold and evaluate the effects of aligned nanofiber density on adhesion of dermal fibroblasts. The suggested spinning collector features an inclined void gap, which allows easy transfer of uniformly aligned fibers onto other surfaces. By undergoing multiple transfers, the density of the nanofibers can be quantitatively controlled. The resultant polycaprolactone (PCL) nanofibers had well-defined nanotopography in a 400–600 nm range. Human dermal fibroblasts were seeded on aligned nanofiber scaffolds of different densities achieved by varying the number of transfers. Cell morphology and actin stress fiber formation was accessed after seven days. The experimental results indicate that the contact guidance of the cells along the fiber alignment can be more activated with more than one guidance feature on a cell; that is, the high density of fiber is attained in so much that fiber spacing gets below the cell size

Factors associated with satisfaction with pediatric emergency department services in Korea: analysis of Korea Health Panel Data 2010 to 2012

Objective We aimed to investigate the factors related to satisfaction with the pediatric emergency department service in Korea. Methods This study examined data from the Korea Health Panel Data from 2010 to 2012. Pediatric patients who visited the emergency department at least once between 2010 and 2012 in Korea were included. Data were collected on patient satisfaction with the emergency department service, and factors related to the patient characteristics, emergency department service process, and medical institution. We compared the dissatisfied and satisfied groups, and calculated the odds ratios for satisfaction according to each variable. Results A total of 1,505 emergency department visits from 947 pediatric patients during the 3-year period were analyzed. We estimated that about 79.5% of patients in the population were satisfied. The odds of expressing satisfaction were higher among males than in females, and among patients who were hospitalized after emergency department treatment compared to those who were transferred to another hospital. Conversely, the odds of expressing satisfaction were lower among patients who had a chronic disease, a financial source other than National Health Insurance, experienced hospitalization within 1 year. Conclusion Our study results might be helpful for establishing a satisfactory pediatric emergency medical service system. In the future, further prospective studies evaluating the causal relationships between the relevant factors and patient satisfaction are warranted

Use of smart glasses for ultrasound-guided peripheral venous access: a randomized controlled pilot study

Objective Smart glasses can provide sonographers with real-time ultrasound images. In the present study, we aimed to evaluate the utility of smart-glasses for ultrasound-guided peripheral venous access. Methods In this randomized, crossover-design, simulation study, 12 participants were recruited from the emergency department residents at a university hospital. Each participant attempted ultrasound-guided peripheral venous access on a pediatric phantom at intervals of 5 days with (glasses group) or without (non-glasses group) the use of smart glasses. In the glasses group, participants confirmed the ultrasound image through the lens of the smart glasses. In the non-glasses group, participants confirmed the ultrasound image through the display viewer located next to the phantom. Procedure time was regarded as the primary outcome, while secondary outcomes included the number of head movements for the participant, number of skin punctures, number of needle redirections, and subjective difficulty. Results No significant differences in procedural time were observed between the groups (non-glasses group: median time, 15.5 seconds; interquartile range [IQR], 10.3 to 27.3 seconds; glasses group: median time, 19.0 seconds; IQR, 14.3 to 39.3 seconds; P=0.58). The number of head movements was lower in the glasses group than in the non-glasses group (glasses group: median, 0; IQR, 0 to 0; non-glasses group: median, 4; IQR, 3 to 5; P<0.01). No significant differences in the number of skin punctures or needle restrictions were observed between the groups. Conclusion Our results indicate that smart-glasses may aid in ensuring ultrasound-guided peripheral venous access by reducing head movements

Effect of Geometric Curvature on Collective Cell Migration in Tortuous Microchannel Devices

Collective cell migration is an essential phenomenon in many naturally occurring pathophysiological processes, as well as in tissue engineering applications. Cells in tissues and organs are known to sense chemical and mechanical signals from the microenvironment and collectively respond to these signals. For the last few decades, the effects of chemical signals such as growth factors and therapeutic agents on collective cell behaviors in the context of tissue engineering have been extensively studied, whereas those of the mechanical cues have only recently been investigated. The mechanical signals can be presented to the constituent cells in different forms, including topography, substrate stiffness, and geometrical constraint. With the recent advancement in microfabrication technology, researchers have gained the ability to manipulate the geometrical constraints by creating 3D structures to mimic the tissue microenvironment. In this study, we simulate the pore curvature as presented to the cells within 3D-engineered tissue-scaffolds by developing a device that features tortuous microchannels with geometric variations. We show that both cells at the front and rear respond to the varying radii of curvature and channel amplitude by altering the collective migratory behavior, including cell velocity, morphology, and turning angle. These findings provide insights into adaptive migration modes of collective cells to better understand the underlying mechanism of cell migration for optimization of the engineered tissue-scaffold design

Status of Emergency Signal Functions in Myanmar Hospitals: A Cross-Sectional Survey

Introduction: Low- and middle-income countries (LMICs) have a large percentage of globalmortality and morbidity rates from non-communicable diseases, including trauma. Theestablishment and development of emergency care systems is crucial for addressing thisproblem. Defining gaps in the resources and capacity to provide emergency healthcare in LMICsis essential for proper design and operation of ECS (emergency care services) reinforcementprograms. Myanmar has particular challenges with road access for providing timely emergencymedical care, and a shortage of trained health workers. To examine the ECS capacity in Myanmar,we used the Emergency Care Assessment Tool (ECAT), which features newly developed toolsfor assessing sentinel conditions and signal functions (key interventions to address morbidity andmortality) in emergency care facilities.Methods: ECAT is composed of six emergent sentinel conditions and corresponding signalfunctions. We surveyed a total of nine hospitals in five states in Myanmar. A constructed surveysheet was delivered by e-mail, and follow-up interviews were conducted via messenger to clarifyambiguous answers.Results: We categorized the nine participating institutions according to predefined criteria:four basic-level hospitals; four intermediate-level; and one advanced-level hospital. All basichospitals were weak in trauma care, and two of 12 signal functions were unavailable. Half of theintermediate hospitals showed weakness in trauma care, as well as critical care such as shockmanagement. Only half had a separate triage area for patients. In contrast, all signal functions andresources listed in ECAT were available in the advanced-level hospital.Conclusion: Basic-level facilities in Myanmar were shown to be suboptimal in traumamanagement, with critical care also inadequate in intermediate facilities. To reinforce signalfunctions in Myanmar health facilities, stakeholders should consider expanding critical functionsin selected lower-level health facilities. A larger scale survey would provide more comprehensivedata to improve emergency care in Myanmar

Status of Emergency Signal Functions in Myanmar Hospitals: A Cross-Sectional Survey

Introduction: Low- and middle-income countries (LMICs) have a large percentage of globalmortality and morbidity rates from non-communicable diseases, including trauma. Theestablishment and development of emergency care systems is crucial for addressing thisproblem. Defining gaps in the resources and capacity to provide emergency healthcare in LMICsis essential for proper design and operation of ECS (emergency care services) reinforcementprograms. Myanmar has particular challenges with road access for providing timely emergencymedical care, and a shortage of trained health workers. To examine the ECS capacity in Myanmar,we used the Emergency Care Assessment Tool (ECAT), which features newly developed toolsfor assessing sentinel conditions and signal functions (key interventions to address morbidity andmortality) in emergency care facilities.Methods: ECAT is composed of six emergent sentinel conditions and corresponding signalfunctions. We surveyed a total of nine hospitals in five states in Myanmar. A constructed surveysheet was delivered by e-mail, and follow-up interviews were conducted via messenger to clarifyambiguous answers.Results: We categorized the nine participating institutions according to predefined criteria:four basic-level hospitals; four intermediate-level; and one advanced-level hospital. All basichospitals were weak in trauma care, and two of 12 signal functions were unavailable. Half of theintermediate hospitals showed weakness in trauma care, as well as critical care such as shockmanagement. Only half had a separate triage area for patients. In contrast, all signal functions andresources listed in ECAT were available in the advanced-level hospital.Conclusion: Basic-level facilities in Myanmar were shown to be suboptimal in traumamanagement, with critical care also inadequate in intermediate facilities. To reinforce signalfunctions in Myanmar health facilities, stakeholders should consider expanding critical functionsin selected lower-level health facilities. A larger scale survey would provide more comprehensivedata to improve emergency care in Myanmar

The characteristics of pediatric emergency department visits in Korea: An observational study analyzing Korea Health Panel data.

OBJECTIVE:We investigated the characteristics of pediatric emergency department (ED) patients in Korea and determined factors associated with hospital admission after ED treatment. METHODS:Korea Health Panel data from 2008 through 2013 were analyzed retrospectively; we included patients under 18 years old who visited the ED at least once. We collected patient and household epidemiologic data such as sex, age group, region of residence, disability, chronic disease, household income quintile, national health insurance type, use of private insurance, and annual frequency of ED visits. We also examined data related to each ED visit, such as reason for visit, medical service provided, and hospital size/ownership. We then investigated which factors were correlated with case disposition (discharge home or hospital admission) after ED treatment. RESULTS:In total, 3,160 pediatric ED visits occurred during the six-year period. Males (57.5%) and children aged 0-5 years (47.7%) made more visits than females and older children, respectively. The proportion of ED visits for disease (67.7%) was much higher than for injury or poisoning (32.2%), and 452 cases (14.3%) required hospital admission. For hospital admission, the odds ratio (OR) of females was 0.73 compared to males, and the OR of children aged 6-11 was 0.68 compared to children aged 0-5. The OR of capital residents was 0.69 compared to province residents, and the OR of the highest income quintile was 0.51 compared to the lowest quintile. The OR of children with private insurance coverage was 0.49 compared to those lacking private insurance, and the OR of ED visits due to disease was 1.82 compared to visits due to injury/poisoning. CONCLUSION:This analysis of clinical and demographic characteristics of pediatric ED visits and hospital admissions can serve as the foundation of future prospective studies required for establishing appropriate policies for the Korean pediatric emergency medical system

Case characteristics during study period.

<p>Case characteristics during study period.</p