Sonoelectrochemical synthesis of submicron metal powders

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 46-48).Pulsed sonoelectrochemical synthesis is a widely used technique for producing nanoparticles. In this technique, alternating pulses of electric current and power ultrasound are applied to an electrochemical cell to create and suspend particles in the electrolyte. The pulsed technique largely separates the particle morphology defining physical action of electrochemistry and ultrasound. Despite the large body of work characterizing the pulsed method, surprisingly little is written about the behavior of particles in the continuous case, where electric current and ultrasound are simultaneously present. In this thesis, continuous ultrasound assisted electrochemical synthesis of nanoparticles is established. Potentially useful mechanisms for particle size and shape control in continuous reactors are discussed. A continuous sonoelectrochemical reactor was designed and demonstrated to produce submicron copper powders. Improvements to the batch reactor design are proposed to extend the technique to a flow reactor useful for commercial production of submicron metal powders.by Joseph Reneker.S.M

Investigation of transportation innovations for food delivery and truck platoons

Studies find that low-income areas are underserved by food retailers and have less access to healthy food, contributing to health disparities. A section of this thesis examines micromobility, drones, and ridesharing that may be suited to deliver food. Using estimated capacities and delivery speeds of several transportation modes, quantitative analysis showed that micromobility is a feasible means of delivery for short-distance, small-quantity orders. Vehicles were the only suitable option once quantity or distance increases, with trucks being the only option for large deliveries of food. Regarding trucks, autonomous truck platooning has potential benefits such as energy savings, increased capacity, and improved safety. A section of this thesis discusses the novel issue of driver behavior interacting with truck platoons in work zones. This research investigates the effects of education, platoon signage, and the number of platooned trucks using a federated simulator study. The study found that education and the use of signage showed increased driver efficiency near platoons. There was a 13 percent increase in speed and 30 percent decrease in distance following a 2-truck platoon after education. Driver speed also increased by at least 14 percent and following distance increased by at least 24 percent, with signage added. Post-simulator survey results showed drivers strongly agree that education helps to clarify how to react to platoons. 90 percent of drivers admitted it is safer to not overtake the platoon, yet only 62 percent indicated they would follow it. Using the results of this research, transportation agencies could formulate policies better accommodate truck platoons as the technology grows.Includes bibliographical references

The Comparative Mental Health Responses Between Post-Musculoskeletal Injury and Post-Concussive Injury Among Collegiate Athletes: A Systematic Review

# Background The average annual national estimate of injuries sustained by collegiate athletes is 210,674, which encompasses both those of a musculoskeletal and a concussive nature. Although athletic injuries are sustained through physical means and produce physical symptoms, sports-related injuries may be a stressor among athletes that is related to mental health. # Purpose The purpose of this systematic review is to summarize existing literature describing mental health responses in collegiate athletes with a concussion compared to those with a musculoskeletal injury. # Study Design Systematic Review # Methods Systematic searches of PubMed, CINAHL, Scopus, ProQuest, and SportDiscus were completed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were utilized. Methodological quality was assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Tool. Data extracted from the included articles included the study design, number of participants, type of injury, sex, age, sport participation, outcome measures, and time to return to play. # Results A total of six articles were included. Peak depressive symptoms in athletes who sustain a concussion or musculoskeletal injury occur within one-week post-injury. No significant differences between the concussive and musculoskeletal groups anxiety scores were found at baseline or at each follow-up session. Athletes from both groups were found to be returning to their respective sports with anxiety scores representative of clinical anxiety. # Conclusion Similar trends in depressive and anxiety symptoms at various time points post-injury were observed in athletes with both musculoskeletal and concussive injuries. This study identified that athletes were returning to play before their psychological symptoms had returned to their baseline. # Level of Evidence 2

ACMES: fast multiple-genome searches for short repeat sequences with concurrent cross-species information retrieval

We have developed a web server for the life sciences community to use to search for short repeats of DNA sequence of length between 3 and 10 000 bases within multiple species. This search employs a unique and fast hash function approach. Our system also applies information retrieval algorithms to discover knowledge of cross-species conservation of repeat sequences. Furthermore, we have incorporated a part of the Gene Ontology database into our information retrieval algorithms to broaden the coverage of the search. Our web server and tutorial can be found at http://acmes.rnet.missouri.edu

Polyvinylidene fluoride molecules in nanofibers, imaged at atomic scale by aberration corrected electron microscopy.

Atomic scale features of polyvinylidene fluoride molecules (PVDF) were observed with aberration corrected transmission electron microscopy. Thin, self-supporting PVDF nanofibers were used to create images that show conformations and relative locations of atoms in segments of polymer molecules, particularly segments near the surface of the nanofiber. Rows of CF2 atomic groups, at 0.25 nm intervals, which marked the paths of segments of the PVDF molecules, were seen. The fact that an electron microscope image of a segment of a PVDF molecule depended upon the particular azimuthal direction, along which the segment was viewed, enabled observation of twist around the molecular axis. The 0.2 nm side-by-side distance between the two fluorine atoms attached to the same carbon atom was clearly resolved. Morphological and chemical changes produced by energetic electrons, ranging from no change to fiber scission, over many orders of magnitude of electrons per unit area, promise quantitative new insights into radiation chemistry. Relative movements of segments of molecules were observed. Promising synergism between high resolution electron microscopy and molecular dynamic modeling was demonstrated. This paper is at the threshold of growing usefulness of electron microscopy to the science and engineering of polymer and other molecules

Polyvinylidene fluoride molecules in nanofibers, imaged at atomic scale by aberration corrected electron microscopy.

Atomic scale features of polyvinylidene fluoride molecules (PVDF) were observed with aberration corrected transmission electron microscopy. Thin, self-supporting PVDF nanofibers were used to create images that show conformations and relative locations of atoms in segments of polymer molecules, particularly segments near the surface of the nanofiber. Rows of CF2 atomic groups, at 0.25 nm intervals, which marked the paths of segments of the PVDF molecules, were seen. The fact that an electron microscope image of a segment of a PVDF molecule depended upon the particular azimuthal direction, along which the segment was viewed, enabled observation of twist around the molecular axis. The 0.2 nm side-by-side distance between the two fluorine atoms attached to the same carbon atom was clearly resolved. Morphological and chemical changes produced by energetic electrons, ranging from no change to fiber scission, over many orders of magnitude of electrons per unit area, promise quantitative new insights into radiation chemistry. Relative movements of segments of molecules were observed. Promising synergism between high resolution electron microscopy and molecular dynamic modeling was demonstrated. This paper is at the threshold of growing usefulness of electron microscopy to the science and engineering of polymer and other molecules