Carbon nanotube synthesis and detection : limiting the environmental impact of novel technologies

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2009Driven by commercial promise, the carbon nanotube (CNT) industry is growing rapidly, yet little is known about the potential environmental impacts of these novel materials. In particular, there are no methods to detect CNTs in environmental matrices (e.g., sediment) and thus, there is no way to study their transport or gauge ecological exposure. Thermal methods were developed to quantify CNTs in coastal sediments down to 10 ug per sample, which is sufficient to for CNTs in laboratory air, but not sufficient to measure contemporary levels of CNTs in the environment (which were estimated to be present at pg g-1 sediment levels using a dynamic mass balance model). In addition to the CNTs themselves, potential impacts of CNT production were assessed by monitoring emissions from a representative synthesis. An ethene-fed chemical vapor deposition process generated several compounds of environmental concern, including the greenhouse gas, methane, the hazardous pollutants, benzene and 1,3-butadiene, and toxic polycyclic aromatic hydrocarbons. By identifying critical CNT precursors (alkynes), I delivered these compounds without thermal pre-treatment and achieved rapid CNT growth. This approach reduced carbonaceous emissions by more than an order of magnitude, and lowered initial feedstock requirements and energetic demands by at least 20%, without sacrificing CNT yield.National Science Foundation (NSF) Graduate Research Fellowship Program, NSF OCE-0221181, the Seaver Institute, the Martin Family Society of Fellows for Sustainability, Arunas and Pam Chesonis through MIT’s Earth System Initiative, and the WHOI Ocean Ventures Fund

Gulf States Marine Fisheries Commission

Headquartered in Ocean Springs, Mississippi, the GSMFC is an organization of the five states (Texas, Louisiana, Mississippi, Alabama, and Florida), whose coastal waters are the Gulf of Mexico. Objective is the conservation, development, and full utilization of the fishery resources of the Gulf, to provide food, employment, income, and recreation. Site features information on Commission programs, publications, meetings, fishing and boating regulations, and area-specific issues. Educational levels: High school, General public

Texas Parks & Wildlife

Magazine discussing natural resources, parks, hunting and fishing, and other information related to the outdoors in Texas

Texas Register

A weekly publication, the Texas Register serves as the journal of state agency rulemaking for Texas. Information published in the Texas Register includes proposed, adopted, withdrawn and emergency rule actions, notices of state agency review of agency rules, governor's appointments, attorney general opinions, and miscellaneous documents such as requests for proposals. After adoption, these rulemaking actions are codified into the Texas Administrative Code

Texas EMS Magazine

Bimonthly magazine containing news and information that pertains to Emergency Medical Service (EMS) providers. "The magazine's goals are to help organizations function professionally as EMS providers, to educate individuals so they can perform lifesaving prehospital skills under stressful conditions, and to help the public get into the EMS system when they need it" (p. 4)

Limiting the environmental impact of novel technologies

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering; and the Woods Hole Oceanographic Institution), 2009.Includes bibliographical references.Driven by commercial promise, the carbon nanotube (CNT) industry is growing rapidly, yet little is known about the potential environmental impacts of these novel materials. In particular, there are no methods to detect CNTs in environmental matrices (e.g.,sediment) and thus, there is no way to study their transport or gauge ecological exposure. Thermal methods were developed to quantify CNTs in coastal sediments down to 10 ug per sample, which is sufficient to for CNTs in laboratory air, but not sufficient to measure contemporary levels of CNTs in the environment (which were estimated to be present at pg g' sediment levels using a dynamic mass balance model). In addition to the CNTs themselves, potential impacts of CNT production were assessed by monitoring emissions from a representative synthesis. An ethene-fed chemical vapor deposition process generated several compounds of environmental concern, including the greenhouse gas, methane, the hazardous pollutants, benzene and 1,3-butadiene, and toxic polycyclic aromatic hydrocarbons. By identifying critical CNT precursors (alkynes), I delivered these compounds without thermal pre-treatment and achieved rapid CNT growth. This approach reduced carbonaceous emissions by more than an order of magnitude, and lowered initial feedstock requirements and energetic demands by at least 20%, without sacrificing CNT yield.by Desirée L. Plata.Ph.D

Synthesis and Optimization of Pipelined Packet Processors

We consider pipelined architectures of packet processors consisting of a sequence of simple packet-processing modules interconnected by first-in first-out buffers. We propose a new model for describing their function, an automated synthesis technique that generates efficient hardware for them, and an algorithm for computing minimum buffer sizes that allow such pipelines to achieve their maximum throughput. Our functional model provides a level of abstraction familiar to a network protocol designer; in particular, it does not require knowledge of register-transfer-level hardware design. Our synthesis tool implements the specified function in a sequential circuit that processes packet data a word at a time. Finally, our analysis technique computes the maximum throughput possible from the modules and then determines the smallest buffers that can achieve it. Experimental results conducted on industrial-strength examples suggest that our techniques are practical. Our synthesis algorithm can generate circuits that achieve 40 Gb/s on field-programmable gate arrays, equal to state-of-the-art manual implementations, and our buffer-sizing algorithm has a practically short runtime. Together, our techniques make it easier to quickly develop and deploy high-speed network switches

Texas Register

A weekly publication, the Texas Register serves as the journal of state agency rulemaking for Texas. Information published in the Texas Register includes proposed, adopted, withdrawn and emergency rule actions, notices of state agency review of agency rules, governor's appointments, attorney general opinions, and miscellaneous documents such as requests for proposals. After adoption, these rulemaking actions are codified into the Texas Administrative Code

German-Texan Heritage Society Journal

Quarterly publication of the German-Texan Heritage Society providing information about news and events related to the work of the organization as well as stories, articles, genealogical data and other information of interest to members collected from representatives across Texas