mit-6

Laboratory Characterization of Mars In-Situ Resource Utilization (ISRU) using the Mars Oxygen ISRU Experiment (MOXIE) FlatSat Testbed

2023-08-01T03:52:14Z

Laboratory Characterization of Mars In-Situ Resource Utilization (ISRU) using the Mars Oxygen ISRU Experiment (MOXIE) FlatSat Testbed Hariharan, Shravan The Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) is a payload onboard NASA’s Perseverance Rover demonstrating the production of oxygen through solid oxide electrolysis of carbon dioxide in the Martian atmosphere. MOXIE has successfully generated oxygen on Mars 14 times since landing in February 2021 and will continue to demonstrate oxygen production during night and day throughout all Martian seasons. As opportunities to run MOXIE on Mars are limited due to mission constraints such as energy usage and a fixed instrument configuration, the MOXIE team at the Massachusetts Institute of Technology (MIT), MIT Haystack Observatory, and NASA Jet Propulsion Laboratory (JPL) developed the MOXIE FlatSat as a ground-based operational testbed to further characterize the MOXIE system, evaluate and validate planned MOXIE operations on Mars, and demonstrate potential operating modes and configurations for a next-generation Mars in-situ resource utilization (ISRU) system. The research presented in this thesis involves a series of experiments conducted on the FlatSat testbed to inform design and operation of a next-generation Martian ISRU system. Specifically, this thesis discusses the capabilities of the FlatSat system, and how experiments analyzing the FlatSat compressor and FlatSat operations at low pressures inform optimal operating conditions for a future full-scale Martian ISRU system that minimize energy usage and maximize oxygen production. In addition, qualitative and quantitative differences between the FlatSat and MOXIE Flight Model are discussed to examine the extensibility of FlatSat data to MOXIE's operations on Mars.

Characterizing the Life Cycle of Online News StoriesUsing Social Media Reactions

2025-02-06T18:44:51Z

Characterizing the Life Cycle of Online News StoriesUsing Social Media Reactions Castillo, Carlos; El-Haddad, Mohammed; Pfeffer, Jürgen; Stempeck, Matt This paper presents a study of the life cycle of news articles posted online. We describe the interplay between website visitation patterns and social media reactions to news content. We show that we can use this hybrid observation method to characterize distinct classes of articles. We also find that social media reactions can help predict future visitation patterns early and accurately.We validate our methods using qualitative analysis as well as quantitative analysis on data from a large inter-national news network, for a set of articles generating more than 3,000,000 visits and 200,000 social media re-actions. We show that it is possible to model accurately the overall traffic articles will ultimately receive by ob-serving the first ten to twenty minutes of social media reactions. Achieving the same prediction accuracy with visits alone would require to wait for three hours of data.We also describe significant improvements on the accuracy of the early prediction of shelf-life for news stories.

Prediction of Large Events in Directed Sandpiles

2025-11-18T06:33:43Z

Prediction of Large Events in Directed Sandpiles Shah, Dhruv The degree of predictability of large avalanche events in the directed sandpile model is studied. This degree is defined in terms of how successfully a strategy can predict such events, as compared to a random guess. A waiting time based prediction strategy which exploits the local anticorrelation of large events is discussed. With this strategy we show analytically and numerically that large events are predictable, and that this predictability persists in the thermodynamic limit. We introduce another strategy which predicts large avalanches in the future based on the present excess density in the sandpile. We obtain the exact conditional probabilities for large events given an excess density, and use this to determine the exact form of the ROC predictability curves. We show that for this strategy, the model is predictable only for finite lattice sizes, and unpredictable in the thermodynamic limit. This behaviour is to be contrasted with previously established numerical studies carried out for Manna sandpiles.

An Immune Response Network Associated with Blood Lipid Levels

2022-09-26T16:57:16Z

An Immune Response Network Associated with Blood Lipid Levels Inouye, Michael; Silander, Kaisa; Hamalainen, Eija; Salomaa, Veikko; Harald, Kennet; Jousilahti, Pekka; Männistö, Satu; Eriksson, Johan G.; Saarela, Janna; Ripatti, Samuli; Perola, Markus; van Ommen, Gert-Jan B.; Taskinen, Marja-Riitta; Palotie, Aarno; Dermitzakis, Emmanouil T.; Peltonen, Leena While recent scans for genetic variation associated with human disease have been immensely successful in uncovering large numbers of loci, far fewer studies have focused on the underlying pathways of disease pathogenesis. Many loci which are associated with disease and complex phenotypes map to non-coding, regulatory regions of the genome, indicating that modulation of gene transcription plays a key role. Thus, this study generated genome-wide profiles of both genetic and transcriptional variation from the total blood extracts of over 500 randomly-selected, unrelated individuals. Using measurements of blood lipids, key players in the progression of atherosclerosis, three levels of biological information are integrated in order to investigate the interactions between circulating leukocytes and proximal lipid compounds. Pair-wise correlations between gene expression and lipid concentration indicate a prominent role for basophil granulocytes and mast cells, cell types central to powerful allergic and inflammatory responses. Network analysis of gene co-expression showed that the top associations function as part of a single, previously unknown gene module, the Lipid Leukocyte (LL) module. This module replicated in T cells from an independent cohort while also displaying potential tissue specificity. Further, genetic variation driving LL module expression included the single nucleotide polymorphism (SNP) most strongly associated with serum immunoglobulin E (IgE) levels, a key antibody in allergy. Structural Equation Modeling (SEM) indicated that LL module is at least partially reactive to blood lipid levels. Taken together, this study uncovers a gene network linking blood lipids and circulating cell types and offers insight into the hypothesis that the inflammatory response plays a prominent role in metabolism and the potential control of atherogenesis.

The mechanical behavior of heavily overconsolidated resedimented Boston Blue Clay

2022-01-13T07:53:59Z

The mechanical behavior of heavily overconsolidated resedimented Boston Blue Clay Vargas Bustamante, Albalyra Geraldine Geotechnical engineers encounter some of the most challenging problems in heavily overconsolidated soils. Clays under this condition originated in nature or man-made construction. This thesis investigates the mechanical behavior heavily overconsolidated Resedimented Boston Blue Clay (RBBC), as an analog test material. The uniformity, reproducibility, and extensive knowledgebase on this clay permit the investigation of only the effect of overconsolidation. A series of undrained triaxial compression shear tests have been performed on specimens that were Ko-consolidated and swelled to overconsolidation ratios (OCR) ranging from 5 to 62 on RBBC, as well as on Intact Presumpscot Maine Clay. Specimens were consolidated to maximum stress levels between 1.1 and 5.4 MPa. The undrained shear behavior revealed an important relationship with overconsolidation ratio. The triaxial compression test results exhibit a significant increase in the undrained strength ratio (su/[sigma]'vc) when normalized to the minimum consolidation stress. It also shows an important increase in the stiffness, increase in the strain ([epsilon]f) to mobilize the peak resistance and a significant increase of friction angle ([phi]') with overconsolidation. The applicability of the SHANSEP equation and impact on its equation parameters are also discussed in detail. A comprehensive comparison of the new results with prior normally consolidated and lightly overconsolidated data is presented, showing the distinct behavior of heavily overconsolidated specimens. The failure envelope displays a non-linear behavior and the undrained shear strength (su) is reduced up to about 80% from a normally consolidated clay to a heavily overconsolidated clay with an OCR = 50. These observations demonstrate the importance of selecting appropriate design values in the presence of overconsolidated soils. Thesis (S.M.)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013.; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 215-219).

Cis-trans isomerization in the S[subscript 1] state of acetylene: Identification of cis-well vibrational levels

2022-09-28T15:35:28Z

Cis-trans isomerization in the S[subscript 1] state of acetylene: Identification of cis-well vibrational levels Merer, Anthony J.; Steeves, Adam H.; Baraban, Joshua H.; Bechtel, Hans A.; Field, Robert W. A systematic analysis of the S[subscript 1]-trans ([bar-over A][superscript 1]A[subscript u]) state of acetylene, using IR-UV double resonance along with one-photon fluorescence excitation spectra, has allowed assignment of at least part of every single vibrational state or polyad up to a vibrational energy of 4200 cm[superscript –1]. Four observed vibrational levels remain unassigned, for which no place can be found in the level structure of the trans-well. The most prominent of these lies at 46 175 cm[superscript –1]. Its [superscript 13]C isotope shift, exceptionally long radiative lifetime, unexpected rotational selection rules, and lack of significant Zeeman effect, combined with the fact that no other singlet electronic states are expected at this energy, indicate that it is a vibrational level of the S[subscript 1-]cis isomer ([bar-over A][superscript 1]A[subscript 2]). Guided by ab initio calculations [J. H. Baraban, A. R. Beck, A. H. Steeves, J. F. Stanton, and R. W. Field, J. Chem. Phys. 134, 244311 (2011)]10.1063/1.3570823 of the cis-well vibrational frequencies, the vibrational assignments of these four levels can be established from their vibrational symmetries together with the [superscript 13]C isotope shift of the 46 175 cm[superscript −1] level (assigned here as cis-3[superscript 1]6[superscript 1]). The S[subscript 1]-cis zero-point level is deduced to lie near 44 900 cm[superscript −1], and the ν[subscript 6] vibrational frequency of the S[subscript 1]-cis well is found to be roughly 565 cm[superscript −1]; these values are in remarkably good agreement with the results of recent ab initio calculations. The 46 175 cm[superscript −1] vibrational level is found to have a 3.9 cm[superscript −1] staggering of its K-rotational structure as a result of quantum mechanical tunneling through the isomerization barrier. Such tunneling does not give rise to ammonia-type inversion doubling, because the cis and trans isomers are not equivalent; instead the odd-K rotational levels of a given vibrational level are systematically shifted relative to the even-K rotational levels, leading to a staggering of the K-structure. These various observations represent the first definite assignment of an isomer of acetylene that was previously thought to be unobservable, as well as the first high resolution spectroscopic results describing cis-trans isomerization.

Development of a low-cost, rapid-cycle hot embossing system for microscale parts

2022-01-13T07:54:36Z

Development of a low-cost, rapid-cycle hot embossing system for microscale parts Hale, Melinda (Melinda Rae) Hot embossing is an effective technology for reproducing micro-scale features in polymeric materials, but large-scale adoption of this method is hindered by high capital costs and low cycle times relative to other technologies, and a general lack of manufacturing equipment. This work details a hot embossing machine design strategy motivated by maximum production speed and quality with minimal capital cost. The approach is to "right-size" the machine for specific product needs while making the design flexible and scalable. Toward this end, a minimal number of components were used, commercially available off-the-shelf components were chosen where possible, system layout was designed to be modular, and system size was scaled for the intended products (in this case microfluidic devices). Innovative design aspects include the use of new ceramic substrate heaters for electrical heating, use of a moveable heat sink to minimize heat load during the heating cycle, and the careful design of the thermal elements to minimize the heating and cooling cycle times. The capital cost and the cost per part produced with this machine are estimated to be an order of magnitude less than currently available hot embossing manufacturing options. The hot embossing machine has been tested extensively to characterize the process variability. The minimum cycle time is two minutes, and microstructures are replicated within a maximum of a 25mm by 75mm area with very low relative variance in dimensions. Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.; Includes bibliographical references (leaves 135-137).

Contracting force fields in robot navigation and extension to other problems

2022-01-13T07:54:05Z

Contracting force fields in robot navigation and extension to other problems Hagg, Alexandre F. (Alexandre Frédèric), 1975- Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.; Includes bibliographical references (leaves 47-48).

BINARY PROPERTIES FROM CEPHEID RADIAL VELOCITIES (CRaV)

2022-09-26T10:21:52Z

BINARY PROPERTIES FROM CEPHEID RADIAL VELOCITIES (CRaV) Evans, Nancy Remage; Berdnikov, Leonid; Lauer, Jennifer L.; Morgan, Douglas L.; Nichols, Joy S.; Gorynya, Natalya; Guenther, Hans Moritz; Rastorguev, Alexey; Moskalik, Pawel We have examined high accuracy radial velocities of Cepheids to determine the binary frequency. The data are largely from the CORAVEL spectrophotometer and the Moscow version, with a typical uncertainty of ⩽ 1 km s[superscript −1], and a time span from 1 to 20 years. A systemic velocity was obtained by removing the pulsation component using a high order Fourier series. From this data we have developed a list of stars showing no orbital velocity larger than ±1 km s[superscript −1]. The binary fraction was analyzed as a function of magnitude, and yields an apparent decrease in this fraction for fainter stars. We interpret this as incompleteness at fainter magnitudes, and derive the preferred binary fraction of 29% ± 8% (20% ± 6% per decade of orbital period) from the brightest 40 stars. A comparison of this fraction in this period range (1–20 years) implies a large fraction for the full period range. This is reasonable in that the high accuracy velocities are sensitive to the longer periods and smaller orbital velocity amplitudes in the period range sampled here. Thus the Cepheid velocity sample provides a sensitive detection in the period range between short period spectroscopic binaries and resolved companions. The recent identification of δ Cep as a binary with very low amplitude and high eccentricity underscores the fact that the binary fractions we derive are lower limits, to which other low amplitude systems will probably be added. The mass ratio (q) distribution derived from ultraviolet observations of the secondary is consistent with a flat distribution for the applicable period range (1–20 years).

Ketogenic essential amino acids modulate lipid synthetic pathways and hepatic steatosis in mice

2022-09-30T15:49:18Z

Ketogenic essential amino acids modulate lipid synthetic pathways and hepatic steatosis in mice Noguchi, Yasushi; Nishikata, Natsumi; Shikata, Nahoko; Kimura, Yoshiko; Aleman, Jose O.; Young, Jamey D.; Koyama, Naoto; Kelleher, Joanne Keene; Takahashi, Michio; Stephanopoulos, Gregory Background Although dietary ketogenic essential amino acid (KAA) content modifies accumulation of hepatic lipids, the molecular interactions between KAAs and lipid metabolism are yet to be fully elucidated. Methodology/Principal Findings We designed a diet with a high ratio (E/N) of essential amino acids (EAAs) to non-EAAs by partially replacing dietary protein with 5 major free KAAs (Leu, Ile, Val, Lys and Thr) without altering carbohydrate and fat content. This high-KAA diet was assessed for its preventive effects on diet-induced hepatic steatosis and whole-animal insulin resistance. C57B6 mice were fed with a high-fat diet, and hyperinsulinemic ob/ob mice were fed with a high-fat or high-sucrose diet. The high-KAA diet improved hepatic steatosis with decreased de novo lipogensis (DNL) fluxes as well as reduced expressions of lipogenic genes. In C57B6 mice, the high-KAA diet lowered postprandial insulin secretion and improved glucose tolerance, in association with restored expression of muscle insulin signaling proteins repressed by the high-fat diet. Lipotoxic metabolites and their synthetic fluxes were also evaluated with reference to insulin resistance. The high-KAA diet lowered muscle and liver ceramides, both by reducing dietary lipid incorporation into muscular ceramides and preventing incorporation of DNL-derived fatty acids into hepatic ceramides. Conclusion Our results indicate that dietary KAA intake improves hepatic steatosis and insulin resistance by modulating lipid synthetic pathways.

Radio-Frequency Spectroscopy

2019-04-12T23:45:26Z

Radio-Frequency Spectroscopy Davis, L., Jr.; Kyhl, Robert L.; Wentink, T., Jr.; Loomis, C. C.; Bitter, F.; Ingersoll, J. G.; Zabel, C. W.; Hill, Albert G.; Lebow, E.; Harvey, George G.; Feld, B. T.; Lawrance, R. B.; Arnold, R. D.; Lehr, C. G.; Zacharias, J. R.; Strandberg, Malcom W. P.; Hillger, R. E.; Weiss, M. T.; Kip, A. F.; Pettingill, G. H.; Nagle, D. E.; Lew, Hin; Alpert, N. L.; Poss, H. L. Contains reports on four research projects.

Choroidal Haller's and Sattler's Layer Thickness Measurement Using 3-Dimensional 1060-nm Optical Coherence Tomography

2022-09-23T09:22:40Z

Choroidal Haller's and Sattler's Layer Thickness Measurement Using 3-Dimensional 1060-nm Optical Coherence Tomography Esmaeelpour, Marieh; Kajic, Vedran; Zabihian, Behrooz; Othara, Richu; Ansari-Shahrezaei, Siamak; Kellner, Lukas; Krebs, Ilse; Nemetz, Susanne; Kraus, Martin Franz Georg; Hornegger, Joachim; Fujimoto, James G.; Drexler, Wolfgang; Binder, Susanne Objectives: To examine the feasibility of automatically segmented choroidal vessels in three-dimensional (3D) 1060-nmOCT by testing repeatability in healthy and AMD eyes and by mapping Haller's and Sattler's layer thickness in healthy eyes Methods: Fifty-five eyes (from 45 healthy subjects and 10 with non-neovascular age-related macular degeneration (AMD) subjects) were imaged by 3D-1060-nmOCT over a 36°x36° field of view. Haller's and Sattler's layer were automatically segmented, mapped and averaged across the Early Treatment Diabetic Retinopathy Study grid. For ten AMD eyes and ten healthy eyes, imaging was repeated within the same session and on another day. Outcomes were the repeatability agreement of Haller's and Sattler's layer thicknesses in healthy and AMD eyes, the validation with ICGA and the statistical analysis of the effect of age and axial eye length (AL) on both healthy choroidalsublayers. Results: The coefficients of repeatability for Sattler's and Haller's layers were 35% and 21% in healthy eyes and 44% and 31% in AMD eyes, respectively. The mean±SD healthy central submacular field thickness for Sattler's and Haller's was 87±56 µm and 141±50 µm, respectively, with a significant relationship for AL (P<.001). Conclusions: Automated Sattler's and Haller's thickness segmentation generates rapid 3D measurements with a repeatability correspondingto reported manual segmentation. Sublayers in healthy eyes thinnedsignificantly with increasing AL. In the presence of the thinned Sattler's layer in AMD, careful measurement interpretation is needed. Automatic choroidal vascular layer mapping may help to explain if pathological choroidal thinning affects medium and large choroidal vasculature in addition to choriocapillaris loss.

Leveling the workload at the interface between internal and external supply chains

2022-01-28T21:15:15Z

Leveling the workload at the interface between internal and external supply chains Guerrero, Trent M. (Trent Mitchell), 1964- Thesis (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; in conjunction with the Leaders for Manufacturing Program at MIT, 2001.; Includes bibliographical references (leaves 95-96).

Evaluating the impact of online influencers on retail property rent : a case study in New York City

2021-07-05T14:03:20Z

Evaluating the impact of online influencers on retail property rent : a case study in New York City Sun, Xudong,M.C.P.Massachusetts Institute of Technology. This study proposes a framework of analyzing online influencer behavior and evaluating its impact on retail rent using spatial econometric methods, in which we also examined the spatial autocorrelation and heterogeneity in New York's retail rent market. We use social media data mining and network analysis techniques to examine influencers and information diffusion in Instagram and develop metrics to quantify the impact. Using spatial econometric models, we construct models of retail rents that include the effect of online influencers and traditional hedonic features. The result suggests that online influencer behavior have a significant correlation with effective rents of retail real estate in the case study area of New York. We also examine the spatial spillover effect and spatial heterogeneity of the influencer effect. Our results provide the first analysis to link online behavior to retail real estate, it also proposes a framework to study the real estate by linking online and offline world, which is meaningful for retail real estate challenged by e-commerce and other forms of new economy. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.; Thesis: M.C.P., Massachusetts Institute of Technology, Department of Urban Studies and Planning, 2019; Cataloged from PDF version of thesis.; Includes bibliographical references (pages 97-101).

Assessment of rainwater harvesting in Northern Ghana

2022-01-13T07:54:23Z

Assessment of rainwater harvesting in Northern Ghana Barnes, David Allen This study assesses the current state of rainwater harvesting in the Northern Region of Ghana and makes recommendations regarding if and how rainwater harvesting could be used to address Pure Home Water's goal of reaching 1 million people in the next five years with safe drinking water. Three principal aspects of the water supply are considered: quality, quantity, and cost. Bacteriological water quality is tested to determine the level of risk. Rainwater supplies ranged from low (1 to 10 E.coli CFU/100ml) to intermediate risk (10 to 99 E. coli CFU/100ml.) Time-based reliability is simulated using a simulation model in Microsoft Excel. Reliability ranges from five percent to ninety-nine percent. Unit cost per cubic meter is calculated for surveyed rainwater harvesting systems in Northern Ghana. The unit cost of water from these designs ranged between approximately $1/m3 and $10/m3. Storage-reliability-yield relationship is developed and graphed for the Northern Region. This curve is useful for properly sizing rainwater harvesting systems. The use of a filter to post-treat rainwater before consumption is recommended, both for use with the rainwater, but also for provision of safe water when the users rely on a supplementary unimproved source, usually a dugout or dug well, for water supply. The feasibility of low-cost underground storage should be investigated. The geology and soil conditions in the Tamale region might provide a suitable match for a cheaper storage mechanism using plastic tarps and constructed pits.; (cont.) If the cost of storage could be lowered, rainwater harvesting could contribute in a larger way to Pure Home Water's mission and reach more people. Do-it-yourself rainwater harvesting in the Northern Region of Ghana is a fairly widespread. Finding ways to improve the quantity and quality of informal harvesting is a potential means for improving water supply for many low income households in the Northern Region. Currently, rainwater harvesting presents an opportunity to extend water supply to rural dwellers where few other alternatives are available. Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009.; Includes bibliographical references (leaves 93-96).

Thermal neutron capture gamma-ray spectra of the elements

2019-04-10T10:40:12Z

Thermal neutron capture gamma-ray spectra of the elements Rasmussen, Norman C.; Hukai, Yoshiyuti; Inouye, Tamon; Orphan, V. J. "January 1969."; Statement of responsibility on title-page reads: Norman C. Rasmussen, Yoshiyuti Hukai, Tamon Inouye, Victor J. Orphan; "Prepared for Air Force Cambridge Research Laboratories, Office of Aerospace Research, United States Air Force, Bedford, Mass."; "AFCRL-69-0071."; Includes bibliographical references

Measurement of cross sections for b jet production in events with a Z boson in p(p)over-bar collisions at root s=1.96 TeV

2025-07-24T01:22:08Z

Measurement of cross sections for b jet production in events with a Z boson in p(p)over-bar collisions at root s=1.96 TeV Aaltonen, T.; Adelman, J.; Akimoto, T.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Apresyan, A.; Arisawa, T.; Artikov, A.; Ashmanskas, W.; Attal, A.; Aurisano, A.; Azfar, F.; Azzurri, P.; Badgett, W.; Barbaro-Galtieri, A.; Barnes, V. E.; Barnett, B. A.; Bartsch, V.; Bauer, Gerry P.; Beauchemin, P.-H.; Bedeschi, F.; Beecher, D.; Behari, S.; Bellettini, G.; Bellinger, J.; Benjamin, D.; Beretvas, A.; Beringer, J.; Bhatti, A.; Binkley, M.; Bisello, D.; Bizjak, I.; Blair, R. E.; Blocker, C.; Blumenfeld, B.; Bocci, A.; Bodek, A.; Boisvert, V.; Bolla, G.; Bortoletto, D.; Boudreau, J.; Boveia, A.; Brau, B.; Bridgeman, A.; Brigliadori, L.; Bromberg, C.; Brubaker, E.; Budagov, J.; Budd, H. S.; Budd, S.; Burke, S.; Burkett, K.; Busetto, G.; Bussey, P.; Buzatu, A.; Byrum, K. L.; Cabrera, S.; Calancha, C.; Campanelli, M.; Campbell, M.; Canelli, F.; Canepa, A.; Carls, B.; Carlsmith, D.; Carosi, R.; Carrillo, S.; Carron, S.; Casal, B.; Casarsa, M.; Castro, A.; Catastini, P.; Cauz, D.; Cavaliere, V.; Cavalli-Sforza, M.; Cerri, A.; Cerrito, L.; Chang, S. H.; Chen, Y. C.; Chertok, M.; Chiarelli, G.; Chlachidze, G.; Chlebana, F.; Cho, K.; Chokheli, D.; Chou, J. P.; Choudalakis, Georgios; Chuang, S. H.; Chung, K.; Chung, W. H.; Chung, Y. S.; Chwalek, T.; Ciobanu, C. I.; Ciocci, M. A.; Clark, A.; Clark, D.; Compostella, G.; Convery, M. E.; Conway, J.; Cordelli, M.; Cortiana, G.; Cox, C. A.; Cox, D. J.; Crescioli, F.; Cuenca Almenar, C.; Cuevas, J.; Culbertson, R.; Cully, J. C.; Dagenhart, D.; Datta, M.; Davies, T.; de Barbaro, P.; De Cecco, S.; Deisher, A.; De Lorenzo, G.; Dell'Orso, M.; Deluca, C.; Demortier, L.; Deng, J.; Deninno, M.; Derwent, P. F.; Di Giovanni, G. P.; Dionisi, C.; Di Ruzza, B.; Dittmann, J. R.; D’Onofrio, M.; Donati, S.; Dong, P.; Donini, J.; Dorigo, T.; Dube, S.; Efron, J.; Elagin, A.; Erbacher, R.; Errede, D.; Errede, S.; Eusebi, R.; Fang, H. C.; Farrington, S.; Fedorko, W. T.; Feild, R. G.; Feindt, M.; Fernandez, J. P.; Ferrazza, C.; Field, R.; Flanagan, G.; Forrest, R.; Frank, M. J.; Franklin, M.; Freeman, J. C.; Furic, I. K.; Gallinaro, M.; Galyardt, J.; Garberson, F.; Garcia, J. E.; Garfinkel, A. F.; Genser, K.; Gerberich, H.; Gerdes, D.; Gessler, A.; Giagu, S.; Giakoumopoulou, V.; Giannetti, P.; Gibson, K.; Gimmell, J. L.; Ginsburg, C. M.; Giokaris, N.; Giordani, M.; Giromini, P.; Giunta, M.; Giurgiu, G.; Glagolev, V.; Glenzinski, D.; Gold, M.; Goldschmidt, N.; Golossanov, A.; Gomez, G.; Gomez-Ceballos, Guillelmo; Goncharov, Maxim; Gonzalez, O.; Gorelov, I.; Goshaw, A. T.; Goulianos, K.; Gresele, A.; Grinstein, S.; Grosso-Pilcher, C.; Group, R. C.; Grundler, U.; Guimaraes da Costa, J.; Gunay-Unalan, Z.; Haber, C.; Hahn, Kristian Allan; Hahn, S. R.; Halkiadakis, E.; Han, B.-Y.; Han, J. Y.; Happacher, F.; Hara, K.; Hare, D.; Hare, M.; Harper, S.; Harr, R. F.; Harris, R. M.; Hartz, M.; Hatakeyama, K.; Hays, C.; Heck, M.; Heijboer, A.; Heinemann, B.; Heinrich, J.; Henderson, C.; Herndon, M.; Heuser, J.; Hewamanage, S.; Hidas, D.; Hill, C. S.; Hirschbuehl, D.; Hocker, A.; Hou, S.; Houlden, M.; Hsu, S.-C.; Huffman, B. T.; Hughes, R. E.; Hussein, M.; Husemann, U.; Huston, J.; Incandela, J.; Introzzi, G.; Iori, M.; Ivanov, A.; James, E.; Jayatilaka, B.; Jeon, E. J.; Jha, M. K.; Jindariani, S.; Johnson, W.; Jones, M.; Joo, K. K.; Jun, S. Y.; Jung, J. E.; Junk, T. R.; Kamon, T.; Kar, D.; Karchin, P. E.; Kato, Y.; Kephart, R.; Keung, J.; Khotilovich, V.; Kilminster, B.; Kim, D. H.; Kim, H. S.; Kim, H. W.; Kim, J. E.; Kim, M. J.; Kim, S. B.; Kim, S. H.; Kim, Y. K.; Kimura, N.; Kirsch, L.; Klimenko, Sergey; Ko, B. R.; Kondo, K.; Kong, D. J.; Konigsberg, J.; Korytov, A.; Kotwal, A. V.; Kreps, M.; Krop, D.; Krumnack, N.; Kruse, M.; Krutelyov, V.; Kubo, T.; Kuhr, T.; Kulkarni, N. P.; Kurata, M.; Kwang, S.; Laasanen, A. T.; Lami, S.; Lammel, S.; Lancaster, M.; Lander, R. L.; Lannon, K.; Lath, A.; Latino, G.; Lazzizzera, I.; LeCompte, T.; Lee, E.; Lee, H. S.; Lee, S. W.; Leone, S.; Lewis, J. D.; Lin, C.-S.; Linacre, J.; Lindgren, M.; Lipeles, E.; Lister, A.; Litvintsev, D. O.; Liu, C.; Liu, T.; Lockyer, N. S.; Loginov, A.; Loreti, M.; Lovas, L.; Lucchesi, D.; Luci, C.; Lueck, J.; Lunjan, P.; Lukens, P.; Lungu, G.; Lyons, L.; Lys, J.; Lysak, R.; MacQueen, D.; Madrak, R.; Maeshima, K.; Makhoul, K.; Maki, T.; Maksimovic, P.; Malde, S.; Malik, S.; Manca, G.; Manousakis-Katsikakis, A.; Margaroli, F.; Marino, C.; Marino, C. P.; Martin, A.; Maruyama, T.; Mastrandrea, P.; Masubuchi, T.; Mathis, M.; Mattson, M. E.; Mazzanti, P.; McFarland, K. S.; Martin, V.; Martinez, M.; Martinez-Ballarin, R.; McIntyre, P.; McNulty, R.; Mehta, A.; Mehtala, P.; Menzione, A.; Merkel, P.; Mesropian, C.; Miao, T.; Miladinovic, N.; Miller, R.; Mills, C.; Milnik, M.; Mitra, A.; Mitselmakher, G.; Miyake, H.; Moggi, N.; Moon, C. S.; Moore, R.; Morello, M. J.; Morlok, J.; Movilla Fernandez, P.; Mulmenstadt, J.; Mukherjee, A.; Muller, Th.; Mumford, R.; Murat, P.; Mussini, M.; Nachtman, J.; Nagai, Y.; Nagano, A.; Naganoma, J.; Nakamura, K.; Nakano, I.; Napier, A.; Necula, V.; Nett, J.; Neu, C.; Neubauer, M. S.; Neubauer, S.; Nielsen, J.; Nodulman, L.; Norman, M.; Norniella, O.; Nurse, E.; Oakes, L.; Oh, S. H.; Oh, Y. D.; Oksuzian, I.; Okusawa, T.; Orava, R.; Pagan Griso, S.; Palencia, E.; Papadimitriou, V.; Papaikonomou, A.; Paramonov, A. A.; Parks, B.; Pashapour, S.; Patrick, J.; Pauletta, G.; Paulini, M.; Paus, Christoph M. E.; Peiffer, T.; Pellett, D. E.; Penzo, A.; Phillips, T. J.; Piacentino, G.; Pianori, E.; Pinera, L.; Pitts, K.; Plager, C.; Pondrom, L.; Poukhov, O.; Pounder, N.; Prakoshyn, F.; Pronko, A.; Proudfoot, J.; Ptohos, F.; Pueschel, E.; Punzi, G.; Pursley, J.; Rademacker, J.; Rahaman, A.; Ramakrishnan, V.; Ranjan, N.; Redondo, I.; Renton, P.; Renz, M.; Rescigno, M.; Richter, S.; Rimondi, F.; Ristori, L.; Robson, A.; Rodrigo, T.; Rodriguez, T.; Rogers, E.; Rolli, S.; Roser, R.; Rossi, M.; Rossin, R.; Roy, P.; Ruiz, A.; Russ, J.; Rusu, V.; Safonov, A.; Sakumoto, W. K.; Salto, O.; Santi, L.; Sarkar, S.; Sartori, L.; Sato, K.; Savoy-Navarro, A.; Schlabach, P.; Schmidt, A.; Schmidt, E. E.; Schmidt, M. A.; Schmidt, M. P.; Schmitt, M.; Schwarz, T.; Scodellaro, L.; Scribano, A.; Scuri, F.; Sedov, A.; Seidel, S.; Seiya, Y.; Semenov, A.; Sexton-Kennedy, L.; Sforza, F.; Shreyber, I.; Sidoti, A.; Sinervo, P.; Sisakyan, A.; Slaughter, A. J.; Slaunwhite, J.; Sliwa, K.; Smith, J. R.; Snider, F. D.; Snihur, R.; Soha, A.; Somalwar, S.; Sorin, V.; Spalding, J.; Spreitzer, T.; Squillacioti, P.; Stanitzki, M.; St. Denis, R.; Stelzer, B.; Stelzer-Chilton, O.; Stentz, D.; Strologas, J.; Strycker, G. L.; Stuart, D.; Suh, J. S.; Sukhanov, A.; Suslov, I.; Suzuki, T.; Taffard, A.; Takashima, R.; Takeuchi, Y.; Tanaka, R.; Tecchio, M.; Teng, P. K.; Terashi, K.; Thom, J.; Thompson, A. S.; Thompson, G. A.; Thomson, E.; Tipton, P.; Ttito-Guzman, P.; Tkaczyk, S.; Toback, D.; Tokar, S.; Tollefson, K.; Tomura, T.; Tonelli, D.; Torre, S.; Torretta, D.; Totaro, P.; Tourneur, S.; Trovato, M.; Tsai, S.-Y.; Tu, Y.; Turini, N.; Ukegawa, F.; Vallecorsa, S.; van Remortel, N.; Varganov, A.; Vataga, E.; Vazquez, F.; Velev, G.; Vellidis, C.; Veszpremi, V.; Vidal, M.; Vidal, R.; Vila, I.; Vilar, R.; Vine, T.; Vogel, M.; Volobouev, I.; Volpi, G.; Wagner, P.; Wagner, R. G.; Wagner, R. L.; Wagner, W.; Wagner-Kuhr, J.; Wakisaka, T.; Wallny, R.; Wang, S. M.; Warburton, A.; Waters, D.; Weinberger, M.; Weinelt, J.; Wester, W. C. III; Whitehouse, B.; Whiteson, D.; Wicklund, A. B.; Wicklund, E.; Wilbur, S.; Williams, G.; Williams, H. H.; Wilson, P.; Winer, B. L.; Wittich, P.; Wolberts, S.; Wolfe, C.; Wright, T.; Wu, X.; Wurthwein, F.; Wynne, S. M.; Yagil, A.; Yamamoto, K.; Yamaoka, J.; Yang, U. K.; Yang, Y. C.; Yao, W. M.; Yeh, G. P.; Yoh, J.; Yorita, K.; Yoshida, T.; Yu, G. B.; Yu, I.; Yu, S. S.; Yun, J. C.; Zanello, L.; Zannetti, A.; Zhang, X.; Zheng, Y.; Zucchelli, S.; Knuteson, Bruce O.; Xie, Si, Ph. D. Massachusetts Institute of Technology A measurement of the b jet production cross section is presented for events containing a Z boson produced in p[overline p] collisions at sqrt(s)=1.96 TeV, using data corresponding to an integrated luminosity of 2 fb[superscript -1] collected by the CDF II detector at the Tevatron. Z bosons are selected in the electron and muon decay modes. Jets are considered with transverse energy ET>20 GeV and pseudorapidity |eta|<1.5 and are identified as b jets using a secondary vertex algorithm. The ratio of the integrated Z+b jet cross section to the inclusive Z production cross section is measured to be 3.32±0.53(stat)±0.42(syst)×10[superscript -3]. This ratio is also measured differentially in jet ET, jet eta, Z-boson transverse momentum, number of jets, and number of b jets. The predictions from leading-order Monte Carlo generators and next-to-leading-order QCD calculations are found to be consistent with the measurements within experimental and theoretical uncertainties.

Development of a co-dispersion binder for the three-dimensional printing process to facilitate handling of ceramic casting shells in the green state

2022-01-13T07:54:36Z

Development of a co-dispersion binder for the three-dimensional printing process to facilitate handling of ceramic casting shells in the green state Yu, Richard Li-Chao Three Dimensional Printing, a rapid prototyping technology, fabricates ceramic casting shells directly from 3-D CAD models. To create a shell, loose alumina powder in thin layers is joined by selectively depositing a colloidal silica binder. Firing fuses the silica to the alumina, and subsequent processing removes the unbound powder from the casting cavity. In some instances, it may be advantageous to perform powder removal before firing. This requires higher green strength than what is obtainable with the current binder. An alternative binder consisting of 18 vol.% colloidal silica co-dispersed with 10 vol.% acrylic emulsion in an aqueous medium was developed. The polymeric component imparts higher green strength to the part (3.6 vs. 0.4 MPa), yet decomposes during firing to minimize interference with the fusion of silica to alumina. The reduction of fired strength in samples printed with co-dispersions was less than 10%. Through designed experiments, performance of the co-dispersion was quantified by additional criteria such as shrinkage, warping, and binder stability. Average linear shrinkage in parts printed with co-dispersions was 0.05% after firing at 900°C. A simple model for warping, based on elastic response of a plate to free thermal strain, predicts that flat plates tend to warp into a paraboloid after firing. The experimental results correlated well with this prediction. Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994.; Includes bibliographical references (leaf 107).

Structural Investigation of Allosteric Regulation in Class III Ribonucleotide Reductases

2026-04-07T03:02:56Z

Structural Investigation of Allosteric Regulation in Class III Ribonucleotide Reductases Andree, Gisele A. Ribonucleotide reductases (RNRs) are essential enzymes that use radical-based chemistry to catalyze the reduction of ribonucleotides to deoxyribonucleotides. Each RNR class uses a different cofactor to generate a catalytically essential thiyl radical in the active site. Anaerobic (class III) RNRs employ an oxygen-sensitive glycyl radical cofactor installed within the adjacent glycyl radical domain. To maintain intracellular nucleotide pool balance, RNRs are allosterically regulated. For the prototypical class Ia RNR from Escherichia coli, this regulation involves the Nterminus of the catalytic subunit in a region known as the ‘cone domain’. ATP or dATP binding to the cone domain results in an association between it and the radical-generating subunit that either allows or prevents, respectively, radical transfer. Most class III RNRs have a cone domain and are allosterically regulated, but the mechanism of how this regulation proceeds is not well understood. Allosteric activity regulation for such a class III RNR, the class III RNR from Streptococcus thermophilus (StNrdD) is the focus of this thesis. We have developed a universal liquid chromatography tandem mass spectrometry based activity assay, which was adapted for use in class III RNR, and used the assay to show that ATP is an allosteric activity enhancer and dATP is an allosteric activity inhibitor of StNrdD. We used a combination of cryogenic electron microscopy (cryo-EM) and X-ray crystallography to show that ATP and dATP bind to the StNrdD cone domain and that the cone domains adopt exceptionally different conformations in the presence of either allosteric effector. Mutagenesis assays and hydrogendeuterium exchange mass spectrometry data show that the flexible region between the cone domain and the core is important for catalysis. Changes between ATP- and dATP-binding in the cone domains underlie the observed conformational and allosteric changes. This work answers some long-standing questions surrounding class III allosteric regulation and lays the groundwork to continue improving our molecular-level understanding of this complex enzyme system.

Studies in duality : discovering a dual catalytic amination reaction and investigating the origin of biphilicity in phosphacycles

2021-07-05T14:03:20Z

Studies in duality : discovering a dual catalytic amination reaction and investigating the origin of biphilicity in phosphacycles Dummit, Krysta A.(Krysta Alanna) First, the development of a novel C-H amination strategy using both a Cu(II) Lewis acid and an organic hydrogen atom transfer (HAT) catalyst to activate benzylic C-H bonds adjacent to aromatic azaheterocycles is described. This simple method demonstrates very high selectivity towards aromatic azaheterocycles without using exogenous directing groups and affords excellent site selectivity in substrates with more than one reactive position. A wide range of aromatic azaheterocyclic structures not compatible with previously reported catalytic systems have proven to be amenable to this approach. Mechanistic investigations indicate a possible radical-mediated H-atom abstraction for select substrates, which would stand in contrast to known closed-shell Lewis acid catalyzed processes. Second, the synthesis and analysis of a series of three homologous [alpha],[alpha],[alpha]',[alpha]'-tetramethyl-[subscript 1]-phenylphosphacycles in order to investigate the theory that 4-membered ring phosphacycles - phosphetanes - are maximally biphilic as a result of bond angle compression that minimizes the HOMO-LUMO gap is reported. Analysis of [superscript 31]P NMR principal components validates the decrease in HOMO-LUMO gap as the intra-ring bond angle is compressed in the synthesized series as predicted by TD-DFT computations; however, ¹J[subscript P-Se] coupling constants, cyclic voltammograms and UV-Vis measurements are less conclusive. Computational modeling of the (3+1) cheletropic addition of the phosphacycles to nitrobiphenyl as a measure of the biphilicity reveals relative activation barriers within computational error for all but the smallest ring, indicating that the effect of intra-ring bond angle compression on phosphorus biphilic reactivity is a generally subtle effect. Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, September, 2020; Cataloged from student-submitted PDF of thesis.; Includes bibliographical references.