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Open Access Dissertations

Theses/Dissertations

2009

Articles 1 - 28 of 28

Full-Text Articles in Physical Sciences and Mathematics

Improved Network Consistency And Connectivity In Mobile And Sensor Systems, Nilanjan Banerjee Sep 2009

Improved Network Consistency And Connectivity In Mobile And Sensor Systems, Nilanjan Banerjee

Open Access Dissertations

Edge networks such as sensor, mobile, and disruption tolerant networks suffer from topological uncertainty and disconnections due to myriad of factors including limited battery capacity on client devices and mobility. Hence, providing reliable, always-on consistency for network applications in such mobile and sensor systems is non-trivial and challenging. However, the problem is of paramount importance given the proliferation of mobile phones, PDAs, laptops, and music players. This thesis identifies two fundamental deterrents to addressing the above problem. First, limited energy on client mobile and sensor devices makes high levels of consistency and availability impossible. Second, unreliable support from the network …

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Climate And Environmental Change In Arctic Canada: Observations From Upper And Lower Murray Lakes, Ellesmere Island, Nunavut, Timothy Cook Sep 2009

Climate And Environmental Change In Arctic Canada: Observations From Upper And Lower Murray Lakes, Ellesmere Island, Nunavut, Timothy Cook

Open Access Dissertations

This study was designed with the overriding goal of improving our understanding of the nature, causes, and impacts of past climatic conditions in the High Arctic and to evaluate the potential impacts of future climatic warming. Specifically, the focus of this project was centered on Upper and Lower Murray Lakes (81° 21’ N, 69° 32’ W) on northern Ellesmere Island, Nunavut, Canada. Sediment cores were collected from each of the lakes in order to reconstruct past climate and environmental variability and space-borne synthetic aperture radar (SAR) data were used to evaluate recent variability in the ice cover of these lakes. …

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The Development Of Hierarchical Knowledge In Robot Systems, Stephen W. Hart Sep 2009

The Development Of Hierarchical Knowledge In Robot Systems, Stephen W. Hart

Open Access Dissertations

This dissertation investigates two complementary ideas in the literature on machine learning and robotics--those of embodiment and intrinsic motivation--to address a unified framework for skill learning and knowledge acquisition. "Embodied" systems make use of structure derived directly from sensory and motor configurations for learning behavior. Intrinsically motivated systems learn by searching for native, hedonic value through interaction with the world. Psychological theories of intrinsic motivation suggest that there exist internal drives favoring open-ended cognitive development and exploration. I argue that intrinsically motivated, embodied systems can learn generalizable skills, acquire control knowledge, and form an epistemological understanding of the world …

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Tailoring The Surface-Coating Of Gold Nanoparticles For Bio-Applications, Partha S. Ghosh Sep 2009

Tailoring The Surface-Coating Of Gold Nanoparticles For Bio-Applications, Partha S. Ghosh

Open Access Dissertations

Functionalized gold nanoparticles (AuNPs) provide an excellent scaffold for numerous biological applications. In these systems, the gold core imparts stability to the assembly, while the monolayer allows tuning of surface characteristics such as charge and hydrophobicity. The nano-scale size and tunable surface properties have made them an ideal candidate for manipulating protein-protein/protein-nucleic acid interactions, and delivery of therapeutics. In this thesis work, it has been demonstrated how the surface coating plays an important role in achieving a desired goal. Using organic synthesis as a tool, the monolayer was tailored to afford useful particles with biocompatibility and the ability to respond …

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Intermolecular Electron Transfer Reactivity And Dynamics Of Cytochrome C – Nanoparticle Adducts, Adrienne M. Carver Sep 2009

Intermolecular Electron Transfer Reactivity And Dynamics Of Cytochrome C – Nanoparticle Adducts, Adrienne M. Carver

Open Access Dissertations

Interprotein electron transfer (ET) is crucial for natural energy conversion and a fundamental reaction in the pursuit of understanding the broader problem of proteinprotein interactions and reactivity. Simplifying the complicated nature of these natural systems has driven development of biomimetic approaches. Functionalized gold nanoparticles offer simplified, tunable surfaces that can serve as a proxy to study the reactivity and dynamics of proteins. Amino-acid functionalized gold nanoparticles (Au-TX) served as a complementary partner to cytochrome c (Cyt c) and catalyzed its ET reactivity without altering the native structure. Redox mediator and EPR experiments confirmed that the redox potential and coordination environment …

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Sensor Control And Scheduling Strategies For Sensor Networks, Victoria U. Manfredi Sep 2009

Sensor Control And Scheduling Strategies For Sensor Networks, Victoria U. Manfredi

Open Access Dissertations

We investigate sensor control and scheduling strategies to most effectively use the limited resources of an ad hoc network or closed-loop sensor network. In this context, we examine the following three problems. Where to focus sensing? Certain types of sensors, such as cameras or radars, are unable to simultaneously collect high fidelity data from all environmental locations, and thus require some sort of sensing strategy. Considering a meteorological radar network, we show that the main benefits of optimizing sensing over expected future states of the environment are when there are multiple small phenomena in the environment. Considering multiple users, we …

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Normal And Extreme Sedimentation And Physical Processes In Lake Tuborg, Ellesmere Island, Nunavut, Edward Lewis Sep 2009

Normal And Extreme Sedimentation And Physical Processes In Lake Tuborg, Ellesmere Island, Nunavut, Edward Lewis

Open Access Dissertations

Lake Tuborg is a large lake on west-central Ellesmere Island, Nunavut. Part of the lake is meromictic, and contains trapped saltwater below about 55 m depth. The lake receives meltwater and sediments from multiple sources, including snowmelt and glacier melt. A lake process study was undertaken from 2001-2003 at Lake Tuborg that involved obtaining profiles of water temperature, salinity, transmissivity, and dissolved oxygen. Networks of short and long sediment cores were also obtained throughout the lake. During the last year of monitoring the lake and its sediments, a large catastrophic drainage of an ice-dammed lake occurred (a jökulhlaup). This was …

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High Temperature Proton Conducting Materials And Fluorescent-Labeled Polymers For Sensor Applications, Surangkhana Martwiset Sep 2009

High Temperature Proton Conducting Materials And Fluorescent-Labeled Polymers For Sensor Applications, Surangkhana Martwiset

Open Access Dissertations

The majority of this dissertation focuses on proton conducting materials that could be used at high operating temperatures. Higher operating temperatures are desirable as they will increase fuel cell efficiency, reduce cost, and simplify the heat management system. The factors governing proton conduction including segmental mobility, protogenic group identity, and charge carrier density were investigated on a variety of polymers containing 1H-1,2,3-triazole moieties. Proton conductivity measurements were made using AC impedance spectroscopy. Random copolymers and terpolymers of triazole-containing acrylates and poly(ethylene glycol)methyl ether acrylate (PEGMEA) have been synthesized. Conductivity increased with increasing degree of PEG incorporation until reaching a maximum …

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Investigation Of Fe(Iii) Reduction In Geobacter Sulfurreducens Characterization Of Outer Surface Associated Electron Transfer Components, Xenlei Qian Sep 2009

Investigation Of Fe(Iii) Reduction In Geobacter Sulfurreducens Characterization Of Outer Surface Associated Electron Transfer Components, Xenlei Qian

Open Access Dissertations

Outer membrane cytochromes OmcB and OmcS of Geobacter sulfurreducens are two important components of the respiratory chain for extracellular Fe(III) reduction. OmcS is a loosely bound cell surface protein involved in the reduction of insoluble Fe(III). OmcB is an outer membrane protein and required for insoluble and soluble Fe(III) reduction. The objective of this study was to understand better the mechanism of dissimilatory Fe(III) reduction, focusing on the cell surface proteins by further localization, identification of protein-protein interactions, and biochemical characterization of OmcB and OmcS. OmcB was found to be surface-exposed but embedded in the outer membrane because mild protease …

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Action-Based Representation Discovery In Markov Decision Processes, Sarah Osentoski Sep 2009

Action-Based Representation Discovery In Markov Decision Processes, Sarah Osentoski

Open Access Dissertations

This dissertation investigates the problem of representation discovery in discrete Markov decision processes, namely how agents can simultaneously learn representation and optimal control. Previous work on function approximation techniques for MDPs largely employed hand-engineered basis functions. In this dissertation, we explore approaches to automatically construct these basis functions and demonstrate that automatically constructed basis functions significantly outperform more traditional, hand-engineered approaches. We specifically examine two problems: how to automatically build representations for action-value functions by explicitly incorporating actions into a representation, and how representations can be automatically constructed by exploiting a pre-specified task hierarchy. We first introduce a technique for …

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More Than One River: Local, Place-Based Knowledge And The Political Ecology Of Restoration And Remediation Along The Lower Neponset River, Massachusetts, Simona Lee Perry Sep 2009

More Than One River: Local, Place-Based Knowledge And The Political Ecology Of Restoration And Remediation Along The Lower Neponset River, Massachusetts, Simona Lee Perry

Open Access Dissertations

This research is an exploration of the local, place-based knowledge surrounding a degraded urban river, the Lower Neponset River and Estuary in southern Boston Harbor, Massachusetts, and its environmental restoration. Through a mixed-methods approach to sociological inquiry that included 18-months of ethnographic interviews and participant observations, Geographic Information System (GIS) mapping, archival document research, and critical environmental history, it explores the different ways local citizens interpret the river as a place of historical importance, personal nostalgia, social and family networks, neighborhood legacies, aesthetics, economic security, danger, psychological refuge, ecology, and political power. Using an interpretive analysis of the narrative, visual, …

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Wrinkling, Folding, And Snapping Instabilities In Polymer Films, Douglas Peter Holmes Sep 2009

Wrinkling, Folding, And Snapping Instabilities In Polymer Films, Douglas Peter Holmes

Open Access Dissertations

This work focuses on understanding deformation mechanisms and responsiveness associated with the wrinkling, folding, and snapping of thin polymer films. We demonstrated the use of elastic instabilities in confined regimes, such as the crumpling and snapping of surface attached sheets. We gained fundamental insight into a thin film's ability to localize strain. By taking advantage of geometric strain localization we were able to develop new strategies for responsive surfaces that will have a broad impact on adhesive, optical, and patterning applications. Using the rapid closure of the Venus flytrap's leafets as dictated by the onset of a snap instability as …

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On The Discrete Differential Geometry Of Surfaces In S4, George Shapiro Sep 2009

On The Discrete Differential Geometry Of Surfaces In S4, George Shapiro

Open Access Dissertations

The Grassmannian space GC(2, 4) embedded in CP5 as the Klein quadric of twistor theory has a natural interpretation in terms of the geometry of “round” 2-spheres in S4. The incidence of two lines in CP3 corresponds to the contact properties of two 2- spheres, where contact is generalized from tangency to include “half-tangency:” 2-spheres may be in contact at two isolated points. There is a connection between the contact properties of 2-spheres and soliton geometry through the classical Ribaucour and Darboux transformations. The transformation theory of surfaces in S4 is investigated using the recently developed theory of “Discrete Differential …

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Galactic Bulge Feedback And Its Impact On Galaxy Evolution, Shikui Tang Sep 2009

Galactic Bulge Feedback And Its Impact On Galaxy Evolution, Shikui Tang

Open Access Dissertations

Galactic bulges of early-type spirals and elliptical galaxies comprise primarily old stars, which account for more than half of the total stellar mass in the local Universe. These stars collectively generate a long-lasting feedback via stellar mass loss and Type Ia supernovae. According to the empirical stellar mass loss and supernova rates, the stellar ejecta can be heated to more than 107 K, forming a very hot, diffuse, and ironrich interstellar medium. Conventionally a strong galactic wind is expected, especially in low- and intermediate-mass early-type galaxies which have a relatively shallow potential well. X-ray observations, however, have revealed that both …

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Semantic Methods For Intelligent Distributed Design Environments, Paul W. Witherell Sep 2009

Semantic Methods For Intelligent Distributed Design Environments, Paul W. Witherell

Open Access Dissertations

Continuous advancements in technology have led to increasingly comprehensive and distributed product development processes while in pursuit of improved products at reduced costs. Information associated with these products is ever changing, and structured frameworks have become integral to managing such fluid information. Ontologies and the Semantic Web have emerged as key alternatives for capturing product knowledge in both a human-readable and computable manner. The primary and conclusive focus of this research is to characterize relationships formed within methodically developed distributed design knowledge frameworks to ultimately provide a pervasive real-time awareness in distributed design processes. Utilizing formal logics in the form …

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Single Molecule Chiroptical Spectroscopy: Fluorescence Excitation Circular Dichroism And Circular Polarized Luminescence Of Bridged Triarylamine Helicenes, Ruthanne Hassey Paradise Sep 2009

Single Molecule Chiroptical Spectroscopy: Fluorescence Excitation Circular Dichroism And Circular Polarized Luminescence Of Bridged Triarylamine Helicenes, Ruthanne Hassey Paradise

Open Access Dissertations

In this thesis, I describe the first exploratory experimental efforts probing light-matter interactions of chiral systems at the single molecule level. The dissymmetric single molecule chiroptical response in both excitation and emission polarization has been studied for different diastereomeric forms of bridged triarylamine helicenes. Fluorescence excitation circular dichroism (FECD), measuring the dissymmetric absorption with respect to excitation polarization, reports on the response to excitation polarization. The magnitude and distribution of chiroptical single molecule responses suggest both surface and orientation effects play a significant role. Computational modeling done to calculate the dissymmetry for specific orientations supports orientational dependence. Using a defocused …

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Developing Novel Electrospray Ionization Mass Spectrometry (Esi Ms) Techniques To Study Higher Order Structure And Interaction Of Biopolymers, Agya K. Frimpong Sep 2009

Developing Novel Electrospray Ionization Mass Spectrometry (Esi Ms) Techniques To Study Higher Order Structure And Interaction Of Biopolymers, Agya K. Frimpong

Open Access Dissertations

Mass spectrometry has enjoyed enormous popularity over the years for studying biological systems. The theme of this dissertation was to develop and use mass spectrometry based tools to solve five biologically oriented problems associated with protein architecture and extend the utility of these tools to study protein polymer conjugation. The first problem involved elucidating the false negatives of how proteins with few basic residues, forms highly charged ions in electrospray ionization mass spectrometry (ESI MS). This study showed that the unfolding of polypeptide chains in solution leads to the emergence of highly charged protein ions in ESI MS mass spectra, …

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Resource Management In Complex And Dynamic Environments, Mohammad Salimullah Raunak Sep 2009

Resource Management In Complex And Dynamic Environments, Mohammad Salimullah Raunak

Open Access Dissertations

Resource management is at the heart of many diverse science and engineering research areas. Although the general notion of what constitutes a resource entity seems similar in different research areas, their types, characteristics, and constraints governing their behavior are vastly different depending on the particular domain of research and the nature of the research itself. Often research related to resource modeling and management focus on largely homogeneous resources in a relatively simplified model of the real world. The problem becomes much more challenging to deal with when working with a complex real life domain with many heterogeneous resource types and …

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A Frequency Selective Bolometer Camera For Measuring Millimeter Spectral Energy Distributions, Daniel William Logan May 2009

A Frequency Selective Bolometer Camera For Measuring Millimeter Spectral Energy Distributions, Daniel William Logan

Open Access Dissertations

Bolometers are the most sensitive detectors for measuring millimeter and submillimeter wavelength astrophysical signals. Cameras comprised of arrays of bolometers have already made significant contributions to the field of astronomy. A challenge for bolometer cameras is obtaining observations at multiple wavelengths. Traditionally, observing in multiple bands requires a partial disassembly of the instrument to replace bandpass filters, a task which prevents immediate spectral interrogation of a source. More complex cameras have been constructed to observe in several bands using beam splitters and dichroic filters, but the added complexity leads to physically larger instruments with reduced efficiencies. The SPEctral Energy Distribution …

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Engineering The Nanoparticle Surface For Protein Recognition And Applications, Mrinmoy De May 2009

Engineering The Nanoparticle Surface For Protein Recognition And Applications, Mrinmoy De

Open Access Dissertations

Proteins and nanoparticles (NPs) provide a promising platform for supramolecular interaction. We are currently exploring both fundamental and applied aspects of this interaction. On the fundamental side, we have fabricated a series of water-soluble anionic and cationic NPs to interact with cationic and anionic proteins respectively. A Varity of studies such as, activity assay, fluorescence titration, isothermal titration calorimetry etc. were carried out to quantify the binding properties of these functional NPs with those proteins. Those studies reveal the prospect of tuning the affinity between the nanoparticles and proteins by the surface modification. On the application side, we have used …

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Class Numbers Of Ray Class Fields Of Imaginary Quadratic Fields, Omer Kucuksakalli May 2009

Class Numbers Of Ray Class Fields Of Imaginary Quadratic Fields, Omer Kucuksakalli

Open Access Dissertations

Let K be an imaginary quadratic field with class number one and let [Special characters omitted.] be a degree one prime ideal of norm p not dividing 6 d K . In this thesis we generalize an algorithm of Schoof to compute the class number of ray class fields [Special characters omitted.] heuristically. We achieve this by using elliptic units analytically constructed by Stark and the Galois action on them given by Shimura's reciprocity law. We have discovered a very interesting phenomena where p divides the class number of [Special characters omitted.] . This is a counterexample to the elliptic …

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Correction Methods, Approximate Biases, And Inference For Misclassified Data, Meng-Shiou Shieh May 2009

Correction Methods, Approximate Biases, And Inference For Misclassified Data, Meng-Shiou Shieh

Open Access Dissertations

When categorical data are misplaced into the wrong category, we say the data is affected by misclassification. This is common for data collection. It is well-known that naive estimators of category probabilities and coefficients for regression that ignore misclassification can be biased. In this dissertation, we develop methods to provide improved estimators and confidence intervals for a proportion when only a misclassified proxy is observed, and provide improved estimators and confidence intervals for regression coefficients when only misclassified covariates are observed. Following the introduction and literature review, we develop two estimators for a proportion , one which reduces the bias, …

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The Aztec Millimeter-Wave Camera: Design, Integration, Performance, And The Characterization Of The (Sub-)Millimeter Galaxy Population, Jason Edward Austermann May 2009

The Aztec Millimeter-Wave Camera: Design, Integration, Performance, And The Characterization Of The (Sub-)Millimeter Galaxy Population, Jason Edward Austermann

Open Access Dissertations

One of the primary drivers in the development of large format millimeter detector arrays is the study of sub-millimeter galaxies (SMGs) - a population of very luminous high-redshift dust-obscured starbursts that are widely believed to be the dominant contributor to the Far-Infrared Background (FIB). The characterization of such a population requires the ability to map large patches of the (sub-)millimeter sky to high sensitivity within a feasible amount of time. I present this dissertation on the design, integration, and characterization of the 144-pixel AzTEC millimeter-wave camera and its application to the study of the sub-millimeter galaxy population. In particular, I …

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Operating System Support For Modern Applications, Ting Yang May 2009

Operating System Support For Modern Applications, Ting Yang

Open Access Dissertations

Computer systems now run drastically different workloads than they did two decades ago. The enormous advances in hardware power, such as processor speed, memory and storage capacity, and network bandwidth, enable them to run new kinds as well as a large number of applications simultaneously. Software technologies, such as garbage collection and multi-threading, also reshape applications and their behaviors, introducing more challenges to system resource management. However, existing general-purpose operating systems do not provide adequate support for these modern applications. These operating systems were designed over two decades ago, when garbage-collected applications were not prevalent and users interacted with systems …

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The Conformational Gymnastics Of The Escherichia Coli Seca Molecular Machine And Its Interactions With Signal Sequences, Jenny Lynn Maki May 2009

The Conformational Gymnastics Of The Escherichia Coli Seca Molecular Machine And Its Interactions With Signal Sequences, Jenny Lynn Maki

Open Access Dissertations

Protein secretion is a selective and regulated process that is essential in all organisms. In bacteria the preprotein translocase SecA, either free in the cytosol or associated with the SecYEG translocon, recognizes and binds most post-translational secretory proteins containing an N-terminal signal sequence. In Gram-negative bacteria, the molecular chaperone SecB binds many of the preproteins to keep them in a translocation-competent state. Subsequently, SecB delivers the preproteins to the translocon-associated SecA, which binds the signal sequence and also interacts with mature regions of the preprotein. After the preprotein/SecA/SecYEG complex has formed, the energy derived from ATP hydrolysis by SecA coupled …

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Numerical Modeling Of Fracturing In Non-Cylindrical Folds: Case Studies In Fracture Prediction Using Structural Restoration, John Ryan Shackleton May 2009

Numerical Modeling Of Fracturing In Non-Cylindrical Folds: Case Studies In Fracture Prediction Using Structural Restoration, John Ryan Shackleton

Open Access Dissertations

This thesis contains several distinct studies aimed at better understanding fracturing in compressional fault-cored folds. At outcrops of growth strata in the Oliana anticline in the Spanish Pyrenees, the relationship of two joint sets may reflect changing mechanical properties (i.e. via diagenesis) during the folding process. Using a Schmidt hammer, I assess the rigidity contrast between the individual units and suggest that late-stage, throughgoing joints formed in strata with conditions similar to those of the present day and that early, bed-contained joints formed when the rigidity contrast between beds was significantly greater than the present day contrast. Modeling algorithms that …

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Structured Topic Models: Jointly Modeling Words And Their Accompanying Modalities, Xuerui Wang May 2009

Structured Topic Models: Jointly Modeling Words And Their Accompanying Modalities, Xuerui Wang

Open Access Dissertations

The abundance of data in the information age poses an immense challenge for us: how to perform large-scale inference to understand and utilize this overwhelming amount of information. Such techniques are of tremendous intellectual significance and practical impact. As part of this grand challenge, the goal of my Ph.D. thesis is to develop effective and efficient statistical topic models for massive text collections by incorporating extra information from other modalities in addition to the text itself. Text documents are not just text, and different kinds of additional information are naturally interleaved with text. Most previous work, however, pays attention to …

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The Role Of Stellar Feedback In Galaxy Evolution, Li Zhiyuan Feb 2009

The Role Of Stellar Feedback In Galaxy Evolution, Li Zhiyuan

Open Access Dissertations

Aiming at understanding the role of stellar feedback in galaxy evolution, I present a study of the hot interstellar medium in several representative galaxies, based primarily on X-ray observations as well as theoretical modelling. I find that, in the massive disk galaxies NGC2613 and M104, the observed amount of hot gas is much less than that predicted by current galaxy formation models. Such a discrepancy suggests a lack of appropriate treatments of stellar/AGN feedback in these models. I also find that stellar feedback, primarily in the form of mass loss from evolved stars and energy released from supernovae, and presumably …

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