VictorJuiz/thesis huggingface dataset:
Nanoscale and ultrafast imaging of magnetic materials with resonant soft X-rays [electronic resource]
Keywords: Materials Science and Engineering.

Magnetic materials are of interest in a wide range of nanotechnologies including those for data storage, memory, logic, and sensing applications. In addition to going smaller for miniaturization and higher densities, there is also interest in exploring faster processes and pathways to manipulate magnetism. These naturally lead to motivations in studying nanoscale and ultrafast magnetism. Resonant soft x-ray scattering and imaging are unique techniques that can combine nanometer spatial resolution and femtosecond time resolution in the study of magnetic materials. In this dissertation, I will first motivate the need for nanoscale and ultrafast studies on magnetic materials. I will then introduce the attractive properties of soft x-rays, and illustrate the critical concepts in resonant x-ray magnetic scattering and holographic imaging. The three subsequent experiments presented here utilize resonant soft x-rays to image and study magnetic materials. The first experiment demonstrates the use of resonant x-ray scattering in the study of perpendicular magnetic recording media used in hard disk drives. Statistical information on the nanoscale granular and magnetic periodicity of the media can be revealed simultaneously, and we study how various materials parameters are used to optimize the properties of past and current media generations. While scattering provides statistically averaged information, the ability to visualize individual structures is desired. Fourier transform holography is a high resolution and ultrafast-compatible microscopy technique that excels in this role. In the second experiment, I will present our imaging results on all optical magnetic switching, a phenomenon in which magnetic domains of ferrimagnetic alloys are switched with individual, femtosecond laser pulses. Using integrated Au plasmonic dipole antennas to define switching spots, we successfully switched 40 nm-sized magnetic domains in a TbFeCo alloy and prove that all optical magnetic switching is a promising candidate for future information storage technologies. Finally, going into the ultrafast regime, holographic imaging can be combined with x-ray free electron lasers to produce single shot, time-resolved magnetic images. In the last part of this dissertation, I will show the first single shot images of ferromagnetic domain patterns in Co/Pd multilayers taken with 80 fs long x-ray pulses. Despite high x-ray fluences, one can outrun x-ray induced damage effects with short enough pulses. Single shot imaging used in a pump-probe approach can potentially generate stroboscopic movies of magnetization dynamics. The unique combination of nanoscale and ultrafast imaging highlights the versatility and power of resonant soft x-rays in the study of magnetism. The use of such techniques will open up many possibilities for time-resolved studies of magnetic nanostructures and relevant dynamic phenomenon.
Nanoscale transverse Fabry-Perot resonators [electronic resource]
Keywords: Electrical Engineering.

The ability to fabricate multiple resonant photodetectors, each with separately engineered wavelength sensitivity, in a single-step process has many potential applications. In this dissertation, we propose and demonstrate the use of nanoscale semiconductor fin structures surrounded by metal as efficient transverse Fabry-Perot resonators which allow one to efficiently excite in-plane resonances under surface-normal incidence. We show that these devices support strong absorption resonances that can be tuned by varying the width of the structure and use this effect to engineer devices for two potential application areas. In the first part of the dissertation, we show how we can engineer nanoscale planar multispectral image sensors based on silicon fins surrounded by metallic slits wherein the resonant wavelength of each pixel is determined by the width of the silicon fin. The same metallic structure is used for both light confinement and carrier extraction in a compact metal-semiconductor-metal (MSM) geometry. We experimentally study how close we can put two of these pixels together and how small we can make an individual pixel. We show that, in principle if the electrical properties of the devices are suitably controlled, one can engineer devices with pixel pitch down to 250 nm and pixel sizes down to 500 nm by 500 nm. In the second part of the dissertation, we use this effect to enhance the indirect absorption in germanium and engineer CMOS-compatible germanium photodetectors with high responsivity across the telecommunications bands (both C and L bands). Finally, we show that this effect can be used to engineer passive devices like novel resonant waveguide couplers that can be used to couple light efficiently from free space to both dielectric and plasmonic slot waveguides with slot widths ~ 50 nm.
Nanosecond pulsed plasma-assisted combustion [electronic resource]
Keywords: Mechanical Engineering.

In this study, the use of non-equilibrium plasmas is examined as possible methods of active control of combustion. The plasmas investigated here include nanosecond-pulsed repetitive discharges as well as nanosecond-pulsed laser-produced breakdowns. These sources are used to stabilize both premixed and jet-diffusion flames of various fuel types. The use of nanosecond-pulsed repetitive discharges to stabilize lean premixed fuel-air mixtures is found to extend the equivalence ratio for complete combustion to lower values, in some cases, below the so-called lean flammability limits. This extension depends strongly on the pulse repetition frequency or average discharge power. Simulations reveal that a significant production of radicals associated with gas heating is responsible for flame stabilization and this is attributed mainly to a dissociative quenching of electronically excited species by molecular oxygen. In jet diffusion flames, anchoring of the flame-base is best when the discharge plasma is positioned where the local equivalence ratio is between 0.8 and 1.9. Lastly, the discharge plasma source is replaced by laser-induced breakdowns. Two successive laser pulses with a variable time delay are employed to mimic repetitive breakdowns expected from a future high frequency laser source of sufficient power. From studies first carried out in pure air, it is found that the first laser breakdown causes a temporal region virtually transparent to the subsequent laser pulse during the interval from 100 ns to 60 µs. This is attributed to heating by the plasma, reducing the density below threshold levels needed for absorption of a laser pulse. In premixed fuel-air mixtures, the first breakdown induces a second region of transparency during the interval from 100 µs to 2 ms after the pulse due to the heat released by combustion. These findings limit the laser repetition rate to a maximum of 500 Hz when the equivalence ratio is 1. Time-resolved imaging of CH* chemiluminescence reveals flame front merging confirming that flame stabilization can be achieved at these moderate laser repetition rates.
Nanostructures in III-V solar cells [electronic resource]
Keywords: Physics.

From the physics and materials viewpoint, III-V materials are ideal for highly efficient photovoltaic conversion. Their major limitations are cost and resource availability. As industrial planar III-V solar cells continue to set the all-time efficiency records, nanostructured III-V solar cells are now being investigated in academia with the goal to further improve the efficiency and lower the required materials volume and cost. However, most previously investigated nano-structured solar cells suffer from low efficiencies. In this dissertation, I first present optical enhancement in nanopyramid III-V ultra-thin films which can potentially reduce the required materials by one order of magnitude. I then demonstrate significant efficiency improvement in GaAs solar cell. Especially, with an AlGaAs nanocone window layer, a 17%-efficiency nanostructured single-junction solar cell is obtained. The first part of my dissertation focuses on optical engineering and absorption improvement in nanopyramid GaAs ultra-thin film. I demonstrate a double-sided nanopyramid GaAs film that is only 160 nm thick, laminated in a flexible transparent superstrate. Without additional antireflection coatings, this nanopyramid film absorbs over 80% more photons than a planar counterpart with equal thickness at normal incidence and is equivalent to a 1um thick film. At large incident angles, this enhancement can be even greater. With similar light trapping design, III-V solar cell film thickness can be potentially reduced from 3-4 um to 200-300 nm, which could significantly reduce III-V cell cost. The second part of my dissertation focuses on efficiency improvement in III-V nanostructured solar cells. First, GaAs solar cell efficiency enhancement using ZnO nanoparticle antireflection coating is briefly demonstrated. I then demonstrate our work on nanostructured p-n junction solar cells and discuss the challenges for nanostructured solar cell. After this, I propose a nanowindow solar cell design that can overcome these challenges by enhancing both optical and electrical properties. A nanowindow solar cell using a nanocone AlGaAs window layer, a GaAs junction and mesa grid contact is demonstrated with a high energy conversion efficiency of 17.0% and high open circuit voltage of 0.982 V.
Narrative ambition [electronic resource] : Victorian self-help and competition
Keywords: English.

This dissertation investigates the Victorian narrative of ambition across its two key genres, the novel and the self-help text. The term and the genre of "self-help" were invented in the nineteenth century, with Thomas Carlyle coining the term in Sartor Resartus (1834), and Samuel Smiles preaching its importance in his 1859 Self-Help, which collected and condensed the biographies of great men in order to illustrate the importance of hard work, perseverance, and energy. Whereas Smiles's brief, condensed biographies focus on the individual, in the novel, the self-help plot expands to explore the dangers of excessive ambition in a competitive and hierarchical society. I suggest that the Victorian narrative of ambition divided into two paths, and whereas Smiles's self-help ethos focuses on the individual's ambition--with each person rising "very much according to his deserts"--the novel takes on the wider social context of ambition, as many ambitious self-helping characters compete, crowding a fictional world that, as one of Anthony Trollope's characters laments, "will soon be like a fishpond, very full of fish, but with very little food for them." Across chapters focusing on Smiles's Self-Help, Dinah Mulock Craik's John Halifax, Gentleman, Charles Dickens's Our Mutual Friend, William Makepeace Thackeray's The Luck of Barry Lyndon and Vanity Fair, and Anthony Trollope's The Three Clerks and An Autobiography, I argue that these Victorian authors used varying narrative strategies to dramatize ambition. Smiles's Self-Help repeats the same story of successful ambition across hundreds of examples, seeming to replicate in its form the perseverance of the characters. But whereas Smiles uses these stories to praise ambitious work, the Victorian novel explores the consequences of ambition--both within the story, as the ambitious subject seeks to displace others in the process of "getting ahead, " and in the telling, as narrators exaggerate, satirize, and judge the ambitions of the novel's characters. Ultimately, this dissertation argues that dramatizing ambition has both formal and stylistic consequences on the Victorian novel.
Navigating variability in the linguistic signal [electronic resource] : learning to interpret contrastive prosody
Keywords: Linguistics.

Prosody is a powerful tool for conveying information beyond that conveyed in the words and phrases constituting a sentence (e.g., nuclear accenting of contrasted items: YOU shouldn't have done that vs. You shouldn't have done THAT). Past studies have proposed links between prosodic representations (pitch accents and intonations in particular) and the semantics and pragmatics of sentences. However, no study has explicitly accounted for how listeners navigate variability across speakers and contexts in order to arrive at intended interpretations. In addition, there is a puzzle in the literature of acquisition of prosody. Preschoolers show difficulties in pragmatic interpretations of prosodic contours even though they can use the same contours in their own production. In this dissertation, I first propose a psycholinguistic approach to the comprehension of prosody in adults. Specifically, I investigate English speakers' pragmatic interpretations of contrastive prosody through large-scale judgment surveys and an eye-tracking experiment. Drawing on insights from recent work on phonetic categorization and adaptation, I demonstrate that the prosodic comprehension goes beyond categorical mappings between acoustic properties of speech and prosodic representations. The process is best represented as inferences about how a particular speaker employs prosody, as well as other linguistic devices, to convey intended meanings. I then report three behavioral experiments with four-year-olds. The results suggest that preschoolers can engage in prosody-based pragmatic inferences if the context provides sufficient support for them. Furthermore, I find that preschoolers' interpretation of prosody involves principled pragmatic inferencing (what would the speaker have said if she had intended another meaning?), proposed for early word learning. The picture emerging from the current experiments contrasts with previous work: Through rich contextual inferences, four-year olds are able to bootstrap their interpretation of prosodic information. The main finding of the present dissertation is that listeners flexibly adjust their interpretations of prosodic contours by integrating high-level contextual expectations and low-level distributional information in the acoustic signal. Ultimately, the current discussion highlights the importance of approaching prosodic comprehension as a dynamic and adaptive process. Listeners — adults and children alike — constantly evaluate linguistic signals against underlying representations, and the outcomes of the evaluation are used to optimize the representations to best represent the current input. Thus the present study constitutes part of a larger inquiry in the psychology of language comprehension: How do listeners learn and maintain flexible mappings between variable linguistic signals and abstract and stable representations?.
The negative feelings that people want to avoid [electronic resource] : cultural differences and consequences for compassion
Keywords: Psychology.

Previous research has documented cultural differences in the positive states that people desire. Less research, however, has examined whether cultural differences exist in the negative states that people want to avoid feeling ("avoided negative affect"). Using a multimethod approach, we examined cultural differences between Americans and Germans in avoided negative affect and whether they are related to different responses to suffering, or compassion. In Study 1, using survey methods, we assessed whether avoided negative affect differs from related constructs, and based on an existing literature, tested our hypothesis that Americans want to avoid negative affect more than do Germans. As predicted, avoided negative affect is distinct from actual negative affect (the negative states people actually feel) and from ideal negative affect (the negative states people ideally want to feel) and European Americans wanted to avoid negative states more than did Germans. In Study 2, we compared the emotional content of American and German sympathy cards to examine cultural differences in responses to suffering. As predicted, American cards contained more positive and less negative content than did German cards. In Study 3, using survey methods, we examined whether cultural differences in responses to suffering were due to cultural differences in avoided negative affect. As predicted, Americans felt less comfortable sending sympathy cards that contained primarily negative content (e.g., "words will not lighten a heavy heart") than did Germans, and these differences were mediated by cultural differences in avoided negative affect. Finally, in a series of experiments, American and German participants were randomly assigned to either "avoid negative affect" or "approach negative affect" conditions. Overall, participants in the "avoid negative affect" conditions preferred sympathy cards with negative content less than those in the "approach negative affect" conditions. These findings suggest that differences in avoided negative affect at least partially drive different responses to suffering (i.e., compassion).
Negotiating Identities: Gay Catholic Men
Keywords: gay
Catholic
church
identity
male
qualitative
interviews
ethnography
religion
Stanford University Program in Feminist Gender and Sexuality Studies
Thesis

Abstract from thesis:
While original research on identity formation located human identity growth and change in discrete (and usually early) stages, contemporary research considers human identity as growing and evolving identity throughout the life cycle. A secondary limitation of earlier research is the narrow population sample. My research uses contemporary theories of identity formation to understand an under-researched (or research-ignored) group: gay Catholic men. Identifying a group of men with two potentially competing identify factors, I ask the research question(s): What common themes exist among gay Catholic men when negotiating their identities? Specifically, what are the common themes for men located in a major US urban center? To answer this question, in 2011 I conducted an exploratory qualitative study of identity formation among 10 gay Catholic men, ages 24 to 68, in the greater New York City area, to illuminate common themes among each participant’s identity formation.
Participants of diverse backgrounds were recruited from DignityUSA for ethnographic interviews averaging one hour in length. Grounded theory practices and deductive analysis were used in this exploratory study. Findings suggest three common themes of identity negotiation and understanding centered on coming out, the institutional and pastoral Church, and acceptance within the family. These themes bring insight to challenges the participants faced when combining two distinct identities.
This is an interdisciplinary Honor Thesis in Feminist Studies and Human Biology.
Neuronal L-type calcium channels are regulated by FMR1 and SPOPL [electronic resource]
Keywords: Chemical and Systems Biology.

Voltage-gated calcium channels (VGCCs) regulate cellular excitability, differentiation and connectivity. The L-type Ca2+ channel (LTC) CaV1.2 is the most abundant VGCC in the brain, and mis-regulation of LTCs has been linked to bipolar disorder, schizophrenia and autism spectrum disorders. However, how LTC activity is regulated in vivo is incompletely understood. Here we describe a new approach using a high throughput genome-wide screen in Drosophila to identify modulators of CaV1.2 activity. This screen uncovered two novel CaV1.2 regulating proteins, Fragile X Mental Retardation 1 (FMR1) and Speckle-type POZ protein-like (SPOPL). Using biochemistry, calcium-imaging, and electrophysiology in mammalian neurons, we show that FMR1 binds directly to CaV1.2 and regulates its surface expression, while SPOPL alters ubiquitination and electrical properties of the channel. These results reveal new regulatory pathways controlling CaV1.2 activity, and describe a generalizable approach to identifying modulators of LTC function in vivo.
Neutron star powered nebulae [electronic resource] : a new view on pulsar wind nebulae with the Fermi Gamma-ray space telescope
Keywords: Physics.

Pulsars are rapidly-rotating neutron stars born out of the death of stars. A diffuse nebula is formed when particles stream from these neutron stars and interact with the ambient medium. These pulsar wind nebulae (PWNe) are visible across the electromagnetic spectrum, producing some of the most brilliant objects ever observed. The launch of the Fermi Gamma-ray Space Telescope in 2008 has offered us an unprecedented view of the cosmic gamma-ray sky. Using data from the Large Area Telescope on board Fermi, we search for new gamma-ray-emitting PWN. With these new observations, we vastly expand the number of PWN observed at these energies. We interpret the observed gamma-ray emission from these PWN in terms of a model where accelerated electrons produce gamma-rays through inverse Compton upscattering when they interact with interstellar photon fields. We conclude by studying how the observed PWN evolve with the age and spin-down power of the host pulsar.
New rounding techniques for the design and analysis of approximation algorithms [electronic resource]
Keywords: Management Science and Engineering.

We study two of the most central classical optimization problems, namely the Traveling Salesman problems and Graph Partitioning problems and develop new approximation algorithms for them. We introduce several new techniques for rounding a fractional solution of a continuous relaxation of these problems into near optimal integral solutions. The two most notable of those are the maximum entropy rounding by sampling method and a novel use of higher eigenvectors of graphs.
On Nietzsche's historical philosophy [electronic resource]
Keywords: Philosophy.

This dissertation takes up the question of exactly why Nietzsche insisted, as he so often did in his writings, that philosophical enquiry needs to be conducted historically, an insistence that shaped Nietzsche's own turn towards the method of genealogy in his later works. The answer proposed is that in Nietzsche's view, some of our most important philosophical concepts (such as the concept of 'good') have undergone radical changes in meaning over the course of history, and yet, the past meanings of these concepts, rather than having been entirely overwritten by their present meanings, continue to have some residual semantic presence in them today. Consequently, our philosophical attempts to understand these concepts today necessarily require that we pay serious attention to their histories, which is why Nietzsche thought that our philosophical enquiries have to be conducted historically. This is the answer developed in this dissertation through an in-depth study of Nietzsche's theory of conceptual change over history, and an analysis of the practical consequences this theory of conceptual change might have for us today.