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Nano-Photonic Platform for Atom-Light Interaction
Get PDFDevelopment of technology can allow access to new regimes in science and creation of new fields of research. The development of ultra-high finesse mirror technology enabled the development of the field of cavity quantum electrodynamics, and an abundance of wonderful physics experiments soon followed. The sophistication of the field of nano-fabrication and nano-photonics would allow unprecedented capability to mold the shape and flow of light, and provide a novel platform for efficient and hopefully integrable quantum systems. In this project, we hope to interface cold atoms, perhaps the most quintessential of quantum systems, to the engineering power of nano-photonics. We believe this field of study will not only lead to the demonstration of new physics in the quantum regime, but work toward building a network with quantum capabilities mediated by optical channels.
In this project, we develop a nano-fabricated platform capable of interfacing nano-photonic devices with cold Cesium atoms in free-space. Nano-photonic waveguide devices are fabricated in a Silicon Nitride device layer on Silicon substrate. The fabrication is compatible with conventional semiconductor fabrication processes, and the chip design has been adapted to allow incorporation with free-space optics to support cold Cesium atom cloud around the waveguides. An ultra-high vacuum system that is compatible to the chip and its supporting structures was constructed to perform experiments.
With our system, we were able to fabricate and characterize nano-photonic structures, including 1D photonic crystal waveguides, cavities, and 2D photonic crystal slabs. For the 1D photonic crystal waveguide devices, enhanced atom-light coupling between localized Cesium atoms in the vicinity of the devices, and also atom-atom interaction between Cesium atoms mediated by the guided mode of the photonic crystal waveguide, has been observed. The 2D photonic devices allow us many capabilities beyond that of the 1D waveguide. Demonstration of exotic optical properties including natural decay rate suppression and circular polarization engineering, should be within reach in the near future.</p
Seasonal and Interannual Variability in South Asian Monsoon Dynamics
Get PDFRecent theoretical advances indicate that the South Asian summer monsoon (SASM) should be viewed as an energetically-direct cross-equatorial Hadley circulation, with the monsoonal precipitation primarily occurring in its ascending branch, rather than its traditional interpretation as a large land-sea breeze circulation. Despite these developments, very few studies have explored the implications of these emerging theories for the observed variability of the SASM.
This is the goal of this PhD thesis, which uses atmospheric reanalysis data from recent decades to investigate seasonal transitions and interannual variability of the SASM. Our approach differs from previous studies in its focus on the large-scale atmospheric dynamics of the SASM: more specifically, we analyze the tropical circulation throughout the SASM sector and its relationship with extratropical weather systems in both hemispheres that can affect transports of momentum and energy.
The atmospheric moisture budget over the SASM region provides a crucial starting point for our work. We use this budget to introduce a novel objective index for the onset and retreat of the SASM, which robustly captures the expected seasonal transitions in precipitation and winds and eliminates the need for arbitrarily selected thresholds. Using this index, we show how the SASM onset and retreat are associated with a coherent set of seasonal transitions in circulation, jet streams, precipitation, energetics, and momentum balance throughout the SASM sector. These transitions closely resemble those of the zonal mean Hadley circulation, indicating that the SASM projects strongly onto the zonal mean and that the observed SASM is consistent with new theoretical interpretations.
We also use the atmospheric moisture budget to define a new index for the SASM strength on interannual time scales. We show that interannual variability in SASM net precipitation is primarily caused by variations in winds rather than variations in humidity, highlighting the importance of understanding drivers of the large-scale circulation and its changes. We then use linear regression analysis to identify robust changes in the circulation associated with SASM year-to-year variability. We find that strong monsoons are associated with a northward expansion of the overturning circulation and a decreased near-surface land-sea thermal contrast, in disagreement with the traditional view of the SASM as a sea-breeze circulation. We also find teleconnections between SASM strength and temperatures, winds, and momentum and energy transports in the southern hemisphere extratropics. These interhemispheric teleconnections, which have not been previously identified, suggest new directions for future research to improve our understanding of the mechanisms involved in SASM variability.
Important advances in modeling and predicting the SASM at all timescales require a deeper understanding of the fundamental processes driving this system. Through theoretically-guided analyses of the SASM observed variability, this dissertation work takes an important step in this direction and provides novel insight into long-standing open questions on the SASM, with crucial implications for its predictability.</p
Structural Study of Piezo Channel, a Unique Family of Eukaryotic Mechanosensitive Channel
Get PDFPiezo is a unique family of eukaryotic mechanosensitive (MS) channel. With over 2500 amino acids per subunit, intact Piezo channel is one of the largest ion channels known to date. Two versions of Piezo can be found in vertebrates, namely PIEZO1 and PIEZO2. PIEZO1 appears to play roles in processes which control physiological homeostasis, whereas PIEZO2 assumes roles in mechanical somatosensation. A number of mutations mapped onto PIEZO1 or PIEZO2 are found in several hereditary human diseases, such as Dehydrated Hereditary Stomatocytosis, Gordon syndrome, and Distal Arthrogryposis. Although biochemical and functional studies provided many insightful findings, structural study of Piezo was very minimal. Herein, I described the structural investigation of Piezo channel. In the first study, we isolated a conserved soluble domain of Piezo (C-terminal loop 2, CTL2) from the C. elegans homolog, and provided the first molecular glimpse into this enigmatic MS channel. Subsequently, I described challenges that are associated with the expression and protein preparation of the full length Piezo channel. Recently, the full length mouse PIEZO1 structure solved by single particle cryo-EM revealed trimeric arrangement of the intact channel. CTL2 domain forms an extracellular cap which makes up the central core in this Piezo model. Lastly, we isolated a stable C-terminal fragment of Piezo. This fragment corresponds to the entire central core of Piezo channel and a few upstream transmembrane helices. This fragment can be localized to the plasma membrane. Further investigation is needed to look at the functionality of this fragment
Dynamics of the Intertropical Convergence Zone
Get PDFPrevious studies have shown that the latitude of the Intertropical Convergence Zone (ITCZ) is negatively correlated with cross-equatorial atmospheric energy transport and that the ITCZ shifts southward as the northern hemisphere cools and the northward cross-equatorial energy transport strengthens. However, it has remained unclear what controls the sensitivity of the ITCZ position to cross-equatorial energy transport, and what other factors may lead to shifts of the ITCZ position. In this thesis, it is shown how an energetic perspective using the vertically-integrated moist static energy balance of the atmosphere can be used to address this question. Climate states with a double-ITCZ around the equator also occur, for example, seasonally over the eastern Pacific, and frequently in climate models. Here it is shown how the ITCZ position is connected to the energy balance near the equator under a wide range of circumstances, including states with single and double ITCZs and using a Taylor expansion of the meridional energy transport around the equator quantitative estimates for the ITCZ location are derived. Simulations with an idealized aquaplanet general circulation model (GCM) confirm the quantitative adequacy of these relations. Using these ideas, an idealized precipitation model for the tropics is presented that is able to capture variations of paleoclimatological precipitation records on orbital time scales. The results provide a framework for assessing and understanding causes of common climate model biases and for interpreting tropical precipitation changes, such as those evident in records of climates of the past
Microfluidics for Molecular Measurements and Quantitative Distributable Diagnostics
Get PDFA major challenge in global health care is a lack of portable and affordable quantitative diagnostic devices. This is because classic quantification of biomolecules is typically performed using kinetic assays that require strict control only found in controlled laboratory environments. By using the power of microfluidics, quantitative assays can be performed robustly in a "digital" format that is decoupled from precise kinetics through highly parallelized qualitative reactions. The benefits of performing quantitative assays in a digital format extend beyond just assay robustness to reduction of instrumental complexity, increase in quantitative precision, and an increase in the amount of information that can be gained from a single experiment. These microfluidic architectures, however, are not limited to usage in scenarios of quantification of biomolecules. These architectures can also potentially be extended to answering complex biological questions in single cells, such as determining the 3-dimensional organization of nuclear DNA and RNA
Insights into the Geologic History of Mars’ Northern Lowlands from Near-Infrared Spectroscopy
Get PDFHydrated minerals, identified on Mars using near-infrared spectroscopy data, reveal new insights into the aqueous processes and evolution of climate in the history of Mars. Through investigations of the mineralogical record using near-infrared spectroscopy, this dissertation focuses on the geologic history and aqueous processes in the northern lowlands of Mars in order to assess the existence of a long-lived global ocean, the extent and volume of Noachian-Hesperian volcanic flows filling the northern lowlands, the nature of aqueous activity in the most recent Amazonian age, and the spectral variability of carbonates. The first chapter reports widespread and diverse mafic and hydrated mineralogy of units associated with impact craters across the northern lowlands. In the lowlands-wide survey, no pervasive carbonate or evaporative salts are found in support of a northern ocean, but we identify widespread phyllosilicates inferred to be Noachian basement materials excavated beneath 1-2 km of mafic lava flows. In the second and third chapters, combined analysis of imagery and spectral data is used to investigate local geologic processes related to liquid water in the knobby terrains of Acidalia and in the vicinity of Lyot crater. Phyllosilicates and hydrated silica are detected in the knobby terrains of Acidalia indicative of a declining prevalence of aqueous alteration through time. We also find diverse mineralogy in the vicinity of Lyot, probably formed in a hydrothermal system and later excavated by the Lyot impact. In contrast, we did not identify mineralization related to local channels that are syn- or post-impact. The fourth study analyzes the spectral properties of unshocked and impact-shocked carbonate rocks on Earth and found similar spectral characteristics between Mars carbonate detections and terrestrial carbonates in impact environments. Using near-infrared spectroscopy, we have identified and characterized the mineralogic record of Mars, and found past environments within the northern lowlands of Mars with varying style and intensity of aqueous alteration through time, with implications for the evolution of Mars climate.</p
Differential Reactivity at Edge and Terrace Sites of Transition Metal Dichalcogenides
Get PDFThis dissertation describes efforts towards understanding the surface reactivity and catalytic properties of a promising class of materials, which have the potential to be integrated as part of a solar-fuels device and help usher-in the solar age. Because of their multifunctional behavior, layered transition metal dichalcogenides are potential candidates for not only light absorption in a solar fuels device, but also as catalysts for the hydrogen evolution reaction.
We begin in chapter one with an introduction related to global energy sources and trends, highlighting the motivation for the work performed in this dissertation. The second chapter describes a discovery into the interplay of pH and morphology for the hydrogen evolution reaction on MoSe2. This discovery suggested a possibility for a different mechanism for the hydrogen evolution reaction being active in acidic and alkaline media. The third chapter describes an exploration into selective small molecule binding to macroscopic edge sites of MoSe2 and WSe2. The fourth chapter is a study of the protective effects of ALD-TiO2 when grown on a variety of MX2’s. The inert nature of terrace sites in MoSe2 and other MX2’s prevented the growth of a conformal thin film of TiO2 but yielded nanoparticles on the surface instead. Finally, in appendix A, I describe the work performed prior to joining the Lewis group relating to the design and synthesis of a binuclear titanium complex that was explored for its ability to copolymerize olefins and enable the incorporation of polar monomers.</p
The Geometry of Moduli Spaces of Maps from Curves
Get PDFA class of moduli spaces that has long been the interest of many algebraic geometers is the class of moduli spaces parametrizing maps from curves to target spaces. Different such moduli spaces have distinct geometry and also invariants associated to them. In this thesis, we will study the geometry of three such moduli spaces. By understanding the global geometry of each moduli space, we will produce a stratification, which plays a central role in proving a result about invariants associated to the space
I: Normal Faulting on the Austroalpine ‘Overthrust’ Constrained by Thermochronometry and Kinematic Analysis, Central Alps, Graubünden Region, Switzerland. II: Clumped Isotope Thermometry of Carbonate Phases Associated with the Copper Deposits of Kennecott, Alaska
Get PDFI. A compilation of 362 cooling ages, including 52 newly reported in this study, from nine thermochronometric systems, 40K/39Ar amphibole, 40K/39Ar white mica, 87Rb/86Sr white mica, 40K/39Ar biotite, 87Rb/86Sr biotite, zircon and apatite fission track, zircon and apatite (U-Th)/He, indicate that the base of the Austroalpine allochthonous ‘orogenic lid’ was not in full thermal equilibrium with its Penninic substrate until at least the middle Oligocene, approximately 29-28 Ma, to allowably as late as the early Miocene, ca. 18 Ma. There is about a factor-of-five difference in cooling rates between the hanging wall (ca. 4°C/m.y.) and footwall (ca. 20°C/m.y.) during this period. In addition, there are demonstrably higher metamorphic grades, including blueschist- and eclogite-facies, in the Pennine footwall compared to lower greenschist-facies in the Austroalpine hanging wall. Together these two facts demonstrate that hot, high-pressure Penninic nappes were forced upward against the cold, low-pressure overriding Austroalpine plate in a very short time window of approximately 7-10 m.y. between the time of peak metamorphism during the Eocene and the time of thermal equilibration with the overriding plate during the Oligo-Miocene. The most likely mechanism to produce such a cold-on-hot juxtaposition is a normal fault, and therefore, we conclude that an important period of nappe emplacement in the Central Swiss Alps occurred concurrently with orogen-perpendicular normal fault motion at the base of the Austroalpine allochthon persisting well into the Oligocene and possibly into the early Miocene, post-dating the 32-30 Ma age of the Bergell intrusion.
Mesoscopic structural measurements made at the top and bottom of the Pennine zone in eastern Switzerland indicate multiple, spatially heterogeneous directions of movement. At the top, in the Oberhalbstein Valley, movement directions vary from dominantly top-east to top-south-southeast a very minor top-north component within Pennine rocks of the Martegnas shear zone and no preferred movement direction within the Austroalpine hanging wall. Near Piz Toissa, a minimum of two kilometers of nearby structural section in the Err and Platta nappes have been faulted out. At the bottom of the Pennine zone in Val Lumnezia and the Chur Rhein Valley at Trimmis, we observe top-northwest, top-north, and top-northeast movements. In Val Lumnezia, the Sub-Penninic Scopi zone (Gotthard cover rocks) shows movement in a top-northwest direction; the superjacent Peidener imbricate fault zone, a relatively thin (ca. 50 to 100 m thick) structural zone consisting of Scopi zone lithologies, shows movement in a northeasterly direction; above that, the basal Penninic Bündnerschiefer shows no dominant movement direction. To the east, in the Chur Rhine Valley, movement is well defined as exclusively top-north. Therefore, movement directions in the lower Bündnerschiefer are broadly top-north but heterogeneous in direction along strike between Val Lumnezia and Chur Rhein Valley, and, as first suggested by Weh and Frotizheim (2001), it may be erroneous to regard the basal Pennine thrust as a simple through-going structure. In Val Lumnezia, the Scopi-Peidener-Pennine nappes resemble a “jelly sandwich” in which the thick Pennine mass utilized the Peidener zone to move in an oblique sinistral-normal slip sense past the southeast-dipping allochthonous Scopi zone and its east-dipping Gotthard “massif” substrate. If the Peidener zone continues northeastward beneath alluvial cover of the Chur Rhein Valley, it may serve as a late, NE-directed shear zone that separates the Pennine nappes from European units. If so, it would explain the apparent truncation and progressive omission of allochthonous elements of European affinity along the zone from southwest to northeast beneath alluvium of the Chur Rhein Valley. We therefore infer that the direct juxtaposition of Penninic units to the east with the Helvetic autochthon to the west at the latitude of Trimmis records an episode of top-northeast, orogen-parallel strike-slip and extensional movement.
Zircon (U-Th)/He (ZHe) cooling ages from the Oberhalbstein Valley indicate that the Austroalpine-Pennine contact was still active at ca. 27 Ma, and that the Martegnas shear zone was active, in part, between ca. 27 and 24 Ma. It is likely that the Piz Toissa klippe formed around this time during the late Oligocene. The pattern of much younger ZHe ages at the bottom of the Pennine zone is independent of any nappe boundaries, including the Peidener imbricate fault zone, but is consistent with the rise of the Aar massif during the Miocene. Tectonic movements, as recorded by the mesostructure in the Austroalpine, Penninic, and Sub-Penninic domains, and local ZHe cooling ages generally support the conclusion drawn strictly from cooling ages that the Pennine zone was emplaced en masse as a coherent ‘piston’ or ‘mega-pip’ during Oligocene to early Miocene time (approximately 29 to 18 Ma), well after juxtaposition of Apulia with cratonic Europe (continent-continent collision) and during the development of Alpine topography and the peripheral basins (viz. Molasse and Lombardi). Additional top-north movement and late uplift and flexure of the nappe stack, along with the Aar massif, occurred primarily in middle to upper Miocene time, following the post-collisional structural interposition of the Pennine zone between Europe and Apulia.
II. Nine carbonate phases at Kennecott, Alaska were measured for their clumped isotope (∆47) equilibration temperatures. The total range for carbonate temperatures spans 38-164°C. Premineral phases are relatively cool (43-71°C); synmineral phases are relatively warm (89-157°C); late postmineral phases are the most cool (38-59°C) but overlap some premineral phases. Zebra dolomite precipitated in the range 130-163°C. Dedolomite, a hallmark alteration feature of the mineralizing fluids, falls into a narrow range of 98-109°C, consistent with the stability field for the low-temperature chalcocite polymorph. Except for one sample, none of the synmineral calcites crystallized within the stability field of djurleite, a volumetrically significant component of the main-stage ore, which suggests that intergrown djurleite may have been a somewhat later recrystallization product of chalcocite rather than a coeval phase.
Calculated compositions for δ18Owater vary from -4.2 to +11.0‰. The most depleted water precipitated hydrothermal baroque dolomite, whereas the most enriched water was associated with recrystallized limestone wallrock on the periphery of the orebody. Waters that precipitated calcite+copper vary from -1.1 to +9.3‰.
Intriguingly, rhythmic layering in zebra dolomite can be resolved in ∆47 space, and preliminary data indicate that the coarser-grained baroque dolomite bands precipitated at temperatures 5-10°C cooler than the surrounding, finer-grained dolomite wall rock bands.
The calculated values of δ18Owater support a genetic model that invokes redox changes associated with fluid mixing as the likely mechanism responsible for copper deposition. In this model a sulfidic, basinal fluid having δ18O similar to seawater mixes with a cuprous fluid having heavier δ18O (5 to 8‰) which was derived from the Nikolai Greenstone during prehnite-pumpellyite-facies metamorphism.</p
Objects of Interpretation in Othello
No full textThe disintegration of female power is central to the progression of Shakespeare’s tragedy Othello . Iago’s rapid ascent and control is facilitated by subjugation of the women in the play. The promise of female power is contained in a seemingly inconsequential wisp of linen, Desdemona’s strawberry-patterned handkerchief. The handkerchief is a tangible symbol of female autonomy, both independently and in marriage. The loss of Desdemona’s handkerchief coincides with a rapid upset of the power dynamic between men and women. This results in the silencing of all three women in the play: Desdemona, Emilia, and Bianca. The most powerful
insults to women are in the form of men assigning interpretations to their bodies, particularly their blood, sweat and tears, ultimately stripping women of their bodily autonomy. A handkerchief’s everyday use is to heal or otherwise contain these physiological substances; thus, the removal of the handkerchief from Desdemona’s possession leaves her vulnerable to Othello’s violence, through misogynistic rhetoric, physical abuse and arbitrary interpretation of her body