• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 214
  • 72
  • 54
  • 38
  • 15
  • 13
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 6
  • 5
  • Tagged with
  • 575
  • 83
  • 76
  • 62
  • 62
  • 54
  • 50
  • 47
  • 46
  • 45
  • 43
  • 43
  • 39
  • 35
  • 32
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
331

Experimental Study of Barium Strontium Titanate High-k Gate Dielectric on Beta Gallium Oxide Semiconductor

Miesle, Adam 15 May 2023 (has links)
No description available.
332

The strontium molecular lattice clock: Vibrational spectroscopy with hertz-level accuracy

Leung, Kon H. January 2023 (has links)
The immaculate control of atoms and molecules with light is the defining trait of modern experiments in ultracold physics. The rich internal degrees of freedom afforded by molecules enrich the toolbox of precision spectroscopy for fundamental physics, and hold great promise for applications in quantum simulation and quantum information science. A vibrational molecular lattice clock with systematic fractional uncertainty at the 14th decimal place is demonstrated for the first time, matching the performance of the earliest optical atomic clocks. Van der Waals dimers of strontium are created at ultracold temperatures and levitated by an optical standing wave, whose wavelength is finely tuned to preserve the delicate molecular vibrational coherence. Guided by quantum chemistry theory refined by highly accurate frequency-comb-assisted laser spectroscopy, record-long Rabi oscillations were demonstrated between vibrational molecular states that span the entire depth of the ground molecular potential. Enabled by the narrow molecular clock linewidth, hertz-level frequency shifts were resolved, facilitating the first characterization of molecular hyperpolarizability in this context. In a parallel effort, deeply bound strontium dimers are coherently created using the technique of stimulated Raman adiabatic passage. Ultracold collisions of alkaline-earth metal molecules in the absolute ground state are studied for the first time, revealing inelastic losses at the universal rate. This thesis reports one of the most accurate measurement of a molecule's vibrational transition frequency to date, which may potentially serve as a secondary representation of the SI unit of time in the terahertz (THz) band where standards are scarce. The prototypical molecular clock lays the important groundwork for future explorations into THz metrology, quantum chemistry, and fundamental interactions at atomic length scales.
333

Air Quality Impacts from Mineral Dust, Fireworks, and Urban Pollution Revealed by Trace Element Chemistry and Strontium Isotopes Ratios in the Wasatch Front, Utah, USA

Marcy, Micah J. 15 August 2022 (has links)
Airborne particulate matter (PM) in urban areas is derived from a combination of natural and anthropogenic sources. To identify PM sources and their effects on air quality, we collected PM using active filter samplers over a two-year period in the urban Wasatch Front, northern Utah, an area affected by multiple pollution sources. Filters from active samplers and other PM samples were analyzed for major and trace element concentrations and 87Sr/86Sr ratios. We identified wind-blown mineral dust from dry lake beds, winter inversions, and fireworks as primary PM sources affecting air quality in the Wasatch Front. Dust contributes Al, Be, Ca, Co, Cs, Fe, Li, Mg, Mn, Rb, Th, U, Y, and REEs which are typical components of carbonate and silicate minerals. Winter inversions entrap As, Cd, Mo, Pb, Sb, Tl, and Zn from brake dust, combustion engine exhaust, and refining processes. Concentrations of common components of fireworks Ba, Cu, K, and Sr greatly increase (>4 times) during holidays. Strontium released from fireworks has a distinct 87Sr/86Sr ratio that dominates the isotopic composition of PM during holidays. Fireworks have 87Sr/86Sr ratios of <0.7080 compared with 0.7100 for Sevier Dry Lake and 0.7150 for Great Salt Lake lakebed. Sources of particulate matter vary seasonally. Dust events dominate the air quality signature during spring and summer while winter inversions occur from November through February. Transport of PM to mountain snowpack negatively affect water quality. This is the first study to describe variations in multiple PM sources and their potential health effects in Utah, USA
334

The use of 87Sr/86Sr isotopic ratios to assess natal areas and movement of juvenile Gulf Sturgeon Acipenser oxyrinchus desotoi in the Pascagoula and Pearl River systems

Neary, Joshua 09 December 2022 (has links)
The effects of water and dietary influence, and time duration for discernment, of pectoral fin spine 87Sr/86Sr were evaluated in Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus. Fish were subjected to 87Sr-enriched water (0.1 mg/L) or diet (0.25 migrogram/g or 0.5 microgram/g) for 1, 2, 3, 6, or 12 weeks. Fish were also held at 15 or 25°C to determine if temperature influenced 87Sr/86Sr. Results found fin spine 87Sr/86Sr changed in water after 1 week and diet after 12 weeks suggesting water is the primary influence. In wild Gulf Sturgeon A. o. desotoi, spot ablations closest to the fin spine core separated fish into four 87Sr/86Sr groups (0.7110, 0.7105, 0.7100, and 0.7906) for both the Pascagoula and Pearl Rivers from 2016-2021. In the Pearl River system, 87.5% of fish (pre-first annuli) had stable 87Sr/86Sr indicating minimal movement, whereas decreasing 87Sr/86Sr in the second and third growth zones indicated downriver movement towards estuaries.
335

The Crystallographic Investigation of a Strontium Labradorite

Cordahi, George 15 June 2015 (has links)
Precession photography was used to determine the lattice parameters, the crystal system, the space group and the structure of an artificial Sr-labradorite of composition: Ab27, SrAn73. C= 7.107Å, Ɣ= 90 degrees, β= 115.834 degrees. The crystal system is monoclinic, space group= C2/ m and structure is albite type, reflections being restricted to the 'a' type. The abundance, lithophile characteristics and appropriate ionic radii of elements in Groups IA and IIA are the factors governing their presence as cations of feldspars in nature. The structures of feldspars are discussed as a function of the relative proportion of cations of a charge of +1 and +2. The crystal symmetry (i.e. monoclinicity or triclinicity) is discussed as a function of the ionic radius of the cation. / Thesis / Bachelor of Science (BSc)
336

THE ARAGONITE TO CALCITE TRANSFORMATION: A LABORATORY STUDY

Croley, Allison L. 02 December 2002 (has links)
No description available.
337

Novel Approaches to Ferroelectric and Gallium Nitride Varactors

Brown, Dustin Anthony 06 June 2014 (has links)
No description available.
338

Middle to Late Ordovician δ<sup>13</sup>C and <sup>87</sup>Sr/<sup>86</sup>Sr stratigraphy in Virginia and West Virginia: implications for the timing of the Knox unconformity

Umholtz, Nicholas Moehle 14 November 2014 (has links)
No description available.
339

Carbon, sulfur, and strontium isotope stratigraphy of the Lower-Middle Ordovician, Great Basin, USA: Implications for oxygenation and causes of global biodiversification

Edwards, Cole T. 29 December 2014 (has links)
No description available.
340

Optimization of BST Thin Film Phase Shifters for Beam Steering Applications

Spatz, Devin 24 May 2017 (has links)
No description available.

Page generated in 0.016 seconds