Superconducting gyroscope research

Four basic areas of research and development of superconducting gyroscopes are studied. Chapter 1 studies the analysis of a SQUID readout for a superconducting gyroscope. Chapter 2 studies the dependence of spin-up torque on channel and gas properties. Chapter 3 studies the theory of super fluid plug operation. And chapter 4 studies the gyro rotor and housing manufacture

The Ryggfonn project. Description of instrumentation and data registration system

The Ryggfonn avalanche path has been instrumented to measure: deflections on a 6 m high steel mast mounted at top of the test embankment by means of weldable strain gauges; wind speed of powder snow fronts by means of a three direciton propeller based wind speed sensor; snow pressure forces on an 18 cm diameter strain gauge based load cell mounted at top of the test embankment; axial tension in three high tension cables crossing the avalanche path by means of strain gauge based in-line load cells; snow pressure forces acting upon a 4.5 m high concrete structure by means of three strain gauge based load cells totally covering the wall facing the avalanche; vertical vibration velocity by means of a seismometer mounted at the concrete structur

Ultrafast terahertz spectroscopy and control of collective modes in semiconductors

In this dissertation we applied methods of ultrafast terahertz (THz) spectroscopy to study several aspects of semiconductor physics and in particular of collective mode excitations in semiconductors. We detect and analyze THz radiation emitted by these collective modes to reveal the underlying physics of many-body interactions. We review a design, implementation and characterization of our ultrafast terahertz (THz) time-domain spectroscopy setup, with additional features of mid-infrared tunability and coherent as well as incoherent detection capabilities. Temperature characterization of the collective plasmon excitation in indium antimonide (InSb) is presented to reveal the importance of non-parabolicity corrections in quantitative description. We also obtain electronic mobility from the radiation signals, which, once corrected for ultrafast scattering mechanisms, is in good agreement with DC Hall mobility measurements. Exhibited sensitivity to non-parabolicity and electronic mobility is applicable to non-contact characterization of electronic transport in nanostructures. As a first goal of this work, we have addressed the possibility of an all-optical control of the electronic properties of condensed matter systems on an ultrafast time scale. Using femtosecond pulses we have demonstrated an ability to impose a nearly 20% blue-shift of the plasma frequency in InSb. Preliminary investigations of control of the electron dynamics using third-order nonlinearity were also carried out in solid state and gaseous media. In particular, we have experimentally verified the THz coherent control in air-breakdown plasmas and have demonstrated the ability to induce quantum-interference current control in indium arsenide crystals. As a second focus of this dissertation, we have addressed manipulation of the plasmon modes in condensed matter systems. After development of the analytical model of radiation from spatially extended longitudinal modes, we have applied it to analysis of two experiments. In first, we established the ability to control plasmon modes in InSb by means of a plasmonic one dimensional cavity. By control of the cavity geometry, we shifted the plasmon mode into the regime where non-local electron-electron interaction is enforced. We observed the consequential Landau damping of the collective mode, in good agreement with the predictions made within the random-phase approximation. In the second experiment we have invoked plasmon confinement in all three dimensions via a nanowire geometry. We observed enhancement of terahertz emission which we attributed to leaky modes of the waveguide. We attributed this emission to the low-energy acoustic surface plasmon mode of the nanowire, which was also supported by our numerical modeling results and independent DC electronic measurements

Effects of substrate-derived cues in driving the selforganization of organoid-derived intestinal epithelia

[eng] Intestinal cells self-organize into 3-dimensional (3D) organoids that recapitulate the in vivo structural and functional characteristics when embedded in a 3D cell-derived protein mixture (Matrigel). However, these very same cells self-organize into 2-dimensional (2D) intestinal epithelial monolayers that recapitulate the in vivo-like cell organization when seeded on thin layers of the same cell-derived protein mixture. Moreover, in vivo, the intestine integrates regulation from paracrine signals to establish its characteristic crypt-villus axis self- organization. However, direct experimental manipulation of these paracrine signals, as well as their functional concentrations and effects at the cellular level, has been hampered by limitations of the in vivo and in vitro currently available systems. In general, changes in epithelial cell organization are characterized by a cross-talk between cell-substrate and cell-cell interactions, but the role of the ECM dimensionality, protein composition and spatial distribution in the intestinal epithelial cells’ organization is not fully understood. In this thesis, we show that intestinal epithelial cells self-organize in 2D-monolayers or 3D-tubular networks depending on the Matrigel protein concentration when the dimensionality is fixed. This self-assembles tubular networks have inner apical polarization and are similar to soap foams or de-wetted collagen networks. They have well defined topological and metrical properties and become spontaneously ordered at large length scales. Interestingly, stem cells have a particular dynamic during the formation of each self-organized patterns. On low Matrigel concentration, stem cells present a confined random movement to form a 2D-monolayer. In contrast, on higher Matrigel concentration, stem cells perform a direct motion towards a specific target to form the 3D- tubular networks. By reducing the proportion of stem cells in the culture, the formation of 3D-tubular networks is impaired. Instead, primary cells form aggregates when seeded above the transition protein concentration, similar to two other epithelial cell types (Caco-2 and MDCK cells). On the other hand, the 2D-monolayers formed on low Matrigel concentration contain crypt- and villus-like domains resembling those found in vivo. These compartments are randomly distributed and their shape is not uniform. However, by producing localized micropatterns of immobilized Wnt and ephrin factors on freeze-dried Matrigel-coated substrates by microcontact printing, we can drive the compartmentalization of the intestinal epithelial monolayers by spatially positioning the crypt- and villus-like domains. Finally, by changing the shape and dimension of the patterns we can control the distance between the crypt-like domains as well as their dimensions and shape. Overall, our experiments illustrate how Matrigel concentration regulates intestinal epithelial cell organization as a function of cell-substrate adhesion, and show that primary intestinal epithelial cells self-organize in structures with well-defined sizes and shapes independently of dimensionality or external signaling gradients. Also, we show that the amount of stem cells in the culture regulates the geometry of those self-organized structures. On the other hand, micropatterns of immobilized proteins to the ECM provides accurate control of the crypt-villus domain positioning in our epithelial monolayers. Thus, our work could yield insights about the roles of stem cells and protein concentration in tissue morphogenesis and their influence in the in vivo tissue morphological features such as the dimension of the crypts. In addition, we believe our platform will allow an easy and reliable manner to analyze the effect of relevant proteins on the epithelial cell compartmentalization, as well as the study of important intestinal epithelial processes such as stem cells proliferation, cell migration and differentiation both in homeostasis and pathological processes.[spa] Las células intestinales cultivadas dentro de Matrigel se auto-organizan en organoides tridimensionales (3D) que recapitulan la organización del tejido in vivo. Sin embargo, estas mismas células cultivadas sobre láminas del mismo sustrato se auto-organizan en monocapas bidimensionales (2D) que también recapitulan la organización del tejido in vivo. Además, in vivo, el intestino integra señales paracrinas para establecer su característica auto- organización en criptas y vellosidades. Sin embargo, la manipulación de estás señalizaciones se ha visto obstaculizada por limitaciones en los sistemas in vivo e in vitro actuales. En general, la organización epitelial se caracteriza por interacciones célula-célula y célula-sustrato. Sin embargo, no se acaba de entender el rol de la dimensión, la composición y la distribución de la matriz extracelular (ECM) sobre la organización de las células epiteliales del intestino. En esta tesis, se analiza la organización de células epiteliales en monocapas 2D o redes tubulares 3D en función de la adhesión célula-sustrato. De esta manera, se ilustra la organización en estructuras con tamaños y formas bien definidas independientemente de la dimensionalidad o señalizaciones externas. Además, la proporción de células madre regula la geometría de dichas estructuras. Por otro lado, en contraste con lo que se observa in vivo, los dominios de cripta de las monocapas están desordenados y su forma no es uniforme. Mediante una plataforma que localiza micropatrones de proteínas sobre la ECM, controlamos el posicionamiento de los dominios de cripta-vellosidad. Para concluir, nuestro trabajo proporciona información sobre como influencia la composición y la distribución de la ECM y las células madre en la morfología del tejido in vivo, como la dimensión de las criptas. Además, la plataforma permite analizar el efecto de diferentes proteínas en la compartimentación de las células y en otros procesos epiteliales como proliferación, migración o diferenciación celular, tanto en homeostasis como en proceso patológicos

Advanced transportation system study: Manned launch vehicle concepts for two way transportation system payloads to LEO

The purpose of the Advanced Transportation System Study (ATSS) task area 1 study effort is to examine manned launch vehicle booster concepts and two-way cargo transfer and return vehicle concepts to determine which of the many proposed concepts best meets NASA's needs for two-way transportation to low earth orbit. The study identified specific configurations of the normally unmanned, expendable launch vehicles (such as the National Launch System family) necessary to fly manned payloads. These launch vehicle configurations were then analyzed to determine the integrated booster/spacecraft performance, operations, reliability, and cost characteristics for the payload delivery and return mission. Design impacts to the expendable launch vehicles which would be required to perform the manned payload delivery mission were also identified. These impacts included the implications of applying NASA's man-rating requirements, as well as any mission or payload unique impacts. The booster concepts evaluated included the National Launch System (NLS) family of expendable vehicles and several variations of the NLS reference configurations to deliver larger manned payload concepts (such as the crew logistics vehicle (CLV) proposed by NASA JSC). Advanced, clean sheet concepts such as an F-1A engine derived liquid rocket booster (LRB), the single stage to orbit rocket, and a NASP-derived aerospace plane were also included in the study effort. Existing expendable launch vehicles such as the Titan 4, Ariane 5, Energia, and Proton were also examined. Although several manned payload concepts were considered in the analyses, the reference manned payload was the NASA Langley Research Center's HL-20 version of the personnel launch system (PLS). A scaled up version of the PLS for combined crew/cargo delivery capability, the HL-42 configuration, was also included in the analyses of cargo transfer and return vehicle (CTRV) booster concepts. In addition to strictly manned payloads, two-way cargo transportation systems (CTRV's) were also examined. The study provided detailed design and analysis of the performance, reliability, and operations of these concepts. The study analyzed these concepts as unique systems and also analyzed several combined CTRV/booster configurations as integrated launch systems (such as for launch abort analyses). Included in the set of CTRV concepts analyzed were the medium CTRV, the integral CTRV (in both a pressurized and unpressurized configuration), the winged CTRV, and an attached cargo carrier for the PLS system known as the PLS caboose

Practical considerations in the reconciliation of the direct and indirect methods or measuring the air-earth current

Progress in any field of scientific interest is often advanced by the failure to find agreement between two different approaches to a particular measurement in the field. This is so because it forces attention on he theory behind the measurements and the conditions under which the measurements were made. Such a problem is identified in the field of Atmospheric electricity. Differing results have been found for the value of the fine weather air-earth current when measured by the "indirect" and "direct" methods of approach. The indirect method involves the recording of the fine weather conductivity and the potential gradient and equating their product with the conduction current. In the direct method, the total charge arriving at a portion of the earths surface is measured. The direct method, though more difficult, appears to be the more fundamental measurement and a critical review of previous experiments and the hypotheses of work at ground level, in that it predicts a system from the examination of one of the systems boundaries, is indicated. The experimental problems associated with the direct and indirect methods and described with particular reference to the site used for the measurement of atmospheric electricity at Durham Observatory. In particular, the effects of pollution and the displacement current are discussed and some details of an unsuccessful attempt to devise a form of the direct method that would enable the true magnitude of any convection current to be found, are given. Suggestions are made for the measurements required and the conditions under which they should be made if the final resolution of these differences in the recording of the fine weather air-earth current is to be achieved

First electrostatic probe results from Explorer 17

Electrostatic probe results from ionospheric sounding by Explorer XVII satellit

Topics in the optimization of millimeter-wave mixers

A user oriented computer program for the analysis of single-ended Schottky diode mixers is described. The program is used to compute the performance of a 140 to 220 GHz mixer and excellent agreement with measurements at 150 and 180 GHz is obtained. A sensitivity analysis indicates the importance of various diode and mount characteristics on the mixer performance. A computer program for the analysis of varactor diode multipliers is described. The diode operates in either the reverse biased varactor mode or with substantial forward current flow where the conversion mechanism is predominantly resistive. A description and analysis of a new H-plane rectangular waveguide transformer is reported. The transformer is made quickly and easily in split-block waveguide using a standard slitting saw. It is particularly suited for use in the millimeter-wave band, replacing conventional electroformed stepped transformers. A theoretical analysis of the transformer is given and good agreement is obtained with measurements made at X-band

Project ORION: Orbital Debris Removal Using Ground-Based Sensors and Lasers

About 100,000 pieces of 1 to 10-cm debris in low-Earth orbit are too small to track reliably but large enough to cripple or destroy spacecraft. The ORION team studied the feasibility of removing the debris with ground-based laser impulses. Photoablation experiments were surveyed and applied to likely debris materials. Laser intensities needed for debris orbit modification call for pulses on the order of lOkJ or continuous wave lasers on the order of 1 MW. Adaptive optics are necessary to correct for atmospheric turbulence. Wavelength and pulse duration windows were found that limit beam degradation due to nonlinear atmospheric processes. Debris can be detected and located to within about 10 microrads with existing radar and passive optical technology. Fine targeting would be accomplished with laser illumination, which might also be used for detection. Bistatic detection with communications satellites may also be possible. We recommend that existing technology be used to demonstrate the concept at a loss of about $20 million. We calculate that an installation to clear altitudes up to 800 km of 1 to 10-cm debris over 2 years of operation would cost about$80 million. Clearing altitudes up to 1,500 km would take about 3 years and cost about $160 million