A self-terminated electrochemical method was used to fabricate microscopic-scale contacts between two Au electrodes in a microfluidic channel. The conductance of contacts varies in a stepwise fashion showing quantization near the integer multiples of the conductance quantum ( ). The mechanism works by a pressure-driven flow parallel to a pair of Au electrodes with a gap on the order of micron in an electrolyte of HCl. When applying a bias voltage between two electrodes, metal atoms are etched off the anode and dissolved into the electrolyte as metal ions, which are then deposited onto the cathode. Consequently, the gap decreases to the atomic scale and then completely closes as the two electrodes form a contact. The electrochemical fabrication approach introduces large variance in the formation and location of individual junctions. Understanding and controlling this process will enable the precise positioning of reproducible geometries into nano-electronic devices.

The relative importance of physical processes occurring on the various scales within molecular clouds is strongly debated, partly due to the lack of systematic cloud-wide observations available until recently. My thesis characterizes the kinematics of star formation across the entire Perseus molecular cloud as well as in a suite of simulations, providing statistical measures that successful theories of star formation will have to explain. My thesis consists of three interconnected projects described below. Dense core survey: The kinematics of the dense cores in Perseus were measured through single pointing observations of the N2H+(1–0) and C18O(2–1) transitions, tracing the dense core gas and surrounding lower density gas respectively. The internal velocity dispersion of the dense cores was observed to be small – dominated by thermal motions, and roughly the size expected for the cores to be in virial equilibrium. The dense cores also have little motion with respect to the surrounding low density gas – usually much less than the ambient sound speed of the medium. Comparison to cloud survey: The dense core observations were compared to a full spectral cube of 13CO(1–0) emission from the COMPLETE Survey, tracing the lower-density cloud material. From this analysis, it was determined that the dense cores have little motion with respect to the larger structures that they inhabit – smaller than the typical velocity dispersion or the estimated virial velocity dispersion of the region. Analysis of simulations: A suite of thin-sheet MHD simulations with varying levels of input magnetic field strengths and turbulence were analyzed in a manner to mimic the above observational surveys. While the small internal velocity dispersion of the dense cores could be reproduced by most of the simulations, the small motion between the core and its surrounding lower density gas could not be produced at the same time as the observed large-scale non-thermal motions. Future directions: The kinematic measures presented here will be straightforward to apply to future multi-cloud surveys as well as other numerical simulations. This will allow the effect of environment on star formation to be better explored in both the observational and simulated domains.

Muon decay is a unique process involving only the four leptons of the first two generations. This makes it an ideal framework to study the weak interaction. The momentum-angle spectrum of the decay positron can be studied using a general 4-fermion interaction model. Only four parameters are needed in this model to entirely describe the spectrum. The measurement of these four muon decay parameters, rho, eta, delta and Pmu xi, provide a direct test of the Standard Model and its extensions. This thesis presents the final results from the blind analysis of the decay parameter delta using the TWIST (TRIUMF Weak Interaction Symmetry Test) spectrometer. The new precision on the parameter delta is a factor of 11.5 better than the last experimental result prior to TWIST achieving the goal of the TWIST collaboration of an order of magnitude improvement. The challenging parameter eta is also measured from the momentum-angle spectrum for the first time since 1969 with a precision improved by a factor of 7.4. The results are included in a global analysis to obtain stringent limits on some of the coupling constants of the 4-fermion interaction. The result of the measurement of delta are used to evaluate the possibility for a non-local tensor interaction.

Microsystem interfaces to the macroscopic surroundings and within the microsystems themselves are formidable challenges that this thesis makes an effort to overcome, specifically for enabling a spacecraft based entirely on microsystems. The NanoSpace-1 nanospacecraft is a full-fledged satellite design with mass below 10 kg. The high performance with respect to mass is enabled by a massive implementation of microsystem technology – the entire spacecraft structure is built from square silicon panels that allow for efficient microsystem integration. The panels comprise bonded silicon wafers, fitted with silicone rubber gaskets into aluminium frames. Each module of the spacecraft is added in a way that strengthens and stiffens the overall spacecraft structure. The structural integrity of the silicon module as a generic building block has been successfully proven. The basic design (silicon, silicone, aluminium) survived considerable mechanical loads, where the silicon material contributed significantly to the strength of the structural element. Structural modeling of the silicon building blocks enables rapid iterative design of e.g. spacecraft structures by the use of pertinent model simplifications. Other microsystem interfaces treats fluidic, thermal, and mechanical functions. First, solder sealing of microsystem cavities was demonstrated, using screen-printed solder and localized resistive heating in the microsystem interface. Second, a dismountable fluidic microsystem connector, using a ridged silicon membrane, intended for monopropellant thruster systems, was developed. Third, a thermally regulated microvalve for minute flows, made by a silicon ridge imprint in a stainless steel nipple, was investigated. Finally, particle filters for gas interfaces to microsystems, or between parts of fluidic microsystems, were made from sets of crossed v-grooves in the interface of a bonded silicon wafer stack. Filter manufacture, mass flow and pressure drop characterization, together with numeric modeling for filter design, was performed. All in all this reduces the weight and volume when microsystems are interfaced in their applications.

Chiral perturbation theory is a useful tool in the study of low energy reactions involving light particles. However the inclusion of heavy particles in chiral perturbation theory results in large contributions from loop diagrams which violate the standard power counting scheme. We review two methods, referred to as heavy baryon chiral perturbation theory and infrared regularization, which remove the high energy effects of the heavy particles and which therefore do not violate the power counting scheme. We then use these two methods to calculate the amplitude for pion photoproduction to fourth order and prove that the two amplitudes are equivalent.

The existence of charged electroweak-scale particles in the early universe can drastically affect the evolution of elemental abundances. Through the formation of Coulombic bound states with light nuclei, these exotic relic particles (hereafter referred to as X–) act to catalyze nuclear reactions by reducing their threshold energies. This thesis examines the properties of the X– bound states, and uses primordial element observations to constrain the abundance, lifetime, and mass of this exotic particle species. If the X– is a Dirac Fermion, its abundance relative to baryons is found to be YX- ~ 0.01, with a lifetime of 1500s ≤ τX- ≤ 3000s, and a mass of order 100 GeV. Assuming that the X– is a Scalar particle that decays into gravitinos, the resulting bounds become, 5x10-4 ≤ YX- ≤ 0.07, 1600s ≤ τX- ≤ 7000s, and 60GeV ≤ mX- ≤ 1000GeV. These ranges are consistent with Dark Matter constraints.

Gamma-ray bursts (GRBs) are some of the most energetic events in the universe. Shocks occurring below the photosphere are likely radiation mediated shocks (RMSs) and are suspected to shape the spectra. Due to computational costs of simulating RMSs, models had not been fitted to data and a faster model was needed. The Kompaneets RMS Approximation (KRA) is an analog model of RMSs, creating spectra which are identical to full RMS simulation spectra and it is significantly faster. For a sample of short GRBs I found that spectra are very hard and close to a non-dissipative photosphere (NDP). Therefore any trace of energy dissipation is lost to thermalization and many KRA solutions are possible with statistics similar to the Band model. A sample of long GRBs have typical spectra, i.e. spectra much broader than a blackbody (BB) and the KRA can model these spectra very well. Statistically, KRA is as good as the Band model and significantly better for GRB211211. I also found two spectral shapes describing observed data equally well. First, a broadened BB for a steady-state outflow, and secondly, optically shallow shocks for a non steady-state outflow. To distinguish between these solutions, upcoming detectors with lower-energy data are important. In conclusion, the KRA can reproduce photospheric spectra altered by a RMS, and these spectra can explain observed GRB spectra. If the spectrum is not thermalized, information about the properties of the shock can be deduced from observed GRB spectra. / Gamma-blixtar är några av de mest energirika händelserna i universum. Chocker som uppkommer under fotosfären är troligtvis strålnings medlade chocker (RMSer) och misstänks forma spektra. Höga beräkningsmässiga kostnader för simuleringar av RMSer har lett till att modeller inte har anpassats till data. The Kompaneets RMS Approximation (KRA) är en analog modell av RMSer som skapar identiska spektra och är mycket snabbare. För ett urval av korta gamma-blixtar hittar jag väldigt hårda spektra, nära en icke-dissiperad fotosfär (NDP). Alla spår av dissipering har därför försvunnit p.g.a. termaliseringen och många olika KRA lösningar kan anpassa dessa spektra lika bra som Band modellen. Ett urval av långa gamma-blixtar har typiska spektra, d.v.s. spektra mycket bredare än svartkropp spektra och KRA kan anpassa dessa spektra väldigt bra. Statistiskt är KRA lika bra som Band modellen och t.o.m. mycket bättre för GRB211211. Jag har också hittat två olika former på spektra som anpassar data lika bra. Först, en breddad svartkropp för ett utflöde i jämvikt och den andra, optiskt grunda shocker för ett utflöde som inte är i jämvikt. För att urskilja mellan dessa lösningar är framtida detektorer med data för lägre energies viktiga. För att sammanfatta, KRA kan reproducera fotosfäriska spektra påverkade av en RMS och dessa spektra can förklara observerade gamma-blixt spektra. Om spektrumet inte är termaliserat kan information om chockens egenskaper hämtas från observerade gamma-blixt spektra.

In high frequency design, harmonic suppression is a persistent struggle. Non-linear devices such as switches and amplifiers produce unwanted harmonics which may interfere with other frequency bands. Filtering is a widely accepted solution, however there are various shortcomings involved. Suppressing multiple harmonics, if desired, with traditional lumped element and distributed component band-stop filters requires using multiple filters. These topologies are not easily made tunable either. A new filter topology is investigated called Electromagnetic Band-Gap (EBG) structures. EBG structures have recently gained the interest of microwave designers due to their periodic nature which prohibits the propagation of certain frequency bands. EBG structures exhibit characteristics similar to that of a band-stop filter, but in periodically repeating intervals making it ideal for harmonic suppression. The band-gap frequency of an EBG structure may be varied by altering the periodicity of the structure. However, EBG materials are generally static in structure making tuning a challenge. In this thesis, a novel solution for tuning the band-gap properties of an EBG structure is investigated. Designs aimed to improve upon existing solutions are reached. These designs involve acoustic and mechanical tuning methods. Performance is simulated using Agilent’s Advanced Design System (ADS) and a device is constructed and evaluated. Comparing all measured test cases to simulation, band-gap center frequency error is on average 4.44% and absolute band-gap rejection error is 1.358 dB.

The radiation environment in space is a threat that engineers and astronauts need to mitigate as exploration into the solar system expands. Passive shielding involves placing as much material between critical components and the radiation environment as possible. However, with mass and size budgets, it is important to select efficient materials to provide shielding. Currently, NASA and other space agencies plan on using water as a shield against radiation since it is already necessary for human missions. Water has been tested thoroughly and has been proven to be effective. Liquid propellants are needed for every mission and also share similar characteristics to water such as their density and hydrogenous composition. This thesis explores the shielding potentials of various liquid propellants as they compare to water for the purpose of providing an additional parameter when choosing propellants for any given mission. Testing propellants is done by first creating an experimental setup involving radioisotope sources Cs-137 and Co-60, a column of liquid with variable depths, and a Geiger-Mueller tube. Water and three other liquids: acetone, 70% isopropyl alcohol, and 12% hydrogen peroxide are physically tested and their linear attenuation coefficients are calculated. Then, the test setup is replicated in CERN’s Monte Carlo base radiation transport code, FLUKA. Although the calculated linear attenuation outputs from FLUKA are discrepant from experimental results by an average of 34%, they produce the same trends. FLUKA is used to expand upon experimental results by simulating a multitude of liquid propellants and comparing them all to water. FLUKA has the ability to simulate all propellants including hydrogen, oxygen, hydrazine, and dinitrogen tetroxide. Most of the tested propellants are found to have similar, to within 35%, gamma radiation linear attenuation coefficients as compared to water. The gamma radiation in this thesis’s experiment and simulations comes from Cs-137 and Co-60 radioisotope sources. For gamma radiation from the Co-60 source, liquid hydrogen provides 90% less attenuation than water and nitric acid and AF-M315E provide 35% and 38% more attenuation than water respectively. For gamma radiation emitted by Cs-137, liquid hydrogen, isopropyl alcohol, and methane have 90%, 35%, and 29% less attenuation than water respectively. Dinitrogen tetroxide, hydrogen peroxide, AF-M315E, and nitric acid have 34%, 41%, 46%, and 52% greater attenuation coefficients than water respectively. The liquids that are similar to water for the Cs-137 source have linear attenuation coefficients within 20% of water’s. Ultimately, most of the tested liquid propellants are shown to shield against radiation at a similar rate to water. Thus, an additional parameter for choosing liquid propellants on any given mission should be their radiation shielding capabilities.

Part B of two Project Reports; Part A can be found at: http://hdl.handle.net/11375/16881 / <p> Procedures have been set up to calculate the reactor kinetics parameters for thorium fuelled CANDU reactors using the perturbation option of the 2-dimensional diffusion code EXTERMINATOR. The procedures are believed to be very accurate. </p> <p> Representative cases of a CANDU thorium converter at different stages during the reactor life have been used to test the developed procedures. Results are presented and discussed. </p> / Thesis / Master of Engineering (ME)