Electromagnetic Transmission Through Resonant Structures.

Electromagnetic resonators store energy in the form of oscillatory electric and magnetic fields and gradually exchange that energy by coupling with their environment. This coupling process can have profound effects on the transmission and reflection properties of nearby interfaces, with rapid transitions from high transmittance to high reflectance over narrow frequency ranges, and has been exploited to design useful optical components such as spectral filters and dielectric mirrors. This dissertation includes analytic, numeric, and experimental investigations of three different electromagnetic resonators, each based on a different method of confining electromagnetic fields near the region of interest. First, we show that a structure with two parallel conducting plates, each containing a subwavelength slit, supports a localized resonant mode bound to the slits and therefore exhibits (in the absence of nonradiative losses), perfect resonant transmission over a narrow frequency range. In practice, the transmission is limited by conduction losses in the sidewalls; nevertheless, experimental results at 10 GHz show a narrowband transmission enhancement by a factor of 10^4 compared to the non-resonant transmission, with quality factor (ratio of frequency to peak width) Q~3000. Second, we describe a narrowband transmission filter based on a single-layer dielectric grating. We use a group theory analysis to show that, due to their symmetry, several of the grating modes cannot couple to light at normal incidence, while several others have extremely large coupling. We then show how selectively breaking the system symmetry using off-normal light incidence can produce transmission peaks by enabling weak coupling to some of the previously protected modes. The narrowband filtering capabilities are validated by an experimental demonstration in the long wavelength infrared, showing transmission peaks of quality factor Q~100 within a free-spectral range of 8-15 um. Third, we demonstrate that defect-free periodic structures of finite extent can support extended, surface-avoiding, high-quality factor resonant modes, even without mirror-like structures at the boundaries to confine electromagnetic energy. After discussing the necessary conditions for mode confinement to occur, several numerical examples are given. Finally, an experiment at microwave frequencies (2-9 GHz) demonstrates mode confinement, with quality factors Q~150, in a 12-period array of short dielectric rods.PhDApplied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120859/1/yms_1.pd

The Yersinia enterocolitica Ysa type III secretion system is expressed during infections both in vitro and in vivo.

Yersinia enterocolitica biovar 1B maintains two type III secretion systems (T3SS) that are involved in pathogenesis, the plasmid encoded Ysc T3SS and the chromosomally encoded Ysa T3SS. In vitro, the Ysa T3SS has been shown to be expressed only at 26°C in a high-nutrient medium containing an exceptionally high concentration of salt - an artificial condition that provides no clear insight on the nature of signal that Y. enterocolitica responds to in a host. However, previous research has indicated that the Ysa system plays a role in the colonization of gastrointestinal tissues of mice. In this study, a series of Ysa promoter fusions to green fluorescent protein gene (gfp) were created to analyze the expression of this T3SS during infection. Using reporter strains, infections were carried out in vitro using HeLa cells and in vivo using the mouse model of yersiniosis. Expression of green fluorescent protein (GFP) was measured from the promoters of yspP (encoding a secreted effector protein) and orf6 (encoding a structural component of the T3SS apparatus) in vitro and in vivo. During the infection of HeLa cells GFP intensity was measured by fluorescence microscopy, while during murine infections GFP expression in tissues was measured by flow cytometry. These approaches, combined with quantification of yspP mRNA transcripts by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), demonstrate that the Ysa system is expressed in vitro in a contact-dependent manner, and is expressed in vivo during infection of mice

Non-normal real estate return distributions by property type in the UK

Investment risk models with infinite variance provide a better description of distributions of individual property returns in the IPD UK database over the period 1981 to 2003 than normally distributed risk models. This finding mirrors results in the US and Australia using identical methodology. Real estate investment risk is heteroskedastic, but the characteristic exponent of the investment risk function is constant across time – yet it may vary by property type. Asset diversification is far less effective at reducing the impact of non‐systematic investment risk on real estate portfolios than in the case of assets with normally distributed investment risk. The results, therefore, indicate that multi‐risk factor portfolio allocation models based on measures of investment codependence from finite‐variance statistics are ineffective in the real estate contex

Serial persistence in individual real estate returns in the UK

Purpose – The purpose of this paper is to examine individual level property returns to see whether there is evidence of persistence in performance, i.e. a greater than expected probability of well (badly) performing properties continuing to perform well (badly) in subsequent periods. Design/methodology/approach – The same methodology originally used in Young and Graff is applied, making the results directly comparable with those for the US and Australian markets. However, it uses a much larger database covering all UK commercial property data available in the Investment Property Databank (IPD) for the years 1981 to 2002 – as many as 216,758 individual property returns. Findings – While the results of this study mimic the US and Australian results of greater persistence in the extreme first and fourth quartiles, they also evidence persistence in the moderate second and third quartiles, a notable departure from previous studies. Likewise patterns across property type, location, time, and holding period are remarkably similar. Research limitations/implications – The findings suggest that performance persistence is not a feature unique to particular markets, but instead may characterize most advanced real estate investment markets. Originality/value – As well as extending previous research geographically, the paper explores possible reasons for such persistence, consideration of which leads to the conjecture that behaviors in the practice of institutional-grade commercial real estate investment management may themselves be deeply rooted and persistent, and perhaps influenced for good or ill by agency effects. - See more at: http://www.emeraldinsight.com/journals.htm?articleid=1602884&show=abstract#sthash.hc2pCmC6.dpu

Instrumental Assessment of Aero-Resistive Expiratory Muscle Strength Rehabilitation Devices

Purpose Expiratory muscle strength training (EMST) is increasingly being used to treat voice, cough, and swallowing deficits in a wide range of conditions. However, a multitude of aero-resistive EMST models are commercially available, and the absence of side-by-side comparative data interferes with clinicians’ ability to assess which model is best suited to a particular client’s needs. The primary aim of this research was to test and compare the pressure and flow parameters of six currently available EMST models to help inform clinical decision making. Method We identified and tested five devices of each of six different EMST models to generate benchmark data for minimum trigger pressures across settings. The reliability was tested within each device and between five devices of the same model across settings using coefficient of variation. Results All six models required higher pressures to initiate flow at the highest setting compared to the lowest setting, as expected. Detailed descriptive statistics for each model/setting combination include average flow-triggering pressure for each model/setting and the variability across trials within a device and across devices of the same model. From these, ranked order of the least to most stable EMST model was derived. Conclusions Systematic testing of several commercially available expiratory re-sistance training devices yielded clinical benchmarks and reliability data to aid clinicians in selecting an appropriate therapy device and regimen for a client based on their available airflow and air pressure as well as reliability of the device. These findings allow clinicians to directly compare key parameters across EMST devices

Bioinspired engineering of exploration systems for NASA and DoD

A new approach called bioinspired engineering of exploration systems (BEES) and its value for solving pressing NASA and DoD needs are described. Insects (for example honeybees and dragonflies) cope remarkably well with their world, despite possessing a brain containing less than 0.01% as many neurons as the human brain. Although most insects have immobile eyes with fixed focus optics and lack stereo vision, they use a number of ingenious, computationally simple strategies for perceiving their world in three dimensions and navigating successfully within it. We are distilling selected insect-inspired strategies to obtain novel solutions for navigation, hazard avoidance, altitude hold, stable flight, terrain following, and gentle deployment of payload. Such functionality provides potential solutions for future autonomous robotic space and planetary explorers. A BEES approach to developing lightweight low-power autonomous flight systems should be useful for flight control of such biomorphic flyers for both NASA and DoD needs. Recent biological studies of mammalian retinas confirm that representations of multiple features of the visual world are systematically parsed and processed in parallel. Features are mapped to a stack of cellular strata within the retina. Each of these representations can be efficiently modeled in semiconductor cellular nonlinear network (CNN) chips. We describe recent breakthroughs in exploring the feasibility of the unique blending of insect strategies of navigation with mammalian visual search, pattern recognition, and image understanding into hybrid biomorphic flyers for future planetary and terrestrial applications. We describe a few future mission scenarios for Mars exploration, uniquely enabled by these newly developed biomorphic flyers

Lumber recovery, a leaf area model, and water use in response to commercial thinning, for plantation grown black spruce (Picea mariana [Mills] B.S.P.) / by Steven M. Young.

Three black spruce (Picea mariana [Mills] B.S.P.) plantations (Airstrip, Boom Lake and Tyrol Lake), in northwestern Ontario, with varied stand densities (2806 stems ha[superscript -1], 2285 stems ha[superscript -1], and 3578 stems ha[superscript -1], respectively) and site indices (11.8 m, 13.3 m, 10.9 m, respectively) were studied to determine lumber properties and yield and to develop a model to predict leaf area. The Boom Lake site was also studied to assess the impacts of site disturbance and residual tree damage from commercial thinning on tree water use. With respect to lumber recovery, all three sites produced over 87% No. 2 and Better grades lumber. Wane and skip were the two most prominent defects causing lumber downgrades. The lowest quality site with the highest stand density produced significantly stronger (modulus of rupture, MOR) and stiffer (modulus of elasticity, MOB) lumber than either the best quality site with a lower stand density or the medium quality site with a similar stand density. The best site with the lowest stand density also produced significantly stronger and stiffer lumber than the medium site with higher stand density. Lumber sawn from log sections taken from below the live crown were significantly stronger but not significantly stiffer than lumber sawn from logs from within the live crown. There were no significant differences in bending MOB and MOR between visual grades. Economy grade lumber was denser than the other grades and had a smaller average ring width than the Grades No. 1 and No. 2. There were weak negative relationships between average ring width and basic wood density. There were weak positive relationships between basic wood density and MOB or MOR. Three scenarios were examined for relative economic return. Regardless of economic scenario, the Boom site (best site quality) produced the highest value per hectare followed by Tyrol (poorest site quality) and then Airstrip. Generally, MSR grading produced the highest value per hectare (maximum $28,000/ha at the Boom site). The model to predict whole tree leaf area was developed from 37 plantation grown black spruce trees collected from all 3 sites. Allometric equations to describe needle weight (W[subscript n]), leaf area (A,) and A[subscript 1]: breast height sapwood area (A[subscript s]) relationships are described. Specific leaf area (SLA, m[superscript 2]/g ) was measured on needles from 4 needle age classes on 4 subsampled branches taken from 3 crown sections of equal length on each of the 37 trees. SLA varied by site, needle age and crown section. SLA of needles from the Airstrip was significantly larger than those from the Tyrol site, while needle SLA from the Boom site was not significantly different from either. Linear and nonlinear allometric models were built to appropriately scale up to whole tree leaf area based on live branch diameters measured in the field, and compared against trees (9 total, 3 from each site) where the entire crown was collected. Nonlinear models for crown sections 1 (top section) and 2 (middle section) revealed an unbiased predictive ability whereas both linear and nonlinear models showed a general tendency to over predict the needle weight of crown section 3 (bottom section). Nevertheless, a linear model to predict A[subscript 1] from A[subscript s] was developed that showed to no evidence of bias. Sapflow was measured from May 2007 to August 2008 to assess the impacts of site disturbance and residual tree damage from commercial thinning on tree water use. Twelve black spruce trees were instrumented with thermal dissipation sap flow sensors in the spring following a fall season harvest. Soil resistance to penetration was measured with an Eijkelkamp 06.15.SA model Penetrologger Set. The twelve trees were classified based on damage and adjacency to trails resulting in 4 treatment groups; TD (adjacent to the trail with apparent damage), TN (adjacent to the trail with no damage), ID (away from the trail with apparent damage) and IN (away from the trail with no damage). There was no significant difference between the soil resistance to penetration on or between harvest trails. Daily water use (Q[subscript d]) was as high as 20.711 day[superscript -1] and as little as 0.06 1 day[superscript-1]. There were no significant differences detected between treatment groups for diameter at breast height (DBH), height (H), length of live crown (EC), sapwood area (A[subscript s]) or leaf area (A[subscript1]). The TD trees appeared to have the lowest Qd, while the TN trees appeared to have lowest mean sap velocity ( v[subscript s]) and low Qd. Transpiration (Qi) and stomatal conductance (G c) levels appeared to generally be lower for the TN group when compared to other treatment groups. The data suggests that Q, and Gc may not be affected by adjacency to trails and/or mechanical damage in the first year following thinning treatment