The Numerical Analysis Of Vegetation Plots In Denali National Park And Preserve

Thesis (M.Sc.) University of Alaska Fairbanks, 198

Spaces of Community in Champaign Urbana

Our research question was to focus on how the research farm at the University of Illinois at Urbana Champaign (UIUC) and the iconic bar KAMS on the UIUC campus town contribute to the culture of Champaign Urbana as a whole. Being a community that represents many different cultures from many different backgrounds we wanted to focus on these locations, which we feel best represent Champaign Urbana

All-optical steering of light via spatial Bloch oscillations in a gas of three-level atoms

A standing-wave control field applied to a three-level atomic medium in a planar hollow-core photonic crystal waveguide creates periodic variations of linear and nonlinear refractive indexes of the medium. This property can be used for efficient steering of light. In this work we study, both analytically and numerically, the dynamics of probe optical beams in such structures. By properly designing the spatial dependence of the nonlinearity it is possible to induce long-living Bloch oscillations of spatial gap solitons, thus providing desirable change in direction of the beam propagation without inducing appreciable diffraction. Due to the significant enhancement of the nonlinearity, such self-focusing of the probe beam can be reached at extremely weak light intensities.Comment: 8 pages, 4 figure

Band splitting and Modal Dispersion induced by Symmetry braking in Coupled-Resonator Slow-Light Waveguide Structures

We study the dispersion relations in slow-light waveguide structures consisting of coupled microdisk resonators. A group theoretical analysis of the symmetry properties of the propagating modes reveals an interesting phenomenon: The degeneracy of the CW and CCW rotating modes is removed, giving rise to two distinct transmission bands. This effect induces symmetry-based dispersion which may limit usable bandwidth of such structures. The properties of this band splitting and its impact on CROW performance for optical communications are studied in detail

The Effect of Jump Distance on Biomechanical Risk Factors for ACL Injury During Landing and Their Relationship with Sensorimotor Characteristics at the Knee

There has been an abundance of research investigating risk factors for anterior cruciate ligament (ACL) injury and demonstrating the importance of biomechanical characteristics, particularly in females. However, there have been many different landing tasks used with varying demands. Previous research has demonstrated that different landing tasks significantly alter demand and biomechanical characteristics. However it is unknown how changes in landing demand using the same task may alter landing biomechanics related to ACL injury. Therefore, the purpose of this study was to examine the effects of jump distance during a double-leg stop-jump on biomechanical risk factors of ACL injury and muscle activation and examine the contribution of sensorimotor characteristics on these biomechanical characteristics. Fifty-three recreationally active healthy females were recruited to participate in this study. Each participant underwent a single test session that included demographic and anthropometric assessment, dominant knee threshold to detect passive motion, landing biomechanics and muscle activation measurement, and dominant knee time to peak torque and peak torque testing. Biomechanical and muscle activation parameters relative to ACL injury were compared between jump distances using repeated measures ANOVA. Multiple linear regression was used to assess the relationship between the biomechanical characteristics and sensorimotor characteristics (threshold to detect passive motion, time to peak torque, and peak torque). The results of this study demonstrated that increases in jump distance significantly increased landing demand and significantly impacted risk factors for ACL injury and muscle activation strategies. These findings illustrated that studies utilizing tasks with different demands cannot directly compare results or make inference to injury risk based previous findings. This study suggested that a jump distance of 40% to 60% body height is used during a double-leg stop-jump task to assess landing biomechanics related to ACL injury. Additionally, sensorimotor characteristics had significant relationships with knee flexion angle at initial contact, peak knee flexion, and peak knee abduction moment. Further research is needed to identify sensorimotor characteristics that contribute to frontal plane knee motion during landing

Combined Driving: Task-Specific Position Impacts Grip Strength of Equestrian Athletes

BACKGROUND: Loss of hand strength is a predictor of mortality in aging populations. Despite reliance on the hands to participate in equestrian driving activity, no existing studies focus on associations of hand strength to athletic performance. Therefore, this study 1) established baseline handgrip of equestrian combined drivers in standing and task-specific positions, 2) determined endurance of task-specific handgrip, 3) compared handgrip strength to normative data, and 4) evaluated associations of handgrip and equestrian-specific variables. METHODS: There were 51 combined drivers (9 males, 42 females) ages 21-78 who completed a survey, standing handgrip, and grip strength and endurance in a task-specific position. Sixty-three percent of participants were 50 years or older. The dynamometer grip bar was normalized by hand size for standing tests; to duplicate sport-specific tasks, the bar was set to the closest setting. Significances were determined at p \u3c 0.05. RESULTS: Drivers with more than 30 years of experience demonstrated highest summed standing (73.1 ± 5.2 kg) and summed sitting (59.9 ± 6.3 kg) grip strength. Females 60-years and older had greater handgrip endurance (Χ2 = 8.323, df = 2, p = .0156) in non-dominant (left) hands. Males (60%) reported more cold weather fatigue than females. Glove wearing was associated with bilateral endurance balance; a higher proportion of endurance balance between dominant and non-dominant (49% high-high and 29% low-low; Χ2 = 11.047, df = 1, p = .0009) was realized. There were no associations of handgrip and prior injury. CONCLUSIONS: Our results have implications in understanding task-specific and normative grip strengths in aging equestrian populations. Bilateral balance in handgrip strength and endurance is important particularly in maintaining strength in non-dominant hands over time. Equestrian driving sport promotes greater endurance in older females. Strength can be improved by participating in combined driving, and engagement in this sport over several years\u27 benefits hand strength over time. This cohort of equestrian participants provides evidence that participating in hand-specific activities promotes greater strength, which has been previously shown to improve aging outcomes

Fast and slow light in zig-zag microring resonator chains

We analyze fast and slow light transmission in a zig-zag microring resonator chain. This novel device permits the operation in both regimes. In the superluminal case, a new ubiquitous light transmission effect is found whereby the input optical pulse is reproduced in an almost simultaneous manner at the various system outputs. When the input carrier is tuned to a different frequency, the system permits to slow down the propagating optical signal. Between these two extreme cases, the relative delay can be tuned within a broad range

Effects of Carbohydrates on Landing Mechanics and Postural Stability During Intermittent High-Intensity Exercise to Fatigue

Please refer to the pdf version of the abstract located adjacent to the title

Backscattering in silicon microring resonators: a quantitative analysis

Silicon microring resonators very often exhibit resonance splitting due to backscattering. This effect is hard to quantitatively and predicatively model. This paper presents a behavioral circuit model for microrings that quantitatively explains the wide variations in resonance splitting observed in experiments. The model is based on an in-depth analysis of the contributions to backscattering by both the waveguides and couplers. Backscattering transforms unidirectional microrings into bidirectional circuits by coupling the clockwise and counterclockwise circulating modes. In high-Q microrings, visible resonance splitting will be induced, but, due to the stochastic nature of backscattering, this splitting is different for each resonance. Our model, based on temporal coupled mode theory, and the associated fitting method, are both accurate and robust, and can also explain asymmetrically split resonances. The cause of asymmetric resonance splitting is identified as the backcoupling in the couplers. This is experimentally confirmed and its dependency on gap and coupling length is further analyzed. Moreover, the wide variation in resonance splitting of one spectrum is analyzed and successfully explained by our circuit model that incorporates most linear parasitic effects in the microring. This analysis uncovers multi-cavity interference within the microring as an important source of this variation