The Effects of Repetitive Drop Jumps on Impact Phase Joint Kinematics and Kinetics

The purpose of the study was to investigate the effects of fatigue on lower extremity joint kinematics, and kinetics during repetitive drop jumps. Twelve recreationally active males (n = 6) and females (n = 6) (nine used for analysis) performed repetitive drop jumps until they could no longer reach 80% of their initial drop jump height. Kinematic and kinetic variables were assessed during the impact phase (100 ms) of all jumps. Fatigued landings were performed with increased knee extension, and ankle plantar flexion at initial contact, as well as increased ankle range of motion during the impact phase. Fatigue also resulted in increased peak ankle power absorption and increased energy absorption at the ankle. This was accompanied by an approximately equal reduction in energy absorption at the knee. While the knee extensors were the muscle group primarily responsible for absorbing the impact, individuals compensated for increased knee extension when fatigued by an increased use of the ankle plantar flexors to help absorb the forces during impact. Thus, as fatigue set in and individuals landed with more extended lower extremities, they adopted a landing strategy that shifted a greater burden to the ankle for absorbing the kinetic energy of the impact

Coherent Cancellation of Photothermal Noise in GaAs/Al0.92_{0.92}Ga0.08_{0.08}As Bragg Mirrors

Thermal noise is a limiting factor in many high-precision optical experiments. A search is underway for novel optical materials with reduced thermal noise. One such pair of materials, gallium arsenide and aluminum-alloyed gallium arsenide (collectively referred to as AlGaAs), shows promise for its low Brownian noise when compared to conventional materials such as silica and tantala. However, AlGaAs has the potential to produce a high level of thermo-optic noise. We have fabricated a set of AlGaAs crystalline coatings, transferred to fused silica substrates, whose layer structure has been optimized to reduce thermo-optic noise by inducing coherent cancellation of the thermoelastic and thermorefractive effects. By measuring the photothermal transfer function of these mirrors, we find evidence that this optimization has been successful.Comment: 10 pages, 7 figure

Aerial Inventories of Waterfowl in Illinois and Estimation of Moist-soil Plant Seed Abundance for Waterfowl on Lands Managed by Illinois Department of Natural Resources

Grant/Contract No: W-43-R 53-54-55Reports on progress and results of inventories of waterfowl along the Illinois and central Mississippi rivers during fall and winter and estimation of moist-soil plant seed abundance for waterfowl on lands managed by Illinois Department of Natural ResourcesINHS Technical Report Prepared for U.S. Fish & Wildlife Service, Illinois Department of Natural Resource

A Role for the Kolliker-Fuse Nucleus in Cholinergic Modulation of Breathing at Night During Wakefulness and NREM Sleep

For many years, acetylcholine has been known to contribute to the control of breathing and sleep. To probe further the contributions of cholinergic rostral pontine systems in control of breathing, we designed this study to test the hypothesis that microdialysis (MD) of the muscarinic receptor antagonist atropine into the pontine respiratory group (PRG) would decrease breathing more in animals while awake than while in NREM sleep. In 16 goats, cannulas were bilaterally implanted into rostral pontine tegmental nuclei (n = 3), the lateral (n = 3) or medial (n = 4) parabrachial nuclei, or the Kölliker-Fuse nucleus (KFN; n = 6). After \u3e2 wk of recovery from surgery, the goats were studied during a 45-min period of MD with mock cerebrospinal fluid (mCSF), followed by at least 30 min of recovery and a second 45-min period of MD with atropine. Unilateral and bilateral MD studies were completed during the day and at night. MD of atropine into the KFN at night decreased pulmonary ventilation and breathing frequency and increased inspiratory and expiratory time by 12–14% during both wakefulness and NREM sleep. However, during daytime studies, MD of atropine into the KFN had no effect on these variables. Unilateral and bilateral nighttime MD of atropine into the KFN increased levels of NREM sleep by 63 and 365%, respectively. MD during the day or at night into the other three pontine sites had minimal effects on any variable studied. Finally, compared with MD of mCSF, bilateral MD of atropine decreased levels of acetylcholine and choline in the effluent dialysis fluid. Our data support the concept that the KFN is a significant contributor to cholinergically modulated control of breathing and sleep

Probabilistic Fluorescence-Based Synapse Detection

Brain function results from communication between neurons connected by complex synaptic networks. Synapses are themselves highly complex and diverse signaling machines, containing protein products of hundreds of different genes, some in hundreds of copies, arranged in precise lattice at each individual synapse. Synapses are fundamental not only to synaptic network function but also to network development, adaptation, and memory. In addition, abnormalities of synapse numbers or molecular components are implicated in most mental and neurological disorders. Despite their obvious importance, mammalian synapse populations have so far resisted detailed quantitative study. In human brains and most animal nervous systems, synapses are very small and very densely packed: there are approximately 1 billion synapses per cubic millimeter of human cortex. This volumetric density poses very substantial challenges to proteometric analysis at the critical level of the individual synapse. The present work describes new probabilistic image analysis methods for single-synapse analysis of synapse populations in both animal and human brains.Comment: Current awaiting peer revie

High quality factor measured in fused silica

We have measured the mechanical dissipation in a sample of fused silica drawn into a rod. The sample was hung from a multiple-bob suspension, which isolated it from rubbing against its support, from recoil in the support structure, and from seismic noise. The quality factor, Q, was measured for several modes with a high value of 57 million found for mode number 2 at 726 Hz. This result is about a factor 2 higher than previous room temperature measurements. The measured Q was strongly dependent on handling, with a pristine flame-polished surface yielding a Q 3-4 times higher than a surface which had been knocked several times against a copper tube.Comment: Preprint - Under review by LSC publications committe

The Effect of Gender on Circulating Adipokines during Weight Loss and Weight Maintenance

During obesity, the altered release of adipokines, leptin and adiponectin, have been strongly associated with development of the metabolic syndrome. Treatment with weight loss has been shown to increase adiponectin, in particular high molecular weight (HMW) adiponectin, and reduce circulating leptin levels indicating an increased leptin sensitizing effect. Interestingly, a gender dichotomy has been identified with women generally possessing higher plasma concentrations of both adipokines. Weight loss effects have been well established; however, it remains to be determined how the gender differences in adiponectin and leptin will affect these adipokines during prolonged weight maintenance. PURPOSE: To identify gender differences in adiponectin and leptin concentrations following a 6-month weight loss and weight maintenance program. METHODS: Sixty-five obese (mean±SEM; age=47.9±1.1 years; BMI=34.3±0.7 kg/m2;) adults (M=20, F=45) completed a 3-month weight loss program that consisted of a reduced energy intake of 1200-1500 kcals/day using a high-volume low-calorie diet combined with a progressive walking program to target 300 min/wk. During the 3-month weight maintenance program, participants consumed sufficient calories to maintain weight loss with continued walking to target 300 min/wk. Fasted (12 hr) blood samples were collected at baseline, post- weight loss (3 months), and weight maintenance (6 months) and assayed for glucose, insulin, total and HMW adiponectin, and leptin. To identify significant changes over time and between gender, a repeated measures (time x gender) ANOVA was performed with significance set at P\u3c0.05. Results: At baseline, no significant difference in BMI or HOMA-IR were observed between genders. Following 3 months of weight loss, BMI was significantly reduced 9.9% and 8.5% in men and women, respectively, and BMI remained unchanged through the weight maintenance program. Interestingly, only men demonstrated a significant reduction in HOMA-IR following weight loss. Following weight maintenance in women, HOMA-IR increased slightly such that it was not significantly different than the baseline or weight loss time points. At baseline, women had significantly higher circulating levels of total and HMW adiponectin, and leptin. No significant changes in total or HMW adiponectin were observed over time for either gender. Following weight-loss, leptin concentrations were reduced 49.6% and 39.2% in men and women, respectively. Interestingly, only women demonstrated a transient reduction in leptin through the weight maintenance program. Conclusions: At baseline, we identified the presence of a clear gender dichotomy for total and HMW adiponectin, and leptin concentrations. Despite these significant differences in circulating adipokines at baseline, both men and women responded similarly to a 6-month weight loss and weight maintenance program