1,742 research outputs found

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    Comparison of CDMA and FDMA for the MobileStar(sm) system

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    Spread-spectrum code division multiple access (CDMA) and single channel per carrier frequency division multiple access (FDMA) systems are compared for spectrum efficiency. CDMA is shown to have greater maximum throughput than FDMA for the MobileStar(sm) system which uses digital voice activated carriers and directive circularly polarized satellite antennas

    The Effects of Tempur Insoles on Ground Reaction Forces and Loading Rates in Running

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    Runners often experience over-use injuries. Ground reaction force (GRFs) patterns have been associated with these over-use injuries; however, it is not solely the magnitude of GRFs, but also the rate at which they are applied that lead to lower extremity injury. Many recreational runners will use over-the-counter insoles as a method of treating or preventing injury. Therefore, the purpose of this study was to examine the efficacy of two insoles on peak GRFs and loading rates. It was hypothesized that no differences in peak GRFs or loading rates would exist with the addition of two insoles during running. Twelve subjects (7 females; 5 males) performed seven running trials in each of the following conditions: no insoles (NORM), over-the-counter insoles (OTC) and memory-foam insoles (TEMPUR). GRFs were recorded using a force plate (1440Hz; AMTI) while subjects ran across a 15 meter lab. A 2 x 3 (gender x insole) repeated measures ANOVA was used to compare the effects of insoles on loading rate and ground reaction forces. Alpha level was set at p \u3c0.05. The current study found no statistical differences in loading rate or GRFs between the insole and no insole conditions. Furthermore, there was no gender effect in any condition. The findings of the current study suggest that insoles do not attenuate shock or decrease loading rate. The lack of shock attenuation associated with insoles suggests they do not protect the lower extremity from injury

    Calling The Dead: Resilience In The WTC Communication Networks

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    Organizations in emergency settings must cope with various sources of disruption, most notably personnel loss. Death, incapacitation, or isolation of individuals within an organizational communication network can impair information passing, coordination, and connectivity, and may drive maladaptive responses such as repeated attempts to contact lost personnel (``calling the dead'') that themselves consume scarce resources. At the same time, organizations may respond to such disruption by reorganizing to restore function, a behavior that is fundamental to organizational resilience. Here, we use empirically calibrated models of communication for 17 groups of responders to the World Trade Center Disaster to examine the impact of exogenous removal of personnel on communication activity and network resilience. We find that removal of high-degree personnel and those in institutionally coordinative roles is particularly damaging to these organizations, with specialist responders being slower to adapt to losses. However, all organizations show adaptations to disruption, in some cases becoming better connected and making more complete use of personnel relative to control after experiencing losses

    Lower Extremity Kinetics in High and Low-Arched Athletes during Landing

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    Abnormal foot function has been associated with an increased rate of injury in the athletic population. It has been shown that high-arched (HA) and low-arched (LA) athletes experience different injury patterns. These may be the manifestation of different loading and joint torque patterns in HA and LA athletes. It has been shown that HA and LA athletes have unique kinematic and kinetic patterns during running. However, little research has examined ground reaction forces (GRF) and lower extremity joint kinetics in HA and LA athletes during landing tasks. PURPOSE: To examine GRF and knee and ankle joint torques in HA and LA athletes during a landing task. METHODS: Ten HA (age: 20.8±2.5 years; height: 1.62±0.07 m; mass: 58.3±5.4 kg; arch index: 0.386±0.010) and 10 LA (age: 21.1±2.3; height: 1.63±0.07m; mass: 58.9±10.9kg; arch index: 0.259±0.043) female recreational athletes participated in this study. Each subject performed five barefooted drop landing trials from a height of 30 cm. GRFs and three-dimensional (3D) kinematics were recorded simultaneously using a force plate (1200 Hz, AMTI) and 7-camera motion analysis system (240 Hz, Vicon). GRFs and joint torques were calculated using Visual 3D (C-Motion, Inc.) and critical events were determined using custom software. A one-way ANOVA was used to compare group differences with an alpha level of p\u3c0.05. RESULTS: The GRF profiles were similar between the HA and LA athletes. However, HA athletes exhibited a mean eversion moment compared to an inversion moment in LA athletes (HA: -0.05±0.08 Nm/kg; LA: 0.04±0.07 Nm/kg). Additionally, the HA athletes generated greater peak knee external rotation torques (HA: 0.18±0.06 Nm/kg; LA: 0.26±0.08 Nm/kg) compared to LA athletes during the landing task. Knee extension and abduction torques were similar between the two groups in contrast to previous findings. CONCLUSIONS: The greater mean eversion torques exhibited by the HA athletes may be a response to being more inverted throughout the landing task. Increased eccentric contraction of the ankle everters would control eversion during landing. Similarly, the increased knee external rotation torques would act to limit knee internal rotation during landing. These altered kinetic patterns may increase the risk of injury within these groups of athletes

    Evolutionary and plastic changes in a native annual plant after a historic drought

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    Severe droughts are forecast to increase with global change. Approaches that enable the study of contemporary evolution, such as resurrection studies, are valuable for providing insights into the responses of populations to global change. In this study, we used a resurrection approach to study the evolution of the California native Leptosiphon bicolor (true babystars, Polemoniaceae) across populations differing in precipitation in response to the state\u27s recent prolonged drought (2011–2017). In the Mediterranean climate region in which L. bicolor grows, this historic drought effectively shortened its growing season. We used seeds collected both before and after this drought from three populations found along a moisture availability gradient to assess contemporary evolution in a common garden greenhouse study. We coupled this with a drought experiment to examine plasticity. We found evolution toward earlier flowering after the historic drought in the wettest of the three populations, while plasticity to experimental drought was observed across all three. We also observed trade-offs associated with earlier flowering. In the driest population, plants that flowered earlier had lower intrinsic water-use efficiency than those flowering later, which was an expected pattern. Unexpectedly, earlier flowering plants had larger flowers. Two populations exhibited evolution and plasticity toward smaller flowers with drought. The third exhibited evolution toward larger flowers, but displayed no plasticity. Our results provide valuable insights into differences among native plant populations in response to drought

    Molecular cloning, expression analysis and assignment of the porcine tumor necrosis factor superfamily member 10 gene (TNFSF10) to SSC13q34 -> q36 by fluorescence in situ hybridization and radiation hybrid mapping

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    We have cloned the complete coding region of the porcine TNFSF10 gene. The porcine TNFSF10 cDNA has an ORF of 870 nucleotides and shares 85 % identity with human TNFSF10, and 75% and 72% identity with rat and mouse Tnfsf10 coding sequences, respectively. The deduced porcine TNFSF10 protein consists of 289 amino acids with the calculated molecular mass of 33.5 kDa and a predicted pI of 8.15. The amino acid sequence similarities correspond to 86, 72 and 70% when compared with human, rat and mouse sequences, respectively. Nor-them blot analysis detected TNFSF10-specific transcripts (similar to 1.7 kb) in various organs of a 10-week-old pig, suggesting ubiquitous expression. Real-time RT-PCR studies of various organs from fetal (days 73 and 98) and postnatal stages (two weeks, eight months) demonstrated developmental and tissue-specific regulation of TNFSF10 mRNA abundance. The chromosomal location of the porcine TNFSF10 gene was determined by FISH of a specific BAC clone to metaphase chromosomes. This TNFSF10 BAC clone has been assigned to SSC13q34 -> q36. Additionally, the localization of the TNFSF10 gene was verified by RH mapping on the porcine IMpRH panel. Copyright (c) 2005S. KargerAG, Basel

    Evaluation of advanced lift concepts and fuel conservative short-haul aircraft, volume 1

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    The performance and economics of a twin-engine augmentor wing airplane were evaluated in two phases. Design aspects of the over-the-wing/internally blown flap hybrid, augmentor wing, and mechanical flap aircraft were investigated for 910 m. field length with parametric extension to other field lengths. Fuel savings achievable by application of advanced lift concepts to short-haul aircraft were evaluated and the effect of different field lengths, cruise requirements, and noise levels on fuel consumption and airplane economics at higher fuel prices were determined. Conclusions and recommendations are presented
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