VHF command system study

Solutions are provided to specific problems arising in the GSFC VHF-PSK and VHF-FSK Command Systems in support of establishment and maintenance of Data Systems Standards. Signal structures which incorporate transmission on the uplink of a clock along with the PSK or FSK data are considered. Strategies are developed for allocating power between the clock and data, and spectral analyses are performed. Bit error probability and other probabilities pertinent to correct transmission of command messages are calculated. Biphase PCM/PM and PCM/FM are considered as candidate modulation techniques on the telemetry downlink, with application to command verification. Comparative performance of PCM/PM and PSK systems is given special attention, including implementation considerations. Gain in bit error performance due to coding is also considered

Activation of Extracellular-signal Regulated Kinase (ERK1/2) by Fluid Shear is Ca\u3csup\u3e2+\u3c/sup\u3e- and ATP-dependent in MC3T3-E1 Osteoblasts

To determine the role of Ca2+ signaling in activation of the Mitogen-Activated Protein Kinase (MAPK) pathway, we subjected MC3T3-E1 pre-osteoblastic cells to inhibitors of Ca2+ signaling during application of fluid shear stress (FSS). FSS only activated ERK1/2, rapidly inducing phosphorylation within 5 min of the onset of shear. Phosphorylation of ERK1/2 (pERK1/2) was significantly reduced when Cai2+ was chelated with BAPTA or when Ca2+ was removed from the flow media. Inhibition of both the L-type voltage-sensitive Ca2+ channel and the mechanosensitive cation-selective channel blocked FSS-induced pERK1/2. Inhibition of phospholipase C with U73122 significantly reduced pERK1/2. This inhibition did not result from blockage of intracellular Ca2+ release, but a loss of PKC activation. Recent data suggests a role of ATP release and purinergic receptor activation in mechanotransduction. Apyrase-mediated hydrolysis of extracellular ATP completely blocked FSS-induced phosphorylation of ERK1/2, while the addition of exogenous ATP to static cells mimicked the effects of FSS on pERK1/2. Two P2 receptors, P2Y2 and P2X7, have been associated with the anabolic responses of bone to mechanical loading. Using both iRNA techniques and primary osteoblasts isolated from P2X7 knockout mice, we found that the P2X7, but not the P2Y2, purinergic receptor was involved in ERK1/2 activation under FSS. These data suggest that FSS-induced ERK1/2 phosphorylation requires Ca2+-dependent ATP release, however both increased Cai2+ and PKC activation are needed for complete activation. Further, this ATP-dependent ERK1/2 phosphorylation is mediated through P2X7, but not P2Y2, purinergic receptors

Bifurcations of two coupled classical spin oscillators

Two classical, damped and driven spin oscillators with an isotropic exchange interaction are considered. They represent a nontrivial physical system whose equations of motion are shown to allow for an analytic treatment of local codimension 1 and 2 bifurcations. In addition, numerical results are presented which exhibit a Feigenbaum route to chaos.Comment: 16 pages, .dvi and postscrip

Nutrition knowledge and attitudes among college students

Objective: Many people have nearly universal access to nutrition information due to the Internet, yet online sources have a wide range of scientific and journalistic integrity that is difficult to predict. This affects the understanding and attitudes of the public regarding nutrition information. Given the academic and research-focused setting of universities, they are points of interest regarding the extent of this effect. The purpose of this study was to determine the nutrition knowledge and misinformation among Oklahoma State University students, relative to their preferred sources of nutritional information.Methods: A survey questionnaire was designed to evaluate the nutrition knowledge, attitudes, and perceptions of college students. It was composed of multiple-choice questions targeting popular sources of nutrition information and what factors participants considered to belong in either a healthy or unhealthy dietary pattern. The survey was released via Qualtrics, and five thousand OSU undergraduate students were randomly selected and contacted via email for participation.Results: At the conclusion of the study, 316 responses were recorded. When asked which factors characterize a healthy pattern of eating, prioritizing fruits and vegetables was the most common response (97%), followed by eating fish regularly (65%), and drinking only water (60%). When asked which factors characterize a non-healthy pattern of eating, eating sweets was the top response (83%), followed by eating snacks like chips (78%) and juice cleanses (68%). When selecting sources of nutrition information, word of mouth/friends and family was the most common (56%), followed by social media (45%) and health websites like Healthline and MayoClinic (42%).Summary: The data collected suggests that most Oklahoma State University students rely primarily on informal sources of nutrition information (i.e. word of mouth, social media). However, our data also suggests that most students understand key principles of a healthy dietary pattern like prioritizing fruits and vegetables and drinking only water, and avoiding foods and snacks that are overly sugary, calorically dense, and of little nutritional benefit. Taken together, these findings potentially suggest that despite students' overreliance on untrustworthy sources, the nutrition field has adequately popularized fundamental tenets of healthy eating

Limits to Sympathetic Evaporative Cooling of a Two-Component Fermi Gas

We find a limit cycle in a quasi-equilibrium model of evaporative cooling of a two-component fermion gas. The existence of such a limit cycle represents an obstruction to reaching the quantum ground state evaporatively. We show that evaporatively the \beta\mu ~ 1. We speculate that one may be able to cool an atomic fermi gas further by photoassociating dimers near the bottom of the fermi sea.Comment: Submitted to Phys. Rev

Deforestation: Correlations, Possible Causes and Some Implications

Changes in national forest areas during 1990-2000 are contrasted with other variables to illustrate correlations and provoke discussion about possible causes. Twenty-five statistically-significant correlations (including rural population, life expectancy, GDP, literacy, commerce, agriculture, poverty and inflation) are illustrated and a statistical model suggests that good governance, alternative employment opportunities, and payments for environmental services may be effective in combating deforestation. The data suggest that a global forest convention may need to be supported by substantial and carefully-targeted development assistance to foster good governance

Hard probes in heavy ion collisions at the LHC: PDFs, shadowing and pApA collisions

This manuscript is the outcome of the subgroup ``PDFs, shadowing and $pA$ collisions'' from the CERN workshop ``Hard Probes in Heavy Ion Collisions at the LHC''. In addition to the experimental parameters for $pA$ collisions at the LHC, the issues discussed are factorization in nuclear collisions, nuclear parton distributions (nPDFs), hard probes as the benchmark tests of factorization in $pA$ collisions at the LHC, and semi-hard probes as observables with potentially large nuclear effects. Also, novel QCD phenomena in $pA$ collisions at the LHC are considered. The importance of the $pA$ program at the LHC is emphasized.Comment: The writeup of the working group "PDFs, shadowing and $pA$ collisions" for the CERN Yellow Report on Hard Probes in Heavy Ion Collisions at the LHC, 121 pages. Subgroup convenors: K.J. Eskola, J.w. Qiu (theory) and W. Geist (experiment). Editor: K.J. Eskol

A framework for the probabilistic analysis of meteotsunamis

This paper is not subject to U.S. copyright. The definitive version was published in Natural Hazards 74 (2014): 123-142, doi:10.1007/s11069-014-1294-1.A probabilistic technique is developed to assess the hazard from meteotsunamis. Meteotsunamis are unusual sea-level events, generated when the speed of an atmospheric pressure or wind disturbance is comparable to the phase speed of long waves in the ocean. A general aggregation equation is proposed for the probabilistic analysis, based on previous frameworks established for both tsunamis and storm surges, incorporating different sources and source parameters of meteotsunamis. Parameterization of atmospheric disturbances and numerical modeling is performed for the computation of maximum meteotsunami wave amplitudes near the coast. A historical record of pressure disturbances is used to establish a continuous analytic distribution of each parameter as well as the overall Poisson rate of occurrence. A demonstration study is presented for the northeast U.S. in which only isolated atmospheric pressure disturbances from squall lines and derechos are considered. For this study, Automated Surface Observing System stations are used to determine the historical parameters of squall lines from 2000 to 2013. The probabilistic equations are implemented using a Monte Carlo scheme, where a synthetic catalog of squall lines is compiled by sampling the parameter distributions. For each entry in the catalog, ocean wave amplitudes are computed using a numerical hydrodynamic model. Aggregation of the results from the Monte Carlo scheme results in a meteotsunami hazard curve that plots the annualized rate of exceedance with respect to maximum event amplitude for a particular location along the coast. Results from using multiple synthetic catalogs, resampled from the parent parameter distributions, yield mean and quantile hazard curves. Further refinements and improvements for probabilistic analysis of meteotsunamis are discussed