5,154 research outputs found
Data Processing for NASA's TDRSS DAMA Channel
A concept for the addition of a Demand Assignment Multiple Access (DAMA) service to NASA's current Space Network (SN) is developed. Specifically, the design of a receiver for the DAMA channel is outlined. Also, an outline of the procedures taken to process the received service request is presented. The modifications to the (SN) system are minimal. The post reception processing is accomplished using standard commercial off the shelf (COTS) packages. The result is a random access system capable of receiving requests for service
Are We Dreaming or Doing? How Health Science Graduates Access Information in their Professional Lives
Metropolitan quantum key distribution with silicon photonics
Photonic integrated circuits (PICs) provide a compact and stable platform for
quantum photonics. Here we demonstrate a silicon photonics quantum key
distribution (QKD) transmitter in the first high-speed polarization-based QKD
field tests. The systems reach composable secret key rates of 950 kbps in a
local test (on a 103.6-m fiber with a total emulated loss of 9.2 dB) and 106
kbps in an intercity metropolitan test (on a 43-km fiber with 16.4 dB loss).
Our results represent the highest secret key generation rate for
polarization-based QKD experiments at a standard telecom wavelength and
demonstrate PICs as a promising, scalable resource for future formation of
metropolitan quantum-secure communications networks
Reynolds number influences in aeronautics
Reynolds number, a measure of the ratio of inertia to viscous forces, is a fundamental similarity parameter for fluid flows and therefore, would be expected to have a major influence in aerodynamics and aeronautics. Reynolds number influences are generally large, but monatomic, for attached laminar (continuum) flow; however, laminar flows are easily separated, inducing even stronger, non-monatomic, Reynolds number sensitivities. Probably the strongest Reynolds number influences occur in connection with transitional flow behavior. Transition can take place over a tremendous Reynolds number range, from the order of 20 x 10(exp 3) for 2-D free shear layers up to the order of 100 x 10(exp 6) for hypersonic boundary layers. This variability in transition behavior is especially important for complex configurations where various vehicle and flow field elements can undergo transition at various Reynolds numbers, causing often surprising changes in aerodynamics characteristics over wide ranges in Reynolds number. This is further compounded by the vast parameterization associated with transition, in that any parameter which influences mean viscous flow development (e.g., pressure gradient, flow curvature, wall temperature, Mach number, sweep, roughness, flow chemistry, shock interactions, etc.), and incident disturbance fields (acoustics, vorticity, particulates, temperature spottiness, even electro static discharges) can alter transition locations to first order. The usual method of dealing with the transition problem is to trip the flow in the generally lower Reynolds number wind tunnel to simulate the flight turbulent behavior. However, this is not wholly satisfactory as it results in incorrectly scaled viscous region thicknesses and cannot be utilized at all for applications such as turbine blades and helicopter rotors, nacelles, leading edge and nose regions, and High Altitude Long Endurance and hypersonic airbreathers where the transitional flow is an innately critical portion of the problem
XO-5b: A Transiting Jupiter-sized Planet With A Four Day Period
The star XO-5 (GSC 02959-00729, V=12.1, G8V) hosts a Jupiter-sized,
Rp=1.15+/-0.12 Rjup, transiting extrasolar planet, XO-5b, with an orbital
period of P=4.187732+/-0.00002 days. The planet mass (Mp=1.15+/-0.08 Mjup) and
surface gravity (gp=22+/-5 m/s^2) are significantly larger than expected by
empirical Mp-P and Mp-P-[Fe/H] relationships. However, the deviation from the
Mp-P relationship for XO-5b is not large enough to suggest a distinct type of
planet as is suggested for GJ 436b, HAT-P-2b, and XO-3b. By coincidence XO-5
overlies the extreme H I plume that emanates from the interacting galaxy pair
NGC 2444/NGC 2445 (Arp 143).Comment: 10 pages, 9 Figures, Submitted to Ap
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Higher measured than modeled ozone production at increased NOx levels in the Colorado Front Range
Abstract. Chemical models must correctly calculate the ozone formation rate, P(O3), to accurately predict ozone levels and to test mitigation strategies. However, air quality models can have large uncertainties in P(O3) calculations, which can create uncertainties in ozone forecasts, especially during the summertime when P(O3) is high. One way to test mechanisms is to compare modeled P(O3) to direct measurements. During summer 2014, the Measurement of Ozone Production Sensor (MOPS) directly measured net P(O3) in Golden, CO, approximately 25âŻkm west of Denver along the Colorado Front Range. Net P(O3) was compared to rates calculated by a photochemical box model that was constrained by measurements of other chemical species and that used a lumped chemical mechanism and a more explicit one. Median observed P(O3) was up to a factor of 2 higher than that modeled during early morning hours when nitric oxide (NO) levels were high and was similar to modeled P(O3) for the rest of the day. While all interferences and offsets in this new method are not fully understood, simulations of these possible uncertainties cannot explain the observed P(O3) behavior. Modeled and measured P(O3) and peroxy radical (HO2 and RO2) discrepancies observed here are similar to those presented in prior studies. While a missing atmospheric organic peroxy radical source from volatile organic compounds co-emitted with NO could be one plausible solution to the P(O3) discrepancy, such a source has not been identified and does not fully explain the peroxy radical modelâdata mismatch. If the MOPS accurately depicts atmospheric P(O3), then these results would imply that P(O3) in Golden, CO, would be NOx-sensitive for more of the day than what is calculated by models, extending the NOx-sensitive P(O3) regime from the afternoon further into the morning. These results could affect ozone reduction strategies for the region surrounding Golden and possibly other areas that do not comply with national ozone regulations. Thus, it is important to continue the development of this direct ozone measurement technique to understand P(O3), especially under high-NOx regimes
An exploratory study looking at the relationship marketing techniques used in the music festival industry
There are current issues and trends in the music festival
market, which may affect the success of an event, and market saturation
is at the forefront of these issues. Previous literature, maintaining
the need for a marketing approach to festivals, identifi es the need
for maintaining strong stakeholder relationships in order to succeed
in a business environment; attention has been focused to the theory
of relationship marketing (RM) because of the recognition that this
practice is complementary to the marketing of festivals. The very nature
of the music festival as an annual, usually, 4-day event means that
effective marketing is needed to keep connections with the consumer
throughout the year. This article focuses on the RM techniques
utilised within the music festival industry from the viewpoint of the
festival organiser in an attempt to establish how festival organisations
value and monitor organisational relationships. This article explores
the extent to which these relationships are valued and managed;
furthermore, the variations between these intricate relationships
are considered by focusing on those held with the organisation â s
consumers and sponsors, the results of which have provided the
ability to establish the importance and relevance of RM to the industry
and further identify the marketing communication methods employed
to establish and maintain such relationships. In-depth, convergent
interviews have been conducted with a segment of music festival
organisers from a range of events. The results have been integrated
with the study of current literature to best exemplify these issues. It
has been established that RM has a strong role in today â s commercial
and independent music festival industry; technological advances are
enabling the organiser to support online relationships further and
increase consumer loyalty. There is a need to expand the research
further because of the complexity of organisational relationships and
the varying categories of festivals
MTHFD1 controls DNA methylation in Arabidopsis.
DNA methylation is an epigenetic mechanism that has important functions in transcriptional silencing and is associated with repressive histone methylation (H3K9me). To further investigate silencing mechanisms, we screened a mutagenized Arabidopsis thaliana population for expression of SDCpro-GFP, redundantly controlled by DNA methyltransferases DRM2 and CMT3. Here, we identify the hypomorphic mutant mthfd1-1, carrying a mutation (R175Q) in the cytoplasmic bifunctional methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase (MTHFD1). Decreased levels of oxidized tetrahydrofolates in mthfd1-1 and lethality of loss-of-function demonstrate the essential enzymatic role of MTHFD1 in Arabidopsis. Accumulation of homocysteine and S-adenosylhomocysteine, genome-wide DNA hypomethylation, loss of H3K9me and transposon derepression indicate that S-adenosylmethionine-dependent transmethylation is inhibited in mthfd1-1. Comparative analysis of DNA methylation revealed that the CMT3 and CMT2 pathways involving positive feedback with H3K9me are mostly affected. Our work highlights the sensitivity of epigenetic networks to one-carbon metabolism due to their common S-adenosylmethionine-dependent transmethylation and has implications for human MTHFD1-associated diseases
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