17,438 research outputs found
Adhesive coating eliminated in new honeycomb-core fabrication process
Technique eliminates use of silicone-based adhesive material as bonding medium. Adhesive requires precise time-temperature cure. Prepreg resin is used as bonding medium, and each layer is laminated together to form honeycomb billet. Process can be used in any application where nonmetallic honeycomb core is being fabricated
Loss Tolerant Optical Qubits
We present a linear optics quantum computation scheme that employs a new
encoding approach that incrementally adds qubits and is tolerant to photon loss
errors. The scheme employs a circuit model but uses techniques from cluster
state computation and achieves comparable resource usage. To illustrate our
techniques we describe a quantum memory which is fault tolerant to photon loss
Quantum Density Fluctuations in Classical Liquids
We discuss the density fluctuations of a fluid due to zero point motion.
These can be regarded as density fluctuations in the phonon vacuum state. We
assume a linear dispersion relation with a fixed speed of sound and calculate
the density correlation function. We note that this function has the same form
as the correlation function for the time derivative of a relativistic massless
scalar field, but with the speed of light replaced by the speed of sound. As a
result, the study of density fluctuations in a fluid can be a useful analog
model for better understanding fluctuations in relativistic quantum field
theory. We next calculate the differential cross section for light scattering
by the zero point density fluctuations, and find a result proportional to the
fifth power of the light frequency. This can be understood as the product of
fourth power dependence of the usual Rayleigh cross section with the linear
frequency dependence of the spectrum of zero point density fluctuations. We
give some estimates of the relative magnitude of this effect compared to the
scattering by thermal density fluctuations, and find that it can be of order
0.5% for water at room temperature and optical frequencies. This relative
magnitude is proportional to frequency and inversely proportional to
temperature. Although the scattering by zero point density fluctuation is
small, it may be observable.Comment: 7 page
Effects of air pollution on natural vegetation and crops
The present report is being submitted for the consideration of the Working Group on Effects in accordance with the request of the Executive Body for the Convention on Longrange Transboundary Air Pollution in the 2012–2013 workplan for the implementation of the Convention (ECE/EB.AIR/109/Add.2, items 3.1 (c) and 3.5).
The report of the International Cooperative Programme on Effects of Air Pollution on Natural Vegetation and Crops presents the results of ozone impacts on ecosystem
services and biodiversity, and the results of the pilot study on mosses as biomonitors of persistent organic pollutants as part of the European moss survey conducted in 2010/11. In addition, the results of the workplan items common to all programmes are presented
Programmed schedule holds for improving launch vehicle holds
Baseline definition and system optimization are used for the analysis of programmed holds developed through prelaunch system analysis. Identification of design specifications for ground support equipment and maintenance concepts, and design specifications are used to describe the functional utilization of the overall flow process
Spin freezing and dynamics in Ca_{3}Co_{2-x}Mn_{x}O_{6} (x ~ 0.95) investigated with implanted muons: disorder in the anisotropic next-nearest neighbor Ising model
We present a muon-spin relaxation investigation of the Ising chain magnet
Ca_{3}Co_{2-x}Mn_{x}O_{6} (x~0.95). We find dynamic spin fluctuations
persisting down to the lowest measured temperature of 1.6 K. The previously
observed transition at around T ~18 K is interpreted as a subtle change in
dynamics for a minority of the spins coupling to the muon that we interpret as
spins locking into clusters. The dynamics of this fraction of spins freeze
below a temperature T_{SF}~8 K, while a majority of spins continue to
fluctuate. An explanation of the low temperature behavior is suggested in terms
of the predictions of the anisotropic next-nearest-neighbor Ising model.Comment: 4 pages, 2 figure
Doxycycline exposure during adolescence and future risk of non-affective psychosis and bipolar disorder: a total population cohort study
Doxycycline has been hypothesized to prevent development of severe mental illness (SMI) through the suppression of microglia, especially if administered during the intense synaptic pruning period of adolescence. However, results from register studies on potential benefits differ considerably. The aim of the present study was to determine whether doxycycline exposure during adolescence is associated with reduced SMI risk, and to investigate if a direct and specific causality is plausible. This is a Swedish national population register-based cohort study of all individuals born from 1993 to 1997, followed from the age of 13 until end of study at the end of 2016. The primary exposure was cumulative doxycycline prescription ≥3000 mg and outcomes were first diagnosis of non-affective psychosis (F20–F29) and first diagnosis of bipolar disorder (F30–F31). Causal effects were explored through Cox regressions with relevant covariates and secondary analyses of multilevel exposure and comparison to other antibiotics. We found no association between doxycycline exposure and risk of subsequent non-affective psychosis (adjusted hazard ratio (HR) 1.15, 95% CI 0.73–1.81, p = 0.541) and an increased risk of subsequent bipolar disorder (adjusted HR 1.95, 95% CI 1.49–2.55, p < 0.001). We do not believe the association between doxycycline and bipolar disorder is causal as similar associations were observed for other common antibiotics
Entangling photons via the double quantum Zeno effect
We propose a scheme for entangling two photons via the quantum Zeno effect,
which describes the inhibition of quantum evolution by frequent measurements
and is based on the difference between summing amplitudes and probabilities.
For a given error probability , our scheme requires that the
one-photon loss rate and the two-photon absorption rate
in some medium satisfy , which is significantly improved in comparison to previous
approaches. Again based on the quantum Zeno effect, as well as coherent
excitations, we present a possibility to fulfill this requirement in an
otherwise linear optics set-up.Comment: 4 pages RevTeX, 2 figure
Economic Impact of a Ban on Use of Antibiotics in U.S. Swine Rations
Antibiotic drugs are currently used in 90% of starter feed, 75% of grower feeds, more than 50% of finishing feeds, and at least 20% of sow feeds (USDA/APHIS). A ban on the use of feed grade antibiotics will lead to changes in production processes and practices in production of pork, and hence is likely to have an economic impact on the U.S. pork industry and pork market. On average, the cost of feed grade antibiotic use for all animal producers has been estimated to be about 3.75% of total ration costs, or about 50% of the value of the compounds to animal producers (1, cited in 2). To anticipate the potential effect on U.S. pork production, this study uses a set of technical impacts that are based in large part on a historical analysis of how the Swedish ban influenced the Swedish pork industr
The Sexual health of pupils in years 4 to 6 of primary schools in rural Tanzania
Background/objectives: There is an urgent need for effective interventions to improve the sexual and\ud
reproductive health of adolescents. Reliable data on the sexual health of adolescents are needed to guide\ud
the development of such interventions. The aim was to describe the sexual health of pupils in years 4 to 6 of\ud
121 rural primary schools in north western Tanzania, before the implementation of an innovative sexual\ud
health intervention in 58 of the schools.\ud
Methods: A cross sectional survey of primary school pupils in rural Tanzania was carried out. The study\ud
population comprised pupils registered in years 4 to 6 of 121 primary schools in 20 rural communities in\ud
1998. Basic demographic information was collected from all pupils seen. Those born before 1 January\ud
1985 (aged approximately 14 years and over) were invited to participate in the survey, and asked about\ud
their knowledge and attitudes towards sexual health issues, and their sexual experience. A urine specimen\ud
was requested and tested for HIV, Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG) and, for\ud
females, pregnancy.\ud
Results: 9283 pupils born before 1 January 1985 were enrolled and provided demographic information\ud
and a urine sample. Male pupils were significantly older than females (mean age 15.5 years v 14.8 years,\ud
p,0.001), but all other demographic characteristics were similar between the sexes. 14 (0.2%) of the\ud
enrolled pupils (four male and 10 female) were HIV positive, 83 (0.9%) were positive for CT, and 12\ud
(0.1%) for NG. 32 female pupils (0.8%) were positive by pregnancy test. Sexual experience was reported\ud
by one fifth of primary school girls, and by almost half of boys. Only 45/114 (39%) girls with biological\ud
markers of sexual activity reported having had sex.\ud
Conclusions: HIV, CT, NG, and pregnancy were present though at relatively low levels among pupils in\ud
years 4 to 6 of primary school. A high proportion of pupils with a biological marker of sexual activity\ud
denied ever having had sex. Alternative ways of collecting sensitive data about the sexual behaviour of\ud
school pupils should be explored
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