978 research outputs found
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Measurement of performance limits in cryogenic heat pipes
This paper describes the results of an experimental study designed to investigate the fabrication and operation of gravity-assist cryogenic heat pipes. Two heat pipes were built, the first having no formal wick but a roughened internal surface, the second having spiral grooves machined with a specially developed tool. The wall material of the heat pipes was brass and hydrogen was used as the working fluid. The wicked heat pipe became operational over the entire temperature range from the triple-point to the critical point. The performance limitation depended on the operating temperature and the tilt angle. Axial heat flux densities of up to 50W/cm/sup 2/ were obtained. 15 refs., 9 figs
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A roadmap for China to peak carbon dioxide emissions and achieve a 20% share of non-fossil fuels in primary energy by 2030
As part of its Paris Agreement commitment, China pledged to peak carbon dioxide (CO2) emissions around 2030, striving to peak earlier, and to increase the non-fossil share of primary energy to 20% by 2030. Yet by the end of 2017, China emitted 28% of the world's energy-related CO2 emissions, 76% of which were from coal use. How China can reinvent its energy economy cost-effectively while still achieving its commitments was the focus of a three-year joint research project completed in September 2016. Overall, this analysis found that if China follows a pathway in which it aggressively adopts all cost-effective energy efficiency and CO2 emission reduction technologies while also aggressively moving away from fossil fuels to renewable and other non-fossil resources, it is possible to not only meet its Paris Agreement Nationally Determined Contribution (NDC) commitments, but also to reduce its 2050 CO2 emissions to a level that is 42% below the country's 2010 CO2 emissions. While numerous barriers exist that will need to be addressed through effective policies and programs in order to realize these potential energy use and emissions reductions, there are also significant local environmental (e.g., air quality), national and global environmental (e.g., mitigation of climate change), human health, and other unquantified benefits that will be realized if this pathway is pursued in China
The influence of depth and velocity on age‐0 Scaphirhynchus sturgeon prey consumption: Implications for aquatic habitat restoration
After the pallid sturgeon (Scaphirhynchus albus) was listed as endangered in 1990, a variety of management actions focusing on early life history needs have been implemented to aid species recovery. Given the scarcity of age‐0 pallid sturgeon, managers and scientists have relied on sympatric congeners to evaluate the effectiveness of management actions in the short term; however, increased understanding of habitat requirements for age‐0 Scaphirhynchus sturgeon is still needed to appropriately focus management efforts. Recently, a lack of food‐producing and foraging habitats were proposed as potential limiting factors for pallid sturgeon, and the purpose of this study was to evaluate the current definition of these habitats at multiple spatial scales using data from age‐0 Scaphirhynchus sturgeon (shovelnose sturgeon [Scaphirhynchus platyrhynchus] or hybrid [shovelnose sturgeon x pallid sturgeon]). Results showed the water depths and velocities that currently define age‐0 pallid sturgeon foraging habitat had little effect on age‐0 Scaphirhynchus sturgeon prey consumption. Similar results occurred when evaluating the relationship between prey consumption and food‐producing habitat present 10, 20, and 30 days before capture. Assuming that individuals captured during this study were a valid surrogate, these results suggest that increasing foraging and food‐producing habitat as defined by the current depth and velocity criteria is unlikely to result in the desired benefits of increased growth and survival of age‐0 pallid sturgeon
Bose-Einstein Correlations in e+e- to W+W- at 172 and 183 GeV
Bose-Einstein correlations between like-charge pions are studied in hadronic
final states produced by e+e- annihilations at center-of-mass energies of 172
and 183 GeV. Three event samples are studied, each dominated by one of the
processes W+W- to qqlnu, W+W- to qqqq, or (Z/g)* to qq. After demonstrating the
existence of Bose-Einstein correlations in W decays, an attempt is made to
determine Bose-Einstein correlations for pions originating from the same W
boson and from different W bosons, as well as for pions from (Z/g)* to qq
events. The following results are obtained for the individual chaoticity
parameters lambda assuming a common source radius R: lambda_same = 0.63 +- 0.19
+- 0.14, lambda_diff = 0.22 +- 0.53 +- 0.14, lambda_Z = 0.47 +- 0.11 +- 0.08, R
= 0.92 +- 0.09 +- 0.09. In each case, the first error is statistical and the
second is systematic. At the current level of statistical precision it is not
established whether Bose-Einstein correlations, between pions from different W
bosons exist or not.Comment: 24 pages, LaTeX, including 6 eps figures, submitted to European
Physical Journal
Measurements of Flavour Dependent Fragmentation Functions in Z^0 -> qq(bar) Events
Fragmentation functions for charged particles in Z -> qq(bar) events have
been measured for bottom (b), charm (c) and light (uds) quarks as well as for
all flavours together. The results are based on data recorded between 1990 and
1995 using the OPAL detector at LEP. Event samples with different flavour
compositions were formed using reconstructed D* mesons and secondary vertices.
The \xi_p = ln(1/x_E) distributions and the position of their maxima \xi_max
are also presented separately for uds, c and b quark events. The fragmentation
function for b quarks is significantly softer than for uds quarks.Comment: 29 pages, LaTeX, 5 eps figures (and colour figs) included, submitted
to Eur. Phys. J.
W+W- production and triple gauge boson couplings at LEP energies up to 183 GeV
A study of W-pair production in e+e- annihilations at Lep2 is presented,
based on 877 W+W- candidates corresponding to an integrated luminosity of 57
pb-1 at sqrt(s) = 183 GeV. Assuming that the angular distributions of the
W-pair production and decay, as well as their branching fractions, are
described by the Standard Model, the W-pair production cross-section is
measured to be 15.43 +- 0.61 (stat.) +- 0.26 (syst.) pb. Assuming lepton
universality and combining with our results from lower centre-of-mass energies,
the W branching fraction to hadrons is determined to be 67.9 +- 1.2 (stat.) +-
0.5 (syst.)%. The number of W-pair candidates and the angular distributions for
each final state (qqlnu,qqqq,lnulnu) are used to determine the triple gauge
boson couplings. After combining these values with our results from lower
centre-of-mass energies we obtain D(kappa_g)=0.11+0.52-0.37,
D(g^z_1)=0.01+0.13-0.12 and lambda=-0.10+0.13-0.12, where the errors include
both statistical and systematic uncertainties and each coupling is determined
setting the other two couplings to the Standard Model value. The fraction of W
bosons produced with a longitudinal polarisation is measured to be
0.242+-0.091(stat.)+-0.023(syst.). All these measurements are consistent with
the Standard Model expectations.Comment: 48 pages, LaTeX, including 13 eps or ps figures, submitted to
European Physical Journal
Search for Neutral Higgs Bosons in e+e- Collisions at sqrt(s) ~189GeV
A search for neutral Higgs bosons has been performed with the OPAL detector
at LEP, using approximately 170 pb-1 of e+e- collision data collected at
sqrt(s)~189GeV. Searches have been performed for the Standard Model (SM)
process e+e- to H0Z0 and the MSSM processes e+e- to H0Z0, A0h0. The searches
are sensitive to the b b-bar and tau antitau decay modes of the Higgs bosons,
and also to the MSSM decay mode h0 to A0A0. OPAL search results at lower
centre-of-mass energies have been incorporated in the limits we set, which are
valid at the 95% confidence level. For the SM Higgs boson, we obtain a lower
mass bound of 91.0 GeV. In the MSSM, our limits are mh>74.8GeV and mA>76.5GeV,
assuming tan(beta)>1, that the mixing of the scalar top quarks is either zero
or maximal, and that the soft SUSY-breaking masses are 1 TeV. For the case of
zero scalar top mixing, we exclude values of tan(beta) between 0.72 and 2.19.Comment: 38 pages, 15 figures, submitted Euro. Phys. J.
Bose-Einstein Correlations of Three Charged Pions in Hadronic Z^0 Decays
Bose-Einstein Correlations (BEC) of three identical charged pions were
studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP.
The genuine three-pion correlations, corrected for the Coulomb effect, were
separated from the known two-pion correlations by a new subtraction procedure.
A significant genuine three-pion BEC enhancement near threshold was observed
having an emitter source radius of r_3 = 0.580 +/- 0.004 (stat.) +/- 0.029
(syst.) fm and a strength of \lambda_3 = 0.504 +/- 0.010 (stat.) +/- 0.041
(syst.). The Coulomb correction was found to increase the \lambda_3 value by
\~9% and to reduce r_3 by ~6%. The measured \lambda_3 corresponds to a value of
0.707 +/- 0.014 (stat.) +/- 0.078 (syst.) when one takes into account the
three-pion sample purity. A relation between the two-pion and the three-pion
source parameters is discussed.Comment: 19 pages, LaTeX, 5 eps figures included, accepted by Eur. Phys. J.
Novel insights into host-fungal pathogen interactions derived from live-cell imaging
Acknowledgments The authors acknowledge funding from the Wellcome Trust (080088, 086827, 075470 and 099215) including a Wellcome Trust Strategic Award for Medical Mycology and Fungal Immunology 097377 and FP7-2007–2013 grant agreement HEALTH-F2-2010-260338–ALLFUN to NARG.Peer reviewedPublisher PD
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