136 research outputs found
Recommended from our members
Thin window Si(Li) detectors for the ISEE-C Telescope
Special detectors have been developed for the NASA ISEE-C Cosmic Ray Telescope. These are Li-drifted silicon detectors 5 mm thick and 1500 mm/sup 2/ area with the criteria that thickness variations on the whole area be less than +-10 ..mu..m and that the Li-diffused contact dead-layer not exceed 15 ..mu..m. Techniques used to fabricate and test these detectors are presented
Impact of a nitrogen emission control area (NECA) on the future air quality and nitrogen deposition to seawater in the Baltic Sea region
Air pollution due to shipping is a serious concern for coastal regions in
Europe. Shipping emissions of nitrogen oxides (NOx) in air
over the Baltic Sea are of similar magnitude (330 kt yr−1) as the
combined land-based NOx emissions from Finland and Sweden in
all emission sectors. Deposition of nitrogen compounds originating from
shipping activities contribute to eutrophication of the Baltic Sea and
coastal areas in the Baltic Sea region. For the North Sea and the Baltic Sea
a nitrogen emission control area (NECA) will become effective in 2021; in
accordance with the International Maritime Organization (IMO) target of
reducing NOx emissions from ships. Future scenarios for 2040
were designed to study the effect of enforced and planned regulation of ship
emissions and the fuel efficiency development on air quality and nitrogen
deposition. The Community Multiscale Air Quality (CMAQ) model was used to
simulate the current and future air quality situation. The meteorological
fields, the emissions from ship traffic and the emissions from land-based
sources were considered at a grid resolution of 4×4 km2
for the Baltic Sea region in nested CMAQ simulations. Model simulations for
the present-day (2012) air quality show that shipping emissions are the major
contributor to atmospheric nitrogen dioxide (NO2) concentrations
over the Baltic Sea. In the business-as-usual (BAU) scenario, with the
introduction of the NECA, NOx emissions from ship traffic in
the Baltic Sea are reduced by about 80 % in 2040. An approximate linear
relationship was found between ship emissions of NOx and the
simulated levels of annual average NO2 over the Baltic Sea in the
year 2040, when following different future shipping scenarios. The burden of
fine particulate matter (PM2.5) over the Baltic Sea region is predicted
to decrease by 35 %–37 % between 2012 and 2040. The reduction in
PM2.5 is larger over sea, where it drops by 50 %–60 % along the
main shipping routes, and is smaller over the coastal areas. The introduction
of NECA is critical for reducing ship emissions of NOx to
levels that are low enough to sustainably dampen ozone (O3)
production in the Baltic Sea region. A second important effect of the NECA
over the Baltic Sea region is the reduction in secondary formation of
particulate nitrate. This lowers the ship-related PM2.5 by 72 % in
2040 compared to the present day, while it is reduced by only 48 %
without implementation of the NECA. The effect of a lower fuel efficiency
development on the absolute ship contribution of air pollutants is limited.
Still, the annual mean ship contributions in 2040 to NO2, sulfur
dioxide and PM2.5 and daily maximum O3 are significantly
higher if a slower fuel efficiency development is assumed. Nitrogen
deposition to the seawater of the Baltic Sea decreases on average by
40 %–44 % between 2012 and 2040 in the simulations. The effect of
the NECA on nitrogen deposition is most significant in the western part of
the Baltic Sea. It will be important to closely monitor compliance of
individual ships with the enforced and planned emission regulations.</p
Recommended from our members
Isotopic composition of neon in the galactic cosmic rays: a high resolution measurement
A measurement of the isotopic composition of galactic cosmic ray neon in the energy range 70 to 260 MeV/amu has been made using the U.C. Berkeley HKH instrument aboard ISEE-3. A combination of high resolution and good statistical accuracy makes possible a precise determination of the local interplanetary neon composition. We find /sup 22/Ne//sup 20/Ne = 0.64 +- 0.07 and /sup 21/Ne//sup 20/Ne < 0.30 in local interplanetary space. These ratios, when interpreted in using standard galactic propagation and solar modulation models, yield cosmic ray source abundances which are inconsistent with a solar-like source composition
The STAR Time Projection Chamber: A Unique Tool for Studying High Multiplicity Events at RHIC
The STAR Time Projection Chamber (TPC) is used to record collisions at the
Relativistic Heavy Ion Collider (RHIC). The TPC is the central element in a
suite of detectors that surrounds the interaction vertex. The TPC provides
complete coverage around the beam-line, and provides complete tracking for
charged particles within +- 1.8 units of pseudo-rapidity of the center-of-mass
frame. Charged particles with momenta greater than 100 MeV/c are recorded.
Multiplicities in excess of 3,000 tracks per event are routinely reconstructed
in the software. The TPC measures 4 m in diameter by 4.2 m long, making it the
largest TPC in the world.Comment: 28 pages, 11 figure
Seasonal ozone vertical profiles over North America using the AQMEII3 group of air quality models: model inter-comparison and stratospheric intrusions
This study evaluates simulated vertical ozone profiles produced in the
framework of the third phase of the Air Quality Model Evaluation
International Initiative (AQMEII3) against ozonesonde observations in North
America for the year 2010. Four research groups from the United States (US)
and Europe have provided modeled ozone vertical profiles to conduct this
analysis. Because some of the modeling systems differ in their meteorological
drivers, wind speed and temperature are also included in the analysis. In
addition to the seasonal ozone profile evaluation for 2010, we also analyze
chemically inert tracers designed to track the influence of lateral boundary
conditions on simulated ozone profiles within the modeling domain. Finally,
cases of stratospheric ozone intrusions during May–June 2010 are investigated
by analyzing ozonesonde measurements and the corresponding model simulations
at Intercontinental Chemical Transport Experiment Ozonesonde Network Study
(IONS) experiment sites in the western United States. The evaluation of the
seasonal ozone profiles reveals that, at a majority of the stations, ozone
mixing ratios are underestimated in the 1–6 km range. The seasonal change
noted in the errors follows the one seen in the variance of ozone mixing
ratios, with the majority of the models exhibiting less variability than the
observations. The analysis of chemically inert tracers highlights the
importance of lateral boundary conditions up to 250 hPa for the
lower-tropospheric ozone mixing ratios (0–2 km). Finally, for the stratospheric
intrusions, the models are generally able to reproduce the location and
timing of most intrusions but underestimate the magnitude of the maximum
mixing ratios in the 2–6 km range and overestimate ozone up to the first kilometer
possibly due to marine air influences that are not accurately described by
the models. The choice of meteorological driver appears to be a greater
predictor of model skill in this altitude range than the choice of air
quality model.</p
The energy dependence of flow in Ni induced collisions from 400 to 1970A MeV
We study the energy dependence of collective (hydrodynamic-like) nuclear
matter flow in 400-1970 A MeV Ni+Au and 1000-1970 A MeV Ni+Cu reactions. The
flow increases with energy, reaches a maximum, and then gradually decreases at
higher energies. A way of comparing the energy dependence of flow values for
different projectile-target mass combinations is introduced, which demonstrates
a common scaling behaviour among flow values from different systems.Comment: 12 pages, 3 figures. Submitted to Physical Review Letter
Statistical signatures of critical behavior in small systems
The cluster distributions of different systems are examined to search for
signatures of a continuous phase transition. In a system known to possess such
a phase transition, both sensitive and insensitive signatures are present;
while in systems known not to possess such a phase transition, only insensitive
signatures are present. It is shown that nuclear multifragmentation results in
cluster distributions belonging to the former category, suggesting that the
fragments are the result of a continuous phase transition.Comment: 31 pages, two columns with 30 figure
- …