4,166 research outputs found
Preparation and analysis of strain-free uranium surfaces for electron and x-ray diffraction analysis
Empirically modelled Pc3 activity based on solar wind parameters
It is known that under certain solar wind (SW)/interplanetary magnetic
field (IMF) conditions (e.g. high SW speed, low cone angle) the occurrence of
ground-level Pc3â4 pulsations is more likely. In this paper we demonstrate
that in the event of anomalously low SW particle density, Pc3 activity is
extremely low regardless of otherwise favourable SW speed and cone angle. We
re-investigate the SW control of Pc3 pulsation activity through a statistical
analysis and two empirical models with emphasis on the influence of SW
density on Pc3 activity. We utilise SW and IMF measurements from the OMNI
project and ground-based magnetometer measurements from the MM100 array to
relate SW and IMF measurements to the occurrence of Pc3 activity. Multiple
linear regression and artificial neural network models are used in iterative
processes in order to identify sets of SW-based input parameters, which
optimally reproduce a set of Pc3 activity data. The inclusion of SW density
in the parameter set significantly improves the models. Not only the density
itself, but other density related parameters, such as the dynamic pressure of
the SW, or the standoff distance of the magnetopause work equally well in the
model. The disappearance of Pc3s during low-density events can have at least
four reasons according to the existing upstream wave theory: 1. Pausing the
ion-cyclotron resonance that generates the upstream ultra low frequency waves
in the absence of protons, 2. Weakening of the bow shock that implies less
efficient reflection, 3. The SW becomes sub-Alfvénic and hence it is not
able to sweep back the waves propagating upstream with the Alfvén-speed,
and 4. The increase of the standoff distance of the magnetopause (and of the
bow shock). Although the models cannot account for the lack of Pc3s during
intervals when the SW density is extremely low, the resulting sets of optimal
model inputs support the generation of mid latitude Pc3 activity
predominantly through upstream waves
Empirically modelled Pc3 activity based on solar wind parameters
It is known that under certain solar wind (SW)/interplanetary magnetic field (IMF) conditions (e.g. high SW speed, low cone angle) the occurrence of ground-level Pc3â4 pulsations is more likely. In this paper we demonstrate that in the event of anomalously low SW particle density, Pc3 activity is extremely low regardless of otherwise favourable SW speed and cone angle. We re-investigate the SW control of Pc3 pulsation activity through a statistical analysis and two empirical models with emphasis on the influence of SW density on Pc3 activity. We utilise SW and IMF measurements from the OMNI project and ground-based magnetometer measurements from the MM100 array to relate SW and IMF measurements to the occurrence of Pc3 activity. Multiple linear regression and artificial neural network models are used in iterative processes in order to identify sets of SW-based input parameters, which optimally reproduce a set of Pc3 activity data. The inclusion of SW density in the parameter set significantly improves the models. Not only the density itself, but other density related parameters, such as the dynamic pressure of the SW, or the standoff distance of the magnetopause work equally well in the model. The disappearance of Pc3s during low-density events can have at least four reasons according to the existing upstream wave theory: 1. Pausing the ion-cyclotron resonance that generates the upstream ultra low frequency waves in the absence of protons, 2. Weakening of the bow shock that implies less efficient reflection, 3. The SW becomes sub-AlfvĂ©nic and hence it is not able to sweep back the waves propagating upstream with the AlfvĂ©n-speed, and 4. The increase of the standoff distance of the magnetopause (and of the bow shock). Although the models cannot account for the lack of Pc3s during intervals when the SW density is extremely low, the resulting sets of optimal model inputs support the generation of mid latitude Pc3 activity predominantly through upstream waves
Prostate involvement during sexually transmitted infections as measured by prostate-specific antigen concentration
Background:We investigated prostate involvement during sexually transmitted infections by measuring serum prostate-specific antigen (PSA) as a marker of prostate infection, inflammation, and/or cell damage in young, male US military members.Methods:We measured PSA before and during infection for 299 chlamydia, 112 gonorrhoea, and 59 non-chlamydial, non-gonococcal urethritis (NCNGU) cases, and 256 controls.Results:Chlamydia and gonorrhoea, but not NCNGU, cases were more likely to have a large rise (â©Ÿ40%) in PSA than controls (33.6%, 19.1%, and 8.2% vs 8.8%, P<0.0001, 0.021, and 0.92, respectively).Conclusion:Chlamydia and gonorrhoea may infect the prostate of some infected men
Dynamical Toroidal Hopfions in a Ferromagnet with Easy-Axis Anisotropy
Three-dimensional toroidal precession solitons with a nonzero Hopf index,
which uniformly move along the anisotropy axis in a uniaxial ferromagnet, have
been found. The structure and existence region of the solitons have been
numerically determined by solving the Landau-Lifshitz equation.Comment: 6 pages, 4 figure
Splitting Proofs for Interpolation
We study interpolant extraction from local first-order refutations. We
present a new theoretical perspective on interpolation based on clearly
separating the condition on logical strength of the formula from the
requirement on the com- mon signature. This allows us to highlight the space of
all interpolants that can be extracted from a refutation as a space of simple
choices on how to split the refuta- tion into two parts. We use this new
insight to develop an algorithm for extracting interpolants which are linear in
the size of the input refutation and can be further optimized using metrics
such as number of non-logical symbols or quantifiers. We implemented the new
algorithm in first-order theorem prover VAMPIRE and evaluated it on a large
number of examples coming from the first-order proving community. Our
experiments give practical evidence that our work improves the state-of-the-art
in first-order interpolation.Comment: 26th Conference on Automated Deduction, 201
TOOLympics 2019: An Overview of Competitions in Formal Methods
Evaluation of scientific contributions can be done in many different ways. For the various research communities working on the verification of systems (software, hardware, or the underlying involved mechanisms), it is important to bring together the community and to compare the state of the art, in order to identify progress of and new challenges in the research area. Competitions are a suitable way to do that. The first verification competition was created in 1992 (SAT competition), shortly followed by the CASC competition in 1996. Since the year 2000, the number of dedicated verification competitions is steadily increasing. Many of these events now happen regularly, gathering researchers that would like to understand how well their research prototypes work in practice. Scientific results have to be reproducible, and powerful computers are becoming cheaper and cheaper, thus, these competitions are becoming an important means for advancing research in verification technology. TOOLympics 2019 is an event to celebrate the achievements of the various competitions, and to understand their commonalities and differences. This volume is dedicated to the presentation of the 16 competitions that joined TOOLympics as part of the celebration of the 25th anniversary of the TACAS conference
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