910 research outputs found
On Urabe's criteria of isochronicity
We give a short proof of Urabe's criteria for the isochronicity of periodical
solutions of the equation . We show that apart from the
harmonic oscillator there exists a large family of isochronous potentials which
must all be non-polynomial and not symmetric (an even function of the
coordinate x).Comment: 8 page
Some combinatorial problems
AbstractThere are many interesting and sophisticated problems posed in the IMO, Putnam and domestic Olympiads. Some of these problems have deep mathematical background, nice generalizations, and lead to new areas of research in combinatorics. We investigate several topics in this category and mention some results and open problems
A study of 15N14N isotopic exchange over cobalt molybdenum nitrides
The 14N/15N isotopic exchange pathways over Co3Mo3N, a material of interest as an ammonia synthesis catalyst and for the development of nitrogen transfer reactions, have been investigated. Both the homomolecular and heterolytic exchange processes have been studied, and it has been shown that lattice nitrogen species are exchangeable. The exchange behavior was found to be a strong function of pretreatment with ca. 25% of lattice N atoms being exchanged after 40 min at 600 °C after N2 pretreatment at 700 °C compared to only 6% following similar Ar pretreatment. This observation, for which the potential contribution of adsorbed N species can be discounted, is significant in terms of the application of this material. In the case of the Co6Mo6N phase, regeneration to Co3Mo3N under 15N2 at 600 °C occurs concurrently with 14N15N formation. These observations demonstrate the reactivity of nitrogen in the CoâMoâN system to be a strong function of pretreatment and worthy of further consideration
Fluctuation of the Top Location and Avalanches in the Formation Process of a Sandpile
We investigate the formation processes of a sandpile using numerical
simulation. We find a new relation between the fluctuation of the motion of the
top and the surface state of a sandpile. The top moves frequently as particles
are fed one by one every time interval T. The time series of the top location
has the power spectrum which obeys a power law, S(f)~f^{\alpha}, and its
exponent \alpha depends on T and the system size w. The surface state is
characterized by two time scales; the lifetime of an avalanche, T_{a}, and the
time required to cause an avalanche, T_{s}. The surface state is fluid-like
when T_{a}~T_{s}, and it is solid-like when T_{a}<<T_{s}. Our numerical results
show that \alpha is a function of T_{s}/T_{a}.Comment: 15 pages, 13 figure
Distribution-based bisimulation for labelled Markov processes
In this paper we propose a (sub)distribution-based bisimulation for labelled
Markov processes and compare it with earlier definitions of state and event
bisimulation, which both only compare states. In contrast to those state-based
bisimulations, our distribution bisimulation is weaker, but corresponds more
closely to linear properties. We construct a logic and a metric to describe our
distribution bisimulation and discuss linearity, continuity and compositional
properties.Comment: Accepted by FORMATS 201
Successful Intra-Arterial Chemotherapy for Extramammary Pagetâs Disease of the Axilla in a Patient with Parkinsonâs Disease
Extramammary Pagetâs disease (EMPD) is a rare intraepithelial neoplasm occurring less frequently in men and even more rarely in the axilla. A 59-year-old man with severe Parkinsonâs disease presented with axillary EMPD. The neurological comorbidity made treatment of the EMPD problematical and prompted us to propose locoregional intra-arterial chemotherapy in single short sessions. Two innovative chemotherapeutic macrocomplexes were used: doxorubicin incorporated in large liposomes and the taxane paclitaxel incorporated in albumin nanoparticles. A therapeutic response was seen right from the first treatment and was macroscopically close to complete after four cycles. Five months after the end of treatment the patient had minimal visible disease and had enjoyed a distinct improvement in quality of life, with no noteworthy complications related to the intra-arterial chemotherapy with percutaneous transfemoral catheterization
Sentiment analysis tools should take account of the number of exclamation marks!!!
There are various factors that affect the sentiment level expressed in textual comments. Capitalization of letters tends to mark something for attention and repeating of letters tends to strengthen the emotion. Emoticons are used to help visualize facial expressions which can affect understanding of text. In this paper, we show the effect of the number of exclamation marks used, via testing with twelve online sentiment tools. We present opinions gathered from 500 respondents towards âlikeâ and âdislikeâ values, with a varying number of exclamation marks. Results show that only 20% of the online sentiment tools tested considered the number of exclamation marks in their returned scores. However, results from our human raters show that the more exclamation marks used for positive comments, the more they have higher âlikeâ values than the same comments with fewer exclamations marks. Similarly, adding more exclamation marks for negative comments, results in a higher âdislikeâ
Le cadre géologique d'un site hydrothermal actif : la campagne STARMER 1 du submersible Nautile dans le Bassin Nord-Fidjien
International audienc
In situ geological and geochemical study of an active hydrothermal site on the North Fiji basin ridge
International audienc
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