Search results for "Trie"
showing 10 items of 4468 documents
Studies on the Correlation of Putrescine and Potassium Contents in the Needles of Spruce Trees
1995
Summary The correlation between the polyamine putrescine and the nutritional element potassium was examined in Picea abies trees at numerous natural stands in Germany. The amounts of potassium and putrescine in needles was analyzed and a linear negative correlation between the K + and putrescine contents was found, which is significant in the bulk of all stands as well as in subsets. The negative correlation becomes even more pronounced when only sites situated over 600 m with trees older than 60 years are included. While former investigations were concerned with experimental conditions of potassium concentrations in soil or nutrient solutions, the data presented here derive from natural ha…
Ernesta Foldāta vēstule Edgaram Vimbam 1994. gada 30. decembrī
1994
Ernesta Foldāta vēstule Edgaram Vimbam, kurā viņš raksta par piedāvājumu vadīt praktiskas lekcijas tropu ekoloģijā latviešu doktorantūras studentiem, par Venecuēlā sastopamajām sēņu sugām, īpaši bekām un gailenēm, par sēņu sālīšanu ziemai. Vēstules beigās Jauna gada novēlējums. Drukāts mašīnrakstā uz 1 lapas. Glabājas Latvijas Universitātes Muzeja Botānikas un mikoloģijas kolekciju krājumā.
Students' attitude towards the use of educational video games to develop competencies
2018
The use of educational video games (EVGs) is gaining momentum as a means to motivate and to engage students in their learning process. Nevertheless, previous research is taking for granted that students have a positive attitude towards EVGs and did not ensure a proper understanding of students' characteristics that might influence their attitude towards them. Therefore, this study's main goal is to explore four students' characteristics (perceived relevance, perceived confidence, media affinity, and perceived self-efficacy) that influence students' attitude towards the use of EVGs to develop competencies. Using the fsQCA method to analyze data gathered on a sample of 128 undergraduate stude…
Education for all by 2015
2002
At the World Education Forum in Dakar, Senegal, in 2000, officials from 180 countries set a challenging goal: ensuring access to primary education for all children by 2015
Essay on the integration of interactions in the treatment effect evaluation : the contribution of spatial econometrics methods
2015
This thesis focuses on the integration of interactions in the estimation of the public policy’s effect. Indeed, the estimation standard methods usually rely on strong assumptions that exclude partially or completely the interaction effect both in the selection process of beneficiaries and in the performance of the policy. However, the validity of these assumptions is questionable, particularly in the context of a non-experimental policy because an individual according as it is the beneficiary or not the policy, is not isolated: he interacts with his neighborhood. Thus, the estimated effect of the policy by traditional methods is likely to be biased (underestimation or overestimation) theref…
Efficient Graph Models for Retrieving Top-k News Feeds from Ego Networks
2012
A key challenge of web platforms like social networking sites and services for news feed aggregation is the efficient and targeted distribution of new content items to users. This can be formulated as the problem of retrieving the top-k news items out of the d-degree ego network of each given user, where the set of all users producing feeds is of size n, with n >> d >> k and typically k
Compton scattering by a pion and off-shell effects
1994
We consider Compton scattering by a pion in the framework of chiral perturbation theory. We investigate off--shell effects in the s-- and u--channel pole diagrams. For that purpose we perform a field transformation which, in comparison with the standard Gasser and Leutwyler Lagrangian, generates additional terms at order $p^4$ proportional to the lowest--order equation of motion. As a result of the equivalence theorem the two Lagrangians predict the same Compton scattering S--matrix even though they generate different off--shell form factors. We conclude that off--shell effects are not only model--dependent but also representation--dependent.
Combined description of N-barN scattering and annihilation with a hadronic model.
1995
A model for the nucleon-antinucleon interaction is presented which is based on meson-baryon dynamics. The elastic part is the {ital G}-parity transform of the Bonn {ital NN} potential. Annihilation into two mesons is described in terms of microscopic baryon-exchange processes including all possible combinations of {pi},{eta},{rho},{omega},{ital a}{sub 0},{ital f}{sub 0},{ital a}{sub 1},{ital f}{sub 1},{ital a}{sub 2},{ital f}{sub 2},{ital K},{ital K}{sup *}. The remaining annihilation part is taken into account by a phenomenological energy- and state-independent optical potential of Gaussian form. The model enables a simultaneous description of nucleon-antinucleon scattering and annihilatio…
Dynamical zeros in neutrino-electron elastic scattering at leading order
1994
We show the existence of dynamical zeros in the helicity amplitudes for neutrino-electron elastic scattering at lowest order in the standard theory. In particular, the $\lambda=1/2$ non-flip electron helicity amplitude in the electron antineutrino process vanishes for an incident neutrino energy $E_{\nu}=m_{e}/(4sin^{2}\theta_{W})$ and forward electrons (maximum recoil energy). The rest of helicity amplitudes show kinematical zeros in this configuration and therefore the cross section vanishes. Prospects to search for neutrino magnetic moment are discussed.
Measurement of ultra-low heating rates of a single antiproton in a cryogenic Penning trap
2019
Physical review letters 122(4), 043201 (2019). doi:10.1103/PhysRevLett.122.043201