294 research outputs found
Breakup phenomena study in7Li+208Pb reaction using 8PLP
No full textInclusive alpha particle spectra for Li-7+Pb-208 reaction has been studied. There are different reaction mechanism such as pickup/transfer including breakup influence the observed alpha particle spectra. Presence of different bands of triton indicates the origin is different which needs more study
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How well do we understand quasi-elastic reactions at energies close to the barrier
No full textIn collisions between too heavy nuclei a wide spectrum of different reaction modes is observed covering the range from simple processes like elastic scattering to complicated multistep transfers and fusion. On the theoretical side heavy ion reactions are usually analyzed using models that were developed first for light ion induced reactions: the optical model for elastic scattering and the DWBA for more inelastic processes like transfer and inelastic scattering. Some of the assumptions going into these approximations, however, are not valid for heavy ion induced reactions. The region between fusion and quasi-elastic reactions is not well understood theoretically. This region is associated with deep inelastic collisions, which are complex multiparticle reactions involving transfer of several protons and neutrons. In this paper, the author discusses to what extent experiments in the field of quasi-elastic scattering are understood within the framework of various theoretical models and in what areas more work is needed
Procesos violentos de formación del Estado en los inicios del Frente Nacional en el Tolima, Colombia
No full textRehm L. Procesos violentos de formación del Estado en los inicios del Frente Nacional en el Tolima, Colombia. Revista Colombiana de Sociología. 2015;38(1):39-62.Recent state anthropology highlights the performative character of the state. State anthropologists call for a greater focus on the so-called (geographical, political, social) margins of the state in order to investigate how the state is constructed. According to Holden (2004), state formation processes are often violent ones that imply armed conflict involving military forces, para-governmental, and anti-state forces in the field of state power, as conceptualized by him.
On the basis of written sources such as newspaper releases, court files, and government memoranda from various archives, this paper analyses the armed struggle against the Communist oppositional groups in the department of Tolima and neighbouring areas. It is shown that the early Colombian National Front government, whose intention was to end the mid-20th century Colombian Civil War, resorted to a variety of measures to defend the contemporary political system. These involved the sometimes informal, sometimes formal employment of Liberal ex-combatants loyal to the government in order to extend state authority to the more marginal areas. In doing so armed political struggles were perpetuated.
The paper concludes with comparing the phenomena analysed in the paper with the rise of the paramilitary groups in the 1990s. Due to several structural parallels the author argues that the origins of Colombian paramilitarism dates back till the 1960s.
Keywords: violent state formation; para-governmental groups; paramilitarism; civil war; origins of Communist guerrilla
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Influence of quasi-elastic channels on fusion
No full textExperiments that measure the strength of different transfer reactions in heavy reaction systems at energies in the vicinity of the Coulomb barrier are discussed. A short discussion is given of experimental techniques that are available in this field and their advantages and shortfalls. The main features of the transfer reactions are summarized. Questions concerning the system dependence and energy dependence of the strongest reaction channels are addressed. A systematic picture of the strength of the neutron transfer cross sections is presented. Some examples for correlations between fusion exchangement and transfer cross sections are given
The time dependence of the variances of charge and mass distributions in deep inelastic collisions
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Nuclear structure in deep-inelastic reactions
No full textThe paper concentrates on recent deep inelastic experiments conducted at Argonne National Laboratory and the nuclear structure effects evident in reactions between super heavy nuclei. Experiments indicate that these reactions evolve gradually from simple transfer processes which have been studied extensively for lighter nuclei such as /sup 16/O, suggesting a theoretical approach connecting the one-step DWBA theory to the multistep statistical models of nuclear reactions. This transition between quasi-elastic and deep inelastic reactions is achieved by a simple random walk model. Some typical examples of nuclear structure effects are shown. 24 refs., 9 figs
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Transition from quasi-elastic to deep-inelastic reactions
No full textHeavy ion induced transfer reactions are usually considered to fall into two categories. Quasi-elastic processes, on one hand, are characterized by small energy transfers, with one-nucleon transfer reactions being a typical example. These processes are dominant for grazing collisions, and are generally described within simple one-step DWBA calculations. Deep inelastic reactions, on the other hand, occur for more central collisions where the interaction time is longer and subsequently more energy and particles can be exchanged. Quasi-elastic collisions dominate transfer reactions induced by light heavy ions (e.g., /sup 16/O) at energies not too high above the barrier, while deep inelastic collisions are observed mainly in reactions induced by heavier projectiles (Kr, Xe). In this contribution, we discuss the transition between these two processes for the system /sup 48/Ti + /sup 208/Pb. /sup 48/Ti is located between light (/sup 16/O) and heavy (Kr) projectiles and should be well suited for a study of the interrelation between quasi- and deep-inelastic reactions. The experiments were performed with a 300 MeV /sup 48/Ti beam obtained from the Argonne National Laboratory superconducting linac. The outgoing particles were momentum analyzed in a split pole magnetic spectrograph and detected in the focal plane by a position sensitive ionization chamber. The specific energy loss, the magnetic rigidity and the total energy of the outgoing particles were measured enabling mass and Z-identification. The energy resolution was about 3 MeV, determined by the thickness of the /sup 208/Pb target, and thus excluded study of transfer reactions to discrete final states. Angular distributions were measured in the range theta/sub lab/ = 20/sup 0/ to 80/sup 0/ in steps of 5/sup 0/. 8 refs
Influence of heavy-ion transfer on fusion reactions
No full textThe influence of inelastic excitations on heavy-ion fusion is well established and can be quantitativly described by coupled-channels calculations. The influence of transfer channels, however, is still under debate. We have analyzed a large set of heavy-ion-induced fusion excitation functions involving nuclei with similar structures and show that there is a universal correlation between the shape (and enhancement) of the excitation function and the strength of the total neutron-transfer cross sections for systems ranging from light to heavy masses
Enriching BERT with Knowledge Graph Embeddings for Document Classification
No full textIn this paper, we focus on the classification of books using short descriptive texts (cover blurbs) and additional metadata. Building upon BERT, a deep neural language model, we demonstrate how to combine text representations with metadata and knowledge graph embeddings, which encode author information. Compared to the standard BERT approach we achieve considerably better results for the classification task. For a more coarse-grained classification using eight labels we achieve an F1- score of 87.20, while a detailed classification using 343 labels yields an F1-score of 64.70. We make the source code and trained models of our experiments publicly availabl
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