Lifted Variable Elimination for Probabilistic Logic Programming

Lifted inference has been proposed for various probabilistic logical frameworks in order to compute the probability of queries in a time that depends on the size of the domains of the random variables rather than the number of instances. Even if various authors have underlined its importance for probabilistic logic programming (PLP), lifted inference has been applied up to now only to relational languages outside of logic programming. In this paper we adapt Generalized Counting First Order Variable Elimination (GC-FOVE) to the problem of computing the probability of queries to probabilistic logic programs under the distribution semantics. In particular, we extend the Prolog Factor Language (PFL) to include two new types of factors that are needed for representing ProbLog programs. These factors take into account the existing causal independence relationships among random variables and are managed by the extension to variable elimination proposed by Zhang and Poole for dealing with convergent variables and heterogeneous factors. Two new operators are added to GC-FOVE for treating heterogeneous factors. The resulting algorithm, called LP$^2$ for Lifted Probabilistic Logic Programming, has been implemented by modifying the PFL implementation of GC-FOVE and tested on three benchmarks for lifted inference. A comparison with PITA and ProbLog2 shows the potential of the approach.Comment: To appear in Theory and Practice of Logic Programming (TPLP). arXiv admin note: text overlap with arXiv:1402.0565 by other author

Study of a spectrometer line for the Linac4 diagnostics movable bench

movable diagnostics bench is currently being designed as part of the Linac4 commissioning plan to characterise the H-beam at the exit of each DTL tank. A spectrometer line has been proposed for installation on the bench to allow performing measurements of the beam energy spread with a slit/dipole/monitor technique. A layout for this diagnostics line is here proposed together with the results of beam dynamics studies to evaluate the resolution achievable and the measurement reach

Transfer Line Studies from LINAC4 to the PS Booster: "South Hall" Option

Linac4 is a new normal conducting H- linac, which is currently under study at CERN as upgrade to the present LHC injectors chain in view of intensifying the proton flux available for the CERN accelerator complex and eventually attain LHC ultimate luminosity goals. The new linac is designed to accelerate a 65 mA H- ion beam from 3 MeV up to 160 MeV for charge-exchange injection into the CERN Proton Synchrotron Booster, thus overcoming the space charge limitations of the present injection mechanism at 50 MeV, which represent the main obstacle to obtaining higher beam brightness into the PS. A new transfer line is also being planned to transport the beam from the end of Linac4 to the PSB and the present paper outlines one of the proposed layouts and gives the status of the beam dynamics studies for this solution

Transfer Line Studies from LINAC4 to the PS Booster: Green Field Option

Linac4 is a normal conducting H- linac, which is currently under study at CERN as upgrade to the present LHC injectors chain in view of intensifying the proton flux available for the CERN accelerator complex and eventually attain LHC ultimate luminosity goals. The new linac is designed to accelerate a 65 mA H- ion beam from 45 keV up to 160 MeV for charge-exchange injection into the CERN Proton Synchrotron Booster, thus overcoming the space charge limitations of the present injection mechanism at 50 MeV, which represent the main obstacle to obtaining higher beam brightness into the PS. A transfer line is being planned to transport the beam from the end of Linac4 to the PSB: a solution corresponding to a siting of the linac in the existing PS South Hall was initially studied [1] but later discarded in favour of a new "green field" arrangement of a whole complex of new machines (including the SPL and PS2) at CERN. The present note outlines this latest layout and presents the results of the relative beam dynamics studies

Tutores, alunos e o curso de graduação em medicina: um círculo virtuoso

BACKGROUND: Mentoring Programs have been developed in several medical schools, but few studies have investigated the mentors'perspective. PURPOSES: To explore mentors'perceptions regarding their experience. METHODS: Mentors at a medical school were invited to participate in an in-depth interview including questions on satisfaction, difficulties, and perception of changes resulting from the program. RESULTS: Mentors' satisfaction and difficulties are strongly associated with students'involvement in the activity. Mentors believe changes observed in students were more related to life issues; for some mentors, there is no recognition or awareness of the program. However, most of the mentors acknowledged important changes in relation to themselves: as teachers, faculty members, and individuals. CONCLUSION: Attendance is crucial for both the mentoring relationship and strengthening of the program. Students involved in the activity motivate mentors in teaching and curriculum development, thereby creating a virtuous circle and benefiting undergraduate medical education as a whole.CONTEXTO: Programas de Mentoring têm sido desenvolvidos em várias escolas médicas, mas poucos estudos investigam essa experiência sob a perspectiva dos mentores. OBJETIVOS: Explorar a percepção de mentores a respeito de suas experiências ao longo do tempo. MÉTODO: Mentores de uma escola médica foram convidados a participar de uma entrevista em profundidade que incluía questões sobre satisfação, dificuldades e percepção de mudanças resultantes do programa. RESULTADOS: A satisfação e as dificuldades relatadas pelos mentores mostraram-se fortemente ao grau de envolvimento dos alunos no programa. Os mentores acreditam que as mudanças observadas nos alunos estão mais relacionadas a questões dessa fase de vida e, para alguns, ainda não há reconhecimento do programa pela instituição. Por outro lado, a maioria dos mentores reconhece importantes mudanças nem si mesmos: como professores, como membros da faculdade e como pessoa. CONCLUSÕES: A adesão dos alunos mostra-se crucial tanto para a relação de Mentoring quanto para a própria consolidação do programa. Alunos envolvidos com a atividade motivam os mentores para o ensino e o aprimoramento do currículo, criando assim um círculo virtuoso, que beneficia o curso e a formação médica como um todo

Updated layout of the LINAC4 transfer line to the PS Booster (Green Field Option)

At the time of defining the site of Linac4 and its integration in the complex of existing infrastructure at CERN (together with the plans for a future Superconducting Proton Linac), a series of radiation protection issues emerged that have since prompted a revision of the Linac4 to PSB transfer line layout, as was described in the document ABâNoteâ2007â037. For radiological safety reasons the distance between the planned SPL tunnel and the basement of building 513 had to be increased, and this led to the decision to lower the Linac4 machine by 2.5m. A vertical ramp was consequently introduced in the transfer line to raise the beam at the same level of LINAC2/PSB for connection to the existing transfer line. A series of error study runs has been carried out on the modified layout to have an estimate of the losses induced by quadrupole alignment and field errors. The two worst cases of each error family have been used as case studies to test the efficiency of possible steering strategies in minimizing beam losses and machine activation. The new layout and beam dynamics issues plus the results of the error and steering studies are discussed in this note

Studies on combined momentum and betatron cleaning in the LHC

Collimation and halo cleaning for the LHC beams are performed separately for betatron and momentum losses, requiring two dedicated insertions for collimation. Betatron cleaning is performed in IR7 while momentum cleaning is performed in IR3. A study has been performed to evaluate the performance reach for a combined betatron and momentum cleaning system in IR3. The results are presented

Accelerator physics concept for upgraded LHC collimation performance

The LHC collimation system is implemented in phases, in view of the required extrapolation by 2-3 orders of magnitude beyond Tevatron and HERA experience in stored energy. All available simulations predict that the LHC proton beam intensity with the "Phase I" collimation system may be limited by the impedance of the collimators or cleaning efficiency. Maximum efficiency requires collimator materials very close to the beam, generating the dominant resistive wall impedance in the LHC. Above a certain intensity the beam is unstable. On the other hand, even if collimators are set very close to the beam, the achievable cleaning efficiency is predicted to be inadequate, requiring either beam stability beyond specifications or reduced intensity. The accelerator physics concept for upgrading cleaning efficiency, for both proton and heavy ion beams, and reducing collimator-related impedance is described. Besides the "Phase II" secondary collimators, new collimators are required in a few super-conducting regions