3,833 research outputs found
Development of diagnostic and manipulation systems for space-charge dominated electron beams and confined electron plasmas in ELTRAP
No full textModifications have been implemented in the Penning-Malmberg device ELTRAP aimed
at performing studies on the dynamics of space-charge dominated nanosecond electron bunches traveling along the magnetic field. In particular, a Thomson backscattering apparatus has been developed where an infrared (IR) laser pulse collides with the bunched electron beam. The frequency-shifted
backscattered radiation, acquired by means of a photomultiplier (PMT), can be exploited to evaluate information on energy, energy spread and density of the bunch. The achievable sensitivity
of the diagnostics has been estimated, and valuable information on the main parameters affecting the signal-to-noise (S/N) ratio has been obtained [B. Paroli, F. Cavaliere, M. Cavenago, F. De Luca, M. Ikram, G. Maero, C. Marini, R. Pozzoli, and M. Romé, JINST 7, P01008 (2012)]. A series of upgrades are under way, aimed at increasing the S/N ratio through the use of a new laser for the electron source, the insertion of a stray light shield, and the optimization of the detection electronics. Moreover, electromagnetic simulations relevant to the design and implementation of a microwave
heating system are presented. The generation of an electron plasma in ELTRAP by means of a low-power radio frequency (RF) drive in the MHz range applied on one of the trap electrodes and under ultra-high vacuum (UHV) conditions has previously been demonstrated [B. Paroli, F. De Luca,
G. Maero, F. Pozzoli, and M. Romé, Plasma Sources Sci. Technol. 19, 045013 (2010)]. The new heating system will allow the extension of the RF studies to the GHz range and in particular the
production of a more energetic electron plasma via cyclotron resonant excitation
Primary prevention of cardiovascular disease: The past, present, and future of blood pressure- and cholesterol-lowering treatments
No full textIn a Perspective, M. Afran Ikram and Maarten Leening discuss the evolving approaches to determining cardiovascular risk.Version of Recor
Nondestructive evaluation of residual stresses in nanostructured coatings by synchotron radiation:
No full textThis thesis presents a strain mapping in nanostructure Al2O3/TiO2 ceramic coatings on metallic Titanium substrates by synchrotron radiation. The mapping is obtained under various boundary conditions (tension/compression loads, four-point bending, etc.) and is accomplished using high energy (deeply penetrating) synchrotron white radiation with photon energies up to 200 keV to perform high precision x-ray diffraction on small volumes (1 µm to a few cm), which are then integrated into high resolution 3D maps of the strain fields. Strain mapping in conventional micro-size ceramic coatings are performed for comparison. The underlining structural and functional parameters in processing of these coatings, which result in dramatic improvements in their performance, are discussed. The thesis also presents mechanical properties such as elastic modulus, yield strength, etc., which are deduced from energy dispersive X-ray diffraction (EDXRD) strain mapping in conjunction with modeling.M.S.Includes bibliographical referencesby Nazia Ikram Ahmed
SCXRD dataset for "Synthesis of 2-amino-5-methylpyridinium tetrachloridocadmate(II) (C6H9N2)2[CdCl4]: Structure, DFT-calculated descriptors and molecular docking study"
No full textDataset del artículo Jomaa, Ikram; Bardak, Fehmi; ISSAOUI, N.; Cabeza, Aurelio; Choquesillo-Lazarte, Duane CSIC ORCID; Atac, A.; Marouani, Houda; Al-Dossary, Omar M. Synthesis of 2-amino-5-methylpyridinium tetrachloridocadmate(II) (C6H9N2)2[CdCl4]: Structure, DFT-calculated descriptors and molecular docking study. Journal of King Saud University - Science 36 (2024)King Saud UniversityPeer reviewe
The impact of a peer-based student conflict management training program in a middle school
No full textTypescript (photocopy).The major purpose of the study was to assess the effectiveness of an experimental Peer-based Conflict Management Training Program in a middle school of South-Central Texas. The purpose of the training program is directed toward empowering students in such a way that they become responsible, capable contributors in resolving their own conflicts, and additionally that they learn how to effectively intervene and assist others in resolving their conflicts. As a result of the program, unproductive conflicts among students are reduced, thus contributing to more effective teaching and learning. The Peer-based Conflict Management Training Program emphasizes an important dimension in school culture as the responsibility of resolving school conflicts is shifted from adults to young adults. Also, it offers school administrators a more appropriate and effective alternative to deal with conflict in the school setting than expulsion, suspension, and detention. The results of the study revealed the extent of improvements in students' attitudes about conflict, improvement in their self-esteem, and improvement in their behavior after participation in the program. A sample of 42 students (6th, 7th, and 8th grades) was selected from an urban middle school's population to determine the effectiveness of the treatment. The Statistical Analysis System (SAS) was used to perform the analysis of covariance to test the difference between two groups on dependent variables of self-esteem, conflict attitudes, and deviant behavior of students. Three instruments (Piers-Harris Scale; Benenson's Survey Questionnaire; Brown and Hamill Teacher Rating Scale) were used to collect the data. Test results were analyzed at the 0.05 level of significance. Based on the data obtained and interpretation of subsequent analyses, the following conclusions were drawn. 1) The Peer-based Conflict Management Training Program had significantly improved student knowledge of constructive approaches to conflict management..
Supplemental Material, JoGPN_supp_matts - Physical Exercise Interventions Targeting Cognitive Functioning and the Cognitive Domains in Nondementia Samples: A Systematic Review of Meta-Analyses
No full textSupplemental Material, JoGPN_supp_matts for Physical Exercise Interventions Targeting Cognitive Functioning and the Cognitive Domains in Nondementia Samples: A Systematic Review of Meta-Analyses by David T. Turner, Mandy X. Hu, Ellen Generaal, Daniel Bos, M. Kamran Ikram, Alis Heshmatollah, Lana Fani, M. Arfan Ikram, Brenda W. J. H. Penninx and Pim Cuijpers in Journal of Geriatric Psychiatry and Neurology</p
Radio-frequency generation of an electron plasma in a Malmberg-Penning trap and its interaction with a stationary or pulsed electron beam.
No full textExperiments and numerical investigations on trapped electron plasmas and traveling electron bunches are discussed.
A Thomson backscattering diagnostics set up was installed in the ELTRAP (Electron TRAP) device, a Penning-Malmberg trap operating at the Department of Physics of the University of Milano since 2001. Here, an infrared (IR) laser pulse collides with nanosecond electron bunches with an energy of 1-20 keV traveling through a longitudinal magnetic field in a dynamical regime where space-charge effects play a significant role. The backscattered radiation is optically filtered and detected by means of a photomultiplier tube. The minimum sensitivity of the backscattering diagnostics has been estimated for the present set-up configuration. Constraints on the number of photons and thus on the information one can obtain with the Thomson backscattering technique are determined by the relatively low density of the electron beam as well as by noise issues. Solutions to increase the signal level and to reduce the noise are briefly discussed.
The generation of an electron plasma by stochastic heating was realized in ELTRAP under ultra-high vacuum conditions by means of the application of low power RF (1-20 MHz) drives on one of the azimuthally sectored electrodes of the trap. The relevant experimental results are reviewed. The electron heating mechanism has been studied by means of a two-dimensional (2D) particle-in-cell (PIC) code, starting with a very low electron density, and applying RF drives of various amplitudes in the range 1-15 MHz on different electrodes. The axial kinetic energy of the electrons is in general increasing for all considered cases. Of course, higher temperature increments are obtained by increasing the amplitude of the RF excitation. The simulation results indicate in particular that the heating is initially higher close to the cylindrical wall of the device. These results on the electron heating point in the same direction of the experimental findings, where the plasma formation due to the ionization of the residual gas is found to be localized close to the trap wall. The simulations indicate also major heating effects when the RF drive is applied close to one end of the trap. Similar results are obtained for an electron plasma at higher densities, simulating a situation in which the RF is applied to an already formed plasma.
With the aim to extend these RF studies to the microwave range, a bench test analysis has been performed of the transmission efficiency of a microwave injection system up to a few GHz. The test was based on the use of a prototype circular waveguide with the same diameter and length of the ELTRAP electrode stack and of a coupled rectangular waveguide with dimensions suitable for a future installation in the device.
Electromagnetic PIC simulations have also been performed of the electron heating effect, again both at very low and relatively high electron densities, applying a microwave drive with a frequency of approximately 3 GHz close to the center and close to one end of the trap.
Both the bench test of the injection system and the numerical simulations indicate that the new microwave heating system will allow the extension of the previous RF studies to the GHz range. In particular, the electron cyclotron resonance heating of the electrons will be aimed to increasing the electron temperature, and possibly its density as a consequence of a higher ionization rate of the residual gas. The installation of the new RF system will open up the possibility to study, e.g., the interaction between the confined plasma and traveling electron bunches
Publisher correction: Novel pleiotropic risk loci for melanoma and nevus density implicate multiple biological pathways
No full textThe original version of this Article contained errors in the spelling of the authors Fan Liu and M. Arfan Ikram, which were incorrectly given as Fan Lui and Arfan M. Ikram.\ua0In addition,\ua0the original version of this Article also\ua0contained errors\ua0in the author affiliations which are detailed in the associated Publisher Correction
Missione Archeologica del Centro di Studi Papirologici dell’Università degli Studi del Salento, Lecce, a Soknopaiou Nesos/Dime (El-Fayyum, Egitto). Tredicesima Campagna, Ottobre-Dicembre 2016
No full textResoconto della settima Campagna di Scavo a Soknopaiou Nesos da parte della Missione Archeologica del Centro di Studi Papirologici dell'Università del Salento
Observation of low-frequency oscillations in a radio frequency-stabilized plasma confined in a Malmberg-Penning trap
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