45 research outputs found
Colloidal ionic complexes on periodic substrates: ground state configurations and pattern switching
We theoretically and numerically studied ordering of "colloidal ionic
clusters" on periodic substrate potentials as those generated by optical
trapping. Each cluster consists of three charged spherical colloids: two
negatively and one positively charged. The substrate is a square or rectangular
array of traps, each confining one such cluster. By varying the lattice
constant from large to small, the observed clusters are first rod-like and form
ferro- and antiferro-like phases, then they bend into a banana-like shape and
finally condense into a percolated structure. Remarkably, in a broad parameter
range between single-cluster and percolated structures, we have found stable
supercomplexes composed of six colloids forming grape-like or rocket-like
structures. We investigated the possibility of macroscopic pattern switching by
applying external electrical fields.Comment: 14 pages, 13 figure
Insulated fixation system of plasma facing components to the divertor cassette in Eurofusion-DEMO
The design activities of an insulated Plasma Facing Components-Cassette Body (PFCs-CB) support has been carried out under the pre-conceptual design phase for Eurofusion-DEMO Work Package DIV-1 \u201cDivertor Cassette Design and Integration\u201d - Eurofusion Power Plant Physics & Technology (PPPT) program. The Eurofusion-DEMO divertor is a key in-vessel component with PFCs which directly interact with the plasma scrape-off layer. The PFCs have to cope with high heat loads, neutron irradiation and electromagnetic loads. The mechanical integrity of the PFCs and water cooling pipes can be jeopardized by high heat loads and by electromagnetic loads generated in a disruption event. In European-DEMO the possibility to estimate the heat load by measuring the relative thermocurrents is under investigation. In order to allow thermocurrents measurements, a divertor design option provides that PFCs are electrically insulated from CB. In this work authors aim to analyze the opportunity that the PFC-CB fixing system incorporates an electrical insulation system, thus acquiring also an important diagnostic role in the measurement of the thermocurrents and in the management of the current flows. The possible use of ceramic material (e.g. alumina) as the insulating layer between the support components is investigated
Microscopic modelling of doped manganites
Colossal magneto-resistance manganites are characterised by a complex
interplay of charge, spin, orbital and lattice degrees of freedom. Formulating
microscopic models for these compounds aims at meeting to conflicting
objectives: sufficient simplification without excessive restrictions on the
phase space. We give a detailed introduction to the electronic structure of
manganites and derive a microscopic model for their low energy physics.
Focussing on short range electron-lattice and spin-orbital correlations we
supplement the modelling with numerical simulations.Comment: 20 pages, 10 figs, accepted for publ. in New J. Phys., Focus issue on
Orbital Physic
Numerical study of the Jahn-Teller polaron and bipolaron
The properties of the polaron and bipolaron are explored in the 1D
Jahn-Teller model with dynamical quantum phonons. The ground-state properties
of the polaron and bipolaron are computed using a recently developed
variational method. Dynamical properties of the ground state of a polaron are
investigated by calculating the optical conductivity . Our
numerical results suggest that the Jahn-Teller and Holstein polarons are
similar. However, in the strong-coupling regime qualitative differences in
between the two models are found and discussed. The influence
of the electron-phonon coupling and the electrostatic repulsion on the
bipolaron binding energy, bipolaron masses, and correlation functions is
investigated.Comment: 9 pages including 11 figures. To appear in PR
Assessment of the Linkages and Leakages in a Cloud-Based Computing Collaboration among Construction Stakeholders
The uniqueness of the construction industry can be understood in the large volumes of information in terms of paper works, processes, and communication disseminated
daily. The voluminous information requires close coordination which cloud based systems offer. The aim of this research is to assess the linkages and leakages in a
cloud-based computing collaboration among construction stakeholders. A purposive sampling technique was used in selecting the participants of the study. A questionnaire based instrument was distributed to eighty (80) construction
stakeholder in Lagos State, Nigeria. The data collected was analyzed using SPSS v.21. Statistical tools such as frequencies, stacked bars, mean scores, factor analysis,
and analysis of variance (ANOVA) were used in the study. The result of the study revealed that construction stakeholders rarely utilize cloud-based technologies for their construction processes. Construction professionals that access cloud based technologies, do so with their smart mobile phones, laptops, and tablet. The study classified the leakages that exist in the use of cloud-based technologies as securitybased factors, cloud-based infrastructure factors, and cloud-based benefits deficiency based factors. In conclusion, the study revealed that the linkages in the use of cloudbased technologies include knowledge sharing, remote access of back-office activities and engendering collaboration among construction stakeholders. It was recommended that construction stakeholders should leverage on the benefits cloud-based technologies has to offer in today’s competitive economy. Construction stakeholdersshould be adequately informed on the available cloud-based computing technologies and the additions it can bring into the construction process. Cloud computing technology vendors should improve on the security and privacy features of the platform for adequate protection of building data
Calculation of excited polaron states in the Holstein model
An exact diagonalization technique is used to investigate the low-lying
excited polaron states in the Holstein model for the infinite one-dimensional
lattice. For moderate values of the adiabatic ratio, a new and comprehensive
picture, involving three excited (coherent) polaron bands below the phonon
threshold, is obtained. The coherent contribution of the excited states to both
the single-electron spectral density and the optical conductivity is evaluated
and, due to the invariance of the Hamiltonian under the space inversion, the
two are shown to contain complementary information about the single-electron
system at zero temperature. The chosen method reveals the connection between
the excited bands and the renormalized local phonon excitations of the
adiabatic theory, as well as the regime of parameters for which the electron
self-energy has notable non-local contributions. Finally, it is shown that the
hybridization of two polaron states allows a simple description of the ground
and first excited state in the crossover regime.Comment: 12 pages, 9 figures, submitted to PR
Development of a concept and basis for the DEMO diagnostic and control system
An initial concept for the plasma diagnostic and control (D&C) system has been developed as part of European studies towards the development of a demonstration tokamak fusion reactor (DEMO). The main objective is to develop a feasible, integrated concept design of the DEMO D&C system that can provide reliable plasma control and high performance (electricity output) over extended periods of operation. While the fusion power is maximized when operating near to the operational limits of the tokamak, the reliability of operation typically improves when choosing parameters significantly distant from these limits. In addition to these conflicting requirements, the D&C development has to cope with strong adverse effects acting on all in vessel components on DEMO (harsh neutron environment, particle fluxes, temperatures, electromagnetic forces, etc.). Moreover, space allocation and plasma access are constrained by the needs for first wall integrity and optimization of tritium breeding. Taking into account these boundary conditions, the main DEMO plasma control issues have been formulated, and a list of diagnostic systems and channels needed for plasma control has been developed, which were selected for their robustness and the required coverage of control issues. For a validation and refinement of this concept, simulation tools are being refined and applied for equilibrium, kinetic and mode control studies
Occurrence and Control of Biogenic Amines in Fresh Fish and Products of Fish
In this study, the detection of biogenic amines in fresh and products of fish is focused and biological trials have been used to reduce their levels. 120 random samples of fresh fish (Lates niloticus), sardine salted, herring smoked, and tuna canned (for every thirty samples) were collected from different markets in Shibine, Menoufia, Egypt. The biogenic amine residues have examined in all samples that were collected (histamine, putrescine, cadaverine and tyramine). The average levels of biogenic amines in the samples under investigation of fresh fish, canned tuna, herring smoked, and sardine salted are 10.74 ± 0.54, 15.08 ± 0.76, 17.93 ± 0.81 and 26.12 ± 0.89 mg % for histamine, 7.61 ± 0.49, 11.13 ± 0.57, 14.35 ± 0.64 and 19.59 ± 0.81 mg% for putrescine, 5.96 ± 0.43, 10.22 ± 0.49, 12.41 ± 0.58 and 16.85 ± 0.62 mg% for cadaverine each, accordingly. Finally, the tyramine mean value was 2.05 ± 0.10 mg % in fresh fish, 6.37 ± 0.19 mg % in tuna canned, 7.9 ± 0.24mg % for herring smoked and10.44 ± 0.27 mg % for sardine salted. Fish fillets were experimentally inoculated with B. polymyxa culture (2x107), the effect was ideal, the level of histamine reduced to 31.4 mg/kg after eight hours, 19.5 mg/kg after 12 hrs and 12.8 mg/kg 24 hours later with reduction percentages of 37.2%, 61.0%, and 74.4%, respectively and cadaverine level reduced to 22.1 mg/kg after 8 hours, 15.4 mg/kg after 12 hrs and 9.7 mg/kg 24 hrs later with reductions percentages were 26.3%, 48.7%, and 67.7%, respectively