Effect of weak disorder on the ground state of uniaxial dipolar spin systems in the upper critical dimension

Extensive Monte Carlo simulations are used to investigate the stability of the ferromagnetic ground state in three-dimensional systems of Ising dipoles with added quenched disorder. These systems model the collective ferromagnetic order observed in various systems with dipolar long-range interactions. The uniaxial dipolar spins are arranged on a face-centred cubic lattice with periodic boundary conditions. Finite-size scaling relations for the pure dipolar ferromagnetic system are derived by a renormalisation group calculation. These functions include logarithmic corrections to the expected mean field behaviour since the system is in its upper critical dimension. Scaled data confirm the validity of the finite-size scaling description and results are compared with subsequent analysis of weakly disordered systems. A disorder-temperature phase diagram displays the preservation of the ferromagnetic ground state with the addition of small amounts of disorder, suggesting the irrelevance of weak disorder in these systems.Comment: 6 pages, 4 figures; proceedings of the 3rd NEXT-Sigma-Phi Conference, Kolymbari, Greece, August 200

Preoperatiewe spesiale ondersoeke en intraoperatiewe arteriele suurstofspanning tydens eenlongnarkose

The value of preoperative lung function tests was examined in 11 patients as a method to predict changes in intraoperative Pa02 (dPa02) during one-lung ventilation in pulmonary surgery. Ventilation (Kr-81m and Xe-133) and perfusion (Tc-99m microspheres) to the lung to be operated upon significantly predicted the intra-operative decrease in Pa02. The correlation between ventilation percentage to the diseased lung and dPa02 was 0,87 (SEE = 9,99) and between perlusion and dPa020,84 (SEE = 9,51).S Afr Med J 1990; 78: 104-10

Tyrosine kinase inhibitors for the therapy of anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is often incurable so new therapeutic approaches are needed. Tyrosine kinases inhibitors (such as imanitib, sunitinib or sorafenib) are under evaluation for the treatment of ATC. Other vascular disrupting agents, such as combretastatin A4 phosphate, and antiangiogenic agents, such as aplidin, PTK787/ZK222584 and human VEGF monoclonal antibodies (bevacizumab, cetuximab), have been evaluated. Small-molecule adenosine triphosphate competitive inhibitors directed intracellularly at EGFRs tyrosine kinase, such as erlotinib or gefitinib, are also studied. Furthermore, new molecules have been shown to be active against ATC, such as CLM94 and CLM3. However, more research is needed to finally identify therapies able to control and to cure this disease

ICT INVESTMENT EFFECTIVENESS IN THE SOUTH AFRICAN POST OFFICE: RECONSIDERING THE APPROACHES OF THE PAST 20 YEARS

Organisations have invested and continue to invest considerable resources in Information and Communication Technology (ICT). Much of this investment is made on the basis of guarantee than an expected return will occur. This study presents the results of an empirical study of the impact of ICT investment on performance at the South African Post office (SAPO). Six years of historical data, from 2005 to 2010, were obtained from the Chief Information Officer (CIO) of the SAPO and analysed. This included appropriate IT data and financial data from the organisation’s financial statements and balance sheet. ICT investments were tested against financial performance indicators such as return on ICT investment, operating leverage, turnover growth, net profit, organisational risk, IT cost efficiency ratio and IT efficiency ratio. Within the period studied, it was observed that ICT investments at SAPO were negatively correlated with most of the financial indicators such as return on ICT investment, operating leverage, turn-over growth, net profit, organisational risk and IT efficiency ratio. This study therefore suggests that ICT investments at SAPO for the mentioned period did not have desirable impact on financial performance of the organisation. In order to realise tangible financial benefits of the ICT investments at SAPO, the research results suggest that a longer period needs to be considered, and should also include like non-technological determinants such as competence and experience levels of IT personnel, alignment of IT strategy with business strategy and business process re-engineering to suit new systems needs to be considered too prior to making any investments in ICT

The furan microsolvation blind challenge for quantum chemical methods: First steps

© 2018 Author(s). Herein we present the results of a blind challenge to quantum chemical methods in the calculation of dimerization preferences in the low temperature gas phase. The target of study was the first step of the microsolvation of furan, 2-methylfuran and 2,5-dimethylfuran with methanol. The dimers were investigated through IR spectroscopy of a supersonic jet expansion. From the measured bands, it was possible to identify a persistent hydrogen bonding OH-O motif in the predominant species. From the presence of another band, which can be attributed to an OH-π interaction, we were able to assert that the energy gap between the two types of dimers should be less than or close to 1 kJ/mol across the series. These values served as a first evaluation ruler for the 12 entries featured in the challenge. A tentative stricter evaluation of the challenge results is also carried out, combining theoretical and experimental results in order to define a smaller error bar. The process was carried out in a double-blind fashion, with both theory and experimental groups unaware of the results on the other side, with the exception of the 2,5-dimethylfuran system which was featured in an earlier publication

Evolution of electronic and ionic structure of Mg-clusters with the growth cluster size

The optimized structure and electronic properties of neutral and singly charged magnesium clusters have been investigated using ab initio theoretical methods based on density-functional theory and systematic post-Hartree-Fock many-body perturbation theory accounting for all electrons in the system. We have systematically calculated the optimized geometries of neutral and singly charged magnesium clusters consisting of up to 21 atoms, electronic shell closures, binding energies per atom, ionization potentials and the gap between the highest occupied and the lowest unoccupied molecular orbitals. We have investigated the transition to the hcp structure and metallic evolution of the magnesium clusters, as well as the stability of linear chains and rings of magnesium atoms. The results obtained are compared with the available experimental data and the results of other theoretical works.Comment: 30 pages, 10 figures, 3 table