An Application of Queueing Theory to a Teletraffic Problem

In planning investment to meet growth in demand on the telephone system, it is highly desirable to be able to predict how well proposed configurations of exchange equipment will meet specified future demand. The methods developed for this purpose form the body of telephone traffic theory.This paper describes approximate queueing theoretic methods used in the analysis of queueing delay in the TXK3 crossbar exchange, and compares the results obtained from these models with results from simulation study. The methods have already been used in the analysis of exchanges but, in the author's view, are not yet fully validated.     

Polymerization and depolymerization by ultrasound

Ultrasound has been reported to cause both initiation of polymerization and depolymerization. The effects of the rate of flow of argon gas through styrene during exposure to ultrasound on the polymerization rate and the molecular weight distribution of the polymer formed were investigated. The results indicate that initiation of polymerization occurs primarily only when there is sufficient gas present to form a field of bubbles undergoing stable cavitation. With no gas present, transient cavitation occurs, resulting in depolymerization and the formation of coloured compounds similar to pyrolysis reaction products. These observations explain discrepancies in the sonochemistry literature.     

Simulation vs Numerical Convolution — The Study of a Discrepancy

In this note, predictions for an M/D/1 queue with alternating high (>1) and low traffic intensities are derived using elementary deterministic and queueing theoretic methods. These are compared with results available from a simulation study. Good agreement between the two sets of results is found except for one discrepancy which an exact analysis by numerical convolution failed to resolve and for which a tentative explanation is given.     

Shears band with a large dynamic moment of inertia in 197Bi

High-spin states in ¹⁹⁷Bi were studied with the AFRODITE γ-ray array at iThemba LABS using the ¹⁸¹Ta( ²²Ne, 6n) reaction at a beam energy of 125 MeV. A new shears band was found and linked to the low-lying states in ¹⁹⁷Bi. Its dynamic moment of inertia, , is considerably larger than the of the shears bands in the neighbouring Pb isotopes. This is probably a result of the involvement of an additional high-K h_9/2 proton orbital.     

Emission of 8Begs in the interaction of 12C with nuclei at incident energies up to 33 MeV/amu

The spectra of ⁸Be_gs fragments emitted in the interaction of 100, 200, 300 and 400 MeV ¹²C with ⁵⁹Co, ⁹³Nb and ¹⁹⁷Au have been measured and analysed. Our analysis suggests that, before breaking up, ¹²C may suffer a considerable energy loss which increases with increasing incident energy. The amount of excitation energy provided to the target nucleus in this process increases with decreasing charge of the target nucleus. Received: 3 May 2001 / Accepted: 5 June 2001     

Therapeutic Pretargeting with Gold Nanoparticles as Drug Candidates for Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) is a binary approach for cancer treatment in which boron-10 atoms and thermal neutrons need to colocalize to become effective. Recent research in the development of BNCT drug candidates focuses increasingly on nanomaterials, with the advantages of high boron loadings and passive targeting due to the enhanced permeability and retention (EPR) effect. The use of small boron-rich gold nanoparticles (AuNPs) in combination with a pretargeting approach is proposed. Small sized polyethylene glycol–stabilized AuNPs (core size 4.1 ± 1.5 nm), are synthesized and functionalized with thiolated cobalt bis(dicarbollide) and tetrazine. To enable in vivo tracking of the AuNPs by positron emission tomography (PET), the core is doped with [⁶⁴Cu]CuCl₂. For the pretargeting approach, the monoclonal antibody Trastuzumab is functionalized with trans-cyclooctene-N-hydroxysuccinimide ester. After proving in vitro occurrence of the antibody conjugation onto the AuNPs by click reaction and the low toxicity of the AuNPs, the boron delivery system is evaluated in vivo using breast cancer xenograft bearing mice and PET imaging. Tumor uptake due to the EPR effect can be witnessed with ≈5% injected dose (ID) cm⁻³ at 24 h postinjection, but with slower clearance than expected. Therefore, no increased retention can be observed using the pretargeting strategy.     

New collective structures in the 163Yb nucleus

The European Physical Journal A - Photon strength functions describing the average response of the nucleus to an electromagnetic probe are key input information in the theoretical modelling of...