Modelling mobile multimedia services

Future multimedia and Internet services will have more complex characteristics than the traditional service types. Accurate planning of mobile networks requires accurate prediction of traffic flows, which involves complex relationships between the services themselves, the mobility of users, and the business environment. This paper describes the work of the Mobile VCE services programme on new traffic models that take all three factors into account     

Structural, thermal and electrochemical properties of layered perovskite SmBaCo2O5+d, a potential cathode material for intermediate-temperature solid oxide fuel cells

The synthesis, conductivity properties, area specific resistance (ASR) and thermal expansion behaviour of the layered perovskite SmBaCo₂O_5+d (SBCO) are investigated for use as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The SBCO is prepared and shows the expected orthorhombic pattern. The electrical conductivity of SBCO exhibits a metal–insulator transition at about 200 °C. The maximum conductivity is 570 S cm⁻¹ at 200 °C and its value is higher than 170 S cm⁻¹ over the whole temperature range investigated. Under variable oxygen partial pressure SBCO is found to be a p-type conductor. The ASR of a composite cathode (50 wt% SBCO and 50 wt% Ce_0.9Gd_0.1O_2−d, SBCO:50) on a Ce_0.9Gd_0.1O_2−d (CGO91) electrolyte is 0.05 Ω cm² at 700 °C. An abrupt increase in thermal expansion is observed in the vicinity of 320 °C and is ascribed to the generation of oxygen vacancies. The coefficients of thermal expansion (CTE) of SBCO is 19.7 and 20.0 × 10⁻⁶ K⁻¹ at 600 and 700 °C, respectively. By contrast, CTE values for SBCO:50 are 12.3, 12.5 and 12.7 × 10⁻⁶ K⁻¹ at 500, 600 and 700 °C, that is, very similar to the value of the CGO91 electrolyte.     

IntegratedIn Situ wafer and system monitoring for the growth of CdTe/ZnTe/GaAs/Si for mercury cadmium telluride epitaxy

Reproducible improvements in the metalorganic vapor phase epitaxy (MOVPE) grown CdTe buffer quality have been demonstrated in a horizontal rectangular duct silica reactor by the use of integratedin situ monitoring that includes laser reflectometry, pyrometry, and Epison concentration monitoring. Specular He-Ne laser reflectance was used toin situ monitor the growth rates, layer thickness, and morphology for both ZnTe and CdTe. The substrate surface temperature was monitored using a pyrometer which was sensitive to the 2–2.6 μm waveband and accurate to ±1°C. The group II and group VI precursor concentrations entering the reactor cell were measured simultaneously using two Epison ultrasonic monitors and significant variations were observed with time, in particular for DIPTe. The surface morphology and growth rates were studied as a function of VI/II ratio for temperatures between 380 and 460°C. The background morphology was the smoothest for VI/IIratio in the vicinity of 1.5–1.75 and could be maintained using Epison monitors. Regularly shaped morphological defects were found to be associated with morphological defects in the GaAs/Si substrate. The x-ray rocking curve widths for CuK_α (531) reflections were in the range of 2.3–3.6 arc-min, with no clear trend with changing VI/II ratio. X-ray topography images of CdTe buffer layers on GaAs/Si showed a mosaic structure that is similar to CdTe/sapphire substrates. The etch pit density in Hg_1-xCd_xTe layers grown onto improved buffer layers was as low as 6 x 10⁶ cm^-2 for low temperature MOVPE growth using the interdiffused multilayer process.     

Declining sperm quality: a review of facts and hypotheses

A substantial body of evidence has accumulated in recent years suggesting that human semen quality may be deteriorating. This has been associated with evidence of other changes in male reproductive health, including increases in congenital malformations and testis cancer in men, and associated problems in wildlife. Unfortunately the evidence remains inconclusive. It has been suggested that these changes may be due to environmental xenoestrogens acting during development. Although there is now a large quantity of data indicating that this is a plausible hypothesis, evidence of causality, rather than association, remains to be provided. The potential importance of these changes for human health is considerable, and urgent research is required to clarify the situation.     

Characteristics of WAP Traffic

This paper considers the characteristics of Wireless Application Protocol (WAP) traffic. We start by constructing a WAP traffic model by analysing the behaviour of users accessing public WAP sites via a monitoring system. A wide range of different traffic scenarios were considered, but most of these scenarios resolve to one of two basic types. The paper then uses this traffic model to consider the effects of large quantities of WAP traffic on the core network. One traffic characteristic which is of particular interest in network dimensioning is the degree of self-similarity, so the paper looks at the characteristics of aggregated traffic with WAP, Web and packet speech components to estimate its self-similarity. The results indicate that, while WAP traffic alone does not exhibit a significant degree of self-similarity, a combined load from various traffic sources retains almost the same degree of self-similarity as the most self-similar individual source.     

Communication mode, affect and recall.

Investigated whether there is an interaction effect of communication mode on the joint recall of affect-laden vs affect-free prose. It was expected that joint recall of a passage of affect-laden prose would be less when the interaction was in an audio-only mode than in a face-to-face condition and that joint recall of affect-free prose would be higher in an audio-only medium than in a face-to-face condition. 64 female undergraduates were randomly assigned to pairs. Each member of the pair individually memorized a vivid, affect-laden narration or a more factual, logical popular science article, and then, together with the partner, jointly recalled the passage. A 2nd passage of the opposite type was then memorized and recalled. The joint memorization sessions took place over face-to-face and audio-only communication modes. Findings indicate that the face-to-face mode showed significantly greater recall than the audio-only mode and that the narrative was recalled better than the popular science passage. The overall effect of mode, whereby face-to-face recall gave better results over both passages, suggests that, contrary to expectations, the face-to-face mode generally supports enhanced recall in a joint-recall task. (French abstract) (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Measuring nursing workload: understanding the variability

We reanalyzed parasitaemia profiles of the trypanotolerant N'Dama cattle (Bos taurus), consecutively infected with the same four clones of Trypanosoma congolense. Our analysis shows that each individual parasitaemia is characterized by progressively longer intervals between parasites waves. This pattern is most visible during the chronic phase of infection. In addition, the last of the four infections had a significantly larger overall duration of inter-wave intervals. We retrieved these patterns by numerical simulations of a mathematical model, which incorporates assumptions about the molecular basis of antigenic variation and about the anti-parasitic major immune processes. Six potential factors that may determine parasitaemia pattern were studied: carrying capacity of the host environment, intrinsic growth rate of the parasite, affinity maturation of the immune response, immune cell birth and death rate, levels of antibodies to variant surface glycoprotein and levels of antibodies to invariant antigens. Our simulations suggest that the first five factors are not likely to determine the chronic phase parasitaemia pattern whereas the sixth one, namely, antibody response to invariant antigens, yielded profiles consistent with the experimental data. Being cumulative, the immune response to anti-invariant antigens may be increasingly effective as infection proceeds and in successive infections. Comparisons between N'Dama and Zebu and between chronic and acute phases will be needed to make a statement on the role of this phenomenon in trypanotolerance.     

Isobaric thermal expansion coefficients for water over large temperature and pressure ranges

Tabular values of the thermal expansion coefficient (Beta) are presented for water for pressure of 0.1 to 50 MPa and temperatures from 0 to 600°C. Currently available Beta values are also reviewed at one atmosphere and one bar for a temperature range of 0 to 100°C.     

The role of CT and MR in imaging the complications of sickle cell disease

Sickle cell disease is the most common inherited haemoglobinopathy described. Complications of sickle cell disease (SCD) are due to chronic haemolysis of fragile red cells or secondary to vascular occlusion by sickled red cells with subsequent tissue infarction. Traditionally plain film radiography has been the mainstay in the assessment of patients with SCD, but increasingly magnetic resonance (MR) imaging and computed tomography (CT) are being used. In this review the imaging features of a range of complications of SCD are demonstrated with particular emphasis on CT and MR.