Laminar compressible flow between close rotating disks: An asymptotic and numerical study

Laminar steady compressible flow between close rotating thermally conducting axisymmetric disks with inflow was investigated by means of a numerical solution of the Navier-Stokes equation and an asymptotic analysis. The approximate solution, obtained for small ?, E and H (Rossby and Ekman numbers, and height/radius, respectively) is valid for “merged”, “close” and “separate” boundary layers on the disks, corresponding to β? 1, $\text{β ? 1}$ and β? 1, respectively (where $\text{β =}\text{H}\text{2}\text{√}\text{E}\text{ρ}$, and ρ is the non-dimensional density). These three cases may appear simultaneously in different regions of the same system due to the large variation of ρ in the radial direction. The small ? (i.e. negligible convection terms) does not necessarily imply small perturbations of the pressure, and a special treatment of the pressure term was used in order to account for this feature, which sometimes culminates in inversion of the radial pressure gradient. Thenumerical solution was obtained by a finite-difference, modified Cheng-Allen method, using a non-uniform mesh. The numerical and the approximate solution are in good agreement.     

Experimental tests of entanglement models of rubber elasticity: 1. Uniaxial extension-compression

The predictions of several entanglement models of rubber elasticity for the uniaxial stress-strain response of crosslinked polymer networks are examined. It is found that the Gaylord tube model and the Flory constrained junction fluctuation model both agree well with the experimental data.     

On the extended binomial distribution

An Extended Binomial random variable tallies the number of successes in n dichotomous and independent experiments with unequal probability of success in each trial, however. The paper describes situations where an Extended Binomial distribution arises and suggests an algorithm for computing its values.     

Aortic arch thrombosis in the neonate

Two cases of neonatal aortic arch thrombosis are reported. One patient, who had ascending aortic thrombosis, died preoperatively. The other had reoperation and is alive and well at 6 months' follow-up. No obvious cause was found.     

Performance and stability of communication networks via robustexponential bounds

A method for evaluating the performance of packet switching communication networks under a fixed, session-based, routing strategy is proposed. The approach is based on properly bounding the probability distribution functions of the system input processes. The suggested bounds which are decaying exponentials, possess three convenient properties. When the inputs to an isolated network element are all bounded, they result in bounded outputs and assure that the delays and queues in this element have exponentially decaying distributions. In some network settings, bounded inputs result in bounded outputs. Natural traffic processes can be shown to satisfy such bounds. Consequently, this method enables the analysis of various previously intractable setups. Sufficient conditions are provided for the stability of such networks, and derive upper bounds for the parameters of network performance are derived     

Monk seal mortality: virus or toxin?

During the past few months, more than half of the total population of about 300 highly endangered Mediterranean monk seals (Monachus monachus) on the western Saharan coast of Africa, died in a mysterious disease outbreak. Epizootiological and postmortem findings were reminiscent of similar outbreaks amongst pinniped and cetacean species in recent years, which were caused by an infection with newly discovered morbilliviruses (for review see osterhaus et al.). Virological, as well as toxicological, analysis performed on tissue samples collected from relatively fresh carcasses during the outbreak indicate that infection with a virus closely related to dolphin morbillivirus (DMV), possibly originating from affected dolphins in the same area, was the primary cause of the outbreak. Therefore it is concluded that vaccination with a safe and effective non-replicating vaccine should be considered as a management tool in the conservation of Mediterranean monk seals.     

On the analysis and solution of certain geographical optimal covering problems

The article formulates, analyses and suggests solutions to some optimal covering problems that often arise in association with geographical coordinates, albeit their mathematical form may be detached from this background. It shows that under a general formulation no favorable mathematical properties can be deduced beyond the “center of gravity”, and thus that computational algorithms are seemingly the best resort for resolving the problem. An algorithm that is based on the steepest descent approach and that exploits the “center of gravity” property is devised, and is shown as a detector of local minima points. A release from the “locality trap” is provided by a stochastic algorithm.Every part of the paper is accompanied by illustrative examples, either of an analytical nature on a segment of the real line or of a numerical nature by computer programs.     

Topochemistry. Part XXXIX. The Solid-state Photochemistry of some 2′-Nitrochalcones

It is shown that the specific pathway of a complex photochemical reaction in the solid state is governed by the molecular conformation and its retention, and by the molecular packing. 2′-Nitrochalcone and those of its derivatives which are isomorphous with it display the s-trans conformation in the solid state and yield indigos upon irradiation. However, this conformation is not sufficient to ensure photoreactivity: thus the s-trans-4-bromo-derivative does not yield indigo. The same derivative in the s-cis conformation (in a second crystal form) has a crystal structure similar to that of the parent compound, and also does not yield indigo.     

A study of machine-level software profile

The instruction mix of a CDC CYBER/74 computer in a university environment was monitored, and in this paper frequencies of execution for the most commonly used instructions are given. From these measurements we make a number of observations about several aspects of computing patterns. One observation is the fact that if we exclude the idle loop of the operating system, the percentage of occurrences for each type of instruction over various time intervals is constant. This fact is used to define a machine-level software profile (MLSP) for the type of machine operations in the given computing environment. It is shown that the MLSP could be used to find machine utilization and the extent to which software takes advantage of machine architecture, and as a consistent method to improve the performance of a machine configuration.