Identification and approximation of queueing systems

A distance-measures approach to the problems of identification and approximation of queueing systems is presented. This approach combines ideas from statistical robustness, information-type measures, and parameter-continuity of stochastic processes.     

Refusal to eat in the elderly

Refusal to eat by the elderly, and subsequent malnutrition, occurs in both institutional and community settings. Causes include physiologic changes associated with aging, mental disorders such as dementia and depression, and medical, social, and environmental factors. Treatment approaches call for management of these causes while considering the roles that medicine, ethics, and culture play in the process.     

Dermatofibrosarcoma protuberans and the Bednar tumor: treatment in the pediatric population

Dermatofibrosarcoma protuberans (DFSP) is a low-intermediate-grade cutaneous sarcoma that has a marked propensity for local recurrence after excision. The Bednar variant of this tumor is even less common and is distinguished histologically by the dispersal of melanin containing cells in an otherwise typical DFSP. Both are considered to be tumors of the third and forth decades of life, but both DFSP and the Bednar variant have been described in children. Until this report of a congenital Bednar tumor, only the DFSP has also been described in the neonate. The histopathology and surgical management of DFSP and Bednar tumors are outlined with emphasis on reported experience in the pediatric population. The surgical management of these lesions in children is based on numerous series in adults and the limited pediatric experience. The recommended treatment is wide excision with 3-cm margins of visibly uninvolved tissue and inclusion of superficial fascia.     

Barriers to the adoption of an energy efficient technology

Solid state electronic ballasts promise significant energy savings in the lighting systems of large buildings. However, organizational factors and standard operating procedures may inhibit the adoption of this technology in the large, bureaucratic public and private sector organizations which represent the major potential users of this technology.     

Effect of hold times on crack retardation in aluminum alloys

Hold time effects on fatigue crack retardation in two high strength aluminum alloys (2219 and 7075) were studied for different metallurgical conditions. Experiments were performed in humid air as well as in vacuum. It was observed that as the hold time at zero load increased, the number of delay cycles decreased in general. This observation is then explained in terms of a strain relaxation phenomenon and a crack closure model. The data indicates that the relaxation effects were greater in humid air than in vacuum. Some visual evidence of surface hammering during retardation was found.     

Estimating the Number of Items on Life Test

If n items are on life test where n is unknown, and failures are observed either until time T has elapsed or until r failures have occurred, then an estimate of n can be obtained. Both maximum likelihood and Bayes estimates are obtained and both known and unknown failure distributions are considered.     

Postinfectious antirabic vaccination of children with duck embryo vaccine and heterologous rabies hyperimmunity serum (author's transl)

After contact with a rabies-infected rabbit, 31 Persons were submitted to complete vaccination treatment with duck embryo vaccine, comprising of injections of 1.0 ml each every fast night and two booster injections of 1.0 ml each, which were administered 10 and 20 days, respectively, after the end of the 14 days' vaccination series. After performance of intracutaneous and ophthalmic tests, 18 children received heterologous rabies immunserum (Behring) in a dose of 0.2 ml per kg of body weight before the beginning of the vaccination series. Six weeks after the start of the vaccination series neutralizing and complement-fixing antibodies (rate of conversion 100 per cent) were detected in all patients. The mean titre of neutralizing antibodies (mouse test 200 LD 50 Fixed virus, strain CVS) amounted to 1:140, that of complement-fixing antibodies to 1:41. Severe incompatibility reactions were not observed. Outpatient treatment with duck embryo vaccine therefore seems to be fully justified.     

Asymptotic expansions and Lie algebras for some nonlinear filtering problems

State estimation problems for systems involving small parameters are treated by both analytical and Lie algebraic approximation techniques. An asymptotic expansion for the unnormalized conditional density corresponding to the case of observations of a Gauss-Markov process through a (weak) polynomial nonlinearity is computed and a convergence result is derived. The expansion is related to certain approximations of the associated estimation Lie algebra. The convergence result is based on arguments used recently to prove existence and uniqueness and to estimate the tail behavior of solutions to nonlinear filtering problems with unbounded coefficients. These arguments are, in turn, adapted from the analytical theory of parabolic PDE's. Simulation results are presented to further assess the performance of the resulting approximate filters.     

Self-assembling of atomic vacancies at an oxide/intermetallic alloy interface

Oxide layers grown on the surface provide an effective way of protecting metallic materials against corrosion for sustainable use in a broad range of applications. However, the growth of cavities at the metal/oxide interface weakens the adherence of the protective layer and can promote its spallation under service conditions, as observed for alumina layers formed by selective oxidation of aluminide intermetallic alloys used in high-temperature applications. Here we show that direct atomic-scale observations of the interface between an ultrathin protective oxide layer (alumina) grown on an intermetallic titanium aluminide substrate (TiAl) can be performed with techniques sensitive to the topmost atomic layers at the surface. Nanocavities resulting from the self-assembling of atomic vacancies injected at the interface by the growth mechanism of the protective oxide are observed for the first time, bringing new insight into the understanding of the fate of injected cavities in oxidation processes.