Sampling and analysis of particulate matter by glow discharge atomic emission and mass spectrometries

The direct introduction of particulate matter into glow discharge atomic emission and mass spectrometry sources through a particle beam/momentum separator apparatus is described. Vacuum action through a narrow (0.0625 in. i.d.) stainless steel tube allows the introduction of discrete samples of NIST SRM 1648 urban particulate matter (UPM) and caffeine in powder form. Introduction of "ambient" airborne particulate matter is also possible. Particles passing through the aerodynamic momentum separator impinge on the heated (～200-250 °C) inner surface of the glow discharge plasma volume and are flash-vaporized. The resultant atoms/molecules are subjected to excitation/ionization collisions within the low-pressure (0.5-5 Torr of He or Ar) plasma, producing characteristic photon emission and/or signature ionic species. In this way, atomic emission and mass spectrometry identification of particle constituents is possible. Basic design aspects of the apparatus are presented, and demonstrations of atomic emission detection of the constituents in the NIST SRM illustrate the general characteristics of the approach. Transient atomic emission signals are captured for the introduction of preweighed, discrete samples, with the integrated areas used to construct analytical response curves. Limits of detection using this relatively simple atomic emission system are on the order of tens of nanograms for sample masses of ～50 μg. Mass spectrometric monitoring of introduced caffeine particles and a mixture of polycyclic aromatic hydrocarbons (PAHs) illustrates the ability of the glow discharge plasma to produce high-quality, library (electron impact) searchable mass spectra of molecular species while also yielding isotopic identification of elemental components of the UPM. Limits of detection for Fe in the NIST SRM are on the order of 175 ng of material, equivalent to ～7 ng of analyte Fe. It is believed that the small size, low power consumption, ease of operation, and multimode sampling capabilities (AES/MS) of the particle beam-glow discharge (PB-GD) apparatus hold promise for applications in continuous monitoring and discrete particle sampling.     

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.     

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.