Nicholas C. Miller

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A new cascade impactor has been designed specifically for pharmaceutical inhaler testing. This impactor, called the Next Generation Pharmaceutical Impactor (NGI), has seven stages and is intended to operate at any inlet flow rate between 30 and 100 L/min. It spans a cut size (D50) range from 0.54-microm to 11.7-microm aerodynamic diameter at 30 L/min and(More)
Design theory for cascade impactors is well developed, and design principles can be summarized quite succinctly. The key geometric parameters of three commonly used impactors have been compared to design guidelines. Calibration theory and practice have undergone improvement in recent years. Published results show distinctly different characteristics for(More)
PURPOSE The purpose of this study is to investigate the effect of drug load, the coating of impactor stages, and the design of cascade impactors on albuterol MDIs particle size distribution measurements. The results of the investigation will be used to explain the "loading effect" recently reported. METHODS Particle size distribution parameters of a(More)
The calibration of the first stage of the twin-stage impinger, an instrument proposed for use in measuring the spray size from metered-dose inhalers, was performed with monodisperse aerosols by a standard technique for cascade impactors. The mean cut point was found to be not particularly sensitive to operating variables which may be expected to occur in(More)
A new test method is described for assessing the loss of prime in metered-dose aerosols. Two representative metered-dose valve designs and two storage positions were used to assess the utility of this test method at three different sites. Loss of prime, defined as a valve delivery 15% below the mean, was detected in three of the four test configurations.(More)
The analysis of fields in periodic dielectric structures arise in numerous applications of recent interest, ranging from photonic bandgap structures and plasmonically active nanostructures to metamaterials. To achieve an accurate representation of the fields in these structures using numerical methods, dense spatial discretization is required. This, in(More)
Genetic programming has been around for over 20 years, yet most implementations are still based on sub-tree crossover and node mutation, in which structural changes are made that manipulate the syntax of programs. However, it is not clear why manipulating program syntax should have any desirable effect on program behavior (or semantics). One sub-field of(More)
A metered dose nebulizer assembly with the capability for repeatable doses is described, comprising a commercial disposable nebulizer and a timing circuit to control the duration of air supply. Data on performance of the nebulizer apparatus under typical operating conditions are presented, using cromolyn sodium as a model compound. Repeat doses from the(More)
PURPOSE This work was performed in order to compare and contrast results obtained from cascade impactor measurements on metered dose inhalers (MDIs) using a variety of inlet ports. METHODS The collection characteristics of four cascade impactor ports (a physical model of the human throat, a simplified geometry intended to mimic the physical model, and two(More)