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677 results on '"Smith, P.A."'

2. Generating contingency tables with fixed marginal probabilities and dependence structures described by loglinear models

Author

Hammond, C., Van der Heijden, P.G.M., Smith, P.A., Hammond, C., Van der Heijden, P.G.M., and Smith, P.A.

Abstract

We present a method to generate contingency tables that follow loglinear models with prescribed marginal probabilities and dependence structures. We make use of (loglinear) Poisson regression, where the dependence structures, described using odds ratios, are implemented using an offset term. Other statistical models related to loglinear models that fall into the scope of this paper, such as the logistic regression model, the latent class model and the extended Rasch are discussed as well. We apply this methodology to carry out simulation studies in the context of population size estimation using dual system and triple system estimators, popular in official statistics. These estimators use contingency tables that summarize the counts of elements enumerated or captured within lists that are linked. The simulation is used to investigate these estimators in the situation that the model assumptions are fulfilled, and the situation that the model assumptions are violated.

Published
2024

4. What Does Performance Qualification Mean for Infrared Instruments?

Author

Smith, P.A. and McDowall, R.D.

Subjects
United States. Food and Drug Administration, Chemistry, Engineering and manufacturing industries, Physics, Science and technology
Abstract

Performance qualification (PQ) tests are a vital component of the steps regulated laboratories do to maintain compliance. Therefore, it is essential to understand and apply meaningful PQ tests. However, what does PQ mean in practice for infrared (IR) instruments? The answer may surprise, or even horrify, you., In last September's 'Focus on Quality' column, we presented an analysis of FDA 483 observations and warning letters for infrared instruments and analysis (1). In this article, we are returning [...]

Published
2020

6. Analysis of FDA Infrared 483 Citations: Have You a Data Integrity Problem? Analysis of 47 FDA Form 483 observations and warning letters for infrared spectrometers reveals a spectrum of data integrity problems and a lack of laboratory procedures for the technique. Is this your laboratory?

Author

Smith, P.A. and McDowall, R.D.

Subjects
United States. Food and Drug Administration -- Ethical aspects, Able Laboratories Inc. -- Ethical aspects, Data centers -- Ethical aspects, Pharmaceutical industry -- Ethical aspects, Compliance audits, Information management, Spectrometers, Chemistry, Engineering and manufacturing industries, Physics, Science and technology
Abstract

Since the Able Laboratories data falsification case in 2005 (1), there has been a regulatory focus on the lack of data integrity with chromatography data systems. This scrutiny has focused [...]

Published
2019

9. Estimating population size of four ethnic groupings in New Zealand

Author

Methodology and statistics for the behavioural and social sciences, Leerstoel Heijden, Smith, P.A., Van der Heijden, P.G.M., Cruyff, Maarten, Pantalone, F., Diener, H., Dunstan, K., Methodology and statistics for the behavioural and social sciences, Leerstoel Heijden, Smith, P.A., Van der Heijden, P.G.M., Cruyff, Maarten, Pantalone, F., Diener, H., and Dunstan, K.

Published
2023

13. Assessing Discontinuities and Rotation Group Bias in Rotating Panel Designs

Author

van den Brakel, Jan A., Smith, P.A., Elliot, D., Krieg, S., Schmid, T., Tzavidis, N., Lynn, Peter, RS: GSBE Theme Data-Driven Decision-Making, and QE Econometrics

Abstract

Rotation group bias (RGB) and discontinuities are in fact similar phenomena – both are systematic differences in non-sampling errors in a survey. Therefore, they can be dealt with using common approaches, and in this chapter, the authors review the methods for planning a transition to a new approach, and estimating and adjusting for the changes in the evolution of the series. The authors also review the available methods to quantify discontinuities induced by redesigns of the survey process. They show how time series models can be fitted to the outputs from rotating panels to account for RGB. The authors extend these times series models to estimate discontinuities. They also present some example applications. There are clear indications that the RGB is time dependent. This suggests that the common assumption that RGB can be ignored since it does not affect period-to-period change under a balanced rotation pattern is questionable.

Published
2021

17. Multiple system estimation using covariates having missing values and measurement error: Estimating the size of the Māori population in New Zealand

Author

van der Heijden, P.G.M., Cruyff, Maarten, Smith, P.A., Bycroft, C., Graham, P., Matheson-Dunning, N., van der Heijden, P.G.M., Cruyff, Maarten, Smith, P.A., Bycroft, C., Graham, P., and Matheson-Dunning, N.

Abstract

We investigate the use of two or more linked lists, for both population size estimation and the relationship between variables appearing on all or only some lists. This relationship is usually not fully known because some individuals appear in only some lists, and some are not in any list. These two problems have been solved simultaneously using the EM algorithm. We extend this approach to estimate the size of the indigenous Māori population in New Zealand, leading to several innovations: (1) the approach is extended to four lists (including the population census), where the reporting of Māori status differs between registers; (2) some individuals in one or more lists have missing ethnicity, and we adapt the approach to handle this additional missingness; (3) some lists cover subsets of the population by design. We discuss under which assumptions such structural undercoverage can be ignored and provide a general result; (4) we treat the Māori indicator in each list as a variable measured with error, and embed a latent class model in the multiple system estimation to estimate the population size of a latent variable, interpreted as the true Māori status. Finally, we discuss estimating the Māori population size from administrative data only. Supplementary materials for our article are available online.

Published
2022

18. Multiple system estimation using covariates having missing values and measurement error: Estimating the size of the Māori population in New Zealand

Author

Methodology and statistics for the behavioural and social sciences, Leerstoel Heijden, van der Heijden, P.G.M., Cruyff, Maarten, Smith, P.A., Bycroft, C., Graham, P., Matheson-Dunning, N., Methodology and statistics for the behavioural and social sciences, Leerstoel Heijden, van der Heijden, P.G.M., Cruyff, Maarten, Smith, P.A., Bycroft, C., Graham, P., and Matheson-Dunning, N.

Published
2022

22. Contributors

Author

Anand, S.C., primary, Chen, X., additional, Conway, R., additional, Gandhi, K.L., additional, Gong, R.H., additional, Hearle, J.W.S., additional, Holme, I., additional, McCarthy, B.J., additional, Miraftab, M., additional, Russell, S.J., additional, Smith, P.A., additional, Sondhelm, W.S., additional, Taylor, L.W., additional, and Tsai, L.-J., additional

Published
2016
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28. Measuring team skills in crime scene investigation: exploring ad hoc teams

Author

Smith, P.A., Baber, C., Hunter J., and Bulter, M.

Subjects
Crime scene searches -- Evaluation, Criminal investigation -- Evaluation, Police administration -- Management, Work groups -- Evaluation, Company business management, Architecture and design industries, Business
Published
2008

29. Processability studies of silica-thermoset polymer matrix nanocomposites

Author

Lekakou, C., Kontodimopoulos, I., Murugesh, A.K., Chen, Y.L., Jesson, D.A., Watts, J.F., and Smith, P.A.

Subjects
Nanoparticles -- Properties, Thermosetting composites -- Composition, Silica -- Properties, Engineering and manufacturing industries, Science and technology, Composition, Properties
Abstract

The aim of this study is to investigate the processability of silica-thermoset polymer matrix nanocomposites in terms of dispersion of silica nanoparticles and their effect on curing. Two thermosetting resins were considered, an epoxy and a polyester resin, with 5% silica, although 1% silica was also used in preliminary studies in the polyester system. Various combinations of mechanical mixing and sonication were investigated for the dispersion of silica nanoparticles under different processing conditions and times in solvent-free and solvent-containing systems. It was found that the best dispersion route involved a solvent-aided dispersion technique. Consequently, different procedures for the solvent removal were investigated. Optical microscopy and SEM were used to characterize the resulting nanocomposites. DSC and rheological DMTA tests demonstrated that the silica nanoparticles shorten the gel time and promote curing in these thermosetting systems. POLYM. ENG. SCI., 48:216-222, 2008. © 2007 Society of Plastics Engineers, INTRODUCTION Silicate and silica nanocomposites form two types of dispersed phase: (a) clays form layered silicates consisting of microplatelets of nanometers thickness; (b) silica nanocomposites contain dispersed silica nanoparticles. Clay [...]

Published
2008

30. The colorimetric determination of copper in wine: total copper

Author

Kontoudakis, N. Smith, M. Smith, P.A. Wilkes, E.N. Clark, A.C.

Subjects
digestive, oral, and skin physiology, food and beverages
Abstract

Background and Aims: The total concentration of copper (Cu) in wine cannot be routinely measured without relatively expensive equipment, reagents and/or without labour-intensive sample pretreatment. The following research describes an approach for the colorimetric measurement of total Cu in wine utilising a spectrophotometer and relatively cheap reagents. Method and Results: The proposed method is based on using bicinchoninic acid as the complexing chromophore for Cu. Copper was measured directly and rapidly in white wine, while a digestion of red wine was required. A key step for the analysis in the non-digested white wine matrix was the addition of silver(I) to aid the dissociation of Cu in the wine from sulfide. For red and white wines, the limit of detection was 0.02 mg/L Cu, and the repeatability was 3 ± 1%. The accuracy of the method was assessed in terms of recovery experiments (102 ± 3%, n = 4), and also by comparing total Cu concentration in 84 wines determined by the colorimetric method with that obtained by inductively coupled plasma with optical emission spectroscopy (R2 = 0.95). Conclusions: The colorimetric determination of total Cu was successfully optimised and validated in white and red wines. Significance of the Study: The methodology will allow wineries and researchers to routinely measure total Cu concentration in wine with a spectrophotometer. © 2020 Australian Society of Viticulture and Oenology Inc.

Published
2020

31. On estimating the size of overcoverage with the latent class model. A critique of the paper “Population Size Estimation Using Multiple Incomplete Lists with Overcoverage” by di Cecco, di Zio, Filipponi and Rocchetti (2018, Journal of Official Statistics 34 557–572).

Author

van der Heijden, P.G.M., Smith, P.A., van der Heijden, P.G.M., and Smith, P.A.

Abstract

We read with interest the article by di Cecco et al. (2018), but have reservations about the usefulness of the latent class model specifically for estimating overcoverage. In particular, we question the interpretation of the parameters of the fitted latent class model.

Published
2020

32. On estimating the size of overcoverage with the latent class model. A critique of the paper “Population Size Estimation Using Multiple Incomplete Lists with Overcoverage” by di Cecco, di Zio, Filipponi and Rocchetti (2018, Journal of Official Statistics 34 557–572).

Author

Methodology and statistics for the behavioural and social sciences, Leerstoel Heijden, van der Heijden, P.G.M., Smith, P.A., Methodology and statistics for the behavioural and social sciences, Leerstoel Heijden, van der Heijden, P.G.M., and Smith, P.A.

Published
2020

34. An experiment in rotational motion with linear and quadratic drag

Author

Thompson, B.G. and Smith, P.A.

Subjects
Physics -- Research, Physics
Abstract

We describe a study of velocity-dependent drag in rotational motion that is suitable for an undergraduate laboratory experiment. Using standard teaching-laboratory equipment to obtain the data, we found that a drag force that is linear in the angular speed describes the data very well; however, the model residuals reveal that quadratic drag is also present. When a combined model is used, the residuals are reduced to the level of measurement uncertainties. An investigation of the effect of airflow on the air bearing used in the experiment confirms that there is a turbine effect on the disk and that the drag is dependent on the airflow suspending the disk. The experiment is simple to perform and analyze, yet reveals interesting physical and analytical complexity with deeper investigation. [DOI: 10.1119/1.1632493]

Published
2004

36. Cobb 700 response to increasing lysine by growth phase

Author

Butler, L.D., primary, Scanes, C.G., additional, Rochell, S.J., additional, Mauromoustakos, A., additional, Caldas, J.V., additional, Keen, C.A., additional, Maynard, C.W., additional, Bolden, S.A., additional, Brister, R.D., additional, Smith, P.A., additional, Latham, R.E., additional, Owens, C.M., additional, and Kidd, M.T., additional

Published
2020
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42. HTS microwave devices and subsystems with pulse tube refrigerators

Author

He, Yusheng, Zhou, Yuan, Liang, Jingtao, Li, Hong, Yang, Luwei, Zhu, Wenxiu, Cai, Jinghui, He, Aisheng, Gong, Zhonglin, Wu, Peiheng, Feng, Yijun, Button, T.W., Smith, P.A., Lancaster, M.J., Wellhofer, F., and Gough, C.E.

Subjects
Microwave devices -- Heating, cooling and ventilation, Refrigerators -- Design and construction, Superconductive devices -- Heating, cooling and ventilation, Business, Electronics, Electronics and electrical industries
Abstract

Two new types of pulse tube refrigerators for high-temperature microwave devices with optimized cooling power of 6 W at 77 K have been designed and constructed. One is a 1.6W/77K U-shaped pulse tube refrigerator driven by a valveless compressor while the other is a coaxial pulse tube refrigerator powered by an air conditioning compressor with a minimum temperature of 38.4 K. The vibration of the refrigerators is observed to be a magnitude lower than that for Stirling coolers.

Published
1999

43. Microstructure and RF property correlation in HTS films

Author

Smith, P.A., Bakar, M.A., Porch, A., and Button, T.W.

Subjects
Dielectric resonators -- Usage, High temperature superconductivity -- Research, High temperature superconductors -- Research, Thick films -- Research, Thin films -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Assessments of a range of high temperature superconducting thin and thick films were conducted using dielectric resonators that are capable of about 3mm-diameter film measurements. The small resonators, which operates close to the 10 GHz range, are high rutile dielectrics with permittivities of about 105 at 77 degrees Kelvin. The setup permits the direct quantification of the grain boundary influence and other microstructure attributes on the film's RF properties.

Published
1999

49. Multiple system estimation for the size of the Māori population in New Zealand

Author

Cruyff, M.J.L.F., van der Heijden, P.G.M., Smith, P.A., Bycroft, C., Graham, P., Methodology and statistics for the behavioural and social sciences, and Leerstoel Heijden

Subjects
missing data, register, dual system estimation, coverage, linkage
Abstract

We investigate the situation where two or more registers, or lists, of individuals are linked both for the purpose of population size estimation and to investigate the relationship between variables appearing on all or only some of the registers. There is usually no full picture of this relationship because there are individuals that are in only some of the lists, and also individuals that are in none of the lists. These two problems have been solved simultaneously in dual system estimation using the EM algorithm. We extend this approach to four registers (including the population census) to estimate the size of the indigenous Māori population in New Zealand, where the reporting of Māori is not the same in each register and where there is a further missing data problem, with individuals included in one or more registers who did not provide their ethnicity. We consider the implications for estimating the size of the Māori population from administrative data only.

Published
2019

50. Multiple potential germ-line helicases are components of the germ-line-specific P granules of Caenorhabditis elegans

Author

Gruidl, M.E., Smith, P.A., Kuznicki, K.A., McCrone, J.S., Kirchner, J., Roussell, D.L., Strome, S., and Bennett, K.L.

Subjects
Caenorhabditis elegans -- Genetic aspects, Proteins -- Structure, Science and technology
Abstract

Two components of the germ-line-specific P granules of the nematode Caenorhabditis elegans have been identified using polyclonal antibodies specific for each. Both components are putative germ-line RNA helicases (GLHs) that contain CCHC zinc fingers of the type found in the RNA-binding nucleocapsid proteins of retroviruses. The predicted GLH-1 protein has four CCHC fingers; GLH-2 has six. Both GLH proteins localize in the P granules at all stages of germ-line development. However, the two glh genes display different patterns of RNA and protein accumulation in the germ lines of hermaphrodites and males. Injection of anti-sense glh-1 or glh-2 RNA into wild-type worms causes some offspring to develop into sterile adults, suggesting that either or both genes are required for normal germ-line development. As these very similar glh genes physically map within several hundred kilobases of one another, it seems likely that they represent a fairly recent gene duplication event.

Published
1996

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