A spatial statistic to determine appropriate field sampling size for linking image and field data

Proceedings of the 11th Australasian Remote Sensing and Photogrammetry Conference

Statistical physics of irregular low-density parity-check codes

Low-density parity-check codes with irregular constructions have recently been shown to outperform the most advanced error-correcting codes to date. In this paper we apply methods of statistical physics to study the typical properties of simple irregular codes. We use the replica method to find a phase transition which coincides with Shannon's coding bound when appropriate parameters are chosen. The decoding by belief propagation is also studied using statistical physics arguments; the theoretical solutions obtained are in good agreement with simulation results. We compare the performance of irregular codes with that of regular codes and discuss the factors that contribute to the improvement in performance.

Sampling and measurement methods for a study of childhood refractive error in a UK population

Background There is a paucity of data describing the prevalence of childhood refractive error in the United Kingdom. The Northern Ireland Childhood Errors of Refraction study, along with its sister study the Aston Eye Study, are the first population-based surveys of children using both random cluster sampling and cycloplegic autorefraction to quantify levels of refractive error in the United Kingdom. Methods Children aged 6–7 years and 12–13 years were recruited from a stratified random sample of primary and post-primary schools, representative of the population of Northern Ireland as a whole. Measurements included assessment of visual acuity, oculomotor balance, ocular biometry and cycloplegic binocular open-field autorefraction. Questionnaires were used to identify putative risk factors for refractive error. Results 399 (57%) of 6–7 years and 669 (60%) of 12–13 years participated. School participation rates did not vary statistically significantly with the size of the school, whether the school is urban or rural, or whether it is in a deprived/non-deprived area. The gender balance, ethnicity and type of schooling of participants are reflective of the Northern Ireland population. Conclusions The study design, sample size and methodology will ensure accurate measures of the prevalence of refractive errors in the target population and will facilitate comparisons with other population-based refractive data.

Quantifying the pathology of neurodegenerative disorders:Quantitative measurements, sampling strategies and data analysis

The use of quantitative methods has become increasingly important in the study of neurodegenerative disease. Disorders such as Alzheimer's disease (AD) are characterized by the formation of discrete, microscopic, pathological lesions which play an important role in pathological diagnosis. This article reviews the advantages and limitations of the different methods of quantifying the abundance of pathological lesions in histological sections, including estimates of density, frequency, coverage, and the use of semiquantitative scores. The major sampling methods by which these quantitative measures can be obtained from histological sections, including plot or quadrat sampling, transect sampling, and point-quarter sampling, are also described. In addition, the data analysis methods commonly used to analyse quantitative data in neuropathology, including analyses of variance (ANOVA) and principal components analysis (PCA), are discussed. These methods are illustrated with reference to particular problems in the pathological diagnosis of AD and dementia with Lewy bodies (DLB).

Subthalamic nucleus neurones in slices from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned mice show irregular, dopamine-reversible firing pattern changes, but without synchronous activity

The loss of dopamine in idiopathic or animal models of Parkinson's disease induces synchronized low-frequency oscillatory burst-firing in subthalamic nucleus neurones. We sought to establish whether these firing patterns observed in vivo were preserved in slices taken from dopamine-depleted animals, thus establishing a role for the isolated subthalamic-globus pallidus complex in generating the pathological activity. Mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) showed significant reductions of over 90% in levels of dopamine as measured in striatum by high pressure liquid chromatography. Likewise, significant reductions in tyrosine hydroxylase immunostaining within the striatum (>90%) and tyrosine hydroxylase positive cell numbers (65%) in substantia nigra were observed. Compared with slices from intact mice, neurones in slices from MPTP-lesioned mice fired significantly more slowly (mean rate of 4.2 Hz, cf. 7.2 Hz in control) and more irregularly (mean coefficient of variation of inter-spike interval of 94.4%, cf. 37.9% in control). Application of ionotropic glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 2-amino-5-phosphonopentanoic acid (AP5) and the GABAA receptor antagonist picrotoxin caused no change in firing pattern. Bath application of dopamine significantly increased cell firing rate and regularized the pattern of activity in cells from slices from both MPTP-treated and control animals. Although the absolute change was more modest in control slices, the maximum dopamine effect in the two groups was comparable. Indeed, when taking into account the basal firing rate, no differences in the sensitivity to dopamine were observed between these two cohorts. Furthermore, pairs of subthalamic nucleus cells showed no correlated activity in slices from either control (21 pairs) or MPTP-treated animals (20 pairs). These results indicate that the isolated but interconnected subthalamic-globus pallidus network is not itself sufficient to generate the aberrant firing patterns in dopamine-depleted animals. More likely, inputs from other regions, such as the cortex, are needed to generate pathological oscillatory activity. © 2006 IBRO.

Some analytical aspects of sampling plans

This thesis reports on the results of the analyses of certain aspects of sampling inspection plans. The investigation has been confined to attributes (as distinct from variables) plans and in this respect.the analyses have been concerned with two main aspects of single and double plans. These are:- (i) the Average Outgoing Quality Limit (AOQL) of the plan. (ii) the Average Sample Number (ASN) of the plan. In the former connection the investigation has been concerned with the evaluation of the AOQL analytically and the determination of the fraction defective of the incoming material to give the AOQL. The analyses have been applied to both single and double sampling plans, In the latter connection the investigation has been concerned with the evaluation of the maximum ASN analytically and the determination of the fraction defective of the incoming material to give the maximum value of ASN. The analyses have been confined only to double sampling plans because in the case of single sampling the ASN is constant and is equal to n, the sample size.

Coherence imaging by use of a Newton rings sampling function

We show that, with suitable optics in the arm of a Michelson interferometer, orthogonal galvo-scanning mirrors build a sampling function in the form of Newton rings when the two interferometer arms are matched. Using a low-coherence source, one can obtain transversal depth-resolved images. A fast display procedure using a storage oscilloscope was devised based on this method.

House building productivity : a study of labour requirements on Scottish house building sites using activity sampling methods

This study is concerned with labour productivity in traditional house building in Scotland. Productivity is a measure of the effective use of resources and provides vital benefits that can be combined in a number of ways. The introduction gives the background to two Scottish house building sites (Blantyre and Greenfield) that were surveyed by the Building Research Establishment (BEE) activity sampling method to provide the data for the study. The study had two main objectives; (1) summary data analysis in average manhours per house between all the houses on the site, and (2) detailed data analysis in average manhours for each house block on the site. The introduction also provides a literature review related to the objectives. The method is outlined in Chapter 2, the sites are discussed in Chapter 3, and Chapter 4 covers the method application on each site and a method development made in the study. The summary data analysis (Chapter 5) compares Blantyre and Greenfield, and two previous BEE surveys in England. The main detailed data analysis consisted of three forms, (Chapters 6, 7 and 8) each applied to a set of operations. The three forms of analysis were variations in average manhours per house for each house block on the site compared with; (1) block construction order, (2) average number of separate visits per house made by operatives to each block to complete an operation, and (3) average number of different operatives per house employed on an operation in each block. Three miscellaneous items of detail data analysis are discussed in Chapter 9. The conclusions to the whole study state that considerable variations in manhours for repeated operations were discovered, that the numbers of visits by operatives to complete operations were large and that the numbers of different operatives employed in some operations were a factor related to productivity. A critique of the activity sampling method suggests that the data produced is reliable in summary form and can give a good context for more detailed data collection. For future work, this could take the form of selected operations, with the context of an activity sampling survey, that wuld be intensively surveyed by other methods.

Sampling of fluids for analysis

Disclosed is a fluid sampling apparatus (12). The apparatus has a sample inlet port (14) in communication with a fluid space (10) containing the fluid to be sampled. An analysis port (16) is provided for communication with an analysis device such as a mass spectrometer. A dilution gas injection port (22) is provided to dilute fluid is sampled from the fluid space via the sample inlet port. The diluted sample fluid is then conducted to the analysis port. The sampling apparatus is intended particularly for use in analysing biomass pyrolysis processes.

Coherence imaging by use of a Newton rings sampling function

We show that, with suitable optics in the arm of a Michelson interferometer, orthogonal galvo-scanning mirrors build a sampling function in the form of Newton rings when the two interferometer arms are matched. Using a low-coherence source, one can obtain transversal depth-resolved images. A fast display procedure using a storage oscilloscope was devised based on this method.