Product Of Factors Research Articles

The use of modeling to understand the impact of screening on US mortality: examples from mammography and PSA testing

Surveillance data represent a vital resource for understanding the impact of cancer control interventions on the population cancer burden. However, population cancer trends are a complex product of many factors, and estimating the contribution of any one of these factors can be challenging. Surveillance modeling is a technique for estimating the contribution of one or more interventions of interest to trends in disease incidence and mortality. In this article, we present several approaches to surveillance modeling of cancer screening interventions. We classify models as biological or epidemiological, depending on whether they model the full unobservable aspects of disease onset and progression, or models which reduce the complex process to simpler terms by summarizing portions of the disease process using mostly observed population level measures. We also describe differences between macrolevel models, microsimulation models and mechanistic models. We discuss procedures for model calibration and validation, and methods for presenting model results which are robust with respect to certain types of biased model estimates. As examples, we present several models of the impact of mammography screening on breast cancer mortality, and PSA screening on prostate cancer mortality. Both these examples are appropriate uses of surveillance modeling, even though for mammography there is extensive (although somewhat controversial) randomized trial evidence, whereas for PSA this biomarker has seen extensive use as a screening test prior to any controlled trial evidence of its efficacy. Some of the models presented here were developed as part of the National Cancer Institute's Cancer Intervention and Surveillance Modeling Network.

Capacity investigation of brine-bearing sands of the Fwwm formation for geologic sequestration of CO{sub 2}

The capacity of fluvial brine-bearing formations to sequester CO{sub 2} is investigated using numerical simulations of CO{sub 2} injection and storage. Capacity is defined as the volume fraction of the subsurface available for CO{sub 2} storage and is conceptualized as a product of factors that account for two-phase flow and transport processes, formation geometry, formation heterogeneity, and formation porosity. The space and time domains used to define capacity must be chosen with care to obtain meaningful results, especially when comparing different authors' work. Physical factors that impact capacity include permeability anisotropy and relative permeability to CO{sub 2}, brine/CO{sub 2} density and viscosity ratios, the shape of the trapping structure, formation porosity and the presence of low-permeability layering.

Efficient recursions for general factorisable models

Let n S‐valued categorical variables be jointly distributed according to a distribution known only up to an unknown normalising constant. For an unnormalised joint likelihood expressible as a product of factors, we give an algebraic recursion which can be used for computing the normalising constant and other summations. A saving in computation is achieved when each factor contains a lagged subset of the components combining in the joint distribution, with maximum computational efficiency as the subsets attain their minimum size. If each subset contains at most r+1 of the n components in the joint distribution, we term this a lag‐r model, whose normalising constant can be computed using a forward recursion in O(Sr+1) computations, as opposed to O(Sn) for the direct computation. We show how a lag‐r model represents a Markov random field and allows a neighbourhood structure to be related to the unnormalised joint likelihood. We illustrate the method by showing how the normalising constant of the Ising or autologistic model can be computed.

Electron dichroism effects in the relativistic (e, 2e) process for K-shell ionization of atoms

In this communication we present theoretical demonstration of electron dichroism in the relativistic (e, 2e) process for K-shell ionization of atoms in non-coplanar asymmetric geometry. The theoretical formalism has been developed in plane wave Born approximation and in this approximation the triple differential cross-section (TDCS) has been expressed as a product of kinematical factors and atomic structure functions. The longitudinal spin asymmetry in the relativistic (e, 2e) process on K-shell of atoms has been shown to depend on the interference between the transition charge and component of the transition current in the direction perpendicular to the scattering plane. Further, the longitudinal spin asymmetry has been shown to depend on incident electron energy, atomic number of the target, azimuthal angle of the ejected electron and scattered electron angle.

A large‐scale study of handedness and pregnancy/birth risk events: Implications for genetic theories of handedness

Whether left‐handedness is due to genetic factors or to pregnancy and birth stress events is an important question for models that attempt to explain the origins and distribution of human handedness. Major genetic theories of handedness, such as those of Annett (1985) and McManus (1981), allow for a nondetermination of some left‐ or right‐handedness by “chance”, but they hold that “pathological left‐handedness”, specifically, is of minimal influence. On the other hand, theorists such as Bakan (1971) and Coren (1995) take the view that right‐handedness is a universal human characteristic, presumably due to a polygenic influence, and that left‐handedness is essentially always the product of pregnancy and birth risk factors. Research attempting to find associations of left‐handedness and unfortunate pregnancy and birthing events has produced very inconsistent results. We report a large‐scale study that employed handedness for writing as the criterion for handedness, mothers' reports regarding the occurrence or nonoccurrence of a large number of possible pregnancy and birth stress events, and mothers' reports regarding the handedness of the biological parents and of their offspring. Of the 25 potential stressors studied, only maternal age showed a significant association with left‐handedness of offspring. Further, this relationship was quite weak and would account for no more than 1/84th of the approximate 11% incidence of left‐handedness in the general population. Implications for theories of handedness are discussed.

Stochastic Approach to the Random Activation Energy Model with a Rate-Determining Step. Universal Behavior for the Probability of Concentration Fluctuations

We study the concentration fluctuations for a reversible overall reaction with a rate-determining step occurring in a system with static disorder described in terms of the random activation energy model. We assume that the rates of the forward and backward reactions can be expressed as products of random rate coefficients times concentration dependent factors, which can also depend on nonrandom quasiequilibrium constants such as adsorption coefficients or Michaelis-Menten constants. Further, we take the activation energies of the forward and backward processes to have a random component ΔE, which is selected from a frozen Maxwell-Boltzmann distribution. We derive a stochastic evolution equation for the joint probability density of the reaction extent ξ and of the random component ΔE of the activation barrier. The solution of this stochastic evolution equation leads to a general expression for the probability density (ξ,t) of the reaction extent ξ at time t. For a long time, the probability density?(ξ,t) of concentration fluctuations approaches its stationary value? s t (ξ), according to a universal power scaling law, which is independent of the detailed kinetics of the process?(ξ,t) ? s t (ξ) + t - α C(ξ) as t → ∞, where a is a fractal exponent between 0 and 1 and C(ξ) is a concentration dependent amplitude factor. A similar behavior is displayed by systems approaching a nonequilibrium steady state. We generalize our analysis to multiple overall reactions and to systems with dynamic disorder and develop methods for extracting kinetic information from experimental data.

Random small Hamming weight products with applications to cryptography

There are many cryptographic constructions in which one uses a random power or multiple of an element in a group or a ring. We describe a fast method to compute random powers and multiples in certain important situations including powers in the Galois field F 2 n , multiples on Koblitz elliptic curves, and multiples in NTRU convolution polynomial rings. The underlying idea is to form a random exponent or multiplier as a product of factors, each of which has low Hamming weight when expanded as a sum of powers of some fast operation.

Fear of gangs: A test of alternative theoretical models*

On the basis of data on 800 randomly selected residents in a large south-western metropolitan city, we assess the influence of four theoretical models on fear of crime and fear of gangs. In doing so, we compare general fear of crime to specific fear of gangs to delineate whether the same factors influence each or whether different fears are the product of different factors. The results indicate that while many of the factors that influence fear of crime and fear of gangs are similar, there are significant differences in the magnitude in which these factors influence our measures of fear.

Is Durkheim the Enemy of Evolutionary Psychology?

Evolutionary psychologists cite Durkheim's sociology as an exemplar of an approach that takes the human mind to be largely the product of social and cultural factors with negligible contributions from biology. The author argues that on the contrary, his sociological theory of the categories is compatible with the possibility of innate cognitive capacities, taking causal cognition as his example. Whether and to what extent there are such innate capacities is a question for research in the cognitive neurosciences. The extent to which these innate capacities can then be explained by natural selection remains an open question for empirical investigation.

On the minimum polynomial of supermatrices

In this paper, a new selection of factors for the construction of the minimum polynomial of a supermatrix M is proposed, leading to null polynomials of M of lower degree than the degree of the corresponding polynomial obtained by using the method proposed in the work of Urrutia and Morales [1]. The case of (1 + 1) × (1 + 1) supermatrices has been completely discussed. Moreover, the main theorem concerning the construction of the minimum polynomial as a product of factors from the characteristic polynomial in the general case of (m + n) × (m + n) supermatrices is given. Finally, we prove that the minimum polynomial of a supermatrix M, in general, is not unique.

Assimilating Giants: The Appropriation of Gog and Magog in Medieval and Early Modern England

Appearing in both Genesis and Revelation, Gog and Magog have long been associated with beginnings and endings. Passing into late classical and medieval literature and history from biblical tradition, the two were sometimes a single being (Gogmagog ), sometimes separate (Gog and Magog ), sometimes ethnic groups (the races of Gog and Magog ), and sometimes lands. Amorphous terms, the names were at one time or another attached to the Scythians, Goths, Saracens, Jews, and the gigantic sons of Albina, among others. For many medieval writers, Gog and Magog functioned as typological metaphors, names that could be appropriated to whatever was alien, threatening, or actively hostile in a manner that paralleled biblical usage. Since their earliest appearances in written history, Gog and Magog — whatever their precise definition —h ave fulfilled a cultural need for a sense of group solidarity, itself a product of many factors including an association with a specific territory, a shared history, and a distinctive shared culture. These elements are central to what Anthony D. Smith calls the “ethnic consciousness” of previous eras, a consciousness that resides chiefly in the “myths, memories, values, and symbols” of cultural communities. 1 Although their role changes over time, the myths of Gog and Magog contribute to the formation of a uniquely Western and, eventually, English consciousness. Their estrangement from a social group has allowed various peoples to identify themselves as part of a community, whether ethnic, religious, national, or local. Over their long history, Gog and Magog have provided a kind of cultural orientation for a whole series of historical communities. Stories in which they appear often use them to stress the solidarity of a people against the alien force represented by the two, the extent to which a given group shares what John Armstrong terms a “common fate.” 2 Even in their earliest

The Transformation of Legislative Elites: The Cases of Britain and Germany since the 1860s

Drawing on databases going back to the middle of the nineteenth century, this article examines how changes in the opportunity structures in political recruitment have influenced the socio-economic backgrounds and career patterns of British and German MPs. Extending opportunity structures enables legislatures to respond to socio-economic changes in society, but there may be a significant time-lag before they are reflected in the legislature. In spite of significant differences in their political history, there has been a convergence of socio-economic backgrounds and career patterns, driven largely by changes in the opportunity structures, which, particularly in the German case, preceded the full impact of changes in political culture. This convergence does not preclude significant differences, but these are principally the product of particular factors, such as party and electoral systems, and changes do not necessarily occur simultaneously, but the tendency towards similar educational and occupational backgrounds and similar career patterns remains.

Interferometric Visibility of a Scintillating Source

I calculate the distribution of the product of complex factors drawn from a bivariate Gaussian distribution. The interferometric visibility of a scintillating point source follows this distribution. I find the distributions of the real part, the imaginary part, and the amplitude of the product. I investigate effects of a small, partially resolved source on the distribution. These effects depend on whether the source is elongated, and if so, on its orientation relative to the interferometer baseline. A single sample of interferometric visibility, for any source, is also the product of complex factors drawn from a bivariate Gaussian distribution.

Recent developments in microvascular angina.

Microvascular angina (Syndrome X) is an extremely heterogeneous clinical entity that is the product of genetic, coronary microvascular, metabolic, and clinical factors, which combine together to produce distinct cardiac manifestations and complications. The interactions of these abnormalities remain poorly understood. The diagnosis is considered in patients with anginal symptoms and no epicardial coronary narrowing. Therapy is also problematic, with beta-blockers as first-line pharmacotherapy followed by angiotensin-converting enzyme inhibitors and calcium channel blockers.

Pathway-Related Factors: The Potential for Human Data to Improve the Scientific Basis of Risk Assessment

The default uncertainty factors used for risk assessment are applied either to allow for different aspects of extrapolation of the dose-response curve or to allow for database deficiencies. Replacement of toxicokinetic or toxicodynamics defaults by chemical-specific data allows the calculation of a chemical-specific “data-derived factor”, which is the product of chemical-specific values and default uncertainty factors. Such chemical-specific composite values will improve the scientific basis of the risk assessment of that chemical, but the necessary chemical-specific data are rarely available. Categorical defaults related to pathways of elimination and mechanisms of toxicity could be used when the overall fate or mechanism is known, but there are no chemical-specific data sufficient to allow replacement of the default, and the development of an overall data-derived factor. The development of pathway-related categorical defaults is being undertaken using data on selected probe substrates for which adequate data are available. The concept and difficulties of this approach are illustrated using data for CYP1A2.

Molecular Mechanisms of Development and Differentiation of the Eye of Drosophila and Vertebrates

The development of the eye is compared in Drosophila and vertebrates. Although the structure of the compound eye of invertebrates and of the cameral eye of vertebrates differs morphologically, there are striking similarities at the molecular level. Three groups of genes control the morphogenesis of the eye: the genes responsible for eye rudiment formation, neurogenic genes, and proneural genes. In the eye rudiments of Drosophila and vertebrates, the homologous regulatory homeobox-containing genes ey/Pax6, so/Six3, rx/Rx, and optix/Optx2 are expressed. Transcription factors encoded by these conservative genes are involved in specific interactions with DNA. Another set of homologous genes, eya/Eya and dac/DACH/Dac, is also expressed during this developmental period. These genes encode nuclear transcription factors that are devoid of DNA-binding domains but are involved in the protein–protein interactions that control gene expression. Transcriptional complexes, which are products of homeobox-containing genes and nuclear factors, control morphogenesis of the eye in Drosophila and vertebrates. A similar set of homologous regulatory and nuclear genes controls morphogenesis during formation of the ectopic eyes in Drosophila and vertebrates. Molecular biology approaches have allowed eye development to be examined at the level of developmental mechanisms. It has become evident that progress in understanding the mechanisms of eye development is due to studies carried out on Drosophila. Supporters of the idea of the polyphyletic origin of the compound and cameral eyes have noted significant differences in their structure and have failed to find distinct common features in their development. The hypothesis of the monophyletic origin of eyes has been substantiated by the results of molecular investigations.

Visual fields in glaucoma: a clinical overview

Static automated visual field testing is now an integral part of the detection and monitoring of primary open angle glaucoma. However, although many aspects of testing are automated, interpretation of the large amounts of data produced by these instruments is not. Two major challenges facing the practitioner are differentiating between the visual fields of a patient with early glaucoma and those of a normal patient, and identifying whether small reductions in sensitivity are due to a true defect or a product of other factors. This paper presents a clinical overview of how to systematically review visual field plots and how to recognise defects arising from patient factors, as well as some of the alternative testing techniques available for the assessment of the glaucoma patient.

Post-Separation Violence: The Male Perspective*

This study investigated the male perspective of violence using a socio-ecological framework wherein violence is seen as the product of individual, social, cultural, environmental, and situational factors. Structured questions were developed for telephone interviews with separated males in Western Australia. Volunteers were recruited via a media campaign focusing on: “Why do some men hit women: Why don’t all men hit women?” One hundred and forty six interviews were analysed using Spearman’s rho and Pearson’s chi-square and thematic analysis. Sixty-one of the men reported having been violent, 14 at separation only. In 23 cases children witnessed the violence. Influencing factors were reported as finances, alcohol/drugs, fatigue/stress, “the system”. No significant association was found between violence and having a source of support. Nearly half of the men believed their violence was justified, either unequivocally or sometimes. Fairness in the legal system was the most frequent suggestion for redressing violence in society, followed by provision of counselling, support, and education appropriate to the needs of males. Implications for individual and societal responses are discussed.

Inter- and Intra-Species Extrapolation in Risk Assessment of Different Classes of Pesticides

Risk assessors routinely use the reference dose (RfD) approach for non-cancer risk assessment. In this approach, No-Observed-Adverse-Effect-Level (NOAEL) is divided by the product of uncertainty factors (UFs) and, occasionally, an additional modifying factor (MF), each usually employed by default as factors of 10. In the present investigation, kinetic and dynamic data have been used in order to reduce uncertainties when establishing exposure guidelines for examples of chemicals representing four classes of pesticides (warfarin, lindane, carbaryl and parathion). An intensive search of databases was conducted for these pesticides, and toxicokinetic and toxicodynamic parameters in inter- and intra-species were evaluated. The kinetic and dynamic subfactors were less than the proposed values of Renwick and the International Programme on Chemical Safety (IPCS). The composite factors for all the examined pesticides were less than 100. The present study indicated that in setting exposure levels it is important to incorporate kinetic and dynamic data, as they become available, rather than rely on default uncertainty factors, which are imprecise in many cases.

Modeling the combined effect of static and varying phase distortions on the performance of adaptive optical systems

The end-to-end performance achieved by an adaptive optical (AO) imaging system is determined by a combination of the residual time-varying phase distortions associated with atmospheric turbulence and the quasi-static unsensed and uncorrectable aberrations in the optical system itself. Although the effects of these two errors on the time-averaged Strehl ratio and the time-averaged optical transfer function (OTF) of the AO system are not formally separable, such an approximation is found to be accurate to within a few percent for a range of representative residual wave-front errors. In these calculations, we combined static optical system aberrations and time-varying residual phase distortion characteristics of a deformable mirror fitting error, wave-front sensor noise, and anisoplanatism. The static aberrations consist of focus errors of varying magnitudes as well as a combination of unsensed and uncorrectable mirror figure errors derived from modeling by the Gemini 8-Meter Telescopes Project. The overall Strehl ratios and OTF's that are due to the combined effect of these error sources are well approximated as products of separate factors for the static and time-varying aberrations, as long as the overall Strehl ratio that is due to both errors is greater than approximately 0.1. For lower Strehl ratios, the products provide lower bounds on the actual values of the Strehl ratio and the OTF. The speckle transfer function is also well approximated by a product of two functions, but only where AO compensation is sufficiently good that speckle imaging techniques are usually not required.