107 research outputs found
Generalized Integral Operators and Schwartz Kernel Theorem
In connection with the classical Schwartz kernel theorem, we show that in the
framework of Colombeau generalized functions a large class of linear mappings
admit integral kernels. To do this, we need to introduce news spaces of
generalized functions with slow growth and the corresponding adapted linear
mappings. Finally, we show that in some sense Schwartz' result is contained in
our main theorem.Comment: 18 page
Generalized Fourier Integral Operators on spaces of Colombeau type
Generalized Fourier integral operators (FIOs) acting on Colombeau algebras
are defined. This is based on a theory of generalized oscillatory integrals
(OIs) whose phase functions as well as amplitudes may be generalized functions
of Colombeau type. The mapping properties of these FIOs are studied as the
composition with a generalized pseudodifferential operator. Finally, the
microlocal Colombeau regularity for OIs and the influence of the FIO action on
generalized wave front sets are investigated. This theory of generalized FIOs
is motivated by the need of a general framework for partial differential
operators with non-smooth coefficients and distributional data
An axiomatic approach to the non-linear theory of generalized functions and consistency of Laplace transforms
We offer an axiomatic definition of a differential algebra of generalized
functions over an algebraically closed non-Archimedean field. This algebra is
of Colombeau type in the sense that it contains a copy of the space of Schwartz
distributions. We study the uniqueness of the objects we define and the
consistency of our axioms. Next, we identify an inconsistency in the
conventional Laplace transform theory. As an application we offer a free of
contradictions alternative in the framework of our algebra of generalized
functions. The article is aimed at mathematicians, physicists and engineers who
are interested in the non-linear theory of generalized functions, but who are
not necessarily familiar with the original Colombeau theory. We assume,
however, some basic familiarity with the Schwartz theory of distributions.Comment: 23 page
Isomorphisms of algebras of Colombeau generalized functions
We show that for smooth manifolds X and Y, any isomorphism between the
special algebra of Colombeau generalized functions on X, resp. Y is given by
composition with a unique Colombeau generalized function from Y to X. We also
identify the multiplicative linear functionals from the special algebra of
Colombeau generalized functions on X to the ring of Colombeau generalized
numbers. Up to multiplication with an idempotent generalized number, they are
given by an evaluation map at a compactly supported generalized point on X.Comment: 10 page
On the Geroch-Traschen class of metrics
We compare two approaches to semi-Riemannian metrics of low regularity. The maximally 'reasonable' distributional setting of Geroch and Traschen is shown to be consistently contained in the more general setting of nonlinear distributional geometry in the sense of Colombea
Evaluation of elicitation methods to quantify Bayes linear models
The Bayes linear methodology allows decision makers to express their subjective beliefs and adjust these beliefs as observations are made. It is similar in spirit to probabilistic Bayesian approaches, but differs as it uses expectation as its primitive. While substantial work has been carried out in Bayes linear analysis, both in terms of theory development and application, there is little published material on the elicitation of structured expert judgement to quantify models. This paper investigates different methods that could be used by analysts when creating an elicitation process. The theoretical underpinnings of the elicitation methods developed are explored and an evaluation of their use is presented. This work was motivated by, and is a precursor to, an industrial application of Bayes linear modelling of the reliability of defence systems. An illustrative example demonstrates how the methods can be used in practice
Psychometric validation of the European Organisation for Research and Treatment of CancerâQuality of Life Questionnaire Sexual Health (EORTC QLQ-SH22)
BACKGROUND:
The European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Group developed a questionnaire to assess sexual health in patients with cancer and cancer survivors. This study evaluates the psychometric properties of the questionnaire.
METHODS:
The 22-item EORTC sexual health questionnaire (EORTC QLQ-SH22) was administered with the EORTC QLQ-C30 to 444 patients with cancer. The hypothesised scale structure, reliability and validity were evaluated through standardised psychometric procedures.
RESULTS:
The cross-cultural field study showed that the majority of patients (94.7%) were able to complete the QLQ-SH22 in less than 20 min; 89% of the study participants did not need any help to fill in the questionnaire. Multi-item multi-trait scaling analysis confirmed the hypothesised scale structure with two multi-item scales (sexual satisfaction, sexual pain) and 11 single items (including five conditional items and four gender-specific items). The internal consistency yielded acceptable Cronbach's alpha coefficients (.90 for the sexual satisfaction scale, .80 for the sexual pain scale). The test-retest correlations (Pearson's r) ranged from .70 to .93 except for the scale communication with professionals (.67) and male body image (.69). The QLQ-SH22 discriminates well between subgroups of patients differing in terms of their performance and treatment status.
CONCLUSION:
The study supports the reliability, the content and construct validity of the QLQ-SH22. The newly developed questionnaire is clinically applicable to assess sexual health of patients with cancer at different treatment stages and during survivorship for clinical trials and for clinical practice
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