Inference from randomized (factorial) experiments

This is a contribution to the discussion of the interesting paper by Ding [Statist. Sci. 32 (2017) 331–345], which contrasts approaches attributed to Neyman and Fisher. I believe that Fisher’s usual assumption was unit-treatment additivity, rather than the “sharp null hypothesis” attributed to him. Fisher also developed the notion of interaction in factorial experiments. His explanation leads directly to the concept of marginality, which is essential for the interpretation of data from any factorial experiment.Publisher PDFPeer reviewe

Randomization-based models for multitiered experiments: I. A chain of randomizations

We derive randomization-based models for experiments with a chain of randomizations. Estimation theory for these models leads to formulae for the estimators of treatment effects, their standard errors, and expected mean squares in the analysis of variance. We discuss the practicalities in fitting these models and outline the difficulties that can occur, many of which do not arise in two-tiered experiments.Publisher PDFPeer reviewe

Relations among partitions

Combinatorialists often consider a balanced incomplete-block design to consist of a set of points, a set of blocks, and an incidence relation between them which satisfies certain conditions. To a statistician, such a design is a set of experimental units with two partitions, one into blocks and the other into treatments: it is the relation between these two partitions which gives the design its properties. The most common binary relations between partitions that occur in statistics are refinement, orthogonality and balance. When there are more than two partitions, the binary relations may not suffice to give all the properties of the system. I shall survey work in this area, including designs such as double Youden rectangles.PostprintPeer reviewe

Estimability of variance components when all model matrices commute

This work was partially supported by national funds of FCT - Foundation for Science and Technology under UID/MAT/00212/2013.This paper deals with estimability of variance components in mixed models when all model matrices commute. In this situation, it is well known that the best linear unbiased estimators of fixed effects are the ordinary least squares estimators. If, in addition, the family of possible variance-covariance matrices forms an orthogonal block structure, then there are the same number of variance components as strata, and the variance components are all estimable if and only if there are non-zero residual degrees of freedom in each stratum. We investigate the case where the family of possible variance-covariance matrices, while still commutative, no longer forms an orthogonal block structure. Now the variance components may or may not all be estimable, but there is no clear link with residual degrees of freedom. Whether or not they are all estimable, there may or may not be uniformly best unbiased quadratic estimators of those that are estimable. Examples are given to demonstrate all four possibilities.PostprintPeer reviewe

A Non-Oxidative Approach toward Chemically and Electrochemically Functionalizing Si(111)

A general method for the non-oxidative functionalization of single-crystal silicon(111) surfaces is described. The silicon surface is fully acetylenylated using two-step chlorination/alkylation chemistry. A benzoquinone-masked primary amine is attached to this surface via Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition (“click” chemistry). The benzoquinone is electrochemically reduced, resulting in quantitative cleavage of the molecule and exposing the amine terminus. Molecules presenting a carboxylic acid have been immobilized to the exposed amine sites. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and contact angle goniometry were utilized to characterize and quantitate each step in the functionalization process. This work represents a strategy for providing a general platform that can incorporate organic and biological molecules on Si(111) with minimal oxidation of the silicon surface

Clinical academic career pathway for nursing and allied health professionals: clinical academic role descriptors

The clinical academic pathway outlined highlights the range of typical practice and research-focused activities that a practitioner on a clinical academic career pathway might normally engage in at different levels and points along this career path. The activities are intended as a guide for practitioners interested in learning more about the practice and research components of a clinical academic career, as well as those already employed in clinical academic roles. They may also be useful for health care organisations and Higher Education Institutions as a tool for developing clinical academic roles

Burkitt's lymphoma

Burkitt's lymphoma is a highly aggressive B-cell non-Hodgkin lymphoma and is the fastest growing human tumour. The disease is associated with Epstein-Barr virus and was one of the first tumours shown to have a chromosomal translocation that activates an oncogene (c-MYC). Burkitt's lymphoma is the most common childhood cancer in areas where malaria is holoendemic. The incidence is very high in immunosuppressed patients in non-endemic areas, especially when associated with HIV infection. Outcome with intensive chemotherapy has improved and is now excellent in children, but the prognosis is poor in elderly adults. The success of intensive treatment relies on good supportive care. The therapy offered in oncology units in low-income countries is not as aggressive as in centres in high-income countries and outcomes are less successful. Adjuvant monoclonal antibody therapy with rituximab shows promise for improved outcomes and reduced toxic effects in the future

Mathematical modelling of fibre-enhanced perfusion inside\ud a tissue-engineering bioreactor

We develop a simple mathematical model for forced flow of culture medium through a porous scaffold in a tissue- engineering bioreactor. Porous-walled hollow fibres penetrate the scaffold and act as additional sources of culture medium. The model, based on Darcy’s law, is used to examine the nutrient and shear-stress distributions throughout the scaffold. We consider several configurations of fibres and inlet and outlet pipes. Compared with a numerical solution of the full Navier–Stokes equations within the complex scaffold geometry, the modelling approach is cheap, and does not require knowledge of the detailed microstructure of the particular scaffold being used. The potential of this approach is demonstrated through quantification of the effect the additional flow from the fibres has on the nutrient and shear-stress distribution

Factors Influencing Breast Cancer Screening in Low-Income African Americans in Tennessee

This study examined demographic and lifestyle factors that influenced decisions and obstacles to being screened for breast cancer in low-income African Americans in three urban Tennessee cities. As part of the Meharry Community Networks Program (CNP) needs assessment, a 123-item community survey was administered to assess demographic characteristics, health care access and utilization, and screening practices for various cancers in low-income African Americans. For this study, only African American women 40 years and older (n = 334) were selected from the Meharry CNP community survey database. There were several predictors of breast cancer screening such as marital status and having health insurance (P \u3c .05). Additionally, there were associations between obstacles to screening and geographic region such as transportation and not having enough information about screenings (P \u3c .05). Educational interventions aimed at improving breast cancer knowledge and screening rates should incorporate information about obstacles and predictors to screening

Migrant African women: tales of agency and belonging

This paper explores issues of belonging and agency among asylum seekers and refugee women of African origin in the UK. It discusses the ways these women engendered resistance in their everyday life to destitution, lack of cultural recognition, and gender inequality through the foundation of their own non-governmental organization, African Women’s Empowerment Forum, AWEF, a collective ‘home’ space. The focus of this account is on migrant women’s agency and self-determination for the exercise of choice to be active actors in society. It points to what might be an important phenomenon on how local grassroots movements are challenging the invisibility of asylum seekers’ and refugees’ lives and expanding the notion of politics to embrace a wider notion of community politics with solidarity. AWEF is the embodiment of a social space that resonates the ‘in-between’ experience of migrant life providing stability to the women members regarding political and community identification