The Case Against Cosmology

It is argued that some of the recent claims for cosmology are grossly overblown. Cosmology rests on a very small database: it suffers from many fundamental difficulties as a science (if it is a science at all) whilst observations of distant phenomena are difficult to make and harder to interpret. It is suggested that cosmological inferences should be tentatively made and sceptically received.Comment: 9 pages, no figure

Tax reform and retirement saving incentives: evidence from the introduction of stakeholder pensions in the UK

Faced with ageing populations, OECD governments are seeking policies to increase individual retirement saving. In April 2001, the UK government introduced Stakeholder Pensions – a low cost retirement saving vehicle. The reform also changed the structure of tax-relieved contribution ceilings, increasing their generosity for lower earning individuals. We examine the impact of these changes on private pension coverage and on contributions to personal pension accounts using individual level micro data. We use a difference-in-differences strategy, and where necessary our estimator is modified to allow for dichotomous outcomes. The results suggest that the change to the contribution ceilings affected both coverage rates and contributions to private pensions among lower earnings individuals, especially among women, and those in couples

Ill-health and retirement in Britain: a panel data-based analysis

We examine the role of ill-health in retirement decisions in Britain, using the first eight waves of the British Household Panel Survey (1991-98). As self-reported health status is likely to be endogenous to the retirement decision, we instrument self-reported health by a constructed ‘health stock’ measure using a set of health indicator variables and personal characteristics, as suggested by Bound et al (1999). Using both linear and non-linear fixed effects estimators, we show that adverse individual health shocks are an important predictor of individual retirement behaviour. We compare the impact of our constructed health measure on economic activity with that arising from the use of other health variables in the data set. We also examine the impact of the 1995 reform of disability benefits on the retirement decision

Implementation of radiation shielding calculation methods. Volume 1: Synopsis of methods and summary of results

The work performed in the following areas is summarized: (1) Analysis of Realistic nuclear-propelled vehicle was analyzed using the Marshall Space Flight Center computer code package. This code package includes one and two dimensional discrete ordinate transport, point kernel, and single scatter techniques, as well as cross section preparation and data processing codes, (2) Techniques were developed to improve the automated data transfer in the coupled computation method of the computer code package and improve the utilization of this code package on the Univac-1108 computer system. (3) The MSFC master data libraries were updated

Assessment of bias in pan-tropical biomass predictions

Above-ground biomass (AGB) is an essential descriptor of forests, of use in ecological and climate-related research. At tree- and stand-scale, destructive but direct measurements of AGB are replaced with predictions from allometric models characterizing the correlational relationship between AGB, and predictor variables including stem diameter, tree height and wood density. These models are constructed from harvested calibration data, usually via linear regression. Here, we assess systematic error in out-of-sample predictions of AGB introduced during measurement, compilation and modeling of in-sample calibration data. Various conventional bivariate and multivariate models are constructed from open access data of tropical forests. Metadata analysis, fit diagnostics and cross-validation results suggest several model misspecifications: chiefly, unaccounted for inconsistent measurement error in predictor variables between in- and out-of-sample data. Simulations demonstrate conservative inconsistencies can introduce significant bias into tree- and stand-scale AGB predictions. When tree height and wood density are included as predictors, models should be modified to correct for bias. Finally, we explore a fundamental assumption of conventional allometry, that model parameters are independent of tree size. That is, the same model can provide predictions of consistent trueness irrespective of size-class. Most observations in current calibration datasets are from smaller trees, meaning the existence of a size dependency would bias predictions for larger trees. We determine that detecting the absence or presence of a size dependency is currently prevented by model misspecifications and calibration data imbalances. We call for the collection of additional harvest data, specifically under-represented larger trees

The existence and detection of optically dark galaxies by 21cm surveys

One explanation for the disparity between Cold Dark Matter (CDM) predictions of galaxy numbers and observations could be that there are numerous dark galaxies in the Universe. These galaxies may still contain baryons, but no stars, and may be detectable in the 21cm line of atomic hydrogen. The results of surveys for such objects, and simulations that do/do not predict their existence, are controversial. In this paper we use an analytical model of galaxy formation, consistent with CDM, to firstly show that dark galaxies are certainly a prediction of the model. Secondly, we show that objects like VIRGOHI21, a dark galaxy candidate recently discovered by us, while rare are predicted by the model. Thirdly, we show that previous 'blind' HI surveys have placed few constraints on the existence of dark galaxies. This is because they have either lacked the sensitivity and/or velocity resolution or have not had the required detailed optical follow up. We look forward to new 21cm blind surveys (ALFALFA and AGES) using the Arecibo multi-beam instrument which should find large numbers of dark galaxies if they exist