Embryonic Stem Cell Research as an Ethical Issue: On the Emptiness of Symbolic Value

The debate over human embryonic stem cell research-scientific and clinical prospects as well as ethical implications-became front-page news only after two teams of university researchers reported in November 1998 that they had isolated and cultured human pluripotent stem cells. The discovery caused a flurry of excitement among patients and researchers and drew attention from President Clinton, who instructed the National Bioethics Advisory Commission (NBAC) to conduct a thorough review of the issues associated with. .. human stem cell research, balancing all medical and ethical issues.

The interplay of classes of algorithmically random objects

We study algorithmically random closed subsets of $2^\omega$, algorithmically random continuous functions from $2^\omega$ to $2^\omega$, and algorithmically random Borel probability measures on $2^\omega$, especially the interplay between these three classes of objects. Our main tools are preservation of randomness and its converse, the no randomness ex nihilo principle, which say together that given an almost-everywhere defined computable map between an effectively compact probability space and an effective Polish space, a real is Martin-L\"of random for the pushforward measure if and only if its preimage is random with respect to the measure on the domain. These tools allow us to prove new facts, some of which answer previously open questions, and reprove some known results more simply. Our main results are the following. First we answer an open question of Barmapalias, Brodhead, Cenzer, Remmel, and Weber by showing that $\mathcal{X}\subseteq2^\omega$ is a random closed set if and only if it is the set of zeros of a random continuous function on $2^\omega$. As a corollary we obtain the result that the collection of random continuous functions on $2^\omega$ is not closed under composition. Next, we construct a computable measure $Q$ on the space of measures on $2^\omega$ such that $\mathcal{X}\subseteq2^\omega$ is a random closed set if and only if $\mathcal{X}$ is the support of a $Q$-random measure. We also establish a correspondence between random closed sets and the random measures studied by Culver in previous work. Lastly, we study the ranges of random continuous functions, showing that the Lebesgue measure of the range of a random continuous function is always contained in $(0,1)$

New safety model for the commercial human spaceflight industry

The aviation and space domains have safety guidelines and recommended practices for Design Organisations (DOs) and Operators alike. In terms of Aerospace DOs there are certification criteria to meet and to demonstrate compliance there are Advisory Circulars or Acceptable Means of Compliance to follow. Additionally there are guidelines such as Aerospace Recommended Practices (ARP), Military Standards (MIL-STD 882 series) and System Safety Handbooks to follow in order to identify and manage failure conditions. In terms of Operators there are FAA guidelines and a useful ARP that details many tools and techniques in understanding Operator Safety Risks. However there is currently no methodology for linking the DO and Operator safety efforts. In the space domain NASA have provided safety standards and guidelines to follow and also within Europe there are European Co-operation of Space Standardization (ECSS) to follow. Within the emerging Commercial Human Spaceflight Industry, the FAA’s Office of Commercial Space Transportation has provided hazard analysis guidelines. However all of these space domain safety documents are based on the existing aerospace methodology and once again, there is no link between the DO and Operator’s safety effort. This paper addresses the problematic issue and presents a coherent methodology of joining up the System Safety effort of the DOs to the Operator Safety Risk Management such that a ‘Total System’ approach is adopted. Part of the rationale is that the correct mitigation (control) can be applied within the correct place in the accident sequence. Also this contiguous approach ensures that the Operator is fully aware of the safety risks (at the accident level) and therefore has an appreciation of the Total System Risk. The authors of this paper contend that it is better practice to have a fully integrated safety model as opposed to disparate requirements or guidelines. Our methodology is firstly to review ‘best practice’ approaches from the aviation and space industries, and then to integrate these approaches into a contiguous safety model for the commercial human spaceflight industry