Introduction

This is the post print version of the chapter - Copyright @ 2003 The editorsThis book is about surrogacy and, more specifically, surrogate motherhood. It is a collection of essays that aims to provide a contemporary and international picture of a practice, traceable to ancient times, devised to solve the problem of childlessness. The collection, which explores surrogacy from a variety of perspectives including law, policy, medicine and psychology, is timely. For although there is nothing new in the notion that a woman might bear a child for someone else, there is some evidence that the incidence of surrogacy is increasing and technology has developed to make ever more complex arrangements possible

Regge Poles in High-Energy Electron Scattering

The possibility that the photon is described by a Regge trajectory is considered, and the effect of this assumption on the analysis of electron-pion, electron-nucleon, and electron-helium scattering is examined in some detail. Partial-wave projections for the various amplitudes are made in the annihilation channel, and a multiparticle unitarity condition is formally imposed by use of the N/D matrix formulation. Since the photon does not have a fixed spin of one, the spin matrix structure is considerably more complicated than in the conventional theory. The amplitudes are written in terms of the Regge poles corresponding to the photon, ρ-ω meson, etc., and the resulting cross sections are given in the interesting high-energy limit. In contrast to the usual analysis, where form factors depend only on the momentum transfer, we find a larger number of independent functions which depend on the energy as well, however, in a characteristic manner. That is, the essential change due to the Regge behavior of the photon is an over-all nonintegral power of the energy occurring in the cross section. The effect of this factor can be experimentally tested and this possibility is discussed

SSME main combustion chamber life prediction

Typically, low cycle fatigue life is a function of the cyclic strain range, the material properties, and the operating temperature. The reusable life is normally defined by the number of strain cycles that can be accrued before severe material degradation occurs. Reusable life is normally signified by the initiation or propagation of surface cracks. Hot-fire testing of channel wall combustors has shown significant mid-channel wall thinning or deformation during accrued cyclic testing. This phenomenon is termed cyclic-creep and appears to be significantly accelerated at elevated surface temperatures. This failure mode was analytically modelled. The cyclic life of the baseline SSME-MCC based on measured calorimeter heat transfer data, and the life sensitivity of local hot spots caused by injector effects were determined. Four life enhanced designs were assessed

Multiple scattering in random mechanical systems and diffusion approximation

This paper is concerned with stochastic processes that model multiple (or iterated) scattering in classical mechanical systems of billiard type, defined below. From a given (deterministic) system of billiard type, a random process with transition probabilities operator P is introduced by assuming that some of the dynamical variables are random with prescribed probability distributions. Of particular interest are systems with weak scattering, which are associated to parametric families of operators P_h, depending on a geometric or mechanical parameter h, that approaches the identity as h goes to 0. It is shown that (P_h -I)/h converges for small h to a second order elliptic differential operator L on compactly supported functions and that the Markov chain process associated to P_h converges to a diffusion with infinitesimal generator L. Both P_h and L are selfadjoint (densely) defined on the space L2(H,{\eta}) of square-integrable functions over the (lower) half-space H in R^m, where {\eta} is a stationary measure. This measure's density is either (post-collision) Maxwell-Boltzmann distribution or Knudsen cosine law, and the random processes with infinitesimal generator L respectively correspond to what we call MB diffusion and (generalized) Legendre diffusion. Concrete examples of simple mechanical systems are given and illustrated by numerically simulating the random processes.Comment: 34 pages, 13 figure

On a suspected ring external to the visible rings of Saturn

The reexamination of a photograph of Saturn taken on 15 November 1966 when the earth was nearly in the ring plane is investigated which indicates that ring material does exist outside the visible rings, extending to more than 6 Saturnian radii. The observed brightness in blue light was estimated per linear arc second, implying a normal optical thickness, for ice-covered particles

Different populations of RNA polymerase II in living mammalian cells

RNA polymerase II is responsible for transcription of most eukaryotic genes, but, despite exhaustive analysis, little is known about how it transcribes natural templates in vivo. We studied polymerase dynamics in living Chinese hamster ovary cells using an established line that expresses the largest (catalytic) subunit of the polymerase (RPB1) tagged with the green fluorescent protein (GFP). Genetic complementation has shown this tagged polymerase to be fully functional. Fluorescence loss in photobleaching (FLIP) reveals the existence of at least three kinetic populations of tagged polymerase: a large rapidly-exchanging population, a small fraction resistant to 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) but sensitive to a different inhibitor of transcription (i.e. heat shock), and a third fraction sensitive to both inhibitors. Quantitative immunoblotting shows the largest fraction to be the inactive hypophosphorylated form of the polymerase (i.e. IIA). Results are consistent with the second (DRB-insensitive but heat-shock-sensitive) fraction being bound but not engaged, while the third (sensitive to both DRB and heat shock) is the elongating hyperphosphorylated form (i.e. IIO)

ROBOSIM: An intelligent simulator for robotic systems

The purpose of this paper is to present an update of an intelligent robotics simulator package, ROBOSIM, first introduced at Technology 2000 in 1990. ROBOSIM is used for three-dimensional geometrical modeling of robot manipulators and various objects in their workspace, and for the simulation of action sequences performed by the manipulators. Geometric modeling of robot manipulators has an expanding area of interest because it can aid the design and usage of robots in a number of ways, including: design and testing of manipulators, robot action planning, on-line control of robot manipulators, telerobotic user interface, and training and education. NASA developed ROBOSIM between 1985-88 to facilitate the development of robotics, and used the package to develop robotics for welding, coating, and space operations. ROBOSIM has been further developed for academic use by its co-developer Vanderbilt University, and has been in both classroom and laboratory environments for teaching complex robotic concepts. Plans are being formulated to make ROBOSIM available to all U.S. engineering/engineering technology schools (over three hundred total with an estimated 10,000+ users per year)

Simulation-based intelligent robotic agent for Space Station Freedom

A robot control package is described which utilizes on-line structural simulation of robot manipulators and objects in their workspace. The model-based controller is interfaced with a high level agent-independent planner, which is responsible for the task-level planning of the robot's actions. Commands received from the agent-independent planner are refined and executed in the simulated workspace, and upon successful completion, they are transferred to the real manipulators

Impaired body perception in developmental prosopagnosia

Developmental prosopagnosia (DP) is a lifelong neurodevelopmental disorder associated with difficulties recognising and discriminating faces. In some cases, the perceptual deficits seen in DP appear to be face-specific. However, DP is known to be a heterogeneous condition, and many cases undoubtedly exhibit impaired perception of other complex objects. There are several well-documented parallels between body and face perception; for example, faces and bodies are both thought to recruit holistic analysis and engage similar regions of visual cortex. In light of these similarities, individuals who exhibit face perception deficits, possibly due to impaired holistic processing or aberrant white matter connectivity, might also show co-occurring deficits of body perception. The present study therefore sought to investigate body perception in DP using a sensitive delayed match-to-sample task and a sizeable group of DPs. To determine whether body perception deficits, where observed, co-vary with wider object recognition deficits, observers’ face and body matching ability was compared with performance in a car matching condition. Relative to age-matched controls, the DP sample exhibited impaired body matching accuracy at the group level, and several members of the sample were impaired at the single-case level. Consistent with previous reports of wider object recognition difficulties, a number of the DPs also showed evidence of impaired car recognition

Innermost stable circular orbits around relativistic rotating stars

We investigate the innermost stable circular orbit (ISCO) of a test particle moving on the equatorial plane around rotating relativistic stars such as neutron stars. First, we derive approximate analytic formulas for the angular velocity and circumferential radius at the ISCO making use of an approximate relativistic solution which is characterized by arbitrary mass, spin, mass quadrupole, current octapole and mass $2^4$-pole moments. Then, we show that the analytic formulas are accurate enough by comparing them with numerical results, which are obtained by analyzing the vacuum exterior around numerically computed geometries for rotating stars of polytropic equation of state. We demonstrate that contribution of mass quadrupole moment for determining the angular velocity and, in particular, the circumferential radius at the ISCO around a rapidly rotating star is as important as that of spin.Comment: 12 pages, 2 figures, accepted for publication in Phys. Rev.