The agency of hybrids: overcoming the symmetrophobic block

We respond to ‘challenge 3’ presented in Rose, Jones and Truex’s excellent polemic by way of elucidating the meanings of hybrids, actants, agency and symmetry in Actor-Network Theory. We provide a (very brief) account of Latour’s project to unravel the modernist epistemological settlement that separates humans and non-humans in the world, and that alas so often results in errors and confusions. We contend that the framing of the challenge itself implies the very distinctions that ANT seeks to reject (namely the dichotomization of the world into mutually exclusive ‘subject’ and ‘object’ divisions). Following Latour, we argue that such pure forms do not exist—and furthermore that ‘agency’ is the property of complex hybrids comprised of various strands of human and non-human materials and abstract elements. This is the true meaning of the principle of symmetry! We conclude with some counter-challenges of our own

Meteoroid detector

A meteoroid detector is described which uses, a cold cathode discharge tube with a gas-pressurized cell in space for recording a meteoroid puncture of the cell and for determining the size of the puncture

SAM 2 data user's guide

This document is intended to serve as a guide to the use of the data products from the Stratospheric Aerosol Measurement (SAM) 2 experiment for scientific investigations of polar stratospheric aerosols. Included is a detailed description of the Beta and Aerosol Number Density Archive Tape (BANAT), which is the SAM 2 data product containing the aerosol extinction data available for these investigations. Also included are brief descriptions of the instrument operation, data collection, processing and validation, and some of the scientific analyses conducted to date

A methodology for design of lightweight robotic arm links in harsh environments

A methodology for the creation of functionally graded material (FGM) parts in harsh environments has been developed. It uses a two-stage optimisation approach that focusses first on the task-dependent material choice and then on the topological optimisation (TO) of the part. Constraints are in place to ensure the part can be manufactured, including the extent/smoothness of material blending and the minimum feature size and layer thickness. Thought is also put into space-specific concerns, such as radiation and cyclic thermal heating. The methodology assumes an initial design solution has already been generated, and covers from the beginning of the CAD phase to the end of the computational testing phase. Design constraints are created with additive manufacture (AM) in mind, and suggestions are made for material mixing processes for FGM, material layout strategies and manufacturability, including scanning strategies and surface finish

The design of a robotic arm link using functionally graded materials : a case study

The development and design of a functionally-graded material (FGM) robotic arm for supporting and manipulating a vision system is discussed in this paper. The aim is to understand if using FGMs effectively reduce mass compared to single material parts. The evolution of ideas using topological optimisation (TO) and FGMs towards the design are shown and reviewed. The final design uses TO, and as such needs to be manufactured using additive manufacture (AM). Constraints have been put in place to ensure physical manufacturability is possible. The final design reduces the mass compared to the original arm by 61.4%

SAM-2 ground-truth plan: Correlative measurements for the Stratospheric Aerosol Measurement-2 (SAM 2) sensor on the Nimbus G satellite

The SAM-2 will fly aboard the Nimbus-G satellite for launch in the fall of 1978 and measure stratospheric vertical profiles of aerosol extinction in high latitude bands. The plan gives details of the location and times for the simultaneous satellite/correlative measurements for the nominal launch time, the rationale and choice of the correlative sensors, their characteristics and expected accuracies, and the conversion of their data to extinction profiles. The SAM-2 expected instrument performance and data inversion results are presented. Various atmospheric models representative of polar stratospheric aerosols are used in the SAM-2 and correlative sensor analyses

Placental Structure in Preterm Birth Among HIV-Positive Versus HIV-Negative Women in Kenya.

BackgroundPreterm birth (PTB) is a major cause of infant morbidity and mortality in developing countries. Recent data suggest that in addition to Human Immunodeficiency Virus (HIV) infection, use of antiretroviral therapy (ART) increases the risk of PTB. As the mechanisms remain unexplored, we conducted this study to determine whether HIV and ART were associated with placental changes that could contribute to PTB.SettingWe collected and evaluated placentas from 38 HIV-positive women on ART and 43 HIV-negative women who had preterm deliveries in Nairobi, Kenya.MethodsAnatomical features of the placentas were examined at gross and microscopic levels. Cases were matched for gestational age and compared by the investigators who were blinded to maternal HIV serostatus.ResultsAmong preterm placentas, HIV infection was significantly associated with thrombosis (P = 0.001), infarction (P = 0.032), anomalies in cord insertion (P = 0.02), gross evidence of membrane infection (P = 0.043), and reduced placental thickness (P = 0.010). Overall, preterm placentas in both groups were associated with immature villi, syncytial knotting, villitis, and deciduitis. Features of HIV-positive versus HIV-negative placentas included significant fibrinoid deposition with villus degeneration, syncytiotrophoblast delamination, red blood cell adhesion, hypervascularity, and reduction in both surface area and perimeter of the terminal villi.ConclusionsThese results imply that HIV infection and/or ART are associated with morphological changes in preterm placentas that contribute to delivery before 37 weeks. Hypervascularity suggests that the observed pathologies may be attributable, in part, to hypoxia. Further research to explore potential mechanisms will help elucidate the pathways that are involved perhaps pointing to interventions for decreasing the risk of prematurity among HIV-positive women