Space shuttle flight readiness firing dress rehearsal for STS-1

The static firing of the Space Shuttle Main Engine in preparation for the launch of the Enterprise Orbiter is discussed. The following were also tested: structures and mechanics; thermal design integration; propulsion and power; avionics and software; guidance, navigation, and control; mechanical systems; communications and tracking; and integrated ground systems

Precise calibration of LIGO test mass actuators using photon radiation pressure

Precise calibration of kilometer-scale interferometric gravitational wave detectors is crucial for source localization and waveform reconstruction. A technique that uses the radiation pressure of a power-modulated auxiliary laser to induce calibrated displacements of one of the ~10 kg arm cavity mirrors, a so-called photon calibrator, has been demonstrated previously and has recently been implemented on the LIGO detectors. In this article, we discuss the inherent precision and accuracy of the LIGO photon calibrators and several improvements that have been developed to reduce the estimated voice coil actuator calibration uncertainties to less than 2 percent (1-sigma). These improvements include accounting for rotation-induced apparent length variations caused by interferometer and photon calibrator beam centering offsets, absolute laser power measurement using temperature-controlled InGaAs photodetectors mounted on integrating spheres and calibrated by NIST, minimizing errors induced by localized elastic deformation of the mirror surface by using a two-beam configuration with the photon calibrator beams symmetrically displaced about the center of the optic, and simultaneously actuating the test mass with voice coil actuators and the photon calibrator to minimize fluctuations caused by the changing interferometer response. The photon calibrator is able to operate in the most sensitive interferometer configuration, and is expected to become a primary calibration method for future gravitational wave searches.Comment: 13 pages, 6 figures, accepted by Classical and Quantum Gravit

Precise calibration of LIGO test mass actuators using photon radiation pressure

Precise calibration of kilometer-scale interferometric gravitational wave detectors is crucial for source localization and waveform reconstruction. A technique that uses the radiation pressure of a power-modulated auxiliary laser to induce calibrated displacements of one of the ~10 kg arm cavity mirrors, a so-called photon calibrator, has been demonstrated previously and has recently been implemented on the LIGO detectors. In this article, we discuss the inherent precision and accuracy of the LIGO photon calibrators and several improvements that have been developed to reduce the estimated voice coil actuator calibration uncertainties to less than 2 percent (1-sigma). These improvements include accounting for rotation-induced apparent length variations caused by interferometer and photon calibrator beam centering offsets, absolute laser power measurement using temperature-controlled InGaAs photodetectors mounted on integrating spheres and calibrated by NIST, minimizing errors induced by localized elastic deformation of the mirror surface by using a two-beam configuration with the photon calibrator beams symmetrically displaced about the center of the optic, and simultaneously actuating the test mass with voice coil actuators and the photon calibrator to minimize fluctuations caused by the changing interferometer response. The photon calibrator is able to operate in the most sensitive interferometer configuration, and is expected to become a primary calibration method for future gravitational wave searches.Comment: 13 pages, 6 figures, accepted by Classical and Quantum Gravit

Gravitational waves from Sco X-1: A comparison of search methods and prospects for detection with advanced detectors

The low-mass X-ray binary Scorpius X-1 (Sco X-1) is potentially the most luminous source of continuous gravitational-wave radiation for interferometers such as LIGO and Virgo. For low-mass X-ray binaries this radiation would be sustained by active accretion of matter from its binary companion. With the Advanced Detector Era fast approaching, work is underway to develop an array of robust tools for maximizing the science and detection potential of Sco X-1. We describe the plans and progress of a project designed to compare the numerous independent search algorithms currently available. We employ a mock-data challenge in which the search pipelines are tested for their relative proficiencies in parameter estimation, computational efficiency, robust- ness, and most importantly, search sensitivity. The mock-data challenge data contains an ensemble of 50 Scorpius X-1 (Sco X-1) type signals, simulated within a frequency band of 50-1500 Hz. Simulated detector noise was generated assuming the expected best strain sensitivity of Advanced LIGO and Advanced VIRGO ($4 \times 10^{-24}$ Hz$^{-1/2}$). A distribution of signal amplitudes was then chosen so as to allow a useful comparison of search methodologies. A factor of 2 in strain separates the quietest detected signal, at $6.8 \times 10^{-26}$ strain, from the torque-balance limit at a spin frequency of 300 Hz, although this limit could range from $1.2 \times 10^{-25}$ (25 Hz) to $2.2 \times 10^{-26}$ (750 Hz) depending on the unknown frequency of Sco X-1. With future improvements to the search algorithms and using advanced detector data, our expectations for probing below the theoretical torque-balance strain limit are optimistic.Comment: 33 pages, 11 figure

Clinical and operative predictors of outcomes of carotid endarterectomy

ObjectiveThe net benefit for patients undergoing carotid endarterectomy is critically dependent on the risk of perioperative stroke and death. Information about risk factors can aid appropriate selection of patients and inform efforts to reduce complication rates. This study identifies the clinical, radiographic, surgical, and anesthesia variables that are independent predictors of deaths and stroke following carotid endarterectomy.MethodsA retrospective cohort study of patients undergoing carotid endarterectomy in 1997 and 1998 by 64 surgeons in 6 hospitals was performed (N = 1972). Detailed information on clinical, radiographic, surgical, anesthesia, and medical management variables and deaths or strokes within 30 days of surgery were abstracted from inpatient and outpatient records. Multivariate logistic regression models identified independent clinical characteristics and operative techniques associated with risk-adjusted rates of combined death and nonfatal stroke as well as all strokes.ResultsDeath or stroke occurred in 2.28% of patients without carotid symptoms, 2.93% of those with carotid transient ischemic attacks, and 7.11% of those with strokes (P < .0001). Three clinical factors increased the risk-adjusted odds of complications: stroke as the indication for surgery (odds ratio [OR], 2.84; 95% confidence interval [CI] = 1.55-5.20), presence of active coronary artery disease (OR, 3.58; 95% CI = 1.53-8.36), and contralateral carotid stenosis ≥50% (OR, 2.32; 95% CI = 1.33-4.02). Two surgical techniques reduced the risk-adjusted odds of death or stroke: use of local anesthesia (OR, 0.30; 95% CI = 0.16-0.58) and patch closure (OR, 0.43; 95% CI = 0.24-0.76).ConclusionsInformation about these risk factors may help physicians weigh the risks and benefits of carotid endarterectomy in individual patients. Two operative techniques (use of local anesthesia and patch closure) may lower the risk of death or stroke

Methods for Reducing False Alarms in Searches for Compact Binary Coalescences in LIGO Data

The LIGO detectors are sensitive to a variety of noise transients of non-astrophysical origin. Instrumental glitches and environmental disturbances increase the false alarm rate in the searches for gravitational waves. Using times already identified when the interferometers produced data of questionable quality, or when the channels that monitor the interferometer indicated non-stationarity, we have developed techniques to safely and effectively veto false triggers from the compact binary coalescences (CBCs) search pipeline

Will He Be There?: Mediating malaria, immobilizing science

This paper focuses on an unsettling example of experimental labour – the Human Landing Catch (HLC). The HLC is a cheap and reliable technique to produce data on mosquito densities in a defined area. It requires only a human volunteer to sit over night with his legs exposed, a headlamp to spot mosquitoes, and a rubber tube and plastic cup to catch them as they come to feed on him. The HLC formed the central methodological and operational strategy for a malaria control that took place in Dar es Salaam, funded by the Bill and Melinda Gates Foundation. This paper analyses the epistemic and economic value of this experimental scenario by examining in detail the work it entails. In conceptualizing the different species of productivity associated with the HLC, of particular interest is the surprising fact that he is there. This paper argues that the interplay of mobility and immobility offers a way to rethink the value of research within interlocking circulations of capital, science, mosquitoes and men

Open Science, Closed Doors?:Countering Marginalization through an Agenda for Ethical, Inclusive Research in Communication

The open science (OS) movement has advocated for increased transparency in certain aspects of research. Communication is taking its first steps toward OS as some journals have adopted OS guidelines codified by another discipline. We find this pursuit troubling as OS prioritizes openness while insufficiently addressing essential ethical principles: respect for persons, beneficence, and justice. Some recommended open science practices increase the potential for harm for marginalized participants, communities, and researchers. We elaborate how OS can serve a marginalizing force within academia and the research community, as it overlooks the needs of marginalized scholars and excludes some forms of scholarship. We challenge the current instantiation of OS and propose a divergent agenda for the future of Communication research centered on ethical, inclusive research practices.</p