39 research outputs found
Using Ozone To Clean and Passivate Oxygen-Handling Hardware
A proposed method of cleaning, passivating, and verifying the cleanliness of oxygen-handling hardware would extend the established art of cleaning by use of ozone. As used here, "cleaning" signifies ridding all exposed surfaces of combustible (in particular, carbon-based) contaminants. The method calls for exposing the surfaces of the hardware to ozone while monitoring the ozone effluent for carbon dioxide. The ozone would passivate the hardware while oxidizing carbon-based residues, converting the carbon in them to carbon dioxide. The exposure to ozone would be continued until no more carbon dioxide was detected, signifying that cleaning and passivation were complete
Elastic-Tether Suits for Artificial Gravity and Exercise
Body suits harnessed to systems of elastic tethers have been proposed as means of approximating the effects of normal Earth gravitation on crewmembers of spacecraft in flight to help preserve the crewmembers physical fitness. The suits could also be used on Earth to increase effective gravitational loads for purposes of athletic training. The suit according to the proposal would include numerous small tether-attachment fixtures distributed over its outer surface so as to distribute the artificial gravitational force as nearly evenly as possible over the wearer s body. Elastic tethers would be connected between these fixtures and a single attachment fixture on a main elastic tether that would be anchored to a fixture on or under a floor. This fixture might include multiple pulleys to make the effective length of the main tether great enough that normal motions of the wearer cause no more than acceptably small variations in the total artificial gravitational force. Among the problems in designing the suit would be equalizing the load in the shoulder area and keeping tethers out of the way below the knees to prevent tripping. The solution would likely include running tethers through rings on the sides. Body suits with a weight or water ballast system are also proposed for very slight spinning space-station scenarios, in which cases the proposed body suits will easily be able to provide the equivalency of a 1-G or even greater load
Evaluation of Solvent Alternatives for Cleaning of Oxygen Systems
The NASA White Sands Test Facility (WSTF) in a joint program with the Naval Sea Systems Command has evaluated a number of solvents as alternatives to the use of chlorofluorocarbons currently utilized for cleaning of oxygen systems. Particular attention has been given to the cleaning of gauges and instrumentation used in oxygen service, since there have been no identified aqueous alternatives. The requirements identified as selection criteria, include toxicity, physical properties consistent with application, flammability, oxygen compatibility, and cleaning ability. This paper provides a summary of results and recommendations for solvents evaluated to date
Aqueous Cleaning and Validation for Space Shuttle Propulsion Hardware at the White Sands Test Facility
The NASA White Sands Test Facility (WSTF) has developed an entirely aqueous final cleaning and verification process to replace the current chlorofluorocarbon (CFC) 113 based process. This process has been accepted for final cleaning and cleanliness verification of WSTF ground support equipment. The aqueous process relies on ultrapure water at 50 C (323 K) and ultrasonic agitation for removal of organic compounds and particulate. The cleanliness is verified bv determining the total organic carbon (TOC) content and filtration with particulate counting. The effectiveness of the aqueous methods for detecting hydrocarbon contamination and particulate was compared to the accepted CFC 113 sampling procedures. Testing with known contaminants, such as hydraulic fluid and cutting and lubricating oils, to establish a correlation between aqueous TOC and CFC 113 nonvolatile residue (NVR) was performed. Particulate sampling on cleaned batches of hardware that were randomly separated and sampled by the two methods was performed. This paper presents the approach and results, and discusses the issues in establishing the equivalence of aqueous sampling to CFC 113 sampling, while describing the approach for implementing aqueous techniques on Space Shuttle Propulsion hardware
Structure and Magnetism of the Rh4+-containing perovskite oxides La0.5Sr0.5Mn0.5Rh0.5O3 and La0.5Sr0.5Fe0.5Rh0.5O3
Synchrotron X-ray powder diffraction data indicate that La0.5Sr0.5Mn0.5Rh0.5O3 and La0.5Sr0.5Fe0.5Rh0.5O3 adopt distorted perovskite structures (space group Pnma) with A-site and B-site cation disorder. A combination of XPS and 57Fe Mössbauer data indicate the transition metal cations in the two phases adopt Mn3+/Rh4+ and Fe3+/Rh4+ oxidation state combinations respectively. Transport data indicate both phases are insulating, with ρ vs. T dependences consistent with 3D variable-range hopping. Magnetisation data reveal that La0.5Sr0.5Mn0.5Rh0.5O3 adopts a ferromagnetic state below Tc ∼ 60 K, which is rationalized on the basis of coupling via a dynamic Jahn–Teller distortion mechanism. In contrast, magnetic data reveal La0.5Sr0.5Fe0.5Rh0.5O3 undergoes a transition to a spin-glass state at T ∼ 45 K, attributed to frustration between nearest-neighbour Fe–Rh and next-nearest-neighbour Fe–Fe couplings
Continuous Hydrothermal Decarboxylation of Fatty Acids and Their Derivatives into Liquid Hydrocarbons Using Mo/Al2O3 Catalyst
Continuous Hydrothermal Decarboxylation of Fatty Acids and Their Derivatives into Liquid Hydrocarbons Using Mo/Al<sub>2</sub>O<sub>3</sub> Catalyst
In
this study, we report a single-step continuous production of
straight-chain liquid hydrocarbons from oleic acid and other fatty
acid derivatives of interest including castor oil, frying oil, and
palm oil using Mo, MgO, and Ni on Al<sub>2</sub>O<sub>3</sub> as catalysts
in subcritical water. Straight-chain hydrocarbons were obtained via
decarboxylation and hydrogenation reactions with no added hydrogen.
Mo/Al<sub>2</sub>O<sub>3</sub> catalyst was found to exhibit a higher
degree of decarboxylation (92%) and liquid yield (71%) compared to
the other two examined catalysts (MgO/Al<sub>2</sub>O<sub>3</sub>,
Ni/Al<sub>2</sub>O<sub>3</sub>) at the maximized conditions of 375
°C, 4 h of space time, and a volume ratio of 5:1 of water to
oleic acid. The obtained liquid product has a similar density (0.85
kg/m<sup>3</sup> at 15.6 °C) and high heating value (44.7 MJ/kg)
as commercial fuels including kerosene (0.78–0.82 kg/m<sup>3</sup> and 46.2 MJ/kg), jet fuel (0.78–0.84 kg/m<sup>3</sup> and 43.5 MJ/kg), and diesel fuel (0.80–0.96 kg/m<sup>3</sup> and 44.8 MJ/kg). The reaction conditions including temperature,
volume ratio of water-to-feed, and space time were maximized for the
Mo/Al<sub>2</sub>O<sub>3</sub> catalyst. Characterization of the spent
catalysts showed that a significant amount of amorphous carbon deposited
on the catalyst could be removed by simple carbon burning in air with
the catalyst recycled and reused
Diagnostic criteria for somatosensory tinnitus:A delphi process and face-to-face meeting to establish consensus
Since somatic or somatosensory tinnitus (ST) was first described as a subtype of subjective tinnitus, where altered somatosensory afference from the cervical spine or temporomandibular area causes or changes a patient's tinnitus perception, several studies in humans and animals have provided a neurophysiological explanation for this type of tinnitus. Due to a lack of unambiguous clinical tests, many authors and clinicians use their own criteria for diagnosing ST. This resulted in large differences in prevalence figures in different studies and limits the comparison of clinical trials on ST treatment. This study aimed to reach an international consensus on diagnostic criteria for ST among experts, scientists and clinicians using a Delphi survey and face-to-face consensus meeting strategy. Following recommended procedures to gain expert consensus, a two-round Delphi survey was delivered online, followed by an in-person consensus meeting. Experts agreed upon a set of criteria that strongly suggest ST. These criteria comprise items on somatosensory modulation, specific tinnitus characteristics, and symptoms that can accompany the tinnitus. None of these criteria have to be present in every single patient with ST, but in case they are present, they strongly suggest the presence of ST. Because of the international nature of the survey, we expect these criteria to gain wide acceptance in the research field and to serve as a guideline for clinicians across all disciplines. Criteria developed in this consensus paper should now allow further investigation of the extent of somatosensory influence in individual tinnitus patients and tinnitus populations.publishersversionpublishe