1,214 research outputs found
The effects of the geosynchronous energetic particle radiation environment on spacecraft charging phenomena
The energetic electron environment at the geosynchronous orbit is responsible for a variety of adverse charging effects on spacecraft components. The most serious of these is the degradation and failure of a complementary-metal-oxide-semiconductor (CMOS) electronic components as a result of internal charge-buildup induced by the energetic electrons. Efforts to accurately determine the expected lifetime of these components in this orbit are hampered by the lack of detailed knowledge of the electron spectrum and intensity, particularly of the more penetrating energies greater than 1.5 MeV. This problem is illustrated through the calculation of the dose received by a CMOS device from the energetic electrons and associated bremsstrahlung as a function of aluminum shielding thickness using the NASA AE-6 and the Aerospace measured electron environments. Two computational codes which were found to be in good agreement were used to perform the calculations. For a given shielding thickness the dose received with the two radiation environments differ by as much as a factor of seven with a corresponding variation in lifetime of the CMOS
Analysis of high resolution satellite data for cosmic gamma ray bursts
Cosmic gamma ray bursts detected a germanium spectrometer on the low altitude satellite 1972-076B were surveyed. Several bursts with durations ranging from approximately 0.032 to 15 seconds were found and are tabulated. The frequency of occurrence/intensity distribution of these events was compared with the S to the -3/2 power curve of confirmed events. The longer duration events fall above the S to the -3/2 power curve of confirmed events, suggesting they are perhaps not all true cosmic gamma-ray bursts. The narrow duration events fall closely on the S to the -3/2 power curve. The survey also revealed several counting rate spikes, with durations comparable to confirmed gamma-ray bursts, which were shown to be of magnetospheric origin. Confirmation that energetic electrons were responsible for these bursts was achieved from analysis of all data from the complete payload of gamma-ray and energetic particle detectors on board the satellite. The analyses also revealed that the narrowness of the spikes was primarily spatial rather than temporal in character
Detailed analysis of radiation data from the Gemini 4 and Gemini 7 proton-electron spectrometer experiments Final report, 13 Jun. 1967 - 30 Dec. 1968
Detailed analysis of radiation data from Gemini 4 and 7 proton-electron spectrometer experiment
Biological properties of plasmin digests of S-carbamidomethylated human growth hormone.
Government review of the Mod-2 wind turbine (as-built)
The findings and recommendations of the Government committee formed to conduct an as-built review of the three Mod-2 wind turbine units at Goldendale, Washington are given. The purpose of the review was to identify any critical deficiencies in machine components that could result in failure, and to recommend any necessary corrective action before resuming safe machine operation. The review concluded that one of the deficiencies identified would preclude planned attended or unattended operation, provided that certain corrective actions were implemented
Proton-electron spectrometer experiments on Gemini-4 and Gemini-7 Final report, 27 May 1963 - 30 Sep. 1966
Fluxes and spectra of electrons and protons in atmosphere measured by spectrometer experiments on Gemini spacecraf
Recommended from our members
Airborne sunphotometer, airborne in-situ, space-borne, and ground-based measurements of tropospheric aerosol in ACE-2
The North Atlantic Regional Aerosol Characterization
Experiment (ACE-2) of the International Global Atmospheric
Chemistry Project (IGAC) ran from 16 June to 25 July 1997.
The results presented in this study are part of the "Clear-sky
column closure experiment" (CLEARCOLUMN) activity,
one of 6 ACE-2 activities [1]. Clear-sky column closure
experiments call for characterization of aerosol layers by
simultaneous measurements using different techniques that
can be related using models [2].
A wide range of aerosol types was encountered throughout
the ACE-2 area, including background Atlantic marine,
European pollution-derived and African mineral dust. In a
series of papers, we reported on ACE-2 CLEARCOLUMN
results obtained by combining airborne sunphotometer and
in-situ measurements taken aboard the Pelican aircraft, spaceborne
NOAA/VHRR data and ground-based lidar and
sunphotometer measurements [3]-[10]. Those and other
CLEARCOLUMN results have been summarized in [11].
In this paper we only report on results not shown in this
form in [3]-[11]
Tropical Herbivorous Phasmids, but Not Litter Snails, Alter Decomposition Rates By Modifying Litter Bacteria
Consumers can alter decomposition rates through both feces and selective feeding in many ecosystems, but these combined effects have seldom been examined in tropical ecosystems. Members of the detrital food web (litter-feeders or microbivores) should presumably have greater effects on decomposition than herbivores, members of the green food web. Using litterbag experiments within a field enclosure experiment, we determined the relative effects of common litter snails (Megalomastoma croceum) and herbivorous walking sticks (Lamponius portoricensis) on litter composition, decomposition rates, and microbes in a Puerto Rican rainforest, and whether consumer effects were altered by canopy cover presence. Although canopy presence did not alter consumers’ effects, focal organisms had unexpected influences on decomposition. Decomposition was not altered by litter snails, but herbivorous walking sticks reduced leaf decomposition by about 50% through reductions in high quality litter abundance and, consequently, lower bacterial richness and abundance. This relatively unexplored but potentially important link between tropical herbivores, detritus, and litter microbes in this forest demonstrates the need to consider autotrophic influences when examining rainforest ecosystem processes
Design of Cationic Multi-Walled Carbon Nanotubes as Efficient siRNA Vectors for Lung Cancer Xenograft Eradication
Polo-Like Kinase (PLK1) has been identified as a potential target in cancer gene therapy via chemical or genetic inhibitory approaches. The biomedical applications of chemically functionalized carbon nanotubes (f-CNTs) in cancer therapy have been studied due to their ability to efficiently deliver siRNA intracellularly. In this study, we established the capacity of cationic MWNT-NH3+ to deliver the apoptotic siRNA against PLK1 (siPLK1) in Calu6 tumor xenografts by direct intratumoural injections. A direct comparison with cationic liposomes was made. This study validates the PLK1 gene as a potential target in cancer gene therapy including lung cancer, as demonstrated by the therapeutic efficacy of siPLK1:MWNT-NH3+ complexes and their ability to significantly improve animal survival. Biological analysis of the siPLK1:MWNT-NH3+ treated tumors by RT-PCR and Western blot, in addition to TUNEL staining confirmed the biological functionality of the siRNA intratumourally, suggesting that tumor eradication was due to PLK1 knockdown. Furthermore, by using a fluorescently labelled, non-coding siRNA sequence complexed with MWNT-NH3+, we established for the first time that the improved therapeutic efficacy observed in f-CNT-based siRNA delivery is directly proportional to the enhanced siRNA retention in the solid tumor and subsequent uptake by tumor cells after local administration in vivo
- …