Determination of lethality rate constants and D-values for heat-resistant Bacillus spores ATCC 29669 exposed to dry heat from 125°C to 200°C

Exposing flight hardware to dry heat is a NASA-approved sterilization method for reducing microbial bioburden on spacecraft. The existing NASA specification only allows heating the flight hardware between 104°C and 125°C to reduce the number of viable microbes and bacterial spores. Also, the NASA specifications only allow a four log reduction by dry heat microbial reduction because very heat-resistant spores are presumed to exist in a diverse population (0.1%). The goal of this research was to obtain data at higher temperatures than 125°C for one of the most heat-resistant microorganisms discovered in a spacecraft assembly area. These data support expanding the NASA specifications to temperatures higher than 125°C and relaxing the four log reduction specification. Small stainless steel vessels with spores of the Bacillus strain ATCC 29669 were exposed to constant temperatures between 125°C and 200°C under both dry and ambient room humidity for set time durations. After exposures, the thermal spore exposure vessels were cooled and the remaining spores recovered and plated out. Survivor ratios, lethality rate constants, and D-values were determined at each temperature. The D-values for the spores exposed under dry humidity conditions were always found to be shorter than those under ambient humidity. The temperature dependence of the lethality rate constants was obtained by assuming that they obeyed Arrhenius behavior. The results are compared to those of B. atrophaeus ATCC 9372. In all cases, the D-values of ATCC 29669 are between 20 and 50 times longer than those of B. atrophaeus ATCC 9372.     

等离子喷涂纳米陶瓷热障涂层组织与性能

采用纳米陶瓷粒子团聚体粉末等离子喷涂制备纳米陶瓷热障涂层,研究了纳米陶瓷热障涂层的组织和性能.试验表明,采用纳米结构的陶瓷涂层有利于增加热障涂层的高温使用寿命.     

积极主动的发动机维修

运营商越来越多地发现发动机预防性维修的长期价值. 要使航空公司能够对发动机维修变得更为积极主动,说起来容易做起来难,即使航空运输回暖和航空公司收入增加的情况下也是这样.     

Controlling Adaptive Antenna Arrays with the Sample Matrix Inversion Algorithm

Considerations are given leading to the selection of the samplematrix inversion algorithm for the control of an airborne narrowbandand adaptive receiving array for use in omnidirecti com communications. Performance is measured for a laboratory nulling system which implements this design concept. This performance ance is compared with predictions based on the component tolerances of the laboratory system.     

Aerospace Capability and Systems Analysis Applied to Urban Problems?Some Views from a Social Scientist

Much has been written about the development of a general systems theory for application to civil problems, but very little documentation exists in the sense of case studies of large-scale programs implemented using the systems approach. The Model Urban Neighborhood Demonstration Program, operating in an inner-city poverty neighborhood in Baltimore, offers some lessons in this regard. With the present state of the art, the techniques of systems analysis are most effective at the subsystem level, and the necessary funding and development time should be afforded to extend their usefulness in the civil order. Existing aerospace companies provide an operating institutional base, with extenasive resources, that can be beneficially translated to solving problems in the public order.     

The Galileo Plasma wave investigation

The purpose of the Galileo plasma wave investigation is to study plasma waves and radio emissions in the magnetosphere of Jupiter. The plasma wave instrument uses an electric dipole antenna to detect electric fields, and two search coil magnetic antennas to detect magnetic fields. The frequency range covered is 5 Hz to 5.6 MHz for electric fields and 5 Hz to 160 kHz for magnetic fields. Low time-resolution survey spectrums are provided by three on-board spectrum analyzers. In the normal mode of operation the frequency resolution is about 10%, and the time resolution for a complete set of electric and magnetic field measurements is 37.33 s. High time-resolution spectrums are provided by a wideband receiver. The wideband receiver provides waveform measurements over bandwidths of 1, 10, and 80 kHz. These measurements can be either transmitted to the ground in real time, or stored on the spacecraft tape recorder. On the ground the waveforms are Fourier transformed and displayed as frequency-time spectrogams. Compared to previous measurements at Jupiter this instrument has several new capabilities. These new capabilities include (1) both electric and magnetic field measurements to distinguish electrostatic and electromagnetic waves, (2) direction finding measurements to determine source locations, and (3) increased bandwidth for the wideband measurements.Deceased     

Mars Global MHD Predictions of Magnetic Connectivity Between the Dayside Ionosphere and the Magnetospheric Flanks

Atmospheric photoelectrons have been observed well above the ionosphere of Mars by the ASPERA-3 ELS instrument on Mars Express. To systematically interpret these observations, field lines from two global MHD simulations were analyzed for connectivity to the dayside ionosphere (allowing photoelectron escape). It is found that there is a hollow cylinder behind the planet from 1–2 R _M away from the Mars-Sun line that has a high probability of containing magnetic field lines with connectivity to the dayside ionosphere. These results are in complete agreement with the ELS statistics. It is concluded that the high-altitude photoelectrons are the result of direct magnetic connectivity to the dayside at the moment of the measurement, and no extra trapping or bouncing mechanisms are needed to explain the data.