1,531 research outputs found
MAS2-8 radar and digital control unit
The design of the MAS 2-8 (2 to 8 GHz microwave-active spectrometer), a ground-based sensor system, is presented. A major modification in 1974 to the MAS 2-8, that of a control subsystem to automate the data-taking operation, is the prime focus. The digital control unit automatically changes all system parameters except FM rate and records the return signal on paper tape. The overall system operation and a detailed discussion of the design and operation of the digital control unit are presented
Analysis and computer programs to calculate acoustic wave properties of baffled chambers
Analytical methods and four computer programs have been developed for calculating wave motion in closed, baffled chambers with rigid and non-rigid boundaries. Application of these methods to design of injector-face baffles in liquid propellant engines will provide significant insight into effects of baffles on combustion stability
Formation rates of complex organics in UV irradiated CH3OH-rich ices I: Experiments
(Abridged) Gas-phase complex organic molecules are commonly detected in the
warm inner regions of protostellar envelopes. Recent models show that
photochemistry in ices followed by desorption may explain the observed
abundances. This study aims to experimentally quantify the broad-band
UV-induced production rates of complex organics in CH3OH-rich ices at 20-70 K
under ultra-high vacuum conditions. The reaction products are mainly identified
by RAIRS and TPD experiments. Complex organics are readily formed in all
experiments, both during irradiation and during a slow warm-up of the ices to
200 K after the UV lamp is turned off. The relative abundances of photoproducts
depend on the UV fluence, the ice temperature, and whether pure CH3OH ice or
CH3OH:CH4/CO ice mixtures are used. C2H6, CH3CHO, CH3CH2OH, CH3OCH3, HCOOCH3,
HOCH2CHO and (CH2OH)2 are all detected in at least one experiment. The derived
product-formation yields and their dependences on different experimental
parameters, such as the initial ice composition, are used to estimate the CH3OH
photodissociation branching ratios in ice and the relative diffusion barriers
of the formed radicals. The experiments show that ice photochemistry in CH3OH
ices is efficient enough to explain the observed abundances of complex organics
around protostars and that ratios of complex molecules can be used to constrain
their formation pathway.Comment: Accepted for publication in A&A. 65 pages including appendice
Ultra-Low-Power Superconductor Logic
We have developed a new superconducting digital technology, Reciprocal
Quantum Logic, that uses AC power carried on a transmission line, which also
serves as a clock. Using simple experiments we have demonstrated zero static
power dissipation, thermally limited dynamic power dissipation, high clock
stability, high operating margins and low BER. These features indicate that the
technology is scalable to far more complex circuits at a significant level of
integration. On the system level, Reciprocal Quantum Logic combines the high
speed and low-power signal levels of Single-Flux- Quantum signals with the
design methodology of CMOS, including low static power dissipation, low latency
combinational logic, and efficient device count.Comment: 7 pages, 5 figure
Genetic and Physiological Responses of \u3ci\u3eBifidobacterium animalis\u3c/i\u3e subsp. \u3ci\u3elactis\u3c/i\u3e to Hydrogen Peroxide Stress
Consumer interest in probiotic bifidobacteria is increasing, but industry efforts to secure high cell viability in foods is determined by these anaerobes’ sensitivity to oxidative stress. To address this limitation, we investigated genetic and physiological responses of two fully sequenced Bifidobacterium animalis subsp. lactis strains, BL-04 and DSM 10140, to hydrogen peroxide (H2O2) stress. Although the genome sequences for these strains are highly clonal, prior work showed they differ in both intrinsic and inducible H2O2 resistance. Transcriptome analysis of early stationary phase cells exposed to a sub-lethal H2O2 concentration detected significant (P2O2 stress resistance might be due to a mutation in a BL-04 gene encoding long chain fatty acid-coA ligase. To explore this possibility, membrane fatty acids were isolated and analyzed by GC-MS. Results confirmed the strains had significantly different lipid profiles; the BL-04 membrane contained higher percentages of C14:0 and C16:0, and lower percentages of C16:1n7 and C18:1n9. Alteration of the DSM 10140 membrane lipid composition using modified growth medium to more closely mimic that of BL-04 yielded cells that showed increased intrinsic resistance to lethal H2O2 challenge, but did not display an inducible H2O2 stress response. Results show deliberate stress induction or membrane lipid modification can be employed to significantly improve H2O2 resistance in B. animalis subsp. lactis strains
USING BEM TO PREDICT THE EFFECTIVE THERMAL CONDUCTIVITY FOR HETEROGENEOUS MATERIALS
This work presents a study on the effective thermal conductivity in material with heterogeneous composition in two dimensions. The Boundary Elements Method (BEM) is used to solve the steady state potential equations. The sub regions technique was implemented in order to take into account the effects of these inclusions inside the domain. In the numerical implementation, the inclusions are randomly generated in a Representative Volume Element (RVE) domain. The Average Field Theory is used to predict the effective properties (macroscopic) of the material with heterogeneous composition. The material is characterized by a specified volume fraction as well as the inclusion’s size. The samples are composed of square domains with defined number of randomly distributed inclusions and submitted to a condition of unidirectional heat conduction. Each set of samples is analyzed several times in order to guarantee statistical stability of the result
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