Space Platforms for NASA -Opportunity or Pitfall?

Described are the NASA efforts to determine if platform to pool payload services are cost effective. The platform concept originated from the short shuttle life on orbit, the shuttle capability to assemble aggregating structures, and the belief that economies might be obtained from shared services and repair. About eighty payloads in NASAs future were identified for consideration. Contractor and in-house studies have produced platform configurations. Comparative cost studies are currently being done. Results have been obtained, but enthusiasm is being reserved (as of March) until sufficient review has been achieved. The platform approach has a large intuitive following; if platforms appear to be cost effective, they are likely to become a very visible part of the NASA space effort

Design of a Base-Board for arrays of closely-packed Multi-Anode Photo-Multipliers

We describe the design of a Base-Board to house Multi-Anode Photo-Multipliers for use in large-area arrays of light sensors. The goals, the design, the results of tests on the prototypes and future developments are presented.Comment: 16 pages, 5 figures, submitted to Nucl. Instrum. and Meth.

Microwave apparatus for gravitational waves observation

In this report the theoretical and experimental activities for the development of superconducting microwave cavities for the detection of gravitational waves are presented.Comment: 42 pages, 28 figure

Study of prognosis in acute myeloid leukemias (AML) by cluster analysis

BACKGROUND. Cluster analysis is particularly effective in detecting homogeneous subgroups among large series of observations. We applied this relatively uncommon approach to the study of prognosis in 137 patients affected by acute myeloid leukemia (AML). METHODS AND RESULTS. Employing simple presentation parameters (age, WBC, splenomegaly, hepatomegaly) we used cluster analysis to define 3 groups with different overall survival (p = 0.0019). This classification was obtained following a rescaling of the variables and principal component analysis. Validation was performed through random definition of a control group. With the same variables, univariate analysis demonstrated age was the only prognostic factor, while Cox's model was not significant. CONCLUSIONS. In our series cluster analysis allowed a better definition of prognosis than Cox's analysis. Since the 3 groups are well identifiable, each patient can be rapidly classified and his allocation confirmed by discriminant functions. For cluster 2 we were able to project a possible myelodysplastic evolution, while cluster 3 was more frequently associated with a monocytic blastic component. We think that cluster analysis deserves consideration as an alternative statistical approach in the analysis of large series of data; its usefulness lies in its power to define homogeneous prognostic or biologic subgroups and to elaborate further hypotheses for new studies

Radio frequency plasma processing effects on the emission characteristics of a MeV electron beam cathode

Experiments have proven that surface contaminants on the cathode of an electron beam diode influence electron emission current and impedance collapse. This letter reports on an investigation to reduce parasitic cathode current loss and to increase high voltage hold off capabilities by reactive sputter cleaning of contaminants. Experiments have characterized effective radio frequency (rf) plasma processing protocols for high voltage anode–cathode (A–K) gaps using a two-stage argon/oxygen and argon rf plasma discharge. Time-resolved optical emission spectroscopy measures contaminant (hydrogen) and bulk cathode (aluminum) plasma emission versus transported axial electron beam current turn on. Experiments were performed at accelerator parameters: V = −0.7V=−0.7 to −1.1 MV,−1.1MV, I(diode)=3–30 kA,I(diode)=3–30kA, and pulse length=0.4–1.0 μs.length=0.4–1.0μs. Experiments using a two-stage low power (100 W) argon/oxygen rf discharge followed by a higher power (200 W) pure argon rf discharge yielded an increase in cathode turn-on voltage required for axial current emission from 662±174 kV662±174kV to 981±97 kV.981±97kV. The turn-on time of axial current was increased from 100±22100±22 to 175±42 ns.175±42ns. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69353/2/APPLAB-75-1-31-1.pd