Study of bonding methods for flip chip and beam leaded devices

The results are presented of a comprehensive study and evaluation for the bonding of flip chip and beam leaded devices onto hybrid microcircuit substrates used in high reliability space applications. The program included the evaluation of aluminum flip chips, solder (silver/tin) bump chips, gold beam leaded devices, and aluminum beam leaded devices

NASA micromin computer Monthly progress letter, Jan. 1967

Microminiature circuit development for flight control computer

Comparison of quantum mechanical and classical trajectory calculations of cross sections for ion-atom impact ionization of negative - and positive -ions for heavy ion fusion applications

Stripping cross sections in nitrogen have been calculated using the classical trajectory approximation and the Born approximation of quantum mechanics for the outer shell electrons of 3.2GeV I$^{-}$ and Cs$^{+}$ ions. A large difference in cross section, up to a factor of six, calculated in quantum mechanics and classical mechanics, has been obtained. Because at such high velocities the Born approximation is well validated, the classical trajectory approach fails to correctly predict the stripping cross sections at high energies for electron orbitals with low ionization potential.Comment: submitted to Phys. Rev.

Nucleation and Growth of GaN/AlN Quantum Dots

We study the nucleation of GaN islands grown by plasma-assisted molecular-beam epitaxy on AlN(0001) in a Stranski-Krastanov mode. In particular, we assess the variation of their height and density as a function of GaN coverage. We show that the GaN growth passes four stages: initially, the growth is layer-by-layer; subsequently, two-dimensional precursor islands form, which transform into genuine three-dimensional islands. During the latter stage, island height and density increase with GaN coverage until the density saturates. During further GaN growth, the density remains constant and a bimodal height distribution appears. The variation of island height and density as a function of substrate temperature is discussed in the framework of an equilibrium model for Stranski-Krastanov growth.Comment: Submitted to PRB, 10 pages, 15 figure

Contributors to the June Issue/Notes

Notes by Henry S. Romano, William C. Malone, Joseph F. Rudd, Leonard D. Bodkin, James D. Sullivan, Robert J. Callahan, Jr., William Meehan, Alphonse Spahn, Robert E. Sullivan, John F. Power, Francis J. Paulson, John Merryman, J. Barrett Guthrie, Robert T. Fanning, Robert T. Stewart, and R. L. Miller

Contributors to the June Issue/Notes

Notes by Henry S. Romano, William C. Malone, Joseph F. Rudd, Leonard D. Bodkin, James D. Sullivan, Robert J. Callahan, Jr., William Meehan, Alphonse Spahn, Robert E. Sullivan, John F. Power, Francis J. Paulson, John Merryman, J. Barrett Guthrie, Robert T. Fanning, Robert T. Stewart, and R. L. Miller

Viking navigation

A comprehensive description of the navigation of the Viking spacecraft throughout their flight from Earth launch to Mars landing is given. The flight path design, actual inflight control, and postflight reconstruction are discussed in detail. The preflight analyses upon which the operational strategies and performance predictions were based are discussed. The inflight results are then discussed and compared with the preflight predictions and, finally, the results of any postflight analyses are presented

Declining 1-year case-fatality of stroke and increasing coverage of vascular risk management: population-based cohort study

Background The authors estimated trends in 1-year case-fatality of stroke in relation to changes in vascular risk management from 1997 to 2005.Methods A cohort study was implemented using data for 407 family practices in the UK General Practice Research Database, including subjects with first acute strokes between 1997 and 2005. One-year case-fatality was estimated by year and sex. Rate ratios were estimated using Poisson regression.Results There were 19 143 women and 16 552 men who had first acute strokes between 1997 and 2005. In women, the 1-year case-fatality declined from 41.2% in 1997 to 29.2% in 2005. In men, the decline was from 29.2% in 1997 to 22.2% in 2005. The proportion of general practices that prescribed antihypertensive drugs to two-thirds or more of new patients with stroke increased from 6% in 1997 to 48% in 2005, for statins from 1% to 39% and for antiplatelet drugs from 11% to 39%. The rate ratio for 1-year mortality in 2005, compared with 1997--1998, adjusted for age group, sex, prevalent coronary heart disease, prevalent hypertension and deprivation quintile was 0.79 (0.74 to 0.86, p<0.001). After adjustment for antihypertensive, statin and antiplatelet prescribing, the rate ratio was 1.29 (1.17 to 1.42).Conclusions Reducing 1-year case-fatality after acute stroke may be partly explained by increased prescribing of antihypertensive, statin and antiplatelet drugs to patients with recent strokes. However, these analyses did not include measures of possible changes over time in stroke severity or acute stroke management