Abstract only
6562
Background: Trial closure due to inadequate accrual presents a common problem in cancer research. We sought to identify factors related to trial design common to trials with ...successful versus unsuccessful accrual. Methods: In 2008, a 30-question web-based survey was sent to the study chair (SC) and lead statistician (LS) for all 248 phase III trials open in 1993–2002 by five national cooperative groups (NCG). SC and LS level of experience, trial design elements, accrual predictions, and perceived accrual influences were queried. Accrual success was categorized based on NCG records: successful trials (ST) closed with complete accrual or at interim analysis while unsuccessful trials (UT) closed due to inadequate accrual. Responses were analyzed by respondent role (SC/LS) and accrual success. Results: 309 eligible responses were included (response rate, 62%: LS 81%, SC 45%). Respondents represented ST (65%) and UT (35%) with no response bias by accrual success. SC academic rank was not linked to accrual success. Literature review, SC experience, and expert opinion within NCG most commonly influenced control arm selection, but did not impact accrual success. NCG experience had the greatest influence on accrual predictions in both ST and UT. Trials comparing novel with established therapies were more likely to be ST (72%) than UT (28%); head-to-head comparisons of established therapies were more equally divided between ST (59%) and UT (41%). Among the 41% of respondents citing significant accrual difficulties, no factors negatively influencing accrual were consistently identified. Among respondents not citing accrual difficulties, factors credited with positively influencing accrual were clinical relevance of study question, lack of competing trials, and protocol paralleling normal practice. Conclusions: No consistent factors were identified to explain poor trial accrual, suggesting that reasons for poor accrual are not well understood and warrant further study. An objective measure of clinical relevance would be useful to inform trial prioritization practices. Research into alternative strategies for accrual prediction is needed since NCG experience is linked to both successful and unsuccessful accrual.
Table: see text
We present results from crystal spectroscopic analysis of silicon aero-gel foams heated by dynamic hohlraums on Z. The dynamic hohlraum on Z creates a radiation source with a 230-eV average ...temperature over a 2.4-mm diameter. In these experiments silicon aero-gel foams with
10
-
mg
/
cm
3
densities and 1.7-mm lengths were placed on both ends of the dynamic hohlraum. Several crystal spectrometers were placed both above and below the z-pinch to diagnose the temperature of the silicon aero-gel foam using the K-shell lines of silicon. The crystal spectrometers were (1) temporally integrated and spatially resolved, (2) temporally resolved and spatially integrated, and (3) both temporally and spatially resolved. The results indicate that the dynamic hohlraum heats the silicon aero-gel to approximately 150-eV at peak power. As the dynamic hohlraum source cools after peak power the silicon aero-gel continues to heat and jets axially at an average velocity of approximately
50
-
cm
/
μ
s
. The spectroscopy has also shown that the reason for the up/down asymmetry in radiated power on Z is that tungsten enters the line-of-sight on the bottom of the machine much more than on the top.
— Weathering effects on meteorite finds from the Acfer region were studied by various analytical techniques and in dependence on the depth of sampling. In thin sections of weathered meteorites, ...weathering effects usually decrease from the outside to the interior of the meteorite. The results of evolved gas analysis indicate that variation in weathering between surface and core is not significant in respect to the formation of Fe‐oxyhydroxides. The secondary alteration effects in the noble gases are distributed unevenly throughout the specimens, as seen in the nonsystematic differences observed for the heavy noble gases. Chemical analyses show significant enrichment of Ba and Sr in the outer parts of the weathered samples due to element contamination through aqueous solution. Iron, Ni, and Co are partly flushed from the system as the metal oxidation proceeds. Oxygen isotopes show increases in δ18O and δ17O with increasing terrestrial age. For a set of H3 chondrites, the degree of weathering determined from the water content was correlated with terrestrial ages and is discussed with respect to possible weathering mechanisms.
The "Target Fabrication Facility" (TFF) of an IFE power plant must supply about 500,000 targets per day. The targets are injected into the target chamber at a rate of 5-10 Hz and tracked precisely so ...the driver beams can be directed to the target. The feasibility of developing successful fabrication and injection methodologies at the low cost required for energy production (about $0.25/target, about 10
4
less than current costs) is a critical issue for inertial fusion. To help identify major cost factors and technology development needs, we have utilized a classic chemical engineering approach to the TFF. The analyses assume an "nth-of-a-kind" TFF and utilize standard industrial engineering cost factors. The results indicate that the direct drive target can be produced for about $0.16 each. Iterations are still underway for the indirect drive target. These cost analyses assume that the process development is accomplished to allow scaling of current laboratory methods to larger sizes, while still meeting target specifications. A development program is underway at various laboratories to support this scale-up.
Hot dense capsule implosions driven by z-pinch x-rays have been measured for
the first time. A ~220 eV dynamic hohlraum imploded 1.7-2.1 mm diameter
gas-filled CH capsules which absorbed up to ~20 kJ ...of x-rays. Argon tracer atom
spectra were used to measure the Te~ 1keV electron temperature and the ne ~ 1-4
x10^23 cm-3 electron density. Spectra from multiple directions provide core
symmetry estimates. Computer simulations agree well with the peak compression
values of Te, ne, and symmetry, indicating reasonable understanding of the
hohlraum and implosion physics.
Hot dense capsule implosions driven by z-pinch x-rays have been measured for the first time. A ~220 eV dynamic hohlraum imploded 1.7-2.1 mm diameter gas-filled CH capsules which absorbed up to ~20 kJ ...of x-rays. Argon tracer atom spectra were used to measure the Te~ 1keV electron temperature and the ne ~ 1-4 x10^23 cm-3 electron density. Spectra from multiple directions provide core symmetry estimates. Computer simulations agree well with the peak compression values of Te, ne, and symmetry, indicating reasonable understanding of the hohlraum and implosion physics.
Summary form only given. In Z-pinch experiments on the Z accelerator, we are evaluating the feasibility of using a radiation-driven vacuum secondary hohlraum for indirect-drive ICF. To develop a ...system with the potential to scale to ignition and high yield, we must demonstrate a high degree of radiation flux symmetry at the capsule position. In initial experiments with single-sided illumination of the secondary, we have used a 5.0-mm-diameter low density foam ball imaged by a gated X-ray framing pinhole camera looking through a 6.5-mm tamped aperture to diagnose the large time-dependent asymmetry in polar radiation flux. For peak hohlraum radiation temperatures in the range of 70 100 eV, foams of about 50 mg/cc will support a transonic radiation front propagating with a sharp total transmission edge (combined foam self-emission and transmitted hohlraum wall backlight). The transmission edge can be tracked for comparison with radiation-hydrodynamics and 3D radiosity simulations.
Multichip assembly with flipped integrated circuits Heinen, K.G.; Schroen, W.H.; Edwards, D.R. ...
IEEE transactions on components, hybrids, and manufacturing technology,
12/1989, Letnik:
12, Številka:
4
Journal Article, Conference Proceeding
A multichip module process has been developed using flipped-chip interconnection. The process uses plated copper bumps for superior thermal transport characteristics, active silicon as a substrate ...material for matched expansion properties, on-chip interconnection metallization that allows bumps to be placed over the active circuitry, and conventional wafer fabrication facilities for low-cost production. For successful design and fabrication of multichip assemblies, an organized methodology similar to that which has proved successful in design and assembly of single VLSI circuits was used. This approach involves: computer-aided modeling of the circuit and package for electrical, thermal, and mechanical simulation; test chips for process development and failure mechanism testing; and fabrication of actual demonstration circuits. Verification of function and reliability was then made through temperature cycle testing (-65 degrees C to 150 degrees C), exposure to accelerated moisture environments, and measure of heat dissipation properties. This approach and an example of its application to a multichip module that demonstrated successful performance on the first design pass are described.< >
PDF
