Evaluation of the ALMA Prototype Antennas

The ALMA North American and European prototype antennas have been evaluated by a variety of measurement systems to quantify the major performance specifications. Nearfield holography was used to set the reflector surfaces to 17 microns RMS. Pointing and fast switching performance was determined with an optical telescope and by millimeter wavelength radiometry, yielding 2 arcsec absolute and 0.6 arcsec offset pointing accuracies. Path length stability was measured to be less than or approximately equal to 20 microns over 10 minute time periods using optical measurement devices. Dynamical performance was studied with a set of accelerometers, providing data on wind induced tracking errors and structural deformation. Considering all measurements made during this evaluation, both prototype antennas meet the major ALMA antenna performance specifications.Comment: 83 pages, 36 figures, AASTex format, to appear in PASP September 2006 issu

Langley's CSI evolutionary model: Phase O

A testbed for the development of Controls Structures Interaction (CSI) technology to improve space science platform pointing is described. The evolutionary nature of the testbed will permit the study of global line-of-sight pointing in phases 0 and 1, whereas, multipayload pointing systems will be studied beginning with phase 2. The design, capabilities, and typical dynamic behavior of the phase 0 version of the CSI evolutionary model (CEM) is documented for investigator both internal and external to NASA. The model description includes line-of-sight pointing measurement, testbed structure, actuators, sensors, and real time computers, as well as finite element and state space models of major components

Automated Generation of User Guidance by Combining Computation and Deduction

Herewith, a fairly old concept is published for the first time and named "Lucas Interpretation". This has been implemented in a prototype, which has been proved useful in educational practice and has gained academic relevance with an emerging generation of educational mathematics assistants (EMA) based on Computer Theorem Proving (CTP). Automated Theorem Proving (ATP), i.e. deduction, is the most reliable technology used to check user input. However ATP is inherently weak in automatically generating solutions for arbitrary problems in applied mathematics. This weakness is crucial for EMAs: when ATP checks user input as incorrect and the learner gets stuck then the system should be able to suggest possible next steps. The key idea of Lucas Interpretation is to compute the steps of a calculation following a program written in a novel CTP-based programming language, i.e. computation provides the next steps. User guidance is generated by combining deduction and computation: the latter is performed by a specific language interpreter, which works like a debugger and hands over control to the learner at breakpoints, i.e. tactics generating the steps of calculation. The interpreter also builds up logical contexts providing ATP with the data required for checking user input, thus combining computation and deduction. The paper describes the concepts underlying Lucas Interpretation so that open questions can adequately be addressed, and prerequisites for further work are provided.Comment: In Proceedings THedu'11, arXiv:1202.453

Status Processes and Mental Ability Test Scores

The expected consequences of a score on an ability test can constrain individual performance. The authors predict that status processes, including status differences and the differences in rewards and costs that result, will produce differences in ability test scores between high-status and low-status individuals. In three controlled experi- ments, participants randomly assigned low status scored lower on a standard test of mental ability (the Raven Progressive Matrices) than did participants assigned high status. For both men and women, the difference in ability test score between low-status and high-status participants was about half a standard deviation. The results suggest the need to account for status differences in any at- tempt to measure mental ability accuratel

Exhaled nitric oxide: a marker of pulmonary hemodynamics in heart failure

AbstractObjectivesWe sought to test the hypothesis that patients with decompensated heart failure (HF) lose a compensatory process whereby nitric oxide (NO) maintains pulmonary vascular tone.BackgroundExhaled nitric oxide (eNO) partially reflects vascular endothelial NO release. Levels of eNO are elevated in patients with compensated HF and correlate inversely with pulmonary artery pressures (PAP), reflecting pulmonary vasodilatory activity.MethodsWe measured the mean mixed expired NO content of a vital-capacity breath using chemiluminescence in patients with compensated HF (n = 30), decompensated HF (n = 7) and in normal control subjects (n = 90). Pulmonary artery pressures were also measured in patients with HF. The eNO and PAP were determined sequentially during therapy with intravenous vasodilators in patients with decompensated HF (n = 7) and in an additional group of patients with HF (n = 13) before and during administration of milrinone.ResultsThe eNO was higher in patients with HF than in control subjects (9.9 ± 1.1 ppb vs. 6.2 ± 0.4 ppb, p = 0.002) and inversely correlated with PAP (r = −0.81, p < 0.00001). In marked contrast, patients with decompensated HF exhibited even higher levels of eNO (20.4 ± 6.2 ppb) and PAP, but there was a loss of the inverse relationship between these two variables. During therapy (7.3 ± 6 days) with sodium nitroprusside and diuresis, hemodynamics improved, eNO concentrations fell (11.2 ± 1.2 ppb vs. before treatment, p < 0.05), and the relationship between eNO and PAP was restored. After milrinone, eNO rose proportionally with decreased PAP (p < 0.05).ConclusionsElevated eNO may reflect a compensatory circulatory mechanism in HF that is lost in patients with clinically decompensated HF. The eNO may be an easily obtainable and quantifiable measure of the response to therapy in advanced HF

A 15.65 solar mass black hole in an eclipsing binary in the nearby spiral galaxy Messier 33

Stellar-mass black holes are discovered in X-ray emitting binary systems, where their mass can be determined from the dynamics of their companion stars. Models of stellar evolution have difficulty producing black holes in close binaries with masses >10 solar masses, which is consistent with the fact that the most massive stellar black holes known so all have masses within 1 sigma of 10 solar masses. Here we report a mass of 15.65 +/- 1.45 solar masses for the black hole in the recently discovered system M33 X-7, which is located in the nearby galaxy Messier 33 (M33) and is the only known black hole that is in an eclipsing binary. In order to produce such a massive black hole, the progenitor star must have retained much of its outer envelope until after helium fusion in the core was completed. On the other hand, in order for the black hole to be in its present 3.45 day orbit about its 70.0 +/- 6.9 solar mass companion, there must have been a ``common envelope'' phase of evolution in which a significant amount of mass was lost from the system. We find the common envelope phase could not have occured in M33 X-7 unless the amount of mass lost from the progenitor during its evolution was an order of magnitude less than what is usually assumed in evolutionary models of massive stars.Comment: To appear in Nature October 18, 2007. Four figures (one color figure degraded). Differs slightly from published version. Supplementary Information follows in a separate postin