X-ray spectroscopy of the SSME plume

In order to examine the potential of using SSME exhaust plume radiation in the soft X-ray spectrum as an early warning system of imminent engine failure, a low cost, low risk experiment was devised. An approach was established, equipment was leased, the system was installed and checked out, and data were successfully acquired demonstrating the proof-of-concept. One spectrum measurement of the SSME plume was acquired during a 300 second burn on the A-1 Test Stand. This spectrum showed a prominent, line emission feature at about 34.5 KeV, a result which was not expected, nor can it be explained at this time. If X-ray spectra are to be useful as a means of monitoring nominal engine operation, it will be necessary to explore this region of the EM spectrum in greater detail. The presence of structure in the spectrum indicates that this technology may prove to be useful as an engine health monitoring system

The construction and validation of an instrument to measure classroom adjustment.

Thesis (Ed.D.)--Boston University.I. Problem: To construct a measure of classroom adjustment which would be easily administered and interpreted by the classroom teacher. II. Procedure: A. Two measures were developed; an 86 item Teacher Checklist and a 40 item Parent Rating Scale. 1. Classroom teachers were asked to submit situations which would give evidence of good classroom adjustment. Ten trait categories were established as follows: concentration, cooperation, courtesy, emotional stability, friendliness, health, initiative, responsib- ility, self-confidence and self-reliance. A list of 86 items, to check the child's performance in these trait areas was complied. i.e. "He is wiilling to lead Opening Exercises (initiative)." Any item which could not be objectively observed was discarded. For ease of checking, the 86 items were so arranged as to follow the routine of a normal classroom day. Each child was rated twice on the Checklist. In 12 classrooms, (299 children) the child was rated by his own teacher first, then by a second person. In 4 classrooms (101 children) the child's teacher did both ratings with a lapse of 4 weeks between the two. 2. The Parent Rating Scale again attempted to get evidence on the same ten traits. i.e. "He can shop by himself (Initiative)." The parents were asked to check each item as "Usually, Often or Occasionally." B. Four hundred first grade children who participated in the study were administered the following tests: 1. Otis Quick Scoring J.iental Ability Test. 2. The Teacher Checklist of Adjustment. 3. The Parent Rating Scale was filled out by parents of the children. 4. The Detroit Word Recognition Test and the Boston University Reading Tests were used to measure reading achievement. III. Major Findings and Conclusions: A. Teachers and parents found both measures were easily administered. B. Reliability was established as follows: 1. For the Teacher Checklist a. Correlation between 2 raters was .73. b. Correlation on same rater twice was .97. c. Split half reliability for whole test corrected by Spearman Brown Formula was .96. d. Item analysis revealed significant differences for 81 out of 86 items for high and low scorers. 2. For the Parent Rating Scale· a. Split half correlation on whole.test, corrected by Spearman Brown Formula, was .70. b. Item analysis revealed significant differences on 24 of the 40 items. c. The Parent Rating Scale did not correlate significantly with the Teacher Checklist (.16). C. Relation of Adjustment to Reading Achievement 1. Positive Correlations of .48 and ·57 were found between adjustment and reading achievement. 2. Children were divided on the basis of adjustment scores into three groups--high, middle and low. a. The means of these three groups on the Detroit Word Recognition Test were 25.76, 19.00 and 13.80, respectively. Means on the Boston University Test were 88.3, 52.0 and 40.5, respectively. The differenees in achievement were statistically significant between high and middle as well as between middle and low groups. b. The mean mental age for the high group was 90.5 months, for the middle 82.5 and for the low 80.0. c. The difference in mental age between the high and the middle group was very significant but the difference between the middle and low groups was not significant. d. The mean IQ's were 118, 107 and 105 for high, middle and low groups, respectively. The difference between the high and middle groups was statistically significant but this was not true between the middle and low groups

On the high coherence of kilo-Hz Quasi-Periodic Oscillations

We have carried out a systematic study of the properties of the kilo-Hertz quasi-periodic oscillations (QPO) observed in the X-ray emission of the neutron star low-mass X-ray binary 4U1608-52, using archival data obtained with the Rossi X-ray Timing Explorer. We have investigated the quality factor, Q, of the oscillations (defined as the ratio of the frequency of the QPO peak to its full width at half maximum). In order to minimise the effect of long-term frequency drifts, power spectra were computed over the shortest times permitted by the data statistics. We show that the high Q of ~200 reported by Berger et al. (1996) for the lower frequency kilo-Hz QPO in one of their observations is by no means exceptional, as we observe a mean Q value in excess of 150 in 14 out of the 21 observations analysed and Q can remain above 200 for thousands of seconds. The frequency of the QPO varies over the wide range 560--890 Hz and we find a systematic trend for the coherence time of the QPO, estimated as tau=Q /(pi nu), to increase with the frequency, up to a maximum level at ~ 800 Hz, beyond which it appears to decrease, at frequencies where the QPO weakens. There is a more complex relationship between tau and the QPO root mean squared amplitude (RMS), in which positive and negative correlations can be found. A higher-frequency QPO, revealed by correcting for the frequency drift of the 560-890 Hz one, has a much lower Q (~10) which does not follow the same pattern. We discuss these results in the framework of competing QPO models and show that those involving clumps orbiting within or above the accretion disk are ruled out.Comment: Accepted for publication in MNRAS, 8 pages, 6 figures, 3 Table

Resonant Destruction as a Possible Solution to the Cosmological Lithium Problem

We explore a nuclear physics resolution to the discrepancy between the predicted standard big-bang nucleosynthesis (BBN) abundance of 7Li and its observational determination in metal-poor stars. The theoretical 7Li abundance is 3-4 times greater than the observational values, assuming the baryon-to-photon ratio, eta_wmap, determined by WMAP. The 7Li problem could be resolved within the standard BBN picture if additional destruction of A=7 isotopes occurs due to new nuclear reaction channels or upward corrections to existing channels. This could be achieved via missed resonant nuclear reactions, which is the possibility we consider here. We find some potential candidate resonances which can solve the lithium problem and specify their required resonant energies and widths. For example, a 1^- or 2^- excited state of 10C sitting at approximately 15.0 MeV above its ground state with an effective width of order 10 keV could resolve the 7Li problem; the existence of this excited state needs experimental verification. Other examples using known states include 7Be+t \rightarrow 10B(18.80 MeV), and 7Be+d \rightarrow 9B(16.71 MeV). For all of these states, a large channel radius (a > 10 fm) is needed to give sufficiently large widths. Experimental determination of these reaction strengths is needed to rule out or confirm these nuclear physics solutions to the lithium problem.Comment: 37 pages, 9 figures. Additional discussion of channel widths and radii. Matches published versio

Simultaneous BeppoSAX and Rossi X-ray Timing Explorer observations of 4U1812-12

4U1812-12 is a faint persistent and weakly variable neutron star X-ray binary. It was observed by BeppoSAX between April 20th and 21st, 2000 in a hard spectral state with a bolometric luminosity of ~2x10^36 ergs/s. Its broad band energy spectrum is characterized by the presence of a hard X-ray tail extending above ~100 keV. It can be represented as the sum of a dominant hard Comptonized component (electron temperature of ~36 keV and optical depth ~3) and a weak soft component. The latter component which can be fitted with a blackbody of about 0.6 keV and equivalent radius of ~2 km is likely to originate from the neutron star surface. We also report on the first measurement of the power density spectrum of the source rapid X-ray variability, as recorded during a simultaneous snapshot observation performed by the Rossi X-ray Timing Explorer. As expected for a neutron star system in such hard spectral state, its power density spectrum is characterized by the presence of a ~0.7 Hz low frequency quasi-periodic oscillation together with three broad noise components, one of which extends above ~200 Hz.Comment: 6 pages, 3 figures, accepted for publication in A&

Comparative US-MRI evaluation of the Insall–Salvati index

Purpose: To investigate whether the universally accepted range of normal patellar height ratio derived from MRI for the Insall–Salvati (IS) method could be similarly applied to ultrasound (US). Materials and methods: This study included 52 patients (age range 11–75 years) who underwent a bi-modality (US and MRI) examination, with a total of 60 knees evaluated. IS index (ratio of the patella tendon length to length of the patella) was acquired with both methods. Two operators, with different experiences of musculoskeletal imaging and blinded to the results of other investigators, separately performed the MRI and US measurements. Results: For the two operators, MRI reported a mean value of patellar height ratio of 1.10 ± 0.16 (mean ± standard deviation SD), while US a mean value of 1.17 ± 0.16 (mean ± SD). For comparable results, the small addition of 0.16 is needed for the measurements on US compared with MRI. Inter-observer agreements using intra-class correlation coefficient (ICC) was, respectively, 0.97 for MRI and 0.98 for US. The difference of mean values in patellar height ratios between MRI and US was not statistically significant (p = 0.15). The ICC between the two modalities was 0.94. Conclusion: According to our experience, IS index can be appropriately evaluated on US images, reducing the need of other imaging techniques