Inelasticity and partial wave dispersion relations

This thesis deals with some general work on the ND(^-1) equations and, more specifically, with two calculations which make use of them. Chapter 1 commences with a brief outline of the subject, followed by a fairly detailed analysis of numerical methods of solution of the equations, including an analysis of cut off and threshold problems. In particular we demonstrate a particular form of numerical solution which appears to be rather superior to any previous ones. Chapter 2 discusses the problems that arise when a multi-channel calculation is approximated to be a single channel one: we show that in general the results are different, and discuss the conditions for them to agree. Chapter 3 investigates what happens when N and D have simultaneous zeroes: it is shown that a potential that leads to this is necessarily singular and repulsive. Chapter 4 opens with a general review of the successes and failures of the quark model in scattering theory. It is shown that the quark model is necessarily inconsistent with what is commonly called bootstrap philosophy, and we investigate whether a reasonably convincing quark model may be constructed. Chapter 5 outlines a calculation of the πN P(_11) phase shift. The previous work on this problem is discussed, and the computational method is outlined along with a discussion of what results can be expected from the calculation

Detection of Earth-like Planets Using Apodized Telescopes

The mission of NASA's Terrestrial Planet Finder (TPF) is to find Earth-like planets orbiting other stars and characterize the atmospheres of these planets using spectroscopy. Because of the enormous brightness ratio between the star and the reflected light from the planet, techniques must be found to reduce the brightness of the star. The current favorite approach to doing this is with interferometry: interfering the light from two or more separated telescopes with a $\pi$ phase shift, nulling out the starlight. While this technique can, in principle, achieve the required dynamic range, building a space interferometer that has the necessary characteristics poses immense technical difficulties. In this paper, we suggest a much simpler approach to achieving the required dynamic range. By simply adjusting the transmissive shape of a telescope aperture, the intensity in large regions around the stellar image can be reduced nearly to zero. This approach could lead to construction of a TPF using conventional technologies, requiring space optics on a much smaller scale than the current TPF approach.Comment: Accepted for publication in ApJ Letters, 9 pages, 6 figure

Interventions to Improve Safer Sleep Practices in Families With Children Considered to Be at Increased Risk for Sudden Unexpected Death in Infancy:A Systematic Review

Background: Advice to families to follow infant care practices known to reduce the risks of Sudden Unexpected Death in Infancy (SUDI) has led to a reduction in deaths across the world. This reduction has slowed in the last decade with most deaths now occurring in families experiencing social and economic deprivation. A systematic review of the literature was commissioned by the National Child Safeguarding Practice Review Panel in England. The review covered three areas: interventions to improve engagement with support services, parental decision-making for the infant sleep environment, and interventions to improve safer sleep practices in families with infants considered to be at risk of SUDI. Aim: To describe the safer sleep interventions tested with families with infants at risk of SUDI and investigate what this literature can tell us about what works to reduce risk and embed safer sleep practices in this group. Methods: Eight online databases were systematically searched in December 2019. Intervention studies that targeted families with infants (0–1 year) at increased risk of SUDI were included. Studies were limited to those from Western Europe, North America or Australasia, published in the last 15 years. The Quality Assessment Tool for Studies with Diverse Designs was applied to assess quality. Data from included studies were extracted for narrative synthesis, including mode of delivery using Michie et al.'s Mode of Delivery Taxonomy. Results: The wider review returned 3,367 papers, with 23 intervention papers. Five types of intervention were identified: (1) infant sleep space and safer sleep education programs, (2) intensive or targeted home visiting services, (3) peer educators/ambassadors, (4) health education/raising awareness interventions, (5) targeted health education messages using digital media. Conclusion: Influencing behavior in families with infants at risk of SUDI has traditionally focused on “getting messages across,” with interventions predominantly using education and awareness raising mechanisms. This review found evidence of interventions moving from “information giving” to “information exchange” models using personalized, longer term relationship-building models. This shift may represent an improvement in how safer sleep advice is implemented in families with infants at risk, but more robust evidence of effectiveness is required. Systematic Review Registration: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/901091/DfE_Death_in_infancy_review.pdf, identifier: CRD42020165302

Book reviews

Teaching/Communication/Extension/Profession,

Experimental Investigation of Solder Joint Defect Formation and Mitigation in Reduced-Gravity Environments

This paper documents a research effort on reduced gravity soldering of plated through hole joints which was conducted jointly by the National Center for Space Exploration Research, NASA Glenn Research Center, and NASA Johnson Space Center. Significant increases in joint porosity and changes in external geometry were observed in joints produced in reduced gravity as compared to normal gravity. Multiple techniques for mitigating the observed increase in porosity were tried, including several combinations of flux and solder application techniques, and demoisturizing the circuit board prior to soldering. Results were consistent with the hypothesis that the source of the porosity is a combination of both trapped moisture in the circuit board itself, as well as vaporized flux that is trapped in the molten solder. Other topics investigated include correlation of visual inspection results with joint porosity, pore size measurements, limited pressure effects (0.08 MPa - 0.1 MPa) on the size and number of pores, and joint cooling rate

Brief report: how adolescents with ASD process social information in complex scenes. Combining evidence from eye movements and verbal descriptions

We investigated attention, encoding and processing of social aspects of complex photographic scenes. Twenty-four high-functioning adolescents (aged 11–16) with ASD and 24 typically developing matched control participants viewed and then described a series of scenes, each containing a person. Analyses of eye movements and verbal descriptions provided converging evidence that both groups displayed general interest in the person in each scene but the salience of the person was reduced for the ASD participants. Nevertheless, the verbal descriptions revealed that participants with ASD frequently processed the observed person’s emotion or mental state without prompting. They also often mentioned eye-gaze direction, and there was evidence from eye movements and verbal descriptions that gaze was followed accurately. The combination of evidence from eye movements and verbal descriptions provides a rich insight into the way stimuli are processed overall. The merits of using these methods within the same paradigm are discussed

Direct Observations of the Ionizing Star in the UC HII Region G29.96-0.02: A Strong Constraint on the Stellar Birth Line for Massive Stars

We have observed the ultracompact HII region G29.96-0.02 in the near infrared J, H, and K bands and in the Br-gamma line. By comparison with radio observations, we determine that the extinction to the nebula is AK = 2.14 with a 3 sigma uncertainty of 0.25. We identify the ionizing star and determine its intrinsic K magnitude. The star does not have an infrared excess and so appears to be no longer accreting. The K magnitude and the bolometric luminosity allow us to place limits on the location of the ionizing star in the HR diagram. The 3 sigma upper limit on the effective temperature of the ionizing star is 42500 K. We favor a luminosity appropriate for star with a mass in excess of about 60 solar masses. The limit on the temperature and luminosity exclude stars on the ZAMS and stars within 10^6 yr of the ZAMS. Since the age of the UC HII region is estimated to be only about 10^5 yr, we suggest that this is direct evidence that the stellar birth line for massive stars at twice solar metallicity must be significantly redder than the ZAMS.Comment: 42 pages; LaTex; 11 Postscript figures; accepted for publication in Ap