VIEWING LEED PATTERNS AS ELECTRON HOLOGRAMS

It is shown theoretically that LEED patterns from ordered overlayer systems bear a strong relationship to electron holograms, and that phase information is recorded in the diffraction intensities. It is, therefore, possible to obtain structural information by direct holographic inversion from conventional LEED I-V spectra.

HOLOGRAPHIC IMAGES OF IODINE ATOMS ON A SILVER SURFACE FROM ELECTRON-EMISSION PATTERNS

BARTON 1 has suggested that photoelectron interference patterns may be used directly as holograms to obtain atomic-resolution images of surface structures. Bulk structures have been obtained previously by this means from experimental patterns of high-energy Kikuchi(quasi-elastically scattered) and Auger electrons 2,3. Here we test the feasibility of this technique for determination of surface structures using Auger intensity patterns obtained 4,5 from iodine chemisorbed on a pseudomorphic silver monolayer on Pt{111}. By direct numerical holographic inversion, we obtain three-dimensional images which show that iodine adatoms are located in hollows of 3-fold symmetry on the surface. The images yield the site symmetry with good atomic resolution in the surface plane, but suffer from poor resolution along the Ag-I axis. We anticipate that data with better angular resolution obtained at low temperatures would improve the spatial resolution of such images.

A study exploring disordered eating patterns in first-year university students: student and service needs

This qualitative study explored disordered eating in a small group of first-year undergraduate students and addresses a gap in the literature by exploring their lived experience.

Aims: To better understand student’s needs in those experiencing or at risk of developing disordered eating during their first year at university and to illustrate what support mechanisms and services are required to better support students experiencing or at risk during their first year at university.

Conclusion: The University could further develop its outreach to new students with a more consistently supportive programme providing better facilities and training for stress appraisal and coping and more support via student buddying. The University could also extend its programme on positive mental health in an attempt to better inform on disordered eating and to reduce a sense of stigma within the student population. Personal tutors and student health care facilities need to be consistently trained in the understanding and person centred approach to students experiencing disordered eating, particularly the sub-clinical group. In addition the University could consider some small changes and adaptations to the refectory eating areas to better facilitate students who may be at risk from disordered eating. Finally the University could perhaps better use the potentially liminal period within the first few months of student's arrival at university (a new beginning) to help embed a program to develop a stronger sense of coherence and well-being.

Temporal and spatial patterns in α- and γ-hexachlorocyclohexane concentrations in industrially contaminated rivers

Fluxes of HCH isomers α- and γ-HCH dynamics were determined in four industrial U.K. rivers feeding the North Sea. Sampling was conducted weekly basis over a 2-year period. This was complemented by discrete studies of events where two hourly sampling periods were used to investigate the fine time scale dynamics of fluxes. Two intensively industrialized rivers had average isomer concentrations of ~20 ng L^-1 for both isomers, while average concentrations in the two less industrialized rivers ranged between 1.5 and 5.0 ng L^-1. α-HCH concentrations showed no strong temporal patterns on any river, which contrasts with γ-HCH levels that increased considerably during late summer/early autumn following sustained periods of low river flow. Sampling during high river flow events on rivers with differing HCH pollution histories both showed the same dynamics in HCH isomer concentrations. γ-HCH concentrations decreased 4-fold during events while α-HCH-concentrations stayed constant. The increases in γ-HCH concentrations under low flow conditions and the rapid dilution of this isomer during events indicate that γ-HCH has current inputs to these river systems. It was calculated that these four rivers export 30.8 kg yr^-1 of γ-HCH and 14.8 kg yr^-1 of α-HCH to the North Sea.

Patterns of hematopoietic chimerism following bone marrow transplantation for childhood acute lymphoblastic leukemia from volunteer unrelated donors

Hematopoietic chimerism was analyzed in serial bone marrow samples taken from 28 children following T-cell depleted unrelated donor bone marrow transplants (UD BMT) for acute lymphoblastic leukemia (ALL). Chimeric status was determined by polymerase chain reaction (PCR) of simple tandem repeat (STR) sequences (maximal sensitivity, 0.1%). At least two serial samples were examined in 23 patients. Of these, two had evidence of complete donor engraftment at all times and eight showed stable low level mixed chimerism (MC) (<1% recipient hematopoiesis). All 10 of these patients remain in remission with a minimum follow-up of 24 months. By contrast, 13 patients demonstrated a progressive return of recipient hematopoiesis. Five of these relapsed (4 to 9 months post BMT), one died of cytomegalovirus pneumonitis and seven remain in remission with a minimum follow-up of 24 months. Five children were excluded from serial analysis as two serial samples were not collected before either relapse (3) or graft rejection (2). We conclude that as with sibling transplants, ex vivo T depleted UD BMT in children with ALL is associated with a high incidence of MC. Stable donor engraftment and low level MC always correlated with continued remission. However, detection of a progressive return of recipient cells did not universally correlate with relapse, but highlighted those patients at greatest risk. Serial chimerism analysis by PCR of STRs provides a rapid and simple screening technique for the detection of relapse and the identification of patients with progressive MC who might benefit from detailed molecular analysis for minimal residual disease following matched volunteer UD BMT for childhood ALL.