Neutron Rietveld Analysis of Anion and Cation Disorder in the Fast-Ion Conducting Pyrochlore System Y2(ZrxTi1−x)2O7

All information on the site occupancies and atomic displacements which relate a pyrochlore superstructure to the parent fluorite-type subcell is contained in the normally-weak superstructure diffraction intensities. As Ti has a negative scattering length, the supercell maxima in the present phases are up to three times as intense as the fluorite-like reflections, and neutron diffraction provides an especially sensitive probe of the state of disorder. Y2Ti2O7 is found to have a fullyordered anion array and slight disorder, Y0.984Ti0.015, among the cations. In Y2(Zro.6TiO.4)2O7 the oxygen site normally vacant in pyrochlore is half filled and on the order of 15% exchange between cation sites has occurred.

Seasonal movements, aggregations and diving behavior of Atlantic bluefin tuna (Thunnus thynnus) revealed with archival tags

Electronic tags were used to examine the seasonal movements, aggregations and diving behaviors of Atlantic bluefin tuna (Thunnus thynnus) to better understand their migration ecology and oceanic habitat utilization. Implantable archival tags (n = 561) were deployed in bluefin tuna from 1996 to 2005 and 106 tags were recovered. Movement paths of the fish were reconstructed using light level and sea-surface-temperature-based geolocation estimates. To quantify habitat utilization we employed a weighted kernel estimation technique that removed the biases of deployment location and track length. Throughout the North Atlantic, high residence times (167+/-33 days) were identified in four spatially confined regions on a seasonal scale. Within each region, bluefin tuna experienced distinct temperature regimes and displayed different diving behaviors. The mean diving depths within the high-use areas were significantly shallower and the dive frequency and the variance in internal temperature significantly higher than during transit movements between the high-use areas. Residence time in the more northern latitude high-use areas was significantly correlated with levels of primary productivity. The regions of aggregation are associated with areas of abundant prey and potentially represent critical foraging habitats that have seasonally abundant prey. Throughout the North Atlantic mean diving depth was significantly correlated with the depth of the thermocline, and dive behavior changed in relation to the stratification of the water column. In this study, with numerous multi-year tracks, there appear to be repeatable patterns of clear aggregation areas that potentially are changing with environmental conditions. The high concentrations of bluefin tuna in predictable locations indicate that Atlantic bluefin tuna are vulnerable to concentrated fishing efforts in the regions of foraging aggregations.

Bridging the research gap: aboriginal and academic collaboration in FASD prevention. The Healthy Communities, Mothers and Children Project

OBJECTIVES

The objective was to assist with the prevention of Fetal Alcohol Spectrum Disorder through a participatory research approach involving local women and health care workers. Our interest was in understanding how well communities could develop culturally appropriate methods of helping women to reduce their alcohol consumption during pregnancy.

STUDY DESIGN

Four geographically distant Aboriginal communities were presented with a task of adapting a standard Brief Alcohol Intervention, and in particular to develop a culturally appropriate means of using the Intervention with women in the community.

METHODS

Academic and Aboriginal community researchers worked together in partnership, using a participatory action research approach to address alcohol use during pregnancy.

RESULTS

The outcome of the project was the design of four differing models of culturally appropriate community interventions designed to support vulnerable women in their childbearing years. The intervention models developed by the four communities have five core characteristics: (1) identification of women at risk; (2) assessment of the woman's drinking/ drug use; (3) provision of information to the women; (4) delivery method facilitates the decision to adopt healthier behaviors; and (5) means to monitor changes.

CONCLUSION

This project was considered successful in many respects: (1) each community developed a culturally-relevant prevention tool; (2) community involvement in the design lead to better understanding of its usefulness; (3) considerable knowledge exchange between academic and community partners took place; and (4) most importantly, it was found that community members can be active members in developing and implementing solutions to important public health issues.

Repetitive and ritualistic behaviour in children with Prader-Willi syndrome and children with autism

BACKGROUND

Recent research has shown that the range of repetitive behaviour seen in individuals with Prader-Willi syndrome (PWS) extends beyond food-related behaviour.

METHODS

The presence and intensity of repetitive, rigid and routinized behaviour in children with PWS was compared with that seen in children with another neurodevelopmental condition in which repetitive behaviour is common: children with autism. Parents completed the Childhood Routines Inventory (CRI).

RESULTS

Contrary to our predictions, controlling for developmental level, children with PWS and children with autism showed similar levels of repetitive and ritualistic behaviour overall and on the two CRI factors measuring 'just right' and 'repetitive' behaviour. Indeed, the majority of the sample of parents of children with PWS endorsed most items on the CRI. However there was some specificity at the level of individual items with parents of children with PWS more frequently endorsing an item on 'collecting and storing objects' and parents of children with autism more frequently endorsing 'lining up objects', 'has a strong preference for certain foods' and 'seems aware of detail at home'.

CONCLUSIONS

These findings confirm the range of repetitive behaviours that form part of the behavioural phenotype of PWS, including insistence on sameness and 'just right' behaviours, and uncover a surprising overlap with those seen in children with autism. Clinical management for children with PWS should include advice and education regarding management of repetitive and rigid behaviour. Future research should investigate whether the repetitive behaviours that form part of the behavioural phenotype of both PWS and autism are associated with a common neuropsychological, neurotransmitter or genetic origin.

A comparison of methods for modeling the effect of axial divergence in powder diffraction

The Edgeworth series model for the modification of diffraction peak shapes because of axial divergence is compared with the peak shapes computed by a numerical convolution method that is computationally slow. It is shown that if the width of an approximately Gaussian instrumental peak shape is comparable with the width of the modifying function, a condition that is generally satisfied in fixed-wavelength neutron diffraction and in many laboratory X-ray diffraction instruments, but not with synchrotron X-ray instruments, the Edgeworth model is nearly identical to the convolution model, while the computation is much simpler.

Trends in treatment performed in the Phelophepa Dental Clinic: 1995-2000

Mobile clinics are a cost-effective method of meeting the dental needs of rural communities in South Africa. Phelophepa, the first primary health care train of its kind world-wide, provides eye care, education, medicine, basic health care and since June 1995 dental treatment to rural communities. All services are rendered by students under supervision of qualified staff. The aim of this study was to analyse and report the data for treatment performed in the dental clinic from June 1995 to May 2000. During its first five years of operation, dental services were provided at 183 towns in all provinces except Gauteng. Of the 42,073 patients treated during this time (an average of 229.9 per town), 67.4% were adults. 71.3% of the 103,283 procedures performed were extractions, 15.7% could be classified as preventive with the remaining 13% as restorative procedures. The average value of the service provided to each patient was R218.53. The exposure of dental, dental therapy and oral hygiene students to rural areas of South Africa serves the important purpose of sensitising students to the realities of oral diseases in these communities.

Materials Research With Neutrons at NIST

The NIST Materials Science and Engineering Laboratory works with industry, standards bodies, universities, and other government laboratories to improve the nation's measurements and standards infrastructure for materials. An increasingly important component of this effort is carried out at the NIST Center for Neutron Research (NCNR), at present the most productive center of its kind in the United States. This article gives a brief historical account of the growth and activities of the Center with examples of its work in major materials research areas and describes the key role the Center can expect to play in future developments.

Anaphylaxis to rabbit: a case report

BACKGROUND

While rabbits are common as pets, severe allergic reactions to domestic rabbits in homes are unusual. Typically, allergic manifestations are mild to moderate allergic rhinitis, conjunctivitis, pruritus and/or asthma in laboratory animal caretakers with frequent exposure.

METHODS

We report an atopic child with a severe allergic reaction following inhalant exposure to a rabbit. We performed percutaneous skin tests and determined serum-specific IgE to commercial preparation of rabbit epithelium and extracts of rabbit fur and serum.

RESULTS

Percutaneous skin test was positive to rabbit epithelium. The patient had elevated serum-specific IgE to rabbit epithelium and fur but not to rabbit serum.

Construction of maximum-entropy density maps, and their use in phase determination and extension

Methods for constructing everywhere-positive electron-density maps with Fourier amplitudes matching those for arbitrarily large sets of observed data, utilizing dual-function methods for maximization of entropy, are described. Possible strategies for utilizing these maps for the determination and extension of phases in macromolecular structure determination are suggested, and problems are discussed.

Programs for phasing by entropy maximization as implemented in Xtal3.2: a crystallographic software system

Xtal3.2, a crystallographic software package, is an international development project involving about 40 researchers over a full spectrum of crystallographic interests. This development has been supported by many national and international agencies and commercial institutions since the first version in 1983. The 1992 release, Xtal3.2, contains software for 95 different calculations. These range from the processing of raw diffraction data to interactive molecular graphics, atomic charge estimation, electronic publication preparation, and the structure solution and refinement of small and large molecules. Tests of the Xtal programs for phase determination and phase refinement by the application of 'maximum entropy' are presented.

Ab initio phase determination for X-ray diffraction data from crystals of a native protein

An efficient algorithm for the determination of an everywhere positive electron-density distribution that agrees with observed structure amplitudes has been used to determine the phases of X-ray diffraction data from recombinant bovine chymosin, a protein with 323 amino-acid residues in the molecular chain whose structure was recently determined using molecular replacement methods. A systematic procedure for testing the signs of centric reflections, using the total entropy of the map as a figure of merit, was used to produce a low-resolution map. The phases of acentric and additional centric reflections were then chosen by adding them to the map with various possible phases and computing the total entropy of the resulting map. Of 159 centric reflections whose phases were chosen by this procedure, 141 had the same phase as in the refined structure. The median absolute phase difference for 1811 acentric reflections was 32 degrees. A map produced from these 1970 reflections, out of 12,346 reflections in the data set, showed a remarkable agreement with the refined structure. This molecule is many times larger than any whose structures have previously been determined without the use of isomorphous replacement, molecular replacement or anomalous dispersion, and the map demonstrates the potential of maximum-entropy methods in macromolecular structure determination.