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Science and Technology at the Center The NIST Center for Neutron Research is involved in a diverse range of scientific topics, and exciting research opportunities abound. The publication record of the NCNR staff and associated researchers attests to the high quality and quantity of work carried out at the centerâs facilities. During the past year, the period of this assessment, NCNR and associated researchers produced more than 350 publications, 33 of which appeared in noteworthy journals. Several of these publications are outstanding contributions to science. The topics, which attest to the breadth of the work, include fundamental neutron physics and a number of directions in condensed-matter science and engineering, such as correlated electron systems and correlated spin systems, glass physics, hydrogen storage, polymer physics, complex fluids, and rheology. The Center for High Resolution Neutron Scattering, which includes six instruments, has played a significant role in this level of accomplishment. Nearly half of the important publications are associated with the CHRNS Program. The Fundamental Neutron Physics Group continues to be productive and innovative. Its scientific goals are well aligned with the national goals for U.S. nuclear physics as articulated in the Nuclear Science Advisory Committee (NSAC) Long Range Plan of 2007.4 As befits a group at NIST, many of the skills of the group are directed toward measuring quantities to unprecedented precision. The most speculative experiment is the proposal to study the neutron electric dipole moment (EDM) by means of neutron transmission in a silicon single crystal. The systematics of the measurement, which will likely represent a formidable challenge, remain to be identified. Nevertheless, the technique is sufficiently novel that proceeding with a test measurement is encouraged. The Fundamental Neutron Physics Group is carrying out excellent science that should be further developed. An important effort at the NCNR, begun over 3 years ago, is being directed at the problem of hydrogen storage. The hydrogen storage project is a key element in the development of fuel cell technology that may well play a future central role in clean, fuel- efficient transportation modules. This is an excellent example of the NCNRâs interfacing with industrial partners. The work on metal hydrides is particularly impressive. Neutron facilities are well suited for studies like this on hydrogen storage. The work should be continued, with an effort to understand the underlying physics. Strong connections should be built to related research at other national laboratories and at universities. It is important that the NCNR continue to commit to research on biological materials and on soft condensed matter. This research is becoming increasingly urgent as the contribution of biotechnology to the nationâs commerce becomes more substantial. Important potential applications for the use of neutrons in studying biologically pertinent systems include resolving the structure and dynamics of membranes, of proteins in membranes, and of genetic material inside viral capsids. Some work on these topics is underway at the NCNR, but there should be more. For example, the collaborative work between the NCNR and the National Institutes of Health (NIH) on neutron scattering of 4 Nuclear Science Advisory Committee, 2007, The Frontiers of Nuclear Science: A Long Range Plan, available at http://www.sc.doe.gov/np/nsac/docs/Nuclear-Science.Low-Res.pdf. Accessed September 2, 2008. 7
osmotically stressed biological systems is worthwhile. In the study of protein-associated water, researchers were able to probe the protein-water structure using small-angle neutron scattering (SANS). There was also an NCNR-NIH collaboration on the study of clathrin, a major component in the protein coats of certain post-Golgi and endocytic vesicles. The transformation between âbasketâ and open forms is visible by dynamic light scattering and SANS, with SANS revealing features not visible by light scattering. A stumbling block to substantially increased research in these areas is the very modest level of expertise in biology and biophysics at the NCNR or elsewhere at NIST. The NRCâs assessment report for FY 2007 encouraged the NCNR to address this perceived problem by means of direct hires and/or the development of new partnerships.5 In the soft-matter area, despite good efforts there was no success in attracting a strong scientific leader. The NCNR made two hiring offers last year, but neither candidate accepted a position. To enhance its biological efforts, the NCNR is looking to partner with NISTâs Chemical Science and Technology Laboratory to search for a biochemist, with the expectation that the personâs primary activity would be to use neutron scattering. There is now an effort to hire a person to lead the research in the structure and dynamics of membranes; that individual will be stationed in the CSTL but would have a neutron focus and thereby be in a position to nucleate future collaborative efforts. Still, there is need at the NCNR for continued network building with scientists in other institutions. The Center for Advanced Research in Biotechnology, involving NIST and the University of Maryland, is a step in the right direction. NIST should continue to undertake such steps. For example, there are continuing possibilities to build connections with NIH, especially if it is possible to support more joint postdoctoral positions. In addition, the NCNR is hoping to develop a consortium with the Polymers Division at NISTâs Materials Science and Engineering Laboratory and the University of Delaware. There is insufficient theoretical guidance at the NCNR in statistical physics. This is not to deny outstanding work in this area. For example, the studies of oxide pyrochlorites are impressive. These materials exhibit transitions between phases of spin matter that are low-temperature analogues of liquid water and ice. The work illustrates how the capabilities of the NCNR can provide insight into the statistical physics of materials. The way in which NCNR capabilities provided information on the behavior of so-called relaxors is also impressive. However, the absence of a strong enough representation in statistical mechanics by the theorists at the NCNR and NIST impedes possible links to scientists interested in measurements on biophysical systems. It also limits the vision associated with the NCNR research on complex fluids, rheology, and materials. While sophisticated and inventive measurements have been made in each of these areasâfor example, on the behavior of structured fluids under shear and on the fracture of solids under strainâapplications of statistical physics have the potential to help NCNR scientists and their co-workers gain even further insight from their measurements. For this reason, as has been noted in previous NRC assessment reports, the theory program at the NCNR would substantially benefit by broadening in the directions of statistical physics and biophysics. 5 National Research Council, 2007, An Assessment of the National Institute of Standards and Technology Center for Neutron Research: Fiscal Year 2007, Washington, D.C.: The National Academies Press. 8