Analysis of Three-Dimensional Protein Images

A fundamental goal of research in molecular biology is to understand protein structure. Protein crystallography is currently the most successful method for determining the three-dimensional (3D) conformation of a protein, yet it remains labor intensive and relies on an expert's ability to derive and evaluate a protein scene model. In this paper, the problem of protein structure determination is formulated as an exercise in scene analysis. A computational methodology is presented in which a 3D image of a protein is segmented into a graph of critical points. Bayesian and certainty factor approaches are described and used to analyze critical point graphs and identify meaningful substructures, such as alpha-helices and beta-sheets. Results of applying the methodologies to protein images at low and medium resolution are reported. The research is related to approaches to representation, segmentation and classification in vision, as well as to top-down approaches to protein structure prediction.Comment: See http://www.jair.org/ for any accompanying file

Shuttle LOX loading transient study. Task 2 milestone report. National space and technology laboratories (NSTL) LOX loading facility analysis

Transient thermodynamic analyses were made of the LOX loading system proposed for the space shuttle main propulsion test article (MPTA). This system is made up of a LOX replenish system and a main LOX line which include the barge tank, the lines, pumps, and valves between the barge and the orbiter (ORB) ground service equipment (GSE) interface, the MPTA fill system, the space shuttle main engine (SSME) chilldown bleed system, and the GSE vent system. System analyses include predictions of system performance sensitivity to operating sequence and LOX flowrate, temperature, and quality at the ORB/GSE interface. The transient thermodynamic conditions at the SSME feed line entrance, ET entrance (tank bottom), and the SSME bleed/GSE vent TEE are also included. The analyses are based on continuous SSME bleed flow during GSE facility chilldown

Shuttle LOX Loading Transient Study

The configuration and operation of the LOX loading facilities to be used for the space shuttle main propulsion test article at the National Space and Technology Laboratories (NSTL), and for the space shuttle launch facilities at John F. Kennedy Space Center (KSC) was investigated. The acceptability of these LOX loading facilities for each application was determined along with the degree of similarity between the systems with respect to the applicability of data developed during operations at NSTL a to the launch site operations at KSC. Results are summarized and final data comparisons, conclusions, and recommendations are presented

Grey Gold: Do Older In-migrants Benefit Rural Communities?

Older Americans retiring to rural areas quickly integrate in their new communities and bring significant social and intellectual capital to those communities, finds a new issue brief from the Carsey Institute at the University of New Hampshire. The brief is among the few studies to consider social rather than economic impacts of older in-migration to rural areas. "Of the ten percent of Americans over 60 who moved between counties from 1995 to 2000, a disproportionate share moved to rural communities," says report author Nina Glasgow, a senior research associate in the Department of Development Sociology at Cornell University. "If this trend continues as more Baby Boomers reach retirement age, older newcomers will continue to have a major impact on some rural areas." Glasgow and co-author David Brown, a Cornell University professor of development sociology, director of the Community and Rural Development Institute and associate director of the Cornell Population Program, note that rural retirement destinations (RRDs) -- a U.S. Department of Agriculture designation for the 274 nonmetropolitan counties that experienced net in-migration of 15 percent or higher among persons 60-plus between 1995 - 2000 -- are one of the only types of nonmetropolitan counties in the country experiencing consistent population growth during the last 30 years. Conducting surveys in 14 RRDs spread across the country, the authors found that concerns about social isolation among older in-migrants were largely unfounded: Older in-migrants quickly became involved in their new communities. Their levels of social integration closely matched those of similarly aged persons who had lived in RRDs for more than 20 years, and by 2005, in-migrants were more likely than longer-term residents to participate in service, social and volunteer activities. Further, one-third of older in-migrants had at least one adult child living within a half-hour drive of their new home (compared to almost 50 percent of longer-term older residents). While many studies have examined the economic impacts of older in-migration, this Carsey brief considered the social impacts of older in-migrants on rural communities. The brief finds that older in-migrants have a positive effect on real estate and construction; provide financial and technical assistance to civic endeavors; and invigorate the cultural scene. "Many of these benefits have associated costs, however," says Brown. "Rising real estate prices can diminish affordable housing, for instance, or older in-migrants who assume positions of community leadership might be insensitive to the traditional ways of doing things." The authors conclude that older in-migration should be seen as neither a burden nor a boon for rural areas but rather as a source of both challenges and opportunities. They recommend that communities can maximize opportunities bypromoting an inclusive environment that encourages high levels of social participation among older residents;creating decision-making processes that include older in-migrants' needs and opinions but do not privilege them above those of longer-term residents; andaddressing both immediate and longer-term needs, such as public transportation and health care, of older in-migrants."The 'grey gold' that older in-migration represents, particularly as Baby Boomers enter older age, should be considered by public officials and community leaders in these RRDs from a balanced perspective," says Glasgow

Progress in materials and structures at Lewis Research Center

The development of power and propulsion system technology is discussed. Specific emphasis is placed on the following: high temperature materials; composite materials; advanced design and life prediction; and nondestructive evaluation. Future areas of research are also discussed

A Short Investigation of the Luminescence Properties of Talc

This report presents results of a short study of the thermoluminescence TL properties of talc. Talc is a magnesium silicate mineral utilised widely in industrial and pharmaceutical applications. It occurs in well defined geological situations with several known formation processes, and is extracted by quarrying and mining. The use in foods and dietary supplements is mainly as a filler. The work was initiated to address questions as to the possible impact of talc on application of EN1788 methods to detect irradiated foods. Authentic samples were obtained from extraction and processing facilities in France and Italy. Supplementary samples from Sardinia, China, Mexico and Australia were obtained indirectly. Irradiated pharmaceutical grade talc was obtained from a UK commercial source for comparison. All samples were characterised by TL analysis after initial preparation, and also following irradiation to a 200 Gy dose. The dose response and behaviour under storage at ambient and elevated temperatures and in a light box, were investigated for two samples in detail. Exploratory kinetic analysis was performed to provide first order estimates of trap parameters. All samples of talc exhibited measurable TL response in the 0-500°C region, with at least four recognisable TL peaks present in response to radiation. Sensitivities vary by some 3 or more orders of magnitude from sample to sample, accompanied by less pronounced changes in glow shape following radiation. The dose response increases progressively in the 100-6400 Gy range investigated. At higher dose levels the response is non-linear with the onset of saturation occurring in the kGy region for the majority of signals. Radiation induced signals from all four peaks were stable at ambient temperatures over the duration of the study. Samples stored at 50°C showed some thermal erosion of the low temperature signals. This observation together with analysis of the distribution of natural TL and the kinetic analyses confirms that lower temperature signals have comparable stability with other silicates, and that higher temperature signals are the dominant components of geologically induced signals. The stability requirements to explain natural signals in terms of simple production mechanisms have been defined. Exploratory kinetic analysis confirms that there are multi-trap contributions to the main TL peaks, but provides broad support for a simple explanation of the natural TL. The TL response following high dose irradiation can be distinguished from geological signals by 1-2 orders of magnitude in low temperature peaks. There may be scope for further investigation of phototransfer effects, but these would clearly be overtaken by bleaching in prolonged exposures to light. Thermal processing of pharmaceutical grades of talc reduces residual low temperature signals by some 1-2 orders of magnitude leading to product with negligible low temperature natural signals. TL could in principle be used to verify the effectiveness of such thermal treatment, and potentially to authenticate commercial products. It can also quite clearly be used to identify irradiated talc, providing the amount of prior exposure to light is limited. In samples containing talc in extreme dilution with other unirradiated products, there might be ambiguity in interpretation of glow curves with minor low temperature peaks dominated by high temperature signals. Care would be needed in interpreting EN1788 results of this sort

Investigation of Statistical and Imaging Methods for Luminescence Detection of Irradiated Ingredients

This project investigated two potential approaches to improving the reliability of lumines-cence methods for detecting minor irradiated ingredients in foods. Whereas in the 1980’s there were no validated methods for laboratory detection of irradiated foods, work conducted in the UK and elsewhere by the mid 1990’s had resulted in the development of a series of physical, chemical and biological methods capable of detecting a range of irradiated food classes. Of these the luminescence methods embodied in EN1788 (Thermoluminescence) and EN13751 (Photostimulated luminescence) standards have been applied to detection of a vari-ety of products including herbs and spices, and seafood. In common with the other EN stan-dard methods almost all validation work had been originally conducted using pure irradiated or unirradiated ingredients. Yet application experience had shown the presence of mixed products containing both irradiated and unirradiated ingredients. A short study was commis-sioned by MAFF to investigate the impact of blending on standard EN1788 methods, and on the provisional draft EN13751 (the standard having been published in the meantime) method. This showed the impact of dilution of irradiated material between 10% and 0.1% concentra-tions on detection rates, which unsurprisingly are reduced by extreme dilution. UK labelling regulation, both before and after adoption of the European Directive on Food Irradiation, call for labelling of all irradiated ingredients regardless of concentration or origin within the final product. This study was therefore motivated by the recognition of the long term need for im-proved methods to improve reliability at low concentrations. Two complementary approaches were investigated. The project first examined whether TL data collected using the EN1788 method could be enhanced using advanced statistical proce-dures. Data sets from the SURRC TL archive, and from project CSA4790 were used both to define the characteristics of irradiated and unirradiated end members, and to assess classifica-tion methods using the controlled blending experimental data sets of CSA 4790. Multivariate analyses, based on principal components analysis and discriminant analysis of glow curve data; kinetic deconvolution approaches coupled to PCA and DA, and neural analyses were investigated and compared with detection rates achieved using expert visual classification. To complement this experiments were undertaken to explore the potential of using focussed laser stimulation to produce spatially resolved measurements from mineral grains separated from foods. Two systems were evaluated based on IR and visible band lasers. Work was under-taken to explore sample presentation and to assess the ability of this approach to distinguish mixtures of irradiated and unirradiated grains. The statistical work was successful in developing three approaches which could be used for objective identification of irradiated materials. Pure irradiated and unirradiated data sets from 150 sample pairs were obtained having searched the SUERC archive of more than 3500 lu-minescence analyses. These were used to set up multivariate analyses based on the ap-proaches outlined above. Performance in recognising irradiated ingredients using these meth-ods was then assessed with data drawn from the MAFF blending investigation, comprising 160 permutations of irradiated and unirradiated herbs and spices at 10%, 1% and 0.1% con-centrations. It was possible to achieve good detection rates with alatistical approaches, the best approaches inigated being the use of glow curve deconvolution coupwith li discrimination, and the use of neural appros. The absolute performance achieved matched that opert visual clfication utilising the revised EN1788 criterwhich were adopted within the international standauring course of this project. The use of ad-vancedtistical methods, while not adding performance, can pde objective support to visual classifications. During performance assessment it was aloted that theformance of all methods wasficiently close to infer that detections rates are most dependent on the statistical presence or absence of irradiated grains within the extracted samples used for TL analysis. This raises practical suggestions for improving detection rates at low concentrations based on the use of larger samples and more specific mineral separation approaches. These may be worth investigating further. Laser scanning approaches were also investigated using highly focussed laser beams to stimulated luminescence sequentially from different parts of separated mineral samples. Work was conducted using a system which had been developed in earlier work at SUERC, and then followed by additional investigation using an improved instrument built during the project. Initial work confirmed the feasibility of using laser scanning approaches to obtain spatially resolved luminescence data at or near the dimensions of individual mineral grains. Practical obstacles included the recognition that laser scattering from surfaces coated with mineral grains introduced an element of cross-talk between different parts of the sample, and difficulties in accurate re-positioning of the sample using the first generation prototype in-strument. Work was conducted to investigate a series of different sample presentation media to improve the former, and to incorporate high precision mechanical and optoelectronic means of re-positioning samples between initial measurements, external irradiation, and sub-sequent re-measurement. Both IR and visible band semiconductor lasers were investigated with successful production of single grain images. The short and medium term reliability of the lasers used was acceptable. The lasers used both however eventually failed, which sug-gests that long term lifetime may be an issue for further work. Of the two lasers the IR laser in particular gave a good signal to background ratio for discriminating between irradiated and unirradiated grains. Quantitative analysis of the grain resolved images confirms the potential of this approach in identifying minor irradiated components. The overall conclusions of the work are that both statistical approaches and imaging instru-ments are able to enhance current methods. The observation that visual classification can match the performance even of deconvolution or neural approaches suggests that future effort should be directed more towards improvement of grain statistics in conventional measure-ments, and in further development and investigation of imaging approaches. In these ways it can anticipated that the performance of standard luminescence methods for detecting dilute mixtures of irradiated and unirradiated food ingredients could be significantly improved. To do so would further enhance work conducted by FSA and other bodies to ensure that regula-tions governing the use of irradiation in food processing and the labelling of imported foods are followed

Novel Technique for Ultra-sensitive Determination of Trace Elements in Organic Scintillators

A technique based on neutron activation has been developed for an extremely high sensitivity analysis of trace elements in organic materials. Organic materials are sealed in plastic or high purity quartz and irradiated at the HFIR and MITR. The most volatile materials such as liquid scintillator (LS) are first preconcentrated by clean vacuum evaporation. Activities of interest are separated from side activities by acid digestion and ion exchange. The technique has been applied to study the liquid scintillator used in the KamLAND neutrino experiment. Detection limits of <2.4X10**-15 g 40K/g LS, <5.5X10**-15 g Th/g LS, and <8X10**-15 g U/g LS have been achieved.Comment: 16 pages, 3 figures, accepted for publication in Nuclear Instruments and Methods