Engaging stakeholders in research to address water-energy-food (WEF) nexus challenges.

The water-energy-food (WEF) nexus has become a popular, and potentially powerful, frame through which to analyse interactions and interdependencies between these three systems. Though the case for transdisciplinary research in this space has been made, the extent of stakeholder engagement in research remains limited with stakeholders most commonly incorporated in research as end-users. Yet, stakeholders interact with nexus issues in a variety of ways, consequently there is much that collaboration might offer to develop nexus research and enhance its application. This paper outlines four aspects of nexus research and considers the value and potential challenges for transdisciplinary research in each. We focus on assessing and visualising nexus systems; understanding governance and capacity building; the importance of scale; and the implications of future change. The paper then proceeds to describe a novel mixed-method study that deeply integrates stakeholder knowledge with insights from multiple disciplines. We argue that mixed-method research designs-in this case orientated around a number of cases studies-are best suited to understanding and addressing real-world nexus challenges, with their inevitable complex, non-linear system characteristics. Moreover, integrating multiple forms of knowledge in the manner described in this paper enables research to assess the potential for, and processes of, scaling-up innovations in the nexus space, to contribute insights to policy and decision making.

Luminescence techniques and characterization of the morphology of polymer latices 2. Fluorescence lifetime, phosphorescence and fluorescence anisotropy studies.

Five poly(n-butyl methacrylate), PBMA, latex dispersions have been prepared, each incorporating a different fluorescent label, via a two-stage seeded emulsion polymerization. The resultant latices contain ca. 35% by weight total solids and are of 80 (+/-10) nm diameter as determined by photon correlation spectrometry. Luminescence spectroscopic techniques, namely fluorescence (and phosphorescence) excited state lifetime measurements in addition to time-resolved anisotropy experiments have provided useful information regarding the morphology, microviscosity and water permeability of the resultant particles. A picture of the PBMA colloid emerges of an interior which is highly viscous and water impermeable in nature. Indeed, the environment is protective enough to sustain room temperature stabilized phosphorescence from both an acenaphthylene and 9-phenanthrylmethyl methacrylate labeled dispersion through simple nitrogen purging of the solutions. However, the current spectroscopic measurements should be viewed with the knowledge that each luminescent label may fashion its own distinctive microenvironment within the latex during polymerization.

Luminescence techniques and characterization of the morphology of polymer latices. 3. An investigation of the microenvironments within stabilized aqueous latex dispersions of poly(n-butyl methacrylate) and polyurethane.

Fluorescence techniques (including time-resolved anisotropy measurements, TRAMS) have been used to probe differences in morphology between two stabilized aqueous latex dispersions (poly(n-butyl methacrylate), PBMA, and polyurethane, PU). Use of the emission characteristics of probes such as pyrene and phenanthrene dispersed within particles reveals that the PU latices are more heterogeneous in nature: evidence exists, particularly from quenching measurements and TRAMS, that voids and channels of water permeate the PU structure, resulting in a relatively soft, open particle, swollen by ingress of the bulk aqueous phase. Fluorescence measurements indicate that PBMA colloids, however, are composed of relatively hard, hydrophobic particles. In addition, TRAMS are considered to be a valuable tool both for probing the morphological characteristics of such dispersions and in estimating the average particle size.

Designing fault-tolerant distributed archives for picture archiving and communication systems.

PURPOSE: Distributed archives in a picture archiving and communication system (PACS) environment can provide added fault tolerance and fail-over capability, as well as increased load capacity at a more economical price than traditional 'high-availability" systems. Systems can be configured with varying levels of fault tolerance, depending on the amount of redundancy desired. There is, however, a direct correlation between the level of hardware redundancy and cost to implement. This presentation details the system design for fault-tolerant distributed archives as well as several options for redundancy, referencing implementation of a fault-tolerant archive system at the University of Utah. METHODS: The distributed archive system described here is based on Image Devices' image archive software, which can be implemented on multiple individual archive servers in order to distribute archive functionality and operational load. The configuration and implementation of the individual servers together make up the distributed archive system and does not impact the ability of the system to be scaled to meet future requirements. Several implementation and configuration options exist, including the ability for servers to maintain replicated databases containing patient and image information. Thus, each archive can be aware of all information and the location of this information within the distributed archive system. RESULTS: The goal is to produce systems that will still be operational in the event of any single point of failure, ie, a network connection failure between facilities or the failure of a single archive server within the distributed system. During normal operation, workload for image acquisition, image routing and image query requests will be distributed between the archive servers. If the system is deployed in a multifacility environment, each archive server can be configured to be responsible for the acquisition and image distribution management within that server's local facility. If the system is deployed in a single facility environment, load can be distributed evenly between the archive servers based on an understanding of the workload requirements generated be each acquisition and display device in the system. In the event that an archive server fails, other archive servers within the system will have the ability to provide some or all of the failed server's functionality. The degree of fail-over capability is dependent on the archive server's configuration as well as hardware redundancy employed. Three levels of fault-tolerant design can be achieved with this system architecture: (1) duplicate work capability only; (2) duplicate work capability and short-term image cache; (3) duplicate work capability, short-term image cache, and longterm image archival. Using the basic fault-tolerant design above, we have implemented a multifacility distributed archive system at the University of Utah. This system was implemented at a fraction of the cost of true "high-availability" archive architectures yet provides constant up time for the PACS system. If the network connection between the two locations goes down, each site is still fully functional for soft-copy read, as well as image acquisition and distribution. If either of the archive servers goes down, the image sources are redirected to the other archive server. The operational server then handles image distribution for both locations. Access to images in the short-term image cache is available to both archive servers and is not affected by loss of the network connection or remote server. Because there is ony one long-term archive device, the ability to retrieve images from long-term storage is the only function compromised by a network or server failure. CONCLUSION: By implementing distributed archives in a PACS environment, it is possible to achieve a highly fault-tolerant system without the expense of high-availability hardware and software. The design concepts outlined here can be applied to any PACS system that supports distributed archive functionality.

Fluorescence anisotropy: a method for early detection of Alzheimer beta-peptide (Abeta) aggregation.

Time-resolved anisotropy measurements (TRAMS) have been used to study the aggregation of the beta-amyloid (Abeta) peptide which is suspected of playing a central role in the pathogenesis of Alzheimer's Disease (AD). The experiments, which employ small quantities of fluorescently-labelled Abeta, in addition to the untagged peptide, have shown that the sensitive TRAMS technique detects the presence of preformed "seed" particles in freshly prepared solutions of Abeta. More importantly, as 100 microM solutions of Abeta containing tagged Abeta at a concentration level of either 0.5 or 1 microM are incubated, the TRAMS prove capable of detection of the peptide aggregation process through the appearance of a continuously increasing "residual anisotropy" within the time-resolved fluorescence data. The method detects Abeta aggregation in its earliest stages, well before complexation becomes apparent in more conventional methods such as the thioflavin T fluorescence assay. The TRAMS approach promises to provide a most attractive route for establishment of a high-throughput procedure for the early detection of the presence of amyloid aggregates in the screening of biological samples.

Modulation of beta-amyloid production and fibrillization.

Alzheimer's disease (AD) is the most common cause of dementia in old age and presently affects an estimated 4 million people in the U.S.A. and 0.75 million people in the U.K. It is a relentless, degenerative brain disease, characterized by progressive cognitive impairment. In the final stages of the disease, patients are often bedridden, doubly incontinent and unable to speak or to recognize close relatives. Pathological changes of Alzheimer's disease include extensive neuronal loss and the presence of numerous neurofibrillary tangles and senile plaques in the brain. The senile plaques contain amyloid fibrils derived from a 39-43-amino-acid peptide referred to as beta-amyloid or A beta. The basic theory of the so-called 'amyloid hypothesis' is that the deposition of aggregated forms of A beta in the brain parenchyma triggers a pathological cascade of events that leads to neurofibrillary tangle formation, neuronal loss and the associated dementia [1]. Here we discuss progress towards the identification of inhibitors of A beta production and fibrillization.

Photophysics of Carbazole-Containing Systems. 3 Fluorescence of Carbazole-Containing Oligoethers in Dilute Solution.

Fluorescence techniques, including quenching and anisotropy measurements, have been used to study the photophysical behavior of the carbazole-based oligoethers poly{9-(2,3-epoxypropyl)carbazole}, PEPCz, and poly{1,2-epoxy-6-(9-carbazolyl)-4-oxahexane}, PECzOH, and their model compounds, in dilute fluid solutions in THF. These compounds show no evidence of excimer formation under these conditions and their fluorescences exhibit first-order decay behavior regardless of the degree of polymerization of the oligomer. Both steady-state and time-resolved anisotropy measurements upon dilute, glassy solutions show that intramolecular energy migration occurs in the oligomers. Fluorescence quenching experiments, using both dimethylterephthalate and oxygen as quenchers, produced evidence which supports the supposition that in the absence of excimer trapping sites, intramolecular energy migration will be encouraged in dilute fluid solutions of the oligoethers. Unfortunately, the fluorescence quenching data did not permit evaluation of the extents of energy migration in the various polymers or the relative efficiencies with which migration occurs in the two different types of oligoether. This limitation would appear to be a general feature of fluorescence quenching measurements, despite their frequent adoption, in the past, in studies of energy migration in polymers.

Hearing screening in Jamaica: prevalence of otitis media with effusion.

Hearing screening is well established in most developed countries, and the data extensively published. However, little information has been presented by the developing, nonwhite populations. A screening study was carried out on 2202 Jamaican children aged 5 to 7 years. This involved tympanometry and pure-tone audiometry (frequencies of 0.5, 1, and 2 kHz.) Failure was considered to have occurred if a type B or C curve was obtained or if the threshold of hearing was greater than 20 dB. These children were further evaluated by a full ear, nose, and throat examination, inclusive of pneumatic otoscopy, and audiologic testing. The prevalence of hearing impairment was 4.9%. Otitis media with effusion (OME) was present in 1.9%. The prevalence of OME in Jamaica is low when compared with that of the same age-group in the developed countries.

Hearing screening in Jamaica: prevalence of otitis media with effusion

Hearing screening is well established in most developed countries, and the data extensively published. However, little information has been presented by the developing, nonwhite populations. A screening study was carried out on 2202 Jamaican children age 5 to 7 years. This involved typanometry and pure-tone audiometry (frequencies of 0.5, 1, and 2 kHz.) Failure was considered to have occurred if a type B or C curve was obtained or if the threshold of hearing was greater than 20 dB. These children were further evaluated by a full ear, nose and throat examination, inclusive of pneumatic otoscopy, and audiologic testing. The prevalence of hearing impairment was 4.9 percent. Otitis media with effusion (OME) was present in 1.9 percent. The prevalence of OME in Jamaica is low when compared with that of the same age-group in the developed countries(AU)

Practical application of a scan-rotate equalization geometry to mammography.

The presence of dense fibroglandular tissue within the breast is the most significant cause of failure to detect breast cancer with mammography. The dense tissue often produces a range of exposure which exceeds the useful dynamic range of film-screen mammography. It has been shown that equalization radiography overcomes the latitude limitations of film-screen imaging. Equalization compensates for regional variations in x-ray transmission within the patient through spatial modulation of the entrance exposure. We have proposed rotary scanning equalization radiography (RSER), a scan-rotate geometry for efficient equalization radiography. In RSER the image receptor is exposed by repeated scans of a source-modulated fan beam. The fan beam is rotated with respect to the patient between scans. Numerical simulations and theoretical analysis have shown that the superposition of exposure from appropriately modulated fan beams at a variety of angles is an entrance exposure that effectively equalizes the film exposure. The design and characteristics of a prototype RSER imaging system are described. Anthropomorphic breast phantom images are used to determine the improvement in image contrast obtained with RSER, the expected tube loading, and the presence of artifacts. RSER increases the fraction of the breast imaged with high contrast (at least 90% of peak gradient) from 46% (conventional mammography) to 80%. Subjective examination of the phantom images show that RSER achieves image quality very similar to that of much less efficient equalization geometries with only 2.7 times greater tube loading than conventional mammography. As predicted by theoretical analysis of exposure artifacts in RSER, the prototype RSER system is relatively immune to artifacts. Exposure artifacts were demonstrated for extreme variations in x-ray transmission within the patient. These results show that RSER is an efficient, practical means of overcoming the latitude limitations of film-screen mammography, and improving the detection of breast cancer.

Magnetic resonance imaging in potential postsurgical recurrence of breast cancer: pitfalls and limitations.

OBJECTIVE: To determine the sensitivity and specificity of magnetic resonance imaging (MRI) of the breast for detecting recurrent carcinoma. PATIENTS AND METHODS: Thirteen patients ranging in age from 47 to 77 years who had undergone lumpectomy 5 months to 8 years earlier and who had mammographic findings suggestive of recurrence underwent contrast-enhanced dynamic MRI. Histologic confirmation was obtained in all cases. RESULTS: Of the eight lesions (in seven patients) for which biopsy proved recurrence, MRI correctly identified six; there were two false negative results. Of the six benign lesions, four were correctly identified by MRI. The two false positive results involved fat necrosis and a foreign-body reaction respectively. CONCLUSION: These results confirm previous reports of the poor specificity of MRI of focal breast lesions. The authors therefore recommend caution in the use of breast MRI in the assessment and management of suspected recurrent carcinoma.

Visualizing tissue compliance with MR imaging.

We propose a method for visualizing the mechanical properties of tissue based on the use of periodic mechanical compression in conjunction with phase-contrast MR imaging. A specialized mechanical transducer was used to provide programmable compression pulses to the surface of compliant phantoms. These compression pulses were synchronized to a spin-echo sequence with motion-sensitizing gradients to generate phase information reflecting spin displacement throughout the phantom. This sequence was tested with two agarose gel phantoms. The first was a cylinder containing three parallel layers of varying compliance and the second was composed of a semirigid sphere suspended in a uniform layer of decreased elastic modulus. Images showed complex patterns of motion throughout the phantom, which correlated with expected motion behavior of the phantom structures. This indicates that the biomechanical properties of tissues may be elucidated through the use of motion-sensitized MR imaging and suggests that a form of image contrast relating to tissue elasticity may be feasible.

A method for practical equalization mammography of the radiographically dense breast.

It has been shown that equalization radiography can overcome the well-known problem of limited film latitude encountered in mammography of the radiographically dense breast. Current equalization geometries based on single scanning beam (SER) or multiple-beam techniques approach the heat-loading limits of mammographic x-ray sources and require excessively long scan times. The authors have proposed an alternative geometry for equalization mammography, rotary scanning equalization radiography (RSER), which uses a slot beam in a translate-rotate geometry. RSER provides the simplicity of a single-beam geometry while offering improved tube efficiency over multiple-beam geometries. Numerical simulations and a prototype imaging system are used to show that equalized mammograms exhibiting high contrast throughout the breast can be obtained with a large scanning beam translated over the image at only four scanning angles. These results indicate that RSER is an efficient, simple, and practical means of imaging the dense breast.

An MR compatible flow simulator for intravascular pressure simulation.

An MR compatible flow simulator is described which generates physiologically realistic pressure and flow waveforms. The simulator is based on a servomotor-driven gear pump which produces pulsatile flow by modulation of the servomotor rotation rate. Operation of the simulator is under the control of a personal computer, which executes an iterative feedback loop to minimize errors between measured and desired pressure waveforms. The simulator is totally automatic, requiring only a few minutes of iteration to generate the desired pressure waveform. Accurate sinusoidal waveforms with frequencies up to 10 Hz have been generated using the simulator, with high-frequency contamination of the measured waveform at least 80 dB below the fundamental frequency. Aortic waveforms have been produced with realistic flow rates and pressure variations. The pump assembly is mechanically straightforward and can operate at an 8-m distance from the flow phantom to allow the device to be isolated from the MR magnet room.

Errors in quantitative dynamic three-dimensional keyhole MR imaging of the breast.

Three-dimensional (3D) keyhole magnetic resonance (MR) imaging has been proposed as a means of providing dynamic monitoring of contrast agent uptake by breast lesions, with complete breast coverage and high spatial and temporal resolution. The 3D keyhole technique dynamically samples the central regions of k-space in both phase-encoding directions and provides high-frequency data from a precontrast acquisition. Errors due to data truncation with two-dimensional and 3D region-of-interest measurements are estimated from a numerical simulation of various implementations of the 3D keyhole technique. Errors were found to increase with increasing temporal resolution and reduced object size. Errors of 75% are possible for objects with a diameter approaching 1 pixel when a 3D keyhole implementation that samples 50% of phase-encoding data in each direction is used. Preliminary clinical images with this approach illustrate artifacts consistent with inadequate k-space sampling.

Role of equalisation mammography of dense breasts.

Parenchymal patterns characteristic of dense breasts are known to degrade the mammographic detection of small breast cancers and microcalcifications. This arises from large variations in exposure of the film, resulting in reduced image contrast over areas of suboptimal exposure. Based on sensitometric measurements of mammograms from a typical patient population, it is shown that over 60% of a typical mammogram in Wolfe's DY classification was found to be exposed suboptimally, suggesting a significant margin for improving mammography for these patients. In order to address this problem, a prototype mammographic version of scanning equalisation radiography (MSER) has been developed, which delivers a patient-specific spatially non-uniform distribution of breast exposure, adjusted to maintain optimal film exposure and contrast over the entire mammogram. Anthropomorphic phantom MSER images show a marked improvement in subjective image quality relative to conventional mammograms, while exhibiting a similar radiation risk. The detection of small microcalcifications and fibrils over clinically significant breast densities is found to be improved by factors eight and four, respectively. Such a system may be clinically practical through the use of multiple-beam equalisation methods with available X-ray tube technology.

Observer performance and dose efficiency of mammographic scanning equalization radiography.

The detection of fibrils, microcalcifications, and low contrast lesions is vital to the detection of early breast cancer. It has been shown through sensitometric measures and anthropomorphic phantom images that mammographic scanning equalization radiography (MSER) overcomes the latitude limitations of conventional mammographic techniques. MSER increases image quality by regional modulation of the entrance exposure to suit the local variations in x-ray transmission within the patient. In order to assess the effect of equalization on the detection of breast lesions, we have compared observer performance in MSER and conventional imaging techniques. The observation tasks were the threshold visualization of fibrils, microcalcifications, and low contrast discs (simulating lesions), located on a uniform background. The performance of the observers was determined for a range of background x-ray transmission simulating the range of transmission generated by variations in breast composition and thickness. For the conventional images, the threshold visible diameter of the fibrils, microcalcifications, and low contrast discs, increased as the x-ray transmission of the phantom changed from that for which the film was optimally exposed. For the MSER images, the performance of the observers was almost independent of the background transmission of the object since MSER ensures that the film is optimally exposed for a large range of object transmission. Even with significant changes in object x-ray transmission, only minor changes in fibril, microcalcification, and disc detection were observed. Utilizing the results of the contrast-detail experiment, a dose efficiency comparison of conventional and MSER imaging techniques was performed. The dose efficiency analysis showed that MSER varied the incident exposure so as to maintain consistent performance of the observer, over the entire breast. These results suggest that MSER would improve the ability of radiologists to detect early breast cancer in women presenting with mammographically dense breasts, in a very dose efficient manner.

Mammographic scanning equalization radiography.

It is well recognized that variations in breast thickness and parenchymal composition can produce a range of exposure which exceeds the latitude of high contrast mammographic film/screen combinations. Optimal imaging of the dense breast is desired since 30%-60% of women present with dense breasts, and they are believed to be at the highest relative risk of developing breast cancer. The application of scanning equalization radiography to mammography has been investigated through the construction and characterization of a prototype mammographic scanning equalization radiography (MSER) system, designed to image mammographic phantoms. The MSER system exposes a Min-R/MRH cassette by raster scanning a 2.0 x 1.6 cm beam of pulsed x-rays across the cassette. A scanning detector behind the cassette measures the local x-ray transmission of the breast. Feedback of the transmission information is used to modulate the duration of each x-ray pulse, to equalize the film exposure. The effective dynamic range of the MSER system is 25 times greater than that of conventional mammography. Artifact-free images of mammographic phantoms show that MSER effectively overcomes the latitude limitations of film/screen mammography, enabling high contrast imaging over a wide range of object x-ray transmission. Anthropomorphic phantom images show that MSER offers up to a sixfold increase in film contrast in the normally underexposed regions of conventional mammograms. Characterization of the entrance exposure shows that there is not a significant difference in exposure between MSER and conventional mammographic techniques, suggesting that both would pose comparable risk to the patient. Calculations show that the construction of a clinical multiple beam MSER system is feasible with minor changes to existing technology.