Multichannel processing of vibrational measurements: A constrained subspace application.

Monitoring mechanical systems operating in uncertain environments contaminated with both environmental disturbances and noise lead directly to low signal-to-noise-ratios, creating an extremely challenging processing problem, especially in real-time. In order to estimate the performance of a particular system from uncertain vibrational data, it is necessary to identify its unique resonant (modal) frequency signature. The monitoring of structural modes to determine the condition of a device under investigation is essential, especially if it is a critical entity of an operational system. The development of a model-based scheme capable of the on-line tracking of the inherent structural modal frequencies by applying both constrained subspace identification techniques to extract the modal frequencies and state estimation methods to track the evolution is discussed. An application of this approach to a cylindrical structural device (pipe-in-air) is analyzed based on theoretical simulations along with controlled validation experiments, including injected anomalies illustrate the approach and performance. Statistics are gathered to bound potential processors for real-time performance employing these constrained techniques.

Using a Bayesian network to clarify areas requiring research in a host-pathogen system.

Bayesian network analyses can be used to interactively change the strength of effect of variables in a model to explore complex relationships in new ways. In doing so, they allow one to identify influential nodes that are not well studied empirically so that future research can be prioritized. We identified relationships in host and pathogen biology to examine disease-driven declines of amphibians associated with amphibian chytrid fungus (Batrachochytrium dendrobatidis). We constructed a Bayesian network consisting of behavioral, genetic, physiological, and environmental variables that influence disease and used them to predict host population trends. We varied the impacts of specific variables in the model to reveal factors with the most influence on host population trend. The behavior of the nodes (the way in which the variables probabilistically responded to changes in states of the parents, which are the nodes or variables that directly influenced them in the graphical model) was consistent with published results. The frog population had a 49% probability of decline when all states were set at their original values, and this probability increased when body temperatures were cold, the immune system was not suppressing infection, and the ambient environment was conducive to growth of B. dendrobatidis. These findings suggest the construction of our model reflected the complex relationships characteristic of host-pathogen interactions. Changes to climatic variables alone did not strongly influence the probability of population decline, which suggests that climate interacts with other factors such as the capacity of the frog immune system to suppress disease. Changes to the adaptive immune system and disease reservoirs had a large effect on the population trend, but there was little empirical information available for model construction. Our model inputs can be used as a base to examine other systems, and our results show that such analyses are useful tools for reviewing existing literature, identifying links poorly supported by evidence, and understanding complexities in emerging infectious-disease systems.

Origin and evolution of the deep thermochemical structure beneath Eurasia.

A unique structure in the Earth's lowermost mantle, the Perm Anomaly, was recently identified beneath Eurasia. It seismologically resembles the large low-shear velocity provinces (LLSVPs) under Africa and the Pacific, but is much smaller. This challenges the current understanding of the evolution of the plate-mantle system in which plumes rise from the edges of the two LLSVPs, spatially fixed in time. New models of mantle flow over the last 230 million years reproduce the present-day structure of the lower mantle, and show a Perm-like anomaly. The anomaly formed in isolation within a closed subduction network ∼22,000 km in circumference prior to 150 million years ago before migrating ∼1,500 km westward at an average rate of 1 cm year-1, indicating a greater mobility of deep mantle structures than previously recognized. We hypothesize that the mobile Perm Anomaly could be linked to the Emeishan volcanics, in contrast to the previously proposed Siberian Traps.

Raman Imaging Spectroscopy of a Putative Microfossil from the ∼3.46 Ga Apex Chert: Insights from Quartz Grain Orientation.

The utility of nondestructive laser Raman for testing the biogenicity of microfossil-like structures in ancient rocks is promising, yet results from deposits like the ∼3.46 Ga Apex chert remain contentious. The essence of the debate is that associated microstructures, which are not purported to be microfossils, also contain reduced carbon that displays Raman D- and G-band peaks similar to those seen in the purported microfossils. This has led to the hypothesis that all features including reported microfossils are due to compression of nonfossil carbon during crystal growth around quartz spherulites or more angular crystals. In this scenario, the precursor to this macromolecular carbon may or may not have been of biogenic origin, while the arcuate and linear features described would be pseudofossils. To test this hypothesis, we have undertaken 2-D micro-Raman imaging of the Eoleptonema apex holotype and associated features using instrumentation with a high spatial and spectral resolution. In addition to this, we utilized the ratio of two Raman active quartz mode intensities (I129/I461) to assess quartz grain orientation and grain-splitting artifacts. These data lead us to conclude that the holotype of Eoleptonema apex is a sheet-shaped pseudofossil that appears to be a carbon infilled intragranular crack; therefore other holotypes should be carefully reexamined for syngenicity.

Gamma ray measurements with photoconductive detectors using a dense plasma focus.

Photons in the MeV range emitted from the dense plasma focus (DPF) at the NSTec North Las Vegas Facility have been measured with both neutron-damaged GaAs and natural diamond photoconductive detectors (PCDs). The DPF creates or "pinches" plasmas of various gases (e.g., H2, D2, Ne, Ar., etc.) that have enough energy to create MeV photons from either bremsstrahlung and/or (n,n(')) reactions if D2 gas is used. The high bandwidth of the PCDs enabled the first ever measurement of the fast micro-pinches present in DPF plasmas. Comparisons between a slower more conventional scintillator/photomultiplier tube based nuclear physics detectors were made to validate the response of the PCDs to fast intense MeV photon signals. Significant discrepancies in the diamond PCD responses were evident.

ToxML, a data exchange standard with content controlled vocabulary used to build better (Q)SAR models.

Development of accurate quantitative structure-activity relationship (QSAR) models requires the availability of high quality validated data. International regulations such as REACH in Europe will now accept (Q)SAR-based evaluations for risk assessment. The number of toxicity datasets available for those wishing to share knowledge, or to use for data mining and modelling, is continually expanding. The challenge is the current use of a multitude of different data formats. The issues of comparing or combining disparate data apply both to public and proprietary sources. The ToxML project addresses the need for a common data exchange standard that allows the representation and communication of these data in a well-structured electronic format. It is an open standard based on Extensible Markup Language (XML). Supporting information for overall toxicity endpoint data can be included within ToxML files. This makes it possible to assess the quality and detail of the data used in a model. The data file model allows the aggregation of experimental data to the compound level in the detail needed to support (Q)SAR work. The standard is published on a website together with tools to view, edit and download it.

Micro Raman spectroscopy of carbonaceous material in microfossils and meteorites: improving a method for life detection.

The identification of biosignatures in Earth's ancient rock record and detection of extraplanetary life is one of the primary goals in astrobiology. Intrinsic to this goal is the improvement of analytical techniques and protocols used to identify an unambiguous signal of life. Micro Raman spectroscopy is a nondestructive method that allows for in situ identification of a wide range of minerals and compounds. The use of D (∼1350 cm(-1)) and G (∼1580 cm(-1)) band parameters to infer the biogenicity of carbonaceous materials in fossils has become a commonly used analytical tool, but carbonaceous compounds from different sources often share the same spectroscopic characteristics. Microfossil studies do not always take into consideration a nonbiological source for the carbon in their samples and therefore still rely on morphology as the primary mode of identification. Comprehensive studies that consider all carbon sources are typically done on metasediments, coals, or meteorites, and the results are not clearly applicable to microfossil identification. In this study, microfossils from a suite of sedimentary rock samples of various ages were analyzed with micro Raman spectroscopy to investigate the nature and provenance of carbonaceous material. To further constrain D- and G-band carbon characteristics, micro Raman analyses were also performed on well-characterized meteorite samples as abiological controls. The results appear to show a correlation of precursor carbonaceous material with D-band parameters and thermal history with G-band parameters. This systematic study lays the groundwork for improving the use of the G- and D-band trends as useful indicators of the origin of carbon in microfossils. Before unambiguous biosignatures can be established, further work characterizing the carbonaceous material in microfossils of different ages, thermal histories, and host rock compositions is needed.

The neutron imaging diagnostic at NIF (invited).

A neutron imaging diagnostic has recently been commissioned at the National Ignition Facility (NIF). This new system is an important diagnostic tool for inertial fusion studies at the NIF for measuring the size and shape of the burning DT plasma during the ignition stage of Inertial Confinement Fusion (ICF) implosions. The imaging technique utilizes a pinhole neutron aperture, placed between the neutron source and a neutron detector. The detection system measures the two dimensional distribution of neutrons passing through the pinhole. This diagnostic has been designed to collect two images at two times. The long flight path for this diagnostic, 28 m, results in a chromatic separation of the neutrons, allowing the independently timed images to measure the source distribution for two neutron energies. Typically the first image measures the distribution of the 14 MeV neutrons and the second image of the 6-12 MeV neutrons. The combination of these two images has provided data on the size and shape of the burning plasma within the compressed capsule, as well as a measure of the quantity and spatial distribution of the cold fuel surrounding this core.

Progress toward the development and testing of source reconstruction methods for NIF neutron imaging.

Development of analysis techniques for neutron imaging at the National Ignition Facility is an important and difficult task for the detailed understanding of high-neutron yield inertial confinement fusion implosions. Once developed, these methods must provide accurate images of the hot and cold fuels so that information about the implosion, such as symmetry and areal density, can be extracted. One method under development involves the numerical inversion of the pinhole image using knowledge of neutron transport through the pinhole aperture from Monte Carlo simulations. In this article we present results of source reconstructions based on simulated images that test the methods effectiveness with regard to pinhole misalignment.

Modeling the National Ignition Facility neutron imaging system.

Numerical modeling of the neutron imaging system for the National Ignition Facility (NIF), forward from calculated target neutron emission to a camera image, will guide both the reduction of data and the future development of the system. Located 28 m from target chamber center, the system can produce two images at different neutron energies by gating on neutron arrival time. The brighter image, using neutrons near 14 MeV, reflects the size and symmetry of the implosion "hot spot." A second image in scattered neutrons, 10-12 MeV, reflects the size and symmetry of colder, denser fuel, but with only ∼1%-7% of the neutrons. A misalignment of the pinhole assembly up to ±175 µm is covered by a set of 37 subapertures with different pointings. The model includes the variability of the pinhole point spread function across the field of view. Omega experiments provided absolute calibration, scintillator spatial broadening, and the level of residual light in the down-scattered image from the primary neutrons. Application of the model to light decay measurements of EJ399, BC422, BCF99-55, Xylene, DPAC-30, and Liquid A suggests that DPAC-30 and Liquid A would be preferred over the BCF99-55 scintillator chosen for the first NIF system, if they could be fabricated into detectors with sufficient resolution.

An actualistic perspective into Archean worlds - (cyano-)bacterially induced sedimentary structures in the siliciclastic Nhlazatse Section, 2.9 Ga Pongola Supergroup, South Africa.

Extensive microbial mats colonize sandy tidal flats that form along the coasts of today's Earth. The microbenthos (mainly cyanobacteria) respond to the prevailing physical sediment dynamics by biostabilization, baffling and trapping, as well as binding. This biotic-physical interaction gives rise to characteristic microbially induced sedimentary structures (MISS) that differ greatly from both purely physical structures and from stromatolites. Actualistic studies of the MISS on modern tidal flats have been shown to be the key for understanding equivalent fossil structures that occur in tidal and shelf sandstones of all Earth ages. However, until now the fossil record of Archean MISS has been poor, and relatively few specimens have been found. This paper describes a study location that displays a unique assemblage with a multitude of exceptionally preserved MISS in the 2.9-Ga-old Pongola Supergroup, South Africa. The 'Nhlazatse Section' includes structures such as 'erosional remnants and pockets', 'multidirected ripple marks', 'polygonal oscillation cracks', and 'gas domes'. Optical and geochemical analyses support the biogenicity of microscopic textures such as filamentous laminae or 'orientated grains'. Textures resembling filaments are lined by iron oxide and hydroxides, as well as clay minerals. They contain organic matter, whose isotope composition is consistent with carbon of biological origin. The ancient tidal flats of the Nhlazatse Section record four microbial mat facies that occur in modern tidal settings as well. We distinguish endobenthic and epibenthic microbial mats, including planar, tufted, and spongy subtypes. Each microbial mat facies is characterized by a distinct set of MISS, and relates to a typical tidal zone. The microbial mat structures are preserved in situ, and are consistent with similar features constructed today by benthic cyanobacteria. However, other mat-constructing microorganisms also could have formed the structures in the Archean tidal flats.

Learning Activities and Third-Year Medical Student Ratings of High Quality Teaching Across Different Clerkships.

OBJECTIVE: To identify and compare learning activities that students associate with high quality teaching across clerkships. METHODS: For six months, 110 third year medical students recorded data on learning activities and teaching quality using personal digital assistants (PDAs) during five different required clinical clerkships. Univariate and multivariate analyses were performed to assess the association between learning activities and student ratings of high teaching quality. RESULTS: 11,450 teaching interactions were recorded. Univariate analysis revealed that feedback was associated with perceptions of high quality teaching in all clerkships. Proposing a plan, formulating an assessment and giving an oral case presentation were associated with high quality teaching in 80% of the clerkships (p < 0.01). Multivariate analysis demonstrated that receiving high quality feedback was an independent predictor of student ratings of high quality teaching for all clerkships. CONCLUSION: Receiving high quality feedback is the learning activity most strongly associated with students' ratings of high quality teaching across four different clerkships.

Designing and implementing E-health Applications in the UK's National Health Service.

Telemedicine/e-health applications have the potential to play an important role in Britain's National Health Service (NHS), including the NHS in Scotland. The Scottish Telemedicine Action Forum (STAF) was established by the Scottish Executive Department of Health in 1999 to take a range of applications, targeted on national priorities, into routine service. In the process it has provided insights into how advanced information and communication technologies (ICTs) can be moved from the research stage into routine service. In this article four of the projects are described and analysed focusing on the key issues that have emerged as critical for carrying projects successfully through to implementation in service as follows: 1. A multisite videoconferencing network linking 15 minor injury units to the main accident and emergency (A&E) centre. 2. A single-site neonatal intensive care "cotside" laptop system to assist communication between parents and clinical staff. 3. A single-site outpatient chronic disease management system. 4. A multisite software audit tool to support the care of cleft lip and palate patients from birth onward.

Implementation of videoconferencing to support a managed clinical network in Scotland: lessons learned during the first 18 months.

Managed clinical networks (MCNs) are usually built on established groups of health professionals from both acute and primary care sectors. We have used videoconferencing to support the gynaecological oncology MCN in the west of Scotland. Videoconferencing was implemented simultaneously at five sites in 2001 and DICOM image-capture software was added in 2003. Videoconferencing and live PC links allowed the multidisciplinary teams to discuss individual cancer diagnoses without the extensive travelling previously required. Our experience of the implementation suggests that local ownership is crucial. In the present project, each of the stakeholders had an important role in the delivery of a successful system. High-quality project management is required during implementation and for some time thereafter to achieve sustainability.

Understanding the careers of physician educators in family medicine.

PURPOSE: Little is known about what contributes to the career decisions of physician educators in family medicine. This study sought to understand the variables that influence these decisions and to identify key sources of vitality for physician educators in family medicine. METHOD: A national sample of randomly selected physician educators in family medicine responded to a postcard survey regarding their contribution(s) to education and career satisfaction. A series of exclusion criteria were applied to 399 useable responses, yielding 24 physician educators who participated in a semi-structured telephone interview focusing on their careers. Using qualitative research methods, themes were identified and categorized from the transcribed interviews and investigators' field notes. RESULTS: The career decisions and actions of physician educators in family medicine emanated from an underlying set of values and beliefs associated with "making the world better." Participants sought challenging, diverse, and stimulating positions from which they could have an impact in ways that were consistent with their values. Three major sources of vitality (learners, colleagues, and patients) complemented the desire for challenging positions. Physician educators in family medicine, however, continually struggled to balance their personal and professional lives. CONCLUSION: The study results highlight the key variables that draw faculty into education and sustain their vitality, and the professional and personal challenges that can derail or support their careers. This information can be used to recruit, develop, and retain successful and productive physician educators in family medicine.

Coping with dementia: evaluation of four nonpharmacologic interventions.

To evaluate nonpharmacologic interventions, caregivers (65 women, 38 men) and their dementia-diagnosed spouses (patients) were randomized to one of four treatment programs (cognitive stimulation, dyadic counseling, dual supportive seminar, and early-stage day care) or to a wait-list control group. Assessments occurred initially and at postintervention (3 months). Patients were evaluated on memory, verbal fluency, and problem-solving ability, and caregivers were assessed on marital interaction, emotional status, and physical health, along with stress, coping, and social support. Caregivers also completed a program evaluation. Repeated measures procedures showed that patients in the cognitive stimulation group demonstrated more improvement over time in cognitive outcomes, and caregivers decreased in depressive symptoms. Early-stage day-care and dual supportive seminar group caregivers reported a decrease in hostility and a decrease in use of negative coping strategies, respectively. Although qualitatively derived benefits differed across groups, similarities in program content reduced the potential for quantitative differentiation among the groups.