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PubMedDate not supplied

Real-time optimal adaptation for planetary geometry and texture: 4-8 tile hierarchies.

The real-time display of huge geometry and imagery databases involves view-dependent approximations, typically through the use of precomputed hierarchies that are selectively refined at runtime. A classic motivating problem is terrain visualization in which planetary databases involving billions of elevation and color values are displayed on PC graphics hardware at high frame rates. This paper introduces a new diamond data structure for the basic selective-refinement processing, which is a streamlined method of representing the well-known hierarchies of right triangles that have enjoyed much success in real-time, view-dependent terrain display. Regular-grid tiles are proposed as the payload data per diamond for both geometry and texture. The use of 4-8 grid refinement and coarsening schemes allows level-of-detail transitions that are twice as gradual as traditional quadtree-based hierarchies, as well as very high-quality low-pass filtering compared to subsampling-based hierarchies. An out-of-core storage organization is introduced based on Sierpinski indices per diamond, along with a tile preprocessing framework based on fine-to-coarse, same-level, and coarse-to-fine gathering operations. To attain optimal frame-to-frame coherence and processing-order priorities, dual split and merge queues are developed similar to the Realtime Optimally Adapting Meshes (ROAM) Algorithm, as well as an adaptation of the ROAM frustum culling technique. Example applications of lake-detection and procedural terrain generation demonstrate the flexibility of the tile processing framework.

Algorithms↗
PubMedDate not supplied

Finite element analysis of deflections in major connectors for maxillary RPDs.

PURPOSE: The effect of major connector design on deflection in maxillary removable partial denture (RPD) frameworks under simulated occlusal loading was analyzed by means of three-dimensional finite element models. MATERIALS AND METHODS: Thirteen maxillary major connectors were produced for a Kennedy Class II case. Eleven frameworks consisted of posterior palatal straps with different anteroposterior widths at the midline. Anteroposterior and horseshoe bars were also constructed for comparison. In each framework, the occlusal rest on the abutment adjacent to the edentulous ridge was fixed in a vertical direction, and the rest on the contralateral side was fixed in all directions. A biting force of 20 N was vertically distributed simultaneously on each of the three missing posterior teeth locations. RESULTS: For the posterior palatal straps, the maximum vertical displacement at the saddle and the buccal displacement at both the saddle and the rest adjacent to the saddle decreased as their connector width increased from 6 to 29 mm, whereas maximum distal displacements were insensitive to the connector width. The posterior straps with anteroposterior widths of more than 18 mm revealed comparable rigidity to the anteroposterior bar. The horseshoe bar and the posterior straps with smaller widths demonstrated greater displacements than the other frameworks. CONCLUSION: The rigid connectors proved to be the most effective in transmitting applied occlusal forces to the contralateral side of the framework.

Bite Force↗
PubMed1989

Adapting IAIMS to a hospital library level.

The Children's Hospital of Michigan Medical Library has adapted several of the Integrated Academic Information Management Systems (IAIMS) concepts and implemented them at a hospital library level. These have included features of network development, electronic interfacing and interlinking, and implementing an integrated information system in the library. The library has incorporated several information systems into library operations, including a variety of in-house, local, and national automated systems and telecommunication networks. Hospital libraries can incorporate IAIMS features and promote an institutional framework of interconnecting communication systems and electronic linkages.

Computer Communication Networks↗
PubMed1998

Computational space reduction and parallelization of a new clustering approach for large groups of sequences.

MOTIVATION: The explosive growth of the biological sequences databases stimulated by genome projects has modified the framework of several applications in the biological sequence analysis area. In most cases, this new scenario is characterized by studies on large sets of sequences, suggesting the need for effective and automatic methods for their clustering. A more effective clustering of the database could be followed by the application of common family analysis schemes to the groups so formed. RESULTS: In this work, we present a new strategy to reduce the computational cost associated with the clustering of large sets of sequences which are expected to contain several families. The strategy is based on the grouping of the sequences into families by using a dynamic threshold on a pairwise sequence similarity criterion. Routine clustering of large data sets can now be done very efficiently. The method developed here achieves a computational space reduction of about an order of magnitude over more traditional ones of all-versus-all comparisons. The outcome of this approach produces family groupings that reproduce closely already accepted biological results. Our work includes a parallel implementation for distributed memory multiprocessors with a dynamic scheduling strategy for performance optimization. AVAILABILITY: By anonymous ftp at ftp.ac.uma.es (/pub/ots/pCluster directory), or from our Web site http://www.cnb. uam.es/www/software/software_index.html CONTACT: ots@ac.uma.es

Algorithms↗
PubMed2004

Removing a barrier to computer-based outbreak and disease surveillance--the RODS Open Source Project.

INTRODUCTION: Computer-based outbreak and disease surveillance requires high-quality software that is well-supported and affordable. Developing software in an open-source framework, which entails free distribution and use of software and continuous, community-based software development, can produce software with such characteristics, and can do so rapidly. OBJECTIVES: The objective of the Real-Time Outbreak and Disease Surveillance (RODS) Open Source Project is to accelerate the deployment of computer-based outbreak and disease surveillance systems by writing software and catalyzing the formation of a community of users, developers, consultants, and scientists who support its use. METHODS: The University of Pittsburgh seeded the Open Source Project by releasing the RODS software under the GNU General Public License. An infrastructure was created, consisting of a website, mailing lists for developers and users, designated software developers, and shared code-development tools. These resources are intended to encourage growth of the Open Source Project community. Progress is measured by assessing website usage, number of software downloads, number of inquiries, number of system deployments, and number of new features or modules added to the code base. RESULTS: During September--November 2003, users generated 5,370 page views of the project website, 59 software downloads, 20 inquiries, one new deployment, and addition of four features. CONCLUSIONS: Thus far, health departments and companies have been more interested in using the software as is than in customizing or developing new features. The RODS laboratory anticipates that after initial installation has been completed, health departments and companies will begin to customize the software and contribute their enhancements to the public code base.

Disease Outbreaks↗
PubMedDate not supplied

A framework for the transition from nursing records to a nursing information system.

The future of patient record keeping is being developed now. Critical aspects are in place with the development of computer communication standards for health care. The Institute of Medicine's report on the computerized patient record has galvanized many in the health care field to rethink their methods of record keeping. Nurses need to examine the history of the nursing record and look toward the development of a comprehensive nursing information system. Nurses, along with the other disciplines, must examine what they want the system of the future to encompass. A suggested framework for the information system has four major nursing components: (1) data storage component, (2) transaction log, (3) nursing decision support systems, and (4) an engine to link and combine the first three components and to present a consistent easy-to-use interface to the nurse. Done properly, this approach will reduce the amount of time nurses spend charting, add dimension to their notation, and increase the efficiency of data usage for clinical practice. The nursing information system must allow information availability in a manner that accentuates quality practice while releasing the nurse from time-consuming record keeping. These goals are possible to meet, but only if nurses plan for the design now, before it becomes a fait accompli.

Databases, Factual↗
PubMed2005

Hippocampal theta rhythms from a computational perspective: code generation, mood regulation and navigation.

In this paper three computer models are summarized discussing different functions of the cortico-hippocampal system. Mood regulation, rhythm and code generation and navigation are integrated into a coherent conceptual framework around the concepts of structural hierarchy and circular causality. First, a model of spatio-temporal code generation is reviewed in which the hippocampal population theta rhythm plays an important role. Next, generation and pharmcological modulation of this rhythm is examined using a computer model of multiple cell populations forming a feed-back loop within the hippocampus and between the septum and the hippocampus. Last, an abstract, but biologically motivated model of navigation is described which achieves a near optimal mode of navigation by composing hierarchical levels of the cortico-hippocampal system. The connections among the different hierarchical structures of the cortico-hippocampal organization and their functional roles are discussed.

Affect↗
PubMed2006

InSilicoSpectro: an open-source proteomics library.

We present a new proteomics open-source project, InSilicoSpectro, aimed at implementing recurrent computations that are necessary for proteomics data analysis. Illustrative examples are mass list file format conversions, protein sequence digestion, theoretical peptide and fragment mass computations, graphical display, matching with experimental data, isoelectric point estimation, and peptide retention time prediction. The project library is written in Perl, a widely used scripting language in bioinformatics, and it offers a unique framework of integrated objects to implement complex proteomics data analyses. For instance, only a few lines of code are required to digest a protein with fixed and variable modifications, label peptides with 18O, compute the fragmentation spectra and display their match with experimental spectra. We believe that InSilicoSpectro will be of great help to bioinformaticians, without detailed knowledge of proteomics specifics, and to mass spectrometrists with computer programming interest as well.

Amino Acid Sequence↗
PubMed2000

Linear classification of low-resolution EEG patterns produced by imagined hand movements.

Electroencephalograph (EEG)-based brain-computer interfaces (BCI's) require on-line detection of mental states from spontaneous EEG signals. In this framework, surface Laplacian (SL) transformation of EEG signals has proved to improve the recognition scores of imagined motor activity. The results we obtained in the first year of an European project named adaptive brain interfaces (ABI) suggest that: 1) the detection of mental imagined activity can be obtained by using the signal space projection (SSP) method as a classifier and 2) a particular type of electrodes can be used in such a BCI device, reconciling the benefits of SL waveforms and the need for the use of few electrodes. Recognition of mental activity was attempted on both raw and SL-transformed EEG data from five healthy people performing two mental tasks, namely imagined right and left hand movements.

Adult↗
PubMed2001

Learning to consult with computers.

OBJECTIVE: To develop and evaluate a strategy to teach skills and issues associated with computers in the consultation. INTERVENTION: An overview lecture plus a workshop before and a workshop after practice placements, during the 10-week general practice (GP) term in the 5th year of the University of Melbourne medical course. DESIGN: Pre- and post-intervention study using a mix of qualitative and quantitative methods within a strategic evaluation framework. OUTCOME MEASURES: Self-reported attitudes and skills with clinical applications before, during and after the intervention. RESULTS: Most students had significant general computer experience but little in the medical area. They found the workshops relevant, interesting and easy to follow. The role-play approach facilitated students' learning of relevant communication and consulting skills and an appreciation of issues associated with using the information technology tools in simulated clinical situations to augment and complement their consulting skills. The workshops and exposure to GP systems were associated with an increase in the use of clinical software, more realistic expectations of existing clinical and medical record software and an understanding of the barriers to the use of computers in the consultation. CONCLUSIONS: The educational intervention assisted students to develop and express an understanding of the importance of consulting and communication skills in teaching and learning about medical informatics tools, hardware and software design, workplace issues and the impact of clinical computer systems on the consultation and patient care.

Attitude to Computers↗
PubMed2006

Generalized multidimensional scaling: a framework for isometry-invariant partial surface matching.

An efficient algorithm for isometry-invariant matching of surfaces is presented. The key idea is computing the minimum-distortion mapping between two surfaces. For this purpose, we introduce the generalized multidimensional scaling, a computationally efficient continuous optimization algorithm for finding the least distortion embedding of one surface into another. The generalized multidimensional scaling algorithm allows for both full and partial surface matching. As an example, it is applied to the problem of expression-invariant three-dimensional face recognition.

Algorithms↗
PubMed2003

Intermittency in turbulence: computing the scaling exponents in shell models.

We discuss a stochastic closure for the equation of motion satisfied by multiscale correlation functions in the framework of shell models of turbulence. We present a plausible closure scheme to calculate the anomalous scaling exponents of structure functions by using the exact constraints imposed by the equation of motion. We present an explicit calculation for fifth-order scaling exponent by varying the free parameter entering in the nonlinear term of the model. The same method applied to the case of shell models for Kraichnan passive scalar provides a connection between the concept of zero-modes and time-dependent cascade processes.

Journal Article↗
PubMed2004

Framework for evaluation of physiologically-based pharmacokinetic models for use in safety or risk assessment.

Proposed applications of increasingly sophisticated biologically-based computational models, such as physiologically-based pharmacokinetic models, raise the issue of how to evaluate whether the models are adequate for proposed uses, including safety or risk assessment. A six-step process for model evaluation is described. It relies on multidisciplinary expertise to address the biological, toxicological, mathematical, statistical, and risk assessment aspects of the modeling and its application. The first step is to have a clear definition of the purpose(s) of the model in the particular assessment; this provides critical perspectives on all subsequent steps. The second step is to evaluate the biological characterization described by the model structure based on the intended uses of the model and available information on the compound being modeled or related compounds. The next two steps review the mathematical equations used to describe the biology and their implementation in an appropriate computer program. At this point, the values selected for the model parameters (i.e., model calibration) must be evaluated. Thus, the fifth step is a combination of evaluating the model parameterization and calibration against data and evaluating the uncertainty in the model outputs. The final step is to evaluate specialized analyses that were done using the model, such as modeling of population distributions of parameters leading to population estimates for model outcomes or inclusion of early pharmacodynamic events. The process also helps to define the kinds of documentation that would be needed for a model to facilitate its evaluation and implementation.

2-Propanol↗
PubMed2005

Statistical dynamic image reconstruction in state-of-the-art high-resolution PET.

Modern high-resolution PET is now more than ever in need of scrutiny into the nature and limitations of the imaging modality itself as well as image reconstruction techniques. In this work, we have reviewed, analysed and addressed the following three considerations within the particular context of state-of-the-art dynamic PET imaging: (i) the typical average numbers of events per line-of-response (LOR) are now (much) less than unity, (ii) due to the physical and biological decay of the activity distribution, one requires robust and efficient reconstruction algorithms applicable to a wide range of statistics and (iii) the computational considerations in dynamic imaging are much enhanced (i.e., more frames to be stored and reconstructed). Within the framework of statistical image reconstruction, we have argued theoretically and shown experimentally that the sinogram non-negativity constraint (when using the delayed-coincidence and/or scatter-subtraction techniques) is especially expected to result in an overestimation bias. Subsequently, two schemes are considered: (a) subtraction techniques in which an image non-negativity constraint has been imposed and (b) implementation of random and scatter estimates inside the reconstruction algorithms, thus enabling direct processing of Poisson-distributed prompts. Both techniques are able to remove the aforementioned bias, while the latter, being better conditioned theoretically, is able to exhibit superior noise characteristics. We have also elaborated upon and verified the applicability of the accelerated list-mode image reconstruction method as a powerful solution for accurate, robust and efficient dynamic reconstructions of high-resolution data (as well as a number of additional benefits in the context of state-of-the-art PET).

Algorithms↗
PubMed2004

Hydrocode simulations of air and water shocks for facility vulnerability assessments.

Hydrocodes are widely used in the study of explosive systems but their use in routine facility vulnerability assessments has been limited due to the computational resources typically required. These requirements are due to the fact that the majority of hydrocodes have been developed primarily for the simulation of weapon-scale phenomena. It is not practical to use these same numerical frameworks on the large domains found in facility vulnerability studies. Here, a hydrocode formulated specifically for facility vulnerability assessments is reviewed. Techniques used to accurately represent the explosive source while maintaining computational efficiency are described. Submodels for addressing other issues found in typical terrorist attack scenarios are presented. In terrorist attack scenarios, loads produced by shocks play an important role in vulnerability. Due to the difference in the material properties of water and air and interface phenomena, there exists significant contrast in wave propagation phenomena in these two medium. These physical variations also require special attention be paid to the mathematical and numerical models used in the hydrocodes. Simulations for a variety of air and water shock scenarios are presented to validate the computational models used in the hydrocode and highlight the phenomenological issues.

Air↗
PubMed2005

Socio-economic and climate change impacts on agriculture: an integrated assessment, 1990-2080.

A comprehensive assessment of the impacts of climate change on agro-ecosystems over this century is developed, up to 2080 and at a global level, albeit with significant regional detail. To this end an integrated ecological-economic modelling framework is employed, encompassing climate scenarios, agro-ecological zoning information, socio-economic drivers, as well as world food trade dynamics. Specifically, global simulations are performed using the FAO/IIASA agro-ecological zone model, in conjunction with IIASAs global food system model, using climate variables from five different general circulation models, under four different socio-economic scenarios from the intergovernmental panel on climate change. First, impacts of different scenarios of climate change on bio-physical soil and crop growth determinants of yield are evaluated on a 5' X 5' latitude/longitude global grid; second, the extent of potential agricultural land and related potential crop production is computed. The detailed bio-physical results are then fed into an economic analysis, to assess how climate impacts may interact with alternative development pathways, and key trends expected over this century for food demand and production, and trade, as well as key composite indices such as risk of hunger and malnutrition, are computed. This modelling approach connects the relevant bio-physical and socio-economic variables within a unified and coherent framework to produce a global assessment of food production and security under climate change. The results from the study suggest that critical impact asymmetries due to both climate and socio-economic structures may deepen current production and consumption gaps between developed and developing world; it is suggested that adaptation of agricultural techniques will be central to limit potential damages under climate change.

Agriculture↗
PubMed2006

Cancer outcomes measurement: Through the lens of the Medical Outcomes Trust framework.

BACKGROUND: In 2001, the U.S. National Cancer Institute established the Cancer Outcomes Measurement Working Group (COMWG) to evaluate and advance the state of the science in patient-reported outcome (PRO) measurement, with a focus on health-related quality of life (HRQOL). To guide its work, the COMWG adopted the revised Medical Outcomes Trust (MOT) attributes and review criteria for evaluating health status and quality-of-life instruments. OBJECTIVE: With the MOT attributes providing the organizing principle, this paper summarizes and draws inferences from key COMWG findings about the methodological soundness of HRQOL assessment in cancer and steps required to move the field forward. RESULTS AND CONCLUSIONS: Across a range of cancer research applications, especially clinical trials, a variety of generic, general cancer, and cancer site-specific measures of HRQOL have demonstrated adequate reliability, validity, responsiveness, feasibility, and cultural and language adaptation. Methodological challenges remain in the interpretability of HRQOL measures, though substantial progress has been made in defining a "minimum important difference" in scale scores. Much work remains in forging a stronger link between the conceptual model and measurement model in HRQOL instrumentation. Progress along all MOT attributes will likely accelerate with the growing application of modern psychometrics, particularly item response theory modeling, which provides the underpinnings for item banking and computer-adaptive assessment of HRQOL. Future research should emphasize prospectively designed studies to evaluate PRO measures within the MOT framework and in-depth investigations of the role of PRO measures in cancer decision making at all levels.

Endpoint Determination↗