Rapid Updates Research Articles

A review of fishery-independent assessment models, and initial evaluation based on simulated data

Large uncertainties in catch data (officially-reported landings and discards) are undermining the ability of scientific organisations to provide valid management advice based on the conventional approach of analytical stock assessments. There is thus an urgent need to consider alternative tools that do not depend on long series of precise age-structured catch data. This paper presents four fishery-independent assessment models developed under the EU project FISBOAT (Fishery Independent Survey Based Operational Assessment Tools). It also reports on rudimentary tests based on simulated data, using the same data sets and protocol as an evaluation study conducted by the US National Research Council in 1997. The survey-based assessment models at hand are able to reliably capture the major signal in biomass and recruitment, although they smooth out transient changes. However, they cannot provide absolute abundance estimates, only relative values on an arbitrary scale. The survey-based approaches could provide more rapid updates of the state of stocks than catch-based methods.

RrnDB: documenting the number of rRNA and tRNA genes in bacteria and archaea

A dramatic exception to the general pattern of single-copy genes in bacterial and archaeal genomes is the presence of 1–15 copies of each ribosomal RNA encoding gene. The original version of the Ribosomal RNA Database (rrnDB) cataloged estimates of the number of 16S rRNA-encoding genes; the database now includes the number of genes encoding each of the rRNAs (5S, 16S and 23S), an internally transcribed spacer region, and the number of tRNA genes. The rrnDB has been used largely by microbiologists to predict the relative rate at which microbial populations respond to favorable growth conditions, and to interpret 16S rRNA-based surveys of microbial communities. To expand the functionality of the rrnDB (http://ribosome.mmg.msu.edu/rrndb/index.php), the search engine has been redesigned to allow database searches based on 16S rRNA gene copy number, specific organisms or taxonomic subsets of organisms. The revamped database also computes average gene copy numbers for any collection of entries selected. Curation tools now permit rapid updates, resulting in an expansion of the database to include data for 785 bacterial and 69 archaeal strains. The rrnDB continues to serve as the authoritative, curated source that documents the phylogenetic distribution of rRNA and tRNA genes in microbial genomes.

Eurosurveillance moves on…

From this issue of Eurosurveillance, the two previous electronic releases (weekly and monthly) of the journal have been merged into one. The new Eurosurveillance is published every Thursday, with rapid updates on major public health events and news items alongside longer scientific articles and reviews. At the same time we are updating our editorial policy (http://www.eurosurveillance.org/editorial_policy/index.asp) and reviewing the types of articles (http://www.eurosurveillance.org/authors/index.asp) to better reflect our commitment to covering all aspects of epidemiology, prevention and control of communicable diseases from a European perspective.

Transforming the traditional discharge planning manual

Discharge planning resources change frequently, and keeping them current, available, and accessible to case management (CM) staff and others is a challenge. Given the time-consuming and labor-intensive nature of updating, many organizations revise them in preparation for the tri-annual survey or when they are hopelessly out-of-date. The reality is that CM staff and others involved with discharges have their own personal "little black book" of resources. Those personal reference tools are treated with reverence and guarded like the family Bible. Organizations are challenged to have up-to-date resources available and accessible for staff in all areas. One approach is to transform the traditional paper-based manual into an electronic document and make it available on the organization's intranet. This approach means that each page of the current paper-based manual must be in electronic format, ending the use of overcopied resources that become difficult to read and "grandfathered in" to each successive edition of the paper manual. This option permits easy and rapid updates when resources and information change.

Biosonar performance of foraging beaked whales (Mesoplodon densirostris)

Toothed whales (Cetacea, odontoceti) emit sound pulses to probe their surroundings by active echolocation. Non-invasive, acoustic Dtags were placed on deep-diving Blainville's beaked whales (Mesoplodon densirostris) to record their ultrasonic clicks and the returning echoes from prey items, providing a unique view on how a whale operates its biosonar during foraging in the wild. The process of echolocation during prey capture in this species can be divided into search, approach and terminal phases, as in echolocating bats. The approach phase, defined by the onset of detectable echoes recorded on the tag for click sequences terminated by a buzz, has interclick intervals (ICI) of 300-400 ms. These ICIs are more than a magnitude longer than the decreasing two-way travel time to the targets, showing that ICIs are not given by the two-way-travel times plus a fixed, short lag time. During the approach phase, the received echo energy increases by 10.4(+/-2) dB when the target range is halved, demonstrating that the whales do not employ range-compensating gain control of the transmitter, as has been implicated for some bats and dolphins. The terminal/buzz phase with ICIs of around 10 ms is initiated when one or more targets are within approximately a body length of the whale (2-5 m), so that strong echo returns in the approach phase are traded for rapid updates in the terminal phase. It is suggested that stable ICIs in the search and approach phases facilitate auditory scene analysis in a complex multi-target environment, and that a concomitant low click rate allows the whales to maintain high sound pressure outputs for prey detection and discrimination with a pneumatically driven, bi-modal sound generator.

Global and Local Precipitation Measurements by Radar

The detection and measurement of precipitation by radar has been pursued since its introduction as a meteorological tool. The main advantage of using radar for precipitation estimation is that measurements can be made over large areas, with either fairly high temporal and spatial resolution or extensive spatial coverage (about 10 000 km2 for ground-based radars and an order of magnitude more for space-based radars). To sample the area covered by a typical ground-based radar, substituting each radar spatial sample with a rain gauge, would require about a quarter-million gauges. Using a similar analogy to space radars, nearly one-half-million gauges would be required per orbit. Since the radar transmitter and receiver normally use the same antenna (monostatic operation), the measurements are sent to a central location at the speed of light by “natural wireless networks.” In addition, radars can provide fairly rapid updates of the three-dimensional structure of precipitation. Because of these advantages, radar measurements of precipitation have enjoyed widespread use for meteorological applications, independent of the accuracy or the type of algorithm used to derive precipitation estimates.

Forest-level models and challenges for their successful application

Significant advances have been made that integrate landscape issues in forest-level models. These advanced models are designed to simulate and evaluate economic, ecological, and social goals that are included in the management of forests. The application of multiple-objective heuristics such as tabu search and simulated annealing, combined with remarkable advances in computing power, now allows us to explore highly complex management scenarios over long time horizons and over vast geographic scales. While the power of these decision support systems is highly appealing, and even intoxicating, we still face three sobering challenges on the path towards generating credible forecasts. First, advanced data acquisition and data management systems are needed to support these systems. Data management systems must have high storage capacity, be capable of rapid updates, and accommodate a seemingly endless demand for queries from customers, government agencies, and the public. Planning is an interdisciplinary, hierarchical process, and team members have different data demands, depending on where they fit in the hierarchy. Second, the models must be verified. Multiple-objective models have dozens of parameters, and when these are combined with random search techniques, they become difficult to understand and replicate. Thorough sensitivity analysis is needed to test model parameters, goal weights, and assumptions of uncertainty. Finally, our ability to formulate and run large-scale, long-term forecasting models often exceeds the scientific credibility of the data, especially for complex forest ecosystems. In the absence of critical thinking, such powerful models can become dangerous weapons.

The influenza vaccine licensing process

Influenza vaccines are unique because they require a licensing process which includes a procedure for rapid annual updates to vaccine strains. The licensing procedures in the European Union and the USA are described as examples. In the event of an influenza pandemic, vaccines will be required urgently and licensing process should reflect such needs.

Stability Analysis of Interconnected Power Systems Coupled with Market Dynamics

The use of market mechanisms to determine generation dispatch, and the natural tendency to seek improved economic efficiency through rapid market updates, raises a critical issue. As the frequency of market-based dispatch updates increases, there will inevitably be interaction between the dynamics of markets determining the generator dispatch commands and the physical response of generators and network interconnections. This paper examines questions of stability in such coupled systems by means of numeric tests using various market update models (including detailed generator/turbine/governor dynamics) for the New England 39 bus test system. The results highlight the nature of potential instabilities and show the interaction modes between physical and market quantities through eigen-analysis. Understanding of potential modes of instability in such coupled systems is crucial both for designing suitable rules for power markets and for designing physical generator controls that are compatible with market-based dispatch.

Incremental Updates for Rapid Glossy Global Illumination

We present an integrated global illumination algorithm including non-diffuse light transport which can handle complex scenes and enables rapid incremental updates. We build on a unified algorithm which uses hierarchical radiosity with clustering and particle tracing for diffuse and non-diffuse transport respectively. We present a new algorithm which chooses between reconstructing specular effects such as caustics on the diffuse radiosity mesh, or special purpose caustic textures, when high frequencies are present. Algorithms are presented to choose the resolution of these textures and to reconstruct the high-frequency non-diffuse lighting effects. We use a dynamic spatial data structure to restrict the number of particles re-emitted during the local modifications of the scene. By combining this incremental particle trace with a line-space hierarchy for incremental update of diffuse illumination, we can locally modify complex scenes rapidly. We also develop an algorithm which, by permitting slight quality degradation during motion, achieves quasi-interactive updates. We present an implementation of our new method and its application to indoors and outdoors scenes.

Optimised real time catheter tracking on a conventional MR Scanner

Commercial high-field magnetic resonance (MR) scanners are generally not equipped with measurement software and hardware to perform interventional studies with active devices that contain small radiofrequency (rf) coils for localisation. In this study, with only minimal modifications to the MR scanner, the active catheter tracking technique is implemented on a clinical MR system. Small rf-coils are attached to a commercial angiography catheter and the movement of the coils is observed with fast MR tracking and imaging techniques. Optimised imaging strategies are explored for both static and moving anatomical regions. Image calculation and display software is implemented using both the MR scanner's fast image reconstruction processor, together with the main console computer and a separate personal computer. With the current implementation, image update rates of up to several Hertz can be achieved, if a roadmap imaging technique is used, where rapid coordinate updates are projected onto previously acquired overview images. To account for cardiac and breathing motion, an interleaved imaging strategy is presented where coordinate and image updates are acquired in rapid succession. With this approach, image update rates of 1–2 Hz are obtained, depending on the details of the image reconstruction process.

Stability analysis of interconnected power systems coupled with market dynamics

The use of market mechanisms to determine generation dispatch, and the natural tendency to seek improved economic efficiency through rapid market updates, raises a critical issue. As the frequency of market-based dispatch updates increases, there will inevitably be interaction between the dynamics of markets determining the generator dispatch commands, and the physical response of generators and network interconnections. This paper examines questions of stability in such coupled systems by means of numeric tests using various market update models, (including detailed generator/turbine/governor dynamics) for the New England 39 bus test system. The results highlight the nature of potential instabilities and show the interaction modes between physical and market quantities through eigen-analysis. Understanding of potential modes of instability in such coupled systems is crucial both for designing suitable rules for power markets, and for designing physical generator controls that are compatible with market-based dispatch.

Methods for providing probe position and temperature information on MR images during interventional procedures.

Interventional magnetic resonance imaging (MRI) can be defined as the use of MR images for guiding and monitoring interventional procedures (e.g., biopsy, drainage) or minimally invasive therapy (e.g., thermal ablation). This work describes the development of a prototype graphical user interface and the appropriate software methods to accurately overlay a representation of a rigid interventional device [e.g., biopsy needle, radio-frequency (RF) probe] onto an MR image given only the probe's spatial position and orientation as determined from a three-dimensional (3-D) localizer used for interactive scan plane definition. This permits 1) "virtual tip tracking," where the probe tip location is displayed on the image without the use of separate receiver coils or a "road map" image data set, and, 2) "extending" the probe to predict its path if it were directly moved forward toward the target tissue. Further, this paper describes the design and implementation of a method to facilitate the monitoring of thermal ablation procedures by displaying and overlaying temperature maps from temperature sensitive MR acquisitions. These methods provide rapid graphical updates of probe position and temperature changes to aid the physician during the actual interventional MRI procedures without altering the usual operation of the MR imager.

Handoffs in Cellular Wireless Networks: The Daedalus Implementation and Experience

Network protocols in cellular wireless data networks must update routes as a mobile host moves between cells. These routing updates combined with some associated state changes are called handoffs. Most current handoff schemes in wireless networks result in data loss or large variations in packet delivery times. Unfortunately, many applications, such as real-time multimedia applications and reliable transport protocols, adapt to long term estimates of end-to-end delay and loss. Violations and rapid fluctuations of these estimates caused by handoff processing often result in degraded performance. For example, loss during handoff adversely affects TCP performance [4], and high packet loss and variable delays result in poor real-time multimedia performance. In this paper, we describe a multicast-based protocol that eliminates data loss and incurs negligible delays during a handoff. The basic technique of the algorithm is to anticipate a handoff using wireless network information in the form of received signal strengths and to multicast data destined for the mobile host to nearby base stations in advance. This routing, combined with intelligent buffering techniques at the base stations, enables very rapid routing updates and eliminates data loss without the use of explicit data forwarding. We have implemented this protocol using IP Multicast and Mobile IP-like routing. In our implementation, handoffs typically take between 8 and 15 ms to complete and result in no data loss.

Imaging temperature changes in an interventional 0.5 T magnet: in-vitro results.

To evaluate the ability of monitoring laser induced temperature changes in an open, interventional 0.5 T magnet, adopting fast T1-weighted sequences. A fast gradient echo- (FGRE) and a fast spoiled gradient echo-sequence (FSPGR), both enabling an image update every 2.5 s, were investigated for their ability to visualize laser tissue effects at 5 Watt. Laser induced temperature was fluorooptically measured and correlated with signal intensity (SI) changes depicted by magnetic resonance imaging (MRI). MRI-lesions were compared with macroscopic findings. SI changes on FGRE images appeared as early as 15 s following the onset of laser application and were significantly more pronounced than those seen on FSPGR images (p < .0001). A correlation of r = 0.94 (FGRE) and r = 0.92 (FSPGR) between temperature and SI loss was established. Owing to a steeper slope, the FGRE sequence was considered more sensitive to temperature changes. The areas of macroscopic tissue change correlated with those of SI loss, but lesion size was generally underestimated by MRI. Laser monitoring is possible with rapid image updates in a midfield (0.5 T) interventional MRI environment using fast gradient echo sequence designs.

Applicability of E-Scan Technology for Future Airport Aviation Weather Radars

Efficiency, capacity, and safety improvements intended to accommodate future air traffic growth will require better predictions of the formation, extent, and movement of hazardous weather in the terminal area airspace. Precise prediction of hazardous weather phenomena such as convective storms, wind shear, and turbulence is a challenging task for meteorological radar to support at affordable cost. Rapid scanning with adequate resolution and improved interference rejection will be required. Although important advances such as Doppler wind measurements have appeared, meteorological radars still use the conventional mechanically scanned antenna and scanning remains constrained by mechanical inertia. This article reviews the current limitations and considers what improvement that might be gained via application of a more advanced antenna technology, that is, the phased array E-Scan antenna. E-Scan’s advantages for military air and space surveillance are well known; but meteorological applications have not been examined fully because the cost was prohibitive for civil systems. However, recent advances indicate that this technology may become affordable for future airport aviation weather radars. The study shows how E-Scan might provide the rapid updates needed for future predictive weather products, facilitate on-airport siting for better coverage, and allow a single radar to efficiently support a number of diverse meteorological functions. The article also assesses various critical risks associated with the introduction of E-Scan. © 1995 John Wiley & Sons, Inc.