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Scale Changes (scale + change)

Distribution by Scientific Domains

Earth and Environmental Science	33%
Medical Sciences	25%
Life Sciences	16%

Selected Abstracts

Treatment of Acute Stroke with Recombinant Tissue Plasminogen Activator and Abciximab

ACADEMIC EMERGENCY MEDICINE, Issue 12 2003
Daniel C. Morris MD
Objectives: Preclinical data suggest that treatment of acute ischemic stroke (AIS) with the combination of recombinant tissue plasminogen activator (rt-PA) and abciximab may increase efficacy and decrease the rate of symptomatic intracranial hemorrhage (sICH). The authors report pilot data of five AIS patients with half-dose rt-PA and abciximab as part of an ongoing phase I safety trial with sICH as the primary outcome. Methods: Five patients with AIS were treated with the combination of half-dose rt-PA (0.45 mg/kg) and abciximab (0.25 mg/kg bolus followed by a 0.125 ,g/kg/min infusion over 12 hours). Head computed tomographic scan was obtained after 24 hours of treatment onset. Results: Four patients received the combination of half-dose abciximab and rt-PA without major complications. One patient experienced a parenchymal hematoma type-1 ICH without significant decline of his neurological status. The average National Institutes of Health Stroke Scale change at discharge in comparison with pretreatment was ,5.4 ± 7.0, and the median change was 6 points with a range of 4 points (worsening) to ,13 points (improvement) (p = 0.07) based on a one-sided t-test. Conclusions: Administration of rt-PA and abciximab to AIS patients was completed without difficulty. No sICH were observed; however, 20% (1 out of 5) experienced an asymptomatic ICH. Based on our observation of five patients, there was a trend of treatment efficacy; however, these results need to be confirmed in a larger-scale placebo-controlled clinical trial. [source]

ENSO variability, teleconnections and climate change,

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2001
Henry F. Diaz
Abstract An overview is presented of the principal features of the El Niño,Southern Oscillation (ENSO) teleconnections in terms of regional patterns of surface temperature, precipitation and mid-tropospheric atmospheric circulation. The discussion is cast in the context of variations in the associations over time, with decadal scale changes emphasized. In the five decades or so for which we have adequate records to reliably analyse the global aspects of ENSO effects on regional climates around the world, we have witnessed one major decadal scale change in the overall pattern of sea-surface temperatures (SST) in the global ocean, and concomitant changes in the atmospheric response to those changes. The analysis underscores the connection between low frequency changes in tropical SST, ENSO and decadal scale changes in the general atmospheric circulation, pointing to the complex interplay between the canonical ENSO system, slow changes in SST in the Indo-Pacific over the last century, and long-term changes in the atmospheric circulation itself. Published in 2001 by John Wiley & Sons, Ltd. [source]

PRICING EQUITY DERIVATIVES SUBJECT TO BANKRUPTCY

MATHEMATICAL FINANCE, Issue 2 2006
Vadim Linetsky
We solve in closed form a parsimonious extension of the Black,Scholes,Merton model with bankruptcy where the hazard rate of bankruptcy is a negative power of the stock price. Combining a scale change and a measure change, the model dynamics is reduced to a linear stochastic differential equation whose solution is a diffusion process that plays a central role in the pricing of Asian options. The solution is in the form of a spectral expansion associated with the diffusion infinitesimal generator. The latter is closely related to the Schrödinger operator with Morse potential. Pricing formulas for both corporate bonds and stock options are obtained in closed form. Term credit spreads on corporate bonds and implied volatility skews of stock options are closely linked in this model, with parameters of the hazard rate specification controlling both the shape of the term structure of credit spreads and the slope of the implied volatility skew. Our analytical formulas are easy to implement and should prove useful to researchers and practitioners in corporate debt and equity derivatives markets. [source]

Understanding ,hot-spot' problems in catchments: the need for scale-sensitive measures and mechanisms to secure effective solutions for river management and conservation

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2010
Malcolm Newson
Abstract 1.Regulatory progress in controlling point sources of chemical river pollution has progressively thrown the attention of public policy towards anthropogenic physical impacts, many of which are scaled to the catchment via the runoff/sediment system. At the same time, concern over diffuse chemical pollution has reinforced ,catchment consciousness': land-use and land-management planning and control must be considered to conserve or restore river ecosystem integrity. 2.The scientific, political and legal elements of this scale change are, however, complex and uncertain: ,myths' abound. Landscape-scale consideration of ,pressures' suggests an unequal distribution of regulatory costs and benefits and large uncertainties in the evidence from a ,land-use hydrology' and fluvial geomorphology perspective. 3.,Hydrological connectivity' brings together a number of knowledge themes about catchment spatial organization which facilitate applying mitigation measures to much smaller areas, helping to offset uncertainty and reduce costs. 4.Instead of blanket ,remedies', more practical use is needed of process evidence from hydrology and fluvial geomorphology; this tends to suggest that ,hot-spots' dominate risks and impacts of factors such as leaching, surface flow generation and silt entrainment. 5.Set in a realistic policy framework, from strategic spatial planning to grant-aided best practice, a ,catchment acupuncture' approach to measures provides a cost-effective contribution to improving ecological status and may also increase resilience to the impacts of climate change. 6.The European Union's Water Framework Directive (WFD) encourages ,joined-up thinking' on this issue but it remains to be seen whether spatial scales, structures and concepts already enshrined in the WFD and the relevant UK national policies for land use and nature conservation can be exploited to permit the much-needed practical uptake of this new riparianism. Copyright © 2010 John Wiley & Sons, Ltd. [source]

Length and sex-specific associations between spiny dogfish (Squalus acanthias) and hydrographic variables in the Bay of Fundy and Scotian Shelf

FISHERIES OCEANOGRAPHY, Issue 2 2002
Travis Shepherd
The associations between spiny dogfish (Squalus acanthias) and hydrographic variables (temperature, salinity and depth) were examined in the Bay of Fundy and Scotian Shelf from 1970 to 1998. Data were obtained from standard groundfish bottom trawl surveys. Dogfish sex affected habitat associations. Males were found to occupy bottom water of significantly higher salinities and depths than that occupied by females. Length also significantly affected habitat associations. Smaller dogfish occupied relatively deep, high salinity bottom water compared with larger dogfish. Overall, the occupied temperatures, salinities and depths were significantly different from those which were available. Dogfish occupied warmer temperatures along a narrow range (6.62,9.19°C) compared with those which were available (1.57,9.35°C). Occupied salinity (32.70,34.43 ppt) and occupied depth (88.62,184.66 m) were also distributed along a narrower range than available salinity (32.16,34.79 ppt) and available depth (55.00,218.10 m). Sex-specific, length-specific and overall environmental preference by dogfish may bias traditional `offshore' groundfish surveys while large scale changes in hydrographic parameters may alter dogfish distribution and their interactions with other marine fauna. [source]

A semi-analytical estimation of the effect of second-order ionospheric correction on the GPS positioning

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2005
H. Munekane
SUMMARY We developed a semi-analytical method to evaluate the effect of the second-order ionospheric correction on GPS positioning. This method is based on the semi-analytical positioning error simulation method developed by Geiger and Santerre in which, assuming the continuous distribution of the satellites, a normal equation is formed to estimate the positioning error taking all the contributions of the ranging error by the visible satellites into account. Our method successfully reproduced the averaged time-series of three IGS sites which is comparable to the rigorous simulation. We then evaluated the effect of the ionospheric error on the determination of the reference frame. We evaluated the additional Helmert parameters that are required for the ionospheric effect. We found that the ionospheric effect can lead to annual scale changes of 0.1 ppb, with an offset of 1.8 mm and a semi-annual oscillation of 1 mm in the z -direction. However, these values are too small to explain the current deviations between the GPS-derived reference frame and the ITRF reference frame. Next, we estimated the apparent scale changes due to the ionospheric error in the GEONET coordinate time-series in Japan. We could qualitatively reproduce the observed semi-annual scale changes peaking at the equinoxes and having asymmetrical amplitudes between the vernal and autumnal equinoxes. [source]

A Comparison of Clinically Important Differences in Health-Related Quality of Life for Patients with Chronic Lung Disease, Asthma, or Heart Disease

HEALTH SERVICES RESEARCH, Issue 2 2005
Kathleen W. Wyrwich
Objective. On the eight scales of the Medical Outcomes Study Short-Form 36-Item Health Survey (SF-36), Version 2, we compared the clinically important difference (CID) thresholds for change over time developed by three separate expert panels of physicians with experience in quality of life assessment among patients with chronic obstructive pulmonary disease (COPD), asthma, and heart disease. Study Design. We used a modified Delphi technique combined with a face-to-face panel meeting within each disease to organize and conduct the consensus process among the expert panelists, who were familiar with the assessment and evaluations of health-related quality of life (HRQL) measures among patients with the panel-specific disease. Principal Findings. Each of the expert panels first determined the magnitude of the smallest numerically possible change on each SF-36 scale, referred to as a state change, and then built their CIDs from this metric. All three panels attained consensus on the scale changes that constituted small, moderate, and large clinically important SF-36 change scores. The CIDs established by the heart disease panel were generally greater than the CIDs agreed on by the asthma and COPD panels. Conclusions. These panel-derived thresholds reflect possible differences in disease management among the represented panel-specific diseases, and are all greater than the minimal CID thresholds previously developed for the SF-36 scales among patients with arthritis. If confirmed among patients with the relevant diseases and those patients' physicians, these disease-specific CIDs could assist both researchers and practicing clinicians in the use and interpretation of HRQL changes over time. [source]

ENSO variability, teleconnections and climate change,

Two-dimensional occluded object matching using petri nets

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 3 2002
Chuan Zhou
This article discusses the use of Petri nets to model the process of object matching between an image and a model under different two-dimensional geometric transformations. This transformation finds its applications in sensor-based robot control, flexible manufacturing systems, industrial inspection, and so on. Its topological structure relation, called point-line relation structure (PLRS), presents a Petri net-based description approach for object structure. It has been shown how Petri nets can be used to model the matching process, and an optimal or near optimal matching can be obtained by tracking the reachability graph of the net. The experiment result shows that objects can be successfully identified and located under two-dimensional transformation such as translations, rotations, scale changes, and distortions due to partial object occlusion. © 2002 Wiley Periodicals, Inc. [source]

A higher-order PDE-based image registration approach

NUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 5 2006
Volker Grimm
Abstract This paper addresses the problem of image registration with higher-order partial differential equation (PDE) methods. From the study of existing affine-linear and non-linear methods, a new framework is proposed that unifies common image registration methods within a generic formulation. Currently image registration strategies are classified into either affine-linear or non-linear methods subject to the underlying transformations. The new approach combines both strategies to obtain proper approximations which are invariant under global geometrical distortion (shearing), anisotropic resolution (scale changes), as well as rotation and translation. To achieve this favourable property, a modified gradient flow approach is proposed which uses an operator with a kernel consisting of affine-linear transformations. An approximation with finite differences leads to a large singular linear system. The pseudo-inverse solution of this system can be computed efficiently by augmenting the singular system to a regular system. Numerical experiments show the improvements compared to unmodified gradient flow approaches. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Junk-food in marine ecosystems

OIKOS, Issue 7 2008
Henrik Österblom
The abundance and availability of food are critical determininants of reproductive success and population dynamics of marine top predators. However, recent work has indicated that the quality of the food may also be critically important for some marine predators. The ,junkfood hypothesis' was originally suggested as a potential explanation for a dramatic population decline of Stellers sea lions Eumetopias jubatus in the Gulf of Alaska. According to the hypothesis, a dietary switch to prey of low energy content led to detrimental effects on the population of sea lions. A number of observations indicate that the hypothesis is relevant for several population parameters. Recent work on piscivorous seabirds has provided substantial evidence indicating the relevance of this hypothesis in food webs in e.g. the North Pacific, the North Sea and the Baltic Sea. The emergence of ,junk-food' in these systems may be coupled to large scale changes in climatological and oceanographic forcing, although predation, fishing and competition provide additional plausible hypotheses. It may be possible to predict which kinds of animals will be particularly sensitive to food quality; these seem to be species with limited ability to carry food loads, with energetically-expensive foraging behaviour, and with digestive anatomy evolved to minimize mass at the cost of digestive efficiency. This review suggests that the junk-food hypothesis is a highly relevant factor in relation to sustaining ecosystem resilience, and is an important consideration in ecosystem management. Sustaining healthy populations of marine top-predators requires an understanding of the role of food quality, in addition to food abundance and availability. [source]

Ethics and Genetic Selection in Purebred Dogs

REPRODUCTION IN DOMESTIC ANIMALS, Issue 1 2003
VN Meyers-Wallen
Contents There is an ongoing revolution in medicine that is changing the way that veterinarians will be counselling clients regarding inherited disorders. Clinical applications will emerge rapidly in veterinary medicine as we obtain new information from canine and comparative genome projects (Meyers-Wallen 2001: Relevance of the canine genome project to veterinary medical practice. International Veterinary Information Service, New York). The canine genome project is described by three events: mapping markers on canine chromosomes, mapping gene locations on canine chromosomes (Breen et al. 2001: Genome Res. 11, 1784,1795), and obtaining the nucleotide sequence of the entire canine genome. Information from such research has provided a few DNA tests for single gene mutations [Aguirre 2000: DNA testing for inherited canine diseases. In: Bonagura, J (ed), Current Veterinary Therapy XIII. Philadelphia WB Saunders Co, 909,913]. Eventually it will lead to testing of thousands of genes at a time and production of DNA profiles on individual animals. The DNA profile of each dog could be screened for all known genetic disease and will be useful in counselling breeders. As part of the pre-breeding examination, DNA profiles of prospective parents could be compared, and the probability of offspring being affected with genetic disorders or inheriting desirable traits could be calculated. Once we can examine thousands of genes of individuals easily, we have powerful tools to reduce the frequency of, or eliminate, deleterious genes from a population. When we understand polygenic inheritance, we can potentially eliminate whole groups of deleterious genes from populations. The effect of such selection on a widespread basis within a breed could rapidly improve health within a few generations. However, until we have enough information on gene interaction, we will not know whether some of these genes have other functions that we wish to retain. And, other population effects should not be ignored. At least initially it may be best to use this new genetic information to avoid mating combinations that we know will produce affected animals, rather than to eliminate whole groups of genes from a population. This is particularly important for breeds with small gene pools, where it is difficult to maintain genetic diversity. Finally, we will eventually have enough information about canine gene function to select for specific genes encoding desirable traits and increase their frequencies in a population. This is similar to breeding practices that have been applied to animals for hundreds of years. The difference is that we will have a large pool of objective data that we can use rapidly on many individuals at a time. This has great potential to improve the health of the dog population as a whole. However, if we or our breeder clients make an error, we can inadvertently cause harm through massive, rapid selection. Therefore, we should probably not be advising clients on polygenic traits or recommend large scale changes in gene frequencies in populations until much more knowledge of gene interaction is obtained. By then it is likely that computer modelling will be available to predict the effect of changing one or several gene frequencies in a dog population over time. And as new mutations are likely to arise in the future, these tools will be needed indefinitely to detect, treat and eliminate genetic disorders from dog populations. Information available from genetic research will only be useful in improving canine health if veterinarians have the knowledge and skills to use it ethically and responsibly. There is not only a great potential to improve overall canine health through genetic selection, but also the potential to do harm if we fail to maintain genetic diversity. Our profession must be in a position to correctly advise clients on the application of this information to individual dogs as well as to populations of dogs, and particularly purebred dogs. [source]