bluuebunny/crossref_metadata_2025 huggingface dataset:
Function of the pupil in vision and information capacity of retinal image
Authors: Hirata Yutaka , Yamaji Kazutsuna , Sakai Hiroyuki , Usui Shiro
Published: June 2003

The light–pupil reflex system has been the object of study in physiological engineering, as a typical example of involuntary biological systems. As regards the variable that actually controls the pupil, however, there has been little discussion of its role in vision. This study notes that the pupil is closely related to the spatial frequency response of the eye's optical system, and discusses the relation between the quality of the retinal image and the pupil size, as determined by the external image and the characteristics of the eye's optical system. By defining the information capacity of the retinal image as the evaluation measure, the quality of the retinal image is represented quantitatively. The relation between the pupil size and the information capacity of the retinal image is examined for various conditions. It is shown that the human pupil is controlled so that the quality of the retinal image is optimized, in the sense of the information capacity of the retinal image for each luminance level, when the external image is a natural image. On the other hand, when the external image is not a natural image, or when the characteristic of the eye's optical system or the relation between the visual cell arrangement and the pupillary diameter differs from the actual situation, it is not necessarily true that the pupil optimizes the quality of the retinal image. The above results suggest that the function of the pupil in vision is optimization of the quality of the retinal image. It is also suggested that the adjustment function of the pupillary diameter is acquired under the constraints of the external image and the hardware of the eye. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(9): 48–57, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10344
A cropping‐robust watermarking method based on singular value decomposition and Haar transformation
Authors: Sugiyama Masaharu , Goto Munehiro , Kovács Szilveszter , Matsumoto Tadahiro , Naoi Tohru
Published: June 2003

This paper proposes a new watermarking method which applies SVD (singular value decomposition) to the watermark image and the Haar transformation to the host image, respectively. In this method, relatively important information which corresponds to larger singular values is embedded as near to the center of the low‐frequency component image of the Haar transformed host image as possible. This method is useful in decreasing degradation of the quality of watermarked host images and thus in making the embedded watermark robust to various attacks. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(9): 38–47, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10371
Structuring of medical information networks for secure information interchange and policy matching by combining VPNs with an autonomous decentralized comparison environment architecture
Authors: Kimura Eizen , Uesugi Shirou , Ohnishi Masahito , Tateishi Norihiko , Ishihara Ken
Published: June 2003

In VPN (virtual private networks), security policy and the services provided have hitherto been modeled separately in determining the specifications. The reason is that VPN is generally characterized as a technology for replacing backbone dedicated links, and is regarded as a still‐developing means to provide a secure connection to the end user. One key to the widespread use of VPN in SOHO (small offices and home offices) is integrating the services offered by various service providers from the viewpoint of the user, and providing the services securely. As a model of SOHO, this paper considers the case of various medical services surrounding the physician and his office as the site of medical care actions. The present status of development is analyzed and problems are pointed out. A new combination of autonomous decentralized comparison environment architecture and VPN is proposed. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(9): 27–37, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10403
Distributed credibility evaluation of an information gathering mobile agent system
Authors: Watanabe Yuji , Ishida Yoshiteru
Published: June 2003

A problem specific to mobile agent systems is that the basis of trustworthiness cannot be ensured. Even during the information gathering stage, it may not be possible to gather information correctly if a host computer is providing false information or if the agent has a bug or has been corrupted. In other words, it is important to ascertain where faults can occur or what can be trusted. Although voting methods have already been proposed for these purposes, the waiting or centralized processing required for voting may ruin the distributed characteristic of a mobile agent system. In the present research, the authors use a dynamic relationship network, which is proposed as a distributed diagnosis model, to execute decentralized evaluations of the credibility of each host and agent in an information gathering system. They use simulations to verify the kinds of parameters needed as a basis for performing credibility evaluations appropriately. They also examine test methods for handling information scattering (probability‐based properties). © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(9): 10–19, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10427
Image authentication based on fractal image coding without contamination of original image
Authors: Haseyama Miki , Kondo Isao
Published: June 2003

Several digital watermarking methods proposed for the purpose of copyright protection embed signature data or images in the original images. Thus, they unavoidably produce degradation of the original images. Authors who create art works, however, desire to distribute their own originals unaltered. Therefore, this paper proposes a system for authentication of original images distributed without embedding any watermarks. The proposed method is based on fractal image coding, an image coding method. The IFS parameters obtained in fractal image coding are utilized as authentication parameters, and signature images for authentication are extracted using these parameters. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(9): 1–9, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10468
A porting symbolic dedicated machine by micro program translation
Authors: Amagai Yoshiji
Published: June 2003

A well‐known technique for inheriting the software resources of computers that were used in the past is to emulate the relevant computer's instructions on a modern computer. One method of using this technique is the static translation method in which the relevant program's binary code is translated in advance and executed. Although this method provides good posttranslation execution performance, each application program must be individually translated. In this paper, the computer's hardware itself is reproduced by statically translating the micro program part of the symbolic processing dedicated machine that had provided the micro program control CPU to the C language, enabling all programs on that dedicated machine to be executed on a UNIX computer. In addition to providing powerful emulation capabilities, translating to the C language enables emulations to be easily executed on computers having different architectures. This paper describes the static translation technique and shows the effectiveness of static micro program translation through static and dynamic performance evaluations of the system that was obtained. © 2003 Wiley Periodicals, Inc. Syst Comp Jpn, 34(9): 105–114, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1213
Evaluating factors associated with STD infection in a study with interval‐censored event times and an unknown proportion of participants not at risk for disease
Authors: Taylor Douglas J. , Weaver Mark A. , Roddy Ronald E.
Published: June 2003

Sexually transmitted diseases (STD) are a major cause of morbidity and mortality world‐wide. Because of their association with an increased risk of infection with human immunodeficiency virus, the prevention and control of STD are particularly important. Studies designed to evaluate factors associated with the transmission of STD can pose a number of statistical challenges, however. Two such concerns are the interval‐censored event times that result from spacing between follow‐up test visits, and an unknown proportion of study participants who are not at risk for infection. Researchers in various fields of study have used parametric mixture models to account for individuals not at risk. Owing to non‐identifiability concerns within the mixture model framework, however, it is not always possible to distinguish between effects of explanatory variables on the distribution of event times for at‐risk individuals and their effects on the probability of being at risk. We address these issues using data from a clinical trial designed to investigate the effectiveness of an intravaginal microbicide in preventing male‐to‐female transmission of STD. Factors associated with time to infection among at‐risk women are initially identified by fitting right‐truncated models to the interval‐censored event times of participants who tested positive for STD, and hence are known to have been at risk. Subsequently, factors associated with the probability of being at risk are evaluated using mixture models that incorporate information contributed by the right‐censored event‐free times of uninfected study participants. Copyright © 2003 John Wiley & Sons, Ltd.
Estimating the stenosis probabilities in arteriosclerosis obliterans using generalized estimating equations
Authors: Nakashima Eiji , Tsuji Shuichi , Fukuoka Haruhito , Ohtaki Megu , Ito Katsuhide
Published: June 2003

For each of 211 arteriosclerosis obliterans patients, the degree of stenosis of arteries at four sites were examined at Hiroshima University Hospital to analyse the relationship between the degree of stenosis and age, sex and site. The generalized estimating equations using a proportional odds model for the stenosis probability with exchangeable correlation was applied to this clustered, ordered polytomous data. Since the correlations between the responses were quite small, we could apply the independence estimating equations. The best mean model selected by Akaike information criterion suggested that age dependency of the stenosis probability was not observed in the central sites but was observed in the peripheral sites, and symmetry of the risk of stenosis was seen in the left and right sites. Details of the analysis will be described. Copyright 2003 John Wiley & Sons, Ltd.
An evaluation of methods for the stratified analysis of clustered binary data in community intervention trials
Authors: Song James X. , Ahn Chul W.
Published: June 2003

A simulation study is conducted in a community intervention setting. Several methods of stratified analysis of clustered binary data are compared in terms of empirical significance and empirical power levels. They are the Mantel–Haenszel test statistic (χ2MH), the adjusted Mantel–Haenszel test statistic of Donald–Donner (χ2DD), Rao–Scott (χ2RSN and χ2RSP), and Zhang–Boos (χ2ZBN and χ2ZBP), Wald (χ2W), robust Wald (χ2RW), score (χ2S), robust score (χ2RS), and the test statistic based on generalized linear mixed model (GLMM) (χ2GLMM). When ρ ≠ 0, χ2MH has inflated type I error, and it should not be used when observations are correlated. The results also warn of the use of χ2RSN and χ2RW due to their poor performance in terms of empirical significance level. χ2ZBP and χ2GLMM have better empirical significance levels as compared to other statistics; however, χ2ZBP tends to have lower empirical powers than other statistics when the number of clusters (N) is less than 24. χ2RSP provides the highest empirical powers when ρ ≥ 0.1 and N ≤ 12. When ρ ≤ 0.01, we recommend the use of χ2RS and χ2GLMM since they have better overall performance in terms of empirical significance levels and empirical power levels. Copyright © 2003 John Wiley & Sons, Ltd.
Evaluating medical diagnostic tests at the subunit level in the presence of verification bias
Authors: Barnhart Huiman X. , Kosinski Andrzej S.
Published: June 2003

We advocate that medical diagnostic tests should be evaluated at the subunit level instead of the patient level if a disease can occur in multiple parts/units within a patient, for example, vessels, segments, ears, eyes etc. When a non‐invasive test is compared to an invasive gold standard test, often not all of the subunits receive the gold standard test and verification bias is present if the subunits without the gold standard test are discarded. Here we address estimation and inference issues in assessing the performance of medical diagnostic tests at the subunit level while accounting for verification bias and the correlation among subunits. We present a weighted least squares approach and demonstrate how the method can be implemented by using the procedure PROC CATMOD from the popular SAS software. A cardiology example is presented and we discuss application of the method to the case of multiple tests and a single gold standard test. Copyright© 2003 John Wiley & Sons, Ltd.
Setting the Stage: Adults in Higher Education
Authors: Kasworm Carol E.
Published: June 2003

Who are adult learners in higher education, and how do they differ from younger college students? In this chapter, the author presents an overview of adult student enrollment patterns, their participation motivators, and their lifestyle differences from younger college students.
Multiple Roles of Adult Learners
Authors: Fairchild Ellen E.
Published: June 2003

Adult learners juggle multiple roles while attending institutions of higher education. Adult students' roles and the implications for adults' success in college are discussed in this chapter.
Recruiting and Retaining Adult Students
Authors: Hadfield Janice
Published: June 2003

Adult learners, long the stepchildren of colleges and universities, have nearly become the norm, and they spend billions of dollars each year on education. Have colleges and universities alienated this rich market pool?
Funding Higher Education for Adult Students
Authors: Hatfield Karen M.
Published: June 2003

This chapter is designed to help student services personnel assist adult students to understand and navigate through the financial aid process and to pursue alternative ways of funding their higher education.
Information Technology and Adult Learners at Empire State College
Authors: Lefor Patricia J. , Benke Meg , Ting Evelyn
Published: June 2003

Successful introduction of technology‐delivered education to adult students can be enhanced by attention to program development, reliance on easy‐to‐use technology readily available to a wide range of students, and the parallel development of online learner supports and student services.
Adult Learners in the Classroom
Authors: Ross‐Gordon Jovita M.
Published: June 2003

Theory and research provide insight into the characteristics, needs, and teaching preferences of adult learners in the college classroom.
Adult Student Services Online
Authors: Rice Penny J.
Published: June 2003

Important components of an adult student services office are the focus of this chapter. Examples of outstanding programs are highlighted, and areas of support for institutions at various planning stages of program development are presented.
Adult Graduate Students Challenge Institutions to Change
Authors: Polson Cheryl J.
Published: June 2003

Changing clienteles challenge institutions to respond to their needs. Today's adult graduate student requires expanded attention from student service providers as they move into, through, and out of their graduate experience. Examples of services for the new graduate student are discussed.
Alternative Programming for Adults
Authors: Flint Thomas A. , Frey Ruth
Published: June 2003

The Council for Adult and Experiential Learning is currently cataloguing alternative programming features that are most effective with adult students in a best‐practices inventory organized around a framework of high‐level descriptive principles of effectiveness. This chapter identifies a few interesting features from a quick survey of this alternative programming landscape.
New Directions for Inquiry and Practice
Authors: Kilgore Deborah , Rice Penny J.
Published: June 2003

With an eye to the other contributions in this volume, the authors provide some recommendations for research and practice.
A methodology for modeling VVT risks and costs
Authors: Engel Avner , Barad Miryam
Published: June 2003

The cost of large systems' Verification, Validation, and Testing (VVT) is in the neighborhood of 40% of the total life cycle cost. The cost associated with systems' failures is even more dramatic, often exceeding 10% of industrial organizations turnover. There is a great potential benefit in streamlining and optimizing the VVT process. The first step in accomplishing this aim is to define a VVT strategy and then to quantify the cost and risk associated with carrying it out. This paper provides an overview of the methodologies for risk and cost monitoring for VVT and proposes a novel approach for modeling VVT strategies as decision problems. A quantitative VVT process and risk model is proposed. Due to the nondeterministic nature of risk, simulation is used to generate distributions of possible costs, schedules, and risk outcomes. These distributions represent a probabilistic approach and are analyzed in relation to impact events. The model provides means to explore different VVT strategies for optimizing relevant decision parameters. To demonstrate the proposed procedure the paper describes a case study depicting a planned avionics suite upgrade program for a fighter aircraft. Some simplified partial quantitative results are also presented. © 2003 Wiley Periodicals, Inc. Syst Eng 6: 135–151, 2003
From a single discipline product to a multidisciplinary system: Adapting the right style to the right project
Authors: Dvir Dov , Shenhar Aaron J. , Alkaher Shlomo
Published: June 2003

The premise of this paper is that systems engineering, and project management as well, are all but universal and that different projects should employ different management and organizational styles. While this idea is not new and many managers use their own ways for identifying project differences, this paper offers to use a more formal, research‐based framework for distinction among projects and adapting management style. Using a recently developed conceptual framework for project classification, this study demonstrates that a proper identification of project characteristics and adaptation of a suitable style is critical for success. To illustrate this concept, we analyzed the evolution and lessons learned from a complex high‐tech defense system development project. The project, seen a priori as an extension of previous experience, turned out to be a completely new kind of effort, particularly in terms of complexity and the use of new technology. Management was not ready for this type of task, and it had initially chosen a traditional style that was successfully used by the company in previous projects. It turned out that what worked in the past, does not necessarily apply to all projects. When the project went into serious trouble, it had to be “saved,” by significant reconstruction and changing of management style. The result was extensive budget overrun and substantial delay in delivery. Using the classification framework for distinction among projects, we show that an early and careful analysis of project characteristics during the project conceptual and planning phases could have led management to a different style from inception, and might have helped avoiding many of the difficulties encountered later. We conclude by a set of implications and recommendations to management at large, and system house organizations in particular. © 2003 Wiley Periodicals, Inc. Syst Eng 6: 123–134, 2003 DOI 10.1002/sys.10041
Risk‐based methodology for scenario tracking, intelligence gathering, and analysis for countering terrorism
Authors: Horowitz Barry M. , Haimes Yacov Y.
Published: June 2003

Disruption of a terrorist attack depends on having information facilitating the identification and location of those involved in supporting, planning, and carrying out the attack. Such information arises from myriad sources, such as human or instrument surveillance by intelligence or law enforcement agencies, a variety of documents concerning transactions, and tips from a wide range of occasional observers. Given the enormous amount of information available, a method is needed to cull and analyze only that which is relevant to the task, confirm its validity, and eliminate the rest. The risk‐based methodology for scenario tracking, intelligence gathering, and analysis for countering terrorism builds on the premise that in planning, supporting, and carrying out a terrorist plot, those involved will conduct a series of related activities for which there may be some observables and other acquirable evidence. Those activities taken together constitute a threat scenario. Information consistent with a realistic threat scenario may be useful in thwarting an impending attack. Information not consistent with any such scenario is irrelevant. Thus, the methodology requires a comprehensive set of realistic threat scenarios that would form a systemic process for collecting and analyzing information. It also requires a process for judging the validity and usefulness of such information. The key questions for intelligence gathering and analysis are: how to produce a comprehensive set of threat scenarios, how to winnow that set to a subset of most likely scenarios, what supplementary intelligence is worth pursuing, how to judge the relevance of available information, and how to validate and analyze the information. The methodology presented in this paper can serve as a vehicle with which to enable the intelligence community to better: (a) assess the intent and capabilities of terrorist groups, (b) develop and compare terrorist scenarios from different sources and aggregate the set that should guide decisions on intelligence collection, (c) assess the possible distributions of responsibility for intelligence gathering and analysis across various homeland security agencies at the federal, state, and local levels, and (d) establish effective collection priorities to meet the demands of counterterrorism. Some of the critical issues addressed in this paper include: (1) how to create a reasonably complete set of scenarios and filter it down to a more manageable set to establish intelligence collection priorities, (2) how to integrate the wide variety of intelligence sources associated with monitoring for terrorism and analytically account for the corresponding disparities in information reliability, and (3) how to incorporate these new methodologies into existing information management efforts related to protecting our nation's critical infrastructures. © 2003 Wiley Periodicals, Inc. Syst Eng 6: 152–169, 2003 7
Assessing the reliability of socio‐technical systems
Authors: Gregoriades Andreas , Sutcliffe Alistair , Shin Jae‐Eun
Published: June 2003

This article presents a Bayesian Belief Network (BBN) approach for socio‐technical system reliability assessment. A human error BBN model quantifies error influences arising from user knowledge, ability, and task environment, combined with factors describing the complexity of user action and user interface quality. System reliability evaluation is achieved by the System Reliability Analyser tool, which enables the iterative manipulation of the human error model according to high‐level scenarios. © 2003 Wiley Periodicals, Inc. Syst Eng 6: 210–223, 2003
Analysis and improvement of product modularization methods: Their ability to deal with complex products
Authors: Holmqvist Tobias K.P. , Persson Magnus L.
Published: June 2003

In recent years, product modularization has attracted increasing interest among both practitioners and academics. To facilitate the decision‐making and management of modularization in the manufacturing industry, tools and methods are needed. The purpose of this paper is to identify existing modularization methods and analyze them regarding their ability to deal with different degrees of product complexity, where complexity has several aspects: many variants, mix of different technologies, and having different solutions for one and the same function. A literature survey results in six different methods for modularization. The results of the analysis show that the modularization methods are useful for products with simple product architecture; i.e., one function is allocated to one physical module. However, concerning higher degrees of product complexity, several functions allocated to several physical modules, or large physical variation of the variants, the methods seem insufficient. Therefore, to make the methods suitable for complex products, areas for further development are suggested and discussed. ©2003 Wiley Periodicals, Inc. Syst Eng 6: 195–209, 2003
Creeping flow past a porous approximate sphere
Authors: Srinivasacharya D.
Published: June 2003

This paper concerns the creeping flow of incompressible viscous fluid past and through a porous approximate sphere. The Brinkman model for the flow inside the porous particle and Stokes model for the flow outside the particle in their stream function formulations are used. The stream function and the pressure distribution, both for the flow inside and outside are obtained in terms of Bessel and Gegenbauer functions of the first kind. The drag force experienced by the particle is determined and its variation with respect to permeability parameter is studied numerically. The special cases of flow past a porous sphere and spheroid are obtained from the present analysis.
Seasonal variability and export of dissolved organic nitrogen in the northwestern Mediterranean Sea
Authors: Pujo‐Pay Mireille , Conan Pascal
Published: June 2003

Hydrodynamic and biogeochemical monthly time series were carried out in the Gulf of Lions (northwestern Mediterranean) between 1993 and 1994. Detailed analysis of vertical profiles of dissolved organic nitrogen (DON) revealed an accumulation of nitrogen in the Upper Mixed Layer (UML) above the seasonal thermocline. DON was not corrected for ammonia concentration because of negligible concentrations of this element during the whole year in the studied area. In midwinter (January–February), DON concentrations were quasi‐homogeneous throughout the water column (about 3.5 μM). Subsequently, surface DON concentrations increased up to autumn, with a subsurface maximum greater than 6.0 μM observed in September. During this time, inorganic nutrients became virtually undetectable in the UML. The total DON content (0–1000 m) increased by about 784 mmol m−2 from winter through to the end of summer. At this time, labile and semilabile DON represented a maximum of 20% of the bulk DON. Assuming that DON was essentially removed from surface water by diffusive process during the stratified period and by vertical mixing during the rest of the year, 210 to 723 mmol m−2 a−1 was exported as DON, which represented 40–90% of the total new production. Following this DON export enabled us to balance the nitrogen budget of the area studied over the duration of the experiment.
Wavelet analysis of deep‐tow magnetic profiles: Modeling the magnetic layer thickness over oceanic ridges
Authors: Pouliquen Gaud , Sailhac Pascal
Published: June 2003

The interpretation of marine magnetic anomalies usually consists either in determining the magnetization distribution assuming the source geometry and magnetization direction or in determining the magnetic layer thickness assuming the magnetization direction and intensity. In this paper, we introduce a new technique that allows modeling of the thickness of the magnetic source layer with very few a priori assumptions about the magnetization: the magnetic layer is assumed to be made of a series of bodies, each having a constant unknown magnetization and an unknown size. This technique is based upon the application of the continuous wavelet transform recently introduced for the interpretation of potential field data as a multipole decomposition. We present applications to synthetic data, to one deep‐tow magnetic profile recorded across the Juan de Fuca Ridge (JDF), and to three deep‐tow magnetic profiles recorded across the Central Indian Ridge (CIR). Our results confirm that despite significant source thickness variations (100–1200 m across the CIR), measured magnetic anomalies mostly reflect past geomagnetic field intensity fluctuations; however, we show that within the axial region of high magnetization, thickness variations have a significant contribution to short‐wavelength variations of deep‐tow magnetic signals (>100 nT).
Distribution, formation, and seasonal variability of Okhotsk Sea Mode Water
Authors: Gladyshev Sergey , Talley Lynne , Kantakov Gennady , Khen Gennady , Wakatsuchi Masaaki
Published: June 2003

Russian historical data and recently completed conductivity‐temperature‐depth surveys are used to examine the formation and spread in the deep Ohkotsk Sea of dense shelf water (DSW) produced in the Okhotsk Sea polynyas. Isopycnal analysis indicates that all of the main polynyas contribute to the ventilation at σθ < 26.80, including the Okhotsk Sea Mode Water (OSMW), which has densities σθ = 26.7–27.0. At densities greater than 26.9 σθ the northwest polynya is the only contributor to OSMW. (Although Shelikhov Bay polynyas produce the densest water with σθ > 27.1, vigorous tidal mixing leads to outflow of water with a density of only about 26.7 σθ). In the western Okhotsk Sea the East Sakhalin Current rapidly transports modified dense shelf water along the eastern Sakhalin slope to the Kuril Basin, where it is subject to further mixing because of the large anticyclonic eddies and tides. Most of the dense water flows off the shelves in spring. Their average flux does not exceed 0.2 Sv in summer and fall. The shelf water transport and water exchange with the North Pacific cause large seasonal variations of temperature at densities of 26.7–27.0 σθ (depths of 150–500 m) in the Kuril Basin, where the average temperature minimum occurs in April–May, and the average temperature maximum occurs in September, with a range of 0.2°–0.7°C. The average seasonal variations of salinity are quite small and do not exceed 0.05 psu. The Soya Water mixed by winter convection, penetrating to depths greater than 200 m, in the southern Kuril Basin also produces freezing water with density greater than 26.7 σθ. Using a simple isopycnal box model and seasonal observations, the OSMW production rate is seen to increase in summer up to 2.2 ± 1.7 Sv, mainly because of increased North Pacific inflow, and drops in winter to 0.2 ± 0.1 Sv. A compensating decrease in temperature in the Kuril Basin implies a DSW volume transport of 1.4 ± 1.1 Sv from February through May. The residence time of the OSMW in the Kuril Basin is 2 ± 1.7 years.
Effect of horizontal grid resolution on simulations of oceanic CFC‐11 uptake and direct injection of anthropogenic CO2
Authors: Wickett M. E. , Caldeira K. , Duffy P. B.
Published: June 2003

We simulate direct injection of CO2 and uptake of CFC‐11 in a global, three‐dimensional ocean general circulation model using two model resolutions: a coarse resolution of 4° in longitude by 2° in latitude and a finer resolution of 1° in both longitude and latitude. We assess the impact of resolution on the relative effectiveness of ocean carbon sequestration for four different injection sites: New York at 710 and 3025 m depths and San Francisco at 710 and 3025 m depths. Results show that deep injection is generally effective, with relatively small differences in retention, transport, and fluxes between the two resolutions. Results for the change in ocean pH due to CO2 injection show that resolution does limit the details at sufficiently small scales, with the finer resolution showing greater maximum pH changes. Model predictions of CFC‐11 uptake generally have shallower penetration than is seen in observations, and the differences between the model resolutions are much smaller than the differences between either simulation and the observations. There is no persuasive evidence of improvement of large‐scale results with globally higher horizontal resolution in these non‐eddy‐resolving simulations to justify the computational expense. However, when local details are the primary interest, the use of higher resolution may be justified. We suggest that the best approach to improving the results of coarse‐resolution ocean models is not to globally increase horizontal resolution outside of the eddy‐resolving regime, but rather to pursue other approaches such as improved numerical methods, better parameterizations of sub‐grid‐scale processes, better forcing data, or perhaps local resolution increases.
Effects of elevated CO2 and N deposition on CH4 emissions from European mires
Authors: Silvola J. , Saarnio S. , Foot J. , Sundh I. , Greenup A. , Heijmans M. , Ekberg A. , Mitchell E. , van Breemen N.
Published: June 2003

Methane fluxes were measured at five sites representing oligotrophic peatlands along a European transect. Five study plots were subjected to elevated CO2 concentration (560 ppm), and five plots to NH4NO3 (3 or 5 g N yr−1). The CH4 emissions from the control plots correlated in most cases with the soil temperatures. The depth of the water table, the pH, and the DOC, N and SO4 concentrations were only weakly correlated with the CH4 emissions. The elevated CO2 treatment gave nonsignificantly higher CH4 emissions at three sites and lower at two sites. The N treatment resulted in higher methane emissions at three sites (nonsignificant). At one site, the CH4 fluxes of the N‐treatment plots were significantly lower than those of the control plots. These results were not in agreement with our hypotheses, nor with the results obtained in some earlier studies. However, the results are consistent with the results of the vegetation analyses, which showed no significant treatment effects on species relationships or biomass production.
Vegetation sensitivity to global anthropogenic carbon dioxide emissions in a topographically complex region
Authors: Diffenbaugh Noah S. , Sloan Lisa C. , Snyder Mark A. , Bell Jason L. , Kaplan Jed , Shafer Sarah L. , Bartlein Patrick J.
Published: June 2003

Anthropogenic increases in atmospheric carbon dioxide (CO2) concentrations may affect vegetation distribution both directly through changes in photosynthesis and water‐use efficiency, and indirectly through CO2‐induced climate change. Using an equilibrium vegetation model (BIOME4) driven by a regional climate model (RegCM2.5), we tested the sensitivity of vegetation in the western United States, a topographically complex region, to the direct, indirect, and combined effects of doubled preindustrial atmospheric CO2 concentrations. Those sensitivities were quantified using the kappa statistic. Simulated vegetation in the western United States was sensitive to changes in atmospheric CO2 concentrations, with woody biome types replacing less woody types throughout the domain. The simulated vegetation was also sensitive to climatic effects, particularly at high elevations, due to both warming throughout the domain and decreased precipitation in key mountain regions such as the Sierra Nevada of California and the Cascade and Blue Mountains of Oregon. Significantly, when the direct effects of CO2 on vegetation were tested in combination with the indirect effects of CO2‐induced climate change, new vegetation patterns were created that were not seen in either of the individual cases. This result indicates that climatic and nonclimatic effects must be considered in tandem when assessing the potential impacts of elevated CO2 levels.
Magmatic cycles and formation of the upper oceanic crust at spreading centers: Geochemical study of a continuous extrusive section in the Oman ophiolite
Authors: Einaudi F. , Godard M. , Pezard P. , Cochemé J.‐J. , Coulon C. , Brewer T. , Harvey P.
Published: June 2003

The data and analysis presented in this paper provide an assessment of lava morphologies and the geochemistry of lavas from the Oman ophiolite. In order to provide detailed constraints on the construction of the upper oceanic crust, a continuous volcanic transect (300 m‐thick) was sampled at high‐frequency in the Semail ophiolite along Wadi Shaffan. The Wadi Shaffan section is composed mainly of pillow lavas interbedded with massive flows and occasional hyaloclastites. The sampling performed along Wadi Shaffan implies temporal variations in the activity of the ridge. The section is characterized by chemical compositions consistent with those of V1‐Geotimes volcanism. The Wadi Shaffan transect was built through two main petrological and geochemical sequences of volcanic activity. Trace element ratios (e.g. Zr/Nb and La/Yb) allow us to distinguish two main sequences with two different parental magmas. Differences in the degree of partial melting are required to explain these trace element ratio variations. Beyond these differences in parent melt composition, variations in trace element abundances (TiO2, Zr, REE) involve differentiation processes prior to emplacement. In the lower sequence, less differentiated lavas are in the upper part of the cycle. Magma mixing is proposed to explain this reversed geochemical evolution through time. In the upper sequence, geochemical analysis suggests a different magma chamber process. This sequence consists of multiple events of magma emplacement. Variations in trace element abundance suggest four magmatic cycles. Each magmatic cycle is characterized by primitive lavas evolving to more differentiated lavas with time. The upper sequence lavas appear to be in equilibrium with clinopyroxene and lower sills from the MTZ (Mantle‐Crust Transition Zone) and with lower gabbros. We propose a model in which the upper sequence lavas were directly derived from the MTZ and lower gabbro sills and then transported to the surface without interaction with higher crustal levels.
Geochemical variability of the Oman ophiolite lavas: Relationship with spatial distribution and paleomagnetic directions
Authors: Godard Marguerite , Dautria Jean‐Marie , Perrin Mireille
Published: June 2003

The multielemental composition of 31 lavas sampled in the extrusive section of the Oman ophiolite was determined by inductively coupled plasma‐source mass spectrometry (ICP‐MS). This study allowed us to define clear geochemical criteria to characterize the different lavas types in Oman. Most of the Oman ophiolite extrusive sequence is composed of lavas of composition similar to present‐day MORB with the exception of slight Nb‐Ta negative anomalies (V1 magmatism). V1 lavas display REE patterns and Zr/Hf ratios in the range of MORB (Zr/Hf = 33.15–38.7). In contrast, the overlaying V2 lavas, which outcrop only in the northern part of the ophiolite, are REE depleted relative to V1 and display low Zr/Hf ratios (23.6–30.5). V2 lavas may be further classified into two sub‐groups. V2 type I lavas display a continuous decrease from HREE to LREE. The upper V2 type II lavas are more depleted in HREE and MREE but they are enriched in LREE. They are also distinguished by their low Nb/Ta ratios (10.53–11.65) relative to other Oman basalts (V1: 12.5–14; V2 Type I: 12.35–14.4). As for N‐MORB, melting of an upwelling mantle beneath an oceanic spreading centre formed V1 lavas. V2 resulted from fluid‐enhanced melting of previously depleted mantle residual after V1 extraction. This process probably occurred at different melt/rock ratios thus resulting in the two V2 sub‐groups, and was enhanced in the northern part of the ophiolite. V3 lavas overlie the V1–V2 sequence in the Salahi area. They display incompatible element rich patterns (LREE > MREE > HREE) and a high Nb/Ta ratio typical of within‐plate basalts. In the different studied areas, the transition from one lava type to the other seems to correlate with the block rotations revealed by paleomagnetic data.
U channel track for susceptibility measurements
Authors: Thomas Ray G. , Guyodo Yohan , Channell James E. T.
Published: June 2003

A lightweight, transportable, and inexpensive magnetic susceptibility track for u channel samples is described. The track utilizes a Sapphire Instruments 3.3 cm square coil having a response function of shape similar to that of the 2G‐Enterprises u channel magnetometer, and a half‐peak width of 3 cm. The instrument has been calibrated using a u channel standard made of manganese dioxide. The software incorporates automated track control and measurement drift correction. Susceptibility measurements on this system compare favorably with the 45 mm circular Bartington loop used for u channel samples at the Laboratoire des Sciences du Climat et de l'Environnement (Gif‐sur‐Yvette, France) and with data from the whole core susceptibility track aboard the Ocean Drilling Program research vessel JOIDES Resolution.
Source of tiny wiggles in Chron C5: A comparison of sedimentary relative intensity and marine magnetic anomalies
Authors: Bowles Julie , Tauxe Lisa , Gee Jeff , McMillan David , Cande Steve
Published: June 2003

In addition to the well‐established pattern of polarity reversals, short‐wavelength fluctuations are often present in both sea‐surface data (“tiny wiggles”) and near‐bottom anomaly data. While a high degree of correlation between different geographical regions suggests a geomagnetic origin for some of these wiggles, anomaly data alone cannot uniquely determine whether they represent short reversals or paleointensity variations. Independent evidence from another geomagnetic recording medium such as deep‐sea sediments is required to determine the true nature of the tiny wiggles. We present such independent evidence in the form of sedimentary relative paleointensity from Chron C5. We make the first comparison between a sedimentary relative paleointensity record (ODP Site 887 at 54°N, 148°W) and deep‐tow marine magnetic anomaly data (43°N, 131°W) [Bowers et al., 2001] for Chron C5. The sediment cores are densely sampled at ∼2.5 kyr resolution. The inclination record shows no evidence for reverse intervals within the ∼1 myr‐long normal Chron C5n.2n. Rock magnetic measurements suggest that the primary magnetic carrier is pseudo‐single domain magnetite. We choose a partial anhysteretic magnetization (pARM) as our preferred normalizer, and the resulting relative paleointensity record is used as input to a forward model of crustal magnetization. We then compare the results of this model with the stacked deep‐tow anomaly records. The two records show a significant degree of correlation, suggesting that the tiny wiggles in the marine magnetic anomalies are likely produced by paleointensity variations. An analysis of our sampling density suggests that if any reverse intervals exist at this site, they are likely to be <5 kyr in duration. Furthermore, we suggest that reverse intervals during Chron C5n.2n documented in other locations are unlikely to be global.
A study of regional waveform calibration in the eastern Mediterranean
Authors: Di Luccio F. , Pino N. A. , Thio H. K.
Published: June 2003

We modeled Pnl phases from several moderate magnitude earthquakes in the eastern Mediterranean to test methods and develop path calibrations for determining source parameters. The study region, which extends from the eastern part of the Hellenic arc to the eastern Anatolian fault, is dominated by moderate earthquakes that can produce significant damage. Our results are useful for analyzing regional seismicity as well as seismic hazard, because very few broadband seismic stations are available in the selected area. For the whole region we have obtained a single velocity model characterized by a 30 km thick crust, low upper mantle velocities and a very thin lid overlaying a distinct low velocity layer. Our preferred model proved quite reliable for determining focal mechanism and seismic moment across the entire range of selected paths. The source depth is also well constrained, especially for moderate earthquakes.
Heliospheric “FALTS”: Favored Acceleration Locations at the Termination Shock
Authors: Schwadron N. A. , McComas D. J.
Published: June 2003

The standard explanation for Anomalous Cosmic Rays requires strong energization at the heliospheric termination shock. However, the tightly wrapped magnetic spiral in the outer heliosphere produces a quasi‐perpendicular shock where it is difficult to accelerate low energy particles. We show that motion of footpoints between regions of fast and slow solar wind at the Sun, create non‐spiral configurations and large radial components of the magnetic field. These regions preferentially inject low energy particles into diffusive shock acceleration. Further, footpoints that move from slow to fast source regions, generate field lines with local polarity inversions that connect to the termination shock at multiple locations. As these regions convect out, they trap particles between what are effectively two converging shocks, producing additional first‐order Fermi acceleration. Heliospheric “FALTS” ‐ Favored Acceleration Locations at the Termination Shock ‐ should play an important role in particle acceleration in the outer heliosphere.
Guided echoes in the magnetosphere: Observations by Radio Plasma Imager on IMAGE
Authors: Fung Shing F. , Benson Robert F. , Carpenter Donald L. , Green James L. , Jayanti Venku , Galkin Ivan A. , Reinisch Bodo W.
Published: June 2003

Long‐range, discrete, radio echo traces observed in the magnetosphere by the Radio Plasma Imager (RPI) on IMAGE have been interpreted as signals guided along geomagnetic field lines. During IMAGE traversals of the plasmapause and near‐equatorial plasmasphere, multiple echo traces, attributed to signals reflected successively between conjugate hemispheres, are often observed. Single traces seen far beyond the plasmapause at high latitudes are attributed to guided echoes from the local hemisphere in the polar region. Here the field lines are either (1) open, (2) closed but too long to be observed within the instrument listening time or (3) closed but not able to maintain the signal‐guiding conditions across the equator to the conjugate hemisphere. In this letter we present examples of guided echoes producing both the single and multiple reflection traces observed by RPI at altitudes of a few Earth radii and discuss possible guiding mechanisms.
Carbon isotopes across the Eocene‐Oligocene boundary sequence of Kutch, western India: Implications to oceanic productivity and pCO2change
Authors: Sarkar A. , Sarangi S. , Bhattacharya S. K. , Ray A. K.
Published: June 2003

Analyses of foraminiferal δ18O (δ18Ocarb), δ13C (δ13Ccarb) and bulk organic matter (δ13Corg) across a tropical Eocene/Oligocene boundary (EOB) section from Kutch basin, western India show that the ocean cooling (at least ∼3°C) is coincident with a rapid enrichment (∼3‰) in δ13Corgbut depletion (∼1.5‰) in δ13Ccarb. The decrease in pCO2in ocean‐atmosphere system across the boundary, possibly resulting from enhanced silicate weathering in rising Himalayas and accompanied organic carbon burial in ocean, caused the cooling and δ13Corgenrichment. The end‐Eocene climatic stress decreased the oceanic productivity (and δ13Ccarb) eventually causing extinction of larger benthic foraminiferal community. The data suggest a critical role of tropical ocean and direct forcing of CO2on global climate change at least for this crucial Cenozoic transition.