bluuebunny/crossref_metadata_2025 huggingface dataset:
Fair Valuation of Liabilities
Authors: Hairs C.J. , Belsham D.J. , Bryson N.M. , George C.M. , Hare D.J.P. , Smith D.A. , Thompson S.
Published: June 2011

A project to develop an Accounting Standard for Insurance, with the aim of enhancing understandability, relevance, reliability and comparability of general purpose financial reporting for insurance worldwide, is being progressed by the International Accounting Standards Board. The basis of the proposals is that assets and liabilities be shown at fair values (market values for quoted instruments). This paper, prepared by a Working Party established by the Life Board of the United Kingdom actuarial profession, summarises and comments upon a number of the principal features of the proposals, as they have emerged up to September 2001. The paper goes on to consider how a system of reporting for prudential regulatory purposes might be built upon a fair value general reporting base, summarising the thinking of a number of other bodies, proposing certain principles and suggesting lines of development. The appendices to the paper discuss a number of issues in further depth and present some illustrative results of some investigations into applying fair value methods in practice. The emphasis of the paper is on reporting for life assurance business, although many of the principles apply equally to general insurance.
Recent Mortality Trends in the Spanish Population
Authors: Felipe A. , Guillen M. , Perez-Marin A. M.
Published: June 2011

Our research deals with the way that calendar time affects mortality patterns in the Spanish population, and how this information can be used to elaborate predictions. A description of the observed mortality evolution has been worked out using data from 1975 to 1993. We have used Heligman-Pollard Law number two to model the evolution of Spanish mortality over the period and using univariate time series analysis, we have obtained a prognosis for years 1994 to 2010.
Natural Catastrophe Probable Maximum Loss
Authors: Woo G.
Published: June 2011

The procedure for estimating probable maximum loss (PML) for natural catastrophes has evolved over the past few decades from a rather simplistic deterministic basis to a more sophisticated methodology based on loss exceedance probability curves, generated using catastrophe modelling software. This development process is reviewed, with an emphasis on the earthquake peril, which, because of its widespread threat to critical industrial installations, has been at the forefront of most PML advances. The coherent risk definition of PML is advocated as an improvement over standard quantile methods, which can give rise to anomalous aggregation results failing to satisfy the fundamental axiom of subadditivity, and so discouraging the pooling of risks.
A Stochastic Approach to Risk Management and Decision Making in Defined Benefit Pension Schemes
Authors: Haberman S. , Day C. , Fogarty D. , Khorasanee M. Z. , McWhirter M. , Nash N. , Ngwira B. , Wright I. D. , Yakoubov Y.
Published: June 2011

The trustees and sponsors of defined benefit schemes rely on the advice of the Scheme Actuary to make important decisions concerning the funding of the scheme, the investment of its assets, and the use of surplus assets to improve benefits. These decisions have to be made in the face of considerable uncertainty about financial and demographic factors that will affect the future experience of the scheme and its success in meeting various objectives.

The traditional actuarial valuation combined with actuarial judgement has played an important role in guiding decision making; but we argue that stochastic methods can add value in certain crucial areas, in particular the financial risk management of defined benefit schemes. Rather than dealing with risk by incorporating margins in the valuation basis, a stochastic approach allows the actuary to evaluate specific and quantifiable risk and performance measures for alternative funding and investment strategies.

This paper recommends a framework that, when combined with a suitable stochastic model, measures the risks inherent in contribution rate and asset allocation decisions, allowing better decisions to be made. In doing this, we suggest and apply various risk and performance measures that may be thought appropriate, although our intention is to illustrate their use rather than prescribe them as objective standards. The framework provides the means to explore the trade-offs involved in possible contribution and asset allocation decisions, and points to decision strategies expected to give improved outcomes for the same level of risk. A feature of the approach that marks it out from current asset/liability techniques is that it examines the funding and investment decisions together. It does not derive a contribution rate in the traditional way, but leaves this as free variable, in the same way that the investment decision is taken to be a free variable. Another distinctive feature of our framework is that it is based on projection rather than on valuation, involving stochastic simulation of the experience of the scheme over a time horizon reflecting the concerns of the trustees and the sponsoring employer.

The paper provides a case study (based on a model final salary pension scheme) showing the advantages of the framework, and goes on to explain how the results may practically be communicated to trustees and scheme sponsors.
Ruin Theory in a Discrete Time Risk Model with Interest Income
Authors: Sun L. , Yang H.
Published: June 2011

In this paper we consider a discrete time insurance risk model with interest income. Using the recursive calculation method of De Vylder & Goovaerts (1988), recursive equations for the finite time ruin probabilities and the distribution of the time of ruin are derived. Fredholm type integral equations for the ultimate ruin probability, the distribution of the severity of ruin, the joint distribution of surplus before and after ruin, and the probability of absolute ruin are obtained. Numerical results are included.
Measuring and Managing the Economic Risks and Costs of With-Profits Business
Authors: Hibbert A.J. , Turnbull C.J.
Published: June 2011

The approaches to liability valuation, assessment of prudential capital and measurement of profit for life offices are undergoing radical change. A common thread runs through all of these proposed changes — each change represents a move away from traditional actuarial approaches towards a more economically coherent, market-consistent approach. These changes should encourage a general improvement in the life industry's risk management processes. However, they will come at a cost. The measurement of the economic risks generated by the complex guarantees written by life offices is far more difficult than applying the latest resilience test equity fall. This will require a step change in the sophistication of life offices' risk and capital measurement and management know-how. The measurement of value, risk and capital will soon demand the application of ‘stochastic’ modelling tools. In this paper, we explore some of the issues raised by the application of these approaches to the valuation and risk management of with-profits business.
Genetics and Insurance– Some Social Policy Issues
Authors: Daykin C. D. , Akers D. A. , Macdonald A. S. , McGleenan T. , Paul D. , Turvey P. J.
Published: June 2011

Rapid developments in genetic science have been accompanied by confusion regarding the predictive power of DNA-based tests and in the impact of such tests on the insurance industry. The United Kingdom actuarial profession has begun to engage in the associated social policy issues and to try to throw some light on the issues through quantitative research and objective analysis. At the same time, many insurance industry actuaries have been involved in work on behalf of the insurance industry to develop a sound basis for permission to be sought to make use of the results of certain predictive genetic tests. This paper briefly outlines some of the history of the development of the debate in the U.K. and draws together some of the debates and discussions which have taken place within the Genetics Group of the Social Policy Board of the U.K. actuarial profession, as well as providing some pointers to the directions which the debate might take in the future, with some important potential consequences for the insurance industry and for actuaries.
Highly Penetrant Genetic Disorders: An Atlas for Critical Illness Insurance
Authors: Macdonald A. S. , Yang S. Y.
Published: June 2011

For estimates of critical illness (CI) insurance premiums in the presence of a known mutation leading to a genetic disorder, the key quantity is the penetrance, that is the probability q(x) that the disease has developed by age x. This function is often estimated in the genetics literature, though typically with large confidence intervals. In this paper we suggest that the main features of real penetrance functions can be represented reasonably well by simple one-parameter families of functions, which can be scaled to fit the age range and lifetime penetrance. This gives a simple, direct, pragmatic way to obtain quick estimates of CI premium rates from published penetrance estimates, and also some indicative bounds for such premium rates, which are useful since confidence intervals usually cannot be estimated. To aid this process, as a short-cut to the solution of Thiele's equations in a multiple-state model, we give extensive tables in another report (Macdonald & Yang, 2003).
The Measurement and Modelling of Commercial Real Estate Performance
Authors: Booth P. M. , Marcato G.
Published: June 2011

In this paper we discuss methods of developing real estate indices, the availability of real estate data, the problems of using published real estate data and how real estate data can be used for stochastic investment modelling for actuarial purposes. In recent years there have been many developments in the collection, presentation and analysis of real estate data that have not found their way into the actuarial literature. We review those developments and suggest and develop ways in which raw real estate investment data can be used for actuarial purposes. We then review the Wilkie real estate stochastic investment model and use the research of real estate finance academics to inform a critique and development of that model. In developing the models, different data sets are used, including data from valuation-based and de-smoothed indices in order to find appropriate parameter estimates. The significance (or otherwise) of the parameter estimates is tested for each of the fitted models and the differences between the fitted models are examined. By reviewing research in the real estate finance field, making use of the latest research and developing original work, the main aim of this paper is to ensure that actuaries have the means to collect, understand and manipulate real estate data for performance measurement and investment modelling purposes.
The Importance of Year of Birth in Two-Dimensional Mortality Data
Authors: Richards S. J. , Kirkby J. G. , Currie I. D.
Published: June 2011

Late-life mortality patterns are of crucial interest to actuaries assessing longevity risk. One important explanatory variable is year of birth. We present the results of various analyses demonstrating this, including a statistical model which lends weight to the importance of year-of-birth effects in both population and insured data. We further find that a model based on age and year of birth fits United Kingdom mortality data better than a model based on age and period, suggesting that cohort effects are more significant than period effects. The financial implications of these cohort effects are considerable for portfolios with long-term longevity exposure, such as annuities written by insurance companies and defined benefit pension schemes.
The Recent Trend of Mortality in the United Kingdom
Authors: Daykin C. D. , Gallop A. P.
Published: June 2011

This note continues a regular series on mortality rates in the United Kingdom. Mortality experienced in each of the years 1999 to 2004 is shown by five-year age groups, and comparisons are made for broad age groups, on a standardised basis, with mortality in earlier years.
Simulating the Relative Solvency of Life Insurers
Authors: Hardy M.R.
Published: June 2011

In this paper a stochastic model office offering UK-style life insurance contracts is used to demonstrate the effect on relative solvency of different investment and bonus strategies. Relative solvency is defined loosely as the probability that an individual insurer does not fall significantly out of line with the rest of the life insurance market, in terms of, for example, asset liability ratios, or payouts to with-profit policyholders. The model uses the Wilkie investment model, extended to incorporate variation between companies in equity performance.
Ownership of the Inherited Estate (the Orphan Estate)
Authors: Smaller S.L. , Drury P. , George C.M. , O'Shea J.W. , Paul D.R.L. , Pountney C.V. , Rathbone J.C.A. , Simmons P.R. , Webb J.H.
Published: June 2011

In recent years there has been increasing interest in clarifying the respective interests of shareholders and participating policyholders in the inherited estate of the proprietary life offices. This paper defines the inherited estate, considers the sources of surplus contributing to it and suggests an approach for quantifying it. Views are expressed on the attribution of the inherited estate to the parties involved with a view to a consensus emerging from a discussion of the underlying factors. The role of the supervisory authorities and of the Appointed Actuary and the independent actuary are considered and methods of accessing the inherited estate attributed to shareholders are examined.
Ownership of the Inherited Estate (The Orphan Estate)
Authors: Smaller S.L. , Drury P. , George C.M. , O'Shea J.W. , Paul D.R.L. , Pountney C.V. , Rathbone J.C.A. , Simmons P.R. , Webb J.H.
Published: June 2011

The text of this paper, together with the abstract of the discussion held by the Institute of Actuaries on 24 June 1996, are printed in British Actuarial Journal, 2, V, pages 1273-1322.
Notes for a Discussion on the European Single Currency
Authors: Wilkie A.D.
Published: June 2011

This paper forms notes for discussions about the European single currency at the Institute of Actuaries and the Faculty of Actuaries. The author assumes (and hopes) that the single currency will start on time in 1999, with most of the Member States of the European Union included. The key dates are 1 January 1999, when the exchange rates between currencies will become irrevocably locked and become conversion rates, and 2002, when euro notes and coins will be introduced, and the retail banking sector will convert to euros. The advantages of a single currency are potentially very great; the costs are also considerable. Governments of Member States will no longer be able to get a competitive advantage by devaluing their currency, or be able to choose an inflation rate that is different from that of the E.U. as a whole. The key document is the Maastricht Treaty, and the conversion criteria included therein are discussed. The author concludes that, if governments choose to interpret the criteria leniently, all countries, except possibly Greece, will be included in 1999, with Greece joining a year or two later. Some of the practical considerations for actuaries, including life insurance, general insurance, pensions, banking and investment are mentioned. The paper is not comprehensive, and is a personal contribution to stimulate discussion.
Notes for a Discussion on the European Single Currency. Abstract of the Discussion held by the Faculty of Actuaries
Authors: Wilkie A.D.
Published: June 2011

The text of this paper, together with the abstract of the discussion held by the Institute of Actuaries on 25 November 1996, are printed in British Actuarial Journal, 3, II, 227-319.
The Financial Theory of Defined Benefit Pension Schemes
Authors: Exley C.J. , Mehta S.J.B. , Smith A.D.
Published: June 2011

Increasingly, modern business and investment management techniques are founded on approaches to measurement of profit and risk developed by financial economists. This paper begins by analysing corporate pension provision from the perspective of such financial theory. The results of this analysis are then reconciled with the sometimes contradictory messages from traditional actuarial valuation approaches and the alternative market-based valuation paradigm is introduced. The paper then proposes a successful blueprint for this mark-to-market valuation discipline and considers whether and how it can be applied to pension schemes both in theory and in practice. It is asserted that adoption of this market based approach appears now to be essential in many of the most critical areas of actuarial advice in the field of defined benefit corporate pension provision and that the principles can in addition be used to establish more efficient and transparent methodologies in areas which have traditionally relied on subjective or arbitrary methods. We extend the hope that the insights gained from financial theory can be used to level the playing field between defined benefit and defined contribution arrangements from both corporate and member perspectives.
Notes on the FTSE Actuaries Share Indices (United Kingdom Series) in 1996
Authors: Brumwell J.C.H.
Published: June 2011

Consolidation of FTSE Actuaries share indices, and of the revised 1994 Industrial Classification system. New Alternative Investment Market (AIM) Index. Closure of Unlisted Securities Market.
Modelling Extreme Market Events. A Report of the Benchmarking Stochastic Models Working Party
Authors: Frankland R. , Smith A. D. , Wilkins T. , Varnell E. , Holtham A. , Biffis E. , Eshun S. , Dullaway D.
Published: June 2011

This paper focusses on some practical issues that can arise when developing methodologies for calculating benchmark figures for extreme market events, particularly in the context of the Financial Services Authority's ICAS regime. The paper limits discussion to equity and interest rate risks. Whilst not intended to constitute formal guidance, it is hoped that the material contained within the paper will be useful to practitioners. The paper acknowledges the role of prior beliefs in the choice of data to be used for modelling and its influence upon the ensuing results.
Cohort Differences in Mortality and Morbidity
Authors: Jagger Carol , Christensen Kaare , Murphy Michael
Published: June 2011

In 1900 life expectancy at birth in the UK was only 46 years for men and 53 years for women. Just over a century later life expectancy at birth has increased by around 30 years and by 2007 had reached 77.5 years for men and 81.7 years for women. The population aged 85 years and over, often termed the ‘oldest old’, are now the fastest growing section of our population. For the 1921 cohort only 18% of men and a third of women reached the age of 85 years but for the 1951 birth cohort it is expected that almost half of men and 60% of women will achieve that age. The important question for health care planners and society is whether the large number of those who will reach 85 years in the future are similar in health characteristics to those attaining 85 years now.

This question was addressed by substantive results and by methodological papers in the ‘Cohort’ theme of the Joining Forces on Mortality and Longevity conference in October 2009. Here we provide an overview of the papers, some of which are presented in full in this issue (see Murphy (2009), Di Cesare & Murphy (2009), O'Connell & Dunstan (2009), Forfar (2009)).
Do Cohort Mortality Trends Emigrate? Insights on The U.K.'s Golden Cohort From A Comparison with a British Settler Country
Authors: O'Connell Alison , Dunstan Kim
Published: June 2011

The assumed rate of future mortality improvement has increased over three recent sets of the United Kingdom's national population projections. This optimism has not been so marked in countries which share ancestors with the U.K. population. New Zealand is one such country that provides a data-rich case example in which to investigate the portability of mortality trends.

This paper compares mortality trends in New Zealand with those in England & Wales. Both countries seem to have a ‘golden cohort’ which enjoys faster improving mortality than people born before or after. The birth of the golden cohort in England & Wales coincided with cohort life expectancy there catching up with New Zealand's.

We show that first generation migrants from the U.K. have better mortality than New Zealand born residents likely to have British ancestry. The advantage lasts into older ages, decades after migration. We hypothesise that migrants from the U.K.'s golden cohort brought with them an early life mortality improvement advantage, and additionally benefited from the healthier environment of New Zealand at middle to older ages. Further, given the recent strong mortality improvement in New Zealand, the U.K.'s assumptions for future mortality look relatively optimistic.
The ‘Golden Generations’ in Historical Context
Authors: Murphy Michael
Published: June 2011

Assumptions about future mortality are more important than those for factors such as fertility, migration, disability trends or real interest rates for cost projections of the U.S. Old Age, Survivors, Disability and Health Insurance scheme. Recently, one factor has been assumed to be the key driver of future mortality in both official British population projections and actuarial ones: a ‘cohort effect’ associated with a group who were born in a period centred on the early 1930s who have been identified as having experienced particularly rapid improvements in mortality rates and are often referred to as the ‘golden generations’ or ‘golden cohorts’. The concept of ‘cohort effects’ is discussed; limitations of national-level cohort data considered; and methods for identifying such effects are reviewed. Particular attention is given to the analysis of populations which have been identified as having clear cut cohort effects; those of Britain and Sweden in the later part of the nineteenth century and early twentieth century, as well as the contemporary British population. The likely magnitude of such effects is discussed using a stylised model to assess the extent to which members of the ‘golden generations’ are especially privileged.
Forecasting Mortality, Different Approaches for Different Cause of Deaths? The Cases of Lung Cancer; Influenza, Pneumonia, and Bronchitis; and Motor Vehicle Accidents
Authors: Cesare Mariachiara Di , Murphy Mike
Published: June 2011

Most of the methods of mortality forecasting have been assessed using performance on overall mortality, and few studies address the issue of identifying the appropriate forecasting models for specific causes of deaths. This study analyses trends and forecasts mortality rates for three major causes of death — lung cancer, influenza-pneumonia-bronchitis, and motor vehicle accidents — using Lee–Carter, Booth–Maindonald–Smith, Age-Period-Cohort, and Bayesian models, to assess how far different causes of death need different forecasting methods. Using data from the Twentieth and Twenty-First Century Mortality databases for England and Wales, results show major differences among the different forecasting techniques. In particular, when linearity is the main driver of past trends, Lee–Carter-based approaches are preferred due to their straightforward assumptions and limited need for subjective judgment. When a clear cohort pattern is detectable, such as with lung cancer, the Age-Period-Cohort model shows the best outcome. When complete and reliable historical trends are available the Bayesian model does not produce better results than the other models.
Time‐dependence of the spatial pattern of accumulation rate in East Antarctica deduced from isochronic radar layers using a 3‐D numerical ice flow model
Authors: Leysinger Vieli Gwendolyn J.‐M. C. , Hindmarsh Richard C. A. , Siegert Martin J. , Bo Sun
Published: June 2011

In East Antarctica surface mass balance data can only be obtained from the sparsely distributed ice cores when considering time periods greater than a few decades. Observations of internal layers measured by airborne ice penetrating radar, in principle, permit extrapolation of mass balance information from these ice cores. We use radar survey lines gathered in the 1970s, and a three‐dimensional numerical model, to investigate the feasibility of such extrapolation, seeking to match the calculations of englacial layer geometry with observations. First, we justify the use of a three‐dimensional model by showing that simple vertical flow models cannot explain all the observations and that horizontal advection is a significant glacial process. Then we examine processes that affect calculations of layer geometry, finding that spatial accumulation‐rate patterns are extremely important while geothermal heat flux and flow mode (sliding or internal deformation) are of substantially less importance. Where the layer is from the Last Glacial Maximum (17.5 ka), we find a very good match between the spatial pattern of accumulation rates inferred from this layer and the modern spatial pattern of accumulation rates. When considering deeper layers from beyond the current interglacial, we find that a different spatial accumulation‐rate pattern must have existed, in addition to the known change in accumulation rate from ice cores. The glacial spatial accumulation‐rate pattern would have had proportionally greater accumulation at the South Pole than now, compared with the Vostok and Dome C ice cores.
Probability distributions for bed form–dominated bed load transport: The Hamamori distribution revisited
Authors: Turowski Jens M.
Published: June 2011

The Hamamori distribution is frequently used to describe the variability of bed load transport rates in bed form–dominated environments. However, the original derivation contains several incorrect steps. Here a corrected and generalized derivation is presented. It is shown that Hamamori's original distribution function arises if the underlying assumptions are adapted slightly. Two formalisms are presented to obtain probability distributions of instantaneous bed load transport rates from growth functions of ripples and from the distribution of ripple heights. Six distribution functions, among them the exponential distribution, the Hamamori distribution, and the gamma distribution, are compared to two laboratory data sets, one for gravel and one for sand transport, and to field data from a sand‐bed river. For the gravel bed laboratory measurements, the Hamamori distribution gives a good description of the data for intermediate transport rates, while the gamma distribution performs best overall. For the sand‐bed laboratory data, the exponential distribution shows the best performance. A distribution function derived from Rayleigh‐distributed ripple heights performs best for the field data.
Early Oligocene glaciation and productivity in the eastern equatorial Pacific: Insights into global carbon cycling
Authors: Coxall Helen K. , Wilson Paul A.
Published: June 2011

The onset of sustained Antarctic glaciation across the Eocene‐Oligocene transition (EOT) marks a pivotal change in Earth's climate, but our understanding of this event, particularly the role of the carbon cycle, is limited. To help address this gap we present the following paleoceanographic proxy records from Ocean Drilling Program Site 1218 in the eastern equatorial Pacific (EEP): (1) stable isotope (δ18O and δ13C) records generated in epifaunal benthic foraminifera (Cibicidoides spp.) to improve (double the resolution) the previously published records; (2) δ18O and δ13C records measured on Oridorsalis umbonatus, a shallow infaunal species; and (3) a record of benthic foraminifera accumulation rate (BFAR). Our new isotope data sets confirm the existence at Site 1218 of a two‐step δ18O increase. They also lend support to the hypothesized existence of a late Eocene transient δ18O increase and early Oligocene Oi‐1a and Oi‐1b glacial maxima. Our record of BFAR indicates a transient (∼500 kyr) twofold to threefold peak relative to baseline Oligocene values associated with the onset of Antarctic glaciation that we attribute to enhanced biological export production in the EEP. This takes the same general form as the history of opal accumulation in the Southern Ocean, suggesting strong high‐to‐low‐latitude oceanic coupling. These findings appear to lend support to the idea that the EOT δ13C excursion is traceable to increased organic carbon (Corg) burial. Paradoxically, early Oligocene sediments in the EEP are extremely Corg‐poor, and proxy records of atmospheric pCO2 indicate a transient increase associated with the EOT.
DETERMINISTIC COASTAL MORPHOLOGICAL AND SEDIMENT TRANSPORT MODELING: A REVIEW AND DISCUSSION
Authors: Amoudry Laurent O. , Souza Alejandro J.
Published: June 2011

Modern coastal ocean modeling systems are now capable of numerically simulating a variety of coastal and estuarine problems and can thus provide useful information for managing coastal zones. Here we review state‐of‐the‐art Eulerian implementations of bottom‐up sediment transport and morphological change in coastal ocean hydrodynamic models. In order to investigate the fate of suspended sediment in coastal and estuarine waters as well as the evolution of sea or river beds, sediment dynamics need to be represented at a scale relevant to the numerical discretized solution, and significant effort is devoted to parameterize sediment processes. We discuss boundary layer hydrodynamics and the computation of the bed shear stress. We also focus on approaches used to represent near‐bed processes such as bed load transport and sediment erosion and deposition. Sediment diffusivities, settling velocities, and cohesive processes such as flocculation all have an impact on suspended sediment throughout the water column. We then describe the implementation of process parameterizations in coastal hydrodynamic models, explicitly reviewing five widely used systems. The approaches implemented in these coastal models may present distinct strengths and shortcomings with regard to some important issues for coastal zones, both numerical and physical. While these detailed limitations need to be considered as part of model assessment, more general issues also hinder present state‐of‐the‐art models. In particular, sediment transport is inherently highly empirical, which is further compounded by issues arising from turbulence closure schemes. We conclude by suggesting some possible directions toward improving sediment dynamics understanding and coastal‐scale predictive ability.
Convergence of approaches toward reducing uncertainty in predictions in ungauged basins
Authors: Wagener Thorsten , Montanari Alberto
Published: June 2011

The focus in the search for more reliable predictions in ungauged basins (PUB) has generally been on reducing uncertainty in watershed models (mainly their parameters). More recently, however, we seem to remember that the ultimate objective is not to define the parameters of a specific model but to understand the watershed: What behavior do we expect the ungauged watershed to exhibit? And what behavior should not occur in a particular ungauged watershed? The answers to these questions actually provide additional information that can be assimilated in watershed models for uncertainty reduction in PUB. This extension to hydrologic modeling approaches provides a quantitative link between watershed modeling and statistical hydrology as well as process hydrology that has to be explored. We witness a convergence of approaches—Bayesian, set theoretic, and optimization based—toward utilizing this link. The result is an opportunity for the (quantitative) dialog between modelers, statistical hydrologists, and experimentalists. We close our discussion of this development by presenting new and exciting research questions that we now have to address.
Predictive uncertainty of chaotic daily streamflow using ensemble wavelet networks approach
Authors: Dhanya C. T. , Nagesh Kumar D.
Published: June 2011

Perfect or even mediocre weather predictions over a long period are almost impossible because of the ultimate growth of a small initial error into a significant one. Even though the sensitivity of initial conditions limits the predictability in chaotic systems, an ensemble of prediction from different possible initial conditions and also a prediction algorithm capable of resolving the fine structure of the chaotic attractor can reduce the prediction uncertainty to some extent. All of the traditional chaotic prediction methods in hydrology are based on single optimum initial condition local models which can model the sudden divergence of the trajectories with different local functions. Conceptually, global models are ineffective in modeling the highly unstable structure of the chaotic attractor. This paper focuses on an ensemble prediction approach by reconstructing the phase space using different combinations of chaotic parameters, i.e., embedding dimension and delay time to quantify the uncertainty in initial conditions. The ensemble approach is implemented through a local learning wavelet network model with a global feed‐forward neural network structure for the phase space prediction of chaotic streamflow series. Quantification of uncertainties in future predictions are done by creating an ensemble of predictions with wavelet network using a range of plausible embedding dimensions and delay times. The ensemble approach is proved to be 50% more efficient than the single prediction for both local approximation and wavelet network approaches. The wavelet network approach has proved to be 30%–50% more superior to the local approximation approach. Compared to the traditional local approximation approach with single initial condition, the total predictive uncertainty in the streamflow is reduced when modeled with ensemble wavelet networks for different lead times. Localization property of wavelets, utilizing different dilation and translation parameters, helps in capturing most of the statistical properties of the observed data. The need for taking into account all plausible initial conditions and also bringing together the characteristics of both local and global approaches to model the unstable yet ordered chaotic attractor of a hydrologic series is clearly demonstrated.
Research infrastructures for Europe's scientists
Authors: Garfinkel Michele
Published: June 2011

The EU is currently negotiating its next budget for research. It needs to invest more in research infrastructures if it wants to become a global leader in research and improve its competitiveness.
Repeated Negative DC Deflections in Rat Cortex following Middle Cerebral Artery Occlusion are Abolished by MK-801: Effect on Volume of Ischemic Injury
Authors: Iijima T. , Mies G. , Hossmann K.-A.
Published: June 2011

Following permanent occlusion of the left middle cerebral artery (MCA) in rats, electrophysiological and hemodynamic characteristics of the periinfarct border zone were investigated in sham-operated (n = 6), untreated (n = 6), and MK-801-treated (3.0 mg/kg; n = 6) animals. For this purpose, direct current potential (DC), EEG, and blood flow (laser-Doppler flowmetry) were recorded from the cortex in the periphery of the MCA territory. In sham-operated rats, a single negative cortical DC deflection was observed after electrocoagulation of the cortex, whereas in untreated MCA-occluded animals, three to eight transient DC deflections were monitored during the initial 3 h of ischemia. The duration of these cortical DC shifts gradually increased from 1.2 ± 0.3 to 3.7 ± 2.7 min (mean ± SD; p < 0.05) during this time. In animals treated intraperitoneally with MK-801 (3.0 mg/kg) immediately after MCA occlusion, the number of cortical DC shifts significantly declined to one to three deflections (p < 0.005). The EEG of the treated animals revealed low-amplitude burst-suppression activity. In the untreated and treated experimental group, the reduction of cortical blood flow amounted to 69 ± 25 and 49 ± 13% of control, respectively. Despite the more pronounced cortical oligemia, MK-801 treatment resulted in a significant decrease of the volume of the ischemically injured tissue from 108 ± 38.5 (untreated group) to 58 ± 11.5 (p < 0.05) mm3. Our results suggest that repetitive cortical DC deflections in the periinfarct border zone contribute to the expansion of ischemic brain infarcts.
Elevated Lactate and Alkalosis in Chronic Human Brain Infarction Observed by 1H and 31P MR Spectroscopic Imaging
Authors: Hugg James W. , Duijn Jeff H. , Matson Gerald B. , Maudsley Andrew A. , Tsuruda Jay S. , Gelinas Deborah F. , Weiner Michael W.
Published: June 2011

The goal of this study was to investigate lactate and pH distributions in subacutely and chronically infarcted human brains. Magnetic resonance spectroscopic imaging (MRSI) was used to map spatial distributions of 1H and 31P metabolites in 11 nonhemorrhagic subacute to chronic cerebral infarction patients and 11 controls. All six infarcts containing lactate were alkalotic (pHi = 7.20 ± 0.04 vs. 7.05 ± 0.01 contralateral, p < 0.01). This finding of elevated lactate and alkalosis in chronic infarctions does not support the presence of chronic ischemia; however, it is consistent with the presence of phagocytic cells, gliosis, altered buffering mechanisms, and/or luxury perfusion. Total 1H and 31P metabolites were markedly reduced (about 50% on average) in subacute and chronic brain infarctions ( p < 0.01), and N-acetyl aspartate (NAA) was reduced more (∼75%) than other metabolites ( p < 0.01). Because NAA is localized in neurons, selective NAA reduction is consistent with pathological findings of a greater loss of neurons than glial cells in chronic infarctions.
Increased Cerebral Blood Flow in Anemic Patients on Long-Term Hemodialytic Treatment
Authors: Vorstrup Sissel , Lass Piotr , Waldemar Gunhild , Brandi Lisbet , Schmidt Jes F. , Johnsen Anni , Paulson Olaf B.
Published: June 2011

CBF was measured in 15 patients on chronic hemodialytic treatment. CBF was measured with xenon-133 inhalation using single photon emission tomography. In addition, computerized tomography (CT) and a neurological examination were done prior to hemodialysis. Mean CBF was 66.2 ± 17.3 (SD) ml 100 g−1 min−1, which was significantly higher ( t-test, p < 0.05) than for an age-matched control group (54.7 ± 10.2 ml 100 g−1 min−1). However, the hematocrit for the patients was considerably lower, 0.30 ± 0.07, as compared to 0.43 ± 0.03 in the controls. A significant negative correlation was observed between CBF and the hematocrit ( y = –1.79x + 120.7, r = −0.71, p < 0.01). Calculating CBF from this equation in the dialyzed patients using a hematocrit of 0.43 yielded a mean CBF value of 43.7 ml 100 g−1 min−1, i.e., 20% below the expected. Two patients showed a focal CBF decrease. CT showed central or cortical atrophy in five patients, and two had small hypodense lesions. The neurological examination revealed slight to moderate dementia in seven cases. Although mean CBF was found to be increased by 21% as compared to the control group, an even higher CBF level would have been expected to outweigh the decreased oxygen carrying capacity of the blood. The findings suggest a lowered metabolic demand of the brain tissue, probably due to subtle brain damage.
Ion Homeostasis in Rat Brain in vivo: Intra- and Extracellular [Ca2+] and [H+] in the Hippocampus during Recovery from Short-Term, Transient Ischemia
Authors: Silver Ian A. , Erecińska Maria
Published: June 2011

Changes in intra- and extracellular [Ca2+] and [H+], together with alterations in tissue Po2 and local blood flow, were measured in areas CA1 and CA3 of the hippocampus during recovery (up to 8 h) after an 8-min period of low-flow ischemia. Restoration of blood supply was followed by an immediate rise in flow and tissue Po2 above normal, with large fluctuations in both persisting for up to 4 h. In area CA1, [Ca2+]i decreased rapidly from an ischemic mean value of 30 μ M to a control mean level of 73.1 n M in 20–30 min, whereas normalization of [Ca2+]e took ∼1 h. Recovery of [Ca2+]i was accelerated by preischemic administration of a calcium antagonist, nifedipine, and a free radical scavenger, N-tert-butyl-α-phenylnitrone (PBN), but not by MK-801, a blocker of N-methyl-d-aspartate receptors. There was a secondary rise in [Ca2+]i in many cells beginning ∼2 h after reperfusion. This was attenuated somewhat by PBN but not clearly influenced by either nifedipine or MK-801. Changes of [Ca2+]i in area CA3 were much smaller and slightly slower than in area CA1 and were not affected by the drugs mentioned above. In both areas CA1 and CA3, pHe and pHi fell during ischemia to an average value of 6.2, from which there was a rapid initial recovery in the first 5–10 min when blood flow was restored. Thereafter tissue pH rose slowly and did not reach control levels for ∼1 h, and in some microareas not at all. It is concluded that (a) effective mechanisms for restoring normal [Ca2+]i remain intact after 8 min of low-flow ischemia; (b) in neurons of area CA1, some insidious change in the homeostasis of calcium triggers a secondary rise in its free cytosolic concentration, which may be causally related to activation of irreversible cell damage; and (c) the changes in [Ca2+]i and [Ca2+]e during and following 8 min of ischemia can be adequately accounted for by movements of a fixed pool of Ca between intra- and extracellular compartments, and possible mechanisms are discussed.
Global Forebrain Ischemia Results in Decreased Immunoreactivity of Calcium/Calmodulin-Dependent Protein Kinase II
Authors: Churn Severn B. , Yaghmai Amy , Povlishock John , Rafiq Azhar , DeLorenzo Robert J.
Published: June 2011

Previous studies utilizing crude brain homogenates have shown that forebrain ischemia results in inhibition of calcium/calmodulin-dependent protein kinase II (CaM kinase II) activity without large-scale proteolysis of the enzyme. In this report, a monoclonal antibody (1C3-3D6) directed against the β- (60-kDa) subunit of CaM kinase II that does not recognize ischemically altered enzyme was utilized to further investigate the ischemia-induced inhibition of CaM kinase II. Immunohistochemical investigations showed that the ischemia-induced decreased immunoreactivity of CaM kinase II occurred immediately following ischemic insult in ischemia-sensitive cells such as pyramidal cells of the hippocampus. No decrease in CaM kinase II immunoreactivity was observed in ischemia-resistant cells such as granule cells of the dentate gyrus. The decreased immunoreactivity was observed for CaM kinase II balanced for protein staining and calmodulin binding in vitro. In addition, autophosphorylation of CaM kinase II in the presence of low (7 μ M) or high (500 μ M) ATP did not alter immunoreactivity of the enzyme with 1C3-3D6. The data demonstrate the production of a monoclonal antibody that recognizes the β-subunit of CaM kinase II in a highly specific manner, but does not recognize ischemic enzyme. Together with previous studies, the data support the hypothesis that rapid, ischemia-induced inhibition of CaM kinase II activity may be involved in the cascade of events that lead to selective neuronal cell loss in stroke.
Influence of Preischemic Hyperglycemia on Osmolality and Early Postischemic Edema in the Rat Brain
Authors: Gisselsson Lars , Smith Maj-Lis , Siesjö Bo K.
Published: June 2011

Preischemic hyperglycemia, which raises tissue lactate content during ischemia, is known to aggravate ischemic brain damage. To explore the possibility that the enhanced lactic acidosis gives rise to osmotic damage, we studied the influence of a varied preischemic plasma glucose concentration on the early postischemic edema. Brain edema was measured by the specific-gravity technique. Brain and plasma osmolality were measured with a vapor pressure osmometer. We examined different brain regions in hyperglycemic and moderately hypoglycemic rats subjected to 15 min of forebrain ischemia, followed by recirculation for 5, 15, and 30 min. The decrease in specific gravity was compared with the increase in osmolality, to study whether the edema formation in the different groups correlated to the increase in tissue osmolality. We found edema formation to be most pronounced in frontoparietal cortex. In this structure and in hippocampus, statistically significant decreases of specific gravity were seen at all recirculation times studied. In caudoputamen, significant edema was seen only in the groups with 5 and 15 min of recirculation. Contrary to expectations, no difference was found between hyperglycemic and hyperglycemic animals. Tissue osmolality increased during ischemia in both the low and high glucose groups, but to a higher level in the latter (hypoglycemia 311 ± 1 mmol kg−1, hyperglycemia 328 ± 10 mmol kg−1; mean ± SD, p < 0.05). In the hyperglycemic group, brain osmolality remained elevated for the first 15 min of recirculation. Plasma osmolality also increased during ischemia in the two situations studied and remained increased during the first 15 min of recirculation. In spite of the higher brain osmolality during ischemia and the early recirculation phase in the hyperglycemic animals, theoretically favoring influx of water into brain tissue, we failed to observe increased edema formation in the hyperglycemic animals, probably due to the increased plasma osmolality, partly balancing the rise in brain osmolality and restricting water influx when cerebral blood flow was restored. We conclude that the fatal outcome in hyperglycemic animals is not likely caused by a more pronounced edema in the early recirculation phase.
Effects of Indomethacin on Myogenic Contractile Activation and Responses to Changes in O2 and CO2 in Isolated Feline Cerebral Arteries
Authors: Norins Nan A. , Wendelberger Karen , Hoffman Raymond G. , Keller Peter A. , Madden Jane A.
Published: June 2011

We used an isolated, pressurized, and perfused feline middle cerebral artery preparation to measure how changes in intraluminal pressure and alterations in O2 and CO2 affect vessel diameter and myogenic contractile activation before and after treatment with indomethacin (IND). Vessel diameters were measured over the pressure range 60–140 mm Hg. The arteries were then exposed to low O2 (50 torr) and/or high CO2 (65 torr) and diameters remeasured over the same range. Under control conditions, the arteries exhibited myogenic contractile activation. Exposure to low O2, high CO2, or a mixture of low O2/high CO2, increased vessel diameter but did not change the vessels' myogenic contractile responsiveness to changes in pressure. Arteries exposed to IND decreased in diameter but retained myogenic contractile activity. In the presence of IND, vessels dilated to both low O2 and a mixture of low O2/high CO2, but did not dilate to high CO2 alone. Under all conditions, vessels retained myogenic contractile activity. Results obtained under control conditions and low O2 confirm those of others using similar systems. Myogenic contractile activity in the presence of high CO2 or a mixture of low O2/high CO2 has not been previously reported. The dilation to low O2 but not to high CO2 in the presence of IND suggests that this drug's effects in cerebral arteries are not limited solely to inhibition of prostaglandin synthesis.
Direct and converse effect in magnetoelectric laminate composites
Authors: Cho Kyung-Hoon , Priya Shashank
Published: June 2011

In this letter, we analyze the direct and converse effect in laminate composites of magnetostrictive and piezoelectric materials. Our results deterministically show that direct magnetoelectric (ME) effect is maximized at antiresonance frequency while the converse ME effect is maximized at resonance frequency of the laminate composite. We explain this phenomenon by using piezoelectric constitutive equations and combining it with resonance boundary conditions. The dominant factor controlling the position of peak ME coefficient was found to be frequency dependent capacitance of piezoelectric layer. This study will provide guidance toward the development of magnetic field sensors based on direct effect and communication components based on converse effect.