Sexual reproduction in Phytophthora infestans

Potato late blight, caused by the oomycete Phytophthora infestans, is one of the most devastating plant diseases worldwide. It is becoming increasingly difficult to control the disease in Sweden, leading to an ever more intensified use of fungicides in the potato production. This unsustainable development could be caused by changes in the pathogen due to the introduction of sexual reproduction. These changes could result in an enhanced capability of the pathogen to adapt to different factors, e. g. weather, cultivar resistance, chemical control or other cultivation measures. This might manifest itself in earlier infections and a late blight that spreads faster in the potato fields requiring increasing efforts to control. Different approaches were taken to clarify the role of sexual reproduction in P. infestans in the epidemiology of potato late blight. The formation of sexually formed oospores and their ability to serve as primary inoculum was studied, both as field observations and by determining within-field genotypic diversity. To further estimate the importance of reproduction on a large spatial scale a population study based on molecular and phenotypic markers was performed on P. infestans isolates from the whole Nordic region. The variation in the aggressiveness of Nordic populations of P. infestans was studied by determining different components of aggressiveness, e.g. sporulation capacity, lesion growth and infection efficacy. The aggressiveness study was combined with an analysis of the phenotypic structure of the Nordic population of P. infestans. The results clearly indicate that the Swedish populations of P. infestans are influenced by sexual reproduction. The facts that both mating types are found all over the country in near 1:1 proportions and that oospores are commonly formed in field crops and serve as inoculum under field conditions support this. Studies of the genetic diversity also indicate that sexual reproduction has an effect on the population structure of P. infestans in Sweden and the Nordic region as a whole

On the Causality Between Saving and Growth: Long- and Short-Run Dynamics and Country Heterogeneity

The temporal interdependence between saving and output has been in focus in a number of recent empirical studies. Results from these studies have compelled some authors to question the traditional notion of a causal chain where saving leads growth through capital accumulation. This paper contributes to this literature. As opposed to the previous studies, which have mainly utilised panel-estimation methods, the tests of causal chains here are carried out in time-series settings. Saving and GDP are estimated in bivariate vector autoregressive or vector error-correction models for Sweden, UK, and USA, and tests of Granger non-causality are performed within the estimated systems. The main results show that the causal chains linking saving and output differ across countries, and also that causality associated with adjustments to long-run relations might go in different directions than causality associated with short-term disturbances.Saving; growth; Granger-causality; cointegration; VAR; VECM

Scandinavian Evidence on Growth and Age Structure

The age distribution is seldom taken into consideration in macroeconomic, and macro-econometric papers. This in spite of the fact that established economic theories predict that demographic factors will affect the aggregate economy. This paper focuses on economic growth and investigates empirically the influence of age variables on growth. Unlike other recent papers on the subject, the focus here is on annual data and individual countries, namely Denmark, Finland, Norway, and Sweden. Estimations of a typical growth specification, augmented with age variables and other, more volatile, economic variables, are carried out, and results from these regressions seem to indicate that economic growth is indeed affected by the age distribution. The effect does not disappear when the specification is reestimated using an instrumental variable estimator in order to correct for the potential endogeneity of the economic variables. Since the age variables are highly correlated with each other, experiments with ridge regressions are also made in order to mitigate the collinearity which obscures the results when all of the age variables are included in the regressions.growth; age structure; Scandinavian countries; ridge regression

Portfolio Allocation over the Life Cycle: Evidence from Swedish Household Data

This paper provides empirical evidence on life-cycle patterns in the asset allocation of Swedish households. Data on household portfolio allocation are collected from the HINK surveys for the period 1982-1992, and portfolio shares of different asset categories are regressed on age, period, and cohort dummies as well as socio-economic and demographic variables. There are evident differences in the age profiles for the demand of different assets. The fraction of "risky" financial assets follows a hump-shaped age profile, as does the share of total real assets. While the probability of ownership of "safe" financial assets increases over life, the weight in the portfolio has a U-shaped age pattern. This is also true for the fraction of total financial assets. Furthermore, there are differences in the asset allocation of different birth cohorts; the portfolio weight of real assets is relatively higher for the "baby-boom" generation, while younger generations are more prone to invest in "risky" financial assets.Life cycle; asset demand; portfolio choice; cohort; differential mortality; Sweden

Linearizability and schedulability

Consider the problem of scheduling a set of tasks on a single processor such that deadlines are met. Assume that tasks may share data and that linearizability, the most common correctness condition for data sharing, must be satisfied. We find that linearizability can severely penalize schedulability. We identify, however, two special cases where linearizability causes no or not too large penalty on schedulability

Schedulability analysis of generalized multiframe traffic on multihop-networks comprising software-implemented ethernet switches

Consider a multihop network comprising Ethernet switches. The traffic is described with flows and each flow is characterized by its source node, its destination node, its route and parameters in the generalized multiframe model. Output queues on Ethernet switches are scheduled by static-priority scheduling and tasks executing on the processor in an Ethernet switch are scheduled by stride scheduling. We present schedulability analysis for this setting

The utilization bound of static-priority preemptive partitioned multiprocessor scheduling is 50%

This paper studies static-priority preemptive scheduling on a multiprocessor using partitioned scheduling. We propose a new scheduling algorithm and prove that if the proposed algorithm is used and if less than 50% of the capacity is requested then all deadlines are met. It is known that for every static-priority multiprocessor scheduling algorithm, there is a task set that misses a deadline although the requested capacity is arbitrary close to 50%

Conjecture about global fixed-priority preemptive multiprocessor scheduling of implicit-deadline sporadic tasks: the utilization bound of SM-US(sqrt(2)-1) is sqrt(2)-1

Consider global fixed-priority preemptive multiprocessor scheduling of implicit-deadline sporadic tasks. I conjecture that the utilization bound of SM-US(√2−1) is √2-1

A pseudo-medium-wide 8-competitive interface for two-level compositional real-time scheduling of constrained- deadline sporadic tasks on a uniprocessor

Compositional real-time scheduling clearly requires that ”normal” real-time scheduling challenges are addressed but challenges intrinsic to compositionality must be addressed as well, in particular: (i) how should interfaces be described? and (ii) how should numerical values be assigned to parameters constituting the interfaces? The real-time systems community has traditionally used narrow interfaces for describing a component (for example, a utilization/bandwidthlike metric and the distribution of this bandwidth in time). In this paper, we introduce the concept of competitive ratio of an interface and show that typical narrow interfaces cause poor performance for scheduling constrained-deadline sporadic tasks (competitive ratio is infinite). Therefore, we explore more expressive interfaces; in particular a class called medium-wide interfaces. For this class, we propose an interface type and show how the parameters of the interface should be selected. We also prove that this interface is 8-competitive

Simulating the Future Pension Wealth and Retirement Saving in Sweden

In this paper the wealth consequences of the Swedish pension system in the transition from a defined benefit to notional defined contribution system are simulated with almost exact institutional detail, using life cycle profiles estimated from detailed longitudinal micro data. Projected wealth, including different types of pension wealth, are computed and compared between cohorts, gender, wealth deciles and occupational categories. Consistent saving rates and replacement rates allowing consumption to stay constant after retirement are computed. Two different macroeconomic scenarios are considered, one using stylised values for growth, inflation etc. and another using demographically based forecasts. Some conclusions are that the cohorts born in the 1940s are relatively favoured, and so are the wealthiest deciles. Stylised macro assumptions yield more optimistic wealth projections than those corresponding to demographically based projections.Future Pension Wealth; Retirement Saving in Sweden