Benthic Foraminiferal Assemblages from Marshes and Mangroves in the Everglades (South Florida, USA) and Their Application as Proxies for Habitat Shifts due to Sea Level Rise

This study examined benthic foraminifera from marsh and mangrove environments along the coasts of the Everglades in South Florida for their use as proxies for salinity and applied the results to assess the nature and rates of past habitat changes due to sea level rise over the last ~3400 years. Research on modern foraminiferal assemblages from the Everglades are scarce, and this is the first foraminifera-based paleoenvironmental study for this region. The study of living assemblages examined the extent to which infaunal foraminifera bias modern and fossil assemblages, and which sediment interval should be used as a modern analog for paleoenvironmental studies in this area. As most benthic foraminifera live in the 0–1 cm of sediment, many of these studies are based on the 0–2 cm of sediment. This study revealed a deepening of the living depths in a landward direction, possibly due to the landward increase in the oxygenation of subsurface sediments. However, subsurface production is negligible, and the 0–2 cm is sufficient as a modern analog. The study of the modern foraminiferal distribution found that diversity decreases, dominance increases, and agglutinated taxa increase from the coastline inland. Factors controlling foraminiferal distribution, in order of importance, are salinity, total organic carbon, and total inorganic carbon. Everglades foraminifera are excellent salinity proxies and can be used to determine this area’s history of habitat change. The study on fossil and subfossil assemblages found that environments changed over time from upper mangrove, to lower mangrove, and finally the marine-influenced habitat of the study site today. The shifts in foraminiferal assemblages over time can be related to an increase in salinity with sea level rise and accelerated toward the present by AD 1950. This the first foraminifera-based paleoenvironmental study for this area, and the results can be used to predict shifts in coastal habitats, of importance to South Florida’s growing coastal population

Quasi-Likelihood Estimation of Benchmark Rates for Excess of Loss Reinsurance Programs

In this paper a method for determining benchmark rates for the excess of loss reinsurance of a Motor Third Party Liability insurance portfolio will be developed based on observed market rates. The benchmark rates are expressed as a percentage of the expected premium income that is available to cover the whole risk of the portfolio. The rates are assumed to be based on a compound process with a heavy tailed severity, such as Burr or Pareto distributions. In the absence of claim data these assumptions propagate the theoretical benchmark rate component of the regression model. Given the whole set of excess of loss reinsurance rates in a given market, the unknown parameters are estimated within the framework of quasi-likelihood estimation. This framework makes it possible to select a theoretical benchmark rate model and to choose a parsimonious submodel for describing the observed market rates over a 4-years observation period. This method is applied to the Belgian Motor Third Party Liability excess of loss rates observed during the years 2001 till 200

Actuariële bedenkingen bij een eenvormig opgelegd bonus-malus stelsel.

Verscheidene actoren van het verzekeringswezen dringen sterk aan om het verplicht eenvormig bonus-malus stelsel in de verzekering B.A.-auto te behouden. In deze nota wordt aan de hand van een theoretisch voorbeeld aangetoond dat dit standpunt vanuit actuariëel oogpunt onhoudbaar is.

A spatial mixed Poisson framework for combination of excess-of-loss and proportional reinsurance contracts

In this paper a purely theoretical reinsurance model is presented, where the reinsurance contract is assumed to be simultaneously of an excess-of-loss and of a proportional type. The stochastic structure of the set of pairs (claim’s arrival time, claim’s size) is described by a Spatial Mixed Poisson Process. By using an invariance property of the Spatial Mixed Poisson Processes, we estimate the amount that the ceding company obtains in a fixed time interval in force of the reinsurance contract

Optimal joint survival reinsurance: An efficient frontier approach

The problem of optimal excess of loss reinsurance with a limiting and a retention level is considered. It is demonstrated that this problem can be solved, combining specific risk and performance measures, under some relatively general assumptions for the risk model, under which the premium income is modelled by any non-negative, non-decreasing function, claim arrivals follow a Poisson process and claim amounts are modelled by any continuous joint distribution. As a performance measure, we define the expected profits at time x of the direct insurer and the reinsurer, given their joint survival up to x, and derive explicit expressions for their numerical evaluation. The probability of joint survival of the direct insurer and the reinsurer up to the finite time horizon x is employed as a risk measure. An efficient frontier type approach to setting the limiting and the retention levels, based on the probability of joint survival considered as a risk measure and on the expected profit given joint survival, considered as a performance measure is introduced. Several optimality problems are defined and their solutions are illustrated numerically on several examples of appropriate claim amount distributions, both for the case of dependent and independent claim severitie

Exploring the Energy Landscape of the Charge Transport Levels in Organic Semiconductors at the Molecular Scale

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Efficient risk allocation within a non-life insurance group under Solvency II Regime

Intra-group transfers are risk management tools that are usually widely used to optimise the risk position of an insurance group. In this paper, it is shown that premium and liability transfers could be optimally made in such a way as to reduce the amount of Technical Provisions and Minimum Capital Requirement for the entire insurance conglomerate. These levels of required capital represent the minimal amount that needs to be held by the insurance group without regulator intervention, according to the Solvency II regulation. We assume that only proportional risk transfers are feasible, since such transfers are not difficult to administer for a large scaled insurance group, as is always the case. In addition, any risk shifting should be made for commercial purposes in order to be considered acceptable by the local regulators that impose restrictions on how much the assets within an insurance group are fungible. Our numerical examples illustrate the efficiency of the optimal proportional risk transfers which can easily be implemented, in terms of computation, in any well-known solver even for an insurance conglomerate with many subsidiaries. We found that our proposed optimal proportional allocations are more beneficial for large insurance group, since the relative reduction in capital requirement tends to be small, whereas the gain in absolute terms is quite significant for large scaled insurance group

Effect of Impurities on Pentacene Thin Film Growth for Field-Effect Transistors

Pentacenequinone (PnQ) impurities have been introduced into a pentacene source material at number densities from 0.001 to 0.474 to quantify the relative effects of impurity content and grain boundary structure on transport in pentacene thin-film transistors. Atomic force microscopy (AFM) and electrical measurements of top-contact pentacene thin-film transistors have been employed to directly correlate initial structure and final film structures, with the device mobility as a function of added impurity content. The results reveal a factor four decrease in mobility without significant changes in film morphology for source PnQ number fractions below ~0.008. For these low concentrations, the impurity thus directly influences transport, either as homogeneously distributed defects or by concentration at the otherwise-unchanged grain boundaries. For larger impurity concentrations, the continuing strong decrease in mobility is correlated with decreasing grain size, indicating an impurity-induced increase in the nucleation of grains during early stages of film growth.Comment: 18 pages, 4 Figures, 1 Tabl

Wide field magnetic luminescence imaging

This study demonstrates how magnetic-field-dependent luminescence from organic films can be used to image the magnetic configuration of an underlying sample. The organic semiconductors tetracene and rubrene exhibit singlet exciton fission, which is a process sensitive to magnetic fields. Here, thin films of these materials were characterized using photoluminescence spectrometry, atomic force microscopy, and photoluminescence magnetometry. The luminescence from these substrate-bound thin films is imaged to reveal the magnetic configuration of underlying Nd-Fe-B magnets. The tendency of rubrene to form amorphous films and produce large changes in photoluminescence under an applied magnetic field makes it more appropriate for magnetic field imaging than tetracene. This demonstration can be extended in the future to allow simple microscopic imaging of magnetic structure