Simple staining method for differentiating live and dead marine zooplankton in field samples

We describe and evaluate a method for the use of neutral red staining to differentiate live and dead zooplankton in marine field samples. The protocol can be easily incorporated into shipboard zooplankton sampling. The use of neutral red in laboratory studies is common, but its application for quantifying natural live/dead zooplankton composition under field conditions has not been evaluated in detail. We tested the accuracy and precision of the method for a range of salinities and temperatures, and for common estuarine zooplankton groups. Detailed descriptions of staining intensities and patterns are provided. In addition, we evaluated potential artifact mortality due to collection and sample handling. The method produced accurate results under conditions tested, and artifact mortality was negligible using the recommended protocol. Neutral red staining is ideal for quantification of zooplankton carcasses in field samples, which will allow for more systematic study of in situ zooplankton mortality and related processes

The probabilities of absolute ruin in the renewal risk model with constant force of interest

In this paper we consider the probabilities of finite- And infinite-time absolute ruins in the renewal risk model with constant premium rate and constant force of interest. In the particular case of the compound Poisson model, explicit asymptotic expressions for the finite- and infinite-time absolute ruin probabilities are given. For the general renewal risk model, we present an asymptotic expression for the infinite-time absolute ruin probability. Conditional distributions of Poisson processes and probabilistic techniques regarding randomly weighted sums are employed in the course of this study. © Applied Probability Trust 2010.postprin

Dead in the water: The fate of copepod carcasses in the York River estuary, Virginia

Using laboratory and field experiments we investigated three fates of copepod carcass organic matter in the York River estuary, Virginia: ingestion by planktivores (necrophagy), microbial decomposition, and removal by gravitational settling in the presence of turbulence (sinking). The ctenophore Mnemiopsis leidyi ingested live copepods and carcasses indiscriminately in feeding experiments. Microbial decomposition led to ca. 50% of carcass dry weight loss within 8 h after death. Carcass settling velocities in still water were ca. 0.1 cm s(-1), implying short residence time (hours) in the shallow estuary. However, turbulent mixing kept carcasses in suspension much of the time, reducing sinking losses. Rates of carcass organic matter removal were combined in a simple mathematical model predicting the fate of estuarine copepod carcasses. When sinking was considered, it removed a large fraction of carcass organic matter (\u3e= 58% for copepodites, \u3e= 35% for nauplii), with most of the remainder being removed by microbial decomposition. In the absence of sinking losses, necrophagy became proportionally more important in removing carcass organic matter (\u3e= 49%, except in summer)

Relative importance of predatory versus non-predatory mortality for dominant copepod species in the northern Chilean (23°S) Humboldt Current System

Using detailed data of live/dead compositions, stage durations and molting rates, we derived for the first time both predatory and non-predatory mortality rates of the three main copepod species, Paracalanus cf. indicus, Acartia tonsa and Calanus chilensis, within the Humboldt Current System (HCS), and examined their relations with environmental factors. Predatory mortality rates of all three species increased with developmental stages (hence body sizes), indicating top-down control by predators that prefer larger prey. Intrusion of oxygen-poor water via upwelling and low chlorophyll a concentration correlated with increased non-predatory mortality rates of P. cf. indicus and A. tonsa, whereas non-predatory mortality rate of C. chilensis increased with water temperature. Overall, non-predatory mortality accounted for 34.8 to 46.3 % of the total mortality among the three species. Changes in upwelling intensity due to climate change may alter the intensities of predatory and non-predatory mortalities in the HCS copepod communities

Effects of microalgal exudates and intact cells on subtropical marine zooplankton

Harmful algal blooms (HABs) affect coastal waters worldwide and very often lead to the disruption of seafood harvesting and commercial activities, because of potential hazards to human health associated with the consumption of contaminated mussels, crustaceans and fish. HAB events are frequently caused by outbreaks of toxin-producing dinoflagellates, which are subject to top-down control by zooplankton. The aim of this study was to analyze the effects of dinoflagellate exudates and intact cells on the survivorship and mobility of zooplankton taxa from a subtropical location (Ubatuba, Brazil). Lethal effects were observed in five out of six taxa investigated, three of which (copepod nauplii, tintinnids and gastropod larvae) when exposed to dinoflagellate exudates and two (rotifers and brachyuran zoeae) when exposed to intact cells. In addition, gastropod larvae displayed mobility impairment during exposure to dinoflagellate exudates. Only polychaete larvae were not apparently affected during the course of the experiments. Zooplankton responses usually varied according to the dinoflagellate species tested. For instance, exudates from Alexandrium tamiyavanichii, Gonyaulax sp. and Gymnodinium sp. decreased survivorship of planktonic copepod nauplii but did not affect bottom-dwelling harpacticoid nauplii, which were in turn killed by exudates from Prorocentrum lima, a epibenthic dinoflagellate. These results suggest that HAB events do not cause indiscriminate zooplankton mortality, but may instead generate community shifts and complex cascading effects through the pelagic and benthic food web. Species-specific monitoring of zooplankton responses to HABs is therefore an important step to understand the ecological implications of dinoflagellate outbreaks in coastal waters, and their impact on marine farming activities

Symmetric and antisymmetric nonlinear modes supported by dual local gain in lossy lattices

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The nested dirichlet distribution and incomplete categorical data analysis

The nested Dirichlet distribution (NDD) is an important distribution defined on the closed n-dimensional simplex. It includes the classical Dirichlet distribution and is useful in incomplete categorical data (ICD) analysis. In this article, we develop the distributional properties of NDD. New large-sample likelihood and small-sample Bayesian approaches for analyzing ICD are proposed and compared with existing likelihood/Bayesian strategies. We show that the new approaches have at least three advantages over existing approaches based on the traditional Dirichlet distribution in both frequentist and conjugate Bayesian inference for ICD. The new methods possess closed-form expressions for both the maximum likelihood and Bayes estimates when the likelihood function is in NDD form; produce computationally efficient EM and data augmentation algorithms when the likelihood is not in NDD form; and provide exact sampling procedures for some special cases. The methodologies are illustrated with simulated and real data.published_or_final_versio

Inviscid two dimensional vortex dynamics and a soliton expansion of the sinh-Poisson equation

The dynamics of inviscid, steady, two dimensional flows is examined for the case of a hyperbolic sine functional relation between the vorticity and the stream function. The 2-soliton solution of the sinh-Poisson equation with complex wavenumbers will reproduce the Mallier-Maslowe pattern, a row of counter-rotating vortices. A special 4-soliton solution is derived and the corresponding flow configuration is studied. By choosing special wavenumbers complex flows bounded by two rigid walls can result. A conjecture regarding the number of recirculation regions and the wavenumber of the soliton expansion is offered. The validity of the new solution is verified independently by direct differentiation with a computer algebra software. The circulation and the vorticity of these novel flow patterns are finite and are expressed in terms of well defined integrals. The questions of the linear stability and the nonlinear evolution of a finite amplitude disturbance of these steady vortices are left for future studies. © 1998 American Institute of Physics.published_or_final_versio

Further properties and new applications of the nested Dirichlet distribution

Recently, Ng et al. (2009) studied a new family of distributions, namely the nested Dirichlet distributions. This family includes the traditional Dirichlet distribution as a special member and can be adopted to analyze incomplete categorical data. However, other important aspects of the family, such as marginal and conditional distributions and related properties are not yet available in the literature. Moreover, diverse applications of the family to the real world need to be further explored. In this paper, we first obtain the marginal and conditional distributions and other related properties of the nested Dirichlet distribution. We then present new applications of the family in fitting competing-risks model, analyzing incomplete categorical data and evaluating cancer diagnosis tests. Three real data involving failure times of radio transmitter receivers, attitude toward the death penalty and ultrasound ratings for breast cancer metastasis are provided. © 2009 Elsevier B.V. All rights reserved.postprin

海浪發電

由於全球人口不斷增長，所以能源需求日益增加。地球上大部份的能源主要來自化石燃料。不過，燃燒化石燃料發電會釋出大量二氧化碳和污染物，造成溫室效應從而導致環境破壞；而且，化石燃料是有限的能源。雖然可用核原料發電，但是核能的安全問題與風險管理不斷受人們爭論。故此，對再生能源的研究及開發是刻不容緩的。本章主要討論其中一種再生能源，海浪發電的好處及近期一些研究成果。published_or_final_versio