Seasonal variations of abundance and live/dead compositions of copepods inMersin Bay, northeastern Levantine Sea (eastern Mediterranean)

The seasonality of abundance and live/dead compositions of copepods was studied in the northeastern Mediterranean Sea. Zooplankton, chlorophyll-a, and PO4 sampling was performed on a monthly basis from March 2006 to February 2007 at both a coastal station and an open water station. At the coastal station, high phytoplankton biomass was driven by PO4 input from the Lamas River. On annual average, copepod abundance was 53,075 and 140,227 ind. m(-2) at the coastal and open water stations, respectively. The most common copepod taxa were Oithona similis, Euterpina acutifrons, Labidocera spp., Oncaea media, and Temora spp. at the coastal station, and Oncaea media, Labidocera spp., Lucicutia spp., Farranula spp., Oithona similis, and Microsetella spp. at the open water station. At the coastal station, dead copepods did not exceed 7% of the population; on annual average, 2.6% of the copepods were dead. At the open water station, on average 10.6% of the copepod population appeared dead; the percentages of dead copepods reached 29.5% in April and 21.7% in May 2006, suggesting that the copepod community suffered higher nonpredatory mortality at the open water station than at the coastal station, especially in the spring

Multiscale resolution continuum theory for elastic plastic material with damage, an implicit 3D implementation

The multiscale resolution continuum theory (MRCT) [1] is a higher order continuum theory in which additional kinematic variables are added to account for the size effect at several distinct length scales. This remedies the deficiency of the conventional continuum approach when predicting both strain softening and strain hardening materials and resolves the microstructure details without extremely fine mesh in the localization zone, however additional nodal degrees of freedom are needed and the requirement of element size at the length scale somewhat adds to the computational burden. This paper is an extension of the simplified 1D multiscale implementation presented in Complas XI 2011 [14]. A 3D elastic-plastic multiscale element, with one additional subscale in which the damage is applied, is implemented implicitly in the general purpose finite element analysis program FEAP

Simplified multiscale resolution theory for elastic material with damage

The multiscale resolution continuum theory (MRCT) is a higher order continuum mechanics. A particle is represented by a point that is deformable. This enables the possibility to include the effect of microstructure features in the continuum model on the deformation behavior through additional nodal variables for the higher order scale. This reduces the need for a very fine mesh in order to resolve microstructure details. It is possible to further reduce the computational effort by keeping the additional degree of freedoms to a minimum by tailoring the theory to specific phenomena. The latter is illustrated in a simplified context for an elastic material with damage

Associations of apolipoprotein E exon 4 and lipoprotein lipase S447X polymorphisms with acute ischemic stroke and myocardial infarction

Background: Because apolipoprotein E (apoE) and lipopoprotein lipase (LPL) polymorphisms interact with each other and with other factors to affect lipid metabolism, we sought to determine their separate and combined effects in association with ischemic vascular disease. Methods: We performed a case-control study of 816 subjects: 246 acute ischemic stroke patients, 234 acute myocardial infarction patients, and 336 controls. APOE exon 4 and LPL S447X genotypes were determined. Results: APOE ε2 and ε4 homozygotes were increased in stroke (4.5% vs. 1.0%, p = 0.008), while in myocardial infarction the ε4 allele was increased (12.6% vs. 9.5%, p = 0.006) but ε2 was decreased (3.7% vs. 12.1%, p = 0.000006). For subjects with either APOE ε2 or ε4 alleles, LPL X alleles were increased in vascular disease (OR = 2.2, p = 0.01). LPL X alleles displayed opposite tendencies toward association with disease when subjects were divided by sex, smoking, or APOE genotype. Meta-analysis and regression analysis of previous studies supported the sex and smoking dichotomies. Conclusion: This is the first report of an association of vascular disease with an interaction of APOE exon 4 and LPL S447X genotypes. Therefore, APOE genotypes and LPL S447X interactions with apoE, sex, and smoking may affect the risk of myocardial infarction and ischemic stroke. © 2006 by Walter de Gruyter.published_or_final_versio

How students cope with part-time study

This study provides a qualitative test and illustration of a model of how students cope with the demands of part-time study. The model shows that students who are successful in finding the time to complete the requirements of part-time courses do so by adopting three mechanisms; sacrifice, support and the negotiation of arrangements. All three mechanisms operate in four domains, namely work, family, social lives and the self. The mechanisms and domains were related together in a three by four matrix. Data to verify and illuminate the model were gathered by the researchers through an on-line forum discussion on the topic of coping with part-time study. The researchers themselves were studying part-time in a course called Adult Education and Professional Development. Analysis of the data showed that the work domain was very important but little adaptation was possible. The family was seen as the most important domain and all three mechanisms were used. Time was commonly found for part-time study by sacrificing social lives. The self-domain was interpreted as important in establishing motivation and self-determination

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Interaction between marine calanoid copepods and dimethylsulfoniopropionate

Copepods and other zooplankters represent a previously overlooked pool of particulate dimethylsulfoniopropionate (DMSP). DMSP content of marine copepods varied from pico-moles in Acartia tonsa to nano-moles in Temora longicornis. In eastern Long Island Sound, zooplankton was a negligible pool of DMSP during most of the year, but in spring when the abundance of T. longicornis was large, zooplankton represented up to 72% of the total particulate DMSP in surface water. ^ In laboratory studies, the DMSP content of Temora longicornis was positively related to salinity and food-DMSP concentration, and was reduced by \u3e50% when salinity decreased from 30‰ to 20‰. This reduction in DMSP content was not a result of DMSP cleavage, demethylation, or conversion of DMSP to methionine. Instead, most of the missing DMSP was recovered as dissolved DMSP in the surrounding medium. Thus, this regulatory mechanism shifts the partitioning of DMSP from the particulate phase to the dissolved phase when ambient salinity decreases. ^ The DMSP content of Acartia tonsa was determined mostly by food availability. In an experiment that simulated the migratory behavior of A. tonsa, the copepods\u27 DMSP content increased when feeding in food-abundant surface water, and 88 to 100% of the ingested DMSP was not retained in the bodies. Actively migrating copepods would transport \u3c10% of the ingested DMSP to deep water. Thus, A. tonsa affects DMSP dynamics likely through fecal pellet production. The DMSP content of fecal pellets was correlated with the copepods\u27 body DMSP content, and ambient food concentration. DMSP concentration within pellets was orders of magnitude higher than typical dissolved DMSP concentrations in the ocean. Thus, fecal pellets may represent “hot spots” for DMSP diffusion and microbial consumption in the water column. ^ Field-collected A. tonsa contained DMSP-consuming bacteria (DCB) in their bodies, Recovered DCB increased by over 10-fold after A. tonsa fed on DMSP-containing algae. DCB were also recovered from the copepods\u27 fecal pellets. Enrichment cultures of DCB from copepod bodies converted only a portion of the consumed DMSP to DMS, compared to ∼100% for DCB from fecal pellets. Copepod-bacteria coupling thus represents a novel mechanism for DMSP consumption and DMS production in the ocean.