Analysis of individual year-classes of a marine fish reveals little evidence of first-generation hybrids between cryptic species in sympatric regions

As settled juveniles and adults, blue rockfish (Sebastes mystinus) are nonmigratory inhabitants of kelp and rocky reef habitats along the California coast, USA, and prior to settlement, they possess a pelagic larval and juvenile stage lasting 3–5 months. A previous study of adults revealed two cryptic species within S. mystinus and evidence of reproductive isolation in a region where both cryptic adults co-occur. Given this pattern of reproductive isolation, we investigated the degree of hybridization or introgression in individual year-classes shortly after juvenile settlement in two different years (2001 and 2002). Using microsatellite markers, we found little indication of hybridization in new juvenile year-classes despite an adult population that comprised both cryptic species. However, we found an average of two percent of hybrid or introgressed individuals in regions with a low frequency of one of the two species. Therefore, while the lack of hybrids or introgression supports the hypothesis of reproductive isolation between the cryptic species within S. mystinus, the age-structured analysis also revealed a spatial pattern of low-frequency differences in the number of introgressed individuals. These results suggest that reproductive barriers may breakdown when one of the two species predominates the regional adult gene pool.     

Prenatal diagnosis in monozygotic twins with Down syndrome who had different phenotypes

We report the case of monozygotic (MZ) male twin fetuses with different Down syndrome (DS) phenotypes. Prenatal fetal sonography showed a bichorial biamniotic pregnancy with increased nuchal translucency in twin A and a cervical cystic hygroma and heart defect in twin B. Cytogenetic analysis performed after double amniocentesis showed free and homogeneous trisomy 21 in both twins. Monozygosity was confirmed by molecular analysis. The pregnancy was terminated at 17 weeks of gestation (WG). Postmortem analysis confirmed the phenotypic discordance. To our knowledge, this is the first reported prenatal diagnosis of MZ male twins with different Down syndrome phenotypes but identical karyotypes. We discuss the mechanisms involved in phenotypic discordance of monozygotic twins and particularly the role of environmental factors. Copyright © 2007 John Wiley & Sons, Ltd.     

An Experimental Study of Hopper Evacuation Effects on Multitube Cyclone Performance

An experimental multitube cyclone facility was constructed and experiments conducted to investigate the influence of hopper evacuation on multitube cyclone performance. The effects of the amount of hopper evacuation and the location of hopper evacuation on individual cyclone tube velocities and particle collection efficiency were determined. Cyclone tube velocities increased with increasing hopper evacuation although hopper evacuation location had little effect on the velocities. Particle collection efficiencies were increased from 89.5 percent to approximately 95 percent with 14 percent hopper evacuation from a location near the center of the hopper. Other hopper evacuation locations were not as effective in increasing collection efficiency. These results suggest that, while the increased velocity in the cyclone tubes is an important effect in the improvement of multitube cyclone performance with hopper evacuation, other factors such as redistribution of gas flow within the hopper are also important.     

Comparison of Solid-Phase and Pore-Water Approaches for Assessing the Quality of Marine and Estuarine Sediments

As part of our continuing evaluation of the pore-water approach for assessing sediment quality, we made a series of side-by-side comparisons between the standard 10-day amphipod whole sediment test with the corophiid Grandidierella japonica and a suite of tests using pore water extracted from the same sediments. the pore-water tests evaluated were the sea urchin (Arbacia punctulata) sperm cell test and morphological development assay, the life-cycle test with the polychaete Dinophilus gyrociliatus, and acute exposures of red drum (Sciaenops ocellatus) embryo-larval stages. Sediment and surface microlayer samples were collected from contaminated sites. Whole-sediment, pore-water, and surface microlayer toxicity tests were performed. Pore-water toxicity tests were considerably more sensitive than the whole-sediment amphipod test, which is currently the most sensitive toxicity test now recommended for determining the acceptability of dredged material for open ocean disposal.     

Serum concentrations and profiles of polychlorinated biphenyls in Taiwan Yu-cheng victims twenty years after the incident

In 1979, about 2000 people in central Taiwan were intoxicated via rice oil consumption that was contaminated with polychlorinated biphenyls (PCBs). This "Yu-cheng" incident was one of the two known major human PCB intoxication episodes. Twenty years after the intoxication, serum samples of 435 Yu-cheng victims, 414 adults and 21 children, were collected. Sixteen PCB congeners were analyzed with a gas chromatograph-electron capture detector. We found the median concentration of total PCBs in the adult serum was 1500 ng/g lipid, still substantially higher than that of the general population in Taiwan (3.7-fold) and most seafood consumers in the world. Most of analyzed PCB congeners in children were below or around the detection limits. Congener #138, however, had the highest concentrations, approximately accounting for 55% and 29% in the child and adult groups, respectively. Given that PCBs are persistent organic pollutants and endocrine disruptors, the concentrations and congener-specific profiles regarding the Yu-cheng victims provide valuable information for the investigation of such chemicals in humans.     

Evaluating the Applicability of a Two‐dimensional Flow Model of a Highly Heterogeneous Domain to Flow and Environmental Management

Two‐dimensional simulation of highly heterogeneous domains, especially those with disparate length scales, roughness conditions, and geometries, often leads to challenges such as long computation times and numerical instability. Simulation of challenging domains is often needed to guide flood management and environmental regulation agencies in operation and potential domain modifications. This work evaluates the ability of a two‐dimensional unsteady hydrodynamic model to represent long‐duration transient flows over a domain with highly heterogeneous roughness, geometric characteristics, and length scales through bed roughness representation. The domain includes 13 km of Cache Creek and the 14.5 km² Cache Creek Settling Basin, which traps both sediment and mercury. Calibration under different bed roughness methods, validation, and modeling results of bathymetric modification scenarios are presented. The modeling approach's performance supports its application as a tool for management of similar domains, such as settling basins, leveed floodplains, and reservoirs. Accurate representation of flow dynamics can also inform environmental management that involves transport of sediments, nutrients, and heavy metals. This study found that a two‐dimensional unsteady flow model can accurately represent long‐duration transient flow in a large settling basin with highly heterogeneous characteristics without parsing of the domain or flow events simulated.     

Academic publishing in disaster risk reduction: past,present, and future

Nowadays there are approximately 80 Anglophone journals that deal primarily with disaster risk reduction (DRR) and allied fields. This large array signals a sustained, if uneven, growth in DRR scholarship but also competition between the offerings of different publishers and institutions. The purpose of this article is first to summarise the development of academic publishing on DRR from its early beginnings to the present day. The paper then evaluates the current state of publishing in this field and discusses possible future trends. Next, it identifies some possible opportunities, challenges, expectations, and commitments for journal editors both within DRR and academia more broadly, including those that refer to changes in the use of terminology, the relentless increase in the number of papers submitted, the expansion and dangers of predatory journals, different peer review models, open access versus paywalls, citations and bibliography metrics, academic social networks, and copyright and distribution issues.