2,387 research outputs found
Seabed foraging by Antarctic krill: Implications for stock assessment, bentho-pelagic coupling, and the vertical transfer of iron
No full textA compilation of more than 30 studies shows that adult Antarctic krill (Euphausia superba) may frequent benthic habitats year-round, in shelf as well as oceanic waters and throughout their circumpolar range. Net and acoustic data from the Scotia Sea show that in summer 2-20% of the population reside at depths between 200 and 2000 m, and that large aggregations can form above the seabed. Local differences in the vertical distribution of krill indicate that reduced feeding success in surface waters, either due to predator encounter or food shortage, might initiate such deep migrations and results in benthic feeding. Fatty acid and microscopic analyses of stomach content confirm two different foraging habitats for Antarctic krill: the upper ocean, where fresh phytoplankton is the main food source, and deeper water or the seabed, where detritus and copepods are consumed. Krill caught in upper waters retain signals of benthic feeding, suggesting frequent and dynamic exchange between surface and seabed. Krill contained up to 260 nmol iron per stomach when returning from seabed feeding. About 5% of this iron is labile, i.e., potentially available to phytoplankton. Due to their large biomass, frequent benthic feeding, and acidic digestion of particulate iron, krill might facilitate an input of new iron to Southern Ocean surface waters. Deep migrations and foraging at the seabed are significant parts of krill ecology, and the vertical fluxes involved in this behavior are important for the coupling of benthic and pelagic food webs and their elemental repositories
Evaluating the contribution of Yr genes to stripe rust resistance breeding through marker-assisted detection in wheat
No full textNumerous stripe rust resistance genes have been identified from wheat, and new virulent races of Puccinia striiformis f. sp. tritici have also emerged in recent years. Deployment of diverse combinations of resistance genes is an efficient way to combat virulent evolution of strip rust pathogen. In this study, publically available molecular markers were used to identify the distribution of 36 Yr genes in 672 wheat accessions. The effectiveness of Yr genes individually and in combinations was also evaluated in field conditions. The result showed effective resistance of some recently applied genes, such as Yr15 and Yr65. It also showed the lost efficacy of some once widely used genes, such as Yr9 and Yr10. Moreover, significant additive effects were observed in some gene combinations, such as Yr9 + Yr18 and Yr30 + Yr46. Proper deploying of Yr genes and utilizing the positive interactions will be helpful for durable resistance breeding in wheat
Hurricane Surge Risk Reduction For Galveston Bay
No full textMore than five years after Hurricane Ike devastated the Galveston Bay Area, the most critical challenge remains; reducing flood vulnerability. In response to Hurricane Ike’s disastrous impact, several structural flood risk reduction strategies have been proposed. Some advocating local solutions, others advocating system-wide coastal barriers. The relationship between storm surge within Galveston Bay and storm surge at the open coast may profoundly affect the performance of these local or system-wide solutions. Limited understanding of bay behavior under hurricane forcing limits the ability to select the optimal solution. To assess the bay behavior under hurricane forcing, a probabilistic behavior-oriented storm surge model has been developed. The model couples meteorological forcing with hydrodynamic response and provides a first-estimate of storm surge within simplified semi-enclosed bays. A large suite of synthetic parametric hurricane wind fields provides input for the storm surge model. Storm surge at the open coast is obtained by solving the one-dimensional depth integrated shallow water equations. Storm surge within the semi-enclosed bay relies on a parametric relation between wind set-up and storm surge at the open-coast. Hindcasts of historic storms show that the model provides a reasonable estimate of storm surge within the bay, with a typical error of ±0.5 meter. Storm surge within Galveston Bay is a delicate balance between inflow and local wind set-up. Simulations show that local wind set-up contributes up to 50% to the surge within the bay, depending on landfall location and storm intensity. Results indicate that the 1/1,000 yr-1 surge at the northern bay end exceeds the 1/1,000 yr-1 surge at the open coast by about 0.5 meter. The 1/10,000 yr-1 surge at the northern bay end exceeds the 1/10,000 yr-1 surge at the open coast by about 1.0 meter. Although significant, obtained results do not indicate that the difference in surge elevation plays a crucial role in strategy selection. To assess the benefits of a coastal spine, ship channel gate or Texas City levee upgrade, a preliminary flood risk assessment has been performed. For each strategy, the benefits in terms of risk reduction are estimated by relating simulated surge probabilities to residential exposure, industrial exposure and surface elevation. Comparing the estimated investment cost and benefits of each strategy allows an informed monetary comparison of the individual risk reduction strategies. The flood risk assessment confirms that the Galveston Bay Area is highly vulnerable to storm surge. Existing regulations solely require industrial complexes to protect up to the 100-year flood level. Consequently, residential exposure significantly exceeds industrial exposure for return periods of up to once per 100 years. Industrial exposure outweighs residential exposure for less frequent events. Considerable benefits can be achieved by protecting both residential property and industrial assets. Preliminary results indicate that a coastal spine significantly reduces storm surge within the bay and yields the highest benefits in terms of risk reduction. The ship channel gate and the Texas City Levee Upgrade yield a similar rate of return but achieve considerably less benefits.Hydraulic EngineeringCivil Engineering and Geoscience
Decreasing pH trend estimated from 25-yr time series of carbonate parameters in the western North Pacific
No full textWe estimated long-term trends of ocean acidification in surface waters in latitudinal zones from 3°N to 33°N along the repeat hydrographic line at 137°E in the western North Pacific Ocean. Estimates were based on the observational records of oceanic CO2 partial pressure and related surface properties over the last two decades. The computed pH time series both for 25 years in winter (late January to early February) and for 21 years in summer (June to July) exhibited significant decreasing trends in the extensive subtropical to equatorial zones, with interannual variations that were larger in summer. The calculated rates of pH decrease ranged from 0.0015 to 0.0021 yr^[-1] (average, 0.0018 ± 0.0002 yr^[-1]) in winter and from 0.0008 to 0.0019 yr^[-1] (average, 0.0013 ± 0.0005 yr^[-1]) in summer. The thermodynamic effects of rising sea surface temperature (SST) accounted for up to 44% (average, 15%) of the trend of pH decrease in the subtropical region in winter, whereas a trend of decreasing SST slowed the pH decrease in the northern subtropical region (around 25°N) in summer. We used the results from recent trends to evaluate future possible thermodynamic changes in the upper ocean carbonate system
Delayed monochromatic hue matches indicate characteristics of visual memory
No full textMeasured short-term memory for 16 monochromatic hues after 6 delays by means of an iterative, momentary stimulus-matching technique. Observers were 4 25-43 yr old males including the 1st author
Assessing bone microstructure at the distal radius in children and adolescents using HR-pQCT: A methodological pilot study
No full textWe examined the use of high-resolution peripheral quantitative computed tomography (HR-pQCT [XtremeCT; Scanco Medical, Switzerland]) to assess bone microstructure at the distal radius in growing children and adolescents. We examined forearm radiographs from 37 children (age 8–14 yr) to locate the position of the ulnar and radial growth plates. We used HR-pQCT to assess bone microstructure in a region of interest (ROI) at the distal radius that excluded the growth plate (as determined from the radiographs) in all children (n = 328; 9–21 yr old). From radiographs, we determined that a ROI in the distal radius at 7% of bone length excluded the radial growth plate in 100% of participants. We present bone microstructure data at the distal radius in children and adolescents. From the HR-pQCT scans, we observed active growth plates in 80 males (aged 9.5–20.7 yr) and 92 females (aged 9.5–20.2 yr). The ulnar plate was visible in 9 male and 17 female participants (aged 11.2 ± 1.9 yr). The HR-pQCT scan required 3 min with a relatively low radiation dose (<3 μSv). Images from the radial ROI were free of artifacts and outlined cortical and trabecular bone microstructure. There is currently no standard method for these measures; therefore, these findings provide insight for investigators using HR-pQCT for studies of growing children.
[ABSTRACT FROM AUTHOR]Peer reviewedFinal article publishedGrowth plateBone imagingBone microstructureHR-pQC
Accretion-erosion conversion in the subaqueous Yangtze Delta in response to fluvial sediment decline
No full textIdentifying the pattern of delta morphological change under decreasing sediment flux due to dam construction is essential for sustainable management in such densely populated coastal areas. In this study, we investigated the morphological processes of the Yangtze mouth bar and prodelta based on bathymetric data on a decadal-interannual scale (1958, 1978, 1997, 2002, 2007, 2010, 2013 and 2015). We found that strong accretion (205.1 Mm3 yr−1) occurred during 1958–1978, when a high sediment load (465 Mt yr−1) was supplied by the Yangtze. Afterwards, the net accumulation rate decreased to 31.9 Mm3 yr−1 in 1978–1997 and 114.6 Mm3 yr−1 in 1997–2002 as a result of riverine sediment loads decreasing to 390 Mt yr−1 and 314 Mt yr−1, respectively. Surprisingly, the net accumulation rate increased to 130.8 Mm3 yr−1 in 2002–2007, though the sediment load sharply decreased to 177 Mt yr−1. This anomaly was attributed to the construction of training walls within the mouth bar area, which induced significant accretion in groyne-sheltered areas and nearby regions. Along with a further decrease in sediment load, the entire study area converted to net erosion of −200.4 Mm3 yr−1 in 2007–2010 and −152.2 Mm3 yr−1 in 2010–2013. Stronger erosion in the former period was partly caused by intensive dredging activities in the mouth bar area. The critical sediment discharge for the Yangtze mouth bar and prodelta to retain net accretion was estimated to be ca. 218 Mt yr−1. If deducting the impacts of estuarine engineering projects on accretion/erosion during 1997–2010, the critical sediment discharge is adjusted to ca. 234 Mt yr−1. In combination with previously reported accretion-erosion conversion elsewhere in the Yangtze Delta, we inferred that most portion of the subaqueous delta has most likely converted from net accretion to net erosion in response to fluvial sediment decline, and the mouth bar area showed the latest conversion among portions of the delta. Integrated assessment and adaptive strategies are urgently required for the Yangtze Delta to survive the coming erosional stage.Accepted author manuscriptCoastal Engineerin
Aging in place in upstate New York
No full textSeniors may find it hard to “age in place” as they grow older because of a growing disparity between the features of the houses they own and the housing they need. The resulting change in demand for housing products and services is of particular significance in upstate New York, where the majority of seniors are homeowners and the housing stock is dominated by older, single-family homes.
The NANOGrav 15 yr Data Set: Search for Gravitational-wave Memory
No full text\ua9 2025. The Author(s). Published by the American Astronomical Society.We present the results of a search for nonlinear gravitational-wave (GW) memory in the NANOGrav 15 yr data set. We find no significant evidence for memory signals in the data set, with a maximum Bayes factor of 3.1 in favor of a model including memory. We therefore place upper limits on the strain of potential GW memory events as a function of sky location and observing epoch. We find upper limits that are not always more constraining than previous NANOGrav results. We show that it is likely due to the increase in common red noise between the 12.5 and 15 yr NANOGrav data sets
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