Microzooplankton Dynamics in Lower Chesapeake Bay and Its Major Tributaries

This study identified the temporal and spatial variability of microzooplankton density and biomass at 14 stations located within Chesapeake Bay and four rivers. Microzooplankton are defined as those heterotrophic organisms which range from 20 to 200 $\mu$m in size, and in this study were mainly composed of copepod nauplii, rotifers, and ciliates. Ciliates were the most abundant microzooplankton, comprising more than 90% of the total density, with copepod nauplii representing approximately 50% of the total microzooplankton biomass (carbon content). Rotifers contributed less than 5% for both density and biomass of the total microzooplankton. Maximum ciliate abundance occurred from spring to early summer based on the cross-correlation coefficients, and was dominated by small oligotrichs and tintinnids. This development was followed by increased concentrations of rotifers and copepod nauplii that peaked in mid summer and early fall. Copepod nauplii and rotifers had an annual cycle (12 month) in density, as determined by time series analysis (ARIMA Model). However, for the smaller components (ciliates) in size, the autocorrelation function coefficients were not significant at most stations, which indicated their seasonal abundance patterns were not periodic. In terms of the spatial variation of microzooplankton density and biomass, oligohaline statons (river-estuary transitional sites) generally had the highest microzooplankton density and biomass. Pearson\u27s correlation analysis identified several consistent relationships between microzooplankton density and the environmental variables. For instance, rotifers had a significant negative correlation with salinity, and total nitrogen and phosphorus were negatively correlated with loricated ciliates, but positively correlated with aloricated ciliates. Physical and chemical variables were much more important in explaining the geographical heterogeneity of microzooplankton density. The zooplankton community structure, including mesozooplankton, was significantly different depending on the trophic status at each site. The relative contribution of aloricated ciliates to total zooplankton biomass was much higher in the hypertrophic Elizabeth River, but loricated ciliates and mesozooplankton comprised a much lower proportion of the total zooplankton biomass when compared to the other meso- or eutrophic sites. The dominance within the zooplanliton community shifted from mesozooplankton to microzooplankton with increasing trophic state, and the microzooplankton constituted over 90% of the total zooplankton biomass in the hypertrophic Elizabeth River. In general, microzooplankton represented over 80% of the total zooplankton biomass (carbon content) and the secondary production by ciliates only (38 $\mu$gC/1/day) was about 16% the primary production in the Bay and Elizabeth River. Given the shorter generation time and faster growth rates of microzooplankton compared to the other metazoans, the microzooplankton are considered to have a greater effect on the trophic dynamics than the mesozooplankton in lower Chesapeake Bay and these tributaries

Estuarine Relationships Between Zooplankton Community Structure and Trophic Gradients

Zooplankton and water quality parameters were investigated at eight mesohaline stations in the lower Chesapeake Bay and Elizabeth River from January through December 1994 to identify the changes of zooplankton community structure with increased eutrophication. The total micro- and mesozooplankton biomass decreased with the increase of eutrophication. However, the relative proportion of microzooplankton increased with increased eutrophication. Within highly eutrophied waters, the small oligotrichs (\u3c30 mu m) and rotifers dominated the total zooplankton biomass (as carbon). However, tintinnids, copepod nauplii and mesozooplankton significantly decreased with the increase of eutrophication. These patterns were consistent throughout the seasons and had significant relationships statistically. These results suggest zooplankton community structures characterize an increasing eutrophication of an ecosystem

Microzooplankton in the Lower Chesapeake Bay, and the Tidal Elizabeth, James, and York Rivers

Results of a one year study in the lower Chesapeake Bay and three tidal rivers indicate an abundant microzooplankton population, with a mean concentration of 4,231.1/Liter. The most abundant components are the non-loricate ciliates (2,518.2L, 59.5% of the annual total) and tintinnids (1,400.1/L 33.1%). In lesser abundance were the rotifers (191.4/L) and nauplii larvae (121.7/L). Seasonal abundance maxima were highest in summer, followed by fall, spring and winter

Empirical estimation of beach-face slope and its use for warning of berm erosion

Typical berm erosion and accretion are closely related to the beach-face slope. Empirical equation for prediction of the beach-face slope is proposed. The beach-face slope is expressed as a function of the wave period and the bed sediment grain size. Coefficients in the equation are obtained from three sets of carefully chosen laboratory data through a multiple linear regression with two independent variables using SPSS version 22. The computed correlation coefficient is as high as 0.983, which is believed to justify the validity of the present formulation. A shore profile is split into beach-face and underwater bed profile in the surf zone, and described with two straight lines. Possibility of using the beach-face slope strategically for warning of future berm erosion at the site is proposed

Empirical estimation of beach-face slope and its use for warning of berm erosion

Typical berm erosion and accretion are closely related to the beach-face slope. Empirical equation for prediction of the beach-face slope is proposed. The beach-face slope is expressed as a function of the wave period and the bed sediment grain size. Coefficients in the equation are obtained from three sets of carefully chosen laboratory data through a multiple linear regression with two independent variables using SPSS version 22. The computed correlation coefficient is as high as 0.983, which is believed to justify the validity of the present formulation. A shore profile is split into beach-face and underwater bed profile in the surf zone, and described with two straight lines. Possibility of using the beach-face slope strategically for warning of future berm erosion at the site is proposed

Empirical estimation of beach-face slope and its use for warning of berm erosion

Typical berm erosion and accretion are closely related to the beach-face slope. Empirical equation for prediction of the beach-face slope is proposed. The beach-face slope is expressed as a function of the wave period and the bed sediment grain size. Coefficients in the equation are obtained from three sets of carefully chosen laboratory data through a multiple linear regression with two independent variables using SPSS version 22. The computed correlation coefficient is as high as 0.983, which is believed to justify the validity of the present formulation. A shore profile is split into beach-face and underwater bed profile in the surf zone, and described with two straight lines. Possibility of using the beach-face slope strategically for warning of future berm erosion at the site is proposed

FINAL ICONE17-75008 DEVELOPMENT OF A NEW SPACER GRID FORM TO ENHANCE THE INTEGRITY OF FUEL ROD SUPPORT AND THE CRUSH STRENGTH OF A SPACER GRID ASSEMBLY

ABSTRACT A spacer grid is one of the most important structural components in a LWR fuel assembly. The spacer grid, which supports nuclear fuel rods laterally and vertically with a friction grip, is an interconnected array of slotted grid straps welded at the intersections to form an egg-crate structure. Dimples and springs are stamped into each grid strap to support the fuel rods. The form of grid straps and spring form is known to be closely related with the crush strength of spacer grid assembly and the integrity of fuel rod support, respectively. Zircaloy is prevailing as the material of the spacer grid because of its low neutron absorption characteristic and its successful extensive in-reactor use. The primary considerations are to provide a Zircaloy spacer grid with crush strength sufficient to resist design basis loads especially due to seismic accidents, without significantly increasing pressure drop across the reactor core. Generally, the thickness and height of the Zircaloy grid strap have been the main design variables in order to meet the above considerations. Recently, it was reported that a dimple location is also a design variable that affects the crush strength of a spacer grid assembly. In this study, a new spacer grid form was developed in order to enhance the integrity of the fuel rod support and the crush strength of the spacer grid assembly by using a systematic optimization technique. Finite element analysis and crush strength tests on the developed new spacer grid form were carried out to check the performance enhancement compared to commercial spacer grids. The enhancement of fuel rod support was confirmed by comparisons of contact area, peak stresses, plastic deformation and etc. According to the results, it is estimated that the actual critical load enhancement of the spacer grid assembly is approximately up to 30 % and the actual contact area, when a fuel rod inserted into a spacer grid cell, is more than double for the developed new spacer grid form. And also, some design variables that effect the crush strength of a PWR spacer grid assembly were classified and their effects on the crush strength were investigated by a finite element analysis and a crush strength test

Initial steroid regimen in idiopathic nephrotic syndrome can be shortened based on duration to first remission

PurposeThe use of a 12-week steroid regimen (long-term therapy, LT) for the first episode of idiopathic nephrotic syndrome (NS) reportedly induces a more sustained remission and lower relapse rate than previous regimens, including an 8-week steroid regimen (short-term therapy, ST). Here, we assessed the potential for selective application of 2 steroid regimens (LT vs. ST) based on the days to remission (early responders [ER] vs. late responders [LR]) for the first idiopathic NS episode in children.MethodsPatients were divided into 4 subgroups (ST+ER, ST+LR, LT+ER, and LT+LR) according to the initial steroid regimen used and rapidity of response; the baseline characteristics, relapse rates, and cumulative percentage of children with sustained remission were then compared among the 4 subgroups.ResultsFifty-four children received ST, and the remaining 45 children received LT. As observed in previous studies, children receiving LT showed significantly lower relapse rates during the first year after the first NS episode than those receiving ST. The ST+ER group showed significantly lower relapse rates during the first one year and two years after the first NS episode than the the ST+LR group, whereas there were no significant differences of the relapse rates and duration to the first relapse between the ST+ER and LT+ER groups.ConclusionWe suggest that the initial steroid regimen in idiopathic NS patients can be shortened according to the duration to remission i.e., LT in patients achieving remission after the first week of steroid therapy, and ST in those achieving remission within the first week of steroid therapy