Surrogate Technologies Research Articles

Bedload Sediment Transport Estimation in Sand-Bed Rivers Comparing Traditional Methods and Surrogate Technologies

Bedload sediment transport in rivers can cause impacts, such as bed erosion/deposition, sandbank formation and changes in flow capacity. Bedload sampling techniques have limitations related to spatial and temporal resolution. These constraints are more relevant in rivers with dunes and high sediment transport. This paper presents a comparison between bedload transport rates estimated with direct and indirect methods in a river with sand dunes. The case study area is a stretch of the Taquari River, in Brazil. Surveys were carried out on three consecutive days, during a flood season. A SonTek M9-ADCP with HydroSurveyor capabilities activated was used to simultaneously measure bathymetry and water velocities throughout a river reach, and also to perform moving-bed tests at six verticals along a predefined cross-section. A mechanical trap (Helley–Smith) was used to collect bedload samples at the same time and positions where the moving-bed tests were performed. Sediment transport was calculated and compared following different approaches: (1) ADCP-BT (Bottom Tracking); (2) modified ISSDOTv2 method (dune tracking); (3) HelleySmith mechanical trap; (4) and five empirical equations. The results showed good agreement between the methodologies, indicating the potential of using ADCPs for hydro sedimentological studies due to the advantages of integrating bathymetry, flow velocity and bedload data.

Heat-induced triploids in Brycon amazonicus: a strategic fish species for aquaculture and conservation.

Triploidization plays an important role in aquaculture and surrogate technologies. In this study, we induced triploidy in the matrinxã fish (Brycon amazonicus) using a heat-shock technique. Embryos at 2 min post fertilization (mpf) were heat shocked at 38°C, 40°C, or 42°C for 2 min. Untreated, intact embryos were used as a control. Survival rates during early development were monitored and ploidy status was confirmed using flow cytometry and nuclear diameter analysis of erythrocytes. The hatching rate reduced with heat-shock treatment, and heat-shock treatments at 42°C resulted in no hatching events. Optimal results were obtained at 40°C with 95% of larvae exhibiting triploidy. Therefore, we report that heat-shock treatments of embryos (2 mpf) at 40°C for 2 min is an effective way to induce triploid individuals in B. amazonicus.

A review of field methods for suspended and bedload sediment measurement

PurposeSediment measurement is usually accessible on a periodic or distinct basis. The measurement of sediment (suspended and bedload), especially in the field, is vital in keeping essential data of sediment transport and deposition. Various techniques for measuring sediment have been used over time each with its merits and demerits. The techniques discussed in this paper for suspended sediment include bottle, acoustic, pump, laser diffraction, nuclear and optical. Other techniques for bedload measurement are; River bedload trap (RBT), CSU/FU bedload trap, Helley–Smith, Polish Hydrological Services (PIHM) device, pit and trough, vortex tube, radioactive traces and bedload–surrogate technologies. However, the choice of technique depends on multiple factors ranging from budget constraint, availability of equipment, manpower and data requirement. The purpose of this paper is to present valuable information on selected techniques used in sediment measurement, to aid researchers/practitioners in the choice of sediment measurement technique.Design/methodology/approachThis paper presents a general review of selected field techniques used in sediment measurement (suspended and bedload). Each techniques mode of operation, merits and demerits are discussed.FindingsThis paper highlights that each technique has its peculiar merits and demerits. However, two techniques are generally preferred over others; the bottle sampling and the Helley–Smith sampler for measuring suspended and bedload sediment. This is because the applicability of these techniques is quite widespread and time-tested.Originality/valueThis review paper provides an in-depth description and comparison of selected existing field sediment measurement techniques. The objective is to ease decision-making about the choice of technique, as well as to identify the suitability and applicability of the chosen technique.

Triploid or hybrid tetra: Which is the ideal sterile host for surrogate technology?

This work was aimed at developing an effective procedure to obtain sterile ideal host fish in mass scale with no endogenous germ cells in the germinal epithelium, owning permanent stem-cell niches able to be colonized by transplanted germ cells in surrogate technology experiments. Thus, triploids, diploid hybrids, and triploid hybrids were produced. To obtain hybrid offspring, oocytes from a single Astyanax altiparanae female were inseminated by sperm from five males (A. altiparanae, A. fasciatus, A. schubarti, Hyphessobrycon anisitsi, and Oligosarcus pintoi). Triploidization was conducted by inhibition of the second polar body release using heat shock treatment at 40 °C for 2 min. At 9-months of age, the offspring from each crossing was histologically evaluated to access the gonadal status of the fish. Variable morphological characteristics of the gonads were found in the different hybrids offspring: normal gametogenesis, gametogenesis without production of gametes, sterile specimens holding germ cells, and sterile specimens without germ cells, which were considered “ideal hosts”. However, only in the hybrid derived from crossing between A. altiparanae and A. fasciatus, 100% of the individuals were completely sterile. Among them 83.3% of the male did not present germ cells inside germinal epithelium, having only somatic cells in the gonad. The other 16.7% also presented spermatogonia inside the niches. Such a methodology allows the production of sterile host in mass scale, opening new insights for application of surrogate technologies.

Triploid Induction in the Yellowtail Tetra, Astyanax altiparanae, Using Temperature Shock: Tools for Conservation and Aquaculture

AbstractTriploidization is an interesting tool to produce sterile fish. In the yellowtail tetra, Astyanax altiparanae, this can be applied for aquaculture and surrogate technologies. In this study, we compared the efficacy of cold (2 C) or heat shock (38 C, 40 C, and 42 C) on triploid induction in the yellowtail tetra. The eggs were treated with cold or heat shock, 2 min postfertilization (30 min in cold shock or 2 min in heat shock). Intact embryos served as the control group. Ploidy status was confirmed by karyotyping, flow cytometry, and nuclear diameter of erythrocytes. The hatching rate decreased after cold shock (12.69 ± 15.76%) and heat shock at 42 C (0.35 ± 0.69%) in comparison with the control group (63.19 ± 16.82%). At 38 C and 40 C, hatching rates (61.29 ± 17.73% and 61.75 ± 22.1%, respectively) were not decreased. Only one triploid arose at 38 C (1/80). At 40 C, a high number of triploids arose (72/78). At 42 C, very few embryos developed into the hatching stage. A large number of haploid individuals arose after cold shock (61/75), with only one triploid. Our results indicate that heat shocking of embryos at 40 C is optimum for triploid production in the yellowtail tetra.

Passive Acoustic Monitoring of Bed Load for Fluvial Applications

Passive Acoustic Monitoring of Bed Load for Fluvial Applications

Hysteresis in suspended sediment to turbidity relations due to changing particle size distributions

[1] Turbidity (T) is the most ubiquitous of surrogate technologies used to estimate suspended-sediment concentration (SSC). The effects of sediment size on turbidity are well documented; however, effects from changes in particle size distributions (PSD) are rarely evaluated. Hysteresis in relations of SSC-to-turbidity (SSC∼T) for single stormflow events was observed and quantified for a dataset of 195 concurrent measurements of SSC, turbidity, discharge, velocity, and volumetric PSD collected during five stormflows in 2009–2010 on Yellow River at Gees Mill Road in metropolitan Atlanta, Georgia. Regressions of SSC-normalized turbidity (T/SSC) on concurrently measured PSD percentiles show an inverse, exponential influence of particle size on turbidity that is not constant across the size range of the PSD. The majority of the influence of PSD on T/SSC is from particles of fine silt and smaller sizes (finer than 16 µm). This study shows that small changes in the often assumed stability of the PSD are significant to SSC∼T relations. Changes of only 5 µm in the fine silt and smaller size fractions of suspended sediment PSD can produce hysteresis in the SSC∼T rating that can increase error and produce bias. Observed SSC∼T hysteresis may be an indicator of changes in sediment properties during stormflows and of potential changes in sediment sources. Trends in the PSD time series indicate that sediment transport is capacity limited for sand-sized sediment in the channel and supply limited for fine silt and smaller sediment from the hillslope.

Technological advances in suspended‐sediment surrogate monitoring

Surrogate technologies to continuously monitor suspended sediment show promise toward supplanting traditional data collection methods requiring routine collection and analysis of water samples. Commercially available instruments operating on bulk optic (turbidity), laser optic, pressure difference, and acoustic backscatter principles are evaluated based on cost, reliability, robustness, accuracy, sample volume, susceptibility to biological fouling, and suitable range of mass concentration and particle size distribution. In situ turbidimeters are widely used. They provide reliable data where the point measurements can be reliably correlated to the river's mean cross section concentration value, effects of biological fouling can be minimized, and concentrations remain below the sensor's upper measurement limit. In situ laser diffraction instruments have similar limitations and can cost 6 times the approximate $5000 purchase price of a turbidimeter. However, laser diffraction instruments provide volumetric‐concentration data in 32 size classes. Pressure differential instruments measure mass density in a water column, thus integrating substantially more streamflow than a point measurement. They are designed for monitoring medium‐to‐large concentrations, are generally unaffected by biological fouling, and cost about the same as a turbidimeter. However, their performance has been marginal in field applications. Acoustic Doppler profilers use acoustic backscatter to measure suspended sediment concentrations in orders of magnitude more streamflow than do instruments that rely on point measurements. The technology is relatively robust and generally immune to effects of biological fouling. Cost of a single‐frequency device is about double that of a turbidimeter. Multifrequency arrays also provide the potential to resolve concentrations by clay silt versus sand size fractions. Multifrequency hydroacoustics shows the most promise for revolutionizing collection of continuous suspended sediment data by instruments that require only periodic calibration for correlation to mean concentrations in river cross sections. Broad application of proven suspended sediment surrogate technologies has the potential to revolutionize fluvial sediment monitoring. Once applied, benefits could be enormous, providing for safer, more frequent and consistent, arguably more accurate, and ultimately less expensive sediment data for managing the world's sedimentary resources.

Measuring bed load discharge in rivers: Bedload‐Surrogate Monitoring Workshop Minneapolis, Minnesota, 11–14 April 2007

The International Bedload‐Surrogate Monitoring Workshop (http://www.nced.umn.edu/BRIC_2007.html), organized by the Bedload Research International Cooperative (BRIC; www.bedloadresearch.org), was held to assess and abet progress in continuous, semiautomated, or fully automated (surrogate) technologies for monitoring bed load discharge in gravel‐, sand‐, and mixed gravel‐sand‐bedded rivers. Direct bed load measurements, particularly at medium and high flows, during which most bed load occurs, tend to be time‐consuming, expensive, and potentially hazardous. Surrogate technologies developed largely over the past decade and used at a number of research sites around the world show considerable promise toward providing relatively dense, robust, and quantifiably reliable bed load data sets. However, information on the efficacy of selected technologies for use in monitoring programs is needed, as is identification of the ways and means for bringing the most promising and practical of the technologies to fruition.

Enabling full service surrogates using the portable channel representation

The simplicity of the basic client/server model of Web services led quickly to its widespread adoption, but also to scalability and performance problems. The technological response to these problems has been the development of technology for the creation of surrogates for Web servers, starting with simple proxy caches and reverse proxies, and leading more recently to the development of content distribution networks. Surrogate technologies based on caches have proved quite successful in reducing the load due to delivery of cacheable content (HTML files and images), but in general they cannot replicate services that are implemented through the execution of programs at the server. A full service surrogate is a technology that is designed to address this issue directly because it is a copy or mirror of the server that is created, managed and updated automatically. One of the central issues in the creation of full service surrogates is portability of interpreted content, and the representation of metadata necessary to support execution. In this paper we describe the Portable Channel Representation (PCR), which is an extensible markup language/resource definition framework encoded data model developed to enable full service surrogates, and we discuss the implications of the increasing importance of executable Web services.