Long-term modelling of reservoir sedimentation with turbid underflows

Purpose

This paper presents the development of a turbid density current module (TDCM) for a one-dimensional quasi-steady reservoir sedimentation model suitable for long-term simulations and an example of its application.

Materials and methods

The module determines the plunging point of a density current based on the criterion of the densimetric Froude number. Following plunging, simulation continues in a supercritical regime as long as the energy of density flow and bed slope are sufficient to support transport in this mode, or until the dam is reached. A muddy pond is then formed. An adapted version of the theory of Toniolo et al. (2007) is used to compute water and sediment balance in a muddy pond. If the level of muddy pond exceeds the lowest level outlet, sediment is vented from the reservoir.

Results and discussion

The model was applied to one of the largest reservoirs in the world, the Nurek reservoir in Tajikistan. Historical data on bed levels and sediment inflow as well as a recent survey from 2015 were used to calibrate and validate the model. The model showed good results both in terms of modelled bed levels and composition of deposited sediment. For comparison purpose, the model was also calibrated without the TDCM module. However, the discrepancy between the observed and modelled data was significantly higher, confirming that the good match in the case of the TDCM module was not achieved solely by calibration, but rather by a more appropriate approach to modelling.

Conclusions

These results support the choice of using the model with TDCM for modelling a general pattern of long-term deposition in the Nurek reservoir, in which turbid density currents play an important role.

     

Design and practical test of a compact phosphorus elimination module for freshwater RAS discharge water

Recirculating aquaculture systems (RAS) can emit total phosphorus (TP) concentrations in their discharge water, which exceed environmentally tolerated restrictions. A compact phosphorus (P) elimination module has been developed and its performance has been tested using the discharge water from a commercial scale freshwater RAS for pike perch (Sander lucioperca) production. To enable its widespread and easy use in practical conditions, the standard principle of chemical-physical phosphorus elimination was adapted to the conditions prevalent in RAS operations. The effect of different precipitants and flocculants in RAS discharge water was studied in laboratory trials. When it came to the TP-elimination performance and the environmental impact, the combination of iron(III) chloride and calcium hydroxide proved highly suitable as the precipitation and flocculation agents. Based on the results that were obtained, a commercial scale P-elimination module was designed. The module was equipped with a 500-L hopper-bottomed reaction tank, dosing units for the precipitation and flocculation agents and valves for the automatic discharge of sludge and cleared water. The TP-elimination potential in different operational modes and retention times was examined. The amounts of excess sludge and cleared water quality were evaluated. The designed 500 L P-elimination module works in automatic batch mode and enables operators to eliminate approx. 95% of the phosphorus emissions from the discharge water from a RAS for annual fish production of about 20 to 25 t. It was possible to achieve TP concentrations of below 1 mg L^?1 in the module’s cleared water discharge.     

Effect of nitrogen species supply and mycorrhizal colonization on organosulfur and phenolic compounds in onions

The aim of the present study was to test whether variations in the root environment affect the content of health-related organosulfur compounds, total phenolic compounds, and flavonol glycoside concentrations in onions. For this purpose, greenhouse-grown onions ( Allium cepa L.) were either inoculated with a commercial arbuscular mycorrhizal inoculum or a sterile inoculum and were provided with two NH(4)(+):NO(3)(-) ratios as a nitrogen source. Onion growth, arbuscular mycorrhizal colonization rate, sugars, and nutrient element concentrations were also quantified. The plant antioxidant activity and quercetin monoglucoside and organosulfur compound concentrations increased with dominant nitrate supply. Furthermore, mycorrhizal colonization increased the antioxidant activity and also concentrations of the major quercetin glucosides. The present study provides clear evidence that antioxidant activity, quercetin glycosides, and organosulfur compounds can be increased in sufficiently supplied onion plants by dominant nitrate supply or application of arbuscular mycorrhizal fungi. This was probably due to increased precursor production and induced defense mechanisms.     

Red fluorescence in reef fish: A novel signalling mechanism?

Background  

At depths below 10 m, reefs are dominated by blue-green light because seawater selectively absorbs the longer, 'red' wavelengths beyond 600 nm from the downwelling sunlight. Consequently, the visual pigments of many reef fish are matched to shorter wavelengths, which are transmitted better by water. Combining the typically poor long-wavelength sensitivity of fish eyes with the presumed lack of ambient red light, red light is currently considered irrelevant for reef fish. However, previous studies ignore the fact that several marine organisms, including deep sea fish, produce their own red luminescence and are capable of seeing it.     

New concepts of coxofemoral joint stability and the development of a clinical stress-radiographic method for quantitating hip joint laxity in the dog

From mechanical principles and postmortem observations of coxofemoral joints of dogs, a hydrostatic mechanism influencing hip joint stability was discovered. This discovery led to the development of a stress-radiographic positioning method to quantitate hip joint laxity in dogs. The method incorporated 2 views with the dog in supine position and hips at neutral flexion/extension angle: a compression view, with the femoral heads fully seated in the acetabula; and a distraction view, with the femoral heads at maximal lateral displacement. An index measurement method was formulated to quantitate the relative degree of joint laxity appearing in either the compression or distraction view. Clinical evaluation of 6 dogs was done to compare the compression/distraction method with the standard hip-extended radiographic method. Also, the stress-radiographic method was performed on 16-week-old Borzoi and German Shepherd Dogs to compare the characteristics of inherent hip joint laxity in these breeds. In all dogs tested, hip joint laxity was masked by the standard hip-extended view as indicated by a 2.5-fold improvement in sensitivity to hip joint laxity of the new method (P less than 0.00001). Moreover, the mean hip joint laxity of 16-week-old German Shepherd Dogs exceeded the mean hip joint laxity of Borzois by 79% (P less than 0.00001). Reports in the literature document the incontrovertible association of hip joint laxity to the development of hip dysplasia in dogs. We believe the ability to accurately quantitate hip joint laxity will provide key diagnostic and prognostic criteria for the selection of pet dogs, and more importantly, breeding stock.     

Contribution to the knowledge of synanthropic flies in the Mongolian People's Republic.

A survey is given of 23 species of synathropic and synbovine Diptera collected in the years 1968, 1969 and 1972 in the Mongolian People's Republic by J. Minár. Besides the faunistical comments, the species of hygienic-epidemiological or public health importance are discussed.     

Canine Ear Disease*

Abstract— —The authors describe briefly the anatomy and histology of the normal ear and the histopathological changes associated with otitis. The bacteria and fungi associated with infections of the ear are discussed. The incidence and results of treatment of otitis externa in out-patient and hospitalised cases are reported and the techniques and results of surgical procedures for conditions of the ear are detailed.     

Parentage assignment with genotyping‐by‐sequencing data

In this paper, we evaluate using genotype‐by‐sequencing (GBS) data to perform parentage assignment in lieu of traditional array data. The use of GBS data raises two issues: First, for low‐coverage (e.g., <2×) GBS data, it may not be possible to call the genotype at many loci, a critical first step for detecting opposing homozygous markers. Second, the amount of sequencing coverage may vary across individuals, making it challenging to directly compare the likelihood scores between putative parents. To address these issues, we extend the probabilistic framework of Huisman (Molecular Ecology Resources, 2017, 17, 1009) and evaluate putative parents by comparing their (potentially noisy) genotypes to a series of proposal distributions. These distributions describe the expected genotype probabilities for the relatives of an individual. We assign putative parents as a parent if they are classified as a parent (as opposed to e.g., an unrelated individual), and if the assignment score passes a threshold. We evaluated this method on simulated data and found that (a) high‐coverage (>2×) GBS data performs similarly to array data and requires only a small number of markers to correctly assign parents and (b) low‐coverage GBS data (as low as 0.1×) can also be used, provided that it is obtained across a large number of markers. When analysing the low‐coverage GBS data, we also found a high number of false positives if the true parent is not contained within the list of candidate parents, but that this false positive rate can be greatly reduced by hand tuning the assignment threshold. We provide this parentage assignment method as a standalone program called AlphaAssign.