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Query: UMLS:C0016382 (flushing)
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Water quality models of urban systems have previously focused on point source (sewerage system) inputs. Little attention has been given to diffuse inputs and research into diffuse pollution has been largely confined to agriculture sources. This paper reports on new research that is aimed at integrating diffuse inputs into an urban water quality model. An integrated model is introduced that is made up of four modules: hydrology, contaminant point sources, nutrient cycling and leaching. The hydrology module, T&T consists of a TOPMODEL (a TOPography-based hydrological MODEL), which simulates runoff from pervious areas and a two-tank model, which simulates runoff from impervious urban areas. Linked into the two-tank model, the contaminant point source module simulates the overflow from the sewerage system in heavy rain. The widely known SOILN (SOIL Nitrate model) is the basis of nitrogen cycle module. Finally, the leaching module consists of two functions: the production function and the transfer function. The production function is based on SLIM (Solute Leaching Intermediate Model) while the transfer function is based on the 'flushing hypothesis' which postulates a relationship between contaminant concentrations in the receiving water course and the extent to which the catchment is saturated. This paper outlines the modelling methodology and the model structures that have been developed. An application of this model in the White Cart catchment (Glasgow) is also included.
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PMID:Application of a water quality model in the White Cart water catchment, Glasgow, UK. 1290 Oct 79

Storage of nuts at a high oxygen concentration results in rancid nuts whereas storage at a low oxygen concentration results in fine-tasting nuts. During a 13 month experiment, packaging of walnuts with an oxygen absorber was compared to packaging in nitrogen or atmospheric air. At the same time, the effects of oxygen permeability of the packaging material and storage temperature (11 and 21 degrees C) were investigated by determination of hexanal and rancid taste of the walnuts. The optimal storage condition for walnuts is at 11 degrees C or lower, eventually combined with an oxygen absorber. However, without chilled storage and use of an oxygen absorber, it is possible to obtain an acceptable quality of walnuts with a packaging material having a very low oxygen permeability (e.g., laminate with EVOH) combined with nitrogen flushing. The results also revealed that the development of hexanal during time can be described by a second-order polynomial regression model.
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PMID:Investigation of packaging systems for shelled walnuts based on oxygen absorbers. 1290 50

Effects of artificial defoliation on defensive needle chemistry in Scots pine (Pitus sylvestris L.) were evaluated with particular emphasis on peroxidases, phenolic compounds, soluble sugars, polyamines, and foliar nitrogen levels. The study was carried out on a nutrient-poor Scots pine stand with 8- to 25-year-old trees. Defoliation treatment consisted of repeated defoliation in two successive years with respective control trees. Defoliation was done before needle flushing by removing all mature needles. Guaiacol peroxidase activity increased in the needles after the first defoliation. The difference between treatments diminished towards autumn, and disappeared before the second defoliation in the next summer. After the second defoliation, the activities showed a similar trend. Apparently, peroxidases are involved in inducible chemical changes and recovery reactions that occur in the intact needles shortly after defoliation. After the second defoliation, total nitrogen concentration in the current year needles was about 20% lower, and free putrescine (a polyamine) concentration was 40% lower in the defoliated trees than in control needles. These changes indicate a loss of nitrogen due to defoliation. Specific phenolic compounds such as quercitrin, (+)-catechin, and two catechin derivatives increased in current year needles in response to defoliation. Accumulation of starch and sucrose in the current year needles of repeatedly defoliated trees may imply decreased assimilate transport. The results are indicative that changes in needle phytochemistry in response to defoliation accompany changes in needle nitrogen metabolism.
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PMID:Defoliation-induced responses in peroxidases, phenolics, and polyamines in scots pine (Pinus sylvestris L.) needles. 1295 14

Results from the first multi-constituent dynamic modelling study of the Humber estuarine system over seasonal time scales are presented. The model, constructed within the ECoS3 simulation software, has been calibrated using data obtained from 27 surveys of the Yorkshire Ouse and Humber estuaries during 1994-1996. The model is tidally averaged, and is one-dimensional in the vertical and in cross-section. Daily-varying longitudinal concentration profiles of SPM, POC, nitrate, nitrite and ammonium have been simulated, and these have been compared with the observations used for model calibration (model confirmation). The fits are generally good. The model captures the marked seasonal variability in concentrations of the particulate constituents (SPM, POC), and places the turbidity maximum in approximately the correct region of the estuary. There was a high degree of scatter in the SPM and POC concentrations measured due to tidal resuspension, which was not reproduced by the tidally averaged model. Comparisons between measured and simulated nitrate+nitrite are satisfactory, although for a number of surveys the modelled values are systematically too low in the lower Yorkshire Ouse and upper Humber. These discrepancies are not readily explained, but may be linked to inadequately characterised source terms for this nitrogen. The general trends in the concentrations and distributions of ammonium are reproduced by the model, despite the plethora of external inputs of this constituent, and significant modifications to ammonium transport by in situ nitrification and benthic exchange. The simulated concentrations and distributions have also been tested against independent data encapsulating axial transects in the Trent and Humber estuaries, and temporal variations at fixed sites on the Trent and Yorkshire Ouse estuaries. With some exceptions, the fits between the model results and these data are also good. The model has also been used to construct constituent budgets (external/internal sources and sinks) for each estuary for 1994, 1995 and 1996. Riverine inputs of SPM, POC, nitrate, nitrite and ammonium decreased over the 3 years, presumably reflecting changing patterns of terrestrial runoff coupled to a reduction in effluent inputs. This trend was also observed in the point discharges of these constituents direct to the estuary. The simulated estuary was a source of sediments to the North Sea during 1994 and 1996, but a sink during 1995. The difference has been ascribed to the exceptionally dry summer and autumn of 1995, in which up-estuary tidal 'pumping' of SPM was dominant over down-estuary flushing by river water. Fluvial inputs represent an important external source of POC to the model estuary (27-55%), as does the North Sea (26-58%). These inputs are exceeded by POC loss via bacterial remineralisation, suggesting that the estuarine bed is a net source of POC. Riverine inputs account for 76-77% of the external inputs of nitrate. This constituent behaves quasi-conservatively in the estuary, reflecting the dilution of nitrate-rich river waters with low-nitrate coastal water, although nitrification is a significant input (approx. 21%). Denitrification is small, and consequently all nitrate added to the estuary is lost to the North Sea. External loads of nitrite are small and ammonium nitrification accounts for approximately 93% of its annual input. Practically all of the nitrite is oxidised to nitrate, and little escapes to the North Sea. The fluvial and direct waste inputs of ammonium to the estuary are of similar size. Most of the ammonium in the model is nitrified (98-100%) and only a few tons are exported to the North Sea. In 1996 the estuary appears to have been a sink for coastal water ammonium. Constituent budgets are compared with independently evaluated fluxes. There is good agreement in a number of cases, but the comparison highlights the main uncertainties in the simulated fluxes. It is concluded that the model as currently formulated provides an excellent basis for heuristic studies of the Humber estuarine system.
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PMID:The fluxes and transformations of suspended particles, carbon and nitrogen in the Humber estuarine system (UK) from 1994 to 1996: results from an integrated observation and modelling study. 1449 58

Seedling growth and nutritional status have been shown to be sensitive to ozone, but the influence of multi-season ozone exposure on mature tree growth and nutrition has not been examined. To determine if seedlings and mature trees were similarly affected by ozone exposure, growth and nutrient concentrations in northern red oak (Quercus rubra L.) 4-year-old seedlings and 32-year-old mature trees were examined after treatment with subambient, ambient and twice ambient concentrations of ozone for three growing seasons. SUM00 values summed over the three growing seasons were 147, 255 and 507 ppm-h, respectively, for the subambient, ambient and twice ambient exposures. For mature trees, no influence of ozone treatment on lower stem diameter growth, stem growth within the mid-canopy and foliar biomass was observed. Seedling height was increased by ozone, but biomass and diameter were unaffected. A reduction in the specific leaf weight of leaves in response to ozone coincident with the loss of recurrent flushing was observed in seedlings. Ozone exposure reduced foliar nitrogen concentrations and increased woody tissue nutrient concentrations in seedlings and mature trees at the end of the third growing season. These results suggest an influence of ozone on retranslocation processes in seedlings and mature trees.
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PMID:Growth and nutrition of Quercus rubra L. seedlings and mature trees after three seasons of ozone exposure. 1509 24

A comprehensive review is given of past and current annually averaged nutrient concentrations (total oxidised nitrogen [TON], phosphate and silicate) in the River Ythan and its estuary. TON concentrations in the River Ythan have increased from ca 100-150 microm in the late 1960s to ca 500-550 microm in the early 1990s, changes which are also shown in the estuary. The interpretation of the phosphate data is more complex but concentrations in the estuary also appear to have increased. Silicate concentrations have remained constant with time. The results of 11 surveys of the estuary completed during 1993 are given. TON and silicate behave conservatively in the estuary, with concentrations determined by those of the fresh water end-member and hence by processes within the catchment. Phosphate and ammonia concentrations at low salinity are affected by the discharge from the Ellon sewage treatment facility at the head of the estuary. Throughout the estuary there is evidence of an input of ammonia to the water column from the sediments, but it represents only ca 0.2-2% of the nitrogen entering from the River Ythan. Despite the increased nutrient loading to the estuary there is no evidence that this has resulted in higher chlorophyll concentrations in the water column, this observation is attributed to the relatively short flushing period of the estuary.
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PMID:Long-term nutrient enrichment of an estuarine system: Ythan, Scotland (1958-1993). 1509 64

In this study, the hyphenation of LC-SPE-NMR-MS at 500 MHz was applied to the structural elucidation of a low concentrated paracetamol metabolite present in human urine. Single or multiple peak trapping of the mass detected metabolite on SPE cartridges was employed to increase the sensitivity and quality NMR measurement over the conventional LC-NMR method. After the elution of the metabolite from the SPE cartridge to the NMR flow probe using deuterated acetonitrile for initial NMR investigation, the fraction was revovered by flushing the sample out of the NMR probe head with nitrogen gas. On the recovered fraction, high resolution FT-ICR-MS measurements were conducted, giving exact mass information about the unknown metabolite. In addition, a cryogenic NMR micro probe head was used to enhance the sensitivity of the NMR measurement by a factor of 5 in order to run 2D experiments for structural elucidation of the unknown metabolite. The combination of both MS and NMR results, led unequivocally to the elucidation of the structure as the ether glucuronide of 3-methoxyparacetamol.
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PMID:Characterization of a paracetamol metabolite using on-line LC-SPE-NMR-MS and a cryogenic NMR probe. 1559 67

This paper reports the fluvial fluxes and estuarine transport of organic carbon and nutrients from a tropical river (Tsengwen River), southwestern Taiwan. Riverine fluxes of organic carbon and nutrients were highly variable temporally, due primarily to temporal variations in river discharge and suspended load. The sediment yield of the drainage basin during the study period (1995-1996, 616 tonne km(-2) year(-1)) was ca. 15 times lower than that of the long-term (1960-1998) average (9379 tonne km2 year(-1)), resulting mainly from the damming effect and historically low record of river water discharge (5.02 m3 s(-1)) in 1995. The flushing time of river water in the estuary varied from 5 months in the dry season to >4.5 days in the wet season and about 1 day in the flood period. Consequently, distributions of nutrients, dissolved organic carbon (DOC) and particulate organic carbon (POC) were of highly seasonal variability in the estuary. Nutrients and POC behaved nonconservatively but DOC behaved conservatively in the estuary. DOC fluxes were generally greater than POC fluxes with the exception that POC fluxes considerably exceeded DOC fluxes during the flood period. Degradation of DOC and POC within the span of flushing time was insignificant and may contribute little amount of CO2 to the estuary during the wet season and flood period. Net estuarine fluxes of nutrients were determined by riverine fluxes and estuarine removals (or additions) of nutrients. The magnitude of estuarine removal or addition for a nutrient was also seasonally variable, and these processes must be considered for net flux estimates from the river to the sea. As a result, nonconservative fluxes of dissolved inorganic phosphorus (deltaDIP) from the estuary are -0.002, -0.09 and -0.59 mmol m(-2) day(-1), respectively, for dry season, wet season and flood period, indicating internal sinks of DIP during all seasons. Due to high turbidity and short flushing time of estuarine water, deltaDIP in the flood period may be derived largely from geochemical processes rather than biological removal, and this deltaDIP should not be included in an annual estimate of carbon budget. The internal sink of phosphorus corresponds to a net organic carbon production (photosynthesis-respiration, p-r) during dry (0.21 mmol m(-2) day(-1)) and wet (9.5 mmol m(-2) day(-1)) seasons. The magnitude of net production (p-r) is 1.5 mol m(-2) year(-1), indicating that the estuary is autotrophic in 1995. However, there is a net nitrogen loss (nitrogen fixation-denitrification < 0) in 1995, but the magnitude is small (-0.17 mol m(-2) year(-1)).
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PMID:Seasonal variations of organic-carbon and nutrient transport through a tropical estuary (Tsengwen) in southwestern Taiwan. 1568 33

Gas-flushed packaging is commonly used for cheese shreds and cubes to prevent aggregation and loss of individual identity. Appearance of a white haze on cubed cheese is unappealing to consumers, who may refrain from buying, resulting in lost revenue to manufacturers. The objective of this study was to determine whether gas flushing of Cheddar cheese contributes to the occurrence of calcium lactate crystals (CLC). Cheddar cheese was manufactured using standard methods, with addition of starter culture, annatto, and chymosin. Two different cheese milk compositions were used: standard (lactose:protein = 1.47, protein:fat = 0.90, lactose = 4.8%) and ultrafiltered (UF; lactose:protein = 1.23, protein:fat = 0.84, lactose = 4.8%), with or without adjunct Lactobacillus curvatus. Curds were milled when whey reached 0.45% titratable acidity, and pressed for 16 h. After aging at 7.2 degrees C for 6 mo, cheeses were cubed (1 x 1 x 4 cm) and either vacuum-packaged or gas-flushed with carbon dioxide, nitrogen, or a 50:50 mixture of carbon dioxide and nitrogen, then aged for an additional 3 mo. Heavy crystals were observed on surfaces of all cubed cheeses that were gas-flushed, but not on cheeses that were vacuum-packaged. Cheeses without Lb. curvatus exhibited L(+)-CLC on surfaces, whereas cheeses with Lb. curvatus exhibited racemic mixtures of L(+)/D(-)-CLC throughout the cheese matrices. The results show that gas flushing (regardless of gas composition), milk composition, and presence of nonstarter lactic acid bacteria, can contribute to the development of CLC on cheese surfaces. These findings stress the importance of packaging to cheese quality.
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PMID:Gas-flushed packaging contributes to calcium lactate crystals in Cheddar cheese. 1623 Jun 83

High plasma urea nitrogen (PUN) concentrations are associated with decreased fertility in lactating dairy cows. Our objective was to evaluate the quality of embryos flushed from superovulated lactating cows having moderate or high PUN concentrations. Subsequent embryo survival was determined after transfer to recipient heifers with either low or high PUN. Lactating Holstein dairy cows (n = 23; 50-120 days in milk) were randomly assigned to one of two diets designed to result in moderate or high PUN concentrations (15.5 +/- 0.7 and 24.4 +/- 1.0 mg/dl, respectively; P < 0.001) and were fed for 30 days before embryo flushing and recovery. Embryos (n = 94) were evaluated morphologically, frozen and subsequently transferred into synchronized virgin heifers that were fed one of two diets designed to result in either low or high PUN concentrations (7.7 +/- 0.9 and 25.2 +/- 1.5 mg/dl, respectively; P < 0.001; 2 x 2 factorial design). The number, quality and stage of development of recovered embryos were similar for cows with moderate or high PUN. Transfer of embryos from moderate PUN donor cows resulted in a higher pregnancy rate (35%; P < 0.02) than the transfer of embryos from high PUN donor cows (11%). Pregnancy rate was not affected by either recipient diet or the interaction of donor and recipient diets (P > 0.05). These results indicate that high PUN concentrations in lactating dairy cows decrease embryo viability through effects exerted on the oocyte or embryo before recovery from the uterus 7 days after insemination.
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PMID:Detrimental effects of high plasma urea nitrogen levels on viability of embryos from lactating dairy cows. 1631 96


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