The effects of fluctuating light fields on the growth of phytoplankton are not well understood and conclusions in the literature have been equivocal. Most studies have examined responses such as ...productivity and chlorophyll a content (laboratory culture and field tests) or growth rates (laboratory culture tests). In this study we examined the in situ growth rates of different types of phytoplankton within two natural populations. Comparisons were made between populations grown in a static environment (suspended in a fixed position in the water column) and an equivalent population moving through the water column simulating the mixing of entrained phytoplankton. Growth under fluctuating light fields in this experiment only significantly (P < 0.05) increased the growth of the diatom Skeletonema and decreased the growth of Anabaena circinalis, Microcystis aeruginosa and Scenedesmus sp. All other phytoplankton, including the genera Nitzschia, Fragilaria and Dactylococcopsis, did not have growth rates that were significantly different between static and fluctuating light treatments. A general pattern where diatoms grew best, followed by chlorophytes with the toxicogenic cyanophytes M. aeruginosa and A. circinalis growing least well, was distinguished under fluctuating irradiance. This seems consistent with the common occurrence of these groups of phytoplankton in the natural environment. The cyanophytes Dactylococcopsis and Aphanothece did not follow this pattern, with the former growing better under fluctuating light and the latter exhibiting an unusual growth pattern where growth was higher under lower light intensities.
The prediction of outcome for patients with gastric cancer is determined largely by the presence of lymph node metastases, which could be detected by sentinel lymph node (SLN) biopsy (SLNB). The ...purpose of this work was to determine the feasibility of SLNB in patients with gastric cancer for the assessment of regional lymph node status, including performing immunohistochemical (IHC) staining of SLN tissue.
We reviewed 137 consecutive patients with operable gastric cancer over a 10-year period using a retrospective (to examine skip metastases) and prospective (to evaluate successful mapping) study design. SLNs were mapped, biopsied and subsequently explored by routine hematoxylin & eosin (H&E) staining and by IHC staining using a cytokeratin 8/18 antibody.
The retrospective study showed a low incidence of skip metastases (3.7%). Mapping of SLNs in the prospective study was highly successful (98.2%). During the prospective study, IHC examination of SLNs from 56 patients showed statistically significant change in disease stage.
This study demonstrated highly successful mapping and biopsy of SLNs (98.2%), as well as highest specificity (100%), sensitivity (100%) and accuracy (100%) to predict metastasis in the surrounding lymph nodes of gastric carcinoma. In addition, we believe that IHC study might enable "ultra staging" and additional selection of patients for further cancer treatment.
The migration patterns of phytoplankton through time and depth were measure in the Darling River at Revallyn, New South Wales, Australia during a bloom of Anabaena circinalis. Anabaena circinalis was ...able to disentrain and maintain position witin surface waters during the early morning, coinciding with the diel period of least wind speeds and a state of no detectable thermocline (0.1°C detection limit). Anabaena circinalis concentrations were up to 10 times higher in the surface waters than in the bottom waters during the morning sampling periods. Afternoon and midnight sampling periods revealed either a small amount of surface accumulation or none. All other phytoplankton were found to have a relatively even distribution throughout the water column at all time periods measured (except Aulacoseira on one occasion). These vertical distribution data were used to determine the potential benefit buoyant A. circinalis could gain over an evenly distributed population using a quantitative estimate of primary productivity. The buoyant population was found to have a daily integral of photosynthetic O2 production of 3.63 mol m –2, five times greater than that for the evenly distributed population. Losses due to respiration were greater for the evenly distributed population (29.5%) than the buoyant population (4.8%), probably due to the amount of time cells spent outside the euphotic zone. It is suggested that buoyancy may offer considerable advantage to A.circinalis in gaining dominance in turbid freshwater rivers. Further, buoyancy may offer some advantage even without strong thermal gradients.
Every existing source of energy is affected by climate variability. The most direct climate impacts are related to power plant cooling and water availability. Local weather conditions affect the ...capacity of cooling towers and natural water bodies to transfer waste heat from steam condensers to the atmosphere. Under hot summer conditions even the inlet water from a river may approach the limit set for discharge, and this will mean that the plant is unable to run at full power. For the given thermal power plant configuration, cooling water temperature change generates changes in the condenser pressure. Those changes have a great influence on the power output of the plant. This effect, due to daily variations of the air humidity and temperature, is even more marked for the close cycle cooling (with cooling towers). Without technology-based improvements in cooling system efficiency, the steam-cycle energy efficiency would decrease. In this article, the overview of cooling water temperature increase impact on the energy efficiency in Serbian power plants is given, based on meteorological data and numerical simulation. Obtained results could be used as useful guidelines in design of the new power plants and also in improving existing power plants' performances.
Microplastic (MP) pollution is an emerging issue in aquatic sciences. Little comparative information currently exists about the problem in coastal systems exposed to different levels of human impact. ...Here we report a year-long study on the abundance of MP in the water column of three estuaries on the east-coast of Australia. The estuaries are subject to different scales of human impact; the Clyde estuary has little human modification, the Bega estuary has a small township and single wastewater treatment works discharging to its waters, and the Hunter estuary which has multiple townships, multiple wastewater treatment plants, and heavy industry. MP abundance followed an expected pattern with the lowest abundance in the low-impact Clyde estuary (98 part. m3), moderate levels of MP in the moderately impacted Bega estuary (246 part. m3), and high MP abundance in the highly impacted Hunter estuary (1032 part. m3). The majority of particles were <200 μm and fragment-like rather than fiber-like. MP abundance was positively related to maximum antecedent rainfall in the Bega estuary, however there are no clear environmental factors that could explain MP variation in the other systems. MP were generally higher in summer and following freshwater inflow events. On the Hunter estuary MP abundance was at times as high as zooplankton abundance, and within the range of numbers reported in other highly impacted systems globally. The results confirm that higher levels of human impact lead to greater plastic pollution and highlight the need to examine aquatic ecosystems under a range of conditions in order to adequately characterize the extent of MP pollution in rivers and coastal systems.
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•Microplastic abundance increased in estuaries with increasing human impact.•68–76% of particles <200 μm.•The majority of microplastics were fragment-like rather than fibers.•Microplastic concentrations positively related to antecedent rainfall.
Microplastic abundance is higher in estuaries with higher human impact. The microplastic pool was dominated by fragment like particles <200 μm in size.
District heating is an efficient way to provide heat to residential, tertiary
and industrial users. The heat storage unit is an insulated water tank that
absorbs surplus heat from the boiler. The ...stored heat in the heat storage
unit makes it possible to heat even when the boiler is not working, thus
increasing the heating efficiency. In order to save primary energy (fuel),
the boiler operates on nominal load every time it is in operation (for the
purpose of this research). The aim of this paper is to analyze the water
temperature variation in the heat storage, depending on the heat load and the
heat storage volume. Heat load is calculated for three reference days, with
average daily temperatures from -5 to 5?C. The primary energy savings are
also calculated for those days in the case of using heat storage in district
heating.
Cyanobacterial blooms are becoming more common in freshwater systems, causing ecological degradation and human health risks through exposure to cyanotoxins. The role of phosphorus and nitrogen in ...cyanobacterial bloom formation is well documented and these are regularly the focus of management plans. There is also strong evidence that trace metals are required for a wide range of cellular processes, however their importance as a limiting factor of cyanobacterial growth in ecological systems is unclear. Furthermore, some studies have suggested a direct link between cyanotoxin production and some trace metals. This review synthesises current knowledge on the following: (1) the biochemical role of trace metals (particularly iron, cobalt, copper, manganese, molybdenum and zinc), (2) the growth limitation of cyanobacteria by trace metals, (3) the trace metal regulation of the phytoplankton community structure and (4) the role of trace metals in cyanotoxin production. Iron dominated the literature and regularly influenced bloom formation, with 15 of 18 studies indicating limitation or colimitation of cyanobacterial growth. A range of other trace metals were found to have a demonstrated capacity to limit cyanobacterial growth, and these metals require further study. The effect of trace metals on cyanotoxin production is equivocal and highly variable. Better understanding the role of trace metals in cyanobacterial growth and bloom formation is an essential component of freshwater management and a direction for future research.
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