Circular Pools Research Articles

Long- and short-read sequencing methods discover distinct circular RNA pools in Lotus japonicus.

Circular RNAs (circRNAs) are covalently closed single-stranded RNAs, generated through a back-splicing process that links a downstream 5' site to an upstream 3' end. The only distinction in the sequence between circRNA and their linear cognate RNA is the back splice junction. Their low abundance and sequence similarity with their linear origin RNA have made the discovery and identification of circRNA challenging. We have identified almost 6000 novel circRNAs from Lotus japonicus leaf tissue using different enrichment, amplification, and sequencing methods as well as alternative bioinformatics pipelines. The different methodologies identified different pools of circRNA with little overlap. We validated circRNA identified by the different methods using reverse transcription polymerase chain reaction and characterized sequence variations using nanopore sequencing. We compared validated circRNA identified in L. japonicus to other plant species and showed conservation of high-confidence circRNA-expressing genes. This is the first identification of L. japonicus circRNA and provides a resource for further characterization of their function in gene regulation. CircRNAs identified in this study originated from genes involved in all biological functions of eukaryotic cells. The comparison of methodologies and technologies to sequence, identify, analyze, and validate circRNA from plant tissues will enable further research to characterize the function and biogenesis of circRNA in L. japonicus.

Technical Guidance for Raising Gourami Fish in the Round Pond System to Pokdakan Karya Maju, Karya Tani Village

The purpose of this service activity is to increase the knowledge and skills of the Karya Maju Fish Farmers Group (Pokdakan) in Karya Tani Village, Barambai District, Barito Kuala Regency regarding the enlargement of gourami in the round pond system. The approach method used is the delivery of material through socialization, hands-on practice in installing circular pools, question and answer which is then carried out by evaluating the knowledge and skills of the target audience. The results showed that there was an increase in knowledge and skills where previously the number of target audience who have no knowledge and skills about growing gouramy in the round pond system 80%, then decreased to 0%. In practices, the gouramy grew 92% for 30 days of rearing with a mortality rate only 8% and the calculation results were declared economically viable.

Effect of circulation on flame heights over liquid fuel pools

A striking feature of fire whirls is that they tend to have higher mean flame heights than free buoyant pool fires at the same heat release rates, which has been extensively studied in the past. Different from the mean flame height, the instantaneous flame height of a fire whirl reflects its dynamic nature in time domain, but has received less attention so far. This work experimentally investigated the effect of imposed circulation on flame heights over liquid fuel pools, including the mean and instantaneous flame heights, as a fundamental model of fire whirls. Both the rotating-screen and half-cylinder types of test facilities with different mechanisms for generating eddies were employed with circular ethanol pools of different diameters as fuel sources. Results showed that the scaling law proposed in previous studies can well estimate the mean flame heights of conical fire whirls, but does not work for the cases when a conical fire whirl-to-extinction transition or vortex breakdown occurs. Meanwhile, the characteristic flame pulsation frequency of a fire whirl is lower than that of a free buoyant pool fire with the same pool diameter, but increases with an increase in the imposed circulation due to enhanced air entrainment. A scaling law based on dimensional analysis is proposed to estimate the dimensionless flame pulsation frequency of a conical fire whirl by a combination of the fuel Froude number and the dimensionless circulation. Furthermore, with an increase in the imposed circulation, the instantaneous flame height transitions from a lower and less volatile position to a higher and more volatile position due to flame precession (an inherent instability of a conical fire whirl). Scaling laws for estimating the maximum instantaneous flame height difference in time domain and the flame precession frequency are deduced to summarize the data from small- and medium-scale tests.

MIDDLE PRECLASSIC HYDRAULIC PLANNING AT NIXTUN-CH'ICH', PETEN, GUATEMALA

AbstractNixtun-Ch'ich', on the western edge of Lake Peten Itza in Peten, northern Guatemala, features an axis urbis and an urban grid dating to the Middle Preclassic period (800–500 b.c.). New research reveals that Middle Preclassic constructions—five circular or oval artificial pools and planned surface drainage—facilitated or impeded the movement of water. Large limestone rubble lines at least two of the pools (aguadas) in the city's core; two pools lie on the axis urbis, demonstrating that they were central ceremonial constructions. The gridded streets facilitated drainage: they consistently slope from west to east and from the center to north and south. In some areas seeing intense water flow, the streets divide into waterways and pedestrian-ways and/or were given special paving. Many scholars argue that water management contributed to the power of despotic kings, but no evidence of such rulers exists among the Middle Preclassic Maya. Nonetheless, we believe that such systems emerged in the Middle Preclassic. Nixtun-Ch'ich' appears to have been cooperative in its organization and its water management system was a public good.

Experimental study on the evolution of heat feedback in multiple pool fires

Heat feedback is an important factor in researching pool fires. This work intends to interpret the evolution of heat feedback in multiple pool fires (MPFs). Identical circular pools with 20 cm diameter and fueled with n–heptane were designed as fire sources. A series of experiments with different pool numbers, spacings (Sp) and geometrical layouts (“linear” and “orthogonal” types) were performed. The fuel mass, flame shape, incident radiative heat flux to fuel surface and temperatures of the pool wall along with the adjacent fuel were measured. Analyses about the mass loss rate (MLR) and heat feedback fractions (radiation, conduction and convection) for MPFs with different spacings, fire numbers and geometrical layouts are provided. The results show that the MLR for double fires and “linear” type triple fires increas monotonically with the reduction of Sp, while the “orthogonal” type triple fires show a non-monotone trend of first increasing and then decreasing MLR. It was found that all the experimental cases are radiation dominated and the evolution of heat feedback for MPFs versus Sp and fire numbers is attributed to the flame characteristics and the burning behaviors. Three regions are determined to interpret the evolution of the heat feedback of MPFs.

Investigation of the center coordinates of a circle with unknown radius using polar measurements

Circular pools or buildings may be encountered in production of maps for making development plans, in the first facility cadaster and on land. Geodetic measurements may be made on at least three different points of the circleshaped pool or building to obtain positions in a coordinate system of measurement points with a geodetic ground-based electronic tachometer after connection to another polygon. It is possible to get a circle from these three points where the coordinates can be calculated, the coordinates of the center of the circle and the radius of the circle with the help of drawing programs (Netcad, Carto CAD, GEOCAD ...). In drawing programs related to cartography, the details of passing the circle from three points, the coordinates of the center of the circle and the radius of the circle cannot be accessed because the details are kept proprietary by software companies. We have been curious about how the coordinates of the center of the circle or the radius of the circle in question are calculated by using the subprograms on a computer. Apart from the information hidden by software companies, two studies which are indirectly close to the subject mentioned in the application have been identified with respect to the solution of the problem on the computer. However, it was found that these studies did not directly illuminate our research topic, so, this issue should be investigated. This study presents theoretical solutions for the topic, makes numerical implementations and provides findings and interpretations.

The formation of low-energy meanders in loess landscapes (Transdanubia, central Europe)

Abstract Despite many models describing the evolution of meandering rivers, little is known about low-energy rivers formed in loess landscapes. This is the first study that focuses on a spatial and temporal evolution of meandering river planforms in Transdanubia (south Hungary). Field research was conducted in the Kapos and Koppany valleys. Geological and geophysical surveys, supported by AMS radiocarbon dating and historical maps, allowed for reconstructing the evolution of a unique low-energy meandering system in the Koppany valley characterized by elongated bends with circular pools near apexes. Silts constituting the river bed, oblique accretion within the inner banks, cutoffs formation between 14,000 and 11,100 cal. BP, and flow discontinuation after 3900 cal. BP, after which the river was turned into wetlands, were specific features of this river course. A spatial transition from compound to large-scale meanders that may have been caused by neotectonic activity, was noted in the Kapos valley. The river floodplains were transformed by canals constructions during the last 250 years. We show the identified fluvial forms and processes against a background of a conceptual model of meander bends evolution for both high- and low-energy rivers evolving in various geomorphic settings. Large-scale meanders are formed by high discharges with a significant content of bed-load in convective regimes characterized by perturbations propagating downstream. However, large meanders can also be formed in low-energy rivers e.g. owing to the formation of faults. Bends with cutoffs and elongate meanders occur both in low- and high-energy rivers. They evolve in absolute conditions when perturbations propagate both downstream and upstream. The occurrence of circular pools allows for distinguishing low- from high-energy courses. In the loess landscape of Transdanubia, the absolute conditions were induced by the downstream base-level rise that, in turn, limited sediment delivery to fines from loess hills. As a result, the low-energy river evolved over a coarser layer inherited from the activity of a high-energy braided river system.

Transient biogeochemistry in intertidal sediments: New insights from tidal pools in Zostera noltei meadows of Arcachon Bay (France)

Several studies highlighted the occurrence of circular pools in intertidal flats of different coastal systems and their transient water chemistry over both tidal and diurnal cycles. However, little is known about (1) the response of benthic biogeochemical reactions and fluxes at the sediment-water interface over such short time scales, and (2) the role of these tidal pools in the biogeochemical functioning of coastal systems. Based on in situ microprofiles and water sampling, we investigated the dynamics of dissolved oxygen (O2), nutrients, sulfides and metals, and the associated fluxes at the sediment-water interface in tidal pools from the Arcachon Bay (Atlantic coast of France). Our integrative approach included several tidal and diurnal cycles over two different seasons in the presence and absence of Zostera noltei. The results show that water temperature and light irradiance were the main factors driving the biogeochemical functioning of the tidal pools, as they controlled the physiological activity of the microphytobenthos. Changes in light radiations induced diurnal fluctuations of O2 concentrations within surficial sediment, thus resulting in fluctuations of the O2 diffusive fluxes at the sediment-water interface and of the O2 penetration depth in sediment. At high tide, the increase in turbulence above the sediment induced the advection of oxygenated water within the first millimeters of sediment, resulting in a significant increase in porewater O2 concentrations and sediment O2 penetration depth. Porewater sulfide concentrations and apparition depth were concomitant with the O2 dynamic over both diurnal and tidal cycles, indicating that intermediate redox diagenetic processes were impacted by O2 dynamic over such short time-scale. The rapid changes in redox processes in the sediment column are confirmed by a significant flux of dissolved manganese toward the water column during nighttime. The consumption of nitrate and the release of ammonium and phosphate, associated to the mineralization of the organic matter in the surface sediment did not appeared related however to such short time cycles. The efflux of dissolved silica from the sediment was most likely associated with the enhanced dissolution of Si-bearing particles in surface sediment at higher temperatures, although silica uptake by Z. noltei was also noted. This study clearly shows that tidal pools function as natural incubators of transient biogeochemical processes. A rough assessment of the nutrient budget at the scale of the bay indicates the tidal pools may contribute significantly to the biogeochemical functioning of Arcachon Bay.

Burning Behavior and Parameter Analysis of Biodiesel Pool Fires

ABSTRACTThe experiments were systematically performed on the burning behavior and parameter analysis of biodiesel pool fires. The circular and square pools were used for axisymmetric source. The effects of pool material, pool size, and fuel thickness on fire evolution were discussed in detail. The typical fire parameters such as burning rate, mean flame height, as well as plume axial temperature, were measured to explore the biodiesel combustion properties. The results indicate that the biodiesel combustion process follows three stages as most ordinary fuels, i.e., initial growth, quasi-steady burning, and decay to extinction. With an increase in pool size or fuel thickness, the burning rate increases gradually. The mean flame height increases along with linearly. A non-dimensional number is proportional to the value of with a 1/10 power. and for biodiesel pool fires were derived to be 0.012 kg•m–2•s–1 and 8.1, based on a modified exponential expression of burning rate. Three correlations were developed to predict burning rate, mean flame height, and plume axial temperature by fitting the experimental data.

Review: Build Something Modern: Ireland’s Modernist Mission in Africa, by Nicky Gogan and Paul Rowley, directors

Nicky Gogan and Paul Rowley, directors Build Something Modern: Ireland’s Modernist Mission in Africa Still Films, 2011, 70 min., http://www.volta.ie/films/build-something-modern A melding of images and colors, voices and rhythms: that’s the impression one is left with after viewing Build Something Modern: Ireland’s Modernist Mission in Africa , a film documenting the Irish architects who, from the 1940s to the 1960s, designed churches, schools, and hospitals for missionary religious orders in Africa. Eschewing a narrator, the collage-like film moves back and forth through interviews with architects and priests, reworked archival footage, animation, experimental presentations of drawings and photographs, accompanied by a distinctive sound track. The different parts come together to leave the viewer with an overall impression, rather than a fully coherent position. The film begins and ends in 2010 in the company of the Kiltegan Fathers, a group of elderly missionary priests now returned to Ireland. We spend time with them at their home: St. Patrick’s Missionary Society in Kiltegan, County Wicklow, a 1950s building designed by Pearse McKenna, one of the Irish architects discussed in the film. Here we learn about the wave of missionary priests and nuns who left the young, recently independent Ireland for an Africa itself experiencing the end of colonialism, emerging independence, and the tensions such transitions bring. If this was a time in which Ireland and the Catholic Church were closely intertwined, it was also a period of tremendous change in the church, consolidated by the modernizing reforms of Vatican II in the early to mid-1960s. The architecture examined in Build Something Modern embodies this moment in modernity. One of the architects interviewed, Dr. Richard Hurley, wittily characterizes McKenna’s pre-1963 modernist church designs in Africa as “old wine in new bottles.” Hurley discusses his own Cathedral of St. John the Baptist in Eldoret, Kenya, designed following the “huge change in ritual and worship” codified by Vatican II, whereby priest and people were brought closer …

Impact of dietary fats on fatty acids profile of threatened Asian cafish (Clarias batrachus, Linnaeus, 1758)

Different fats in the diets were used to examine their impact on the fatty acid profile of asian catfish(Clarias batrachus) on feeding the diets for 12-weeks. There were seven treatments (FISOL, BETAL, SOYAL, LINOL, MIXOL, SATOL and NATFO containing Fish oil, Beef tallow, Soybean oil, Linseed oil, Mixed oil (i.e. containing in 1:1:1:1 ratio of Fish oil, Beef tallow, Soybean oil, Linseed oil), Vegetable oil and minced chicken meat as natural food, respectively, each with three replications, stocked with 30 grow-out having an initial average weight 55.83 + 3.14g in a circular plastic pools (capacity 300 L). The six feeds were formulated with basic ingredients (Soybean meal, 35%; soluble starch, 29%; Casein, 19.5%; carboxy - methyl - cellulose, 2%; papain, 0.5%; vitamin and mineral mix, 4.0%) with iso-energetic (19.55 kJ/g, F1-F6 ) diets and results were compared with natural food (F7) fed fishes. Each diet was hand fed two times daily during experimental period to triplicate homogenous groups of 30 fish. The muscle fillet polyunsaturated fatty acids (PUFA) content varied with different lipid levels suggesting that the dietary fat has impact on deposition of fatty acid in flesh. The muscle unsaturated fatty acids, including Docosa-hexaenoic acid (22:6n3, DHA) level, were comparatively higher in MIXOL diet followed by NATFO and LINOL diets, indicating selective deposition of fatty acids. It was concluded that addition of various fats in the diet has role in the composition of carcass fatty acid profile in Clarias batrachus and the MIXOL (Fish Oil : Tallow : Soybean Oil : Linseed Oil :: 1 : 1 :1 :1 w/w) could be safely used for better and/ or more deposition of healthy fatty acids (EPA and DHA) which are considered as human health beneficial fatty acids and also useful to economize the cost of the broodstock feed.

Effects of Predators on Fish and Crayfish Survival in Intermittent Streams

Predation from aquatic and terrestrial predators are important factors structuring the size and depth distribution of aquatic prey. We conducted mesocosm and tethering experiments on Little Mulberry Creek in northwest Arkansas during low flows to examine the effects of predators on fish and crayfish survival in intermittent streams. Using shallow artificial pools (10 cm deep) and predator exclusions, we tested the hypothesis that large-bodied fish are at greater risk from terrestrial predators in shallow habitats compared to small-bodied individuals. Twenty-four circular pools (12 open top, 12 closed top) were stocked with two size classes of Campostoma anomalum (Central Stoneroller) and deployed systematically in a single stream pool. In addition, we used a crayfish tethering experiment to test the hypothesis that the survival of small and large crayfish is greater in shallow and deep habitats, respectively. We tethered two size classes of Orconectes meeki meeki (Meek's Crayfish) along shallow and deep transects in two adjacent stream pools and measured survival for 15 days. During both experiments, we monitored the presence or absence of predators by visual observation and from scat surveys. We demonstrated a negative effect of terrestrial predators on Central Stoneroller survival in the artificial pools, and larger individuals were more susceptible to predation. In contrast, small crayfish experienced low survival at all depths and large crayfish were preyed upon much less intensively during the tethering study, particularly in the pool with larger substrate. More studies are needed to understand how stream drying and environmental heterogeneity influence the complex interactions between predator and prey populations in intermittent streams.

Influence of Different Sources of Dietary Lipid on the Growth, Feed Efficiency and Survival of Snakehead Channa striatus (Bloch, 1793) Grow-Out

A 84-days-long experiment was conducted with a view to observe the effects of different feeds on growth and survival of Channa striatus grow-outs to develop a rearing technique for promoting its aquaculture. There were seven treatments (L3HUF, H3HUF, MUSOL, LINOL, MIXOL, SATOL and NATFO), each having two replications, stocked with 20 grow-out having an initial average weight 27.36 ± 0.09 to 32.54 ± 0.41 g in a circular plastic pools (300 l capacity). The six feeds were formulated with basic ingredients (soybean meal, 41 %; soluble starch, 25 %; casein, 20 %; carboxy methyl cellulose, 2 %; papain, 0.5 %; vitamin and mineral mix, 3.5 %) with iso-energetic (19.3 kJ/g, F1–F6) diets and results were compared with natural food fed fishes. Each diet was hand fed two times daily for 84 days to triplicate homogenous groups of 20 fishes. The fishes fed with live tubificid worms showed significantly better results in terms of weight gain and specific growth rate (%) compared to the rest six treatments. The survival was recorded cent percent in all the treatments. Results showed that the feed efficiency and growth performance significantly (p < 0.05) changed with various types of dietary lipid. At the end of the 84 days study the weight gain was recorded as 51.65 ± 0.35, 51.15 ± 0.21, 50.95 ± 0.35, 53.20 ± 0.28, 59.15 ± 0.21, 55.53 ± 0.41 and 61.44 ± 0.24 g for L3HUF, H3HUF, MUSOL, LINOL, MIXOL, SATOL and NATFO respectively. The best growth recorded in natural food fed fishes followed by MIXOL, SATOL, H3HUF, LINOL, L3HUF and MUSOL. The hepatosomatic and viscerosomatic indices ranged between 2.1–2.5 and 3.4–4.3 respectively in F1–F7. The feed efficiency in terms of feed conversion ratio recorded as 2.02–3.04 among all the feeding trials. It could be concluded, based on the results of this trial, that a diet formulated with a gross energy of 19.3 kJ/g is sufficient to promote good feed efficiency and growth performance in C. striatus grow-out however, the best growth recorded in mixed oil (MIXOL) containing 50 % mustard oil and 50 % linseed oil.

Growth Responses of Animal and Plant Origin Dietary Lipids on the Survival,Growth and Feed Efficiency of Asian Catfish, Clarias batrachus (Linnaeus,1758) Grow-out

A 84-days long experiment was conducted with a view to observe the effects of different feeds on growth and survival of Clarias batrachus grow-out. There were seven treatments (FISOL, BETAL, SOYAL, LINOL, MIXOL, SATOL and NATFO containing Fish oil, Beef tallow, Soybean oil, Linseed oil, Mixed oil (i.e. containing in 1:1:1:1 ratio of Fish oil, Beef tallow, Soybean oil, Linseed oil), Vegetable oil and minced chicken meat as natural food, respectively, each having three replications, stocked with 30 grow-out having an initial average weight 55.83 + 3.14 in a circular plastic pools (capacity 300 L). The six feeds were formulated with basic ingredients (Soybean meal, 35%; soluble starch, 29%; Casein, 19.5%; carboxy - methyl - cellulose, 2%; papain, 0.5%; vitamin and mineral mix, 4.0%) with iso-energetic (19.55 kJ/g, F1-F6 ) diets and results were compared with natural food fed fishes. Each diet was hand fed two times daily for 84-days to duplicate homogenous groups of 30 fish. The fishes fed with live chicken waste showed significantly poor results (p > 0.05) in terms of weight gain and Specific Growth Rate (SGR%) compared to the rest six treatments. The survival was recorded as 100% in all the treatments. Results showed that the growth performance significantly (p < 0.05) different with various lipid of animal and plant origin. At the end of the 84-days study the highest weight gain % was recorded in LINOL (F4) as 105.1%. For other treatment weight gain was recorded as 40.3%, 75.4%, 25.6%, 60.2%, 37.0%, and 44.1%for FISOL, BETAL, SOYAL, MIXOL, SATOL and NATFO respectively. The feed efficiency in terms of Feed Conversion Ratio (FCR) recorded as 2.46 to 3.22 among all the feeding trials. It could be concluded, based on the results of this trial, that a diet formulated with a gross energy of 19.55kJ/g is sufficient to promote better feed efficiency and growth performance in C. batrachus grow-out however, the best growth was recorded in linseed oil (LINOL) followed by BETAL and MIXOL.

A Density Current Parameterization Coupled with Emanuel’s Convection Scheme. Part I: The Models

AbstractThe aim of the present series of papers is to develop a density current parameterization for global circulation models. This first paper is devoted to the presentation of this new wake parameterization coupled with Emanuel’s convective scheme. The model represents a population of identical circular cold pools (the wakes) with vertical frontiers. The wakes are cooled by the precipitating downdrafts while the outside area is warmed by the subsidence induced by the saturated drafts. The budget equations for mass, energy, and water yield evolution equations for the prognostic variables (the vertical profiles of the temperature and humidity differences between the wakes and their exterior). They also provide additional terms for the equations of the mean variables. The driving terms of the wake equations are the differential heating and drying due to convective drafts. The action of the convection on the wakes is implemented by splitting the convective tendency and attributing the effect of the precipitating downdrafts to the wake region and the effect of the saturated drafts to their exterior. Conversely, the action of the wakes on convection is implemented by introducing two new variables representing the convergence at the leading edge of the wakes. The available lifting energy (ALE) determines the triggers of deep convection: convection occurs when ALE exceeds the convective inhibition. The available lifting power (ALP) determines the intensity of convection; it is equal to the power input into the system by the collapse of the wakes. The ALE/ALP closure, together with the splitting of the convective heating and drying, implements the full coupling between wake and convection. The coupled wake–convection scheme thus created makes it possible to represent the moist convective processes more realistically, to prepare the coupling of convection with boundary layer and orographic processes, and to consider simulating the propagation of convective systems.

A Risk Assessment Methodology for Toxic Chemicals Evaporation from Circular Pools

This study presents a method for determining the mass transfer coefficient for the toxic chemicals evaporation from circular pools formed due to the failure of plant integrity or escape from valves. The approach used in this present research work is to develop a correlation by a robust optimization technique known as Genetic Algorithm from the experimental data. The developed correlation can be used to model the hydrocarbon evaporation from spills or releases at different wind speeds. From the mass transfer coefficient, the vapor concentration of the hydrocarbon spillage in the environment can be determined which can be used in quantitative risk analysis to predict the effect of toxic release.

SWIMMING BEHAVIOR OF ISOLATED AYU IN STATISTIC WATER

Schooling behavior of fish and interaction between a few individual fish in schooling have been investigated. However, swimming behavior of isolated fish has not been investigated. In this study, the swimming behavior of isolated ayu in the circular pools with changing the radius was recorded with a digital video camera. It was found that the swimming trajectory of ayu can be described by nodes and branches. The frequencies of the swimming distance and angle between each branch are modeled by the gamma distribution. The mean swimming distance of each branch divided by the body length is 2.51 and the mean angle between each branch is 72.5. The directions of angle between each branch do not depend on the swimming distance and also the angle just before the swimming.

Predicting the emissive power of hydrocarbon pool fires

The emissive power ( E) of a flame depends on the size of the fire and the type of fuel. In fact, it changes significantly over the flame surface: the zones of luminous flame have high emittance, while those covered by smoke have low E values. The emissive power of each zone (that is, the luminous or clear flame and the non-luminous or smoky flame) and the portion of total flame area they occupy must be assessed when a two-zone model is used. In this study, data obtained from an experimental set-up were used to estimate the emissive power of fires and its behaviour as a function of pool size. The experiments were performed using gasoline and diesel oil as fuel. Five concentric circular pools (1.5, 3, 4, 5 and 6 m in diameter) were used. Appropriate instruments were employed to determine the main features of the fires. By superimposing IR and VHS images it was possible to accurately identify the luminous and non-luminous zones of the fire. Mathematical expressions were obtained that give a more accurate prediction of E lum, E soot and the average emissive power of a fire as a function of its luminous and smoky zones. These expressions can be used in a two-zone model to obtain a better prediction of the thermal radiation. The value of the radiative fraction was determined from the thermal flux measured with radiometers. An expression is also proposed for estimating the radiative fraction.

Direct labelling of BAC‐DNA by rolling‐circle amplification

Efficient amplification and labelling of probes are crucial for successful sequence detection by fluorescent in situ hybridization (FISH). In particular, chromosome painting to visualize chromosome segments or entire chromosomes by FISH requires large amounts of probes derived from extended templates. There are a number of techniques for probe labelling. The most widespread is nick translation, based on the replicational incorporation of modified nucleotides. Here we demonstrate successful rolling-circle amplification (RCA) of very low amounts of long circular template sequences (single bacterial artificial chromosomes (BACs) or pools of BACs). The amplicons were suitable for labelling by nick translation and subsequent FISH. A novel achievement is the use of RCA for simultaneous amplification and labelling of single BACs or BAC pools in a labour- and cost-effective manner.

Circular pools in the seagrass beds of the Banc d’Arguin, Mauritania, and their possible origin

The tidal flats of the Banc d’Arguin, Mauritania, are covered by vast beds of Zostera noltii. At low tide these seagrass beds appear to be interspersed with partly vegetated, circular pools of 5–25 m diameter. Between February and May 2001 we described these pools and studied their possible origin. Several hypotheses regarding the origin have been developed. The first group of hypotheses assumes that the pools result from erosion activity. Since human disturbance of seagrass beds at the Banc d’Arguin is virtually non-existent, causes should be found in natural bed disturbances and/or tide or wave action. Therefore, small gaps, simulating holes dug by the crab Callinectes marginatus, were made to see if they would further erode by tidal currents or waves. The experiments showed no erosion. Neither we found support for other hypotheses assuming erosion to be the cause of circular pools. The alternative group of hypotheses stated that sedimentation on the flats would be responsible. We conclude that accretion of creek remnants is the most likely process behind the development of the pools; this conclusion is based on both mapping of the pattern of pools, the sediment profile in and around the pools and the distribution of seagrass biomass. Also the disturbance experiments showed bed accretion rather than bed erosion and support this hypothesis.