Search

Clinical guidelines often make recommendations on the use of diagnostic tests. Compared with sensitivity and specificity, the use of pre- and post-test probabilities allows a more explicit and rational selection [...]

Context. Among optical stellar interferometers, the CHARA Array located at Mt Wilson in California offers the potential of very long baselines (up to 330 m) and the prospect of coupling multiple beam combiners. This paper presents the principle and the measured performance of VEGA, Visible spEctroGraph and polArimeter installed in September 2007 at the coherent focus of the array.

Context.Interferometry can provide spatially resolvedobservations of massive star binary systems and their colliding winds, which thus far have been studied mostly with spatially unresolvedobservations.

Context.Optical long-baseline interferometry is moving a crucial step forward with the advent of general-user scientific instruments that equip large aperture and hectometric baseline facilities, such as the Very Large Telescope Interferometer (VLTI).

Aims.We investigate the origin of the ${\rm Br}\gamma$emission of the Herbig Ae star HD 104237 on Astronomical Unit (AU) scales.

The young stellar object MWC 297is an embedded B1.5Ve star exhibiting strong hydrogen emission lines and a strong near-infrared continuum excess. This object has been observed with the VLT interferometer equipped with the AMBER instrument during its first commissioning run. AMBER/VLTI is currently the only near infrared interferometer that can observe spectrally dispersed visibilities. MWC 297has been spatially resolved in the continuum with a visibility of $0.50^{+0.08}_{-0.10}$as well as in the Brγemission line where the visibility decreases to $0.33\pm0.06$. This change in the visibility with wavelength can be interpreted by the presence of an optically thick disk responsible for the visibility in the continuum and of a stellar wind traced by the Brγemission line and whose apparent size is 40% larger. We validate this interpretation by building a model of the stellar environment that combines a geometrically thin, optically thick accretion disk model consisting of gas and dust, and a latitude-dependent stellar wind outflowing above the disk surface. The continuum emission and visibilities obtained from this model are fully consistent with the interferometric AMBER data. They agree also with existing optical, near-infrared spectra and other broad-band near-infrared interferometric visibilities. We also reproduce the shape of the visibilities in the Brγline as well as the profile of this line obtained at an higher spectral resolution with the VLT/ISAAC spectrograph, and those of the Hαand Hβlines. The disk and wind models yield a consistent inclination of the system of approximately 20°. A picture emerges in which MWC 297is surrounded by an equatorial flat disk that is possibly still accreting and an outflowing wind that has a much higher velocity in the polar region than at the equator. The AMBER/VLTI unique capability of measuring spectral visibilities therefore allows us for the first time to compare the apparent geometry of a wind with the disk structure in a young stellar system.

Aims.We present the first NIR spectro-interferometryof the LBV ηCarinae. The observations were performed with the AMBER instrument of the ESO Very Large Telescope Interferometer(VLTI) using baselines from 42 to 89 m. The aim of this work is to study the wavelength dependence of ηCar's optically thick wind region with a high spatial resolution of 5 mas (11 AU) and high spectral resolution.

Aims.We study the geometry and kinematics of the circumstellar environment of the Be star κCMa in the Brγemission line and its nearby continuum.

Aims.This paper describes the design goals and engineering efforts that led to the realization of AMBER (Astronomical Multi BEam combineR) and to the achievement of its present performance.

Aims.In this paper, we present an innovative data reduction method for single-mode interferometry. It has been specifically developed for the AMBER instrument, the three-beam combiner of the Very Large Telescope Interferometer, but it can be derived for any single-mode interferometer.

Lowland waters in Northern Ireland experience elevated agricultural phosphorus (P) inputs, and in response a variety of control measures targeting farm nutrient management have been implemented. Their efficacy in lowering nitrogen (N) and P exports and improving water quality is examined in 40 headwater streams from 1990 to 2009, and to 2014 for 24 of these. Over this period manure production in the study catchments declined by 7%, but regional chemical fertilizer inputs declined by 37% for N and 79% for P, and the regional nutrient surplus was lowered by 18% for N and 49% for P. Diminished pollution by organic wastes meant that 85% of streams exhibited chemistry suitable for salmonids in 2009 compared to 40% in 1990. Flow‐weighted mean concentrations (FWMCs) of nutrients declined between 1990 and 2009, and their correlations with catchment stocking rates became stronger over time. For catchments with manure inputs <16.6 kg P ha−1, total P and nitrate FWMCs declined from 123 ± 19 μg P L−1and 1.92 ± 0.5 mg N L−1in 1990 at rates of 2.2 ± 0.5 and 30 ± 10 μg L−1yr−1, respectively. For catchments with higher manure inputs the respective rates of decline were greater at 5.8 ± 1.0 μg P L−1yr−1and 160 ± 20 μg N L−1yr−1from 1990 concentrations of 270 ± 25 μg P L−1and 5.99 ± 0.4 mg N L−1. Although now lower, P concentrations in the more highly stocked catchments still exceed regional nutrient standards so that the identification of further factors impinging on nutrient losses is critical if such standards are to be achieved. Amelioration of point source and diffuse agricultural pollution over 20 years.Reductions to diffuse N export more rapid and pronounced than for P.Nutrient versus land use intensity correlations stronger after pollution amelioration.

The increasing use of concentrate feedstuffs within Northern Ireland dairy systems has resulted in significant farm gate phosphorus (P) surpluses, and these have contributed to increased soil P levels and risk of P loss to overland flow. However, the P content of feed concentrates can be lowered without compromising animal performance. This study focuses on P losses from grassland and evaluates how adjusting the P content of manure impacts on the P composition and concentration in overland flow. Dairy cows were offered diets containing 5.3 to 3.0 g P kg−1dry matter (DM) and produced manures with a range of P contents. Manure was applied at a rate of 50 m3ha−1to 0.5‐m2grassland plots, and simulated rainfall (40 mm h−1) was applied repeatedly 2, 9, 28, and 49 d after during the summer, winter, and spring. Decreasing the P content in the diet, from the highest to the lowest P treatment (43%), produced a proportionately greater reduction in manure TP content (63%), but reductions were not exclusively in the water‐soluble fraction. Following surface applications of manure, P concentrations in overland flow increased in all seasons (P≤ 0.001), while the greatest impact of varying the manure P content was most evident during the first simulated overland flow event. When diet P content was reduced from 5.4 to 3.0 g P kg−1DM, a statistically significant reduction in runoff P concentration was observed in all seasons. Elevated P concentrations in overland flow were observed for 28 d in spring and 9 d in summer and winter. The large drop in P concentrations between simulated rainfall events on Day 2 and Day 9 suggests that increasing the time interval between manure application and the generation of overland flow has a greater impact on P losses than does varying the dietary P content.

Total phosphorus (TP) exports from the rivers draining into Lough Neagh increased between 1974 and 2000 despite lower TP inputs to the rivers from point sources. Over this period annual diffuse exports of dissolved reactive P (DRP) increased by 238%, from 17 to 57 kg P km−2with an annual rate increase of 1.6 ± 0.3 kg P km−2yr−1. Dissolved unreactive P exports increased by 0.4 ± 0.2 kg P km−2yr−1, but particulate P exports did not increase. Annual exports of these three P fractions were positively correlated with annual runoff. The catchment of Lough Neagh has experienced an intensification of agriculture, with phosphorus inputs of manures and fertilizers to agricultural land increasing from 1,176 kg P km−2yr−1in 1925 to 3,823 kg P km−2yr−1in 2000. However 85% of this increase predated 1975. Increasing DRP exports after 1974 were better correlated with increasing soil P, and 70% of the increase in P accumulation by soils since 1925 occurred after 1974. Land use remained stable after 1974 with a historically low component of arable (>5%) and a dominance of grassland (<63%). The principal decade of intensification was in the 1940s, but this coincided with a greater arable component of land use. This period predated the increase in diffuse DRP exports. Intensively managed grasslands appear to be vulnerable to high DRP exports, reflecting surface application of manures, accumulation of soil P at the surface, and the creation of bypass flow pathways that facilitate the loss of P from soil to water.

Failure to recruit adequate numbers of participants represents a major barrier to the completion of randomized controlled trials in primary care and is associated with substantial opportunity costs. However, uncertainty exists regarding the relative effectiveness of different methods to promote recruitment.

The resistance to growth inhibition commonly observed in a variety of TGFb disabled human cancers, the potential role of TGFb in the exacerbation of malignancy and the effects of TGFb in suppressing the immune system, all emphasize the importance of pathways mediated by this polypeptide to the neoplastic process. Early investigations to understand the molecular basis of cancer due to defects in TGFb signaling were concentrated on examining the abundance of biologically active TGFb and its binding to TGFb receptors. However, major breakthroughs in understanding the molecular basis of the TGFb mediated effects in cancer came from genetic evidence for inactivation of the various players in its signaling cascade. The vast majority of current evidence is derived from the identification of mutations causing structural defects in TGFb receptors and Smad genes, the downstream effectors of the TGFb signaling pathway that have emerged from the analysis of human cancers. The involvement of Smads at the receptor level upon activation by a TGFb bound receptor, their participation in signal transmission to the nucleus and their direct roles in the regulation of target genes have made the various Smad genes critical targets for inactivation of TGFb signaling in cancer. To date, eight human homologues of the Smad genes have been identified and are classified into three distinct classes based on their structure and function. In this review, we discuss TGFb signaling via the Smads and the known and predicted points at which TGFb signaling could become altered in human cancer.

Soil testing to determine phosphorus (P) availability to crops is a well established process. Today, however, there is increasing emphasis on relating existing or new soil tests to the potential for P loss from soils to surface waters. The objective of this study was to determine how well short-term soil P measurements (water soluble P (WSP), Mehlich-1 P, degree of P saturation (DPS), and 1-day desorbable P) predicted long-term P release and P sorption in relation to soil properties. Topsoils and subsoils with widely differing properties were collected from four sites in Northern Ireland, the Republic of Ireland, and the U.S. mid-Atlantic coastal plain, with topsoils and subsoils sampled at each site. All soils were analyzed for water soluble P, Mehlich-1 P, oxalate extractable Al, Fe, and P (Alox, Feox, Pox), degree of P saturation (DPS = (Pox/0.5Alox+Feox) × 100, free Alox+Feox= 0.5Alox+Feox−Pox), long-term desorbable P (using Fe-oxide-filled dialysis membranes), and long-term P sorption for "remaining P sorption capacity" (from a solution maintained at 5 mg P L−1). Long-term desorbable P followed a pattern of initial fast P release followed by a slower release of P that was still in progress after 39 days. Water soluble P, Mehlich-1 P, and the DPS were all correlated with the cumulative amount of P desorbed in 39 days (r= 0.82*, 0.79*, and 0.83*, respectively). However, for short-term (1 day) desorbable P, correlations followed the order WSP (r= 0.94***) > DPS (r= 0.83*) > Mehlich-1 P (r= 0.72*). When P was added to the soils, all of the soils exhibited an initial period of rapid P sorption, followed by a period of slower sorption still in progress after 38 days. The soil components found to be related most closely to remaining P sorption capacity were free Alox+Feox(r= 0.73*) and free Alox(r= 0.80*), indicating that amorphous Fe and Al are the major soil components responsible for long-term (38 days) P sorption. Overall, a single oxalate extraction for Al, Fe, and P proved to be most useful for predicting both long-term P release, through calculation of the DPS and for predicting the ability of the soils to sorb more P by calculating free Alox+Feox.

Agricultural intensification of grassland has led to serious imbalances between inputs of nutrients (in purchased fertilizers, feeds and atmospheric deposition) and outputs (mainly milk and meat). Excess nutrients are lost into the wider environment with consequences for soil, water and atmospheric quality. This paper examines the environmental impacts of nitrogen and phosphorus use by the grassland-based agricultural industry of Northern Ireland. Results are presented from a recently completed experimental programme, which was undertaken to define the losses associated with nitrogen inputs to grazed grassland. Also examined is the contention that P use in grassland agriculture is now the major cause of the P enrichment of Lough Neagh, the largest lake in the British Isles. A combination of strategies involving fertilizer management, manure management and dietary manipulation can have a significant impact on the flow and excesses of N and P in grassland systems. However, the rate at which improved management strategies will be introduced in practice depends on regulatory controls, the applicability of new techniques and the financial implications.

Agriculture in Northern Ireland depends on grass-based production, but since 1980, expansion of output has been effectively constrained by production limits set by the European Union agricultural policy. Despite this, long-term monitoring over several decades has shown significant degradation of water quality in Lough Neagh, with persistent high biomass of blue-green algae. Similar long-term studies have revealed a marked decline in the freshwater survival of salmon in the nearby River Bush. These changes may be related and reflect the impact of farming on water quality and salmonid production. Regular sampling of the inflowing rivers to Lough Neagh has shown that continued increase in lake phosphorus concentration has been primarily due to an increase in the soluble reactive phosphorus loading from agricultural diffuse sources. Similar diffuse inputs of agriculturally derived nutrients to the River Bush, leading to increased plant growth together with the accumulation of fine sediment in salmon spawning redds, are considered to be important in the decline of freshwater survival of salmon from egg to smolt. The impact of farming practices on lakes and rivers is considered in relation to understanding of the complex and interacting factors that link land use to water quality.

During the winter of 1996–1997, somatic energy content and diets of age-0 Pacific herring Clupea pallasifrom Prince William Sound, Alaska, were examined. From October to March, the standard length of age-0 recruits continued to increase, indicating either growth or mortality of smaller fish. The whole-body energy content averaged 4.4 kJ/g wet weight for fish captured in October and increased to 5.0 kJ/g wet weight in November. Thereafter, somatic energy continually declined, reaching 3.9 kJ/g wet weight in March. The December–March decline in nutritional status of the recruits verified that the energy derived from feeding was not enough to meet metabolic needs. The energy density of taxa found in the diets remained steady through the winter and increased in March. Total zooplankton biomass, however, decreased as the mean water temperature decreased. Estimated assimilation rates were lower for smaller fish than larger fish and decreased as winter progressed. We concluded that juvenile herring rely on energy stores to overwinter and that smaller fish are more likely to be affected by starvation. Also, the duration of overwinter starvation may be related more to photoperiod than to mean water temperature.

The Lough Neagh catchment area covers about one‐third of the land area of Northern Ireland. This report documents NO2−concentrations in the major rivers entering Lough Neagh, which are frequently in the range of 100 to 150 μg N L−1and exceed the European Community (EC) water quality guide values. The contribution of land drainage to NO2−loads carried by these rivers was estimated to be about 40%. The remaining 60% of NO2−appears to originate from N transformations at the sediment‐water interface of the river system. The available evidence suggests that NH+4originating from agricultural pollution provides the N substrate for nitrification by Nitrosomonasto NO2−. What is anomalous is why this NO2−is not further oxidized rapidly to NO−3by Nitrobacter. A possible mechanism is that the Nitrobacteris retarded by the presence of free ammonia concentrations that can be predicted to be present in the range of 65 to 76 μg N L−1.

We present the detailed analysis of fourteen cool stars, nine of which have been associated by Eggen with four moving groups from the kinematics and the photometric properties; the five remaining stars are characterized by a large-spatial velocity. From the scatter of the chemical composition among the program stars belonging to a same group, we discuss that the moving groups ? Her, Wolf 630, and Kapteyn could really exist, and that Groombridge 1830 do not. No peculiar abundance relative to iron is found except a possible relative overabundance of Ni for the most metal-poor stars in this sample. The results of the detailed analyses are discussed in terms of the chemical abundances of our Galaxy.

The growth rates under a 3:21 light:dark cycle of Oscillatoria redekei van Goor and O. agardhii Gom. were measured over a range of temperatures (5-23°C), and irradiances (5-200 µE m-2s-1). The temperature quotient of light-saturating growth, Q10, was close to 2·0 only over limited temperature ranges, 14-20°C for O. agardhii and 11-20°C for O. redekei. The temperature quotient of growth rate was greater than 2·0 at lower temperatures which coincided with increases in algal carbohydrate at the start of the light period. Carbohydrate increases during the light period were proportional to growth rate for both species. At subsaturating irradiances the growth rates of the two species were independent of temperature. A comparison of laboratory growth rates indicated that O. agardhii grew faster than O. redekei only at temperatures greater than 11°C when irradiances were greater than 100 µE m-2s-1. This is in broad agreement with the succession of the two species in Lough Neagh where O. redekei begins growth in the early spring, then gives way to O. agardhii in the summer.

Growth rate data of Oscillatoria redekei van Goor grown under a range of irradiances and light:dark cycles were used to examine the relationship between growth rate and light dose (irradiance × duration), the growth efficiency. When growth efficiency was greatest, growth rate responded directly to light dose and similar values for growth efficiency could be obtained at a range of temperatures. This suggests that under these conditions, respiration losses throughout the light:dark cycle were controlled by the photosynthetic carbon input. The maximum growth efficiency observed was 1·7 E m-2 (400-700 nm) per population doubling. Under continuous light, photosynthesis saturated at higher than incident irradiances so that photosynthesis proceeded at a fraction of the maximum rate; under light:dark cycling, photosynthesis was saturated below the highest growth irradiance and therefore proceeded at the saturation value.

The photosynthetic characteristics and pigment contents of Oscillatoria redekei van Goor were measured under a range of photoperiods (6:18 light-dark to continuous light) and irradiances (13-260 µE m-2 s-1) at 15°C. The light saturated rate of photosynthesis (Pmax) per cell protein was found to be comparatively constant under different light regimes but cells grown under low irradiances and/or short light-dark (LD) cycles showed marked increases in the efficiency with which they harvested low light. The increase in efficiency under low light doses corresponded to an increase in the phycocyanin and chlorophyll a content of the cultures but phycocyanin content was observed to increase by a greater proportion than chlorophyll a. The increase in the ratio of phycocyanin to chlorophyll a was highly correlated with increases in the efficiency of light harvesting. Cells grown under 6:18 LD cycles had a pigment composition similar to low light cultures grown under continuous light. Because of wide differences in the pigment content of continuous light cultures, the light saturation characteristic Ik varied over a wide range from 77 to 462 µE m-2 s-1, compared to a range of 78-140 µE m-2 s-1 for cells grown under a 6:18 LD cycle. In addition, the range of compensation irradiances for continuous light cells was 4-82 µE m-2 s-1 compared to 3-6 µE m-2 s-1 for 6:18 LD cells. The large difference between continuous light and LD cells was due in part to the high respiration rates of continuous light cells.

The relationship between photosynthetic rate and irradiance was measured for 20 strains of blue-green algae from the genera Anabaena, Aphanizomenon and Oscillatoria. Cells were grown at 20°C under 6:18 light-dark at 30 or 150 µE m-2 s-1. Under high light the mean light saturated rate of photosynthesis (Pmax) of the Oscillatoria cultures was 14·8 mg O2 mg Chl a-1 h-1, but under low light this was depressed by 42%. Anabaena and Aphanizomenon cultures showed a similar mean Pmax under high light (13·8 mg O2 mg Chl a-1 h-1), but only a 13% depression of this value under low light. Oscillatoria cultures were more efficient than Anabaena and Aphanizomenon cultures at harvesting low irradiances, as measured by the initial slope of the photosynthesis-irradiance plot. The efficiency of light harvesting at low irradiances increased in Anabaena and Aphanizomenon cultures grown under low light. Oscillatoria cultures on the other hand showed little increase in efficiency when grown under low light. Mainly due to the depression of Pmax, but also because of increased low light efficiency, the light saturation characteristic Ik was lower in low light cultures. In the Oscillatoria cultures the mean Ik value decreased from 175 to 100 µE m-2 s-1 and in the Anabaena and Aphanizomenon cultures from 215 to 164 µE m-2 s-1. Probably due to the low short wavelength component of the light source used, little or no inhibition (mean 4·2%) of Pmax was observed even at irradiances exceeding 700 µE m-2 s-1.

We describe the multislit spectrograph “SFM”. It is designed to obtain simultaneously spectrograms of faint objects over a field of 10 arcminutes for an entrance aperture ratio f/10, or of 15 arcmin for f/8. The SFM makes the dispersed image of the entrance slits directly, without any fiber optics. The number of entrance slits can be as large as a few hundreds, depending on the distribution of the sources on the sky and on the wavelength range. The present reciprocal dispersion is 79Åmm-1 in the wavelength range 3600 – 6400Å. The SFM is expected to reachmv˜22 with a signal to noise ratio of 10 for a spectral resolution of 3.3Å and an integration time of 5 hours, when used with the photon counting detector CP40.

A new medium is described for the growth of the freshwater diatom Melosira italica subsp. subarctica which allows prolonged exponential growth in batch culture. The medium was optimized for cell yield and observations are reported on varying the pH, shaking rate and trace-metal concentrations in the medium. The medium contained no vitamins. Preliminary results suggest that the silica usage was 0·163 mg Si mm-3 filament volume, the molar ratio of Si:P uptake varied between 46:1 during exponential growth and 30:1 during silica limitation; the molar N:P ratio of the cells averaged 5·6:1.

We have constructed an analytical model to simulate the behaviour of an adaptive optics system coupled with a sodium laser guide star. The code is applied to 3.6‐ and 8‐m class telescopes. The results are given in terms of Strehl ratio and full width at half‐maximum of the point spread function. Two atmospheric models are used, one representing good atmospheric conditions (20 per cent of the time), the other median conditions.  Sky coverage is computed for natural guide star and laser guide star systems, with two different methods. The first one is a statistical approach, using stellar densities to compute the probability of finding a nearby reference. The second is a cross‐correlation of a science‐object catalogue and the USNO catalogue. Results are given in terms of percentage of the sky that can be accessed with given performances, and in terms of the number of science objects that can be observed, with Strehls greater than 0.2 and 0.1 in the Kand Jbands.

Previous studies have reporled that only 40% of nitrite (NO−2) in major rivers in Northern Ireland originates from land drainage. The remainder appears to originale from N transformations at the interface between sediment and water within river systems. Streams in two major river catchments in Northern Ireland were monitored for the presence of NO−2. Mean NO2concentrations (which all exceeded 3.0 µg N L−1which is the European Community (EC) guide values for supporting salmonid fish) ranged from 3.8 to 84.5 µg N L−1in 14 streams in the Upper Bann and 10.7 to 60.0 µg N L−1in 14 streams in the Colebrooke river system. Evidence from multiple regression analysis suggested that NO2accumulation in these streams was associated with the presence of free NH3. Incubation and differential 15N labeling of sediment extracts with ammonium nitrale (NH4NO3) provided support for this hypothesis that showed that the mechanistic process involved in NO−2accumulation is nitrification inhibition rather than denitrification. Free NH3partially inhibils NO−2oxidation by Nitrobacter, but does not inhibit the oxidation of ammonium (NH+4) by Nitrosomonas. Most of the NH+4in streams originates from pollution by agricultural effluents and must be curtailed to prevent NO−2accumulation.

This study was designed to determine the subtypes of 5-HT receptors present in bovine large coronary arteries and to characterize the response mediated by each subtype of receptor. Concentration-response relationships for 8-hydroxy-2-(di-n-propylamino)-tetralin (5-HT1A agonist) (0.3-100 microM), CGS-12066B maleate (5-HT1B agonist) (0.01-30 microM), alpha-methylserotonin maleate (5-HT2 agonist) (0.01-30 microM), 1-(m-chlorophenyl)-biguanide (5-HT3 agonist) (0.1-100 microM) and serotonin (0.1-300 microM) were studied in vitro using 2-mm segments of bovine proximal left anterior descending coronary artery. Each segmental ring was mounted in a 70-ml tissue bath for the measurement of isometric tension. 8-Hydroxy-2-(di-n-propylamino)-tetralin (10-100 microM), alpha-methylserotonin maleate (0.01-30 microM) and serotonin (0.1-300 microM) induced endothelium-independent contraction, whereas CGS-12066B maleate and 1-(m-chlorophenyl)-biguanide had no effect in this species. Contractions induced by 8-hydroxy-2-(di-n-propylamino)-tetralin or alpha-methylserotonin maleate were attenuated by pretreatment with S(-)propranolol (2.6 microM), a relatively selective 5-HT1A and 5-HT1B receptor antagonist, and ketanserin (0.3 microM), a selective 5-HT2 receptor antagonist, respectively. Pretreatment with S(-)propranolol or ketanserin also attenuated serotonin-induced contraction, demonstrating that serotonin mediates contraction through both 5-HT1A and 5-HT2 receptors in bovine large coronary arteries.

Six hydrogen ion buffers, piperazine-N, N'-bis (2-ethanesulphonic acid) (PIPES), N(-2-acetamido)-2-aminoethanesulphonic acid (ACES), N, N-bis (2-hydroxyethyl)-2-aminoethanesulphonic acid (BES), N-tris (hydroxymethyl)-methyl-2-aminoethanesulphonic acid (TES), N-2-hydroxyethylpiperazine-N'-2-ethanesulphonic acid (HEPES) and N-tris (hydroxymethyl) methylglycine (TRICINE), employed at 0·02 m concentration in freshwater media at their pKa values, were found to have no adverse effects on the growth rates of Oscillatoria redekei van Goor, Chlorella vulgaris Beij. and Pediastrum boryanum (Turp.) Menegh. The doubling times of Aphanizomenon flos-aquae fa. gracile (Ralfs) Lemm. and Anabaena flos-aquae Bréb. were lengthened by the presence of PIPES and ACES but this was interpreted as an effect of their low pKa values. Further results with HEPES and Oscillatoria redekei during exponential growth showed that, with a 1% CO2-in-air gas phase, a pH variation of only 0·06 pH units was obtained compared with 2·77 units in the media alone. These results contrasted favourably with tris (hydroxymethyl) aminomethane (TRIS) buffer which severely inhibited the growth of the blue-green algae tested. This inhibition was shown to be partially counteracted in the case of Oscillatoria redekei by the addition of potassium chloride. With the other buffers, the use of the hydroxides of monovalent cations other than sodium to set the buffers at their pKS values caused inhibition of growth. Of the buffers examined, HEPES was considered to have potentially the most versatile application because of its favourable pKa of 7·55 and its negligible metalbinding capacity.

Study objectiveTo assess the role of testing for Helicobacter pylori in the management of dyspeptic patients in primary care.DesignSelective review of literature frequently quoted to support use of H pylori testing.Main resultsTesting for H pylori and referral of only positive cases for endoscopy aims to reduce the number of "unnecessary" endoscopies. Patients with negative results may receive short-term reassurance and subsequently place fewer demands on health services. However, studies to date have only assessed this practice in secondary care settings. Given the relatively high prevalence of both dyspepsia and H pylori infection, the transfer of this practice to primary care may lead to a paradoxical increase in endoscopy referrals. Identification of H pylori and prescribing of eradication treatment also aims to reduce endoscopy referrals. No primary care trials have yet assessed this approach. Given that fewer than one in four of dyspeptic patients have peptic ulceration, a high proportion may fail to respond to eradication treatment and subsequently require referral for endoscopy. The longer term clinical and psychosocial sequelae of treating or labelling patients with an infection associated with gastric cancer remain unknown.ConclusionsGiven uncertainty concerning the possible adverse effects of H pylori testing in primary care, we suggest a moratorium on its use in this setting until results from relevant clinical trials become available.

The in vitro growth rates under continuous light of the four dominant blue-green algae in Lough Neagh, Anabaena flos-aquae Bréb., Aphanizomenon flos-aquae Ralfs fa. gracile Lemm., Oscillatoria agardhii Gom. and Oscillatoria redekei van Goor were slower than in situ rates from Lough Neagh that had been corrected for hours of light received by the algae. However, by culturing on a 6: 18 light-dark cycle in vitro growth rates were obtained that were similar to the in situ rates. Under continuous light small species showed the fastest growth with Oscillatoria redekei the dominant species. However, this pattern was almost completely reversed under the light-dark cycle with Oscillatoria redekei only exhibiting the fastest growth rate under low light conditions. This observation showed agreement with Lough Neagh field data which showed that Oscillatoria redekei reached its maximum crop in April while the other three species were dominant during the summer months. Compared to the generally assumed high thermal tendency of blue-green algae the temperature maxima of the four species were low. No growth was observed at 35°C for any species while Anabaena flos-aquae was severely inhibited at 25°C.

Twenty-two strains of planktonic blue-green algae belonging to the genera Anabaena, Aphanizomenon and Oscillatoria were grown under controlled conditions at 20°C under continuous light. Growth rates were found to be positively correlated with size but less than half the variation in growth rates observed could be associated with changes in the surface/volume ratio. Cultures of the same species often showed wide variation in cell morphology and growth rates. The maximum growth rate observed was K = 2·74 doublings day-1 for a culture of Oscillatoria limnetica.

Laboratory growth experiments with two blue-green algae, Oscillatoria redekei Van Goor and Oscillatoria agardhii Gomont showed improved growth efficiencies under light/dark cycles compared with continuous light. This was due to photosynthetic production in the light period in excess of the protein synthesis requirement being stored in the algae as carbohydrate which in turn was used to generate cell protein, DNA and chlorophyll a during the following dark period. The optimum light/dark cycles observed were when the algae were able to store all their surplus production as carbohydrate. Under longer light periods the cells had either insufficient storage capacity or insufficient dark time to use all their stored carbohydrate. The larger species, O. agardhii, had a low rate of protein synthesis in the light which led to a higher rate of carbohydrate accumulation compared to O. redekei. As a result O. agardhii showed maximum efficiency under short light/dark cycles (3:21 and 6:18 L:D) while O. redekei showed maximum growth efficiencies up to 12:12 L:D cycle. Dark nitrate uptake was the main source of nitrogen for dark protein synthesis and the maximum dark nitrate uptake rate observed was 29% of that in the light. Under L:D cycles of less than 9 h light protein synthesis and nitrate uptake in the light were depressed so that 39% of the total N uptake in an O. redekei culture took place in the dark under 6:18 L:D cycle. Both species showed evidence of metabolic control because carbohydrate synthesis was reduced on long light periods. No evidence was found for any extracellular production of nitrogenous compounds.

The influence of irradiance, photoperiod and temperature was determined for the growth kinetics of the diatoms Aulacoseira subarctica, Stephanodiscus astraea and Stephanodiscus hantzschii and the results compared with those of cyanobacteria. Irradiance and photoperiod relationships were qualitatively similar to those for cyanobacteria in that: (1) growth rate (K) was proportionally greater under short photoperiods, with ratios of K under continuous light to K under 3:21 light:dark (LD) cycles of 1·50, 1·80 and 2·96 for A. subarctica, S. astraea and S. hantzschii respectively; (2) at subsaturating irradiances, K was proportional to irradiance and independent of temperature with a negligible predicted maintenance growth rate requirement. Apparent growth efficiencies (GE) at subsaturating irradiances were 0·26±0·03, 0·42±0·03 and 0·50±0·03 divisions mol-1m2 for A. subarctica, S. astraea and S. hantzschii with the values for Stephanodiscus species comparable to values for Oscillatoria species. Under a 3:21 LD cycle at 4 °C, light-saturated growth rates were 0·066±0·004, 0·197±0·033 and 0·285±0·018 divisions day-1 for A. subarctica, S. astraea and S. hantzschii. S. hantzschii growth rate at 4 °C exceeded maximum Oscillatoria growth rates at 23 °C and the S. astraea growth rate at 4 °C was equivalent to O. agardhii growth rate at 20 °C. Temperature increases above 4 °C gave Q10 values between 4 °C and 12 °C of 3·68, 2·39 and 1·92 for A. subarctica, S. astraea and S. hantzschii, but higher temperatures resulted in minor increases in K. S. astraea growth rate peaked at 16 °C, declining sharply at higher temperatures. February to March in situ growth rates in Lough Neagh, mean temperature 4·3 °C, showed that the A. subarctica in situ K of 0·058 divisions day-1 was close to the laboratory K at 4 °C, but that S. astraea in situ K of 0·101 divisions day-1 was lower than the laboratory K at 4 °C.