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The final stages of low-mass stellar evolution are characterized by significant mass loss due to stellar pulsations during the AGB phase, which lead to the development of planetary nebulae. Molecular masers of H2O, SiO, and ground state OH transitions are commonly detected in oxygen-rich late-type stars (OH/IR objects). In contrast, excited OH maser transitions are rare. We discuss our study of the carbon-rich pre-planetary nebula CRL618 (a prototypical post-AGB star). Observations conducted in May 2008 with the 305m Arecibo Telescope resulted in the first detection of a 4765MHz OH maser line in a late-type stellar object; the detection was confirmed a few months later also with Arecibo. Subsequent observations in 2015 and 2017 resulted in non-detection of the 4765MHz OH line. Our observations indicate that the 4765MHz OH maser in CRL 618 is highly variable, possibly tracing a short-lived phenomenon during the development of a pre-planetary nebula.
Two classes of elliptical galaxies are now recognised (Kormendy & Bender 1996). Luminous ellipticals rotate slowly (Davies et al. 1983and tend to have boxy isophotes. Ellipticals fainter than L∗ exhibit an increasing tendency to be rotationally supported and to possess a stellar disk component. This dichotomy led Bender, Burstein & Faber (1992) to suggest that the physical variable that controls the ultimate nature of a forming galaxy is the degree of gaseous dissipation that occurs in the final merger it experiences. Low luminosity systems experience more dissipative mergers which generate high rotation, disky end products. As bigger galaxies are formed, the mergers become increasingly stellar, producing the classical slow rotating ellipticals. They termed this the gas/stellar continuum. This global dichotomy is also reflected in the bimodality of core morphologies of the heterogeneous sample of local ellipticals observed with HST. The low luminosity disky galaxies have ‘hard’ cores with a steep slope in the luminosity profile at small radii, whereas the luminous galaxies have ‘soft’ cores with flat profiles at small radii (e.g. Faber et al. 1997).
A method is presented that will enable the bivariate luminosity/surface brightness distribution of galaxies to be determined from a relatively small HI selected sample. This will be taken from the HI Parkes All Sky Survey (HIPASS). The advantages of using an HI sample in order to avoid the selection effects that are present at optical wavelengths are discussed. We are developing an algorithm to automatically extract a uniform sample of galaxies from the HIPASS data cubes and to determine the parameters of these galaxies. We have so far conducted tests involving both simulated sources injected into cubes with real noise and data from the Multibeam Deep survey. Results from these tests are encouraging.
We report on a preliminary analysis of a 5600 sec per point survey of 32 square degrees in Centaurus, carried out with the Parkes 13-beam system. The signal-to-noise ratio is found to improve as for the whole integration. We have detected 102 HI sources between +250 and +12,700 km s−1 either by eye or by using the new galaxy-finding algorithm PICASSO. Over half of these are new HI detections. Around a dozen of these are not associated with catalogued galaxies and, in two of these cases, we have not identified an optical counterpart on the Digitized Sky Survey. Arguments are put forward to explain why deep integrations are needed to find low surface brightness objects.
We present 21 cm observations of 5×1 square degrees centered on the local Abell cluster 1367 obtained as part of the Arecibo Galaxy Environment Survey. This represents the first HI selected sample covering the core and the outskirts of a local cluster of galaxies. Combining the HI data with SDSS optical imaging we show that in HI selected samples follow scaling relations similar to the ones usually observed in optically selected samples. The most striking difference between HI and optically selected samples resides in their large scale distribution: while optical and X-ray observations trace the cluster potential very well, at radio wavelengths there is almost no evidence of the cluster presence.
The Arecibo Galaxy Environment Survey is a blind neutral hydrogen survey using the ALFA multibeam receiver at Arecibo Observatory to reach unprecedented sensitivities in a number of selected fields in the local Universe. When completed the survey will cover 200 square degrees out to a distance of at least 270 Mpc. If a population of gas-rich dark galaxies exists, then this survey is in a prime position to uncover that population.
So far 20 square degrees have been covered in the regions of Abell 1367, the Virgo Cluster, the NGC 7332/9 galaxy pair and the isolated galaxy NGC 1156. Over 200 sources have been found, including a number that have no obvious optical counterparts. We discuss here the potential of AGES for uncovering more such objects and the characteristics of the dark sources identified to date.
The Arecibo L-band Feed Array Zone of Avoidance Survey (ALFA ZOA) will map 1350-1800 deg2 at low Galactic latitude, providing HI spectra for galaxies in regions of the sky where our knowledge of local large scale structure remains incomplete, owing to obscuration from dust and high stellar confusion near the Galactic plane. Because of these effects, a substantial fraction of the galaxies detected in the survey will have no optical or infrared counterparts. However, near infrared follow up observations of ALFA ZOA sources found in regions of lowest obscuration could reveal whether some of these sources could be objects in which little or no star formation has taken place (“dark galaxies”). We present here the results of ALFA ZOA precursor observations on two patches of sky totaling 140 deg2 (near l = 40°, and l = 192°). We have measured HI parameters for detections from these observations, and cross-correlated with the NASA/IPAC Extragalactic Database (NED). A significant fraction of the objects have never been detected at any wavelength. For those galaxies that have been previously detected, a significant fraction have no previously known redshift, and no previous HI detection.
It has been shown that the rate of lipolysis and proteolysis differs significantly between red clover genotypes with different levels of polyphenol oxidase (PPO) activity (Lee et al. 2004). Sullivan and Hatfield, (2006) reported the development of genetically modified isolines of red clover with the PPO1 gene silenced. This material was used to examine the role of the red clover PPO enzyme on lipolysis and ultimately C18 polyunsaturated fatty acid biohydrogenation in batch culture. If the role of PPO in reducing ruminal lipolysis of plant lipids is proven it would influence breeding strategies for forages which exhibit this trait in an attempt to increase the levels of beneficial PUFA and decrease detrimental trans and saturated fatty acids in animal products.
The Arecibo Galaxy Environment Survey (AGES, Auld et al. 2006) will map ~200 square degrees over the next years using the ALFA feed array at the 305-m Arecibo Telescope. AGES is specifically designed to investigate various galactic environments from local voids to interacting groups and cluster of galaxies. AGES will map 20 square degrees in the Coma-Abell1367 supercluster including the Abell cluster 1367 and its outskirts (up to ~2 virial radii). In Spring 2006 we nearly completed the observations of 5 square degrees in the range 11:34< RA< 11:54, 19:20<Dec<20:20 covering all the cluster core and part of its infalling region reaching a 5 sigma detection limit of M(HI)~4×108M⊙ (assuming a velocity width ~200 km~s−1) at the distance of Abell1367 (~92 Mpc). An HI selected sample has been extracted from the datacube obtaining a catalogue of fluxes, recessional velocities, positions and velocity widths. We present a preliminary analysis of the properties of the HI sources and report the discovery of HI diffuse features within interacting groups at the periphery of Abell1367.
The Arecibo Galaxy Environments Survey (AGES) is a 2000-hour neutral hydrogen (H I) survey using the new Arecibo L-band Feed Array (ALFA) multibeam instrument at Arecibo Observatory. It will cover 200 square degrees of sky, sampling a range of environments from the Local Void through to the Virgo Cluster with higher sensitivity, spatial resolution and velocity resolution than previous neutral hydrogen surveys.
The enzyme polyphenol oxidase (PPO) requires both plant tissue damage and the presence of oxygen to become activated. It has been shown that with a large window of opportunity for oxygen activation, such as during ensilage of red clover, increases in both dietary-nitrogen utilisation and the concentration of polyunsaturated fatty acids in ruminant products can be achieved. However, there is little evidence as to whether such responses can be achieved during the grazing of fresh red clover, where the window of opportunity for oxygen activation is limited to the mastication period (Lee et al. 2006). This experiment investigated whether mastication of fresh red clover would result in the activation of PPO and its potential effects on protein and lipid profiles in the resulting bolus.
The enzyme polyphenol oxidase (PPO) may be responsible for increases in both dietary-nitrogen utilisation and the concentration of polyunsaturated fatty acids in ruminant products when animals eat red clover (Lee et al. 2004). The enzymatic reaction requires the presence of oxygen and therefore is assumed to be inhibited in the anaerobic rumen. However, little information exists as to the concentration of oxygen in boluses and whether this could sustain the aerobic enzymes activity in the reticulo-rumen. This study investigated the concentration of oxygen in grass-boluses measured in vitro or in vivo in the rumen of two rumen fistulated cows.
Plants of two genotypes of chickpea (Cicer arietinum), classified as early or late-maturing in the field, and relying either on dinitrogen fixation by nodules or on nitrate-N, were grown in various simulated tropical environments in growth cabinets. Plants were transferred between cabinets at various times so that they experienced either warm (30°C) or hot (35°C) days (both in combination with a typical night temperature of 10°C) for different durations of reproductive growth, after growing in average (30°C day - 10°C night) or warmer than average (30° - 18°C) temperatures for the first 28 days from sowing and then average temperatures until transferred into the hot regime. Diurnal vapour pressure deficits were adjusted so that plants experienced a constant atmospheric relative himidity (70%) in all thermal regimes. The greater the proportion of the reproductive period spent in hot days the smaller the seed yields produced; plants transferred at 50% flowering were almost barren. The implications of these data for breeding chickpeas well adapted to hot environments are discussed.
Effectively nodulated plants of 3 cultivars of chickpea, classified as early, mid-late and late-maturing, were grown to reproductive maturity in 12 factorial combinations of simulated tropical environments in growth cabinets. Cultivars varied in sensitivity but all responded as quantitative long-day plants and flowered earlier in longer photoperiods. Differences in temperature had important consequences, especially on the duration of the reproductive phase and overall crop longevity; they also induced plants to flower at the same time in different photo-periods. Early flowering plants did not necessarily mature early; others taking twice as long to come into flower had short reproductive periods and came to maturity at the same time. Relations between phenology, morphology and seed yield are described and compared with similar data for field-grown plants. Screening for ‘adaptation to environment’ in chickpeas is discussed.
A technique has been developed and tested for successfully grafting large, leafy cowpea shoots onto roots, which may be nodulated or not. Grafting per se had no significant effect on either the production or distribution of vegetative or reproductive dry matter compared with control plants left intact throughout growth. Furthermore, numerical components of yield and the concentration (%) and content (mg) of nitrogen in respective plant components were remarkably invariant. Examples are discussed of the variations in nitrogen nutrition which can be achieved and the potentials of the technique in general.
Factorial combinations of three daylengths (11, 12 and 15 h), warm and cool days (30° and 22° C) and warm and cool nights (18° and 10°C) were imposed on nodulated plants of three chickpea cultivars grown in pots in controlled environment growth cabinets. The treatments had large effects on growth, phenology and seed yield and no single environmental regime was optimal for all successive stages of development. Root growth and nodulation were extremely responsive to the environment experienced by the shoot. Conclusions are drawn on the potential contribution of these data to the development of empirical screening techniques suitable for large, segregating populations in field programmes devoted to the production of chickpea cultivars better adapted to their intended environments.
When cowpea plants were grown in large pots under simulated tropical conditions, and were dependent on either symbiotic fixation or inorganic N for their total nitrogen requirements, short periods of waterlogging had adverse effects on vegetative growth and seed production. The effects of waterlogging were more acute as plants experienced stress at progressively earlier stages of development. In plants depending either on biologically fixed N or inorganic N, waterlogging before flowering reduced vegetative growth by about 50%. Although some compensation in vegetative growth occurred during the reproductive development of nodulated plants, seed yields in both cases were still 48% less than in unstressed plants. Depending on the stage of plant development, treatment effects were mediated largely through changes in branch, peduncle and flower production and/or abortion, which contributed directly to variations in the number of pods retained to maturity. Inorganic nitrogen stimulated vegetative growth but did not significantly improve seed yield compared with effectively nodulated plants.
Effectively nodulated, pot-grown cowpea plants were irrigated with nutrient solution containing 25 ppm 15N, and the relative contributions to total plant N status of inorganic and nodule-fixed N were determined. Maximum rates of N assimilation occurred during pod-fill, with nodules contributing ten times more nitrogen than the applied source. Symbiotic fixation supplied over 80% of total plant N throughout growth, and contributed significantly to seed N during late pod-fill, when nutrient N assimilation was negligible. Vegetative N content was greatest at mid pod-fill, and mobilization from this 'pool' was equivalent to 44% of total seed N. The implications of these (and previously reported) data are discussed.